JP7539554B2 - Method for producing carbon precursor for non-aqueous electrolyte secondary battery and method for producing carbonaceous material for non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a method for producing a carbon precursor for a non-aqueous electrolyte secondary battery and a method for producing a carbonaceous material for a non-aqueous electrolyte secondary battery.

In recent years, growing concern about environmental issues has led to the development of electric vehicles (xEVs). Lithium-ion secondary batteries are used as in-vehicle secondary batteries, which are large, superior secondary batteries with high energy density. Carbonaceous materials are used as the negative electrode material, and further increases in capacity are expected.

Conventionally, in order to obtain a carbonaceous material for a negative electrode material for lithium ion secondary batteries, a method for producing the carbonaceous material using a carbon precursor impregnated with an alkali metal compound has been proposed. When the alkali metal compound is uniformly impregnated to the carbon precursor, an aqueous solution containing an alkali metal compound (hereinafter referred to as an "alkali aqueous solution") is added to the carbon precursor to prepare a carbon precursor impregnated with the alkali metal compound (hereinafter referred to as an "alkali impregnated carbon precursor"). It is desirable to remove the moisture contained in the obtained alkali impregnated carbon precursor. If a large amount of moisture is present, the moisture evaporates from the slurried state, and the particles tend to aggregate to form a mass-like processed material. Therefore, it may be necessary to subject the obtained alkali impregnated carbon precursor to a crushing process or a pulverization process, which is not preferable.

For example, Patent Document 1 discloses a method for producing a carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery, which includes an alkali impregnation step in which a compound containing an alkali metal element is added to a carbonaceous precursor to obtain an alkali-impregnated carbonaceous precursor. Example 3 of the patent describes how a pulverized carbon precursor having an average particle size of 20 to 25 μm is impregnated with an aqueous solution of sodium hydroxide (NaOH) in a nitrogen atmosphere, and then dehydrated by heating under reduced pressure to obtain a pulverized carbonaceous precursor impregnated with NaOH (paragraph [0065]). Furthermore, it describes how when an aqueous solution is used to impregnate the alkali metal compound, the alkali metal-impregnated carbon precursor may become lumpy, and thus it is preferable to disintegrate the carbon precursor before firing (paragraph [0028]).

Patent Document 2 discloses a method for producing a carbon material, which includes a step of obtaining an alkali metal-supported precursor by supporting an alkali metal-containing compound on the surface of a carbon material precursor. Example 1 describes that 100 parts of a carbon material precursor having an average particle size of 20 μm is immersed for 1 hour in an alkaline aqueous solution in which 6 parts of aqueous sodium hydroxide are dissolved in 100 parts of water, and then only the water is removed using a vacuum dehydration device to obtain an alkali metal-supported precursor (paragraph [0043]).

Patent Document 3 describes how crushed coconut shell char with an average particle size of 7 to 12 μm was mixed with an aqueous solution in which 10% by mass of NaOH based on the mass of the crushed coconut shell char was dissolved in 200% by mass of water based on the mass of the crushed coconut shell char, and ultrasonic waves were irradiated for 30 minutes to allow the solution to penetrate the char, and then the char was dried under reduced pressure of 1 Torr at 80°C for 8 hours to obtain an alkali-impregnated char (paragraph [0093]).

International Publication No. 2016/021737 JP 2006-264993 A JP 2020-4589 A

Conventionally, as shown in Patent Documents 1 to 3, in the method for producing an alkali-impregnated carbon precursor, an alkali aqueous solution and a carbon precursor are mixed, and the water in the mixture is evaporated in a slurried state to prepare an alkali-impregnated carbon precursor. However, the alkali-impregnated carbon precursor obtained by such a production method has a lump-like form due to particle aggregation. Therefore, when producing a carbonaceous material by calcining an alkali-impregnated carbon precursor, it is necessary to subject the alkali-impregnated carbon precursor to a process such as crushing or fine grinding before or after the calcination to obtain a raw material with a particle size suitable for a battery negative electrode material. Fine grinding after calcination is not preferable because the pore structure may be destroyed by the impact.

Because the alkali-impregnated carbon precursor is strongly alkaline, when it is crushed or pulverized, fine powder of the alkali-impregnated carbon precursor scatters into the surroundings, which may worsen the working environment. In addition, when the alkali impregnation process is carried out by forming a slurry from a mixture of an aqueous alkali solution and a carbon precursor, the viscosity of the slurry increases during the process of removing the water from the mixture, which may make mixing difficult.

For these reasons, when an alkaline aqueous solution is mixed with a carbon precursor to perform an alkali impregnation process, a method is desired for efficiently producing an alkali-impregnated carbon precursor while suppressing particle aggregation.

The present invention aims to provide a method for efficiently producing a carbon precursor by adding an alkaline aqueous solution to the carbon precursor while preventing particles of the alkali-added carbon precursor from adhering to each other and forming agglomerates.

The inventors discovered that by stirring and heating the carbon precursor in a reaction vessel, and then adding an aqueous alkali solution, and subjecting the carbon precursor to an alkali impregnation process without essentially passing through a slurry state, it is possible to efficiently produce an alkali-impregnated carbon precursor while preventing particles from adhering to each other and forming lumps, and thus completed the present invention. Specifically, the present invention includes the following aspects (1) to (8).

