JP2014067680A - Graphite particle for nonaqueous secondary battery, negative electrode for nonaqueous secondary battery using the same, and nonaqueous secondary battery - Google Patents

Abstract

Disclosed is a negative electrode for producing a non-aqueous secondary battery having high initial efficiency and excellent cycle characteristics even when charging and discharging a large current even when a negative electrode active material layer is densified, and a negative electrode material thereof. As a result, to provide a non-aqueous secondary battery having high capacity, high input / output characteristics, and high cycle characteristics.
A negative electrode for a non-aqueous secondary battery, wherein the liquid absorption coefficient is 0.11 mg / sec ^0.5 or more.
[Selection figure] None

Description

  The present invention relates to a negative electrode used for a non-aqueous secondary battery, graphite particles used for manufacturing the negative electrode, a manufacturing method thereof, and a non-aqueous 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 have attracted attention as compared to nickel / cadmium batteries and nickel / hydrogen batteries. Conventionally, higher capacity of lithium ion secondary batteries has been widely studied, but in recent years, due to the increasing demand for higher performance of lithium ion secondary batteries, further increase in capacity, large current charge / discharge characteristics, high temperature storage characteristics, It is required to satisfy high cycle characteristics.

  As a negative electrode material of a lithium ion secondary battery, graphite material and amorphous carbon are often used in terms of cost and durability. However, the amorphous carbon material has a problem that the reversible capacity in a material range that can be put into practical use is small, and it is difficult to increase the density of the active material layer, so that the battery cannot be increased in capacity. It is known that a graphite material has a capacity close to 372 mAh / g, which is the theoretical capacity of lithium storage, and is preferable as an active material. On the other hand, when the active material layer containing the negative electrode material is densified to increase the capacity, the irreversible charge / discharge capacity increases during the initial cycle of the battery due to the destruction and deformation of the material, the large current charge / discharge characteristics decrease, the cycle There was a problem of deterioration of characteristics.

  In order to solve the above problems, for example, Patent Document 1 uses a high density isotropic graphite powder having a specific range of oil absorption, powder bulk density, particle size distribution, and specific resistance as a carbon material. It is disclosed that a carbon material for a negative electrode of a lithium secondary battery having excellent conductivity, excellent adhesion with a copper foil, large discharge capacity, small initial irreversible capacity, and excellent cycle characteristics can be obtained.

  In Patent Document 2, by mixing two types of graphite powders that are equally crushed and have different oil absorption and circularity, the secondary lithium is excellent in liquid immersion and high cycle characteristics. It is disclosed that a carbon material for a battery negative electrode can be obtained.

  Furthermore, as a prior art relating to a lithium ion secondary battery, for example, Patent Document 3 discloses that a specific resin is dispersed in an aqueous solvent by mechanochemically treating graphite particles and hydrophilizing the surfaces of the graphite particles. In addition, it is disclosed that a lithium ion secondary battery using a water-based binder can be charged at high speed.

  Patent Document 4 discloses a non-aqueous electrolyte secondary battery using a negative electrode active material made of a carbonaceous material formed by mixing two types of graphite particles having a particle diameter of 5 μm or more different from each other. By mixing graphite particles having different particle sizes in this manner, particles having a small particle size can enter the gaps between the particles having a large particle size, thereby absorbing the electrolyte while maintaining contact between the graphite particles. Cited Document 4 describes that liquidity can be improved.

  Patent Document 5 discloses a negative electrode material for a non-aqueous electrolyte secondary battery including carbon materials A and B satisfying specific parameters. In the invention described in the document, the ratio of the average particle diameters of the carbon materials A and B is preferably 0.7 to 1.3, and the invention satisfies the parameters and includes the constituent carbon materials. The present invention provides a negative electrode for a non-aqueous electrolyte secondary battery having both high capacity, rapid charge / discharge characteristics and cycle characteristics by sharpening the particle size distribution.

Japanese Patent No. 3605256 JP 2010-92649 A JP 2003-132889 A JP 2005-108611 A JP 2010-251315 A

  In the technique described in Patent Document 1, pitch is mixed with coke, molded by a cold isostatic pressing method, the obtained molded body is heat-treated to form a high-density isotropic graphite block, and then pulverized and classified. By doing so, graphite powder is produced. However, according to the study by the present inventors, since the material is hard when pulverizing the molded body, the specific surface area is increased, the reactivity with the electrolytic solution cannot be suppressed, the initial efficiency is reduced, and the cycle characteristics are reduced. The problem of causing a decline was confirmed.

  In the technique described in Patent Document 2, scaly natural graphite or coke and pitch having a low degree of circularity as a starting material, and spherical natural graphite having a high degree of circularity are separately molded, fired and graphitized, and the DBP oil absorption is 50. ˜90 mL / 100 g and 30-45 mL / 100 g of graphite powder are obtained. By mixing these two, a material with a high DBP oil absorption and a low specific surface area has been obtained. However, since two types of mixtures are used, there is a problem with uniformity in the micro area within the electrode. Yes, for example, in a portion where a large amount of graphite derived from scaly natural graphite exists, the movement of Li ions is slow in a high-density electrode, and there is no special rule for the Raman R value. ), It was difficult to increase the density of the active material layer and to increase the capacity of the battery, and the large current charge / discharge characteristics were insufficient. Furthermore, in order to manufacture two types of materials separately, there exists a subject that a manufacturing method is complicated.

  The technique described in Patent Document 3 can improve the fast charge characteristics for lithium ion secondary batteries, but cannot improve the cycle characteristics desired for lithium ion secondary batteries. The same applies to Patent Document 4.

  The present invention has been made in view of the background art, and the problem is that even when the negative electrode active material layer is densified, the initial efficiency is high, and the non-aqueous system has excellent cycle characteristics even during large current charge / discharge. An object of the present invention is to provide a negative electrode for producing a secondary battery and a negative electrode material thereof, and as a result, to provide a non-aqueous secondary battery having high capacity, high input / output characteristics, and high cycle characteristics.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that the electrolyte absorption property parameter, that is, the liquid absorption coefficient of the negative electrode for a non-aqueous secondary battery is 0.11 mg / sec ^0.5. By doing so, the initial efficiency is high even when the density of the negative electrode active material layer is increased, and high cycle characteristics can be satisfied even during large current charge / discharge. A non-aqueous secondary battery having output characteristics and high cycle characteristics can be obtained, and graphite particles and a manufacturing method thereof for achieving such parameters have been found, and the present invention has been completed.

That is, the present invention is a negative electrode for a non-aqueous secondary battery, wherein the liquid absorption coefficient is 0.11 mg / sec ^0.5 or more.

  As a method for producing the graphite particles used for forming such a negative electrode for a non-aqueous secondary battery, Step 1 of roughening raw material graphite, Step 2 of mixing roughened raw material graphite and organic matter, and A method for producing graphite particles for a non-aqueous secondary battery, which includes a step 3 of firing the mixture obtained in the step 2 at a temperature of 2300 ° C. or higher, can be mentioned.

  Also, graphite mixed particles in which three or more types of graphite particles having different particle diameters are mixed, and the absolute value of the difference in d50 between the three types of graphite particles having a high degree of circularity is 2.5 μm. The negative electrode for a non-aqueous secondary battery can also be formed by the graphite particles for a non-aqueous secondary battery characterized by the above.

  The non-aqueous secondary battery of the present invention includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, and the negative electrode is the negative electrode for a non-aqueous secondary battery of the present invention. It is a non-aqueous secondary battery.

  By using the negative electrode for a non-aqueous secondary battery formed using the graphite particles of the present invention, a non-aqueous secondary battery having high capacity, high input / output characteristics, and high cycle characteristics can be provided.

FIG. 1 is an explanatory diagram of a method for calculating the pore volume Vi of graphite particles measured by mercury porosimetry. FIG. 2 is an SEM photograph of the graphite particles obtained in Example 1. FIG. 3 is an SEM photograph of the graphite particles obtained in Comparative Example 1.

  Hereinafter, the negative electrode for a non-aqueous secondary battery of the present invention (hereinafter also simply referred to as “the negative electrode of the present invention”), the graphite particles for a non-aqueous secondary battery used for the formation thereof (hereinafter simply referred to as “the graphite particles of the present invention”). The contents of the non-aqueous secondary battery using the negative electrode will be described in detail. In addition, description of the component requirements of the invention described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these forms unless it exceeds the gist.

[Negative electrode for non-aqueous secondary battery of the present invention]
The negative electrode for a non-aqueous secondary battery of the present invention (hereinafter also referred to as “electrode sheet” as appropriate) includes a current collector and an active material layer formed on the current collector. The graphite particle for non-aqueous secondary batteries of this invention mentioned later is contained.

<Physical Properties of Negative Electrode for Nonaqueous Secondary Battery of the Present Invention>
(Liquid absorption coefficient)
The liquid absorption coefficient of the negative electrode for a non-aqueous secondary battery according to the present invention was calculated from the PC solvent uptake rate into the negative electrode when the negative electrode piece was placed perpendicular to the ground and the end face was immersed in a PC (polycarbonate) solvent. a value, preferably 0.11 mg ^{/ sec 0.5} or more, more preferably 0.12 mg ^{/ sec 0.5} or more, more preferably 0.15 mg ^{/ sec 0.5} or more, particularly preferably 0.16 mg / sec It is ^0.5 or more. If the liquid absorption coefficient falls below the above range, the electrolyte solution does not move sufficiently smoothly during charging / discharging of the non-aqueous secondary battery obtained from the negative electrode of the present invention, and lithium ion There is a tendency that the insertion / desorption is not in time, and lithium metal is deposited accordingly, and the cycle characteristics are deteriorated. The liquid absorption coefficient is usually 1 mg / sec ^0.5 or less.

The measuring method of the liquid absorption coefficient is as follows. Using an automatic surface tension meter (Kruss K100), the amount of PC solvent sucked into the negative electrode when the negative electrode piece cut to 1 cm x 4 cm was vertically placed on the ground and the end face was immersed in PC solvent was the rate of change in weight. Measured as (mg / sec). The liquid absorption coefficient (mg / sec ^0.5 ) is calculated from the obtained weight change rate (mg / sec).

(Micropore volume with a pore diameter of 80 nm to 900 nm)
The fine pore volume having a pore diameter of 80 nm or more and 900 nm or less of the negative electrode for a non-aqueous secondary battery of the present invention is a value measured using a mercury intrusion method (mercury porosimetry), preferably 0.08 mL / g or more. Preferably it is 0.1 mL / g or more, More preferably, it is 0.15 mL / g or more, Most preferably, it is 0.3 mL / g or more. Moreover, it is 1 mL / g or less normally, Preferably it is 0.8 mL / g or less, More preferably, it is 0.5 mL / g or less.

  When the micropore volume with a pore diameter of 80 nm or more and 900 nm or less falls below the above range, the electrolyte solution does not move sufficiently smoothly during charge / discharge of the non-aqueous secondary battery, and lithium ions are inserted when rapid charge / discharge is performed. There is a tendency that the desorption is not in time, and lithium metal is deposited accordingly, and the cycle characteristics are deteriorated. On the other hand, when it exceeds the above range, the binder is easily absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength and initial efficiency tend to decrease.

  In the measurement of the mercury intrusion method, a mercury porosimeter (Autopore 9520 manufactured by Micromeritex Co., Ltd.) was used, and a sample (negative electrode) was weighed around 0.2 g in terms of the negative electrode active material in a cell and sealed at room temperature under vacuum (50 μmHg After performing degassing pretreatment for 10 minutes in the following), the pressure is reduced stepwise to 4 psia, mercury is introduced, the pressure is increased stepwise from 4 psia to 40000 psia, and the pressure is further decreased to 25 psia. The pore distribution is calculated from the obtained mercury intrusion curve using the Washburn equation. Note that the surface tension of mercury is calculated as 485 dyne / cm and the contact angle is 140 °.

  Based on the pore distribution (integral curve) obtained here, the micropore volume in the range of the pore diameter of 80 nm to 900 nm is calculated.

<Method for Forming Negative Electrode for Nonaqueous Secondary Battery of the Present Invention>
As described above, the negative electrode of the present invention includes an active material layer containing the graphite particles of the present invention on a current collector, and the active material layer further preferably contains a binder.

  The binder here means a binder added for the purpose of binding active materials and holding the active material layer on a current collector when producing a negative electrode for a non-aqueous secondary battery. It is different from the binder that can be converted.

