JP2017054581A - Carbon material and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon material with which a nonaqueous secondary battery high in capacity and having excellent input/output characteristics can be obtained, and as a result, to provide a high-performance nonaqueous secondary battery.SOLUTION: A carbon material for a nonaqueous secondary battery contains a plurality of granulated particles made of a carbon material. When any 30 particles are selected among the granulated particles from a cross sectional SEM image of the carbon material for a nonaqueous secondary battery, the average value of the 30 particles in Box-counting dimension in a gap region is 1.55 or more, the average value being obtained by separating a cross sectional SEM image of each of the granulated particles into the gap region and a region other than gaps and calculating from an image having been subjected to binarization processing. The cross sectional SEM image is a reflected electron image obtained at an accelerating voltage of 10 kV.SELECTED DRAWING: None

Description

  The present invention relates to a non-aqueous secondary battery including a carbon material and a negative electrode for a non-aqueous secondary battery using the carbon material.

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

  For lithium ion secondary batteries, it is known to use a carbon material such as graphite as the negative electrode active material. Among them, graphite having a high degree of graphitization, when used as an active material for a negative electrode for a lithium ion secondary battery, has a capacity close to 372 mAh / g, which is the theoretical capacity for lithium occlusion of graphite. Since it is excellent also in the property, it is known that it is preferable as an active material for negative electrodes. On the other hand, when the active material layer containing the negative electrode material is densified to increase the capacity, the destruction / deformation of the material increases the irreversible capacity of charge / discharge during the initial cycle, decreases the large current charge / discharge characteristics, reduces the cycle characteristics. There was a problem of decline.

In order to solve the above problem, for example, in Patent Document 1, spheroidized natural graphite is produced by subjecting scaly natural graphite to mechanical energy treatment, and spheroidized natural graphite is used as nuclear graphite on its surface. A technique for improving fillability and high-speed charge / discharge characteristics by coating amorphous carbon is disclosed.
Patent Document 2 discloses a technique for further suppressing spheronization of spherical graphite, thereby suppressing crystal orientation in graphite particles and reducing swelling during charging and discharging. Further, in Patent Document 3, by producing isotropic graphite obtained by spheroidizing flaky graphite and isotropically pressurizing it, voids in the particles are eliminated and densified graphite is manufactured with high density. Discloses a technique for improving high-speed charge / discharge characteristics and cycle characteristics.

Japanese Patent No. 3534391 JP 2011-086617 A Japanese Patent Laying-Open No. 2005-50807

  However, according to the study by the present inventors, the spheroidized natural graphite disclosed in Patent Document 1 and Patent Document 2 has a higher capacity and better rapid charge / discharge characteristics than the flaky graphite used as a raw material. Is obtained, but because the void in the particle is coarse and lacks in density, the electrolyte does not spread smoothly and efficiently to the void in the particle, and the Li ion insertion / desorption site in the particle cannot be effectively used. Their properties were still inadequate.

Further, in the isotropically pressurized spheroidized natural graphite disclosed in Patent Document 3, since the particles are densified and the filling property is increased, the electrolyte moves smoothly between the electrodes, so that the constant rapidity is achieved. Although the charge / discharge characteristics are improved, the low-temperature input / output characteristics are insufficient because the electrolyte does not enter the particles due to the elimination of voids in the particles and the Li ion insertion / desorption sites in the particles cannot be used efficiently. Met.

  The present invention has been made in view of the background art, and the problem is to provide a carbon material capable of obtaining a non-aqueous secondary battery having high capacity and excellent input / output characteristics, and as a result. It is to provide a high-performance non-aqueous secondary battery.

As a result of diligent studies to solve the above problems, the present inventors have made non-aqueous secondary batteries having high capacity and excellent low-temperature input / output characteristics and cycle characteristics by miniaturizing the pores in the particles. The inventors have found that a negative electrode material can be obtained, and have completed the present invention.
The reason why the carbon material according to the present invention has the above effect is considered as follows.
That is, by making the pores in the particles finer, the electrolyte solution can be smoothly and efficiently distributed to the inside of the particles. It is considered that ion insertion / desorption sites can be used effectively and efficiently, and high capacity and good low-temperature input / output characteristics can be obtained.

That is, the gist of the present invention is as follows.
<1> A carbon material for a non-aqueous secondary battery containing granulated particles made of a plurality of carbon materials,
When 30 particles of the granulated particles are arbitrarily selected from the cross-sectional SEM image of the carbon material for non-aqueous secondary battery, each cross-sectional SEM image of each granulated particle is divided into a void region and a region other than the void. A carbon material for a non-aqueous secondary battery, wherein an average value of 30 particles in the Box count dimension with respect to a void region, which is calculated from a value-processed image, is 1.55 or more.

However, the cross-sectional SEM image is a reflected electron image acquired at an acceleration voltage of 10 kV.
<2> the granulated particles have a volume-based average particle diameter X as measured by laser diffraction, relationships circular equivalent diameter _{X 1,} which is measured from a cross-sectional SEM image _| at / _{X 1} ≦ 0.2 | X 1 -X The carbon material for non-aqueous secondary batteries according to <1>.
<3> and roundness R measured in the granulated particles flow particle image analyzer, the relationship between circularity R _1, which is measured from a cross-sectional SEM image | is ≦ 0.1 _| R-R 1 , <1> or <2> The carbon material for non-aqueous secondary batteries.
<4> The carbon material for a non-aqueous secondary battery according to any one of <1> to <3>, wherein the tap density is 0.7 g / cm ³ or more.
<5> The carbon material for a non-aqueous secondary battery according to any one of <1> to <4>, wherein the circularity obtained by flow-type particle image analysis of the carbon material is 0.88 or more.
<6> The carbon material for a non-aqueous secondary battery according to any one of <1> to <5>, wherein the graphite particles are spherical graphite particles obtained by granulating scaly graphite, scaly graphite, and massive graphite.
<7> The carbon material for a non-aqueous secondary battery according to <6>, wherein the granulation treatment is a treatment that imparts at least mechanical energy of any one of impact, compression, friction, and shearing force.
<8> In the apparatus having a rotor in which the granulation process includes a rotating member that rotates at a high speed in a casing and a plurality of blades are installed in the casing, the graphite introduced into the interior by rotating the rotor at a high speed The carbon material for nonaqueous secondary batteries according to <7> or <8>, wherein the carbon material is granulated by applying any of impact, compression, friction, and shearing force to the surface. <9> A non-aqueous secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is a current collector and a negative electrode active material layer formed on the current collector, And the negative electrode active material layer contains the carbon material according to any one of <1> to <8>.

  By using the carbon material of the present invention as a negative electrode active material for a non-aqueous secondary battery, a non-aqueous secondary battery having a high capacity and good low-temperature input / output characteristics can be provided.

The logarithm graph which plotted the box size on the horizontal axis and the number of the counted boxes on the vertical axis according to the binarized image of one granulated particle in the carbon material of Example 1 and the BOX COUNT method is shown. The logarithmic graph which plotted the box size on the horizontal axis and the number of the counted boxes on the vertical axis | shaft according to the binarized image of the one granulated particle in the carbon material of the comparative example 1 and the BOX COUNT method is shown. The cross-sectional SEM image and the binarized image of one granulated particle in the carbon material of Example 1 are shown. The example in the case of excluding in the binarization process of a SEM image is shown. SEM image of one granulated particle in the carbon material of Example 1 SEM image of one granulated particle in the carbon material of Comparative Example 2

Hereinafter, the contents of the present invention will be described in detail. The description of the invention constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these forms unless it exceeds the gist.
The carbon material for a non-aqueous secondary battery of the present invention is a carbon material for a non-aqueous secondary battery characterized in that a large number of voids having a fine structure are present in the particles.

<Types of carbon materials for non-aqueous secondary batteries>
The carbon material for a non-aqueous secondary battery capable of occluding and releasing lithium ions of the present invention is not particularly limited. For example, it is a carbon material such as graphite or a carbonaceous material having a low degree of graphitization, and particularly easily commercially available. Graphite that is available and theoretically has a high charge / discharge capacity of 372 mAh / g, and has a large effect of improving charge / discharge characteristics at a high current density as compared with the case of using other negative electrode active materials. Preferably there is. Further, examples of graphite include natural graphite and artificial graphite, and natural graphite is more preferable from the viewpoint of good charge / discharge characteristics at a high capacity and a high current density.

