JPWO2015146960A1 - Non-aqueous secondary battery negative electrode carbon material, method for producing non-aqueous secondary battery negative electrode carbon material, and non-aqueous secondary battery - Google Patents

Abstract

Negative electrode material capable of obtaining a non-aqueous secondary battery having sufficiently low charge / discharge irreversible capacity during initial cycle, excellent low-temperature input / output characteristics, and low gas generation during initial cycle and high-temperature storage As a result, a high-performance non-aqueous secondary battery is provided. A carbon material for a non-aqueous secondary battery negative electrode containing a carbon material (A) capable of occluding and releasing lithium ions and an organic compound (B), wherein the mesopore surface area ratio (SAa / SAb) is 0.67 or more, Carbon material (C) for non-aqueous secondary battery negative electrode. (Formula 1) SAa / SAb = Mesopore surface area of 2 nm or more and less than 4 nm obtained by nitrogen adsorption method / Mesopore surface area of 4 nm or more and 35 nm or less obtained by nitrogen adsorption method

Description

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

  In recent years, demand for high-capacity secondary batteries has increased with the downsizing of electronic devices. In particular, lithium ion secondary batteries having higher energy density and excellent large current charge / discharge characteristics have attracted attention as compared to nickel / cadmium batteries and nickel / hydrogen batteries. Conventionally, high capacity of lithium ion secondary batteries has been widely studied, but in recent years, the demand for higher performance of lithium ion secondary batteries has been increasing. Therefore, there is a demand to achieve a long life.

  For lithium ion secondary batteries, it is known to use a carbon material such as graphite as the negative electrode active material. Among them, graphite having a high degree of graphitization, when used as an active material for a negative electrode for a lithium ion secondary battery, has a capacity close to 372 mAh / g, which is the theoretical capacity for lithium occlusion of graphite. Since it is excellent also in the property, it is known that it is preferable as an active material for negative electrodes. On the other hand, when the active material layer containing the negative electrode material is densified to increase the capacity, the destruction / deformation of the material increases the irreversible capacity of charge / discharge during the initial cycle, decreases the large current charge / discharge characteristics, reduces the cycle characteristics. There was a problem of decline.

In addition, when the carbon material as described above is used as an active material for a negative electrode of a lithium ion secondary battery, usually, the surface of the carbon material is combined with a polymer compound used for a binder or the like and a non-aqueous electrolyte solution. A protective coating called SEI (Solid Electrolyte Interface) is formed by the reaction. It is known that SEI prevents contact between the carbon material and the electrolytic solution, suppresses decomposition of the electrolytic solution by the active carbon material, and maintains the chemical stability of the negative electrode surface.
However, in a lithium ion secondary battery using a carbon material as an active material for a negative electrode, the charge / discharge irreversible capacity during the initial cycle increases due to the generation of SEI film and the generation of gas as a side reaction product. There was a problem that the capacity could not be increased. In addition, the formation of a stable SEI film increases the interfacial resistance of the negative electrode, which reduces the input / output characteristics of the battery.

  In order to solve the above problem, for example, in Patent Document 1, spheroidized natural graphite is produced by performing spheronization treatment (mechanical energy treatment) using natural graphite, and the spheroidized natural graphite is used as a core. A technique for forming graphite and coating amorphous carbon on the surface thereof has been developed. However, the spheroidized natural graphite disclosed in Patent Document 1 has a high capacity and good rapid charge / discharge characteristics, but excessive decomposition of the electrolyte occurs. Therefore, the initial irreversible capacity and charge / discharge cycle characteristics are low. Insufficient amount of side reaction product gas was generated, and further improvement was necessary.

On the other hand, as a technique for suppressing excessive decomposition of an electrolytic solution, a method of coating a carbon material, which is an active material for a negative electrode, with a polymer or the like is known. For example, Patent Document 2 discloses carbon for the purpose of suppressing decomposition of a nonaqueous electrolytic solution and deposition of the decomposition product on the surface of the negative electrode and improving initial charge / discharge efficiency and charge / discharge cycle characteristics. A method of providing a coating layer made of an ion conductive polymer such as polyethylene oxide or a water-soluble polymer such as polyvinyl alcohol on the surface of the material is disclosed.
Patent Document 3 discloses that when manufacturing a negative electrode, a water-soluble polymer substance (polystyrene sulfonic acid in which polystyrene sulfonic acid or maleic acid is copolymerized) that is negatively charged in water is used and at least part of the surface thereof A non-aqueous secondary battery using a material containing coated carbon as a negative electrode active material and a non-aqueous electrolyte containing a compound that is reduced at a higher potential than propylene carbonate is disclosed. . Patent Document 4 discloses a method of attaching a water-soluble polymer to spheroidized natural graphite having a surface oxygen functional group added to improve adhesion to the water-soluble polymer. In Patent Document 5, for the purpose of improving initial efficiency and input / output characteristics, a polymer material (C-1) having high solubility in an electrolytic solution is attached to pores of 1 μm or less, and further dissolved in the electrolytic solution. A method of attaching a polymer material (C-2) having a low property to a place different from C-1 is disclosed. Patent Document 6 discloses a technique for reducing irreversible capacity and gas generation by coating spheroidized graphite with an organic compound that is hardly soluble in a non-aqueous electrolyte and has a π-conjugated structure and specific electrical conductivity. Yes. Patent Document 7 discloses a technique for reducing an irreversible capacity by reducing a cumulative pore volume having a pore diameter of 2 nm to 3.5 nm by coating a carbonaceous material with a water-soluble polymer such as polystyrene sulfonic acid. Has been.

Japanese Patent No. 3534391 JP-A-11-129992 Japanese Patent No. 4134504 JP 2011-198710 A Japanese Patent No. 4967268 WO2013 / 122115 JP 2014-011093 A

However, according to the study by the present inventors, the spheroidized natural graphite disclosed in Patent Document 1 has a high capacity and good rapid charge / discharge characteristics, but excessive decomposition of the nonaqueous electrolyte occurs. Therefore, the initial charge / discharge efficiency and charge / discharge cycle characteristics are insufficient, the amount of side reaction product gas generated is large, and further improvement is required.
In addition, when the carbon material is coated with an ion conductive polymer or a water-soluble polymer disclosed in Patent Document 2, the adhesion to the carbon material is insufficient and the electrolyte solution is swellable. When such a carbon material is used as the negative electrode active material, initial charge / discharge efficiency, charge / discharge cycle characteristics, and stability are still insufficient.
In the technique disclosed in Patent Document 3, although the initial charge / discharge efficiency is somewhat improved as compared with the carbon material not coated with anything, the interface resistance of the negative electrode (negative electrode resistance) due to insufficient ionic conductivity of the polymer. ) And reductive decomposition of the electrolytic solution could not be sufficiently suppressed, and thus gas generation suppression and sufficient improvement in cycle characteristics could not be obtained.
In the carbon material in which the polymer disclosed in Patent Document 4 is attached to the carbon material, the initial charge / discharge efficiency and stability are improved by improving the adhesion between the polymer and the carbon material. The insertion / desorption site was covered excessively, and the ionic conductivity of the polymer used was insufficient, which revealed that the low-temperature input / output characteristics were insufficient.
In the technique described in Patent Document 5, by adding a polymer material (C-1) having high solubility in an electrolyte solution to pores of 1 μm or less, negative electrode interface resistance is reduced and input / output characteristics are improved. Although a certain effect was obtained, only the relatively large pores with a pore size of 1 μm are of interest, and attention is paid to pores in the mesopore region of about several nm corresponding to the Li ion insertion / desorption site As a result, the input / output characteristics were still insufficient. Furthermore, since C-1 has solubility in an electrolytic solution, the electrolytic solution comes into contact with the graphite surface, and initial charge / discharge efficiency, storage characteristics, and charge / discharge cycle characteristics are insufficient.
With the techniques described in Patent Document 6 and Patent Document 7, it has become clear that the low-temperature input / output characteristics are insufficient because the insertion and desorption sites of Li ions are excessively covered.

  The present invention has been made in view of the background art, and the problem is that the charge / discharge efficiency at the initial cycle is sufficiently high, and has excellent low-temperature input / output characteristics, at the initial cycle, and at high-temperature storage. The object is to provide a carbon material capable of obtaining a non-aqueous secondary battery with less gas generation, and as a result, to provide a high-performance non-aqueous secondary battery.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a carbon material (A) capable of occluding and releasing lithium ions (hereinafter also referred to as “carbon material (A)”), and an organic compound. In the carbon material for a non-aqueous secondary battery negative electrode containing (B), a surface area derived from mesopores having a pore diameter of 2 nm or more and less than 4 nm (SAa) and a surface area derived from mesopore diameters of a pore diameter of 4 nm or more and 35 nm or less (SAb) By setting the ratio (SAa / SAb) within a specific high value range, the charge / discharge efficiency at the initial cycle (hereinafter also referred to as the initial efficiency) is high, and it has excellent low-temperature input / output characteristics. And it discovered that the non-aqueous secondary battery negative electrode material with few gas generation | occurrence | production at the time of high temperature storage was obtained, and came to complete this invention.
In addition, as a preferable new production method for producing such a carbon material, a specific mesopore volume, sulfur oxide desorbed at a specific temperature rise is within a specific range, That is, an organic compound having a specific structure using a carbon material (A) having a sulfur component present in a highly active state within a specific range and having a pH within a specific range as a dispersion. B) was conceived and it was found that mesopores having a pore diameter of 4 nm to 35 nm on the surface of the carbon material (A) can be coated with high selectivity. As a result, it was found that the organic compound (B) can be attached so that the SAa / SAb falls within a specific high value range.
The reason why the carbon material according to the present invention has the above effect is considered as follows.

  That is, it is considered that the mesopores of 2 nm or more and less than 4 nm among the pores existing on the surface of the carbon material (A) have a large contribution to the Li ion insertion / desorption reaction in charge / discharge. Without covering the surface of the mesopores having a pore diameter of 2 nm or more and less than 4 nm, the mesopore surface having a pore diameter of 4 nm or more and 35 nm or less that is less involved in the insertion / desorption reaction of Li ions is selectively formed with an organic compound (B). By protecting ("SAa / SAb" in a specific high value range), the decomposition reaction of the electrolytic solution is suppressed without increasing the resistance of Li ion insertion / desorption reaction, and the initial charge / discharge efficiency It is considered that the effect of improving the gas and reducing the generation of gas could be remarkably exhibited.

That is, the gist of the present invention is as follows.
<1> A carbon material for a negative electrode of a non-aqueous secondary battery containing a carbon material (A) capable of inserting and extracting lithium ions and an organic compound (B), and a mesopore represented by the following formula (1) A carbon material (C) for a non-aqueous secondary battery negative electrode, wherein the surface area ratio (SAa / SAb) is 0.67 or more.
Formula (1) SAa / SAb = mesopore surface area of pore diameter 2 nm or more and less than 4 nm determined by nitrogen adsorption method / mesopore surface area of pore diameter 4 nm or more and 35 nm or less determined by nitrogen adsorption method <2> The carbon material (C) for a non-aqueous secondary battery negative electrode according to <1>, wherein the mesopore surface area ratio (SAa / SAb) is 0.90 or less.
<3> The charcoal for a nonaqueous secondary battery negative electrode according to <1> or <2>, wherein a mesopore volume having a pore diameter of 35 nm or less determined by a nitrogen adsorption method is 0.008 mL / g or more. Material (C).
<4> The carbon material (C) for a nonaqueous secondary battery negative electrode according to any one of <1> to <3>, wherein the carbon material (A) is spheroidized natural graphite.
<5> Any one of <1> to <4>, wherein a mesopore volume of a pore diameter of 35 nm or less determined by a nitrogen adsorption method of the carbon material (A) is 0.008 mL / g or more. The carbon material (C) for non-aqueous secondary battery negative electrodes as described in one.
<6> The carbon material (C) for a non-aqueous secondary battery negative electrode according to any one of <1> to <5>, wherein the organic compound (B) has a π-conjugated structure.
<7> The carbon material for a nonaqueous secondary battery negative electrode according to any one of <1> to <6>, wherein the content of the organic compound (B) is less than 1% by mass. C).
<8> A method for producing a carbon material for a non-aqueous secondary battery negative electrode (C) according to any one of <1> to <7>, wherein the carbon material (A) is capable of occluding and releasing lithium ions. And the manufacturing method which contains an organic compound (B) and has the following process (1) and (2).
Step (1): Step of mixing carbon material (A) and organic compound (B) in a solvent Step (2): Step of stirring and drying the mixture obtained in Step (1) <9> The carbon material ( A) is a carbon material which satisfies (a) and (b), The manufacturing method of the carbon material for nonaqueous secondary battery negative electrodes (C) as described in <8> characterized by the above-mentioned.
(A) The amount of desorbed sulfur oxide gas up to 500 ° C. by a temperature rising pyrolysis mass spectrometer (TPD-MS) of the carbon material is 1.0 μmol / g or less.
(B) The pH of the dispersion when 5 parts by mass of the carbon material is suspended and dispersed in 30 parts by mass of distilled water is 4.5 or more.
<10> The method for producing a carbon material for a nonaqueous secondary battery negative electrode (C) according to <8> or <9>, wherein the organic compound (B) has a π-conjugated structure.
<11> In the step (2), using a stirrer having a stirring blade in a fixed container, the stirring blade is stirred and mixed at a peripheral speed of 0.01 m / s to 40 m / s. The method for producing a carbon material (C) for a non-aqueous secondary battery negative electrode according to any one of <8> to <10>, wherein the carbon material (C) is dried.
<12> A non-aqueous secondary battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, wherein the negative electrode comprises a current collector and an active material layer formed on the current collector And the active material layer is any one of <1> to <7>, the carbon material for a non-aqueous secondary battery negative electrode (C), or <8> to <11> A non-aqueous secondary battery comprising a carbon material (C) for a non-aqueous secondary battery negative electrode produced by the method according to one.

  By using the carbon material of the present invention as a negative electrode active material for a non-aqueous secondary battery, the non-aqueous secondary battery is excellent in charge / discharge efficiency and low-temperature input / output characteristics at the initial cycle and has a small amount of gas generation. Can be provided.

  Hereinafter, the contents of the present invention will be described in detail. The description of the invention constituent elements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these forms unless it exceeds the gist. Moreover, in this invention, all the aspects can be used together.

<Carbon material (A)>
The carbon material (A) used in the present invention is not particularly limited as long as it is a carbon material capable of occluding and releasing lithium ions, and examples thereof include graphite, amorphous carbon, and a carbonaceous material having a low graphitization degree. Among them, graphite is preferable because it is easily available commercially and theoretically has a high charge / discharge capacity of 372 mAh / g. As graphite, those having few impurities are preferable, and they can be used after being subjected to various known purification treatments, if necessary. Examples of the type of graphite include natural graphite and artificial graphite, and natural graphite is more preferable from the viewpoint of cost.
Further, a carbonaceous material such as amorphous carbon or graphitized material may be used. In this invention, these can be used individually or in combination of 2 or more types.

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

  Examples of natural graphite include highly purified flaky graphite and spheroidized graphite. Among these, spherical natural graphite (also referred to as “spherical natural graphite”) subjected to spheroidizing treatment is more preferable from the viewpoint of particle filling properties and charge / discharge load characteristics.

  As an apparatus used for the spheronization treatment, for example, an apparatus that repeatedly gives mechanical effects such as compression, friction, shearing force, etc. including the interaction of graphite carbonaceous particles, mainly to impact force, to the particles can be used.

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

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

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

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

The carbon material (A) may also contain an oxide or other metal. Other metals include metals that can be alloyed with Li, such as Sn, Si, Al, Bi.
The carbon material which comprises a carbon material (A) can also be used in combination with 1 type, or 2 or more types of another carbon material.

