JP2016136452A - Carbon material for sodium ion secondary battery, active material for sodium ion secondary battery negative electrode, sodium ion secondary negative electrode, sodium ion secondary battery, resin composition for sodium ion secondary battery negative electrode, and method of manufacturing carbon material for sodium ion secondary battery negative electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon material for a sodium ion secondary battery negative electrode for which difficulty of a coating work in a negative electrode fabricating step can be improved while enabling exertion of a high charge/discharge capacity in the sodium ion secondary battery.SOLUTION: In a carbon material for a sodium ion secondary battery negative electrode, the average spacing dof (002) planes which is calculated by an X-ray diffraction method using CuKα ray as a radiation source is equal to 0.375 nm or more, the pore volume having a pore size exceeding 0.33 nm formed on the surface is equal to 0.1 ml/g or less, and the following initial water absorption coefficient is equal to 3% or less. Initial water absorption coefficient (%)=[((the mass of carbon material after left for 60 minutes under the constant temperature and constant humidity of 40°C and 90%) - (the mass of carbon material before left under the constant temperature and constant humidity))/(the mass of carbon material before left under the constant temperature and constant humidity)]×100.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a carbon material for a sodium ion secondary battery negative electrode, an active material for a sodium ion secondary battery negative electrode, a sodium ion secondary battery negative electrode, a sodium ion secondary battery, a sodium ion secondary battery negative electrode resin composition, and sodium The present invention relates to a method for producing a carbon material for a negative electrode of an ion secondary battery.

  In recent years, the use of secondary batteries has been studied in various technical fields ranging from small electrical products such as mobile phones to large machine products such as automobiles. As the secondary battery, various types such as a non-aqueous electrolyte secondary battery using an organic electrolyte solution or the like as an electrolyte or a solid battery using a solid electrolyte have been studied.

The mainstream of current secondary batteries in practical use is lithium ion secondary batteries, and many studies have been made on carbon materials used in lithium ion secondary batteries. For example, in Patent Document 1 below, carbonaceous particles having an average surface distance d ₀₀₂ of 002 planes determined by X-ray diffractometer (XRD) measurement of 0.340 nm or more and 0.370 nm or less are used as negative electrodes for lithium ion secondary batteries. Use as a material is disclosed. This document describes that according to such a configuration, it is possible to provide a lithium ion secondary battery with excellent initial charge / discharge efficiency.

  However, since lithium is a rare metal, the cost is high and the amount of resources is limited. Therefore, a sodium ion secondary battery that uses sodium, which has abundant resources and is inexpensive, as a charge carrier is expected as a next-generation secondary battery.

JP, 2014-116155, A

  The present inventor conducted various studies on the negative electrode of a sodium ion secondary battery with the aim of developing a practical sodium ion secondary battery. As a result, when the negative electrode active material of a lithium ion secondary battery and the carbon material used for the negative electrode active material are used as they are in a sodium ion secondary battery, it is difficult to provide a practical sodium ion secondary battery. It turns out that there are cases.

  More specifically, for example, when a carbon material suitable for a negative electrode material for a lithium ion secondary battery as described in Patent Document 1 is used, the sodium ion secondary battery does not necessarily exhibit a high charge / discharge capacity. I understood.

On the other hand, it has been found that a carbon material that can exhibit a high charge / discharge capacity in a sodium ion secondary battery has the following problems.
That is, when a negative electrode is generally produced, a carbon material is appropriately dispersed in a dispersion medium such as water together with other additives such as a conductive material to prepare a dispersion. Then, the negative electrode is formed by applying the dispersion to a current collector. Accordingly, the dispersion is adjusted to have a viscosity suitable for the application work to the current collector. However, when a dispersion is prepared using a carbon material that can exhibit a high charge / discharge capacity in a sodium ion secondary battery, the dispersion has a viscosity suitable for work such as coating immediately after preparation, but for a certain period of time. It has been found that the viscosity may increase significantly over time. Dispersions with increased viscosity make it difficult to apply the current collector and cause negative effects in the negative electrode preparation process, which is not practical. Hereinafter, the problem of the negative effect of the coating operation in the negative electrode manufacturing process described above is also simply referred to as “problem of poor coating property”.

The present invention has been made in view of the above problems. That is, the present invention provides a carbon material for a negative electrode of a sodium ion secondary battery in which the difficulty of the coating operation is improved in the negative electrode preparation process while allowing a high charge / discharge capacity to be exhibited in the sodium ion secondary battery.
Further, the present invention provides a sodium ion secondary battery negative electrode active material produced by including the sodium ion secondary battery negative electrode carbon material, and sodium ions configured using the sodium ion secondary battery negative electrode active material. A secondary battery negative electrode, a sodium ion secondary battery using the sodium ion secondary battery negative electrode, a resin composition for a sodium ion secondary battery negative electrode, and a method for producing a carbon material for a sodium ion secondary battery negative electrode are provided.

The carbon material for a negative electrode of the sodium ion secondary battery of the present invention has an average interplanar spacing d ₀₀₂ of (002) planes of 0.375 nm or more, which is obtained by an X-ray diffraction method using CuKα rays as a radiation source, and is formed on the surface. The pore volume having a pore diameter exceeding 0.33 nm is 0.1 ml / g or less, and the following initial water absorption is 3% or less.
Initial water absorption rate (%) = [((mass of carbon material after standing for 60 minutes under constant temperature and humidity at 40 ° C., 90% humidity) − (mass of carbon material before standing at constant temperature and humidity)) / ( The mass of the carbon material before leaving it at constant temperature and humidity)] × 100.

  Moreover, the active material for sodium ion secondary battery negative electrodes of this invention contains the carbon material for sodium ion secondary battery negative electrodes of this invention, It is characterized by the above-mentioned.

  Moreover, the sodium ion secondary battery negative electrode of the present invention includes a sodium ion secondary battery negative electrode active material layer containing the sodium ion secondary battery negative electrode active material of the present invention, and the sodium ion secondary battery negative electrode active material layer. And a laminated negative electrode current collector.

  Moreover, the sodium ion secondary battery of this invention is equipped with the sodium ion secondary battery negative electrode of this invention, an electrolysis layer, and a sodium ion secondary battery positive electrode, It is characterized by the above-mentioned.

  The resin composition for a sodium ion secondary battery negative electrode contains aniline resin, melamine, and hexamethylenetetramine, and the total of the melamine and hexamethylenetetramine is 25 parts by mass or more and 80 parts by mass with respect to 100 parts by mass of the aniline resin. It is characterized by the following.

  A method for producing a carbon material for a sodium ion secondary battery negative electrode is a method for producing a carbon material for a sodium ion secondary battery negative electrode for producing a sodium ion secondary battery negative electrode according to the present invention, comprising: an aniline resin and an amino group. A first firing step of firing a resin composition containing three or more nitrogen-containing compounds to produce a carbon material precursor; and firing the carbon material precursor at a temperature higher than the firing temperature of the first firing step. And a second firing step for carbonization.

