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

Abstract

The present invention pertains to a carbon material composition containing: a carbon material (A) that contains graphite having an amorphous carbonaceous substance or a graphitic substance and that has a pore distribution having two or more peaks as measured by mercury intrusion method; y < =-0.0084 x + 0.13 is satisfied, where y (mL / g) is the cumulative pore volume equal to or less than the minimum value between the peak having the smallest pore diameter and the next peak, and x (%) is the coating rate of an amorphous carbonaceous substance or a graphitic substance of graphite; the carbon material (B) has a pellet density of 1.80 g / cm3 or more.

Description

[0001] This application is a divisional application of the application filed on February 13, 2023, with application number 202380011271.4 and invention title "Carbon Material Composition, Method for Manufacturing Carbon Material Composition, Negative Electrode and Secondary Battery". Technical Field

[0002] This invention relates to carbon material compositions, methods for manufacturing carbon material compositions, negative electrodes, and secondary batteries. Background Technology

[0003] In recent years, with the miniaturization of electronic devices, the demand for high-capacity rechargeable batteries has been gradually increasing. In particular, rechargeable batteries with higher energy density and superior charge-discharge characteristics compared to nickel-cadmium and nickel-metal hydride batteries, especially lithium-ion rechargeable batteries, have attracted much attention. As lithium-ion rechargeable batteries, non-aqueous lithium rechargeable batteries, consisting of positive and negative electrodes capable of absorbing and releasing lithium ions, and a non-aqueous electrolyte containing dissolved lithium salts such as LiPF6 and LiBF4, have been developed and put into practical use.

[0004] Previously, the improvement of high performance in lithium-ion secondary batteries has been extensively studied, but in recent years, there has been a demand for further improvement in the performance of lithium-ion secondary batteries. For example, Patent Document 1 discloses a negative electrode material in which the pore volume and the peak value of the voids within the particles per unit coverage of the negative electrode material are controlled.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2021-158043 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, the negative electrode material disclosed in Patent Document 1, if used at high density, will be damaged during pressing, leading to a decrease in the initial efficiency of the secondary battery. Furthermore, commonly used negative electrode materials still suffer from issues such as electrode plate expansion.

[0010] This invention was made in view of the following issues, and its object is to provide a carbon material composition that will not be damaged during pressing even when used at high density, can maintain a high initial efficiency of the secondary battery, and can suppress the expansion of the electrode plates to a low level. Furthermore, an object of this invention is to provide a method for manufacturing the carbon material composition for obtaining the above-mentioned carbon material composition.

[0011] Methods for solving problems

[0012] Previously, various negative electrode materials have been explored, but none have been found that can maintain a high initial efficiency of the secondary battery and suppress plate expansion to a low level. To solve these problems, the inventors conducted in-depth research and discovered that by combining the two carbon materials described below, it is possible to maintain a high initial efficiency of the secondary battery and suppress plate expansion to a low level, thus completing this invention.

[0013] That is, the main idea of ​​this invention is as follows.

[0014] [1] A carbon material composition comprising carbon material (A) and carbon material (B), wherein the carbon material (A) comprises graphite having amorphous carbonaceous material or graphitic material, and the pore distribution of the carbon material (A) as determined by mercury indentation method has two or more peaks, and the cumulative pore volume below the minimum value between the peak with the smallest pore diameter and the next peak in the pore distribution is set as y (mL / g), and the coating rate of the graphite having the amorphous carbonaceous material or graphitic material is set as x (%), and the carbon material (A) satisfies the following formula (1); the particle density of the carbon material (B) is 1.80 g / cm³. 3 above.

[0015] y≤-0.0084x+0.13 (1)

[0016] [2] According to the carbon material composition of [1], wherein the carbon material (A) further satisfies the following formula (2).

[0017] y≥0.005 (2)

[0018] [3] The carbon material composition according to [1] or [2], wherein the pore diameter of the peak of the smallest pore diameter is less than 500 nm.

[0019] [4] The carbon material composition according to any one of [1] to [3], wherein x in the above formula (1) is 0.1 to 15.

[0020] [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 / cm³. 3 above.

[0021] [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 m². 2 / g or less.

[0022] [7] The carbon material composition according to any one of [1] to [6], wherein the carbon material (B) is spherical graphite.

[0023] [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 m². 2 / g or more.

[0024] [9] The carbon material composition according to any one of [1] to [8], wherein, in 100% by mass of the carbon material composition, the content of the carbon material (A) is 40% to 90% by mass and the content of the carbon material (B) is 10% to 60% by mass.

[0025]

[10] A method for manufacturing a carbon material composition, the method comprising a step of mixing carbon material (A) and carbon material (B), wherein the carbon material (A) comprises graphite having amorphous carbonaceous material or graphitic material, and the pore distribution of the carbon material (A) as determined by mercury infiltration method has two or more peaks, wherein the cumulative pore volume below the minimum value between the peak with 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 carbonaceous material or graphitic material of graphite is set as x (%), and the carbon material (A) satisfies the following formula (1); the particle density of the carbon material (B) is 1.80 g / cm³. 3 above.

[0026] y≤-0.0084x+0.13 (1)

[0027]

[11] A negative electrode comprising a current collector and an active material layer formed on the current collector, wherein the active material layer comprises any one of the carbon material compositions described in [1] to [9].

[0028]

[12] A secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode is the negative electrode described in

[11] .

[0029] The effects of the invention

[0030] When the carbon material composition of the present invention is used as the active material of the negative electrode in a secondary battery, it will not be damaged during pressing even when used at high density, thus maintaining a high initial efficiency of the secondary battery and suppressing plate expansion to a low level. Furthermore, the method for manufacturing the carbon material composition of the present invention can yield the aforementioned carbon material composition. Detailed Implementation

[0031] The present invention will now be described in detail, but it is not limited to the embodiments described below, and various modifications can be made within its scope. It should be noted that in this specification, the use of expressions such as "~" is used to indicate the inclusion of numerical or physical property values ​​preceding or following it.

[0032] (Carbon material composition)

[0033] The carbon material composition of this embodiment includes carbon material (A) and carbon material (B). Carbon material (A) includes graphite having amorphous carbonaceous material or graphitic material, and its pore distribution, as measured by mercury indentation method, has two or more peaks. When the cumulative pore volume below the minimum value between the peak with the smallest pore diameter and the next peak in the above pore distribution is set as y (mL / g), and the coating rate of the amorphous carbonaceous material or graphitic material of graphite is set as x (%), it satisfies the following formula (1). In addition, the particle density of carbon material (B) is 1.80 g / cm³. 3 above.

[0034] y≤-0.0084x+0.13 (1)

[0035] Compared to carbon material (A), carbon material (B) can be selectively deformed to a high density. Therefore, the carbon material composition, by including carbon material (B), can suppress the destruction of carbon material (A) and fully utilize the high initial efficiency and low expansion performance of carbon material (A). Thus, the carbon material composition of this embodiment, by including both carbon material (A) and carbon material (B), will not be destroyed during pressing even when used at high density, maintaining a high initial efficiency of the secondary battery and suppressing plate expansion to a low level.

[0036] (Carbon materials (A))

[0037] The carbon material (A) contains graphite with amorphous carbonaceous material or graphitic material, and the pore distribution measured by mercury infiltration method has more than two peaks. When the cumulative pore volume below the minimum value between the peak with the smallest pore diameter and the next peak in the above pore distribution is set as y (mL / g), and the coating rate of amorphous carbonaceous material or graphitic material of graphite is set as x (%), the following formula (1) is satisfied.

[0038] y≤-0.0084x+0.13 (1)

[0039] The carbon material composition of this embodiment, by including the aforementioned carbon material (A), can maintain the initial efficiency of the secondary battery at a high level and suppress the expansion of the electrode plates at a low level for the following reasons.

[0040] The cumulative pore volume below the minimum value between the peak with the smallest pore diameter and the next peak, as measured by mercury infiltration, is an indicator of the pore volume existing inside the carbon material (A). By reducing its coverage relative to amorphous carbonaceous or graphitic materials of graphite to a specific range, the porosity within the particles is reduced. This reduction in porosity results in denser particles compared to the porous particles found in traditional natural graphite, allowing for pressing with less particle deformation.

[0041] The pore size distribution of carbon material (A), as measured by mercury infiltration, has two or more peaks, preferably two peaks. The peaks in the pore size distribution represent both inter-particle and intra-particle voids. Therefore, if there is only one peak, it indicates that only inter-particle voids exist. If there are two or more peaks, it indicates that both inter-particle and intra-particle voids exist, which is superior to particles with no voids in terms of the particle's potential for deformation.

[0042] For carbon material (A), when the cumulative pore volume below the minimum value between the peak with the smallest pore diameter and the next peak in the pore distribution is set as y (mL / g), and the coating rate of amorphous carbonaceous material or graphitic material of graphite is set as x (%), the following formula (1) is satisfied.

