JP2019087460A - Manufacturing method of negative electrode material for lithium ion secondary battery - Google Patents

Abstract

To provide a manufacturing method of a negative electrode material for lithium ion secondary battery capable of manufacturing a lithium ion secondary battery excellent in input/output characteristics and high temperature storage characteristics.SOLUTION: A manufacturing method of a negative electrode material for a lithium ion secondary battery includes a step of performing heat treatment on a mixture containing an organic compound that can be converted into carbonaceous by the heat treatment and a compound containing nitrogen atom, and the softening point X (°C) of the organic compound that can be converted into carbonaceous by the heat treatment, and the thermal decomposition temperature Y (°C) of the compound containing the nitrogen atom satisfy X/Y=0.2 to 0.9.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of manufacturing a negative electrode material for a lithium ion secondary battery.

Lithium ion secondary batteries are widely used in electronic devices such as laptop PCs, mobile phones, smart phones, tablet PCs, etc., taking advantage of the characteristics of small size, light weight and high energy density. In recent years, on the background of environmental problems such as global warming caused by CO ₂ emissions, clean electric vehicles (EVs) that run with only batteries, hybrid electric vehicles (HEVs) that combine a gasoline engine and batteries, etc. have become widespread . Recently, it is also used for power storage, and its application is expanding in various fields.

  The performance of the negative electrode material of the lithium ion secondary battery largely affects the output characteristics and the life characteristics. A carbon material is widely used as a material of the negative electrode material for lithium ion secondary batteries. The carbon materials used for the negative electrode material are roughly classified into graphite and carbon materials (such as amorphous carbon) which are less crystalline than graphite. Graphite has a structure in which hexagonal network planes of carbon atoms are regularly stacked, and when it is used as a negative electrode material of a lithium ion secondary battery, insertion and desorption reactions of lithium ions proceed from the end of the hexagonal network plane, Discharge is performed. In addition, it is known that a film (Solid Electrolyte Interphase: SEI) grows on the surface of carbon during cycling and storage.

  Amorphous carbon has irregular stacking of hexagonal mesh faces or does not have hexagonal mesh faces. For this reason, in the negative electrode material using amorphous carbon, insertion and desorption reactions of lithium ions proceed on the entire surface of the negative electrode material. Therefore, it is easy to obtain a lithium ion battery having excellent output characteristics as compared to the case of using graphite as the negative electrode material (see, for example, Patent Document 1 and Patent Document 2). On the other hand, amorphous carbon has lower energy density than graphite because it has lower crystallinity than graphite. Moreover, coexistence of input / output characteristics and life characteristics is disclosed by coating graphite particles with carbon which is crystalline lower than graphite particles.

Unexamined-Japanese-Patent No. 4-370662 Unexamined-Japanese-Patent No. 5-307956

  In consideration of the characteristics of the carbon material as described above, by combining amorphous carbon and graphite to maintain high energy density and enhancing output characteristics, and by making graphite coated with amorphous carbon A negative electrode material has also been proposed in which the output characteristics are enhanced while reducing the surface reactivity and maintaining the initial charge and discharge efficiency well. However, input / output characteristics and life characteristics are in a trade-off relationship. From the above-mentioned background, in the automotive lithium ion secondary battery such as EV and HEV, further, input / output characteristics and high temperature storage characteristics are also required.

  An object of this invention is to provide the manufacturing method of the negative electrode material for lithium ion secondary batteries in which the lithium ion secondary battery which is excellent in an input-output characteristic and a high temperature storage characteristic in view of the said subject is obtained.

<1> A process of subjecting a mixture containing an organic compound that can change to carbonaceous by heat treatment and a compound that contains a nitrogen atom to a heat treatment, and softening point X of the organic compound that can change to carbonaceous by the heat treatment The manufacturing method of the negative electrode material for lithium ion secondary batteries that thermal decomposition temperature Y (degree C) of the compound containing said nitrogen atom satisfy | fills X / Y = 0.2-0.9.
The manufacturing method of the negative electrode material for lithium ion secondary batteries as described in <1> which satisfy | fills at least any one of <2> following (A) or (B).
(A) A mixture containing an organic compound that can be converted to carbonaceous by heat treatment and a compound containing a nitrogen atom further includes a carbon material.
(B) Heat treatment of a mixture containing a heat treatment product of a mixture containing an organic compound that can change to carbonaceous by heat treatment and a compound containing a nitrogen atom, an organic compound that can change to carbonaceous by heat treatment, and a carbon material It has the process of mixing things and.
The manufacturing method of the negative electrode material for lithium ion secondary batteries as described in <2> whose volume average particle diameter of the <3> above-mentioned carbon material is 1 micrometer-40 micrometers.
<4> Production of Anode Material for Lithium Ion Secondary Battery According to any one of <1> to <3>, wherein the volume average particle diameter of the obtained anode material for lithium ion secondary battery is 1 μm to 40 μm Method.
Any one of <1>-<4> whose heat processing temperature in the process of heat-treating the mixture containing the organic compound which can be changed into carbonaceous by the said heat processing, and the compound containing a nitrogen atom is 700 degreeC-1500 degreeC. The manufacturing method of the negative electrode material for lithium ion secondary batteries of any one of-.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the negative electrode material for lithium ion secondary batteries in which the lithium ion secondary battery which is excellent in an input-output characteristic and a high temperature storage characteristic is obtained is provided.

It is a graph which shows an example of the measurement result of the thermal decomposition temperature of the compound (melamine) containing a nitrogen atom.

  Hereinafter, modes for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and ranges thereof, and does not limit the present invention.

In the present specification, the term "step" includes, in addition to steps independent of other steps, such steps as long as the purpose of the step is achieved even if it can not be clearly distinguished from other steps. Be
In the numerical value range indicated by using “to” in the present specification, the numerical values described before and after “to” are included as the minimum value and the maximum value, respectively.
In the numerical ranges that are described stepwise in the present specification, the upper limit or the lower limit described in one numerical range may be replaced with the upper limit or the lower limit of the numerical range described in the other stepwise Good. In addition, in the numerical range described in the present specification, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the example.
In the present specification, the content or content of each component in the composition is the number of the plurality of types present in the composition unless a plurality of substances corresponding to each component are present in the composition. The total content or content of substances is meant.
In the present specification, the particle diameter of each component in the composition is the mixture of the plurality of particles present in the composition unless a plurality of particles corresponding to each component are present in the composition. Means a value about.

  The manufacturing method of the negative electrode material for lithium ion secondary batteries of the present embodiment (hereinafter, also simply referred to as “negative electrode material”) includes an organic compound which can be changed to carbonaceous by heat treatment, and a compound containing nitrogen atoms. Heat treatment of the mixture (hereinafter, also simply referred to as “mixture”), the softening point X (° C.) of the organic compound that can change to carbonaceous by the heat treatment, and the thermal decomposition temperature of the compound containing the nitrogen atom Y (° C.) satisfies X / Y = 0.2 to 0.9.

