Positive electrode and lithium-ion battery

Abstract

The present invention provides a positive electrode and a lithium-ion battery suitable for constructing a lithium-ion battery with excellent voltage characteristics during high-power discharge. [Solution] A positive electrode comprising a current collector and a positive electrode composite layer formed on the current collector, wherein the positive electrode composite layer contains a positive electrode active material, a binder, and a conductive additive containing a carbon material, and in the Raman spectrum of the carbon material measured in the positive electrode composite layer, the intensity of the D band is higher than the intensity of the 2D band.

Description

[Technical Field]

[0001] This invention relates to a positive electrode and a lithium-ion battery. [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). As a result, lithium-ion battery manufacturing faces ongoing competition in terms of cost, as well as continuous demands for higher performance in the market. For EVs, which emit less carbon dioxide (CO2), to replace gasoline-powered vehicles in order to protect the global environment, the lithium-ion batteries they use need to have high performance characteristics such as rapid discharge, long lifespan, high capacity, and charge / discharge characteristics.

[0003] In lithium-ion batteries, where such high performance is required, carbon materials are widely used. For example, Patent Document 1 discloses that in a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte, flaky graphite and carbon black are used as conductive additives, and high-rate discharge characteristics can be improved. However, even with the use of such carbon materials, there is a problem, for example, that the voltage characteristics during high-power discharge are not sufficient. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2004-22177 [Overview of the project] [Problems that the invention aims to solve]

[0005] The object of the present invention is to provide a positive electrode and a lithium-ion battery suitable for constructing a lithium-ion battery with excellent voltage characteristics during high-power discharge. [Means for solving the problem]

[0006] To achieve the above object, the gist configuration of the present invention is as follows. [1] A positive electrode comprising a current collector and a positive electrode composite layer formed on the current collector, where the positive electrode composite layer contains a positive electrode active material, a binder, and a conductive auxiliary agent containing a carbon material, a positive electrode in which the intensity of the D band is higher than the intensity of the 2D band in the Raman spectrum of the carbon material measured in the positive electrode composite layer. [2] The positive electrode according to [1], wherein the Raman spectrum is measured at the position of the surface of the positive electrode composite layer. [3] The positive electrode according to [1] or [2], wherein the carbon material has a space in at least one of the outside and the inside. [4] The intensity ratio (I 2D , D , G , D , , , G , 2D , , D , , G , D , G , 2D ) of the intensity of the D band (I D ) to the intensity of the 2D band (I 2D / I D ) in the Raman spectrum is 0.10 or more and 0.90 or less. The positive electrode according to any one of [1] to [3]. [5] The intensity ratio (I D ) of the intensity of the D band (I G ) to the intensity of the G band (I D / I G ) in the Raman spectrum is 0.5 or more. The positive electrode according to any one of [1] to [4]. [6] The intensity ratio (I[4]] 2D ) of the intensity of the 2D band (I G ) to the intensity of the G band (I 2D / I G ) in the Raman spectrum is 0.10 or more. The positive electrode according to any one of [1] to [5]. [7] The carbon material includes one or more connected structures having an extended shape in which a plurality of hollow particle-like portions formed of an enclosure wall made of a carbonaceous material including a graphene structure and partitioning an internal space are connected in a bead-like manner, and pores are formed in the connected structure. The positive electrode according to any one of [1] to [6]. [8] A lithium ion battery comprising the positive electrode according to any one of [1] to [7]. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide electrodes and lithium-ion batteries that are suitable for constructing lithium-ion batteries with excellent voltage characteristics during high-power discharge. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing an example of a lithium-ion battery according to an embodiment. [Figure 2] Figure 2 is a diagram used to explain the Raman mapping measurement in the example. [Figure 3] Figure 3 shows the results of the Raman spectra measured for Example 13. [Figure 4] Figure 4 is a schematic diagram illustrating the ultra-high-sensitivity vacuum thermodynamic desorption mass spectrometer used for thermodynamic desorption mass spectrometry. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below, and various modifications are possible without altering the essence of the invention.

[0010] <<Positive electrode>> The positive electrode of this embodiment is a positive electrode comprising a current collector and a positive electrode composite layer formed on the current collector, wherein the positive electrode composite layer contains a positive electrode active material, a binder, and a conductive additive containing a carbon material, and the intensity of the D band in the Raman spectrum of the carbon material measured in the positive electrode composite layer is higher than the intensity of the 2D band.

[0011] In the Raman spectrum of the carbon material measured in the positive electrode composite layer, the D band is at wavenumber 1356 cm⁻¹. -1 This is a peak located nearby, indicating sp3 bonding (CH stretching motion) in carbon materials. The 2D band is at wavenumber 2680 cm⁻¹. -1The nearby peak indicates secondary phonon scattering (CH stretching motion) in carbon materials. The 2D band indicates the number of graphene layers in the carbon material. The G band corresponds to wavenumber 1593 cm⁻¹. -1 This is a peak located nearby, indicating sp2 bonding (aromatic ring C=C stretching motion) in carbon materials.

[0012] The higher intensity of the D-band compared to the 2D-band allows for lithium-ion batteries with superior voltage characteristics during high-power discharge. While the reason for this is not entirely clear, it is presumed to be as follows: The D band originates from the disordered structure resulting from the breaking of sp2 bonds in layers where the six-membered ring structure of carbon extends planarly, while the 2D band indicates the number of graphene layers stacked. Because carbon materials adopt a so-called structural structure in which primary particles are linked, spaces for holding electrolyte are easily created. When the intensity of the D band is higher than the intensity of the 2D band, the disordered structure increases compared to the stacked structure, and the space for holding electrolyte increases, which is thought to reduce the voltage fluctuation range during high-power discharge.

[0013] Intensity of 2D bands in Raman spectra (I 2D ) D-band intensity (I D Intensity ratio (I 2D / I D The value is preferably between 0.10 and 0.90, more preferably between 0.20 and 0.85, and even more preferably between 0.25 and 0.80. Within the above numerical range, excellent voltage characteristics during high-power discharge are more likely to be obtained.

[0014] Intensity of the D band in the Raman spectrum (I D ) G-band intensity (I G Intensity ratio (I D / I G The voltage range is preferably 0.50 to 2.50, more preferably 1.00 to 2.20, and even more preferably 1.40 to 2.00. Within the above numerical range, excellent voltage characteristics during high-power discharge are more likely to be obtained.

[0015] Intensity of 2D bands in Raman spectra (I 2D ) G-band intensity (I G Intensity ratio (I 2D / I G The value is preferably between 0.10 and 2.00, more preferably between 0.25 and 1.60, and even more preferably between 0.38 and 1.40. Within the above numerical range, excellent voltage characteristics during high-power discharge are more likely to be obtained.

[0016] The Raman spectrum can be measured at any position in the positive electrode composite layer, for example, at the surface of the positive electrode composite layer.

[0017] <Current collector> The current collector is not particularly limited as long as it is one that is normally used in the positive electrode of a lithium-ion battery, but aluminum foil, nickel foil, titanium foil, and stainless steel foil are preferred, and rolled aluminum foil is more preferred.

[0018] <Positive electrode composite layer> The positive electrode composite layer contains a positive electrode active material, a binder, and a conductive additive containing a carbon material.

[0019] [Cathode active material] Examples of positive electrode active materials include those used in the positive electrodes of lithium-ion batteries.

[0020] The positive electrode active material is not particularly limited, and the optimal composition can be appropriately selected from viewpoints such as material manufacturability, electrode manufacturability, charge / discharge capacity, cycle characteristics, storage characteristics, and safety.

[0021] Examples of positive electrode active materials include transition metal compounds containing lithium. Preferably, the material is highly improved so that the deintercalation and deintercalation reactions of lithium ions in the compound crystal structure during charge-discharge cycles are less prone to crystal structure destruction or defects in deintercalation and deintercalation.

[0022] The positive electrode active material is an ABO2 type lithium transition metal compound, where A is Li x(x = 0.96 to 1.05), and B is preferably a compound containing Ni (when Ni α is used, α = 0.8 to 1.05). B may further contain Mn (when Mn β is used, β = 0.3 or less) and / or Co (when Co γ is used, γ = 0.2 or less), and may also contain elements other than Ni, Mn, and Co.

[0023] Examples of other elements that the above transition metal compound may contain include Mg, Ti, V, Nb, Ta, Cr, Fe, Cu, Zn, Al, Ga, Ge, Sn, Si, S, P, F, B, Na, etc. These elements preferably exist in a single-phase solid solution form incorporated into the crystal structure or in a compound form such as an oxide. These preferably function as skeleton reinforcing elements that stabilize the whole or part of the crystal structure in the positive electrode active material.

[0024] By making the above skeleton reinforcing element present on the crystal surface, it is also possible to confine the catalytic activity of the transition metal oxide, prevent contact with an electrolytic solution, etc., and suppress oxidative degradation.

[0025] Also, as the positive electrode active material, lithium-manganese-based oxides (preferably LiMnO2, LiMn2O4), lithium-cobalt-based oxides (preferably LiCoO2), lithium-nickel-based oxides (preferably LiNiO2), lithium-nickel-manganese-based oxides (preferably LiNi 1-a Mn a O2(0 < a < 1), LiMn 2-b Ni b O4(0 < b < 2)), lithium-nickel-cobalt-based oxides (preferably LiNi 1-c Co c O2(0 < c < 1)), lithium-manganese-cobalt-based oxides (preferably LiCo 1-d Mn d O2(0 < d < 1), LiMn 2-e Co e O4(0 < e < 2)), lithium-nickel-manganese-cobalt-based oxides (preferably Li(Ni f Mng Co h )O2 (0 < f < 1, 0 < g < 1, 0 < h < 1, f + g + h = 1), Li(Ni j Mn k Co m )O4 (0 < j < 2, 0 < k < 2, 0 < m < 2, j + k + m = 2)), lithium-nickel-cobalt-transition metal (M) oxide (preferably Li(Ni p Co q Mn r M S )O2 (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, where 0 < p < 1, 0 < q < 1, 0 < r < 1, 0 < s < 1, and p + q + r + s = 1)) is preferred, and one or more of these compounds may be included.

[0026] Among these, from the viewpoint of enhancing the capacity characteristics and stability of the battery, LiCoO2, LiMnO2, LiNiO2, lithium-nickel-manganese-cobalt-based oxide (preferably Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.8 Mn 0.1 Co 0.1 )O2)), lithium-nickel-cobalt-aluminum-based oxide (preferably LiNi 0.8 Co 0.15 Al 0.05 O2), Li 0.975 Ni 1.025 O2 are preferred.

[0027] Also, as the positive electrode active material, the following compounds are also preferred. Li y Ni d M2 e O​​(In the formula, M2 is at least one element selected from the group consisting of cobalt, manganese, magnesium, aluminum, boron, titanium, vanadium, chromium, iron, copper, zinc, molybdenum, tin, calcium, strontium, tungsten, zirconium, and silicon, and y, d, e, and f are 0.8 ≤ y ≤ 1.2, 0.3 ≤ d ≤ 0.98, 0.02 ≤ e ≤ 0.7, and -0.1 ≤ f ≤ 0.2, respectively.)

[0028] Furthermore, as a positive electrode active material, a lithium atom-containing oxide (preferably an olivine-type lithium-containing phosphate compound) that is represented by the following formula (4) and has an olivine-type crystal structure is preferred as a highly stable material.

[0029] Li 1-x M x (AO4) Equation (4)

[0030] In formula (4) above, M is at least one metallic element 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 element selected from the group consisting of Si, S, P, and V, and x is greater than 0 and less than 1. Note that the value of x in formula (4) is selected according to the valencies of M and A such that the overall valency of formula (4) becomes 0.

[0031] Examples of olivine-type lithium-containing phosphate compounds include LiFePO4, LiCoPO4, LiMnPO4, Li 0.90 Ti 0.05 Nb 0.05 Fe 0.30 Co 0.30 Mn 0.30 PO4 is preferred, and LiFePO4 is more preferred because the iron compounds used as raw materials are readily available and inexpensive.

[0032] Furthermore, suitable positive electrode active materials include organic compounds such as polyaniline, polypyrrole, polyacene, disulfide compounds, polysulfide compounds, and N-fluoropyridinium salts.

[0033] The physical properties of the positive electrode active material are determined by requirements in the battery design and manufacturing process, which are constrained by the usage patterns of lithium-ion batteries. In the manufacturing of the positive electrode active material, process design and other measures are taken to achieve these desired physical properties. Examples of physical properties include powder particle size and distribution, specific surface area, and density.

[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 μm to 30 μm is preferred, and 1 μm to 10 μm is more preferred.

[0035] These positive electrode active materials can be used individually or in combination of two or more.

[0036] The proportion of active material in 100% by weight of the electrode composite film is not particularly limited, but is preferably 90.0% by weight or more and 99.5% by weight or less, more preferably 95.0% by weight or more and 99.0% by weight or less, and even more preferably 96.0% by weight or more and 99.0% by weight or less. When the proportion of active material is within the above range, battery capacity, conductivity, and adhesion are highly balanced.

[0037] [binder] Examples of binders include those used in the positive electrode of lithium-ion batteries.

[0038] The binder is a component that helps bond the positive electrode active material, conductive additive, and current collector, and is usually an organic polymer. Suitable binders 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. Furthermore, the binder may be a modified or derivative of the above-mentioned organic polymer.

[0039] In particular, fluororesins are preferred as binders, and polyvinylidene fluoride (PVDF) is especially preferred. The weight-average molecular weight of the binder can be appropriately selected according to the intended use of the electrode, and is preferably 10,000 to 8,000,000, with the following order of preference: 10,000 to 5,000,000, 50,000 to 5,000,000, 80,000 to 3,000,000, and 100,000 to 1,000,000. When the weight-average molecular weight of the binder is 10,000 or more, the strength of the coating film is improved, and when the weight-average molecular weight of the binder is 8,000,000 or less, the viscosity is reduced, making electrode formation easier.

