JP2014165079A - Carbon material for nonaqueous secondary battery and production method therefor, negative electrode and nonaqueous secondary battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellent negative electrode material for nonaqueous secondary battery having excellent output characteristics, and combining high capacity and high cycle characteristics.SOLUTION: A carbon material for nonaqueous secondary battery has the characteristics for adsorbing dimethyl bibenzyl. A negative electrode material using the carbon material for nonaqueous secondary battery having the characteristics for adsorbing dimethyl bibenzyl has high affinity for lithium ions forming a conjugate with a part of electrolyte, and high ability to capture lithium ions from the carbon material surface, and thereby excellent I/O characteristics as a lithium battery are ensured, while combining high capacity and high cycle characteristics.

Description

  The present invention relates to a carbon material for a non-aqueous secondary battery used in a non-aqueous secondary battery, a negative electrode formed using the carbon material, and a non-aqueous secondary battery having the negative electrode.

  In recent years, demand for high-capacity secondary batteries has increased with the downsizing of electronic devices. In particular, lithium ion secondary batteries having higher energy density and excellent large current charge / discharge characteristics have attracted attention as compared to nickel / cadmium batteries and nickel / hydrogen batteries. Conventionally, higher capacity of lithium ion secondary batteries has been widely studied, but in recent years, due to the increasing demand for higher performance of lithium ion secondary batteries, further increase in capacity, large current charge / discharge characteristics, high temperature storage characteristics, It is required to satisfy high cycle characteristics, high-speed charge / discharge characteristics, high lithium input / output characteristics, and high storage characteristics. In particular, lithium ion secondary batteries for automobiles require large energy during acceleration and deceleration. High input / output characteristics are required because large energy generated at times must be efficiently regenerated. Similarly, a high output power tool is required to have high output characteristics.

  As a carbon material for a lithium ion secondary battery, a graphite material or amorphous carbon is often used in terms of cost and durability. Amorphous carbon is excellent in the input / output characteristics of lithium, but because lithium is taken into the internal pores, the reversible capacity is small, and it is difficult to increase the density of the active material layer, leading to high capacity. There was a problem that there was no. On the other hand, the graphite material has a capacity close to 372 mAh / g, which is the theoretical capacity of lithium occlusion, and is preferable as an active material. However, since the reaction resistance with lithium ions is larger than that of amorphous carbon, the input / output characteristics of lithium ions are improved. There was a problem of being inferior.

  In order to solve the above problems, for example, Patent Document 1 discloses a multi-layer structure carbon material obtained by adhering an organic carbide to the surface of a graphitic carbonaceous material, and the amount of the organic carbide is determined as the graphitic carbonaceous material. By adjusting the amount of residual carbon to 100 parts by mass to be not more than 12 parts by mass and not less than 0.1 parts by mass, the discharge capacity is high, and the charge / discharge irreversible capacity at the initial cycle is suppressed to a low level. It is disclosed that a non-aqueous solvent secondary battery having high safety can be obtained.

  Patent Document 2 uses spheroidized graphite obtained by applying mechanical energy treatment to scaly graphite carbon particles, and after mixing the obtained spheroidized graphite with an organic compound, the organic It is disclosed that by using a multi-layer structure carbon material carbonized with a compound, a non-aqueous solvent secondary battery excellent in carbon material fillability, capacity, large current charge / discharge characteristics, particularly high-speed charge / discharge characteristics can be obtained. ing.

Japanese Patent No. 3712288 Japanese Patent No. 3534391

In general, it is known that when charging a lithium ion secondary battery, lithium ions enter the carbon particles from the surface of the carbon particles, and also discharge from the surface of the carbon particles during discharge. ing. However, Patent Documents 1 and 2 propose a multi-layer structure carbon material in which the surface of graphite is coated with a carbonaceous material derived from an organic compound as a carbon material for electrodes, but a raw material for coating the surface of graphite. No mention is made of the characteristics of the organic compound used as the coating material and the characteristics of the coating layer of the obtained multilayer carbon material. In view of this, the present inventors considered that controlling the surface state of the carbon material particles is important in the characteristics of the lithium ion secondary battery.

  Therefore, the present invention has been made in view of such background art, and its problem is particularly suitable for the use of electric vehicles and power tools in recent years, exhibiting high input / output characteristics, and having high capacity and high cycle characteristics. Is to provide a carbon material for a non-aqueous secondary battery.

  As a result of intensive studies by the present inventors to solve the above problems, as a method for controlling the surface state of the carbon material particles, in the step of obtaining a carbon material in which the surface of the graphite particles is coated with a carbonaceous material derived from an organic compound, It has become clear that it is important to select an organic compound as a coating raw material. Therefore, as a result of trial and error by the present inventors, as an organic compound to be used as a coating raw material from a myriad of organic compounds, a value obtained by subtracting the quinoline insoluble content QI from the toluene insoluble content TI (measurement method will be described later). A non-aqueous secondary battery that has surprisingly high input / output characteristics, combined with high capacity and high cycle characteristics, when a carbon material is produced using a β resin amount of 1% by mass or more and used as a negative electrode. It was found that can be manufactured.

Furthermore, when the carbon material obtained by this production method is analyzed and examined, it becomes clear that the carbon material is a novel carbon material having a characteristic different from the conventional one, that is, a characteristic of adsorbing a specific amount of dimethylbibenzyl. I came.
Here, the details of the carbon material having the adsorption property of methylbibenzyl according to the present invention exhibiting the above-mentioned effects are unclear, but as a result of the study by the inventors, the excellent battery characteristics are due to the following effects. It is believed that there is.

  In other words, non-aqueous electrolytes generally used in lithium ion secondary batteries are mainly composed of carbonates such as ethylene carbonate and ethyl carbonate, which are also the same organic substances as dimethylbibenzyl, and lithium ion secondary batteries. In the battery, lithium ions are known to form a conjugate with carbonate, which is an electrolytic solution, and reach the negative electrode surface. In other words, the fact that this negative electrode surface has the property of adsorbing dimethylbibenzyl means that lithium ions that form a complex with carbonate, which is an organic substance, are also easily adsorbed, so that lithium ions can be taken from the carbon material surface. Lithium ions that form a complex with carbonate react with the carbon material surface to form a coating of lithium and carbonate-derived organic substances on the carbon material surface, stabilize the carbon material surface, and as a result It is thought that the discharge can be performed smoothly.

Incidentally, dimethylbibenzyl is an organic substance having a structure in which two benzene rings with a methyl group are bonded via an ethylene group. The methyl group attached to the benzene ring has a meta position, an ortho position, and a para position, and dimethylbibenzyl as used herein refers to a single compound or a mixture thereof.
That is, the gist of the present invention resides in a carbon material for a non-aqueous secondary battery, wherein the adsorption amount of dimethylbibenzyl obtained by the following measurement method is 30 ppm or more.

(Measurement method)
Disperse 5 g of carbon material for negative electrode in 5 g of xylene solution containing 300 ppm of dimethylbibenzyl, and adsorb dimethylbibenzyl at 20 ° C. with an oscillation frequency of 45 KHz and an output of 80 W for 30 minutes. The xylene solution after the filter was removed was subjected to gas chromatography, and the amount of dimethylbibenzyl remaining in the xylene solution was measured.
This amount is subtracted from the amount of dimethylbibenzyl before dispersion to obtain an adsorption amount per gram of carbon material.

  Another object of the present invention is to provide a carbon material for a non-aqueous secondary battery by attaching an organic compound to graphite particles and performing firing, wherein the amount of β resin in the organic compound is 1% by mass or more. It exists in the manufacturing method of the carbon material of a non-aqueous secondary battery characterized by being.

  The carbon material for non-aqueous secondary batteries of the present invention is a non-aqueous secondary battery that exhibits high input / output characteristics and has both high capacity and high cycle characteristics by using it as a negative electrode material for non-aqueous secondary batteries. Can be provided.

Hereinafter, the contents of the present invention will be described in detail. The description of the invention constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these forms unless it exceeds the gist.
<Carbon material for non-aqueous secondary batteries>
The carbon material for a non-aqueous secondary battery according to the present invention has a characteristic of adsorbing a specific amount of dimethylbibenzyl.
Here, “wt%” and “mass%” are synonymous, and “ppm” simply means “mass ppm”.

  Carbon materials for non-aqueous secondary batteries that have the property of adsorbing a specific amount of dimethylbibenzyl are one of the electrolytes that are organic substances because the surface condition of the carbon materials is highly lipophilic to organic substances. The affinity with the lithium ion that forms the bonded portion with the part is high, and the ability to take in the lithium ion from the carbon material surface is increased. In addition, since the affinity between lithium ions forming part of the electrolyte solution and the combined body is high, the lithium ions are easily attracted to the surface of the carbon material, and lithium ions can be taken in at a higher speed. Furthermore, the lithium ion that forms a conjugate with the electrolyte solution reacts on the surface of the carbon material to make a film derived from lithium and a carbonate that is the main component of the electrolyte solution on the carbon material surface. Excellent film production ability. That is, due to these characteristics, the carbon material for a non-aqueous secondary battery of the present invention has characteristics as a carbon material for a non-aqueous secondary battery that exhibits high input / output characteristics and has both high capacity and high cycle characteristics. It is.

