JP2014146607A - Carbon material for lithium ion secondary battery - Google Patents

Abstract

A negative electrode material capable of obtaining a lithium ion secondary battery excellent in charge / discharge load characteristics and cycle characteristics, in which both the irreversible capacity of charge / discharge seen during the initial cycle and the swelling of the electrode accompanying the initial charge / discharge cycle are sufficiently small. I will provide a.
A carbon material capable of inserting and extracting lithium ions is a carbon material for a lithium ion secondary battery that satisfies the following requirements (1) to (3) and further (4).
(1) From the wide-angle X-ray diffraction measurement of the electrode (a) prepared so that the electrode density is 1.7 g / cm ³ after adding a binder to the carbon material, applying to a metal current collector and drying. The peak intensity ratio R _1.7 = I (110) / I (004) corresponding to the obtained lattice planes (110) and (004) is 0.05 to 0.2,
(2) In an electrode (b) prepared by adding a binder to the carbon material, applying the material to a metal current collector, and drying, R ₀ is 0.14 to 0.3, and (3) the electrode (a ) Peak intensity ratio (R _1.7 ) and the peak intensity ratio (R ₀ ) of the electrode (b) (R _1.7 / R ₀ ) is 0.35 to 0.7, (4) The peak intensity ratio R _c (= I (110) / I (004)) corresponding to the lattice planes (110) and (004) obtained by wide-angle X-ray diffraction measurement of the carbon material is 0.14 to 0.3.
[Selection figure] None

Description

  The present invention relates to a carbon material used for a lithium ion secondary battery, a negative electrode formed using the carbon material, and a lithium ion secondary battery having the negative electrode.

  In recent years, demand for high-capacity secondary batteries has increased with the downsizing of electronic devices. In particular, lithium ion secondary batteries having higher energy density and excellent large current charge / discharge characteristics are attracting attention as compared to nickel / cadmium batteries and nickel / hydrogen batteries. High capacity lithium-ion secondary batteries have been widely studied, but the demand for higher performance of lithium-ion secondary batteries in recent years is increasing, and there is a need to achieve higher capacities. It has been.

  In many cases, a carbon material typified by a graphite material or amorphous carbon is used as a negative electrode material for a lithium ion secondary battery in terms of cost and durability. As a method for increasing the capacity of a lithium ion secondary battery, a design has been made in which as many charge / discharge active materials as possible are packed into a limited battery volume by increasing the electrode density.

  The carbon material used for the negative electrode material undergoes volume expansion / contraction due to insertion / extraction of lithium ions accompanying charge / discharge. This volume expansion is theoretically calculated to have an expansion rate of about 10% in the C-axis direction.

  In general, graphite particles are formed as a polycrystal of crystallites having in-plane crystallites (La) and C-axis crystallites (Lc) of several tens of nanometers or more. In the grains, the C-axis of each crystallite tends to be oriented in almost the same direction. In addition, in an electrode prepared by adding a binder to such a graphite particle and applying, drying, and pressing the metal current collector, the C axis of each crystallite of each graphite particle is the surface of the metal current collector. There is a tendency to orient in the direction.

  In an electrode in which such graphite particles are oriented in the plane direction of the metal current collector, the volume expansion in the C-axis direction of the graphite particles due to the insertion / extraction of lithium ions is related to the vertical expansion of the metal current collector. Since it is directly reflected, there is a problem that the amount of swelling of the negative electrode increases as a result.

  In particular, in the case of a square type battery, the battery case expands in the thickness direction due to swelling of the negative electrode accompanying charge / discharge. Therefore, in anticipation of the battery bulge, in order to perform a battery design that secures a void volume that absorbs the bulge in advance, it becomes insufficient to effectively use the limited battery volume as a volume for stuffing the active material. The battery cell capacity is reduced.

  In addition, since the graphite particles are oriented in the plane direction of the metal current collector, not only the cell capacity of the battery is reduced as described above, but also the abundance ratio of the basal surface of the graphite crystal on the electrode surface is increased. The abundance ratio of the edge surface of the graphite crystal where lithium ion intercalation occurs is reduced. For this reason, during the charge / discharge reaction, lithium ions do not move smoothly at the interface between the electrolyte and the electrode, resulting in deterioration of the high-speed charge / discharge characteristics, or due to repeated insertion / extraction of lithium into the graphite crystal. There are problems such as deterioration of cycle characteristics due to electrode deterioration due to expansion / contraction in the C-axis direction.

  In order to suppress the negative electrode swelling caused by charging / discharging, it has been proposed to suppress the crystal orientation of the negative electrode active material itself and to suppress the orientation of the active material on the electrode.

  For example, Patent Document 1 discloses a graphite material having a unique appearance in a cabbage shape in which a roundness is high and a graphite section is directed in various directions by microscopic observation of a fractured surface by modifying scaly natural graphite particles. And a method for randomizing the crystal orientation of the graphite material is disclosed. However, the above-mentioned problems are not completely improved by these methods, and in particular, no investigation is made on improvement of the orientation of graphite particles on the electrode.

  Patent Document 2 discloses a method using a negative electrode in which the orientation of graphite particles on an electrode is suppressed. However, there is no description about the change in the orientation of the graphite particles by changing the electrode density, and there has been no study on the improvement of the orientation of the graphite particles particularly in the high-density region. Therefore, it must be said that the response is insufficient.

Patent Document 3 discloses a method using a negative electrode having an active material layer containing graphite particles and an organic binder and suppressing the orientation of the graphite particles on the electrode. Here, even when a relatively high density negative electrode having an active material layer density of 1.5 to 1.95 g / cm ³ is produced, the orientation of graphite particles on the electrode is successfully suppressed. However, since an organic binder that is inferior in electrode plate strength to that of an aqueous binder is used when producing an electrode, the problem of inferior electrode plate productivity remains unresolved. Furthermore, in order to improve the electrode plate strength, it is necessary to add a larger amount of an organic binder than in the case of using an aqueous binder, which reduces the amount of active material contained in the negative electrode, and increases the battery capacity. There is a risk of lowering.

JP-A-11-263612 JP 11-154513 A International Patent Publication WO2005 / 066941

  The present invention has been made in view of the background art, and the problem is that both the charge / discharge irreversible capacity observed during the initial cycle and the swelling of the electrode accompanying the initial charge / discharge cycle are sufficiently small, and the high-speed charge / discharge characteristics and cycle characteristics The object is to provide a negative electrode material for producing a lithium ion secondary battery excellent in performance, and as a result, to provide a lithium ion secondary battery having a high capacity and excellent in high-speed charge / discharge characteristics and cycle characteristics.

