JP2013196842A - Carbon material for nonaqueous secondary battery, anode for nonaqueous secondary battery, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon material for a nonaqueous secondary battery having a high tapping density irrespective of having a small particle diameter and a specific surface area, an anode for a nonaqueous secondary battery manufactured using the carbon material, and a nonaqueous secondary battery including the anode and having a high output and a high electrode plate strength.SOLUTION: A carbon material for a nonaqueous secondary battery includes graphite having an average grain diameter (d50) which is 1 μm or more and 9 μm or less when measured with a laser diffraction type grain size analyzer, a tapping density of 0.9 g/cmor more and 1.3 g/cmor less, and a specific surface area (SA) of 8 m/g or more and 60 m/g or less.

Description

  The present invention provides a carbon material for a non-aqueous secondary battery capable of producing a negative electrode capable of producing a negative electrode capable of achieving high output and high electrode plate strength with a small particle size, a large specific surface area, a high tapping density, and the carbon material. The present invention relates to a non-aqueous secondary battery negative electrode and a non-aqueous secondary battery having the negative electrode.

  In recent years, demand for high-capacity secondary batteries has increased with the downsizing of electronic devices. In particular, non-aqueous secondary batteries such as lithium ion secondary batteries having higher energy density and excellent large current charge / discharge characteristics have attracted attention as compared with nickel / cadmium batteries and nickel / hydrogen batteries.

  It is known to use graphite as a carbon material for non-aqueous secondary batteries. In particular, when graphite having a high degree of graphitization is used as a carbon material for a non-aqueous secondary battery, a capacity close to 372 mAh / g, which is the theoretical capacity for lithium occlusion of graphite, can be obtained. -Since it is excellent also in durability, it is known that it is preferable as an active material for negative electrodes.

  Conventionally, it has been known that the specific surface area of graphite particles increases when the particle size of the graphite is reduced, so that the resulting nonaqueous secondary battery has a high output.

  However, in the conventional technology, when the particle size is reduced, the specific surface area increases, but on the other hand, the tapping density of the carbon material cannot be increased (for example, Table 4 of Patent Document 1), and the slurry containing such a carbon material. Cannot be applied to the electrode plate as the current collector, or even if it can be applied to the electrode plate, the density of the electrode plate is lowered, resulting in a secondary battery with insufficient output and strength. That is, since the carbon material cannot be reduced in particle size while maintaining the tapping density, conventionally, the effect of improving the output of the non-aqueous secondary battery by increasing the specific surface area by reducing the particle size of graphite is However, it was not large, and there was a problem in terms of the strength of the battery.

  For this reason, it was thought that the commercialization of the graphite-containing carbon material having a small particle diameter was difficult. Even if the particle size is small, a high specific surface area may not be achieved depending on the production method (Patent Document 2).

Japanese Patent No. 3534391 Special table 2008-542981 gazette

  Thus, the present invention provides a carbon material for a non-aqueous secondary battery that simultaneously achieves a high tapping density despite a small particle size and a large specific surface area, and a negative electrode for a non-aqueous secondary battery manufactured using the carbon material. And it aims at providing the non-aqueous secondary battery of the high output which has the said negative electrode, and a high electrode plate intensity | strength.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has made non-aqueous two-dimensional graphite containing graphite having a high tapping density and a specific surface area by reducing the particle size of graphite by a specific operation. Succeeded in developing carbon materials for secondary batteries.

That is, the gist of the present invention is as follows.
The average particle diameter (d50) measured using a laser diffraction particle size distribution meter is 1 μm or more and 9 μm or less, and the tapping density is 0.9 g / cm ³ or more and 1.3 g / cm ³ or less, measured by the BET method. The non-aqueous secondary battery carbon material includes graphite having a specific surface area (SA) of 8 m ² / g or more and 60 m ² / g or less.

  ADVANTAGE OF THE INVENTION According to this invention, the carbon material for non-aqueous secondary batteries which can provide the non-aqueous secondary battery which has the effect of the high output and the high electrode plate intensity | strength conventionally desired, It is obtained using the said carbon material. A negative electrode for a non-aqueous secondary battery and a non-aqueous secondary battery having the negative electrode are provided.

The SEM photograph of the spheroidized natural graphite (A) used in Comparative Example 1 is shown. The SEM photograph of the spheroidized natural graphite (B) prepared in Example 1 is shown. The SEM photograph of the scale-like natural graphite (C) used in the comparative example 2 is shown. The SEM photograph of the negative electrode produced using the graphite of Example 1 in an Example is shown. The SEM photograph of the negative electrode produced using the graphite of the comparative example 1 in an Example is shown.

  Hereinafter, the contents of the present invention will be described in detail. The description of the constituent features of the invention described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these forms unless it exceeds the gist.

[Carbon material for non-aqueous secondary batteries]
The carbon material for non-aqueous secondary batteries of the present invention (hereinafter also simply referred to as “carbon material of the present invention”) has an average particle diameter (d50), tapping density and BET measured using a laser diffraction particle size distribution meter. The specific surface area (SA) measured by the method includes graphite having a specific range. Hereinafter, these characteristics relating to the graphite will be described in order.

<Types of graphite>
The shape of the graphite is not particularly limited and can be appropriately selected from spherical, flaky, fibrous, and irregularly shaped particles, but is preferably spherical.

  As graphite, either natural graphite or artificial graphite may be used. As graphite, those with few impurities are preferable, and they are used after being subjected to various purification treatments as necessary.

  Examples of the natural graphite include scaly graphite, scaly graphite, and soil graphite. Examples of the artificial graphite include graphite particles such as coke, needle coke, and high-density carbon material, which are produced by heat-treating a pitch raw material. Natural graphite is preferred from the viewpoint of low cost and ease of electrode production.

  Among natural graphites, from the viewpoint of exerting the effect of the present invention, it is preferably spheroidized graphite, more preferably spheroidized natural graphite, and more specifically, spheroidized natural obtained by subjecting flaky graphite to spheronization treatment. It is preferably graphite and includes a step of purification. A spheroidizing method and the like will be described later.

<Average particle diameter (d50)>
The graphite constituting the carbon material of the present invention has a volume-based average particle diameter (d50) measured by using a laser diffraction particle size distribution meter of 1 m or more and 9 μm or less. The details of the method of measuring the particle size by the laser diffraction particle size distribution meter will be described in Examples described later.

  Since the graphite has a d50 in such a small range, the specific surface area is high, and the tapping density is high despite the small particle size. Therefore, the non-aqueous secondary material obtained using the carbon material of the present invention is used. In the battery, high output based on excellent electrode plate strength and a high specific surface area of the carbon material is achieved.

  In addition, it is extremely difficult to produce graphite having a d50 of less than 1 μm. On the other hand, if d50 exceeds 9 μm, high output characteristics cannot be obtained in the battery. From these viewpoints, d50 is preferably 3 μm or more, more preferably 5 μm or more, and further preferably 6 μm or more. On the other hand, it is preferably 8.5 μm or less, more preferably 8 μm or less.

<Tapping density>
The tapping density of the graphite constituting the carbon material of the present invention is 0.9 g / cm ³ or more and 1.3 g / cm ³ or less, and maintains a high value despite the high d50 of graphite as described above. . For this reason, the non-aqueous secondary battery which is excellent in electrode plate intensity | strength and an output can be obtained using the carbon material of this invention. The method for measuring the tapping density will be described in detail in examples described later.

When the tapping density of the graphite is less than 0.9 g / cm ³ , sufficient electrode plate strength and output cannot be obtained, while when the tapping density exceeds 1.3 g / cm ³ , Productivity will be low and the production cost will be high. From these viewpoints, the tapping density is preferably 1.2 g / cm ³ or less, more preferably 1.1 g / cm ³ or less.

<BET specific surface area (SA)>
The specific surface area (SA) measured by the BET method of the graphite constituting the carbon material of the present invention is as high as 8 m ² / g or more and 60 m ² / g or less, and a high-power nonaqueous secondary battery can be obtained from the carbon material. . Details of the method for measuring the specific surface area by the BET method will be described in Examples described later.

When the SA is less than 8 m ² / g, it is difficult to obtain high output characteristics in the battery. On the other hand, when the SA exceeds 60 m ² / g, there is a concern that the irreversible capacity increases and the battery capacity decreases. From these viewpoints, SA of the graphite preferably ^9m 2 / g or more, more preferably 10 m ² / g or more, preferably ^{30 m} 2 / g or less, more preferably ^{20 m} 2 / g or less, more preferably 18m ² / g or less.