  According to the present invention, a carbon material for a negative electrode of a sodium ion secondary battery in which difficulty in coating work in the negative electrode preparation process is improved while being able to exhibit a high charge / discharge capacity in a sodium ion secondary battery, and sodium ion An active material for a secondary battery negative electrode is provided. Moreover, the sodium ion secondary battery negative electrode and the sodium ion secondary battery of the present invention can be manufactured without problems of poor coatability and can exhibit a high charge / discharge capacity. The resin composition for a sodium ion secondary battery negative electrode and the method for producing a carbon material for a sodium ion secondary battery negative electrode of the present invention make it possible to provide the carbon material for a sodium ion secondary battery negative electrode of the present invention.

It is a schematic diagram which shows an example of a sodium ion secondary battery provided with the negative electrode manufactured using the carbon material of this invention.

The present inventor conducted various studies on the negative electrode of the Na ion secondary battery with the aim of developing a practical sodium ion secondary battery (hereinafter also referred to as Na ion secondary battery). As a result, it has been found that when the knowledge of a lithium ion secondary battery (hereinafter also referred to as a Li ion secondary battery) is directly transferred to a Na ion secondary battery, sufficient charge / discharge capacity may not be obtained. It was. One of the factors was estimated as follows. That is, when the carbon material used for the Li ion secondary battery negative electrode is used as the carbon material of the Na ion secondary battery negative electrode, the average spacing between the carbon materials is not suitable for sodium ions (hereinafter also referred to as Na ions). Therefore, it was speculated that Na ions were not occluded and released with respect to the carbon material. Therefore, as a result of various studies, it has been found that an average interplanar spacing suitable for Na ions can be sought, and Na ions can be occluded and released smoothly in the carbon material, and as a result, the charge / discharge capacity of the Na ion secondary battery can be increased. It was.
Incidentally, the average spacing referred herein means the average spacing d ₀₀₂ of which is determined by X-ray diffraction using CuKα ray as a radiation source (002) plane.

  However, it has been found that the problem of poor coatability described above tends to become conspicuous as the average spacing between the carbon materials is designed to be suitable for Na ions. The tendency is that the average interplanar spacing is increased in accordance with Na ions having a molecular diameter larger than that of lithium ions, so that the average interplanar spacing is increased, and accordingly, the pore volume of the carbon material is increased and the water absorption is increased. It seemed to be caused by that. Therefore, a dispersion containing a carbon material exhibits a viscosity suitable for coating immediately after preparation, but absorbs moisture contained in the dispersion as time passes, and the viscosity of the dispersion is unsuitable for coating. Seemed to increase. Therefore, the present inventor can solve the initial problem as long as it is a carbon material in which the average interplanar spacing is increased to a level suitable for Na ions, and the pore volume is appropriately reduced to suppress the water absorption rate. As a result, the present invention has been completed.

  The following is a carbon material for Na ion secondary battery negative electrode (hereinafter also simply referred to as carbon material), a carbon material manufacturing method for Na ion secondary battery negative electrode (hereinafter also simply referred to as carbon material manufacturing method), Na ion secondary of the present invention. A secondary battery negative electrode active material (hereinafter also simply referred to as a negative electrode active material), a Na ion secondary battery negative electrode (hereinafter also simply referred to as a negative electrode), and a Na ion secondary battery will be described in this order. In the description of the carbon material production method, the resin composition for the negative electrode of the Na ion secondary battery of the present invention (hereinafter also simply referred to as a resin composition) will be described together.

  The present invention relates to a secondary battery using sodium ions as a charge carrier. The secondary battery is of various types such as a non-aqueous electrolyte secondary battery or a solid electrolyte secondary battery. Is included.

<Carbon material>
The carbon material of the present invention has the following three characteristics.
That is, the first feature of the carbon material of the present invention is that the average interplanar spacing d ₀₀₂ of the (002) plane obtained by X-ray diffraction using CuKα rays as a radiation source is 0.375 nm or more.
The second feature of the present invention is that the pore volume formed on the surface and having a pore diameter exceeding 0.33 nm (hereinafter also simply referred to as pore volume) is 0.1 ml / g or less.
The third feature of the present invention is that the following initial water absorption is 3% or less.
Initial water absorption rate (%) = [((mass of carbon material after standing for 60 minutes under constant temperature and humidity at 40 ° C., 90% humidity) − (mass of carbon material before standing at constant temperature and humidity)) / ( The mass of the carbon material before leaving it at constant temperature and humidity)] × 100.

  Since the carbon material of the present invention has the above three characteristics, it is possible to exhibit a high charge / discharge capacity in a Na ion secondary battery, while Na ion secondary having improved difficulty in coating work in the negative electrode manufacturing process. A carbon material for a secondary battery negative electrode can be provided. That is, by providing the first feature, a high charge / discharge capacity can be realized, and the problem of poor coatability is solved by the second feature and the third feature. That is, the carbon material of the present invention is designed to have a sufficiently large average surface spacing from the viewpoint of occlusion and release of Na ions, while suppressing an increase in pore volume and exhibiting an appropriate initial water absorption rate. Therefore, the carbon material of the present invention greatly contributes to the provision of a practical Na ion secondary battery. Below, the carbon material of this invention is demonstrated in detail.

  The average interplanar spacing relating to the first feature of the carbon material of the present invention can be calculated from the spectrum obtained from the X-ray diffraction measurement of the carbon material using the following Bragg equation. The X-ray diffraction spectrum can be measured, for example, by an X-ray diffraction apparatus “XRD-7000” manufactured by Shimadzu Corporation.

λ = 2d _hkl sin θ (Bragg equation) (d _hkl = d ₀₀₂ )
λ: wavelength of characteristic X-ray K _α1 output from the cathode θ: reflection angle of spectrum

  In the carbon material of the present invention, the average plane spacing is 0.375 nm or more, preferably 0.377 nm or more. With this configuration, it is considered that the storage and release of Na ions in the carbon material become smooth and the charge / discharge capacity increases. In the carbon material of the present invention, the upper limit of the average spacing is not particularly limited. For example, by setting the average spacing to 0.400 nm or less, preferably 0.395 nm or less, a high charge / discharge capacity is maintained, and the Na ion secondary battery It can make a significant contribution to improving battery performance.

The pore volume relating to the second aspect of the present invention can be measured as follows.
That is, a measurement sample (carbon material) is preheated by vacuum heating at 473.15 K for 2 hours using a micro-distribution bell pore distribution measuring device “BELSORP-max”. Thereafter, CO ₂ (molecular diameter; 0.33 nm) was used as a measurement gas, an adsorption isotherm at 298.15 K was measured, and the pore volume of each adsorption gas was calculated using the Dubinin-Radushkevic equation. Based on this, the pore volume of each carbon material was calculated based on the following equation.
W = W ₀ · exp [− (A / E) n], A = RT [ln (Ps / P)]
W: Energy occupied by adsorbed molecules [ml / g]
E: Adsorption characteristic energy [J / mol]
P: Equilibrium vapor pressure [KPA]
T: Adsorption temperature [K]
W ₀ : pore volume [ml / g]
Ps: saturated vapor pressure [KPA]
n: Structural index = 2 [-]
R: Gas constant

  The pore volume of the carbon material of the present invention is 0.1 ml / g or less, preferably 0.07 ml / g or less, more preferably 0.03 ml / g or less, particularly preferably 0.01 ml / g or less. When the pore volume is in the above range, it seems that the initial water absorption rate of the carbon material can be easily realized within a preferable range. That is, the carbon material of the present invention is intended to achieve the intended problem of the present invention by suppressing the pore volume to a moderately low level while ensuring a large average interplanar spacing to such an extent that Na ions can be smoothly occluded and released. To solve.

