JP2014165018A - Carbon material for nonaqueous secondary battery negative electrode, negative electrode for nonaqueous secondary battery, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon material for a nonaqueous secondary battery negative electrode, which has little occurrence of initial gas and storage gas due to the decomposition of a nonaqueous electrolyte, excellent stability, small irreversible capacity, and suffers only a small reduction in charge/discharge rate characteristics and cycle efficiency, and to provide a nonaqueous secondary battery using the carbon material.SOLUTION: A carbon material for a nonaqueous secondary battery negative electrode contains a scale-like graphite particles (A) and carbonaceous particles (B). The scale-like graphite particles (A) are impregnated with a polymer sparingly soluble in a nonaqueous electrolyte, and the carbonaceous particles (B) have an aspect ratio of 1 or more and 4 or less.

Description

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

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

Amorphous carbon materials are also used because they are relatively stable with respect to some electrolyte solutions. Furthermore, a carbon material is also used in which amorphous carbon is coated or adhered on the surface of the graphitic carbon particles to combine the characteristics of graphite and amorphous carbon.
For example, Patent Document 1 uses a negative electrode material composed of spherical graphite particles obtained by spheroidizing scaly particles having a circularity of 0.86 or more and scaly graphite particles having a circularity of less than 0.86. A technique for achieving both discharge capacity and slurry characteristics is disclosed.

Patent Document 2 discloses a negative electrode material made of a mixture of flaky graphitized carbon having an aspect ratio of 3 or more and spherical carbon having an aspect ratio of 1 to 2. It has been reported that, due to this, voids are secured between the scaly graphite particles, the penetration of the electrolytic solution into the negative electrode is improved, and the discharge capacity and load characteristics are improved.
Patent Document 3 discloses that a carbon material having an aspect ratio of 5 or less and an aspect ratio of 6 or more and an 80% particle diameter (d80) are 1.7 times or more the average particle diameter (d50) of the carbon material. A negative electrode material made of a mixture with scaly graphite particles is disclosed. As a result, even if the carbon materials are separated from each other due to the expansion and contraction of the carbon material due to repeated cycles of charge and discharge, the carbon materials ensure conductivity because the scaly graphite particles are in contact across the carbon material. It has been reported that improved cycle characteristics can be achieved.

  On the other hand, in a lithium ion secondary battery using a carbon material such as scaly graphite particles as a negative electrode active material, initial purification is performed by refining a film called SEI (Solid Electrolyte Interface) or by generating gas as a side reaction product. There is a problem that the irreversible charge / discharge capacity during the cycle increases, and as a result, the capacity cannot be increased. Furthermore, the excessive formation of the SEI film has a problem that the negative electrode resistance is increased and the input / output characteristics of the battery are deteriorated.

  As a solution to this, for example, Patent Document 4 proposes coating the surface of the massive graphite particles with a water-soluble cellulose derivative, polyuronide, and a water-soluble synthetic resin. For example, Patent Document 5 proposes a carbon negative electrode coated with an organic polymer having an aliphatic amino group in the side chain.

JP 2000-226206 A Japanese Patent Laid-Open No. 9-147862 JP 2012-216532 A JP 2001-291516 A JP 2002-117851 A

However, according to the study by the present inventors, the negative electrode materials described in Patent Documents 1 to 3 are irreversible because measures against excessive side reaction between the graphite particle surface and the electrolytic solution are insufficient. It has been found that an increase in capacity, an increase in gas generation, and a decrease in cycle characteristics are problems.
In addition, the negative electrode materials described in Patent Documents 4 and 5 are slightly suppressed in the side reaction of the electrolyte solution, but have insufficient measures to suppress the conduction path breakage during repeated charging and discharging, and thus cycle characteristics. It turned out that the decline of the is a problem. Moreover, since the charge transfer resistance on the surface of the negative electrode material was increased, it was revealed that the input / output characteristics of the battery were insufficient.

  The present invention solves the above-mentioned problems of the prior art, is excellent in initial charge / discharge efficiency, generates less gas, and has a good charge / discharge rate characteristic and cycle characteristic. It aims at providing the negative electrode for non-aqueous secondary batteries obtained by using, and a non-aqueous secondary battery provided with the said negative electrode.

As a result of intensive studies to solve the above problems, the present inventors have mixed scaly graphite particles impregnated with a poorly soluble polymer in a non-aqueous electrolyte and carbonaceous particles having a specific aspect ratio. Thus, it has been found that a carbon material for a negative electrode of a non-aqueous secondary battery having reduced irreversible capacity, suppression of gas generation, and good charge / discharge rate characteristics and cycle characteristics can be produced.
Although 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, it is likely that (1) the conductive material has a scaly shape between the carbonaceous particles as the negative electrode active material. In addition to ensuring the conductive path of the carbonaceous particles by entering the graphite particles, (2) by combining the flaky graphite and the non-aqueous electrolyte solution with a poorly soluble polymer, This is considered to be caused by preventing contact with the solution and suppressing side reactions with the electrolyte.

  That is, the gist of the present invention is a carbon material for a non-aqueous secondary battery negative electrode containing scaly graphite particles (A) and carbonaceous particles (B), wherein the scaly graphite particles (A) are non-aqueous. A carbon material for a non-aqueous secondary battery negative electrode is characterized in that a poorly soluble polymer is attached to an electrolytic solution, and the aspect ratio of the carbonaceous particles (B) is 1 or more and 4 or less.

  According to the present invention, there is little generation of initial gas and storage gas due to decomposition of a non-aqueous electrolyte solution, excellent stability, small irreversible capacity, and excellent charge / discharge rate characteristics and cycle characteristics for a non-aqueous secondary battery negative electrode A carbon material and a non-aqueous secondary battery using the carbon material can be provided.

Hereinafter, the contents of the present invention will be described in detail. In addition, description of the invention structural requirements described below is an example (representative example) of the embodiment of the present invention, and the present invention is not limited to these forms unless it exceeds the gist.
The carbon material for a non-aqueous secondary battery negative electrode of the present invention is a scaly graphite particle (A) (also referred to as a scaly graphite particle (A) in the present specification) in which a poorly soluble polymer is attached to a non-aqueous electrolyte solution. And carbonaceous particles (B) having an aspect ratio of 1 or more and 4 or less (also referred to herein as carbonaceous particles (B)).
Hereinafter, the scaly graphite particles (A) and the carbonaceous particles (B) used in the present invention will be described.

[Scale-like graphite particles (A)]
The scaly graphite particles (A) obtained by attaching a polymer that is sparingly soluble in the non-aqueous electrolyte to the scaly graphite particles in the present invention will be described below.
The scaly graphite particles (A) of the present invention contain at least a polymer that is hardly soluble in a non-aqueous electrolyte (also referred to simply as a polymer in this specification) and scaly graphite particles.

In the present specification, “insoluble in a non-aqueous electrolyte” means that the polymer is immersed in a solvent in which ethyl carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3: 7 for 24 hours, and the dry weight loss rate before and after immersion is 10 It shall be below mass%.
Further, in this specification, the term “attachment” refers to a state in which a polymer is attached to, attached to, or combined with the surface of the scaly graphite particles, a state in which the polymer is attached to the pores of the scaly graphite particles, and the like. In order to observe the state, for example, a particle cross section is observed using a technique such as field emission scanning electron microscope-energy dispersive X-ray (SEM-EDX) analysis, X-ray photoelectron spectroscopy (XPS) analysis, or the like. This can be confirmed.
In general, the shape of the scaly graphite particles (A) can be easily discriminated by observing them with an SEM photograph or the like.

(Characteristics of scale-like graphite particles (A))
The scaly graphite particles (A) of the present invention are not particularly limited as long as a polymer hardly soluble in the non-aqueous electrolyte described below is attached to the scaly graphite particles, but the scaly graphite particles ( A) preferably has the following characteristics.

(A) _Interplanar spacing of scale-like graphite particles (A) (d ₀₀₂ )
The interplanar spacing (d ₀₀₂ ) of the 002 plane by the X-ray wide angle diffraction method is usually 0.337 nm or less, preferably 0.336 nm or less. If the d value is too large, the crystallinity decreases and the discharge capacity tends to decrease. On the other hand, the lower limit of 0.3356 nm is a theoretical value of graphite.
The crystallite size (Lc) of the scaly graphite 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.

(B) Volume-based average particle diameter d50 of scaly graphite particles (A)
The volume-based average particle diameter d50 (hereinafter also referred to as average particle diameter d50) of the scaly graphite particles (A) is usually 2 μm or more, preferably 3 μm or more, more preferably 4 μm or more, and usually 30 μm or less. Preferably it is 15 micrometers or less, More preferably, it is 10 micrometers or less, More preferably, it is 8 micrometers or less. Further, the average particle diameter d50 of the scaly graphite particles (A) usually tends to be about the same as or larger than the average particle diameter d50 of the scaly graphite particles before being combined with the polymer. 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. On the other hand, if the average particle size is too large, the total number of particles decreases, and the proportion of carbonaceous particles (B) existing between the particles decreases, which tends to reduce the effect of suppressing conduction path breakage and decrease cycle characteristics. .

  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.

(C) Aspect ratio of scaly graphite particles (A) The aspect ratio of the scaly graphite particles (A) is usually 5 or more, preferably 6 or more, more preferably 7 or more, usually 50 or less, preferably 25 or less. , More preferably 20 or less, particularly preferably 10 or less. When the aspect ratio is too small, there is a tendency that the effect of suppressing the conduction path breakage is reduced and the cycle characteristics are lowered. If the aspect ratio is too large, the particles tend to be aligned in the direction parallel to the current collector when used as an electrode, so that there are not enough continuous voids in the thickness direction of the electrode, and Li ion migration in the thickness direction. Tend to decrease, and the rapid charge / discharge characteristics tend to decrease. Further, the aspect ratio of the scaly graphite particles (A) usually tends to be the same as or smaller than the aspect ratio of the scaly graphite particles before being combined with the polymer.
The aspect ratio can be determined by the measurement method described in the examples described later.