  As a result of intensive studies to solve the above-described problems, the present inventors have determined that a carbon material satisfying a predetermined relationship between the electrode density and the negative electrode orientation index (I (110) / I (004)) is a negative electrode active material. It has been found that by using it as a substance, a lithium ion secondary battery having high capacity and excellent high-speed charge / discharge characteristics and cycle characteristics can be obtained, and the present invention has been achieved.

  That is, the gist of the present invention is as follows.

(Invention 1) A carbon material for a lithium ion secondary battery, wherein the carbon material capable of inserting and extracting lithium ions satisfies the following requirements (1) to (3):
(1) From the wide-angle X-ray diffraction measurement of the electrode (a) prepared so that the electrode density is 1.7 g / cm ³ after adding a binder to the carbon material, applying to a metal current collector and drying. The peak intensity ratio R _1.7 = I (110) / I (004) corresponding to the obtained lattice planes (110) and (004) is 0.05 to 0.2,
(2) In the electrode (b) produced by adding a binder to the carbon material, applying to a metal current collector, and drying, corresponding to the lattice planes (110) and (004) obtained by wide-angle X-ray diffraction measurement The peak intensity ratio R ₀ = I (110) / I (004) is 0.14 to 0.3, and (3) the peak intensity ratio (R _1.7 ) of the electrode (a) and the electrode ( The ratio (R _1.7 / R ₀ ) of the peak intensity ratio (R ₀ ) of b) is 0.35 to 0.7.

(Invention 2) A carbon material for a lithium ion secondary battery, wherein the carbon material further satisfies the following requirement (4):
(4) The peak intensity ratio R _c (= I (110) / I (004)) corresponding to the lattice planes (110) and (004) obtained by wide-angle X-ray diffraction measurement of the carbon material is 0.14 to 0.3.

(Invention 3) An electrode prepared by adding a water-based binder to the carbon material and applying and drying it on a metal current collector satisfies the requirements (1) to (3) of the invention 1 above. Carbon material.

(Invention 4) The carbon material is obtained by spheroidizing natural graphite, has a BET specific surface area (SA) of 4 to 11 m ² / g, a tap density of 0.95 to 1.15 g / cm ³ , and an average circularity. Is 0.9 or more, and the Raman R value is 0.15-0.4, The carbon material for lithium ion secondary batteries.

(Invention 5) A carbon material for a lithium ion secondary battery, wherein the volume-based average particle diameter (d50) of the carbon material particles is 5 to 40 μm.

(Invention 6) The spheroidized graphite is formed by adhering fine powder to base particles which are made spherical by pulverizing natural graphite in a scale shape or by pulverizing the peripheral edge part into spherical particles. A carbon material for a lithium ion secondary battery in which the particle diameter and particle number frequency measured for the carbon material particles with an image analyzer satisfy the following requirements (1) and (2):
(1) In the carbon material particles irradiated with 28 kHz ultrasonic waves at 60 W for 10 minutes, the number frequency of particles having a particle diameter of 5 μm or less is 40 to 85%, and (2) 28 kHz ultrasonic waves are irradiated at 60 W for 10 minutes. In the carbon material particles, the ratio of the particle number frequency of 0.6 to 0.7 μm and the particle number frequency of 0.7 to 5 μm (particle number frequency of 0.6 to 0.7 μm / 0.0. The particle frequency of 7-5 μm) is 0.4-0.7.

(Invention 7) A negative electrode for a lithium ion secondary battery comprising a current collector and an active material layer formed on the current collector, wherein the active material layer contains the carbon material described above.

(Invention 8) A lithium ion secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is the above-described negative electrode for a lithium ion secondary battery.

  By using the carbon material of the present invention as an active material for a lithium ion secondary battery, an excellent effect of being able to provide a lithium ion secondary battery having high capacity and excellent high-speed charge / discharge characteristics and cycle characteristics can be provided. Play.

  Hereinafter, the contents of the present invention will be described in detail. The description of the constituent features of the present invention described below is an example and a representative example of embodiments of the present invention, and the present invention is not limited to these embodiments unless departing from the gist thereof. .

  In the carbon material for a lithium ion secondary battery of the present invention, the carbon material capable of occluding and releasing lithium ions satisfies the following requirements (1) to (3) and (4).

(1) From the wide-angle X-ray diffraction measurement of the electrode (a) prepared so that the electrode density is 1.7 g / cm ³ after adding a binder to the carbon material, applying to a metal current collector and drying. The peak intensity ratio R _1.7 = I (110) / I (004) corresponding to the obtained lattice planes (110) and (004) is 0.05 to 0.2.
(2) In the electrode (b) produced by adding a binder to the carbon material, applying to a metal current collector, and drying, corresponding to the lattice planes (110) and (004) obtained by wide-angle X-ray diffraction measurement The peak intensity ratio R ₀ = I (110) / I (004) is 0.14 to 0.3.
(3) The ratio (R _1.7 / R ₀ ) of the peak intensity ratio (R _1.7 ) of the electrode (a) to the peak intensity ratio (R ₀ ) of the electrode (b) is 0.35 to 0.7.
(4) The peak intensity ratio R _c (= I (110) / I (004)) corresponding to the lattice planes (110) and (004) obtained by wide-angle X-ray diffraction measurement of the carbon material is 0.14 to 0.3.

Method for Producing Negative Electrode Sheet Using the carbon material of the present invention as a negative electrode material, an electrode plate having an active material layer with an active material layer density of 1.70 ± 0.03 g / cm ³ was produced. Specifically, 20.00 ± 0.02 g of a negative electrode material, 20.00 ± 0.02 g of a 1% by mass aqueous solution of carboxymethylcellulose sodium salt (0.200 g in terms of solid content), and styrene having a weight average molecular weight of 270,000 -Aqueous dispersion of butadiene rubber 0.50 ± 0.05 g (0.2 g in terms of solid content) was stirred for 5 minutes with a hybrid mixer manufactured by Keyence, and defoamed for 30 seconds to obtain a slurry.

This slurry was applied to a width of 5 cm using a doctor blade so that the negative electrode material was 11.8 ± 0.1 mg / cm ² on a 18 μm-thick copper foil as a current collector, and air-dried at room temperature. Then, it was dried at 110 ° C. for 30 minutes to obtain an unprocessed electrode plate. Next, it roll-pressed using the roller of diameter 20cm so that the density of an active material layer might be 1.70 +/- 0.03g / cm < ³ >, and the negative electrode sheet was obtained. In order to obtain the above-mentioned numerical value of the active material layer density, a rolling process may be used instead of the pressing process.

