JP2014067643A - Carbon material for nonaqueous secondary battery, negative electrode, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a negative electrode active material having high density without destroying a surface structure to provide a carbon material for a nonaqueous secondary battery which has excellent cycle characteristics.SOLUTION: A carbon material for a nonaqueous secondary battery contains a composite carbon material (A) including a carbon material subjected to pressurization treatment and coated with a carbonaceous substance, and a composite carbon material (B) in which a graphite substance is compounded.

Description

  The present invention relates to a carbon material for a non-aqueous secondary battery used for a non-aqueous secondary battery, 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 negative electrode material of a lithium ion secondary battery, a graphite material or amorphous carbon is often used from the viewpoint of cost and durability. However, amorphous carbon material has a small reversible capacity within the range of materials that can be put to practical use, and graphite material breaks down when the active material layer containing the negative electrode material is densified for high 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 problems, for example, Patent Document 1 discloses a negative electrode material for a lithium ion secondary battery containing isotropic graphite that is isotropically pressurized and densified. A manufacturing method is disclosed.
Patent Document 2 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.

  Patent Document 3 discloses a graphite material for a lithium ion secondary battery characterized by mixing two types of graphite powder having equal ease of crushing (compressibility) and different powder oil absorption and circularity. ing.

Japanese Patent Laying-Open No. 2005-50807 JP 2011-060465 A JP 2010-92649 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 Patent Document 2, 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 3, it is described that a high electrode density can be obtained and the permeability of the electrolytic solution is excellent. However, since it is a mixture of materials with equal ease of crushing (compressibility), There is a concern that the surface structure of graphite is destroyed.
This invention is made | formed in view of this subject, By mixing the material from which hardness differs, a negative electrode can be manufactured with a high density, without destroying the surface structure of a hard material.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention have combined a hard composite carbon material (A) and a graphitic material which are pressurized and coated with a carbonaceous material, and the inside of the particles is densified. By applying the carbon material for a non-aqueous secondary battery including the composite carbon material (B) to the negative electrode, the side reaction with the electrolytic solution is suppressed, the deterioration during the cycle is reduced, and the non-aqueous secondary battery excellent in cycle characteristics is obtained. The present inventors have found that a secondary battery can be obtained and have completed the present invention.
The composite carbon material in which the graphite material or the carbonaceous material is compounded here indicates a state in which the graphite material or the carbonaceous material is attached to the surface or inside of the carbon material as a core, and the graphitic material Examples include a material or carbonaceous material coated with a carbon material, a graphitic material or carbonaceous material taken into the carbon material, or a carbon material in which a granulated body is formed via the graphite material.

  The gist of the present invention is characterized by containing a composite carbon material (A) obtained by coating a pressure-treated carbon material with a carbonaceous material or a graphite material, and a composite carbon material (B) in which the graphite material is composited. It exists in the carbon material for non-aqueous secondary batteries.

  By using the carbon material for a non-aqueous secondary battery including the composite carbon material (A) and the composite carbon material (B) of the present invention as a carbon material for a non-aqueous secondary battery, the reaction with the electrolyte is further suppressed. It is possible to provide an excellent non-aqueous secondary battery with little deterioration during the cycle. 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 as it is, the surface structure of the composite carbon material (A) is destroyed during the step of forming the negative electrode (particularly, the electrode density is set to a predetermined value), which is excellent. Battery characteristics may be difficult to obtain.
On the other hand, the negative electrode material according to the present invention includes the composite carbon material (A) and the composite carbon material (B), without impairing the battery characteristics that the composite carbon material (A) originally has, It is considered that further excellent battery characteristics can be obtained.

Illustration of internal void volume calculation method by mercury intrusion method (example)

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 for composite carbon materials (A) and (B)>
Although it shows below as an example about the raw material carbon material which is a raw material of composite carbon material (A) * (B) of this invention, it does not restrict | limit in particular. The raw material carbon materials that are the raw materials of the composite carbon materials (A) and (B) may be the same, or the types and physical properties thereof may be different. Moreover, in this specification, the carbon material used for each raw material may be generically called a raw material carbon material.

-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. Natural graphite made spherical is preferable in terms of low cost and ease of electrode production. Further, from the viewpoint of safety, a highly purified carbon material or spherical natural graphite with few impurities is preferable. 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, the battery capacity is more preferable when used as a negative electrode material.

  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.
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) Raw carbon material d ₀₀₂
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%. 2% to 3.6%, preferably 2% to 3.6%.
More preferably, it is 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)
Although there is no restriction | limiting in particular about the particle size of raw material carbon material, As a range used, an average particle diameter (median diameter) is 50 micrometers or less normally, Preferably it is 30 micrometers or less, More preferably, it is 25 micrometers 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 the measurement cell is rotated in a plane perpendicular to the laser beam while irradiating the measurement cell with an argon ion laser beam. Measure.
Argon ion laser light wavelength: 514.5 nm
Laser power on sample: 25 mW
Resolution: 4cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
Peak intensity measurement, peak half-width measurement: background processing, smoothing processing (convolution 5 points by simple averaging)

(8) Internal porosity of raw material carbon material The internal porosity of the raw material carbon material is usually 1% or more, preferably 3% or more, more preferably 5% or more, and further preferably 7% or more. Further, it is usually 40% or less, preferably 35% or less, more preferably 30% or less, and still more preferably less than 23%. If the internal porosity is too small, the amount of liquid in the particles tends to decrease, and charge / discharge characteristics tend to deteriorate. If the internal porosity is too large, there are few interparticle voids in the case of an electrode, and the electrolyte diffuses. Tend to be insufficient.