  According to the above method, it is possible to efficiently manufacture a negative electrode material for a lithium ion secondary battery from which a lithium ion secondary battery having excellent output characteristics and high temperature storage characteristics can be obtained.

  The kind in particular of the organic compound which can be changed into carbonaceous by heat treatment contained in a mixture is not restricted, but pitch, organic polymer compound, etc. are mentioned. As the pitch, ethylene heavy-end pitch, crude oil pitch, coal tar pitch, asphalt decomposition pitch, pitch produced by thermal decomposition of polyvinyl chloride etc., pitch produced by polymerizing naphthalene etc. in the presence of super strong acid Can be mentioned. Examples of the organic polymer compound include thermoplastic resins such as polyvinyl chloride, polyvinyl alcohol, polyvinyl acetate and polyvinyl butyral, and natural substances such as starch and cellulose. The organic compound which can be changed to carbonaceous by the heat treatment contained in the mixture may be only one type or two or more types.

  The type of the compound containing a nitrogen atom contained in the mixture is not particularly limited. For example, a compound in which only nitrogen atoms and carbon atoms remain in the negative electrode material after heat treatment is preferable, and an organic compound containing nitrogen atoms is more preferable. Specific examples of nitrogen-containing compounds include nitrogen-containing cyclic organic substances such as melamine, guanamine, N-methylpyrrolidone, pyridine and pyrrole, compounds having an amino group such as aniline and urea, and amide bonds such as acetamide and acetanilide. And compounds having a nitrile group such as acetonitrile and acrylonitrile. The compound containing a nitrogen atom may be a high molecular compound obtained by using a low molecular weight compound containing a nitrogen atom as a raw material. The compound containing a nitrogen atom contained in the mixture may be only one or two or more.

  In the above-mentioned method, the method for preparing a mixture containing an organic compound which can be converted to carbonaceous by heat treatment and a compound containing a nitrogen atom is not particularly limited. For example, a method of mixing an organic compound that can change to carbonaceous by heat treatment and an organic compound containing nitrogen atoms into a solvent and then removing the solvent (wet mixing method), an organic compound that can change to carbonaceous by heat treatment, and a nitrogen atom Method of mixing in a powder state (powder mixing method), a method of mixing an organic compound that can change to carbonaceous by heat treatment and a compound containing nitrogen atoms while applying mechanical energy (mechanical mixing Method etc. From the viewpoint of efficient production, the wet mixing method and the powder mixing method are preferable, and the powder mixing method is more preferable. With this method, the number of heat treatments can be reduced.

  In the above-mentioned method, the amount of the organic compound which can be converted to carbonaceous by the heat treatment used is not particularly limited. From the viewpoint of the input / output characteristics of the lithium ion secondary battery, the ratio of the carbonaceous substance obtained from the organic compound which can be changed to carbonaceous by the heat treatment in the total mass of the obtained negative electrode material is 0.1 mass% or more The amount is preferably 0.5% by mass or more, more preferably 1% by mass or more. From the viewpoint of suppressing the decrease in capacity of the lithium ion secondary battery, the ratio of the carbonaceous substance obtained from the organic compound which can be changed to carbonaceous by the heat treatment in the total mass of the obtained negative electrode material is 30% by mass or less The amount is preferably, more preferably 20% by mass or less, and still more preferably 10% by mass or less.

  In the above method, the amount of the compound containing a nitrogen atom to be used is not particularly limited. From the viewpoint of the output characteristics of the lithium ion secondary battery, the content of nitrogen atoms in the manufactured negative electrode material is preferably 0.2% by mass or more, and preferably 0.3% by mass or more. It is more preferable that From the viewpoint of making the band gap between the carbon-nitrogen bond appropriate and maintaining the electron conductivity well, the amount of nitrogen source in the mixture before heat treatment is 5 mass of nitrogen atom content in the obtained negative electrode material The amount is preferably at most%, and more preferably at most 2% by mass. The content of the nitrogen source in the negative electrode material or the mixture, or the content of nitrogen atoms in the obtained negative electrode material can be determined by an inert gas melting-thermal conductivity method (based on JIS G 1228 2006).

  From the viewpoint of improving the output characteristics, the softening point X (° C.) of the organic compound that can change to carbonaceous matter and the thermal decomposition temperature Y (° C.) of the compound containing the nitrogen atom satisfy X / Y = 0.2. It is preferable to satisfy -0.9 and to satisfy 0.4-0.7.

  From the viewpoint of improving the output characteristics, the softening point of the organic compound that can change to carbonaceous matter is preferably 70 ° C. to 120 ° C., and more preferably 80 ° C. to 110 ° C.

  From the viewpoint of improving output characteristics, the thermal decomposition temperature of the compound containing a nitrogen atom is preferably 130 ° C. to 300 ° C., and more preferably 140 ° C. to 280 ° C.

In the present disclosure, “mixture” means that in which some or all of the respective materials contained in the mixture are complexed. The “complexed state” means a state in which some or all of the respective materials are in physical or chemical contact.
The negative electrode material produced through the step of heat treatment in the state where the organic compound that can change to carbonaceous by heat treatment and the compound containing nitrogen atoms are complexed is an organic compound that can change to carbonaceous by heat treatment and nitrogen Compared with the negative electrode material manufactured by heat-processing in the state which is not compounded with the compound containing an atom, it is excellent by the output characteristic and the high temperature storage characteristic.

  Preferably, the method further uses a carbon material. The carbon material used in the above method is not particularly limited. Specifically, graphite, low crystalline carbon, amorphous carbon, mesophase carbon and the like can be mentioned. Examples of the graphite include artificial graphite, natural graphite, graphitized mesophase carbon, graphitized carbon fiber and the like. Examples of carbon materials having lower crystallinity than graphite include acetylene black, oil furnace black, ketjen black, channel black, thermal black, soil graphite and the like. The carbon material used may be only one kind or two or more kinds.

  The carbon material used in the above method is preferably a material having higher crystallinity than a carbonaceous substance obtained from an organic compound that can be converted to a carbonaceous substance by heat treatment, and more preferably graphite.

  The negative electrode material produced by the above method preferably includes a first carbon material serving as a core and a second carbon material present in at least a part of the surface of the first carbon material, and the second carbon material More preferably, it contains a carbonaceous substance obtained from an organic compound that can be converted to carbonaceous by heat treatment.

Even if the negative electrode material manufactured by the above method is provided with the first carbon material, all of which becomes a core, and the second carbon material, which is present in at least a part of the surface of the first carbon material, You may provide the 1st carbon material used as a nucleus, and the 2nd carbon material which exists in at least one copy of the surface of the 1st carbon material.
It is confirmed by, for example, transmission electron microscope observation whether or not the negative electrode material has a first carbon material as a core and a second carbon material present on at least a part of the surface of the first carbon material. Can.

  The above method in the case of using a carbon material is a method (manufacturing method A) in which a mixture containing an organic compound that can change to carbonaceous by heat treatment and a compound containing nitrogen atoms further includes a carbon material (heat treatment method A) A heat-treated product of a mixture containing an organic compound that can change to carbonaceous by the following, a compound containing a nitrogen atom, an organic compound that can change to carbonaceous by heat treatment, and a heat-treated product of a mixture that includes a carbon material The method (manufacturing method B) which has the process to mix, and these combination are mentioned.