  For the production of the negative electrode sheet, an aqueous binder is preferably used as the binder. Examples thereof include water-based binders such as styrene / butadiene rubber, isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer. This is because there is a risk that the electrode plate strength may decrease when an organic binder is used. In order to improve the electrode plate strength, a larger amount of organic binder is usually added than when an aqueous binder is used. There is a need to. For this reason, the amount of the active material contained in the negative electrode is reduced, and the battery capacity is likely to be reduced.

Graphite crystal orientation ratio (I (110) / I (004))
(I) Measurement method: Graphite crystal orientation ratio on the electrode plate The electrode plate prepared by the electrode plate preparation method described above was subjected to black X-ray diffraction on the electrode plate by X-ray diffraction and (110) plane of graphite on the electrode plate ( The (004) plane is measured, and the measured chart is fitted using asymmetric Pearson VII as a profile function to perform peak separation, and the integrated intensity of the (110) plane and (004) plane peaks is calculated. did. From the obtained integrated intensity, a ratio represented by “(110) area intensity / (004) area intensity”, that is, a ratio represented by I (110) / I (004) is calculated, and this ratio is calculated based on the graphite crystal orientation on the electrode plate. Defined as ratio. This orientation ratio was measured on both the unprocessed electrode (b) and the electrode (a) after being roll-pressed so that the density of the active material layer was 1.70 ± 0.03 g / cm ^3. R ₀ and R _1.7 were set. Here, the graphite crystal orientation ratio on the electrode plate is an index representing the degree of orientation of the hexagonal network surface of the graphite crystal with respect to the thickness direction of the electrode. The larger the orientation ratio, the more inconsistent the direction of the graphite crystal hexagonal network plane of the particles.

Carbon material (powder) orientation ratio 0.5 g of graphite powder sample is put in a pressure cell, pressed at 600 Kgf / cm ² for 5 seconds, and the above-mentioned graphite crystal orientation ratio on the electrode plate is calculated for a pellet shape. in the same manner as to measure the I (110) / I (004 ), which was used as a _{R c.}

Here, the X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
-Target: Cu (Kα ray) graphite monochromator-Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree-Measurement range and step angle / measurement time:
(110) plane: 76.5 degrees ≦ 2θ ≦ 78.5 degrees 0.01 degrees / 3 seconds (004) plane: 53.5 degrees ≦ 2θ ≦ 56.0 degrees 0.01 degrees / 3 seconds Sample preparation: A predetermined plate is fixed to a glass plate with double-sided tape of 0.1 mm thickness.

(B) Scope of the present invention (1) When the electrode (a) adjusted to an electrode density of 1.7 g / cm ³ is produced by the above electrode plate production method, it is obtained from wide-angle X-ray diffraction measurement of the electrode. The intensity ratio (graphite crystal orientation ratio on the electrode plate) R _1.7 = I (110) / I (004) corresponding to the lattice planes (110) and (004) is 0.05 to 0.20, Preferably it is 0.06 or more, preferably 0.15 or less, more preferably 0.10 or less.

(2) When an unprocessed electrode (b) is manufactured by the above electrode plate manufacturing method, the intensity ratio of the peaks corresponding to the lattice planes (110) and (004) obtained by wide-angle X-ray diffraction measurement of the electrode (electrode) On-plate graphite crystal orientation ratio) R ₀ = I (110) / I (004) is 0.14 to 0.3, preferably 0.15 or more, more preferably 0.16 or more, and preferably Is 0.25 or less, more preferably 0.20 or less.

When the graphite crystal orientation ratio R _1.7, R ₀ on the electrode plate is lower than the lower limit values 0.05, 0.14 of the present invention, the electrode expansion during battery charging when the battery is produced increases. It is difficult to increase the battery capacity per unit volume. For this reason, the cycle characteristics are liable to deteriorate due to dropping of the active material due to expansion and contraction during the cycle test, and the abundance ratio of the edge surface of the graphite crystal where lithium ion intercalation occurs is reduced on the electrode surface. During the charge / discharge reaction, lithium ions cannot move smoothly at the interface between the electrolyte and the electrode, resulting in a decrease in high-speed charge / discharge characteristics. On the other hand, when the graphite crystal orientation ratios R _{1.7 and} R ₀ on the electrode plate exceed the upper limit values 0.2 and _{0.3 of the} present invention, the basal plane of the graphite particles is isotropic without being oriented in a specific direction. Therefore, the electron conduction due to the contact between the graphite particles cannot be sufficiently obtained, and the high-speed charge / discharge characteristics are likely to be deteriorated.

(3) A lattice plane (110) obtained by wide-angle X-ray diffraction measurement of an electrode (a) adjusted to an electrode density of 1.7 g / cm ³ and an unprocessed electrode (b) prepared by the above electrode plate manufacturing method The ratio (R _1.7 / R ₀ ) of the peak intensity ratio corresponding to (004) is 0.35 to 0.7, preferably 0.36 or more, and preferably 0.6 or less, More preferably, it is 0.5 or less. When R _1.7 / R ₀ is less than the lower limit of 0.35 of the present invention, the basal plane of the graphite particles on the electrode is easily oriented in the surface direction of the current collector by pressing (rolling) the electrode. For this reason, since the electrode expansion at the time of battery charging becomes large, it is difficult to increase the battery capacity per unit volume of the electrode. In addition, the cycle characteristics are liable to deteriorate due to the dropping of the active material due to expansion and contraction during the cycle test, and further, the abundance ratio of the edge surface of the graphite crystal where lithium ion intercalation occurs becomes small on the electrode surface. During the charge / discharge reaction, lithium ions cannot move smoothly at the interface between the electrolyte and the electrode, resulting in a decrease in high-speed charge / discharge characteristics. On the other hand, if R _1.7 / R ₀ exceeds the upper limit of 0.7 of the present invention, it may be difficult to increase the active material packing density of the electrode by pressing (rolling).

