Carbonaceous material, method of manufacturing the same, and electrochemical device

Abstract

This invention relates to carbonaceous materials, where the micropore volume is determined to be 0.05 cm³ using a grand canonical ensemble Monte Carlo simulation of the adsorption-desorption isotherms of carbon dioxide. 3 / g or more and 0.20cm 3 For g and below, in the aforementioned adsorption-desorption isotherms, the ratio of desorption to adsorption (desorption / adsorption) at a relative pressure of 0.01 is 1.05 or higher.

Description

Technical Field

[0001] This patent application claims priority under the Paris Convention to Japanese Patent Application No. 2020-074737 (filed on April 20, 2020) and Japanese Patent Application No. 2020-217413 (filed on December 25, 2020), which are incorporated herein by reference in their entirety.

[0002] This invention relates to carbonaceous materials, methods for manufacturing them, and electrochemical devices. Background Technology

[0003] Carbonaceous materials are used in electrochemical devices such as lithium-ion rechargeable batteries, non-aqueous electrolyte batteries like sodium-ion batteries, and lithium-ion capacitors, requiring carbonaceous materials with properties suitable for their applications. For example, in small portable devices such as mobile phones and laptops, battery capacity per unit volume becomes important, thus requiring increased discharge capacity. Furthermore, automotive lithium-ion rechargeable batteries are large and expensive, making replacement during use difficult; therefore, they require at least the same durability as automobiles, demanding high cycle durability where discharge capacity does not decrease even after repeated charging and discharging.

[0004] To address such requirements, for example, Patent Document 1 discloses a carbonaceous material for non-aqueous electrolyte secondary batteries that exhibits good discharge capacity and good resistance to oxidative degradation. Patent Document 2 discloses a carbonaceous material that achieves suppressed hygroscopicity and good battery characteristics.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-152226

[0008] Patent document 2: Japanese Patent No. 6237781. Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, the carbonaceous material described in Patent Document 1 is fired at a relatively high temperature, and the discharge capacity of a non-aqueous electrolyte secondary battery containing this carbonaceous material may not be sufficiently high. Furthermore, if the heat treatment temperature is lowered to increase the discharge capacity, there is a tendency for poor durability. In addition, the carbonaceous material described in Patent Document 2 has a skin portion containing volatile components derived from organic materials; therefore, it can be considered that its pores are covered, thereby achieving moisture absorption suppression and a higher discharge capacity. However, there is a demand for carbonaceous materials that possess both higher discharge capacity and high durability while maintaining their discharge capacity.

[0011] Therefore, the object of the present invention is to provide a carbonaceous material with excellent discharge capacity and cycle durability and high initial efficiency, and a method for manufacturing the same.

[0012] means for solving problems

[0013] In order to solve the aforementioned problems, the inventors conducted repeated and detailed studies and found that by having fine pores that show the inconsistency (hysteresis) between the adsorption curve and the desorption curve in the adsorption-desorption isotherm of carbon dioxide even when the heat treatment temperature is reduced, a carbonaceous material that maintains both discharge capacity and high durability can be obtained, thus completing the present invention.

[0014] That is, the present invention includes the following suitable modes.

[0015] [1] The pore volume of the carbonaceous material, calculated using a grand canonical ensemble Monte Carlo simulation of the adsorption-desorption isotherms of carbon dioxide, is 0.05 cm³. 3 / g or more and 0.20cm 3 For g and below, in the aforementioned adsorption-desorption isotherms, the ratio of desorption to adsorption (desorption / adsorption) at a relative pressure of 0.01 is 1.05 or higher.

[0016] [2] The carbonaceous material described in [1] has an oxygen content of 0.5% by mass or more.

[0017] [3] According to the carbonaceous material described in [1] or [2], wherein the BET specific surface area obtained by nitrogen adsorption is 1 m². 2 / g or more and 20m 2 / g or less.

[0018] [4] According to the carbonaceous material described in [1], the mesopore volume determined by the BJH method is 3.7 mm. 3 / g or more and 41mm 3 / g or less.

[0019] [5] According to the carbonaceous material described in [4], its average particle size (D) 50 The size ranges from 1.3μm to 9.5μm.

[0020] [6] According to the carbonaceous material described in [4] or [5], wherein the BET specific surface area obtained by nitrogen adsorption is 3 m². 2 / g or more and 60m 2 / g or less.

[0021] [7] The carbonaceous material according to any one of [1] to [6], wherein the average interplanar spacing d of the (002) plane is calculated using the Bragg formula based on wide-angle X-ray diffraction. 002It is above 0.36nm and below 0.42nm.

[0022] [8] The carbonaceous material according to any one of [1] to [7] is used in an electrochemical device.

[0023] [9] The carbonaceous material described in [8] is used with pre-doped metal ions.

[0024]

[10] An electrochemical device comprising any one of [1] to [9] a carbonaceous material.

[0025]

[11] A method for manufacturing a carbonaceous material according to any one of [1] to [9], comprising: having a BET specific surface area of ​​500 m² obtained by nitrogen adsorption. 2 In the process of heating a carbon precursor of less than / g to 900°C, the heating rate between 600°C and 900°C in the aforementioned process is less than 60°C / minute.

[0026]

[12] According to the method described in

[11] , the aforementioned heating process is carried out in the presence of volatile organic compounds.

[0027]

[13] A method for manufacturing a carbonaceous material according to any one of [1] to [9], comprising: making the BET specific surface area obtained by nitrogen adsorption method to be 500 m². 2 A process in which carbon precursors of less than / g are heat-treated for more than 5 minutes at a temperature of 600°C or higher and less than 900°C in the presence of volatile substances derived from volatile organic compounds.

[0028]

[14] The method according to any one of

[11] to

[13] further includes, after the aforementioned heating step or heat treatment step, a heat treatment step at 900°C or higher and 1180°C or lower.

[0029]

[15] The method according to any one of

[11] to

[14] further includes a pulverizing step of pulverizing the aforementioned carbon precursor and / or the heat-treated aforementioned carbon precursor.

[0030] Invention Effects

[0031] According to the present invention, a carbonaceous material with excellent discharge capacity and cycle durability and high initial efficiency, and a method for manufacturing the same, are available.

[0032] In another embodiment of the present invention, a carbonaceous material capable of high-speed predoping while simultaneously satisfying high capacity, high initial efficiency, and high cycle durability can also be provided. Detailed Implementation

[0033] The embodiments of the present invention will now be described in detail. It should be noted that the following description is merely illustrative of embodiments of the present invention and does not imply that the present invention is limited to these embodiments.

[0034] <Carbon-based materials>

[0035] The micropore volume of the carbonaceous material of this invention, determined by grand canonical ensemble Monte Carlo simulation of the adsorption-desorption isotherms of carbon dioxide, is 0.05 cm³. 3 / g or more and 0.20cm 3 For g and below, in the aforementioned adsorption-desorption isotherms, the ratio of desorption to adsorption (desorption / adsorption) at a relative pressure of 0.01 is 1.05 or higher.

[0036] [Volume of fine pores]

[0037] In this invention, the pore volume (hereinafter referred to as "pore volume") obtained by performing a grand canonical ensemble Monte Carlo simulation of the adsorption-desorption isotherm of carbon dioxide is 0.05 cm³. 3 / g or more and 0.20cm 3 / g or less. In this invention, if the pore volume is less than 0.05cm³... 3 If the pore volume is / g, it can be considered that excessive clogging of the pores due to thermal shrinkage may reduce the discharge capacity of the electrochemical device containing the carbonaceous material of the present invention. If the pore volume exceeds 0.20 cm³, the discharge capacity may be reduced. 3 If the concentration of carbonaceous material increases by a certain percentage (g), the number of active sites that can become the starting point for side reactions will increase, and therefore, the cycle durability of electrochemical devices containing the carbonaceous material of this invention may decrease. The preferred pore volume is 0.07 cm³. 3 / g or more, more preferably 0.10cm 3 / g or more, further preferably 0.13cm 3 / g or more, and preferably 0.19cm 3 / g or less, more preferably 0.18cm 3 / g or less, more preferably 0.17cm 3 / g or less. If the pore volume is above or below the aforementioned lower limit and below the aforementioned upper limit, the initial discharge capacity of the electrochemical device containing the carbonaceous material of the present invention is high, and the cycle durability is easily improved. The pore volume of the carbonaceous material of the present invention can be adjusted to be above or below the aforementioned lower limit and below the aforementioned upper limit by appropriately adjusting the type of carbon precursor, the temperature or time of the heating and / or heat treatment process, or the type or amount of volatile organic compounds and / or volatile substances in the manufacturing method of the carbonaceous material of the present invention described later. By performing a grand canonical ensemble Monte Carlo simulation on the adsorption-desorption isotherm of carbon dioxide, the pore volume, for example, when the pore diameter is 0.35 to 1.47 nm, can be determined. The pore volume can be determined by the method described in the examples described later.

[0038] Here, we will explain the pore volume obtained by performing a grand canonical ensemble Monte Carlo simulation of the adsorption-desorption isotherm of carbon dioxide in this invention. Typically, the pore volume of mesopores (pores with a diameter of approximately 2 nm or more and approximately 50 nm or less) or micropores (pores with a diameter less than approximately 2 nm) can be determined by applying analytical methods known as the BJH method or MP method to the adsorption-desorption isotherm of nitrogen at 77 K. However, in this invention, the adsorption-desorption isotherm of carbon dioxide at 273 K is used. This method uses carbon dioxide, whose molecular size is smaller than nitrogen, and the measurement is performed at a higher temperature; therefore, the molecules do not cluster together, and thus, a more detailed evaluation of the pore structure can be performed. It is clear that this allows for a more precise evaluation of pores, which can be the starting point of side reactions that are difficult to evaluate in conventional methods and affect cycle durability. It also allows for a more precise determination of discrepancies (hysteresis) between the adsorption and desorption curves, which can be considered to originate from the ink bottle-type pores described later.

[0039] [Ratio of carbon dioxide desorption to adsorption]

[0040] In this invention, in the adsorption-desorption isotherm of carbon dioxide, the ratio of desorption to adsorption (desorption / adsorption) at a relative pressure of 0.01 is 1.05 or higher. If the desorption / adsorption ratio is less than 1.05, side reactions are more likely to occur, leading to a decrease in cycle durability. The desorption / adsorption ratio is preferably 1.06 or higher, more preferably 1.08 or higher, further preferably 1.10 or higher, even more preferably 1.20 or higher, particularly preferably 1.30 or higher, extremely preferably 1.40 or higher, even more preferably 2.31 or higher, and particularly extremely preferably 2.37 or higher. If the desorption / adsorption ratio is above the aforementioned lower limit, there is a tendency to improve the cycle durability of electrochemical devices incorporating the carbonaceous material of this invention. When the desorption / adsorption ratio is large, the cycle durability is further improved due to the decrease in active sites that become the starting point of side reactions, which is associated with the increased number of ink bottle-shaped pores (described later). Therefore, the upper limit is not particularly limited and is typically 10.0 or lower. The desorption / adsorption capacity of the present invention can be adjusted to above the aforementioned lower limit by appropriately adjusting the temperature or time of the heating and / or heat treatment steps in the method for manufacturing the carbonaceous material of the present invention described later, or by adjusting the type or amount of volatile organic compounds and / or volatile substances. The desorption and adsorption capacity of carbon dioxide can be determined by the methods described in the examples described later.

[0041] Here, we explain the ratio of desorption to adsorption (desorption / adsorption) in the carbon dioxide adsorption-desorption isotherm at a relative pressure of 0.01. Theoretically, the adsorption and desorption curves should coincide when considering a cylindrical pore with one end blocked. However, sometimes the structure of the pore causes a discrepancy (hysteresis) between the adsorption and desorption curves. Various explanations exist for this phenomenon; for example, the "Journal of the Color Materials Association" (1994, Vol. 67, No. 2, pp. 115-123) suggests hysteresis occurs in the case of a bottle-shaped pore. According to this explanation, because the bottle-shaped pore has a head (the head radius is shorter than the bottom radius), it has different saturated vapor pressures. If the direction changes towards a lower relative pressure, the adsorbed layer at the head will not evaporate until it reaches the saturated vapor pressure corresponding to the head radius. In other words, even if evaporation were to begin from the bottom adsorbed layer, it would be squeezed by the condensation layer at the inlet, making desorption difficult. It can be argued that such operation easily leads to a shift in the adsorption and desorption amounts, with the desorption amount tending to exceed the adsorption amount. Therefore, based on this statement, the ratio of desorption to adsorption (desorption / adsorption) at a relative pressure of 0.01 in the adsorption-desorption isotherm within the aforementioned range indicates the possible existence of ink bottle-shaped pores.

