High-durability storage battery

Abstract

We provide lithium-ion batteries with high durability. [Solution] A truly durable rechargeable battery is realized by employing an advanced battery design that encompasses each component of the positive electrode, and / or negative electrode, and / or electrolyte, and / or separator, and / or conductive additive, all of which have high durability. In one embodiment, an electrode element comprising a positive electrode consisting of a current collector containing Al as a conductor, a positive electrode material, a conductive additive, and a binder; a negative electrode consisting of a current collector containing Cu as a conductor, a negative electrode material, and a binder; an electrolyte consisting of an organic solvent and an electrolyte salt; and a porous separator is sealed in an outer material, wherein the electrolyte salt concentration of the electrolyte is greater than 1 mol / L, the total pore volume determined by nitrogen adsorption / desorption is greater than 1.0 cc / g, and the value obtained by dividing the BET specific surface area by the total pore volume is 400 m 2 A lithium-ion battery characterized by containing at least one carbon material with a value less than / cc in the positive electrode conductive additive.

Description

[Technical Field]

[0001] The present invention relates to a lithium-ion storage battery with high durability performance, comprising a highly durable positive electrode or negative electrode or electrolyte or separator or outer casing material, and having a battery design that ensures high durability. [Background technology]

[0002] Since its inception, lithium-ion batteries have seen a wide range of applications in everyday life, including smartphones and electric vehicles (EVs). However, for EVs to replace gasoline-powered vehicles and contribute to environmental protection, extending their driving range is a necessary condition. This requires longer lifespans, higher performance, and more efficient battery response in the lithium-ion batteries they utilize. As a result, lithium-ion battery manufacturing faces ongoing competition in terms of cost, as well as continued demand for higher performance from the market.

[0003] Normally, lithium-ion batteries are discarded once they reach the end of their lifespan. However, in recent years, there has been a growing movement to secure resources and materials globally for the manufacture and stable supply of lithium-ion batteries. For this reason, there have been calls for the use of materials in an urban mining-like manner by recycling used lithium-ion batteries, under the guise of resource recovery.

[0004] However, recycling and remanufacturing lithium-ion batteries requires the same amount of energy as manufacturing new batteries from raw materials. Furthermore, the same amount of CO2 is re-emitted, making it difficult to stop environmental damage even through recycling and remanufacturing.

[0005] Currently, various power generation methods exist, but there is a need for battery storage systems that can utilize the generated electricity efficiently. If this is achieved, true resource conservation and energy efficiency will be realized in power facilities, and it will be a major step forward towards a sustainable society. For this reason, there is a strong demand for long-life lithium-ion batteries that can withstand long-term operation as infrastructure and have greater durability against performance degradation than ever before.

[0006] Patent Document 1 discloses that by arranging a boron compound on the surface of secondary particles of a lithium transition metal composite oxide, which is a positive electrode material, and improving the bonding force of the secondary particles, particle cracking is suppressed, and the increase in resistance during high-temperature degradation is suppressed, thereby enabling the realization of a battery with high energy density and high cycle characteristics. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2023-183651 [Patent Document 2] Japanese Patent Publication No. 2013-232402 [Patent Document 3] Japanese Patent Publication No. 1999-213987 [Patent Document 4] Japanese Patent Publication No. 2019-145449 [Patent Document 5] Japanese Patent Publication No. 2022-063588 [Patent Document 6] Japanese Patent Publication No. 2024-504152 [Patent Document 7] Japanese Patent Publication No. 2014-216263 [Patent Document 8] Japanese Patent Publication No. 2021-036506 [Overview of the project] [Problems that the invention aims to solve]

[0008] Numerous research and development efforts have been undertaken to suppress lifespan degradation in order to realize lithium-ion batteries with high durability, but the objective has yet to be achieved.

[0009] Patent Document 1 does not describe a fundamental improvement to the positive electrode material, nor do Patent Documents 2 and 3 describe a fundamental improvement to the negative electrode material. Indeed, in lithium-ion batteries with a wide oxidation-reduction potential, the degradation and decomposition of the organic electrolyte (solvent and electrolyte salt), which is less stable electrochemically (the lowest Li potential of the negative electrode and the high positive electrode potential of 4V or more) and chemically (the generation of strong acids due to electrolyte decomposition and the strong alkalinity of deposited metallic Li), often causes the degradation of the entire battery, rather than the positive or negative electrode material. Therefore, many inventions focus on suppressing the degradation of the electrolyte (Patent Documents 4, 5, and 6). Furthermore, Patent Documents 7 and 8 approach the issue from the perspective of charge-discharge methods and battery design, but these also end up being unsatisfactory improvements. Thus, unless fundamental or comprehensive measures are taken against battery degradation, truly durable rechargeable batteries cannot be realized. [Means for solving the problem]

[0010] This invention was made in view of the above circumstances, and it has been found that the above objective can be achieved by providing a battery configuration that encompasses each component of the positive electrode and / or negative electrode, and / or electrolyte, and / or separator, and / or outer casing, which have high durability performance and are equipped with advanced improvement measures to realize a truly highly durable rechargeable battery.

[0011] In other words, a highly durable rechargeable battery is one in which degradation reactions occurring within the battery are significantly suppressed, and this can only be achieved by employing battery components that have been improved in relation to the following degradation behaviors.

[0012] The degradation behavior that serves as the origin for the invention is described below.

[0013] Degradation of lithium-ion batteries occurs when Li ions, which contribute to the reaction between the positive and negative electrodes, are consumed and reduced by being incorporated into degradation reaction products, or when the ability of the positive and negative electrode materials to insert and remove Li ions decreases. As a result, the battery's charge and discharge capacity decreases, and the products become a resistive component, leading to a decrease in output characteristics relative to the current used.

[0014] The cause is that, in the high oxidation-reduction state that does not occur in conventional secondary batteries using aqueous electrolytes, unstable organic materials such as organic electrolytes and polyolefin separators undergo decomposition reactions, which trigger a deterioration in the performance of the positive and negative electrodes.

[0015] Simultaneously, degradation reaction products remain and accumulate within the battery, forming an insulating film that inhibits the electron conduction necessary for the positive and negative electrode reaction. Furthermore, the reaction overpotential increases, exposing the positive and negative electrodes to potentials exceeding normal levels. As a result, oxidative degradation occurs at the positive electrode, and metallic lithium deposition occurs at the negative electrode, leading to reduced degradation. Furthermore, secondary degradation can occur when degradation reaction products clog the separator or when reaction products with the electrolyte are further generated on the surface of highly reducing metallic lithium, leading to an accelerated degradation due to a decrease in lithium ions and an increase in resistance.

[0016] This invention is achieved by using highly durable components and combining multiple such components as much as possible, making it possible to realize a conventionally highly durable storage battery that exhibits high performance even when exposed to various environmental conditions. [Effects of the Invention]

[0017] According to the present invention, by combining innovative technologies such as positive electrodes, negative electrodes, electrolytes, separators, and conductive additives to implement fundamental and comprehensive improvement measures against battery degradation that hinders high durability, the realization of a truly highly durable rechargeable battery is achieved. [Brief explanation of the drawing]

[0018] [Figure 1]This is a transmission electron microscope (TEM) image of an example of a carbon material according to one embodiment of the present invention, measured at an accelerating voltage of 80 kV. [Figure 2] This is a transmission electron microscope (TEM) image of an example of a carbon material according to one embodiment of the present invention. [Figure 3] This is a schematic cross-sectional view showing an example of the cross-sectional structure of a lithium-ion battery according to one embodiment of this product. [Figure 4] This diagram shows the battery testing and evaluation flow of the present invention. [Figure 5] This diagram illustrates an ultra-high-sensitivity vacuum TPD-MS apparatus used for temperature-induced desorption analysis. [Modes for carrying out the invention]

[0019] Embodiments of the present invention will be described in detail below.

[0020] <Positive electrode> This section explains the positive electrode of a lithium-ion battery. Generally, a positive electrode is obtained by applying a slurry, which is a mixture of a positive electrode active material, a conductive additive to enhance electronic conductivity, a binder resin, and a solvent, onto a metal foil body for current collection, such as rolled aluminum foil, to form a coating film. After heating and drying to remove the solvent, the film is formed to a predetermined size and density.

[0021] (Positive electrode material) As a cathode material, an optimal composition can be selected from the viewpoints of cathode material manufacturability, electrode manufacturability, charge / discharge capacity, cycle characteristics, storage characteristics, and safety, and it can be used in lithium-ion batteries.

[0022] The cathode material of the present invention is a transition metal compound containing lithium, and is a highly improved material that is less prone to crystal structure breakdown or insertion failure in the insertion and removal reaction of Li ions in the compound crystal structure during charge-discharge cycles.

[0023] The main form of the positive electrode material is the ABO2 type lithium transition metal compound, where A=Li xWhen it is so, it is in the range of x = 0.96 to 1.05, the transition metal B is mainly selected from Ni, Mn, and Co, and when it is Niα, Mnβ, Coγ, the atomic ratio is in the range of α = 0.8 to 1.0, β = 0 to 0.3, γ = 0 to 0.2, and a positive electrode material in which B partially contains an element other than the transition metal can be preferably used.

[0024] Examples of elements other than Ni, Co, and Mn to be included in the positive electrode material include Mg, Ti, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Ge, Sn, Si, S, P, F, B, Na, etc., and it is preferable that at least one element selected from these groups exists in a single-phase solid solution form incorporated into the crystal structure or in a compound form such as an oxide. These elements preferably function as skeleton reinforcing elements that stabilize the crystal structure of the entire or part of the positive electrode material.

[0025] Although the above skeleton reinforcing element is incorporated into the crystal structure, by installing it on the crystal surface, it is also possible to confine the catalytic active action of the transition metal oxide, prevent contact with an electrolytic solution, etc., and suppress oxidative degradation.

[0026] It is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, it may contain a lithium composite metal oxide containing one or more metals such as cobalt, manganese, nickel, or aluminum and lithium.

[0027] Specific examples of the positive electrode material include lithium-manganese-based oxides (for example, LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (for example, LiCoO2, etc.), lithium-nickel-based oxides (for example, LiNiO2, etc.), lithium-nickel-manganese-based oxides (for example, LiNi 1-a Mn a O2 (where 0 < a < 1), LiMn 2-b Ni b O4 (where 0 < b < 2), etc.), lithium-nickel-cobalt-based oxides (for example, LiNi 1-c Co cO2 (where 0 < c < 1), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-d Mn d O2 (where 0 < d < 1), LiMn 2-e Co e O4 (where 0 < e < 2), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni f Co g Mn h )O2 (where 0 < f < 1, 0 < g < 1, 0 < h < 1, f + g + h = 1) or Li(Ni j Co k Mn m )O4 (where 0 < j < 2, 0 < k < 2, 0 < m < 2, j + k + m = 2), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni p Co q Mn r M S )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p, q, r, and s are the atomic fractions of the respective independent elements, 0 < p < 1, 0 < q < 1, 0 < r < 1, 0 < s < 1, and p + q + r + s = 1), etc.), and any one or two or more of these compounds may be included.

[0028] Among these, from the viewpoint of being able to enhance the capacity characteristics and stability of the battery, LiCoO2, LiMnO2, LiNiO2, lithium nickel manganese cobalt oxide (e.g., Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxide (e.g., LiNi 0.8 Co 0.15 Al 0.05 O2, etc.) are preferred.

[0029] As the positive electrode material, a lithium atom-containing oxide (olivine-type lithium-containing phosphate compound) represented by the following general formula (1) and having an olivine-type crystal structure can be used as a highly stable one.

[0030] Li 1-x M x (AO4)·····(1) (In formula (1), M is an ion of at least one metal selected from the group consisting of Mg, Ti, V, Nb, Ta, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Ge, and Sn, A is at least one selected from the group consisting of Si, S, P, and V, and x is a number satisfying the relationship 0 < x < 1) Note that the value of x in the general formula (1) is selected so that the valence of the entire general formula (1) becomes 0 in accordance with the valences of M and A.

[0031] Specific examples of the olivine-type lithium-containing phosphate compound include LiFePO4, LiCoPO4, LiMnPO4, Li 0.90 Ti 0.05 Nb 0.05 Fe 0.30 Co 0.30 Mn 0.30 PO4 and the like. Among these, LiFePO4 (lithium iron phosphate) is particularly preferable because the iron compound used as a raw material is easily available and inexpensive.

[0032] As the positive electrode material, organic compounds such as polyaniline, polypyrrole, polyacene, disulfide-based compounds, polysulfide-based compounds, and N-fluoropyridinium salts can also be used. [[ID=e33]]

[0033] The physical properties of the positive electrode material are determined from the required items in the battery design and manufacturing process due to constraints such as the usage form of the lithium-ion battery. In the production of the positive electrode material, process design and the like are carried out so as to realize its physical properties. Examples of the physical property values include powder particle size and distribution, specific surface area, density, and the like.

[0034] 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 value of 1 to 30 μm is usually preferred, and 1 to 10 μm is even more preferred.

[0035] These cathode materials can be used individually or in combination of two or more types.

[0036] When synthesizing the cathode material described above, a highly stable structure can be synthesized by selecting the atomic composition of the raw materials and the heat treatment conditions. While firing promotes the crystallization of the cathode material structure, lithium tends to scatter during firing, and lithium may be deficient after completion, so it is acceptable to overcharge the lithium, taking the process conditions into consideration.

[0037] (Positive electrode: conductive additive) Since the above-mentioned positive electrode material and binder resin generally have low electronic conductivity, it is preferable to include a conductive additive to enhance electronic conductivity within the positive electrode, and carbon-based materials are generally preferred. The amount of carbon material used in the present invention is appropriately selected depending on the purpose of use, but is usually in the range of 0.01 to 4 parts by weight, preferably 0.05 to 3 parts by weight, more preferably 0.1 to 2 parts by weight, even more preferably 0.2 to 1.5 parts by weight, and most preferably 0.5 to 1.5 parts by weight per 100 parts by weight of positive electrode active material.

[0038] Among the carbon-based materials used as conductive additives for the positive electrode, carbon black is preferred due to its conductivity, availability, and cost-effectiveness. Carbon black has a relatively low carbonization and calcination temperature, and because it is synthesized in the gas phase, the carbon layer grows in a point-oriented manner, resulting in a carbon material that mainly has an amorphous structure and low crystallinity.

[0039] Such carbon-based materials have many edges on their surface, which are the structural ends of the carbon layer, and most of these ends are oxygen-containing functional groups. When a battery is charged to a high voltage, these parts are oxidized and decomposed together with the electrolyte, causing the battery to deteriorate.

[0040] The following describes a highly durable conductive additive that can improve upon these conventional challenges. Depending on the battery's set voltage, carbon blacks can be used appropriately, but to achieve higher performance batteries, battery reaction aids with fewer oxygen-containing functional groups or graphene mesosponges are more preferably used.

[0041] The battery reaction aid comprises multiple primary particles containing carbonaceous material and having a three-dimensional framework with internal spaces. Some of these primary particles are bonded together to form secondary particles. These secondary particles exhibit mechanical properties such as plastic deformation during micro-loading and unloading tests, with some parts remaining unchanged. Furthermore, since the carbonaceous material consists of graphene, it is a carbon-based material with an extremely low number of oxygen-containing functional groups.

[0042] The battery reaction auxiliary mechanism simultaneously assists in the supply of electrons and ions necessary for the battery reaction, thereby achieving a faster and more efficient battery reaction. Its structure is mainly formed from particles made of a thin layer of graphene, and it has a space within the particles that can hold the electrolyte. Because the graphene layer is relatively thin, it is flexible, and while it will permanently deform under pressure, it exhibits high electronic conductivity due to its graphene properties, while maintaining a space to hold lithium ions when not deformed.

[0043] Among battery reaction assisting materials, graphene mesosponge is more preferable because its structural form is easy to control, it can suitably assist the desired battery reaction, and it can be efficiently produced industrially.

[0044] The following describes carbon materials suitable as conductive additives for the present invention.

[0045] -Carbonaceous structure- The carbon material for electrode conductive additives of the present invention consists of a carbonaceous material having a six-membered carbon ring structure, preferably a carbonaceous material having a graphene structure in which the six-membered carbon ring structures are linked in a network structure. Figure 1 shows a TEM image observed using a transmission electron microscope (TEM: JEM-ARM300F, manufactured by JEOL Ltd.) at an acceleration voltage of 80 kV. Graphene is a sheet-like material of sp2-bonded carbon, and as shown in Figure 1, the six-membered carbon ring structures are linked together to form a honeycomb-like hexagonal lattice structure. Furthermore, when the carbon material of the present invention consists of a carbonaceous material having a graphene structure, the intensity ratio of the G band to the 2D band in the Raman spectroscopy measurement described later is G / I 2D This can also be confirmed by the value being 0.2 or higher. Furthermore, the carbonaceous material may be graphene mesosponge.

[0046] Carbon materials typically consist of structures that exhibit elastic deformability and structures that exhibit plastic deformability. Such plastically deformable structures either exhibit high strength against stress or, once deformed, cannot be restored to their original state even after unloading. The degree of elastic and plastic deformation in carbon materials can be measured by micro-load unloading tests.

[0047] The carbon material of the present invention has been found to have the property of returning to its original shape without deforming under weak stress, such as in an extremely small load unloading test, i.e., it has a large elastic deformation work rate. In the case of the carbon material of the present invention, the portion consisting of graphene, which makes up the majority, exhibits elastic deformability, while the defective parts of the graphene structure other than graphene and the amorphous carbon parts exhibit plastic deformability, resulting in good properties against stress deformation. On the other hand, when the number of carbonaceous (graphene) layers is excessively exceeded (e.g., graphite), elastic deformability is maintained within a certain stress range, but when a predetermined threshold is exceeded, plastic deformation occurs rapidly, and the particle shape and linkage shape tend to be destroyed.

[0048] -Structure (connecting structure)- The carbon material of the present invention is not particularly limited as long as it has the above carbonaceous material, but as one example of this embodiment, a suitable example is a shell-like body consisting of a series of granular shapes having pores surrounded by the carbonaceous shell. Such a shell-like body is more preferably one which has a plurality of branched structures, and even more preferably one which has a ring shape formed by the connection of one end of the connecting structure, although the one end of the ring-shaped connecting structure does not necessarily have to be connected to the other end.

[0049] The size of the pores surrounded by the carbonaceous shell is not particularly limited, but is usually in the range of 0.1 to 100 nm, preferably 1 to 80 nm, and more preferably 5 to 50 nm. The length of the shell-like structure formed by multiple connected grains having the above-mentioned pores is not particularly limited, but is usually in the range of 0.01 to 100 μm, preferably 0.05 to 80 μm, and more preferably 0.1 to 50 μm. The average particle size of the shell-like structure is not particularly limited, but is usually 0.05 to 50 μm, preferably in the range of 0.05 μm to 6 μm, 0.1 to 10 μm, 0.1 μm to 5 μm, or 0.5 to 5 μm.

[0050] Figure 2 shows a TEM image of an example of the carbon material according to this embodiment, observed using a transmission electron microscope (TEM: JEM-2100Plus model, manufactured by JEOL) at an acceleration voltage of 100 kV. The degree of transmission of particles in Figure 2 also indicates that the inside of the particle shape is hollow. It can be seen that the carbon material of the present invention is a shell-like body in which pores surrounded by carbonaceous shells are intricately linked together.

[0051] The shell-like structure may have constrictions at the joints between adjacent granular shapes. For example, when two particles are joined together, they may take on a peanut shell-like or dumbbell-like shape. Multiple such granular shapes are combined to form a linked structure (shell-like structure). Figure 2 shows an example of a carbon material, and the linked structure has a complex, non-standard shape.

