JP2016184581A - Method of manufacturing negative electrode material for nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method that can manufacture a negative electrode material for nonaqueous secondary batteries having various types of particle structures, enables mass processing, and can stably manufacture a negative electrode material which is high in sphere degree, excellent in filling performance and less in anisotropy and contains less fine particles.SOLUTION: In a manufacturing method for a negative electrode material for a nonaqueous secondary battery having a granulation step of granulating raw material graphite by applying mechanical energy of at least impact, compression, friction and shearing force, the step of granulating the raw material graphite is performed under the presence of granulation agent satisfying the following conditions (1) and (2): (1) the granulation agent is liquid in the step of granulating the raw material graphite; and (2) the granulation agent does not contain organic solvent, or when the granulation agent contains organic solvent, at least one of the organic solvent has no flash point or the flash point is equal to 5°C or more when the at least one of the organic solvent has a flash point.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a negative electrode material for a non-aqueous secondary battery.

In recent years, there has been an increasing demand for higher performance for non-aqueous secondary batteries with high energy density and excellent high-current charge / discharge characteristics, achieving higher capacity, higher input / output, and longer life. It is requested to do.
For non-aqueous secondary batteries, it is known to use a carbon material such as graphite as the negative electrode material. And as a negative electrode material for lithium ion secondary batteries among non-aqueous secondary batteries, a capacity close to 372 mAh / g, which is the theoretical capacity of lithium storage, can be obtained, and furthermore, it is excellent in cost and durability. Therefore, graphite having a high degree of graphitization is considered preferable as a negative electrode material.

  As the negative electrode material, for example, in Patent Document 1, flaky natural graphite is spheroidized by applying mechanical energy, and the obtained spherical natural graphite is used as a core to coat amorphous carbon on the surface. Thus, a technique for improving filling properties and high-speed charge / discharge characteristics is disclosed.

  In Patent Document 2, scaly natural graphite, a fusible organic substance, and a pitch having a softening point of 70 ° C. are heated and kneaded, and after mechanical impact is applied by a hybridizer apparatus, carbon black is added to further mechanical impact. Is disclosed in which a spheroidized powder is obtained by firing and a negative electrode material powder is obtained by firing it. Patent Document 3 discloses a method of obtaining spherical graphite particles having a smooth particle surface by introducing a resin binder into raw graphite particles and spheroidizing the particles. In Patent Document 4, a method is known in which coal-based calcined coke and paraffin wax are heated and stirred at high speed to form a spherical shape.

Japanese Patent No. 3534391 JP 2008-305722 A JP 2014-114197 A WO2014 / 141372

However, according to the study by the present inventors, the spheroidized natural graphite disclosed in Patent Document 1 has a high capacity and good rapid charge / discharge characteristics compared to the flaky graphite used as a raw material. Since the adhesion between the particles is poor, there is a problem that battery characteristics and processability are deteriorated due to the remaining of scaly graphite and generation of fine powder during spheroidization.
In addition, the negative electrode material powder disclosed in Patent Document 2 is in a state in which the meltable organic matter and pitch contained in the spheroidized graphite contain a softened solid, so that the adhesion between the raw material graphites is inadequate. It was sufficient, and the effect of improving the battery characteristics by suppressing the scale-like graphite remaining and the generation of fine powder during spheroidization was insufficient.
Similarly, in the method for producing spheroidized graphite disclosed in Patent Document 3, the adhesive force between graphite particles by adding a resin binder is small, and the effect of improving battery characteristics by suppressing the generation of fine powder is insufficient. On the other hand, a technique of adding a resin binder solution dissolved in a toluene solvent to spheroidize is also disclosed as an example, but since the flash point of the solvent is low, the temperature rises above the flash point due to the temperature rise during the spheronization treatment, Further improvements are necessary because of the risk of explosion and fire during manufacture.
Further, Patent Document 4 does not disclose a method of granulating graphite into a spherical shape, and paraffin wax is solid, so that the effect of suppressing the generation of fine powder during spheronization and the effect of improving battery characteristics are insufficient.

  The present invention has been made in view of the background art, and the problem is that in a method for producing a negative electrode material for a non-aqueous secondary battery having a step of granulating raw material graphite, non-aqueous secondary particles having various types of particle structures are provided. Production capable of producing a negative electrode material for a secondary battery, capable of mass processing, having a high degree of spheroidization, good fillability, low anisotropy, and having a small amount of fine powder. It is to provide a method. Furthermore, by the above manufacturing method, a negative electrode material capable of obtaining a non-aqueous secondary battery having high capacity and excellent input / output characteristics is provided, and as a result, a high-performance non-aqueous secondary battery is provided. There is to do.

As a result of intensive studies to solve the above problems, the present inventors,
A method for producing a negative electrode material for a non-aqueous secondary battery, comprising a granulation step of granulating raw material graphite by applying at least one of mechanical energy of impact, compression, friction and shear force, wherein the raw material graphite A method for producing a negative electrode material for a non-aqueous secondary battery, characterized in that the step of granulating is performed in the presence of a granulating agent that satisfies the following conditions 1) and 2):
1) Liquid at the time of granulating the raw material graphite 2) When the granulating agent does not contain an organic solvent or contains an organic solvent, at least one of the organic solvents has no flash point, or the flash point When it has, the flash point is 5 ° C. or more, and the above-mentioned problems have been solved.

A more specific summary of the present invention is as follows.
(1) A method for producing a negative electrode material for a non-aqueous secondary battery, comprising a granulation step of granulating raw material graphite by applying at least one of mechanical energy of impact, compression, friction, and shear force, The said granulation process is performed in presence of the granulating agent which satisfies the conditions of following 1) and 2), The manufacturing method characterized by the above-mentioned.
1) Liquid at the time of granulating the raw material graphite 2) When the granulating agent does not contain an organic solvent or contains an organic solvent, at least one of the organic solvents has no flash point, or the flash point (2) The granulation agent has a contact angle θ of less than 90 ° with graphite measured by the following measurement method. Method.
<Measuring method of contact angle θ with graphite>
When 1.2 μl of the granulating agent is dropped on the HOPG surface and the wetting spread converges and the dripping granulated agent has a contact angle θ change rate of 3% or less per second, the contact angle is defined as the contact angle. It measures with a measuring apparatus (Kyowa Interface Co., Ltd. automatic contact angle meter DM-501). Here, when using a granulating agent having a viscosity at 25 ° C. of 500 cP or less, the value at 25 ° C. is used, and when using a granulating agent having a viscosity at 25 ° C. of more than 500 cP, the viscosity reaches 500 cP or less. The value at the heated temperature is taken as the measured value of the contact angle θ.
(3) The manufacturing method according to (1) or (2), wherein the granulating agent has a viscosity of 1 cP or more during the granulating step.
(4) The method according to any one of (1) to (3), wherein the granule has a viscosity at 25 ° C. of 1 cP or more and 100,000 cP or less.
(5) The production according to any one of (1) to (4), wherein the raw graphite contains at least one selected from the group consisting of scaly, scaly, and massive natural graphite. Method.
(6) The manufacturing method according to any one of (1) to (5), wherein the raw material graphite has d002 of 0.34 nm or less.
(7) In the granulation step, the raw material graphite is granulated in the presence of at least one selected from the group consisting of a metal that can be alloyed with Li and its oxide, amorphous carbon, and raw coke. The manufacturing method according to any one of (1) to (6).
(8) The production method according to any one of (1) to (7), wherein the granulation step is performed in an atmosphere of 0 ° C. or higher and 250 ° C. or lower.
(9) The granulation step includes a rotating member that rotates at a high speed in the casing, and in a device having a rotor in which a plurality of blades are installed in the casing, the graphite introduced into the interior by rotating the rotor at a high speed. The method according to any one of (1) to (8), wherein granulation is performed by applying any one of impact, compression, friction, and shearing force. (10) The method according to any one of (1) to (9), further including a step of attaching a carbonaceous material having lower crystallinity than raw graphite to the granulated graphite obtained by the granulation step. Production method.

  According to the production method of the present invention, in the method for producing a negative electrode material for non-aqueous secondary batteries having a step of granulating raw material graphite, various types of particle structure negative electrode materials for non-aqueous secondary batteries can be produced, Massive processing is possible, and it is possible to stably produce spheroidized graphite particles having a moderately increased particle size, a high degree of spheroidization, good filling properties, small anisotropy and few fine powders.

The present inventors consider the reason why the above effect is achieved as follows.
By adding a granulating agent, a liquid bridge is formed between a plurality of particles to form a liquid bridge (which means that a bridge is formed between particles by a liquid). The attractive force generated by the capillary negative pressure and the surface tension of the liquid acts as a liquid crosslinking adhesion force between the particles, the liquid crosslinking adhesion force between the raw material graphites increases, and the raw material graphites can adhere more firmly. Further, the granulating agent acts as a lubricant, thereby reducing the pulverization of the raw material graphite. Furthermore, since most of the fine powder generated during the granulation step adheres to the raw material graphite due to the above-described effect of increasing the liquid-crosslinking adhesion, particles independent as fine powder are reduced. As a result, it becomes possible to produce spheroidized graphite particles in which the raw graphites adhere more firmly, the particle size increases moderately, the degree of spheroidization is high, and the amount of fine powder is small.

In addition, when the granulating agent contains an organic solvent, the organic solvent does not have a flash point, or when it has a flash point, the flash point is 5 ° C. or higher, so that the impact and heat generation during the granulation step. Therefore, it is possible to prevent the risk of ignition, fire, and explosion of the granulating agent, which makes it possible to produce spheroidized graphite particles stably and efficiently.
The negative electrode material produced by the production method of the present invention has a structure in which fine powder having many insertion and desorption sites of Li ions is present on the particle surface and inside. Furthermore, by having a structure granulated by a plurality of raw material graphites, it is possible to effectively and efficiently use not only the outer peripheral part of the particle but also the Li ion insertion / desorption site existing inside the particle. As a result, it is considered that excellent input / output characteristics could be obtained by using the negative electrode material obtained according to the present invention for a non-aqueous secondary battery.

  Hereinafter, the contents of the present invention will be described in detail. In addition, description of the invention structural requirements 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.

The present invention is a method for producing a negative electrode material for a non-aqueous secondary battery having a granulation step of granulating raw material graphite by applying at least one of mechanical energy of impact, compression, friction and shear force. The granulation step is performed in the presence of a granulating agent that satisfies the following conditions 1) and 2), and is a method for producing a negative electrode material for a non-aqueous secondary battery.
1) Liquid at the time of granulating the raw material graphite 2) When the granulating agent does not contain an organic solvent or contains an organic solvent, at least one of the organic solvents has no flash point, or the flash point The flash point is 5 ° C. or higher.
If it has the said granulation process, you may further have another process as needed. Another process may be implemented independently and multiple processes may be implemented simultaneously. As one embodiment, the following first to sixth steps are included.

(1st process) The process of adjusting the particle size of raw material graphite (2nd process) The process of mixing raw material graphite and a granulating agent (3rd process) The process of granulating raw material graphite (4th process) Step of removing (fifth step) Step of purifying granulated graphite (sixth step) Step of adding a carbonaceous material having lower crystallinity than raw graphite to the granulated graphite Hereinafter, these steps will be described.

(1st process) The process of adjusting the particle size of raw material graphite The raw material graphite used by this invention is not specifically limited, Artificial graphite and natural graphite can be used. Among them, it is preferable to use natural graphite because of its high crystallinity and high capacity.

Examples of the artificial graphite include coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, polyvinyl Examples include those obtained by baking and graphitizing organic substances such as alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin.
The firing temperature can be in the range of 2500 ° C. or more and 3200 ° C. or less, and a silicon-containing compound, a boron-containing compound, or the like can be used as a graphitization catalyst during firing.

  Natural graphite is classified into flake graphite (Crystalline Graphite), massive graphite (Vein Graphite), and soil graphite (Amorphous Graphite) according to the properties (“granular process technology assembly”). (See, Industrial Technology Center Co., Ltd., published in 1974) Graphite section, and “HANDBOOK OF CARBON, GRAPHITE, DIAMOND AND FULLLENES” (issued by Noyes PubLications)). The degree of graphitization is the highest at 100% for scaly graphite and massive graphite, followed by graphite with the highest degree of scaly graphite at 99.9% and high degree of graphitization in the present invention. Among them, those having few impurities are preferable, and can be used after being subjected to various known purification treatments, if necessary.

  Natural graphite is produced in Madagascar, China, Brazil, Ukraine, Canada, etc. Of the natural graphite, the production area of scaly graphite is mainly Sri Lanka, and the main production area of soil graphite is the Korean Peninsula, China, Mexico, and the like. Examples of natural graphite include scaly, scaly, massive, or plate-like natural graphite. Among these, scaly graphite is preferable.

  The average particle diameter (d50) of these raw material graphites is preferably 1 μm or more, more preferably 2 μm or more, further preferably 3 μm or more, preferably 80 μm or less, more preferably 50 μm or less, still more preferably 35 μm or less, and very preferably It is 20 μm or less, particularly preferably 10 μm or less, and most preferably 8 μm or less. The average particle diameter can be measured by the method described later.

When the average particle size is in the above range, the fine powder generated during the granulation step adheres to the base material that becomes granulated graphite (hereinafter referred to as granulated graphite) or is wrapped inside the base material. It becomes possible to granulate, and granulated graphite having a high degree of spheroidization and a small amount of fine powder can be obtained.

As a method of adjusting the average particle diameter (d50) of the raw material graphite to the above range, for example, a method of pulverizing and / or classifying graphite particles can be mentioned.
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 mechanical pulverizer, an airflow pulverizer, and a swirl flow pulverizer. Specific examples include a ball mill, a vibration mill, a pin mill, a stirring mill, a jet mill, a cyclone mill, and a turbo mill. In particular, when obtaining graphite particles of 10 μm or less, it is preferable to use an airflow pulverizer or a swirl flow pulverizer.
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 classifiers, inertial force classifiers, centrifugal classifiers (classifiers, cyclones, etc.) can be used. A centrifugal wet classifier or the like can be used.

The raw material graphite preferably satisfies the following physical properties.
The ash contained in the raw material graphite is preferably 1% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.1% by mass or less with respect to the total mass. Moreover, it is preferable that the minimum of ash content is 1 ppm or more.
When the ash content is within the above range, when the non-aqueous secondary battery is used, it is possible to suppress deterioration of battery performance due to the reaction between the negative electrode material and the electrolytic solution during charge / discharge to a level that can be ignored. Moreover, since a great amount of time, energy, and equipment for preventing contamination are not required for manufacturing the negative electrode material, an increase in cost can be suppressed.