(D) Circularity of scaly graphite particles (A) The circularity of the scaly graphite particles (A) is usually 0.1 or more, preferably 0.4 or more, more preferably 0.7 or more. The circularity is usually 0.87 or less, preferably 0.85 or less, more preferably 0.83 or less.
If the circularity is too small, particles tend to be arranged in parallel with the current collector when used as an electrode, so that there is not enough continuous void in the thickness direction of the electrode, and Li 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, and 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 value of the circularity, a value measured by a measuring method described in Examples described later is used.
(E) Surface functional group amount of scaly graphite particles (A) The scaly graphite particles (A) usually have a surface functional group amount O / C value represented by the following formula (2) of 2% or more. , Preferably 3%, more preferably 4%, while usually 30% or less, preferably 20% or less, more preferably 15% or less.

  If this surface functional group amount O / C value is too small, it indicates that the polymer is unevenly distributed and the coating is insufficient, and the effect of preventing contact with the electrolyte is poor, and the initial efficiency and cycle characteristics tend to decrease and the gas amount tends to increase. is there. On the other hand, if the surface functional group amount O / C value is too large, it indicates an excessive coating state of the polymer, which causes an increase in resistance and tends to deteriorate the input / output characteristics.

Formula (2)
O / C value (%) = {O atom concentration obtained based on the peak area of the O1s spectrum in the X-ray photoelectron spectroscopy (XPS) analysis / C atom obtained based on the peak area of the C1s spectrum in the XPS analysis Density} × 100
The surface functional group amount O / C value in the present invention can be measured using X-ray photoelectron spectroscopy (XPS) as follows.

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

(F) Average particle diameter (d10) of scaly graphite particles (A)
Particle size d1 corresponding to a cumulative 10% from the small particle side on a volume basis of the scaly graphite particles (A)
0 is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, further preferably 1.5 μm or more, and usually 15 μm or less, preferably 10 μm or less, more preferably 5 μm or less, Preferably it is 3 micrometers or less. Further, the average particle diameter d10 of the scaly graphite particles (A) usually tends to be about the same as or larger than the average particle diameter d10 of the scaly particles before being combined with the polymer.

If the average particle diameter d10 is too small, the tendency of the particles to agglomerate becomes strong, which may cause inconveniences such as an increase in slurry viscosity, a decrease in electrode strength and a decrease in initial charge / discharge efficiency in the nonaqueous secondary battery. If the average particle diameter d10 is too large, the cycle characteristics may be deteriorated due to the deterioration of the high current density charge / discharge characteristics, the low temperature input / output characteristics, and the effect of suppressing the conduction path breakage.
The average particle diameter d10 is defined as a value in which the volume frequency (%) of particles is 10% in total from a particle diameter distribution in a particle size distribution obtained by the same method as that for measuring the average particle diameter d50.

(G) Average particle diameter d90 of scaly graphite particles (A)
The average particle diameter d90 of the scaly graphite particles (A) obtained by the laser diffraction / scattering method (particle diameter which is 90% cumulative from the small particle side on a volume basis) is usually 3 μm or more, preferably 5 μm or more, more preferably. Is 8 μm or more, and is usually 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less, and still more preferably 15 μm or less. Further, the average particle diameter d90 of the scaly graphite particles (A) usually tends to be the same as or larger than the average particle diameter d90 of the scaly graphite particles before being combined with the polymer.

Generally, the large particle size graphite has a large average particle size d90 and tends to be easily drawn during the application of the slurry containing the scaly graphite particles (A) of the present invention. It is also important to prevent the average particle diameter d90 of the graphite particles from becoming as large as possible in order to exhibit the effects of the present invention.
If the average particle size d90 is too small, the electrode strength and initial charge / discharge efficiency of the non-aqueous secondary battery may be reduced. If the average particle diameter d90 is too large, process inconveniences such as striping during slurry application may occur. In some cases, the high current density charge / discharge characteristics and the low temperature input / output characteristics may be deteriorated.
The average particle diameter d90 is defined as a value in which the volume frequency% of the particles is 90% integrated from the small particle diameter in the particle size distribution obtained by the same method as that used for measuring the average particle diameter d50.

(H) BET specific surface area (SA) of scaly graphite particles (A)
The specific surface area of the scaly graphite particles (A) measured by the BET method is usually 1 m ² / g or more, preferably 2 m ² / g or more, more preferably 3 m ² / g or more. Moreover, it is 20 m < ² > / g or less normally, Preferably it is 15 m < ² > / g or less, More preferably, it is 12 m < ² > / g or less, More preferably, it is 11 m < ² > / g or less, Most preferably, it is 8 m < ² > / g or less. Further, the specific surface area of the scaly graphite particles (A) usually tends to be smaller than the specific surface area of the scaly graphite particles before being combined with the polymer.

If the specific surface area is too small, there are few sites where Li enters and exits, and the high-speed charge / discharge characteristics and output characteristics are inferior. On the other hand, if the specific surface area is too large, the activity of the active material with respect to the electrolyte becomes excessive and the initial irreversible capacity is low. Since it becomes large, there exists a tendency which cannot manufacture a high capacity battery.
In addition, the measuring method of a BET specific surface area is measured by a BET 1 point method by a nitrogen gas adsorption circulation method using a specific surface area measuring device.

The tap density of the tap density scaly graphite particles (A) of (i) the scaly graphite particles (A) is usually 0.05 g / cm ³ or more, 0.1 g / cm ³ or more preferably, 0.2 g / More preferably, it is cm ³ or more. Moreover, normally 1.5 g / cm < ³ > or less and 1.0 g / cm < ³ > or less are preferable, and 0.6 g / cm < ³ > or less is more preferable. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the cycle characteristics may be deteriorated due to a reduction in the effect of suppressing the conduction path breakage.

Further, the tap density of the scaly graphite particles (A) usually tends to be the same as or smaller than the tap density of the scaly graphite particles before being combined with the polymer.
In the present invention, the tap density is measured by using a powder density meter and passing a sample (flaky graphite particles (A)) through a sieve having a diameter of 1.6 cm and a volume capacity of 20 cm ³ through a sieve having an opening of 300 μm. After dropping and filling the cell fully, tap with a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume and the weight of the sample is defined as the tap density.

(J) Pore volume in the range of pore diameter of 10 nm to 100,000 nm by the mercury intrusion method of the flaky graphite particles (A) Pore in the range of pore diameter of 10 nm to 100000 nm by the mercury intrusion method of the flaky graphite particles (A) The volume is usually 1 mL / g or less, preferably 0.9 mL / g or less, more preferably 0.8 mL / g or less, usually 0.05 mL / g or more, preferably 0.1 mL / g or more, More preferably, it is 0.15 mL / g or more. If the total pore volume is below the above range, the number of voids that can be infiltrated by the non-aqueous electrolyte solution tends to be small, and when lithium ions are rapidly charged and discharged, lithium ions are not inserted and released in time, and lithium metal is deposited accordingly. Characteristics tend to deteriorate. On the other hand, if the above range is exceeded, the strength of the electrode plate is reduced due to the binder being easily absorbed into the gap during electrode plate production, and the initial efficiency is reduced due to the increase of side reactions due to increased contact with the electrolyte. Tend.

(K) Fine pore volume in the range of pore diameters from 80 nm to 900 nm by the mercury intrusion method of the flaky graphite particles (A) The fine pore volume in the range of the pore diameters from 80 nm to 900 nm of the flaky graphite particles (A) is mercury. It is a value measured using a press-fitting method (mercury porosimetry), and is usually 0.08 mL / g or more, preferably 0.1 mL / g or more, more preferably 0.15 mL / g or more, and further preferably 0.3 mL / g. g or more. Moreover, it is 1 mL / g or less normally, Preferably it is 0.8 mL / g or less, More preferably, it is 0.5 mL / g or less.

  When the fine pore volume in the range of the pore diameter of 80 nm to 900 nm is less than the above range, the electrolyte solution does not move sufficiently smoothly during charging / discharging of the non-aqueous secondary battery, and lithium ions are not charged when rapidly charging / discharging. There is a tendency that the insertion / desorption is not in time, and lithium metal is deposited accordingly, and the cycle characteristics are deteriorated. On the other hand, if it exceeds the above range, the binder is easily absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength and initial efficiency tend to be reduced.

As the mercury porosimetry apparatus, a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) can be used. A sample (scale-like graphite particles (A)) is weighed to a value of about 0.2 g, sealed in a powder cell, and deaerated at room temperature under vacuum (50 μmHg or less) for 10 minutes for pretreatment. To implement.
Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced into the cell, the pressure is increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure is reduced to 25 psia (about 170 kPa).

The number of steps at the time of pressure increase is 80 points or more, and the mercury intrusion amount is measured after an equilibration time of 10 seconds in each step. The pore distribution is calculated from the mercury intrusion curve thus obtained using the Washburn equation.
Note that the surface tension (γ) of mercury is calculated as 485 dyne / cm and the contact angle (ψ) is 140 °. The average pore diameter is defined as the pore diameter when the cumulative pore volume is 50%.

(L) Fine pore volume in a pore diameter range of 1 nm to 30 nm by the nitrogen adsorption method of the flaky graphite particles (A) The fine pore volume in the pore diameter range of 1 nm to 30 nm of the flaky graphite particles (A) is nitrogen It is a value measured using the BJH method analysis of the adsorption method, usually 0.001 mL / g or more, preferably 0.002 mL / g or more, usually 0.1 mL / g or less, preferably 0.03 mL / g or less, and more Preferably it is 0.01 mL / g or less, More preferably, it is 0.008 mL / g or less.

  If the fine pore volume in the range of pore diameters of 1 nm to 30 nm is less than the above range, the input / output characteristics tend to deteriorate due to the inability to insert and desorb lithium ions in time when the nonaqueous secondary battery is charged and discharged. Further, along with this, lithium metal precipitates and the cycle characteristics tend to deteriorate. On the other hand, when the above range is exceeded, there is a tendency that the side reaction with the electrolytic solution increases and the initial efficiency is lowered. In addition, the binder is easily absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength and initial efficiency tend to decrease.

