JP2013229343A - Composite graphite particle for nonaqueous secondary battery, negative electrode material containing the same, negative electrode and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous secondary battery in which the initial charge and discharge irreversible capacity is sufficiently small even if an active material layer that has a negative electrode material on a current collector is highly densified for higher capacity, and which has superior electric discharge load characteristics, charge receiving characteristics, and cycle characteristics.SOLUTION: A method of manufacturing a composite graphite particle for a nonaqueous secondary battery in which a graphite particle and a carbonaceous or graphitic material are compounded, includes: a step 1 in which a graphite particle and a graphitizable binder are mixed with each other; a step 2 in which a mixture obtained in the step 1 is molded under pressure; and a step 3 in which a molded product obtained in the step 2 is calcined.

Description

  The present invention relates to composite graphite particles used in a non-aqueous secondary battery, a negative electrode material containing the composite graphite particles, a negative electrode formed using the negative electrode material, and a non-aqueous secondary battery having the negative electrode. It is.

In recent years, demand for high-capacity secondary batteries has increased with the downsizing of electronic devices. In particular, non-aqueous secondary batteries having higher energy density and excellent large current charge / discharge characteristics have attracted attention as compared to nickel / cadmium batteries and nickel / hydrogen batteries.
As a negative electrode material for a non-aqueous secondary battery, graphite is often used in terms of cost, durability, and capacity. However, when the density of the active material layer including the negative electrode material on the electrode is increased to increase the capacity, the initial charge / discharge irreversible capacity increases, the discharge load characteristics are low, and the charge acceptance is deteriorated. .

  In Patent Document 1, natural graphite and a binder are combined to obtain a composite, and the binder is carbonized by primary heating at 700 to 1500 ° C., and then secondary heating at 2400 to 3000 ° C. Describes a method for producing a carbon composite material that simultaneously purifies and graphitizes a carbonized binder. However, in Patent Document 1, scaly or scaly natural graphite is assumed as a starting material, and densification of the active material layer and reduction of charge / discharge irreversible capacity were insufficient.

JP 2000-086343 A

  The present invention has been made in view of the background art, and the problem is that the initial charge / discharge irreversible capacity is increased even if the active material layer having the negative electrode material on the current collector is densified in order to increase the capacity. Is a sufficiently small non-aqueous secondary battery having excellent discharge load characteristics, charge acceptance, and cycle characteristics.

As a result of intensive studies to solve the above-mentioned problems, the inventor used composite graphite particles having a specific structure and physical properties, in which spherical graphite particles and graphitizable binder graphitized materials were combined as a negative electrode active material. It has been found that a non-aqueous secondary battery that solves the above problems can be obtained by using it, and has reached the present invention.
That is, the gist of the present invention is as follows.
(1) A method for producing composite graphite particles for a non-aqueous secondary battery comprising a composite of graphite particles and carbonaceous or graphite, which comprises the following steps 1 to 3. A method for producing composite graphite particles for a secondary battery. Step 1: Step of mixing graphite particles and graphitizable binder Step 2: Step of applying pressure to the mixture obtained in Step 1 and molding Step 3: Step of firing the molded product obtained in Step 2 ( 2) The method for producing composite graphite particles for nonaqueous secondary batteries according to (1) above, wherein the molding method in step 2 is selected from the group consisting of an extrusion molding method, a mold molding method and an isostatic pressure molding method. Method.
(3) The method for producing composite graphite particles for a non-aqueous secondary battery as described in (1) or (2) above, further comprising a pulverizing step.
(4) The method for producing composite graphite particles for non-aqueous secondary batteries according to any one of (1) to (3) above, wherein the mixing temperature in step 1 is not lower than the softening point of the binder.
(5) Composite graphite particles for non-aqueous secondary batteries manufactured using the manufacturing method according to any one of (1) to (4) above.
(6) A negative electrode having a current collector and an active material layer formed thereon, wherein the active material layer is formed using the negative electrode material for a non-aqueous secondary battery described in (5) above. A negative electrode for a non-aqueous secondary battery.
(7) A nonaqueous secondary battery having a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is a negative electrode for a nonaqueous secondary battery according to (6) above. Non-aqueous secondary battery characterized.

  When the composite graphite particles for a non-aqueous secondary battery of the present invention are used, the active material layer on the negative electrode current collector is densified by the equal area circle diameter, the in-electrode porosity, and the particle contact rate specific to the particles. Even in this case, it is possible to provide a non-aqueous secondary battery having a small initial charge / discharge load reverse capacity, a high capacity, and excellent discharge load characteristics, charge acceptability, cycle characteristics, and electrolyte permeability.

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described in detail below. However, the description of the invention constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention has its gist. As long as it does not exceed, it is not limited to these forms.
In the present invention, terms are defined and used as follows. That is, in the composite graphite particles of the present invention, the portion where the carbonaceous particles are fired may be referred to as graphite particles. The carbonaceous composite particles of the present invention and, if necessary, those including a mixture of carbonaceous particles are defined as negative electrode materials. An active material layer is obtained by using at least a negative electrode material and a binder, and a material having at least an active material layer on a negative electrode current collector is defined as an electrode or a negative electrode, and has at least a negative electrode, a positive electrode, and an electrolyte. Thus, a non-aqueous secondary battery is configured.
The characteristics of the electrode using the composite graphite particles for a non-aqueous secondary battery of the present invention can be measured by image analysis shown below.

(Image analysis method)
A cross-sectional image of the electrode sheet obtained by applying the negative electrode active material particles on the copper foil is photographed with an optical microscope, a laser microscope, or a scanning electron microscope, and the particle portion and the void portion are binarized. To distinguish. At this time, a cross-sectional image is taken with a reference so that the copper foil is horizontal.
This is repeated for 100 fields of view, and the calculated numerical values are averaged. Also, the particle perimeter, particle contact length, etc. are calculated from the image, and the numerical values are averaged.
For image processing, Image Pro Plus manufactured by Nippon Roper Co., Ltd. was used.

(Void ratio in electrode)
The in-electrode porosity is calculated by the following equation using the void area and negative electrode overall area values obtained by image analysis. The total area of the negative electrode refers to the total area of the void portion and the particle portion. The void portion is a portion where particles are not present, and the particle portion is a portion where negative electrode material particles are present.

Porosity in electrode (%) = void area (μm ² ) × 100 / total area of negative electrode (μm ² )
Although the porosity in an electrode is not specifically limited, 7.5% or more and 30% or less are preferable. More preferably, they are 8% or more and 25% or less, Especially preferably, they are 8.5% or more and 15% or less. When the porosity is larger than this range, the contact between the negative electrode active materials becomes insufficient, the conductivity cannot be ensured, and the battery characteristics are remarkably deteriorated. If it is smaller than this range, it is difficult for the electrolytic solution to penetrate into the electrode because the space in the electrode cannot be secured, leading to a significant decrease in the discharge load characteristics and charge acceptance. Furthermore, the deterioration of the cycle characteristics becomes remarkable.

(Particle contact rate)
For the particle contact rate, the particle contour obtained by analyzing the particle contour determined by image analysis, the length of the portion in contact with the particle contour (μm), and the perimeter of all particles (μm) are used. Is calculated by the following formula.
Particle contact rate (%) = Particle contact part length (μm) × 100 / [Particle contact part length (μm) + void part length (μm)]

  The particle contact rate is preferably 5% or more and 48% or less, more preferably 10% or more and 47% or less, and particularly preferably 20% or more and 45% or less. Beyond this range, the particles are in excessive contact with each other, making it difficult for the electrolyte to penetrate into the electrode, leading to a significant decrease in discharge load characteristics and charge acceptance. In some cases, exceeding this range indicates that the particles have been destroyed, leading to an increase in initial irreversible capacity due to excessive reaction with the electrolyte. Below this range, the contact of the negative electrode active material particles becomes insufficient, the conductivity cannot be ensured, and the battery characteristics are remarkably deteriorated. Furthermore, the deterioration of the cycle characteristics becomes remarkable.

(Cumulative number of equal area circle diameter%)
From the image, a circle diameter μm of equal area for each particle having different shapes is calculated, and the cumulative number is calculated.
The increase rate from 1 μm to 4 μm is preferably 8% or more and 38% or less, and more preferably 8.5% or more and 30% or less. If it is higher than this, there are too many particles with a small particle size, which may cause an increase in specific surface area and an increase in the initial irreversible capacity, and if lower than this, the in-electrode conductivity cannot be secured, The cycle characteristics may be degraded. The increase rate from 4 μm to 12 μm is preferably 47% or more and 80% or less, more preferably 48% or more and 70% or less, and particularly preferably 49% or more and 60% or less. If it is higher than this, there will be too many particles of small and medium diameters, and the voids in the electrode will tend to be reduced, resulting in a decrease in electrolyte permeability, discharge load characteristics and charge acceptance. . If it is lower than this, a structure suitable as a high-density electrode cannot be obtained, and the cycle characteristics may deteriorate. The increase rate from 8 μm to 12 μm is preferably 27% or more and 80% or less, more preferably 28% or more and 50% or less, and particularly preferably 29% or more and 40% or less. If it is higher than this, there are too many coarse particles, and the electrical conductivity in the electrode cannot be ensured, and the cycle characteristics may be deteriorated. If it is lower than this, since the electrode structure is composed of particles of small and medium particle diameter, it cannot be a structure suitable as a high-density electrode, it is not possible to ensure a sufficient gap in the electrode, the electrolyte permeability decreases, The discharge load characteristics and the charge acceptance may be reduced.
In addition, the characteristics of the electrode using the negative electrode material of the present invention can be measured by the following image analysis.