(1) A method for producing an alkali-impregnated carbon precursor comprising: stirring and heating a carbon precursor in a reaction vessel; adding an alkaline aqueous solution containing an alkali metal compound to the stirred carbon precursor; and removing moisture from the alkaline aqueous solution to obtain an alkali-impregnated carbon precursor in which the alkali metal compound is impregnated into the carbon precursor;
a water content of the alkali-impregnated carbon precursor in the reaction vessel is 20 mass% or less, the water content being a water content at a time point when 80 mass% of a total amount of the alkaline aqueous solution has been added.

(2) The method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery described in (1) above, wherein the alkaline aqueous solution has a concentration of the alkali metal compound of 40 mass% or less.

(3) A method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery described in (1) or (2) above, in which the average temperature within the stirred particle layer of the carbon precursor is 70 to 125°C.

(4) A method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery described in any one of (1) to (3) above, wherein the water addition rate (kg/h/kg-C) at which water in the alkaline aqueous solution is added per 1 kg of the stirred carbon precursor is 0.1 or more and 10.0 or less.

(5) A method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery according to any one of (1) to (4) above, wherein the reaction vessel is provided with a supply port for introducing the carbon precursor into the reaction vessel, a discharge port for removing the alkali-impregnated carbon precursor from the reaction vessel, a heating means for heating the carbon precursor, a stirring means for stirring the carbon precursor, and an adding means for adding the alkaline aqueous solution to the carbon precursor.

(6) A method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery described in any one of (1) to (5) above, wherein the carbon precursor is derived from petroleum-based pitch or coal-based pitch or a mixture thereof.

(7) The method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery according to any one of (1) to (6), wherein the alkali-impregnated carbon precursor has a particle diameter _DV90 corresponding to a cumulative 90% by volume of 150 μm or less.

(8) A method for producing a carbonaceous material for a non-aqueous electrolyte secondary battery, comprising heat treating an alkali-impregnated carbon precursor described in any one of (1) to (7) above at 800°C to 1500°C in an inert atmosphere to produce a carbonaceous material.

According to the present invention, an alkali-impregnated carbon precursor for a carbonaceous material for a non-aqueous electrolyte secondary battery can be efficiently produced by uniformly adding and mixing an alkaline aqueous solution to a carbon precursor. The alkali-impregnated carbon precursor obtained by the production method of the present invention can be used as a raw material for preparing a carbonaceous material for a negative electrode in a non-aqueous electrolyte secondary battery. Since the alkali-impregnated carbon precursor obtained by the present invention is substantially particulate, there is no need to subsequently disintegrate or grind the carbon precursor, or the degree of disintegration or grinding is small, which provides useful effects in improving work efficiency and the work environment.

FIG. 2 is a schematic diagram showing an example of a manufacturing apparatus according to the present embodiment.

The following is a detailed description of an embodiment of the present invention. The present invention is not limited to the following embodiment, and can be implemented with appropriate modifications within the scope of the object of the present invention. In this specification, the expression "X to Y" (X and Y are arbitrary numbers) means "X or more and Y or less."

<Method for producing alkali-impregnated carbon precursor>
The present embodiment is a method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery, and its features include the following.
Heating and stirring the carbon precursor in the reaction vessel.
An alkali aqueous solution containing an alkali metal compound is added to the carbon precursor while being stirred to obtain an alkali-impregnated carbon precursor in which the alkali metal is impregnated into the carbon precursor.
The water content of the alkali-impregnated carbon precursor in the reaction vessel is 20 mass % or less, and this water content is the water content at the time when 80 mass % of the total amount of the alkaline aqueous solution has been added.

<Carbon Precursor>
The present embodiment is a method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery by subjecting a carbon precursor to an alkali impregnation treatment. The carbon precursor to be subjected to the alkali impregnation treatment is preferably one having a particulate form.

The carbon precursor may be one that has been made infusible by a crosslinking treatment such as an oxidation treatment. Examples of crosslinking treatments for making the carbon precursor infusible include a method using a crosslinking agent or a method of treating the carbon precursor with an oxidizing agent such as air.

The carbon precursor is placed in a reaction vessel and stirred and heated. In this specification, the state in which the carbon precursor particles are filled in the reaction vessel is sometimes referred to as a "particle layer."

The carbon source in the carbon precursor is not particularly limited. For example, petroleum pitch, coal pitch, thermoplastic resin (e.g., ketone resin, polyvinyl alcohol, polyacrylonitrile, styrene/divinylbenzene copolymer, acrylonitrile/styrene/divinylbenzene copolymer, polyamideimide, aramid resin), thermosetting resin (e.g., urea resin, polyimide nylon resin, furan resin, phenolic resin, amino resin, and amide resin), or a mixture thereof can be mentioned.

The shape and size of the carbon precursor are not particularly limited. The shape of the carbon precursor when the alkaline aqueous solution is added is preferably particulate. The particulate shape means the same shape as the powder shape. If the average particle diameter D _V50 is too large, it is difficult to penetrate the alkali metal compound into the inside of the carbon precursor particles, which is not preferable. Therefore, the average particle diameter is preferably 50 μm or less, more preferably 30 μm or less, even more preferably 20 μm or less, and particularly preferably 10 μm or less. On the other hand, if the average particle diameter is too small, the aggregate (powder) of the carbon precursor particles becomes bulky and difficult to handle, which is not preferable. The average particle diameter is preferably 0.1 μm or more, and more preferably 1 μm or more. Here, the average particle diameter D _V50 means the particle diameter at the point where the cumulative volume is 50% when a cumulative curve is obtained from the small particle diameter to the large particle diameter, with the total volume of the particles being 100%.