  In the carbon material of the present invention, the lower limit of the pore volume is not particularly limited. For example, from the viewpoint of easily obtaining a preferable average surface separation, the pore volume is preferably 0.0005 ml / g or more, more preferably 0.001 ml / g or more.

  The initial water absorption rate relating to the third feature of the carbon material of the present invention can be obtained from the above-described equation for the initial water absorption rate (%). The initial water absorption rate is obtained by measuring the initial water absorption rate of the carbon material itself, and the carbon material contained in the dispersion used to form the negative electrode is subject to moisture (dispersion) in the dispersion over time. It is an index for judging how much water is absorbed. The initial water absorption rate of the carbon material of the present invention is 3% or less, preferably 2% or less, more preferably 1% or less. A dispersion containing a carbon material exhibiting such an initial water absorption rate exhibits good coatability on the current collector both immediately after preparation and after 60 minutes have elapsed after preparation. Moreover, the dispersion containing the carbon material does not change to a gel after 24 hours, and can be applied with a coating property.

  The lower limit of the initial water absorption rate of the carbon material is not particularly limited. For example, from the viewpoint of easily obtaining a preferable average surface separation, the initial water absorption is 0.05% or more, preferably 0.1% or more.

  For example, as an example of a preferable carbon material of the present invention, a carbon material produced by performing the following first firing and performing the following second firing after the first firing can be given. The first firing is a step of producing a carbon material precursor (primary carbide) by firing and curing a resin composition containing an aniline resin and a nitrogen-containing compound having three or more amino groups. The second firing step is a step of firing and carbonizing the carbon material precursor at a temperature higher than the temperature of the first firing after the first firing. In the second firing, the “temperature higher than the temperature of the first firing” means the highest temperature higher than the highest temperature in the first firing.

  The carbon material produced by performing the first firing and the second firing described above can have any of the average interplanar spacing, pore volume, and initial water absorption specified in the present invention.

Here, the aniline resin is a resin produced by condensing aniline and formaldehyde in the presence of an acid. In the present invention, an amino group means a functional group of —NH ₂ , —NHR, or —NRR ′, or a binding site composed of a nitrogen atom bonded to methylene in the compound and the methylene. Examples of nitrogen-containing compounds having three or more amino groups used in the first baking include, for example, melamine, hexamethylenetetramine, 1,2,3-propanetriamine, or 4,5,6, -pyrimidinetriamine. However, the present invention is not limited to this.

In particular, the nitrogen-containing compound preferably contains at least one of melamine and hexamethylenetetramine.
That is, the nitrogen-containing compound contains either melamine having three amino groups or hexamethylenetetramine having four amino groups, and preferably contains both melamine and hexamethylenetetramine. By using such a nitrogen-containing compound, the carbon material of the present invention can be easily provided. Although the reason for this is not clear, it is assumed that the raw material resin for the carbon material can be cured in a desired state by the crosslinking agent containing a large amount of amino groups. In particular, when the nitrogen-containing compound contains melamine and hexamethylenetetramine, the average interplanar spacing of the carbon material formed using this compound is increased in a desired range, and the pore volume and initial water absorption are in a preferred range. It is easy to be suppressed to small.

  The carbon material of the present invention contains carbon as a main material, and may further contain components other than carbon as necessary. Here, the term “carbon is a main material” means that carbon is contained in an amount of 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more when the carbon material is 100% by mass. Say.

  The optional component other than carbon in the carbon material is not particularly limited, and examples thereof include nitrogen. By including nitrogen in the carbon material, electrical characteristics suitable for the carbon material can be imparted due to the electronegativity of nitrogen. Thereby, the occlusion discharge | release of the sodium ion with respect to a carbon material can be accelerated | stimulated, and a high charging / discharging characteristic can be provided. In addition, when producing the carbon material of the present invention, any additive such as a curing agent and an additive can be appropriately used in addition to the carbon material, and a part of the additive remains in the carbon material. It is not excluded that the present invention.

  One of the preferable embodiments of the carbon material of the present invention has a nitrogen content of 2% by mass or more. That is, it is preferable that 2% by mass or more of nitrogen is contained with respect to 100% by mass of the carbon material of the present invention, more preferably 2.2% by mass or more, and more preferably 2.5% by mass or more. More preferably, it is more preferably 3% by mass or more. The carbon material containing nitrogen in the above-described range tends to have the first to third features specified in the present invention in a well-balanced manner. As described above, the amount of nitrogen in the carbon material can be significantly increased by using the nitrogen-containing compound in the production of the carbon material. In the first firing, nitrogen derived from amino groups is significantly incorporated into the carbon skeleton of the cured product due to the reaction between the raw material resin of the carbon material and the above-mentioned nitrogen-containing compound, which is suitable for the structure of the generated carbon material. It is presumed that

In the present invention, the nitrogen content is measured by a thermal conductivity method as follows. That is, the measurement sample (carbon material) is converted into a simple gas (CO ₂ , H ₂ O, and N ₂ ) using a combustion method, and the measurement sample converted to gas is homogenized and then passed through the column. Let Thereby, gas is isolate | separated in steps and content of carbon, hydrogen, and nitrogen is measured from each thermal conductivity. More specifically, for example, the nitrogen content in the carbon material can be measured using an elemental analyzer (PE2400) manufactured by PerkinElmer.

<Method for producing carbon material>
Next, the manufacturing method of the carbon material of this invention is demonstrated. The carbon material of the present invention is produced by firing and carbonizing a raw material resin of the carbon material. For example, a carbon material can be produced by sequentially performing a first firing step, a pulverization step, and a second firing step described below using a resin composition prepared in advance. However, either or both of the first baking step and the pulverization step may be omitted as appropriate.

(Preparation of resin composition)
The resin composition used in the method for producing a carbon material includes a carbon material raw resin.
The raw material resin for the carbon material is not particularly limited, and examples thereof include a resin material such as a thermosetting resin or a thermoplastic resin.
The thermosetting resin is not particularly limited. For example, aniline resin; phenol resin such as novolac type phenol resin or resol type phenol resin; epoxy resin such as bisphenol type epoxy resin or novolac type epoxy resin; melamine resin; Examples include resins; furan resins; ketone resins; unsaturated polyester resins; and urethane resins. The carbon resin raw material resin may be a modified product obtained by modifying the above-described resin with various components.
The thermoplastic resin is not particularly limited. For example, polyethylene, polystyrene, polyacrylonitrile, acrylonitrile-styrene (AS) resin, acrylonitrile-butadiene-styrene (ABS) resin, polypropylene, vinyl chloride, methacrylic resin, polyethylene terephthalate, Examples include polyamide, polycarbonate, polyacetal, polyphenylene ether, polybutylene terephthalate, polyphenylene sulfide, polysulfone, polyether sulfone, polyether ether ketone, polyether imide, polyamide imide, polyimide, and polyphthalamide.