<Physical properties of carbon material (A)>
-Mesopore volume and mesopore surface area In the carbon material (A) used in the present invention, the mesopore volume and mesopore surface area are determined by the BJH method analysis using the adsorption isotherm measured by the nitrogen adsorption method. It is the value which calculated | required the mesopore volume in and the mesopore surface area. The mesopore surface area by BJH method area analysis was calculated by accumulating the side area assuming that the mesopore was cylindrical. Note that the same method can be used for a carbon material (C) for a non-aqueous secondary battery negative electrode (hereinafter also referred to as “carbon material (C)”) described later.

-Mesopore volume within a pore diameter range of 35 nm or less The mesopore volume within a pore diameter range of 35 nm or less is preferably 0.001 mL / g or more, more preferably 0.007 mL / g or more, and further preferably 0.008 mL / g. Above, particularly preferably 0.009 mL / g or more, most preferably 0.01 mL / g or more, preferably 0.1 mL / g or less, more preferably 0.05 mL / g or less, Preferably it is 0.02 mL / g or less.

  If it is within the above range, the gap that allows the nonaqueous electrolyte to enter can be adjusted appropriately, so that lithium ions can be smoothly inserted and desorbed when rapidly charged and discharged, and the low-temperature input / output characteristics are improved. In addition, the deterioration of cycle characteristics due to precipitation of lithium metal can be further suppressed. Furthermore, excessive decomposition of the electrolytic solution can be suppressed, and a decrease in initial efficiency and an increase in the amount of gas generated can be further suppressed.

-Mesopore surface area (SAa) in the pore diameter range of 2 nm or more and less than 4 nm, Mesopore surface area (SAb) in the pore diameter range of 4 nm to 35 nm, Mesopore surface area ratio (SAa / SAb)
The mesopore surface area (SAa) in the pore diameter range of 2 nm or more and less than 4 nm is preferably 0.1 m ² / g or more, more preferably 0.5 m ² / g or more, still more preferably 1 m ² / g or more, particularly preferably. 2 m ² / g or more, most preferably 2.2 m ² / g or more, preferably 10 m ² / g or less, more preferably 5 m ² / g or less, still more preferably 4 m ² / g or less. Particularly preferably, it is 3 m ² / g or less.

The mesopore surface area (SAb) having a pore diameter in the range of 4 nm to 35 nm is preferably 0.1 m ² / g or more, more preferably 0.5 m ² / g or more, still more preferably 1 m ² / g or more, particularly preferably. 2 m ² / g or more, most preferably 2.4 m ² / g or more, preferably 10 m ² / g or less, more preferably 5 m ² / g or less, still more preferably 4 m ² / g or less. Particularly preferably, it is 3 m ² / g or less.

  The mesopore surface area ratio (SAa / SAb) is preferably 0.1 or more, more preferably 0.3 or more, still more preferably 0.5 or more, particularly preferably 0.7 or more, and most preferably 0.8. In addition, it is preferably 2 or less, more preferably 1.5 or less, still more preferably 1.2 or less, and particularly preferably 1 or less.

  The mesopore surface area (SAa) in the pore diameter range of 2 nm or more and less than 4 nm correlates with the amount of active end face into which Li ions can be inserted / desorbed, and it is considered that the decomposition reaction activity of the electrolytic solution is higher. On the other hand, it is considered that the mesopore surface area (SAb) having a pore diameter in the range of 4 nm to 35 nm correlates with the amount of the basal surface that has a small contribution to the insertion / desorption of Li ions.

  When the mesopore surface area (SAa) in the pore diameter range of 2 nm or more and less than 4 nm is within the above range, the insertion / desorption site of the Li ion of the carbon material is not reduced so much. Since smooth insertion and removal can be performed, there is a tendency that a decrease in low-temperature input / output characteristics can be further suppressed. Moreover, since excessive decomposition | disassembly of electrolyte solution can be suppressed, the fall of initial efficiency and the increase in the amount of gas generation can be suppressed more.

  In addition, when the mesopore surface area (SAb) in the pore diameter range of 4 nm to 35 nm is within the above range, the graphite crystallite is not so small, and at the same time, the mesopore surface area (SAa) in the pore diameter range of 2 nm to less than 4 nm. Therefore, it is possible to further suppress a reduction in capacity and a decrease in low-temperature input / output characteristics. Furthermore, since excessive decomposition of the electrolytic solution can be suppressed, a decrease in initial efficiency and an increase in the amount of gas generated can be further suppressed.

  When the mesopore surface area ratio (SAa / SAb) is within the above range, the ratio of Li ion insertion / desorption sites in the carbon material is unlikely to be low, and the smooth insertion of Li ions into the carbon material is possible. Since desorption is possible, a decrease in low-temperature input / output characteristics can be further suppressed. Moreover, since excessive decomposition | disassembly of electrolyte solution can be suppressed, the fall of initial efficiency and the increase in the amount of gas generation can be suppressed more.

・ Desorbed sulfur oxide gas amount up to 500 ° C. by carbon material temperature rising pyrolysis mass spectrometer (TPD-MS) Carbon material (A) temperature rising pyrolysis mass spectrometer (TPD-MS) used in the present invention The amount of desorbed sulfur oxide gas up to 500 ° C. is usually larger than 0 μmol / g, preferably 0.01 μmol / g or more, more preferably 0.02 μmol / g or more, further preferably 0.03 μmol / g or more, particularly Preferably it is 0.04 μmol / g or more, most preferably 0.05 μmol / g or more, and 0.39 μmol / g or less, preferably 0.35 μmol / g or less, more preferably 0.30 μmol / g or less, More preferably, it is 0.25 μmol / g or less, and particularly preferably 0.2 μmol / g or less.

The amount of desulfurized sulfur oxide gas up to 500 ° C. means that sulfur components existing in a highly active state such as sulfur-containing organic compounds such as sulfuric acid, thiol and thiophene, and graphite surface sulfur-containing functional groups such as sulfo groups and sulfonyl groups. means.
When the amount of desorbed sulfur oxide gas is within the above range, the interaction between the organic compound (B) having a π-conjugated structure and the π plane structure portion of the carbon material (A) is effectively prevented. Therefore, the mesopores having a pore diameter of 4 nm or more and 35 nm or less on the surface of the carbon material (A) are highly selectively coated, and the surface area (SAa) derived from mesopores having a pore diameter of 2 nm or more and less than 4 nm, and the pore diameter of 4 nm or more. The organic compound (B) can be attached so that the ratio (SAa / SAb) of the surface area (SAb) derived from the mesopore diameter of 35 nm or less is in a specific high value range. As a result, it is possible to obtain a non-aqueous secondary battery negative electrode material with high charge / discharge efficiency at the initial cycle, excellent input / output characteristics, high temperature storage characteristics, and low gas generation during the initial cycle and high temperature storage. preferable.
On the other hand, if the amount of the desorbed sulfur oxide gas is too large, the side reaction with the electrolyte proceeds excessively, which tends to cause a decrease in initial efficiency, a high temperature storage characteristic, and a cycle characteristic. On the other hand, among sulfur organic compounds, specific sulfur-containing organic compounds and graphite surface sulfur-containing functional groups play an important role in battery characteristics, such as being the starting point of reaction and promoting the reaction in SEI formation. It is preferable that a high sulfur component is present in a very small amount from the viewpoint of good charge / discharge irreversible capacity, high-temperature storage characteristics and cycle characteristics.

-Sulfur element amount determined by fluorescent X-ray analysis (XRF) The sulfur element amount determined by XRF of the carbon material (A) of the present invention is usually 90 ppm or less, preferably 70 ppm or less, more preferably 50 ppm or less, and further It is preferably 40 ppm or less, more preferably 30 ppm or less, particularly preferably 25 ppm or less, and usually 1 ppm or more, preferably 5 ppm or more, more preferably 10 ppm or more, and further preferably 15 ppm or more.
When the sulfur element amount is within the above range, the organic compound (B) having a π-conjugated structure and the π plane structure portion of the carbon material (A) work effectively without being hindered. The surface of the material (A) is highly selectively coated with mesopores having a pore diameter of 4 nm or more and 35 nm or less, and a mesopore-derived surface area (SAa) having a pore diameter of 2 nm or more and less than 4 nm and a mesopore having a pore diameter of 4 nm or more and 35 nm or less. The organic compound (B) can be attached so that the ratio (SAa / SAb) of the surface area (SAb) derived from the pore diameter falls within a specific high value range. As a result, it is possible to obtain a non-aqueous secondary battery negative electrode material with high charge / discharge efficiency at the initial cycle, excellent input / output characteristics, high temperature storage characteristics, and low gas generation during the initial cycle and high temperature storage. preferable.
Further, when the sulfur element amount is less than or equal to the above upper limit value, there is a tendency that a decrease in initial efficiency, a decrease in high temperature storage characteristics and a decrease in cycle characteristics tend to be suppressed. There is a sufficient amount of active sulfur trace components necessary to reduce the generation amount, and the gas generation amount during high-temperature storage tends to decrease.

  Further, in this specification, the amount of sulfur element (ppm) obtained by X-ray fluorescence analysis (XRF) was mixed with 5 g of graphite particles to be measured, 1 g of stearic acid, and 600 μL of ethanol, and dried at 80 ° C. After that, it was made into a molded body, and this was used as a measurement sample, and X-ray fluorescence analysis was performed using a fluorescent X-ray analyzer (ZSX Primus II) manufactured by RIGAKU, and the amount of sulfur element (ppm) calculated using the attached SQX software It is defined as

-PH of the dispersion when 5 parts by mass of carbon material is suspended and dispersed in 30 parts by mass of distilled water
The pH of the dispersion when 5 parts by mass of the carbon material (A) used in the present invention is suspended and dispersed in 30 parts by mass of distilled water is preferably 4.5 or more, more preferably 5.0 or more, and still more preferably. Is 5.4 or more, particularly preferably 5.7 or more, and most preferably 6.0 or more. Moreover, it is 9 or less normally, Preferably it is 8.5 or less, More preferably, it is 8 or less, More preferably, it is 7.5 or less, Most preferably, it is 7 or less. In other words, it is particularly preferable that the dispersion when 5 parts by mass of the carbon material (A) is suspended and dispersed in 30 parts by mass of distilled water is between weakly acidic and neutral.

  The pH of the dispersion when 5 parts by mass of the carbon material (A) is suspended and dispersed in 30 parts by mass of distilled water is present in the amount of inorganic acid such as sulfuric acid, hydrochloric acid or nitric acid contained as impurities, or on the graphite surface. It is thought to correlate with the amount of acidic functional groups such as carboxy groups and phenol groups.

When 5 parts by mass of the carbon material (A) is suspended and dispersed in 30 parts by mass of distilled water, the pH of the dispersion is within the above range, and the organic compound (B) having a π-conjugated structure and the carbon material (A ) Effectively works without hindering the interaction with the π-plane structure portion of the carbon material (A), so that the mesopores of 4 nm to 35 nm on the surface of the carbon material (A) are coated with high selectivity, and the pore diameter is 2 nm or more. The organic compound (SAa / SAb) is such that the ratio (SAa / SAb) between the surface area derived from mesopores less than 4 nm (SAa) and the surface area derived from mesopore diameters having pore diameters of 4 nm to 35 nm (SAa / SAb) falls within a specific high value range. It becomes possible to attach B). As a result, it is possible to obtain a non-aqueous secondary battery negative electrode material with high charge / discharge efficiency at the initial cycle, excellent input / output characteristics, high temperature storage characteristics, and low gas generation during the initial cycle and high temperature storage. preferable.
In addition, if the pH is too low due to residual inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid contained as impurities, side reaction with the electrolyte proceeds excessively, resulting in a decrease in initial efficiency, a decrease in high-temperature storage characteristics, There is a tendency to cause deterioration of cycle characteristics. On the other hand, if the pH is too high due to complete removal of acidic functional groups such as carboxy groups and phenol groups existing on the graphite surface, the slurry viscosity may be reduced or extremely reduced due to a change in the chemical or physical state of the binder. There is a tendency that the plate strength is lowered and the cycle characteristics are also lowered.

-Surface functional group amount O / C value An X-ray photoelectron spectrometer (for example, ESCA manufactured by ULVAC-PHI) is used as an X-ray photoelectron spectroscopy measurement (XPS), and the surface of the object to be measured (here, graphite material) is flat. The sample is placed on the sample stage, and the spectrum of C1s (280 to 300 eV) and O1s (525 to 545 eV) is measured by multiplex measurement using the Kα ray of aluminum as an X-ray source. The obtained C1s peak top is corrected to be 284.3 eV, the peak areas of the C1s and O1s spectra are obtained, and the device sensitivity coefficient is multiplied to calculate the surface atomic concentrations of C and O, respectively. The obtained atomic concentration ratio O / C of O and C (O atomic concentration / C atomic concentration) is defined as the surface functional group amount O / C value of the carbon material.
The O / C value of the carbon material (A) used in the present invention determined from XPS is preferably 0.8 or more, more preferably 1 or more, still more preferably 1.5 or more, particularly preferably 2 or more, preferably It is 8 or less, more preferably 4 or less, still more preferably 3.5 or less, and particularly preferably 3 or less.

-Volume-based average particle size (average particle size d50)
The volume-based average particle diameter (also referred to as “average particle diameter d50”) of the carbon material (A) used in the present invention is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, and particularly preferably 15 μm or more. It is. The average particle diameter d50 is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, and particularly preferably 31 μm or less. If the average particle size d50 is too small, the non-aqueous secondary battery obtained using the carbon material tends to increase the irreversible capacity and cause a loss of initial battery capacity. On the other hand, if the average particle size d50 is too large, slurry coating may occur. May cause inconveniences such as line drawing, deterioration of high current density charge / discharge characteristics, and deterioration of low temperature input / output characteristics.

  In this specification, the average particle size d50 is obtained by adding 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) as a surfactant to a carbon material. 0.01 g was suspended, and this was introduced as a measurement sample into a commercially available laser diffraction / scattering particle size distribution measurement device (for example, LA-920 manufactured by HORIBA), and the measurement sample was irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. After that, the volume is defined as a volume-based median diameter measured by the measuring device.

-Circularity The circularity of the carbon material (A) used in the present invention is 0.88 or more, preferably 0.90 or more, more preferably 0.91 or more. The circularity is preferably 1 or less, more preferably 0.98 or less, and still more preferably 0.97 or less. When the circularity is within the above range, the high current density charge / discharge characteristics of the non-aqueous secondary battery tend to be suppressed. The circularity is defined by the following formula, and when the circularity is 1, a theoretical sphere is obtained.
Circularity = (perimeter of equivalent circle having the same area as the particle projection shape) / (actual circumference of particle projection shape)

  As the circularity value, for example, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.) is used, and about 0.2 g of a sample (carbon material) is added to polyoxyethylene (20) sorbitan as a surfactant. After dispersing in a 0.2% by weight monolaurate aqueous solution (about 50 mL) and irradiating the dispersion with an ultrasonic wave of 28 kHz for 1 minute at an output of 60 W, the detection range is specified as 0.6 to 400 μm, and the particle size is The value measured for particles in the range of 1.5-40 μm is used.

  A method for improving the degree of circularity is not particularly limited, but a spheroidized sphere is preferable because the shape of the interparticle voids when the negative electrode is formed is preferable. Examples of spheroidizing treatment include a method of mechanically approaching a sphere by applying a shearing force and a compressive force, and a mechanical / physical treatment in which a plurality of carbon material fine particles are granulated by the adhesive force of the binder or the particles themselves. Methods and the like.