(9) Method for producing raw carbon material The raw 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 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, 40 to 100 m / sec, and more preferably 50 to 100 m / sec. 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 compounds that are raw materials for composite carbon materials (A) and (B)>
The organic compound that is a precursor of the carbonaceous material for coating or the graphite material that is the other raw material of the composite carbon materials (A) and (B) of the present invention is shown below as an example, but is not particularly limited. The organic compounds that are the raw materials of the composite carbon materials (A) and (B) may be the same, or the types and physical properties may be different.
Moreover, it is preferable to satisfy | fill the physical property shown below.

-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 whose d value is usually 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, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural furfuryl alcohol polymers , Polyphenylene sulfide, polyphenylene oxide, resin, phenol-formaldehyde resin, imide resin, and the like. 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)
<Physical properties of carbonaceous material fired 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.

<Physical Properties in Graphite Materials Firing Organic Compounds>
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))
<Physical properties of carbonaceous material fired 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

<Physical Properties in Graphite Materials Firing Organic Compounds>
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) Quinoline insoluble matter (QI), toluene insoluble matter (TI)
The quinoline insoluble content of the organic compound is usually 0.6% or more, preferably 1% or more, more preferably 5% or more, still more preferably 6% or more, and particularly preferably 8% or more. Further, it is usually 30% or less, preferably 25% or less, more preferably 20% or less, still more preferably 15% or less, and particularly preferably 12% or less.

The toluene insoluble content is usually 16% or more, preferably 20% or more, more preferably 25% or more. Moreover, it is 60% or less normally, Preferably it is 50% or less, More preferably, it is 40% or less. When the quinoline insoluble content and the toluene insoluble content are within this range, the charge / discharge reactivity becomes a preferable range because the crystallinity of the carbon material for the non-aqueous secondary battery becomes a preferable range, so the charge / discharge capacity is improved, There is a tendency to reduce gas generation during storage at high temperatures, to improve large current charge / discharge characteristics, and to improve cycle characteristics.
In addition, the measuring method of a quinoline insoluble content (QI) and a toluene insoluble content (TI) shall follow the method as described in an Example.

(Graphitization catalyst)
In order to increase the charge / discharge capacity and improve the pressability, a graphitization catalyst may be added when mixing the carbonaceous particles and the organic compound. Examples of the graphitization catalyst include metals such as iron, nickel, titanium, silicon, and boron, and compounds such as carbides, oxides, and nitrides thereof. Of these, silicon, silicon compounds, iron, and iron compounds are preferable, and silicon carbide is particularly preferable among silicon compounds, and iron oxide is particularly preferable among iron compounds. The addition amount of these graphitization catalysts is usually 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 5% by mass or less with respect to the carbonaceous primary particles as a raw material. . When there are too many graphitization catalysts, graphitization will advance too much and the characteristic at the time of lithium ion secondary battery manufacture, especially the problem that immersion property may not be enough may arise. At the same time, the strength of the particles may decrease because of the formation of pores in the graphite composite particles, and as a result, the surface may be smoothed during the pressing process during electrode plate production, and ion migration may be inhibited. On the other hand, if there is too little graphitization catalyst, graphitization is insufficient and there is a problem of reduction in charge / discharge capacity when a non-aqueous secondary battery is made, and high pressure is required in the pressing process during electrode plate production. It may be difficult to increase the density. Furthermore, because the graphite composite particles do not have an appropriate amount of pores, the strength of the particles becomes too high, and a high pressure is applied when the active material layer applied to the current collector is pressed to a predetermined bulk density. And it may be difficult to increase the density of the negative electrode active material layer.

<Method for producing composite carbon material (A)>
The method for producing the composite carbon material (A) is not particularly limited as long as it is a composite carbon material formed by coating a carbonaceous material that has been subjected to pressure treatment. Preferably, the composite carbon material (A) is pressurized against the composite carbon material (A). Method of processing, after the above-mentioned raw material carbon material is pressurized, crushed and mixed with an organic compound for obtaining a carbonaceous material-coated portion, and the resulting mixture is baked and pulverized, or raw material After mixing the carbon material with an organic compound for obtaining a carbonaceous material-coated portion and pressurizing it, the carbon material used in the present invention was coated with the carbonaceous material in the step of firing and pulverizing the resulting mixture. A composite carbon material (A) can be manufactured. More preferably, after mixing the raw material carbon material with a small number of pulverization steps and an organic compound for obtaining a carbonaceous material-coated portion and pressurizing, the obtained mixture is baked and subjected to the pulverization step in the present invention. This is a method for producing a composite carbon material (A) in which the carbon material used is coated with a carbonaceous material.

-The process of mixing a raw material carbon material and an organic compound The mixing of a raw material carbon material 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 raw material carbon material, 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 can be coated more efficiently and uniformly.

