JP6422208B2 - Non-aqueous secondary battery negative electrode carbon material, non-aqueous secondary battery negative electrode and non-aqueous secondary battery using the same - Google Patents

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 secondary battery comprising 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 in which graphite particles having different hardnesses are mixed is used.

For example, Patent Document 1, the amorphous carbon-coated graphite of the compressed density 1.80~1.90g / cm ^3, amorphous carbon coated graphite compression density 1.45~1.65g / cm ³ It is reported that the use of a negative electrode material comprising the following can provide a non-aqueous secondary battery having a high capacity and high charge acceptability and a small irreversible capacity.
Patent Document 2 discloses a negative electrode material made of artificial graphite, graphite-coated graphite, and amorphous carbon-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 Documents 3 and 4 propose a method for producing Si composite carbon particles by firing a mixture of fine powder of Si compound, graphite, and a pitch of carbonaceous material precursor.

Patent Document 5 proposes Si composite carbon particles in which a metal that can be alloyed with Li, scaly graphite, and a carbonaceous material are main components, and the metal is sandwiched between a plurality of scaly graphites.
In patent document 6, it is a granulated body obtained by pulverizing and granulating a mixture of a graphite raw material and a metal powder, and a part of graphite used as a raw material is pulverized to aggregate the graphite raw material and the pulverized product. There has been proposed Si composite carbon particles comprising a granulated body having a laminated structure and a metal powder dispersed on the surface and inside thereof.

  Patent Document 7 proposes to use a mixture of Si composite carbon particles obtained by coating Si compound particles with a carbon material and a carbon material. Thus, it has been reported that a non-aqueous secondary battery having a high capacity and excellent cycle characteristics can be provided.

International Publication No. 2010/113783 Pamphlet JP 2007-324067 A Japanese Patent Laid-Open No. 2003-223892 JP 2012-043546 A JP 2005-243508 A JP 2008-027897 A JP 2003-331832 A

  However, according to the study by the present inventors, the technique described in Patent Document 3 is Si composite carbon particles obtained by combining graphite and Si compound fine powder with a carbonaceous material composed of carbon. Since the carbonaceous material responsible for binding is weak, due to volume expansion of the Si compound fine powder that accompanies charge and discharge, the Si composite carbon particles collapse and there are problems such as cycle deterioration due to the disconnection of the conductive path. There wasn't.

  In the technique described in Patent Document 4, in Si composite carbon particles containing Si compound particles, scaly graphite particles, and carbonaceous material derived from coal tar pitch, by sufficiently stirring and mixing before compositing (firing), Has proposed a structure in which the surfaces of Si compound particles and scaly graphite particles are covered with amorphous carbon (Raman R value range definition), but the binding property of the composite is weak, so Si accompanying charging / discharging Due to the volume expansion of the compound fine powder, the Si composite carbon particles collapsed, and there were problems such as cycle deterioration due to the disconnection of the conductive path, and the practical level was not reached.

  In the technique described in Patent Document 5, a metal that can be alloyed with Li, scaly graphite, and a carbonaceous material are main components, and the metal is sandwiched between a plurality of randomly arranged scaly graphites, and the graphite is sandwiched between them. Si composite carbon particles connected by carbonaceous materials have been proposed. However, if they are only connected by carbonaceous materials, the binding properties of the composite are weak, and the volume of Si compound fine powder that accompanies charging / discharging causes volume expansion of the Si composite. There were problems such as cycle deterioration due to the collapse of the conductive particles due to the collapse of the carbon particles, and the practical level was not reached.

  In the technique described in Patent Document 6, Si composite carbon particles are produced by pulverizing a part of graphite used as a raw material in a high-speed air flow, and the pulverized product is aggregated to form a lump particle and a plurality of lump particles. Since it is a granulated body in which the metal powder is dispersed inside and on the surface and inside thereof, the binding property between the bulk particles is weak, and the volume expansion of the Si compound fine powder accompanying charge / discharge causes the Si composite carbon particles to There have been problems such as cycle deterioration due to collapse of the conductive path, and it has not reached a practical level.

On the other hand, the technique described in Patent Document 7 describes that the conductive path breakage due to the volume expansion of the Si composite carbon particles accompanying charge / discharge can be improved by mixing a carbon material and cycle deterioration can be suppressed. However, there is a problem in that the discharge capacity is reduced by mixing a carbon material having a low theoretical capacity.
The present invention solves the above-mentioned problems of the prior art, has a high capacity and cycle characteristics, and has a low irreversible capacity. Carbon material for a non-aqueous secondary battery negative electrode, and a negative electrode for a non-aqueous secondary battery obtained using the carbon material And a non-aqueous secondary battery including the negative electrode.

As a result of intensive studies to solve the above problems, the present inventors have found that the composite carbon particles (A) (hereinafter sometimes referred to as Si composite carbon particles (A)) containing at least graphite particles and silicon elements, By mixing the composite carbon particles (B) (hereinafter sometimes referred to as Si composite carbon particles (B)) that are harder than the composite carbon particles (A) and contain at least graphite particles, silicon element, and carbonaceous matter, It has been found that a carbon material for a negative electrode of a non-aqueous secondary battery can be produced with a high capacity, excellent cycle characteristics, and little decrease in irreversible capacity.

The mechanism by which the carbon material for a non-aqueous secondary battery negative electrode of the present invention exhibits excellent battery characteristics has not been clarified, but the particles can be appropriately deformed by using soft Si composite carbon particles (A). Thus, the contact between the particles is improved, and the conduction path breakage during charging / discharging can be suppressed. In addition, the electrode can be rolled with a smaller force, and the active material can be prevented from being broken. Furthermore, by adding the hard Si composite carbon particles (B), while having a high capacity derived from Si, deformation of the particles is moderately suppressed in the press at the time of forming the negative electrode, and it is possible to secure a high capacity and a flow path for the electrolyte. It becomes possible. For this reason, it is thought that the carbon material for non-aqueous secondary battery negative electrodes was able to be obtained with high capacity | capacitance, excellent cycling characteristics, and a little fall of an irreversible capacity | capacitance.

  That is, the gist of the present invention is a carbon material for a nonaqueous secondary battery negative electrode containing composite carbon particles (A) and composite carbon particles (B), wherein the composite carbon particles (A) include at least graphite particles and silicon elements. And the composite carbon particles (B) include at least graphite particles, silicon element and carbonaceous material, and the composite carbon particles (B) have a larger press load value than the composite carbon particles (A). It exists in the carbon material for secondary battery negative electrodes.

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, it is possible to provide a non-aqueous secondary battery negative electrode carbon material excellent in stability, high capacity, small irreversible capacity, excellent cycle characteristics, and a non-aqueous secondary battery using the same. it can.

The contents of the present invention will be described in detail below. 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 carbon material for a nonaqueous secondary battery negative electrode of the present invention contains Si composite carbon particles (A) and Si composite carbon particles (B), and the Si composite carbon particles (A) include at least graphite particles and silicon elements, and Si The composite carbon particles (B) include at least graphite particles, silicon element, and carbonaceous material, and the Si composite carbon particles (B) have a larger press load value than the Si composite carbon particles (A).