-Tap density The tap density of the carbon material (A) used in the present invention is preferably 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, still more preferably 0.85 g / cm ³ or more, particularly Preferably it is 0.9 g / cm ³ or more, most preferably 0.95 g / cm ³ or more, preferably 1.3 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, still more preferably 1 .1 g / cm ³ or less.

  When the tap density is within the above range, the processability such as streaking during the production of the electrode plate is good, and the high-speed charge / discharge characteristics are excellent. In addition, since the carbon density in the particles is difficult to increase, the rolling property is good and the high-density negative electrode sheet tends to be easily formed.

For the tap density, the carbon material of the present invention was dropped into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ through a sieve having an opening of 300 μm by using a powder density measuring device, and the cell was fully filled. Thereafter, a tap having a stroke length of 10 mm is performed 1000 times and defined as the density obtained from the volume and mass of the sample at that time.

-X-ray parameter The d value (interlayer distance) of the lattice plane (002 plane) of the carbon material (A) used in the present invention determined by X-ray diffraction by the Gakushin method is preferably 0.335 nm or more, 0. It is less than 340 nm. Here, the d value is more preferably 0.339 nm or less, and still more preferably 0.337 nm or less. When the d002 value is within the above range, the crystallinity of graphite is high, and thus the increase in initial irreversible capacity tends to be suppressed. Here, 0.335 nm is a theoretical value of graphite.

  The crystallite size (Lc) of the carbon material determined by X-ray diffraction by the Gakushin method is preferably 1.5 nm or more, more preferably 3.0 nm or more. Within the above range, the crystallinity is not too low, and the reversible capacity is difficult to decrease when a non-aqueous secondary battery is obtained. The lower limit of Lc is the theoretical value of graphite.

-Ash content The ash content contained in the carbon material (A) used in the present invention is preferably 1% by mass or less, more preferably 0.5% by mass or less, and more preferably 0.5% by mass or less, based on the total mass of the carbon material (A). Preferably it is 0.1 mass% or less. Moreover, it is preferable that the minimum of ash content is 1 ppm or more.

  When the ash content is within the above range, when a non-aqueous secondary battery is used, deterioration of battery performance due to the reaction between the carbon material and the electrolyte during charge / discharge can be suppressed to a negligible level. Further, since a great amount of time, energy, and equipment for preventing contamination are not required for producing the carbon material, an increase in cost can be suppressed.

・ BET specific surface area (SA)
The specific surface area (SA) measured by the BET method of the carbon material (A) used in the present invention is preferably 3 m ² / g or more, more preferably 4 m ² / g or more, still more preferably 4.5 m ² / g or more. Particularly preferably, it is 5.1 m ² / g or more. Moreover, it is preferably 11 m ² / g or less, more preferably 9 m ² / g or less, and still more preferably 8 m ² / g or less.
If the specific surface area is within the above range, the portion where Li enters and exits can be secured sufficiently, so that the high-speed charge / discharge characteristic output characteristics are excellent, and the activity of the carbon material against the electrolyte can be moderately suppressed. The capacity does not increase and a high capacity battery tends to be manufactured.

  In addition, when a negative electrode is formed using a carbon material, an increase in reactivity with the electrolytic solution can be suppressed and gas generation can be suppressed, so that a preferable nonaqueous secondary battery can be provided.

  The BET specific surface area was measured using a surface area meter (for example, a specific surface area measuring device “Gemini 2360” manufactured by Shimadzu Corp.), preliminarily dried at 100 ° C. for 3 hours in a nitrogen stream on a carbon material sample, and then liquid nitrogen. It is defined as a value measured by a nitrogen adsorption BET 6-point method using a gas flow method using a nitrogen-helium mixed gas that is cooled to a temperature and adjusted accurately so that the relative pressure value of nitrogen with respect to atmospheric pressure is 0.3.

-Pore volume in the range of 10 nm to 1000 nm pore diameter In the carbon material (A) used in the present invention, the pore volume in the range of 10 nm to 1000 nm pore diameter was measured using a mercury intrusion method (mercury porosimetry). Value, preferably 0.05 mL / g or more, more preferably 0.07 mL / g or more, still more preferably 0.1 mL / g or more, and preferably 0.3 mL / g or less, more preferably Is 0.28 mL / g or less, more preferably 0.25 mL / g or less.

  When the pore volume in the range of the pore diameter of 10 nm to 1000 nm is within the above range, it is difficult for the voids into which the non-aqueous electrolyte solution can enter, and lithium ion insertion / desorption is not in time when rapid charge / discharge is performed, Accordingly, the tendency for lithium metal to precipitate and the cycle characteristics to deteriorate can be further avoided. Furthermore, the tendency that the binder becomes difficult to be absorbed in the gap during the electrode plate production and the electrode plate strength and the initial efficiency are reduced accordingly can be avoided.

  The total pore volume of the carbon material (A) used in the present invention is preferably 0.1 mL / g or more, more preferably 0.2 mL / g or more, still more preferably 0.25 mL / g or more, particularly preferably. Is 0.5 mL / g or more. The total pore volume is preferably 10 mL / g or less, more preferably 5 mL / g or less, still more preferably 2 mL / g or less, and particularly preferably 1 mL / g or less.

  When the total pore volume is within the above range, it is not necessary to make the amount of the binder excessive when forming the electrode plate, and it is easy to obtain the effect of dispersing the thickener or the binder when forming the electrode plate.

  The average pore diameter of the carbon material (A) used in the present invention is preferably 0.03 μm or more, more preferably 0.05 μm or more, still more preferably 0.1 μm or more, and particularly preferably 0.5 μm or more. . The average pore diameter is preferably 80 μm or less, more preferably 50 μm or less, and still more preferably 20 μm or less.

  When the average pore diameter is within the above range, it is not necessary to make the amount of the binder excessive when forming the electrode plate, and it tends to avoid deterioration of the high current density charge / discharge characteristics of the battery.

  As the mercury porosimetry apparatus, a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) can be used. A sample (carbon material) is weighed to a value of about 0.2 g, enclosed in a powder cell, and pretreated by degassing at room temperature and under vacuum (50 μmHg or less) for 10 minutes.

  Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced into the cell, the pressure is increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure is reduced to 25 psia (about 170 kPa).

  The number of steps at the time of pressure increase is 80 points or more, and the mercury intrusion amount is measured after an equilibration time of 10 seconds in each step. The pore distribution is calculated from the mercury intrusion curve thus obtained using the Washburn equation.

  Note that the surface tension (γ) of mercury is calculated as 485 dyne / cm and the contact angle (ψ) is 140 °. The average pore diameter is defined as the pore diameter when the cumulative pore volume is 50%.

True density The true density of the carbon material (A) used in the present invention is preferably 1.9 g / cm ³ or more, more preferably 2 g / cm ³ or more, still more preferably 2.1 g / cm ³ or more, and particularly preferably is a 2.2 g / cm ³ or more, the upper limit is 2.26 g / cm ^3. The upper limit is the theoretical value of graphite. When the true density is within the above range, the crystallinity of the carbon is not too low, and an increase in the initial irreversible capacity when the nonaqueous secondary battery is obtained tends to be suppressed.

Aspect ratio The aspect ratio of the carbon material (A) used in the present invention in a powder state is theoretically 1 or more, preferably 1.1 or more, more preferably 1.2 or more. The aspect ratio is preferably 10 or less, more preferably 8 or less, and still more preferably 5 or less.

  When the aspect ratio is within the above range, streaking of the slurry containing the carbon material (negative electrode forming material) hardly occurs at the time of forming the electrode plate, and a uniform coated surface is obtained, and high current density charge / discharge of the non-aqueous secondary battery is obtained. There is a tendency to avoid deterioration of characteristics.

  The aspect ratio is expressed as A / B, where the longest diameter A of the carbon material particles when observed three-dimensionally and the shortest diameter B among the diameters orthogonal to the carbon material particles. The carbon material particles are observed with a scanning electron microscope capable of magnifying observation. Arbitrary 50 carbon material particles fixed to the end face of a metal having a thickness of 50 microns or less are selected, and the stage on which the sample is fixed is rotated and tilted to measure A and B, and A / B Find the average value of.

・ Maximum particle size dmax
The maximum particle diameter dmax of the carbon material (A) used in the present invention is preferably 200 μm or less, more preferably 150 μm or less, still more preferably 120 μm or less, particularly preferably 100 μm or less, and most preferably 80 μm or less. When dmax is within the above range, the occurrence of process inconveniences such as line drawing tends to be suppressed.

  The maximum particle size is defined as the value of the largest particle size at which particles are measured in the particle size distribution obtained when measuring the average particle size d50.

-Raman R value As for the Raman R value of the carbon material (A) used for this invention, the value becomes like this. Preferably it is 0.1 or more, More preferably, it is 0.15 or more, More preferably, it is 0.2 or more. The Raman R value is preferably 0.6 or less, more preferably 0.5 or less, and still more preferably 0.4 or less.

Incidentally, the Raman R value is measured and the intensity I _A of the peak P _A in the vicinity of 1580 cm ^-1 in the Raman spectrum obtained by Raman spectroscopy, the intensity I _B of a peak P _B in the vicinity of 1360 cm ^-1, the intensity Defined as the ratio (I _B / I _A ).

Incidentally, the scope of 1580～1620Cm ^-1 A "1580cm around ^-1" in the present specification, "1360cm around ^-1" refers to the range of 1350 ^-1.

  When the Raman R value is within the above range, the crystallinity of the carbon material particle surface is unlikely to be high, and when the density is increased, the crystal is difficult to be oriented in a direction parallel to the negative electrode plate, and a tendency to avoid deterioration of load characteristics is avoided. It is in. Furthermore, the crystal on the particle surface is not easily disturbed, and the increase in reactivity with the electrolyte solution of the negative electrode is suppressed, and the decrease in charge / discharge efficiency of the nonaqueous secondary battery and the increase in gas generation tend to be avoided.

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

Argon ion laser light wavelength: 514.5 nm
Laser power on sample: 25 mW
Resolution: 4cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
Peak intensity measurement, peak half-width measurement: background processing, smoothing processing (convolution 5 points by simple averaging)

DBP oil absorption The DBP (dibutyl phthalate) oil absorption of the carbon material (A) used in the present invention is preferably 65 mL / 100 g or less, more preferably 62 mL / 100 g or less, still more preferably 60 ml / 100 g or less, particularly preferably. Is 57 mL / 100 g or less. The DBP oil absorption is preferably 30 mL / 100 g or more, more preferably 40 mL / 100 g or more.

  If the DBP oil absorption amount is within the above range, it means that the progress of spheroidization of the carbon material is sufficient, and there is a tendency that streaking is difficult to occur during the application of the slurry containing the carbon material. However, since the pore structure exists, the reaction surface tends to be prevented from lowering.

  The DBP oil absorption amount is defined as a measured value when 40 g of a measurement material (carbon material) is added, a dropping speed is 4 mL / min, a rotation speed is 125 rpm, and a set torque is 500 N · m, in accordance with JIS K6217. For the measurement, for example, Absorbometer E type manufactured by Brabender can be used.

・ Average particle diameter d10
The particle diameter (d10) corresponding to a cumulative 10% from the small particle side of the particle diameter measured on a volume basis of the carbon material (A) used in the present invention is preferably 30 μm or less, more preferably 20 μm or less, and still more preferably. It is 17 μm or less, preferably 1 μm or more, more preferably 5 μm or more, further preferably 10 μm or more, particularly preferably 11 μm or more, and most preferably 13 μm or more.

  When d10 is within the above range, the tendency of the particles to agglomerate does not become too strong, and it is possible to avoid the occurrence of process inconveniences such as an increase in slurry viscosity, a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a nonaqueous secondary battery. In addition, the high current density charge / discharge characteristics and the low temperature input / output characteristics tend to be avoided.

  d10 is defined as a value obtained by integrating 10% from a particle size having a small particle frequency% in the particle size distribution obtained when measuring the average particle size d50.

・ Average particle size d90
The particle size (d90) corresponding to 90% cumulative from the small particle side of the particle size measured on the volume basis of the carbon material (A) used in the present invention is preferably 100 μm or less, more preferably 70 μm or less, and still more preferably. It is 60 μm or less, more preferably 50 μm or less, particularly preferably 45 μm or less, most preferably 42 μm or less, preferably 20 μm or more, more preferably 26 μm or more, still more preferably 30 μm or more, and particularly preferably 34 μm or more.

  When d90 is within the above range, it is possible to avoid a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a non-aqueous secondary battery, generation of process inconveniences such as striation during application of slurry, and high current density charge / discharge characteristics. There is a tendency to avoid the decrease in the temperature and the low-temperature input / output characteristics.

  d90 is defined as a value in which the frequency% of particles is 90% integrated from a small particle size in the particle size distribution obtained when measuring the average particle size d50.

<Organic compound (B)>
The organic compound (B) used in the present invention is not limited as long as it can highly selectively cover mesopores having a pore diameter of 4 nm or more and 35 nm or less, but is preferably an organic compound having a π-conjugated structure. Further, it is preferably insoluble in a non-aqueous electrolyte and has an electric conductivity at 25 ° C. of 0.1 S / cm or less. The organic compound (B) is considered to effectively coat the carbon material (A) particularly in the carbon material (C) for a nonaqueous secondary battery negative electrode of the present invention.
When the organic compound (B) is used for a negative electrode for a non-aqueous secondary battery, the mesopores having a pore diameter of 4 nm or more and 35 nm or less on the surface of the carbon material (A) are coated with high selectivity. Without increasing the resistance of the insertion / desorption reaction, the reaction with the non-aqueous electrolyte is suppressed, and the generation of gas is effectively suppressed.

  The organic compound (B) is non-aqueous electrolyzed in that the resistance of the non-aqueous secondary battery carbon material (C) of the present invention to the electrolytic solution is improved and the coating of the carbon material (A) layer is difficult to elute into the electrolytic solution. What is hardly soluble in a liquid is more preferable. In addition, when it is immersed in a solvent in which the organic compound (B) is mixed with ethylene carbonate and ethylmethyl carbonate at a volume ratio of 3: 7 for 24 hours, the rate of decrease in dry weight before and after immersion is insoluble in the non-aqueous electrolyte. Means 10% by mass or less.

  The organic compound that is hardly soluble in the non-aqueous electrolyte preferably has an ionic group. The ionic group is a group capable of generating an anion or a cation in water, and examples thereof include a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a phosphonic acid group, and salts thereof. Examples of the salt include lithium salt, sodium salt, potassium salt and the like. Among these, a sulfonic acid group and a lithium salt or a sodium salt thereof are preferable from the viewpoint of the initial irreversible capacity in the case of a non-aqueous secondary battery.

The electrical conductivity of the organic compound (B) at 25 ° C. is preferably 0.1 S / cm or less, more preferably 0.01 S / cm or less, and still more preferably 0.001 S / cm or less. Moreover, it is usually larger than 0 S / cm. The organic compound (B) contained in the non-aqueous secondary battery negative electrode carbon material (C) is a low conductivity material having an electrical conductivity at 25 ° C. of 0.1 S / cm or less. It is possible to suppress the electrolytic solution from being reduced and decomposed on the surface. If the electrical conductivity is too large, an excessive decomposition reaction of the electrolytic solution occurs, which may cause a decrease in initial charge / discharge efficiency, an increase in gas generation, and a decrease in cycle characteristics.
For example, the electrical conductivity is obtained by film formation on a glass substrate by spin coater film formation or drop cast film formation, and the film thickness is multiplied by the surface resistance measured by the four-terminal method. It can be calculated from the reciprocal of the obtained value. The film thickness can be measured with a KLA step, surface roughness and fine shape measuring device, Tencor α-step type, and the surface resistance value by a four-terminal method can be measured with a Loresta GP MCP-T610 type manufactured by Mitsubishi Chemical Analytech.