The present invention further relates to a carbon material for a lithium ion secondary battery, wherein the carbon material itself further satisfies the following requirement (4).
(4) The intensity ratio of the peaks corresponding to the lattice planes (110) and (004) obtained by wide-angle X-ray diffraction measurement of the carbon material (graphite crystal orientation ratio on the electrode plate) R _c (= I (110) / I (004)) is preferably 0.14 to 0.3, more preferably 0.15 or more, further preferably 0.16 or more, more preferably 0.25 or less, still more preferably. It is 0.20 or less. When the orientation ratio R _c of the carbon material is less than the lower limit 0.14 of the present invention, the electrode expansion increases during battery charging when a battery was prepared, and to increase the battery capacity per unit volume of the electrode Tend to be difficult. In addition, the cycle characteristics are liable to deteriorate due to the dropping of the active material due to expansion and contraction during the cycle test, and further, the abundance ratio of the edge surface of the graphite crystal where lithium ion intercalation occurs becomes small on the electrode surface. During the charge / discharge reaction, lithium ions cannot move smoothly at the interface between the electrolytic solution and the electrode, and the high-speed charge / discharge characteristics tend to deteriorate. On the other hand, when the orientation ratio R _c of the carbon material exceeds the upper limit value 0.3 of the present invention, since the isotropically existed electrodes basal plane of the graphite particles without orientation in a specific direction, each graphite particle Electron conduction due to contact between the electrodes cannot be sufficiently obtained, the high-speed charge / discharge characteristics are likely to be deteriorated, and further, it may be difficult to increase the active material packing density of the electrode by pressing.

BET specific surface area (SA)
(I) Measuring method Using a specific surface area measuring device “AMS8000” manufactured by Okura Riken Co., Ltd., the BET one-point method was measured by a nitrogen gas adsorption flow method. Specifically, 0.4 g of a sample (carbon material) is filled in a cell, heated to 350 ° C., pretreated, cooled to liquid nitrogen temperature, and saturated with 30% nitrogen and 70% He gas. The amount of gas adsorbed and then heated to room temperature and desorbed was measured, and the specific surface area was calculated from the obtained results by a normal BET method.

(Ii) Preferred range for the measured specific surface area by the BET method of the carbon material of the present invention preferably satisfies the 4m ² / g or more 11m ² / g or less. Usually 4 m ² / g or more, preferably 5 m ² / g or more. Moreover, it is 11 m < ² > / g or less normally, Preferably it is 9 m < ² > / g or less, More preferably, it is 8 m < ² > / g or less. When the specific surface area is below 4m 2 ^{/ g,} less sites Li enters and exits, poor high-speed charge-discharge characteristics output characteristics, whereas, if the specific surface area exceeds 11m 2 / ^g, the activity is excessive for the electrolyte of the active material Therefore, since the initial irreversible capacity increases, it tends to be difficult to manufacture a high capacity battery.

Average circularity (a) Definition of average circularity The average circularity is 0.2 g of a 0.2 vol% aqueous solution of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, to be measured (composite graphite particles) 0.2 g. And using a flow particle image analyzer “FPIA-2000 manufactured by Sysmex Industrial Co., Ltd.”, after irradiating a 28 kHz ultrasonic wave at an output of 60 W for 1 minute, the detection range is specified as 0.6 to 400 μm, It is defined as the average value of circularity values given by the following formula measured for particles in the range of 10 to 40 μm.
Circularity = circumference of a circle with the same area as the projected particle area / circumference of the projected particle image

(B) Preferred range In the electrode (a) in the present invention, the average circularity is preferably 0.85 or more, more preferably 0.90 or more. When the average circularity is less than 0.85, the basal plane of the graphite particles is oriented in a specific direction on the electrode, thereby increasing the electrode expansion during battery charging. For this reason, it tends to be difficult to increase the battery capacity per unit volume of the electrode. In addition, the cycle characteristics are liable to deteriorate due to the dropping of the active material due to expansion and contraction during the cycle test, and further, the abundance ratio of the edge surface of the graphite crystal where lithium ion intercalation occurs becomes small on the electrode surface. During the charge / discharge reaction, lithium ions cannot move smoothly at the interface between the electrolyte and the electrode, and the high-speed charge / discharge characteristics tend to deteriorate.

Definitions The present invention tap density (i) tap density, tap density, a powder density measuring instrument (Inc.) Seishin using Enterprise Co., Ltd. "Tap Denser KYT-4000", diameter 1.6 cm, volume capacity 20 cm ³ The carbon material is dropped into a cylindrical tap cell of 300 μm through a sieve having an opening of 300 μm, and the cell is fully filled, and then a stroke with a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume and the weight of the sample at that time Is defined as the tap density.

(B) Preferred range The tap density of the carbon material of the present invention is preferably 0.95 g / cm ³ or more, and more preferably 1.0 g / cm ³ or more. And is preferably 1.15 g / cm ³ or less, 1.12 g / cm ³ or less is more preferable. If the tap density is too low, the high-speed charge / discharge characteristics tend to be inferior. If the tap density is too high, the intra-particle carbon density increases, the rollability is insufficient, and it becomes difficult to form a high-density negative electrode sheet. There is.

Raman spectrum (a) Raman spectrum measurement method Raman spectrometer: Measured with "Raman spectrometer manufactured by JASCO Corporation".
Particles to be measured are naturally dropped into the measurement cell, filled with the sample, and measured with the following conditions while rotating the measurement cell in a plane perpendicular to the laser beam while irradiating the measurement cell with argon ion laser light. To do.
-Wavelength of argon ion laser light: 514.5nm
・ Laser power on the sample: 25 mW
・ Resolution: 4cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
-Peak intensity measurement, peak half-width measurement: background processing, smoothing processing (convolution 5 points by simple average)

(Ii) for the preferred range resulting Raman spectrum, the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and an intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1 were measured, and the intensity ratio R (R = I _B / I _A ) is calculated and defined as the Raman R value of the carbon material. The Raman R value of the carbon material of the present invention is preferably 0.15 or more. Moreover, it is preferable that it is 0.4 or less, and 0.3 or less is more preferable. When the Raman R value is less than 0.15, the crystallinity of the particle surface becomes too high, and when the density is increased, the crystal tends to be oriented in a direction parallel to the electrode plate, and the load characteristics tend to be lowered. . On the other hand, if it exceeds 0.4, the crystal on the particle surface is disturbed, the reactivity with the electrolytic solution increases, and the efficiency tends to decrease and the generation of gas tends to increase.

Particle Size (I) Measuring Method 0.01 g of carbon material is suspended in 10 mL of 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) which is a surfactant. What was measured as a volume-based median diameter in a measuring apparatus after being introduced into a commercially available laser diffraction / scattering type particle size distribution measuring apparatus “LA-920 made by HORIBA” and irradiated with an ultrasonic wave at 28 kHz for 1 minute, The volume-based average particle diameter d50 of the carbon material particles in the present invention is defined.