  According to production method A, it is possible to produce a negative electrode material in which a nitrogen atom is contained in the inside of the second carbon material present in at least a part of the surface of the first carbon material as a nucleus.

  According to production method B, it is possible to produce a negative electrode material in which a nitrogen atom is contained outside the second carbon material present on at least a part of the surface of the first carbon material serving as a nucleus.

  From the viewpoint of increasing the charge and discharge capacity of the lithium ion secondary battery, the carbon material used in the above method preferably contains graphite, and more preferably contains graphite as a first carbon material serving as a core. The shape of the graphite is not particularly limited, and scaly, spherical, massive, fibrous and the like can be mentioned. From the viewpoint of obtaining a high tap density, it is preferably spherical.

The volume average particle diameter (D ₅₀ ) of the carbon material is not particularly limited, but is preferably 1 μm to 40 μm, more preferably 3 μm to 30 μm, and still more preferably 5 μm to 25 μm.

When the volume average particle diameter (D ₅₀ ) of the carbon material is 1 μm or more, sufficient tap density of the obtained negative electrode material and good coatability can be obtained when the obtained negative electrode material is the negative electrode material composition There is a tendency. On the other hand, when the volume average particle diameter of the carbon material is 40 μm or less, the diffusion distance of lithium from the surface of the obtained negative electrode material to the inside is not too long, and the input / output characteristics of the lithium ion secondary battery are well maintained. Tend to

The volume average particle diameter (D ₅₀ ) of the carbon material is a particle diameter at which the accumulation from the small diameter side is 50% in the volume-based particle diameter distribution obtained by the laser diffraction / scattering method. The volume average particle size (D ₅₀ ) is measured, for example, by dispersing a carbon material in purified water containing a surfactant, and using a laser diffraction type particle size distribution measuring apparatus (eg, SALD-3000 J, manufactured by Shimadzu Corporation). be able to.

  As a carbon material, you may use what processed the surface previously (pre-processing). The method for treating the surface of the carbon material is not particularly limited. For example, from the viewpoint of suppressing the pulverization of the carbon material and modifying the surface state, for example, a process of filling the carbon material in an alumina crucible and leaving at 300 ° C. or higher in an air atmosphere, dry particle composite device The treatment which has been done is preferable. It is preferable to carry out the heat treatment in advance according to the filling amount, the treatment time, the oxygen concentration, etc., so that it is preferable to carry out these conditions appropriately, but the BET specific surface area is increased by 2% to 50% compared to before the treatment. It is preferable to A lithium ion secondary battery excellent in output characteristics and storage characteristics, which tends to obtain a surface state that is easily complexed with a carbonaceous substance obtained from an organic compound that can change to carbonaceous by heat treatment, by performing pretreatment Anode materials tend to be obtained.

  The firing temperature in the step of heat treating the mixture is not particularly limited. For example, the temperature is preferably 700 ° C. to 1500 ° C., more preferably 750 ° C. to 1300 ° C., and still more preferably 800 ° C. to 1200 ° C. The heat treatment temperature is preferably 700 ° C. or higher from the viewpoint of sufficiently advancing carbonization of the organic compound that can change to carbonaceous by heat treatment, and the nitrogen content by desorption of nitrogen from the compound containing a nitrogen atom It is preferable that the heat processing temperature is 1500 degrees C or less from a viewpoint of suppressing the fall of these. The temperature of the heat treatment may be constant or change from the start to the end of the heat treatment.

  In the negative electrode material manufactured by the above method, the content of nitrogen atom is not particularly limited. From the viewpoint of obtaining a sufficient improvement effect of high temperature storage characteristics, the content of nitrogen atoms in the entire negative electrode material is preferably 0.2 mass% or more, and more preferably 0.3 mass% or more. From the viewpoint of making the band gap between the carbon-nitrogen bond appropriate and maintaining the electron conductivity well, the content of nitrogen atoms in the entire negative electrode material is preferably 5% by mass or less, and 2% by mass or less It is more preferable that The nitrogen atom content can be determined by the inert gas melting-thermal conductivity method (based on JIS G 1228 2006).

  In the negative electrode material of the present embodiment, the carbon atom content is not particularly limited. From the viewpoint of suppressing the capacity reduction, the content of carbon atoms in the entire negative electrode material is preferably 90% by mass or more, more preferably 93% by mass or more, and further preferably 95% by mass or more. preferable. The carbon atom content can be determined by an inert gas melting-thermal conductivity method (based on JIS G 1228 2006).

  From the viewpoint of suppressing the side reaction during charge and discharge, the total content of nitrogen atoms and carbon atoms in the entire negative electrode material is preferably 92% by mass or more, more preferably 95% by mass or more, and 99% by mass % Or more, and more preferably substantially 100% by mass.

  When the first carbon material in which the negative electrode material forms a core and the second carbon material present on at least a part of the surface of the first carbon material, the first carbon material and the second carbon material in the negative electrode material The proportion of the amount is not particularly limited. From the viewpoint of improving input / output characteristics, the ratio of the amount of the second carbon material to the total mass of the negative electrode material is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more, More preferably, it is 1% by mass or more. From the viewpoint of suppressing a decrease in capacity, the proportion of the second carbon material in the total mass of the negative electrode material is preferably 30% by mass or less, more preferably 20% by mass or less, and 10% by mass or less It is further preferred that

  When the amount of the second carbon material in the negative electrode material is calculated from the amount of the organic compound that can be changed to carbonaceous by the heat treatment, the residual carbon ratio (mass%) to the amount of the organic compound that can be changed to carbonaceous by the heat treatment It can be calculated by multiplying The residual carbon ratio of the organic compound that can be changed to carbonaceous by heat treatment is the organic compound that can be changed to carbonaceous by heat treatment alone (or the organic compound and first carbon material that can be changed to carbonaceous by a predetermined ratio of heat treatment) Heat treatment at a temperature at which an organic compound that can change to carbonaceous matter can change to carbonaceous matter by heat treatment, and the mass of the organic compound that can change to carbonaceous matter by heat treatment before heat treatment, and carbon by heat treatment after heat treatment From the mass of the carbonaceous substance derived from the organic compound which can be changed to the quality, it can be calculated by thermogravimetric analysis or the like.

(X-ray photoelectron spectroscopy)
The negative electrode material obtained by the manufacturing method of the present embodiment preferably has at least two peaks in the range of 395 eV to 405 eV in the X-ray photoelectron spectroscopy spectrum. As a result, the negative electrode material having excellent output characteristics tends to be easily obtained while maintaining the high temperature storage characteristics.
The X-ray photoelectron spectroscopy spectrum in the invention can be measured by X-ray photoelectron spectroscopy (XPS). For measurement, ULVAC-PHI "Versa Probe II" can be used, and the measurement conditions shown in the examples described later can be adopted.

