JP6906891B2 - Carbon material for non-aqueous secondary batteries and lithium ion secondary batteries - Google Patents

Description

The present invention relates to a carbon material for a non-aqueous secondary battery and a lithium ion secondary battery using the carbon material.

In recent years, with the miniaturization of electronic devices, the demand for high-capacity secondary batteries has been increasing. In particular, lithium-ion secondary batteries having a higher energy density and excellent high-current charge / discharge characteristics than nickel-cadmium batteries and nickel-hydrogen batteries have been attracting attention. Conventionally, increasing the capacity of lithium-ion secondary batteries has been widely studied, but in recent years, there has been an increasing demand for higher performance of lithium-ion secondary batteries, especially for automobiles and the like. It is required to achieve high input / output and long life.

It is known that a carbon material such as graphite is used as an active material for a negative electrode in a lithium ion secondary battery. Above all, when graphite having a high degree of graphitization is used as an active material for a negative electrode for a lithium ion secondary battery, a capacity close to the theoretical capacity of graphite occlusion of 372 mAh / g can be obtained, and further, cost and durability can be obtained. It is known that it is preferable as an active material for a negative electrode because of its excellent properties. On the other hand, when the density of the active material layer containing the negative electrode material is increased in order to increase the capacity, the material is destroyed and deformed, resulting in an increase in charge / discharge irreversible capacity during the initial cycle, a decrease in input / output characteristics, and a decrease in cycle characteristics. There was a problem.

In order to solve the above problem, for example, in Patent Document 1, coke powder having an average particle size of 5 μm as a graphitizable aggregate and pitch or coal tar as a binder are mixed, calcined, graphitized, and pulverized. by a plurality of flat particles, aggregate or coupled such that the orientation surface is non-parallel, in the range of 10 ² to 10 ⁶ Å the size of the pore volume of pores from 0.4 to 2. A technique for improving rapid charge / discharge characteristics by setting the value to 0 cc / g is disclosed.

Patent Document 2 discloses a technique for adhering scaly graphite to the surface of granular graphite by mixing, firing, and pulverizing granular graphite, scaly graphite, and a binder.
Further, in Patent Document 3, the coking coal composition obtained by caulking a heavy oil composition by a delayed caulking process is provided with 5% or more of fine particles having a particle size of 1/3 or less of the average particle size. After adjusting the particle size distribution, a compressive stress and a shear stress are applied to produce a granulated spherical graphite precursor, and the graphite precursor is further heated to be graphitized to obtain cycle characteristics and storage characteristics. Techniques for improvement are disclosed.

JP-A-2002-083587 Japanese Unexamined Patent Publication No. 2004-127723 JP 2013-079173

According to the study by the present inventors, in the technique disclosed in Patent Document 1, granulated particles are produced by binding coke particles with a binder, so that the pores in the particles remain in the binder. The charcoal was buried, and as a result, the amount of pores in the particles tended to decrease. In particular, although there are many relatively large pores, the reduction of micropores limits the movement of the electrolytic solution to the details, and the capacity, charge / discharge load characteristics, and input / output characteristics are still insufficient.

In the technique disclosed in Patent Document 2, since granular graphite and scaly graphite are attached via a binder, there are few voids around the granular graphite nucleus, and the movement of the electrolytic solution is restricted. The input / output characteristics were still insufficient. In addition, since the scaly graphite is attached and fired only by mixing the granular graphite, the scaly graphite, and the binder, the arrangement of the scaly graphite cannot be controlled, and the scaly graphite attached vertically to the granular graphite in a fluffy state. There is a problem that the charge / discharge load characteristics and the input / output characteristics are deteriorated because the graphite is peeled off during pulverization and becomes fine powder, and the graphite is oriented in the electrode.

In the technique disclosed in Patent Document 3, the formation of granulated bodies was insufficient because the shape of the adherent coke breeze fine powder was not controlled. Furthermore, the parent coke and the adherent raw coke fine powder are fused to assimilate the primary particles of the granulated body, and the granulated body structure cannot be maintained and the particles become substantially one particle, and the fine pores in the particles are reduced. However, since the movement of the electrolytic solution is restricted, the capacity, charge / discharge load characteristics, and input / output characteristics are still insufficient.

The present invention has been made in view of the above technical background, and the problem is that it is possible to obtain a non-aqueous secondary battery having a high capacity and excellent input / output characteristics, high temperature storage characteristics, and cycle characteristics. It is an object of the present invention to provide a carbon material that can be stably and efficiently manufactured, and as a result, to provide a non-aqueous secondary battery having high performance and excellent productivity.

As a result of diligent studies to solve the above problems, the present inventors have made a carbon material for a non-aqueous secondary battery in which graphite particles (A) capable of occluding and releasing a plurality of lithium ions are composited. The mode diameter in the pore distribution obtained by the mercury press-fitting method for powder is 0.1 μm or more and 2 μm or less, and the volume reference average particle diameter (d50) is 5 μm or more and 40 μm or less. We found that by using a carbon material for an aqueous secondary battery, a non-aqueous secondary battery with high capacity, excellent charge / discharge load characteristics and input / output characteristics, excellent cycle characteristics, and excellent productivity can be obtained. The present invention has been completed.

That is, the gist of the present invention is a carbon material for a non-aqueous secondary battery in which graphite particles (A) capable of occluding and releasing a plurality of lithium ions are composited, and is obtained by a mercury press-fitting method for powder. It exists in a carbon material for a non-aqueous secondary battery, characterized in that the mode diameter in the pore distribution is 0.1 μm or more and 2 μm or less, and the volume-based average particle size (d50) is 5 μm or more and 40 μm or less.

Another gist of the present invention is a lithium ion secondary battery including a positive electrode and a negative electrode capable of storing and releasing lithium ions and an electrolyte, wherein the negative electrode is a current collector and the current collector. The active material layer is provided in the above-mentioned lithium ion secondary battery, which is characterized by containing the carbon material for a non-aqueous secondary battery.

By using the composite carbon particles of the present invention and the composite carbon material containing the composite carbon particles as the negative electrode active material for a non-aqueous secondary battery, the charge / discharge load characteristics and input / output characteristics are excellent, and the cycle characteristics are also excellent. It is possible to stably and efficiently provide a lithium secondary battery having excellent productivity.
The mechanism by which the composite carbon particles of the present invention exhibit excellent battery characteristics has not been clarified, but as a result of the studies by the inventors, it is considered that the excellent battery characteristics are due to the following effects.

By setting the volume-based average particle diameter (d50) to 5 μm or more and 40 μm or less, it becomes possible to suppress aggregation between composite particles, so that inconveniences in the process such as an increase in slurry viscosity and a decrease in electrode strength may occur. It can be prevented. Further, the graphite particles (A) having a d50 smaller than that of the composite carbon material are composited by applying at least one of the mechanical energies of impact, compression, friction, and shearing force without using a binder that fills the voids. By doing so, it becomes possible to form a particle structure having many fine pores in the particles of the composite carbon material, and the mode diameter in the pore distribution obtained by the mercury press-fitting method for the powder is set to 0.1 μm or more and 2 μm or less. be able to. As a result, the electrolytic solution can be efficiently moved to the insertion / desorption site of Li ions inside the composite carbon material particles, and the volume expansion / contraction during charging / discharging can be relaxed by the pores, so that the capacity is high. It is considered that the charge / discharge load characteristics and the low temperature input / output characteristics can be improved.

It is a cross-sectional SEM image of the composite carbon particles of Example 2. It is a figure which shows an example of the pore distribution map which concerns on one Embodiment of this invention.

Hereinafter, the contents of the present invention will be described in detail. The description of the constituent requirements of the invention described below is an example (representative example) of the embodiment of the present invention, and the present invention is not specified in these forms unless the gist thereof is exceeded.
The carbon material for a non-aqueous secondary battery of the present invention is a carbon material for a non-aqueous secondary battery in which graphite particles (A) capable of storing and releasing a plurality of lithium ions are composited, and is a carbon material for a powder. The mode diameter in the pore distribution determined by the mercury intrusion method is 0.1 μm or more and 2 μm or less, and the volume-based average particle diameter (d50) is 5 μm or more and 40 μm or less.

<Graphite particles (A)>
The carbon material for a non-aqueous secondary battery of the present invention contains graphite particles (A) capable of occluding and releasing a plurality of lithium ions.
Here, examples of the graphite particles (A) include natural graphite and artificial graphite. Among them, artificial graphite particles, especially bulk mesophase artificial graphite particles, have few defects on the surface of graphite and have a structure with few voids in which the inside of the particles is densely packed. Therefore, compared to natural graphite, they have cycle characteristics, high temperature storage characteristics, and safety. It is preferable because it has excellent properties.

Here, the bulk mesophase artificial graphite particles refer to artificial graphite particles produced by graphitizing coke obtained by heat-treating a pitch raw material such as coal tar pitch or petroleum pitch at a predetermined temperature.
Of these, artificial graphite particles obtained by graphitizing mosaic coke in which the optically anisotropic structure constituting the structure does not grow significantly and artificial graphite particles obtained by graphitizing needle coke in which the optically anisotropic structure grows significantly are preferable. In particular, artificial graphite particles obtained by graphitizing needle coke having a large optically anisotropic structure are preferable.

<Physical characteristics of graphite particles (A)>
-Volume-based average particle size (d50)
In the present specification, the volume-based average particle size (d50) refers to the median size (d50) in the volume-based particle size distribution measured by the laser diffraction / scattering method particle size distribution measurement.
The average particle size d50 of the graphite particles (A) of the present invention is preferably 1 μm or more, more preferably 1.5 μm or more, still more preferably 1.7 μm or more, particularly preferably 2 μm or more, preferably 20 μm or less, more preferably. It is 10 μm or less, more preferably 7 μm or less, particularly preferably 5 μm or less, and most preferably 4 μm or less.

When the average particle size d50 is within the above range, it becomes possible to have a dense void structure in the composite carbon particles, and a non-aqueous secondary battery having a high capacity and excellent charge / discharge load characteristics and low temperature input / output. It becomes easy to obtain. In addition, the increase in slurry viscosity and uneven coating during electrode coating are less likely to occur.
For the volume-based particle size distribution, a laser diffraction type particle size distribution meter (for example, LA-700, manufactured by HORIBA, Ltd.) was used to obtain a 2 volume% aqueous solution of polyoxyethylene (20) sorbitan monolaurate as a surfactant. Approximately 1 ml) is mixed with the graphite negative electrode material, and the value measured using ion-exchanged water as a dispersion medium can be used. The average particle size (median diameter) is measured from the volume-based particle size distribution 50% particle size (d50).

-Minimum particle size (dmin), maximum particle size (dmax)
The graphite particles (A) of the present invention have a minimum particle size (dm) of preferably 0.1 μm or more, more preferably 0.2 μm or more, and a maximum particle size (dmax) of usually 100 μm or less, preferably 100 μm or less. Is 50 μm or less, more preferably 30 μm or less. When the minimum particle size (dmin) and the maximum particle size (dmax) are within the above ranges, it becomes possible to introduce a pore structure having an appropriate diameter in the composite carbon material particles, and a good charge / discharge load is obtained. It tends to show characteristics and low temperature input / output.
The minimum particle size (dmin) and the maximum particle size (dmax) are measured from the volume-based particle size distribution by laser diffraction / scattering particle size distribution measurement using a laser diffraction type particle size distribution meter, similar to the volume-based average particle size. can.

-Tap Density The graphite particles (A) of the present invention have a tap density of preferably 0.40 to 1.50 g / cm ³ , more preferably 0.60 to 1.00 g / cm ³ . When the tap density is within the above range, the filling density of the active material is improved, and a high-capacity battery can be obtained.
As the tap density, a sieve having a mesh size of 300 μm is used ^{, a graphite material is dropped into a tapping cell of 20 cm 3} to fill the cell fully, and then a powder density measuring instrument (for example, a tap density manufactured by Seishin Enterprise Co., Ltd.) is used. It is possible to use the value obtained by performing tapping with a stroke length of 10 mm 1000 times and measuring the tapping density at that time.

_-Surface spacing d 002
In the graphite particles (A) of the present invention, the surface spacing d ₀₀₂ of the (002) plane measured by X-ray diffraction is preferably 0.36 nm or less, more preferably 0.345 nm or less, still more preferably 0.341 nm or less. be. If it is within the above range, that is, if the crystallinity is high, the discharge capacity per unit weight of the active material becomes large when the electrode is manufactured. On the other hand, _{the lower limit of the surface spacing d 002} is usually 0.3354 nm or more as a theoretical limit.