[0042] [Oxygen content]

[0043] In a preferred embodiment of the present invention (hereinafter sometimes referred to as "Scheme I"), the oxygen content of the carbonaceous material is preferably 0.5% by mass or more, more preferably 0.6% by mass or more, further preferably 1.0% by mass or more, and even more preferably 1.1% by mass or more. Furthermore, the upper limit of the oxygen content is not particularly limited, and is typically 5.0% by mass or less, preferably 2.0% by mass or less, and more preferably 1.5% by mass or less. By setting the oxygen content to the aforementioned lower limit or above, a carbonaceous material with excellent solvent affinity can be easily obtained. The oxygen content can be adjusted to the aforementioned lower limit or above by, for example, adjusting the type of carbon precursor in the manufacturing method of the carbonaceous material of the present invention described later, or by adjusting the temperature or time of the heating and / or heat treatment process. Additionally, the oxygen content can be determined by, for example, elemental analysis or fluorescence X-ray analysis.

[0044] [BET specific surface area using nitrogen adsorption in Method I]

[0045] In Embodiment I of the present invention, the BET specific surface area (hereinafter also referred to as "specific surface area") of the carbonaceous material using the nitrogen adsorption method is preferably 1 m². 2 / g or more, preferably 2m 2 / g or more, preferably 3m 2 / g or more, and more preferably 4m 2 / g or more, preferably 5m2 / g or more, and preferably 20m 2 / g or less, more preferably 15m 2 / g or less, more preferably 10m 2 / g or less. If the specific surface area is above the aforementioned lower limit and below the aforementioned upper limit, the number of active sites that could become the starting point of side reactions decreases. Therefore, the input-output characteristics of the electrochemical device incorporating the carbonaceous material of the present invention become better, and the irreversible capacity is easily reduced. The specific surface area can be adjusted to be above the aforementioned lower limit and below the aforementioned upper limit by appropriately adjusting the temperature and time of the heating and / or heat treatment steps in the manufacturing method of the carbonaceous material of the present invention, or the type and amount of volatile organic compounds and / or volatile substances. The specific surface area of ​​the carbonaceous material of the present invention can be determined by the method described in the examples described later.

[0046] Average particle size (D) in Method I 50 )

[0047] The average particle size (D) of the carbonaceous material in method I can be used as a metric. 50 The carbonaceous material is prepared in a manner that, for example, ranges from 1 to 200 μm. If the average particle size is within this range, it is less likely to produce fine powder, the increase in specific surface area is suppressed, and side reactions of the resulting carbonaceous material are less likely to occur. Furthermore, when fabricating electrodes from the resulting carbonaceous material, it is easier to reduce the thickness of the active material coated onto the current collector, thus improving input / output characteristics and enabling an increase in electrode area. In Embodiment I, the average particle size of the carbonaceous material of the present invention is preferably 1 μm or more, more preferably 2 μm or more, further preferably 3 μm or more, particularly preferably 4 μm or more, and preferably 200 μm or less, more preferably 150 μm or less, further preferably 100 μm or less, and particularly preferably 50 μm or less.

[0048] [Mesoporous volume]

[0049] In another preferred embodiment of the invention (hereinafter sometimes referred to as "Scheme II"), the mesopore volume of the carbonaceous material determined by the BJH method is preferably 3.7 mm. 3 / g or more and 41mm 3 / g or less. If the mesopore volume is 3.7mm 3 / g or more and 41mm 3 When the density is below a certain value (e.g., g), the rate of ion diffusion from the electrolyte into the carbonaceous material is moderate, thus enabling easy and rapid pre-doping. Furthermore, since the number of active sites that become initiation points for side reactions is limited, it is easy to form carbonaceous materials that satisfy both high initial efficiency and high cycle durability. The preferred mesopore volume is 4.0 mm². 3 / g or more, preferably 8.0mm 3 / g or more, more preferably 10.5mm3 / g or more, and more preferably 10.9mm 3 / g or more, and preferably 35mm 3 / g or less, more preferably 22mm 3 / g or less, more preferably 14.4mm 3 / g or less. If the mesopore volume is within the aforementioned range, high-speed predoping is possible, and it is easier to achieve high capacity, high initial efficiency, and high cycle durability, especially high-speed predoping. Here, "mesopore volume" generally refers to the volume of pores with a diameter of about 2 nm or more and about 50 nm or less, but in this invention, especially from the viewpoint of evaluating active sites that become the starting point of side reactions and electrolyte diffusivity, it sometimes refers to pores of 2.5 nm or more and 33 nm or less. The mesopore volume can be adjusted to the aforementioned range by appropriately adjusting, for example, the type and particle size of the carbon precursor in the method for manufacturing the carbonaceous material of this invention described later, the temperature and / or time of the heat treatment process, the type and / or amount of volatile organic compounds, etc. The mesopore volume can be measured using a gas adsorption device and can be determined by, for example, the method described in the examples.

[0050] [Average particle size (D) in Method II] 50 )

[0051] The average particle size (D) of the carbonaceous material in Embodiment II of the present invention 50 The average particle size (D) of the carbonaceous material in Method II is preferably 1.3 μm or more, more preferably 2.2 μm or more, further preferably 2.6 μm or more, and preferably 9.5 μm or less, more preferably 8.0 μm or less, further preferably 5.5 μm or less, even more preferably 4.9 μm or less, and particularly preferably 4.7 μm or less. 50 If the average particle size is above the aforementioned lower limit, it is less likely to generate active sites that could become the starting point of side reactions, thus easily improving cycle durability and initial efficiency. 50 If the average particle size (D) is below the aforementioned upper limit, it is easier to increase the electrode density and the ion diffusion rate, thus exhibiting a tendency for high-speed predoping. Furthermore, it is easier to adjust the mesopore volume to the aforementioned range. Here, the average particle size (D) in this invention... 50 The average particle size (D) refers to the volume average particle size that accounts for 50% of the cumulative volume from the microparticle side in a particle size distribution measured by laser scattering. 50The particle size can be adjusted to the aforementioned range by appropriately adjusting, for example, the particle size of the carbon precursor in the method for manufacturing carbonaceous materials according to the present invention described later, the conditions of the pulverizing process, the temperature and / or time of the heat treatment process, and the mixing ratio of carbonaceous materials with different particle sizes. In particular, in order to produce carbonaceous materials with a desired average particle size, the average particle size can be adjusted to the aforementioned range by mixing two or more carbonaceous materials with different average particle sizes.

[0052] [BET specific surface area using nitrogen adsorption method in Method II]

[0053] In embodiment II of the present invention, the specific surface area of ​​the carbonaceous material is preferably 3m². 2 / g or more, preferably 9m 2 / g or more, further preferably 13m 2 / g or more, and more preferably 16m 2 / g or more, with 22m being a particularly preferred size. 2 / g or more, and preferably 60m 2 / g or less, more preferably 40m 2 / g or less, more preferably 35m 2 / g or less. In Method II, if the specific surface area is within the aforementioned range, the number of active sites that become the starting point of side reactions is easily reduced. In addition, an appropriate reaction area for reaction with the electrolyte can be ensured. Therefore, pre-doping can be easily performed quickly, and high capacity, high initial efficiency, and high cycle durability can be easily satisfied simultaneously. The specific surface area can be adjusted to the aforementioned range by appropriately adjusting the type and / or particle size of the carbon precursor, the temperature and / or time of the heat treatment process, the conditions of the pulverization process, the type and / or amount of volatile organic compounds, etc., in the method for manufacturing the carbonaceous material of the present invention described later. The specific surface area of ​​the carbonaceous material of the present invention can be measured using a gas adsorption device and can be determined by, for example, the method described in the examples.

[0054] The average inter-face spacing d of (002) surfaces 002 ]

[0055] The average interplanar spacing d of the (002) plane of the carbonaceous material of the present invention is calculated using wide-angle X-ray diffraction and the Bragg formula. 002 Preferably, the wavelength is 0.36 nm or more, more preferably 0.38 nm or more, and preferably 0.42 nm or less, more preferably 0.40 nm or less. If the average interplanar spacing d of the (002) surface... 002If the values ​​are above the aforementioned lower limit and below the aforementioned upper limit, then electrochemical devices incorporating the carbonaceous material of the present invention tend to exhibit excellent capacity retention at low temperatures. Furthermore, since ions readily invade, it is easy to form carbonaceous materials suitable for various electrochemical devices. The average interplanar spacing d of the (002) facet of the carbonaceous material of the present invention... 002 The temperature can be adjusted to be above the aforementioned lower limit and below the aforementioned upper limit by appropriately adjusting, for example, the temperature of the heating and / or heat treatment process in the manufacturing method described later. The average interplanar spacing d of the (002) facet of the carbonaceous material of the present invention... 002 It can be determined by, for example, X-ray diffraction.

[0056] <Manufacturing Methods of Carbonaceous Materials>

[0057] The carbonaceous material of the present invention can be manufactured, for example, by a method comprising achieving a BET specific surface area of ​​500 m² using a nitrogen adsorption method. 2 In the process of heating a carbon precursor of less than / g to 900°C, the heating rate between 600°C and 900°C in the aforementioned process is less than 60°C / minute.

[0058] In the aforementioned manufacturing method, the heating process is preferably carried out in the presence of volatile organic compounds.

[0059] Alternatively, the carbonaceous material of the present invention can also be manufactured by the following method, the method comprising: using a nitrogen adsorption method to obtain a BET specific surface area of ​​500 m². 2 A process in which carbon precursors of less than / g are heat-treated for more than 5 minutes at a temperature of 600°C or higher and less than 900°C in the presence of volatile substances derived from volatile organic compounds.

[0060] It can be inferred that in this invention, by heating the volatile organic compound and the carbon precursor, and / or by heat-treating the carbon precursor in the presence of volatile substances derived from the volatile organic compound, the following reaction occurs. It can be assumed that during the heating and / or heat-treating process, a skin portion can be formed on the surface of the sintered product (heat-treated product) of the carbon precursor, with the volatile components as its core. It can be assumed that by appropriately adjusting the heating rate of the heating and / or heat-treating process, the skin portion can be effectively formed, resulting in narrowed pores in the carbon precursor, forming inkwell-shaped pores with openings (hereinafter, the formation of the skin portion is sometimes referred to as modification). Carbonaceous materials with this structure, even at low heat-treating temperatures, will have fewer active sites for side reaction initiation due to the modification caused by volatile substances derived from the volatile organic compound, thus becoming carbonaceous materials that maintain both discharge capacity and high cycle durability. It is assumed that even if the actual method differs from the foregoing assumption, it is still included within the scope of this invention.

[0061] [Carbon precursor]

[0062] In this invention, the carbon precursor only needs to form a carbonaceous material, and its raw materials are not particularly limited. A wide range of carbon precursors can be selected from those derived from plants, minerals, natural raw materials, and synthetic raw materials. From both environmental and commercial perspectives, the carbonaceous material of this invention is preferably based on a plant-derived carbon precursor; in other words, the carbon precursor that becomes the carbonaceous material of this invention is preferably derived from plants.

[0063] Examples of carbon precursors derived from minerals include petroleum-based asphalt and coal-based asphalt, and coke. Examples of carbon precursors derived from natural raw materials include natural fibers such as cotton and hemp; regenerated fibers such as rayon and adhesive rayon; and semi-synthetic fibers such as acetate and triacetate. Examples of carbon precursors derived from synthetic raw materials include polyamide-based fibers such as nylon; polyvinyl alcohol-based fibers such as vinylon; polyacrylonitrile-based fibers such as polyacrylonitrile fibers; polyolefin-based fibers such as polyethylene and polypropylene; and polyurethane, phenolic resins, and vinyl chloride resins.

[0064] There are no particular limitations on the plants that can serve as raw materials for plant-derived carbon precursors (hereinafter sometimes referred to as "plant-derived char"). Examples include, for instance, coconut husks, coffee beans, tea leaves, sugarcane, fruits (e.g., oranges, bananas), wheat straw, rice husks, broadleaf trees, coniferous trees, and bamboo. This includes waste materials after their original use (e.g., used tea leaves) or parts of plants that become raw materials (e.g., banana peels, orange peels). These plants can be used alone or in combination of two or more. Among these plants, coconut husks, which are readily available in large quantities, are preferred.