  The lower limit of the amount for adsorbing dimethylbibenzyl is 30 ppm or more, preferably 50 ppm or more, more preferably 100 ppm or more, and particularly preferably 200 ppm or more. When the amount of dimethylbibenzyl adsorbed on the carbon material for non-aqueous secondary batteries is below the lower limit, the surface condition of the carbon material is weak in lipophilicity with respect to organic matter, so that the electrolyte is an organic substance. Lithium ions that have formed a conjugate with a part of the lithium ion have a weak affinity, and the ability to incorporate lithium ions from the surface of the carbon material tends to be poor. In addition, the lithium ion that forms a conjugate with the electrolyte solution reacts on the surface of the carbon material and tends to be inferior in the ability to form a coating of lithium and an organic substance derived from carbonate, which is the main component of the electrolyte solution, on the carbon material surface. The ability to stabilize and smooth charge / discharge tends to be weakened.

  The upper limit of the amount for adsorbing dimethylbibenzyl is not particularly limited, but is preferably 100,000 ppm or less, more preferably 50000 ppm or less, and particularly preferably 10,000 ppm or less. Adsorption more than the upper limit may cause a loss of lithium amount because the amount of lithium ions used as a coating of the organic substance formed on the surface of the carbon material is excessively large.

The amount of dimethylbibenzyl adsorbed is measured as follows. First, 5 g of a carbon material for a negative electrode was dispersed in 5 g of a xylene solution containing 300 ppm of dimethylbibenzyl, and dimethylbibenzyl was adsorbed by applying ultrasonic waves at an oscillation frequency of 45 KHz and an output of 80 W for 30 minutes. After removing the carbon material in the dispersion with a filter, the xylene solution is subjected to gas chromatography to measure the amount of dimethylbibenzyl remaining in the xylene solution, and this amount is subtracted from the amount of dimethylbibenzyl before dispersion. The amount of adsorption per gram of carbon material is expressed in ppm.
The other features of the carbon material for non-aqueous secondary batteries of the present invention are as follows.

Raman R value of the Raman R value nonaqueous secondary battery carbon material is measured and the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and an intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, its The intensity ratio R (R = I _B / I _A ) is calculated and defined. That is, the Raman value is expressed by the following formula 1.
Formula 1:
Raman R value = Intensity I _B of peak P _B near 1360 cm ⁻¹ in Raman spectrum analysis Intensity I _A of peak P _A near 1580 cm ⁻¹
The Raman R value is usually 0.15 or more, preferably 0.18 or more, more preferably 0.20 or more, and further preferably 0.22 or more. Further, it is usually 1 or less, preferably 0.8 or less, more preferably 0.6 or less, still more preferably 0.5 or less, particularly preferably 0.39 or less.

When the Raman R value is too small, the rapid charge / discharge characteristics tend to be deteriorated. Further, when the Raman R value of the carbon material is too large, it indicates that the amount of amorphous carbon covering the graphite particles is large, and the influence of the irreversible capacity of the amorphous carbon amount is large. As a result, the battery capacity tends to decrease.
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.
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

-002 plane spacing (d002), crystallite size (Lc)
The interplanar spacing (d002) of the carbon material for non-aqueous secondary batteries according to the X-ray wide angle diffraction method is usually 0.337 nm or less and the normal crystallite size (Lc) is 90 nm or more. The fact that the surface spacing (d002) of the 002 plane and the crystallite size (Lc) by the X-ray wide angle diffraction method are within the above ranges means that most of the crystallinity excluding the surface of the carbon material particles for non-aqueous secondary batteries. This means that the carbon material is a high capacity electrode that does not cause a reduction in capacity due to the large irreversible capacity found in amorphous carbon materials.

-Tap density The tap density of the carbon material for non-aqueous secondary batteries is usually 0.7 g / cm ³ or more, preferably 1.04 g / cm ³ or more and 1.3 g / cm ³ or less.
If the tap density is too small, sufficient continuous voids are not secured especially in the electrode rolled to a high density, and the mobility of Li ions in the electrolyte held in the voids decreases, resulting in large current charge / discharge characteristics. Tends to decrease. When the tap density is too high, the intra-particle carbon density increases, the rollability is lacking, and it tends to be difficult to form a high-density negative electrode sheet.
In the present invention, the tap density is filled with a powder density measuring instrument by dropping the object to be measured through a sieve having a diameter of 1.6 cm and a volume capacity of 20 cm ³ through a sieve having a mesh opening of 300 μm. After that, a tap having a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume at that time and the weight of the sample is defined as the tap density.

-Specific surface area by BET method The specific surface area by the BET method of the carbon material for non-aqueous secondary batteries is usually 0.2 m ² / g or more, preferably 0.5 m ² / g or more. Moreover, it is 8 m < ² > / g or less normally, More preferably, it is 7 m < ² > / g or less. If the specific surface area is too large, the reactivity with the electrolyte may increase, leading to a decrease in charge / discharge efficiency. If the specific surface area is too small, the charge / discharge reactivity will decrease, resulting in increased gas generation during high-temperature storage. There is a tendency for the current charge / discharge characteristics to decrease.
In addition, the measuring method of a BET specific surface area is measured by a BET 1 point method by a nitrogen gas adsorption circulation method using a specific surface area measuring device.

・ Average particle size (d50)
The average particle size (d50) of the carbon material for non-aqueous secondary batteries is usually 40 μm or less, preferably 30 μm or less, more preferably 25 μm or less, usually 3 μm or more, preferably 4 μm or more, more preferably 5 μm or more. It is. If the average particle size is too large, there are many inconveniences in the process such as striping when the plate is made beyond this particle size range, and if it is below this particle size range, the surface area becomes too large. It tends to be difficult to suppress the activity with the electrolytic solution.

  The particle size is measured by suspending 0.01 g of a carbon material in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate, which is a surfactant, and measuring a commercially available laser diffraction / scattering particle size distribution. The sample was introduced into the apparatus, irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, and then measured as a volume-based median diameter in the measuring apparatus, which is defined as d50 in the present invention.

..Average particle diameter (d10)
The average particle size (d10) of the carbon material for non-aqueous secondary batteries is usually 40 μm or less, preferably 30 μm or less, more preferably 25 μm or less, and usually 3 μm or more, preferably 4 μm or more, more preferably 5 μm or more. It is. If the average particle size is too large, there are many inconveniences in the process such as striping when the plate is made beyond this particle size range, and if it is below this particle size range, the surface area becomes too large. It tends to be difficult to suppress the activity with the electrolytic solution.

  The particle size is measured by suspending 0.01 g of a carbon material in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate, which is a surfactant, and measuring a commercially available laser diffraction / scattering particle size distribution. After being introduced into the apparatus and irradiating a 28 kHz ultrasonic wave at an output of 60 W for 1 minute, measured as a volume-based median diameter in the measuring apparatus is defined as d10 in the present invention.

・ Average particle size (d90)
The average particle size (d90) of the carbon material for non-aqueous secondary batteries is usually 40 μm or less, preferably 30 μm or less, more preferably 25 μm or less, usually 3 μm or more, preferably 15 μm or more, more preferably 17 μm or more. . If the average particle size is too large, there are many inconveniences in the process such as striping when the plate is made beyond this particle size range, and if it is below this particle size range, the surface area becomes too large. It tends to be difficult to suppress the activity with the electrolytic solution.

The particle size is measured by suspending 0.01 g of a carbon material in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate, which is a surfactant, and measuring a commercially available laser diffraction / scattering particle size distribution. After being introduced into the apparatus and irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, what was measured as the volume-based median diameter in the measuring apparatus is d9 in the present invention.
It is defined as 0.

Average circularity Circularity given by the following equation measured for particles having a particle diameter of 1.5 μm to 40 μm of a carbon material for a non-aqueous secondary battery (= circumference of a circle having the same area as the particle projection area / particle projection) The peripheral length of the image) is usually 0.85 or more, preferably 0.87 or more, more preferably 0.9 or more. When the average circularity is below this range, the large current charge / discharge characteristics tend to be reduced. The average circularity is 1 in a flow type particle analyzer capable of photographing several thousand particles dispersed in a liquid one by one using a CCD camera and calculating an average shape parameter thereof. Measured by the method of the examples described later, targeting particles in the range of 5 to 40 μm. The average circularity is a ratio in which the circumference of a circle equivalent to the particle area is the numerator and the circumference of the photographed particle projection image is the denominator. The closer the particle image is to a perfect circle, the closer it is to 1 and the particle image is elongated or bumpy. The smaller the value, the smaller the value.

-True density The true density of the carbon material for non-aqueous secondary batteries is usually 10 g / cm ³ or less, preferably 5 g / cm ³ or less, more preferably 4 g / cm ³ or less, and usually 0.1 g / cm ³ or more. , Preferably 1 g / cm ³ or more, more preferably 2.2 g / cm ³ or more.

