KR20140016925A - Graphite particles for nonaqueous secondary battery and method for producing same, negative electrode and nonaqueous secondary battery - Google Patents

Abstract

Provided is a negative electrode material for a non-aqueous secondary battery having a high capacity and good cycle characteristics. The negative electrode material for non-aqueous secondary batteries as graphite particle which satisfy | fills three requirements of following (A), (B), (C). (A) The DBP oil absorption amount is 0.42 ml / g or more and 0.85 ml / g or less. (B) The specific surface area is 0.5 m <2> / g or more and 6.5 m <2> / g or less. (C) Raman R value is 0.03 or more and 0.19 or less.

Description

Graphite particles for a non-aqueous secondary battery, a method for manufacturing the same, a negative electrode and a non-aqueous secondary battery TECHNICAL FIELD

The present invention relates to graphite particles used for a non-aqueous secondary battery, a negative electrode formed by using the graphite particles, and a non-aqueous secondary battery having the negative electrode.

In recent years, with the miniaturization of electronic devices, the demand for high capacity secondary batteries is increasing. In particular, attention has been paid to lithium-ion secondary batteries having higher energy density and excellent high-current charge / discharge characteristics than nickel-cadmium batteries and nickel-hydrogen batteries. Conventionally, although high capacity | capacitance of a lithium ion secondary battery has been extensively examined, as the demand for high performance regarding a lithium ion secondary battery increases in recent years, it is required to satisfy | fill further high capacity | capacitance, large current charge-discharge characteristics, high temperature storage characteristics, and high cycle characteristics.

As a negative electrode material of a lithium ion secondary battery, graphite material and amorphous carbon are used in many cases from cost and durability. However, the amorphous carbon material has a problem that the reversible capacity in the material range that can be put to practical use is small, and the capacity of the active material layer is difficult to be increased, leading to high capacity. Graphite materials can obtain a capacity close to 372 mAh / g, which is a theoretical capacity for lithium occlusion, and are known to be suitable as an active material. On the other hand, when the active material layer containing the negative electrode material is made high in order to increase the capacity, problems such as increase in charge / discharge irreversible capacity during initial cycle, decrease in large current charge / discharge characteristics, and deterioration in cycle characteristics are caused by material destruction and deformation. there was.

In order to solve the said problem, for example, as a carbon material, by using the high density isotropic graphite powder which has oil absorption amount, powder volume density, particle size distribution, and specific resistance in a specific range, it is excellent in electroconductivity, It is disclosed that the carbon material for lithium secondary battery negative electrode which is excellent in adhesiveness, has large discharge capacity, small initial irreversible capacity, and excellent cycle characteristics.

In patent document 2, the carbon material for lithium secondary battery negative electrodes which is excellent in immersion property and excellent in cycling characteristics is obtained by mixing two types of graphite powders with the same grinding | pulverization ease, and the oil absorption amount and circularity of a powder are different. It is disclosed that it can.

Japanese Patent Publication No. 3605256 Japanese Unexamined Patent Publication No. 2010-92649

In the technique described in Patent Document 1, graphite powder is produced by mixing pitch with coke, forming by cold hydrostatic molding, heat treating the obtained molded body to form a high density isotropic graphite block, and then pulverizing and classifying. However, according to the studies by the present inventors, since the material is hard when the molded body is pulverized, the specific surface area becomes large and the reactivity with the electrolyte solution cannot be suppressed, resulting in a problem of lowering initial efficiency and lowering cycle characteristics. It became.

In the technique described in Patent Literature 2, as a starting material, flaky natural graphite and coke having a low circularity and pitch and spherical natural graphite having a high circularity are molded, calcined, and graphitized separately to obtain DBP oil absorption. The graphite powder which is 50-90 ml / 100g and 30-45 ml / 100g is obtained. By mixing these two, a material having a high DBP oil absorption and a low specific surface area is obtained. However, since two kinds of mixtures are used, there is a problem in uniformity in the micro-regions in the electrode. In the part where a lot of graphite derived from natural graphite exists, the movement of Li ions is slowed in the high-density electrode, and since the Raman R value is not specified, the water solubility (reactivity) of Li falls and the density of the active material layer is increased. High capacity was difficult and the large current charge-discharge characteristics were insufficient. Moreover, since two types of materials are manufactured separately, there existed a problem that a manufacturing method was complicated.

This invention is made | formed in view of such a background art, The subject is a negative electrode material for manufacturing the lithium ion secondary battery which is high in initial stage efficiency and excellent cycling characteristics also at the time of high current charge / discharge even when the negative electrode active material layer is made high density. It is providing the lithium ion secondary battery which has a high capacity, a high input / output characteristic, and a high cycle characteristic as a result.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the said subject, when the negative electrode material which DBP oil absorption amount, specific surface area, and Raman R value satisfy | fills specific conditions is used as graphite particle which compounded graphite, the negative electrode active material layer made high density Also in this case, since the initial efficiency is high and high cycle characteristics can be satisfied even at a large current charge / discharge, as a result, it was found that a lithium ion secondary battery having a high capacity and a high cycle characteristic was obtained, and the present invention was reached.

That is, the gist of the present invention lies in the negative electrode material for a non-aqueous secondary battery characterized by satisfying the following three requirements as (A), (B) and (C) as graphite particles.

(A) The DBP oil absorption amount is 0.42 ml / g or more and 0.85 ml / g or less.

(B) The specific surface area is 0.5 m <2> / g or more and 6.5 m <2> / g or less.

(C) Raman R value is 0.03 or more and 0.19 or less.

The negative electrode material of the present invention can provide a non-aqueous secondary battery having high capacity, high input / output characteristics, high temperature storage characteristics, and high cycle characteristics by using it as a negative electrode material for a non-aqueous secondary battery. Moreover, according to the manufacturing method of the negative electrode material for nonaqueous secondary batteries of this invention, it becomes possible to manufacture the negative electrode material which has the above-mentioned advantage.

BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing of the calculation method of the pore volume Vi of the graphite particle measured by the mercury porosimetry.
2 is a SEM photograph of the graphite particles obtained in Example 1 (substitute drawing)
3 is a SEM photograph of the graphite particles obtained in Comparative Example 1 (drawing substitute photograph)

EMBODIMENT OF THE INVENTION Hereinafter, the content of this invention is described in detail. In addition, description of the invention structural requirements described below is an example (representative example) of embodiment of this invention, This invention is not specific to these forms, unless the summary is deviated from the summary.

<Physical Properties of Graphite Particles>

The physical properties of the graphite particles in the present invention are characterized by satisfying at least the following three conditions.

(A) The DBP oil absorption amount is 0.42 ml / g or more and 0.85 ml / g or less.

(B) The specific surface area is 0.5 m <2> / g or more and 6.5 m <2> / g or less.

(C) Raman R value is 0.03 or more and 0.19 or less.

Representative physical property values are described below.

(A: DBP oil absorption)

The DBP oil absorption amount of the graphite particles of the present invention is at least 0.42 ml / g, preferably at least 0.45 ml / g, more preferably at least 0.50 ml / g. Moreover, it is 0.85 ml / g or less, Preferably it is 0.80 ml / g or less, More preferably, it is 0.76 ml / g or less.

If the DBP oil absorption is too small in this range, there are fewer pores into which the non-aqueous electrolyte can infiltrate. Therefore, when rapid charging and discharging is performed, the insertion and desorption of lithium ions is delayed, resulting in deposition of lithium metal and deterioration in cycle characteristics. There is this. On the other hand, when it is too large than this range, a binder becomes easy to be absorbed by a space | gap at the time of electrode plate manufacture, and it exists in the tendency which leads to the fall of pole plate strength and initial stage efficiency.

In addition, the measurement of DBP (dibutyl phthalate) oil absorption amount can be performed in the following procedures using a negative electrode material.

The measurement of DBP oil absorption amount was carried out in 40 g of measurement materials based on JIS K 6217, and it measured until a maximum value of a torque was confirmed by making dropping speed 4 ml / min and rotation speed 125rpm, and start measurement. It is defined by the value (DBP dripping flow rate per 1g of negative electrode material) calculated from the dripping flow rate when the torque of 70% of the maximum torque is shown in the range during which the maximum torque is shown.

(B: specific surface area)

The specific surface area of the graphite particles of the present invention is a value of the specific surface area measured using the BET method, and is 0.5 m 2 · g ⁻¹ or more, preferably 1.0 m 2 · g ⁻¹ or more, more preferably 1.3 m 2 · g ^-1 or more, Especially preferably, it is 1.5 m <2> * g <^-1> or more, and 6.5 m <2> * g <^-1> or less, Preferably it is 6.0 m <2> * g <^-1> or less, More preferably, 5.5 m <2> * g <^-1> or less, Especially preferably, it is 5.0 m <2> * g <^-1> or less.

When the value of the specific surface area is less than this range, the water solubility of lithium tends to deteriorate during charging when used as the negative electrode material, and lithium metal tends to precipitate on the electrode surface, and the cycle characteristics tend to be deteriorated. On the other hand, when it exceeds this range, when used as a negative electrode material, the reactivity with a non-aqueous electrolyte solution increases and initial stage efficiency falls easily, and a preferable battery is hard to be obtained.