In addition, in this invention, a press load is a press load at the time of producing an electrode plate using particle | grains, and is used as a parameter | index of particle | grain hardness. Negative electrodes made using hard particles tend to have a higher press load, while negative electrodes made using soft particles tend to have a lower press load.
Hereinafter, the Si composite carbon particles (A) and the Si composite carbon 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 contain at least graphite particles and silicon elements and are softer than the Si composite carbon particles (B).

(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 Si composite carbon particles (B) between the particles decreases, so that particle deformation cannot be sufficiently suppressed in the press at the time of forming the negative electrode. There is a tendency that the ability to secure the liquid flow path is lowered and the input / output characteristics are lowered. 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. A volume-based average particle diameter d50 in the present invention is defined as a volume-based median diameter measured by a measuring apparatus after being introduced into the apparatus and irradiated with an ultrasonic wave of 28 kHz for 1 minute at an output of 60 W.

(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.
The circularity is defined by the following formula (1). When the circularity is 1, a theoretical sphere is obtained.

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 value of 0.3354 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 spectrum can be measured with a Raman spectrometer. Specifically, the sample particles are naturally dropped into the measurement cell to fill the sample, and the measurement cell is rotated in a plane perpendicular to the laser beam while irradiating the measurement cell with an argon ion laser beam. Measure.

Argon ion laser light wavelength: 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 average)

(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 active material becomes excessively active with respect to the electrolyte solution, 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.

(I) Press load (Pa) of Si composite carbon particles (A)
The value of the press load (Pa) of the Si composite carbon particles (A) is usually 100 kg / 5 cm or more, preferably 200 kg / 5 cm or more, more preferably 300 kg / 5 cm or more, still more preferably 400 kg / 5 cm or more, and usually 1200 kg / It is 5 cm or less, preferably 1000 kg / 5 cm or less, more preferably 800 kg / 5 cm or less, and still more preferably 700 kg / 5 cm or less.

If the value of the press load (Pa) is too large, the effect of suppressing the conduction path break during charging and discharging tends to be low, and the cycle characteristics tend to decrease. If it is too small, the flow path of the electrolyte is caused by excessive particle deformation. It tends to be crushed and deteriorate input / output characteristics.
The press load of the present invention is defined as a linear pressure (kg / 5 cm) necessary for forming a negative electrode active material on a current collector by rolling it to a density of 1.6 g / cm ³ .

  The measuring method of the press load is as follows: 1.5% by mass of styrene-butadiene rubber as a binder, 1% by mass of sodium carboxymethylcellulose as a thickener, and 102. 5% by mass of water is added to form a slurry, which is applied onto a current collector and dried. Adjust this electrode so that the width of the active material layer is 5 cm (the coating width may be adjusted at the time of coating), roll press, and measure by measuring the stress at the time of pressing. Can do.

(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, Si, SiOx, SiNx, SiCx, SiZxOy (Z = C, N) and the like, and these are collectively referred to as Si compounds in the present invention. Of these, Si and SiOx are 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, and further preferably 0.6 or more and 1.4 or less. If it is this range, it becomes high capacity | capacitance and it becomes possible to reduce the irreversible capacity | capacitance by the coupling | bonding of Li and oxygen.

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 abundance ratio of silicon element in the Si composite carbon particles (A) The abundance ratio of silicon element calculated by the following measurement method of the Si composite carbon particles (A) of the present invention is usually 0.2 or more. , Preferably 0.3 or more, more preferably 0.4 or more, further 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 abundance ratio of silicon element in 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
It is as follows. 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.

(L) Content of carbonaceous material in Si composite carbon particles (A) The content of carbonaceous material in Si composite carbon particles (A) is usually 0% by mass or more, preferably 0.5% by mass or more, more preferably. Is 1% by mass or more, more preferably 1.5% by mass or more, particularly preferably 2% by mass or more, and usually 10% by mass or less, preferably 8% by mass or less, more preferably 6% by mass or less, still more preferably. It is 4% by mass or less, particularly preferably 3.5% by mass or less.

When the content of the carbonaceous material is too large, the particles become hard, the contact property of the particles is reduced, and the conductive path may be cut off during charging. In addition, the reversible capacity when the battery is assembled tends to be small. If the content is too small, strong granulation is not achieved, and the particle size tends to be too small when pulverized after firing.
The content of the carbonaceous material is determined by the micro method based on the mass of the graphite particles and the mass of the Si compound particles contained in the Si composite carbon particles (A), the amount of the organic compound that becomes the carbonaceous material, and JIS K 2270. It can be calculated by the following formula (3) based on the measured residual carbon ratio.

Formula (3)
Carbonaceous material content (% by mass)
= (Mass of organic compound to be carbonaceous material × residual carbon ratio × 100) / {sample (Si
Total mass of graphite particles and Si compound particles contained in composite carbon particles (A)) + (mass of organic compound to be carbonaceous material × residual carbon 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 contains graphite particles and silicon element. For example, (i) Si compound particles are dispersed in a granulated body made of graphite particles. (B) Si compound particles attached or coated on the outer periphery of the material made of graphite particles, (c) At least Si compound particles dispersed in the material made of spheroidized graphite particles A combination of these may be used. 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, Easier to show high capacity, high cycle characteristics, high initial efficiency by preventing side reaction by preventing contact with electrolyte and particle hardness (press load) In view of controllability and the like, (c) a material in which at least Si compound particles are dispersed in a material made of spheroidized graphite particles is preferable. At this time, it is preferable that at least one of the Si compound particles is in contact with the graphite particles from the viewpoint of suppressing an increase in irreversible capacity.

  In this specification, the term “attachment” refers to a state in which Si compound particles are attached to, adhered to, or combined with the surface of the graphite particles. In order to observe the state, for example, a field emission scanning electron microscope—energy dispersion This can be confirmed by observing the cross section of the particle using a technique such as type 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 containing at least silicon element and graphite particles. For example, graphite particles, Si compound particles, and optionally a carbonaceous material. It can manufacture using the organic compound used.

Graphite particles Examples of the graphite particles constituting the Si composite carbon particles (A) of the present invention include, for example, scaly, massive, or plate-like natural graphite, or, for example, petroleum coke, coal pitch coke, coal needle coke, and mesophase pitch. The scale-like, lump-like or plate-like artificial graphite produced by heating the above to 2500 ° C. or higher can be obtained by removing impurities, pulverizing, sieving or classifying as necessary.

Among these, natural graphite is classified into flake black (FlakeGraphite), scaly graphite (CrystalLine (Vein) Graphite), and soil graphite (Amorphous Graphite) (“Granule Process Technology Assembly” ) Graphite section of Industrial Technology Center, published in 1974), and "HANDBOOKOF
CARBON, GRAPHITE, DIAMOND AND FULLLINES "(N
(see publishes oysPublications)). Graphite crystallinity (degree of graphitization) is the highest at 100% for scaly graphite, followed by 99.9% for scaly graphite. Therefore, it is preferable to use these graphites.