<Method for producing carbon material for non-aqueous secondary battery>
The method for producing the carbon material for a non-aqueous secondary battery of the present invention is not particularly limited, for example, a step of attaching an organic compound to graphite particles, a step of carbonizing an organic compound attached to the surface of the graphite particles by firing, Manufacture can be performed through a step of pulverizing or crushing as necessary, and a step of adjusting the particle size by sieving or air classification if necessary. Among these, in the “step of attaching an organic compound to graphite particles”, a production method using an organic compound used as a raw material having a β-resin amount of 1% by mass or more is more effective for the dimethylbibenzyl of the present invention. Since the carbon material for non-aqueous secondary batteries which has the characteristic to adsorb | suck can be manufactured, it is preferable.
Hereinafter, a method (hereinafter referred to as a method for producing a carbon material for a non-aqueous secondary battery) in which an organic compound having an amount of β resin in an organic compound of 1% by mass or more is attached to graphite particles and fired will be described in detail.

(Organic compounds)
In addition to the above characteristics, the organic compound preferably satisfies the following conditions. The organic compound in the present invention refers to a raw material used for coating graphite particles with an amorphous carbon material or a graphite material.
-Β resin amount The β resin amount of the organic compound in the present invention can be obtained by subtracting the quinoline insoluble content amount QI from the toluene insoluble content amount TI.
Toluene insoluble matter (TI) and quinoline insoluble matter (QI) are measured as follows.
・ Toluene insoluble matter (TI)
Put 50 ml of toluene and 5 g of organic compound in a glass flask and dissolve in an oil bath at 130 ° C. for 40 minutes. The toluene solution in which the organic compound is dispersed and dissolved is filtered through a filter, the toluene insoluble matter is separated, dried at 110 ° C. for 60 minutes, and the weight is measured. The toluene insoluble matter weight is divided by the organic matter weight before dissolution, and the value expressed as a percentage is defined as the toluene insoluble matter (TI).

・ Quinoline insoluble matter (QI)
Add 10 ml of quinoline and 5 g of organic compound to a glass flask and dissolve in a water bath at 75 ° C. for 40 minutes. The quinoline solution in which the organic compound is dispersed and dissolved is filtered through a filter, the quinoline insoluble matter is separated, dried at 110 ° C. for 60 minutes, and the weight of the quinoline insoluble matter is measured. Divide the weight of the quinoline insoluble matter by the weight of the organic matter before dissolution and give the percentage value as the percentage of quinoline insoluble matter (Q
I).

  The organic compound adhering to the graphite is carbonized by decomposition and polycondensation of the low-boiling substances by the subsequent calcination by evaporation. Toluene-insoluble matter becomes the main component to be carbonized residually, and the properties of the carbonized material differ depending on the amount. On the other hand, most of the quinoline insoluble matter in organic compounds is an impurity called free carbon or metaphase, which acts to inhibit the organic compounds from polycondensation, carbonization and crystallization, and further firing Even after carbonization, it remains as an impurity in the carbon material, which tends to destabilize the lithium / electrolyte film formed on the carbon material surface and destabilize the charge / discharge properties of lithium ions.

  Therefore, the present inventors have coated the graphite particles with the amount of β-resin obtained by subtracting the quinoline-insoluble component that inhibits carbonization crystallization from the toluene-insoluble component that constitutes the main component of the residual carbonized component in the organic compound. It was found that the surface of the carbonized material is important for the property of adsorbing dimethylbibenzyl, and this carbon material adsorbing dimethylbibenzyl has excellent input / output characteristics for non-aqueous secondary batteries It came to discover that it becomes a carbon material.

The lower limit of the amount of β resin in the organic compound is 1% by mass or more, preferably 2.5% by mass or more, more preferably 3% by mass or more. When an organic compound having a β-resin amount equal to or lower than the lower limit is used as a raw material, the carbon material obtained by calcination carbonization tends to be a carbon material with a small amount of adsorbing dimethylbibenzyl, and does not exhibit high input / output characteristics. Become a trend.
The upper limit of the amount of β resin in the organic compound is not particularly limited, but is usually 80% by mass or less, preferably 70% by mass or less, and more preferably 60% by mass or less. When the amount of β-resin is equal to or more than the upper limit value, there is a tendency to have a large amount of toluene insoluble, which means that the molecular weight of the organic compound is large and it is often a high melting point product. If the melting point is high, mixing of the graphite particles and the organic compound tends to be inhomogeneous, which is not desirable.

  The lower limit of the toluene insoluble matter (TI) in the organic compound is not particularly limited, but is usually 0.01% by mass or more, preferably 3% by mass or more, more preferably 4% by mass or more, and further preferably 5% by mass or more. . When the toluene insoluble content (TI) is below the lower limit, the amount of β-resin in the organic compound also tends to be lower than the lower limit, and the carbon material obtained by calcination carbonization has a small amount of adsorbing dimethylbibenzyl. It tends to be a material and does not show high input / output characteristics.

  The upper limit of the toluene insoluble matter (TI) in the organic compound is not particularly limited, but is usually 80% by mass or less, preferably 70% by mass or less, and more preferably 60% by mass or less. When the toluene insoluble content (TI) is equal to or higher than the upper limit, the toluene insoluble content tends to be large, which means that the organic compound has a large molecular weight and is often a high melting point product. If the melting point is high, mixing of the graphite particles and the organic compound tends to be inhomogeneous, which is not desirable.

  The upper limit of the quinoline insoluble matter (QI) in the organic compound is not particularly limited, but is usually 30% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less. When the quinoline insoluble content (QI) is more than the upper limit, the tendency of preventing the organic compound from being carbonized and crystallized during firing becomes strong, and when used as a negative electrode for a non-aqueous secondary battery, the discharge capacity decreases. There is a tendency. In addition, it remains as an impurity in the carbon material after calcination, and it tends to destabilize the lithium ion and electrolyte solution formed on the carbon material surface and destabilize the charge / discharge characteristics of lithium ions. . The lower limit of the quinoline insoluble matter (QI) in the organic compound is not particularly limited, but is usually greater than 0% by mass, preferably 0.021% by mass or more, more preferably 0.025% by mass or more, and further preferably 2% by mass. % Or more. The lower limit of the quinoline insoluble matter (QI) is not limited because it tends to prevent the organic compound from being carbonized and crystallized during firing.

The amount of sulfur component in the organic compound The lower limit of the amount of sulfur component in the organic compound is not particularly limited, but is usually 0.01% by mass or more, preferably 0.15% by mass or more, more preferably 0.2% by mass. Above, more preferably 0.3% by mass or more, particularly preferably 0.4% by mass or more. The upper limit is not particularly limited, but is usually 3% by mass or less, preferably 2% by mass or less, more preferably 1.5% by mass or less, and still more preferably 1% by mass or less. Too much sulfur component in the organic compound tends to prevent the organic compound from carbonizing and crystallizing during firing, and when used as a negative electrode for a non-aqueous secondary battery, the discharge capacity tends to decrease. It is in. However, an appropriate amount of sulfur component has the effect of changing the crystallinity of the carbonaceous material when carbonizing the organic compound, and is an important factor for the carbon material surface to adsorb dimethylbibenzyl, As a result, a negative electrode for a non-aqueous secondary battery exhibiting excellent input / output characteristics is obtained.

The amount of sulfur component in the organic compound was measured by the following method.
0.2 g of an organic compound is accurately measured, placed on a magnetic board, set in a magnetic tube heated to 1350 ° C. in an oxygen stream, and burned for 10 minutes to change sulfur in the organic compound to sulfur dioxide. The generated sulfur dioxide is absorbed and reacted with hydrogen peroxide solution to change into sulfuric acid, and the amount of sulfuric acid, that is, the amount of sulfur is quantified from the change in the electrical conductivity of the hydrogen peroxide solution. The amount of sulfur was divided by the amount of the organic compound measured and expressed in%.

Specific gravity of organic compound The lower limit of the specific gravity of the organic compound is not particularly limited, but is usually 1.0 or more, preferably 1.1 or more, more preferably 1.13 or more, still more preferably 1.15 or more, particularly preferably 1.17 or more. The upper limit is not particularly limited, but is usually 1.5 or less, preferably 1.45 or less, more preferably 1.4 or less, and still more preferably 1.35 or less. If the specific gravity is too small, the amount of β resin in the organic compound tends to be small, and a preferable carbon surface tends not to be obtained. When the specific gravity is too large, the molecular weight of the organic compound is large, and it is often a high melting point product. If the melting point is high, mixing of the graphite particles and the organic compound tends to be inhomogeneous, which is not desirable. In addition, the specific gravity used the value of 15 degreeC.

-Conradson residual carbon ratio of organic compound The lower limit of the residual carbon ratio of the organic compound is not particularly limited, but is usually 5% or more, preferably 15% or more, more preferably 20% or more, and further preferably 20% or more. The upper limit is 90% or less, preferably 80% or less, more preferably 70% or less. If the residual carbon ratio is too small, the amount of β resin in the organic compound tends to be small, and the carbon surface tends not to be preferred. If the residual carbon ratio is too large, the molecular weight of the organic compound is large, and it is often a high melting point product. If the melting point is high, mixing of the graphite particles and the organic compound tends to be inhomogeneous, which is not desirable.
The Conradson residual carbon ratio was measured by the JIS K2270) petroleum product residual carbon content test method “Conradson method”. 5 g of organic compound was collected in a crucible, heated for 30 minutes to distill off volatile components in the organic compound, and the weight of the remaining carbon remaining in the crucible was divided by the weight of the organic compound before heating and expressed in%. .