Organic solvents include pentane, hexane, isohexane, heptane, octane,
Hydrocarbons such as isooctane, decane, dimethylbutane, cyclohexane, and methylcyclohexane; ethers such as ethyl ether, isopropyl ether, diisoamyl ether, methylphenyl ether, amylphenyl ether, and ethylbenzyl ether; acetone, methylacetone, methylethylketone, and methylisobutyl Ketones such as ketone and diethyl ketone; esters such as methyl formate, ethyl formate, isobutyl formate, methyl acetate, isoamyl acetate, methoxybutyl acetate, cyclohexyl acetate, methyl butyrate, ethyl butyrate, butyl benzoate, isoamyl benzoate; benzene, toluene , Xylene, ethylbenzene, diethylbenzene, isopropylbenzene, amylbenzene, diamylbenzene, triamylbenzene, tetraamylbenze , Dodecylbenzene, didodecylbenzene, amyl toluene, tetralin, there are aromatic hydrocarbons such as cyclohexylbenzene, but is not limited thereto.

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.

-Step of pressurizing raw carbon material In the method for producing a composite carbon material (A) in the present invention, it is preferable to perform a pressurization treatment on the raw carbon material after mixing the organic compound and 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. 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 is increased.

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.

Although the pressure which pressurizes raw material carbon material is not specifically limited, Usually, it is 50 kgf / cm < ² > or more, Preferably it is 100 kgf / cm < ² > or more. 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. In particular, when the pressure is too high, the intra-particle porosity decreases, but a large amount of energy is required when the molded body is crushed, leading to an increase in specific surface area. From the above, it is considered that both the reduction of the void ratio within the particle and the suppression of the increase of the specific surface area can be achieved by the pressurizing treatment at a low pressure.

  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 step of firing the mixture The obtained mixture is heated in a non-oxidizing atmosphere, preferably under a flow of nitrogen, argon, carbon dioxide, or the like, so that the organic compound coated with the pressurized carbon material is carbonized or Graphitized to produce the 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 carbon material in the mixture, and is usually 2000 ° C. or less, preferably 1500 ° C. or less, preferably 1300 ° 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 steps may be subjected to pulverization, pulverization, classification, BR>, and powder processing as necessary. Moreover, you may perform a pressurization process suitably.
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) obtained by the above-described manufacturing method is a composite carbon material obtained by coating a carbon material subjected to pressure treatment with a carbonaceous material. The carbonaceous material is preferably amorphous carbon, and this aspect can be confirmed by the physical properties and SEM photographs shown below.
The composite carbon material (A) obtained by the above production method 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 argon ion laser Raman spectrum of the Raman R value composite carbon material (A) is usually 0.45 or less, preferably 0 .40 or less, more preferably 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 9 m ² / g or less, more preferably 8 m ² / g or less. 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 the mercury intrusion method is usually 1.0 mL / g or less, preferably 0.9 mL / g or less, more preferably 0. 0.8 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 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, and usually 1 μm or more, preferably 3 μm or more, more preferably 5 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. Among these, it is preferable that it is coated with a carbonaceous material, preferably an amorphous carbonaceous material, from the viewpoint of lithium ion acceptability, and this coverage is usually 0.5% or more and 10.0% or less, preferably 1. It is 0% or more and 9.0% or less, and 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 (2) based on the remaining charcoal rate.
Formula (2)
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)}

(8) Internal porosity The internal porosity of the composite carbon material (A) is 1% or more, preferably 3% or more, more preferably 5% or more, and further preferably 7% or more. Further, it is less than 23%, preferably 22.5% or less, more preferably 22% or less, and still more preferably 20% or less. If the internal porosity is too small, the amount of liquid in the particles tends to decrease, and charge / discharge characteristics tend to deteriorate. If the internal porosity is too large, there are few interparticle voids in the case of an electrode, and the electrolyte diffuses. Tend to be insufficient. For example, as shown in FIG. 1, the internal porosity is obtained by drawing a tangent (M) with respect to the minimum value of the slope based on the pore distribution (integral curve) (L) obtained by a known mercury intrusion method, A branch point (P) between the tangent line (M) and the integral curve (L) is obtained, and a pore volume smaller than the branch point is defined as an intraparticle pore amount (cm ³ / g) (V). The internal porosity can be calculated from the amount of pores in the particles obtained and the true density of graphite. The true density of graphite used for calculation is 2.26 g / cm ³ , which is the true density of general graphite. The calculation formula is shown in Formula (3).

Formula (3)
Internal porosity (%) = [intraparticle pore volume / {intraparticle pore volume + (1 / true graphite density)}] × 100

<Method for producing composite carbon material (B)>
The method for producing the composite carbon material (B) is not particularly limited as long as it is a composite carbon material in which a graphite material is composited. Mixing with an organic compound to obtain a carbonaceous material covering part, and graphitizing and pulverizing the resulting mixture, or mixing with a raw material carbon material and an organic compound to obtain a carbonaceous material covering part, and pressure treatment After that, the composite carbon material (B) in which the carbon material used in the present invention is coated with the graphite material in the step of graphitizing and pulverizing the obtained mixture can be produced. More preferably, it is the latter with fewer pulverization steps.
The step of mixing the raw carbon material and the organic compound and the step of pressure treatment can be carried out in the same manner as the method for producing the composite carbon material (A).