  As the binder, one having an olefinically unsaturated bond in the molecule is used. The type is not particularly limited, and specific examples include styrene-butadiene rubber, styrene / isoprene / styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene / propylene / diene copolymer. By using such a binder having an olefinically unsaturated bond, the swellability of the active material layer with respect to the electrolytic solution can be reduced. Of these, styrene-butadiene rubber is preferred because of its availability.

  By using such a binder having an olefinically unsaturated bond in combination with the above active material, the strength of the negative electrode plate can be increased. When the strength of the negative electrode is high, deterioration of the negative electrode due to charging / discharging of the nonaqueous secondary battery obtained using the negative electrode of the present invention is suppressed, and the cycle life can be extended. Further, in the negative electrode according to the present invention, since the adhesive strength between the active material layer and the current collector is high, even when the binder content in the active material layer is reduced, the negative electrode is wound to produce a battery. It is assumed that the problem that the active material layer peels from the current collector does not occur.

As the binder having an olefinically unsaturated bond, those having a large molecular weight or those having a large proportion of unsaturated bonds are desirable. Specifically, in the case of a binder having a high molecular weight, it is desirable that the weight average molecular weight is usually 10,000 or more, preferably 50,000 or more, and usually 1,000,000 or less, preferably 300,000 or less. In the case of a binder having a large proportion of unsaturated bonds, the number of moles of olefinically unsaturated bonds per gram of all binders is usually 2.5 × 10 ⁻⁷ or more, preferably 8 × 10 ⁻⁷ or more. Further, it is usually 1 × 10 ⁻⁶ or less, preferably 5 × 10 ⁻⁶ or less.

  The binder only needs to satisfy at least one of these regulations regarding molecular weight and regulations regarding the proportion of unsaturated bonds, but it is more preferable to satisfy both regulations simultaneously. When the molecular weight of the binder having an olefinically unsaturated bond is too small, the mechanical strength is inferior, and when it is too large, the flexibility is inferior. Moreover, when the ratio of the olefinic unsaturated bond in a binder is too small, the strength improvement effect will fade, and when too large, it will be inferior to flexibility.

  The binder having an olefinically unsaturated bond has a degree of unsaturation of usually 15% or more, preferably 20% or more, more preferably 40% or more, and usually 90% or less, preferably 80% or less. Is desirable. The degree of unsaturation represents the ratio (%) of the double bond to the repeating unit of the polymer.

  In the present invention, a binder having no olefinically unsaturated bond can also be used in combination with the above-mentioned binder having an olefinically unsaturated bond as long as the effects of the present invention are not lost. The mixing ratio of the binder having no olefinically unsaturated bond to the binder having an olefinically unsaturated bond is usually 150% by mass or less, preferably 120% by mass or less.

  By using a binder that does not have an olefinically unsaturated bond, the coating property can be improved. However, if the combined amount is too large, the strength of the active material layer is lowered.

  Examples of binders having no olefinic unsaturated bond include thickening polysaccharides such as methylcellulose, carboxymethylcellulose, starch, carrageenan, pullulan, guar gum, xanthan gum (xanthan gum), polyethers such as polyethylene oxide and polypropylene oxide, Vinyl alcohols such as polyvinyl alcohol and polyvinyl butyral, polyacids such as polyacrylic acid and polymethacrylic acid, or metal salts of these polymers, fluorine-containing polymers such as polyvinylidene fluoride, alkane polymers such as polyethylene and polypropylene, and these A copolymer etc. are mentioned.

  The negative electrode of the present invention is formed by dispersing graphite particles for a non-aqueous secondary battery of the present invention, which will be described later, and a binder in a dispersion medium, and applying this to a current collector. As the dispersion medium, an organic solvent such as alcohol or water can be used. If necessary, a conductive material may be added to the slurry. Examples of the conductive material include carbon black such as acetylene black, ketjen black, and furnace black, and fine powder made of Cu, Ni, or an alloy thereof having an average particle size of 1 μm or less. The amount of the conductive material added is usually about 10% by mass or less with respect to the negative electrode material of the present invention.

  A conventionally well-known thing can be used as a collector which apply | coats a slurry. Specific examples include metal thin films such as rolled copper foil, electrolytic copper foil, and stainless steel foil. The thickness of the current collector is usually 4 μm or more, preferably 6 μm or more, and usually 30 μm or less, preferably 20 μm or less.

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. I do. Further, after drying at 110 ° C. for 30 minutes, roll pressing is 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.

  After applying the slurry on the current collector, the slurry is usually dried at a temperature of 60 ° C. or higher, preferably 80 ° C. or higher, and usually 200 ° C. or lower, preferably 195 ° C. or lower, in dry air or an inert atmosphere. A material layer is formed.

  The thickness of the active material layer obtained by applying and drying the slurry is usually 5 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 200 μm or less, preferably 100 μm or less, more preferably 75 μm or less. . If the active material layer is too thin, it is not practical as a negative electrode due to the balance with the particle size of the active material.

Density of the active material layer varies depending on the application, the application that emphasizes capacity, preferably 1.5 g / cm ³ or more, especially 1.6 g / cm ³ or more, further 1.65 g / cm ³ or more, especially 1. 7 g / cm ³ or more is preferable. If the density is too low, the capacity of the battery per unit volume is not always sufficient. Moreover, since a rate characteristic will fall when a density is too high, 1.9 g / cm < ³ > or less is preferable.

  When producing the negative electrode for non-aqueous secondary batteries using the graphite particles for non-aqueous secondary batteries of the present invention described later, the method and selection of other materials are not particularly limited. Also,

[Graphite particles for non-aqueous secondary battery of the present invention]
Next, various characteristics of the graphite particles for a non-aqueous secondary battery of the present invention that can be used to form the negative electrode for a non-aqueous secondary battery of the present invention described above, a manufacturing method thereof, and the like will be described.

<Physical Properties of Graphite Particles for Nonaqueous Secondary Battery of the Present Invention>
(DBP oil absorption)
The DBP oil absorption of the graphite particles of the present invention is 0.38 mL / g or more, preferably 0.43 mL / g or more, more preferably 0.45 mL / g or more, and further preferably 0.50 mL / g or more. Moreover, it is 0.85 mL / g or less, Preferably it is 0.80 mL / g or less, More preferably, it is 0.76 mL / g or less.

  If the DBP oil absorption amount is too smaller than this range, the number of voids into which the non-aqueous electrolyte solution can enter decreases, so that the non-aqueous electrolyte solution absorbability in the negative electrode is lowered and the liquid absorption coefficient tends to decrease. There is. For this reason, when the non-aqueous secondary battery is rapidly charged and discharged, a portion where the non-aqueous electrolyte is withered is generated in the negative electrode, and the entire negative electrode active material cannot be used uniformly and effectively. There is a tendency that the desorption is not in time, and lithium metal is deposited accordingly, and the cycle characteristics are deteriorated. On the other hand, if it is larger than this range, the binder is likely to be absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength and initial efficiency tend to be reduced.

  The measurement of DBP (dibutyl phthalate) oil absorption can be performed by the following procedure using graphite particles.

  DBP oil absorption is measured in accordance with JIS K6217, 40 g of measurement material is added, dripping speed is 4 ml / min, rotation speed is 125 rpm, and measurement is performed until the maximum value of torque is confirmed. It is implemented by defining the value (DBP dripping oil amount per 1 g of the negative electrode material) calculated from the dripping oil amount when showing a torque of 70% of the maximum torque in the range shown.

(Specific surface area)
The specific surface area of the graphite particles of the present invention is a value of the specific surface area measured using the BET method, and is 0.5 m ² · g ⁻¹ or more, preferably 1.0 m ² · g ⁻¹ or more, more preferably 1 .3m ² · g ^-1 or more, particularly preferably at 1.5 m ² · g ^-1 or more,, 10 m ² · g ^-1 or less, preferably 7.5 m ² · g ^-1 or less, more preferably 6m ² · g ⁻¹ or less, particularly preferably 5 m ² · g ⁻¹ or less.

  When the value of the specific surface area is less than this range, the acceptability of lithium at the time of charging the negative electrode tends to be poor, the lithium metal tends to precipitate on the electrode surface, and the cycle characteristics tend to deteriorate. On the other hand, if it exceeds this range, the reactivity of the negative electrode with the non-aqueous electrolyte increases, the initial efficiency tends to decrease, and a preferable battery is difficult to obtain.

  The specific surface area was measured by the BET method using a surface area meter (a fully automated surface area measuring device manufactured by Okura Riken), preliminarily drying the sample at 350 ° C. for 15 minutes under nitrogen flow, Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure becomes 0.3, the nitrogen adsorption BET one-point method by the gas flow method is used. The specific surface area determined by the measurement is defined as the specific surface area of the graphite particles of the present invention.

(Raman R value)
The Raman R value of the graphite particles of the present invention is a value measured using an argon ion laser Raman spectrum method, and is 0.03 or more, preferably 0.05 or more, more preferably 0.07 or more, It is 0.6 or less, preferably 0.4 or less, more preferably 0.35 or less, and particularly preferably 0.3 or less.

  When the Raman R value is less than the above range, the crystallinity of the particle surface becomes too high, and there are cases where the sites where lithium enters between layers are decreased along with charge / discharge. That is, the charge acceptance may be reduced and the cycle characteristics may be deteriorated. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, when the above range is exceeded, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the initial efficiency may be lowered and the gas generation may be increased.

The measurement of the Raman spectrum, using a Raman spectrometer (manufactured by JASCO Corporation Raman spectrometer), the sample is naturally dropped into the measurement cell and filled, and while irradiating the sample surface in the cell with argon ion laser light, This is done by rotating the cell in a plane perpendicular to the laser beam. The resulting Raman spectrum, the intensity I _A of the peak P _A in the vicinity of 1580 cm ^-1, and measuring the intensity I _B of a peak P _B in the vicinity of 1360 cm ^-1, the intensity ratio _{R (R = I B / I} A) Is calculated. The Raman R value calculated by the measurement is defined as the Raman R value of the graphite particles of the present invention.

Moreover, said Raman measurement conditions are as follows.
Argon ion laser wavelength: 514.5nm
・ Laser power on the sample: 15-25mW
・ Resolution: 10-20cm ^-1
・ Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹・ Raman R value,
・ Raman half-value analysis: Background processing / Smoothing processing: Simple average, 5 points of convolution

  In general, the DBP oil absorption is used for evaluating a low crystalline material having a large specific surface area such as carbon black. When a conventional negative electrode material is measured by this method, a material having a high DBP oil absorption is likely to have a high specific surface area and a high Raman R value, and as described above, a material with further improved cycle characteristics and initial efficiency is obtained. I couldn't.

  Considering cycle characteristics during rapid charge / discharge, a negative electrode with high non-aqueous electrolyte absorption (high liquid absorption coefficient) and a material with high lithium acceptability and low reactivity with non-aqueous electrolyte Is considered to be excellent in cycle characteristics because of a small loss of lithium deposited on the electrode surface and a loss of consumption as a surface coating (SEI). Similarly, a material having low reactivity with the non-aqueous electrolyte is also advantageous for the initial efficiency.

  A material capable of producing a negative electrode having a high non-aqueous electrolyte solution absorbability is a material having a large number of voids into which the non-aqueous electrolyte solution can enter and a large number of fine paths through which the non-aqueous electrolyte solution can move, that is, a high DBP oil absorption amount. It is considered that the material is a material capable of forming a negative electrode having high non-aqueous electrolyte solution absorbability.

  A material having high lithium acceptability is a material having a wide contact area with the electrolyte, a large reaction area, and low crystallinity on the surface of the negative electrode particles (wide graphite layer, low La · Lc). It is considered that a material having a high DBP oil absorption, a large specific surface area, and a high Raman R value has a high lithium acceptability.

  On the other hand, a material having low reactivity with the electrolytic solution is considered to be a material having a small reaction area with the electrolytic solution and high crystallinity on the surface of the negative electrode material particles (narrow graphite layers and large La · Lc). That is, it is considered that a material having a low DBP oil absorption, a small specific surface area, and a low Raman R value is considered to have a low reactivity with the electrolytic solution, and is considered to have a tendency to conflict with the lithium acceptability.

  From the above, it is considered that both the cycle characteristics and the initial efficiency can be achieved by setting the contact area with the electrolytic solution to a certain extent, the reaction area to a certain extent, and the crystallinity of the negative electrode material particle surface within a certain range.

  That is, while maintaining the DBP oil absorption amount of the negative electrode material (graphite particles) in a high range, the specific surface area is suppressed to a low range, and the Raman R value is set in the above range, so that the non-aqueous electrolyte solution absorbability is high. A negative electrode material that can provide a non-aqueous secondary battery that accelerates the insertion and desorption of lithium ions and can suppress the reactivity with the non-aqueous electrolyte solution, thereby providing excellent cycle characteristics and high initial efficiency. Can be achieved.