The production area of scaly graphite, which is natural graphite, is Madagascar, China, Brazil, Ukraine, Canada, etc., and the production area of scaly graphite is mainly Sri Lanka. The main producers of soil graphite are the Korean Peninsula, China and Mexico.
Among these natural graphites, scaly graphite and scaly graphite have advantages such as high graphite crystallinity and low impurity content, and therefore can be preferably used in the present invention. Visual methods for confirming that graphite is scaly include particle surface observation with a scanning electron microscope, embedding particles in a resin to produce a thin piece of resin, and cutting out the particle cross section, or coating consisting of particles Examples of the method include a method of observing a particle cross section with a scanning electron microscope after a cross-section polisher is used to produce a cross-section of the coating film and the particle cross-section is cut out.

Scaly graphite and scaly graphite have natural graphite that is highly purified so that the crystallinity of graphite is almost completely crystallized, and artificially formed graphite. Natural graphite is soft and folded. It is preferable in that it is easy to fabricate the structure.
The graphite particles used as the raw material in the present invention preferably have the following physical properties.
The volume-based average particle diameter (d50) of the graphite particles used as a raw material is not particularly limited, but is usually 1 to 120 μm, preferably 3 to 100 μm, more preferably 5 to 90 μm. If the average particle diameter d50 of the graphite particles used as the 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 graphite particles 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.

Preferably a BET specific surface area of the graphite particles used as a raw material is usually ^{1~40m 2 / g, 2~35m 2 /} g, more preferably 3~30m ² / g. The specific surface area of the graphite particles used as the 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 graphite particles used as a raw material is usually 0.337 nm or less. On the other hand, it is usually 0.3354 nm or more, which is the theoretical value of graphite. Moreover, Lc by the X-ray wide angle diffraction method of the graphite particles used as a raw material is 90 nm or more, preferably 95 nm or more. When the interplanar spacing (d002) of the 002 plane is 0.337 nm or less, it indicates that the crystallinity of graphite particles used as a raw material is high, 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, it is preferable that the graphite particle in Si composite carbon particle (A) has the property similar to the physical property of the graphite particle used as a raw material.

-Si compound particle The Si compound particle used as a raw material in the present invention preferably exhibits 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 according to the BET method of the Si compound particles used as the raw material is usually preferably 0.5 to 120 m ² / g and 1 to 100 m ² / g. 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 to 12% by mass and preferably 0.05 to 10% by mass. The oxygen distribution state in the particle may exist near the surface, may exist inside the particle, or may exist uniformly within the particle, but is preferably present near the surface. It is preferable 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.
The crystallite size of the (111) plane calculated from D is usually 0.05 nm or more, preferably 1 nm or more, and is usually preferably 100 nm or less and 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.

-Organic compound used as carbonaceous material As an organic compound used as a carbonaceous material used as a raw material in this invention, the carbon material as 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 is preferably a coal tar pitch from a soft pitch to a hard pitch, dry distillation liquefied oil, etc., and the DC heavy oil is preferably an atmospheric residue, a vacuum residue, etc. As the heavy petroleum oil, ethylene tar or the like by-produced during thermal decomposition of crude oil, naphtha or the like is preferable, and as the aromatic hydrocarbon, acenaphthylene, decacyclene, anthracene, phenanthrene or the like is preferable, and the N-ring compound is , Phenazine, acridine and the like are preferable, the S ring compound is preferably thiophene, bithiophene and the like, the polyphenylene is preferably biphenyl, terphenyl and the like, and the organic synthetic polymer is polyvinyl chloride, polyvinyl alcohol, Polyvinyl butyral, insolubilized products of these, polyacrylonitrile Preferred are nitrogen-containing polymers such as poly (pyrrole), polypyrrole, polyallylamine, polyvinylamine, polyethyleneimine, urethane resin, urea resin, polythiophene, polystyrene, polymethacrylic acid, etc., and the natural polymers include cellulose, lignin, mannan, poly Polysaccharides such as galacturonic acid, chitosan, saccharose and the like are preferable, and the thermoplastic resin is preferably polyphenylene sulfide, polyphenylene oxide, etc., and the thermosetting resin is furfuryl alcohol resin, phenol-formaldehyde resin, imide Resins are preferred.

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, and 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 a lower graphite crystallinity than the graphite particles. Specifically, what shows the following physical properties is preferable.

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 graphite crystallinity is low, and the cycle characteristics tend to deteriorate. If the d ₀₀₂ value is too small, the effect of combining the carbonaceous materials tends to be difficult to obtain.

  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 (A) in which silicon element and graphite particles are combined. For example, the following methods (i) and ( It can be manufactured by ii).
(Method (i))
The Si compound carbon particles (A) in which the Si compound particles are dispersed in the granulated body made of the graphite particles (A) or (b) the material made of the graphite particles are attached or coated on the outer periphery of the material. In order to manufacture Si composite carbon particle (A), the method of mixing and granulating the graphite compound, Si compound particle | grains, and the organic compound used as a carbonaceous material, for example is mentioned.

As a specific process,
(1) Step of mixing Si compound particles, graphite particles, and organic compound to be carbonaceous material (2) Step of firing the mixture obtained in (1) A method comprising at least the above steps (1) to (2) Can produce Si composite carbon particles (A).

(1) Step of mixing Si compound particles, graphite particles, and organic compound that becomes carbonaceous material Mixing Si compound particles, graphite particles, and organic compound that becomes carbonaceous material, and obtaining a mixture, in particular the order of charging the raw materials Although there is no limitation, for example, a method of mixing an organic compound that becomes a carbonaceous material after mixing graphite particles with Si compound particles, a method of mixing Si compound particles after mixing an organic compound that becomes carbonaceous materials with graphite particles, Si Examples thereof include a method of mixing graphite particles after mixing an organic compound that becomes a carbonaceous material with compound particles, a method of mixing Si compound particles, graphite particles, 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 graphite particles with Si compound particles, the carbonaceous material is adhered to the surface and / or inside of the graphite particles 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, preferably, the method of mixing the organic compound that becomes the carbonaceous material after mixing the graphite particles with the Si compound particles mixes the Si compound particles and the graphite particles 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 graphite particles, and the carbonaceous organic compound 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. The solvent used in the solution mixing method with the Si compound particles, the graphite particles, 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, graphite particles, 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 graphite particles, 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, mixing efficiency can be improved by using a combination of an apparatus suitable for rough mixing and an apparatus suitable for fine 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, graphite particles, and carbonaceous organic compound 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. 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 graphite particles to the total of the Si compound particles, the graphite particles, 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 there are too many graphite particles, the amount of voids formed by the graphite particles increases, and it tends to be difficult to increase the electrode density. Moreover, when there are too few graphite particles, 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.

In addition, when the organic compound that becomes the carbonaceous material is mixed, 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 graphite particles, and the carbonaceous material is based on the total mass of the graphite particles and the Si compound particles. Usually, it is 1% by mass or more, preferably 1.5% by mass or more, more preferably 2% by mass or more, and further preferably 2.5% by mass or more. 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, it will become easy to produce aggregation of active materials 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, sufficient effect will not be acquired in progress of a reductive reaction, or suppression of aggregation of an active material.