[0065] It should be noted that charcoal refers to a powdery solid rich in carbon that is obtained by heating coal without melting or softening. Here, it also refers to a powdery solid rich in carbon that is obtained by heating organic matter without melting or softening.

[0066] There are no particular limitations on the coconut shell; examples include those from oil palm (oil coconut), coconut, snake fruit, and sea coconut. These coconut shells can be used alone or in combination. Coconut shells from coconuts and oil palms are particularly preferred, as they are biomass waste generated in large quantities for use in food, detergents, and biodiesel.

[0067] There is no particular limitation on the method for producing charcoal from coconut shells, and methods known in the art can be used. For example, it can be produced by heat-treating the coconut shells at a temperature of about 300 to 1000°C in an atmosphere of inert gases such as nitrogen, carbon dioxide, helium, argon, carbon monoxide or fuel exhaust, a mixture of these inert gases, or a mixture of these inert gases as the main component and other gases (e.g., a mixture of nitrogen and halogen gases).

[0068] Alternatively, it can be obtained in the form of charcoal (such as coconut shell charcoal).

[0069] Carbonaceous materials made from plant-derived charcoal can be incorporated with a large amount of active substances, making them generally suitable for use in electrochemical devices such as non-aqueous electrolyte secondary batteries. However, plant-derived charcoal often contains a large amount of metallic elements (especially potassium and iron) found in plant materials. Using electrodes made from carbonaceous materials with high levels of these metallic elements in electrochemical devices can sometimes have undesirable effects on electrochemical characteristics and safety. Therefore, it is preferable to minimize the content of elements such as potassium and iron in carbonaceous materials.

[0070] In addition to potassium and iron, plant-derived charcoal often contains alkali metals (e.g., sodium), alkaline earth metals (e.g., magnesium or calcium), transition metals (e.g., copper), and other elements (hereinafter collectively referred to as "ash"). When electrodes containing carbonaceous materials with these metal elements are used as the negative electrode in non-aqueous electrolyte secondary batteries such as lithium-ion batteries, impurities can dissolve into the electrolyte during dedoping from the negative electrode, negatively impacting battery performance and potentially compromising the reliability of the non-aqueous electrolyte secondary battery. Therefore, it is preferable to reduce the content of these metals.

[0071] Therefore, in order to obtain carbonaceous materials, it is preferable to reduce the ash content (alkali metals, alkaline earth metals, transition metals, and other elements) in char derived from plant materials or plants before heating and heat-treating the carbon precursor. Here, the reduction of the ash content in char derived from plant materials or plants will also be referred to as "deashing". There are no particular limitations on the deashing method, and methods such as the following can be used: deashing by extracting metal components using an acidic solution containing inorganic acids such as hydrochloric acid and sulfuric acid, and organic acids such as acetic acid and formic acid (liquid-phase deashing); and deashing by exposure in a high-temperature gas phase containing halogen compounds such as hydrogen chloride (gas-phase deashing).

[0072] Liquid-phase deashing can be carried out in any form from plant-derived raw materials or plant char. Liquid-phase deashing can be performed, for example, by impregnating plant-derived raw materials or plant char in an acidic solution. The acidic solution is a mixture of an acid and an aqueous solution. The acid is not particularly limited, and examples include inorganic acids such as hydrochloric acid and sulfuric acid; and aqueous solutions of organic acids such as acetic acid, butyric acid, and citric acid. From the viewpoint of avoiding the presence of unwanted ions in the deashed material, organic acids are preferred as the acid. From the viewpoints of deashing efficiency, acid price, and ease of wastewater treatment, acetic acid and / or citric acid are more preferred. Examples of aqueous solutions include water and mixtures of water and water-soluble organic solvents. Examples of water-soluble organic solvents include alcohols such as methanol, ethanol, propylene glycol, and ethylene glycol.

[0073] The acid concentration in the acidic solution is not particularly limited. Since the acid concentration affects the deashing rate, it is preferably in the range of 0.001 to 1 M, more preferably in the range of 0.002 to 0.9 M, and even more preferably in the range of 0.005 to 0.5 M. The amount of acidic solution is also not particularly limited. Preferably, it is the degree to which the plant-derived raw material or plant charcoal to be impregnated is impregnated in the acidic solution. For example, the mass of the acidic solution relative to the mass of the plant-derived raw material or plant charcoal to be impregnated is preferably 100 to 1000% by mass, more preferably 200 to 900% by mass, and even more preferably 250 to 800% by mass.

[0074] The temperature for liquid-phase deashing can be determined based on the plant-derived raw material or plant charcoal used for deashing. For example, it can be 10–120°C, preferably 20–100°C, and more preferably 25–95°C. If the deashing temperature is within the above range, it is possible to both suppress the decrease in carbon content caused by the hydrolysis of organic matter constituting the plant and to carry out deashing efficiently.

[0075] The time for liquid-phase deashing is not particularly limited; for example, it can be 0.1 to 100 hours, preferably 0.2 to 50 hours, and more preferably 0.5 to 20 hours. Liquid-phase deashing can be carried out continuously by impregnating plant-derived raw materials or plant charcoal in an acidic solution, or it can be carried out in multiple stages while refreshing the acidic solution used in deashing. When liquid-phase deashing is carried out in multiple stages, the total deashing time is taken as the liquid-phase deashing time.

[0076] The apparatus used in liquid-phase deashing is not particularly limited to any device capable of impregnating plant-derived raw materials or plant charcoal in an acidic solution. For example, a glass-lined stirring tank can be used.

[0077] Gas-phase deashing can be carried out in any form from plant-derived raw materials or plant char. Gas-phase deashing can be performed, for example, by heat-treating plant-derived raw materials or plant char in a gas phase containing a halogen compound. The halogen compound is not particularly limited, and examples include fluorine, chlorine, bromine, iodine, hydrogen fluoride, hydrogen chloride, hydrogen bromide, iodine bromide, chlorine fluoride (ClF), iodine chloride (ICl), iodine bromide (IBr), bromine chloride (BrCl), etc. Compounds or mixtures thereof that produce these halogen compounds through thermal decomposition can also be used. From the viewpoint of supply stability and the stability of the halogen compound used, hydrogen chloride is preferred.

[0078] Gas-phase deashing can be carried out in a gas phase containing halogen compounds and inert gases. The inert gas is any gas that does not react with the deashed material (derived from plant materials or plant char) and the deashed plant materials or plant char at the deashing temperature; there are no particular limitations. Examples include nitrogen, helium, argon, krypton, or mixtures thereof. From the viewpoint of supply stability and economy, nitrogen is preferred as the inert gas.

[0079] When performing gas-phase deashing in a gas phase mixed with halogen compounds and inert gases, the mixing ratio of halogen compounds to inert gases is not particularly limited as long as sufficient deashing can be achieved. For example, the amount of halogen compounds relative to inert gases is preferably 0.01 to 10.0 vol%, more preferably 0.05 to 8.0 vol%, and even more preferably 0.1 to 5.0 vol%.

[0080] The temperature for gas-phase deashing can be determined based on the plant-derived raw material or plant charcoal used for deashing. For example, it can be 500–1100°C, preferably 600–1050°C, more preferably 650–1000°C, and even more preferably 850–1000°C. If the deashing temperature is too low, the deashing efficiency may decrease, and deashing may not be complete. If the deashing temperature is too high, activation based on halogen compounds may occur.

[0081] There is no particular limitation on the time for gas phase deashing, for example, it is 5 to 300 minutes, preferably 10 to 200 minutes, and more preferably 15 to 150 minutes.

[0082] The supply rate (flow rate) of the gas phase in the gas phase deashing is not particularly limited. For example, it is preferably 1 ml / min or more, more preferably 5 ml / min or more, and even more preferably 10 ml / min or more, relative to 1 g of char derived from plant materials or plants.

[0083] The apparatus used in gas-phase deashing is not particularly limited to any device capable of simultaneously mixing and heating a gas phase containing halogen compounds with char derived from plant materials or plants. For example, a device using a fluidized bed reactor and employing a continuous or intermittent intralayer flow method based on a fluidized bed can be used.

[0084] In the case of gas-phase deashing, heat treatment can be performed in a gas phase containing halogen compounds, followed by further heat treatment under conditions free of halogen compounds. Typically, halogens are contained in plant-derived raw materials or plant charcoal. Halogens contained in plant-derived raw materials or plant charcoal can be removed by heat treatment under conditions free of halogen compounds. For example, halogens can be removed by blocking the supply of halogen compounds after the aforementioned heat treatment in a gas phase containing halogen compounds. Specifically, heat treatment under conditions free of halogen compounds can be performed in an inert gas atmosphere free of halogen compounds at 500°C to 1100°C, preferably 600°C to 1050°C, more preferably 650°C to 1000°C, and even more preferably 850°C to 1000°C. The temperature of the heat treatment under conditions free of halogen compounds is preferably the same as, or higher than, the temperature of the heat treatment in the gas phase containing halogen compounds. Furthermore, the heat treatment time under conditions where no halogen compounds are present is not particularly limited, but is preferably 5 to 300 minutes, more preferably 10 to 200 minutes, and even more preferably 10 to 100 minutes.

[0085] In this embodiment, liquid-phase deashing and gas-phase deashing are processes for removing ash such as potassium and iron contained in plant-derived raw materials or plant charcoal. The potassium content of the carbon precursor obtained after liquid-phase deashing or gas-phase deashing is preferably 1000 ppm (0.1% by mass) or less, more preferably 500 ppm or less, and even more preferably 300 ppm or less. The iron content of the carbon precursor obtained after liquid-phase deashing or gas-phase deashing is preferably 200 ppm or less, more preferably 150 ppm or less, and even more preferably 100 ppm or less. If the potassium and iron content of the carbon precursor is below the above upper limits, when the resulting carbonaceous material is used as an electrode in electrochemical devices such as non-aqueous electrolyte secondary batteries, the dissolution of impurities during dedoping in the electrolyte can be reduced, which is preferable from the viewpoint of improving the performance and reliability of the electrochemical device.

[0086] In the manufacturing method of the present invention, in order to produce carbonaceous materials with a desired particle size, a pulverizing step of crushing carbon precursors and / or heat-treated carbon precursors (described later) may be performed as needed. When the pulverizing step is performed, a grading step is preferably also performed.

[0087] In the pulverization process, from the viewpoint of processability when manufacturing electrochemical equipment, it is preferable to pulverize the carbon precursor and / or the heat-treated carbon precursor in such a way that the average particle size after the heating / heat treatment process becomes the desired particle size.

[0088] It should be noted that the carbon precursor shrinks by about 0 to 20% depending on the conditions of the heating and / or heat treatment processes described later. Therefore, when pulverizing the carbon precursor before the heating and / or heat treatment processes, it is preferable to prepare it in a manner where the average particle size of the carbon precursor is about 0 to 20% larger than the average particle size desired as a carbonaceous material.

[0089] Since the carbon precursor does not dissolve during the heating and / or heat treatment processes described later, the order of the pulverization process is not particularly limited. From the viewpoint of suppressing the decrease in the specific surface area of ​​carbonaceous materials and surface oxidation caused by pulverization, it is preferable to perform the pulverization process on the carbon precursor before the heating and / or heat treatment processes. This is because if the carbon precursor is heated with volatile organic compounds and / or heat-treated in the presence of volatile substances before pulverization, the reduction in specific surface area may not be sufficiently achieved. However, performing the pulverization process after the aforementioned processes is not excluded.

[0090] There are no particular limitations on the pulverizer used in the pulverizing process; for example, jet mills, ball mills, hammer mills, or rod mills can be used. From the viewpoint of minimizing the generation of fine powder, jet mills with a classification function are preferred. When using ball mills, hammer mills, or rod mills, fine powder can be removed by classification after the pulverizing process.

[0091] The grinding can be either wet grinding or dry grinding. From the viewpoint that no post-grinding such as drying is required, dry grinding is preferred.

[0092] The grading process allows for more precise adjustment of the average particle size of carbonaceous materials. For example, it can remove particles with a diameter of less than 1 μm.

[0093] When removing particles smaller than 1 μm by grading, in the carbonaceous material of the present invention, it is preferable that the content of particles smaller than 1 μm is 3.0 vol% or less. The removal of particles smaller than 1 μm is not particularly limited as long as it occurs after pulverization, but it is preferable to perform the pulverization and grading simultaneously. In the carbonaceous material of the present invention, from the viewpoint of reducing specific surface area and reducing irreversible capacity, the content of particles smaller than 1 μm is preferably 3.0 vol% or less, more preferably 2.5 vol% or less, and even more preferably 2.0 vol% or less.