(Run length measurement)
A binarized image of the void is superimposed on a black and white striped pattern image (vertical and horizontal images) to form a composite image, and the horizontal and vertical lengths of the image are calculated.
When this negative electrode material is used, the number frequency of 1 μm in the direction perpendicular to the electrode is preferably 5% or more and 40% or less, and the number frequency of 3 μm is preferably 10% or more and 30% or less. If it is out of this range, the gap in the electrode is not suitable, so that the permeability of the electrolyte is poor, and further, the discharge load characteristics and the charge acceptance may be lowered.

In the horizontal direction of the electrode, the number frequency of 1 μm and 2 μm is preferably 10% or more and 30% or less. If it is out of this range, the gap in the electrode is not suitable, so that the permeability of the electrolyte is poor, and further, the discharge load characteristics and the charge acceptance may be lowered. Furthermore, since the diffusion rate of lithium ions is deteriorated, cycle characteristics may be deteriorated.

(Vertical void ratio measurement)
The density cross section in the horizontal and vertical directions of the electrode in the binarized void image was divided by the length of the electrode, and the void ratio depending on the position was measured. The void ratio in the electrode horizontal direction is preferably 1% or more and 50% or less, and more preferably 5% or more and 45% or less. If it is out of this range, the gap in the electrode is not suitable, so that the permeability of the electrolyte is poor, and further, the discharge load characteristics and the charge acceptance may be lowered. Furthermore, since the diffusion rate of lithium ions is deteriorated, cycle characteristics may be deteriorated. The void ratio in the vertical direction is preferably 1% or more and 50% or less, and more preferably 3% or more and 45% or less. If it is out of this range, the gap in the electrode is not suitable, so that the permeability of the electrolyte is poor, and further, the discharge load characteristics and the charge acceptance may be lowered. Furthermore, since the diffusion rate of lithium ions is deteriorated, cycle characteristics may be deteriorated.

(Other measurements)
From each image, an ellipse major / minor axis ratio, an ellipse angle, a rectangular aspect ratio, a roundness, and the like are calculated for the particle portion and the void portion. In addition, about a specific measurement part, it performs according to the procedure of the image processing software to be used.
These numerical values are all affected by the shape, crystallinity and surface properties of the negative electrode material particles in the present invention, the presence and amount of conductive material in electrode production, rolling load, etc., electrode pore distribution, electrode specific surface area, There is a correlation with the immersion property and the like, and the characteristics of the negative electrode material can be expressed.
In calculating numerical values, CV value calculation or volume weighting calculation may be performed as appropriate.

[1] Composite graphite particles for non-aqueous secondary battery (A) Configuration of composite graphite particles The negative electrode material of the present invention contains the composite graphite particles of the present invention as a main component. The composite graphite particles of the present invention are obtained by, for example, combining spherical graphite particles and a graphitizable binder (hereinafter, sometimes simply referred to as “binder”), and comminuting a molded product after pulverization. It is obtained by pulverizing or grinding after conversion. That is, in this case, the composite graphite particles formed are composed of at least a part (part or all) of the composite graphite particles obtained by firing carbonaceous particles and a product obtained by firing the binder (also graphite). Is a composite structure. Hereinafter, as shown in the production method 2, in some cases, it may be a powder instead of a molded body. For example, this is the case when the amount of binder to be mixed is small.

The carbonaceous particles that are the raw material of the composite graphite particles of the present invention are not particularly limited as long as they are carbon particles that can be graphitized by firing, but natural graphite, artificial graphite, spheroidized graphite, coke powder, needle coke. Examples thereof include powder and resin carbide powder.
Among these, it is preferable to use natural graphite because it is easy to increase the density of the active material layer when the active material layer is formed. Among them, spheroidized graphite obtained by spheroidizing graphite is particularly preferable. The spherical graphite particles of the present invention are preferably composed of a plurality of curved or bent scaly or scaly graphites.

  The graphitizable binder is not particularly limited as long as it is carbonaceous that can be graphitized by firing, and petroleum-based and coal-based condensed polycyclic aromatics from tar, soft pitch to hard pitch are preferably used. . Specifically, petroleum heavy oil such as impregnated pitch, coal tar pitch, coal heavy oil such as coal liquefied oil, straight run heavy oil such as asphalten, cracked heavy oil such as ethylene heavy end tar, etc. Oil etc. are mentioned.

(B) Features of Composite Graphite Particles The composite graphite particles of the present invention contain composite graphite particles in which at least a part of the spherical graphite particles are exposed on the surface or the non-existence of the spherical graphite particles in the vicinity of the surface. Contains composite graphite particles having a complete laminate structure.

  The composite graphite particle for non-aqueous secondary battery of the present invention is a composite using spherical or elliptical spherical graphite particles formed as primary particles, and is pulverized and ground at the time of producing composite graphite particles. As a result, the surface of the spherical graphite particles is roughened. The composite graphite particles are pulverized and ground at the time of production, so that at least a part of the spherical graphite particles has a surface exposed; the fracture surface generated by the pulverization and grinding at the time of production of the composite graphite particles The graphite particles in the spherical graphite particles are floating on the surface of the composite graphite particles; or the spherical graphite particles in the composite graphite particles peeled off by pulverization / grinding during the production of the composite graphite particles. It means a state where a part is attached to the surface.

  In this way, the graphite particles in the spherical graphite particles on the surface of the composite graphite particles are converted into graphite particles in the spherical graphite particles that are in the raw material state before being combined by pulverization and grinding during the production of the composite graphite particles. In comparison, by standing at least a part thereof, the permeability of the electrolytic solution into the composite graphite particles is improved, the lithium ions are smoothly diffused, and good charge acceptability is exhibited. Moreover, by having such a shape of the composite graphite particles, an appropriate gap is secured inside the electrode after coating and rolling, and the immersion of the electrolytic solution into the electrode is improved.

Furthermore, it will be described in detail that composite graphite particles having an incomplete laminated structure of spherical graphite particles are contained in the vicinity of the surface of the composite graphite particles.
Here, the “incomplete laminated structure” means a state in which a part of the spherical graphite particles is folded in various directions on the surface of the composite graphite particles. The composite graphite particles for non-aqueous secondary batteries in the present invention are crushed and ground so that the sections of the graphite particles that are the primary particles of the spherical graphite particles that are the starting materials are directed in various directions on the surface of the composite graphite particles. It has a state etc. Such a surface state facilitates the diffusion of lithium ions into the particles, thereby improving the charge acceptance and improving the electrolyte immersion property to the electrode.

<Median diameter>
(A) Definition of particle median diameter The particle median diameter is a volume-based diameter determined by laser scattering particle size distribution measurement, and the measurement method is as follows.
0.01 g of graphite composite particles are suspended in 10 mL of a 0.2 wt% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) which is a surfactant, and commercially available laser diffraction / The sample was introduced into a scattering type particle size distribution measuring apparatus “LA-920 manufactured by HORIBA”, irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, and then measured as a volume reference median diameter in the measuring apparatus.

(B) Range The particle median diameter of the composite graphite particles of the present invention is not particularly limited, but is preferably 5 μm to 30 μm, more preferably 8 μm to 28 μm, and particularly preferably 10 μm to 25 μm. If the particle median diameter is too small, the porosity in the electrode is too low, and if the particle median diameter is too large, the particle contact property is deteriorated, so that the effects of the present invention may not be obtained.

<Tap density>
(A) Definition of Tap Density In the present invention, the tap density is a cylinder having a diameter of 1.6 cm and a volume capacity of 20 cm ³ using “Tap Denser KYT-4000” manufactured by Seishin Enterprise Co., Ltd., which is a powder density measuring device. After dropping the composite graphite particles through the sieve with a mesh size of 300 μm and filling the cell fully, tap with a stroke length of 10 mm is performed 1000 times, and the density obtained from the volume at that time and the weight of the sample is obtained. Defined as tap density.

(B) is not particularly limited tap density of the composite graphite particles of the scope the present invention, 0.5 g / cm ³ or more, more preferably 0.70 g / cm ³ or more, 0.75 g / cm ³ or more and particularly preferable. Moreover, 1.5 g / cm ³ or less is preferable, 1.4 g / cm ³ or less is more preferable, and 1.3 g / cm ³ or less is particularly preferable. If the tap density is too low, it is difficult to apply to the current collector during the production of the negative electrode, the density of the coating film becomes small, the composite graphite particles are likely to be destroyed when rolled, and the battery performance may be lowered. On the other hand, if the tap density is too high, the particle contact in the electrode is insufficient, so that the in-electrode conductivity is insufficient and the battery characteristics are deteriorated.

<BET specific surface area>
-Specific surface area measuring method In addition, in this invention, a BET specific surface area is measured and defined by the following method. That is, using a specific surface area measuring device “AMS8000” manufactured by Okura Riken Co., Ltd., the BET one-point method is measured by a nitrogen gas adsorption flow method. Specifically, 0.4 g of a sample (composite graphite particles) is filled in a cell, heated to 350 ° C. and pretreated, then cooled to liquid nitrogen temperature, and 30% nitrogen and 70% He gas is added. The amount of gas desorbed by saturation adsorption and then heated to room temperature is measured, and the specific surface area is calculated from the obtained results by a normal BET method.