Further, graphite having a small amount of impurities is preferable, and graphite having a small amount of impurities can be obtained by performing various known purification treatments.
Natural graphites are classified according to their properties into scale-like black (Flake Graphite), scale-like (Crystal Line Graphite), massive graphite (Vein Graphite), and soil graphite (Amorphous Graphite). (See Industrial Technology Center Co., Ltd., published in 1974), Graphite section, and "HANDBOOKOF CARBON, GRAPHITE, DIAMOND AND FULLERENES" (published by NoyesPubLications)). The degree of graphitization is the highest at 100% for scaly graphite and massive graphite, followed by scaly graphite at 99.9%, which is suitable in the present invention.

The production area of scaly natural graphite is mainly Madagascar, China, Brazil, Ukraine, Canada, etc., and the production area of scaly graphite is mainly Sri Lanka. The main producers of soil graphite are the Korean Peninsula, China and Mexico.
Among natural graphites, for example, scaly, scaly, or massive natural graphite, highly purified scaly graphite, spheroidized natural graphite described below (hereinafter sometimes referred to as spheroidized natural graphite), and the like. It is done. Among them, it is preferable from the viewpoint of forming fine pores suitable for the inside of the carbon material and exhibiting excellent particle filling properties and charge / discharge load characteristics.

As artificial graphite, for example, 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 Some organic products such as alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin are calcined and graphitized, or bulk mesophase is graphitized. Can be mentioned.

Also, use granulated artificial graphite obtained by adding a graphitization catalyst to a graphitizable aggregate or graphite such as bulk mesophase, and a graphitizable organic substance, mixing, firing, and pulverizing. You can also
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.

  Examples of the carbonaceous material having a low degree of graphitization include those obtained by firing an organic material at a temperature of usually less than 2500 ° C., and specifically, for example, bulk mesophase and amorphous carbon. Organic substances include coal-based heavy oil such as coal tar pitch and dry distillation liquefied oil; straight-run heavy oil such as atmospheric residual oil and vacuum residual oil; ethylene tar produced as a by-product during thermal decomposition of crude oil, naphtha, etc. Heavy oils such as cracked heavy oils; aromatic hydrocarbons such as acenaphthylene, decacyclene and anthracene; nitrogen-containing cyclic compounds such as phenazine and acridine; sulfur-containing cyclic compounds such as thiophene; and aliphatic cyclics such as adamantane Compounds: Polyphenylene such as biphenyl and terphenyl, polyvinyl esters such as polyvinyl chloride, polyvinyl acetate, and polyvinyl butyral, and thermoplastic polymers such as polyvinyl alcohol.

Examples of the bulk mesophase include a carbonaceous material obtained by heat-treating petroleum heavy oil, coal heavy oil, and straight heavy oil at 400 to 600 ° C.
Examples of the amorphous carbon include particles obtained by firing a bulk mesophase and particles obtained by infusibilizing and firing a carbonaceous material precursor.
Depending on the degree of crystallinity of amorphous carbon, the firing temperature can be 600 ° C. or higher, preferably 900 ° C. or higher, more preferably 950 ° C. or higher, and usually less than 2500 ° C. , Preferably it is 2000 degrees C or less, More preferably, it is the range of 1400 degrees C or less.

At the time of baking, acids such as phosphoric acid, boric acid and hydrochloric acid, alkalis such as sodium hydroxide and the like can be mixed with the organic matter.
Moreover, the carbon material for nonaqueous secondary batteries of this invention may contain the oxide and the other metal. Other metals include metals that can be alloyed with Li, such as Sn, Si, Al, Bi.

<Method for producing carbon material for non-aqueous secondary battery>
The method for producing the carbon material for a non-aqueous secondary battery of the present invention is not particularly limited, but as one means for achieving it, at least one of mechanical energy of impact, compression, friction and shear force is applied. The raw material carbon material is granulated, and the granulation step can be obtained in the presence of a granulating agent that satisfies the following conditions 1) and 2).
1) Liquid during the step of granulating the raw carbon material 2) When the granulating agent contains an organic solvent, at least one of the organic solvents does not have a flash point or has a 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 carried out independently or a plurality of processes may be carried out simultaneously.
When the granulation treatment is performed by the above method, a liquid crosslinking adhesion force between graphite particles is generated by a granulating agent with specified physical properties, and carbon material particles can adhere more firmly to each other. Fine powder with many detachment sites adheres to a base material that becomes a granulated carbon material (hereinafter referred to as a granulated carbon material) and / or has a structure enclosed in granulated carbon material particles. It is possible to produce a granulated carbon material with many Li insertion / extraction sites.

Furthermore, physical damage to the carbon material surface is reduced by the granulating agent acting as a lubricant, and contact of the granulating agent with oxygen is suppressed to prevent the carbon material surface during the granulating treatment. Since oxidation is also suppressed, it is possible to suppress the generation / increase of unstable carbon due to the collapse of the conjugated system of the molecular structure of the carbon material.
As a result, since fine powder adheres more firmly, the unevenness of the particle surface is reduced, and it becomes possible to have a carbon material having a value within the range of the prescribed formula.

As a more preferable embodiment of the above manufacturing method, a manufacturing method including the following first to fifth steps can be mentioned. 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 fifth steps are included.
(1st process) The process of adjusting the particle size of raw material carbon material (2nd process) The process of mixing raw material carbon material and a granulating agent (3rd process) The process of granulating raw material carbon material (4th process) Step of removing granules (fifth step) Step of purifying granulated carbon material Hereinafter, these steps will be described.

(1st process) The process of adjusting the particle size of raw material carbon material The raw material carbon material used by this invention is not specifically limited, Artificial graphite and natural graphite mentioned above can be used. Among them, it is preferable to use natural graphite because of its high crystallinity and high capacity. Examples of natural graphite include scaly, scaly, massive, or plate-like natural graphite. Among these, scaly graphite is preferable.

  The average particle diameter (volume-based median diameter: d50) of the raw material carbon material such as graphite on scales, which is the raw material of spheroidized graphite, obtained in the first step is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably. Is not more than 3 μm, preferably not more than 80 μm, more preferably not more than 50 μm, still more preferably not more than 35 μm, very preferably not more than 20 μm, particularly preferably not more than 10 μm, most preferably not more than 8 μm. 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 is attached to the base material that becomes the granulated graphite (hereinafter referred to as the granulated carbon material) or encased in the base material. Therefore, it is possible to obtain a granulated carbon material having a high degree of spheroidization and a small amount of fine powder.
As a method for adjusting the average particle diameter (d50) of the raw material carbon material to the above range, for example, there is a method of pulverizing and / or classifying (natural) graphite particles.

  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 classifier, inertial classifier, centrifugal classifier (classifier, cyclone, etc.) can be used, wet sieving, mechanical wet classifier, hydraulic classifier, sedimentation classifier A centrifugal wet classifier or the like can be used.

Further, it is preferable that the raw material carbon material obtained in the first step satisfies the following physical properties.
The ash contained in the raw carbon 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, with respect to the total mass of the carbon 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 a non-aqueous secondary battery is used, deterioration of battery performance due to the reaction between the carbon material and the electrolyte during charge / discharge can be suppressed to a negligible level. 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.
The aspect ratio of the raw carbon material 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 method 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, and on the other hand, when the pressure is applied from one direction, the contact area is appropriate, so it is easy to obtain a strong granulated carbon material. Become. When the aspect ratio is too large, there is a tendency that large particles having a particle size of about 100 μm tend to be formed. Too small particles do not form a strong granule because the contact area is small when pressed from one direction. Even if the particles are granulated, the small specific surface area of the flake graphite is reflected, and the specific surface area tends to be a granulated body exceeding 30 m ² / g.

