JP2017010650A - Carbon material and non-aqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon material capable of obtaining a non-aqueous secondary battery, which has high capacity, excellent input/output characteristics, excellent high-temperature preservation characteristics, and excellent cycle characteristics and a high performance non-aqueous secondary battery including the same.SOLUTION: The carbon material for a non-aqueous secondary battery capable of occluding/discharging lithium ions is characterized in that a degree of dispersion of an oxygen functional group and a volume reference average particle size satisfy specific values.SELECTED DRAWING: None

Description

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

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

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

  In order to solve the above problem, for example, Patent Document 1 discloses a technique for producing granulated natural graphite by applying mechanical energy treatment to scaly natural graphite to improve filling properties and high-speed charge / discharge characteristics. It is disclosed.

  Patent Document 2 discloses a technique for further suppressing the crystal orientation in graphite particles and reducing swelling during charge and discharge by further granulating the spherical graphite. Moreover, in patent document 3, the technique which suppresses excess reactivity with electrolyte solution and improves a high-speed charge / discharge characteristic by heat-processing granulated natural graphite at 500 to 1250 degreeC by nitrogen atmosphere. It is disclosed. Patent Document 4 discloses a method in which coal-based calcined coke and paraffin wax are heated and stirred at a high speed to granulate into a spherical shape.

JP 2000-340232 A JP 2011-086617 A JP 2010-135314 A International Publication No. 2014/141372

However, according to studies by the present inventors, the granulated natural graphite disclosed in Patent Document 1 and Patent Document 2 has a high capacity and good rapid charge / discharge characteristics compared to the flake graphite used as a raw material. However, because there are few Li ion insertion and desorption sites inside the graphite, its characteristics are still insufficient, and since the amount of oxygen functional groups is large, there are many side reactions with the electrolyte, irreversible capacity and gas. There was a problem of frequent occurrence.
In granulated natural graphite that has been heat-treated at 500 ° C. to 1250 ° C. in a nitrogen atmosphere disclosed in Patent Document 3, it is possible to reduce side reactions with the electrolyte by reducing the oxygen functional groups. In addition, although the low-temperature charging characteristics are improved by moderately disturbing the surface crystal structure, the insertion and desorption sites of Li ions in the graphite are insufficient, and the characteristics are insufficient.
In the technique of Patent Document 4, since coal-based calcined coke is granulated into a spherical shape, the discharge capacity is low and the characteristics thereof are insufficient.

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

As a result of intensive studies to solve the above problems, the inventors of the present invention are carbon materials for non-aqueous secondary batteries that can occlude / release lithium ions, and the carbon materials are represented by the following formula 1. The inventors have found that a non-aqueous secondary battery negative electrode material having high capacity and excellent low-temperature input / output characteristics and cycle characteristics can be obtained by using graphite particles satisfying the relationship, and the present invention has been completed.
(Formula 1)
100Y + 0.26X> α
(In the formula, Y is the oxygen functional group dispersity represented by the following formula 2, and X is the volume-based average particle diameter (d50) (μm), α = 9.4)
(Formula 2)
Oxygen functional group dispersity (Y) = total oxygen content obtained from elemental analysis (mol%) / surface oxygen content obtained from X-ray photoelectron spectroscopy (O / C) (mol%)
The reason why the carbon material according to the present invention has the above effect is considered as follows.

  That is, the fact that Y (oxygen functional group dispersion degree expressed by the above formula 2) and X (volume-based average particle diameter (d50) (μm)) of the carbon material are in this range means that the oxygen functional groups on the particle surface It is shown that the oxygen functional groups are dispersed inside the particles. Since the oxygen functional group is present at the end surface of the graphite crystal that functions as an insertion / extraction site for Li ions, the carbon material has appropriate Li ion insertion / extraction sites not only on the particle surface but also inside. Is suggested. For this reason, it is possible to perform Li ion insertion / desorption efficiently even inside the particle, and it is considered that high capacity and good low-temperature input / output characteristics 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, the carbon material being graphite particles satisfying the relationship of the following formula 1. It exists in the carbon material for non-aqueous secondary batteries.
(Formula 1)
100Y + 0.26X> α
(In the formula, Y is the oxygen functional group dispersity represented by the following formula 2, and X is the volume-based average particle diameter (d50) (μm), α = 9.4)
(Formula 2)
Oxygen functional group dispersity (Y) = total oxygen content obtained from elemental analysis (mol%) / surface oxygen content obtained from X-ray photoelectron spectroscopy (O / C) (mol%)
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 (12.7, 0.108), Example 2 is a point of (12.9, 0.071), and Example 3 is (16.3, 0.03). , 0.063), Example 4 is the point (19.4, 0.047), Comparative Example 1 is the point (10.9, 0.066), and Comparative Example 2 is (11.3, 0.060), Comparative Example 3 is (15.4, 0.053), and Comparative Example 4 is (18.2, 0.047).

Hereinafter, the contents of the present invention will be described in detail. The description of the invention constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these forms unless it exceeds the gist.
The carbon material for a non-aqueous secondary battery of the present invention is a carbon material for a non-aqueous secondary battery capable of occluding and releasing lithium ions, and the carbon material satisfies the relationship of the following formula 1. It is the carbon material for non-aqueous secondary batteries characterized by being.
(Formula 1)
100Y + 0.26X> α
(In the formula, Y is the oxygen functional group dispersity represented by the following formula 2, and X is the volume-based average particle diameter (d50) (μm), α = 9.4)
(Formula 2)
Oxygen functional group dispersity (Y) = total oxygen content obtained from elemental analysis (mol%) / surface oxygen content obtained from X-ray photoelectron spectroscopy (O / C) (mol%)

<Types of carbon materials for non-aqueous secondary batteries>
The carbon material for a non-aqueous secondary battery capable of occluding and releasing lithium ions of the present invention is a graphite particle in which the oxygen functional group dispersity and the volume-based average particle diameter (d50) (μm) satisfy a prescribed relationship. Although not particularly limited, for example, as graphite, natural graphite, artificial graphite and the like are mentioned, and scaly, scaly, and massive natural graphite is granulated from the viewpoint of good charge / discharge characteristics at high capacity and high current density. More preferred is graphite.
Further, graphite having a small amount of impurities is preferable, and graphite having a small amount of impurities can be obtained by performing various known purification treatments.

  Natural graphites are classified according to their properties into scale-like black (FlakeGraphite), scale-like (Crystal Line Graphite), massive graphite (Vein Graphite), and soil graphite (Amorphousu Graphite). (Refer to "HANDBOOKOF CARBON, GRAPHITE, DIAMOND AND FULLERENES" (published by NoyesPubLications)). The degree of graphitization is the highest at 100% for scaly graphite and massive graphite, followed by scaly graphite at 99.9%, which is suitable in the present invention.

