JP2022092077A - Carbonaceous material for battery - Google Patents

Abstract

To provide a carbonaceous material for a battery manufactured in a small number of steps, which can obtain a battery having excellent discharge capacity, charge/discharge efficiency, resistance, and output characteristics, and a manufacturing method thereof, an electrode containing the carbonaceous material for the battery, and a battery using the electrode.SOLUTION: A carbonaceous material for a battery has a sulfur element content of 0.8 mass% or more and a true density determined by the butanol method is 1.48 g/cm3 or more and 1.62 g/cm3 or less.SELECTED DRAWING: None

Description

The present invention relates to a carbonaceous material for a battery and a method for producing the same, an electrode containing the carbonaceous material for a battery, and a battery having the electrode.

Carbonaceous materials are used for various electrodes such as water-based electrolyte batteries such as lead carbon batteries, lithium ion batteries, non-aqueous electrolyte batteries such as sodium ion batteries, all-solid-state batteries, and fuel cells, depending on the application. There is a demand for a carbonaceous material having such properties. For example, non-aqueous electrolyte batteries mounted on electric vehicles and hybrid vehicles are required to have high output characteristics due to their size. Further, since charging / discharging of the battery is performed when the brake or the accelerator is depressed, rapid charging / discharging characteristics in a short time are required.

A carbonaceous material derived from graphitized carbon is used for the electrodes of such a non-aqueous electrolyte battery. Until now, petroleum pitch or coal pitch has been used as the carbon source for graphitic carbon, but in recent years, due to concerns about the impact on the global environment and the decrease in reserves, carbon sources have been used instead. There is a demand for carbonaceous materials. One example is a carbonaceous material that uses lignin as a carbon source, which is discharged in large quantities as a by-product in the pulp manufacturing process of the paper industry. Non-Patent Document 1 describes a carbonaceous material obtained by carbonizing lignin dissolved in a potassium hydroxide solution.

Non-Patent Document 2 describes a carbonaceous material obtained by carbonizing and firing a lignin-melamine resin prepared by dissolving melamine and lignin in formaldehyde as a polymer for introducing nitrogen.

Non-Patent Document 3 describes a carbonaceous material obtained by dissolving lignin and an epoxy resin in an alcohol solution and carbonizing after curing.

Electrochimica Acta 176 (2015) 1136-1142 Journal of Energy Chemistry 000 (2018) 1-7 Chemical Engineering Journal 341 (2018) 280-288

However, the method described in Non-Patent Document 1 has a large number of steps such as removal of the alkali metal used in the reaction. Further, the methods described in Non-Patent Document 2 and Non-Patent Document 3 have a problem that the process is complicated, such as compounding with other substances. Further, the carbonaceous material obtained by either method has low charging efficiency and a small discharge capacity, so that the performance as a battery material is not sufficient.

Therefore, the subject of the present invention includes a carbonaceous material for a battery manufactured in a small number of steps, a method for producing the same, and the carbonaceous material for the battery, which can obtain a battery excellent in discharge capacity, charge / discharge efficiency, resistance and output characteristics. It is to provide an electrode and a battery using the electrode.

As a result of diligent studies, the present inventors have found that the above problems can be solved, and have completed the present invention.

That is, the present invention includes the following preferred embodiments.
[1] A carbonaceous material for a battery, which has a sulfur element content of 0.8% by mass or more and a true density determined by the butanol method of 1.48 g / cm ³ or more and 1.62 g / cm ³ or less.
[2] The carbonaceous material for a battery according to [1], wherein the carbonaceous material has an oxygen element content of 0.7% by mass or less.
[3] The carbonaceous material for a battery according to [1] or [2], wherein the carbonaceous material has a size of Lc in the hexagonal net area layer direction of 10 Å or less.
[4] The carbonaceous material for a battery according to any one of [1] to [3], wherein the average particle size is 2 μm or more and 200 μm or less.
[5] The carbon for batteries according to any one of [1] to [4], wherein the surface spacing d ₀₀₂ of the (002) plane of the carbonaceous material measured using CuKα rays is 3.8 Å or more. Quality material.
[6] A carbonization step of carbonizing lignin having a sulfur element content of 0.1% by mass or more and a melting point of 300 ° C. or more to obtain a carbide.
A firing step of calcining the carbide at 1000 ° C. or higher and 1400 ° C. or lower in a non-oxidizing atmosphere to obtain a carbonaceous material.
The method for producing a carbonaceous material for a battery according to any one of [1] to [5].
[7] The method according to [6], further comprising an atomization step of pulverizing the carbide to an average particle size of 200 μm or less.
[8] The method according to [6] or [7], wherein the carbonization step comprises heating the lignin in a non-oxidizing atmosphere at 300 ° C. or higher and 800 ° C. or lower.
[9] An electrode comprising the carbonaceous material for a battery according to any one of [1] to [5].
[10] A battery comprising the electrodes according to [9].

A carbonaceous material for a battery and a manufacturing method thereof, which can obtain a battery having excellent discharge capacity, charge / discharge efficiency, resistance and output characteristics, and an electrode containing the carbonaceous material for the battery and the electrode were used. Batteries can be provided.

The following is an example of an embodiment of the present invention, and is not intended to limit the present invention to the following embodiments.

<Carbonaceous material for batteries>
The carbonaceous material for a battery of the present invention has a sulfur element content of 0.8% by mass or more and a true density determined by the butanol method of 1.48 g / cm ³ or more and 1.62 g / cm ³ or less.

<Sulfur element content>
The sulfur element content of the carbonaceous material for a battery of the present invention is 0.8% by mass or more, preferably 0.9% by mass or more, and more preferably 1.0% by mass or more. The sulfur element content of the carbonaceous material for a battery of the present invention is not particularly limited, but is usually 3.0% by mass or less, preferably 2.0% by mass or less, and more preferably 1.8% by mass. It is as follows. When the sulfur element content of the carbonaceous material for a battery is within the above range, a battery having an excellent battery capacity can be obtained.