[0043] y≤-0.0084x+0.13 (1)

[0044] By making the carbon material (A) satisfy equation (1), the pores of graphite are suitably covered by amorphous carbonaceous material or graphitic material, that is, covered by less amorphous carbonaceous material or graphitic material, thus mitigating the hardness of the carbon material (A) particles.

[0045] When equation (1) is expressed as y≤αx+β, the coverage 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 equation (1), and β represents the y-intercept of equation (1).

[0046] As for α, based on the relationship between the coating rate of amorphous carbonaceous or graphitic materials of graphite and the efficiency of filling the internal voids of graphite particles, α is -0.0084.

[0047] β is the void space within the graphite particles before coating, and is therefore 0.13. It is preferable that the value of β in equation (1) is set to 0.13~0.11, more preferably that it is set to 0.09, and even more preferably that it is set to 0.07.

[0048] For carbon materials (A), it is necessary to minimize the voids within the particles, and therefore it is preferable to further satisfy the following equation (2).

[0049] y≥0.005 (2)

[0050] When equation (2) is expressed as y≥γ, considering that the particle itself has room for deformation, γ is preferably 0.005, more preferably when the value of γ in equation (2) is set to 0.005~0.010, and even more preferably when it is set to 0.015, equation (2) is also satisfied.

[0051] The carbon material (A) preferably satisfies both equation (1) and equation (2). In this case, the value of β on the right side of equation (1) is more preferably 0.11 instead of 0.13, even more preferably 0.09, and even more preferably 0.07. The value of γ on the right side of equation (2) is also more preferably 0.010 instead of 0.005, and even more preferably 0.015.

[0052] For the peak value of the carbon material (A) with the smallest pore diameter, considering the small pore size within the particles, the more compact scales within the particles, and the reduction of electrode expansion, it is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. The lower limit of the pore diameter is not particularly limited, and is usually 5 nm.

[0053] 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, even more preferably 0.005 to 0.070, and particularly preferably 0.010 to 0.050. Here, considering the smooth migration of lithium ions within the electrode during charging and discharging, excellent fast charging and discharging characteristics, and excellent low-temperature input / output characteristics, it is preferably 0.002 or more, more preferably 0.003 or more, even more preferably 0.005 or more, and particularly preferably 0.010 or more. Furthermore, it is preferably 0.120 or less, more preferably 0.090 or less, even more preferably 0.070 or less, and particularly preferably 0.050 or less.

[0054] In this specification, the pore size distribution is determined by mercury infiltration method.

[0055] Specifically, using a mercury porosimeter, a sample weighing approximately 0.2 g was sealed in a powder cell and pretreated by degassing for 10 minutes at 25°C and below 50 μmHg. Next, the pressure was reduced to 4 psia, and mercury was introduced into the cell. The pressure was then increased stepwise from 4 psia to 40,000 psia, and then reduced to 25 psia. The number of pressure increases was set to at least 80 points, and the mercury infiltration rate was measured after each step had a 10-second equilibration period. Based on the resulting mercury infiltration curve, the pore size distribution was calculated using the Washburn equation. The surface tension (γ) of mercury was calculated at 485 dyne / cm, and the contact angle (ψ) at 140°. A coordinate graph was created with the pore diameter on the horizontal axis and the pore volume on the vertical axis based on the results. The peaks are identified from the coordinate graph. The minimum value between the peak with the smallest pore diameter and the next peak (between the two peaks on the side with the smallest pore diameter) is identified. The cumulative pore volume below this minimum value is taken as the cumulative pore volume (mL / g). A peak is defined as the apex of the waveform, and its height (the difference between the apex and the cumulative pore volumes of the adjacent minimum values ​​on both sides) is greater than 0.002 mL / g.

[0056] The coating percentage x (%) of the carbon material (A) is preferably 0.1 to 15, more preferably 1 to 12, further preferably 2 to 10, and even more preferably 3 to 8. Here, considering the ability to facilitate smooth migration of lithium ions from graphite, excellent fast charge / discharge characteristics, and low-temperature input / output characteristics, the coating percentage x (%) is preferably 0.1 or more, more preferably 1 or more, further preferably 2 or more, and particularly preferably 3 or more. Furthermore, considering the sufficient proportion of graphite and ease of achieving high capacity, the coating percentage x (%) is preferably 15 or less, more preferably 12 or less, further preferably 10 or less, and particularly preferably 8 or less.

[0057] In this specification, the coating rate x (%) is calculated using the following formula (3). That is, it is calculated based on the mixing ratio of graphite with amorphous carbonaceous material or graphitic material and the firing yield after firing.

[0058] Coverage rate x (%) = ([mass of the fired sample - mass of graphite] / [mass of the fired sample]) × 100 (3)

[0059] When the above mixing ratio and firing yield are unknown, the coating rate x (%) is estimated by using the difference in true density between graphite and amorphous carbonaceous material or graphitic material.

[0060] Specifically, the crystallinity of graphite in carbon materials is confirmed by the d002 value. If the d002 value is 3.357... For the following high crystallinity, the coating rate x (%) is estimated using the following formula (4).

[0061] Coverage rate x (%) = 596.72 - 264.02 × true density (4)

[0062] The theoretical d002 value of graphite is 3.354. The d002 value of highly crystalline natural graphite is close to the theoretical value. On the other hand, for artificial graphite, the d002 value varies greatly depending on the type of raw coke and the graphitization temperature.

[0063] Considering that graphite is highly crystalline and has sufficient charge / discharge capacity, the preferred d002 value for carbon material (A) is 3.357. The preferred value is 3.356. The following is a further preferred value: 3.354 .

[0064] Considering that graphite is highly crystalline and has sufficient charge / discharge capacity, the Lc of carbon material (A) is preferably 900. The above, more preferably 1000 The above. There is no specific upper limit for Lc; however, as an upper limit for measurement accuracy, it is typically 1000. .

[0065] In this specification, d002 is the interplanar spacing of the lattice plane (002 plane) measured by X-ray diffraction based on the vibrational method, and Lc is the crystallite size measured by X-ray diffraction based on the vibrational method. The X-ray diffraction measurement conditions are as follows.

[0066] Sample: The sample is prepared by adding approximately 15% by mass of high-purity X-ray standard silicon powder to the test object and mixing them together.

[0067] X-rays: CuKα rays

[0068] Measurement range: 20°≤2θ≤30°

[0069] Step angle: 0.013°

[0070] Sample preparation: A flat sample surface is prepared by filling the recess of the sample plate with powder sample to a depth of 0.2 mm.

[0071] In this specification, the true density is defined as the value obtained by liquid-phase displacement method (specific gravity bottle method) using butanol. The true density was measured five times, and the average value was used.

[0072] Considering its excellent filling properties and capacity, the true density of carbon material (A) is preferably 2.200 g / cm³. 3 The above, more preferably 2.210 g / cm³ 3The above is further preferred to be 2.220 g / cm³. 3 The theoretical true density of graphite is 2.262 g / cm³. 3 .

[0073] (Physical properties of carbon material (A))

[0074] The volume-based average particle size (d50) of the carbon material (A) is preferably 1 to 50 μm, more preferably 3 to 30 μm, and even more preferably 5 to 20 μm. Here, considering the prevention of irreversible capacity increase and initial battery capacity loss, the volume-based average particle size of the carbon material (A) is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. Furthermore, considering the ability to suppress process defects such as scratches during electrode fabrication, excellent fast charge / discharge characteristics, and excellent low-temperature input / output characteristics, the volume-based average particle size of the carbon material (A) is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less.

[0075] In this specification, the volumetric average particle size (d50) is set as the value of the median particle size of the volumetric reference measured using a laser diffraction / scattering particle size distribution measuring device.

[0076] Specifically, 0.01 g of the sample was suspended in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate as a surfactant, and introduced into a laser diffraction / scattering particle size distribution measuring device. After irradiating with 28 kHz ultrasound for 1 minute at an output power of 60 W, the median particle size of the volume reference in the measuring device was measured.

[0077] The specific surface area (SA) of the carbon material (A) is preferably 0.5~10.0 m². 2 / g, more preferably 0.8~6.5m 2 / g, more preferably 1.0~5.0m 2 / g, more preferably 1.0~3.0m 2 / g. Here, considering factors such as ensuring the extent of lithium ion entry and exit, rapid charge / discharge characteristics, and excellent low-temperature input / output characteristics, the specific surface area of ​​the carbon material (A) is preferably 0.5m². 2 / g or more, preferably 0.8m 2 / g or more, further preferably 1.0m 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 (A) is preferably 10.0 m². 2 / g or less, more preferably 6.5m 2 / g or less, preferably 5.0m 2 / g or less, more preferably 3.0m 2 / g or less, more preferably 2.0m 2 / g or less.

[0078] In this specification, the specific surface area (SA) is the value measured by the BET (Brunauer-Emmett-Teller) method.

