Carbon material composition, method for producing carbon material composition, negative electrode, and secondary battery

Abstract

The present invention relates to a carbon material composition comprising a carbon material (A) and a carbon material (B), the carbon material (A) comprising graphite having amorphous carbonaceous matter or graphitic matter, the pore distribution determined by mercury porosimetry having two or more peaks, the cumulative pore volume below the minimum value between the peak of the smallest pore diameter and the next peak being set as y (mL / g), the coating rate of the amorphous carbonaceous matter or graphitic matter of the graphite being set as x (%), when y ≤ -0.0084x + 0.13 is satisfied; the carbon material (B) having a pellet density of 1.80 g / cm 3 The above.

Description

TECHNICAL FIELD

[0001] The present application relates to a carbon material composition, a method for manufacturing a carbon material composition, a negative electrode, and a secondary battery. BACKGROUND

[0002] In recent years, along with the miniaturization of electronic devices, the demand for secondary batteries with high capacity is gradually increasing. In particular, secondary batteries, especially lithium ion secondary batteries, which have higher energy density and more excellent charge-discharge characteristics than nickel-cadmium batteries and nickel-hydrogen batteries, have attracted attention. As a lithium ion secondary battery, a nonaqueous lithium secondary battery composed of a positive electrode and a negative electrode capable of occluding and releasing lithium, and a nonaqueous electrolyte in which a lithium salt such as LiPF6 or LiBF4 is dissolved has been developed and put into practical use.

[0003] In the past, the high performance of lithium ion secondary batteries has been extensively studied, but in recent years, further high performance of lithium ion secondary batteries has been required. For example, Patent Literature 1 discloses a negative electrode material in which the peak of the pore volume in the particle and the void in the particle per unit coating rate of the negative electrode material is controlled.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2021-158043 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, the negative electrode material disclosed in Patent Literature 1, if used at a high density, is broken at the time of pressing, and there is a problem that the initial efficiency of the secondary battery is reduced. In addition, there is a problem that the expansion of the electrode plate occurs in the negative electrode material commonly used.

[0009] The present application was completed in view of such a problem, and an object of the present application is to provide a carbon material composition which is not broken at the time of pressing even if used at a high density, can maintain the initial efficiency of the secondary battery at a high level, and can suppress the expansion of the electrode plate at a low level. In addition, an object of the present application is to provide a method for manufacturing a carbon material composition for obtaining the above-described carbon material composition.

[0010] METHOD FOR SOLVING THE PROBLEM

[0011] Hitherto, various negative electrode materials have been investigated, but a negative electrode material capable of maintaining the initial efficiency of a secondary battery at a high level and capable of suppressing the expansion of an electrode plate at a low level has not been found. The present inventors have conducted intensive studies in order to solve the above problem, and as a result, have found that by combining two carbon materials described below, it is possible to maintain the initial efficiency of a secondary battery at a high level and to suppress the expansion of an electrode plate at a low level, thereby completing the present invention.

[0012] That is, the gist of the present invention is as described below.

[0013] [1] A carbon material composition comprising a carbon material (A) and a carbon material (B), wherein the carbon material (A) comprises graphite having an amorphous carbon content or a graphitic content, the pore distribution of the carbon material (A) measured by a mercury intrusion method has two or more peaks, and when the cumulative pore volume below the minimum value between the peak of the smallest pore diameter and the next peak in the pore distribution is set as y (mL / g) and the coating rate of the amorphous carbon content or the graphitic content of the graphite is set as x (%), the carbon material (A) satisfies the following formula (1); the pellet density of the carbon material (B) is 1.80 g / cm 3 or more.

[0014] y ≤ -0.0084x + 0.13 (1)

[0015] [2] The carbon material composition according to [1], wherein the carbon material (A) further satisfies the following formula (2).

[0016] y ≥ 0.005 (2)

[0017] [3] The carbon material composition according to [1] or [2], wherein the peak value of the peak of the smallest pore diameter is 500 nm or less.

[0018] [4] The carbon material composition according to any one of [1] to [3], wherein x in the formula (1) is 0.1 to 15.

[0019] [5] The carbon material composition according to any one of [1] to [4], wherein the tap density of the carbon material (A) is 1.15 g / cm 3 or more.

[0020] [6] The carbon material composition according to any one of [1] to [5], wherein the specific surface area of the carbon material (A) is 3.0 m 2 / g or less.

[0021] [7] The carbon material composition according to any one of [1] to [6], wherein the carbon material (B) is spheroidized graphite.

[0022] [8] The carbon material composition according to any one of [1] to [7], wherein the specific surface area of the carbon material (B) is 3.0 m 2 / g or more.

[0023] [9] The carbon material composition according to any one of [1] to [8], wherein the content of the carbon material (A) is 40 mass% to 90 mass% and the content of the carbon material (B) is 10 mass% to 60 mass% in 100 mass% of the carbon material composition.

[0024]

[10] A method for producing a carbon material composition, the method comprising a step of mixing a carbon material (A) and a carbon material (B), the carbon material (A) comprising graphite having an amorphous carbon component or a graphitic component, the pore distribution of the carbon material (A) measured by a mercury intrusion method having two or more peaks, and when a cumulative pore volume of the carbon material (A) below a minimum value between a peak of the smallest pore diameter and a next peak in the pore distribution is set as y (mL / g) and a coating ratio of the amorphous carbon component or the graphitic component of the graphite is set as x (%), the carbon material (A) satisfies the following formula (1); and the carbon material (B) has a pellet density of 1.80 g / cm 3 or more.

[0025] y < -0.0084x + 0.13 (1)

[0026]

[11] A negative electrode comprising a current collector and an active material layer formed on the current collector, the active material layer comprising the carbon material composition according to any one of [1] to [9].

[0027]

[12] A secondary battery which is a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode according to

[11] .

[0028] Effects of the Invention

[0029] The carbon material composition of the present application, when used as an active material for a negative electrode of a secondary battery, is not damaged at the time of pressing even if used at a high density, can maintain the initial efficiency of the secondary battery at a high level, and can suppress the swelling of the electrode plate at a low level. In addition, the production method of the carbon material composition of the present application can obtain the above-described carbon material composition. DETAILED DESCRIPTION

[0030] Hereinafter, the present application will be described in detail, but the present application is not limited to the following embodiments, and can be implemented with various modifications within the scope of the gist thereof. Note that, in the present specification, in the case where such expressions as "to" are used, they are used as expressions including numerical values or physical values before and after them.

[0031] (Carbon material composition)

[0032] The carbon material composition of the present embodiment contains the carbon material (A) and the carbon material (B). The carbon material (A) contains graphite having amorphous carbon or graphitic material, the pore distribution measured by mercury porosimetry has two or more peaks, and when the cumulative pore volume below the minimum value between the peak of the smallest pore diameter and the next peak in the pore distribution is set as y (mL / g) and the coating rate of the amorphous carbon or graphitic material of the graphite is set as x (%), the following formula (1) is satisfied. In addition, the carbon material (B) has a pellet density of 1.80 g / cm 3 or more.

[0033] y≤-0.0084x+0.13 (1)

[0034] The carbon material (B) can be selectively deformed to a high density with respect to the carbon material (A), and therefore, the carbon material composition is able to suppress the destruction of the carbon material (A) by having the carbon material (B), and is able to sufficiently exert the performance of the carbon material (A) having a high initial efficiency and a low expansion. Therefore, the carbon material composition of the present embodiment, by containing both the above-described carbon material (A) and the above-described carbon material (B), is not destroyed at the time of pressing even if used at a high density, is able to maintain the initial efficiency of the secondary battery at a high level, and is able to suppress the expansion of the electrode plate at a low level.

[0035] (Carbon material (A))

[0036] The carbon material (A) contains graphite having amorphous carbon or graphitic material, the pore distribution measured by mercury porosimetry has two or more peaks, and when the cumulative pore volume below the minimum value between the peak of the smallest pore diameter and the next peak in the pore distribution is set as y (mL / g) and the coating rate of the amorphous carbon or graphitic material of the graphite is set as x (%), the following formula (1) is satisfied.

[0037] y≤-0.0084x+0.13 (1)

[0038] The carbon material composition of the present embodiment, by containing the above-described carbon material (A), is able to maintain the initial efficiency of the secondary battery at a high level and is able to suppress the expansion of the electrode plate at a low level for the following reasons.

[0039] The minimum value below the peak of the smallest pore diameter and the next peak in the pore volume distribution of the carbon material (A) measured by mercury porosimetry is an index of the pore volume present inside the carbon material (A). By reducing the coating ratio of the amorphous carbonaceous or graphitic substance of graphite to a specific range, the voids within the particles are reduced. By reducing the voids within the particles, the particles are more compact compared to the particles of the related art, such as natural graphite, in which the voids within the particles are large, and the particles can be pressed in a state in which the particles are less deformed.

[0040] The pore distribution of the carbon material (A) measured by mercury porosimetry has two or more peaks, and preferably has two peaks. The peaks of the pore distribution indicate the voids between the particles and the voids within the particles, and therefore, in the case where the peaks of the pore distribution are one, it indicates that only the voids between the particles are present. In the case where the peaks of the pore distribution are two or more, it indicates that not only the voids between the particles are present, but also the voids within the particles are present, and is excellent in terms of the fact that the particles themselves have room for deformation compared to the particles in which there are no voids at all.

[0041] For the carbon material (A), when the minimum value below the peak of the smallest pore diameter and the next peak in the pore volume distribution is set as y (mL / g), and the coating ratio of the amorphous carbonaceous or graphitic substance of graphite is set as x (%), the following formula (1) is satisfied.

[0042] y ≤ -0.0084x + 0.13 (1)

[0043] By satisfying formula (1) for the carbon material (A), the pores of the graphite are appropriately coated with the amorphous carbonaceous or graphitic substance, that is, the pores of the graphite are coated with less amorphous carbonaceous or graphitic substance, and therefore, the hardness of the particles of the carbon material (A) can be moderated.

[0044] In the case where formula (1) is expressed as y ≤ αx + β, and the coating ratio x is set as the x axis and the cumulative pore volume y is set as the y axis, α represents the slope of formula (1), and β represents the y-intercept of formula (1).

[0045] In terms of α, α is -0.0084 in accordance with the relationship between the coating ratio of the amorphous carbonaceous or graphitic substance of graphite and the efficiency of filling the voids within the particles of graphite.

[0046] β is the voids within the particles of graphite before coating, and therefore is 0.13, and it is preferable that formula (1) is satisfied when the value of β in formula (1) is set to 0.13 to 0.11, it is more preferable that formula (1) is satisfied when it is set to 0.09, and it is further preferable that formula (1) is satisfied when it is set to 0.07.

[0047] For the carbon material (A), it is necessary to have the voids within the particles to the minimum extent, and therefore, it is preferable that the following formula (2) is further satisfied.

[0048] y > 0.005 (2)

[0049] In the case where the formula (2) is expressed as y > γ, from the aspect that the particle itself has a margin for deformation, γ is preferably 0.005, more preferably satisfies the formula (2) when the value of γ in the formula (2) is set to 0.005 to 0.010, further preferably satisfies the formula (2) when it is set to 0.015.