The measurement of the specific surface area by the BET method is performed by preliminary drying at 350 ° C. under nitrogen flow for 15 minutes using a surface area meter (automatic surface area measuring apparatus manufactured by Okura Riken), and then relative pressure of nitrogen to atmospheric pressure. The nitrogen adsorption BET1 point method by the gas flow method is performed using the nitrogen helium mixed gas correctly adjusted so that the value of may be 0.3. The specific surface area determined by the measurement is defined as the specific surface area of the negative electrode material of the present invention.

(C: Raman R value)

The Raman R value of the graphite particles of the present invention is a value measured using argon ion laser Raman spectroscopy, and is 0.03 or more, preferably 0.05 or more, more preferably 0.07 or more, and 0.19 or less, preferably Is 0.18 or less, more preferably 0.16 or less, particularly preferably 0.14 or less.

When Raman R value is less than the said range, the crystallinity of a particle surface will become high too much, and there may be few sites which lithium enters between layers with charge and discharge. That is, charge water solubility may fall and cycling characteristics may deteriorate. In addition, when the negative electrode is densified by applying it to the current collector after pressing it, the crystal tends to be oriented in the direction parallel to the electrode plate, resulting in a decrease in load characteristics. On the other hand, when it exceeds the said range, the crystallinity of a particle surface will fall, the reactivity with a non-aqueous electrolyte solution may increase, and it may cause the fall of initial stage efficiency and the increase of gas generation.

Here, the relationship between (A) DBP oil absorption amount, (B) specific surface area, and (C) Raman R value which are components of this invention is described. Generally, DBP oil absorption amount is used for evaluation of low crystalline material etc. which have big specific surface areas, such as carbon black. When the conventional negative electrode material is measured by this method, a material having a high DBP oil absorption is likely to be a material having a high specific surface area and a high Raman R value, and as shown in the foregoing and comparative examples, the cycle characteristics and initial efficiency are improved. Further improved materials could not be obtained.

In consideration of the cycle characteristics at the time of rapid charging and discharging, materials having a high water solubility of lithium and low reactivity with an electrolyte solution have a low loss of lithium deposited on the surface of the electrode as lithium metal and a loss of loss as a surface coating (SEI). It is thought that cycle characteristics are excellent. In addition, similarly to the initial efficiency, it is considered that a material having low reactivity with the electrolyte solution is advantageous.

In addition, a material having a high water solubility of lithium is a material having a large contact area with the electrolyte solution and having a large reaction area and low crystallinity on the surface of the negative electrode particles (large interlayer of graphite and small La · Lc). In other words, it is considered that a material having a high DBP oil absorption, a large specific surface area, and a high Raman R value has a high water solubility of lithium.

On the other hand, a material having low reactivity with an electrolyte solution is a material having a narrow contact area with the electrolyte solution, and has a small reaction area and high crystallinity on the surface of the negative electrode material particles (narrow interlayer of graphite and large La · Lc). It is considered to be a material, that is, a material having a low DBP oil absorption, a small specific surface area, and a low Raman R value is considered to have low reactivity with an electrolyte solution, which is considered to be in a tendency to be incompatible with the aqueous solubility of lithium.

In other words, it is considered that the contact area with the electrolyte is somewhat wide, the reaction area is somewhat small, and the crystallinity of the surface of the negative electrode material particles is in a certain range so that both the cycle characteristics and the initial efficiency can be achieved.

In short, the present invention maintains the DBP oil absorption amount of the negative electrode material in a high range, suppresses the specific surface area in a low range, and further sets the Raman R value to a specific range, thereby speeding up the insertion and removal of lithium ions, It is possible to obtain a negative electrode material having excellent cycle characteristics and high initial efficiency by suppressing reactivity with an aqueous electrolyte solution.

The measurement of the Raman spectrum is performed by using a Raman spectrometer (Raman spectrometer manufactured by Nippon Bunko Corporation) to naturally drop the sample into the measurement cell and to fill the sample, and to irradiate the sample surface in the cell with argon ion laser light, thereby perpendicularing the cell to the laser light. It carries out by rotating in phosphorus surface. With respect to the obtained Raman spectrum, the intensity I _A of the peak P _A near 1580 cm ⁻¹ and the intensity I _B of the peak P _B near 1360 cm ⁻¹ were measured, and the intensity ratio R (R = I _B / I _A ) To calculate. The Raman R value calculated by the measurement is defined as the Raman R value of the negative electrode active material of the present invention.

Moreover, said Raman measurement conditions are as follows.

· Argon ion laser wavelength: 514.5 nm

Laser power on sample: 15 to 25 mW

Resolution: 10-20 cm ^-1

Measuring range: 1100 cm ^-1 to 1730 cm ^-1

Raman R value, Raman half width analysis: background processing

Smoothing process: simple average, 5 convolution points

As other physical properties of the graphite particle of this invention, it is preferable to have the following physical properties.

(Raman half width)

The Raman half width in the vicinity of 1580 cm ⁻¹ of the graphite particles of the present invention is not particularly limited, but is usually 10 cm ⁻¹ or more, preferably 15 cm ⁻¹ or more, and usually 100 cm ⁻¹ or less, preferably 80 It is cm- ¹ or less, More preferably, it is 60 cm <^-1> or less, Especially preferably, it is 40 cm <^-1> or less.

If the Raman half width is less than the above range, the crystallinity of the particle surface may be too high, and there may be fewer sites at which Li enters between layers with charging and discharging. That is, charge water solubility may fall and cycling characteristics may fall. Moreover, after apply | coating to an electrical power collector, when densifying a negative electrode by pressing, it becomes easy to orient crystal in the direction parallel to an electrode plate, and may cause the fall of a load characteristic. On the other hand, if it exceeds the above-mentioned range, the crystallinity of the particle surface is lowered and the reactivity with the non-aqueous liquid electrolyte is increased, which may result in reduction of efficiency and increase of gas generation.

The half value width of the peak P _A near 1580 cm <^-1> of the obtained Raman spectrum is measured, and this is defined as the Raman half value width of the negative electrode active material of this invention.

(Surface functional group (O / C))

As for the surface functional group (O / C) of the graphite particle of this invention, O / C represented by following formula 1 is 0.1% or more normally, Preferably it is 0.2% or more, More preferably, it is 0.3% or more, Especially preferably, It is 0.5 or more, Usually 2.0% or less, Preferably it is 1.4% or less, More preferably, it is 1.0% or less.

If the surface functional group (O / C) is too small, the reactivity with the electrolyte solution may be insufficient, and stable SEI formation may not be possible and cycle characteristics may deteriorate. On the other hand, when the surface functional group (O / C) is too large, the crystals on the surface of the particles are disturbed and the reactivity with the electrolyte solution increases, which may cause an increase in irreversible capacity and increase in gas generation.

Equation 1

O / C (%) = C obtained based on the peak area of the spectrum of C1s in O atom concentration x 100 / XPS analysis determined based on the peak area of the spectrum of O1s in X-ray photoelectron spectroscopy (XPS) analysis Atomic concentration

The surface functional group (O / C) of the graphite particle of this invention can be measured using X-ray photoelectron spectroscopy (XPS).

The surface functional group (O / C) uses an X-ray photoelectron spectrometer as an X-ray photoelectron spectroscopy measurement, and puts a measurement object on a sample stage so that the surface becomes flat, and sets the Kα ray of aluminum as an X-ray source and performs multiplex measurement. By this, the spectra of C1s (280 to 300 eV) and O1s (525 to 545 eV) are measured. The peak top of the obtained C1s is charged to 284.3 eV, charge correction is performed, the peak areas of the spectra of C1s and O1s are obtained, and the device sensitivity coefficients are further multiplied to calculate the surface atom concentrations of C and O, respectively. The obtained atomic concentration ratio O / C (O atomic concentration / C atomic concentration) of the O and C is defined as the surface functional group (O / C) of the graphite particles of the present invention.

(Working volume (Vi))

The pore volume Vi of the graphite particles of the present invention is a value measured using a mercury porosimetry (mercury porosimetry), and is usually 0.10 ml / g or more, preferably 0.12 ml / g or more, more preferably 0.14 It is ml / g or more, and is usually 0.30 ml / g or less, preferably 0.28 ml / g or less, and more preferably 0.25 ml / g or less.

If the pore volume (Vi) is lower than the above range, there are fewer pores into which the non-aqueous electrolyte solution can penetrate. Therefore, when rapid charging and discharging is performed, the insertion and removal of lithium ions is delayed, resulting in deposition of lithium metal and deteriorating cycle characteristics. Tends to be. On the other hand, when it exceeds the said range, a binder becomes easy to be absorbed by a space | gap at the time of electrode plate manufacture, and there exists a tendency which leads to the fall of pole plate strength and initial stage efficiency.

As a measurement of the mercury porosimetry, 0.2 g of a sample (negative electrode material) was weighed and encapsulated in a powder cell using a mercury porosimeter (Autopora 9520 manufactured by Micromeritics Co., Ltd.), and at room temperature and under vacuum (50 µm). Hg or less), after 10 minutes of degassing pretreatment, mercury was introduced by depressurizing to 4 psia in a step phase, and stepped up from 4 psia to 40000 psia and stepped down to 25 psia. Pore distribution was computed using the formula of Washburn from the obtained mercury intrusion curve. In addition, the surface tension of mercury was calculated to be 485 dyne / cm, and the contact angle was 140 degrees.

