JP2019008910A - Hardly graphitizable carbonaceous material for nonaqueous electrolyte secondary battery, negative electrode for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To have a high charge capacity and a high charge/discharge efficiency as well as a high output characteristic due to a low electrode resistance, and a difficult graphite to be used as a negative electrode of a non-aqueous electrolyte secondary battery (for example, a lithium ion battery) to be fully charged and used. To provide a carbonized carbonaceous material. A non-graphitizable carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery that is fully charged, and is based on lithium chloride observed by 7Li nucleus-solid state NMR analysis when fully charged. The main resonance peak position of the chemical shift value is greater than 115 ppm, and the expansion coefficient of the negative electrode containing the non-graphitizable carbonaceous material when fully charged is 107% or less based on the thickness of the negative electrode before charging. Non-graphitizable carbonaceous material. [Selection diagram] None

Description

  The present invention relates to a non-graphitizable carbonaceous material suitable as a negative electrode for a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) that is fully charged, a method for producing the same, a negative electrode for a non-aqueous electrolyte secondary battery, The present invention relates to a charged nonaqueous electrolyte secondary battery.

  Lithium ion secondary batteries are widely used in small portable devices such as mobile phones and laptop computers. The non-graphitizable carbonaceous material is capable of doping (charging) and dedoping (discharging) lithium in an amount exceeding the theoretical capacity of 372 mAh / g of graphite, and also has input / output characteristics, cycle durability and low temperature characteristics. Since it is excellent, it has been developed and used as a negative electrode for lithium ion secondary batteries.

The non-graphitizable carbonaceous material can be obtained using, for example, petroleum pitch, coal pitch, phenol resin, or plant as a carbon source. Among these carbon sources, plants are attracting attention because they are raw materials that can be continuously and stably supplied by cultivation and can be obtained at low cost. Moreover, since the carbonaceous material obtained by baking the plant-derived carbon raw material has many pores, a favorable charge / discharge capacity is expected.
For example, Patent Document 1 and Patent Document 2 describe a carbonaceous material for an electrode of a non-aqueous solvent secondary battery, and describe that the carbonaceous material is obtained by carbonizing a plant-derived organic material. Yes.

In a lithium ion secondary battery, if it exceeds the fully charged state during charging and becomes overcharged, the decomposition reaction of the solvent occurs, the temperature of the lithium ion secondary battery rises, and the reaction at the positive electrode Lithium ions are generated and metal lithium is deposited on the surface of the negative electrode, which cannot be accepted, and the thermal stability of the lithium ion secondary battery is lowered. In order to solve this problem, usually, safety against overcharge is ensured. For example, Patent Document 3 describes a lithium ion secondary battery provided with a current interrupting device, and Patent Document 4 discloses an electrolytic solution for a lithium secondary battery containing an additive that effectively acts on overcharge. A lithium secondary battery with a liquid is described.
On the other hand, in order to ensure safety more reliably, the charging of the lithium ion secondary battery is normally performed until the negative electrode terminal potential based on metallic lithium becomes a predetermined potential of 0 mV or more (for example, 0.5 mA / A method of performing constant current charging (at cm ² ), performing constant voltage charging after the negative electrode terminal potential reaches a predetermined potential, and completing charging when the current value is constant for a predetermined time (for example, at 20 μA) (constant current constant voltage) Act). In this case, actually, even if there is room for accepting lithium ions in the negative electrode, it is not charged until it is fully charged.

JP-A-9-161801 JP-A-10-21919 Japanese Patent Laying-Open No. 2015-88354 JP 2001-15155 A

  On the other hand, in recent years, due to increasing interest in environmental problems, development of lithium ion secondary batteries for in-vehicle applications has been promoted and is being put to practical use. Therefore, there is a need for a non-graphitizable carbonaceous material for producing a lithium ion battery having higher charge capacity and higher charge / discharge efficiency.

  An object of the present invention is to have a high output characteristic due to a low electrode resistance in addition to a high charge capacity and a high charge / discharge efficiency, and is used for a negative electrode of a non-aqueous electrolyte secondary battery (for example, a lithium ion battery) that is fully charged. It is an object of the present invention to provide a non-graphitizable carbonaceous material and a method for producing the same. The subject of the present invention also comprises a negative electrode for a non-aqueous electrolyte secondary battery comprising such a non-graphitizable carbonaceous material, as well as a negative electrode for such a non-aqueous electrolyte secondary battery, and is fully charged. A non-aqueous electrolyte secondary battery is provided.

As a result of intensive studies, the present inventor has found that a non-graphite carbonaceous material that gives a specific ⁷ Li nucleus-solid NMR analysis chemical shift value and a specific electrode expansion coefficient to the negative electrode of a fully charged nonaqueous electrolyte secondary battery. It has been found that the above problems can be solved by using a material, and the present invention has been completed.

That is, the present invention includes the following preferred embodiments.
[1] A non-graphitized carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery to be fully charged, which is based on lithium chloride observed by ⁷ Li nucleus-solid NMR analysis when fully charged. The main resonance peak position of the chemical shift value to be greater than 115 ppm, and the expansion rate at the time of full charge of the negative electrode comprising the non-graphitizable carbonaceous material is 107% or less based on the thickness of the negative electrode before charging, Non-graphitizable carbonaceous material.
[2] The non-graphitizable carbonaceous material according to [1], wherein the oxygen element content is 0.30% by mass or less.
[3] The non-graphitizable carbonaceous material according to [1] or [2], which is derived from a plant-derived carbon precursor.
[4] In any one of the above [1] to [3], an average interplanar spacing d ₀₀₂ of (002) planes calculated using the Bragg equation by a wide-angle X-ray diffraction method is 0.36 to 0.42 nm. The non-graphitizable carbonaceous material described.
[5] The non-graphitizable carbonaceous material according to any one of [1] to [4], wherein the potassium element content is 0.1% by mass or less and the iron element content is 0.02% by mass or less.
[6] The process according to any one of [1] to [5], including a step of acid-treating a plant-derived carbon precursor and a step of firing the acid-treated carbon precursor in an inert gas atmosphere at 1050 ° C. to 1400 ° C. The manufacturing method of the non-graphitizable carbonaceous material in any one.
[7] A negative electrode for a non-aqueous electrolyte secondary battery comprising the non-graphitizable carbonaceous material according to any one of [1] to [5].
[8] A fully charged nonaqueous electrolyte secondary battery comprising a negative electrode for a nonaqueous electrolyte secondary battery comprising a non-graphitizable carbonaceous material, and when fully charged, ⁷ Li nucleus— The main resonance peak position of the chemical shift value based on lithium chloride observed by solid-state NMR analysis is larger than 115 ppm, and the expansion rate at the time of full charge of the negative electrode comprising the non-graphitizable carbonaceous material is A non-aqueous electrolyte secondary battery that is 107% or less based on the thickness of the negative electrode.
[9] The nonaqueous electrolyte secondary battery according to [8], wherein the oxygen element content is 0.30% by mass or less.
[10] The nonaqueous electrolyte secondary battery according to [8] or [9], wherein the non-graphitizable carbonaceous material is derived from a plant-derived carbon precursor.
[11] The [8] to [8] above, wherein the average interplanar spacing d ₀₀₂ of the (002) plane of the non-graphitizable carbonaceous material calculated using the Bragg equation by the wide-angle X-ray diffraction method is 0.36 to 0.42 nm. [10] The nonaqueous electrolyte secondary battery according to any one of [10].
[12] The [8] to [11], wherein the non-graphitizable carbonaceous material has a potassium element content of 0.1% by mass or less, and the non-graphitizable carbonaceous material has an iron element content of 0.02% by mass or less. ] The nonaqueous electrolyte secondary battery in any one of.

  Using the non-graphitizable carbonaceous material of the present invention for the negative electrode and producing a fully charged nonaqueous electrolyte secondary battery, such a nonaqueous electrolyte secondary battery has high charge capacity and high charge / discharge efficiency. In addition, it has high output characteristics due to low electrode resistance.

2 shows a ⁷ Li nucleus-solid NMR diagram of a non-graphitizable carbonaceous material prepared according to Example 1. FIG. The ⁷ Li nucleus-solid NMR figure of the carbonaceous material prepared according to the comparative example 5 is shown.

<Non-graphitizable carbonaceous material>
The non-graphitizable carbonaceous material of the present invention is a non-graphitizable carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery that is fully charged and is observed by ⁷ Li nucleus-solid NMR analysis when fully charged. The main resonance peak position of the chemical shift value based on lithium chloride is greater than 115 ppm, and the expansion rate of the negative electrode comprising the non-graphitizable carbonaceous material when fully charged is based on the thickness of the negative electrode before charging. 107% or less.

In this specification, “used fully charged” means that a non-aqueous electrolyte secondary battery is assembled using a negative electrode including a non-graphitizable carbonaceous material and a positive electrode including lithium, and deposition of metallic lithium is performed. ⁷ Li core is charged (doped) with lithium until just before it is confirmed by solid-state NMR analysis, and is usually charged to a range of 580 to 700 mAh / g per unit mass of the negative electrode active material at a constant current value. Means that. Therefore, it has a completely different meaning from the case where the charging is completed by the conventional constant current constant voltage method as described above. Note that the charge capacity of the negative electrode when lithium was charged to the negative electrode until just before the precipitation of metallic lithium was confirmed by ⁷ Li nucleus-solid NMR analysis was the discharge capacity or charge relative to the charge capacity at which lithium precipitation was confirmed. From the viewpoint of keeping the discharge efficiency high, it is preferably set at 80 to 98%, more preferably set at 85 to 95%, and particularly preferably set at 88 to 92%.

<Main resonance peak position of chemical shift value>
Regarding the non-graphitizable carbonaceous material of the present invention, the chemical shift value based on lithium chloride observed when lithium is charged (dope) until it is fully charged and ⁷ Li nucleus-solid NMR analysis is performed. The main resonance peak position is greater than 115 ppm, preferably greater than 117 ppm, more preferably greater than 119 ppm.

  The main resonance peak position of the chemical shift value based on lithium chloride is larger than 115 ppm, that is, the above main resonance peak position is observed on the lower magnetic field side than 115 ppm. It means that the storage amount of lithium is large, that is, the charging capacity of the battery is high. The occluded clustered lithium is reversible lithium that can be discharged (dedoped) from the non-graphitizable carbonaceous material, and the fact that the occluded amount of clustered lithium in the non-graphitizable carbonaceous material is large. This means that the charge / discharge efficiency calculated from “capacity / charge capacity” is high.

  High charge / discharge efficiency means that there is little loss of lithium in the negative electrode due to side reactions during charge / discharge. If the loss of lithium in the negative electrode is small, there is no need to use the positive electrode excessively and supplement lithium with the negative electrode, which is advantageous in terms of capacity per battery volume and cost.

  The carbonaceous material having a main resonance peak position of a chemical shift value based on lithium chloride of 115 ppm or less has a high charge capacity as in the non-graphitizable carbonaceous material of the present invention because the amount of occlusion of clustered lithium is small. It is extremely difficult to provide both high charge / discharge efficiency.

In order to adjust the main resonance peak position to a value larger than the above value, for example, a material containing carbon is removed at a temperature of 1050 ° C. to 1400 ° C. while actively removing pyrolysis gas such as carbon monoxide and hydrogen. A non-graphitizable carbonaceous material produced by firing in an active gas atmosphere may be used for the negative electrode. Details of the ⁷ Li nucleus-solid NMR analysis are as described in the examples.

<Expansion coefficient of electrode>
The expansion rate of the negative electrode comprising the non-graphitizable carbonaceous material of the present invention when fully charged is 107% or less based on the thickness of the negative electrode before charging. When the expansion coefficient exceeds 107%, contact failure between the active materials occurs in the electrode, and the electrode resistance becomes high. Therefore, a non-aqueous electrolyte secondary battery having good output characteristics (high discharge capacity retention rate) is obtained. Absent.
The expansion coefficient is preferably 106% or less, particularly preferably 105% or less. When the expansion coefficient is less than or equal to the above upper limit value, it is easy to ensure good conduction paths and lithium ion diffusion between the active materials (non-graphitizable carbonaceous materials) in the electrode, so that low electrode resistance is easily obtained and good Easy output characteristics.

  In order to adjust the electrode expansion coefficient to the above value or less, for example, in an inert gas atmosphere at 1050 ° C. to 1400 ° C. while actively removing pyrolysis gas such as carbon monoxide and hydrogen from a material containing carbon. What is necessary is just to use the non-graphitizable carbonaceous material manufactured by baking with a negative electrode. In the negative electrode comprising the non-graphitizable carbonaceous material manufactured by the above method, many lithium ions are charged not only between the carbon crystal layers but also in the gaps between the carbon crystals, so that the lithium ions are charged only between the carbon crystal layers. It is thought that the electrode expansion coefficient is significantly smaller than the conventional negative electrode. The details of the measurement of the expansion coefficient are as described in the examples.