-Range Although there is no limitation in particular about the BET specific surface area measured by BET method of the composite graphite particle of this invention, Usually, it is 1 m < ² > / g or more, Preferably it is 1.5 m < ² > / g or more. Moreover, it is 10 m < ² > / g or less normally, Preferably it is 6 m < ² > / g or less, More preferably, it is 5.5 m < ² > / g or less, Most preferably, it is 5 m < ² > / g or less. When the specific surface area is less than this range, the charge acceptance characteristics may deteriorate. On the other hand, if the specific surface area exceeds this range, the initial irreversible capacity increases, and the cycle characteristics may further deteriorate.

<Rolling load>
There is no particular limitation on the range of the rolling load required when producing an electrode plate having an electrode active material density of 1.8 ± 0.03 g / cm ³ by the electrode plate production method described later. Converted per 5 cm, preferably 200 kgf / 5 cm or more, particularly preferably 250 kgf / 5 cm or more, more preferably 300 kgf / 5 cm or more, and usually 1200 kgf / 5 cm or less, preferably 1000 kgf / 5 cm or less, particularly preferably A negative electrode material that is 850 kgf / 5 cm or less is desirable.

A negative electrode material whose rolling load falls below this lower limit is liable to be crushed during rolling, and the immersion of the electrolytic solution may be deteriorated when an electrode is formed. Further, the negative electrode material may be crushed to prevent the diffusion of lithium ions, and the discharge load characteristics and charge acceptance may be reduced. Moreover, when the particles are crushed and broken, the electrolyte solution reactivity on the particle surface is increased, which may increase the irreversible capacity. On the other hand, in a negative electrode material in which the rolling load exceeds this upper limit, it may be difficult to obtain a target electrode active material density, which may further reduce productivity.
Although the manufacturing method of the negative electrode material which has the rolling load of the said range is not specifically limited, It can obtain by devising composite graphite particles, the amount of binders, a graphitization degree, etc.

<Electrode pore volume>
(A) Measurement method and definition of pore volume of composite graphite particle by mercury porosimeter The electrode pore volume by the mercury porosimeter in the present invention was measured using a pore volume measuring device “Autopore IV9520 manufactured by Micromeritics” and attached. A sample (electrode sheet 2000 mm ² was sealed in the cell, pretreated for 10 minutes at room temperature under reduced pressure (50 μm / Hg), and then mercury was applied in multiple stages from 4.0 psia (pound square inch absolute pressure) to 40000 psia. It is defined by the amount of mercury intrusion measured by reducing the pressure to 3.0 psia in multiple stages after the pressure increase, and more specifically, the Washburn equation (D = − (1 / P) 4γcosψ) is calculated from the pressure P applied to the mercury. And is defined by the mercury intrusion / retraction curve obtained by calculating the pore diameter D. γ is the surface tension of mercury and ψ is the contact angle.

(B) Range The electrode pore volume was measured by the above measuring method, and the electrode pore volume change amount was calculated by the following equation.
Electrode pore volume change (ml / g) = Unrolled electrode pore volume (ml / g) −Electrode pore volume after rolling (ml / g)
The amount of change in electrode rolling is preferably 0.1 ml / g or more and 0.8 ml / g or less, more preferably 0.2 ml / g or more, 0.7 ml / g or less, particularly preferably 0.3 ml / g or more, 0
. 6 ml / g. Below this lower limit, it may be difficult to obtain a desired electrode density because the negative electrode material is too hard, and if it exceeds, the particle breakage has occurred extremely during rolling, and therefore the particle surface This may increase the reactivity with the electrolyte, resulting in deterioration of irreversible capacity, deterioration of discharge load characteristics, and reduction of charge acceptance.

<Change in electrode specific surface area>
(A) Definition of change amount of electrode specific surface area It measures using the said BET specific surface area method with respect to an electrode of 35 cm ² area. In the case of an electrode, the pretreatment temperature is 100 ° C., different from the above.
The electrode specific surface area change amount was calculated by the following calculation method.
Electrode specific surface area change (m ² / g) = Rolled electrode specific surface area (m ² / g) −Unrolled electrode specific surface area (m ² / g)

(B) Range electrode specific surface area change amount, -3.0m ² / g or more, preferably 3.0 m ² / g or less, more preferably, -2.8m ² / g or more, 2.8 m ² / g or less , particularly preferably -2.5m ² / g or more, or less 2.5 m ² / g. Below this lower limit, there is a possibility that some abnormalities have occurred in the particles during binder modification and electrode rolling, and if it exceeds, particle destruction has occurred extremely during rolling. The reactivity with the electrolytic solution on the surface may increase, and the irreversible capacity may deteriorate, the discharge load characteristics may deteriorate, and the charge acceptance may deteriorate.

<Electrolytic solution permeability>
(A) Definition of electrolyte permeability The electrode punched out to the size of 12.5 mmφ, which was punched out by the electrode preparation method described later, was vacuum-dried for 11 hours, and then punched in a glove box under an argon atmosphere. 1 μl of diethyl carbonate solvent is dropped from the top height of 1 cm, and the time until it completely disappears from the electrode is measured. Similarly, the average value of the measured time is called penetration time.

(B) Range In the present invention, the disappearance time of the solvent on the electrode is not particularly limited, but is preferably 30 seconds or less, and more preferably 28 seconds or less. When the solvent disappearance time is long, it takes time in the process of injecting the electrolytic solution at the time of producing the battery, and the productivity may be reduced. In addition, the long disappearance time of the solvent means that the permeability of the electrolytic solution inside the electrode is poor, which leads to deterioration of battery characteristics, particularly discharge load characteristics, charge acceptance, and cycle characteristics. There is. Therefore, an electrode that exhibits good immersion properties and a material for obtaining such an electrode are required. The composite graphite particles for non-aqueous secondary batteries in the present invention are particles that can exhibit good electrolyte immersion properties due to their characteristic particle structure.

[2] Anode material for non-aqueous secondary battery The composite graphite particle for non-aqueous secondary battery of the present invention (hereinafter sometimes abbreviated as “composite graphite particle (A)”) alone is a non-aqueous secondary battery. Can be used as a negative electrode material, but natural graphite, artificial graphite, vapor-grown carbon fiber, conductive carbon black, amorphous-coated graphite, resin-coated graphite, amorphous carbon, and appropriate treatments for them And further including one or more carbonaceous particles selected from the group consisting of the above-mentioned composite graphite particles having different shapes or physical properties (hereinafter abbreviated as “carbonaceous particles (B)”). A negative electrode material for a non-aqueous secondary battery is also preferable.

  By appropriately selecting and mixing the carbonaceous particles (B), it is possible to improve cycle characteristics by improving conductivity, improve charge acceptability, reduce irreversible capacity, and improve rollability. The lower limit of the amount in the case of mixing the carbonaceous particles (B) is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 0.6% by weight or more with respect to the whole negative electrode material. The upper limit is usually 80% by weight or less, preferably 50% by weight or less, more preferably 40% by weight or less. Below this range, the effect of improving conductivity may be difficult to obtain. On the other hand, an increase in the initial irreversible capacity may be caused.

Among the carbonaceous particles (B), as the natural graphite, for example, highly purified flaky graphite or spheroidized graphite can be used. The volume-based average particle size of natural graphite is usually 1 μm or more, preferably 3 μm or more, and usually 60 μm or less, preferably 40 μm or less. Natural graphite has a BET specific surface area of usually 2 m ² / g or more, preferably 3 m ² / g or more, usually 30 m ² / g or less, preferably 15 m ² / g or less.

As the artificial graphite, for example, particles obtained by combining coke powder or natural graphite with a binder, particles obtained by firing and graphitizing single graphite precursor particles while powdered, and the like can be used.
As amorphous-coated graphite, for example, natural graphite or artificial graphite coated with an amorphous precursor and fired, or natural graphite or artificial graphite coated with an amorphous surface can be used.
As the resin-coated graphite, for example, particles obtained by coating and drying a polymer material on natural graphite or artificial graphite can be used, and as amorphous carbon, for example, particles obtained by firing bulk mesophase, Particles obtained by infusibilizing and firing a carbon precursor can be used.

  Among these, when blended and used as the carbonaceous particles (B) in the composite graphite particles of the present invention, natural graphite and those obtained by appropriately treating them are preferable because a high capacity is maintained. The above-mentioned appropriate treatment may be a heat treatment of oxidized graphite as described below. This may be achieved by subjecting the spherical treated graphite as a raw material to an additional mechanical grinding treatment for a long time, or contacting the graphite with oxygen gas, heated sulfuric acid, nitric acid, or hydrochloric acid. It may be processed. Examples include baking under air, plasma treatment, and ozone treatment.

  The negative electrode material of the present invention is not particularly limited as long as it is a graphitized carbon particle, but examples thereof include natural graphite, artificial graphite, coke powder, needle coke powder, and powdered resin graphitized powder. It is done. Of these, natural graphite is preferable, and spheroidal graphite particles subjected to spheroidizing treatment are particularly preferable. The spherical graphite particles used in the present invention are preferably composed of a plurality of curved or bent scaly or scaly graphites and ground graphite fine powder. Graphite that has been further oxidized after the spherical treatment may be heat-treated. This may be achieved by subjecting the spherical treated graphite as a raw material to an additional mechanical grinding treatment for a long time, or contacting the graphite with oxygen gas, heated sulfuric acid, nitric acid, or hydrochloric acid. It may be processed. Examples include baking under air, plasma treatment, and ozone treatment.

  The heat treatment temperature is preferably 500 to 1250 ° C, more preferably 700 to 1100 ° C, and most preferably 800 to 1050 ° C. If the temperature is lower than this, the functional group on the outermost surface of the raw material graphite does not change to a preferable structure, and thus the effect of reducing the irreversible capacity is not sufficiently observed. Since the removal occurs remarkably, it lacks charge acceptance.