Here, pore volume Vi draws a tangent line as shown in FIG. 1 mentioned later on the basis of the obtained pore distribution (integration curve), calculates the branch point of a tangent line and an integration curve, and makes pore volume at that time Vp. . The value obtained by subtracting the pore volume Vp from the total pore volume is defined as the pore volume Vi.

Pore volume (Vi) = total pore volume-pore volume (Vp)

The pore volume Vi is considered to mainly reflect the internal pore amount of the graphite particles, and it is assumed that the larger the pore volume Vi, the more voids therein. On the other hand, pore volume Vp is considered to mainly reflect the space | gap between particle | grains.

(Total pore volume)

The total pore volume of the graphite particles of the present invention is a value measured using the mercury porosimetry (mercury porosimetry), and is usually 0.48 ml / g or more, preferably 0.50 ml / g or more, more preferably Is 0.52 ml / g or more, and is usually 0.95 ml / g or less, preferably 0.93 ml / g or less, and more preferably 0.90 ml / g or less.

When the total pore volume is less than the above range, there are less pores into which the non-aqueous electrolyte can penetrate, and when the rapid charging and discharging is performed, the insertion and desorption of lithium ions is delayed, whereby lithium metal precipitates and the cycle characteristics deteriorate. There is this. On the other hand, when it exceeds the said range, a binder becomes easy to be absorbed by a space | gap at the time of electrode plate manufacture, and there exists a tendency which leads to the fall of pole plate strength and initial stage efficiency.

(Tap density)

The tap density of the graphite particles of the present invention is usually 0.70 g · cm ⁻³ or more, preferably 0.80 g · cm ⁻³ or more, more preferably 0.90 g · cm ⁻³ or more, and usually 1.25 g · cm ^-3 or less, Preferably it is 1.20 g * cm <^-3> or less, More preferably, it is 1.18 g * cm <^-3> or less, Especially preferably, it is 1.15 g * cm <^-3> or less. When the tap density is lower than the above range, the charge density is difficult to rise when used as the negative electrode, and a high capacity battery may not be obtained. Moreover, when it exceeds the said range, the space | gap between particle | grains in an electrode will become small too much, the electroconductivity between particle | grains will become difficult to be ensured, and preferable battery characteristic may be hard to be acquired.

The measurement of the tap density was carried out through a sieve with a 300 µm graduation interval, and the sample was dropped into a 20 cm 3 tapping cell to fill the sample up to the top surface of the cell, followed by a powder density measuring instrument (e.g., a tap manufactured by Seishin Corporation). Using a denser), tapping with a stroke length of 10 mm is performed 1000 times, and the tap density is calculated from the volume at that time and the mass of the sample. The tap density calculated by the measurement is defined as the tap density of the negative electrode active material of the present invention.

(Average particle size by volume)

The volume-based average particle diameter of the graphite particles of the present invention, the average particle diameter (median diameter) of the volume basis determined by the laser diffraction and scattering method is usually 1 µm or more, preferably 3 µm or more, more preferably 5 µm or more, Especially preferably, it is 7 micrometers or more, and is usually 100 micrometers or less, Preferably it is 50 micrometers or less, More preferably, it is 40 micrometers or less, Especially preferably, it is 30 micrometers or less.

If the volume-based average particle diameter is less than the above range, the irreversible capacity may increase, resulting in a loss of initial battery capacity. Moreover, when it exceeds the said range, when manufacturing an electrode by application | coating, it will become a nonuniform figure easily, and may be undesirable in a battery manufacturing process.

The volume-based average particle diameter was measured by dispersing the carbon powder in a 0.2 mass% aqueous solution (about 10 mL) of polyoxyethylene (20) sorbitan monolaurate as a surfactant, and using a laser diffraction scattering particle size distribution system (produced by Horiba). And LA-700 manufactured by Sosa. The median diameter determined by the measurement is defined as the volume reference average particle diameter of the negative electrode material of the present invention.

(X-ray parameter)

The crystallite sizes (Lc) and (La) of the carbonaceous material determined by X-ray diffraction by the method for studying graphite particles of the present invention are each preferably 30 nm or more, more preferably 100 nm or more. If the crystallite size is within this range, the amount of lithium that can be charged in the negative electrode material increases, which is preferable because high capacity is easily obtained.

(Orientation ratio)

The orientation ratio of the powder of the graphite particles of the present invention is usually 0.005 or more, preferably 0.01 or more, more preferably 0.015 or more, and usually 0.67 or less, preferably 0.5 or less, and more preferably 0.4 or less. When an orientation ratio is too small and it is less than the said range, there exists a tendency for a high density charge / discharge characteristic to fall. In addition, the normal upper limit of the said range is a theoretical upper limit of the orientation ratio of carbonaceous material.

The orientation ratio is measured by X-ray diffraction after pressure-molding the sample. 0.47 g of the sample filled in a molding machine having a diameter of 17 ㎜ to 58.8 MN · m ^- a molded body obtained by compressing to ^2, and set by using the clay so that the same plane as the surface of the sample holder for measurement to measure the X-ray diffraction. From the peak intensity of (110) diffraction and (004) diffraction of the obtained carbon, a ratio represented by (110) diffraction peak intensity / (004) diffraction peak intensity is calculated. The orientation ratio computed by the measurement is defined as the orientation ratio of the negative electrode material of this invention.

The X-ray diffraction measurement conditions are as follows. Further, &quot; 2 &amp;thetas; &quot; indicates a diffraction angle.

Target: Cu (Kα-ray) graphite monochromator

Slit:

   Divergence slit = 0.5 degree

   Light receiving slit = 0.15 mm

   Scattering slit = 0.5 degree

Measurement range and step angle / measurement time:

   (110) plane: 75 degrees ≤ 2θ ≤ 80 degrees 1 degree / 60 seconds

   (004) plane: 52 degrees ≤ 2θ ≤ 57 degrees 1 degree / 60 seconds

<Form of Graphite Particles>

Although the form of the graphite particle of this invention is not specifically limited, A spherical form, an ellipse form, a block form, a plate form, a polygonal form etc. are mentioned, Especially, when a spherical form, an ellipse form, a block form, and a polygonal form make a negative electrode, the particle filling is carried out. It is preferable because the property can be improved.

Moreover, although the surface form of the graphite particle of this invention is not specifically limited, It is preferable to have an uneven structure as shown to the SEM photograph of FIG. 3 mentioned later. Examples of the uneven structure include (1) a concave portion structure in which holes are formed in the surface of particles such as spherical shape and ellipse shape, and (2) convex portion structure in which fine particles are bound to the surface of particles such as spherical shape or ellipse shape. Can be. If the surface of the particles has an uneven structure, it is possible to secure voids into which the non-aqueous electrolyte can penetrate even when the negative electrode has a high density, so that the cycle characteristics can be improved.

Moreover, although the magnitude | size of an uneven structure is not specifically limited, When converted into the circular area, it is preferable that it corresponds to the diameter of about 0.1 micrometer-about 4 micrometers. If the size of the concave-convex structure is within this range, it is possible to secure voids into which the non-aqueous electrolytic solution can penetrate even when the negative electrode has a high density, so that the cycle characteristics can be improved.

<Method for Producing Graphite Particles>

Although the manufacturing method of the graphite particle of this invention is not specifically limited, The method etc. which are shown to following (I) and (II) are mentioned.

In addition, the graphite particles of the present invention are not particularly limited, but are preferably graphite particles coated with carbonaceous material, and graphite particles coated with amorphous carbon, graphite particles coated with graphite material, and more preferably raw material graphite and Preferred are graphite particles coated with amorphous carbon obtained by mixing and firing a carbon precursor, and graphite particles coated with a graphite substance obtained by mixing and firing raw material graphite and a carbon precursor.

 Although the manufacturing method of the graphite particle coated with the graphite substance is described below as one aspect of a preferable manufacturing method, it does not limit the graphite particle of this invention.

(Manufacturing method (Ⅰ))

As a method of forming the form (1) and / or (2) of the graphite particles, at least the step of roughening the raw graphite, the step of mixing the roughened raw graphite and the raw organic material, and firing at a temperature of 2300 ° C. or higher The manufacturing method which consists of a process is mentioned.

(Production method (II))

As the method for mainly forming the form (2) of the graphite particles, the particles are composed of large particles serving as nuclei such as spheres or ellipses, and fine particles bound to the surface of nuclear particles such as plates and flakys to form convex structures. The manufacturing method which consists of a process of mixing a raw material graphite and a raw material organic substance at least using the some raw material graphite (mixture) more than a kind, and the process baked at the temperature of 2300 degreeC or more are mentioned.

In the manufacturing method of said (I), (II), manufacturing method (I) is preferable because it is easy to form an uneven structure.

(Raw graphite)

The raw graphite is not particularly limited as long as it is a graphitized carbon particle (or graphitized by firing at a temperature of 2300 ° C. or higher), but natural graphite, artificial graphite, and coke powder, needle coke powder, and graphitized material of resin ( Or powders of graphitizable carbon materials). Among these, natural graphite is preferable because it is easy to process.

