JP2016189319A - Carbon material and non-aqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbonaceous material ensuring production of a high capacity nonaqueous secondary battery, excellent in I/O characteristics, high-temperature storage characteristics, and cycle characteristics and, as a result, to provide a high performance nonaqueous secondary battery.SOLUTION: A carbonaceous material for nonaqueous secondary battery capable of occluding and releasing lithium ions contains a carbonaceous matter on the particle surface, and satisfies the relationship of following formula (1). (formula 1)Y-0.01X≤α (1) (Y=true density (g/cm), X=specific surface area (SA)(m/g) of the carbonaceous material measured by BET method, α=2.20).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, There was a problem of decline.

  In order to solve the above problem, for example, in Patent Documents 1 and 2, spheroidized natural graphite is produced by subjecting scaly natural graphite to mechanical energy treatment, and spheroidized natural graphite is used as nuclear graphite. A technique for improving filling properties and input / output characteristics by coating amorphous carbon on the surface is disclosed.

JP 2000-340232 A JP 2012-074297 A

According to the study by the present inventors, the spheroidized natural graphite disclosed in Patent Document 1 and Patent Document 2 has a structure lacking in the density of particles, and the particle surface is covered with amorphous carbon. The specific surface area was reduced, the Li ion insertion / desorption sites of the particles were small, and there was room for improvement in improving the input / output characteristics of the battery.
In general, it is known that by using graphite particles having a large specific surface area, the Li ion insertion / desorption sites of the graphite particles can be used greatly, so that the input / output characteristics of the battery are improved.

On the other hand, the carbonaceous material of graphite particles coated with a carbonaceous material has a lower crystallinity than graphite and has a structure that facilitates Li ion insertion and desorption, so that the input / output characteristics of a battery can be improved. I know. That is, it is considered that the input / output characteristics can be further improved by increasing the specific surface area and reducing the crystallinity of the graphite particles. However, when graphite particles are coated with a carbonaceous material in order to increase the low-crystalline region where Li ion insertion and desorption is likely to occur, the fine structure of the particle surface is covered. The increase in the low crystalline region due to the coating of is in a trade-off relationship.

  The present invention has been made in view of the background art, and the problem is a non-aqueous secondary battery having excellent input / output characteristics, which has escaped from the trade-off relationship between the conventional specific surface area and the low crystalline region. It is to provide a high-performance non-aqueous secondary battery as a result.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention are carbon materials for non-aqueous secondary batteries that can occlude and release lithium ions, and the carbon material particles carbonaceous particles. A carbon material for a non-aqueous secondary battery having excellent input / output characteristics when the relationship between the true density and the specific surface area (SA) measured by the BET method satisfies a specific value. As a result, the present invention was completed. The true density is one of physical properties that is an index of crystallinity of graphite particles.

  The carbon material according to the present invention has a large specific surface area (SA) measured by the BET method compared with a carbon material containing a conventional carbonaceous material on the particle surface. It can be used, and despite its large specific surface area (SA) measured by the BET method, the true density is low (ie, there are many low-crystalline carbonaceous material components), so Good insertion and removal. That is, a carbon material for a non-aqueous secondary battery having both the effect of improving the input / output characteristics due to the specific surface area and the effect of improving the input / output characteristics due to the low crystalline carbonaceous material could be obtained.

That is, the gist of the present invention is a carbon material for a non-aqueous secondary battery capable of occluding and releasing lithium ions, and the carbon material contains a carbonaceous material on the particle surface. The carbon material for non-aqueous secondary batteries is characterized by satisfying the relationship of
(Formula 1)
Y-0.01X ≦ α (1)
(Y = true density (g / cm ³ ), X = specific surface area (SA) of carbon material measured by BET method (m ^{2 /} g), α = 2.20)

  Another aspect of the present invention includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte. The negative electrode includes a current collector and a negative electrode active material layer formed on the current collector. In addition, the present invention resides in a non-aqueous secondary battery in which the negative electrode active material layer contains the above carbon material.

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

It is a figure which shows the relationship between X and Y. In Example 1, (X, Y) is a point of (7.38, 2.25), Example 2 is a point of (5.79, 2.24), and Example 3 is (5.15). , 2.24), Example 4 is the point (4.30, 2.23), Example 5 is the point (2.88, 2.22), and Example 6 is (8.69, 2.23), Example 7 is (6.21, 2.22), and Comparative Example 1 is (3.92, 2.25). Comparative Example 2 is the point of (2.97, 2.24), Comparative Example 3 is the point of (3.53, 2.25), and Comparative Example 4 is the point of (2.51, 2.24). Comparative Example 5 is the point (4.48, 2.25), and Comparative Example 6 is the point (1.82, 2.23).

  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.

<Carbon material that is the core 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 one in which the carbon material contains a carbonaceous material on the particle surface and satisfies the relationship of the above formula (1). Although not particularly limited, for example, a carbon material (eg, amorphous carbon or graphitized material) coated with a carbon material serving as a core, such as graphite, amorphous carbon, or a carbonaceous material (bulk mesophase) having a low degree of graphitization Is mentioned.

Since the DBP (dibutyl phthalate) oil absorption amount is reduced by coating the unevenness on the surface of the carbon material, the viscosity of the paint can be lowered by forming a paint at the time of producing the electrode, and the coating property can be expected to be improved.
The term “coated” as used herein refers to an embodiment in which at least a part or the entire surface of the carbon material is coated or attached with a carbonaceous material.

  As the carbon material as the core, graphite is readily available commercially, theoretically has a high charge / discharge capacity of 372 mAh / g, and further compared to the case of using another negative electrode active material, This is preferable because the effect of improving the charge / discharge characteristics at a high current density is great. As graphite, those having few impurities are preferable, and they can be used after being subjected to various known purification treatments, if necessary.

Examples of the type of graphite include natural graphite, artificial graphite and the like, and natural graphite is more preferable from the viewpoint of good charge / discharge characteristics at a high capacity and a high current density.
Moreover, in this invention, these can be used individually or in combination of 2 or more types.

  The natural graphite is classified into scale black (FlakeGraphite), scale (Crystalline Graphite), bulk graphite (Vein Graphite), and soil graphite (Amorphous Graphite) according to the properties ("Powder Process Technology Assembly" ( (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. Among them, those having few impurities are preferable, and can be used after being subjected to various known purification treatments, if necessary.

Natural graphite is produced in Madagascar, China, Brazil, Ukraine, Canada, etc., and scaly graphite is produced mainly in 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 referred to as spheroidized natural graphite), and the like. Among these, spheroidized natural graphite is most preferable from the viewpoints that suitable fine pores can be formed inside the carbon material and that excellent particle filling properties and charge / discharge load characteristics are exhibited.