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

As artificial graphite, for example, coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, polyvinyl Some organic products such as alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin are calcined and graphitized, or bulk mesophase is graphitized. Can be mentioned.
Also, use granulated artificial graphite obtained by adding a graphitization catalyst to a graphitizable aggregate or graphite such as bulk mesophase, and a graphitizable organic substance, mixing, firing, and pulverizing. You can also
The firing temperature can be in the range of 2500 ° C. or more and 3200 ° C. or less, and a silicon-containing compound, a boron-containing compound, or the like can be used as a graphitization catalyst during firing.

  Moreover, the carbon material for nonaqueous secondary batteries of this invention may contain the oxide and the other metal. Other metals include metals that can be alloyed with Li, such as Sn, Si, Al, Bi.

<Method for producing carbon material for non-aqueous secondary battery>
The carbon material for a non-aqueous secondary battery of the present invention is not particularly limited as long as it is produced so that the oxygen functional group dispersion degree and the volume-based average particle diameter (d50) (μm) satisfy the specified relationship. However, as one of the achievement means, at least mechanical energy of any one of impact, compression, friction, and shear force is applied to granulate the raw graphite, and the granulation step includes the following 1) and 2). It can be obtained by carrying out in the presence of a granulating agent satisfying the above conditions.
1) Liquid at the time of granulating the raw material graphite 2) When the granulating agent contains an organic solvent, at least one of the organic solvents does not have a flash point or has a flash point, the flash point The point is 5 ° C or higher.
If it has the said granulation process, you may further have another process as needed. Another process may be carried out independently or a plurality of processes may be carried out simultaneously.
When the granulation treatment is performed by the above-described method, a liquid crosslinking adhesion force between the graphite particles is generated by the granulating agent having the specified physical properties, and the carbon material particles can be more firmly adhered to each other. A structure in which fine powder having a high amount of Li ion insertion and desorption sites is attached to a base material that becomes a granulated carbon material (hereinafter referred to as a granulated carbon material) and / or is encapsulated in granulated carbon material particles. Therefore, it becomes possible to produce a granulated carbon material having a high Raman R value and a large number of Li insertion / release sites.
Furthermore, physical damage to the carbon material surface is reduced by the granulating agent acting as a lubricant, and contact of the granulating agent with oxygen is suppressed to prevent the carbon material surface during the granulating treatment. Since oxidation is also suppressed, it is possible to suppress the generation / increase of unstable carbon due to the collapse of the conjugated system of the molecular structure of the carbon material.
As a result, it is possible to produce a carbon material in which the oxygen functional group dispersity and the volume-based average particle diameter satisfy a specified relationship.
As a more preferable embodiment of the above manufacturing method, a manufacturing method including the following first to fifth steps can be mentioned.

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

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

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

  When the average particle size is in the above range, the fine powder produced during the granulation process can be granulated while adhering to the base material that becomes the granulated carbon material or wrapping it inside the base material. Granulated graphite with high and low fine powder can be obtained.

As a method of adjusting the average particle diameter (d50) of the raw material graphite to the above range, for example, a method of pulverizing and / or classifying carbon material particles can be mentioned.
There are no particular restrictions on the apparatus used for pulverization, for example, the coarse pulverizer includes a shearing mill, jaw crusher, impact crusher, cone crusher, etc., and the intermediate pulverizer includes a roll crusher, hammer mill, etc. Examples of the fine pulverizer include a mechanical pulverizer, an airflow pulverizer, and a swirl flow pulverizer. Specific examples include a ball mill, a vibration mill, a pin mill, a stirring mill, a jet mill, a cyclone mill, and a turbo mill. In particular, when obtaining carbon material 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.

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

The amount of water contained in the 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 0.1% by mass with respect to the total mass of the raw material graphite. Hereinafter, it is 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. For example, the moisture content is JIS M881.
It can be measured by a method based on 1. 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.

  In order to make the moisture content of the graphite used as the raw material 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 aspect ratio of the raw material graphite is preferably 3 or more, more preferably 5 or more, still more preferably 10 or more, and particularly preferably 15 or more. Further, it is preferably 1000 or less, more preferably 500 or less, still more preferably 100 or less, and particularly preferably 50 or less. An aspect ratio is measured by the method of the Example mentioned later. When the aspect ratio is within the above range, it is difficult to produce large particles having a particle size of about 100 μm, while it becomes easy to obtain a strong granulated carbon material.

The interplanar spacing (d002) and crystallite size (Lc) of the raw graphite by the X-ray wide angle diffraction method are usually (d002) of 3.37 mm or less and (Lc) of 900 mm or more, (d00
2) is preferably 3.36 mm or less and (Lc) is preferably 950 mm or more. Surface spacing (d00
2) and the size of the crystallite (Lc) are values indicating the crystallinity of the negative electrode material bulk. The smaller the value of the interplanar spacing (d002) of the 002 plane, the larger the size of the crystallite (Lc). It shows that the negative electrode material has high crystallinity, and the capacity increases because the amount of lithium entering the graphite layer approaches the theoretical value. If the crystallinity is low, excellent battery characteristics (high capacity and low irreversible capacity) when a highly crystalline carbon material is used for the electrode are not exhibited. It is particularly preferable that the above-mentioned ranges are combined for the interplanar spacing (d002) and the crystallite size (Lc).
X-ray diffraction is measured by the following method. Carbon powder is mixed with X-ray standard high-purity silicon powder of about 15% by mass of the total amount, and CuKα ray monochromatized with a graphite monochromator is used as a radiation source. A line diffraction curve is measured. Thereafter, the interplanar spacing (d002) and the crystallite size (Lc) are obtained using the Gakushin method.

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

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

The X-ray wide angle diffraction method of raw material graphite is used as an index representing the crystallinity of the entire particle, and the 101 plane intensity 3R (101) based on the rhombohedral crystal structure by the X ray wide angle diffraction method and the 101 based on the hexagonal crystal structure. The ratio 3R / 2H of the surface strength 2H (101) is preferably 0.1 or more, more preferably 0.15 or more, and 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 material graphite by the BET method is preferably 1 m ² / g or more and 30 m ² / g or less, more preferably 2 m ² / g or more and 20 m ² / g or less, further preferably 5 m ² / g or more and 15 m ² / g or less. It is. The specific surface area by BET method is measured by the method of the Example mentioned later. When the specific surface area of the raw material graphite is within the above range, the acceptability of Li ions becomes good, and a decrease in battery capacity due to an increase in irreversible capacity can be prevented.

(2nd process) The process which mixes raw material graphite and a granulating agent In order to obtain the carbon material for non-aqueous secondary batteries of this invention, it is preferable to granulate raw material graphite using a granulating agent. The granulating agent is 1) liquid during the step of granulating the raw graphite and 2) when the granulating agent contains an organic solvent, at least one of the organic solvents does not have a flash point, or has a flash point. When it has, the flash point satisfies the condition of 5 ° C. or more.
By having a granulating agent that satisfies the above requirements, the granulating agent is liquid-crosslinked between the raw material graphites in the subsequent step of granulating the raw material graphite in the third step, so Since the attractive force generated by the capillary negative pressure and the surface tension of the liquid acts as the liquid cross-linking adhesion force between the particles, the liquid cross-linking adhesion force between the raw material graphites increases and the raw material graphite can adhere more firmly.