Although it does not specifically limit as a form of the particle | grains of raw material graphite, A spherical shape, an ellipse shape, a block shape, a plate shape, a flaky shape, a polygonal shape etc. are mentioned, The spherical shape and ellipse shape used by manufacturing method (I) or (II) are mentioned. Since the filling property of particle | grains can be improved when agglomerate and a polygonal shape are made into graphite particle | grains, it is preferable. In the manufacturing method (I), when the natural graphite spheroidized in spherical shape or ellipse shape is used, the said effect is easy to be obtained, and it is preferable.

As a device for obtaining spherical and elliptic graphite used in the production method (I) or (II), for example, the particles are formed by repeating mechanical actions such as compression, friction, and shear force, including impact interaction as the main component. The device attached to can be used. Specifically, the rotor has a rotor provided with a plurality of blades inside the casing, and the rotor rotates at a high speed to impart mechanical actions such as impact compression, friction, and shear force to the carbon material introduced therein, thereby performing surface treatment. The apparatus to make is preferable. Moreover, it is preferable to have a mechanism which repeatedly gives a mechanical effect by circulating a carbon material. Preferred apparatuses include, for example, hybridization systems (manufactured by Nara Machinery Co., Ltd.), kryptron (manufactured by Earth Technica), CF mill (manufactured by Ubekosan Co., Ltd.), mechanofusion system (manufactured by Hosokawa Micron Co., Ltd.), citacomposer (Made by Tokuju Works Co., Ltd.), etc. are mentioned. Among these, a hybridization system manufactured by Nara Machinery Co., Ltd. is preferable.

The spherical or ellipsoidal graphite is mainly formed by pulverization on the mother particles that are spherical due to the spherical natural graphite being folded or spherical grinding of the peripheral edge portion by performing the spheroidization step by the surface treatment. The spheroidization treatment is carried out under the condition that fine powders of mu m or less are attached and the surface functional groups (O / C) of the graphite particles after the surface treatment are usually 0.5% or more and 10% or less, preferably 1% or more and 4% or less. It is manufactured by carrying out. At this time, it is preferable to carry out in an active atmosphere so that the oxidation reaction of the graphite surface may be advanced by the energy of mechanical treatment, and an acidic functional group may be introduced into the graphite surface. For example, when processing using the apparatus mentioned above, it is preferable to set the main speed of the rotating rotor to 30-100 m / sec and 40-100 m / sec normally, and to set it as 50-100 m / sec. More preferred. In addition, although the process can be performed simply by passing a carbonaceous material, it is preferable to circulate or hold | maintain the apparatus in a device for 30 second or more, and it is more preferable to process by circulating or staying in an apparatus for 1 minute or more. As an apparatus for obtaining the plate-like or flaky graphite used in the manufacturing method (II), for example, an apparatus for imparting mechanical action such as compression, friction, shear force, including impact interaction as a main component, to particles, Can be used. Specifically, a jet mill, a hammer mill, a pin mill, a turbo mill, a pulverizer, etc. are mentioned.

(Particle diameter of raw graphite)

The volume-based average particle diameter of the raw graphite is not particularly limited, but is usually 1 µm or more, preferably 3 µm or more, more preferably 5 µm or more, particularly preferably 7 µm or more, and usually 100 µm. Hereinafter, Preferably it is 50 micrometers or less, More preferably, it is 40 micrometers or less, Especially preferably, it is 30 micrometers or less.

In the case of particles such as spherical or elliptic particles used in the production methods (I) and (II) of the graphite particles, the volume-based average particle diameter is usually 5 µm or more, preferably 7 µm or more, more preferably 10 µm or more. Moreover, it is 50 micrometers or less normally, Preferably it is 40 micrometers or less, More preferably, it is 30 micrometers or less.

Moreover, in the case of fine particles, such as plate-like, flaky, and agglomerate used by the manufacturing method (II) of graphite particle, a volume average particle diameter is 1 micrometer or more normally, Preferably it is 3 micrometers or more, More preferably, it is 5 micrometers or more, Moreover, it is 20 micrometers or less normally, Preferably it is 15 micrometers or less, More preferably, it is 10 micrometers or less.

When the particle size of the raw graphite is in this range, when the graphite particles are used, it is preferable to easily form the uneven structure on the particle surface.

(Roughening of raw graphite)

The roughening process of the said raw graphite refers to the process of providing an uneven structure to the surface of raw graphite. The method used in the roughening step is not particularly limited as long as the concave-convex structure is provided on the surface of the raw graphite, but for example, mechanical energy such as compression, friction, shear force or the like is applied to the raw graphite. Thereby, there exists a method etc. which provide a concavo-convex structure to the surface, and you may carry out in a dry state or a wet state. As a specific example, the method of giving a concavo-convex structure to the surface of raw graphite is enumerated below.

(Iii) When performing the roughening process in the dry state

As a method of roughening in a dry state, for example, a pin mill (manufactured by Makino Industries), a turbo mill (manufactured by Turbo Industries, Ltd.), a cryptotron of (manufactured by Earth Technica), and a jet mill (manufactured by Nippon Pneumatics) Crushing apparatuses, such as these, can be used. Among them, it is preferable to use a grinding device such as a turbo mill made of a rotor and a stator because the productivity can be improved.

Although the grinding | pulverization speed in a dry state changes with apparatuses to be used, when raw graphite is spherical or elliptical, the shape and rotation speed of the rotor of the grinding apparatus used are suitably selected, and are computed by the following formula | equation. It is preferable to set the main speed of a rotor to 50 m / sec or more, It is more preferable to set to 80 m / sec or more, It is further more preferable to set to 100 m / sec or more. In addition, as an upper limit, it is 300 m / sec or less normally.

Circumferential speed (m / sec) = diameter of the rotor of the roughening device × 3.14 ÷ revolutions

As long as the rotor and / or stator of the grinding apparatus to be used can set the said main speed, the specific shape will not be specifically limited, but it is preferable that the rotor has a blade and the stator has a groove.

If the grinding speed is too high, a lot of fine powder may be generated, and even if the roughened raw graphite and raw organic materials are mixed and calcined at a temperature of 2300 ° C. or higher, the specific surface area of the obtained graphite particles tends to be large, thereby suppressing reactivity with the electrolyte solution. There is a possibility that initial efficiency and cycle characteristics may deteriorate. Moreover, when it is too slow than this grinding | pulverization speed, the effect of a roughening will hardly appear, and there exists a tendency which is difficult to improve initial stage efficiency and cycling characteristics.

The feed rate of the raw material at the time of grinding | pulverization is 10 kg / hr or more normally, Preferably it is 50 kg / hr or more, More preferably, it is 100 kg / hr or more, More preferably, it is 200 kg / hr or more. Moreover, it is 1000 kg / hr or less normally, Preferably it is 700 kg / hr or less, More preferably, it is 500 kg / hr or less.

If the feed rate is too fast, mechanical energy is hardly imparted to the raw graphite, the effect of roughening is less likely to appear, and it tends to be difficult to improve initial efficiency and cycle characteristics. Moreover, when it is too slow than this injection speed, there exists a possibility that productivity may fall.

(Ii) When the roughening process is performed in the wet state

As a method of roughening in a wet state, an ultrasonic homogenizer, an ultrasonic cleaner, etc. are mentioned specifically ,.

As the dispersion medium of the carbon material, water and alcohols are preferable in terms of mass production, and the grinding aid particles and the like may be mixed as appropriate. In addition, it is more effective in combination with mechanical energy imparting shear force to the stirring blades.

For example, the case where an ultrasonic cleaner is used is performed as follows. The raw graphite and the ion-exchanged water are mixed at a predetermined mass ratio, followed by ultrasonic irradiation with stirring the mixed liquid, followed by drying.

When performing ultrasonic irradiation, it is preferable to perform so that foam | bubble generation and disappearance may generate | occur | produce in a short time.

The frequency is usually 10 Hz to 50000 Hz, preferably 20 Hz to 40000 Hz, and more preferably 30 Hz to 30000 Hz.

The output is usually 10 W to 30000 W, preferably 20 W to 20000 W, and more preferably 30 W to 16000 W.

Ultrasonic irradiation time is 30 second-20 hours normally, Preferably it is 60 second-10 hours, More preferably, it is 120 second-3 hours, If this time is short, there exists a tendency for the said processing effect to not fully be obtained, Particle breakdown is promoted, battery characteristics not only remarkably deteriorate, but also mass productivity tends to decrease.

In mixing a carbon material (A) and ion-exchange water, mass ratio 1: 1.1-1: 30 are preferable. Preferably it is 1:20, More preferably, it is 1:10. When it is thinner than 1:30, there exists a tendency for productivity to fall. On the contrary, when it becomes a thick liquid of 1: 1.1 or less, it is difficult to stir.

In mixing a carbon material (A) and ion-exchange water, surfactant can also be used. As a surfactant, a general commercial item can be selected. Moreover, it is also effective to improve dispersibility by mixing carbon after wetting with alcohol, for example, ethanol, isopropyl alcohol, etc.

Although drying of a shelf is easy, drying is possible, and the model which can be dried while stirring, and a kiln can also be used.