[0040] Binders can be used individually or in combination of two or more types.

[0041] The binder content is preferably 0.7% to 5.0% by weight, more preferably 1.0% to 2.5% by weight, and even more preferably 1.0% to 2.2% by weight, relative to 100% by weight of the electrode composite film. When the binder content is within the above range, the adhesive strength between the active materials and between the active materials and the conductive additive can be improved, and consequently, the bonding strength between these materials and the current collector can be improved.

[0042] [Conductive additive] The conductive additive contains carbon material.

[0043] [Carbon materials] Examples of carbon materials include carbon materials (A) described below; such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black, among other types of carbon black.

[0044] The total pore volume (V) of the carbon material is a value measured by nitrogen adsorption / desorption measurement, and is preferably 0.05 cc / g or more, in the order of 0.50 cc / g or more, 1.00 cc / g or more, 1.50 cc / g or more, 2.00 cc / g or more, 2.20 cc / g or more, and 2.95 cc / g or more. Furthermore, the upper limit of the total pore volume (V) of the carbon material is preferably 20.00 cc / g or less, in the order of 15.00 cc / g or less, 10.00 cc / g or less, 8.00 cc / g or less, 7.00 cc / g or less, 6.10 cc / g or less, and 5.70 cc / g or less. Within the above range, the voltage characteristics during high-power discharge are further improved.

[0045] The BET specific surface area (S) of the carbon material is the specific surface area calculated from nitrogen adsorption as specified in JIS Z8830, preferably 50 m². 2 / g or more 2700m 2 It is less than / g and 100m 2 / g or more 2500m 2 / g or less, 300m 2 / g or more 2500m 2 / g or less, 500m 2 / g2000m 2 / g or less, 600m2 / g or more 1800m 2 / g or less, 800m 2 / g or more 1500m 2 The order of preference is from / g to below. Within the above range, the voltage characteristics during high-power discharge are further improved.

[0046] It is preferable that carbon materials have space on at least one side of their structure, both externally and internally. An example of a carbon material having external space is when it has a so-called structural structure. Carbon materials such as carbon black have a structural structure, which is an aggregate structure in which multiple primary particles are linked together with multiple branching points. The outer edge of this aggregate structure functions as a space that can hold an electrolyte. Furthermore, if the carbon material has large pores or other spaces inside, this also exhibits favorable electrolyte retention performance. When the carbon material has spaces on the outside and at least one of the inside, it is not necessarily limited to a structural structure; any structure, whether external or internal, can retain electrolyte, and this is thought to further reduce the voltage fluctuation range during high-power discharge.

[0047] (Carbon material (A)) The total pore volume (V) of the carbon material (A) is a value measured by nitrogen adsorption / desorption measurement, and is preferably 1.00 cc / g or more, in the order of 1.50 cc / g or more, 2.00 cc / g or more, 2.20 cc / g or more, and 2.95 cc / g or more. Furthermore, the upper limit of the total pore volume (V) of the carbon material (A) is preferably 20.00 cc / g or less, in the order of 15.00 cc / g or less, 10.00 cc / g or less, 8.00 cc / g or less, 7.00 cc / g or less, 6.10 cc / g or less, and 5.70 cc / g or less.

[0048] When the total pore volume of the carbon material (A) is 20.00 cc / g or less, the strength of the carbon material (A) is improved and the shape of the carbon material (A) tends to be maintained well. When the total pore volume of the carbon material (A) is 1.00 cc / g or more, the amount of electrolyte retained in the carbon material (A) increases. Thus, when the total pore volume of the carbon material (A) is within the above range, the carbon material (A) has good strength, contributes to the stability of the carbon material (A), and the shape of the carbon material (A) is maintained well. Therefore, the carbon material (A) can keep the balance between the electronic conductivity and the supply of ions retained in the pores well.

[0049] The state of the fine crystal structure of the carbon material (A) can be analyzed by Raman spectroscopy. In the Raman spectrum obtained by Raman spectroscopic measurement of the carbon material (A), the peak existing around the wave number 1593 cm -1 is called the G band and indicates the sp2 bond (aromatic ring C=C stretching motion) of the carbon material (A). Also, in the above Raman spectrum, the peak existing around the wave number 1356 cm -1 is called the D band and indicates the sp3 bond (C-H stretching motion) of the carbon material (A). When the sp2 bond is broken and the sp3 bond is formed, the D band increases. Also, in the above Raman spectrum, the peak existing around the wave number 2680 cm -1 is called the 2D band and indicates the second-order phonon scattering (C-H stretching motion). Also, the 2D band indicates the number of graphene layer stacks.

[0050] The intensity ratio (I G ) of the G band to the intensity of the 2D band (I 2D ) (I G / I 2D ) is said to be an index indicating the stacking state of the graphene layers (D. Graf, et al., NANO LETTERS, 7, 238-^{242}; (2007)). In the same paper, it is described that when the intensity ratio (I G / I 2D ) is 0.2, the graphene layer is one layer.

[0051] The intensity of the G band (I) in the Raman spectrum of carbon material (A) obtained by Raman spectroscopy. G ) 2D band intensity (I 2D Intensity ratio (I G / I 2D The strength ratio (I) is preferably 0.40 or higher, more preferably 1.00 or higher, even more preferably 1.10 or higher, particularly preferably 1.20 or higher, and most preferably 1.43 or higher. G / I 2D The coefficient of the

[0052] The above strength ratio (I G / I 2D When the above strength ratio (I) is within the above range, the strength properties and elastic deformability that maintain the hollow structure of the carbon material (A) are highly balanced. Furthermore, when the carbon material (A) is used as a conductive additive in lithium-ion batteries, the battery properties such as rapid discharge performance, capacity characteristics, and durability of the lithium-ion batteries can be improved. Also, the above strength ratio (I) of the carbon material (A) G / I 2D If the intensity ratio (I) of the carbon material (A) is less than 0.40, the formation of the graphene crystal structure tends to be insufficient. As a result, a decrease in electronic conductivity occurs, and the discharge capacity tends to decrease. G / I 2D If the ratio exceeds 5.00, the number of graphene layers increases excessively, resulting in reduced flexibility of the carbon material (A). Consequently, the electrode density decreases, and the battery capacity decreases.

[0053] The carbon material (A) preferably comprises a connected structure having an extended shape. The connected structure having an extended shape consists of a plurality of hollow particulate parts connected in a bead-like manner. The hollow particulate parts have surrounding walls, and the interior of the hollow particulate parts is hollow. The surrounding walls partition the internal space of the hollow particulate parts in the connected structure. Furthermore, the surrounding walls have a plurality of pores and possess a graphene crystalline structure.

[0054] The carbon material (A) is preferably hollow. At least the internal spaces of the connecting structures are in communication with each other, including the internal space of the hollow particulate portion. Such a carbon material (A) is porous, having micropores, mesopores, and macropores.

[0055] The surrounding wall of carbon material (A) is preferably composed of graphene or multilayer graphene, and graphene and multilayer graphene may be mixed. The surrounding wall of carbon material (A) is preferably composed mainly of thin-layer graphene. In this specification, the structure of multilayer graphene is a structure in which single layers of graphene are stacked, but with fewer layers than graphite. Among these, the structure of thin-layer graphene has a relatively small number of layers, and therefore provides good elastic deformability. When the surrounding wall of carbon material (A) is mainly composed of thin-layer graphene, it may be partially composed of graphene, or partially composed of multilayer graphene with a relatively large number of layers. The fact that the surrounding wall of carbon material (A) is mainly composed of thin-layer graphene is due to the above strength ratio (I G / I 2D This can also be confirmed from the fact that the ratio is between 0.40 and 5.00. Graphene is a sheet-like material of SP2-bonded carbon, and the six-membered carbon ring structure is linked together to form a honeycomb-like hexagonal lattice structure. Thus, the surrounding wall has a six-membered carbon ring structure. The connecting structure is preferably graphene mesosponge (GMS).

[0056] Carbon material (A) consists of an elastically deformable structure and a plastically deformable structure. The plastically deformable structure deforms and produces strain when an external force below a predetermined value is applied, but when an external force exceeding the elastic limit is applied, it does not return to its original shape even after the external force is removed, and permanent strain occurs. The degree of elastic and plastic deformation of carbon material (A) can be measured by an ultra-small load unloading test.

[0057] Carbon material (A) has the property of returning to its original shape without plastic deformation under weak external forces, such as in a micro-load unloading test, i.e., it has a large elastic deformation work rate. In carbon material (A), the portion consisting of graphene, which makes up the majority, mainly exhibits elastic deformability, while structural parts other than graphene, such as defective parts of the graphene structure and amorphous carbon parts, mainly exhibit plastic deformability. Therefore, carbon material (A) is considered to have good properties against deformation by external forces. In other words, the structure that gives this good elastic deformability is thin-layer graphene. Furthermore, if the number of graphene layers is excessively large, elastic deformability is maintained under external forces below a certain value, but under external forces exceeding the elastic limit, plastic deformation occurs all at once, and hollow particulate parts tend to break.

[0058] Furthermore, the carbon material (A) preferably has branched sections in the connecting structure, and more preferably has multiple branched sections. Furthermore, the carbon material (A) preferably has ring-shaped sections in the connecting structure, and more preferably has multiple ring-shaped sections. The connecting structure having an extended shape may have only branched sections, only ring-shaped sections, or both branched sections and ring-shaped sections. For example, one end of the connecting structure may be connected to the other end to form a ring-shaped section. Alternatively, the tips of multiple branched and extending sections may be connected to form a ring-shaped section. Also, ring-shaped sections may be formed in parts of the connecting structure other than the ends.

[0059] The size of the multiple pores provided in the connecting structure is preferably 0.1 nm to 100.0 nm, more preferably 1.0 nm to 80.0 nm, and even more preferably 5.0 nm to 50.0 nm. The length of the connecting structure is preferably 0.01 μm to 100.00 μm, more preferably 0.05 μm to 80.00 μm, and even more preferably 0.10 μm to 50.00 μm. The average particle size (average outer diameter) of the hollow particulate portion in the connecting structure is preferably 0.05 μm to 50.00 μm, more preferably 0.05 μm to 6.00 μm, even more preferably 0.10 μm to 10.00 μm, particularly preferably 0.10 μm to 5.00 μm, and most preferably 0.50 μm to 5.00 μm.

[0060] A constricted portion may be provided at the connecting (joining) parts of the interconnected hollow particulate matter. For example, when two hollow particulate matter are connected, they may take on a peanut shell-like or dumbbell-like shape. Multiple such hollow particulate matter are connected to form a connected structure. The connected structure is a complex structure that does not have a fixed shape.

[0061] As described above, the carbon material (A) is preferably a linked structure in which multiple hollow particulate parts are linked together in a bead-like manner. The term "structure" is used to describe the complex structure of carbon black and refers to an aggregate structure in which multiple primary particles in carbon black are linked together while having multiple branching points. In other words, the linked structure carbon material (A) can be likened to a structure in which the inside of the highly conductive primary particles of carbon black is hollow, the outer shell (the surrounding wall that constitutes the hollow particulate parts in carbon material (A)) is made up of multiple carbon atoms having a graphene crystal structure, and the internal spaces of the carbon black aggregates are interconnected. Therefore, the linked structure carbon material (A) has high conductivity and can also stably secure an electrolyte. The carbon material (A) can significantly improve the battery characteristics of lithium secondary batteries, such as rapid discharge performance, battery capacity characteristics, and charge / discharge characteristics.

[0062] As more hollow particulate matter connects, and the surface area of ​​the connected structure increases, the electronic conductivity of the carbon material (A) improves. Furthermore, as the overall complexity of the connected structure increases, voids are formed not only within the internal space of the connected structure but also surrounded by the outer surface of the surrounding walls. When a carbon material (A) with such a connected structure is included in the electrodes of a battery, the electrolyte fills these spaces and voids. In other words, the larger the volume of the internal space of the connected structure and the volume of the voids surrounded by the surrounding walls, the greater the amount of electrolyte that the carbon material (A) can hold. The volume of the internal space of the connected structure and the volume of the voids surrounded by the surrounding walls in the carbon material (A) can be compared with the volume of conventionally used conductive additives, using the oil absorption amount described later as an indicator.

[0063] The positive electrode material of lithium-ion batteries uses a lithium-containing transition metal oxide powder with a particle size distribution and low electronic conductivity. In conventional technology, an electron conduction path is established by pressing and fixing a mixture of a conductive additive (A) made of a carbon material that assists electron conduction and a binder resin onto a current collector for the battery reaction. 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 to actively place the electrolyte, or in other words lithium ions, near the positive electrode material using conventional technology.

[0064] Furthermore, conventionally, complexly shaped carbon black has been widely used as a conductive additive. In contrast, by using a carbon material (A), which is a linked structure, instead of the conventionally used conductive additive, the hollow particulate portion of the linked structure has internal space, allowing it to retain the electrolyte. The carbon material (A), which is a linked structure, has a larger internal space compared to carbon black, which has been conventionally used as a conductive additive. Therefore, the carbon material (A), which is a linked structure, is a material that can simultaneously assist in the supply of electrons and ions necessary for the battery reaction, enabling a rapid battery reaction.

[0065] The oil absorption of carbon material (A), measured in accordance with JIS K5101-13-1:2004 (Pigment Test Methods - Part 13: Oil Absorption - Section 1: Refined Linseed Oil Method), is preferably 500 mL / 100g or more, more preferably 600 mL / 100g or more, even more preferably 800 mL / 100g or more, particularly preferably 1000 mL / 100g or more, and most preferably 1400 mL / 100g or more. When the oil absorption of carbon material (A) is within the above range, battery characteristics such as the 2C maintenance rate can be improved. Furthermore, there is no particular upper limit to the oil absorption of carbon material (A), but for example, it is preferable in the following order: 5000 mL / 100g or less, 4000 mL / 100g or less, 3500 mL / 100g or less, 3000 mL / 100g or less, and 2500 mL / 100g or less.