  Further, the graphite constituting the carbon material of the present invention preferably satisfies any one or more of the following characteristics.

<X-ray parameters>
The d value (interlayer distance) of the lattice plane (002 plane) of the graphite constituting the carbon material of the present invention determined by X-ray wide angle diffraction measurement by the Gakushin method is usually 0.337 nm or less. If the d002 value is too large, it indicates that the crystallinity is low, and the initial irreversible capacity may increase when a non-aqueous secondary battery is used. On the other hand, since the theoretical value of the interplanar spacing of the 002 plane of graphite is 0.335 nm, the d value is usually 0.335 nm or more.

  Further, the crystallite size (Lc) of the graphite obtained by X-ray wide angle diffraction measurement by the Gakushin method is 100 nm or more in order to obtain the effect of the present invention. Below this range, the particles have low crystallinity, and the reversible capacity may decrease when a non-aqueous secondary battery is formed.

<Particle size d10>
Of the graphite constituting the carbon material of the present invention, the particle size (d10) corresponding to the 10% integration part from the small particle side of the volume-based particle size measured using a laser diffraction particle size distribution meter is usually 8 μm. Hereinafter, it is preferably 6 μm or less, usually 1 μm or more, preferably 3 μm or more, more preferably 4 μm or more.

  If d10 is too small, the tendency of the particles to agglomerate becomes strong, which may cause inconveniences such as an increase in slurry viscosity, a decrease in electrode plate strength in a non-aqueous secondary battery, and a decrease in initial charge / discharge efficiency. On the other hand, if d10 is too large, the high current density charge / discharge characteristics may be deteriorated and the low temperature input / output characteristics may be deteriorated.

<Particle size d90>
Of the graphite constituting the carbon material of the present invention, the particle size (d90) corresponding to the 90% integration part from the small particle side of the volume-based particle size measured using a laser diffraction particle size distribution meter is usually 15 μm. In the following, it is preferably 12 μm or less, more preferably 11 μm or less, usually 3 μm or more, preferably 6 μm or more, more preferably 8 μm or more.

  If d90 is too small, the strength of the electrode plate and the initial charge / discharge efficiency in the non-aqueous secondary battery may be reduced. On the other hand, if d90 is too large, process inconveniences such as striation at the time of slurry application, In some cases, density charge / discharge characteristics and low-temperature input / output characteristics may deteriorate.

<Ratio of d90 / d10>
The ratio of d90 / d10 of the graphite constituting the carbon material of the present invention is preferably 1 or more, more preferably 1.5 or more, preferably 4 or less, and more preferably 3 or less.

  The d90 / d10 of 1 or more and 4 or less means that the particle size distribution of the graphite is sharp, thereby improving the slurry application density and reducing the damage to the carbon material during pressing during electrode production. It is easy to obtain the high input / output effect according to the present invention. On the other hand, if d90 / d10 exceeds 4, streaking may occur during application due to aggregation of fine powder or the like.

<Ash content>
The ash contained in the graphite constituting the carbon material of the present invention is usually 1% by mass or less, preferably 0.5% by mass or less, and 0.1% by mass or less, based on the total mass of the graphite. More preferred. Moreover, it is preferable that the minimum of ash content is 1 ppm.

  When the ash content exceeds the above range, in the case of a non-aqueous secondary battery, deterioration of battery performance due to the reaction between the carbon material and the electrolyte during charge / discharge may not be negligible. On the other hand, if it falls below the above range, the production of the carbon material requires a great amount of time, energy, and equipment for preventing contamination, which may increase the production cost.

<Orientation ratio>
The orientation ratio of the graphite constituting the carbon material of the present invention is usually 0.05 or more, preferably 0.08 or more, more preferably 0.10 or more, still more preferably 0.15 or more, and the upper limit is 0.00. 67.

  The upper limit of the orientation ratio is a theoretical value. On the other hand, below the above range, the active material may be arranged when an electrode is produced using the carbon material of the present invention, and high output may not be obtained.

<DBP oil absorption>
The DBP (dibutyl phthalate) oil absorption amount of graphite constituting the carbon material of the present invention is usually 70 ml / 100 g or less, preferably 65 ml / 100 g or less, more preferably 60 ml / 100 g or less, still more preferably 55 ml / 100 g or less. . The DBP oil absorption is usually 20 ml / 100 g or more, preferably 30 ml / 100 g or more.

  If the DBP oil absorption is too large, the progress of the spheroidization of the graphite is not sufficient, and there is a tendency to cause streaking when applying the slurry (negative electrode forming material) containing the carbon material of the present invention containing the graphite. If it is too small, there may be almost no pore structure in the particles, and the reaction surface tends to decrease. The details of the DBP oil absorption measuring method will be described in Examples described later.

<Pore distribution>
In the graphite constituting the carbon material of the present invention, the amount of voids in the particles corresponding to a diameter of 0.01 μm or more and 1 μm or less, and the unevenness due to the step of the particle surface, which is determined by mercury porosimetry (mercury intrusion method), is usually 0 0.01 mL / g or more, preferably 0.05 mL / g or more, more preferably 0.1 mL / g or more. The amount is usually 0.6 mL / g or less, preferably 0.4 mL / g or less, more preferably 0.3 mL / g or less.

  If the amount of irregularities is too large, a large amount of binder may be required when forming a negative electrode when forming a negative electrode. On the other hand, if the amount of irregularities is too small, the high current density charge / discharge characteristics of the nonaqueous secondary battery tend to be lowered, and the effect of mitigating the expansion and contraction of the electrode during charge / discharge tends to be not obtained.

  The total pore volume of the graphite is usually 0.1 mL / g or more, preferably 0.2 mL / g or more, more preferably 0.25 mL / g or more. The total pore volume is usually 10 mL / g or less, preferably 5 mL / g or less, more preferably 2 mL / g or less.

  If the total pore volume is too large, a large amount of binder tends to be required when forming an electrode plate. On the other hand, if the total pore volume is too small, there is a tendency that the effect of dispersing the thickener or the binder cannot be obtained when forming an electrode plate.

  The average pore diameter of the graphite is usually 0.03 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, and further preferably 0.5 μm or more. The average pore diameter is usually 80 μm or less, preferably 50 μm or less, more preferably 20 μm or less.

  If the average pore diameter is too large, a large amount of binder tends to be required when forming an electrode plate, and if the average pore diameter is too small, the high current density charge / discharge characteristics of the nonaqueous secondary battery tend to deteriorate. .

  As the mercury porosimetry apparatus, a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) can be used. A sample (graphite) is weighed to a value of about 0.2 g, sealed in a powder cell, and pretreated by degassing at room temperature and under vacuum (50 μmHg or less) for 10 minutes.

  Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced into the cell, the pressure is increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure is reduced to 25 psia (about 170 kPa).

  The number of steps at the time of pressure increase is 80 points or more, and the mercury intrusion amount is measured after an equilibration time of 10 seconds in each step. The pore distribution is calculated from the mercury intrusion curve thus obtained using the Washburn equation.

  Note that the surface tension (γ) of mercury is calculated as 485 dyne / cm and the contact angle (ψ) is 140 °. The average pore diameter is defined as the pore diameter when the cumulative pore volume is 50%.

<Circularity>
The circularity of the graphite constituting the carbon material of the present invention is usually 0.85 or more, more preferably 0.87 or more, and still more preferably 0.88 or more. Further, the circularity is usually 1 or less, preferably 0.98 or less, more preferably 0.97 or less. If the circularity is too small, the high current density charge / discharge characteristics of the non-aqueous secondary battery tend to deteriorate. The circularity is defined by the following formula, and when the circularity is 1, a theoretical sphere is obtained.

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

  As the circularity value, for example, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.) is used, and about 0.2 g of a sample (graphite) is added to polyoxyethylene (20) sorbitan mono surfactant. After dispersing in a 0.2% by weight aqueous solution of laurate (about 50 mL) and irradiating the dispersion with ultrasonic waves at 28 kHz for 1 minute at an output of 60 W, the detection range is specified as 0.6 to 400 μm, and the particle size is 1 Use the value measured for particles in the range of 5-40 μm.

