JP2017091784A - Carbon material for secondary battery negative electrode, active material for secondary battery negative electrode, secondary battery negative electrode, and method of manufacturing secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon material for a secondary battery negative electrode, achieving a secondary battery negative electrode exhibiting a high charge/discharge efficiency.SOLUTION: A carbon material for a secondary battery negative electrode is obtained by: using a dihydro-1,3-benzoxazine compound having a dihydro-1,3-benzoxazine skeleton represented by the following chemical formula (1) (in the chemical formula (1), n represents an integer of 1 or more); and firing the dihydro-1,3-benzoxazine compound in a first firing step and a second firing step performed after the first firing step, the maximum temperature during the first firing step and the second firing step being 450°C or above.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a carbon material for a secondary battery negative electrode, and an active material for a secondary battery negative electrode including the production method, a secondary battery negative electrode, and a method for producing each 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 as an electrolyte or a solid battery using a solid electrolyte have been studied. In both types of secondary batteries, chemical species (for example, lithium ions) that serve as charge carriers for the secondary battery move between the positive electrode active material layer and the negative electrode active material layer to charge and discharge. Is repeated.

  In such secondary batteries, the electrode active material layer provided on the negative electrode generally contains a carbon material as an electrode active material. The electrode active material layer absorbs chemical species such as lithium ions between carbon material layers having a layer structure, and discharges the chemical species stored from the interlayer, thereby charging and discharging in a secondary battery. Is possible.

  The carbon material is generally produced using graphite, but it can also be produced using a phenol resin as a starting material. In order to further improve battery performance, Patent Document 1 proposes producing a carbon material for a secondary battery negative electrode using a benzoxazine compound as a starting material.

  That is, Patent Document 1 proposes an invention of a non-aqueous lithium secondary battery using a carbonaceous material obtained by heat-treating a dihydro-1,3-benzoxazine compound at a temperature within a predetermined range.

JP-A-11-97011

  When this inventor earnestly examined about the dihydro-1,3-benzoxazine compound, it carbonized by baking and manufactured a carbon material, and it was confirmed that this can be used as a carbon material for secondary battery negative electrodes. However, it has been found that sufficient charge capacity tends not to be obtained only by firing once in the temperature range specified in Patent Document 1 (specifically, from 400 ° C. to 3000 ° C.).

  In addition, in Examples of Patent Document 1 (see paragraphs [0017] and [0018] in the same document), a benzoxazine compound is heated in advance at 140 ° C. in a vacuum, and the obtained carbide is pulverized, and then in vacuum at 200 ° C. And then pulverized and powdered again, and then fired at 1000 ° C. to produce a carbon material. However, in the carbon material obtained by the method of the above example, significant tar generation was confirmed, powder fusion occurred, handling was poor, charge / discharge efficiency was low, and there was still room for examination. I found out.

The present invention has been made in view of the above problems. That is, this invention provides the manufacturing method of the carbon material for secondary battery negative electrodes which makes it possible to implement | achieve the secondary battery negative electrode which exhibits high charging / discharging efficiency.
Moreover, this invention provides each manufacturing method of the active material for secondary battery negative electrodes, a secondary battery negative electrode, and a secondary battery including the manufacturing method of the said carbon material for secondary battery negative electrodes.

  The method for producing a carbon material for a secondary battery negative electrode (hereinafter, also simply referred to as “carbon material”) according to the present invention includes a dihydro-1,3-benzoxazine skeleton represented by chemical formula (1) described later (in chemical formula (1), n is an integer of 1 or more) and a dihydro-1,3-benzoxazine compound having 1 or more is subjected to a first firing step to produce a carbon material precursor, and the carbon material precursor is used after the first firing step. A carbon material is produced by firing in the second firing step to be performed, and the maximum temperature of the first firing step and the second firing step is 450 ° C. or higher.

  Moreover, the manufacturing method of the active material for secondary battery negative electrodes of this invention (henceforth only a "active material for negative electrodes") includes the manufacturing method of the carbon material for secondary battery negative electrodes of this invention.

  Moreover, the manufacturing method of the secondary battery negative electrode (henceforth only a "negative electrode") of this invention includes the manufacturing method of the active material for secondary battery negative electrodes of this invention.

  Moreover, the manufacturing method of the secondary battery of this invention includes the manufacturing method of the secondary battery negative electrode of this invention.