[0066] The carbon material (A), which is a linked structure, can hold a large amount of electrolyte because it can retain electrolyte in the internal space of the linked structure and in the voids surrounded by the outer surface of the surrounding wall of the linked structure. Therefore, the oil absorption capacity of carbon material (A) is significantly higher than that of carbon black, which is commonly used as a conductive additive in lithium-ion batteries, making it possible to stably supply lithium ions and contributing to improvements in battery characteristics such as rapid charging, charge / discharge characteristics, and battery capacity of lithium-ion batteries. On the other hand, if the oil absorption capacity of carbon material (A) is less than 500 mL / 100 g, the amount of electrolyte that can be retained is small, which can cause a delay in ion supply during rapid reactions and tend to reduce the discharge capacity. Furthermore, if the oil absorption capacity of carbon material (A) is excessively high, it can be difficult to maintain the structure of carbon material (A), and it may become difficult to control the amount of electrolyte that can be retained.

[0067] Furthermore, the intensity of the D band (I) in the Raman spectrum obtained by Raman spectroscopy of carbon material (A) D ) G-band intensity (I G Intensity ratio (I D / I G The strength ratio (I) of the carbon material (A) is preferably 0.1 to 10.0, more preferably 0.5 to 5.0, even more preferably 1.0 to 3.0, particularly preferably 1.2 to 2.5, and most preferably 1.4 to 2.0. D / IG When the above range is maintained, the sp2 and sp3 orbitals in the carbon material (A) are in an even better state, and the electron conduction paths and ion conduction paths are highly balanced. Furthermore, the rapid discharge performance, capacity characteristics, and charge-discharge characteristics of the lithium-ion battery are further improved.

[0068] Furthermore, the interplanar spacing d002 of the (002) plane measured by X-ray diffraction (XRD) of the carbon material (A) is preferably 0.30 nm or more and 0.50 nm or less, more preferably 0.33 nm or more and 0.45 nm or less, even more preferably 0.30 nm or more and 0.50 nm or less, particularly preferably 0.33 nm or more and 0.39 nm or less, and most preferably 0.33 nm or more and 0.38 nm or less.

[0069] Furthermore, the size of crystallites in the c-axis direction Lc(002) measured by X-ray diffraction of the carbon material (A) is preferably 0.10 nm or more, with 0.30 nm or more, 0.50 nm or more, 1.00 nm or more, and 1.10 nm or more being preferred in that order. Also, the upper limit of the size of crystallites in the c-axis direction Lc(002) is preferably 20.00 nm or less, with 5.00 nm or less, 3.00 nm or less, 2.50 nm or less, 2.00 nm or less, 1.90 nm or less, 1.50 nm or less, 1.25 nm or less, and 1.21 nm or less being preferred in that order. When the above Lc(002), which indicates the degree of crystallinity of the carbon material (A), is within the above range, the carbon material (A) tends to have mesopores and macropores.

[0070] Furthermore, the lower limit of the crystallite size La(10) in the a-axis direction of the (10) plane, as measured by X-ray diffraction of the carbon material (A), is preferably 0.1 nm or more, and is preferred in the order of 0.5 nm or more, 1.0 nm or more, 1.5 nm or more, and 1.8 nm or more. The upper limit of the above La(10) is preferably 10.0 nm or less, and is preferred in the order of 5.0 nm or less, 4.5 nm or less, 4.0 nm or less, and 3.8 nm or less.

[0071] Furthermore, the BET specific surface area (S) of the carbon material (A) is the specific surface area calculated from nitrogen adsorption as specified in JIS Z8830, preferably 100 m². 2 / g or more 2700m 2 It is less than / g and 300m 2 / g or more 2500m 2 / g or less, 500m 2 / g2000m 2 / g or less, 600m 2 / g or more 1800m 2 / g or less, 800m 2 / g or more 1200m 2 The following ranges are preferred: less than / g. When the BET specific surface area of ​​carbon material (A) is within the above range, the conductivity and oil absorption of carbon material (A) are further improved.

[0072] Furthermore, the micropore volume of carbon material (A) is the pore volume of pores with a diameter of less than 2 nm, preferably 5.00 cc / g or less, and preferably in the order of 2.00 cc / g or less, 1.00 cc / g or less, 0.50 cc / g or less, and 0.40 cc / g or less. Also, the lower limit of the micropore volume of carbon material (A) is preferably 0.01 cc / g or more, and preferably in the order of 0.05 cc / g or more, 0.10 cc / g or more, 0.20 cc / g or more, and 0.30 cc / g or more. When the micropore volume of carbon material (A) is 5.00 cc / g or less, the ionic conductivity is further improved, and when the micropore volume of carbon material (A) is 0.01 cc / g or more, the strength properties of carbon material (A) are further improved.

[0073] Furthermore, the ratio of micropore volume to total pore volume in carbon material (A) is preferably 20% or less, and is preferably 15% or less, 12% or less, 10% or less, and 9% or less, in that order. The lower limit of the above ratio of micropore volume in carbon material (A) is preferably 5% or more. When the above ratio of micropore volume is 20% or less, the ionic conductivity is further improved, and when the above ratio of micropore volume is 5% or more, the strength properties of carbon material (A) are further improved.

[0074] Furthermore, the mesopore volume of carbon material (A) is a pore volume with a pore diameter of 2 nm to 50 nm, preferably 0.1 cc / g or more, and preferably in the order of 0.5 cc / g or more, 1.0 cc / g or more, 1.5 cc / g or more, and 2.0 cc / g or more. Also, the upper limit of the mesopore volume of carbon material (A) is preferably 15.0 cc / g or less, and preferably in the order of 10.0 cc / g or less, 5.0 cc / g or less, 4.0 cc / g or less, and 3.5 cc / g or less. When the mesopore volume of carbon material (A) is within the above range, the ionic conductivity and strength characteristics of carbon material (A) are further balanced.

[0075] Furthermore, the ratio of mesopore volume to total pore volume in carbon material (A) is preferably 10% or more, and is preferably 20% or more, 30% or more, 40% or more, and 50% or more in that order. Also, the upper limit of the above ratio of mesopore volume in carbon material (A) is preferably 90% or less, and is preferably 85% or less, 80% or less, 75% or less, and 70% or less in that order. When the above mesopore volume of carbon material (A) is within the above range, carbon material (A) has good strength, contributes to the stability of carbon material (A), and maintains the shape of carbon material (A) well. Therefore, carbon material (A) can maintain a good balance between electronic conductivity and the supply of ions held in the pores.

[0076] Furthermore, the pore volume of the carbon material (A) with a pore diameter of 2 nm or more and less than 10 nm is preferably 0.05 cc / g or more, and is preferred in the order of 0.01 cc / g or more, 0.05 cc / g or more, 0.10 cc / g or more, and 0.50 cc / g or more. Also, the upper limit of the pore volume of the carbon material (A) is preferably 10.00 cc / g or less, and is preferred in the order of 5.00 cc / g or less, 2.00 cc / g or less, 1.50 cc / g or less, and 1.00 cc / g or less. When the pore volume of the carbon material (A) with a pore diameter of 2 nm or more and less than 10 nm is within the above range, the ionic conductivity and strength characteristics of the carbon material (A) are highly balanced.

[0077] Furthermore, in carbon material (A), the ratio of pore volume with a pore diameter of 2 nm or more and less than 10 nm to the total pore volume is preferably 0.1% or more, and is preferred in the order of 1.0% or more, 3.0% or more, 5.0% or more, and 10.0% or more. Also, the upper limit of the above ratio of pore volume in carbon material (A) is preferably 50.0% or less, and is preferred in the order of 40.0% or less, 30.0% or less, 26.0% or less, and 20.0% or less. When the ratio of pore volume with a pore diameter of 2 nm or more and less than 10 nm to the total pore volume in carbon material (A) is within the above range, the ionic conductivity and strength characteristics of carbon material (A) are highly balanced.

[0078] Furthermore, the pore volume of the carbon material (A) with a pore diameter of 10 nm to 50 nm is preferably 0.05 cc / g or more, and is preferred in the order of 0.10 cc / g or more, 0.50 cc / g or more, 1.00 cc / g or more, 1.35 cc / g or more, 1.50 cc / g or more, and 2.00 cc / g or more. Also, the upper limit of the pore volume of the carbon material (A) is preferably 15.00 cc / g or less, and is preferred in the order of 10.00 cc / g or less, 5.00 cc / g or less, 4.00 cc / g or less, and 3.00 cc / g or less. When the pore volume of the carbon material (A) with a pore diameter of 10 nm to 50 nm is within the above range, the carbon material (A) has good strength, contributes to the stability of the carbon material (A), and maintains its shape well. Therefore, the carbon material (A) can maintain a good balance between electronic conductivity and the supply of ions held in the pores.

[0079] Furthermore, in carbon material (A), the ratio of pore volume with a pore diameter of 10 nm to 50 nm to the total pore volume is preferably 10% or more, and is preferably 15% or more, 20% or more, 25% or more, and 30% or more in that order. Also, the upper limit of the above ratio of pore volume in carbon material (A) is preferably 80% or less, and is preferably 70% or less, 60% or less, 55% or less, and 50% or less in that order. When the ratio of pore volume with a pore diameter of 10 nm to 50 nm to the total pore volume in carbon material (A) is within the above range, the ionic conductivity and strength characteristics of carbon material (A) are highly balanced.

[0080] Furthermore, the macropore volume of carbon material (A) is the pore volume of pores with a diameter of more than 50 nm, preferably 0.01 cc / g or more, and preferably in the order of 0.05 cc / g or more, 0.10 cc / g or more, 0.48 cc / g or more, and 1.00 cc / g or more. Also, the upper limit of the macropore volume of carbon material (A) is preferably 15.00 cc / g or less, and preferably in the order of 10.00 cc / g or less, 5.00 cc / g or less, 3.00 cc / g or less, and 2.57 cc / g or less. When the macropore volume of carbon material (A) is within the above range, carbon material (A) has good strength, contributes to the stability of carbon material (A), and maintains its shape well. Therefore, carbon material (A) can maintain a good balance between electronic conductivity and the supply of ions held in the pores.

[0081] Furthermore, the ratio of macropore volume to total pore volume in carbon material (A) is preferably 5% or more, and is preferably 10% or more, 15% or more, 20% or more, and 25% or more in that order. Also, the upper limit of the above ratio of macropore volume in carbon material (A) is preferably 80% or less, and is preferably 70% or less, 60% or less, 50% or less, and 45% or less in that order. When the above ratio of macropore volume in carbon material (A) is 5% or more, the ionic conductivity of carbon material (A) is further improved, and when the above ratio of macropore volume in carbon material (A) is 80% or less, the strength properties of carbon material (A) are further improved.

[0082] Furthermore, in carbon material (A), the ratio of pore volume with a diameter of 10 nm or more to the total pore volume is preferably 50% or more, and is preferred in the order of 55% or more, 60% or more, 65% or more, and 70% or more. Also, the upper limit of the above ratio of pore volume in carbon material (A) is preferably 95% or less, and is preferred in the order of 92% or less, 90% or less, 88% or less, and 85% or less. When the ratio of pore volume with a diameter of 10 nm or more to the total pore volume in carbon material (A) is 50% or more, the ionic conductivity of carbon material (A) is further improved, and when the above ratio is 95% or less, the strength characteristics of carbon material (A) are further improved.

[0083] Furthermore, the mode pore diameter (M) in the pore distribution of the carbon material (A) is the value of the peak top in the pore distribution curve, preferably between 1 nm and 500 nm, and preferably in the order of 5 nm to 100 nm, 10 nm to 50 nm, 15 nm to 40 nm, and 15 nm to 30 nm. When the mode pore diameter of the carbon material (A) is within the above range, the oil absorption capacity is further improved, and high levels of ionic conductivity and electronic conductivity can be achieved.

[0084] Furthermore, the average pore diameter of the carbon material (A) is preferably 1 nm to 500 nm, and is most preferably 5 nm to 100 nm, 10 nm to 75 nm, 15 nm to 50 nm, and 20 nm to 40 nm, in that order. When the average pore diameter of the carbon material (A) is within the above range, the oil absorption capacity is further improved, and high levels of ionic and electronic conductivity can be achieved.

[0085] Furthermore, the volume-based particle size distribution curve of carbon material (A), measured by laser diffraction scattering, was obtained by immersing the unground carbon material (A) in a solvent for 9 minutes before measurement, revealing the difference in cohesive force of carbon material (A).

[0086] D50, obtained from the volume-based particle size distribution curve measured by laser diffraction scattering, is the particle size at which 50% of particles have a particle size of D50 or less, preferably between 1 μm and 100 μm, and in order of preference between 5 μm and 90 μm, 10 μm and 80 μm, 15 μm and 60 μm, 20 μm and 50 μm, 25 μm and 45 μm, and 30 μm and 40 μm. When the D50 of carbon material (A) is within the above range, the electronic conductivity and ionic conductivity of carbon material (A) are further improved.

[0087] Furthermore, D10 obtained from the above particle size distribution curve is a particle size where the proportion of particles with a particle size of D10 or less is 10%, preferably 0.1 μm to 100.0 μm, and preferably in the order of 0.5 μm to 50.0 μm, 1.0 μm to 50.0 μm, 5.0 μm to 30.0 μm, and 10.0 μm to 15.0 μm.