[0052] Furthermore, as shown in Figure 2, in structures where multiple granular shapes are connected over a long distance, the multiple granular objects are connected and extend in multiple directions, with interconnected voids. Also, when the connected structure takes the form of a long connected shape, one end and the other end may exhibit a ring shape. Alternatively, the tips of branches that branch out and extend over multiple distances may also exhibit a ring shape. Such ring shapes may or may not have their tips connected.

[0053] As described above, the carbon material of the present invention preferably has a linked structure in which granular shapes, each having a single pore surrounded by a carbonaceous shell, are linked together in a bead-like manner with multiple branching points. The term "structure" in carbon materials is used to describe the complex structure of carbon black, and refers to an aggregate structure in which primary particles are linked together with multiple branching points. In other words, the carbon material of the present invention has a structure in which aggregates are interconnected by voids, with the interior of the highly conductive carbon black primary particles being hollow, and the outer shell being made of carbonaceous material having a six-membered carbon ring structure, preferably a graphene structure. As a result, the carbon material of the present invention has a structure that is highly conductive and can stably secure an electrolyte, and is therefore thought to have significantly improved the rapid discharge performance, battery capacity characteristics, and charge / discharge characteristics of lithium secondary batteries.

[0054] When many granular materials are linked together, and the total surface area of ​​the linked structure increases, the electronic conductivity increases. Furthermore, as the overall complexity of the linked structure increases, voids are formed not only within the internal space of the linked structure but also in the areas where the outer shells of the linked structures meet. When a carbon material having such a linked structure is incorporated into the electrodes of a battery, the electrolyte enters these spaces and voids. In other words, the larger the volume of the internal space of the linked structure and the volume of the voids formed by the outer shells, the greater the amount of electrolyte that can be held. The size of the volume of spaces and voids in the linked structure of the carbon material of the present invention can be compared with the volume of conventionally used conductive additives, using the oil absorption amount described later as an indicator.

[0055] The positive electrode material of a lithium-ion battery is a lithium-containing transition metal oxide with low electronic conductivity and a particle size distribution. In conventional methods, an electron conduction path is established by mixing a conductive additive made of carbon material, which assists electron conduction for the battery reaction, with a binder resin and then pressing and fixing it to a current collector. The materials other than the binder resin are powder particles, and the electrolyte exists in the spaces between the particles. For this reason, it has been difficult with conventional techniques to actively place the electrolyte, or in other words lithium ions, near the positive electrode material.

[0056] Conventionally, complexly shaped carbon black has been widely used as a conductive additive. In contrast, by using the carbon material of this embodiment instead of conventionally used conductive additives, the carbon material has a space inside its carbonaceous outer shell, which allows it to hold an electrolyte. The carbon material of the present invention has a larger internal space compared to carbon black, which has been conventionally used as a conductive additive. Therefore, the carbon material of the present invention can simultaneously assist in the supply of electrons and ions necessary for battery reactions, and can be said to be a material that enables rapid battery reactions.

[0057] (Characteristics of carbon material) In this invention, the state of the carbonaceous microcrystalline structure of the carbon material can be analyzed by Raman spectroscopy. The Raman spectrum includes the state at wavenumber 1593 cm⁻¹. -1 The peak in the surrounding region is called the G band, and this band represents the sp2 bond (aromatic ring C=C stretching motion) in carbon materials. This is the Raman spectrum at wavenumber 1356 cm⁻¹. -1 The peak present in this vicinity is called the D band, which represents sp3 bonding (CH stretching motion) in carbon materials. This band increases when sp2 bonds in the six-membered carbon ring structure of the carbonaceous layer are broken and replaced with sp3 bonds. This occurs in the Raman spectrum at wavenumber 2680 cm⁻¹. -1 The peaks in the surrounding region are called 2D bands, and they are bands that show second-order phonon scattering (CH stretching motion), and they represent the number of layers of carbon material.

[0058] Strength ratio of the G band and 2D band of carbon material I G / I2D This is said to be an index indicating the stacking state of graphene layers (D. Graf, et al., NANO LETTERS, 7, 238-242; (2007)). The same paper states that when the (G / 2D) intensity ratio is 0.2, there is one graphene layer.

[0059] Strength ratio of the G band to the 2D band of the carbon material of the present invention G / I 2D The I of the carbon material is 1 or more, preferably 1.10 or more, more preferably 1.20 or more, most preferably 1.43 or more, and 5.0 or less, with the following preferences being in order: 4.5 or less, 4.0 or less, 3.57 or less, 3.0 or less, 2.5 or less, and 2.08 or less. G / I 2D When the value of is within this range, the strength properties and elastic deformability that maintain the hollow structure of the carbon material are highly balanced, and the desired properties such as rapid discharge, capacity characteristics and durability when used as a conductive additive in lithium-ion secondary batteries are greatly improved, making it suitable. G / I 2D However, if the lower limit is exceeded excessively, the graphene material will not be sufficiently formed, resulting in a decrease in electronic conductivity and a reduction in discharge capacity. If the upper limit is exceeded excessively, the number of graphene layers will increase, resulting in reduced flexibility and a decrease in electrode density, which reduces the battery charging capacity. Neither of these is desirable.

[0060] Strength ratio of D-band to G-band of the carbon material of the present invention D / I G The I of the carbon material is preferably 0.1 to 10, preferably 0.5 to 5, more preferably 1 to 3, even more preferably 1.2 to 2.5, and most preferably 1.4 to 2. D / I G When this range is maintained, the sp2 and sp3 orbitals of the carbonaceous carbon material are in an optimal state, and the electron conduction paths and ion conduction paths are highly balanced, which is thought to greatly enhance the rapid discharge performance, capacity characteristics, and charge / discharge characteristics of lithium-ion batteries.

[0061] The oil absorption capacity of the carbon material of the present invention is 400 mL / 100g or more, preferably 600 mL / 100g or more, more preferably 800 mL / 100g or more, even more preferably 1000 mL / 100g or more, and most preferably 1400 mL / 100g or more, based on the oil absorption capacity of refined linseed oil measured in accordance with JIS K5101-13-1 (Pigment Test Methods - Part 13: Oil Absorption Capacity - Section 1: Refined Linseed Oil Method). When the oil absorption capacity is within this range, it is possible to improve battery characteristics such as the 2C maintenance rate. Furthermore, there is no particular upper limit to the oil absorption capacity, but it is usually 5000 mL / 100g or less, preferably 4000 mL / 100g or less, more preferably 3500 mL / 100g or less, even more preferably 3000 mL / 100g or less, and most preferably 2500 mL / 100g or less.

[0062] The oil absorption capacity of the carbon material of the present invention is significantly higher than that of carbon black, which is commonly used as a conductive additive in lithium-ion batteries. This allows for a large amount of electrolyte to be held not only in the internal space of the granular structure, but also in the gaps created in the areas surrounded by the connecting outer shell and the areas surrounded by the connecting aggregate structure. This enables a stable supply of lithium ions, contributing to the rapid charging performance, charge-discharge characteristics, and battery capacity of lithium-ion batteries. If the oil absorption capacity of the carbon material is excessively low, the amount of electrolyte that can be held is small, causing a delay in ion supply during rapid reactions and reducing the discharge capacity. Conversely, if it is excessively high, it becomes difficult to maintain the structure of the carbon material, and the amount of electrolyte held tends to be difficult to control.

[0063] The average interplanar spacing d002, determined from the 002 diffraction line measured by X-ray diffraction (XRD) of the carbon material of the present invention, is in the range of 3 to 5 Å, preferably 3.3 to 4.5 Å, more preferably 3.3 to 4 Å, even more preferably 3.3 to 3.9 Å, and most preferably 3.3 to 3.8 Å.

[0064] The crystallite size Lc(002) in the c-axis direction of the

[0002] plane, as measured by X-ray diffraction (XRD) of the carbon material of the present invention, is preferably 0.1 nm or more, or preferably 0.3 nm or more, 0.5 nm or more, 1.0 nm or more, or 1.1 nm or more. Furthermore, the upper limit of the crystallite size Lc(002) in the c-axis direction of the

[0002] plane is not particularly limited, but is preferably 20 nm or less, or preferably 5 nm or less, 3 nm or less, 2.5 nm or less, 2.0 nm or less, 1.9 nm or less, 1.5 nm or less, 1.25 nm or less, or 1.21 nm or less. When Lc(002), which measures the degree of crystallinity of the carbon material, is within this range, there is a tendency for large mesopores and macropores to be easily formed.

[0065] The size of the crystallites La(10) in the a-axis direction of the

[10] plane of the carbon material of the present invention, as measured by X-ray diffraction (XRD), is not particularly limited, but is preferably 0.1 nm or more, or preferably 0.5 nm or more, 1.0 nm or more, 1.5 nm or more, or 1.8 nm or more. Its upper limit is preferably 10 nm or less, or preferably 5.0 nm or less, 4.5 nm or less, 4.0 nm or less, or 3.8 nm or less.

[0066] The BET specific surface area of ​​the carbon material of the present invention is not particularly limited, but is the specific surface area calculated from nitrogen adsorption as specified in JIS Z8830, preferably 100 to 2700 m². 2 / g, or 300-2500m 2 / g, 500~2000m 2 / g, 600~1800m 2 / g, 800~1200m 2 It is also preferable that the BET specific surface area of ​​the carbon material of the present invention is within this range, as this allows for a high degree of conductivity and oil absorption.

[0067] The theoretical value of the specific surface area of ​​single-layer graphene is 2627 m². 2Since it is calculated as / g, the closer the specific surface area is to that value, the more ideal the carbon conductive material becomes. However, the carbon material of the present invention combines electronic and ionic conductivity as a graphene layer that can maintain a pore and void structure, and greatly improves the rapid discharge performance, capacity characteristics, and charge / discharge characteristics of lithium-ion batteries.

[0068] The total pore volume of the carbon material of the present invention is not particularly limited, but is a value measured by nitrogen adsorption / desorption measurement and is preferably 0.1 cc / g or more, or preferably 1 cc / g or more, 1.5 cc / g or more, 2 cc / g or more, or 2.95 cc / g or more. The upper limit is not particularly limited, but is preferably 20 cc / g or less, or preferably 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. If the total pore volume of the carbon material is excessively large, the skeletal strength of the pore structure weakens and the particle shape cannot be maintained, and if the total pore volume is excessively small, the amount of electrolyte held within the particle shape tends to decrease. In the carbon material of the present invention, when the total pore volume is as described above, the particle shape has appropriate strength, contributing to the stability of the particle shape and maintaining the shape. As a result, a good balance can be maintained between electronic conductivity and the supply of ions held within the pores.

[0069] The micropore volume of the carbon material of the present invention is the pore volume of pores with a pore diameter of less than 2 nm, and there are no particular limitations, but it is preferably 5 cc / g or less, or 2 cc / g or less, 1 cc / g or less, 0.5 cc / g or less, or 0.4 cc / g or less. The lower limit is preferably 0.01 cc / g or more, or it is also preferable that it is in the range of 0.05 cc / g or more, 0.1 cc / g or more, 0.2 cc / g or more, or 0.3 cc / g or more. If the micropore volume of the carbon material is excessively large, the ionic conductivity will be poor, and conversely, if it is excessively small, the strength properties of the carbonaceous material tend to be poor.

[0070] The proportion of micropore volume in the carbon material of the present invention is not particularly limited, but it is the proportion of pore volume with a size of less than 2 nm in the total pore volume, preferably 20% or less, or preferably 15% or less, 12% or less, 10% or less, or 9% or less. The lower limit is preferably 5% or more. If the proportion of micropore volume in the carbon material is excessively large, the ionic conductivity tends to be poor, and conversely, if it is excessively small, the strength properties of the carbonaceous material tend to be poor.

[0071] The mesopore volume of the carbon material of the present invention is not particularly limited, but is a pore volume with a pore diameter of 2 to 50 nm, preferably 0.1 cc / g or more, or preferably 0.5 cc / g or more, 1 cc / g or more, 1.5 cc / g or more, or 2 cc / g or more. The upper limit is preferably 15 cc / g or less, or preferably in the range of 10 cc / g or less, 5 cc / g or less, 4 cc / g or less, or 3.5 cc / g or less. When the mesopore volume of the carbon material is within this range, the ionic conductivity and strength characteristics are well balanced and preferable.

[0072] The proportion of mesopore volume in the carbon material of the present invention is not particularly limited, but it is the proportion of pore volume with a pore diameter in the range of 2 to 50 nm in the total pore volume, preferably 10% or more, or preferably 20% or more, 30% or more, 40% or more, or 50% or more. The upper limit is preferably 90% or less, or preferably 85% or less, 80% or less, 75% or less, or 70% or less. When the mesopore volume of the carbon material is within this range, the grain shape has appropriate strength, contributes to grain shape stability, and maintains its shape. As a result, a good balance can be maintained between electronic conductivity and the supply of ions retained in the pores.

[0073] The pore volume of the carbon material of the present invention, with a pore diameter of 2 nm or more and less than 10 nm, is not particularly limited, but is preferably 0.05 cc / g or more, or preferably 0.01 cc / g or more, 0.05 cc / g or more, 0.1 cc / g or more, or 0.5 cc / g or more. The upper limit is preferably 10 cc / g or less, or preferably within the range of 5 cc / g or less, 2 cc / g or less, 1.5 cc / g or less, or 1 cc / g or less. When the pore volume of the carbon material with a pore diameter of 2 nm or more and less than 10 nm is within this range, the ionic conductivity and strength characteristics are well balanced and preferable.

[0074] The proportion of the total pore volume of the carbon material of the present invention in which the pore diameter is between 2 nm and less than 10 nm is not particularly limited, but is preferably 0.1% or more, or preferably 1% or more, 3% or more, 5% or more, or 10% or more. The upper limit is preferably 50% or less, or preferably within the range of 40% or less, 30% or less, 26% or less, or 20% or less. When the pore volume of the total pore volume of the carbon material in which the pore diameter is between 2 nm and less than 10 nm is within this range, the ionic conductivity and strength characteristics are well balanced and preferable.

[0075] The pore volume of the carbon material of the present invention with a pore diameter of 10 to 50 nm is not particularly limited, but is preferably 0.05 cc / g or more, or preferably 0.1 cc / g or more, 0.5 cc / g or more, 1 cc / g or more, 1.35 cc / g or more, 1.50 cc / g or more, or 2 cc / g or more. The upper limit is preferably 15 cc / g or less, or preferably within the range of 10 cc / g or less, 5 cc / g or less, 4 cc / g or less, or 3 cc / g or less. When the pore volume of the carbon material with a pore diameter of 10 to 50 nm is within this range, the grain shape has appropriate strength, contributes to the stability of the grain shape, and maintains its shape. As a result, a good balance can be maintained between electronic conductivity and the supply of ions retained in the pores.

[0076] The percentage of pore volume in the total pore volume of the carbon material of the present invention where the pore diameter is in the range of 10 to 50 nm is preferably 10% or more, or preferably 15% or more, 20% or more, 25% or more, or 30% or more. The upper limit is preferably 80% or less, or preferably 70% or less, 60% or less, 55% or less, or 50% or less. When the pore volume in the total pore volume of the carbon material where the pore diameter is less than 10 to 50 nm is in this range, the ionic conductivity and strength characteristics are well balanced and preferable.

[0077] The macropore volume of the carbon material of the present invention is not particularly limited, but is a pore volume with a pore diameter exceeding 50 nm, preferably 0.01 cc / g or more, or preferably 0.05 cc / g or more, 0.1 cc / g or more, 0.48 cc / g or more, or 1 cc / g or more. The upper limit is preferably 15 cc / g or less, or preferably within the range of 10 cc / g or less, 5 cc / g or less, 3 cc / g or less, or 2.57 cc / g or less. When the macropore volume of the carbon material is within this range, the grain shape has appropriate strength, contributes to the stability of the grain shape, and maintains its shape. As a result, a good balance can be maintained between electronic conductivity and the supply of ions retained in the pores.

[0078] The macropore volume ratio of the carbon material of the present invention is not particularly limited, but it is the ratio of pore volume with a pore diameter of more than 50 nm to the total pore volume, preferably 5% or more, or preferably 10% or more, 15% or more, 20% or more, or 25% or more. The upper limit is preferably 80% or less, or preferably within the range of 70% or less, 60% or less, 50% or less, or 45% or less. If the macropore volume ratio of the carbon material is excessively small, the ionic conductivity tends to be poor, and conversely, if it is excessively large, the strength properties of the carbonaceous material tend to be poor.

[0079] The proportion of pore volume of 10 nm or larger in the carbon material of the present invention is not particularly limited, but it is the proportion of pore volume with a pore diameter of 10 nm or larger in the total pore volume, preferably 50% or more, or preferably 55% or more, 60% or more, 65% or more, or 70% or more. The upper limit is preferably 95% or less, or preferably within the range of 92% or less, 90% or less, 88% or less, or 85% or less. If the proportion of pore volume of 10 nm or larger in the carbon material is excessively small, the ionic conductivity tends to be poor, and conversely, if it is excessively large, the strength characteristics of the carbonaceous material tend to be poor.

[0080] The mode pore diameter (M) in the pore distribution of the carbon material of the present invention is not particularly limited, but is the value of the peak top in the pore distribution curve, and is preferably in the range of 1 to 500 nm, or 5 to 100 nm, 10 to 50 nm, 15 to 40 nm, or 15 to 30 nm. When the peak top pore diameter of the pore distribution of the carbon material of the present invention is within this range, it is preferable to improve oil absorption and achieve high ionic conductivity and electronic conductivity.

[0081] The carbon material of the present invention is characterized by having pores, but by optimally controlling the surface area of ​​the spaces constituting the pores above a certain total pore volume, a larger pore space can be obtained. In other words, a large, continuous space that allows electrolyte to easily penetrate can be realized, resulting in high electrolyte storage capacity and excellent ion supply, which is desirable because it significantly increases the charge-discharge reaction rate.

[0082] This index is obtained by dividing the BET specific surface area by the total pore volume. In this invention, it is effective when the total pore volume exceeds 1.0 cc / g. The value is 150 m 2 A value greater than / cc is preferable, and the lower limit is preferably 250m. 2 / cc or more, more preferably 300m 2 The value is 1 / cc or more, and preferably 700m as the upper limit. 2 / cc or less, more preferably 500m 2 / cc or less, more preferably 400m 2 It is less than or equal to / cc.

[0083] The average pore diameter of the carbon material of the present invention is not particularly limited, but is preferably in the range of 1 to 500 nm, or preferably in the range of 5 to 100 nm, 10 to 75 nm, 15 to 50 nm, or 20 to 40 nm. When the average pore diameter of the carbon material of the present invention is within this range, oil absorption can be improved and high ionic and electronic conductivity can be achieved.

[0084] The particle size distribution curve of the carbon material of the present invention was measured after immersing the unground material in a solvent for 9 minutes, and it shows the difference in cohesive force of the linked structures.

[0085] The median diameter D50 of the carbon material of the present invention, where half of the particles are located in the particle size distribution curve, is not particularly limited, but may be 1 to 100 μm, or any of the ranges of 5 to 90 μm, 10 to 80 μm, 15 to 60 μm, 20 to 50 μm, 25 to 45 μm, or 30 to 40 μm. When the median diameter D50 of the carbon material is within this range, the electronic conductivity and ionic conductivity are greatly enhanced.

[0086] There are no particular limitations on the particle size D10 in the particle size distribution curve of the carbon material of the present invention, in which 10% of the particles are located, but it is preferably 0.1 to 100 μm, or preferably in the range of 0.5 to 50 μm, 1 to 50 μm, 5 to 30 μm, or 10 to 15 μm.

[0087] The particle size D90 of the carbon material of the present invention, where 90% of the particles are located in the particle size distribution curve, is not particularly limited, but is preferably 5 to 250 μm, and any of 10 to 150 μm, 20 to 100 μm, 30 to 70 μm, 45 to 65 μm, 45 to 55 μm, or 40 to 60 μm is also preferred. When the D90 of the carbon material is within this range, the conductivity can be greatly enhanced.