  By selecting a thermosetting resin as the raw material resin for the carbon material, it is easy to produce a carbon material that combines the third feature with the first feature described above. It is preferable to select. Moreover, raw material resin can be used by 1 type or in combination of 2 or more types.

  The resin composition may contain other additives as appropriate. Examples of the additive include a crosslinking agent. The crosslinking agent used in the production of the carbon material of the present invention is preferably a nitrogen-containing compound having three or more amino groups as described above, but is not limited thereto.

  As mentioned above, it is preferable that the resin composition for Na ion secondary battery negative electrodes used for manufacture of the carbon material of this invention contains an aniline resin, a melamine, and hexamethylenetetramine. As for the compounding quantity in the said resin composition, it is preferable that the sum total of a melamine and a hexamethylenetetramine is 25 to 80 mass parts with respect to 100 mass parts of aniline resins. In particular, the resin composition preferably includes both melamine and hexamethylenetetramine, and the total amount thereof is 25 parts by mass or more and 80 parts by mass or less.

  By using the resin composition, it is possible to easily produce a carbon material having the first to third features specified in the present invention in a well-balanced manner. The reason for this is not clear, but when the aniline resin is cured by the first baking in a state where the aniline resin, melamine, and hexamethylenetetramine are mixed, it is presumed that the following excellent action occurs. The That is, when the aniline resin is cured, the cross-linking effect due to the amino group effectively acts, and the specific three-dimensional structure of melamine and hexamethylenetetramine seems to favorably affect the structure of the cured product of the aniline resin. As a result, it seems that a cured product (primary carbide) having a structure suitable as a precursor of the carbon material is easily obtained. Here, the preferable structure means a structure in which any of the first to third features of the present invention can be secured in the finally produced carbon material. In the said resin composition, when the sum total of a melamine and hexamethylenetetramine is 25 mass parts or more, it is easy to adjust the average space | interval of the carbon material produced | generated using this to 0.375 nm or more. In addition, the excessive melamine and hexamethylenetetramine with respect to the raw material resin of a carbon material may not contribute effectively to bridge | crosslinking of the said raw material resin, and may exert an undesirable influence on a carbon material as a surplus material. From this viewpoint, in the resin composition, the total of melamine and hexamethylenetetramine is preferably 80 parts by mass or less.

The apparatus for preparing the resin composition is not particularly limited. For example, when the raw material resin and the additive are melt-mixed, a kneading apparatus such as a kneading roll, a uniaxial or biaxial kneader can be used. . In addition, when the raw material resin and the additive are dissolved and mixed, a mixing device such as a Henschel mixer or a disperser can be used. When performing pulverization and mixing, for example, a device such as a hammer mill or a jet mill is used. Can be used.
In addition, in order to give desired characteristics to the carbon material to be produced, a metal, a pigment is used during the preparation of the resin composition or after the first firing step described later and before the second firing step. One or more additives such as a lubricant, an antistatic agent, or an antioxidant may be added.

(First firing step)
Next, the 1st baking process which hardens the resin composition prepared as mentioned above and produces | generates hardened | cured material is implemented. By curing the resin composition, the raw material resin contained in the resin composition can be cured and infusible. Moreover, when hardening raw material resin, the crosslinking agent (for example, melamine or hexamethylenetetramine) suitably contained in a resin composition is introduce | transduced into the structure of hardened | cured material, and the precursor for obtaining a desired carbon material is obtained. it can.

  The firing conditions in the first firing step are not particularly limited. For example, heating is performed for 1 hour or more and 10 hours or less at a temperature (for example, 200 ° C. or more and 600 ° C. or less) that can cause a curing reaction in the raw material contained in the resin composition. be able to. The heating device used in the first firing step is not particularly limited, and a large continuous furnace, a medium batch furnace, or a small furnace can be appropriately selected and used.

(Crushing process)
Next, the grinding | pulverization process process of the hardened | cured material obtained as mentioned above is performed. The pulverization treatment step is generally performed after the first firing step and before the second firing step described later, but can be omitted as appropriate.

  The pulverization method in the pulverization process is not particularly limited, and for example, an arbitrary pulverizer can be used. Examples of the pulverizer include an impact pulverizer such as a ball mill, a vibration ball mill, a rod mill, or a bead mill, or an air pulverizer such as a cyclone mill, a jet mill, or a dry air pulverizer. It is not limited to this. In the pulverization treatment, these devices may be used alone or in combination of two or more, or may be used by pulverizing a plurality of times with one device. In the pulverization treatment, in addition to these apparatuses, classification may be appropriately performed using a sieve or a pulverization apparatus having a classification function may be used.

(Second firing step)
Next, a 2nd baking process is demonstrated. A 2nd baking process is a process for baking and carbonizing the hardened | cured material produced | generated at the 1st baking process. Or when a 1st baking process is abbreviate | omitted, you may use for the 2nd baking process the resin composition prepared as mentioned above directly.
The firing conditions in the second firing step are not particularly limited, and a firing condition such as a temperature at which the cured product can be sufficiently carbonized is selected. For example, the temperature is raised from room temperature at a temperature rising rate in the range of 1 ° C./hour to 200 ° C./hour, and the temperature in the range of 800 ° C. to 3000 ° C. is 0.1 hour to 50 hours, preferably 0.5 It can be carried out by holding for at least 10 hours. The atmosphere during the second firing step is not particularly limited, and for example, an inert gas atmosphere containing an inert gas such as nitrogen or helium gas, a mixed gas atmosphere containing a small amount of oxygen in the inert gas atmosphere, or a reduction such as hydrogen It is preferable to employ a reducing gas atmosphere mainly containing gas. By selecting such a gas atmosphere, it is possible to suppress thermal decomposition (oxidative decomposition) of raw materials such as a resin and obtain a carbon material containing desired carbon particles.

In the carbon material manufacturing method described above, the carbon material manufacturing method of the present invention described below is particularly recommended.
The carbon material production method of the present invention is a carbon material production method of the present invention, wherein a carbon material precursor is obtained by firing a resin composition containing an aniline resin and a nitrogen-containing compound having three or more amino groups. And a second firing step of firing and carbonizing the carbon material precursor at a temperature higher than the firing temperature of the first firing step. That is, the carbon material manufacturing method of the present invention uses a resin composition containing an aniline resin as a raw material resin for a carbon material and a nitrogen-containing compound having three or more amino groups as a crosslinking agent. According to the carbon material manufacturing method of the present invention, the carbon material of the present invention can be manufactured particularly easily. In addition, since the description regarding the resin composition of this invention mentioned above is referred suitably for the resin composition used in the said recommended carbon material manufacturing method, description is omitted suitably here.

As a more preferred embodiment of the carbon material production method of the present invention, the nitrogen-containing compound contains at least one of melamine and hexamethylenetetramine. In this embodiment, the total of melamine and hexamethylenetetramine is preferably 25 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the aniline resin.
In particular, in the said aspect, it is more preferable that the total of melamine and hexamethylenetetramine is 25 to 80 mass parts with respect to 100 mass parts of aniline resin including both melamine and hexamethylenetetramine.