As the raw material for the artificial graphite, amorphous carbon, and carbonaceous material (bulk mesophase) having a low degree of graphitization, graphitizable carbon and non-graphitizable carbon can be used. 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 alcohol, polyacrylonitrile, Examples include those obtained by firing organic substances such as polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin at a predetermined temperature.

  The artificial graphite can be obtained by graphitizing a raw material containing a large amount of graphitizable carbon in a range of 2500 ° C. or higher and 3200 ° C. or lower. During firing, a silicon-containing compound or a boron-containing compound is graphitized as a catalyst. Can also be used.

  As graphitizable carbon, coal heavy oil such as coal tar pitch and dry distillation liquefied oil; straight heavy oil such as atmospheric residue and vacuum residue; by-product during thermal decomposition of crude oil, naphtha, etc. Petroleum heavy oils such as cracked heavy oils such as ethylene tar; Aromatic hydrocarbons such as acenaphthylene, decacyclene and anthracene; Nitrogen-containing cyclic compounds such as phenazine and acridine; Sulfur-containing cyclic compounds such as thiophene; Aliphatic cyclic compounds; polyphenylenes such as biphenyl and terphenyl; polyvinyl esters such as polyvinyl chloride, polyvinyl acetate, and polyvinyl butyral; thermoplastic polymers such as polyvinyl alcohol.

The amorphous carbon can be obtained by calcining non-graphitizable carbon or a carbon precursor in which the graphitization is inhibited and firing at 600 ° C. or more and 3200 ° C. or less.
Examples of the non-graphitizable carbon include carbon black, polyvinylidene chloride, sugar, cellulose, and phenol formaldehyde resin.

  Furthermore, the amorphous carbon can also be easily graphitized carbon. Examples thereof include those obtained by firing graphitizable carbon at a temperature usually lower than 2500 ° C. Depending on the degree of the chemical structure of the amorphous carbon, the firing temperature can usually be 600 ° C. or higher, preferably 900 ° C. or higher, more preferably 950 ° C. or higher, and usually lower than 2500 ° C. , Preferably it is 2000 degrees C or less, More preferably, it is the range of 1400 degrees C or less.

Examples of the carbonaceous material (bulk mesophase) having a small degree of graphitization include those obtained by heat-treating graphitizable carbon at a temperature of 400 to 600 ° C.
At the time of firing, 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.

  As a carbon material for non-aqueous secondary batteries, an oxide and other metals may be included. 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 carbon material for a non-aqueous secondary battery according to the present invention is one in which the carbon material contains a carbonaceous material on the particle surface and is not particularly limited as long as it is produced so as to satisfy the relationship of the above formula (1). As one of the means for achieving the above, graphite obtained by spheroidizing fine powder produced when spheroidizing (granulating) flaky natural graphite whose particle size is adjusted so that the average particle diameter d50 is 80 μm or less is obtained. After obtaining a spheronized carbon material by spheronizing while adhering to the base material and / or encapsulating in particles of spheroidized graphite (hereinafter referred to as spheroidizing treatment, the non-aqueous secondary of the present invention obtained Obtained by carbonizing or graphitizing an organic compound by mixing and heat-treating the obtained spherical carbon material and an organic compound after the carbon material of the carbon material for the battery is referred to as a spherical carbon material) Can do. As the spheronization treatment, the fine powder generated from the carbon material during the spheronization treatment is attached to the base material to be the spheroidized carbon material and / or spheroidized while being included in the particles of the spheroidized carbon material. It is preferable. Specifically, it has 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, and the granulation step includes the following 1) and It may be performed in the presence of a granulating agent that satisfies the condition of 2).

1) Liquid at the time of granulating the raw material carbon material 2) When the granulating agent 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 ignites When it has a point, the flash point is 5 ° C or higher. Moreover, you may perform other processes, such as the process of refinement | purification, and a classification process, by arbitrary processes as needed.

  When the average particle diameter d50 of the carbon material used as the raw material for the spherical carbon material is 80 μm or less, the specific surface area (SA) measured by the BET method of the spherical carbon material tends to be easily controlled. Furthermore, it becomes difficult for the spheroidized carbon material to be flat, and it is easy to provide a suitable tap density. Furthermore, the fine powder generated during the spheronization treatment is adhered to the base material that becomes the spheroidized carbon material and / or the spheronization process is performed while encapsulating in the particles of the spheroidized carbon material, thereby further densifying the particle structure. Thus, a material having a relatively high specific surface area (SA) measured by the BET method can be obtained, and the relationship of the above formula (1) can be satisfied.

  If it has the said granulation process, you may further have another process as needed. Another process may be implemented independently and multiple processes may be implemented simultaneously. As one embodiment, the following first to sixth steps are included.

(1st process) The process of adjusting the particle size of raw material 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 the granule (fifth step) Step of purifying the granulated carbon material (sixth step) Step of adding a carbonaceous material having lower crystallinity than the raw carbon material to the granulated carbon material. The process 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, an increase in irreversible capacity and a decrease in cycle characteristics can be prevented. In addition, the void structure in the particles of spheroidized graphite can be precisely controlled. As a result, the electrolyte can efficiently spread to the voids in the particles, and the Li ion insertion / desorption sites in the particles can be used efficiently, improving the low-temperature output characteristics and cycle characteristics. Tend to. Furthermore, since the circularity of the spheroidized graphite can be adjusted to be high, the electrolyte solution can smoothly move in the interparticle void without increasing the bending degree of Li ion diffusion, and the rapid charge / discharge characteristics are improved.

  In addition, when the average particle size is in the above range, the fine powder generated during the granulation step is attached to the base material to be granulated graphite (hereinafter referred to as a granulated carbon material) or inside the base material. It is possible to granulate while wrapping, and 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 CuKα ray monochromatized with a graphite monochromator is used as a radiation source. A line diffraction curve is measured. Thereafter, the interplanar spacing (d002) and the crystallite size (Lc) are obtained using the Gakushin method.

The filling structure of 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, 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, alkylnaphthalenes such as methylnaphthalene, ethylnaphthalene and propylnaphthalene, and aromatic carbonization such as allylbenzene such as styrene and allylnaphthalene. Hydrogen, aliphatic hydrocarbons such as octane, nonane, decane, ketones such as methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, esters such as propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, methanol , Ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene Alcohols such as lenglycol and glycerine, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, methoxypropanol, methoxypropyl-2- Acetate, methoxymethyl butanol, methoxybutyl acetate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, triethylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol monophenyl Glycol derivatives such as nyl ether, ethers such as 1,4-dioxane, nitrogen-containing compounds such as dimethylformamide, pyridine, 2-pyrrolidone and N-methyl-2-pyrrolidone, and sulfur-containing compounds such as dimethyl sulfoxide , 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, still more 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 imparting mechanical action 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 Nihon Coke Industries), etc. 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. In addition, since the granulating agent can be removed also in the following sixth step, this step may be omitted.