[0088] The ratio of D90 to D10 in the carbon material of the present invention is not particularly limited, but the (D90 / D10) ratio is preferably 100 or less, or preferably in the range of 50 or less, 10 or less, or 5 or less. If the (D90 / D10) ratio of the carbon material is excessively large, it tends to aggregate and not disperse well, resulting in insufficient conductivity of the lithium-ion secondary battery.

[0089] The ratio of D90 to mode pore diameter M (D90 / M / 1000) of the carbon material of the present invention is not particularly limited, but it is the value obtained by dividing the value of D90 by the mode pore diameter M and multiplying by 1000, and is preferably 50 or less, or preferably in the range of 20 or less, 10 or less, 6 or less, or 4 or less. If the (D90 / M / 1000) ratio of the carbon material is excessively large, the cohesiveness will be strong and the dispersibility will be poor, and the conductivity of the lithium-ion battery will not be sufficiently obtained.

[0090] The carbon material contained in the electrodes of lithium-ion batteries preferably has high conductivity. Since electron transfer in carbon occurs through the movement of π electrons, in order to form ideal conductive paths within the electrode using carbon material, it is necessary to arrange single-layer graphene, in which carbon atoms are bonded in the planar direction, in a mesh-like structure. Furthermore, when a conductive material such as carbon material is filled into a non-conductive material such as a positive electrode material, conductivity will not be exhibited if the filling rate of the conductive material is low. Once a certain filling rate is reached, paths of the conductive material are formed within the compound, causing a rapid increase in electronic conductivity, which then stabilizes at a constant value. The lower the threshold of the filling ratio at which this rapid increase in electronic conductivity occurs, the more suitable the material is as a conductive material. Therefore, the carbon material of the present invention consists of carbonaceous material having a graphene structure that extends in the planar direction, and the carbonaceous material forms a linked structure in which granular shapes with a hollow outer shell are connected, resulting in a highly balanced in-plane conductivity and path-forming conductivity, which is thought to exhibit high conductivity.

[0091] The electrical conductivity of carbon materials can be evaluated by measuring the electrical conductivity of the powder using uniaxial compression with lateral constraint, as described below. A dry sample is filled into a cylindrical container consisting of an insulating cylinder and a negative electrode. A positive electrode is inserted into the insulating cylindrical container filled with the sample, and the sample is placed on a force gauge stand, sandwiched between the negative and positive electrodes. A spring-type force gauge mounted on the force gauge stand is lowered to apply force to the sample inside the cylindrical container and compress it. While measuring the compressive force and the height of the sample with a length measuring instrument, the resistance value of the sample is measured with a digital multimeter connected to the positive and negative electrodes. The electrical conductivity of the powder during compression is calculated from the obtained resistance value, the filled cross-sectional area of ​​the sample, and the filled height.

[0092] The conductivity of the carbon material of the present invention is not particularly limited, but is preferably in the range of 1 to 100 S / cm, or 5 to 70 S / cm, 10 to 50 S / cm, or 20 to 30 S / cm when pressurized at 10 MPa. The conductivity of the carbon material can be determined by the reciprocal of its electrical resistivity. For example, the electrical resistivity of the carbon material can be measured according to JIS K1469.

[0093] One indicator of the structural complexity of carbon materials is the shape index and aggregate shape classification, which are measured using the image analysis method described later.

[0094] The circularity calculated by the image analysis method for carbon materials of the present invention is not particularly limited, but may be 0.1 or higher, 0.2 or higher, 0.25 or higher, or 0.8 or lower, 0.6 or lower, 0.5 or lower, or 0.4 or lower. The circularity in image analysis is an indicator of the complexity of the aggregate structure, and it is preferable that the oil absorption amount of the carbon material improves when it is within this range.

[0095] The shape factor (ML2 / A) indicating sphericity calculated by the image analysis method for carbon materials of the present invention is not particularly limited, but may be 1.0 or higher, 2.0 or higher, 2.25 or higher, 2.40 or higher, or 4.0 or lower, 3.5 or lower, or 3.10 or lower.

[0096] The shape coefficient (PM2 / A), which indicates the degree of surface roughness calculated by the image analysis method for carbon materials of the present invention, is not particularly limited, but may be 2.0 or more, 3.0 or more, 3.5 or more, or 8.0 or less, 7.0 or less, 6.0 or less, or 5.5 or less.

[0097] In the carbon material of the present invention, (PM2 / A)-(ML2 / A) is preferably 0 or greater, or preferably 0.4 or greater, or 1.0 or greater. When ML2 / A and PL2 / A satisfy this relationship, the amount of oil absorbed increases, which is preferable.

[0098] The area circle equivalent diameter calculated by the carbon material image analysis method of the present invention is not particularly limited, but may be 100 nm or more, 200 nm or more, 250 nm or more, or 1 μm or less, 800 nm or less, 600 nm or less, or 400 nm or less.

[0099] The proportion of "spheroidal" shapes in the shape classification calculated by the image analysis method for carbon materials of the present invention is not particularly limited, but is preferably 50% or less, or preferably 30% or less, 20% or less, 10% or less, 5% or less, or 2% or less. When the proportion of spherical shapes in the image analysis of carbon materials is within the above range, the amount of oil absorbed can be optimized, which is preferable.

[0100] The proportion of "ellipsoidal" shapes in the shape classification calculated by the image analysis method for carbon materials of the present invention is not particularly limited, but is preferably 5-80%, or preferably in the range of 10-70%, 15-60%, 20-50%, or 25-45%. When the proportion of ellipsoidal shapes in the image analysis of carbon materials is within the above range, the amount of oil absorbed can be optimized, which is preferable.

[0101] The proportion of "branched" shapes in the shape classification calculated by the image analysis method for carbon materials of the present invention is not particularly limited, but is preferably 5% or more and 80% or less, or is also preferably within any of the following ranges: 10% or more and 70% or less, 20% or more and 50% or less, 15% or more and 45% or less, 25% or more and 45% or less, or 15% or more and 36% or less. When the proportion of branched shapes in the image analysis of carbon materials is within the above range, the amount of oil absorbed can be optimized and is therefore preferable.

[0102] The apparent density of the carbon material of the present invention is not particularly limited, but is preferably 2 g / cc or less, or preferably in the range of 1.5 g / cc or less, 1 g / cc or less, 0.5 cc / g or less, or 0.3 cc / g or less, and also preferably in the range of 0.05 g / cc or more, 0.1 g / cc or more, or 0.15 g / cc or more. When the apparent density is within this range, the hollow structure in the carbon material is maintained, making it suitable for use as a carbon material for batteries. The apparent density can be calculated, for example, using the total pore volume and true density from the following formula. Apparent density (g / cc) = 1 / (Total pore volume + (1 / True density)) The total pore volume (cc / g) can be calculated using the formula P / P0 = 0.99, and the true density can be the graphite value of 2.2 g / cc.

[0103] The bulk density of the carbon material of the present invention is not particularly limited, but is preferably in the range of 0.01 to 1000 g / L, or 0.1 to 100 g / L, 0.5 to 50 g / L, or 1 to 25 g / L. When the bulk density of the carbon material is in this range, it is preferable because it has high conductivity and the electrolyte penetrates the carbon material easily. Bulk density is the mass per unit volume exhibited by carbon material filled in a container of a certain volume under certain conditions. For example, bulk density can be measured according to JIS K6219-2.

[0104] The number density of the carbon material of the present invention is not particularly limited, but is a value calculated by the method described later, and is preferably in the range of 5E+14 to 1E+20 particles / g, or 1E+16 to 1E+19 particles / g, 5E+16 to 5E+18 particles / g, 1E+17 to 1E+18 particles / g, or 3E+17 to 7E+17 particles / g. The amount of oil absorbed is optimal and preferred when the number density of the carbon material is within this range. The number density P (particles / g) is equal to the volume V (m³) of one primary particle. 3 ) and carbon density ρ(g / m³) 3 ) can be calculated using the following formula. P = 1 / (V × ρ) Here, the carbon density can be the true density of graphite, which is 2.2 g / cc. V(m 3 ) can be calculated from the following formula. V = π × (D1 - D0) 3 / 6 Here, D0 is the inner diameter of the primary particle, and D1 is the outer diameter of the primary particle. D0 can be obtained using the mode pore diameter as described above. D1 can be obtained by adding twice the value obtained by multiplying the average number of layers n by the interplanar spacing of the (002) plane to the mode diameter. Alternatively, D1 may be obtained by TEM image analysis or other methods. Furthermore, for solid carbon materials, calculations can be performed by setting D0=0. For example, the known DENKA BLACK Li-100 can be calculated with an average particle size of 35 nm as the particle outer diameter (D1) and D0=0.

[0105] The carbon content of the carbon material of the present invention is not particularly limited, but can be determined by thermal desorption mass spectrometry (TPD-MS) measurement with the configuration shown in Figure 5, and is preferably 95% or more, or preferably 97% or more, 98% or more, 99% or more, or 99.3% or more. The thermal desorption mass spectrometer 50 includes a quartz reactor equipped with a radioactive thermometer 41, a sample holder 42, and a high-frequency induction coil 43, and a detection unit connected to the quartz reactor. The detection unit includes, for example, a gas reservoir, a turbomolecular pump TMP, a rotary pump RP, a cold cathode Pirani gauge P1, and a capacitance gauge P2.

[0106] The oxygen content of the carbon material of the present invention is not particularly limited, but is a value calculated from the H2O, CO, and CO2 emissions measured by thermal desorption mass spectrometry (TPD-MS), and is preferably 5% or less, or preferably 3% or less, 2% or less, 1% or less, or 0.6% or less. When the oxygen content of the carbon material of the present invention is within these ranges, it can contribute to the stability and high performance of lithium-ion batteries.

[0107] To improve the performance and lifespan of lithium-ion batteries, high-efficiency battery reactions that do not experience efficiency reduction due to side reactions are required. Therefore, the carbon material within the electrodes needs electrochemical stability, i.e., oxidation resistance and corrosion resistance. Electrochemical side reactions such as oxidation are said to originate from the oxygen-containing functional groups and edge surfaces of the carbon material. To improve the oxidation resistance of the carbon material, it is effective to reduce the oxygen-containing functional groups and decrease the amount of edge surfaces with low oxidation resistance.

[0108] The TPD-MS measurement method used to measure the oxygen content of the carbon material of the present invention measures the amounts of H2, H2O, CO, and CO2 released from the carbon material. These gases originate from oxygen-containing functional groups such as hydroxyl groups (including phenolic groups), carbonyl groups (including quinones), ethers, acid anhydrides, carboxyl groups, and lactones at the edges of the carbon material. Therefore, a high amount of oxygen-containing functional groups in the carbon material means a high amount of oxygen-containing functional groups and edges in the structure of the carbon material, resulting in poor durability and posing a barrier to extending the lifespan and performance of lithium-ion batteries. The amount of oxygen-containing functional groups and edges in the carbon material can be adjusted by the CVD conditions and heat treatment temperature.

[0109] The ratio of oxygen content to carbon content in the carbon material of the present invention is not particularly limited, but is preferably 1 or less in terms of O / C ratio, or preferably 0.5 or less, 0.1 or less, 0.05 or less, or 0.01 or less. When the O / C ratio of the carbon material is within this range, it can contribute to extending the lifespan and improving the performance of lithium-ion batteries.

[0110] The amount of gas measured by TPD-MS of the carbon material of the present invention is not particularly limited, but is preferably 5000 μmol / g or less, or 3000 μmol / g or less, 1000 μmol / g or less, 750 μmol / g or less, or 500 μmol / g or less. When the amount of gas generated by the carbon material is within this range, it can contribute to extending the lifespan and improving the performance of lithium-ion batteries.

[0111] The edge amount of the carbon material of the present invention is not particularly limited, but is a value calculated from the amount of gas measured by TPD-MS, and is preferably 500m. 2 / g or less, or 300m 2 / g or less, 100m 2 / g or less, 50m 2 / g or less, 30m 2 The edge content of the carbon material of the present invention is preferably 750 μmol / g or less, or 500 μmol / g or less. When the edge content of the carbon material is within this range, it exhibits excellent durability and can contribute to the stability and high performance of lithium-ion batteries.

[0112] The ash content of the carbon material of the present invention is not particularly limited, but is preferably 10,000 ppm or less, or preferably 5,000 ppm or less, 4,000 ppm or less, 3,500 ppm or less, or 3,000 ppm or less. When the ash content of the carbon material is within this range, the stability of the electrolyte is excellent, and the durability and performance of the lithium-ion battery can be improved.

[0113] The pH of the carbon material of the present invention is not particularly limited, but is preferably 5 to 10, or preferably in the range of 5.5 to 9.5, 6 to 9, 6.5 to 8.5, or 7 to 8. Stability is increased and preferable when the pH of the carbon material is within this range. The pH of the carbon material can be, for example, the value of a 4% by weight aqueous dispersion.

[0114] The combustion temperature of the carbon material of the present invention is not particularly limited, but is preferably 300°C or higher, or preferably 400°C or higher, 450°C or higher, 500°C or higher, or 550°C or higher. Combustion temperature tests of carbon materials are performed as a simple test of corrosion resistance, and if the combustion temperature is excessively low, the electrochemical stability within the electrode tends to deteriorate.

[0115] The carbon material of the present invention contains graphene and therefore exhibits excellent electron transfer properties. For this reason, when incorporated into the electrodes of a lithium-ion battery, the carbon material of the present invention can function to assist the battery reaction in the lithium-ion battery. Furthermore, the carbon material of the present invention has a linked structure in which hollow granular materials, each covered by an outer shell made of carbonaceous material containing graphene, are connected. Because there is space inside the granular material and inside the area surrounded by the linked structure, the electrolyte containing dissolved lithium ions can penetrate and be retained, resulting in excellent ion supply during the reaction. Therefore, the carbon material of the present invention can suitably assist the battery reaction.

[0116] <Method for manufacturing carbon materials> Next, a method for manufacturing carbon material according to the present invention will be described. The carbon material of the present invention can be easily manufactured, for example, in a method for manufacturing a carbon material in which a carbonaceous layer is formed on the surface of a mold and then the mold is removed, by using an aggregate in which primary particles have multiple branched structures and are linked together in a bead-like manner as the mold material.

[0117] (Mold material) The mold material used in this invention is not particularly limited as long as it can realize a complex and elongated higher-order structure in which the manufactured carbon material has interconnected internal spaces. For example, a material having an aggregate structure in which primary particle diameters are linked together in a bead-like manner with multiple branching structures can be used.

[0118] The primary particle size of the mold material used in this invention is 1 to 150 nm, preferably 5 to 100 nm, more preferably 10 to 60 nm, even more preferably 15 to 50 nm, and most preferably 20 to 40 nm. When the primary particle size of the mold material is within this range, the oil absorption and mesopore volume of the manufactured carbon material can be significantly increased, which is advantageous. Furthermore, when the primary particle size of the mold material is within this range, it is easy to handle, and the permeability of the raw material gas that serves as the carbon source for the carbonaceous layer is good, making it easy to achieve uniform carbon coating.

[0119] The BET specific surface area of ​​the mold material used in this invention is not particularly limited, but is usually 1 to 1000 m². 2 / g, preferably 10-500m 2 / g, more preferably 20-200m 2 / g, more preferably 40-160m 2 / g, most preferably 50-120m 2 The range is / g. When the BET specific surface area of ​​the mold material is within this range, it is preferable to significantly increase the oil absorption and mesopore volume of the manufactured carbon material.

[0120] The specific surface area of ​​the manufactured carbon material depends on the specific surface area of ​​the mold. The ratio of particle volume to surface area increases as the particle diameter decreases; therefore, a smaller particle diameter results in a larger surface area per unit volume, i.e., a larger surface area per unit mass. Consequently, a carbon material with a high specific surface area can be obtained by using nanoparticles with a small primary particle diameter in the mold material.

[0121] The mold material used in this invention has an aggregate structure in which the above-mentioned primary particles are linked together in a bead-like manner with multiple branching structures. Such a complex aggregate structure is similar to the structure of carbon black.

[0122] The average primary particle size of the template material (aggregate) of the present invention is not particularly limited, but may usually be in the range of 1 to 100 nm, or in the range of 2 to 50 nm, 4 to 50 nm, or 3 to 30 nm. The length of the aggregate structure is not particularly limited, but is usually in the range of 0.01 to 100 μm, preferably 0.05 to 10 μm, and preferably 0.1 to 5 μm. The average particle size of the aggregate structure is not particularly limited, but is usually in the range of 0.05 to 10 μm, and preferably 0.1 to 5 μm.

[0123] The bulk density of the mold material used in the present invention is not particularly limited, but is usually in the range of 0.1 to 500 g / L, preferably 0.5 to 250 g / L, more preferably 1 to 200 g / L, even more preferably 10 to 100 g / L, and most preferably 30 to 70 g / L. When the bulk density of the mold material is in this range, it is preferable because it can increase the conductivity of the carbon material produced and significantly increase the oil absorption and mesopore volume.

[0124] The mold material used in the present invention is preferably basic or acidic. Suitable basic compounds include, for example, magnesium oxide and calcium carbonate. Suitable acidic compounds include, for example, aluminum oxide and silica compounds containing silanol. The acidic pH is usually 7 or less, preferably 6.5 or less, more preferably 6 or less, even more preferably 5.5 or less, and most preferably 5 or less, based on a 4% water content. The lower limit is usually 1 or more, preferably 2 or more, more preferably 3 or more, even more preferably 3.5 or more, and most preferably 4 or more.

[0125] The carbon content of the mold material used in the present invention is not particularly limited, but is usually 0.0001% by weight or more, preferably 0.01% by weight or more, more preferably 0.05% or more, even more preferably 0.1% by weight or more, most preferably 0.5% or more, with an upper limit of usually 5% or less, preferably 4% or less, more preferably 3% or less, even more preferably 2.5% or less, and most preferably 2% or less. When the carbon content of the mold material is within this range, it is preferable because it facilitates the formation of a carbonaceous layer on the mold surface.

[0126] The template material used in the present invention is not particularly limited as long as it has an aggregate structure in which primary particles have multiple branched structures and are linked together in a bead-like manner, but preferably it is a compound that has catalytic activity in carbon deposition reactions. Examples of template materials include nonmetallic compounds, metalloid compounds, and metallic compounds, with metalloid compounds and metallic compounds being preferred.

[0127] There are no particular limitations on nonmetallic compounds, but examples include ceramic compounds (nonmetallic inorganic solid materials). Examples of ceramics include glass, cement, and fine ceramics.

[0128] There are no particular limitations on the metalloid (semimetallic) compound, but examples include compounds of boron, silicon, germanium, and antimony, with silicon compounds being preferred. Examples of silicon compounds include silicon monoxide, silicon dioxide, silicon nitride, silicon carbide, and silicone, with silicon dioxide being preferred.

[0129] Examples of metal compound mold materials include monovalent metal compounds and polyvalent metal compounds, but polyvalent metal compounds are preferred. Examples of monovalent metal compounds include chlorides, sulfates, nitrates, phosphates, and carbonates of alkali metals such as sodium and potassium. Examples of polyvalent metal compounds include alkali metal compounds such as calcium and magnesium, and trivalent metal compounds such as aluminum, but calcium compounds, magnesium compounds, and aluminum compounds are preferred. Examples of calcium compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, but carbonates and oxides are preferred, and oxides are more preferred. Examples of magnesium compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, but carbonates and oxides are preferred, and oxides are more preferred. Examples of aluminum compounds include chlorides, sulfates, nitrates, phosphates, carbonates, and oxides, but carbonates and oxides are preferred, and oxides are more preferred.

[0130] As a mold material, atomized compounds can be suitably used because they form aggregate structures in which primary particles have multiple branched structures and are linked together in a bead-like manner. Examples of atomized compounds include compounds obtained by flame hydrolysis, which is one of the dry manufacturing methods for inorganic materials.