Softening point of organic compound There is no particular limitation on the softening point of the organic compound, but it is usually 400 ° C. or lower, preferably 200 ° C. or lower, more preferably 150 ° C. or lower, more preferably 100 ° C. or lower, particularly preferably liquid at room temperature. is there. Above this range, when mixing and mixing with graphite particles, it becomes difficult to mix uniformly, and it may be necessary to carry out at a high temperature, resulting in poor productivity. The lower limit is not particularly limited, and even a liquid that is liquid at normal temperature can be used, and is preferably normal temperature (20 ° C.) or higher.

・ X-ray parameters (d002)
The upper limit of the 002 plane spacing (d002) according to the X-ray wide angle diffraction method of carbon powder obtained by calcination and carbonization of an organic compound at 1300 ° C. is not particularly limited, but is usually 0.3455 nm or less, preferably 0.3452 nm or less. More preferably, it is 0.3451 nm or less, Most preferably, it is 0.3450 nm or less. The lower limit is not particularly limited, but is usually 0.3420 or more, preferably 0.3430 nm or more, more preferably 0.3435 nm or more, and further preferably 0.3440 nm or more. If the d002 value is too large, it indicates that the crystallinity is low, and the carbon material for non-aqueous secondary batteries may become particles with low crystallinity and the charge / discharge capacity may be reduced. If d002 is too small, the charge / discharge is performed. There is a possibility that the reactivity is lowered, and gas generation during high-temperature storage is increased and large current charge / discharge characteristics are deteriorated.

-Crystallite size (Lc)
The lower limit of the crystallite size (Lc) of the organic compound obtained by X-ray diffraction of the carbon powder obtained by firing and carbonizing the organic compound at 1300 ° C. is not particularly limited, but is usually 34 nm or more, preferably 35 nm. As described above, it is preferably 36 nm or more, more preferably 39 nm or more, and the upper limit is not particularly limited, but is usually 80 nm or less, preferably 60 nm or less, and more preferably 50 nm or less.
If this range is exceeded, the carbon material for non-aqueous secondary batteries may become particles with low crystallinity and the charge / discharge capacity may be reduced. If this range is exceeded, the charge / discharge reactivity will be reduced and stored at high temperatures. There is a risk of increased gas generation and reduced large current charge / discharge characteristics.

・ Type of organic compound As the type of organic compound, there is no particular problem if the one having the above-mentioned physical properties is appropriately selected. Usually, carbonaceous material that can be graphitized or made amorphous by firing. If it is, there will be no restriction | limiting in particular, Tar and the petroleum-type and coal-type condensed polycyclic aromatics from a soft pitch to a hard pitch are used preferably. Specifically, petroleum heavy oil such as impregnated pitch, coal tar pitch, coal heavy oil such as coal liquefied oil, cracked heavy oil such as straight heavy oil such as asphaltene, etc. .

(Graphite particles)
The graphite particles are not particularly limited as long as they are materials that can absorb and release lithium ions in the production of a carbon material for a non-aqueous secondary battery. For example, graphite, amorphous carbon, graphite Examples of the carbonaceous material or silicon having a small degree of conversion include graphite. These can be used alone or in combination of two or more.

  Graphite is easily available commercially, theoretically has a high charge / discharge capacity of 372 mAh / g, and further has a high current density compared to the case where other negative electrode active materials are used. This is preferable because the effect of improving the discharge characteristics can be expected greatly. Of these, graphite preferably has few impurities, and can be used after being subjected to various known purification treatments, if necessary. Examples of the graphite include natural graphite and artificial graphite, but natural graphite is more preferable.

  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 Examples include those obtained by baking and graphitizing organic substances such as alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin.

The firing temperature can be in the range of 2500 ° C. or more and 3200 ° C. or less, and a silicon-containing compound, a boron-containing compound, or the like can be used as a graphitization catalyst during firing.
Examples of natural graphite include highly purified flaky graphite and spheroidized graphite. Among these, natural graphite subjected to spheroidizing treatment is more preferable from the viewpoint of particle filling properties and charge / discharge load characteristics.

As an apparatus used for the spheronization treatment, for example, an apparatus that repeatedly gives mechanical effects such as compression, friction, shearing force, etc. including the interaction of graphite carbonaceous particles, mainly to impact force, to the particles can be used.
Specifically, it has a rotor with a large number of blades installed inside the casing, and when the rotor rotates at high speed, mechanical action such as impact compression, friction, shearing force, etc. is applied to the carbon material introduced inside. An apparatus that provides a surface treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating graphite.

  As a preferable apparatus for giving a mechanical action to the carbon material, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), a kryptron (manufactured by Earth Technica), a CF mill (manufactured by Ube Industries), a mechano-fusion system (Hosokawa Micron) And theta composer (manufactured by Deoksugaku Kosakusha). Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable.

  The graphite particles are produced by pulverizing the base particles that have been made spherical by applying the spheroidizing process by the surface treatment described above, so that the scale-like natural graphite is folded or the peripheral edge portion is spherically pulverized. Produced by spheroidizing under the condition that the surface functional group amount O / C value (%) of the graphite particles after the surface treatment is usually 1% or more and 4% or less. It is preferable to do. In this case, it is preferable to carry out in an active atmosphere so that the oxidation reaction of the graphite surface can be advanced by the energy of mechanical treatment and acidic functional groups can be introduced into the graphite surface. For example, when processing using the above-mentioned apparatus, the peripheral speed of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / sec, and 50 to 100 m / sec. Is more preferable. The treatment can be performed by simply passing a carbonaceous material, but it is preferable to circulate or stay in the apparatus for 30 seconds or longer, and it is preferable to circulate or stay in the apparatus for 1 minute or longer. More preferred.

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

Depending on the degree of graphitization of the carbonaceous material, the firing temperature can be 600 ° C. or higher, preferably 900 ° C. or higher, more preferably 950 ° C. or higher, and usually less than 2500 ° C., Preferably it is 2000 degrees C or less, More preferably, it is the range of 1400 degrees C or less.
At the time of baking, acids such as phosphoric acid, boric acid and hydrochloric acid, alkalis such as sodium hydroxide and the like can be mixed with the organic matter.

The graphite particles may contain oxides and other metals. Other metals include S
Examples thereof include metals that can be alloyed with Li, such as n, Si, Al, and Bi.
The carbon material constituting the graphite particles can be used in combination with one or more of the other carbon materials.
The graphite particles in the present invention preferably have the following physical properties. In addition, there is no restriction | limiting in particular in the measuring method in this invention, According to the measuring method as described in an Example, unless there is a special situation.

-Graphite particle size (d50)
Although there is no restriction | limiting in particular about the particle size of graphite particle | grains, As a range to be used, d50 is 50 micrometers or less normally, Preferably it is 40 micrometers or less, More preferably, it is 30 micrometers or less. Moreover, it is 1 micrometer or more normally, Preferably it is 4 micrometers or more, More preferably, it is 8 micrometers or more. If this particle size range is exceeded, inconveniences such as striping often occur when the plate is made, and if it is less than this, the surface area becomes too large and the activity with the electrolyte is suppressed. Becomes difficult.

-BET specific surface area (SA) of graphite particles
The specific surface area of the graphite particles measured by the BET method is usually 4 m ² / g or more, preferably 5 m ² / g or more. Moreover, it is 20 m < ² > / g or less normally, Preferably it is 15 m < ² > / g or less, More preferably, it is 12 m < ² > / g or less. When the specific surface area is below this range, there are few sites where Li enters and exits, and the high-speed charge / discharge characteristic output characteristics are inferior. On the other hand, when the specific surface area exceeds this range, the activity of the active material with respect to the electrolytic solution becomes excessive. Since the irreversible capacity becomes large, a high-capacity battery may not be manufactured.

-Tap density of graphite particles The tap density of graphite particles is usually preferably 0.7 g / cm ³ or more and 0.8 g / cm ³ or more. Further, it is usually preferably 1.3 g / cm ³ or less and 1.2 g / cm ³ or less. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the intra-particle carbon density increases, the rollability is insufficient, and it may be difficult to form a high-density negative electrode sheet.
In the present invention, the tap density is filled with a powder density measuring instrument by dropping the object to be measured through a sieve having a diameter of 1.6 cm and a volume capacity of 20 cm ³ through a sieve having a mesh opening of 300 μm. After that, a tap having a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume at that time and the weight of the sample is defined as the tap density.

Raman R value of Raman (Raman) spectrum graphite particles of the graphite particles was measured and the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and an intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity The ratio R (R = I _B / I _A ) is calculated and defined. The value is usually 0.1 or more, preferably 0.15 or more, more preferably 0.17 or more, and still more preferably 0.2 or more. Further, it is 1 or less, preferably 0.9 or less, more preferably 0.8 or less. Moreover, 1 or less and 0.4 or less are preferable normally, and 0.3 or less are more preferable. If the Raman R value is below this range, the crystallinity of the particle surface becomes too high, and when the density is increased, the crystals are likely to be oriented in a direction parallel to the electrode plate, which may lead to a reduction in load characteristics. On the other hand, if it exceeds this range, the crystal on the particle surface is disturbed, the reactivity with the electrolytic solution is increased, and the charge / discharge efficiency may be lowered and the gas generation may be increased.