  The aspect ratio of the raw material graphite is preferably 3 or more, more preferably 5 or more, still more preferably 10 or more, and particularly preferably 15 or more. Further, it is preferably 1000 or less, more preferably 500 or less, still more preferably 100 or less, and particularly preferably 50 or less. The aspect ratio is measured by the same method as the method for measuring the aspect ratio in the powder state of the negative electrode material described later. When the aspect ratio is within the above range, it is difficult to obtain large particles having a particle size of about 100 μm, while it becomes easy to obtain strong granulated graphite.

002 plane spacing (d002) and crystallite size (Lc) of raw graphite by X-ray wide angle diffraction method are usually d002 of 3.37 mm or less, (Lc) of 900 mm or more, and d002 of 3.36 mm. In the following, it is preferable that (Lc) is 950 mm or more. The face spacing d002 and the crystallite size (Lc) are values indicating the crystallinity of the negative electrode material bulk. The smaller the face spacing d002 value of the 002 face and the larger the crystallite size (Lc). This indicates that the negative electrode material has high crystallinity, and the capacity increases because the amount of lithium entering the graphite layer approaches the theoretical value. When the crystallinity is low, excellent battery characteristics (high capacity and low irreversible capacity) when high crystalline graphite is used for the electrode are not exhibited. It is particularly preferable that the above-mentioned ranges are combined for the interplanar spacing d002 and the crystallite size (Lc).
X-ray diffraction is measured by the following method. Carbon powder is mixed with X-ray standard high-purity silicon powder of about 15% by mass of the total amount, and CuKα ray monochromatized with a graphite monochromator is used as a radiation source. A line diffraction curve is measured. Thereafter, the interplanar spacing (d002) and the crystallite size (Lc) are obtained using the Gakushin method.

The filling structure of raw material graphite depends on the size, shape, degree of interaction force between particles, etc., but in this specification, tap density is applied as one of the indicators for quantitatively discussing the filling structure. It is also possible. In the study by the present inventors, it has been confirmed that in the case of lead-like particles having a true density and an average particle size substantially equal, the tap density increases as the shape is spherical and the particle surface is smoother. In other words, in order to increase the tap density, it is important to round the shape of the particle so that it is close to a sphere, and to maintain smoothness except for the surface and chipping of the particle surface. When the particle shape approaches a spherical shape and the particle surface is smooth, the powder filling property is greatly improved. The tap density of the raw material graphite is preferably 0.1 g / cm ³ or more, more preferably 0.2 g / cm ³ or more, and further preferably 0.3 g / cm ³ or more. The tap density is measured by the method described later in the examples.

The argon ion laser Raman spectrum of the raw graphite is used as an index showing the surface properties of the particles. Raman R value is the peak intensity ratio in the vicinity of 1360 cm ^-1 to the peak intensity near 1580 cm ^-1 in the argon ion laser Raman spectrum of the raw material graphite is preferably 0.05 to 0.9, more preferably 0. It is 05 or more and 0.7 or less, More preferably, it is 0.05 or more and 0.5 or less. The R value is an index representing the crystallinity in the vicinity of the surface of the carbon particle (from the particle surface to about 100 °), and the smaller the R value, the higher the crystallinity or the disordered crystal state. The Raman spectrum is measured by the method shown below. Specifically, the sample particle is naturally dropped into the Raman spectrometer measurement cell, and the sample cell is filled with the sample. While irradiating the measurement cell with an argon ion laser beam, Measure while rotating. Note that the wavelength of the argon ion laser light is 514.5 nm.

  Information obtained by the X-ray wide angle diffraction method of raw graphite is used as an index representing the crystallinity of the entire particle. The scaly graphite preferably has a ratio 3R / 2H of 101 plane strength 3R (101) based on rhombohedral crystal structure by X-ray wide angle diffraction method and 101 plane strength 2H (101) based on hexagonal crystal structure. .1 or more, more preferably 0.15 or more, still more preferably 0.2 or more. The rhombohedral crystal structure is a crystal form in which a stack of graphite network structures is repeated every three layers. Moreover, the hexagonal crystal structure is a crystal form in which the stacking of the graphite network structure is repeated every two layers. In the case of scaly graphite showing a crystal form with a large ratio of rhombohedral crystal structure 3R, the acceptability of Li ions is higher than that of graphite with a small ratio of rhombohedral crystal structure 3R.

The specific surface area of the raw material graphite by the BET method is preferably 1 m ² / g or more and 30 m ² / g or less, more preferably 2 m ² / g or more and 20 m ² / g or less, further preferably 5 m ² / g or more and 15 m ² / g or less. It is. The specific surface area by BET method is measured by the method of the Example mentioned later. When the specific surface area of the raw material graphite is within the above range, the acceptability of Li ions becomes good, and a decrease in battery capacity due to an increase in irreversible capacity can be prevented.

  The amount of water contained in the scaly graphite as a raw material for the spheroidized graphite of the raw graphite is preferably 1% by mass or less, more preferably 0.5% by mass or less, and more preferably 0.5% by mass or less, based on the total mass of the scaly graphite. Preferably it is 0.1 mass% or less, Especially preferably, it is 0.05 mass% or less, Most preferably, it is 0.01 mass% or less. Moreover, it is preferable that the minimum of a moisture content is 1 ppm or more. The water content can be measured by a method based on JIS M8811, for example. When the amount of water is within the above range, the electrostatic attractive force between the particles increases during the spheronization treatment, so that the interparticle adhesion increases, and the fine powder adheres to the base material and is encapsulated in the spheroidized particles. It is easy and preferable. Moreover, the wettability fall when using a hydrophobic granule can be prevented.

In order to make the moisture content of the flake graphite used as the raw material of the spheroidized graphite within the above range, a drying treatment can be performed as necessary. The treatment temperature is usually 60 ° C. or higher, preferably 100 ° C. or higher, more preferably 200 ° C. or higher, more preferably 250 ° C. or higher, particularly preferably 300 ° C. or higher, most preferably 350 ° C., and usually 1500 ° C. or lower. , Preferably 1000
° C or lower, more preferably 800 ° C or lower, still more preferably 600 ° C or lower. If it is too low, there is a tendency that the amount of water cannot be sufficiently reduced, and if it is too high, there is a tendency that productivity is lowered and cost is increased.

The drying treatment time is usually 0.5 to 48 hours, preferably 1 to 40 hours, more preferably 2 to 30 hours, and further preferably 3 to 24 hours. If it is too long, the productivity will be lowered, and if it is too short, the heat treatment effect will not be sufficiently exhibited.
The atmosphere of the heat treatment includes an active atmosphere such as an air atmosphere or an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere. When heat treatment is performed at 200 ° C. to 300 ° C., there is no particular limitation, but the heat treatment is performed at 300 ° C. or higher. In the case of performing the above, an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere is preferable from the viewpoint of preventing oxidation of the graphite surface.

(Second step) Step of mixing raw material graphite and granulating agent The granulating agent used in the present invention is 1) liquid during the step of granulating the raw material graphite and 2) does the granulating agent contain no organic solvent? When an organic solvent is contained, at least one of the organic solvents does not have a flash point, or when it has a flash point, the flash point satisfies the condition of 5 ° C. or higher.
By having a granulating agent that satisfies the above requirements, the granulating agent is liquid-crosslinked between the raw material graphites in the subsequent step of granulating the raw material graphite in the third step, so Since the attractive force generated by the capillary negative pressure and the surface tension of the liquid acts as the liquid cross-linking adhesion force between the particles, the liquid cross-linking adhesion force between the raw material graphites increases and the raw material graphite can adhere more firmly.

  In the present invention, the strength of the liquid cross-linking adhesion force between the raw material graphite due to the liquid cross-linking between the raw material graphite is proportional to the γ cos θ value (where γ: surface tension of the liquid, θ: liquid and Particle contact angle). That is, when granulating the raw material graphite, it is preferable that the granulating agent has high wettability with the raw material graphite. Specifically, a granulating agent that satisfies cos θ> 0 is selected so that γ cos θ value> 0. It is preferable that the contact angle θ with graphite measured by the following measuring method of the granulating agent is less than 90 °.

<Measuring method of contact angle θ with graphite>
When 1.2 μl of a granulating agent is dropped on the surface of HOPG (Highly Oriented Pyrolytic Graphite), the wetting spread converges and the rate of change of the contact angle θ per second becomes 3% or less (also called steady state). The contact angle is measured with a contact angle measuring device (automatic contact angle meter DM-501 manufactured by Kyowa Interface Co., Ltd.). Here, when using a granulating agent having a viscosity at 25 ° C. of 500 cP or less, the value at 25 ° C. is used, and when using a granulating agent having a viscosity at 25 ° C. of more than 500 cP, the viscosity reaches 500 cP or less. The measured value of the contact angle θ at the heated temperature.

  Furthermore, as the contact angle θ between the raw material graphite and the granulating agent is closer to 0 °, the γ cos θ value increases, so that the liquid crosslinking adhesion between graphite particles increases and the graphite particles can adhere more firmly. It becomes. Accordingly, the contact angle θ of the granulating agent with graphite is more preferably 85 ° or less, further preferably 80 ° or less, further preferably 50 ° or less, and more preferably 30 ° or less. It is particularly preferable that the angle is 20 ° or less.

  Even when a granulating agent having a large surface tension γ is used, the γ cos θ value is increased and the adhesion of graphite particles is improved. Therefore, γ is preferably 0 or more, more preferably 15 or more, and further preferably 30 or more. .

  The surface tension γ of the granulating agent used in the present invention is measured by a Wilhelmy method using a surface tension meter (for example, DCA-700 manufactured by Kyowa Interface Science Co., Ltd.).

In addition, a viscous force acts as a resistance component against the elongation of the liquid bridge accompanying the movement of the particles, and its magnitude is proportional to the viscosity. For this reason, the viscosity of the granulating agent is not particularly limited as long as it is liquid during the granulation step of granulating the raw material graphite, but is preferably 1 cP or more during the granulation step.
Further, the viscosity at 25 ° C. of the granulating agent is preferably 1 cP or more and 100,000 cP or less, more preferably 5 cP or more and 10000 cP or less, further preferably 10 cP or more and 8000 cP or less, and 50 cP or more and 6000 cP or less. Is particularly preferred. When the viscosity is within the above range, it is possible to prevent the adhered particles from being detached due to an impact force such as a collision with a rotor or a casing when the raw graphite is granulated.

The viscosity of the granulating agent used in the present invention is measured by using a rheometer (for example, ARES manufactured by Rheometric Scientific Co.), putting an appropriate amount of a measuring object (in this case, a granulating agent) in a cup and adjusting the temperature to a predetermined temperature. When the shear stress at a shear rate of 100 s ⁻¹ is 0.1 Pa or more, the value measured at the shear rate of 100 s ⁻¹ is measured, and when the shear stress at the shear rate of 100 s ⁻¹ is less than 0.1 Pa, measured at 1000 s ⁻¹ . When the shear stress at a shear rate of 1000 s ⁻¹ is less than 0.1 Pa, the value measured at the shear rate at which the shear stress is 0.1 Pa or more is defined as the viscosity in this specification. Note that the shear stress can be set to 0.1 Pa or more by making the spindle to be used in a shape suitable for a low-viscosity fluid.

  Furthermore, the granulating agent used in the present invention does not contain an organic solvent, or when it contains an organic solvent, at least one of the organic solvents does not have a flash point or has a flash point. It is 5 ° C or higher. As a result, when granulating the raw material graphite in the subsequent third step, it is possible to prevent the danger of ignition, fire, and explosion of organic compounds induced by impact or heat generation, so that stable and efficient production is possible. Can be implemented.

Examples of the granulating agent used in the present invention include, for example, paraffinic oil such as coal tar, petroleum heavy oil, liquid paraffin, synthetic oil such as olefinic oil, naphthenic oil and aromatic oil, and vegetable oils and fats. Organic oils such as resin binder solutions in which a resin binder is dissolved in an organic solvent having a flash point of 5 ° C. or higher, preferably 21 ° C. or higher, natural oils such as fatty acids of animals, esters, higher alcohols, etc. And aqueous solvents thereof, and mixtures thereof. Organic solvents with a flash point of 5 ° C or higher include alkylbenzenes such as xylene, isopropylbenzene, ethylbenzene and propylbenzene, alkylnaphthalenes such as methylnaphthalene, ethylnaphthalene and propylnaphthalene, and aromatic carbonization such as allylbenzene such as styrene and allylnaphthalene. Hydrogen, aliphatic hydrocarbons such as octane, nonane, decane, ketones such as methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, esters such as propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, methanol , Ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene Alcohols such as lenglycol and glycerine, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, methoxypropanol, methoxypropyl-2- Acetate, methoxymethyl butanol, methoxybutyl acetate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, triethylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol monophenyl Glycol derivatives such as nyl ether, ethers such as 1,4-dioxane, nitrogen-containing compounds such as dimethylformamide, pyridine, 2-pyrrolidone and N-methyl-2-pyrrolidone, and sulfur-containing compounds such as dimethyl sulfoxide , Dichloromethane, chloroform, carbon tetrachloride,
Examples include halogen-containing compounds such as dichloroethane, trichloroethane, and chlorobenzene, and mixtures thereof. For example, those having a low flash point such as toluene are not included. These organic solvents can be used alone as a granulating agent. In the present specification, the flash point can be measured by a known method.

  A well-known thing can be used as a resin binder. For example, cellulose-based resin binders such as ethyl cellulose, methyl cellulose, and salts thereof, acrylic resin binders such as polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, polyacrylic acid, and salts thereof, polymethyl methacrylate, Methacrylic resin binders such as polyethyl methacrylate and polybutyl methacrylate, and phenol resin binders can be used. Among these, coal tar, petroleum heavy oil, paraffinic oil such as liquid paraffin, and aromatic oil are preferable because they can produce a negative electrode material having a high degree of spheroidization and a small amount of fine powder.