[0131] A typical example of an atomized compound is atomized silicon dioxide. Atomized silicon dioxide produced by flame hydrolysis does not undergo a liquid-phase process, resulting in slow aggregation. Therefore, atomized silicon dioxide exhibits excellent dispersibility in both liquid and solid phases. Atomized silicon dioxide is produced by high-temperature gas-phase hydrolysis of silicon tetrachloride in an oxyhydrogen flame, producing hydrochloric acid as a by-product. By varying production conditions such as flame temperature, oxygen and hydrogen supply ratio, raw material supply amount, and residence time, average particle size of 7-40 nm and specific surface area of ​​50-380 m² can be achieved. 2 Particles of silicon dioxide are obtained at a density of / g.

[0132] Other examples of atomized compounds produced by flame hydrolysis include atomized alumina, atomized titania, and atomized wet zirconia. Other examples of atomized metal compounds include chlorides of Na, Ba, or Sr, sulfates of K, Na, Sr, or Mg, nitrates of Na or K, phosphates of Na or K, carbonates of Na, K, Ca, or Mg, and metal oxides of Na, K, Ca, or Ba. The shape of the mold material is preferably in an atomized form.

[0133] Precipitating silica can also be used as a mold material. Precipitating silica is obtained by reacting a sodium silicate solution with an acid in the liquid phase, followed by precipitation, filtration, washing, drying, and grinding. By adjusting the reaction conditions, an average particle size of approximately 7-140 nm and a specific surface area of ​​approximately 20-400 m² can be obtained. 2 Particles of silicon dioxide are obtained at a density of / g.

[0134] The moisture content of the mold material used in the present invention is not particularly limited, but is usually in the range of 5% or less, preferably 3% or less, more preferably 1.5% or less, even more preferably 1% or less, and most preferably 0.5% or less.

[0135] In the present invention, when the CVD method is used as a means to form a carbonaceous layer on the mold surface, the amount of carbon deposited on the mold material surface is affected by CVD reaction conditions such as the type of raw material gas, raw material gas concentration, flow rate, reaction temperature, and reaction time, but is greatly influenced by the mold material surface. Compounds having a surface suitable for carbon deposition by the CVD method include, for example, compounds containing oxygen atoms, where carbon in the raw material gas is replaced by oxygen atoms in the CVD reaction, and this becomes the starting point for the precipitation of carbonaceous material. Examples of oxygen-containing compounds include metal oxides and metal carbonates. Among oxygen-containing compounds, acidic or basic compounds are particularly suitable. Examples of basic oxygen-containing compounds include magnesium oxide and calcium carbonate.

[0136] Silica is a suitable template compound for the CVD method. As an acidic oxygen-containing compound, silica's oxygen atoms initiate the deposition of a carbonaceous layer. Furthermore, acidic sites on the silica surface catalyze the deposition of carbon onto the silica surface. This function is called solid acid catalysis, and silica acts as a solid acid. When the acidic sites of the solid acid come into contact with hydrocarbons, the acidic sites act as catalysts for the hydrocarbon reforming reaction. Also, contact between the acidic sites and hydrocarbons causes a carbonaceous deposition reaction, and carbonaceous material can precipitate on the surface of the solid acid. By utilizing the catalytic activity of the solid acid, the molecules of the source gas, which serve as the carbon source for the carbonaceous layer, can be decomposed at a temperature below the decomposition temperature of the source gas. The carbon radicals generated by the decomposition of the source gas can be polymerized and deposited on the surface of the solid acid as a carbonaceous layer.

[0137] Furthermore, suitable surfaces for carbonaceous layer formation by CVD are those that have hydrocarbons that serve as a carbon source. Hydrocarbons include compounds that become the raw material gases described later, such as compounds having methyl groups or carbon-carbon unsaturated bonds. Suitable template materials are inorganic compounds that have hydrocarbons on their surface.

[0138] There are no particular limitations on the inorganic compound having hydrocarbons on its surface, but suitable examples include inorganic materials surface-treated with a silane coupling agent, and silica compounds surface-treated with a silane coupling agent are particularly preferred. As the silane coupling agent, those commonly used as surface pretreatment agents can be used without particular limitations, such as methoxy-type silane coupling agents, ethoxy-type silane coupling agents, vinyl-type silane coupling agents, dialkoxy-type silane coupling agents, and trialkoxy-type silane coupling agents. Among these, trialkoxy-type silane coupling agents with a large number of methyl groups per molecule are preferred, and trimethoxysilane compounds are particularly preferred. The amount of silane coupling agent is appropriately selected depending on the intended use, and is expressed as the amount of hydrocarbons in the inorganic material, usually in the range of 0.01 to 10% by weight, preferably 0.02 to 8% by weight, more preferably 0.05 to 5% by weight, even more preferably 0.1 to 3% by weight, and most preferably 0.5 to 1.5% by weight. When the amount of silane coupling agent (hydrocarbon content) in the inorganic compound is within this range, the carbon mass on the mold surface can be easily adjusted, making it preferable.

[0139] These mold materials can be used individually or in combination of two or more types.

[0140] (Carbon layer formation and carbonization process) In this invention, the formation of a carbonaceous layer on the surface of the mold material can be achieved by contacting the mold material with an organic substance that serves as a carbon source and performing a carbonization heat treatment. Contact with the carbon source and the carbonization heat treatment can be performed simultaneously or separately. Contact between the mold material and the carbon source is usually carried out in a temperature range of room temperature to 1000°C.

[0141] Methods for bringing a carbon source into contact with a mold material can be broadly classified into liquid-phase contact methods and gas-phase contact methods, with gas-phase contact methods being preferred. Liquid-phase contact methods include, for example, immersing the mold material in a liquid of organic matter. Gas-phase contact methods involve, for example, introducing an organic gas at high temperatures and bringing it into contact with the mold material; this is the so-called CVD method.

[0142] -Liquid phase contact method- In the liquid-phase contact method, organic compounds having functional groups on the mold surface, specifically functional groups that can react with hydroxyl groups, are preferably used, and benzene-based hydrocarbon compounds having functional groups that can react with hydroxyl groups are particularly preferred. Among these, benzene-based aromatic hydrocarbon compounds having hydroxyl groups and / or carboxyl groups are preferred, with phenol, hydronaphthalene, and dihydronaphthalene being more preferred. This is because using organic compounds having functional groups that can react with functional groups on the mold surface creates strong bonds, such as ester bonds, between the mold material and the organic compound, making it easier for the organic compound to carbonize in situ during the carbonization heat treatment without volatilizing.

[0143] In the liquid-phase contact method, an organic compound, used as a carbon source, is dissolved in a solvent and impregnated into the mold material at room temperature, thereby bringing them into contact. To strongly bond the organic material and the mold material, the temperature is maintained in the range of 250-600°C for a certain period of time. This causes the hydroxyl groups on the surface of the mold material and the organic material to undergo dehydration condensation reactions such as esterification, fixing them through bonds such as ester bonds, making it easier to obtain a carbon layer with a graphene sheet structure. After that, the temperature is lowered, and any excess organic material that did not react with the mold material can be washed and removed with a solvent or the like.

[0144] The organic compound used as a carbon source, which is in contact with the mold material, is subjected to heat treatment to carbonize it. This heat treatment causes dehydrogenation reactions in organic substances such as hydrocarbons, transforming them into carbon such as graphene sheet structures. The heat treatment temperature is usually 600°C or higher, preferably 600 to 1500°C, more preferably 750 to 1500°C, and particularly preferably 800 to 1000°C. However, the heat treatment may be performed at 1500°C or higher, as long as the mold material does not collapse or melt.

[0145] -Vapor-phase contact method- In the vapor-phase contact method, an organic compound as a carbon source is brought into contact with the mold material, and in order to strongly bond the carbon source and the mold material, it is preferable to carry out the CVD (Chemical Vapor Deposition) method in a temperature range in which the dehydrogenation reaction can proceed, specifically 400 to 1000°C.

[0146] As an organic compound used as a carbon source in the gas-phase contact method, it may be appropriately selected according to the intended use, but hydrocarbons such as saturated hydrocarbons, unsaturated hydrocarbons having double and / or triple bonds, alicyclic hydrocarbons, and aromatic hydrocarbons are preferably used. Saturated hydrocarbons may be either straight-chain or branched-chain, and examples include methane, ethane, and propane. Unsaturated hydrocarbons may be either straight-chain or branched-chain, and examples include ethylene, propylene, isoprene, and acetylene. Examples of alicyclic hydrocarbons include cyclopropane and cyclohexane. Examples of aromatic hydrocarbons include benzene and toluene. Among these hydrocarbons, it is desirable to use methane, ethane, acetylene, ethylene, propylene, and benzene, and from the viewpoint of precipitating highly crystalline carbon, methane, propylene, and benzene are preferred. In particular, methane is preferably used from the viewpoint of obtaining highly crystalline carbon at a high thermal decomposition temperature.

[0147] Organic compounds that can be used in the gas-phase contact process include alcohols such as methanol, ethanol, propanol, and butanol, as well as nitrogen-containing compounds such as acetonitrile and acrylonitrile.

[0148] The reaction temperature in the CVD reaction is appropriately selected according to the decomposition temperature of the organic compound used as the carbon source, but is usually in the range of 400 to 1000°C, preferably 600 to 950°C, and preferably 800 to 900°C.

[0149] In the method for manufacturing the carbon material of the present invention, the number of carbonaceous layers is preferably 1.7 or more, more preferably 1.9 or more, preferably 5.0 or less, and more preferably 4.5 or less. When the number of carbonaceous layers is within this range, the strength characteristics and elastic deformation of the carbonaceous layer are excellent, the hollow structure can be maintained, and the lithium-ion battery characteristics described above can be greatly enhanced. Specifically, the number of carbonaceous layers of the carbon material is calculated according to the examples described later, but after laminating the carbon layer on the mold particles, the weight of the carbon layer is calculated using thermogravimetric analysis (TG), and the weight of the carbon layer per mold area is calculated from this weight of the carbon layer and the surface area of ​​the mold particles, and this is used as the weight of the carbon layer per unit area of ​​single-layer graphene (7.61 × 10⁻¹⁰). -4 g / m 2 This value is calculated by dividing by ).

[0150] The reaction time in a CVD reaction (CVD treatment time at a predetermined heating temperature) is appropriately selected depending on the type of template material, the type of organic compound used as the carbon source, or the number of carbon layers deposited, but is usually in the range of 0.1 to 10 hours, preferably 0.5 to 5 hours, and more preferably 1 to 3 hours. Furthermore, the product can be analyzed by applying the analytical methods disclosed herein, and the time required for sufficient carbon deposition can be appropriately set based on the results.

[0151] CVD reactions can be carried out under an inert gas atmosphere if necessary. Examples of inert gases include nitrogen, helium, neon, and argon, with argon being preferred. In the CVD method, carbon can usually be easily adsorbed or deposited on the mold material in the gas phase by heating while passing a gaseous organic compound in contact with the mold material together with a carrier gas. The type of carrier gas, flow rate, flow rate, and heating temperature can be appropriately adjusted depending on the type of organic compound used. Examples of carrier gases include the inert gases mentioned above, but a mixture with oxygen gas or hydrogen gas may also be used. Argon is preferably used as the carrier gas.

[0152] The number of carbon layers introduced onto the mold material can be appropriately selected by the CVD reaction time, but for the formation of a thin graphene layer, the carrier gas flow rate is preferably adjusted to 0.05 to 5 m / min, more preferably 0.1 to 1 m / min, even more preferably 0.2 to 0.8 m / min, and most preferably 0.32 to 0.64 m / min. For the formation of the optimal number of graphene layers, the amount of organic compound introduced is also adjusted to a range of preferably 1 to 70 volume%, more preferably 5 to 50 volume%, even more preferably 10 to 40 volume%, and most preferably 15 to 35 volume%, relative to the total amount of carrier gas and organic compound.

[0153] Since carbonization of the carbon layer can also proceed by CVD reactions, no other special carbonization treatment is necessary, but it may be performed.

[0154] (Mold removal process) In the manufacturing method of the present invention, any method that removes the mold after the formation of the carbonaceous layer is acceptable, as long as the mold is removed and the formed carbonaceous layer remains. Examples include dissolution with acid or alkali, and dissolution with acid is preferred.

[0155] The acid used in this invention is appropriately selected depending on the type of mold material, but examples include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, and hydrofluoric acid, with hydrochloric acid and hydrofluoric acid being preferred. The acid concentration used for dissolving and removing the mold is appropriately adjusted within a range that allows for the dissolution and removal of the mold. The amount of acid used is not particularly limited as long as it is within a range that allows for the dissolution and removal of the mold material, but for example, it may be 30 times or more the stoichiometric ratio or 50 times or more the stoichiometric ratio relative to the mold material.

[0156] The temperature for dissolving and removing the mold material is not particularly limited, but is usually in the range of 5 to 100°C, preferably 10 to 50°C, and more preferably 20 to 30°C. The dissolving and removal process of the mold material may be carried out with stirring, vibration, and other operations. The time required for the removal process is appropriately selected within a range in which the mold can be dissolved and removed.

[0157] The carbon material after mold removal can be recovered, for example, by filtration, and then washed with pure water. Washing conditions can be selected as appropriate, but the process can be terminated after confirming that the pH of the washing solution is neutral.

[0158] The carbon material, after cleaning and removal of the mold material, can be dried by vacuum heating and drying. The conditions for vacuum heating and drying are not particularly limited, but for example, the vacuum heating and drying temperature can be 100 to 200°C and the vacuum heating and drying time can be 1 to 10 hours.

[0159] (Heat treatment process) In the method for manufacturing carbon materials of the present invention, the carbon material (separated carbonaceous layer) after the removal of the mold material can be heat-treated as needed. By heat-treating the carbonaceous layer from which the mold material has been removed, the crystallinity of the carbon is enhanced and stabilized, making it possible to produce a carbon material with higher levels of conductivity, corrosion resistance, and / or high specific surface area.

[0160] The conditions for the heat treatment process are not particularly limited as long as they enhance the crystallinity of the carbon. The holding temperature during the heat treatment process is usually in the range of 1000 to 3000°C, preferably 1300 to 2500°C, more preferably 1500 to 2000°C, even more preferably 1600 to 1900°C, and most preferably 1750 to 1850°C. A heat treatment temperature within this range is preferable because it allows for the acquisition of carbon materials with higher levels of conductivity, corrosion resistance, and / or high specific surface area. The heat treatment time (holding time at a predetermined heat treatment temperature) is usually in the range of 0.1 to 10 hours, preferably 0.2 to 5 hours, and more preferably 0.5 to 5 hours. The atmospheric pressure during the heat treatment process is not particularly limited, but it is preferably carried out under atmospheric pressure or reduced pressure.

[0161] Furthermore, through the heat treatment process, functional groups that bond to carbon (mainly oxygen-containing functional groups) and carbon chains that do not form six-membered rings detach above 1000°C, forming unbonded bonds. When these unbonded bonds bond to other nearby carbon atoms, the surface of the carbon material becomes less receptive to the bonding of functional groups. By heat-treating at 1500°C or higher, preferably 1600°C or higher, the carbon material of the present invention can exhibit desirable functions such as electronic conductivity and the maintenance of internal spaces.

[0162] These heat treatments adjust structural defects in the graphene and non-graphene components that make up the carbonaceous material. These structural defects include spaces created within the aggregate structure due to the dissolution of the template material and intrusion pores created in the outer shell formed from the carbonaceous material. By changing reaction conditions such as heat treatment temperature and time, the degree of these structural defects can be adjusted; that is, the size of the spaces within the carbon material and the size of the intrusion pores that allow the electrolyte to penetrate into the particles can be adjusted.

[0163] The surface functional groups that change due to heat treatment, and the structural defects terminated by hydrogen without functional groups, affect the battery properties of the carbon material and the preparation of the dispersion. Therefore, the required characteristics can be satisfied by strictly adjusting the treatment conditions. To do this, the treatment temperature of the heat treatment process is important.

[0164] Thus, the carbon material of the present invention can be easily manufactured.

[0165] In the present invention, other conductive substances can be combined with the carbon material of the present invention as a conductive additive. Examples of other conductive substances include graphite; carbon-based materials such as carbon black, carbon nanotubes, acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0166] These other conductive materials can be used individually or in combination of two or more. The amount of other conductive materials used is appropriately selected according to the intended use and within the range of use of the carbon material of the present invention described above. The ratio of the carbon material of the present invention to the other conductive materials is appropriately selected according to the intended use and is typically in the range of 10:90 to 90:10 by weight ratio of [carbon material of the present invention] to [other conductive materials], preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0167] Furthermore, among the above, the carbon material of the present invention can be made even more effective when combined with conventionally used conductive additives. For example, carbon blacks such as acetylene black are composed of linked structural particles with a diameter of several tens of nanometers. On the other hand, carbon does not have high crystallinity, its structural length is short, and it is easily broken down, making it poor at long-distance electron transport. By combining it with the carbon material of the present invention, it is possible to realize a system that maintains electron conductivity and ion supply ability, whether the three-dimensional structure is maintained or the three-dimensional structure is flattened into a flaky graphite-like state.

[0168] <Dispersion> When using the carbon material of the present invention to fabricate electrodes for a lithium-ion battery, it may be used as a dispersion liquid that has been pre-dispersed in a volatile dispersion medium.

[0169] Next, we will describe the dispersion according to the present invention. The dispersion of the present invention is obtained by dispersing the above-mentioned carbon material in a dispersion medium.

[0170] (dispersion medium) There are no particular limitations on the dispersion medium used in the present invention, and it can be selected according to the purpose of use. For example, organic or inorganic dispersants (e.g., monomolecules or plastic resin materials) can be suitably used to maintain good dispersion of powder in the solvent. When used in the manufacture of lithium-ion secondary batteries, polar solvents are suitably used, and from the viewpoint of affinity with binder polymers, N,N-dimethylformamide, N-methylpyrrolidone (NMP), and N,N-dimethylacetamide are preferred, and it is more preferable to include N-methylpyrrolidone (NMP). N-methylpyrrolidone (NMP) is suitable for dispersing graphene-containing carbon materials.

[0171] The ratio of the carbon material of the present invention to the above dispersion medium is appropriately selected according to the intended use, but the ratio of the carbon material of the present invention to 100 parts by weight of the dispersion medium is usually in the range of 0.01 to 50 parts by weight, preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, even more preferably 0.15 to 4.5 parts by weight, and most preferably 0.2 to 4 parts by weight. If the ratio of the carbon material is too low, it is difficult to form conductive paths in the lithium-ion secondary battery, and conversely, if the content is too high, the fluidity of the carbon material dispersion liquid is easily impaired.

[0172] (Dispersant) In this invention, since carbon materials with a high specific surface area tend to aggregate due to van der Waals interactions, a dispersant can be used to improve dispersibility. The dispersant may be attached to the carbon material in advance or added directly to the dispersion medium. The dispersant can be appropriately selected depending on the intended use, but typically one having an acidic group or a basic group can be used.

[0173] Dispersants having acidic groups exert the effect of improving the dispersibility of carbon materials by having at least a portion of them adhering to the surface of the carbon material. A phenolic hydroxyl group is preferred as the acidic group of the dispersant. Examples of compounds having phenolic hydroxyl groups include phenol, nitrophenol, cresol, catechol, and compounds having structures in which parts of these are substituted.

[0174] Among these, compounds having a catechol group are preferred as dispersants because they have good adhesion to carbon materials and good dispersibility in dispersion media. Examples of compounds having a catechol group include catechol, dopamine hydrochloride, 3-(3,4-dihydroxyphenyl)-L-alanine, 4-(1-hydroxy-2-aminoethyl)catechol, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, caffeic acid, 4-methylcatechol, and 4-tert-butylpyrocatechol.