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.
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)

Average circularity Circularity given by the following equation measured for particles having a particle diameter of 1.5 μm to 40 μm of a carbon material for a non-aqueous secondary battery (= circumference of a circle having the same area as the particle projection area / particle projection) The peripheral length of the image) is usually 0.85 or more, preferably 0.87 or more, more preferably 0.9 or more. When the average circularity is below this range, the large current charge / discharge characteristics tend to be reduced. The average circularity is 1 in a flow type particle analyzer capable of photographing several thousand particles dispersed in a liquid one by one using a CCD camera and calculating an average shape parameter thereof. Measured by the method of the examples described later, targeting particles in the range of 5 to 40 μm. The average circularity is a ratio in which the circumference of a circle equivalent to the particle area is the numerator and the circumference of the photographed particle projection image is the denominator. The closer the particle image is to a perfect circle, the closer it is to 1 and the particle image is elongated or bumpy. The smaller the value, the smaller the value.

(Manufacturing process of carbon material for non-aqueous secondary battery)
As one of preferred embodiments of the process for producing the carbon material for a non-aqueous secondary battery of the present invention, (1) a process of attaching an organic compound to graphite particles, (2) the graphite particles obtained in (1) are not treated. A step of carbonizing an organic compound adhering to the surface of the graphite particles by firing in an active atmosphere to obtain a carbon material in which the graphite particles are coated with a carbonaceous material derived from the organic compound; (3) coated with the carbonaceous material In the case where the graphite particles are aggregated and bonded, a production method including at least a step of adjusting the particle size by pulverization or pulverization as necessary, and further by sieving or air classification as necessary may be mentioned.

More specifically, the carbon material for a non-aqueous secondary battery of the present invention is manufactured by attaching graphite particles and an organic compound that satisfy the above-described conditions and performing a carbonization treatment of the organic compound in the mixture. The carbonization treatment means an amorphization treatment or graphitization treatment. In this specification, a carbon material in which graphite particles are coated with amorphous carbon or graphite is sometimes referred to as a multilayer carbon material. Among these, a carbon material that has been amorphized and has graphite particles coated with amorphous carbon is preferable. The term “coated” as used herein refers to an embodiment in which at least a part or the entire surface of the carbon material is coated or attached with an amorphous carbonaceous material.
For example, it can be manufactured by the following method.

(1) Step of attaching an organic compound to graphite particles There is no particular limitation on the method of attaching the organic compound to the graphite particles. For example, the graphite particles and the organic compound may be mixed using various commercially available mixers and kneaders. A method of mixing to obtain a mixture in which an organic compound adheres to graphite particles is mentioned. In that case, the organic compound has a ratio of the residual carbon component derived from the organic compound in the carbon material for non-aqueous secondary batteries that has undergone the heat treatment obtained by carbonization, usually 0.3% by mass or more, preferably 0.5%. The mixing amount is adjusted and mixed so as to be at least mass%, more preferably at least 1 mass%. The upper limit is an amount such that this ratio is usually 30% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less. If the amount of the organic compound mixed is too large, the charge / discharge capacity decreases, and the press load required for high-density rolling of the active material layer applied to the current collector increases, resulting in a non-aqueous secondary battery. It may be difficult to increase the capacity. On the other hand, if the mixing amount of the organic compound is too small, particles may be destroyed or deformed when the active material layer applied to the current collector is rolled to a high density, and good large current charge / discharge characteristics may not be obtained. is there.

The graphite particles and the organic compound are mixed under heating as necessary. When the organic compound is liquid at normal temperature, the heating temperature is preferably mixed at a temperature equal to or higher than normal temperature. When the organic compound is solid at normal temperature, it is higher than the softening point of the organic compound and is usually 10 ° C. above the softening point. It is carried out at a temperature higher than this, preferably at a temperature 20 ° C. or higher than the softening point, usually 450 ° C. or lower, preferably 250 ° C. or lower. If the heating temperature is too low, the viscosity of the organic compound may be high and mixing may be difficult. If the heating temperature is too high, the viscosity of the mixed system may be too high due to volatilization and polycondensation of the organic compound.

Commercially available mixers such as ribbon mixers, MC processors, pro-shear mixers, and KRC kneaders can be used as the mixer. The lower limit of the mixing time is usually 1 minute or longer, preferably 2 minutes or longer, more preferably 5 minutes or longer, and the upper limit is usually 120 minutes or shorter, preferably 100 minutes or shorter, more preferably 80 minutes or shorter. When the mixing time is too short, there is a tendency that the organic compound does not adhere uniformly around the graphite particles, and when it is too long, the cost increases.
(2) A carbon material obtained by firing the graphite particles obtained in (1) in an inert atmosphere to carbonize the organic compound attached to the surface of the graphite particles and coating the graphite particles with carbonaceous material derived from the organic compound. The mixture (graphite particles) obtained in the step (1) for obtaining is heated and fired in a non-oxidizing atmosphere to carbonize the organic compound. The organic compound in the mixture to be baked is first heated to 400 ° C. to 500 ° C. to distill off the low-boiling fraction contained in the organic compound, and simultaneously with the distillation of the low-boiling fraction or the After distilling off the low-boiling fraction, a polycondensation reaction or decomposition reaction of the organic compound occurs, and the decomposed components are dissipated and are not decomposed by the high-boiling fraction or those having a high molecular weight by the polycondensation reaction. Things remain on or near the graphite particle surface. When the temperature is further raised, polycondensation of the high molecular weight substance and high boiling point substance remaining on or near the graphite particle surface further proceeds, and the high molecular weight substance and high boiling point substance are carbonized.

The lower limit of the firing temperature is usually 500 ° C. or higher, preferably 600 ° C. or higher, more preferably 700 ° C. or higher. The upper limit of the temperature is usually 2000 ° C. or lower, preferably 1700 ° C. or lower, more preferably 1500 ° C. or lower, and further preferably 1400 ° C. or lower. If the firing temperature is too low, the degree of carbonization of organic substances is small, so the degree of carbonization tends to be small, and when used as a negative electrode material for lithium batteries, irreversible capacity (incorporated into the negative electrode during charging) The amount that a part of lithium ions does not return by discharge tends to increase, which is not preferable. If the firing temperature is too high, the carbonization of the organic compound tends to proceed too much, and when used as a negative electrode material for a lithium battery, the input / output rate of lithium ions tends to decrease.
Step (2) can be carried out in two stages if necessary.
By carrying out the firing in two stages, the low boiling point substances contained in the organic compound in the mixture in the first stage and the substances that are decomposed by the firing reaction of the organic compound are excluded, and in the second stage, Polycondensation and carbonization of high molecular weight substances and high-boiling substances remaining on the particle surface or in the vicinity thereof can be performed.

When firing is performed in two stages, the lower limit of the first stage firing temperature is usually 400 ° C. or higher,
Preferably it is 450 degreeC or more, More preferably, it is 500 degreeC or more. The upper limit is usually 1000 ° C. or lower, preferably 900 ° C. or lower, more preferably 800 ° C. or lower. If the calcination temperature is too low, the degree of exclusion of low-boiling substances contained in the organic compound and substances that are decomposed by the calcination reaction of the organic compound becomes low, which is undesirable because it places a burden on the second-stage calcination. The lower limit of the firing temperature in the second stage when carrying out in two stages is usually 500 ° C. or higher, preferably 600 ° C. or higher, more preferably 700 ° C. or higher. The upper limit is usually 2000 ° C. or lower, preferably 1700 ° C. or lower, more preferably 1500 ° C. or lower, and further preferably 1400 ° C. or lower. If the firing temperature is too low, the degree of carbonization of organic substances is small, so the degree of carbonization tends to be small, and when used as a negative electrode material for lithium batteries, irreversible capacity (incorporated into the negative electrode during charging) The amount that a part of lithium ions does not return by discharge tends to increase, which is not preferable. If the firing temperature is too high, the carbonization of the organic compound tends to proceed too much, and when used as a negative electrode material for a lithium battery, the input / output rate of lithium ions tends to decrease.

The heating rate during firing is not particularly limited, but is usually 2 ° C./hr or more, preferably 3 ° C./hr or more, more preferably 4 ° C./hr or more, and the upper limit is usually 3000 ° C./hr or less, preferably 2000 ° C./hr. hr or less, more preferably 1000 ° C./hr or less. If the temperature increase rate during firing is too small, firing takes time and the heating cost tends to increase. If the rate of temperature increase is too high, the polycondensation reaction will not be sufficiently performed, the amount of carbonization will be small, and the specific surface area and irreversible capacity will tend to increase. During firing, stirring may be performed as necessary.
The equipment used for firing is, for example, a shuttle furnace, a tunnel furnace, a lead hammer furnace, a rotary kiln, a roller hearth furnace, a pusher furnace, an autoclave reaction tank, a coker (heat treatment tank for coke production), an electric furnace, a gas furnace, etc. There is no particular limitation as long as firing in an oxidizing atmosphere is possible.