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 immersion 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 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) A step of attaching a carbonaceous material having lower crystallinity than the raw carbon material to the granulated carbon material. Further, in the present invention, for the purpose of suppressing side reactions with the electrolytic solution and improving rapid charge / discharge characteristics. And a step of attaching a carbonaceous material having lower crystallinity than the raw carbon material to the granulated carbon material. That is, a carbonaceous material is 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)

  Further, 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., a carbon material different from the granulated carbon material can be mixed. (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 productivity 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 productivity 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 productivity 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 electrode plate swelling and productivity 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 electrode plate swelling and productivity 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 electrode plate swelling and productivity 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. Further, particles coated with a carbonaceous material by chemical vapor deposition (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 productivity 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 productivity 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 productivity 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 productivity 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 productivity 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 productivity are improved.

Examples of carbon materials containing metal particles and metal compounds include Fe, Co, Sb, Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, Nb, and Mo. , Cu, Zn, Ge, In, Ti, and the like, or a material obtained by combining a metal selected from the group consisting of, for example, graphite with graphite. As the metal or the compound that can be used, an alloy composed of two or more kinds of metals may be used, and the metal particles may be alloy particles formed of two or more kinds of metal elements. Among these, a metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn, and W or a compound thereof is preferable, and among these, Si and Si are preferable.
Ox. 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, more preferably It is 0.4 or more, more preferably 0.6 or more, preferably 1.8 or less, more preferably 1.6 or less, and still more preferably 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 size 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 carbon material different from the granulated carbon material and the granulated carbon material is not particularly limited. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylinder mixer, Double cone type mixer, regular cubic type mixer, vertical type mixer, fixed type mixer: spiral type mixer, ribbon type mixer, Muller type mixer, Helical Flight type mixer, Pugm
An ill type mixer, a fluidized type mixer, or the like can be used.

<Physical properties of carbon materials for non-aqueous secondary batteries>
-Relationship between tap density and specific surface area (SA) measured by BET method The carbon material of the present invention satisfies the relationship of the following formula (1).
(Formula 1)
Y-0.01X ≦ α (1)
(Y = true density (g / cm ³ ), X = specific surface area (SA) of carbon material measured by BET method (m ^{2 /} g), α = 2.20)

In the carbon material of the present invention, α represented by the above formula (1) is 2.20, preferably 2.195, more preferably 2.19, and further preferably 2.16.
When the relationship represented by the above formula (1) cannot be satisfied, the balance between the usable region of the Li ion insertion / desorption site in the particle and the crystalline carbonaceous material that is liable to insert and desorb Li ions is deteriorated. There is a tendency for output characteristics to deteriorate.

- True Density The true density of the carbon material of the present invention is preferably 2.15 g / cm ³ or more, more preferably 2.16 g / cm ³ or more, more preferably 2.17 g / cm ³ or more, particularly preferably 2.18g / cm ³ or more, most preferably 2.19 g / cm ³ or higher, preferably 2.26 g / cm ³ or less, more preferably 2.25 g / cm ³ or less.

  When the true density is within the above range, a structure with low crystallinity in which Li ions can be easily inserted and desorbed can be appropriately obtained, so that favorable input / output characteristics can be obtained.

・ Specific surface area (SA) measured by BET method
The specific surface area (SA) measured by the BET method of the carbon material of the present invention is preferably 2 m ² / g or more, more preferably 2.5 m ² / g or more, still more preferably 3 m ² / g or more, particularly preferably 4 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 17 m ² / g or less, and particularly preferably 15 m ² / g or less.

  If the specific surface area is within the above range, the portion where Li enters and exits can be sufficiently secured, so that the input / output characteristics are excellent, and the activity of the active material with respect to the electrolytic solution can be moderately suppressed. However, there is a tendency that a high-capacity battery can be manufactured.

  As a specific surface area measured by the BET ratio method, a specific surface area meter (for example, Tristar II3020 manufactured by Micromeritics Co., Ltd.) is used, and a measurement object (here, a graphite negative electrode material) is subjected to nitrogen flow at 350 ° C. for 60 minutes. The value measured by the nitrogen adsorption BET multipoint method by the gas flow method using a nitrogen helium mixed gas that was precisely adjusted so that the relative pressure of nitrogen relative to atmospheric pressure was 0.3 after preliminary drying. Can be used.

-Volume-based average particle size (average particle size d50)
The volume-based average particle diameter (also referred to as “average particle diameter d50”) of the carbon material of the present invention is preferably 1 μm or more, more preferably 3 μm or more, still more preferably 4 μm or more, particularly preferably 5 μm or more, and most preferably 6 μm. That's it. The average particle diameter d50 is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, and particularly preferably 31 μm or less.
Within the above range, an increase in irreversible capacity and a loss of initial battery capacity tend to be suppressed.

Tap density of the carbon material of the tap density the invention preferably 1.00 g / cm ³ or more, more preferably 1.05 g / cm ³ or more, more preferably 1.10 g / cm ³ or more, particularly preferably 1.12g / cm ³ or more, most preferably 1.14 g / cm ³ or higher, preferably 1.40 g / cm ³ or less, more preferably 1.35 g / cm ³ or less, more preferably 1.30 g / cm ³ Or less, particularly preferably 1.25 g / cm ³ or less.

  When the tap density is within the above range, sufficient filling property can be obtained, so that the capacity can be increased. In addition, since the carbon density in the particles is difficult to increase, the rolling property is good, and a high-density negative electrode sheet tends to be easily formed.

-X-ray parameter The d ₀₀₂ 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 d ₀₀₂ value is within the above range, the initial irreversible capacity tends to suppress an increase because the crystallinity of graphite is high. Here, 0.335 nm is a theoretical value of graphite.

The crystallite size (Lc) of the carbon material determined by X-ray diffraction by the Gakushin method is usually 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more, still more preferably 500 nm or more, particularly preferably 1000 nm or more. Range.
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.

-Circularity The carbon material of the present invention has a circularity of 0.88 or more, preferably 0.90 or more, more preferably 0.91 or more. The circularity is preferably 1 or less, more preferably 0.98 or less, and still more preferably 0.97 or less. When the circularity is within the above range, the high current density charge / discharge characteristics of the non-aqueous secondary battery tend to be suppressed. The circularity is defined by the following formula, and when the circularity is 1, a theoretical sphere is obtained.

  When the circularity is within the above range, 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)

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

-Ash content The ash content contained in the carbon material of the present invention 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. It is. 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.

  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.