The drying temperature should just be 110 degreeC or more, and can select as needed.

You may perform a modification process with respect to a carbon material. For example, it is also effective to coat heat treatment by coating coal tar pitch, resin, or the like, or simply heat treatment. Moreover, it is also effective to perform a regrinding process as an additional process.

(Raw organic matter)

The raw material organic material is not particularly limited as long as it is carbonaceous which can be graphitized by firing, and is based on coal-based heavy oil, DC-based heavy oil, cracked petroleum heavy oil, aromatic hydrocarbon, N-ring compound, S-ring compound, polyphenylene, and organic synthetic polymer. And carbonizable organics selected from the group consisting of natural polymers, thermoplastic resins and thermosetting resins. Moreover, in order to adjust the viscosity at the time of mixing, you may melt and use a raw material organic substance.

As coal-based heavy oil, coal tar pitch from soft pitch to light pitch, dry liquefied oil, etc. are preferable. As DC-based heavy oil, normal-pressure residual oil, reduced-pressure residual oil, etc. are preferable. Ethylene tar and the like produced by-product are preferable, and as the aromatic hydrocarbon, acenaphthylene, decacyclene, anthracene, phenanthrene and the like are preferred. As the N-ring compound, phenazine, acridine and the like are preferable, and an S-ring compound As thiophene, bithiophene, etc. are preferable, As polyphenylene, biphenyl, terphenyl, etc. are preferable, As an organic synthetic polymer, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, these insolubilization processes Product, polyacrylonitrile, polypyrrole, polythiophene, polystyrene, and the like, and as the natural polymer, cellulose, lignin, met, polygalac Polysaccharides, such as lactic acid, chitosan, sucrose, etc. are preferable, As a thermoplastic resin, polyphenylene sulfide, polyphenylene oxide, etc. are preferable, As a thermosetting resin, Furfuryl alcohol resin, a phenol- formaldehyde resin, an imide resin, etc. This is preferred.

Moreover, as a low molecular organic solvent, benzene, toluene, xylene, quinoline, n-hexane, etc. are preferable.

(Mixing process)

Although the method of mixing the raw material graphite and raw material organic substance in the said manufacturing method is not specifically limited, A general mixing apparatus can be used. Specifically, a mixer, a kneader, a biaxial kneader, etc. are mentioned. In the mixing step, as described above, in order to adjust the viscosity at the time of mixing, the raw material organic substance dissolved or diluted with the low molecular organic solvent may be used, or the viscosity of the raw material organic substance may be adjusted by heating. The mixing ratio (mass ratio) of the raw graphite and the raw organic material is appropriately selected depending on the type of the raw graphite and the raw organic material to be used. The amount of the raw organic material relative to 100 parts by mass of the raw graphite is not particularly limited, but is usually 5 parts by mass. As mentioned above, Preferably it is 10 mass parts or more, More preferably, it is 20 mass parts or more, Usually 50 mass parts or less, Preferably it is 40 mass parts or less, More preferably, it is 35 mass parts or less.

(Firing step)

The method for firing the mixture of the raw graphite and the raw organic material in the production method is not particularly limited, but includes a carbonization step of removing volatile matter and a step of graphitization at a temperature of 2300 ° C or higher.

As a carbonization process which removes volatile matter, it is normally performed at 600 degreeC or more, Preferably it is 650 degreeC or more, and usually at 1300 degreeC or less, Preferably it is 1100 degreeC or less, 0.1 to 10 hours normally. In order to prevent oxidation, heating is usually performed in a non-oxidizing atmosphere in which a gap is filled with a particulate carbon material such as breeze or packing coke, or under an inert gas such as nitrogen or argon.

The equipment used for the carbonization process of removing volatile matters includes, for example, a shuttle furnace, a tunnel furnace, a lead hammer, a rotary kiln, an autoclave, a reaction tank, a coker (heat treatment tank made of coke), an electric furnace, a gas furnace, etc. It will not specifically limit, if it can bake in a non-oxidizing atmosphere. It is preferable that the temperature increase rate at the time of heating is low for the removal of volatile matter, and usually, the temperature is raised from around 200 ° C. at which low-volume volatilization starts to near 700 ° C. where only hydrogen is generated at 3 to 100 ° C./hr. In the case of a process, you may perform stirring as needed.

The carbide obtained by the carbonization step is then graphitized by heating at a high temperature. The heating temperature at the time of graphitization heats at 2300 degreeC or more, Preferably it is 2600 degreeC or more, More preferably, it is 2800 degreeC or more. Moreover, when heating temperature is too high, since sublimation of graphite will become remarkable, 3300 degreeC or less is preferable. The heating time may be performed until the binder and the carbonaceous particles become graphite, and are usually 1 to 24 hours.

At the time of graphitization, in order to prevent oxidation, in order to prevent oxidation, inert gas, such as nitrogen and argon, is carried out, or in non-oxidizing atmosphere in which granular carbon materials, such as a breeze and packing coke, were filled in the clearance gap. The equipment used for the graphitization is not particularly limited as long as it meets the above-mentioned purposes, such as an electric furnace, a gas furnace, an acheson furnace for electrode materials, and the like. The temperature raising rate, cooling rate, and heat treatment time may be arbitrarily set within the allowable range of the equipment to be used. Can be.

(Other processes)

The fired product is subjected to powder processing such as pulverization, pulverization, grinding, classification, etc. as necessary. Although there is no restriction | limiting in particular in the apparatus used for grinding | pulverization, For example, a coarse grinding machine includes a shear mill, jaw crusher, impact crusher, cone crusher, etc., As an intermediate grinder, a roll crusher, a hammer mill, etc. are mentioned, As a mill, a ball mill, a vibration mill, a pin mill, a stirring mill, a jet mill, etc. are mentioned.

There is no restriction | limiting in particular as an apparatus used for classification processing, For example, in the case of dry sieve classification, a rotary sieve, a shake-up sieve, an agitated sieve, a vibrating sieve, etc. can be used, and in the case of a dry air-class classification, it is a gravity type sieve. Air supply, inertial force classifier, centrifugal classifier (classifier, cyclone, etc.) can be used, and wet body fractionation, mechanical wet classifier, hydraulic classifier, sediment classifier, centrifugal wet classifier, etc. Can be used.

<Mixed with other carbon materials>

Although the graphite particle for nonaqueous secondary batteries of this invention mentioned above can be used suitably as a negative electrode material of a lithium ion secondary battery, using any 1 type individually or in combination of 2 or more types by arbitrary compositions and combinations, You may mix species or 2 or more types with another 1 type, or 2 or more types of other carbon materials, and use this as a negative electrode material of a non-aqueous secondary battery, Preferably a lithium ion secondary battery.

When the other carbon material is mixed with the negative electrode material for non-aqueous secondary batteries described above, the mixing ratio of the negative electrode material for non-aqueous secondary batteries and the negative electrode material for non-aqueous secondary batteries to the total amount of the other carbon material is usually 10% by mass or more, Preferably it is 20 mass% or more, Moreover, it is 90 mass% or less normally, Preferably it is the range of 80 mass% or less. If the mixing ratio of other carbon materials is less than the above range, the added effect tends to be less likely to be observed. On the other hand, when it exceeds the said range, there exists a tendency for the characteristic of the negative electrode material for non-aqueous secondary batteries to not show easily.

As other carbon materials, materials selected from natural graphite, artificial graphite, amorphous coated graphite, and amorphous carbon are used. These materials may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a composition.

As natural graphite, high purity scaly graphite and spherical graphite can be used, for example. The volume-based average particle diameter of the natural graphite is usually 8 µm or more, preferably 12 µm or more, and usually 60 µm or less, preferably 40 µm or less. The BET specific surface area of natural graphite is usually 3.5 m 2 / g or more, preferably 4.5 m 2 / g or more, and usually 8 m 2 / g or less, preferably 6 m 2 / g or less.

Examples of the artificial graphite include particles obtained by graphitizing a carbon material, and for example, particles obtained by calcining and graphitizing single graphite precursor particles in the form of powder can be used.

As amorphous coated graphite, for example, particles obtained by coating and firing an amorphous precursor on natural graphite or artificial graphite, or particles coated by amorphous CVD on natural graphite or artificial graphite can be used.

As amorphous carbon, the particle which calcined the bulk mesophase, the pitch which can be carbonized, etc. can be used, and the particle which calcined can be used, for example.

There is no restriction | limiting in particular as an apparatus used for mixing the negative electrode material for non-aqueous secondary batteries, and other carbon materials, For example, in the case of a rotary mixer: a cylindrical mixer, a twin cylindrical mixer, a double cone mixer, a cubic mixer, For hoe mixers and fixed mixers: spiral mixers, ribbon mixers, muller mixers, helical flight mixers, pugmill mixers, fluidized mixers, and the like.

<Negative electrode for non-aqueous secondary battery>

The negative electrode for nonaqueous secondary batteries of the present invention (hereinafter also referred to as "electrode sheet" as appropriate) includes a current collector and an active material layer formed on the current collector, and the active material layer contains at least the negative electrode material for a non-aqueous secondary battery of the present invention. It is characterized by containing. More preferably, it contains a binder.