  The method for producing a carbon material for a secondary battery negative electrode according to the present invention includes selecting a benzoxazine compound that is a starting material of the carbon material, and then firing the carbon material in a first firing step and a second firing step at a predetermined temperature or more. Further, it is possible to provide a carbon material that suppresses tarting of the carbon material, has high charge capacity and charge / discharge efficiency, and is excellent in occlusion / release of chemical species such as lithium ions. This is because the fusion of the carbon material precursor powder does not substantially occur, and thus impurities such as impurities other than carbon atoms (for example, oxygen atoms and nitrogen atoms) inside the powder particles are efficiently removed. This is thought to be possible. Moreover, the active material for negative electrodes containing the carbon material obtained by the said manufacturing method can improve the charging / discharging efficiency of a negative electrode provided with this. Therefore, a secondary battery provided with such a negative electrode can exhibit high charge capacity and charge / discharge efficiency, and is excellent in battery performance.

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

Hereinafter, a carbon material for a secondary battery according to an embodiment of the present invention and a manufacturing method thereof (hereinafter sometimes referred to as the present manufacturing method) will be described.
This production method uses a dihydro-1,3-benzoxazine compound having at least one dihydro-1,3-benzoxazine skeleton represented by the following chemical formula (1). In this production method, a dihydro-1,3-benzoxazine compound is subjected to a first firing step to produce a carbon material precursor. And the said carbon material precursor is baked in the 2nd baking process implemented after a 1st baking process, and a carbon material is manufactured. The maximum temperature of the first firing step and the second firing step described above is 450 ° C. or higher.

<Carbon material>
The carbon material of the present embodiment obtained by this production method can exhibit a charge capacity that is higher than that of a phenol-derived carbon material that has been generally used, and is also excellent in charge and discharge efficiency. The reason for this is not clear, but it is presumed that a carbon skeleton suitable for a carbon material for a secondary battery negative electrode can be realized by subjecting the above-described dihydro-1,3-benzoxazine compound to at least two high-temperature firings. Is done.
Moreover, the carbon material of the present embodiment tends not to cause significant tarification of the dihydro-1,3-benzoxazine compound in the firing step. As a result, substantially no fusion occurs in the powder of the carbon material precursor in the firing process, so that impurities such as impurities other than carbon atoms (for example, oxygen atoms and nitrogen atoms) inside the powder particles can be efficiently removed. The fact that it can be removed is also presumed to be one of the reasons why the carbon material of this embodiment is excellent in charge and discharge efficiency.

Below, the detail of the carbon material of this embodiment is demonstrated.
As the carbon material of the present embodiment, the above-described dihydro-1,3-benzoxazine compound is selected as a starting material. The dihydro-1,3-benzoxazine compound has a dihydro-1,3-benzoxazine skeleton represented by the chemical formula (1) described above. N in the chemical formula (1) is an integer of 1 or more, preferably 1 or more and 50 or less, more preferably 1 or more and 10 or less, still more preferably 1 or more and 5 or less, and particularly preferably n. = 1.

  In the dihydro-1,3-benzoxazine skeleton, the bond between the carbon atom sandwiched between the oxygen atom and the nitrogen atom forming a 6-membered ring and the adjacent oxygen atom is weaker than the other bond part, Easy to do. Therefore, when the dihydro-1,3-benzoxazine compound is baked at a low temperature (for example, 200 ° C. or less), it is considered that the bond is broken and tarring is likely to occur. In contrast, by subjecting the dihydro-1,3-benzoxazine compound to the high-temperature firing step at least twice, the bonding portion can be ring-opened and polymerized with other molecules to form a good carbon skeleton. It is guessed.

In this production method, the first firing step is a step of firing the dihydro-1,3-benzoxazine compound. The dihydro-1,3-benzoxazine compound may be appropriately pulverized and adjusted to an appropriate particle size before the first firing step.
The second firing step is a step of firing the carbon material precursor fired in the first firing step. The first firing step and the second firing step are independent as steps by including any step other than the firing step in the middle thereof. Examples of the optional step include a pulverization step, a cooling step, or a combination thereof. The pulverization step is a step of pulverizing the carbon material precursor obtained in the first firing step. In the case of carrying out the pulverization step, it includes a case where the carbon material precursor is cooled between the first firing step and the second firing step, and a case where the carbon material precursor is not cooled and maintains a high temperature state. Details of the grinding step will be described later. The cooling step includes natural cooling, ventilation cooling, and cooling using various cooling devices, and means cooling to a temperature lower than the maximum temperature of the first firing step. Although the cooling temperature is not particularly limited, for example, cooling is performed so that the temperature of the carbon material precursor is 100 ° C. or less, preferably 50 ° C. or less, more preferably 30 ° C. or less, and particularly preferably about room temperature (22 ° C. ± 2 ° C.). It is preferable to do.