  The organic compound (B) of the present invention preferably contains an organic compound (B) having a π-conjugated structure from the viewpoint of effectively suppressing gas generation and suppressing increase in negative electrode resistance. . Since this π-conjugated structure acts with a π plane structure portion of the carbon material (A), the mesopores having a pore diameter of 4 nm to 35 nm on the surface of the carbon material (A) are highly selectively covered. It is considered that the generation of gas can be effectively suppressed and the increase in negative electrode resistance can be suppressed.

  In the present specification, the compound having the π-conjugated structure is an unsaturated cyclic compound having a structure in which atoms having π electrons are arranged in a ring, satisfying the Hückel rule, and the π electrons are not on the ring. It is localized and the ring has a planar structure.

  Examples of such a π-conjugated structure include furan, pyrrole, imidazole, thiophene, phosphole, pyrazole, oxazole, isoxazole, and thiazole, which are monocyclic five-membered rings; benzene, pyridine, pyrazine, which are monocyclic six-membered rings, Pyrimidine, pyridazine, triazine; bicyclic 5-membered ring + 6-membered ring benzofuran, isobenzofuran, indole, isoindole, benzothiophene, benzophosphole, benzimidazole, purine, indazole, benzoxazole, benzoisoxazole, benzothiazole A bicyclic 6-membered ring + a 6-membered naphthalene, quinoline, isoquinoline, quinoxaline, quinazoline, cinnoline; a ring having a skeleton such as polycyclic anthracene, pyrene;

  Among these, at least one selected from the group consisting of a benzene ring, a condensed aromatic ring, and an aromatic heterocycle is preferable from the viewpoint of suppressing gas generation when a non-aqueous secondary battery is used. As the condensed aromatic ring, a naphthalene ring is preferable.

  The organic compound (B) may be a low molecular compound or a high molecular compound. However, from the viewpoint of effectively suppressing gas generation, the organic compound (B) is hereinafter referred to as a polymer (b). In some cases).

In the carbon material (C) of the present invention, the organic compound (B) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and preferably 9.% by mass relative to the carbon material (C). It is contained in a proportion of 99% by mass or less, more preferably 5% by mass or less. If it is less than 0.01% by mass, it may be difficult to effectively coat the carbon material (A). On the other hand, if it is 10% by mass or more, the interfacial resistance between the carbon material (A) and the coating layer increases and the temperature is low. Input / output characteristics may deteriorate.
As the organic compound (B) described above, a commercially available one may be used, or it can be synthesized by a known method. In addition, in this invention, it can be used individually by 1 type or in combination of 2 or more types.

  When the organic compound (B) is a low molecular compound, the organic compound (B) includes naphthalene sulfonic acid, lithium naphthalene sulfonate, sodium naphthalene sulfonate, benzene sulfonic acid, sodium benzene sulfonate, anthracene sulfonic acid, anthracene sulfone. Examples include sodium acid.

When the organic compound (B) is a polymer (b) which is a polymer compound, the polymer (b) has an ionic group and an aromatic ring.
Examples of the monomer from which the structural unit constituting the polymer (b) is derived include a monomer having an ionic group and an aromatic ring. The polymer (b) may be a copolymer of a monomer having an ionic group and not having an aromatic ring and a monomer having an aromatic ring and not having an ionic group.

Examples of the monomer having an ionic group and an aromatic ring include styrene sulfonic acid, lithium styrene sulfonate, sodium styrene sulfonate, vinyl benzoate and vinyl benzoate salts.
Examples of the monomer having an ionic group and not having an aromatic ring include vinyl sulfonic acid, lithium vinyl sulfonate, sodium vinyl sulfonate, acrylic acid, sodium acrylate, lithium acrylate, methacrylic acid, and methacrylic acid. Examples include sodium and lithium methacrylate.
Examples of the monomer having an aromatic ring and not having an ionic group include styrene, benzyl acrylate, benzyl methacrylate and the like.

Specific examples of the polymer containing a structural unit derived from such a monomer include a styrene-vinyl sulfonic acid copolymer, a styrene-vinyl sulfonic acid sodium copolymer, a styrene-vinyl sulfonic acid lithium copolymer, and polystyrene. Sulfonic acid, lithium polystyrene sulfonate, sodium polystyrene sulfonate, styrene-styrene sulfonic acid copolymer, styrene-lithium sulfonic acid lithium copolymer, styrene-sodium styrene sulfonate copolymer, polyvinyl benzoic acid, lithium polyvinyl benzoate , Polyvinyl sodium benzoate, styrene-vinyl benzoic acid copolymer, styrene-vinyl benzoic acid lithium copolymer, styrene-vinyl benzoic acid sodium copolymer, and the like.
Among them, from the viewpoint of effectively suppressing gas generation, polystyrene sulfonic acid, lithium polystyrene sulfonate, sodium polystyrene sulfonate, styrene-styrene sulfonic acid copolymer, styrene-lithium sulfonic acid lithium copolymer, styrene-styrene Sodium sulfonate copolymer, polyvinyl benzoic acid, polyvinyl benzoate lithium, polyvinyl benzoate sodium, styrene-vinyl benzoate copolymer, styrene-vinyl benzoate lithium copolymer and styrene-vinyl benzoate sodium copolymer preferable.
Further, polystyrene sulfonic acid, lithium polystyrene sulfonate, sodium polystyrene sulfonate, styrene-lithium lithium sulfonate copolymer and styrene-sodium styrene sulfonate copolymer are more preferable, and lithium polystyrene sulfonate, sodium polystyrene sulfonate, styrene. -Particularly preferred are lithium styrene sulfonate copolymers and styrene-sodium styrene sulfonate copolymers.

The weight average molecular weight of the polymer (b) is not particularly limited, but is preferably 200 or more, more preferably 1000 or more, still more preferably 2000 or more, and particularly preferably 2500 or more. On the other hand, the weight average molecular weight is preferably 1,000,000 or less, more preferably 500,000 or less, still more preferably 300,000 or less, and particularly preferably 200,000 or less.
In the present specification, the weight average molecular weight is a weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as the solvent, or the solvent is aqueous or N, N-dimethylformamide. It is a weight average molecular weight in terms of standard polyethylene glycol measured by GPC of (DMF) or dimethyl sulfoxide (DMSO).

<Carbon material (C)>
The carbon material (C) of the present invention is not particularly limited as long as it contains the carbon material (A) and the organic compound (B) described above, and the mesopore surface area ratio (SAa / SAb) is 0.67 or more.
The compound (B) may be an organic compound having a π-conjugated structure, and other components may be mixed and / or reacted.
Moreover, in this specification, "it contains a carbon material (A) and an organic compound (B)" means the state in which the carbon material (A) and the organic compound (B) are mixed, on the surface of the carbon material (A). A state in which the organic compound (B) is attached, a state in which the organic compound (B) is attached in the pores of the carbon material (A), and the like, in a state of the carbon material (A) and the organic compound (B). It does not depend on the relationship.

  The state of the carbon material (A) and the organic compound (B) is, for example, field emission scanning electron microscope-energy dispersive X-ray (FE-SEM-EDX) analysis, X-ray photoelectron spectroscopy (XPS) analysis, etc. It can confirm by observing the particle | grain cross section of the carbon material (C) for nonaqueous secondary battery negative electrodes using the method of. These confirmation methods may be performed at the time when the non-aqueous secondary battery negative electrode carbon material (C) is manufactured, or the negative electrode containing the non-aqueous secondary battery negative electrode carbon material (C) according to the present invention You may perform about the product manufactured as a non-aqueous secondary battery.

<Physical properties of carbon material (C)>
-Mesopore volume, mesopore surface area In the carbon material (C) of the present invention, the mesopore volume and mesopore surface area are measured by the BJH method analysis using the adsorption isotherm measured by the nitrogen adsorption method. It is the value which calculated | required the pore volume and the mesopore surface area. The mesopore surface area by BJH method area analysis was calculated by accumulating the side area assuming that the mesopore was cylindrical.

-Mesopore volume within a pore diameter range of 35 nm or less The mesopore volume within a pore diameter range of 35 nm or less is preferably 0.001 mL / g or more, more preferably 0.005 mL / g or more, and still more preferably 0.008 mL / g. In addition, it is preferably 0.1 mL / g or less, more preferably 0.05 mL / g or less, still more preferably 0.02 mL / g or less, and particularly preferably 0.01 mL / g or less.

  If it is within the above range, the gap that allows the nonaqueous electrolyte to enter can be adjusted appropriately, so that lithium ions can be smoothly inserted and desorbed when rapidly charged and discharged, and the low-temperature input / output characteristics are improved. In addition, the deterioration of cycle characteristics due to precipitation of lithium metal can be further suppressed. Furthermore, excessive decomposition of the electrolytic solution can be suppressed, and a decrease in initial efficiency and an increase in the amount of gas generated can be further suppressed.

-Mesopore surface area (SAa) in the pore diameter range of 2 nm or more and less than 4 nm, mesopore surface area (SAb) in the range of 4 nm to 35 nm, mesopore surface area ratio (SAa / SAb)
The mesopore surface area (SAa) in the pore diameter range of 2 nm or more and less than 4 nm is preferably 0.1 m ² / g or more, more preferably 0.5 m ² / g or more, and further preferably 1.0 m ² / g or more. In particular, it is 1.2 m ² / g or more, preferably 8 m ² / g or less, more preferably 4 m ² / g or less, still more preferably 3 m ² / g or less, particularly preferably 2.3 m. ² / g or less, most preferably 2 m ² / g or less.

The mesopore surface area (SAb) having a pore diameter in the range of 4 nm or more and less than 35 nm is preferably 0.1 m ² / g or more, more preferably 0.5 m ² / g or more, still more preferably 1 m ² / g or more, particularly preferably. 1.6m and ² / g or more, and most preferably 1.8 m ² / g or more, and preferably not more than 8m ² / g, more preferably 4m ² / g or less, more preferably 3m ² / g or less.

  The pore diameter mesopore surface area ratio (SAa / SAb) is usually 0.67 or more, preferably 0.71 or more, more preferably 0.73 or more, still more preferably 0.75 or more, and preferably 10 or less. More preferably, it is 5 or less, more preferably 2 or less, still more preferably 1 or less, particularly preferably 0.90 or less.

  The mesopore surface area (SAa) in the pore diameter range of 2 nm or more and less than 4 nm correlates with the amount of active end face into which Li ions can be inserted / desorbed, and it is considered that the decomposition reaction activity of the electrolytic solution is higher. On the other hand, it is considered that the mesopore surface area (SAb) having a pore diameter in the range of 4 nm to 35 nm correlates with the amount of the basal surface that has a small contribution to the insertion / desorption of Li ions.

  When the mesopore surface area (SAa) in the pore diameter range of 2 nm or more and less than 4 nm is within the above range, the insertion / desorption site of the Li ion of the carbon material is not reduced so much. Since smooth insertion and removal can be performed, there is a tendency that a decrease in low-temperature input / output characteristics can be further suppressed. Moreover, since excessive decomposition | disassembly of electrolyte solution can be suppressed, the fall of initial efficiency and the increase in the amount of gas generation can be suppressed more.

  In addition, when the mesopore surface area (SAb) in the pore diameter range of 4 nm to 35 nm is within the above range, the graphite crystallite is not so small, and at the same time, the mesopore surface area (SAa) in the pore diameter range of 2 nm to less than 4 nm. Therefore, it is possible to further suppress a reduction in capacity and a decrease in low-temperature input / output characteristics. Furthermore, since excessive decomposition of the electrolytic solution can be suppressed, a decrease in initial efficiency and an increase in the amount of gas generated can be further suppressed.

The mesopore surface area ratio (SAa / SAb) being less than 0.67 indicates that the insertion / desorption sites of Li ions are excessively covered, and the resistance of insertion / desorption of Li ions is reduced. Since it tends to increase and lower the low-temperature input / output characteristics, it is important that it is 0.67 or more.
And when it is in the above preferred range, the insertion / desorption site of the Li ion of the carbon material is not reduced so much, and the smooth insertion / desorption of the Li ion to the carbon material can be performed. There is a tendency that deterioration of input / output characteristics can be further suppressed. Moreover, since excessive decomposition | disassembly of electrolyte solution can be suppressed, the fall of initial efficiency and the increase in the amount of gas generation can be suppressed more.

-Volume-based average particle size (average particle size d50)
The volume-based average particle diameter (also referred to as “average particle diameter d50”) of the carbon material (C) of the present invention is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, and particularly preferably 15 μm or more. . The average particle diameter d50 is preferably 50 μm or less, more preferably 40 μm or less, still more preferably 35 μm or less, and particularly preferably 31 μm or less. When the average particle diameter d50 is within the above range, there is a tendency to suppress an increase in the irreversible capacity of the nonaqueous secondary battery obtained by using the carbon material, loss of the initial battery capacity, Generation of process inconvenience, deterioration of high current density charge / discharge characteristics, and deterioration of low temperature input / output characteristics can also be suppressed.

  In this specification, the average particle size d50 is obtained by adding 10 mL of a 0.2 mass% aqueous solution of polyoxyethylene sorbitan monolaurate (for example, Tween 20 (registered trademark)) as a surfactant to a carbon material. 0.01 g was suspended, and this was introduced as a measurement sample into a commercially available laser diffraction / scattering particle size distribution measurement device (for example, LA-920 manufactured by HORIBA), and the measurement sample was irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute. After that, the volume is defined as a volume-based median diameter measured by the measuring device.

-Circularity The circularity of the carbon material (C) of the present invention is 0.88 or more, preferably 0.90 or more, more preferably 0.91 or more. The circularity is preferably 1 or less, more preferably 0.98 or less, and still more preferably 0.97 or less. There exists a tendency which can suppress the fall of the high current density charge / discharge characteristic of a non-aqueous secondary battery as circularity is in the said range. The circularity is defined by the following formula, and when the circularity is 1, a theoretical sphere is obtained.
Circularity = (perimeter of equivalent circle having the same area as the particle projection shape) / (actual circumference of particle projection shape)

  As the circularity value, for example, a flow type particle image analyzer (for example, FPIA manufactured by Sysmex Industrial Co., Ltd.) is used, and about 0.2 g of a sample (carbon material) is added to polyoxyethylene (20) sorbitan as a surfactant. After dispersing in a 0.2% by weight monolaurate aqueous solution (about 50 mL) and irradiating the dispersion with an ultrasonic wave of 28 kHz for 1 minute at an output of 60 W, the detection range is specified as 0.6 to 400 μm, and the particle size is The value measured for particles in the range of 1.5-40 μm is used.

  A method for improving the degree of circularity is not particularly limited, but a spheroidized sphere is preferable because the shape of the interparticle voids when the negative electrode is formed is preferable. Examples of spheroidizing treatment include a method of mechanically approaching a sphere by applying a shearing force and a compressive force, and a mechanical / physical treatment in which a plurality of carbon material fine particles are granulated by the adhesive force of the binder or the particles themselves. Methods and the like.

Tap density The carbon material (C) of the present invention preferably has a tap density of 0.7 g / cm ³ or more, more preferably 0.8 g / cm ³ or more, still more preferably 0.85 g / cm ³ or more, particularly preferably. 0.9 g / cm ³ or more, most preferably 0.95 g / cm ³ or more, preferably 1.3 g / cm ³ or less, more preferably 1.2 g / cm ³ or less, and even more preferably 1.1 g / Cm ³ or less.

  When the tap density is within the above range, the processability such as streaking during the production of the electrode plate is good, and the high-speed charge / discharge characteristics are excellent. In addition, since the carbon density in the particles is difficult to increase, the rolling property is good and the high-density negative electrode sheet tends to be easily formed.