[0094] There are no particular limitations on the grading method; examples include grading using sieves, wet grading, and dry grading. For wet grading machines, examples include those utilizing gravity grading, inertial grading, hydraulic grading, and centrifugal grading principles. For dry grading machines, examples include those utilizing sedimentation grading, mechanical grading, and centrifugal grading principles.

[0095] The pulverizing and grading processes can also be implemented using a single device. For example, a jet mill with dry grading capabilities can be used to perform both processes. Alternatively, a device can be used where the pulverizer and grader are independent. In this case, pulverizing and grading can be performed continuously or discontinuously.

[0096] To obtain carbonaceous materials with a desired average particle size, two or more specific carbon precursors or heat-treated carbon precursors (carbonaceous materials) with different average particle sizes can be mixed after undergoing a pulverizing process and, depending on the circumstances, a grading process.

[0097] In this invention, the specific surface area of ​​the carbon precursor (the specific surface area after the pulverization process when the carbon precursor is pulverized) is preferably 500 m². 2 / g or less, more preferably 450m 2 / g or less. If the specific surface area of ​​the carbon precursor is below the aforementioned upper limit, then by sufficiently performing the modification achieved by volatile substances in the heating and / or heat treatment processes described later, the cycle durability of electrochemical devices containing the carbonaceous material of the present invention can easily become good. The lower limit of the specific surface area of ​​the carbon precursor is not particularly limited, and is typically 25m². 2 / g or higher. The specific surface area of ​​the carbon precursor can be adjusted to below the aforementioned upper limit by appropriately adjusting the pre-firing temperature or time, or the pre-firing atmosphere. The specific surface area of ​​the carbon precursor can be determined using, for example, the BET method.

[0098] [Heating process]

[0099] One aspect of the invention includes, for example, setting the BET specific surface area to 500 m². 2 In the process of heating a carbon precursor of less than / g to 900°C, the heating rate between 600°C and 900°C in the aforementioned process is less than 60°C / min. The aforementioned heating process is preferably carried out in the presence of volatile organic compounds.

[0100] By heating the carbon precursor and volatile organic compounds to 600–900°C at a rate of less than 60°C / min, the volatile organic compounds are slowly volatilized, and the volatile substances derived from the volatile organic compounds remain in the system, thereby facilitating sufficient surface modification of the carbon precursor.

[0101] The preferred volatile organic compounds are those with a residual carbon content of less than 5% by mass, especially when ashing at 800°C. The volatile organic compounds preferably produce volatile substances (e.g., hydrocarbon gases, tar) that reduce the specific surface area of ​​carbon precursors. It should be noted that the content of volatile substances (e.g., hydrocarbon gases or tar components) that reduce specific surface area in the volatile organic compounds is not particularly limited, but from the viewpoint of stable operation of the machine, it is preferably 10% by mass or more. Furthermore, the upper limit of the volatile component content is not particularly limited, but from the viewpoint of suppressing the formation of tar components in the machine, it is preferably 95% by mass or less, more preferably 80% by mass or less, and even more preferably 50% by mass or less. The volatile component content is calculated based on the residual heat after strong heating of the sample in an inert gas and the feed rate. Regarding the intense heating, approximately 1g of volatile organic compounds (its exact mass is denoted as W0(g)) is added to a crucible. While circulating nitrogen gas at a rate of 20 liters per minute, the crucible is heated to 800°C using an electric furnace at a rate of 10°C / minute. This intense heating is then maintained at 800°C for 1 hour. The residue at this point is designated as the intense heating residue, denoted as W(g). The volatile component P(%) is calculated using the following formula.

[0102] [Mathematical Expression 1]

[0103]

[0104] Examples of volatile organic compounds include thermoplastic resins and low-molecular-weight organic compounds. Specifically, examples of thermoplastic resins include polystyrene, polyethylene, polypropylene, poly(meth)acrylic acid, and poly(meth)acrylate. It should be noted that in this specification, (meth)acrylic acid refers to the general term for methacrylic acid and acrylic acid compounds. Examples of low-molecular-weight organic compounds include toluene, xylene, mesitylene, styrene, naphthalene, phenanthrene, anthracene, and pyrene. From the perspective of preferably volatilizing within a certain temperature range and not oxidizing and activating the surface of the carbon precursor during thermal decomposition, polystyrene, polyethylene, and polypropylene are preferred as thermoplastic resins. From a safety perspective, low volatility at room temperature is preferred as a low-molecular-weight organic compound, and naphthalene, phenanthrene, anthracene, and pyrene are preferred.

[0105] In one embodiment of the present invention, olefin-based resins, styrene-based resins, and (meth)acrylic resins can be listed as thermoplastic resins. Examples of olefin-based resins include polyethylene, polypropylene, random copolymers of ethylene and propylene, and block copolymers of ethylene and propylene. Examples of styrene-based resins include polystyrene, poly(α-methylstyrene), and copolymers of styrene and alkyl (meth)acrylates (the alkyl group having 1 to 12 carbon atoms, preferably 1 to 6). Examples of (meth)acrylic resins include polyacrylic acid, polymethacrylic acid, and alkyl (meth)acrylate polymers (the alkyl group having 1 to 12 carbon atoms, preferably 1 to 6).

[0106] In one aspect of the present invention, a hydrocarbon compound having 1 to 20 carbon atoms can be used as a low-molecular-weight organic compound. The hydrocarbon compound preferably has 2 to 18 carbon atoms, more preferably 3 to 16. The hydrocarbon compound can be a saturated hydrocarbon compound or an unsaturated hydrocarbon compound, and can be a chain hydrocarbon compound or a cyclic hydrocarbon compound. In the case of an unsaturated hydrocarbon compound, the unsaturated bond can 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 examples include straight-chain or branched alkanes, alkenes, or alkynes. Examples of cyclic hydrocarbon compounds include alicyclic hydrocarbon compounds (e.g., cycloalkanes, cycloalkenes, cycloalkynes) or aromatic hydrocarbon compounds. Specifically, examples of aliphatic hydrocarbon compounds include methane, ethane, propane, butane, pentane, hexane, octane, nonane, decane, ethylene, propylene, butene, pentene, hexene, or acetylene. Examples of alicyclic hydrocarbon compounds include cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclopropane, cyclopentene, cyclohexene, cycloheptene, cyclooctene, decahydronaphthalene, norbornene, methylcyclohexane, or norbornadiene. Furthermore, examples of aromatic hydrocarbon compounds include monocyclic aromatic compounds such as benzene, toluene, xylene, mesitylene, cumene, butylbenzene, styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinylxylene, p-tert-butylstyrene, and ethylstyrene; and fused polycyclic aromatic compounds of tricyclic to hexacyclic rings such as naphthalene, phenanthrene, anthracene, and pyrene, preferably fused polycyclic aromatic compounds, and more preferably naphthalene, phenanthrene, anthracene, or pyrene. Here, the aforementioned hydrocarbon compounds may optionally have any substituents. Substituents are not particularly limited, but can be listed as alkyl groups with 1 to 4 carbon atoms (preferably alkyl groups with 1 to 2 carbon atoms), alkenyl groups with 2 to 4 carbon atoms (preferably alkenyl groups with 2 carbon atoms), and cycloalkyl groups with 3 to 8 carbon atoms (preferably cycloalkyl groups with 3 to 6 carbon atoms).

[0107] The volatile organic compounds are preferably solid at room temperature, more preferably thermoplastic resins such as polystyrene, polyethylene, or polypropylene that are solid at room temperature; or low-molecular-weight organic compounds such as naphthalene, phenanthrene, anthracene, or pyrene that are solid at room temperature. From the viewpoint of not oxidizing and activating the surface of the carbon precursor in the event of volatilization and thermal decomposition within a heating temperature range, olefin-based resins and styrene-based resins are preferred as thermoplastic resins, more preferably polystyrene, polyethylene, and polypropylene. From a safety perspective, hydrocarbon compounds with 1 to 20 carbon atoms are preferred as low-molecular-weight organic compounds, more preferably fused polycyclic aromatic compounds, and even more preferably naphthalene, phenanthrene, anthracene, or pyrene. Furthermore, from the viewpoint of residual carbon content, thermoplastic resins are preferred, more preferably olefin-based resins and styrene-based resins, even more preferably polystyrene, polyethylene, and polypropylene, and particularly preferably polystyrene and polyethylene.

[0108] The carbon residue rate is determined quantitatively by measuring the carbon content of the residual material after intense heating of the sample in an inert gas. Intensive heating refers to the following: approximately 1 g of volatile organic compounds (its accurate mass is denoted as W1(g)) is added to a crucible, and the crucible is heated from room temperature to 800°C at a rate of 10°C / min while nitrogen gas is passed through it at a rate of 20 liters per minute. This mixture is then heated at 800°C for 1 hour. The residue at this point is defined as the residual material after intense heating, and its mass is denoted as W2(g).

[0109] Next, elemental analysis was performed on the aforementioned residual carbon content according to the method specified in JIS M8819 to determine the carbon mass percentage P1 (mass%). The carbon residue rate P2 (mass%) was calculated using the following formula.

[0110] [Mathematical Expression 2]

[0111]

[0112] In this invention, the method of heating the carbon precursor and volatile organic compound is not particularly limited. The carbon precursor and organic compound can be premixed before heating, or the carbon precursor and volatile organic compound can be added to the heating system separately. To facilitate uniform modification of the carbon precursor surface, premixing is preferred.

[0113] The mixing of carbon precursors with volatile organic compounds can be carried out at any stage before or after the pulverization process.

[0114] When mixing is carried out before the pulverization process, pulverization and mixing can be carried out simultaneously by metering carbon precursors and volatile organic compounds and feeding them to the pulverization device at the same time.

[0115] When mixing after the pulverization process, any method that uniformly mixes the two components is acceptable, and any known mixing method can be used. When the volatile organic compounds are solid at room temperature, mixing in particulate form is preferred; the shape and size of the particles are not particularly limited. From the viewpoint of uniformly dispersing the volatile organic compounds into the pulverized carbon precursor, the average particle size of the volatile organic compounds is preferably 0.1–2000 μm, more preferably 1–1000 μm, and even more preferably 2–600 μm.

[0116] The aforementioned mixture may contain other components besides carbon precursors and volatile organic compounds. It may contain, for example, natural graphite, artificial graphite, metallic materials, alloying materials, or oxide-based materials. The content of other components is not particularly limited, but is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, further preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less, relative to 100 parts by mass of the mixture of carbon precursors and volatile organic compounds.

[0117] The mass ratio of carbon precursor to volatile organic compounds in the heating system is not particularly limited, but preferably 97:3 to 40:60, more preferably 95:5 to 60:40, and even more preferably 93:7 to 80:20. If the volatile organic compounds are 3 parts by mass or more, the modification can be easily and thoroughly carried out. On the other hand, if there are too many volatile organic compounds, excessive reaction will occur on the surface of the powder, which can easily form lumps, and therefore is not preferred.

[0118] The heating rate in the heating process at 600–900°C is preferably 60°C / min or less, more preferably less than 60°C / min, further preferably 50°C / min or less, even more preferably 40°C / min or less, particularly preferably 30°C / min or less, even more preferably 20°C / min or less, and extremely preferably 10°C / min or less. The lower limit of the heating rate is usually 5°C / min or more. If the heating rate is 60°C / min or more, the volatile organic compounds evaporate quickly, and the volatile substances are not easily retained. Therefore, the modification of the carbon precursor surface may not be sufficient. The reaction time in the heating process at 600–900°C, converted according to the aforementioned heating rate, is preferably 5 minutes or more, more preferably more than 5 minutes, further preferably 6 minutes or more, even more preferably 7.5 minutes or more, particularly preferably 10 minutes or more, even more preferably 15 minutes or more, and extremely preferably 30 minutes or more.

[0119] The heating rate from the initial temperature (e.g., room temperature) up to 600°C is not particularly limited, but from a commercial point of view, it is preferably 5 to 300°C / minute, more preferably 10 to 60°C / minute.

[0120] As the heating device, any device commonly used in the manufacture of carbonaceous materials can be used. Examples of such devices include circulating dryers, ovens, or rotary furnaces. To ensure uniform heating, the mixture can be heated while being properly stirred.