  Other physical properties of the graphite particles of the present invention include the following physical properties, and it is desirable to satisfy these physical properties.

(Raman half-width)
The Raman half-width in the vicinity of 1580 cm ⁻¹ of the graphite particles of the present invention is not particularly limited, but is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and is usually 100 cm ⁻¹ or less, preferably 80 cm ⁻¹ or less. More preferably, it is 60 cm ⁻¹ or less, and particularly preferably 40 cm ⁻¹ or less.

  If the Raman half width is less than the above range, the crystallinity of the particle surface becomes too high, and there are cases where the number of sites where Li enters between layers decreases with charge and discharge. That is, the charge acceptance may be reduced and the cycle characteristics may be reduced. In addition, when the negative electrode is densified by applying it to the current collector and then pressing it, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a decrease in load characteristics. On the other hand, if it exceeds the above range, the crystallinity of the particle surface is lowered, the reactivity with the non-aqueous electrolyte is increased, and the efficiency may be lowered and the gas generation may be increased.

The resulting measured half width of the peak P _A in the vicinity of 1580 cm ^-1 of the Raman spectrum, which is defined as the Raman half-value width of the graphite particles of the present invention.

(Surface functional group O / C)
The surface functional group O / C of the graphite particles of the present invention is represented by the following formula 1, and the O / C is usually 0.1% or more, preferably 0.2% or more, more preferably 0.3% or more. Yes, particularly preferably 0.5 or more, usually 3.5% or less, preferably 2.5% or less, more preferably 1.4% or less, and further preferably 1.0% or less.

  If the surface functional group O / C is too small, the reactivity with the electrolytic solution is poor, and stable SEI formation cannot be performed and the cycle characteristics may be deteriorated. On the other hand, if the surface functional group O / C is too large, the crystal on the particle surface is disturbed, the reactivity with the electrolytic solution is increased, and there is a risk of increasing the irreversible capacity and increasing gas generation.

Formula 1
O / C (%) = O atom concentration obtained based on the peak area of the O1s spectrum in X-ray photoelectron spectroscopy (XPS) analysis × 100 / C atom obtained based on the peak area of the C1s spectrum in XPS analysis concentration

  The surface functional group O / C of the graphite particles of the present invention can be measured using X-ray photoelectron spectroscopy (XPS).

  The measuring method of the surface functional group O / C by X-ray photoelectron spectroscopy is as follows. Using an X-ray photoelectron spectrometer, the object to be measured is placed on a sample stage so that the surface is flat, and K1 ray of aluminum is used as an X-ray source, and C1s (280 to 300 eV) and O1s (525 to 545 eV) are obtained by multiplex measurement. ) Spectrum. The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and O1s spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and O, respectively. The obtained atomic concentration ratio O / C of O and C (O atomic concentration / C atomic concentration) is defined as the surface functional group O / C of the graphite particles of the present invention.

(Pore volume Vi)
The pore volume Vi of the graphite particles of the present invention is a value measured using a mercury intrusion method (mercury porosimetry), and is usually 0.1 mL / g or more, preferably 0.13 mL / g or more, more preferably 0. .14 mL / g or more, usually 0.3 mL / g or less, preferably 0.28 mL / g or less, more preferably 0.25 mL / g or less.

  When the pore volume Vi is less than the above range, the number of voids into which the nonaqueous electrolyte solution can enter decreases, so that when lithium ion is rapidly charged / discharged, lithium ion insertion / desorption is not in time, and lithium metal is deposited accordingly. Characteristics tend to deteriorate. On the other hand, when it exceeds the above range, the binder is easily absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength and initial efficiency tend to decrease.

  The method of measurement by mercury intrusion method is as follows. Using a mercury porosimeter (Autopore 9520 manufactured by Micromeritex Co., Ltd.), a sample cell (graphite particles) is weighed around 0.2 g in a powder cell, and degassed for 10 minutes at room temperature under vacuum (50 μmHg or less). After the treatment is performed, the pressure is reduced stepwise to 4 psia, mercury is introduced, the pressure is increased stepwise from 4 psia to 40000 psia, and the pressure is further decreased to 25 psia. The pore distribution is calculated from the obtained mercury intrusion curve using the Washburn equation. Note that the surface tension of mercury is calculated as 485 dyne / cm and the contact angle is 140 °.

  Here, the pore volume Vi is defined as follows. Based on the pore distribution (integral curve) obtained above, a tangent line is drawn as shown in FIG. 1 to determine the branch point between the tangent line and the integral curve, and the pore volume at that time is defined as Vp. A value obtained by subtracting the pore volume Vp from the total pore volume is defined as the pore volume Vi. It can be expressed as the following formula.

  Pore volume Vi = total pore volume−pore volume Vp

  The pore volume Vi is considered to mainly reflect the amount of internal voids of the graphite particles, and it is estimated that the larger the pore volume Vi, the more voids inside the particles. On the other hand, the pore volume Vp is considered to mainly reflect voids between particles.

(Total pore volume)
The total pore volume i of the graphite particles of the present invention is a value measured using the mercury intrusion method (mercury porosimetry), and is usually 0.48 mL / g or more, preferably 0.50 mL / g or more, more preferably. Is 0.52 mL / g or more, and is usually 0.95 mL / g or less, preferably 0.93 mL / g or less, more preferably 0.9 mL / g or less.

  If the total pore volume is below the above range, the number of voids that can be infiltrated by the non-aqueous electrolyte solution tends to be small, and when lithium ions are rapidly charged and discharged, lithium ions are not inserted and released in time, and lithium metal is deposited accordingly. Characteristics tend to deteriorate. On the other hand, when it exceeds the above range, the binder is easily absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength and initial efficiency tend to decrease.

(Tap density)
The tap density of the graphite particles of the present invention is usually 0.7 g · cm ⁻³ or more, preferably 0.8 g · cm ⁻³ or more, more preferably 0.9 g · cm ⁻³ or more. It is 25 g · cm ⁻³ or less, preferably 1.2 g · cm ⁻³ or less, more preferably 1.18 g · cm ⁻³ or less, and particularly preferably 1.15 g · cm ⁻³ or less. If the tap density is below the above range, the packing density is difficult to increase when used as a negative electrode, and a high-capacity battery may not be obtained. On the other hand, when the above range is exceeded, there are too few voids between particles in the electrode, it is difficult to ensure conductivity between the particles, and it may be difficult to obtain preferable battery characteristics.

The tap density is measured by passing a sieve having a mesh opening of 300 μm, dropping the sample onto a 20 cm ³ tapping cell and filling the sample to the upper end surface of the cell, and then measuring a powder density measuring instrument (for example, manufactured by Seishin Enterprise Co., Ltd.). Using a tap denser, tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the mass of the sample. The tap density calculated by the measurement is defined as the tap density of the graphite particles of the present invention.

(Volume standard average particle diameter (d50))
The volume-based average particle diameter (d50) of the graphite particles of the present invention is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, based on the volume-based average particle diameter (median diameter) determined by the laser diffraction / scattering method. Particularly preferably, it is 7 μm or more, and is usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less.

  If the volume-based average particle size is below the above range, the irreversible capacity may increase, leading to loss of initial battery capacity. On the other hand, when the above range is exceeded, when an electrode is produced by coating, an uneven coating surface tends to be formed, which may be undesirable in the battery production process.

  The volume-based average particle size is measured by dispersing graphite particles in a 0.2% by mass aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate, which is a surfactant, and laser diffraction / scattering particle size distribution. This is carried out using a meter (LA-700 manufactured by Horiba, Ltd.). The median diameter determined by the measurement is defined as the volume-based average particle diameter of the graphite particles of the present invention.

(X-ray parameters)
The crystallite sizes (Lc) and (La) obtained by X-ray diffraction of the graphite particles according to the present invention are preferably 30 nm or more, more preferably 100 nm or more. If the crystallite size is within this range, the amount of lithium that can be charged into the graphite particles increases, and a high capacity is easily obtained, which is preferable.

(Orientation ratio)
The orientation ratio of the graphite particle powder of the present invention is usually 0.005 or more, preferably 0.01 or more, more preferably 0.05 or more, particularly preferably 0.1 or more, and usually 0. .67 or less, preferably 0.5 or less, more preferably 0.4 or less. When the orientation ratio is too small or below the above range, the high-density charge / discharge characteristics may deteriorate. In addition, the normal upper limit of the said range is the theoretical upper limit of the orientation ratio of graphite particles.

The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. Set the molded body obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8 MN · m ^{-2 so} that it is flush with the surface of the sample holder for measurement. X-ray diffraction is measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the graphite particles of the present invention.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Divergence slit = 0.5 degree Light receiving slit = 0.15 mm
Scattering slit = 0.5 degree / measurement range and step angle / measurement time:
(110) plane: 75 degrees ≦ 2θ ≦ 80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ≦ 2θ ≦ 57 degrees 1 degree / 60 seconds

(Particle size distribution half width (log (μm)))
In one aspect of the graphite particles for a non-aqueous secondary battery of the present invention, the particle size distribution half width (log (μm)) is preferably 0.3 or more. The particle size distribution half-width (log (μm)) is a volume-based particle size distribution (μm) spectrum obtained by laser diffraction / scattering particle size distribution measurement of the graphite particles (frequency on the vertical axis and frequency on the horizontal axis). The particle size is taken as a half-width of the spectrum when the horizontal axis is expressed in the common logarithm (log (μm)). The method of laser diffraction / scattering particle size distribution measurement is as follows.

  A laser diffraction particle size distribution analyzer (Horiba, Ltd.) was prepared by adding about 20 mg of a sample to about 1 ml of a 2% (volume) aqueous solution of polyoxyethylene (20) sorbitan monolaurate and dispersing it in about 200 ml of ion-exchanged water. The volume-based particle size distribution is measured using LA-920). The measurement conditions are ultrasonic dispersion for 1 minute, ultrasonic intensity 2, circulation speed 2, and relative refractive index 1.50.

  The use of graphite particles with a wide half-value width, that is, a broad particle size distribution as described above, makes it possible to create a high-strength, high-electrolyte-immersible electrode sheet. Workability in the production of non-aqueous secondary batteries is improved, and a non-aqueous secondary battery excellent in charge / discharge efficiency, high current density charge / discharge characteristics, low temperature input / output characteristics, and cycle characteristics is obtained.

  In addition, as long as the effect of the present invention is exhibited, there is no limit to the upper limit of the particle size distribution half width (log (μm)), but the upper limit is usually 1.5, more preferably 1, and still more preferably 0.8. Particularly preferably 0.5. The particle size distribution half width (log (μm)) is preferably 0.3 or more, more preferably 0.33 or more, particularly preferably 0.37 or more, and most preferably 0.4 or more. If the particle size distribution half-value width (log (μm)) is too large, it becomes difficult to control fine powder and coarse particles, which may cause process inconveniences such as stringing and increased slurry viscosity during electrode preparation, and initial efficiency of non-aqueous secondary batteries. On the other hand, if it is too small, the high current density charge / discharge characteristics of the battery, the low temperature input / output characteristics and the cycle characteristics may be deteriorated.

(Particle size distribution half width (log (μm)) / log (d90-d10))
In one embodiment, the graphite particles for a non-aqueous secondary battery of the present invention have a value obtained by dividing the particle size distribution half width (log (μm)) by the common logarithm of (d90-d10) (particle size distribution half width (log ( μm)) / log (d90−d10)) is preferably greater than 0.25.

  Here, d90 represents the particle diameter of the 90% integration part from the small particle side measured on the volume basis by laser diffraction / scattering particle size distribution measurement for the graphite particles in μm, and d10 represents the graphite particles. The particle diameter of the 10% integration part from the small particle side measured in the same manner for the particles is expressed in μm units.

  The particle size distribution half-width (log (μm)) / log (d90-d10)> 0.25 represents a state in which the generation of coarse particles and fine powder is appropriately controlled in the graphite particles of the present invention. The numerical value is preferably 0.26 or more, more preferably 0.31 or more, still more preferably 0.33 or more, particularly preferably 0.34 or more, most preferably 0.4 or more, usually 1 or less, Preferably it is 0.8 or less, More preferably, it is 0.6 or less, More preferably, it is 0.5 or less.

  If the value of the particle size distribution half-width (log (μm)) / log (d90-d10) is out of the above range, the production efficiency of the graphite particles decreases, the occurrence of process inconveniences such as stringing and slurry viscosity increase, non-aqueous secondary There are cases where the initial efficiency of the battery, the high current density charge / discharge characteristics, the low temperature input / output characteristics and the cycle characteristics are deteriorated.

