JP2015026579A - Carbon material for nonaqueous secondary battery negative electrode, negative electrode for nonaqueous secondary battery, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon material for a nonaqueous secondary battery negative electrode having excellent stability, high output, high capacity, small irreversible capacity, and excellent cycle characteristics, and also to provide a nonaqueous secondary battery using the same.SOLUTION: Disclosed is a carbon material for a nonaqueous secondary battery negative electrode containing a composite carbon particle (A) including a silicon element and a graphite particle (B). The carbon material for the nonaqueous secondary battery negative electrode is characterized in that the graphite particle (B) is a particle in which a graphite particle (C) and an amorphous material are compounded or the graphite particle (C) and a graphitic material different in orientation from the graphite particle (C) are compounded.

Description

  The present invention relates to a carbon material for a non-aqueous secondary battery negative electrode 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.

A nonaqueous lithium secondary battery composed of a positive electrode and a negative electrode capable of inserting and extracting lithium ions and a nonaqueous electrolyte solution in which lithium salts such as LiPF ₆ and LiBF ₄ are dissolved has been developed and put into practical use.
Various materials have been proposed as the negative electrode material of this battery, but because of its high capacity and excellent discharge potential flatness, natural graphite, artificial graphite obtained by graphitization of coke, etc., Graphite carbon materials such as graphitized mesophase pitch and graphitized carbon fiber are used.

On the other hand, non-aqueous secondary batteries, especially lithium ion secondary batteries, have been developed recently. In addition to conventional notebook computers, mobile communication devices, portable cameras, portable game machines, etc., electric tools, There is a demand for lithium ion secondary batteries that are required for rapid charge / discharge performance that has been increased in the past, such as those for automobiles, and that have high capacity and high cycle characteristics.
Therefore, in order to increase the filling rate of the carbon material in the electrode plate and improve the discharge capacity, a carbon material mixed with graphite particles having different properties is used.

  For example, Patent Document 1 discloses a negative electrode material made of artificial graphite, graphite-coated graphite, and amorphous-coated graphite. By mixing these three types of graphite powders with different characteristics of hardness and shape, lithium has excellent electrolyte permeability, low capacity loss due to charge / discharge, and good cycle performance even at high electrode density. It has been reported that a negative electrode for a secondary battery and a negative electrode active material constituting the negative electrode can be obtained.

However, while a high capacity is desired in this way, in a carbon-centered negative electrode, the theoretical capacity of carbon is 372 mAh, so it is impossible to desire a capacity higher than this. Therefore, application of metal particles having various theoretical capacities, especially metal particles, to the negative electrode has been studied.
For example, Patent Document 2 proposes a method for producing Si composite carbon particles by firing a mixture of fine powder of an Si compound, graphite, and a pitch of carbonaceous material precursor.

  In Patent Document 3, it is proposed to perform different electrochemical reduction reactions as an active material and use a mixture of two types of materials (metal oxide and carbon material) having different equilibrium potentials. Thus, it has been reported that a non-aqueous secondary battery having a high capacity and excellent cycle characteristics can be provided.

JP 2007-324067 A Japanese Patent Laid-Open No. 2003-223892 Japanese Patent Laid-Open No. 11-135106

However, according to the study by the present inventors, the technique described in Patent Document 2 is Si composite carbon particles obtained by compounding graphite and Si compound fine powder with a carbonaceous material composed of carbon. Lithium migration is hindered by the difference in connectivity during charging and discharging, and the decrease in conductivity inside and outside the particles due to expansion, and as a result, there is a problem that performance cannot be sufficiently obtained at high speed charging and discharging. It did not arrive. On the other hand, the technology described in Patent Document 3 can prevent structural destruction of metal oxides by mixing a metal oxide capable of occluding and releasing lithium and a carbon material, and has a high capacity and excellent cycle. It is described that a non-aqueous secondary battery having characteristics can be obtained. However, since the metal oxide is not a composite particle with carbon, it is not possible to suppress the destruction of the electrode due to the swelling of the metal oxide, and the carbon material has no special provision, and thus the battery having the high cycle characteristics required recently. It must be said that further improvement is necessary to obtain this.

  The present invention solves the above-described problems of the prior art, and has a high capacity, high output, excellent cycle characteristics, low irreversible capacity, and a non-aqueous secondary battery negative electrode carbon material obtained by using the carbon material. It aims at providing the non-aqueous secondary battery provided with the negative electrode for secondary batteries, and the said negative electrode.

  As a result of intensive studies to solve the above problems, the present inventors have found that composite carbon particles (A) containing silicon element (hereinafter, sometimes referred to as Si composite carbon particles (A)) and graphite particles (B) Is a carbon material for a negative electrode of a non-aqueous secondary battery in which graphite particles (B) and graphite or amorphous or graphite particles (C) having a different orientation are combined as graphite particles (B). It has been found that by using the graphite particles, a carbon material for a negative electrode of a non-aqueous secondary battery can be produced with high capacity, high output, excellent cycle characteristics, and little decrease in irreversible capacity.

  The mechanism by which the carbon material for a nonaqueous secondary battery negative electrode of the present invention exhibits excellent battery characteristics is not clear, but is probably as shown below. The composite carbon particle (A) containing silicon element has a high capacity because it contains the silicon element, and also has excellent cycle characteristics because the volume expansion of the silicon element during charge / discharge can be relaxed by the composite with the carbon particles. On the other hand, the movement of lithium is hindered by the difference in bonding during charging and discharging, and the decrease in conductivity inside and outside the particles due to expansion, and as a result, sufficient performance cannot be obtained by charging and discharging at high speed. There was a problem. On the other hand, graphite particles (B) in which graphite particles (C) and amorphous or graphite particles (C) having a different orientation are combined are excellent in conductivity and lithium movement in the particles is also good. Therefore, it has a feature that an increase in resistance can be suppressed even during charging and discharging at high speed. Therefore, by mixing these two materials, the increase in overvoltage in the entire electrode is suppressed by preferentially causing lithium movement in the graphite particles (B) in which lithium ions are more likely to move during charge and discharge at high speed, It has been found that high input / output can be maintained, and the present invention has been achieved.

That is, the gist of the present invention is a carbon material for a non-aqueous secondary battery negative electrode containing composite carbon particles (A) containing silicon element and graphite particles (B), wherein the graphite particles (B) are graphite particles (C ) And amorphous or graphite particles (C) are particles in which graphites having different orientations are combined, and the carbon material for a non-aqueous secondary battery negative electrode.
Another gist of the present invention resides in a negative electrode for a non-aqueous secondary battery, characterized by being formed using the carbon material for a non-aqueous secondary battery negative electrode.

  Another aspect of the present invention is a non-aqueous secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is the negative electrode for a non-aqueous secondary battery. Next battery.

  According to the present invention, a carbon material for a non-aqueous secondary battery negative electrode having excellent stability, high capacity, high main force, small irreversible capacity and excellent cycle characteristics, and a non-aqueous secondary battery using the same are provided. can do.

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.
The non-aqueous secondary battery negative electrode carbon material of the present invention contains Si composite carbon particles (A) and graphite particles (B). The Si composite carbon particles (A) contain silicon element, and the graphite particles (B) are particles in which graphite particles (C) and amorphous are combined, or graphite particles (C) and graphite. The particle (C) is a particle in which graphite having different orientation is combined. In the present invention, “the graphite particles (C) and the amorphous or graphite particles (C) are compounded with graphite having different orientations” means that the graphite particles (C) are amorphous. Or, a graphite having a different orientation from that of the graphite particles (C) is attached, adhered, or combined, and more specifically, amorphous or graphite particles (C) in the pores of the graphite particles (C). Is a state in which graphite having different orientation is adhered, graphite particles having orientation different from that of amorphous or graphite particles (C) are bound to the whole or part of the surface of the graphite particles (C). The above graphite particles (C) and amorphous or graphite particles (C) represent a composite state of graphites having different orientations. To observe the state, for example, field emission scanning electron View particle cross-sections using techniques such as microscope-energy dispersive X-ray (SEM-EDX) analysis and X-ray photoelectron spectroscopy (XPS) analysis. It can be confirmed by.

  The term “different in orientation” as used in the present invention means that when the powder is observed with a polarizing microscope, the pattern of the anisotropic unit of the optically anisotropic structure, that is, the size and direction of the anisotropic unit. When the number is visually observed and compared, at least one of the size, direction, number, etc. is different. For example, among graphite particles (C) and graphite particles having a different orientation from graphite particles (C), one graphite has crystal orientation in one direction, and the other graphite has random crystal orientation. In other cases, the graphite particles (C) and the graphite particles having a different orientation from the graphite particles (C) have crystal orientation in one direction, and the directions are different.

When one or both of the graphite particles (C) and the graphite having a different orientation from the graphite particles (C) are not a single crystal but an aggregate of a plurality of crystals, the unit of the aggregate is 1 What is necessary is just to contrast the aggregate pattern of the anisotropic unit of the optically anisotropic structure as a region. As a method for confirming the orientation of graphite, observation with a polarizing microscope can be given. This utilizes the fact that when light emitted from one light source enters an anisotropic body with an anisotropic crystal structure direction, the light changes in a limited vibration direction. A single color or several colors are observed, and the orientation of the particles can be observed due to the difference.
Hereinafter, the Si composite carbon particles (A) and the graphite particles (B) used in the present invention will be described.

[Si composite carbon particles (A)]
The Si composite carbon particles (A) in the present invention will be described below.
The Si composite carbon particles (A) of the present invention are not particularly limited as long as they are Si composite carbon particles composed of at least silicon element and carbon particles, and known materials may be used. Examples thereof include Si composite carbon particles disclosed in JP 2012-043546 A, JP 2005-243508 A, JP 2008-027897 A, JP 2008-186732 A, and the like. In addition, it describes below about Si composite carbon particle (A) in which the effect of this invention is improved further.

(Characteristics of Si composite carbon particles (A))
The Si composite carbon particles (A) preferably have the following characteristics.
(A) Volume-based average particle diameter (d50) of Si composite carbon particles (A)
The volume-based average particle diameter (d50) (hereinafter also referred to as average particle diameter d50) of the Si composite carbon particles (A) is usually 1 μm or more, preferably 4 μm or more, more preferably 7 μm or more, and usually 50 μm or less. The thickness is preferably 40 μm or less, more preferably 30 μm or less, and still more preferably 25 μm or less. If the average particle diameter d50 is too large, the total number of particles decreases and the existence ratio of the graphite particles (B) between the particles decreases, so that sufficient movement of lithium in the particles cannot be obtained. There is a tendency to reduce the output characteristics. On the other hand, if the average particle size d50 is too small, the specific surface area increases, so that the decomposition of the electrolyte increases and the initial efficiency tends to decrease.

  The particle size is measured by suspending 0.01 g of a carbon material in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate, which is a surfactant, and measuring a commercially available laser diffraction / scattering particle size distribution. The volume-based average particle diameter (d50) in the present invention is defined as the volume-based median diameter measured in the 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.

(B) Aspect ratio of Si composite carbon particles (A) The aspect ratio of the Si composite carbon particles (A) is usually 1 or more, preferably 1.3 or more, more preferably 1.4 or more, and still more preferably 1.5. As described above, it is usually 4 or less, preferably 3 or less, more preferably 2.5 or less, and further preferably 2 or less.
If the aspect ratio is too large, particles tend to be aligned in the direction parallel to the current collector when used as an electrode, so there is not enough continuous void in the thickness direction of the electrode, and lithium ion mobility in the thickness direction. Tends to decrease, leading to a decrease in rapid charge / discharge characteristics. The aspect ratio is measured by polishing a resin embedding or electrode plate of a particle perpendicular to a flat plate, taking a cross-sectional photograph thereof, extracting 50 or more particles at random, and extracting the longest diameter of the particle. (Parallel to the plate) and the shortest diameter (
It can be measured by measuring the image in the direction perpendicular to the flat plate by image analysis and taking the average of the longest diameter / shortest diameter. Since particles embedded in a resin or made into an electrode plate usually tend to have the thickness direction of the particles aligned perpendicular to a flat plate, the above-mentioned method can obtain the longest and shortest diameters characteristic of the particles. I can do it.

(C) Circularity of Si composite carbon particles (A) The circularity of the Si composite carbon particles (A) is usually 0.85 or more, preferably 0.88 or more, more preferably 0.89 or more, and still more preferably 0. .90 or more. The circularity is usually 1 or less, preferably 0.99 or less, more preferably 0.98 or less, and still more preferably 0.97 or less. In addition, the spherical shape in this specification can also be expressed in the range of the circularity.