In the first firing step and / or the second firing step, an additive other than the dihydro-1,3-benzoxazine compound or the carbon material precursor may be appropriately added to carry out the firing step.
Examples of the additive include a curing agent, an organic acid, an inorganic acid, a nitrogen-containing compound, an oxygen-containing compound, an aromatic compound, and a non-ferrous metal atom. These additives can be used alone or in combination of two or more depending on the type and properties of the resin used. It does not matter whether the additive remains in the finally provided carbon material.

  The curing agent used when producing the carbon material is an agent for promoting thermal curing of the starting material of the carbon component. The said hardening | curing agent is not specifically limited, It is good to determine suitably by the combination with the starting material of the carbon component used. For example, hexamethylenetetramine or polyacetal is preferably used as the curing agent, but is not limited thereto.

  The first firing step and the second firing step are performed so that the maximum temperature is 450 ° C. or higher. Preferably, the maximum temperature in the first firing step is maintained for a predetermined time. The predetermined time is, for example, several tens of minutes to several hours, more specifically, for example, not less than 10 minutes and not more than 8 hours, preferably not less than 30 minutes and not more than 5 hours.

  The maximum temperature of the first firing step and the second firing step may be the same or different. For example, the maximum temperature of the second baking step may be higher than the maximum temperature of the first baking step. Specifically, in the first firing step, the dihydro-1,3-benzoxazine compound may be fired at a maximum temperature of 450 ° C. or higher and lower than 1000 ° C. to generate a carbon material precursor. In the second firing step, the carbon material precursor may be fired at a maximum temperature of 1000 ° C. or higher to form a carbon material.

  The starting temperature, the rate of temperature increase, the temperature increase time, etc. of the first baking step and the second baking step are not particularly limited, and are appropriately determined depending on the type and amount of the dihydro-1,3-benzoxazine compound used. Good.

  Although the gas atmosphere of the 1st baking process mentioned above and the 2nd baking process is not specifically limited, It is preferable to carry out by inert gas atmosphere. Here, the inert gas atmosphere includes both an atmosphere composed only of an inert gas and an atmosphere composed of a mixed gas of an inert gas and oxygen. Examples of the inert gas include nitrogen gas, argon gas, helium gas, and water vapor. The gas atmosphere in the first firing step and the second firing step may be the same or different.

For example, this manufacturing method may further include a pulverization step of pulverizing the carbon material precursor baked in the first baking step to an average particle size (D50) of 1 μm to 20 μm before the second baking step. . The pulverization step is performed between the first firing step and the second firing step. From the viewpoint of making the thermal history of the carbon material precursor uniform in the second firing step, it is preferable to carry out the pulverization step. The particle size of the pulverized carbon material precursor obtained in the pulverization step is not particularly limited, but is 1 μm or more and 20 μm or less, more preferably 5 μm or more and 15 μm or less. When the particle size of the pulverized product is not less than the lower limit of the above numerical range, the handleability of the pulverized product is good. Moreover, when the particle size of the pulverized product is not more than the upper limit of the above-mentioned number range, the heat history of the carbon material in the second firing step can be made uniform. Moreover, according to this manufacturing method, since the carbon material precursor after a 1st baking process has sufficient hardness, it can grind | pulverize to the above-mentioned range of a particle size.
The particle size of the pulverized product means the particle size (D50, average particle size) at 50% accumulation in the volume-based cumulative distribution.

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

Next, R ₁ in the above chemical formula (1) will be described. The carbon material of the present embodiment does not limit R ₁ to a specific substituent, but R ₁ is selected from the group consisting of a phenyl group, a substituted phenyl group, a triazine ring, a substituted triazine ring, and a cyclohexyl group. Any one is preferred. Thereby, in the carbon material of the present embodiment, a significant improvement in charge / discharge efficiency is expected. As the triazine ring, for example, a 1,3,5-triazine ring is preferable.

The substituted phenyl group in R ₁ means a phenyl group in which one or more hydrogens bonded to carbon constituting the 6-membered ring of the phenyl group are substituted with other substituents. The substituted triazine ring means a triazine ring in which one or more hydrogens bonded to carbon constituting the triazine ring are substituted with other substituents.

Next, R ₂ in the above chemical formula (1) will be described. Carbon material of the present embodiment is not limited to the R ₂ on the particular substituents, is preferably any one selected below from (a) from the group of (j). Thereby, in the carbon material of the present embodiment, a significant improvement in charge / discharge efficiency is expected.

Examples of desirable dihydro-1,3-benzoxazine compounds having a combination of preferred examples of R ₁ and R ₂ described above include compounds represented by the following chemical formula (2) or (3).

