JP2014067639A - Carbon material for nonaqueous secondary battery, negative electrode for nonaqueous secondary battery, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode material for a nonaqueous secondary battery, reduced in deterioration in cycles by being suppressed in a side reaction with an electrolyte, high in capacity, and excellent in cycle characteristics and rate characteristics.SOLUTION: A carbon material for a nonaqueous secondary battery, which includes metal fine particles (B) and a composite carbon material (A) including a carbon material (a) subjected to pressurization treatment and coated with a carbonaceous substance or a graphite substance, is manufactured.

Description

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

In recent years, demand for high-capacity secondary batteries has increased with the downsizing of electronic devices. In particular, lithium ion secondary batteries having higher energy density and excellent large current charge / discharge characteristics have attracted attention as compared to nickel / cadmium batteries and nickel / hydrogen batteries.
As a carbon material for a negative electrode of a lithium ion secondary battery, a graphite material or amorphous carbon is often used from the viewpoint of cost and durability. However, the amorphous carbon material has a small reversible capacity within the range of materials that can be put to practical use, and the graphite material breaks down when the active material layer containing the carbon material is densified to increase the capacity. As a result, the irreversible charge / discharge capacity at the initial cycle increases, and as a result, there is a problem that the capacity cannot be increased.

In order to solve the above-mentioned problem, for example, Patent Document 1 discloses a carbon material for a lithium ion secondary battery containing isotropic graphite that is isotropically pressurized and densified. A manufacturing method is disclosed.
Patent Document 2 discloses a method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery obtained by mixing graphite and a carbon precursor and then firing and combining them.

Further, Patent Document 3 discloses a method for producing a carbon powder for a negative electrode of a lithium secondary battery in which carbon powder is isotropically pressurized.
Patent Document 4 is characterized in that a coating layer made of carbide is formed on the surface of pressurized graphite particles in which at least one of natural graphite spheroidized particles and natural graphite agglomerated particles is subjected to pressure treatment. A graphite material for a lithium ion secondary battery is disclosed.
On the other hand, Patent Document 5 proposes using silicon oxide as a negative electrode material together with a carbon material in order to improve the capacity. The average Patent Document 6, in order to maintain a high capacity, by a mechanical surface fusion treatment, the average particle diameter d ₅₀ of the SiO _x powder 0.2~20μm as nuclei, the surface of the core A negative electrode material has been proposed that includes conductive SiO _x powder covered with a conductive material such as artificial graphite having a particle size d ₅₀ of 20 nm to 13 μm, and graphite.

Japanese Patent Laying-Open No. 2005-50807 JP 2010-165580 A Japanese Patent No. 3528671 JP 2011-060465 A JP 11-31518 A JP 2002-373653 A

However, according to the study by the present inventors, Patent Document 1 describes a lithium ion secondary battery that has high graphite density by isotropic pressurization of spheroidized graphite and is excellent in load characteristics, cycle characteristics, and the like. However, this method has room for improvement because the surface structure of graphite is destroyed.
In the technique described in Patent Document 2, there is a description of a non-aqueous electrolyte secondary battery that exhibits high output characteristics excellent in cycle characteristics using a negative electrode active material obtained by mixing graphite and a carbon precursor and then firing and combining them. Therefore, further improvement in cycle characteristics was necessary.

  In Patent Document 3, the fluidity of the carbon powder for the negative electrode is improved by subjecting the carbon powder to isotropic pressure treatment, and the density variation is reduced, so that the adhesion with the current collector is improved. It is disclosed that carbon powder for negative electrode can be manufactured. And although there exists description that the cycle characteristic of a lithium secondary battery improves by using this carbon powder for negative electrodes, since the surface structure of graphite was destroyed in this method, there was room for improvement.

Further, in Patent Document 4, a lithium ion secondary in which a coating layer made of carbide is formed on the surface of pressurized graphite particles in which at least one of natural graphite spheroidized particles and natural graphite agglomerated particles is subjected to pressure treatment. Although a graphite material for a battery is disclosed, such a carbon material does not satisfy the required performance of the market.
In Patent Document 5, natural graphite is used as graphite, and the capacity is increased by addition of Si oxide, but the graphite is not densified by pressurization, and an amorphous carbon layer is formed on the graphite surface. Therefore, high capacity and high rate characteristics have not been achieved.
In Patent Document 6, although the capacity is increased by the Si oxide subjected to conductivity, artificial graphite having low input / output characteristics is exemplified as the graphite used, and an amorphous carbon layer is formed on the graphite surface. Therefore, it is difficult to achieve high rate characteristics.

  The present invention has been made in view of such a problem, and by mixing the carbon material with an organic compound after pressure treatment, and further firing the carbon material, the high density can be obtained without destroying the surface structure of the carbon material. A negative electrode active material can be manufactured, and high capacity and high rate characteristics can be achieved by mixing metal fine particles typified by Si compounds such as Si and SiOx having high capacity. An object of the present invention is to provide a non-aqueous secondary battery having excellent output characteristics and cycle characteristics more adapted to market requirements by mixing this negative electrode active material with specific carbon materials and metal fine particles. is there.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have not understood the mechanism in detail. However, according to the study by the present inventors, the pressure-treated carbon material (a) is treated with carbon. By applying a carbon material for a non-aqueous secondary battery containing a composite carbon material (A) coated with a carbonaceous material or a graphite material and a metal fine particle (B) to the negative electrode, side reactions with the electrolyte are suppressed, and during the cycle It has been found that a non-aqueous secondary battery having a high capacity and excellent cycle characteristics and rate characteristics can be obtained, and the present invention has been completed.
That is, the gist of the present invention is that carbon for a non-aqueous secondary battery including a composite carbon material (A) obtained by coating a pressurized carbon material (a) with a carbonaceous material or a graphite material, and metal fine particles (B). Lies in the material.

  Composite carbon material (A) (herein simply referred to as composite carbon material (A)) and metal fine particles (B) obtained by coating the pressure-treated carbon material (a) of the present invention with a carbonaceous material or a graphite material. By using a carbon material for a non-aqueous secondary battery containing as a negative electrode material for a non-aqueous secondary battery, the non-aqueous secondary battery has a high capacity, a reaction with an electrolytic solution is further suppressed, and a deterioration during cycling is small. Can be provided. In addition, it is possible to obtain a high capacity non-aqueous secondary battery with less electrode expansion and gas generation and excellent charge / discharge rate characteristics.

Although the details of the effect are not clear here, as a result of investigations by the inventors, it is considered that excellent battery characteristics are due to the following effects. That is, when the composite carbon material (A) is used, it is possible to increase the electrode density particularly in the step of forming the negative electrode, but the high density prevents the diffusion of Li ions, resulting in an excellent rate. It may be difficult to obtain characteristics.
On the other hand, the carbon material for non-aqueous secondary batteries according to the present invention includes the composite carbon material (A) and the metal fine particles (B), so that the composite carbon material (A) originally has battery characteristics. It is possible to increase the capacity by adding metal fine particles having a high capacity without impairing (densification), and by adding metal fine particles (B) to the composite carbon material (A), Li ions It is considered that the diffusion path is ensured and further excellent rate characteristics can be obtained.

Hereinafter, the contents of the present invention will be described in detail. In addition, description of the invention structural requirements 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. Further, “weight%” and “mass%” are synonymous.
<Raw material carbon material that is a raw material of the composite carbon material (A)>
Although the raw material carbon material which is a raw material of the composite carbon material (A) of this invention is shown below as an example, it is not restrict | limited in particular.

-Types of raw material carbon material Examples of the raw material carbon material include raw material carbon materials having various degrees of graphitization ranging from graphite to amorphous materials.
In addition, graphite or a raw material carbon (amorphous carbon) material having a low degree of graphitization is particularly preferable in that it can be easily obtained commercially. When such graphite or graphite (amorphous carbon) having a low degree of graphitization is used as a raw material carbon material, the effect of improving the charge / discharge characteristics at a high current density is significantly higher than when other negative electrode active materials are used. It is preferable because it is large.

As the 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.
Specific examples of natural graphite include scaly graphite, scaly graphite, and soil graphite. Examples of artificial graphite include graphite particles such as coke, needle coke, and high-density carbon material produced by high-temperature heat treatment of pitch raw materials. Preferred is spherical natural graphite from the viewpoint of low cost and ease of electrode production.

  Specific examples of artificial graphite include coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, Organic substances such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin are usually used at a temperature in the range of 2500 ° C. to 3200 ° C. Examples thereof include those fired and graphitized.

  The raw material carbon material may be used by appropriately mixing the raw material carbon material with particles such as metal particles and metal oxide particles in any combination. Further, a plurality of materials may be mixed in each particle. For example, carbonaceous particles having a structure in which the surface of graphite is coated with a carbon material having a low degree of graphitization, or particles obtained by re-graphitizing a carbon material with an appropriate organic substance may be used. Furthermore, the composite particles may contain a metal that can be alloyed with Li, such as Sn, Si, Al, Bi.

-Physical property of raw material carbon material The raw material carbon material in this invention shows the following physical properties. In addition, there is no restriction | limiting in particular in the measuring method in this invention, According to the measuring method as described in an Example, unless there is a special situation.
(1) X-ray parameters of raw carbon material (d ₀₀₂ value)
The d value (interlayer distance) of the lattice plane (002) obtained by X-ray diffraction by the Gakushin method is usually 0.335 nm or more and less than 0.340 nm. Here, the d value is preferably 0.339 nm or less, more preferably 0.337 nm or less. If the d value is too large, the crystallinity may decrease and the initial irreversible capacity may increase. On the other hand, the lower limit of 0.335 nm is a theoretical value of graphite.

(2) Surface functional group amount of raw material carbon material The raw material carbon material which is the raw material of the composite carbon material (A) of the present invention has a surface functional group amount O / C value represented by the following formula (1) of usually 1%. It is 4% or less, preferably 2% or more and 3.6% or less, and more preferably 2.6% or more and 3% or less.
When the surface functional group amount O / C value is too small, the affinity with the binder is lowered, the interaction between the negative electrode surface and the coating material becomes weak, and the coating material tends to be peeled off. On the other hand, if the surface functional group amount O / C value is too large, it becomes difficult to adjust the O / C value, and there is a tendency that the manufacturing process needs to be performed for a long time or the number of steps needs to be increased. There is a risk of lowering the property and increasing the cost.