-The step of firing the mixture Specifically, the mixture is heated in a non-oxidizing atmosphere, preferably under a flow of nitrogen, argon, carbon dioxide, etc., to graphitize the organic compound, and thus a composite coal for non-aqueous secondary batteries. This is a process for manufacturing a material.
The firing temperature varies depending on the organic compound used for the preparation of the mixture, but when obtaining a composite carbon material for a non-aqueous secondary battery in which a graphite material is composited, it may be at or above the temperature at which the organic compound graphitizes, Specifically, it is normally carbonized by heating to 2000 ° C. or higher, preferably 2500 ° C. or higher, more preferably 2700 ° 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 carbon material in the mixture, and is usually 3300 ° C. or lower, preferably 3100 ° C. or lower and 3000 ° C. or lower.

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. As the Atchison furnace and heating method, a high-frequency induction heating furnace, direct resistance heating, indirect resistance heating, direct combustion heating, radiant heat heating, or the like can be used. During the treatment, stirring may be performed as necessary.

The composite carbon material that has undergone the above-described steps is subjected to powder processing such as pulverization, crushing, and classification again as necessary to obtain a composite carbon material for a non-aqueous secondary battery.
There are no particular restrictions on the apparatus used for pulverization and pulverization, for example, the coarse pulverizer includes a shearing mill, jaw crusher, impact crusher, cone crusher, etc., and the intermediate pulverizer includes roll crusher, hammer mill, etc. Examples of the pulverizer include a ball mill, a vibration mill, a pin mill, a stirring mill, and a jet mill.

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

<Composite carbon material (B)>
The composite carbon material (B) obtained by the above production method is not particularly limited as long as it is a composite carbon material (B) in which a graphite material is composited. The graphitic material is preferably a graphitized material obtained by graphitizing the above-described organic compound by firing, and it is more preferable that the graphitic material is combined with the pressure-treated carbon material.
This aspect can be confirmed by the following physical properties and SEM photographs. Moreover, it is preferable to have the following characteristics:

(1) 002 plane spacing (d002)
The interplanar spacing (d002) of the 002 plane according to the X-ray wide angle diffraction method of the composite carbon material (B) is 3.37 mm or less and Lc is 900 mm or more. The 002 plane spacing (d002) by X-ray wide-angle diffraction method is 3.37 mm or less and Lc is 900 mm or more, which means that the crystallinity of most of the composite carbon material (B) excluding the surface is high. This indicates that the composite carbon material is a high-capacity electrode that does not cause a reduction in capacity due to the large irreversible capacity found in amorphous carbon materials.

(2) Tap density The tap density (Tap density) of the composite carbon material (B) is usually 0.8 g / cm ³ or more, preferably 0.85 g / cm ³ or more, more preferably 1 g / cm ³ or more, More preferably, it is 1.1 g / cm ³ or more.
That the tap density of the composite carbon material (B) is 0.8 g / cm ³ or more is one of the indices indicating that the composite carbon material (B) has a spherical shape. When the tap density is less than 0.8 g / cm ³ , this is one of the indexes indicating that the spherical carbon material, which is the raw material of the composite carbon material (B), is not 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 that are not 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 argon ion laser Raman spectrum of the Raman R value composite carbon material (B) is usually 0.45 or less, preferably 0 .40 or less, more preferably 0.35 or less, and usually 0.01 or more, preferably 0.03 or more, more preferably 0.05 or more. If the Raman value is within this range, the crystallinity on 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 (B) is usually 15 m ² / g or less, preferably 10 m ² / g or less, more preferably 9 m ² / g or less, more preferably 8 m ^2. / G or less, usually 0.1 m ² / g or more, preferably 0.7 m ² / g or more, more preferably 1 m ² / g or more. If the specific surface area is too large, the reactivity between the portion exposed to the electrolyte when used as the negative electrode active material and the electrolyte increases, gas generation tends to increase, and a favorable battery tends to be difficult to obtain. If it is too small, the lithium acceptability tends to deteriorate during charging when used as a negative electrode active material.

(5) Volume-based average particle diameter (d50)
The volume-based average particle size of the composite carbon material (B) is usually 60 μm or less, preferably 40 μm or less, more preferably 30 μm or less, still more preferably 20 μm or less, usually 3 μm or more, preferably 5 μm or more, more preferably 7 μm. That's it. If the average particle size is too large, a large amount of binder tends to be required, and if the average particle size is too small, high current density charge / discharge characteristics tend to decrease.

(6) Coverage The composite carbon material (B) is coated with a graphite material. Among these, it is preferable to be coated with a graphite material, but this coverage is usually 1% by mass or more, preferably 5% by mass or more, more preferably 8% by mass or more, and further preferably 10% or more. Usually 30% by mass or less,
Preferably it is 25 mass% or less, More preferably, it is 20 mass% or less. If the content is too large, the low crystalline 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 low crystalline portion is not uniformly coated on the scale graphite. At the same time, strong granulation is not achieved, and the particle size tends to be small when pulverized after firing.
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 (2) based on the remaining charcoal rate.