[0175] As a compound having a basic group, a compound having an amino group is preferred due to its good dispersibility. In particular, a compound having both an aromatic ring and an amino group is preferred. Examples of such compounds include benzylamine and phenylethylamine. As a dispersant, it is also preferable to have both a basic group and a catechol group, such as dopamine hydrochloride.

[0176] As a dispersant, surfactants having acidic or basic groups are also suitably used. Cationic surfactants, anionic surfactants, and nonionic surfactants can all be used as such surfactants, but since anions and cationic surfactants can themselves participate in electrochemical reactions, nonionic surfactants that are not ionized are preferred when used as battery materials.

[0177] Examples of dispersants for polymer compounds that can also be used as battery binders include polyvinylidene fluoride, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride maleic acid modified product, polyvinylpyrrolidone, polyvinyl alcohol, polymethyl vinyl ether, polyacrylonitrile, nitrile rubber, acrylonitrile butadiene rubber, hydrogenated acrylonitrile butadiene rubber, poly(meth)acrylic acid and its esters, polyvinyl acetal, polyvinyl butyral, and cellulose ether.

[0178] These dispersants can be used individually or in combination of two or more, and the amount added to a dispersion should be appropriately selected according to the intended use.

[0179] (Other carbon materials) The dispersion of the present invention may optionally contain other carbon materials other than the carbon material of the present invention. While there are no particular limitations on the other carbon materials, examples include at least one carbon material selected from the group consisting of carbon black, graphite, activated carbon, carbon nanotubes, carbon nanofibers, carbon fibers, and fullerenes.

[0180] Examples of carbon black include acetylene black, Ketjen black, and furnace black, with acetylene black and Ketjen black being preferred from an conductivity standpoint. Graphite, also known as graphite or crystalline sphagnum, is used, typically consisting of multiple layers of graphene. Examples of carbon nanotubes include single-walled carbon nanotubes and multi-walled carbon nanotubes (multi-walled carbon nanotubes include cup-stacked types). Examples of carbon fibers include mesophase-pitch carbon fibers, isotropic-pitch carbon fibers, and vapor-grown carbon fibers (VGCF). Milled carbon fibers obtained by crushing polymer fibers after firing can also be used.

[0181] For example, flake-shaped graphite and highly linear carbon nanotubes have high electronic conductivity but low ion storage capacity. However, if they can be used in combination with the carbon material of the present invention, it is possible to construct a good battery reaction support system that adds ion storage capacity to electronic conductivity.

[0182] Carbon nanotubes, in particular, are preferred because they have high mechanical rigidity and are highly effective in suppressing electrode collapse in response to volume changes that occur during the charging and discharging of metallic anode materials.

[0183] Carbon nanotubes have a cylindrical shape formed by winding planar graphite. Carbon nanotubes may also consist of a mixture of single-walled carbon nanotubes. Single-walled carbon nanotubes have a structure consisting of a single layer of wound graphite. Multi-walled carbon nanotubes have a structure consisting of two or more layers of wound graphite. Furthermore, the sidewalls of carbon nanotubes do not necessarily have to be graphite. For example, carbon nanotubes with amorphous sidewalls can also be used as carbon nanotubes.

[0184] The shape of the carbon nanotube is not limited. Examples of such shapes include needle-shaped, cylindrical, fishbone-shaped (fishbone or cup-stacked), and coil-shaped forms. Alternatively, the carbon nanotube may be a plate-like or platelet-shaped secondary aggregate obtained by dry processing of cylindrical carbon nanotubes. In this embodiment, the shape of the carbon nanotube is preferably needle-shaped or cylindrical. The carbon nanotube may be a single shape or a combination of two or more shapes.

[0185] Examples of carbon nanotube forms include, but are not limited to, graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. Carbon nanotubes may have these forms individually or in combination of two or more of them.

[0186] The average outer diameter of the carbon nanotubes is preferably between 1 nm and 25 nm, more preferably between 1 nm and 20 nm, and even more preferably between 1 nm and 15 nm. When the average outer diameter of the carbon nanotubes is within the above range, the surface of the active material described later is more easily coated with carbon nanotubes, improving the conductivity and adhesion of the electrode film.

[0187] The outer diameter and average outer diameter of the carbon nanotubes are determined as follows. First, the carbon nanotubes are observed and imaged using a transmission electron microscope. Next, in the observation photograph, 300 arbitrary carbon nanotubes are selected and the outer diameter of each is measured. Next, the average outer diameter (nm) of the carbon nanotubes is calculated as the number average of the outer diameters.

[0188] The BET specific surface area of the carbon nanotubes is preferably 150 to 1500 m 2 / g, and more preferably 200 to 1300 m 2 / g.

[0189] For the carbon nanotubes, it is preferable that the product of the addition amount in the composite layer and the specific surface area of the carbon nanotubes is 10 to 1000, and more preferably 40 to 700.

[0190] Carbon nanotubes usually exist as secondary particles. The shape of these secondary particles may be, for example, a state in which carbon nanotubes, which are typical primary particles, are intricately intertwined. It may also be an aggregate of carbon nanotubes made linear. Secondary particles that are an aggregate of linear carbon nanotubes are more likely to unravel compared to those that are intertwined. Also, linear ones have better dispersibility compared to those that are intertwined and can be suitably used as carbon nanotubes.

[0191] The carbon nanotubes may be carbon nanotubes that have been surface-treated. The carbon nanotubes may also be carbon nanotube derivatives to which a functional group typified by a carboxyl group is imparted. Also, carbon nanotubes encapsulating substances typified by organic compounds, metal atoms, or fullerenes can also be used.

[0192] Carbon nanotubes can be produced by any method. While carbon nanotubes can generally be produced by laser ablation, arc discharge, thermal CVD, plasma CVD, and combustion, they are not limited to these methods. For example, carbon nanotubes can be produced by contacting a carbon source with a catalyst at 500-1000°C in an atmosphere with an oxygen concentration of 1 volume% or less.

[0193] Any conventionally known raw material gas can be used as the carbon source for carbon nanotubes. For example, hydrocarbons such as methane, ethylene, propane, butane, and acetylene, carbon monoxide, and alcohols can be used as carbon-containing raw material gases, but are not limited to these. Particularly from the viewpoint of ease of use, it is desirable to use at least one of hydrocarbons and alcohols as the raw material gas.

[0194] Examples of commercially available carbon nanotubes include VGCF-H and VGCF-X from Showa Denko Corporation; carbon nanotubes from Meijo Nanocarbon Co., Ltd.; NTP3003, NTP3021, NTP3121, NTP8012, NTP8022, NTP9012, NTP9112 from NTP Corporation; 10B and 6A from JEIO Corporation; and TUBALL, Canno:FT6120, FT7010 from OCSiAl Corporation.

[0195] These other carbon materials can be used individually or in combination of two or more. The amount of other carbon materials used can be selected according to the intended use, for example, within the same range as the carbon materials of the present invention described above. The ratio of the carbon materials of the present invention to the other carbon materials can be selected according to the intended use, for example, in the weight ratio of [carbon materials of the present invention]:[other carbon materials], it can be in the range of 10:90 to 90:10, 20:80 to 80:20, or 40:60 to 60:40.

[0196] The solid content concentration of the dispersion of the present invention is appropriately selected depending on the intended use, but is usually in the range of 0.01 to 50% by mass, preferably 0.05 to 30% by mass, more preferably 0.1 to 20% by mass, even more preferably 0.5 to 10% by mass, and most preferably 1 to 5% by mass. If the solid content concentration of the carbon material dispersion of the present invention is excessively high, stacking of carbon materials is likely to occur in the dispersion, making it difficult to maintain a good dispersion state. Conversely, if it is excessively low, when the carbon material dispersion is used to manufacture an electrode slurry, the viscosity of the electrode paste decreases, which tends to worsen the coating properties. Here, the solid content of the carbon material dispersion refers to the material remaining after the dispersion medium has been dried and removed from the carbon material dispersion. The solid content ratio of the carbon material dispersion can be calculated by measuring the weight after the dispersion medium has been dried and removed from the carbon material dispersion and dividing the measured value by the weight of the carbon material dispersion itself. Specifically, approximately 1 g of carbon material dispersion is weighed, applied to a glass substrate of known weight, and heated on a hot plate heated to 120°C for 1.5 hours to volatilize the dispersion medium. The weight of the remaining carbon material is then measured.

[0197] The viscosity of the dispersion of the present invention can be appropriately selected depending on the intended use, but the viscosity of the dispersion with a solid content concentration of 3% by mass is as follows: temperature 23°C, shear rate 1s -1 The viscosity under these conditions is typically 20,000 cP or less, preferably 15,000 cP or less, and more preferably 10,000 cP or less. The lower limit is typically 100 cP or more, preferably 500 cP or more, more preferably 1,000 cP or more, even more preferably 2,000 cP or more, and most preferably 4,000 cP or more. Furthermore, the viscosity of the carbon material dispersion of the present invention is measured in a liquid-liquid solution with a solid content concentration adjusted to 2% by weight, at a temperature of 23°C and a shear rate of 1 s. -1 It is preferable that the viscosity under these conditions is 30 cP or less. In the carbon material dispersion of the present invention, the viscosity can be adjusted to a preferred level by adding the surface treatment agent, etc.

[0198] (Method for producing dispersion) The method for producing the dispersion of the present invention is not particularly limited, and can be carried out by mixing the carbon material of the present invention, and optionally a dispersant or other carbon material, in a dispersion medium.

[0199] Since the carbon material of the present invention has a relatively large BET specific surface area, in order to disperse it well in a dispersion, it is effective to apply a high shear force using a mixer with strong stirring power while the carbon material and dispersion medium are present. Examples of mixing devices that can apply a high shear force include planetary mixers, "Filmix" (registered trademark) (Primix Corporation), rotational and revolutionary mixers, planetary ball mills, and three-roll mills. In order to eliminate stacking of carbon materials, a strong stirring process may be performed using a high-shear mixer at a shear rate of 5,000 to 50,000 per second. For high shear mixers, thin-film swirling type, rotor / stator type, and media mill type are preferred. Examples include the "Filmix" (registered trademark) 30-30 type (Primix Co., Ltd.), "Clearmix" (registered trademark) CLM-0.8S (M-Technic Co., Ltd.), "Labostar" (registered trademark) Mini LMZ015 (Ashizawa Finetech Co., Ltd.), and the Super Shear Mixer SDRT0.35-0.75 (Satake Chemical Machinery Industry Co., Ltd.).

[0200] (Positive electrode: Binder) The binder used is a component that helps bond the positive electrode active material, conductive additive, and electrode current collector, and is usually an organic polymer. Examples include fluororesins such as polyvinyl fluoride, polyvinylidene fluoride (PVDF), 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 polyacrylate, polyethyl polyacrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide. Modified or derivative products of the above organic polymers may also be used.

[0201] Among these binders, fluororesins are preferred, and PVDF is particularly preferred. The weight-average molecular weight of these binders can be appropriately selected depending on the intended use, and may be, for example, 10,000 to 8,000,000, 10,000 to 3,000,000, 50,000 to 5,000,000, 80,000 to 3,000,000, or 100,000 to 1,000,000. If the weight-average molecular weight of the binder is too small, the strength of the coating film will decrease, and if it is too large, the viscosity will increase, making electrode formation difficult.

[0202] These binders can be used individually or in combination of two or more types. The amount used is appropriately selected according to the purpose of use, and is typically in the range of 0.01 to 4 parts by weight, preferably 0.05 to 3 parts by weight, more preferably 0.1 to 2 parts by weight, even more preferably 0.2 to 1.5 parts by weight, and most preferably 0.5 to 1.5 parts by weight per 100 parts by weight of positive electrode active material. When the amount of binder used is within this range, the adhesive strength between the electrode active materials and between the electrode active materials and the conductive material can be improved, and consequently the bonding strength with the electrode current collector can be improved, which is preferable.

[0203] (Positive electrode: slurry) The electrode formation slurry used is prepared by mixing the above-mentioned positive electrode material, conductive additive, binder, and other compounding agents as needed, in a dispersion medium. Other compounding agents are selected appropriately according to the intended use, and those commonly used in lithium-ion batteries can be used within their normal operating range.

[0204] There are no particular limitations on the dispersion medium used, but for example, in order to sufficiently uniformly distribute the binder and form a coating film of a predetermined size in the slurry, a medium that dissolves only the binder and does not dissolve other materials is preferably used. Specifically, for example, organic solvents such as dimethylformamide, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, and acetone, or water may be used, and one of these solvents alone or a mixture of two or more solvents may be used.

[0205] When polyvinylidene fluoride (PVDF) is used as the binder, dimethylformamide or N-methyl-2-pyrrolidone (NMP) is preferred as the dispersion medium, with NMP being particularly preferred.

[0206] The solid content concentration of the electrode-forming slurry, excluding the dispersion medium, can be appropriately selected depending on the method of applying the slurry to the electrode, and is typically in the range of 10 to 90% by weight, preferably 20 to 80% by weight, more preferably 40 to 80% by weight, even more preferably 40 to 70% by weight, and most preferably 50 to 65% by weight.

[0207] The viscosity of the electrode-forming slurry is not particularly limited, but at a temperature of 24 to 26°C, it is usually in the range of 1,000 to 50,000 cP, preferably 2,000 to 40,000 cP, more preferably 5,000 to 35,000 cP, even more preferably 10,000 to 35,000 cP, and most preferably 10,000 to 30,000 cP. When the viscosity of the electrode-forming slurry is within this range, the solid components excluding the dispersion medium are uniformly dispersed, and when the electrode-forming slurry is applied to the electrode current collector, it is applied with a uniform thickness, which is preferable.

[0208] <Electrode compositions, electrode slurries, and electrodes> Next, the electrode composition, electrode slurry, and electrode according to the present invention will be described.

[0209] The electrodes containing the carbon material of the present invention, preferably electrodes for lithium-ion secondary batteries, are suitable because they have excellent fast discharge properties, capacity characteristics, and charge-discharge characteristics. To manufacture such electrodes, it is useful to use electrode compositions and electrode slurries containing the carbon material of the present invention.

[0210] (Composition for electrode) The electrode composition of the present invention comprises the carbon material, active material, and binder of the present invention.

[0211] There are no particular limitations on the positive electrode material used in the present invention. Examples include the active material used in the positive electrode described later, and the active material used in the negative electrode described later. The ratio of the active material to the carbon material of the present invention is appropriately selected according to the purpose of use, and the ratio of the carbon material of the present invention to 100 parts by weight of the active material is usually in the range of 0.005 to 20 parts by weight, preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, even more preferably 0.1 to 2 parts by weight, and most preferably 0.5 to 1 part by weight.

[0212] There are no particular limitations on the binder used in the present invention, and examples include binders used in the positive electrode and binders used in the negative electrode, as described later. The amount of binder used is appropriately selected according to the purpose of use, and is usually in the range of 0.05 to 10 parts by weight, preferably 0.1 to 8 parts by weight, more preferably 0.5 to 6 parts by weight, even more preferably 1 to 5 parts by weight, and most preferably 2 to 4 parts by weight per 100 parts by weight of active material.

[0213] In addition to the carbon material, positive and negative electrode material, and binder described above, other compounding agents may be added to the electrode composition of the present invention as needed. The other compounding agents are not particularly limited as long as they are commonly used in electrode compositions for lithium-ion secondary batteries, and the amount used is typically 20 parts by weight or less, preferably 15 parts by weight or less, more preferably 10 parts by weight or less, even more preferably 5 parts by weight or less, and most preferably 2 parts by weight or less, per 100 parts by weight of the active material.

[0214] There are no particular limitations on the mixing method for the electrode composition of the present invention, but examples include a dry mixing method and a wet mixing method using a dispersion medium.

[0215] (Electrode slurry) The electrode slurry of the present invention is obtained by mixing the above electrode composition using a dispersion medium in a wet mixing method. Any dispersion medium that can dissolve or disperse the binder may be used, such as the dispersion medium used in the positive electrode described later, the dispersion medium used in the negative electrode described later, and the dispersion medium used in the carbon material-containing dispersion liquid of the present invention described above. The amount of dispersion medium used may be an appropriate amount, and should be adjusted so that the electrode slurry in the next step can be applied to the current collector.

[0216] The method for producing the electrode slurry of the present invention is not particularly limited, and examples include a method in which the carbon material, binder, and dispersion medium of the present invention are mixed, and then the active material is mixed. In the mixing of the carbon material, binder, and dispersion medium of the present invention, there are methods such as mixing the binder into a dispersion liquid containing the carbon material, and mixing the dispersion liquid containing the carbon material with a binder liquid obtained by dissolving or dispersing the binder in the dispersion medium.

[0217] There are no particular limitations on the mixing method, and any known mixer or kneader can be used. Known mixers include automatic mortars, homogenizers, planetary mixers, homodispersers, and revolving mixers, with planetary mixers being particularly preferred.

[0218] (electrode) The electrode of the present invention may be either a negative electrode or a positive electrode, and can be obtained by applying the electrode slurry to a current collector and then drying it. The current collector may be either one used for the positive electrode or one used for the negative electrode, as described later.

[0219] The method for applying the electrode slurry onto the current collector is not particularly limited, and known methods can be used. Specifically, it can be applied using a Baker applicator, a film applicator with a micrometer, a bar coater, a doctor blade, etc., either manually or automatically. The drying method is not particularly limited, and known methods can be used, such as drying with hot air, hot air, low humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. After the drying process, the electrode composite layer may be subjected to pressure treatment using a die press or a roll press. Pressure treatment allows the positive electrode composite layer to adhere well to the current collector.

[0220] (Current collector and positive electrode) The positive electrode can be manufactured by applying the above electrode molding slurry onto a current collector and drying it. There are no particular limitations on the current collector material, as long as it is a commonly used material. For example, single metals such as aluminum foil, nickel foil, titanium foil, and stainless steel foil, or lightweight materials made by laminating metal layers onto resin using methods such as vapor deposition, can be used. Among these, rolled aluminum foil is particularly preferred.

[0221] For applying the electrode-forming slurry to the current collector, commonly used printing techniques can be employed. For small coating thicknesses, gravure printing is preferable, while for larger thicknesses, doctor blade printing or die printing are more suitable. Subsequently, the coating film is heat-dried. Any drying method is available, and the method that allows for the desired bonding strength with the binder to be achieved is preferably used.

[0222] Then, when forming the positive electrode to the predetermined dimensions, industrially available cutting blades and the like, and methods thereof, are preferably used. Furthermore, in order to achieve the predetermined density, industrially available pressurizing devices and the like, and methods thereof, are preferably used as needed.

[0223] <Negative electrode> Next, I will explain the negative electrode. The negative electrode is obtained by coating a slurry obtained by mixing, for example, a negative electrode material, a binder, a conductive assistant as needed, and a dispersion medium on a current collecting metal foil such as rolled copper foil, heating and drying to remove the solvent, and then forming it into a predetermined size and density.

[0224] (Negative electrode material) As the negative electrode material, an optimal material is selected from the viewpoints of negative electrode material manufacturability, electrode manufacturability, charge-discharge capacity, cycle characteristics, storage characteristics, safety, etc., and in some cases, it can be compounded and used in a lithium-ion battery.

[0225] The negative electrode reaction can bind and stabilize Li ions and electrons flowing from the external circuit, and it is preferable to have a large number of stabilization sites inside. For example, those originating from organic substances, whether highly crystalline or lowly crystalline, can all be used, and graphite, coke, amorphous carbon, hard carbon, polymer carbon, etc. can be preferably used. In this case, in principle, Li ions are sandwiched between graphene layers and the like and combined with electrons to be stabilized. In addition, as another stabilization mechanism, a method of forming an intermetallic compound electrochemically can also be used, and silicon, tin, zinc, bismuth, antimony, cadmium, lead, germanium, etc. can be preferably used. In addition, other materials showing a low electrochemical reaction potential that control the negative electrode side of the lithium-ion battery can also be used. Preferably, compounds of metals and oxygen, sulfur, halogen, nitrogen, phosphorus, etc. are included.