  A method for improving the degree of circularity is not particularly limited, but a spheroidized sphere is preferable because the shape of the interparticle voids when the negative electrode is formed is preferable. Examples of spheroidizing treatment include a method of mechanically approaching a sphere by applying a shearing force and a compressive force, and a mechanical / physical processing method of granulating a plurality of graphite fine particles by the adhesive force of the binder or the particles themselves. Etc.

<True density>
The true density of the graphite constituting the carbon material of the present invention is usually 1.9 g / cm ³ or more, preferably 2 g / cm ³ or more, more preferably 2.1 g / cm ³ or more, still more preferably 2.2 g / cm. ³ or more, and the upper limit is 2.26 g / cm ³ . The upper limit is the theoretical value of graphite. Below this range, the crystallinity of the carbon is too low, and the initial irreversible capacity of a non-aqueous secondary battery may increase.

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

  If the aspect ratio is too large, streaks of the slurry containing the carbon material (negative electrode forming material) may occur during electrode plate formation, or a uniform coated surface may not be obtained, and the high current density charge / discharge characteristics of the non-aqueous secondary battery Tends to decrease.

  The aspect ratio is expressed as A / B when the longest diameter A of the graphite particles when observed three-dimensionally and the shortest diameter B among the diameters orthogonal to the diameter A. The graphite particles are observed with a scanning electron microscope capable of magnifying observation. Arbitrary 50 graphite particles fixed on the end face of a metal having a thickness of 50 microns or less are selected, and the stage on which the sample is fixed is rotated and tilted, and A and B are measured. Find the average value.

<Maximum particle size dmax>
The maximum particle diameter dmax of the graphite constituting the carbon material of the present invention is usually 100 μm or less, preferably 70 μm or less, more preferably 50 μm or less, still more preferably 40 μm or less, and particularly preferably 30 μm or less. If dmax is too large, there is a tendency to cause inconveniences such as line drawing.

  The maximum particle size is defined as the value of the largest particle size at which particles are measured in the particle size distribution obtained when measuring the average particle size d50.

<Raman R value>
The Raman R value of the graphite constituting the carbon material of the present invention is usually 0.1 or more, preferably 0.15 or more, more preferably 0.20 or more. The Raman R value is usually 0.6 or less, preferably 0.55 or less, more preferably 0.5 or less.

Incidentally, the Raman R value is measured and the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1 in the Raman spectrum obtained by Raman spectroscopy, the intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1, the intensity Defined as the ratio (I _B / I _A ).

Incidentally, the scope of 1580～1620Cm ^-1 A "1580cm around ^-1" in the present specification, "1360cm around ^-1" refers to the range of 1350 ^-1.

  If the Raman R value is too small, the crystallinity of the graphite particle surface becomes too high, and when the density is increased, the crystals tend to be oriented in a direction parallel to the negative electrode plate, and the load characteristics tend to deteriorate. On the other hand, if the Raman R value is too large, the crystal on the particle surface is disturbed, the reactivity of the negative electrode with the electrolytic solution increases, and the charge / discharge efficiency of the non-aqueous secondary battery tends to decrease and the gas generation tends to increase.

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

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

[Other ingredients]
The carbon material of the present invention may be composed only of the graphite described above, but may contain other components as necessary.

  Examples of other components include various known graphites that do not satisfy any one or more of the average particle size (d50), tapping density, and specific surface area (SA) described above for graphite. The graphite can be used without particular limitation as long as the effects of the present invention are not hindered.

[Carbon material for non-aqueous secondary batteries]
The carbon material for a non-aqueous secondary battery of the present invention includes the graphite described above, and further includes the other components as necessary.

The various parameters described for the graphite of the carbon material of the present invention are substantially in the same range as the parameters of graphite. Therefore, the average particle diameter (d50) of the carbon material of the present invention measured using a laser diffraction particle size distribution analyzer is 1 μm or more and 9 μm or less, and the tapping density is 0.9 g / cm ³ or more and 1.3 g / cm ^3. The specific surface area (SA) measured by the BET method is 8 m ² / g or more and 60 m ² / g or less. Other parameters are the same as those described for the graphite.

  Therefore, the amount of the other components used is also in a range in which the carbon material of the present invention satisfies the parameters described for the graphite described above.

[Method for producing graphite]
The graphite constituting the carbon material of the present invention described above can be obtained, for example, by subjecting arbitrary natural graphite to a specific spheroidizing process described below.
Natural graphite is classified into flake graphite (Flake Graphite), scale graphite (Crystalline (Vein) Graphite), and soil graphite (Amorphousu Graphite), depending on the properties (“granular process technology assembly” (Inc.) (Refer to "HANDBOOKOF CARBON, GRAPHITE, DIAMOND AND FULLERENES" (published by Noyes Publications)). The degree of graphitization is highest at 100% for scaly graphite, followed by 99.9% for scaly graphite, but as low as 28% for soil graphite.

  The production area of scaly graphite, which is natural graphite, is Madagascar, China, Brazil, Ukraine, Canada, etc., and the production area of scaly graphite is mainly Sri Lanka. The main producers of soil graphite are the Korean Peninsula, China and Mexico.

  Among these natural graphites, soil graphite generally has a small particle size and low purity. On the other hand, scaly graphite and scaly graphite have advantages such as a high degree of graphitization and a low amount of impurities, and therefore can be preferably used in the present invention.

  The apparatus used for spheroidizing natural graphite has a rotor in which a large number of blades are installed inside a casing, and the rotor rotates at high speed, whereby impact compression, friction, It is a device that gives mechanical action such as shearing force and performs surface treatment. Note that the natural graphite to be subjected to the spheronization treatment may have already been subjected to a certain spheronization treatment under the conditions of the conventional method.

  Further, an apparatus having a mechanism for repeatedly supplying a mechanical action by circulating the raw material or performing the above-described steps a plurality of times is preferable. Preferable apparatuses include, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), a CF mill (manufactured by Ube Industries, Ltd.), a mechano-fusion system (manufactured by Hosokawa Micron Corporation), a theta composer (manufactured by Tokusu Kosakusha Co., Ltd.), and the like. Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable.

  The spheroidizing process is performed using such an apparatus. In this process, the rotational speed of the rotor is 5000 to 7000 rpm, preferably 5500 to 6500 rpm, 30 to 60 minutes, high speed rotation and long time spherical shape. Process.

The obtained particles are usually classified once, but if they are not within the specified physical property range of the present invention, they are classified repeatedly (usually 2 to 10 times, preferably 2 to 5 times). Thus, the average particle size (d50) is 1 μm or more and 9 μm or less, the tapping density is 0.9 g / cm ³ or more and 1.3 g / cm ³ or less, and the specific surface area (SA) measured by the BET method is 8 m ^2. It becomes easy to obtain small particle size spheroidized natural graphite having a particle size of not less than / g and not more than 60 m ² / g. Examples of the classification include dry (aerodynamic classification, sieving), wet classification, and the like, but dry classification, particularly aerodynamic classification is preferable from the viewpoint of cost and productivity.

  As described in [Background Art], when the carbon material is made to have a small particle size, it is expected that the specific surface area becomes large and the battery has a high output, but on the other hand, the tapping density of the carbon material cannot be increased. Even if the slurry containing the material cannot be applied to the current collector electrode plate, or even if it can be applied to the electrode plate, the electrode plate density will be lowered, resulting in a secondary battery with insufficient output and strength. There was a problem.

  From such conventional technical common sense, it is impossible to adopt a high-speed rotation / long-time spheronization process. Has found that by combining repeated classification treatments, it is possible to obtain graphite having a high tapping density while achieving a high specific surface area with a small particle size. In particular, from the viewpoint of demonstrating the effects of the present invention, the graphite used in the present invention is natural graphite (preferably scaly graphite or scaly graphite that has already undergone a certain spheroidizing treatment). Spheroidized natural graphite obtained by spheroidizing treatment) is preferred.

  In addition, if the rotational speed of the rotor is less than 5000 rpm, the process of forming a sphere is weak and the tapping density may not be sufficiently increased. On the other hand, if the rotation speed exceeds 7000 rpm, the effect of being crushed becomes stronger than the process of forming a sphere. There is a possibility that the tapping density is lowered due to collapse. Further, if the spheronization treatment is less than 30 minutes, the particle size is sufficiently reduced and a high tapping density cannot be achieved. On the other hand, if it exceeds 60 minutes, the graphite is shattered, and the object of the present invention is achieved. May not be achieved.

<Coating treatment>
As described above, the graphite used in the present invention can be obtained. The graphite may be coated with at least a part of its surface with a carbonaceous material. This coating mode can be confirmed by SEM photographs or the like.