  As a granulating agent, it can be efficiently removed in the step of removing the granulating agent (fourth step), which will be described later, and has an adverse effect on battery characteristics such as capacity, input / output characteristics and storage / cycle characteristics. Those having no properties are preferred. Specifically, when heated to 700 ° C. in an inert atmosphere, the weight loss is usually 50% or more, preferably 80% or more, more preferably 95% or more, still more preferably 99% or more, and particularly preferably 99.9% or more. Can be selected as appropriate.

  As a method of mixing raw material graphite and a granulating agent, for example, a method of mixing raw material graphite and a granulating agent using a mixer or a kneader, or granulation in which an organic compound is dissolved in a low viscosity diluent solvent (organic solvent) And a method of removing the diluent solvent (organic solvent) after mixing the agent and the raw material graphite. Further, when granulating the raw material graphite in the subsequent third step, the step of introducing the granulating agent and the raw material graphite into the granulating device, mixing the raw material graphite and the granulating agent, and the step of granulating The method of performing simultaneously is also mentioned.

  The amount of the granulating agent added is preferably 0.1 parts by weight or more, more preferably 1 part by weight or more, still more preferably 3 parts by weight or more, still more preferably 6 parts by weight or more, relative to 100 parts by weight of the raw material graphite. More preferably 10 parts by weight or more, particularly preferably 12 parts by weight or more, most preferably 15 parts by weight or more, preferably 1000 parts by weight or less, more preferably 100 parts by weight or less, still more preferably 80 parts by weight or less, Particularly preferred is 50 parts by weight or less, and most preferred is 20 parts by weight or less. Within the above range, problems such as a decrease in spheroidization due to a decrease in adhesion between particles and a decrease in productivity due to adhesion of raw graphite to the apparatus are less likely to occur.

(Third step) Step of granulating raw material graphite The present invention has a granulating step of granulating raw material graphite by applying at least one of mechanical energy of impact, compression, friction, and shear force. As an apparatus used in this step, for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force and the like including interaction of raw material graphite mainly with impact force can be used.

Specifically, it has a rotor with a large number of blades installed inside the casing, and the rotor rotates at a high speed, so that mechanical graphite such as impact, compression, friction, and shear force is applied to the raw material graphite introduced inside. An apparatus that provides an action and performs surface treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating raw material graphite.
As such an apparatus, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), kryptron, kryptron orb (manufactured by Earth Technica), CF mill (manufactured by Ube Industries), mechano-fusion system, nobilta, faculty ( Hosokawa Micron Co., Ltd.), Theta Composer (manufactured by Tokuju Kogakusho Co., Ltd.), COMPOSI (manufactured by Nippon Coke Industries), and the like. Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable.

When processing using the apparatus, for example, the peripheral speed of the rotating rotor is preferably 30 m / second or more, more preferably 50 m / second or more, still more preferably 60 m / second or more, particularly preferably 70 m / second or more, most preferably Preferably it is 80 m / sec or more, preferably 100 m / sec or less. Within the above range, it is preferable because the fine powder can be adhered to the base material and enclosed by the base material at the same time as the spheroidization.
Further, the treatment that gives mechanical action to the raw graphite can be performed simply by passing the raw graphite, but the raw graphite is preferably processed by circulating or staying in the apparatus for 30 seconds or more, more preferably. The treatment is performed by circulating or staying in the apparatus for 1 minute or more, more preferably 3 minutes or more, particularly preferably 5 minutes or more.

  In the step of granulating raw material graphite, raw material graphite may be granulated in the presence of other substances. Examples of other substances include metals that can be alloyed with lithium or oxides thereof, and amorphous substances. Examples include carbon and raw coke. By granulating together with materials other than raw material graphite, negative electrode materials for non-aqueous secondary batteries having various types of particle structures can be produced.

  In addition, the raw material graphite, the granulating agent, and the other substances described above may be charged all in the apparatus, or may be sequentially added separately, or may be continuously added. In addition, the raw material graphite, the granulating agent, and the other substances may be simultaneously charged into the apparatus, may be mixed, or may be separately charged. The raw material graphite, the granulating agent, and the above other substances may be mixed simultaneously, or the above other substances may be added to the mixture of the raw material graphite and the granulating agent, or the other substances and the granulating agent. Raw material graphite may be added to the mixture. In addition to the particle design, it can be added and mixed separately at an appropriate timing.

(4th process) The process of removing a granulating agent In this invention, you may have the process of removing the said granulating agent. Examples of the method for removing the granulating agent include a method of washing with a solvent and a method of volatilizing and decomposing and removing the granulating agent by heat treatment.
The heat treatment temperature is preferably 60 ° C. or higher, more preferably 100 ° C. or higher, further preferably 200 ° C. or higher, still more preferably 300 ° C. or higher, particularly preferably 400 ° C. or higher, most preferably 500 ° C., preferably 1500 ° C. ° C or lower, more preferably 1000 ° C or lower, still more preferably 800 ° C or lower. Within the above range, the granulating agent can be sufficiently volatilized and decomposed and productivity can be improved.

  The heat treatment time is preferably 0.5 to 48 hours, more preferably 1 to 40 hours, still more preferably 2 to 30 hours, and particularly preferably 3 to 24 hours. Within the above range, the granulating agent can be sufficiently volatilized and decomposed and productivity can be improved.

  The atmosphere of the heat treatment includes an active atmosphere such as an air atmosphere or an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere. When heat treatment is performed at 200 ° C. to 300 ° C., there is no particular limitation, but the heat treatment is performed at 300 ° C. or higher. In the case of performing the above, an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere is preferable from the viewpoint of preventing oxidation of the graphite surface.

(Fifth Step) Step of Purifying Granulated Graphite In the present invention, a step of purifying granulated graphite may be included. Examples of a method for purifying granulated graphite include a method of acid treatment including nitric acid and hydrochloric acid, and metals and metal compounds in graphite without introducing a sulfate which can be a highly active sulfur source into the system. It is preferable because impurities such as inorganic compounds can be removed.
The acid treatment may be performed using an acid containing nitric acid or hydrochloric acid. Other acids such as inorganic acids such as bromic acid, hydrofluoric acid, boric acid or iodic acid, or citric acid, formic acid, acetic acid, An acid in which an organic acid such as acid, trichloroacetic acid or trifluoroacetic acid is appropriately mixed can also be used. Concentrated hydrofluoric acid, concentrated nitric acid and concentrated hydrochloric acid are preferable, and concentrated nitric acid and concentrated hydrochloric acid are more preferable. In the present invention, graphite may be treated with sulfuric acid, but it is used in such an amount and concentration that does not impair the effects and physical properties of the present invention.

  When a plurality of acids are used, for example, a combination of hydrofluoric acid, nitric acid, and hydrochloric acid is preferable because the impurities can be efficiently removed. As described above, the mixing ratio of the mixed acids when the types of acids are combined is usually 10% by mass or more, preferably 20% by mass or more, and more preferably 25% by mass or more. The upper limit is a value obtained by mixing all equal amounts (represented by 100% by mass / acid type).

  The mixing ratio (mass ratio) of graphite and acid in the acid treatment is usually 100: 10 or more, preferably 100: 20 or more, more preferably 100: 30 or more, and still more preferably 100: 40 or more. : 1000 or less, preferably 100: 500 or less, more preferably 100: 300 or less.

The acid treatment is performed by immersing graphite in the acidic solution as described above. The immersion time is usually 0.5 to 48 hours, preferably 1 to 40 hours, more preferably 2 to 30 and even more preferably 3 to 24 hours.
The immersion temperature is usually 25 ° C. or higher, preferably 40 ° C. or higher, more preferably 50 ° C. or higher, and still more preferably 60 ° C. or higher. The theoretical upper limit in the case of using an aqueous acid is 100 ° C., which is the boiling point of water.

  It is preferable to carry out further water washing for the purpose of removing the remaining acid content by acid washing and raising the pH from weakly acidic to neutral range. For example, if the treated graphite has a pH of usually 3 or higher, preferably 3.5 or higher, more preferably 4 or higher, and still more preferably 4.5 or higher, washing with water can be omitted, and if the above range is satisfied. Otherwise, it is preferable to wash with water as necessary. It is preferable to use ion-exchanged water or distilled water as the water to be washed from the viewpoint of improving the washing efficiency and preventing impurities from being mixed. The specific resistance that is an indicator of the amount of ions in water is usually 0.1 MΩ · cm or more, preferably 1 MΩ · cm or more, more preferably 10 MΩ · cm or more. The theoretical upper limit at 25 ° C. is 18.24 MΩ · cm.

The time for washing with water, that is, stirring the treated graphite and water is usually 0.5 to 48 hours, preferably 1 to 40 hours, more preferably 2 to 30 hours, still more preferably 3 to 24 hours. is there.
The mixing ratio of the treated graphite and water is usually 100: 10 or more, preferably 100: 30 or more, more preferably 100: 50 or more, still more preferably 100: 100 or more, and 100: 1000 or less. Preferably it is 100: 700 or less, More preferably, it is 100: 500 or less, More preferably, it is 100: 400 or less.

  The stirring temperature is usually 25 ° C. or higher, preferably 40 ° C. or higher, more preferably 50 ° C. or higher, and still more preferably 60 ° C. or higher. The upper limit is 100 ° C., which is the boiling point of water. Moreover, when performing a water washing process by a batch type, it is preferable from a viewpoint of an impurity and acid content removal to wash by repeating the process process of stirring-filtration in a pure water in multiple times. The above treatment may be repeated so that the above-mentioned treated graphite has a pH in the above range. Usually, it is 1 or more times, preferably 2 or more times, more preferably 3 or more times.

  By performing the treatment as described above, the wastewater ion concentration of the obtained graphite is usually 200 ppm or less, preferably 100 ppm or less, more preferably 50 ppm or less, more preferably 30 ppm or less, and usually 1 ppm or more, preferably 2 ppm or more. More preferably, it is 3 ppm or more, and further preferably 4 ppm or more.

(Sixth step) Step of attaching a carbonaceous material having lower crystallinity to the raw graphite than the raw material graphite In the present invention, the step of attaching a carbonaceous material having lower crystallinity to the raw graphite It may be. According to this process, the negative electrode material which can suppress a side reaction with electrolyte solution and can improve rapid charge / discharge property can be obtained.
A composite graphite obtained by adding a carbonaceous material having a lower crystallinity than the raw graphite to the granulated graphite is sometimes referred to as “carbonaceous material composite graphite”.

  The carbonaceous material adhering treatment to the granulated graphite is a mixture of an organic compound that becomes a carbonaceous material and granulated graphite, and heated in a non-oxidizing atmosphere, preferably under a flow of nitrogen, argon, carbon dioxide, etc. Is carbonization or graphitization.

(Mixing of granulated graphite particles and organic compounds)
The step of mixing the granulated graphite particles with the organic compound to be the carbonaceous material precursor is as follows.

  There are no particular restrictions on the method of mixing the granulated graphite particles with the organic compound that becomes the carbonaceous material precursor. For example, the granulated graphite particles and the organic compound that becomes the carbonaceous material precursor can be mixed with various commercial mixers and kneaders. And the like to obtain a mixture in which an organic compound adheres to graphite particles.

  The granulated graphite particles, the organic compound that becomes the carbonaceous material precursor, and the raw materials such as a solvent as necessary are mixed under heating as necessary. Thereby, it will be in the state by which the organic compound used as a liquid carbonaceous material precursor was attached to the granulated graphite particle. In this case, all the raw materials may be charged into the mixer and mixing and heating may be performed at the same time, or components other than the organic compound serving as the carbonaceous material precursor may be charged into the mixer and preheated in a stirred state until the temperature reaches the mixing temperature. An organic compound that becomes a carbonaceous material precursor that has been melted by normal temperature or preheating after the temperature rises may be added. When the granulated graphite particles and the organic compound that becomes the carbonaceous material precursor come into contact with each other, the organic compound that becomes the carbonaceous material precursor is cooled to increase the viscosity to prevent the coating form from becoming uneven. Ingredients other than the organic compound that becomes the carbonaceous material precursor are charged into the machine, preheated with stirring, and after the temperature rises to the mixing temperature, the organic compound becomes the carbonaceous material precursor that is preheated to the mixing temperature and is in a molten state It is more preferable to add.

  The heating temperature is usually higher than the softening point of the organic compound that becomes the carbonaceous material precursor, preferably higher than the softening point by 10 ° C., more preferably higher than the softening point by 20 ° C., more preferably higher by 30 ° C. It is carried out at a temperature, particularly preferably at a temperature of 50 ° C. or higher, usually 450 ° C. or lower, preferably 250 ° C. or lower. If the heating temperature is too low, the viscosity of the organic compound that becomes the carbonaceous material precursor becomes high and mixing becomes difficult and the coating form may become uneven. If the heating temperature is too high, the organic compound that becomes the carbonaceous material precursor Due to volatilization and polycondensation, the viscosity of the mixed system becomes high and mixing becomes difficult and the coating form may become non-uniform.

  As the mixer, a model having a stirring blade is preferable. For example, a commercially available product such as a ribbon mixer, an MC processor, a pro-shear mixer, or a KRC kneader can be used. The mixing time is usually 1 minute or longer, preferably 2 minutes or longer, more preferably 5 minutes or longer, usually 300 minutes or shorter, preferably 120 minutes or shorter, more preferably 80 minutes or shorter. If the mixing time is too short, the coating form may be non-uniform, and if it is too long, the productivity tends to decrease and the cost increases.

(Organic compound that becomes a carbonaceous material precursor)
<Types of organic compounds used as carbonaceous material precursors>
Specific organic compounds that become carbonaceous materials include various heavy or carbon oils such as coal tar pitch and coal liquefied oil, petroleum heavy oil such as crude oil normal pressure or vacuum distillation residue oil, Various things such as cracked heavy oil which is a byproduct of ethylene production by naphtha cracking can be used.
Moreover, heat treatment pitches such as ethylene tar pitch, FCC decant oil, and Ashland pitch obtained by heat-treating cracked heavy oil can be exemplified. Furthermore, vinyl polymers such as polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, and polyvinyl alcohol, substituted phenol resins such as 3-methylphenol formaldehyde resin and 3,5-dimethylphenol formaldehyde resin, and aromatics such as acenaphthylene, decacyclene, and anthracene Examples thereof include hydrocarbons, nitrogen ring compounds such as phenazine and acridine, and sulfur ring compounds such as thiophene. Examples of organic compounds that promote carbonization in the solid phase include natural polymers such as cellulose, chain vinyl resins such as polyvinylidene chloride and polyacrylonitrile, aromatic polymers such as polyphenylene, furfuryl alcohol resins, phenol- Examples thereof include thermosetting resins such as formaldehyde resin and imide resin, and thermosetting resin raw materials such as furfuryl alcohol. Among these, petroleum heavy oil is preferable.