A known particle manufacturing method can be used to turn the carbon precursor into particles. For example, there is a method of turning the carbon precursor into particles during the polymerization process of a polymer, a method of turning a thermoplastic carbon precursor into particles by dispersing the precursor in a liquid and forming droplets, and a method of crushing a carbon precursor such as a petroleum-based or coal-based pitch to turn it into pitch particles having a predetermined average particle diameter D _V50 range. The pulverizer used for crushing is not particularly limited. For example, a jet mill, a rod mill, a vibrating ball mill, or a hammer mill can be used.

<Reaction vessel shape>
The shape of the reaction vessel in the manufacturing method according to this embodiment may be cylindrical, conical, spherical, or the like. Since the particles in the vessel are mixed by the rotating stirring means, a structure having a curved surface on the inner surface of the vessel is preferable from the viewpoint of increasing the mixability of the carbon precursor and the stirring efficiency of the stirring means. For example, in the case of a cylindrical or conical reaction vessel, the inner surface is composed of a curved side surface and a flat bottom surface. In the case of a spherical reaction vessel, it is composed of a curved inner surface. Since the carbon precursor flows along the curved surface, the retention of the carbon precursor is suppressed.

<Stirring and Heating>
In the manufacturing method according to this embodiment, an alkali metal compound is impregnated into the entire carbon precursor described below, and in order to efficiently remove moisture from the carbon precursor during the impregnation process, it is preferable to stir and heat the carbon precursor in the reaction vessel. At that time, the stirring and heating process removes moisture from the alkali-impregnated carbon precursor, and the moisture content of the alkali-impregnated carbon precursor is reduced, thereby preventing the particle layer in the reaction vessel from becoming a slurry. The aspect of removing moisture by evaporation is sometimes referred to as "distilling off moisture."

A method for stirring the carbon precursor can be applied that rotates a stirring blade of a specified shape. The stirring conditions, such as the installation position of the stirring blade and the rotation speed, can be set appropriately depending on the type of carbon precursor and the processing amount.

<Alkaline impregnation treatment>
The production method according to the present embodiment is characterized in that an aqueous alkali solution is added to the carbon precursor being stirred and heated in a reaction vessel, thereby carrying out alkali impregnation and moisture removal. By carrying out such an alkali impregnation process in which alkali impregnation and moisture removal are carried out together, it is possible to obtain a particulate alkali-impregnated carbon precursor in which an alkali metal is uniformly impregnated in the carbon precursor.

<Alkali metal compounds>
The alkali metal compound according to the present embodiment means a compound containing an alkali metal element. The alkali metal element contained in the alkali metal compound used in the alkali impregnation treatment may be an alkali metal element such as lithium, sodium, or potassium. As the alkali metal element, sodium is preferred. By using sodium, a carbon precursor for producing a carbonaceous material exhibiting a high charge/discharge capacity can be obtained.

As for the type of alkali metal compound, hydroxides, carbonates, hydrogen carbonates, halogen compounds, etc. can be used. Hydroxides or carbonates are preferred from the viewpoint of high permeability and ability to uniformly impregnate the carbonaceous precursor particles, and hydroxides are particularly preferred due to their high solubility in water. By adding an alkali metal to water, a hydroxide of the alkali metal can be obtained.

<Moisture content>
In the manufacturing method according to the present embodiment, the moisture content of the alkali-impregnated carbon precursor in the reaction vessel is preferably 20 mass% or less in the alkali impregnation treatment. Here, the moisture content is the moisture content at the time when 80 mass% of the total amount of the added alkaline aqueous solution has been added. The moisture content corresponds to the moisture content measured by sampling the alkali-impregnated carbon precursor during the alkali impregnation treatment at the time when 80 mass% of the total amount of the added alkaline aqueous solution has been added.

In the manufacturing method according to the present embodiment, an alkali impregnation process is performed by adding an alkaline aqueous solution to the carbon precursor. In this case, in order to prevent the particle layer in the reaction vessel from becoming a slurry, it is preferable to remove the moisture in the alkaline aqueous solution added to the particle layer. The lower the moisture content of the alkali impregnated carbon precursor in the reaction vessel, the more the slurrying is suppressed. If the moisture content is 20% by mass or less, the alkali impregnation process can be performed in a state where the slurrying is not substantially performed, so that the obtained alkali impregnated carbon precursor maintains its particulate form before the process, not in a lump form. When this is fired to produce a carbonaceous material, there is no need to perform a crushing process such as crushing or fine grinding in advance. Alternatively, even if crushing is performed, a mild crushing process is sufficient. Therefore, it is useful in terms of improving work efficiency. Furthermore, there is no risk of powder scattering around after the crushing process, and deterioration of the work environment can be avoided. From this viewpoint, the moisture content is preferably 20% by mass or less, more preferably 16% by mass or less, and even more preferably 10% by mass. On the other hand, if the water content is too low, the proportion of the added alkaline aqueous solution that is discharged without being impregnated increases, which is undesirable. From this viewpoint, the water content is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more.

The moisture content can be measured by sampling the alkali-impregnated carbon precursor in the reaction vessel during the alkali impregnation process and calculating based on the difference between its mass and the dry mass.