  The 002 plane spacing (d002) and crystallite size (Lc) of the raw carbon material by X-ray wide angle diffraction method are usually (d002) of 3.37 mm or less and (Lc) of 900 mm or more, (d002 ) Is 3.36 mm or less and (Lc) is preferably 950 mm or more. The interplanar spacing (d002) and the crystallite size (Lc) are values indicating the crystallinity of the carbon material bulk. The smaller the interplanar spacing (d002), the smaller the crystallite size (Lc). ) Indicates that the carbon material has high crystallinity, and the amount of lithium entering the graphite layer approaches the theoretical value, so that the capacity increases. 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 the material is CuKα rays monochromatized with a graphite monochromator, and the wide angle X is measured by the reflective diffractometer method. 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 the raw carbon material 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 quantitative discussion of the filling structure. It is also possible to do. 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 carbon material is preferably 0.1 g / cm ³ or more, more preferably 0.15 g / cm ³ or more, still more preferably 0.2 g / cm ³ or more, and particularly 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 carbon material is used as an index indicating 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 carbon material is preferably 0.05 to 0.9, more preferably 0 .05 or more and 0.7 or less, more preferably 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, the measurement cell is placed in a plane perpendicular to the laser beam. Measure while rotating. Note that the wavelength of the argon ion laser light is 514.5 nm.

  The X-ray wide angle diffraction method of the raw material carbon material 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. The hexagonal crystal structure is a crystal form in which a stack of graphite network structures 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 carbon material by the BET method is preferably 0.3 m ² / g or more, more preferably 0.5 m ² / g or more, still more preferably 1 m ² / g or more, particularly preferably 2 m ² / g or more, most preferably at ^{5 m} 2 / g or more, preferably ^{30 m} 2 / g or less, more preferably ^{20 m} 2 / g or less, still more preferably not more than ^{15 m} 2 / g. 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 carbon material is within the above range, the acceptability of Li ions is improved, and the decrease in battery capacity due to the increase in irreversible capacity can be prevented. If the specific surface area of the flaky graphite is too small, the acceptability of Li ions is deteriorated, and if it is too large, a decrease in battery capacity due to an increase in irreversible capacity tends to be prevented.

The amount of water contained in the raw carbon material (raw material graphite) of the granulated carbon material is preferably 1% by mass or less, more preferably 0.5% by mass or less, and still more preferably with respect to the total mass of the raw material graphite. It is 0.1% by mass or less, particularly preferably 0.05% by mass or less, and most preferably 0.01% by 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 raw carbon material (raw material graphite) of the granulated carbon material 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. The temperature is preferably 1000 ° C. or lower, more preferably 800 ° C. or lower, and 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.

  The surface functional group amount O / C value (%) obtained from XPS of the scaly graphite used as the raw material of the spheroidized graphite as the raw carbon material is preferably 0.01 or more, more preferably 0.1 or more, and still more preferably. Is 0.3 or more, particularly preferably 0.5 or more, preferably 5 or less, more preferably 3 or less, still more preferably 2.5 or less, particularly preferably 2 or less, and most preferably 1.5 or less. Within the above range, the hygroscopicity is suppressed and the particles are easily kept dry, and the electrostatic attraction between the particles is increased during the spheronization treatment, so that the adhesion between particles is increased and fine powder adheres to the base material. , And is preferable because it tends to be in a state of being encapsulated in spheroidized particles.

(Second step) Step of mixing raw material carbon material and granulating agent The granulating agent used in the embodiment of the present invention is 1) liquid during the step of granulating the raw carbon material and 2) the granulating agent is organic. When it does not contain a solvent or contains an organic solvent, 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 liquid-crosslinks between the raw material carbon materials in the subsequent step of granulating the raw material carbon material in the third step, so that the liquid between the raw material carbon materials. The attractive force generated by the capillary negative pressure in the bridge and the surface tension of the liquid acts as the liquid cross-linking adhesion force between the particles, so the liquid cross-linking adhesion force between the raw carbon materials increases and the raw carbon material adheres more firmly. It becomes possible.
In the embodiment of the present invention, the strength of the liquid cross-linking adhesive force between the raw material carbon materials due to the liquid crosslinking between the raw material carbon materials is proportional to the γ cos θ value (where γ: surface tension of the liquid) , Θ: contact angle between liquid and particles). That is, when granulating the raw material carbon material, it is preferable that the granulating agent has high wettability with the raw material carbon material. Specifically, a granulating agent satisfying cos θ> 0 so that γ cos θ value> 0 is obtained. The contact angle θ with the graphite measured by the following measuring method of the granulating agent is preferably less than 90 °.

<Measuring method of contact angle θ with graphite>
Contact angle measurement when 1.2 μL of granulating agent is dropped on the HOPG surface and the wetting spread converges and the change rate of the contact angle θ per second becomes 3% or less (also called steady state). It measures with an 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 measured value of the contact angle θ at the heated temperature.

  Furthermore, as the contact angle θ between the raw carbon material 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 adhere more firmly. It becomes possible. 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 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 particles, and the magnitude thereof is proportional to the viscosity. For this reason, if it is a liquid at the time of the granulation process which granulates a raw material carbon material, the viscosity of a granulating agent will not be specifically limited, However, It is preferable that it is 1 cP or more at the time of a granulation process.
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 the rotor or casing when the raw carbon material 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 the present 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, when the granulating agent used in the embodiment of the present invention does not contain an organic solvent or contains an organic solvent, at least one of the organic solvents does not have a flash point or has a flash point. The flash point is 5 ° C or higher. As a result, when granulating the raw material carbon material in the subsequent third step, it is possible to prevent the risk of ignition, fire, and explosion of organic compounds induced by impact and heat generation, so stable and efficient production. Can be implemented.

Examples of granulating agents include, for example, coal tar, petroleum heavy oil, paraffinic oil such as liquid paraffin, synthetic oil such as olefinic oil, naphthenic oil and aromatic oil, vegetable oil and animal fat, and the like. An organic compound such as a resin binder solution 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, an aqueous solvent such as water, And mixtures thereof. Organic solvents with a flash point of 5 ° C or higher include alkylbenzenes such as xylene, isopropylbenzene, ethylbenzene, and propylbenzene; 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 , Halogen-containing compounds such as dichloromethane, chloroform, carbon tetrachloride, 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 carbon material having a high degree of sphericity (roundness) and a small amount of fine powder.

  As the granulating agent, it can be efficiently removed in the step of removing the granulating agent described later (fourth step), which may adversely affect the battery characteristics such as capacity, 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 the raw carbon material and the granulating agent, for example, a method of mixing the raw carbon material and the granulating agent using a mixer or a kneader, or an organic compound dissolved in a low viscosity diluent solvent (organic solvent). Examples thereof include a method of removing the dilution solvent (organic solvent) after mixing the granulating agent and the raw material carbon material. In addition, when the raw material carbon material is granulated in the subsequent third step, the granulation device and the raw material carbon material are added to the granulating apparatus, and the raw material carbon material and the granulating agent are mixed and granulated. The method of performing a process simultaneously is also mentioned.

  The amount of the granulating agent added is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, further preferably 3 parts by mass or more, and still more preferably 6 parts by mass or more with respect to 100 parts by mass of the raw carbon material. More preferably, it is 10 parts by mass or more, particularly preferably 12 parts by mass or more, most preferably 15 parts by mass or more, preferably 1000 parts by mass or less, more preferably 100 parts by mass or less, still more preferably 80 parts by mass or less. Particularly preferably, it is 50 parts by mass or less, and most preferably 20 parts by mass 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 the raw carbon material to the apparatus are less likely to occur.

(Third step) Step of granulating raw material carbon material (step of spheroidizing raw material carbon material)
The carbon material is preferably a material obtained by subjecting the raw material carbon material to a spheroidizing treatment (hereinafter also referred to as granulation) by applying mechanical actions such as impact compression, friction, and shearing force. Further, the spheroidized graphite is preferably composed of a plurality of scaly or scaly graphites and ground graphite fine powder, and particularly preferably composed of a plurality of scaly graphites.

The embodiment of the present invention preferably includes a granulation step of granulating the raw material carbon material 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 including interaction of raw material carbon materials 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 the raw material carbon material introduced inside is a machine such as impact, compression, friction, shear force, etc. An apparatus that imparts a functional effect and performs surface treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating the raw carbon material.

  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.