-Surface functional group amount O / C value (%)

  The O / C value obtained from XPS is preferably 0.1 or more, more preferably 1 or more, still more preferably 1.5 or more, particularly preferably 2 or more, preferably 8 or less, more preferably 4 or less, still more preferably. Is 3.5 or less, particularly preferably 3 or less. If the surface functional group amount O / C value is within the above range, the desolvation reactivity of Li ions and the electrolyte solvent on the negative electrode active material surface is promoted, the rapid charge / discharge characteristics are improved, and the reaction with the electrolyte Tend to be suppressed and charge / discharge efficiency tends to be good.

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

Aspect ratio The aspect ratio of the carbon material of the present invention in a powder state is theoretically 1 or more, preferably 1.1 or more, more preferably 1.2 or more. The aspect ratio is preferably 10 or less, more preferably 8 or less, and still more preferably 5 or less.

  When the aspect ratio is within the above range, streaking of the slurry containing the carbon material (negative electrode forming material) hardly occurs at the time of forming the electrode plate, and a uniform coated surface is obtained, and high current density charge / discharge of the non-aqueous secondary battery is obtained. There is a tendency to avoid deterioration of characteristics.

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

-Raman R value The Raman R value of the carbon material of the present invention is usually 0.01 or more, preferably 0.05 or more, more preferably 0.1 or more, still more preferably 0.15 or more, particularly preferably. 0.2 or more. The Raman R value is usually 1 or less, preferably 0.6 or less, more preferably 0.5 or less, and still more preferably 0.4 or less.

Incidentally, the Raman R value is measured and the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1 in the Raman spectrum obtained by Raman spectroscopy, the intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity Defined as the ratio (I _B / I _A ).
Incidentally, the scope of 1580～1620Cm ^-1 A "1580cm around ^-1" in the present specification, "1360cm around ^-1" refers to the range of 1350 ^-1.

  The Raman 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 °). The smaller the Raman R value, the higher the crystallinity or the disordered crystal state. When the Raman R value is within the above range, the crystallinity of the carbon material particle surface is unlikely to be high, and when the density is increased, the crystal is difficult to be oriented in a direction parallel to the negative electrode plate, and a tendency to avoid deterioration of load characteristics is avoided. It is in. Furthermore, the crystal on the particle surface is not easily disturbed, and the increase in reactivity with the electrolyte solution of the negative electrode is suppressed, and the decrease in charge / discharge efficiency of the nonaqueous secondary battery and the increase in gas generation tend to be avoided.

  The Raman spectrum can be measured with a Raman spectrometer. Specifically, the sample particles are naturally dropped into the measurement cell to fill the sample, and the measurement cell is rotated in a plane perpendicular to the laser beam while irradiating the measurement cell with an argon ion laser beam. Measure. The measurement conditions are as follows.

Argon ion laser light wavelength: 514.5 nm
Laser power on sample: 25 mW
Resolution: 4cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
Peak intensity measurement, peak half-width measurement: background processing, smoothing processing (convolution 5 points by simple averaging)

-DBP oil absorption amount The DBP (dibutyl phthalate) oil absorption amount of the carbon material of the present invention is preferably 85 ml / 100 g or less, more preferably 70 ml / 100 g or less, still more preferably 65 ml / 100 g or less, particularly preferably 60 ml / 100 g or less. It is. The DBP oil absorption is preferably 30 ml / 100 g or more, more preferably 40 ml / 100 g or more.

  If the DBP oil absorption amount is within the above range, it means that the progress of spheroidization of the carbon material is sufficient, and there is a tendency that streaking is difficult to occur during the application of the slurry containing the carbon material. However, since the pore structure exists, the reaction surface tends to be prevented from lowering.

  The DBP oil absorption amount is defined as a measured value when 40 g of a measurement material (carbon material) is added, a dropping speed is 4 ml / min, a rotation speed is 125 rpm, and a set torque is 500 N · m, in accordance with JIS K6217. For the measurement, for example, Absorbometer E type manufactured by Brabender can be used.

・ Average particle diameter d10
The particle size (d10) corresponding to 10% cumulative from the small particle side of the particle size measured on a volume basis of the carbon material of the present invention is preferably 30 μm or less, more preferably 20 μm or less, still more preferably 17 μm or less, preferably It is 1 μm or more, more preferably 3 μm or more, and further preferably 5 μm or more.

When d10 is within the above range, the tendency of the particles to agglomerate does not become too strong, and it is possible to avoid the occurrence of process inconveniences such as an increase in slurry viscosity, a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a nonaqueous secondary battery. In addition, the high current density charge / discharge characteristics and the low temperature input / output characteristics tend to be avoided.
d10 is defined as a value obtained by integrating 10% from a particle size having a small particle frequency% in the particle size distribution obtained when measuring the average particle size d50.

・ Average particle size d90
The particle size (d90) corresponding to 90% of the particle size measured on the volume basis of the carbon material of the present invention is preferably 100 μm or less, more preferably 70 μm or less, still more preferably 60 μm or less, and even more. The thickness is preferably 50 μm or less, particularly preferably 45 μm or less, most preferably 42 μm or less, preferably 20 μm or more, more preferably 26 μm or more, still more preferably 30 μm or more, and particularly preferably 34 μm or more.

When d90 is within the above range, it is possible to avoid a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a non-aqueous secondary battery, generation of process inconveniences such as striation during application of slurry, and high current density charge / discharge characteristics. There is a tendency to avoid the decrease in the temperature and the low-temperature input / output characteristics.
d90 is defined as a value in which the frequency% of particles is 90% integrated from a small particle size in the particle size distribution obtained when measuring the average particle size d50.

The ratio (d90 / d10) of 90% particle size (d90) and 10% particle size (d10) in the volume-based particle size distribution
The ratio (d90 / d10) of 90% particle size (d90) and 10% particle size (d10) in the volume-based particle size distribution of the carbon material of the present invention is usually 2.0 or more, preferably 2.2 or more. Preferably it is 2.4 or more, More preferably, it is 2.5 or more, More preferably, it is 2.6 or more, Especially preferably, it is 2.7 or more, Usually 5.0 or less, Preferably it is 4.5 or less, More preferably, 4. 0 or less, more preferably 3.8 or less, particularly preferably 3.5 or less.

-Battery performance The initial discharge capacity of the battery produced by the method described in Examples below using the carbon material of the present invention is usually 300 mAh / g or more, preferably 320 mAh / g, more preferably 340 mAh / g or more. More preferably, it is 350 mAh / g or more. If the initial discharge capacity is too low, there is a tendency that it cannot be applied to a device with large power consumption or used for a long time.

[Negative electrode for non-aqueous secondary battery]
The present invention also relates to a negative electrode for a non-aqueous secondary battery formed using the carbon material of the present invention, and specific examples thereof include a negative electrode for a lithium ion secondary battery.