Formula (1)
O / C value (%) = {O atom concentration obtained based on the peak area of the O1s spectrum in the X-ray photoelectron spectroscopy (XPS) analysis / C atom obtained based on the peak area of the C1s spectrum in the XPS analysis Density} × 100
The surface functional group amount O / C value in the present invention can be measured using X-ray photoelectron spectroscopy (XPS) as follows.

  An X-ray photoelectron spectrometer is used as an X-ray photoelectron spectroscopy measurement, the measurement object is placed on a sample stage so that the surface is flat, an aluminum Kα ray is used as an X-ray source, and C1s (280 to 300 eV) is obtained by multiplex measurement. ) And O1s (525-545 eV). The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and O1s spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and O, respectively. The obtained atomic concentration ratio O / C (O atomic concentration / C atomic concentration) of O and C is defined as the surface functional group amount O / C value of the raw material carbon material.

(3) Volume-based average particle diameter of raw material carbon material (d50)
The particle diameter of the raw carbon material is not particularly limited, but as a range to be used, the median diameter d50 is usually 50 μm or less, preferably 30 μm or less, more preferably 25 μm or less. Moreover, it is 1 micrometer or more normally, Preferably it is 4 micrometers or more, More preferably, it is 10 micrometers or more.
If this particle size is too large, inconveniences such as striping tend to occur when it is made into a plate, and if the particle size is too small, the surface area becomes too large and the activity against the electrolyte is suppressed. Tend to be difficult to do.

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

(4) BET specific surface area (SA) of raw carbon material
About the specific surface area measured by BET method of the raw material carbon material of this invention, it is 4 m < ² > / g or more normally, Preferably it is 5 m < ² > / g or more. Moreover, it is 11 m < ² > / g or less normally, Preferably it is 9 m < ² > / g or less, More preferably, it is 8 m < ² > / g or less.
If the specific surface area is too small, there are few sites where Li enters and exits, and the high-speed charge / discharge characteristics and output characteristics are inferior. On the other hand, if the specific surface area is too large, the activity of the active material with respect to the electrolyte becomes excessive and the initial irreversible capacity is low. Since it becomes large, there exists a tendency which cannot manufacture a high capacity battery.
In addition, the measuring method of a BET specific surface area is measured by a BET 1 point method by a nitrogen gas adsorption circulation method using a specific surface area measuring device.

(5) X-ray diffraction structure analysis of raw material carbon materials (XRD)
The abundance ratio (3R / 2H) of hexagonal crystals to rhombohedral (3R / 2H) obtained from X-ray diffraction structure analysis (XRD) of the raw carbon material is usually 0.20 or more and 0.25 or more. Preferably, 0.30 or more is more preferable. If 3R / 2H is too small, the high-speed charge / discharge characteristics tend to be reduced.
The X-ray diffraction structure analysis (XRD) is measured by filling a 0.2 mm sample plate so that the raw material carbon material is not oriented and measuring with an X-ray diffractometer at an output of 30 kV and 200 mA with CuKα rays. . After subtracting the background from the obtained 3R (101) near 43.4 ° and 2H (101) near 44.5 °, the intensity ratio 3R (101) / 2H (101) can be calculated. .

(6) Tap density of raw material carbon material The tap density of the raw material carbon material of the present invention is usually preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and more preferably 1 g / cm ³ or more. Moreover, 1.3 g / cm ³ or less and 1.2 g / cm ³ or less are usually preferable, and 1.1 g / cm ³ or less is more preferable. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the intra-particle carbon density increases, the rollability is insufficient, and it may be difficult to form a high-density negative electrode sheet.

In the present invention, the tap density is measured by using a powder density meter to drop the raw carbon material through a sieve having a diameter of 1.6 cm and a volume capacity of 20 cm ³ through a sieve having a mesh opening of 300 μm to fill the cell. After filling, a tap having a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume at that time and the weight of the sample is defined as the tap density.

(7) Raman R value of Raman spectrum (Raman) spectrum raw carbon material of the raw carbonaceous material, and the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, and an intensity _{I B} of a peak _{P B} in the vicinity of 1360 cm ^-1 Measure and define the intensity ratio R (R = I _B / I _A ). The value is usually 0.15 or more, preferably 0.4 or less, and more preferably 0.3 or less. When the Raman R value is less than this range, the crystallinity of the particle surface becomes too high, and when the density is increased, the crystals tend to be oriented in the direction parallel to the electrode plate, and the load characteristics tend to be lowered. On the other hand, if it exceeds this range, the crystallinity of the particle surface will be disturbed, the reactivity with the electrolyte will increase, and the charge / discharge efficiency will tend to decrease and the gas generation will 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 while irradiating the measurement cell with the laser beam, the measurement cell is rotated in a plane perpendicular to the laser beam, and the measurement is performed. Do. As the excitation laser, for example, an argon ion laser (514.5 nm), a solid laser (532 nm), or the like can be used. The following is an example of measurement conditions.

Laser light wavelength: 514.5 nm, 532 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)

(8) Production method of raw material carbon material The raw material carbon material of the present invention is not particularly limited as long as it is graphitized carbon particles, but as described above, natural graphite, artificial graphite, and coke powder. Needle coke powder, and powders of graphitized materials such as resins can be used. Of these, natural graphite is preferable, and spheroidized natural graphite that has been subjected to spheroidizing treatment is particularly preferable because the effect of pressure treatment tends to appear. Below, the manufacturing method of spherical natural graphite is described as an example.

  For the spheronization treatment, for example, an apparatus that spheroidizes by repeatedly applying mechanical actions such as compression, friction, shearing force, etc., including the interaction of particles mainly with impact force, to the carbon particles can be used. Specifically, it has a rotor with a large number of blades installed inside the casing, and the rotor rotates at high speed, so that the raw material carbon material introduced into the casing is mechanically compressed such as impact compression, friction, shear force, etc. An apparatus that provides an action and performs surface treatment is preferable.

  Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating the raw carbon material. Preferred devices include, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), a kryptron (manufactured by Earth Technica), a CF mill (manufactured by Ube Industries), a mechano-fusion system (manufactured by Hosokawa Micron), and a theta composer (Tokuju Kosakusho). Etc.). Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable.

For example, when the raw material carbon material used in the present invention is scaly graphite, the scaly natural graphite is folded into a spherical shape by performing the spheronization step by the surface treatment. Alternatively, the peripheral edge portion of the raw carbon material is spherically pulverized into a spherical shape, and fine particles of 5 μm or less generated by the pulverization adhere to the base particles.
It is preferable to manufacture by performing the spheronization treatment under the condition that the surface functional group amount O / C value of the raw material carbon material after the surface treatment is usually 1% or more and 4% or less. In this case, it is preferable to carry out in an active atmosphere so that the oxidation reaction of the graphite surface can be advanced by the energy of mechanical treatment and acidic functional groups can be introduced into the graphite surface.

  For example, when processing using the above-mentioned apparatus, the peripheral speed of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / sec, and 50 to 100 m / sec. Is more preferable. The spheroidizing treatment can be performed by simply passing the carbonaceous material, but it is preferable to circulate or stay in the apparatus for 30 seconds or more, and to circulate or stay in the apparatus for 1 minute or more. Is more preferable.

<Organic compound as raw material for composite carbon material (A)>
The organic compound that is the precursor of the carbonaceous material for coating or the graphite material that is the other raw material of the composite carbon material (A) of the present invention is not particularly limited as long as the physical properties shown below are satisfied.
-Kind of organic compound The organic compound in this invention is a raw material used as a carbonaceous material or a graphite material by baking. Here, the carbonaceous material is carbon having a d value of 0.340 nm or more, and the carbonaceous material and the amorphous carbonaceous material are synonymous. On the other hand, the graphite material is graphite having a d value of less than 0.340 nm.

  Specifically, petroleum heavy oil such as impregnated pitch, coal tar pitch, coal heavy oil such as coal liquefied oil, straight run heavy oil such as asphalten, and cracked heavy oil such as ethylene heavy end tar. Graphitizable organic compounds exemplified by quality oils, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymers, polyphenylenesil Examples thereof include fido, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin. Among these, graphitizable organic compounds that can be graphitized or carbonized by firing are preferable.

-Physical properties of organic compounds (1) X-ray parameters (d ₀₀₂ values)
<In the case of a carbonaceous material obtained by firing an organic compound>
The interplanar spacing (d ₀₀₂ ) of the (002) plane according to the X-ray wide angle diffraction method of the carbonaceous material powder obtained by baking only the organic compound is usually 0.340 nm or more, preferably 0.342 nm or more. Moreover, it is less than 0.380 nm normally, Preferably it is 0.370 nm or less, More preferably, it is 0.360 nm or less. If the d ₀₀₂ value is too large, it indicates that the crystallinity is low, and the composite carbon material (A) may become particles with low crystallinity and increase the irreversible capacity. If the d ₀₀₂ value is too small, the carbonaceous material It is difficult to obtain the effect of compounding.

<In the case of a graphite material obtained by firing an organic compound>
The (002) plane spacing (d ₀₀₂ ) of the graphite powder obtained by graphitizing only the organic compound by X-ray wide angle diffraction method is usually 0.3354 nm or more, preferably 0.3357 nm or more, more preferably It is 0.3359 nm or more. Moreover, it is less than 0.340 nm normally, Preferably it is 0.338 nm or less, More preferably, it is 0.337 nm or less. that d ₀₀₂ value is too large indicate low crystallinity, may composite carbon material (A) is hard to obtain the effect obtained by compounding graphite pledge becomes low crystallinity particles, d ₀₀₂ If the value is too small, the charge / discharge reactivity decreases, and there is a risk of increased gas generation during high-temperature storage and reduced large current charge / discharge characteristics.

(2) Crystallite size (Lc (002))
<In the case of a carbonaceous material obtained by firing an organic compound>
The crystallite size (Lc (002)) of the carbon material obtained by the X-ray diffraction method of the Gakushin method of the carbonaceous material powder obtained by baking the organic compound is usually 5 nm or more, preferably 10 nm or more, more preferably Is 20 nm or more. Moreover, it is 300 nm or less normally, Preferably it is 200 nm or less, More preferably, it is 100 nm or less. If the crystallite size is too large, the composite carbon material (A) tends to increase the irreversible capacity as particles having low crystallinity. If the crystallite size is too small, the effect of compounding the carbonaceous material is obtained. It is difficult

<In the case of a graphite material obtained by firing an organic compound>
The crystallite size (Lc (002)) of the carbon material obtained by X-ray diffraction analysis based on the Gakushin method of graphitic powder obtained by graphitizing an organic compound is usually 300 nm or more, preferably 400 nm or more. Preferably it is 500 nm or more. Moreover, it is 1000 nm or less normally, Preferably it is 800 nm or less, More preferably, it is 600 nm or less. If the crystallite size is too large, the composite carbon material (A) may become particles with low crystallinity and it may be difficult to obtain the effect of combining the graphite material. If the crystallite size is too small, the charge / discharge reaction may occur. As a result, the gas generation tends to increase and the large current charge / discharge characteristics decrease during high temperature storage.