  According to the preferred embodiment, the aniline resin cured in the first baking step effectively has a crosslinking effect due to an amino group, and the specific three-dimensional structure of melamine and hexamethylenetetramine is the aniline resin cured product. It seems to have an advantageous effect on the structure. By providing the cured product obtained by performing the first firing step to the second firing step, it is possible to easily provide the carbon material having any of the first to third features specified by the present invention. it can.

  Below, the negative electrode active material of the present invention containing the carbon material of the present invention, the Na ion secondary battery negative electrode of the present invention comprising the negative electrode active material layer containing the negative electrode active material, and the Na ion secondary battery negative electrode The Na ion secondary battery of the present invention including the above will be described.

<Active material for negative electrode>
The active material for Na ion secondary battery negative electrode of the present invention contains the carbon material for Na ion secondary battery negative electrode of the present invention.
The negative electrode active material of the present invention enjoys the effects of the carbon material of the present invention relating to charge / discharge capacity. In addition, since the negative electrode active material of the present invention contains the carbon material of the present invention in which the problem of poor coating is improved, when dispersed in a dispersion, the dispersion medium absorbs water and the coating property is poor. It is possible to avoid increasing the viscosity of the dispersion to such an extent that. In the present invention, the negative electrode active material refers to a material that can occlude and release Na ions that are charge carriers in the secondary battery negative electrode.

  The negative electrode active material of the present invention may be substantially composed of only the carbon material of the present invention, but may further include a material different from the carbon material. Examples of such a material include materials generally known as additives for negative electrode materials such as silicon, silicon monoxide, and other graphite materials.

<Sodium ion secondary battery negative electrode and sodium ion secondary battery>

The Na ion secondary battery negative electrode of the present invention comprises a Na ion secondary battery negative electrode active material layer containing the Na ion secondary battery negative electrode active material of the present invention and a Na ion secondary battery negative electrode active material layer. And a negative electrode current collector.
The Na ion secondary battery of the present invention includes the Na ion secondary battery negative electrode of the present invention, an electrolytic layer, and a Na ion secondary battery positive electrode.

  The negative electrode of the present invention can be produced without the problem of poor coatability during production by using the negative electrode active material of the present invention. Therefore, the negative electrode of the present invention can be produced industrially as well as experimentally. Moreover, since the negative electrode active material of the present invention can exhibit a high charge / discharge capacity, the Na ion secondary battery of the present invention including the negative electrode of the present invention can enjoy such effects and exhibit a high charge / discharge capacity. is there.

  Below, an example of the Na ion secondary battery containing the carbon material of this invention is demonstrated using FIG. FIG. 1 is a schematic view showing an example of a Na ion secondary battery 100 including the carbon material of the present invention. As shown in FIG. 1, the Na ion secondary battery 100 includes a negative electrode 10, a positive electrode 20, a separator 30, and an electrolytic layer 40.

As shown in FIG. 1, the negative electrode 10 includes a negative electrode active material layer 12 and a negative electrode current collector 14.
The negative electrode active material layer 12 contains the above-described carbon material (not shown) of the present invention. The negative electrode current collector 14 is not particularly limited, and a current collector that can be used for the negative electrode can be appropriately selected and used. For example, an aluminum foil, a copper foil, or a nickel foil can be used, but the present invention is not limited thereto. Not.

The negative electrode 10 can be manufactured as follows, for example.
An additive such as an organic polymer binder or a conductive material is appropriately blended with the above-described negative electrode active material, and an appropriate amount of a dispersion medium is added and kneaded to prepare a dispersion. The dispersion is adjusted to a viscosity suitable for a coating operation on the surface of the negative electrode current collector 14 or a viscosity suitable for a molding operation into a predetermined shape such as a sheet. By adjusting the addition amount of the dispersion medium, the viscosity of the dispersion can be adjusted. Since the initial water absorption rate of the carbon material contained in the dispersion of the present invention is sufficiently low, the viscosity of the dispersion is maintained within a good range of the coating operation or the molding operation even after a certain time has elapsed.

The organic polymer binder may be appropriately selected from generally known binders and used, for example, a fluorine-based polymer such as polyvinylidene fluoride or polytetrafluoroethylene, or styrene-butadiene rubber, Examples thereof include rubbery polymers such as butyl rubber or butadiene rubber. Although the compounding quantity of an organic polymer binder is not specifically limited, For example, it is suitable to set it as 1 to 30 mass parts with respect to 100 mass parts of negative electrode active materials.
The conductive material only needs to be capable of imparting appropriate conductivity in the negative electrode active material layer 12, and for example, any one or combination of acetylene black, ketjen black, vapor grown carbon fiber, and the like can be used. . Although the compounding quantity of an electrically conductive material is not specifically limited, For example, 1 mass part or more and 10 mass parts or less are preferable with respect to 100 mass parts of negative electrode active materials, More preferably, they are 2 mass parts or more and 6 mass parts or less. Although it can be used outside these ranges, if the amount of the conductive material is too large, the amount of the negative electrode active material present in the electrode may be reduced more than necessary, and the charge / discharge capacity of the negative electrode may be reduced. is there.
Any dispersion medium may be used as long as it can prepare a dispersion having an appropriate viscosity by dispersing the negative electrode active material and any additive. For example, N-methyl-2-pyrrolidone, dimethylformamide, alcohol, or water may be used. Can be mentioned.

The negative electrode 10 can be manufactured by applying the dispersion prepared as described above to the negative electrode current collector 14 and drying it.
Further, by using the dispersion, a negative electrode active material layer 12 having a desired shape such as a sheet shape or a pellet shape is formed by compression molding, roll molding, and the like, and this is laminated on the negative electrode current collector 14, whereby the negative electrode 10 can also be obtained.

  The electrolytic layer 40 fills between the positive electrode 20 and the negative electrode 10, and is a layer in which Na ions move by charging and discharging.

  The electrolytic layer 40 is not particularly limited, and can be generally configured by filling a known electrolyte. As the electrolyte, for example, a nonaqueous electrolytic solution in which a sodium salt serving as an electrolyte is dissolved in a nonaqueous solvent is used.

  Examples of the non-aqueous solvent include cyclic esters such as propylene carbonate, ethylene carbonate, or γ-butyrolactone; chain esters such as dimethyl carbonate or diethyl carbonate; chain ethers such as dimethoxyethane; A mixture or the like can be used.

The electrolyte is not particularly limited, and generally known electrolytes can be used. For example, sodium perchlorate (NaClO ₄ ), sodium hexafluorophosphate (NaPF ₆ ), sodium tetrafluoroborate (NaBF) ₄ ) A sodium metal salt such as can be used.

  In the case of a Na ion secondary battery other than the nonaqueous electrolyte Na ion secondary battery, the electrolytic layer 40 may be configured using a solid electrolyte. Examples of the solid electrolyte include, but are not limited to, an embodiment having a gel polymer electrolyte containing a polymer material such as polyethylene oxide or polyacrylonitrile, or zirconia.