The compound represented by the chemical formula (2) is a compound having a phenyl group as R _{1 and} hydrogen as R _{2 in} a dihydro-1,3-benzoxazine skeleton.
The compound represented by the chemical formula (3) is a compound having a substituted triazine ring as R _{1 and} hydrogen as R _{2 in} a dihydro-1,3-benzoxazine skeleton. The substituted triazine ring is formed by arranging two dihydro-1,3-benzoxazine skeletons on the triazine ring. That is, the chemical formula (3) has two or more (specifically, 3) dihydro-1,3-benzoxazine skeletons in one molecule.
Chemical formulas (2) and (3) have two or more benzene rings in one molecule, and are likely to form a good carbon skeleton upon firing. Specifically, chemical formula (2) has two benzene rings, and chemical formula (3) has three benzene rings.

  The carbon material in this embodiment uses the above-mentioned dihydro-1,3-benzoxazine compound as a main material as a starting material containing carbon. The main material means that the dihydro-1,3-benzoxazine compound is used in excess of 20% by mass as a carbon-containing starting material, preferably 50% by mass or more, more preferably 70% by mass or more, Preferably it is 80 mass% or more, Most preferably, it is 90 mass% or more.

That is, the carbon material of the present embodiment may use substantially only the above-mentioned dihydro-1,3-benzoxazine compound as a starting material containing carbon, but as the above-mentioned dihydro-1,3-benzoxazine compound. May be a mixture of a polymer, a by-product, or an unreacted monomer of the compound. In addition, other carbon-containing materials (hereinafter, also referred to as carbon components) may be appropriately mixed and used.
As another carbon component to be mixed, a phenolic hydroxyl group-containing resin, or a petroleum-based material such as acenaphthylene or petroleum pitch can be used.

Here, the phenolic hydroxyl group-containing resin refers to a resin having a phenolic hydroxyl group in the molecule. The phenolic hydroxyl group-containing resin in the present embodiment is a resin synthesized using a phenol such as a novolac-type phenol resin or a resol-type phenol resin as a starting material; phenols other than phenol such as an m-cresol resin, a xylenol resin, or a naphthol resin. Resin synthesized using a compound other than phenol and an aldehyde such as formaldehyde in the presence of an acid or alkaline catalyst; a resin having a phenolic hydroxyl group in the molecule; or the above-mentioned resin contains a modifier. Modified phenolic hydroxyl group-containing resin.
For example, the phenolic hydroxyl group-containing compound can be synthesized by reacting phenols with an arbitrary reaction compound.

  Regarding the production method for producing the carbon material of the present embodiment, the dihydro-1,3-benzoxazine compound, the first firing step, the second firing step, and between the first firing step and the second firing step can be performed. For any arbitrary process (for example, the pulverization process or the cooling process), the description regarding the carbon material of the present embodiment described above is referred to as appropriate. Therefore, detailed description is omitted here.

  Below, the negative electrode active material containing the carbon material of this embodiment, the negative electrode provided with the negative electrode active material layer containing the said negative electrode active material, and a secondary battery provided with the said negative electrode are demonstrated.

<Active material for negative electrode>
The negative electrode active material of this embodiment contains the carbon material of this embodiment described above. Thereby, the active material for negative electrodes of this embodiment has a large charge capacity of alkali metal ions such as lithium ions or sodium ions, and can exhibit high charge / discharge capacity efficiency.

  Here, the negative electrode active material is a substance that can occlude and release chemical species such as alkali metal ions (for example, lithium ions or sodium ions) in a secondary battery such as an alkali metal ion battery. The negative electrode active material described in this specification means a material containing the carbon material of the present embodiment.

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

<Secondary battery negative electrode and secondary battery>
Hereinafter, the negative electrode of this embodiment and a secondary battery including the negative electrode will be described.

The negative electrode of the present embodiment is a secondary battery negative electrode active material layer containing the negative electrode active material of the present embodiment described above, and a negative electrode for which the secondary battery negative electrode active material layer is disposed on at least a part of the surface. And a current collector.
Further, the secondary battery of the present embodiment includes the above-described negative electrode, an electrolyte, and a secondary battery positive electrode.

The negative electrode of the present embodiment is configured using the negative electrode active material of the present embodiment, so that the charge capacity is high and the charge / discharge capacity efficiency is also excellent.
Moreover, the secondary battery of this embodiment provided with the negative electrode of this embodiment can show the battery performance which reflected the charge capacity and charging / discharging efficiency which were excellent in the negative electrode. For example, the secondary battery of the present embodiment can shorten the charging time and exhibit a high discharge amount in a short time.

