JP7032857B2 - Method for manufacturing carbonaceous material for negative electrode active material of non-aqueous electrolyte secondary battery, negative electrode for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery and carbonaceous material - Google Patents

Description

The present invention relates to a carbonaceous material suitable for a negative electrode active material of a non-aqueous electrolyte secondary battery, a negative electrode for a non-aqueous electrolyte secondary battery containing the carbonaceous material, a non-aqueous electrolyte secondary battery having the negative electrode, and the carbonaceous material. Regarding the manufacturing method of the material.

Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries are widely used in small portable devices such as mobile phones and notebook computers because of their high energy density and excellent output characteristics. In recent years, its application to in-vehicle applications such as hybrid vehicles and electric vehicles has been promoted. As a negative electrode material for a lithium ion secondary battery, non-graphitizable carbon capable of doping (charging) and dedoping (discharging) lithium in an amount exceeding the theoretical capacity of graphite of 372 mAh / g has been developed (for example, Patent Document 1). ), Has been used.

The non-graphitizable carbon can be obtained, for example, from petroleum pitch, coal pitch, phenolic resin, plants and the like as a carbon source. Among these carbon sources, plants are very useful because they are raw materials that can be continuously and stably supplied by cultivation and can be obtained at low cost. Further, since the carbonaceous material obtained by firing a carbon raw material derived from a plant has many pores, good charge / discharge capacity is expected.

When carbonaceous materials are obtained using plant-derived carbon raw materials, attempts have been made to reduce the amount of plant-derived potassium before calcination. For example, Patent Document 2 describes a carbonaceous material obtained by immersing a plant-derived carbon precursor in an acid such as hydrochloric acid or water and then carbonizing it. Patent Document 3 describes a carbonaceous material obtained by heat-treating a plant-derived organic substance in an atmosphere of an inert gas containing a halogen compound and then main firing.

Further, Patent Document 4 is obtained by subjecting dry coal to a halogenation treatment, a preliminary pore adjustment treatment, a dehalogenation treatment, and a pore adjustment treatment for the purpose of improving the charge / discharge characteristics of a lithium ion secondary battery. Further, a carbon material for a lithium secondary battery is disclosed.

Japanese Unexamined Patent Publication No. 9-161801 Japanese Unexamined Patent Publication No. 10-21919 International Publication No. 2014/034858 Pamphlet Japanese Unexamined Patent Publication No. 11-135108

In recent years, application of lithium ion secondary batteries to in-vehicle applications and the like has been studied, and further increase in capacity of lithium ion secondary batteries is required. Further, in order to further enhance the input / output characteristics of the non-aqueous electrolyte secondary battery, a carbonaceous material that provides a battery having high charge / discharge efficiency and low internal resistance is required.

Therefore, the present invention provides a carbonaceous material suitable for a negative electrode active material of a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) having high charge / discharge capacity, charge / discharge efficiency, and low resistance. It is an object of the present invention to provide a negative electrode including a negative electrode, a non-aqueous electrolyte secondary battery having the negative electrode, and a method for producing the carbonaceous material.

The present inventors have found that the above object can be achieved by the carbonaceous material of the present invention described below.
That is, the present invention includes the following preferred embodiments.
[1] A carbonaceous material for the negative electrode active material of a non-aqueous electrolyte secondary battery, the carbonaceous material is derived from a plant and has a peak near 1360 cm ^-1 of the Raman spectrum observed by laser Raman spectroscopy. A carbonaceous material having a half-price range value of 240 to 280 cm ^-1 and an oxygen element content determined by elemental analysis of 0.40% by weight or less.
[2] The hydrogen element content determined by element analysis is 0.10% by weight or more, and the ratio _{RH / O} (hydrogen element content / oxygen element content) between the hydrogen element content and the oxygen element content is The carbonaceous material according to the above [1], which is 0.30 or more.
[3] The true density determined by the helium method is 1.20 to 1.50 g / cm ³ , and the specific surface area determined by the BET method is 10 m ² / g or less, according to the above [1] or [2]. Carbonaceous material.
[4] The carbonaceous material according to any one of [1] to [3] above, wherein the calcium element content is 50 ppm or less.
[5] When the carbonaceous material was doped with lithium until it was fully charged and ⁷ Li nuclei-solid-state NMR analysis was performed, the resonance peak of LiCl, which is the reference material, was shifted to the low magnetic field side by 115 to 145 ppm. The carbonaceous material according to any one of [1] to [4] above, wherein the main resonance peak is observed.
[6] The carbonaceous material according to any one of [1] to [5] above, wherein the true density determined by the butanol method is 1.35 to 1.50 g / cm ³ .
[7] A negative electrode for a non-aqueous electrolyte secondary battery containing the carbonaceous material according to any one of [1] to [6] above.
[8] A non-aqueous electrolyte secondary battery having the negative electrode for the non-aqueous electrolyte secondary battery according to the above [7].
[9] (1) A vapor phase decalcification step of heat-treating a plant-derived char at 1100 to 1300 ° C. in an inert gas atmosphere containing a halogen compound to obtain a vapor phase decalcification char, wherein the halogen compound is used. The supply of the inert gas contained is 14 L / min or more per 50 g of the plant-derived char, and (2) the non-aqueous electrolyte comprising at least a step of subjecting the gas phase decalcified char to a CVD treatment using a hydrocarbon compound. A method for producing a carbonaceous material for the negative electrode active material of a secondary battery.
[10] Before the gas phase decalcification step,
(A) The method for producing a carbonaceous material according to the above [9], further comprising an alkali imposition step of adding a compound containing an alkali metal element to a plant-derived char to obtain an alkali-impregnated plant-derived char.
[11] The above-mentioned [11] further comprising a crushing step of crushing a plant-derived char before the vapor phase decalcification step and / or a crushing step of crushing the vapor phase decalcified char after the vapor phase decalcification step. 9] or the method for producing a carbonaceous material according to [10].

The non-aqueous electrolyte secondary battery using the negative electrode containing the carbonaceous material of the present invention has high charge / discharge capacity, charge / discharge efficiency, and low resistance.

It is a figure which shows the Raman spectrum of the carbonaceous material of Example 1. FIG. It is a figure which shows the Raman spectrum of the carbonaceous material of the comparative example 1. FIG. It is a figure which shows the ⁷ Li nucleus-solid-state NMR spectrum of the carbonaceous material of Example 1. FIG. It is a figure which shows the ⁷ Li nucleus-solid-state NMR spectrum of the carbonaceous material of the comparative example 1. FIG.

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described here, and various modifications can be made without impairing the gist of the present invention.

The carbonaceous material of the present invention is a carbonaceous material for a negative electrode active material of a non-aqueous electrolyte secondary battery, and is a carbonaceous material derived from a plant. In the carbonaceous material of the present invention, the value of the half width of the peak near 1360 cm ^-1 in the Raman spectrum observed by laser Raman spectroscopy is 240 to 280 cm ^-1 . Here, the peak near 1360 cm ^-1 is a Raman peak generally referred to as a D band, and is a peak caused by disturbance / defect of the graphite structure. Peaks near 1360 cm ^-1 are usually observed in the range of 1345 cm ^-1 to 1375 cm ^-1 , preferably 1350 cm ^-1 to 1370 cm ^-1 .

The half width of this peak is related to the amount of disturbance / defect of the graphite structure contained in the carbonaceous material. If the half-value width is smaller than 240 cm ^-1 , the graphite structure contained in the carbonaceous material has too few disturbances and defects, and the development of the graphite structure reduces the number of micropores between crystals, resulting in sites where lithium ions are occluded. It will be less. Therefore, there arises a problem such as a decrease in charge / discharge capacity. From the viewpoint of easily increasing the charge / discharge capacity, the half width of the peak near 1360 cm ^-1 is preferably 250 cm ^-1 or more, and more preferably 260 cm ^-1 or more. If the half-value width is larger than 280 cm ^-1 , the graphite structure contained in the carbonaceous material has many disturbances and defects, many amorphous materials, many carbon edges, and carbon-terminal reactive groups that react with lithium. Will increase. Therefore, the utilization efficiency of lithium ions is lowered, and the charge / discharge efficiency is lowered. From this point of view, the half width of the peak near 1360 cm ^-1 is preferably 275 cm ^-1 or less.

The Raman spectrum is measured using a Raman spectroscope (for example, a Raman spectroscope "LabRAM ARAMIS (VIS)" manufactured by HORIBA, Ltd.). Specifically, for example, the measurement target particle is set on the observation table stage, the magnification of the objective lens is set to 100 times, the focus is adjusted, and the measurement cell is irradiated with an argon ion laser beam of 532 nm while the exposure time is 1. Measure in seconds, the number of integrations is 100, and the measurement range is 50-2000 cm ^-1 .

The method for adjusting the half-price width of the peak near 1360 cm ^-1 to the above range is not limited, but for example, the plant-derived char is charged at a temperature of 1100 to 1300 ° C. A method of heat-treating while supplying at an amount of 14 L / min or more and then heat-treating at 500 to 1000 ° C. in an atmosphere of an inert gas containing a hydrocarbon compound can be used.

In the carbonaceous material of the present invention, the content of oxygen element determined by elemental analysis is 0.40% by weight or less. If the content of oxygen element in the carbonaceous material exceeds 0.40% by weight, irreversible side reactions that may occur during charging / discharging cannot be suppressed, the discharge capacity decreases, and the charging / discharging efficiency decreases. .. The content of oxygen element in the carbonaceous material of the present invention is preferably 0.35% by weight or less from the viewpoint of suppressing irreversible side reactions during charging / discharging and easily increasing the discharging capacity and charging / discharging efficiency. It is more preferably 0.31% by weight or less, still more preferably 0.30% by weight or less. The smaller the content of the oxygen element in the carbonaceous material of the present invention, the better, and the lower limit thereof is 0% by weight or more, but usually 0.10% by weight or more. The details of the measurement of the oxygen element content are as described in Examples, and the measurement is performed by the elemental analysis method (inert gas dissolution method) described later. The method for adjusting the oxygen element content to the above range is not limited, but for example, the plant-derived char is subjected to the gas phase decalcification treatment and then heat-treated at 500 to 1000 ° C. in an inert gas atmosphere containing a hydrocarbon compound. The method can be used.