[0079] Specifically, after the sample was pre-depressurized and dried at 350°C for 15 minutes under nitrogen flow using a specific surface area measuring device, it was cooled to liquid nitrogen temperature and then measured using a nitrogen-helium mixed gas with a nitrogen relative pressure of 0.3 relative to atmospheric pressure by the nitrogen adsorption BET1 point method based on gas flow.

[0080] The tap density of carbon material (A) is preferably 1.15~1.40 g / cm³. 3 More preferably, it is 1.17~1.35 g / cm³. 3 Further preferred values ​​are 1.20~1.30 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 (A) is preferably 1.15 g / cm³. 3 The above, more preferably 1.17 g / cm³ 3 The above is further preferred to be 1.20 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 (A) is preferably 1.40 g / cm³. 3 The following is a preferred value: 1.35 g / cm³ 3 The following is a further preferred value of 1.30 g / cm³. 3 the following.

[0081] In this specification, the tap density is set to the following value: using a powder density meter, the sample is passed through a sieve with a mesh size of 300 μm and a diameter of 1.6 cm and a volumetric density of 20 cm³. 3 The cylindrical vibratory unit is dropped down, and after the unit is filled, it is vibrated 1000 times with a stroke length of 10mm. The density value is calculated based on the volume and mass of the sample at this time.

[0082] The value obtained by subtracting the tap density from the particle density of carbon material (A) is preferably 0.10~0.80 g / cm³.3 More preferably, it is 0.15~0.60 g / cm³. 3 Further 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.

[0083] 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.

[0084] The value obtained by subtracting the tapped density from the particle density (g / cm³) 3 = Particle density - Tapped density (5)

[0085] In this specification, the particle density is a value obtained by the following method.

[0086] 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.

[0087] The preferred particle density of carbon material (A) is 1.30~1.79 g / cm³. 3 More preferably, it is 1.40~1.70 g / cm³. 3 Here, the preferred particle density is 1.30 g / cm³. 3 The above, more preferably 1.40 g / cm³ 3 In addition, the preferred value is 1.79 g / cm³. 3 The preferred value is 1.70 g / cm³. 3 the following.

[0088] The sphericity of the carbon material (A) 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 the excellent fast charge / discharge characteristics, the sphericity of the carbon material (A) 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 (A) is preferably 0.99 or lower, more preferably 0.98 or lower, and even more preferably 0.97 or lower.

[0089] In this specification, for roundness, the particle size distribution of the equivalent circle diameter is determined by flow cytometry particle image analysis and calculated using the following formula (6).

[0090] Specifically, deionized water was used as the dispersion medium, and polyoxyethylene sorbitan monolaurate was used as the surfactant. The particles were dispersed using ultrasound to obtain a dispersion. Then, the particle shape was captured using a flow cytometry imager. Based on images of at least 1000 particles, the sphericity of particles with an equivalent circular diameter ranging from 1.5 μm to 40 μm was averaged and used as the sphericity.

[0091] [Circularity] = [Circumference of an equivalent circle with the same area as the particle projection shape] / [Actual circumference of the particle projection shape] (6)

[0092] (Manufacturing method of carbon material (A))

[0093] The method for manufacturing carbon material (A) is not particularly limited as long as it can produce graphite containing amorphous carbonaceous material or graphitic material, wherein the pore distribution of the carbon material (A) as measured by mercury infiltration method has two or more peaks, the cumulative pore volume y (mL / g) is less than or equal to the minimum value between the peak with the smallest pore diameter and the next peak in the pore distribution, and the coating rate x (%) of amorphous carbonaceous material or graphitic material of graphite satisfies the above formula (1). For example, from the perspective of making the pores within the particles dense and being able to efficiently reduce the cumulative pore volume y, a method of spheroidizing the carbon material raw material in the presence of a granulating agent, pressurizing it, and adding an amorphous carbon precursor or graphitic precursor is preferred. Specifically, a manufacturing method including the following steps (1) to (6) is preferred.

[0094] Process (1): Adjusting the particle size of carbon material raw materials

[0095] Process (2): The process of mixing carbon material raw materials and granulating agent.

[0096] Process (3): The process of spheroidizing carbon material raw materials.

[0097] Step (4): Step to remove granulating agent

[0098] Process (5): The process of pressurizing.

[0099] Process (6): The process of adding amorphous carbonaceous or graphitic materials.

[0100] The following describes steps (1) to (6), but steps other than steps (1) to (6) may also be included before and after each step. The manufacturing method is not limited to steps (1) to (6).

[0101] (Process (1))

[0102] Process (1) is the process of adjusting the particle size of carbon material raw materials.

[0103] The carbon material raw material is graphite. Considering its high crystallinity and excellent capacity, natural graphite and artificial graphite are preferred. Considering its even higher crystallinity, superior capacity, and the elimination of the need for heat treatment during manufacturing, natural graphite is more preferred. The graphite is preferably low in impurities, and it is more preferably purified as needed.

[0104] Examples of natural graphite include amorphous graphite, vein graphite, and flake graphite. Among these natural graphites, vein graphite and flake graphite are preferred, and flake graphite is more preferred, considering high graphitization and low impurities.

[0105] As artificial graphite, examples include materials obtained by heating organic materials such as coal tar pitch, coal-based heavy oil, atmospheric residue oil, petroleum-based heavy oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene sulfide, polyphenylene ether, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin to above 2500℃ for graphitization.

[0106] Considering that graphite is highly crystalline and has sufficient charge / discharge capacity, the preferred d002 value of the carbon material raw material is 3.360. The preferred value is 3.357. The lower limit of the d002 value is not specifically defined, but theoretically it is 3.354. .

[0107] Considering that graphite is highly crystalline and has sufficient charge / discharge capacity, the preferred Lc value for carbon material raw materials is 900. The above, more preferably 1000 That's all. There is no specific upper limit for Lc; the upper limit for measurement is 1000. .

[0108] From the perspective of excellent capacity and battery safety, the purity of carbon material raw materials is preferably 99.0% or higher, more preferably 99.5% or higher, even more preferably 99.9% or higher, and especially preferably 100%.

[0109] In this specification, purity is a value calculated based on the mass of the carbon material raw material before and after heating, by accurately weighing approximately 10g of thoroughly dried carbon material raw material and heating it at 815°C for 10 hours.

[0110] The volumetric average particle size (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. From the perspective of excellent transportability, the volumetric average particle size 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. Furthermore, from the perspective of excellent productivity, the volumetric average particle size 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.

[0111] From the perspective of shape control, the specific surface area (SA) of the carbon material raw material is preferably 1.0 m². 2 / g or more, preferably 1.5m 2 / g or more, further preferably 2.0m 2 For values ​​above / g, considering excellent control of irreversible capacity, 30.0m³ is preferred. 2 / g or less, more preferably 20.0m 2 / g or less, more preferably 10.0m 2 / g or less.

[0112] The tap density of the carbon material raw material is preferably 0.60~1.40 g / cm³. 3 More preferably, it is 0.70~1.30 g / cm³. 3 Further preferred values ​​are 0.80~1.20 g / cm³. 3 Here, considering excellent transportability, the tap density of the carbon material raw material is preferably 0.60 g / cm³. 3 The above, more preferably 0.70 g / cm³ 3 The above is further preferred to be 0.80 g / cm³. 3 That's all. Furthermore, considering ease of control during crushing, the tap density of the carbon material raw material is preferably 1.40 g / cm³. 3 The preferred value is 1.30 g / cm³. 3 The following is a further preferred value of 1.20 g / cm³. 3 the following.

[0113] The method for adjusting the particle size of carbon material raw materials is as long as it can be adjusted to the volume-based average particle size and specific surface area described later. There are no particular limitations, and it can be crushed, broken, or graded.

[0114] Crushing, breaking, and grading can be done using well-known methods.

[0115] The volumetric average particle size (d50) of the carbon material raw material after particle size adjustment is preferably 1 to 20 μm, more preferably 2 to 15 μm, and even more preferably 3 to 12 μm. Here, from the perspective of easy control of spheroidization process, the volumetric average particle size after particle size adjustment is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. In addition, it is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 12 μm or less.

[0116] The preferred specific surface area (SA) of the carbon material raw material after particle size adjustment is 5.0~30.0 m². 2 / g, more preferably 7.0~25.0m 2 / g, further preferably 9.0~20.0m 2 / g. Here, considering factors such as ensuring adequate lithium-ion entry and exit, excellent fast charge / discharge characteristics, and superior low-temperature input / output characteristics, the preferred specific surface area after particle size adjustment is 5.0 m². 2 / g or more, preferably 7.0m 2 / g or more, further preferably 7.5m 2 / g or higher, and more preferably 9.0m 2 / g or more, especially preferably 10.0m 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 after particle size adjustment is preferably 30.0 m². 2 / g or less, more preferably 25.0m 2 / g or less, more preferably 20.0m 2 / g or less.