[0088] Furthermore, D90 obtained from the above particle size distribution curve is the particle size at which 90% of the particles have a particle size of D90 or less, preferably 5 μm to 250 μm, and preferably in the order of 10 μm to 150 μm, 20 μm to 100 μm, 30 μm to 70 μm, 40 μm to 60 μm, 45 μm to 65 μm, and 45 μm to 55 μm. When the D90 of carbon material (A) is within the above range, the conductivity of carbon material (A) is further improved.

[0089] Furthermore, the ratio of D90 to D10 (D90 / D10) of the carbon material (A) obtained from the above particle size distribution curve is preferably 100 or less, and is preferred in the order of 50 or less, 10 or less, and 5 or less. When the above ratio (D90 / D10) of the carbon material (A) is 100 or less, the dispersibility of the carbon material (A) is further improved, and the conductivity of the lithium-ion battery is further improved.

[0090] Furthermore, the ratio of D90 of carbon material (A) obtained from the above particle size distribution curve to the mode pore size M (D90 / M) of carbon material (A), divided by 1000 (D90 / M × 1000), is preferably 50 or less, and is preferred in the order of 20 or less, 10 or less, 6 or less, and 4 or less. When (D90 / M × 1000) is 50 or less, the dispersibility of carbon material (A) is further improved, and the conductivity of the lithium-ion battery is further improved.

[0091] Furthermore, the carbon material (A) contained in the electrodes of a lithium-ion battery 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 (A), it is necessary to arrange single-layer graphene, in which carbon atoms are bonded in the planar direction, in a mesh-like structure. Also, when a conductive material such as carbon material (A) is filled into a non-conductive material such as a positive electrode material, if the filling rate of the conductive material is low, conductivity will not be exhibited. When the filling rate of the conductive material reaches a certain level, paths of the conductive material are formed within the compound, causing a rapid increase in electronic conductivity, after which the electronic conductivity becomes constant. The lower the threshold for the filling rate at which such a rapid increase in electronic conductivity occurs, the more suitable carbon material (A) is as a conductive material. Therefore, when multiple hollow particulate portions having surrounding walls of graphene structures that extend in the planar direction are connected, it is thought that carbon material (A) exhibits higher conductivity because the in-plane conductivity and path-forming conductivity are more highly balanced.

[0092] Furthermore, the conductivity of carbon material (A) can be measured by the following method of measuring the electrical conductivity of powder by uniaxial compression with lateral constraint. Dry carbon material (A) 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 carbon material (A), and the carbon material (A) is sandwiched between the negative and positive electrodes and placed on a force gauge stand. A spring-type force gauge installed on the force gauge stand is lowered to apply force to the carbon material (A) inside the cylindrical container and compress it. While measuring the compressive force and the height of carbon material (A) with a length measuring instrument, the resistance value of carbon material (A) is measured with a digital multimeter connected to the positive and negative electrodes. The conductivity of the carbon material (A) powder during compression is calculated from the obtained resistance value, the filling cross-sectional area of ​​carbon material (A), and the filling height.

[0093] The conductivity of carbon material (A), when pressurized at 10 MPa, is preferably 1 S / cm to 100 S / cm, with a preference for 5 S / cm to 70 S / cm, 10 S / cm to 50 S / cm, and 20 S / cm to 30 S / cm, in that order. The conductivity of carbon material (A) can be determined by the reciprocal of its electrical resistivity. The electrical resistivity of carbon material (A) can be measured according to JIS K1469.

[0094] Furthermore, one indicator of the structural complexity of carbon material (A) is the shape index and aggregate shape classification, which are measured by the image analysis method described later.

[0095] The circularity calculated by the image analysis method for carbon material (A) 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 the image analysis method is an indicator of the complexity of the aggregate structure, and if it is within the above range, the oil absorption capacity of carbon material (A) will further improve.

[0096] Furthermore, the shape factor (ML2 / A) indicating sphericity calculated by the image analysis method of the carbon material (A) may be 1.00 or greater, 2.00 or greater, 2.25 or greater, 2.40 or greater, or 4.00 or less, 3.50 or less, or 3.10 or less.

[0097] Furthermore, the shape factor (PM2 / A), which indicates the degree of surface roughness calculated by the image analysis method of the carbon material (A), may be 2.0 or higher, 3.0 or higher, 3.5 or higher, or 8.0 or lower, 7.0 or lower, 6.0 or lower, or 5.5 or lower.

[0098] Furthermore, the (PM2 / A)-(ML2 / A) value calculated by the image analysis method of the carbon material (A) is preferably 0 or greater, and is preferably 0.4 or greater, followed by 1.0 or greater. When the above value ((PM2 / A)-(ML2 / A)) is within the above range, the oil absorption capacity of the carbon material (A) is further improved.

[0099] Furthermore, the area circle equivalent diameter calculated by the image analysis method of the carbon material (A) may be 100 nm or more, 200 nm or more, 250 nm or more, or 1000 nm or less, 800 nm or less, 600 nm or less, or 400 nm or less.

[0100] Furthermore, the proportion of "spheroidal" shapes in the shape classification calculated by the image analysis method of carbon material (A) is preferably 50% or less, and is preferably in the order of 30% or less, 20% or less, 10% or less, 5% or less, and 2% or less. When the proportion of spherical shapes in the image analysis method of carbon material (A) is within the above range, the oil absorption capacity of carbon material (A) is further improved.

[0101] Furthermore, the proportion of "ellipsoidal" shapes in the shape classification calculated by the image analysis method of carbon material (A) is preferably 5% to 80%, with the following preference being 10% to 70%, 15% to 60%, 20% to 50%, and 25% to 45%. When the proportion of ellipsoidal shapes in the image analysis method of carbon material (A) is within the above range, the oil absorption capacity of carbon material (A) is further improved.

[0102] Furthermore, the proportion of "branched" shapes in the shape classification calculated by the image analysis method of carbon material (A) is preferably 5% to 80%, with the following preference being in order: 10% to 70%, 20% to 50%, 20% to 45%, 25% to 45%, and 25% to 36%. When the proportion of branched shapes in the image analysis method of carbon material (A) is within the above range, the oil absorption capacity of carbon material (A) is further improved.

[0103] Furthermore, the apparent density of the carbon material (A) is preferably 2.00 g / cc or less, and is preferably 1.50 g / cc or less, 1.00 g / cc or less, 0.50 g / cc or less, and 0.30 g / cc or less, in that order. Also, the lower limit of the apparent density of the carbon material (A) is preferably 0.05 g / cc or more, 0.10 g / cc or more, and 0.15 g / cc or more, in that order. When the apparent density of the carbon material (A) is within the above range, the hollow structure in the carbon material (A) is maintained, and the carbon material (A) is suitably used as a material constituting a battery.

[0104] The apparent density of carbon material (A) can be calculated using the total pore volume and true density from the following formula (1). The total pore volume (cc / g) is calculated using P / P0 = 0.99, and the true density is the value for graphite, 2.2 g / cc.

[0105] Apparent density (g / cc) = 1 / (total pore volume + (1 / true density)) Equation (1)

[0106] Furthermore, the bulk density of the carbon material (A) is preferably 0.01 g / L or more and 1000.00 g / L or less, with the following ranges being preferable: 0.10 g / L or more and 100.00 g / L or less, 0.50 g / L or more and 50.00 g / L or less, and 1.00 g / L or more and 25.00 g / L or less. When the bulk density of the carbon material (A) is within the above range, the conductivity of the carbon material (A) is further increased, and the electrolyte penetrates the carbon material (A) more easily. Bulk density is the mass per unit volume of carbon material (A) when filled in a container of a certain volume under certain conditions. Bulk density can be measured according to JIS K6219-2.

[0107] Furthermore, the number density of the carbon material (A) is a value calculated by the method described later, preferably 5 × 10⁻¹⁶. 14 pcs / g or more 1×10 20 It is less than or equal to 1 × 10⁻¹⁰ pieces / g. 16 pcs / g or more 1×10 19 pcs / g or less, 5×10 16 pcs / g or more 5×10 18 pcs / g or less, 1×10 17 pcs / g or more 1×10 18 pcs / g or less, 3×10 17 pcs / g or more 7×10 17 The order of preference is from less than or equal to the number of particles / g. When the number density of carbon material (A) is within the above range, the amount of oil absorbed by carbon material (A) is further improved.

[0108] The number density P (particles / g) of carbon material (A) is equal to the volume V (m³) per primary particle. 3 ) and carbon density ρ(g / m³) 3From this, it can be calculated from the following formula (2). Here, the carbon density ρ is the true density of graphite, which is 2.2 g / cc. Volume V (m³ 3 ) can be calculated from the following formula (3).

[0109] Number density P = 1 / (V × ρ) Equation (2)

[0110] Volume V = π × (D1 - D0) 3 / 6 formula (3)

[0111] 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 described above. D1 can be obtained by adding twice the value obtained by multiplying D0 by the average number of layers n and the interplanar spacing d002 of the (002) plane to the mode pore diameter. Alternatively, D1 may be obtained by TEM image analysis or the like. Although it is not the carbon material (A) of the embodiment, for example, the known DENKA BLACK Li-100 can be calculated with an average particle size of 35 nm and D0=0 as the particle outer diameter (D1).

[0112] To improve the performance and lifespan of lithium-ion batteries, a highly efficient battery reaction is required that does not result in a decrease in efficiency due to side reactions. Therefore, the carbon material (A) in the electrode needs to have electrochemical stability, i.e., oxidation resistance and corrosion resistance. Side reactions such as oxidation that occur electrochemically are said to originate from the oxygen-containing functional groups and edge surfaces of the carbon material (A). To improve the oxidation resistance of the carbon material (A), it is effective to reduce the oxygen-containing functional groups and the edge surfaces with low oxidation resistance.

[0113] The ultra-high-sensitivity vacuum desorption mass spectrometer 300 (developed at Tohoku University, see T. Ishii et al. CARBON 80, 2014, 135-145) shown in Figure 4 allows for accurate qualitative and quantitative analysis of oxygen-containing functional groups and hydrogen-terminated edge sites using TPD-MS. More specifically, 1 to 3 mg of each carbon material (A) is placed on a graphite sample stage, vacuum-heated to 1800°C at a heating rate of 10°C / min, and the gas released during heating is analyzed by the mass spectrometer 300 to accurately qualitatively and quantitatively analyze oxygen-containing functional groups and hydrogen-terminated edge sites. The TPD-MS 300 includes a radioactive thermometer 311, a sample holder 312, a quartz reactor 310 equipped with a high-frequency induction coil 313, and a detection unit 320 connected to the quartz reactor 310. The detection unit 320 includes, for example, a gas storage unit 327, a turbomolecular pump 324, a rotary pump 325, a cold cathode Pirani gauge 321, and a capacitance gauge 322.

[0114] The oxygen content of the carbon material (A) is a value calculated from the amount of H2O, CO, and CO2 released by temperature-controlled desorption mass spectrometry, and is preferably 5.0% by mass or less, with 3.0% by mass or less, 2.0% by mass or less, 1.0% by mass or less, and 0.6% by mass or less being preferred in that order. When the oxygen content of the carbon material (A) is within the above range, the stability of the lithium-ion battery is further improved, and this can further contribute to the high performance of the lithium-ion battery.

[0115] The temperature-controlled desorption mass spectrometer 300, which measures the desorbed gases from carbon material (A) during heating, measures the amount of H2, H2O, CO, and CO2 released from carbon material (A). These released 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 edge ends of carbon material (A). Therefore, a high amount of oxygen-containing functional groups in carbon material (A) means a high amount of oxygen-containing functional groups and edge elements in the structure of carbon material (A). The amount of oxygen-containing functional groups and edge elements in carbon material (A) can be adjusted by the CVD conditions and heat treatment temperature described later.

[0116] Furthermore, the amount of gas measured by the thermal desorption mass spectrometer 300 of the carbon material (A) is preferably 5000 μmol / g or less, and is preferably in the order of 3000 μmol / g or less, 1000 μmol / g or less, 750 μmol / g or less, and 500 μmol / g or less. When the above amount of gas of the carbon material (A) is within the above range, it can further contribute to extending the lifespan and improving the performance of lithium-ion batteries.

[0117] Furthermore, the edge amount of the carbon material (A) is a value calculated from the amount of gas measured by the temperature-controlled desorption mass spectrometer 300, and is preferably 500 m. 2 It is less than / g and 300m 2 / g or less, 100m 2 / g or less, 50m 2 / g or less, 30m 2 The order of preference is from 750 μmol / g or less to 500 μmol / g or less. Furthermore, the edge content of carbon material (A) is preferably 750 μmol / g or less, followed by 500 μmol / g or less. When the edge content of carbon material (A) is within the above range, durability is further improved, which can further contribute to the stability and high performance of lithium-ion batteries.

[0118] Furthermore, the ash content of the carbon material (A) is preferably 10,000 ppm or less, and is preferably 5,000 ppm or less, 4,000 ppm or less, 3,500 ppm or less, and 3,000 ppm or less, in that order. When the ash content of the carbon material (A) is within the above range, the stability of the electrolyte is further improved, and the durability and performance of the lithium-ion battery can be further enhanced.

[0119] Furthermore, the carbon content of the carbon material (A) is preferably 95.0% by mass or more, and is preferably 97.0% by mass or more, 98.0% by mass or more, 99.0% by mass or more, and 99.3% by mass or more, in that order. The carbon content is calculated using the following formula. The amount of generated gas is the total amount of gas (H2, H2O, CO and CO2) measured by the temperature-controlled desorption mass spectrometer 300. Carbon content (mass%) of carbon material (A) = 100 - (Ash content (mass%) + Gas generation amount (mass%))

[0120] Furthermore, the ratio of oxygen content to carbon content (O / C) of the carbon material (A) is preferably 1.00 or less, and is preferably 0.50 or less, 0.10 or less, 0.05 or less, and 0.01 or less, in that order. When the above ratio (O / C) of the carbon material (A) is within the above range, it can further contribute to extending the lifespan and improving the performance of lithium-ion batteries.