<Oxygen element content>
The lower the oxygen element content of the non-graphitizable carbonaceous material of the present invention, the better. The oxygen element content is preferably 0.30% by mass or less, more preferably 0.28% by mass or less. More preferably, the non-graphitizable carbonaceous material contains substantially no oxygen element. Here, “substantially free of oxygen element” means that the oxygen element content is 10 ⁻⁶ % by mass, which is the detection limit of the method for measuring the oxygen element content (inert gas melting-non-dispersed infrared absorption method) described later. It means the following. When the oxygen element content is less than the above value, the lithium ion is consumed due to the reaction between lithium ions and oxygen, the use efficiency of lithium ions is reduced, oxygen attracts moisture in the air, and water is adsorbed. Reduction in utilization efficiency of lithium ions due to not easily desorbing, generation of gas in the electrode due to side reaction caused by moisture, and increase in electrode expansion coefficient due to the generation of gas (increase in electrode resistance, decrease in output characteristics) Is easily suppressed.

  A method for adjusting the oxygen element content to the above value or less is not limited. For example, a carbon precursor of plant origin is acid-treated at a predetermined temperature, mixed with a volatile organic substance, and baked in an inert gas atmosphere at a temperature of 1050 ° C. to 1400 ° C. The following can be adjusted. Details of the measurement of the oxygen element content are as described in the examples.

<Plant-derived carbon precursor>
The hardly graphitized carbonaceous material of the present invention is preferably derived from a plant-derived carbon precursor. In the present invention, “plant-derived carbon precursor” means a plant-derived material before carbonization, or a plant-derived material after carbonization (char derived from plants). The plant as a raw material (hereinafter sometimes referred to as “plant raw material”) is not particularly limited. Examples include coconut shells, peas, tea leaves, sugar cane, fruits (eg, tangerines, bananas), cocoons, rice husks, hardwoods, conifers, and bamboo. Examples of this include waste (e.g. used tea leaves) after subjecting it to its intended use, or part of a plant material (e.g. banana or tangerine peel). These plants can be used alone or in combination of two or more. Among these plants, coconut shells that are easily available in large quantities are preferred.

  The coconut shell is not particularly limited. For example, palm coconut (coconut palm), coconut palm, salak or coconut palm can be mentioned. These coconut shells can be used alone or in combination. Coconut palm and palm palm coconut shells, which are biomass wastes that are used as foods, detergent raw materials, biodiesel oil raw materials and the like and are generated in large quantities, are particularly preferable.

  The method for carbonizing the plant material, that is, the method for producing the plant-derived char is not particularly limited. For example, it is performed by heat-treating the plant material in an inert gas atmosphere of 300 ° C. or higher (hereinafter sometimes referred to as “temporary firing”).

  It can also be obtained in the form of char (eg, coconut shell char).

As a raw material of the non-graphitizable carbonaceous material of the present invention, by using a carbon precursor having moderate microvoids of plant origin, micropores capable of occluding a large amount of clustered lithium inside the non-graphitizable carbonaceous material. It is formed. In addition, the low expansion coefficient of the electrode containing the non-graphitizable carbonaceous material of the present invention is that many micropores of the non-graphitizable carbonaceous material cause the volume change of the electrode active material accompanying charge / discharge. Partial absorption is considered to be contributing.

<Average surface distance _d002 >
The non-graphitizable carbonaceous material of the present invention preferably has an average interplanar spacing d ₀₀₂ of (002) plane of 0.36 nm to 0.42 nm calculated using the Bragg equation by wide-angle X-ray diffraction. It is more preferably 0.38 nm to 0.40 nm, and particularly preferably 0.381 nm to 0.389 nm. When the average interplanar spacing d ₀₀₂ of the (002) plane is within the above range, the lithium ion battery has an increased resistance when lithium ions are inserted into the carbonaceous material or an increased output resistance. It is easy to suppress the deterioration of input / output characteristics. In addition, a decrease in stability as a battery material due to the repeated expansion and contraction of the non-graphitizable carbonaceous material is easily suppressed. Furthermore, although the diffusion resistance of lithium ions is reduced, a decrease in effective capacity per volume due to an increase in the volume of the non-graphitizable carbonaceous material is easily avoided. In order to adjust the average spacing to the above range, for example, the carbon precursor that gives the non-graphitizable carbonaceous material may be fired at a temperature in the range of 1050 to 1400 ° C. Moreover, the method of baking by mixing with thermally decomposable resin, such as a polystyrene, and the method of giving CVD processing, such as hydrocarbon gas, to the non-graphitizable carbonaceous material baked at 1050-1400 degreeC can also be used. Here, the details of the measurement of the average surface distance _d002 are as described in the examples.

<True density ρ _Bt >
The non-graphitizable carbonaceous material of the present invention preferably has a true density ρ _Bt by the butanol method of 1.40 to 1.70 g / cm ³ from the viewpoint of increasing the capacity per mass in the battery. more preferably 42~1.65g / cm ^3, particularly preferably 1.44~1.60g / cm ^3. The true density in the above range can be obtained, for example, by setting the firing process temperature when producing a non-graphitizable carbonaceous material from plant raw materials to 1050 to 1400 ° C. Here, the details of the measurement of the true density ρ _Bt are as described in the examples.

<Potassium element content and iron element content>
The potassium element content of the non-graphitizable carbonaceous material of the present invention is preferably 0.1% by mass or less from the viewpoint of increasing the dedoping capacity and decreasing the non-dedoping capacity, and is 0.05% by mass. More preferably, it is more preferably 0.03% by mass or less. It is particularly preferred that the non-graphitizable carbonaceous material contains substantially no potassium element. Further, the iron element content of the non-graphitizable carbonaceous material of the present invention is preferably 0.02% by mass or less from the viewpoint of increasing the dedoping capacity and decreasing the non-dedoping capacity, The content is more preferably at most mass%, further preferably at most 0.01 mass%. It is particularly preferable that the non-graphitizable carbonaceous material contains substantially no iron element. Here, the phrase “substantially containing no potassium element or iron element” means that the potassium element content or the iron element content is determined by the fluorescent X-ray analysis described later (for example, analysis using “LAB CENTER XRF-1700” manufactured by Shimadzu Corporation). It means that it is below the detection limit value. When the potassium element content and the iron element content are not more than the above values, sufficient dedoping capacity and undoping capacity are easily obtained in the nonaqueous electrolyte secondary battery using the non-graphitizable carbonaceous material. Furthermore, it is easy to avoid the safety problem of the nonaqueous electrolyte secondary battery resulting from short-circuiting when these metal elements are eluted and re-deposited in the electrolytic solution. Details of the measurement of the potassium element content and the iron element content are as described in the examples.

<Moisture absorption>
The moisture absorption of the non-graphitizable carbonaceous material of the present invention is preferably 10,000 ppm or less, more preferably 9000 ppm or less, and particularly preferably 8000 ppm or less. The smaller the moisture absorption amount, the more the moisture adsorbed on the non-graphitizable carbonaceous material decreases, and the more lithium ions adsorbed on the non-graphitizable carbonaceous material increase. Further, it is preferable that the amount of moisture absorption is small because self-discharge due to the reaction between adsorbed moisture and lithium ions can be reduced, and further, side reaction products and gas generation due to the reaction between adsorbed moisture and lithium ions can be suppressed. The moisture absorption amount of the non-graphitizable carbonaceous material can be reduced, for example, by reducing the amount of oxygen atoms contained in the non-graphitizable carbonaceous material. The moisture absorption of the non-graphitizable carbonaceous material is measured using, for example, a Karl Fischer. Details of the measurement of the amount of moisture absorption are as described in the examples.

<Specific surface area>
Non-graphitizable carbonaceous material of the present invention has a specific surface area determined by nitrogen adsorption BET3 point method is preferably from 1~75m ² / g, more preferably 2~60m ² / g, 3~ Particularly preferred is 50 m ² / g. When the specific surface area is within the above range, in a non-aqueous electrolyte secondary battery manufactured using a non-graphitizable carbonaceous material, lithium ions are suppressed while excessive side reaction between the electrolyte and the non-graphitizable carbonaceous material is suppressed. Is easy to be doped into the non-graphitizable carbonaceous material, and furthermore, the contact area for dedoping lithium ions from the non-graphitizable carbonaceous material is likely to be kept high, so that both high charge capacity and high output characteristics are easily achieved. The specific surface area can be adjusted, for example, by controlling the temperature of the decalcification step described later.

<Method for producing non-graphitizable carbonaceous material>
The method for producing a non-graphitizable carbonaceous material of the present invention comprises a step of acid-treating a plant-derived carbon precursor, and a step of firing the acid-treated carbon precursor in an inert gas atmosphere at 1050 ° C. to 1400 ° C. Including.

<Plant-derived carbon precursor>
The “plant-derived carbon precursor” means a plant-derived material before carbonization or a plant-derived material after carbonization (char derived from plants) as described above. The plant (plant raw material) used as a raw material is not specifically limited. Plants as exemplified above can be used alone or in combination of two or more. Among these, coconut shells that can be easily obtained in large quantities are preferable.

  The coconut shell is not particularly limited. The coconut shells as exemplified above can be used alone or in combination. Coconut palm and palm palm coconut shells, which are used as foods, detergent raw materials, biodiesel oil raw materials and the like and are biomass wastes generated in large quantities, are particularly preferable.

  The method for carbonizing the plant material, that is, the method for producing the plant-derived char is not particularly limited. For example, it is performed by calcining a plant material in an inert gas atmosphere at 300 ° C. or higher.

  It can also be obtained in the form of char (eg, coconut shell char).

  Generally, plant raw materials include alkali metal elements (eg, potassium and sodium), alkaline earth metal elements (eg, magnesium and calcium), transition metal elements (eg, iron and copper), and non-metallic elements (eg, phosphorus). Contains a lot. When such a non-graphitizable carbonaceous material containing a large amount of metal elements and non-metal elements is used as the negative electrode, it may adversely affect the electrochemical characteristics and safety of the non-aqueous electrolyte secondary battery.

<Acid treatment>
Therefore, the method for producing a hardly graphitized carbonaceous material of the present invention includes a step of acid-treating a plant-derived carbon precursor. Here, reducing the content of the metal element and / or the non-metal element in the carbon precursor by acid treatment of the plant-derived carbon precursor is hereinafter also referred to as decalcification.

  The acid treatment method, that is, the decalcification method is not particularly limited. For example, a method of extracting and demineralizing metal using acidic water containing mineral acid such as hydrochloric acid or sulfuric acid, or organic acid such as acetic acid or formic acid (liquid phase demineralization), or containing halogen compounds such as hydrogen chloride A method of deashing by exposing to a high temperature gas phase (vapor phase deashing) can be used.

<Liquid phase demineralization>
In liquid phase demineralization, a plant-derived carbon precursor is immersed in an organic acid aqueous solution, and an alkali metal element, an alkaline earth metal element, a transition metal element and / or a non-metal element is extracted from the plant-derived carbon precursor. It is preferable to remove by elution.

  When carbonaceous plant-derived carbon precursors containing these metal elements are carbonized, carbon necessary for carbonization may be decomposed. Further, since non-metallic elements such as phosphorus are easily oxidized, the degree of oxidation on the surface of the carbide changes and the properties of the carbide change greatly, which is not preferable. Furthermore, when liquid phase decalcification is performed after carbonizing the carbon precursor, phosphorus, calcium, magnesium, potassium and iron may not be sufficiently removed. Further, depending on the content of the metal element and / or non-metal element in the carbide, the liquid-phase deashing time and the remaining amount of the metal element and / or non-metal element in the carbide after the liquid-phase deashing vary greatly. Therefore, it is preferable that the content of the metal element and / or non-metal element in the carbon precursor is sufficiently removed before carbonization. That is, in liquid phase decalcification, it is preferable to use a plant-derived material before carbonization as a “plant precursor carbon precursor”.

  It is preferable that the organic acid used in the liquid phase decalcification does not contain an element serving as an impurity source such as phosphorus, sulfur and halogen. When the organic acid does not contain elements such as phosphorus, sulfur and halogen, it is suitable as a carbon material even if the water precursor after liquid phase decalcification is omitted and the carbon precursor in which the organic acid remains is carbonized. This is advantageous because a carbide that can be used for the above is obtained. Further, it is advantageous because the waste liquid treatment of the organic acid after use can be performed relatively easily without using a special apparatus.

  Examples of organic acids include saturated carboxylic acids such as formic acid, acetic acid, propionic acid, oxalic acid, tartaric acid and citric acid, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and fumaric acid Carboxylic acids such as benzoic acid, phthalic acid and naphthoic acid. Acetic acid, oxalic acid and citric acid are preferred from the viewpoint of availability, corrosion due to acidity, and influence on human body.

  In the present invention, the organic acid is mixed with an aqueous solution and used as an organic acid aqueous solution from the viewpoints of solubility of the eluted metal compound, waste disposal, environmental compatibility, and the like. Examples of the aqueous solution include water and a mixture of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent include alcohols such as methanol, ethanol, propylene glycol, and ethylene glycol.