  Examples of the secondary battery include, but are not limited to, alkali metal secondary batteries such as lithium ion secondary batteries and sodium ion secondary batteries. The secondary battery includes various types using different electrolytes such as a non-aqueous electrolyte secondary battery and a solid secondary battery. In the following description, a lithium ion secondary battery will be described as an example of a secondary battery.

Below, an example of the lithium ion secondary battery containing the carbon material of this embodiment is demonstrated using FIG. FIG. 1 is a schematic diagram illustrating an example of a lithium ion secondary battery 100 including the carbon material of the present embodiment.
As shown in FIG. 1, the lithium ion secondary battery 100 includes a negative electrode 10, a positive electrode 20, a separator 30, and an electrolytic solution 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 carbon material of the present embodiment described above.
The negative electrode current collector 14 is not particularly limited, and generally known negative electrode current collectors can be used. For example, copper foil or nickel foil can be used.

The negative electrode 10 can be manufactured as follows, for example.
For 100 parts by mass of the negative electrode active material described above, generally known organic polymer binders (for example, fluorine-based polymers such as polyvinylidene fluoride and polytetrafluoroethylene; styrene-butadiene rubber, butyl rubber, butadiene) Rubber-like polymers such as rubber; etc.) 1 to 30 parts by mass and an appropriate amount of a viscosity adjusting solvent (N-methyl-2-pyrrolidone, dimethylformamide, alcohol, water, etc.) or water is added and kneaded. Then, a negative electrode slurry is prepared.
Moreover, you may add a electrically conductive material further with respect to the active material for negative electrodes mentioned above as needed. As the conductive material, for example, any one or a 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, in 100 mass% of active materials for negative electrodes, 2 to 10 mass% is preferable, More preferably, it is 3 to 7 mass%. Although it can be used outside these ranges, if the amount of the conductive agent is too large, the amount of the negative electrode active material present in the electrode may be reduced more than necessary, and the volume capacity of the negative electrode may be reduced. .

The obtained slurry can be formed into a sheet shape, a pellet shape, or the like by compression molding, roll molding, or the like, and the negative electrode active material layer 12 can be obtained. The negative electrode 10 can be obtained by laminating the negative electrode active material layer 12 and the negative electrode current collector 14 thus obtained.
Moreover, the negative electrode 10 can also be manufactured by apply | coating the obtained negative electrode slurry to the negative electrode collector 14, and drying.

  The electrolyte solution 40 fills between the positive electrode 20 and the negative electrode 10, and is a layer in which lithium ions move by charge / discharge.

  The electrolytic solution 40 is not particularly limited, and a generally known electrolytic solution can be used. For example, a nonaqueous electrolytic solution in which a lithium 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, and γ-butyrolactone; chain esters such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; chain ethers such as dimethoxyethane; These mixtures can be used.

Is not particularly limited as electrolytes generally be a known electrolyte, for example, it may be used lithium metal salt such as LiClO _4, LiPF _6. Further, the above salts can be mixed with polyethylene oxide, polyacrylonitrile, etc. and used as a solid electrolyte.

  It does not specifically limit as the separator 30, Generally a well-known separator can be used, For example, the porous film comprised using polyethylene or a polypropylene, a nonwoven fabric, etc. can be used.

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. Is not particularly limited as the cathode active material include lithium cobalt oxide (LiCoO _2), lithium nickel oxide (LiNiO _2), lithium manganese oxide (LiMn ₂ O _4), lithium nickel cobalt manganese oxide (LiNi _x Co _y Mn _z O ₂ , x + y + z = 1) and the like; conductive polymers such as polyaniline and polypyrrole; and the like can be used.
The positive electrode active material contains 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.
And the positive electrode 20 in this embodiment can be manufactured with the manufacturing method of a well-known positive electrode generally.

  Although the lithium ion secondary battery 100 has been described above as an example, the above description does not exclude that the carbon material of the present embodiment is used for a secondary battery other than the lithium ion secondary battery. The carbon material of this embodiment can also be used for a secondary battery using alkali ions other than lithium ions such as sodium ions as chemical species. At this time, each alkaline ion secondary battery may be configured using a member similar to the member used for the lithium ion secondary battery 100 described above, or may be configured using a different member. For example, as the negative electrode current collector in the sodium ion secondary battery, an aluminum foil can be selected in addition to the negative electrode current collector exemplified above.

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, and 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 solution 40. You may comprise a secondary battery by making it oppose.
Further, the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.

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

  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 benzoxazine)
First, benzoxazine used in Examples was prepared as follows.