  The separator 30 is not particularly limited, and a generally known separator can be used as a member that is permeable to Na ions. For example, a glass filter; a porous film composed of polyethylene or polypropylene; cellulose Examples thereof include a filter; a ceramic filter; or a nonwoven fabric.

As illustrated in FIG. 1, the positive electrode 20 includes a positive electrode active material layer 22 and a positive electrode current collector 24.
It does not specifically limit as the positive electrode active material layer 22, Generally, it can form with a well-known positive electrode active material. The positive electrode active material used in the present invention can be appropriately selected from materials that can occlude and release Na ions. For example, the positive electrode active material is NaxMe ¹ yO ₂ (0 <x ≦ ¹ , 0.95 ≦ y <1.05, Me ¹ is at least selected from the group consisting of Fe, Mn, Ni, Co, Cr and Ti. Transition metal oxides such as NaFeF ₃ , NaMnF ₃ and NaNiF ₃ ; NaMe ² PO ₄ , Na ₃ Me ² ₂ (PO ₄ ) ₃ , Na ₄ Me ² ₃ (PO ₄ ) ₂ P ₂ O ₇ , Na ₂ Me ² PO ₄ F and Na ₃ Me ² ₂ (PO ₄ ) ₂ F ₃ (Me ² is a group consisting of Fe, Mn, Ni, Co, Ti, V and Mo) A polyanion or a fluorinated polyanion material including, but not limited to, at least one selected from
The positive electrode active material may contain an organic polymer binder and a conductive material in the same manner as the negative electrode active material described above. The blending amounts of the organic polymer binder and the conductive material in the positive electrode active material are not particularly limited, and may be the same as the negative electrode active material or may be blended in an amount different from the negative electrode active material.

  It does not specifically limit as the positive electrode electrical power collector 24, A generally well-known positive electrode electrical power collector can be used, For example, aluminum foil, stainless steel foil, titanium foil, nickel foil, copper foil etc. can be used. The positive electrode 20 in the present embodiment can be manufactured by a generally known positive electrode manufacturing method.

  The Na ion secondary battery can be formed by appropriately disposing the negative electrode 10, the positive electrode 20, the separator 30, and the electrolytic layer 40 in a case suitable for a Na ion secondary battery. The type of the Na ion secondary battery is not specified, and examples thereof include a cylindrical type, a coin type, a square type, and a film type.

As mentioned above, although embodiment of this invention was described, these are illustrations of this invention and various structures other than the above are also employable. For example, in FIG. 1, an example in which the negative electrode active material layer 12 is formed on one surface of the negative electrode current collector 14 and the positive electrode active material layer 22 is formed on one surface of the positive electrode current collector 24. Indicated. As a modification, the negative electrode active material layer 12 is formed on both surfaces of the negative electrode current collector 14, the positive electrode active material layer 22 is formed on both surfaces of the positive electrode current collector 24, and these are interposed via the separator 30 and the electrolytic layer 40. A Na ion secondary battery may be configured to face each other.
The present invention is not limited to the above-described embodiments, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

  Examples of the present invention and comparative examples will be described below. However, the present invention is not limited to the following examples and comparative examples. In Examples, “part” indicates “part by mass”, and “%” indicates “% by mass”.

<Preparation of carbon material for secondary battery negative electrode>
The carbon material used for an Example or a comparative example was prepared as follows. First, a resin (carbon material raw material) blended in a resin composition used for producing a carbon material was prepared as follows.
(Synthesis of aniline resin)
100 parts of aniline, 697 parts of a 37% formaldehyde aqueous solution, and 2 parts of oxalic acid were placed in a three-necked flask equipped with a stirrer and a cooling tube, reacted at 100 ° C. for 3 hours, dehydrated at elevated temperature, and 110 parts of aniline resin were obtained. .
(Synthesis of novolac type phenolic resin)
100 parts of phenol, 64.5 parts of 37% formaldehyde aqueous solution, and 3 parts of oxalic acid were placed in a three-necked flask equipped with a stirrer and a condenser, reacted at 100 ° C. for 3 hours, dehydrated at elevated temperature, and novolak-type phenolic resin 90 Got a part.
(Synthesis of resorcin resin)
100 parts of resorcin, 150 parts of 37% aqueous formaldehyde solution, and 1035 parts of water were placed in a three-necked flask equipped with a stirrer and a condenser and mixed until completely dissolved. Thereafter, sodium carbonate was added to adjust the pH to 6.50. Reaction was performed at a stirring speed of 60 rpm and 80 ° C. for 3 hours to obtain a resin spherical cured product.

  An aniline resin, a novolak type phenol resin, or a resorcin resin obtained as described above was used, and additives were appropriately blended, followed by firing (first firing) under the following conditions to perform a curing treatment, thereby obtaining a primary carbide.

(First firing)
Example 1: A resin composition obtained by blending 20 parts of melamine and 20 parts of hexamethylenetetramine with 100 parts of the aniline resin, and pulverizing and mixing with a vibration ball mill, was added at a temperature of 100 to 100 under a nitrogen atmosphere. The temperature was raised at a rate of temperature rise of ℃ / hour, and after reaching 550 ° C., the fired state was maintained for 1.5 hours to carry out the curing treatment.
Example 2: A primary carbide was obtained by performing first firing in the same manner as in Example 1 except that the blending amounts of melamine and hexamethylenetetramine were changed to the contents shown in Table 1.
Comparative Example 1: A primary carbide was obtained by performing first firing in the same manner as in Example 1 except that melamine was not used and the amount of hexamethylenetetramine was changed to the contents shown in Table 1.
Comparative example 2: Except having changed the compounding quantity of the hexamethylene tetramine into the content shown in Table 1, the 1st baking was performed similarly to the comparative example 1, and the primary carbide was obtained.
Comparative example 3: Except having changed the compounding quantity of the hexamethylenetetramine into the content shown in Table 1, the 1st baking was performed similarly to the comparative example 1, and the primary carbide was obtained.
Comparative Example 4: A primary carbide was obtained by performing first firing in the same manner as in Example 1 except that the blending amounts of melamine and hexamethylenetetramine were changed to the contents shown in Table 1.
Comparative Example 5: First firing was performed in the same manner as in Example 1 except that 10 parts of hexamethylenetetramine was added to 100 parts of the novolak-type phenol resin, thereby obtaining a primary carbide.
Comparative Example 6: First firing was performed in the same manner as in Example 1 except that 100 parts of the resorcin resin was used and melamine and hexamethylenetetramine were not used to obtain a primary carbide.

  The primary carbides of Examples and Comparative Examples obtained as described above were each pulverized under the same conditions, fired at a heating rate of 100 ° C./hour from room temperature in a nitrogen atmosphere, reached 1200 ° C., and then fired. Was held for 2 hours to perform second firing (carbonization treatment) to obtain carbon materials of Examples and Comparative Examples.

<Manufacture of sodium ion secondary batteries>
For 100 parts of the carbon material obtained in each of the examples and comparative examples, 1.5 parts of carboxymethyl cellulose (manufactured by Daicel Finechem Co., Ltd., CMC Daicel 2200), styrene-butadiene rubber (manufactured by JSR Corporation, TRD-2001) 3 parts, 2 parts of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., Denka Black) and 100 parts of distilled water were added and stirred and mixed with a rotating / revolving mixer to prepare a slurry dispersion.