  The concentration of the acid in the organic acid aqueous solution is not particularly limited. The concentration can be adjusted according to the type of acid used. In the present invention, usually 0.001% to 20% by mass, more preferably 0.01% to 18% by mass, and particularly preferably 0.02% to 15% by mass based on the total amount of the organic acid aqueous solution. An organic acid aqueous solution having an acid concentration in the range is used. If the acid concentration is within the above range, an appropriate metal element and / or nonmetal element elution rate can be obtained, so that liquid phase deashing can be performed in a practical time. Moreover, since the residual amount of acid in the carbon precursor is reduced, the influence on the subsequent product is also reduced.

  The pH of the organic acid aqueous solution is preferably 3.5 or less, more preferably 3 or less. When the pH of the aqueous organic acid solution is not more than the above value, the removal of the metallic element and / or the nonmetallic element is efficiently performed without decreasing the dissolution rate of the metallic element and / or the nonmetallic element in the aqueous organic acid solution. Easy to be done.

  The temperature of the organic acid aqueous solution when dipping the carbon precursor is not particularly limited. Preferably it is 45 to 120 ° C, more preferably 50 to 110 ° C, particularly preferably 60 to 100 ° C. If the temperature of the organic acid aqueous solution at the time of immersing the carbon precursor is within the above range, the decomposition of the acid to be used is suppressed, and the liquid element deashing can be performed in a practical time. It is preferable because the elution rate is easily obtained. Moreover, it is preferable because liquid phase demineralization can be easily performed without using a special apparatus.

  The time for immersing the carbon precursor in the organic acid aqueous solution can be appropriately adjusted according to the acid used. In the present invention, the immersion time is usually in the range of 1 to 100 hours, preferably 2 to 80 hours, more preferably 2.5 to 50 hours, from the viewpoint of economy and decalcification efficiency.

  The ratio of the mass of the carbon precursor to be immersed with respect to the mass of the organic acid aqueous solution can be appropriately adjusted according to the type, concentration and temperature of the organic acid aqueous solution to be used, and is usually 0.1% by mass to 200% by mass. The range is preferably 1% by mass to 150% by mass, and more preferably 1.5% by mass to 120% by mass. If it is in the said range, since the metal element and / or nonmetallic element which were eluted to organic acid aqueous solution are hard to precipitate from organic acid aqueous solution, and reattachment to a carbon precursor is easy to be suppressed, it is preferable. Moreover, if it is in the said range, since volume efficiency becomes appropriate, it is preferable from an economical viewpoint.

  It does not specifically limit as atmosphere which performs liquid phase demineralization, According to the method used for immersion, you may differ. In the present invention, liquid phase demineralization is usually performed in an air atmosphere.

  These operations may be repeated preferably 1 to 8 times, more preferably 2 to 5 times.

  In this invention, you may perform a washing | cleaning process and / or a drying process as needed after liquid phase demineralization.

<Gas phase demineralization>
As the vapor phase decalcification, it is preferable to heat-treat the plant-derived carbon precursor in a vapor phase containing a halogen compound. In vapor phase deashing, if a pyrogenic reaction of a plant-derived carbon precursor is accompanied during heat treatment, the efficiency of vapor phase demineralization is reduced due to the generation of pyrolysis components, and the heat treatment components cause the inside of the heat treatment apparatus to Contaminated and may interfere with stable operation. From these viewpoints, it is preferable to use a plant-derived material after carbonization as the “plant-derived carbon precursor”.

  The halogen compound used in the gas phase deashing is not particularly limited. For example, fluorine, chlorine, bromine, iodine, hydrogen fluoride, hydrogen chloride, hydrogen bromide, iodine bromide, chlorine fluoride (ClF), iodine chloride (ICl), iodine bromide (IBr), bromine chloride (BrCl) And mixtures thereof can be used. A compound that generates these halogen compounds by thermal decomposition, or a mixture thereof can also be used. From the viewpoint of supply stability and stability of the halogen compound used, it is preferable to use hydrogen chloride.

  In vapor phase deashing, a halogen compound and an inert gas may be mixed and used. An inert gas will not be specifically limited if it is a gas which does not react with the carbon component which comprises the carbon precursor of plant origin. For example, nitrogen, helium, argon, krypton, or a mixed gas thereof can be used. From the viewpoint of supply stability and economy, it is preferable to use nitrogen.

  In the gas phase deashing, the mixing ratio of the halogen compound and the inert gas is not limited as long as sufficient deashing can be achieved. For example, from the viewpoint of safety, economy, and persistence in the carbon precursor, the amount of the halogen compound with respect to the inert gas is preferably 0.01 to 10.0% by volume, more preferably 0.05. It is -8.0 volume%, Most preferably, it is 0.1-5.0 volume%.

  The temperature of the vapor phase demineralization may vary depending on the plant-derived carbon precursor to be demineralized, but from the viewpoint of easily obtaining the desired oxygen element content and specific surface area, for example, 500 to 950 ° C., preferably Is 600 to 940 ° C, more preferably 650 to 940 ° C, and particularly preferably 850 to 930 ° C. When the deashing temperature is within the above range, good deashing efficiency is obtained, and the deashing is easily performed sufficiently, and activation by the halogen compound is easily avoided.

  The time for vapor phase demineralization is not particularly limited. From the viewpoint of the economic efficiency of the reaction equipment and the carbon structure retention, it is, for example, 5 to 300 minutes, preferably 10 to 200 minutes, more preferably 20 to 150 minutes.

  The average particle diameter of the plant-derived carbon precursor to be subjected to vapor phase demineralization is not particularly limited. If the average particle size is too small, it may be difficult to separate the vapor phase containing removed potassium and the carbon precursor of plant origin, so the lower limit of the average particle size is preferably 100 μm or more. 300 μm or more is more preferable, and 500 μm or more is particularly preferable. The upper limit of the average value of the particle diameter is preferably 10,000 μm or less, more preferably 8000 μm or less, and particularly preferably 5000 μm or less from the viewpoint of the fluidity of the carbon precursor in the mixed gas stream. Here, the details of the measurement of the average particle diameter are as described in the examples.

  The apparatus used for vapor phase demineralization is not particularly limited as long as it can be heated while mixing a carbon precursor derived from a plant and a vapor phase containing a halogen compound. For example, using a fluidized furnace, a continuous or batch type in-bed flow system using a fluidized bed or the like can be used. The supply amount (flow amount) of the gas phase is not particularly limited. From the viewpoint of the fluidity of the carbon precursor in the mixed gas stream, for example, the gas phase is preferably 1 mL / min or more, more preferably 5 mL / min or more, particularly preferably 10 mL / min or more per 1 g of the carbon precursor of plant origin. Supply.

  In vapor phase deashing, after heat treatment in an inert gas atmosphere containing a halogen compound (hereinafter sometimes referred to as “halogen heat treatment”), further heat treatment in the absence of a halogen compound (hereinafter referred to as “vapor phase”). It is preferable to perform “deoxidation treatment”. Since halogen is contained in the plant-derived carbon precursor by the halogen heat treatment, it is preferable to remove the halogen contained in the plant-derived carbon precursor by gas phase deoxidation treatment. Specifically, the gas phase deoxidation treatment is usually performed at 500 ° C. to 940 ° C., preferably 600 to 940 ° C., more preferably 650 to 940 ° C., and particularly preferably 850 in an inert gas atmosphere containing no halogen compound. The heat treatment is performed at ˜930 ° C. The temperature of this heat treatment is preferably the same as or higher than the temperature of the preceding halogen heat treatment. For example, after the halogen heat treatment, the vapor phase deoxidation treatment can be performed by performing the heat treatment while shutting off the supply of the halogen compound. Further, the time for the vapor phase deoxidation treatment is not particularly limited. It is preferably 5 minutes to 300 minutes, more preferably 10 minutes to 200 minutes, and particularly preferably 10 minutes to 100 minutes.

  The acid treatment in the present invention is to remove (decalcify) potassium and / or iron contained in the plant-derived carbon precursor. The potassium element content contained in the plant-derived carbon precursor obtained after the acid treatment is preferably reduced to 0.1% by mass or less, more preferably 0.05% by mass or less, and further preferably 0.03% by mass or less. The Particularly preferably, the potassium element content is reduced to such an extent that the hardly graphitized carbonaceous material does not substantially contain. Further, the content of iron element contained in the carbon precursor obtained after the acid treatment is preferably 0.02% by mass or less, more preferably 0.015% by mass or less, and further preferably 0.01% by mass or less. . Particularly preferably, the iron element content is reduced to such an extent that the hardly graphitized carbonaceous material does not substantially contain. Here, the phrase “substantially containing no potassium element or iron element” means that the potassium element content or the iron element content is determined by the fluorescent X-ray analysis described later (for example, analysis using “LAB CENTER XRF-1700” manufactured by Shimadzu Corporation). It means that it is below the detection limit value. If the potassium element content and the iron element content are less than the above values, as described above, sufficient dedoping capacity and undoping capacity are easily obtained, and safety problems of nonaqueous electrolyte secondary batteries are avoided. Easy to be. Details of the measurement of the potassium element content and the iron element content are as described in the examples.

  In the acid treatment in the present invention, a part of the carbon component is removed simultaneously with deashing. Specifically, in the case of liquid phase deashing, a part of the carbon component is removed by elution, and in the case of gas phase deashing, a part of the carbon component is removed by chlorine activation. This removed portion provides an occlusion point for clustered lithium after the firing step described below.

  In the present invention, the acid treatment is performed at least once. The acid treatment may be performed twice or more using the same or different acids.

  The plant-derived carbon precursor that is the subject of acid treatment is a plant-derived material before carbonization or a plant-derived material after carbonization, but when acid treatment is performed by liquid phase decalcification, an increase in elution of carbon components, That is, from the viewpoint of increasing the lithium occlusion point, it is preferable to perform liquid phase decalcification on the plant raw material itself before carbonization.

  If the carbon precursor after acid treatment is a carbon precursor that has not been subjected to carbonization treatment, that is, if it is a carbon precursor after acid treatment of the plant raw material before carbonization, then carbonization treatment is performed. . The carbonization method is not particularly limited as described above. For example, it is performed by pre-baking an acid-treated plant material before carbonization in an inert gas atmosphere of 300 ° C. or higher.

  Plant-derived carbon precursors are pulverized and classified as necessary, and the average particle size thereof is adjusted. The pulverization step and the classification step are preferably performed after the acid treatment.

<Crushing>
In the pulverization step, the plant-derived carbon precursor is preferably pulverized so that the average particle size after the calcination step is in the range of, for example, 1 to 30 μm, from the viewpoint of coatability during electrode production. That is, the average particle diameter (Dv ₅₀ ) of the non-graphitizable carbonaceous material of the present invention is adjusted to be in the range of 1 to 30 μm, for example. When the average particle diameter of the non-graphitizable carbonaceous material is 1 μm or more, the fine powder increases, the specific surface area increases, the reactivity with the electrolyte increases, and the irreversible capacity is the capacity that does not discharge even when charged. , And the tendency of increasing the proportion of wasted positive electrode capacity tends to be suppressed. In addition, when a negative electrode is produced using the obtained non-graphitizable carbonaceous material, it is easy to ensure sufficient gaps formed between the carbonaceous materials, and good migration of lithium ions in the electrolyte is ensured. Cheap. The average particle diameter (Dv ₅₀ ) of the carbonaceous material of the present invention is preferably 1 μm or more, more preferably 1.5 μm or more, and particularly preferably 2 μm or more. On the other hand, it is preferable that the average particle diameter is 30 μm or less because the diffusion free process of lithium ions in the particles is small and rapid charge / discharge is likely to be possible. Further, in the lithium ion secondary battery, it is important to increase the electrode area for improving the input / output characteristics. For this reason, it is necessary to reduce the coating thickness of the active material on the current collector plate during electrode preparation. In order to reduce the coating thickness, it is necessary to reduce the average particle diameter of the active material. From such a viewpoint, the average particle size is preferably 30 μm or less, more preferably 19 μm or less, still more preferably 17 μm or less, still more preferably 16 μm or less, and particularly preferably 15 μm or less.

  In addition, the carbon precursor of plant origin contracts by about 0 to 20% depending on the conditions of the main firing described later. Therefore, in order for the average particle diameter after firing to be 1 to 30 μm, the average particle diameter of the plant-derived carbon precursor is 0 to 20% larger than the desired average particle diameter after firing. It is preferable to adjust so that it may become a diameter. Therefore, the average particle size after pulverization is preferably 1 to 36 μm, more preferably 1 to 22.8 μm, still more preferably 1 to 20.4 μm, still more preferably 1 to 19.2 μm, and particularly preferably 1 to 18 μm. It is preferable to perform pulverization.

  Since the carbon precursor does not dissolve even when the firing step described later is performed, the order of the pulverization step is not particularly limited. In view of the recovery rate (yield) of the carbon precursor in the acid treatment, it is preferable to carry out after the acid treatment, and from the viewpoint of sufficiently reducing the specific surface area of the carbonaceous material, it may be carried out before the firing step. preferable. However, it is not excluded to perform the pulverization step before the acid treatment or after the baking step.