(Benzoxazine 1)
Benzoxazine 1 of the following formula (2) was synthesized as follows.
That is, 1725 parts of a 37% formaldehyde aqueous solution was weighed into a three-necked flask equipped with a thermometer, a stirrer and a cooling tube, heated to 100 ° C., and a mixed solution of 1000 parts of phenol and 991 parts of arinin was added to it over 60 minutes. After the sequential addition, stirring was continued for another 60 minutes. Then, it heated up to 110 degreeC under pressure reduction, the water | moisture content was removed, and the benzoxazine 1 shown to following Chemical formula 2 was prepared.

(Benzoxazine 2)
Benzoxazine 2 of the following formula (4) was synthesized as follows. That is, a suspension solution containing 1622 parts of a 37% by weight aqueous formaldehyde solution and 1000 parts of bisphenol F was weighed in a three-necked flask equipped with a thermometer, a stirrer, and a condenser, and 50 parts of triethylamine was added as a catalyst. The part was dripped. After completion of dropping, the mixture was heated at 85 ° C. to 95 ° C. for 1 hour. Then, it heated up to 110 degreeC under pressure reduction, the water | moisture content was removed, and the benzoxazine 2 shown to following Chemical formula 4 was prepared.

(Synthesis of resol type phenol resin)
100 parts of phenol, 55 parts of paraformaldehyde, and 1 part of zinc acetate are placed in a three-necked flask equipped with a stirrer and a condenser, reacted at 100 ° C. for 3 hours, dehydrated, and then subjected to reaction conditions at 100 ° C. for 2 hours. And 90 parts of a solid resol type phenol resin was obtained.

(Synthesis of novolac type phenolic resin)
100 parts of phenol, 64.5 parts of a 37% by weight 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 90 parts of phenolic resin were obtained.

<Example 1>
Using benzoxazine 1 synthesized as described above as a carbon material starting material, the temperature was raised from room temperature to 100 ° C./hour in a nitrogen atmosphere, and after reaching 550 ° C., the fired state was 1.5. The carbonization treatment was performed while maintaining the time (first firing step). Then, the grinding | pulverization process was implemented and the carbon material precursor was obtained.
The carbon material precursor is naturally allowed to cool to room temperature (about 22 ° C.), and is placed in a container containing 5000 g of φ15 mm alumina balls and 900 g of φ10 mm alumina balls in a ball mill crusher, Obtained. Subsequently, the pulverized intermediate was passed through a sieve having an opening of 75 μm to remove coarse particles, and a pulverized product (carbon material precursor) was obtained. The ball mill pulverizer used was a rotary ball mill (one-stage type-B, provided by Irie Shokai Co., Ltd.).

  The pulverized product (carbon material precursor) obtained as described above is calcined at a temperature increase rate of 100 ° C./hour from room temperature in a nitrogen atmosphere, and after reaching 1200 ° C., the calcined state is maintained for 2 hours. (Second firing step). The carbon material thus obtained was named Example 1.

<Example 2>
Except for changing the carbon material starting material to benzoxazine 2 described above, the first firing step, pulverization step, and second firing step were performed in the same manner as in Example 1 to obtain a carbon material. This was designated Example 2.

<Comparative Example 1>
A carbon material was obtained by carrying out the first firing step, the pulverization step, and the second firing step in the same manner as in Example 1 except that the carbon material starting material was changed to the resol-type phenol resin synthesized as described above. . This was designated as Comparative Example 1.

<Comparative example 2>
As the carbon material starting material, the first firing step, the pulverization step, the second step were carried out in the same manner as in Example 1 except that the mixed material was 100 parts of the novolak type phenolic resin synthesized as described above and 10 parts of hexamethylenetetramine. A firing process was performed to obtain a carbon material. This was designated as Comparative Example 2.

<Creation of half-cell lithium-ion secondary battery>
(Creation of negative electrode)
In order to evaluate the battery characteristics of the carbon materials of Examples and Comparative Examples obtained as described above, negative electrodes were prepared as follows.
For 100 parts of the carbon material of each example or comparative example, 3 parts of styrene-butadiene rubber as a binder, 1.5 parts of carboxymethyl cellulose as a thickener, and 2 parts of acetylene black as a conductive material, An appropriate amount of pure water was added and diluted and mixed to obtain a slurry-like negative electrode mixture.
The slurry-like negative electrode mixture obtained above was applied to a copper foil (current collector) having a thickness of 10 μm in the same amount, and vacuum dried at 110 ° C. for 1 hour. Next, a disk-shaped lithium ion secondary battery having a diameter of 13 mm and an electrode active material layer (a portion excluding the current collector) having a thickness of 50 μm is punched out into a predetermined shape by being pressed into a thickness of 60 μm by a roll press. A negative electrode was prepared.