Further, in the graphite particles (A) of the present invention, the crystallite size Lc in the c-axis direction measured by X-ray diffraction is preferably 10 nm or more, more preferably 20 nm or more. If it is within the above range, the discharge capacity per weight of the active material when the electrode is manufactured becomes large.
_{As the plane spacing d 002} and the crystallite size Lc measured by the above X-ray diffraction, values measured according to the Gakushin method of the Society of Carbon Materials can be used. In the Gakushin method, values of 100 nm (1000 Å) or more are not distinguished, and all are described as "> 1000 (Å)".

<Natural graphite particles (B)>
The composite carbon particles for a non-aqueous secondary battery of the present invention are highly charged to contain natural graphite particles (B) in addition to graphite particles (A) capable of occluding and releasing a plurality of lithium ions. It is preferable because it has a discharge capacity and has good charge / discharge characteristics at a high current density.
The natural graphite preferably has few impurities, and can be used after being subjected to various known purification treatments, if necessary.

Natural graphite is classified into scaly black (FlakeGraphite), scaly (Crystal Line Graphite), lump graphite (Vein Graphite), and soil graphite (Amorphousu Graphite) according to its properties ("Powder and Granule Process Technology Collection" (((() See the section on graphite of Industrial Technology Center Co., Ltd. (published in 1974) and "HANDBOOK OF CARBON, GRAPHITE, DIAMOND AND FULLERENES" (published by Noyes PubLications)). The degree of graphitization is highest in scaly graphite and massive graphite at 100%, followed by scaly graphite at 99.9%, which is suitable in the present invention. Among them, those having few impurities are preferable, and various known purification treatments can be applied and used as needed.
The production areas of natural graphite are Madagascar, China, Brazil, Ukraine, Canada, etc., and the production areas of scaly graphite are mainly Sri Lanka. The main production areas of soil graphite are the Korean Peninsula, China, Mexico, etc. Among the natural graphites, for example, scaly, scaly, or lumpy natural graphite, highly purified scaly graphite, and the like can be mentioned.

<Physical characteristics of natural graphite particles (B)>
-Aspect ratio The aspect ratio of the graphite particles (B) is 5 or more, preferably 7 or more, more preferably 10 or more, and further preferably 15 or more. Further, it is usually 1000 or less, preferably 500 or less, more preferably 100 or less, still more preferably 50 or less. When the aspect ratio is within the above range, it is possible to manufacture a composite carbon material for a non-aqueous secondary battery having excellent input / output characteristics. Further, the graphite particles (B) are less likely to be separated from the surface of the graphite particles (A), and it is possible to prevent a decrease in diffusivity of the electrolytic solution due to orientation in the electrode.

The aspect ratio is represented by A / B when the longest diameter A (major diameter) of the negative electrode material particles when observed three-dimensionally and the longest diameter B (minor diameter) among the diameters orthogonal to it. Is done. The negative electrode material particles are observed with a scanning electron microscope capable of magnified observation. Select any 50 negative electrode material particles fixed to the end face of a metal having a thickness of 50 microns or less, rotate and incline the stage on which the sample is fixed for each, measure A and B, and measure A / B. Find the average value of.

・ Average particle size d50
The average particle size d50 of the graphite particles (B) is preferably smaller than that of the graphite particles (A). The specific average particle size d50 is preferably 1 μm or more, more preferably 2 μm or more, particularly preferably 3 μm or more, preferably 40 μm or less, more preferably 20 μm or less, still more preferably 10 μm or less, and very preferably 8 μm. Below, it is particularly preferably 7 μm or less. When the volume average particle diameter is within the above range, it is possible to prevent deterioration of charge / discharge efficiency, charge / discharge load characteristics, low temperature input / output characteristics, and cycle characteristics.

-Ash content The ash content contained in the graphite particles (B) is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.1% by mass or less, based on the total mass of the carbon material. Is. Further, the lower limit of the ash content is preferably 1 ppm or more.
When the ash content is within the above range, when a non-aqueous secondary battery is used, the deterioration of battery performance due to the reaction between the carbon material and the electrolytic solution during charging and discharging can be suppressed to a negligible extent. In addition, since the production of carbon material does not require a large amount of time, energy and equipment for pollution prevention, the cost increase can be suppressed.

_-Surface spacing d 002
_{The interplanar spacing d 002} of the 002 planes of the graphite particles (B) by the X-ray wide-angle diffraction method is usually 0.337 nm or less, preferably 0.336 nm or less, and the crystallite size Lc is usually 90 nm or more, preferably 95 nm or more. .. The interplanar spacing d ₀₀₂ and the crystallinity size Lc are values indicating the crystallinity of the negative electrode material bulk, and the _{smaller the value of the (002) plane interplanar spacing d 002 and} the larger the crystallinity size Lc, the more. It indicates that the negative electrode material has high crystallinity, and the amount of lithium entering the graphite layers approaches the theoretical value, so that the capacity increases. If the crystallinity is low, excellent battery characteristics (high capacity and low irreversible capacity) when highly crystalline graphite is used for the electrode will not be exhibited. It is particularly preferable that the interplanar spacing d ₀₀₂ and the crystallite size Lc are combined in the above ranges. X-ray diffraction is measured by the following method. The material is a mixture of carbon powder and X-ray standard high-purity silicon powder, which is about 15% by mass of the total amount, and the CuKα ray monochromated with a graphite monochromator is used as the radiation source. Measure the line diffraction curve. Then, the plane spacing d ₀₀₂ and the crystallite size Lc are obtained using the Gakushin method.

-Tap density The packed structure of graphite particles (B) depends on the size and shape of the particles, the degree of interaction between the particles, etc., but in this specification, it is one of the indexes for quantitatively discussing the packed structure. It is also possible to apply the tap density as. In the study by the present inventors, it has been confirmed that, in the case of graphite particles having substantially the same true density and volume average particle size, the more spherical the shape and the smoother the particle surface, the higher the tap density. That is, in order to increase the tap density, it is important to make the shape of the particles rounded to make them spherical, and to maintain smoothness by removing hangnail and defects on the particle surface. When the particle shape approaches a spherical shape and the particle surface is smooth, the filling property of the powder is greatly improved. The tapping density of the graphite particles (B) before the graphite particles (B) are combined with the composite carbon particles is usually 0.1 g / cm ³ or more, preferably 0.15 g / cm ³ or more. 0.2 g / cm ³ or more is more preferable, and 0.3 g / cm ³ or more is further preferable.

-Raman R value The argon ion laser Raman spectrum of the graphite particles (B) is used as an index showing the properties of the surface of the particles. Raman R value is the peak intensity ratio in the vicinity of 1360 cm ^-1 to the peak intensity near 1580 cm ^-1 in the argon ion laser Raman spectrum of the flake graphite is usually 0.01 to 0.9, 0.01 or 0. It is preferably 7 or less, and more preferably 0.01 or more and 0.5 or less. The R value is an index showing the crystallinity near the surface of the carbon particles (from the particle surface to about 100 Å), and the smaller the R value, the higher the crystallinity or the undisturbed crystal state. The Raman spectrum is measured by the method shown below. Specifically, the particles to be measured are naturally dropped into the measurement cell of the Raman spectrometer to fill the sample, and while irradiating the measurement cell with an argon ion laser beam, the measurement cell is placed in a plane perpendicular to the laser beam. Measure while rotating. The wavelength of the argon ion laser light is 514.5 nm.

・ Specific surface area (SA)
The lower limit of the specific surface area of the graphite particles (B) by the BET method before the graphite particles (B) are compounded with the composite carbon particles is usually 0.3 m ² / g or more, ^{preferably 1 m 2} / g or more. It is more preferably 3 m ² / g, and even more preferably 5 m ² / g. On the other hand, the upper limit is usually 50 m ² / g or less, ^{preferably 30 m 2} / g or less, ^{more preferably 20 m 2} / g or less, and further preferably 15 m ² / g or less. When the specific surface area is within the above range, the acceptability of Li ions is improved, the charge / discharge load characteristics and the low temperature input / output characteristics are improved, the increase in irreversible capacity can be suppressed, and the decrease in battery capacity can be prevented. ..

<Carbon material for non-aqueous secondary batteries>
In the carbon material for a non-aqueous secondary battery of the present invention, a plurality of graphite particles (A) capable of occluding and releasing the above-mentioned lithium ions are composited, and the mode in the pore distribution obtained by the mercury intrusion method for powder is obtained. A carbon material having a diameter of 0.1 μm or more and 2 μm or less and a volume-based average particle size (d50) of 5 μm or more and 40 μm or less.
The term "plural composite" as used herein means that the carbon material for a non-aqueous secondary battery contains at least two or more graphite particles (A). When the carbon material for a non-aqueous secondary battery contains a plurality of graphite particles (A), it becomes easy to have fine pores in the particles of the carbon material for a non-aqueous secondary battery, and the effect of the present invention is more likely to be exhibited. It tends to be.

<Physical characteristics of carbon materials for non-aqueous secondary batteries>
The preferable physical properties of the carbon material for a non-aqueous secondary battery of the present invention are as follows.

-Pore distribution mode diameter The mode diameter (particle diameter corresponding to the mode of distribution) in the pore distribution obtained by the mercury press-fitting method for the powder of the carbon material for a non-aqueous secondary battery of the present invention is preferably 0. 1 μm or more, more preferably 0.5 μm or more, still more preferably 0.7 μm or more, particularly preferably 0.9 μm or more, preferably 2.0 μm or less, more preferably 1.8 μm or less, still more preferably 1.5 μm or less, Particularly preferably, it is 1.3 μm or less. If the pore distribution mode diameter is too large than the above range, it indicates that there are many large pores between the particles and few small pores in the particles, and the Li ion insertion / desorption site inside the composite carbon material particles is indicated. Since it becomes difficult for the electrolytic solution to permeate, the low-temperature input / output characteristics tend to deteriorate. On the other hand, if the pore distribution mode diameter is too small than the above range, it means that there are many intraparticle pores but the diameter is small, and the electrolytic solution reaches the insertion / desorption site of Li ions inside the composite carbon material particles. Since it becomes difficult for the particles to penetrate, the charge / discharge load characteristics and the low temperature input / output characteristics tend to deteriorate. Further, since the volume expansion / contraction during charging / discharging cannot be relaxed, the electrode expansion tends to increase.

-Pore volume of 0.1 μm or more and 2 μm or less The pore volume of 0.1 μm or more and 2 μm or less in the pore distribution obtained by the mercury intrusion method for the powder of the carbon material for a non-aqueous secondary battery of the present invention is usually 0. .2 ml / g or more, preferably 0.3 ml / g or more, more preferably 0.35 ml / g or more, still more preferably 0.4 ml / g or more, particularly preferably 0.45 ml / g or more, most preferably 0. It is 47 ml / g or more. Further, it is preferably 1 ml / g or less, more preferably 0.8 ml / g or less, still more preferably 0.7 l / g or less, and particularly preferably 0.6 ml / g or less.

When the pore volume of 0.1 μm or more and 2 μm or less is within the above range, the electrolytic solution can move smoothly into the particles because it has appropriate voids, so that the charge / discharge load characteristics and the low temperature input / output characteristics are deteriorated. It is improved and the filling property of the particles is increased, so that the capacity can be increased.
The pore distribution mode diameter and the pore volume in the present invention are values measured by using a mercury intrusion method (mercury porosimeter), and as an apparatus for mercury porosimeter, a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Co., Ltd.) ) Can be used. The sample (carbon material) is weighed so as to have a value of about 0.2 g, sealed in a powder cell, degassed at room temperature and under vacuum (50 μmHg or less) for 10 minutes, and pretreatment is performed.

Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced into the cell, the pressure is stepped up from 4 psia (about 28 kPa) to 40,000 psia (about 280 MPa), and then the pressure is lowered to 25 psia (about 170 kPa).
The number of steps at the time of pressurization is 80 points or more, and in each step, the amount of mercury injection is measured after an equilibrium time of 10 seconds. From the mercury intrusion curve thus obtained, the pore distribution is calculated using the Washburn formula.
The surface tension (γ) of mercury is calculated as 485 dyne / cm, and the contact angle (ψ) is calculated as 140 °.

-Volume-based average particle size (average particle size d50)
The volume-based average particle size (also referred to as "average particle size d50") of the carbon material for a non-aqueous secondary battery of the present invention is 5 μm or more, preferably 6 μm or more, more preferably 7 μm or more, particularly preferably 8 μm or more, 40 μm. Hereinafter, it is preferably 30 μm or less, more preferably 20 μm or less, particularly preferably 17 μm or less, and most preferably 14 μm or less. If the average particle size d50 is too small, aggregation tends to occur between the composite particles, which tends to cause process inconveniences such as an increase in slurry viscosity and a decrease in electrode strength. On the other hand, if the average particle size d50 is too large, inconveniences in the process such as streaks in slurry coating may occur, the high current density charge / discharge characteristics may be deteriorated, and the low temperature input / output characteristics may be deteriorated.