  Having at least two peaks in the range of 395 eV to 405 eV in the X-ray photoelectron spectroscopy spectrum means that there is a bond of carbon atom and nitrogen atom in the negative electrode material, and two or more bond states of carbon atom and nitrogen atom It means that there is. That is, in the negative electrode material obtained by the manufacturing method of the present embodiment, it is preferable that a bond of a carbon atom and a nitrogen atom exists, and the bonding state of the carbon atom and the nitrogen atom is two or more.

  The negative electrode material obtained by the manufacturing method of the present embodiment has at least two peaks in the range of 395 eV to 405 eV in the X-ray photoelectron spectrum, and the at least two peaks are peaks in the range of 395 eV to less than 400 eV; It is preferable to include a peak in the range of 400 eV or more and 405 eV or less.

From the viewpoint of high temperature storage characteristics, the negative electrode material obtained by the manufacturing method of the present embodiment has the second largest peak and the second largest peak among the peaks existing in the range of 395 eV to 405 eV in the X-ray photoelectron spectroscopy spectrum Among the peaks, the ratio (A / B) of the peak intensities of the peak A closer to 395 eV and the peak B closer to 405 eV is preferably 0.1 to 10.
More preferably, it has at least one peak in the range of 395 eV or more and less than 400 eV and the range of 400 eV or more and 400 eV or less in the X-ray photoelectron spectroscopy spectrum, and the peak A ′ having the largest intensity in the range of 395 eV or more and less than 400 eV The ratio (A '/ B') of the peak intensity to the peak B 'having the largest intensity in the range of 400 eV or more and 405 eV or less is 0.1 to 10.

  From the viewpoint of obtaining a lithium ion secondary battery in which the balance of the electronic state is better and the input / output characteristics and the life are more excellent, the peak intensity ratio (A / B or A ′ / B ′) is respectively 0.3 to It is more preferable that it is 3, and it is still more preferable that it is 0.5-2.

  In one aspect, the negative electrode material obtained by the manufacturing method of the present embodiment includes a nitrogen atom (graphite type) bonded to three carbon atoms and a nitrogen atom (pyridine type) bonded to two carbon atoms. And. Whether or not the negative electrode material contains a nitrogen atom bonded to three carbon atoms can be confirmed by, for example, whether or not a peak exists in the vicinity of 401 eV in the X-ray photoelectron spectroscopy spectrum, and the negative electrode material Whether or not a nitrogen atom bonded to two carbon atoms is contained can be confirmed by, for example, whether or not a peak is present around 398 eV in an X-ray photoelectron spectroscopy spectrum.

  From the viewpoint of high temperature storage characteristics, the negative electrode material obtained by the manufacturing method of the present embodiment has at least two peaks in the range of 395 eV to 405 eV in the X-ray photoelectron spectroscopy spectrum, and at least two peaks thereof are around 398 eV It is preferable to include the peak of and the peak around 401 eV.

(Average spacing d ₀₀₂ determined by X-ray diffraction)
The negative electrode material obtained by the manufacturing method of this embodiment preferably has an average interplanar spacing d ₀₀₂ of 0.340 nm or less as determined by X-ray diffraction. If the average interplanar spacing d ₀₀₂ is 0.340 nm or less, both the initial charge and discharge efficiency and the energy density of the lithium ion secondary battery tend to be excellent. The energy density tends to be larger as the value of the average interplanar spacing d ₀₀₂ is closer to 0.3354 nm, which is the theoretical value of the graphite crystal.

The average interplanar spacing d ₀₀₂ of the negative electrode material is such that X-rays (CuKα rays) are irradiated to the sample which is the negative electrode material and the diffraction line is measured with a goniometer, and the diffraction angle 2θ = 24 ° to 2
From the diffraction peak corresponding to the carbon 002 surface appearing around 7 °, it can be calculated using Bragg's equation.

The value of the average interplanar spacing d ₀₀₂ of the negative electrode material tends to decrease, for example, by raising the temperature of heat treatment at the time of producing the negative electrode material. Therefore, the average interplanar spacing d ₀₀₂ of the negative electrode material can be controlled by adjusting the temperature of the heat treatment at the time of producing the negative electrode material.

(R value of Raman spectroscopy)
The negative electrode material obtained by the manufacturing method of the present embodiment preferably has an R value obtained by Raman spectroscopy of 0.1 to 1.0, more preferably 0.2 to 0.8, and 0 It is further more preferable that it is .3 to 0.7. If the R value is 0.1 or more, graphite lattice defects used for insertion and desorption of lithium ions are sufficiently present, and a decrease in input / output characteristics tends to be suppressed. When the R value is 1.0 or less, the decomposition reaction of the electrolytic solution is sufficiently suppressed, and a decrease in the initial efficiency tends to be suppressed.

The R value is the Raman spectrum obtained in the Raman spectrometry, to define the intensity Ig of the maximum peak in the vicinity of 1580 cm ^-1, the intensity ratio of the intensity Id of the maximum peak around 1360 cm ^-1 and (Id / Ig) . Here, the peak appearing near 1580 cm ^-1, generally a peak identified as corresponding to the graphite crystal structure, means a peak observed for example ^{1530cm -1 ~1630cm} -1. The peak appearing around 1360 cm ⁻¹ is usually a peak identified as corresponding to the amorphous structure of carbon, for example, 1300.
It means a peak observed in cm ^-1 ~1400cm ^-1.

In the present disclosure, Raman spectroscopy is performed by using a laser Raman spectrophotometer (for example, model number: NRS-1000, JASCO Corporation) and using argon as a sample plate in which a negative electrode material for lithium ion secondary batteries is set to be flat. It is performed by irradiating a laser beam. The measurement conditions are as follows.
Wavelength of argon laser light: 532 nm
Wavenumber resolution: 2.56 cm ^-1
Measurement range: 1180 cm ^{-1 to} 1730 cm ^-1
Peak research: background removal

(Volume average particle size (D ₅₀ ))
The volume average particle diameter (D ₅₀ ) of the negative electrode material obtained by the manufacturing method of the present embodiment is preferably 1 μm to 40 μm, more preferably 3 μm to 30 μm, and still more preferably 5 μm to 25 μm. .
When the volume average particle diameter of the negative electrode material is 1 μm or more, sufficient tap density and good coatability when used as a negative electrode composition tend to be obtained. On the other hand, when the volume average particle diameter of the negative electrode material is 40 μm or less, the diffusion distance of lithium from the surface of the negative electrode material to the inside is not too long, and the input / output characteristics of the lithium ion secondary battery tend to be well maintained. It is in. The volume average particle diameter (D ₅₀ ) of the negative electrode material can be measured in the same manner as the above-mentioned volume average particle diameter of the carbon material.