If the circularity is too small, particles tend to be aligned in the direction parallel to the current collector when used as an electrode, so there is not enough space in the thickness direction of the electrode, and lithium ion mobility in the thickness direction. Tends to decrease, leading to a decrease in rapid charge / discharge characteristics. If the circularity is too large, there is a tendency that the effect of suppressing the conduction path breakage is reduced and the cycle characteristics are lowered.
In the present invention, the degree of circularity is defined by the following formula (1).

Formula (1)
Circularity = (perimeter of equivalent circle having the same area as the particle projection shape) / (actual circumference of particle projection shape)
As the circularity value, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co.) is used, polyoxyethylene (20) monolaurate is used as a surfactant, and ion-exchanged water is used as a dispersion medium. In addition, the degree of circularity is calculated by calculating the equivalent circle diameter. The equivalent circle diameter is the diameter of a circle (equivalent circle) having the same projected area as the photographed particle image, and the circularity is the circumference of the equivalent particle as a molecule and the circumference of the photographed particle projection image. The ratio is the denominator. The circularity of particles having a measured equivalent diameter in the range of 10 to 40 μm is averaged to obtain the circularity in the present invention.

(D) Interplanar spacing of Si composite carbon particles (A) (d ₀₀₂ )
The interplanar spacing (d ₀₀₂ ) of the 002 plane by the X-ray wide angle diffraction method is usually 0.337 nm or less, preferably 0.336 nm or less. If the d value is too large, the crystallinity decreases and the discharge capacity tends to decrease. On the other hand, the lower limit of 0.3356 nm is a theoretical value of graphite.
The crystallite size (Lc) of the Si composite carbon particles (A) is usually in the range of 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more. Below this range, the crystallinity decreases and the discharge capacity of the battery tends to decrease.

Raman R value of the Raman R value Si composite carbon particles (A) in (e) Si composite carbon particles (A), the intensity _{I A} of the peak _{P A} in the vicinity of 1580 cm ^-1, the peak _{P B} in the vicinity of 1360 cm ^-1 The intensity I _B is measured, and the intensity ratio R (R = I _B / I _A ) is calculated and defined. The value is usually 1 or less, preferably 0.8 or less, more preferably 0.6 or less, still more preferably 0.5 or less, and usually 0.05 or more, preferably 0.1 or more, more preferably 0. 2 or more, more preferably 0.25 or more. When the Raman R value is less than this range, the crystallinity of the particle surface becomes too high, the number of Li insertion sites decreases, and rapid charge / discharge characteristics tend to be deteriorated. 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 R value 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: 532 nm
Laser power on sample: 25 mW
Resolution: 4cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
Peak intensity measurement, peak half-width measurement: background processing, smoothing processing (convolution 5 points by simple averaging)

(F) Surface functional group amount of Si composite carbon particle (A) The Si composite carbon particle (A) has a surface functional group amount O / C value represented by the following formula (2) of usually 0.1% or more. , Preferably 1%, more preferably 2%, while usually 30% or less, preferably 20% or less, more preferably 15% or less. If the surface functional group amount O / C value is too small, the desolvation reactivity between the Li ions and the electrolyte solvent on the surface of the negative electrode active material tends to decrease, and the large current charge / discharge characteristics tend to decrease. If the is too large, the reactivity with the electrolytic solution increases, and the charge / discharge efficiency tends to decrease.

Formula (2)
O / C value (%)
= {(O atom concentration determined based on peak area of O1s spectrum in X-ray photoelectron spectroscopy (XPS) analysis) / (C atom concentration determined based on peak area of C1s spectrum in XPS analysis)} × 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 O / C atomic concentration ratio O / C (O atom concentration / C atom concentration) is defined as the surface functional group amount O / C value of the sample (Si composite carbon particles (A)).

(G) BET specific surface area (SA) of Si composite carbon particles (A)
About the specific surface area measured by BET method of Si composite carbon particle (A), it is 0.1 m < ² > / g or more normally, Preferably it is 0.7 m < ² > / g or more, More preferably, it is 1 m < ² > / g or more. Moreover, it is 40 m < ² > / g or less normally, Preferably it is 30 m < ² > / g or less, More preferably, it is 20 m < ² > / g or less, More preferably, it is 15 m < ² > / g or less, Most preferably, it is 13 m < ² > / g or less.

If the specific surface area is too small, the number of sites where lithium ions enter and exit is small, 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 Therefore, there is a tendency that a high capacity battery cannot be manufactured.
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.

(H) Tap density of Si composite carbon particles (A) The tap density of Si composite carbon particles (A) is usually 0.5 g / cm ³ or more, preferably 0.6 g / cm ³ or more, more preferably 0. .8g / cm ³ or more, more preferably 0.85 g / cm ³ or more, particularly preferably 0.9 g / cm ³ or more and usually less than 1.3 g / cm ^3, preferably 1.2 g / cm ³ or less Yes, more preferably 1.1 g / cm ³ or less. If the tap density is too low, the high-speed charge / discharge characteristics are inferior, and if the tap density is too high, the cycle characteristics may be deteriorated due to the disconnection of the conductive path due to the decrease in particle contact property.

In the present invention, the tap density is measured by dropping a sample (Si composite carbon particles (A)) through a sieve having a mesh size of 300 μm through a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ using a powder density measuring device. After the cell is fully filled, a tap with 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.

Further, the tap density of the Si composite carbon particles (A) usually tends to be the same as or higher than the tap density of the graphite particles (B).
In the present invention, the tap density is measured by dropping a sample (Si composite carbon particles (A)) through a sieve having a mesh size of 300 μm through a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ using a powder density measuring device. After the cell is fully filled, a tap with 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.

(I) Ratio R (A) / R (B) of resistance R (A) of Si composite carbon particles (A) and resistance R (B) of graphite particles (B)
The ratio R (A) / R (B) of the resistances R (A) and R (B) calculated by the following measuring method for the Si composite carbon particles (A) and the graphite particles (B) of the present invention is usually 1 It is larger, preferably 3 or more, more preferably 5 or more, while usually 500 or less, preferably 100 or less, more preferably 50 or less. Within this range, the lithium migration preferentially occurs in the graphite particles (B) in which lithium ions are more likely to move during high-speed charging / discharging, thereby suppressing an increase in overvoltage across the entire electrode and obtaining a sufficient output. This is preferable in that it is possible and a high capacity derived from silicon element can be secured.

In addition, resistance R with respect to each active material particle is calculated using the charging / discharging curve with respect to the counter electrode metal Li measured using a coating film electrode etc. That is, when the potential difference ΔV at the same charging depth in the charging and discharging directions and the current I used for the measurement are used, the resistance R soc for each charging depth is calculated by the following equation (3).
Formula (3)
Resistance at each charging depth: Rsoc
= ΔV / I
The resistance R is a numerical value averaged over the entire charging depth using Rsoc.

(J) Aspect of silicon element in Si composite carbon particle (A) As an aspect of silicon element contained in the Si composite carbon particle (A) in the present invention, SiOx, SiNx, SiCx, SiZxOy (Z = C, N) and the like, and in the present invention, these are collectively referred to as Si compounds. Of these, SiOx is preferred. This general formula SiOx is obtained using Si dioxide (SiO ₂ ) and metal Si (Si) as raw materials, and the value of x is usually 0 ≦ x <2, preferably 0.2 or more, 1.8 Hereinafter, more preferably 0.4 or more and 1.6 or less, further preferably 0.6 or more and 1.4 or less, and x = 0 is particularly preferable. If it is this range, it becomes high capacity | capacitance and it becomes possible to reduce the irreversible capacity | capacitance by the coupling | bonding of Li and oxygen.

As a preferable aspect of the silicon element in the Si composite carbon particles (A) of the present invention, Si compound particles in which a Si compound is formed into particles are preferable.
Moreover, as content of the silicon element in Si composite carbon particle (A) of this invention, it is 0.5 mass% or more normally with respect to Si composite carbon particle (A), Preferably it is 1 mass% or more, More preferably It is 1.5 mass% or more, More preferably, it is 2 mass% or more. Moreover, it is 99 mass% or less normally, Preferably it is 70 mass% or less, More preferably, it is 50 mass% or less, More preferably, it is 30 mass% or less, Most preferably, it is 25 mass% or less. This range is preferable in that a sufficient capacity can be obtained.

  The method for measuring the content of silicon element in the Si composite carbon particles (A) is as follows. The sample is completely melted with an alkali, then dissolved and fixed in water, and an inductively coupled plasma emission spectrometer (HORIBA, Ltd. ULTIMA2C). The amount of silicon element is calculated from the calibration curve. Thereafter, the silicon element content of the Si composite carbon particles (A) can be calculated by dividing the silicon element amount by the weight of the Si composite carbon particles (A).

(K) The silicon element abundance ratio of the Si composite carbon particles (A) The silicon element abundance ratio calculated by the following measurement method of the Si composite carbon particles (A) of the present invention is usually 0.2 or more, Preferably it is 0.3 or more, more preferably 0.4 or more, more preferably 0.5 or more, particularly preferably 0.6 or more, and usually 1.5 or less, preferably 1.2 or less, more preferably Is 1.0 or less. The higher this value, the more silicon element present inside the Si composite carbon particles (A) compared to the silicon element present outside the Si composite carbon particles (A), and the negative electrode was formed. At this time, there is a tendency that a decrease in charge / discharge efficiency due to the disconnection of the conductive path between particles can be suppressed.

  The silicon element abundance ratio of the Si composite carbon particles (A) is calculated as follows. First, a coating film of Si composite carbon particles (A) or Si composite carbon particles (A) is embedded in a resin to produce a thin piece of resin, and a cross section of the particle is cut out by focused ion beam (FIB) or ion milling. After that, it is possible to observe by an observation method such as particle cross-sectional observation by SEM (scanning electron microscope).

The accelerating voltage when observing the cross section of one Si composite carbon particle (A) with an SEM (scanning electron microscope) is preferably 1 kV or more, more preferably 2 kV or more, and further preferably 3 kV or more. 10 kV or less, more preferably 8 kV or less, still more preferably 5 kV or less. Within this range, the graphite particles and the Si compound can be easily identified due to the difference in the reflected secondary electron image in the SEM image. The imaging magnification is usually 500 times or more, more preferably 1000 times or more, still more preferably 2000 times or more, and usually 10000 times or less. If it is said range, the whole image of 1 particle | grains of Si composite carbon particle (A) is acquirable. The resolution is 200 dpi (ppi) or more, preferably 256 dpi (ppi) or more. The number of pixels is preferably evaluated at 800 pixels or more. Next, while observing the image, the graphite and silicon elements are identified by the energy dispersion type (EDX) and the wavelength dispersion type (WDX).

One Si composite carbon particle (A) particle is extracted from the acquired image, and the area (a) of the Si compound in the particle is calculated. Next, after binarizing the extracted 1 particle and the background other than the 1 particle, the shrinking process is repeated on the particle, and a figure with an area of 70% of the extracted 1 particle is extracted. The area (b) of the silicon element present is calculated. In addition, in the area when the reduction process is repeatedly performed, when the value of 70% cannot be accurately shown, the value closest to 70% in the value of 70% ± 3% is 70% in this patent. A figure. The extraction of one particle, the calculation of the area, the binarization process, and the reduction process can be performed by using general image processing software. For example, software such as “Image J” and “Image-Pro plus” Is raised.
The value obtained by dividing the area (b) calculated above by the area (a) is measured with arbitrary three particles, and the value obtained by averaging the values of these three particles is the silicon element in the Si composite carbon particles (A). The abundance ratio.

(Aspect of Si composite carbon particles (A))
The aspect of the Si composite carbon particle (A) of the present invention is not particularly limited as long as it is a carbon material containing silicon element. For example, (i) Si compound particles are dispersed in a granulated body made of a carbon material. (B) Si compound particles attached or coated on the outer periphery of the carbon material to be the nucleus, (c) At least Si compound particles dispersed in the spheroidized carbon material, ) Examples in which the carbon compound is attached or coated on the outer periphery of the Si compound particles serving as the nucleus, and a combination of these. By encapsulating Si compound particles inside the Si composite carbon particles (A), by suppressing the stress due to volume expansion associated with charge and discharge of the Si compound, particle breakage and the accompanying conduction path interruption are suppressed, It tends to show high capacity and high cycle characteristics, has a tendency to show high initial efficiency by preventing side-reaction by preventing contact with the electrolyte, and hard to control particle hardness easily From the viewpoint of easy production of particles, it is preferable that (iii) at least Si compound particles are dispersed inside the spheroidized carbon material. At this time, it is preferable that at least one of the Si compound particles is in contact with the carbon material from the viewpoint of suppressing an increase in irreversible capacity.