  The crusher used for a crushing process is not specifically limited. For example, a jet mill, a ball mill, a hammer mill, a mixer mill, a bead mill or a rod mill can be used. From the viewpoint of generating less fine powder, a jet mill having a classification function is preferable. When using a ball mill, a hammer mill, a mixer mill, a bead mill, a rod mill or the like, fine powder can be removed by classification after the pulverization step.

<Classification>
By the classification step, the average particle diameter of the carbonaceous material can be adjusted more accurately. For example, particles having a particle diameter of less than 1 μm can be removed.

  When removing particles having a particle diameter of less than 1 μm by classification, it is preferable that the content of particles having a particle diameter of less than 1 μm is 3% by volume or less in the non-graphitizable carbonaceous material of the present invention. The removal of particles having a particle diameter of less than 1 μm is not particularly limited as long as it is performed after pulverization, but it is preferably performed simultaneously with classification in pulverization. In the non-graphitizable carbonaceous material of the present invention, the content of particles having a particle size of less than 1 μm is 3% by volume or less from the viewpoint of suppressing side reactions between the electrolyte and the non-graphitizable carbonaceous material and reducing the irreversible capacity. It is preferable that it is 2.5 volume% or less, and it is especially preferable that it is 2.0 volume% or less.

  The classification method is not particularly limited. Examples include classification using a sieve, wet classification, or dry classification. Examples of the wet classifier include a classifier using a principle such as gravity classification, inertia classification, hydraulic classification, or centrifugal classification. Examples of the dry classifier include a classifier using a principle such as sedimentation classification, mechanical classification, or centrifugal classification.

  The pulverization step and the classification step can be performed using one apparatus. For example, the pulverization step and the classification step can be performed using a jet mill having a dry classification function. Furthermore, an apparatus in which the pulverizer and the classifier are independent can be used. In this case, pulverization and classification can be performed continuously, but pulverization and classification can also be performed discontinuously.

<Baking>
After optionally pulverizing and classifying, the non-graphitizable carbonaceous material of the present invention can be produced by firing the carbon precursor that has been subjected to acid treatment and carbonization treatment. The firing step is a step of firing at a firing temperature after the temperature is raised from room temperature to a predetermined firing temperature. The carbon precursor may be calcined at (a) 1050 to 1400 ° C. (main calcining), or the carbon precursor is calcined at (b) less than 350 to 1050 ° C. (preliminary calcining), and then further 1050 After baking at 1400 ° C. (main baking) or (c) baking at 1050 to 1400 ° C. (main baking), heat treatment (CVD processing) at 500 to 1000 ° C. in an inert gas atmosphere containing a hydrocarbon compound. Good. Below, an example of the procedure of preliminary baking, main baking, and a CVD process is demonstrated in order.

<Pre-baking>
The preliminary firing step in the method for producing a non-graphitizable carbonaceous material of the present invention can be performed, for example, by firing a carbon precursor subjected to acid treatment and carbonization treatment at a temperature of less than 350 to 1050 ° C. By removing volatile components (for example, CO ₂ , CO, CH _4, H _2, etc.) and tar components by pre-calcination, their generation in the main calcination can be reduced, and the burden on the calciner can be reduced. The pre-baking temperature is usually less than 350 to 1050 ° C, preferably less than 400 to 1050 ° C. Pre-baking can be performed according to a normal pre-baking procedure. Specifically, the preliminary firing can be performed in an inert gas atmosphere, and examples of the inert gas include nitrogen or argon. Pre-baking can also be performed under reduced pressure, for example, 10 KPa or less. The pre-baking time is not particularly limited, and is usually 0.5 to 10 hours, preferably 1 to 5 hours.

  In addition, when pre-baking is performed in the method for producing a non-graphitizable carbonaceous material of the present invention, it is considered that the carbon precursor is covered with a tar component and a hydrocarbon gas in the pre-baking step. This carbonaceous film is considered to favorably reduce the specific surface area of the non-graphitizable carbonaceous material.

<Main firing>
The main-firing step in the method for producing a non-graphitizable carbonaceous material of the present invention can be performed according to a normal main-firing procedure, and a non-graphitizable carbonaceous material is obtained after the main-firing.

  The main firing temperature is usually from 1050 to 1400 ° C, preferably from 1100 to 1380 ° C, more preferably from 1150 to 1350 ° C. The main firing can be performed in an inert gas atmosphere, and examples of the inert gas include nitrogen and argon. In addition, the main baking can be performed in an inert gas containing a halogen gas. Furthermore, the main firing can be performed under reduced pressure, for example, at 10 KPa or less.

  When the carbon precursor is heat-treated in the main firing step, gases such as carbon monoxide and hydrogen are generated from the carbon precursor itself. These gases are highly reactive, and in order to destroy voids between carbon crystals that can occlude clustered lithium, it is important to control the reaction between the gas generated during the heat treatment and the carbon precursor. For example, in WO2017 / 022486, a non-graphitizable carbonaceous material that can occlude a larger amount of clustered lithium during charging is obtained by performing heat treatment after performing vapor phase decalcification or liquid phase demineralization. Although it is possible to obtain a carbonaceous material for a non-aqueous electrolyte secondary battery having high charge capacity and high charge / discharge efficiency by WO2017 / 022486, the present invention further positively removes pyrolysis gas during firing. Thus, it has been found that higher output characteristics can be obtained. The method of firing while actively removing the pyrolysis gas from the carbon precursor is not particularly limited. For example, the heat treatment is performed by increasing the supply amount of the inert gas during the firing, or the sample at the time of the firing is prepared. There is a method of positively removing the gas staying in the sample by reducing the stacking height. By these methods, it is possible to remove the reactive gas generated from the carbon precursor itself before reacting with the carbon precursor. Therefore, a non-graphitizable carbonaceous material having a more controlled carbon structure can be produced. The time for the main baking is not particularly limited, and is, for example, 0.05 to 10 hours, preferably 0.05 to 8 hours, and more preferably 0.05 to 6 hours.

  In the present invention, when the carbon precursor is fired, it can be fired by mixing with a volatile organic substance. The specific surface area of the non-graphitizable carbonaceous material obtained from the carbon precursor by mixing with a volatile organic substance and firing is more suitable for a nonaqueous electrolyte secondary battery, for example, a negative electrode for a lithium ion secondary battery. It can be.

<Volatile organic matter>
The volatile organic substance that can be used in the present invention is a volatile organic substance that is solid at room temperature when it is incinerated at 800 ° C. and the residual carbon ratio is less than 5% by mass based on the mass of the volatile organic substance before incineration. Although it does not specifically limit, What generate | occur | produces the volatile substance (For example, hydrocarbon type gas and a tar component) which can reduce the specific surface area of the non-graphitizable carbonaceous material manufactured from a carbon precursor is preferable. Although the content of the volatile substance capable of reducing the specific surface area in the volatile organic substance is not particularly limited, it is usually 1 to 20% by mass, preferably 3 to 15% by mass based on the mass of the volatile organic substance. %. In addition, in this specification, normal temperature refers to 25 degreeC.

  Examples of volatile organic substances include thermoplastic resins and low molecular organic compounds. More specifically, examples of the thermoplastic resin include polystyrene, polyethylene, polypropylene, poly (meth) acrylic acid or poly (meth) acrylic acid ester, and low molecular organic compounds include toluene, xylene, mesitylene, Examples thereof include styrene, naphthalene, phenanthrene, anthracene, and pyrene. In view of not volatilizing and oxidatively activating the surface of the carbon precursor when pyrolyzed at the firing temperature, the thermoplastic resin is preferably polystyrene, polyethylene or polypropylene, and the low molecular organic compound is naphthalene, phenanthrene, anthracene or pyrene. preferable. It is more preferable to use naphthalene, phenanthrene, anthracene or pyrene from the viewpoint of safety because of low volatility at room temperature.

The residual carbon ratio can be measured by quantifying the carbon content of the ignition residue after the sample is ignited in an inert gas. Ignition is about 1 g of volatile organic matter (this exact mass is W ₁ (g)) in a crucible, and 20 liters of nitrogen is allowed to flow for 1 minute in an electric furnace at 10 ° C./min. It means that the temperature is raised to 800 ° C. and then held at 800 ° C. for 1 hour. Let the residue at this time be an ignition residue, and let the mass be W ₂ (g).

Next, the ignition residue is subjected to elemental analysis in accordance with the method defined in JIS M8819, and the carbon mass ratio P ₁ (%) is measured. The remaining coal rate P ₂ (%) is calculated by the following equation.

  When the carbon precursor and the volatile organic substance are mixed and fired, the carbon precursor and the volatile organic substance are preferably mixed at a mass ratio of 97: 3 to 40:60. This mixing ratio is more preferably 95: 5 to 60:40, particularly preferably 93: 7 to 80:20. By setting the mixing ratio within the above range, it is easy to sufficiently reduce the specific surface area of the non-graphitizable carbonaceous material. On the other hand, it is easy to avoid wasteful consumption of volatile organic substances due to saturation of the specific surface area reduction effect.

  Mixing of the carbon precursor and the volatile organic substance may be performed at any stage before or after the carbon precursor is pulverized. When mixing before pulverization of the carbon precursor, pulverization and mixing can be performed simultaneously by metering and supplying the carbon precursor and the volatile organic substance to the pulverizer. It is also preferable to mix a volatile organic substance after pulverization of the carbon precursor. The mixing method in this case may be any mixing method as long as both are uniformly mixed.

  The volatile organic substance is preferably mixed in the form of particles, but the particle shape and average particle diameter are not particularly limited. From the viewpoint of uniformly dispersing in the pulverized carbon precursor, the average particle diameter of the volatile organic material is preferably 0.1 to 2000 μm, more preferably 1 to 1000 μm, and particularly preferably 2 to 600 μm.

  The mixture of the carbon precursor and the volatile organic substance is used as long as the effect of the non-graphitizable carbonaceous material of the present invention is obtained, that is, as long as the specific surface area of the non-graphitizable carbonaceous material is reduced. And other components other than volatile organic substances. For example, natural graphite, artificial graphite, metal material, alloy material or oxide material may be included. The content of the other components is not particularly limited, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, with respect to 100 parts by mass of the mixture of the carbon precursor and the volatile organic substance. More preferably, it is 20 mass parts or less, Most preferably, it is 10 mass parts or less.

<CVD process>
In the present invention, a CVD process using a hydrocarbon compound may be performed after the main firing step. The CVD process is a chemical vapor deposition (CVD) process that coats the non-graphitizable carbonaceous material obtained in the main firing step with a thermally decomposed hydrocarbon compound. The conditions for the CVD treatment are not particularly limited as long as the chemical vapor deposition is achieved. For example, the CVD treatment may be performed by a method of heat treatment at 500 to 1000 ° C. in an inert gas atmosphere containing a hydrocarbon compound. In the CVD process, the hydrocarbon compound is thermally decomposed, for example, by a heat treatment at 500 to 1000 ° C., and the resulting pyrolyzed product adheres to the non-graphitizable carbonaceous material and covers the surface of the non-graphitizable carbonaceous material. As a result, the mechanism is not limited to the following mechanism, but the specific surface area can be reduced while maintaining the voids between the carbon crystals that can be occluded by the clustered lithium of the non-graphitizable carbonaceous material. It is thought that it can be made. Therefore, it is considered that the charge / discharge efficiency can be increased while maintaining a high charge capacity. In addition, the functional group on the surface of the non-graphitizable carbonaceous material such as —OH group or —COOH group that can inhibit the occlusion of lithium ions reacts with the radical of the thermally decomposed hydrocarbon compound and is removed by the CVD process. It is thought. Therefore, it is thought that the charge capacity and charge / discharge efficiency are improved by reducing the oxygen element content in the carbonaceous material and suppressing irreversible side reactions during charge / discharge.

  The hydrocarbon compound used in the CVD process is a compound mainly composed of carbon atoms and hydrogen atoms. As a hydrocarbon compound, a low molecular organic hydrocarbon compound etc. are mentioned, for example. In the CVD process, one type of hydrocarbon compound may be used, or two or more types of hydrocarbon compounds may be used in combination. The hydrocarbon compound 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 mass of the hydrocarbon compound. It means preferably 80% by mass or more, more preferably 85% by mass or more.