  In order to prevent oxidation, the atmosphere at the time of heating and firing is performed under a non-oxidizing atmosphere in which an inert gas such as nitrogen or argon is circulated or a granular carbon material such as breeze or packing coke is filled in the gap. Further, the coverage of the carbonaceous material derived from the organic compound in the carbon material for a non-aqueous secondary battery of the present invention indicates the coverage of the carbonaceous material derived from the organic compound with respect to the graphite particles, and is usually 0.01 in the present invention. % By mass or more, preferably 0.1% by mass or more, more preferably 0.3% or more, particularly preferably 0.7% by mass or more, and the coverage is usually 20% by mass or less, preferably 15% by mass. % Or less, more preferably 10% by mass or less, particularly preferably 7% by mass or less, and most preferably 5% by mass or less.

If the coverage is too high, the carbon material will be damaged and material destruction will occur when rolling at a sufficient pressure to achieve high capacity in non-aqueous secondary batteries. There is a tendency to increase capacity and decrease initial efficiency.
On the other hand, if the coverage is too small, the effect of being covered tends to be difficult to obtain. That is, the side reaction with the electrolytic solution in the battery cannot be sufficiently suppressed, and the charge / discharge irreversible capacity during the initial cycle tends to increase and the initial efficiency tends to decrease. Even if the carbonaceous layer is thin, the effect of the present invention can be obtained as long as the carbonaceous layer is uniformly present over the entire surface of the carbon material. When many appear on the outermost surface of the carbon material for a non-aqueous secondary battery of the invention, it becomes difficult to obtain the effect of the present invention.

Further, the carbonaceous coverage in the present invention can be calculated from the sample mass before and after the material firing. At this time, the calculation is made assuming that there is no mass change before and after firing the carbon material.
Covering rate (% by weight) = 100− (K × D) / ((K + T) × N) × 100
In this formula, K is the weight (Kg) of the graphite particles subjected to mixing with the organic compound, T is the weight (kg) of the organic compound subjected to mixing with the graphite particles, and D is the actual amount of the mixture of K and T. The amount of the mixture subjected to firing, N, indicates the weight of the carbon material after firing.

(3) A step of adjusting the particle size by pulverization or pulverization, if necessary, and, if necessary, by sieving or air classification when graphite particles coated with carbonaceous material are agglomerated and bonded. The battery carbon material is pulverized, crushed, ground, classified, etc. as required. There are no particular restrictions on the apparatus used for pulverization. Examples of the coarse pulverizer include a shearing mill, jaw crusher, impact crusher, and cone crusher. Examples of the fine pulverizer include a ball mill, a vibration mill, a pin mill, and a stirring mill. And a jet mill.

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

<Mixing with other carbon materials>
The carbon material for non-aqueous secondary batteries of the present invention can be suitably used as a negative electrode material for a lithium ion secondary battery by using any one of them alone or in combination of two or more of them in any composition and combination. it can. One or two or more carbon materials for non-aqueous secondary batteries of the present invention are mixed with other one or two or more other carbon materials, and this is mixed with a non-aqueous secondary battery, preferably a negative electrode of a lithium ion secondary battery. It may be used as a material.

  When other carbon materials are mixed with the carbon material for non-aqueous secondary batteries described above, the mixing ratio of the carbon material for non-aqueous secondary batteries to the total amount of carbon materials for non-aqueous secondary batteries and other carbon materials is usually 10 wt. % Or more, preferably 20% by weight or more, and usually 90% by weight or less, preferably 80% by weight or less. When the mixing ratio of other carbon materials is below the above range, the added effect tends to hardly appear. On the other hand, when the above range is exceeded, the characteristics of the carbon material for non-aqueous secondary batteries tend to hardly appear.

In addition, as the carbon material, a material selected from Si, SiC, natural graphite, artificial graphite, amorphous-coated graphite, and amorphous carbon is used. Any one of these materials may be used alone, or two or more of these materials may be used in any combination and composition.
As natural graphite, for example, highly purified flaky graphite or spheroidized graphite can be used. The volume-based average particle diameter of natural graphite is usually 8 μm or more, preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less. Natural graphite has a BET specific surface area of usually 3.5 m ² / g or more, preferably 4.5 m ² / g or more, and usually 8 m ² / g or less, preferably 6 m ² / g or less.

Examples of the artificial graphite include particles obtained by graphitizing a carbon material. For example, particles obtained by firing and graphitizing a single graphite precursor particle while it is powdered can be used.
As amorphous-coated graphite, for example, natural graphite or artificial graphite coated with an amorphous precursor pair and fired, or natural graphite or artificial graphite coated with amorphous by CVD can be used.

As the amorphous carbon, for example, particles obtained by firing a bulk mesophase, or particles obtained by firing an infusible organic compound can be used.
There are no particular restrictions on the device used to mix the carbon material for non-aqueous secondary batteries with other carbon materials. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylinder mixer, a double cone Type mixer, regular cubic mixer, vertical mixer, stationary mixer: spiral mixer, ribbon mixer, Muller mixer, Helical Flyt mixer, Pugmill mixer, fluidized mixer A mixer or the like can be used.

<Negative electrode for non-aqueous secondary battery>
A negative electrode for a non-aqueous secondary battery of the present invention (hereinafter also referred to as an “electrode sheet” as appropriate) includes a current collector and an active material layer formed on the current collector, and the active material layer is at least the present material layer. It contains the carbon material for non-aqueous secondary batteries of the invention. More preferably, it contains a binder.
The binder here means a binder that is added for the purpose of binding the active materials and holding the active material layer on the current collector when creating the negative electrode for the non-aqueous secondary battery. It is different from the organic compound mentioned in the specification.

As the binder, it is preferable to use a binder having an olefinically unsaturated bond in the molecule. 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 large molecular weight, it is desirable that the weight average molecular weight is usually 10,000 or more, preferably 50,000 or more, and usually 1,000,000 or less, preferably 300,000 or less. In the case of a binder having a large ratio of unsaturated bonds, the number of moles of olefinically unsaturated bonds per gram of all binders is usually 2.5 × 10 ⁻⁷ or more, preferably 8 × 10 ⁻⁷ or more, In addition, it is usually 1 × 10 ⁻⁶ or less, preferably 5 × 10 ⁻⁶ or less. The binder only needs to satisfy at least one of these regulations regarding molecular weight and regulations regarding the proportion of unsaturated bonds, but it is more preferable to satisfy both regulations simultaneously. When the molecular weight of the binder having an olefinically unsaturated bond is too small, the mechanical strength is inferior, and when it is too large, the flexibility is inferior. Moreover, if the ratio of the olefinically unsaturated bond in the binder is too small, the effect of improving the strength is reduced, and if it is too large, the flexibility is poor.

The binder having an olefinically unsaturated bond has a degree of unsaturation of usually 15% or more, preferably 20% or more, more preferably 40% or more, and usually 90% or less, preferably 80% or less. Is desirable. The degree of unsaturation represents the ratio (%) of the double bond to the repeating unit of the polymer.
In the present invention, a binder 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 usually 150% by weight or less, preferably 120% by weight 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.

  The negative electrode of the present invention is formed by dispersing the above-described negative electrode 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 usually about 10% by weight or less with respect to the negative electrode material of the present invention.

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

  The thickness of the active material layer obtained by applying and drying the slurry is usually 5 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 200 μm or less, preferably 100 μm or less, more preferably 75 μm or less. . If the active material layer is too thin, it is not practical as a negative electrode because of the balance with the particle size of the active material, and if it is too thick, it is difficult to obtain a sufficient Li occlusion / release function for high-density current values.

The density of the carbon material for the non-aqueous secondary battery in the active material layer varies depending on the application, but is preferably 1.0 g / cm ³ or more, particularly 1.2 g / cm ³ or more, and more preferably 1. It is preferably 25 g / cm ³ or more, particularly 1.3 g / cm ³ or more. If the density is too low, the capacity of the battery per unit volume is not always sufficient. Moreover, since a rate characteristic will fall when a density is too high, 1.9 g / cm < ³ > or less is preferable.

  When producing the non-aqueous secondary battery negative electrode using the non-aqueous secondary battery 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 batteries and the lithium ion secondary battery using the negative electrode material of the present invention will be exemplified, but the materials that can be used and the method of production 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. things, sulfides of titanium, transition metal sulfides such as _CuS, NIPS 3, FEPS phosphorus transition metals, such as ₃ - sulfur _compounds, VSe 2, NbSe ₃ selenium compounds of transition metals such as, Fe0.25V0.75S _2, Na0.1CrS ₂ composite oxide of a transition metal such _as, LiCoS _2, LiNiS 2 composite sulfide of a transition metal, such as and the like.

Among _{these, V 2 O 5, V 5} O 13, VO 2, Cr 2 O 5, MnO 2, TiO, MoV 2 O 8, LiCoO 2, LiNiO 2, LiMn 2 O 4, TiS 2, V 2 S 5 , Cr0.25V0.75S ₂ , Cr0.5V0.5S _{2 and the} like are preferable, and LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _4, and lithium transitions in which some of these transition metals are replaced with other metals are particularly preferable. It is a metal complex oxide. These positive electrode active materials may be used alone or in combination.

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

The positive electrode active material layer may contain a conductive material in order to improve the conductivity of the electrode. The conductive 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 current collector of the positive electrode, aluminum, nickel, SUS, or the like is used, but is not limited at all.