(B) Preferred range d50 is usually 40 μm or less, preferably 30 μm or less, more preferably 25 μm or less, usually 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more. If the particle size exceeds 40 μm, inconveniences such as striping may occur when the electrode plate is formed. If the particle size is less than 5 μm, the surface area becomes too large and the activity with the electrolyte is suppressed. Tend to be difficult to do.

Particle Number Frequency (I) Measuring Method A carbon material 0.2 g is mixed with 50 mL of a 0.2 vol% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) which is a surfactant, and flow Using a chemical particle image analyzer “FPIA-2000 manufactured by Sysmex Industrial Co., Ltd.”, 28 kHz ultrasonic waves were irradiated at an output of 60 W for a predetermined time, and then the detection range was specified as 0.6 to 400 μm, and the number of particles was measured.

(B) Preferred range (1) The frequency of the number of particles having a particle diameter of 5 μm or less of the carbon material particles irradiated with 28 kHz ultrasonic waves at 60 W for 10 minutes is usually 40% or more, preferably 50% or more, and more preferably 55 % Or more, usually 85% or less, preferably 75% or less, more preferably 70% or less. When the particle number frequency is less than 40%, there are few sites where Li enters and exits, and the high-speed charge / discharge characteristics tend to be inferior. On the other hand, in the carbon material in which the fine powder adhered to the particle surface such that the particle number frequency exceeds 85% easily peels off, when the electrode is rolled, the fine powder is partially peeled and easily arranged in one direction. There is a tendency that the amount of expansion of the electrode due to charging increases. Moreover, when there is too much amount of fine powder which peeled, since the activity with respect to the electrolyte solution of an active material will become excess and an initial irreversible capacity | capacitance will become large, it may become impossible to manufacture a high capacity battery. Furthermore, when charging / discharging is repeated, the fine powder on the surface of the graphite peels off, so that material deterioration tends to increase.

(2) In the carbon material particles irradiated with 28 kHz ultrasonic waves at an output of 60 W for 10 minutes, the ratio of the particle number frequency with a particle size of 0.6 to 0.7 μm and the particle number frequency with a particle size of 0.7 to 5 μm is 0.4 to 0.7. When the ratio of the particle number frequency is included in this range, a moderately fine powder is attached to the surface of the graphite particles, so that the basal plane of the graphite particles is not oriented in a specific direction. Since the particles are held, the expansion of the electrode during battery charging can be suppressed. For this reason, it is possible to increase the battery capacity per unit volume of the electrode, and it is possible to suppress deterioration of the cycle characteristics due to, for example, dropping of the active material due to expansion and contraction during the cycle test. When the ratio of the number of particles is less than 0.4, the size of the fine powder attached to the particle surface increases, the number of sites where Li enters and exits is small, and the high-speed charge / discharge characteristics tend to be inferior. On the other hand, when the ratio of the particle number frequency exceeds 0.7, the activity of the active material with respect to the electrolytic solution becomes excessive, and the initial irreversible capacity increases, which tends to make it difficult to manufacture a high capacity battery.

Carbon Material for Electrode The carbon material of the present invention performs a surface treatment that pulverizes and modifies the surface of the carbon material by imparting mechanical action such as impact compression, friction, and shear force to the carbon material. In the present invention, it is preferable to use spherical graphite which has been subjected to spheroidization treatment by surface treatment in advance as a raw material because it is possible to efficiently obtain a target carbon material. The spherical graphite is particularly preferably composed of a plurality of scaly or scaly graphites and ground graphite fine powder. As an apparatus used for the spheroidization treatment, for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force, etc. including the interaction of particles mainly with impact force to the particles can be used. Specifically, it has a rotor with a large number of blades installed inside the casing, and when the rotor rotates at high speed, mechanical action such as impact compression, friction, shearing force, etc. is applied to the carbon material introduced inside. An apparatus that provides a surface treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating the carbon material. Preferred devices include, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), a kryptron (manufactured by Earth Technica), a CF mill (manufactured by Ube Industries), a mechano-fusion system (manufactured by Hosokawa Micron), and a theta composer (Tokuju Kosakusho). Etc.). Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable. When processing using this apparatus, it is preferable to set the peripheral speed of the rotating rotor to 30 to 100 m / sec. The peripheral speed is more preferably 40 m / second or more, and further preferably 500 m / second or more. The treatment can be performed by simply passing a carbonaceous material, but it is preferable to circulate or stay in the apparatus for 30 seconds or longer, and it is preferable to circulate or stay in the apparatus for 1 minute or longer. More preferred.

  By subjecting the carbon material of the present invention to the spheronization step by the above surface treatment, the scale-like natural graphite is folded, or the peripheral edge portion is spherically pulverized to spheroidize the base particles by pulverization. The resulting fine powder of 5 μm or less adheres. In order to produce the carbon material of the present invention, the size of the adhering fine powder of the surface-treated graphite particles measured by a flow type particle image analyzer is 0.6 to 0.7 μm in number of particles and 0. Sphericalization by the above surface treatment until the ratio of particle number frequency of 7 to 5 μm (particle number frequency of 0.6 to 0.7 μm / particle number frequency of 0.7 to 5 μm) becomes 0.4 to 0.7. Continue the process. Moreover, the carbon material of the present invention is preferably in a state where fine powder is firmly attached to the base particles. For example, the amount of fine powder that is peeled off by ultrasonic treatment can be used as an index of the fine powder adhesion strength to the base particles. As an example of the embodiment of this evaluation method, there is a method of measuring the frequency of the number of particles having a particle size of 5 μm or less irradiated with 28 kHz ultrasonic waves at an output of 60 W for 10 minutes using a flow particle image analyzer. . In order to produce the carbon material of the present invention, it is preferable to continue the spheronization step by the surface treatment until the number frequency of the treated carbon material having a particle size of 5 μm or less becomes 85% or less.

Configuration of Lithium Ion Secondary Battery The lithium ion secondary battery of the present invention manufactured using the carbon material of the present invention and the negative electrode sheet containing the same is a positive electrode, an electrolyte, a separator, a cylindrical shape, a rectangular shape, a laminate, an automobile It is configured with a large can body for use, a stationary battery, or the like, or a member necessary for battery configuration such as a housing, a PTC element, and an insulating plate. The selection of the constituent members is not particularly limited as long as the gist of the invention is not exceeded. The lithium ion secondary battery of the present invention usually has at least the following negative electrode, positive electrode and electrolyte of the present invention.