(Carbonaceous material)
Examples of the carbonaceous material include amorphous carbon and graphitized material depending on the difference in heating temperature in the production method described later.

  Specifically, the carbonaceous material can be obtained by heat-treating the carbon precursor as described later. The carbon material described in the following (a) or (b) is preferable as the carbon precursor.

  (A) Coal heavy oil, DC heavy oil, cracked heavy oil, aromatic hydrocarbon, N ring compound, S ring compound, polyphenylene, organic synthetic polymer, natural polymer, thermoplastic resin and Carbonizable organic substance selected from the group consisting of thermosetting resins

  (B) Carbonized organic substance dissolved in a low molecular organic solvent

(Coating treatment)
In the coating treatment, coated graphite is obtained by using the above graphite as core graphite, using a carbon precursor for obtaining a carbonaceous material as a coating raw material, and mixing and firing these.

  When the firing temperature is usually 600 ° C. or higher, preferably 700 ° C. or higher, more preferably 900 ° C. or higher, usually 2000 ° C. or lower, preferably 1500 ° C. or lower, more preferably 1200 ° C. or lower, amorphous carbon is obtained as a carbonaceous material. When a heat treatment is usually performed at 2000 ° C. or higher, preferably 2500 ° C. or higher, and usually 3200 ° C. or lower, a graphitized product is obtained as a carbonaceous material. The amorphous carbon is carbon having low crystallinity, and the graphitized material is carbon having high crystallinity.

[Method for producing carbon material for non-aqueous secondary battery]
The carbon material for a non-aqueous secondary battery of the present invention may be composed of the above-described (coated) graphite alone, but may contain other components as described above.

  When other components are included, the carbon material of the present invention can be obtained by mixing this with (coated) graphite by a known method.

[Negative electrode for non-aqueous secondary battery]
The negative electrode for a non-aqueous secondary battery according to the present invention is a slurry obtained by blending the carbon material of the present invention with a binder resin in an aqueous or organic medium, and if necessary, a thickener is added to the collector and applied to a current collector. And drying to form an active material layer on the current collector.

  As the binder resin, it is preferable to use a resin that is stable with respect to the non-aqueous electrolyte and is water-insoluble. For example, rubbery polymers such as styrene-butadiene rubber, isoprene rubber and ethylene / propylene rubber; synthetic resins such as polyethylene, polypropylene, polyethylene terephthalate and aromatic polyamide; styrene / butadiene / styrene block copolymers and hydrogenated products thereof , Thermoplastic elastomers such as styrene / ethylene / butadiene, styrene copolymers, styrene / isoprene and styrene block copolymers and hydrides thereof; syndiotactic-1,2-polybutadiene, ethylene / vinyl acetate copolymers, and Soft resinous polymers such as copolymers of ethylene and C3-C12 α-olefins; polytetrafluoroethylene / ethylene copolymers, polyvinylidene fluoride, polypentafluoropropylene and polyhexene And fluorinated polymers such as hexafluoropropylene may be used.

  Examples of the organic medium include N-methylpyrrolidone and dimethylformamide.

  The binder resin is usually used in an amount of 0.1 parts by mass or more, preferably 0.2 parts by mass or more with respect to 100 parts by mass of the carbon material of the present invention. By setting the ratio of the binder resin to 0.1 parts by mass or more with respect to 100 parts by mass of the carbon material, the binding force between the carbon materials and between the carbon material and the current collector is sufficient, and the carbon material is removed from the negative electrode. It is possible to prevent a decrease in battery capacity and deterioration in recycling characteristics due to peeling.

  The binder resin is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, with respect to 100 parts by mass of the carbon material of the present invention. By setting the ratio of the binder resin to 10 parts by mass or less with respect to 100 parts by mass of the carbon material, it is possible to prevent a decrease in the capacity of the negative electrode and prevent problems such as preventing lithium ions from entering and exiting the carbon material. Can do.

  Examples of the thickener added to the slurry include water-soluble celluloses such as carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose, salts thereof, polyvinyl alcohol, polyethylene glycol and the like. Of these, carboxymethylcellulose is preferred. The thickener is preferably used in an amount of usually 0.1 to 10 parts by mass, preferably 0.2 to 7 parts by mass with respect to 100 parts by mass of the carbon material of the present invention.

  As the negative electrode current collector, for example, copper, copper alloy, stainless steel, nickel, titanium, and carbon that are conventionally known for use in this application can be used. The shape of the current collector is usually a sheet, and it is also preferable to use a surface with irregularities, a net, a punching metal, or the like.

After the slurry of the carbon material and the binder resin of the present invention is applied to the current collector and dried, the density of the negative electrode formed on the current collector is increased by pressurization, whereby the negative electrode layer per unit volume It is preferable to increase the battery capacity. The density of the negative electrode is preferably in a range of 1.2~1.8g / cm ^3, more preferably 1.3~1.6g / cm ^3.

By setting the density of the negative electrode to 1.2 g / cm ³ or more, it is possible to prevent a decrease in battery capacity accompanying an increase in the thickness of the negative electrode. In addition, by setting the negative electrode density to 1.8 g / cm ³ or less, the amount of electrolyte retained in the voids decreases as the interparticle voids in the negative electrode decrease, and the mobility of lithium ions decreases, resulting in rapid charge and discharge. It is possible to prevent the property from becoming smaller.

[Non-aqueous secondary battery]
Hereinafter, although the details of the member regarding the non-aqueous secondary battery using the negative electrode for non-aqueous secondary batteries of the present invention containing the carbon material of the present invention are exemplified, the materials that can be used and the method of production thereof are as follows. It is not limited to a specific example.

  The basic configuration of the non-aqueous secondary battery of the present invention is the same as that of a conventionally known non-aqueous secondary battery, and includes a positive electrode and a negative electrode capable of occluding and releasing lithium ions, and a non-aqueous electrolyte (including an electrolyte). The negative electrode is a negative electrode for a non-aqueous secondary battery according to the present invention. Hereinafter, each of these components will be described.

<Positive electrode>
The positive electrode is obtained by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current collector.

-Positive electrode active material The said positive electrode active material (lithium transition metal type compound) used for a positive electrode is described below.

・ Lithium transition metal compounds
The lithium transition metal-based compound is a compound having a structure capable of desorbing and inserting Li ions, and examples thereof include sulfides, phosphate compounds, and lithium transition metal composite oxides.

The sulfide is represented by a compound having a two-dimensional layered structure such as TiS ₂ or MoS ₂ or a general formula Me _x Mo ₆ S ₈ (Me is various transition metals including Pb, Ag, Cu). Examples include a chevrel compound having a strong three-dimensional skeleton structure.

Examples of the phosphate compound include those belonging to the olivine structure, which are generally represented by LiMePO ₄ (Me is at least one transition metal), specifically, LiFePO ₄ , LiCoPO ₄ , LiNiPO ₄ , Examples include LiMnPO ₄ .

Examples of the lithium transition metal composite oxide include spinel structures capable of three-dimensional diffusion and those belonging to a layered structure capable of two-dimensional diffusion of lithium ions. Those having a spinel structure are generally expressed as LiMe ₂ O ₄ (Me is at least one transition metal), specifically, LiMn ₂ O ₄ , LiCoMnO ₄ , LiNi _0.5 Mn _1.5 O _4. , LiCoVO _{4 and the} like. Those having a layered structure are generally expressed as LiMeO ₂ (Me is at least one transition metal). LiCoO _{2 Specifically, LiNiO 2, LiNi 1-x} Co x O 2, LiNi 1-x-y Co x Mn y O 2, LiNi 0.5 Mn 0.5 O 2, Li 1.2 Cr 0. _{4 Mn 0.4 O 2, Li 1.2} Cr 0.4 Ti 0.4 O 2, such as LiMnO ₂ and the like.

·composition
Moreover, as said lithium transition metal type compound, the lithium transition metal type compound shown by the following composition formula (A) or (B) is mentioned, for example.

1) In the case of a lithium transition metal compound represented by the following composition formula (A)
Li _{1 + x} MO ₂ (A)
However, x is usually 0 or more and 0.5 or less. M is an element composed of Ni and Mn or Ni, Mn and Co, and the Mn / Ni molar ratio is usually 0.1 or more and 5 or less. The Ni / M molar ratio is usually 0 or more and 0.5 or less. The Co / M molar ratio is usually 0 or more and 0.5 or less. In addition, the rich portion of Li represented by x may be replaced with the transition metal site M.