As a method for adjusting the sulfur element content within the above range, for example, hydrolysis is performed by heating a substance that is a raw material of a carbonaceous material with a caustic soda aqueous solution, or a substance that is a raw material of a carbonaceous material is sulfuric acid or the like. Examples thereof include a method of modifying with a component containing sulfur and adjusting the amount of the modification. The sulfur element content can be determined, for example, by elemental analysis or fluorescent X-ray analysis.

<True density>
The true density (ρBt) of the carbonaceous material for a battery of the present invention is 1.48 g / cm ³ or more and 1.62 g / cm ³ or less, preferably 1.50 g / cm ³ or more and 1.61 g / cm ³ or less. Yes, more preferably 1.51 g / cm ³ or more and 1.61 g / cm ³ or less. When the true density of the carbonaceous material for a battery is within the above range, the battery capacity tends to be better.

In order to adjust the true density within the above range, it can be adjusted, for example, by changing the temperature at the time of heating and firing. Here, the true density can be determined, for example, according to the method specified in JIS R 7212.

<Oxygen element content>
The oxygen element content of the carbonaceous material for a battery of the present invention is preferably 0.7% by mass or less, and more preferably 0.6% by mass or less. The oxygen element content of the carbonaceous material for a battery of the present invention is usually 0.2% by mass or more, preferably 0.25% by mass or more. When the oxygen element content of the carbonaceous material for a battery is within the above range, a battery having excellent electrolyte affinity while suppressing irreversibility due to ion adsorption can be obtained.

In order to adjust the oxygen element content within the above range, it can be adjusted by, for example, the temperature at the time of heating and firing. The oxygen element content can be determined, for example, by elemental analysis or fluorescent X-ray analysis.

<Size of hexagonal net area Lc in the layer direction>
The size of the hexagonal net area layer direction Lc of the carbonaceous material for a battery of the present invention is preferably 10 Å or less, more preferably 9 Å or less. The lower limit of the size of Lc is usually 4 Å or more, preferably 5 Å or more. When the size of Lc is within the above range, metal ions and hydrogen ions can easily move, and a battery having more excellent output characteristics can be obtained.

The size of Lc can be adjusted by an appropriate firing temperature. The magnitude of Lc can be determined by X-ray diffraction based on the half-value range obtained from the peak intensity near 2θ = 26 °. Further, the carbonaceous material having an Lc size as described above tends to have a large output characteristic, and can be suitable not only for a lithium ion secondary battery but also for a sodium ion secondary battery and a lead battery.

<Average particle size>
The average particle size (Dv ₅₀ ) of the carbonaceous material for batteries of the present invention is preferably 2 μm or more and 200 μm or less. When the average particle size is 2 μm or more, the amount of fine powder, which is a factor of increasing the specific surface area of the carbonaceous material, is small, excessive reaction with the electrolytic solution is suppressed, and as a result, the capacity is irreversible so that it does not discharge even when charged. It is preferable because the capacity can be reduced and the capacity of the positive electrode can be prevented from being wasted. The lower limit of the average particle size is preferably 2 μm or more, more preferably 2.2 μm or more, and further preferably 2.5 μm or more. On the other hand, when the average particle size is 200 μm or less, the diffusion free stroke of metal ions and hydrogen ions in the particles is small, and it is preferable as a conductive material for conducting electrons to increase the contact rate between the particles. Further, the carbonaceous material for a battery of the present invention can also be applied to a lead battery or the like. When applied as a lead battery, the average particle size is preferably 80 μm or more, and preferably 100 μm or more. When it is at least this lower limit, oxidative decomposition by the electrolytic solution of the lead battery is suppressed and the battery life is excellent. The average particle size is adjusted by the pulverization step described later, and can be obtained by, for example, a laser diffraction / scattering method or a Coulter method.

<Surface spacing of (002) plane d ₀₀₂ >
The surface spacing d ₀₀₂ of the (002) plane of the carbonaceous material for a battery of the present invention is preferably 3.80 Å or more, and more preferably 3.82 Å or more. The upper limit is preferably 3.95 Å or less, and more preferably 3.92 Å or less. When d ₀₀₂ is within the above range, the capacity retention rate at low temperature is excellent. Further, since the invasion of ions becomes easy, it can be suitable not only for lithium ion secondary batteries but also for sodium ion secondary batteries and lead batteries. In order to adjust the size of d ₀₀₂ within the above range, it can be adjusted, for example, by the temperature at the time of heating and firing. Further, d ₀₀₂ can be obtained by, for example, X-ray diffraction.

<Specific surface area>
The lower limit of the BET specific surface area of the carbonaceous material for batteries of the present invention is preferably 1 m ² / g or more, more preferably 1.5 m ² / g or more, still more preferably 2 m ² / g or more. Particularly preferably, it is 3 m ² / g or more. On the other hand, the upper limit of the BET specific surface area of the carbonaceous material for a battery of the present invention is preferably 130 m ² / g or less, more preferably 90 m ² / g or less, still more preferably 80 m ² / g or less. It is even more preferably 75 m ² / g or less, particularly preferably 70 m ² / g or less, and most preferably 65 m ² / g or less. When the BET specific surface area is within the above range, the decomposition reaction with the electrolytic solution can be suppressed and the input / output characteristics are excellent. In order to adjust the BET specific surface area to the above range, it can be adjusted by, for example, the temperature at the time of heating and firing.