Formula (2)
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)}

(7) Orientation ratio (110/004)
The orientation ratio of the composite carbon material (B) powder is usually 0.1 or more, preferably 0.27 or more, more preferably 0.29 or more, still more preferably 0.0.3 or more, and particularly preferably. It is 0.4 or more, and is usually 0.7 or less, preferably 0.6 or less, more preferably 0.5 or less. When the orientation ratio is too small and is below the above range, the high-density charge / discharge characteristics may tend to deteriorate. In addition, the normal upper limit of the said range is a theoretical upper limit of the orientation ratio of a carbonaceous material.

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

<Mixing of composite carbon material (A) and composite carbon material (B)>
The carbon material for non-aqueous secondary batteries of the present invention is characterized by including a composite carbon material (A) and a composite carbon material (B).
When the composite carbon material (B) is mixed with the composite carbon material (A), the mixing ratio of the composite carbon material (A) to the total amount of the composite carbon material (A) and the composite carbon material (B) is not particularly limited. However, it is usually 5% by mass or more, preferably 10% by mass or more, and usually 95% by mass or less, preferably 90% by mass or less. When the mixing ratio of the composite carbon material (B) is lower than the above range, the surface structure of the composite carbon material (A) is destroyed during the step of forming a negative electrode (particularly, the electrode density is set to a predetermined value), and thus excellent. The battery characteristics tend to be difficult to obtain. On the other hand, if the above range is exceeded, the characteristics of the composite carbon material (A) hardly appear, the composite carbon material (B) tends to be deformed excessively, and the liquid diffusion into the electrode tends to deteriorate.

  An apparatus used for mixing the composite carbon material (A) and the composite carbon material (B) is not particularly limited. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylindrical mixer, a double Conical mixers, regular cubic mixers, vertical mixers, and the like can be used. In the case of stationary mixers: spiral mixers, ribbon mixers, Muller mixers, Helical Flight mixers, Pugmill A mold mixer, a fluidized mixer, or the like can be used.

<Carbon material for non-aqueous secondary batteries>
The physical properties of the mixture of the composite carbon material (A) and the composite carbon material (B) (non-aqueous secondary battery carbon material) are preferably as follows.
The volume-based average particle diameter d50 of the carbon 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 carbon 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 8 m ² / g or less, preferably 6 m ^2. / G or less. If it is in the said range, it is preferable from the point that the irreversible capacity | capacitance at the time of setting it as a negative electrode material is small.

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. <Other carbon materials>
In addition to the composite carbon material (A) and the composite carbon material (B), a known carbon material may be mixed as long as the effects of the present invention are not impaired.

<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 composite carbon material for a non-aqueous secondary battery 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 (negative electrode) of the negative electrode 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 negative electrode material of the present invention and a binder in a dispersion medium to form a slurry, which is applied to a current collector. As the dispersion medium, an organic solvent such as alcohol or water can be used. If necessary, a conductive agent may be added to the slurry.

(Conductive agent)
Examples of the conductive agent include carbon black such as flaky natural graphite, acetylene black, ketjen black, and furnace black, and fine powder made of Cu, Ni having an average particle size of 1 μm or less, or an alloy thereof. Among these, scaly natural graphite is preferable from the viewpoint of a relatively small specific surface area, and it is preferable to add a conductive additive to the carbon material of the present invention from the viewpoint of uniform current distribution in the electrode plate. The addition amount of the conductive agent is usually about 10% by mass or less with respect to the negative electrode material of the present invention.

Conductive agent, spacing of 002 surface (d002) is 3.37Å or less by X-ray wide angle diffraction method, a peak intensity ratio in the vicinity of 1360 cm ^-1 to the peak intensity near 1580 cm ^-1 in the argon ion laser Raman spectrum Raman R The value is 0.18 or more and 0.7 or less, the aspect ratio is 4 or more, and the average particle size (d50) satisfies the condition of 2 μm or more and 12 μm or less. Below, the typical characteristic of the electrically conductive agent of this invention is described.

(A) 002 plane spacing (d002)
The surface spacing (d002) of the 002 plane by the X-ray wide angle diffraction method of the conductive agent is 3.37 mm or less, preferably 3.36 mm or less. Lc is usually 900 mm or more, preferably 950 mm or more. The inter-surface distance (d002) of the 002 surface by the X-ray wide angle diffraction method is measured by the method described later in the examples. If the interplanar spacing (d002) of the 002 plane is too large, the crystallinity of most parts except the surface of the carbon material particles will be low, and the capacity will decrease due to the large irreversible capacity found in amorphous carbon materials. Tend to. If Lc is too small, the crystallinity tends to be low.

(B) Raman R value is the peak intensity ratio in the vicinity of 1360 cm ^-1 to the peak intensity near 1580 cm ^-1 in the argon ion laser Raman spectrum of the Raman R value conductive agent, 0.1 or more, preferably 0.15 or more Yes, more preferably 0.2 or more, usually 0.7 or less, preferably 0.6 or less, more preferably 0.5 or less.

  If the Raman R value is too small, the crystallinity of the particle surface becomes too high, and when the density is increased, the crystals are likely to be oriented in a direction parallel to the electrode plate, and the load characteristics may be deteriorated. On the other hand, if the Raman R value is too large, the crystal on the particle surface is disturbed, the reactivity with the electrolytic solution increases, and the efficiency tends to decrease and the gas generation increases.