[0226] Specific examples of the negative electrode material include compounds capable of reversible intercalation and deintercalation of lithium, such as carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; metal oxides capable of doping and undoping lithium, such as SiOx (0 < x = 2), SnO2, vanadium oxides, and lithium vanadium oxides; or composites containing the metallic compound and the carbonaceous material, such as Si-C composites or Sn-C composites.

[0227] As the negative electrode material, a thin film of metallic lithium may also be used. Further, any of low-crystalline carbon and highly crystalline carbon may be used as the carbonaceous material. Soft carbon and hard carbon are typical of low-crystalline carbon, and examples of highly crystalline carbon include amorphous, plate-like, scaly, spherical or fibrous natural graphite or artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitch, and high-temperature calcined carbon such as petroleum and coal-based cokes.

[0228] The physical property values of the negative electrode material are determined from the required items in the device design and manufacturing process due to constraints such as the usage form of the lithium ion battery. In the manufacture of the material, process design and the like are carried out so as to realize its physical properties. Examples of the physical property values include powder particle diameter and distribution, specific surface area, density, and the like.

[0229] As an example, the powder particle diameter is appropriately selected in consideration of the balance with other constituent elements of the lithium ion battery. From the viewpoint of improving battery characteristics such as rate characteristics and cycle characteristics, usually, the average value is preferably 1 to 70 μm, more preferably 3 to 30 μm.

[0230] These negative electrode materials can be used alone or in combination of two or more. The ratio of the negative electrode material in the slurry for electrode formation is not particularly limited, but is usually in the range of 95.5 to 99 parts by weight, preferably 96 to 98.7 parts by weight, more preferably 97 to 98 parts by weight, based on 100 parts by weight of the solid content excluding the dispersion medium. When the content of the negative electrode material is within this range, the battery capacity, conductivity, and adhesiveness are highly balanced and suitable.

[0231] (Composition protection layer near negative electrode material particles) The composition disposed near the negative electrode material of the present invention is composed of elements of Li, C, N, O, F, P, and S, and functions as a conductive auxiliary, a deterioration reaction protection layer, and the like.

[0232] As for the conductive aid, as in the case of the positive electrode conductive aid described above, a so-called carbon material made of C (carbon) can, if necessary, assist in conductivity during the battery reaction, or if it has pores in its structure, can assist in holding the electrolyte solution and supplying ions for the battery reaction.

[0233] As the degradation reaction protective layer, a plurality of compounds in which elements of Li, C, N, O, F, P, and S are combined are formed on the negative electrode surface, suppressing the direct contact of the electrolyte solution solvent, etc. with the negative electrode, and having a function of suppressing degradation reactions such as reduction and decomposition, and can be preferably used.

[0234] These compounds may sometimes have a composition similar to the SEI (Solid Electrolyte Interface) of the negative electrode generated during the initial charging of a normal storage battery, but have a high degree of perfection in terms of density and passivation. Utilizing the reaction in the reduction potential environment of the negative electrode, by precisely adjusting the temperature, potential, and application time of the potential and current, adding an organic compound that is not usually used as an organic solvent of the electrolyte solution, adjusting the reaction to preferably generate a compound, and installing a protective layer suitable for the purpose is possible.

[0235] An example of this is LiF, but F decomposed from PF6 present as an impurity in the electrolyte solution - anion - anion is reduced by Li during the first charging of the negative electrode to become LiF, first creating a reaction starting point, and then by keeping the storage battery at a high temperature, the decomposition of PF6 - anion is promoted, and Li and F - anion can be further reacted to widely and thinly generate LiF, which can become a suitable protective layer. By going through such an aging process, a suitable protective layer can be made on the entire negative electrode. During the aging, Li3PO4 generated as a decomposition product from PF6 - anion and the product reacted with a part of the organic solvent also preferably function as a protective layer. Another example is N(SO2F)2 such as LiFSI -Similarly, reaction products such as R-OSO2Li and Li2SO3 also function as suitable protective layers.

[0236] (Negative electrode conductive additive) The carbon material intended for conductivity enhancement can be suitably used as a conductivity enhancer for the negative electrode material, similar to the conductivity enhancer for the positive electrode. For example, while the negative electrode active material generally has high electronic conductivity, some materials have a smooth surface, and in cases where particle-to-particle contact is insufficient, the carbon material of the present invention can be used as a conductivity enhancer to improve electronic conductivity. Furthermore, while flake-shaped graphite and artificial graphite used as negative electrode materials have high electronic conductivity, they have low ion storage capacity and poor ionic conductivity. By combining these materials with the carbon material of the present invention, it is possible to construct a good battery reaction support system that adds ionic conductivity to electronic conductivity. Moreover, even when the three-dimensional structure of the negative electrode active material is compressed and flattened like flake-shaped graphite, adding the carbon material of the present invention is suitable because it adds ionic conductivity while maintaining electronic conductivity.

[0237] The proportion of the carbon material of the present invention in the electrode forming slurry is typically in the range of 0.8 to 3 parts by weight, preferably 1 to 2.5 parts by weight, and more preferably 1 to 2.2 parts by weight, per 100 parts by weight of solid content excluding the dispersion medium. When the carbon material content of the present invention is within this range, the high-speed charging performance, life characteristics, capacity characteristics, and charge / discharge characteristics of the lithium-ion secondary battery can be greatly enhanced, making it preferable.

[0238] In the present invention, the carbon material of the present invention and other carbon materials can be used in combination. Other carbon materials are not particularly limited as long as they are conventional materials used as electrode materials. Examples include acetylene black, Ketjen black, lamp black, furnace black, carbon black, graphite, carbon fiber, graphite fiber, nanofiber, nanotube, coke, hard carbon, amorphous carbon, and the like.

[0239] These other carbon materials can be used individually or in combination of two or more, and the amount used is selected according to the purpose of use, and can usually be used within the same range as the carbon material of the present invention described above. The ratio of the carbon material of the present invention to the other carbon materials is usually in the range of 10:90 to 90:10 by weight ratio of [carbon material of the present invention] to [other carbon materials], preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0240] By combining these conventional materials with the carbon material of the present invention, further benefits can be obtained. For example, highly linear carbon nanotubes have high electronic conductivity but low ion storage capacity. Therefore, by combining them with the carbon material of the present invention, it is possible to construct a good battery reaction support system that adds ionic conductivity to electronic conductivity. Also, carbon blacks such as acetylene black are composed of linked structural particles with a diameter of several tens of nanometers. On the other hand, carbon does not have high crystallinity, its structural length is short, and it is easily broken down, making it poor at long-distance electron transport. Despite these properties, by combining them with the carbon material of the present invention, it is possible to realize a system that maintains its three-dimensional structure while also possessing ion supply capabilities.

[0241] (Negative electrode: Binder) The binders used are components that help bond the electrode active material, conductive additive, and electrode current collector. Examples include fluororesins 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 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 polyacrylate, polyethyl polyacrylate, polyacrylic acid, polymethacrylic acid, and polyacrylamide; carboxymethylcellulose and styrene-butadiene rubber. Modified or derivative products of the above organic polymers may also be used.

[0242] Among these binders, carboxymethylcellulose and styrene-butadiene rubber are preferred. The weight-average molecular weight of these binders can be appropriately selected depending on the intended use, for example, it may be in the range of 10,000 to 8,000,000, 10,000 to 3,000,000, 50,000 to 5,000,000, 80,000 to 3,000,000, or 100,000 to 1,000,000. If the weight-average molecular weight of the binder is too small, the strength of the coating film will decrease, and if it is too large, the viscosity will increase, making electrode formation difficult.

[0243] These binders can be used individually or in combination of two or more types. The amount used is appropriately selected according to the purpose of use, and is typically in the range of 0.01 to 4 parts by weight, preferably 0.05 to 3 parts by weight, more preferably 0.1 to 2 parts by weight, even more preferably 0.2 to 1.5 parts by weight, and most preferably 0.5 to 1.5 parts by weight per 100 parts by weight of negative electrode material. When the amount of binder used is within this range, the adhesive strength between the negative electrode materials and between the negative electrode material and the conductive additive can be improved, and consequently the bonding strength with the electrode current collector can be improved, which is preferable.

[0244] These binders can be used individually or in combination of two or more types. The proportion of each binder in the electrode-forming slurry is typically in the range of 0.8 to 3 parts by weight, preferably 1 to 2.5 parts by weight, and more preferably 1 to 2.2 parts by weight, per 100 parts by weight of solids excluding the dispersion medium. When the binder content in the electrode-forming slurry is within this range, it is preferable because it can improve the adhesion between negative electrode materials and between negative electrode materials and conductive additives, and consequently improve the bonding force with the electrode current collector.

[0245] (Negative electrode: dispersion medium) The dispersion medium used is not particularly limited as long as it is a solvent commonly used in the art. For example, organic solvents such as N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, and acetone, or water may be used, and one of these alone or a mixture of two or more solvents may be used. The dispersion medium is used to dissolve or disperse the negative electrode material, conductive additive, and binder, taking into consideration the coating thickness of the electrode forming slurry and the manufacturing yield.

[0246] (Negative electrode: slurry) There are no particular limitations on the amount of dispersion medium used, but for example, the concentration of solids including the negative electrode material, conductive material, and binder is usually adjusted to be in the range of 10 to 90% by weight, preferably 20 to 80% by weight, more preferably 30 to 75% by weight, preferably 40 to 70% by weight, and more preferably 50 to 65% by weight.

[0247] (Current collector and negative electrode) As the current collector for the negative electrode, there is no particular limitation. For example, a material that does not have electrochemical reactivity with respect to the potential exhibited by the negative electrode is used. Specifically, a single metal such as copper foil, nickel foil, titanium foil, stainless steel foil, etc., or a material in which a metal layer is laminated by a method such as vapor deposition on a resin to reduce the weight can also be used. Among them, electrolytic copper foil and rolled copper foil are preferred.

[0248] For the application of the electrode-forming slurry onto the current collector, generally used printing techniques can be utilized. When the thickness dimension is small, gravure printing, etc. is used, and when it is large, printing methods such as doctor blade printing and die printing are preferably used.

[0249] Thereafter, the coating film is dried by heating, and any drying method can be used, and a method that can achieve the binding strength by the desired binder is preferably used. And then, when forming the negative electrode into a predetermined dimension, industrially available cutting blades, etc. and their methods are preferably used. Also, in order to achieve a predetermined density, industrially available pressurizing devices, etc. and methods are preferably used as necessary.

[0250] <Lithium-ion secondary battery> Next, the lithium-ion secondary battery according to the present invention will be described. The lithium-ion secondary battery of the present invention is characterized by containing the carbon material of the present invention. Specifically, it includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and at least one or more of the positive electrode and the negative electrode use the electrode (positive electrode and / or negative electrode) of the present invention described above. On the other hand, the lithium-ion storage battery may further selectively include a battery container that houses the electrode assembly composed of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container. On the other hand, since the positive electrode and the negative electrode are the same as those described above, specific descriptions are omitted. (Separator)

[0251] A separator separates the positive and negative electrodes, preventing short circuits caused by contact between the two electrodes while allowing lithium ions to pass through. A porous membrane made of resin is preferably used.

[0252] Suitable membrane forms include stretched membranes, which are created by stretching bulk resin to create pores, and nonwoven fabrics, which can form a porous structure similar to a porous membrane by laminating many fibrous resin fibers.

[0253] Polyolefins are suitable resin materials, with polyethylene being particularly preferred. Polyethylene has a relatively low melting point, and when the battery temperature rises for any reason (for example, due to unsafe conditions such as a short circuit), thermal melting blocks the pores in the film, inhibiting the movement of driving ions, thereby stopping the reaction and ensuring safety.

[0254] Porous membranes formed by stretching typically involve adding plasticizers to polyolefins. The plasticizers are removed before and after stretching, and the areas where the plasticizers were present become starting points, resulting in a relatively uniform microporous structure.

[0255] In the manufacture of stretched films, stretching is usually performed in both the longitudinal and widthwise directions. By appropriately combining the removal of plasticizers, etc., with the appropriate atmospheric medium, temperature, speed, stress, and number of process repetitions, a suitable stretched film can be obtained.

[0256] While the above manufacturing process yields high-quality stretched films, it involves multiple steps. This makes it difficult to reduce manufacturing costs, such as process fees, which can be a negative factor in the widespread adoption of lithium-ion batteries.

[0257] On the other hand, by simplifying the process to perform stretching only in the longitudinal direction without using plasticizers, it is possible to obtain a porous film that can be manufactured at an industrial level and has reduced manufacturing costs. The resin applicable in this case is a polyolefin, and polypropylene is preferably used.

[0258] The separator interposed between the positive and negative electrodes may be made of an electrically insulating porous material. Suitable separators include polymer films or nonwoven fabrics made of materials such as polyethylene, polypropylene, polyester, polyethylene terephthalate, and polyimide. The separator material may be a single type or multiple types. The separator may also be a single layer or a multilayer (composite film). Furthermore, the separator may contain inorganic material nanoparticles such as ceramics. Additionally, polymer compounds such as polyvinylidene fluoride may be coated on both sides of the separator.

[0259] In the non-aqueous electrolyte battery according to this embodiment, an electrolyte that has become gel-like by including a polymer compound that swells with an organic solvent and becomes a retainer that holds the non-aqueous electrolyte may be used. This is because including a polymer compound that swells with an organic solvent can provide high ionic conductivity, excellent charge and discharge efficiency, and prevent leakage of the battery. When the non-aqueous electrolyte contains a polymer compound, it is preferable that the content of the polymer compound be within the range of 0.1% by mass or more and 10% by mass or less of the non-aqueous electrolyte.

[0260] Furthermore, when using a separator coated with a polymer compound such as polyvinylidene fluoride on both sides, it is preferable to set the mass ratio of the non-aqueous electrolyte to the polymer compound within the range of 50:1 to 10:1. By keeping it within this range, higher charge and discharge efficiency can be obtained.

[0261] Examples of the polymer compounds mentioned above include ether-based polymer compounds such as polyvinyl formal, polyethylene oxide, and crosslinked polyethylene oxide; ester-based polymer compounds such as polymethacrylate; acrylate-based polymer compounds; polyvinylidene fluoride; and polymers of vinylidene fluoride such as copolymers of vinylidene fluoride and hexafluoropropylene. A single polymer compound may be used, or multiple compounds may be used in combination. In particular, from the viewpoint of preventing swelling during high-temperature storage, it is desirable to use fluorine-based polymer compounds such as polyvinylidene fluoride.

[0262] Furthermore, when using high electrolyte salt concentrations to achieve high durability, the viscosity of the electrolyte increases, which can slow down or make the penetration of the electrolyte into the separator insufficient. However, depending on the application, there may be a margin in the design values ​​of the battery shape and energy capacity, in which case the material, thickness, porosity, and curvature of the separator can be adjusted to suitably use a separator with excellent permeability. Examples include separators made of glass fiber alone or those compounded with resin fibers such as polyester or polyolefin.

[0263] (electrolyte) Typically, an organic electrolyte solution is used, which consists of an electrolyte salt dissolved in an organic solvent.

[0264] -Organic solvents- Chemical formula H t C u N v O w F x P y S z Organic solvents represented by (t, u, v, w, x, y, or z being integers greater than 0 and less than 16) can be suitably used.

[0265] The type of organic solvent is not particularly limited as long as it can dissolve the electrolyte mentioned above, but solvents such as cyclic carbonates, linear carbonates, linear carboxylic acid esters, linear ethers, cyclic ethers, sulfur-containing compounds, and nitrogen-containing compounds are preferably used. These organic solvents can be used individually or in combination of two or more.

[0266] Among these, cyclic carbonates and linear carbonates are preferred because they have high dielectric constants and suitable viscosity and solvation capacity that affect the movement of Li ions. Solvation capacity is the force that dissociates dissolved ions; if it is too strong, it inhibits ion movement, so there is an optimal value.

[0267] Examples of cyclic carbonates include alkylene carbonates having alkylene groups with 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.

[0268] As for the chain-like carbonates, dialkyl carbonates are preferred, and the number of carbon atoms in each constituent alkyl group is preferably 1 to 5, and particularly preferably 1 to 4. Specifically, examples include symmetric chain-like alkyl carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; and dialkyl carbonates such as asymmetric chain-like alkyl carbonates such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate. Among these, dimethyl carbonate and diethyl carbonate are preferred from the viewpoint of viscosity and boiling point, and diethyl carbonate is particularly preferred.

[0269] Furthermore, practical lithium-ion batteries operate under a wide range of environmental conditions, and in particular, the physical properties of non-aqueous solvents, such as their melting and boiling points, must be kept within a certain range. Therefore, it is preferable to use a mixture of cyclic carbonates and linear carbonates.

[0270] There are no particular limitations on the combination of cyclic carbonates and linear carbonates, but for example, a combination of ethylene carbonate and a linear carbonate is preferred. Specifically, combinations such as ethylene carbonate and dimethyl carbonate, ethylene carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate, and ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate are preferred because they offer a good balance between cycle characteristics and high-power discharge characteristics.

[0271] The mixing ratio of cyclic carbonates and linear carbonates is appropriately selected according to the desired practical properties. For example, the weight ratio of [cyclic carbonates]:[linear carbonates] is usually in the range of 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40.

[0272] The content of cyclic carbonates in the electrolyte may be 1 to 70% by weight, or 1 to 35%, 3 to 30%, or 4 to 50% by weight. Multiple cyclic carbonates can be used in mixture form. The content of linear carbonates in the electrolyte is preferably 40-70% by weight, and more preferably 43-68% by weight. Multiple linear carbonates can be used in mixture form.

[0273] As the organic solvent used in the electrolyte, cyclic carbonates having unsaturated bonds or aromatic compounds with 7 to 18 carbon atoms may also be mixed into the electrolyte.

[0274] As cyclic carbonates having unsaturated bonds, 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 particularly preferred.

[0275] Aromatic compounds having 7 to 18 carbon atoms are suitable because they suppress the significant decrease in discharge characteristics after high-temperature storage by suppressing side reactions with the negative and positive electrodes. Examples of suitable aromatic compounds include biphenyl, alkylbiphenyl, terphenyl, terphenyl, and their partially hydrogenated forms, as well as cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran.

[0276] These cyclic carbonates having unsaturated bonds and aromatic compounds with 7 to 18 carbon atoms can be used individually or in combination of two or more, and the proportion of each in the electrolyte is usually in the range of 0.001 to 5% by weight, preferably 0.1 to 4% by weight, more preferably 0.3 to 3% by weight, even more preferably 0.4 to 2.5% by weight, and most preferably 0.5 to 2% by weight.

[0277] The following are examples of chain-like ethers. 1,1-dimethoxyethane, 1,2-dimethoxypropane, 2,2-dimethoxypropane, 1,3-dimethoxybutane, 1,2-dimethoxybutane, 2,2-dimethoxybutane, 2,3-dimethoxybutane, 1,2-diethoxypropane, 1,2-diethoxybutane, 2,3-diethoxybutane, and diethoxyethane can be suitably used as organic solvents.

[0278] The following are examples of linear carboxylic acid esters. Chain-like carboxylic acid esters such as propyl acetate, butyl acetate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, and propyl butyrate can be suitably used as organic solvents.