  Further, d90 is usually 100 μm or less, preferably 60 μm or less, more preferably 50 μm or less, further preferably 40 μm or less, particularly preferably 30 μm or less, most preferably 25 μm or less, usually 10 μm or more, preferably 15 μm or more, more preferably 20 μm. That's it. If d90 is too small, electrode strength and initial charge / discharge efficiency may be reduced. If d90 is too large, process inconveniences such as line drawing may occur, battery high current density charge / discharge characteristics may be reduced, and low temperature input / output characteristics may be reduced. It may cause a decrease.

  d10 is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, further preferably 6 μm or more, usually 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. If d10 is too small, it may cause inconveniences such as an increase in slurry viscosity, decrease in electrode strength and initial charge / discharge efficiency, and if it is too large, decrease in high current density charge / discharge characteristics and low temperature input / output characteristics of the battery. May be reduced.

  Further, d90 / d10 is usually 2 or more, preferably 2.3 or more, more preferably 2.6 or more, particularly preferably 2.8 or more, and usually 5 or less, preferably 4 or less. An electrode using a material whose d90 / d10 is too small tends to have a small number of fine holes and a low liquid absorption coefficient, and tends to cause a decrease in cycle characteristics. On the other hand, if d90 / d10 is too large, it indicates that there are a lot of fine powders or coarse powders, and there is a tendency to deteriorate the electrode forming processability and the initial efficiency.

<Form of graphite particles>
The form of the graphite particles of the present invention is not particularly limited, and examples thereof include a spherical shape, a spheroid shape, a lump shape, a plate shape, and a polygonal shape. Among these, a spherical shape, a spheroid shape, a lump shape, and a polygonal shape are used as a negative electrode. It is sometimes preferable because the packing property of the particles can be improved.

  Moreover, the surface form of the graphite particles of the present invention is not particularly limited, but preferably has a concavo-convex structure as shown in the SEM photograph of FIG. Examples of the concavo-convex structure include, for example, (1) a concave structure in which a hole is formed in the surface of a particle such as a sphere or a spheroid, or (2) a convex portion in which fine particles are bound to the particle surface such as a sphere or a spheroid Examples include the structure. When the particle surface has a concavo-convex structure, even when a high-density negative electrode is formed, a void into which a nonaqueous electrolytic solution can enter can be secured, so that improvement in cycle characteristics can be expected.

  The size of the concavo-convex structure is not particularly limited, but preferably corresponds to a diameter of about 0.1 μm to 4 μm when converted into a circular area. When the size of the concavo-convex structure is within this range, even when the negative electrode has a high density, it is possible to secure a void into which the non-aqueous electrolyte solution can enter, so that improvement in cycle characteristics can be expected.

<Method for producing graphite particles>
Next, the manufacturing method of the graphite particle of this invention is demonstrated. The graphite particles may be produced by any method as long as they have the above properties, and may be composed of one kind of graphite particles or a mixture of a plurality of graphite particles. . Although the manufacturing method of the graphite particle of this invention is not specifically limited, The method shown to following (I) to (IV) etc. are mentioned.

<When configured with a single carbon material>
The graphite particles of the present invention are not particularly limited, but are preferably multi-layered graphite particles coated with a carbonaceous material, and more preferably multi-layered graphite particles coated with amorphous carbon or a graphite material. , Coated with amorphous graphite coated with amorphous carbon obtained by mixing and firing raw material graphite and raw material organic material, or coated with graphite material obtained by mixing and firing raw material graphite and raw material organic material It is preferably a multilayer structure graphite particle.

(Production method (I))
As a method of forming the above-mentioned graphite particle form (1) and / or (2), at least the step 1 of roughening the raw material graphite, the step 2 of mixing the roughened raw material graphite and the raw material organic matter, and obtaining The manufacturing method which consists of the process 3 which bakes the obtained mixture is mentioned. Further, pulverization and classification may be performed as necessary after firing.

(Production method (II))
As a method of mainly forming the form (2) of the graphite particles, a convex structure is formed by binding to the surface of a core particle such as a spherical shape or a spheroidal shape and a core particle shape such as a plate shape or a scale shape. A production method comprising at least a step of mixing raw material graphite and a raw material organic material and a firing step using two or more types of raw material graphite (mixture) composed of fine particles to be formed is mentioned. Further, pulverization and classification may be performed as necessary after firing.

  Among the manufacturing methods (I) and (II), the manufacturing method (I) is preferable because it can easily form an uneven structure.

(Production method (III))
As a method of forming the graphite particles of the present invention satisfying the above half-value width of particle size distribution (log (μm)), step 1 and step 1 for producing flake graphite having different particle sizes (d50) by pulverization and classification From the small particle size product (for example, the average particle size (d50) is 5 to 50 μm) to the large particle size product (for example, the average particle size (d50) is 51 to 500 μm), which is the flaky graphite produced, in order to the spheronizer A production method comprising at least step 2 in which spheronization is performed while being sequentially added.

(Raw material graphite)
The raw material graphite used in the production methods (I) and (II) is not particularly limited as long as it is graphitized (or graphitized by firing at a temperature of 2300 ° C. or higher), Examples thereof include natural graphite, artificial graphite, coke powder, needle coke powder, resin graphitized (or graphitizable carbon) powder, and the like. Of these, natural graphite is preferable because it is easy to process.

  The form of the raw material graphite particles is not particularly limited, and examples thereof include a spherical shape, a spheroid shape, a lump shape, a plate shape, a scale shape, and a polygonal shape, and are used in the production methods (I) and (II). When the spheroid shape, the lump shape, and the polygonal shape are graphite particles, the particle filling property can be improved, which is preferable. Further, in the production method (I), it is preferable to use natural graphite spheroidized into a spherical shape or a spheroid shape because the above-mentioned effect can be easily obtained.

  As an apparatus for obtaining spherical or spheroid graphite used in the production methods (I) and (II), for example, compression, friction, shearing force, etc. including the interaction of particles mainly with impact force. An apparatus that repeatedly gives mechanical action 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 effects such as impact compression, friction, shearing force, etc. are applied to the graphite introduced inside. An apparatus that provides and performs surface treatment is preferred. 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.

  Spherical or spheroidal graphite is formed into base particles that are made spherical by applying the spheroidizing step by the surface treatment described above, whereby the scale-like natural graphite is folded or the peripheral edge portion is spherically pulverized. The surface functional group O / C of the surface-treated graphite particles is usually 0.5% or more and 10% or less, preferably 1% or more and 4% or less. It manufactures by performing a spheronization process on the conditions which become. In this case, it is preferable to carry out in an active atmosphere so that the oxidation reaction of the graphite surface can be advanced by the energy of mechanical treatment and acidic functional groups can be introduced into the graphite surface. For example, when processing using the above-mentioned apparatus, the peripheral speed of the rotating rotor is usually preferably 30 to 100 m / sec, preferably 40 to 100 m / sec, and more preferably 50 to 100 m / sec. Further, the treatment can be performed simply by passing graphite, but it is preferable to circulate or stay in the apparatus for 30 seconds or more, and it is more preferable to circulate or stay in the apparatus for 1 minute or more. preferable. As an apparatus for obtaining plate-like or scale-like graphite used in the production method (II), for example, mechanical action such as compression, friction, shearing force including particle interaction mainly including impact force is performed. A device for feeding particles can be used. Specific examples include a jet mill, a hammer mill, a pin mill, a turbo mill, and a pulverizer.

(Particle size of raw graphite)
The volume-based average particle diameter of the raw material graphite is not particularly limited, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and usually 100 μm or less, preferably 50 μm or less. More preferably, it is 40 μm or less, particularly preferably 30 μm or less.

  In the case of spherical or spheroidal particles used in the graphite particle production methods (I) and (II), the volume-based average particle diameter is usually 5 μm or more, preferably 7 μm or more, more preferably 10 μm or more. Also, it is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less.

  Further, in the case of fine particles such as plate, scale, and lump used in the method (II) for producing graphite particles, the volume-based average particle size is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 20 μm. Hereinafter, it is preferably 15 μm or less, more preferably 10 μm or less.

  If the particle size of the raw material graphite is within this range, it is preferable to form a concavo-convex structure on the particle surface when the graphite particles are used.

(Roughening raw material graphite (Step 1 in production method (I)))
The roughening step of the raw material graphite refers to a step of imparting an uneven structure to the surface of the raw material graphite. The method used in the roughening step is not particularly limited as long as the surface of the raw graphite can be provided with a concavo-convex structure. For example, by adding mechanical energy (for example, pulverization) such as compression, friction, and shear force to the raw graphite. There is a method of imparting a concavo-convex structure to the surface, and it may be performed in a dry state or a wet state. As specific examples below, methods for imparting a concavo-convex structure to the surface of raw graphite are listed.

(I) When performing a roughening process in a dry state In a method for roughening in a dry state, for example, a pin mill (manufactured by Hadano Sangyo Co., Ltd.), a turbo mill (manufactured by Turbo Industrial Co., Ltd.), a kryptron orb (earth technica) Etc.) and a pulverizer such as a jet mill (manufactured by Nippon Pneumatic Co., Ltd.) can be used. Among them, it is preferable to use a crusher such as a turbo mill composed of a rotor and a stator because productivity can be improved.

  The pulverization speed in the dry state varies depending on the apparatus to be used, but when the raw material graphite is spherical or spheroid, select the shape and rotational speed of the rotor of the pulverizer to be used as appropriate, and The rotor peripheral speed calculated by the equation is preferably set to 50 m / sec or more, more preferably set to 80 m / sec or more, and further preferably set to 100 m / sec or more. The upper limit is usually 300 m / sec or less.

  Peripheral speed (m / sec) = Roughening device rotor diameter × 3.14 ÷ Rotation speed

  The rotor and / or stator of the crusher to be used is not particularly limited as long as the peripheral speed can be set, but the rotor has blades, and the stator preferably has grooves. .

  If the pulverization speed is too high, a lot of fine powder may be generated. Even if the roughened raw material graphite and the raw material organic material are mixed and fired at a temperature of 2300 ° C. or higher, the specific surface area of the obtained graphite particles is large. In the non-aqueous secondary battery, the reactivity between the negative electrode and the electrolytic solution cannot be suppressed, and the initial efficiency and cycle characteristics may be deteriorated. On the other hand, if it is slower than this pulverization rate, the effect of roughening hardly appears, and it tends to be difficult to improve the initial efficiency and cycle characteristics.

  The raw material charging speed at the time of pulverization is usually 10 kg / hr or more, preferably 50 kg / hr or more, more preferably 100 kg / hr or more, and further preferably 200 kg / hr or more. Moreover, it is 1000 kg / hr or less normally, Preferably it is 700 kg / hr or less, More preferably, it is 500 kg / hr or less.

  If the charging speed is too high, mechanical energy is hardly imparted to the raw material graphite, the effect of roughening is difficult to appear, and the initial efficiency and cycle characteristics tend to be difficult to improve. Further, if it is slower than the charging speed, the productivity may be lowered.

(Ii) When performing the roughening process in a wet state Specific examples of the method for performing the roughening process in a wet state include an ultrasonic homogenizer and an ultrasonic cleaner.

  As a dispersion medium of raw material graphite, water and alcohols are preferable from the viewpoint of mass production, and pulverization aid particles and the like may be appropriately mixed. Furthermore, it is more effective when combined with mechanical energy that gives a shearing force with a stirring blade.

  For example, when an ultrasonic cleaner is used, it is performed as follows. After mixing raw material graphite and ion exchange water at a predetermined mass ratio, the mixture is stirred and then subjected to ultrasonic irradiation and then dried.

  When ultrasonic irradiation is performed, it is preferable to generate and disappear bubbles in a short time.

  The frequency is usually 10 Hz to 50000 Hz, preferably 20 Hz to 40000 Hz, and more preferably 30 Hz to 30000 Hz.

  The output is normally 10 W to 30000 W, preferably 20 W to 20000 W, and more preferably 30 W to 16000 W.

  The ultrasonic irradiation time is usually from 30 seconds to 20 hours, preferably from 60 seconds to 10 hours, more preferably from 120 seconds to 3 hours. If this time is short, the treatment effect tends to be insufficient. If the length is too long, particle destruction is promoted, battery characteristics are remarkably lowered, and mass productivity tends to be lowered.