  The heating temperature (firing temperature) varies depending on the organic compound used for the preparation of the mixture, but is usually 800 ° C. or higher, preferably 900 ° C. or higher, more preferably 950 ° C. or higher to sufficiently carbonize or graphitize. The upper limit of the heating temperature is a temperature at which the carbide of the organic compound does not reach a crystal structure equivalent to that of the scaly graphite in the mixture, and is usually 3500 ° C. at the highest. The upper limit of the heating temperature is preferably 3000 ° C, preferably 2000 ° C, more preferably 1500 ° C.

After performing the treatment as described above, the carbonaceous material composite graphite can be obtained by crushing and / or crushing treatment.
Although the shape is arbitrary, the average particle diameter is usually 2 to 50 μm, preferably 5 to 35 μm, and particularly 8 to 30 μm. Crushing and / or crushing and / or classification is performed as necessary so that the particle size is in the above range.
The content of the carbonaceous material in the carbonaceous material composite graphite is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% or more, particularly with respect to the granulated graphite as a raw material. Preferably, the content is 0.7% by mass or more, and the content is usually 20% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, particularly preferably 7% by mass or less, most preferably 5%. It is below mass%.

If the carbonaceous material content in the carbonaceous material composite graphite is too high, the negative electrode material will be damaged and the material will be destroyed when rolling at a sufficient pressure to achieve a high capacity in a non-aqueous secondary battery. Tends to increase the irreversible capacity of charge / discharge during the initial cycle and decrease the initial efficiency.
On the other hand, if the content is too small, the effect of coating tends to be difficult to obtain.

  Further, the content of the carbonaceous material in the carbonaceous material composite graphite can be calculated from the sample mass before and after the material firing as in the following formula. At this time, the calculation is made on the assumption that there is no mass change before and after the firing of the granulated graphite.

Content of carbonaceous material (mass%) = [(w2-w1) / w1] × 100
(W1 is the mass (kg) of granulated graphite, and w2 is the mass (kg) of carbonaceous composite graphite)

(Mixed with other carbon materials)
Further, in the present invention, a carbon material different from the granulated graphite is mixed for the purpose of improving the orientation of the electrode plate, the permeability of the electrolytic solution, the conductive path, etc., and improving the cycle characteristics, electrode plate swelling, etc. (Hereinafter, a carbon material obtained by mixing the granulated graphite with a carbon material different from the granulated graphite may be referred to as a “mixed carbon material”).
Examples of the carbon material different from the carbon material include natural graphite, artificial graphite, coated graphite obtained by coating a carbon material with a carbonaceous material, amorphous carbon, and a carbon material containing metal particles and a metal compound. Can be 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, a highly purified carbon material or a spherical natural graphite can be used. In the present invention, high purification means that ash contained in low-purity natural graphite is usually treated in an acid such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or a combination of a plurality of acid treatment steps. It means an operation of dissolving and removing metal and metal, etc., and usually, after the acid treatment step, a water washing treatment or the like is performed to remove the acid content used in the high purification treatment step. Moreover, you may evaporate and remove ash, a metal, etc. by processing at high temperature 2000 degreeC or more instead of an acid treatment process. Moreover, you may remove ash, a metal, etc. by processing in halogen gas atmosphere, such as chlorine gas, at the time of high temperature heat processing. Furthermore, these methods may be used in any combination.

The volume-based average particle diameter of natural graphite is usually 5 μm or more, preferably 8 μm or more, more preferably 10 μm or more, particularly preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less, particularly preferably 30 μm or less. . If the average particle diameter is within this range, it is preferable because high-speed charge / discharge characteristics and processability are improved.
Natural graphite has a BET specific surface area of usually 1 m ² / g or more, preferably 2 m ² / g or more, and usually 30 m ² / g or less, preferably 15 m ² / g or less. If the specific surface area is within this range, it is preferable because high-speed charge / discharge characteristics and processability are improved.
The tap density of natural graphite is usually preferably 0.6 g / cm ³ or more, 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and further preferably 0.85 g / cm ³ or more. Moreover, 1.3 g / cm ³ or less and 1.2 g / cm ³ or less are usually preferable, and 1.1 g / cm ³ or less is more preferable. If it is this range, since a high-speed charge / discharge characteristic and process property become favorable, it is preferable.

Examples of the artificial graphite include particles obtained by graphitizing a carbon material. For example, a single graphite precursor particle is fired while being powdered, a graphitized particle, and a plurality of graphite precursor particles are molded and fired. Granulated particles that have been graphitized and crushed can be used.
The volume-based average particle size of artificial graphite is usually 5 μm or more, preferably 10 μm or more, and usually 60 μm or less, preferably 40 μm, more preferably 30 μm or less. If it is this range, since suppression of an electrode plate swelling and process property become favorable, it is preferable.
BET specific surface area of the artificial graphite is usually 0.5 m ² / g or more, preferably 1.0 m ² / g or more and usually ^8m 2 / g or less, preferably ^{6 m} 2 / g or less, more preferably ^4m 2 / It is the range below g. If it is this range, since suppression of an electrode plate swelling and process property become favorable, it is preferable.

Further, the tap density of the artificial graphite is usually preferably 0.6 g / cm ³ or more, 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and further preferably 0.85 g / cm ³ or more. Moreover, normally 1.5 g / cm < ³ > or less and 1.4 g / cm < ³ > or less are preferable, and 1.3 g / cm < ³ > or less is more preferable. If it is this range, since suppression of an electrode plate swelling and process property become favorable, it is preferable.

  Examples of the coated graphite obtained by coating a carbon material with a carbonaceous material include, for example, particles obtained by coating, firing and / or graphitizing an organic compound which is a precursor of the above-described carbonaceous material on natural graphite or artificial graphite, natural graphite or artificial graphite. In addition, particles obtained by coating a carbonaceous material by CVD can be used.

The volume-based average particle diameter of the coated graphite is usually 5 μm or more, preferably 8 μm or more, more preferably 10 μm or more, particularly preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less, particularly preferably 30 μm or less. . If the average particle diameter is within this range, it is preferable because high-speed charge / discharge characteristics and processability are improved.
The BET specific surface area of the coated graphite is usually 1 m ² / g or more, preferably 2 m ² / g or more, more preferably 2.5 m ² / g or more, and usually 20 m ² / g or less, preferably 10 m ² / g or less. More preferably, it is 8 m ² / g or less, particularly preferably 5 m ² / g or less. If the specific surface area is within this range, it is preferable because high-speed charge / discharge characteristics and processability are improved.

The tap density of the coated graphite is usually preferably 0.6 g / cm ³ or more, 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and further preferably 0.85 g / cm ³ or more. Moreover, 1.3 g / cm ³ or less and 1.2 g / cm ³ or less are usually preferable, and 1.1 g / cm ³ or less is more preferable. A tap density in this range is preferable because high-speed charge / discharge characteristics and processability are improved.

As amorphous carbon, for example, particles obtained by firing a bulk mesophase or particles obtained by infusibilizing an easily graphitizable organic compound and firing can be used.
The volume-based average particle size of the amorphous carbon is usually in the range of 5 μm or more, preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less. If it is this range, since a high-speed charge / discharge characteristic and process property become favorable, it is preferable.
BET specific surface area of the amorphous carbon is usually ^{1 m} 2 / g or more, preferably ^2m 2 / g or more, more preferably 2.5 m ² / g or more and usually ^8m 2 / g or less, preferably ^{6 m} 2 / g or less, more preferably 4 m ² / g or less. If the specific surface area is within this range, it is preferable because high-speed charge / discharge characteristics and processability are improved.

Moreover, the tap density of amorphous carbon is usually preferably 0.6 g / cm ³ or more, preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and further more preferably 0.85 g / cm ³ or more. preferable. Moreover, 1.3 g / cm ³ or less and 1.2 g / cm ³ or less are usually preferable, and 1.1 g / cm ³ or less is more preferable. A tap density in this range is preferable because high-speed charge / discharge characteristics and processability are improved.

Examples of carbon materials containing metal particles and metal compounds include Fe, Co, Sb, Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, Nb, and Mo. , Cu, Zn, Ge, In, Ti, and the like, or a material obtained by combining a metal selected from the group consisting of, for example, graphite with graphite. As the metal or the compound that can be used, an alloy composed of two or more kinds of metals may be used, and the metal particles may be alloy particles formed of two or more kinds of metal elements. Among these, a metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn and W or a compound thereof is preferable, and Si and SiOx are particularly preferable. This general formula SiOx is obtained using Si dioxide (SiO ₂ ) and metal Si (Si) as raw materials, and the value of x is usually 0 <x <2, preferably 0.2 or more, 1.8 Hereinafter, more preferably 0.4 or more and 1.6 or less, and further preferably 0.6 or more and 1.4 or less. If it is this range, it becomes high capacity | capacitance and it becomes possible to reduce the irreversible capacity | capacitance by the coupling | bonding of Li and oxygen.

From the viewpoint of cycle life, the volume-based average particle size of the metal particles is usually 0.005 μm or more, preferably 0.01 μm or more, more preferably 0.02 μm or more, and still more preferably 0.0.
It is 3 μm or more, usually 10 μm or less, preferably 9 μm or less, more preferably 8 μm or less. When the average particle diameter is within this range, volume expansion associated with charge / discharge is reduced, and good cycle characteristics can be obtained while maintaining charge / discharge capacity.
BET specific surface area of the metal particles is usually 0.5 m ² / g or more 120 m ² / g or less and a ^{1 m} 2 / g or more 100m ² / g or less. When the specific surface area is within the above range, the charge / discharge efficiency and discharge capacity of the battery are high, lithium is quickly taken in and out during high-speed charge / discharge, and the rate characteristics are excellent.

  The apparatus used for mixing the granulated graphite and the carbonaceous material having lower crystallinity than the granulated graphite is not particularly limited. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylindrical mixer, Double cone type mixer, regular cubic type mixer, vertical type mixer, fixed type mixer: spiral type mixer, ribbon type mixer, Muller type mixer, Helical Flight type mixer, Pugmill type mixer, A fluidized mixer or the like can be used.

<Physical properties of negative electrode material for non-aqueous secondary battery>
Hereinafter, preferable physical properties of the negative electrode material obtained by the production method of the present invention will be described.

-Volume-based average particle size (average particle size d50)
The volume-based average particle size (also referred to as “average particle size d50”) of the negative electrode material is preferably 1 μm or more, more preferably 5 μm or more, further preferably 8 μm or more, particularly preferably 10 μm or more, and most preferably 12 μm or more. . The average particle diameter d50 is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, and particularly preferably 31 μm or less. If the average particle diameter d50 is too small, the non-aqueous secondary battery obtained by using the negative electrode material tends to increase the irreversible capacity and cause a loss of initial battery capacity. May cause inconveniences such as line drawing, deterioration of high current density charge / discharge characteristics, and deterioration of low temperature input / output characteristics.

  The average particle diameter d50 is obtained by suspending 0.01 g of a negative electrode material in 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) as a surfactant. This was introduced into a commercially available laser diffraction / scattering particle size distribution measuring apparatus (for example, LA-920 manufactured by HORIBA) as a measurement sample, and the measurement apparatus was irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. It is defined to be measured as a volume-based median diameter.

Tap density The negative electrode material preferably has a tap density of 0.8 g / cm ³ or more, more preferably 0.85 g / cm ³ or more, still more preferably 0.88 g / cm ³ or more, and particularly preferably 0.9 g / cm ^3. Above, most preferably 0.95 g / cm ³ or more, preferably 1.3 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, still more preferably 1.1 g / cm ³ or less. .

  When the tap density is within the above range, the processability such as streaking during the production of the electrode plate is good, and the high-speed charge / discharge characteristics are excellent. In addition, since the carbon density in the particles is difficult to increase, the rolling property is good and the high-density negative electrode sheet tends to be easily formed.

The tap density was filled using a powder density measuring device by dropping the negative electrode material of the present invention through a sieve having a mesh size of 300 μm into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ . After that, a tap having a stroke length of 10 mm is performed 1000 times and defined as the density obtained from the volume at that time and the mass of the sample.

-Mode pore diameter (PD) in the range of 0.01 to 1 μm pore diameter
In the negative electrode material, the mode pore diameter (PD) in the pore diameter range of 0.01 μm or more and 1 μm or less is a value measured using a mercury intrusion method (mercury porosimetry), and is usually 0.01 μm or more, preferably 0.8. 03 μm or more, more preferably 0.05 μm or more, still more preferably 0.06 μm or more, particularly preferably 0.07 μm, usually 1 μm or less, preferably 0.65 μm or less, more preferably 0.5 μm or less, further It is preferably 0.4 μm or less, particularly preferably 0.3 μm or less, particularly preferably 0.2 μm or less, and most preferably 0.1 μm or less.
If the mode pore diameter (PD) in the range of 0.01 μm or more and 1 μm or less of the pore diameter is out of the above range, the electrolyte cannot efficiently spread to the voids in the particles, and the Li ion insertion / desorption sites in the particles Can not be used efficiently, so the low-temperature input / output characteristics and cycle characteristics tend to deteriorate.

-Pore volume in the range of 0.01 to 1 μm pore diameter In the negative electrode material, the pore volume in the range of 0.01 to 1 μm pore diameter is a value measured using a mercury intrusion method (mercury porosimetry). Even in the case of pressure treatment, it is usually 0.07 mL / g or more, preferably 0.08 mL / g or more, more preferably 0.09 mL / g or more, and most preferably 0.10 mL / g. That's it. Moreover, it is preferably 0.3 mL / g or less, more preferably 0.25 mL / g or less, still more preferably 0.2 mL / g or less, and particularly preferably 0.18 mL / g or less.

  If the pore volume in the pore diameter range of 0.01 μm or more and 1 μm or less is less than 0.07 mL / g, the electrolyte cannot enter the particles and the Li ion insertion / desorption sites in the particles cannot be used efficiently. When lithium ion is rapidly charged and discharged, it becomes difficult to smoothly insert and desorb lithium ions, and the low-temperature input / output characteristics tend to decrease. On the other hand, when it is included in the above-mentioned range, the electrolyte solution can be smoothly and efficiently distributed inside the particle, so that Li ion insertion not only in the particle outer periphery but also in the particle inside at the time of charge / discharge The desorption site can be used effectively and efficiently, and tends to exhibit good low-temperature input / output characteristics.