  These may be obtained by applying or coating a carbon precursor such as pitch, tar, or resin on graphite, and heat-treating it at an appropriate temperature. Since a part of the surface of graphite as a substrate is covered, the active surface where lithium enters and exits is reduced, and the rapid charge characteristic at room temperature is lacking. In addition, these precursors are often stochastically attached to the base graphite at the raw material mixing stage, so it is difficult to change the structure of only the graphite edge surface where lithium enters and exits. There is a concern that the reactivity to the electrolyte may be excessive. In the manufacturing process of this material, since a carbon source material other than graphite, such as pitch, is not used, a uniform process is possible. Moreover, since the mixing process of these raw materials can be omitted, there is an advantage that it can be provided easily and inexpensively to the process enemy.

  In this process, the nitrogen gas may be packed while nitrogen gas is flowed or when the material is sealed in a container used during the process while remaining air is expelled. Although air may be included, in that case, the surface functional group state is preferable when the treatment temperature is 950 ° C. or higher. In addition, when it processes in detail in a thermobalance nitrogen gas, an increase in weight may be observed, and when it measures using TPD-MS, it turns out that the addition is based on nitrogen gas. This phenomenon is also considered to be the cause of the basicity of the pH of the inventive material, and the weight increase rate is typically 7% by weight or less and 0% or more by weight with respect to the weight of the raw graphite.

When the carbonaceous particles (B) are mixed with the composite graphite particles (A) to form the negative electrode material, the mixing ratio of the carbonaceous particles (B) is such that the carbonaceous particles of less than 5 μm are mixed with the whole negative electrode material. In the case of mixing 0.1% by weight or more, preferably 0.5% by weight or more and 30% by weight or less, more preferably 1% by weight or more and 20% by weight or less. When carbonaceous particles of 5 μm or more are mixed, The content is preferably 5% by weight or more and 90% by weight or less, more preferably 10% or more and 70% by weight or less. When the mixing ratio of the carbonaceous particles (B) is less than the above range, the above effect of adding the carbonaceous particles (B) may be difficult to appear. On the other hand, when the above range is exceeded, it may be difficult to obtain the characteristics of the composite graphite particles (A).
The example of the manufacturing method of the negative electrode material of this invention is shown below.

<Manufacturing method 1>
The composite graphite particles of the present invention are mixed with spherical graphite particles as raw materials, a graphitizable binder (hereinafter also simply referred to as “binder”), etc., and molded, devolatilized component fired, graphite, if necessary. It is manufactured by performing crystallization, pulverization and classification. In order to produce the composite graphite particles of the present invention that satisfy the above-mentioned physical properties, it is important to combine the following ideas.

As a contrivance for the raw material, for example, spheroidized graphite having a high average circularity is selected as the main component of the spherical graphite particles.
In addition, when the spherical graphite particles and the binder are combined, a device for optimizing the type and amount of the pitch as the binder and the strength at the time of pulverization are optimized.
Hereinafter, a suitable method for producing the composite graphite particles of the present invention will be described in detail.
First, the spherical graphite particles and the binder are combined while being heated. At this time, a graphitization catalyst may be added if desired. Suitable carbonaceous particles, binders and graphitization catalysts are as follows.

(I) Spherical graphite particles As a main component of the spherical graphite particles, those having a high sphericity are preferable, and spheroidized natural graphite is particularly preferable from the viewpoint of obtaining a high tap density in order to improve coatability. A typical example is one using natural graphite with high crystallinity such that the (002) plane spacing (d ₀₀₂ ) of 0.340 nm or less by the X-ray wide angle diffraction method is 0.340 nm or less. Specifically, natural graphite or those obtained by adding a mechanically pulverized product to these to improve the circularity is preferable.

  The median diameter of the volume-based particle size distribution measured by laser diffraction / scattering particle size distribution measurement of the spherical graphite particles is not particularly limited, but is usually 5 μm or more, preferably 6 μm or more, particularly preferably 8 μm or more, and usually 60 μm or less. , Preferably 35 μm or less, particularly preferably 30 μm or less. If the median diameter of the carbonaceous particles deviates from the upper and lower limits, the carbon particles tend to cause defects during coating, and the porosity in the electrode tends to be lowered and the particle contact rate tends to be inappropriate. The median diameter of the carbonaceous particles can be measured in the same manner as the median diameter of the negative electrode material described above.

  The spherical graphite particles as the raw material for the composite graphite particles of the present invention are particularly preferably those that have undergone spheroidization treatment. As an apparatus used for the spheroidization treatment, for example, an apparatus that repeatedly gives mechanical action such as compression, friction, shearing force, etc. including the interaction of particles mainly with 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 the carbon material. Preferred devices include, for example, a hybridization system (manufactured by Nara Machinery Co., Ltd.), a kryptron (manufactured by Earth Technica), a CF mill (manufactured by Ube Industries), a mechano-fusion system (manufactured by Hosokawa Micron), and a theta composer (Tokuju Kosakusho). Etc.).

  Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable. When processing using this apparatus, the peripheral speed of the rotating rotor is preferably 30 to 100 m / sec, more preferably 40 to 100 m / s, and even more preferably 50 to 100 m / s. preferable. Further, the treatment can be performed by simply passing the carbonaceous material, but it is preferable to circulate or stay in the apparatus for 30 seconds or longer, and it is more preferable to circulate or stay in the apparatus for 1 minute or longer. preferable.

  The average circularity of the spherical graphite particles is usually 0.85 or more, preferably 0.9 or more, and usually 1.0 or less, preferably 0.96 or less. If the average circularity of the carbonaceous particles is below this lower limit, the degree of orientation tends to decrease, and if it exceeds the upper limit, the cost tends to increase. The average circularity of the spherical graphite particles is the same as the average circularity of the negative electrode material described above.

The tap density of the spherical graphite particles is usually 0.8 g / cm ³ or more, preferably 0.9 g / cm ³ or more, more preferably 0.95 g / cm ³ or more, and usually 1.4 g / cm ³ or less, preferably Is in the range of 1.2 g / cm ³ or less. When the tap density of the spherical graphite particles is below this range, the packing density when used as an active material is difficult to increase, and a high-capacity battery may not be obtained. On the other hand, if it exceeds this range, it becomes difficult to obtain spherical graphite particles with good yield, which may lead to an increase in cost. In addition, the measuring method of tap density is the same as the description of the composite graphite particle for secondary batteries.

The BET specific surface area of the spherical graphite particles is usually 2 m ² / g or more, preferably 3 m ² / g or more, more preferably 4 m ² / g or more, and usually 15 m ² / g or less, preferably 12 m.
² / g, more preferably 10 m ² / g. If the BET specific surface area of the spherical graphite particles deviates from this range from the upper and lower ranges, there is a possibility that the combination with the binder can be made uniform. Here, in this specification, the “spherical” of the spherical graphite particles means a shape including a shape close to a so-called sphere, such as an ellipsoid.

(Ii) Graphitizable binder Specific examples of the graphitizable binder include impregnated pitch, binder pitch, coal tar pitch, coal-based heavy oil such as coal liquefied oil, and straight-run heavy such as asphaltene. And heavy petroleum oils such as oils and cracked heavy oils such as ethylene heavy end tar.
The quinoline insoluble component contained in the binder is usually 0 to 30% by weight, but the smaller the amount, the better the reversible capacity. If the content of the quinoline-insoluble component in the binder is too large, the reversible capacity may decrease.

  In the binder, the ratio of the binder-derived material occupying the composite graphite particles obtained through carbonization / graphitization is usually 0.5% by weight or more, preferably 1% by weight or more, more preferably 3% by weight or more. It is used so that The upper limit is an amount such that this ratio is usually 60% by weight or less, preferably 40% by weight or less, and more preferably 30% by weight or less. If the amount of the binder is too large, the resulting composite graphite particles become stiff, so that when the active material layer applied to the current collector is rolled, the active material particles are easily destroyed. On the other hand, if the amount of the binder is too small, the effect derived from the binder is lost, and the active material particles are soft and particle breakage is likely to occur during rolling. Therefore, good battery characteristics may not be obtained at high density. .

The amount of the binder in the composite graphite particles is controlled by the amount of the binder added at the stage before combining. For example, when the residual carbon ratio of the binder obtained by the method described in JIS K2270 is p%, a desired amount of 100 / p times the binder is added.
In addition, as a device for adding a binder such as pitch and tar, it is preferable to uniformly disperse as much as possible at a low temperature and in a short time in order to reduce the initial irreversible capacity and the rolling load. In order to perform dispersion at a low temperature and in a short time, stirring should be strengthened to such an extent that the carbonaceous particles are not broken.

(Iii) Graphitization catalyst In order to increase the charge / discharge capacity and improve the rollability, a graphitization catalyst may be added when mixing the carbonaceous particles and the binder. Examples of the graphitization catalyst include metals such as iron, nickel, titanium, silicon, and boron, and compounds such as carbides, oxides, and nitrides thereof. Of these, silicon, silicon compounds, iron, and iron compounds are preferable, and silicon carbide is particularly preferable among silicon compounds, and iron oxide is particularly preferable among iron compounds.