Negative electrode for non-aqueous secondary battery and negative electrode sheet The carbon material of the present invention can be suitably used as a negative electrode active material for non-aqueous secondary batteries, particularly lithium ion secondary batteries. The carbon material (A) of the present invention is selected from the group consisting of natural graphite, artificial graphite, vapor-grown carbon fiber, conductive carbon black, amorphous-coated graphite, resin-coated graphite, and amorphous carbon. The negative electrode is also composed of one or more types and further containing carbonaceous particles (hereinafter abbreviated as “carbon active particles (B)”) having different shapes or physical properties from the carbon material (A) of the present invention. It can be suitably used as an active material material.

  By appropriately selecting and mixing the carbonaceous particles (B), it becomes possible to prevent Li diffusion path inhibition on the electrode plate surface due to particle deformation and to reduce the irreversible capacity. The lower limit of the amount in the case of mixing the carbonaceous particles (B) is usually 5% by mass or more, preferably 10% by mass or more, more preferably 20% by mass or more with respect to the whole negative electrode material. 95% by mass or less, preferably 90% by mass or less, more preferably 80% by mass or less. If it is less than 5% by mass, the initial irreversible capacity may be increased, and if it exceeds 95% by mass, the conductivity may be decreased.

  Although there is no restriction | limiting in particular as an apparatus used for mixing with the carbon material (A) and carbonaceous active material particle (B) of this invention, For example, as a rotary mixer, a cylindrical mixer, a twin cylinder mixer , Double cone type mixers, regular cubic type mixers, vertical type mixers, etc., as fixed type mixers, spiral type mixers, ribbon type mixers, Muller type mixers, Helical Flight type mixers , Pugmill type mixer, fluidized type mixer, theta composer, hybridizer, mechano-fusion, and the like.

Further, a part of the active material constituting the negative electrode sheet may contain an alloy that can be alloyed with Li, a silicide, and a semiconductor electrode. Specifically, Si, Al, Sn, SnSb, SnAs, SiO, SnO, SnO ₂ , SiC, diamond containing impurities such as B, N, P and the like as a semiconductor, composite alloys composed of these, Non-stoichiometric oxides are possible.

The configuration of the negative electrode sheet is composed of the current collector coated with the active material layer containing the carbon material of the present invention, the carbonaceous particles described above, an electrode plate forming binder, a thickener, and a conductive material. The active material layer is usually obtained by applying slurry dried from members other than the current collector onto the current collector, drying, and rolling (pressing) to a desired density.
As the electrode plate-forming binder, a material that is stable with respect to the solvent and the electrolyte used during electrode production can be used. Examples include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene / butadiene rubber, isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer. Aqueous binders such as butadiene rubber, isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer are preferred. In addition, there is a possibility that the electrode plate strength may be reduced when using an organic binder, and in order to improve the electrode plate strength, it is necessary to add a larger amount of organic binder than when using an aqueous binder. As a result, the active material contained in the negative electrode decreases, which may lead to a decrease in battery capacity. The electrode plate-forming binder is usually 90/10 or more, preferably 95/5 or more, and usually 99.9 / 0.1 or less, preferably 99, in a weight ratio of negative electrode material / electrode plate-forming binder. It is used in the range of 0.5 / 0.5 or less.
Examples of the thickener include carboxymethyl cellulose, or its Na salt, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein. These thickeners can be used without limitation, but those having no structural change on the basic side are preferable.
Examples of the conductive material include fine metal powder materials such as copper and nickel, and small particle size carbon materials such as graphite and carbon black.
Examples of the material of the current collector include copper, nickel, and stainless steel. Among these, a copper foil is preferable from the viewpoint of easy processing into a thin film and cost.

The density of the active material layer varies depending on the application, but is usually 1.55 g / cm ³ or more in an application in which capacity is important. In order to obtain a sufficient battery capacity per unit volume, 1.60 g / cm ³ or more is preferable. On the other hand, if the density is too high, the high-speed charge / discharge characteristics tend to be lowered. Therefore, in the case of a negative electrode sheet generally composed of only a carbon material, 1.90 g / cm ³ or less is preferable. Here, the active material layer means a mixture layer made of an active material on a current collector, an electrode plate forming binder, a thickener, a conductive material, etc., and its density means the active material at the time of assembling the battery. It refers to the bulk density of the layer.

Nonaqueous secondary battery The negative electrode for nonaqueous secondary batteries of the present invention produced using the carbon material of the present invention is extremely useful as a negative electrode for nonaqueous secondary batteries such as lithium ion secondary batteries. There is no particular limitation on the selection of members necessary for the battery configuration such as the positive electrode and the electrolytic solution constituting such a non-aqueous secondary battery.

  Although the material of the member which comprises a non-aqueous secondary battery is illustrated below, the material which can be used is not limited to these specific examples. The nonaqueous secondary battery of the present invention usually has at least the negative electrode, the positive electrode and the electrolyte of the present invention.

The positive electrode is formed by forming an active material layer containing a positive electrode active material, a conductive agent, and an electrode plate forming binder on a positive electrode current collector. The active material layer is usually obtained by preparing a slurry containing a positive electrode active material, a conductive material and an electrode plate forming binder, and applying and drying the slurry on a current collector.
Examples of the positive electrode active material include lithium transition metal composite oxide materials such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide, transition metal oxide materials such as manganese dioxide, and carbonaceous materials such as graphite fluoride. A material capable of occluding / releasing lithium can be used. Specifically, for example, LiFePO ₄ , LiFeO ₂ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and non-stoichiometric compounds thereof, MnO ₂ , TiS ₂ , FeS ₂ , Nb ₃ S ₄ , Mo ₃ S ₄ , can be used _{CoS 2, V 2 O 5,} P 2 O 5, CrO 3, V 3 O 3, TeO 2, GeO 2, LiNi 0.33 Mn 0.33 Co 0.33 O 2 and the like.
Examples of the positive electrode conductive material include carbon black and small particle size graphite.
As the positive electrode current collector, it is preferable to use a metal or an alloy thereof that forms a passive film on the surface by anodic oxidation in an electrolytic solution, and belongs to IIIa, IVa, and Va groups (3B, 4B, and 5B groups). And alloys thereof. Specifically, for example, Al, Ti, Zr, Hf, Nb, Ta and alloys containing these metals can be exemplified, and Al, Ti, Ta and alloys containing these metals are preferably used. Can do. In particular, Al and its alloys are desirable because of their light weight and high energy density.