Further, in the present specification, the average particle size d50 is a carbon material in 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) which is a surfactant. 0.01 g was suspended, and this was introduced as a measurement sample into a commercially available laser diffraction / scattering particle size distribution measuring device (for example, LA-920 manufactured by HORIBA), and the measurement sample was irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. After that, it is defined as the one measured as the volume-based median diameter in the measuring device.

Grain size ratio between average particle size d50 and graphite particles (A) The average particle size d50 of the carbon material for non-aqueous secondary batteries of the present invention is usually 1.5 times the average particle size d50 of graphite particles (A). The above is preferably 2 times or more, more preferably 2.5 times or more, still more preferably 3 times or more, usually 15 times or less, preferably 12 times or less, more preferably 10 times or less, still more preferably 8 times or less. ..
Within the above range, process inconveniences such as particle aggregation and increase in slurry viscosity and conductive path breakage can be suppressed, and the electrode strength and initial charge / discharge efficiency in a non-aqueous secondary battery tend to be good.

・ Average particle size d10
The average particle size d10 (particle size that is 10% cumulative from the small particle side on a volume basis) of the carbon material for non-aqueous secondary batteries of the present invention determined by the laser diffraction / scattering method, usually 2 μm or more, preferably 3 μm or more. , More preferably 3.5 μm or more, further preferably 4 μm or more, and usually 30 μm or less, preferably 15 μm or less, more preferably 10 μm or less, still more preferably 7 μm or less, and particularly preferably 6 μm or less.

Within the above range, process inconveniences such as particle aggregation and increase in slurry viscosity and conductive path breakage can be suppressed, and the electrode strength and initial charge / discharge efficiency in a non-aqueous secondary battery tend to be good.
The average particle size d10 is defined as a value obtained by integrating the particle size with a small volume frequency (%) of the particles in the particle size distribution obtained by the same method as in the measurement of the average particle size d50.

-Average particle size d90
The average particle size d90 (particle size of 90% from the small particle side on a volume basis) determined by the laser diffraction / scattering method of the carbon material for a non-aqueous secondary battery of the present invention is usually 10 μm or more, preferably 15 μm. As described above, it is more preferably 18 μm or more, and usually 100 μm or less, preferably 50 μm or less, more preferably 40 μm or less, still more preferably 30 μm or less.
Within the above range, it tends to be possible to suppress the occurrence of process inconveniences such as streaks during slurry application, and deterioration of the high current density charge / discharge characteristics and low temperature input / output characteristics of the battery.
The average particle size d90 is defined as a value obtained from a particle size having a small volume frequency% of particles to an integrated value of 90% in the particle size distribution obtained by the same method as in the measurement of the average particle size d50.

・ D90 / d10
The d90 / d10 of the carbon material for a non-aqueous secondary battery of the present invention is usually 3.5 or more, more preferably 4 or more, still more preferably 4.5 or more, and usually 10 or less, preferably 7 or less, more preferably. It is 6 or less. When d90 / d10 is within the above range, small particles enter the voids between large particles, so that the filling property of the carbon material for a non-aqueous secondary battery is improved, and the interparticle pores, which are relatively large pores, are improved. Since the volume can be reduced and the volume can be reduced, the mode diameter in the pore distribution obtained by the mercury press-fitting method for the powder can be reduced. As a result, it tends to exhibit high capacity, excellent charge / discharge load characteristics, and low temperature input / output characteristics.
The d90 / d10 of the carbon material for a non-aqueous secondary battery of the present invention is defined as a value obtained by dividing d90 measured by the above method by d10.

-Bulk density The bulk density of the carbon material for a non-aqueous secondary battery of the present invention is preferably 0.3 g / cm ³ or more, more preferably 0.31 g / cm ³ or more, still more preferably 0.32 g / cm ³ or more. Particularly preferably 0.33 g / cm ³ or more, more preferably 1.3 g / cm ³ or less, still ^{more preferably 1.2 g / cm 3} or less, particularly preferably 1.1 g / cm ³ or less, most preferably 1 g. / Cm ³ or less.

When the bulk density is within the above range, the processability such as streaking at the time of producing the electrode plate is improved, and the high-speed charge / discharge characteristics are excellent. Further, since it has appropriate pores, the electrolytic solution can move smoothly, and tends to exhibit good charge / discharge load characteristics and low temperature input / output characteristics.
The bulk density is determined by using a powder density measuring device to drop the composite carbon material of the present invention into a cylindrical tap cell having a ^{diameter of 1.6 cm and a volume capacity of 20 cm 3 through a sieve having a mesh size of 300 μm to fill the cell.} It is defined as the density obtained from the volume and the mass of the sample.

-Tap density The tap density of the carbon material for a non-aqueous secondary battery of the present invention is preferably 0.6 g / cm ³ or more, more preferably 0.63 g / cm ³ or more, still more preferably 0.66 g / cm ³ or more. Particularly preferably 0.7 g / cm ³ or more, 1.4 g / cm ³ or less, more preferably 1.3 g / cm ³ or less, still ^{more preferably 1.2 g / cm 3} or less, and particularly preferably 1. It is 1 g / cm ³ or less, most preferably 1 g / cm ³ or less.

When the tap density is within the above range, the processability such as streaking at the time of producing the electrode plate is improved, and the high-speed charge / discharge characteristics are excellent. Further, since it has appropriate pores, the electrolytic solution can move smoothly, and tends to exhibit good charge / discharge load characteristics and low temperature input / output characteristics.
The tap density is determined by using a powder density measuring instrument to drop the composite carbon material of the present invention into a cylindrical tap cell having a ^{diameter of 1.6 cm and a volume capacity of 20 cm 3 through a sieve having a mesh size of 300 μm to fill the cell.} After that, tapping with a stroke length of 10 mm is performed 1000 times, and the density is defined as the density obtained from the volume at that time and the mass of the sample.

X-ray parameters The d value (interlayer distance) of the lattice planes (002 planes) of the carbon material for non-aqueous secondary batteries of the present invention determined by X-ray diffraction by the Gakushin method is preferably 0.335 nm or more and 0. It is less than 360 nm. Here, the d value is more preferably 0.345 nm or less, further preferably 0.341 nm or less, and particularly preferably 0.338 nm or less. When the d002 value is within the above range, the crystallinity of graphite is high, so that the initial irreversible capacity tends to suppress the increase. Here, 0.3354 nm is a theoretical value of graphite.
The crystallite size (Lc) of the carbon material determined by X-ray diffraction by the Gakushin method is preferably in the range of 10 nm or more, more preferably 20 nm or more. Within the above range, the particles have not too low crystallinity, and the reversible capacity is unlikely to decrease when a non-aqueous secondary battery is used. The lower limit of Lc is the theoretical value of graphite.

-Ash content The ash content contained in the carbon material for the non-aqueous secondary battery of the present invention is preferably 1% by mass or less, more preferably 0.5% by mass or less, still more preferably 0.5% by mass or less, based on the total mass of the carbon material. It is 0.1% by mass or less. Further, the lower limit of the ash content is preferably 1 ppm or more.
When the ash content is within the above range, when a non-aqueous secondary battery is used, the deterioration of battery performance due to the reaction between the carbon material and the electrolytic solution during charging and discharging can be suppressed to a negligible extent. In addition, since the production of carbon material does not require a large amount of time, energy and equipment for pollution prevention, the cost increase can be suppressed.

・ BET specific surface area (SA)
The specific surface area (SA) of the carbon material for a non-aqueous secondary battery of the present invention measured by the BET method is preferably 0.3 m ² / g or more, more preferably 1 m ² / g or more, still more preferably 2 m ² / g. The above is particularly preferably 3 m ² / g or more. Further, it is preferably 30 m ² / g or less, more preferably 20 m ² / g or less, further preferably 17 m ² / g or less, particularly preferably 15 m ² / g or less, and most preferably 10 m ² / g or less.

When the specific surface area is within the above range, it is possible to secure a sufficient portion for Li to enter and exit, so that it is excellent in high-speed charge / discharge characteristics and low-temperature input / output characteristics, and the activity of the active material with respect to the electrolytic solution can be appropriately suppressed. The initial irreversible capacity does not increase, and there is a tendency to manufacture high-capacity batteries.
Further, when a negative electrode is formed by using a carbon material, an increase in reactivity with the electrolytic solution can be suppressed and gas generation can be suppressed, so that a preferable non-aqueous secondary battery can be provided.

The BET specific surface area is determined by using a surface area meter (for example, Shimadzu Corporation's specific surface area measuring device "Gemini 2360") to perform preliminary vacuum drying of a carbon material sample at 100 ° C. for 3 hours under nitrogen flow, and then liquid nitrogen. It is defined as a value measured by the nitrogen adsorption BET 6-point method by the gas flow method using a nitrogen helium mixed gas that has been cooled to a temperature and accurately adjusted so that the value of the relative pressure of nitrogen with respect to atmospheric pressure is 0.3.

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

-Average circularity The average circularity of the carbon material for a non-aqueous secondary battery of the present invention is preferably 0.9 or more, more preferably 0.91 or more, still more preferably 0.92 or more. On the other hand, the circularity is usually 1 or less, preferably 0.99 or less, and more preferably 0.98 or less. When the circularity is within the above range, the deterioration of the high current density charge / discharge characteristics of the non-aqueous secondary battery tends to be suppressed. The circularity is defined by the following equation, and when the circularity is 1, it becomes a theoretical true sphere.

When the circularity is within the above range, when the circularity is within the above range, the bending degree of Li ion diffusion is lowered, the movement of the electrolytic solution in the interparticle voids becomes smooth, and the carbon materials are in appropriate contact with each other. It tends to show good rapid charge / discharge characteristics and cycle characteristics.
Circularity = (perimeter of a corresponding circle having the same area as the projected particle shape) / (actual perimeter of the projected particle shape)
As the value of circularity, for example, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.) is used, and about 0.2 g of a sample (carbon material) is used as a surfactant, polyoxyethylene (20) sorbitan. After dispersing in a 0.2 mass% aqueous solution of monolaurate (about 50 mL) and irradiating the dispersion with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, the detection range was specified as 0.6 to 400 μm, and the particle size was changed. Use the values measured for particles in the range of 1.5-40 μm.

-Aspect ratio The aspect ratio of the carbon material for a non-aqueous secondary battery of the present invention in a powder state is theoretically 1 or more, preferably 1.1 or more, and more preferably 1.2 or more. The aspect ratio is preferably 10 or less, more preferably 8 or less, still more preferably 5 or less, and particularly preferably 3 or less.
When the aspect ratio is within the above range, the slurry (negative electrode forming material) containing the carbon material is less likely to be streaked during electrode plate formation, a uniform coated surface can be obtained, and the high current density charge / discharge of the non-aqueous secondary battery is obtained. It tends to avoid deterioration of characteristics.

Raman R value The Raman R value of the carbon material for a non-aqueous secondary battery of the present invention is preferably 0.001 or more, more preferably 0.01 or more, still more preferably 0.02 or more, and particularly preferably 0.02 or more. It is 0.03 or more. The Raman R value is preferably 0.6 or less, more preferably 0.3 or less, and even more preferably 0.1 or less.

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

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

<Manufacturing method of carbon material for non-aqueous secondary batteries>
The method for producing the carbon material for a non-aqueous secondary battery of the present invention is not particularly limited, but it can be obtained by, for example, the following production methods.
First step: Step for producing graphite particles (A) Second step: Step for producing natural graphite particles (B) Third step: Step for combining graphite particles (A) and natural graphite particles (B) This When the production method is used, for example, a plurality of graphite particles (A) and natural graphite particles (B) may be composited, and a bulk mesophase carbon material (pitch raw material) which is a precursor of the plurality of graphite particles (A) may be used. The raw coke obtained by heat-treating the raw coke at 400 to 600 ° C. or the calcined coke obtained by further heat-treating the raw coke at 800 to 1800 ° C.) and the natural graphite particles (B) may be combined. Above all, granulating raw coke and natural graphite particles (B), which are precursors of a plurality of graphite particles (A), causes defects in graphite crystals that occur during the compositing process, which is an artificial graphite product after graphitization. It is preferable because it does not remain in the graphite.

-First step: Step of producing graphite particle (A) precursor (starting material)
As a starting material for the graphite particle (A) precursor, it is preferable to use a pitch raw material. In addition, in this specification, "pitch raw material" means the pitch and the thing which conforms to it, and can be graphitized by performing an appropriate process. As specific examples of pitch raw materials, petroleum-based heavy oils, coal-based heavy oils, DC-based heavy oils, cracked petroleum heavy oils, etc. described in the above-mentioned section on organic compounds to be carbonaceous substances are used. be able to. Among these, petroleum-based heavy oils and coal-based heavy oils are more preferable because random and uniform crystal growth is likely to occur. Any one of these pitch raw materials may be used alone, or two or more of them may be used in any combination and ratio.