  When silicon or a silicon compound is used as the graphitization catalyst, all of the silicon carbide produced by heating is pyrolyzed at a temperature of 2800 ° C. or higher to grow graphite with extremely good crystallinity, and when silicon is volatilized, graphite crystals Since pores are formed between them, the charge transfer reaction and diffusion of lithium ions inside the particles can be promoted, and the battery performance can be improved. Further, when iron or a compound thereof is used as the graphitization catalyst, graphite having good crystallinity can be grown by the mechanism of dissolution and precipitation of carbon in the catalyst, and the same effect as silicon can be exhibited.

The addition amount of these graphitization catalysts is usually 30% by weight or less, preferably 20% by weight or less, more preferably 10% by weight or less, and particularly preferably 5% by weight or less based on the carbonaceous primary particles as a raw material. . When there are too many graphitization catalysts, graphitization will advance too much and the characteristic at the time of lithium ion secondary battery manufacture, especially the problem that immersion property may not be enough may arise. At the same time, BR>. In order to generate pores in the graphite particles, the strength of the particles may decrease, and as a result, the surface may be smoothed during the rolling process during electrode preparation, and ion migration may be inhibited.
On the other hand, if the graphitization catalyst is too small, the graphitization is insufficient and the charge / discharge capacity of the non-aqueous secondary battery may be reduced, and a high pressure is required in the rolling process during electrode preparation. It may be difficult to increase the density.

(Iv) Combined (mixed)
Raw materials such as carbonaceous particles, a binder, and a graphitization catalyst added if desired are first combined under heating. As a result, the liquid binder is attached to the carbonaceous particles and the raw material that does not melt at the compounding temperature. In this case, all the raw materials may be charged into the compounding machine and the mixing and heating may be performed at the same time. Alternatively, components other than the binder may be charged into the compounding machine and heated in a stirred state. A sulfur melted binder may be charged.

  The heating temperature is equal to or higher than the softening point of the binder. If the heating temperature is too low, the viscosity of the binder becomes high and mixing becomes difficult. Therefore, the temperature is usually 10 ° C or higher than the softening point, preferably 20 ° C higher than the softening point. It is performed at a higher temperature. If the heating temperature is too high, the viscosity of the mixed system becomes too high due to the volatilization and polycondensation of the binder, and is usually 400 ° C. or lower, preferably 3000 ° C. or lower.

  The combination machine is preferably a model having a stirring blade, and the stirring blade may be a general-purpose one such as a Z type or a gusset type. The amount of raw material charged into the compounding machine is usually 10% by volume or more, preferably 15% by volume or more, and 50% by volume or less, preferably 30% by volume or less of the volume of the mixer. The mixing time is 5 minutes or more, and is the time until the maximum viscosity change due to the volatilization of the volatile matter at the longest, usually 30 to 120 minutes. The compounding machine is preferably preheated to the compounding temperature prior to compounding.

(V) Molding The obtained compound may be subjected to a removal VM firing step for the purpose of removing volatile components (hereinafter abbreviated as “VM”) and carbonization as it is, but for easy handling, It is preferable to use for a VM removal baking process after shaping | molding.
The molding method is not particularly limited as long as the shape can be maintained, and extrusion molding, mold molding, isostatic pressing, and the like can be employed. Among these, extrusion is easy to orient the particles in the molded body, and operation is relatively easy compared to isostatic pressing that maintains the random orientation of the particles but has a problem with productivity. Mold molding that can obtain a molded body without destroying the oriented structure is preferred.

  The molding temperature may be room temperature (cold) or under heating (hot, temperature above the softening point of the binder). In the case of cold forming, it is desirable to preliminarily crush the mixture cooled to a maximum size of 1 mm or less in advance in order to improve the moldability and obtain the uniformity of the formed body. The shape and size of the molded body are not particularly limited, but in hot forming, if the molded body is too large, there is a problem that it takes time to perform uniform preheating prior to molding. It is preferable to set it as the magnitude | size.

If the molding pressure is too high, removal of devolatilized components through the pores of the molded body (de-VM) becomes difficult, and carbonaceous particles that are not perfect circles may be oriented, making pulverization in subsequent processes difficult. Therefore, the upper limit of the molding pressure is usually 3 tf / cm ² (294 MPa) or less, preferably 500 kgf / cm ² (49 MPa) or less, more preferably 10 kgf / cm ² (0.98 MPa) or less. The lower limit pressure is not particularly limited, but is preferably set to such an extent that the shape of the molded body can be maintained in the VM removal step.

(Vi) De-VM firing In order to remove the carbonaceous particles and the volatile component (VM) of the binder, the obtained molded body prevents contamination of the filler during graphitization and fixing of the filler to the molded body. De-VM firing is performed. The de-VM firing is usually performed at a temperature of 600 ° C. or higher, preferably 650 ° C. or higher, usually 1300 ° C. or lower, preferably 1100 ° C. or lower, usually for 0.1 hour to 10 hours. In order to prevent oxidation, heating is usually performed in a non-oxidizing atmosphere in which an inert gas such as nitrogen or argon is circulated or a granular carbon material such as breeze or packing coke is filled in the gap.

  The equipment used for the de-VM firing is not particularly limited as long as it can be fired in a non-oxidizing atmosphere, such as an electric furnace, a gas furnace, and a lead hammer furnace for electrode materials. The heating rate during heating is desirably a low speed for removing volatile components. Usually, from about 200 ° C. where low-boiling components start to volatilize to about 700 ° C. where only hydrogen is generated, 3-100 ° C. The temperature is raised at / hr.

(Vii) Graphitization The carbide molded body obtained by de-VM firing is then graphitized by heating at a high temperature. The heating temperature during graphitization is usually 2600 ° C. or higher, preferably 2800 ° C. or higher. Moreover, since the sublimation of graphite will become remarkable when heating temperature is too high, 3300 degrees C or less is preferable. The heating time may be performed until the binder and the carbonaceous particles become graphite, and is usually 1 to 24 hours.

  In order to prevent oxidation, the atmosphere during graphitization is performed under a non-oxidizing atmosphere in which an inert gas such as nitrogen or argon is circulated or a granular carbon material such as breeze or packing coke is filled in the gap. The equipment used for graphitization is not particularly limited as long as it meets the above purpose, such as an electric furnace, a gas furnace, an electrode material Atchison furnace, etc. The heating rate, cooling rate, heat treatment time, etc. are acceptable for the equipment used. It can be set arbitrarily within the range.

(Viii) Grinding Usually, the graphitized product thus obtained does not satisfy the requirements of the present invention as it is, and is thus ground or ground. The process is roughly divided into three steps: coarse pulverization, medium pulverization, and fine pulverization.
The method for pulverizing and grinding the graphitized product is not particularly limited, but as a means for pulverizing and grinding, for example, a mechanical grinding means such as a ball mill, a hammer mill, a CF mill, an atomizer mill, a pulverizer, Examples thereof include a pulverizing means using wind power, such as a jet mill. For coarse pulverization and medium pulverization, a pulverization method using impact force such as a jaw crusher, a hammer mill, or a roller mill may be used. Here, the timing of pulverization may be before graphitization or after graphitization. The latter is more preferable because an operation such as crucible filling is unnecessary and can be manufactured at low cost.

(Viii-1) Coarse pulverization, medium pulverization In order to satisfy the requirements described in the present invention, in the coarse pulverization / medium pulverization of the graphitized product, for example, “VM-32 type pulverizer manufactured by Orient Kogyo Co., Ltd.” is used. When used, the graphitized material is carried into a pulverizer at a speed of 300 kg / min with a belt-conveying feeder, and pulverized and ground at a rotation speed of pulverization blades of 1000 rpm / min or more. In addition, if excessive pulverization / grinding is performed in this pulverization stage, a lot of fine powder is generated on the surface of the graphitized particles. The irreversible capacity during discharge may increase.

(Viii-2) Fine pulverization Further, in the fine pulverization, for example, when using “TB-250 type pulverizer manufactured by Turbo Kogyo Co., Ltd.”, the graphitized material is 50 kg / min with a quantitative spiral feeder. Carry in and grind at 55 kg / min or 60 kg / min. If the speed at which the graphitized material is carried into the pulverizer is increased, the specific surface area of the graphitized material after pulverization may decrease when the rotation speed of the pulverization blade is kept constant.

  In order to satisfy the requirements described in the present invention, the rotation speed of the pulverization blades during fine pulverization is, for example, 6450 rotations / minute, 7800 rotations / minute, or 8000 rotations when using a “TB-250 type pulverizer manufactured by Turbo Industries” Grind at / min. When the rotation speed of the pulverization blade of the pulverizer is increased during fine pulverization, the specific surface area of the graphitized material after pulverization increases when the carry-in speed of the graphitized material is constant.

(Ix) Classification Large particles / small particles (fine powder) may be removed from the obtained pulverized or ground product as necessary.
By removing the large-diameter granular material, occurrence of a short circuit and unevenness during application may be reduced. Moreover, the initial irreversible capacity may be reduced by removing small-diameter granular materials (fine powder). In addition, by removing large particles and fine particles, the volume reference particle size distribution by laser diffraction / scattering particle size measurement is such that the particle size of 100 μm or more is 3% by volume or less and the particle size is 1 μm or less. It is desirable to adjust the size so that the total amount is 1% by volume or less.

  There are various methods for removing large-diameter granular materials and small-diameter granular materials, but it is preferable to remove them by sieving and classification in terms of simplicity of the equipment, operability and cost. Furthermore, sieving or classification has the advantage that the particle size distribution and average particle size of the composite graphite particles can be readjusted as needed by changing the graphitization and removal of the particulates.