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

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

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

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

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

The viscosity of the granulating agent used in the present invention is measured by using a rheometer (for example, ARES manufactured by Rheometric Scientific Co.), putting an appropriate amount of a measuring object (in this case, a granulating agent) in a cup and adjusting the temperature to a predetermined temperature. When the shear stress at a shear rate of 100 s ⁻¹ is 0.1 Pa or more, the value measured at the shear rate of 100 s ⁻¹ is measured, and when the shear stress at the shear rate of 100 s ⁻¹ is less than 0.1 Pa, measured at 1000 s ⁻¹ . When the shear stress at a shear rate of 1000 s ⁻¹ is less than 0.1 Pa, the value measured at the shear rate at which the shear stress is 0.1 Pa or more is defined as the viscosity in 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 present invention 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 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 the granulating agent used in the present invention include, for example, paraffinic oil such as coal tar, petroleum heavy oil, liquid paraffin, synthetic oil such as olefinic oil, naphthenic oil and aromatic oil, and vegetable oils and fats. Organic compounds such as resin binder solutions in which a resin binder is dissolved in a solvent such as natural oils such as animal aliphatics, esters and higher alcohols, a flash point of 5 ° C or higher, preferably 21 ° C or higher. Examples thereof include aqueous solvents and mixtures thereof. Organic solvents with a flash point of 5 ° C or higher include alkylbenzenes such as xylene, isopropylbenzene, ethylbenzene, and propylbenzene; Hydrogen, aliphatic hydrocarbons such as octane, nonane, decane, ketones such as methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, esters such as propyl acetate, butyl acetate, isobutyl acetate, amyl acetate, methanol , Ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene Alcohols such as lenglycol and glycerine, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, methoxypropanol, methoxypropyl-2- Acetate, methoxymethyl butanol, methoxybutyl acetate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, triethylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol monophenyl Glycol derivatives such as nyl ether, ethers such as 1,4-dioxane, nitrogen-containing compounds such as dimethylformamide, pyridine, 2-pyrrolidone and N-methyl-2-pyrrolidone, and sulfur-containing compounds such as dimethyl sulfoxide , Halogen-containing compounds such as dichloromethane, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, and chlorobenzene, and mixtures thereof, for example, those having a low flash point such as toluene are not included. These organic solvents can be used alone as a granulating agent.

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

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

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

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

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

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

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

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

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

If the manufacturing method concerning this invention is used, the granulated carbon material of various types of particle structures can be manufactured stably. Typical particle structures include a granulated carbon material produced by folding scale graphite having a large or medium average particle size of raw material graphite, and a granulated coal produced by granulating scale graphite having a small average particle size. Examples include materials.
As an example of the ability to stably produce a granulated carbon material having such various types of particle structures, the yield expressed by the weight ratio of the granulated carbon material to the total solid raw material weight (granulated carbon material weight / total solid raw material) Weight) is usually 60% or more, preferably 80% or more, and more preferably 95% or more.

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

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

  The atmosphere of the heat treatment includes an active atmosphere such as an air atmosphere or an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere. When heat treatment is performed at 200 ° C. to 300 ° C., there is no particular limitation, but the heat treatment is performed at 300 ° C. or higher. When 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 carbon material 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 that can be a highly active sulfur source into the system, a metal in the carbon material, This is preferable because impurities such as metal compounds and inorganic compounds can be removed.
The acid treatment may be performed using an acid containing nitric acid or hydrochloric acid. Other acids such as inorganic acids such as bromic acid, hydrofluoric acid, boric acid or iodic acid, or citric acid, formic acid, acetic acid, An acid in which an organic acid such as acid, trichloroacetic acid or trifluoroacetic acid is appropriately mixed can also be used. Concentrated hydrofluoric acid, concentrated nitric acid and concentrated hydrochloric acid are preferable, and concentrated nitric acid and concentrated hydrochloric acid are more preferable. In the present invention, graphite may be treated with sulfuric acid, but it is used in such an amount and concentration that does not impair the effects and physical properties of the present invention.

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

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

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

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

The time for washing with water, that is, stirring the treated carbon material and water is usually 0.5 to 48 hours, preferably 1 to 40 hours, more preferably 2 to 30 hours, and still more preferably 3 to 24 hours. It is.
The mixing ratio of the treated carbon material 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. The ratio is preferably 100: 700 or less, more preferably 100: 500 or less, and still more preferably 100: 400 or less.

The stirring temperature is usually 25 ° C. or higher, preferably 40 ° C. or higher, more preferably 50 ° C. or higher, and still more preferably 60 ° C. or higher. The upper limit is 100 ° C., which is the boiling point of water. Moreover, when performing a water washing process by a batch type, it is preferable from a viewpoint of an impurity and acid content removal to wash by repeating the process process of stirring-filtration in a pure water in multiple times. The treatment may be repeated so that the pH of the treated carbon material is 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 waste water ion concentration of the obtained carbon material 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. As mentioned above, More preferably, it is 3 ppm or more, More preferably, it is 4 ppm or more.

(Sixth step) Step of heat-treating the granulated carbon material In the present invention, in order to adjust the unstable carbon amount and crystallinity of the granulated carbon material, a step of heat-treating may be included. When the above granulation treatment is performed, the anxiety low carbon content on the surface of the carbon material particles may increase excessively, and the anxiety low carbon content can be appropriately reduced by performing heat treatment.
The temperature conditions during the heat treatment are not particularly limited, but are usually 300 ° C. or higher, preferably 500 ° C., more preferably 700 ° C., particularly preferably 800 ° C. or higher, and usually 2000 ° C., depending on the degree of crystallinity desired. C. or lower, preferably 1500 ° C. or lower, particularly preferably 1200 ° C. or lower. When the temperature condition is satisfied, the crystallinity of the carbon material particle surface can be appropriately increased.
Moreover, when a carbon material with low crystallinity is contained as the granulated carbon material, the carbon material with low crystallinity can be graphitized in this step to increase the crystallinity for the purpose of increasing the discharge capacity. The temperature condition during the heat treatment is not particularly limited, but is usually 600 ° C. or higher, preferably 900 ° C., more preferably 1600 ° C., particularly preferably 2500 ° C. or higher, and usually 3200 depending on the degree of crystallinity of interest. The range is not higher than ° C, preferably not higher than 3100 ° C. The crystallinity of the carbon material particle surface can be improved as it is the said temperature conditions.
When the heat treatment is performed, the holding time for keeping the temperature condition within the above range is not particularly limited, but is usually longer than 10 seconds and not longer than 72 hours.
The heat treatment is performed in an inert gas atmosphere such as nitrogen gas or in a non-oxidizing atmosphere by a gas generated from raw graphite. Although there is no restriction | limiting in particular as an apparatus used for heat processing, For example, a shuttle furnace, a tunnel furnace, an electric furnace, a lead hammer furnace, a rotary kiln, a direct current furnace, an Atchison furnace, a resistance heating furnace, an induction heating furnace etc. can be used.