(3) Softening point The softening point of the organic compound is usually 400 ° C or lower, preferably 300 ° C or lower, more preferably 200 ° C or lower, and further preferably 150 ° C or lower. If the softening point is too high, it becomes difficult to uniformly mix or combine with the raw carbon material, and it may be necessary to handle at a high temperature, resulting in poor productivity. Although a minimum in particular is not restrict | limited, Usually, it is 40 degreeC or more.

(4) Surface functional group amount of organic compound (N / C, S / C, O / C) The amount of surface functional group of organic compound (N / C, S / C, O / C) is 1000 for the organic compound. When carbon powder obtained by pulverizing for 30 seconds in the atmosphere using a CNT high-speed vibration sample mill (TI-100 type) after carbonization by firing at ℃, the following conditions must be satisfied: preferable.
(4-1) Surface functional group amount (N / C)
The surface functional group amount (N / C) represented by the following formula 2 of the organic compound is usually 0.05% or more, preferably 0.07% or more, more preferably 0.1% or more, and still more preferably 0.00. It is 43% or more, usually 6% or less, preferably 4% or less, more preferably 3% or less, and still more preferably 1% or less. If N / C is too small, the desolvation reactivity of Li ions and the electrolyte solvent on the negative electrode active material surface may be reduced, and the large current charge / discharge characteristics may be reduced. If it is too large, the reaction with the electrolyte will occur. There is a possibility that the chargeability increases due to the increase in the chargeability.

N / C is defined by the following formula 2.
Formula 2
N / C (%) = N atom concentration obtained based on the peak area of the N1s spectrum in X-ray photoelectron spectroscopy (XPS) analysis / C atom concentration obtained based on the peak area of the C1s spectrum in XPS analysis × 100
The surface functional group amount N / C of the organic compound can be measured using X-ray photoelectron spectroscopy (XPS).

  An X-ray photoelectron spectrometer is used as an X-ray photoelectron spectroscopy measurement, the measurement object is placed on a sample stage so that the surface is flat, an aluminum Kα ray is used as an X-ray source, and C1s (280 to 300 eV) is obtained by multiplex measurement. ) And N1s (390 to 410 eV). The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and N1s spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and N, respectively. Using the obtained N and C surface atom concentrations, the N / C value is calculated using Equation 1.

(4-2) Surface functional group amount (S / C)
The surface functional group amount (S / C) represented by the following formula 3 of the organic compound is usually 0.01% or more, preferably 0.05% or more, more preferably 0.07% or more, and usually 6%. Hereinafter, it is preferably 4% or less, more preferably 3% or less, and still more preferably 1% or less. If S / C is too small, the desolvation reactivity of Li ions and electrolyte solvent on the surface of the negative electrode active material may be reduced, and the large-current charge / discharge characteristics may be reduced. Tends to increase, leading to a decrease in charge / discharge efficiency.

S / C is defined by the following formula 3.
Formula 3
S / C (%) = S atom concentration obtained based on the peak area of the S2s spectrum in X-ray photoelectron spectroscopy (XPS) analysis / C atom concentration obtained based on the peak area of the C1s spectrum in XPS analysis × 100
The surface functional group amount S / C of the organic compound can be measured using X-ray photoelectron spectroscopy (XPS).

  An X-ray photoelectron spectrometer is used as an X-ray photoelectron spectroscopy measurement, the measurement object is placed on a sample stage so that the surface is flat, an aluminum Kα ray is used as an X-ray source, and C1s (280 to 300 eV) is obtained by multiplex measurement. ) And S2p (160 to 175 eV). The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and S2p spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and S, respectively. Using the obtained S and C surface atom concentrations, S / C is calculated using Equation 2.

(4-3) Surface functional group amount (O / C)
The surface functional group amount (O / C) of the organic compound is usually 0.1% or more, preferably 1% or more, more preferably 4.1% or more. Moreover, it is 10% or less normally, Preferably it is 8% or less, More preferably, it is 5% or less. If this surface functional group amount O / C is too small, the desolvation reactivity of Li ions and the electrolyte solvent on the negative electrode active material surface may be reduced, and the large current charge / discharge characteristics may be reduced. There is a possibility that the reactivity with the electrolytic solution increases and the charge / discharge efficiency decreases.
O / C is defined by the following formula 4.
Formula 4
O / C (%) = O atom concentration determined based on the peak area of the O1s spectrum in the X-ray photoelectron spectroscopy (XPS) analysis / C atom concentration determined based on the peak area of the C1s spectrum in the XPS analysis × 100
The surface functional group amount O / C in the present invention can be measured using X-ray photoelectron spectroscopy (XPS).

  An X-ray photoelectron spectrometer is used as an X-ray photoelectron spectroscopy measurement, the measurement object is placed on a sample stage so that the surface is flat, an aluminum Kα ray is used as an X-ray source, and C1s (280 to 300 eV) is obtained by multiplex measurement. ) And O1s (525-545 eV). The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and O1s spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and O, respectively. Using the obtained surface atomic concentrations of O and C, O / C is calculated using Equation 3.

(4-4) Sum of S / C and N / C The sum of S / C and N / C in the organic compound is usually 0.3% or more, preferably 0.4% or more, more preferably 0.5. % Or more, usually 10% or less, preferably 8% or less, more preferably 5% or less. If the sum of S / C and N / C is too small, the desolvation reactivity of Li ions and the electrolyte solvent on the negative electrode active material surface may be reduced, and the large current charge / discharge characteristics may be reduced. There is a tendency that the reactivity with the electrolytic solution increases and the charge / discharge efficiency decreases.

<Method for producing composite carbon material (A)>
The composite carbon material (A) is produced by subjecting the above-mentioned raw material carbon material to pressure treatment (hereinafter also referred to as carbon material (a)) and crushing to form an (amorphous) carbonaceous material or graphitic material coating portion. A composite carbon material (A) in which the carbon material (a) used in the present invention is coated with a carbonaceous material or a graphite material is produced by mixing with an organic compound to obtain, and firing and pulverizing the resulting mixture. be able to.

-Process of pressurizing raw material carbon material In the manufacturing method of composite carbon material (A) in the present invention, before mixing the organic compound and the raw material carbon material, pressurizing the raw material carbon material is performed. Features.
By pressurizing the raw carbon material, the internal voids of the raw carbon material are compressed. As a result, the density of the raw carbon material crushed after the pressure treatment increases, and the organic compound to be mixed is efficiently absorbed on the surface of the raw carbon material without being absorbed by the internal voids of the raw carbon material. . The method of pressing and molding is not particularly limited, and a roll compactor, a roll press, a rivet machine, a cold isostatic pressing device (CIP), a uniaxial molding machine, a tablet machine, and the like can be used.

Further, if necessary, the raw carbon material can be molded simultaneously with the press according to the pattern carved in the roll. Moreover, the method of exhausting the air which exists between raw material carbon material particles, and vacuum-pressing can also be applied.
The pressure treatment may be a pressure treatment by pressing from one direction or an isotropic pressure treatment, but it is difficult to flatten the particles, can maintain a spherical shape, and is made into a paint. It is preferable to apply an isotropic pressure treatment in terms of preventing a decrease in fluidity.

The pressure for pressurizing the raw material carbon material is not particularly limited, usually 50 kgf / cm ² or higher, preferably 100 kgf / cm ² or more, more preferably 300 kgf / cm ² or more, most preferably 1000 kgf / cm ² or more It is. The upper limit of the pressure treatment is not particularly limited, but is usually 2000 kgf / cm ² or less, preferably 1500 kgf / cm ² or less. When the pressure is too low, strong granulation is not achieved and the internal voids tend not to decrease, and when the pressure is too high, the cost of the process tends to increase.

The pressurizing time is usually 0.1 seconds or longer, preferably 3 seconds or longer, more preferably 1 minute or longer. Moreover, it is 30 minutes or less normally, Preferably it is 10 minutes or less, More preferably, it is 3 minutes or less. If the time is too long, it adversely affects the manufacturing process. On the other hand, if the time is too short, strong granulation is not achieved and the internal voids tend not to decrease.
The raw material carbon material (a) obtained by the pressure treatment preferably exhibits the following physical properties.

-Intraparticle porosity The in-particle porosity of the compressed and crushed raw carbon material (a) is usually 30% or less, preferably 25% or less, more preferably 20% or less, and usually 5% or more, preferably Is 7% or more, more preferably 10% or more. If the intra-particle porosity is too high, the organic compound to be mixed is excessively absorbed in the internal voids of the raw carbon material (a), and there is a tendency that the raw carbon material (a) cannot be efficiently coated. . If the void ratio in the particles is too low, there will be an excess of organic compounds to be mixed, and the raw carbon materials (a) tend to be aggregated so that the raw carbon materials (a) cannot be efficiently coated. is there. In addition, the measuring method of the particle | grain porosity is according to the measuring method of an Example.

-Density The density of the compressed raw material carbon material (a) is usually 1.2 g / cm ³ or more, preferably 1.3 g / cm ³ or more. Moreover, although there is no restriction | limiting in particular regarding an upper limit, Usually, it is 1.8 g / cm < ³ > or less.

-The process which mixes the raw material carbon material (a) compressed and pulverized, and an organic compound The mixing of the compressed carbon material (a) and an organic compound can be performed by a conventional method. The mixing temperature is usually from room temperature to 150 ° C., more preferably from 50 to 150 ° C., and more preferably from 100 to 130 ° C. from the viewpoint that the raw material carbon material and the organic compound are easily mixed uniformly.
When mixing with the compressed and crushed raw material carbon material (a), the organic compound is preferably diluted with an organic solvent. The reason for diluting is that by diluting with an organic solvent, the viscosity of the organic compound to be mixed is lowered, and the raw material carbon material (a) can be coated more efficiently and uniformly.