In addition, the treatment that gives mechanical action to the raw carbon material can be performed simply by passing the raw carbon material, but it is preferable to circulate or retain the raw carbon material 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.
Further, in the step of granulating the raw material carbon material, the raw material carbon material may be granulated in the presence of other substances. Examples of other substances include metals that can be alloyed with lithium or oxides thereof, scales, and the like. Examples thereof include flake graphite, scaly graphite, ground graphite fine powder, amorphous carbon, and raw coke. By granulating together with substances other than the raw material carbon material, carbon materials for non-aqueous secondary batteries having various types of particle structures can be produced.

  In addition, the raw material carbon material, the granulating agent, and the other substances may be introduced in the whole amount into the apparatus, may be separately added, or may be continuously added. In addition, the raw carbon material, the granulating agent and the other substances may be charged simultaneously into the apparatus, may be mixed and may be charged separately. The raw material carbon material, the granulating agent, and the above-mentioned other substances may be mixed simultaneously, or the above-mentioned other substances may be added to the mixture of the raw carbon material and the granulating agent. A raw material carbon material may be added to a mixture of granules. In addition to the particle design, it can be added and mixed separately at an appropriate timing.

  In the spheroidizing treatment of the carbon material, it is more preferable to spheroidize the fine powder generated during the spheroidizing treatment while adhering to the base material and / or enclosing it in the spheroidized particles. By attaching the fine powder generated during the spheronization treatment to the base material and / or spheronizing the particles while enclosing them in the spheroidized particles, it is possible to further refine the void structure in the particles. For this reason, the electrolytic solution spreads effectively and efficiently into the voids in the particles, and the Li ion insertion / desorption sites in the particles cannot be used efficiently, so that there is a tendency to exhibit good low-temperature output characteristics and cycle characteristics. In addition, the fine powder adhering to the base material is not limited to that generated during the spheronization treatment, and may be adjusted so as to include fine powder at the same time as the scale-like graphite particle size adjustment, or added and mixed separately at an appropriate timing. May be.

  In order to attach fine powder to the base material and encapsulate it in the spheroidized particles, the adhesion between the flaky graphite particles and the flaky graphite particles, between the flaky graphite particles and the fine powder particles, and between the fine powder particles and the fine powder particles is strengthened. It is preferable. Specific examples of the adhesion force between particles include van der Waals force and electrostatic attraction without intervening inclusions, and physical and / or chemical crosslinking force via interparticle inclusions.

The van der Waals force becomes “self-weight <adhesion force” as the average particle size (d50) becomes smaller at 100 μm. For this reason, the smaller the average particle diameter (d50) of the flaky graphite (raw carbon material) that is the raw material for the spheroidized graphite, the greater the interparticle adhesion, and the fine powder adheres to the base material and is encapsulated in the spheroidized particles. It is preferable because it tends to be in a state. The average particle diameter (d50) of the flaky graphite is preferably 1 μm or more, more preferably 2 μm or more, still more 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 electrostatic attraction is derived from charging due to particle friction or the like, and the more the particles are dried, the more easily they are charged, and the interparticle adhesion tends to increase. Therefore, for example, by reducing the amount of water contained in the graphite before the spheronization treatment, the adhesion between particles can be increased.
The spheroidizing treatment is preferably performed in a low-humidity atmosphere so that the scaly graphite being treated does not absorb moisture, and the oxidation reaction of the scaly graphite surface proceeds due to the energy of mechanical treatment during the treatment. It is preferable to perform spheronization treatment in an inert atmosphere for the purpose of preventing the introduction of a functional group.

  Examples of the physical and / or chemical cross-linking force through interparticle inclusions include physical and / or chemical cross-linking force through liquid inclusions and solid inclusions. Examples of the chemical cross-linking force include a cross-linking force when a covalent bond, an ionic bond, a hydrogen bond, or the like is formed between a particle and an inclusion between particles due to a chemical reaction, sintering, a mechanochemical effect, or the like. .

(4th process) The process of removing a granulating agent In embodiment of 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.

(5th process) The process of purifying a granulated carbon material In this invention, you may have the process of purifying a granulated carbon material. Examples of a method for purifying a granulated carbon material include a method of performing an acid treatment including nitric acid and hydrochloric acid. Without introducing a sulfate which can be a highly active sulfur source into the system, the metal in the graphite, the metal It is preferable because impurities such as a compound and an inorganic compound 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. If the amount is too small, the impurities tend not to be efficiently removed. On the other hand, if the amount is too large, the amount of graphite that can be washed at one time is reduced, which leads to a decrease in productivity and an increase in cost.

The acid treatment is performed by immersing graphite in the acidic solution as described above. The soaking 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. If the length is too long, the productivity tends to decrease and the cost increases. If the length is too short, the impurities cannot be sufficiently removed.
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. If this temperature is too low, the impurities tend not to be sufficiently removed.

  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. When this numerical value is small, it indicates that the amount of ions in water increases, and there is a tendency for contamination by impurities and a reduction in cleaning efficiency.

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. If it is too long, the production efficiency tends to decrease, and if it is too short, the residual impurities / acid content tends to increase.
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. If the amount is too large, the production efficiency tends to decrease. If the amount is too small, the residual impurities and acid content tend to increase.

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. If it is too low, residual impurities and acid content tend to increase.
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. If the ion concentration is too high, the acid content remains and the pH tends to decrease. If the ion concentration is too low, the treatment takes time and the productivity tends to decrease.

(Sixth step) Step of attaching a carbonaceous material having lower crystallinity than the raw carbon material to the granulated carbon material In the embodiment of the present invention, a carbonaceous material having lower crystallinity than the raw carbon material in the granulated carbon material. You may have the process of attaching. That is, a carbonaceous material can be combined with the carbon material. According to this step, it is possible to obtain a carbon material that can suppress side reactions with the electrolytic solution and improve rapid charge / discharge characteristics.

Composite graphite in which a carbonaceous material having lower crystallinity than the raw carbon material is further added to the granulated carbon material may be referred to as “carbonaceous material composite carbon material” or “composite carbon material”.
The carbonaceous material adhering (compositing) treatment to the granulated carbon material is performed by mixing the organic compound that becomes the carbonaceous material and the granulated carbon material, and in a non-oxidizing atmosphere, preferably under the flow of nitrogen, argon, carbon dioxide, etc. This is a treatment for heating and carbonizing or graphitizing the organic compound.

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 carbon material can be obtained by performing 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.

In addition, as long as the effect of this embodiment is not impaired, the addition of another process and the control conditions not described above may be added.
The content of the carbonaceous material in the carbonaceous material composite carbon material is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.3% or more with respect to the granulated carbon material as a raw material. More preferably, it is 0.7% by mass or more, particularly preferably 1% by mass or more, most preferably 1.5% 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, and most preferably 5% by mass or less.

If the carbonaceous material content in the carbonaceous material composite carbon material is too high, the carbon material will be damaged when rolled with sufficient pressure to achieve high capacity in non-aqueous secondary batteries. There is a tendency for destruction to occur, leading to an increase in charge / discharge irreversible capacity during an initial cycle and a decrease in 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 carbon material can be calculated from the sample mass before and after the material firing as shown in the following formula. At this time, the calculation is made on the assumption that there is no mass change before and after firing the granulated carbon material.
Content of carbonaceous material (mass%) = [(w2-w1) / w1] × 100
(W1 is the mass (kg) of the granulated carbon material, and w2 is the mass (kg) of the carbonaceous composite carbon material)

Moreover, the carbonaceous material composite carbon material may contain carbon fine particles in order to improve conductivity. The method for containing the carbon fine particles is not particularly limited, and specifically, the method described in JP-A-2014-060148 can be used.
The volume average particle diameter (d50) of the carbon fine particles is usually 0.01 μm or more and 10 μm or less, preferably 0.05 μm or more, more preferably 0.07 μm or more, further preferably 0.1 μm or more, preferably Is 8 μm or less, more preferably 5 μm or less, and still more preferably 1 μm or less.
When the carbon fine particles have a secondary structure in which primary particles are aggregated and aggregated, other physical properties and types are not particularly limited as long as the primary particle size is 3 nm or more and 500 nm or less, but the primary particle size is preferably 3 nm or more, more preferably 15 nm or more, further preferably 30 nm or more, particularly preferably 40 nm or more, preferably 500 nm or less, more preferably 200 nm or less, still more preferably 100 nm or less, particularly preferably 70 nm. It is as follows. The primary particle diameter of the carbon fine particles can be measured by electron microscope observation such as SEM or a laser diffraction particle size distribution analyzer.