(C) Aspect ratio The aspect ratio of the conductive agent is 4 or more, preferably 4.5 or more, more preferably 5 or more, usually 25 or less, preferably 20 or less, more preferably 15 or less. If the aspect ratio is too small, the irreversible capacity tends to increase. On the other hand, if the aspect ratio is too large, the adsorption capacity of the binder resin tends to be low when the electrode is used.

(D) Average particle diameter The average particle diameter (d50) of the conductive agent is 2 μm or more, preferably 3 μm or more, more preferably 4 μm or more, and 12 μm or less, preferably 10 μm or less, more preferably 8 μm or less. . If the average particle size is too small, the specific surface area tends to be small and it is difficult to prevent an increase in irreversible capacity. On the other hand, if the average particle size is too large, it is difficult to prevent the rapid charge / discharge performance from being lowered due to the reduction of the contact area between the electrolyte and the conductive agent particles.

(E) Tap density The tap density of the conductive agent is usually 0.6 g / cm ³ or less, preferably 0.5 g / cm ³ or less, more preferably 0.4 g / cm ³ or less. When the tap density of the conductive agent is too large, the scaly graphite particles are less likely to have a sufficient bulk, and when used as an electrode, the adsorption capacity of the binder resin (CMC, SBR, etc.) is low, and the binder resin (CMC, SBR) Etc.) tends to be difficult to prevent.

The specific surface area by BET method specific surface area conductive agent according to (f) the BET method is preferably from normal ^{30 m} 2 / g, more preferably not more than ^27m 2 / g. Further, it is preferably ^{5 m} 2 / g or more, more preferably ^7m 2 / g or more.
If the specific surface area of the conductive agent is too large, it tends to be difficult to prevent a decrease in capacity due to an increase in irreversible capacity. On the other hand, if the specific surface area is too small, the adsorption capacity of the binder resin (CMC, SBR, etc.) is lowered when the electrode is used, and it is difficult to prevent wasteful eating of the binder resin (CMC, SBR, etc.).

(G) Type of conductive agent and production method As the type of conductive agent, scaly graphitic carbon is preferable among various carbon materials. By mixing such a conductive agent, the binder resin (CMC, SBR, etc.) is adsorbed to the conductive agent when it is made into an electrode, and the waste of the binder resin (CMC, SBR, etc.) is prevented, and the carbon material is more evenly distributed. The surface can be covered with a binder resin (CMC, SBR, etc.), and the irreversible capacity can be reduced.

  As long as the method for producing the conductive agent satisfies the above-mentioned characteristics, any production method can be used. For example, a carbon material produced as a by-product when producing the spherical graphite particles can be used as the conductive agent. . Conventionally, when producing spheroidized graphite particles, a very large amount of fine powders having various physical properties are by-produced. In the present invention, a carbon material controlled to have a specific physical property value obtained by subjecting these by-products to various classifications, crushing, and the like is selected, and the carbon material is selected as a graphite particle (A). By blending, it can be applied to a carbon material for non-aqueous electrolyte secondary batteries with high utility value. Further, as another method for producing the conductive agent, it may be produced as a target substance. As a specific production method, for example, as a method for producing spheroidized graphite particles, scaly, scaly, plate-like and lump-like graphite produced naturally, for example, petroleum coke, coal pitch coke, coal needle coke and mesophase pitch are used at 2500 ° C. The artificial graphite produced by heating as described above can also be produced by subjecting it to various pulverization, pulverization, classification, etc. so as to obtain specific physical property values.

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 negative electrode 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.
Moreover, the composite carbon material (A) and the carbon material (B) are each made into an electrode sheet, and the ratio of the load when the density is set to a predetermined density with a roll press machine, the value of the composite carbon material (A) / carbon material (B) is 1 to 50 is preferable, 1.1 to 30 is more preferable, and 1.2 to 20 is more preferable. When the ratio is 1 or less, the surface structure of the composite carbon material may be disturbed, and when it exceeds 50, the change in density with respect to the load becomes severe, and it becomes difficult to control the density.

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 the negative electrode for lithium ion secondary batteries and the lithium ion secondary battery using the negative electrode material of the present invention will be exemplified, but the materials that can be used and the method of production are not limited to the following specific examples. Absent.

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

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

<Battery performance>
The battery produced as described above exhibits the following performance.
The output is usually 1.0 W or more, preferably 1.5 W or more, more preferably 1.8 W or more. If the output is too low, when a lithium ion secondary battery is used as a power source for an electric vehicle, large energy cannot be taken out at the time of start and acceleration, and large energy generated at the time of deceleration cannot be efficiently regenerated.
The cycle maintenance ratio is usually 70% or more, preferably 75% or more, more preferably 80% or more. If the cycle maintenance ratio is too low, it is not suitable for applications in which charging and discharging are repeated and used for a long period of time. Here, the cycle maintenance ratio represents the discharge capacity at the 200th cycle relative to the discharge capacity at the first cycle.

EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
(Measuring method)
(1) Volume-based average particle diameter (d50)
The particle diameter 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 (for example, Tween 20 (registered trademark)) as a surfactant. What was measured as a volume-based median diameter in a measuring apparatus after being introduced into a commercially available laser diffraction / scattering type particle size distribution measuring apparatus “LA-920 made by HORIBA” and irradiated with an ultrasonic wave at 28 kHz for 1 minute, It is defined as a volume-based average particle diameter d50 in the present invention.