  In the composition formula (A), the atomic ratio of the oxygen amount is described as 2 for convenience, but there may be some non-stoichiometry. Moreover, x in the said compositional formula is the preparation composition in the manufacture stage of a lithium transition metal type compound. Usually, batteries on the market are aged after the batteries are assembled. For this reason, the amount of lithium in the positive electrode may be deficient with charge and discharge. In this case, x may be measured to be −0.65 or more and 1 or less when discharged to 3 V in composition analysis.

  In addition, as the lithium transition metal compound, those obtained by firing at a high temperature in an oxygen-containing gas atmosphere in order to enhance the crystallinity of the positive electrode active material are excellent in battery characteristics.

Furthermore, the lithium transition metal-based compound represented by the composition formula (A) may be a solid solution with Li ₂ MO ₃ called a 213 layer as shown in the following general formula (A ′).
αLi ₂ MO ₃ · (1-α) LiM′O ₂ (A ′)

  In the general formula, α is a number satisfying 0 <α <1.

M is at least one metallic element average oxidation number of 4 ^+, specifically, at least one metal element Mn, Zr, Ti, Ru, selected from the group consisting of Re and Pt.

M 'is at least one metallic element average oxidation number of 3 ^+, preferably, V, Mn, Fe, at least one metallic element selected from the group consisting of Co and Ni, more preferably , At least one metal element selected from the group consisting of Mn, Co and Ni.

2) A lithium transition metal compound represented by the following composition formula (B).
_{Li [Li a M b Mn 2} -b-a] O 4 + δ ··· (B)

  However, M is an element comprised from at least 1 sort (s) of the transition metals chosen from Ni, Cr, Fe, Co, Cu, Zr, Al, and Mg.

  The value of b is usually 0.4 or more, preferably 0.6 or less.

  If the value of b is this range, the energy density per unit mass in a lithium transition metal type compound will be high.

  The value of a is usually 0 or more, preferably 0.3 or less. Moreover, a in the above composition formula is a charged composition in the production stage of the lithium transition metal compound. Usually, batteries on the market are aged after the batteries are assembled. For this reason, the Li amount of the positive electrode may be deficient with charge / discharge. In this case, a may be measured to be −0.65 or more and 1 or less when discharged to 3 V in composition analysis.

  When the value of a is within this range, the energy density per unit mass in the lithium transition metal compound is not significantly impaired, and good load characteristics can be obtained.

  Furthermore, the value of δ is usually in the range of −0.5 to 0.5.

  If the value of δ is within this range, the stability as a crystal structure is high, and the cycle characteristics and high-temperature storage of a battery having an electrode produced using this lithium transition metal compound are good.

  Here, the chemical meaning of the lithium composition in the lithium nickel manganese composite oxide, which is the composition of the lithium transition metal compound, will be described in more detail below.

  In order to obtain a and b in the composition formula of the lithium transition metal compound, each transition metal and lithium are analyzed with an inductively coupled plasma emission spectrometer (ICP-AES) to obtain a ratio of Li / Ni / Mn. It is calculated by the thing.

  From a structural point of view, it is considered that lithium related to a is substituted for the same transition metal site. Here, due to the lithium according to a, the average valence of M and manganese becomes larger than 3.5 due to the principle of charge neutrality.

Further, the lithium transition metal based compound may be substituted with fluorine, it is expressed as _{LiMn 2 O 4-x F 2x} .

Blend As specific examples of the lithium transition metal-based compound having the above composition, for example, Li _{1 + x} Ni _0.5 Mn _0.5 O ₂ , Li _{1 + x} Ni _0.85 Co _0.10 Al _0.05 O ₂ , Li _{1 + x} Ni _0.33 Mn _0.33 Co _0.33 O ₂ , Li _{1 + x} Ni _0.45 Mn _0.45 Co _0.1 O ₂ , Li _{1 + x} Mn _1.8 Al _0.2 O ₄ , Li _{1 + x} Mn _{1 .5} Ni _0.5 O ₄ and the like (the value of x is as described above). These lithium transition metal compounds may be used alone or in a blend of two or more.

-Introduction of a different element A different element may be introduced into the lithium transition metal compound. As the different elements, B, Na, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Sr, Y, Zr, Nb, Ru, Rh, Pd, Ag, In, Sb, Te , Ba, Ta, Mo, W, Re, Os, Ir, Pt, Au, Pb, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Bi , N, F, S, Cl, Br, I, As, Ge, P, Pb, Sb, Si, and Sn. These foreign elements may be incorporated into the crystal structure of the lithium transition metal compound, or may not be incorporated into the crystal structure of the lithium transition metal compound, and may be a single element or compound on the particle surface or grain boundary. May be unevenly distributed.

・ Positive electrode for non-aqueous secondary battery The positive electrode for non-aqueous secondary battery is a collection of positive electrode active material layers containing the above-mentioned lithium transition metal compound powder for non-aqueous secondary battery positive electrode material and a binder. It is formed on an electric body.

  The positive electrode active material layer is usually formed by mixing a positive electrode material, a binder, and a conductive material and a thickener, which are used as necessary, in a dry form into a sheet shape, and then pressing the positive electrode current collector on the positive electrode current collector. Alternatively, these materials are dissolved or dispersed in a liquid medium to form a slurry, which is applied to the positive electrode current collector and dried.

  As the positive electrode current collector, metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum, and carbon materials such as carbon cloth and carbon paper are usually used. In addition, as the shape of the current collector, in the case of a metal material, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punch metal, a foam metal shape, etc. , Carbon thin film, carbon columnar shape and the like. The metal thin film and the carbon thin film may be appropriately formed in a mesh shape.

  When a thin film is used as the positive electrode current collector, its thickness is arbitrary, but a range of usually 1 μm or more and 100 mm or less is suitable. If it is thinner than the above range, the strength required for the current collector may be insufficient. On the other hand, if it is thicker than the above range, the handleability may be impaired.

  Further, the ratio of the thickness of the current collector to the active material layer is not particularly limited, but the value of (thickness of active material layer on one side immediately before electrolyte injection) / (thickness of current collector) is 150. Hereinafter, it is preferably 20 or less, more preferably 10 or less, and the lower limit is 0.1 or more, preferably 0.4 or more, more preferably 1 or more. Above this range, the current collector may generate heat due to Joule heat during high current density charge / discharge. On the other hand, below this range, the volume ratio of the current collector to the carbon material increases, and the battery capacity may decrease.

  The binder used for the production of the positive electrode active material layer is not particularly limited, and in the case of the coating method, any material that is stable with respect to the liquid medium used at the time of electrode production may be used. , Polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose and other resin polymers, SBR (styrene butadiene rubber), NBR (acrylonitrile butadiene rubber), fluorine rubber, isoprene rubber, butadiene rubber, Rubbery polymers such as ethylene / propylene rubber, styrene / butadiene / styrene block copolymers and hydrogenated products thereof, EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene / butadiene / ethylene copolymers , Styrene and isoprene styrene Thermoplastic elastomeric polymers such as lock copolymers and their hydrogenated products, syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene / vinyl acetate copolymers, propylene / α-olefin copolymers, etc. Fluorine polymers such as soft resinous polymers, polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoroethylene / ethylene copolymers, ion conductivity of alkali metal ions (especially lithium ions) And a polymer composition having the same. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The ratio of the binder in the positive electrode active material layer is usually 0.1% by mass or more and 80% by mass or less. If the proportion of the binder is too low, the positive electrode active material cannot be sufficiently retained, and the mechanical strength of the positive electrode is insufficient, and the battery performance such as cycle characteristics may be deteriorated. Battery capacity and conductivity may be reduced.

  The positive electrode active material layer usually contains a conductive material in order to increase conductivity. There are no particular restrictions on the type, but specific examples include metal materials such as copper and nickel, graphite such as natural graphite and artificial graphite, carbon black such as acetylene black, and amorphous carbon such as needle coke. And carbon materials. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio. The proportion of the conductive material in the positive electrode active material layer is usually 0.01% by mass or more and 50% by mass or less. If the proportion of the conductive material is too low, the conductivity may be insufficient, and conversely if it is too high, the battery capacity may be reduced.