<Alkaline aqueous solution>
If the concentration of the alkaline aqueous solution is excessively high, the amount of the liquid decreases, and the mixed state of the carbon precursor and the alkali metal compound may become non-uniform. Therefore, the concentration of the alkali metal compound in the alkaline aqueous solution is preferably 40 mass% or less, more preferably 20 mass% or less, and even more preferably 10 mass%. If the concentration of the alkaline aqueous solution is too low, a lot of energy is required to volatilize water in the alkali impregnation treatment, and the impregnation time becomes long, which is disadvantageous in terms of treatment time and treatment cost. Therefore, the concentration of the alkali metal compound in the alkaline aqueous solution is preferably 0.1% or more, more preferably 0.5 mass% or more, and even more preferably 1.0 mass% or more.

<Average temperature in particle layer>
In the manufacturing method according to the present embodiment, the average temperature in the particle layer of the carbon precursor being stirred during the addition of the alkaline aqueous solution can be 70 to 130°C. In this specification, "in the particle layer" is simply described as "in the layer", and the average temperature in the layer may be described as "average temperature in the layer". If the average temperature in the layer is less than 70°C, the evaporation of the water contained in the stirred carbon precursor may be insufficient, resulting in slurrying. The average temperature in the layer is more preferably 80°C or higher, and even more preferably 90°C or higher. On the other hand, if the average temperature in the layer exceeds 130°C, the alkaline aqueous solution may evaporate before arriving at the surface of the carbon precursor, or a part of the water may be exhausted outside the system by the airflow of the water evaporating from the carbon precursor, making it difficult to obtain a predetermined amount of impregnation. From this viewpoint, the average temperature in the layer is preferably 130°C or lower, more preferably 125°C or lower, and even more preferably 110°C or lower.

<Moisture addition rate>
In the production method according to this embodiment, the alkaline aqueous solution is added to the carbon precursor, and thus the moisture in the alkaline aqueous solution is added to the carbon precursor being stirred. The moisture addition rate (kg/h) at which the moisture in the alkaline aqueous solution is added per 1 kg of the carbon precursor is preferably 0.1 or more and 10.0 or less. In this specification, the rate at which the moisture in the alkaline aqueous solution is added to the carbon precursor being stirred is referred to as the "moisture addition rate". The moisture addition rate can be calculated using the following formula. In the unit (kg/h/kg-C) in the formula, "kg-C" means per 1 kg of the carbon precursor.

If the water addition rate (kg/h/kg-C) is less than 0.1 per kg of carbon precursor, the proportion of water discharged outside the system increases and the impregnation efficiency decreases, which is not preferred. Therefore, the water addition rate (kg/h/k-C) is 0.1 or more per kg of carbon precursor, more preferably 0.2 or more, and even more preferably more than 0.3. On the other hand, if the water addition rate (kg/h/kg-C) is more than 10.0 per kg of carbon precursor, the amount of water impregnated into the carbon precursor increases, and the carbon precursor may become a slurry, which is not preferred. Therefore, the water addition rate is more preferably 5.0 or less, and even more preferably 3.0 or less.

<Reaction vessel equipment>
In the production method according to this embodiment, in order to subject the carbon precursor to an alkali impregnation treatment, it is preferable to use a reaction vessel equipped with the following equipment: That is, the reaction vessel is equipped with a supply port for introducing the carbon precursor into the reaction vessel, a discharge port for removing the alkali-impregnated carbon precursor from the reaction vessel, a heating device for heating the carbon precursor, a stirring device for stirring the carbon precursor, and an adding device for adding the alkaline aqueous solution to the carbon precursor.

An example of a manufacturing apparatus using the manufacturing method according to this embodiment is shown in FIG. 1. The manufacturing apparatus in FIG. 1 includes a reaction vessel 1, a stirrer 30, a carbon precursor supply port 7, an alkali-impregnated carbon precursor discharge port 8, and a gas inlet 10. The carbon precursor 13 is supplied to the reaction vessel 1 by opening the top lid 6 of the supply port 7, and filled into the reaction vessel 1. After the carbon precursor 13 is subjected to a predetermined alkali impregnation treatment, the alkali-impregnated carbon precursor is discharged through the discharge port 8. When discharging the alkali-impregnated carbon precursor, for example, the partition (not shown) installed between the side wall 4 and the discharge port 8 of the reaction vessel 1 is opened, and the alkali-impregnated carbon precursor can be discharged by slowly rotating the stirring blade 32. The alkali-impregnated carbon precursor attached to the inner surface of the reaction vessel 1 can be collected by opening the top lid 6. The state of the carbon precursor 13 in the reaction vessel 1 can be confirmed through the observation window 9 provided in the top lid 6.

The agitator 30 has a rotating shaft 31, an agitating blade 32 attached to the rotating shaft, and a motor 33 that drives the rotating shaft, and is a means for agitating and mixing the carbon precursor 13 charged into the reaction vessel. The rotation of the agitating blade 32 forms an agitation flow 36, which agitates the carbon precursor 13.

<Atmosphere inside reaction vessel>
In order to improve the stirring efficiency of the carbon precursor in the reaction vessel and efficiently discharge the moisture during impregnation, it is preferable to introduce a replacement gas 12 into the reaction vessel 1. The introduction point of the replacement gas 12 in the reaction vessel 1 is not particularly limited. From the viewpoint of uniformly flowing gas in the particle layer to be subjected to the alkali impregnation treatment, it is preferable to provide a gas inlet 10 in the bottom wall 5 of the reaction vessel 1 and introduce the replacement gas 12 from the bottom surface 3 of the reaction vessel 1. The gas inlet 10 may be provided at a plurality of locations. The pressure of the replacement gas is monitored and adjusted by one or more gas pressure gauges 11 provided in the gas introduction path.