(2) Step of firing the mixture obtained in (1) In this step, a mixture containing Si compound particles, graphite particles, 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 Si compound particles, graphite particles, and carbonaceous materials.

  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. 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.

(3) Other process The composite carbon material which passed through the said process processes powder, 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 produce Si composite carbon particles (A) in which at least Si compound particles are dispersed inside the above-mentioned (c) spheroidized graphite particles, for example, graphite particles and Si compound particles are mixed, Then, the method of encapsulating Si compound particle | grains inside Si composite carbon particle by giving a spheroidization process is mentioned. In addition, the graphite particles, Si compound particles, and organic compounds that become carbonaceous materials as raw materials in the method (ii) are not particularly limited, and can be manufactured using the same materials as those in the method (i).
A preferable production method includes the following steps.
(1) Step of mixing and fixing graphite particles and Si compound particles (2) Step of subjecting the particles obtained in (1) to spheroidization treatment

(1) Step of mixing and fixing graphite particles and Si compound particles The mixing ratio of Si compound particles to the total of Si compound particles and graphite particles 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 is no particular limitation on the method of mixing and fixing the graphite particles and the 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. Such a Si slurry suppresses aggregation of the Si compound particles, and thus is preferable because the Si compound particles are easily fixed on the surface of the graphite particles.

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 graphite particles. For that purpose, the dispersion solvent used in wet pulverizing the Si compound particles may be added excessively during mixing. In the present specification, when the Si compound particles are mixed with the graphite particles 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 graphite particles. 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 graphite particle | grains by evaporating and removing a dispersion | distribution 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 fix the Si compound particles to the graphite particles, 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 fixing the Si compound particles to the graphite particles but also to prevent the Si compound particles from being detached from the graphite particles 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, mixing efficiency can be improved by using a combination of an apparatus suitable for rough mixing and an apparatus suitable for fine 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, 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. 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 graphite particles are 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 graphite particles in the composite, and the graphite particles in the composite obtained in the step (1), and the graphite particles, walls and blades in the composite obtained in the step (1) The graphite particles 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 performs mechanical treatment such as impact compression, friction, shearing force, etc. on the graphite particles 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 Kosakusho Co., Ltd.), pulperizer and the like. Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is particularly preferable.

In addition, the graphite particles 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 rotational speed of the rotor is too low, the spherical process is weak and the tap density may not increase sufficiently. On the other hand, if it exceeds 8000 rpm, the effect of being crushed becomes stronger than the spherical process, and the particles There is a possibility that the tap density will decrease due to collapse. Furthermore, if the spheronization treatment is less than 1 minute, the particle size may be sufficiently reduced and a high tapping density may not be achieved. On the other hand, if it exceeds 60 minutes, the composite obtained in the step (1) above may be obtained. The graphite particles in the body may be shattered.

Classification processing may be performed on the obtained Si composite carbon particles (A). In addition, when the obtained Si composite carbon particle (A) is not in the physical property range defined in the present invention, it is classified repeatedly (usually 2 times to 10 times, preferably 2 times to 5 times). The desired physical property range can be obtained. 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) may contain a carbonaceous material. As a more specific embodiment, at least a part of the surface may be coated with a carbonaceous material.
In the coating treatment, an Si compound carbon particle (A) coated with a carbonaceous material is prepared 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. ) Is obtained.

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

  In the coating treatment, Si composite carbon particles (A) described above are used as a core material, an organic compound that becomes a carbonaceous material is used as a coating raw material, and these are mixed and fired to form Si composite carbon particles (A ) Is obtained. 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 Si composite carbon particles (A) coated with carbonaceous material)
Each physical property value of the Si composite carbon particles (A) coated with the carbonaceous material is preferably within the range of each physical property value of the Si composite carbon particles (A) described above.
[Si composite carbon particles (B)]
The Si composite carbon particles (B) in the present invention will be described below.

The Si composite carbon particles (B) of the present invention are not particularly limited as long as the value of the press load is larger than that of the composite carbon particles (A) and those containing at least graphite particles, silicon elements and carbonaceous materials are selected. By selecting the Si composite carbon particles (B) as described above, deformation of the particles is moderately suppressed in the press at the time of forming the negative electrode while having a high capacity derived from Si, and the flow path for the high capacity and electrolyte solution It is possible to obtain a carbon material for a negative electrode of a non-aqueous secondary battery with a high capacity, excellent cycle characteristics, and a small decrease in irreversible capacity.

(Characteristics of Si composite carbon particles (B))
The Si composite carbon particles (B) preferably have the following characteristics.
(A) Volume-based average particle diameter (d50) of Si composite carbon particles (B)
The volume-based average particle diameter (d50) (hereinafter also referred to as average particle diameter d50) of the Si composite carbon particles (B) 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 proportion of Si composite carbon particles (A) existing between the particles decreases, so that particle deformation cannot be sufficiently suppressed in the press at the time of forming the negative electrode. There is a tendency that the ability to secure the liquid flow path is lowered and the input / output characteristics are lowered. 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.

(B) Aspect ratio of Si composite carbon particles (B) The aspect ratio of the Si composite carbon particles (B) 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.

(C) Circularity of Si composite carbon particles (B) The circularity of the Si composite carbon particles (B) 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.
(D) Interplanar spacing of Si composite carbon particles (B) (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 value of 0.3354 nm is a theoretical value of graphite.
The crystallite size (Lc) of the Si composite carbon 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.

Raman R value of the Raman R value Si composite carbon particles (B) in (e) Si composite carbon particles (B), 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.

(F) Surface functional group amount of Si composite carbon particles (B) The Si composite carbon particles (B) have a surface functional group amount O / C value represented by the above 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.

(G) BET specific surface area (SA) of Si composite carbon particles (B)
About the specific surface area measured by BET method of Si composite carbon particle (B), 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 active material becomes excessively active with respect to the electrolyte solution Therefore, there is a tendency that a high capacity battery cannot be manufactured.

(H) Tap density of Si composite carbon particles (B) The tap density of Si composite carbon particles (B) 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.

(H) Press load (Pb) of Si composite carbon particles (B)
The value of the press load (Pb) of the Si composite carbon particles (B) is usually 500 kg / 5 cm or more, preferably 800 kg / 5 cm or more, more preferably 1000 kg / 5 cm or more, still more preferably 1200 kg / 5 cm or more, particularly preferably 1400 kg. / 5 cm or more, most preferably 1500 kg / 5 cm or more, usually 4000 kg / 5 cm or less, preferably 3000 kg / 5 cm or less, more preferably 2500 kg / 5 cm or less, more preferably 2300 kg / 5 cm or less, particularly preferably 2200 kg / 5 cm or less, Most preferably, it is 2000 kg / 5 cm or less.