<Manufacturing method of carbonaceous materials for batteries>
The starting material of the carbonaceous material for a battery of the present invention is not particularly limited, and examples of the raw material that can be used include sulfonic acid type ion exchange resins, but the sulfur element content is preferably 0.1% by mass or more. It is more preferable to use lignin having a melting point of 0.5% by mass or more, preferably 300 ° C. or higher, and more preferably 320 ° C. or higher. Such lignin is generally called kraft lignin, and is obtained by acidifying a waste liquid called black liquor, which is produced in the process of obtaining pulp from raw wood in the papermaking industry, and washing the precipitated precipitate. be able to. The number average molecular weight of the lignin thus obtained is usually 3500 to 4500 because the ether bond, which is the main bond thereof, is cleaved and the molecular weight is remarkably reduced in the step. Therefore, in order to melt the lignin at a relatively low temperature before carbonization and change the crystalline state to a dense state at the time of melting, a lignin that melts at preferably 300 ° C. or higher, more preferably 320 ° C. or higher is used. Is particularly preferred. In addition, kraft lignin usually has a large amount of phenolic hydroxyl groups as compared with lignin obtained by other methods, and is rich in chemical activity, which is also preferable for high-density carbon formation.

<Carbonization process>
In the method for producing a carbonaceous material for a battery of the present invention, carbonization may be performed after adjusting the particle size of lignin. The preferred particle size is 0.001 mm or more and 50 mm or less, more preferably 0.01 mm or more and 20 mm or less, and further preferably 0.1 mm or more and 10 mm or less. Normally, lignin does not shrink in the carbonization step, and the particle size does not change before and after the carbonization step. Particles that are too fine are not preferable because they increase the risk of dust suction and dust explosion, and particles that are too large are not preferable because lignin may be oxidized by water generated during carbonization and the carbon properties may be impaired. The lignin used in the present invention may be further washed with acidic water before use to reduce residual metals.

In the method for producing a carbonaceous material for a battery of the present invention, lignin containing 0.1% by mass or more of sulfur element is preferably used. The content of the sulfur element is usually 0.2% by mass or more and 5% by mass or less, preferably 0.5% by mass or more and 4.5% by mass or less. When the sulfur element content is not more than the above upper limit, the emission of sulfur dioxide and the like which may corrode the equipment used is suppressed, which is preferable. When the sulfur element content is at least the above lower limit, it is possible to prevent the molecular weight of lignin from decreasing, and carbon condensation proceeds sufficiently, which is preferable. In order to adjust the sulfur element content within the above range, hydrolysis such as heating with an aqueous solution of caustic soda is performed. The sulfur element content can be measured by, for example, elemental analysis or fluorescent X-ray analysis.

The carbonization temperature in the method for producing a carbonaceous material for a battery of the present invention is preferably 400 ° C. or higher and 1000 ° C. or lower, more preferably 500 ° C. or higher and 900 ° C. or lower. When the carbonization temperature is within the above range, it is preferable that the carbonic material has a desired structure such as d ₀₀₂ , size in the hexagonal network area layer direction, element content, true density, and specific surface area.

Carbonization is usually carried out under an inert gas such as nitrogen or argon. The lower the concentration of the oxidizing gas in the gas used, the more preferable. The amount of the oxidizing gas, particularly oxygen, is usually 1% or less, more preferably 0.1% or less. When the oxygen concentration is smaller than the above value, oxidation in the carbide formation process can be suppressed, so that a structure having desired characteristics can be obtained, or oxidative decomposition of the produced structure can be suppressed.

The heating rate is not particularly limited and varies depending on the heating method, but is preferably 1 ° C./min or more and 20 ° C./min or less, and more preferably 2 ° C./min or more and 18 ° C./min or less. .. When the rate of temperature rise is within the above range, good productivity can be obtained, which is preferable from the viewpoint of economy. In addition, the progress of activation by the carbonization gas generated is suppressed, and a good carbon density can be obtained.

The time for maintaining the maximum temperature after heating is not particularly limited, and is preferably in the range of 0.1 hours or more and 20 hours or less, and more preferably in the range of 0.5 hours or more and 15 hours or less. When the time for maintaining the maximum temperature is within the above range, carbonization proceeds sufficiently and ignition is less likely to occur, which is preferable. Further, from the viewpoint of economy, it is preferable because the time is appropriate.

<Crushing>
The method for producing a carbonaceous material for a battery of the present invention may include a pulverization step. The pulverization step is a step of pulverizing the carbides that have undergone the carbonization step so that the average particle size after firing becomes a target size. Further, the pulverization step preferably includes classification. The average particle size can be adjusted more accurately by classification, and particles with a particle size of 1 μm or less can be excluded. The order of the pulverization step of the carbonized product derived from carbonized lignin is not particularly limited, but it is preferably performed before the firing step described later. The reason for this is that by increasing the surface area, the influence of structural changes due to the oxidizing gas generated during firing can be minimized, and when the final firing is performed, the crystal plane newly generated by pulverization is formed. , It is not preferable because it reacts with an electrolytic solution or the like in the battery and impairs the battery function. However, crushing after the firing step is not excluded.

The crusher used for crushing is not particularly limited, and for example, a jet mill, a ball mill, a hammer mill, a rod mill, or the like can be used alone or in combination, but the classification function is that the generation of fine powder is small. A jet mill equipped with is preferable. On the other hand, when a ball mill, a hammer mill, a rod mill or the like is used, fine powder can be removed by classifying after pulverization.

<Classification>
As the classification, classification by sieving, wet classification, or dry classification can be mentioned. Examples of the wet classifier include a classifier using a principle such as gravity classification, inertial classification, hydraulic classification, or centrifugal classification. Further, examples of the dry classifier include a classifier using the principle of sedimentation classification, mechanical classification, or centrifugal classification. In the crushing step, crushing and classification can also be performed using one device. For example, pulverization and classification can be performed using a jet mill equipped with a dry classification function. Further, a device in which the crusher and the classifier are independent can be used. In this case, crushing and classification can be performed continuously, but crushing and classification can also be performed discontinuously.

<Baking process>
The firing step in the method for producing a carbonaceous material for a battery of the present invention is a step of heat-treating the carbide after the carbonization step at 1000 ° C. or higher and 1400 ° C. or lower in a non-oxidizing gas atmosphere.