Regarding the type of replacement gas, an oxidizing gas is not preferred because it may oxidize the alkali-impregnated carbon precursor and the alkali metal compound may absorb the oxidizing gas and change its properties. Therefore, a non-oxidizing gas is preferred, and nitrogen gas or a rare gas may be used alone or in combination. If the flow rate of the replacement gas is too high, the added aqueous alkali solution may be directly discharged outside the reaction vessel, which is not preferred. Also, if the flow rate of the replacement gas is too low, the effect of replacing the atmosphere is reduced, which is not preferred. Taking these points into consideration, the amount of replacement gas can be appropriately selected depending on the processing conditions such as the amount of carbon precursor introduced and the amount of aqueous alkali solution added.

In addition, the particle layer is fluidized by the introduction of the replacement gas, which has the effect of assisting the stirring by the stirrer. Furthermore, since the replacement gas is non-oxidizing, it also has a sealing effect of preventing the particle layer from being oxidized. In addition, a gas dispersion device (not shown) such as a gas dispersion plate or a dispersion tube (sparger) may be installed on the bottom surface of the reaction vessel, and the replacement gas may be introduced into the particle layer through the gas dispersion device. When installing the gas dispersion device, it is necessary to separate the surface of the gas dispersion device from the surface of the lower end of the stirring blade so that they do not come into contact with each other. Depending on the shape and structure of the reaction vessel, a gas inlet may be provided on the side wall of the reaction vessel.

By reducing the pressure inside the vessel, it is possible to efficiently evaporate water and exhaust the evaporated water outside the reaction vessel. The degree of pressure reduction is not particularly limited. The gauge pressure is preferably -10 kPa (-0.01 MPa) or less, more preferably -20 kPa (-0.02 MPa) or less, and even more preferably -30 kPa (-0.03 MPa) or less.

<Heating Means>
In the manufacturing method according to the present embodiment, the alkali impregnation treatment is performed while the carbon precursor is heated. Therefore, as the alkali impregnation treatment progresses, the alkali impregnated carbon precursor containing moisture is stored in the reaction vessel. Methods for heating the alkali impregnated carbon precursor in the reaction vessel include heat transfer heating from the side and bottom of the reaction vessel. On the other hand, as the moisture contained in the alkali impregnated carbon precursor evaporates, the alkali impregnated carbon precursor is cooled by the latent heat of evaporation. When the alkali impregnated carbon precursor is heated from the outside of the reaction vessel (hereinafter, this will be referred to as "external heating"), it is preferable to perform the alkali impregnation treatment by maintaining the carbon precursor in a predetermined temperature range while adjusting both the external heating and the latent heat of moisture evaporation.

Regarding the heating means, the heating method using a heating medium (hereinafter also referred to as "heat medium") as shown in FIG. 1 is an example of external heating. A flow passage 22 for the heat medium 20 is installed facing the side wall 4 and bottom wall 5 of the reaction vessel 1, and the heat medium 20 at a predetermined temperature is supplied from the heat medium supply port 21 of the flow passage 22 and discharged from the heat medium discharge port 23. The carbon precursor 13 in the reaction vessel 1 is heated by heat transfer from the heat medium through the side wall 4 and the bottom wall 5. The heat medium flow passage may be attached to only one of the side wall or the bottom wall. The heat medium is not particularly limited as long as it is a heat medium that can be used at the temperature of external heating. Superheated steam can be used. In addition, mineral oil-based, synthetic, inorganic, and other heat mediums may be used. The temperature at which the carbon precursor is treated can be controlled by the supply amount and supply speed of the heat medium.

As shown in Figure 1, in order to measure the temperature of external heating by the heat medium (hereinafter also referred to as "external temperature"), a temperature measuring device 24 on the heat medium inlet side is installed in the pipe leading to the heat medium supply port 21, and a temperature measuring device 25 on the heat medium outlet side is installed in the pipe leading to the heat medium outlet 23. In order to measure the temperature in the particle layer of the carbon precursor, the temperature measuring device 14 is inserted into the particle layer through the side wall 4 of the reaction vessel 1.

<Means for Supplying Alkaline Aqueous Solution>
In order to perform the alkali impregnation treatment of the carbon precursor, an alkaline aqueous solution is added to the particle layer in the reaction vessel. The means for adding the alkaline aqueous solution is not particularly limited. In order to add the alkaline aqueous solution to the entire particle layer, it is preferable to use a spraying means such as a spray nozzle. An example of this is shown in FIG. 1, where a spray nozzle 51 is disposed near the upper part of the reaction vessel 1. An alkaline aqueous solution 50 stored in a storage vessel 54 installed outside the reaction vessel 1 is supplied to the spray nozzle 51 by a supply pipe 52, and is sprayed to the particle layer of the carbon precursor 13 through the spray nozzle 51. As an example of a control method for supplying the alkaline aqueous solution, as shown in FIG. 1, the temperature of the alkaline aqueous solution 50 is monitored by a temperature measuring instrument 57. Furthermore, while monitoring the fluctuation of the alkaline aqueous solution 50 in the storage vessel 54 by a weight meter 53, pressurizing air 56 adjusted based on the measured value of a pressure measuring instrument 55 is introduced into the storage vessel 54, and the liquid surface of the alkaline aqueous solution 50 is pressed to supply a required amount of the alkaline aqueous solution 50 to the spray nozzle 51.