  There are several types of sieving to remove large-diameter granular materials, such as fixed screen, in-plane motion, and rotary sieve. From the viewpoint of processing capacity, the blow-through type screen in the fixed screen is used. Particularly preferred. The size of the sieve mesh used can be any if it is 80 μm or less and 30 μm or more, and the production status (particularly the amount and particle size) of the particulates to be removed, the particle size distribution and average of the composite graphite particles Select and use as appropriate according to the particle size adjustment requirements. When the size exceeds 80 μm, the removal of the particulate matter becomes insufficient. When the size is less than 30 μm, it leads to excessive removal of composite graphite particles, resulting in a lot of product loss and adjustment of the particle size distribution. There is a case. In addition, sieves with a mesh size of 45 μm and 38 μm that are commercially available as general-purpose sizes can be preferably used.

  Classification can be performed by methods such as wind classification, wet classification, and specific gravity classification, and is not particularly limited for removing particulates of 100 μm or more, but the influence on the properties of the composite graphite particles and the particle size distribution of the composite graphite particles In consideration of adjusting the average particle size, it is preferable to use an air classifier such as a swirling flow classifier. In this case, by controlling the air volume and the wind speed, it is possible to adjust the removal of the particulate matter and the particle size distribution and average particle size of the composite graphite particles, as well as adjusting the size of the mesh openings. .

(Manufacturing method 2)
Spherical graphite particles and scaly particles or a mixture thereof and a binder are mixed, and the binder becomes carbonaceous or graphitic by heat treatment, for example, carbonization and / or graphitization. Specifically, heat treatment is performed in a powder state without molding the combined product in the same manner as in manufacturing method 1. The amount of the binder to be mixed at the time of mixing is such that the carbonaceous material derived from the binder occupied in the finally obtained composite graphite particles, or the ratio of the graphite is usually 0.1% by weight or more, preferably 1% by weight or more. Preferably, it is 1.5% by weight or more. The upper limit is an amount such that this ratio is usually 15% by weight or less, preferably 10% by weight or less, more preferably 8% by weight or less. For the binder amount and heat treatment, the Raman R value measured by the above method is preferably 0.1 or more and 0.3 or less, more preferably 0.15 or more and 0.28 or less, particularly preferably 0.18. As mentioned above, it is possible to select freely so that it may become 0.25 or less.

(Definition of Raman R value)
In the Raman spectrum obtained in the Raman measurement as described later, the intensity _{I A} of the maximum peak around 1580 cm ^-1, the intensity ratio _I B / _{I A} Raman R value of the intensity _{I B} of the maximum peak in the vicinity of 1360 cm ^-1 It is defined as
Maximum peak around 1580 cm ^-1 is a peak derived from a graphite crystalline structure, the maximum peak in the vicinity of 1360 cm ^-1 is a peak derived from reduced carbon atoms symmetry by structural defects.

Raman measurement uses a Raman spectrometer “Raman Spectrometer manufactured by JASCO Corporation”. Samples are filled by letting the particles to be measured fall naturally into the measurement cell, and the measurement cell is irradiated with an argon ion laser beam. Measurement is performed while rotating the cell in a plane perpendicular to the laser beam. The measurement conditions are as follows.
Argon ion laser light wavelength: 514.5 nm
Laser power on sample: 15-25mW
Resolution: 14cm ^-1
Measurement ^range: 1100cm ^-1 ~1730cm -1 peak intensity measurement, peak half-width measurement: background processing, smoothing processing
(Simple average, 5 points of convolution)
Maximum peak around 1580 cm ^-1 is a peak derived from a graphite crystalline structure, the maximum peak in the vicinity of 1360 cm ^-1 is a peak derived from reduced carbon atoms symmetry by structural defects.

<Range>
The Raman R value of the graphite particles of the present invention is 0.13 or more, preferably 0.15 or more, particularly preferably 0.18 or more. When the Raman R value is below this lower limit, the amount of lithium metal deposited on the negative electrode surface accompanying charge / discharge tends to increase.

<Active material orientation ratio when electrode is formed>
The active material orientation ratio of the electrode formed so that the electrode density is 1.7 ± 0.03 g / cm ³ using the graphite material of the present invention as an active material is usually 0.05 or more, preferably 0.06 or more, Moreover, it is 0.15 or less normally, Preferably it is 0.14 or less. If it falls below the range, the charge acceptability tends to decrease. On the other hand, if it exceeds the range, the particles tend to be very hard, and it may be difficult to roll the electrode to a desired electrode density. .
Here, the active material orientation ratio of the electrode is an index representing the degree of orientation of the hexagonal network surface of the graphite crystal with respect to the thickness direction of the electrode. A larger orientation ratio represents a state in which the directions of the graphite crystal hexagonal planes of the particles are not aligned.
The specific procedure for measuring the active material orientation ratio of the electrode is the same as described in the examples below.

<Measurement of active material orientation ratio>
About the electrode after rolling, the active material orientation ratio of the electrode is measured by X-ray diffraction. Although a specific method is not particularly limited, as a standard method, a chart of (110) plane and (004) plane of graphite is measured by X-ray diffraction, and asymmetric Pearson VII is used as a profile function for the measured chart. Peak separation by fitting with (110)
) Plane and (004) plane peak integrated intensity is calculated. From the obtained integrated intensity, a ratio represented by (110) area intensity / (004) area intensity is calculated and defined as the active material orientation ratio of the electrode.

The X-ray diffraction measurement conditions here are as follows. In the following description, 2θ represents a diffraction angle.
Target: Cu (Kα ray) graphite monochromator Slit: Divergence slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree Measurement range and step angle / measurement time:
(110) plane: 76.5 degrees ≦ 2θ ≦ 78.5 degrees 0.01 degrees / 3 seconds (004) plane: 53.5 degrees ≦ 2θ ≦ 56.0 degrees 0.01 degrees / 3 seconds Sample preparation: glass Fix the electrode to the plate with double-sided tape with a thickness of 0.1 mm As described above, determine the active material orientation ratio by X-ray diffraction for the electrode formed to have an electrode density of 1.7 ± 0.03 g / cm ^3. be able to.

[3] Negative electrode for non-aqueous secondary battery The composite graphite particles of the present invention can be suitably used as a negative electrode material for non-aqueous secondary batteries, particularly lithium ion secondary batteries. Further, as described above, the compounded graphite particles (A) and carbonaceous particles (B) of the present invention can be suitably used as the negative electrode material.
Although there is no restriction | limiting in particular as an apparatus used for mixing a composite graphite particle (A) and a carbonaceous particle (B), For example, as a rotary mixer, a cylindrical mixer, a twin cylinder mixer, a double cone Type mixers, regular cubic mixers, vertical mixers, etc. Fixed type mixers include spiral mixers, ribbon mixers, Muller type mixers, Helical Flight type mixers, Pugmill type mixers Machine, fluidized mixer and the like.

  The negative electrode constituting the non-aqueous secondary battery is formed by forming an active material layer containing a negative electrode material, an electrode molding binder, a thickener, and a conductive material on a current collector. The active material layer is usually obtained by preparing a slurry containing a negative electrode material, an electrode forming binder, a thickener, a conductive material and a solvent, and applying, drying and rolling the slurry on a current collector.

  As the electrode forming binder, any material can be used as long as it is a material that is stable with respect to the solvent and the electrolyte used during electrode production. Examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, styrene / butadiene rubber, isoprene rubber, butadiene rubber, ethylene-acrylic acid copolymer, and ethylene-methacrylic acid copolymer. The electrode forming binder is a weight ratio of negative electrode material / electrode forming binder of usually 90/10 or more, preferably 95/5 or more, and usually 99.9 / 0.1 or less, preferably 99.3. /0.7 or less is used.

Examples of the thickener include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, polyvinyl alcohol, oxidized starch, phosphorylated starch, and casein.
Examples of the conductive material include metal materials such as copper and nickel, and carbon materials such as graphite and carbon black.

Examples of the material of the current collector include copper, nickel, and stainless steel. Among these, a copper foil is preferable from the viewpoint of easy processing into a thin film and cost.
Although the electrode active material density varies depending on the application, it is usually 1.70 g / cm ³ or more in applications where capacity is important, but is preferably 1.75 g / cm ³ or more, and more preferably 1.78 g / cm ³ or more. . If the density is too low, the battery capacity per unit volume may not always be sufficient. Further, if the density is too high, the battery characteristics are generally deteriorated, so 2.00 g / cm ³ or less is preferable. Here, the electrode active material density means a mixture layer made of an active material on the current collector, an electrode molding binder, a thickener, a conductive material, etc., and the density is the value at the time of assembling the battery. It refers to the density of the active material layer.

[4] Nonaqueous secondary battery The negative electrode for a nonaqueous secondary battery of the present invention produced using the composite graphite particles of the present invention and the negative electrode material of the present invention is a nonaqueous secondary battery such as a lithium ion secondary battery. It is extremely useful as a negative electrode for a battery.
There is no particular limitation on the selection of members necessary for the battery configuration such as the positive electrode and the electrolytic solution constituting such a non-aqueous secondary battery. Although the material of the member which comprises a non-aqueous secondary battery etc. is illustrated below, the material which can be used is not limited to these specific examples.

The nonaqueous secondary battery of the present invention usually has at least the above-described negative electrode, positive electrode and electrolyte of the present invention.
The positive electrode is formed by forming an active material layer containing a positive electrode active material, a conductive agent, and an electrode forming binder on a positive electrode current collector. The active material layer is usually obtained by preparing a slurry containing a positive electrode active material, a conductive agent and an electrode molding binder, and applying and drying the slurry on a current collector.