The firing in the method for producing a carbonaceous material for a battery of the present invention can be performed according to a normal procedure, and the carbonaceous material for a battery can be obtained by firing. The firing temperature is preferably 1000 ° C. or higher and 1400 ° C. or lower. The lower limit of the firing temperature is 1000 ° C. or higher, more preferably 1100 ° C. or higher, and particularly preferably 1150 ° C. or higher. The upper limit of the firing temperature is 1400 ° C. or lower, more preferably 1380 ° C. or lower, and particularly preferably 1350 ° C. or lower. When the firing temperature is within the above range, the residual amount of the functional group of the carbonaceous material can be reduced, and the reaction with lithium, which leads to an increase in the irreversible capacity, can be suppressed, which is preferable. Further, it is preferable because it is possible to suppress a decrease in the discharge capacity due to an increase in the selective orientation of the carbon hexagonal plane.

The firing is preferably performed in a non-oxidizing gas atmosphere. Examples of the non-oxidizing gas include helium, nitrogen and argon, and these can be used alone or in combination. Further, it is also possible to perform firing in a gas atmosphere in which a halogen gas such as chlorine is mixed with the non-oxidizing gas. The supply amount (distribution amount) of the gas is also not limited, but is 1 mL / min or more, preferably 5 mL / min or more, and more preferably 10 mL / min or more per 1 g of the carbide after the carbonization step. Further, the main firing can be performed under reduced pressure, and can be performed at, for example, 10 KPa or less. The time of the main firing is also not particularly limited, but for example, the time for staying at 1000 ° C. or higher can be 0.05 hours or more and 10 hours or less, preferably 0.05 hours or more and 3 hours or less. More preferably, it is 0.05 hours or more and 1 hour or less.

<Electrode>
The carbonaceous material for batteries of the present invention can be used for electrodes.

<Manufacturing of electrodes>
The electrode using the carbonaceous material for a battery of the present invention is a current collector made of a metal plate or the like after adding a binder to the carbonaceous material, adding an appropriate amount of an appropriate solvent, kneading the mixture to prepare an electrode mixture, and the like. It can be manufactured by applying it to a coating material, drying it, and then pressure-molding it. By using the carbonaceous material for a battery of the present invention, it is possible to produce an electrode having high conductivity without adding a conductive additive, but it is necessary for the purpose of imparting higher conductivity. Accordingly, a conductive auxiliary agent can be added at the time of preparation of the electrode mixture. As the conductive auxiliary agent, conductive carbon black, vapor phase grown carbon fiber (VGCF), nanotubes and the like can be used, and the amount added varies depending on the type of the conductive auxiliary agent used, but the amount added is too small. It is not preferable because the expected conductivity cannot be obtained, and if it is too much, the dispersion in the electrode mixture becomes poor, which is not preferable. From this point of view, the preferable ratio of the conductive auxiliary agent to be added is 0.5% by weight or more and 10% by weight or less (here, the amount of the active material (carbonaceous material) + the amount of the binder + the amount of the conductive auxiliary agent = 100% by weight). It is more preferably 0.5% by weight or more and 7% by weight or less, and particularly preferably 0.5% by weight or more and 5% by weight or less. The binder is not particularly limited as long as it does not react with an electrolytic solution such as PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene butadiene rubber) and CMC (carboxymethyl cellulose). Among them, PVDF is preferable because PVDF adhering to the surface of the active material does not hinder the movement of lithium ions and obtains good input / output characteristics. A polar solvent such as N-methylpyrrolidone (NMP) is preferably used to dissolve PVDF to form a slurry, but an aqueous emulsion such as SBR or CMC can also be used by dissolving it in water. If the amount of the binder added is too large, the resistance of the obtained electrode increases, which increases the internal resistance of the battery and deteriorates the battery characteristics, which is not preferable. Further, if the amount of the binder added is too small, the negative electrode material particles interconnect and the current collector are insufficiently bonded, which is not preferable. The preferable amount of the binder added varies depending on the type of binder used, but is preferably 3% by weight or more and 13% by weight or less, and more preferably 3% by weight or more and 10% by weight or less in the PVDF-based binder. On the other hand, in a binder that uses water as a solvent, a plurality of binders such as a mixture of SBR and CMC are often mixed and used, and the total amount of all the binders used is 0.5% by weight or more and 5% by weight or less. It is preferable, more preferably 1% by weight or more and 4% by weight or less. The electrode active material layer is basically formed on both sides of the current collector plate, but may be one side if necessary. The thicker the electrode active material layer, the smaller the number of current collector plates and separators, which is preferable for increasing the capacity. If it is too much, the input / output characteristics will deteriorate, which is not preferable. The thickness of the active material layer (per one side) is preferably 10 μm or more and 80 μm or less, more preferably 20 μm or more and 75 μm or less, and particularly preferably 20 μm or more and 60 μm or less. The electrode obtained here is preferably used as a negative electrode.

<Battery>
Electrodes made from the carbonaceous material for batteries of the present invention can be used in batteries. The battery using the electrode using the carbonaceous material of the present invention, for example, the non-aqueous electrolyte secondary battery is excellent in discharge capacity, charge / discharge efficiency, resistance and output characteristics.

<Manufacturing of non-aqueous electrolyte secondary batteries>
When the negative electrode of the non-aqueous electrolyte secondary battery is formed by using the carbonaceous material for a battery of the present invention, other materials constituting the battery such as a positive electrode material, a separator, and an electrolytic solution are not particularly limited. It is possible to use various materials conventionally used or proposed as a non-aqueous electrolyte secondary battery. For example, as the positive electrode material, a layered oxide system (represented as LiMO ₂ and M is a metal: for example, LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , or LiNi _x Coy Mo _z O ₂ (here x, _y ). , Z represents the composition ratio)), olivine type (represented by LiMPO ₄ , M is a metal: for example LiFePO ₄ ), spinel type (represented by LiM ₂ O ₄ and M is a metal: for example LiMn ₂ O ₄ etc.) ), The composite metal chalcogen compound is preferable, and these chalcogen compounds may be mixed as necessary. A positive electrode is formed by molding these positive electrode materials together with an appropriate binder and a carbon material for imparting conductivity to the electrodes and forming a layer on the conductive current collector.