The half-value width of the peak near 1360 cm ^-1 of the Raman spectrum observed by laser Raman spectroscopy is 240 to 280 cm ^-1 , and the oxygen element content determined by elemental analysis is 0.40% by weight or less. According to the carbonaceous material of the present invention, since the carbonaceous material has sufficient micropores to occlude lithium ions, a high charge / discharge capacity can be obtained, and a side reaction occurs during charging / discharging or hinders charging / discharging of lithium ions. Since the content of the obtained oxygen atom is low, low resistance and high charge / discharge efficiency are achieved.

In the carbonaceous material of the present invention, the content of hydrogen element determined by elemental analysis is preferably 0.10% by weight or more, more preferably 0.11% by weight or more, still more preferably 0.12% by weight. That is all. It is preferable that the content of the hydrogen element in the carbonaceous material is at least the above lower limit from the viewpoint of increasing the carbon edge portion and facilitating the insertion of Li ions during charging / discharging. The content of the hydrogen element in the carbonaceous material of the present invention is preferably 0.20% by weight or less, more preferably 0.18% by weight or less, and further preferably 0.18% by weight or less from the viewpoint of suppressing side reactions during charging and discharging. It is preferably 0.16 or less, particularly preferably 0.14 or less, and extremely preferably 0.13 or less. The details of the measurement of the hydrogen element content are as described in Examples, and the measurement is performed by the elemental analysis method (inert gas dissolution method) described later. The method for adjusting the hydrogen element content to the above range is not limited, but for example, the plant-derived char is subjected to the gas phase decalcification treatment and then heat-treated at 500 to 1000 ° C. in an inert gas atmosphere containing a hydrocarbon compound. The method can be used.

In the carbonaceous material of the present invention, the ratio _{RH / O} (hydrogen element content / oxygen element content) between the hydrogen element content and the oxygen element content reduces the oxygen element content, and the discharge capacity and charge / discharge. From the viewpoint of easily increasing the efficiency, it is preferably 0.30 or more, more preferably 0.33 or more, and further preferably 0.34 or more. Further, the ratio _{RH / O} (hydrogen element content / oxygen element content) between the hydrogen element content and the oxygen element content is a viewpoint that the hydrogen element content is reduced and side reactions during charging and discharging are easily suppressed. From the above, it is preferably 1.0 or less, more preferably 0.80 or less, and further preferably 0.70 or less. The ratio _{RH / O} between the hydrogen element content and the oxygen element content is _{RH / O} = hydrogen element content / oxygen element content from the hydrogen element content and the oxygen element content measured as described above. It is calculated by the formula of.

The true density _ρHe by the helium method in the carbonaceous material of the present invention is preferably 1.20 to 1.50 g / cm ³ and more preferably 1.30 to 1.30 to 1.50 g / cm 3 from the viewpoint of increasing the capacity per mass of the battery. It is 1.48 g / cm ³ , more preferably 1.35 to 1.46 g / cm ³ . The details of the measurement of the true density _ρHe are as described in Examples, and the measurement can be performed by the helium method according to the method specified in JIS Z8807. The carbonaceous material having such a true density is, for example, heat-treated plant-derived char at a temperature of 1100 to 1300 ° C. while supplying an inert gas containing a halogen compound at an amount of 14 L / min or more per 50 g of char. Then, a method of heat-treating at 500 to 1000 ° C. in an atmosphere of an inert gas containing a hydrocarbon compound can be used.

The specific surface area of the carbonaceous material of the present invention determined by the nitrogen adsorption BET method is preferably 10 m ² / g or less, more preferably 8 m ² / g or less, still more preferably 5 m ² / g or less. When the specific surface area of the carbonaceous material is not more than the above upper limit, it is easy to suppress side reactions of lithium ions on the surface of the carbonaceous material and increase the utilization efficiency of lithium ions. In addition, the hygroscopicity of the carbonaceous material tends to decrease, and the generation of acid and gas due to the hydrolysis of the electrolytic solution and water due to the water present in the carbonaceous material is suppressed. Further, since the contact area between the air and the carbonaceous material is reduced, it is easy to suppress the oxidation of the carbonaceous material itself. The specific surface area is preferably 1.0 m ² / g or more, more preferably 1.5 m, from the viewpoint of increasing the amount of lithium ions adsorbed on the carbonaceous material and easily increasing the charge capacity of the non-aqueous electrolyte secondary battery. It is ² / g or more, more preferably 2.0 m ² / g or more. Details of the measurement of the specific surface area by the nitrogen adsorption BET method are as described in Examples.

The method for adjusting the specific surface area to the above range is not limited, but for example, the plant-derived char is added at a temperature of 1100 to 1300 ° C., and the inert gas containing a halogen compound is added at an amount of 14 L / min or more per 50 g of the char. A method comprising a vapor phase decalcification step of heat-treating while supplying, and then a heat treatment step at 500 to 1000 ° C. in an atmosphere of an inert gas containing a hydrocarbon compound can be used. In particular, since the specific surface area tends to decrease as the heat treatment temperature is increased or the time is lengthened, the temperature and time may be adjusted so that the specific surface area in the above range can be obtained.

In the carbonaceous material of the present invention, the content of the calcium element is preferably 50 ppm or less, more preferably 40 ppm or less, and further preferably 35 ppm or less. When the content of the calcium element is not more than the above upper limit, it is easy to suppress problems such as a short circuit of the battery which may occur due to elution and reprecipitation of the calcium element in the electrolytic solution. Further, since the pores of the carbonaceous material are not easily closed, it is easy to maintain the charge / discharge capacity of the battery. The smaller the calcium element content in the carbonaceous material, the better, and it is particularly preferable that the calcium element is not substantially contained. Here, "substantially free" means that it is 10 to ⁶ % by mass or less, which is the detection limit of the elemental analysis method (inert gas melting-heat conduction method) described later.
The method for adjusting the calcium element content to the above range is not limited, and for example, a method of heat-treating a plant-derived char while supplying an inert gas containing a halogen compound can be used.

The details of the measurement of the calcium element content are as described in Examples, and the measurement can be performed using a fluorescent X-ray analyzer (for example, "ZSX Primus-μ" manufactured by Rigaku Co., Ltd.).

In the carbonaceous material of the present invention, the content of the potassium element is preferably 50 ppm or less, more preferably 30 ppm or less, still more preferably 10 ppm or less. When the content of the potassium element is not more than the above upper limit, it is easy to suppress problems such as a short circuit of the battery which may occur due to elution and reprecipitation of the potassium element in the electrolytic solution. Further, since the pores of the carbonaceous material are not easily closed, it is easy to maintain the charge / discharge capacity of the battery. The smaller the potassium element content in the carbonaceous material, the better, and it is particularly preferable that the potassium element is substantially not contained. Here, "substantially free" means that it is 10 to ⁶ % by mass or less, which is the detection limit of the elemental analysis method (inert gas melting-heat conduction method) described later. The method for adjusting the potassium element content to the above range is not limited, but a method for heat-treating a plant-derived char while supplying an inert gas containing a halogen compound can be used. The potassium element content can be measured in the same manner as the calcium element content measurement described above.

In the carbonaceous material of the present invention, when the carbonaceous material was doped with lithium until it was fully charged and ⁷ Li nuclei-solid-state NMR analysis was performed, the low magnetic field side with respect to the resonance peak of LiCl, which is the reference material. It is preferable to observe the main resonance peak shifted by 115 to 145 ppm. The large shift value of the main resonance peak toward the low magnetic field indicates that the amount of lithium present in a cluster is large. In the carbonaceous material of the present invention, the shift value toward the low magnetic field side is more preferably 142 ppm or less, and more preferably 138 ppm or less, from the viewpoint of rapidly dissociating the clusters and easily achieving rapid charge / discharge. Is even more preferable. The small shift value of the main resonance peak toward the low magnetic field indicates that the amount of lithium present between the carbon layers is large. From the viewpoint of easily increasing the charge / discharge capacity, the shift value toward the low magnetic field side is more preferably 120 ppm or more.

Here, in the present invention, "the main resonance peak is observed" means that the lithium species giving the main resonance peak is present at 3% or more, which is the detection limit of the ⁷ Li nuclear-solid-state NMR analysis method described later. do.

Further, in the present invention, "doping lithium until it is fully charged" means assembling and ending a non-aqueous electrolyte secondary battery having an electrode containing a carbonaceous material as a positive electrode and an electrode containing metallic lithium as a negative electrode. It means that charging is performed with a voltage usually in the range of 0.1 to 0 mV, preferably 0.05 to 0 mV, and more preferably 0.01 to 0 mV. In the present invention, the fully charged carbonaceous material usually has a capacity of 300 to 600 mAh / g, preferably 350 to 580 mAh / g.

⁷ The details of the method for measuring the Li nucleus-solid-state NMR spectrum are as described later, and the measurement can be performed using a nuclear magnetic resonance apparatus (for example, "AVANCE300" manufactured by BRUKER).

The method for adjusting the chemical shift value of the main resonance peak to the low magnetic field side is not limited to the above range, but for example, a plant-derived char is charged with an inert gas containing a halogen compound at a temperature of 1100 to 1300 ° C. A method including a gas phase decalcification step of heat-treating while supplying at an amount of 14 L / min or more per 50 g and then a heat treatment step at 500 to 1000 ° C. in an inert gas atmosphere containing a hydrocarbon compound can be used.