  If the value of the press load (Pb) is too large, it is very difficult to press the electrode and it becomes impossible to press to the target density, and the side reaction with the electrolyte increases due to particle breakage caused by the press and the initial efficiency decreases. Or when a large residual stress is generated on the electrode during pressing, the electrode tends to expand during electrode thermal drying or charge / discharge. On the other hand, if it is too small, the particle deformation cannot be sufficiently suppressed in the press at the time of producing the negative electrode, so that the ability to secure the flow path of the electrolytic solution is lowered, and the input / output characteristics tend to be lowered.

(J) Aspect of silicon element in Si composite carbon particle (B) The aspect of silicon element contained in the Si composite carbon particle (B) in the present invention is the same as that of the above-mentioned Si composite carbon particle (A). It is preferable that it is an aspect.

As a preferable aspect of the silicon element in the Si composite carbon particles (B) 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 (B) of this invention, it is 0.5 mass% or more normally with respect to Si composite carbon particle (B), 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.

(K) The abundance ratio of silicon element in the Si composite carbon particles (B) The abundance ratio of silicon element calculated by the following measurement method for the Si composite carbon particles (B) of the present invention is usually 0.2 or more. , Preferably 0.3 or more, more preferably 0.4 or more, further 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 number, the more silicon element present inside the Si composite carbon particles (B), compared to the silicon element present outside the Si composite carbon particles (B), 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 abundance ratio of silicon element in the Si composite carbon particles (B) is calculated by a method similar to the method described in the section of the Si composite carbon particles (A) described above.

(L) Content of carbonaceous material in Si composite carbon particles (B) The content of carbonaceous material in Si composite carbon particles (B) is usually 1% by mass or more, preferably 1.5% by mass or more, more preferably. Is 2% by mass or more, more preferably 2.5% by mass or more, particularly preferably 3% by mass or more, and usually 40% by mass or less, preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably. 15% by mass or less, particularly preferably 10% by mass or less, and most preferably 5% by mass or less.

When the content of the carbonaceous material is too large, the particles become hard, the contact property of the particles is reduced, and the conductive path may be cut off during charging. In addition, the reversible capacity when the battery is assembled tends to be small. If the content is too small, strong granulation is not achieved, and the particle size tends to be too small when pulverized after firing.
In addition, content of the carbonaceous material in Si composite carbon particle (B) is computed by the method similar to the method demonstrated by the term of the above-mentioned Si composite carbon particle (A).

(Aspect of Si composite carbon particles (B))
The aspect of the Si composite carbon particle (B) of the present invention is not particularly limited as long as it includes graphite particles, silicon element and carbonaceous material, and has a larger press load value than the Si composite carbon particle (A). For example, (A) Si compound particles dispersed in a granulated product made of graphite particles, (B) Si compound particles attached or coated on the outer periphery of graphite particles as cores, (C) Sphericalization Examples include a case where at least Si compound particles are dispersed inside the treated graphite particles, a combination of these, and the like. By encapsulating Si compound particles inside the Si composite carbon particles (B), by suppressing stress due to volume expansion associated with charge and discharge of the Si compound, particle breakage, and accompanying conduction path breakage are suppressed, Presses that tend to exhibit high capacity and high cycle characteristics, tend to exhibit high initial efficiency by preventing side reactions by preventing contact with electrolytes, and can easily control particle hardness From the viewpoint of easy production of particles having a large load value, it is preferable that (iii) at least Si compound particles are dispersed inside the spheroidized graphite particles. 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.

<Method for producing Si composite carbon particles (B)>
If the Si composite carbon particles (B) of the present invention have a larger press load value than the Si composite carbon particles (A), the production method is the same as that for the Si composite carbon particles (A). It is also possible to use another method.
In order to produce the Si composite carbon particles (B) having a larger press load value than the Si composite carbon particles (A), the following methods (Means 1) to (Means 5) are exemplified, and these (Means 1) It is preferable to combine (means 5) and methods (i) and (ii) of the Si composite carbon particles (A).
(Means 1) The carbonaceous material content of the Si composite carbon particles (B) is made larger than the carbonaceous material content of the Si composite carbon particles (A).
(Means 2) The internal voids of the Si composite carbon particles (B) are made smaller than the internal voids of the Si composite carbon particles (A).
(Means 3) The silicon element content of the Si composite carbon particles (B) is made larger than the silicon element content of the Si composite carbon particles (A).
(Means 4) The average particle diameter d50 of the silicon element contained in the Si composite carbon particles (B) is made larger than the average particle diameter d50 of the silicon element contained in the Si composite carbon particles (A).
(Means 5) The average particle diameter d50 of the Si composite carbon particles (B) is made smaller than the average particle diameter d50 of the Si composite carbon particles (A).

  Among these, (Means 1), (Means 3), and (Means 5) are preferable, and (Means 1) is more preferable because of easy adjustment of the value of the press load. The combination of one or more of these means makes it easier to adjust the value of the press load.

(Raw material for Si composite carbon particles (B))
If the Si composite carbon particles (B) include at least graphite particles, silicon element and carbonaceous material, and the Si composite carbon particles (B) have a larger press load value than the Si composite carbon particles (A), Although a raw material is not specifically limited, For example, it can manufacture using the organic compound used as graphite particle | grains, Si compound particle | grains, and a carbonaceous material.

-Graphite particles As the graphite particles used as the raw material in the Si composite carbon particles (B) of the present invention, those appropriately selected from the graphite particles described in the section of the Si composite carbon particles (A) described above can be used.
The graphite particles used as these raw materials may be different from or different from the Si composite carbon particles (A) and the Si composite carbon particles (B). From the stability of the battery, It is preferable to use the same one.
Moreover, it is preferable that the graphite particle in Si composite carbon particle (B) has the property similar to the physical property of the graphite particle used as a raw material.

-Si compound particle As Si compound particle | grains used as a raw material in Si composite carbon particle (B) of this invention, what was suitably selected from Si compound particle | grains as described in the term of Si composite carbon particle (A) mentioned above is used. Can do.
The Si compound particles used as these raw materials may be different from or different from the Si composite carbon particles (A) and the Si composite carbon particles (B). It is preferable to use the same one.
Further, the Si compound particles in the Si composite carbon particles (B) preferably have the same properties as the physical properties of the Si compound particles used as a raw material.

-Organic compound that becomes a carbonaceous material As an organic compound that becomes a carbonaceous material used as a raw material in the Si composite carbon particles (B) of the present invention, an organic compound that becomes a carbonaceous material described in the section of the Si composite carbon particles (A) described above. Those appropriately selected from the compounds can be used.
The organic compound used as the carbonaceous material used as the raw material may be different for the Si composite carbon particles (A) and the Si composite carbon particles (B), or may be the same. From the viewpoint of stability, it is preferable to use the same one.

(Type of manufacturing method)
The Si composite carbon particle (B) described above is a composite of graphite particles, silicon element and carbonaceous material, and its production method is as long as the press load value is larger than that of the Si composite carbon particle (A). Is not particularly limited, but can be produced, for example, by the method (i) or the method (ii) described in the section of (Type of production method) of the Si composite carbon particles (A).
In the methods (i) and (ii), it is possible to suppress the swelling of the electrode plate and the destruction of the particles by encapsulating the silicon element in the spheroidized graphite, and to suppress the reactivity between the electrolytic solution and the silicon element. The method (ii) is more preferable from the viewpoint, and it is more preferable to include a step of coating the carbon composite material on the Si composite carbon particles (B) obtained by the methods (ii) (3) and (2).