  The method for producing the negative electrode for nonaqueous secondary battery and the selection of materials other than the carbon material for nonaqueous secondary battery negative electrode of the present invention constituting the negative electrode for nonaqueous secondary battery are not particularly limited.

  The negative electrode for a non-aqueous secondary battery of the present invention includes a current collector and an active material layer formed on the current collector, and the active material layer is a carbon material for a non-aqueous secondary battery negative electrode of the present invention. It contains. The active material layer preferably further contains a binder.

  The binder is not particularly limited, but a binder having an olefinically unsaturated bond in the molecule is preferable. 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 in the molecule, the swellability of the active material layer with respect to the electrolytic solution can be reduced. Of these, styrene-butadiene rubber is preferred because of its availability.

  By using such a binder having an olefinically unsaturated bond in the molecule and the carbon material for a nonaqueous secondary battery negative electrode of the present invention in combination, the mechanical strength of the negative electrode plate can be increased. When the mechanical strength of the negative electrode plate is high, deterioration of the negative electrode due to charging / discharging of the nonaqueous secondary battery is suppressed, and the cycle life can be extended.

  The binder having an olefinically unsaturated bond in the molecule preferably has a large molecular weight and / or a large proportion of unsaturated bonds.

  As the molecular weight of the binder, the weight average molecular weight can usually be 10,000 or more, and can usually be 1,000,000 or less. If it is this range, both mechanical strength and flexibility can be controlled to a favorable range. The weight average molecular weight is preferably 50,000 or more, and preferably 300,000 or less.

As the ratio of olefinically unsaturated bonds in the binder molecule, the number of moles of olefinically unsaturated bonds per 1 g of the total binder can be usually 2.5 × 10 ⁻⁷ mol or more, and usually 5 × It can be 10 <^-6> mol or less. If it is this range, the intensity | strength improvement effect will be acquired sufficiently and flexibility will also be favorable. The number of moles is preferably 8 × 10 ⁻⁷ mol or more, and preferably 1 × 10 ⁻⁶ mol or less.

  Moreover, about the binder which has an olefinically unsaturated bond in a molecule | numerator, the unsaturation degree can be normally 15% or more and 90% or less. The degree of unsaturation is preferably 20% or more, more preferably 40% or more, and preferably 80% or less. In the present specification, the degree of unsaturation represents the ratio (%) of the double bond to the repeating unit of the polymer.

  As the binder, a binder having no olefinically unsaturated bond in the molecule can also be used. By using a binder having an olefinically unsaturated bond in the molecule and a binder having no olefinically unsaturated bond in the molecule, improvement in coating property can be expected.

When the binder having an olefinically unsaturated bond in the molecule is 100% by mass, the mixing ratio of the binder having no olefinically unsaturated bond in the molecule is to suppress the strength of the active material layer from being lowered. Usually, it can be 150 mass% or less, Preferably it is 120 mass% or less.

Examples of the binder having no olefinically unsaturated bond in the molecule 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 thereof;
Fluorine-containing polymers such as polyvinylidene fluoride;
Examples thereof include alkane polymers such as polyethylene and polypropylene, and copolymers thereof.

  In order to improve the electroconductivity of a negative electrode, you may make the active material layer in the negative electrode for non-aqueous secondary batteries of this invention contain a conductive support agent. The conductive aid is not particularly limited, and examples thereof include carbon black such as acetylene black, ketjen black, and furnace black, fine powder made of Cu, Ni having an average particle size of 1 μm or less, or an alloy thereof.

  It is preferable that the addition amount of a conductive support agent is 10 mass parts or less with respect to 100 mass parts of carbon materials for non-aqueous secondary battery negative electrodes of this invention.

  The negative electrode for a non-aqueous secondary battery of the present invention is a slurry obtained by dispersing the carbon material for a non-aqueous secondary battery negative electrode of the present invention and optionally a binder and / or a conductive additive in a dispersion medium. It can be formed by coating and drying. As the dispersion medium, an organic solvent such as alcohol or water can be used.

  It does not specifically limit as a collector which apply | coats a slurry, A well-known thing can be used. Specific examples include metal thin films such as rolled copper foil, electrolytic copper foil, and stainless steel foil.

  The thickness of the current collector can usually be 4 μm or more, and can usually be 30 μm or less. The thickness is preferably 6 μm or more, and preferably 20 μm or less.

  The thickness of the active material layer obtained by applying and drying the slurry is usually 5 μm or more from the viewpoint of practicality as a negative electrode and sufficient lithium ion occlusion / release function for high-density current values. In addition, it can usually be 200 μm or less. Preferably it is 20 micrometers or more, More preferably, it is 30 micrometers or more, Preferably it is 100 micrometers or less, More preferably, it is 75 micrometers or less.

  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.

Although the density of the carbon material for the non-aqueous secondary battery negative electrode in the active material layer varies depending on the application, for example, in an application in which input / output characteristics such as an in-vehicle application and a power tool application are important, 1.1 g / cm ³ or more 1.65 g / cm ³ or less. Within this range, it is possible to avoid an increase in contact resistance between particles due to the density being too low, and it is also possible to suppress a decrease in rate characteristics due to the density being too high.

The density is preferably 1.2 g / cm ³ or more, more preferably 1.25 g / cm ³ or more.

In applications in which capacity is important, such as portable device applications such as mobile phones and personal computers, it is usually 1.45 g / cm ³ or more, and usually 1.9 g / cm ³ or less.

  If it is this range, the capacity | capacitance fall of the battery per unit volume by a density being too low can be avoided, On the other hand, the fall of the rate characteristic by a density being too high can also be suppressed.

Density is preferably 1.55 g / cm ³ or more, more preferably 1.65 g / cm ³ or more, and particularly preferably 1.7 g / cm ³ or more.

[Non-aqueous secondary battery]
The basic configuration of the nonaqueous secondary battery according to the present invention can be the same as, for example, a known lithium ion secondary battery, and usually includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte. The negative electrode is a negative electrode for a non-aqueous secondary battery according to the present invention described above.

<Positive electrode>
The positive electrode can include a current collector and an active material layer formed on the current collector. The active material layer preferably contains a binder in addition to the positive electrode active material.

  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. Of these, metal chalcogen compounds capable of inserting and extracting lithium ions are preferred.

Examples of metal chalcogen compounds include transition metal oxides such as vanadium oxide, molybdenum oxide, manganese oxide, chromium oxide, titanium oxide, and tungsten oxide;
Transition metal sulfides such as vanadium sulfide, molybdenum sulfide, titanium sulfide, CuS;
Phosphorus-sulfur compounds of transition metals such as NiPS ₃ and FePS ₃ ;
Selenium compounds of transition metals such as VSe ₂ and NbSe ₃ ;
Complex oxides of transition metals such as Fe _0.25 V _0.75 S ₂ , Na _0.1 CrS ₂ ;
Examples thereof include composite sulfides of transition metals such as LiCoS ₂ and LiNiS ₂ .