[0279] The following are examples of sulfate esters. Examples of cyclic sulfonic acid esters include 1,3-propanesultone, 1-fluoro-1,3-propanesultone, 2-fluoro-1,3-propanesultone, 3-fluoro-1,3-propanesultone, 1-methyl-1,3-propanesultone, 2-methyl-1,3-propanesultone, 3-methyl-1,3-propanesultone, 1-propene-1,3-sultone, 2-propene-1,3-sultone, 1-fluoro-1-propene-1,3-sultone, 2-fluoro-1-propene-1,3-sultone, 3-fluoro-1-propene-1,3-sultone, and 1-fluoro-2-propene-1,3 Examples include sultone compounds such as -sultone, 2-fluoro-2-propene-1,3-sultone, 3-fluoro-2-propene-1,3-sultone, 1-methyl-1-propene-1,3-sultone, 2-methyl-1-propene-1,3-sultone, 3-methyl-1-propene-1,3-sultone, 1-methyl-2-propene-1,3-sultone, 2-methyl-2-propene-1,3-sultone, 3-methyl-2-propene-1,3-sultone, 1,4-butanesultone, and 1,5-pentanesultone; and disulfonate compounds such as methylenemethanedisulfonate and ethylenemethanedisulfonate. The cyclic sulfonic acid ester may be at least one selected from the group consisting of 1,3-propanesultone, 1-propene-1,3-sultone, and methylenemethanedisulfonate.

[0280] Examples of cyclic sulfuric acid esters include alkylene sulfate compounds such as 1,2-ethylene sulfate (1,3,2-dioxathiolane-2,2-dioxide), 1,2-propylene sulfate, 1,3-propylene sulfate, 1,2-butylene sulfate, 1,3-butylene sulfate, 1,4-butylene sulfate, 1,2-pentylene sulfate, 1,3-pentylene sulfate, 1,4-pentylene sulfate, and 1,5-pentylene sulfate. Among these, the cyclic sulfuric acid ester may be 1,2-ethylene sulfate (1,3,2-dioxathiolane-2,2-dioxide).

[0281] Examples of cyclic sulfite esters include alkylene sulfite compounds such as 1,2-ethylene sulfite, 1,2-propylene sulfite, 1,3-propylene sulfite, 1,2-butylene sulfite, 1,3-butylene sulfite, 1,4-butylene sulfite, 1,2-pentylene sulfite, 1,3-pentylene sulfite, 1,4-pentylene sulfite, and 1,5-pentylene sulfite.

[0282] Examples of cyclic sulfones include alkylene sulfone compounds such as sulfolane, methylsulfolane, and 4,5-dimethylsulfolane; and alkylylene sulfone compounds such as sulfolene. The above sulfuric acid esters can be suitably used as organic solvents.

[0283] The following are examples of phosphate esters. Trimethyl phosphate, triethyl phosphate, triisopropyl phosphate, and tributyl phosphate are preferred, trimethyl phosphate, triethyl phosphate, and tributyl phosphate are more preferred, triethyl phosphate and trimethyl phosphate are even more preferred, and triethyl phosphate is particularly preferred.

[0284] Furthermore, partially halogen-substituted dimethyl monochlorophosphate, diethyl monochlorophosphate, dimethyl monofluorophosphate, and diethyl monofluorophosphate are preferred, and dimethyl monofluorophosphate and diethyl monofluorophosphate are more preferred.

[0285] Methyl dichlorophosphate, ethyl dichlorophosphate, methyl difluorophosphate, and diethyl difluorophosphate are preferred, with methyl difluorophosphate and diethyl difluorophosphate being more preferred.

[0286] Below, dinitrile compounds are shown as examples of nitrogen-containing compounds. Malononitrile (n=1), succinonitrile (n=2), glutalonitrile (n=3), adiponitrile (n=4), pimeronitrile (n=5), suberonitrile (n=6), azeranitrile (n=7), sebaconitrile (n=8), undecanenitrile (n=9), and dodecanenitrile (n=10) can be suitably used as organic solvents. Furthermore, ethers having nitrile groups at their termini can also be suitably used. Examples include ethylene glycol bis(propionitrile) ether and 1,2,3-tris(2-cyanoethoxy)propane.

[0287] Furthermore, in order to realize high-performance, highly durable storage batteries, fluorine compounds with fluorine (F) in their structure, which have high oxidation resistance, can also be suitably used as organic solvents.

[0288] As the organic solvent used in the electrolyte, fluorine-containing carbonates can also be suitably used. Specifically, examples include cyclic carbonates having one fluorine atom, chain carbonates having one fluorine atom, cyclic carbonates having two or more fluorine atoms, and chain carbonates having two or more fluorine atoms. From the viewpoint of improving battery characteristics, fluorine-containing cyclic carbonates having two or more fluorine atoms are preferred.

[0289] Specific examples of fluorine-containing cyclic carbonates having two or more fluorine atoms include, for example, cis-4,5-difluoro-1,3-dioxolan-2-one, trans-4,5-difluoro-1,3-dioxolan-2-one, and 4,4-difluoro-1,3-dioxolan-2-one.

[0290] These fluorine-containing carbonates can be used individually or in combination of two or more. While there are no particular limitations on the proportion of fluorine-containing carbonate in the electrolyte, it is typically in the range of 0.001 to 10% by weight, preferably 0.01 to 5% by weight, more preferably 0.1 to 2% by weight, even more preferably 0.2 to 1% or more by weight, and most preferably 0.25 to 0.5% by weight. If the fluorine-containing carbonate content is excessively low, the effect of the addition may not be readily apparent; conversely, if it is excessively high, the internal pressure of the battery may increase during high-temperature storage.

[0291] Furthermore, fluorine-containing compounds (such as ethers) will be explained. Examples of primary fluorine solvents include 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethoxy-2,2,3,3-tetrafluoropropoxymethane, and 1,1,2,2-tetrafluoroethoxy-2,2,3,3-tetrafluoropropoxyethane. From the viewpoint of effectively and reliably achieving the effects of the above-mentioned fluorine compounds, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is preferred as the primary fluorine solvent.

[0292] Examples of secondary fluorine solvents include 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, methyl-1,1,2,2-tetrafluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, propyl-1,1,2,2-tetrafluoroethyl ether, and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether. From the viewpoint of effectively and reliably achieving the effects of the above fluorine compounds, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, methyl-1,1,2,2-tetrafluoroethyl ether, ethyl-1,1,2,2-tetrafluoroethyl ether, and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether are preferred as secondary fluorine solvents.

[0293] Examples of tertiary fluorine solvents include difluoromethyl-2,2,3,3-tetrafluoropropyl ether, trifluoromethyl-2,2,3,3-tetrafluoropropyl ether, difluoromethyl-2,2,3,3-tetrafluoropropyl ether, and methyl-2,2,3,3-tetrafluoropropyl ether. From the viewpoint of effectively and reliably achieving the effects of the above-mentioned fluorine compounds, difluoromethyl-2,2,3,3-tetrafluoropropyl ether is preferred as the tertiary fluorine solvent.

[0294] Examples of fluorine compounds include methyl nonafluorobutyl ether, ethyl nonafluorobutyl ether, 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethylpentane, methyl-2,2,3,3,3-pentafluoropropyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, ethyl-1,1,2,3,3,3-hexafluoropropyl ether, and tetrafluoroethyltetrafluoropropyl ether. From the viewpoint of effectively and reliably achieving the effects of the above fluorine compounds, methyl nonafluorobutyl ether, ethyl nonafluorobutyl ether, and 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethylpentane are preferred as quaternary fluorine solvents.

[0295] As the solvent for the electrolyte, the above-mentioned fluorine compounds, fluorine-containing compounds other than the above-mentioned fluorine compounds, ether subsolvents, and non-ether subsolvents can be freely combined and used. The fluorine solvent may be used alone or in combination of two or more types. In the electrolyte, compounds that do not contain fluorine atoms may be used alone as an ether subsolvent, or in combination of two or more types of ether subsolvents with further ether subsolvents or non-ether subsolvents.

[0296] The fluorine compound content in the electrolyte is more than 50% by volume relative to the total amount of solvent components in the electrolyte. Because the fluorine compound content is within the above range, the SEI layer is more easily formed, resulting in lithium secondary battery 100 having excellent cycle characteristics. While the fluorine compound content is not particularly limited as long as it is within the above range, it is preferably 51% or more by volume, 55% or more by volume, 60% or more by volume, 65% or more by volume, 70% or more by volume, 75% or more by volume, 80% or more by volume, 85% or more by volume, or 90% or more by volume relative to the total amount of solvent components in the electrolyte. The upper limit of the fluorine compound content is not particularly limited; the fluorine compound content may be less than 100% by volume, 99% or less by volume, 98% or less by volume, 95% or less by volume, 90% or less by volume, 85% or less by volume, 80% or less by volume, 70% or less by volume, or 60% or less by volume. By having the fluorine compound content within the above range, the solubility of the electrolyte in the electrolyte is further improved.

[0297] When the electrolyte contains two or more fluorine compounds from primary, secondary, or tertiary fluorine solvents, the content of primary fluorine solvent is not particularly limited, but may be 5% or more by volume, or 10% or more by volume, or 50% or less by volume, 40% or less by volume, 30% or less by volume, 20% or less by volume, or 15% or less by volume, relative to the total amount of the fluorine compounds.

[0298] In the above case, the content of the secondary fluorine solvent is not particularly limited, but may be 50% or more by volume, 60% or more by volume, 65% or more by volume, 70% or more by volume, or 75% or more by volume, relative to the total amount of the fluorine compound, or it may be 95% or less by volume, 90% or less by volume, or 85% or less by volume.

[0299] In the above case, the content of the tertiary fluorine solvent is not particularly limited, but may be 0% by volume, 5% or more by volume, or 10% or more by volume relative to the total amount of the fluorine compound, or it may be 50% or less by volume, 40% or less by volume, 30% or less by volume, 20% or less by volume, or 15% or less by volume.

[0300] Furthermore, if the electrolyte contains two or more primary fluorine solvents, the content of the primary fluorine solvent shall be calculated using the total amount of these solvents. The same calculation shall apply if the electrolyte contains two or more secondary or tertiary fluorine solvents.

[0301] When the electrolyte contains a quaternary fluorine solvent, the amount of the quaternary fluorine solvent is not particularly limited, but it is preferably more than 0 vol%, 5 vol% or more, 10 vol% or more, or 15 vol% or more relative to the total amount of solvent components in the electrolyte. When the amount of the quaternary fluorine solvent is within the above range, the solubility of the electrolyte in the electrolyte tends to be further improved, or the SEI layer tends to be formed more easily. The upper limit of the amount of the quaternary fluorine solvent is not particularly limited, and the amount of the quaternary fluorine solvent may be 40 vol% or less, 35 vol% or less, 30 vol% or less, 25 vol% or less, or 20 vol% or less, or 15 vol% or less, relative to the total amount of solvent components in the electrolyte.

[0302] The content of the ether subsolvent in the electrolyte is not particularly limited, but it is preferably 5% or more by volume, 10% or more by volume, 15% or more by volume, 20% or more by volume, 25% or more by volume, 30% or more by volume, or 35% or more by volume, relative to the total amount of solvent components in the electrolyte. The content of the ether subsolvent may be 50% or less by volume, 45% or less by volume, 40% or less by volume, 35% or less by volume, 30% or less by volume, 25% or less by volume, 20% or less by volume, 15% or less by volume, or 10% or less by volume. When the ether subsolvent is within the above range, the cycle characteristics of the battery tend to improve further.

[0303] If the electrolyte contains a non-ether secondary solvent, the content of the non-ether secondary solvent is not particularly limited and may be 0% or more by volume, 5% or more by volume, 10% or more by volume, or 15% or more by volume, relative to the total amount of solvent components of the electrolyte. Alternatively, the content of the non-ether secondary solvent may be 50% or less by volume, 40% or less by volume, 30% or less by volume, 25% or less by volume, 20% or less by volume, 15% or less by volume, or 10% or less by volume.

[0304] In addition, compounds containing fluorine functional groups in aromatic compounds such as benzene can also be suitably used. Examples include fluorobenzene, fluoroanisole, fluorobiphenyl, and fluorocyclohexylbenzene.

[0305] -Electrolytes- For example, lithium salts are used as electrolytes. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, (SO2F)2NLi, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, (C2F5SO2)NLi, LiN(CF3SO2)(C4F9SO2), LiC(CF3SO2)3, and LiPF Examples include 4(CF3)2, LiPF4(C2F5)2, LiPF4(CF3SO2)2, LiPF4(C2F5SO2)2, LiBF2(CF3)2, LiBF2(C2F5)2, LiBF2(CF3SO2)2, LiBF2(C2F5SO2)2, Li-cyclic 1,2-perfluoroethanedisulfonylimide, and Li-cyclic 1,3-perfluoropropanedisulfonylimide. Among these, LiPF6, LiBF4, LiClO4, (SO2F)2NLi, LiN(CF3SO2)2, and LiN(C2F5SO2)2 are preferred because they are easily soluble in solvents and exhibit a high degree of dissociation, with LiPF6, LiBF4(SO2F)2NLi, and (CF3SO2)2NLi being particularly preferred.

[0306] These electrolytes can be used individually or in combination of two or more types.

[0307] Furthermore, to enhance the function of the protective layer that suppresses degradation reactions in the negative and positive electrodes, LiBOB (Lithium bis(oxalate)boric acid), LiDFOB (Lithium difluoro(oxalato)borate), etc., can be suitably added and used at concentrations that yield the optimal effect.

[0308] Also, the cation is Na + , K + Adding at least one electrolyte salt selected from the above changes the chemical structure of SEI, which enhances the effect of suppressing degradation reactions and is therefore preferable.

[0309] The electrolyte of the present invention can be suitably used at higher electrolyte salt concentrations than usual in order to achieve high durability. The lower limit of the electrolyte salt concentration is greater than 1.0 mol / L, preferably 1.5 mol / L or higher, more preferably 2.0 mol / L or higher, more preferably 3.0 mol / L or higher, more preferably 5.0 mol / L or higher, more preferably 6.0 mol / L or higher, and more preferably 7.0 mol / L or higher.

[0310] The upper limit of the electrolyte salt concentration is preferably greater than 1.0 mol / L, preferably 8.0 mol / L or less, more preferably 7.0 mol / L or more, even more preferably 6.0 mol / L or less, even more preferably 5.0 mol / L or less, even more preferably 4.0 mol / L or less, and even more preferably 2.0 mol / L or less.

[0311] A significant phenomenon in battery degradation is the decrease in the number of lithium ions moving between the positive and negative electrodes during charging and discharging. This decrease is due to degradation reactions at the positive and / or negative electrodes, where lithium ions are incorporated into the compounds produced during degradation. To suppress the increase in resistance due to ion deficiency at the starting point of this degradation, it is possible to suitably maintain a certain amount or more of ions, which are normally in excess.

[0312] This standard can be suitably defined per unit weight of positive electrode material, and its effectiveness is achieved by dissolving 0.1 mmol or more lithium ions per gram of positive electrode material in the electrolyte. Since this ion amount is proportional to the amount of electrolyte, it is related to the space within the electrode where the electrolyte can exist. In other words, it varies depending on the surface weight and volume density of the electrode material, which are design parameters of the positive and negative electrodes, and the amount of electrolyte is most limited in the case of a high electrode material content composition, low surface weight, and high volume density.

[0313] Previously, high electrolyte salt concentrations in battery manufacturing were problematic due to the time it took for them to penetrate separators and electrodes. However, in addition to conventional vacuum impregnation methods and high-temperature storage before and after charging and discharging, methods such as heating methods, which involve heating the battery, injection equipment, and electrolyte before injection, and multi-stage pressurization methods with time differences, can now be used to manufacture them industrially.

[0314] Previously, high electrolyte salt concentrations in battery manufacturing were problematic due to the time it took for them to penetrate the separator and electrodes. Therefore, low-viscosity organic solvents that do not degrade during charge-discharge reactions, low-molecular-weight organic solvents, and various additives that improve impregnation properties can be suitably used. Furthermore, suitable manufacturing methods include conventional vacuum impregnation methods and high-temperature standing before and after charge-discharge, as well as heating methods in which batteries, injection equipment, and electrolytes are heated before injection, and multi-stage pressurization methods with time differences, making industrial production possible.

[0315] As the electrolyte, a gel-like electrolyte may be used that contains a polymer compound that swells in an organic solvent to form a retainer that holds the non-aqueous electrolyte. Including a polymer compound that swells in an organic solvent allows for high ionic conductivity, excellent charge-discharge efficiency, and prevention of battery leakage, making it preferable. The content of such polymer compound is preferably in the range of 0.1 to 10% by weight of the electrolyte.

[0316] (Specific examples of lithium-ion batteries) Figure 3 shows an example of the cross-sectional structure of a coin-type lithium-ion battery 200 according to one embodiment of this model. This lithium-ion battery 200 has a disc-shaped positive electrode 212 housed in a metal casing 211 and a disc-shaped negative electrode 214 housed in a metal casing 113, which are stacked via a separator 215. A metal spring 218 and a spacer 219 are placed between the casing 213 and the negative electrode 214. The interiors of the casing 211 and 213 are filled with a liquid electrolyte, and the peripheral edges of the casing 211 and 213 are sealed by crimping via a seal gasket 217.

[0317] (Manufacturing method for lithium-ion secondary batteries) A lithium-ion secondary battery according to the present invention can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator in between, winding or folding them as needed according to the battery shape, placing them in a battery container made of an outer material, injecting an electrolyte into the battery container, and sealing it. To prevent pressure rise inside the secondary battery, overcharging and discharging, etc., an overcurrent prevention element such as a fuse or PTC element, expanded metal, lead plates, etc. may be provided as needed. The shape of the secondary battery may be any of the following: coin type, button type, sheet type, cylindrical type, rectangular type, flat type, etc.

[0318] Laminated batteries, in particular, which use an outer casing made of a polymer sheet laminated onto a lightweight, high-performance metal core, are preferably used.

[0319] Typically, an aluminum core foil is used, laminated with multiple polymer sheets according to its function. However, by appropriately selecting the materials of the core foil and polymer sheets, it is possible to suitably use an exterior material that is optimal for the application.

[0320] Depending on the application, factors such as bending and vibration in mechanical properties, ambient temperature, and altitude (atmospheric pressure) may be important, and by designing according to each purpose, the application can be optimally satisfied. For example, when manufacturing large cells for EV batteries, the laminate film is deeply pressed and molded, so flexible and stretch-resistant core foil and resin can be optimally selected. When EVs such as commercial vehicles and transport vehicles experience significant vibration during operation, the material and thickness of the core foil and resin can be optimally selected to withstand this vibration. Furthermore, for space applications, the material and thickness of the core foil and resin can be optimally selected to withstand vacuum and minimize electrolyte evaporation.

[0321] Suitable materials for the core foil include aluminum, copper, stainless steel, nickel, gold, and silver. The thickness of the metal foil is preferably about 1 to 200 μm. The laminate film outer packaging material consists of at least a metal core foil laminated with a polymer resin layer (hereinafter referred to as the sealing resin layer) as a sealing material. Examples of materials that can be used for the sealing resin layer include polyethylene, polypropylene, ionomer resin, acid-modified polyethylene such as maleic acid-modified polyethylene, acid-modified polypropylene such as maleic acid-modified polypropylene, ethylene acrylic acid copolymer, ethylene methacrylic acid copolymer, and heat-sealable resins such as carboxylated resins. The thickness of the sealing resin layer is preferably about 1 to 200 μm. A heat-resistant resin layer made of polyethylene terephthalate or nylon may be formed on the metal foil surface opposite to the sealing resin layer.

[0322] During heat fusion, the surface resin (outer layer) of the sealant resin needs to melt. Furthermore, it is desirable that the resin being combined (inner layer) does not melt or flow under any circumstances. The same materials as those used for the single-layer application can be used for the outer layer of the heat-fused resin, with polyethylene and polypropylene being practical choices.