(Create working electrode)
Lithium metal having a thickness of 1 mm was prepared as a working electrode.

(Preparation of electrolyte)
An electrolytic solution was prepared by dissolving lithium hexafluorophosphate at a concentration of 1 mol / liter in a mixed solution of ethylene carbonate and diethyl carbonate (volume ratio 3: 7).

(Creation of lithium ion secondary battery)
Using the negative electrode, working electrode, and electrolytic solution obtained as described above, a lithium ion secondary battery was prepared as follows.
A negative electrode, a separator (polypropylene porous film: thickness 25 μm) and a working electrode are arranged in this order at a predetermined position of a bipolar electrode manufactured by Hosen Co., Ltd., and an electrolytic solution is injected to create a lithium ion secondary battery. did.

[Charge / discharge characteristics evaluation]
Charging / discharging conditions: The lithium ion secondary battery was charged with a constant current at a measurement temperature of 25 ° C. and a current density during charging of 25 mA / g. When the potential reached 0 mV, the voltage was maintained at 0 mV. Voltage charge was performed, and the amount of electricity charged until the current density reached 2.5 mA / g was defined as the charge capacity. The amount of electricity charged during constant current charging was defined as a constant current charging capacity.
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 discharge capacity.
A total of two cycles of charging / discharging under the above conditions were performed.
Charging / discharging in the first cycle is important in evaluating the initial characteristics of the battery. Since the battery characteristics are stabilized by accustoming the electrode interface in the first cycle, the first cycle is completed. In order to evaluate the battery characteristics after habituation, the charge / discharge characteristics at the second cycle are important. At that time, when charging and discharging are used repeatedly, constant current charging is performed, so the constant current charging capacity in the second cycle is important.
The charge / discharge efficiency was calculated using the following mathematical formula (1). Table 1 shows the results of the charge / discharge characteristic evaluation and the constant current charge capacity of the second cycle.

[Equation 1]
Charge / Discharge Efficiency (%) = Discharge Capacity (mAh / g) / Charge Capacity (mAh / g) × 100 (1)

  In the charge / discharge characteristic evaluation described above, “charging” refers to moving lithium ions from a working electrode made of metallic lithium to a negative electrode made of a carbon material by applying a voltage. “Discharge” refers to a phenomenon in which lithium ions move from a negative electrode made of a carbon material to a working electrode made of metallic lithium.

  As shown in Table 1, all the secondary batteries using the examples showed high discharge capacity, and the charge / discharge efficiency was high accordingly. Further, when comparing the constant current charge capacity at the second cycle, all the secondary batteries using the examples showed high charge capacity. As a result, it was confirmed that all of the carbon materials of the examples had high lithium charge / discharge efficiency and excellent lithium occlusion / release, and high charge capacity after battery acclimation. In addition, no remarkable tarting was confirmed in any of the carbon materials of the examples.

（ｉｖ）前記ジヒドロ−１，３−ベンゾオキサジン化合物が、上述する化学式（２）または（３）に示す化合物である上記（ｉ）から（ｉｉｉ）のいずれか一項に記載の二次電池負極用炭素材の製造方法。
（ｖ）前記第二焼成工程の前に、前記第一焼成工程で焼成された前記炭素材前駆体を平均粒径（Ｄ５０）にて１μｍ以上２０μｍ以下に粉砕する粉砕工程を更に含む上記（ｉ）から（ｉｖ）のいずれか一項に記載の二次電池負極用炭素材の製造方法。
（ｖｉ）上記（ｉ）から（ｖ）のいずれか一項に記載の二次電池負極用炭素材の製造方法を含む、二次電池負極用活物質の製造方法。
（ｖｉｉ）上記（ｖｉ）に記載の二次電池負極用活物質の製造方法を含む、二次電池負極の製造方法。
（ｖｉｉｉ）上記（ｖｉｉ）に記載された二次電池負極の製造方法を含む、二次電池の製造方法。
（ｉｘ）上述する化学式（１）に示すジヒドロ−１，３−ベンゾオキサジン骨格を１以上有するジヒドロ−１，３−ベンゾオキサジン化合物を用い、前記ジヒドロ−１，３−ベンゾオキサジン化合物を第一焼成工程、および前記第一焼成工程後に実施する第二焼成工程にて焼成してなる二次電池用負極用炭素材であって、
前記第一焼成工程および前記第二焼成工程の最高温度が４５０℃以上であることを特徴とする二次電池負極用炭素材。
（ｘ）所定範囲のタールの焼成物を有する二次電池負極用炭素材。 The above embodiment includes the following technical idea.
(I) A dihydro-1,3-benzoxazine compound having one or more dihydro-1,3-benzoxazine skeletons (wherein n is an integer of 1 or more in chemical formula (1)) represented by the above-mentioned chemical formula (1). Carbon material for a secondary battery for producing a carbon material by producing a carbon material by subjecting it to a first firing step to produce a carbon material precursor and firing the carbon material precursor in a second firing step performed after the first firing step. A method of manufacturing a material,
The manufacturing method of the carbon material for secondary battery negative electrodes characterized by the maximum temperature of said 1st baking process and said 2nd baking process being 450 degreeC or more.
(Ii) In the above (i), R ₁ in the above chemical formula (1) is any one selected from the group consisting of a phenyl group, a substituted phenyl group, a triazine ring, a substituted triazine ring, and a cyclohexyl group. The manufacturing method of the carbon material for secondary battery negative electrodes of description.
(Iii) The secondary described in the above (i) or (ii), wherein R ₂ in the chemical formula (1) is any one selected from the following groups (a) to (j): The manufacturing method of the carbon material for battery negative electrodes.