The binder here means a binder added for the purpose of binding the active materials and retaining the active material layer to the current collector when producing the negative electrode for a non-aqueous secondary battery, and is different from the binder that can be graphitized.

As a binder, what has an olefinic unsaturated bond in a molecule | numerator is used.

Although the kind in particular is not restrict | limited, A styrene butadiene rubber, a styrene isoprene styrene rubber, an acrylonitrile butadiene rubber, butadiene rubber, an ethylene propylene diene copolymer etc. are mentioned as a specific example. By using such a binder having an olefinically unsaturated bond, the swelling property of the active material layer with respect to the electrolytic solution can be reduced. Among them, styrene-butadiene rubber is preferable from the availability.

By using the binder which has such an olefinic unsaturated bond, and the above-mentioned active material in combination, the intensity | strength of a negative electrode plate can be raised. When the strength of the negative electrode is high, deterioration of the negative electrode due to charge and discharge can be suppressed, and the cycle life can be extended. Moreover, in the negative electrode which concerns on this invention, since the adhesive strength of an active material layer and an electrical power collector is high, even if content of the binder in an active material layer is reduced, the subject that an active material layer peels from an electrical power collector when winding a negative electrode to manufacture a battery It is inferred that neither happens.

As a binder which has an olefinic unsaturated bond in a molecule, the thing with the large molecular weight or the ratio of an unsaturated bond is preferable. Specifically, in the case of a binder having a large molecular weight, the weight average molecular weight is preferably 10,000 or more, preferably 50,000 or more, and usually 1 million or less, preferably 300,000 or less. In the case of a binder having a large proportion of unsaturated bonds, the number of moles of olefinic unsaturated bonds per 1 g of the total binder is usually 2.5 × 10 ⁻⁷ or more, preferably 8 × 10 ⁻⁷ or more, and usually 1 × 10 ^{It is -6} or less, Preferably it exists in the range of 5x10 <^-6> or less. As a binder, what is necessary is just to satisfy | fill at least either one of the prescription | regulation concerning these molecular weights and the ratio of an unsaturated bond, but it is more preferable to satisfy both prescription | regulation simultaneously. When the molecular weight of the binder which has an olefinic unsaturated bond is too small, mechanical strength will fall, and when too large, flexibility will fall. Moreover, when the ratio of the olefinic unsaturated bond in a binder is too small, the strength improvement effect is weak, and when too large, flexibility will be inferior.

In addition, the binder having an olefinically unsaturated bond has an unsaturation of 15% or more, preferably 20% or more, more preferably 40% or more, and usually 90% or less, preferably 80% or less. It is desirable to have. In addition, an unsaturated degree shows the ratio (%) of a double bond with respect to the repeating unit of a polymer.

In this invention, the binder which does not have an olefinic unsaturated bond can also be used together with the binder which has the above-mentioned olefinic unsaturated bond in the range which does not lose the effect of this invention. The mixing ratio of the binder which does not have an olefinic unsaturated bond with respect to the binder which has an olefinic unsaturated bond is 150 mass% or less normally, Preferably it is the range of 120 mass% or less.

By using together the binder which does not have an olefinic unsaturated bond, applicability | paintability can be improved, but when there are too many bottle capacities, the intensity | strength of an active material layer will fall.

As an example of the binder which does not have an olefinic unsaturated bond, thickener polysaccharides, such as methylcellulose, carboxymethylcellulose, starch, carrageenan, pullulan, guar gum, xanthan gum (xanthan gum), a polyether, such as polyethylene oxide and polypropylene oxide Vinyl alcohols such as polyvinyl alcohol and polyvinyl butyral, polyacids such as polyacrylic acid and polymethacrylic acid, metal salts of these polymers, fluorine-containing polymers such as polyvinylidene fluoride, polyethylene, polypropylene, and the like Alkanes type polymer, these copolymers, etc. are mentioned.

The negative electrode of this invention is formed by disperse | distributing the negative electrode material and binder of this invention mentioned above to a dispersion medium to make a slurry, and apply | coating this to an electrical power collector. As a dispersion medium, organic solvents, such as alcohol, and water can be used. You may add a electrically conductive agent to this slurry further as needed. Examples of the conductive agent include carbon black such as acetylene black, Ketjen black and furnace black, Cu, Ni having an average particle diameter of 1 µm or less, or a fine powder composed of these alloys. The addition amount of a electrically conductive agent is about 10 mass% or less normally with respect to the negative electrode material of this invention.

As a collector which apply | coats a slurry, a conventionally well-known thing can be used. Specifically, metal thin films, such as a rolled copper foil, an electrolytic copper foil, and stainless steel foil, are mentioned. The thickness of the current collector is usually 4 µm or more, preferably 6 µm or more, and usually 30 µm or less, preferably 20 µm or less.

This slurry was apply | coated to width 5cm using the doctor blade, and it air-dried at room temperature so that the negative electrode material might adhere to 14.5 +/- 0.3 mg / cm <2> on the copper foil of 18 micrometers thick which is an electrical power collector. After drying at 110 degreeC for 30 minutes again, it roll-pressed using the roller of diameter 20cm, was prepared so that the density of an active material layer might be 1.70 ± 0.03 g / cm <3>, and the electrode sheet was obtained.

After the slurry is applied onto the current collector, the active material layer is formed by drying in a dry air or an inert atmosphere at a temperature of usually 60 ° C. or higher, preferably 80 ° C. or higher, and usually 200 ° C. or lower, preferably 195 ° C. or lower. do.

The thickness of the active material layer obtained by applying and drying the slurry is usually 5 µm or more, preferably 20 µm or more, more preferably 30 µm or more, and usually 200 µm or less, preferably 100 µm or less, more preferably. Is 75 μm or less. If the active material layer is too thin, practicality as a negative electrode is insufficient from the balance with the particle size of the active material, and if too thick, sufficient Li occlusion and release function for a high density current value is difficult to obtain.

The density of the negative electrode material for a non-aqueous secondary battery in the active material layer varies depending on the use, but in applications where capacity is important, it is preferably 1.55 g / cm 3 or more, especially 1.60 g / cm 3 or more, further 1.65 g / cm 3 or more, In particular, 1.70 g / cm <3> or more is preferable. If the density is too low, the capacity of the battery per unit volume is not necessarily sufficient. In addition, when the density is too high, the rate characteristic is lowered, so 1.9 g / cm 3 or less is preferable.

When manufacturing the negative electrode for non-aqueous secondary batteries using the negative electrode material for non-aqueous secondary batteries of this invention demonstrated above, the method and selection of another material are not specifically limited. Moreover, also when manufacturing a lithium ion secondary battery using this negative electrode, there is no restriction | limiting in particular about selection of the member required in the battery structure, such as a positive electrode and electrolyte solution which comprise a lithium ion secondary battery. Hereinafter, although the detail of the negative electrode for lithium ion secondary batteries and the lithium ion secondary battery using the negative electrode material of this invention is illustrated, the material, manufacturing method, etc. which can be used are not limited to the following specific example.

<Non-aqueous secondary battery>

The basic configuration of the non-aqueous secondary battery, in particular, a lithium ion secondary battery of the present invention is the same as that of a conventionally known lithium ion secondary battery, and usually includes a positive electrode, a negative electrode, and an electrolyte capable of occluding and releasing lithium ions. As a negative electrode, the negative electrode of this invention mentioned above is used.

A positive electrode forms the positive electrode active material layer containing a positive electrode active material and a binder on an electrical power collector.

Examples of the positive electrode active material include metal chalcogen compounds that can occlude and release alkali metal cations such as lithium ions during charging and discharging. Examples of the metal chalcogen compounds include transition metal oxides such as oxides of vanadium, oxides of molybdenum, oxides of manganese, oxides of chromium, oxides of titanium, and oxides of tungsten, sulfides of vanadium, sulfides of molybdenum, sulfides of titanium, and CuS. transition metal sulfides, NiPS _3, FePS the transition metal, such as _3-1002 of sulfur compounds, VSe _2, NbSe transition metal selenide compound such as _{3, Fe 0 .25 V 0 .75} S 2, Na 0.1 CrS 2 etc. Complex sulfides of transition metals such as metal complex oxides, LiCoS ₂ , LiNiS _2, and the like.

Among these, V ₂ O ₅ , V ₅ O ₁₃ , VO ₂ , Cr ₂ O ₅ , MnO ₂ , TiO, MoV ₂ O ₈ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , TiS ₂ , V ₂ S ₅ , _{Cr 0 .25 V 0 .75 S 2} , Cr 0 .5 V 0 .5 S 2 such as the preferred, and particularly preferred are _{LiCoO 2, LiNiO 2, LiMn 2} O 4 , or these other transition metal for a portion of the metal It is the substituted lithium transition metal composite oxide. These positive electrode active materials may be used alone or in combination of a plurality thereof.

As a binder which binds a positive electrode active material, a well-known thing can be arbitrarily selected and used. As an example, inorganic compounds, such as a silicate and water glass, resin which does not have unsaturated bonds, such as Teflon (trademark) and polyvinylidene fluoride, etc. are mentioned. Among these, preferable is resin which does not have an unsaturated bond. When resin which has an unsaturated bond is used as resin which binds a positive electrode active material, there exists a possibility that it may decompose | disassemble at the time of an oxidation reaction. The weight average molecular weight of these resins is usually 10,000 or more, preferably 100,000 or more, and usually 3 million or less, preferably 1 million or less.