  The liquid medium for forming the slurry for forming the positive electrode active material layer includes a lithium transition metal compound powder as a positive electrode material, a binder, and a conductive material and a thickening agent as required. If it is a solvent which can melt | dissolve or disperse | distribute a material, there will be no restriction | limiting in particular, Either an aqueous solvent or an organic solvent may be used. Examples of the aqueous solvent include water and alcohol. Examples of the organic solvent include N-methylpyrrolidone (NMP), dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, N , N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran (THF), toluene, acetone, dimethyl ether, dimethylacetamide, hexamethylphosphalamide, dimethyl sulfoxide, benzene, xylene, quinoline, pyridine, methylnaphthalene, hexane, etc. be able to. In particular, when an aqueous solvent is used, it is preferable to add a dispersant together with the thickener and slurry it using a latex such as SBR. In addition, these solvents may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The content ratio of the lithium transition metal-based compound powder as the positive electrode material in the positive electrode active material layer is usually 10% by mass or more and 99.9% by mass or less. If the proportion of the lithium transition metal compound powder in the positive electrode active material layer is too large, the strength of the positive electrode tends to be insufficient, and if it is too small, the capacity may be insufficient.

  The thickness of the positive electrode active material layer is usually about 10 to 200 μm.

The electrode density after pressing of the positive electrode is usually 2.2 g / cm ³ or more and 4.2 g / cm ³ or less.

The positive electrode active material layer obtained by coating and drying is preferably consolidated by a roller press or the like in order to increase the packing density of the positive electrode active material.
Thus, a positive electrode for a non-aqueous secondary battery can be prepared.

<Electrolyte>
There is no restriction | limiting in the electrolyte used for the non-aqueous electrolyte in the non-aqueous secondary battery of this invention, The well-known thing used as an electrolyte can be employ | adopted arbitrarily and can be contained. The electrolyte is preferably a lithium salt. Specific examples of the electrolyte include LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , lithium bis (oxalato) borate, lithium difluorooxalatoborate. Lithium tetrafluorooxalato phosphate, lithium difluorobis (oxalato) phosphate, lithium fluorosulfonate, and the like. These electrolytes may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The concentration of the lithium salt in the non-aqueous electrolyte is arbitrary, but is usually 0.5 mol / L or more, preferably 0.6 mol / L or more, more preferably 0.8 mol / L or more, and usually 3 mol / L or less. , Preferably 2 mol / L or less, more preferably 1.5 mol / L or less. When the total molar concentration of the lithium salt is within the above range, the electrical conductivity of the nonaqueous electrolytic solution becomes sufficient, while the decrease in electrical conductivity due to increase in viscosity and the decrease in battery performance can be prevented.

<Non-aqueous solvent>
The non-aqueous solvent contained in the non-aqueous electrolyte solution is not particularly limited as long as it does not adversely affect the battery characteristics when used as a battery. Examples of commonly used non-aqueous solvents include dimethyl Carbonates, chain carbonates such as ethyl methyl carbonate and diethyl carbonate, cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate, chain carboxylates such as methyl acetate, ethyl acetate, methyl propionate and ethyl propionate, γ- Cyclic carboxylic acid esters such as butyrolactone, chain ethers such as dimethoxyethane and diethoxyethane, cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran and tetrahydropyran, acetonitrile, propionitrile, benzonitrile, Examples include nitriles such as tyronitrile and valeronitrile, phosphate esters such as trimethyl phosphate and triethyl phosphate, sulfur-containing compounds such as ethylene sulfite, 1,3-propane sultone, methyl methanesulfonate, sulfolane, and dimethyl sulfone. In these compounds, hydrogen atoms may be partially substituted with halogen atoms.

  These may be used alone or in combination of two or more, but it is preferable to use two or more compounds in combination. For example, it is preferable to use a high dielectric constant solvent such as cyclic carbonate or cyclic carboxylic acid ester in combination with a low viscosity solvent such as chain carbonate or chain carboxylic acid ester.

  Here, the high dielectric constant solvent means a compound having a relative dielectric constant of 20 or more at 25 ° C. Among the high dielectric constant solvents, it is preferable that ethylene carbonate, propylene carbonate, and compounds in which hydrogen atoms thereof are substituted with other elements such as halogen or alkyl groups are contained in the electrolytic solution. The proportion of the high dielectric constant solvent in the non-aqueous electrolyte is preferably 15% by mass or more, more preferably 20% by mass or more, and most preferably 25% by mass or more. If the content of the high dielectric constant solvent is less than the above range, desired battery characteristics may not be obtained.

<Auxiliary>
In addition to the above-described electrolyte and non-aqueous solvent, an auxiliary may be appropriately added to the non-aqueous electrolyte depending on the purpose. As an auxiliary agent that has the effect of improving the battery life in order to form a film on the negative electrode surface, unsaturated cyclic carbonates such as vinylene carbonate, vinyl ethylene carbonate, and ethynyl ethylene carbonate, and cyclic compounds having fluorine atoms such as fluoroethylene carbonate Examples thereof include fluorinated unsaturated cyclic carbonates such as carbonate and 4-fluorovinylene carbonate.

  Biphenyl, cyclohexylbenzene, diphenyl ether, t-butylbenzene, t-pentylbenzene, diphenyl carbonate, methyl as an overcharge inhibitor that effectively suppresses battery explosion and ignition when the battery is overcharged. Examples include aromatic compounds such as phenyl carbonate.

  Lithium monofluorophosphate, lithium difluorophosphate, lithium fluorosulfonate, lithium bis (oxalato) borate, lithium difluorooxalatoborate, lithium tetrafluorooxalatophosphate as auxiliary agents to improve battery cycle characteristics and low temperature discharge characteristics And lithium salts such as lithium difluorobis (oxalato) phosphate.

  As auxiliary agents that can improve capacity maintenance characteristics and cycle characteristics after high-temperature storage, sulfur-containing compounds such as ethylene sulfite, propane sultone, propene sultone, carboxylic acids such as succinic anhydride, maleic anhydride, and citraconic anhydride Examples include nitrile compounds such as anhydride, succinonitrile, glutaronitrile, adiponitrile, and pimelonitrile.

  The amount of these auxiliaries is not particularly limited, and is arbitrary as long as the effects of the present invention are not significantly impaired.

<Separator>
Usually, a separator is interposed between the positive electrode and the negative electrode in order to prevent a short circuit. In this case, the non-aqueous electrolyte described above is usually used by impregnating the separator.

  The material and shape of the separator are not particularly limited, and known ones can be arbitrarily adopted as long as the effects of the present invention are not significantly impaired. Among them, a resin, glass fiber, inorganic material, or the like formed of a material that is stable with respect to the non-aqueous electrolyte solution is used, and it is preferable to use a porous sheet or a nonwoven fabric-like material excellent in liquid retention.

  As materials for the resin and glass fiber separator, for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, glass filters and the like can be used. Of these, glass filters and polyolefins are preferred, and polyolefins are more preferred. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  The thickness of the separator is arbitrary, but is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less. If the separator is too thin than the above range, the insulating properties and mechanical strength may decrease. On the other hand, if it is thicker than the above range, not only the battery performance such as the rate characteristic may be lowered, but also the energy density of the whole non-aqueous electrolyte secondary battery may be lowered.

  Furthermore, when using a porous material such as a porous sheet or nonwoven fabric as the separator, the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, more preferably 45% or more, Further, it is usually 90% or less, preferably 85% or less, and more preferably 75% or less. If the porosity is too smaller than the above range, the membrane resistance tends to increase and the rate characteristics tend to deteriorate. Moreover, when larger than the said range, it exists in the tendency for the mechanical strength of a separator to fall and for insulation to fall.

  Moreover, although the average pore diameter of a separator is also arbitrary, it is 0.5 micrometer or less normally, 0.2 micrometer or less is preferable, and it is 0.05 micrometer or more normally. If the average pore diameter exceeds the above range, a short circuit tends to occur. On the other hand, below the above range, the film resistance may increase and the rate characteristics may deteriorate.

  On the other hand, as inorganic materials, for example, oxides such as alumina and silicon dioxide, nitrides such as aluminum nitride and silicon nitride, and sulfates such as barium sulfate and calcium sulfate are used. Used.

  As a form of these materials in a separator, thin film shapes, such as a nonwoven fabric, a woven fabric, and a microporous film, are mentioned. In the thin film shape, those having a pore diameter of 0.01 to 1 μm and a thickness of 5 to 50 μm are preferably used. In addition to the above-described independent thin film shape, a separator formed by forming a composite porous layer containing the inorganic particles on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used. Examples of such a separator include a separator in which a porous layer made of alumina particles having a 90% particle size of less than 1 μm is formed on both surfaces of a positive electrode using a fluororesin as a binder.