(3) BET specific surface area (SA)
The BET specific surface area is measured by, for example, using a specific surface area measuring device “AMS8000” manufactured by Okura Riken Co., Ltd., by the nitrogen gas adsorption flow method, using the BET one-point method. Specifically, 0.4 g of sample (carbon material) is filled in a cell, heated to 350 ° C., pretreated, cooled to liquid nitrogen temperature, and saturated with 30% nitrogen and 70% He gas. The amount of gas adsorbed and then heated to room temperature and desorbed was measured, and the specific surface area was calculated from the obtained results by a normal BET method.

Example 1
Biaxial kneading with petroleum heavy oil (graphitizable organic compound) obtained during naphtha pyrolysis using spheroidized natural graphite with an average particle size (d50) and BET specific surface area as shown in Table 1 as a carbon material After mixing in a machine, isotropic pressure treatment was performed at 100 kgf / cm ² for 2 minutes using a CIP molding machine, and the resulting mixture was then heated in an inert gas at 700 ° C. for 2 hours, and further 1300 A composite carbon material (A), which is a multilayer carbon structure in which a carbonaceous material having different crystallinity was coated on the surface of a spheroidized natural carbon material, was obtained by heat treatment at 1 ° C. for 1 hour. Table 1 shows the powder physical properties of the obtained composite carbon material.

Spherical natural graphite having an average particle size (d50) and BET specific surface area as shown in Table 1 is used as a carbon material, and the above spherical natural graphite and binder pitch are mixed at a mass ratio of 100: 20 and charged into a kneader. And mixed for 20 minutes. This composite is subjected to isotropic pressure treatment at 100 kgf / cm ² for 2 minutes using a CIP molding machine to form a molded body, which is heated from room temperature to 1000 in an electric furnace.
The temperature was raised to 0 ° C., and the fired body was then graphitized by heating at 3000 ° C. The obtained molded product was crushed and pulverized to obtain a composite carbon material (B). Table 1 shows the powder physical properties of the obtained composite carbon material. The composite carbon material (A) and the composite carbon material (B) are weighed so that the mixing ratio of the composite carbon material (A) with respect to the total amount of the composite carbon material (B) is 10% by mass and mixed for 20 minutes using a twin cylinder mixer. A carbon material for an aqueous secondary battery was obtained. Table 2 shows the powder physical properties of the obtained carbon material.

・ Production of positive electrode, negative electrode, electrolyte and battery (Production of negative electrode)
A negative electrode active material obtained by adding 10% of a conductive assistant having an average particle diameter (d50) of 8 μm and a BET specific surface area (SA) of 10 m 2 / g to the negative electrode material of Example 1 was used. , 1% by weight of sodium carboxymethylcellulose and 1% by weight of aqueous dispersion of styrene-butadiene rubber (40% by weight of styrene-butadiene rubber) were added as a thickener and a binder, respectively, and mixed by biaxial kneading. Slurried. The obtained slurry was coated on one side of 18 μm rolled copper foil, dried, and rolled with a press. The active material layer size was 32 mm in width, 42 mm in length, and the uncoated part as a current collector tab welded part. It cut out in the shape which has and was set as the negative electrode. At this time, the density of the active material of the negative electrode was 1.6 g / cm ³ .

(Preparation of positive electrode)
The positive electrode active material is a lithium transition metal composite oxide synthesized by the method shown below, and is represented by the composition formula LiMn _0.33 Ni _0.33 Co _0.33 O ₂ . Mn ₃ O ₄ as a manganese raw material, NiO as a nickel raw material, and Co (OH) ₂ as a cobalt raw material are weighed so as to have a molar ratio of Mn: Ni: Co = 1: 1: 1, and pure water is added thereto. In addition, a slurry was added, and while stirring, the solid content in the slurry was wet-ground using a circulating medium stirring wet bead mill so that the volume-based average particle diameter d50 was 0.2 μm.

The obtained slurry was spray-dried with a spray drier to obtain substantially spherical granulated particles having a particle size of about 5 μm and consisting only of manganese raw material, nickel raw material and cobalt raw material. To the obtained granulated particles, LiOH powder having a volume-based average particle diameter d50 of 3 μm was added so that the ratio of the number of moles of Li to the total number of moles of Mn, Ni, and Co was 1.05. Mixing with a speed mixer gave a mixed powder of nickel raw material, cobalt raw material, granulated particles of manganese raw material and lithium raw material. This mixed powder was calcined at 950 ° C. for 12 hours under air flow (climbing temperature 5 ° C./min), then crushed and passed through a sieve having an opening of 45 μm to obtain a positive electrode active material. The positive electrode active material had a BET specific surface area of 1 m ² / g, an average primary particle size of 1 μm, a volume-based average particle size d50 of 8 μm, and a tap density of 1.7 g / cm ³ .

90% by mass of the positive electrode active material described above, 7% by mass of acetylene black as a conductive material, and 3% by mass of polyvinylidene fluoride (PVdF) as a binder were mixed in an N-methylpyrrolidone solvent, Slurried. The obtained slurry was applied to a 15 μm aluminum foil, dried, and rolled to a thickness of 100 μm with a press machine. The positive electrode active material layer had a width of 30 mm, a length of 40 mm, and an uncoated part for current collection. It was cut out into a shape having a positive electrode. The density of the positive electrode active material layer was 2.6 g / cm ³ .