For the tap density, the carbon material of the present invention was dropped into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ through a sieve having an opening of 300 μm by using a powder density measuring device, and the cell was fully filled. Thereafter, a tap having a stroke length of 10 mm is performed 1000 times and defined as the density obtained from the volume at that time and the mass of the sample.

-X-ray parameter The d value (interlayer distance) of the lattice plane (002 plane) of the carbon material (C) of the present invention determined by X-ray diffraction by the Gakushin method is preferably 0.335 nm or more and less than 0.340 nm. More preferably, it is 0.339 nm or less, More preferably, it is 0.337 nm or less. When the d002 value is within the above range, the initial irreversible capacity tends to suppress an increase because the crystallinity of graphite is high. Here, 0.335 nm is a theoretical value of graphite.

  The crystallite size (Lc) of the carbon material (C) determined by X-ray diffraction by the Gakushin method is preferably 1.5 nm or more, more preferably 3.0 nm or more. Within this range, the particles are not too low in crystallinity, and a reduction in reversible capacity can be suppressed when a non-aqueous secondary battery is formed. The lower limit of Lc is the theoretical value of graphite.

-Ash content The ash content contained in the carbon material (C) of the present invention is preferably 1% by mass or less, more preferably 0.5% by mass or less, and still more preferably based on the total mass of the carbon material (C). It is 0.1 mass% or less. Moreover, it is preferable that the minimum of ash content is 1 ppm or more.

  When the ash content is within the above range, when a non-aqueous secondary battery is used, deterioration of battery performance due to the reaction between the carbon material and the electrolyte during charge / discharge can be suppressed to a negligible level. Further, since a great amount of time, energy, and equipment for preventing contamination are not required for producing the carbon material, an increase in cost can be suppressed.

・ BET specific surface area (SA)
The specific surface area (SA) measured by the BET method of the carbon material (C) of the present invention is preferably 1 m ² / g or more, more preferably 2 m ² / g or more, still more preferably 3 m ² / g or more, particularly preferably. 4 m ² / g or more, most preferably 4.5 m ² / g or more. Further, it is preferably 11 m ² / g or less, more preferably 9 m ² / g or less, further preferably 8 m ² / g or less, particularly preferably 7 m ² / g or less, and most preferably 6 m ² / g or less.
If the specific surface area is within the above range, a sufficient area for Li to enter and exit can be secured, so that the high-speed charge / discharge characteristic output characteristics are excellent, and the activity of the carbon material (C) against the electrolyte can be moderately suppressed. The initial irreversible capacity does not increase, and a high-capacity battery tends to be manufactured.

  Moreover, when a negative electrode is formed using a carbon material (C), an increase in reactivity with the electrolytic solution can be suppressed, and gas generation can be suppressed, so that a preferable nonaqueous secondary battery is provided. Can do.

  The BET specific surface area was measured using a surface area meter (for example, a specific surface area measuring device “Gemini 2360” manufactured by Shimadzu Corp.), preliminarily dried at 100 ° C. for 3 hours in a nitrogen stream on a carbon material sample, and then liquid nitrogen. It is defined as a value measured by a nitrogen adsorption BET 6-point method using a gas flow method using a nitrogen-helium mixed gas that is cooled to a temperature and adjusted accurately so that the relative pressure value of nitrogen with respect to atmospheric pressure is 0.3.

-Pore volume in the range of 10 nm to 1000 nm pore diameter In the carbon material of the present invention, the pore volume in the range of 10 nm to 1000 nm is a value measured using a mercury intrusion method (mercury porosimetry), preferably 0. 0.01 mL / g or more, more preferably 0.03 mL / g or more, still more preferably 0.05 mL / g or more, preferably 0.3 mL / g or less, more preferably 0.25 mL / g or less. More preferably, it is 0.2 mL / g or less.

  If the pore volume in the pore diameter range of 10 nm to 1000 nm is less than the above range, the number of voids into which the non-aqueous electrolyte solution can enter decreases, so that insertion and desorption of lithium ions will not be in time when rapid charge / discharge is performed, Along with this, lithium metal precipitates and the cycle characteristics tend to deteriorate. On the other hand, if it exceeds the above range, the binder is likely to be absorbed into the gap during electrode plate production, and accordingly the electrode plate strength and initial efficiency tend to decrease.

  The total pore volume of the carbon material (C) of the present invention is preferably 0.1 mL / g or more, more preferably 0.2 mL / g or more, still more preferably 0.25 mL / g or more, particularly preferably 0. .5 mL / g or more. The total pore volume is preferably 10 mL / g or less, more preferably 5 mL / g or less, still more preferably 2 mL / g or less, and particularly preferably 1 mL / g or less.

  When the total pore volume is within the above range, it is not necessary to make the amount of the binder excessive when forming the electrode plate, and it is easy to obtain the effect of dispersing the thickener or the binder when forming the electrode plate.

  The average pore diameter of the carbon material (C) of the present invention is preferably 0.03 μm or more, more preferably 0.05 μm or more, still more preferably 0.1 μm or more, and particularly preferably 0.5 μm or more. The average pore diameter is preferably 80 μm or less, more preferably 50 μm or less, and still more preferably 20 μm or less.

  When the average pore diameter is within the above range, it is not necessary to make the amount of the binder excessive when forming the electrode plate, and it tends to avoid deterioration of the high current density charge / discharge characteristics of the battery.

  As the mercury porosimetry apparatus, a mercury porosimeter (Autopore 9520: manufactured by Micromeritex Corporation) can be used. A sample (carbon material) is weighed to a value of about 0.2 g, enclosed in a powder cell, and pretreated by degassing at room temperature and under vacuum (50 μmHg or less) for 10 minutes.

  Subsequently, the pressure is reduced to 4 psia (about 28 kPa), mercury is introduced into the cell, the pressure is increased stepwise from 4 psia (about 28 kPa) to 40000 psia (about 280 MPa), and then the pressure is reduced to 25 psia (about 170 kPa).

  The number of steps at the time of pressure increase is 80 points or more, and the mercury intrusion amount is measured after an equilibration time of 10 seconds in each step. The pore distribution is calculated from the mercury intrusion curve thus obtained using the Washburn equation.

  Note that the surface tension (γ) of mercury is calculated as 485 dyne / cm and the contact angle (ψ) is 140 °. The average pore diameter is defined as the pore diameter when the cumulative pore volume is 50%.

-True density The true density of the carbon material (C) of the present invention is preferably 1.9 g / cm ³ or more, more preferably 2 g / cm ³ or more, still more preferably 2.1 g / cm ³ or more, and particularly preferably 2 0.2 g / cm ³ or more, and the upper limit is 2.26 g / cm ³ . The upper limit is the theoretical value of graphite. Within this range, the crystallinity of carbon is not too low, and an increase in the initial irreversible capacity in the case of a non-aqueous secondary battery can be suppressed.

Aspect ratio The aspect ratio of the carbon material (C) of the present invention in a powder state is theoretically 1 or more, preferably 1.1 or more, more preferably 1.2 or more. The aspect ratio is preferably 10 or less, more preferably 8 or less, still more preferably 5 or less, and particularly preferably 3 or less.

  When the aspect ratio is within the above range, streaking of the slurry containing the carbon material (negative electrode forming material) hardly occurs at the time of forming the electrode plate, and a uniform coated surface is obtained, and high current density charge / discharge of the non-aqueous secondary battery is obtained. There is a tendency to avoid deterioration of characteristics.

  The aspect ratio is expressed as A / B, where the longest diameter A of the carbon material particles when observed three-dimensionally and the shortest diameter B among the diameters orthogonal to the carbon material particles. The carbon material particles are observed with a scanning electron microscope capable of magnifying observation. Arbitrary 50 carbon material particles fixed to the end face of a metal having a thickness of 50 microns or less are selected, and the stage on which the sample is fixed is rotated and tilted to measure A and B, and A / B Find the average value of.

・ Maximum particle size dmax
The maximum particle diameter dmax of the carbon material (C) of the present invention is preferably 200 μm or less, more preferably 150 μm or less, still more preferably 120 μm or less, particularly preferably 100 μm or less, and most preferably 80 μm or less. When dmax is within the above range, the occurrence of process inconveniences such as line drawing tends to be suppressed.

  The maximum particle size is defined as the value of the largest particle size at which particles are measured in the particle size distribution obtained when measuring the average particle size d50.

-Raman R value The value of the Raman R value of the carbon material (C) of the present invention is preferably 0.1 or more, more preferably 0.15 or more, and further preferably 0.2 or more. The Raman R value is preferably 0.6 or less, more preferably 0.5 or less, and still more preferably 0.4 or less.

Incidentally, the Raman R value is measured and the intensity I _A of the peak P _A in the vicinity of 1580 cm ^-1 in the Raman spectrum obtained by Raman spectroscopy, the intensity I _B of a peak P _B in the vicinity of 1360 cm ^-1, the intensity Defined as the ratio (I _B / I _A ).

Incidentally, the scope of 1580～1620Cm ^-1 A "1580cm around ^-1" in the present specification, "1360cm around ^-1" refers to the range of 1350 ^-1.

  When the Raman R value is within the above range, the crystallinity of the carbon material particle surface is unlikely to be high, and when the density is increased, the crystal is difficult to be oriented in a direction parallel to the negative electrode plate, and a tendency to avoid deterioration of load characteristics is avoided. It is in. Furthermore, the crystal on the particle surface is not easily disturbed, and the increase in reactivity with the electrolyte solution of the negative electrode is suppressed, and the decrease in charge / discharge efficiency of the nonaqueous secondary battery and the increase in gas generation tend to be avoided.

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

Argon ion laser light wavelength: 514.5 nm
Laser power on sample: 25 mW
Resolution: 4cm ^-1
Measurement range: 1100 cm ^{−1 to} 1730 cm ⁻¹
Peak intensity measurement, peak half-width measurement: background processing, smoothing processing (convolution 5 points by simple averaging)

-DBP oil absorption amount The DBP (dibutyl phthalate) oil absorption amount of the carbon material (C) of the present invention is preferably 65 mL / 100 g or less, more preferably 62 mL / 100 g or less, still more preferably 60 ml / 100 g or less, and particularly preferably 57 mL. / 100g or less. The DBP oil absorption is preferably 30 mL / 100 g or more, more preferably 40 mL / 100 g or more.

  If the DBP oil absorption amount is within the above range, it means that the progress of spheroidization of the carbon material is sufficient, and there is a tendency that streaking is difficult to occur during the application of the slurry containing the carbon material. However, since the pore structure exists, the reaction surface tends to be prevented from lowering.

  The DBP oil absorption amount is defined as a measured value when 40 g of a measurement material (carbon material) is added, a dropping speed is 4 mL / min, a rotation speed is 125 rpm, and a set torque is 500 N · m, in accordance with JIS K6217. For the measurement, for example, Absorbometer E type manufactured by Brabender can be used.

・ Average particle diameter d10
The particle size (d10) corresponding to a cumulative 10% from the small particle side of the particle size measured on a volume basis of the carbon material (C) of the present invention is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 17 μm or less. The thickness is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, particularly preferably 11 μm or more, and most preferably 13 μm or more.

  When d10 is within the above range, the tendency of the particles to agglomerate does not become too strong, and it is possible to avoid the occurrence of process inconveniences such as an increase in slurry viscosity, a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a nonaqueous secondary battery. In addition, the high current density charge / discharge characteristics and the low temperature input / output characteristics tend to be avoided.

  d10 is defined as a value obtained by integrating 10% from a particle size having a small particle frequency% in the particle size distribution obtained when measuring the average particle size d50.

・ Average particle size d90
The particle size (d90) corresponding to 90% cumulative from the small particle side of the particle size measured on a volume basis of the carbon material (C) of the present invention is preferably 100 μm or less, more preferably 70 μm or less, still more preferably 60 μm or less. More preferably, it is 50 μm or less, particularly preferably 45 μm or less, most preferably 42 μm or less, preferably 20 μm or more, more preferably 26 μm or more, still more preferably 30 μm or more, and particularly preferably 34 μm or more.

  When d90 is within the above range, it is possible to avoid a decrease in electrode strength and a decrease in initial charge / discharge efficiency in a non-aqueous secondary battery, generation of process inconveniences such as striation during application of slurry, and high current density charge / discharge characteristics. There is a tendency to avoid the decrease in the temperature and the low-temperature input / output characteristics.

  d90 is defined as a value in which the frequency% of particles is 90% integrated from a small particle size in the particle size distribution obtained when measuring the average particle size d50.

-Elution property of organic compound (B) The elution property of the organic compound (B) in the carbon material (C) for a non-aqueous secondary battery negative electrode of the present invention is determined at room temperature (25 ° C) in a non-aqueous solvent containing no salt. When the carbon material is immersed for 5 hours, it can be evaluated by measuring the elution amount of the organic compound (B) into the solution.
The amount of elution can be preferably 20% by mass or less, more preferably 15% by mass or less of the total amount of the organic compound (B) contained in the carbon material (C) for the non-aqueous secondary battery negative electrode. Preferably it is 10 mass% or less, Most preferably, it is 5 mass% or less.
When it is within the above range, the organic compound (B) is hardly peeled off during high-temperature storage or charge / discharge cycles, and deterioration of storage characteristics and charge / discharge cycle characteristics can be effectively suppressed.

  The non-aqueous solvent used in the elution evaluation is a non-aqueous solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 3: 7.

  As a method for quantifying the elution amount of the organic compound (B), a carbon material (C) for a nonaqueous secondary battery negative electrode was mixed with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 3: 7. After dipping in a non-aqueous solvent, the supernatant is recovered and dried to drive off the solvent, and a method of calculating the ratio of the peak intensity of the eluted component to the peak intensity when 100% is eluted by NMR or GPC can be mentioned.

<Method for producing carbon material (C)>
The carbon material (C) for a non-aqueous secondary battery negative electrode according to the present invention can be produced, for example, by the following method.
The organic compound (B) is added to the organic solvent, water, or a mixed solvent thereof in the mixing step (1), and the solution (D) is mixed with the carbon material (A) and then heated in the drying step (2). Alternatively, the carbon material (C) for a nonaqueous secondary battery negative electrode in which the carbon material (A) contains the organic compound (B) can be obtained by drying under reduced pressure.

  The solvent to be used is not particularly limited as long as the organic compound (B) is dissolved or dispersed, and preferably water, ethyl methyl ketone, toluene, acetone, methyl isobutyl ketone, ethanol, methanol, and the like. Among these, water, ethyl methyl ketone, acetone, methyl isobutyl ketone, ethanol, and methanol are more preferable because of cost and ease of drying.

Step (1): Mixing Step The method for mixing the carbon material (A) and the organic compound (B) is not particularly limited, but the carbon material (A) is used from the viewpoint of suppressing the initial gas amount and the storage gas amount. It is desirable that the organic compound (B) can be uniformly coated on the surface.

  As a mixing method, there are a method of stirring using a stirring blade in a fixed container, a method of rotating and mixing powder by rotating the container itself, and a method of mixing by fluidizing with an air flow. Can be mentioned. Among them, the method of stirring using a stirring blade in a fixed container is preferable from the viewpoint of mixing uniformity.

In this case, the fixed container includes an inverted conical type, a vertical cylinder type, a horizontal cylinder type, and a U-shaped trough. From the viewpoint of in-machine adhesion and uniform mixing, a horizontal cylinder type is preferable.
If the shape of the stirring blade is a horizontal axis method, it is a ribbon type, a screw type, a single-axis paddle type, a double-axis paddle type, a squid type, a saddle type, and if it is a vertical axis type, a ribbon type, a screw type, There are a planetary type, a conical screw type, and a lower high-speed rotating blade, but from the viewpoint of uniform mixing, a horizontal axis type saddle type is preferable.
For example, it is preferable to use a mixer having a horizontal axis type vertical stirring blade in a horizontally placed cylindrical container.