  The characteristics of the separator in the non-aqueous secondary battery can be grasped by the Gurley value. The Gurley value indicates the difficulty of air passage in the film thickness direction, and is expressed as the number of seconds required for 100 ml of air to pass through the film. It means that it is harder to go through. That is, a smaller value means better communication in the thickness direction of the film, and a larger value means poor communication in the thickness direction of the film. Communication is the degree of connection of holes in the film thickness direction. If the Gurley value of the separator is low, it can be used for various purposes. For example, when used as a separator for a non-aqueous secondary battery, a low Gurley value means that lithium ions can be easily transferred and is preferable because of excellent battery performance.

  Although the Gurley value of a separator is arbitrary, Preferably it is 10-1000 second / 100ml, More preferably, it is 15-800 second / 100ml, More preferably, it is 20-500 second / 100ml. If the Gurley value is 1000 seconds / 100 ml or less, the electrical resistance is substantially low, which is preferable as a separator.

<Battery design>
-Electrode group The electrode group has either a laminated structure in which the positive electrode and the negative electrode are interposed via the separator, and a structure in which the positive electrode and the negative electrode are spirally wound through the separator. But you can. The ratio of the volume of the electrode group to the internal volume of the battery (hereinafter referred to as the electrode group occupation ratio) is usually 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less. .

  When the electrode group occupancy is below the above range, the battery capacity decreases. Also, if the above range is exceeded, the void space is small, the battery expands, and the member expands or the vapor pressure of the electrolyte liquid component increases and the internal pressure rises. In some cases, the gas release valve that lowers various characteristics such as storage at high temperature and the like, or releases the internal pressure to the outside is activated.

<Exterior case>
The material of the outer case is not particularly limited as long as it is a substance that is stable with respect to the non-aqueous electrolyte used. Specifically, a nickel-plated steel plate, stainless steel, aluminum, an aluminum alloy, a metal such as a magnesium alloy, or a laminated film (laminate film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, an aluminum or aluminum alloy metal or a laminate film is preferably used.

  In an exterior case using metals, the metal is welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed sealed structure, or a caulking structure using the above metals via a resin gasket. Things. Examples of the outer case using the laminate film include a case where a resin-sealed structure is formed by heat-sealing resin layers. In order to improve sealing performance, a resin different from the resin used for the laminate film may be interposed between the resin layers. In particular, when the resin layer is heat-sealed through a current collecting terminal to form a sealed structure, since the metal and the resin are joined, a modification having a polar group or a polar group introduced as the intervening resin Resins are preferably used.

<Protective element>
As a protective element, PTC (Positive Temperature Coefficient) thermistor that increases in resistance when abnormal heat generation or excessive current flows, thermal fuse, shuts off the current flowing through the circuit due to sudden increase in battery internal pressure or internal temperature during abnormal heat generation A valve (current cutoff valve) or the like can be used. It is preferable to select a protective element that does not operate under normal use at a high current, and it is more preferable that the protective element is designed so as not to cause abnormal heat generation or thermal runaway even without the protective element.

  EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

  In this example, the particle size, tapping density, BET specific surface area (SA), X-ray wide-angle diffraction measurement, orientation ratio, and DBP oil absorption were measured by the methods described below.

<Particle size>
A commercially available laser diffraction / scattering type is prepared by suspending 0.01 g of a carbon material in 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) as a surfactant. The sample was introduced into a particle size distribution measuring apparatus “LA-920 manufactured by HORIBA” and irradiated with an ultrasonic wave of 28 kHz at an output of 60 W for 1 minute, and then the volume-based particle size distribution in the measuring apparatus was measured.

  From the measurement result of the particle size distribution, the average particle size (d50), d10 particle size of 10% integration part, d90 particle size of d90 integration part, and dmax were obtained. The measurement conditions are an ultrasonic dispersion of 1 minute, an ultrasonic intensity of 2, a circulation speed of 2, and a relative refractive index of 1.50.

<Tapping density>
Tapping density is measured by using a powder density meter (powder tester PT-N manufactured by Hosokawa Micron Corporation). A cap is attached to a cylindrical tap cell having a diameter of 5 cm and a volume capacity of 100 cm ³ , and the sample is dropped through a sieve to fill the cell. Then, taps with a stroke length of 18 mm were performed 500 times.

The cap was removed from the cylindrical tap cell, and the sample raised in the upper part of the cell volume capacity of 100 cm ³ was ground. The density obtained from the volume at this time and the weight of the sample is defined as the tapping density.

<BET specific surface area (SA)>
Micromeritics Gemini 2360 was used. Under nitrogen flow, the sample was pre-dried at 350 ° C. for 10 minutes, and after flowing nitrogen gas for 5 minutes, the specific surface area of the sample was measured by the BET 6-point method by nitrogen gas adsorption.

<X-ray wide angle diffraction measurement>
About 15% X-ray standard high-purity silicon powder is added to the sample and mixed. The sample is CuKα ray monochromatized with a graphite monochromator. The wide-angle X-ray of the sample is reflected using a reflection diffractometer method. The diffraction curve was measured, and the interplanar spacing (d002) and crystallite size (Lc) of the sample were determined using the Gakushin method.

<Orientation ratio>
The orientation ratio was measured by X-ray diffraction after pressure-molding the sample. Set the molding obtained by filling 0.47 g of the sample into a molding machine with a diameter of 17 mm and compressing it with 58.8 MN · m ^{-2 so} that it is flush with the surface of the sample holder for measurement. X-ray diffraction was measured. From the (110) diffraction and (004) diffraction peak intensities of the obtained carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity was calculated. The orientation ratio calculated by the measurement is defined as the orientation ratio of the carbon material of the present invention.

The X-ray diffraction measurement conditions are as follows. “2θ” indicates a diffraction angle.
・ Target: Cu (Kα ray) graphite monochromator ・ Slit:
Divergence slit = 0.5 degree Light receiving slit = 0.15 mm
Scattering slit = 0.5 degree / measurement range and step angle / measurement time:
(110) plane: 75 degrees ≦ 2θ ≦ 80 degrees 1 degree / 60 seconds (004) plane: 52 degrees ≦ 2θ ≦ 57 degrees 1 degree / 60 seconds

<DBP oil absorption>
The DBP oil absorption amount in the present invention is based on JIS 6217, and 30 g of a measurement sample was introduced (measured at 20 g because only the scale-like natural graphite (C) has a low bulk density), and the dropping rate of DBP (dibutyl phthalate) The measurement was performed at 4 ml / min and a rotation speed of 125 rpm. The measured value is defined by the amount of oil absorption that results in a torque that is 70% of the peak torque value. For the measurement, S410 type manufactured by Asahi Soken Co., Ltd. was used.

[Comparative Example 1]
Non-aqueous secondary by the following method using spherical natural graphite (A) made in China with an average particle size of 11.4 μm, BET specific surface area of 8.2 m ² / g and tapping density of 0.84 g / cm ^3. A battery was prepared and evaluated. A SEM photograph of spheroidized natural graphite (A) is shown in FIG.

[Example 1]
(Production of spheroidized natural graphite (B))
150 g of Chinese spheroidized natural graphite (A) of Comparative Example 1 is treated under the conditions of a rotation speed of 6000 rpm for 40 minutes using a hybridization system (NHS-1 type) manufactured by Nara Machinery Co., Ltd. Thus, advanced spheronization treatment was performed while damaging the graphite particle surface, and fine powder removal was further repeated (5 times) by classification treatment.

The obtained spheroidized natural graphite (B) has a 002 plane spacing (d002) of 3.36 mm by X-ray wide-angle diffraction measurement, a crystallite size (Lc) of 100 nm or more, and a tapping density of 0.94 g / cm ^3. The average particle size was 6.9 μm, the BET specific surface area was 15.2 m ² / g, and the orientation ratio was 0.18.

  Using this spheroidized natural graphite (B), a non-aqueous secondary battery was produced and evaluated by the following method. An SEM photograph of spheroidized natural graphite (B) is shown in FIG.

[Comparative Example 2]
An attempt was made to produce a non-aqueous secondary battery using as it is, Chinese scale-like natural graphite (C) having an average of 5.1 μm, a BET specific surface area of 15.3 m ² / g, and a tapping density of 0.43 g / cm ³ . An SEM photograph of scale-like natural graphite (C) is shown in FIG.