(Specific surface area)
Specific surface area determined from nitrogen adsorption measurements at 77K of the negative electrode material obtained by the production method of this embodiment (hereinafter sometimes referred to as _{N 2} specific surface area) ^is a 0.5m ² / g ~10m 2 / g preferably ^there, more preferably 1m ² / g~8m 2 / ^g, and further preferably from 2m ² / g~6m 2 / g. If the N ₂ specific surface area is within the above range, a good balance between input / output characteristics and initial charge / discharge efficiency tends to be obtained. Specifically, the N ₂ specific surface area can be determined from the adsorption isotherm obtained by nitrogen adsorption measurement at 77 K using the BET method.

(Roundness)
The circularity of the negative electrode material obtained by the manufacturing method of the present embodiment is preferably 0.70 or more, more preferably 0.80 or more, still more preferably 0.85 or more, and 0. It is particularly preferred that it is 90 or more. When the degree of circularity is 0.70 or more, continuous charge acceptance tends to be improved. The circularity of the negative electrode material can be determined by flow type particle analysis. For example, it can measure using a wet flow type | formula particle diameter and shape analyzer (FPIA-3000, Malvern company).

  Since the negative electrode material obtained by the manufacturing method of the present embodiment is excellent in high-temperature storage characteristics, it can be used as an electric vehicle (EV), a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), a power tool, a power storage device, etc. It is suitable as a negative electrode material for a large capacity lithium ion secondary battery to be used. In particular, it is suitable as a negative electrode material for lithium ion secondary batteries used in EVs, PHEVs, HEVs and the like for which adaptation in various environments is required.

<Method of Manufacturing Negative Electrode for Lithium Ion Secondary Battery>
The method for producing a negative electrode for a lithium ion secondary battery of the present embodiment has a step of producing a negative electrode material for a lithium ion secondary battery by the above method.
The negative electrode for a lithium ion secondary battery manufactured by the above method may be provided with a negative electrode material layer containing the negative electrode material for a lithium ion secondary battery manufactured by the above method, and a current collector, and it is necessary May be provided with other components depending on

  For example, a negative electrode material for lithium ion secondary battery is prepared by kneading a negative electrode material and a binder together with a solvent to prepare a slurry-like negative electrode material composition, and applying it on a current collector to form a negative electrode material layer. Thus, the negative electrode material composition can be formed into a sheet-like shape, a pellet-like shape, or the like and integrated with a current collector. The kneading can be carried out using a dispersing device such as a stirrer, a ball mill, a super sand mill, a pressure kneader or the like.

  The binder used for preparation of the negative electrode material composition is not particularly limited. For example, ethylenically unsaturated carboxylic acid esters such as styrene-butadiene copolymer, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, acrylonitrile, methacrylonitrile, hydroxyethyl acrylate, hydroxyethyl methacrylate, etc. Ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid, and maleic acid; and ion conductive materials such as polyvinylidene fluoride, polyethylene oxide, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, etc. Large macromolecular compounds can be mentioned. When the negative electrode material composition contains a binder, the amount is not particularly limited. For example, it may be 0.5 parts by mass to 20 parts by mass with respect to a total of 100 parts by mass of the negative electrode material and the binder.

The negative electrode material composition may contain a thickener. As a thickener, carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, polyacrylic acid or salts thereof, oxidized starch, phosphorylated starch, casein and the like can be used. When the negative electrode material composition contains a thickener, the amount is not particularly limited.
For example, it may be 0.1 parts by mass to 5 parts by mass with respect to 100 parts by mass of the negative electrode material.

  The negative electrode material composition may contain a conductive auxiliary material. Examples of the conductive aid include carbon materials such as carbon black, graphite and acetylene black, and compounds such as oxides and nitrides exhibiting conductivity. When the negative electrode material composition contains a conductive aid, the amount is not particularly limited. For example, 0.5 parts by mass to 15 parts by mass may be used with respect to 100 parts by mass of the negative electrode material.

  The material of the current collector is not particularly limited, and can be selected from aluminum, copper, nickel, titanium, stainless steel and the like. The state of the current collector is not particularly limited, and can be selected from foil, perforated foil, mesh and the like. In addition, porous materials such as porous metal (foam metal), carbon paper, and the like can also be used as the current collector.

  When the negative electrode material composition is applied to a current collector to form a negative electrode layer, the method is not particularly limited, and metal mask printing, electrostatic coating, dip coating, spray coating, roll coating, A known method such as a doctor blade method, a comma coating method, a gravure coating method, or a screen printing method can be adopted. After the negative electrode material composition is applied to the current collector, the solvent contained in the negative electrode material composition is removed by drying. Drying can be performed, for example, using a hot air dryer, an infrared dryer, or a combination of these devices. A rolling process may be performed as needed. The rolling process can be performed by a method such as a flat plate press or a calender roll.

  When the negative electrode composition molded into a sheet, pellet, or the like is integrated with a current collector to form a negative electrode material layer, the method of integration is not particularly limited. For example, it can be performed by a roll, a flat plate press, or a combination of these means. The pressure at the time of integration is preferably, for example, about 1 MPa to 200 MPa.

The negative electrode density of the negative electrode material is not particularly limited. For ^example, is preferably ^{1.1g / cm 3 ~1.8g / cm 3} , more preferably from ^{1.2g / cm 3 ~1.7g / cm 3} , 1.3g / cm 3 ~1. More preferably, it is 6 g / cm ³ . Negative electrode density is 1.1
By setting it as g / cm ³ or more, the increase in electron resistance is suppressed and the capacity tends to be increased. By setting it as 1.8 g / cm ³ or less, the deterioration of rate characteristics and cycle characteristics is suppressed. There is.

<Method of manufacturing lithium ion secondary battery>
The manufacturing method of the lithium ion secondary battery of this embodiment has the process of manufacturing the negative electrode material for lithium ion secondary batteries by the said method.
The lithium ion secondary battery may be provided with a negative electrode including a negative electrode material for lithium ion secondary battery manufactured by the above method, a positive electrode, and an electrolytic solution, and other components may be used if necessary. It may be provided.

  The positive electrode can be obtained by forming a positive electrode layer on a current collector in the same manner as the above-described method of manufacturing a negative electrode. As the current collector, a metal or an alloy of aluminum, titanium, stainless steel or the like in the form of a foil, a perforated foil, a mesh or the like can be used.

The positive electrode material used to form the positive electrode layer is not particularly limited. For example, metal compounds (metal oxides, metal sulfides, etc.) and conductive polymer materials that can be doped or intercalated with lithium ions can be mentioned. More specifically, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), these double oxides (LiCo _x Ni _y Mn _z O ₂ , x + y + z = 1), Mixed oxides containing additive element M ′ (LiCo _a Ni _b Mn _c M ′ _d O ₂ , a + b + c + d = 1, M ′: Al, Mg, Ti, Zr or Ge), spinel type lithium manganese oxide (LiMn ₂ O) ₄ ), lithium vanadium compounds, V ₂ O ₅ , V ₆ O ₁₃ , VO ₂ , MnO ₂ , TiO ₂ , MoV ₂ O ₈ , TiS ₂ , V ₂ S ₅ , VS ₂ , MoS ₂ , MoS ₃ , Cr _{3 O 8, Cr} 2 O _5, olivine-type _{LiMPO 4 (M: Co, Ni} , Mn, Fe) lithium-containing compounds such as polyacetylene, Poriani Emissions, polypyrrole, polythiophene, electrically conductive polymers such as polyacene, a porous carbon and the like. The positive electrode materials may be used alone or in combination of two or more.