  In the present specification, the term “adhesion” means a state in which Si compound particles are attached, adhered, or complexed on the surface of a carbon material. In order to observe the state, for example, a field emission scanning electron microscope-energy This can be confirmed by observing the cross section of the particle using a technique such as dispersive X-ray (SEM-EDX) analysis or X-ray photoelectron spectroscopy (XPS) analysis.

<Method for producing Si composite carbon particles (A)>
(Raw material for Si composite carbon particles (A))
The Si composite carbon particles (A) described above are not particularly limited as long as they are Si composite carbon particles in which a silicon element and a carbon material are composited. For example, carbon materials, Si compound particles, and organic substances that become carbonaceous materials are used. It can be produced using a compound.

The carbon material used as a raw material is not particularly limited, but when producing (B) or (C) Si composite carbon particles (A), graphite particles such as natural graphite and artificial graphite, or crystals slightly more than these Examples thereof include a fired material of a material selected from the group consisting of coal-based coke, petroleum-based coke, furnace black, acetylene black, and pitch-based carbon fiber having low properties. Of these, scaly or scaly natural graphite or artificial graphite is more preferable because it tends to uniformly disperse the Si compound particles. In addition, when producing (B) Si composite carbon particles (A), from the viewpoint of maintaining the shape as the core of the particles, for example, graphite particles obtained by spheroidizing by applying mechanical stress to flaky graphite or the like and graphite and carbonaceous material It is preferable to use graphite particles obtained by mixing and granulating an organic compound.

In addition, what shows the following physical properties for the carbon material used as a raw material in this invention is preferable.
The volume-based average particle diameter (d50) of the carbon material used as a raw material is not particularly limited, but is usually 1 μm or more and 120 μm or less, preferably 3 μm or more and 100 μm or less, more preferably 5 μm or more and 90 μm or less. If the average particle diameter d50 of the carbon material used as a raw material is too large, the particle diameter of the Si composite carbon particles (A) becomes large, and the negative electrode active material mixed with the Si composite carbon particles (A) is applied as a slurry. In this process, streaks or irregularities due to large particles may occur. If the flat body particle size d50 is too small, it may be difficult to make a composite, and it may be difficult to produce Si composite carbon particles (A).

The tap density of the carbon material used as a raw material is usually less than 0.1 g / cm ³ or more 1.0 g / cm ^3, preferably 0.13 g / cm ³ or more 0.8 g / cm ³ or less, more preferably 0 .15 g / cm ³ or more and 0.6 g / cm ³ or less.
When the tap density is within the above range, minute voids are easily formed in the Si composite carbon particles (A), and thus the destruction of the Si composite carbon particles (A) due to the expansion and contraction of the Si compound particles can be suppressed.

BET specific surface area of the carbon material used as a raw material is usually ^{1 m} 2 / g or more ^{40 m} 2 / g or less, preferably less ^2m 2 / g or more ^{35m 2 / g, 3m 2 /} g or more ^{30 m} 2 / g The following is more preferable. The specific surface area of the carbon material used as a raw material is reflected in the specific surface area of the Si composite carbon particles (A), and the battery capacity due to an increase in the irreversible capacity of the Si composite carbon particles (A) by being 40 m ² / g or less. Can be prevented.

  The interplanar spacing (d002) of the 002 plane according to the X-ray wide angle diffraction method of the carbon material used as a raw material is usually 0.337 nm or less. On the other hand, it is usually 0.334 nm or more. The carbon material used as a raw material has an Lc of 90 nm or more, preferably 95 nm or more by X-ray wide angle diffraction. When the interplanar spacing (d002) of the 002 plane is 0.337 nm or less, it indicates that the carbon material used as a raw material has high crystallinity, and high-capacity Si composite carbon particles (A) can be obtained. Further, when Lc is 90 nm or more, Si composite carbon particles (A) exhibiting high crystallinity and having a high capacity can be obtained.

In addition, the Si compound particles used as a raw material in the present invention preferably have the following physical properties.
The volume average particle diameter (d50) of the Si compound particles used as a raw material is usually 0.005 μm or more, preferably 0.01 μm or more, more preferably 0.02 μm or more, and further preferably 0.03 μm, from the viewpoint of cycle life. These are usually 10 μm or less, preferably 9 μm or less, more preferably 8 μm or less. When the average particle diameter (d50) is within the above range, volume expansion associated with charge / discharge is reduced, and good cycle characteristics can be obtained while maintaining charge / discharge capacity.

The specific surface area by the BET method of the Si compound particles used as a raw material is usually preferably 0.5 m ² / g or more and 120 m ² / g or less, and 1 m ² / g or more and 100 m ² / g or less. When the specific surface area is within the above range, the charge / discharge efficiency and discharge capacity of the battery are high, lithium is quickly taken in and out during high-speed charge / discharge, and the rate characteristics are excellent.
The amount of oxygen contained in the Si compound particles used as a raw material is not particularly limited, but is usually 0.01
It is preferable that they are mass% or more and 12 mass% or less, 0.05 mass% or more and 10 mass% or less. The oxygen distribution state in the particle may exist near the surface, may exist inside the particle, or may exist uniformly within the particle, but is preferably present near the surface. It is preferable for the oxygen content of the metal particles to be within the above-mentioned range because volume expansion associated with charge / discharge is suppressed due to strong bonding between Si and O, and cycle characteristics are excellent.

  The crystallite size of the Si compound particles used as a raw material is not particularly limited, but is usually 0.05 nm or more, preferably 1 nm or more, and usually 100 nm in the (111) plane crystallite size calculated from XRD. Hereinafter, it is preferably 50 nm or less. It is preferable that the crystallite size of the metal particles is within the above range because the reaction between Si and Li ions proceeds rapidly and is excellent in input / output.

In addition, it is preferable that Si compound particle | grains in Si composite carbon particle (A) have the property similar to the physical property of Si compound particle | grains used as a raw material.
Moreover, what shows the following physical properties as an organic compound used as the carbonaceous material used as a raw material in this invention is preferable.
As an organic compound used as a carbonaceous material used as a raw material, the carbon material described in the following (a) or (b) is preferable.

(A) Coal heavy oil, DC heavy oil, cracked heavy oil, aromatic hydrocarbon, N ring compound, S ring compound, polyphenylene, organic synthetic polymer, natural polymer, thermoplastic resin and Carbonizable organic substance selected from the group consisting of thermosetting resins (b) Carbonized organic substance dissolved in low molecular organic solvent The coal-based heavy oil includes coal tar from soft pitch to hard pitch. Pitch, dry distillation liquefied oil, etc. are preferable. As the DC heavy oil, normal pressure residual oil, reduced pressure residual oil, etc. are preferable. As the cracked petroleum heavy oil, by-products are generated during pyrolysis of crude oil, naphtha, etc. Ethylene tar or the like is preferable, and the aromatic hydrocarbon is preferably acenaphthylene, decacyclene, anthracene, phenanthrene, or the like, and the N-ring compound is preferably phenazine, acridine, or the like. As the S ring compound, thiophene, bithiophene and the like are preferable. As the polyphenylene, biphenyl, terphenyl and the like are preferable. As the organic synthetic polymer, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, and insolubilized products of these compounds. Preferred are nitrogen-containing polymers such as polyacrylonitrile, polypyrrole, polyallylamine, polyvinylamine, polyethyleneimine, urethane resin, urea resin, polythiophene, polystyrene, polymethacrylic acid, etc., and the natural polymers include cellulose, lignin, mannan , Polysaccharides such as polygalacturonic acid, chitosan, saccharose and the like are preferable, and the thermoplastic resin is preferably polyphenylene sulfide, polyphenylene oxide, and the like. For example, furfuryl alcohol resin, phenol-formaldehyde resin, imide resin and the like are preferable.

Further, the carbonizable organic substance may be a carbide such as a solution dissolved in a low-molecular organic solvent such as benzene, toluene, xylene, quinoline, or n-hexane.
Moreover, these may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations.
The carbonaceous material in the Si composite carbon particles (A) preferably has the following physical properties.

The interplanar spacing (d ₀₀₂ ) of the (002) plane of the carbonaceous material powder by X-ray wide angle diffraction method 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 cycle characteristics tend to deteriorate. If the d ₀₀₂ value is too small, it is difficult to obtain the effect of combining the carbonaceous materials.

  The crystallite size (Lc (002)) of the carbonaceous material obtained by X-ray diffraction based on the Gakushin method of the carbonaceous material powder is usually 5 nm or more, preferably 10 nm or more, more preferably 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 cycle characteristics tend to decrease, and if the crystallite size is too small, the charge / discharge reactivity decreases, and there is a risk of increased gas generation during high-temperature storage and reduced high-current charge / discharge characteristics. There is.

(Type of manufacturing method)
The Si composite carbon particles (A) described above are not particularly limited as long as they are Si composite carbon particles in which a silicon element and a carbon material are combined. For example, the following methods (i) to (iii) are used. Can be manufactured.

(Method (i))
(B) Si compound carbon particles (A) in which Si compound particles are dispersed in the granulated body made of carbon material (A) and (b) Si compound particles are attached or coated on the outer periphery of the carbon material that becomes the nucleus. In order to manufacture Si composite carbon particle (A), the method of mixing and granulating the carbon compound, Si compound particle | grains, and the organic compound used as a carbonaceous material is mentioned, for example.

As a specific process,
(1) Step of mixing Si compound particles, carbon material, and organic compound to be carbonaceous material (2) Step of firing the mixture obtained in (1),
Si composite carbon particles (A) can be produced by a method including at least the steps (1) to (2).

(1) Step of mixing Si compound particles, carbon material, and organic compound that becomes carbonaceous material Mixing Si compound particles, carbon material, and organic compound that becomes carbonaceous material, and if a mixture can be obtained, in order to prepare the raw materials in particular Although there is no restriction, for example, a method of mixing an organic compound that becomes a carbonaceous material after mixing a carbon material with Si compound particles, a method of mixing an Si compound particle with an organic compound that becomes a carbonaceous material, and Si Examples thereof include a method of mixing a carbon material after mixing an organic compound that becomes a carbonaceous material into compound particles, a method of mixing an Si compound particle, a carbon material, and an organic compound that becomes a carbonaceous material at once.

  In the method of mixing an organic compound that becomes a carbonaceous material after mixing a carbon material with Si compound particles, the carbonaceous material is adhered to the surface and / or inside of the carbon material by mechanical treatment. You may mix the organic compound which becomes. The mechanical treatment here is not particularly limited. For example, a dry ball mill, a wet bead mill, a planetary ball mill, a vibrating ball mill, a mechano-fusion system, an agromaster (Hosokawa Micron Corporation), a hybridization system, a micros, a mirror ( (Manufactured by Nara Machinery Co., Ltd.).

Among these, the method of mixing an organic compound that becomes a carbonaceous material after mixing a carbon material with Si compound particles preferably mixes the Si compound particles and the carbon material in a powder state, so that the dispersibility is good. It is preferable in that it is.
Examples of the method of mixing the Si compound particles, the carbon material, and the organic compound that becomes the carbonaceous material include a powder mixing method, a melt mixing method, and a solution mixing method.

The mixing temperature is usually from room temperature to 300 ° C., and can be appropriately determined depending on the type of organic compound that becomes a carbonaceous material. The mixing time is usually 10 minutes or more and 1 hour or less. In addition, the solvent used in the solution mixing method with the Si compound particles, the carbon material, and the organic compound that becomes the carbonaceous material can be appropriately selected from water or an organic solvent in which the organic compound is dissolved or dispersed. Two or more different solvents may be mixed and used.

When a solution mixing method with Si compound particles, a carbon material, and an organic compound that becomes a carbonaceous material is used, drying is usually performed in a range of 40 ° C. or more and 300 ° C. or less. Although drying time can be suitably determined according to the kind of solvent used, it is normally 1 hour or more and 24 hours or less. Vacuum drying can be selected as appropriate.
When mixing the Si compound particles, the carbon material, and the organic compound that becomes the carbonaceous material, it is usually performed under normal pressure, but can be performed under reduced pressure or under pressure if desired. Mixing can be carried out either batchwise or continuously. In any case, the mixing efficiency can be improved by using a combination of an apparatus suitable for rough mixing and an apparatus suitable for precision mixing.