As the nitrogen adsorption method measuring apparatus, Autosorb (Canter Chrome) can be used. The sample is sealed in a powder cell, pretreated for 2 hours at 350 ° C. under vacuum (1.3 Pa or less), and then an adsorption isotherm (adsorbed gas: nitrogen) is measured at a liquid nitrogen temperature.
Using the obtained adsorption isotherm, the fine pore distribution is obtained by BJH analysis, and the fine pore volume within the pore diameter range of 1 nm to 30 nm is calculated therefrom.

<Poorly soluble polymer in non-aqueous electrolyte>
The polymer that is hardly soluble in the non-aqueous electrolyte solution that is a constituent component of the scaly graphite particles (A) of the present invention will be described.
The polymer that is hardly soluble in the non-aqueous electrolyte solution may be any polymer that is hardly soluble in the non-aqueous electrolyte solution and can be combined with the scaly graphite particles. It is a polymer having. In addition, a polymer having a π-conjugated structure is preferable. A polymer having a π-conjugated structure is considered to be effectively coated because the π-conjugated structure of the polymer is attracted by the basal surface of the scaly graphite particles and the π-π interaction. In this case, the reaction between the basal surface of the scaly graphite particles and the non-aqueous electrolyte is suppressed, and the generation of gas is effectively suppressed.

  Among polymers, a polymer having an ionic group is preferable, and the ionic group referred to in the present invention is a group capable of generating an anion or a cation in water. Specific examples include carboxylic acid groups, sulfonic acid groups, phosphoric acid groups, phosphonic acid groups, and salts thereof. Examples of the salt include lithium salt, sodium salt, potassium salt and the like. Among these, from the viewpoint of the initial irreversible capacity in the case of a lithium ion secondary battery, a sulfonic acid group and a lithium salt or sodium salt thereof are preferable.

The compound having the π-conjugated structure is an unsaturated cyclic compound having a structure in which atoms having π electrons are arranged in a ring, satisfying the Hückel rule, and the π electrons are delocalized on the ring. Has a planar structure.
Examples of the compound having such a π-conjugated structure include compounds having an aromatic ring. Specifically, furan, pyrrole, imidazole, thiophene, phosphole, pyrazole, oxazole, isoxazole, thiazole, which are monocyclic five-membered rings; benzene, pyridine, pyrazine, pyrimidine, pyridazine, which are monocyclic six-membered rings, Triazine; bicyclic 5-membered ring + 6-membered ring benzofuran, isobenzofuran, indole, isoindole, benzothiophene, benzophosphole, benzimidazole, purine, indazole, benzoxazole, benzoisoxazole, benzothiazole; bicyclic Examples include 6-membered ring + 6-membered ring naphthalene, quinoline, isoquinoline, quinoxaline, quinazoline, cinnoline; rings having a skeleton such as polycyclic anthracene and pyrene.

Among these, benzene or naphthalene is preferable from the viewpoint of suppressing gas generation when used in a negative electrode for a non-aqueous secondary battery.
The electrical conductivity of the polymer is usually 0.1 S / cm or less, preferably 0.01 S / cm or less, more preferably 0.001 S / cm or less at 25 ° C. Moreover, it is usually larger than 0 S / cm. If the electrical conductivity is too high, a side reaction of the electrolytic solution may occur, leading to a decrease in initial efficiency, an increase in gas generation, and a decrease in cycle characteristics.

For example, the electrical conductivity is obtained by film formation on a glass substrate by spin coater film formation or drop cast film formation, and the film thickness is multiplied by the surface resistance measured by the four-terminal method. It can be calculated from the reciprocal of the obtained value.
The film thickness can be measured with a KLA step, surface roughness and fine shape measuring device, Tencor α-step type, and the surface resistance value measured by the four-terminal method can be measured with Mitsubishi Chemical Analytech's Loresta GP MCP-T610 type.

  The weight average molecular weight of the polymer is not particularly limited, but is usually 500 or more, preferably 1000 or more, more preferably 2000 or more, and further preferably 2500 or more. On the other hand, the weight average molecular weight is usually 1,000,000 or less, preferably 500,000 or less, more preferably 300,000 or less, and still more preferably 200,000 or less. In the present specification, the weight average molecular weight is a weight average molecular weight in terms of standard polystyrene measured by GPC in the solvent THF, or a weight average molecular weight in terms of standard polyethylene glycol measured by GPC in which the solvent is aqueous, DMF or DMSO. .

Examples of the monomer serving as the structural unit constituting the polymer include a monomer having an ionic group and a monomer having an aromatic ring. Moreover, the monomer which has both an ionic group and an aromatic ring may be sufficient.
In this case, the polymer may be a copolymer of a monomer having an ionic group and not having an aromatic ring, and a monomer having an aromatic ring and not having an ionic group. And a monomer polymer having both aromatic rings. Further, it may be a mixture of a monomer polymer having an ionic group and a monomer polymer having an aromatic ring.

Among these, from the viewpoint of the stability of the polymer coated on the scaly graphite particles (A) in the electrolytic solution, the polymer is preferably a polymer of a monomer having both an ionic group and an aromatic ring.
The ionic group possessed by the monomer is the same as the ionic group described above, and among them, a carboxylic acid group, a sulfonic acid group or a salt thereof is preferable from the viewpoint of stability in the battery and suppression of resistance increase. .

Examples of monomers having an ionic group and an aromatic ring include styrene sulfonic acid, lithium styrene sulfonate, sodium styrene sulfonate, aniline, aniline sulfonic acid, aniline sulfonic acid salt, vinyl benzoate and vinyl benzoate salt. Etc.
Examples of monomers having an ionic group and no aromatic ring include vinyl sulfonic acid, lithium vinyl sulfonate, sodium vinyl sulfonate, acrylic acid, sodium acrylate, lithium acrylate, methacrylic acid, sodium methacrylate And lithium methacrylate.

Examples of the monomer having an aromatic ring and not having an ionic group include styrene, benzyl acrylate, benzyl methacrylate and the like.
Specific examples of the polymer containing a structural unit derived from such a monomer include a styrene-vinyl sulfonic acid copolymer, a styrene-vinyl sulfonic acid sodium copolymer, a styrene-vinyl sulfonic acid lithium copolymer, and polystyrene. Sulfonic acid, lithium polystyrene sulfonate, sodium polystyrene sulfonate, polyaniline sulfonic acid, lithium polyaniline sulfonate, sodium polyaniline sulfonate, styrene-styrene sulfonate copolymer, styrene-lithium sulfonate lithium copolymer, styrene-styrene sulfone Acid sodium copolymer, polyvinyl benzoic acid, polyvinyl lithium benzoate, sodium polyvinyl benzoate, styrene-vinyl benzoic acid copolymer, styrene-vinyl lithium benzoate copolymer, Len - Sodium copolymer vinyl benzoate, and the like.

  From the viewpoint of effectively suppressing the generation of gas, polystyrene sulfonic acid, polystyrene lithium sulfonate, sodium polystyrene sulfonate, styrene-styrene sulfonic acid copolymer, styrene-lithium sulfonic acid copolymer, styrene-styrene sulfonic acid Sodium copolymers, polyvinyl benzoic acid, lithium polyvinyl benzoate, sodium polyvinyl benzoate, styrene-vinyl benzoic acid copolymers, styrene-vinyl lithium benzoate copolymers and styrene-sodium vinyl vinyl copolymers are preferred.

Furthermore, polystyrene sulfonate, lithium polystyrene sulfonate, sodium polystyrene sulfonate, styrene-styrene sulfonate lithium copolymer and styrene-sodium styrene sulfonate copolymer are more preferable.
Among them, lithium polystyrene sulfonate, sodium polystyrene sulfonate, styrene-lithium sulfonate lithium copolymer, and styrene-sodium styrene sulfonate copolymer are particularly preferable because of their high adsorptivity to the active material surface, particularly the graphite basal surface. .
As the polymers described above, commercially available polymers may be used, or they may be synthesized by a known method. In the present invention, one kind may be used alone, or two or more kinds may be used in combination.

<Scaly graphite particles before polymer composite>
As the scaly graphite particles before the polymer composite, which is the raw material of the scaly graphite particles (A) of the present invention (in this specification, simply referred to as scaly graphite particles), either natural graphite or artificial graphite is used. May be used. As graphite, those with few impurities are preferable, and they are used after being subjected to various purification treatments as necessary.

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

Among these natural graphites, soil graphite generally has a small particle size and low purity. On the other hand, scaly graphite and scaly graphite have advantages such as a high degree of graphitization and a low amount of impurities, and therefore can be preferably used in the present invention.
Examples of the artificial graphite include graphite particles such as coke, needle coke, and high-density carbon material, which are produced by heat-treating a pitch raw material.

Specific examples of artificial graphite include coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, Organic substances such as polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin are usually used at a temperature in the range of 2500 ° C. to 3200 ° C. Examples thereof include those fired and graphitized.
The scaly graphite particles used in the present invention are not particularly limited as long as they are graphitized scaly carbon particles, but as described above, natural graphite, artificial graphite, coke powder, needle coke powder, and resin A graphitized powder such as the like can be used. Of these, scaly natural graphite is preferred from the standpoints of high discharge capacity and ease of production.

(Physical properties of scaly graphite particles)
It is preferable that the scaly graphite particles in the present invention satisfy any one or more of the following physical properties. In the present invention, one type of scaly graphite particles exhibiting such physical properties may be used alone, or two or more types may be used in any combination.

(A) Volume-based average particle diameter d50 of scaly graphite particles
The average particle size d50 of the scaly graphite particles is usually 2 μm or more, preferably 3 μm or more, more preferably 4 μm or more, and usually 30 μm or less, preferably 15 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less. It is. If the average particle diameter d50 is too small, the specific surface area increases, so that decomposition with the initial electrolytic solution increases and initial efficiency tends to decrease. On the other hand, if the average particle size is too large, the total number of particles decreases, and the proportion of carbonaceous particles (B) existing between the particles decreases, which tends to reduce the effect of suppressing conduction path breakage and decrease cycle characteristics. .