<Stirring means>
The stirring means according to the present embodiment includes a rotating shaft and a stirring blade provided on the rotating shaft. The shape of the stirring blade is not particularly limited. A stirring blade of an existing shape can be used. For example, a paddle blade with a blade plate attached perpendicular to the rotating shaft, a disk turbine blade, a curved blade, a Pfaudle blade, or an inclined paddle blade or a propeller blade with an inclination angle can be selected. The rotating shaft is driven by a driving means such as a motor, and the stirring blade rotates, thereby stirring the carbon precursor charged in the reaction vessel. In addition, since the carbon precursor tends to accumulate on the lower side of the reaction vessel, in order to sufficiently stir the accumulated particle layer, it is preferable that the stirring blade 32 has a shape in which the lower end 35 of the stirring blade is parallel to the bottom surface 3 of the reaction vessel, as shown in FIG. 1.

Regarding the positioning of the agitator blades, it is preferable that when the reaction vessel is placed on a horizontal surface, the center of the height of the agitator blades is located below half the height of the vessel. Because the agitator blades rotate in the lower region of the reaction vessel, clumps of particles that have settled to the lower region can be efficiently broken down.

In addition, this embodiment is not limited to a form in which the bottom surface of the reaction vessel is placed on a horizontal plane. Even if the angle between the rotation axis of the agitator and the horizontal plane is less than 90 degrees by tilting the reaction vessel, it is sufficient that the rotation axis of the agitator is held perpendicular to the cross section of the reaction vessel. By holding it in this manner, the agitator can rotate while maintaining a constant separation distance between the agitator and the inner surface of the reaction vessel, and the agitation action required to uniformly flow the entire workpiece (carbon precursor and alkali-imparted carbon precursor) in the reaction vessel can be obtained. In addition, since the direction of gravity relative to the workpiece does not change significantly during rotation, the clumps of particles settle downward and are crushed by the agitator, and good agitation efficiency is maintained. On the other hand, if the angle at which the reaction vessel is tilted is too large, the proportion of the agitator protruding outside the particle layer of the workpiece increases, and the proportion of the workpiece contacting the agitator decreases, resulting in a decrease in agitation efficiency. From the above, it is preferable that the angle between the rotation axis of the agitator and the horizontal plane is 60 degrees or more and 90 degrees or less. The lower limit of the angle may be 70 degrees or more, or 80 degrees or more.

As shown in FIG. 1, the agitator blade 32 extends around the rotation axis 31. In this specification, the outermost part of the agitator blade 32 is called the tip 34, and the part extending from the center of rotation to the tip 34 that faces the bottom surface 3 of the reaction vessel is called the lower end 35. In order to prevent the agitator blade 32 from contacting the inner surface of the reaction vessel 1, the side surface 2 and bottom surface 3, which are the inner surface of the reaction vessel 1, must be separated from the surface of the agitator blade 32. Specifically, it is necessary to separate the surface of the tip 34 of the agitator blade 32 from the side surface 2 of the reaction vessel 1, and the surface of the lower end 35 of the agitator blade 32 from the bottom surface 3 of the reaction vessel 1 by leaving a certain distance between them. On the other hand, if the distance is too large, the action of the agitator blade does not reach the material near the inner surface of the reaction vessel sufficiently, and the flow state of the material to be treated is insufficient. As a result, there is a risk that the carbon precursor particles will remain in a region in the reaction vessel, and the particle agglomerates will not be broken down. If the particles remain in agglomerated form, contact with the alkaline aqueous solution will be hindered for each particle, making it difficult to obtain an alkali-impregnated carbon precursor of good quality. From this perspective, the closest distance between the inner surface of the reaction vessel and the surface of the stirring blade is preferably set to 50 mm or less, and may be 30 mm or less.

<Attachment means>
The example of the manufacturing apparatus shown in FIG. 1 further includes a bag filter, a chopper, a support stand, and the like.

The gas in the reaction vessel is discharged outside the reaction vessel as exhaust gas 63. The bag filter 60 is installed midway through the gas exhaust pipe 62 through which the exhaust gas 63 flows. Furthermore, a backwash gas introduction pipe 61 is installed downstream of the bag filter 60. Powder scattered upward from the particle layer of the material to be treated during stirring is collected by the bag filter. By flowing the backwash gas through the bag filter, the collected powder can be returned to the reaction vessel for reuse.

The chopper 40 is a stirring means having a structure in which multiple chopper blades 42 are attached perpendicular to a rotating shaft 41. The rotating shaft 41 and chopper blades 42 are rotated by a motor 43, which is a driving means. The rotation of the chopper blades has the effect of stirring the material to be processed and breaking down clumps of particles, so they can be attached to assist the stirring means using the stirring blades.

The reaction vessel may be structured so as to be placed on a support stand 15. By adopting this structure, a space is formed below the reaction vessel for installing a stirring means.

<Particle size of alkali-impregnated carbon precursor>
The alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery according to this embodiment preferably has a particle diameter _DV90 corresponding to a cumulative 90% by volume of 150 μm or less. When a cumulative curve is obtained from small particle diameters to large particle diameters, with the total volume of the alkali-impregnated carbon precursor being taken as 100%, the particle diameter _DV90 means the particle diameter at the point where the cumulative volume is 90% by volume. The carbonaceous material obtained by firing the alkali-impregnated carbon precursor is used by coating the surface of an electrode for a secondary battery, and the coating thickness of the electrode is about 200 μm, so the particle diameter _DV90 of the alkali-impregnated carbon precursor is preferably in the range of 150 μm or less, more preferably 100 μm or less, and even more preferably 50 μm.