  Each dispersion obtained as described above was applied to one side of a 14 μm thick copper foil (Furukawa Electric Co., Ltd., NC-WS), then pre-dried in air at 60 ° C. for 1 hour, And vacuum drying at 120 ° C. for 15 hours. The electrode was pressure-formed by a roll press and then vacuum-dried. This was cut into a disk shape having a diameter of 13 mm to produce a negative electrode. The thickness of the negative electrode material layer was 50 μm.

  As the counter electrode, a sodium metal formed into a disk shape with a diameter of 12 mm was used.

  As the separator, a polyolefin porous film (manufactured by Celgard, trade name: Celgard 2400) was used.

Using the above negative electrode, counter electrode (sodium metal), and separator, NaPF ₆ was added at a ratio of 1 mol / dm ³ to a mixed solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 5: 5 as an electrolytic solution. A 2032 type coin cell Na ion secondary battery was manufactured in a glove box under an argon atmosphere.

Evaluation was performed as follows using the carbon materials or dispersions of the respective Examples and Comparative Examples obtained as described above. Table 1 shows the results of the measurement of the average interplanar spacing d ₀₀₂ , the pore volume, the initial water absorption rate, the nitrogen content rate, and the coating property evaluation shown below.

[Average surface distance d ₀₀₂ ]
Using an X-ray diffractometer “XRD-7000” manufactured by Shimadzu Corporation, the average interplanar spacing d ₀₀₂ of the (002) planes of the carbon materials of the examples and comparative examples was measured. Specifically than spectrum obtained from X-ray diffraction measurement of each carbon material was calculated from the following Bragg equation Average spacing d ₀₀₂ of (002) plane.
λ = 2d _hkl sinθ Bragg equation (d _hkl = d ₀₀₂ )
λ: wavelength of characteristic X-ray K _α1 output from the cathode θ: reflection angle of spectrum

[Pore volume]
Specifically, each carbon material was subjected to a vacuum heating pretreatment at 473.15 K for 2 hours using a pore distribution measuring device “BELSORP-max” manufactured by Microtrack Bell Co., Ltd. ₂ (molecular diameter; 0.33 nm) is used to measure the adsorption isotherm at 298.15 K, and the pore volume of each adsorbed gas is calculated using the Dubinin-Radushkevich equation. Each pore volume was calculated based on the following equation.
W = W ₀ · exp [− (A / E) n], A = RT [ln (Ps / P)]
W: Energy occupied by adsorbed molecules [ml / g]
E: Adsorption characteristic energy [J / mol]
P: Equilibrium vapor pressure [KPA]
T: Adsorption temperature [K]
W ₀ : pore volume [ml / g]
Ps: saturated vapor pressure [KPA]
n: Structural index = 2 [-]
R: Gas constant

[Initial water absorption]
The initial water absorption rates of the carbon materials of the examples and comparative examples were determined as follows. That is, the mass of each carbon material before being left to stand at constant temperature and humidity was measured. Thereafter, each carbon material was allowed to stand for 60 minutes at a constant temperature and humidity of 40 ° C. and a humidity of 90%. Then, the mass was measured again, and the initial water absorption rate (%) was calculated using the following equation.
Initial water absorption rate (%) = [((mass of the carbon material after being left for 60 minutes under constant temperature and humidity at 40 ° C. and 90% humidity) − (mass of the carbon material before being allowed to stand at constant temperature and humidity)) / (The mass of the carbon material before leaving it at constant temperature and humidity)] × 100.

[Nitrogen content]
The nitrogen content of the carbon material of each example and comparative example was measured using an elemental analyzer (PE2400) manufactured by PerkinElmer.

[Coating property evaluation]
The coating properties of the dispersions containing the carbon materials of the examples and comparative examples were evaluated as follows. That is, the dispersion immediately after preparation of each Example and each Comparative Example was applied to the surface of the current collector, and it was confirmed that the coating property was good. Thereafter, each dispersion was placed in a sealed container and allowed to stand at room temperature for 24 hours. The properties of the dispersions left for 24 hours and the properties of the current collectors were evaluated as good and bad as follows.
The properties of the dispersion after being left for 24 hours were in the form of a slurry and could be applied well to the current collector .... Whether the properties of the dispersion after being allowed to stand for 24 hours were gel-like, Or it could not be applied well to the current collector ...

  Evaluation was performed as follows using the Na ion secondary batteries of each Example and each Comparative Example obtained as described above.

[Evaluation of initial charge / discharge characteristics]
Battery performance was evaluated as follows using the Na ion secondary battery of each Example or Comparative Example.
Constant current charging was performed at a measurement temperature of 25 ° C. and a current density during charging of 25 mA / g. When the potential reached 0 V, constant voltage charging was performed while maintaining 0 V, and the current density was 2.5 mA / g. The amount of electricity at the time of charging until reaching g was defined as the initial charge capacity (mAh / g).
Next, constant current discharge was performed at a current density of 25 mA / g during discharge, and the amount of electricity when the potential reached 2.5 V was defined as the initial discharge capacity (mAh / g).

As shown in the following formula, the value obtained by dividing the initial discharge capacity by the initial charge capacity was multiplied by 100 to calculate the initial charge / discharge efficiency (%).
Initial charge / discharge efficiency (%) = initial discharge capacity (mAh / g) / initial charge capacity (mAh / g) × 100

As shown in Table 1, Examples 1 and 2 have high initial charge capacity and initial discharge capacity, good coating properties, excellent practical carbon material, and Na using the carbon material. It was confirmed to be an ion secondary battery. In Examples 1 and 2, the nitrogen content in the carbon material was 2% by mass or more.
In Comparative Examples 1 to 3, although there was no problem in coatability, the average surface spacing was small, and the initial charge capacity and the initial discharge capacity were not sufficient.
In Comparative Examples 4 to 6, the pore volume and the water absorption increased as the average interplanar spacing increased. In particular, Comparative Examples 5 and 6 showed a large average interplanar spacing and high initial charge capacity and initial discharge capacity, but poor coatability and were not practical carbon materials.

The following effective suggestions were obtained from each of the comparative examples described above.
Compared to Comparative Example 1 in which the raw material resin of the carbon material is aniline resin, Comparative Example 3 has an average interplanar spacing increased by 0.003 nm, a pore volume increased by 0.008 ml / g, and an initial water absorption rate of 0.5. % Increase.
On the other hand, as compared with Comparative Example 1, Comparative Example 5 in which the raw material resin of the carbon material is a novolac type phenol resin has an average interplanar spacing increased by 0.016 nm, a pore volume increased by 0.15 ml / g, and an initial water absorption rate. Increased by 9.13%.
Similarly, in Comparative Example 6 in which the carbon material raw resin is resorcin resin compared to Comparative Example 1, the average interplanar spacing is increased by 0.021 nm, the pore volume is increased by 0.166 ml / g, and the initial water absorption is increased. 12.13% increase.
From this tendency, it was suggested that when an aniline resin is selected as the carbon resin, it is possible to make the increase in the average interplanar spacing remarkable and suppress the increase in the pore volume and the initial water absorption rate. That is, in order to solve the intended problem of the present invention, it was suggested that it is preferable to select an aniline resin as the raw material resin for the negative electrode material.