  In mixing raw material graphite and ion-exchanged water, a mass ratio of 1: 1.1 to 1:30 is preferable. Preferably it is 1:20, More preferably, it is 1:10. When it becomes thinner than 1:30, the productivity tends to decrease. Conversely, when it becomes a concentrated liquid of 1: 1.1 or less, it is difficult to stir.

  In mixing raw material graphite and ion-exchanged water, a surfactant can be used. As the surfactant, a general commercial product can be selected. It is also effective for improving the dispersibility to mix the raw graphite after wetting it with an alcohol such as ethanol or isopropyl alcohol.

For drying, shelf drying is simple, but a model that can be dried while stirring or a baking furnace can also be used.
The drying temperature should just be 110 degreeC or more, and can be selected as needed.

  You may perform a modification | reformation process with respect to raw material graphite. For example, it is effective to coat coal tar pitch, resin, etc. and heat-treat, or simply heat-treat. Further, it is also effective to perform a regrinding process as an additional step.

(Raw organic material)
The raw material organic material used in the above production methods (I) and (II) is not particularly limited as long as it is a carbonaceous material that can be graphitized by firing. Coal heavy oil, DC heavy oil, cracked petroleum Examples include heavy oil, aromatic hydrocarbon, N ring compound, S ring compound, polyphenylene, organic synthetic polymer, natural polymer, carbonizable organic substance selected from the group consisting of thermoplastic resin and thermosetting resin. It is done. Moreover, in order to adjust the viscosity at the time of mixing, a raw material organic substance may be used by dissolving in a low molecular organic solvent.

  As coal-based heavy oil, coal tar pitch from dry pitch to hard pitch, dry distillation liquefied oil, etc. are preferable, and as DC heavy oil, normal pressure residual oil, reduced pressure residual oil, etc. are preferable, cracked petroleum heavy oil, etc. The crude oil is preferably ethylene tar or the like by-produced during thermal decomposition of crude oil, naphtha, etc., and the aromatic hydrocarbon is preferably acenaphthylene, decacyclene, anthracene, phenanthrene, etc., and the N-ring compound is phenazine, acridine, etc. Preferably, the S ring compound is preferably thiophene, bithiophene, etc., the polyphenylene is preferably biphenyl, terphenyl, etc., and the organic synthetic polymer is polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, insolubilization treatment thereof. Products, polyacrylonitrile, polypyrrole, polythiophene Polystyrene, etc. are preferred, natural polymers are preferably polysaccharides such as cellulose, lignin, mannan, polygalacturonic acid, chitosan, saccharose, etc., and thermoplastic resins are preferably polyphenylene sulfide, polyphenylene oxide, etc. As the curable resin, a furfuryl alcohol resin, a phenol-formaldehyde resin, an imide resin or the like is preferable.

  Moreover, as a low molecular organic solvent, benzene, toluene, xylene, quinoline, n-hexane, etc. are preferable.

(Mixing process)
The method of mixing the raw material graphite and the raw material organic material in the production methods (I) and (II) is not particularly limited, but the mixing can be performed using a general mixing apparatus. Specific examples include a mixer, a kneader, and a twin-screw kneader. In the mixing step, as described above, in order to adjust the viscosity at the time of mixing, a raw material organic material dissolved or diluted with a low molecular organic solvent may be used, or the viscosity of the raw material organic material may be adjusted by heating. . Moreover, the mixing ratio (mass ratio) of the raw material graphite and the raw material organic material is appropriately selected depending on the type of the raw material graphite and the raw material organic material to be used, and the amount of the raw material organic material with respect to 100 parts by mass of the raw material graphite is not particularly limited. Usually 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and usually 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 35 parts by mass or less.

(Baking process)
The method for firing the mixture of the raw material graphite and the raw material organic material in the production methods (I) and (II) is not particularly limited, but comprises a carbonization step for removing volatile components and a main heat treatment step.

  The carbonization step for removing volatile components is usually performed at a temperature of 600 ° C. or higher, preferably 650 ° C. or higher, usually 1300 ° C. or lower, preferably 1100 ° C. or lower, usually for 0.1 hour to 10 hours. In order to prevent oxidation, heating is usually performed in a non-oxidizing atmosphere in which an inert gas such as nitrogen or argon is circulated or a granular carbon material such as breeze or packing coke is filled in the gap.

  The equipment used for the carbonization process to remove volatiles is, for example, non-oxidizing reactors such as shuttle furnaces, tunnel furnaces, lead hammer furnaces, rotary kilns, autoclaves, cokers (heat treatment tanks for coke production), electric furnaces, gas furnaces, etc. The equipment is not particularly limited as long as it can be fired in an acidic atmosphere. The heating rate during heating is desirably a low speed for removing volatile components. Usually, from about 200 ° C. where low-boiling components start to volatilize to about 700 ° C. where only hydrogen is generated, 3-100 ° C. The temperature is raised at / hr. During the treatment, stirring may be performed as necessary.

  Next, the carbide obtained by the carbonization step is heated at a high temperature to perform the main heat treatment. When producing multi-layer graphite particles coated with amorphous carbon, it is usually 600 ° C. or higher, preferably 800 ° C. or higher, more preferably 900 ° C. or higher, more preferably 1000 ° C. or higher, in a non-oxidizing atmosphere. Usually, it may be fired at 2600 ° C. or less, preferably 2200 ° C. or less, more preferably 1800 ° C. or less, more preferably 1500 ° C. or less. In a neutral atmosphere, usually at 2300 ° C. or higher, preferably 2600 ° C. or higher, more preferably 2800 ° C. or higher. Moreover, since the sublimation of graphite will become remarkable when heating temperature is too high, 3300 degrees C or less is preferable. The heating may be performed for a period of time until the raw material organic material and the raw material graphite become graphite having a coated multilayer structure, and is usually 1 to 24 hours.

  In order to prevent oxidation, the atmosphere during graphitization is performed under a non-oxidizing atmosphere in which an inert gas such as nitrogen or argon is circulated or a granular carbon material such as breeze or packing coke is filled in the gap. The equipment used for graphitization is not particularly limited as long as it meets the above purpose, such as an electric furnace, a gas furnace, an electrode material Atchison furnace, etc. The heating rate, cooling rate, heat treatment time, etc. are acceptable for the equipment used. It can be set arbitrarily within the range.

(Other processes)
The fired product is subjected to powder processing such as pulverization, pulverization, grinding, and classification as required. There are no particular restrictions on the apparatus used for pulverization, for example, the coarse pulverizer includes a shearing mill, jaw crusher, impact crusher, cone crusher, etc., and the intermediate pulverizer includes a roll crusher, hammer mill, etc. Examples of the fine pulverizer include a ball mill, a vibration mill, a pin mill, a stirring mill, and a jet mill.

  There is no particular limitation on the apparatus used for classification, but for example, in the case of dry sieving, a rotary sieving, a swaying sieving, a rotating sieving, a vibrating sieving, etc. can be used. In this case, gravity classifier, inertial classifier, centrifugal classifier (classifier, cyclone, etc.) can be used, wet sieving, mechanical wet classifier, hydraulic classifier, sedimentation classifier A centrifugal wet classifier or the like can be used.

(About production method (III))
The details of steps 1 and 2 in the production method (III) are as follows.

  The apparatus used for the pulverization process in step 1 is not particularly limited. Examples of the coarse pulverizer include a shearing mill, a jaw crusher, an impact crusher, and a cone crusher. Examples of the intermediate pulverizer include a roll crusher and a hammer mill. Examples of the pulverizer include a ball mill, a vibration mill, a pin mill, a stirring mill, and a jet mill. As appropriate, classification treatment is performed to produce flake graphite having different particle sizes. And the process of the process 2 is performed to the scaly graphite obtained at the process 1.

  As an apparatus used for the spheroidizing process in the step 2, 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. Specific examples of the apparatus and conditions for the rotor of the apparatus are the same as those of the apparatus used for the production of raw material graphite in the production methods (I) and (II).

  By performing the spheronization step, the flaky graphite is folded, and spheroidized graphite having a high degree of circularity is obtained.

  Also, by using the spheroidized graphite as a raw material and coating at least a part of its surface with amorphous carbon or graphite, the particle size distribution half-value width (log (μm)) is 0.4 or more broad. Certain graphite particles can be produced.

  In order to coat with the amorphous carbon, the spheroidized graphite is mixed with a petroleum or coal-based tar or pitch, a resin such as polyvinyl alcohol, polyacrylonitrile, phenol resin, or cellulose, if necessary, using a solvent or the like. In a non-oxidizing atmosphere, it is usually 600 ° C. or higher, preferably 800 ° C. or higher, more preferably 900 ° C. or higher, more preferably 1000 ° C. or higher, usually 2600 ° C. or lower, preferably 2200 ° C. or lower, more preferably 1800 ° C. or lower, Preferably, it may be fired at 1500 ° C. or lower. If necessary, pulverization and classification may be performed after firing.

  The mass ratio of amorphous carbon covering the spheroidized graphite (spheroidized graphite: amorphous carbon) is preferably 1: 0.001 or more, and 1: 0.01 or more. It is more preferable. The mass ratio is preferably 1: 1 or less. That is, it is preferably in the range of 1: 0.001 to 1: 1. The mass ratio of the coating can be determined from the firing yield by a known method.

  By setting the mass ratio of the coating to 1: 0.001 or more, the high acceptability of lithium ions possessed by amorphous carbon can be fully utilized, and good rapid chargeability can be obtained in a non-aqueous secondary battery. . On the other hand, by setting the mass ratio of the coating to 1: 1 or less, it is possible to prevent a decrease in battery capacity due to an increase in the irreversible capacity of amorphous carbon.

  Next, in order to coat the spheroidized graphite with graphite, a resin or the like is added to the spheroidized graphite with a resin such as petroleum-based or coal-based tar or pitch, polyvinyl alcohol, polyacrylonitrile, phenol resin, cellulose or the like. The mixture may be used and baked in a non-oxidizing atmosphere at a temperature of usually 2000 ° C. or higher, preferably 2500 ° C. or higher and usually 3200 ° C. or lower.

  By firing at such a high temperature, the spheroidized graphite is coated with graphite. Note that pulverization and classification may be performed as necessary after firing.

  The mass ratio (spheroidized graphite: graphite) of the spheroidized graphite and the graphite covering it is preferably 1: 0.001 or more, and more preferably 1: 0.01 or more. The mass ratio is preferably 1: 1 or less. That is, it is preferably in the range of 1: 0.001 to 1: 1. The said mass ratio can be calculated | required by a well-known method from a baking yield.

  By setting the mass ratio to 1: 0.001 or more, side reactions with the electrolyte can be suppressed, and the irreversible capacity can be reduced in the lithium ion secondary battery, and the mass ratio is preferably 1: 1. The following is preferable because the charge / discharge capacity is improved and a high-capacity battery tends to be obtained.

(Mixed with other carbon materials)
The graphite particles for non-aqueous secondary batteries of the present invention produced by any one of the production methods (I) to (III) described above may be used alone or in any composition and combination of two or more. In combination, it can be suitably used as a negative electrode material for a non-aqueous secondary battery, but one or two or more kinds are mixed with another one or two or more other carbon materials, and this is mixed with a non-aqueous secondary battery. You may use as a negative electrode material of a battery, Preferably a lithium ion secondary battery.

  When the other carbon material is mixed with the non-aqueous secondary battery negative electrode material, the mixing ratio of the non-aqueous secondary battery negative electrode material to the total amount of the non-aqueous secondary battery negative electrode material and other carbon materials is usually 10% by mass. Above, preferably 20% by mass or more, and usually 90% by mass or less, preferably 80% by mass or less. When the mixing ratio of the negative electrode material for a non-aqueous secondary battery exceeds the above range, the effect of adding other carbon materials tends to hardly appear. On the other hand, if it falls below the above range, the characteristics of the negative electrode material for non-aqueous secondary batteries tend to hardly appear.

  As the other carbon material, a material selected from natural graphite, artificial graphite, amorphous-coated graphite, and amorphous carbon is used. Any one of these materials may be used alone, or two or more of these materials may be used in any combination and composition.

As the natural graphite, for example, highly purified flaky graphite or spheroidized graphite can be used. The volume-based average particle diameter of natural graphite is usually 8 μm or more, preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less. The natural graphite has a BET specific surface area of usually 3.5 m ² / g or more, preferably 4.5 m ² / g or more, and usually 8 m ² / g or less, preferably 6 m ² / g or less.

  Examples of the artificial graphite include particles obtained by graphitizing a carbon material. For example, particles obtained by firing and graphitizing a single graphite precursor particle while it is powdered can be used.

  As the amorphous coated graphite, for example, natural graphite or artificial graphite coated with an amorphous precursor and fired, or natural graphite or artificial graphite coated with amorphous by CVD can be used. .