Among them, the content of the quinoline insoluble matter contained in the pitch raw material is 0.000 to 20.000% by mass, preferably 0.001 to 10.000% by mass, and more preferably 0.002 to 7,000% by mass. It is preferably in the range. Quinoline insoluble components are submicron-sized carbon particles and extremely fine sludge contained in a trace amount in pitch raw materials such as coal tar. If this amount is too large, the improvement of crystallinity in the graphitization process is significantly hindered. It causes a significant decrease in discharge capacity after graphitization. As a method for measuring the quinoline insoluble matter, for example, the method specified in JIS K2425 can be used.
In addition to the above-mentioned pitch raw material, various thermosetting resins, thermoplastic resins, and the like may be used in combination as a starting material as long as the effects of the present invention are not impaired.

(Heat treatment)
First, using the selected pitch raw material as a starting material, heat treatment is performed to obtain a bulk mesophase which is a precursor of graphite crystals (in the present invention, the bulk mesophase is also referred to as a graphite crystal precursor).
After crushing this bulk mesophase, when reheat treatment such as firing, part or all of it melts, but by adjusting the content of volatile matter by heat treatment here, the melted state is appropriately controlled. be able to. Examples of the volatile matter contained in the bulk mesophase include hydrogen, benzene, naphthalene, anthracene, pyrene and the like.

The temperature condition during the heat treatment is preferably 400 to 600 ° C. If the heat treatment temperature is less than 400 ° C, the amount of volatile matter increases, making it difficult to pulverize the bulk mesophase safely in the atmosphere. On the other hand, if the temperature exceeds 600 ° C, graphite crystals develop excessively and the bulk mesophase occurs. Since the defects of the graphite crystals generated at the time of pulverization remain in the artificial graphite product after graphitization, the side reaction with the electrolytic solution may increase, and the initial efficiency, storage characteristics, and cycle characteristics may decrease.

The time for performing the heat treatment is preferably 1 to 48 hours, more preferably 10 to 24 hours. If the heat treatment time is less than 1 hour, it becomes a non-uniform bulk mesophase, which is inappropriate. On the other hand, if it exceeds 48 hours, the productivity is not good, the processing cost is high, and it is difficult to manufacture. If the temperature and cumulative time of the heat treatment are within the above ranges, the heat treatment may be performed in a plurality of times.

The heat treatment is preferably carried out in an atmosphere of an inert gas such as nitrogen gas or in an atmosphere of volatile matter generated from the pitch raw material.
The apparatus used for the heat treatment is not particularly limited, and for example, a shuttle furnace, a tunnel furnace, an electric furnace, a reaction tank such as an autoclave, a coker (a heat treatment tank for coke production), or the like can be used. At the time of heat treatment, stirring may be performed in a furnace or the like, if necessary.

The volatile content (VM: Volatile Matter) of the bulk mesophase is
It is preferably 4 to 30% by mass, more preferably 8 to 20% by mass. If the volatile content is less than 4% by mass, the particles tend to be broken into single crystals at the time of pulverization, and tend to become flat particles, and tend to be oriented when formed into a plate. If the volatile content exceeds 30% by mass, it is difficult to safely pulverize in the atmosphere because the volatile content is large.

(Crushing)
Next, the bulk mesophase is crushed. By pulverizing with the volatile content controlled to 8 to 20% by mass, damage at the time of pulverization can be reduced, and defects can be repaired at the time of graphitization after pulverization, which is preferable.
In addition, ordinary pulverization refers to an operation of applying a force to a substance to reduce its size and adjusting the particle size and particle size distribution of the substance.

The pulverization is carried out so that the particle size of the bulk mesophase is preferably 1 to 2000 μm, more preferably 5 to 1000 μm, preferably 5 to 500 μm, more preferably 5 to 200 μm, and particularly preferably 5 to 50 μm. If the particle size is less than 1 μm, the surface of the bulk mesophase may be oxidized by contact with air during or after pulverization, which hinders the improvement of crystallinity in the graphitization process and causes a decrease in the discharge capacity after graphitization. be.

On the other hand, when the particle size exceeds 5000 μm, the miniaturization effect by pulverization is weakened and the crystals are easily oriented, the active material orientation ratio of the electrode using the graphite material is lowered, and the charge / discharge load characteristics and the low temperature output characteristics are deteriorated. Inviting, it becomes difficult to suppress electrode expansion when charging the battery.
_{The particle size means, for example, a 50% particle size (d 50} ) obtained from a volume-based particle size distribution measured by a laser diffraction / scattering method particle size distribution measurement.
The apparatus used for crushing is not particularly limited, and examples thereof include a jaw crusher, an impact type crusher, a cone crusher and the like as a coarse crusher, and a roll crusher, a hammer mill and the like as an intermediate crusher, and fine crushing. Examples of the machine include a turbo mill, a ball mill, a vibration mill, a pin mill, a stirring mill, a jet mill and the like.

(Baking)
The pulverized bulk mesophase may be calcined. In the present invention, the calcined bulk mesophase is also referred to as a calcined product of the graphite crystal precursor.
Baking is performed to completely remove volatile matter derived from organic matter in the bulk mesophase.
The temperature at which the firing is performed is preferably 800 to 1800 ° C, more preferably 1000 to 1500 ° C. If the temperature is less than 800 ° C., it becomes difficult to completely remove the volatile matter. On the other hand, if the temperature exceeds 2000 ° C., the firing equipment may be costly.
The holding time for keeping the temperature in the above range at the time of firing is not particularly limited, but is 30 minutes or more and 72 hours or less.

Firing is performed in an atmosphere of an inert gas such as nitrogen gas or in a non-oxidizing atmosphere of a gas generated from the bulk mesophase. Further, when a graphitization step is required, it is possible to directly perform graphitization without incorporating a firing step in order to simplify the manufacturing process.
The apparatus used for firing is not particularly limited, and for example, a shuttle furnace, a tunnel furnace, an electric furnace, a reed hammer furnace, a rotary kiln, or the like can be used.

(Graphitization)
The calcined graphite crystal precursor can be graphitized to obtain the preferred graphite particles (A) of the present invention. The graphitization step may be carried out after obtaining a calcined product of the graphite crystal precursor, or may be carried out after the third step described later.
Graphitization is performed to improve the crystallinity of the carbon material in order to increase the discharge capacity in the battery evaluation.

The temperature at which graphitization is performed is preferably 2000 to 3300 ° C, more preferably 3000 to 3200 ° C. If the graphitization temperature exceeds 3200 ° C, the amount of sublimation of graphite tends to increase, and if the graphitization temperature is less than 2000 ° C, the reversible capacity of the battery may decrease, making it difficult to manufacture a high-capacity battery. In some cases.
The holding time is not particularly limited when graphitizing, but it is usually longer than 1 minute, and is 72 hours or less.

Graphitization is carried out in an atmosphere of an inert gas such as argon gas or in a non-oxidizing atmosphere of a gas generated from the calcined graphite crystal precursor.
The apparatus used for graphitization is not particularly limited, and examples thereof include a direct energization furnace, an Achison furnace, and as an indirect energization type, a resistance heating furnace, an induction heating furnace, and the like.
In addition, at the time of graphitization or in the step before that, that is, in the step from heat treatment to firing, a graphitization catalyst such as Si, B, Ni is incorporated into the material (pitch raw material or heat-treated graphite crystal precursor). Alternatively, the graphitization catalyst may be brought into contact with the surface of the material.

(Other processing)
In addition to the above-mentioned treatments, various treatments such as reclassification treatment can be performed as long as the effects of the invention are not impaired. The reclassification treatment is for removing coarse powder and fine powder so that the particle size after firing and graphitization treatment is the desired particle size.
The device used for the classification process is not particularly limited, but for example, in the case of dry sieving: rotary sieving, swaying sieving, rotary sieving, vibration sieving, dry air flow sieving: gravity sieving machine, An inertial force classifier, a centrifugal force classifier (classifier, cyclone, etc.), a wet sieving machine, a mechanical wet classifier, a hydraulic classifier, a settling classifier, a centrifugal wet classifier, and the like can be used.
In the reclassification treatment, when graphitization is performed after firing, the reclassification treatment may be performed after firing and then graphitized, or the reclassification treatment may be performed after firing and graphitization. It is also possible to omit the reclassification process.

Second step: Step of producing natural graphite particles (B) In order to produce the carbon material for a non-aqueous secondary battery of the present invention, for example, scaly natural graphite is crushed or classified to obtain an average particle size d50. It can be obtained by adjusting and purifying if necessary.
Hereinafter, the second step and the second two steps will be described separately.
(Second step) Step of adjusting the average particle size d50 of natural graphite particles (second two steps) Step of purifying the obtained graphite particles as necessary.

(Second step) Step of adjusting the average particle size d50 of the graphite particles As a method of adjusting the average particle size d50 of the natural graphite particles (B) within the above range, for example, scaly natural graphite is pulverized and / or classified. There is a way to do it. The apparatus used for crushing is not particularly limited, and examples of the coarse crusher include a shear mill, a jaw crusher, an impact crusher, a cone crusher, and the like, and examples of the intermediate crusher include a roll crusher and a hammer mill. Examples of the fine crusher include a mechanical crusher, an air flow crusher, a swirling flow crusher, and the like. Specific examples thereof include ball mills, vibration mills, pin mills, stirring mills, jet mills, cyclone mills, and turbo mills.

The apparatus used for the classification process is not particularly limited. For example, in the case of dry sieving, a rotary sieve, a swaying sieve, a rotating sieve, a vibrating sieve and the like can be used, and the dry air flow type sieving can be used. In this case, a gravity type classifier, an inertial force type classifier, a centrifugal force type classifier (classifier, cyclone, etc.) can be used, and a wet sieving machine, a mechanical wet classifier, a hydraulic classifier, and a settling classifier can be used. , A centrifugal wet classifier or the like can be used.

(Second two steps) If necessary, a step of purifying the obtained graphite The natural graphite particles (B) specified in the present invention can be subjected to a high purification treatment, if necessary.
Acid treatment containing nitric acid or hydrochloric acid is preferable because impurities such as metals, metal compounds, and inorganic compounds in graphite can be removed without introducing sulfate, which can be a highly active sulfur source, into the system.

For the acid treatment, an acid containing nitric acid or hydrochloric acid may be used, and other acids such as bromine acid, hydrofluoric acid, boric acid or iodic acid or other inorganic acids, or citric acid, formic acid, acetic acid, etc. An acid obtained by appropriately mixing an organic acid such as oxalic acid, trichloroacetic acid or trifluoroacetic acid can also be used. Concentrated hydrofluoric acid, concentrated nitric acid and concentrated hydrochloric acid are preferable, and concentrated nitric acid and concentrated hydrochloric acid are more preferable. Although graphite may be treated with sulfuric acid in this production method, it is used in an amount and concentration that does not impair the effects and physical characteristics of the present invention. When a plurality of acids are used, for example, a combination of hydrofluoric acid, nitric acid, and hydrochloric acid is preferable because the above impurities can be efficiently removed.

-Third step: Step of combining graphite particles (A) and natural graphite particles (B) As one of the means to achieve combining graphite particles (A) and natural graphite particles (B), at least impact, The raw material graphite is granulated by applying any mechanical energy of compression, friction, or shearing force, and the granulation step is performed in the presence of a granulator satisfying the following conditions 1) and 2). Can be obtained by

1) Liquid during the step of granulating the raw material graphite 2) When the granulator contains an organic solvent, at least one of the organic solvents does not have a flash point, or if it has a flash point, the ignition point The point is 5 ° C. or higher.
If the granulation step is provided, another step may be further provided if necessary. Another step may be carried out independently, or a plurality of steps may be carried out at the same time.

When the granulation treatment is performed by the above method, a liquid cross-linking adhesive force is generated between the graphite particle (A) precursor and the graphite particles (B) by the granulator having the specified physical properties, and the particles adhere to each other more firmly. Therefore, it is possible to produce good composite carbon particles having strong adhesive strength and little peeling of graphite particles (B).
Hereinafter, the third step and the third two steps will be described separately.
(Third step) A step of mixing the graphite particles (A) precursor and / or the graphite particles (B) and a granulator (third two steps) A step of granulating the obtained mixed product.

(Third step) Step of mixing graphite particles (A) precursor and / or graphite particles (B) with a granulator To obtain the carbon material for a non-aqueous secondary battery of the present invention, granulate. It is preferable to combine the graphite particle (A) precursor and the graphite particle (B) with an agent. The granulators are 1) a liquid during the step of granulating the raw material graphite and 2) when the granulator contains an organic solvent, at least one of the organic solvents does not have a flash point or has a flash point. If it has, the condition that the flash point is 5 ° C. or higher is satisfied.