[0117] The preferred tap density of the carbon material raw material after particle size adjustment is 0.40~1.40 g / cm³. 3 More preferably, it is 0.450~1.30 g / cm³. 3 More preferably, it is 0.50~1.20 g / cm³. 3 Here, considering the excellent sphericity during the sphericification process, the preferred tap density after particle size adjustment is 0.40 g / cm³. 3 The above, more preferably 0.45 g / cm 3 The above is further preferred to be 0.50 g / cm³. 3 The above is further preferred to be 0.60 g / cm³. 3 The above is further preferred to be 0.70 g / cm³. 3 The above, especially preferred, is 0.80 g / cm³. 3 That's all. Additionally, the preferred tap density after particle size adjustment is 1.40 g / cm³. 3 The preferred value is 1.30 g / cm³. 3 The following is a further preferred value of 1.20 g / cm³. 3 the following.

[0118] (Process (2))

[0119] Process (2) is the process of mixing carbon material raw materials and granulating agent.

[0120] The granulating agent is preferably a liquid when spherizing carbon material raw materials.

[0121] In addition, the granulating agent preferably contains an organic compound that becomes amorphous carbon.

[0122] Furthermore, the granulating agent is preferably a granulating agent that does not contain organic solvents, a granulating agent that contains organic solvents in which at least one of the organic solvents does not have a flash point, or a granulating agent that contains organic solvents with a flash point of 5°C or higher.

[0123] If the granulating agent meets the above requirements, when spheroidizing carbon material raw materials, the granulating agent will form liquid bridges between the carbon material raw materials. The capillary negative pressure of the liquid bridges and the surface tension of the liquid will generate attraction between the carbon material raw materials, which can effectively shorten the distance between the carbon material raw materials.

[0124] Methods for mixing carbon material raw materials and granulating agents include, for example, mixing the carbon material raw materials and granulating agents using a mixer or kneader, and removing the solvent after adding the carbon material raw materials to a solution containing the granulating agent. Among these methods, the method of mixing the carbon material raw materials and granulating agents using a mixer or kneader is preferred from the perspective of effectively reducing micropores of 1 nm to 4 nm.

[0125] The amount of granulating agent added relative to 100 parts by weight of carbon material raw material is preferably 0.1 to 100 parts by weight, more preferably 1 to 80 parts by weight, and even more preferably 10 to 50 parts by weight. Here, from the viewpoint of being able to suppress the decrease in sphericity caused by the decrease in adhesion between carbon material raw materials and the decrease in productivity caused by the carbon material raw materials adhering to the device, the amount of granulating agent added relative to 100 parts by weight of carbon material raw material is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, even more preferably 10 parts by weight or more, and preferably 1000 parts by weight or less, more preferably 100 parts by weight or less, more preferably 80 parts by weight or less, and even more preferably 50 parts by weight or less.

[0126] (Process (3))

[0127] Process (3) is a process of spheroidizing carbon material raw materials.

[0128] By spherizing the carbon material raw material, it exhibits excellent rapid charge and discharge characteristics.

[0129] From the perspective of easily controlling the shape of particles, the preferred method for spheroidizing carbon material raw materials is to impart mechanical energy to the carbon material raw materials to spheroidize them.

[0130] Examples of mechanical energy include impact, compression, friction, and shear force. These mechanical energies can be used individually or in combination.

[0131] A method for spherizing carbon material raw materials by imparting mechanical energy can be achieved using a device that applies mechanical energy.

[0132] The viscosity of the granulating agent used in the spheroidization treatment of carbon material raw materials is preferably 1 to 1000 cP, more preferably 5 to 800 cP, even more preferably 10 to 600 cP, and even more preferably 20 to 500 cP. Here, considering the ability to suppress the re-detachment of spheroidized particles caused by impact forces with the rotor and housing during spheroidization, the ability to enter the 1 nm to 4 nm micropores through the granulating agent to become amorphous carbon thus reducing micropores, and excellent low-temperature input / output characteristics and high-temperature storage characteristics, the viscosity of the aforementioned granulating agent is preferably 1 cP or more, more preferably 5 cP or more, even more preferably 10 cP or more, particularly preferably 20 cP or more, and preferably 1000 cP or less, more preferably 800 cP or less, even more preferably 600 cP or less, and particularly preferably 500 cP or less.

[0133] The viscosity of the granulating agent used in the spheroidization process of carbon materials can be adjusted by the amount of organic solvent and the temperature of the spheroidization process.

[0134] In this specification, viscosity is the value measured using a rheometer at 25°C. Shear rate: 100 s. -1 When the shear stress is above 0.1 Pa, the shear rate is 100 s⁻¹. -1 The measured value is a shear rate of 100 s. -1 When the shear stress is less than 0.1 Pa, it is within 1000 s. -1 The measured value is a shear rate of 1000 s. -1 When the shear stress is less than 0.1 Pa, the value is the value measured at the shear rate when the shear stress reaches 0.1 Pa or more.

[0135] When spheroidizing carbon raw materials, granulation can also be performed in the presence of other substances. Examples of such other substances include: metals that can form alloys with lithium, their oxides, amorphous carbon, and raw coke.

[0136] When spheroidizing carbon material raw materials, it is preferable to perform the spheroidizing process simultaneously, allowing the micropowder generated during the process to adhere to the surface of the carbon material. By performing the spheroidizing process while simultaneously allowing the micropowder generated during the process to adhere to the surface of the carbon material, the porosity within the carbon material can be effectively reduced when coating the carbon material with amorphous carbonaceous or graphitic materials. Furthermore, the amount of edges that can be utilized as lithium ion insertion and detachment sites increases, the electrolyte effectively distributes throughout the porosity of the carbon material, and the low-temperature input / output characteristics and cycle performance are excellent.

[0137] Micronized powder is not only produced during spheroidization, but also can be added separately with adjusted particle size.

[0138] In order to enable the micro powder to adhere effectively to the surface of carbon materials, it is preferable to enhance the adhesion between carbon material particles, between carbon material particles and micro powder particles, and between micro powder particles.

[0139] As a form of adhesion between particles, examples include van der Waals forces without interparticle inclusions, electrostatic attraction, physical cross-linking forces with interparticle inclusions, and chemical cross-linking forces.

[0140] Regarding van der Waals forces, with a volumetric average particle size (d50) of 100 μm as the boundary, the smaller the particle size, the less the [self-weight] becomes [adhesion]. Therefore, the smaller the volumetric average particle size of the carbon material raw material, the stronger the adhesion between particles, and the easier it is to form a state where micropowder adheres to the carbon material and is encapsulated in the spherical carbon material, which is therefore preferred.

[0141] Carbon material raw materials and granulating agents can be added into the spheroidizing treatment device, and processes (2) and (3) can be carried out simultaneously.

[0142] (Process (4))

[0143] Step (4) is the process of removing the granulating agent.

[0144] The granulating agent can be completely or partially removed.

[0145] In cases where granulating agents containing organic solvents are used, it is preferable to remove the organic solvents as well.

[0146] Methods for removing granulating agents and organic solvents include, for example, methods of cleaning with solvents and methods of heating to volatilize / decompose them. Among these methods, the method of heating to volatilize / decompose them is preferred from the perspectives of productivity and excellent removal efficiency.

[0147] (Process (5))

[0148] Step (5) is the process of pressurizing.

[0149] Examples of pressurization processes include isotropic pressurization and anisotropic pressurization. Among these pressurization processes, isotropic pressurization is preferred from the perspective of being able to control the resulting carbon material (A) to satisfy equation (1).

[0150] Examples of pressurization methods include: hydrostatic isotropic pressurization using water as the pressurizing medium; air pressure-based isotropic pressurization using gases such as air as the pressurizing medium; and pressurization processes in which the contents are filled into a mold and pressurized in a certain direction using a uniaxial press.

[0151] The pressure applied is preferably 50 to 300 MPa, more preferably 100 to 280 MPa, and even more preferably 150 to 260 MPa. Here, from the viewpoint of easy control so that the obtained carbon material (A) satisfies formula (1), the pressure applied is preferably 50 MPa or more, more preferably 100 MPa or more, even more preferably 150 MPa or more, and preferably 300 MPa or less, more preferably 280 MPa or less, and even more preferably 260 MPa or less.

[0152] Step (5) can be performed at any time from step (1) to step (6), but from the perspective of being able to efficiently pressurize in a state where excess granulating agent has been removed, it is preferred to be between step (4) and step (6).

[0153] (Process (6))

[0154] Step (6) is the process of adding amorphous carbonaceous material or graphite material.

[0155] By adding amorphous carbonaceous or graphitic materials to carbon materials, side reactions between the negative electrode and the electrolyte can be suppressed, resulting in high capacity, excellent high-temperature input / output characteristics, and excellent high-temperature storage characteristics.

[0156] Amorphous carbonaceous materials refer to carbon with a d002 value of 0.340 nm or higher.

[0157] Graphite refers to graphite with a d002 value of less than 0.340 nm.

[0158] From the perspective of easily controlling the amount of voids within the particles, the preferred method for adding amorphous carbonaceous or graphitic materials to carbon materials is to mix the carbon material with an amorphous carbonaceous precursor or a graphitic precursor, and then heat it in a non-oxidizing gas atmosphere to carbonize the amorphous carbonaceous precursor or graphitize the graphitic precursor.