(Seventh step) Step of attaching carbonaceous material having lower crystallinity than granulated carbon material to granulated carbon material In the present invention, a carbonaceous material having lower crystallinity than granulated carbon material is further added to the granulated carbon material. You may have the process of attaching. According to this process, the negative electrode material which can suppress a side reaction with electrolyte solution and can improve rapid charge / discharge property can be obtained.
A composite carbon material in which a carbonaceous material having lower crystallinity than the granulated carbon material is further added to the granulated carbon material may be referred to as a “carbonaceous material composite carbon material”).

  The carbonaceous material adhering treatment to the granulated carbon material is performed by mixing an organic compound that becomes a carbonaceous material and the granulated carbon material, and heating in a non-oxidizing atmosphere, preferably under a flow of nitrogen, argon, carbon dioxide, This is a treatment for carbonizing or graphitizing an 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 the crystal structure of natural graphite, and is usually at most 3500 ° C. 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.
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 graphite as a raw material. Particularly preferably, it is 0.7% by mass or more, and the content is usually 20% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, particularly preferably 7% by mass or less, most preferably. 5% by mass or less.

If the carbonaceous material content in the carbonaceous material composite carbon material is too large, the negative electrode material will be damaged when rolled at a sufficient pressure to achieve a high capacity in a non-aqueous secondary battery. There is a tendency for destruction to occur, leading to an increase in charge / discharge irreversible capacity during initial cycles 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)

[Mixing of carbon materials]
Further, in the present invention, a carbon material different from the granulated carbon material is mixed for the purpose of improving the orientation of the electrode plate, the permeability of the electrolytic solution, the conductive path, etc., and improving the cycle characteristics, electrode plate swelling, etc. (Hereinafter, a carbon material obtained by mixing the granulated carbon material with a carbon material different from the granulated carbon material may be referred to as a “mixed carbon material”).
Examples of the carbon material different from the carbon material include natural graphite, artificial graphite, coated graphite obtained by coating a carbon material with a carbonaceous material, amorphous carbon, and a carbon material containing metal particles and a metal compound. Can be used. Any one of these materials may be used alone, or two or more of these materials may be used in any combination and composition.

  As the natural graphite, for example, a highly purified carbon material or granulated natural graphite can be used. In the present invention, high purification means that ash contained in low-purity natural graphite is usually treated in an acid such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, or a combination of a plurality of acid treatment steps. It means an operation of dissolving and removing metal and metal, etc., and usually, after the acid treatment step, a water washing treatment or the like is performed to remove the acid content used in the high purification treatment step. Moreover, you may evaporate and remove ash, a metal, etc. by processing at high temperature 2000 degreeC or more instead of an acid treatment process. Moreover, you may remove ash, a metal, etc. by processing in halogen gas atmosphere, such as chlorine gas, at the time of high temperature heat processing. Furthermore, these methods may be used in any combination.

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

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

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

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

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

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

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

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

Carbon materials containing metal particles and metal compounds include, for example, Fe, Co, Sb, Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, Nb, Mo, Examples thereof include a material in which a metal selected from the group consisting of Cu, Zn, Ge, In, Ti, or the like or a compound thereof is combined with graphite. As the metal or the compound that can be used, an alloy composed of two or more kinds of metals may be used, and the metal particles may be alloy particles formed of two or more kinds of metal elements. Among these, a metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn and W or a compound thereof is preferable, and Si and SiOx are particularly preferable. This general formula SiOx is obtained using Si dioxide (SiO ₂ ) and metal Si (Si) as raw materials, and the value of x is usually 0 <x <2, preferably 0.2 or more, 1.8 Hereinafter, more preferably 0.4 or more and 1.6 or less, and further preferably 0.6 or more and 1.4 or less. If it is this range, it becomes high capacity | capacitance and it becomes possible to reduce the irreversible capacity | capacitance by the coupling | bonding of Li and oxygen.
The volume-based average particle diameter of the metal particles is usually 0.005 μm or more, preferably 0.01 μm or more, more preferably 0.02 μm or more, further preferably 0.03 μm or more, and usually 10 μm or less from the viewpoint of cycle life. , Preferably 9 μm or less, more preferably 8 μm or less. When the average particle diameter is within this range, volume expansion associated with charge / discharge is reduced, and good cycle characteristics can be obtained while maintaining charge / discharge capacity.
BET specific surface area of the metal particles is usually 0.5 m ² / g or more 120 m ² / g or less and a ^{1 m} 2 / g or more 100m ² / g or less. When the specific surface area is within the above range, the charge / discharge efficiency and discharge capacity of the battery are high, lithium is quickly taken in and out during high-speed charge / discharge, and the rate characteristics are excellent.

The apparatus used for mixing the granulated carbon material and the carbon material different from the granulated carbon material is not particularly limited. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylindrical mixer Machine, double cone type mixer, regular cubic type mixer, vertical type mixer, fixed type mixer: spiral type mixer, ribbon type mixer, Muller type mixer, Helical Flight type mixer,
A Pugmill type mixer, a fluidized type mixer, or the like can be used.

<Physical properties of carbon materials for non-aqueous secondary batteries>
-Relationship between oxygen functional group dispersity and volume-based average particle diameter (d50) The carbon material of the present invention satisfies the relationship of the following formula (1).
(Formula 1)
100Y + 0.26X> α
(In the formula, Y is the oxygen functional group dispersity represented by the following formula 2, and X is the volume-based average particle diameter (d50) (μm), α = 9.4)
(Formula 2)
Oxygen functional group dispersity (Y) = total oxygen content obtained from elemental analysis (mol%) / surface oxygen content obtained from X-ray photoelectron spectroscopy (O / C) (mol%)

In the carbon material of the present invention, α represented by the above formula (1) is 9.4, preferably 9.5, more preferably 9.6, still more preferably 9.7, particularly preferably 9.8, Most preferably 10.0.
When the relationship represented by the above formula (1) cannot be satisfied, Li ion insertion / desorption cannot be performed efficiently inside the particles, and the low-temperature input / output characteristics and capacity tend to decrease.