  Examples of the low molecular organic hydrocarbon compound include hydrocarbon compounds having 1 to 20 carbon atoms. Carbon number of a hydrocarbon compound becomes like this. Preferably it is 2-18, More preferably, it is 3-16. 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 can include a linear or branched alkane, alkene, or alkyne. Examples of the cyclic hydrocarbon compound include alicyclic hydrocarbon compounds (for example, cycloalkane, cycloalkene, cycloalkyne) and aromatic hydrocarbon compounds. Specifically, 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, cycloheptane, cyclooctane, cyclononane, cyclopropane, cyclopentene, cyclohexene, cycloheptene, cyclooctene, decalin, norbornene, methylcyclohexane, and norbornadiene. Furthermore, aromatic hydrocarbon compounds include benzene, toluene, xylene, mesitylene, cumene, butylbenzene, styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinylxylene, p- Examples thereof include monocyclic aromatic compounds such as tert-butylstyrene and ethylstyrene, and condensed polycyclic aromatic compounds having 3 to 6 rings such as naphthalene, phenanthrene, anthracene, and pyrene. A group compound, more preferably naphthalene, phenanthrene, anthracene or pyrene. Here, the hydrocarbon compound may have an arbitrary substituent. The substituent is not particularly limited, and for example, an alkyl group having 1 to 4 carbon atoms (preferably an alkyl group having 1 to 2 carbon atoms) or an alkenyl group having 2 to 4 carbon atoms (preferably alkenyl having 2 carbon atoms). Group) and a cycloalkyl group having 3 to 8 carbon atoms (preferably a cycloalkyl group having 3 to 6 carbon atoms).

  In the CVD process, it is preferable to continuously supply the hydrocarbon compound in a gas state from the viewpoint of performing the CVD process uniformly and easily obtaining 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 previous step of the CVD treatment may be supplied to the CVD treatment step. For example, using a hydrocarbon compound that is in a gaseous state at a temperature of 500 to 1000 ° C. and performing the CVD treatment by heat treatment at the temperature, the viewpoint of productivity and the mixing property between the hydrocarbon compound and the non-graphitizable carbonaceous material To preferred. 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 be preferably performed in an inert gas atmosphere containing a hydrocarbon compound. Examples of the inert gas used in the CVD process include nitrogen and argon. The same inert gas may be used in the main baking step and the CVD treatment step, 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 main baking process and the CVD treatment process.

  When the CVD treatment step is performed in an inert gas atmosphere 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 1 to 60% by volume, more preferably 5 to 50% by volume, Especially preferably, it is 10 to 45 volume%. According to the manufacturing method of this embodiment in which heat treatment is performed in an inert gas atmosphere containing a hydrocarbon compound, it is easy to efficiently remove oxygen elements from the carbonaceous material.

  The heat treatment temperature in the CVD treatment step may vary depending on the carbonaceous material and the type of hydrocarbon compound used, but from the viewpoint of obtaining a desired carbon structure, preferably 500 to 1000 ° C, more preferably 600 to 900 ° C, More preferably, it is 700-850 degreeC. If the heat treatment temperature is too low, the oxygen element is not sufficiently removed from the carbonaceous material, and if the heat treatment temperature is too high, the carbon structure derived from a hydrocarbon compound that does not contribute to the charge capacity adheres and the charge capacity tends to decrease. .

  When the CVD treatment step is performed 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 / min per 50 g of the carbonaceous material. Above, more preferably 0.3 L / min or more, particularly preferably 0.5 L / min or more. It is preferable to perform the heat treatment at a supply amount equal to or higher than the above lower limit value because carbon coating is easily performed uniformly. The upper limit of the supply amount is preferably 10 L / min or less, more preferably 5 L / min or less. It is preferable to perform the heat treatment at a supply amount equal to or less than the above upper limit value because the supplied hydrocarbon compound easily acts efficiently.

<Negative electrode for non-aqueous electrolyte secondary battery>
The negative electrode for nonaqueous electrolyte secondary batteries of the present invention comprises the non-graphitizable carbonaceous material of the present invention.

<Manufacture of negative electrode>
The negative electrode material containing the non-graphitizable carbonaceous material of the present invention, after adding a binder (binder) to the non-graphitizable carbonaceous material, adding an appropriate amount of an appropriate solvent, kneading to make an electrode mixture, It can be manufactured by applying an electrode mixture to a current collector plate made of a metal plate, etc., drying, and pressure forming. By using the non-graphitizable carbonaceous material of the present invention, an electrode having high conductivity can be produced without adding a conductive auxiliary agent. However, in order to impart higher conductivity, a conductive aid can be added as necessary when preparing the electrode mixture.

  As the conductive assistant, conductive carbon black, vapor grown carbon fiber (VGCF), nanotubes, and the like can be used. The addition amount of the conductive auxiliary agent varies depending on the type of conductive auxiliary agent to be used, but is preferably 0.5 to 10% by mass [wherein the amount of active material (non-graphitizable carbonaceous material) + the amount of binder + conductivity Auxiliary amount = 100 mass%], more preferably 0.5-7 mass%, particularly preferably 0.5-5 mass%. By setting the addition amount of the conductive assistant within the above range, the expected conductivity can be easily obtained without deteriorating the dispersion of the conductive assistant in the electrode mixture.

  The binder to be added is not particularly limited as long as it does not react with the electrolytic solution. Examples thereof include PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene butadiene rubber) and CMC (carboxymethyl cellulose). Among these, PVDF is preferable because PVDF attached to the surface of the active material hardly inhibits lithium ion migration and provides favorable input / output characteristics. The amount of the binder added varies depending on the type of the binder used, but in the case of a PVDF-based binder, it is preferably 3 to 13 based on the total mass of the non-graphitizable carbonaceous material, the binder and the conductive additive. It is mass%, More preferably, it is 3-10 mass%. By making the addition amount of the binder within the above range, the resistance of the obtained electrode is increased, the internal resistance of the battery is increased, the battery characteristics are deteriorated, or the negative electrode particles and the negative electrode particles and the current collector plate It is easy to avoid problems such as insufficient coupling.

  In order to dissolve PVDF to form a slurry, a polar solvent such as N-methylpyrrolidone (NMP) is preferably used as a solvent. In order to form an aqueous emulsion such as SBR or an aqueous solution such as CMC, water is preferably used as a solvent. In a binder that uses water as a solvent, a plurality of binders such as a mixture of SBR and CMC are often mixed and used. The addition amount of the solvent is preferably 10 to 200 parts by mass, more preferably 50 to 150 parts by mass based on the total mass (100 parts by mass) of the non-graphitizable carbonaceous material, binder and conductive additive used. Part.

  The electrode active material layer is basically formed on both sides of the current collector plate, but may be on one side if necessary. The thickness of the active material layer (per one side) is preferably 10 to 100 μm, more preferably 20 to 90 μm, and particularly preferably 20 to 80 μm. By setting this thickness within the above range, it is easy to achieve high capacity because fewer current collectors and separators are required, while high input / output characteristics can be obtained because a large electrode area facing the counter electrode can be secured. Cheap.

<Nonaqueous electrolyte secondary battery>
The nonaqueous electrolyte secondary battery of the present invention includes, for example, a lithium ion secondary battery, a sodium ion secondary battery, a lithium sulfur battery, an all-solid battery, and an organic radical battery, and the nonaqueous electrolyte secondary battery of the present invention. It comprises a negative electrode for a battery. The fully charged nonaqueous electrolyte secondary battery produced using the negative electrode for a nonaqueous electrolyte secondary battery comprising the non-graphitizable carbonaceous material of the present invention exhibits high charge / discharge efficiency with a high charge capacity.

  When the non-graphite carbonaceous material of the present invention is used to form a negative electrode for a non-aqueous electrolyte secondary battery, other materials constituting the battery, such as a positive electrode material, a separator, and an electrolyte solution, are particularly limited. Absent. Various materials conventionally used or proposed as non-aqueous solvent secondary batteries can be used.

For example, as the cathode material, layered oxide [LiMO ₂ [M represents a metal] those represented as, for _{example, LiCoO 2, LiNiO 2, LiMnO} 2, or _{LiNi x Co y Mo z O 2} ( where , X, y, z represent the composition ratio)], olivine system (LiMPO ₄ [M represents a metal], for example, LiFePO ₄ etc.), and spinel system (LiM ₂ O ₄ [M represents a metal And a metal complex chalcogen compound such as LiMn ₂ O ₄ is preferable, and these chalcogen compounds may be mixed as necessary. These positive electrode materials are molded together with a suitable binder and a carbon material for imparting conductivity to the electrodes, and a positive electrode is formed by forming a layer on the conductive current collector.

The nonaqueous solvent electrolyte used in combination with these positive electrode and negative electrode is generally formed by dissolving an electrolyte in a nonaqueous solvent. Examples of the non-aqueous solvent include organic solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, γ-butyllactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, and 1,3-dioxolane. A solvent can be used individually or in combination of 2 or more types. As the electrolyte, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiAsF ₆ , LiCl, LiBr, LiB (C ₆ H ₅ ) ₄ , or LiN (SO ₃ CF ₃ ) ₂ is used.

  A non-aqueous electrolyte secondary battery is generally immersed in an electrolytic solution, with a positive electrode and a negative electrode formed as described above facing each other through a liquid-permeable separator made of a nonwoven fabric or other porous material as necessary. Is formed. As a separator, the permeable separator which consists of a nonwoven fabric normally used for a secondary battery or another porous material can be used. Alternatively, a solid electrolyte made of a polymer gel impregnated with an electrolytic solution can be used instead of or together with the separator.

In the present specification, the “fully charged nonaqueous electrolyte secondary battery” means that the nonaqueous electrolyte secondary battery of the present invention is assembled, and lithium is precipitated until just before the deposition of metallic lithium is confirmed by ⁷ Li nucleus-solid NMR analysis. Is a non-aqueous electrolyte secondary battery that is charged (doped) into the negative electrode, and is normally charged to a range of 580 to 700 mAh / g per mass of the negative electrode active material at a constant current value. Means that.

<Main resonance peak position of chemical shift value>
About the non-graphitized carbonaceous material in the nonaqueous electrolyte secondary battery of the present invention, lithium was charged (dope) until it was fully charged, and lithium chloride observed when ⁷ Li nucleus-solid NMR analysis was performed The main resonance peak position of the reference chemical shift value is greater than 115 ppm, preferably greater than 117 ppm, and more preferably greater than 119 ppm.

  As described above, the fact that the main resonance peak position of the chemical shift value based on lithium chloride is larger than 115 ppm means that the charge capacity of the battery is high and charge / discharge calculated from “discharge capacity / charge capacity”. Means high efficiency. High charge / discharge efficiency is advantageous in terms of capacity per battery volume and cost. A carbonaceous material having a main resonance peak position of a chemical shift value based on lithium chloride of 115 ppm or less provides both a high charge capacity and a high charge / discharge efficiency like the non-graphitizable carbonaceous material of the present invention. Is extremely difficult.

In order to adjust the main resonance peak position to a value larger than the above value, for example, a material containing carbon is removed at a temperature of 1050 ° C. to 1400 ° C. while actively removing pyrolysis gas such as carbon monoxide and hydrogen. A non-graphitizable carbonaceous material produced by firing in an active gas atmosphere may be used for the negative electrode. Details of the ⁷ Li nucleus-solid NMR analysis are as described in the examples.

<Expansion coefficient of electrode>
Regarding the nonaqueous electrolyte secondary battery of the present invention, the expansion rate of the negative electrode containing the non-graphitizable carbonaceous material at the time of full charge is 107% or less based on the thickness of the negative electrode before charging. When the expansion coefficient exceeds 107%, contact failure between the active materials occurs in the electrode, and the electrode resistance becomes high. Therefore, a non-aqueous electrolyte secondary battery having good output characteristics (high discharge capacity retention rate) is obtained. Absent.
The expansion coefficient is preferably 106% or less, particularly preferably 105% or less. When the expansion coefficient is less than or equal to the above upper limit value, it is easy to ensure good conduction paths and lithium ion diffusion between the active materials (non-graphitizable carbonaceous materials) in the electrode, so that low electrode resistance is easily obtained and good Easy output characteristics.

  In order to adjust the electrode expansion coefficient to the above value or less, for example, in an inert gas atmosphere at 1050 ° C. to 1400 ° C. while actively removing pyrolysis gas such as carbon monoxide and hydrogen from a material containing carbon. What is necessary is just to use the non-graphitizable carbonaceous material manufactured by baking with a negative electrode. In the negative electrode comprising the non-graphitizable carbonaceous material manufactured by the above method, many lithium ions are charged not only between the carbon crystal layers but also in the gaps between the carbon crystals, so that the lithium ions are charged only between the carbon crystal layers. It is thought that the electrode expansion coefficient is significantly smaller than the conventional negative electrode. The details of the measurement of the expansion coefficient are as described in the examples.

<Oxygen element content>
In the nonaqueous electrolyte secondary battery of the present invention, it is better that the non-graphitizable carbonaceous material has a lower oxygen element content. The oxygen element content is preferably 0.30% by mass or less, more preferably 0.28% by mass or less. More preferably, the non-graphitizable carbonaceous material contains substantially no oxygen element. Here, “substantially free of oxygen element” means that the oxygen element content is 10 ⁻⁶ % by mass, which is the detection limit of the method for measuring the oxygen element content (inert gas melting-non-dispersed infrared absorption method) described later. It means the following. As described above, when the oxygen element content is less than the above value, the lithium ion is consumed due to the reaction between lithium ions and oxygen, the utilization efficiency of lithium ions is reduced, and oxygen attracts moisture in the air. As a result, water is adsorbed and does not easily desorb, resulting in a decrease in lithium ion utilization efficiency, gas generation in the electrode due to moisture-induced side reactions, and an increase in electrode expansion coefficient due to the gas generation (increase in electrode resistance). , Deterioration of output characteristics) is easily suppressed.