-Pore distribution half width at half maximum (log (nm))
The half width at half maximum (log (nm)) of the pore distribution of the negative electrode material is obtained by displaying the horizontal axis of the pore distribution (nm) obtained by the mercury intrusion method (mercury porosimetry) in the common logarithm (log (nm)). The half-width on the fine pore side of the peak existing in the pore diameter range of 0.01 μm to 1 μm.

(When d50 of the negative electrode material is 13 μm or more)
When the negative electrode material having a d50 of 13 μm or more is a negative electrode material obtained by spheroidizing flaky, scaly graphite, and massive graphite, the half-width (log (nm)) of pore distribution is preferably 0.45 or more. Preferably 0.5 or more, more preferably 0.6 or more, particularly preferably 0.65 or more, most preferably 0.7 or more, preferably 10 or less, more preferably 5 or less, still more preferably 3 or less, particularly preferably Is 1 or less.
Further, when the negative electrode material having a d50 of 13 μm or more is composite graphite in which graphite obtained by spheroidizing scaly, scaly graphite, and massive graphite and a carbonaceous material are combined, the half-width of pore distribution (log (nm)) ) Is preferably 0.3 or more, more preferably 0.35 or more, still more preferably 0.4 or more, particularly preferably 0.45 or more, preferably 10 or less, more preferably 5 or less, still more preferably 3 or less. Particularly preferably, it is 1 or less.

(When d50 of the negative electrode material is less than 13 μm)
When d50 of the negative electrode material is less than 13 μm, the pore distribution half-width (log (nm)) is preferably 0.01 or more, more preferably 0.05 or more, still more preferably 0.1 or more, preferably 0. .33 or less, more preferably 0.3 or less, still more preferably 0.25 or less, and particularly preferably 0.23 or less.

  If the pore distribution half-width (log (nm)) is within the above range, the intraparticle voids having a pore diameter in the range of 0.01 μm to 1 μm form a denser structure, so that the electrolyte solution enters the particles. It is possible to spread smoothly and efficiently, and during charging and discharging, it becomes possible to effectively and efficiently use the Li ion insertion / desorption site existing inside the particle as well as the outer periphery of the particle, which is favorable. Tend to show low temperature input / output characteristics and cycle characteristics.

Total pore volume The total pore volume of the negative electrode material is a value measured using a mercury intrusion method (mercury porosimetry), preferably 0.1 mL / g or more, more preferably 0.3 mL / g or more, More preferably, it is 0.5 mL / g or more, Especially preferably, it is 0.6 mL / g or more, Most preferably, it is 0.7 mL / g or more. Moreover, Preferably it is 10 mL / g or less, More preferably, it is 5 mL / g or less, More preferably, it is 2 mL / g or less, Most preferably, it is 1 mL / g or less.

  When the total pore volume is within the above range, it is not necessary to make the amount of the binder excessive when forming the electrode plate, and it is easy to obtain the effect of dispersing the thickener or the binder when forming the electrode plate.

  As the mercury porosimetry apparatus, a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) can be used. A sample (negative electrode material) is weighed so as to have a value of about 0.2 g, sealed in a powder cell, and pretreated by degassing at room temperature and under vacuum (50 μmHg or less) for 10 minutes.

  Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced into the cell, the pressure is increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure is reduced to 25 psia (about 170 kPa).

  The number of steps at the time of pressure increase is 80 points or more, and the mercury intrusion amount is measured after an equilibration time of 10 seconds in each step. The pore distribution is calculated from the mercury intrusion curve thus obtained using the Washburn equation.

  Note that the surface tension (γ) of mercury is calculated as 485 dyne / cm and the contact angle (ψ) is 140 °. The average pore diameter is defined as the pore diameter when the cumulative pore volume is 50%.

-Ratio of mode pore diameter (PD) and volume-based average particle diameter (d50) in the range of pore diameters of 0.01 μm or more and 1 μm or less (PD / d50 (%))
The ratio (PD / d50) of the mode pore diameter (PD) and the volume-based average particle diameter (d50) in the pore diameter range of 0.01 μm or more and 1 μm or less of the negative electrode material is expressed by the following (formula 1). 8 or less, preferably 1.80 or less, more preferably 1.00 or less, further preferably 0.90 or less, particularly preferably 0.80 or less, most preferably 0.70 or less, usually 0.01 or more, preferably It is 0.10 or more, More preferably, it is 0.20 or more.
(Formula 1) PD / d50 (%) = Mode pore diameter (PD) / volume-based average particle diameter (d50) × 100 in the range of 0.01 μm or more and 1 μm or less in the pore distribution determined by the mercury intrusion method.
If the mode pore diameter (PD) in the range of 0.01 μm or more and 1 μm or less of the pore diameter is out of the above range, the electrolyte cannot efficiently spread to the voids in the particles, and the Li ion insertion / desorption sites in the particles Can not be used efficiently, so the low-temperature input / output characteristics and cycle characteristics tend to deteriorate.

-Number frequency of particles of 3 μm or less The number frequency of particles having a particle size of 3 μm or less when irradiated with 28 kHz ultrasonic waves of negative electrode material at 60 W for 5 minutes is preferably 1% or more, more preferably 10% or more, preferably 60 % Or less, more preferably 55% or less, still more preferably 50% or less, particularly preferably 40% or less, and most preferably 30% or less.
When the frequency of the number of particles is within the above range, particle collapse or fine powder separation is unlikely to occur during slurry kneading, electrode rolling, charge / discharge, etc., and the low temperature input / output characteristics and cycle characteristics tend to be good.

  The frequency of the number of particles having a particle size of 3 μm or less when the 28 kHz ultrasonic wave is irradiated at an output of 60 W for 5 minutes is that of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) as a surfactant. Detection was performed by mixing 0.2 g of a negative electrode material in 50 mL of a 0.2% by volume aqueous solution and irradiating a 28 kHz ultrasonic wave at an output of 60 W for a predetermined time using a flow type particle image analyzer “FPIA-2000 manufactured by Sysmex Industrial Co., Ltd.” A value obtained by measuring the number of particles by using a range of 0.6 to 400 μm is used.

-Circularity The circularity of the negative electrode material is 0.88 or more, preferably 0.90 or more, more preferably 0.91 or more. The circularity is preferably 1 or less, more preferably 0.98 or less, and still more preferably 0.97 or less. When the circularity is within the above range, the high current density charge / discharge characteristics of the non-aqueous secondary battery tend to be suppressed. The circularity is defined by the following formula, and when the circularity is 1, a theoretical sphere is obtained.
When the circularity is within the above range, the flexibility of Li ion diffusion decreases, the electrolyte solution moves smoothly in the interparticle voids, and the negative electrode materials can be appropriately brought into contact with each other. There is a tendency to exhibit charge / discharge characteristics and cycle characteristics.
Circularity = (perimeter of equivalent circle having the same area as the particle projection shape) / (actual circumference of particle projection shape)

  As the circularity value, for example, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.) is used, and about 0.2 g of a sample (negative electrode material) is added to polyoxyethylene (20) sorbitan as a surfactant. After dispersing in a 0.2% by weight monolaurate aqueous solution (about 50 mL) and irradiating the dispersion with an ultrasonic wave of 28 kHz for 1 minute at an output of 60 W, the detection range is specified as 0.6 to 400 μm, and the particle size is The value measured for particles in the range of 1.5-40 μm is used.

-X-ray parameter The d value (interlayer distance) of the lattice plane (002 plane) obtained by X-ray diffraction by the Gakushin method of the negative electrode material is preferably 0.335 nm or more and less than 0.340 nm. Here, the d value is more preferably 0.339 nm or less, and still more preferably 0.337 nm or less. When the d002 value is within the above range, the initial irreversible capacity tends to suppress an increase because the crystallinity of graphite is high. Here, 0.335 nm is a theoretical value of graphite.

  The crystallite size (Lc) of the negative electrode material determined by X-ray diffraction by the Gakushin method is preferably 1.5 nm or more, more preferably 3.0 nm or more. Within the above range, the crystallinity is not too low, and the reversible capacity is difficult to decrease when a non-aqueous secondary battery is obtained. The lower limit of Lc is the theoretical value of graphite.

-Ash content The ash content contained in the negative electrode material is preferably 1% by mass or less, more preferably 0.5% by mass or less, and still more preferably 0.1% by mass or less, based on the total mass of the negative electrode material. Moreover, it is preferable that the minimum of ash content is 1 ppm or more.

  When the ash content is within the above range, when the non-aqueous secondary battery is used, it is possible to suppress deterioration of battery performance due to the reaction between the negative electrode material and the electrolytic solution during charge / discharge to a level that can be ignored. Further, since a great amount of time, energy, and equipment for preventing contamination are not required for producing the carbon material, an increase in cost can be suppressed.

・ BET specific surface area (SA)
The specific surface area (SA) measured by the BET method of the negative electrode material is preferably 1 m ² / g or more, more preferably 2 m ² / g or more, still more preferably 3 m ² / g or more, particularly preferably 4 m ² / g or more. is there. Further, it is preferably 30 m ² / g or less, more preferably 20 m ² / g or less, still more preferably 17 m ² / g or less, particularly preferably 15 m ² / g or less.
When the specific surface area is within the above range, it is possible to sufficiently secure the portion where Li enters and exits, so the high speed charge / discharge characteristics output characteristics are excellent, and the activity of the active material against the electrolytic solution can be moderately suppressed. However, the high-capacity battery tends to be manufactured.
In addition, when a negative electrode is formed using a negative electrode material, an increase in reactivity with the electrolytic solution can be suppressed and gas generation can be suppressed, so that a preferable nonaqueous secondary battery can be provided.

  The BET specific surface area was measured by using a surface area meter (for example, a specific surface area measuring device “Gemini 2360” manufactured by Shimadzu Corporation), preliminarily dried at 100 ° C. for 3 hours under a nitrogen flow, and then subjected to liquid nitrogen. It is defined as a value measured by a nitrogen adsorption BET 6-point method using a gas flow method using a nitrogen-helium mixed gas that is cooled to a temperature and adjusted accurately so that the relative pressure value of nitrogen with respect to atmospheric pressure is 0.3.

-Surface functional group amount O / C value (%)
An X-ray photoelectron spectrometer (for example, ESCA manufactured by ULVAC-PHI) is used as an X-ray photoelectron spectroscopy measurement (XPS), and an object to be measured (here, a negative electrode material) is placed on a sample stage so that the surface is flat, and aluminum The spectra of C1s (280 to 300 eV) and O1s (525 to 545 eV) are measured by multiplex measurement using the Kα rays of X. 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. The obtained O / C atomic concentration ratio O / C (O atom concentration / C atom concentration) × 100 is defined as the surface functional group amount O / C value of the negative electrode material.
The O / C value obtained from XPS is preferably 0.1 or more, more preferably 1 or more, still more preferably 1.5 or more, particularly preferably 2 or more, preferably 8 or less, more preferably 4 or less, still more preferably. Is 3.5 or less, particularly preferably 3 or less. If the surface functional group amount O / C value is within the above range, the desolvation reactivity of Li ions and the electrolyte solvent on the negative electrode surface is promoted, the rapid charge / discharge characteristics are improved, and the reactivity with the electrolyte is improved. The charge / discharge efficiency tends to be suppressed.

True density The true density of the negative electrode material is preferably 1.9 g / cm ³ or more, more preferably 2 g / cm ³ or more, still more preferably 2.1 g / cm ³ or more, and particularly preferably 2.2 g / cm ³ or more. The upper limit is 2.26 g / cm ³ . The upper limit is the theoretical value of graphite. When the true density is within the above range, the crystallinity of the carbon is not too low, and an increase in the initial irreversible capacity in the case of a non-aqueous secondary battery tends to be suppressed.

Aspect ratio The aspect ratio in the powder state of the negative electrode material is theoretically 1 or more, preferably 1.1 or more,
More preferably, it is 1.2 or more. The aspect ratio is preferably 10 or less, more preferably 8 or less, and still more preferably 5 or less.
When the aspect ratio is within the above range, streaking of the slurry containing the negative electrode material (negative electrode forming material) hardly occurs at the time of forming the electrode plate, and a uniform coated surface is obtained, and high current density charge / discharge of the non-aqueous secondary battery is achieved. There is a tendency to avoid deterioration of characteristics.
The aspect ratio is represented by A / B, where the longest diameter A of the negative electrode material particles when observed three-dimensionally and the shortest diameter B among the diameters orthogonal thereto. The negative electrode material particles are observed with a scanning electron microscope capable of magnifying observation. Arbitrary 50 negative electrode material particles fixed to an end surface of a metal having a thickness of 50 microns or less are selected, and the stage on which the sample is fixed is rotated and tilted, and A and B are measured. Find the average value of.

・ Maximum particle size dmax
The maximum particle diameter dmax of the negative electrode material is preferably 200 μm or less, more preferably 150 μm or less, still more preferably 120 μm or less, particularly preferably 100 μm or less, and most preferably 80 μm or less. When dmax is within the above range, the occurrence of process inconveniences such as line drawing tends to be suppressed.
The maximum particle size is defined as the value of the largest particle size at which particles are measured in the particle size distribution obtained when measuring the average particle size d50.

-Raman R value The value of the Raman R value of the negative electrode material is preferably 0.01 or more, more preferably 0.1 or more, still more preferably 0.15 or more, and particularly preferably 0.2 or more. The Raman R value is preferably 0.6 or less, more preferably 0.5 or less, and still more preferably 0.4 or less.
Incidentally, the Raman R value is measured and the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1 in the Raman spectrum obtained by Raman spectroscopy, the intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity Defined as the ratio (I _B / I _A ).
Incidentally, the scope of 1580～1620Cm ^-1 A "1580cm around ^-1" in the present specification, "1360cm around ^-1" refers to the range of 1350 ^-1.