[0121] The heating process can be carried out in a non-reactive gas atmosphere. Examples of non-reactive gases include nitrogen and argon. Furthermore, the heating process can be performed under atmospheric pressure or reduced pressure; when performed under reduced pressure, it can be carried out at, for example, below 10 kPa.

[0122] [Heat treatment process]

[0123] Another aspect of the present invention includes having a BET specific surface area of ​​500m². 2 This method involves heat-treating a carbon precursor of less than / g at a temperature of 600°C to less than 900°C for more than 5 minutes in the presence of volatile substances derived from volatile organic compounds.

[0124] Volatile substances derived from volatile organic compounds are substances that volatilize into gaseous form from the aforementioned volatile organic compounds and substances that can reduce the specific surface area of ​​carbon precursors produced by the thermal decomposition of volatile organic compounds. Specific examples of substances that volatilize into gaseous form from volatile organic compounds can be, for example, hydrocarbon compounds with 1 to 20 carbon atoms. The number of carbon atoms in the hydrocarbon compound is preferably 2 to 18, more preferably 3 to 16. The hydrocarbon compound can be a saturated hydrocarbon compound or an unsaturated hydrocarbon compound, and can be a chain hydrocarbon compound or a cyclic hydrocarbon compound. In the case of unsaturated hydrocarbon compounds, the unsaturated bonds can be double bonds or triple bonds, and the number of unsaturated bonds contained in one molecule is not particularly limited. For example, chain hydrocarbon compounds are aliphatic hydrocarbon compounds, and examples include straight-chain or branched alkanes, alkenes, or alkynes. Examples of cyclic hydrocarbon compounds include alicyclic hydrocarbon compounds (e.g., cycloalkanes, cycloalkenes, cycloalkynes) or aromatic hydrocarbon compounds. Specifically, aliphatic hydrocarbon compounds include methane, ethane, propane, butane, pentane, hexane, octane, nonane, decane, ethylene, propylene, butene, pentene, hexene, or acetylene. Alicyclic hydrocarbon compounds include cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclopropane, cyclopentene, cyclohexene, cycloheptene, cyclooctene, decahydronaphthalene, norbornene, methylcyclohexane, or norbornadiene. Furthermore, aromatic hydrocarbon compounds include monocyclic aromatic compounds such as benzene, toluene, xylene, mesitylene, cumene, butylbenzene, styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinylxylene, p-tert-butylstyrene, and ethylstyrene; and fused polycyclic aromatic compounds of tricyclic to hexacyclic rings such as naphthalene, phenanthrene, anthracene, and pyrene. From the viewpoint of reactivity and processability with carbonaceous materials, monocyclic aromatic compounds such as benzene, toluene, xylene, mesitylene, cumene, butylbenzene, styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinylxylene, p-tert-butylstyrene, and ethylstyrene are preferred.

[0125] The concentration of the aforementioned volatile substances in the heat treatment system is preferably 1.0 vol% or more, more preferably 1.5 vol% or more, even more preferably 5 vol% or more, and preferably 95 vol% or less, more preferably 85 vol% or less, even more preferably 75 vol% or less. If the concentration of the volatile substances is within the aforementioned range, the modification of the carbon precursor is sufficiently carried out, and the impact on the heat treatment machine is easily reduced.

[0126] Gases included in a heat treatment system, excluding volatile substances, can include inactive gases, specifically nitrogen and argon. Furthermore, the heat treatment process can be carried out under atmospheric pressure or reduced pressure; when further reduced pressure is applied, it can be performed at, for example, below 10 kPa.

[0127] In the aforementioned heat treatment process, for example, volatile organic compounds may be added separately to a furnace or similar container and heated. After the system is filled with volatile substances derived from the volatile organic compounds, a carbon precursor is added to the system to allow it to react. Alternatively, volatile gaseous substances may be introduced into the reaction system containing the carbon precursor. The characteristic of this process is that the volatile gaseous substances react with the carbon precursor. By reacting with the volatile gaseous substances, the modification of the carbon precursor by the volatile substances is easily and fully achieved.

[0128] The heat treatment process is carried out at a temperature of 600°C or higher, more preferably 650°C or higher and less than 900°C, and most preferably 850°C or lower. If the heat treatment temperature is within the aforementioned range, excessive structural construction is difficult to achieve, thus easily suppressing the development of fine pores.

[0129] The heat treatment time is more than 5 minutes, preferably 15 minutes or more, and more preferably 30 minutes or more. Alternatively, it can be a fixed temperature within the aforementioned range, or it can involve temperature variations within the aforementioned range. When temperature variations occur, the rate of change is preferably less than 60°C / minute, more preferably less than 30°C / minute.

[0130] As the heating device, any device commonly used in the manufacture of carbonaceous materials can be used. Examples of such devices include circulating dryers, ovens, or rotary furnaces. To ensure uniform modification by volatile substances, the carbon precursor can be heated while being properly stirred.

[0131] [Additional heat treatment process]

[0132] In the method for manufacturing carbonaceous materials of the present invention, after the aforementioned heating step and / or heat treatment step, a heat treatment step of performing heat treatment at a temperature of 900°C or higher and 1180°C or lower may be further included.

[0133] The temperature of the additional heat treatment step is preferably 900°C or higher, more preferably 1000°C or higher, and preferably 1180°C or lower, more preferably 1100°C or lower. If the additional heat treatment temperature is within the aforementioned range, it is easy to obtain a carbonaceous material with high discharge capacity. As an embodiment of the present invention, when the heating is carried out under conditions where there are no volatile organic compounds and volatile substances, the lower limit of the temperature of the additional heat treatment step is preferably greater than 1100°C, more preferably 1140°C or higher.

[0134] The duration of the additional heat treatment step is preferably 10 minutes or more, more preferably 20 minutes or more, and more preferably 350 minutes or less, more preferably 120 minutes or less, and even more preferably 60 minutes or less. If the duration of the additional heat treatment step is within the aforementioned range, it is easy to obtain a carbonaceous material with high discharge capacity.

[0135] Similar to the aforementioned heating and heat treatment processes, the additional heat treatment process can be carried out in a non-reactive gas atmosphere. Examples of non-reactive gases include nitrogen and argon. Furthermore, the additional heat treatment process can be performed under atmospheric pressure or reduced pressure; in the case of reduced pressure, it can be performed at, for example, below 10 kPa.

[0136] The additional heat treatment process can be carried out continuously after the aforementioned heating process and / or heat treatment process, or it can be carried out after temporary cooling.

[0137] <Electrochemical Equipment>

[0138] The carbonaceous material of the present invention can be suitably used in electrochemical devices.

[0139] Examples of electrochemical devices include aqueous electrolyte batteries such as lead-carbon batteries; non-aqueous electrolyte batteries such as lithium-ion batteries, nickel-metal hydride batteries, nickel-cadmium batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-air batteries, all-solid-state batteries, and organic radical batteries; various batteries such as fuel cells; and capacitors such as electric double-layer capacitors, hybrid capacitors, and lithium-ion capacitors. Among these, non-aqueous electrolyte batteries (such as lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-air batteries, all-solid-state batteries, and organic radical batteries) are preferred, and lithium-ion batteries are particularly preferred.

[0140] When using pre-doped metal ions in electrochemical devices, alkali metal ions are preferred, lithium ions, sodium ions, and potassium ions are more preferred, and lithium ions are particularly preferred.

[0141] When used in batteries, the carbonaceous material of the present invention can be used, for example, as an electrode, a conductive material in an electrode, or an active material. Furthermore, when used in capacitors, it can be used, for example, as an electrode or an active material.

[0142] Therefore, the present invention also targets electrochemical devices incorporating the carbonaceous material of the present invention.

[0143] In such electrochemical devices, conventionally used constituent elements can be used as components other than the carbonaceous material of the present invention. For example, in a lithium-ion secondary battery, a negative electrode containing the carbonaceous material of the present invention can be manufactured as follows: a binder (adhesive) is added to the carbonaceous material of the present invention, an appropriate amount of suitable solvent is added, and the mixture is kneaded to form an electrode mixture, which is then coated onto a current collector formed of a metal plate or the like, dried, and then pressed and formed.

[0144] By using the carbonaceous material of the present invention, it is possible to manufacture electrodes with high conductivity even without the addition of conductive additives. For the purpose of imparting higher conductivity, conductive additives can be added as needed during the preparation of the electrode mixture. Conductive additives such as conductive carbon black, vapor-grown carbon fiber (VGCF), and nanotubes can be used. The amount of conductive additive added varies depending on the type of conductive additive used; if the amount added is too small, the desired conductivity may not be obtained, while if the amount added is too large, the dispersion in the electrode mixture may become poor. From this viewpoint, the preferred proportion of the added conductive additive is 0.5 to 10% by mass (here, the amount of active material (carbonaceous material) + binder + conductive additive = 100% by mass), more preferably 0.5 to 7% by mass, and particularly preferably 0.5 to 5% by mass. As a binder, any binder that does not react with electrolytes such as PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and mixtures of SBR (styrene-butadiene rubber) and CMC (carboxymethyl cellulose) is acceptable and is not particularly limited. Among these, PVDF is preferred because it causes less hindrance to lithium-ion movement and provides good input / output characteristics when attached to the surface of the active material. To dissolve PVDF and form a slurry, a polar solvent such as N-methylpyrrolidone (NMP) is preferred, but aqueous emulsions such as SBR and CMC can also be dissolved in water. If too much binder is added, the resistance of the resulting electrode increases, which can sometimes increase the internal resistance of the battery and reduce its performance. Conversely, if too little binder is added, the bonding between the particles of the negative electrode material and between it and the current collector material may be insufficient. The preferred amount of binder varies depending on the type of binder used; for example, for PVDF-based binders, 3 to 13% by mass is preferred, and more preferably 3 to 10% by mass. On the other hand, in binders using water as the solvent, multiple binders are often used in combination, such as mixtures of SBR and CMC. The total amount of all binders used is preferably 0.5 to 5% by mass, and more preferably 1 to 4% by mass.

[0145] The electrode active material layer is primarily formed on both sides of the current collector, but it can also be formed on one side as needed. A thicker electrode active material layer requires fewer current collectors and separators, which is preferable for high capacity applications. However, a larger electrode area opposite the counter electrode is advantageous for improving input-output characteristics; therefore, if the electrode active material layer is too thick, the input-output characteristics may sometimes decrease. From the viewpoint of battery output during discharge, the preferred thickness of the active material layer (on each side) is 10–500 μm, more preferably 20–280 μm, and particularly preferably 20–80 μm.

[0146] When using the carbonaceous material of the present invention to form the negative electrode for a lithium-ion secondary battery, there are no particular limitations on other materials constituting the battery, such as the positive electrode material, separator, and electrolyte, and various materials conventionally used or proposed as lithium-ion secondary batteries can be used.

[0147] For example, as a cathode material, a layered oxide system (represented by LiMO2, where M is a metal, such as LiCoO2, LiNiO2, LiMnO2, or LiNi) is preferred. x Co y Mo z A composite metal chalcogenide compound consisting of O2 (where x, y, and z represent the composition ratio), olivine-based (represented by LiMPO4, where M is a metal, such as LiFePO4), and spinel-based (represented by LiM2O4, where M is a metal, such as LiMn2O4) can be mixed as needed. The positive electrode is formed by molding these materials together with a suitable binder and a carbon material to impart conductivity to the electrode, and then forming a layer on the conductive current collector material.

[0148] These non-aqueous solvent-based electrolytes, used in combination with positive and negative electrodes, are typically formed by dissolving the electrolyte in a non-aqueous solvent. As non-aqueous solvents, one or more of the following organic solvents can be used: propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, γ-butyl lactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, or 1,3-dioxolane. Additionally, as electrolytes, LiClO4, LiPF6, LiBF4, LiCF3SO3, LiAsF6, LiCl, LiBr, LiB(C6H5)4, or LiN(SO3CF3)2 can be used.

[0149] Lithium-ion secondary batteries are generally formed by separating the positive and negative electrodes, which are created as described above, from each other as needed, using a permeable separator made of nonwoven fabric, other porous materials, etc., and then immersing them in an electrolyte. The separator can be a permeable separator made of nonwoven fabric, other porous materials, commonly used in secondary batteries. Alternatively, a solid electrolyte made of polymer gel, impregnated in the electrolyte, can be used instead of or in conjunction with the separator.