[0323] Examples of resins to be combined (inner layer) include polyethylene terephthalate, polytetrafluoroethylene, aramid resins, polyimide, polyamide, and polyester. Furthermore, even if different materials are not used, such as with popylene, it is possible to achieve a difference in melting point between the surface and lower layers by using a copolymer with a low melting point for the resin in the heat-sealed portion. In this case, even if there is no difference in melting point, it is possible to make the lower layer have a high melt viscosity and obtain dimensional stability of the resin by controlling the molecular weight, copolymerization ratio, and molecular structure. In these cases, there is also the advantage that an integrated structure can be easily obtained by co-extrusion or multi-layer coating without adopting a bonded structure.

[0324] By using a resin core material with a melting point at least 20°C higher than the surface layer, and by positioning the resin covering the terminals to protrude beyond the end face of the heat-sealed portion when sealing the terminals, it is possible to provide a battery in which short circuits between terminals are extremely unlikely to occur.

[0325] When adopting a multilayer structure of two or more layers as described above, the multilayer structure may be created by laminating sheet-like resin layers, or by forming a multilayer structure by applying, for example, a heat-sealable layer (outer layer). In the latter case, the heat-sealable resin is diluted with a solvent such as toluene to make a solution, which is then applied to a high-melting-point resin substrate with a brush or dispenser, and then heated and dried.

[0326] Specifically, commercially available moisture-resistant grade polyethylene, polypropylene, modified polyethylene, modified polypropylene, and other olefin resins can be used. For the bonding surface with the electrode terminal lead, metal-adhesive polyolefin resins such as Bondine (manufactured by Sumitomo Chemical Co., Ltd.) and Polytac (manufactured by Idemitsu Petrochemical Co., Ltd.) can also be used. Furthermore, to achieve both good adhesion to the electrode terminal lead and good heat fusion with the exterior material, acid-modified polyolefins such as acid-modified polypropylene are preferable. It is also possible to use a mixture of two or more of these. In addition, to prevent short circuits even at higher pressures and temperatures, it is effective to provide a stronger, higher-melting-point resin layer in the sealant structure.

[0327] <Application> The carbon material of the present invention can exhibit its functionality and be effectively utilized in any electrochemical device other than the lithium-ion secondary battery described above. Specifically, it has functions such as acting as an internal conductive path in electrodes when electron transfer is involved in device reactions, providing reinforcement when electrodes undergo physical deformation, and preventing direct contact between a third material (such as a catalyst) and the reaction material by utilizing the durability of graphene when the reaction material is in an oxidized or reduced state.

[0328] Examples of usable devices include non-aqueous electrolyte batteries such as lithium-ion batteries, sodium-ion batteries, potassium-ion batteries, magnesium-ion batteries, calcium-ion batteries, aluminum-ion batteries, lithium-sulfur batteries, and lithium-air batteries; inorganic solid electrolyte batteries such as sulfide-based solid electrolytes and oxide-based solid electrolytes; and semi-solid batteries such as polymer solid electrolyte batteries such as polyethylene oxide-based batteries, and polymer gel electrolyte batteries in which electrolyte is contained in PVDF, etc.

[0329] These devices utilize readily graphitizable carbon, non-graphitizable carbon, graphite, lithium alloy materials such as silicon and tin, and other metallic materials such as lithium as negative electrode active materials. Similarly, lithium-containing metal oxides, particularly lithium-containing transition metal oxides with layered, spinel, or olivine structures, lithium-free metal oxides, organic positive electrode materials, charge-transfer complex positive electrode materials, sulfur, and fluoride-based materials are used as positive electrode active materials. The carbon material of the present invention is capable of effectively enhancing conductivity for any of these active materials. Furthermore, the carbon material of the present invention is also suitable as a material for lithium-sulfur batteries, as described in publications such as WO2018 / 225619, JP 2023-501679, JP 2019-517116, and JP 2022-191280.

[0330] The carbon material of the present invention can also be suitably used in organic electrolyte capacitors, aqueous electrolyte capacitors, and aqueous solution batteries. In fuel cells, it can be used in PEFCs, SOFCs, DMPCs, etc., and in particular, it can be used not only to impart conductivity to electrodes but also as a support for oxidation-reduction catalysts.

[0331] The carbon material of the present invention can be used for applications other than electrochemical devices. Other suitable applications include, for example, electronic device systems such as graphene-based sensors, electromagnetic interference suppression materials, antenna modules, heat dissipation substrates, heat exchange devices, separation membranes, reverse osmosis membranes, transparent electrode materials, structural materials that take advantage of mechanical flexibility, and conductive inks and pastes. Furthermore, in response to the demand for vehicle weight reduction, which directly contributes to reducing carbon dioxide emissions and saving energy, the material can be suitably used in applications that lead to weight reduction by taking advantage of its hollow shape, such as reinforcing agents for various types of rubber including tires, paints, coloring pigments, conductive fillers for various polymers, and additives for magnetic recording media. [Examples]

[0332] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%", "ppm", and "parts" used to express quantities refer to weight unless otherwise specified.

[0333] (Experiment 1): Fabrication of carbon material, dispersion, battery composition, battery slurry, electrodes, and lithium-ion secondary battery, and evaluation of battery testing. <Example 1> (Manufacturing of carbon material A for positive electrode conductive additive) -CVD reaction: carbon layer formation- Fumed silica (SiO2 / AEROSIL(registered trademark) NX90G; particle size 38 nm, BET specific surface area 71 m²) is used as a template for carbonaceous films. 2 Approximately 1 g of carbonaceous earth (carbon content 0.5-1.5%, manufactured by Nippon Aerosil Co., Ltd.) was spread on a quartz boat and placed in the center of a quartz reaction tube in a horizontal CVD apparatus (transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). Argon gas was flowed into the reaction tube at a flow rate of 400 mL / min while the temperature was raised to 900°C at a heating rate of 10°C / min and held for 30 minutes. While maintaining 900°C, argon gas was flowed at a flow rate of 320 mL / min while methane gas was flowed at a flow rate of 80 mL / min (raw material gas concentration 20%) and held for 90 minutes. After that, the mixture was cooled to room temperature while argon gas was flowed at a flow rate of 400 mL / min, and the carbonaceous-template laminate was removed. At this time, it was confirmed by electron microscopy that the template was an aggregate in which primary particles had multiple branched structures linked together in a bead-like manner.

[0334] -Mold removal- Next, the template was removed from the resulting laminate by the following procedure to obtain the carbon material. (1) The carbonaceous template laminate was placed in a 100 mL PFA beaker, and ultrapure water was added until the entire sample was wet. (2) After adding 46% hydrofluoric acid, the mixture was stirred with a stirrer for 2 hours. (3) After stirring was stopped, the sample was left to stand until it settled. (4) Using a PTFE membrane filter (47 mmφ, pore size 0.1 μm), the supernatant was filtered by suction. (5) The sample on the filter paper was washed with approximately 39 mL of ultrapure water and filtered by suction. This procedure was repeated three times. (6) The sample on the filter paper was collected and returned to the original PFA beaker. (7) Repeated the operations in (2) to (6). (8) Add approximately 40 mL of ultrapure water and stir with a stirrer for 1 hour. (9) After stirring was stopped, the sample was allowed to stand until it settled. (10) Discard the supernatant, add 5% caustic soda, and stir for 12 hours while heating to 80°C. (11) After stirring was stopped, the sample was allowed to stand until it settled. (12) Using a PTFE membrane filter (47 mmφ, pore size 0.1 μm), the supernatant was filtered by suction. (13) The sample on the filter paper was washed with ultrapure water and filtered by suction. This procedure was repeated until the filtrate was neutral. (14) The sample on the filter paper was collected in a Petri dish and dried in a 110°C oven for 8 hours.

[0335] -Heat treatment- The carbon material obtained above was placed in a rectangular high-temperature heating furnace (manufactured by Izumi Tech Co., Ltd.) under reduced pressure (10 -1 After heating to the Pa order, the material was heated to 1800°C under argon gas flow (10 mL / min) at a heating rate of 15°C / min and held at that temperature for 1 hour for calcination. After that, it was cooled to room temperature, and the calcined carbon material was removed to obtain heat-treated graphene-containing carbon material A.

[0336] (Method for measuring the oil absorption of carbon materials) The amount of oil absorbed by the obtained carbon material was measured in accordance with "JIS K5101-13-1 Pigment Test Methods - Part 13: Oil Absorption - Section 1: Refined Linseed Oil Method". The results are shown in Table 1.

[0337] [Table 1]

[0338] (Transmission electron microscope observation) The shape of the obtained carbon material was observed using a transmission electron microscope (TEM: JEM-ARM300F, manufactured by JEOL Ltd.). The observation of the carbon material using a transmission electron microscope (TEM) was performed at an acceleration voltage of 80 kV. From the TEM image (Figure 1), it was confirmed that the carbonaceous layer of the carbon material of the present invention has a graphene structure consisting of a six-membered carbon ring structure. Furthermore, it was confirmed that the carbon material of the example has a structure in which granular shapes with pores surrounded by carbonaceous shells are connected.

[0339] (Nitrogen adsorption / desorption measurement) Nitrogen adsorption and desorption measurements were performed on the obtained carbon material using an automated specific surface area / pore size distribution analyzer (BELSORP MINI, manufactured by Microtrac-Bel Co., Ltd.). Before measurement, the sample was dried under reduced pressure at 150°C for 6 hours using BEL pre. From the obtained adsorption isotherms, the BET specific surface area was determined using the BET method. The applicable range of the BET method was set to P / P0 = 0.05 to 0.3. Furthermore, based on the obtained adsorption and desorption isotherms, the total pore volume was measured by converting the amount of nitrogen adsorbed at -196°C and a relative pressure of P / P0 = 0.96 to the volume of liquid nitrogen density. The results are shown in Table 1. The pore size distribution was determined by the BJH method.

[0340] (Raman spectroscopy measurement) Raman spectroscopy was performed on the obtained carbon material using a micro-Raman spectrometer (LabRAM HR-800, Horiba, Ltd.). A 532 nm laser was used, with the filter set to D1 and the hole to 100 μm. The measurement range was 300–3500 cm². -1 This was determined from the measured Raman spectrum (I G / I 2D ), (I D / I G The intensity ratios of ) and other factors were calculated and are shown in Table 1.

[0341] (Fabrication of positive electrode) The active material is a ternary cathode material NCM (Li) with an average particle size of 11 μm. 1.0Ni 0.5 Co 0.2 Mn 0.3 97.0 wt% of O2 (Kelong) powder, 1.0 wt% of the above-mentioned carbon material A as a conductive additive, and 2 wt% of PVDF (Soleph) were mixed with N-methylpyrrolidone (NMP) as a solvent. The conductive additive used was a dispersion of carbon material A in NMP solvent. The mixture of the active material, conductive additive, and PVDF was placed in a planetary mixer and kneaded at a rotation speed of 2000 rpm while adding NMP in several batches until a uniform and appropriate viscosity was achieved to prepare a cathode slurry. This slurry was applied to 15 μm thick aluminum foil at a constant speed using a doctor blade coating device with a micrometer. Then, it was dried in a vacuum dryer set to 110°C to obtain a cathode base. Subsequently, the cathode base was punched out using a φ14 mm punch-type die-cutting machine, pressurized with 45 kN using a cylinder-type jig, and then vacuum dried at 120°C to obtain a cathode electrode for battery integration.

[0342] (Fabrication of negative electrode) As the negative electrode material, 96.5% spheroidized natural graphite powder (manufactured by Eitan Co., Ltd.) with an average particle size of 15 μm was used. As conductive additives, 2.0% by weight of the above-mentioned acetylene black, 1% by weight of CMC, and 1% by weight of SBR (styrene-butadiene rubber) were added and mixed with distilled water as the solvent. The mixture of negative electrode material, conductive additive, CMC, and SBR was placed in a planetary mixer and kneaded at a rotation speed of 2000 rpm while adding NMP in several batches until a uniform and appropriate viscosity was achieved, thereby preparing a negative electrode slurry. This slurry was applied to 10 μm thick rolled copper foil at a constant speed using a doctor blade coating device with a micrometer. After that, it was dried in a vacuum dryer set to 110°C to obtain a negative electrode base. Subsequently, the negative electrode base was punched out using a φ15 mm punch-type die-cutting machine, pressurized with 10 kN using a cylinder-type jig, and then vacuum dried at 120°C to obtain a positive electrode for battery integration.

[0343] (Manufacturing of lithium-ion secondary batteries) Using the positive electrode and negative electrode prepared as described above, a 25 μm thick separator (microporous film made of polypropylene) was placed between the positive electrode mixture layer and the negative electrode mixture layer. A 1.0 mol / L solution of the electrolyte salt LiPF6 (a 1:1 mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC)) was added as the electrolyte, and the device was crimped and sealed to produce a 2032 size coin-type test battery. After that, it was washed with ethanol and subjected to the battery evaluation described below.

[0344] <Comparative Example 1> The positive electrode composition is a ternary positive electrode material NCM (LiNi 0.5 Co 0.2 Mn 0.3 A test battery was manufactured under the same conditions as in Example 1, except that it contained 97.0% by weight of O2 powder (manufactured by Kelong), 1.0% by weight of acetylene black (manufactured by Denka Co., Ltd., product name: DENKA BLACK Li-100) and 2% by weight of PVDF (manufactured by Soref) as conductive additives.

[0345] <Comparative Example 2> The positive electrode composition is a ternary positive electrode material NCM (LiNi 0.5 Co 0.2 Mn 0.3 A test battery was manufactured under the same conditions as in Example 1, except that it contained 97.0% by weight of O2 powder (manufactured by Kelong), 1.0% by weight of Ketjenblack (manufactured by Lion Specialty Chemicals, trade name: Ketjenblack EC600JD) and 2% by weight of PVDF (manufactured by Solev) as conductive additives.

[0346] (Battery durability performance evaluation method) The battery durability performance was evaluated using the fabricated test batteries according to the following procedure, and the capacity retention rate and 2C rate maintenance rate after the durability test were determined.

[0347] This test evaluation method combines conditions that reduce durability, such as high temperature, high voltage, and continuous charging, and is a good indicator for understanding durability performance.

[0348] Each test battery was energized at room temperature with a constant current of 1.17mA (equivalent to 0.2C) until it reached 4.4V. After reaching 4.4V, it was charged at a constant voltage until it reached 0.29mA (0.05C). Then, it was discharged to 2.7V with a constant current of 1.17mA. Next, using the same test battery, float charging was performed at 45°C with a constant current of 1.17mA (equivalent to 0.2C) until it reached 4.4V, and charging was continued for 4 weeks.

[0349] Subsequently, the battery was returned to room temperature and discharged to 2.7V at room temperature with a constant current of 1.17mA. Then, it was energized again at room temperature with a constant current of 1.17mA (equivalent to 0.2C) to 4.4V, and after reaching 4.4V, it was charged at a constant voltage and continued until it reached 0.29mA (0.05C). After that, it was discharged to 2.7V with a constant current of 11.7mA (equivalent to 2C). From the discharge capacity of the obtained test battery, the 2C maintenance rate after float (2C capacity ÷ 0.2C capacity) was calculated. The evaluation test flow is shown in Figure 4. The physical properties of the positive electrode conductive additive used in Experiment 1 are shown in Table 1. The battery evaluation test results are shown in Table 2. It was found that by using the carbon material of the present invention as a positive electrode conductive additive, a rechargeable battery with excellent durability can be realized.

[0350] [Table 2]

[0351] (Experiment 2): Test evaluation based on different electrolyte salt concentrations in the electrolyte solution. <Example 2> A test battery was manufactured under the same conditions as in Example 1, except that a 1.0 mol / L solution of LiFSI (a 1:4 mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC)) was added as the electrolyte, and a polyester fiber-containing glass fiber separator (30 μm thick, 70% porosity) was used as the separator.

[0352] <Example 3> A test battery was manufactured under the same conditions as in Example 2, except that a 1.5 mol / L solution of LiFSI (a 1:4 mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC)) was added as the electrolyte.

[0353] <Example 4> A test battery was manufactured under the same conditions as in Example 2, except that a 2.0 mol / L solution of LiFSI (a 1:4 mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC)) was added as the electrolyte.

[0354] <Example 5> A test battery was manufactured under the same conditions as in Example 2, except that a 3.0 mol / L solution of LiFSI (a 1:4 mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC)) was added as the electrolyte.

[0355] <Example 6> A test battery was manufactured under the same conditions as in Example 2, except that a 4.0 mol / L solution of LiFSI (a 1:4 mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC)) was added as the electrolyte.

[0356] <Example 7> A test battery was manufactured under the same conditions as in Example 2, except that a 5.0 mol / L solution of LiFSI (a 1:4 mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC)) was added as the electrolyte.

[0357] <Example 8> A test battery was manufactured under the same conditions as in Example 2, except that a 5.5 mol / L solution of LiFSI (a 1:4 mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC)) was added as the electrolyte.

[0358] In Experiment 2, as in Experiment 1, the evaluation test was conducted according to the evaluation test flow (Figure 4), and the results are shown in Table 3.

[0359] Table 3

Claims

1. A positive electrode consisting of a current collector containing Al as a conductor, a positive electrode material, a conductive additive, and a binder. A negative electrode consisting of a current collector containing Cu as a conductor, a negative electrode material, and a binder. An electrode element containing an electrolyte solution consisting of an organic solvent and an electrolyte salt, and a porous separator is enclosed in an outer casing, and the electrolyte salt concentration of the electrolyte solution is greater than 1 mol / L. The total pore volume determined by nitrogen adsorption / desorption is greater than 1.0 cc / g The value obtained by dividing the BET specific surface area by the total pore volume is 400 m². ２ Carbon material smaller than / cc A lithium-ion battery characterized by containing at least one positive electrode conductive additive.

2. ABO ２ In lithium transition metal compounds of type A = Li ｘ In this case, x is in the range of 0.96 to 1.05, and the transition metal B is mainly selected from Ni, Mn, and Co. α Mn β Co γ The lithium-ion storage battery according to claim 1, wherein the cathode material has an atomic ratio in the range of α = 0.8 to 1.0, β = 0 to 0.3, and γ = 0 to 0.

2.

3. The above ABO ２ A lithium-ion battery according to claim 1, which uses a cathode material in which metal elements excluding transition metals are included in B.

4. A lithium-ion battery according to claim 1, using a negative electrode material comprising at least one selected from graphite, non-graphitizable carbon, easily graphitizable carbon, silicon, and tin.

5. Chemical formula H ｔ C ｕ N ｖ O ｗ F ｘ P ｙ S ｚ The lithium ion battery according to claim 1, characterized in that an organic solvent represented by (where t or u or v or w or x or y or z is an integer greater than 0 and less than 16) is used as an electrolytic solution solvent.

6. A lithium-ion battery according to claim 1, wherein at least one selected from carbonate esters, carboxylic acid esters, ethers, sulfate esters, phosphate esters, and nitrogen compounds is used as an organic solvent.

7. Cation Li ＋ To use anions as PF ６ － , BF ４ － , FSI － TFSI － , BOB － DFOB － A lithium-ion battery according to claim 1, using an electrolyte salt for the electrolyte solution which is selected from at least one of the following.

8. A lithium-ion battery according to claim 1, using an electrolyte solution having an electrolyte salt concentration of 3 mol / L or more.

9. A lithium-ion battery according to claim 1, wherein at least one selected from Ketjenblack, carbon nanotubes, and graphene mesosponge is mixed with a positive electrode conductive additive.

10. A lithium-ion battery according to claim 1, comprising a porous separator having at least a coating layer made of organic and / or inorganic material.

11. A lithium-ion battery according to claim 1, which uses a cathode material having a composition containing at least one of the elements Li, C, N, O, F, P, and S arranged on the surface of the cathode material particles.

12. A lithium-ion battery according to claim 1, which uses a negative electrode in which a compound containing at least one of the elements Li, C, N, O, F, P, and S is placed near the negative electrode material particles.

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