X: Volume-based average particle diameter (d50)
The volume-based average particle diameter (also referred to as “d50”) of the carbon material of the present invention is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 8 μm or more, particularly preferably 10 μm or more, and most preferably 12 μm or more. . The average particle diameter d50 is usually 50 μm or less, preferably 40 μm or less, more preferably 35 μm or less, still more preferably 30 μm or less, and particularly preferably 25 μm or less. If the average particle size d50 is too small, the non-aqueous secondary battery obtained using the carbon material tends to increase the irreversible capacity and cause a loss of initial battery capacity. On the other hand, if the average particle size d50 is too large, slurry coating may occur. May cause inconveniences such as line drawing, deterioration of high current density charge / discharge characteristics, and deterioration of low temperature input / output characteristics.

  In this specification, the average particle size d50 is obtained by adding 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) as a surfactant to a carbon material. 0.01 g was suspended, and this was introduced as a measurement sample into a commercially available laser diffraction / scattering particle size distribution measurement device (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. After that, the volume is defined as a volume-based median diameter measured by the measuring device.

-Surface functional group amount O / C value (mol%)
An X-ray photoelectron spectrometer (for example, ESCA manufactured by ULVAC-PHI) is used as an X-ray photoelectron spectroscopy measurement (XPS), and a measurement target (here, a graphite material) is placed on a sample table so that the surface is flat, and aluminum The spectra of C1s (280 to 300 eV) and O1s (525 to 545 eV) are measured by multiplex measurement using the Kα rays of X. The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and O1s spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and O. The obtained O / C atomic concentration ratio O / C (O atom concentration / C atom concentration) × 100 is defined as the surface functional group amount O / C value of the carbon material.
The O / C value obtained from XPS is preferably 0.01 or more, more preferably 0.1 or more, still more preferably 0.3 or more, particularly preferably 0.5 or more, most preferably 0.7 or more, preferably Is 2 or less, more preferably 1.5 or less, still more preferably 1.2 or less, particularly preferably 1 or less, and most preferably 0.8 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.

・ Total oxygen content (mol%)
To measure the amount of oxygen, nitrogen and hydrogen, an oxygen / nitrogen analyzer (ONCO analyzer TCH600 manufactured by LECO) was used to melt and decompose 50 mg of carbon material in an inert gas atmosphere in an impulse furnace. The total amount of oxygen contained in the carbon material (mol%) is calculated by detecting the amount of carbon oxide and the amount of carbon dioxide with an infrared detector.
The total oxygen content (mol%) determined from the oxygen nitrogen hydrogen content measurement is preferably 0.001 mol% or more, more preferably 0.01 mol% or more, still more preferably 0.02 mol% or more, and particularly preferably 0.03 mol%. % Or more, most preferably 0.04 mol% or more, preferably 0.5 mol% or less, more preferably 0.2 mol% or less, still more preferably 0.15 mol% or less, particularly preferably 0.1 mol% or less, most preferably 0.08 mol% or less. If the total oxygen content (mol%) is within the above range, the desolvation reactivity of Li ions and the electrolyte solvent on the surface of the negative electrode active material is promoted, the rapid charge / discharge characteristics are improved, and the reactivity with the electrolyte is improved. Is suppressed and the charge / discharge efficiency tends to be good.

Y: oxygen functional group dispersity The oxygen functional group dispersity of the carbon material of the present invention is usually 0.01 or more, preferably 0.04 or more, more preferably 0.06 or more, and further preferably 0.07 or more. Usually, it is 1 or less, preferably 0.5 or less, more preferably 0.3 or less, and still more preferably 0.2 or less.
Being within the above range indicates that the uneven distribution of oxygen functional groups on the particle surface is suppressed, and the oxygen functional groups are also dispersed inside the particles. Since the oxygen functional group is present at the end surface of the graphite crystal that functions as an insertion / extraction site for Li ions, the carbon material has appropriate Li ion insertion / extraction sites not only on the particle surface but also inside. Is suggested. For this reason, if it is within the above range, Li ion insertion / desorption can be performed efficiently even inside the particles, and there is a tendency to exhibit high capacity and good low-temperature input / output characteristics.

-Raman R value The Raman R value represented by the following formula 3 of the carbon material of the present invention is usually 0.01 or more, preferably 0.1 or more, more preferably 0.2 or more, and further preferably 0.25 or more. Particularly preferred is 0.3 or more, and most preferred is 0.35 or more. Moreover, although there is no restriction | limiting in particular in the upper limit of a Raman R value, Usually, it is 1 or less, Preferably it is 0.7 or less, More preferably, it is 0.6 or less, More preferably, it is 0.5 or less.

Formula 3
Raman value R = Intensity I _B of peak P _B near 1360 cm ⁻¹ in Raman spectral analysis Intensity I _A of peak P _A near 1580 cm ⁻¹
Incidentally, the scope of 1580～1620Cm ^-1 A "1580cm around ^-1" in the present specification, "1360cm around ^-1" refers to the range of 1350 ^-1.

  If the Raman R value is within the above range, since the crystallinity of the carbon material particle surface is appropriate, Li ion insertion and desorption sites can sufficiently exist, so that the carbon material has good low-temperature input / output characteristics and discharge capacity. Tends to be obtained.

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

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

・ BET specific surface area (SA)
Measured specific surface area by the BET method of the carbon material of the present invention (SA) is preferably ^{1 m} 2 / g or more, more preferably ^{5 m} 2 / g or more, more preferably ^8m 2 / g or more, and most preferably ^12m 2 / g or more, most preferably 13 m ² / g or more. Moreover, Preferably it is 30 m < ² > / g or less, More preferably, it is 20 m < ² > / g or less, More preferably, it is 17 m < ² > / g or less. When the specific surface area is within the above range, it is possible to sufficiently secure the portion where Li enters and exits, so the high speed charge / discharge characteristics output characteristics are excellent, and the activity of the active material against the electrolytic solution can be moderately suppressed. However, the high-capacity battery tends to be manufactured.

  In addition, when a negative electrode is formed using a carbon material, an increase in reactivity with the electrolytic solution can be suppressed and gas generation can be suppressed, so that a preferable nonaqueous secondary battery can be provided. The BET specific surface area was measured using a surface area meter (for example, a specific surface area measuring device “AMS8000” manufactured by Okura Riken Co., Ltd.), preliminarily dried at 100 ° C. for 3 hours in a nitrogen stream, and then subjected to a liquid nitrogen temperature. It is defined as a value measured by a nitrogen adsorption BET method by a gas flow method using a nitrogen helium mixed gas that is accurately adjusted so that the value of the relative pressure of nitrogen with respect to atmospheric pressure is 0.3.

-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, and further preferably 0.92 or more. The circularity is preferably 1 or less, more preferably 0.98 or less, and still more preferably 0.97 or less. When the circularity is within the above range, the high current density charge / discharge characteristics of the non-aqueous secondary battery tend to be suppressed. The circularity is defined by the following formula, and when the circularity is 1, a theoretical sphere is obtained.
When the circularity is within the above range, when the circularity is within the above range, the bending degree of Li ion diffusion decreases, the electrolyte solution moves smoothly in the interparticle voids, and the carbon materials are appropriately in contact with each other. Therefore, it tends to exhibit good rapid charge / discharge characteristics and cycle characteristics.