From the viewpoint of increasing the capacity per mass of the carbonaceous material of the present invention, the true density ρ _Bt by the butanol method is preferably 1.35 to 1.50 g / cm ³ , and more preferably 1.40. It is ~ 1.50 g / cm ³ , and more preferably 1.44 to 1.49 g / cm ³ . The details of the measurement of the true density ρ _Bt are as described in Examples, and the measurement can be performed by the butanol method according to the method specified in JIS R 7212. The carbonaceous material having such a true density is a method of heat-treating a plant-derived char at a temperature of 1100 to 1300 ° C. while supplying an inert gas containing a halogen compound at an amount of 14 L / min or more per 50 g of the char. Can be used.

The average particle size (D ₅₀ ) of the carbonaceous material of the present invention is preferably 2 to 30 μm from the viewpoint of coatability at the time of electrode production. It is preferable that the average particle size is at least the above lower limit because it is easy to suppress an increase in the specific surface area and reactivity with the electrolytic solution due to the fine powder in the carbonaceous material, and it is easy to suppress an increase in the irreversible capacity. Further, when the negative electrode is manufactured using the obtained carbonaceous material, it is possible to secure voids formed between the carbonaceous materials, and it is difficult to suppress the movement of lithium ions in the electrolytic solution. From such a viewpoint, the average particle size (D ₅₀ ) of the carbonaceous material of the present invention is more preferably 3 μm or more, still more preferably 4 μm or more, particularly preferably 5 μm or more, and most preferably 7 μm or more. On the other hand, it is preferable that the mean particle diameter is not more than the above upper limit because the diffusion free path of lithium ions in the particles is small and rapid charge / discharge can be easily obtained. Furthermore, in lithium-ion secondary batteries, it is important to increase the electrode area in order to improve the input / output characteristics, and for that purpose, it is necessary to reduce the coating thickness of the active material on the current collector plate when preparing the electrodes. There is. In order to reduce the coating thickness, it is necessary to reduce the particle size of the active material. From this point of view, the average particle size is more preferably 20 μm or less, still more preferably 18 μm or less, particularly preferably 16 μm or less, and most preferably 15 μm or less. D ₅₀ is a particle size having a cumulative volume of 50%, and the particle size distribution is measured by a laser scattering method using, for example, a particle size / particle size distribution measuring device (“Microtrack MT3300EXII” manufactured by Microtrac Bell Co., Ltd.). It can be obtained by.

The hygroscopic amount of the carbonaceous material of the present invention is preferably 3000 ppm or less, more preferably 1000 ppm or less, still more preferably 500 ppm or less, and particularly preferably 400 ppm or less. The smaller the amount of moisture absorbed, the less water is adsorbed on the carbonaceous material, and the more lithium ions are adsorbed on the carbonaceous material, which is preferable. Further, the smaller the amount of moisture absorbed, the more preferable it is because the reaction between the adsorbed water and the nitrogen atom of the carbonaceous material and the self-discharge due to the reaction between the adsorbed water and the lithium ion can be reduced. The lower limit of the moisture absorption amount of the carbonaceous material of the present invention is not particularly limited, and may be 0 ppm or more. The amount of moisture absorbed by the carbonaceous material can be reduced, for example, by reducing the amount of oxygen atoms and nitrogen atoms contained in the carbonaceous material. The hygroscopic amount of the carbonaceous material can be measured by using, for example, Karl Fischer or the like.

The present invention also provides a method for producing a carbonaceous material suitable for a negative electrode active material of a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) having high charge / discharge capacity and charge / discharge efficiency and low resistance. The manufacturing method is as follows:
(1) A vapor phase decalcification step of heat-treating a plant-derived char at 1100 to 1300 ° C. in an inert gas atmosphere containing a halogen compound to obtain a vapor phase decalcification char, wherein the inert gas containing the halogen compound is inert. The amount of gas supplied is 14 L / min or more per 50 g of plant-derived char, and (2) at least includes a step of subjecting the gas phase decalcified char to a CVD treatment using a hydrocarbon compound.

As described above, the carbonaceous material of the present invention is derived from a plant and can be produced by using a plant-derived char as a raw material. The char is generally a powdery solid rich in carbon content that is not melt-softened and is obtained when coal is heated, but in the present specification, the carbon content that is not melt-softened and is obtained by heating an organic substance. Also shown is a powdery solid rich in carbon.

The plant that is the raw material of the plant-derived char (hereinafter, also referred to as “plant raw material”) is not particularly limited. For example, coconut husks, coffee beans, tea leaves, sugar cane, fruits (eg, mandarin oranges, bananas), straw, rice husks, hardwoods, conifers, and bamboo can be exemplified. This example includes waste after use for its intended purpose (eg, used tea leaves) or some plant material (eg, banana or tangerine peel). These plants can be used alone or in combination of two or more. Among these plants, palm husks are preferable because they are easily available in large quantities.

The coconut shell is not particularly limited, and examples thereof include palm husks of palm palm (oil palm), coconut palm, salak, and Lodoicea palm. These palm shells can be used alone or in combination of two or more. Coconut and palm palm husks, which are used as raw materials for foods, detergents, biodiesel oils and the like and generate a large amount of biomass waste, are particularly preferable.

The method for producing char from the plant raw material is not particularly limited, and for example, the plant raw material can be produced by heat treatment (dry distillation) in an atmosphere of an inert gas at 300 ° C. or higher. It can also be obtained directly in the form of char (eg, palm shell char).

A crushed plant-derived char (hereinafter also referred to as "crushed char") obtained by crushing a plant-derived char may be used. The specific surface area of the pulverized char obtained in the pulverization step is preferably 100 to 800 m ² / g, more preferably 200 to 700 m ² / g, and further preferably 200 to 600 m ² / g. It is preferable to carry out the pulverization step so as to obtain a pulverized char having a specific surface area in the above range. When the specific surface area of the crushed char is at least the above lower limit, the micropores of the carbonaceous material are reduced, and the hygroscopicity of the carbonaceous material can be reduced. The presence of water in the carbonaceous material can cause problems due to the generation of acid due to the hydrolysis of the electrolytic solution and the generation of gas due to the electrolysis of water, and the oxidation of the carbonaceous material progresses in an air atmosphere. Battery performance may change significantly. When the specific surface area of the crushed char is not more than the above upper limit, the specific surface area of the obtained carbonaceous material tends to be within the range described later, and as a result, the resistance is lowered and the utilization efficiency of lithium ions in the non-aqueous electrolyte secondary battery is high. It becomes easy to improve. In the present specification, the specific surface area means the specific surface area (BET specific surface area) determined by the BET method (nitrogen adsorption BET multipoint method). Specifically, it can be measured by using the method described later.

When a crushed char is used, crushing the plant-derived char so that the average particle size (D ₅₀ ) of the crushed char is in the range of 2 to 100 μm is uniform during alkali imposition and vapor phase decalcification, which will be described later. It is preferable from the viewpoint of. When the average particle size is 2 μm or more, fine powder is less likely to be scattered in the furnace during gas phase decalcification, the recovery rate of the carbonaceous material produced is excellent, and the load on the apparatus can be suppressed. On the other hand, when the average particle size is 100 μm or less, the contact with the halogen compound becomes easy, which leads to an increase in decalcification efficiency and an improvement in the activation effect, and it is easy to remove the gas generated from the plant-derived char during the heat treatment. From such a viewpoint, the average particle size of the pulverized char is more preferably 80 μm or less, further preferably 60 μm or less, particularly preferably 40 μm or less, extremely preferably 30 μm or less, and most preferably 20 μm or less. The average particle size of the pulverized char is more preferably 3 μm or more, further preferably 4 μm or more, particularly preferably 5 μm or more, and extremely preferably 6 μm or more. Note that D ₅₀ is a particle size having a cumulative volume of 50%, and is, for example, a particle size distribution by a laser scattering method using a particle size / particle size distribution measuring device (“Microtrack MT3300EXII” manufactured by Microtrac Bell Co., Ltd.). Can be obtained by measuring.

The crushing device used for crushing is not particularly limited, and for example, a jet mill, a ball mill, a bead mill, a hammer mill, a rod mill, or the like can be used. From the viewpoint of crushing efficiency, a method of crushing in the coexistence of crushing media such as a ball mill and a bead mill is preferable, and from the viewpoint of equipment load, the use of a ball mill is preferable.

After crushing the plant-derived char, the crushed char may be classified as needed. By classifying, it becomes easy to obtain a pulverized char having the above-mentioned specific surface area and average particle size, and it becomes easy to more accurately adjust the specific surface area and average particle size of the obtained carbonaceous material. It is preferable that the specific surface area and the average particle size after crushing and classifying the plant-derived char are within the above ranges.

The classification method is not particularly limited, and examples thereof include classification using a sieve, wet classification, and dry classification. Examples of the wet classifier include a classifier using principles such as gravity classification, inertial classification, hydraulic classification, and centrifugal classification. Examples of the dry classifier include a classifier using principles such as sedimentation classification, mechanical classification, and centrifugal classification.

The grinding and classification steps may be carried out using one device. For example, a jet mill equipped with a dry classification function can be used to perform pulverization and classification. Further, a device in which the crusher and the classifier are independent may be used. In this case, pulverization and classification may be performed continuously or discontinuously.

The production method of the present invention includes at least a vapor phase decalcification step of (1) heat-treating a plant-derived char at 1100 to 1300 ° C. in an inert gas atmosphere containing a halogen compound to obtain a vapor phase decalcification char. Here, the supply amount of the inert gas containing the halogen compound is 14 L / min or more per 50 g of plant-derived char. In the step of heat-treating a plant-derived char under an inert gas stream containing a halogen compound, decalcification and activation by the halogen compound are performed, and at the same time, calcining of a carbonaceous material is performed.

As mentioned above, the carbonaceous material of the present invention is derived from plants. A carbonaceous material produced from a plant-derived char is basically suitable as a negative electrode material for a non-aqueous electrolyte secondary battery because it can be doped with a large amount of Li ions. On the other hand, plant-derived char contains a large amount of metal elements contained in plants. For example, palm shell char contains about 0.3% of potassium element and about 0.03% of calcium element. When such a carbonaceous material containing a large amount of metal elements is used as the negative electrode, it may adversely affect the electrochemical characteristics and safety of the non-aqueous electrolyte secondary battery.