  Organic solvents include pentane, hexane, isohexane, heptane, octane, isooctane, decane, dimethylbutane, cyclohexane, methylcyclohexane and other hydrocarbons; ethyl ether, isopropyl ether, diisoamyl ether, methylphenyl ether, amylphenyl ether Ethers such as ethyl benzyl ether; ketones such as acetone, methyl acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone; methyl formate, ethyl formate, isobutyl formate, methyl acetate, isoamyl acetate, methoxybutyl acetate, cyclohexyl acetate, methyl butyrate, Esters such as ethyl butyrate, butyl benzoate, isoamyl benzoate; benzene, toluene, xylene, ethylbenzene, diethylbenzene, isopropylben Aromatic hydrocarbons such as but not limited to benzene, amylbenzene, diamylbenzene, triamylbenzene, tetraamylbenzene, dodecylbenzene, didodecylbenzene, amyltoluene, tetralin, cyclohexylbenzene, etc. .

Moreover, what mixed these 2 or more types may be used. Among these, benzene, toluene, and xylene are organic solvents having a relatively high boiling point and a low viscosity, and are particularly preferable in that the concentration change due to volatilization hardly occurs and the viscosity of the organic compound can be lowered.
The dilution ratio with an organic solvent is usually 5% or more, preferably 25% or more, more preferably 40% or more, still more preferably 50% or more, and usually 90%, based on the mass of the organic solvent. % Or less, preferably 80% or less, more preferably 70% or less, and still more preferably 60% or less. If this dilution factor is too large, the concentration of the organic compound tends to decrease, and the raw carbon material tends not to be coated efficiently. If the dilution factor is too small, the concentration of the organic compound is not sufficiently lowered and the raw material carbon material tends not to be coated efficiently.

Mixing is usually carried out under normal pressure, but if desired, it can also be carried out under reduced pressure or under pressure. Mixing can be carried out either batchwise or continuously. In any case, mixing efficiency can be improved by using a combination of an apparatus suitable for rough mixing and an apparatus suitable for fine mixing.
As a batch type mixing device, a mixer with a structure in which two frame molds rotate and revolve; a single plate such as a dissolver that is a high-speed, high-shear mixer and a butterfly mixer for high viscosity is contained in the tank. A device having a structure for stirring and dispersing; a so-called kneader-type device having a structure in which a stirring blade such as a sigma type rotates along the side surface of a semi-cylindrical mixing tank; a trimix type device having three stirring blades A so-called bead mill type apparatus having a rotating disk and a dispersion medium in a container is used.

  It also has a container with a paddle that is rotated by a shaft, and the inner wall surface of the container is formed substantially along the outermost line of rotation of the paddle, preferably in a long twin cylinder shape, and the paddle has side surfaces facing each other. A device having a structure in which many pairs are arranged in the axial direction of the shaft so as to be slidably engaged (for example, KRC reactor manufactured by Kurimoto Iron Works, SC processor, TEM manufactured by Toshiba Machine Celmac, TEX-K manufactured by Nippon Steel Works) Furthermore, it has a container in which a single inner shaft and a plurality of pavement or sawtooth paddles fixed to the shaft are arranged in different phases, and the inner wall surface is the outermost line of rotation of the paddle (External heat type) apparatus (for example, a Redige mixer manufactured by Redige Co., Ltd., a flow share mixer manufactured by Taiyo Koki Co., Ltd., and Tsukishima Kikai Co., Ltd.) DT dryers, etc.) can also be used. In order to perform mixing in a continuous manner, a pipeline mixer, a continuous bead mill, or the like may be used.

  The viscosity of the mixture or diluted mixture obtained in this step is usually 100 cP or less, preferably 70 cP or less, more preferably 50 cP or less. Moreover, it is 1 cP or more, preferably 10 cP or more. If the viscosity is too high, deterioration during cycling tends to occur, and cycle characteristics tend to deteriorate.

A step of firing the mixture An organic compound coated with the pressure-treated carbon material (a) by heating the obtained mixture in a non-oxidizing atmosphere, preferably under a flow of nitrogen, argon, carbon dioxide, etc. Is carbonized or graphitized to produce a composite carbon material (A).
The firing temperature varies depending on the organic compound used for the preparation of the mixture, but when obtaining a composite carbon material (A) coated with an (amorphous) carbonaceous material or graphite material, it is usually 500 ° C. or higher, preferably 800 ° C. or higher. More preferably, the organic compound is sufficiently carbonized by heating to 900 ° C. or higher. 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 the raw material carbon material (a) in the mixture, and is usually 3000 ° C. or lower, preferably 2000 ° C. or lower, 1500 degrees C or less is more preferable.

In the firing treatment conditions, the heat history temperature condition, the temperature rise rate, the cooling rate, the heat treatment time, etc. are appropriately set. Further, after heat treatment in a relatively low temperature region, the temperature can be raised to a predetermined temperature. In addition, the reactor used for this process may be a batch type or a continuous type, and may be one or more.
The furnace used for firing is not particularly limited as long as the above requirements are satisfied. For example, a reactor such as a shuttle furnace, a tunnel furnace, a lead hammer furnace, a rotary kiln, an autoclave, a coker (heat treatment tank for coke production), a Tamman furnace, and Atchison A furnace, a high-frequency induction heating furnace, or the like can be used, and a direct resistance heating, an indirect resistance heating, a direct combustion heating, a radiant heat heating, or the like can also be used as a heating method. During the heat treatment, stirring may be performed as necessary.

The composite carbon material (A) that has undergone the above-described steps may be subjected to powder processing such as pulverization, pulverization, and classification treatment again as necessary.
There are no particular restrictions on the apparatus used for re-pulverization or crushing, but examples of the coarse pulverizer include a shearing mill, a jaw crusher, an impact crusher, and a cone crusher. Examples of the intermediate pulverizer include a roll crusher and a hammer mill, and examples of the fine pulverizer include a ball mill, a vibration mill, a pin mill, a stirring mill, and a jet mill.

  Although there is no restriction | limiting in particular as an apparatus used for a classification process, For example, in the case of dry-type sieving, a rotary sieving, a swaying sieving, a rotating sieving, a vibrating sieving, etc. can be used. In the case of dry airflow classification, a gravity classifier, an inertial force classifier, or a centrifugal force classifier (classifier, cyclone, etc.) can be used. Also, wet sieving, mechanical wet classifiers, hydraulic classifiers, sedimentation classifiers, centrifugal wet classifiers and the like can be used.

<Composite carbon material (A)>
The composite carbon material (A) is not particularly limited as long as the pressurized carbon material (a) is coated with a carbonaceous material or a graphite material. In addition, the coating as used in this specification means the aspect by which at least one part or the whole surface of the carbon material (a) by which pressure treatment was carried out is coat | covered or attached with the carbonaceous material or the graphite material. This aspect can be confirmed by the following physical properties and SEM photographs.
The composite carbon material (A) obtained by the above production method preferably has the following characteristics.

(1) (002) plane spacing (d ₀₀₂ )
The interplanar spacing (d ₀₀₂ ) of the (002) plane according to the X-ray wide angle diffraction method of the composite carbon material (A) is 3.37 mm or less, and the crystallite size Lc is 900 mm or more. The interplanar spacing (d ₀₀₂ ) of (002) plane by X-ray wide angle diffraction method is 3.37 mm or less and Lc is 900 mm or more. This means that most of the crystallinity excluding the surface of the composite carbon material (A) particles is. This is a high-capacity composite electrode that does not cause a reduction in capacity due to the irreversible capacity seen in amorphous carbon materials when used as a negative electrode material for non-aqueous secondary batteries. Indicates a carbon material.

(2) Tap density The tap density of the composite carbon material (A) is usually 0.8 g / cm ³ or more, preferably 0.85 g / cm ³ or more.
That the tap density of the composite carbon material (A) is 0.8 g / cm ³ or more is one of the indexes indicating that the composite carbon material (A) has a spherical shape. The fact that the tap density is smaller than 0.8 g / cm ³ is one of indices indicating that the spherical carbon material, which is the raw material of the composite carbon material (A), does not have sufficient spherical particles. If the tap density is less than 0.8 g / cm ³ , sufficient continuous voids are not secured in the electrode, and the mobility of Li ions in the electrolyte held in the voids is reduced, thereby reducing rapid charge / discharge characteristics. Tend to.

(3) 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 Raman spectrum of the Raman R value composite carbon material (A) it is usually 0.45 or less, preferably 0.40 or less More preferably, it is 0.35 or less, usually 0.20 or more, preferably 0.23 or more, more preferably 0.25 or more. If the Raman value is within this range, the crystallinity of the surface of the negative electrode active material is in an appropriate range, which is preferable because high output can be easily obtained.

(4) Specific surface area by BET method The specific surface area by the BET method of the composite carbon material (A) is usually 10 m ² / g or less, preferably 3 m ² / g or less, more preferably 1.5 m ² / g or less. It is 0.1 m ² / g or more, preferably 0.7 m ² / g or more, more preferably 1 m ² / g or more. When the specific surface area is too large, the reactivity between the portion exposed to the electrolytic solution when used as the negative electrode active material and the electrolytic solution increases, gas generation tends to increase, and a preferable battery tends to be difficult to obtain. If the specific surface area is too small, the lithium ion acceptability tends to deteriorate during charging when used as a negative electrode active material.

(5) Pore volume The pore volume of the composite carbon material (A) in the range of 10 nm to 100000 nm by mercury porosimetry is usually 0.8 mL / g or less, preferably 0.6 mL / g or less, more preferably 0. 4 mL / g or less, usually 0.01 mL / g or more, preferably 0.05 mL / g or more, more preferably 0.1 mL / g or more. If the pore volume is too large, there is a tendency to require a large amount of binder during electrode plate formation. If the pore volume is too small, the high current density charge / discharge characteristics deteriorate, and the expansion / contraction of the electrode during charge / discharge is alleviated. There is a tendency that the effect cannot be obtained.

(6) Volume-based average particle diameter (d50)
The average particle diameter (median diameter) of the composite carbon material (A) is usually 60 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and usually 1 μm or more, preferably 4 μm or more, more preferably 10 μm or more. . If the average particle size is too large, the amount of binder required per carbon particle tends to be large, and if the average particle size is too small, the high current density charge / discharge characteristics tend to decrease.