Circularity = (perimeter of equivalent circle having the same area as the particle projection shape) / (actual circumference of particle projection shape)

  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.

-Tap density The tap density of the carbon material of the present invention is preferably 0.7 g / cm ³ or more, more preferably 0.75 g / cm ³ or more, still more preferably 0.80 g / cm ³ or more, and particularly preferably 0.85 g. / Cm ³ or more, preferably 1.3 g / cm ³ or less, more preferably 1.2 g / c
m ³ or less, more preferably 1.1 g / cm ³ or less.

When the tap density is within the above range, the processability such as streaking during the production of the electrode plate is good, and the high-speed charge / discharge characteristics are excellent. In addition, since the carbon density in the particles is difficult to increase, the rolling property is good and the high-density negative electrode sheet tends to be easily formed.
The tap density was filled into the cell by dropping the carbon material of the present invention through a sieve having a mesh size of 300 μm into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ using a powder density measuring device. After that, a tap having a stroke length of 10 mm is performed 1000 times and defined as the density obtained from the volume at that time and the mass of the sample.

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

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

<Negative electrode for non-aqueous secondary battery>
The negative electrode for a non-aqueous secondary battery of the present invention (hereinafter also referred to as “electrode sheet” as appropriate) includes a current collector and a negative electrode active material layer formed on the current collector, and the active material layer is at least The carbon material of the present invention is contained. More preferably, it contains a binder.
As the binder, one having an olefinically unsaturated bond in the molecule is used. The type is not particularly limited, and specific examples include styrene-butadiene rubber, styrene / isoprene / styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene / propylene / diene copolymer. By using such a binder having an olefinically unsaturated bond, the swellability of the active material layer with respect to the electrolytic solution can be reduced. Of these, styrene-butadiene rubber is preferred because of its availability.

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

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

The binder having an olefinically unsaturated bond has an unsaturation degree of preferably 15% or more, more preferably 20% or more, still more preferably 40% or more, and preferably 90% or less, more preferably 80%. % Or less. The degree of unsaturation represents the ratio (%) of the double bond to the repeating unit of the polymer.
In the present invention, a binder that does not have an olefinically unsaturated bond can also be used in combination with the above-described binder that has an olefinically unsaturated bond as long as the effects of the present invention are not lost. The mixing ratio of the binder having no olefinically unsaturated bond to the binder having an olefinically unsaturated bond is preferably 150% by mass or less, more preferably 120% by mass or less.

By using a binder that does not have an olefinically unsaturated bond, the coatability can be improved. However, if the combined amount is too large, the strength of the active material layer is lowered.
Examples of the binder having no olefinic unsaturated bond include thickening polysaccharides such as methylcellulose, carboxymethylcellulose, starch, carrageenan, pullulan, guar gum, xanthan gum (xanthan gum), polyethers such as polyethylene oxide and polypropylene oxide, Vinyl alcohols such as polyvinyl alcohol and polyvinyl butyral, polyacids such as polyacrylic acid and polymethacrylic acid, or metal salts of these polymers, fluorine-containing polymers such as polyvinylidene fluoride, alkane polymers such as polyethylene and polypropylene, and these A copolymer etc. are mentioned.

  When the carbon material of the present invention is used in combination with the above-mentioned binder having an olefinically unsaturated bond, the ratio of the binder used for the active material layer can be reduced as compared with the conventional material. Specifically, the carbon material of the present invention and a binder (in some cases, it may be a mixture of a binder having an unsaturated bond and a binder having no unsaturated bond as described above). The mass ratio of each is preferably 90/10 or more, more preferably 95/5 or more, preferably 99.9 / 0.1 or less, more preferably 99.5 / 0.5 in terms of the dry mass ratio. The range is as follows. When the ratio of the binder is within the above range, a decrease in capacity and an increase in resistance can be suppressed, and the electrode plate strength is also excellent.

  The negative electrode of the present invention is formed by dispersing the above-described carbon material of the present invention and a binder in a dispersion medium to form a slurry, which is applied to a current collector. As the dispersion medium, an organic solvent such as alcohol or water can be used. If necessary, a conductive agent may be added to the slurry. Examples of the conductive agent include carbon black such as acetylene black, ketjen black, and furnace black, and fine powder made of Cu, Ni having an average particle diameter of 1 μm or less, or an alloy thereof. The addition amount of the conductive agent is preferably about 10% by mass or less with respect to the carbon material of the present invention.

A conventionally well-known thing can be used as a collector which apply | coats a slurry. Specific examples include metal thin films such as rolled copper foil, electrolytic copper foil, and stainless steel foil. The thickness of the current collector is preferably 4 μm or more, more preferably 6 μm or more, preferably 30 μm or less, more preferably 20 μm or less.
After applying the slurry on the current collector, it is preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and preferably 200 ° C. or lower, more preferably 195 ° C. or lower, in dry air or an inert atmosphere. Dry to form an active material layer.

The thickness of the active material layer obtained by applying and drying the slurry is preferably 5 μm or more, more preferably 20 μm or more, still more preferably 30 μm or more, and preferably 200 μm or less, more preferably 100 μm or less, still more preferably. 75 μm or less. When the thickness of the active material layer is within the above range, it is excellent in practicality as a negative electrode in consideration of the particle size of the active material, and a sufficient Li occlusion / release function for a high-density current value can be obtained. .

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

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

<Non-aqueous secondary battery>
The basic configuration of the non-aqueous secondary battery of the present invention, particularly the lithium ion secondary battery, is the same as that of a conventionally known lithium ion secondary battery, and usually includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte. Is provided. The negative electrode of the present invention described above is used as the negative electrode.
The positive electrode is obtained by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector.

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

Among these, V ₂ O ₅ , V ₅ O ₁₃ , VO ₂ , Cr ₂ O ₅ , MnO ₂ , TiO ₂ , MoV ₂ O ₈ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , TiS ₂ , V ₂ S ₅ , Cr _0.25 V _0.75 S ₂ , Cr _0.5 V _0.5 S _{2 and the} like are preferable, and LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and some of these transition metals are particularly preferable. Is a lithium transition metal composite oxide in which is substituted with another metal. These positive electrode active materials may be used alone or in combination.

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

The positive electrode active material layer may contain a conductive material in order to improve the conductivity of the electrode. The conductive agent is not particularly limited as long as it can be mixed with an active material in an appropriate amount to impart conductivity, but is usually carbon powder such as acetylene black, carbon black, and graphite, various metal fibers, powder, and foil. Etc.
The positive electrode plate is formed by slurrying a positive electrode active material or a binder with a solvent in the same manner as in the production of the negative electrode as described above, and applying and drying on a current collector. As the positive electrode current collector, aluminum, nickel, stainless steel (SUS), or the like is used, but is not limited at all.