The non-aqueous solvent type electrolytic solution used in combination with the positive electrode and the negative electrode is generally formed by dissolving the electrolyte in a non-aqueous solvent. Examples of the non-aqueous solvent include organic solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, γ-butyl lactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, and 1,3-dioxolane. Can be used alone or in combination of two or more. Further, as the electrolyte, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiCl, LiBr, LiB (C ₆ H ₅ ) 4, LiN (SO ₃ CF ₃ ) ₂ , or the like is used. In a secondary battery, a positive electrode layer and a negative electrode layer formed as described above are generally opposed to each other via a liquid permeable separator made of a non-woven fabric, other porous material, etc., and immersed in an electrolytic solution, if necessary. Is formed by. As the separator, a permeable separator made of a non-woven fabric or other porous material usually used for a secondary battery can be used. Alternatively, instead of the separator or together with the separator, a solid electrolyte composed of a polymer gel impregnated with an electrolytic solution can be used.

<Manufacturing of lead-acid batteries>
When the electrode of a lead battery is formed by using the carbonaceous material for a battery of the present invention, other materials constituting the battery such as a counter electrode material, a separator, and an electrolytic solution are not particularly limited and are conventionally used as a lead battery. It is possible to use a variety of materials that have been or have been proposed. For example, the carbonaceous material for a battery of the present invention can be used as the negative electrode, lead powder having an average primary particle diameter of about 0.1 to 5 μm, and sodium lignin sulfonate and barium sulfate can be used as the binder. These can be mixed and pasted, and the expanded current collector (lead-calcium-tin alloy) is filled with the negative electrode material paste to prepare a negative electrode plate. Further, the negative electrode plate can be aged in an atmosphere of a temperature of 50 ° C. and a humidity of 95% for 20 hours, and then dried in an atmosphere of a temperature of 50 ° C. to obtain an unmodified negative electrode plate. As the positive electrode, lead powder having an average primary particle size of about 0.1 to 5 μm and reinforcing short fibers (acrylic fibers) are dry-mixed, and dilute sulfuric acid and water are added and kneaded to prepare a positive electrode material paste. An expanded current collector (lead-calcium-tin alloy) is filled with a positive electrode material paste and aged for 20 hours in an atmosphere of a temperature of 50 ° C. and a humidity of 95%, and then dried in an atmosphere of a temperature of 50 ° C. and not yet dried. A chemical positive electrode plate can be obtained. After laminating via a polyethylene separator so that the positive and negative electrodes obtained in this way are alternately laminated, the current collectors of the same polarity are welded together with a strap to form a electrode plate group, and the electrodes are formed. A lead storage battery is obtained by inserting a group of plates into an electric tank to assemble a 2V single cell battery and injecting dilute sulfuric acid into the battery.

Hereinafter, the present invention will be specifically described with reference to Examples, but these do not limit the scope of the present invention.

The measurement of the physical property values in the examples was carried out according to the method described below.

<Sulfur element content>
The sulfur element content was measured using "Carbon / Sulfur Analyzer EMIA-920V2 HORIBA" manufactured by HORIBA, Ltd. The detection method of this device is sulfur: combustion in oxygen stream (high frequency induction heating furnace method) -non-dispersion infrared absorption method (NDIR), and the calibration is (oxygen / nitrogen) alumina crucible with W (fuel aid). (Tungsten) and Sn (tin) were added to make a blank, and the standard substances JSS152-18 [C: 0.277%, S: 0.0056%] and JSS150-16 [S: 0.0296%] were used. I went there. As a pretreatment, 50 mg of a sample that had been dehydrated at 250 ° C. for about 10 minutes was weighed into an alumina crucible with 1.5 g of particulate tungsten and 0.3 g of particulate tin, degassed in an elemental analyzer for 30 seconds, and then degassed. The measurement was carried out by heating and burning with a high frequency under a pure oxygen stream. Three samples were analyzed and the average value was used as the analysis value.

<True density>
The true density ρBt was measured by the butanol method according to the method specified in JIS R 7212. Accurately weigh the weight bottle with side tube (m ₁ ) with an internal volume of about 40 mL, then place the sample flat on the bottom to a thickness of about 10 mm, and then the mass (m ₂ ). Was measured accurately. 1-Butanol was gently added to this to a depth of about 20 mm from the bottom. Next, a light vibration was applied to the specific gravity bottle to confirm that the generation of large bubbles disappeared, and then the bottle was placed in a vacuum desiccator and gradually exhausted to 2.0 to 2.7 kPa. Keep the pressure at that pressure for 20 minutes or more, and after the generation of air bubbles has stopped, take out the specific gravity bottle, fill it with 1-butanol, plug it, and put it in a constant temperature water tank (adjusted to 30 ± 0.03 ° C). After soaking for more than a minute, the liquid level of 1-butanol was aligned with the marked line. Next, it was taken out, wiped well and cooled to room temperature, and then the mass (m ₄ ) was accurately weighed. Next, the same density bottle was filled with only 1-butanol, immersed in a constant temperature water tank in the same manner as described above, marked with a line, and then weighed (m ₃ ). Distilled water from which the gas dissolved by boiling immediately before use was removed was placed in a specific gravity bottle, immersed in a constant temperature water tank in the same manner as described above, aligned with the marked lines, and then weighed (m ₅ ). The true density ρBt was calculated by the following formula. At this time, d is the specific gravity (0.9946) of water at 30 ° C.
(Equation 1)

<Oxygen element content>
The oxygen element content was measured using "Oxygen / Nitrogen / Hydrogen Analyzer EMGA-930" manufactured by HORIBA, Ltd. The detection methods of this device are oxygen: inert gas melting-non-dispersive infrared absorption method (NDIR), nitrogen: inert gas melting-thermal conductivity method (TCD), hydrogen: inert gas melting-non-dispersive infrared rays. It was an absorption method (NDIR) and was calibrated by (oxygen / nitrogen) Ni capsules, TiH ₂ (H standard sample), and SS-3 (N, O standard sample). As a pretreatment, 20 mg of a sample dehydrated at 250 ° C. for about 10 minutes was weighed into Ni capsules, degassed in an elemental analyzer for 30 seconds, and then measured. Three samples were analyzed and the average value was used as the analysis value.