Examples of the electrolyte include an electrolytic solution, a solid electrolyte, and a gel electrolyte. Among them, an electrolytic solution, particularly a nonaqueous electrolytic solution is preferable. As the non-aqueous electrolyte solution, a solution obtained by dissolving a solute in a non-aqueous solvent can be used.
As the solute, an alkali metal salt, a quaternary ammonium salt, or the like can be used. Specifically, for example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C _It is preferable to use one or more compounds selected from the group consisting of ₄ F ₉ SO ₂ ) and LiC (CF ₃ SO ₂ ) ₃ .
Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate, butylene carbonate, and propylene carbonate; cyclic ester compounds such as γ-butyrolactone; chain ethers such as 1,2-dimethoxyethane; crown ether, 2-methyltetrahydrofuran, Cyclic ethers such as 1,2-dimethyltetrahydrofuran, 1,3-dioxolane and tetrahydrofuran, and chain carbonates such as diethyl carbonate, ethyl methyl carbonate and dimethyl carbonate can be used. One kind of solute and solvent may be selected and used, or two or more kinds may be mixed and used. Among these, the non-aqueous solvent preferably contains a cyclic carbonate and a chain carbonate. Further, compounds such as vinylene carbonate, vinyl ethylene carbonate, succinic anhydride, maleic anhydride, propane sultone, diethyl sulfone, difluorophosphate such as lithium difluorophosphate, and the like may be added. Furthermore, an overcharge inhibitor such as diphenyl ether or cyclohexylbenzene may be added.
The content of these solutes in the electrolytic solution is preferably 0.2 mol / L or more, particularly preferably 0.5 mol / L or more, preferably 2 mol / L or less, and particularly preferably 1.5 mol / L or less. .

Among these, the lithium ion secondary battery prepared by combining the negative electrode of the present invention, the metal chalcogenide-based positive electrode, and the non-aqueous electrolyte mainly composed of a carbonate-based solvent has a large capacity and is irreversible that is recognized in the initial cycle. Small capacity and excellent high-speed charge / discharge characteristics.
A separator is usually provided between the positive electrode and the negative electrode so that the positive electrode and the negative electrode are not in physical contact. The separator preferably has high ion permeability and low electrical resistance. The material and shape of the separator are not particularly limited, but those that are stable with respect to the electrolyte and excellent in liquid retention are preferable. Specifically, a porous sheet or a non-woven fabric made of a polyolefin such as polyethylene or polypropylene is used.

  The shape of the lithium ion secondary battery of the present invention is not particularly limited, and a cylinder type in which a sheet electrode and a separator are spiral, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a coin in which a pellet electrode and a separator are stacked Type.

  EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(I) Method for Producing Electrode Sheet Using the carbon material of the present invention as a negative electrode material, an electrode plate having an active material layer with an active material layer density of 1.70 ± 0.03 g / cm ³ was produced. Specifically, 20.00 ± 0.02 g of a negative electrode material, 20.00 ± 0.02 g of a 1% by mass aqueous solution of carboxymethylcellulose sodium salt (0.200 g in terms of solid content), and styrene having a weight average molecular weight of 270,000 -Aqueous dispersion of butadiene rubber 0.50 ± 0.05 g (0.2 g in terms of solid content) was stirred for 5 minutes with a hybrid mixer manufactured by Keyence, and defoamed for 30 seconds to obtain a slurry. This slurry was applied to a width of 5 cm using a doctor blade so that the negative electrode material was 14.5 ± 0.3 mg / cm ² on a 18 μm-thick copper foil as a current collector, and air-dried at room temperature. Went. Further, after drying at 110 ° C. for 30 minutes, roll pressing was performed using a roller having a diameter of 20 cm to adjust the density of the active material layer to 1.70 ± 0.03 g / cm ³ to obtain an electrode sheet.

(Ii) Method for Producing Nonaqueous Secondary Battery The electrode sheet produced by the above method was punched into a disk shape having a diameter of 12.5 mm, and a lithium metal foil was punched into a disk shape having a diameter of 14 mm as a counter electrode. Between the two electrodes, a separator (porous polyethylene film) impregnated with an electrolytic solution in which LiPF ₆ was dissolved at 1 mol / L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7). And a 2016 coin-type battery was manufactured.

(Iii) Method for measuring electrode expansion coefficient during battery charging The electrode expansion coefficient during battery charging was measured by the following measurement method using the non-aqueous secondary battery.
After charging to 5 mV with respect to the lithium counter electrode at a current density of 0.16 mA / cm ² , charging to a current value of 0.02 mA at a constant voltage of 5 mV, and doping the lithium into the negative electrode, 0. A charge / discharge cycle of discharging to 1.5 V with respect to the lithium counter electrode at a current density of 33 mA / cm ² was repeated three times. The coin battery in the discharged state was disassembled in an argon atmosphere, the electrode was taken out, the electrode thickness at this time was measured, and the electrode expansion coefficient d _dc (%) at the time of discharge was calculated according to the following formula (I). Further, the coin battery after the above three cycles of charge / discharge was further charged with 300 mAh / g at a current density of 0.16 mA / cm ² , the electrode thickness was measured in the same manner, and d _c ( %) Was calculated. Furthermore, according to the following formula (III), the net electrode expansion coefficient d (%) by Li ion intercalation was calculated.

(I) d _dc = (electrode thickness during discharge−copper foil thickness) / (electrode thickness during drying−copper foil thickness) × 100
(II) d _c = (electrode thickness during charging of 300 mAh / g−copper foil thickness) − (electrode thickness during drying−copper foil thickness) / (electrode thickness during drying−copper foil thickness) × 100
(III) d = d _c −d _dc

Example 1
Spherical natural graphite having a particle size d50, a tap density, and a specific surface area of 19.8 μm, 1.07 g / cm ³ , and 6.7 m ² / g, respectively, measured by the above-described measurement method was used as a hybridization system NHS manufactured by Nara Machinery Co., Ltd. In the carbon material particles irradiated with ultrasonic waves of 28 kHz for 10 minutes by further performing a spheroidization process by mechanical action for 4 minutes at a rotor peripheral speed of 60 m / second in type-3, flow type particles The ratio of the particle number frequency of 0.6 to 0.7 μm and the particle number frequency of 0.7 to 5 μm measured by an image analyzer (particle number frequency of 0.6 to 0.7 μm / 0.7 A sample having a particle number frequency (˜5 μm) of 0.45 was obtained. About this, the particle size d50, tap density, specific surface area, XRD, RamanR value, and FPIA were measured by the said measuring method. The results are shown in Tables 1 and 2. Moreover, according to the said measuring method, the electrode expansion coefficient d was measured. The results are shown in Table 3.