Among them, 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 _4, and their transitions A lithium transition metal composite oxide in which a part of the metal is substituted with another metal is particularly preferable.

  These positive electrode active materials may be used alone or in combination.

  The binder for positive electrodes is not specifically limited, A well-known thing can be selected arbitrarily and can be 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 them, a resin having no unsaturated bond is preferable because it is difficult to decompose during the oxidation reaction.

  The weight average molecular weight of the binder can usually be 10,000 or more, and can usually be 3 million or less. The weight average molecular weight is preferably 100,000 or more, and preferably 1,000,000 or less.

  The positive electrode active material layer may contain a conductive additive in order to improve the conductivity of the positive electrode. The conductive auxiliary agent is not particularly limited, and examples thereof include carbon powders such as acetylene black, carbon black, and graphite, and various metal fibers, powders, and foils.

  In the present invention, in the same manner as the above-described negative electrode manufacturing method, the positive electrode is dispersed in a dispersion medium with an active material and, optionally, a binder and / or a conductive auxiliary agent, and this is applied to the surface of the current collector. Can be formed. The current collector of the positive electrode is not particularly limited, and examples thereof include aluminum, nickel, stainless steel (SUS), and the like.

<Electrolyte>
The electrolyte (sometimes referred to as “electrolyte”) is not particularly limited, and a non-aqueous electrolyte obtained by dissolving a lithium salt as an electrolyte in a non-aqueous solvent, or an organic polymer compound or the like is added to the non-aqueous electrolyte. By doing so, a gel-like, rubber-like, or solid sheet-like shape can be mentioned.

  The non-aqueous solvent used for the non-aqueous electrolyte is not particularly limited, and a known non-aqueous solvent can be used.

Examples thereof include chain carbonates such as diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate;
Cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate;
Chain ethers such as 1,2-dimethoxyethane;
Cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, 1,3-dioxolane;
Chain esters such as methyl formate, methyl acetate and methyl propionate;
and cyclic esters such as γ-butyrolactone and γ-valerolactone.

  A non-aqueous solvent may be individual or may use 2 or more types together. In the case of a mixed solvent, a combination of a mixed solvent containing a cyclic carbonate and a chain carbonate is preferable from the balance of conductivity and viscosity, and the cyclic carbonate is preferably ethylene carbonate.

The lithium salt used in the non-aqueous electrolyte is not particularly limited, and a known lithium salt can be used. For example, halides such as LiCl and LiBr;
Perhalogenates such as LiClO ₄ , LiBrO ₄ , LiClO ₄ ;
Inorganic lithium salts such as inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ ;
Perfluoroalkanesulfonates such as LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ ;
Fluorine-containing organic lithium salts such as perfluoroalkanesulfonic acid imide salts such as Li trifluoromethanesulfonylimide ((CF ₃ SO ₂ ) ₂ NLi) can be used. Among 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 can be in the range of 0.5 mol / L to 2.0 mol / L.

When the organic polymer compound is included in the non-aqueous electrolyte solution described above 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;
A crosslinked polymer of a polyether polymer compound;
Vinyl alcohol polymer compounds such as polyvinyl alcohol and polyvinyl butyral; insolubilized vinyl alcohol polymer compounds;
Polyepichlorohydrin;
Polyphosphazene;
Polysiloxane;
Vinyl polymer compounds such as polyvinylpyrrolidone, polyvinylidene carbonate, and polyacrylonitrile;
Examples thereof include polymer copolymers such as poly (ω-methoxyoligooxyethylene methacrylate), poly (ω-methoxyoligooxyethylene methacrylate-co-methyl methacrylate) and 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 methyl phenyl carbonate;
Alkene sulfides such as ethylene sulfide and propylene sulfide;
Sultone compounds such as 1,3-propane sultone and 1,4-butane sultone;
Examples of the acid anhydride include maleic acid anhydride and succinic acid anhydride.

  Further, an overcharge inhibitor such as diphenyl ether or cyclohexylbenzene may be added to the non-aqueous electrolyte.

  When using the above-mentioned various additives, the total content of the additives is the total amount of the non-aqueous electrolyte so as not to adversely affect other battery characteristics such as an increase in initial irreversible capacity, low temperature characteristics, and deterioration in rate characteristics. In general, it can be 10% by mass or less, in particular, 8% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

  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 those obtained by dissolving a Li salt in the aforementioned polyether polymer compound, and polymers in which the terminal hydroxyl group of the polyether is substituted with an alkoxide.

<Others>
In order to prevent a short circuit between the electrodes, a porous separator such as a porous membrane or a nonwoven fabric can usually be interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte is impregnated into the porous separator. It is convenient to use it. As a material for the separator, polyolefin such as polyethylene and polypropylene, polyethersulfone, and the like are used, and polyolefin is preferable.

The form of the non-aqueous secondary battery is not particularly limited, for example, a cylinder type in which a sheet electrode and a separator are spiraled;
Examples include an inside-out structure cylinder type 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 is not particularly limited, and can be assembled by an appropriate procedure according to the structure of the battery. For example, a negative electrode can be placed on an outer case, an electrolyte and a separator can be provided thereon, and a positive electrode can be placed so as to face the negative electrode, and can be caulked together with a gasket and a sealing plate to form a battery.

  By using the carbon material for a non-aqueous secondary battery negative electrode of the present invention, it is possible to provide a non-aqueous secondary battery having excellent stability, high output, high capacity, small irreversible capacity, and excellent cycle retention. it can.

  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.

<Production of electrode sheet>
An electrode plate having an active material layer with an active material layer density of 1.50 ± 0.03 g / cm ³ was prepared using the graphite particles of Examples or Comparative Examples. Specifically, 50.00 ± 0.02 g of negative electrode material, 50.00 ± 0.02 g of 1 mass% carboxymethylcellulose sodium salt aqueous solution (0.500 g in terms of solid content), and styrene having a weight average molecular weight of 270,000 -Aqueous dispersion of butadiene rubber 1.00 ± 0.05 g (0.5 g in terms of solid content) was stirred for 5 minutes with a hybrid mixer manufactured by Keyence and defoamed for 30 seconds to obtain a slurry.

This slurry is made by ITOCHU Machining so that the negative electrode material adheres to 6.00 ± 0.3 mg / cm ² or 12.00 ± 0.3 mg / cm ² on a 10 μm thick copper foil as a current collector. Application to a width of 10 cm using a small die coater and roll press using a roller having a diameter of 20 cm to adjust the density of the active material layer to 1.50 ± 0.03 g / cm ³ to obtain an electrode sheet .