The electrolyte solution is not particularly limited, and for example, one obtained by dissolving a lithium salt as an electrolyte in a non-aqueous solvent (so-called organic electrolyte solution) can be used.
Examples of lithium salts include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSO ₃ CF _{3 and the} like. The lithium salt may be used alone or in combination of two or more.
As a non-aqueous solvent, ethylene carbonate, fluoroethylene carbonate, chloroethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, cyclopentanone, cyclohexylbenzene, sulfolane, propane sultone, 3-methyl sulfolane, 2,4-dimethyl sulfolane, 3-Methyl-1,3-oxazolidin-2-one, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, butyl methyl carbonate, ethyl propyl carbonate, butyl ethyl carbonate, dipropyl carbonate, 2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, methyl acetate Ethyl acetate, trimethyl phosphate ester, triethyl ester, and the like. The non-aqueous solvent may be used alone or in combination of two or more.

  The state of the positive electrode and the negative electrode in the lithium ion secondary battery is not particularly limited. For example, the positive electrode and the negative electrode, and, if necessary, the separator disposed between the positive electrode and the negative electrode may be spirally wound or may be stacked in a flat plate shape.

  The separator is not particularly limited, and for example, resin non-woven fabric, cloth, microporous film, or a combination thereof can be used. As resin, what has polyolefin, such as polyethylene and a polypropylene, as a main component is mentioned. If the positive electrode and the negative electrode are not in direct contact with each other due to the structure of the lithium ion secondary battery, the separator may not be used.

  The shape of the lithium ion secondary battery is not particularly limited. For example, laminate type batteries, paper type batteries, button type batteries, coin type batteries, laminated type batteries, cylindrical type batteries and square type batteries can be mentioned.

  Hereinafter, the present invention will be more specifically described by way of examples, but the present invention is not limited to the following examples.

Example 1
(1) Preparation and evaluation of negative electrode material 100 parts by mass of spherical natural graphite (volume average particle diameter: 10 μm) as a carbon material and 10 parts by mass of coal tar pitch (softening point) as an organic compound which can be changed to carbonaceous by heat treatment : 98 ° C., residual carbon content: 50% by mass) and 5 parts by mass of melamine (Wako Pure Chemical Industries, Ltd., thermal decomposition temperature: 230 ° C.) as a compound containing a nitrogen atom to obtain a mixture The Next, the mixture is heat-treated to form a first carbon material as a core, and a second carbon material present on at least a part of the surface of the first carbon material and having a crystallinity lower than that of the first carbon material. The carbon material containing was produced. The heat treatment was performed by raising the temperature from 25 ° C. to 1000 ° C. at a temperature rising rate of 200 ° C./hour under nitrogen flow and holding at 1000 ° C. for 1 hour. The obtained carbon material was crushed by a cutter mill, screened with a 300 mesh sieve, and the lower part of the sieve was used as a negative electrode material.

[Calculation of X / Y]
The softening point X (.degree. C.) of the organic compound which can be changed to carbonaceous by heat treatment and the thermal decomposition temperature Y (.degree. C.) of the compound containing a nitrogen atom are measured by the method shown below, and the value obtained is X / Y. I asked for.

(Softening point of organic compounds that can change to carbonaceous by heat treatment)
The softening point of the organic compound that can be changed to carbonaceous by heat treatment was measured in accordance with JIS K 2425: 2006.

(Thermal decomposition temperature of the compound containing nitrogen atom)
The thermal decomposition temperature (° C.) of the compound containing a nitrogen atom was measured under the following conditions, and from the obtained graph, the point at which the baseline and the weight loss line were connected by a straight line was taken as the thermal decomposition temperature. As an example, a graph obtained by measuring melamine is shown in FIG.
Device: TG-DTA (TG / DTA 6200, Seiko Instruments Inc.)
Atmosphere: Nitrogen atmosphere Temperature rising rate: 10 ° C / min
Bread: platinum bread

[XPS analysis]
XPS analysis was performed using Versa Probe II (ULVAC-PHI) under the following conditions, and the number of peaks in the range of 395 eV to 405 eV was examined in an X-ray photoelectron spectroscopy spectrum. In addition, the ratio (A / B) of the peak intensities of the peak A closer to 395 eV and the peak B closer to 405 eV among the peak having the largest intensity and the second largest peak in the range of 395 eV to 405 eV Examined.
Equipment: ULVAC-PHI, PHI 5000 Versa Probe II
X-ray source: monochromized Al K-L 2,3 line (1486.6 eV)
Detection angle: 45 degrees Analysis area: 200 μmφ
X-ray beam diameter: 200 μmφ
X-ray output: 50 W, 15 kV
Pass energy C (1s): 23.5 eV, N (1s): 29.35 eV, O (1s): 29.35 eV
Neutralization gun: Use Charge correction: Correct the peak top of C (1s) to 284.8 eV

[Measurement of nitrogen content rate]
The nitrogen content (% by mass) was determined by melting a negative electrode material sample at 3000 ° C. in an inert atmosphere using TC-600 (LECO Japan Ltd.), generating nitrogen gas, and determining it by the thermal conductivity method .

[Measurement of average interplanar spacing d ₀₀₂ ]
The measurement of the average interplanar spacing d ₀₀₂ (nm) was performed by the X-ray diffraction method. Specifically, the negative electrode material sample was filled in the concave portion of the sample holder made of quartz and set on the measurement stage, and the measurement was performed using the wide-angle X-ray diffractometer (Rigaku Co., Ltd.) under the following measurement conditions.
Radiation source: CuKα ray (wavelength = 0.15418 nm)
Output: 40kV, 20mA
Sampling width: 0.010 °
Scanning range: 10 ° to 35 °
Scanning speed: 0.5 ° / min

[Measurement of R value]
R value, performs Raman spectrometry under the following conditions, in the obtained Raman spectrum, the intensity Ig of the maximum peak in the vicinity of 1580 cm ^-1, the intensity ratio of the intensity Id of the maximum peak in the vicinity of 1360 cm ^-1 (Id / Ig).
The Raman spectroscopy measurement was performed using a laser Raman spectrophotometer (model number: NRS-1000, JASCO Corporation) and irradiating a sample plate set so that the negative electrode material sample was flat with argon laser light. The measurement conditions are as follows.
Wavelength of argon laser light: 532 nm
Wavenumber resolution: 2.56 cm ^-1
Measurement range: 1180 cm ^{-1 to} 1730 cm ^-1
Peak research: background removal

[Measurement of N ₂ specific surface area]
N ₂ specific surface area (m ² / g) is a multi-point nitrogen adsorption at liquid nitrogen temperature (77 K) using a high-speed specific surface area / pore distribution measurement device (Flow Soap II 2300, Tokai Riki Co., Ltd.) Measured by the method and calculated by the BET method.