[0150] When using the above-mentioned lithium-ion secondary battery with pre-doping, before combining the positive electrode, negative electrode, separator and electrolyte to form the battery and before the first charge, a pre-doping process can be performed to pre-absorb metal ions in the negative electrode active material.

[0151] There are no particular limitations on the method of doping lithium ions into the negative electrode active material. Examples of such methods include: preparing a slurry by dispersing the negative electrode active material and metallic lithium in an electrolyte; mixing the prepared slurry (in which case, an amount of lithium ions corresponding to the amount of metallic lithium added can be doped into the negative electrode active material); sequentially stacking a negative electrode active material layer, a separator, and a lithium metal layer (e.g., lithium metal foil) made using the negative electrode active material; clamping the resulting stack with a pair of current collectors (e.g., copper foil); using a known charge-discharge device to externally short-circuit the negative electrode active material layer and the lithium metal layer of the stack; and performing electrochemical pre-doping by charging the negative electrode active material layer.

[0152] Example

[0153] Determination of the adsorption-desorption isotherm of carbon dioxide

[0154] For each carbonaceous material, the adsorption and desorption of carbon dioxide at 273 K were measured using a gas adsorption measurement device (Quantachrome, AUTOSORB-iQMP-XR) at a relative pressure (p / p0) of 0.00075 to 0.030, thereby obtaining adsorption and desorption isotherms.

[0155] [Volume of fine pores]

[0156] For the aforementioned adsorption-desorption isotherms, the "CO2 at 273K oncarbon" calculation model was used to perform Grand Canonical Monte Carlo analysis to determine the pore volume with a diameter of 0.35–1.47 nm.

[0157] [Adsorption and desorption of carbon dioxide]

[0158] Using the adsorption-desorption isotherms obtained above, the desorption / adsorption amount is calculated based on the ratio of desorption to adsorption at a relative pressure of 0.01.

[0159] <Oxygen content>

[0160] The oxygen content was determined using the "Oxygen, Nitrogen and Hydrogen Analyzer EMGA-930" manufactured by Horiba Manufacturing Co., Ltd.

[0161] The detection method of this device is oxygen: non-reactive gas melting-non-dispersive infrared absorption (NDIR), and calibration is performed using Ni capsules, TiH2 (H standard sample), and SS-3 (oxygen standard sample). As a pretreatment, 20 mg of the sample after water content determination at 250°C for approximately 10 minutes is measured into a Ni capsule, degassed for 30 seconds in the elemental analysis device, and then measured. The three samples are analyzed, and their average value is taken as the analytical value.

[0162] <Mesoporous volume>

[0163] Using a BELSORP-mini instrument manufactured by BEL Corporation of Japan, the carbonaceous materials obtained in the examples and comparative examples were filled into test tubes. After heating at 300°C for 5 hours under reduced pressure, the nitrogen adsorption isotherm of the carbonaceous materials at 77 K was measured. For the obtained adsorption isotherms, the Barrett-Joyner-Halenda (BJH) method was applied, defining the range of pore diameters from 2.5 nm to 33 nm as the mesopore volume.

[0164] Average particle size (D) 50 )>

[0165] The carbon precursors used in the examples and comparative examples, and the average particle size D of the carbonaceous materials obtained in the examples and comparative examples. 50 (Particle size distribution) was determined by laser scattering as follows. Samples of the carbon precursor and carbonaceous material from the examples and comparative examples described later were added to an aqueous solution containing 0.3% by mass of a surfactant (Toriton X 100, manufactured by Wako Pure Chemical Industries, Ltd.), and treated with an ultrasonic cleaner for at least 10 minutes to disperse them in the aqueous solution. The particle size distribution was then determined using this dispersion. The particle size distribution was determined using a particle size / particle size distribution meter (MICROTRAC MT3000, manufactured by Nikkiso Corporation), with the solvent refractive index set to 1.33 and particle permeability set to absorption. The particle size at which the cumulative volume reaches 50% was defined as the average particle size D. 50 .

[0166] <BET specific surface area using nitrogen adsorption>

[0167] The specific surface area of ​​carbonaceous materials and carbon precursors is determined by the BET method (Nitrogen Adsorption BET Three-Point Method) (BET specific surface area). The approximate formula derived from the BET formula is described below.

[0168] [Mathematical Expression 3]

[0169] p / [v(p0-p)]=(1 / v m c)+[(c-1) / v m c](p / p0)

[0170] Using the aforementioned approximation, v can be determined using the three-point method based on nitrogen adsorption at liquid nitrogen temperature. m The specific surface area of ​​the sample is calculated using the following formula.

[0171] [Mathematical Expression 4]

[0172]

[0173] At this time, v m This is the necessary adsorption amount (cm³) for forming a monolayer on the sample surface. 3 / g), v is the measured adsorption amount (cm³). 3 / g), p0 is the saturated vapor pressure, p is the absolute pressure, c is a constant (reflecting the heat of adsorption), and N is Avogadro's constant 6.022 × 10⁻⁶. 23 ,a(nm 2 ) represents the area occupied by the adsorbate molecules on the sample surface (the cross-sectional area occupied by the molecules).

[0174] Specifically, using the "BELL Sorb Mini" manufactured by BELL Corporation of Japan, the adsorption amount of nitrogen on the sample at liquid nitrogen temperature was determined as follows: The sample was filled into a test tube, and the pressure was temporarily reduced while the test tube was cooled to -196°C. Subsequently, nitrogen gas (99.999% purity) was adsorbed onto the sample using a desired relative pressure. The amount of nitrogen gas adsorbed by the sample at the equilibrium pressure reached under each desired relative pressure is defined as the adsorbed gas volume v.

[0175] <(002) interface spacing d 002 >

[0176] Using a "MiniFlexII" instrument manufactured by RIGAKU, carbonaceous material was filled into the sample holder, and CuKα rays monochromated with a Ni filter were used as the X-ray source to obtain X-ray diffraction patterns. The peak positions of the diffraction patterns were determined by the centroid method (the method of finding the centroid position of the diffracted rays and using the corresponding 2θ value to determine the peak position), and the diffraction peaks of the (111) plane of high-purity silicon powder were used as a standard material for correction. The wavelength λ of CuKα rays was set to 0.15418 nm, and d was calculated using the Bragg formula described below. 002 .

[0177] [Mathematical Expression 5]

[0178]

[0179] <Determination of Residual Carbon Content>

[0180] The carbon residue was determined quantitatively by measuring the amount of carbon in the residual material after intense heating of the sample in an inert gas. In the intense heating process, approximately 1 g of volatile organic compounds (its exact mass is denoted as W1(g)) was added to a crucible. While passing nitrogen gas at a rate of 20 liters per minute, the crucible was heated from room temperature to 800°C using an electric furnace at a rate of 10°C / minute. This temperature was then maintained at 800°C for 1 hour. The residue at this point was defined as the residual material after intense heating, and its mass was recorded as W2(g).

[0181] Next, elemental analysis was performed on the aforementioned residual carbon content according to the method specified in JIS M8819 to determine the carbon mass percentage P1 (mass%). The residual carbon percentage P2 (mass%) was calculated using the following formula.

[0182] [Mathematical Expression 6]

[0183]

[0184] <Preparation of carbon precursors>

[0185] 100g of coconut shell char A (containing 98% by mass of particles with a diameter of 0.850–2.360 mm) obtained by crushing and dry distilling coconut shells at 500°C was supplied with nitrogen gas containing 1% by volume of hydrogen chloride gas at a flow rate of 10 L / min and treated at 950°C for 80 minutes. Then, the supply of hydrogen chloride gas was stopped, and the product was heat-treated at 950°C for 30 minutes.

[0186] Subsequently, the particles were coarsely pulverized to an average particle size of 10 μm using Finmill SF5 (manufactured by Japan Cornex Corporation), and then further pulverized using a small jet mill ("Coating System α-mkIII" manufactured by Seishin Enterprises Co., Ltd.). Finally, they were classified using Labclast N-01 (manufactured by Seishin Enterprises Co., Ltd.), yielding particles with a specific surface area of ​​410 m². 2 / g, carbon precursor A with an average particle size of 5.1μm and a specific surface area of ​​400m 2 / g, carbon precursor B with an average particle size of 9.7μm.

[0187] The carbon precursor A with an average particle size of 5.1 μm was further pulverized with powder SF5 (manufactured by Japan Coxs Corporation) to obtain carbon precursors with average particle sizes of 1.3 μm, 2.2 μm, 2.6 μm and 3.1 μm (denoted as carbon precursors C, D, E and F, respectively).

[0188] 1. Experimental examples related to carbonaceous materials of method I

[0189] <Example 1>

[0190] 0.9 g of polystyrene (manufactured by Sekisui Chemicals, Inc., with an average particle size of 400 μm and a carbon residue of 1.2% by mass) was mixed with 9.1 g of carbon precursor B. 10 g of this mixture was added to a graphitic crucible to form a sample layer approximately 3 mm thick. The crucible was placed in a high-speed heating furnace manufactured by Motoyama Corporation. The heating rate was set to 5 °C per minute for 60 minutes, with a nitrogen flow rate of 5 L per minute, between 600 °C and 900 °C. Outside this temperature range, the rate was set to 60 °C per minute. After reaching 900 °C, the temperature was held at this temperature for 60 minutes, followed by natural cooling. Once the furnace temperature was confirmed to have dropped below 200 °C, the carbonaceous material was removed from the furnace.

[0191] <Example 2>

[0192] The heating rate was set to 10°C per minute (heating time was 30 minutes) from 600°C to 900°C. After heating to 900°C, the temperature was maintained at that temperature for 20 minutes. Otherwise, the process was the same as in Example 1 to obtain carbonaceous material.

[0193] <Example 3>

[0194] The heating rate was set to 20°C per minute (heating time was 15 minutes) from 600°C to 900°C. Then, the temperature was increased to 1000°C at a rate of 60°C per minute and held at that temperature for 20 minutes. Otherwise, the process was the same as in Example 1 to obtain carbonaceous material.

[0195] <Example 4>

[0196] The heating rate was set to 20°C per minute (heating time was 15 minutes) from 600°C to 900°C. Then, the temperature was increased to 1100°C at a rate of 60°C per minute and held at that temperature for 20 minutes. Otherwise, the process was the same as in Example 1 to obtain carbonaceous material.

[0197] <Example 5>

[0198] The heating rate was set to 5°C per minute (heating time was 60 minutes) from 600°C to 900°C. Then, the temperature was increased to 1175°C at a rate of 60°C per minute and held at that temperature for 20 minutes. Otherwise, the process was the same as in Example 1 to obtain carbonaceous material.

[0199] <Example 6>

[0200] 6.4 g of carbon precursor B was added to a graphitic crucible to form a sample layer thickness of approximately 3 mm. The crucible was placed in a tubular furnace manufactured by Motoyama Corporation. The temperature was increased to 600°C at a nitrogen flow rate of 5 L / min and a heating rate of 60°C / min. After reaching 600°C, toluene was introduced into the furnace using a syringe pump at a nitrogen concentration of 1.5% by volume, and the temperature was increased to 900°C at a heating rate of 5°C / min (for 60 minutes). This temperature was then held for 60 minutes and allowed to cool naturally. Once the furnace temperature was confirmed to have dropped below 200°C, the carbonaceous material was removed from the furnace.

[0201] <Comparative Example 1>

[0202] 0.6 g of polystyrene (manufactured by Sekisui Chemicals, Inc., with an average particle size of 400 μm and a residual carbon content of 1.2% by mass) was mixed with 6.4 g of carbon precursor B. 7 g of this mixture was added to a graphitic crucible with a sample layer thickness of approximately 3 mm, and then placed into a tubular furnace manufactured by Motoyama Co., Ltd., preheated to 900 °C at a nitrogen flow rate of 5 L / min. The furnace temperature was measured; at the moment the sample was added, the furnace temperature decreased, but it took 1 minute to rise from 600 °C to 900 °C. It was then maintained at 900 °C for 20 minutes. After treatment, it was allowed to cool naturally until the furnace temperature dropped below 200 °C, at which point the carbonaceous material was removed from the furnace.

[0203] <Comparative Example 2>

[0204] 9.1 g of carbon precursor B was added to a graphitic crucible to form a sample layer thickness of approximately 3 mm. The crucible was placed in a high-speed heating furnace manufactured by Motoyama Corporation. The heating rate was set to 10°C per minute (for 30 minutes) within the range of 600°C to 900°C, and 60°C per minute in the remaining temperature range. After reaching 900°C, the temperature was held for 20 minutes, followed by natural cooling. Once the furnace temperature was confirmed to have dropped below 200°C, the carbonaceous material was removed from the furnace.