<Hexagonal net area layer direction>
The hexagonal net area layer direction Lc was determined by an X-ray diffraction test using "MiniFlexII" manufactured by Rigaku Co., Ltd. A sample holder was filled with carbonaceous material powder, and CuKα rays monochromaticized by a Ni filter were used as a radiation source to obtain an X-ray diffraction pattern. The peak position of the diffraction pattern is obtained by the center of gravity method (a method of obtaining the position of the center of gravity of the diffraction line and the peak position by the corresponding 2θ value), and the diffraction peak on the (111) plane of the high-purity silicon powder for a standard material is used. Corrected. The wavelength of the CuKα ray was set to 0.15418 nm, and Lc was calculated by substituting it into the Scherrer equation.
(Equation 2)

Here, K is a shape factor (0.9), λ is an X-ray wavelength (CuKαm = 0.15418 nm), θ is a diffraction angle, and β is a half width.

<Average particle size>
The average particle size (particle size distribution) was measured using "Microtrac MT3000" manufactured by Nikkiso Co., Ltd. The sample was put into an aqueous solution containing 0.3% by mass of a surfactant (“Toriton X100” manufactured by Wako Pure Chemical Industries, Ltd.), treated with an ultrasonic cleaner for 10 minutes or more, and dispersed in the aqueous solution. The particle size distribution was measured using this dispersion. D50 is a particle size having a cumulative volume of 50%, and this value was used as the average particle size.

<Average surface spacing>
The average surface spacing d ₀₀₂ was determined by an X-ray diffraction test using "MiniFlex II" manufactured by Rigaku Co., Ltd. A sample holder was filled with carbonaceous material powder, and CuKα rays monochromaticized by a Ni filter were used as a radiation source to obtain an X-ray diffraction pattern. The peak position of the diffraction pattern is obtained by the center of gravity method (a method of obtaining the position of the center of gravity of the diffraction line and the peak position by the corresponding 2θ value), and the diffraction peak on the (111) plane of the high-purity silicon powder for a standard material is used. Corrected. The wavelength of the CuKα ray was set to 0.15418 nm, and _d002 was calculated by the Bragg's formula shown below.
(Equation 3)

<Specific surface area>
The specific surface area was measured by the nitrogen adsorption method. Equation 4 describes an approximate equation derived from the equation of BET.
(Equation 4)

Using the approximate formula of Equation 4, _vm was obtained by the three-point method by nitrogen adsorption at the liquid nitrogen temperature, and the specific surface area of the sample was calculated by the following equation 5.
(Equation 5)

At this time, v _m is the adsorption amount (cm ³ / g) required to form a monomolecular layer on the sample surface, v is the measured adsorption amount (cm ³ / g), p ₀ is the saturated vapor pressure, and p is p. Absolute pressure, c is a constant (reflecting heat of adsorption), N is Avogadro's number 6.022 × 10 ²³ , and a (nm ² ) is the area occupied by the adsorbent molecule on the sample surface (molecular occupied cross-sectional area).

Specifically, using "BELL MAX" manufactured by Nippon BELL Co., Ltd., the amount of nitrogen adsorbed on the carbonaceous material at the liquid nitrogen temperature was measured as follows. The sample tube is filled with a carbonaceous material crushed to a particle size of about 5 μm to 50 μm, the sample tube is cooled to -196 ° C., the pressure is reduced once, and then nitrogen (purity 99) is added to the carbonaceous material at a desired relative pressure. .999%) was adsorbed. The amount of nitrogen adsorbed on the sample when the equilibrium pressure was reached at each desired relative pressure was defined as the adsorbed gas amount v.

<Manufacturing of carbonaceous materials>
(Example 1)
18.0 g of lignin having a sulfur element content of 2% by mass was placed in a boat-shaped crucible and introduced into an annular furnace manufactured by Motoyama Co., Ltd. (tube diameter 200 mmφ × 1800 mm). Nitrogen was introduced at a flow rate of 10 _LN / min for 1 hour to replace the inside of the system with nitrogen, then the temperature was raised from room temperature to 600 ° C (heating rate 2.5 ° C / min), held at 600 ° C for 1 hour, and 12 After allowing it to cool naturally from 600 ° C. to room temperature over time, the charcoal was taken out. 8.18 g of carbide was obtained (recovery rate 45.4%). The obtained carbide was coarsely pulverized with a mixer mill to an average particle size of 8.13 μm, then 7.06 g of the pulverized material was placed in a boat-shaped crucible and introduced again into an annular furnace, and nitrogen was introduced at a flow rate of 5 _LN / min for 1 hour. After replacing the inside of the crucible with nitrogen, the temperature is raised from room temperature to 1000 ° C (heating rate 10 ° C / min), held at 1000 ° C for 30 minutes, fired, and then cooled to room temperature over 12 hours to reach 6.37 g. Carbonaceous material was obtained (yield 90.3%). Table 1 shows the physical characteristics of the obtained carbonaceous material.

(Example 2)
A carbonaceous material was obtained in a yield of 88.3% in the same manner as in Example 1 except that the firing temperature was set to 1200 ° C. Table 1 shows the physical characteristics of the obtained carbonaceous material.