As the electrolyte, a non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent, or a gel, rubber, or solid sheet obtained by using an organic polymer compound or the like from the non-aqueous electrolyte is used.
The non-aqueous solvent used in the non-aqueous electrolyte is not particularly limited, and can be appropriately selected from known non-aqueous solvents that have been conventionally proposed as solvents for non-aqueous electrolytes. For example, chain carbonates such as diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; chain ethers such as 1,2-dimethoxyethane; tetrahydrofuran, 2-methyl Examples include cyclic ethers such as tetrahydrofuran, sulfolane, and 1,3-dioxolane; chain esters such as methyl formate, methyl acetate, and methyl propionate; and cyclic esters such as γ-butyrolactone and γ-valerolactone.

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

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

Lithium salts may be used alone or in combination of two or more. The concentration of the lithium salt in the nonaqueous electrolytic solution is usually in the range of 0.5 mol / L or more and 2.0 mol / L or less.
In addition, when an organic polymer compound is included in the above non-aqueous electrolyte and used in the form of a gel, rubber, or solid sheet, specific examples of the organic polymer compound include polyethylene oxide, polypropylene oxide, and the like. Polyether polymer compounds; Cross-linked polymers of polyether polymer compounds; Vinyl alcohol polymer compounds such as polyvinyl alcohol and polyvinyl butyral; Insolubilized vinyl alcohol polymer compounds; Polyepichlorohydrin; Polyphosphazene; Siloxane; vinyl polymer compounds such as polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile; poly (ω-methoxyoligooxyethylene methacrylate), poly (ω-methoxyoligooxyethylene methacrylate-co-methyl methacrylate) Rate) and polymer copolymers such as poly (hexafluoropropylene-vinylidene fluoride).

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

Further, as the electrolyte, a polymer solid electrolyte which is a conductor of an alkali metal cation such as lithium ion can be used. Examples of the polymer solid electrolyte include a polymer in which a lithium salt is dissolved in the aforementioned polyether polymer compound, and a polymer in which the terminal hydroxyl group of the polyether is substituted with an alkoxide.
In order to prevent a short circuit between the electrodes, a porous separator such as a porous film or a nonwoven fabric is usually interposed between the positive electrode and the negative electrode. In this case, the nonaqueous electrolytic solution is used by impregnating a porous separator. As a material for the separator, polyolefin such as polyethylene and polypropylene, polyethersulfone, and the like are used, and polyolefin is preferable.

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

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

  EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, the physical properties of the manufactured negative electrode material were measured by the following methods. Further, the viscosity, contact angle, surface tension, and rcos θ of the granulating agent were measured by the methods described in the specification.

<Production of electrode sheet>
Using the graphite particles of Examples or Comparative Examples, the active material layer density is 1.35 ± 0.03 g / cm ³ ,
Alternatively, an electrode plate having an active material layer of 1.60 ± 0.03 g / cm ³ was produced. Specifically, 50.00 ± 0.02 g of negative electrode material, 50.00 ± 0.02 g of 1 mass% carboxymethylcellulose sodium salt aqueous solution (0.500 g in terms of solid content), and styrene having a weight average molecular weight of 270,000 -Aqueous dispersion of butadiene rubber 1.00 ± 0.05 g (0.5 g in terms of solid content) was stirred for 5 minutes with a hybrid mixer manufactured by Keyence and defoamed for 30 seconds to obtain a slurry.

This slurry is placed on a copper foil having a thickness of 10 μm as a current collector, and the negative electrode material is 6.0 ± 0.3 m.
g / cm ² , or 9.0 ± 0.3 mg / cm ^2, so that it is applied to a width of 10 cm using a small die coater made by ITOCHU machining, roll-pressed using a roller having a diameter of 20 cm, and active material The density of the layer was adjusted to 1.35 ± 0.03 g / cm ³ or 1.60 ± 0.03 g / cm ³ to obtain an electrode sheet.

<Preparation of non-aqueous secondary battery (2016 coin type battery)>
An electrode sheet prepared by the above method and having a negative electrode material of 9.0 ± 0.3 mg / cm ² and an active material layer density of 1.60 ± 0.03 g / cm ³ is formed into a disk shape having a diameter of 12.5 mm. The lithium metal foil was punched into a disk shape having a diameter of 14 mm and used as a counter electrode. Between the two electrodes, a separator (porous polyethylene film) impregnated with an electrolytic solution in which LiPF ₆ was dissolved at 1 mol / L in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7). 2016 coin type batteries were prepared.

<Production method of non-aqueous secondary battery (laminated battery)>
The negative electrode material 6.0 ± 0.3 mg / cm ² attached and the density of the active material layer 1.35 ± 0.03 g / cm ³ produced by the above method was cut out into 4 cm × 3 cm as a negative electrode,
A positive electrode made of NMC was cut out in the same area, and a separator (made of a porous polyethylene film) was placed between the negative electrode and the positive electrode to combine them. A laminate type battery was prepared by injecting 200 μl of an electrolytic solution in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio = 3: 3: 4) to a concentration of 1.2 mol / L. Was made.

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

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

<Surface oxygen content (O / C)>
An X-ray photoelectron spectrometer is used as an X-ray photoelectron spectroscopy measurement, the measurement object is placed on a sample stage so that the surface is flat, an aluminum Kα ray is used as an X-ray source, and C1s (280 to 300 eV) is obtained by multiplex measurement. ) And O1s (525-545 eV).

  The obtained C1s peak top was 284.3 eV, and the charge was corrected. The peak areas of the C1s and O1s spectra were calculated, and the surface sensitivity of C and O were calculated by multiplying the device sensitivity coefficient. The obtained O / C atomic concentration ratio O / C (O atomic concentration / C atomic concentration) × 100 was defined as the surface oxygen content O / C value of the carbon material.

<Total oxygen content>
Using an oxygen-nitrogen-hydrogen analyzer (ONCO analyzer TCH600 manufactured by LECO), 50 mg of carbon material was melted and decomposed in an inert gas atmosphere in an impulse furnace, and the amount of carbon monoxide in the discharged carrier gas and carbon dioxide The total amount of oxygen contained in the carbon material was calculated by detecting the amount with an infrared detector.

<BET specific surface area (SA)>
After using a surface area meter (specific surface area measuring device “AMS8000” manufactured by Okura Riken Co., Ltd.) to fill the cell with 0.4 g of a carbon material and preliminarily drying the carbon material sample at 350 ° C. for 15 minutes under nitrogen flow, Measurement was performed by a nitrogen adsorption BET method using a gas flow method, using a nitrogen-helium mixed gas accurately adjusted so that the relative pressure value of nitrogen with respect to atmospheric pressure was 0.3.
<D50>
A carbon material (0.01 g) is suspended in 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)), which is a surfactant, and this is a measurement sample. And introduced into a commercially available laser diffraction / scattering particle size distribution measuring apparatus (for example, LA-920 manufactured by HORIBA), and the measurement sample was irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, and then the volume-based median diameter was measured in the measuring apparatus. As measured.