Plant-derived chars also contain alkali metals other than potassium (eg, sodium), alkaline earth metals (eg, magnesium, calcium), transition metals (eg, iron, copper) and other metals. If the carbonaceous material contains these metals, impurities may elute into the electrolyte during dedoping from the negative electrode of the non-aqueous electrolyte secondary battery, adversely affecting the battery performance and impairing safety. be. Further, the ash content may block the pores of the carbonaceous material, which may adversely affect the charge / discharge capacity of the battery.

By performing the vapor phase decalcification step, potassium element, calcium element, iron element and the like which may adversely affect the electrochemical characteristics and safety of the non-aqueous electrolyte secondary battery can be efficiently removed. It is also possible to remove other alkali metals, alkaline earth metals, and transition metals such as copper and nickel.

The halogen compound used in the vapor phase decalcification step is not particularly limited, and examples thereof include at least one compound containing an element selected from the group consisting of fluorine, chlorine and iodine, and specific examples thereof include fluorine, chlorine and the like. Examples thereof include bromine, iodine, hydrogen fluoride, hydrogen chloride, hydrogen bromide, iodine bromide, chlorine fluoride (ClF), iodine chloride (ICl), iodine bromide (IBr), bromine chloride (BrCl) and the like. Compounds that generate these halogen compounds by thermal decomposition, or mixtures thereof, can also be used. From the viewpoint of supply stability and stability of the halogen compound used, the halogen compound is preferably hydrogen chloride or hydrogen bromide, and more preferably hydrogen chloride.

The inert gas used in the gas phase decalcification step is not particularly limited as long as it is a gas that does not react with the carbon component constituting the plant-derived char at the temperature of the heat treatment, and is, for example, nitrogen, helium, argon, krypton, or. Examples thereof include a mixed gas thereof. From the viewpoint of supply stability and economy, the inert gas is preferably nitrogen. The lower the concentration of the impurity gas (particularly oxygen) contained in the inert gas, the more preferable, but the normally acceptable oxygen concentration is preferably 0 to 2000 ppm, more preferably 0 to 1000 ppm.

The mixing ratio of the halogen compound and the inert gas is not particularly limited as long as sufficient decalcification is achieved. For example, from the viewpoint of safety, economy and persistence in carbon, the amount of the halogen compound with respect to the inert gas is preferably 0.01 to 10% by volume, more preferably 0.05 to 8% by volume. It is even more preferably 0.1 to 5% by volume. According to the production method of the present invention, since the gas phase decalcification step is performed in the atmosphere of an inert gas containing a halogen compound, it is not necessary to perform a drying treatment, which is industrially advantageous. Further, according to the production method of the present invention, since the gas phase decalcification step is performed under an inert gas stream containing a halogen compound, not only the reduction of metal elements but also the reduction of hydrogen elements and oxygen elements at the ends of the carbon structure is reduced. It can reduce the number of active sites in carbonaceous materials.

The heat treatment temperature in the vapor phase decalcification step may be changed depending on the type of plant-derived char as a raw material, but is preferably 1100 to 1300 ° C., more preferably 1120, from the viewpoint of obtaining a desired carbon structure and decalcification effect. It is ~ 1250 ° C, and even more preferably 1150-1200 ° C. If the heat treatment temperature is too low, the decalcification efficiency may decrease and sufficient decalcification may not be possible. In addition, activation with a halogen compound may not be sufficiently performed. On the other hand, if the heat treatment temperature becomes too high, the effect of heat shrinkage is superior to the effect of activation by the halogen compound, and the BET specific surface area becomes excessively small, which may not be preferable.

The heat treatment time in the gas phase decalcification step is not particularly limited, but is, for example, 5 to 300 minutes, preferably 10 to 200 minutes, more preferably 10 to 200 minutes, from the viewpoint of economic efficiency of the reaction equipment and structural retention of carbon content. Is 20 to 150 minutes.

The supply amount of the inert gas stream containing the halogen compound in the gas phase decalcification step is preferably 14 L / min or more, more preferably 15 L / min or more, still more preferably 16 L / min or more per 50 g of plant-derived char. .. It is preferable to perform the heat treatment with a supply amount equal to or higher than the above lower limit because the gas generated from the char itself in the heat treatment can be sufficiently removed and a carbonaceous material having a half width in the above range can be easily obtained. The upper limit of the supply amount is preferably 25 L / min or less, and more preferably 20 L / min or less. When the heat treatment is performed with a supply amount equal to or less than the above upper limit, the halogen compound is easily adsorbed on the plant-derived char and reacted with the metal element, and a sufficient decalcification effect is easily obtained, which is preferable.

Here, when the plant-derived char is heat-treated at a high temperature, gases such as carbon monoxide and hydrogen are generated from the char itself. Since these gases have high reactivity, it is difficult to control the reaction between the gas and the char generated during the heat treatment. For example, by performing the heat treatment by increasing the supply amount of the inert gas (increasing the supply rate) as described above, it becomes possible to remove the reactive gas generated from the char itself before reacting with the char. .. Therefore, it is considered that a carbonaceous material having a more controlled carbon structure can be produced.

Although the mechanism by which potassium, calcium, other alkali metals, alkaline earth metals, transition metals, etc. can be efficiently removed by the vapor phase decalcification step is not clear, it is considered as follows. Metals such as potassium contained in plant-derived chars react with halogen compounds diffused in the chars to form metal halides (eg, chlorides or bromides). Then, it is considered that the produced metal halide can decalcify potassium, calcium and the like by volatilizing (dissipating) by heating. In such a mechanism of diffusion of a halide into char and formation of a metal halide by a reaction, it is considered that potassium, calcium and the like can be efficiently removed by high diffusion of the halide in the gas phase. Is not limited to the above description.

In the present invention, it is preferable to further perform a step of heating the carbonaceous material in an inert gas atmosphere (hereinafter, also referred to as “deoxidation treatment”) in the absence of the halogen compound after the vapor phase decalcification step. Metallic elements such as calcium element can be efficiently removed by contact with the halogen compound in the vapor phase decalcification step. However, contact with the halogen compound results in halogen being contained in the carbonaceous material. Therefore, it is preferable to perform a deoxidation treatment in which the carbonaceous material is heated in the absence of the halogen compound, and the halogen contained in the carbonaceous material can be removed by such treatment. Specifically, the deoxidizing treatment is usually carried out by heating at 800 ° C. to 1300 ° C. in an inert gas atmosphere containing no halogen compound, but the temperature of the deoxidizing treatment is the temperature in the gas phase decalcification step. It is preferable to carry out at the same or higher temperature. The temperature of the deoxidizing treatment is preferably 850 to 1300 ° C, more preferably 900 to 1250 ° C, and even more preferably 1000 to 1200 ° C. For example, after the vapor phase decalcification step, the deoxidation treatment can be performed by cutting off the supply of the halogen compound and continuously performing the heat treatment, thereby removing the halogen in the carbonaceous material. be able to. The time of the deoxidizing treatment is not particularly limited, and is preferably 5 minutes to 300 minutes, more preferably 10 minutes to 200 minutes, still more preferably 20 minutes to 150 minutes, and most preferably 30 minutes to 30 minutes. It's 100 minutes.

Examples of the inert gas used in the deoxidizing treatment include the gas used in the gas phase decalcification step. From the viewpoint of simplifying the manufacturing process, it is preferable that the inert gas in the gas phase decalcification step and the inert gas in the deoxidizing treatment are the same. The supply amount (distribution amount) of the inert gas is not limited, but is preferably the same as the supply amount of the inert gas in the gas phase decalcification step from the viewpoint of production.

The apparatus used for the heat treatment in the vapor phase decalcification step is not particularly limited as long as it can heat while mixing the plant-derived char and the inert gas containing the halogen compound. For example, a fluidized bed can be used, and a continuous or batch type intra-layer distribution system using a fluidized bed or the like can be used.

In the production method of the present invention, before the vapor phase decalcification step (step (1)), (a) a compound containing an alkali metal element is added to a plant-derived char, and an alkali-impregnated plant-derived char is obtained. It may further include the resulting alkali imposition step.

In the alkali imposition step, a compound containing an alkali metal element is added to a plant-derived char that has been crushed in some cases. By performing the alkali imposition step, carbon erosion by the alkali metal element is promoted in the temperature raising process up to the subsequent vapor phase decalcification step, and micropore formation is brought about. Specifically, although not limited to the mechanism described later, diffusion of the impregnated alkali metal into the plant-derived char is started at a temperature near the melting point of the compound containing an alkali metal element, and at a temperature of around 500 ° C. It is considered that the dehydration reaction in the compound containing the alkali metal element and the erosion reaction of the char carbon by the compound containing the alkali metal element are started, and the alkali metal element volatilizes at a temperature near the boiling point of the alkali metal element. When the alkaline impregnation step is performed, it is preferable to perform the above-mentioned pulverization step of pulverizing the plant-derived char before the alkaline impregnation.

In the alkali-impregnated step, a compound containing an alkali metal element is added to a plant-derived char that has been crushed in some cases to obtain a char (hereinafter, also referred to as “alkali-impregnated char”) impregnated with the alkali metal element. The compound containing an alkali metal element is a compound containing an alkali metal element (lithium, sodium, potassium, rubidium, cesium, etc.), and is, for example, a halide (fluoride, chloride, bromide, etc.) of the alkali metal element, water. Examples include oxides, carbonates and hydrogen carbonates. Specifically, as the compound containing an alkali metal element, lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, carbonic acid Examples thereof include lithium, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, rubidium hydrogen carbonate, cesium hydrogen carbonate and the like. Among them, the compound containing an alkali metal element is preferably a compound containing sodium or potassium from the viewpoint of fine pore forming ability and safety. Further, from the viewpoint of excellent affinity with the pulverized char, the compound containing the alkali metal element is preferably a hydroxide, carbonate or hydrogen carbonate of the alkali metal element. From the above viewpoint, sodium or sodium hydroxide or carbonate is more preferable, and sodium hydroxide or sodium carbonate is more preferable.