[0159] Examples of methods for mixing carbon materials with amorphous carbonaceous precursors or graphitic precursors include: mixing carbon materials with amorphous carbonaceous precursors or graphitic precursors using a mixer or kneader; and removing the solvent after adding carbon materials to a solution containing dissolved amorphous carbonaceous precursors or graphitic precursors. Among these methods, the method of mixing carbon materials with amorphous carbonaceous precursors or graphitic precursors using a mixer or kneader is preferred from the perspective of effectively reducing micropores of 1 nm to 4 nm.

[0160] The mixing ratio of carbon materials with amorphous carbonaceous precursors or graphitic precursors can be appropriately set to achieve the desired coating rate x.

[0161] The gas atmosphere during heating can be any non-oxidizing gas atmosphere, and there are no particular limitations. However, from the perspective of suppressing the formation of micropores caused by oxidation, nitrogen, argon, and carbon dioxide are preferred, and nitrogen is more preferred.

[0162] From the perspective of ease of control so that the resulting carbon material (A) satisfies equation (1), the oxygen concentration is preferably 1 vol% or less, more preferably 0.1 vol% or less. There is no particular limitation on the lower limit of the oxygen concentration, which is typically 0 vol%.

[0163] The heating temperature differs in the amorphous carbonization of amorphous carbonaceous precursors and the graphitization of graphitic precursors.

[0164] The heating temperature for amorphous carbonaceous precursor carbonization is not particularly limited as long as it does not reach a crystalline structure equivalent to that of graphite. Preferably, it is 500-2000°C, more preferably 600-1800°C, and even more preferably 700-1600°C. Here, the heating temperature is preferably 500°C or higher, more preferably 600°C or higher, and even more preferably 700°C or higher. Furthermore, it is preferably 2000°C or lower, more preferably 1800°C or lower, and even more preferably 1600°C or lower.

[0165] The heating temperature for graphitizing the graphitic precursor is not particularly limited, as long as it reaches a crystal structure equivalent to that of graphite. Preferably, it is 2100-3300°C, more preferably 2500-3200°C, and even more preferably 2700-3100°C. Here, the heating temperature is preferably 2100°C or higher, more preferably 2500°C or higher, and even more preferably 2700°C or higher. Furthermore, it is preferably 3300°C or lower, more preferably 3200°C or lower, and even more preferably 3100°C or lower.

[0166] The heating time is preferably 0.1 to 1000 hours, more preferably 1 to 100 hours. Here, from the viewpoint of easy control so that the obtained carbon material (A) satisfies formula (1), the heating time is preferably 0.1 hours or more, more preferably 1 hour or more, and preferably 1000 hours or less, more preferably 100 hours or less.

[0167] Examples of precursors for amorphous carbonaceous materials and graphitic materials include: aromatic hydrocarbons such as tar, pitch, naphthalene, and anthracene, and thermoplastic resins such as phenolic resins and polyvinyl alcohol resins. These precursors can be used individually or in combination of two or more. Among these precursors, tar, pitch, and aromatic hydrocarbons are preferred from the perspective of ease of carbon structure development and the ability to coat with a small amount. From the perspective of ease of control to ensure that the resulting carbon material (A) satisfies formula (1), precursors with a residual carbon content of 50% or more are more preferred, and precursors with a residual carbon content of 60% or more are even more preferred.

[0168] In 100% by mass of the amorphous carbonaceous precursor and the graphitic precursor, the ash content in the amorphous carbonaceous precursor and the graphitic precursor is preferably 0.00001 to 1% by mass. Here, from the viewpoint of easy control so that the resulting carbon material (A) satisfies formula (1), in 100% by mass of the amorphous carbonaceous precursor and the graphitic precursor, the above-mentioned ash content is preferably 0.00001% by mass or more, and preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less.

[0169] The metal impurity content in the amorphous carbonaceous precursor and the graphitic precursor is preferably 0.1 to 1000 ppm by mass. Here, from the viewpoint of easy control so that the obtained carbon material (A) satisfies formula (1), the metal impurity content is preferably 0.1 ppm by mass or more, and preferably 1000 ppm by mass or less, more preferably 500 ppm by mass or less, and even more preferably 100 ppm by mass or less.

[0170] In this 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 and the graphitic precursor by the residual carbon content.

[0171] From the perspective of ease of control so that the resulting carbon material (A) satisfies formula (1), in 100% by mass of the amorphous carbon precursor and the graphitic precursor, the Qi (quinoline insolubles) in the amorphous carbon precursor and the graphitic precursor is preferably 5% by mass or less, more preferably 3% by mass or less. The lower limit of the above-mentioned Qi is not particularly limited, and is usually 0% by mass.

[0172] In order to make the volume-based average particle size of carbon material (A) within the desired range, the carbon material obtained through processes (1) to (6) can be crushed, broken and graded as needed.

[0173] Crushing, breaking, and grading can be done using well-known methods.

[0174] (Carbon materials (B))

[0175] The particle density of carbon material (B) is 1.80 g / cm³. 3 above.

[0176] The carbon material composition of this embodiment, by including the aforementioned carbon material (B), can be selectively densified when the electrode is pressed to a given density when used in combination with the aforementioned carbon material (A). Furthermore, the surface area of ​​the aforementioned carbon material (B) does not easily increase even when deformed during pressing; therefore, by using carbon material (A) and carbon material (B) in combination, the increase in the reaction area of ​​the electrode plate when used at high density can be suppressed.

[0177] The preferred particle density of carbon material (B) is 1.80~2.262 g / cm³. 3 Here, considering its excellent compressibility during pressing, the particle density of carbon material (B) is 1.80 g / cm³. 3 The preferred value is 1.85 g / cm³. 3 The above, more preferably 1.88 g / cm³ 3 The above is further preferred to be 1.90 g / cm³. 3 In addition, the preferred value is 2.262 g / cm³. 3 the following.

[0178] To achieve a particle density of 1.80 g / cm³ for carbon material (B) 3 The above allows for adequate porosity within the particles and proper stacking of the flakes. Therefore, carbon material (B) is preferably flake-spheroidized natural graphite.

[0179] (Physical properties of carbon materials (B))

[0180] Considering that higher crystallinity of graphite results in better compressibility and greater charge / discharge capacity during pressing, the preferred d002 value for carbon material (B) is 3.360. More preferably 3.357 The lower limit of the d002 value mentioned above is not specifically limited; the theoretical value is 3.354. above.

[0181] Considering that higher crystallinity of graphite results in better compressibility and greater charge / discharge capacity during pressing, the preferred Lc value for carbon material (B) is 900. The above, more preferably 1000 That's all. There is no specific upper limit for Lc mentioned above; the upper limit for measurement is 1000. .

[0182] The volume-based average particle size (d50) of the carbon material (B) is preferably 1 to 50 μm, more preferably 4 to 30 μm, and even more preferably 10 to 25 μm. Here, considering the prevention of irreversible capacity increase and initial battery capacity loss, the volume-based average particle size of the carbon material (B) is preferably 1 μm or more, more preferably 4 μm or more, and even more preferably 10 μm or more. Furthermore, considering the ability to suppress process defects such as scratches during electrode fabrication, excellent fast charge / discharge characteristics, and low-temperature input / output characteristics, the volume-based average particle size of the carbon material (B) is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less.

[0183] The specific surface area (SA) of the carbon material (B) is preferably 3.0~11.0 m². 2 / g, more preferably 4.0~9.0m 2 / g, further preferably 5.0~8.0m 2 / g. Here, considering factors such as ensuring adequate lithium-ion entry and exit, excellent fast charge / discharge characteristics, and superior low-temperature input / output characteristics, the specific surface area of ​​the carbon material (B) is preferably 3.0 m². 2 / g or more, preferably 4.0m 2 / g or more, further preferably 5.0m 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 (B) is preferably 11.0 m². 2 / g or less, preferably 9.0m 2 / g or less, more preferably 8.0m 2 / g or less.

[0184] The tap density of carbon material (B) is preferably 0.70~1.30 g / cm³. 3 More preferably, it is 0.80~1.20 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 filler content, 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 (B) 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. 3That'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 (B) is preferably 1.30 g / cm³. 3 The following is more preferably 1.20 g / cm³ 3 The following is a further preferred value of 1.10 g / cm³. 3 the following.

[0185] The sphericity of the carbon material (B) 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 the excellent fast charge / discharge characteristics, the sphericity of the carbon material (B) 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 (B) is preferably 0.99 or lower, more preferably 0.98 or lower, and even more preferably 0.97 or lower.

[0186] 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 even more preferably 0.050 to 0.100 mL / g. Here, considering ease of moderate deformation during 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 even more preferably 0.050 mL / g or more. Furthermore, 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, even more preferably 0.120 mL / g or less, even more preferably 0.100 mL / g or less, even more preferably 0.090 mL / g or less, and particularly preferably 0.070 mL / g or less.