The peripheral speed of the stirring blade is preferably 0.1 m / s or more, more preferably 1 m / s or more, still more preferably 2 m / s or more, particularly preferably 3 m / s or more from the viewpoint of mixing uniformity. Yes, preferably 100 m / s or less, more preferably 80 m / s or less, and even more preferably 50 m / s or less.
The treatment time is preferably 0.5 min or more, more preferably 1 min or more, further preferably 5 min or more, preferably 5 hr or less, more preferably 1 hr or less, still more preferably 20 min or less. When the processing time is within the above range, it is possible to mix more uniformly while maintaining the processing capability.
The mixing temperature is preferably 1 ° C or higher, more preferably 10 ° C or higher, preferably 100 ° C or lower, more preferably 60 ° C or lower. When the mixing temperature is within the above range, an increase in the viscosity of the organic compound (B) can be suppressed, and more uniform mixing can be achieved. Moreover, the cost for temperature control can also be suppressed.
In order to enhance the uniform mixing property, when the solution of the organic compound (B) is in a high-viscosity state, solid, or gel, when the carbon material (A) is mixed, from the viewpoint of uniform mixing, the organic compound (B) is preferably diluted in advance with a solvent.
The ratio of the solution obtained by diluting the organic compound (B) to the carbon material (A) is preferably 1% by mass or more, more preferably 5% by mass or more, preferably 100% by mass or less, more preferably 30% by mass or less. Good to do. By setting it within the above range, the ratio can be uniformly mixed, and the drying time in the subsequent process can be shortened.

Further, it is preferable to add a solution of the organic compound (B) at the time of preparing the slurry in which the carbon material (A) is dispersed. This can be achieved by applying the carbon material for the negative electrode of the non-aqueous secondary battery to the negative electrode plate, and then drying the solvent of the organic compound (B), thereby improving the initial charge / discharge efficiency and suppressing gas generation. This is because it can be simplified.
The slurry in which the carbon material (A) is dispersed is a step of applying the non-aqueous secondary battery negative electrode carbon material according to the present invention to the negative electrode surface in order to produce a non-aqueous secondary battery negative electrode. It is one of the modes used in the above.

  Above all, from the viewpoint of initial charge / discharge efficiency, a solution of the organic compound (B) is prepared separately, and the solution and the carbon material (A) are mixed at the same time to prepare a slurry in which the carbon material (A) is dispersed. preferable. In addition, from the viewpoint that the surface of the carbon material (A) can be uniformly coated, it is more preferable to simultaneously mix the solution of the organic compound (B) and the carbon material (A) and then filter or dry the mixed solution.

  The concentration of the organic compound (B) in the solvent when mixed with the carbon material (A) is preferably 0.01% by mass or more and 70% by mass or less, respectively. Within this range, it can be expected that the organic compound (B) is uniformly present on the surface of the carbon material (A) in the active material for the negative electrode of the non-aqueous secondary battery, and an effect can be obtained efficiently.

The concentration of the organic compound (B) in the solution is preferably 0.03% by mass or more, more preferably 0.05% by mass or more, and preferably 60% by mass or less, more preferably. Is 40% by mass or less.
However, said solution density | concentration is a density | concentration of the solution at the time of making it contact with a carbon material (A).

  Moreover, the addition amount of an organic compound (B) can be adjusted suitably, and it is preferable to adjust a compounding quantity so that it may become preferable content in the carbon material for non-aqueous secondary battery negative electrodes of this invention mentioned above.

Step (2): Drying Step When drying the solution of the organic compound (B) by heating, the temperature is preferably not higher than the decomposition temperature of the organic compound (B), and may be not lower than the boiling point of the solvent. More preferred. Preferably they are 50 degreeC or more and 300 degrees C or less. Within this range, the drying efficiency is sufficient, battery performance deterioration due to residual solvent is avoided, the organic compound (B) is prevented from being decomposed, and the carbon material (A) and the organic compound (B) It is possible to easily prevent the effect from being reduced due to weak action.
The temperature is preferably 250 ° C. or lower, and preferably 100 ° C. or higher.

When drying the solution of the organic compound (B) under reduced pressure, the pressure is usually 0 MPa or less and −0.2 MPa or more in gauge pressure notation (difference from atmospheric pressure). If it is this range, it can dry comparatively efficiently. The pressure is preferably −0.03 MPa or less, and preferably −0.15 MPa or more.
In the drying step, there is no particular limitation as a method for drying the mixture of the carbon material (A) and the organic compound (B), but it is desirable that the coating can be uniformly performed from the viewpoint of suppressing the initial gas amount and the storage gas amount. . By making it uniform, the organic compound (B) can be efficiently adsorbed on the surface of a specific mesopore, and an effect of suppressing gas generation is easily obtained.
Examples of the heat transfer method include a convection heat transfer method in which hot air is directly applied and drying, and a conduction heat transfer method in which heat is transferred from a heat medium through a conductive heating plate, but a conduction heat transfer method is preferable from the viewpoint of yield.
The moving form of the object to be dried includes stationary drying in which the object to be dried is allowed to dry, hot air conveyance drying in which the object to be dried is dispersed or sprayed with hot air in the hot air, and agitation drying in which drying is performed while stirring. In that case, it is preferable to carry out stirring drying from a viewpoint of drying particles uniformly. Moreover, even if it implements a drying process with the same installation as a mixing process, and it is a separate installation, it is sufficient if the mixing uniformity and the drying capability are hold | maintained.

As a method of stirring and drying, a method of drying the mixture while stirring with a stirring blade in a fixed container, a method of drying while rotating the powder by rotating the container itself, From the viewpoint of uniformity and yield, a method of drying the mixture while stirring using a stirring blade in a fixed vessel is preferable. It is preferable to use it.
The stirring tank at that time includes an inverted conical type, a vertical cylinder type, a horizontal cylinder type, and a U-shaped trough. The horizontal cylinder type is preferable from the viewpoint of yield, workability, and installation space.
If the shape of the stirring blade is a horizontal axis method, it is a ribbon type, screw type, single-axis paddle type, double-axis paddle type, squid type, saddle type, hollow wedge type, and if it is a vertical axis method, a ribbon type, There are a screw type, a conical screw type, and a lower high-speed rotating blade, and a horizontal axis type single-axis paddle type and a saddle type are preferable.
Although the peripheral speed of the stirring blade varies depending on the stirring / drying method, it is preferably 0.01 m / s or more, more preferably 0.2 m / s or more, still more preferably 1 m / s or more, particularly preferably from the viewpoint of uniformity. It is 2 m / s or more, preferably 40 m / s or less, more preferably 20 m / s or less, and still more preferably 10 m / s or less.
In the case of the conduction heat transfer system, the heat medium includes heat medium oil, steam, and electric heater, but steam is preferred from the viewpoint of cost. In addition, the heat medium is transferred to the object to be dried through the heat transfer surface by flowing it through the stirring tank jacket, stirring blade, or stirring shaft, but from the viewpoint of heat transfer efficiency, the stirring tank jacket, stirring blade, and stirring It is preferable to flow a heating medium on all of the shafts.
For example, a horizontal cylindrical type stirring tank that can be heated by flowing a heat medium through the stirring tank jacket and has a horizontal axis type vertical stirring blade, and two horizontal shaft type hollow wedge stirring blades that mesh with each other CD dryer that can be heated by flowing a heat medium through both the rotating shaft and the casing with a horizontal jacket (Kurimoto Tsukuko), and a horizontal cylindrical stirring tank to flow the heating medium to the stirring tank jacket and stirring blade With a horizontal axis type single-shaft paddle type stirring blade, a ribo-cone with a vertical axis type ribbon type stirring blade that can be heated by flowing a heat medium through the stirring tank jacket in an inverted conical stirring tank (Okawara) Mixon (Toyo High-Tech), which has a vertical axis type ribbon type stirring blade that can be heated by flowing a heat medium through the stirring tank jacket and the stirring blade in a vertically installed cylindrical stirring tank.

  Prior to drying, a step of filtering the solution containing the carbon material (A) and the organic compound (B) and a step of washing the obtained residue with water may be included. As a result, the excess organic compound (B) not directly attached to the carbon material (A) can be removed, and the low temperature input / output characteristics are improved without reducing the effects such as improvement of initial efficiency and suppression of gas generation. This is preferable.

  In addition, when making the carbon material for nonaqueous secondary battery negative electrodes (C) of this invention contain other components, it adds to an organic solvent, water, or these mixed solvents similarly to an organic compound (B). The solution is mixed with the carbon material (A) and then dried by heating or / and decompression.

  When other components are added, a solution of other components may be prepared separately from the solution of the organic compound (B), or the solution may be added to the same solvent as the solution of the organic compound (B). You may prepare.

<Content of organic compound (B)>
The carbon material (C) for a non-aqueous secondary battery negative electrode of the present invention contains a carbon material (A) and an organic compound (B), and the mesopore surface area ratio (SAa / SAb) is 0.67 or more. Although it will not specifically limit, content of an organic compound (B) can be 0.01 mass% or more with respect to a carbon material (C), and can be 10 mass% or less. In addition, when the organic compound (B) is a polymer (b) which is a polymer compound, the content of the polymer (b) with respect to the carbon material (C) is the same value as the value of the organic compound (B), including a preferable range. It is.
The content of the organic compound (B) is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably with respect to the carbon material (C). Is 5% by mass or less, more preferably 3% by mass or less, particularly preferably 1% by mass or less, particularly preferably 0.8% by mass or less, and most preferably 0.4% by mass or less. Within the above range, the carbon material (A) can be effectively coated, and the effects of improving the initial efficiency and suppressing the generated gas can be further exhibited. In addition, an increase in interface resistance between the carbon material (A) and the coating layer can be suppressed, and a decrease in low-temperature input / output characteristics can be suppressed.

  When the solution containing the organic compound (B) is dried at the time of production, the content of the organic compound (B) is, in principle, the amount of the organic compound (B) added at the time of production. When the organic compound (B) not attached to the raw material (A) is removed, it should be calculated from the weight loss in the TG-DTA analysis of the obtained carbon material or the amount of the organic compound (B) contained in the filtrate. Can do.

The non-aqueous secondary battery negative electrode carbon material according to the present invention may contain any organic compound in addition to the organic compound (B). Although the kind of this arbitrary organic compound is not specifically limited, A polymer is preferable at the point by which adsorption | suction to a carbon material (A) is stably hold | maintained.
Although content of the said arbitrary organic compound is not specifically limited, 0.01 mass% or more and 10 mass% or less are preferable with respect to a carbon material (C).

<Negative electrode for non-aqueous secondary battery>
The negative electrode for a non-aqueous secondary battery of the present invention (hereinafter also referred to as “electrode sheet” as appropriate) includes a current collector and a negative electrode active material layer formed on the current collector, and the active material layer is at least The carbon material of the present invention is contained. More preferably, it contains a binder.

  As the binder, one having an olefinically unsaturated bond in the molecule is used. The type is not particularly limited, and specific examples include styrene-butadiene rubber, styrene / isoprene / styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene / propylene / diene copolymer. By using such a binder having an olefinically unsaturated bond, the swellability of the active material layer with respect to the electrolytic solution can be reduced. Of these, styrene-butadiene rubber is preferred because of its availability.

  By using a binder having such an olefinically unsaturated bond in combination with the carbon material described above, the strength of the negative electrode plate can be increased. When the strength of the negative electrode is high, deterioration of the negative electrode due to charge / discharge is suppressed, and the cycle life can be extended. In addition, since the negative electrode according to the present invention has high adhesive strength between the active material layer and the current collector, even when the binder content in the active material layer is reduced, the negative electrode is wound to produce a battery. It is speculated that the problem that the active material layer peels from the current collector does not occur.

As the binder having an olefinically unsaturated bond in the molecule, one having a large molecular weight or one having a large proportion of unsaturated bonds is desirable. Specifically, in the case of a binder having a high molecular weight, the weight average molecular weight is preferably 10,000 or more, more preferably 50,000 or more, and preferably 1,000,000 or less, more preferably 300,000 or less. Is desirable. In the case of a binder having a large proportion of unsaturated bonds, the number of moles of olefinically unsaturated bonds per gram of all binders is preferably 2.5 × 10 ⁻⁷ mol or more, more preferably 8 × 10 ^{−. It} is desirable that the amount is ⁷ mol or more, preferably 1 × 10 ⁻⁶ mol or less, more preferably 5 × 10 ⁻⁶ mol or less. The binder only needs to satisfy at least one of these regulations regarding molecular weight and regulations regarding the proportion of unsaturated bonds, but it is more preferable to satisfy both regulations simultaneously. When the molecular weight of the binder having an olefinically unsaturated bond is within the above range, mechanical strength and flexibility are excellent.

The binder having an olefinically unsaturated bond has an unsaturation degree of preferably 15% or more, more preferably 20% or more, still more preferably 40% or more, and preferably 90% or less, more preferably 80%. % Or less. The degree of unsaturation represents the ratio (%) of the double bond to the repeating unit of the polymer.
In the present invention, a binder that does not have an olefinically unsaturated bond can also be used in combination with the above-described binder that has an olefinically unsaturated bond as long as the effects of the present invention are not lost. The mixing ratio of the binder having no olefinically unsaturated bond to the binder having an olefinically unsaturated bond is preferably 150% by mass or less, more preferably 120% by mass or less.

By using a binder that does not have an olefinically unsaturated bond, the coatability can be improved. However, if the combined amount is too large, the strength of the active material layer is lowered.
Examples of the binder having no olefinic unsaturated bond include thickening polysaccharides such as methylcellulose, carboxymethylcellulose, starch, carrageenan, pullulan, guar gum, xanthan gum (xanthan gum), polyethers such as polyethylene oxide and polypropylene oxide, Vinyl alcohols such as polyvinyl alcohol and polyvinyl butyral, polyacids such as polyacrylic acid and polymethacrylic acid, or metal salts of these polymers, fluorine-containing polymers such as polyvinylidene fluoride, alkane polymers such as polyethylene and polypropylene, and these A copolymer etc. are mentioned.

  When the carbon material of the present invention is used in combination with the above-mentioned binder having an olefinically unsaturated bond, the ratio of the binder used in the active material layer can be reduced as compared with the conventional material. Specifically, the carbon material of the present invention and a binder (in some cases, it may be a mixture of a binder having an unsaturated bond and a binder having no unsaturated bond as described above). The mass ratio of each is preferably 90/10 or more, more preferably 95/5 or more, preferably 99.9 / 0.1 or less, more preferably 99.5 / 0.5 in terms of the dry mass ratio. The range is as follows. When the ratio of the binder is within the above range, a decrease in capacity and an increase in resistance can be suppressed, and the electrode plate strength is also excellent.

  The negative electrode of the present invention is formed by dispersing the above-described carbon material of the present invention and a binder in a dispersion medium to form a slurry, which is applied to a current collector. As the dispersion medium, an organic solvent such as alcohol or water can be used. If necessary, a conductive agent may be added to the slurry. Examples of the conductive agent include carbon black such as acetylene black, ketjen black, and furnace black, and fine powder made of Cu, Ni having an average particle diameter of 1 μm or less, or an alloy thereof. The addition amount of the conductive agent is preferably about 10% by mass or less with respect to the carbon material of the present invention.