When the Raman R value is within the above range, the crystallinity of the surface of the negative electrode material particles is difficult to increase, and when the density is increased, the crystal is difficult to be oriented in a direction parallel to the negative electrode plate, and a tendency to avoid deterioration of load characteristics is avoided. It is in. Furthermore, the crystal on the particle surface is not easily disturbed, and the increase in reactivity with the electrolyte solution of the negative electrode is suppressed, and the decrease in charge / discharge efficiency of the nonaqueous secondary battery and the increase in gas generation tend to be avoided.
The Raman spectrum can be measured with a Raman spectrometer. Specifically, the sample particles are naturally dropped into the measurement cell to fill the sample, and the measurement cell is rotated in a plane perpendicular to the laser beam while irradiating the measurement cell with an argon ion laser beam. Measure. The measurement conditions are as follows.
Argon ion laser light wavelength: 514.5 nm
Laser power on sample: 25 mW
Resolution: 4cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
Peak intensity measurement, peak half-width measurement: background processing, smoothing processing (convolution 5 points by simple averaging)

DBP oil absorption The DBP (dibutyl phthalate) oil absorption of the negative electrode material is preferably 85 ml / 100 g or less, more preferably 70 ml / 100 g or less, still more preferably 65 ml / 100 g or less, and particularly preferably 60 ml / 100 g or less. The DBP oil absorption is preferably 30 ml / 100 g or more, more preferably 40 ml / 100 g or more.
If the DBP oil absorption is within the above range, it means that the progress of the spheroidization of the negative electrode material is sufficient, and there is a tendency that streaking is difficult to occur during the application of the slurry containing the negative electrode material. However, since the pore structure exists, the reaction surface tends to be prevented from lowering.
The DBP oil absorption amount is defined as a measured value when 40 g of a measurement material (negative electrode material) is added, a dropping speed is 4 ml / min, a rotation speed is 125 rpm, and a set torque is 500 N · m, in accordance with JIS K6217. For the measurement, for example, Absorbometer E type manufactured by Brabender can be used.

・ Average particle diameter d10
The particle diameter (d10) corresponding to the cumulative 10% from the small particle side of the particle diameter measured on the volume basis of the negative electrode material is preferably 30 μm or less, more preferably 20 μm or less, still more preferably 17 μm or less, preferably 1 μm or more, More preferably, it is 3 micrometers or more, More preferably, it is 5 micrometers or more.
When d10 is within the above range, the tendency of the particles to agglomerate does not become too strong, and it is possible to avoid the occurrence of process inconveniences such as an increase in slurry viscosity, a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a nonaqueous secondary battery. In addition, the high current density charge / discharge characteristics and the low temperature input / output characteristics tend to be avoided.
d10 is defined as a value obtained by integrating 10% from a particle size having a small particle frequency% in the particle size distribution obtained when measuring the average particle size d50.

・ Average particle size d90
The particle size (d90) corresponding to 90% cumulative from the small particle side of the particle size measured on the volume basis of the negative electrode material is preferably 100 μm or less, more preferably 70 μm or less, still more preferably 60 μm or less, and even more preferably 50 μm. Hereinafter, it is particularly preferably 45 μm or less, most preferably 42 μm or less, preferably 20 μm or more, more preferably 26 μm or more, still more preferably 30 μm or more, and particularly preferably 34 μm or more.
When d90 is within the above range, it is possible to avoid a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a non-aqueous secondary battery, generation of process inconveniences such as striation during application of slurry, and high current density charge / discharge characteristics. There is a tendency to avoid the decrease in the temperature and the low-temperature input / output characteristics.
d90 is defined as a value in which the frequency% of particles is 90% integrated from a small particle size in the particle size distribution obtained when measuring the average particle size d50.

  When the negative electrode material is not a negative electrode material composed of a composite of graphite particles and other metal particles such as Si, the amount of silicon element determined by fluorescent X-ray analysis (XRF) of the negative electrode material is usually 5 ppm or more, preferably 10 ppm or more. More preferably, it is 15 ppm or more, more preferably 20 ppm or more, and usually 500 ppm or less, preferably 300 ppm or less, more preferably 200 ppm or less, still more preferably 170 ppm or less, particularly preferably 150 ppm or less, most preferably 100 ppm or less. .

  When the amount of silicon element is within the above range, it tends to avoid a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a non-aqueous secondary battery.

The negative electrode material manufactured by the manufacturing method according to the present invention can stably manufacture negative electrode materials having various types of particle structures. Typical particle structures include a negative electrode material produced by folding scale graphite having a large or medium average particle diameter of raw graphite, a negative electrode material produced by granulating scale graphite having a small average particle diameter, and natural graphite. And negative electrode material made of a composite of graphite particles and other metal particles such as Si.
As an example of the ability to stably produce negative electrode materials having such various types of particle structures, the yield (negative electrode material weight / total solid raw material weight) represented by the weight ratio of the negative electrode material to the total solid raw material weight is usually 60%. Or more, preferably 80% or more, and more preferably 95% or more.

<Negative electrode for non-aqueous secondary battery>
A negative electrode for a non-aqueous secondary battery (hereinafter also referred to as an “electrode sheet” as appropriate) using a negative electrode material produced by the production method of the present invention includes a current collector and a negative electrode active material formed on the current collector And the active material layer contains at least a negative electrode material produced by the production method of the present invention. More preferably, it contains a binder.

  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 a binder having such 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 charge / discharge is suppressed, and the cycle life can be extended. In addition, since the negative electrode according to the present invention has high adhesive strength between the active material layer and the current collector, even when the binder content in the active material layer is reduced, the negative electrode is wound to produce a battery. It is speculated that the problem that the active material layer peels from the current collector does not occur.

As the binder having an olefinically unsaturated bond in the molecule, one having a large molecular weight or one having a large proportion of unsaturated bonds is desirable. Specifically, in the case of a binder having a high molecular weight, the weight average molecular weight is preferably 10,000 or more, more preferably 50,000 or more, and preferably 1,000,000 or less, more preferably 300,000 or less. Is desirable. In the case of a binder having a large ratio of unsaturated bonds, the number of moles of olefinically unsaturated bonds per gram of all binders is preferably 2.5 × 10 ⁻⁷ or more, more preferably 8 × 10 ^{−. It} is desirable that the amount is ⁷ mol or more, preferably 1 × 10 ⁻⁶ mol or less, more preferably 5 × 10 ⁻⁶ mol 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 within the above range, mechanical strength and flexibility are excellent.

The binder having an olefinically unsaturated bond has an unsaturation degree of preferably 15% or more, more preferably 20% or more, still more preferably 40% or more, and preferably 90% or less, more preferably 80%. % Or less. The degree of unsaturation represents the ratio (%) of the double bond to the repeating unit of the polymer.
In the present invention, a binder that does not have an olefinically unsaturated bond can also be used in combination with the above-described binder that has 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 preferably 150% by mass or less, more preferably 120% by mass or less.

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

  When the negative electrode material according to the present invention is used in combination with the above-described binder having an olefinically unsaturated bond, the ratio of the binder used in the active material layer can be reduced as compared with the conventional material. Specifically, the negative electrode material according to the present invention and a binder (this may be a mixture of a binder having an unsaturated bond and a binder having no unsaturated bond as described above). The mass ratio is preferably 90/10 or more, more preferably 95/5 or more, preferably 99.9 / 0.1 or less, more preferably 99.5 / 0. The range is 5 or less. When the ratio of the binder is within the above range, a decrease in capacity and an increase in resistance can be suppressed, and the electrode plate strength is also excellent.

  The negative electrode is formed by dispersing the above-described negative electrode material and binder in a dispersion medium to form a slurry, 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 agent may be added to the slurry. Examples of the conductive agent include carbon black such as acetylene black, ketjen black, and furnace black, and fine powder made of Cu, Ni having an average particle diameter of 1 μm or less, or an alloy thereof. The addition amount of the conductive agent is preferably about 10% by mass or less with respect to the carbon 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 preferably 4 μm or more, more preferably 6 μm or more, preferably 30 μm or less, more preferably 20 μm or less.

After applying the slurry on the current collector, it is preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and preferably 200 ° C. or lower, more preferably 195 ° C. or lower, in dry air or an inert atmosphere. Dry to form an active material layer.
The thickness of the active material layer obtained by applying and drying the slurry is preferably 5 μm or more, more preferably 20 μm or more, still more preferably 30 μm or more, and preferably 200 μm or less, more preferably 100 μm or less, still more preferably. 75 μm or less. When the thickness of the active material layer is within the above range, it is excellent in practicality as a negative electrode in consideration of the particle size of the active material, and a sufficient Li occlusion / release function for a high-density current value can be obtained. .

The density of the negative electrode material in the active material layer varies depending on the application, but in an application in which capacity is important, it is preferably 1.55 g / cm ³ or more, more preferably 1.6 g / cm ³ or more, and even more preferably 1.65 g / cm ³ or more, particularly preferably 1.7 g / cm ³ or more. Moreover, Preferably it is 1.9 g / cm < ³ > or less. When the density is within the above range, a sufficient battery capacity per unit volume can be secured, and the rate characteristics are hardly lowered.

  When producing a negative electrode for a non-aqueous secondary battery using the negative electrode material described above, the method and selection of other materials are not particularly limited. Moreover, when producing a lithium ion secondary battery using this negative electrode, there is no particular limitation on the selection of members necessary for the battery configuration such as the positive electrode and the electrolytic solution constituting the lithium ion secondary battery. Hereinafter, the details of the negative electrode for a lithium ion secondary battery and the lithium ion secondary battery using the negative electrode material of the present invention will be exemplified, but the materials that can be used, the production method, etc. are not limited to the following specific examples. Absent.

<Non-aqueous secondary battery>
The basic configuration of a non-aqueous secondary battery, particularly a lithium ion secondary battery is the same as that of a conventionally known lithium ion secondary battery, and usually includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte. The negative electrode is formed using the negative electrode material produced by the production method of the present invention described above.
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. , Transition metal sulfides such as titanium sulfide, transition metal sulfides such as NiS ₃ and FePS ₃ , selenium compounds of transition metals such as VSe ₂ and NbSe ₃ , Fe _0.25 V _0. Examples thereof include composite oxides of transition metals such as ₇₅ S ₂ and 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 ₂ , 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 and the} like are preferable, and LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and some of these transition metals are particularly preferable. Is a lithium transition metal composite oxide in which is substituted with another metal. 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 agent is not particularly limited as long as it can be mixed with an active material in an appropriate amount 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 or 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 positive electrode current collector, aluminum, nickel, stainless steel (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 from the viewpoint that the impossible characteristics are improved. Among these, propylene carbonate is preferably in a range of 2% by mass to 80% by mass, more preferably in a range of 5% by mass to 70% by mass, and further in a range of 10% by mass to 60% by mass with respect to the entire non-aqueous solvent. preferable. When the proportion of propylene carbonate is lower than the above, the ionic conductivity at low temperature decreases, and when the proportion of propylene carbonate is higher than the above, when a graphite-based electrode is used, propylene carbonate solvated with lithium ions enters between the graphite phases. The co-insertion causes a delamination degradation of the graphite-based negative electrode active material, and there is a problem that a 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 nonaqueous electrolytic solution is usually in the range of 0.5 mol / L or more and 2.0 mol / L or less.
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 lithium salt 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 non-aqueous secondary battery 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 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 electrolyte and separator are placed thereon. The battery can be formed by further mounting the positive electrode so as to face the negative electrode and caulking together with the gasket and the sealing plate.

  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 the examples, the physical properties of the manufactured negative electrode material were measured by the following methods. Further, the viscosity, contact angle, surface tension, and γ cos θ of the granulating agent were measured by the methods described in the specification.

<D50>
0.01 g of a negative electrode material is suspended in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate (Tween 20 (registered trademark)), which is a surfactant, and this is used as a measurement sample. The sample was introduced into a scattering particle size distribution measuring apparatus (LA-920 manufactured by HORIBA), and the measurement sample was irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, and then measured as a volume-based median diameter in the measuring apparatus.
<D10> d10 is a value obtained by integrating 10% from a small particle size in the particle size distribution obtained when measuring the average particle size d50.
<D90> d90 is a value obtained by integrating 90% from a particle size in which the frequency% of particles is small in the particle size distribution obtained when measuring the average particle size d50.

<Tap density>
Using a powder density meter, drop the negative electrode material through a sieve with a mesh size of 300 μm into a cylindrical tap cell with a diameter of 1.6 cm and a volume capacity of 20 cm ³ , fill the cell fully, and then tap a tap with a stroke length of 10 mm. This was performed 1000 times and defined as the density obtained from the volume at that time and the mass of the sample.

<Specific surface area SA>
The specific surface area SA was measured by subjecting the negative electrode material sample to preliminary vacuum drying at 100 ° C. for 3 hours under a nitrogen flow using a surface area meter (Shimadzu Corporation specific surface area measuring device “Gemini 2360”), and then to the liquid nitrogen temperature. It was defined as a value measured by a nitrogen adsorption BET 6-point method using a gas flow method using a nitrogen-helium mixed gas that was cooled and accurately adjusted so that the value of the relative pressure of nitrogen with respect to atmospheric pressure was 0.3.

<Remaining charcoal rate of granulating agent>
The residual carbon ratio of the granulating agent was calculated by measuring the weight of the sample before and after the granulating agent was heat-treated at 700 ° C. for 1 hour under an inert atmosphere, and calculated as follows.
Residual charcoal rate of granulating agent (mass%) = [w2 / w1] × 100
(W1 is the mass (g) of the granulation agent before heat treatment, and w2 is the mass (g) of the granulation agent after heat treatment)

Example 1
The scaly natural graphite having a d50 of 100 μm was pulverized by a dry swirling pulverizer to obtain scaly natural graphite having a d50 of 8.1 μm, a Tap of 0.39 g / cm ³ and a water content of 0.08% by mass. Obtained after adding 9 g of N-methyl-2-pyrrolidone (NMP) (manufactured by Wako Pure Chemical Industries, special grade, flash point 86 ° C.) as a granulating agent to 100 g of the obtained scaly natural graphite and stirring and mixing. The sample was pulverized and mixed with a hammer mill (MF10 manufactured by IKA) at a rotation speed of 3000 rpm to obtain scaly natural graphite with a granulating agent uniformly attached. The obtained sample was spheroidized by mechanical action at a rotor peripheral speed of 85 m / sec for 10 minutes using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. The obtained sample was heat-treated at 700 ° C. in a nitrogen atmosphere to obtain a spheroidized graphite sample from which the granulating agent was removed. By the measurement method, the residual carbon ratio of the granulating agent, the viscosity of the granulating agent, the contact angle with graphite, and the surface tension were measured, and d50, SA, and Tap of the obtained sample were measured. The results are shown in Table 1.