(Example 3)
18.0 g of lignin having a sulfur element content of 2% by mass was placed in a boat-shaped crucible and introduced into an annular furnace manufactured by Motoyama Co., Ltd. (tube diameter 200 mmφ × 1800 mm). Nitrogen was introduced at a flow rate of 10 _LN / min for 1 hour to replace the inside of the system with nitrogen, then the temperature was raised from room temperature to 600 ° C (heating rate 2.5 ° C / min), held at 600 ° C for 1 hour, and 12 After allowing it to cool naturally from 600 ° C. to room temperature over time, the charcoal was taken out. 8.21 g of carbide was obtained (recovery rate 45.6%). The obtained carbide is roughly pulverized in a dairy pot to an average particle size of 190 μm, then 7.33 g of the pulverized substance is placed in a boat-shaped crucible, introduced into the annular furnace again, and nitrogen is introduced into the system at a flow rate of 5 _LN / min for 1 hour. After replacing with nitrogen, the temperature was raised from room temperature to 1000 ° C (heating rate 10 ° C / min), held at 1000 ° C for 30 minutes, calcined, and then cooled to room temperature over 12 hours to obtain 6.41 g of carbonaceous material. The material was obtained (yield 87.4%). Table 1 shows the physical characteristics of the obtained carbonaceous material.

(Comparative Example 1)
A carbonaceous material was obtained in a yield of 98.4% in the same manner as in Example 1 except that the firing temperature was set to 800 ° C. Table 1 shows the physical characteristics of the obtained carbonaceous material.

(Comparative Example 2)
A carbonaceous material was obtained in a yield of 84.5% in the same manner as in Example 1 except that lignin having a sulfur element content of 0.1% by mass and a melting point of 212 ° C. was used. Table 1 shows the physical characteristics of the obtained carbonaceous material.

(Comparative Example 3)
25.0 g of lignin having a sulfur element content of 2% by mass was added to 250 g of a 1N sodium hydroxide aqueous solution, dissolved, and heated and stirred at 20 ° C. for 8 hours. 300 g of 1N hydrochloric acid was added, and the precipitated lignin was recovered and washed with 500 g of ion-exchanged water. After drying, it was confirmed that the sulfur element content was 0.4%. 18.0 g of the obtained lignin was put into a boat-shaped crucible and introduced into an annular furnace manufactured by Motoyama Co., Ltd. (tube diameter 200 mmφ × 1800 mm). Nitrogen was introduced at a flow rate of 10 _LN / min for 1 hour to replace the inside of the system with nitrogen, then the temperature was raised from room temperature to 600 ° C (heating rate 2.5 ° C / min), held at 600 ° C for 1 hour, and 12 After allowing it to cool naturally from 600 ° C. to room temperature over time, the charcoal was taken out. 7.81 g of carbide was obtained (recovery rate 43.3%). The obtained carbide is roughly pulverized in a dairy pot to an average particle size of 201 μm, then 7.00 g of the pulverized substance is placed in a boat-shaped crucible, introduced into the annular furnace again, and nitrogen is introduced into the system at a flow rate of 5 _LN / min for 1 hour. After replacing with nitrogen, the temperature was raised from room temperature to 800 ° C (heating rate 10 ° C / min), held at 800 ° C for 30 minutes, calcined, and then cooled to room temperature over 12 hours to achieve 6.63 g of carbonaceous material. The material was obtained (yield 94.8%). Table 1 shows the physical characteristics of the obtained carbonaceous material.

(Comparative Example 4)
25.0 g of lignin having a sulfur element content of 2% by mass was added to 250 g of a 1N sodium hydroxide aqueous solution, dissolved, and heated and stirred at 20 ° C. for 8 hours. 300 g of 1N hydrochloric acid was added, and the precipitated lignin was recovered and washed with 500 g of ion-exchanged water. After drying, it was confirmed that the sulfur element content was 0.4%. 18.0 g of the obtained lignin was put into a boat-shaped crucible and introduced into an annular furnace manufactured by Motoyama Co., Ltd. (tube diameter 200 mmφ × 1800 mm). Nitrogen was introduced at a flow rate of 10 _LN / min for 1 hour to replace the inside of the system with nitrogen, then the temperature was raised from room temperature to 600 ° C (heating rate 2.5 ° C / min), held at 600 ° C for 1 hour, and 12 After allowing it to cool naturally from 600 ° C. to room temperature over time, the charcoal was taken out. 7.81 g of carbide was obtained (recovery rate 43.3%). The obtained carbide was coarsely pulverized in a dairy pot to an average particle size of 6.4 μm, then 7.00 g of the pulverized material was placed in a boat-shaped crucible and introduced again into an annular furnace, and nitrogen was introduced at a flow rate of 5 _LN / min for 1 hour. After replacing the inside of the system with nitrogen, the temperature is raised from room temperature to 800 ° C (heating rate 10 ° C / min), held at 800 ° C for 30 minutes, fired, and then cooled to room temperature over 12 hours to 5.22 g. A carbonaceous material was obtained (yield 74.6%). Table 1 shows the physical characteristics of the obtained carbonaceous material.

<Dope-dedoping test>
Using the carbonaceous materials obtained in Examples and Comparative Examples, a negative electrode and a non-aqueous electrolyte secondary battery were prepared and their performance was evaluated.

-Preparation of electrodes NMP was added to 90 parts by weight of the above carbonaceous material and 10 parts by weight of polyvinylidene fluoride ("KF # 1100" manufactured by Kureha Corporation) to form a paste, which was uniformly applied onto a copper foil. After drying, it was punched from a copper foil into a disk shape having a diameter of 15 mm, and this was pressed into an electrode. The amount of carbonaceous material in the electrode was adjusted to be about 10 mg.