(7) Coverage The composite carbon material (A) of the present invention is coated with a carbonaceous material or a graphite material. Among these, it is preferable that it is coated with an amorphous carbonaceous material from the viewpoint of lithium ion acceptability, and this coverage is usually 0.5% to 10.0%, preferably 1.0% to 9. It is 0% or less, more preferably 2.0% or more and 8.0% or less. If this content is too large, the amorphous carbon portion of the negative electrode material increases, and the reversible capacity when the battery is assembled tends to be small. If the content is too small, the amorphous carbon portion is not uniformly coated on the pressure-treated carbon material (a) and strong granulation is not performed, and the particle size becomes small when pulverized after firing. It tends to be too much.

In addition, the content (coverage) of the carbide derived from the organic compound of the carbon material for the electrode finally obtained is measured by the amount of the raw material carbon material used, the amount of the organic compound, and a micro method based on JIS K 2270. It can be calculated by the following formula (5) based on the remaining charcoal rate.
Formula (5)
Covering rate of carbide derived from organic compound (%) = (mass of organic compound × residual carbon rate × 100) / {
Mass of raw carbon material + (mass of organic compound x residual carbon ratio)}

<Mixing of composite carbon material (A) and metal fine particles (B)>
The carbon material for a non-aqueous secondary battery of the present invention is characterized by including the above-described composite carbon material (A) which is one of the constituent elements and metal fine particles (B) defined below. The metal fine particles (B) to be combined with the composite carbon material (A) are suitably used as a carbon material for a non-aqueous secondary battery by using one or two or more of the following metal compounds in any composition and combination. Other carbon materials (C) (described later) may be included in the composite carbon material (A) that can be used.

  When the metal fine particles (B) are mixed with the composite carbon material (A) described above, the mixing ratio of the metal fine particles (B) to the total amount of the composite carbon material (A) and the metal fine particles (B) is not particularly limited. It is usually 1% by mass or more, preferably 5% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less. If the metal fine particle (B) falls below the previous period range, the capacity cannot be increased. On the other hand, if the metal fine particle (B) exceeds the previous period range, cracks in the electrode accompanying the volume expansion of Si occur, resulting in cycle deterioration due to the disconnection of the conductive path. Become prominent.

<Metal fine particles (B)>
In the carbon material for a non-aqueous secondary battery of the present invention, as described above, the metal fine particles (B) are characterized by being mixed with at least the composite carbon material (A). The metal fine particles (B) are preferably metal particles that can be alloyed with Li, but as a method for confirming this, identification of the metal particle phase by X-ray diffraction, particle structure by an electron microscope, and the like. Observation and elemental analysis, elemental analysis by fluorescent X-rays, and the like can be mentioned.

  Any conventionally known metal fine particles (B) can be used. From the viewpoint of capacity and cycle life, the metal particles are, for example, Fe, Co, Sb, Bi, Pb, Ni, Ag, Si, A metal selected from the group consisting of Sn, Al, Zr, Cr, P, S, V, Mn, Nb, Mo, Cu, Zn, Ge, In, Ti and the like, or a compound thereof is preferable. Further, an alloy composed of two or more kinds of metals may be used, and the metal particles may be alloy particles formed of two or more kinds of metal elements. Among these, a metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn, and W or a compound thereof is preferable.

Examples of the metal compound include a metal oxide, a metal nitride, and a metal carbide. Moreover, you may use the alloy which consists of 2 or more types of metals.
Among these, Si or Si compound is preferable in terms of increasing capacity. In this specification, Si or Si compounds are collectively referred to as Si compounds. Specific examples of the Si compound include SiOx, SiNx, SiCx, SiZxOy (Z = C, N) and the like, and preferably SiOx when expressed by a general formula. The general formula SiOx is obtained using Si dioxide (SiO ₂ ) and metal Si (Si) as raw materials, and the value of x is usually 0 ≦ x <2. SiOx has a larger theoretical capacity than graphite. Furthermore, amorphous Si or nano-sized Si crystals easily allow alkali ions such as lithium ions to enter and exit, so that a high capacity can be obtained.

  Specifically, it is expressed as SiOx, and x is 0 ≦ x <2, more preferably 0.2 or more and 1.8 or less, and further preferably 0.4 or more and 1.6 or less. Hereinafter, it is particularly preferably 0.6 or more and 1,4 or less. If it is this range, it becomes high capacity | capacitance and it becomes possible to reduce the irreversible capacity | capacitance by the coupling | bonding of Li and oxygen.

-Average particle diameter (d50) of metal fine particles (B)
The average particle diameter (d50) of the metal fine particles (B) is usually 0.01 μm or more, preferably 0.05 μm or more, more preferably 0.1 μm or more, and further preferably 0.3 μm or more from the viewpoint of cycle life. Usually, it is 10 μm or less, preferably 9 μm or less, more preferably 8 μm or less. When the average particle diameter (d50) is within the above range, volume expansion associated with charge / discharge is reduced, and good cycle characteristics can be obtained while maintaining charge / discharge capacity.
The average particle diameter (d50) is determined by a laser diffraction / scattering particle size distribution measuring method or the like.

-BET specific surface area of metal fine particles (B) The specific surface area of the metal fine particles (B) by the BET method is usually preferably 0.5 to 60 m ² / g, preferably ^{1 to} 40 m ² / g. It is preferable that the specific surface area of the metal fine particles (B) by the BET method be in the above range because the battery has high charge / discharge efficiency and high discharge capacity, and lithium can be taken in and out at high speed charge / discharge and excellent in rate characteristics.

-Content of oxygen in metal fine particles (B) The content of oxygen in the metal fine particles (B) is not particularly limited, but is preferably 0.01 to 8% by mass and preferably 0.05 to 5% by mass. The oxygen distribution state in the particle may exist near the surface, may exist inside the particle, or may exist uniformly within the particle, but is preferably present near the surface. It is preferable that the amount of oxygen contained in the metal fine particles (B) is in the above-mentioned range because the volume expansion associated with charging / discharging is suppressed due to strong bonding between Si and O and the cycle characteristics are excellent.

-Manufacturing method of metal fine particles (B) As long as the metal fine particles (B) satisfy the characteristics of the present invention, commercially available metal particles that can be alloyed with Li may be used. In addition, metal particles can be produced by applying mechanical energy treatment to a lump larger than metal particles made of a metal having the same composition as the metal particles that can be alloyed with Li by a ball mill or the like described later.
The production method is not particularly limited, but metal particles that can be alloyed with Li produced by a method as described in, for example, Japanese Patent No. 3952118 can also be used. For example, when producing SiOx, Si dioxide powder and metal Si powder are mixed at a specific ratio, and after filling this mixture into the reactor, the pressure is reduced to normal pressure or a specific pressure, and the temperature is raised to 1000 ° C. or higher. Then, it is held to generate SiOx gas, which is then cooled and deposited to obtain the general formula SiOx particles. Precipitates can be used as particles by applying mechanical energy treatment.

  For mechanical energy treatment, for example, using a device such as a ball mill, a vibrating ball mill, a planetary ball mill, or a rolling ball mill, a raw material charged in the reactor and a moving body that does not react with the raw material are placed, and this is vibrated and rotated. Alternatively, metal particles that can be alloyed with Li satisfying the above-described characteristics can be formed by a method that gives a combined movement.

<Carbon material (C)>
Examples of the carbon material (C) include natural graphite (D), artificial graphite (E), coated graphite (F) obtained by coating a raw carbon material not subjected to pressure treatment with a carbonaceous material or a graphite material, and amorphous carbon ( A material selected from the group consisting of G) is used. Any one of these materials may be used alone, or two or more of these materials may be used in any combination and composition. Among these, the carbon material (B) is a combination of the carbon materials (D) to (G) and at least one material selected from the group consisting of (D) to (G) in combination with the composite carbon material (A). In addition, it is preferable because an effect including the composite carbon material (A) is easily obtained.

The volume-based average particle diameter d50 of the carbon material (C) is preferably 3 μm or more and 60 μm or less from the viewpoint of easily obtaining an effect including the composite carbon material (A) in combination with the composite carbon material (A). In addition, the specific surface area is usually preferably 1 m ² / g or more and 20 m ² / g or less, more preferably 1 m ² / g or more and 8 m ² / g or less because the irreversible capacity of the carbon material is small. The effect of including the composite carbon material (A) in combination with the composite carbon material (A) is that the tap density of the carbon material (C) is 0.6 g / cm ³ or more and 1.5 g / cm ³ or less. It is preferable because it is easy.
Further, it is preferable that the carbon material (C) is highly purified from the viewpoint of the safety of the battery because there are few impurities. Further, the carbon material (C) is particularly preferable from the viewpoint that the spheroidized carbon material easily exhibits the effect of the pressure treatment.

  As the natural graphite (D), for example, a highly purified carbon material or a spherical natural graphite can be used. High purification in the present invention means a state in which ash, metals, and the like are removed. Usually, ash and metals contained in low-purity natural graphite are dissolved and removed by treatment in acids such as hydrochloric acid, sulfuric acid, nitric acid and hydrofluoric acid, or by combining one or more of these acid treatment steps. Yes (high purity treatment process). And after the said acid treatment process, a water washing process etc. are normally performed and the acid content used at the high purification process is removed.

By treating at a high temperature of 2000 ° C. or higher instead of the acid treatment step, ash, metal, etc. may be evaporated and removed. Further, ash and metals may be removed by treatment in a halogen gas atmosphere such as chlorine gas during high-temperature heat treatment. Furthermore, these high purification techniques may be used in any combination.
Among natural graphites (D), it is preferable to use highly purified natural graphite (D) from the viewpoint of battery safety because there are few impurities.

Here, the purity of the highly purified natural graphite is usually 98.0% by mass or more, preferably 99.0% by mass or more, more preferably 99.6% by mass or more. When the purity is within this range, it is more preferable when used as a carbon material because the battery capacity becomes high.
The volume-based average particle diameter d50 of natural graphite (D) is usually 3 μm or more, preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less. If it is in the said range, it is preferable from the point which is easy to acquire the effect containing a composite carbon material (A) in a combination with a composite carbon material (A).

Here, the volume reference average particle diameter means d50, and can be measured by the same method as the volume reference average particle diameter of the raw material carbon material described above.
The BET specific surface area of natural graphite (D) is usually 3.5 m ² / g or more, preferably 4.5 m ² / g or more, and usually 20 m ² / g or less, preferably 15 m ² / g or less, more preferably. Is in the range of 8 m ² / g or less, more preferably 6 m ² / g or less. If it is in the said range, it is preferable from the point with a small irreversible capacity | capacitance at the time of setting it as a carbon material.