By having a granulating agent that satisfies the above requirements, the granulating agent is liquid between the raw material graphites in the step of compounding the graphite particles (A) precursor and the graphite particles (B) in the subsequent third two steps. By cross-linking, the attractive force generated by the negative pressure of the capillary tube in the liquid bridge and the surface tension of the liquid acts as the liquid cross-linking adhesive force between the particles, so that the liquid cross-linking adhesive force between the raw material graphite increases and the raw material graphite Can adhere more firmly.

In the present invention, liquid cross-linking between the graphite particle (A) precursor and the graphite particles (B) is caused by liquid cross-linking between the graphite particle (A) precursor and the graphite particles (B) by the granulating agent. The strength of the adhesive force is proportional to the γcos θ value (where γ: surface tension of the liquid, θ: contact angle between the liquid and the particles). That is, when the graphite particle (A) precursor and the graphite particle (B) are composited, the granulating agent preferably has high wettability with the graphite particle (A) precursor and the graphite particle (B). Specifically, it is preferable to select a granulating agent having cosθ> 0 so that the γcosθ value> 0, and the contact angle θ of the granulating agent with graphite measured by the following measuring method is less than 90 °. Is preferable.

<Measurement method of contact angle θ with graphite>
1.2 μl of granulating agent is dropped on the surface of HOPG, and the contact angle is measured when the wet spread converges and the rate of change of the contact angle θ per second becomes 3% or less (also called the steady state). Measure with an apparatus (automatic contact angle meter DM-501 manufactured by Kyowa Interface Co., Ltd.). Here, when a granulator having a viscosity at 25 ° C. of 500 cP or less is used, the value at 25 ° C. is used, and when a granulator having a viscosity at 25 ° C. higher than 500 cP is used, the temperature is up to a temperature at which the viscosity is 500 cP or less. It is the measured value of the contact angle θ at the heated temperature.

Further, as the contact angle θ between the graphite particle (A) precursor and the graphite particle (B) and the granulating agent is closer to 0 °, the γcosθ value becomes larger, so that the graphite particle (A) precursor and the graphite particle (B) ) Is increased, and the graphite particle (A) precursor and the graphite particle (B) can be more firmly adhered to each other. Therefore, the contact angle θ of the granulator with graphite is more preferably 85 ° or less, further preferably 80 ° or less, further preferably 50 ° or less, and even more preferably 30 ° or less. It is particularly preferable, and most preferably 20 ° or less.

By using a granulator having a large surface tension γ, the γcosθ value becomes large and the adhesive force of the carbon material particles is improved. Therefore, the γ is preferably 0 or more, more preferably 15 or more, still more preferably 30 or more. be.
The surface tension γ of the granulating agent used in the present invention is measured by the Wilhelmy method using a surface tension meter (for example, DCA-700 manufactured by Kyowa Interface Science Co., Ltd.).

In addition, a viscous force acts as a resistance component against the elongation of the liquid bridge due to the movement of particles, and its size is proportional to the viscosity. Therefore, the viscosity of the granulator is not particularly limited as long as it is a liquid in the granulation step in which the graphite particle (A) precursor and the graphite particles (B) are composited, but it is 1 cP or more in the granulation step. Is preferable. Further, the viscosity of the granulating agent at 25 ° C. is preferably 1 cP or more and 100,000 cP or less, more preferably 5 cP or more and 10000 cP or less, further preferably 10 cP or more and 8000 cP or less, and 50 cP or more and 6000 cP or less. Is particularly preferable. When the viscosity is within the above range, it is possible to prevent the adhered particles from being detached due to an impact force such as collision with the rotor or the casing when granulating the raw material graphite.

The viscosity of the granulator used in the present invention is measured by using a rheometer (for example, ARES manufactured by Rheometric Scientific), placing an appropriate amount of a measurement target (here, a granulator) in a cup, and adjusting the temperature to a predetermined temperature. When the shear stress at a shear rate of 100 s ^-1 is 0.1 Pa or more, ^{the value measured at a shear rate of 100 s -1} is measured, and when the shear stress at a shear rate of 100 s ^-1 is less than 0.1 Pa ^{, the value is measured at 1000 s -1} . The value measured at a shear rate at which the shear stress is 0.1 Pa or more when the shear stress is less than 0.1 Pa at a shear rate of 1000 s- ^{1 is defined as the viscosity in the present specification.} The shear stress can be 0.1 Pa or more by making the spindle to be used a shape suitable for a low-viscosity fluid.

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

Examples of the granulating agent used in the present invention include paraffin oils such as coal tar, petroleum heavy oil and liquid paraffin, synthetic oils such as olefin oils, naphthen oils and aromatic oils, and vegetable oils and fats. Natural oils such as animal aliphatics, esters and higher alcohols, organic compounds such as resin binder solutions in which a resin binder is dissolved in a solvent with a ignition point of 5 ° C or higher, preferably 21 ° C or higher, water, etc. Examples thereof include aqueous solvents and mixtures thereof. Organic solvents with a ignition point of 5 ° C or higher include alkylbenzenes such as xylene, isopropylbenzene, ethylbenzene, and propylbenzene, alkylnaphthalene such as methylnaphthalene, ethylnaphthalene, and propylnaphthalene, allylbenzenes such as styrene, and aromatic carbides such as allylnaphthalene. Hydrogens, aliphatic hydrocarbons such as octane, nonane, and decane, ketones such as methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone, esters such as propyl acetate, butyl acetate, isobutyl acetate, and amyl acetate, and methanol. , Ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, glycerin and other alcohols, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono Butyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, methoxypropanol, methoxypropyl-2-acetate, methoxymethylbutanol, methoxybutyl acetate, diethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, diethylene glycol ethylmethyl ether, tri Glycol derivatives such as ethylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol monophenyl ether, ethers such as 1,4-dioxane, dimethylformamide, pyridine, 2-pyrrolidone, N- Examples thereof include nitrogen-containing compounds such as methyl-2-pyrrolidone, sulfur-containing compounds such as dimethylsulfoxide, halogen-containing compounds such as dichloromethane, chloroform, carbon tetrachloride, dichloroethane, trichloroethane, and chlorobenzene, and mixtures thereof. Those with a low ignition point are not included. These organic solvents can be used as a simple substance as a granulator.

As the resin binder, known ones can be used. For example, cellulose-based resin binders such as ethyl cellulose, methyl cellulose, and salts thereof, polymethyl acrylates, polyethyl acrylates, polybutyl acrylates, polyacrylic acids, and acrylic resin binders such as salts thereof, polymethyl methacrylate, and the like. A methacrylic resin binder such as polyethyl methacrylate or polybutyl methacrylate, a phenol resin binder, or the like can be used. Among the above, coal tar, petroleum-based heavy oil, paraffin-based oil such as liquid paraffin, and aromatic-based oil are preferable because they can produce a negative electrode material having a high degree of circularity and a small amount of fine powder.

The granulating agent has properties that can be efficiently removed in the process of removing the granulating agent, which will be described later, and does not adversely affect the battery characteristics such as capacity, input / output characteristics, storage / cycle characteristics, etc. Is preferable. Specifically, it is usually 50% when heated to 700 ° C. in an inert atmosphere.
As described above, those having a weight reduction of preferably 80% or more, more preferably 95% or more, further preferably 99% or more, and particularly preferably 99.9% or more can be appropriately selected.

As a method of mixing the graphite particles (A) precursor and / or the graphite particles (B) with the granulator, for example, the graphite particles (A) precursor and / or the graphite particles (B) and the granulator are used. A method of mixing using a mixer or a kneader, or a granulator in which an organic compound is dissolved in a low-viscosity diluting solvent, a precursor of graphite particles (A), and / or the diluting solvent after mixing the graphite particles (B). Examples include a method of removing the particles. Further, when the graphite particle (A) precursor and the graphite particle (B) are composited in the subsequent third two steps, the granulator, the graphite particle (A) precursor, and / or the granulator are added to the granulator. There is also a method in which the graphite particles (B) are charged and the step of mixing the graphite particles (A) precursor and / or the graphite particles (B) and the granulating agent and the step of granulating are performed at the same time.

Among them, only the graphite particles (B) are granulated in the step of mixing only the graphite particle (A) precursor and the granulating agent, and then mixing and compounding the graphite particles (B) to which the granulating agent is not attached. This is preferable because it is possible to efficiently produce the target carbon material for a non-aqueous secondary battery.
The amount of the granulating agent added is preferably 0.1 part by weight or more, more preferably 1 part by weight or more, still more preferably 1 part by weight or more, based on 100 parts by weight of the total amount of the graphite particle (A) precursor and the graphite particles (B). Is 3 parts by weight or more, more preferably 6 parts by weight or more, further preferably 10 parts by weight or more, particularly preferably 12 parts by weight or more, most preferably 15 parts by weight or more, and preferably 1000 parts by weight or less. It is preferably 100 parts by weight or less, more preferably 80 parts by weight or less, particularly preferably 50 parts by weight or less, and most preferably 30 parts by weight or less. If it is within the above range, problems such as a decrease in the degree of compounding due to a decrease in the adhesion between particles and a decrease in productivity due to the adhesion of the graphite particle (A) precursor and the graphite particles (B) to the apparatus are less likely to occur. ..

(Third two steps) Step of granulating the obtained mixed product The non-aqueous secondary battery carbon material of the present invention can be obtained by the following manufacturing method or the like.
As an apparatus used for compounding, for example, an apparatus can be used in which mechanical actions such as compression, friction, and shearing force including the interaction of carbonaceous particles are repeatedly applied to the particles mainly by impact force.

Specifically, it has a rotor with a large number of blades installed inside the casing, and when the rotor rotates at high speed, the graphite particles (A) precursor to which the granulator introduced inside is attached, and the graphite particles. A device that applies mechanical actions such as impact compression, friction, and shearing force to (B) to perform surface treatment is preferable. Further, it is preferable that the graphite has a mechanism for repeatedly giving a mechanical action by circulating graphite.

Preferred devices for exerting a mechanical action on the graphite particle (A) precursor and the graphite particles (B) include, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), Cryptron, Cryptron Orb (manufactured by EarthTechnica Co., Ltd.), and the like. CF mill (manufactured by Ube Kosan Co., Ltd.), mechanofusion system (manufactured by Hosokawa Micron Co., Ltd.), Theta Composer (manufactured by Tokuju Kosakusho Co., Ltd.), etc. can be mentioned. Of these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable.

When processing using the above device, for example, the peripheral speed of the rotating rotor is usually 30 m / sec or more, preferably 50 m / sec or more, more preferably 60 m / sec or more, still more preferably 70 m / sec or more, particularly preferably 70 m / sec or more. 80 m / sec or more, usually 100 m / sec or less. Within the above range, the graphite particles (A) precursor and the graphite particles (B) are more efficiently sphericalized, and the graphite particles (A) are placed on at least a part of the surface of the graphite particles (A) precursor. It is preferable because the graphite crystal layered structure of B) can be composited so as to be arranged in the same direction as the outer peripheral surface of the artificial graphite particles (A).

Further, the treatment of giving a mechanical action to the graphite particle (A) precursor and the graphite particle (B) can be performed by simply passing the graphite particle (A) precursor and the graphite particle (B), but the graphite particle. (A) The precursor and the graphite particles (B) are preferably circulated or retained in the apparatus for 30 seconds or longer, more preferably 1 minute or longer, further preferably 3 minutes or longer, and particularly preferably 5 minutes or longer. The inside is circulated or retained for processing. When simply passing the graphite particle (A) precursor and the graphite particle (B), it is preferable that the total treatment time is 30 seconds or more, more preferably 1 minute or more, and further, by passing the graphite particles (B) a plurality of times. The treatment is preferably performed for 3 minutes or longer, particularly preferably 5 minutes or longer.

・ Other processes (process of removing granulators)
In the embodiment of the present invention, there may be a step of removing the granulating agent. Examples of the method for removing the granulating agent include a method of cleaning with a solvent and a method of volatilizing / decomposing and removing the granulating agent by heat treatment.

The heat treatment temperature is preferably 60 ° C. or higher, more preferably 100 ° C. or higher, still more preferably 200 ° C. or higher, still more preferably 300 ° C. or higher, particularly preferably 400 ° C. or higher, most preferably 500 ° C. or higher, and preferably 1500 ° C. ° C. or lower, more preferably 1000 ° C. or lower, still more preferably 800 ° C. or lower. If it is within the above range, the granulating agent can be sufficiently volatilized, decomposed and removed, and the productivity can be improved.