  Further, as described above, the method for adjusting the oxygen element content is not limited at all. For example, a carbon precursor of plant origin is acid-treated at a predetermined temperature, mixed with a volatile organic substance, and baked in an inert gas atmosphere at a temperature of 1050 ° C. to 1400 ° C. The following can be adjusted. Details of the measurement of the oxygen element content are as described in the examples.

<Plant-derived carbon precursor>
The non-graphitizable carbonaceous material in the nonaqueous electrolyte secondary battery of the present invention is preferably derived from a plant-derived carbon precursor. In the present invention, “plant-derived carbon precursor” means a plant-derived material before carbonization, or a plant-derived material after carbonization (char derived from plants). As described above, the plant material is not particularly limited. Plants as described above can be used alone or in combination of two or more. Of these, coconut shells that are easily available in large quantities are preferred.

  The coconut shell is not particularly limited. The coconut shells as exemplified above can be used alone or in combination. Coconut palm and palm palm coconut shells, which are used as foods, detergent raw materials, biodiesel oil raw materials and the like and are biomass wastes generated in large quantities, are particularly preferable.

  The method for carbonizing the plant material, that is, the method for producing the plant-derived char is not particularly limited. For example, it is performed by calcining a plant material in an inert gas atmosphere at 300 ° C. or higher.

  It can also be obtained in the form of char (eg, coconut shell char).

<Average surface distance _d002 >
The non-graphitizable carbonaceous material in the non-aqueous electrolyte secondary battery of the present invention has an average interplanar spacing d ₀₀₂ of (002) plane calculated using the Bragg equation by wide-angle X-ray diffraction method is 0.36 nm to 0.00. It is preferably 42 nm, more preferably 0.38 nm to 0.40 nm, and particularly preferably 0.381 nm to 0.389 nm. When the average spacing d ₀₀₂ of (002) plane is within the above range, as described above, easy reduction of the input-output characteristics of the lithium ion battery is suppressed, decrease in the stability of the cell material is suppressed It is easy to avoid a decrease in execution capacity per volume. In order to adjust the average spacing to the above range, for example, the firing temperature of the carbon precursor that gives the non-graphitizable carbonaceous material may be in the range of 1050 to 1400 ° C. Moreover, it is also possible to use a method of mixing and baking with a thermally decomposable resin such as polystyrene. The details of the measurement of the average surface distance d ₀₀₂ are as described in the examples.

<True density ρ _Bt >
The non-graphitized carbonaceous material in the non-aqueous electrolyte secondary battery of the present invention has a true density ρ _Bt by the butanol method of 1.40 to 1.70 g / cm ³ from the viewpoint of increasing the capacity per mass in the battery. Preferably, it is 1.42-1.65 / cm ³ , more preferably 1.44-1.60 / cm ³ . The true density in the above range can be obtained, for example, by setting the firing process temperature to 1050 to 1400 ° C. Details of the measurement of the true density ρ _Bt are as described in the examples.

<Potassium element content and iron element content>
As described above, the potassium element content of the non-graphitizable carbonaceous material in the nonaqueous electrolyte secondary battery of the present invention is preferably 0.1% by mass or less, and 0.05% by mass or less. More preferably, it is 0.03 mass% or less, and it is especially preferable that a non-graphitizable carbonaceous material does not contain a potassium element substantially. In addition, the iron element content of the non-graphitizable carbonaceous material in the nonaqueous electrolyte secondary battery of the present invention is preferably 0.02% by mass or less, as described above, and 0.015% by mass or less. It is more preferable that the content is 0.01% by mass or less, and it is particularly preferable that the non-graphitizable carbonaceous material does not substantially contain an iron element. Here, the phrase “substantially containing no potassium element or iron element” means that the potassium element content or the iron element content is determined by the fluorescent X-ray analysis described later (for example, analysis using “LAB CENTER XRF-1700” manufactured by Shimadzu Corporation). It means that it is below the detection limit value. If the potassium element content and the iron element content are less than the above values, as described above, sufficient dedoping capacity and undoping capacity are easily obtained, and safety problems of nonaqueous electrolyte secondary batteries are avoided. Easy to be. Details of the measurement of the potassium element content and the iron element content are as described in the examples.

<Moisture absorption>
The moisture absorption of the non-graphitizable carbonaceous material in the nonaqueous electrolyte secondary battery of the present invention is preferably 10,000 ppm or less, more preferably 9000 ppm or less, and particularly preferably 8000 ppm or less. As described above, the smaller the amount of moisture absorption, the more lithium ions adsorbed on the non-graphitizable carbonaceous material, and this is preferable because self-discharge due to the reaction between the adsorbed moisture and lithium ions can be reduced. The moisture absorption amount of the non-graphitizable carbonaceous material can be reduced, for example, by reducing the amount of oxygen atoms contained in the non-graphitizable carbonaceous material. The amount of moisture absorption of the non-graphitizable carbonaceous material can be measured using, for example, a Karl Fischer. Details of the measurement of the amount of moisture absorption are as described in the examples.

<Specific surface area>
Non-graphitizable carbonaceous material in the non-aqueous electrolyte secondary battery of the present invention has a specific surface area determined by nitrogen adsorption BET3 point method is preferably from 1~75m ² / g, is 2~60m ² / g It is more preferable, and it is especially preferable that it is 3-50 m < ² > / g. As described above, when the specific surface area is within the above range, in the nonaqueous electrolyte secondary battery produced using the non-graphitizable carbonaceous material, excessive side reaction between the electrolyte and the non-graphitizable carbonaceous material. Lithium ions are easily doped into the non-graphitizable carbonaceous material while suppressing lithium ions, and the contact area for dedoping lithium ions from the non-graphitizable carbonaceous material is easy to maintain, resulting in high charge capacity and high output characteristics. And are easy to balance. The specific surface area can be adjusted, for example, by controlling the temperature of the decalcification step described above.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but these do not limit the scope of the present invention. In addition, although the measuring method of the physical-property value of a hardly graphitized carbonaceous material is described below, the physical-property value described in this specification including an Example is based on the value calculated | required by the following method. .

<Measurement of main resonance peak position of chemical shift value by ⁷ Li nucleus-solid NMR analysis>
The negative electrode containing the non-graphitizable carbonaceous material doped with lithium ions in a fully charged state was taken out of the cell, and all the negative electrode from which the electrolytic solution had been wiped was filled in an NMR sample tube. The measurement of the main resonance peak position of the chemical shift value by ⁷ Li nucleus-solid NMR analysis was performed using “Nuclear Magnetic Resonance Device AVANCE300” manufactured by BRUKER. In the measurement, lithium chloride was used as a reference material, and this was set to 0 ppm.

<Measurement of oxygen element content>
The oxygen element content was measured using an “oxygen / nitrogen / hydrogen analyzer EMGA-930” manufactured by HORIBA, Ltd.
The detection method of this apparatus is oxygen: inert gas melting-non-dispersive infrared absorption method (NDIR), nitrogen: inert gas melting-thermal conductivity method (TCD), hydrogen: inert gas melting-non-dispersive infrared ray. It was an absorption method (NDIR), and calibration was performed with (oxygen / nitrogen) Ni capsules, TiH ₂ (H standard sample), and SS-3 (N, O standard sample). As a pretreatment, 20 mg of a sample subjected to dehydration at 250 ° C. for about 10 minutes was weighed into a Ni capsule, degassed for 30 seconds in an elemental analyzer, and then measured. Three samples were analyzed, and the average value was taken as the analysis value.

<Measurement of Average Plane Distance _d002 of (002) Plane>
Using “MiniFlex II” manufactured by Rigaku Corporation, an X-ray diffraction pattern was obtained using CuKα rays monochromatized by a Ni filter by filling a non-graphitizable carbonaceous material powder in a sample holder. The peak position of the diffraction pattern is obtained by the barycentric method (a method of obtaining the barycentric position of the diffraction line and obtaining the peak position by the corresponding 2θ value), and using the diffraction peak on the (111) plane of the high-purity silicon powder for standard materials. Corrected. The wavelength of the CuKα ray was 0.15418 nm, and d ₀₀₂ was calculated according to the Bragg formula shown below.

このとき、ｄは水の３０℃における比重（０．９９４６）である。 <Measurement of true density ρ _Bt by butanol method>
The true density was measured by a butanol method according to a method defined in JIS R 7212. The mass (m ₁ ) of a specific gravity bottle with a side tube having an internal volume of about 40 mL was accurately measured. Next, the sample was put flat on the bottom so as to have a thickness of about 10 mm, and the mass (m ₂ ) was accurately measured. To this, 1-butanol was gently added to a depth of about 20 mm from the bottom. Next, light vibration was applied to the specific gravity bottle, and it was confirmed that no large bubbles were generated. Then, the bottle was placed in a vacuum desiccator and gradually evacuated to 2.0 to 2.7 kPa. Hold at that pressure for 20 minutes or more, and after the generation of bubbles has stopped, take it out, fill it with 1-butanol, plug it and immerse it in a constant temperature water bath (adjusted to 30 ± 0.03 ° C) for 15 minutes or more. The liquid level of 1-butanol was adjusted to the marked line. Next, this was taken out, wiped outside well and cooled to room temperature, and then the mass (m ₄ ) was accurately measured. Next, the same specific gravity bottle was filled with only 1-butanol, immersed in a constant temperature water bath in the same manner as described above, and after aligning the marked lines, the mass (m ₃ ) was measured. Moreover, distilled water excluding the gas that had been boiled and dissolved immediately before use was taken in a specific gravity bottle, immersed in a constant temperature water bath in the same manner as described above, and after aligning the marked lines, the mass (m ₅ ) was measured.
The true density ρ _Bt was calculated by the following formula.

At this time, d is the specific gravity of water at 30 ° C. (0.9946).

<Measurement of potassium element content and iron element content>
The potassium element content and the iron element content were measured by the following methods. A carbon sample containing a predetermined potassium element and iron element is prepared in advance, and using a fluorescent X-ray analyzer, the relationship between the intensity of potassium Kα ray and the potassium element content, and the intensity of iron Kα ray and iron element content A calibration curve for the relationship was created. Subsequently, the intensity | strength of the potassium K alpha ray and iron K alpha ray in a fluorescent X ray analysis was measured about the sample, and the potassium element content and the iron element content were calculated | required from the analytical curve created previously. The fluorescent X-ray analysis was performed by the following procedure using “LAB CENTER XRF-1700” manufactured by Shimadzu Corporation. Using the upper irradiation system holder, the sample measurement area was within the circumference of 20 mm in diameter. The sample to be measured was placed by placing 0.5 g of the sample to be measured in a polyethylene container having an inner diameter of 25 mm, pressing the back with a plankton net, and covering the measurement surface with a polypropylene film. The X-ray source was set to 40 kV and 60 mA. For potassium, LiF (200) was used for the spectroscopic crystal and a gas flow proportional coefficient tube was used for the detector, and 2θ was measured in the range of 90 to 140 ° at a scanning speed of 8 ° / min. For iron, LiF (200) was used for the spectroscopic crystal, and a scintillation counter was used for the detector, and 2θ was measured in the range of 56 to 60 ° at a scanning speed of 8 ° / min.

<Measurement of moisture absorption>
10 g of a non-graphitizable carbonaceous material pulverized 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 reduced pressure of 133 Pa, transferred to a glass petri dish of 50 mmφ, 25 ° C., humidity 50 % Exposure in a constant temperature and humidity chamber. 1 g of a sample was taken, heated to 250 ° C. by Karl Fischer (manufactured by Mitsubishi Chemical Analytech Co., Ltd.), and the water content was measured under a nitrogen stream.

<Measurement of average particle size by laser scattering method>
The average particle diameter (particle size distribution) of plant-derived char, carbon precursor, and volatile organic substance was measured by the following method. The sample was put into an aqueous solution containing 0.3% by mass of a surfactant (“Toriton X100” manufactured by Wako Pure Chemical Industries, Ltd.), treated with an ultrasonic cleaner for 10 minutes or more, and dispersed in the aqueous solution. The particle size distribution was measured using this dispersion. The particle size distribution measurement was performed using a particle size / particle size distribution measuring instrument (“Microtrack MT3000” manufactured by Nikkiso Co., Ltd.). Dv ₅₀ is the particle diameter at which the cumulative volume is 50%, and this value was taken as the average particle diameter.