(Physical properties of Si composite carbon particles (B) coated with carbonaceous material)
Each physical property value of the Si composite carbon particle (B) coated with the carbonaceous material obtained by the above production method is preferably within the range of each physical property value of the Si composite carbon particle (B) described above.

[Carbon material for negative electrode of non-aqueous secondary battery]
The carbon material for a non-aqueous secondary battery negative electrode of the present invention contains Si composite carbon particles (A) and Si composite carbon particles (B), so that appropriate particle deformation is possible when the electrode plate is formed. It is possible to achieve a negative electrode structure that satisfies both the flow path securing and the particle-to-particle contact characteristics, and has a high capacity, low irreversible capacity, excellent input / output characteristics, excellent cycle characteristics, and low loss of irreversible capacity. There is.
Below, the preferable characteristic of the carbon material for nonaqueous secondary battery negative electrodes of this invention is described.

(A) Ratio of press load (Pa) of Si composite carbon particles (A) to press load (Pb) of Si composite carbon particles (B) (Pb / Pa)
Ratio of the value of the press load (Pa) of the Si composite carbon particles (A) and the value of the press load (Pb) of the Si composite carbon particles (B) in the carbon material for a nonaqueous secondary battery negative electrode of the present invention (Pb / Pa ) Is usually greater than 1, preferably 3 or more, more preferably 5 or more, and even more preferably 5.
5 or more, particularly preferably 5.8 or more, most preferably 6 or more, usually 30 or less, preferably 25 or less, more preferably 20 or less, still more preferably 15 or less, particularly preferably 10 or less, most preferably 8 or less. is there.
When the value of (Pb / Pa) is too large, a large force is required at the time of producing the negative electrode. As a result, the active material may be destroyed, and the irreversible capacity and cycle characteristics may be deteriorated.

(B) Press load of carbon material for non-aqueous secondary battery negative electrode The value of the press load of the carbon material for non-aqueous secondary battery negative electrode of the present invention is usually 200 kg / 5 cm or more, preferably 300 kg / 5 cm or more, more preferably 400 kg / 5 cm or more, more preferably 500 kg / 5 cm or more, particularly preferably 550 kg / 5 cm or more, most preferably 600 kg / 5 cm or more, and usually 3000 kg / 5 cm or less, preferably 2000 kg / 5 cm or less, more preferably 1700 kg / 5 cm or less. More preferably, it is 1500 kg / 5 cm or less, particularly preferably 1000 kg / 5 cm, most preferably 900 kg / 5 cm or less.

If the value of the press load is too large, pressing the electrode becomes very difficult and it becomes impossible to press to the target density, as well as a decrease in initial efficiency due to increased side reaction with the electrolyte due to particle breakage due to pressing, When a large residual stress is generated in the electrode during pressing, the electrode tends to expand during electrode thermal drying or charge / discharge. On the other hand, if it is too small, the particle deformation cannot be sufficiently suppressed in the press at the time of producing the negative electrode, so that the ability to secure the flow path of the electrolytic solution is lowered, and the input / output characteristics tend to be lowered.

(C) X-ray parameter of carbon material for non-aqueous secondary battery negative electrode The surface spacing (d ₀₀₂ ) of the 002 plane by the X-ray wide angle diffraction method of the carbon material for a non-aqueous secondary battery negative electrode 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 graphite crystallinity is low, and the initial irreversible capacity may increase when a non-aqueous secondary battery is used. On the other hand, since the theoretical value of the interplanar spacing of the 002 plane of graphite is 0.3354 nm, the d value is usually 0.3354 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.

(D) Volume-based average particle diameter of carbon material for negative electrode of non-aqueous secondary battery (d50)
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, 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. .

(E) Aspect ratio of carbon material for nonaqueous secondary battery negative electrode The aspect ratio of the carbon material for nonaqueous 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.

(F) BET specific surface area (SA) of carbon material for negative electrode of non-aqueous secondary battery
The specific surface area by the BET method of the carbon material for a nonaqueous 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, and further 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.

(G) Circularity of carbon material for non-aqueous secondary battery negative electrode The circularity of the carbon material for non-aqueous secondary battery negative electrode 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.

(H) 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.

(I) Tap density of non-aqueous secondary battery negative electrode carbon material The tap density of the non-aqueous secondary battery negative electrode carbon material of the present invention is 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 Si composite carbon 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 Si composite carbon particles (B) is not particularly limited. Usually more than 0% by weight, preferably 1% by weight or more, more preferably 10% by weight or more, further preferably 20% by weight or more, particularly preferably 30% by weight or more, usually 90% by weight or less, preferably 80% by weight. % Or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, and 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 Si composite carbon particles (B) is too large, it is difficult to secure the flow path of the electrolytic solution, and the recycling characteristics tend to be deteriorated. . 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 Si composite carbon particles (B) are uniformly mixed. For example, as a batch type mixing apparatus, two frame molds are rotated. A mixer with a structure that revolves while rotating; An apparatus with a blade that stirs and disperses in a tank, such as a dissolver that is a high-speed high-shear mixer and a butterfly mixer for high viscosity; a 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 side surface; a trimix type device having three stirring blades; a so-called bead mill type having a rotating disk and a dispersion medium in a container A device or the like 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 is suitable as a negative electrode material for a non-aqueous secondary battery by using Si composite carbon particles (A) and Si composite carbon particles (B) in any composition and combination. However, it may be used as a negative electrode material for a non-aqueous secondary battery, preferably a non-aqueous secondary battery, by mixing with one or more other materials not corresponding to the present invention.

  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-coated 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 amorphous carbon-coated graphite, for example, natural graphite or artificial graphite coated with an amorphous carbon precursor and fired, or natural graphite or artificial graphite coated with amorphous carbon by CVD are used. Can do.

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 polyvinyl pyrrolidone, 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.

  EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition, the measuring method of each physical property shall follow the measuring method mentioned above.

<Measuring method of average particle diameter d50>
The particle diameter is measured by suspending 0.01 g of a carbon material in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) as a surfactant. This was introduced into a commercially available laser diffraction / scattering particle size distribution measuring apparatus “LA-920 manufactured by HORIBA”, irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, and then measured as a volume-based median diameter in the measuring apparatus. Was defined as the average particle diameter d50.

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

<Measurement method of tap density>
The tap density was measured by dropping the raw carbon material into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ through a sieve having an opening of 300 μm and filling the cell to a full capacity using a powder density measuring device. A tap with a stroke length of 10 mm was performed 1000 times, and the density was determined from the volume at that time and the weight of the sample.

<Content of silicon element in Si composite carbon particles>
The content of silicon element in the Si composite carbon particles was measured with a sample (the Si composite carbon particles were completely melted with alkali, then dissolved and fixed in water, and measured with an inductively coupled plasma emission spectrometer (HORIBA, Ltd. ULTIMA2C)). The amount of silicon element was calculated from the calibration curve, and then the content of silicon element in the Si composite carbon particles was calculated by dividing the amount of silicon element by the weight of the Si composite carbon particles.