The method of adding the compound containing an alkali metal element to the crushed plant-derived char is not particularly limited. For example, a compound containing an alkali metal element may be added to a plant-derived char in a dry or wet manner, and then mixed to obtain an alkali-impregnated char in which the compound containing the alkali metal element is carried. Wet addition is preferable from the viewpoint of making it easy to uniformly adhere the compound containing the alkali metal element to the plant-derived char.

In the case of dry addition, an alkali-impregnated char can be obtained by adding a compound containing a solid alkali metal element to a plant-derived char and mixing the mixture. In this case, from the viewpoint of uniformly adhering the compound containing the alkali metal element to the plant-derived char, it is preferable to add the compound in the form of powder and mix them.

In the case of wet addition, a compound containing an alkali metal element is dissolved in a solvent to prepare a solution, and then the solution is carried on an optionally ground plant-derived char. Regarding carrying, the solution is made into a plant-derived char by immersing the plant-derived char in the solution, spraying the solution on the plant-derived char (spray spraying, etc.), or adding and mixing the solution to the plant-derived char. Can be carried. A compound containing a solid alkali metal element may be added to a mixture of a solvent and a plant-derived char to carry the support. After the carrier, the solvent may be evaporated if necessary. By such treatment, an alkaline impregnated char can be obtained. The solvent is not particularly limited, but is, for example, water, an alcohol solvent (ethanol, methanol, ethylene glycol, isopropyl alcohol, etc.), an ester solvent (ethyl acetate, butyl acetate, ethyl lactate, etc.), an ether solvent (tetratetraethan, 1,4). -Dioxane, etc.), Ketone solvent (acetone, 2-butanone, cyclopentanone, cyclohexanone, etc.), aliphatic hydrocarbon solvent (pentane, hexane, heptane, etc.), aromatic hydrocarbon solvent (toluene, xylene, mesitylen, etc.), Examples thereof include nitrile solvents (acetoyl, etc.), chlorinated hydrocarbon solvents (dimethane, chloroform, chlorobenzene, etc.), and mixtures thereof. Since it is effective to increase the affinity between the solvent and the plant-derived char in order to uniformly attach the compound containing the alkali metal element to the plant-derived char, water, an alcohol solvent and a mixture thereof are used as the solvent. preferable. The method for evaporating the solvent is not particularly limited, and examples thereof include heat treatment and decompression treatment, and combinations thereof. The temperature of the heat treatment may be a temperature at which oxidation of the plant-derived char is unlikely to occur, and varies depending on the type of solvent, but is preferably 40 to 200 ° C, more preferably 50 to 150 ° C, still more preferably 60 to 100 ° C. be.

In some cases, the amount (impregnation amount) of the compound containing an alkali metal element to be adhered to the crushed plant-derived char is preferably 0.5% by mass or more, more preferably 1 with respect to the mass of the obtained alkali impregnated char. By mass or more, more preferably 3% by mass or more, particularly preferably 5% by mass or more, particularly preferably 10% by mass or more, preferably 20% by mass or less, more preferably 18% by mass or less, still more preferably 17% by mass. % Or less, particularly preferably 16% by mass or less, and particularly preferably 15% by mass or less. When the amount of the compound containing the alkali metal element to be impregnated is not more than the above lower limit, the formation of fine pores can be promoted in the gas phase decalcification step described later. When the amount of the compound containing the alkali metal element to be impregnated is not more than the above upper limit, excessive fine pore formation can be suppressed, and the obtained non-aqueous electrolyte secondary battery containing the carbonaceous material has a high charge / discharge capacity. , High charge / discharge efficiency, and easy to show low resistance.

The average particle size (D ₅₀ ) of the alkali-impregnated char obtained in the alkali-impregnation step is preferably 2 to 100 μm, more preferably 3 to 80 μm, still more preferably 4 to 60 μm, particularly preferably 4 to 40 μm, and particularly preferably 5. It is ~ 30 μm, very preferably 6-20 μm, and most preferably 7-15 μm. When the average particle size of the alkaline impregnated char is at least the above lower limit, powder scattering can be reduced even if firing is performed at a high air flow rate. When the average particle size of the alkaline impregnated char is not more than the above upper limit, the impregnated alkaline compound is easily removed in the vapor phase decalcification step.

The specific surface area of the alkali-impregnated char obtained in the alkali-impregnated step is preferably 100 to 800 m ² / g, more preferably 150 to 700 m ² / g, and further preferably 200 to 600 m ² / g. When the specific surface area of the alkaline impregnated char is at least the above lower limit, the micropores of the carbonaceous material are reduced, and the hygroscopicity of the carbonaceous material is likely to be lowered. When the specific surface area of the alkaline impregnated char is not more than the above upper limit, the specific surface area of the obtained carbonaceous material tends to be within the above range, and as a result, the resistance is lowered and the utilization efficiency of lithium ions in the non-aqueous electrolyte secondary battery is high. It becomes easy to improve. The average particle size and specific surface area of the alkaline impregnated char may be adjusted by pulverization and / or classification. Examples of the crushing method and the classification method include the same methods as described above. As a means for adjusting the average particle size of the alkaline impregnated char, in addition to the pulverization and classification after the alkaline impregnation, the particle size of the pulverized char may be adjusted by the pulverization and the classification before the alkaline impregnation. In the present specification, the specific surface area of the alkaline impregnated char can be measured by the BET method (nitrogen adsorption BET multipoint method).

If the alkali metal element remains in the carbonaceous material, the alkali metal element moves to the counter electrode side when the non-aqueous secondary battery is discharged, and as a result, the battery performance may deteriorate. The production method of the present invention may include a removal step of removing a compound containing an alkali metal element, but even when the production method of the present invention does not include the removal step, the alkali metal in the obtained carbonaceous material. It is possible to keep the element content low. The reason for this is not clear, but the reaction between the halogen compound introduced in the gas phase decalcification step and the alkali metal element produces a reactant having a relatively low melting point, which is volatilized by the heat treatment in the gas phase decalcification step. It is probable that it was removed. The present invention is not limited to the above description.

When the alkali imposition step is performed before the vapor phase decalcification step, it is considered that the alkali metal is bonded to the crystal terminal of the graphite structure and then the terminal radical is generated, although the mechanism is not limited to that described later. After that, it is considered that radicals form new bonds between the crystal ends and bonds are formed between the crystallite structures of graphite. Due to such a structure, it is considered that micropores between crystals are retained in the subsequent gas phase decalcification step. This is confirmed, for example, by the large half-value width of the peak near 1360 cm ^-1 in the Raman spectrum observed by laser Raman spectroscopy. In carbonaceous materials, the retention of micropores increases the number of sites where lithium ions are occluded, which makes it easier to increase the charge / discharge capacity.

The production method of the present invention further includes (2) a step of subjecting the vapor phase decalcification char to a CVD treatment using a hydrocarbon compound. Hereinafter, this step is also referred to as a CVD processing step. The CVD treatment, as used herein, is a chemical vapor deposition (CVD) treatment in which a pyrolyzed hydrocarbon compound is used to coat a vapor phase decalcified char. The conditions of the CVD treatment are not particularly limited as long as the above chemical vapor deposition is achieved, but may be carried out by, for example, a method of heat treatment at 500 to 1000 ° C. in an atmosphere of an inert gas containing a hydrocarbon compound. In the CVD treatment step, for example, the hydrocarbon compound is thermally decomposed by heat treatment at 500 to 1000 ° C., and the resulting thermal decomposition product adheres to the vapor phase decalcification char and covers the surface of the vapor phase decalcification char. It is considered that this changes the pore structure of the gas phase decalcification char, and leads to a decrease in specific surface area while maintaining micropores capable of storing lithium ions, although not limited to the following mechanism. Therefore, it is considered that the charge / discharge efficiency can be improved while maintaining a high charge / discharge capacity. Further, it is considered that the char surface functional groups such as -OH group and -COOH group, which can inhibit the insertion of lithium ions, react with the radicals of the thermally decomposed hydrocarbon compound and are removed by the CVD treatment. Therefore, it is considered that the oxygen element content in the carbonaceous material is lowered and the irreversible side reaction at the time of charging / discharging is suppressed, so that the discharging capacity and the charging / discharging efficiency are improved.

The hydrocarbon compound used in the CVD processing step is a compound mainly composed of a carbon atom and a hydrogen atom. Examples of the hydrocarbon compound include a hydrocarbon-based thermoplastic resin and a low-molecular-weight organic hydrocarbon compound. In the CVD treatment step, one kind of hydrocarbon compound may be used, or two or more kinds of hydrocarbon compounds may be used in combination. The fact that a hydrocarbon compound is mainly composed of carbon atoms and hydrogen atoms means that the total amount of carbon atoms and hydrogen atoms in the hydrocarbon compound is preferably 75% by mass or more based on the total weight of the hydrogen compound. It is preferably 80% by mass or more, more preferably 85% by mass or more.

Examples of the hydrocarbon-based thermoplastic resin include olefin-based resins and styrene-based resins. Examples of the olefin resin include polyethylene, polypropylene, a random copolymer of ethylene and propylene, and a block copolymer of ethylene and propylene. Examples of the styrene resin include polystyrene, poly (α-methylstyrene), and a copolymer of styrene and acrylonitrile.