<Preparation of non-aqueous secondary battery (2016 coin type battery)>
The electrode sheet with 12.00 ± 0.3 mg / cm ^{2 of} the negative electrode material produced by the above method was punched into a disk shape with a diameter of 12.5 mm, and a lithium metal foil was punched into a disk shape with a diameter of 14 mm as a counter electrode. Between the two electrodes, a separator (porous polyethylene film) impregnated with an electrolytic solution in which LiPF ₆ was dissolved at 1 mol / L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7). 2016 coin type batteries were prepared.

<Production method of non-aqueous secondary battery (laminated battery)>
4 electrode sheets to which 6.00 ± 0.3 mg / cm ^{2 of} the negative electrode material produced by the above method was adhered
A positive electrode made of NMC was cut out with the same area as a negative electrode cut out in cm × 3 cm, 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 initial 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.
5 mV to the lithium counter electrode at a current density of 0.04C
Then, the battery is charged at a constant voltage of 5 mV until the current density becomes 0.005 C, doped with lithium in the negative electrode, and then discharged to 1.5 V with respect to the lithium counter electrode at a current density of 0.08 C. It was. Subsequently, the second charge and discharge was performed at the same current density, and the discharge capacity at the second cycle was defined as the initial discharge capacity of the material.

<Low temperature output characteristics>
Using the laminate type non-aqueous electrolyte secondary battery produced by the method for producing the non-aqueous electrolyte secondary battery, low temperature output characteristics were measured by the following measuring method.

  For non-aqueous electrolyte secondary batteries that have not undergone charge / discharge cycles, a voltage range of 4.1 V to 3.0 V at 25 ° C., a current value of 0.2 C (the rated capacity with a discharge capacity of 1 hour rate is discharged in 1 hour) 3C for the current value to be 1C, the same applies hereinafter), voltage range of 4.2V to 3.0V, current value of 0.2C (at the time of charging 4.2V constant voltage charging for another 2.5 hours) Implementation) Initial charge and discharge was performed for 2 cycles.

  Furthermore, after charging at a current value of 0.2 C to SOC 50%, in a low temperature environment of −30 ° C., each current value of 1/8 C, 1/4 C, 1/2 C, 1.5 C, 2 C is 2 seconds. Measure the drop in battery voltage after 2 seconds of discharge under each condition, and calculate the current value I that can flow for 2 seconds when the upper limit of charge voltage is 3V. The value calculated by the formula 3 × I (W) was used as the low temperature output characteristic of each battery.

  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 rc ｓsθ of the granulating agent were measured by the methods described in the specification.

<Average particle diameter d50; d50>
A carbon material (0.01 g) is suspended in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate (Tween 20 (registered trademark)), which is a surfactant, and this is used as a measurement sample. The sample was introduced into a scattering type 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 measured as a volume-based median diameter in the measuring apparatus.

<Average particle diameter d90; d90>
The particle size measured on a volume basis was measured as the particle size corresponding to 90% cumulative from the small particle side.

<Average particle diameter d10; d10>
The particle size measured on a volume basis was measured as the particle size corresponding to 10% cumulative from the small particle side.

<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.

<Specific surface area measured by BET method; SA (X)>
Using a surface area meter (Tristar II3020 manufactured by Micromeritics), the carbon material sample was preliminarily dried at 350 ° C. for 60 minutes under a nitrogen flow, and then the value of the relative pressure of nitrogen with respect to atmospheric pressure was 0.3. Measurement was performed by a nitrogen adsorption BET multipoint method using a gas flow method, using a nitrogen-helium mixed gas that was accurately adjusted.

<True density>
The true density of the carbon material sample was measured by a liquid phase replacement method using a true density measuring device (Auto Truedenser MAT-7000 manufactured by Seishin Enterprise Co., Ltd.).

Example 1
The flaky natural graphite having a d50 of 100 μm was pulverized by a mechanical pulverizer having a pulverizing rotor and a liner to obtain flaky natural graphite having a d50 of 30 μm and a water content of 0.03 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 After adding 6 g of 7 mN / m, rcos θ = 30.9) and stirring and mixing, the obtained sample was pulverized and mixed at a rotation speed of 3000 rpm with a hammer mill (MF10 manufactured by IKA), 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, a spheronization treatment was performed by mechanical action for 10 minutes at a rotor peripheral speed of 85 m / sec to obtain spheroidized natural graphite having a d50 of 19.4 μm. The obtained spheroidized natural graphite and a coal tar pitch as an amorphous carbon precursor are mixed, subjected to heat treatment at 1300 ° C. in an inert gas, and then the fired product is crushed and classified to obtain graphite particles. A multi-layer carbon material in which amorphous carbon was combined was obtained. From the firing yield, the mass ratio of the spheroidized graphite particles and amorphous carbon (spheroidized graphite particles: amorphous carbon) in the obtained multilayer carbon material is 1: 0.03. Was confirmed. D50, d90, d10, SA, Tap, initial discharge capacity, and low-temperature output characteristics were measured by the above measurement methods. The results are shown in Table 1.

(Example 2)
By mixing the spheroidized natural graphite obtained in Example 1 and coal tar pitch as an amorphous carbon precursor and subjecting it to 1300 ° C. heat treatment 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: 0.042. Was confirmed. Table 1 shows the results of the same measurement as in Example 1.

Example 3
By mixing the spheroidized natural graphite obtained in Example 1 and coal tar pitch as an amorphous carbon precursor and subjecting it to 1300 ° C. heat treatment 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: 0.05. Was confirmed. Table 1 shows the results of the same measurement as in Example 1.

Example 4
By mixing the spheroidized natural graphite obtained in Example 1 and coal tar pitch as an amorphous carbon precursor and subjecting it to 1300 ° C. heat treatment 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. Table 1 shows the results of the same measurement as in Example 1.

(Example 5)
By mixing the spheroidized natural graphite obtained in Example 1 and coal tar pitch as an amorphous carbon precursor and subjecting it to 1300 ° C. heat treatment 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 structure carbon material is 1: 0.10. Was confirmed. Table 1 shows the results of the same measurement as in Example 1.

(Example 6)
The scaly natural graphite having a d50 of 100 μm was pulverized by a mechanical pulverizer having a pulverizing rotor and a liner to obtain scaly natural graphite having a d50 of 6 μm 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 to obtain spheroidized natural graphite having a d50 of 9.2 μm. The obtained spheroidized natural graphite and a coal tar pitch as an amorphous carbon precursor are mixed, subjected to heat treatment at 1300 ° C. in an inert gas, and then the fired product is crushed and classified to obtain graphite particles. A multi-layer carbon material in which amorphous carbon was 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. Table 1 shows the results of the same measurement as in Example 1.