Example 2
Spherical natural graphite having a particle size d50, a tap density, and a specific surface area of 16.9 μm, 1.02 g / cm ³ , and 6.8 m ² / g, respectively, measured by the above-described measurement method was used as a hybridization system NHS manufactured by Nara Machinery Co., Ltd. The number frequency of particles having a particle diameter of 0.6 to 0.7 μm measured by the same method as in Example 1 by further performing spheroidization treatment for 4 minutes at a rotor peripheral speed of 60 m / sec. A sample having a ratio of the number of particles having a particle size of 0.7 to 5 μm (particle number frequency of 0.6 to 0.7 μm / particle number frequency of 0.7 to 5 μm) of 0.49 was obtained. About this, the same measurement as Example 1 was performed. These results are shown in Tables 1 to 3.

Comparative Example 1
Using the raw material spheroidized graphite described in Example 1 (particle size d50, tap density, specific surface area 19.8 μm, 1.07 g / cm ³ and 6.7 m ² / g, respectively), the same measurement as in Example 1 Went. These results are shown in Tables 1 to 3 for the raw graphite particles. In the same manner as in Example 1, the ratio of the number frequency of particles having a particle size of 0.6 to 0.7 μm and the number frequency of particles having a particle size of 0.7 to 5 μm (0.6 to 0.7 μm). Particle number frequency / particle number frequency of 0.7 to 5 μm) was 0.39.

Comparative Example 2
Natural graphite (particle size d50, tap density) using the same raw material as that used in producing the raw material spheroidized graphite described in Example 1 and having a spheroidization degree lower than that of the raw material spheroidized graphite described in Example 1 The specific surface area was 18.9 μm, 0.90 g / cm ³ , and 5.4 m ² / g, respectively. For the raw graphite particles, the ratio of the number frequency of particles having a particle size of 0.6 to 0.7 μm and the number frequency of particles having a particle size of 0.7 to 5 μm (in the same manner as in Example 1) (0. The particle number frequency of 6 to 0.7 μm / the particle number frequency of 0.7 to 5 μm) was 0.27. These results are shown in Tables 1 to 3.

In the carbon materials of Comparative Example 1 and Comparative Example 2, the surface treatment by mechanical action and the resulting spheronization process are not sufficient. Therefore, when forming the electrode, especially by pressing the electrode, the crystallite C of each graphite particle The axis is oriented in the plane direction of the metal current collector. For this reason, the orientation ratio (110) / (004) of the electrode manufactured to have an electrode density of 1.7 g / cm ³ is 0.04, 0.02, which is far below the range of the present invention. As a result, Li The net electrode expansion coefficient (d) due to ion insertion is increased.

On the other hand, in the carbon materials of Example 1 and Example 2, a high degree of spheronization was obtained by further spheronizing natural spheroidized graphite, so that the crystallite C of each graphite particle was obtained. The orientation ratio of the electrodes prepared so that the axis is less likely to be oriented in the plane direction of the metal current collector and the electrode density is 1.7 g / cm ³ is included in the specified range of 0.06 and 0.08. ing. As a result, the net electrode expansion coefficient (d) due to Li ion insertion is reduced.

  By using the carbon material of the present invention as an active material for a lithium ion battery, it is possible to provide a lithium ion secondary battery having high capacity and excellent high-speed charge / discharge characteristics. Moreover, according to the manufacturing method of the said material, since there are few processes, it can manufacture stably and efficiently and cheaply.

Claims (8)

A carbon material for a lithium ion secondary battery, wherein the carbon material capable of inserting and extracting lithium ions satisfies the following requirements (1) to (3):
(1) From the wide-angle X-ray diffraction measurement of the electrode (a) prepared so that the electrode density is 1.7 g / cm ³ after adding a binder to the carbon material, applying to a metal current collector and drying. The peak intensity ratio R _1.7 = I (110) / I (004) corresponding to the obtained lattice planes (110) and (004) is 0.05 to 0.2,
(2) In the electrode (b) produced by adding a binder to the carbon material, applying to a metal current collector, and drying, corresponding to the lattice planes (110) and (004) obtained by wide-angle X-ray diffraction measurement The peak intensity ratio R ₀ = I (110) / I (004) is 0.14 to 0.3, and (3) the peak intensity ratio (R _1.7 ) of the electrode (a) and the electrode ( The ratio (R _1.7 / R ₀ ) of the peak intensity ratio (R ₀ ) of b) is 0.35 to 0.7. The carbon material for a lithium ion secondary battery according to claim 1, wherein the carbon material further satisfies the following requirement (4):
(4) The peak intensity ratio R _c (= I (110) / I (004)) corresponding to the lattice planes (110) and (004) obtained by wide-angle X-ray diffraction measurement of the carbon material is 0.14 to 0.3.   A carbon material for a lithium ion secondary battery, wherein an electrode produced by adding a water-based binder to the carbon material and applying and drying to a metal current collector satisfies the requirements (1) to (3) of claim 1. The carbon material is obtained by spheroidizing natural graphite, has a BET specific surface area (SA) of 4 to 11 m ² / g, a tap density of 0.95 to 1.15 g / cm ³ , and an average circularity of 0.9. The carbon material for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the Raman R value is 0.15 to 0.4.   The carbon material for a lithium ion secondary battery according to any one of claims 1 to 4, wherein the volume-based average particle diameter (d50) of the particles of the carbon material is 8 to 40 µm. The carbon material is spheroidized graphite, and the spheroidized graphite is formed by attaching fine powder to base particles that have been made spherical by folding scale-like natural graphite or by spherically pulverizing the peripheral edge portion. The particle diameter and particle number frequency measured for the carbon material particles by a flow type particle image analyzer satisfy the following requirements (1) and (2): Carbon materials for lithium ion secondary batteries:
(1) In the carbon material particles irradiated with 28 kHz ultrasonic waves at 60 W for 10 minutes, the number frequency of particles having a particle size of 5 μm or less is 40 to 85%, and (2) 28 kHz ultrasonic waves are irradiated at 60 W for 10 minutes. In the carbon material particles, the ratio of the particle number frequency of 0.6 to 0.7 μm and the particle number frequency of 0.7 to 5 μm (particle number frequency of 0.6 to 0.7 μm / 0.0. The particle frequency of 7-5 μm) is 0.4-0.7.   A lithium ion secondary comprising a current collector and an active material layer formed on the current collector, wherein the active material layer contains the carbon material according to any one of claims 1 to 6. Battery negative electrode.   A lithium ion secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is a negative electrode for a lithium ion secondary battery according to claim 7.