<Measurement method of discharge capacity, irreversible capacity, initial efficiency, cycle charge / discharge efficiency>
Using a non-aqueous secondary battery (2016 coin-type battery) produced by the method described later, the discharge capacity (mAh / g) during battery charging / discharging was measured by the following measurement method.
Charge to 5 mV with respect to the lithium counter electrode at a current density of 0.05 C, and further charge to a current density of 0.005 C at a constant voltage of 5 mV. After doping lithium into the negative electrode, the current density of 0.1 C Then, the lithium counter electrode was discharged to 1.5V. The discharge capacity (mAh / g) at this time is defined as the discharge capacity (mAh / g) of the present carbon material, and the difference between the charge capacity (mAh / g) and the discharge capacity (mAh / g) is the irreversible capacity (mAh / g). did. Further, the first cycle discharge capacity (mAh / g) obtained here was divided by the charge capacity (mAh / g), and a value multiplied by 100 was defined as the initial efficiency (%).

  Further, this cell was charged to 5 mV with respect to the lithium counter electrode at a current density of 0.2 C, further charged to a current density of 0.02 C at a constant voltage of 5 mV, and after doping lithium into the negative electrode, 0 The battery was discharged to 1.5 V with respect to the lithium counter electrode at a current density of 2 C. When this charge / discharge is repeated 30 cycles, the discharge capacity (mAh / g) at the 30th cycle is divided by the charge capacity (mAh / g) at the 30th cycle, and the value multiplied by 100 is the cycle charge / discharge efficiency (%) It was.

<Method for producing electrode sheet and measuring press load>
An electrode plate having an active material layer with an active material layer density of 1.60 ± 0.03 g / cm ³ was produced using the Si composite carbon particles and / or carbon particles of Examples or Comparative Examples. Specifically, 20.00 ± 0.02 g of a negative electrode material, 20.00 ± 0.02 g of a 1% by mass aqueous solution of carboxymethylcellulose sodium salt (0.200 g in terms of solid content), and styrene having a weight average molecular weight of 270,000 -Aqueous dispersion of butadiene rubber 0.75 ± 0.05 g (0.3 g in terms of solid content) was added, stirred for 5 minutes with a hybrid mixer manufactured by Keyence, and defoamed for 30 seconds to obtain a slurry.

This slurry was applied to a width of 5 cm using a doctor blade so that the negative electrode material was attached to a current collector of 18 μm thick copper foil with a thickness of 5.0 ± 0.5 mg / cm ² and air-dried at room temperature. Went. Further, after drying at 110 ° C. for 30 minutes, roll pressing was performed using a roller having a diameter of 20 cm to adjust the density of the active material layer to be 1.60 ± 0.03 g / cm ³ to obtain an electrode sheet.
The load at this time was set as a press load (kg / 5 cm).

<Preparation of non-aqueous secondary battery (2016 coin type battery)>
The electrode sheet produced by the above method was punched into a disk shape with a diameter of 12.5 mm, and a lithium metal foil was punched into a disk shape with a diameter of 14 mm as a counter electrode. Between both electrodes, a separator (porous polyethylene film) impregnated with an electrolytic solution in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7) so as to be 1 mol / L. 2016 coin type batteries were prepared.

<Carbon material>
Si composite carbon particles (A):
Polycrystalline Si (manufactured by Wako) having an average particle diameter d50 of 30 μm is pulverized with a bead mill (Ashizawa Finetech) together with NMP (N-methyl-2-pyrrolidone), and an Si slurry having an average particle diameter d50 of 0.2 μm (I) was produced. 350 g of this Si slurry (I) (solid content 30%) was charged into 750 g of NMP in which 60 g of polyacrylonitrile was uniformly dissolved, and mixed with a mixing stirrer. Next, 1000 g of scaly natural graphite having an average particle diameter d50 of 45 μm was added and mixed to obtain slurry (II) in which polyacrylonitrile, Si, and graphite were uniformly dispersed. The slurry (II) was appropriately dried under reduced pressure for 3 hours at 150 ° C., which is lower than the thermal decomposition temperature of polyacrylonitrile, so that the polyacrylonitrile is not denatured. In addition, the decomposition temperature of polyacrylonitrile was 270 degree | times from DSC analysis.

  The obtained lump was crushed with a hammer mill (MF10 manufactured by IKA) at a rotation speed of 6000 rpm, and then charged into a hybridization system (manufactured by Nara Machinery Co., Ltd.). The rotor rotation speed was 7000 rpm for 180 seconds. Circulation or stagnation was performed to give a spheronization treatment to obtain Si composite carbon particles (A0). The Si composite carbon particles (A0) were introduced into a firing furnace and fired at 1000 ° C. for 1 hour in a nitrogen atmosphere. The fired product was pulverized with a hammer mill (MF10, manufactured by IKA) at a rotation speed of 3000 rpm, and then classified with a vibrating screen having an opening of 45 μm to obtain Si composite carbon particles (A).

The content of silicon element, average particle diameter d50, tap density, and specific surface area measured by the measurement method were 7.4% by mass, 14 μm, 1.0 g / cm ³ , and 12.0 m ² / g, respectively. . Further, when the cross-sectional structure was observed by the measurement method, the Si composite carbon particles (A) had a structure in which scaly natural graphite was folded, and Si compound particles were present in the gaps in the folded structure. Was. Further, it was observed that there was a portion where the Si compound particles and the scaly natural graphite were in contact.

Si composite carbon particles (B) -1:
Coal tar pitch was mixed with Si composite carbon particles (A0) as an organic compound to be a carbonaceous material so that the coverage after firing was 7.5%, and kneaded and dispersed by a biaxial kneader. The obtained dispersion was introduced into a firing furnace and fired at 1000 ° C. for 1 hour in a nitrogen atmosphere. The fired product is crushed with a hammer mill (MF10 manufactured by IKA) at a rotational speed of 3000 rpm, and then classified with a vibrating screen having a mesh opening of 45 μm, and composite carbon particles (B) − coated with amorphous carbon as a carbonaceous material 1 was obtained.

The content of silicon element, average particle diameter d50, tap density, and specific surface area measured by the measurement method were 7.4% by mass, 14 μm, 1.1 g / cm ³ , and 5.7 m ² / g, respectively. . Further, when the cross-sectional structure was observed by the measurement method, the composite carbon particle (B) -1 had a structure in which the scale-like natural graphite was folded, and the Si compound particles were in the gap in the folded structure. Existed. Further, it was observed that there was a portion where the Si compound particles and the scaly natural graphite were in contact.