  Moreover, the comparative example 1 and the comparative example 4 which used the aniline resin as raw material resin of carbon material were the same in the compounding quantity of a crosslinking agent, and differed in the kind of crosslinking agent. As a result, they differed as follows in terms of average spacing, pore volume, and water absorption. That is, in contrast to Comparative Example 1 using 20 parts of hexamethylenetetramine as a crosslinking agent, Comparative Example 4 using melamine and 10 parts of hexamethylenetetramine as crosslinking agents each had an average interplanar spacing of 0.06 nm larger and finer. The pore volume was 0.009 ml / g smaller and the initial water absorption was 0.54% smaller. From these results, it was suggested that when melamine and hexamethylenetetramine were used as the cross-linking agent, it was possible to increase the average interplanar spacing while keeping the pore volume and initial water absorption small.

The above embodiment includes the following technical idea.
(1) The average interplanar spacing d ₀₀₂ of (002) plane obtained by X-ray diffraction using CuKα rays as a radiation source is 0.375 nm or more,
The pore volume having a pore diameter of more than 0.33 nm formed on the surface is 0.1 ml / g or less,
The following initial water absorption is 3% or less, a carbon material for a sodium ion secondary battery negative electrode,
Initial water absorption rate (%) = [((mass of the carbon material after being left for 60 minutes under constant temperature and humidity at 40 ° C. and 90% humidity) − (mass of the carbon material before being left to stand at constant temperature and humidity)) / (Mass of the carbon material before leaving it at constant temperature and humidity)] × 100.
(2) The carbon material for a sodium ion secondary battery negative electrode according to (1), wherein the nitrogen content is 2% by mass or more.
(3) performing a first firing to produce a carbon material precursor by firing a resin composition containing an aniline resin and a nitrogen-containing compound having three or more amino groups; The charcoal for a sodium ion secondary battery negative electrode according to the above (1) or (2), which is formed by performing second firing in which the carbon material precursor is fired and carbonized at a temperature higher than the temperature of the first firing. Material.
(4) The carbon material for a sodium ion secondary battery negative electrode according to (3), wherein the nitrogen-containing compound contains at least one of melamine and hexamethylenetetramine.
(5) A sodium ion secondary battery negative electrode active material comprising the sodium ion secondary battery negative electrode carbon material according to any one of (1) to (4) above.
(6) For a negative electrode in which a sodium ion secondary battery negative electrode active material layer containing the sodium ion secondary battery negative electrode active material described in (5) above and the sodium ion secondary battery negative electrode active material layer are laminated A sodium ion secondary battery negative electrode comprising: a current collector;
(7) A sodium ion secondary battery comprising the sodium ion secondary battery negative electrode described in (6) above, an electrolytic layer, and a sodium ion secondary battery positive electrode.
(8) including aniline resin, melamine, and hexamethylenetetramine;
The resin composition for a sodium ion secondary battery negative electrode, wherein the total of the melamine and the hexamethylenetetramine is 25 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the aniline resin.
(9) A method for producing a carbon material for a sodium ion secondary battery negative electrode, comprising producing the carbon material for a sodium ion secondary battery negative electrode according to any one of (1) to (4) above,
A first firing step of firing a resin composition containing an aniline resin and a nitrogen-containing compound having three or more amino groups to produce a carbon material precursor;
And a second firing step of firing and carbonizing the carbon material precursor at a temperature higher than the firing temperature of the first firing step.
(10) The nitrogen-containing compound contains at least one of melamine or hexamethylenetetramine,
The method for producing a carbon material for a sodium ion secondary battery negative electrode according to (9), wherein the total of the melamine and the hexamethylenetetramine is 25 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the aniline resin.

DESCRIPTION OF SYMBOLS 10 ... Negative electrode 12 ... Active material layer 14 for negative electrodes ... Negative electrode collector 20 ... Positive electrode 22 ... Positive electrode active material layer 24 ... Positive electrode collector 30 ... Separator 40- ..Electrolytic layer 100 ... Sodium ion secondary battery

Claims (10)

An average interplanar spacing d ₀₀₂ of (002) planes determined by X-ray diffraction using CuKα rays as a radiation source is 0.375 nm or more,
The pore volume having a pore diameter of more than 0.33 nm formed on the surface is 0.1 ml / g or less,
The following initial water absorption is 3% or less, a carbon material for a sodium ion secondary battery negative electrode,
Initial water absorption rate (%) = [((mass of the carbon material after being left for 60 minutes under constant temperature and humidity at 40 ° C. and 90% humidity) − (mass of the carbon material before being left to stand at constant temperature and humidity)) / (Mass of the carbon material before leaving it at constant temperature and humidity)] × 100.   The carbon material for a sodium ion secondary battery negative electrode according to claim 1, wherein the nitrogen content is 2% by mass or more.   First firing is performed to fire a resin composition containing an aniline resin and a nitrogen-containing compound having three or more amino groups to produce a carbon material precursor, and after the first firing, the first firing 3. The carbon material for a sodium ion secondary battery negative electrode according to claim 1, wherein the carbon material precursor is formed by performing second firing in which the carbon material precursor is fired and carbonized at a temperature higher than the temperature.   The carbon material for a sodium ion secondary battery negative electrode according to claim 3, wherein the nitrogen-containing compound contains at least one of melamine and hexamethylenetetramine.   A sodium ion secondary battery negative electrode active material comprising the sodium ion secondary battery negative electrode carbon material according to any one of claims 1 to 4.   An active material layer for a sodium ion secondary battery negative electrode comprising the sodium ion secondary battery negative electrode active material according to claim 5, and a negative electrode current collector in which the sodium ion secondary battery negative electrode active material layer is laminated, A sodium ion secondary battery negative electrode comprising:   A sodium ion secondary battery comprising the sodium ion secondary battery negative electrode according to claim 6, an electrolytic layer, and a sodium ion secondary battery positive electrode. Including aniline resin, melamine, and hexamethylenetetramine;
The resin composition for a sodium ion secondary battery negative electrode, wherein the total of the melamine and the hexamethylenetetramine is 25 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the aniline resin. A method for producing a carbon material for a sodium ion secondary battery negative electrode, wherein the carbon material for a sodium ion secondary battery negative electrode according to any one of claims 1 to 4 is produced,
A first firing step of firing a resin composition containing an aniline resin and a nitrogen-containing compound having three or more amino groups to produce a carbon material precursor;
And a second firing step of firing and carbonizing the carbon material precursor at a temperature higher than the firing temperature of the first firing step. The nitrogen-containing compound contains at least one of melamine or hexamethylenetetramine,
The method for producing a carbon material for a negative electrode of a sodium ion secondary battery according to claim 9, wherein the total amount of the melamine and the hexamethylenetetramine is 25 parts by mass or more and 80 parts by mass or less with respect to 100 parts by mass of the aniline resin.

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