[0187] (Manufacturing method of carbon material (B))

[0188] The manufacturing method of carbon material (B) only needs to produce particles with a density of 1.80 g / cm³. 3 The above methods are acceptable and there are no particular limitations. Considering the high crystallinity and excellent compressibility, flake-spheroidized natural graphite is preferred as the carbon material (B).

[0189] The raw material for carbon material (B) is preferably graphite. Considering its high crystallinity and excellent capacity, natural graphite or artificial graphite is more preferred. Considering its even higher crystallinity, superior capacity, and the elimination of the need for heat treatment during manufacturing, natural graphite is even more preferred. The graphite is preferably graphite with few impurities, and it is more preferably used after purification treatment as needed.

[0190] Examples of natural graphite include: earthy graphite, vein graphite, and flake graphite. Among these natural graphites, vein graphite and flake graphite are preferred, and flake graphite is even more preferred, considering high graphitization and low impurities.

[0191] As artificial graphite, examples include materials obtained by heating organic materials such as coal tar pitch, coal-based heavy oil, atmospheric residue oil, petroleum-based heavy oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polystyrene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylene sulfide, polyphenylene ether, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin to above 2500℃ for graphitization.

[0192] From the perspective of easily controlling the shape of particles, the preferred method for sphericalization is to impart mechanical energy to the particles.

[0193] Examples of mechanical energy include impact, compression, friction, and shear force. These mechanical energies can be used individually or in combination.

[0194] The method of spheroidizing by imparting mechanical energy can be achieved using a device that applies mechanical energy.

[0195] During spheroidization, the raw materials can be granulated in the presence of other substances. Examples of such other substances include metals that can form alloys with lithium, their oxides, and raw coke.

[0196] (Composition of the carbon material composition)

[0197] In the 100% by mass of the carbon material composition, the content of carbon material (A) is preferably 40-90% by mass, more preferably 45-85% by mass, and even more preferably 55-75% by mass. Here, from the viewpoint of suppressing electrode expansion to a low level, the content of carbon material (A) in the 100% by mass of the carbon material composition is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 55% by mass or more. Furthermore, from the viewpoint of maintaining a high level of initial efficiency of the secondary battery, the content of carbon material (A) is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 75% by mass or less.

[0198] In the carbon material composition, the content of carbon material (B) in 100% by mass is preferably 10-60% by mass, more preferably 15-55% by mass, and even more preferably 25-45% by mass. Here, from the viewpoint of maintaining a high level of initial efficiency of the secondary battery, the content of carbon material (B) in the carbon material composition is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 25% by mass or more. Furthermore, from the viewpoint of suppressing plate expansion to a low level, the content of carbon material (B) is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 45% by mass or less.

[0199] In addition to carbon material (A) and carbon material (B), the carbon material composition of this embodiment may also contain other substances. Examples of other substances include metals capable of forming alloys with lithium, their oxides, and conductive materials.

[0200] From the perspective of not impairing the original functions of carbon material (A) and carbon material (B), the total content of other substances is preferably 20% by mass or less, more preferably 10% by mass or less.

[0201] (Physical properties of carbon material compositions)

[0202] The volume-based average particle size (d50) of the carbon material composition is preferably 1 to 50 μm, more preferably 4 to 30 μm, and even more preferably 10 to 25 μm. Here, from the perspective of preventing irreversible capacity increase and initial battery capacity loss, the volume-based average particle size of the carbon material composition is preferably 1 μm or more, more preferably 4 μm or more, and even more preferably 10 μm or more. Furthermore, from the perspective of suppressing process defects such as scratches during electrode fabrication, excellent fast charge / discharge characteristics, and excellent low-temperature input / output characteristics, the volume-based average particle size of the carbon material composition is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 25 μm or less.

[0203] The specific surface area (SA) of the carbon material composition is preferably 1.0 to 11.0 m². 2 / g, more preferably 2.0~9.0m 2 / g, further preferably 3.0~8.0m 2 / g. Here, considering factors such as ensuring adequate lithium-ion entry and exit, excellent fast charge / discharge characteristics, and superior low-temperature input / output characteristics, the specific surface area of ​​the carbon material composition is preferably 1.0 m². 2 / g or more, preferably 2.0m 2 / g or more, further preferably 3.0m 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.

[0204] 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.

[0205] 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.

[0206] 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 even more preferably 0.010 to 0.070 mL / g. Here, from the viewpoint of easy and moderate deformation during pressing, 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 even more preferably 0.010 mL / g or more. Furthermore, it is preferably 0.120 mL / g or less, more preferably 0.090 mL / g or less, and even more preferably 0.070 mL / g or less.

[0207] The preferred particle density of the carbon material composition is 1.40~1.80 g / cm³. 3 More preferably, it is 1.50~1.70 g / cm³. 3 More preferably, it is 1.55~1.60 g / cm³. 3 Here, considering ease of moderate deformation during pressing, the particle density of the carbon material composition is preferably 1.40 g / cm³. 3 The above, more preferably 1.50 g / cm³ 3 The above is further optimized to be 1.55 g / cm³. 3 In addition, the preferred value is 1.80 g / cm³. 3 The preferred value is 1.70 g / cm³. 3 The following is a further preferred value: 1.60 g / cm³ 3 the following.

[0208] (Method for manufacturing carbon material compositions)

[0209] The method for manufacturing the carbon material composition of this embodiment includes a step of mixing the carbon material (A) and the carbon material (B) described above.

[0210] The mixing method is not particularly limited as long as it can mix carbon material (A) and carbon material (B) into the desired composition.

[0211] The ratio Rd50 ([volume-based average particle size (d50) of carbon material (A) to the volume-based average particle size (d50) of carbon material (B)] / [volume-based average particle size (d50) of carbon material (A)] is preferably 0.1 to 10, more preferably 0.2 to 5, and even more preferably 0.5 to 2. Here, the above-mentioned ratio Rd50 is preferably 0.1 or more, more preferably 0.2 or more, even more preferably 0.5 or more, and preferably 10 or less, more preferably 5 or less, and even more preferably 2 or less.

[0212] When Rd50 is within the aforementioned range, carbon material (B) can exist in the gaps between carbon materials (A), or carbon material (A) can exist in the gaps between carbon materials (B). As a result, by having carbon material (B) surrounding carbon material (A), carbon material (B) can be selectively deformed while maintaining the shape of carbon material (A). Even when used at high density, it will not be damaged during pressing, achieving both high initial efficiency and low expansion. Furthermore, the gaps formed by carbon materials (A) and (B) absorb the volume changes of carbon materials (A) and (B) associated with the adsorption and release of lithium ions during charging and discharging. Therefore, the disruption of conductive pathways associated with the volume changes of carbon materials (A) and (B) can be suppressed, enabling improved cycle characteristics, fast charge / discharge characteristics, and high capacity.

[0213] The ratio of the specific surface area (SA) of carbon material (A) to the specific surface area (SA) of carbon material (B), RSA([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 even more preferably 0.2 to 5. Here, the above-mentioned ratio RSA is preferably 0.01 or more, more preferably 0.1 or more, even more preferably 0.2 or more, and preferably 100 or less, more preferably 10 or less, even more preferably 6 or less, even more preferably 5 or less, and particularly preferably 3 or less.

[0214] When the RSA is within the above range, it can ensure the entry and exit of lithium ions, has excellent fast charge and discharge characteristics and low temperature input and output characteristics, can suppress side reactions with electrolyte, prevent the reduction of initial charge and discharge efficiency and the increase of gas generation, and improve battery capacity.

[0215] The ratio of the cumulative pore volume of carbon material (A) to the cumulative pore volume of carbon material (B), RCPV ([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 even more preferably 5 to 20. Here, the above-mentioned ratio RCPV is preferably 1 or more, more preferably 3 or more, even more preferably 5 or more, and preferably 50 or less, more preferably 40 or less, and even more preferably 20 or less.

[0216] When the RCPV is within the above range, the carbon material (B) is selectively deformed relative to the carbon material (A) during the fabrication of the electrode plate, so that high initial efficiency and low expansion can be achieved even when used at high density.

[0217] (negative electrode)

[0218] The negative electrode of this embodiment includes a current collector and an active material layer formed on the current collector, the active material layer comprising the carbon material composition of this embodiment. The carbon material composition of this embodiment has the effect of being an active material for a negative electrode.

[0219] The manufacturing method of the negative electrode is not particularly limited as long as it can form an active material layer on the current collector. However, from the perspective of low cost and excellent productivity, a method of coating a slurry containing the carbon material composition of this embodiment and a binder resin onto the current collector and then drying it is preferred. A thickener may be further added to the slurry.

[0220] Preferably, the density of the active material layer formed on the current collector is increased by pressing after the slurry containing the carbon material composition and the binder resin of this embodiment is coated onto the current collector and dried, thereby increasing the battery capacity per unit volume of the active material layer.