The shape of the carbon fine particles is not particularly limited, and may be any of granular, spherical, chain-like, needle-like, fibrous, plate-like, and scale-like shapes.
Specifically, the carbon fine particles are not particularly limited, and examples thereof include substances having nanostructures such as coal fine powder, vapor phase carbon powder, carbon black, ketjen black, fullerene, carbon nanofiber, carbon nanotube, and carbon nanowall. Among these, carbon black is particularly preferable. Carbon black has the advantage that the input / output characteristics are improved even at low temperatures, and at the same time, it can be obtained inexpensively and easily.
The “carbon fine particles” are usually 0.01 parts by mass or more, preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and usually 20 parts by mass or less with respect to 100 parts by mass of the “granulated carbon material”. , Preferably 10 parts by mass or less, more preferably 5 parts by mass or less.

[Mixing of carbon materials]
Further, in the present invention, a carbon material different from the granulated carbon material 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 carbon material with a carbon material different from the granulated carbon material 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.

Carbon materials containing metal particles and metal compounds include, for example, Fe, Co, Sb, Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, Nb, Mo, Examples thereof include a material in which a metal selected from the group consisting of Cu, Zn, Ge, In, Ti, or the like or a compound thereof is combined 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.

The volume-based average particle diameter of the metal particles is usually 0.005 μm or more, preferably 0.01 μm or more, more preferably 0.02 μm or more, further preferably 0.03 μm or more, and usually 10 μm or less from the viewpoint of cycle life. , 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 carbon material and the carbon material different from the granulated carbon material is not particularly limited. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylindrical mixer Machine, 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,
A Pugmill type mixer, a fluidized type mixer, or the like can be used.

<Physical properties of carbon materials for non-aqueous secondary batteries>
The carbon material for a non-aqueous secondary battery of the present invention contains granulated particles made of a plurality of carbon materials, and further has a feature in the particle cross section, and the Box count dimension of the present invention is based on the image of the particle cross section. Identified.

-About the granulated particle which consists of a plurality of carbon materials which the carbon material for non-aqueous secondary batteries contains In the present invention, the granulated particle which consists of a plurality of carbon materials means that the granulated particles are at least two or more graphite particles. Including.
The granulated particles contained in the carbon material for non-aqueous secondary batteries are not particularly limited as long as they are composed of a plurality of carbon materials, but are measured from the volume-based average particle diameter X measured by laser diffraction and the cross-sectional SEM image. Further, the relationship | X ₁ −X | / X _{1 of the} equivalent circular diameter X ₁ is usually 0.2 or less, preferably 0.15 or less, more preferably 0.1 or less.
When | X ₁ −X | / X ₁ is too large, representative particles cannot be selected, and the overall tendency may not be expressed.

The volume-based average particle size X is determined by adding 10 mL of a 0.2% by weight aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)), which is a surfactant, to the non-aqueous system of the present invention. Suspend 0.01 g of carbon material for secondary battery, and introduce it as a measurement sample into a commercially available laser diffraction / scattering type particle size distribution measuring device (for example, LA-920 manufactured by HORIBA), and output 28 kHz ultrasonic wave to the measurement sample After irradiating at 60 W for 1 minute, the volume is defined as the volume-based median diameter measured by the measurement apparatus.
Sectional SEM image circle measured from the equivalent diameter X ₁ is represented by Formula 1 below using a particle peripheral length L [μm].

Also, granulated particles containing a non-aqueous secondary battery carbon material of the present invention, a flow-type particle image analyzer measured roundness R, the cross-sectional SEM image from the measured roundness R ₁ relationship | R -R ₁ | is usually 0.1 or less, preferably 0.08 or less, more preferably 0.06 or less.
When | R−R ₁ | is too large, the particle boundary is not properly captured and overestimated, and therefore there is a possibility that the analysis cannot be performed correctly.

As the value of circularity R measured by the flow type particle image analyzer, for example, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co.) is used, and a sample (charcoal for non-aqueous secondary battery of the present invention) is used. Material) About 0.2 g is dispersed in a 0.2% by mass aqueous solution (about 50 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and 28 kHz ultrasonic waves are output to the dispersion at a power of 60 W. After irradiating for minutes, the detection range is specified as 0.6 to 400 μm, and the values measured for the particles having a particle size in the range of 1.5 to 40 μm are used.
The circularity R ₁ measured from the cross-sectional SEM image is the particle area S [μm ² ] obtained from the image.
, And is calculated from the following formula 2 using the circumference L [μm].

  Although it is the method of taking a particle boundary, there is no restriction | limiting in particular, What is necessary is just to carry out automatically or manually with commercially available analysis software. It is preferable to approximate with a polygon, but in this case, it is preferable to approximate a polygon with 15 or more. This is because if it is less than this, the background portion will be treated as inside the particle when the curved portion is approximated.

-Acquisition of a particle cross-sectional image The image of a particle cross-section uses a backscattered electron image acquired using an SEM (scanning electron microscope) at an acceleration voltage of 10 kV. The method for obtaining the particle cross-sectional image is not particularly limited, but it is cut by a focused ion beam (FIB) or ion milling using an electrode plate containing a carbon material for a non-aqueous secondary battery and a coating film of a carbon material for a non-aqueous secondary battery. Then, after cutting out the particle cross-section, a particle cross-sectional image is acquired using SEM.

The acceleration voltage at the time of observing the cross section of the carbon material for non-aqueous secondary batteries with SEM (scanning electron microscope) is 10 kV.
With this accelerating voltage, it becomes easy to distinguish the void region of the non-aqueous secondary battery carbon material from the other regions due to the difference in the reflected secondary electron image in the SEM image. The imaging magnification is usually 500 times or more, more preferably 1000 times or more, still more preferably 2000 times, and usually 10,000 times or less. If it is said range, the whole image of 1 particle | grains of the carbon material for non-aqueous secondary batteries is acquirable. The resolution is 200 dpi (ppi) or more, preferably 256 dpi (ppi) or more. The number of pixels is preferably evaluated at 800 pixels or more.

-Average value of Box count dimension for void area of cross-sectional SEM image When the carbon material for non-aqueous secondary battery of the present invention arbitrarily selects 30 particles of granulated particles made of a plurality of carbon materials from the cross-sectional SEM image, A box for a void area, which is calculated from an image obtained by dividing each cross-sectional SEM image of each granulated particle into a void area and an area other than the void and binarized.
The average value of count dimension is 1.55 or more, preferably 1.60 or more, more preferably 1.62 or more, usually 1.80 or less, preferably 1.75 or less, more preferably 1.70 or less. .

If the average value of the Box count dimension for the void region is too small, it means that the amount of fine structure is less than that, and the output that is the effect of the present invention cannot be obtained, and conversely if it is too large, the specific surface area of the particles increases. The initial efficiency will be low.
Box count dimensions of each particle of the carbon material for the non-aqueous secondary battery are the following (a) to (d).
To calculate.

(A) Definition and calculation method of Box count dimension The Box count dimension is an examination of how many fractal figures are included when a certain area is divided by a certain size (box size). This is a method for estimating the fractal dimension (see JP2013-77702A). It is an index that represents the complexity of the shape, the degree of unevenness on the surface, etc., and the larger the fractal dimension value, the more complex the unevenness, and it is defined as follows. Assuming that the number of boxes necessary to cover a certain figure F with a square box (box) having a side size δ is Nδ (F), the fractal dimension is defined by the following equation 3.

In the present invention, a particle cross-sectional SEM image composed of voids and carbon is divided into lattice-like regions (boxes) at equal intervals δ (divided into small square regions with a side size of δ), and δ The number of boxes including voids is counted while changing the size of. Next, the number of counted boxes is plotted on the log-log graph with the vertical axis representing the number of boxes and the horizontal axis representing the magnitude of δ, and the fractal dimension is obtained from the slope of the graph.