A conventionally well-known thing can be used as a collector which apply | coats a slurry. Specific examples include metal thin films such as rolled copper foil, electrolytic copper foil, and stainless steel foil. The thickness of the current collector is preferably 4 μm or more, more preferably 6 μm or more, preferably 30 μm or less, more preferably 20 μm or less.
This slurry was applied to a width of 5 cm using a doctor blade so that the negative electrode material was 14.5 ± 0.3 mg / cm ² on a 18 μm-thick copper foil as a current collector, and air-dried at room temperature. Went. Further, after drying at 110 ° C. for 30 minutes, roll pressing was performed using a roller having a diameter of 20 cm to adjust the density of the active material layer to 1.70 ± 0.03 g / cm ³ to obtain an electrode sheet.

After applying the slurry on the current collector, it is preferably 60 ° C. or higher, more preferably 80 ° C. or higher, and preferably 200 ° C. or lower, more preferably 195 ° C. or lower, in dry air or an inert atmosphere. Dry to form an active material layer.
The thickness of the active material layer obtained by applying and drying the slurry is preferably 5 μm or more, more preferably 20 μm or more, still more preferably 30 μm or more, and preferably 200 μm or less, more preferably 100 μm or less, still more preferably. 75 μm or less. When the thickness of the active material layer is within the above range, it is excellent in practicality as a negative electrode in consideration of the particle size of the active material, and a sufficient Li occlusion / release function for a high-density current value can be obtained. .

The density of the carbon material in the active material layer varies depending on the application, but in an application in which capacity is important, it is preferably 1.55 g / cm ³ or more, more preferably 1.6 g / cm ³ or more, and still more preferably 1.65 g / cm. cm ³ or more, particularly preferably 1.7 g / cm ³ or more. Further, it is preferably 1.9 g / cm ³ or less. When the density is within the above range, a sufficient battery capacity per unit volume can be secured, and the rate characteristics are hardly lowered.

  When producing the negative electrode for non-aqueous secondary batteries using the carbon material of the present invention described above, the method and selection of other materials are not particularly limited. Moreover, when producing a lithium ion secondary battery using this negative electrode, there is no particular limitation on the selection of members necessary for the battery configuration such as the positive electrode and the electrolytic solution constituting the lithium ion secondary battery. Hereinafter, the details of the negative electrode for lithium ion secondary battery and the lithium ion secondary battery using the carbon material of the present invention will be exemplified, but usable materials, production methods and the like are not limited to the following specific examples. Absent.

<Non-aqueous secondary battery>
The basic configuration of the non-aqueous secondary battery of the present invention, particularly the lithium ion secondary battery, is the same as that of a conventionally known lithium ion secondary battery, and usually includes a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte. Is provided. The negative electrode of the present invention described above is used as the negative electrode.
The positive electrode is obtained by forming a positive electrode active material layer containing a positive electrode active material and a binder on a current 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 charge and discharge. Examples of metal chalcogen compounds include vanadium oxide, molybdenum oxide, manganese oxide, chromium oxide, titanium oxide, tungsten oxide and other transition metal oxides, vanadium sulfide, molybdenum sulfide. Transition metal sulfides such as NiPS ₃ and FePS ₃ , selenium compounds of transition metals such as VSe ₂ and NbSe ₃ , Fe _0.25 V _0.75 S ₂ , Examples include transition metal composite oxides such as Na _0.1 CrS ₂ and transition metal composite sulfides such as LiCoS ₂ and LiNiS ₂ .

Among these, V ₂ O ₅ , V ₅ O ₁₃ , VO ₂ , Cr ₂ O ₅ , MnO ₂ , TiO ₂ , MoV ₂ O ₈ , LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , TiS ₂ , V ₂ S ₅ , Cr _0.25 V _0.75 S ₂ , Cr _0.5 V _0.5 S _2, etc. are preferable, and LiCoO ₂ , LiNiO ₂ , LiMn ₂ O _4, and lithium in which a part of these transition metals are replaced with other metals are particularly preferable. It is a transition metal complex oxide. These positive electrode active materials may be used alone or in combination.

  A known binder can be arbitrarily selected and used as the binder for binding the positive electrode active material. Examples include inorganic compounds such as silicate and water glass, and resins having no unsaturated bond such as Teflon (registered trademark) and polyvinylidene fluoride. Among these, a resin having no unsaturated bond is preferable. If a resin having an unsaturated bond is used as the resin for binding the positive electrode active material, the resin may be decomposed during the 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 mixed with an active material in an appropriate amount to impart conductivity, but is usually carbon powder such as acetylene black, carbon black, and graphite, various metal fibers, powder, and foil. Etc.
The positive electrode plate is formed by slurrying a positive electrode active material or a binder with a solvent in the same manner as in the production of the negative electrode as described above, and applying and drying on a current collector. As the positive electrode current collector, aluminum, nickel, stainless steel (SUS), or the like is used, but is not limited at all.

As the electrolyte, a non-aqueous electrolyte obtained by dissolving a lithium salt in a non-aqueous solvent, or a gel, rubber, or solid sheet obtained by using an organic polymer compound or the like from the non-aqueous electrolyte is used.
The non-aqueous solvent used in the non-aqueous electrolyte is not particularly limited, and can be appropriately selected from known non-aqueous solvents that have been conventionally proposed as solvents for non-aqueous electrolytes. For example, chain carbonates such as diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate; cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; chain ethers such as 1,2-dimethoxyethane; tetrahydrofuran, 2-methyl Examples include cyclic ethers such as tetrahydrofuran, sulfolane, and 1,3-dioxolane; chain esters such as methyl formate, methyl acetate, and methyl propionate; and cyclic esters such as γ-butyrolactone and γ-valerolactone.

  Any one of these non-aqueous solvents may be used alone, or two or more thereof may be mixed and used. In the case of a mixed solvent, a combination of a mixed solvent containing a cyclic carbonate and a chain carbonate is preferable, and the cyclic carbonate is a mixed solvent of ethylene carbonate and propylene carbonate. This is particularly preferable in that load characteristics are improved. Among these, propylene carbonate is preferably in a range of 2% by mass to 80% by mass, more preferably in a range of 5% by mass to 70% by mass, and further in a range of 10% by mass to 60% by mass with respect to the entire non-aqueous solvent. preferable. When the proportion of propylene carbonate is lower than the above, the ionic conductivity at low temperature decreases, and when the proportion of propylene carbonate is higher than the above, when a graphite-based electrode is used, propylene carbonate solvated with lithium ions enters between the graphite phases. The co-insertion causes a delamination degradation of the graphite-based negative electrode active material, and there is a problem that a sufficient capacity cannot be obtained.

The lithium salt used in the non-aqueous electrolytic solution is not particularly limited, and can be appropriately selected from known lithium salts that can be used for this purpose. For example, halides such as LiCl and LiBr, perhalogenates such as LiClO ₄ , LiBrO ₄ and LiClO ₄ , inorganic lithium salts such as inorganic fluoride salts such as LiPF ₆ , LiBF ₄ and LiAsF ₆ , LiCF ₃ SO ₃ , 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) Of these, LiClO ₄ , LiPF ₆ , and LiBF ₄ are preferable.

Lithium salts may be used alone or in combination of two or more. The concentration of the lithium salt in the nonaqueous electrolytic solution is usually in the range of 0.5 mol / L or more and 2.0 mol / L or less.
In addition, when an organic polymer compound is included in the above non-aqueous electrolyte and used in the form of a gel, rubber, or solid sheet, specific examples of the organic polymer compound include polyethylene oxide, polypropylene oxide, and the like. Polyether polymer compounds; Cross-linked polymers of polyether polymer compounds; Vinyl alcohol polymer compounds such as polyvinyl alcohol and polyvinyl butyral; Insolubilized vinyl alcohol polymer compounds; Polyepichlorohydrin; Polyphosphazene; Siloxane; vinyl polymer compounds such as polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile; poly (ω-methoxyoligooxyethylene methacrylate), poly (ω-methoxyoligooxyethylene methacrylate-co-methyl methacrylate) Rate) and polymer copolymers such as poly (hexafluoropropylene-vinylidene fluoride).

The non-aqueous electrolytic solution described above may further contain a film forming agent. Specific examples of the film forming agent include carbonate compounds such as vinylene carbonate, vinylethyl carbonate, and methylphenyl carbonate; alken sulfides such as ethylene sulfide and propylene sulfide; sultone compounds such as 1,3-propane sultone and 1,4-butane sultone And acid anhydrides such as maleic acid anhydride and succinic acid anhydride. Furthermore, an overcharge inhibitor such as diphenyl ether or cyclohexylbenzene may be added.
When the above additives are used, the content is usually 10% by mass or less, preferably 8% by mass or less, more preferably 5% by mass or less, and particularly preferably 2% by mass or less. If the content of the additive is too large, other battery characteristics such as an increase in initial irreversible capacity, low temperature characteristics, and deterioration in rate characteristics may be adversely affected.

Further, as the electrolyte, a polymer solid electrolyte which is a conductor of an alkali metal cation such as lithium ion can be used. Examples of the polymer solid electrolyte include a polymer in which a lithium salt is dissolved in the aforementioned polyether polymer compound, and a polymer in which the terminal hydroxyl group of the polyether is substituted with an alkoxide.
In order to prevent a short circuit between the electrodes, a porous separator such as a porous film or a nonwoven fabric is usually interposed between the positive electrode and the negative electrode. In this case, the nonaqueous electrolytic solution is used by impregnating a porous separator. As a material for the separator, polyolefin such as polyethylene and polypropylene, polyethersulfone, and the like are used, and polyolefin is preferable.

  The form of the nonaqueous secondary battery of the present invention is not particularly limited. Examples include a cylinder type in which a sheet electrode and a separator are spiral, a cylinder type having an inside-out structure in which a pellet electrode and a separator are combined, a coin type in which a pellet electrode and a separator are stacked, and the like. In addition, by storing batteries of these forms in an optional outer case, the battery can be used in an arbitrary shape such as a coin shape, a cylindrical shape, or a square shape.

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

  EXAMPLES Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Production of electrode sheet>
An electrode plate having an active material layer with an active material layer density of 1.60 ± 0.03 g / cm ³ was prepared using the graphite particles of the examples or comparative examples. Specifically, 50.00 ± 0.02 g of negative electrode material, 50.00 ± 0.02 g of 1 mass% carboxymethylcellulose sodium salt aqueous solution (0.500 g in terms of solid content), and styrene having a weight average molecular weight of 270,000 -Aqueous dispersion of butadiene rubber 1.00 ± 0.05 g (0.5 g in terms of solid content) was stirred for 5 minutes with a hybrid mixer manufactured by Keyence and defoamed for 30 seconds to obtain a slurry.

This slurry was applied to a width of 10 cm using a small die coater made by ITOCHU machining so that the negative electrode material was 12.00 ± 0.3 mg / cm ² on a 10 μm thick copper foil as a current collector. Then, roll pressing was performed using a roller having a diameter of 20 cm to adjust the density of the active material layer to 1.60 ± 0.03 g / cm ³ to obtain an electrode sheet.

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

<Production method of non-aqueous secondary battery (laminated battery)>
The electrode sheet produced by the above method was cut into 4 cm × 3 cm to form a negative electrode, a positive electrode made of NMC was cut out with the same area, and a separator (made of a porous polyethylene film) was placed between the negative electrode and the positive electrode for combination. A laminate type battery was prepared by injecting 250 μL of an electrolytic solution in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio = 3: 3: 4) so as to be 1.2 mol / L. Was made.

<Measurement method of discharge capacity and initial efficiency>
Using the non-aqueous secondary battery (2016 coin-type battery) produced by the above method, the capacity during battery charging / discharging was measured by the following measurement method.
Charge to 5 mV with respect to the lithium counter electrode at a current density of 0.05 C, and further charge to a current density of 0.005 C at a constant voltage of 5 mV. After doping lithium into the negative electrode, the current density of 0.1 C Then, the lithium counter electrode was discharged to 1.5V. Subsequently, the second charge / discharge was performed at the same current density, and the sum of the difference between the charge capacity and the discharge capacity of the total two cycles was calculated as the irreversible capacity. The discharge capacity at the second cycle was defined as the discharge capacity of the material, and the discharge capacity of the material / (discharge capacity of the material + irreversible capacity) was defined as the initial efficiency.

<Initial gas volume, storage gas volume>
The laminate type battery produced by the above-described method was left for 12 hours, and then charged at a current density of 0.2 CmA / cm ³ until the potential difference between both electrodes reached 4.1 V, and then until the voltage became 3 V. Discharge was performed at 2 CmA / cm ³ . This was repeated twice, and further charging was carried out with the same current value until the potential difference between both electrodes reached 4.2V. The amount of swelling a (mL) generated so far was measured by the immersion volume method (solvent replacement method based on Archimedes' principle). Then, it was left to stand in an 85 degreeC thermostat for 24 hours, and the amount b (mL) which swells further was calculated | required. At this time, a (mL) was set as “initial gas amount”, and b (mL) was set as “preserved gas amount”.

<Low temperature output characteristics>
Using the laminate type non-aqueous electrolyte secondary battery produced by the method for producing the non-aqueous electrolyte secondary battery, low temperature output characteristics were measured by the following measuring method.
For non-aqueous electrolyte secondary batteries that have not undergone charge / discharge cycles, a voltage range of 4.1 V to 3.0 V and a current value of 0.2 C at 25 ° C. 3C for the current value to be 1C, the same applies hereinafter), voltage range of 4.2V to 3.0V, current value of 0.2C (at the time of charging 4.2V constant voltage charging for another 2.5 hours) Implementation) Initial charge and discharge was performed for 2 cycles.
Furthermore, after charging at a current value of 0.2 C to SOC 50%, in a low temperature environment of −30 ° C., each current value of 1/8 C, 1/4 C, 1/2 C, 1.5 C, 2 C is 2 seconds. Measure the drop in battery voltage after 2 seconds of discharge under each condition, and calculate the current value I that can flow for 2 seconds when the upper limit of charge voltage is 3V. The value calculated by the formula 3 × I (W) was used as the low temperature output characteristic of each battery.

<D50>
A carbon material (0.01 g) is suspended in 10 mL of a 0.2% by mass aqueous solution of polyoxyethylene sorbitan monolaurate (Tween 20 (registered trademark)), which is a surfactant, and this is used as a measurement sample. The sample was introduced into a scattering type particle size distribution measuring apparatus (for example, LA-920 manufactured by HORIBA), and the measurement sample was irradiated with 28 kHz ultrasonic waves at an output of 60 W for 1 minute, and then measured as a volume-based median diameter in the measuring apparatus.

<BET specific surface area (SA)>
Using a surface area meter (Shimadzu Corporation specific surface area measuring device “Gemini 2360”), the carbon material sample was subjected to preliminary vacuum drying at 100 ° C. for 3 hours under nitrogen flow, then cooled to liquid nitrogen temperature, and atmospheric pressure. Using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen to 0.3 is 0.3, the nitrogen adsorption BET 6-point method by the gas flow method was used.

<Tap density>
The carbon material of the present invention was dropped into a cylindrical tap cell having a diameter of 1.6 cm and a volume capacity of 20 cm ³ using a powder density measuring instrument through a sieve having an opening of 300 μm and filled into the cell, and then the stroke length was 10 mm. Was defined as the density obtained from the volume at that time and the mass of the sample.

<Mesopore volume and mesopore surface area by nitrogen adsorption method>
After performing heat treatment under reduced pressure at 100 ° C. for 3 hours, an adsorption isotherm (adsorbed gas: nitrogen) was measured at a liquid nitrogen temperature using an autosorb 3B manufactured by Cantachrome. Using the obtained adsorption isotherm, the mesopore volume and mesopore area at each pore size were determined by BJH method analysis.