[0121] Furthermore, the pH of the carbon material (A) is preferably 5.0 to 10.0, with the following ranges being preferable: 5.5 to 9.5, 6.0 to 9, 6 or less, 5.0 to 8.5, and 7.0 to 8.0. When the pH of the carbon material (A) is within the above range, its stability is further improved.

[0122] Furthermore, the combustion temperature of the carbon material (A) is preferably 300°C or higher, and is preferably 400°C or higher, 450°C or higher, 500°C or higher, and 550°C or higher, in that order. The combustion temperature test of the carbon material (A) is performed as a simple corrosion resistance test, and when the combustion temperature of the carbon material (A) is 300°C or higher, the electrochemical stability within the electrode is good.

[0123] Furthermore, when carbon material (A) contains graphene, it exhibits excellent electron transport properties. For this reason, such carbon material (A) can be incorporated into the electrodes of lithium-ion batteries to assist in the battery reaction in lithium-ion batteries. In addition, carbon material (A) has a linked structure in which multiple hollow particulate parts, each having a surrounding wall with multiple pores, are linked together in a bead-like fashion. If the linked structure has an internal space within the hollow particulate parts, it can permeate and retain the electrolyte containing dissolved lithium ions, thus providing excellent ion supply during the reaction. For this reason, such carbon material (A) can suitably assist in secondary battery reactions and is therefore suitable as a material for secondary batteries.

[0124] The carbon material content in 100% by weight of the conductive additive is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 90% by weight or more, particularly preferably 95% by weight or more, and may also be 100% by weight.

[0125] The proportion of carbon material is preferably 0.01% to 20% by weight, more preferably 0.1% to 10% by weight, and even more preferably 0.2% to 5% by weight, relative to 100% by weight of the electrode composite film. The desired effect is more likely to be obtained within the above numerical range.

[0126] (Method for manufacturing carbon material (A)) A method for producing carbon material (A) includes a removal step to obtain carbon material (A) by removing the template material of the carbon material (A) precursor, which is an aggregate in which multiple primary particles are aggregated and linked together in a bead-like manner, and whose surface is covered with a carbonaceous layer.

[0127] In the removal process, the template material in the carbon material (A) precursor, which has a carbonaceous layer covering its surface, is removed. In this way, carbon material (A) can be obtained.

[0128] The carbonaceous layer covers the entire surface of the mold material. The mold material removed in the removal process is an aggregate in which multiple primary particles are clustered together in a bead-like manner. Preferably, the primary particles constituting the aggregate are nano-primary particles with a size on the order of nanometers. The aggregate has an extended shape.

[0129] Furthermore, it is preferable that the mold material has branched portions where the aggregate is divided. If the mold material has branched portions, the resulting carbon material (A) will have branched portions. It is also preferable that the mold material has one or more ring-shaped portions where the aggregate is divided. If the mold material has ring-shaped portions, the resulting carbon material (A) will have ring-shaped portions. For example, one end of the aggregate may be connected to the other to form a ring-shaped portion, or the tips of branches extending from the branched portion may be connected to form a ring-shaped portion, or a link-shaped portion may be formed in a part of the aggregate other than the end.

[0130] The particle size of the primary particles constituting the mold material is preferably 1 nm to 150 nm, more preferably 5 nm to 100 nm, even more preferably 10 nm to 60 nm, particularly preferably 15 nm to 50 nm, and most preferably 20 nm to 40 nm. When the particle size of the primary particles is within the above range, the oil absorption capacity and mesopore volume of the resulting carbon material (A) can be further increased. Furthermore, the mold material is easy to handle. In addition, the permeability of the raw material gas that serves as the carbon source for the carbonaceous layer formed on the surface of the mold material is improved, making it easier to uniformly coat the surface of the mold material with the carbonaceous layer.

[0131] Furthermore, the BET specific surface area of ​​the mold material is preferably 1 m². 2 / g or more 1000m 2 / g or less, more comfortably 10m 2 / g or more 500m 2 / g or less, more preferably 20m 2 / g or more 200m 2 / g or less, particularly preferably 40m 2 / g or more 160m 2 / g or less, most preferably 50m 2 / g or more 120m 2 It is less than / g. If the BET specific surface area of ​​the mold material is within the above range, the oil absorption and mesopore volume of the resulting carbon material (A) can be further increased.

[0132] The specific surface area of ​​the resulting carbon material (A) depends on the specific surface area of ​​the template material. The ratio of particle volume to surface area increases as the particle size decreases; therefore, the smaller the particle size, the larger the surface area per unit volume, i.e., the surface area per unit mass. Consequently, a carbon material (A) with a high specific surface area can be obtained by using aggregates of nanoparticles with small primary particle sizes.

[0133] The average particle size of the primary particles constituting the mold material is preferably 1 nm to 100 nm, followed by 2 nm to 50 nm, 4 nm to 50 nm, and 3 nm to 30 nm in that order. The length of the aggregate is preferably 0.01 μm to 100.00 μm, more preferably 0.05 μm to 10.00 μm, and even more preferably 0.10 μm to 5.00 μm. The average particle size of the aggregate is preferably 0.05 μm to 10.00 μm, and more preferably 0.10 μm to 5.00 μm.

[0134] Furthermore, the bulk density of the mold material is preferably 0.1 g / L to 500.0 g / L, more preferably 0.5 g / L to 250.0 g / L, even more preferably 1.0 g / L to 200.0 g / L, particularly preferably 10.0 g / L to 100.0 g / L, and most preferably 30.0 g / L to 70.0 g / L. When the bulk density of the mold material is within the above range, the conductivity of the resulting carbon material (A) can be further increased, and the oil absorption and mesopore volume can be further increased.

[0135] Furthermore, the mold material is preferably basic or acidic. Suitable basic mold materials include magnesium oxide and calcium carbonate. Suitable acidic mold materials include aluminum oxide and silica compounds containing silanol. The acidic pH is 7.0 or less in 4% moisture, preferably 6.5 or less, more preferably 6.0 or less, even more preferably 5.5 or less, and particularly preferably 5.0 or less. The above acidic pH is preferably 1.0 or higher, more preferably 2.0 or higher, even more preferably 3.0 or higher, particularly preferably 3.5 or higher, and most preferably 4.0 or higher.

[0136] Furthermore, the carbon content of the mold material is preferably 0.0001% by weight or more, more preferably 0.0100% by weight or more, even more preferably 0.0500% by weight or more, particularly preferably 0.100% by weight or more, and most preferably 0.500% by weight or more. The upper limit of the carbon content of the mold material is preferably 5.0000% by weight or less, more preferably 4.0000% by weight or less, even more preferably 3.0000% by weight or less, particularly preferably 2.5000% by weight or less, and most preferably 2.0000% by weight or less. When the carbon content of the mold material is within the above range, the formation of a carbonaceous layer on the mold surface becomes easier.

[0137] Furthermore, the mold material is preferably a compound that has catalytic activity in the carbon deposition reaction. Such compounds are preferably nonmetallic compounds, metalloid (semimetallic) compounds, and metallic compounds, and more preferably metalloid compounds and metallic compounds.

[0138] As nonmetallic compounds, ceramic compounds (nonmetallic inorganic solid materials) are preferred. As ceramics, glass, cement, and fine ceramics are preferred.

[0139] Preferably, the metalloid compound is a boron compound, a silicon compound, a germanium compound, or an antimony compound, and more preferably a silicon compound. Preferably, the silicon compound is silicon monoxide, silicon dioxide, silicon nitride, silicon carbide, or silicone, and more preferably silicon dioxide.

[0140] Preferably, the metal compound is a monovalent metal compound or a polyvalent metal compound, and more preferably a polyvalent metal compound. Suitable monovalent metal compounds include chlorides, sulfates, nitrates, phosphates, and carbonates of alkali metals such as sodium and potassium. Preferably, the polyvalent metal compound is an alkaline earth metal compound such as calcium and magnesium, or a trivalent metal compound such as aluminum, and more preferably a calcium compound, a magnesium compound, or an aluminum compound. Preferably, the calcium compound is a chloride, sulfate, nitrate, phosphate, carbonate, or oxide, more preferably a carbonate, an oxide, and even more preferably an oxide. Preferably, the magnesium compound is a chloride, sulfate, nitrate, phosphate, carbonate, or oxide, more preferably a carbonate, an oxide, and even more preferably an oxide. Preferably, the aluminum compound is a chloride, sulfate, nitrate, phosphate, carbonate, or oxide, more preferably a carbonate, an oxide, and even more preferably an oxide.

[0141] Furthermore, since atomized compounds form aggregates in which multiple nanoprimary particles are linked together in a bead-like manner with multiple branching structures, they can be suitably used as template materials. As atomized compounds, compounds obtained by flame hydrolysis, which is one of the dry manufacturing methods for inorganic materials, are preferred.

[0142] As the atomized compound, atomized silicon dioxide is preferred. Atomized silicon dioxide produced by flame hydrolysis does not go through a liquid phase process during its production, resulting in slow aggregation. Therefore, atomized silicon dioxide has excellent dispersibility in the liquid phase and in the compound (solid phase). Atomized silicon dioxide is produced by high-temperature gas-phase hydrolysis of silicon tetrachloride in an oxyhydrogen flame, accompanied by hydrochloric acid as a byproduct. By changing the production conditions such as the flame temperature, the supply ratio of oxygen and hydrogen, the amount of raw materials supplied, and the residence time, an average particle size of 7 nm to 40 nm and a specific surface area of ​​50 m² can be obtained. 2 / g or more 380m 2 Particles of silicon dioxide less than / g can be obtained.

[0143] Besides fumid silicon dioxide, suitable atomized compounds produced by flame hydrolysis include fumidized alumina, fumidized titania, and fumidized wet zirconia. Suitable other 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 a fumid form.

[0144] Furthermore, precipitated silica can also be used as a mold material. Precipitated 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 nm to 140 nm and a specific surface area of ​​approximately 20 nm can be obtained. 2 / g or more 400m 2 Particles of silicon dioxide less than / g can be obtained.

[0145] The moisture content of the mold material is preferably 5.0% or less, more preferably 3.0% or less, even more preferably 1.5% or less, particularly preferably 1.0% or less, and most preferably 0.5% or less.

[0146] When using the CVD method to form a carbonaceous layer on the surface of a mold material, the amount of carbon deposited on the mold material surface is influenced by CVD reaction conditions such as the type of raw material gas, raw material gas concentration, flow rate, reaction temperature, and reaction time, as well as the surface of the mold material, with the surface having the greatest influence. Suitable mold materials for carbon deposition by the CVD method are compounds containing oxygen atoms (oxygen-containing compounds), where the carbon in the raw material gas is replaced by the oxygen atoms of the oxygen-containing compound, and this becomes the starting point for the precipitation of carbonaceous material. Preferably, the oxygen-containing compound is a metal oxide or metal carbonate, and more preferably an acidic or basic compound. Suitable basic oxygen-containing compounds include magnesium oxide and calcium carbonate.

[0147] Furthermore, for a mold material surface suitable for carbonaceous layer formation in the CVD method, it is preferable that the surface contains hydrocarbons that serve as a carbon source. Hydrocarbons are compounds that act as raw material gases, and are preferably compounds containing methyl groups or carbon-carbon unsaturated bonds. Suitable mold materials are inorganic compounds that have hydrocarbons on their surface.

[0148] Furthermore, the inorganic compound having hydrocarbons on its surface is preferably an inorganic material surface-treated with a silane coupling agent, and more preferably a silica compound surface-treated with a silane coupling agent. As the silane coupling agent, those commonly used as surface pretreatment agents can be used without limitation, with 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 being preferred, trialkoxy-type silane coupling agents with a high number of methyl groups per molecule being more preferred, and trimethoxysilane compounds being even more preferred.

[0149] The amount of silane coupling agent is appropriately selected depending on the intended use, but is expressed as the amount of hydrocarbons in the inorganic material, preferably 0.01% to 10.00% by weight, more preferably 0.02% to 8.00% by weight, even more preferably 0.05% to 5.00% by weight, particularly preferably 0.10% to 3.00% by weight, and most preferably 0.50% to 1.50% by weight. When the amount of silane coupling agent (amount of hydrocarbons) in the inorganic material is within the above range, the amount of carbonaceous layer formed on the surface of the mold material can be easily adjusted.

[0150] The mold material can be used individually or in combination of two or more types.

[0151] In the removal process, any method for removing the mold material that removes the mold material while leaving a carbonaceous layer is acceptable, preferably a dissolution method using an acid or alkali, and more preferably an acid dissolution method.

[0152] The acid used to dissolve and remove the mold material is appropriately selected depending on the type of mold material, but is preferably hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, or hydrofluoric acid, and more preferably hydrochloric acid or hydrofluoric acid. The concentration of the acid used to dissolve and remove the mold material is appropriately adjusted within a range that allows for the dissolution and removal of the mold material. 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 is 30 times or more the stoichiometric ratio or 50 times or more the stoichiometric ratio relative to the mold material.

[0153] The temperature for dissolving and removing the mold material is preferably 5°C to 100°C, more preferably 10°C to 50°C, and even more preferably 20°C to 30°C. The removal process may be carried out with stirring, vibration, and other operations. The time required for the removal process is appropriately selected within a range that allows for the removal of the mold material.

[0154] The carbonaceous layer, after the mold material has been removed, can be recovered, for example, by filtration, and then washed with pure water. Washing conditions can be selected as appropriate, and the process is completed after confirming that the pH of the washing solution used on the carbonaceous layer is neutral.

[0155] The carbonaceous layer after washing can be dried by vacuum heating and drying. The conditions for vacuum heating and drying are not particularly limited, but it is preferable to set the vacuum heating and drying temperature to 100°C or higher and 200°C or lower, and the vacuum heating and drying time to 1 hour or higher and 10 hours or lower.