(B) Average particle size of flaky graphite particles (d10)
The particle size d10 corresponding to 10% cumulative from the small particle side on the volume basis of the scaly graphite particles is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1 μm or more, and further preferably 1.5 μm or more. Moreover, it is 15 micrometers or less normally, Preferably it is 10 micrometers or less, More preferably, it is 5 micrometers or less, More preferably, it is 3 micrometers or less.

  If the average particle diameter d10 is too small, the tendency of the particles to agglomerate becomes strong, which may cause inconveniences such as an increase in slurry viscosity, a decrease in electrode strength and a decrease in initial charge / discharge efficiency in the nonaqueous secondary battery. If the average particle diameter d10 is too large, the cycle characteristics may be deteriorated due to the deterioration of the high current density charge / discharge characteristics, the low temperature input / output characteristics, and the effect of suppressing the conduction path breakage.

(C) Average particle diameter d90 of scaly graphite particles
The average particle diameter d90 of the scaly graphite particles determined by the laser diffraction / scattering method (particle diameter that is 90% cumulative from the small particle side on a volume basis) is usually 3 μm or more, preferably 5 μm or more, more preferably 8 μm or more. Also, it is usually 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less, and still more preferably 15 μm or less.

In general, large particle size graphite has a large average particle size d90 and tends to be easily drawn when a slurry containing the scaly graphite particles of the present invention is applied. In order to exhibit the effect of the present invention, it is effective to prevent the average particle diameter d90 of the graphite particles from becoming as large as possible.
If the average particle size d90 is too small, the electrode strength and initial charge / discharge efficiency of the non-aqueous secondary battery may be reduced. If the average particle diameter d90 is too large, process inconveniences such as striping during slurry application may occur. There is a tendency for the high current density charge / discharge characteristics to decrease and the low temperature input / output characteristics to decrease.

(D) BET specific surface area (SA) of scaly graphite particles
The specific surface area of the flaky graphite particles measured by the BET method is usually 3 m ² / g or more, preferably 4 m ² / g or more. Moreover, it is 30 m < ² > / g or less normally, Preferably it is 25 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 10 m < ² > / g or less.
If the specific surface area is too small, there are few sites where Li enters and exits, and the high-speed charge / discharge characteristics and output characteristics are inferior. On the other hand, if the specific surface area is too large, the activity of the active material with respect to the electrolyte becomes excessive and the initial irreversible capacity is low. Since it becomes large, there exists a tendency which cannot manufacture a high capacity battery.

(E) a tap density of tap density scaly graphite particles of scaly graphite particles is usually 0.05 g / cm ³ or more, 0.1 g / cm ³ or more preferably, 0.2 g / cm ³ or more and more preferably . Moreover, normally 1.5 g / cm < ³ > or less and 1.0 g / cm < ³ > or less are preferable, and 0.6 g / cm < ³ > or less is more preferable. If the tap density is too low, the high-speed charge / discharge characteristics are inferior. If the tap density is too high, the cycle characteristics may be deteriorated due to a reduction in the effect of suppressing the conduction path breakage.

(F) Aspect ratio of scaly graphite particles The aspect ratio of the scaly graphite particles is usually 5 or more, preferably 6 or more, more preferably 7 or more, usually 50 or less, preferably 25 or less, more preferably 20 or less. Particularly preferably, it is 10 or less. When the aspect ratio is too small, there is a tendency that the effect of suppressing the conduction path breakage is reduced and the cycle characteristics are lowered. If the aspect ratio is too large, the particles tend to be aligned in the direction parallel to the current collector when used as an electrode, so that there are not enough continuous voids in the thickness direction of the electrode, and Li ion migration in the thickness direction. Tend to decrease, and the rapid charge / discharge characteristics tend to decrease.

(G) Circularity of scaly graphite particles The circularity of the scaly graphite particles is usually 0.1 or more, preferably 0.4 or more, more preferably 0.7 or more. The circularity is usually 0.87 or less, preferably 0.85 or less, more preferably 0.83 or less.
If the circularity is too small, particles tend to be arranged in parallel with the current collector when used as an electrode, so that there is not enough continuous void in the thickness direction of the electrode, and Li 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 spectrum (Raman) spectrum of flaky graphite particles The Raman R value of the flaky graphite particles is usually 0.05 or more, preferably 0.1 or more, more preferably 0.2 or more, usually 0.7 or less, preferably 0.6 or less, more preferably 0.5 or less. 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) Pore volume in the range of 10 nm to 100,000 nm by the mercury intrusion method of the flaky graphite particles The pore volume in the range of 10 nm to 100,000 nm by the mercury intrusion method of the flaky graphite particles is usually 1.2 mL / g or less. 1 mL / g or less, more preferably 0.9 mL / g or less, usually 0.1 mL / g or more, preferably 0.15 mL / g or more, more preferably 0.2 mL / g or more. is there. If the total pore volume is below the above range, the number of voids that can be infiltrated by the non-aqueous electrolyte solution tends to be small, and when lithium ions are rapidly charged and discharged, lithium ions are not inserted and released in time, and lithium metal is deposited accordingly. Characteristics tend to deteriorate. On the other hand, when the above range is exceeded, the binder is easily absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength tends to be lowered.

(J) Fine pore volume in the range of 80 nm to 900 nm pore diameter by the mercury intrusion method of flaky graphite particles The fine pore volume in the range of 80 nm to 900 nm pore size of the flaky graphite particles is determined by the mercury intrusion method (
Mercury porosimetry), usually 0.08 mL / g or more, preferably 0.1 mL / g or more, more preferably 0.15 mL / g or more, still more preferably 0.3 mL / g or more. is there. Moreover, it is 1 mL / g or less normally, Preferably it is 0.8 mL / g or less, More preferably, it is 0.5 mL / g or less.

  When the fine pore volume in the range of the pore diameter of 80 nm to 900 nm is less than the above range, the electrolyte solution does not move sufficiently smoothly during charging / discharging of the non-aqueous secondary battery, and lithium ions are not charged when rapidly charging / discharging. There is a tendency that the insertion / desorption is not in time, and lithium metal is deposited accordingly, and the cycle characteristics are deteriorated. On the other hand, if it exceeds the above range, the binder is easily absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength and initial efficiency tend to be reduced.

(J) Fine pore volume in the range of pore diameters of 1 nm to 30 nm by the nitrogen adsorption method of flaky graphite particles The fine pore volume in the range of pore diameters of 1 nm to 30 nm of the flaky graphite particles is analyzed by the BJH method of the nitrogen adsorption method. Is usually 0.001 mL / g or more, preferably 0.002 mL / g or more, usually preferably 0.1 mL / g or less, preferably 0.03 mL / g or less, more preferably 0.001 mL / g or more. 01 mL / g or less, more preferably 0.008 mL / g or less.

  If the fine pore volume in the range of pore diameters of 1 nm to 30 nm is less than the above range, the input / output characteristics tend to deteriorate due to the inability to insert and desorb lithium ions in time when the nonaqueous secondary battery is charged and discharged. Further, along with this, lithium metal precipitates and the cycle characteristics tend to deteriorate. On the other hand, when the above range is exceeded, there is a tendency that the side reaction with the electrolytic solution increases and the initial efficiency is lowered. In addition, the binder is easily absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength and initial efficiency tend to decrease.

(K) X-ray parameter of scaly graphite particles The interplanar spacing (d ₀₀₂ ) of the 002 plane according to the X-ray wide angle diffraction method is usually 0.337 nm or less, preferably 0.336 nm or less. If the d value is too large, the crystallinity decreases and the discharge capacity tends to decrease. On the other hand, the lower limit of 0.3356 nm is a theoretical value of graphite.
Further, the crystallite size (Lc) of the scaly graphite particles before the polymer is combined 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.

(L) Surface functional group amount of scaly graphite particles The scaly graphite particles have a surface functional group amount O / C value represented by the above formula (1) of usually 1% or more, preferably 1.5. %, More preferably 2%, still more preferably 2.5% or less, while usually 10% or less, preferably 5% or less, more preferably 4% or less.
If the surface functional group amount O / C value is too small, the interaction with the poorly soluble polymer becomes weak and the polymer tends to peel off, which may lead to a decrease in initial efficiency, an increase in gas, and a decrease in cycle characteristics. . In addition, the peel strength of the electrode may decrease, leading to deterioration of processability. On the other hand, if the surface functional group amount O / C value is too large, it becomes difficult to adjust the O / C value, and there is a tendency that the manufacturing process needs to be performed for a long time or the number of steps needs to be increased. There is a risk of lowering the property and increasing the cost.

[Method for producing scale-like graphite particles (A)]
The production method of the scaly graphite particles (A) of the present invention is not particularly limited as long as it is at least a scaly graphite particle in which a poorly soluble polymer is attached to a nonaqueous electrolytic solution. A method is mentioned.

<Method (i)>
For example, a step of dissolving the polymer in an organic solvent or water, or a mixed solvent of organic solvent / water, mixing the solution with scaly graphite particles, and then drying by heating or / and reducing pressure can be mentioned.
The solvent to be used is not particularly limited as long as the polymer dissolves, but preferably water, ethyl methyl ketone, toluene, acetone, methyl isobutyl ketone, ethanol, methanol and the like can be mentioned. Among these, water, ethyl methyl ketone, acetone, methyl isobutyl ketone, ethanol, and methanol are more preferable because of cost and ease of drying.