[0050] The carbon material (A) preferably satisfies the formula (2) in addition to the formula (1), in which case the value of β on the right side of the formula (1) is more preferably 0.11 instead of 0.13, further preferably 0.09, more further preferably 0.07, and the value of γ on the right side of the formula (2) is also more preferably 0.010 instead of 0.005, further preferably 0.015.

[0051] For the pore diameter of the peak value of the peak of the carbon material (A) having the smallest pore diameter, from the aspect that the pores within the particle are small, the flakes within the particle are more densified with each other, and the expansion of the electrode can be reduced, it is preferably 500 nm or less, more preferably 400 nm or less, further preferably 300 nm or less. The lower limit of the pore diameter is not particularly limited, and is usually 5 nm.

[0052] The cumulative pore volume y (mL / g) of the carbon material (A) is preferably 0.002 to 0.120, more preferably 0.003 to 0.090, further preferably 0.005 to 0.070, particularly preferably 0.010 to 0.050. Here, from the aspect that the lithium ion can migrate smoothly within the electrode at the time of charge and discharge, the rapid charge and discharge characteristics are excellent, and the low-temperature input and output characteristics are excellent, it is preferably 0.002 or more, more preferably 0.003 or more, further preferably 0.005 or more, particularly preferably 0.010 or more, and on the other hand, it is preferably 0.120 or less, more preferably 0.090 or less, further preferably 0.070 or less, particularly preferably 0.050 or less.

[0053] In the present specification, the pore distribution is measured by the mercury press-in method.

[0054] Specifically, using a mercury porosimeter, a sample of which the value of about 0.2 g was weighed was sealed in a powder cell, and degassing was performed at 25°C under 50 μmHg or less for 10 minutes to perform pretreatment. Subsequently, the pressure was reduced to 4 psia, mercury was introduced into the above cell, and after the pressure was increased in steps from 4 psia to 40,000 psia, the pressure was reduced to 25 psia. The number of steps at the time of pressure increase was set to 80 points or more, and after 10 seconds of equilibrium time at each step, the mercury penetration amount was measured. The pore distribution was calculated from the mercury penetration curve thus obtained using the Washburn equation. The surface tension (γ) of mercury was calculated to be 485 dyne / cm, and the contact angle (ψ) was calculated to be 140°. A graph with the horizontal axis as the pore diameter and the vertical axis as the pore volume was prepared from the results obtained. From the graph, the peak was identified, the minimum value between the peak of the smallest pore diameter and the next peak (between the two peaks on the side of the smaller pore diameter) was identified, and the cumulative pore volume below the minimum value was taken as the cumulative pore volume (mL / g). The peak refers to a peak showing a vertex of a wave shape, and having a height (difference between the vertex and the cumulative pore volume of the minimum value adjacent to both sides of the vertex) of 0.002 mL / g or more.

[0055] The coating rate x (%) of the carbon material (A) is preferably 0.1 to 15, more preferably 1 to 12, further preferably 2 to 10, and more further preferably 3 to 8. Here, from the viewpoint of smooth migration of lithium ions from the graphite, rapid charge-discharge characteristics, and excellent low-temperature input-output characteristics, the coating rate x (%) is preferably 0.1 or more, more preferably 1 or more, further preferably 2 or more, and particularly preferably 3 or more. In addition, from the viewpoint of sufficient proportion of the graphite and ease of high capacity, the coating rate x (%) is preferably 15 or less, more preferably 12 or less, further preferably 10 or less, and particularly preferably 8 or less.

[0056] In the present specification, the coating rate x (%) is calculated by the following equation (3). That is, it is calculated from the mixing ratio of the graphite to the amorphous carbonaceous substance or the graphitic substance and the firing yield after firing.

[0057] Coating rate x (%) = ([mass of the sample after firing - mass of the graphite] / [mass of the sample after firing]) x 100 (3)

[0058] In the case where the above mixing ratio and the above firing yield are not clear, the coating rate x (%) is estimated using the difference between the true densities of the graphite and the amorphous carbonaceous substance or the graphitic substance.

[0059] Specifically, the crystallinity of the graphite in the carbon material is confirmed by the d002 value, and if the d002 value is the high crystallinity, the coating rate x (%) is estimated using the following equation (4).

[0060] Coating rate x (%) = 596.72 - 264.02 x true density (4)

[0061] The theoretical d002 value of graphite is The d002 value of natural graphite having high crystallinity shows a value close to the theoretical value. On the other hand, for artificial graphite, the d002 value greatly varies depending on the kind of raw material coke and the graphitization temperature.

[0062] The d002 value of the carbon material (A) is preferably 0.3400 nm or more from the viewpoint of the graphite being highly crystalline and having sufficient charge and discharge capacity. More preferably, the d002 value is 0.3410 nm or more. Further preferably, the d002 value is 0.3420 nm or more.

[0063] The Lc of the carbon material (A) is preferably 0.3400 nm or more from the viewpoint of the graphite being highly crystalline and having sufficient charge and discharge capacity. More preferably, the Lc is 0.3410 nm or more. More preferably, the Lc is 0.3420 nm or more. The upper limit value of the Lc is not particularly limited, and is generally 0.3500 nm as the upper limit of the measurement accuracy.

[0064] In the present specification, the d002 value is the value of the interplanar spacing of the crystal plane (002 plane) measured by X-ray diffraction method based on the Jisshin method, and the Lc is the value of the size of the crystallite measured by X-ray diffraction method based on the Jisshin method. The measurement conditions of the X-ray diffraction are described below.

[0065] Sample: a sample obtained by adding and mixing a total amount of about 15 mass% of X-ray standard high-purity silicon powder in the measurement object

[0066] X-ray: Cu Kα ray

[0067] Measurement range: 20° ≤ 2θ ≤ 30°

[0068] Stepping angle: 0.013°

[0069] Sample preparation: a flat sample surface was prepared by filling the powder sample in the 0.2 mm deep sample plate recess

[0070] In the present specification, the true density is set to the value measured by liquid displacement method (pycnometer method) using butanol. The number of times of measurement of the true density is set to 5 times, and the average value thereof is used.

[0071] The true density of the carbon material (A) is preferably 2.200 g / cm3 or more from the viewpoint of the filling property and the capacity being excellent. 3 More preferably, the true density is 2.210 g / cm3 or more. 3 Further preferably, the true density is 2.220 g / cm3 or more. 3 More preferably, the true density is 2.210 g / cm3 or more. The theoretical true density of graphite is 2.262 g / cm3.3 .

[0072] (Physical properties of carbon material (A))

[0073] The volume-based average particle diameter (d50) of the carbon material (A) is preferably 1 to 50 μm, more preferably 3 to 30 μm, and further preferably 5 to 20 μm. Here, the volume-based average particle diameter of the carbon material (A) is preferably 1 μm or more, more preferably 3 μm or more, and further preferably 5 μm or more from the viewpoint of preventing an increase in irreversible capacity and a loss in initial battery capacity. In addition, the volume-based average particle diameter of the carbon material (A) is preferably 50 μm or less, more preferably 30 μm or less, and further preferably 20 μm or less from the viewpoint of being able to suppress process defects such as scratches during the production of the electrode plate, excellent rapid charge / discharge characteristics, and excellent low-temperature input / output characteristics.

[0074] In the present specification, the volume-based average particle diameter (d50) is set to the value of the median particle diameter on a volume basis measured using a laser diffraction / scattering type particle size distribution measuring device.

[0075] Specifically, 0.01 g of a sample is suspended in 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate as a surfactant, introduced into a laser diffraction / scattering type particle size distribution measuring device, and after irradiation with ultrasonic waves at 60 W for 1 minute at 28 kHz, the median particle diameter on a volume basis in the above measuring device is measured.

[0076] The specific surface area (SA) of the carbon material (A) is preferably 0.5 to 10.0 m 2 / g, more preferably 0.8 to 6.5 m 2 / g, further preferably 1.0 to 5.0 m 2 / g, and further more preferably 1.0 to 3.0 m 2 / g. Here, the specific surface area of the carbon material (A) is preferably 0.5 m 2 / g or more, more preferably 0.8 m 2 / g or more, and further preferably 1.0 m 2 / g or more from the viewpoint of ensuring a portion for the entry / exit of lithium ions, excellent rapid charge / discharge characteristics, and excellent low-temperature input / output characteristics. In addition, the specific surface area of the carbon material (A) is preferably 10.0 m 2 / g or less, more preferably 6.5 m 2 / g or less, more preferably 5.0 m 2 / g or less, further preferably 3.0 m 2 / g or less, and further more preferably 2.0 m 2 / g or less.

[0077] In the present specification, the specific surface area (SA) is a value measured by the BET (Brunauer-Emmett-Teller) method.

[0078] Specifically, after the sample was subjected to pre-deaeration drying at 350°C for 15 minutes under nitrogen flow using a specific surface area measuring device, it was cooled to liquid nitrogen temperature, and nitrogen-helium mixed gas adjusted to a value of 0.3 for the relative pressure of nitrogen with respect to atmospheric pressure was used to measure the sample by nitrogen adsorption BET 1-point method based on the gas flow method.

[0079] The tap density of the carbon material (A) is preferably 1.15 to 1.40 g / cm 3 , more preferably 1.17 to 1.35 g / cm 3 , and further preferably 1.20 to 1.30 g / cm 3 . Here, the tap density of the carbon material (A) is preferably 1.15 g / cm 3 or more, more preferably 1.17 g / cm 3 or more, and further preferably 1.20 g / cm 3 or more, from the aspects of being able to suppress process defects such as scratches during the production of the electrode plate, easily forming a negative electrode sheet having good calenderability and high density due to the increased filling property, the degree of curvature of the migration path of lithium ions becoming small during the production of the electrode body, the migration of the electrolyte becoming smooth due to the regular shape of the inter-particle voids, and the improvement of the rapid charge / discharge characteristics. In addition, the tap density of the carbon material (A) is preferably 1.40 g / cm 3 or less, more preferably 1.35 g / cm 3 or less, and further preferably 1.30 g / cm 3 or less, from the aspects of the particles not becoming too hard due to the moderate space on the surface and inside of the particles, excellent electrode pressing properties, and excellent rapid charge / discharge characteristics and low-temperature input / output characteristics.

[0080] In the present specification, the tap density is set to the following value: using a powder density measuring device, the sample is dropped into a cylindrical tap density cell having a diameter of 1.6 cm and a volume capacity of 20 cm 3 , and after filling the cell, 1000 strokes of 10 mm in length are performed, and the value of the density calculated from the volume at this time and the mass of the sample is used.