The tap density of natural graphite (D) is usually preferably 0.6 g / cm ³ or more, preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and 0.85 g / cm ³ or more. Further preferred. Moreover, 1.3 g / cm ³ or less and 1.2 g / cm ³ or less are usually preferable, and 1.1 g / cm ³ or less is more preferable. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the intra-particle carbon density increases, the rollability is insufficient, and it may be difficult to form a high-density negative electrode sheet.

Examples of the artificial graphite (E) include particles obtained by graphitizing a raw material carbon material. For example, particles obtained by firing a single graphite precursor particle while it is powdered and graphitizing, or a plurality of graphite precursor particles It is possible to use granulated particles that are formed, calcined, graphitized and pulverized.
The volume-based average particle diameter d50 of the artificial graphite (E) is usually 3 μm or more, preferably 8 μm or more, more preferably 10 μm or more, and usually 60 μm or less, preferably 40 μm, more preferably 30 μm or less. If it is in the said range, it is preferable from the point which is easy to acquire the effect containing a composite carbon material (A) in a combination with a composite carbon material (A).

The artificial graphite (E) has a BET specific surface area of usually 0.5 m ² / g or more, preferably 1.0 m ² / g or more, and usually 8 m ² / g or less, preferably 6 m ² / g or less, more preferably. Is in the range of 4 m ² / g or less. If it is in the said range, it is preferable from the point with a small irreversible capacity | capacitance at the time of setting it as a carbon material.
In addition, the tap density of the artificial graphite (E) is usually preferably 0.6 g / cm ³ or more, preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and 0.85 g / cm ³ or more. Further preferred. Moreover, normally 1.5 g / cm < ³ > or less and 1.4 g / cm < ³ > or less are preferable, and 1.3 g / cm < ³ > or less is more preferable. If it is in the said range, a tap density is high and it is preferable from the point which is easy to fill a particle | grain, and is excellent in rolling property.

As the coated graphite (F) obtained by coating a raw carbon material not subjected to pressure treatment with a carbonaceous material or a graphite material, for example, natural graphite or artificial graphite not subjected to pressure treatment is coated with an amorphous precursor, calcined, and Particles that have been subjected to any one or more treatments of graphitization, or particles obtained by coating amorphous carbon with non-pressurized natural graphite or artificial graphite by a CVD method can be used.
The volume-based average particle diameter d50 of the coated graphite (F) is usually 5 μm or more, preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less. If it is in the said range, it is preferable from the point which is easy to acquire the effect containing a composite carbon material (A) in a combination with a composite carbon material (A).

The BET specific surface area of the coated graphite (F) is usually 1.0 m ² / g or more, preferably 2.0 m ² / g or more, more preferably 2.5 m ² / g or more, and usually 20 m ² / g or less. , Preferably 15 m ² / g or less, more preferably 8 m ² / g or less, still more preferably 6 m ² / g or less, and most preferably 4 m ² / g or less. If it is in the said range, it is preferable from the point with a small irreversible capacity | capacitance at the time of setting it as a carbon material.

Further, the tap density of the coated graphite (F) is usually preferably 0.6 g / cm ³ or more, preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and 0.85 g / cm ³ or more. Further preferred. Moreover, 1.3 g / cm ³ or less and 1.2 g / cm ³ or less are usually preferable, and 1.1 g / cm ³ or less is more preferable. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the intra-particle carbon density increases, the rollability is insufficient, and it may be difficult to form a high-density negative electrode sheet.

As amorphous carbon (G), the particle | grains which baked the bulk mesophase and the particle | grains which carried out the infusibilization process of the graphitizable organic compound and can be used can be used, for example.
The volume-based average particle diameter d50 of amorphous carbon (G) is usually in the range of 5 μm or more, preferably 8 μm or more, more preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less. If it is in the said range, it is preferable from the point which is easy to acquire the effect containing a composite carbon material (A) in a combination with a composite carbon material (A).

Amorphous BET specific surface area of carbon (G) is usually 1.0 m ² / g or more, preferably, 2.0 m ² / g or more, more preferably 2.5 m ² / g or more and usually ^8m 2 / g or less, preferably 6 m ² / g or less, more preferably 4 m ² / g or less. If it is in the said range, it is preferable from the point with a small irreversible capacity | capacitance at the time of setting it as a carbon material.
The tap density of amorphous carbon (G) is usually preferably 0.6 g / cm ³ or more, preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and 0.85 g / cm ^3. The above is more preferable. Moreover, 1.3 g / cm ³ or less and 1.2 g / cm ³ or less are usually preferable, and 1.1 g / cm ³ or less is more preferable. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the intra-particle carbon density increases, the rollability is insufficient, and it may be difficult to form a high-density negative electrode sheet.

<Mixing of composite carbon material (A) and metal fine particles (B)>
An apparatus used for mixing the composite carbon material (A) and the metal fine particles (B) is not particularly limited. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylinder mixer, a double cone Type mixers, regular cubic mixers, vertical mixers, and the like can be used. In the case of fixed type mixers: spiral mixers, ribbon mixers, Muller type mixers, Helical Flight type mixers, Pugmill type A mixer, a fluidized mixer or the like can be used. Moreover, you may mix using the mechanochemical process by mechanical energy. As a specific method, there are a method in which the raw material powder is put on a moving gas and the powders are hit against each other, or the powder is hit against a strong wall, for example, a jet mill or hybridization. Further, a method of applying a shearing force to the powder by a method such as passing a narrow space with a large force and utilizing the energy at that time can be adopted. Examples include Mechano Fusion manufactured by Hosokawa Micron Corporation.
When giving a shearing force, the shear rate to provide the 10 sec ^-1 or more, preferably 100 sec ^-1 or more, and more preferably not less than 1,000 sec ^-1. The upper limit is usually 50,000 sec ^-1 or less.

  Also, a method of putting raw material powder and a moving body not involved in the reaction in the pot and giving it vibration, rotation, or a combination of these, such as ball mill, vibration ball mill, planetary ball mill, rolling ball mill Etc. can also be used. In addition, when using these treatments, it is necessary to devise the order in which the raw material powders are charged and the mixing method so that the carbon particles are not excessively pulverized. For example, first, only metal particles are pulverized by applying large mechanical energy, and after the metal particles are refined, carbon particles are added and uniformly mixed in a short time with weak mechanical energy. Can be mentioned.

In addition, when the carbon material (C) is mixed with the composite carbon material (A), the mixing procedure is not particularly limited.
(1) Composite carbon material (A), metal fine particles (B) and carbon material (C) are mixed simultaneously (2) Composite carbon material (A) and metal fine particles (B) are mixed, and then carbon material (C) is mixed Examples thereof include mixing the composite carbon material (A) and the carbon material (C) and then mixing the metal fine particles (B).

<Carbon material for non-aqueous secondary batteries>
The physical properties of the mixture of the composite carbon material (A) and the metal fine particles (B) (the negative electrode material for non-aqueous secondary batteries) are preferably as follows.
<Presence form of composite carbon material (A) and fine metal particles (B)>
In the negative electrode material for a non-aqueous lithium ion secondary battery of the present invention, mechanical energy is added to each raw material particle, each raw material particle may be composited into composite metal particles, or each particle may be independently May be present. As a form of the carbon material for non-aqueous secondary batteries, a surface coating type, a metal surface embedding type, an embedding type, and a mixed type are mentioned as described below. Hereinafter, each structural type will be described. The negative electrode material for a non-aqueous lithium ion secondary battery of the present invention is not limited to the following structural types and manufacturing methods, and may be a combination of the structural types and manufacturing methods.

・ Surface coating type:
This is a structure in which the metal fine particles (B) are bound to the surface of the carbonaceous material and / or the graphite material covered with the pressure-treated carbon material (a).
・ Metal surface embedding type:
A part of the metal fine particles (B) is embedded in the carbon material (a) subjected to the pressure treatment, and the whole or part of the metal fine particles (B) and the pressure-treated carbon material (a) are carbonaceous material or graphite. It is a structure covered with quality materials.
・ Embedded type:
This is a structure in which the metal fine particles (B) are embedded in a carbonaceous material and a graphite material covered with a carbon material (a) subjected to pressure treatment.
・ Mixed type:
The metal fine particles (B) and the composite carbon material (A) obtained by coating the pressure-treated carbon material (a) with a carbonaceous material or a graphite material exist independently.

Among these, the mixed type is preferable because the effects of the present invention can be further exhibited.
The volume-based average particle diameter d50 of the negative electrode material for a non-aqueous secondary battery of the present invention is usually in the range of 5 μm or more, preferably 10 μm or more, and usually 60 μm or less, preferably 40 μm or less. If it is in the said range, it is preferable from the point which is easy to acquire the effect containing a composite carbon material (A).
The BET specific surface area of the negative electrode material for a non-aqueous secondary battery of the present invention is usually 1.5 m ² / g or more, preferably 2.0 m ² / g or more, and usually 10 m ² / g or less, preferably 8 m ^2. / G or less. If it is in the said range, it is preferable from the point with a small irreversible capacity | capacitance at the time of setting it as a carbon material.

Moreover, the tap density of the carbon material for a non-aqueous secondary battery of the present invention is usually preferably 0.6 g / cm ³ or more, preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, and 85 g / cm ³ or more is more preferable. And usually 1.4 g / cm ³ or less, preferably 1.3 g / cm ³ or less, 1.2 g / cm ³ or less is more preferable. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the intra-particle carbon density increases, the rollability is insufficient, and it may be difficult to form a high-density negative electrode sheet.

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

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

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

As the binder having an olefinically unsaturated bond in the molecule, a binder having a high molecular weight or a high proportion of unsaturated bonds is desirable.
Specifically, in the case of a binder having a large molecular weight, it is desirable that the weight average molecular weight is usually 10,000 or more, preferably 50,000 or more, and usually 1,000,000 or less, preferably 300,000 or less. In the case of a binder having a high ratio of unsaturated bonds, the number of moles of olefinically unsaturated bonds per gram of all binders is usually 2.5 × 10 ⁻⁷ or more, preferably 8 × 10 ⁻⁷ or more, Further, it is usually 5 × 10 ⁻⁶ or less, preferably 1 × 10 ⁻⁶ or less.