(Iv) The secondary battery negative electrode according to any one of (i) to (iii), wherein the dihydro-1,3-benzoxazine compound is a compound represented by the chemical formula (2) or (3) described above. Carbon material manufacturing method.
(V) The step (i) further comprising a step of crushing the carbon material precursor calcined in the first calcining step to an average particle size (D50) of 1 μm to 20 μm before the second calcining step. ) To (iv). The method for producing a carbon material for a secondary battery negative electrode according to any one of (iv).
(Vi) A method for producing an active material for a secondary battery negative electrode, comprising the method for producing a carbon material for a secondary battery negative electrode according to any one of (i) to (v).
(Vii) A method for producing a secondary battery negative electrode, including the method for producing an active material for a secondary battery negative electrode described in (vi) above.
(Viii) A method for producing a secondary battery, including the method for producing a secondary battery negative electrode described in (vii) above.
(Ix) A dihydro-1,3-benzoxazine compound having at least one dihydro-1,3-benzoxazine skeleton represented by the chemical formula (1) described above is used, and the dihydro-1,3-benzoxazine compound is first calcined. A carbon material for a negative electrode for a secondary battery obtained by firing in a step, and a second firing step performed after the first firing step,
The carbon material for a secondary battery negative electrode, wherein a maximum temperature in the first firing step and the second firing step is 450 ° C or higher.
(X) A carbon material for a secondary battery negative electrode having a fired product of tar in a predetermined range.

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- ..Electrolyte 100 ... Lithium ion secondary battery

Claims (8)

A first baking step of a dihydro-1,3-benzoxazine compound having at least one dihydro-1,3-benzoxazine skeleton represented by the following chemical formula (1) (wherein n is an integer of 1 or more in chemical formula (1)) The method for producing a carbon material for a negative electrode for a secondary battery, wherein a carbon material precursor is produced by firing the carbon material precursor in a second firing step performed after the first firing step to produce a carbon material. Because
The manufacturing method of the carbon material for secondary battery negative electrodes characterized by the maximum temperature of said 1st baking process and said 2nd baking process being 450 degreeC or more.

2. The secondary battery according to claim 1, wherein R ₁ in the chemical formula (1) is any one selected from the group consisting of a phenyl group, a substituted phenyl group, a triazine ring, a substituted triazine ring, and a cyclohexyl group. Manufacturing method of carbon material for negative electrode. The production of the carbon material for a secondary battery negative electrode according to claim 1 or 2, wherein R ₂ in the chemical formula (1) is any one selected from the following groups (a) to (j): Method.

The method for producing a carbon material for a secondary battery negative electrode according to any one of claims 1 to 3, wherein the dihydro-1,3-benzoxazine compound is a compound represented by the following chemical formula (2) or (3).

  5. The pulverization step of pulverizing the carbon material precursor baked in the first baking step to an average particle size (D50) of 1 μm to 20 μm before the second baking step. The manufacturing method of the carbon material for secondary battery negative electrodes as described in any one.   The manufacturing method of the active material for secondary battery negative electrodes including the manufacturing method of the carbon material for secondary battery negative electrodes as described in any one of Claim 1 to 5.   The manufacturing method of a secondary battery negative electrode including the manufacturing method of the active material for secondary battery negative electrodes of Claim 6.   The manufacturing method of a secondary battery including the manufacturing method of the secondary battery negative electrode described in Claim 7.

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