Example 1 (gas phase demineralization, addition of volatile organic substances, full cell evaluation)
<Preparation of carbon precursor>
The coconut shell was subjected to dry distillation at 500 ° C. and then crushed to obtain coconut shell char having an average particle diameter of about 2 mm. While supplying nitrogen gas containing 1% by volume of hydrogen chloride gas at a flow rate of 18 L / min to 100 g of this coconut shell char, halogen heat treatment was performed at 870 ° C. for 30 minutes, and then only hydrogen chloride gas was supplied. Then, while supplying nitrogen gas at a flow rate of 18 L / min, a gas phase deoxidation treatment was carried out by further heat treatment at 870 ° C. for 30 minutes to obtain a carbon precursor.
The obtained carbon precursor was pulverized to an average particle size of 6 μm using a mixer mill (manufactured by Vander Scientific Co., Ltd., MM400), and then classified using Nanojet Mizer (manufactured by Aisin Nanotechnology Co., Ltd.). A carbon precursor (1) having an average particle diameter of 5 μm was obtained.

<Preparation of non-graphitizable carbonaceous material>
5 g of the carbon precursor prepared as described above and 0.5 g of polystyrene (manufactured by Sekisui Plastics Co., Ltd., average particle diameter of 400 μm, residual carbon ratio of 1.2%) were mixed. 5.5 g of this mixture is placed in a graphite sheath so that the sample layer height is about 2 mm, and up to 1290 ° C. at a rate of 10 ° C. per minute under a nitrogen flow rate of 5 L / min in a tube furnace manufactured by Motoyama Co., Ltd. After raising the temperature, it was kept for 30 minutes and cooled naturally. After confirming that the furnace temperature had dropped to 200 ° C. or lower, the non-graphitizable carbonaceous material was taken out from the furnace. The recovered non-graphitizable carbonaceous material was 4.9 g, and the recovery rate was 89%.
For the non-graphitizable carbonaceous material prepared as described above, the measurement of the main resonance peak position of the chemical shift value by ⁷ Li nucleus-solid NMR analysis, the measurement of the oxygen element content, the average interplanar spacing d ₀₀₂ of the (002) plane Measurement, measurement of true density ρ _Bt by butanol method, measurement of potassium element content and iron element content, and measurement of moisture absorption were performed. The results are shown in Table 1.

<Estimation of full-cell negative electrode full charge capacity>
94 parts by mass of the non-graphitizable carbonaceous material prepared as described above, 6 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 one side of a copper foil having a thickness of 14 μm, dried and pressed to obtain an electrode having a thickness of 70 to 80 μm. The density of the obtained electrode was 0.9 to 1.1 g / cm ³ .
A negative electrode was used as a working electrode, and metallic lithium was used as a counter electrode and a reference electrode. As a solvent, ethylene carbonate and methyl ethyl carbonate were mixed and used at a volume ratio of 3: 7. LiPF ₆ was dissolved in this solvent to a concentration of 1 mol / L and used as an electrolyte. A glass fiber nonwoven fabric was used for the separator. A coin cell was produced in a glove box under an argon atmosphere.
About the negative electrode half cell of the said structure, the charging / discharging test was done using the charging / discharging test apparatus (The Toyo System Co., Ltd. make, "TOSCAT"). Lithium doping was performed at a rate of 30 mA / g up to a predetermined capacity at which no metallic lithium was deposited with respect to the active material mass, and was terminated. The capacity (mAh / g) at this time was defined as the charge capacity. Here, the “predetermined capacity at which metallic lithium does not precipitate” refers to the upper limit charging capacity (mAh / g) at which metallic lithium is not precipitated by Li-NMR.

<Full cell evaluation>
-Preparation of positive electrode 92 parts by mass of a ternary oxide (LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) as a positive electrode active material, 3 parts by mass of PVDF (polyvinylidene fluoride), 5 parts by mass of acetylene black, 120 parts by mass of NMP (N-methylpyrrolidone) was mixed to obtain a slurry. The obtained slurry was applied to one side of an aluminum foil having a thickness of 20 μm, dried and pressed to obtain a positive electrode. The density of the obtained electrode was 2.4 to 2.6 g / cm ³ . This electrode was punched into a disk shape having a diameter of 14 mm to obtain a positive electrode plate.

-Preparation of positive electrode half cell Metal lithium was used as a counter electrode and a reference electrode with respect to the obtained positive electrode. As a solvent, ethylene carbonate and methyl ethyl carbonate were mixed and used at a volume ratio of 3: 7. LiPF ₆ was dissolved in this solvent to a concentration of 1 mol / L and used as an electrolyte. A glass fiber nonwoven fabric was used for the separator. A coin cell was produced in a glove box under an argon atmosphere.
About the positive electrode half cell of the said structure, the charging / discharging test was done using the charging / discharging test apparatus (The Toyo System Co., Ltd. make, "TOSCAT"). Lithium dedoping from the positive electrode was performed at a rate of 15 mA / g with respect to the mass of the active material until 4.2 V with respect to the lithium potential, and the capacity at this time was defined as the charge capacity. Next, lithium doping to the positive electrode was performed at a rate of 15 mA / g with respect to the active material mass until 3.0 V with respect to the lithium potential, and the capacity at this time was defined as the discharge capacity. The obtained charge capacity was 174 mAh / g, the discharge capacity was 154 mAh / g, and the charge / discharge efficiency (initial charge / discharge efficiency) calculated as a percentage of “discharge capacity / charge capacity” was 88.5%.

-Production and evaluation of full cell The mixture coating surface of the negative electrode and the positive electrode was opposed to each other through a separator made of a glass fiber nonwoven fabric so that the positive electrode (diameter 14 mm) did not protrude from the negative electrode surface having a diameter of 15 mm. At this time, the ratio (negative electrode capacity / positive electrode capacity) of the negative electrode charge capacity (mAh) and the positive electrode charge capacity (mAh) per facing area was adjusted to 1. As a solvent, ethylene carbonate and methyl ethyl carbonate were mixed and used at a volume ratio of 3: 7. LiPF ₆ was dissolved in this solvent to a concentration of 1 mol / L and used as an electrolyte. A coin cell was produced in a glove box under an argon atmosphere.

-Charging / discharging test About the coin cell (full cell) of the said structure, the charging / discharging test was done using the charging / discharging test apparatus (The Toyo System Co., Ltd. make, "TOSCAT"). First, charging was performed at a rate of 30 mA / g with respect to the mass of the negative electrode active material until 4.2 V was reached, and the capacity at this time was defined as the charging capacity. Next, discharge was performed at a rate of 30 mA / g with respect to the mass of the negative electrode active material until 2.0 V was reached, and the capacity at this time was defined as the discharge capacity. Moreover, the value calculated by the difference of “charge capacity−discharge capacity” was irreversible capacity, and the value calculated by the percentage of “discharge capacity / charge capacity” was the charge / discharge efficiency (initial charge / discharge efficiency). Table 1 shows the obtained charge capacity, discharge capacity, irreversible capacity, and charge / discharge efficiency.

-Output characteristic test About the coin cell (full cell) of the said structure, charge is first performed at the speed | rate of 30 mA / g with respect to the negative electrode active material mass until it becomes 4.2V, Then, discharge is carried out to the negative electrode active material mass. On the other hand, it was carried out at a rate of 30 mA / g until it reached 2.0 V, and the capacity at this time was defined as the discharge capacity (A). Further, charging is performed at a rate of 30 mA / g with respect to the mass of the negative electrode active material until 4.2 V is reached, and then discharging is performed at 2.0 mA at a rate of 150 mA / g with respect to the mass of the negative electrode active material. The capacity at this time was defined as the discharge capacity (B). A value calculated as a percentage of “discharge capacity (B) / discharge capacity (A)” was defined as a discharge capacity maintenance ratio. As the electrode resistance is lower, lithium ions are more easily dedope from the negative electrode, and this discharge capacity retention rate shows a higher value, so it can be said that the output characteristics are higher. The obtained output characteristics (discharge capacity retention ratio) are shown in Table 1.

-Electrode expansion coefficient About the coin cell (full cell) of the said structure, it charges until it becomes 4.2V at the speed | rate of 30 mA / g with respect to negative electrode active material mass, and discharge is 30 mA / with respect to negative electrode active material mass. It carried out until it became 2.0V at the speed | rate of g. After this charge / discharge cycle was repeated 5 times, the coin cell was disassembled in a glove box under an argon atmosphere, the negative electrode was taken out, and the taken out negative electrode was washed with diethyl carbonate and dried. The thickness (D) of the negative electrode after drying was measured, and the ratio [percentage of “thickness (D) / thickness (C)” to the negative electrode thickness (C) measured before charging / discharging was determined as the electrode expansion coefficient. In addition, the negative electrode thickness (C) and the negative electrode thickness (D) are respectively the negative electrode thicknesses obtained by measuring the total thickness of the mixture layer and the copper foil in several places and subtracting the copper foil thickness from each total thickness. Average value. The obtained electrode expansion coefficient is shown in Table 1.

Example 2 (gas phase demineralization, addition of volatile organic substances, full cell evaluation)
<Preparation of carbon precursor>
Until the vapor phase deoxidation treatment, the same procedure as in Example 1 was performed to obtain a carbon precursor.
The obtained carbon precursor was pulverized using a dry bead mill (SDA5 manufactured by Ashizawa Finetech Co., Ltd.) under the conditions of a bead diameter of 3 mmφ, a bead filling rate of 75%, and a raw material feed rate of 1 kg / hour. A carbon precursor (2) of .7 μm was obtained.

<Preparation of non-graphitizable carbonaceous material>
Except having used the carbon precursor prepared as mentioned above, it baked like Example 1 and the non-graphitizable carbonaceous material was prepared. The recovered non-graphitizable carbonaceous material was 4.9 g, and the recovery rate was 89%.
The characteristic values of the non-graphitizable carbonaceous material prepared as described above were measured in the same manner as in Example 1. The results are shown in Table 1.

<Estimation of full-cell negative electrode full charge capacity>
Except for using the non-graphitizable carbonaceous material prepared as described above, a negative electrode was prepared and a coin cell using metallic lithium as a counter electrode and a reference electrode was prepared in the same manner as in Example 1. The charge / discharge test was conducted using a charge / discharge test apparatus.

<Full cell evaluation>
Full cell evaluation was performed in the same manner as in Example 1 except that the non-graphitizable carbonaceous material prepared as described above was used. The characteristic values obtained are shown in Table 1.

Example 3 (gas phase demineralization, CVD treatment, full cell evaluation)
<Preparation of carbon precursor>
The same carbon precursor (2) as in Example 2 was used.

<Preparation of non-graphitizable carbonaceous material>
The main baking was performed in the same manner as in Example 2 except that polystyrene, which is a volatile organic substance, was not used. Next, 3 g of the obtained carbonaceous material was put in an inner case made of quartz, and the temperature was raised to 780 ° C. at a rate of 20 ° C. per minute under a nitrogen flow rate of 0.1 L per minute in a rotary tube furnace. After reaching 780 ° C., the vaporized hexane gas was mixed with nitrogen gas at a flow rate of 0.04 L / min, and the nitrogen / hexane mixed gas was circulated in the tubular furnace for 30 minutes for CVD treatment. Thereafter, the hexane gas flow was stopped, and heat treatment was further performed for 30 minutes under a nitrogen flow rate of 0.1 L / min, followed by natural cooling. After confirming that the furnace temperature had dropped to 200 ° C. or lower, the non-graphitizable carbonaceous material was taken out from the furnace. The recovered non-graphitizable carbonaceous material was 2.95 g, and the recovery rate was 98%.
The characteristic values of the non-graphitizable carbonaceous material prepared as described above were measured in the same manner as in Example 1. The results are shown in Table 1.

<Estimation of full-cell negative electrode full charge capacity>
Except for using the non-graphitizable carbonaceous material prepared as described above, a negative electrode was prepared and a coin cell using metallic lithium as a counter electrode and a reference electrode was prepared in the same manner as in Example 1. The charge / discharge test was conducted using a charge / discharge test apparatus.

<Full cell evaluation>
Full cell evaluation was performed in the same manner as in Example 1 except that the non-graphitizable carbonaceous material prepared as described above was used. The characteristic values obtained are shown in Table 1.

Example 4 (Liquid phase demineralization, CVD treatment, full cell evaluation)
<Preparation of carbon precursor>
An approximately 5 mm square coconut shell chip of Mindanao Island, Philippines, 100 g was immersed in 150 g of a 7.4% by mass citric acid aqueous solution, heated to 80 ° C., and heated for 4 hours. Subsequently, it cooled to room temperature and liquid-removed by filtration. This operation was performed 5 times and decalcification was performed. The decalcified coconut shell was dried at 80 ° C. for 24 hours under 1 Torr. 20 g of coconut shell chips after deashing and drying were put into a crucible, and 10 ° C. under a flow rate of nitrogen flow of 3 L / min (0.012 m / sec) with an oxygen content of 15 ppm using a KTF1100 furnace (inner diameter 70 mmΦ) manufactured by Koyo Thermo. The temperature was raised to 750 ° C./minute and held for 60 minutes, and then cooled for 6 hours. After confirming that the furnace temperature had dropped to 50 ° C. or less, the carbon precursor was taken out from the furnace.
The obtained carbon precursor was pulverized using a dry bead mill (SDA5 manufactured by Ashizawa Finetech Co., Ltd.) under the conditions of a bead diameter of 3 mmφ, a bead filling rate of 75%, and a raw material feed rate of 1 kg / hour. A carbon precursor (3) of 7 μm was obtained.