[Measurement of Volume Average Particle Size]
A solution in which a negative electrode material sample and a surfactant were dispersed in purified water was placed in a sample water tank of a laser diffraction type particle size distribution measuring apparatus (SALD-3000J, manufactured by Shimadzu Corporation). Next, the solution was circulated by a pump while applying ultrasonic waves, and the volume cumulative 50% particle diameter (D ₅₀ ) of the obtained particle size distribution was defined as the volume average particle diameter (μm).

[Measurement of circularity]
In a 10 ml test tube, add 5 ml of an aqueous solution containing 0.2% by weight of surfactant (trade name: Liponol T / 15, manufactured by Lion Corporation) to a particle concentration of 10000 to 30000. The negative electrode material sample was put. Then, after stirring the test tube with a vortex mixer (manufactured by Corning) at a rotational speed of 2,000 rpm for 1 minute, the wet flow type particle size / shape analyzer (FPIA-3000 manufactured by Malvern, Inc.) is immediately made. Was used to measure the degree of circularity. The measurement conditions are as follows.
Measurement environment: 25 ° C ± 3
Measurement mode: HPF
Counting method: Total count Effective analysis number: 10000
Particle concentration: 10000 to 30000
Sheath fluid: Particle sheath Objective lens: 10 times

(2) Preparation of lithium ion secondary battery With respect to 98 parts by mass of the negative electrode material, an aqueous solution (CMC concentration: 2% by mass) of CMC (Carboxymethylcellulose, Daiichi Kogyo Seiyaku Co., Ltd., Serogen WS-C) as a thickener And the solid content of CMC was 1 part by mass, and kneading was performed for 10 minutes. Next, purified water was added such that the total solid concentration of the negative electrode material and the CMC was 40% by mass to 50% by mass, and kneading was performed for 10 minutes. Subsequently, an aqueous dispersion (SBR concentration: 40% by mass) of SBR (BM400-B, Nippon Zeon Co., Ltd.) as a binder is added so that the solid content of SBR is 1 part by mass, and mixed for 10 minutes. Thus, a paste-like negative electrode material composition was produced. Next, the negative electrode material composition was coated on an electrolytic copper foil with a thickness of 11 μm by a comma coater whose clearance was adjusted so that the coating amount per unit area was 4.5 mg / cm ² , to form a negative electrode layer. . Thereafter, the electrode density was adjusted to 1.5 g / cm ³ with a hand press. The electrolytic copper foil on which the negative electrode layer was formed was punched into a disk shape having a diameter of 14 mm to produce a sample electrode (negative electrode).

The manufactured sample electrode (negative electrode), the separator, and the counter electrode (positive electrode) were sequentially placed in a coin-type battery container, and the electrolytic solution was injected to produce a coin-type lithium ion secondary battery. That the LiPF ₆ in a mixed solvent of dissolved to a concentration of 1.0 mol / L: As an electrolyte solution, ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (7 EC and the volume ratio of MEC is 3) It was used. Metallic lithium was used as the counter electrode (positive electrode). As a separator, a polyethylene microporous membrane with a thickness of 20 μm was used. Evaluation of the first time charge / discharge characteristic, the output characteristic, and the high temperature storage characteristic was performed by the following method using the produced lithium ion secondary battery.

[Evaluation of initial charge and discharge characteristics]
(1) The battery was charged to 0 V (V vs. Li / Li ⁺ ) with a constant current of 0.48 mA, and then constant voltage charging was performed at 0 V until the current value became 0.048 mA. The capacity at this time was taken as the initial charge capacity.
(2) After a rest time of 30 minutes, discharge was performed to 1.5 V (V vs. Li / Li ⁺ ) at a constant current of 0.48 mA. The capacity at this time was taken as the initial discharge capacity.
(3) The initial charge and discharge efficiency (%) was determined from the charge and discharge capacities obtained in the above (1) and (2) using the following (formula 1).
Initial charge / discharge efficiency (%) = initial discharge capacity (mAh / g) / initial charge capacity (mAh / g) × 100 ... (Equation 1)

[Evaluation of output characteristics]
(1) The battery was charged to 0 V (V vs. Li ^/ Li ⁺ ) with a constant current of 0.48 mA, and then constant voltage charging was performed at 0 V until the current value became 0.048 mA.
(2) After 30 minutes of rest time, it was discharged to 1.5 V (V vs. Li / Li ⁺ ) at a constant current of 0.48 mA.
(3) (1) and (2) were performed again, and the discharge capacity at this time was defined as "discharge capacity 1" (mAh / g).
(4) After a rest time of 30 minutes, charge to 0 V (V vs. Li / Li ⁺ ) with a constant current of 0.48 mA, and then perform constant voltage charge at 0 V until the current value becomes 0.048 mA.
(5) After a rest time of 30 minutes, the battery was discharged to 1.5 V (V vs. Li / Li ⁺ ) at a constant current of 12 mA, and the discharge capacity at this time was made “discharge capacity 2” (mAh / g).
(6) From the discharge capacity obtained in (3) and (5), the output characteristic was obtained using (Expression 2) below.
Output characteristic (%) = discharge capacity 2 (mAh / g) / discharge capacity 1 (mAh / g) × 100 ... (formula 2)

[Evaluation of high temperature storage characteristics]
(1) The battery was charged to 0 V (V vs. Li ^/ Li ⁺ ) with a constant current of 0.48 mA, and then constant voltage charging was performed at 0 V until the current value became 0.048 mA.
(2) After 30 minutes of rest time, it was discharged to 1.5 V (V vs. Li / Li ⁺ ) at a constant current of 0.48 mA.
(3) After a rest time of 30 minutes, it was charged to 0 V (V vs. Li / Li ⁺ ) at a constant current of 0.48 mA. The charge capacity (mAh / g) at this time was measured.
(4) The battery of (3) was left at 60 ° C. for 5 days.
(5) Discharged to 1.5 V (V vs. Li / Li ⁺ ) at a constant current of 0.48 mA. The discharge capacity (mAh / g) at this time was measured.
The high temperature storage characteristics were determined from the charge capacity obtained in (6) and (3) and the discharge capacity obtained in (5) using the following formula 3.
High temperature storage characteristics (%) = discharge capacity (mAh / g) / charge capacity (mAh / g) × 100 formula 3