[0081] The value obtained by subtracting the tap density from the bulk density of the carbon material (A) is preferably 0.10 to 0.80 g / cm 3 , more preferably 0.15 to 0.60 g / cm 3More preferably, it is 0.20–0.40 g / cm³. 3 Here, considering that the particles will not become too hard and can be compressed to a high density, the aforementioned difference is preferably 0.10 g / cm³. 3 The above, more preferably 0.15 g / cm³ 3 The above is further preferred to be 0.20 g / cm³. 3 That's all. Furthermore, considering that the particles have appropriate hardness, are not excessively damaged even when pressed onto the surface of a high-density electrode, and allow for smooth electrolyte migration, the aforementioned difference is preferably 0.80 g / cm³. 3 The following is more preferably 0.60 g / cm³. 3 The following is a further preferred value: 0.40 g / cm³ 3 the following.

[0082] In this specification, the value obtained by subtracting the tapped density from the particle density is calculated using the following formula (5). The value obtained by subtracting the tapped density from the particle density represents the clogging ease under load and can be used as an indicator of particle hardness.

[0083] The value obtained by subtracting the tapped density from the particle density (g / cm³) 3 = Particle density - Tapped density (5)

[0084] In this specification, the particle density is a value obtained by the following method.

[0085] Two clamps were inserted into a mold with an inner diameter of 10mm: a 10mm diameter, 35mm long shaft as a pressing clamp and a 10mm diameter, 6mm long shaft as a receiving clamp. The mold was then placed in a device capable of measuring the load and height during clamping. A 15kgf load was applied using a hydraulic pump, and the clamp height was measured. Then, only the pressing clamp was removed, 0.6g of carbon material was added, and the pressing clamp was reinserted. The mold was placed on a hydraulic jack, the pressure valve was tightened, and the pressure was slowly increased to 0.9t / cm². 2 Rapidly pressurize to 2.4 t / cm 2 Then, hold for 3 seconds, remove your hand from the hydraulic jack, and wait 60 seconds before releasing the pressure valve to depressurize. Next, set up the device capable of measuring the load and height during clamping, apply a 15 kgf load using the hydraulic pump, and measure the height of the clamp after pressurization. Also, measure the mass of the pressurized carbon material, and use the density calculated based on the difference in clamp height and mass as the granular density. The load per unit area is calculated based on the hydraulic jack's scale, the hydraulic cylinder diameter, and the mold's inner diameter.

[0086] The preferred particle density of carbon material (A) is 1.30–1.79 g / cm³. 3more preferably 1.40 to 1.70 g / cm 3 Here, the above pellet density is preferably 1.30 g / cm 3 More preferably, the above is 1.40 g / cm 3 More preferably, the above is 1.40 g / cm 3 More preferably, the above is 1.40 g / cm 3 More preferably, the above is 1.40 g / cm

[0087] The circularity of the carbon material (A) is preferably 0.88 to 0.99, more preferably 0.90 to 0.98, and further preferably 0.92 to 0.97. Here, the circularity of the carbon material (A) is preferably 0.88 or more, more preferably 0.90 or more, and further preferably 0.92 or more, from the viewpoint of the decrease in tortuosity of diffusion of lithium ions, the smooth migration of electrolyte in the interstitial space between particles, and excellent rapid charge-discharge characteristics. In addition, the circularity of the carbon material (A) is preferably 0.99 or less, more preferably 0.98 or less, and further preferably 0.97 or less, from the viewpoint of ensuring the contactability of the carbon materials with each other and excellent cycle characteristics.

[0088] In the present specification, for the circularity, the particle size distribution of the equivalent circle diameter is measured by flow-type particle image analysis and calculated using the following formula (6).

[0089] Specifically, ion exchange water is used as a dispersion medium, and polyoxyethylene sorbitan monolaurate is used as a surfactant, and dispersed by ultrasonic waves to obtain a dispersion liquid. Then, a flow image analysis device is used to take an image of the shape of the particles. From the image of at least 1000 or more particles taken, the circularity of the particles having an equivalent circle diameter in the range of 1.5 μm to 40 μm is averaged to be the circularity.

[0090] [Circularity] = [circumference of an equivalent circle having the same area as the projected shape of the particle] / [actual circumference of the projected shape of the particle] (6)

[0091] (Method for producing carbon material (A))

[0092] The production method of the carbon material (A) is not particularly limited as long as it is a method capable of producing a carbon material (A) containing graphite having amorphous carbon or graphitic material, the pore distribution of the carbon material (A) measured by the mercury intrusion method has two or more peaks, the cumulative pore volume y (mL / g) of the minimum peak of the pore diameter in the pore distribution and the next peak, and the coating rate x (%) of the amorphous carbon or graphitic material of the graphite satisfy the above formula (1). For example, from the viewpoint of densifying the pores in the particles and efficiently reducing the cumulative pore volume y, a method in which the carbon material raw material is subjected to a spheronization treatment in the presence of a granulating agent, subjected to a pressurization treatment, and attached with an amorphous carbon precursor or a graphitic material precursor is preferable. Specifically, a production method including the following steps (1) to (6) is preferable.

[0093] Step (1): Step of adjusting the particle size of the carbon material raw material

[0094] Step (2): Step of mixing the carbon material raw material and the granulating agent

[0095] Step (3): Step of spheronizing the carbon material raw material

[0096] Step (4): Step of removing the granulating agent

[0097] Step (5): Step of performing a pressurization treatment

[0098] Step (6): Step of attaching an amorphous carbon or graphitic material

[0099] Hereinafter, the steps (1) to (6) will be described, but a step other than the steps (1) to (6) can be included before and after each step, and the production method can not be limited to the production method including the steps (1) to (6).

[0100] (Step (1))

[0101] Step (1) is a step of adjusting the particle size of the carbon material raw material.

[0102] The carbon material raw material is graphite, and from the viewpoint of high crystallinity and excellent capacity, a natural graphite or an artificial graphite is preferable, and from the viewpoint of higher crystallinity and more excellent capacity, and the need for heat treatment at the time of production, a natural graphite is more preferable. The graphite is preferably graphite having less impurities, and is preferably used after purification treatment as needed.

[0103] As the natural graphite, for example, Amorphous Graphite, Vein Graphite, Flake Graphite, and the like can be exemplified. Among these natural graphites, from the viewpoint of high graphitization degree and small amount of impurities, Vein Graphite, Flake Graphite are preferable, and Flake Graphite is more preferable.

[0104] As the artificial graphite, for example, a material obtained by graphitizing an organic substance such as coal-tar pitch, coal-based heavy oil, atmospheric residue, petroleum-based heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene ether, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin, and the like at 2500°C or higher can be exemplified.

[0105] From the viewpoint of high crystallinity of the graphite and sufficient charge / discharge capacity, the d002 value of the carbon material raw material is preferably 0.3400 nm or less, more preferably 0.3350 nm or less, and even more preferably 0.3300 nm or less. The d002 value is more preferably 0.3350 nm or less, and even more preferably 0.3300 nm or less. The d002 value is more preferably 0.3350 nm or less, and even more preferably 0.3300 nm or less.

[0106] From the viewpoint of high crystallinity of the graphite and sufficient charge / discharge capacity, the Lc of the carbon material raw material is preferably 0.1400 nm or more, more preferably 0.1450 nm or more, and even more preferably 0.1500 nm or more. The Lc is more preferably 0.1450 nm or more, and even more preferably 0.1500 nm or more. The Lc is more preferably 0.1450 nm or more, and even more preferably 0.1500 nm or more. The upper limit of the Lc is not particularly limited, and the upper limit of the measurement is 0.2000 nm.

[0107] From the viewpoint of capacity and excellent safety of the battery, the purity of the carbon material raw material is preferably 99.0% or more, more preferably 99.5% or more, even more preferably 99.9% or more, and particularly preferably 100%.

[0108] In the present specification, the purity is a value calculated from the mass of the carbon material raw material before and after heating of about 10 g of the carbon material raw material which has been sufficiently dried, under the atmosphere to 815°C for 10 hours, by accurately weighing.

[0109] The volume-based average particle diameter (d50) of the carbon material raw material is preferably 1 to 150 μm, more preferably 3 to 130 μm, and even more preferably 5 to 120 μm. Here, from the viewpoint of excellent transportability, the volume-based average particle diameter of the carbon material raw material is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. In addition, from the viewpoint of excellent productivity, the volume-based average particle diameter of the carbon material raw material is preferably 150 μm or less, more preferably 130 μm or less, and even more preferably 120 μm or less.

[0110] The specific surface area (SA) of the carbon material raw material is preferably 1.0 m 2 / g or more, more preferably 1.5 m 2 / g or more, further preferably 2.0 m 2 / g or more, and preferably 30.0 m 2 / g or less, more preferably 20.0 m 2 / g or less, further preferably 10.0 m 2 / g or less.

[0111] The tap density of the carbon material raw material is preferably 0.60 to 1.40 g / cm 3 , more preferably 0.70 to 1.30 g / cm 3 , further preferably 0.80 to 1.20 g / cm 3 . Here, the tap density of the carbon material raw material is preferably 0.60 g / cm 3 or more, more preferably 0.70 g / cm 3 or more, further preferably 0.80 g / cm 3 or more, from the viewpoint of excellent transportability. In addition, the tap density of the carbon material raw material is preferably 1.40 g / cm 3 or less, more preferably 1.30 g / cm 3 or less, further preferably 1.20 g / cm 3 or less, from the viewpoint of easy control at the time of pulverization.

[0112] The method of adjusting the particle size of the carbon material raw material is not particularly limited as long as it can adjust the volume-based average particle diameter and the specific surface area described later, and pulverization, crushing, and classification can be performed.

[0113] The pulverization, crushing, and classification can use publicly known methods.

[0114] The volume-based average particle diameter (d50) of the carbon material raw material after adjustment of the particle size is preferably 1 to 20 μm, more preferably 2 to 15 μm, further preferably 3 to 12 μm. Here, the volume-based average particle diameter after adjustment of the particle size is preferably 1 μm or more, more preferably 2 μm or more, further preferably 3 μm or more, and preferably 20 μm or less, more preferably 15 μm or less, further preferably 12 μm or less, from the viewpoint of easy control of the spheroidization treatment.

[0115] The specific surface area (SA) of the carbon material raw material after adjustment of the particle size is preferably 5.0 to 30.0 m 2 / g, more preferably 7.0 to 25.0 m 2 / g, further preferably 9.0 to 20.0 m 2m2 / g. Here, the specific surface area after the particle size adjustment is preferably 5.0 m2 / g or more, more preferably 7.0 m2 / g or more, further preferably 7.5 m2 / g or more, still further preferably 9.0 m2 / g or more, particularly preferably 10.0 m2 / g or more, and particularly preferably 12.0 m2 / g or more, from the viewpoint of ensuring the lithium ion passage, the rapid charge / discharge characteristics, and the low-temperature input / output characteristics. 2 / g or more, more preferably 7.0 m 2 / g or more, further preferably 7.5 m 2 / g or more, still further preferably 9.0 m 2 / g or more, particularly preferably 10.0 m 2 / g or more. In addition, the specific surface area after the particle size adjustment is preferably 30.0 m2 / g or less, more preferably 25.0 m2 / g or less, further preferably 20.0 m2 / g or less, and particularly preferably 15.0 m2 / g or less, from the viewpoint of suppressing the side reaction with the electrolyte, preventing the decrease in initial charge / discharge efficiency and the increase in gas generation amount, and improving the battery capacity. 2 / g or less, more preferably 25.0 m 2 / g or less, further preferably 20.0 m 2 / g or less.