The solution concentration of the scaly graphite particles and the polymer is usually 70% by mass or less, preferably 60% by mass or less, and more preferably 50% by mass or less. If it is out of this range, the polymer solution does not sufficiently penetrate into the pores of the scaly graphite particles, and the contained polymer is present non-uniformly, and the effect tends to be difficult to be obtained. About the said drying (heating) temperature, 300 degrees C or less and 250 degrees C or less are preferable normally. Moreover, 50 degreeC or more and 100 degreeC or more are preferable normally. Above this temperature, the polymer may be partially decomposed, or the interaction between the scaly graphite particles and the polymer will be weak, and the effects of reducing the specific surface area, improving the cycle characteristics, shortening the charging rate, etc. tend to be reduced. . On the other hand, the battery performance due to residual solvent tends to decrease because the solvent does not dry at a sufficient rate below this temperature.
In addition, when drying the solution of scaly graphite particles and polymer under reduced pressure, the pressure is usually 0 MPa or less and −0.2 MPa or more in gauge pressure notation. If it is this range, it can dry comparatively efficiently. The pressure is preferably −0.03 MPa or less, and preferably −0.15 MPa or more.

<Method (ii)>
Further, as another method (ii) for producing the scale-like graphite particles (A) to which the polymer is attached, for example, by utilizing that the polymer has adsorptivity to the surface of the scale-like graphite, There is also a step in which the flaky graphite is put into the solution and stirred, the excess polymer solution is removed by filtration, and then the flaky graphite and the polymer are combined by drying. Furthermore, it is preferable to heat-treat after drying.
As a method for measuring the solution concentration of the polymer, for example, in the case of an aqueous solution, a method of measuring with a moisture meter such as Sartorius moisture meter MA45, and in the case of an organic solvent solution, the solution is placed in a container such as an aluminum cup and vacuum dried For example, a method of calculating the original concentration based on a weight difference before and after the operation of removing the solvent in the machine may be used.

<Method (iii)>
Further, a method using a mechanofusion system (manufactured by Hosokawa Micron) may be used.
By performing mechanochemical treatment on the powder obtained by mixing the flaky graphite particles and the polymer powder, the step of combining the polymer particles on the surface of the flaky graphite particles can be raised. Preferable apparatuses used for mechanochemical treatment include, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), a mechanofusion system (manufactured by Hosokawa Micron Corporation), and the like. Of these, the mechanofusion system is preferred.
In the methods (i) to (iii), the method (i) is more preferable in terms of simplicity.

(Amount of polymer attached to scaly graphite particles (A))
The amount of the polymer attached to the flaky graphite particles (A) is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.2% by mass with respect to the flaky graphite particles. As mentioned above, More preferably, it is 0.3 mass% or more. Moreover, it is 10 mass% or less normally, 5 mass% or less is preferable, 1 mass% or less is more preferable, and 0.6 mass% or less is still more preferable. If the amount of the poorly soluble polymer added to the non-aqueous electrolyte is too large, the charge / discharge capacity and the charge transfer resistance will tend to decrease, leading to a decrease in input / output characteristics. If the amount of adhesion is too small, the side reaction reaction suppressing effect of the electrolytic solution is poor, and the initial charge / discharge efficiency tends to decrease and the cycle characteristics tend to decrease.

The amount of polymer attached to the scaly graphite particles (A) is, in principle, the amount of polymer added during production when the solution containing the polymer is dried during production. When the polymer not attached to (A) is removed, it can be calculated from the weight loss in the TG-DTA analysis of the obtained carbon material or the amount of polymer contained in the filtrate.
The above confirmation method may be performed at the time when the scaly graphite particles (A) are produced, or may be detected from a product produced as a negative electrode or a battery.

[Carbonaceous particles (B)]
The carbonaceous particles (B) of the present invention are carbonaceous particles having an aspect ratio of 1 or more and 4 or less. Among these, 1.5 or more is preferable, 1.6 or more is more preferable, and 1.7 or more is particularly preferable. On the other hand, 3 or less is preferable, 2.5 or less is more preferable, and 2 or less is particularly preferable.
If the aspect ratio is too small, the effect of suppressing the conduction path breakage is reduced and the cycle characteristics are lowered. If the aspect ratio is too large, the particles tend to be aligned in the direction parallel to the current collector when used as an electrode, so that there are not enough continuous voids in the thickness direction of the electrode, and Li ion migration in the thickness direction. Lowers the charge and discharge characteristics.

(Characteristics of carbonaceous particles (B))
Moreover, it is preferable that the carbonaceous particle (B) of the present invention has the following physical properties.

(A) X-ray parameters The interplanar spacing (d ₀₀₂ ) of the carbonaceous particles (B) by the X-ray wide angle diffraction method is usually 0.337 nm or less, preferably 0.336 nm or less. If the d002 value is too large, it indicates that the crystallinity is low, and the initial irreversible capacity may increase when a non-aqueous secondary battery is used. On the other hand, since the theoretical value of the surface spacing of the 002 plane of graphite is 0.3356 nm, the d value is usually 0.3356 nm or more.
The crystallite size (Lc) of the carbonaceous particles (B) is usually in the range of 30 nm or more, preferably 50 nm or more, more preferably 100 nm or more. Below this range, the crystallinity decreases and the discharge capacity of the battery tends to decrease. The lower limit of Lc is the theoretical value of graphite.

(B) Volume-based average particle diameter (d50)
The average particle diameter (median diameter) of the carbonaceous particles (B) is usually 50 μm or less, preferably 40 μm or less, more preferably 30 μm or less, still more preferably 25 μm or less, usually 1 μm or more, preferably 4 μm or more, more preferably. Is 10 μm or more. If the average particle diameter d50 is too small, the specific surface area increases, so that the decomposition of the electrolyte increases, and the initial efficiency tends to decrease. If the average particle diameter d50 is too large, the rapid charge / discharge characteristics tend to decrease. .

(C) Average particle diameter d10
The particle size (d10) corresponding to a cumulative 10% from the small particle side of the particle size measured on a volume basis of the carbonaceous particles (B) is usually 1 μm or more, preferably 5 μm or more, more preferably 8 μm or more. Usually, it is 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less.
If d10 is too small, the tendency of the particles to agglomerate tends to increase, resulting in process inconveniences such as an increase in slurry viscosity, a decrease in electrode strength in a nonaqueous secondary battery, and a decrease in initial charge / discharge efficiency. If d10 is too large, high current density charge / discharge characteristics and low temperature input / output characteristics tend to deteriorate.

(D) Average particle diameter d90
The particle size (d90) corresponding to 90% cumulative from the small particle side of the particle size measured on a volume basis of the carbonaceous particles (B) is usually 5 μm or more, preferably 10 μm or more, more preferably 20 μm or more. Usually, it is 100 μm or less, preferably 50 μm or less, more preferably 30 μm or less.
If d90 is too small, the electrode strength and initial charge / discharge efficiency of the non-aqueous secondary battery may be reduced. If it is too large, process inconveniences such as striping during the application of slurry will occur, and high current density charge may occur. In some cases, the discharge characteristics and the low-temperature input / output characteristics may deteriorate.

(E) Specific surface area by BET method The specific surface area of the carbonaceous particles (B) by the BET method is usually 0.5 m ² / g or more, preferably 1 m ² / g or more, more preferably 2 m ² / g or more, more preferably It is 3 m ² / g or more. Moreover, it is 15 m < ² > / g or less normally, Preferably it is 10 m < ² > / g or less, More preferably, it is 8 m < ² > / g or less, More preferably, it is 7 m < ² > / g or less, Most preferably, it is 6 m < ² > / g or less. If the specific surface area is too large, the reactivity between the portion exposed to the electrolyte and the electrolyte when used as the negative electrode active material is increased, which tends to cause a decrease in initial efficiency and an increase in the amount of gas generated, making it difficult to obtain a preferable battery. Tend. When the specific surface area is too small, there are few sites where Li enters and exits, and high-speed charge / discharge characteristics and output characteristics tend to be inferior.

(F) Tap density The tap density of the carbonaceous particles (B) is preferably 0.8 g / cm ³ or more, more preferably 0.9 g / cm ³ or more, and still more preferably 0.95 g / cm ³ or more. Further, usually 1.8 g / cm ³ or less and 1.5 g / cm ³ or less are preferable, and 1.3 g / cm ³ or less is more preferable. The tap density is 0.8 g / cm ³ or more. (B) is one of the indicators showing that it is spherical. The fact that the tap density is smaller than 0.8 g / cm ³ is one of indices indicating that the spherical carbon material as the raw material of the carbonaceous particles (B) is not sufficient spherical particles. If the tap density is less than 0.8 g / cm ³ , sufficient continuous voids are not secured in the electrode, and the mobility of Li ions in the electrolyte held in the voids is reduced, thereby reducing rapid charge / discharge characteristics. Tend to.

(G) Circularity The circularity of the carbonaceous particles (B) is usually 0.88 or more, more preferably 0.9 or more, and further preferably 0.92 or more. Further, the circularity is usually 1 or less, preferably 0.99 or less, more preferably 0.97 or less. If the circularity is too small, the high current density charge / discharge characteristics of the non-aqueous secondary battery tend to deteriorate.

(H) Raman R value The Raman R value of the carbonaceous particles (B) is usually 1 or less, preferably 0.8 or less, more preferably 0.6 or less, still more preferably 0.5 or less, usually 0.05. As mentioned above, Preferably it is 0.1 or more, More preferably, it is 0.2 or more, More preferably, it is 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) Pore volume The pore volume of carbonaceous particles (B) in the range of 10 nm to 100000 nm by mercury porosimetry is usually 1.0 mL / g or less, preferably 0.9 mL / g or less, more preferably 0. 0.8 mL / g or less, usually 0.05 mL / g or more, preferably 0.1 mL / g or more, more preferably 0.15 mL / g or more. If the total pore volume is below the above range, the number of voids that can be infiltrated by the non-aqueous electrolyte solution tends to be small, and when lithium ions are rapidly charged and discharged, lithium ions are not inserted and released in time, and lithium metal is deposited accordingly. Characteristics tend to deteriorate. On the other hand, when the above range is exceeded, the binder is easily absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength tends to be lowered.