Example 2
A negative electrode material and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the content of melamine was changed to 10 parts by mass in Example 1. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 3
A negative electrode material and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the compound containing nitrogen atoms was changed to 10 parts by mass of urea (thermal decomposition temperature: 148 ° C.) in Example 1. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 4
A negative electrode material and a lithium ion secondary battery were produced in the same manner as in Example 1 except that, in Example 1, the nitrogen atom-containing compound was changed to 10 parts by mass of pyrrole (thermal decomposition temperature: 120 ° C.). The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 5
A negative electrode material and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the volume average particle diameter of spherical natural graphite as a carbon material was changed from 10 μm to 5 μm in Example 1. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 6
A negative electrode material and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the volume average particle diameter of spherical natural graphite as a carbon material was changed from 10 μm to 23 μm in Example 1. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 7
A negative electrode material and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the temperature (maximum) of the heat treatment was changed from 1000 ° C. to 800 ° C. in Example 1. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 8
A negative electrode material and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the temperature (maximum) of the heat treatment in Example 1 was changed from 1000 ° C. to 1300 ° C. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 9
As a carbon material, a spherical natural graphite (volume average particle diameter: 10 μm) filled with 20% by volume with respect to the volume of the alumina crucible and left to stand in an air atmosphere at 500 ° C. for 1 hour for pretreatment A negative electrode material and a lithium ion secondary battery were produced in the same manner as in Example 1 except for the above. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 10
100 parts by weight of spherical natural graphite (volume average particle diameter: 10 μm) as a carbon material, and 10 parts by weight of coal tar pitch (softening point: 98 ° C., residual carbon ratio: 50) as an organic compound that can change to carbonaceous by heat treatment Mass%) and were mixed to obtain a mixture. Next, the mixture is heat-treated to form a heat-treatment comprising a first carbon material as a core and a second carbon material present on at least a part of the surface of the first carbon material and having a crystallinity lower than that of the first carbon material. I got a thing. The obtained heat-treated material was crushed with a cutter mill and sieved with a 300 mesh sieve to obtain the material under the sieve (carbon material a).
Next, 50 parts by mass of coal tar pitch (softening point: 98 ° C., residual carbon content: 50% by mass) and 50 parts by mass of melamine as a compound containing nitrogen atoms (Wako Pure Chemical Industries, Ltd., thermal decomposition temperature : 230 ° C.) were mixed to obtain a mixture. The mixture was then heat treated. The heat treatment was performed by raising the temperature from 25 ° C. to 1000 ° C. at a temperature rising rate of 200 ° C./hour under nitrogen flow and holding at 1000 ° C. for 1 hour. The obtained heat-treated product was crushed in a mortar and sieved with a 300-mesh sieve to obtain the material under the sieve (carbon material b).
A carbon material a (99 parts by mass) and a carbon material b (1 parts by mass) were mixed to obtain a negative electrode material. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 11
A negative electrode material was obtained in the same manner as in Example 10 except that 95 parts by mass of the carbon material a and 5 parts by mass of the carbon material b were used. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 12
A negative electrode material was obtained in the same manner as in Example 10 except that 99.9 parts by mass of the carbon material a and 0.1 parts by mass of the carbon material b were used. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 1
A mixture of 100 parts by mass of spherical natural graphite (average particle diameter: 10 μm) as a carbon material and 5 parts by mass of melamine (Wako Pure Chemical Industries, thermal decomposition temperature: 230 ° C.) as a compound containing nitrogen atoms The mixture was obtained. Next, the mixture was heat treated to produce a carbon material. The heat treatment was performed by raising the temperature from 25 ° C. to 1000 ° C. at a temperature rising rate of 200 ° C./hour under nitrogen flow and holding at 1000 ° C. for 1 hour. The obtained carbon material was crushed by a cutter mill, screened with a 300 mesh sieve, and the lower part of the sieve was used as a negative electrode material. Using this negative electrode material, a lithium ion secondary battery was produced in the same manner as in Example 1. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 2
A lithium ion secondary battery was produced in the same manner as in Example 1 except that melamine was not mixed. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 3
A pitch (softening point: 250 ° C., remainder) prepared from 100 parts by mass of spherical natural graphite (volume average particle diameter: 10 μm) as a carbon material and 10 parts by mass of polyvinyl chloride as an organic compound that can change to carbonaceous by heat treatment A mixture was obtained by mixing a carbon content of 70% by mass and 5 parts by mass of melamine (Wako Pure Chemical Industries, Ltd., thermal decomposition temperature: 230 ° C.) as a compound containing a nitrogen atom. Next, the mixture is heat-treated to form a carbon containing a first carbon material as a core and a second carbon material present on at least a part of the surface of the first carbon material and having a crystallinity lower than that of the first carbon material. The material was made. The heat treatment was performed by raising the temperature from 25 ° C. to 1000 ° C. at a temperature rising rate of 200 ° C./hour under argon gas flow and holding the temperature at 1000 ° C. for 1 hour. The obtained carbon material was crushed by a cutter mill, screened with a 300 mesh sieve, and the lower part of the sieve was used as a negative electrode material. Using this negative electrode material, a lithium ion secondary battery was produced in the same manner as in Example 1. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 4
A negative electrode material and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the compound containing nitrogen atoms was changed to 20 parts by mass of polyacrylonitrile (thermal decomposition temperature: 550 ° C.) in Example 1. . The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 5
100 parts by weight of spherical natural graphite (volume average particle diameter: 10 μm) as a carbon material, and 10 parts by weight of coal tar pitch (softening point: 98 ° C., residual carbon ratio: 50) as an organic compound that can change to carbonaceous by heat treatment Mass%) and were mixed to obtain a mixture. Subsequently, 5 parts by mass of melamine (Wako Pure Chemical Industries, Ltd., thermal decomposition temperature: 230 ° C.) as a compound containing a nitrogen atom is disposed in the same space as the mixture, and heat treatment is performed, except for heat treatment. Similarly, a negative electrode material was obtained. The characteristics of the negative electrode material and the lithium ion secondary battery were evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Claims (5)

  And heat treating a mixture containing an organic compound that can change to carbonaceous matter and a compound containing a nitrogen atom, and softening point X (° C.) of the organic compound that can change to carbonaceous matter by the heat treatment The method for producing a negative electrode material for a lithium ion secondary battery, wherein the thermal decomposition temperature Y (° C.) of the nitrogen atom-containing compound satisfies X / Y = 0.2 to 0.9. The manufacturing method of the negative electrode material for lithium ion secondary batteries of Claim 1 which satisfy | fills at least any one of following (A) or (B).
(A) A mixture containing an organic compound that can be converted to carbonaceous by heat treatment and a compound containing a nitrogen atom further includes a carbon material.
(B) Heat treatment of a mixture containing a heat treatment product of a mixture containing an organic compound that can change to carbonaceous by heat treatment and a compound containing a nitrogen atom, an organic compound that can change to carbonaceous by heat treatment, and a carbon material It has the process of mixing things and.   The manufacturing method of the negative electrode material for lithium ion secondary batteries of Claim 2 whose volume average particle diameter of the said carbon material is 1 micrometer-40 micrometers.   The manufacturing method of the negative electrode material for lithium ion secondary batteries of any one of Claims 1-3 whose volume average particle diameter of the negative electrode material for lithium ion secondary batteries obtained is 1 micrometer-40 micrometers.   The heat processing temperature in the process of heat-treating the mixture containing the organic compound which can be changed into carbonaceous by the said heat processing, and the compound containing a nitrogen atom is 700 degreeC-1500 degreeC any one of Claims 1-4. The manufacturing method of the negative electrode material for lithium ion secondary batteries as described in-.