  Batch-type mixing devices include high-speed mixers, homogenizers, ultrasonic homogenizers, mixers with a structure in which two frame types rotate and revolve, dissolvers that are high-speed, high-shear mixers, and butterfly mixers for high viscosity. An apparatus having a structure in which one blade stirs and disperses in a tank, a so-called kneader type apparatus having a structure in which a stirring blade such as a sigma type rotates along the side surface of a semi-cylindrical mixing tank, and a stirring blade A trimix type apparatus having a three axis, a so-called bead mill type apparatus having a rotating disk and a dispersion medium in a container, and the like are 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) Etc.), and a container having a plurality of pavement or sawtooth paddles fixed to the shaft and arranged in multiple phases, the inner wall surface of which is the outermost line of rotation of the paddle Substantially along the (externally heated) device, preferably in the form of a cylinder (for example, a Redige mixer manufactured by Redige, a flow share mixer manufactured by Taiyo Kiko Co., Ltd., a Tsukishima Machine Co., Ltd. T dryer, 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 mixing ratio of the Si compound particles with respect to the total of the Si compound particles, the carbon material, and the organic compound as the carbonaceous material is usually 1% by mass or more, preferably 1.5% by mass or more, more preferably 2% by mass or more, and still more preferably. Is 2.5% by mass or more. Moreover, it is 50 mass% or less normally, Preferably it is 40 mass% or less, More preferably, it is 30 mass% or less, More preferably, it is 20 mass% or less. When there are too many Si compound particles, the volume expansion accompanying charging / discharging becomes large, and there exists a tendency for capacity deterioration to become remarkable. Moreover, when there are too few Si compound particles, there exists a tendency for sufficient capacity | capacitance not to be obtained.

  The mixing ratio of the carbon material to the total of the Si compound particles, the carbon material, and the organic compound as the carbonaceous material is usually 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, and further preferably 5% by mass. That's it. Moreover, it is 95 mass% or less normally, Preferably it is 90 mass% or less, More preferably, it is 85 mass% or less, More preferably, it is 80 mass% or less. If the carbon material is too much, the amount of voids formed by the carbon material increases, and it tends to be difficult to increase the electrode density. Moreover, when there are too few carbon materials, the space | gap which suppresses volume expansion cannot be formed, it becomes difficult to take a conductive path, and there exists a tendency for the effect which improves cycling characteristics not to be fully acquired.

The mixing ratio of the organic compound that becomes the carbonaceous material to the total of the organic compound that becomes the Si compound particles, the carbon material and the carbonaceous material is usually 1% by mass or more, preferably 1.5% with respect to the total mass of the carbon material and the Si compound particles. It is at least 2 mass%, more preferably at least 2.5 mass%. Moreover, it is 60 mass% or less normally, Preferably it is 50 mass% or less, More preferably, it is 40 mass% or less, More preferably, it is 30 mass% or less. When there are too many organic compounds used as a carbonaceous material, there exists a tendency for active material to aggregate easily in a baking process. Moreover, it becomes easy to remain as amorphous carbon, and when a battery is produced using the active material containing a large amount of amorphous carbon, the charge / discharge efficiency tends to decrease in the initial stage of charging. Moreover, when there are too few organic compounds used as a carbonaceous material, there exists a tendency for sufficient effect not to be acquired in progress of a reductive reaction, or aggregation suppression of an active material.

(2) Step of firing the mixture obtained in (1) In this step, a mixture containing Si compound particles, a carbon material, and an organic compound that becomes a carbonaceous material is fired.
The atmosphere at the time of firing is a non-oxidizing atmosphere. Preferably, nitrogen, argon, carbon dioxide, ammonia, hydrogen, or the like is circulated to form a non-oxidizing atmosphere.
The reason may be that it is necessary to prevent oxidation of the Si compound particles, the carbon material, and the carbonaceous material.

  The firing temperature varies depending on the firing atmosphere and the organic compound that becomes the carbonaceous material, but as an example, the firing temperature is usually 500 ° C. or higher, preferably 800 ° C. or higher, more preferably 850 ° C. or higher in a nitrogen circulation atmosphere. Further, it is usually at most 3000 ° C., preferably 2000 ° C. or less, more preferably 1500 ° C. or less, even if it is high. If the calcination temperature is too low, carbonization does not proceed sufficiently, there is a risk that the irreversible capacity reduction at the beginning of charge / discharge increases, and the reduction rate of the Si compound decreases, so that it is necessary to take a longer calcination time. However, the reduction rate can be increased even at a low temperature by setting the firing atmosphere to a stronger reducing atmosphere such as a hydrogen atmosphere. On the other hand, if the firing temperature is too high, the carbonized organic compound carbide will reach a crystal structure equivalent to the crystal structure of the raw material carbon material in the mixture, making it difficult to obtain the coating effect, and vaporizing the silicon element. This tends to reduce the yield and increase the manufacturing cost.

  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, 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.

-Other process The composite carbon material which passed through the said process carries out powder processing, such as a grinding | pulverization, crushing, and a classification process, and obtains Si composite carbon particle (A).
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.
Si composite carbon particles (A) can be produced by the production method as described above. However, Si composite carbon particle (A) is not limited to the said manufacturing method.

(Method (ii))
In order to manufacture the Si composite carbon particles (A) in which at least Si compound particles are dispersed in the above-described (c) spheroidized carbon material, for example, the carbon material and the Si compound particles are mixed, and then the spherical shape is obtained. An example is a method of encapsulating Si compound particles inside Si composite carbon particles by performing a chemical treatment. In addition, the carbon material, Si compound particle | grains, and the organic compound used as a carbonaceous material as a raw material in the method (ii) are not specifically limited, It can manufacture using the same thing as the method (i).
A preferable production method includes the following steps.
(1) Step of mixing and fixing the carbon material and Si compound particles (2) Step of subjecting the material obtained in (1) to spheronization treatment

(1) Step of mixing and fixing carbon material and Si compound particles The mixing ratio of Si compound particles to the total of Si compound particles and carbon material is usually 1% by mass or more, preferably 3% by mass or more, more preferably 5%. It is at least 7% by mass, more preferably at least 7% by mass, particularly preferably at least 10% by mass. Moreover, it is 95 mass% or less normally, Preferably it is 70 mass% or less, More preferably, it is 60 mass% or less, More preferably, it is 50 mass% or less, Most preferably, it is 40 mass% or less, Most preferably, it is 35 mass% or less. This range is preferable in that a sufficient capacity can be obtained.

  There are no particular restrictions on the method of mixing and fixing the carbon material and Si compound particles. For example, there is a method in which a Si slurry in which Si compound particles are dispersed in a solvent is used and mixed with a carbon material so that the wet Si compound particles are not dried. Since such Si slurry suppresses aggregation of Si compound particles, it is preferable because the Si compound particles are easily fixed on the surface of the carbon material.

  Examples of the dispersion solvent for the Si compound particles include a nonpolar compound having an aromatic ring and an aprotic polar solvent. The type of the nonpolar compound having an aromatic ring is not particularly limited, but reacts with the Si compound. It is more preferable if it does not have the property. For example, aromatic compounds such as benzene, toluene, xylene, cumene, and methylnaphthalene that are liquid at room temperature, alicyclic hydrocarbons such as cyclohexane, methylcyclohexane, methylcyclohexene, and bicyclohexyl, petrochemicals such as light oil and heavy oil Residual oil in coal chemistry. Among these, xylene is preferred, methylnaphthalene is more preferred, and heavy oil is more preferred because of its high boiling point. In wet pulverization, heat generation tends to occur when the pulverization efficiency is increased. A solvent having a low boiling point may volatilize and become a high concentration. On the other hand, as the aprotic polar solvent, NMP (N-methyl-2-pyrrolidone), GBL (γ-butyrolactone), DMF (NN dimethylformamide) and the like which dissolve not only water but also organic solvents are preferable. NMP (N-methyl-2-pyrrolidone) is preferred because it is difficult to resist and has a high boiling point.

The mixing ratio of the Si compound particles and the dispersion solvent is usually 10% by mass or more, preferably 20% by mass or more, and usually 50% by mass or less, preferably 40% by mass or less with respect to the Si compound particles.
If the mixing ratio of the dispersion solvent is too high, the cost tends to increase, and if the mixing ratio of the dispersion solvent is too low, uniform dispersion of the Si compound particles tends to be difficult.
The Si compound particles are preferably uniformly dispersed on the surface of the carbon material. For this purpose, the dispersion solvent used in wet pulverization of the Si compound particles may be added excessively during mixing. In the present specification, when mixing the Si compound particles into the carbon material as a slurry, the solid content of the Si compound particles is usually 10% or more, preferably 15% or more, more preferably 20% or more. Usually, it is 90% or less, preferably 85% or less, more preferably 80% or less. If the ratio of the solid content is too large, the fluidity of the slurry is lost, and the Si compound particles tend to be difficult to disperse in the carbon material. If the ratio is too small, the process tends to be difficult to handle.

And after mixing, Si compound particle | grains can be fix | immobilized on a carbon material by evaporating and removing a dispersion solvent using an evaporator, a dryer, etc. and drying.
Alternatively, mixing and fixing may be performed while evaporating the dispersion solvent while heating in a high-speed stirrer without adding an excessive dispersion solvent. At this time, in order to immobilize the Si compound particles on the carbon material, a buffer material such as resin or pitch can be used, and it is preferable to use the resin among them. This resin is considered not only to play a role of immobilizing the Si compound particles to the carbon material but also to prevent the Si compound particles from being detached from the carbon material during the spheronization process. In addition, when adding a buffering material, you may add at this stage and may add at the time of the wet grinding | pulverization of Si compound particle | grains.

  The resin that can be used as the buffer material in the step (1) is not particularly limited, but may be a resin contained in the organic compound that becomes the carbonaceous material described above, preferably polystyrene, polymethacrylic acid, Polyacrylonitrile is exemplified, and polyacrylonitrile is particularly preferably used because it has a large amount of residual carbon during firing and a relatively high decomposition temperature. The decomposition temperature of the resin can be measured in an inert gas atmosphere by differential scanning calorimetry (DSC). The decomposition temperature of the resin is preferably 50 ° C. or higher, more preferably 75 ° C. or higher, and still more preferably 100 ° C. or higher. When the decomposition temperature is too high, there is no particular problem. However, when the decomposition temperature is too low, there is a possibility of decomposition in the drying step described below.

The buffer may be used in a state where it is dispersed in a solvent or in a dry state, but when a solvent is used, the same solvent as the dispersion solvent of the Si compound particles can be used.
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, the mixing efficiency can be improved by using a combination of an apparatus suitable for rough mixing and an apparatus suitable for precision mixing. Moreover, you may utilize the apparatus which performs mixing and fixation (drying) simultaneously. Drying can usually be carried out under reduced pressure or under pressure, and preferably dried under reduced pressure.

The drying time is usually 5 minutes or longer, preferably 10 minutes or longer, more preferably 20 minutes or longer, more preferably 30 minutes or longer, and usually 2 hours or shorter, preferably 1 hour and a half or shorter, more preferably 1 hour or shorter. is there. If the time is too long, the cost increases. If the time is too short, uniform drying tends to be difficult.
Although drying temperature changes with solvents, it is preferable that it is time which can implement | achieve the said time. Moreover, it is preferable that it is below the temperature which resin does not modify | denature.

  As a batch-type mixing device, a mixer with a structure in which two frame molds rotate and revolve; a blade such as a dissolver that is a high-speed high-shear mixer and a butterfly mixer for high viscosity is placed 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 solvent body 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, T manufactured by Toshiba Machine Celmac)
EM, Nippon Steel Works TEX-K, etc.); furthermore, it has a container in which a single internal shaft and a plurality of pavement or sawtooth paddles fixed to the shaft are arranged in multiple phases, The inner wall surface substantially follows the outermost line of rotation of the paddle, and preferably has a cylindrical structure (external heating type) (for example, a Redige mixer manufactured by Redige Corporation, a flow manufactured by Taiyo Kiko Co., Ltd.) A share mixer, a DT dryer manufactured by Tsukishima Kikai Co., Ltd., 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. It is also possible to homogenize by means such as ultrasonic dispersion.