  As the amorphous carbon, for example, particles obtained by firing a bulk mesophase, or particles obtained by firing an infusible carbonizable pitch or the like can be used.

  There are no particular restrictions on the device used for mixing the negative electrode material for non-aqueous secondary batteries and other carbon materials. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylinder mixer, a double cone Type mixer, regular cubic mixer, vertical mixer, fixed mixer: spiral mixer, ribbon mixer, Muller mixer, Helical Flyt mixer, Pugmill mixer, fluidization A type mixer or the like can be used.

<When mixing 3 or more types of carbon materials>
(Production method (IV))
The graphite particles for non-aqueous secondary batteries of the present invention can be produced by mixing three or more types of graphite particles having high circularity and different particle sizes.

  The above “three or more types of graphite particles having a high degree of circularity and different particle diameters” are, for example, graphite particles produced separately and having a circularity of 0.88 or more and a d50 of 0.5 μm or more. The three or more types of graphite particles in which the absolute value of the difference in d50 between the three types of graphite particles having a high degree of circularity among the graphite particles is 1 μm or more.

  The three or more types of graphite particles constituting the graphite particles of the present invention are not particularly limited, but are multilayered graphite particles coated with a carbonaceous material, particularly multilayered graphite coated with amorphous carbon or a graphite material. Particles are preferred, multi-layer structure graphite particles coated with amorphous carbon obtained by mixing and firing raw graphite and carbon precursor, and graphite obtained by mixing and firing raw graphite and carbon precursor Multi-layered graphite particles coated with a material are preferred.

  Moreover, the graphite particles of the present invention preferably contain 10% by mass or more of natural graphite, more preferably 30% by mass or more, and still more preferably 50% by mass or more, as the three or more types of graphite particles. The content is preferably 95% by mass or less, more preferably 90% by mass or less, and still more preferably 80% by mass or less. If the natural graphite ratio is too lower than this range, it is necessary to apply a larger load in order to increase the density of the electrode, which tends to cause a decrease in initial efficiency and cycle characteristics due to particle destruction. If the natural graphite ratio is too high, the cost will increase, and when the electrode is densified, particles on the electrode surface will be deformed, and electrolyte diffusion into the electrode will be hindered. There is a tendency for the cycle characteristics to deteriorate over time.

(Absolute value of d50 difference between three kinds of graphite particles with large circularity)
For the three or more types of graphite particles having different particle diameters, the absolute value of the difference in d50 between the graphite particles among the three types of graphite particles having a large degree of circularity, that is,
The absolute value (| d50 _(S1) −d50 _(S2) |) of the difference in d50 between the graphite particles having the highest circularity and the graphite particles having the second highest circularity,
The absolute value (| d50 _(S2) −d50 _(S3) |) of the difference in d50 between the graphite particles having the second highest circularity and the graphite particles having the third highest circularity;
The absolute value (| d50 _(S3) −d50 _(S1) |) of the difference in d50 between the graphite particles with the third highest circularity and the graphite particles with the highest circularity is:
In any case, the thickness is preferably 1 μm or more, more preferably 2 μm or more, and further preferably 2.5 μm or more. The absolute value of the difference in d50 between the three types of graphite particles is usually 30 μm or less, preferably 15 μm or less, and more preferably 10 m or less.

(Circularity of three kinds of graphite particles with large circularity)
The present invention is a graphite mixed particle obtained by mixing three or more types of graphite having different particle diameters, and the circularity of the three types of graphite particles having a large circularity is preferably 0.88 or more. The total mass ratio of the three types of graphite particles having a large degree of circularity, preferably 0.88 or more, is preferably 60% by mass or more, more preferably, the entire mixed particles (that is, the graphite particles of the present invention). It is 80 mass% or more, More preferably, it is 100 mass%.

  The circularity is determined by using a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial), using polyoxyethylene (20) monolaurate as a surfactant, and using ion-exchanged water as a dispersion medium. In addition, the degree of circularity is calculated by calculating the equivalent circle diameter. The equivalent circle diameter is the diameter of a circle (equivalent circle) having the same projected area as the photographed particle image, and the circularity is the circumference of the equivalent particle as a molecule and the circumference of the photographed particle projection image. The ratio is the denominator. When the circularity is 1, it becomes a theoretical sphere. The circularity of particles having a measured equivalent diameter in the range of 10 to 40 μm is averaged to obtain the circularity in the present invention.

(Ratio of press load of three kinds of graphite particles with large circularity)
Of the three types of graphite particles having a high degree of circularity, the press load of at least one graphite particle single material among them is preferably at least 3 times the press load of other graphite particle single materials, more preferably 3 .5 times or more, more preferably 3.8 times or more, and usually 10 times or less.

  As described above, the graphite particles of the present invention obtained by the production method (IV) are graphite mixed particles obtained by mixing three or more types of graphite particles having different particle diameters, and are provided between three types of graphite particles having a large degree of circularity. When the negative electrode for a non-aqueous secondary battery is produced using the graphite particles of the present invention, the absolute value of the difference in d50, the respective circularity, and the ratio of the press load are in the above ranges. Even when the electrode density is high and the total pore volume is small, the micropores that can move the electrolyte uniformly in the electrode can be maintained without being crushed. This makes it possible to produce a non-aqueous secondary battery that is excellent in performance.

(Raw material graphite)
As described above, there are no particular limitations on the three or more types of graphite particles constituting the graphite particles of the present invention obtained by the production method (IV), and in particular, non-obtainable material obtained by mixing and firing raw material graphite and a carbon precursor. Preferred are multilayer structured graphite particles coated with crystalline carbon, and multilayer structured graphite particles coated with a graphite obtained by mixing raw material graphite and a carbon precursor and firing.

  The raw graphite is not particularly limited as long as it is graphitized (or graphitized by firing at a temperature of 2300 ° C. or higher), but examples thereof include natural graphite, artificial graphite, and coke powder. Needle coke powder, resin graphitized (or graphitizable carbon) powder, and the like can be mentioned. Of these, natural graphite is preferable because it is easy to process.

  The form of the raw material graphite particles is not particularly limited, and examples thereof include a spherical shape, a spheroid shape, a lump shape, a plate shape, a scale shape, and a polygonal shape. A spherical shape, spheroid shape, lump shape, or polygonal shape is preferable because the particle filling property can be improved when graphite particles are used.

  As a device for obtaining spherical or spheroid graphite, for example, a device that repeatedly gives mechanical action such as compression, friction, shearing force, etc., including impact of the particles, including the interaction of particles, to the particles is used. Can do. 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 graphite. 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.

  Spherical or spheroidal graphite is formed into base particles that are made spherical by applying the spheroidizing step by the surface treatment described above, whereby the scale-like natural graphite is folded or the peripheral edge portion is spherically pulverized. The surface functional group O / C of the surface-treated graphite particles is usually 0.5% or more and 10% or less, preferably 1% or more and 4% or less. It manufactures by performing a spheronization process on the conditions which become. In this case, it is preferable to carry out in an active atmosphere so that the oxidation reaction of the graphite surface can be advanced by the energy of mechanical treatment and acidic functional groups can be introduced into the graphite surface. For example, when processing using the above-mentioned apparatus, the peripheral speed of the rotating rotor is usually preferably 30 to 100 m / sec, preferably 40 to 100 m / sec, and more preferably 50 to 100 m / sec. Further, the treatment can be performed simply by passing graphite, but it is preferable to circulate or stay in the apparatus for 30 seconds or more, and it is more preferable to circulate or stay in the apparatus for 1 minute or more. preferable.

(Particle size of raw graphite)
The volume-based average particle diameter of the raw graphite used in the production method (IV) is not particularly limited, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and particularly preferably 7 μm or more. Usually, it is 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, and particularly preferably 30 μm or less.

(Carbon precursor)
The carbon precursor is not particularly limited as long as it is carbonaceous that can be graphitized by firing. Examples thereof include coal-based heavy oil, direct-current heavy oil, cracked heavy oil, aromatic hydrocarbon. , N ring compounds, S ring compounds, polyphenylene, organic synthetic polymers, natural polymers, organic materials that can be carbonized selected from the group consisting of thermoplastic resins and thermosetting resins. Moreover, in order to adjust the viscosity at the time of mixing, a carbon precursor may be dissolved and used in a low molecular organic solvent.

  As coal-based heavy oil, coal tar pitch from dry pitch to hard pitch, dry distillation liquefied oil, etc. are preferable, and as DC heavy oil, normal pressure residual oil, reduced pressure residual oil, etc. are preferable, cracked petroleum heavy oil, etc. The crude oil is preferably ethylene tar or the like by-produced during thermal decomposition of crude oil, naphtha, etc., and the aromatic hydrocarbon is preferably acenaphthylene, decacyclene, anthracene, phenanthrene, etc., and the N-ring compound is phenazine, acridine, etc. Preferably, the S ring compound is preferably thiophene, bithiophene, etc., the polyphenylene is preferably biphenyl, terphenyl, etc., and the organic synthetic polymer is polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, insolubilization treatment thereof. Products, polyacrylonitrile, polypyrrole, polythiophene Polystyrene, etc. are preferred, natural polymers are preferably polysaccharides such as cellulose, lignin, mannan, polygalacturonic acid, chitosan, saccharose, etc., and thermoplastic resins are preferably polyphenylene sulfide, polyphenylene oxide, etc. As the curable resin, a furfuryl alcohol resin, a phenol-formaldehyde resin, an imide resin or the like is preferable.

  Moreover, as a low molecular organic solvent, benzene, toluene, xylene, quinoline, n-hexane, etc. are preferable.

(Mixing process)
The method of mixing the raw material graphite and the carbon precursor in the production of the multilayer structure graphite particles is not particularly limited, but can be carried out by a general mixing apparatus. Specific examples include a mixer, a kneader, and a twin-screw kneader. In the mixing step, as described above, a carbon precursor dissolved or diluted with a low molecular organic solvent may be used to adjust the viscosity at the time of mixing, and the viscosity of the carbon precursor is adjusted by heating. Also good. The mixing ratio (mass ratio) of the raw graphite and the carbon precursor is appropriately selected according to the type of raw graphite and carbon precursor used, and the amount of the carbon precursor with respect to 100 parts by mass of the raw graphite is particularly limited. However, it is usually 5 parts by mass or more, preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and usually 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 35 parts by mass or less.

(Baking process)
The method for firing the mixture of the raw material graphite and the carbon precursor in the production of the multilayer structure graphite particles is not particularly limited, but includes a carbonization step for removing volatile components and a main heat treatment step.

  The carbonization step for removing volatile components is usually performed at a temperature of 600 ° C. or higher, preferably 650 ° C. or higher, usually 1300 ° C. or lower, preferably 1100 ° C. or lower, usually for 0.1 to 10 hours. In order to prevent oxidation, heating is usually performed in a non-oxidizing atmosphere in which an inert gas such as nitrogen or argon is circulated or a granular carbon material such as breeze or packing coke is filled in the gap.

  The equipment used in the carbonization process to remove volatiles is non-oxidizing, for example, reactors such as shuttle furnaces, tunnel furnaces, reed hammer furnaces, rotary kilns, autoclaves, cokers (heat treatment tanks for coke production), electric furnaces, gas furnaces, etc. There is no particular limitation as long as it can be baked in a neutral atmosphere. The heating rate during heating is desirably a low speed for removing volatile components. Usually, from about 200 ° C. where low-boiling components start to volatilize to about 700 ° C. where only hydrogen is generated, 3-100 ° C. The temperature is raised at / hr. During the treatment, stirring may be performed as necessary.

  The carbide obtained by the carbonization step is then heated at a high temperature to perform the main heat treatment. When producing multi-layer graphite particles coated with amorphous carbon, it is usually 600 ° C. or higher, preferably 800 ° C. or higher, more preferably 900 ° C. or higher, more preferably 1000 ° C. or higher, in a non-oxidizing atmosphere. Usually, it may be fired at 2600 ° C. or less, preferably 2200 ° C. or less, more preferably 1800 ° C. or less, more preferably 1500 ° C. or less. In a neutral atmosphere, usually at 2300 ° C. or higher, preferably 2600 ° C. or higher, more preferably 2800 ° C. or higher. Moreover, since the sublimation of graphite will become remarkable when heating temperature is too high, 3300 degrees C or less is preferable. The heating time may be performed until the binder and the carbonaceous particles become graphite, and is usually 1 to 24 hours.