The impregnation rate of the alkali metal compound impregnated in the alkali-impregnated carbonaceous precursor obtained by the manufacturing method according to this embodiment is not particularly limited. The impregnation rate is preferably 1 to 50 mass%. The purpose of impregnation of the alkali metal compound is to provide a battery electrode with a large charge/discharge capacity by forming a pore structure for doping and dedoping in the carbonaceous material obtained by the alkali-impregnated carbon precursor. Therefore, the impregnation rate of the alkali metal compound is preferably 1 mass% or more, more preferably 3 mass% or more, even more preferably 5 mass% or more, and particularly preferably 10 mass% or more. On the other hand, if the impregnation rate is excessive, excessive alkali activation occurs. Therefore, the specific surface area of the carbonaceous material increases, which increases the irreversible capacity of the battery, which is not preferable. Therefore, the impregnation rate of the alkali metal compound is preferably 50 mass% or less, more preferably 40 mass% or less, even more preferably 30 mass% or less, and particularly preferably 20 mass% or less. The impregnation rate of the alkali metal compound is a numerical value obtained by the following procedure. That is, the content of the alkali metal in the alkali-impregnated carbon precursor is obtained in accordance with the "General Rules for X-ray Fluorescence Analysis" of the Japanese Industrial Standard JIS K0119: 2008. Then, based on the conversion formula described below, the content is multiplied by the ratio between the molecular weight of the alkali metal compound and the molecular weight of the alkali metal to obtain the impregnation rate of the alkali metal compound.

<Method of producing carbonaceous material>
The alkali-impregnated carbon precursor obtained by the manufacturing method according to the present embodiment can be used as a raw material for manufacturing a carbonaceous material for a non-aqueous electrolyte secondary battery. The alkali-impregnated carbon precursor is preferably applied to a manufacturing method for a carbonaceous material for a non-aqueous electrolyte secondary battery, which includes a step of performing heat treatment at 800°C to 1500°C in an inert atmosphere. In the manufacturing method, in order to advance carbonization, the heat treatment is preferably performed at 800°C or higher, more preferably 1000°C or higher, even more preferably 1050°C or higher, and particularly preferably 1100°C or higher. If the heat treatment temperature is too high, the lithium storage sites are reduced due to thermal contraction, so the heat treatment temperature is preferably 1500°C or lower, more preferably 1400°C or lower, and even more preferably 1350°C or lower. The heat treatment step includes a firing step. In the calcination step, the alkali-impregnated carbonaceous precursor is (a) calcined in an inert atmosphere at 800° C. to 1500° C., or (b) pre-calcined in an inert atmosphere at 400° C. or higher and lower than 800° C., and then calcined in an inert atmosphere at 800° C. to 1500° C. In the heat treatment step for obtaining the carbonaceous material for a non-aqueous electrolyte secondary battery according to this embodiment, pre-calcination may be performed according to the procedure of (b) above, and then calcination may be performed, or calcination may be performed without pre-calcination according to the procedure of (a).

The present invention will be described in more detail below with reference to the following examples. The present invention is not limited to these examples.

The methods for measuring (i) the moisture addition rate, (ii) the temperature inside the carbon precursor layer during the impregnation process, (iii) the moisture content of the alkali-impregnated carbon precursor, (iv) the rate of expansion of the particle size of the alkali-impregnated carbon precursor, and (v) the impregnation efficiency of the alkali metal compound used in this example are described below.

<Moisture addition rate>
The water addition rate (kg/h/kg-C) in the alkaline aqueous solution added to 1 kg of carbon precursor can be calculated by the following formula. Here, "kg-C" in the unit (kg/h/kg-C) in this formula is an indication of per 1 kg of carbon precursor. For the part "(1 - concentration of alkaline aqueous solution)" in this formula, a numerical value of mass concentration is applied. When a numerical value of mass % is used as the concentration of the alkaline aqueous solution, this part is expressed as "(100 - concentration of alkaline aqueous solution)/100".

<Average temperature in carbon precursor layer during impregnation treatment>
An alkaline aqueous solution is added to the carbon precursor particle layer, and the layer temperature T ₀ at the start of the alkaline impregnation treatment and the layer temperature T _i of the particle layer i minutes after the start of the addition of the alkaline aqueous solution are measured. When the addition of the alkaline aqueous solution is completed after n minutes, the average layer temperature T _Ave during the alkaline impregnation treatment can be calculated by the following formula. Here, the portion of the numerical value of the addition time of the alkaline aqueous solution that is less than 1 minute (60 seconds) is rounded down. This means that, for example, when the numerical value is 30 minutes and 15 seconds, the 15 second portion is rounded down to obtain a numerical value of 30 minutes.

<Moisture content of alkali-impregnated carbon precursor>
When 80% by mass of the planned amount of the aqueous alkaline solution is added to the carbon precursor in the reaction vessel, the addition of the aqueous alkaline solution is temporarily stopped, and stirring is continued for 1 minute. Then, 100 g or more of the alkali-impregnated carbon precursor is collected from the reaction vessel. Then, a sample of about 5 g is collected from the collected alkali-impregnated carbon precursor, and its mass A is measured. Next, the sample is heated to 120° C. at normal pressure, and its dry mass D is measured. The moisture content W (mass%) can be calculated by the following formula:

Specifically, about 5 g of the alkali-impregnated carbon precursor was placed in an infrared moisture meter FD-660 manufactured by Kett Electric Laboratory, and its mass A was measured. It was then held at normal pressure and 120°C, and the mass at which the mass loss rate over 30 minutes was 0.1% by mass or less was taken as the dry mass D of the alkali-impregnated carbon precursor. The moisture content W was then calculated using the above formula.