(2) A step of spheroidizing the product obtained in (1) Through this step (2), a structure in which a carbon material is folded is observed, and a gap in the folded structure is observed. Si composite carbon particles (A) in which Si compound particles are present can be produced.
That is, as a preferable production method for obtaining the Si composite carbon particles (A), a composite in which Si compound particles are immobilized on the surface of the carbon material obtained before the step (1) is folded (this specification). Is referred to as a composite), but in the present invention, the Si compound particles within a predetermined range are present in the gaps in the folded structure, as will be described later. It is preferable to set the manufacturing conditions as appropriate.

  The spheronization process is basically a process using mechanical energy (mechanical action such as impact compression, friction and shear force), and specifically, a process using a hybridization system is preferable. The system has a rotor having a large number of blades that apply mechanical actions such as impact compression, friction and shearing force, and a large air flow is generated by the rotation of the rotor, and thus obtained in step (1) above. A large centrifugal force is applied to the carbon material in the composite, the carbon materials in the composite obtained in the step (1), and the carbon material, the wall and the blade in the composite obtained in the (1) step. The carbon material in the composite obtained in the step (1) can be neatly folded.

  The apparatus used for the spheronization treatment has, for example, a rotor in which a large number of blades are installed inside a casing, and when the rotor rotates at a high speed, the composite in the composite obtained in the step (1) introduced into the inside is provided. An apparatus or the like that applies a mechanical action such as impact compression, friction, or shear force to the carbon material to perform surface treatment can be used. For example, dry ball mill, wet bead mill, planetary ball mill, vibration ball mill, mechano-fusion system, Agromaster (Hosokawa Micron Corporation), hybridization system, Micros, Miraro (manufactured by Nara Machinery Co., Ltd.), CF mill (Ube) And theta composer (manufactured by Tokuju Kogakusho Co., Ltd.) and the like. Preferred examples of the apparatus include a dry ball mill, a wet bead mill, a planetary ball mill, a vibrating ball mill, a mechano-fusion system, and an agromaster (Hosokawa Micron). Co., Ltd.), hybridization system, Micros, Miraro (manufactured by Nara Machinery Co., Ltd.), CF mill (manufactured by Ube Industries), theta composer (manufactured by Tokuju Kosakusha), pulperizer and the like. Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is particularly preferable.

Note that the carbon material in the composite obtained in the step (1) to be subjected to the spheronization treatment may have already been subjected to a certain spheronization treatment under the conditions of the conventional method. Moreover, you may give a mechanical action repeatedly by circulating the composite_body | complex obtained at the said (1) process, or passing through this process in multiple times.
A spheronization process is performed using such an apparatus. In this process, the rotation speed of the rotor is usually 2000 rpm or more and 8000 rpm or less, preferably 4000 rpm or more and 7000 rpm or less, and usually in a range of 1 minute or more and 60 minutes or less. Then, the spheronization process is performed.

If the number of rotations of the rotor is too small, the process of spheroidizing is weak and the tapping density may not increase sufficiently, while if it is too large, the effect of pulverization becomes stronger than the process of spheroidizing, and the particles collapse As a result, the tapping density may decrease. Further, if the spheroidizing time is too short, the particle size is sufficiently reduced and a high tapping density cannot be achieved. On the other hand, if it is too long, the carbon material in the composite obtained in the step (1) is used. May be shattered.

  Classification processing may be performed on the obtained Si composite carbon particles (A). In addition, when the obtained Si composite carbon particles (A) are not within the specified physical property range of the present invention, a desired classification treatment is performed repeatedly (usually 2 or more and 10 or less times, preferably 2 to 5 times). It can be in the physical property range. Examples of the classification include dry (aerodynamic classification, sieving), wet classification, and the like, but dry classification, particularly aerodynamic classification is preferable from the viewpoint of cost and productivity.

(3) The step of coating the Si composite carbon particles (A) obtained in (2) with a carbonaceous material The Si composite carbon particles (A) are obtained as in the above step (2). (A) preferably contains a carbonaceous material, and as a more specific embodiment, at least a part of the surface thereof is more preferably coated with the carbonaceous material. (Hereinafter also referred to as carbonaceous material-coated Si composite carbon particles (D)). In the present specification, the carbonaceous material-coated Si composite carbon particles (D) are distinguished from the Si composite carbon particles (A) for convenience, but in this specification, the carbonaceous material-coated Si composite carbon particles (D) are also described. It shall be interpreted by being included in the Si composite carbon particles (A).

In the coating treatment, coated carbon particles can be obtained by using an organic compound that becomes a carbonaceous material as a coating material for the Si composite carbon particles (A) described above, and mixing and firing them.
When the firing temperature is usually 600 ° C. or higher, preferably 700 ° C. or higher, more preferably 900 ° C. or higher, usually 2000 ° C. or lower, preferably 1500 ° C. or lower, more preferably 1200 ° C. or lower, an amorphous material is obtained as a carbonaceous material. When a heat treatment is usually performed at 2000 ° C. or higher, preferably 2500 ° C. or higher and usually 3200 ° C. or lower, a graphite material is obtained as a carbonaceous material. The amorphous material is carbon with low crystallinity, and the graphite material is carbon with high crystallinity.
In the coating treatment, the above-described Si composite carbon particles (A) are used as a core material, an organic compound that becomes a carbonaceous material is used as a coating material, and these are mixed and fired to obtain carbonaceous material-coated Si composite carbon particles (D). can get. The coating layer may contain Si compound particles and carbon fine particles. The shape of the carbon fine particles is not particularly limited, and may be any of granular, spherical, chain-like, needle-like, fibrous, plate-like, and scale-like shapes.

Specifically, the carbon fine particles are not particularly limited, and examples thereof include coal fine powder, vapor phase carbon powder, carbon black, ketjen black, and carbon nanofiber. Among these, carbon black is particularly preferable. Carbon black has the advantage that the input / output characteristics are improved even at low temperatures, and at the same time, it can be obtained inexpensively and easily.
The average particle d50 of the carbon fine particles is usually 0.01 μm or more and 10 μm or less, preferably 0.05 μm or more, more preferably 0.07 μm or more, further preferably 0.1 μm or more, preferably 8 μm or less, more Preferably it is 5 micrometers or less, More preferably, it is 1 micrometer or less.

When the carbon fine particles have a secondary structure in which primary particles are aggregated and aggregated, other physical properties and types are not particularly limited as long as the primary particle size is 3 nm or more and 500 nm or less, but the primary particle size is preferable. Is at least 3 nm, more preferably at least 15 nm, even more preferably at least 30 nm, particularly preferably at least 40 nm, preferably at most 500 nm, more preferably at most 200 nm, still more preferably at most 100 nm, particularly preferably at most 70 nm. It is. The primary particle diameter of the carbon fine particles can be measured by electron microscope observation such as SEM or a laser diffraction particle size distribution analyzer.

(Physical properties of carbonaceous material-coated Si composite carbon particles (D))
The carbonaceous material-coated Si composite carbon particles (D) exhibit the same physical properties as the above-mentioned (A), but the preferred physical properties of the carbonaceous material-coated Si composite carbon particles (D) that change depending on the coating treatment are described below. .
-(002) plane spacing (d ₀₀₂ )
The interplanar spacing (d ₀₀₂ ) of the (002) plane of the carbonaceous material-coated Si composite carbon particles (D) by the X-ray wide angle diffraction method is usually 0.336 nm or more, preferably 0.337 nm or more, more preferably 0.340 nm or more, Preferably it is 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 cycle characteristics tend to deteriorate. If the d ₀₀₂ value is too small, it is difficult to obtain the effect of combining the carbonaceous materials.

-Coverage The carbonaceous material-coated Si composite carbon particles (D) are coated with an amorphous material or a graphite material, and among them, the amorphous carbonaceous material is coated with lithium ions. The coverage is usually 0.5% or more and 30% or less, preferably 1% or more and 25% or less, and more preferably 2% or more and 20% or less. When this coverage is too large, the amorphous material portion of the negative electrode material increases, and the reversible capacity when the battery is assembled tends to be small. If the coverage is too small, the amorphous Si compound carbon particles (A) that are the core are not uniformly coated, and strong granulation is not performed, and when pulverized after firing, the particle size tends to be too small. There is.

In addition, the content rate (coverage) of the organic compound-derived amorphous substance finally obtained was based on the amount of Si composite carbon particles (A) to be used, the amount of organic compound to be a carbonaceous material, and JIS K 2270. It can be calculated by the following formula (4) based on the residual carbon ratio measured by the micro method.
Formula (4)
Covering rate of amorphous material derived from organic compounds (%)
= (Mass of organic compound to be carbonaceous material × residual carbon ratio × 100) / {mass of Si composite carbon particles (A) + (mass of organic compound to be carbonaceous material × residual carbon ratio)}
The method (ii) may include a pulverization process, a particle size classification process, and a mixing process with another negative electrode active material in addition to the above-described carbonaceous material coating process.

(Method (iii))
In order to produce the Si composite carbon particles (A) in which the carbon compound is attached or coated on the outer periphery of the Si compound particles as the core described above (d), for example, solid phase reaction, liquid phase reaction, sputtering, chemical vapor deposition, etc. The method used is mentioned.
Here, a synthesis method using a solid phase reaction will be described. The solid phase reaction is a method in which a solid raw material such as a powder is weighed and mixed so as to have a predetermined composition, and then subjected to heat treatment for synthesis. For the Si composite carbon particles (A) according to the present invention, for example, a method in which Si compound particles and an organic compound that becomes a carbonaceous material are brought into contact with each other at a high temperature to cause a reaction is applicable.

The contact between the Si compound particles and the carbonaceous organic compound in the solid phase reaction step is performed under an oxygen-free (low oxygen) environment at a high temperature of 1000 ° C. or higher, and thus an apparatus capable of setting such an environment. For example, a high-frequency induction heating furnace, a graphite furnace, an electric furnace or the like can be used. The temperature condition in the solid phase reaction step is not particularly limited, but is usually not lower than the melting temperature of the Si compound particles, preferably 10 ° C. or higher than the melting temperature of the Si compound particles, and more preferably 30 ° C. or higher. The specific temperature is usually 1420 ° C. or higher, preferably 1430 ° C. or higher, more preferably 1450 ° C. or higher. As an upper limit, it is 2000 degrees C or less normally, Preferably it is 1900 degrees C or less, More preferably, it is 1800 degrees C or less. In addition, the oxygen-free (low oxygen) environment is preferably performed under an inert atmosphere such as argon, under reduced pressure (vacuum), and when performed under reduced pressure (vacuum), usually Pa or less, preferably 1000 Pa or less. Preferably it is 500 Pa or less. Further, the treatment time is usually 0.1 hour or longer, preferably 0.5 hour or longer, more preferably 1 hour or longer, and usually 3 hours or shorter, preferably 2.5 hours or shorter, more preferably 2 hours or shorter.

The technique (iii) may include a pulverization process, a particle size classification process, and a mixing process with another negative electrode active material, in addition to the solid phase reaction process described above.
Examples of the coarse pulverizer used in the pulverization process include a jaw crusher, an impact crusher, and a cone crusher. Examples of the intermediate pulverizer include a roll crusher and a hammer mill. Examples of the fine pulverizer include a ball mill, A vibration mill, a pin mill, a stirring mill, a jet mill, etc. are mentioned.
Among these, a ball mill, a vibration mill and the like are preferable from the viewpoint of processing speed because of a short grinding time.

  The grinding speed is appropriately set depending on the type and size of the apparatus. For example, in the case of a ball mill, it is usually 50 rpm or more, preferably 100 rpm or more, more preferably 150 rpm or more, and further preferably 200 rpm or more. Moreover, it is 2500 or less normally, Preferably it is 2300 or less, More preferably, it is 2000 or less. If the speed is too high, control of the particle size tends to be difficult, and if the speed is too low, the processing speed tends to be slow.

The grinding time is usually 30 seconds or longer, preferably 1 minute or longer, more preferably 1 minute 30 seconds or longer, and further preferably 2 minutes or longer. Moreover, it is usually 3 hours or less, preferably 2.5 hours or less, more preferably 2 hours or less. If the pulverization time is too short, the particle size control tends to be difficult, and if the pulverization time is too long, the productivity tends to decrease.
In the case of a vibration mill, the grinding speed is usually 50 rpm or more, preferably 100 rpm or more, more preferably 150 rpm or more, and still more preferably 200 rpm or more. Moreover, it is 2500 rpm or less normally, Preferably it is 2300 rpm or less, More preferably, it is 2000 rpm or less. If the speed is too high, control of the particle size tends to be difficult, and if the speed is too low, the processing speed tends to be slow.