  The binder only needs to satisfy at least one of these regulations regarding molecular weight and regulations regarding the proportion of unsaturated bonds, but it is more preferable to satisfy both regulations simultaneously. When the molecular weight of the binder having an olefinically unsaturated bond is too small, the mechanical strength is inferior, and when it is too large, the flexibility is inferior. Moreover, when the ratio of the olefinically unsaturated bond in the binder is too low, the effect of improving the strength is reduced, and when it is too high, the flexibility is inferior.

The binder having an olefinically unsaturated bond has a degree of unsaturation of usually 15% or more, preferably 20% or more, more preferably 40% or more, and usually 90% or less, preferably 80% or less. Is desirable. The degree of unsaturation represents the ratio (%) of the double bond to the repeating unit of the polymer.
In the present invention, a binder that does not have an olefinically unsaturated bond can also be used in combination with the above-described binder that has an olefinically unsaturated bond as long as the effects of the present invention are not lost. The mixing ratio of the binder not having an olefinically unsaturated bond to the amount of the binder having an olefinically unsaturated bond is usually 150% by mass or less, preferably 120% by mass or less.

By using a binder that does not have an olefinically unsaturated bond, the coatability can be improved. However, if the combined amount is too large, the strength of the active material layer is lowered.
Examples of binders having no olefinically unsaturated bond include polysaccharides such as methylcellulose, carboxymethylcellulose, and starch; thickening polysaccharides such as carrageenan, pullulan, guar gum, and xanthan gum; polyethylene oxide, polypropylene oxide, and the like. Polyethers; vinyl alcohols such as polyvinyl alcohol and polyvinyl butyral; polyacids such as polyacrylic acid and polymethacrylic acid; or metal salts of these polymers; fluorine-containing polymers such as polyvinylidene fluoride; alkanes such as polyethylene and polypropylene Examples thereof include polymers and copolymers thereof.

  When the carbon material of the present invention is used in combination with the above-mentioned binder having an olefinically unsaturated bond, the ratio of the binder used in the active material layer can be reduced as compared with the conventional material. Specifically, the mass ratio (carbon) of the carbon material of the present invention and a binder (may be a mixture of a binder having an unsaturated bond and a binder having no unsaturated bond as described above). (Material / binder) is usually in the range of 90/10 or more, preferably 95/5 or more, and usually 99.9 / 0.1 or less, preferably 99.5 / 0.5 or less, in each dry mass ratio. It is.

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

A conventionally well-known thing can be used for the electrical power collector which apply | coats a slurry. Specific examples include metal thin films such as rolled copper foil, electrolytic copper foil, and stainless steel foil. The thickness of the current collector is usually 4 μm or more, preferably 6 μm or more, and usually 30 μm or less, preferably 20 μm or less.
The slurry is applied to a width of 5 cm by using a doctor blade so that the carbon material adheres to 5 to 15 mg / cm ² on a copper foil as a current collector, and air-dried at room temperature. Furthermore, after drying at 110 degreeC for 30 minutes, a preferable electrode sheet can be obtained by adjusting so that the density of an active material layer may be set to 1.7 g / cm < ³ > with a roll press.

After applying the slurry on the current collector, the slurry is usually dried at a temperature of 60 ° C. or higher, preferably 80 ° C. or higher, and usually 200 ° C. or lower, preferably 195 ° C. or lower, in dry air or an inert atmosphere. A physical layer is formed.
The thickness of the active material layer obtained by applying and drying the slurry is usually 5 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and usually 200 μm or less, preferably after roll pressing. It is 100 μm or less, more preferably 75 μm or less. If the active material layer is too thin, practicality as a negative electrode is lacking due to the balance with the particle size of the active material, and if it is too thick, it is difficult to obtain a sufficient Li ion occlusion / release function for a high-density current value.

The density of the carbon material in the active material layer varies depending on the application, the application that emphasizes capacity, preferably 1.55 g / cm ³ or more, especially 1.6 g / cm ³ or more, further 1.65 g / cm ³ or more, In particular, 1.7 g / cm ³ or more is preferable. If the density is too low, the capacity of the battery per unit volume is not always sufficient. Moreover, since a rate characteristic will fall when a density is too high, 1.9 g / cm < ³ > or less is preferable.

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

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

Examples of the positive electrode active material include metal chalcogen compounds that can occlude and release alkali metal cations such as lithium ions during charge and discharge. Examples of metal chalcogen compounds include vanadium oxide, molybdenum oxide, manganese oxide, chromium oxide, titanium oxide, tungsten oxide, and other transition metal oxides; vanadium sulfide, molybdenum sulfide things, sulfides of titanium, transition metal sulfides such as _CuS; NiPS _3, FePS 3 phosphate of a transition metal such as - 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 ; composite sulfides of transition metals such as LiCoS ₂ and LiNiS ₂ .

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

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

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

  The non-aqueous solvent used in the non-aqueous electrolyte is not particularly limited, and can be appropriately selected from known non-aqueous solvents that have been conventionally proposed as solvents for non-aqueous electrolytes. For example, chain carbonates such as diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate; chain ethers such as 1,2-dimethoxyethane; tetrahydrofuran, 2-methyl Examples include cyclic ethers such as tetrahydrofuran, sulfolane, and 1,3-dioxolane; chain esters such as methyl formate, methyl acetate, and methyl propionate; and cyclic esters such as γ-butyrolactone and γ-valerolactone.

  Any one of these non-aqueous solvents may be used alone, or two or more thereof may be mixed and used. In the case of a mixed solvent, a combination of a mixed solvent containing a cyclic carbonate and a chain carbonate is preferable, and the cyclic carbonate is a mixed solvent of ethylene carbonate and propylene carbonate. This is particularly preferable in that load characteristics are improved.

  Among them, propylene carbonate is preferably in the range of 2% by weight to 80% by weight, more preferably in the range of 5% by weight to 70% by weight, and more preferably in the range of 10% by weight to 60% by weight with respect to the whole non-aqueous solvent. preferable. When the proportion of propylene carbonate is lower than the above, the ionic conductivity at low temperature decreases, and when the proportion of propylene carbonate is higher than the above, when a graphite-based electrode is used for the negative electrode, propylene carbonate solvated with Li ions is graphite. By co-inserting between the phases, delamination degradation of the graphite-based negative electrode active material occurs, and there is a problem that sufficient capacity cannot be obtained.

The lithium salt used in the non-aqueous electrolytic solution is not particularly limited, and can be appropriately selected from known lithium salts that can be used for this purpose. For example, halides such as LiCl and LiBr; perhalogenates such as LiClO ₄ , LiBrO ₄ and LiClO ₄ ; inorganic lithium salts such as inorganic fluoride salts such as LiPF ₆ , LiBF ₄ and LiAsF ₆ ; LiCF ₃ SO ₃ , Examples include perfluoroalkane sulfonates such as LiC ₄ F ₉ SO ₃ ; fluorine-containing organic lithium salts such as perfluoroalkane sulfonic acid imide salts such as Li trifluorosulfonimide ((CF ₃ SO ₂ ) ₂ NLi), and the like. Of these, LiClO ₄ , LiPF ₆ , and LiBF ₄ are preferable.
Lithium salts may be used alone or in combination of two or more. The concentration of the lithium salt in the nonaqueous electrolytic solution is usually in the range of 0.5 mol / L or more and 2.0 mol / L or less.

In addition, when an organic polymer compound is included in the above non-aqueous electrolyte and the electrolyte is used in the form of a gel, rubber, or solid sheet, specific examples of the organic polymer compound include polyethylene oxide, polypropylene oxide. Polyether polymer compounds such as: cross-linked polymers of polyether polymer compounds; vinyl alcohol polymer compounds such as polyvinyl alcohol and polyvinyl butyral; insolubilized vinyl alcohol polymer compounds; polyepichlorohydrin; polyphosphazene Polysiloxane; polyvinyl polymer compounds such as polyvinylpyrrolidone, polyvinylidene carbonate and polyacrylonitrile; poly (ω-methoxyoligooxyethylene methacrylate), poly (ω-methoxyoligooxyethylene methacrylate-co-methyl); Methacrylate) and polymer copolymers such as poly (hexafluoropropylene-vinylidene fluoride).

  The non-aqueous electrolyte solution described above may further contain a film forming agent. Specific examples of the film forming agent include carbonate compounds such as vinylene carbonate, vinylethyl carbonate, and methylphenyl carbonate; alkene sulfides such as ethylene sulfide and propylene sulfide; sultone compounds such as 1,3-propane sultone and 1,4-butane sultone And acid anhydrides such as maleic acid anhydride and succinic acid anhydride.

  Furthermore, an overcharge inhibitor such as diphenyl ether or cyclohexylbenzene may be added. When the above additives are used, the content is usually 10% by mass or less, preferably 8% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less. If the content of the additive is too large, other battery characteristics such as an increase in initial irreversible capacity, low temperature characteristics, and deterioration in rate characteristics may be adversely affected.

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

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

The procedure for assembling the lithium ion secondary battery of the present invention is not particularly limited, and may be assembled by an appropriate procedure according to the structure of the battery. For example, the negative electrode is placed on the outer case, and the electrolytic solution is placed thereon. A separator is provided, and a positive electrode is placed so as to face the negative electrode, and it is caulked together with a gasket and a sealing plate to form a battery.
EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

In the present specification, the measurement of the carbon layer coverage, average particle diameter, tap density, BET specific surface area, Raman value, etc. of the carbonaceous particles was performed as follows.
The carbon layer coverage of the carbonaceous particles;
Coverage (mass%) = 100− (K × D) / ((K + T) × N) × 100
In this equation, K is the mass (Kg) of the graphite particles subjected to mixing with the tar pitch, T is the mass (kg) of the tar pitch that is the coating raw material used for mixing with the graphite particles, and D is the amount of K and T Of the mixture, the amount of the mixture actually subjected to firing, N, indicates the mass of the carbonaceous particles provided with a carbon layer after firing on at least a part of the surface of the graphite particles.

Volume-based average particle diameter (d50): About 1 ml of a 2 (volume)% aqueous solution of polyoxyethylene (20) sorbitan monolaurate, about 20 mg of carbon powder is added and dispersed in about 200 ml of ion-exchanged water. The volume-based particle size distribution was measured using a laser diffraction particle size distribution meter (LA-920, manufactured by Horiba, Ltd.), and the volume-based average particle size (d50) was determined.
Tap density; For example, it is measured using a powder density measuring device Tap Denser KYT-3000 (manufactured by Seishin Enterprise Co., Ltd.). After dropping the carbonaceous particles into a 10 cc tap cell and filling the cell to the full, tap with a stroke length of 10 mm was performed 500 times, and the density at that time was defined as the tap density.