(J) Fine pore volume in the range of 80 nm to 900 nm pore diameter of carbonaceous particles (B) by mercury porosimetry The fine pore volume in the range of 80 nm to 900 nm pore diameter of carbonaceous particles (B) is determined by mercury porosimetry (mercury (Porosimetry), usually 0.08 mL / g or more, preferably 0.1 mL / g or more, more preferably 0.15 mL / g or more, still more preferably 0.3 mL / g or more. . Moreover, it is 1 mL / g or less normally, Preferably it is 0.8 mL / g or less, More preferably, it is 0.5 mL / g or less.

  When the fine pore volume in the range of the pore diameter of 80 nm to 900 nm is less than the above range, the electrolyte solution does not move sufficiently smoothly during charging / discharging of the non-aqueous secondary battery, and lithium ions are not charged when rapidly charging / discharging. There is a tendency that the insertion / desorption is not in time, and lithium metal is deposited accordingly, and the cycle characteristics are deteriorated. On the other hand, if it exceeds the above range, the binder is easily absorbed into the gap during electrode plate production, and accordingly, the electrode plate strength and initial efficiency tend to be reduced.

<Method for producing carbonaceous particles (B)>
The carbonaceous particles (B) of the present invention are not particularly limited as long as the aspect ratio is 1 or more and 4 or less, but various carbon materials represented by graphite, amorphous carbon, and carbonaceous materials having a low graphitization degree are available. Among them, graphite is preferably used. In this invention, these can be used individually or in combination of 2 or more types. Further, these carbonaceous particles (B) may be used in a composite with amorphous carbon, graphitized material, oxide or other metal.

  Graphite is easily available commercially, theoretically has a high charge / discharge capacity of 372 mAh / g, and further has a high current density compared to the case where other negative electrode active materials are used. This is preferable because the effect of improving the discharge characteristics can be expected greatly. Of these, graphite preferably has few impurities, and can be used after being subjected to various known purification treatments, if necessary. Examples of the graphite include natural graphite and artificial graphite, but natural graphite is more preferable.

As artificial graphite, for example, coal tar pitch, coal heavy oil, atmospheric residue, petroleum heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, polyvinyl Examples include those obtained by baking and graphitizing organic substances such as alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin.
The firing temperature can be in the range of 2500 ° C. or more and 3200 ° C. or less, and a silicon-containing compound, a boron-containing compound, or the like can be used as a graphitization catalyst during firing.
Examples of the amorphous carbon include particles obtained by baking a bulk mesophase and particles obtained by infusibilizing and baking a carbon precursor.

Examples of the carbonaceous material having a low graphitization degree include those obtained by firing an organic material at a temperature of usually less than 2500 ° C. Organic substances include coal-based heavy oil such as coal tar pitch and dry distillation liquefied oil; straight-run heavy oil such as atmospheric residual oil and vacuum residual oil; ethylene tar produced as a by-product during thermal decomposition of crude oil, naphtha, etc. Heavy oils such as cracked heavy oils; aromatic hydrocarbons such as acenaphthylene, decacyclene and anthracene; nitrogen-containing cyclic compounds such as phenazine and acridine; sulfur-containing cyclic compounds such as thiophene; and aliphatic cyclics such as adamantane Compounds: Polyphenylene such as biphenyl and terphenyl, polyvinyl esters such as polyvinyl chloride, polyvinyl acetate, and polyvinyl butyral, and thermoplastic polymers such as polyvinyl alcohol.

Depending on the degree of graphitization of the carbonaceous material, the firing temperature can be 600 ° C. or higher, preferably 900 ° C. or higher, more preferably 950 ° C. or higher, and usually less than 2500 ° C., Preferably it is 2000 degrees C or less, More preferably, it is the range of 1400 degrees C or less.
At the time of baking, acids such as phosphoric acid, boric acid and hydrochloric acid, alkalis such as sodium hydroxide and the like can be mixed with the organic matter.

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

(Sphericalization of carbonaceous particles (B))
In order to obtain the carbonaceous particles (B) having an aspect ratio of 1 or more and 4 or less, for example, a method of spheroidizing the raw material carbon material can be mentioned. Hereinafter, a method of performing the spheroidization process will be described, but the method is not limited to this method.
As an apparatus used for the spheronization treatment, for example, an apparatus that repeatedly gives mechanical effects such as compression, friction, shearing force, etc. including the interaction of graphite carbonaceous particles, mainly to impact force, to the particles can be used.

Specifically, it has a rotor with a large number of blades installed inside the casing, and when the rotor rotates at high speed, mechanical action such as impact compression, friction, shearing force, etc. is applied to the carbon material introduced inside. An apparatus that provides a surface treatment is preferable. Moreover, it is preferable to have a mechanism that repeatedly gives mechanical action by circulating graphite.
As a preferable apparatus for giving a mechanical action to the carbon material, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), a kryptron (manufactured by Earth Technica), a CF mill (manufactured by Ube Industries), a mechano-fusion system (Hosokawa Micron) And theta composer (manufactured by Deoksugaku Kosakusha). Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable.

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

(Carbonaceous particles coated with carbonaceous material (B))
The carbonaceous particles (B) used in the present invention may be those in which at least a part of the surface is coated with a carbonaceous material.
Examples of the carbonaceous material include amorphous carbon and graphitized material depending on the difference in heating temperature in the production method described later. As used herein, amorphous carbon refers to carbon having a d value of usually 0.34 nm or more and has low crystallinity. On the other hand, the graphite material is graphite having a d value of less than 0.34 nm and has high crystallinity.

Specifically, the carbonaceous material can be obtained by a method of heat-treating the carbon precursor as described later. The carbon material described in the following (a) or (b) is preferable as the carbon precursor.
(A) Coal heavy oil, DC heavy oil, cracked heavy oil, aromatic hydrocarbon, N ring compound, S ring compound, polyphenylene, organic synthetic polymer, natural polymer, thermoplastic resin and Carbonizable organic substance selected from the group consisting of thermosetting resins

(B) What dissolved carbonizable organic substance in low molecular organic solvent As said coal type heavy oil, coal tar pitch from a soft pitch to a hard pitch, dry distillation liquefied oil, etc. are preferable, The said DC type heavy oil As preferred, atmospheric residual oil, reduced pressure residual oil, etc., the cracked petroleum heavy oil is preferably ethylene tar produced as a by-product during thermal decomposition of crude oil, naphtha, etc., and the aromatic hydrocarbon is Acenaphthylene, decacyclene, anthracene, phenanthrene and the like are preferable, the N ring compound is preferably phenazine, acridine and the like, the S ring compound is preferably thiophene, bithiophene and the like, and the polyphenylene is biphenyl, terphenyl and the like. Preferably, the organic synthetic polymer includes polyvinyl chloride, polyvinyl alcohol, polyvinyl Tillal, insolubilized products of these, polyacrylonitrile, polypyrrole, polythiophene, polystyrene and the like are preferable, and as the natural polymer, polysaccharides such as cellulose, lignin, mannan, polygalacturonic acid, chitosan, saccharose and the like are preferable, As the thermoplastic resin, polyphenylene sulfide, polyphenylene oxide and the like are preferable, and as the thermosetting resin, a furfuryl alcohol resin, a phenol-formaldehyde resin, an imide resin and the like are preferable.
Further, the carbon precursor may be a carbide such as a solution dissolved in a low molecular organic solvent such as benzene, toluene, xylene, quinoline, n-hexane and the like.
Moreover, these may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations.

(Coating treatment)
In the coating treatment, although not particularly limited, for example, by using the above-described carbon material as a core material, using a carbon precursor for obtaining a carbonaceous material as a coating raw material, mixing or coating them, and then firing them. The carbonaceous particles (B) coated with the carbonaceous material can be obtained. In addition, a carbon material that has not been spheroidized is used as a core material, and a carbon precursor for obtaining a carbonaceous material is used as a coating raw material. After mixing these, spheronization may be performed and firing may be performed. Processing may be performed.

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

(Amount of carbonaceous material attached)
The amount of carbonaceous material attached to the carbonaceous particles (B) of the present invention indicates the coating amount of the carbonaceous material on the core material. In the present invention, this is usually 0.01% by mass or more, preferably 0.1% by mass. % Or more, more preferably 0.3% or more, particularly preferably 0.7% by weight or more, and the amount of attachment is usually 20% by weight or less, preferably 15% by weight or less, more preferably 10% by weight or less. Especially preferably, it is 7 mass% or less, Most preferably, it is 5 mass% or less.

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

Moreover, the amount of carbonaceous material attached can be calculated from the mass of the sample before and after firing the material. At this time, the calculation is made assuming that there is no mass change before and after firing the core material.
When w1 is the mass (kg) of the core material and w2 is the mass (kg) of the carbonaceous particles (B) after firing,
Amount of carbonaceous material attached (mass%) = [(w2-w1) / w1] × 100
Is calculated as

[Carbon material for negative electrode of non-aqueous secondary battery]
The negative electrode material of the present invention is a mixed carbon material containing the above scaly graphite particles (A) and carbonaceous particles (B).
<Mixing ratio of scaly graphite particles (A) and carbonaceous particles (B)>
In the negative electrode material of the present invention, the mass ratio of the scaly graphite particles (A) to the total amount of the scaly graphite particles (A) and the carbonaceous particles (B) is usually greater than 0% by mass, preferably 0.1%. % By mass or more, more preferably 1% by mass or more, particularly preferably 3% by mass or more, and usually 40% by mass or less, preferably 15% by mass or less, more preferably 10% by mass or less, still more preferably 8% by mass or less. Especially preferably, it is 6 mass% or less.

When the ratio of the scaly graphite particles (A) to the total amount of the scaly graphite particles (A) and the carbonaceous particles (B) is too large, the initial efficiency tends to decrease and the electrode plate strength decreases. On the other hand, if the ratio of the scaly graphite particles (A) is too small, the cycle characteristics tend to be deteriorated due to the reduction of the effect of suppressing the conduction path breakage of the scaly graphite particles (A).
The method of mixing is not particularly limited as long as the scaly graphite particles (A) and the carbonaceous particles (B) are uniformly mixed. For example, as a batch-type mixing apparatus, two frame molds are rotated. A mixer that revolves while revolving; A high-speed, high-shear mixer, such as a dissolver or a high-viscosity butterfly mixer; a single blade that stirs and disperses in the tank; 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.