<Preparation of non-graphitizable carbonaceous material>
Except for using the carbon precursor (3), in the same manner as in Example 3, firing and CVD treatment were performed to prepare a non-graphitizable carbonaceous material. The recovered non-graphitizable carbonaceous material was 2.95 g, and the recovery rate was 98%.
The characteristic values of the non-graphitizable carbonaceous material prepared as described above were measured in the same manner as in Example 1. The results are shown in Table 1.

<Estimation of full-cell negative electrode full charge capacity>
Except for using the non-graphitizable carbonaceous material prepared as described above, a negative electrode was prepared and a coin cell using metallic lithium as a counter electrode and a reference electrode was prepared in the same manner as in Example 1. The charge / discharge test was conducted using a charge / discharge test apparatus.

<Full cell evaluation>
Full cell evaluation was performed in the same manner as in Example 1 except that the non-graphitizable carbonaceous material prepared as described above was used. The characteristic values obtained are shown in Table 1.

Comparative Example 1 (gas phase demineralization, change in sample layer height, full cell evaluation)
<Preparation of carbon precursor>
The same carbon precursor (1) as in Example 1 was used.

<Preparation of non-graphitizable carbonaceous material>
75 g of the carbon precursor prepared as described above and 7.5 g of polystyrene (manufactured by Sekisui Plastics Co., Ltd., average particle size 400 μm, residual carbon ratio 1.2%) were mixed. 82.5 g of this mixture is placed in a graphite sheath so that the sample layer height is about 30 mm, and the temperature is increased to 1290 ° C. at a rate of 10 ° C. per minute under a 1 L / min nitrogen flow rate in a tube furnace manufactured by Motoyama Co., Ltd. After warming, it was kept for 30 minutes and naturally cooled. After confirming that the furnace temperature had dropped to 200 ° C. or lower, the non-graphitizable carbonaceous material was taken out from the furnace. The recovered non-graphitizable carbonaceous material was 73.4 g, and the recovery rate was 89%.
The characteristic values of the non-graphitizable carbonaceous material prepared as described above were measured in the same manner as in Example 1. The results are shown in Table 1.

<Estimation of full-cell negative electrode full charge capacity>
Except for using the non-graphitizable carbonaceous material prepared as described above, a negative electrode was prepared and a coin cell using metallic lithium as a counter electrode and a reference electrode was prepared in the same manner as in Example 1. The charge / discharge test was conducted using a charge / discharge test apparatus.

<Full cell evaluation>
Full cell evaluation was performed in the same manner as in Example 1 except that the non-graphitizable carbonaceous material prepared as described above was used. The characteristic values obtained are shown in Table 1.

Comparative example 2 (gas phase demineralization, change of sample layer height, full cell evaluation)
<Preparation of carbon precursor>
The same carbon precursor (2) as in Example 2 was used.

<Preparation of non-graphitizable carbonaceous material>
Except for using the carbon precursor (2), the same firing was performed as in Comparative Example 1 to prepare a hardly graphitized carbonaceous material. The recovered non-graphitizable carbonaceous material was 72 g, and the recovery rate was 87%.
The characteristic values of the non-graphitizable carbonaceous material prepared as described above were measured in the same manner as in Example 1. The results are shown in Table 1.

<Estimation of full-cell negative electrode full charge capacity>
Except for using the non-graphitizable carbonaceous material prepared as described above, a negative electrode was prepared and a coin cell using metallic lithium as a counter electrode and a reference electrode was prepared in the same manner as in Example 1. The charge / discharge test was conducted using a charge / discharge test apparatus.

<Full cell evaluation>
Full cell evaluation was performed in the same manner as in Example 1 except that the non-graphitizable carbonaceous material prepared as described above was used. The characteristic values obtained are shown in Table 1.

Comparative example 3 (gas phase demineralization, volatile organic substances not added, full cell evaluation)
<Preparation of carbon precursor>
The same carbon precursor (2) as in Example 2 was used.

<Preparation of non-graphitizable carbonaceous material>
Except that polystyrene, which is a volatile organic substance, was not used, main firing was performed in the same manner as in Example 2 to prepare a non-graphitizable carbonaceous material. The recovered non-graphitizable carbonaceous material was 4.75 g, and the recovery rate was 95%.
The characteristic values of the non-graphitizable carbonaceous material prepared as described above were measured in the same manner as in Example 1. The results are shown in Table 1.

<Estimation of full-cell negative electrode full charge capacity>
Except for using the non-graphitizable carbonaceous material prepared as described above, a negative electrode was prepared and a coin cell using metallic lithium as a counter electrode and a reference electrode was prepared in the same manner as in Example 1. The charge / discharge test was conducted using a charge / discharge test apparatus.

<Full cell evaluation>
Full cell evaluation was performed in the same manner as in Example 1 except that the non-graphitizable carbonaceous material prepared as described above was used. The characteristic values obtained are shown in Table 1.

Comparative Example 4 (liquid phase decalcification after carbonization, CVD treatment, full cell evaluation)
<Preparation of carbon precursor>
About 20 mm square coconut shell chips from Mindanao Island, Philippines, are put in a crucible and using a KTF1100 furnace (inner diameter 70 mmΦ) manufactured by Koyo Thermo under a flow of nitrogen of 3 L / min (0.012 m / sec) with an oxygen content of 15 ppm. The temperature was raised to 750 ° C. at 10 ° C./min, held for 60 minutes, then cooled over 6 hours, and it was confirmed that the furnace temperature had dropped to 50 ° C. or less, and the carbide was taken out from the furnace. The obtained carbide was immersed in a 35% by mass hydrochloric acid aqueous solution for 1 hour, and then washed with 80 ° C. water for 1 hour twice to perform deashing. The decalcified coconut shell was dried at 80 ° C. for 24 hours under 1 Torr.
The obtained decalcified and dried carbon precursor was pulverized using a dry bead mill (SDA5 manufactured by Ashizawa Finetech Co., Ltd.) under the conditions of a bead diameter of 3 mmφ, a bead filling rate of 75%, and a feed rate of 1 kg / hour. A carbon precursor (4) having an average particle diameter of 2.7 μm was obtained.

<Preparation of non-graphitizable carbonaceous material>
Except for using the carbon precursor (4), in the same manner as in Example 4, firing and CVD treatment were performed to prepare a non-graphitizable carbonaceous material. The recovered non-graphitizable carbonaceous material was 2.95 g, and the recovery rate was 98%.
The characteristic values of the non-graphitizable carbonaceous material prepared as described above were measured in the same manner as in Example 1. The results are shown in Table 1.

<Estimation of full-cell negative electrode full charge capacity>
Except for using the non-graphitizable carbonaceous material prepared as described above, a negative electrode was prepared and a coin cell using metallic lithium as a counter electrode and a reference electrode was prepared in the same manner as in Example 1. The charge / discharge test was conducted using a charge / discharge test apparatus.

<Full cell evaluation>
Full cell evaluation was performed in the same manner as in Example 1 except that the non-graphitizable carbonaceous material prepared as described above was used. The characteristic values obtained are shown in Table 1.

Comparative Example 5 (Carbotron PJ, full cell evaluation)
<Measurement of characteristic value of Carbotron PJ>
The characteristic value of Carbotron PJ was measured in the same manner as in Example 1. The results are shown in Table 1.

<Estimation of full-cell negative electrode full charge capacity>
A negative electrode was produced in the same manner as in Example 1 except that Kureha's Carbotron PJ was used, a coin cell using metallic lithium as a counter electrode and a reference electrode was produced, and a charge / discharge test apparatus was used for the produced negative electrode half cell. The charge / discharge test was conducted.

<Full cell evaluation>
A full cell evaluation was performed in the same manner as in Example 1 except that Kureha's Carbotron PJ was used. The characteristic values obtained are shown in Table 1.

Comparative Example 6 [Carbotron PS (F), full cell evaluation]
<Measurement of the characteristic value of Carbotron PS (F)>
The characteristic value of Carbotron PS (F) was measured in the same manner as in Example 1. The results are shown in Table 1.

<Estimation of full-cell negative electrode full charge capacity>
A negative electrode was prepared in the same manner as in Example 1 except that Kureha Carbotron PS (F) was used, a coin cell using metallic lithium as a counter electrode and a reference electrode was prepared, and a charge / discharge test was performed on the prepared negative electrode half cell. A charge / discharge test was performed using the apparatus.

<Full cell evaluation>
A full cell evaluation was performed in the same manner as in Example 1 except that Kureha Carbotron PS (F) was used. The characteristic values obtained are shown in Table 1.

As shown in Table 1, the non-electrolyte secondary battery used in a fully charged state is provided with a specific ⁷ Li nucleus-solid NMR analysis chemical shift value and a specific electrode expansion coefficient according to the present invention. In addition to high charge capacity and high charge / discharge efficiency, high output characteristics were also achieved by using the carbonized carbonaceous materials (Examples 1 to 4).

On the other hand, when a non-graphitizable carbonaceous material that does not give a chemical shift value of a specific ⁷ Li nucleus-solid NMR analysis is used (Comparative Examples 1 to 3), the chemical shift value of a specific ⁷ Li nucleus-solid NMR analysis is also When a non-graphitizable carbonaceous material that does not cause a specific electrode expansion coefficient is used (Comparative Examples 4 to 5), and when a non-graphitizable carbonaceous material that does not provide a specific electrode expansion coefficient is used (Comparative Example 6) It is not possible to manufacture a non-aqueous electrolyte secondary battery having a high charge capacity and a high charge / discharge efficiency and a high discharge capacity maintenance rate. Such a non-aqueous electrolyte secondary battery has a low charge / discharge efficiency and a low discharge. It had only capacity retention (ie low output characteristics).

  The non-aqueous electrolyte secondary battery that is fully charged and comprises the non-graphitizable carbonaceous material of the present invention has high output characteristics due to low electrode resistance in addition to high charge capacity and high charge / discharge efficiency. Therefore, it can be suitably used for in-vehicle applications such as a hybrid vehicle (HEV) and an electric vehicle (EV).

Claims (12)

A non-graphitized carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery to be used fully charged, and when fully charged, chemical shift based on lithium chloride observed by ⁷ Li nucleus-solid NMR analysis The main resonance peak position of the value is greater than 115 ppm, and the negative electrode comprising the non-graphitizable carbonaceous material has a coefficient of expansion when fully charged of 107% or less based on the thickness of the negative electrode before charging. Carbonaceous material.   The non-graphitizable carbonaceous material according to claim 1, wherein the oxygen element content is 0.30 mass% or less.   The non-graphitizable carbonaceous material according to claim 1 or 2, derived from a plant-derived carbon precursor. Mean spacing _{d 002} of the calculated using Bragg equation by wide angle X-ray diffraction (002) plane is 0.36～0.42Nm, non-graphitizable carbon as claimed in claim 1 Quality material.   The non-graphitizable carbonaceous material according to any one of claims 1 to 4, wherein the potassium element content is 0.1 mass% or less and the iron element content is 0.02 mass% or less.   The difficulty according to any one of claims 1 to 5, comprising a step of acid-treating a carbon precursor of plant origin, and a step of firing the acid-treated carbon precursor in an inert gas atmosphere at 1050 ° C to 1400 ° C. A method for producing a graphitized carbonaceous material.   A negative electrode for a non-aqueous electrolyte secondary battery comprising the non-graphitizable carbonaceous material according to any one of claims 1 to 5. A non-aqueous electrolyte secondary battery comprising a negative electrode for a non-aqueous electrolyte secondary battery comprising a non-graphitizable carbonaceous material, and when fully charged, ⁷ Li nucleus-solid NMR analysis The main resonance peak position of the chemical shift value with respect to lithium chloride as observed with reference to is larger than 115 ppm, and the negative electrode comprising the non-graphitizable carbonaceous material has a coefficient of expansion when fully charged, the thickness of the negative electrode before charging. A non-aqueous electrolyte secondary battery that is 107% or less based on   The nonaqueous electrolyte secondary battery according to claim 8, wherein the oxygen element content is 0.30 mass% or less.   The nonaqueous electrolyte secondary battery according to claim 8 or 9, wherein the non-graphitizable carbonaceous material is derived from a plant-derived carbon precursor. The average interplanar spacing d ₀₀₂ of the (002) plane of the non-graphitizable carbonaceous material calculated using the Bragg equation by wide-angle X-ray diffraction method is 0.36 to 0.42 nm. The non-aqueous electrolyte secondary battery described in 1.   The potassium element content of the non-graphitizable carbonaceous material is 0.1% by mass or less, and the iron element content of the non-graphitizable carbonaceous material is 0.02% by mass or less. Non-aqueous electrolyte secondary battery.

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