Examples of the low molecular weight organic hydrocarbon compound include hydrocarbon compounds having 1 to 20 carbon atoms. The hydrocarbon compound has preferably 2 to 18 carbon atoms, more preferably 3 to 16 carbon atoms. The hydrocarbon compound may be a saturated hydrocarbon compound or an unsaturated hydrocarbon compound, and may be a chain hydrocarbon compound or a cyclic hydrocarbon compound. In the case of an unsaturated hydrocarbon compound, the unsaturated bond may be a double bond or a triple bond, and the number of unsaturated bonds contained in one molecule is not particularly limited. For example, the chain hydrocarbon compound is an aliphatic hydrocarbon compound and may include linear or branched alkanes, alkenes, or alkynes. Examples of the cyclic hydrocarbon compound include an alicyclic hydrocarbon compound (for example, cycloalkane, cycloalkyne, cycloalkyne) or an aromatic hydrocarbon compound. Specific examples of the aliphatic hydrocarbon compound include methane, ethane, propane, butane, pentane, hexane, octane, nonane, decane, ethylene, propylene, butene, pentene, hexene and acetylene. Examples of the alicyclic hydrocarbon compound include cyclopentane, cyclohexane, cycloheptan, cyclooctane, cyclononane, cyclopropane, cyclopentene, cyclohexene, cycloheptene, cyclooctene, decalin, norbornen, methylcyclohexane, norbornadiene and the like. Further, examples of the aromatic hydrocarbon compound include benzene, toluene, xylene, mesitylene, cumene, butylbenzene, styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinylxylene and p-. Examples thereof include monocyclic aromatic compounds such as tert-butylstyrene and ethylstyrene, and 3- to 6-ring fused polycyclic aromatic compounds such as naphthalene, phenanthrene, anthracene, and pyrene, but condensed polycyclic aromatic compounds are preferable. Compounds, more preferably naphthalene, phenylene, anthracene or pyrene. Here, the hydrocarbon compound may have any substituent. The substituent is not particularly limited, but for example, an alkyl group having 1 to 4 carbon atoms (preferably an alkyl group having 1 to 2 carbon atoms) and an alkenyl group having 2 to 4 carbon atoms (preferably an alkenyl having 2 carbon atoms). Group), a cycloalkyl group having 3 to 8 carbon atoms (preferably a cycloalkyl group having 3 to 6 carbon atoms).

In the CVD treatment step, it is preferable to continuously supply the hydrocarbon compound in a gaseous state from the viewpoint of uniformly performing the CVD treatment and easily obtaining the desired characteristics of the carbonaceous material. A hydrocarbon compound that is in a gaseous state at the temperature at which the CVD treatment is performed may be used, or a hydrocarbon compound that is in a gaseous state in the pre-process of the CVD treatment may be supplied to the CVD processing step. For example, using a hydrocarbon compound that is in a gaseous state at a temperature of 500 to 1000 ° C. and heat-treating at that temperature to perform a CVD treatment is possible from the viewpoint of productivity and mixing of the hydrocarbon compound and the gas phase decalcification char. preferable. From the above viewpoint, the boiling point of the hydrocarbon compound is preferably equal to or lower than the temperature at which the CVD treatment is performed.

The CVD treatment step may preferably be carried out in an atmosphere of an inert gas containing a hydrocarbon compound. Examples of the inert gas used in the CVD treatment step include those described above for the vapor phase decalcification step. The same inert gas may be used in the vapor phase decalcification step (step (1)) and the CVD treatment step (step (2)), or different inert gases may be used. From the viewpoint of simplifying the manufacturing process and increasing the manufacturing efficiency, it is preferable to use the same inert gas in the vapor phase decalcification step and the CVD treatment step.

When the CVD treatment step is carried out in an atmosphere of an inert gas containing a hydrocarbon compound, the mixing ratio of the hydrocarbon compound and the inert gas is not particularly limited. For example, from the viewpoint of safety, economy and contamination in the firing furnace, the amount of the hydrocarbon compound with respect to the inert gas is preferably 5 to 60% by volume, more preferably 10 to 50% by volume. Even more preferably, it is 15 to 45% by volume. According to the production method of the present embodiment in which the heat treatment is performed in an atmosphere of an inert gas containing a hydrocarbon compound, oxygen can be easily removed efficiently.

The heat treatment temperature in the CVD treatment step may be changed depending on the type of the plant-derived char as a raw material, the type of the hydrocarbon compound used, and the like, but is preferably 500 to 1000 ° C., more preferably from the viewpoint of obtaining a desired carbon structure. Is 600 to 900 ° C, more preferably 700 to 850 ° C. If the heat treatment temperature is too low, oxygen cannot be sufficiently removed. On the other hand, if the heat treatment temperature becomes too high, a large amount of carbon structure derived from a hydrocarbon compound that does not contribute to the battery capacity adheres, and the battery capacity is lowered.

When the CVD treatment step is carried out in an inert gas atmosphere containing a hydrocarbon compound, the supply amount of the inert gas stream containing the hydrocarbon compound is not particularly limited, but is preferably 0.1 L per 50 g of gas phase decalcification char. It is / min or more, more preferably 0.3 L / min or more, and even more preferably 0.5 L / min or more. It is preferable to perform the heat treatment with a supply amount equal to or higher than the above lower limit because a uniform carbon coating can be obtained. The upper limit of the supply amount is preferably 10 L / min or less, and more preferably 5 L / min or less. It is preferable to perform the heat treatment with a supply amount equal to or less than the above upper limit because the supplied hydrocarbon compound acts efficiently.

The carbonaceous material of the present invention or the carbonaceous material obtained by the production method of the present invention can be suitably used as a negative electrode active material for a non-aqueous electrolyte secondary battery. The present invention also provides a negative electrode for a non-aqueous electrolyte secondary battery containing the carbonaceous material of the present invention.

Hereinafter, a method for manufacturing a negative electrode for a non-aqueous electrolyte secondary battery of the present invention will be specifically described. The negative electrode of the present invention is prepared by adding a binder to the carbonaceous material of the present invention, adding an appropriate amount of an appropriate solvent, kneading the mixture to prepare an electrode mixture, and then applying the negative electrode to a current collector plate made of a metal plate or the like. After drying, it can be manufactured by pressure molding.

By using the carbonaceous material of the present invention, it is possible to produce an electrode having high conductivity without adding a conductive auxiliary agent. If necessary, a conductive auxiliary agent can be added at the time of preparation of the electrode mixture for the purpose of imparting higher conductivity. As the conductive auxiliary agent, conductive carbon black, vapor phase grown carbon fiber (VGCF), nanotubes and the like can be used. The amount of the conductive auxiliary agent added varies depending on the type of the conductive auxiliary agent used, but if the amount added is too small, the expected conductivity may not be obtained, and if it is too large, the dispersion in the electrode mixture is poor. May become. From this point of view, the preferable ratio of the conductive auxiliary agent to be added is 0.5 to 10% by mass (here, the amount of the active material (carbonaceous material) + the amount of the binder + the amount of the conductive auxiliary agent = 100% by mass). Yes, more preferably 0.5 to 7% by mass, and particularly preferably 0.5 to 5% by mass. 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 good input / output characteristics can be obtained. A polar solvent such as N-methylpyrrolidone (NMP) is preferably used to dissolve PVDF and 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 becomes large, so that the internal resistance of the battery becomes large and the battery characteristics may be deteriorated. Further, if the amount of the binder added is too small, the bonding between the particles of the negative electrode material and the current collecting material may be insufficient. The preferable amount of the binder added varies depending on the type of binder used, but for example, a PVDF-based binder is preferably 3 to 13% by mass, more preferably 3 to 10% by mass. On the other hand, in the binder using 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 the total binder used is preferably 0.5 to 5% by mass. -4% by mass is more preferable.

The electrode active material layer is basically formed on both sides of the current collector plate, but may be formed on 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. However, the wider the electrode area facing the counter electrode is, the more advantageous it is to improve the input / output characteristics. Therefore, if the electrode active material layer is too thick, the input / output characteristics may deteriorate. The thickness of the active material layer (per one side) is preferably 10 to 80 μm, more preferably 20 to 75 μm, and even more preferably 30 to 75 μm from the viewpoint of output when the battery is discharged.

The non-aqueous electrolyte secondary battery of the present invention includes the negative electrode for the non-aqueous electrolyte secondary battery of the present invention. The non-aqueous electrolyte secondary battery having a negative electrode for a non-aqueous electrolyte secondary battery containing the carbonaceous material of the present invention has high charge / discharge capacity and charge / discharge efficiency, and low resistance.

When the negative electrode for a non-aqueous electrolyte secondary battery is formed by using the carbonaceous material 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 and are non-aqueous. It is possible to use various materials conventionally used or proposed as a solvent 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 Mod O ₂ (here x, _y ). , Z represents the composition ratio)), olivine-based (represented by LiMPO ₄ , M is a metal: eg LiFePO ₄ ), spinel-based (represented by LiM ₂ O ₄ and M is represented by a metal: eg LiMn ₂ O ₄ ). ), The composite metal chalcogen compound is preferable, and these chalcogen compounds may be mixed and used 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 these positive electrodes and negative electrodes is generally formed by dissolving an 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. 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 non-aqueous electrolyte secondary battery, a positive electrode and a negative electrode formed as described above are generally opposed to each other via a liquid permeable separator made of a non-woven fabric, another porous material, or the like as necessary, and immersed in the electrolytic solution. It is formed by letting it. 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.

The carbonaceous material of the present invention is suitable as a carbonaceous material for a battery (typically, a non-aqueous electrolyte secondary battery for driving a vehicle) mounted on a vehicle such as an automobile. In the present invention, the vehicle can be a target without particular limitation, such as a vehicle usually as an electric vehicle, a hybrid vehicle with a fuel cell or an internal combustion engine, and the like, but at least a power supply device including the above battery. And an electric drive mechanism driven by power supply from the power supply device, and a control device for controlling the electric drive mechanism. The vehicle may further be provided with dynamic braking and regenerative braking, and may be provided with a mechanism for converting energy from braking into electricity to charge the non-aqueous electrolyte secondary 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 method for measuring the physical characteristic value of the carbonaceous material of the present invention is described below, but the physical characteristic value described in the present specification including the examples is based on the value obtained by the following method. ..