[0156] Furthermore, it is preferable that the method for producing the carbon material (A) further includes a heating step after the removal step in which the carbon material (A) is heated to a temperature of 1000°C or higher and 3000°C or lower.

[0157] In the heating step performed after the removal step, the carbon material (A) obtained in the removal step is heated. The heating temperature is 1000°C to 3000°C, preferably 1300°C to 2500°C, more preferably 1500°C to 2000°C, even more preferably 1600°C to 1900°C, and particularly preferably 1750°C to 1850°C.

[0158] Furthermore, the heating time in the heating process (holding time at a predetermined heating temperature) is preferably 0.1 hours or more and 10.0 hours or less, more preferably 0.2 hours or more and 5.0 hours or less, and even more preferably 0.5 hours or more and 5.0 hours or less. In addition, the atmospheric pressure in the heating process is preferably atmospheric pressure or reduced pressure.

[0159] Furthermore, by performing the heating process, functional groups (mainly oxygen-containing functional groups) that bond to the carbon atoms constituting the carbon material (A), and carbon chains that do not form six-membered rings, detach from the carbon material (A) at temperatures above 1000°C, forming unbonded bonds. When these unbonded bonds bond to other nearby carbon atoms, the surface of the carbon material (A) becomes less receptive to the bonding of functional groups. By heat-treating the carbon material (A) preferably at 1500°C or higher, and more preferably at 1600°C or higher, the carbon material (A) can acquire functions such as further improved electronic conductivity and maintenance of internal space.

[0160] Furthermore, the heating process allows for the adjustment of structural defects in the graphene and non-graphene components that constitute the surrounding wall of the carbon material (A). These structural defects include spaces created within the interconnected structure of the carbon material (A) due to the dissolution of the template material, and intrusion holes created in the surrounding wall of the carbon material (A). By adjusting the heating process conditions, such as heating temperature and heating time, the degree of these structural defects can be controlled; that is, the size of the spaces within the carbon material (A) and the size of the intrusion holes that allow the electrolyte to penetrate into the carbon material (A) can be adjusted.

[0161] (Carbon material (A) precursor) The carbon material (A) precursor comprises a template material composed of aggregates in which multiple primary particles are aggregated and linked together in a bead-like manner, and a carbonaceous layer covering the surface of the template material and having multiple pores.

[0162] The template material for the carbon material (A) precursor is an aggregate in which multiple primary particles are aggregated and linked together in a bead-like manner, and preferably has the same configuration as the template material that constitutes the carbon material (A) precursor used in the method for producing carbon material (A) of the above embodiment.

[0163] The carbonaceous layer formed on the surface of the mold material has multiple pores. Preferably, the carbonaceous layer covers the entire surface of the mold material. Furthermore, it is preferable that the carbonaceous layer has a graphene crystalline structure.

[0164] (Method for producing a carbon material (A) precursor) A method for producing a carbon material (A) precursor includes a coating step in which the surface of a template material, which is an aggregate in which multiple primary particles are aggregated and linked together in a bead-like manner, is coated with a carbonaceous layer to obtain a carbon material (A) precursor.

[0165] In the coating step, the surface of the template material is coated with a carbonaceous layer to obtain a carbon material (A) precursor. The template material is an aggregate in which multiple primary particles are aggregated and linked together in a bead-like manner, and preferably has the same configuration as the template material that constitutes the carbon material (A) precursor in the above embodiment.

[0166] A carbonaceous layer can be formed on the surface of the mold material by bringing an organic substance that serves as a carbon source into contact with the mold material and performing a carbonization heat treatment. Contact with the carbon source and the carbonization heat treatment can be performed simultaneously or separately. The contact between the mold material and the carbon source is preferably carried out at room temperature (25°C) or higher and 1000°C or lower.

[0167] The number of carbonaceous layers is appropriately selected according to the intended use, preferably 1.0 layers or more, more preferably 1.2 layers or more, even more preferably 1.5 layers or more, particularly preferably 2.0 layers or more, and most preferably 2.2 layers or more. The upper limit of the number of carbonaceous layers is preferably 15.0 layers or less, more preferably 10.0 layers or less, even more preferably 8.0 layers or less, particularly preferably 6.0 layers or less, and most preferably 5.0 layers or less. When the number of carbonaceous layers is within the above range, the strength characteristics and elastic deformation of the carbon material (A) obtained by heating the carbonaceous layers are excellent, and the hollow structure of the hollow particulate portion in the carbon material (A) can be well maintained, thereby greatly improving the characteristics of the lithium-ion battery. The number of carbonaceous layers is calculated by forming a carbonaceous layer on the surface of the mold material, then calculating the weight of the carbonaceous layer using thermogravimetric analysis (TG), and calculating the weight of the carbonaceous layer per unit area of ​​the mold material from the weight of the carbonaceous layer and the surface area of ​​the mold material, and this value is used as the weight per unit area of ​​single-layer graphene (7.61 × 10⁻⁶). -4 g / m 2 This value is calculated by dividing by ).

[0168] 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 involve, for example, immersing the mold material in a liquid of organic matter. Gas-phase contact methods involve, for example, introducing an organic gas at a high temperature and bringing it into contact with the mold material; this is the so-called CVD method.

[0169] In the liquid-phase contact method, organic compounds having functional groups that react with functional groups present on the surface of the mold material, specifically hydroxyl groups, are preferably used, and benzene-based hydrocarbon compounds having functional groups that react with hydroxyl groups are particularly preferred. Among these, benzene-based aromatic hydrocarbon compounds having at least one of a hydroxyl group and a carboxyl group are preferred, with phenol, hydronaphthalene, and dihydronaphthalene being more preferred. When an organic compound having a functional group that reacts with functional groups present on the surface of the mold material is used, strong bonds such as ester bonds are formed between the mold material and the organic compound, and the organic compound tends to carbonize in situ during the carbonization heat treatment without volatilizing.

[0170] In the liquid-phase contact method, an organic compound acting as a carbon source is dissolved in a solvent, and the template material is impregnated into the solution at room temperature, thereby bringing the template material into contact with the organic carbon source. To strongly bond the template material and the organic material, the mixture is then maintained at a temperature range of 250°C to 600°C for a certain period of time. In this way, the hydroxyl groups on the surface of the template material and the organic material undergo dehydration condensation reactions such as esterification, fixing them through bonds such as ester bonds, making it easier to obtain a carbonaceous layer with a graphene structure. After that, the temperature is lowered, and any excess organic material that did not react with the template material is washed and removed with a solvent.

[0171] Subsequently, heat treatment is performed to carbonize the organic compound acting as a carbon source in contact with the mold material. This heat treatment causes dehydrogenation reactions in organic substances such as hydrocarbons, further promoting graphene structuring in the carbonaceous layer. The heat treatment temperature is preferably 600°C to 1500°C, more preferably 750°C to 1500°C, and even more preferably 800°C 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.

[0172] In the vapor-phase contact method, an organic compound as a carbon source is brought into contact with the template material. To strongly bond the carbon source and the template material, the CVD (Chemical Vapor Deposition) method is preferably carried out in a temperature range in which the dehydrogenation reaction can proceed, specifically between 400°C and 1000°C.

[0173] As organic compounds used as carbon sources in the gas-phase contact method, they can be appropriately selected according to the intended use, and hydrocarbons such as saturated hydrocarbons, unsaturated hydrocarbons having at least one of a double bond and a triple bond, alicyclic hydrocarbons, and aromatic hydrocarbons are preferably used. As saturated hydrocarbons, they can be either straight-chain or branched-chain, and methane, ethane, and propane are preferred. As unsaturated hydrocarbons, they can be either straight-chain or branched-chain, and ethylene, propylene, isoprene, and acetylene are preferred. As alicyclic hydrocarbons, cyclopropane and cyclohexane are preferred. As aromatic hydrocarbons, benzene and toluene are preferred. Among these hydrocarbons, methane, ethane, acetylene, ethylene, propylene, and benzene are preferred, and from the viewpoint of precipitating highly crystalline carbon, methane, propylene, and benzene are preferred. In particular, methane is preferred from the viewpoint of obtaining highly crystalline carbon at a high thermal decomposition temperature.

[0174] In addition to the substances mentioned above, suitable organic compounds used in the gas-phase contact method include alcohols such as methanol, ethanol, propanol, and butanol, as well as nitrogen-containing compounds such as acetonitrile and acrylonitrile.

[0175] Furthermore, the reaction temperature in the CVD reaction is appropriately selected depending on the type of template material and the decomposition temperature of the organic compound used as a carbon source, but is preferably 400°C to 1000°C, more preferably 600°C to 950°C, and even more preferably 800°C to 900°C.

[0176] Furthermore, the reaction time in the CVD reaction (CVD treatment time at a predetermined heating temperature) is appropriately selected depending on the type of template material and organic compound used as a carbon source, and the number of carbonaceous layers deposited, but is preferably 0.1 hours or more and 10.0 hours or less, more preferably 0.5 hours or more and 5.0 hours or less, and even more preferably 1.0 hour or more and 3.0 hours or less. In addition, 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.

[0177] Furthermore, the CVD reaction may be carried out under an inert gas atmosphere if necessary. Preferably, the inert gas is nitrogen, helium, neon, or argon, and more preferably argon. In the CVD method, carbon can 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. The carrier gas may be, for example, one of the inert gases mentioned above, but may also be a mixture with oxygen gas or hydrogen gas. Preferably, the carrier gas is argon.

[0178] Furthermore, the number of carbonaceous layers formed on the mold material can be appropriately selected by the CVD reaction time. To form a small number of carbonaceous layers, the carrier gas flow rate is preferably 0.05 m / min or more and 5.00 m / min or less, more preferably 0.10 m / min or more and 1.00 m / min or less, even more preferably 0.20 m / min or more and 0.80 m / min or less, and particularly preferably 0.32 m / min or more and 0.64 m / min or less. In addition, the amount of organic compound introduced is preferably 1 volume% or more and 70 volume% or less, more preferably 5 volume% or more and 50 volume% or less, even more preferably 10 volume% or more and 40 volume% or less, and particularly preferably 15 volume% or more and 35 volume% or less, relative to the total amount of carrier gas and organic compound.

[0179] Since carbonization of the carbonaceous layer can also proceed by CVD reactions, other special carbonization treatments are not necessary, but they may be performed.

[0180] [Other conductive additives] Conductive additives can be a combination of carbon materials and other conductive substances. Suitable other conductive substances include conductive fibers such as metal fibers; metal powders such as aluminum powder and nickel powder; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0181] 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 of the electrode and is selected within the same range as the carbon material. The ratio of carbon material to other conductive materials is appropriately selected according to the intended use of the electrode and is preferably 10:90 to 90:10 by weight ratio of [carbon material] to [other conductive materials], more preferably 20:80 to 80:20, even more preferably 30:70 to 70:30, and particularly preferably 40:60 to 60:40.

[0182] Furthermore, carbon materials can be made even more effective by combining them with conventionally used conductive additives. For example, carbon blacks such as acetylene black are composed of linked particles with a diameter of several tens of nanometers, but the crystallinity of carbon is not very high, the structural length is short, and it is easily broken down, making it poor at long-distance electron transport. By combining carbon blacks with carbon materials, it is possible to realize a system that maintains electron conductivity and ion supply capabilities, whether the three-dimensional structure is maintained or the three-dimensional structure is compressed and flattened like flaky graphite.

[0183] <Manufacturing method for positive electrode> The positive electrode can be obtained, for example, by applying a slurry for forming a positive electrode onto a current collector to form a coating, and then drying the coating.

[0184] The slurry for forming the positive electrode is a mixture of the above-mentioned positive electrode active material, conductive additive, and binder in a dispersion medium. The slurry for forming the positive electrode may also contain an electrolyte. When the slurry for forming the positive electrode contains an electrolyte, the slurry is preferably in the form of a clay-like substance in which the above-mentioned positive electrode active material, conductive additive, and electrolyte are kneaded together. In this case, the slurry for forming the positive electrode does not need to contain a binder.

[0185] Furthermore, the cathode forming slurry may contain other compounding agents as needed. These other compounding agents can be appropriately selected according to the intended use of the cathode, and those used in lithium-ion batteries can be used in amounts within the normal usage range.

[0186] While there are no particular limitations on the dispersion medium for the slurry, it is preferable to use a medium that dissolves only the binder and not the other constituent materials in order to sufficiently distribute the binder uniformly and to form a coating film of the slurry to a predetermined size. Among these, organic solvents such as dimethylformamide, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), isopropyl alcohol, and acetone, as well as water, are preferred, and one of these can be used alone or in combination of two or more.

[0187] When polyvinylidene fluoride is used as a binder, dimethylformamide and N-methyl-2-pyrrolidone (NMP) are preferred as dispersion media, with NMP being more preferred.

[0188] Furthermore, the solid content concentration of the cathode forming slurry, excluding the dispersion medium, can be appropriately selected depending on the method of applying the slurry to the current collector, preferably 10% by weight or more and 90% by weight or less, more preferably 20% by weight or more and 80% by weight or less, even more preferably 40% by weight or more and 80% by weight or less, particularly preferably 40% by weight or more and 70% by weight or less, and most preferably 50% by weight or more and 65% by weight or less.

[0189] The viscosity of the cathode forming slurry is preferably 1000 cP to 50000 cP, more preferably 2000 cP to 40000 cP, even more preferably 5000 cP to 35000 cP, particularly preferably 10000 cP to 35000 cP, and most preferably 10000 cP to 30000 cP at a temperature of 24°C to 26°C. When the viscosity of the cathode forming slurry is within the above range, the slurry can be applied with a uniform thickness while maintaining a constant dispersion of the solid content excluding the dispersion medium.

[0190] The positive electrode can be manufactured by applying the above-mentioned slurry for forming the positive electrode onto a current collector and drying it as necessary.