The grinding time is usually 30 seconds or longer, preferably 1 minute or longer, more preferably 1 minute 30 seconds or longer, and further preferably 2 minutes or longer. Moreover, it is usually 3 hours or less, preferably 2.5 hours or less, more preferably 2 hours or less. If the pulverization time is too short, the particle size control tends to be difficult, and if the pulverization time is too long, the productivity tends to decrease.
As the classification treatment condition of the classification treatment step, the opening is usually 53 μm or less, preferably 45 μm or less, more preferably 38 μm or less so as to have the above particle diameter.

There are no particular restrictions on the equipment used for classification, but for example, when dry sieving: rotary sieving, oscillating sieving, rotating sieving, vibrating sieving, etc. can be used. : Gravity classifier, inertial classifier, centrifugal classifier (classifier, cyclone, etc.) can be used. For wet sieving: mechanical wet classifier, hydraulic classifier, settling classifier, A centrifugal wet classifier or the like can be used.
Among the methods (i) to (iii), by encapsulating silicon element in the spheroidized graphite, the swelling of the electrode plate and the destruction of the particles can be suppressed, and the reactivity between the electrolyte and the silicon element is suppressed. The method (ii) is more preferable because it can be performed.

[Graphite particles (B)]
The graphite particles (B) in the present invention will be described below.
The graphite particles (B) of the present invention are not particularly limited as long as the graphite particles (C) and the amorphous or graphite particles (C) are combined with graphite having different orientations. May be used. Examples thereof include graphite particles disclosed in JP 2000-340232 A, JP 10-158005 A, and the like. Below, it describes about the graphite particle (B) from which the effect of this invention is improved further. The graphite particles (B) of the present invention are particles in which graphite particles (C) and amorphous or graphite particles (C) having different orientations are combined to form Si composite carbon. Since the graphite particles (B) relieve the increase in overvoltage of the particles (A), the resistance of the entire electrode plate can be reduced.

(Characteristics of graphite particles (B))
The graphite particles (B) of the present invention preferably have the following characteristics.
(A) X-ray parameters of graphite particles (B) The interplanar spacing (d ₀₀₂ ) of graphite particles (B) by the X-ray wide angle diffraction method is usually 0.337 nm or less, preferably 0.336 nm or less. . If the d002 value is too large, it indicates that the crystallinity is low, and the initial irreversible capacity may increase when a non-aqueous secondary battery is used. On the other hand, since the theoretical value of the surface spacing of the 002 plane of graphite is 0.3356 nm, the d value is usually 0.3356 nm or more.

  The crystallite size (Lc) of the graphite particles (B) is usually in the range of 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more. Below this range, the crystallinity decreases and the discharge capacity of the battery tends to decrease. The lower limit of Lc is the theoretical value of graphite.

(B) Volume-based average particle diameter (d50) of graphite particles (B)
The average particle diameter d50 of the graphite particles (B) is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, further preferably 25 μm or less, and usually 1 μm or more, preferably 4 μm or more, more preferably 7 μm or more. . If the average particle diameter d50 is too small, the specific surface area increases, so that the decomposition of the electrolyte increases, and the initial efficiency tends to decrease. If the average particle diameter d50 is too large, the rapid charge / discharge characteristics tend to decrease. .

(C) Aspect ratio of graphite particles (B) The aspect ratio of the graphite particles (B) is usually 1 or more, preferably 1.3 or more, more preferably 1.4 or more, still more preferably 1.5 or more, usually 4 Hereinafter, it is preferably 3 or less, more preferably 2.5 or less, and still more preferably 2 or less.
If the aspect ratio is too large, particles tend to be aligned in the direction parallel to the current collector when used as an electrode, so there is not enough continuous void in the thickness direction of the electrode, and lithium ion mobility in the thickness direction. Tends to decrease, leading to a decrease in rapid charge / discharge characteristics.

(D) BET specific surface area (SA) of graphite particles (B)
The specific surface area of the graphite particles (B) by the BET method is usually 0.5 m ² / g or more, preferably 1 m ² / g or more, more preferably 2 m ² / g or more, and further preferably 3 m ² / g or more. Moreover, it is 15 m < ² > / g or less normally, Preferably it is 12 m < ² > / g or less, More preferably, it is 10 m < ² > / g or less, More preferably, it is 8 m < ² > / g or less, Most preferably, it is 6 m < ² > / g or less. If the specific surface area is too large, the reactivity between the portion exposed to the electrolyte and the electrolyte when used as the negative electrode active material is increased, which tends to cause a decrease in initial efficiency and an increase in the amount of gas generated, making it difficult to obtain a preferable battery. Tend. When the specific surface area is too small, there are few sites where lithium ions enter and exit, and the high-speed charge / discharge characteristics and output characteristics tend to be inferior.

The tap density of the (e) tap density graphite particles of the graphite particles (B) (B) is usually 0.8 g / cm ³ or more, 0.85 g / cm ³ or more preferably, 0.9 g / cm ³ or more preferably 0.95 g / cm ³ or more is more preferable. Moreover, 1.8 g / cm ³ or less is usually preferable and 1.5 g / cm ³ or less is preferable, and 1.3 g / cm ³ or less is more preferable.
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 lithium ions in the electrolyte held in the voids is reduced, resulting in reduced rapid charge / discharge characteristics. Tend to.

(F) Circularity of the graphite particles (B) The circularity of the graphite particles (B) is usually 0.85 or more, preferably 0.88 or more, more preferably 0.89 or more, still more preferably 0.90 or more, It is. The circularity is usually 1 or less, preferably 0.99 or less, more preferably 0.98 or less, and still more preferably 0.97 or less. If the circularity is too small, particles tend to be aligned in the direction parallel to the current collector when used as an electrode, so there is not enough space in the thickness direction of the electrode, and lithium ion mobility in the thickness direction. Tends to decrease, leading to a decrease in rapid charge / discharge characteristics. If the circularity is too large, there is a tendency that the effect of suppressing the conduction path breakage is reduced and the cycle characteristics are lowered.

(G) Raman R value of graphite particles (B) The Raman R value of graphite particles (B) is usually 1 or less, preferably 0.8 or less, more preferably 0.6 or less, and even more preferably 0.5 or less. Usually, it is 0.05 or more, preferably 0.1 or more, more preferably 0.2 or more, and further preferably 0.25 or more. When the Raman R value is less than this range, the crystallinity of the particle surface becomes too high, the number of Li insertion sites decreases, and rapid charge / discharge characteristics tend to be deteriorated. 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.

<Method for Producing Graphite Particles (B)>
The graphite particles (B) of the present invention are a composite of graphite particles (C) and amorphous or graphite particles having different orientation from the graphite particles (C).
Either natural graphite or artificial graphite may be used as the graphite particle (C) as a raw material of the graphite particle (B). As graphite, those with few impurities are preferable, and they are used after being subjected to various purification treatments as necessary.

The shape of the graphite particles (C) is not particularly limited, and can be appropriately selected from flaky, fibrous, amorphous particles, etc., but is preferably flaky.
Examples of the natural graphite include scaly graphite, scaly graphite, and soil graphite. The production area of the scaly graphite is mainly Sri Lanka, the production area of the scaly graphite is Madagascar, China, Brazil, Ukraine, Canada, etc., and the main production area of the soil graphite is the Korean Peninsula, China, Mexico, etc. It is.

Among these natural graphites, soil graphite generally has a small particle size and low purity. On the other hand, scaly graphite and scaly graphite have advantages such as a high degree of graphitization and a low amount of impurities, and therefore can be preferably used in the present invention.
Examples of the artificial graphite include graphite particles such as coke, needle coke, and high-density carbon material, which are produced by heat-treating a pitch raw material. 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, and imide resin are usually used at a temperature in the range of 2500 ° C. to 3200 ° C. Examples thereof include those fired and graphitized.

As the graphite particles (C) used in the present invention, natural graphite, artificial graphite, coke powder, needle coke powder, and powder of graphitized material such as resin can be used as described above. Of these, natural graphite is preferable from the viewpoint of high discharge capacity and easy manufacture.

(Spheroidization of graphite particles (C))
The graphite particles (B) are preferably spherical from the viewpoint of suppressing swelling and improving packing density when formed into an electrode. In order to obtain such graphite particles (B), for example, a method of spheroidizing the graphite particles (C) can be mentioned. Hereinafter, a method of performing the spheroidization process will be described, but the method is not limited to this method.
As an apparatus used for the spheronization treatment, for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force and the like including interaction between carbon material particles mainly to impact force to particles can be used. .

  Specifically, it has a rotor with a large number of blades installed inside the casing, and when the rotor rotates at high speed, mechanical action such as impact compression, friction, shearing force, etc. is applied to the carbon material introduced inside. An apparatus that provides a surface treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating graphite.

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

  When processing using the apparatus, for example, the peripheral speed of the rotating rotor is usually 30 m / sec or more and 100 m / sec or less, preferably 40 m / sec or more and 100 m / sec or less, and preferably 50 m / sec or more and 100 m / sec or less. It is more preferable to make it less than second. Further, the treatment that gives a mechanical action to the carbon material can be performed simply by passing graphite. However, it is preferable that the graphite is circulated or retained in the apparatus for 30 seconds or more, and is preferably treated for 1 minute or more in the apparatus. More preferably, the treatment is performed by circulation or retention.

(Composite of graphite particles (C) and amorphous or graphite particles (C) with graphite having different orientations)
The graphite particles (B) used in the present invention are a composite of graphite particles (C) and amorphous or graphite particles having different orientations.
Note that the term “amorphous” as used in the present invention refers to carbon whose d value is usually 0.34 nm or more and has a low crystallinity structure. On the other hand, the graphite is a graphite having a d value of less than 0.34 nm and has a structure with high crystallinity.

  Specifically, the graphite particles (B) in which the graphite particles (C) and the amorphous or graphite particles (C) are combined with graphite having different orientations are combined with the Si composite carbon particles (A) described above. It can be obtained by using a method similar to the step of coating the carbonaceous material. That is, the carbon compound can be obtained by mixing the organic compound to be the carbonaceous material and the graphite particles (C) and heat-treating them.

In the heat treatment, when the firing temperature is usually 600 ° C. or higher, preferably 700 ° C. or higher, more preferably 900 ° C. or higher, usually 2000 ° C. or lower, preferably 1500 ° C. or lower, more preferably 1200 ° C. or lower, amorphous is obtained. In general, when heat treatment is performed at 2000 ° C. or higher, preferably 2500 ° C. or higher, and usually 3200 ° C. or lower, graphite is obtained as a carbonaceous material.
Moreover, you may perform classification and crushing processing suitably.

(Content of graphite having different orientation from that of amorphous or graphite particles (C))
In the graphite particles (B) of the present invention, the amorphous content or the graphite content different from the orientation of the graphite particles (C) is usually 0.01% by mass or more with respect to the graphite particles (C) as a raw material. Preferably it is 0.1% by mass or more, more preferably 0.3% or more, particularly preferably 0.7% by mass or more, and the content is usually 20% by mass or less, preferably 15% by mass or less, Preferably it is 10 mass% or less, Especially preferably, it is 7 mass% or less, Most preferably, it is 5 mass% or less.

If the content is too high, the carbon material will be damaged and material destruction will occur when rolling at a sufficient pressure to achieve a high capacity in a non-aqueous secondary battery. There is a tendency to increase capacity and decrease initial efficiency.
On the other hand, if the content is too small, the effect of coating tends to be difficult to obtain. That is, the side reaction with the electrolytic solution in the battery cannot be sufficiently suppressed, and the charge / discharge irreversible capacity during the initial cycle tends to increase and the initial efficiency tends to decrease.

Further, the content of the graphite having an orientation different from that of the amorphous or graphite particles (C) can be calculated from the sample mass before and after the material firing as in the following formula (5). At this time, the calculation is made assuming that there is no mass change before and after firing the core material.
When w1 is the mass (kg) of the graphite particles (C) and w2 is the mass (kg) of the graphite particles (B), the formula (5)
Content of graphite (% by mass) with different orientation from amorphous or graphite particles (C)
= [(W2-w1) / w1] × 100
Is calculated as

[Carbon material for negative electrode of non-aqueous secondary battery]
The carbon material for a nonaqueous secondary battery negative electrode of the present invention contains Si composite carbon particles (A) and graphite particles (B), and the graphite particles (B) are graphite particles (C) and amorphous or graphite particles (C ) Is not particularly limited as long as it is a composite of graphites having different orientations, but those having the following characteristics are preferred.