[0116] The tap density after the particle size adjustment of the carbon material raw material is preferably 0.40 to 1.40 g / cm 3 , more preferably 0.450 to 1.30 g / cm 3 , further preferably 0.50 to 1.20 g / cm 3 . Here, the tap density after the particle size adjustment is preferably 0.40 g / cm 3 or more, more preferably 0.45 g / cm 3 or more, further preferably 0.50 g / cm 3 or more, still further preferably 0.60 g / cm 3 or more, still further preferably 0.70 g / cm 3 or more, particularly preferably 0.80 g / cm 3 or more. In addition, the tap density after the particle size adjustment is preferably 1.40 g / cm 3 or less, more preferably 1.30 g / cm 3 or less, further preferably 1.20 g / cm 3 or less.

[0117] (Step (2))

[0118] Step (2) is a step of mixing the carbon material raw material and the granulating agent.

[0119] The granulating agent is preferably liquid at the time of the spheroidization treatment of the carbon material raw material.

[0120] In addition, the granulating agent preferably contains an organic compound that becomes amorphous carbon.

[0121] Further, the granulating agent is preferably a granulating agent not containing an organic solvent, a granulating agent containing an organic solvent and at least one of the organic solvents not having a flash point, or a granulating agent containing an organic solvent having a flash point of 5°C or higher.

[0122] If the granulating agent satisfies the above requirements, when the carbon material raw material is subjected to the spheroidization treatment, the granulating agent forms a liquid bridge between the carbon material raw materials, and a force of attraction due to capillary negative pressure of the liquid bridge and surface tension of the liquid is generated between the carbon material raw materials, so that the distance between the carbon material raw materials can be effectively shortened.

[0123] As a method of mixing the carbon material raw material and the granulating agent, for example, a method of mixing the carbon material raw material and the granulating agent using a blender or a kneader, a method of adding the carbon material raw material to a solution in which the granulating agent is dissolved and then removing the solvent, and the like can be given. Among these methods, from the viewpoint of being able to effectively reduce fine pores of 1 nm to 4 nm, a method of mixing the carbon material raw material and the granulating agent using a blender or a kneader is preferred.

[0124] The amount of the granulating agent to be added is preferably 0.1 to 100 parts by mass, more preferably 1 to 80 parts by mass, and further preferably 10 to 50 parts by mass, relative to 100 parts by mass of the carbon material raw material. Here, from the viewpoint of being able to suppress a decrease in the degree of spheroidization due to a decrease in the adhesion between the carbon material raw materials and being able to suppress a decrease in productivity due to the carbon material raw material adhering to the device, the amount of the granulating agent to be added is preferably 0.1 parts by mass or more, more preferably 1 parts by mass or more, and further preferably 10 parts by mass or more, relative to 100 parts by mass of the carbon material raw material, and is preferably 1000 parts by mass or less, more preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and further preferably 50 parts by mass or less.

[0125] (Step (3))

[0126] Step (3) is a step of subjecting the carbon material raw material to spheroidization treatment.

[0127] By subjecting the carbon material raw material to spheroidization treatment, the rapid charge-discharge characteristics are excellent.

[0128] From the viewpoint of being easy to control the shape of the particles, the method of subjecting the carbon material raw material to spheroidization treatment is preferably a method of subjecting the carbon material raw material to spheroidization treatment by imparting mechanical energy.

[0129] As the mechanical energy, for example, impact, compression, friction, shear force, and the like can be given. These mechanical energies can be used singly or in combination of two or more.

[0130] The method of subjecting the carbon material raw material to spheroidization treatment by imparting mechanical energy can use a device that applies mechanical energy.

[0131] The viscosity of the granulating agent when the carbon material raw material is subjected to the spheroidization treatment is preferably 1 to 1000 cP, more preferably 5 to 800 cP, further preferably 10 to 600 cP, and further preferably 20 to 500 cP. Here, the viscosity of the above granulating agent is preferably 1 cP or more, more preferably 5 cP or more, further preferably 10 cP or more, and particularly preferably 20 cP or more, from the viewpoint of being able to suppress the re-detachment of the spheroidized particles due to the impact force with the rotor and the housing when the spheroidization treatment is performed, being able to reduce the fine pores by the granulating agent entering the fine pores of 1 nm to 4 nm to become amorphous carbon, and being excellent in low-temperature input-output characteristics, high-temperature storage characteristics, and the like, and is preferably 1000 cP or less, more preferably 800 cP or less, further preferably 600 cP or less, and particularly preferably 500 cP or less.

[0132] The viscosity of the granulating agent when the carbon material raw material is subjected to the spheroidization treatment can be adjusted by the amount of the organic solvent and the temperature of the spheroidization treatment.

[0133] In the present specification, the viscosity is a value measured at 25°C using a rheometer. The shear stress at a shear rate of 100 s -1 -1 is 0.1 Pa or more, and the shear stress at a shear rate of 1000 s -1 -1 is less than 0.1 Pa. -1 -1 is less than 0.1 Pa, and the shear stress at a shear rate of 1000 s -1 -1 is less than 0.1 Pa. -1 -1 is less than 0.1 Pa.

[0134] When the carbon material raw material is subjected to the spheroidization treatment, the carbon material raw material can also be granulated in the presence of other substances. As the other substances, for example, metals capable of forming alloys with lithium, oxides thereof, amorphous carbon, green coke, and the like can be given.

[0135] When the carbon material raw material is subjected to the spheroidization treatment, it is preferable to perform the spheroidization treatment while allowing the fine powder generated in the spheroidization treatment to adhere to the surface of the carbon material. By performing the spheroidization treatment while allowing the fine powder generated in the spheroidization treatment to adhere to the surface of the carbon material, when the carbon material is coated with amorphous carbon or graphite, it is possible to effectively reduce the voids in the carbon material. In addition, the amount of edges that can be utilized as sites for the insertion and extraction of lithium ions increases, and the electrolyte effectively spreads to the voids in the carbon material, and the low-temperature input-output characteristics and cycle characteristics are excellent.

[0136] The fine powder is not only the fine powder generated in the spheroidization treatment, but a fine powder having a particle size adjusted can also be separately added.

[0137] In order to effectively adhere the fine powder to the surface of the carbon material, it is preferable to enhance the adhesion between carbon material particles, between carbon material particles and fine powder particles, and between fine powder particles.

[0138] As the adhesion between particles, there can be mentioned, for example, van der Waals force without the aid of inter-particle inclusions, electrostatic attraction, physical cross-linking force with the aid of inter-particle inclusions, chemical cross-linking force, and the like.

[0139] In the case of van der Waals force, it is preferable that the average particle diameter (d50) on a volume basis be 100 μm or less. That is, the smaller the average particle diameter (d50) on a volume basis, the more the [self weight] becomes < [adhesion force]. Therefore, the smaller the average particle diameter (d50) on a volume basis of the carbon material raw material, the stronger the adhesion between particles, and the more easily the fine powder is formed in a state of being adhered to and encapsulated by the carbon material that has been spheroidized, and thus it is preferable.

[0140] The carbon material raw material and the granulating agent can be simultaneously charged in the spheroidization treatment device, and processes (2) and (3) can be simultaneously performed.

[0141] (Step (4))

[0142] Step (4) is a step of removing the granulating agent.

[0143] The granulating agent can be removed in whole or in part.

[0144] In the case where a granulating agent containing an organic solvent is used, it is preferable to remove the organic solvent as well.

[0145] As the method of removing the granulating agent and the method of removing the organic solvent, there can be mentioned, for example, a method of washing with a solvent, a method of performing heating to volatilize / decompose, and the like. Among these methods, from the viewpoint of productivity and removal efficiency, the method of performing heating to volatilize / decompose is preferable.

[0146] (Step (5))

[0147] Step (5) is a step of performing pressurization treatment.

[0148] As the pressurization treatment, there can be mentioned, for example, isotropic pressurization treatment, anisotropic pressurization treatment, and the like. Among these pressurization treatments, from the viewpoint of being able to control so that the obtained carbon material (A) satisfies formula (1), the isotropic pressurization treatment is preferable.

[0149] As the pressurization method, there can be mentioned, for example, hydrostatic isotropic pressurization treatment using water as a pressurization medium, isotropic pressurization treatment based on air pressure using a gas such as air as a pressurization medium, pressurization treatment of filling in a mold and performing pressurization in a certain direction with a uniaxial press, and the like.

[0150] The pressure at which the pressurization is performed is preferably 50 to 300 MPa, more preferably 100 to 280 MPa, and further preferably 150 to 260 MPa. Here, the pressure at which the pressurization is performed is preferably 50 MPa or greater, more preferably 100 MPa or greater, and further preferably 150 MPa or greater, from the aspect of easily controlling so that the resulting carbon material (A) satisfies formula (1), and is preferably 300 MPa or less, more preferably 280 MPa or less, and further preferably 260 MPa or less.

[0151] The step (5) can be performed at any timing of the steps (1) to (6), and is preferably between the step (4) and the step (6) from the aspect of being able to efficiently perform the pressurization in a state in which the excess granulating agent is removed.

[0152] (Step (6))

[0153] The step (6) is a step of adding amorphous carbonaceous matter or graphitic matter.

[0154] By adding the amorphous carbonaceous matter or the graphitic matter to the carbon material, the side reaction of the negative electrode with the electrolyte solution can be suppressed, the capacity is high, and the high-temperature input-output characteristics and the high-temperature storage characteristics are excellent.

[0155] The amorphous carbonaceous matter refers to carbon having a d002 value of 0.340 nm or greater.

[0156] The graphitic matter refers to graphite having a d002 value of less than 0.340 nm.

[0157] From the aspect of easily controlling the amount of the voids within the particles, the method of adding the amorphous carbonaceous matter or the graphitic matter to the carbon material is preferably a method of mixing the carbon material with an amorphous carbonaceous matter precursor or a graphitic matter precursor, and heating in a non-oxidizing gas atmosphere to perform amorphous carbonization of the amorphous carbonaceous matter precursor or graphitization of the graphitic matter precursor.

[0158] As the mixing method of the carbon material and the amorphous carbonaceous matter precursor or the graphitic matter precursor, there can be mentioned, for example, a method of mixing the carbon material and the amorphous carbonaceous matter precursor or the graphitic matter precursor using a blender or a kneader; a method of adding the carbon material to a solution in which the amorphous carbonaceous matter precursor or the graphitic matter precursor is dissolved, and then removing the solvent; and the like. Among these methods, the method of mixing the carbon material and the amorphous carbonaceous matter precursor or the graphitic matter precursor using a blender or a kneader is preferred from the aspect of being able to effectively reduce the fine pores of 1 nm to 4 nm.

[0159] The mixing ratio of the carbon material and the amorphous carbonaceous matter precursor or the graphitic matter precursor is appropriately set in such a manner that the desired coating rate x is achieved.