[0191] For applying the slurry for forming the positive electrode to the current collector, commonly used printing techniques can be employed. When the thickness of the coating is small, gravure printing is suitable, while when the thickness of the coating is large, printing methods such as doctor blade printing and die printing are suitable.

[0192] Subsequently, the coating film is heat-dried as needed. Any drying method is available, but the method that achieves the desired bonding strength with the binder is preferred.

[0193] When forming the positive electrode to the predetermined dimensions after drying, it is preferable to use a method employing industrially available cutting blades. Furthermore, to achieve the predetermined density, it is preferable to use a method employing industrially available pressurizing equipment as needed.

[0194] <<Lithium-ion battery>> The lithium-ion battery comprises the positive electrode described above. Specifically, the lithium-ion battery has a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an electrolyte, where the positive electrode is the positive electrode of the embodiment described above. The lithium-ion battery may further include a battery container that houses the electrode assembly consisting of the positive electrode, negative electrode, and separator, and a sealing member that seals the battery container. Note that the positive electrode of the lithium-ion battery is substantially the same as the positive electrode described above, so a detailed explanation is omitted.

[0195] The separator in a lithium-ion battery separates the negative electrode and the positive electrode and provides a pathway for lithium ions to move. It is not particularly limited as long as it is a material that is normally used as a separation membrane in a lithium-ion battery, but it is preferable that it has low resistance to ion movement of the electrolyte while having excellent electrolyte impregnation ability.

[0196] Specifically, examples of separators include porous polymer films, and porous polymer films made from polyolefins such as polyethylene, polypropylene, polybutene, polyvinyl chloride, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers of these films are preferred. Alternatively, ordinary porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, are also preferred as separators. Furthermore, coated separation membranes containing ceramic components or polymeric substances are preferred to ensure heat resistance or mechanical strength. Separators may be used selectively in single-layer or multi-layer structures.

[0197] Polyethylene and polypropylene are suitable materials for porous polymer films. Polyethylene has a relatively low melting point, and when the battery temperature rises for any reason (for example, an unsafe condition such as a short circuit), the pores in the film become blocked by thermal melting, inhibiting the movement of driving ions, thereby stopping the reaction and ensuring safety. Polypropylene is also suitable because it can be made porous by stretching without the use of plasticizers.

[0198] Furthermore, polymer compounds can be applied to both sides of the separator for use. The polymer compound provided on the surface of the separator may be gelled with an electrolyte. Suitable polymer compounds 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 fluorine-based polymer compounds such as polyvinylidene fluoride-hexafluoropropylene copolymer. Among these, fluorine-based polymer compounds are preferred from the viewpoint of preventing swelling during high-temperature storage and gelation, and polyvinylidene fluoride is more preferred.

[0199] For lithium-ion batteries, a non-aqueous electrolyte solution, typically obtained by dissolving the electrolyte in an organic solvent, is usually used.

[0200] Lithium salts are preferred as electrolytes for lithium-ion batteries. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, (C2F5SO2)NLi, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(CF3SO2)(C4F9SO2), and LiC(CF3SO2) LiPF4(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 are preferred. Among these, LiPF6, LiBF4, LiClO4, CF3SO3Li, LiN(CF3SO2)2, and LiN(C2F5SO2)2 are preferred because they are easily soluble in the solvent and exhibit a high degree of dissociation, with LiPF6 and LiBF4 being more preferred.

[0201] Furthermore, as the electrolyte, a gel-like electrolyte is preferred, which contains a polymer compound that swells in an organic solvent to form a retainer that holds the non-aqueous electrolyte. By including a polymer compound that swells in an organic solvent, high ionic conductivity can be obtained, excellent charge and discharge efficiency can be achieved, and leakage of the battery can be prevented. The content of this polymer compound is preferably 0.1% by weight or more and 10.0% by weight or less of the electrolyte. The polymer compound is preferably polyvinylidene fluoride.

[0202] The above electrolytes can be used individually or in combination of two or more. The concentration of the electrolyte in the electrolyte solution is preferably 5% by weight or more and 15% by weight or less, more preferably 5% by weight or more and 13% by weight or less, and even more preferably 5% by weight or more and 10% by weight or less.

[0203] The organic solvent for the electrolyte is not particularly limited as long as it can dissolve the above electrolyte, but cyclic carbonates; linear carbonates; esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolanes and dimethyl sulfoxide are preferred. These organic solvents can be used individually or in combination of two or more.

[0204] 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.

[0205] As cyclic carbonates, alkylene carbonates having alkylene groups with 2 to 4 carbon atoms, such as ethylene carbonate, propylene carbonate, and butylene carbonate, are preferred. Among these, ethylene carbonate and propylene carbonate are preferred from the viewpoint of improving battery characteristics, and ethylene carbonate is more preferred.

[0206] Dialkyl carbonates are preferred as chain-like carbonates. The number of carbon atoms in the constituent alkyl group is preferably 1 to 5, and more preferably 1 to 4. Specifically, 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 are preferred. Among these, dimethyl carbonate and diethyl carbonate are preferred from the viewpoint of viscosity and boiling point, and diethyl carbonate is more preferred.

[0207] 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.

[0208] As a combination of cyclic carbonates and linear carbonates, a combination of ethylene carbonate and linear carbonate is preferred. Specifically, because it offers a good balance between cycle characteristics and high-power discharge characteristics, the following combinations are preferred: 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.

[0209] The mixing ratio of cyclic carbonates and linear carbonates is appropriately selected according to the desired practical properties, and the weight ratio of [cyclic carbonates]:[linear carbonates] is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, even more preferably 30:70 to 70:30, and particularly preferably 40:60 to 60:40.

[0210] The content of cyclic carbonates in the electrolyte is preferably 1% to 70% by weight, with the following order of preference: 1% to 35% by weight, 3% to 30% by weight, and 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% to 70% by weight, with the following order of preference: 43% to 68% by weight. Multiple linear carbonates can be used in mixture form.

[0211] Furthermore, fluorine-containing carbonates are preferred as organic solvents. Specifically, 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 are preferred, and fluorine-containing cyclic carbonates having two or more fluorine atoms are more preferred from the viewpoint of improving battery characteristics.

[0212] Preferred fluorine-containing cyclic carbonates having two or more fluorine atoms include 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.

[0213] The above-mentioned fluorine-containing carbonates can be used individually or in combination of two or more types. The proportion of fluorine-containing carbonate in the electrolyte is preferably 0.001% by weight or more and 10.000% by weight or less, more preferably 0.010% by weight or more and 5.000% by weight or less, even more preferably 0.100% by weight or more and 2.000% by weight or less, particularly preferably 0.200% by weight or more and 1.000% by weight or more, and most preferably 0.250% by weight or more and 0.500% by weight or less. When the content of fluorine-containing carbonate is 0.001% by weight or more, the effect of the fluorine-containing carbonate is well expressed, and when the content of fluorine-containing carbonate is 10.000% by weight or less, the increase in internal pressure of the battery during high-temperature storage can be suppressed.

[0214] Furthermore, cyclic carbonates having unsaturated bonds or aromatic compounds with 7 to 18 carbon atoms may be mixed into the electrolyte as organic solvents.

[0215] 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 properties, and vinylene carbonate and vinylethylene carbonate are more preferred.

[0216] As aromatic compounds having 7 to 18 carbon atoms, from the viewpoint of suppressing a significant decrease in discharge characteristics after high-temperature storage by suppressing side reactions with the negative and positive electrodes, partially hydrogenated forms of biphenyl, alkylbiphenyl, terphenyl, terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, and dibenzofuran are preferred.

[0217] 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. The proportion of each in the electrolyte is preferably 0.001% to 5.000% by weight, more preferably 0.100% to 4.000% by weight, even more preferably 0.300% to 3.000% by weight, particularly preferably 0.400% to 2.500% by weight, and most preferably 0.500% to 2.000% by weight. A proportion of 0.001% by weight or more further improves safety during overcharging. A proportion of 5.000% by weight or less further improves battery characteristics such as high-temperature storage characteristics.

[0218] Figure 1 is a cross-sectional view showing an example of a lithium-ion battery according to an embodiment, and more specifically, a cross-sectional view showing an example of the cross-sectional structure of a coin-type lithium-ion battery. As shown in Figure 1, the 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 213, with the positive electrode 212 and the negative electrode 214 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 casing 213 are filled with a liquid electrolyte. The peripheral edges of the casing 211 and casing 213 are sealed by crimping via a seal gasket 217.

[0219] For example, a lithium-ion battery can be manufactured by stacking a positive electrode and a negative electrode with a separator in between, winding, folding, etc. according to the battery shape as needed, placing it in a battery container, injecting an electrolyte into the battery container, and sealing it. In order to prevent the occurrence of internal pressure increase, overcharging / discharging, etc. in the lithium-ion battery, overcurrent prevention elements such as fuses and PTC elements, expandable metals, lead plates, etc. may be provided as needed. The shape of the lithium-ion battery may be, for example, coin type, button type, sheet type, cylindrical type, rectangular type, flat type, etc., any of them is acceptable.

Example

[0220] Next, examples and comparative examples will be described, but the present invention is not limited to these examples. In the following, “%”, “ppm” and “parts” representing amounts are based on weight unless otherwise specified.

[0221] <Example 1> (Manufacture of Carbon Material A-1) -CVD reaction: Formation of carbonaceous layer on template material- As the raw material of the template material, about 1 g of fumed silica (SiO2 / AEROSIL (registered trademark) NX90G; particle size 38 nm, BET specific surface area 71 m 2 / g, carbon content 0.5 - 1.5%, manufactured by Nippon Aerosil Co., Ltd.) spread in a quartz boat was set in the center of a quartz reaction tube of a horizontal CVD apparatus (transparent electric furnace manufactured by Ishikawa Sangyo Co., Ltd.). While flowing argon gas into the reaction tube at a flow rate of 400 mL / min, it was heated to 910°C at a heating rate of 15°C / min and held for 30 minutes. While maintaining 910°C, methane gas was flowed at a flow rate of 80 mL / min while flowing argon gas at a flow rate of 320 mL / min (raw material gas concentration 20%), and held for 30 minutes. Then, while flowing argon gas at a flow rate of 400 mL / min, it was cooled to room temperature, the quartz boat was taken out, and a carbon material precursor with the surface of the template material coated with a carbonaceous layer was obtained. At this time, it was confirmed by an electron microscope that the template material was an aggregate in which a plurality of nano-primary particles were connected in a bead-like manner with a plurality of branched structures.

[0222] -Removal of mold material- Next, the template material was removed from the obtained carbon material precursor by the following procedure to obtain the carbon material.

[0223] (1) A carbon material precursor was placed in a 100 ml PFA beaker, and ultrapure water was added until the entire carbon material precursor 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) Repeat the operations in (2) to (6) above. (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.

[0224] -Heat treatment- The carbonaceous layer 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 1600°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. It was then cooled to room temperature to obtain carbon material A-1.

[0225] (Specific surface area and total pore volume) Nitrogen adsorption and desorption measurements were performed on the obtained carbon material A-1 using a specific surface area and pore distribution analyzer (BELSORP MAX, manufactured by Microtrac-Bel Co., Ltd.) at -196°C under relative pressure P / P0 = 0.96. Before measurement, the sample underwent degassing treatment by vacuum drying at 150°C for 6 hours. The equilibrium judgment condition when measuring the pressure in the sample tube was set to 300 seconds. From the obtained nitrogen adsorption and desorption isotherms, the BET specific surface area S(m²) was calculated using the BET method. 2 We calculated / g). Based on the obtained adsorption / desorption isotherms, analysis was performed using the software Autosorb 1 (Anton Paar Japan). For type I adsorption / desorption isotherms, the pore size distribution was analyzed by referring to a kernel calculated using density functional theory (DFT) assuming slit-type pores, and the total pore volume was determined. For type IV adsorption / desorption isotherms, the pore size distribution was analyzed by applying the Barrett-Joyner-Halenda method (BJH method) to each adsorption / desorption isotherm, and the total pore volume V (cc / g) was determined. These results are shown in Table 1.

[0226] (Fabrication of positive electrode) The active material is a ternary cathode material NCM (LiNi) with an average particle size of 10 μm. 0.5 Co 0.3 Mn 0.296.5% by weight of O2 powder (manufactured by Tianjin Guoan Guoli New Materials Co., Ltd.), 0.5% by weight of the carbon material A-1 obtained above as a conductive additive, and 3% by weight of PVDF (manufactured by Kureha Corporation) were added to the solvent N-methylpyrrolidone (NMP) and mixed. The conductive additive used was a dispersion of carbon material A-1 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 material slurry. The cathode material 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 positive electrode material was punched out using a φ15mm punch-type die-cutting machine, pressurized with 45kN using a cylinder-type jig, and then vacuum-dried at 120°C to form the positive electrode for battery integration.

[0227] (Raman spectroscopy measurement) The Raman spectrum was measured on the surface of the positive electrode using a micro-Raman spectrometer (DXR3 micro-laser Raman; Thermo Fisher Scientific). A 532 nm (2 mW) laser was used for the measurement, with the following settings: grating: 900 lines / mm, spectrometer aperture: 50 μmφ, measurement range: 100 μm × 100 μm (within the white-lined area in Figure 2A), exposure time: 0.033 sec (30 Hz), step size: 1.0 μm, and number of integrations: 1. The measurement range was 50 to 3400 cm². -1 That's what I decided. Raman mapping measurements were performed within the white lines in Figure 2A to obtain Raman data and mapping images of the positive electrode active material (Figure 2B) and the carbon material (Figure 2C). Figure 3 shows the spectra of the positive electrode active material and carbon material superimposed with the Y-axis scale aligned. The 2D peaks in the obtained spectrum, specifically those of the carbon material, are due to the 2D peaks at 2500–3000 cm⁻¹. -1 The height of the nearby peak is I 2D , 1500-1700cm caused by the G band -1 The height of the nearby peak is I G, 1200-1500cm caused by the D band -1 The height of the nearby peak is I D The macrocrystalline structure index is calculated as follows: D / I G Micrographene stacking index = I 2D / I G , stacking fault ratio = I 2D / I D The results for each are shown in Table 2.