  In order to prevent oxidation, the atmosphere during graphitization is performed under a non-oxidizing atmosphere in which an inert gas such as nitrogen or argon is circulated or a granular carbon material such as breeze or packing coke is filled in the gap. The equipment used for graphitization is not particularly limited as long as it meets the above purpose, such as an electric furnace, a gas furnace, an electrode material Atchison furnace, etc. The heating rate, cooling rate, heat treatment time, etc. are acceptable for the equipment used. It can be set arbitrarily within the range.

  In the multi-layer structure graphite particles obtained by the above steps, the mass ratio of the amorphous carbon covering the raw material graphite as a nucleus (raw material graphite: amorphous carbon) is 1: 0.001 or more. It is preferable that the ratio is 1: 0.01 or more. The mass ratio is preferably 1: 1 or less, more preferably 1: 0.2 or less, and still more preferably 1: 0.1 or less. That is, it is preferably in the range of 1: 0.001 to 1: 1. By setting the mass ratio of the coating to 1: 0.001 or more, high acceptability of lithium ions possessed by amorphous carbon can be sufficiently utilized, and good rapid chargeability can be obtained in a lithium ion secondary battery. . On the other hand, by setting the mass ratio of the coating to 1: 1 or less, it is possible to prevent a decrease in battery capacity due to an increase in the irreversible capacity of amorphous carbon.

  The mass ratio of the graphite material (raw material graphite: graphite material) is preferably 1: 0.01 or more, more preferably 1: 0.05 or more, and 1: 0.1 or more. Is more preferable. The mass ratio is preferably 1: 1 or less, more preferably 1: 0.5 or less, and further preferably 1: 0.2 or less. That is, it is preferably in the range of 1: 0.01 to 1: 1. By setting the mass ratio of the graphite material to 1: 0.01 or more, when the active material layer applied to the current collector is rolled to a high density, particle breakage / deformation is suppressed, and a good large current charge / discharge There is a tendency to obtain characteristics. On the other hand, when the mass ratio of the graphite material is set to 1: 1 or less, the press load required when the active material layer applied to the current collector is rolled at a high density is moderately low. It tends to lead to higher capacity of the secondary battery. The mass ratio of the coating can be determined from the firing yield by a known method.

(Other processes)
The fired product is subjected to powder processing such as pulverization, pulverization, grinding, and classification as required. There are no particular restrictions on the apparatus used for pulverization, for example, the coarse pulverizer includes a shearing mill, jaw crusher, impact crusher, cone crusher, etc., and the intermediate pulverizer includes a roll crusher, hammer mill, etc. Examples of the fine pulverizer include a ball mill, a vibration mill, a pin mill, a stirring mill, and a jet mill.

  There is no particular limitation on the apparatus used for classification, but for example, in the case of dry sieving, a rotary sieving, a swaying sieving, a rotating sieving, a vibrating sieving, etc. can be used. In this case, gravity classifier, inertial classifier, centrifugal classifier (classifier, cyclone, etc.) can be used, wet sieving, mechanical wet classifier, hydraulic classifier, sedimentation classifier A centrifugal wet classifier or the like can be used.

[Non-aqueous secondary battery]
The basic configuration of the non-aqueous secondary battery of the present invention, particularly the lithium ion secondary battery, is the same as that of a conventionally known non-aqueous secondary battery, and usually includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte. Is provided. The negative electrode of the present invention described above is used as the negative electrode. When producing a non-aqueous secondary battery using this negative electrode, there is no particular limitation on selection of members necessary for the battery configuration such as a positive electrode and an electrolyte constituting the non-aqueous secondary battery. Hereinafter, although the detail of the non-aqueous secondary battery using the negative electrode of this invention is illustrated, the material which can be used, the manufacturing method, etc. are not limited to the following specific examples.

  First, the positive electrode is obtained by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector.

Examples of the positive electrode active material include metal chalcogen compounds that can occlude and release alkali metal cations such as lithium ions during charge and discharge. Examples of metal chalcogen compounds include vanadium oxide, molybdenum oxide, manganese oxide, chromium oxide, titanium oxide, tungsten oxide and other transition metal oxides, vanadium sulfide, molybdenum sulfide. things, sulfides of titanium, transition metal sulfides such as CuS, NIPS _3, FEPS phosphorus transition metals, such as ₃ - sulfur compounds, VSe _2, NbSe ₃ selenium compounds of transition metals, such as, Fe _0.25 V _0.75 S _2, Examples thereof include composite oxides of transition metals such as Na _0.1 CrS ₂ and composite sulfides of transition metals such as LiCoS ₂ and LiNiS ₂ .

Among these, V ₂ O ₅ , V ₅ O ₁₃ , VO ₂ , Cr ₂ O ₅ , MnO ₂ , TiO, MoV ₂ O ₈ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , TiS ₂ , V ₂ S ₅ , Cr _0.25 V _0.75 S ₂ , Cr _0.5 V _0.5 S _2, etc. are preferable. LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _4, and lithium transitions in which some of these transition metals are replaced with other metals are particularly preferable. It is a metal complex oxide. These positive electrode active materials may be used alone or in combination.

  A known binder can be arbitrarily selected and used as the binder for binding the positive electrode active material. Examples include inorganic compounds such as silicate and water glass, and resins having no unsaturated bond such as Teflon (registered trademark) and polyvinylidene fluoride. Among these, a resin having no unsaturated bond is preferable. If a resin having an unsaturated bond is used as the resin for binding the positive electrode active material, the resin may be decomposed during the oxidation reaction. The weight average molecular weight of these resins is usually 10,000 or more, preferably 100,000 or more, and usually 3 million or less, preferably 1 million or less.

  The positive electrode active material layer may contain a conductive material in order to improve the conductivity of the electrode. The conductive material is not particularly limited as long as it can be mixed with an appropriate amount in the active material to impart conductivity, but is usually carbon powder such as acetylene black, carbon black, and graphite, various metal fibers, powder, and foil. Etc.

  The positive electrode plate is formed by slurrying a positive electrode active material and a binder with a solvent in the same manner as in the production of the negative electrode as described above, and applying and drying on a current collector. As the current collector of the positive electrode, aluminum, nickel, SUS, or the like is used, but is not limited at all.

  As the electrolyte, a non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent, or a gel, rubber, or solid sheet obtained by using an organic polymer compound or the like from the non-aqueous electrolyte is used.

  The non-aqueous solvent used in the non-aqueous electrolyte is not particularly limited, and can be appropriately selected from known non-aqueous solvents that have been conventionally proposed as solvents for non-aqueous electrolytes. For example, chain carbonates such as diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate; chain ethers such as 1,2-dimethoxyethane; tetrahydrofuran, 2-methyl Examples include cyclic ethers such as tetrahydrofuran, sulfolane, and 1,3-dioxolane; chain esters such as methyl formate, methyl acetate, and methyl propionate; and cyclic esters such as γ-butyrolactone and γ-valerolactone.

  Any one of these non-aqueous solvents may be used alone, or two or more thereof may be mixed and used. In the case of a mixed solvent, a combination of a mixed solvent containing a cyclic carbonate and a chain carbonate is preferable, and the cyclic carbonate is a mixed solvent of ethylene carbonate and propylene carbonate. This is particularly preferable in that load characteristics are improved. Among them, propylene carbonate is preferably in the range of 2 wt% to 80 wt%, more preferably in the range of 5 wt% to 70 wt%, and still more preferably in the range of 10 wt% to 60 wt% with respect to the entire non-aqueous solvent. When the proportion of propylene carbonate is lower than the above, the ionic conductivity at low temperature is lowered, and when the proportion of propylene carbonate is higher than the above, when a graphite electrode is used, the PC solvated with Li ions coexists between the graphite phases. Insertion causes delamination degradation of the graphite-based negative electrode active material, and there is a problem that sufficient capacity cannot be obtained.

The lithium salt used in the non-aqueous electrolytic solution is not particularly limited, and can be appropriately selected from known lithium salts that can be used for this purpose. For example, halides such as LiCl and LiBr, perhalogenates such as LiClO ₄ , LiBrO ₄ and LiClO ₄ , inorganic lithium salts such as inorganic fluoride salts such as LiPF ₆ , LiBF ₄ and LiAsF ₆ , LiCF ₃ SO ₃ , Fluorine-containing organic lithium salts such as perfluoroalkanesulfonic acid salts such as LiC ₄ F ₉ SO ₃ and perfluoroalkanesulfonic acid imide salts such as Li trifluorosulfonimide ((CF ₃ SO ₂ ) ₂ NLi) Of these, LiClO ₄ , LiPF ₆ , and LiBF ₄ are preferable.

  Lithium salts may be used alone or in combination of two or more. The concentration of the lithium salt in the non-aqueous electrolyte is usually in the range of 0.5M to 2.0M.

  In addition, when an organic polymer compound is included in the above non-aqueous electrolyte and used in the form of a gel, rubber, or solid sheet, specific examples of the organic polymer compound include polyethylene oxide, polypropylene oxide, and the like. Polyether polymer compounds; Cross-linked polymers of polyether polymer compounds; Vinyl alcohol polymer compounds such as polyvinyl alcohol and polyvinyl butyral; Insolubilized vinyl alcohol polymer compounds; Polyepichlorohydrin; Polyphosphazene; Siloxane; vinyl polymer compounds such as polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile; poly (ω-methoxyoligooxyethylene methacrylate), poly (ω-methoxyoligooxyethylene methacrylate-co-methyl methacrylate) Rate) and polymer copolymers such as poly (hexafluoropropylene-vinylidene fluoride).

  The non-aqueous electrolytic solution described above may further contain a film forming agent. Specific examples of the film forming agent include carbonate compounds such as vinylene carbonate, vinylethyl carbonate, and methylphenyl carbonate; alken sulfides such as ethylene sulfide and propylene sulfide; sultone compounds such as 1,3-propane sultone and 1,4-butane sultone And acid anhydrides such as maleic acid anhydride and succinic acid anhydride. Furthermore, an overcharge inhibitor such as diphenyl ether or cyclohexylbenzene may be added. When the above additives are used, the content is usually 10% by mass or less, preferably 8% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less. If the content of the additive is too large, other battery characteristics such as an increase in initial irreversible capacity, low temperature characteristics, and deterioration in rate characteristics may be adversely affected.

  Further, as the electrolyte, a polymer solid electrolyte which is a conductor of an alkali metal cation such as lithium ion can be used. Examples of the polymer solid electrolyte include a polymer in which a salt of Li is dissolved in the aforementioned polyether polymer compound, and a polymer in which the terminal hydroxyl group of the polyether is substituted with an alkoxide.

  In order to prevent a short circuit between the electrodes, a porous separator such as a porous film or a nonwoven fabric is usually interposed between the positive electrode and the negative electrode. In this case, the nonaqueous electrolytic solution is used by impregnating a porous separator. As a material for the separator, polyolefin such as polyethylene and polypropylene, polyethersulfone, and the like are used, and polyolefin is preferable.

  The form of the nonaqueous secondary battery of the present invention is not particularly limited. Examples include 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 type in which a pellet electrode and a separator are stacked, and the like. In addition, by storing batteries of these forms in an optional outer case, the battery can be used in an arbitrary shape such as a coin shape, a cylindrical shape, or a square shape.

  The procedure for assembling the non-aqueous secondary battery of the present invention is not particularly limited, and may be assembled by an appropriate procedure according to the structure of the battery. For example, the negative electrode is placed on the outer case, and the electrolytic solution is placed thereon. A separator is provided, and a positive electrode is placed so as to face the negative electrode, and it is caulked together with a gasket and a sealing plate to form a battery.

  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. In addition, the measuring method of each physical property shall follow the measuring method mentioned above.

<Measurement method of initial efficiency>
Using a non-aqueous secondary battery (2016 coin-type battery) produced by the method described later, the initial efficiency during battery charging / discharging was measured by the following measurement method.

After charging to 5 mV with respect to the lithium counter electrode at a current density of 0.16 mA / cm ² , and further charging until the charge capacity value becomes 350 mAh / g at a constant voltage of 5 mV, after doping lithium in the negative electrode, 0 The battery was discharged to 1.5 V with respect to the lithium counter electrode at a current density of .33 mA / cm ² . Subsequently, the second and third times were charged at 10 mV and 0.005 Ccut by cc-cv charging at the same current density, and the discharge was discharged to 1.5 V at 0.04 C at all times. The sum of the difference between the charge capacity and the discharge capacity for a total of three cycles was calculated as an irreversible capacity. The discharge capacity at the third cycle was defined as the discharge capacity of the material, and the discharge capacity of the material / (discharge capacity of the material + irreversible capacity) was defined as the initial efficiency.