The heat treatment time is preferably 0.5 to 48 hours, more preferably 1 to 40 hours, still more preferably 2 to 30 hours, and particularly preferably 3 to 24 hours. If it is within the above range, the granulating agent can be sufficiently volatilized, decomposed and removed, and the productivity can be improved.
The atmosphere of the heat treatment may be an active atmosphere such as an air atmosphere or an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere. The heat treatment is not particularly limited when the heat treatment is performed at 200 ° C to 300 ° C, but the heat treatment is performed at 300 ° C or higher. From the viewpoint of preventing oxidation of the graphite surface, an inert atmosphere such as a nitrogen atmosphere or an argon atmosphere is preferable.

(Process for purifying)
In the present invention, there may be a step of purifying the granulated and composited carbon material with high purity. Examples of a method for purifying the composite carbon material include an acid treatment containing nitric acid and hydrochloric acid, which is a metal in graphite without introducing a sulfate which can be a highly active sulfur source into the system. It is preferable because impurities such as metal compounds and inorganic compounds can be removed.

For the above acid treatment, an acid containing nitric acid or hydrochloric acid may be used, and other acids such as bromine acid, hydrofluoric acid, boric acid or iodic acid, or citric acid, formic acid, acetic acid and shu An acid in which an organic acid such as an acid, trichloroacetic acid or trifluoroacetic acid is appropriately mixed can also be used. Concentrated hydrofluoric acid, concentrated nitric acid and concentrated hydrochloric acid are preferable, and concentrated nitric acid and concentrated hydrochloric acid are more preferable. In the present invention, graphite may be treated with sulfuric acid, but it is used in an amount and concentration that does not impair the effects and physical characteristics of the present invention.

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

The mixing ratio (mass ratio) of graphite and acid in the acid treatment is usually 100:10 or more, preferably 100:20 or more, more preferably 100:30 or more, still more preferably 100:40 or more, and 100. : 1000 or less, preferably 100: 500 or less, more preferably 100: 300 or less. If the amount is too small, the above impurities tend to be unable to be removed efficiently. On the other hand, if it is too large, the amount of graphite that can be washed at one time is reduced, which leads to a decrease in productivity and an increase in cost, which is not preferable.

The acid treatment is performed by immersing graphite in an acidic solution as described above. The immersion time is usually 0.5 to 48 hours, preferably 1 to 40 hours, more preferably 2 to 30, and even more preferably 3 to 24 hours. If it is too long, it tends to cause a decrease in productivity and an increase in cost, and if it is too short, it tends to be difficult to sufficiently remove the above impurities.
The immersion temperature is usually 25 ° C. or higher, preferably 40 ° C. or higher, more preferably 50 ° C. or higher, still more preferably 60 ° C. or higher. When an aqueous acid is used, the theoretical upper limit is 100 ° C., which is the boiling point of water. If this temperature is too low, the impurities tend to be unable to be sufficiently removed.

It is preferable to carry out further water washing for the purpose of removing the acid content remaining by the acid washing and raising the pH from weakly acidic to the neutral range. For example, if the pH of the treated graphite is usually 3 or more, preferably 3.5 or more, more preferably 4 or more, still more preferably 4.5 or more, washing with water can be omitted, and if the above range If not, it is preferable to wash with water if necessary. It is preferable to use ion-exchanged water or distilled water as the cleaning water from the viewpoint of improving cleaning efficiency and preventing impurities from being mixed. The specific resistance, which is an index of the amount of ions in water, is usually 0.1 MΩ · cm or more, preferably 1 MΩ · cm or more, and more preferably 10 MΩ · cm or more. The theoretical upper limit at 25 ° C. is 18.24 MΩ · cm. When this value is small, it indicates that the amount of ions in water increases, and there is a tendency for impurities to be mixed and the cleaning efficiency to decrease.

The time for washing with water, that is, stirring the treated graphite and water is usually 0.5 to 48 hours, preferably 1 to 40 hours, more preferably 2 to 30 hours, still more preferably 3 to 24 hours. be. If it is too long, the production efficiency tends to decrease, and if it is too short, residual impurities and acids tend to increase.
The mixing ratio of the treated graphite and water is usually 100:10 or more, preferably 100:30 or more, more preferably 100:50 or more, still more preferably 100: 100 or more, and 100: 1000 or less. It is preferably 100: 700 or less, more preferably 100: 500 or less, and even more preferably 100: 400 or less. If it is too large, the production efficiency tends to decrease, and if it is too small, residual impurities and acids tend to increase.

The stirring temperature is usually 25 ° C. or higher, preferably 40 ° C. or higher, more preferably 50 ° C. or higher, still more preferably 60 ° C. or higher. The upper limit is 100 ° C., which is the boiling point of water. If it is too low, residual impurities and acid content tend to increase.
When the water cleaning treatment is performed in a batch manner, it is preferable to repeat the stirring-filtration treatment step in pure water a plurality of times for cleaning from the viewpoint of removing impurities and acids. The above treatment may be repeated so that the pH of the above-mentioned treated graphite is within the above range. Usually, it is once or more, preferably twice or more, and more preferably three times or more.

By performing the treatment as described above, the wastewater ion concentration of the obtained graphite is usually 200 ppm or less, preferably 100 ppm or less, more preferably 50 ppm or less, further preferably 30 ppm or less, and usually 1 ppm or more, preferably 2 ppm or more. , More preferably 3 ppm or more, still more preferably 4 ppm or more. If the ion concentration is too high, the acid content tends to remain and the pH tends to decrease, and if it is too low, the treatment takes time and tends to lead to a decrease in productivity.

(The process of adhering a carbonaceous material with lower crystallinity than the raw material carbon material to the composite carbon material)
In the embodiment of the present invention, the composite carbon material may be further attached with a carbonaceous material having a lower crystallinity than the raw material carbon material. That is, a carbonaceous substance can be compounded with the carbon material. According to this step, it is possible to obtain a carbon material capable of suppressing side reactions with the electrolytic solution and improving the rapid charge / discharge property.

Composite graphite in which a composite carbon material is further impregnated with a carbon material having a lower crystallinity than the raw material carbon material may be referred to as a "carbon material composite carbon material" or a "composite carbon material".
In the carbonaceous substance attachment (composite) treatment to the composited carbon material, the organic compound to be the carbonaceous material and the composited carbon material are mixed, and nitrogen, argon, carbon dioxide, etc. are preferably distributed in a non-oxidizing atmosphere. It is a process of heating down to carbonize or graphitize an organic compound.

Specific organic compounds to be carbonaceous substances include various soft to hard coal tar pitches, carbon-based heavy oils such as coal liquefaction oil, and petroleum-based heavy oils such as crude oil at normal pressure or vacuum distillation residue oil. Various substances such as decomposition heavy oil, which is a by-product of ethylene production by naphtha decomposition, can be used.
Further, heat treatment pitches such as ethylene tar pitch, FCC decant oil, and Ashland pitch obtained by heat-treating the cracked heavy oil can be mentioned. Further, vinyl-based polymers such as polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, and polyvinyl alcohol, substituted phenol resins such as 3-methylphenol formaldehyde resin and 3,5-dimethylphenol formaldehyde resin, and aromatics such as acenaphthylene, decacyclene, and anthracene. Examples thereof include hydrocarbons, nitrogen ring compounds such as phenadine and acrydin, and sulfur ring compounds such as thiophene. Examples of organic compounds that promote carbonization in the solid phase include natural polymers such as cellulose, chain vinyl resins such as polyvinylidene chloride and polyacrylonitrile, aromatic polymers such as polyphenylene, furfuryl alcohol resins, and phenols. Examples thereof include thermosetting resins such as formaldehyde resin and imide resin, and thermosetting resin raw materials such as furfuryl alcohol. Of these, petroleum-based heavy oils are preferable.

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

After the above-mentioned treatment, crushing and / or crushing treatment can be carried out to obtain a carbonaceous composite carbon material.
The shape is arbitrary, but the average particle size is usually 2 to 50 μm, preferably 5 to 35 μm, and particularly 8 to 30 μm. Crush and / or crush and / or classify as necessary so as to have the above particle size range.

In addition, as long as the effect of this embodiment is not impaired, other steps may be added or control conditions not described above may be added.
The content of the carbonaceous material in the carbonaceous material composite carbon material is usually 0.01% by mass or more, preferably 0.1% by mass or more, and more preferably 0.3% or more with respect to the granulated carbon material as a raw material. It is more preferably 0.7% by mass or more, particularly preferably 1% by mass or more, most preferably 1.5% by mass or more, and the content is usually 20% by mass or less, preferably 15% by mass. % Or less, more preferably 10% by mass or less, particularly preferably 7% by mass or less, and most preferably 5% by mass or less.

If the content of carbonaceous material in the carbonaceous material composite carbon material is too high, the carbon material will be damaged when rolling with sufficient pressure to achieve high capacity in a non-aqueous secondary battery. Destruction tends to occur, leading to an increase in irreversible charge / discharge capacity during the initial cycle and a decrease in initial efficiency.
On the other hand, if the content is too small, it tends to be difficult to obtain the effect of coating.

In addition, the content of carbonaceous material in the carbonaceous material composite carbon material can be calculated from the sample mass before and after firing the material as shown in the following formula. At this time, it is calculated assuming that there is no change in mass of the core carbon material before and after firing.
Carbonaceous content (% by mass) = [(w2-w1) / w1] × 100
(W1 is the mass of the core carbon material (kg), and w2 is the mass of the carbonaceous composite carbon material (kg))

-Blend with other materials Further, in the present invention, the carbon material is used for the purpose of improving the orientation of the electrode plate, the permeability of the electrolytic solution, the conductive path, etc., and improving the cycle characteristics, the swelling of the electrode plate, etc. Different carbon materials can be mixed (hereinafter, the carbon material obtained by mixing the carbon material with a carbon material different from the carbon material may be referred to as a "mixed carbon material").

Examples of the carbon material different from the carbon material include natural graphite, artificial graphite, coated graphite in which the carbon material is coated with a carbonaceous material, amorphous carbon, and a material selected from carbon materials containing metal particles and metal compounds. Can be used. Any one of these materials may be used alone, or two or more of these materials may be used in any combination and composition.
As the natural graphite, for example, the following can be used.

The volume-based average particle size of natural graphite is usually in the range of 5 μm or more, preferably 8 μm or more, more preferably 10 μm or more, particularly preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less, particularly preferably 30 μm or less. .. When the average particle size is in this range, high-speed charge / discharge characteristics and processability are good, which is preferable.
The BET specific surface area of natural graphite is usually in the range of 1 m ² / g or more, preferably 2 m ² / g or more, and usually 30 m ² / g or less, preferably 15 m ² / g or less. When the specific surface area is in this range, high-speed charge / discharge characteristics and processability are good, which is preferable.

The tap density of natural graphite is usually 0.6 g / cm ³ or more, 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and even more preferably 0.85 g / cm ³ or more. Further, usually 1.3 g / cm ³ or less, 1.2 g / cm ³ or less is preferable, and 1.1 g / cm ³ or less is more preferable. Within this range, high-speed charge / discharge characteristics and processability are good, which is preferable.

Examples of artificial graphite include particles obtained by graphitizing carbon material. For example, single graphite precursor particles are calcined in powder form, graphitized particles, or a plurality of graphite precursor particles are molded and calcined. Granulated particles that have been graphitized and crushed can be used.
The volume-based average particle size of the artificial graphite is usually in the range of 5 μm or more, preferably 10 μm or more, and usually 60 μm or less, preferably 40 μm, and more preferably 30 μm or less. Within this range, swelling of the electrode plate is suppressed and processability is improved, which is preferable.

BET specific surface area of the artificial graphite is usually 0.5 m ² / g or more, preferably 1.0 m ² / g or more and usually ^8m 2 / g or less, preferably ^{6 m} 2 / g or less, more preferably ^4m 2 / g
The range is as follows. Within this range, swelling of the electrode plate is suppressed and processability is improved, which is preferable.
The tap density of the artificial graphite is usually 0.6 g / cm ³ or more, 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and even more preferably 0.85 g / cm ³ or more. In addition, usually 1.5 g / cm ³ or less, 1.4 g / cm ³ or less is preferable, and 1.3 g / cm ³ or less is more preferable. Within this range, swelling of the electrode plate is suppressed and processability is improved, which is preferable.

Examples of the coated graphite in which the carbon material is coated with a carbonaceous material include particles obtained by coating, calcining and / or graphitizing an organic compound which is a precursor of the above-mentioned carbonaceous material on natural graphite or artificial graphite, or natural graphite or artificial graphite. Particles coated with a carbonaceous material by CVD can be used.
The volume-based average particle size of the coated graphite is usually in the range of 5 μm or more, preferably 8 μm or more, more preferably 10 μm or more, particularly preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less, particularly preferably 30 μm or less. .. When the average particle size is in this range, high-speed charge / discharge characteristics and processability are good, which is preferable.