BET specific surface area; measured using AMS-8000 manufactured by Okura Riken Co., Ltd. After pre-drying at 250 ° C. and flowing nitrogen gas for 30 minutes, the BET one-point method by nitrogen gas adsorption was used for measurement.
Pore volume (pore volume in the range of 10 nm to 100000 nm): The mercury porosimeter (model name: manufactured by Micromeritics, Autopore 9520) was used to carry out the mercury intrusion method. After pressing or approximately 2000 mm ² of an unpressed electrode sheet is accurately cut out and weighed and pretreated (degassed) for 10 minutes at room temperature (24 ° C.) under vacuum (50 μm / Hg), then mercury. The pressure was increased from 4.0 psia to 40,000 psia and then decreased to 15 psia (total measurement points of 120 points). At the measured 120 points, the intrusion amount of mercury was measured after an equilibration time of 5 seconds until 30 psia, and thereafter 10 seconds for each pressure.

  From the mercury intrusion curve thus obtained, the pore distribution was calculated using the Washburn equation (D = − (1 / P) 4γcos ψ). D represents the pore diameter, P represents the pressure, γ represents the surface tension of mercury (using 485 dynes / cm), and ψ represents the contact angle (using 140 °).

Raman R value; Raman spectrometer (Nicolet Almega XR manufactured by Thermo Fisher Scientific)
Was used, and the negative electrode material powder was put into a sample container, and laser light was irradiated and measured at any 10 locations. The Raman R value, the average value of the intensity ratio _I D / _{I G} peak around 1580 cm ^-1 1350 cm ^-1 vicinity of the peak and _{(P D)} which is observed in the Raman spectrum _{(P G)} to be R value. Each peak intensity was based on the entire measurement range (830 cm ^{−1 to} 1940 cm ⁻¹ ) as a baseline, and an arithmetic average of intensity ratios measured 10 times was used as an average value.
Laser light wavelength: 532 nm
Excitation output: 10%
Irradiation diameter: 10μmΦ (uses 10x objective lens)
Measurement range: 830 cm ^{−1 to} 1940 cm ⁻¹
Peak intensity measurement, peak half-width measurement: background processing, smoothing processing (convolution by simple averaging 10 points)

[Example 1]
(Production of composite carbon material (A))
Petroleum heavy oil obtained by spheroidizing natural graphite as a raw material carbon material, isotropically pressed at 1000 kgf / cm ² for 2 minutes using a CIP molding machine, and then crushed and obtained during naphtha pyrolysis (Easily graphitizable organic compound) was mixed with a biaxial kneader. Next, the obtained mixture was heat-treated in an inert gas at 700 ° C. for 2 hours, and further at 1300 ° C. for 1 hour, and a multi-layer carbon structure in which carbonaceous materials having different crystallinity were deposited on the surface of the spherical natural carbon material A composite carbon material (A) was obtained. Here, the volume-based average particle diameter (d50) of the composite carbon material (A) is 23.0 μm, the BET specific surface area (SA) is 1.9 m ² / g, the tap density (tap) is 1.17 g / cm ³ , The Raman R value was 0.33.

The intra-particle porosity after the isotropic pressure treatment is 18%, and the obtained carbon material powder has a coverage calculated from the calcined residual carbon ratio of 92.5% of graphite. It was confirmed that it was coated with 7.5% amorphous carbonaceous material.
(Metal fine particles (B))
As the metal fine particles (B), commercially available SiO particles (SiO _x X = 1) particles (Osaka Titanium Technologies) were used. The SiO particles had a volume-based average particle diameter (d50) of 6 μm and a BET specific surface area of 6 m ² / g.

(Non-aqueous secondary battery negative electrode material which is a mixture of composite carbon material (A) and silicon oxide particles (B))
100 parts by mass of the carbonaceous particles (A) and 12 parts by mass of silicon oxide particles (B) were dry-mixed to obtain a mixture. The volume reference average particle diameter (d50) of the composite carbon material (A) was 23 μm, and the volume reference average particle diameter (d50) of the silicon oxide (SiO _x ) particles was 6 μm. Moreover, the tap density of the mixture was 1.4 g / cm ³ .

(Production of battery for performance evaluation)
5. 100 parts by weight of the mixture of carbonaceous particles (A) and silicon oxide particles (B), 300 parts by weight of a 1% by weight aqueous solution of carboxymethylcellulose (CMC) as a binder and 48% by weight of aqueous dispersion of styrene butadiene rubber (SBR) 25 parts by mass was kneaded with a hybridizing mixer to form a slurry. This slurry was applied onto a rolled copper foil having a thickness of 18 μm by a blade method so as to have a basis weight of 7 to 8 mg / cm ² and dried. Then, it roll-presses with a 250 mφ roll press with a load cell so that the density of the negative electrode active material layer is 1.4 to 1.5 g / cm ³ , punched into a circular shape with a diameter of 12.5 mm, and 110 ° C. for 2 hours. It vacuum-dried and set it as the negative electrode for evaluation. As a result of measuring the pore volume of the electrode with a mercury porosimeter in an unpressed state, it was 0.25 ml / g.

The negative electrode and a Li foil as a counter electrode were stacked through a separator impregnated with an electrolytic solution to produce a battery for a charge / discharge test. As the electrolytic solution, a solution obtained by dissolving LiPF _{6 in a} mixed solution of ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 3: 3: 4 (weight ratio) to 1 mol / liter was used.

(Evaluation of charge capacity and discharge capacity)
The positive electrode and the negative electrode were charged to 5 mV at a current density of 0.12 mA / cm ² , further charged to a current value of 0.012 mA at a constant voltage of 5 mV, and lithium was doped into the negative electrode. The charge capacity measured at this time is obtained by subtracting the weight of the copper foil punched out in the same area as the negative electrode from the negative electrode weight to obtain the negative electrode active material weight, and the charge capacity is divided by the negative electrode active material weight to obtain the weight. The charge capacity per unit was obtained. On the other hand, with respect to the discharge capacity, after the previous charge, the positive electrode and the negative electrode were discharged to 1.5 V at a current density of 0.12 mA / cm ² , and the discharge capacity at this time was measured. The discharge capacity per unit weight was determined by dividing the discharge capacity by the weight of the substance.

(Rate characteristics evaluation)
The rate characteristics were determined according to the following formula (1) from the discharge capacity at the second cycle and the discharge capacity at the third cycle determined by the discharge capacity evaluation. In the third cycle, the positive electrode and the negative electrode are charged to 5 mV at a current density of 0.49 mA / cm ² , and further charged to a current value of 0.049 mA at a constant voltage of 5 mV. After doping, the positive electrode and the negative electrode were discharged to 1.5 V at a current density of 0.49 mA / cm ² . The discharge capacity is obtained by subtracting the weight of the copper foil punched out in the same area as the negative electrode from the negative electrode weight to obtain the negative electrode active material weight, and dividing the discharge capacity by the negative electrode active material weight to obtain the discharge capacity per weight. It was.
Rate characteristic (%) = {discharge capacity at the third cycle (mAh / g) / 2 discharge capacity at the second cycle (mAh / g)} × 100 (1)

[Comparative Example 1]
A battery for performance evaluation was produced in the same manner as in Example 1 except that the graphite particles before having a carbon layer made of amorphous carbon were used. As a result of measuring the pore volume of the electrode with a mercury porosimeter in an unpressed state, it was 0.13 ml / g.
Table 1 below shows the charge capacity, discharge capacity, and rate characteristics of Example 1 and Comparative Example 1.

  As shown in Table 1, the negative electrode material of Example 1 containing a composite carbon material (A) having a high density and a low specific surface area and silicon oxide particles that are metal fine particles (B) that were subjected to pressure treatment was used. Compared to the battery using the negative electrode material of Comparative Example 1 containing graphite particles and metal fine particles (B) that are not subjected to pressure treatment, the battery has both a high charge capacity and a high discharge capacity, thereby realizing a high capacity. It was confirmed that the high rate characteristics were maintained while suppressing the deterioration of the rate characteristics.

  A non-aqueous secondary battery including an electrode using the negative electrode material of the present invention has a high capacity and has a characteristic of improving rate characteristics, and therefore is required for use in recent power tools and electric vehicles. It is also useful in the industry.

Claims (10)

  A carbon material for a non-aqueous secondary battery, comprising: a composite carbon material (A) obtained by coating a pressurized carbon material (a) with a carbonaceous material or a graphite material; and metal fine particles (B).   2. The non-aqueous secondary battery according to claim 1, wherein a mixing ratio of the metal fine particles (B) to the total amount of the composite carbon material (A) and the metal fine particles (B) is 1% by mass or more and 30% by mass or less. Carbon material.   The carbon material for a non-aqueous secondary battery according to claim 1 or 2, wherein the metal fine particles (B) have an average particle diameter (d50) of 0.01 µm or more and 10 µm or less.   The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 3, wherein the metal fine particles (B) are Si and / or SiOx (0≤x <2). The non-aqueous secondary battery further comprising at least one carbon material (C) selected from the following in the non-aqueous secondary battery carbon material according to claim 1. Carbon material for batteries.
Carbon material (C): natural graphite (D, artificial graphite (E), coated graphite (F) obtained by coating a raw carbon material not subjected to pressure treatment with a carbonaceous material or a graphite material, and amorphous carbon (G).   The carbon material for a nonaqueous secondary battery according to any one of claims 1 to 5, wherein the carbon material (A) has an average particle diameter (d50) of 1 µm or more and 60 µm or less.   The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 6, wherein the pressure-treated carbon material (a) is isotropic pressure-treated spheroidized natural graphite.   The carbon material for non-aqueous secondary batteries according to any one of claims 1 to 7, wherein the carbon material (a) subjected to the pressure treatment has an intra-particle porosity of 5% or more and 30% or less.   It is a negative electrode for non-aqueous secondary batteries provided with an electrical power collector and the active material layer formed on the said electrical power collector, Comprising: The said active material layer is any one of Claims 1-8. A negative electrode for a non-aqueous secondary battery, comprising a carbon material for a non-aqueous secondary battery.   A nonaqueous secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode for a nonaqueous secondary battery according to claim 9.