[・ Production of non-aqueous secondary batteries]
(<Production of negative electrode>)
97.7 parts by mass of natural graphite of Example or Comparative Example, 130 parts by mass of aqueous dispersion of sodium carboxymethylcellulose (concentration of 1% by mass of sodium carboxymethylcellulose) as a thickener and binder, and styrene-butadiene rubber Aqueous dispersion (concentration of styrene-butadiene rubber 40% by mass) of 2.5 parts by mass was added and mixed with a rotation / revolution mixer to form a slurry.

The obtained slurry was applied to both sides of a 10 μm rolled copper foil, dried, and rolled to 75 μm with a press machine. The active material layer size was 30 mm in width, 40 mm in length, and was not used as a current collector tab weld. It cut out in the shape which has a coating part, and was set as the negative electrode. At this time, the density of the active material of the negative electrode was 1.35 g / cm ³ .

  At this time, the scaly natural graphite (C) of Comparative Example 2 peels off due to a large amount of granular agglomeration on the slurry-coated surface and a low binding strength between the negative electrode active material and the current collector. Could not be created. Moreover, the SEM photograph of the negative electrode produced using the graphite of Example 1 and Comparative Example 1 is shown in FIGS. 4 and 5, respectively.

(<Preparation of positive electrode>)
The positive electrode active material is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by the composition formula LiMn _0.33 Ni _0.33 Co _0.33 O ₂ .

Mn ₃ O ₄ as a manganese raw material, NiO as a nickel raw material, and Co (OH) ₂ as a cobalt raw material are weighed so as to have a molar ratio of Mn: Ni: Co = 1: 1: 1, and pure water is added thereto. In addition, it was made into a slurry, and the solid content in the slurry was wet-pulverized so that the average particle size (d50) was 0.2 μm using a circulating medium stirring type wet bead mill while stirring.

  The slurry was spray-dried with a spray drier to obtain substantially spherical granulated particles having an average particle diameter of about 5 μm and consisting only of a manganese raw material, a nickel raw material, and a cobalt raw material.

  To the obtained granulated particles, LiOH powder having an average particle size of 3 μm was added so that the ratio of the number of moles of Li to the total number of moles of Mn, Ni, and Co was 1.05, and a high speed mixer was used. By mixing, a mixed powder of granulated particles of nickel raw material, cobalt raw material, manganese raw material and lithium raw material was obtained.

This mixed powder was fired at 950 ° C. for 12 hours under air flow (climbing temperature rate 5 ° C./min), then crushed and passed through a sieve having an opening of 45 μm to obtain a positive electrode active material. This positive electrode active material had a BET specific surface area of 1.2 m ² / g, an average primary particle size of 0.8 μm, an average particle size of 4.4 μm, and a tapping density of 1.6 g / cm ³ .

  90% by mass of this positive electrode active material, 5% by mass of acetylene black as a conductive material, and 5% by mass of polyvinylidene fluoride (PVdF) as a binder are mixed in an N-methylpyrrolidone solvent to obtain a slurry. Turned into.

  The obtained slurry was applied to an aluminum foil (current collector) having a thickness of 15 μm, dried, and rolled to a thickness of 81 μm with a press machine. The positive electrode active material layer had a width of 30 mm, a length of 40 mm and a current collector. A positive electrode was cut out into a shape having an uncoated part.

The density of the positive electrode active material layer was 2.35 g / cm ³ and (thickness of the positive electrode active material layer on one side) / (thickness of the current collector) was 2.2.

(<< Preparation of non-aqueous electrolyte >>)
Hexafluoroline sufficiently dried at a concentration of 1 mol / L in a mixture (volume ratio 3: 3: 4) of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) under an inert atmosphere Lithium acid (LiPF ₆ ) was dissolved to obtain a non-aqueous electrolyte.

(<< Preparation of non-aqueous secondary battery >>)
One positive electrode and one negative electrode were disposed so that the active material surfaces face each other, and a porous polyethylene sheet separator (25 μm) was sandwiched between the electrodes. At this time, the positive electrode active material surface was opposed so as not to be separated from the negative electrode active material carbon material surface.

  A current collector tab was welded to the uncoated part of each of the positive electrode and the negative electrode to form an electrode body, and a laminate sheet (total of a polypropylene film, an aluminum foil having a thickness of 0.04 mm, and a nylon film laminated in this order) With a thickness of 0.1 mm), the polypropylene film was sandwiched between laminate sheets so that the polypropylene film came to the side in contact with the electrode body. Except for the piece for injecting the electrolyte, the area without the electrode was heat sealed.

  Thereafter, 200 μL of a non-aqueous electrolyte was injected into the active material layer to sufficiently penetrate the electrode, and the laminate was sealed to prepare a laminate cell. The rated capacity of this battery is 20 mAh.

<< Measurement method of electrode plate strength >>
The negative electrode before rolling produced in the production of the negative electrode is cut into a width of 20 mm, and is attached to a test SUS plate with a double-sided tape (the active material layer side is attached with a double-sided tape) and fixed in the horizontal direction. The end of was sandwiched between the clamps of the universal testing machine. In this state, the end of the negative electrode of the universal testing machine was lowered in the vertical direction, and the negative electrode was peeled off by pulling it from the double-sided tape while maintaining an angle of 90 degrees. At this time, the average value of the load applied between the negative electrode and the double-sided tape was measured, and the value divided by the negative electrode sample width (20 mm) was defined as the electrode plate strength (mN / mm).

<< Battery evaluation >>
(Capacity measurement)
Compared to the non-aqueous secondary battery produced above, which has not undergone a charge / discharge cycle, a voltage range of 4.1 V to 3.0 V at 25 ° C., a current value of 0.2 C (a rated capacity based on a discharge capacity of 1 hour rate is 1 Two cycles of initial charge / discharge were performed at a current value of 1 C discharged over time, the same applies hereinafter.

  At this time, constant voltage charging was performed at 4.1 V for 2.5 hours during charging. Further, the battery was charged at 0.2 C to 4.1 V, charged at a constant voltage of 4.1 V for 2.5 hours, and then discharged to 3.0 V at a current value of 0.33 C. Then, output measurement was performed.

(Output measurement)
The battery was charged for 150 minutes at a constant current of 0.2 C in a 25 ° C. environment, and then stored in a thermostatic bath at −30 ° C. for 3 hours or more, and then 0.25 C, 0.50 C, 0 .75C, 1.00C, 1.25C, 1.50C, 1.75C, 2.00C were discharged for 2 seconds, and the voltage at the time point of 2 seconds was measured.

  From this measurement result, the area of a triangle surrounded by the current-voltage straight line and the lower limit voltage (3 V) was defined as output (W).

  The physical properties of the natural graphites (A) to (C) used in the above evaluation results and Examples and Comparative Examples are shown in Tables 1 and 2 below.

Claims (7)

The average particle diameter (d50) measured using a laser diffraction particle size distribution meter is 1 μm or more and 9 μm or less, and the tapping density is 0.9 g / cm ³ or more and 1.3 g / cm ³ or less, measured by the BET method. nonaqueous secondary battery carbon material with specific surface area (SA) comprises a graphite or less 8m ² / g or more 60 m ² / g.   The carbon material for a non-aqueous secondary battery according to claim 1, wherein a crystallite size (Lc) obtained by X-ray wide-angle diffraction measurement by the Gakushin method of graphite is 100 nm or more.   3. The carbon material for a non-aqueous secondary battery according to claim 1, wherein a ratio of d90 / d10 of the graphite is 1 or more and 4 or less (where d90 is measured by a laser diffraction particle size distribution meter of the graphite). The particle size of the 90% cumulative part from the small particle side, and d10 is the particle size of the 10% cumulative part from the small particle side measured by the laser diffraction particle size distribution meter of the graphite.   4. The carbon material for a non-aqueous secondary battery according to claim 1, wherein the graphite has an average particle diameter (d50) of 3 μm or more and 8.5 μm or less.   The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 4, wherein the graphite is spheroidized natural graphite.   A current collector and an active material layer formed on the current collector, the active material layer including the carbon material for a non-aqueous secondary battery according to any one of claims 1 to 5. A negative electrode for a non-aqueous secondary battery. A non-aqueous secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte,
A nonaqueous secondary battery, wherein the negative electrode is a negative electrode for a nonaqueous secondary battery according to claim 6.