<Tap density>
The negative electrode material of the present invention has a tap density of usually 0.6 g / cm ³ or more, preferably 0.7 g / cm ³ or more, and usually 1.8 g / cm ³ or less, preferably 1.5 g / cm ^3. Hereinafter, it is more preferably 1.3 g / cm ³ or less.
When the tap density is smaller than the above range, sufficient continuous voids are not secured in the electrode, and the mobility of Li ions in the electrolyte held in the voids tends to decrease, so that rapid charge / discharge characteristics tend to deteriorate. .

<Mixing with other materials>
The negative electrode material according to the present invention is a non-aqueous two-component catalyst that uses any one of the scaly graphite particles (A) and / or the carbonaceous particles (B) alone or in combination of two or more in any composition and combination. Although it can be used suitably as a negative electrode material of a secondary battery, one or two or more kinds are mixed with another kind or two or more other materials, and this is mixed with a nonaqueous secondary battery, preferably a nonaqueous secondary battery. You may use as a negative electrode material of a secondary battery.

  When mixing other carbon materials with the above-mentioned non-aqueous secondary battery negative electrode carbon material, the mixing ratio of the non-aqueous secondary battery negative electrode carbon material to the total amount of the non-aqueous secondary battery negative electrode carbon material and other carbon materials is: It is usually 10% by mass or more, preferably 20% by mass or more, and usually 90% by mass or less, preferably 80% by mass or less. When the mixing ratio of other carbon materials 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, materials selected from natural graphite, artificial graphite, amorphous-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 BET specific surface area of natural graphite is usually 3.5 m ² / g or more, preferably 4.5 m ² / g or more, and usually 8 m ² / g.
Hereinafter, the range is 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-coated graphite, for example, natural graphite or artificial graphite coated with an amorphous precursor pair and fired, or natural graphite or artificial graphite coated with amorphous by CVD can be used.

As the amorphous carbon, for example, particles obtained by firing a bulk mesophase, or particles obtained by firing an infusible carbonized pitch or the like can be used.
There is no particular limitation on the apparatus used for mixing the carbon material for the nonaqueous secondary battery negative electrode and other carbon materials. For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylinder mixer, a double For conical mixers, regular cubic mixers, vertical mixers, fixed mixers: spiral mixers, ribbon mixers, Muller mixers, HelicalFlight mixers, Pugmill mixers, fluidized mixers A 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 or Si compound is preferable in terms of increasing capacity. Specific examples of the Si compound include SiOx, SiNx, SiCx, SiZxOy (Z = C, N) and the like, and preferably SiOx when expressed by a general formula. This general formula SiOx represents Si dioxide (
SiO ₂ ) and metal Si (Si) are obtained as raw materials, and the value of x is usually 0 ≦ x <2. SiOx has a larger theoretical capacity than graphite. Furthermore, amorphous Si or nano-sized Si crystals easily allow alkali ions such as lithium ions to enter and exit, so that a high capacity can be obtained.

Specifically, it is expressed as SiOx, and x is usually 0 ≦ x <2, more preferably 0.2 or more and 1.8 or less, and still more preferably 0.4 or more. 6 or less, particularly preferably 0.6 or more and 1,4 or less. Within this range, the capacity is high and at the same time Li
It becomes possible to reduce the irreversible capacity due to the bond between oxygen and oxygen.
<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.

  In order to improve the electroconductivity of a negative electrode, you may contain a conductive support agent in addition to the scaly graphite particle (A) which the poorly soluble polymer was attached to the non-aqueous electrolyte solution in the active material layer. 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.
For applications that place emphasis on capacity, such as mobile devices such as mobile phones and personal computers, it is usually 1.4.
It can be 5 g / cm ³ or more, and can usually be 1.9 g / cm ³ or less.

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

<Non-aqueous secondary battery>
The basic configuration of the nonaqueous secondary battery according to the present invention can be the same as, for example, a known lithium ion secondary battery, and usually includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte. The negative electrode is a negative electrode for a non-aqueous secondary battery according to the present invention described above.
<Positive electrode>
The positive electrode can include a current collector and an active material layer formed on the current collector. The active material layer preferably contains a binder in addition to the positive electrode active material.

Examples of the positive electrode active material include metal chalcogen compounds that can occlude and release alkali metal cations such as lithium ions during charge and discharge. Of these, metal chalcogen compounds capable of inserting and extracting lithium ions are preferred.
Examples of metal chalcogen compounds include transition metal oxides such as vanadium oxide, molybdenum oxide, manganese oxide, chromium oxide, titanium oxide, and tungsten oxide; vanadium sulfide, molybdenum sulfide, titanium sulfide, CuS, and the like transition metal _sulfides; NIPS 3, phosphorus transition metals such as FEPS ₃ - sulfur _compounds; VSe 2, selenium compounds of transition metals such as _{NbSe 3; Fe 0.25 V 0.75 S} 2, Na 0.1 CrS Composite oxides of transition metals such as ₂ ; composite sulfides of transition metals such as LiCoS ₂ and LiNiS ₂ .

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

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

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

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

<Electrolyte>
The electrolyte (sometimes referred to as “electrolyte”) is not particularly limited, and a non-aqueous electrolyte obtained by dissolving a lithium salt as an electrolyte in a non-aqueous solvent, or an organic polymer compound or the like is added to the non-aqueous electrolyte. By doing so, a gel-like, rubber-like, or solid sheet-like shape can be mentioned.
The non-aqueous solvent used for the non-aqueous electrolyte is not particularly limited, and a known non-aqueous solvent can be used.
For example, chain carbonates such as diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate; chain ethers such as 1,2-dimethoxyethane; tetrahydrofuran, 2-methyl Examples include cyclic ethers such as tetrahydrofuran, sulfolane, and 1,3-dioxolane; chain esters such as methyl formate, methyl acetate, and methyl propionate; and cyclic esters such as γ-butyrolactone and γ-valerolactone.

A non-aqueous solvent may be individual or may use 2 or more types together. In the case of a mixed solvent, a combination of a mixed solvent containing a cyclic carbonate and a chain carbonate is preferable from the balance of conductivity and viscosity, and the cyclic carbonate is preferably ethylene carbonate.
The lithium salt used in the non-aqueous electrolyte is not particularly limited, and a known lithium salt can be used. For example, halides such as LiCl and LiBr; perhalogenates such as LiClO ₄ , LiBrO ₄ and LiClO ₄ ; inorganic lithium salts such as inorganic fluoride salts such as LiPF ₆ , LiBF ₄ and LiAsF ₆ ; LiCF ₃ SO ₃ , Examples include perfluoroalkane sulfonates such as LiC ₄ F ₉ SO ₃ ; fluorine-containing organic lithium salts such as perfluoroalkane sulfonic acid imide salts such as Li trifluoromethanesulfonyl imide ((CF ₃ SO ₂ ) ₂ NLi), and the like. . Of these, LiClO ₄ , LiPF ₆ , and LiBF ₄ are preferable.

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

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

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

Further, as the electrolyte, a polymer solid electrolyte which is a conductor of an alkali metal cation such as lithium ion can be used.
Examples of the polymer solid electrolyte include those obtained by dissolving a Li salt in the aforementioned polyether polymer compound, and polymers in which the terminal hydroxyl group of the polyether is substituted with an alkoxide.

<Others>
In order to prevent a short circuit between the electrodes, a porous separator such as a porous membrane or a nonwoven fabric can usually be interposed between the positive electrode and the negative electrode, and the non-aqueous electrolyte is impregnated into the porous separator. It is convenient to use it. As a material for the separator, polyolefin such as polyethylene and polypropylene, polyethersulfone, and the like are used, and polyolefin is preferable.

  The form of the non-aqueous secondary battery is not particularly limited. For example, a cylinder type in which a sheet electrode and a separator are spiraled; a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined; a coin type in which a pellet electrode and a separator are stacked Etc. Further, by storing batteries of these forms in an optional outer case, the battery can be used in an arbitrary shape and size such as a coin shape, a cylindrical shape, and a square shape.

  The procedure for assembling the non-aqueous secondary battery is not particularly limited, and can be assembled by an appropriate procedure according to the structure of the battery. For example, a negative electrode can be placed on an outer case, an electrolyte and a separator can be provided thereon, and a positive electrode can be placed so as to face the negative electrode, and can be caulked together with a gasket and a sealing plate to form a battery.

<Battery performance>
The battery produced as described above exhibits the following performance.
The initial efficiency is usually 70% or more, preferably 80% or more, more preferably 90% or more, still more preferably 91% or more, and particularly preferably 92% or more. The discharge capacity is usually 200 mAh / g or more, preferably 300 mAh / g, more preferably 320 mAh / g or more, further preferably 340 mAh / g or more, particularly preferably 350 mAh / g or more, and most preferably 360 mAh / g or more. is there. If the initial efficiency or the discharge capacity is too low, there is a tendency that it cannot be applied to a device with large power consumption or used for a long time.

  The cycle maintenance ratio is usually 70% or more, preferably 75% or more, more preferably 80% or more, and further preferably 90% or more. If the cycle maintenance ratio is too low, it is not suitable for applications in which charging and discharging are repeated and used for a long period of time. Here, the cycle maintenance ratio represents the discharge capacity at the 200th cycle relative to the discharge capacity at the first cycle.

EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In addition, the measuring method of each physical property shall follow the measuring method mentioned above.
<Average particle size>
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. Commercially available laser diffraction / scattering type particle size distribution analyzer “LA- from HORIBA
920 ", 28 kHz ultrasonic waves were irradiated for 1 minute at an output of 60 W, and then measured as a volume-based median diameter in a measuring apparatus, and defined as a volume-based average particle diameter d50 in the present invention.

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

<Tap density>
In the present invention, the tap density is measured by using a powder density meter to drop the raw carbon material through a sieve having a diameter of 1.6 cm and a volume capacity of 20 cm ³ through a sieve having a mesh opening of 300 μm to fill the cell. After filling, a tap 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.