(Preparation of electrolyte)
Dissolve fully dried lithium hexafluorophosphate (LiPF ₆ ) at a concentration of 1 mol / L in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio 3: 7) under an inert atmosphere. I let you. Furthermore, what added 1 mass% of vinylene carbonate (VC) to the electrolyte solution was used.

(Production of battery)
One positive electrode and one negative electrode were disposed so that the active material surfaces face each other, and a porous polyethylene sheet separator (thickness: 25 μm) was sandwiched between the electrodes. At this time, the positive electrode active material surface was faced so as not to deviate from the negative electrode active material surface. A current collector tab is welded to the uncoated portion of each of the positive electrode and the negative electrode to form an electrode body, and a laminate sheet (total thickness) in which a polypropylene film, an aluminum foil having a thickness of 0.04 mm, and a nylon film are laminated in this order. 0.1 mm) was sandwiched with a laminate sheet so that the polypropylene film was on the inner surface side, and the area without electrodes was heat-sealed except for one piece for injecting the electrolyte solution. Thereafter, 200 μL of the non-aqueous electrolyte was injected into the active material layer, sufficiently infiltrated into the electrode, and sealed to prepare a laminate cell. The rated capacity of this battery is 40 mAh.

(Cycle maintenance rate measurement)
Initially in a voltage range of 4.2 to 3.0 V and a current value of 0.2 C in a 25 ° C. environment (the rated capacity due to the discharge capacity at 1 hour rate is 1 C, and the same applies hereinafter). Conditioning was performed. Further, after aging at 60 ° C., a cycle test was conducted. Using the discharge capacity at the first cycle as a reference, the cycle maintenance factor was calculated from the discharge capacity at the 200th cycle according to the following equation.

Cycle maintenance ratio (%) = (discharge capacity at the 200th cycle / discharge capacity at the first cycle) × 100
The obtained results are shown in Table 2.
(Example 2)
The same experiment as in Example 1 was performed except that the mixing ratio of the composite carbon material (A) to the total amount of the composite carbon material (A) and the composite carbon material (B) was 30% by mass. Table 2 shows the powder physical properties and battery evaluation results of the obtained carbon material.

(Comparative Example 1)
A petroleum heavy oil (easily graphitizable organic compound) obtained during naphtha pyrolysis using a spherical natural graphite having an average particle size (d50) and BET specific surface area (SA) shown in FIG. 1 as a carbon material. After mixing with a twin-screw kneader, the resulting mixture was heat-treated in an inert gas at 700 ° C. for 2 hours and further at 1300 ° C. for 1 hour without passing through a pressurizing step to form a spherical natural carbon material surface. A carbon material (C) which is a multi-layer carbon structure coated with carbonaceous materials having different crystallinity was obtained. Table 1 shows the powder physical properties of the obtained carbon material.
The carbon material (C) and the composite carbon material (B) are weighed so that the mixing ratio of the carbon material (C) is 10% by mass, and mixed for 20 minutes using a twin cylinder mixer. Obtained. Table 2 shows powder physical properties and battery results.

(Comparative Example 2)
The same experiment as Comparative Example 2 was performed except that the mixing ratio of the carbon material (C) to the total amount of the composite carbon material (C) and the composite carbon material (B) was 30% by mass. Table 2 shows the powder physical properties and battery evaluation results of the obtained negative electrode material.
(Comparative Example 3)
Table 2 shows the powder physical properties and battery evaluation results of the obtained negative electrode material using only the composite carbon material (B) described in Example (1) as the negative electrode material.

  From Table 2, a material obtained by mixing the composite carbon material (A) and the composite carbon material (B) as in Examples 1 and 2 is a combination of a material not subjected to pressure treatment and the composite carbon material (B), and It is confirmed that the cycle maintenance rate is higher than that of the composite carbon material (B) alone.

  By using the negative electrode material of the present invention as a negative electrode material for a non-aqueous secondary battery, it is possible to provide a carbon material for a non-aqueous secondary battery with high capacity and good cycle characteristics.

Claims (9)

  A carbon material for a non-aqueous secondary battery, comprising: a composite carbon material (A) obtained by coating a carbon material subjected to pressure treatment with a carbonaceous material; and a composite carbon material (B) in which a graphite material is combined.   The carbon material for a non-aqueous secondary battery according to claim 1, wherein a graphite material is combined with a carbon material obtained by pressurizing the composite carbon material (B).   The carbon material for a non-aqueous secondary battery according to claim 1 or 2, wherein the composite carbon material (B) has an average particle size (d50) of 3 µm or more and 60 µm or less. 4. The carbon material for a non-aqueous secondary battery according to claim 1, wherein the composite carbon material (B) has a specific surface area of 0.1 m ² / g or more and 15 m ² / g or less.   The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 4, wherein the pressure-treated carbon material is spheroidized natural graphite.   The carbon material for a non-aqueous secondary battery according to any one of claims 2 to 5, wherein the pressure-treated carbon material is spheroidized natural graphite.   The carbon material for a non-aqueous secondary battery according to any one of claims 1 to 6, wherein the pressure treatment is an isotropic pressure treatment.   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 1-7. 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 8.

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