(Example 7)
The scaly natural graphite having a d50 of 100 μm was pulverized by a mechanical pulverizer having a pulverizing rotor and a liner to obtain scaly natural graphite having a d50 of 6 μm 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 to obtain spheroidized natural graphite having a d50 of 9.2 μm. The obtained spheroidized natural graphite and a coal tar pitch as an amorphous carbon precursor are mixed, subjected to heat treatment at 1300 ° C. in an inert gas, and then the fired product is crushed and classified to obtain graphite particles. A multi-layer carbon material in which amorphous carbon was 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: 0.1. Was confirmed. Table 1 shows the results of the same measurement as 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 flaky graphite adhering to the base material and not encapsulated and flaky graphite-like fine powder generated during the spheronization treatment were present. The scale graphite fine powder was removed from this sample by classification to obtain spheroidized graphite having a d50 of 10.8 μm. The obtained spheroidized natural graphite and a coal tar pitch as an amorphous carbon precursor are mixed, subjected to heat treatment at 1300 ° C. in an inert gas, and then the fired product is crushed and classified to obtain graphite particles. A multi-layer carbon material in which amorphous carbon was 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: 0.02. Was confirmed. Table 1 shows the results of the same measurement as in Example 1.

(Comparative Example 2)
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 flaky graphite adhering to the base material and not encapsulated and flaky graphite-like fine powder generated during the spheronization treatment were present. The scale graphite fine powder was removed from this sample by classification to obtain spheroidized graphite having a d50 of 10.8 μm. The obtained spheroidized natural graphite and a coal tar pitch as an amorphous carbon precursor are mixed, subjected to heat treatment at 1300 ° C. in an inert gas, and then the fired product is crushed and classified to obtain graphite particles. A multi-layer carbon material in which amorphous carbon was 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: 0.04. Was confirmed. Table 1 shows the results of the same measurement as in Example 1.

(Comparative Example 3)
The scaly natural graphite having a d50 of 100 μm was spheroidized by a mechanical action for 3 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. In the obtained sample, it was confirmed that a lot of flaky graphite adhering to the base material and not encapsulated and flaky graphite-like fine powder generated during the spheronization treatment were present. The scale graphite fine powder was removed from this sample by classification to obtain spheroidized graphite having a d50 of 15.7 μm. The obtained spheroidized natural graphite and a coal tar pitch as an amorphous carbon precursor are mixed, subjected to heat treatment at 1300 ° C. in an inert gas, and then the fired product is crushed and classified to obtain graphite particles. A multi-layer carbon material in which amorphous carbon was combined was obtained. From the firing yield, the mass ratio of the spheroidized graphite particles and amorphous carbon (spheroidized graphite particles: amorphous carbon) in the obtained multilayer carbon material is 1: 0.015. Was confirmed. Table 1 shows the results of the same measurement as in Example 1.

(Comparative Example 4)
The scaly natural graphite having a d50 of 100 μm was spheroidized by a mechanical action for 3 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. In the obtained sample, it was confirmed that a lot of flaky graphite adhering to the base material and not encapsulated and flaky graphite-like fine powder generated during the spheronization treatment were present. The scale graphite fine powder was removed from this sample by classification to obtain spheroidized graphite having a d50 of 15.7 μm. The obtained spheroidized natural graphite and a coal tar pitch as an amorphous carbon precursor are mixed, subjected to heat treatment at 1300 ° C. in an inert gas, and then the fired product is crushed and classified to obtain graphite particles. A multi-layer carbon material in which amorphous carbon was 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: 0.04. Was confirmed. Table 1 shows the results of the same measurement as in Example 1.

(Comparative Example 5)
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 flaky graphite adhering to the base material and not encapsulated and flaky graphite-like fine powder generated during the spheronization treatment were present. The scale graphite fine powder was removed from this sample by classification to obtain spheroidized graphite having a d50 of 10.8 μm. The obtained spheroidized natural graphite and a coal tar pitch as an amorphous carbon precursor are mixed, subjected to heat treatment at 1300 ° C. in an inert gas, and then the fired product is crushed and classified to obtain graphite particles. A multi-layer carbon material in which amorphous carbon was combined was obtained. From the firing yield, the mass ratio of the spheroidized graphite particles and amorphous carbon (spheroidized graphite particles: amorphous carbon) in the obtained multilayer carbon material is 1: 0.013. Was confirmed. Table 1 shows the results of the same measurement as in Example 1.

(Comparative Example 6)
The scaly natural graphite having a d50 of 100 μm was spheroidized by a mechanical action for 3 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. In the obtained sample, it was confirmed that a lot of flaky graphite adhering to the base material and not encapsulated and flaky graphite-like fine powder generated during the spheronization treatment were present. The scale graphite fine powder was removed from the sample by classification to obtain spheroidized graphite having a d50 of 19.5 μm. The obtained spheroidized natural graphite and a coal tar pitch as an amorphous carbon precursor are mixed, subjected to heat treatment at 1300 ° C. in an inert gas, and then the fired product is crushed and classified to obtain graphite particles. A multi-layer carbon material in which amorphous carbon was 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: 0.075. Was confirmed. Table 1 shows the results of the same measurement as in Example 1.

  In Examples 1 to 7, the flaky natural graphite adjusted to the specified particle size is subjected to spheronization treatment while adhering fine powder generated during spheronization treatment to the base material and / or encapsulating in spheroidized particles. Since the formula (1) could be satisfied, the high capacity and excellent low temperature output characteristics were exhibited.

  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 (6)

A carbon material for a non-aqueous secondary battery capable of occluding and releasing lithium ions, the carbon material containing a carbonaceous material on the particle surface,
A carbon material for a nonaqueous secondary battery, characterized by satisfying the relationship of the following formula (1).
(Formula 1)
Y-0.01X ≦ α (1)
(Y = true density (g / cm ³ ), X = specific surface area (SA) of carbon material measured by BET method (m ^{2 /} g), α = 2.20) ^{2. The} carbon material for a non-aqueous secondary battery according to claim 1, wherein the specific surface area (SA) (m ² / g) of the carbon material measured by a BET method is 2 or more.   The carbon material for a non-aqueous secondary battery according to claim 1 or 2, wherein the carbon material contains a plurality of graphites selected from the group consisting of at least one of scaly graphite, scaly graphite, and massive graphite. .   4. The carbon material for a non-aqueous secondary battery according to claim 1, wherein a first discharge capacity of the carbon material is 300 mAh / g or more. 5.   5. The ratio (d90 / d10) of 90% particle size (d90) to 10% particle size (d10) in a volume-based particle size distribution is 2.6 or more, or any one of claims 1 to 4. The carbon material for non-aqueous secondary batteries described in 1.   A positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, the negative electrode includes a current collector and a negative electrode active material layer formed on the current collector, and the negative electrode active material layer includes A nonaqueous secondary battery comprising the carbon material according to any one of claims 1 to 5.

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