(A) X-ray parameter of carbon material for negative electrode of non-aqueous secondary battery The interplanar spacing (d ₀₀₂ ) of the 002 surface according to the X-ray wide angle diffraction method of the carbon material for negative electrode of the non-aqueous secondary battery of the present invention is usually 0. It is 337 nm or less, preferably 0.336 nm or less. If the d002 value is too large, it indicates that the crystallinity is low, and the initial irreversible capacity may increase when a non-aqueous secondary battery is used. On the other hand, since the theoretical value of the surface spacing of the 002 plane of graphite is 0.3356 nm, the d value is usually 0.3356 nm or more.

  In addition, the crystallite size (Lc) of the carbon material for a nonaqueous secondary battery negative electrode of the present invention is usually in the range of 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more. Below this range, the crystallinity decreases and the discharge capacity of the battery tends to decrease. The lower limit of Lc is the theoretical value of graphite.

(B) Volume-based average particle diameter (d50) of carbon material for negative electrode of non-aqueous secondary battery
The average particle diameter d50 of the carbon material for a non-aqueous secondary battery negative electrode of the present invention is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, still more preferably 25 μm or less, and particularly preferably 22 μm or less. It is 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, further preferably 15 μm, and particularly preferably 18 μm or more. If the average particle diameter d50 is too small, the specific surface area increases, so that the decomposition of the electrolyte increases, and the initial efficiency tends to decrease. If the average particle diameter d50 is too large, the rapid charge / discharge characteristics tend to decrease. .

(C) Aspect ratio of carbon material for non-aqueous secondary battery negative electrode The aspect ratio of the carbon material for non-aqueous secondary battery negative electrode of the present invention is usually 1 or more, preferably 1.3 or more, more preferably 1.4 or more. More preferably, it is 1.5 or more, usually 4 or less, preferably 3 or less, more preferably 2.5 or less, and still more preferably 2 or less.
If the aspect ratio is too large, particles tend to be aligned in the direction parallel to the current collector when used as an electrode, so there is not enough continuous void in the thickness direction of the electrode, and lithium ion mobility in the thickness direction. Tends to decrease, leading to a decrease in rapid charge / discharge characteristics.

(D) BET specific surface area (SA) of carbon material for negative electrode of non-aqueous secondary battery
The specific surface area according to the BET method of the carbon material for a non-aqueous secondary battery negative electrode of the present invention is usually 0.5 m ² / g or more, preferably 1 m ² / g or more, more preferably 3 m ² / g or more, still more preferably 5 m ^2. / G or more, particularly preferably 8 m ² / g. Moreover, it is 30 m < ² > / g or less normally, Preferably it is 20 m < ² > / g or less, More preferably, it is 18 m < ² > / g or less, More preferably, it is 16 m < ² > / g or less, Most preferably, it is 14 m < ² > / g or less. If the specific surface area is too large, the reactivity between the portion exposed to the electrolyte and the electrolyte when used as the negative electrode active material is increased, which tends to cause a decrease in initial efficiency and an increase in the amount of gas generated, making it difficult to obtain a preferable battery. Tend. When the specific surface area is too small, there are few sites where lithium ions enter and exit, and the high-speed charge / discharge characteristics and output characteristics tend to be inferior.

(E) Circularity of carbon material for negative electrode of nonaqueous secondary battery The circularity of the carbon material for negative electrode of the nonaqueous secondary battery of the present invention is usually 0.85 or more, preferably 0.88 or more, more preferably 0.8. 89 or more, more preferably 0.90 or more. The circularity is usually 1 or less, preferably 0.99 or less, more preferably 0.98 or less, and still more preferably 0.97 or less. If the circularity is too small, particles tend to be aligned in the direction parallel to the current collector when used as an electrode, so there is not enough space in the thickness direction of the electrode, and lithium ion mobility in the thickness direction. Tends to decrease, leading to a decrease in rapid charge / discharge characteristics. If the circularity is too large, there is a tendency that the effect of suppressing the conduction path breakage is reduced and the cycle characteristics are lowered.

(F) Raman R value of carbon material for nonaqueous secondary battery negative electrode The Raman R value of the carbon material for nonaqueous secondary battery negative electrode of the present invention is usually 1 or less, preferably 0.8 or less, more preferably 0.6. In the following, it is more preferably 0.5 or less, usually 0.05 or more, preferably 0.1 or more, more preferably 0.2 or more, and further preferably 0.25 or more. When the Raman R value is less than this range, the crystallinity of the particle surface becomes too high, the number of Li insertion sites decreases, and rapid charge / discharge characteristics tend to be deteriorated. 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.

(G) Tap density of carbon material for non-aqueous secondary battery negative electrode The carbon material for non-aqueous secondary battery negative electrode of the present invention has a tap density of usually 0.6 g / cm ³ or more, preferably 0.7 g / cm ³ or more. , more preferably 0.8 g / cm ³ or more, more preferably 0.9 g / cm ³ or more, and particularly preferably 1.1 g / cm ³ or more, whereas, usually 1.8 g / cm ³ or less, preferably 1 .5g / cm ³ or less, more preferably 1.3 g / cm ³ or less, further preferably 1.2 g / cm ³ or less.
When the tap density is smaller than the above range, sufficient continuous voids are not ensured in the electrode, and the mobility of lithium ions in the electrolyte held in the voids tends to decrease, so that the rapid charge / discharge characteristics tend to deteriorate. .

<Mass ratio of Si composite carbon particles (A) and graphite particles (B)>
In the carbon material for a nonaqueous secondary battery negative electrode of the present invention, the mass ratio of the Si composite carbon particles (A) to the total amount of the Si composite carbon particles (A) and the graphite particles (B) is not particularly limited, but is usually 0. More than 1% by mass, preferably 1% by mass or more, more preferably 10% by mass or more, particularly preferably 20% by mass or more, and usually 90% by mass or less, preferably 80% by mass or less, more preferably 70% by mass or less. More preferably, it is 60% by mass or less, particularly preferably 50% by mass or less.

  If the ratio of the Si composite carbon particles (A) to the total amount of the Si composite carbon particles (A) and the graphite particles (B) is too large, the initial efficiency tends to decrease and the electrode plate strength tends to decrease. Moreover, when there are too few ratios of Si composite carbon particle (A), there exists a tendency for a cycle characteristic to fall by the reduction | decrease of the conduction | electrical_connection path | pass interruption | blocking suppression effect especially of Si composite carbon particle (A).

  The mixing method is not particularly limited as long as the Si composite carbon particles (A) and the graphite particles (B) are uniformly mixed. For example, as a batch type mixing apparatus, two frame molds are rotating. Revolving mixer; High-speed and high-shear mixer such as dissolver and high-viscosity butterfly mixer, one blade is agitated and dispersed in the tank; on the side of semi-cylindrical mixing tank A so-called kneader-type device having a structure in which a stirring blade such as a sigma type rotates along; a trimix-type device with three stirring blades; a so-called bead mill-type device having a rotating disk and a dispersion medium in a container, etc. 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.

<Mixing with other materials>
The carbon material for a non-aqueous secondary battery negative electrode of the present invention may be any one of Si composite carbon particles (A) and / or graphite particles (B), or a combination of two or more in any composition and combination. Can be suitably used as a negative electrode material for a non-aqueous secondary battery, but one or two or more kinds are mixed with another kind or two or more other materials that do not fall within the scope of the present invention. You may use as a negative electrode material of an aqueous secondary battery, Preferably a non-aqueous secondary battery.

  When other carbon materials not corresponding to the present invention are mixed with the carbon material for nonaqueous secondary battery negative electrode described above, the nonaqueous secondary for the total amount of carbon materials for nonaqueous secondary battery negative electrode and other carbon materials not corresponding to the present invention The mixing ratio of the carbon material for battery negative electrode is usually 10% by mass or more, preferably 20% by mass or more, and usually 90% by mass or less, preferably 70% by mass or less, more preferably 50% by mass or less, still more preferably 40%. It is in the range of not more than mass%, particularly preferably not more than 30 mass%. When the mixing ratio of other carbon materials not corresponding to the present invention is less than the above range, the added effect tends to hardly appear. On the other hand, when the above range is exceeded, the characteristics of the carbon material for a non-aqueous secondary battery negative electrode of the present invention tend to hardly appear.

As other materials not corresponding to the present invention, materials selected from natural graphite, artificial graphite, amorphous carbon, metal particles, and metal compounds are used. Any one of these materials may be used alone, or two or more of these materials may be used in any combination and composition.
As the natural graphite, for example, highly purified scaly graphite particles or scaly graphite can be used. The volume-based average particle diameter of natural graphite is usually 8 μm or more, preferably 12 μm or more, and usually 60 μm or less, preferably 40 μm or less. The natural graphite has a BET specific surface area of usually 3.5 m ² / g or more, preferably 4.5 m ² / g or more, and usually 8 m ² / g or less, preferably 6 m ² / g or less.

Examples of the artificial graphite include particles obtained by graphitizing a carbon material. For example, particles obtained by firing and graphitizing a single graphite precursor particle while it is powdered can be used.
As the amorphous carbon, for example, particles obtained by firing a bulk mesophase, or particles obtained by firing an infusible carbonized pitch or the like can be used.
There is no particular limitation on the apparatus used for mixing the carbon material for the nonaqueous secondary battery negative electrode and other carbon materials. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylinder mixer, a double For conical mixers, regular cubic mixers, vertical mixers, fixed mixers: spiral mixers, ribbon mixers, Muller mixers, Helical Flyt mixers, Pugmil
An l-type mixer, a fluidized type mixer, or the like can be used.

  Examples of metal particles include Fe, Co, Sb, Bi, Pb, Ni, Ag, Si, Sn, Al, Zr, Cr, P, S, V, Mn, Nb, Mo, Cu, Zn, Ge, In A metal selected from the group consisting of Ti and the like or a compound thereof is preferable. Further, an alloy composed of two or more kinds of metals may be used, and the metal particles may be alloy particles formed of two or more kinds of metal elements. Among these, a metal selected from the group consisting of Si, Sn, As, Sb, Al, Zn, and W or a compound thereof is preferable.

Examples of the metal compound include metal oxides, metal nitrides, metal carbides, and the like. Moreover, you may use the alloy which consists of 2 or more types of metals.
Among these, Si compounds are preferable. As the Si compound, the same compound as the Si compound in the Si composite carbon particles (A) can be used.

<Negative electrode for non-aqueous secondary battery>
The present invention also relates to a negative electrode for a non-aqueous secondary battery formed using the carbon material for a non-aqueous secondary battery negative electrode of the present invention, and examples thereof include a negative electrode for a lithium ion secondary battery.
The method for producing the negative electrode for nonaqueous secondary battery and the selection of materials other than the carbon material for nonaqueous secondary battery negative electrode of the present invention constituting the negative electrode for nonaqueous secondary battery are not particularly limited.
The negative electrode for a non-aqueous secondary battery of the present invention comprises a current collector and an active material layer formed on the current collector, and the active material layer is at least a carbon for the negative electrode of the non-aqueous secondary battery of the present invention. Contains material. The active material layer preferably further contains a binder.

The binder is not particularly limited, but a binder having an olefinically unsaturated bond in the molecule is preferable. 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 such a binder having an olefinically unsaturated bond in the molecule and the carbon material for a nonaqueous secondary battery negative electrode of the present invention in combination, the mechanical strength of the negative electrode plate can be increased. When the mechanical 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.
The binder having an olefinically unsaturated bond in the molecule preferably has a large molecular weight and / or a large proportion of unsaturated bonds.

As the molecular weight of the binder, the weight average molecular weight can usually be 10,000 or more, and can usually be 1,000,000 or less. If it is this range, both mechanical strength and flexibility can be controlled to a favorable range. The weight average molecular weight is preferably 50,000 or more, and preferably 300,000 or less.
As the ratio of olefinically unsaturated bonds in the binder molecule, the number of moles of olefinically unsaturated bonds per 1 g of the total binder can be usually 2.5 × 10 ⁻⁷ mol or more, and usually 5 × It can be 10 <^-6> mol or less. If it is this range, the intensity | strength improvement effect will be acquired sufficiently and flexibility will also be favorable. The number of moles is preferably 8 × 10 ⁻⁷ mol or more, and preferably 1 × 10 ⁻⁶ mol or less.