Examples of the positive electrode active material include lithium transition metal composite oxide materials such as lithium cobalt oxide, lithium nickel oxide, and lithium manganese oxide; transition metal oxide materials such as manganese dioxide; carbonaceous materials such as graphite fluoride A material capable of inserting and extracting lithium, such as lithium, can be used. Specifically, for example, LiFePO ₄ , LiFeO ₂ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ and non-stoichiometric compounds thereof, MnO ₂ , TiS ₂ , FeS ₂ , Nb ₃ S ₄ , Mo ₃ S ₄ , can be used _{CoS 2, V 2 O 5,} P 2 O 5, CrO 3, V 3 O 3, TeO 2, GeO 2 or the like.

  As the positive electrode current collector, it is preferable to use a metal or an alloy thereof that forms a passive film on the surface by anodic oxidation in an electrolytic solution, and a metal belonging to group IIIa, IVa, or Va (group 3B, 4B, or 5B). And alloys thereof. Specifically, for example, Al, Ti, Zr, Hf, Nb, Ta and alloys containing these metals can be exemplified, and Al, Ti, Ta and alloys containing these metals are preferably used. Can do. In particular, Al and its alloys are desirable because of their light weight and high energy density.

Examples of the electrolyte include an electrolytic solution, a solid electrolyte, a gel electrolyte, and the like, and among them, an electrolytic solution, particularly a nonaqueous electrolytic solution is preferable. As the non-aqueous electrolyte solution, a solution obtained by dissolving a solute in a non-aqueous solvent can be used.
As the solute, an alkali metal salt, a quaternary ammonium salt, or the like can be used. Specifically, for example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C _It is preferable to use one or more compounds selected from the group consisting of ₄ F ₉ SO ₂ ) and LiC (CF ₃ SO ₂ ) ₃ .

  Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate and butylene carbonate, cyclic ester compounds such as γ-butyrolactone; chain ethers such as 1,2-dimethoxyethane; crown ether, 2-methyltetrahydrofuran, 1,2 -Cyclic ethers such as dimethyltetrahydrofuran, 1,3-dioxolane and tetrahydrofuran; chain carbonates such as diethyl carbonate, ethylmethyl carbonate and dimethyl carbonate can be used. One kind of solute and solvent may be selected and used, or two or more kinds may be mixed and used. Among these, the non-aqueous solvent preferably contains a cyclic carbonate and a chain carbonate. In addition, compounds such as vinylene carbonate, vinyl ethylene carbonate, succinic anhydride, maleic anhydride, propane sultone, and diethyl sulfone may be added.

The content of these solutes in the electrolytic solution is preferably 0.2 mol / L or more, particularly preferably 0.5 mol / L or more, preferably 2 mol / L or less, and particularly preferably 1.5 mol / L or less. .
Among these, the non-aqueous secondary battery prepared by combining the negative electrode of the present invention, the metal chalcogenide-based positive electrode, and the organic electrolyte mainly composed of a carbonate-based solvent has a large capacity and an irreversible capacity that is recognized in the initial cycle. , High rapid charge / discharge capacity, excellent cycle characteristics, high storage stability and reliability of the battery when left at high temperature, and extremely excellent high-efficiency discharge characteristics and low-temperature discharge characteristics.

  A separator is usually provided between the positive electrode and the negative electrode so that the positive electrode and the negative electrode are not in physical contact. The separator preferably has high ion permeability and low electrical resistance. The material and shape of the separator are not particularly limited, but those that are stable with respect to the electrolyte and excellent in liquid retention are preferable. Specifically, a porous sheet or a non-woven fabric made of a polyolefin such as polyethylene or polypropylene is used.

  The shape of the non-aqueous secondary battery of the present invention is not particularly limited, and a cylinder type in which a sheet electrode and a separator are spiral, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a coin in which a pellet electrode and a separator are stacked Type.

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.
Example 1
Spherical graphite particles having an average particle diameter of 16 μm were obtained by subjecting graphite particles having an average particle diameter of 100 μm to spheroidization treatment for 9 minutes at a rotor peripheral speed of 70 m / sec using a hybridization system NHS-3 manufactured by Nara Machinery Co., Ltd.

The spherical graphite particles and a binder pitch having a softening point of 90 ° C. as a graphitizable binder are mixed at a weight ratio of 100: 30, and put into a kneader having a gussetar type stirring blade preheated to 130 ° C. Combined for 20 minutes.
The fully mixed mixture is filled into a mold of a mold rolling mill preheated to 110 ° C., and left for 5 minutes. When the temperature of the mixture is stabilized, the plunger is pushed and 2 kgf / cm ³ (0.20 MPa). Was molded by applying a pressure of. After maintaining this pressure for 1 minute, driving was stopped, and after the pressure drop had subsided, the molded body was taken out.

The obtained molded body was housed in a metal sagar as a heat-resistant container, and the gap was filled with graphite breeze. The temperature was raised from room temperature to 1000 ° C. in an electric furnace over 48 hours, held at 1000 ° C. for 3 hours, and de-VM firing was performed. Next, the compact was stored in a graphite crucible and filled with graphite breeze in the gap. Graphitization was performed by heating to 3000 ° C. for 4 hours in an Atchison furnace.
The obtained graphite compact was roughly crushed with a jaw crusher, and then finely pulverized with a mill whose pulverization blade rotation speed was set to 8000 rpm, and the coarse particles were removed with a 45 μm sieve to obtain composite graphite particles. . The composite graphite particles and spherical graphite particles mixed at a ratio of 6: 4 was used as the negative electrode material of Example 1. The negative electrode material had a median diameter of 18 μm, a BET specific surface area of 4.3 m ² / g, and a Tap density of 1.13 g / cm ³ .

<Electrode production method>
A negative electrode material, a CMC aqueous solution as a thickener, and an SBR dispersion as a binder were mixed and stirred to a slurry so that CMC and SBR were 1% by weight with respect to the negative electrode material after drying. The slurry was applied onto the copper foil using a blade. For the coating thickness, the gap was selected so that the electrode basis weight (excluding the copper foil) after drying was 11.8 mg / cm ² .

After this electrode was dried at 110 ° C. in a nitrogen stream atmosphere, the electrode density (excluding copper foil) was 1.8.
Rolling was performed so as to be ± 0.03 g / cm ³ . In addition, a 12.5 mmφ electrode was punched from the rolled electrode, and the weight of the negative electrode active material was determined from the following formula based on the weight.
(Weight of negative electrode active material) = (Weight of electrode) − (Copper foil weight) − (Binder amount) − (Thickener weight)
<Electrode rolling method>
Rolling was performed using a roll having a diameter of 25 cm so that the electrode density (excluding copper foil) was 1.8 ± 0.03 g / cm ³ to obtain a desired negative electrode.

<Method for producing lithium secondary battery>
After the electrode produced by the above electrode production method was vacuum dried at 110 ° C., it was transferred to a glove box, and in an argon atmosphere, as an electrolyte, ethylene carbonate (EC) / dimethyl carbonate (DMC) / ethyl methyl carbonate (EMC) = A coin battery (lithium secondary battery) was prepared using a 1M-LiPF ₆ electrolyte solution with a 2/3/3 mixed solution as a solvent, a polyethylene separator as a separator, and a lithium metal counter electrode as a counter electrode.

<Measurement method of discharge capacity>
The lithium counter electrode is charged to 5 mV at a current density of 0.2 mA / cm ² , and further charged to a current value of 0.02 mA at a constant voltage of 5 mV. A charge / discharge cycle of discharging to 1.5 V with respect to the lithium counter electrode at a current density of 4 mA / cm ² was repeated three times, and the discharge value at the third cycle was measured as the discharge capacity.

<Calculation method of irreversible capacity for first charge / discharge>
When measuring the discharge capacity, it was calculated according to the following.
Initial charge / discharge irreversible capacity (mAh / g) =
Initial charge capacity (mAh / g)-Initial discharge capacity (mAh / g)

<Calculation method of discharge load characteristics>
Following the measurement of the discharge capacity, the battery was charged in the same manner, and then discharged at a current density of 10.0 mA / cm ² .
-2C discharge capacity (mAh / g):
Discharge capacity when discharged at a current density of 10.0 (mA / cm ² ) · 0.2 C discharge capacity (mAh / g):
Discharge capacity and load characteristics (%) when discharged at a current density of 1 (mA / cm ² ) =
{2C discharge capacity (mAh / g) /0.2C discharge capacity (mAh / g)} × 100

<Charge acceptance test>
A coin battery was prepared by the method described above, charged and discharged three times at 25 ° C. under the same conditions as in the discharge capacity measurement, and then charged at 0 ° C. with a current density of 1 mA / cm ² . The charging capacity at this time is called a charge acceptance value.
Charge acceptance value (mAh / g) = 0.2C charge capacity (mAh / g)

<Method for producing cycle test laminate>
The negative electrode sheet produced by the above method was punched into a 4 cm × 3 cm plate to make a negative electrode, and a positive electrode made of LiCoO ₂ was punched in the same area and combined. The electrolyte was 1M-LiP using a 3/7 mixture of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) as a solvent.
To F ₆ electrolytic solution used was a vinylene carbonate was added 2% by weight further additives. A separator (made of a porous polyethylene film) was sandwiched between the positive electrode and the negative electrode, and the electrolyte solution was injected. Then, the laminate film was sealed with a vacuum sealer to produce a laminate type battery.