[0205] <Comparative Example 3>

[0206] Mix 0.9g of polystyrene (manufactured by Sekisui Chemicals, Inc., with an average particle size of 400μm and a residual carbon content of 1.2% by mass) into 9.1g of carbon precursor B. Place 10g of the mixture in a high-speed heating furnace manufactured by Motoyama Co., Ltd., and heat it to 1270°C at a nitrogen flow rate of 5L / min and a heating rate of 60°C / min. Hold it at this temperature for 11 minutes and then allow it to cool naturally. Once the furnace temperature has dropped below 200°C, remove the carbonaceous material from the furnace.

[0207] <Comparative Example 4>

[0208] Mix 0.9g of polystyrene (manufactured by Sekisui Chemicals, Inc., with an average particle size of 400μm and a residual carbon content of 1.2% by mass) into 9.1g of carbon precursor B. Place 10g of the mixture in a high-speed heating furnace manufactured by Motoyama Corporation, and heat it to 1290°C at a nitrogen flow rate of 5L / min and a heating rate of 60°C / min. Hold it at this temperature for 11 minutes, and then allow it to cool naturally. Once the furnace temperature has dropped below 200°C, remove the carbonaceous material from the furnace.

[0209] The conditions of the heating process and / or heat treatment process, as well as the physical properties of the resulting carbonaceous materials, are shown in Tables 1 and 2, respectively.

[0210] [Table 1]

[0211]

[0212] [Table 2]

[0213]

[0214] <Battery Review>

[0215] [Fabrication of carbon electrodes]

[0216] A slurry was prepared by mixing 96.2 parts by weight of carbonaceous material, 2 parts by weight of conductive carbon black (TIMCAL's "Super-P" (registered trademark)), 1 part by weight of CMC, a specified amount of SBR, and water. The slurry was then coated onto copper foil, dried, and pressurized to obtain an electrode with a thickness of 60–80 μm. The density of the resulting electrode was 0.95 g / cm³. 3 The electrode was punched into a circular plate with a diameter of 14 mm to obtain a carbon electrode plate.

[0217] [Preparation of the negative electrode half-cell]

[0218] The resulting carbon electrode was punched into a circular plate with a diameter of 14 mm to form the active electrode, and metallic lithium was used as the counter electrode. Ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were mixed in a volume ratio of 1:1:1 as the solvent. 1 mol / L LiPF6 was dissolved in this solvent as the electrolyte. A polypropylene membrane was used as the separator. The coin cell was fabricated in a glove box under an argon atmosphere.

[0219] [Determination of discharge capacity and initial efficiency]

[0220] For the aforementioned negative electrode half-cell, charge-discharge tests were conducted using a charge-discharge test apparatus (TOSCAT, manufactured by Toyo Systems). Lithium doping was performed at a rate of 70 mA / g relative to the mass of the active material until the lithium potential reached 1 mV. Then, a constant voltage of 1 mV relative to the lithium potential was applied for 8 hours to stop the doping. The capacity at this point was defined as the charge capacity (mAh / g). Next, dedoping was performed at a rate of 70 mA / g relative to the mass of the active material until the lithium potential reached 1.5 V. The capacity discharged at this point was defined as the discharge capacity (mAh / g). The percentage obtained by dividing the discharge capacity (mAh / g) by the charge capacity (mAh / g) was used as the charge-discharge efficiency (initial efficiency) (%), which is an indicator of the lithium-ion utilization efficiency within the battery. The results are shown in Table 3.

[0221] [The production of the positive electrode]

[0222] As the positive electrode active material, 90 parts by weight of lithium iron phosphate (LiFePO4), 5 parts by weight of PVDF (polyvinylidene fluoride), 5 parts by weight of acetylene black, and NMP (N-methylpyrrolidone) were mixed to obtain a slurry. The slurry was coated onto aluminum foil, dried, and then pressurized to obtain an electrode with a thickness of 80–140 μm. The density of the obtained electrode was 1.8 g / cm³. 3 The electrode was punched into a circular plate with a diameter of 14 mm to obtain the positive electrode plate.

[0223] [Preparation of the positive half-cell]

[0224] Lithium metal was used as both the counter and reference electrode, relative to the resulting positive electrode. Ethylene carbonate and ethyl methyl carbonate were mixed in a volume ratio of 3:7 as the solvent. 1 mol / L LiPF6 was dissolved in this solvent as the electrolyte. Glass fiber nonwoven fabric was used as the separator. The coin cell was fabricated in a glove box under an argon atmosphere.

[0225] For the aforementioned positive electrode half-cell, charge-discharge tests were conducted using a charge-discharge testing apparatus (TOSCAT, manufactured by Toyo Systems). Lithium dedoping from the positive electrode was carried out at a rate of 15 mA / g relative to the active material mass until the lithium potential reached 4.0 V; this capacity was defined as the charge capacity. Next, lithium doping into the positive electrode was carried out at a rate of 15 mA / g relative to the active material mass until the lithium potential reached 2.0 V; this capacity was defined as the discharge capacity. The resulting charge capacity was 153 mAh / g, and the discharge capacity was 141 mAh / g. The charge-discharge efficiency (initial charge-discharge efficiency), calculated as the percentage of discharge capacity to charge capacity, was 92%.

[0226] [Making a coin cell battery (full cell)]

[0227] The resulting carbon electrode was punched into a circular plate with a diameter of 15 mm and used as the negative electrode. The coated surfaces of the negative and positive electrodes were positioned opposite each other, separated by a separator made of glass fiber nonwoven fabric, with the positive electrode (14 mm in diameter) not exposed from the negative electrode surface. The ratio of negative electrode charging capacity (mAh) to positive electrode charging capacity (mAh) per unit relative area (negative electrode capacity / positive electrode capacity) was adjusted to 1.05. Ethyl carbonate and ethyl methyl carbonate were mixed in a volume ratio of 3:7 as the solvent. 1 mol / L of LiPF6 was dissolved in this solvent as the electrolyte. The coin battery was fabricated in a glove box under an argon atmosphere.

[0228] [Charge-discharge test (cycle endurance test)]

[0229] For the aforementioned coin cell battery (full cell), charge-discharge tests were conducted using a charge-discharge testing apparatus (TOSCAT, manufactured by Toyo Systems). Charging was performed at a rate of 70 mA / g relative to the mass of the negative electrode active material until the lithium potential reached 4.0V. Then, discharging was performed at a rate of 70 mA / g relative to the mass of the negative electrode active material until the lithium potential reached 2.0V. This cycle was repeated three times.

[0230] Subsequently, the electrode was charged at a rate of 500 mA / g relative to the mass of the negative electrode active material until it reached 4.0 V relative to the lithium potential; the capacity at this point was recorded as the charge capacity. Next, it was discharged at a rate of 500 mA / g relative to the mass of the negative electrode active material until it reached 2.0 V relative to the lithium potential; the capacity at this point was recorded as the discharge capacity. This cycle was repeated 500 times. The percentage obtained by dividing the discharge capacity of the 500th cycle by the discharge capacity of the 1st cycle was recorded as the maintenance rate over 500 cycles. The results are shown in Table 3.

[0231] [Table 3]

[0232]

[0233] It is evident that the lithium-ion secondary battery having a negative electrode comprising the carbonaceous material obtained in Examples 1-6 has high initial efficiency and discharge capacity. Furthermore, it is evident that the discharge capacity retention rate after 500 cycles is also high. On the other hand, the lithium-ion secondary battery having a negative electrode comprising the carbonaceous material obtained in Comparative Examples 1-4 has at least one of the following: discharge capacity and retention rate after 500 cycles.

[0234] 2. Experimental examples related to carbonaceous materials of method II

[0235] <Example 7>

[0236] 9.1 g of carbon precursor B with an average particle size of 9.7 μm was mixed with 0.9 g of polystyrene (manufactured by Sekisui Chemicals Co., Ltd., with an average particle size of 400 μm and a residual carbon content of 1.2% by mass). 10 g of this mixture was added to a graphitic crucible with a sample layer thickness of approximately 3 mm and placed in a high-speed heating furnace manufactured by Motoyama Co., Ltd. The heating rate was set to 5 °C per minute (60 minutes) at a nitrogen flow rate of 5 L per minute between 600 °C and 900 °C, and 60 °C per minute in other temperature ranges. After reaching 900 °C, the temperature was held at that temperature for 20 minutes, followed by natural cooling. Once the furnace temperature was confirmed to have dropped below 200 °C, the carbonaceous material was removed from the furnace, yielding a carbonaceous material with an average particle size of 9.6 μm.

[0237] Using the same method as carbon precursor B with an average particle size of 9.7 μm, carbon precursor D with an average particle size of 2.2 μm was processed to obtain carbonaceous material with an average particle size of 2.1 μm.

[0238] Next, carbonaceous material with an average particle size of 2.1 μm and carbonaceous material with an average particle size of 9.7 μm were mixed at a mass ratio of 1:1 to obtain carbonaceous material with an average particle size of 4.5 μm.

[0239] <Example 8>

[0240] The heating rate was set to 20°C per minute (heating time was 15 minutes) from 600°C to 900°C. After heating to 1000°C, the temperature was maintained at that temperature for 20 minutes. Otherwise, the process was the same as in Example 7 to obtain carbonaceous material.

[0241] <Example 9>

[0242] 9.1 g of carbon precursor D with an average particle size of 2.2 μm was mixed with 0.9 g of polystyrene (manufactured by Sekisui Chemicals Co., Ltd., with an average particle size of 400 μm and a residual carbon content of 1.2% by mass). 10 g of this mixture was added to a graphitic crucible with a sample layer thickness of approximately 3 mm and placed in a high-speed heating furnace manufactured by Motoyama Co., Ltd. The heating rate was set at 20 °C per minute (for 15 minutes) at a nitrogen flow rate of 5 L per minute between 600 °C and 900 °C, and at 60 °C per minute in other temperature ranges. After heating to 1100 °C, the temperature was held at this temperature for 20 minutes, followed by natural cooling. Once the furnace temperature was confirmed to have dropped below 200 °C, the carbonaceous material was removed from the furnace, yielding a carbonaceous material with an average particle size of 2.1 μm.

[0243] <Example 10>

[0244] Using carbon precursor E with an average particle size of 2.6 μm, and otherwise treated in the same manner as in Example 9, a carbonaceous material with an average particle size of 2.5 μm was obtained.

[0245] <Example 11>

[0246] Using carbon precursor F with an average particle size of 3.1 μm, the same process as in Example 9 was performed to obtain carbonaceous material with an average particle size of 3.0 μm.

[0247] <Example 12>

[0248] The carbonaceous material with an average particle size of 3.0 μm obtained in Example 11 was mixed with a carbonaceous material with an average particle size of 9.6 μm obtained by using carbon precursor B with an average particle size of 9.7 μm and treating it in the same manner as in Example 9, at a mass ratio of 1:1. The resulting carbonaceous material had an average particle size of 4.8 μm.

[0249] <Example 13>

[0250] The carbonaceous material with an average particle size of 2.1 μm obtained in Example 9 was mixed with a carbonaceous material with an average particle size of 9.6 μm obtained by using carbon precursor B with an average particle size of 9.7 μm and treating it in the same manner as in Example 9, at a mass ratio of 1:1. The resulting carbonaceous material had an average particle size of 4.5 μm.

[0251] <Example 14>

[0252] The heating rate was set to 20°C per minute (heating time was 15 minutes) from 600°C to 900°C. After heating to 1175°C, the temperature was maintained at that temperature for 20 minutes. Otherwise, the process was the same as in Example 7 to obtain carbonaceous material.

[0253] <Example 15>

[0254] 9.1 g of carbon precursor A with an average particle size of 5.1 μm was added to a graphitic crucible with a sample layer thickness of approximately 3 mm. The crucible was placed in a high-speed heating furnace manufactured by Motoyama Corporation. The heating rate was set to 60 °C per minute (for 5 minutes) within the range of 600 °C to 900 °C, and also at 60 °C per minute in other temperature ranges. After heating to 1150 °C, the temperature was held for 20 minutes, followed by natural cooling. Once the furnace temperature was confirmed to have dropped below 200 °C, the carbonaceous material was removed from the furnace, yielding a carbonaceous material with an average particle size of 5.0 μm.