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

<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.

Example 1
The scaly natural graphite having a d50 of 100 μm was pulverized by a dry swirling pulverizer to obtain scaly natural graphite having a d50 of 8.1 μm, a Tap of 0.39 g / cm ³ and a water content of 0.08% by mass. Liquid paraffin (manufactured by Wako Pure Chemical Industries, grade 1, physical properties at 25 ° C .: viscosity = 95 cP, contact angle = 13.2 °, surface tension = 31.7)
12 g of mN / m, rcos θ = 30.9) was added and stirred and mixed, and then the obtained sample was pulverized and mixed at a rotation speed of 3000 rpm with a hammer mill (MF10 manufactured by IKA), and a granulating agent was attached. Scaly natural graphite was obtained. The obtained sample was subjected to granulation treatment by mechanical action for 10 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. The obtained sample was subjected to a heat treatment at 500 ° C. in a nitrogen atmosphere to obtain a granulated carbon material from which the granulating agent was removed. The d50, SA, Tap, circularity, O / C, total oxygen content, oxygen functional group dispersity, discharge capacity, and low-temperature output characteristics were measured by the above measurement methods. The results are shown in Tables 1 and 2.

(Example 2)
A sample was obtained in the same manner as in Example 1 except that the heat treatment temperature was 700 ° C. Tables 1 and 2 show the results of measurements similar to those in Example 1.

(Example 3)
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%. Liquid paraffin (manufactured by Wako Pure Chemical Industries, grade 1, physical properties at 25 ° C .: viscosity = 95 cP, contact angle = 13.2 °, surface tension = 31.7 mN / 100 g of the obtained scaly natural graphite
m, rcos θ = 30.9) was added and stirred and mixed, and the obtained sample was pulverized and mixed with a hammer mill (MF10, manufactured by IKA) at a rotation speed of 3000 rpm, and a scaly shape attached with a granulating agent. Natural graphite was obtained. The obtained sample was subjected to granulation treatment by mechanical action for 10 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. The obtained sample was subjected to a heat treatment at 700 ° C. in a nitrogen atmosphere to obtain a granulated carbon material from which the granulating agent was removed. Tables 1 and 2 show the results of measurements similar to those in Example 1.

Example 4
A sample was obtained in the same manner as in Example 3 except that 6 g of liquid paraffin (manufactured by Wako Pure Chemical Industries, Ltd., first grade) was added as a granulating agent. Tables 1 and 2 show the results of measurements similar to those in Example 1.

(Comparative Example 1)
The scaly natural graphite having a d50 of 100 μm was granulated by a mechanical action of 10 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. In the obtained sample, it was confirmed that a lot of scaly graphite-like fine powders were attached to the base material and not encapsulated in the granulated particles. This sample was classified to remove the scale-like graphite fine powder, and a granulated carbon material having a d50 of 10.9 μm was obtained. Tables 1 and 2 show the results of measurements similar to those in Example 1.

(Comparative Example 2)
A sample was obtained in the same manner as in Example 1 except that the granulated carbon material of Comparative Example 1 was heat treated at 700 ° C. under a nitrogen atmosphere. Tables 1 and 2 show the results of measurements similar to those in Example 1.

(Comparative Example 3)
The scaly natural graphite having a d50 of 100 μm was granulated by a mechanical action of 5 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. In the obtained sample, it was confirmed that a lot of scaly graphite-like fine powders were attached to the base material and not encapsulated in the granulated particles. This sample was subjected to classification to remove the scaly graphite-like fine powder to obtain a granulated carbon material having a d50 of 15.4 μm. Tables 1 and 2 show the results of measurements similar to those in Example 1.

(Comparative Example 4)
Granule treatment was performed on scaly natural graphite having a d50 of 100 μm by a mechanical action of 3 minutes at a rotor peripheral speed of 70 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. In the obtained sample, it was confirmed that a lot of scaly graphite-like fine powders were attached to the base material and not encapsulated in the granulated particles. This sample was subjected to classification to remove the scale-like graphite fine powder to obtain a granulated carbon material having a d50 of 19.5 μm. The resulting granulated carbon material is further granulated by mechanical action for 3 minutes at a rotor peripheral speed of 70 m / sec using a hybrid system NHS-1 manufactured by Nara Machinery Co., Ltd. The scaly graphite-like fine powder in the state of adhesion and not encapsulated in the granulated particles was removed to obtain a granulated carbon material having a d50 of 18.2 μm. Tables 1 and 2 show the results of measurements similar to those in Example 1.

  In Examples 1 to 4, the relationship between oxygen functional group dispersity and d50 (μm) is defined by adding a granulating agent having specified physical properties to scale-like natural graphite adjusted to a specified particle size. Since it was within the range, it showed high capacity and excellent low-temperature input / output characteristics. On the other hand, in Comparative Examples 1 to 4 in which the relationship between the oxygen functional group dispersity and d50 (μm) was outside the specified range, a decrease in low-temperature input / output characteristics was confirmed.

  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 (8)

A non-aqueous secondary battery carbon material capable of occluding and releasing lithium ions, wherein the carbon material is graphite particles satisfying the relationship of the following formula 1. Carbon material.
(Formula 1)
100Y + 0.26X> α
(In the formula, Y is the oxygen functional group dispersity represented by the following formula 2, and X is the volume-based average particle diameter (d50) (μm), α = 9.4)
(Formula 2)
Oxygen functional group dispersity (Y) = total oxygen content obtained from elemental analysis (mol%) / surface oxygen content obtained from X-ray photoelectron spectroscopy (O / C) (mol%)   The carbon material for a non-aqueous secondary battery according to claim 1, wherein the surface oxygen content (O / C) determined by X-ray photoelectron spectroscopy is 2 mol% or less. The carbon material for a non-aqueous secondary battery according to claim 1 or 2, wherein the carbon material has a Tap density of 0.7 g / cm ³ or more.   4. The carbon material for a non-aqueous secondary battery according to claim 1, wherein an average circularity obtained by flow type particle image analysis of the carbon material is 0.88 or more. 5.   The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 4, wherein the graphite particles are spherical graphite particles obtained by granulating flaky, scaly graphite, and massive graphite.   6. The non-aqueous system according to claim 1, wherein the granulation treatment is a treatment that imparts at least mechanical energy of any one of impact, compression, friction, and shearing force. Carbon material for secondary batteries.   The granulation process includes a rotating member that rotates at a high speed in a casing, and a rotor having a rotor in which a plurality of blades are installed in the casing. The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 6, wherein the carbon material is granulated by applying any one of impact, compression, friction, and shearing force.   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 non-aqueous secondary battery comprising the carbon material according to claim 1.

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