As a specific method, in a particle cross-sectional SEM image composed of voids and carbon, the voids and other portions of the image in the particles are binarized. It is assumed that binarization is performed in pixel units of the image. The analysis target is a binarized portion that represents a pixel in the gap.
In addition, it is necessary to perform value conversion so that the region outside the particle (outside the particle outline) is not regarded as a void. The image is divided into grid-like areas (boxes) having a specific pixel size. There are no particular restrictions on the arrangement of the boxes, but it is preferable to arrange the boxes so that they are parallel to the long axis of the particles (the longest diameter passing through the center of gravity). At that time, the image is divided into boxes as shown in FIGS. Count the number of pixels that contain even one pixel in the divided box. The logarithmic graph is plotted with the vertical axis representing the number of boxes counted by changing the size of the box and performing the same operation, and the horizontal axis representing the box size δ at that time. A line approximation of this plot is performed, and the slope of the line is multiplied by −1 is the fractal dimension by the BOX COUNT method. The slope may be calculated by the least square method.

  The fractal dimension is an index indicating the strength of self-similarity, but is an index indicating the complexity and fineness of the structure when expressing a binarized image. This means that in a binarized image with a more complicated partial structure, if the box size decreases, the proportion of the fine structure included in the box increases accordingly, that is, the inclination tends to increase. Therefore, it expresses the fineness of the substructure and the large amount. That is, the Box count dimension in the present invention is an index representing the complexity of the fine structure of the void and the number of the structures.

(B) Definition of Box Size (δ) The box size to be divided is not particularly limited, but is preferably 10 divisions or more, more preferably 15 divisions or more, on the logarithmic graph with respect to the maximum pixel of the image. The number is preferably 15 or more, particularly preferably 20 or more, and usually 50 or less, preferably 40 or less, and more preferably 30 or less. If it is the said range, it will not produce a difference with a pixel and it is not necessary to use a high-resolution image.

(C) Binarization method The binarization method is not particularly limited, but it must be a method in which the voids in the particles and the carbon part are clearly separated. In the binarization process, when an 8-bit grayscale image such as an SEM image is targeted, the luminance is divided into two, and the two divided images are divided into two values (e.g., divided into 0 and 255 for 8 bits). To do. The binarization may be performed with any image processing software. There are various algorithms for dividing the threshold value. For example, there are a mode method and an ISOData method, and a method capable of clearly dividing the void portion and the carbon portion may be used. It must also be an image that can be binarized. In this case, an image that can be binarized means an image that is clearly separated at a certain threshold value with respect to the brightness of the air gap and the brightness of the carbon part. In some images, the surface is rough due to the accuracy of processing, the cross-section is tanned, or the brightness of the void portion and the carbon portion is close due to factors such as the contrast and brightness settings. Since such an image may show a void distribution different from the original when binarized, it is preferably excluded from the analysis target. For example, FIG. 4 shows an image in which the surface of the graphite portion in the middle is low and the luminance is low and the luminance of fine voids is high. If you try to binarize by picking up fine things in such a figure, the carbon part will also be expressed as a gap, and conversely, if you set the brightness with no gap in the carbon part as the threshold, you can display the fine gap that would originally be a gap Disappear. It is preferable not to select such particles, but since there is a possibility of a typical cross section, it is necessary not to analyze such an SEM image which is difficult to binarize.

(D) Definition of Particle Boundary The method of dividing the particle boundary may be implemented freehand or approximate to a polygon, for example, but it must be a method of dividing the boundary well. Although there is no particular limitation, it is necessary to delimit the boundary between the particle and the other region so that the region of interest (ROI) indicating the shape of the particle does not leak. When the boundary is not a simple ellipse but a complicated shape, the particle region may be approximated by a polygon by dividing the boundary by an arbitrary number at equal intervals, for example. However, the boundary is set so as not to deviate from the circularity R measured by the flow type particle image analyzer. As a ≦ 0.1 _| here without departing The measured by a flow type particle image analyzer was sphericity R, relationship between the section of sphericity R ₁ from SEM images measured is | R-R 1 It is to be. In addition, when an electrode coated with a binder having poor conductivity is used, there are some cases where the boundary is difficult to distinguish under the measurement conditions of the present invention. This is a phenomenon that occurs due to poor conductivity of the binder when the side surface of the particle is visible behind the cross section of the particle. In such a case, it is necessary to judge the boundary by separately taking an image in which the boundary is clear by lowering the acceleration voltage.

(Other parameters)
-Tap density The tap density of the carbon material of the present invention is usually 0.70 g / cm ³ or more, more preferably 0.75 g / cm ³ or more, still more preferably 0.80 g / cm ³ or more, and particularly preferably 0.85 g / cm ³ . cm ³ or more, preferably 1.3 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, and even more preferably 1.1 g / cm ³ or less.

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.
When the amount is within the above range, the filling property is good and an appropriate space can be formed in the interparticle space. Therefore, an appropriate space can be arranged between the intraparticle space and the interparticle space, and higher output can be obtained.

Volume average particle size X (d50)
The volume-based average particle size X (also referred to as “d50”) of the carbon material of the present invention is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 8 μm or more. The average particle diameter d50 is usually 50 μm or less, preferably 40 μm or less, more preferably 35 μm or less, still more preferably 30 μm or less, and particularly preferably 25 μm or less. If the average particle size d50 is too small, the non-aqueous secondary battery obtained using the carbon material tends to increase the irreversible capacity and cause a loss of initial battery capacity. On the other hand, if the average particle size d50 is too large, slurry coating may occur. May cause inconveniences such as line drawing, deterioration of high current density charge / discharge characteristics, and deterioration of low temperature input / output characteristics.

-Raman R value The Raman R value represented by the following formula of the carbon material of the present invention is usually 0.01 or more, preferably 0.1 or more, more preferably 0.2 or more, still more preferably 0.25 or more, Particularly preferred is 0.3 or more, and most preferred is 0.35 or more. Moreover, although there is no restriction | limiting in particular in the upper limit of a Raman R value, Usually, it is 1 or less, Preferably it is 0.7 or less, More preferably, it is 0.6 or less, More preferably, it is 0.5 or less.

Intensity _{I A} of the intensity _I B / 1580 cm ^-1 vicinity of the peak _{P A} of the peak _{P B} in the vicinity of 1360 cm ^-1 in the Raman value R = Raman spectroscopy
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.
If the Raman R value is within the above range, since the crystallinity of the carbon material particle surface is appropriate, Li ion insertion and desorption sites can sufficiently exist, so that the carbon material has good low-temperature input / output characteristics and discharge capacity. Tends to be obtained.

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)

・ BET specific surface area (SA)
Measured specific surface area by the BET method of the carbon material of the present invention (SA) is preferably ^{1 m} 2 / g or more, more preferably ^{5 m} 2 / g or more, more preferably ^8m 2 / g or more, and most preferably ^12m 2 / g or more, most preferably 13 m ² / g or more. Moreover, Preferably it is 30 m < ² > / g or less, More preferably, it is 20 m < ² > / g or less, More preferably, it is 17 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 carbon 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 using a surface area meter (for example, a specific surface area measuring device “AMS8000” manufactured by Okura Riken Co., Ltd.), preliminarily dried at 100 ° C. for 3 hours in a nitrogen stream, and then subjected to a liquid nitrogen temperature. It is defined as a value measured by a nitrogen adsorption BET method by a gas flow method using a nitrogen helium mixed gas that is accurately adjusted so that the value of the relative pressure of nitrogen with respect to atmospheric pressure is 0.3.

・ Roundness R
The circularity of the carbon material of the present invention is 0.88 or more, preferably 0.90 or more, more preferably 0.91 or more, and still more preferably 0.92 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, when the circularity is within the above range, the bending degree of Li ion diffusion decreases, the electrolyte solution moves smoothly in the interparticle voids, and the carbon materials are appropriately in contact with each other. Therefore, it tends to exhibit good rapid 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)

-X-ray parameter The d value (interlayer distance) of the lattice plane (002 plane) of the carbon material of the present invention determined by X-ray diffraction by the Gakushin method 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.