[0221] The density of the active material layer is preferably 1.2~2.0 g / cm³. 3 More preferably, it is 1.5~1.8 g / cm³. 3 Here, considering the ability to suppress the decrease in battery capacity caused by the increase in electrode thickness, the density of the active material layer is preferably 1.2 g / cm³. 3 The above, more preferably 1.5 g / cm³ 3 That's all. Furthermore, considering that reducing the gaps within the electrode reduces the amount of electrolyte retained in the gaps, decreases the migration of alkaline ions such as lithium ions, and suppresses the degradation of rapid charge / discharge characteristics, the density of the active material layer is preferably 2.0 g / cm³. 3 The following is more preferably 1.8 g / cm³ 3 the following.

[0222] (Secondary battery)

[0223] The secondary battery of this embodiment includes a positive electrode, a negative electrode of this embodiment, and an electrolyte.

[0224] The positive electrode and the negative electrode of this embodiment are preferably capable of absorbing and releasing lithium ions.

[0225] (positive electrode)

[0226] The positive electrode can use a known positive electrode.

[0227] (electrolytes)

[0228] The electrolyte can be a known electrolyte.

[0229] (partition)

[0230] The secondary battery of this embodiment preferably has a separator sandwiched between the positive and negative electrodes. However, the secondary battery of this embodiment does not exclude the use of a solid electrolyte as the electrolyte.

[0231] The partition can be a known type of partition.

[0232] The carbon material composition of this embodiment can maintain a high initial efficiency of the secondary battery and suppress plate expansion to a low level. Therefore, it is suitable as an active material for the negative electrode of a secondary battery, and even more suitable as an active material for the negative electrode of a non-aqueous secondary battery, especially suitable as an active material for the negative electrode of a lithium-ion secondary battery.

[0233] Example

[0234] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples as long as it does not depart from its spirit.

[0235] (Method for determining the average particle size based on volume)

[0236] 0.01 g of the sample was suspended in 10 mL of a 0.2% (w / w) aqueous solution of polyoxyethylene sorbitan monolaurate (trade name "Tween 20") as a surfactant. The sample was then introduced into a laser diffraction / scattering particle size distribution measuring device (model name "LA-920", manufactured by Horiba Corporation). After irradiating the sample with 28 kHz ultrasound for 1 minute at an output power of 60 W, the median particle size of the volume reference in the measuring device was measured, and the median particle size of the volume reference was taken as the average particle size of the volume reference.

[0237] (Methods for determining specific surface area)

[0238] Using a specific surface area measuring device (model name "Macsorb HM-1210", manufactured by MOUNTECH), the sample was pre-depressurized and dried at 350°C for 15 minutes under nitrogen flow, then cooled to liquid nitrogen temperature. The specific surface area was determined by nitrogen adsorption BET1 point method based on gas flow using a nitrogen-helium mixed gas with a nitrogen relative pressure of 0.3 adjusted accurately relative to atmospheric pressure.

[0239] (Method for determining tap density)

[0240] Using a powder density meter (model name "Tap Denser KYT-3000", manufactured by Seishin Enterprise), carbonaceous material was passed through a 300μm mesh sieve to a diameter of 1.6cm and a volumetric density of 20cm³. 3The cylindrical vibratory unit is dropped down, and after the unit is filled, it is vibrated 1000 times with a stroke length of 10mm. The density value calculated based on the volume and mass of the sample at this time is taken as the vibratory density.

[0241] (Method for determining the cumulative pore volume y)

[0242] Using a mercury porosimeter (AutoPore 9520, Micromeritics), approximately 0.2 g of carbon material was sealed in a powder cell and pretreated by degassing at 25°C under vacuum (below 50 μmHg) for 10 minutes. Next, the pressure was reduced to 4 psia (approximately 28 kPa), and mercury was introduced into the cell. The pressure was then increased stepwise from 4 psia (approximately 28 kPa) to 40,000 psia (approximately 280 MPa), and then reduced to 25 psia (approximately 170 kPa). The number of pressure steps was set to at least 80, and the mercury infiltration rate was measured after each step had a 10-second equilibration period. Based on the resulting mercury infiltration curve, the pore size distribution was calculated using the Washburn equation. The surface tension (γ) of mercury was calculated as 485 dyne / cm, and the contact angle (ψ) as 140°. Based on the results, a coordinate graph was created with the horizontal axis representing the pore diameter and the vertical axis representing the pore volume. Peaks were identified from this graph, and the minimum value between the peak with the smallest pore diameter and the next peak (between the two peaks on the side with the smallest pore diameter) was determined. The cumulative pore volume below this minimum value was set as the peak value y (mL / g).

[0243] (Method for calculating coverage ratio x)

[0244] The coating rate x is calculated using the following formula (3) based on the mixing ratio of graphite with amorphous carbonaceous material or graphitic material and the firing yield after firing.

[0245] Coverage rate x (%) = ([mass of the fired sample - mass of graphite] / [mass of the fired sample]) × 100 (3)

[0246] (Methods for determining particle density)

[0247] 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.

[0248] (Making of the negative electrode)

[0249] 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 1% sodium carboxymethyl cellulose aqueous solution and 1.00±0.05 g (equivalent to 0.50 g in solids) of 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.

[0250] 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.

[0251] (The production of positive electrode plates)

[0252] A slurry was obtained by mixing 85% by mass of lithium nickel-manganese-cobalt oxide (LiNiMnCoO2) as the positive electrode active material, 10% by mass of acetylene black as the conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as the binder in N-methylpyrrolidone.

[0253] The resulting slurry was applied to a 15 μm thick aluminum foil (used as a current collector) using a scraper coater and dried at 130°C, resulting in an adhesion of 22.5 ± 0.2 mg / cm². 2 The positive electrode material is further subjected to rolling and adjustment to achieve a density of 2.60 ± 0.05 g / cm³. 3 Thus, the positive electrode sheet was obtained.

[0254] (Fabrication of sheet-shaped secondary batteries)

[0255] The obtained negative electrode, polyethylene separator, and positive electrode were sequentially stacked. The stack was then wrapped with a cylindrical aluminum laminate, injected with electrolyte, and vacuum-sealed to fabricate a sheet-like non-aqueous secondary battery. The electrolyte was prepared by dissolving LiPF6 in a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate (volume ratio 30:30:40) at a concentration of 1 mol / L. Furthermore, to improve the sealing between the electrodes, the sheet-like secondary battery was sandwiched between glass plates and pressurized.

[0256] (Method for measuring the expansion of a secondary battery)

[0257] For sheet-shaped secondary batteries that had not undergone charge-discharge cycles, three cycles were performed at 25°C with a voltage range of 4.1V to 3.0V and a current of 0.2C. Two initial charge-discharge cycles were then performed with a voltage range of 4.2V to 3.0V and a current of 0.2C (further charged at a constant voltage of 4.2V for 2.5 hours during charging). At this point, the glass plate used for fixing was removed, and the thickness of one secondary battery was measured at nine points using a contact thickness gauge (manufactured by Mitutoyo Corporation). The average value was taken as the thickness before cycling. Then, after clamping the glass plate again, a cycle test was performed in a 45°C constant temperature bath under the conditions of 0.8C-CCCV charge-0.8C-CC discharge 1.5V cutoff. Then, for secondary batteries at 0% SOC (States of Charge), the thickness at nine points in the same locations as before cycling was measured, and the average value was taken as the thickness after cycling. The expansion of the secondary battery during cycling was calculated based on the difference between the thickness before and after cycling.

[0258] (Making a coin-shaped battery)

[0259] The obtained negative electrode sheet was punched into a disk shape with a diameter of 12.5 mm to form the negative electrode, and the lithium metal foil was punched into a disk shape with a diameter of 14 mm to form the counter electrode. A separator (made of porous polyethylene membrane) impregnated with electrolyte was placed between the two electrodes to produce a 2016 coin-shaped battery. The electrolyte was prepared by dissolving LiPF6 in a mixed solvent of ethylene carbonate and methyl ethyl carbonate (volume ratio 30:70) at a concentration of 1 mol / L.

[0260] (Method for determining the initial efficiency of a secondary battery)

[0261] For the obtained coin-shaped battery, the lithium counter electrode was charged to 5mV at a current density of 0.05C, and then further charged at a constant voltage of 5mV until the current density reached 0.005C. After lithium doping in the negative electrode, the lithium counter electrode was discharged to 1.5V at a current density of 0.1C. The ratio of the discharge capacity to the charge capacity at this point ((discharge capacity / charge capacity) × 100) was taken as the initial efficiency (%).