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

  Any one of these non-aqueous solvents may be used alone, or two or more thereof may be mixed and used. In the case of a mixed solvent, a combination of a mixed solvent containing a cyclic carbonate and a chain carbonate is preferable, and the cyclic carbonate is a mixed solvent of ethylene carbonate and propylene carbonate. This is particularly preferable 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 is lowered, and when the proportion of propylene carbonate is higher than the above, when a graphite electrode is used, the PC solvated with Li ions coexists between the graphite phases. Insertion causes delamination degradation of the graphite-based negative electrode active material, and there is a problem that sufficient capacity cannot be obtained.

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

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

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

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

  The form of the lithium ion 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 lithium ion 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.
(Measuring method)
(1) Dimethylbibenzyl adsorption amount 5 g of a carbon material for a negative electrode was dispersed in 5 g of a xylene solution containing 300 ppm of dimethylbibenzyl, and dimethylbibenzyl was adsorbed for 30 minutes at an oscillation frequency of 45 kHz and an output of 80 W. After removing the carbon material in the dispersion with a filter, the xylene solution is subjected to gas chromatography to measure the amount of dimethylbibenzyl remaining in the xylene solution, and this amount is subtracted from the amount of dimethylbibenzyl before dispersion. The amount of adsorption per gram of carbon material is expressed in ppm.

(2) Particle size About 0.01 g of carbon material is suspended in 10 mL of 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate, which is a surfactant, and a commercially available laser diffraction / scattering type particle size distribution analyzer is used. After introducing and irradiating an ultrasonic wave of 28 kHz at an output of 60 W for 1 minute, a value measured as a volume-based median diameter in a measuring apparatus is defined as d50 in the present invention. Further, the particle size of the cumulative 10% part is defined as d10, and the particle size of the cumulative 90% part is defined as d90.

(3) BET specific surface area Measured using AMS-8000 manufactured by Okura Riken Co., Ltd. After pre-drying at 250 ° C. and flowing nitrogen gas for 30 minutes, the BET one-point method by nitrogen gas adsorption was used for measurement.
(4) β resin amount of organic compound It was determined by subtracting the quinoline insoluble content (QI) from the toluene insoluble content (TI).

(5) Toluene insoluble matter (TI)
Put 50 ml of toluene and 5 g of organic compound in a glass flask and dissolve in an oil bath at 130 ° C. for 40 minutes. The toluene solution in which the organic compound is dispersed and dissolved is filtered through a filter, the toluene insoluble matter is separated, dried at 110 ° C. for 60 minutes, and the weight is measured. The toluene insoluble matter weight was divided by the organic matter weight before dissolution, and the value expressed as a percentage was defined as the toluene insoluble matter (TI).

(6) Quinoline insoluble matter (QI)
Add 10 ml of quinoline and 5 g of organic compound to a glass flask and dissolve in a water bath at 75 ° C. for 40 minutes. The quinoline solution in which the organic compound is dispersed and dissolved is filtered through a filter, the quinoline insoluble matter is separated, dried at 110 ° C. for 60 minutes, and the weight of the quinoline insoluble matter is measured. The quinoline insoluble matter weight was divided by the organic matter weight before dissolution, and the value expressed as a percentage was defined as the quinoline insoluble matter (QI).

(7) Specific gravity and softening point of organic compound Measured according to JIS K2425.
(8) Amount of sulfur in organic compounds (%)
0.2 g of an organic compound is accurately measured, placed on a magnetic board, set in a magnetic tube heated to 1350 ° C. in an oxygen stream, and burned for 10 minutes to change sulfur in the organic compound to sulfur dioxide. The generated sulfur dioxide is absorbed and reacted with hydrogen peroxide solution to change into sulfuric acid, and the amount of sulfuric acid, that is, the amount of sulfur is quantified from the change in the electrical conductivity of the hydrogen peroxide solution. The amount of sulfur was divided by the amount of the organic compound measured and expressed in%.

(9) Conradson residual coal rate The Conradson residual coal rate was measured by JIS K2270) Petroleum Product Residual Carbon Content Test Method "Conradson Method". 5 g of organic compound was collected in a crucible, heated for 30 minutes to distill off volatile components in the organic compound, and the weight of the remaining carbon remaining in the crucible was divided by the weight of the organic compound before heating and expressed in%. .

(10) d002 (nm), Lc (nm) of organic compound 1300 ° C. fired product
Reflective diffractometer method using CuKα rays monochromatized with graphite monochromator as a source, with a mixture of approximately 15% X-ray standard high-purity silicon powder mixed with powder of 1300 ° C fired organic compound A wide-angle X-ray diffraction curve was measured using the Gakushin method, and the interplanar spacing (d002) and crystallite size (Lc) were determined.

(11) XRD of carbon material: d002 (nm), Lc (nm)
About 15% X-ray standard high-purity silicon powder mixed with carbon powder is used as a material, CuKα ray monochromatized with a graphite monochromator is used as a radiation source, and a wide angle X-ray diffraction curve is obtained by a reflection diffractometer method. Was measured, and the interplanar spacing (d002) and crystallite size (Lc) were determined using the Gakushin method.

(12) Tap density The tap density is a powder density measuring device manufactured by Seishin Enterprise Co., Ltd. “Tap Denser KYT-4000”, and is open to a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ^3. After dropping the carbon material through a 300 μm sieve and filling the cell completely, tap with a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume and the weight of the sample is defined as the tap density.

(13) Raman spectrum (Raman) spectrum The Raman spectrum can be measured with a Raman spectrometer: "Raman spectrometer manufactured by JASCO Corporation". 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.
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)

(14) Average circularity Using a flow-type particle image analyzer (FPIA-2000 manufactured by Toa Medical Electronics Co., Ltd.), measurement of particle size distribution by equivalent circle diameter and calculation of circularity were performed. 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 measured circularity of particles in the range of 1.5 to 40 μm was averaged to obtain the average circularity.

(15) True density Measured using a pycnometer and a 0.1% aqueous solution of a surfactant as a medium.
(16) Coverage Coverage (weight%) = 100− (K × D) / ((K + T) × N) × 100
In this formula, K is the weight (Kg) of the graphite particles subjected to mixing with the organic compound, T is the weight (kg) of the organic compound subjected to mixing with the graphite particles, and D is the actual amount of the mixture of K and T. The amount of the mixture subjected to firing, N, indicates the weight of the carbon material after firing.

(17) Battery evaluation (Preparation and evaluation of battery for initial battery characteristic evaluation)
100 parts by mass of a carbon material for a non-aqueous secondary battery, 100 parts by mass of a 1% aqueous solution of carboxymethyl cellulose, and 2 parts by mass of a 50% aqueous dispersion of styrene butadiene rubber were added and kneaded to obtain a slurry. The slurry was applied to a weight of 12 mg / cm ² on a copper foil by a doctor blade method. After drying at 110 ° C., it was consolidated by a roll press so that the density was 1.35 g / cc. This was cut into 12.5 mmφ and dried under reduced pressure at 190 ° C. to obtain a negative electrode.
The above-described negative electrode and a 0.5 mm-thick lithium metal were stacked via a separator impregnated with an electrolytic solution to produce a coin-type battery for a charge / discharge test. As the electrolytic solution, a solution in which LiPF6 was dissolved to 1.2 mol / liter in a mixed solution of ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 3: 3: 4 (mass ratio) was used.

(Initial capacity, irreversible capacity)
The battery was charged to 5 mV at 0.05 C (charged at 20 hours) at 25 ° C., 0.1
The discharge was repeated twice to 1.5 V at C (discharge at 10 hr), and the discharge capacity at the second time was converted into the capacity per weight of the carbon material, and the initial capacity (mAh / g) was shown in Table-1. In addition, in the above two charging / discharging operations, the value obtained by subtracting the discharging capacity from each charging capacity is summed twice, and converted into the capacity per weight of the carbon material, as irreversible capacity (mAh / g). It was written in.

(Production of battery for evaluation of output characteristics and cycle characteristics)
100 parts by mass of a carbon material for a non-aqueous secondary battery, 100 parts by mass of a 1% aqueous solution of carboxymethyl cellulose, and 2 parts by mass of a 50% aqueous dispersion of styrene butadiene rubber were added and kneaded to obtain a slurry. This slurry was applied to a copper foil with a basis weight of 6 mg / cm ² by a doctor blade method. After drying at 110 ° C., it was consolidated by a roll press so that the density was 1.35 g / cc. This was cut into a 32 mm × 42 mm square and dried under reduced pressure at 190 ° C. to obtain a negative electrode.

To 94 parts by mass of lithium nickel manganese cobalt based composite oxide powder, 4 parts by mass of carbon black, 25 parts by mass of a 12% N-methylpyrrolidone polyvinylidene fluoride solution, and an appropriate amount of N-methylpyrrolidone are added and kneaded to form a slurry. It was. This slurry was applied to an aluminum foil with a basis weight of 24.3 mg / cm ² by a doctor blade method. It dried at 110 degreeC, and also consolidated by the roll press so that the density of a positive electrode layer might be 2.7 g / cm < ³ >. This was cut into a 30 mm × 40 mm square and dried at 140 ° C. to obtain a positive electrode.
A battery for a charge / discharge test was prepared by stacking the negative electrode and the positive electrode with a separator impregnated with an electrolyte solution. As an electrolytic solution, LiPF6 was dissolved in a mixed solution of ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 3: 3: 4 (mass ratio) to 1.2 mol / liter, and 2% by mass of vinylene carbonate was added. Things were used.