The BET specific surface area of the coated graphite is usually 1 m ² / g or more, preferably 2 m ² / g or more, more preferably 2.5 m ² / g or more, and usually 20 m ² / g or less, preferably 10 m ² / g or less. More preferably, it is in the range of 8 m ² / g or less, and particularly preferably in ^{the range of 5 m 2} / g or less. When the specific surface area is in this range, high-speed charge / discharge characteristics and processability are good, which is preferable.
The tap density of the coated graphite is usually 0.6 g / cm ³ or more, 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and even more preferably 0.85 g / cm ³ or more. Further, usually 1.3 g / cm ³ or less, 1.2 g / cm ³ or less is preferable, and 1.1 g / cm ³ or less is more preferable. When the tap density is in this range, high-speed charge / discharge characteristics and processability are good, which is preferable.

As the amorphous carbon, for example, particles obtained by calcining bulk mesophase or particles obtained by insolubilizing an easily graphitizing organic compound and calcining can be used.
The volume-based average particle size of amorphous carbon is usually in the range of 5 μm or more, preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less. Within this range, high-speed charge / discharge characteristics and processability are good, which is preferable.

BET specific surface area of the amorphous carbon is usually ^{1 m} 2 / g or more, preferably ^2m 2 / g or more, more preferably 2.5 m ² / g or more and usually ^8m 2 / g or less, preferably ^{6 m} 2 / The range is g or less, more preferably 4 m ² / g or less. When the specific surface area is in this range, high-speed charge / discharge characteristics and processability are good, which is preferable.
The tap density of amorphous carbon is usually 0.6 g / cm ³ or more, 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and further preferably 0.85 g / cm ³ or more. preferable. Further, usually 1.3 g / cm ³ or less, 1.2 g / cm ³ or less is preferable, and 1.1 g / cm ³ or less is more preferable. When the tap density is in this range, high-speed charge / discharge characteristics and processability are good, which is preferable.

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

From the viewpoint of cycle life, the volume-based average particle size of the metal particles is usually 0.005 μm or more, preferably 0.01 μm or more, more preferably 0.02 μm or more, still more preferably 0.03 μm or more, and usually 10 μm or less. It is preferably 9 μm or less, more preferably 8 μm or less. When the average particle size is in this range, the volume expansion due to charge / discharge is reduced, and good cycle characteristics can be obtained while maintaining the charge / discharge capacity.

The BET specific surface area of the metal particles is usually preferably 0.5 m ² / g or more and 120 m ² / g or less, 1 m ² / g or more and 100 m ² / g or less. When the specific surface area is within the above range, the charge / discharge efficiency and discharge capacity of the battery are high, lithium is taken in and out quickly in high-speed charge / discharge, and the rate characteristics are excellent, which is preferable.
The device used for adjusting the mixed carbon material is not particularly limited, but for example, in the case of a rotary mixer: a cylindrical mixer, a twin cylindrical mixer, a double conical mixer, and an cubic mixer. In the case of a machine, a stag beetle type mixer, a fixed type mixer: a spiral type mixer, a ribbon type mixer, a Muller type mixer, a Helical Flicht type mixer, a Pugmill type mixer, a fluidization type mixer, etc. can be used. ..

<Negative electrode for non-aqueous secondary batteries>
The negative electrode for a non-aqueous secondary battery of the present invention (hereinafter, also appropriately referred to as an “electrode sheet”) includes a current collector and a negative electrode active material layer formed on the current collector, and the active material layer is at least. It is characterized by containing the carbon material for a non-aqueous secondary battery of the present invention. More preferably, it contains a binder.

As the binder, one having an olefinically unsaturated bond in the molecule is used. The type is not particularly limited, and specific examples thereof include styrene-butadiene rubber, styrene / isoprene / styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene / propylene / diene copolymer. By using a binder having such an olefinically unsaturated bond, the swelling property of the active material layer with respect to the electrolytic solution can be reduced. Of these, styrene-butadiene rubber is preferable because of its availability.

By using a binder having such an olefinically unsaturated bond in combination with the above-mentioned 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 charging and discharging is suppressed, and the cycle life can be extended. Further, in the negative electrode according to the present invention, since the adhesive strength between the active material layer and the current collector is high, even if the binder content in the active material layer is reduced, when the negative electrode is wound to manufacture a battery. It is presumed that the problem of the active material layer peeling off from the current collector does not occur.

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

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

The coatability can be improved by using a binder having no olefinically unsaturated bond in combination, but if the amount used in combination is too large, the strength of the active material layer decreases.
Examples of binders that do not have olefinic unsaturated bonds include thickening polysaccharides such as methyl cellulose, carboxymethyl cellulose, starch, caraginan, purulan, guar gum, and zansan gum (xanthan gum), and 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, metal salts of these polymers, fluoropolymers such as polyvinylidene fluoride, alcan polymers such as polyethylene and polypropylene, and theirs. Examples include copolymers.

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

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

As the current collector to which the slurry is applied, a conventionally known current collector can be used. Specific examples thereof include metal thin films such as rolled copper foil, electrolytic copper foil, and stainless steel foil. The thickness of the current collector is preferably 4 μm or more, more preferably 6 μm or more, preferably 30 μm or less, and more preferably 20 μm or less.
After applying the slurry on the current collector, the temperature is preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and preferably 200 ° C. or lower, more preferably 195 ° C. or lower, under dry air or an inert atmosphere. It dries and forms an active layer.

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

The density of the carbon material in the active material layer varies depending on the application, but in applications where capacity is important, it is preferably 1.55 g / cm ³ or more, more preferably 1.6 g / cm ³ or more, still more preferably 1.65 g / cm. It is cm ³ or more, particularly preferably 1.7 g / cm ³ or more. Further, it is preferably 1.9 g / cm ³ or less. When the density is within the above range, the capacity of the battery per unit volume can be sufficiently secured, and the rate characteristics are less likely to deteriorate.

When the negative electrode for a non-aqueous secondary battery is produced using the carbon material for a non-aqueous secondary battery of the present invention described above, the method and selection of other materials are not particularly limited. Further, even when a lithium ion secondary battery is manufactured using this negative electrode, the selection of members necessary for the battery configuration such as the positive electrode and the electrolytic solution constituting the lithium ion secondary battery is not particularly limited. Hereinafter, the details of the negative electrode for a lithium ion secondary battery and the lithium ion secondary battery using the composite carbon material of the present invention will be illustrated, but the materials that can be used, the manufacturing method, and the like are limited to the following specific examples. is not it.

<Non-water secondary battery>
The basic configuration of the non-aqueous secondary battery of the present invention, particularly a lithium ion secondary battery, is the same as that of a conventionally known lithium ion secondary battery, and usually has a positive electrode and a negative electrode capable of occluding and releasing lithium ions, and an electrolyte. To be equipped. As the negative electrode, the negative electrode of the present invention described above is used.
The positive electrode is formed 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 charging and discharging. Metallic chalcogen compounds include transition metal oxides such as vanadium oxide, molybdenum oxide, manganese oxide, chromium oxide, titanium oxide, and tungsten oxide, vanadium sulfide, and 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, selenium compounds of transition metals such as NbSe _{3, Fe 0.25} V _0. Examples thereof include composite oxides of transition metals such as ₇₅ S ₂ and Na _0.1 CrS _2, and composite sulfides of transition metals such as _{LiCo S 2} and LiNi S _2.

Among _{these, V 2 O 5, V 5} O 13, VO 2, Cr 2 O 5, MnO 2, TiO 2, MoV 2 O 8, LiCoO 2, LiNiO 2, LiMn 2 O 4, TiS 2, V 2 S ₅ , Cr _0.25 V _0.75 S ₂ , Cr _0.5 V _0.5 S _2, etc. are preferable, and LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and some of these transition metals are particularly preferable. Is a lithium transition metal composite oxide in which is replaced with another metal. These positive electrode active materials may be used alone or in combination of two or more.

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

A conductive material may be contained in the positive electrode active material layer 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 usually, carbon powder such as acetylene black, carbon black, and graphite, various metal fibers, powder, and foil are used. And so on.
The positive electrode plate is formed by slurrying a positive electrode active material or a binder with a solvent, applying it on a current collector, and drying it in the same manner as in the production of the negative electrode as described above. Aluminum, nickel, stainless steel (SUS) and the like are used as the current collector of the positive electrode, but the current collector is not limited in any way.

As the electrolyte, a non-aqueous electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent, or a gel-like, rubber-like, or solid sheet-like electrolyte obtained by dissolving this non-aqueous electrolyte solution in an organic polymer compound or the like is used.
The non-aqueous solvent used for the non-aqueous electrolyte solution is not particularly limited, and can be appropriately selected and used from known non-aqueous solvents that have been conventionally proposed as solvents for the non-aqueous electrolyte solution. 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. Cyclic ethers such as tetrahydrofuran, sulfolane and 1,3-dioxolane; chain esters such as methyl formate, methyl acetate and methyl propionate; 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 when the cyclic carbonate is a mixed solvent of ethylene carbonate and propylene carbonate, high ionic conductivity can be exhibited even at a low temperature, and low-temperature charging is performed. It is particularly preferable in that the non-characteristics are improved. Among them, propylene carbonate is preferably in the range of 2% by mass or more and 80% by mass or less, more preferably in the range of 5% by mass or more and 70% by mass or less, and further preferably in the range of 10% by mass or more and 60% by mass or less with respect to the whole non-aqueous solvent. preferable. If the proportion of propylene carbonate is lower than the above, the ionic conductivity at low temperature decreases, and if the proportion of propylene carbonate is higher than the above, propylene carbonate solvated with lithium ions moves between the graphite phases when a graphite-based electrode is used. The co-insertion causes delamination deterioration of the graphite-based negative electrode active material, and there is a problem that a sufficient capacity cannot be obtained.

The lithium salt used in the non-aqueous electrolyte solution is not particularly limited, and can be appropriately selected and used from known lithium salts known to be usable for this purpose. For example, halides such as LiCl, LiBr, perhalonates _{such as LiClO 4 , LiBrO 4} , LiClO ₄ , inorganic lithium salts such as inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF _{6 , LiCF 3} SO ₃ , Examples thereof include _{perfluoroalcan sulfonates such as LiC 4} F ₉ SO ₃ and fluoroalquinate organic lithium salts such as perfluoroalcan sulfonic acid imide salts such as Li trifluorosulphonimide ((CF ₃ SO ₂ ) _{2 NLi).} Of these, LiClO ₄ , LiPF ₆ , and LiBF ₄ are preferable.

The lithium salt may be used alone or in combination of two or more. The concentration of the lithium salt in the non-aqueous electrolyte solution is usually in the range of 0.5 mol / L or more and 2.0 mol / L or less.
Further, when the above-mentioned non-aqueous electrolyte solution contains an organic polymer compound and is used in the form of a gel, rubber, or solid sheet, specific examples of the organic polymer compound include polyethylene oxide and polypropylene oxide. Polyether-based polymer compound; Crosslinked polymer of polyether-based polymer compound; Vinyl alcohol-based polymer compound such as polyvinyl alcohol and polyvinyl butyral; Insoluble material of vinyl alcohol-based polymer compound; Polyepicrolhydrin; Polyphosphazene; Poly Siloxane; Vinyl-based polymer compounds such as polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile; poly (ω-methoxyoligooxyethylene methacrylate), poly (ω-methoxyoligooxyethylene methacrylate-co-methylmethacrylate), poly (hexafluoro) Examples thereof include polymer copolymers such as propylene-vinylidene fluoride).

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

Further, as the electrolyte, a polymer solid electrolyte which is a conductor of an alkali metal cation such as lithium ion can also be used. Examples of the polymer solid electrolyte include those in which a salt of lithium is dissolved in the above-mentioned polyether polymer compound, and a polymer in which the terminal hydroxyl group of the polyether is replaced with an alkoxide.
Usually, a porous separator such as a porous membrane or a non-woven fabric is interposed between the positive electrode and the negative electrode in order to prevent a short circuit between the electrodes. In this case, the non-aqueous electrolyte solution is used by impregnating the porous separator. As the material of the separator, polyolefins such as polyethylene and polypropylene, polyether sulfone and the like are used, and polyolefins are preferable.

The form of the non-aqueous secondary battery of the present invention is not particularly limited. Examples include a cylinder type in which the sheet electrode and the separator are spirally formed, a cylinder type having an inside-out structure in which the pellet electrode and the separator are combined, a coin type in which the pellet electrode and the separator are laminated, and the like. Further, by storing the batteries of these forms in an arbitrary outer case, they can be used in any shape such as a coin type, a cylindrical type, and a square type.