[0160] The gas atmosphere during heating is not particularly limited as long as it is a non-oxidizing gas atmosphere, and is preferably nitrogen, argon, carbon dioxide, and more preferably nitrogen from the viewpoint of suppressing the generation of fine pores due to oxidation.

[0161] The oxygen concentration is preferably 1 vol% or less, and more preferably 0.1 vol% or less, from the viewpoint of easily controlling the obtained carbon material (A) to satisfy formula (1). The lower limit of the oxygen concentration is not particularly limited, and is usually 0 vol%.

[0162] The heating temperature is different between the amorphous carbonization of the amorphous carbonaceous precursor and the graphitization of the graphitic precursor.

[0163] The heating temperature in the case of amorphous carbonization of the amorphous carbonaceous precursor is not particularly limited as long as it is a temperature that does not reach a crystalline structure equivalent to that of graphite, and is preferably 500 to 2000°C, more preferably 600 to 1800°C, and further preferably 700 to 1600°C. Here, the above heating temperature is preferably 500°C or higher, more preferably 600°C or higher, and further preferably 700°C or higher, and is also preferably 2000°C or lower, more preferably 1800°C or lower, and further preferably 1600°C or lower.

[0164] The heating temperature in the case of graphitization of the graphitic precursor is not particularly limited as long as it is a temperature that reaches a crystalline structure equivalent to that of graphite, and is preferably 2100 to 3300°C, more preferably 2500 to 3200°C, and further preferably 2700 to 3100°C. Here, the above heating temperature is preferably 2100°C or higher, more preferably 2500°C or higher, and further preferably 2700°C or higher, and is also preferably 3300°C or lower, more preferably 3200°C or lower, and further preferably 3100°C or lower.

[0165] The heating time is preferably 0.1 to 1000 hours, and more preferably 1 to 100 hours. Here, the heating time is preferably 0.1 hours or more, and more preferably 1 hour or more, from the viewpoint of easily controlling the obtained carbon material (A) to satisfy formula (1), and is also preferably 1000 hours or less, and more preferably 100 hours or less.

[0166] As the amorphous carbonaceous precursor, graphite precursor, for example, tar, pitch, naphthalene, anthracene and the like aromatic hydrocarbons, phenol formaldehyde resin, polyvinyl alcohol resin and the like thermoplastic resins can be exemplified. These precursors can be used singly or in combination of two or more. Among these precursors, from the viewpoint of easy development of carbon structure and the ability to coat in a small amount, tar, pitch and aromatic hydrocarbons are preferred, and from the viewpoint of easy control to satisfy the carbon material (A) of formula (1), precursors having a carbon residue of 50% or more are more preferred, and precursors having a carbon residue of 60% or more are further preferred.

[0167] The ash content in the amorphous carbonaceous precursor, graphite precursor is preferably 0.00001 to 1% by mass in 100% by mass of the amorphous carbonaceous precursor, graphite precursor. Here, from the viewpoint of easy control to satisfy the carbon material (A) of formula (1), the ash content is preferably 0.00001% by mass or more, and is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.1% by mass or less.

[0168] The metal impurity content in the amorphous carbonaceous precursor, graphite precursor is preferably 0.1 to 1000 ppm by mass. Here, from the viewpoint of easy control to satisfy the carbon material (A) of formula (1), the metal impurity content is preferably 0.1 ppm by mass or more, and is preferably 1000 ppm by mass or less, more preferably 500 ppm by mass or less, and further preferably 100 ppm by mass or less.

[0169] In the present specification, the metal impurity content is a value obtained by dividing the total content of Fe, Al, Si and Ca in the amorphous carbonaceous precursor, graphite precursor by the carbon residue.

[0170] From the viewpoint of easy control to satisfy the carbon material (A) of formula (1), Qi (quinoline insolubles) in the amorphous carbonaceous precursor, graphite precursor is preferably 5% by mass or less, and more preferably 3% by mass or less in 100% by mass of the amorphous carbonaceous precursor, graphite precursor. The lower limit of Qi is not particularly limited, and is usually 0% by mass.

[0171] In order to make the volume-based average particle diameter of the carbon material (A) fall within a desired range, the carbon material obtained by the processes (1) to (6) can be subjected to pulverization, crushing or classification as necessary.

[0172] The pulverization, crushing or classification can be performed using a publicly known method.

[0173] (Carbon material (B))

[0174] The pellet density of the carbon material (B) is 1.80 g / cm 3 or more.

[0175] The carbon material composition of the present embodiment, by containing the above-described carbon material (B), can be selectively densified when combined with the above-described carbon material (A) and used to press an electrode to a given density. Further, the above-described carbon material (B) does not easily increase in surface area even when deformed upon pressing, and thus, by combining the carbon material (A) and the carbon material (B), the increase in reaction area of the electrode when used at high density can be suppressed.

[0176] The pellet density of the carbon material (B) is preferably 1.80 to 2.262 g / cm 3 Here, from the aspect of excellent compressibility upon pressing, the pellet density of the carbon material (B) is 1.80 g / cm 3 or more, preferably 1.85 g / cm 3 or more, more preferably 1.88 g / cm 3 or more, further preferably 1.90 g / cm 3 or more, and additionally, 2.262 g / cm 3 or less.

[0177] In order for the pellet density of the carbon material (B) to be 1.80 g / cm 3 or more, the particles can be made to have moderate voids, and the scales can be made to moderately stack together, and thus, the carbon material (B) is preferably a scale-spheroidized natural graphite.

[0178] (Properties of the carbon material (B))

[0179] From the aspect that the more crystalline the graphite, the more excellent the compressibility upon pressing, and the more sufficient the charge and discharge capacity, the d002 value of the carbon material (B) is preferably or more, more preferably or less. The lower limit of the above-described d002 value is not particularly limited, and the theoretical value is or more.

[0180] From the aspect that the more crystalline the graphite, the more excellent the compressibility upon pressing, and the more sufficient the charge and discharge capacity, the Lc of the carbon material (B) is preferably or more, more preferably or less. The upper limit of the above-described Lc is not particularly limited, and the upper limit of the measured value is

[0181] The volume-based average particle diameter (d50) of the carbon material (B) is preferably 1 to 50 μm, more preferably 4 to 30 μm, and further preferably 10 to 25 μm. Here, the volume-based average particle diameter of the carbon material (B) is preferably 1 μm or more, more preferably 4 μm or more, and further preferably 10 μm or more from the viewpoint of preventing an increase in irreversible capacity and a loss in initial battery capacity. In addition, the volume-based average particle diameter of the carbon material (B) is preferably 50 μm or less, more preferably 30 μm or less, and further preferably 25 μm or less from the viewpoint of being able to suppress process defects such as scratches during the production of the electrode plate, excellent rapid charge / discharge characteristics, and excellent low-temperature input / output characteristics.

[0182] The specific surface area (SA) of the carbon material (B) is preferably 3.0 to 11.0 m 2 / g, more preferably 4.0 to 9.0 m 2 / g, and further preferably 5.0 to 8.0 m 2 / g. Here, the specific surface area of the carbon material (B) is preferably 3.0 m 2 / g or more, more preferably 4.0 m 2 / g or more, and further preferably 5.0 m 2 / g or more from the viewpoint of ensuring a portion for the entry / exit of lithium ions, excellent rapid charge / discharge characteristics, and excellent low-temperature input / output characteristics. In addition, the specific surface area of the carbon material (B) is preferably 11.0 m 2 / g or less, more preferably 9.0 m 2 / g or less, and further preferably 8.0 m 2 / g or less from the viewpoint of suppressing side reactions with the electrolyte, preventing a decrease in initial charge / discharge efficiency and an increase in gas generation, and improving battery capacity.

[0183] The tap density of the carbon material (B) is preferably 0.70 to 1.30 g / cm 3 , more preferably 0.80 to 1.20 g / cm 3 , and further preferably 0.90 to 1.10 g / cm 3 . Here, the tap density of the carbon material (B) is preferably 0.70 g / cm 3 or more, more preferably 0.80 g / cm 3 or more, and further preferably 0.90 g / cm 3The above. In addition, from the viewpoint that the particles do not become too hard due to the moderate space in the surface and inside of the particles, the electrode has excellent pressability, and the rapid charge-discharge characteristics and low-temperature input-output characteristics are excellent, the tap density of the carbon material (B) is preferably 1.30 g / cm 3 More preferably, the above. 3 Further preferably, the above. 3 The above.

[0184] The circularity of the carbon material (B) is preferably 0.88 to 0.99, more preferably 0.90 to 0.98, and further preferably 0.92 to 0.97. Here, from the viewpoint that the tortuosity of lithium ion diffusion decreases, the migration of the electrolyte in the interstitial space between the particles becomes smooth, and the rapid charge-discharge characteristics are excellent, the circularity of the carbon material (B) is preferably 0.88 or more, more preferably 0.90 or more, and further preferably 0.92 or more. In addition, from the viewpoint that the contactability of the carbon materials with each other can be ensured and the cycle characteristics are excellent, the circularity of the carbon material (B) is preferably 0.99 or less, more preferably 0.98 or less, and further preferably 0.97 or less.

[0185] The cumulative pore volume of the carbon material (B) is preferably 0.030 to 0.140 mL / g, more preferably 0.040 to 0.130 mL / g, and further preferably 0.050 to 0.100 mL / g. Here, from the viewpoint that the carbon material (B) is easily moderately deformed at the time of pressing, the cumulative pore volume of the carbon material (B) is preferably 0.030 mL / g or more, more preferably 0.040 mL / g or more, and further preferably 0.050 mL / g or more. In addition, the cumulative pore volume of the carbon material (B) is preferably 0.140 mL / g or less, more preferably 0.130 mL / g or less, further preferably 0.120 mL / g or less, more further preferably 0.100 mL / g or less, more further preferably 0.090 mL / g or less, and particularly preferably 0.070 mL / g or less.

[0186] (Method for producing carbon material (B))

[0187] The method for producing the carbon material (B) is not particularly limited as long as it can be produced so that the pellet density satisfies 1.80 g / cm 3 The above method is sufficient, and there is no particular limitation, and from the viewpoint that the crystallinity is high and the compressibility is excellent, it is preferable to use flake-spheroidized natural graphite as the carbon material (B).

[0188] The raw material of the carbon material (B) is preferably graphite, and more preferably natural graphite or artificial graphite from the viewpoint of high crystallinity and excellent capacity, and further preferably natural graphite from the viewpoint of higher crystallinity, more excellent capacity, and no need for heat treatment at the time of production. The graphite is preferably graphite having few impurities, and is preferably used after purification treatment as necessary.

[0189] As the natural graphite, for example, earthy graphite, vein graphite, flaky graphite, and the like can be given. Among these, vein graphite and flaky graphite are preferable from the viewpoint of high degree of graphitization and few impurities, and flaky graphite is more preferable.

[0190] As the artificial graphite, for example, a material obtained by graphitizing an organic substance such as coal-tar pitch, coal-based heavy oil, atmospheric residue, petroleum-based heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenyl, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene ether, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin, or the like at 2500°C or higher can be given.