[0262] [Manufacturing Example 1] Manufacturing of carbon material (A-1)

[0263] Flake-like natural graphite with a volume average particle size of 100 μm was pulverized to obtain graphite with a volume average particle size of 11 μm. 100 parts by weight of the obtained graphite were mixed with 12 parts by weight of a granulating agent and then subjected to spheroidization treatment. The granulating agent was further removed by heat treatment to obtain spherical graphite (volume average particle size of 16 μm, specific surface area of ​​15 m²). 2 / g, tap density 0.96g / cm³ 3 The obtained spherical graphite was filled into a rubber container, which was then sealed and subjected to isotropic pressurization. Following this, it was crushed / graded to obtain spherical graphite powder. The obtained spherical graphite powder was mixed with pitch (ash content 0.02 wt%, metal impurity content 20 ppm wt%, Qi 1 wt%), a precursor for amorphous carbonaceous materials. The furnace pressure was reduced to below 10 torr, then restored to atmospheric pressure using nitrogen. Nitrogen was further circulated to ensure an oxygen concentration below 0.01 vol% within the furnace. Heat treatment was then performed at 1300°C in an inert gas environment. The resulting calcined material was crushed / graded to obtain carbon material (A-1).

[0264] The evaluation results of the obtained carbon material (A-1) are shown in Table 1.

[0265] [Manufacturing Example 2] Manufacturing of carbon material (A-2)

[0266] By changing the mixing ratio of spherical graphite powder to amorphous carbon precursor, the same operation as in Manufacturing Example 1 was performed to obtain carbon material (A-2).

[0267] The evaluation results of the obtained carbon material (A-2) are shown in Table 1.

[0268] [Manufacturing Example 3] Manufacturing of carbon material (A-3)

[0269] By changing the mixing ratio of spherical graphite powder to amorphous carbon precursor, the same operation as in Manufacturing Example 1 was performed to obtain carbon material (A-3).

[0270] The evaluation results of the obtained carbon material (A-3) are shown in Table 1.

[0271] [Manufacturing Example 4] Manufacturing of carbon material (A-4)

[0272] Spheroidizing treatment was performed on flake-like natural graphite with a volumetric average particle size of 100 μm to obtain spheroidized graphite (volumetric average particle size of 16 μm, specific surface area of ​​6.9 m²). 2 / g, tap density 1.00g / cm³ 3 The obtained spherical graphite was mixed with tar (ash content less than 0.01% by mass, metal impurity content less than 60 ppm by mass, and Qi less than 0.1% by mass) as a precursor for amorphous carbonaceous materials. The furnace pressure was reduced to less than 10 torr, and then restored to atmospheric pressure using nitrogen. Nitrogen was further circulated to ensure that the oxygen concentration in the furnace was less than 0.01% by volume. Heat treatment was carried out at 1300°C in an inert gas environment. The resulting calcined product was crushed / classified to obtain carbon material (A-4).

[0273] The evaluation results of the obtained carbon material (A-4) are shown in Table 1.

[0274] [Manufacturing Example 5] Manufacturing of Carbon Material (B-1)

[0275] Spheroidization treatment was performed on flake-like natural graphite with a volume-based average particle size of 100 μm, resulting in a particle density of 1.96 g / cm³. 3 Carbon materials (B-1).

[0276] The evaluation results of the obtained carbon material (B-1) are shown in Table 2.

[0277] [Manufacturing Example 6] Manufacturing of Carbon Material (B-2)

[0278] Spheroidization treatment was performed on flake-like natural graphite with a volume-based average particle size of 100 μm to obtain a particle density of 1.95 g / cm³. 3 Carbon materials (B-2).

[0279] The evaluation results of the obtained carbon material (B-2) are shown in Table 2.

[0280] [Manufacturing Example 7] Manufacturing of Carbon Material (B-3)

[0281] Spheroidizing treatment was performed on flake-like natural graphite with a volumetric average particle size of 100 μm to obtain spheroidized graphite (volumetric average particle size of 13 μm, specific surface area of ​​7.8 m²). 2 / g, tap density 0.90g / cm³ 3 The obtained spherical graphite was mixed with pitch (ash content less than 0.1% by mass, Qi less than 0.2% by mass) as a graphitic precursor, and the mixture was filled into a rubber container. The rubber container was then sealed and subjected to isotropic pressurization. Next, it was heat-treated at 1000°C in an inert gas, followed by graphitization at 3000°C in an inert gas. The resulting graphitized material was crushed / graded to obtain carbon material (B-3).

[0282] [Manufacturing Example 8] Manufacturing of Carbon Material (B-4)

[0283] Spheroidizing treatment was performed on flake-like natural graphite with a volume-based average particle size of 100 μm to obtain spheroidized graphite (volume-based average particle size of 8 μm and specific surface area of ​​11 m²). 2 / g, tap density 1.00g / cm³ 3 The obtained spherical graphite was mixed with pitch (ash content less than 0.1% by mass, Qi less than 0.2% by mass) as a graphitic precursor, and the mixture was filled into a rubber container. The rubber container was then sealed and subjected to isotropic pressurization. Next, it was heat-treated at 1000°C in an inert gas, followed by graphitization at 3000°C in an inert gas. The resulting graphitized material was crushed / graded to obtain carbon material (B-4).

[0284] [Example 1]

[0285] A carbon material composition was obtained by mixing 70% by mass of carbon material (A-1) and 30% by mass of carbon material (B-1).

[0286] The evaluation results of the obtained carbon material compositions are shown in Table 4.

[0287] [Examples 2-7]

[0288] As shown in Table 3, the type and content of carbon materials were changed, but otherwise the operation was carried out in the same manner as in Example 1 to obtain a carbon material composition.

[0289] The evaluation results of the obtained carbon material compositions are shown in Table 4.

[0290] [Comparative Examples 1-5]

[0291] As shown in Table 3, the type and content of carbon materials were changed, but otherwise the operation was carried out in the same manner as in Example 1 to obtain a carbon material composition.

[0292] The evaluation results of the obtained carbon material compositions are shown in Table 4.

[0293]

[0294]

[0295]

[0296]

[0297] As shown in Table 4, compared with secondary batteries containing negative electrodes using the carbon material compositions of Comparative Examples 1-5, secondary batteries containing negative electrodes using the carbon material compositions of Examples 1-7 of this embodiment can maintain a high level of initial efficiency and suppress plate expansion to a low level. This result can be attributed to the combination of dense and low-expansion carbon material (A) with high-density granular carbon material (B).

[0298] The present invention has been described in detail with reference to specific embodiments; however, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2022-048746, filed on March 24, 2022, the contents of which are incorporated herein by reference.

[0299] Industrial applicability

[0300] The carbon material composition of the present invention will not be damaged during pressing even when used at high density, thus maintaining a high initial efficiency of the secondary battery and suppressing plate expansion to a low level. Therefore, it is preferable to use as an active material for the negative electrode of a secondary battery, more preferably as an active material for the negative electrode of a non-aqueous secondary battery, and particularly preferably as an active material for the negative electrode of a lithium-ion secondary battery.

Claims

1. A carbon material composition comprising carbon material (A) and carbon material (B), The carbon material (A) comprises graphite having amorphous carbonaceous material or graphitic material. The pore distribution of the carbon material (A), as determined by mercury infiltration method, has more than two peaks. When the cumulative pore volume below the minimum value between the peak with 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 carbonaceous material or graphitic material of the graphite is set as x (%), the carbon material (A) satisfies the following formula (1). y≤-0.0084x+0.13 (1) The particle density of the carbon material (B) is 1.80 g / cm³. 3 above.

2. The carbon material composition according to claim 1, wherein, The carbon material (A) further satisfies the following equation (2), y≥0.005 (2)。 3. The carbon material composition according to claim 1, wherein, The peak with the smallest pore diameter has a pore diameter of less than 500 nm.

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

5. The carbon material composition according to claim 1, wherein, The tap density of the carbon material (A) is 1.15 g / cm³. 3 above.

6. The carbon material composition according to claim 1, wherein, The specific surface area of ​​the carbon material (A) is 3.0 m². 2 / g or less.

7. The carbon material composition according to claim 1, wherein, The carbon material (B) is spherical graphite.

8. The carbon material composition according to claim 1, wherein, The specific surface area of ​​the carbon material (B) is 3.0 m². 2 / g or more.

9. The carbon material composition according to claim 1, wherein, In 100% by mass of the carbon material composition, the carbon material (A) contains 40% to 90% by mass and the carbon material (B) contains 10% to 60% by mass.

10. A method for manufacturing a carbon material composition, the method comprising a step of mixing carbon material (A) and carbon material (B), The carbon material (A) comprises graphite having amorphous carbonaceous material or graphitic material. The pore distribution of the carbon material (A), as determined by mercury infiltration method, has more than two peaks. When the cumulative pore volume below the minimum value between the peak with 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 carbonaceous material or graphitic material of graphite is set as x (%), the carbon material (A) satisfies the following formula (1). y≤-0.0084x+0.13 (1) The particle density of the carbon material (B) is 1.80 g / cm³. 3 above.

11. A negative electrode comprising: Current collector, and An active material layer formed on the current collector, The active material layer comprises the carbon material composition according to any one of claims 1 to 9.

12. A secondary battery, comprising: positive electrode, Negative electrode, and Electrolytes, The negative electrode is the negative electrode as described in claim 11.

Images