In the cycle test, constant current (CC) charging / discharging was repeated 4 times at a current density of 14 mA / cm ² , and then charged at a constant current constant voltage (CC-CV) to 4.2 V at a current density of 49 mA / cm ² . A constant current discharge is performed up to 3.0 V at a current density of 70 mA / cm ² , and this is repeated as 200 cycles. The cycle maintenance rate (%) was calculated by the following method.
Cycle maintenance ratio (%) = discharge capacity at 200 cycles (mAh) × 100 / discharge capacity at the first cycle (mAh)
Table 1 shows the results of the cycle test performed by this method.

  Further, when image analysis was performed by the above-described method from a cross-sectional photograph of this electrode, the porosity in the electrode was 10.6% and the particle contact rate was 32.1%. Further, the increase rate from 1 to 4 μm in the equal area circle diameter was 9.0%, the increase rate from 4 to 12 μm was 49.6%, and the increase rate from 8 to 12 μm was 29.3%. The solvent permeation time was 24 seconds.

(Example 2)
A mixture of the composite graphite particles obtained in Example 1 and the lightly spheroidized graphite particles in a weight ratio of 6: 4 was used as the negative electrode material of Example 2. The negative electrode material had a median diameter of 13 μm, a BET specific surface area of 4.6 m 2 / g, and a Tap density of 0.91 g / cm 3. Specifically, the lightly spheroidized graphite particles were obtained by subjecting graphite particles having an average particle size of 100 μm to a hybridization system NHS-3 manufactured by Nara Machinery Co., Ltd. for 5 minutes at a rotor peripheral speed of 50 m / sec.

  In the same manner as in Example 1, an electrode (negative electrode sheet) of the negative electrode material of Example 2 and a non-aqueous secondary battery were produced, and battery characteristics were measured. These measurement results are shown in Table 1. Further, when image analysis was carried out by the above-described method from a cross-sectional photograph of this electrode, the in-electrode porosity was 9.1% and the particle contact rate was 44.2%. Furthermore, the increase rate from 1 to 4 μm in the equal area circle diameter was 10.6%, the increase rate from 4 to 12 μm was 55.0%, and the increase rate from 8 to 12 μm was 32.1%. The solvent penetration time was 29 seconds.

(Example 3)
As in Example 1, graphite particles having an average particle diameter of 100 μm were subjected to spheroidization treatment for 9 minutes at a rotor peripheral speed of 70 m / sec using a hybridization system NHS-3 manufactured by Nara Machinery Co., Ltd., and spherical particles having an average particle diameter of 16 μm. Graphite particles were obtained.
The spherical graphite particles and a binder pitch having a softening point of 90 ° C. as a graphitizable binder are mixed at a weight ratio of 100: 6 and put into a kneader having a gussetar type stirring blade preheated to 130 ° C. Combined for 20 minutes.

The fully combined mixture was stored in a metal sagar as a heat-resistant container and sealed in a nitrogen atmosphere. The temperature was raised from room temperature to 1000 ° C. in an electric furnace over 48 hours, held at 1000 ° C. for 3 hours, and de-VM firing was performed. Next, the fired powder was stored in a graphite crucible and heated in an Atchison furnace for 4 hours.
The obtained graphite was finely pulverized with a mill having a blade rotation speed set to 3000 rpm, and coarse particles were removed with a 45 μm sieve to obtain composite graphite particles. The composite graphite particles and spherical graphite particles mixed at a ratio of 6: 4 was used as the negative electrode material of Example 3. The negative electrode material had a median diameter of 19 μm, a BET specific surface area of 4.4 m ² / g, and a tap density of 1.07 g / cm ³ . In the same manner as in Example 1, an electrode (negative electrode sheet) of a negative electrode material and a non-aqueous secondary battery were prepared, and battery characteristics were measured. These measurement results are shown in Table 1. Further, when image analysis was performed by the above-described method from the cross-sectional photograph of this electrode, the in-electrode void ratio was 10.1% and the particle contact ratio was 31.3%. Further, the increase rate from 1 to 4 μm in the equal area circle diameter was 9.5%, the increase rate from 4 to 12 μm was 51.2%, and the increase rate from 8 to 12 μm was 30.4%. The solvent penetration time was 25 seconds.

Example 4
The composite graphite particles obtained in Example 1 and the lightly spheroidized graphite particles used in Example 2 were further heat-treated at 1000 ° C. and mixed at a weight ratio of 6: 4 with the negative electrode material of Example 4 did. The negative electrode material had a median diameter of 14 μm, a BET specific surface area of 4.8 m ² / g, and a tap density of 0.90 g / cm ³ .

In the same manner as in Example 1, an electrode (negative electrode sheet) of the negative electrode material of Example 4 and a non-aqueous secondary battery were produced, and battery characteristics were measured. These measurement results are shown in Table 1. Further, when image analysis was performed by the above-described method from the cross-sectional photograph of this electrode, the in-electrode porosity was 8.9% and the particle contact rate was 44.1%. Furthermore, the increase rate from 1 to 4 μm in the equal area circle diameter is 10.1%.
The increase rate from 4 to 12 μm was 54.3%, and the increase rate from 8 to 12 μm was 32.0%. The solvent penetration time was 29 seconds.

(Comparative Example 1)
Using scaly graphite particles having a median diameter of 5 μm, a tap density of 0.4 g / cm ³ , and a BET specific surface area of 12 m ² / g as raw materials, the same binder, mixing, molding, firing, and graphitization as in Example 1 were performed. The grinding process was performed. The graphite particles thus obtained were used as the negative electrode material of Comparative Example 2. The negative electrode material has a median diameter of 18 μm, a BET specific surface area of 4.5 m ² / g, and a tap density of 0.84 g /
cm ³ .

  In the same manner as in Example 1, an electrode (negative electrode sheet) of a negative electrode material and a non-aqueous secondary battery were prepared, and battery characteristics were measured. These measurement results are shown in Table 1. Further, when image analysis was carried out by the above-described method from a cross-sectional photograph of this electrode, the porosity in the electrode was 7.4% and the particle contact ratio was 49.3%. Further, the increase rate from 1 to 4 μm in the equal area circle diameter was 39.4%, the increase rate from 4 to 12 μm was 37.4%, and the increase rate from 8 to 12 μm was 16.4%. The solvent penetration time was 31 seconds.

(Comparative Example 2)
The spherical graphite particles used as the raw material of Example 1 were used as the negative electrode material of Comparative Example 2. The negative electrode material had a median diameter of 17 μm, a BET specific surface area of 6.5 m ² / g, and a tap density of 1.07 g / cm ³ .
In the same manner as in Example 1, an electrode (negative electrode sheet) of the negative electrode material of Comparative Example 1 and a nonaqueous secondary battery were produced, and the battery characteristics were measured. These measurement results are shown in Table 1. Further, when image analysis was carried out by the above-described method from a cross-sectional photograph of this electrode, the in-electrode porosity was 5.1% and the particle contact rate was 60.8%. Further, the increase rate from 1 to 4 μm in the equal area circle diameter was 7.1%, the increase rate from 4 to 12 μm was 45.2%, and the increase rate from 8 to 12 μm was 25.9%. The solvent penetration time was 80 seconds.

In Examples 1 to 4, it can be seen from the high in-electrode porosity and solvent penetration time that lithium ion diffusion is excellent, and accordingly, a small initial irreversible capacity, high discharge load characteristics, and high charge acceptance. Indicated. Furthermore, Examples 1 to 4 were excellent in cycle characteristics due to an appropriate particle contact rate. On the contrary, in Comparative Examples 1 and 2, it can be seen that the voids in the electrode are remarkably small from the low porosity in the electrode and the extremely slow solvent penetration time.
This is considered to have occurred due to the destruction of the negative electrode material particles during the electrode rolling, and resulted in a decrease in initial irreversible capacity, discharge load characteristics, charge acceptance, and cycle characteristics.

  When the composite graphite particles for a non-aqueous secondary battery of the present invention are used, the active material layer on the negative electrode current collector is densified by the equal area circle diameter, the in-electrode porosity, and the particle contact rate specific to the particles. Even in this case, it is possible to provide a non-aqueous secondary battery having a small initial charge / discharge load reverse capacity, a high capacity, and excellent discharge load characteristics, charge acceptability, cycle characteristics, and electrolyte permeability.

Claims (7)

A method for producing composite graphite particles for a non-aqueous secondary battery comprising a composite of graphite particles and carbonaceous or graphite, comprising the following steps 1 to 3 for a non-aqueous secondary battery A method for producing composite graphite particles.
Step 1: Step of mixing graphite particles and graphitizable binder Step 2: Step of forming pressure by applying pressure to the mixture obtained in Step 1 Step 3: Step of firing the molded product obtained in Step 2   The method for producing composite graphite particles for a non-aqueous secondary battery according to claim 1, wherein the molding method in step 2 is selected from the group consisting of an extrusion molding method, a mold molding method, and a hydrostatic pressure molding method.   The method for producing composite graphite particles for a non-aqueous secondary battery according to claim 1, further comprising a pulverizing step.   The method for producing composite graphite particles for a non-aqueous secondary battery according to any one of claims 1 to 3, wherein the mixing temperature in step 1 is equal to or higher than the softening point of the binder.   The composite graphite particle for non-aqueous secondary batteries manufactured using the manufacturing method of any one of Claim 1 to 4.   A negative electrode having a current collector and an active material layer formed thereon, wherein the active material layer is formed using the composite graphite particles for a non-aqueous secondary battery according to claim 5. A negative electrode for a non-aqueous secondary battery.   A nonaqueous secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode is a negative electrode for a nonaqueous secondary battery according to claim 6. Water-based secondary battery.