[0191] From the viewpoint of ease of controlling the shape of the particles, the method of performing the spheroidization treatment is preferably a method of imparting mechanical energy to perform the spheroidization treatment.

[0192] As the mechanical energy, for example, impact, compression, friction, shear force, and the like can be given. These mechanical energies can be used singly or in combination of two or more.

[0193] The method of imparting mechanical energy to perform the spheroidization treatment can use a device that applies mechanical energy.

[0194] In the spheroidization treatment, the raw material can be granulated in the presence of other substances. As the other substances, for example, a metal capable of forming an alloy with lithium, an oxide thereof, green coke, and the like can be given.

[0195] (Composition of the Carbon Material Composition)

[0196] The content ratio of the carbon material (A) in the carbon material composition 100% by mass is preferably 40 to 90% by mass, more preferably 45 to 85% by mass, and further preferably 55 to 75% by mass. Here, from the viewpoint of being able to suppress the expansion of the electrode plate to a low level, the content ratio of the carbon material (A) in the carbon material composition 100% by mass is preferably 40% by mass or more, more preferably 45% by mass or more, and further preferably 55% by mass or more. In addition, from the viewpoint of being able to maintain the initial efficiency of the secondary battery at a high level, the content ratio of the carbon material (A) is preferably 90% by mass or less, more preferably 85% by mass or less, and further preferably 75% by mass or less.

[0197] The content of the carbon material (B) in the carbon material composition 100 mass% is preferably 10 to 60 mass%, more preferably 15 to 55 mass%, and further preferably 25 to 45 mass%. Here, from the viewpoint of being able to maintain the initial efficiency of the secondary battery at a high level, the content of the carbon material (B) in the carbon material composition 100 mass% is preferably 10 mass% or more, more preferably 15 mass% or more, and further preferably 25 mass% or more. In addition, from the viewpoint of being able to suppress the expansion of the electrode plate at a low level, the content of the carbon material (B) is preferably 60 mass% or less, more preferably 55 mass% or less, and further preferably 45 mass% or less.

[0198] The carbon material composition of the present embodiment can contain other substances in addition to the carbon material (A) and the carbon material (B). As the other substances, for example, metals capable of forming alloys with lithium, oxides thereof, conductive materials, and the like can be given.

[0199] From the viewpoint of not impairing the functions of the carbon material (A) and the carbon material (B) as such, the total content of the other substances is preferably 20 mass% or less, and more preferably 10 mass% or less.

[0200] (Physical properties of the carbon material composition)

[0201] The volume-based average particle diameter (d50) of the carbon material composition is preferably 1 to 50 μm, more preferably 4 to 30 μm, and further preferably 10 to 25 μm. Here, from the viewpoint of preventing an increase in irreversible capacity and a loss in initial battery capacity, the volume-based average particle diameter of the carbon material composition is preferably 1 μm or more, more preferably 4 μm or more, and further preferably 10 μm or more. In addition, from the viewpoint of being able to suppress process defects such as scratches during the production of the electrode plate, excellent rapid charge-discharge characteristics, and excellent low-temperature input-output characteristics, the volume-based average particle diameter of the carbon material composition is preferably 50 μm or less, more preferably 30 μm or less, and further preferably 25 μm or less.

[0202] The specific surface area (SA) of the carbon material composition is preferably 1.0 to 11.0 m 2 / g, more preferably 2.0 to 9.0 m 2 / g, and further preferably 3.0 to 8.0 m 2 / g. Here, from the viewpoint of ensuring a portion for the entry and exit of lithium ions, excellent rapid charge-discharge characteristics, and excellent low-temperature input-output characteristics, the specific surface area of the carbon material composition is preferably 1.0 m 2 / g or more, more preferably 2.0 m 2 / g or more, and further preferably 3.0 m 2 / g or more. Furthermore, considering the suppression of side reactions with the electrolyte, prevention of decreased initial charge / discharge efficiency and increased gas generation, and improvement of battery capacity, the specific surface area of ​​the carbon material composition is preferably 11.0 m². 2 / g or less, preferably 9.0m 2 / g or less, more preferably 8.0m 2 / g or less.

[0203] The tap density of the carbon material composition is preferably 0.70–1.40 g / cm³. 3 More preferably, it is 0.80–1.30 g / cm³. 3 More preferably, it is 0.90–1.10 g / cm³. 3 Here, considering the ability to suppress defects such as scratches during electrode fabrication, the ease of forming a high-density negative electrode sheet with good calendering properties due to increased filling capacity, the reduced curvature of the lithium-ion migration path during electrode fabrication, the smoother electrolyte migration due to the regular shape of the interparticle voids, and the improved fast charge / discharge characteristics, the tap density of the carbon material composition is preferably 0.70 g / cm³. 3 The above, more preferably 0.80 g / cm 3 The above is further preferred to be 0.90 g / cm³. 3 That's all. Furthermore, considering that the particles don't become overly hard due to adequate space on their surface and inside, excellent electrode compressibility, fast charge / discharge characteristics, and excellent low-temperature input / output characteristics, the tap density of the carbon material composition is preferably 1.40 g / cm³. 3 The preferred value is 1.30 g / cm³. 3 The following is a further preferred value of 1.10 g / cm³. 3 the following.

[0204] The sphericity of the carbon material composition is preferably 0.88 to 0.99, more preferably 0.90 to 0.98, and even more preferably 0.92 to 0.97. Here, considering the reduction in the tortuosity of lithium-ion diffusion, the smoother migration of the electrolyte in the interparticle gaps, and excellent fast charge / discharge characteristics, the sphericity of the carbon material composition is preferably 0.88 or higher, more preferably 0.90 or higher, and even more preferably 0.92 or higher. Furthermore, considering the ability to ensure good contact between carbon materials and excellent cycle characteristics, the sphericity of the carbon material composition is preferably 0.99 or lower, more preferably 0.98 or lower, and even more preferably 0.97 or lower.

[0205] The cumulative pore volume of the carbon material composition is preferably 0.003 to 0.120 mL / g, more preferably 0.005 to 0.090 mL / g, and further preferably 0.010 to 0.070 mL / g. Here, the cumulative pore volume of the carbon material composition is preferably 0.003 mL / g or more, more preferably 0.005 mL / g or more, and further preferably 0.010 mL / g or more, from the viewpoint of facilitating moderate deformation at the time of pressing, and is preferably 0.120 mL / g or less, more preferably 0.090 mL / g or less, and further preferably 0.070 mL / g or less.

[0206] The pellet density of the carbon material composition is preferably 1.40 to 1.80 g / cm 3 , more preferably 1.50 to 1.70 g / cm 3 , and further preferably 1.55 to 1.60 g / cm 3 . Here, the pellet density of the carbon material composition is preferably 1.40 g / cm 3 or more, more preferably 1.50 g / cm 3 or more, and further preferably 1.55 g / cm 3 or more, from the viewpoint of facilitating moderate deformation at the time of pressing, and is preferably 1.80 g / cm 3 or less, more preferably 1.70 g / cm 3 or less, and further preferably 1.60 g / cm 3 or less.

[0207] (Method for producing carbon material composition)

[0208] The method for producing the carbon material composition of the present embodiment includes a step of mixing the above-described carbon material (A) and the above-described carbon material (B).

[0209] The mixing method is not particularly limited as long as the carbon material (A) and the carbon material (B) can be mixed into a desired composition.

[0210] The ratio Rd50 ([volume-based average particle diameter (d50) of carbon material (B)] / [volume-based average particle diameter (d50) of carbon material (A)] of the volume-based average particle diameter (d50) of the carbon material (A) to the volume-based average particle diameter (d50) of the carbon material (B) is preferably 0.1 to 10, more preferably 0.2 to 5, and further preferably 0.5 to 2. Here, the above-described ratio Rd50 is preferably 0.1 or more, more preferably 0.2 or more, and further preferably 0.5 or more, and is preferably 10 or less, more preferably 5 or less, and further preferably 2 or less.

[0211] When the specific gravity Rd50 is within the above range, the carbon material (B) can be present in the gaps between the carbon materials (A) or the carbon material (A) can be present in the gaps between the carbon materials (B). As a result, by having the carbon material (B) present around the carbon material (A), the carbon material (B) can be selectively deformed while maintaining the shape of the carbon material (A), and even when used at a high density, the carbon material (B) will not be broken during pressing, and both high initial efficiency and low expansion can be achieved. In addition, the gaps formed by the carbon material (A) and the carbon material (B) can absorb the volume change of the carbon material (A) and the carbon material (B) accompanying the occlusion and release of lithium ions caused by charging and discharging. Thus, the disconnection of the conductive path accompanying the volume change of the carbon material (A) and the carbon material (B) can be suppressed, and improved cycle characteristics, rapid charging and discharging characteristics, and high capacity can be achieved.

[0212] The ratio RSA of the specific surface area (SA) of the carbon material (A) to the specific surface area (SA) of the carbon material (B) ([specific surface area (SA) of carbon material (B)] / [specific surface area (SA) of carbon material (A)]) is preferably 0.01 to 100, more preferably 0.1 to 10, and further preferably 0.2 to 5. Here, the above ratio RSA is preferably 0.01 or more, more preferably 0.1 or more, and further preferably 0.2 or more, and is preferably 100 or less, more preferably 10 or less, further preferably 6 or less, and more further preferably 5 or less, and particularly preferably 3 or less.

[0213] When the ratio RSA is within the above range, the portion where lithium ions enter and exit can be ensured, the rapid charging and discharging characteristics and the low-temperature input and output characteristics are excellent, the side reaction with the electrolyte can be suppressed, the decrease in initial charging and discharging efficiency and the increase in gas generation amount can be prevented, and the battery capacity can be improved.

[0214] The ratio RCPV of the cumulative pore volume of the carbon material (A) to the cumulative pore volume of the carbon material (B) ([cumulative pore volume of carbon material (B)] / [cumulative pore volume of carbon material (A)]) is preferably 1 to 50, more preferably 3 to 40, and further preferably 5 to 20. Here, the above ratio RCPV is preferably 1 or more, more preferably 3 or more, and further preferably 5 or more, and is preferably 50 or less, more preferably 40 or less, and further preferably 20 or less.

[0215] When the ratio RCPV is within the above range, the carbon material (B) is selectively deformed with respect to the carbon material (A) when the electrode plate is produced, and both high initial efficiency and low expansion can be achieved even when used at a high density.

[0216] (Negative electrode)

[0217] The negative electrode of the present embodiment includes a current collector and an active material layer formed on the current collector, and the active material layer includes the carbon material composition of the present embodiment. The carbon material composition of the present embodiment has the effect of serving as an active material of a negative electrode.

[0218] The method for producing the negative electrode is not particularly limited as long as it can form an active material layer on a current collector, and from the viewpoint of being inexpensive and excellent in productivity, a method in which a slurry in which the carbon material composition of the present embodiment and a binder resin are compounded is applied to a current collector and dried is preferred. A thickening agent can be further compounded in the slurry.

[0219] It is preferred that the density of the active material layer formed on the current collector be increased by performing pressing after the slurry in which the carbon material composition of the present embodiment and a binder resin are compounded is applied to a current collector and dried, and the battery capacity per unit volume of the active material layer be increased.