The positive electrode active material layer may contain a conductive material in order to improve the conductivity of the electrode. The conductive agent is not particularly limited as long as it can be appropriately mixed with the active material to impart conductivity, but usually includes carbon powder such as acetylene black, carbon black, graphite, various metal fibers, powder, foil, and the like.

A positive electrode plate is formed by slurrying a positive electrode active material and a binder with a solvent by the method similar to manufacture of a negative electrode as mentioned above, apply | coating and drying on an electrical power collector. As a current collector of a positive electrode, although aluminum, nickel, SUS, etc. are used, it is not limited at all.

As an electrolyte, the non-aqueous electrolyte which melt | dissolved lithium salt in the non-aqueous solvent, the thing which made this non-aqueous electrolyte into gel form, rubber | gum, a solid sheet form with organic polymer compounds, etc. are used.

The non-aqueous solvent used for the non-aqueous electrolyte is not particularly limited and can be appropriately selected from known nonaqueous solvents that have conventionally been proposed as solvents for the non-aqueous electrolyte. Chain carbonates such as diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate; Cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; Chain ethers such as 1,2-dimethoxyethane; Cyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, and 1,3-dioxolane; Chain esters such as methyl formate, methyl acetate and methyl propionate; Cyclic ester, such as (gamma) -butyrolactone and (gamma) -valerolactone, etc. are mentioned.

These non-aqueous solvents may be used individually by 1 type, or may mix and use 2 or more types. In the case of a mixed solvent, a combination of a mixed solvent containing a cyclic carbonate and a linear carbonate is preferable, and the cyclic carbonate being a mixed solvent of ethylene carbonate and propylene carbonate can express high ionic conductivity even at low temperatures. In particular, the low temperature charging load characteristics are particularly preferable. Especially, the range of 2 wt% or more and 80 wt% or less is preferable with respect to the whole non-aqueous solvent, The range of 5 wt% or more and 70 wt% or less is more preferable, 10 wt% or more and 60 wt% or less The range is more preferred. When the ratio of propylene carbonate is lower than the above, the ionic conductivity at low temperature is lowered. When the ratio of propylene carbonate is higher than the above, when the graphite electrode is used, the PC solvated in Li ions is separated between the graphite phases. Co-insertion causes a problem that the interlayer peeling deterioration of the graphite negative electrode active material occurs, and a sufficient capacity cannot be obtained.

The lithium salt used for the non-aqueous electrolytic solution is not particularly limited, and may be appropriately selected from known lithium salts known to be usable for this use. For example, inorganic lithium salts such as halides such as LiCl, LiBr, perhalogenates such as LiClO ₄ , LiBrO ₄ , LiClO ₄ , and inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Fluorine-containing organic lithium salts such as perfluoroalkanesulfonic acid salts such as LiC ₄ F ₉ SO ₃ , and perfluoroalkanesulfonic acid imide salts such as Li trifluorosulfonimide ((CF ₃ SO ₂ ) ₂ NLi) Among these, LiClO ₄ , LiPF ₆ and LiBF ₄ are preferable.

The lithium salt may be used alone or in combination of two or more thereof. The concentration of the lithium salt in the non-aqueous electrolyte is usually in the range of 0.5 M or more and 2.0 M or less.

Moreover, when using the organic polymer compound in the non-aqueous electrolyte solution mentioned above and using it as a gel form, a rubber form, or a solid sheet form, As a specific example of an organic polymer compound, Polyether type polymers, such as polyethylene oxide and a polypropylene oxide, are used. Compound; A cross-linked polymer of a polyether-based polymer compound; Vinyl alcohol-based polymer compounds such as polyvinyl alcohol and polyvinyl butyral; An insoluble product of a vinyl alcohol-based polymer compound; Polyepichlorohydrin; Polyphosphazene; Polysiloxanes; Vinyl-based polymer compounds such as polyvinyl pyrrolidone, polyvinylidene carbonate, and polyacrylonitrile; Polymeric aerosols such as poly (omega -methoxy oligooxyethylene methacrylate), poly (omega-methoxy oligooxyethylene methacrylate-co-methyl methacrylate) and poly (hexafluoropropylene-vinylidene fluoride) And the like.

The above-mentioned non-aqueous liquid electrolyte may further contain a film-forming agent. As a specific example of a film forming agent, Alkene sulfide, such as carbonate compounds, such as vinylene carbonate, vinyl ethyl carbonate, and methylphenyl carbonate, ethylene sulfide, propylene sulfide; Sultone compounds such as 1,3-propane sultone and 1,4-butane sultone; Acid anhydrides, such as maleic anhydride and succinic anhydride, etc. are mentioned. Moreover, overcharge inhibitors, such as diphenyl ether and cyclohexylbenzene, may be added. When using the said additive, the content is 10 mass% or less normally, Especially 8 mass% or less, Furthermore, 5 mass% or less, Especially the range of 2 mass% or less is preferable. When there is too much content of the said additive, there exists a possibility that it may adversely affect other battery characteristics, such as an increase of an initial irreversible capacity | capacitance, low temperature characteristic, and a fall of a rate characteristic.

As the electrolyte, a polymer solid electrolyte which is a conductive material of an alkali metal cation such as lithium ion may be used. As a polymer solid electrolyte, what melt | dissolved the salt of Li in the polyether polymer compound mentioned above, the polymer etc. which the terminal hydroxyl group of the polyether is substituted by the alkoxide are mentioned.

In order to prevent a short circuit between electrodes, porous separators, such as a porous membrane and a nonwoven fabric, are interposed between a positive electrode and a negative electrode normally. In this case, the non-aqueous electrolyte solution is used by impregnating the porous separator. As a material of a separator, polyolefin, such as polyethylene and a polypropylene, polyether sulfone, etc. are used, Preferably it is polyolefin.

The form of the lithium ion secondary battery of the present invention is not particularly limited. As an example, the cylinder type which made the sheet electrode and the separator spiral, the cylinder type of the inside out structure which combined the pellet electrode, and the separator, the coin type which laminated | stacked the pellet electrode, and separator etc. are mentioned. Moreover, by storing these types of batteries in arbitrary exterior cases, it can be used as arbitrary shapes, such as a coin shape, a cylindrical shape, and a square shape.

The order of assembling the lithium ion secondary battery of the present invention is not particularly limited, but may be assembled in an appropriate order according to the structure of the battery. For example, the negative electrode is placed on an outer case, an electrolyte and a separator are formed thereon, and the negative electrode is formed. The positive electrode is raised so as to face the battery and fixed together with the gasket and the sealing plate to form a battery.

Example

Next, although the specific aspect of this invention is demonstrated in detail by an Example, this invention is not limited by these examples.

In addition, each physical property measuring method shall be based on the measuring method mentioned above.

<Measurement method of initial stage efficiency>

Using the non-aqueous secondary battery, the initial efficiency at the time of battery charge / discharge was measured by the following measuring method.

Charge up to 5 kW against the lithium counter electrode at a current density of 0.16 mA / cm 2, charge again at a constant voltage of 5 mA until the charge capacity value reaches 350 mAh / g, and doping lithium in the negative electrode, followed by 0.33 mA The lithium electrode was discharged to 1.5 V at a current density of / cm 2. Subsequently, the second and third times were charged at 10 mA and 0.005 Ccut by cc-cv charging at the same current density, and the discharges were discharged to 0.04 C at 1.5 times at all times. The sum total of the difference of the charge capacity and discharge capacity of 3 cycles in total was computed as irreversible capacity. In addition, the discharge capacity of this material was made into the discharge capacity of the 3rd cycle, discharge capacity of the 3rd cycle / (the sum of the difference of the discharge capacity of the 3rd cycle + the charge capacity of the 3rd cycle, and discharge capacity) was made into initial stage efficiency.

<Measurement method of cycle retention rate>

The laminate battery produced by the method described below was repeatedly charged at 0.8 C to 4.2 V and discharged at 0.5 C to 3.0 V to cycle the ratio x100 of the discharge capacity at the 100th cycle to the discharge capacity at the 1st cycle. It was set as retention rate (%).

<Manufacture of an electrode sheet>

Using the negative electrode material of the present invention, an electrode plate having an active material layer having an active material layer density of 1.70 ± 0.03 g / cm 3 was produced. Specifically, 20.00 ± 0.02 g (0.200 g in terms of solid content) of 1 mass% carboxymethylcellulose sodium salt aqueous solution and 20.00 ± 0.02 g of negative electrode material, and the weight average molecular weight 270,000 styrene butadiene rubber aqueous dispersion 0.50 ± 0.05 g (0.2 g in terms of solid content) was stirred for 5 minutes with a Keyense hybrid mixer, and degassed for 30 seconds to obtain a slurry.

This slurry was apply | coated to width 5cm using the doctor blade, and it air-dried at room temperature so that the negative electrode material might adhere to 14.5 +/- 0.3 mg / cm <2> on the copper foil of 18 micrometers thick which is an electrical power collector. After drying at 110 degreeC again for 30 minutes, it roll-pressed using the roller of diameter 20cm, and prepared so that the density of an active material layer might be 1.70 ± 0.03g / cm <3>, and obtained the electrode sheet.