Moreover, about the binder which has an olefinically unsaturated bond, the unsaturation degree can be normally made into 15% or more and 90% or less. The degree of unsaturation is preferably 20% or more, more preferably 40% or more, and preferably 80% or less. In the present specification, the degree of unsaturation represents the ratio (%) of the double bond to the repeating unit of the polymer.
As the binder, a binder having no olefinically unsaturated bond can also be used. By using in combination a binder having an olefinically unsaturated bond and a binder having no olefinically unsaturated bond in the molecule, improvement in coatability and the like can be expected.

When the binder having an olefinically unsaturated bond is 100% by mass, the mixing ratio of the binder having no olefinically unsaturated bond is usually 150% by mass or less in order to suppress a decrease in the strength of the active material layer. Preferably, it is 120 mass% or less.
Examples of binders having no olefinically unsaturated bond include thickening polysaccharides such as methylcellulose, carboxymethylcellulose, starch, carrageenan, pullulan, guar gum, xanthan gum (xanthan gum); polyethers such as polyethylene oxide and polypropylene oxide; Vinyl alcohols such as polyvinyl alcohol and polyvinyl butyral; polyacids such as polyacrylic acid and polymethacrylic acid or metal salts thereof; fluorine-containing polymers such as polyvinylidene fluoride; alkane polymers such as polyethylene and polypropylene; Examples include coalescence.

The active material layer may contain a conductive additive in order to improve the conductivity of the negative electrode. The conductive aid is not particularly limited, and examples thereof include carbon black such as acetylene black, ketjen black, and furnace black, fine powder made of Cu, Ni having an average particle size of 1 μm or less, or an alloy thereof.
It is preferable that the addition amount of a conductive support agent is 10 mass% or less with respect to the carbon material for non-aqueous secondary battery negative electrodes of this invention.

The negative electrode for a non-aqueous secondary battery of the present invention is a slurry obtained by dispersing the carbon material for a non-aqueous secondary battery negative electrode of the present invention and optionally a binder and / or a conductive additive in a dispersion medium. It can be formed by coating and drying. As the dispersion medium, an organic solvent such as alcohol or water can be used.
It does not specifically limit as a collector which apply | coats a slurry, A well-known thing can be used. Specific examples include metal thin films such as rolled copper foil, electrolytic copper foil, and stainless steel foil.

The thickness of the current collector can usually be 4 μm or more, and can usually be 30 μm or less. The thickness is preferably 6 μm or more, and preferably 20 μm or less.
The thickness of the carbon material layer for a negative electrode of a non-aqueous secondary battery (hereinafter sometimes simply referred to as “active material layer”) obtained by applying and drying the slurry is practical as a negative electrode and has a high-density current. From the viewpoint of sufficient lithium ion occlusion / release function with respect to the value, it can be usually 5 μm or more, and can be usually 200 μm or less. Preferably it is 20 micrometers or more, More preferably, it is 30 micrometers or more, Preferably it is 100 micrometers or less, More preferably, it is 75 micrometers or less.

You may adjust the thickness of an active material layer so that it may become the thickness of the said range by pressing after application | coating of a slurry and drying.
Although the density of the carbon material for the non-aqueous secondary battery negative electrode in the active material layer varies depending on the application, for example, in an application in which input / output characteristics such as an in-vehicle application and a power tool application are emphasized, usually 1.1 g / cm ³ or more, 1.65 g / cm ³ or less.

Within this range, it is possible to avoid an increase in contact resistance between particles due to the density being too low, and it is also possible to suppress a decrease in rate characteristics due to the density being too high.
The density is preferably 1.2 g / cm ³ or more, more preferably 1.25 g / cm ³ or more.
In applications in which capacity is important, such as portable device applications such as mobile phones and personal computers, it is usually 1.45 g / cm ³ or more, and usually 1.9 g / cm ³ or less.

If it is this range, the capacity | capacitance fall of the battery per unit volume by a density being too low can be avoided, On the other hand, the fall of the rate characteristic by a density being too high can also be suppressed.
Density is preferably 1.55 g / cm ³ or more, more preferably 1.65 g / cm ³ or more, and particularly preferably 1.7 g / cm ³ or more.

<Non-aqueous secondary battery>
The basic configuration of the nonaqueous secondary battery according to the present invention can be the same as, for example, a 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. The negative electrode is a negative electrode for a non-aqueous secondary battery according to the present invention described above.

<Positive electrode>
The positive electrode can include a current collector and an active material layer formed on the current collector. The active material layer preferably contains a binder in addition to the positive electrode active material.
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. Of these, metal chalcogen compounds capable of inserting and extracting lithium ions are preferred.

Examples of metal chalcogen compounds include transition metal oxides such as vanadium oxide, molybdenum oxide, manganese oxide, chromium oxide, titanium oxide, and tungsten oxide; vanadium sulfide, molybdenum sulfide, titanium sulfide, CuS, and the like transition metal _sulfides; NIPS 3, phosphorus transition metals such as FEPS ₃ - sulfur _compounds; VSe 2, selenium compounds of transition metals such as _{NbSe 3; Fe 0.25 V 0.75 S} 2, Na 0.1 CrS Composite oxides of transition metals such as ₂ ; composite sulfides of transition metals such as LiCoS ₂ and LiNiS ₂ .

Among them, from the viewpoint of occlusion / release of lithium ions, V ₂ O ₅ , V ₅ O ₁₃ , VO ₂ , Cr ₂ O ₅ , MnO ₂ , TiO ₂ , MoV ₂ O ₈ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , TiS ₂ , V ₂ S ₅ , Cr _0.25 V _0.75 S ₂ , Cr _0.5 V _0.5 S _{2 and the} like are preferable, and LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _4, and their transitions A lithium transition metal composite oxide in which a part of the metal is substituted with another metal is particularly preferable.

These positive electrode active materials may be used alone or in combination.
The binder for positive electrodes is not specifically limited, A well-known thing can be selected arbitrarily and can be used. Examples include inorganic compounds such as silicate and water glass, and resins having no unsaturated bond such as Teflon (registered trademark) and polyvinylidene fluoride. Among them, a resin having no unsaturated bond is preferable because it is difficult to decompose during the oxidation reaction.

The weight average molecular weight of the binder can usually be 10,000 or more, and can usually be 3 million or less. The weight average molecular weight is preferably 100,000 or more, and preferably 1,000,000 or less.
The positive electrode active material layer may contain a conductive additive in order to improve the conductivity of the positive electrode. The conductive aid is not particularly limited, and examples thereof include carbon powders such as acetylene black, carbon black, and graphite, various metal fibers, powders, and foils.

  The positive electrode of the present invention is a slurry obtained by dispersing an active material and, optionally, a binder and / or a conductive auxiliary agent in a dispersion medium in the same manner as the above-described negative electrode manufacturing method, and applying this to the surface of the current collector. Can be formed. The current collector for the positive electrode is not particularly limited, and examples thereof include aluminum, nickel, and stainless steel (SUS).

<Electrolyte>
The electrolyte (sometimes referred to as “electrolyte”) is not particularly limited, and a non-aqueous electrolyte obtained by dissolving a lithium salt as an electrolyte in a non-aqueous solvent, or an organic polymer compound or the like is added to the non-aqueous electrolyte. By doing so, a gel-like, rubber-like, or solid sheet-like shape can be mentioned.
The non-aqueous solvent used for the non-aqueous electrolyte is not particularly limited, and a known non-aqueous solvent can be used.

  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.

A non-aqueous solvent may be individual or may use 2 or more types together. In the case of a mixed solvent, a combination of a mixed solvent containing a cyclic carbonate and a chain carbonate is preferable from the balance of conductivity and viscosity, and the cyclic carbonate is preferably ethylene carbonate.
The lithium salt used in the non-aqueous electrolyte is not particularly limited, and a known lithium salt can be used. 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 trifluoromethanesulfonyl imide ((CF ₃ SO ₂ ) ₂ NLi), and the like. . Of these, LiClO ₄ , LiPF ₆ , and LiBF ₄ are preferable.

A lithium salt may be used independently or may use 2 or more types together. The concentration of the lithium salt in the non-aqueous electrolyte can be in the range of 0.5 mol / L or more and 2.0 mol / L or less.
When the organic polymer compound is included in the non-aqueous electrolyte solution described above and used in the form of a gel, rubber, or solid sheet, specific examples of the organic polymer compound include polyethylene oxide, polypropylene oxide, and the like. Polyether polymer compounds; Cross-linked polymers of polyether polymer compounds; Vinyl alcohol polymer compounds such as polyvinyl alcohol and polyvinyl butyral; Insolubilized vinyl alcohol polymer compounds; Polyepichlorohydrin; Polyphosphazene; Siloxane; vinyl polymer compounds such as polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile; poly (ω-methoxyoligooxyethylene methacrylate), poly (ω-methoxyoligooxyethylene methacrylate-co-methyl methacrylate) 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; and 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.

Further, an overcharge inhibitor such as diphenyl ether or cyclohexylbenzene may be added to the non-aqueous electrolyte.
When using the above-mentioned various additives, the total content of the additives is the total amount of the non-aqueous electrolyte so as not to adversely affect other battery characteristics such as an increase in initial irreversible capacity, low temperature characteristics, and deterioration in rate characteristics. In general, it can be 10% by mass or less, in particular, 8% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less.

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 those obtained by dissolving a Li salt in the aforementioned polyether polymer compound, and polymers in which the terminal hydroxyl group of the polyether is substituted with an alkoxide.

<Others>
In order to prevent a short circuit between the electrodes, a porous separator such as a porous membrane or a nonwoven fabric can usually be interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte is impregnated into the porous separator. It is convenient to use it. 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 non-aqueous secondary battery is not particularly limited. For example, a cylinder type in which a sheet electrode and a separator are spiraled; 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 Etc. Further, by storing batteries of these forms in an optional outer case, the battery can be used in an arbitrary shape and size such as a coin shape, a cylindrical shape, and a square shape.

The procedure for assembling the non-aqueous secondary battery is not particularly limited, and can be assembled by an appropriate procedure according to the structure of the battery. For example, a negative electrode can be placed on an outer case, an electrolyte and a separator can be provided thereon, and a positive electrode can be placed so as to face the negative electrode, and can be caulked together with a gasket and a sealing plate to form a battery.
By using the carbon material for a non-aqueous secondary battery negative electrode of the present invention, the carbon material for a non-aqueous secondary battery negative electrode having excellent stability, high output, high capacity, small irreversible capacity, and excellent cycle retention rate, and A non-aqueous secondary battery using the same can be provided.

Claims (9)

  A carbon material for a non-aqueous secondary battery negative electrode containing composite carbon particles (A) containing silicon element and graphite particles (B), wherein the graphite particles (B) are amorphous particles or graphite particles. A carbon material for a negative electrode of a non-aqueous secondary battery, wherein (C) is a particle in which graphite having different orientation is compounded.   The carbon material for a nonaqueous secondary battery negative electrode according to claim 1, wherein the graphite particles (C) are spheroidized natural graphite. The carbon material for a non-aqueous secondary battery negative electrode according to claim 1 or 2, wherein the graphite particles (C) have a tap density of 0.8 g / cm ³ or more and 1.8 g / cm ³ or less.   The carbon material for a nonaqueous secondary battery negative electrode according to any one of claims 1 to 3, wherein the silicon element is a Si compound represented by SiOx (0≤x <2). The ratio R (A) / R (B) of the resistance R (A) of the composite carbon particles (A) containing silicon element and the resistance R (B) of the graphite particles (B) is greater than 1 and 500 or less. The carbon material for a non-aqueous secondary battery negative electrode according to any one of claims 1 to 4, characterized in that: The composite carbon particles (A) containing silicon element have a structure in which flaky graphite is folded, and Si compound particles are present in gaps in the folded structure. The carbon material for a non-aqueous secondary battery negative electrode according to any one of 5.   The carbon material for a nonaqueous secondary battery negative electrode according to claim 6, wherein at least one of the Si compound particles is in contact with the scaly graphite.   A non-aqueous secondary battery negative electrode comprising a current collector and an active material layer formed on the current collector, wherein the active material layer is according to any one of claims 1 to 7. A negative electrode for a non-aqueous secondary battery, comprising a carbon material for a non-aqueous secondary battery negative electrode. A nonaqueous secondary battery comprising a positive electrode and a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode for a nonaqueous secondary battery according to claim 8.