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

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.

<Preparation of electrode sheet>
Using the graphite particles of Examples or Comparative Examples, a electrode plate having an active material layer having an active material layer density of 1.35 ± 0.03 g / cm ^{3 was prepared.} Specifically, 50.00 ± 0.02 g of the negative electrode material, 50.00 ± 0.02 g of a 1 mass% carboxymethyl cellulose sodium salt aqueous solution (0.500 g in terms of solid content), and styrene having a weight average molecular weight of 270,000. 1.00 ± 0.05 g (0.5 g in terms of solid content) of butadiene rubber aqueous dispersion was stirred with a hybrid mixer manufactured by Keyence for 5 minutes and defoamed for 30 seconds to obtain a slurry.
This slurry is 10 cm wide using a small die coater manufactured by ITOCHU Machining so that the negative electrode material adheres to a copper foil with a thickness of 10 μm, which is a current collector, at 9.00 ± 0.3 mg / cm ^2.
And roll-pressed with a roller having a diameter of 20 cm to adjust the density of the active material layer to 1.35 ± 0.03 g / cm ³ to obtain an electrode sheet.

<Manufacturing of non-aqueous secondary batteries (2016 coin type batteries)>
The electrode sheet produced by the above method was punched into a disk shape having a diameter of 12.5 mm, and the lithium metal foil was punched into a disk shape having a diameter of 14 mm to serve as a counter electrode. Between the two poles, add 1 mol / mol of _{LiPF 6} to a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7).
A separator (made of a porous polyethylene film) impregnated with an electrolytic solution dissolved so as to be L was placed, and 2016 coin type batteries were produced respectively.

<Measurement method of discharge capacity and discharge load characteristics>
Using the electrode sheet produced by the above method and the non-aqueous secondary battery (2016 coin type battery) produced by the above method, the capacity at the time of battery charging / discharging was measured by the following measuring method.
Charge to 5 mV with respect to the lithium counter electrode with a current density of 0.05 C, further charge with a constant voltage of 5 mV until the current density reaches 0.005 C, dope lithium into the negative electrode, and then with a current density of 0.1 C. The discharge capacity when discharging to 1.5 V with respect to the lithium counter electrode was defined as the discharge capacity in the present invention.

Further, the lithium counter electrode is discharged to 1.5 V at current densities of 0.2 C and 3.0 C, and [Discharge capacity when discharged at 3.0 C] / [Discharge when discharged at 0.2 C]. Capacity] x100 (%) was defined as the discharge load characteristic.

<Manufacturing method of non-aqueous secondary battery (laminated battery)>
The electrode sheet produced by the above method was cut out to a size of 4 cm × 3 cm to form a negative electrode, a positive electrode made of NMC was cut out in the same area, and a separator (made of a porous polyethylene film) was placed between the negative electrode and the positive electrode and combined. A laminated battery is prepared by injecting 225 μl of an electrolytic solution in which LiPF6 is dissolved at 1.2 mol / L in a mixed solvent of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio = 3: 3: 4). Made.

<Low temperature output characteristics>
Using the electrode sheet produced by the above method, the low temperature output characteristics were measured by the following measurement method using the laminated non-aqueous electrolyte secondary battery produced by the method for producing the non-aqueous electrolyte secondary battery. ..
For a non-aqueous electrolyte secondary battery that has not undergone a charge / discharge cycle, the voltage range is 4.1V to 3.0V and the current value is 0.2C at 25 ° C. The current value is 1C, the same applies hereinafter) for 3 cycles, the voltage range is 4.2V to 3.0V, and the current value is 0.2C (when charging, constant voltage charging is performed at 4.2V for another 2.5 hours). Implementation) Initial charging and discharging were performed for 2 cycles.

Further, after charging to 50% SOC at a current value of 0.2C, the current values of 1 / 8C, 1 / 4C, 1 / 2C, 1.5C, and 2C are used for 2 seconds in a low temperature environment of -30 ° C. Discharge with a constant current, measure the drop in battery voltage after 2 seconds in discharging under each condition, and calculate the current value I that can be passed in 2 seconds when the upper limit charging voltage is set to 3V from those measured values. Then, the value calculated by the formula of 3 × I (W) was used as the low temperature output characteristic of each battery.

<D50, d90, d10, d90 / d10>
0.01 g of carbon material was suspended in 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) as a surfactant, and this was used as a measurement sample. Introduced into a commercially available laser diffraction / scattering particle size distribution measuring device (for example, LA-920 manufactured by HORIBA), the measurement sample was irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, and then the volume-based d50, d90 and d10 were measured, and d90 / d10 was calculated.

<BET specific surface area (SA)>
Using a surface meter (Shimadzu Seisakusho's specific surface area measuring device "Gemini 2360"), the carbon material sample was preliminarily dried under nitrogen flow at 100 ° C. for 3 hours, cooled to liquid nitrogen temperature, and then cooled to atmospheric pressure. Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen with respect to the gas was 0.3, the measurement was carried out by the nitrogen adsorption BET 6-point method by the gas flow method.

<Bulk density, Tap density>
Using a powder density measuring instrument, the composite carbon material of the present invention is dropped into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ^{3 through a sieve having a mesh size of 300 μm, and the volume when the cell is fully filled.} The density obtained from the mass of the sample was defined as the bulk density.
Further, tapping with a stroke length of 10 mm was performed 1000 times, and the density obtained from the volume at that time and the mass of the sample was defined as the Tap density.

<Pore distribution mode diameter, pore volume of 0.1 μm to 2 μm>
For the measurement of the mercury press-fitting method, a mercury porosimeter (Autopore 9520 manufactured by Micromeritex Co., Ltd.) is used to weigh around 0.2 g of a sample (negative electrode material) in a powder cell and weigh it at room temperature under vacuum (50 μmHg or less). After performing the degassing pretreatment for 10 minutes, the pressure was reduced stepwise to 4 psia, mercury was introduced, the pressure was increased stepwise from 4 psia to 40,000 psia, and the pressure was further reduced to 25 psia. From the obtained mercury intrusion curve, the pore distribution was calculated using the Washburn formula. The surface tension of mercury was calculated as 485 dyne / cm, and the contact angle was calculated as 140 °. From the obtained pore distribution, the pore distribution mode diameter and the pore volume in the range of 0.1 μm or more and 1 μm or less were calculated.

(Example 1)
Liquid paraffin (manufactured by Wako Pure Chemical Industries, Ltd., first grade, physical properties at 25 ° C.: viscosity = 95 cP, contact angle = 13) as a granulator on 100 g of raw coke particles having d50, which is a precursor of graphite particles (A), of 3.3 μm. .2 °, surface tension = 31.7 mN / m, rcosθ = 30.9) 20 g
After adding and stirring and mixing, the obtained mixture was crushed and mixed with a hammer mill (MF10 manufactured by IKA) at a rotation speed of 3000 rpm. 120 g of raw coke particles impregnated with the obtained granulator were subjected to impact, compression, friction, and shear by mechanical action for 5 minutes at a rotor peripheral speed of 85 m / sec using a hybridization system NHS-1 manufactured by Nara Machinery Co., Ltd. Granulation processing was performed while applying force. The obtained composite graphite particle precursor was calcined in an electric furnace in a nitrogen atmosphere at 1000 ° C. for 1 hour, and then graphitized and classified at 3000 ° C. in an electric furnace under Ar circulation to obtain a plurality of graphites. A carbon material for a non-aqueous secondary battery in which particles (A) were compounded was obtained. With respect to the obtained sample, d50, SA, Tap, pore distribution mode diameter, pore volume of 0.1 μm to 2 μm, charge / discharge efficiency, discharge capacity, discharge load characteristic, and low temperature output characteristic were measured by the above-mentioned measurement method. The results are shown in Tables 1 and 2.

(Example 2)
Liquid paraffin (manufactured by Wako Pure Chemical Industries, Ltd., first grade, physical properties at 25 ° C.: viscosity = 95 cP, contact angle = 13) as a granulator on 100 g of raw coke particles having d50, which is a precursor of graphite particles (A), of 3.3 μm. .2 °, surface tension = 31.7 mN / m, rcosθ = 30.9) 20 g
After adding and stirring and mixing, the obtained mixture was crushed and mixed with a hammer mill (MF10 manufactured by IKA) at a rotation speed of 3000 rpm. The raw coke particles impregnated with the obtained granulating agent have d50 of 8.9 μm, SA of 11.4 m ² / g, Tap density of 0.42 g / cm ³ , and an aspect ratio of 8 as natural graphite particles (B). 25 g of scaly natural graphite particles of No. 1 was added and mixed by stirring. 120 g of the obtained mixture is granulated by a hybridization system NHS-1 manufactured by Nara Kikai Seisakusho for 5 minutes at a rotor peripheral speed of 85 m / sec while applying impact, compression, friction, and shearing force due to mechanical action. went. The obtained composite graphite particle precursor was calcined in an electric furnace in a nitrogen atmosphere at 1000 ° C. for 1 hour, and then graphitized and classified at 3000 ° C. in an electric furnace under Ar circulation to obtain a plurality of graphites. A carbon material for a non-aqueous secondary battery in which the particles (A) and the natural graphite particles (B) were composited was obtained. With respect to the obtained sample, d50, SA, Tap, pore distribution mode diameter, pore volume of 0.1 μm to 2 μm, charge / discharge efficiency, discharge capacity, discharge load characteristic, and low temperature output characteristic were measured by the above-mentioned measurement method. The results are shown in Tables 1 and 2. An SEM image of the particle cross section is shown in FIG.

(Comparative Example 1)
Raw coke particles having a d50 of 3.3 μm, which is a precursor of the graphite particles (A), were calcined, graphitized, and classified in the same manner as in Example 1. The same measurement as in Example 1 was performed on the obtained sample. The results are shown in Table 1.
(Comparative Example 2)
A carbon material was obtained in the same manner as in Example 1 except that the d50, which is a precursor of the graphite particles (A), was sphericalized only with 19.5 μm raw coke particles. The same measurement as in Example 1 was performed on the obtained sample. The results are shown in Tables 1 and 2.

(Comparative Example 3)
Non-composite graphite particles (A) and natural graphite particles (B) in the same manner as in Example 1 except that raw coke particles having a d50 of 17.7 μm, which is a precursor of graphite particles (A), were used. A carbon material for an aqueous secondary battery was obtained. The same measurement as in Example 1 was performed on the obtained sample. The results are shown in Tables 1 and 2.

In Examples 1 and 2, high capacity and excellent discharge load characteristics and low temperature output characteristics were exhibited by setting the granulator pore distribution mode diameter and d50 within the specified range. On the other hand, in Comparative Examples 1 to 3 in which the pore mode diameter and d50 are not within the specified range, deterioration of the discharge load characteristic and the low temperature output characteristic was confirmed.

The composite carbon material of the present invention is a non-aqueous material having high capacity, excellent input / output characteristics, high temperature storage characteristics, cycle characteristics, and excellent productivity by using it as an active material for a negative electrode of a non-aqueous secondary battery. The secondary battery can be provided stably and efficiently.

Claims (8)

A carbon material for non-aqueous secondary batteries in which graphite particles (A) capable of occluding and releasing a plurality of lithium ions are composited, and the mode diameter in the pore distribution obtained by the mercury press-fitting method for powder is It is 0.1 μm or more and 2 μm or less, and the volume-based average particle size (d50) is 5.
It is μm or more and 40 μm or less ,
A carbon material for a non-aqueous secondary battery, characterized in that the pore volume of 0.1 μm or more and 2 μm or less is 0.2 ml / g or more. The carbon material for a non-aqueous secondary battery according to claim 1, wherein the bulk density is 0.3 g / cm ^{3 or more.} The carbon material for a non-aqueous secondary battery according to claim 1 or 2 , wherein the tap density is 0.6 g / cm ^{3 or more.} The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 3 , wherein d90 / d10 is 3.5 or more. Any of claims 1 to 4 , wherein the average particle size d50 of the carbon material for a non-aqueous secondary battery is 1.5 times or more and 15 times or less the average particle size d50 of the graphite particles (A). The carbon material for a non-aqueous secondary battery according to item 1. The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 5 , wherein the graphite particles (A) are artificial graphite particles. The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 6 , wherein the carbon material for a non-aqueous secondary battery further contains natural graphite particles (B). A lithium ion secondary battery including a positive electrode and a negative electrode capable of storing and releasing lithium ions and an electrolyte, wherein the negative electrode includes a current collector and an active material layer formed on the current collector. A lithium ion secondary battery, wherein the active material layer contains the carbon material for a non-aqueous secondary battery according to any one of claims 1 to 7.

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