<Production of Non-Aqueous Secondary Battery (2016 Coin Type Battery)>

The electrode sheet produced by the above method was punched into a disk shape having a diameter of 12.5 mm, and the lithium metal foil was punched out into a disk shape having a diameter of 14 mm to obtain a counter electrode. Between the positive electrodes, an electrolyte solution in which LiPF ₆ was dissolved to 1 mol / l in a mixed solvent of A: ethylene carbonate and ethyl methyl carbonate (volume ratio = 3: 7), B: mixing of ethylene carbonate, propylene carbonate, and diethyl carbonate In an electrolyte solution in which LiPF ₆ was dissolved to 1 mol / l in a solvent (volume ratio = 2: 4: 4), and a mixed solvent (volume ratio = 1: 5: 4) of C: ethylene carbonate, propylene carbonate, and diethyl carbonate, A 2016 coin-type battery in which a separator (made of porous polyethylene film) impregnated with an electrolyte solution (indicated by electrolyte solutions A, B, and C, respectively) in which LiPF ₆ was dissolved to 1 mol / L was used, and the electrolyte solution of A to C was used. Were prepared respectively.

<Manufacturing method of a nonaqueous secondary battery (laminate type battery)>

The negative electrode sheet produced by the above method was cut into a square of 4 cm × 3 cm to form a negative electrode, and the positive electrode made of LiCoO ₂ was cut out and combined. Between the negative electrode and the positive electrode, LiPF ₆ is dissolved in a mixed solvent of ethylene carbonate, ethyl methyl carbonate and dimethyl carbonate (volume ratio = 20:20:60) to 1 mol / l, and 2 volumes of vinylene carbonate as an additive. A separator (made of a porous polyethylene film) impregnated with the added electrolyte solution was placed to prepare a laminate battery.

Example 1

As raw material graphite, the spherical natural graphite having a volume-based average particle diameter of 17 μm was used, and as a roughening process, a pulverization device consisting of a rotor and a stator was used to grind the rotor at a main speed of 145 m / sec and an injection speed of 200 kg / hr. Thus, graphite having a concave-convex structure on the surface was obtained. The pitch of raw material organic substance was mixed using the kneader in the ratio of 30 mass parts with respect to 100 mass parts of the obtained graphite. After the obtained mixture was molded, it was calcined and carbonized in an inert atmosphere at 1000 ° C, and graphitized at 3000 ° C. The obtained graphite molded object was pulverized and finely pulverized to obtain a powder sample composed of graphite particles. About this sample, DBP oil absorption amount, specific surface area, Raman R value, pore volume (Vi), total pore volume, O / C, tap density, and average particle diameter were measured with the said measuring method. Moreover, the presence or absence of the uneven structure was judged from the SEM observation of the particle surface.

As a result, and the result of having measured cycling retention rate and initial stage efficiency by the said measuring method is shown in Table 1. Moreover, the example of SEM observation photograph is shown in FIG. As a result of SEM observation, it was observed that the uneven structure was formed on the particle surface.

Example 2

As a roughening process, it carried out similarly to Example 1 except having set the rotor's main speed to 145 m / sec, and obtained the powder sample which consists of graphite particles. On the other hand, physical properties, battery characteristics were evaluated, and SEM observation was carried out in the same manner as in Example 1. The results are shown in Table 1.

Example 3

As a roughening process, it carried out similarly to Example 1 except having set the rotor main speed to 130 m / sec, and obtained the powder sample which consists of graphite particles. On the other hand, physical properties, battery characteristics were evaluated, and SEM observation was carried out in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1

A powder sample consisting of graphite particles was obtained in the same manner as in Example 1 except that the roughening step was not performed. On the other hand, physical properties and battery characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Moreover, the example of SEM observation photograph is shown in FIG. As a result of SEM observation, no uneven structure was observed on the particle surface.

Comparative Example 2

The powder sample which consists of graphite particles was obtained like Example 1 except having set the rotor's main speed to 48 m / sec. On the other hand, physical properties, battery characteristics were evaluated, and SEM observation was carried out in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3

The roughened graphite used in Example 1 was used as a sample as it is. On the other hand, physical properties, battery characteristics were evaluated, and SEM observation was carried out in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 4

The roughened graphite used in Example 3 was used as a sample as it is. In the same manner as in Example 1, physical properties, battery characteristics were evaluated, and SEM observation was performed. The results are shown in Table 1.

Comparative Example 5

Spherical natural graphite having a volume-based average particle diameter of 21 µm was used as a sample as it is. On the other hand, physical properties, battery characteristics were evaluated, and SEM observation was carried out in the same manner as in Example 1. The results are shown in Table 1.

From the above result, the following is understood.

Although the comparative example 1 does not perform the process of roughening a raw material graphite, (B) specific surface area and (C) Raman R value are in the range of this invention, (A) DBP oil absorption amount is 0.37 ml / g. It became out of the specification range of this invention, and as a result, high cycle retention was not acquired.

Although the comparative example 2 performs the process of roughening raw material graphite, it carries out on the conditions whose main velocity is less than 50 m / sec, and (B) specific surface area and (C) Raman R value are in the range of this invention. However, (A) DBP oil absorption amount was 0.40 ml / g, it was out of the specification range of this invention. As a result, high cycle retention could not be obtained.

Moreover, the comparative example 3 does not perform the process of mixing the roughened raw graphite and organic substance, and the process of baking the mixture, (A) DBP oil absorption amount is in the scope of the present invention, but (B) specific surface area and (C) The Raman R value fell outside the prescribed range of the present invention, and as a result, high initial efficiency could not be obtained.

Moreover, the comparative example 4 does not perform the process of mixing the roughened raw material graphite and an organic substance, and the process of baking a mixture, and it is a thing of (A) DBP oil absorption amount, (B) specific surface area, and (C) Raman R value. All the requirements fall outside the scope of the present invention, and as a result, high initial efficiency could not be obtained.

Moreover, the comparative example 5 does not perform any of the process of roughening raw material graphite, the process of mixing the roughened raw material graphite and an organic substance, and the process of baking a mixture, (A) DBP oil absorption amount and (B) Although the specific surface area is in the scope of the present invention, the (C) Raman R value is outside the prescribed range of the present invention, and as a result, high cycle retention was not obtained.

On the other hand, the negative electrode material of this invention of Examples 1-3 is satisfy | filled all the requirements of (A) DBP oil absorption amount, (B) specific surface area, and (C) Raman R value. By using such a negative electrode material, a high performance battery having excellent cycle characteristics and high initial efficiency can be obtained.

Industrial availability

By using the negative electrode material of the present invention as a negative electrode material for a non-aqueous secondary battery, it is possible to provide a negative electrode material for a non-aqueous secondary battery having high initial efficiency and good cycle characteristics. Moreover, according to the manufacturing method of the said material, since the number of processes is few, it can manufacture efficiently, efficiently, and inexpensively.

Claims (11)

Graphite particles for non-aqueous secondary batteries, which satisfy the following requirements (A), (B) and (C).
(A) The DBP oil absorption amount is 0.42 ml / g or more and 0.85 ml / g or less.
(B) The specific surface area is 0.5 m <2> / g or more and 6.5 m <2> / g or less.
(C) Raman R value is 0.03 or more and 0.19 or less. The method of claim 1,
The surface functional group (O / C) of graphite particle is 0.1% or more and 2.0% or less, The graphite particle for non-aqueous secondary batteries characterized by the above-mentioned. 3. The method according to claim 1 or 2,
Graphite particles for non-aqueous secondary batteries, characterized by having a concave-convex structure on the surface of the graphite particles. The method according to any one of claims 1 to 3,
The pore volume Vi of the graphite particles is 0.10 ml / g or more and 0.30 ml / g or less, the graphite particles for non-aqueous secondary batteries. 5. The method according to any one of claims 1 to 4,
The tap density of graphite particles is 0.7 g / cm 3 or more and 1.25 g / cm 3 or less, graphite particles for non-aqueous secondary batteries. A method for producing graphite particles for a non-aqueous secondary battery, comprising a step of roughening the raw graphite, a step of mixing the roughened raw graphite and an organic substance, and a step of firing the mixture at a temperature of 2300 ° C. or higher. The method according to claim 6,
The raw material graphite is natural graphite, The manufacturing method of the graphite particle for nonaqueous secondary batteries. A non-aqueous system comprising the step of roughening spherical or elliptic raw graphite at a rotational speed of 50 m / sec or more, a step of mixing the roughened raw graphite with an organic substance, and firing the mixture. The manufacturing method of the graphite particle for secondary batteries. The graphite particle for non-aqueous secondary batteries obtained by the manufacturing method in any one of Claims 6-8. In addition to providing a current collector and an active material layer formed on the current collector, the active material layer contains graphite particles for non-aqueous secondary batteries according to any one of claims 1 to 5 and 9. A negative electrode for non-aqueous secondary batteries. A lithium ion secondary battery, comprising a positive electrode and a negative electrode capable of occluding and releasing lithium ions, and an electrolyte, and the negative electrode is a negative electrode for a non-aqueous secondary battery according to claim 10.

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