(Raman spectrum)
Using a Raman spectroscope (“LabRAM ARAMIS (VIS)” manufactured by HORIBA, Ltd.), the particle to be measured, which is a carbonaceous material, is set on the observation table stage, the magnification of the objective lens is set to 100 times, the focus is adjusted, and the argon ion. The measurement was performed while irradiating the laser beam. The details of the measurement conditions are as follows. Raman spectra of carbon electrodes prepared using the carbonaceous materials of Example 1 and Comparative Example 1 are shown in FIGS. 1 and 2, respectively.
Wavelength of argon ion laser light: 532 nm
Laser power on sample: 15mW
Resolution: 5-7 cm ^-1
Measurement range: 50-2000 cm ^-1
Exposure time: 1 second Total number of times: 100 times Peak intensity measurement: Baseline correction Polynom-Automatic correction in 3rd order
Peak Search & Fitting Processing GaussLaren

(Elemental analysis)
Elemental analysis was performed based on the inert gas dissolution method using the oxygen / nitrogen / hydrogen analyzer EMGA-930 manufactured by Horiba Seisakusho Co., Ltd.
The detection method of the device is oxygen: inert gas melting-non-dispersive infrared absorption method (NDIR), nitrogen: inert gas melting-heat conduction method (TCD), hydrogen: inert gas melting-non-dispersive infrared absorption method. It is a method (NDIR), and calibration is performed with (oxygen / nitrogen) Ni capsule, TiH ₂ (H standard sample), SS-3 (N, O standard sample), and the pretreatment is 250 ° C., moisture in about 10 minutes. 20 mg of the measured sample was taken in a Ni capsule, degassed in an element analyzer for 30 seconds, and then measured. The test was analyzed with 3 samples, and the average value was used as the analysis value.

(Specific surface area by nitrogen adsorption BET method)
The approximate expression derived from the BET equation is described below.

Using the above approximation formula, substitute the measured adsorption amount (v) at a predetermined phase body pressure (p / p ₀ ) by the multipoint method by nitrogen adsorption at the liquid nitrogen temperature to obtain v _m , and then obtain v m. The specific surface area of the sample was calculated by the formula.

In the above formula, v _m is the adsorption amount (cm ³ / g) required to form a single molecule layer on the sample surface, v is the measured adsorption amount (cm ³ / g), and p ₀ is the saturated vapor pressure. p is the absolute pressure, c is the constant (reflecting the heat of adsorption), N is the Avogadro 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 "Autosorb-iQ-MP" manufactured by Kantachrome, the amount of nitrogen adsorbed on plant-derived char or carbonaceous material at liquid nitrogen temperature was measured as follows. A plant-derived char or carbonaceous material as a measurement sample is filled in a sample tube, the sample tube is cooled to -196 ° C., the pressure is reduced once, and then nitrogen (purity 99.) is added to the measurement sample at a desired relative pressure. 999%) is 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.

( ⁷ Li nucleus-solid-state NMR)
N-Methyl-2-pyrrolidone was added to 94 parts by mass of the carbonaceous material and 6 parts by mass of polyvinylidene fluoride prepared in Examples and Comparative Examples described later to obtain a paste. The paste was applied onto a film to a uniform thickness, dried and pressed. The obtained pressed product was peeled off from the film to obtain a disk-shaped punched carbon electrode having a diameter of 14 mm, which was used as a positive electrode. As the negative electrode, a metal lithium thin film having a thickness of 0.2 mm was punched into a disk shape having a diameter of 14 mm. As the electrolytic solution, a mixed solvent in which ethylene glycol dimethyl ether and propylene carbonate were mixed at a volume ratio of 1: 1 and LiClO ₄ was added at a ratio of 1 mol / liter was used. A polypropylene fine pore film was used as the separator. A separator was sandwiched between the carbon electrode and the negative electrode, and an electrolytic solution was injected to prepare a coin cell.

Using the produced coin cell, doping is performed with an electric current density of 0.2 mA / cm ² until it reaches 0 mV, and then the lithium ion is fully charged by charging until the specific capacity reaches 1000 mAh / g. A carbon electrode doped until it was obtained was obtained. After the dope was completed, the dope was paused for 2 hours, the carbon electrode was taken out under an argon atmosphere, the electrolytic solution was wiped off, and all the obtained carbon electrodes were filled in a sample tube for NMR.

For NMR analysis, MAS- ⁷ Li-NMR was measured using a nuclear magnetic resonance apparatus (“AVANCE300” manufactured by BRUKER). In the measurement, lithium chloride was used as a reference substance, and the peak of lithium chloride was set to 0 ppm. The NMR spectra of the carbon electrodes prepared using the carbonaceous materials of Example 1 and Comparative Example 1 are shown in FIGS. 3 and 4, respectively.

(Metal content)
The calcium element content and the potassium element content were measured by, for example, the following methods. A carbon sample containing a predetermined calcium element and potassium element is prepared in advance, and a relationship between the calcium Kα ray intensity and the calcium element content and the potassium Kα ray intensity and the potassium element content are prepared using a fluorescent X-ray analyzer. A calibration line was created for the relationship with. Then, the intensities of calcium Kα rays and potassium Kα rays in the fluorescent X-ray analysis of the sample were measured, and the calcium element content and the potassium element content were determined from the calibration curve prepared earlier. Fluorescent X-ray analysis was performed using "ZSX Primus-μ" manufactured by Rigaku Co., Ltd. under the following conditions. A holder for the upper irradiation method was used, and the sample measurement area was set within the circumference of a diameter of 30 mm. 2.0 g of the sample to be measured and 2.0 g of the polymer binder (Spectro Blend 44μ Powder manufactured by Chemplex) were mixed in a mortar and placed in a molding machine. A load of 15 tons was applied to the molding machine for 1 minute to prepare pellets having a diameter of 40 mm. The prepared pellets were wrapped in a polypropylene film and placed in a sample holder for measurement. The X-ray source was set to 40 kV and 75 mA. For the calcium element, LiF (200) was used for the spectral crystal and a gas flow type proportional coefficient tube was used for the detector, and the range of 2θ of 110 to 116 ° was measured at a scanning speed of 30 ° / min. For the potassium element, LiF (200) was used for the spectral crystal and a gas flow type proportional coefficient tube was used for the detector, and the range of 2θ of 133 to 140 ° was measured at a scanning speed of 4 ° / min.

(True density by helium method ρ _He )
The true density ρ _He was measured by the helium method according to the method specified in JIS Z 8807. Specifically, it was measured as follows. The measuring container having an internal volume of about 4.5 cm ³ was washed and sufficiently dried. A device in which a sample chamber having a gas supply valve and an expansion chamber having an exhaust valve were connected by a connecting valve was used as a measuring device. The gas supply valve in the sample chamber was closed and the measuring container was placed in the sample chamber. The gas supply valve and the connection valve were opened, and helium gas was allowed to flow into the sample chamber for 1 minute to replace the sample chamber and the expansion chamber with helium gas. Then, the exhaust valve and the connection valve were closed, the sample chamber was pressurized to 18 psi, the gas supply valve was closed, and the pressure (p _1C ) in the sample chamber was measured with a pressure gauge. The connection valve was opened and the pressure (p _2C ) in the sample chamber and the expansion chamber was measured with a pressure gauge. Then, put the volume standard substance in the measuring container, repeat the same operation as above, and measure the pressure when the gas is introduced (p _1S ) and the pressure when the connection valve is opened and the gas is expanded (p _2S ). did. The exhaust valve was opened and the measuring container and volume standard material were taken out. Subsequently, after measuring the weight of the measurement sample, it was placed in a measurement container. The same operation as above was repeated, and the pressure (p ₁ ) when the gas was introduced and the pressure (p ₂ ) when the gas was expanded by opening the connection valve were measured. The true density ρ was calculated from the above measurement results according to the calculation formula described in JIS Z 8807.

(True density by butanol method ρ _Bt )
The true density ρ _Bt was measured by the butanol method according to the method specified in JIS R 7212. Specifically, it was measured as follows. The mass (m ₁ ) of the specific gravity bottle with a side tube having an internal volume of about 40 mL was accurately measured. Next, the sample was placed flat on the bottom to a thickness of about 10 mm, and then its mass (m ₂ ) was accurately weighed. 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 ρ _Bt was calculated by the following formula. At this time, d is the specific gravity (0.9946) of water at 30 ° C.

(Average particle size by laser scattering method)
The average particle size (particle size distribution) of plant-derived char and carbonaceous materials was measured by the following method. The sample was put into an aqueous solution containing 5% 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. The particle size distribution measurement was performed using a particle size / particle size distribution measuring device (“Microtrack MT3300EXII” manufactured by Microtrack Bell Co., Ltd.). D ₅₀ is a particle diameter having a cumulative volume of 50%, and this value was used as the average particle diameter.

(Hygroscopic amount)
10 g of carbon material crushed to a particle size of about 5 to 50 μm is placed in a sample tube, pre-dried at 120 ° C. for 2 hours under a reduced pressure of 133 Pa, transferred to a glass petri dish of 50 mmφ, and kept at a constant temperature of 25 ° C. and 50% humidity. It was exposed in a wet tank for a predetermined time. 1 g of a sample was taken, heated to 250 ° C. by Karl Fischer (manufactured by Mitsubishi Chemical Analytech), and the water content was measured under a nitrogen stream.

(Manufacturing Example 1)
The coconut shell was pulverized and carbonized at 500 ° C. under a nitrogen gas atmosphere to obtain a coconut shell char having a particle size of 0.5 to 2.0 mm. The specific surface area obtained by the BET multipoint method was 390 m ² / g.