<Measurement method of cycle maintenance ratio>
The laminate type battery manufactured by the method described later is charged to 4.2V at 0.8C, and discharged to 3.0V at 0.5C. The 100th and 200th cycles of the discharge capacity of the first cycle are repeated. The ratio of discharge capacity × 100 was defined as the cycle retention rate (%).

<Production of electrode sheet>
An electrode plate having an active material layer with an active material layer density of 1.80 ± 0.03 g / cm ³ was produced using the graphite particles of the examples or comparative examples. Specifically, 20.00 ± 0.02 g of negative electrode material 20.00 ± 0.02 g of a 1% by mass aqueous solution of sodium carboxymethylcellulose (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.

Further, the linear pressure (kg / 5 cm) necessary for rolling so that the density of the negative electrode active material layer was 1.8 g / cm ³ was obtained as a press load.

<Preparation of non-aqueous secondary battery (2016 coin type battery)>
The electrode sheet produced by the above method was punched into a disk shape with a diameter of 12.5 mm, and a lithium metal foil was punched into a disk shape with 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). 2016 coin type batteries were prepared.

<Production method of non-aqueous secondary battery (laminated battery)>
The electrode sheet produced by the above method was cut into a square of 4 cm × 3 cm to form a negative electrode, a positive electrode made of LiCoO ₂ was cut out with the same area, and a separator (made of a porous polyethylene film) was placed between the negative electrode and the positive electrode. A: LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio = 20: 20: 60) to 1 mol / L, and 2% by volume of vinylene carbonate was added as an additive. LiPF ₆ was dissolved in a mixed electrolyte (B: ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate) (volume ratio = 30:40:30) to 1 mol / L, and vinylene carbonate was further added as an additive. 500 μl of an electrolyte solution containing 2% by volume of electrolyte was injected to prepare a laminate type battery.

[Example of constituting graphite particles of the present invention with a single carbon material]
[Example 1]
Spherical natural graphite having a volume-based average particle diameter of 17 μm is used as raw material graphite, and a grinding device comprising a rotor and a stator is used as a roughening process, and the rotor is ground at a peripheral speed of 145 m / sec and an input speed of 200 kg / hr. A graphite having an uneven structure was obtained. With respect to 100 parts by mass of the obtained graphite, a raw material organic matter pitch having a quinoline insoluble content ≦ 0.5% and a softening point of 80 ° C. was mixed at a ratio of 30 parts by mass using a kneader. After making this compound into a molded body by performing pressure treatment at ² kgf / cm ² (0.20 MPa) for 1 minute using a mold press molding machine, de-VM firing is performed at 1000 ° C. in an inert atmosphere, Further, graphitization was performed at 3000 ° C. The obtained graphite compact was roughly crushed, finely pulverized, and classified to obtain a powder sample made of graphite particles. In the obtained powder sample, it was confirmed that the mass ratio of the spherical natural graphite particles to the graphite material (spherical natural graphite particles: graphitic material) was 1: 0.15. With respect to this sample, the liquid absorption coefficient, particle size, SA, Tap density, DBP oil absorption, Raman R value, pore volume Vi, total pore volume, and surface functional group O / C were measured by the above measurement methods.

  The results and the results of measuring the cycle retention ratio (using the electrolytic solution A) and the initial efficiency according to the measurement method are shown in Table 1 below. Moreover, the SEM observation photograph of the said powder sample is shown in FIG. As a result of SEM observation, it was observed that an uneven structure was formed on the particle surface.

[Example 2]
A powder sample made of graphite particles was obtained in the same manner as in Example 1 except that the circumferential speed of the rotor was set to 125 m / sec as the roughening step. About this, the physical property, the evaluation of battery characteristics, and SEM observation were performed by the same method as Example 1. The results are shown in Table 1 below.

[Comparative Example 1]
A powder sample made of graphite particles was obtained in the same manner as in Example 1 except that the roughening step was not performed. About this, the physical property and the battery characteristic were evaluated by the same method as Example 1. The results are shown in Table 1 below.

  FIG. 3 shows an SEM observation photograph of the powder sample obtained in this example. As a result of SEM observation, an uneven structure was not observed on the particle surface.

[Example of mixing three or more types of carbon materials]
<Carbon material>
Next, the structure of the graphite particles used in Examples 3 and 4 and Comparative Example 2 below will be described.

  Graphite particles A: As a raw material graphite, 100 parts by mass of spherical natural graphite having a volume-based average particle diameter of 16.8 μm was mixed with a pitch of the raw material organic substance at a ratio of 30 parts by mass using a kneader. After the resulting mixture was molded, it was fired and carbonized at 1000 ° C. in an inert atmosphere, and further graphitized at 3000 ° C. The obtained graphite compact was roughly crushed and pulverized to obtain a powder sample made of graphite particles.

  Multi-layer structure carbon particle B: Spherical natural graphite having a volume-based average particle size of 11.3 μm as raw material graphite is mixed with petroleum heavy oil obtained at the time of naphtha pyrolysis as an amorphous carbon precursor, and inert gas In this, heat treatment at 1300 ° C. was performed. The fired product obtained was pulverized and classified to obtain multi-layered carbon particles B. Further, from the firing yield, in the obtained multi-layer structure carbon particle B, the mass ratio of the spheroidized graphite particles to the amorphous carbon (spherical natural graphite particles: amorphous carbon) is 1: 0.03. It was confirmed that there was.

  Multi-layer structure carbon particle C: A spherical heavy graphite having a volume-based average particle diameter of 11.3 μm as a raw material graphite is mixed with a petroleum heavy oil obtained at the time of naphtha pyrolysis as an amorphous carbon precursor, and an inert gas. In this, heat treatment at 1300 ° C. was performed. The fired product obtained was pulverized and classified to obtain multi-layered carbon particles C. Further, from the firing yield, in the obtained multi-layer structure carbon particles C, the mass ratio of the spheroidized graphite particles to the amorphous carbon (spherical natural graphite particles: amorphous carbon) is 1: 0.06. It was confirmed that there was.

  Multi-layer structure carbon particle D: A spherical heavy graphite having a volume-based average particle diameter of 16.3 μm as a raw material graphite and a heavy petroleum oil obtained at the time of naphtha pyrolysis as an amorphous carbon precursor are mixed with an inert gas. In this, heat treatment at 1300 ° C. was performed. The fired product obtained was pulverized and classified to obtain multi-layered carbon particles D. Further, from the firing yield, in the obtained multi-layer structure carbon particle D, the mass ratio of the spheroidized graphite particles to the amorphous carbon (spherical natural graphite particles: amorphous carbon) is 1: 0.03. It was confirmed that there was.

  Spherical natural graphite particles E: Spherical natural graphite whose volume-based average particle diameter, Tap density, specific surface area (SA), and circularity are values shown in Table 2 below.

  Spherical natural graphite particles F: Spherical natural graphite whose volume-based average particle diameter, Tap density, specific surface area (SA), and circularity are values shown in Table 2 below.

  Spherical natural graphite particles G: Spherical natural graphite whose volume-based average particle diameter, Tap density, specific surface area (SA), and circularity are values shown in Table 2 below.

  The physical properties of the above carbon materials are shown in Table 2 below.

[Example 3]
Graphite particles A, multi-layered carbon particles B, spherical natural graphite particles E, and spherical natural graphite particles F were mixed at a ratio of 20% by mass: 40% by mass: 27% by mass: 13% by mass to obtain samples. . About this sample and the non-aqueous secondary battery produced therefrom, the liquid absorption coefficient, the fine pore volume of 80 nm to 900 nm, the particle size, SA, Tap density, initial efficiency, cycle maintenance rate (electrolytic solution) B was used). The results are shown in Table 3 below. In addition, | d50 _(S1) -d50 _(S2) |, | d50 _(S2) -d50 _(S3) |, | d50 _(S3) -d50 _(S1) | The press load ratio (the press load ratio between the multi-layer structure carbon particles B and the spherical natural graphite particles E) between the large and small ones was calculated. The results are shown in Table 4 below.

[Example 4]
Graphite particles A, multi-layered carbon particles C, spherical natural graphite particles E, and spherical natural graphite particles F were mixed at a ratio of 20% by mass: 40% by mass: 27% by mass: 13% by mass to obtain samples. . About this sample and the non-aqueous secondary battery produced therefrom, the liquid absorption coefficient, the fine pore volume of 80 nm to 900 nm, the particle size, SA, Tap density, initial efficiency, cycle maintenance rate (electrolytic solution) B was used). The results are shown in Table 3 below. In addition, | d50 _(S1) -d50 _(S2) |, | d50 _(S2) -d50 _(S3) |, | d50 _(S3) -d50 _(S1) | The press load ratio (the press load ratio between the multi-layer structure carbon particles C and the spherical natural graphite particles E) between the large and small ones was calculated. The results are shown in Table 4 below.

[Comparative Example 2]
Graphite particles A, multi-layered carbon particles D, spherical natural graphite particles E, and spherical natural graphite particles G were mixed at a ratio of 20% by mass: 40% by mass: 27% by mass: 13% by mass to obtain samples. . About this sample and the non-aqueous secondary battery produced therefrom, the liquid absorption coefficient, the fine pore volume of 80 nm to 900 nm, the particle size, SA, Tap density, initial efficiency, cycle maintenance rate (electrolytic solution) B was used). The results are shown in Table 3 below. In addition, | d50 _(S1) -d50 _(S2) |, | d50 _(S2) -d50 _(S3) |, | d50 _(S3) -d50 _(S1) | The press load ratio (the press load ratio between the multi-layer structure carbon particles D and the spherical natural graphite particles E) between the large and small ones was calculated. The results are shown in Table 4 below.

From the above results, the following can be understood.
From Table 1, the comparative example 1 did not perform the process of roughening the raw material graphite, and the liquid absorption coefficient was outside the specified range of the present invention. As a result, a high cycle retention rate was not obtained. On the other hand, in Examples 1 and 2, by performing the process of roughening the raw material graphite, the liquid absorption coefficient was within the range of the present invention, and as a result, a high cycle retention rate was obtained.

From Tables 3 and 4, in Comparative Example 2, | d50 _(S1) -d50 _(S2) | is 0.6 μm among d50 of the three types of graphite particles selected in descending order of circularity, and the press load ratio Since the liquid absorption coefficient is outside the specified range of the present invention, as a result, a high cycle maintenance ratio was not obtained.

  On the other hand, in Examples 3 and 4, d50 between the three types of graphite particles selected in descending order of circularity differs by 2.5 μm or more, and the press load ratio is also within the range of the present invention. Within the scope of the present invention, as a result, a high cycle retention rate was obtained.

  By using the graphite particles of the present invention as a negative electrode material for a non-aqueous secondary battery, it is possible to provide a non-aqueous secondary battery with high initial efficiency and good cycle characteristics.

Claims (10)

A negative electrode for a non-aqueous secondary battery, wherein the liquid absorption coefficient is 0.11 mg / sec ^0.5 or more.   2. The negative electrode for a non-aqueous secondary battery according to claim 1, wherein a fine pore volume having a pore diameter of 80 nm or more and 900 nm or less is 0.08 ml / g or more. Nonaqueous secondary of claim 1 or 2, wherein the density of the active material layer constituting the negative electrode for nonaqueous secondary battery is not more than 1.5 g / cm ³ or more 1.9 g / cm ³ Battery negative electrode.   A graphite mixed particle in which three or more types of graphite particles having different particle diameters are mixed, and the absolute value of the difference in d50 between the three types of graphite particles having a high degree of circularity is 2.5 μm or more. A graphite particle for a non-aqueous secondary battery.   The non-aqueous secondary battery graphite particles according to claim 4, wherein the three types of graphite particles having a large degree of circularity each have a circularity of 0.88 or more.   5. The press load of at least one kind of graphite particle single material among these three kinds of graphite particles having a large circularity is three times or more the press load of other graphite particle single materials. Or the graphite particle for non-aqueous secondary batteries of 5.   The total mass ratio of the three types of graphite particles having a large degree of circularity in the entire graphite particles for non-aqueous secondary batteries is 60% by mass or more, according to any one of claims 4 to 6. The graphite particle for non-aqueous secondary batteries as described.   The graphite particles for nonaqueous secondary batteries according to any one of claims 4 to 7, comprising natural graphite.   A non-aqueous secondary battery graphite particle according to any one of claims 4 to 8, wherein the active material layer includes a current collector and an active material layer formed on the current collector. A negative electrode for a non-aqueous 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 negative electrode for a non-aqueous secondary battery according to any one of claims 1 to 3 and 9. A non-aqueous secondary battery.