(Initial adjustment)
This battery was charged to 4.1 V at 0.2 C (charged at 5 hr) at 25 ° C., charged to 4.1 mA at 4.1 V, and then discharged to 3.0 V at 0.2 C (discharged at 5 hr). And then charge to 0.5V (charged at 2hr) to 4.2V, further charge to 4.2mA at 4.2V, and then repeat the discharge twice to 3.0V at 0.2C. did.

(aging)
The battery after initial adjustment was charged to 4.1 V at 0.5 C at 25 ° C., then held in a constant temperature bath at 60 ° C. for 24 hours, then returned to 25 ° C., and then to 3.0 V at 0.2 C. Discharge was performed.
(Low temperature output characteristics)
The battery after the aging was charged to 50% of the battery capacity at 0.2 C at 25 ° C., and then stored in a thermostatic bath at −30 ° C. for 3 hours or more, and then 0.25 C, 0.50 C, 0 The battery was discharged at .75 C, 1.00, 1.25 C, 1.50 C, 1.75, and 2.00 C for 2 seconds, and the voltage at the second second was measured. The area of the triangle surrounded by the current-voltage straight line and the lower limit voltage (3 V) is shown in Table 1 as the low temperature output characteristic (mW).

(Remaining rate of storage capacity at 60 ° C for 4 weeks, Recovery rate of storage capacity at 60 ° C for 4 weeks)
The battery after the aging was charged to 4.1 V at 0.5 C at 25 ° C., and 4
. After charging to 1 mA at 1 V, the battery was discharged to 3.0 V at 0.2 C. The discharge capacity at this time was defined as the capacity before storage. Next, charge to 4.1V at 0.5C and 2 at 4.1V.
After charging to mA, it was placed in a constant temperature bath at 60 ° C. for 4 weeks. This battery was discharged to 3.0 V at 0.2 C at 25 ° C., and the discharge capacity at this time was defined as the storage capacity after 60 ° C. for 4 weeks. The capacity after storage at 60 ° C. for 4 weeks and expressed as a percentage by the capacity before storage is shown in Table 1 as the remaining capacity at 60 ° C. for 4 weeks.

The battery was then charged to 4.1 V at 0.5 C at 25 ° C. and then 4.1 V
Then, the battery was charged to 2 mA and discharged to 3.0 V at 0.2C. The discharge capacity at this time was defined as the recovery capacity after storage at 60 ° C. for 4 weeks. The recovery capacity after storage at 60 ° C. for 4 weeks and expressed as a percentage by the pre-storage capacity is shown in Table 1 as the storage capacity recovery rate at 60 ° C. for 4 weeks.
(Cycle characteristic evaluation)
After the above aging treatment, the battery was charged to 4.2V at 2C (charging in 30 minutes) at 60 ° C, and repeatedly discharged to 3.0V at 2C. The discharge capacity at the 500th cycle relative to the discharge capacity at the first cycle Is expressed in% as a 500 cycle maintenance rate and is shown in Table-1.

Example 1
Naturally produced graphite with a 002 plane spacing (d002) by X-ray wide angle diffraction method of 3.36 mm, Lc of 1000 mm or more, tap density of 0.46 g / cm ³ , and 1580 cm ⁻¹ in an argon ion laser Raman spectrum. Scale-like graphite particles having a Raman R value which is a peak intensity ratio in the vicinity of 1360 cm ^{−1 to} a peak intensity in the vicinity of 0.13, an average particle diameter (d50) of 28.7 μm and a true density of 2.27 g / cm ³ , By using a hybridization system manufactured by Nara Machinery Co., Ltd., graphite particles are continuously processed at a processing speed of 20 kg / hr under conditions of a rotor peripheral speed of 60 m / second and 10 minutes. Spheroidization was performed while damaging the surface, and then fine powder was removed by classification. The obtained spherical graphite particles had a 002 plane distance (d002) of 3.36 mm by L-ray wide angle diffraction method, Lc of 1000 mm or more, a tap density of 0.83 g / cm ³ , and 1580 cm in an argon ion laser Raman spectrum. ^The Raman R value, which is the peak intensity ratio near 1360 cm ^{−1 with} respect to the peak intensity near ^−1, is 0.24, the average particle diameter (d50) is 11.6 μm, the BET specific surface area is 8.1 m ² / g, the true density is 2 The average circularity was 0.909, .27 g / cm ³ .

  Next, 100 parts by mass of the graphite particles and 24 parts by mass of coal-derived tar as an organic compound were charged into a mixer and mixed by heating at 60 ° C. to obtain a mixture of graphite particles and an organic compound. Table 1 shows the properties of the coal tar-derived tar used. The resulting mixture was baked to 1100 ° C. over 2 hours in a non-oxidizing atmosphere and then cooled to room temperature. Furthermore, the carbon material for non-aqueous secondary batteries was obtained by grind | pulverizing and classifying.

  5 g of this carbon material for non-aqueous secondary batteries was dispersed in 5 g of a xylene solution containing 300 ppm of dimethylbibenzyl, and 5 g of the carbon material for negative electrode was dispersed, and ultrasonic waves were applied for 30 minutes to adsorb dimethylbibenzyl. The xylene solution after removing the carbon material in the dispersion with a filter was subjected to gas chromatography, and the amount of dimethylbibenzyl remaining in the xylene solution was measured to be 20 ppm, and the adsorbed dimethylbibenzyl was 280 ppm. . Other characteristics of this carbon material for non-aqueous secondary batteries are shown in Table 1.

Example 2
100 parts by mass of the graphite particles used in Example 1 and 10 parts by mass of coal-derived pitch as an organic compound were heated and mixed at 160 ° C. with a mixing mixer.
Then baked to 1000 ° C. in a non-oxidizing atmosphere over 2 weeks, then cooled to room temperature,
Furthermore, the carbon material for non-aqueous secondary batteries was obtained by grind | pulverizing and classifying. Table 1 shows the characteristics of the carbon material for the non-aqueous secondary battery.

Comparative Example 1
It implemented like Example 1 except using 33 mass parts of petroleum origin tars as an organic compound. Table 1 shows the properties of the petroleum-derived tar used and the characteristics of the carbon material for the non-aqueous secondary battery.

  By using the carbon material of the present invention as a carbon material for a non-aqueous secondary battery, an excellent negative electrode material for a non-aqueous secondary battery having excellent low-temperature output characteristics, high capacity, and high cycle characteristics is provided. Can do.

Claims (11)

A carbon material for a non-aqueous secondary battery, wherein the adsorption amount of dimethylbibenzyl determined by the following measurement method is 30 ppm or more.
(Measurement method)
5 g of carbon material for negative electrode was dispersed in 5 g of xylene solution containing 300 ppm of dimethylbibenzyl, and dimethylbibenzyl was adsorbed at 20 ° C. with an oscillation frequency of 45 KHz and an output of 80 W for 30 minutes. After removing the carbon material in the dispersion with a filter, the xylene solution is subjected to gas chromatography to measure the amount of dimethylbibenzyl remaining in the xylene solution, and this amount is subtracted from the amount of dimethylbibenzyl before dispersion. The amount of adsorption per gram of carbon material.   The carbon material for a non-aqueous secondary battery according to claim 1, wherein the carbon material is a multi-layer structure carbon material in which graphite particles are coated with amorphous carbon.   3. The carbon material for a non-aqueous secondary battery according to claim 1, wherein the Raman R value is 0.15 or more and 1 or less.   The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 3, wherein the graphite particles are natural graphite.   In the production method of obtaining a carbon material for a non-aqueous secondary battery by attaching an organic compound to graphite particles and performing firing, the amount of β resin in the organic compound is 1% by mass or more. Manufacturing method of battery carbon material.   The method for producing a carbon material for a non-aqueous secondary battery according to claim 5, wherein the amount of the toluene insoluble component in the organic compound is 3% by mass or more.   The interplanar spacing (d002) of the 002 plane according to the X-ray wide angle diffraction method of carbon powder obtained by firing and carbonizing an organic compound after firing at 1300 ° C. is 0.3452 nm or less. The manufacturing method of the non-aqueous secondary battery carbon material as described in 2.   The crystallite size (Lc (004)) by X-ray wide angle diffraction of the carbon powder obtained by firing and carbonizing the organic compound after firing at 1300 ° C. is 34 nm or more. A method for producing a carbon material for a non-aqueous secondary battery according to claim 1.   A nonaqueous secondary battery carbon material obtained by the method for producing a nonaqueous secondary battery carbon material according to any one of claims 5 to 8.   10. A non-aqueous secondary battery charcoal according to claim 1, comprising a current collector and an active material layer formed on the current collector, wherein the active material layer is any one of claims 1 to 4 and 9. A negative electrode for a non-aqueous secondary battery containing a material.   A lithium ion secondary battery comprising a positive electrode and a negative electrode capable of occluding and releasing lithium ions, and an electrolyte, wherein the negative electrode is a negative electrode for a non-aqueous secondary battery according to claim 10.