(Example 1)
The coconut shell char obtained in Production Example 1 was heat-treated at 1200 ° C. for 60 minutes under a nitrogen gas stream containing 2% by volume of hydrogen chloride gas to perform a vapor phase decalcification treatment. The supply amount of nitrogen gas containing 2% by volume of hydrogen chloride gas was 18 L / min per 50 g of coconut shell char. Then, only the supply of hydrogen chloride gas was stopped, and heat treatment was performed at 1200 ° C. for 60 minutes to perform deoxidation treatment to obtain a vapor phase decalcification char. The amount of nitrogen gas supplied in the deoxidizing treatment was 18 L / min per 50 g of coconut shell char. Then, by pulverizing with a ball mill, a gas phase decalcification char having an average particle diameter D ₅₀ of 9 μm was obtained. Then, a carbonaceous material was obtained by heat-treating at 780 ° C. for 30 minutes under a nitrogen gas stream containing 40% by volume of hexane. The supply amount of nitrogen gas containing 40% by volume of hexane was 1 L / min per 100 g of gas phase decalcification char.

(Example 2)
In the gas phase decalcification treatment, nitrogen gas containing 1% by volume of hydrogen chloride gas is used instead of nitrogen gas containing 2% by volume of hydrogen chloride gas, and the supply amount of nitrogen gas containing 1% by volume of hydrogen chloride gas is coconut palm. A carbonaceous material was obtained in the same manner as in Example 1 except that the volume was 16 L / min per 50 g of shell char.

(Example 3)
In the gas phase decalcification treatment, instead of performing the heat treatment at 1200 ° C. for 60 minutes under a nitrogen gas stream containing 2% by volume of hydrogen chloride gas, at 1150 ° C. under a nitrogen gas stream containing 2% by volume of hydrogen chloride gas. A carbonaceous material was obtained in the same manner as in Example 1 except that the heat treatment was performed for 70 minutes.

(Example 5)
In the gas phase decalcification treatment, instead of performing the heat treatment at 1200 ° C. for 60 minutes under a nitrogen gas stream containing 2% by volume of hydrogen chloride gas, at 1150 ° C. under a nitrogen gas stream containing 1% by volume of hydrogen chloride gas. A carbonaceous material was obtained in the same manner as in Example 1 except that the heat treatment was performed for 70 minutes.

(Comparative Example 1)
A carbonaceous material was obtained in the same manner as in Example 1 except that the heat treatment was not performed under a nitrogen gas stream containing 40% by volume of hexane.

(Comparative Example 3)
A carbonaceous material was obtained in the same manner as in Example 3 except that the heat treatment was not performed under a nitrogen gas stream containing 40% by volume of hexane.

(Comparative Example 4)
In the gas phase decalcification treatment, a carbonaceous material was obtained in the same manner as in Example 1 except that the supply amount of nitrogen gas containing 2% by volume of hydrogen chloride gas was 10 L / min per 50 g of coconut shell char.

(Comparative Example 5)
In the gas phase decalcification treatment, the supply amount of nitrogen gas containing 2% by volume of hydrogen chloride gas was set to 10 L / min per 50 g of coconut shell char, and the heat treatment temperature under a nitrogen gas stream containing 40% by volume of hexane was set to 1000 ° C. A carbonaceous material was obtained in the same manner as in Example 1 except that.

(Comparative Example 7)
Except for the fact that in the gas phase decalcification treatment, the supply amount of nitrogen gas containing 2% by volume of hydrogen chloride gas was 10 L / min per 50 g of coconut shell char, and the temperature of the gas phase decalcification treatment and deoxidation treatment was 900 ° C. Obtained a carbonaceous material in the same manner as in Example 1.

(Comparative Example 8)
The coconut shell char obtained in Production Example 1 was heat-treated at 870 ° C. for 60 minutes under a nitrogen gas stream containing 2% by volume of hydrogen chloride gas to perform a vapor phase decalcification treatment. The supply amount of nitrogen gas containing 2% by volume of hydrogen chloride gas was 10 L / min per 50 g of coconut shell char. Then, only the supply of hydrogen chloride gas was stopped, and heat treatment was performed at 870 ° C. for 60 minutes to perform deoxidation treatment to obtain a carbonaceous material. The amount of nitrogen gas supplied in the deoxidizing treatment was 10 L / min per 50 g of coconut shell char. Then, by pulverizing with a jet mill, a powder having an average particle diameter D ₅₀ of 5 μm was obtained. Further, the carbonaceous raw material and polystyrene particles having an average particle diameter of 0.3 mm were mixed as an organic material and fired at 1320 ° C. for 30 minutes in a nitrogen atmosphere to obtain a particulate carbonaceous material. The mixing ratio of the carbonaceous raw material and the organic material was 10: 1 on a mass basis.

Table 1 shows the physical characteristics of the carbonaceous materials obtained in Examples 1 to 3 , 5 and Comparative Examples 1, 3 to 5 , 7, and 8.

(Method of manufacturing electrodes)
Using the carbonaceous materials obtained in Examples 1 to 3 and 5 and Comparative Examples 1 , 3 to 5 , 7 and 8, respectively, a negative electrode was prepared according to the following procedure.
96 parts by mass of carbonaceous material, 4 parts by mass of PVDF (polyvinylidene fluoride) and 90 parts by mass of NMP (N-methylpyrrolidone) were mixed to obtain a slurry. The obtained slurry was applied to a copper foil having a thickness of 14 μm, dried, and pressed to obtain an electrode having a thickness of 75 μm. The density of the obtained electrodes was 0.8 to 1.0 g / cm ³ .

(Impedance)
Using the electrode created above, using an electrochemical measuring device (“1255WB type high-performance electrochemical measuring system” manufactured by Solartron), an amplitude of 10 mV centered on 0 V is applied at 25 ° C, and a frequency of 10 MHz to 1 MHz is applied. The constant voltage AC impedance was measured at the frequency, and the real resistance at frequencies 1k, 1 and 0.1 Hz was measured as the impedance resistance.

(DC resistance value, initial battery capacity and charge / discharge efficiency)
The electrode prepared above was used as the working electrode, and metallic lithium was used as the counter electrode and the reference electrode. As a solvent, propylene carbonate and ethylene glycol dimethyl ether were mixed and used so as to have a volume ratio of 1: 1. LiClO ₄ was dissolved in this solvent at 1 mol / L and used as an electrolyte. A polypropylene film was used for the separator. A coin cell was made in a glove box under an argon atmosphere.
The lithium secondary battery having the above configuration was subjected to a charge / discharge test after measuring the DC resistance value before the initial charge using a charge / discharge test device (“TOSCAT” manufactured by Toyo System Co., Ltd.). Lithium was doped at a rate of 70 mA / g with respect to the mass of the active material, and doped until it reached 1 mV with respect to the lithium potential. Further, a constant voltage of 1 mV was applied to the lithium potential for 8 hours to complete the doping. The capacity (mAh / g) at this time was taken as the charge capacity. Next, dedoping was performed at a rate of 70 mA / g with respect to the mass of the active material until it reached 2.5 V with respect to the lithium potential, and the capacity discharged at this time was defined as the discharge capacity. The percentage of discharge capacity / charge capacity was used as the charge / discharge efficiency (initial charge / discharge efficiency), and was used as an index of the lithium ion utilization efficiency in the battery. The results obtained are shown in Table 2.

The batteries prepared using the carbonaceous materials of Examples 1 to 3 and 5 had a low resistance value, and showed a high discharge capacity and a good charge / discharge efficiency. On the other hand, in the battery manufactured by using the carbonaceous materials of Comparative Examples 1, 3 to 5 , 7, and 8 which do not have a half width in a predetermined range or do not have an oxygen element content in a predetermined range. A sufficiently low resistance value was not achieved, and it could not be said that the discharge capacity and charge / discharge efficiency were sufficient.

Claims (11)

A carbonaceous material for the negative electrode active material of a non-aqueous electrolyte secondary battery, which is a plant-derived carbonaceous material and has a peak near 1360 cm ^-1 in the Raman spectrum observed by laser Raman spectroscopy. A carbonaceous material having a half-price range value of 240 to 280 cm ^-1 and an oxygen element content determined by elemental analysis of 0.40% by weight or less. The hydrogen element content determined by elemental analysis is 0.10% by weight or more, and the ratio _{RH / O} (hydrogen element content / oxygen element content) between the hydrogen element content and the oxygen element content is 0.30. The carbonaceous material according to claim 1, which is the above. The carbonaceous material according to claim 1 or 2, wherein the true density determined by the helium method is 1.20 to 1.50 g / cm ³ , and the specific surface area determined by the BET method is 10 m ² / g or less. The carbonaceous material according to any one of claims 1 to 3, wherein the calcium element content is 50 ppm or less. When the carbonaceous material was doped with lithium until it was fully charged and ⁷ Li nuclear-solid-state NMR analysis was performed, the main resonance was shifted to the low magnetic field side by 115 to 145 ppm with respect to the resonance peak of LiCl, which is the reference material. The carbonaceous material according to any one of claims 1 to 4, wherein a peak is observed. The carbonaceous material according to any one of claims 1 to 5, wherein the true density determined by the butanol method is 1.35 to 1.50 g / cm ³ . A negative electrode for a non-aqueous electrolyte secondary battery containing the carbonaceous material according to any one of claims 1 to 6. The non-aqueous electrolyte secondary battery having the negative electrode for the non-aqueous electrolyte secondary battery according to claim 7. (1) A vapor phase decalcification step of heat-treating a plant-derived char at 1100 to 1300 ° C. in an atmosphere containing a halogen compound and an inert gas to obtain a vapor phase decalcification char, wherein the halogen compound and the inert gas are inert. The amount of gas supplied is 14 L / min or more per 50 g of plant-derived char, and (2) a non-aqueous electrolyte secondary battery including at least a step of subjecting the gas phase decalcified char to a CVD treatment using a hydrocarbon compound. A method for manufacturing a carbonaceous material for a negative electrode active material. Before the gas phase decalcification step,
(A) The method for producing a carbonaceous material according to claim 9, further comprising an alkali imposition step of adding a compound containing an alkali metal element to a plant-derived char to obtain an alkali-impregnated plant-derived char. 9. The method for producing a carbonaceous material according to.

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