[0228] (Manufacturing of lithium-ion secondary batteries) Using the positive electrode prepared as described above and a φ16mm die-cut piece of metallic Li punched out in a glove box under an argon gas atmosphere, a 25μm thick separator (microporous film made of polypropylene) was placed between the positive electrode composite layer and the negative electrode's metallic Li. A 1M LiPF6 solution (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. Afterwards, it was washed with ethanol and subjected to the battery evaluation described below.

[0229] (Voltage characteristics during high-power discharge) At room temperature (25°C), the test batteries were charged from the open-circuit voltage to 4.2V with a constant current of 1.25mA (equivalent to 0.2C) (constant current charging). After reaching 4.2V, constant voltage charging was performed and continued until the current reached 0.31mA (0.05C). Subsequently, the batteries were discharged to 3V with a high-rate constant current of 31.3mA (equivalent to 5C). The voltage was measured 1 second after the start of discharge, and the difference from the voltage at the end of charging was calculated. The results are shown in Table 2. Lower values ​​indicate superior voltage characteristics during high-power discharge.

[0230] <Example 2> Except for a CVD reaction time of 90 minutes, the procedure was the same as in Example 1 to obtain graphene-containing carbon material A-2, and a 2032-size coin-type battery was fabricated using this carbon material A-2. Material properties were measured and the battery was evaluated using the obtained carbon material A-2, cathode, and test battery, and the results are shown in Tables 1 and 2.

[0231] <Example 3> The operation was the same as in Example 1 except that the CVD reaction time was 40 minutes, to obtain a carbon material A-3 containing graphene, and a 2032-size coin-type battery was fabricated using this carbon material A-3. Using the obtained carbon material A-3, the positive electrode, and the test battery, material property measurements and battery evaluations were performed, and the results are shown in Tables 1 and 2.

[0232] <Example 4> The operation was the same as in Example 1 except that the CVD reaction time was 60 minutes, to obtain a carbon material A-4 containing graphene, and a 2032-size coin-type battery was fabricated using this carbon material A-4. Using the obtained carbon material A-4, the positive electrode, and the test battery, material property measurements and battery evaluations were performed, and the results are shown in Tables 1 and 2.

[0233] <Example 5> The operation was the same as in Example 1 except that the CVD reaction time was 80 minutes, to obtain a carbon material A-5 containing graphene, and a 2032-size coin-type battery was fabricated using this carbon material A-5. Using the obtained carbon material A-5, the positive electrode, and the test battery, material property measurements and battery evaluations were performed, and the results are shown in Tables 1 and 2.

[0234] <Example 6> The operation was the same as in Example 1 except that the CVD reaction time was 130 minutes, to obtain a carbon material A-6 containing graphene, and a 2032-size coin-type battery was fabricated using this carbon material A-6. Using the obtained carbon material A-6, the positive electrode, and the test battery, material property measurements and battery evaluations were performed, and the results are shown in Tables 1 and 2.

[0235] <Example 7> (CVD process and mold heat conversion process) As the mold, synthetic calcium carbonate (Nippon Talc O; average particle size 40 nm, BET specific surface area 50 m 2Approximately 8g of (product code: / g, maximum probability void diameter 35nm, linseed oil absorption 38mL / 100g, bulk density 0.28g / mL, pH 8.4, rosinic acid 2-5%, calcium carbonate purity 90% or higher, melting point 825℃, manufactured by Shiraishi Kogyo Co., Ltd.) was spread on a quartz boat and set 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 400mL / min and heated to 540℃ at a heating rate of 10℃ / min. Then, argon gas was flowed at a flow rate of 320mL / min and acetylene gas at a flow rate of 80mL / min (raw material gas concentration 18%) and the temperature was maintained at 545℃ for 180 minutes. After that, argon gas was flowed at a flow rate of 400mL / min and the temperature was maintained at 900℃ for 120 minutes, then cooled to room temperature and the mold carbonaceous laminate was removed. Furthermore, XRD measurements confirmed that the calcium carbonate particles were converted to calcium oxide after heating at 900°C for 2 hours.

[0236] Furthermore, the amount of mold loss was determined when 100g of mold material was held at each temperature for 90 minutes. 540℃: 5.2g (Example 7 temperature) 600℃: 5.8g 650℃: 9.0g 700℃: 18.7g 900℃: 47.3g Therefore, the mold reduction at the CVD reaction temperature (540°C) in Example 7 was 11% of the reduction at 900°C.

[0237] (Mold removal) Next, the mold was removed from the obtained mold carbonaceous laminate by the following procedure to obtain the carbon material. (1) Approximately 8 g of the mold carbonaceous laminate was placed in a 500 mL glass beaker, and approximately 40 mL of ultrapure water was added and stirred with a stirrer. (2) After adding approximately 40 mL of 8% (2.3 M) hydrochloric acid, the mixture was stirred with a stirrer for 2 hours. (3) The stirred liquid was filtered by suction using a PTFE membrane filter (90 mm diameter, pore size 1 μm). (4) The sample remaining in the beaker was rinsed with a small amount of ultrapure water and filtered by suction. (5) The sample on the filter was collected back into the original glass beaker, and steps (2) to (4) were repeated. (6) Ultrapure water was added to the filter and allowed to stand for 5 minutes, then filtered by suction. (7) Repeat the procedure in (6) using pH test paper until the filtrate is confirmed to be neutral. (8) The sample on the filter paper was collected in a beaker and dried overnight in a 200°C oven.

[0238] (Heat treatment) The carbon material obtained above was placed in a rectangular high-temperature heating furnace (manufactured by Izumi Tech Co., Ltd.), and under reduced pressure (on the order of 10 Pa), it was heated to 1600°C at a heating rate of 15°C / min under argon gas flow (10 mL / min), and held at that temperature for 1 hour for firing. After that, it was cooled to room temperature, and the fired carbon material was removed to obtain 0.57 g of heat-treated graphene-containing carbon material B. A 2032-size coin-type battery was fabricated in the same manner as in Example 1, except that carbon material B was used. Material properties were measured and the battery was evaluated using the obtained carbon material B, cathode, and test battery, and the results are shown in Tables 1 and 2.

[0239] <Example 8> A 2032-size coin-type battery was fabricated in the same manner as in Example 1, except that commercially available carbon black (model number: Denka Black Li-100, manufactured by Denka Co., Ltd.) was used as the carbon material C. Material properties were measured and the battery was evaluated using the carbon material C, the positive electrode, and the test battery, and the results are shown in Tables 1 and 2.

[0240] <Example 9> A 2032-size coin cell was fabricated in the same manner as in Example 1, except that commercially available carbon black (model number: Ketjenblack ECP-3000, manufactured by Lion Specialty Chemicals) was used as carbon material D. Material properties were measured and the battery was evaluated using carbon material D, the cathode, and the test battery, and the results are shown in Tables 1 and 2.

[0241] <Example 10> A 2032-size coin cell was fabricated in the same manner as in Example 1, except that commercially available carbon black (model number: Ketjenblack EC-600JD, manufactured by Lion Specialty Chemicals) was used as carbon material E. Material properties were measured and the battery was evaluated using carbon material E, the cathode, and the test battery, and the results are shown in Tables 1 and 2.

[0242] <Comparative Example 1> A 2032-size coin-type battery was fabricated in the same manner as in Example 1, except that commercially available graphite (model number: KS-6, manufactured by Imerys Co., Ltd.) was used as the carbon material F. Material properties were measured and the battery was evaluated using the carbon material F, the positive electrode, and the test battery, and the results are shown in Tables 1 and 2.

[0243] <Example 11> In the preparation of the positive electrode, a 2032-size coin-type battery was fabricated in the same manner as in Example 2, except that the amount of ternary positive electrode material NCM powder was changed to 96.9% by weight and the amount of carbon material A-1 was changed to 0.1% by weight. Material properties were measured and the battery was evaluated using the positive electrode and test battery, and the results are shown in Table 3.

[0244] <Example 12> In the preparation of the positive electrode, a 2032-size coin-type battery was fabricated in the same manner as in Example 2, except that the amount of ternary positive electrode material NCM powder was changed to 96.75% by weight and the amount of carbon material A-1 was changed to 0.25% by weight. Material properties were measured and the battery was evaluated using the positive electrode and test battery, and the results are shown in Table 3.

[0245] <Example 13> In the preparation of the positive electrode, a 2032-size coin-type battery was fabricated in the same manner as in Example 2, except that the amount of ternary positive electrode material NCM powder was changed to 96.0% by weight and the amount of carbon material A-1 was changed to 1.0% by weight. Material properties were measured and the battery was evaluated using the positive electrode and test battery, and the results are shown in Table 3.

[0246] <Example 14> In the preparation of the positive electrode, a 2032-size coin-type battery was fabricated in the same manner as in Example 2, except that the amount of ternary positive electrode material NCM powder was changed to 95.0% by weight and the amount of carbon material A-1 was changed to 2.0% by weight. Material properties were measured and the battery was evaluated using the positive electrode and test battery, and the results are shown in Table 3.

[0247] (Battery capacity) For Example 2 and the test batteries of 11-14, the following battery capacity evaluations were also performed. At room temperature (25°C), the test batteries were charged from the open-circuit voltage to 4.2V with a constant current of 1.25mA (equivalent to 0.2C) (constant current charging). After reaching 4.2V, constant voltage charging was performed and continued until the current reached 0.31mA (0.05C). Subsequently, the batteries were discharged to 3V with a constant current of 1.25mA. The capacity ratio of each example was calculated using the capacity of Example 2 as a baseline of 100. A higher value indicates superior capacity.

[0248] <Example 15> A 2032-size coin-type battery was fabricated in the same manner as in Example 1, except that 0.25 wt% carbon material A-2 and 0.25 wt% carbon material D were used instead of 0.5 wt% carbon material A-1 in the preparation of the positive electrode. Material properties were measured and the battery was evaluated using the positive electrode and test battery, and the results are shown in Table 4.

[0249] <Example 16> A 2032-size coin-type battery was fabricated in the same manner as in Example 1, except that 0.25 wt% carbon material A-2 and 0.25 wt% carbon material E were used instead of 0.5 wt% carbon material A-1 in the preparation of the positive electrode. Material properties were measured and the battery was evaluated using the positive electrode and test battery, and the results are shown in Table 4.

[0250] [Table 1]

[0251] [Table 2]

[0252] [Table 3]

[0253] [Table 4]

[0254] As is clear from Tables 2-4, in the Raman spectra of the carbon material measured in the positive electrode composite layer, the examples in which the intensity of the D band was higher than the intensity of the 2D band showed higher performance in voltage characteristics during high-power discharge compared to the comparative examples in which the intensity of the D band was less than or equal to the intensity of the 2D band.

[0255] <Reference example> In the examples of patent documents listed in Tables 5 to 7 below, if the conductive additive used is changed to carbon materials A-1 to A-6 and B used in the embodiments of the present invention, each example of the patent documents listed in Tables 5 to 7 can have its properties described in Tables 5 to 7 improved by the improvement rates described in Tables 5 to 7.

[0256] [Table 5]

[0257] [Table 6]

[0258] [Table 7] [Explanation of Symbols]

[0259] 200 Lithium-ion batteries 211 Exterior parts 212 Positive electrode 213 Exterior parts 214 Negative electrode 215 Separator 217 Seal gasket 218 Spring 219 Spacer 300 Ultra-high sensitivity vacuum temperature-controlled desorption mass spectrometer 310 Quartz Reactor 311 Radioactive Thermometer 312 Sample holder 313 High-frequency induction coil 320 detection units 321 Cold Cathode Pirani Gauge 322 Capacitance Gauge 323 Quadrupole mass spectrometer 324 Turbomolecular pump 325 Rotary Pump 326 Valves 327 Gas storage 328 resistors g Calibration gas w Cooling water

Claims

1. A positive electrode comprising a current collector and a positive electrode composite layer formed on the current collector, The positive electrode composite layer contains a positive electrode active material, a binder, and a conductive additive containing a carbon material. A positive electrode in which, in the Raman spectrum of the carbon material measured in the positive electrode composite layer, the intensity of the D band is higher than the intensity of the 2D band.

2. The positive electrode according to claim 1, wherein the Raman spectrum is measured at a position on the surface of the positive electrode composite layer.

3. The positive electrode according to claim 1, wherein the carbon material has a space on the outside and at least one of the inside.

4. The intensity of the 2D band in the Raman spectrum (I ２Ｄ The intensity of the D band (I Ｄ ) intensity ratio (I ２Ｄ / I Ｄ The positive electrode according to claim 1, wherein the coefficient of the positive electrode is 0.10 or more and 0.90 or less.

5. The intensity of the D band in the aforementioned Raman spectrum (I Ｄ The intensity of the G band (I Ｇ ) intensity ratio (I Ｄ / I Ｇ The positive electrode according to claim 1, wherein the coefficient of the positive electrode is 0.50 or greater.

6. The intensity ratio (I ２Ｄ ) of the intensity of the 2D band (I Ｇ ) in the Raman spectrum to the intensity of the G band (I ２Ｄ / I Ｇ ) is 0.10 or more. The positive electrode according to claim 1.

7. The positive electrode according to claim 1, wherein the carbon material comprises one or more connected structures having an extended shape in which a plurality of hollow particulate portions, formed by surrounding walls made of carbonaceous material including a graphene structure, are linked together in a bead-like manner, and pores are formed in the connected structures.

8. A lithium-ion battery comprising the positive electrode according to any one of claims 1 to 7.

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