[0220] The density of the active material layer is preferably 1.2 to 2.0 g / cm 3 , and more preferably 1.5 to 1.8 g / cm 3 . Here, from the viewpoint of being able to suppress a decrease in battery capacity due to an increase in electrode thickness, the density of the active material layer is preferably 1.2 g / cm 3 or more, and more preferably 1.5 g / cm 3 or more. In addition, from the viewpoint of being able to suppress a decrease in rapid charge-discharge characteristics by reducing the amount of electrolyte held in the voids due to a decrease in voids in the electrode, the density of the active material layer is preferably 2.0 g / cm 3 or less, and more preferably 1.8 g / cm 3 or less.

[0221] (Secondary battery)

[0222] The secondary battery of the present embodiment includes a positive electrode, the negative electrode of the present embodiment, and an electrolyte.

[0223] The positive electrode and the negative electrode of the present embodiment preferably can occlude and release lithium ions.

[0224] (Positive electrode)

[0225] The positive electrode can use a publicly known positive electrode.

[0226] (Electrolyte)

[0227] The electrolyte can use a publicly known electrolyte.

[0228] (Separator)

[0229] The secondary battery of the present embodiment preferably has a separator interposed between the positive electrode and the negative electrode. However, the secondary battery of the present embodiment does not exclude the case where a solid electrolyte is used as the electrolyte.

[0230] The separator can use a publicly known separator.

[0231] The carbon material composition of the present embodiment can maintain the initial efficiency of a secondary battery at a high level and can suppress the expansion of the electrode plate at a low level. Therefore, it can be suitably used as an active material for the negative electrode of a secondary battery, and more suitably used as an active material for the negative electrode of a nonaqueous secondary battery, and particularly suitably used as an active material for the negative electrode of a lithium ion secondary battery.

[0232] Examples

[0233] Hereinafter, the present application will be described more specifically using examples, but the present application is not limited to the description of the following examples as long as it does not depart from the gist thereof.

[0234] (Method for measuring volume-based average particle diameter)

[0235] A sample 0.01 g was suspended in 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (trade name "Tween 20") as a surfactant, and introduced into a laser diffraction / scattering particle size distribution measuring device (model name "LA-920", manufactured by HORIBA, Ltd.) to irradiate 1 minute of ultrasonic waves at 28 kHz at an output power of 60 W, and the volume-based median particle diameter in the above measuring device was measured, and the volume-based median particle diameter was used as the volume-based average particle diameter.

[0236] (Method for measuring specific surface area)

[0237] A sample was subjected to pre-decompression drying at 350°C for 15 minutes under nitrogen flow using a specific surface area measuring device (model name "Macsorb HM-1210", manufactured by MOUNTECH), cooled to liquid nitrogen temperature, and the specific surface area was measured by nitrogen adsorption BET 1-point method based on the gas flow method using a nitrogen-helium mixed gas accurately adjusted to a value of 0.3 for the relative pressure of nitrogen with respect to atmospheric pressure.

[0238] (Method for measuring tap density)

[0239] A carbon material was passed through a sieve having a mesh size of 300 μm using a powder density measuring device (model name "Tap Denser KYT-3000", manufactured by Seishin Enterprise), and the carbon material was measured for tap density using a volumeter (model name "Tap Denser KYT-3000", manufactured by Seishin Enterprise) having a diameter of 1.6 cm and a volume capacity of 20 cm 3The cylindrical vibration unit was dropped, and after the unit was filled, the vibration was performed 1000 times with a stroke length of 10 mm. The value of the density calculated from the volume at this time and the mass of the sample was taken as the tap density.

[0240] (Method for measuring cumulative pore volume y)

[0241] A carbon material of which the value of 0.2 g or so was weighed was enclosed in a powder cell, and pretreatment was performed by degassing at 25°C under vacuum (50 μm Hg or less) for 10 minutes using a mercury porosimeter (model name "AutoPore 9520", manufactured by Micromeritics Corporation). Next, the pressure was reduced to 4 psia (about 28 kPa), mercury was introduced into the cell, and after the pressure was increased in steps from 4 psia (about 28 kPa) to 40,000 psia (about 280 MPa), the pressure was reduced to 25 psia (about 170 kPa). The number of steps in the increase in pressure was set to 80 points or more, and after 10 seconds of equilibration time at each step, the amount of mercury penetration was measured. The pore distribution was calculated from the mercury penetration curve thus obtained using the Washburn equation. The surface tension (γ) of mercury was calculated to be 485 dyne / cm, and the contact angle (ψ) was calculated to be 140°. A graph in which the horizontal axis is the pore diameter and the vertical axis is the pore volume was prepared from the results obtained. From this graph, the peak was identified, and the minimum value between the peak of the smallest pore diameter and the next peak (between the two peaks on the side of the smaller pore diameter) was identified. The cumulative pore volume below this minimum value was taken as the peak value y (mL / g).

[0242] (Method for calculating coating rate x)

[0243] The coating rate x was calculated from the mixing ratio of graphite to amorphous carbonaceous or graphitic material and the firing yield after firing by the following equation (3).

[0244] Coating rate x (%) = ([mass of sample after firing - mass of graphite] / [mass of sample after firing]) x 100 (3)

[0245] (Method for measuring pellet density)

[0246] Two clamps were inserted into a 10mm inner diameter mold: a 10mm diameter, 35mm long shaft as a pressing clamp and a 10mm diameter, 6mm long shaft as a pressure clamp. The mold was then fitted with a device (powder impedance measurement system, Nittoseiko Analytech) capable of measuring the load and height during clamping. A 15kgf load was applied using a hydraulic pump, and the clamp height was measured. Then, only the pressing clamp was removed, 0.6g of carbon material was added, and the pressing clamp was reinserted. The mold was then fitted with a high-pressure jack (AS ONE), the pressure valve was tightened, and the pressure was slowly increased to 0.9t / cm². 2 Rapidly pressurize to 2.4 t / cm 2 Then, hold for 3 seconds, remove your hand from the hydraulic jack, and wait 60 seconds before releasing the pressure valve to depressurize. Next, set up the device capable of measuring the load and height during clamping, apply a 15 kgf load using the hydraulic pump, and measure the height of the clamp after pressurization. Furthermore, measure the mass of the pressurized carbon material, and use the density calculated based on the difference in clamp height and mass as the granular density. The load per unit area was calculated based on the hydraulic jack's scale of 500 kgf, the hydraulic cylinder diameter of the hydraulic jack of 22 mm, and the inner diameter of the mold.

[0247] (Making of the negative electrode)

[0248] Using the carbon material composition obtained in the Examples / Comparative Examples as the negative electrode active material, an active material layer with a density of 1.65 ± 0.03 g / cm³ was prepared. 3 The active material layer of the electrode plate. Specifically, 50.00±0.02 g (equivalent to 0.50 g in solids) of a 1% sodium carboxymethyl cellulose aqueous solution and 1.00±0.05 g (equivalent to 0.50 g in solids) of a styrene-butadiene rubber aqueous dispersion with a weight average molecular weight of 270,000 were stirred for 5 minutes and degassed for 30 seconds to obtain a slurry.

[0249] The prepared paste was applied in a 10 cm wide layer onto a 10 μm thick copper foil (serving as a current collector) using a die-coating machine and dried to achieve an adhesion of 10.00 ± 0.20 mg / cm². 2 The negative electrode material is then cut into 5cm wide pieces and rolled using a 20cm diameter roller to adjust the density of the active material layer to 1.65±0.03g / cm³. 3 Thus, a negative electrode sheet was obtained.

[0250] (The production of positive electrode plates)

[0251] A slurry was obtained by mixing 85 mass% of lithium nickel-manganese-cobalt oxide (LiNiMnCoO2) as a positive electrode active material, 10 mass% of acetylene black as a conductive material, and 5 mass% of polyvinylidene fluoride (PVdF) as a binder in N-methylpyrrolidone.

[0252] The obtained slurry was coated on an aluminum foil having a thickness of 15 μm as a current collector using a doctor blade coater and dried at 130°C to make a positive electrode material attached at 22.5 ± 0.2 mg / cm 2 Further, rolling was performed, and adjustment was performed so that the density of the positive electrode material reached 2.60 ± 0.05 g / cm 3 , to obtain a positive electrode sheet.

[0253] (Production of a coin-type battery)

[0254] The obtained negative electrode sheet, a separator made of polyethylene, and the obtained positive electrode sheet were sequentially stacked. The obtained stack was wrapped with a cylindrical aluminum laminate film, and a non-aqueous secondary battery in a coin shape was produced by vacuum sealing after injecting an electrolyte solution, which was an electrolyte solution obtained by dissolving LiPF6 at 1 mol / L in a mixed solvent (volume ratio 30:30:40) of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate. Further, in order to improve the adhesion between the electrodes, the secondary battery in a coin shape was sandwiched with a glass plate and pressurized.

[0255] (Measurement method of expansion of a secondary battery)

[0256] An initial charge-discharge was performed for 3 cycles at 25°C with a voltage range of 4.1 V to 3.0 V and a current value of 0.2 C, and 2 cycles with a voltage range of 4.2 V to 3.0 V and a current value of 0.2 C (2.5 hours of constant voltage charging at 4.2 V was further performed at the time of charging) for the secondary battery in a coin shape which had not undergone charge-discharge cycles. At this time, the glass plate for fixation was removed, and the thickness of 9 points was measured for one secondary battery using a contact type thickness gauge (manufactured by Mitutoyo Corporation), and the average value thereof was taken as the thickness before cycles. Then, after being sandwiched with a glass plate again, a cycle test was performed for 25 times of charge-discharge under the conditions of 0.8 C-CCCV charging-0.8 C-CC discharging with a 1.5 V cutoff in a constant temperature bath at 45°C. Then, for the secondary battery in a state of SOC (State Of Charge) 0%, the thickness of 9 points at the same positions as before cycles was measured, and the average value thereof was taken as the thickness after cycles. The expansion of the secondary battery in cycles was calculated from the difference between the thickness before cycles and the thickness after cycles.

[0257] (Production of a coin-type battery)

[0258] The obtained negative electrode sheet was punched into a disc shape with a diameter of 12.5 mm to produce a negative electrode, and a lithium metal foil was punched into a disc shape with a diameter of 14 mm to produce a counter electrode. A 2016 coin-type battery was produced by placing a separator (porous polyethylene film) impregnated with an electrolyte solution between the electrodes, the electrolyte solution being an electrolyte solution in which LiPF6 was dissolved at 1 mol / L in a mixed solvent of ethylene carbonate and methyl ethyl carbonate (volume ratio 30:70).

[0259] (Measurement method of initial efficiency of secondary battery)

[0260] The obtained coin-type battery was charged at a current density of 0.05 C to 5 mV with respect to the lithium counter electrode, and further charged at a constant voltage of 5 mV until the current density reached 0.005 C. After doping lithium in the negative electrode, the lithium counter electrode was discharged at a current density of 0.1 C to 1.5 V. The ratio of the discharge capacity to the charge capacity ((discharge capacity / charge capacity) x 100) at this time was taken as the initial efficiency (%).