(Example 2)
A sample was obtained in the same manner as in Example 1 except that 12 g of NMP (manufactured by Wako Pure Chemical Industries, Ltd., special grade, flash point 86 ° C.) was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

Example 3
A sample was obtained in the same manner as in Example 1 except that 15 g of NMP (manufactured by Wako Pure Chemical Industries, Ltd., special grade, flash point 86 ° C.) was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

Example 4
Implemented except that 12 g of NMP (Wako Pure Chemical Industries, special grade, flash point 86 ° C.) solution in which 3 wt% of methyl methacrylate polymer (PMMA) (Wako Pure Chemical Industries) was dissolved was added as a granulating agent. A sample was obtained in the same manner as in Example 1. Table 1 shows the results of the same measurement as in Example 1.

(Example 5)
The same method as in Example 1 except that 12 g of NMP (manufactured by Wako Pure Chemical Industries, Ltd., special grade, flash point 86 ° C.) in which 10 wt% of PMMA (manufactured by Wako Pure Chemical Industries) was dissolved was added as a granulating agent. A sample was obtained. Table 1 shows the results of the same measurement as in Example 1.

(Example 6)
The same method as Example 1 except that 12 g of NMP (manufactured by Wako Pure Chemical Industries, Ltd., special grade, flash point 86 ° C.) solution in which 15 wt% of PMMA (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved was added as a granulating agent. A sample was obtained. Table 1 shows the results of the same measurement as in Example 1.

(Example 7)
A sample was obtained in the same manner as in Example 1 except that 12 g of pure water was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

(Example 8)
A sample was obtained in the same manner as in Example 1 except that 12 g of a 10 wt% ammonium polyacrylate (PAANH ₃ ) (manufactured by Wako Pure Chemical Industries, Ltd., first grade) aqueous solution was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

Example 9
A sample was obtained in the same manner as in Example 1 except that 12 g of 30 wt% ammonium polyacrylate (PAANH ₃ ) (manufactured by Wako Pure Chemical Industries, Ltd., first grade) aqueous solution was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

(Example 10)
A sample was obtained in the same manner as in Example 1 except that 12 g of a 44 wt% PAANH ₃ (manufactured by Wako Pure Chemical Industries, Ltd., primary) aqueous solution was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

(Example 11)
A sample was obtained in the same manner as in Example 1 except that 15 g of coal tar (flash point 70 ° C.) was added as a granulating agent. Since the viscosity of coal tar was 500 cP or more at 25 ° C., the temperature was heated to 60 ° C. in order to make the viscosity 500 cP or less, and the contact angle was measured according to the measurement method. The other measurements were the same as in Example 1. The results are shown in Table 1.

(Example 12)
A sample was obtained in the same manner as in Example 1 except that 9 g of creosote oil (flash point 70 ° C.) was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

(Example 13)
A sample was obtained in the same manner as in Example 1 except that 12 g of creosote oil was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

(Example 14)
A sample was obtained in the same manner as in Example 1 except that 15 g of creosote oil was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

(Example 15)
A sample was obtained in the same manner as in Example 1 except that 9 g of paraffinic oil (liquid paraffin, manufactured by Wako Pure Chemical Industries, grade 1, flash point 238 ° C.) was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

(Example 16)
A sample was obtained in the same manner as in Example 1 except that 12 g of paraffinic oil (liquid paraffin, manufactured by Wako Pure Chemical Industries, grade 1, flash point 238 ° C.) was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

(Example 17)
A sample was obtained in the same manner as in Example 1 except that 15 g of paraffinic oil (liquid paraffin, manufactured by Wako Pure Chemical Industries, grade 1, flash point 238 ° C.) was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

(Example 18)
A sample was obtained in the same manner as in Example 1 except that 9 g of aromatic oil (1) (flash point 242 ° C., aniline point 29 ° C., containing naphthalene ring structure in the molecule) was added as a granulating agent. It was. Table 1 shows the results of the same measurement as in Example 1.

(Example 19)
A sample was obtained in the same manner as in Example 1 except that 12 g of aromatic oil (1) (flash point 242 ° C., aniline point 29 ° C., containing naphthalene ring structure in the molecule) was added as a granulating agent. It was. Table 1 shows the results of the same measurement as in Example 1.

(Example 20)
A sample was obtained in the same manner as in Example 1 except that 15 g of aromatic oil (1) (flash point 242 ° C., aniline point 29 ° C., containing naphthalene ring structure in the molecule) was added as a granulating agent. It was. Table 1 shows the results of the same measurement as in Example 1.

(Example 21)
The same method as in Example 1 except that 9 g of aromatic oil (2) (flash point 150 ° C., no aniline point, mixed aniline point 15 ° C., containing benzene ring structure in the molecule) was added as a granulating agent. A sample was obtained. Table 1 shows the results of the same measurement as in Example 1.

(Example 22)
The same method as in Example 1 except that 12 g of aromatic oil (2) (flash point 150 ° C., no aniline point, mixed aniline point 15 ° C., containing benzene ring structure in the molecule) was added as a granulating agent. A sample was obtained. Table 1 shows the results of the same measurement as in Example 1.

(Example 23)
The same method as in Example 1 except that 15 g of aromatic oil (2) (flash point 150 ° C., no aniline point, mixed aniline point 15 ° C., containing benzene ring structure in the molecule) was added as a granulating agent. A sample was obtained. Table 1 shows the results of the same measurement as in Example 1.

(Comparative Example 1)
A sample was obtained in the same manner as in Example 1 except that no granulating agent was added. Table 1 shows the results of the same measurement as in Example 1.

(Comparative Example 2)
A sample was obtained in the same manner as in Example 1 except that 12 g of coal tar pitch (softening point 90 ° C., solid at the time of granulation) was added as a granulating agent. Table 1 shows the results of the same measurement as in Example 1.

(Comparative Example 3)
A sample was obtained in the same manner as in Example 1 except that 12 g of PMMA (manufactured by Wako Pure Chemical Industries, Ltd., melting point 105 ° C., solid at the time of granulation) was added as an organic compound. Table 1 shows the results of the same measurement as in Example 1.

(Comparative Example 4)
From the sample obtained in Comparative Example 1, flaky graphite fine powder that was not granulated by airflow classification was removed to obtain spheroidized graphite having a d50 of 10.9 μm and a Tap density of 0.88 g / cm ³ . Table 1 shows the results of the same measurement as in Example 1.

In Examples 1 to 23, granulation spheroidization is promoted by adding a granulating agent having specified physical properties to flaky natural graphite adjusted to an appropriate particle size, and spheroidizing powder is promoted. It was confirmed that d10 and d50 were increased because of less generation, and that the packing density of particles was improved by spheroidization, so that the Tap density was increased.
On the other hand, in Comparative Examples 1 and 4 in which flaky natural graphite to which no granulating agent was added was spheroidized, and in Comparative Examples 2 and 3 in which spheroidizing was added to add a granulating agent outside the specified range, flaky Since the adhesion between natural graphites is poor, granulation spheroidization is not sufficiently promoted, and d50 and Tap are insufficiently increased.

<Evaluation of granulation stability>
Battery evaluation in the case of using the negative electrode material of Example 16 and Comparative Example 4 was performed by the following method. The results are shown in Table 2.

<Production of electrode sheet>
Using the negative electrode material of Example or Comparative Example, an electrode plate having an active material layer with an active material layer density of 1.60 ± 0.03 g / cm ³ or 1.35 ± 0.03 g / cm ³ was produced. Specifically, 50.00 ± 0.02 g of negative electrode material, 50.00 ± 0.02 g of 1 mass% carboxymethylcellulose sodium salt aqueous solution (0.500 g in terms of solid content), and styrene having a weight average molecular weight of 270,000 -Aqueous dispersion of butadiene rubber 1.00 ± 0.05 g (0.5 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 ITOCHU machining so that the negative electrode material was 12.00 ± 0.3 mg / cm ² or 6.00 ± 0.3 mg / cm ² on a 10 μm thick copper foil as a current collector. It is applied to a width of 10 cm using a small die coater and roll-pressed using a roller having a diameter of 20 cm, and the density of the active material layer is 1.60 ± 0.03 g / cm ³ , or 1.35 ± 0.03 g. / cm ³ to become as to obtain the adjusted electrode sheet.

<Preparation of non-aqueous secondary battery (2016 coin type battery)>
An electrode sheet prepared by the above method and having an anode material of 12.00 ± 0.3 mg / cm ² adhered and an active material layer having a density of 1.60 ± 0.03 g / cm ³ was adjusted to a diameter of 12. A 5 mm disk was punched out, and a lithium metal foil was punched into a disk with a diameter of 14 mm as a counter electrode. Between both electrodes, a separator (porous polyethylene film) impregnated with an electrolytic solution in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7) so as to be 1 mol / L. 2016 coin type batteries were prepared.

<Production of non-aqueous secondary battery (laminated battery)>
Produced by the above method, the negative electrode material is 6.00 ± 0.3mg / cm ² to adhere, 4 cm × 3 cm the adjusted electrode sheet such that the density of the active material layer is 1.35 ± 0.03g / cm ³ A positive electrode made of NMC (lithium nickel manganese cobalt composite oxide) was cut out in the same area, and a separator (made of a porous polyethylene film) was placed between the negative electrode and the positive electrode for combination. A laminate type battery was prepared by injecting 200 μl of an electrolytic solution in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio = 3: 3: 4) to a concentration of 1.2 mol / L. Was made.

<Measurement method of discharge capacity>
Using the non-aqueous secondary battery (2016 coin-type battery) produced by the above method, the capacity during battery charging / discharging was measured by the following measurement method.
Charge to 5 mV with respect to the lithium counter electrode at a current density of 0.05 C, and further charge to a current density of 0.005 C at a constant voltage of 5 mV. After doping lithium into the negative electrode, the current density of 0.1 C Then, the lithium counter electrode was discharged to 1.5V. The discharge capacity at this time was defined as the discharge capacity of the material.

<Low temperature output characteristics>
Using the laminate type non-aqueous electrolyte secondary battery produced by the method for producing the non-aqueous electrolyte secondary battery, low temperature output characteristics were measured by the following measuring method.
For non-aqueous electrolyte secondary batteries that have not undergone charge / discharge cycles, a voltage range of 4.1 V to 3.0 V at 25 ° C., a current value of 0.2 C (the rated capacity with a discharge capacity of 1 hour rate is discharged in 1 hour) 3C for the current value to be 1C, the same applies hereinafter), voltage range of 4.2V to 3.0V, current value of 0.2C (at the time of charging 4.2V constant voltage charging for another 2.5 hours) Implementation) Initial charge and discharge was performed for 2 cycles.
Furthermore, after charging at a current value of 0.2 C to SOC 50%, in a low temperature environment of −30 ° C., each current value of 1/8 C, 1/4 C, 1/2 C, 1.5 C, 2 C is 2 seconds. Measure the drop in battery voltage after 2 seconds of discharge under each condition, and calculate the current value I that can flow for 2 seconds when the upper limit of charge voltage is 3V. The value calculated by the formula 3 × I (W) was used as the low temperature output characteristic of each battery.

  It was confirmed that the negative electrode material produced in Example 16 was sufficiently excellent in discharge capacity and low temperature input / output characteristics as compared with the negative electrode material produced in Comparative Example 4.

  A negative electrode material obtained by adding a carbonaceous material having lower crystallinity than the raw material graphite to the negative electrode material obtained according to the present invention was prepared, and battery evaluation was performed when the negative electrode material was used. The production of the negative electrode material (Examples 24 and 25) and Comparative Example 5 are shown below, and the results of battery evaluation are shown in Table 3.

(Example 24)
The scaly natural graphite having a d50 of 100 μm was pulverized by a dry swirling pulverizer to obtain scaly natural graphite having a d50 of 8.1 μm, a Tap of 0.39 g / cm ³ and a water content of 0.08% by mass. To 100 g of the obtained scaly natural graphite, liquid paraffin (manufactured by Wako Pure Chemical Industries, Ltd., first grade, physical properties at 25 ° C .: viscosity = 95 cP, contact angle = 13.2 °, surface tension = 31.7 mN / m , Γcos θ = 30.9) was added and mixed with stirring, and the obtained sample was pulverized and mixed with a hammer mill (MF10 manufactured by IKA) at a rotation speed of 3000 rpm, and a scaly powder uniformly attached with a granulating agent. A natural graphite was obtained. The obtained sample was subjected to spheronization treatment by mechanical action for 10 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. to obtain granulated graphite particles.
After mixing the obtained granulated graphite particles and a carbonaceous material precursor having a lower crystallinity than raw graphite with a coal tar pitch at 120 ° C. for 20 minutes and performing heat treatment at 1300 ° C. for 1 hour in an inert gas. The fired product was pulverized and classified to obtain multilayered graphite particles in which the granulated graphite particles and the carbonaceous material having lower crystallinity than the raw graphite were combined. From the firing yield, the mass ratio (granulated graphite particles: amorphous carbon) between the granulated graphite particles and the carbonaceous material having lower crystallinity than the raw graphite is 1: 0.065. It was confirmed that. The d50, SA, and Tap of the obtained sample, the discharge capacity of the nonaqueous secondary battery, and the low temperature input / output characteristics were measured. The results are shown in Table 3.

(Example 25)
Implementation was performed except that the mass ratio (granulated graphite particles: amorphous carbon) of the granulated graphite particles and the carbonaceous material having lower crystallinity than the raw graphite was set to 1: 0.08 in the obtained multilayered graphite particles. In the same manner as in Example 24, multilayer structure graphite particles were obtained. The results of the same measurement as in Example 24 are shown in Table 3.

(Comparative Example 5)
A multilayer carbon material was obtained in the same manner as in Example 24 except that the sample obtained in Comparative Example 4 was used instead of the granulated graphite particles. Table 3 shows the results of measurements similar to those in Example 24.

  It was confirmed that Examples 24 and 25 were sufficiently excellent in discharge capacity and low-temperature input / output characteristics as compared with Comparative Example 5.

  The battery evaluation using the negative electrode material of Example 26 in which the sample obtained by granulating raw graphite in the presence of raw coke was graphitized and Comparative Example 6 in which raw coke raw material was graphitized as it was was evaluated by the following method. It went by. The results are shown in Table 4.