<TPD-MS analysis method; amount of sulfur oxide gas>
Amount of desorbed sulfur oxide gas up to 500 ° C. by a temperature rising pyrolysis mass spectrometer (TPD-MS);
A 300 mg graphite powder sample was placed on a sample stage, heated at a rate of temperature increase of 10 ° C./min from helium gas at a flow rate of 60 mL / min, from room temperature to 500 ° C., and the amount of sulfur oxide gas generated at that time (m / z = 48) was measured with a mass spectrometer. This measured value is calculated based on the amount of sulfur oxide gas (m / z = 48) from room temperature to 400 ° C. by TPD-MS of sodium pyrosulfite (Na ₂ S ₂ O ₅ ). Converted to (μmol).

<PH>
For the measurement of pH, a pH meter (pH Meter F-51 manufactured by HORIBA) and a pH measurement electrode (LAQUA 9615-10D manufactured by HORIBA) were used. 5 g of graphite powder and 30 g of ultrapure water were placed in a polypropylene container, and the mixture was stirred to adjust the graphite and water. Then, ultrasonic dispersion treatment was performed for 30 minutes. The slurry solution was allowed to stand at 25 ° C. for 30 minutes, and then the pH measurement electrode was placed in the supernatant to measure the pH at 25 ° C.

<Fluorescent X-ray analysis (XRF): Amount of sulfur element>
5 g of graphite particles to be measured, 1 g of stearic acid, and 600 μL of ethanol are mixed and dried at 80 ° C., and then formed into a molded body. X-ray fluorescence analysis was performed, and the amount of sulfur element (ppm) calculated using the attached SQX software was defined as the amount of sulfur element (ppm) determined by X-ray fluorescence analysis (XRF) in this specification.

<Example 1>
As the carbon material (A), d50, SA, Tap, SAa / SAb, mesopore volume having a pore diameter of 35 nm or less, pH, sulfur element amount, sulfur oxide gas amount are 17.4 μm, 6.5 m ² / g, 1.04 g / cm ³ , 0.91, 0.01 mL / g, 6.11, 21 ppm, 15 kg of spheroidized natural graphite and sodium polystyrene sulfonate (Tosoh Organics) as the organic compound (B) 15 kg of an aqueous solution prepared by adjusting and mixing (PS-5) manufactured by Chemical Co., Ltd. to a concentration of 0.5% by mass was mixed with a mixer having a horizontal cylindrical-type vertical stirring blade. The obtained sample was filtered and further washed with 10 kg of pure water. Furthermore, it was statically dried by convection heat transfer in an air atmosphere at 120 ° C. for 7 hours, and sieved to obtain a powdery non-aqueous secondary battery negative electrode carbon material (C). From the amount of resin contained in the filtrate, the amount of resin attached to the non-aqueous secondary battery negative electrode carbon material (C) was calculated to be 0.16% by mass, respectively. With respect to this, d50, SA, Tap, SAa / SAb, mesopore volume of 35 nm or less, initial efficiency, discharge capacity, initial gas amount, storage gas amount, and low-temperature output characteristics were measured by the above measurement methods. The results are shown in Tables 1 and 2.

<Example 2>
As the carbon material (A), d50, SA, Tap, SAa / SAb, mesopore volume having a pore diameter of 35 nm or less, pH, sulfur element amount, sulfur oxide gas amount are 17.4 μm, 6.5 m ² / g, 1.04 g / cm ³ , 0.91, 0.01 mL / g, 6.11, 21 ppm, 0.1 μmol / g spheroidized natural graphite 30 kg, and sodium polystyrene sulfonate (Tosoh Organics) as the organic compound (B) 3 kg of an aqueous solution prepared by adjusting and mixing a chemical company (PS-5) with a concentration of 1.6% by mass was mixed with a mixer having a horizontal cylindrical-type vertical stirring blade. The obtained sample was statically dried by convection heat transfer at 120 ° C. for 7 hours in an air atmosphere and sieved to obtain a powdery carbon material (C) for a non-aqueous secondary battery negative electrode. About this, the same measurement as Example 1 was performed. The results are shown in Tables 1 and 2.

<Example 3>
As the carbon material (A), d50, SA, Tap, SAa / SAb, mesopore volume having a pore diameter of 35 nm or less, pH, sulfur element amount, sulfur oxide gas amount are 17.4 μm, 6.5 m ² / g, 1.04 g / cm ³ , 0.91, 0.01 mL / g, 6.11, 21 ppm, 0.1 μmol / g spheroidized natural graphite 30 kg, and sodium polystyrene sulfonate (Tosoh Organics) as the organic compound (B) 3 kg of an aqueous solution prepared by adjusting and mixing a chemical company (PS-5) with a concentration of 1.6% by mass was mixed with a mixer having a horizontal cylindrical-type vertical stirring blade. It is a horizontal cylindrical type stirring tank that can be heated by flowing a heat medium through the stirring tank jacket. The mixture was dried for 90 minutes in an air atmosphere to obtain a carbon material (C) for a non-aqueous secondary battery negative electrode. About this, the same measurement as Example 1 was performed. The results are shown in Tables 1 and 2.

<Example 4>
A non-aqueous two-phase system was used in the same manner as in Example 2 except that sodium polystyrene sulfonate (manufactured by Tosoh Organic Chemical Co., Ltd. (PS-5)) was used as the organic compound (B) after adjusting and mixing to a concentration of 5.0% by mass. A carbon material (C) for a secondary battery negative electrode was obtained. About this, the same measurement as Example 1 was performed. The results are shown in Tables 1 and 2.

<Example 5>
A non-aqueous two-phase system was used in the same manner as in Example 2 except that sodium polystyrene sulfonate (manufactured by Tosoh Organic Chemical Co., Ltd. (PS-5)) was used as the organic compound (B) after adjusting and mixing to a concentration of 10.0% by mass. A carbon material (C) for a secondary battery negative electrode was obtained. About this, the same measurement as Example 1 was performed. The results are shown in Tables 1 and 2.

<Comparative Example 1>
As carbon material (C) for non-aqueous secondary battery negative electrode, d50, SA, Tap, SAa / SAb, mesopore volume with a pore diameter of 35 nm or less, pH, sulfur element amount, sulfur oxide gas amount are 17.4 μm, Spherical natural graphites of 6.5 m ² / g, 1.04 g / cm ³ , 0.91, 0.01 mL / g, 6.11, 21 ppm, 0.1 μmol / g were used as they were. About this, the same measurement as Example 1 was performed. The results are shown in Tables 1 and 2.

<Comparative example 2>
As the carbon material (A), d50, SA, Tap, SAa / SAb, mesopore volume having a pore diameter of 35 nm or less, pH, sulfur element amount, sulfur oxide gas amount are 17.4 μm, 6.5 m ² / g, 1.04 g / cm ³ , 0.91, 0.01 mL / g, 6.11, 21 ppm, 1 kg of spheroidized natural graphite and 5% polyacrylamide (PAAm) as the organic compound (B) 200 g of the aqueous solution was mixed in a mixer having a horizontal cylindrical cylindrical stirring blade. The obtained sample was statically dried at 120 ° C. for 7 hours in an air atmosphere and sieved to obtain a powdery non-aqueous secondary battery negative electrode carbon material (C). About this, the same measurement as Example 1 was performed. The results are shown in Tables 1 and 2.

<Comparative Example 3>
A carbon material (C) for a non-aqueous secondary battery negative electrode was obtained in the same manner as in Comparative Example 2 except that 200 g of 5 mass% polyacrylamide aqueous solution was changed to 400 g of 2 mass% carboxymethyl cellulose sodium salt (CMC) aqueous solution. About this, the same measurement as Example 1 was performed. The results are shown in Tables 1 and 2.

<Example 6>
As carbon material (A), d50, SA, Tap, SAa / SAb, mesopore volume with pore diameter of 35 nm or less, pH, sulfur element amount, sulfur oxide gas amount are 10.9 μm, 8.6 m ² / g, 1 kg of spheroidized natural graphite with 0.94 g / cm ³ , 0.81, 0.014 ml / g, 5.6, 45 ppm, 0.3 μmol / g and sodium polystyrene sulfonate (Tosoh Organics) as the organic compound (B) 100 g of an aqueous solution prepared by adjusting and mixing a chemical company (PS-5) to a concentration of 1.8% was mixed by a mixer having a horizontal cylindrical-type vertical stirring blade. The obtained sample was statically dried at 120 ° C. for 7 hours in an air atmosphere and sieved to obtain a powdery non-aqueous secondary battery negative electrode carbon material (C). About this, the same measurement as Example 1 was performed. The results are shown in Tables 1 and 2.

<Comparative example 4>
As carbon material (C) for non-aqueous secondary battery negative electrode, d50, SA, Tap, SAa / SAb, mesopore volume with a pore diameter of 35 nm or less, pH, sulfur element amount, sulfur oxide gas amount are 10.9 μm, Spherical natural graphite having 8.6 m ² / g, 0.94 g / cm ³ , 0.81, 0.014 mL / g, 5.6, 45 ppm, 0.3 μmol / g was used as it was. About this, the same measurement as Example 1 was performed. The results are shown in Tables 1 and 2.

<Comparative Example 5>
As carbon material (A), d50, SA, Tap, SAa / SAb, mesopore volume with a pore diameter of 35 nm or less, pH, sulfur element amount, sulfur oxide gas amount are 17.4 μm, 6.7 m ² / g, 1.02 g / cm ³ , 0.91, 0.01 mL / g, 4.0, 100 ppm, 1.2 gmol / g spheroidized natural graphite 50 g, and sodium polystyrene sulfonate (Tosoh Organic as organic compound (B)) 50 g of an aqueous solution prepared by adjusting and mixing a chemical company (PS-5) to a concentration of 0.5% by mass was mixed in a flask. The obtained sample was heated to 95 ° C., dried with stirring, and then subjected to sieving to obtain a powdery non-aqueous secondary battery negative electrode carbon material (C). About this, the same measurement as Example 1 was performed. The results are shown in Tables 3 and 4.

<Comparative Example 6>
Carbon material for non-aqueous secondary battery negative electrode (C) as in Comparative Example 5 except that lithium polystyrene sulfonate (manufactured by Aldrich) was adjusted to 1.0% and mixed as the organic compound (B). ) About this, the same measurement as Example 1 was performed. The results are shown in Tables 3 and 4.

<Reference Example 1>
As the carbon material (C) for the non-aqueous secondary battery negative electrode, d50, SA, Tap, SAa / SAb, mesopore volume of 35 nm or less, pH, sulfur element amount, and sulfur oxide gas amount are 17.4 μm, 6. Spherical natural graphite of 7 m ² / g, 1.02 g / cm ³ , 0.91, 0.01 ml / g, 4.0, 100 ppm, 1.2 μmol / g was used as it was. About this, the same measurement as Example 1 was performed. The results are shown in Tables 3 and 4.

In Examples 1 to 5, by adding the specified organic compound (B) to the carbon material (A) having a sulfur oxide gas amount of 1.0 μmol or less and a pH of 4.5 or more, SAa / SAb Therefore, it was possible to effectively suppress side reactions with the electrolyte solution, and good initial efficiency, initial / preserved gas amount, and low-temperature output characteristics were exhibited. Further, Examples 1 to 3 are particularly excellent in low-temperature output characteristics because the pore volume is in a more suitable range.
On the other hand, in Comparative Examples 1 and 4 in which the organic compound (B) was not added, the initial efficiency decreased and the initial and storage gas amounts increased due to excessive side reactions with the electrolytic solution. Also, in Comparative Examples 2 and 3 to which an organic compound that is not specified is attached, since SAa / SAb is outside the specified range, the low-temperature output characteristics are decreased, the initial efficiency is decreased, and the initial and storage gas amounts are increased. It was. Further, Comparative Example 5 in which SAa / SAb is outside the specified range, the sulfur oxide gas amount exceeds 1.0 μmol, and the pH is less than 4.5, and the carbon compound (A) is attached to the organic compound (B), As for No. 6, the low temperature output characteristics were also deteriorated.

  By using the carbon material of the present invention as an active material for a negative electrode of a non-aqueous secondary battery, a lithium ion secondary battery having excellent charge / discharge efficiency and low temperature input / output characteristics at the initial cycle and a small amount of gas generation can be obtained. Can be provided. Moreover, according to the manufacturing method of the said material, since there are few processes, it can manufacture stably and efficiently and cheaply.

Claims (12)

A carbon material for a non-aqueous secondary battery negative electrode containing a carbon material (A) capable of occluding and releasing lithium ions and an organic compound (B), wherein the mesopore surface area ratio (SAa / SAb) is 0.67 or more, Carbon material (C) for non-aqueous secondary battery negative electrode.
(Formula 1) SAa / SAb = Mesopore surface area of 2 nm or more and less than 4 nm obtained by nitrogen adsorption method / Mesopore surface area of 4 nm or more and 35 nm or less obtained by nitrogen adsorption method   The carbon material (C) for a non-aqueous secondary battery negative electrode according to claim 1, wherein the mesopore surface area ratio (SAa / SAb) represented by Formula 1 is 0.90 or less.   The carbon material (C) for a non-aqueous secondary battery negative electrode according to claim 1 or 2, wherein a mesopore volume of 35 nm or less determined by a nitrogen adsorption method is 0.008 ml / g or more.   The carbon material (C) for a non-aqueous secondary battery negative electrode according to any one of claims 1 to 3, wherein the carbon material (A) is spheroidized natural graphite.   5. The non-aqueous system according to claim 1, wherein a mesopore volume of 35 nm or less determined by a nitrogen adsorption method of the carbon material (A) is 0.008 ml / g or more. Carbon material for secondary battery negative electrode (C).   The carbon material (C) for a nonaqueous secondary battery negative electrode according to any one of claims 1 to 5, wherein the organic compound (B) has a π-conjugated structure.   The carbon material (C) for a non-aqueous secondary battery negative electrode according to any one of claims 1 to 6, wherein the content of the organic compound (B) is less than 1% by mass. It is a manufacturing method of the carbon material (C) for nonaqueous secondary battery negative electrodes of any one of Claim 1 to 7, Comprising: Carbon material (A) which can occlude / release lithium ion, Organic compound ( The manufacturing method which contains B) and has the following process (1) and (2).
Step (1): Step of mixing carbon material (A) and organic compound (B) in a solvent Step (2): Step of stirring and drying the mixture obtained in Step (1) The method for producing a carbon material (C) for a nonaqueous secondary battery negative electrode according to claim 8, wherein the carbon material (A) is a carbon material satisfying (a) and (b).
(A) The amount of desorbed sulfur oxide gas up to 500 ° C. by a temperature rising pyrolysis mass spectrometer (TPD-MS) of the carbon material is 1.0 μmol / g or less.
(B) The pH of the dispersion when 5 parts by mass of the carbon material is suspended and dispersed in 30 parts by mass of distilled water is 4.5 or more.   The method for producing a carbon material (C) for a non-aqueous secondary battery negative electrode according to claim 8 or 9, wherein the organic compound (B) has a π-conjugated structure.   In the step (2), using a stirring device having a stirring blade in a fixed container, the stirring blade is dried with stirring and mixing by stirring at a peripheral speed of 0.01 m / s to 40 m / s. The method for producing a carbon material (C) for a non-aqueous secondary battery negative electrode according to any one of claims 8 to 10, wherein:   A nonaqueous secondary battery including a positive electrode and a negative electrode capable of inserting and extracting lithium ions, and an electrolyte, the negative electrode including a current collector and an active material layer formed on the current collector In addition, the active material layer is formed of the negative electrode carbon material (C) for a non-aqueous secondary battery according to any one of claims 1 to 7 or the method according to any one of claims 8 to 11. A non-aqueous secondary battery comprising the produced carbon material for a negative electrode of a non-aqueous secondary battery (C).