Si composite carbon particles (B) -2:
When producing the Si composite carbon particles (A0), the composite carbon particles (B) -1 were used in the same manner as the Si composite carbon particles (B) -1, except that the Si slurry (I) was 500 g (solid content 40%). B) -2 was obtained.
The content of silicon element, average particle diameter d50, tap density, and specific surface area measured by the above measuring methods were 16.3% by mass, 21 μm, 1.1 g / cm ³ , and 12.1 m ² / g, respectively. . Further, when the cross-sectional structure was observed by the measurement method, the composite carbon particles (B) -2 had a structure in which the scale-like natural graphite was folded, and the Si compound particles were found in the gaps in the folded structure. Existed. Further, it was observed that there was a portion where the Si compound particles and the scaly natural graphite were in contact.

[Example 1]
Si composite carbon particles (A) and Si composite carbon so that the mass ratio of Si composite carbon particles (A) to the total amount of Si composite carbon particles (A) and Si composite carbon particles (B) -1 is 30% by mass. Particles (B) -1 were mixed to obtain a sample (mixing ratio was Si composite carbon particles (A): Si composite carbon particles (B) -1 = 30: 70). About this sample and the non-aqueous secondary battery produced using this, the press load, the initial efficiency, the irreversible capacity, the discharge capacity, and the cycle maintenance factor were measured by the above-described measurement methods. The results are shown in Table 1 below.

[Example 2]
Si composite carbon particles (A) and Si composite carbon so that the mass ratio of Si composite carbon particles (A) to the total amount of Si composite carbon particles (A) and Si composite carbon particles (B) -1 is 50% by mass. Particle (B) -1 was mixed to obtain a sample (mixing ratio was Si composite carbon particle (A): Si composite carbon particle (B) -1 = 50: 50). About this sample and the non-aqueous secondary battery produced using this, the press load, the discharge capacity, the irreversible capacity, the initial efficiency, and the cycle maintenance ratio were measured by the above-described measurement methods. The results are shown in Table 1 below.

[Example 3]
Si composite carbon particles (A) and Si composite carbon so that the mass ratio of Si composite carbon particles (A) to the total amount of Si composite carbon particles (A) and Si composite carbon particles (B) -1 is 70% by mass. Particles (B) -1 were mixed to obtain a sample (mixing ratio was Si composite carbon particles (A): Si composite carbon particles (B) -1 = 70: 30). About this sample and the non-aqueous secondary battery produced using this, the press load, the discharge capacity, the irreversible capacity, the initial efficiency, and the cycle maintenance ratio were measured by the above-described measurement methods. The results are shown in Table 1 below.

[Comparative Example 1]
The battery characteristics were evaluated in the same manner as in Example 1 using the Si composite carbon particles (A) as they were. The results are shown in Table 1 below.
[Comparative Example 2]
The battery characteristics were evaluated in the same manner as in Example 1 using the Si composite carbon particles (B) -1 as they were. The results are shown in Table 1 below.

[Comparative Example 3]
Spherical natural having an average particle diameter d50, a tap density, and a specific surface area of 11 μm, 0.94 g / cm ³ and 8.8 m ² / g, respectively, measured by the above measurement method instead of the Si composite carbon particles (A) Graphite particles were used, and Si composite carbon particles (B) -2 were further used. Spherical natural graphite particles and Si composite carbon particles (B) -2 are mixed so that the mass ratio of spherical natural graphite particles and spherical natural graphite particles to the total amount of spherical natural graphite particles and Si composite carbon particles (B) -2 is 70% by mass. Thus, a sample was obtained (mixing ratio was spherical natural graphite particles: Si composite carbon particles (B) -2 = 70: 30). About this sample and the non-aqueous secondary battery created using this, the battery characteristic was evaluated similarly to Example 1. FIG. The results are shown in Table 1 below.

As can be seen from Table 1, a non-aqueous secondary battery including Si composite carbon particles (A) having a small press load value (A) and Si composite carbon particles (B) -1 having a large (hard) press load value. The carbon materials for negative electrodes (Examples 1 to 3) are Si composite carbon particles (A) and Si composite carbon particles (B)-
Compared with the carbon material for a non-aqueous secondary battery negative electrode composed only of 1 (Comparative Example 1 and Comparative Example 2), it was confirmed that high initial efficiency, improvement in irreversible capacity, and high cycle charge / discharge efficiency were exhibited.

  Further, a carbon material for a negative electrode of a non-aqueous secondary battery containing Si composite carbon particles (A) having a small press load value (A) and Si composite carbon particles (B) -1 having a large (hard) press load value ( In Examples 1 to 3, a high discharge capacity was confirmed as compared with a carbon material for a non-aqueous secondary battery negative electrode (Comparative Example 3) using spheroidized natural graphite instead of Si composite carbon particles (A) as a soft material. It was done.

  From these results, by mixing Si composite carbon particles (A) having a small press load value (soft) and Si composite carbon particles (B) -1 having a large press load value (hard), appropriate particles can be obtained. Since it became possible to achieve a negative electrode structure that can ensure the flow path of the electrolyte solution and the contact between the particles, it is possible to maintain a high discharge capacity derived from silicon without rate deterioration, and an irreversible capacity It is thought that the reduction of the cycle rate and the improvement of the cycle maintenance rate have become possible.

  From this, by using the carbon material for a nonaqueous secondary battery negative electrode of the present invention, a carbon material for a nonaqueous secondary battery negative electrode having a high capacity, a small irreversible capacity, and an excellent cycle retention rate, and the same were used. A non-aqueous secondary battery can be provided.

Claims (8)

A carbon material for a nonaqueous secondary battery negative electrode containing composite carbon particles (A) and composite carbon particles (B), wherein the composite carbon particles (A) include at least graphite particles and silicon elements,
B) contains at least graphite particles, silicon element and carbonaceous material, and the composite carbon particles (B) have a larger press load value than the composite carbon particles (A), and the carbon material for a non-aqueous secondary battery negative electrode . The composite carbon particle (A) has a carbonaceous material content of 0% by mass to 10% by mass, and the composite carbon particle (B) has a carbonaceous material content of 1% by mass to 40% by mass. particle(
2. The carbon material for a non-aqueous secondary battery negative electrode according to claim 1, wherein the content of the carbonaceous material in B) is larger than the content of the carbonaceous material in the composite carbon particles (A). Press load (Pa) of the composite carbon particles (A) and press load (P) of the composite carbon particles (B)
The carbon material for a nonaqueous secondary battery negative electrode according to claim 1 or 2, wherein the ratio (b) of b) is greater than 1 and 30 or less. 4. The carbon material for a non-aqueous secondary battery negative electrode according to claim 1, wherein the carbonaceous material has lower graphite crystallinity than graphite particles. 5. 5. The non-aqueous secondary battery negative electrode according to claim 1, wherein the silicon element is a Si compound containing at least one of Si and SiOx (0 <x <2). Carbon material . 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. 5
The carbon material for non-aqueous secondary battery negative electrodes as described in any one of these. It is a negative electrode for non-aqueous secondary batteries provided with an electrical power collector and the active material layer formed on the said electrical power collector, Comprising: The said active material layer is as described in any one of Claims 1 thru | or 6. 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, a negative electrode, and an electrolyte, wherein the negative electrode is claimed in claim 7.
A non-aqueous secondary battery, which is the negative electrode for a non-aqueous secondary battery described in 1.