<Production of electrode sheet>
An electrode plate having an active material layer with an active material layer density of 1.60 ± 0.03 g / cm ³ was produced using the graphite particles of Example 26 or Comparative Example 6 described later. Specifically, 50.00 ± 0.02 g of negative electrode material, 50.00 ± 0.02 g of 1 mass% carboxymethylcellulose sodium salt aqueous solution (0.500 g in terms of solid content), and styrene having a weight average molecular weight of 270,000 -Aqueous dispersion of butadiene rubber 1.00 ± 0.05 g (0.5 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 10 cm using a small die coater made by ITOCHU machining so that 9.00 ± 0.3 mg / cm ² of the negative electrode material was deposited on a 10 μm thick copper foil as a current collector. Then, roll pressing was performed using a roller having a diameter of 20 cm to adjust the density of the active material layer to 1.60 ± 0.03 g / cm ³ to obtain an electrode sheet.

<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 both electrodes, a separator (porous polyethylene film) impregnated with an electrolytic solution in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7) so as to be 1 mol / L. 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 4 cm × 3 cm to form a negative electrode, a positive electrode made of NMC 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 for combination. A laminate type battery was prepared by injecting 225 μl of an electrolytic solution in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio = 3: 3: 4) so as to be 1.2 mol / L. Was made.

<Measurement method of discharge capacity>
Using the non-aqueous secondary battery (2016 coin-type battery) produced by the above method, the capacity during battery charging / discharging was measured by the following measurement method.
Charge to 5 mV with respect to the lithium counter electrode at a current density of 0.05 C, and further charge to a current density of 0.005 C at a constant voltage of 5 mV. After doping lithium into the negative electrode, the current density of 0.1 C Then, the lithium counter electrode was discharged to 1.5V. The discharge capacity at this time was defined as the discharge capacity of the material.

<Low temperature output characteristics>
Using the laminate type non-aqueous electrolyte secondary battery produced by the method for producing the non-aqueous electrolyte secondary battery, low temperature output characteristics were measured by the following measuring method.
For non-aqueous electrolyte secondary batteries that have not undergone charge / discharge cycles, a voltage range of 4.1 V to 3.0 V at 25 ° C., a current value of 0.2 C (the rated capacity with a discharge capacity of 1 hour rate is discharged in 1 hour) 3C for the current value to be 1C, the same applies hereinafter), voltage range of 4.2V to 3.0V, current value of 0.2C (at the time of charging 4.2V constant voltage charging for another 2.5 hours) Implementation) Initial charge and discharge was performed for 2 cycles.
Furthermore, after charging at a current value of 0.2 C to SOC 50%, in a low temperature environment of −30 ° C., each current value of 1/8 C, 1/4 C, 1/2 C, 1.5 C, 2 C is 2 seconds. Measure the drop in battery voltage after 2 seconds of discharge under each condition, and calculate the current value I that can flow for 2 seconds when the upper limit of charge voltage is 3V. The value calculated by the formula 3 × I (W) was used as the low temperature output characteristic of each battery.

(Example 26)
20 g of paraffinic oil (liquid paraffin, manufactured by Wako Pure Chemical Industries, Ltd., first grade, flash point 238 ° C.) is added to 100 g of raw coke particles having a d50 of 17.7 μm as a precursor of bulk mesophase artificial graphite particles. After stirring and mixing, the obtained sample was pulverized and mixed with a hammer mill (MF10 manufactured by IKA) at a rotation speed of 3000 rpm to obtain raw coke particles uniformly attached with a granulating agent. After adding 20 g of the obtained sample and scaly natural graphite particles having a d50 of 8.1 μm and stirring and mixing, in a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd., for 5 minutes at a rotor peripheral speed of 85 m / sec. The composite granulation treatment was performed while applying impact, compression, friction and shearing force due to mechanical action.
The obtained composite granulated graphite particle precursor was calcined at 1000 ° C. for 1 hour in a nitrogen atmosphere in an electric furnace, and then graphitized at 3000 ° C. under Ar circulation in an electric furnace to produce bulk mesophase artificial graphite particles. Composite granulated graphite particles were obtained in which graphite particles were combined. When the cross section of the obtained sample was observed by SEM, a structure in which the graphite crystal layered structure of the flake graphite particles was arranged in the same direction as the outer peripheral surface of the bulk mesophase artificial graphite particles on at least a part of the surface of the bulk mesophase artificial graphite particles. Was observed.
About the obtained sample, d50, SA, and Tap were measured by the said measuring method, and the discharge capacity and the low temperature input / output characteristic were measured about the non-aqueous secondary battery. The results are shown in Table 4.

(Comparative Example 6)
Raw coke particles having a d50 of 17.7 μm, which is a precursor of bulk mesophase artificial graphite particles, were baked as they were in an electric furnace in a nitrogen atmosphere at 1000 ° C. for 1 hour, and then further flowed at 3000 ° C. under Ar flow in the electric furnace. To obtain bulk mesophase artificial graphite particles. Table 4 shows the results of measurements similar to those of Example 26 for the obtained samples.

  It was confirmed that Example 26 was sufficiently excellent in discharge capacity and low-temperature input / output characteristics as compared with Comparative Example 6.

  Table 5 shows the results of battery evaluation when a negative electrode material obtained by granulating raw material graphite in the presence of Si metal is used. Here, the discharge capacity and the initial efficiency were measured by the following methods.

<Production of electrode sheet>
An electrode plate having an active material layer with an active material layer density of 1.35 ± 0.03 g / cm ³ was prepared using negative electrode materials of Examples 27 and 28 described later or Comparative Example 5. 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 0.75 ± 0.05 g (0.3 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 4.5 ± 0.5 mg / cm ² on a 18 μm thick copper foil as a current collector, and air-dried at room temperature. Then, the electrode plate was obtained by drying at 110 ° C. for 30 minutes. Furthermore, it roll-pressed using the roller of diameter 20cm, and it adjusted so that the density of an active material layer might be 1.35 +/- 0.03g / cm < ³ >, and obtained the electrode sheet.

<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 both electrodes, a separator (porous polyethylene film) impregnated with an electrolytic solution in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7) so as to be 1 mol / L. 2016 coin type batteries were prepared.

<Measurement method of discharge capacity and initial efficiency>
Using the non-aqueous secondary battery (2016 coin-type battery) produced by the above method, the capacity during battery charging / discharging was measured by the following measurement method.
Charge to 5 mV with respect to the lithium counter electrode at a current density of 0.05 C, and further charge to a current density of 0.005 C at a constant voltage of 5 mV. After doping lithium into the negative electrode, the current density of 0.1 C Then, the lithium counter electrode was discharged to 1.5V. The charge capacity and discharge capacity at this time were defined as the charge capacity and discharge capacity of the present material, and the difference between the charge capacity and the discharge capacity was calculated as the irreversible capacity. The initial efficiency was defined as the discharge capacity of the material / the charge capacity of the amount of the material (discharge capacity of the material + irreversible capacity).

(Example 27)
Polycrystalline Si having an average particle diameter d50 of 1 μm was wet pulverized with LMZ10 (manufactured by Ashizawa Finetech) to an average particle diameter d50 of 0.2 μm to prepare Si slurry (I). To 300 g (solid content 40%) of this Si slurry (I), 1500 g of NMP (special grade, flash point 86 ° C.) manufactured by Wako Pure Chemical Industries, Ltd. and 1000 g of scaly natural graphite (average particle diameter d50: 13 μm) as raw material graphite are added. Then, the mixture was mixed with a mixing stirrer (manufactured by Dalton) at 40% by mass of NV to obtain slurry (II) in which Si compound particles and graphite were uniformly dispersed. This slurry (II) was dried under reduced pressure at 150 ° C. until NMP remained at 15 parts by mass with respect to 100 parts by mass of scaly natural graphite. The obtained sample was pulverized and mixed with a hammer mill (MF10 manufactured by IKA) at a rotation speed of 3000 rpm to obtain scale-like natural graphite to which Si fine particles and a granulating agent (NMP) were attached. The obtained sample is granulated by mechanical action for 3 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd., and granulated graphite particles encapsulating Si compound particles (Composite graphite particles) were obtained. The composite graphite particles encapsulating the obtained Si compound particles are mixed with coal tar as a carbonaceous material precursor having lower crystallinity than the raw material graphite, subjected to heat treatment at 1000 ° C. for 1 hour in an inert gas, and then fired. By pulverizing and classifying the product, multilayer graphite particles in which composite graphite particles and carbonaceous material having lower crystallinity than raw graphite were combined were obtained. From the firing yield, in the obtained multilayer structure graphite particles, the mass ratio of the composite graphite particles and the carbonaceous material having lower crystallinity than the raw graphite (composite graphite particles: amorphous carbon) is 1: 0.075. It was confirmed. The sample obtained was measured for d50, SA, Tap, discharge capacity of the nonaqueous secondary battery, and initial efficiency. The results are shown in Table 5.

(Example 28)
Polycrystalline Si having an average particle diameter d50 of 1 μm was wet pulverized with LMZ10 (manufactured by Ashizawa Finetech) to an average particle diameter d50 of 0.2 μm to prepare Si slurry (I). 300 g of this Si slurry (I) (solid content 40%), 1500 g of NMP (manufactured by Wako Pure Chemical Industries, special grade, flash point 86 ° C.), 1000 g of scaly natural graphite (average particle diameter d50: 13 μm) as raw material graphite, and paraffin System oil (liquid paraffin, manufactured by Wako Pure Chemical Industries, grade 1, flash point 238 ° C., boiling point> 300 ° C.) 150 g, and mixed with a mixing stirrer (manufactured by Dalton) at 40% NV by mass, A slurry (II) in which graphite was uniformly dispersed was obtained. The slurry (II) was dried at 150 ° C. under reduced pressure to remove NMP, and the obtained sample was pulverized and mixed at a rotation speed of 3000 rpm with a hammer mill (MF10 manufactured by IKA) to obtain Si fine particles and flaky natural graphite. Scale-like natural graphite to which 15 parts by mass of a granulating agent (paraffinic oil) was attached per 100 parts by mass was obtained. The obtained sample is granulated by mechanical action for 3 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd., and granulated graphite particles encapsulating Si compound particles (Composite graphite particles) were obtained. The composite graphite particles encapsulating the obtained Si compound particles are mixed with coal tar as a carbonaceous material precursor having lower crystallinity than the raw material graphite, subjected to heat treatment at 1000 ° C. for 1 hour in an inert gas, and then fired. By pulverizing and classifying the product, multilayer graphite particles in which composite graphite particles and carbonaceous material having lower crystallinity than raw graphite were combined were obtained. From the firing yield, in the obtained multilayer structure graphite particles, the mass ratio of the composite graphite particles and the carbonaceous material having lower crystallinity than the raw graphite (composite graphite particles: amorphous carbon) is 1: 0.075. It was confirmed. The sample obtained was measured for d50, SA, Tap, discharge capacity of the nonaqueous secondary battery, and initial efficiency. The results are shown in Table 5.

(Comparative Example 7)
Composite particles were obtained in the same manner as in Example 27 except that the slurry (II) prepared in Example 27 was dried and used so that the amount of NMP was less than 0.1%. The d50, SA, Tap, discharge capacity, and initial efficiency of the obtained sample were measured. The results are shown in Table 5.

  In Examples 27 and 28, as compared with Comparative Example 7, it was confirmed that granulation spheroidization was promoted, d50 and Tap density increased, and discharge capacity and initial efficiency were sufficiently excellent.

  According to the production method of the present invention, since the number of steps is small, the negative electrode material can be produced stably, efficiently and inexpensively. In addition, negative electrode materials for non-aqueous secondary batteries having various types of particle structures can be stably produced.

Claims (10)

A method for producing a negative electrode material for a non-aqueous secondary battery comprising a granulation step of granulating raw material graphite by applying at least mechanical energy of impact, compression, friction, and shear force,
The said granulation process is performed in presence of the granulating agent which satisfies the conditions of following 1) and 2), The manufacturing method characterized by the above-mentioned.
1) Liquid at the time of granulating the raw material graphite 2) When the granulating agent does not contain an organic solvent or contains an organic solvent, at least one of the organic solvents has no flash point, or the flash point When it has a flash point of 5 ° C or higher The manufacturing method according to claim 1, wherein the granulating agent has a contact angle θ of less than 90 ° with graphite measured by the following measuring method.
<Measuring method of contact angle θ with graphite>
When 1.2 μl of the granulating agent is dropped on the HOPG surface and the wetting spread converges and the dripping granulated agent has a contact angle θ change rate of 3% or less per second, the contact angle is defined as the contact angle. It measures with a measuring apparatus (Kyowa Interface Co., Ltd. automatic contact angle meter DM-501). Here, when using a granulating agent having a viscosity at 25 ° C. of 500 cP or less, the value at 25 ° C. is used, and when using a granulating agent having a viscosity at 25 ° C. of more than 500 cP, the viscosity reaches 500 cP or less. The value at the heated temperature is taken as the measured value of the contact angle θ.   The manufacturing method according to claim 1, wherein the granulating agent has a viscosity of 1 cP or more during the granulating step.   The manufacturing method according to any one of claims 1 to 3, wherein the granulating agent has a viscosity at 25 ° C of 1 cP or more and 100,000 cP or less.   The method according to any one of claims 1 to 4, wherein the raw graphite contains at least one selected from the group consisting of scaly, scaly, and massive natural graphite.   6. The manufacturing method according to claim 1, wherein the raw graphite has d002 of 0.34 nm or less.   The granulation step is characterized in that the raw material graphite is granulated in the presence of at least one selected from the group consisting of a metal alloyable with Li and its oxide, amorphous carbon, and raw coke. The manufacturing method according to any one of claims 1 to 6.   The manufacturing method according to any one of claims 1 to 7, wherein the granulating step is performed in an atmosphere of 0 ° C or higher and 250 ° C or lower.   The granulation step includes a rotating member that rotates at a high speed in a casing and has a rotor in which a plurality of blades are installed in the casing. The method according to any one of claims 1 to 8, wherein granulation is performed by applying any one of impact, compression, friction, and shearing force.   The production method according to any one of claims 1 to 9, further comprising a step of attaching a carbonaceous material having lower crystallinity than raw graphite to the granulated graphite obtained by the granulation step.