[0261] [Manufacturing Example 1] Production of carbon material (A-1)

[0262] Flaky natural graphite having a volume-based average particle diameter of 100 μm was pulverized to obtain graphite having a volume-based average particle diameter of 11 μm. The obtained graphite (100 parts by mass) and a granulating agent (12 parts by mass) were mixed, and then subjected to a spheroidization treatment. The granulating agent was further removed by heat treatment to obtain spheroidized graphite (volume-based average particle diameter 16 μm, specific surface area 15 m 2 / g, tap density 0.96 g / cm 3 ). The obtained spheroidized graphite was filled in a rubber-made container, and after the rubber-made container was closed and subjected to isotropic pressure treatment, crushing / classification treatment was performed to obtain a spheroidized graphite powder. The obtained spheroidized graphite powder and pitch (ash content 0.02 mass%, metal impurity content 20 mass ppm, Qi 1 mass%) as an amorphous carbonaceous substance precursor were mixed, the pressure in the furnace was reduced to 10 torr or less, and then restored to atmospheric pressure using nitrogen. Further, nitrogen was circulated to make the oxygen concentration in the furnace 0.01% by volume or less, and heat treatment at 1300°C was performed in a non-reactive gas. The obtained fired product was subjected to crushing / classification treatment to obtain a carbon material (A-1).

[0263] The evaluation results of the obtained carbon material (A-1) are shown in Table 1.

[0264] [Manufacturing Example 2] Production of carbon material (A-2)

[0265] The mixing ratio of the spheroidized graphite powder and the amorphous carbonaceous substance precursor was changed, and otherwise, the same operations as in Manufacturing Example 1 were performed to obtain a carbon material (A-2).

[0266] The evaluation results of the obtained carbon material (A-2) are shown in Table 1.

[0267] [Production Example 3] Production of Carbon Material (A-3)

[0268] The carbon material (A-3) was obtained by changing the mixing ratio of the spheroidized graphite powder and the amorphous carbonaceous substance precursor, and otherwise similarly to Production Example 1.

[0269] The evaluation results of the obtained carbon material (A-3) are shown in Table 1.

[0270] [Production Example 4] Production of Carbon Material (A-4)

[0271] Spheroidization treatment was performed on flaky natural graphite having a volume-based average particle diameter of 100 μm, and spheroidized graphite (volume-based average particle diameter 16 μm, specific surface area 6.9 m 2 / g, tap density 1.00 g / cm 3 ) was obtained. The obtained spheroidized graphite and tar (ash content 0.01 mass% or less, metal impurity content 60 mass ppm, Qi 0.1 mass% or less) as an amorphous carbonaceous substance precursor were mixed, the pressure in the furnace was reduced to 10 torr or less, and nitrogen was supplied to restore the pressure to atmospheric pressure. Further, nitrogen was circulated to make the oxygen concentration in the furnace 0.01 vol% or less, and heat treatment at 1300°C was performed in a non-reactive gas. The obtained fired product was subjected to crushing / classification treatment, and a carbon material (A-4) was obtained.

[0272] The evaluation results of the obtained carbon material (A-4) are shown in Table 1.

[0273] [Production Example 5] Production of Carbon Material (B-1)

[0274] Spheroidization treatment was performed on flaky natural graphite having a volume-based average particle diameter of 100 μm, and a carbon material (B-1) having a pellet density of 1.96 g / cm 3 was obtained.

[0275] The evaluation results of the obtained carbon material (B-1) are shown in Table 2.

[0276] [Production Example 6] Production of Carbon Material (B-2)

[0277] Spheroidization treatment was performed on flaky natural graphite having a volume-based average particle diameter of 100 μm, and a carbon material (B-2) having a pellet density of 1.95 g / cm 3 was obtained.

[0278] The evaluation results of the obtained carbon material (B-2) are shown in Table 2.

[0279] [Manufacture Example 7] Manufacture of Carbon Material (B-3)

[0280] Spheroidized graphite (volume-based average particle diameter 13 μm, specific surface area 7.8 m 2 / g, tap density 0.90 g / cm 3 ) was obtained by subjecting flaky natural graphite having a volume-based average particle diameter of 100 μm to spheroidization treatment. The obtained spheroidized graphite and pitch (ash content 0.1 mass%, Qi 0.2 mass% or less) as a precursor of a graphitic substance were mixed, filled in a rubber-made container, and subjected to isotropic pressurization treatment with the rubber-made container being closed. Then, heat treatment was performed at 1000°C in an inert gas, and graphitization treatment was performed at 3000°C in an inert gas. The obtained graphitized substance was subjected to crushing / classification treatment, and a carbon material (B-3) was obtained.

[0281] [Manufacture Example 8] Manufacture of Carbon Material (B-4)

[0282] Spheroidized graphite (volume-based average particle diameter 8 μm, specific surface area 11 m 2 / g, tap density 1.00 g / cm 3 ) was obtained by subjecting flaky natural graphite having a volume-based average particle diameter of 100 μm to spheroidization treatment. The obtained spheroidized graphite and pitch (ash content 0.1 mass%, Qi 0.2 mass% or less) as a precursor of a graphitic substance were mixed, filled in a rubber-made container, and subjected to isotropic pressurization treatment with the rubber-made container being closed. Then, heat treatment was performed at 1000°C in an inert gas, and graphitization treatment was performed at 3000°C in an inert gas. The obtained graphitized substance was subjected to crushing / classification treatment, and a carbon material (B-4) was obtained.

[0283] [Example 1]

[0284] A carbon material composition was obtained by mixing 70 mass% of the carbon material (A-1) and 30 mass% of the carbon material (B-1).

[0285] The evaluation results of the obtained carbon material composition are shown in Table 4.

[0286] [Examples 2 to 7]

[0287] A carbon material composition was obtained by changing the kind and content of the carbon material as shown in Table 3, and otherwise, in the same manner as in Example 1.

[0288] The evaluation results of the obtained carbon material composition are shown in Table 4.

[0289] [Comparative Examples 1 to 5]

[0290] The kind and content of the carbon material were changed as shown in Table 3, and otherwise, the operation was performed similarly to Example 1 to obtain a carbon material composition.

[0291] The results of evaluation of the obtained carbon material composition are shown in Table 4.

[0292] [Table 1]

[0293]

[0294] [Table 2]

[0295]

[0296] [Table 3]

[0297]

[0298] [Table 4]

[0299]

[0300] As is apparent from Table 4, the secondary battery containing the negative electrode using the carbon material composition of Examples 1 to 7 of the present embodiment can maintain the initial efficiency at a high level and can suppress the expansion of the electrode plate at a low level, as compared with the secondary battery containing the negative electrode using the carbon material composition of Comparative Examples 1 to 5. It is considered that this result is due to the combination of the carbon material (A) which is dense and has low expansion and the carbon material (B) which has high pellet density.

[0301] The present application has been described in detail and with reference to specific embodiments, but it will be apparent to one skilled in the art that various changes, modifications and corrections can be made without departing from the spirit and scope of the present application. This application is based on Japanese Patent Application (Tokugan 2022-048746) filed on March 24, 2022, the contents of which are incorporated herein by reference.

[0302] Industrial Applicability

[0303] The carbon material composition of the present application is not damaged at the time of pressing even if it is used at a high density, can maintain the initial efficiency of the secondary battery at a high level, and can suppress the expansion of the electrode plate at a low level. Therefore, it is preferably used as an active material for the negative electrode of a secondary battery, more preferably used as an active material for the negative electrode of a nonaqueous secondary battery, and particularly preferably used as an active material for the negative electrode of a lithium ion secondary battery.

Claims

1. A carbon material composition comprising a carbon material (A) and a carbon material (B), the carbon material (A) comprising graphite having an amorphous carbon content or a graphitic carbon content, the pore distribution of the carbon material (A) measured by a mercury porosimetry having two or more peaks, the carbon material (A) satisfying the following formula (1) when a cumulative pore volume below a minimum value between a peak of the smallest pore diameter and a next peak in the pore distribution is set as y (mL / g) and a coating rate of the amorphous carbon content or the graphitic carbon content of the graphite is set as x (%), y < -0.0084x + 0.13 (1) The pellet density of the carbon material (B) is 1.80 g / cm 3 The tap density is 0.70 to 1.30 g / cm3 3 , the content of the carbon material (A) being 45 to 75% by mass and the content of the carbon material (B) being 25 to 55% by mass in 100% by mass of the carbon material composition, The specific surface area of the carbon material (A) is 0.5 to 3.0 m 2 / g, The specific surface area of the carbon material (B) is 3.0 to 11.0 m 2 / g.

2. The carbon material composition according to claim 1, wherein the carbon material (A) further satisfies the following formula (2), y≥0.005 (2)。 3. The carbon material composition according to claim 1, wherein the peak value of the peak of the smallest pore diameter is 500 nm or less.

4. The carbon material composition according to claim 1, wherein x in the formula (1) is 0.1 to 15.

5. The carbon material composition according to claim 1, wherein The carbon material (A) has a tap density of 1.15 g / cm 3 The above.

6. The carbon material composition according to claim 1, wherein the carbon material (B) is spheroidized graphite.

7. The carbon material composition according to claim 1, wherein the content of the carbon material (A) is 55 to 75% by mass and the content of the carbon material (B) is 25 to 45% by mass in 100% by mass of the carbon material composition.

8. The carbon material composition according to claim 1, wherein the circularity of the carbon material composition is 0.88 to 0.

99.

9. The carbon material composition according to claim 1, wherein the cumulative pore volume of the carbon material composition is 0.003 to 0.120 mL / g.

10. The carbon material composition according to claim 1, wherein the ratio of the cumulative pore volume of the carbon material (B) to the cumulative pore volume of the carbon material (A) is 1 to 50.

11. A method for producing a carbon material composition, the method comprising a step of mixing a carbon material (A) and a carbon material (B), the carbon material (A) comprising graphite having an amorphous carbon content or a graphitic carbon content, the pore distribution of the carbon material (A) measured by a mercury porosimetry having two or more peaks, the carbon material (A) satisfying the following formula (1) when a cumulative pore volume below a minimum value between a peak of the smallest pore diameter and a next peak in the pore distribution is set as y (mL / g) and a coating rate of the amorphous carbon content or the graphitic carbon content of the graphite is set as x (%), y < -0.0084x + 0.13 (1) The pellet density of the carbon material (B) is 1.80 g / cm 3 The above, The specific surface area of the carbon material (A) is 0.5 to 3.0 m 2 / g, The specific surface area of the carbon material (B) is 3.0 to 11.0 m 2 / g.

12. A negative electrode comprising: a current collector, and an active material layer formed on the current collector, the active material layer comprising the carbon material composition according to any one of claims 1 to 10.

13. A secondary battery comprising: a positive electrode, a negative electrode, and an electrolyte, The negative electrode is the negative electrode according to claim 12. The negative electrode is the negative electrode according to claim 12. The negative electrode is the negative electrode according to claim

Images