  In addition, the crystallite size (Lc) of the carbon material determined by X-ray diffraction by the Gakushin method is preferably 90 nm or more, more preferably 100 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.

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

  Although it does not specifically limit as a binder, It is preferable to use what has an olefinically unsaturated bond in a molecule | numerator. 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 a carbon material that is an 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 and / or 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 carbon material of the present invention is used in combination with the above-mentioned binder having an olefinically unsaturated bond, the ratio of the binder used for the active material layer can be reduced as compared with the conventional material. Specifically, the carbon material of the present invention and a binder (in some cases, it may be a mixture of a binder having an unsaturated bond and a binder having no unsaturated bond as described above). The mass ratio of each is preferably 90/10 or more, more preferably 95/5 or more, preferably 99.9 / 0.1 or less, more preferably 99.5 / 0.5 in terms of the dry mass ratio. The range is as follows. 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 of the present invention is formed by dispersing the above-described carbon material of the present invention and a binder in a dispersion medium to form a slurry, which is applied to a current collector. As the dispersion medium, an organic solvent such as alcohol or water can be used. If necessary, a conductive agent (conductive aid) 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. .

You may adjust the thickness of an active material layer so that it may become the thickness of the said range by pressing after application | coating of a slurry and drying.
The density of the carbon 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 still more preferably 1.65 g / cm. 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 the negative electrode for non-aqueous secondary batteries using the carbon material of the present invention 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 lithium ion secondary battery and the lithium ion secondary battery using the carbon material of the present invention will be exemplified, but usable materials, production methods and the like are not limited to the following specific examples. Absent.

<Non-aqueous secondary battery>
The basic configuration of the non-aqueous secondary battery of the present invention, particularly the lithium ion secondary battery, is the same as that of a conventionally known lithium ion secondary battery, and usually includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte. Is provided. As the negative electrode, a negative electrode using the above-described carbon material of the present invention is used.

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, from the viewpoint of occlusion / release of lithium ions, 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 are particularly preferable. ₄ or a lithium transition metal composite oxide obtained by substituting a part of these transition metals with another metal. These positive electrode active materials may be used alone or in combination.

  The binder for binding the positive electrode active material is not particularly limited, and any known one can be selected and used. 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 because it is difficult to decompose during the oxidation reaction. 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 agent (conductive aid) 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 an electrolyte (sometimes referred to as “electrolytic solution”), a non-aqueous electrolytic solution in which a lithium salt is dissolved in a non-aqueous solvent, an organic polymer compound or the like by adding an organic polymer compound to the non-aqueous electrolytic solution, A rubber or solid sheet 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 used in combination. 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 Litrifluoromethanesulfonylimide ((CF ₃ SO ₂ ) ₂ NLi) Of these, LiClO ₄ , LiPF ₆ , and LiBF ₄ are preferable.

A lithium salt may be used independently or may use 2 or more types together. 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 electrolyte solution described above may further contain a film forming agent. Specific examples of the film forming agent include carbonate compounds such as vinylene carbonate, vinyl ethyl 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 additive is used, the content thereof 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 with respect to the total mass of the non-aqueous electrolyte solution. The range is as follows. 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 nonaqueous secondary battery of the present invention is not particularly limited. Examples include a cylinder type in which a sheet electrode and a separator are spiral, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a coin type in which a pellet electrode and a separator are stacked, and the like. Further, by storing batteries of these forms in an optional outer case, the battery can be used in an arbitrary shape and size such as a coin shape, a cylindrical shape, and a square shape.

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

  EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In 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 rcos θ of the granulating agent were measured by the methods described in the specification.

<Production of electrode sheet>
An electrode plate having an active material layer having an active material layer density of 1.35 ± 0.03 g / cm ³ was prepared using the graphite particles of the example or the comparative example. 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 -0.5 g of butadiene rubber aqueous dispersion in terms of solid content was stirred for 5 minutes with a KEYENCE hybrid mixer and defoamed for 30 seconds to obtain a slurry.

Using this slurry, a small die coater made by Itochu Machining was used so that the negative electrode material was 12.00 ± 0.3 mg / cm ² on a 10 μm thick copper foil as a current collector.
The electrode sheet was obtained by adjusting the density of the active material layer to 1.60 ± 0.03 g / cm ³ by roll pressing using a roller having a diameter of 20 cm.

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

<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 250 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. Subsequently, the second charge / discharge was performed at the same current density, and the discharge capacity of the second cycle 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 and a current value of 0.2 C at 25 ° C. 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.

<Roundness R measured with a flow particle image analyzer>
Using a flow type particle image analyzer (FPIA-2000 manufactured by Toa Medical Electronics Co., Ltd.), the particle size distribution was measured based on the equivalent circle diameter and the average circularity was calculated. Ion exchange water was used as a dispersion medium, and polyoxyethylene (20) monolaurate was used as a surfactant. The equivalent circle diameter is the diameter of a circle (equivalent circle) having the same projected area as the photographed particle image, and the circularity is the circumference of the equivalent particle as a molecule and the circumference of the photographed particle projection image. The ratio is the denominator. The circularity of the particles having a measured equivalent diameter in the range of 1.5 to 40 μm was averaged to obtain a circularity R.

<Volume standard average particle diameter X: d50 measured by laser diffraction>
A carbon material (0.01 g) is suspended in 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)), which is a surfactant, and this is a measurement sample. And introduced into a commercially available laser diffraction / scattering particle size distribution measuring apparatus (for example, 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 the volume-based median diameter was measured in the measuring apparatus. It was measured as (d50).

<Tap density>
The carbon material of the present invention was dropped into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ using a powder density measuring instrument through a sieve having an opening of 300 μm and filled into the cell, and then the stroke length was 10 mm. Was defined as the density obtained from the volume at that time and the mass of the sample.

<Acquisition of cross-sectional SEM image>
The cross-sectional SEM image of the carbon material was measured as follows. As the electrode plate containing the carbon material, the same electrode plate as that used in the production of the battery for performance evaluation was used. First, the cross section of the electrode was processed using a cross section polisher (IB-09020CP manufactured by JEOL Ltd.). As for the processed electrode cross section, a reflected electron image was obtained by SEM (SU-70, manufactured by Hitachi High-Technologies Corporation). The SEM acquisition conditions were an acceleration voltage of 10 kV and a magnification of 1000 times, and an image in a range where one particle could be acquired at a resolution of 256 dpi was obtained. Thereafter, in accordance with the measurement method and conditions of the above-described degree of dispersion, | X ₁ −X | / X ₁ ≦ 0.2, | R− using two 150 μm × 100 μm SEM images
More than 30 particles satisfying R ₁ | ≦ 0.1 were extracted. In addition, 30 particles having an average luminance of the graphite portion of 80 or more and an average of 65 or less of the luminance of the space portion were selected as an image that can be binarized.

<Setting the particle boundary>
In the image processing software imageJ, the particle boundary is defined as a polygon boundary by polygon approximation. At this time, it was made to be 15 or more in accordance with the particle shape. The region outside the particle was processed so that the luminance was 255 in all pixels.

<Binarization of cross-sectional SEM image (separation of void region and region other than void)>
The void region of the carbon material observed from the cross-sectional SEM image and the region other than the void were binarized by using the image software imageJ and setting the threshold value at a luminance of 80 to 85.

<Circular equivalent diameter X ₁ measured from cross-sectional SEM image>
The total value of the lengths of the line segments of the polygonal particle boundary was calculated from the following formula as the particle peripheral length L [μm].

<Roundness R ₁ measured from cross-sectional SEM image>
The polygonal area set as the particle boundary was set as S, and the following calculation was performed from the particle circumference L calculated above.

<Box count dimension for void area>
Since the maximum length of the obtained image was about 260 pixels, the analysis was performed with Box size as 2, 3, 4, 6, 8, 16, 32, 64. For each 30 particles satisfying | X ₁ −X | / X ₁ ≦ 0.2 and | R−R ₁ | ≦ 0.1 in the cross-sectional SEM image, the Box count dimension for the void region is calculated and averaged. The value B for the void area
The average value of the ox count dimension was used.