< _D002 , Lc>
About 15% X-ray standard high-purity silicon powder mixed with carbon powder is used as a material, CuKα ray monochromatized with a graphite monochromator is used as a radiation source, and a wide angle X-ray diffraction curve is obtained by a reflection diffractometer method. Was measured, and the interplanar spacing (d ₀₀₂ ) and crystallite size (Lc) were determined using the Gakushin method.

<Circularity>
Using a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co.), using polyoxyethylene (20) monolaurate as a surfactant, using ion-exchanged water as a dispersion medium, and circular with an equivalent circle diameter It is obtained by calculating the degree. 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. When the circularity is 1, it becomes a theoretical sphere. 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.

<Aspect ratio>
The resin embedding of the negative electrode material or the negative electrode is polished perpendicularly to the flat plate, a cross-sectional photograph thereof is taken, 50 or more particles are randomly extracted, and the longest particle diameter (in the direction parallel to the flat plate) ) And the shortest diameter (perpendicular to the flat plate) were measured by image analysis, and the average of the longest diameter / shortest diameter was taken as the aspect ratio. 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.

<Measurement method of initial efficiency>
Using a non-aqueous secondary battery (2016 coin-type battery) produced by the method described later, the initial efficiency during battery charging / discharging was measured by the following measurement method.
The lithium counter electrode is charged to 5 mV at a current density of 0.16 mA / cm ² , and 5
The battery was charged at a constant voltage of mV until the charge capacity value became 350 mAh / g, and after doping lithium into the negative electrode, the battery was discharged to 1.5 V with respect to the lithium counter electrode at a current density of 0.33 mA / cm ² . . Subsequently, the second and third times were charged at 10 mV and 0.005 Ccut by cc-cv charging at the same current density, and the discharge was discharged to 1.5 V at 0.04 C at all times. The sum of the difference between the charge capacity and the discharge capacity for a total of three cycles was calculated as an irreversible capacity. The discharge capacity at the third cycle was defined as the discharge capacity of the material, and the discharge capacity of the material / (discharge capacity of the material + irreversible capacity) was defined as the initial efficiency.

<Measurement method of cycle maintenance ratio>
A laminate type battery manufactured by the method described later is charged to 4.2 V at 0.8 C, and discharged to 3.0 V at 0.5 C. The ratio of the discharge capacity at the 200th cycle to the discharge capacity at the first cycle × 100 was defined as the cycle retention rate (%).

<Production of electrode sheet>
An electrode plate having an active material layer with an active material layer density of 1.60 ± 0.03 g / cm ³ was prepared using the graphite particles of the examples or comparative examples. Specifically, 20.00 ± 0.02 g of negative electrode material 20.00 ± 0.02 g of a 1% by mass aqueous solution of sodium carboxymethylcellulose (0.200 g in terms of solid content), and styrene having a weight average molecular weight of 270,000 -Aqueous dispersion of butadiene rubber 0.50 ± 0.05 g (0.2 g in terms of solid content) was 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 14.5 ± 0.3 mg / cm ² on a 18 μm-thick copper foil as a current collector, 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.

<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 mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7) and LiPF ₆ of 1 mol /
A separator (made of a porous polyethylene film) impregnated with an electrolytic solution dissolved so as to be L was placed, and 2016 coin-type batteries were produced.

<Production method of non-aqueous secondary battery (laminated battery)>
The electrode sheet produced by the above method was cut into a square of 4 cm × 3 cm to form a negative electrode, a positive electrode made of LiCoO ₂ was cut out with the same area, and a separator (made of a porous polyethylene film) was placed between the negative electrode and the positive electrode. 250 μl of an electrolytic solution in which 1% by volume of vinylene carbonate was further added as an additive was dissolved in a mixed solvent of ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7) so that LiPF ₆ was dissolved at 1 mol / L. Thus, a laminate type battery was produced.

<Carbon material>
Carbonaceous particles (B): Volume-based average particle diameter (d50) as raw material graphite is 16.1 μm, BET specific surface area (SA) is 6.3 m ² / g, tap density is 0.98 g / cm ³ , circularity Is mixed with spheroidized natural graphite having an aspect ratio of 1.9 and an oily heavy oil obtained at the time of naphtha pyrolysis as an amorphous carbon precursor at 1300 ° C. in an inert gas. The heat treatment was performed. The obtained fired product was pulverized and classified to obtain carbonaceous particles (B). From the firing yield, it was confirmed that the amount of amorphous carbon added was 3% by mass in the obtained carbonaceous particles (B). The particle size, SA, Tap density, circularity, and aspect ratio were measured by the above measurement methods. The results are shown in Table 1 below.

Scale-like graphite particles in which a poorly soluble polymer is attached to a non-aqueous electrolyte (A): scale-like natural graphite particles (volume-based average particle size (d50) = 5.1 μm, BET specific surface area (SA) as raw material graphite) 14.7 m ² / g, tap density = 0.42 g / cm ³ , circularity = 0.81, aspect ratio = 8.3), and 50 g of scaly natural graphite particles and Aldrich-made lithium polystyrene sulfonate 30 % Aqueous solution (weight average molecular weight: 75000) obtained by adding 49.17 g of distilled water to 0.83 g and diluting it into a flask immersed in an oil bath (scale-like natural graphite particles 1: lithium polystyrene sulfonate = 100 : 0.5). While stirring, the oil bath was heated to 95 ° C. to distill off the solvent, and powdery scaly graphite particles (A) were obtained. The particle size, specific surface area (SA), Tap density, circularity, and aspect ratio were measured by the above measurement methods. The results are shown in Table 1 below.

[Example 1]
The flaky graphitic particles (A) and the carbonaceous particles so that the mass ratio of the flaky graphite particles (A) to the total amount of the flaky graphite particles (A) and the carbonaceous particles (B) is 95% by mass. (B) was mixed to obtain a sample. About this sample and the non-aqueous secondary battery produced from it, the initial efficiency and the cycle maintenance factor were measured with the said measuring method. The results are shown in Table 2 below.

[Comparative Example 1]
The battery characteristics were evaluated in the same manner as in Example 1 using the carbonaceous particles (B) as they were. The results are shown in Table 2 below.
[Comparative Example 2]
The sample is prepared by mixing the scaly natural graphite particles and the carbonaceous particles (B) so that the mass ratio of the scaly graphite particles to the total amount of the scaly graphite particles and the carbonaceous particles (B) is 95% by mass. Obtained. Using this sample, the battery characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 2 below.

  As can be seen from Table 2, a non-aqueous secondary battery negative electrode carbon material (Example 1) containing scaly graphite particles (A) in which a poorly soluble polymer is attached to a non-aqueous electrolyte and carbonaceous particles (B). ) Was confirmed to have a higher cycle retention rate than the non-aqueous secondary battery negative electrode material (Comparative Example 1) consisting only of the carbonaceous particles (B). From this result, it can be seen that the scaly graphite particles (A) obtained by complexing a poorly soluble polymer in the electrolyte have properties suitable as a conductive additive.

  Moreover, the carbon material (Example 1) for the nonaqueous secondary battery negative electrode containing the scaly graphite (A) in which the poorly soluble polymer is combined with the nonaqueous electrolyte and the carbonaceous particles (B) is a scaly natural product. It was confirmed that both the initial efficiency and the cycle retention ratio were high as compared with the non-aqueous secondary battery negative electrode carbon material (Comparative Example 2) containing graphite and carbonaceous particles (B). This is thought to be due to the suppression of the SEI coating and gas generation by suppressing the contact between the scaly graphite particles and the electrolyte by combining a polymer that is sparingly soluble in the non-aqueous electrolyte with the scaly graphite particles. .

Claims (10)

  A carbon material for a non-aqueous secondary battery negative electrode containing scaly graphite particles (A) and carbonaceous particles (B), wherein the scaly graphite particles (A) are made of a polymer that is hardly soluble in a non-aqueous electrolyte. A carbon material for a negative electrode of a non-aqueous secondary battery, characterized in that the carbonaceous particles (B) have an aspect ratio of 1 or more and 4 or less. 2. The carbon material for a negative electrode of a non-aqueous secondary battery according to claim 1, wherein the ₀₀₂ plane spacing (d ₀₀₂ ) of the scaly graphite particles (A) by an X-ray wide angle diffraction method is 0.337 nm or less. .   3. The carbon material for a nonaqueous secondary battery negative electrode according to claim 1, wherein d50 of the scaly graphite particles (A) is 2 μm or more and 15 μm or less.   The carbon material for a nonaqueous secondary battery negative electrode according to any one of claims 1 to 3, wherein the scale-like graphite particles (A) have an aspect ratio of 5 or more.   A polymer that is sparingly soluble in a non-aqueous electrolyte solution is immersed in a solvent in which ethyl carbonate and ethyl methyl carbonate are mixed at a volume ratio of 3: 7 for 24 hours, and the dry weight reduction rate before and after immersion is 10% by mass or less. The carbon material for a non-aqueous secondary battery negative electrode according to any one of claims 1 to 4.   The carbon material for a nonaqueous secondary battery negative electrode according to any one of claims 1 to 5, wherein the scaly graphite particles (A) and / or the carbonaceous particles (B) are natural graphite. .   The carbon material for a nonaqueous secondary battery negative electrode according to any one of claims 1 to 6, wherein the carbonaceous particles (B) are coated with a carbonaceous material.   The non-aqueous system according to any one of claims 1 to 7, wherein a polymer that is hardly soluble in the non-aqueous electrolyte solution has a π-conjugated structure and has an electric conductivity of 0.1 S / cm or less. Carbon material for secondary battery negative electrode.   It is a negative electrode for non-aqueous secondary batteries provided with an electrical power collector and the active material layer formed on the said electrical power collector, Comprising: The said active material layer is any one of Claims 1 thru | or 8. A negative electrode for a nonaqueous secondary battery, comprising a carbon material for a nonaqueous secondary battery negative electrode.   A nonaqueous secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode is the negative electrode for a nonaqueous secondary battery according to claim 9.