-Manufacture of test battery The carbonaceous material of the present invention is suitable for forming the negative electrode of a non-aqueous electrolyte secondary battery, but the discharge capacity (dedoped amount) and irreversible capacity (non-dedoped amount) of the battery active material. ) Is evaluated accurately without being affected by the variation in the performance of the counter electrode, a lithium secondary battery is constructed using the electrodes obtained above with a lithium metal having stable characteristics as the counter electrode, and its characteristics. Was evaluated. Lithium poles were prepared in a glove box in an Ar atmosphere. A stainless steel mesh disk with a diameter of 16 mm is spot-welded to the outer lid of a 2016-size coin-cell battery can, and then a 0.8 mm-thick metal lithium thin plate is punched into a disk with a diameter of 15 mm. It was crimped to the electrode (counter electrode). Using the pair of electrodes produced in this way, the electrolyte was a mixture of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate in a volume ratio of 1: 2: 2, and LiPF ₆ at a ratio of 1.5 mol / L. 2016 size coin-type non-aqueous electrolyte-based lithium battery in an Ar glove box using a polyethylene gasket as a separator for fine pore membranes made of borosilicate glass fiber with a diameter of 19 mm. I assembled the next battery.

-Measurement of battery capacity The lithium secondary battery having the above configuration was subjected to a charge / discharge test at 25 ° C. using a charge / discharge test device (“TOSCAT” manufactured by Toyo System Co., Ltd.). The lithium doping reaction to the carbon electrode was carried out by the constant current constant voltage method, and the dedoping reaction was carried out by the constant current method. Here, in a battery using a lithium chalcogen compound for the positive electrode, the doping reaction of lithium to the carbon electrode is "charging", and in a battery using a lithium metal as the counter electrode like the test battery of the present invention, the carbon electrode is used. The dope reaction of lithium is called "discharge", and the way of calling the dope reaction of lithium to the same carbon electrode differs depending on the counter electrode used. Therefore, here, for convenience, the doping reaction of lithium to the carbon electrode will be described as "charging". On the contrary, "discharge" is a charge reaction in a test battery, but since it is a dedoped reaction of lithium from a carbonaceous material, it is described as "discharge" for convenience. The charging method adopted here is a constant current constant voltage method. Specifically, constant current charging is performed at 0.5 mA / cm ² until the terminal voltage reaches 0 mV, and after the terminal voltage reaches 0 mV, the terminal voltage is reached. Constant voltage charging was performed at 0 mV, and charging was continued until the current value reached 20 μA. At this time, the value obtained by dividing the amount of supplied electricity by the weight of the carbonaceous material of the electrode was defined as the total charge capacity (mAh / g) per unit weight of the carbonic material. After the charging was completed, the battery circuit was opened for 30 minutes, and then the battery was discharged. The discharge was a constant current discharge at 0.5 mA / cm ² , and the final voltage was 1.5 V. The value obtained by dividing the amount of electricity discharged at this time by the weight of the carbonaceous material of the electrode is defined as the total discharge capacity (mAh / g) per unit weight of the carbonic material. The irreversible capacity is calculated as charge capacity-discharge capacity. The charge / discharge capacity and the irreversible capacity were determined by averaging the measured values of n = 3 for the test batteries prepared using the same sample. The charge / discharge efficiency is the ratio of the total discharge capacity to the total charge capacity expressed as a percentage, and the CC discharge capacity and CV discharge capacity are calculated from the charge / discharge curves obtained when measuring the total charge capacity and the charge / discharge capacity. And the DC resistance was calculated. The results are shown in Table 2.

-Output characteristics In the battery capacity measurement, the measured temperature was measured at -20 ° C, and the obtained discharge capacity was divided by the capacity when discharged at 25 ° C to obtain the discharge retention rate at -20 ° C.

As shown in Table 2, it can be seen that by using the carbonaceous material for a battery of the present invention, a battery having excellent discharge capacity, charge / discharge efficiency, resistance and output characteristics can be obtained.

Further, as shown in Example 3, it is possible to obtain a carbonaceous material having a relatively large particle size, which maintains the physical characteristics of the carbonaceous material of the present invention, such as the sulfur element content and the true density of butanol. It can also be applied to lead battery applications.

The carbonaceous material for a battery of the present invention is produced in a small number of steps, and a battery using an electrode using the carbonaceous material is excellent in discharge capacity, charge / discharge efficiency, resistance and output characteristics. Therefore, it may be applicable to various batteries.

Claims (10)

A carbonaceous material for a battery having a sulfur element content of 0.8% by mass or more and a true density determined by the butanol method of 1.48 g / cm ³ or more and 1.62 g / cm ³ or less. The carbonaceous material for a battery according to claim 1, wherein the carbonaceous material has an oxygen element content of 0.7% by mass or less. The carbonaceous material for a battery according to claim 1 or 2, wherein the carbonaceous material has a size of Lc in the hexagonal net area layer direction of 10 Å or less. The carbonaceous material for a battery according to any one of claims 1 to 3, wherein the average particle size is 2 μm or more and 200 μm or less. The carbonaceous material for a battery according to any one of claims 1 to 4, wherein the (002) plane spacing d ₀₀₂ of the carbonaceous material measured using CuKα rays is 3.8 Å or more. A carbonization step of carbonizing lignin having a sulfur element content of 0.1% by mass or more and a melting point of 300 ° C. or more to obtain a carbide.
A firing step of calcining the carbide at 1000 ° C. or higher and 1400 ° C. or lower in a non-oxidizing atmosphere to obtain a carbonaceous material.
The method for producing a carbonaceous material for a battery according to any one of claims 1 to 5. The method according to claim 6, further comprising an atomization step of pulverizing the carbide to an average particle size of 200 μm or less. The method according to claim 6 or 7, wherein the carbonization step comprises heating the lignin in a non-oxidizing atmosphere at 300 ° C. or higher and 800 ° C. or lower. An electrode comprising the carbonaceous material for a battery according to any one of claims 1 to 5. A battery comprising the electrode according to claim 9.