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. Liquid paraffin (manufactured by Wako Pure Chemical Industries, grade 1, physical properties at 25 ° C .: viscosity = 95 cP, contact angle = 13.2 °, surface tension = 31.7)
12 g of mN / m, rcos θ = 30.9) was added and stirred and mixed, and then the obtained sample was pulverized and mixed at a rotation speed of 3000 rpm with a hammer mill (MF10 manufactured by IKA), and a granulating agent was attached. Scaly natural graphite was obtained. The obtained flaky natural graphite uniformly attached with the granulating agent is adhered to the base material by the fine powder produced during the spheroidizing treatment by the hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. While being encapsulated, spheroidizing treatment was performed by mechanical action for 10 minutes at a rotor peripheral speed of 85 m / sec, and heat treatment was performed at 720 ° C. in an inert gas, thereby obtaining spheroidized graphite having a d50 of 12.9 μm. . The d50, Tap, circularity, box count dimension average value, discharge capacity, and low-temperature output characteristics were measured by the above measurement methods. The results are shown in Tables 1 and 2.

(Example 2)
The flaky natural graphite having a d50 of 100 μm was pulverized by a dry airflow pulverizer to obtain a flaky natural graphite having a d50 of 6 μm, a Tap of 0.13 g / cm ³ and a water content of 0.08% by mass. Paraffinic oil (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 to 100 g of the obtained scaly natural graphite 0.7 mN / m, rc оsθ = 30.9) was added and stirred and mixed, and then the resulting sample was pulverized and mixed with a hammer mill (MF10 made by IKA) at a rotation speed of 3000 rpm, and the granulating agent was uniform. A scaly natural graphite adhering to was obtained. The obtained flaky natural graphite uniformly attached with the granulating agent is adhered to the base material by the fine powder produced during the spheroidizing treatment by the hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. While being encapsulated, spheroidizing treatment was performed by mechanical action for 10 minutes at a rotor peripheral speed of 85 m / sec, and heat treatment was performed at 720 ° C. in an inert gas to obtain spheroidized graphite having a d50 of 9.2 μm. Tables 1 and 2 show the results of measurements similar to those in Example 1.

(Example 3)
A flaky natural graphite having a d50 of 100 μm was pulverized by a dry swirling flow pulverizer with a pulverizer to obtain a flaky natural graphite having a d50 of 6 μm, a Tap of 0.38 g / cm ³ , and a water content of 0.08% by mass. . Paraffinic oil (liquid paraffin, manufactured by Wako Pure Chemical Industries, Ltd., first grade, physical properties at 25 ° C .: viscosity = 95 cP, contact angle = 1) to 100 g of the obtained scaly natural graphite
After adding 12 g of 3.2 °, surface tension = 31.7 mN / m, rc ｓsθ = 30.9) and stirring and mixing, the obtained sample was solved with a hammer mill (MF10 manufactured by IKA) at a rotation speed of 3000 rpm. By crushing and mixing, scaly natural graphite to which a granulating agent was uniformly applied was obtained. The obtained flaky natural graphite uniformly attached with the granulating agent is adhered to the base material by the fine powder produced during the spheroidizing treatment by the hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. While encapsulating, spheroidizing treatment was performed by mechanical action for 10 minutes at a rotor peripheral speed of 85 m / sec, and heat treatment was performed at 720 ° C. in an inert gas to obtain spheroidized graphite having a d50 of 9.9 μm. Tables 1 and 2 show the results of measurements similar to those in Example 1.

(Comparative Example 1)
The scaly natural graphite having a d50 of 100 μm was spheroidized by a 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. In the obtained sample, it was confirmed that a lot of scaly graphite-like fine powders adhered to the base material and not encapsulated in the spherical particles were present. This sample was classified to remove the above-mentioned scaly graphite-like fine powder to obtain spheroidized graphite having a d50 of 10.8 μm. Tables 1 and 2 show the results of measurements similar to those in Example 1.

(Comparative Example 2)
The scaly natural graphite having a d50 of 100 μm was granulated by a mechanical action of 5 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. In the obtained sample, it was confirmed that a lot of scaly graphite-like fine powders were attached to the base material and not encapsulated in the granulated particles. This sample was subjected to classification to remove the scaly graphite-like fine powder to obtain a granulated carbon material having a d50 of 15.4 μm. Tables 1 and 2 show the results of measurements similar to those in Example 1.

Example 4
Spherical natural graphite before heat treatment obtained in Example 1 and coal tar pitch as an amorphous carbon precursor are mixed and subjected to heat treatment at 1300 ° C. in an inert gas, and then the fired product is crushed and classified. As a result, a multi-layer structure carbon material in which graphite particles and amorphous carbon were combined was obtained. From the firing yield, the mass ratio of spheroidized graphite particles and amorphous carbon (spheroidized graphite particles: amorphous carbon) in the obtained multilayer carbon material is 1: 0.08. Was confirmed. Tables 3 and 4 show the results of the same measurements as in Example 1.

(Comparative Example 3)
By mixing the spheroidized natural graphite obtained in Comparative Example 1 and coal tar pitch as an amorphous carbon precursor and subjecting it to a heat treatment at 1300 ° C. in an inert gas, the fired product is crushed and classified. Thus, a multi-layer structure carbon material in which graphite particles and amorphous carbon were combined was obtained. From the firing yield, the mass ratio of spheroidized graphite particles and amorphous carbon (spheroidized graphite particles: amorphous carbon) in the obtained multilayer carbon material is 1: 0.065. Was confirmed. Tables 3 and 4 show the results of the same measurements as in Example 1.

  By using the carbon material of the present invention as an active material for a non-aqueous secondary battery negative electrode, it is possible to provide a non-aqueous secondary battery having excellent capacity, input / output characteristics, high-temperature storage characteristics, and cycle characteristics. it can. Moreover, according to the manufacturing method of the said material, since there are few processes, it can manufacture stably and efficiently and cheaply.

Claims (9)

A carbon material for a non-aqueous secondary battery containing granulated particles made of a plurality of carbon materials,
When 30 particles of the granulated particles are arbitrarily selected from the cross-sectional SEM image of the carbon material for non-aqueous secondary battery, each cross-sectional SEM image of each granulated particle is divided into a void region and a region other than the void. A carbon material for a non-aqueous secondary battery, wherein an average value of 30 particles in the Box count dimension with respect to a void region, which is calculated from a value-processed image, is 1.55 or more.
However, the cross-sectional SEM image is a reflected electron image acquired at an acceleration voltage of 10 kV. The granulated particles are volume-based average particle diameter X as measured by laser diffraction, relationships circular equivalent diameter X _1, which is measured from a cross-sectional SEM image | X 1 _-X | a / X ₁ ≦ 0.2, wherein Item 2. The carbon material for a non-aqueous secondary battery according to Item 1. The granulated particles relationship of circularity R, roundness R _1, which is measured from a cross-sectional SEM images measured by the flow particle image analyzer | R-R 1 _| is ≦ 0.1, according to claim 1 or 2. The carbon material for non-aqueous secondary batteries according to 2. Tap density of 0.7 g / cm ³ or more, a non-aqueous secondary battery carbon material according to any one of claims 1 to 3.   The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 4, wherein a circularity obtained by flow-type particle image analysis of the carbon material is 0.88 or more.   The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 5, wherein the graphite particles are spherical graphite particles obtained by granulating scaly graphite, scaly graphite, and massive graphite.   The carbon material for a non-aqueous secondary battery according to claim 6, wherein the granulation treatment is a treatment that imparts at least mechanical energy of any one of impact, compression, friction, and shear force.   The granulation process includes a rotating member that rotates at a high speed in a casing, and a rotor having a rotor in which a plurality of blades are installed in the casing. The carbon material for a non-aqueous secondary battery according to claim 6 or 7, wherein the carbon material is granulated by applying any one of impact, compression, friction, and shearing force.   A non-aqueous secondary battery comprising a positive electrode and a negative electrode capable of occluding and releasing lithium ions, and an electrolyte, the negative electrode comprising a current collector and a negative electrode active material layer formed on the current collector, A non-aqueous secondary battery in which the negative electrode active material layer contains the carbon material according to claim 1.