[0255] <Comparative Example 5>

[0256] The heating rate of 600℃~900℃ was set to 300℃ per minute (heating time was 1 minute). Otherwise, the process was the same as in Example 7 to obtain carbonaceous material.

[0257] <Comparative Example 6>

[0258] The heating rate was set to 60°C per minute (heating time was 5 minutes) from 600°C to 900°C. After heating to 1270°C, the temperature was maintained at that temperature for 20 minutes. Otherwise, the process was the same as in Example 7 to obtain carbonaceous material.

[0259] <Comparative Example 7>

[0260] The heating rate was set to 60°C per minute (heating time was 5 minutes) from 600°C to 900°C. After heating to 1100°C, the temperature was maintained for 20 minutes. Otherwise, the process was the same as in Example 15 to obtain carbonaceous material.

[0261] <Comparative Example 8>

[0262] The heating rate was set to 60°C per minute (heating time was 5 minutes) from 600°C to 900°C. After heating to 1050°C, the temperature was maintained at that temperature for 360 minutes. Otherwise, the process was the same as in Example 15 to obtain carbonaceous material.

[0263] For the carbonaceous materials obtained in the examples and comparative examples, the pore volume, mesopore volume, adsorption amount of carbon dioxide, desorption amount, and the ratio of adsorption amount to desorption amount (adsorption amount / desorption amount), and the average particle size (D) were measured. 50 ), specific surface area and inter-face distance d 002 As shown in Table 4.

[0264] [Table 4]

[0265]

[0266] Using the carbonaceous materials of Examples 7-15 and Comparative Examples 5-8, battery evaluation (discharge capacity, initial efficiency, and cycle durability) was performed using the same methods as those used in the experimental examples related to the carbonaceous materials of Method I. Furthermore, based on the aforementioned battery evaluation, input characteristics were measured using the following methods. The results are shown in Table 5.

[0267] [Determination of input characteristics]

[0268] After determining the discharge capacity and initial efficiency, charge-discharge tests were conducted on the negative electrode half-cell using a charge-discharge test apparatus (TOSCAT, manufactured by Toyo Systems) to evaluate its input characteristics. Doping was performed at a rate of 500 mA / g relative to the mass of the negative electrode active material in a 25°C constant-temperature bath until the lithium potential reached 0 mV. Then, dedoping was performed at a rate of 100 mA / g relative to the active material until the lithium potential reached 1.5 V. The capacity discharged at this point was taken as the discharge capacity (mAh / g) at 25°C and 1C.

[0269] Next, in a constant temperature bath at -20°C, doping is performed at a rate of 100 mA / g relative to the mass of the negative electrode active material until the lithium potential is 0 mV. Then, dedoping is performed at a rate of 100 mA / g relative to the mass of the active material until the lithium potential is 1.5 V. The capacity discharged at this point is taken as the discharge capacity (mAh / g) at -20°C and 0.2C.

[0270] Next, in a constant temperature bath at -20°C, doping is performed at a rate of 500 mA / g relative to the mass of the negative electrode active material until the lithium potential is 0 mV. Then, dedoping is performed at a rate of 100 mA / g relative to the mass of the active material until the lithium potential is 1.5 V. The capacity discharged at this point is taken as the discharge capacity (mAh / g) at -20°C and 1C.

[0271] Furthermore, -20°C and 1C / 25°C and 1C and -20°C and 1C / -20°C and 0.2C are used as indicators of input characteristics and pre-doping. When measured according to this embodiment, the value of -20°C and 1C / 25°C and 1C is preferably 30% or more, more preferably 40% or more, and even more preferably 45% or more; the value of -20°C and 1C / -20°C and 0.2C is preferably 50% or more, more preferably 70% or more, and even more preferably 75% or more.

[0272] [Table 5]

[0273]

[0274] It can be seen that the non-aqueous electrolyte secondary battery with a negative electrode containing the carbonaceous material obtained in Examples 7 to 15 can be pre-doped at high speed and simultaneously meet the requirements of high capacity, high initial efficiency and high cycle durability. On the other hand, the carbonaceous materials obtained in Comparative Examples 5, 7 and 8 have low initial efficiency and cycle retention rate, and the carbonaceous material obtained in Comparative Example 6 has low discharge capacity.

[0275] Industrial practicality

[0276] The carbonaceous material of the present invention can be used in the manufacture of electrochemical devices that can have high capacity and high cycle durability.

Claims

1. Carbonaceous materials, among which, In the adsorption-desorption isotherms of carbon dioxide obtained by measuring the adsorption and desorption of carbon dioxide at 273 K under relative pressures p / p0 of 0.00075 to 0.030, the ratio of desorption to adsorption (i.e., desorption / adsorption) at a relative pressure of 0.01 is greater than 1.

05. The average interplanar spacing d of the (002) plane calculated using the Bragg formula based on wide-angle X-ray diffraction is... 002 It is between 0.36nm and 0.42nm. The carbonaceous material is manufactured by a manufacturing method that includes a heating step and a heat treatment step following the heating step. The heating process involves increasing the specific surface area of ​​the BET sample to 500 m² using nitrogen adsorption. 2 The process of heating a carbon precursor of less than / g to 900°C in the presence of volatile organic compounds, wherein the heating rate between 600°C and 900°C in the heating process is less than 60°C / min. The heat treatment process is a process of raising the temperature to above 900°C and below 1180°C and maintaining it.

2. The carbonaceous material according to claim 1, wherein the oxygen content is 0.5% by mass or more.

3. The carbonaceous material according to claim 1 or 2, wherein, The specific surface area of ​​BET obtained by nitrogen adsorption is 1 m². 2 / g or more and 20m 2 / g or less.

4. The carbonaceous material according to claim 1, wherein, The mesopore volume determined by the BJH method is 3.7 mm. 3 / g or more and 41mm 3 / g or less.

5. The carbonaceous material according to claim 4, wherein the average particle size D 50 It is between 1.3μm and 9.5μm.

6. The carbonaceous material according to claim 4 or 5, wherein, The specific surface area of ​​BET obtained by nitrogen adsorption is 3 m². 2 / g or more and 60m 2 / g or less.

7. The carbonaceous material according to claim 1 or 2, wherein, The average interplanar spacing d of the (002) plane was calculated using the Bragg formula based on wide-angle X-ray diffraction. 002 It is above 0.38nm and below 0.40nm.

8. The carbonaceous material according to claim 1 or 2, used in electrochemical devices.

9. The carbonaceous material according to claim 8, wherein it is pre-doped with metal ions.

10. Carbonaceous materials, among which, In the adsorption-desorption isotherms of carbon dioxide obtained by measuring the adsorption and desorption of carbon dioxide at 273 K under relative pressures p / p0 of 0.00075 to 0.030, the ratio of desorption to adsorption (i.e., desorption / adsorption) at a relative pressure of 0.01 is greater than 1.

05. The average interplanar spacing d of the (002) plane calculated using the Bragg formula based on wide-angle X-ray diffraction is... 002 It is between 0.36nm and 0.42nm. The carbonaceous material is manufactured by a manufacturing method that includes a heating step and a heat treatment step following the heating step. The heating process involves increasing the specific surface area of ​​the BET sample to 500 m² using nitrogen adsorption. 2 The process of heating a carbon precursor of less than / g to 900°C in the absence of volatile organic compounds, wherein the heating rate between 600°C and 900°C in the heating process is less than 60°C / min. The heat treatment process is a process of raising the temperature to above 1100°C and below 1180°C and maintaining it.

11. The carbonaceous material according to claim 10, wherein the oxygen content is 0.5% by mass or more.

12. The carbonaceous material according to claim 10 or 11, wherein, The specific surface area of ​​BET obtained by nitrogen adsorption is 1 m². 2 / g or more and 20m 2 / g or less.

13. The carbonaceous material according to claim 10, wherein, The mesopore volume determined by the BJH method is 3.7 mm. 3 / g or more and 41mm 3 / g or less.

14. The carbonaceous material according to claim 13, wherein the average particle size D 50 It is between 1.3μm and 9.5μm.

15. The carbonaceous material according to claim 13 or 14, wherein, The specific surface area of ​​BET obtained by nitrogen adsorption is 3 m². 2 / g or more and 60m 2 / g or less.

16. The carbonaceous material according to claim 10 or 11, wherein, The average interplanar spacing d of the (002) plane was calculated using the Bragg formula based on wide-angle X-ray diffraction. 002 It is above 0.38nm and below 0.40nm.

17. The carbonaceous material according to claim 10 or 11, used in electrochemical devices.

18. The carbonaceous material according to claim 17, wherein it is pre-doped with metal ions.

19. Carbonaceous materials, among which, In the adsorption-desorption isotherms of carbon dioxide obtained by measuring the adsorption and desorption of carbon dioxide at 273 K under relative pressures p / p0 of 0.00075 to 0.030, the ratio of desorption to adsorption (i.e., desorption / adsorption) at a relative pressure of 0.01 is greater than 1.

05. The average interplanar spacing d of the (002) plane calculated using the Bragg formula based on wide-angle X-ray diffraction is... 002 It is between 0.36nm and 0.42nm. The carbonaceous material is manufactured by a manufacturing method that includes a heat treatment step and an additional heat treatment step. The heat treatment process involves reducing the BET specific surface area to 500 m² using nitrogen adsorption. 2 A process in which carbon precursors of less than / g are subjected to heat treatment for more than 5 minutes at a temperature of 600°C or higher but less than 900°C in the presence of volatile substances derived from volatile organic compounds. The additional heat treatment process is a process of raising the temperature to above 900°C and below 1180°C and maintaining it.

20. The carbonaceous material according to claim 19, wherein the oxygen content is 0.5% by mass or more.

21. The carbonaceous material according to claim 19 or 20, wherein, The specific surface area of ​​BET obtained by nitrogen adsorption is 1 m². 2 / g or more and 20m 2 / g or less.

22. The carbonaceous material according to claim 19, wherein, The mesopore volume determined by the BJH method is 3.7 mm. 3 / g or more and 41mm 3 / g or less.

23. The carbonaceous material according to claim 22, wherein the average particle size D 50 It is between 1.3μm and 9.5μm.

24. The carbonaceous material according to claim 22 or 23, wherein, The specific surface area of ​​BET obtained by nitrogen adsorption is 3 m². 2 / g or more and 60m 2 / g or less.

25. The carbonaceous material according to claim 19 or 20, wherein, The average interplanar spacing d of the (002) plane was calculated using the Bragg formula based on wide-angle X-ray diffraction. 002 It is above 0.38nm and below 0.40nm.

26. The carbonaceous material according to claim 19 or 20, used in electrochemical devices.

27. The carbonaceous material according to claim 26, wherein it is pre-doped with metal ions.

28. An electrochemical device comprising the carbonaceous material according to any one of claims 1 to 27.

29. A method for manufacturing a carbonaceous material according to any one of claims 1 to 9, comprising a heating step and a heat treatment step following the heating step. The heating process involves increasing the specific surface area of ​​the BET sample to 500 m² using nitrogen adsorption. 2 The process of heating a carbon precursor of less than / g to 900°C in the presence of volatile organic compounds, wherein the heating rate between 600°C and 900°C in the heating process is less than 60°C / min. The heat treatment process is a process of raising the temperature to above 900°C and below 1180°C and maintaining it.

30. A method for manufacturing a carbonaceous material according to any one of claims 10 to 18, comprising a heating step and a heat treatment step following the heating step. The heating process involves increasing the specific surface area of ​​the BET sample to 500 m² using nitrogen adsorption. 2 The process of heating a carbon precursor of less than / g to 900°C in the absence of volatile organic compounds, wherein the heating rate between 600°C and 900°C in the heating process is less than 60°C / min. The heat treatment process is a process of raising the temperature to above 1100°C and below 1180°C and maintaining it.

31. A method for manufacturing a carbonaceous material according to any one of claims 19-27, comprising a heat treatment step and an additional heat treatment step, wherein the heat treatment step is to achieve a BET specific surface area of ​​500 m² using nitrogen adsorption. 2 A process in which carbon precursors of less than / g are subjected to heat treatment for more than 5 minutes at a temperature of 600°C or higher but less than 900°C in the presence of volatile substances derived from volatile organic compounds. The additional heat treatment process is a process of raising the temperature to above 900°C and below 1180°C and maintaining it.

32. The method according to any one of claims 29 to 31, further comprising: A pulverizing process for pulverizing the carbon precursor and / or the heat-treated carbon precursor.

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