<Expansion rate of particle size of alkali-impregnated carbon precursor>
The particle size enlargement rate is a value obtained by dividing a particle size _{DV90 corresponding to a cumulative 90% by volume from the small particle size side of the alkali-impregnated carbon precursor by a particle size DV90 corresponding} to a cumulative 90% by volume from the small particle size side of the carbon precursor before the alkali impregnation treatment, as shown in the following formula: "alkali-impregnated carbon precursor" in this formula refers to the alkali-impregnated carbon precursor after the completion of alkali impregnation.

<Target impregnation rate of alkali metal compounds>
The target impregnation rate (mass%) of the alkali metal compound can be calculated by the following formula. In this formula, the "charged amount of carbon precursor" refers to the amount of carbon precursor charged in the reaction vessel. In this formula, the "added amount of alkali metal compound" is given by the product of the added amount (kg) of the alkaline aqueous solution and the concentration of the alkali metal compound in the alkaline aqueous solution.

<Impregnation rate of alkali metal compound>
The impregnation rate of the alkali metal compound in the alkali-impregnated carbon precursor was measured by measuring the content of the alkali metal in the alkali-impregnated carbon precursor in accordance with "General rules for fluorescent X-ray analysis" of Japanese Industrial Standard JIS K0119: 2008. The content was converted into the impregnation rate of the alkali metal compound by the following formula, and the impregnation rate (mass%) was calculated.

The impregnation efficiency of the alkali metal compound was calculated by dividing the impregnation rate (mass%) of the alkali metal compound by the target impregnation rate (mass%) of the alkali metal compound. The impregnation efficiency can be multiplied by 100 to express it as a percentage (%).

In the alkali impregnation treatment in the following examples and comparative examples, a carbon precursor that was made infusible by introducing oxygen was used. Hereinafter, this carbon precursor will be referred to as "infusible carbon." In addition, hereinafter, the alkali-impregnated carbon precursor obtained by this alkali impregnation treatment will be referred to as "impregnated carbon."

Example 1
A reaction vessel having an internal volume of 30 L and a stirring means equipped with a rotating shaft and a stirring blade attached to the rotating shaft was used, similar to the reaction vessel shown in FIG. 1. 6.0 kg of particles of infusibilized carbon (infusibilized carbon precursor) derived from petroleum pitch having an average particle size _Dv50 of 15.7 μm and _Dv90 of 34.2 μm was placed in the reaction vessel. The oxygen content of the infusibilized carbon was 13 mass%. Nitrogen gas was introduced from the bottom of the reaction vessel at 2 L/min, and while rotating the stirring blade at 150 rpm, superheated steam was introduced into the outer jacket of the reaction vessel, and the external temperature was heated to 135 to 150 ° C.

While maintaining the internal pressure of the reaction vessel at a gauge pressure of -0.03 MPa to -0.06 MPa, 6.0 kg of a 20% by mass aqueous solution of sodium hydroxide was sprayed onto the infusible coal over a period of 136 minutes. The addition time of the aqueous solution is hereinafter sometimes referred to as the "spraying time". The average temperature inside the layer of the infusible coal during the addition of the aqueous solution was 115°C. After spraying was completed, the temperature was maintained for 30 minutes. The internal pressure of the reaction vessel was then returned to normal pressure, and the superheated steam introduced into the jacket of the reaction vessel was replaced with water for cooling, yielding impregnated coal (alkali-impregnated carbon precursor).

Example 2
A reaction vessel with an internal volume of 100 L having the same structure as in Fig. 1 was used. The same infusible coal as in Example 1 was used, except that the average particle diameter _Dv50 was 23.7 µm and _Dv90 was 57.0 µm. 30.0 kg of infusible coal was placed in the reaction vessel, nitrogen gas was introduced into the bottom of the reaction vessel at 2 L/min, and superheated steam was introduced into the outer jacket of the reaction vessel while rotating the stirring blade at 80 rpm, and the external temperature was heated to 140 to 150°C.

After the temperature inside the bed reached 130°C, 16.7 kg of a 20% by mass aqueous solution of sodium hydroxide was sprayed onto the infusible coal over a period of 56 minutes while maintaining the internal pressure at a gauge pressure of -0.02 to -0.06 MPa. The average temperature inside the infusible coal during the addition of the aqueous solution was 105°C. After spraying was completed, the temperature inside the bed rose to 130°C. The internal pressure of the reaction vessel was then returned to normal pressure, and the superheated steam introduced into the jacket of the reaction vessel was replaced with water for cooling, yielding impregnated coal.

Example 3
Impregnated coal was obtained by the same procedure as in Example 2, except that the average particle size _Dv50 of the infusible coal was 8.8 μm, the _Dv90 was 20.2 μm, the rotation speed of the stirring blade was 130 rpm, the spraying time of 16.7 kg of a 20 mass% aqueous sodium hydroxide solution was 23 minutes, and the average temperature within the layer of the infusible coal during the addition of the aqueous solution was 102°C.

Example 4
Impregnated coal was obtained by the same procedure as in Example 3, except that the particle size _Dv50 of the infusible coal was 8.8 μm, _Dv90 was 20.0 μm, the concentration of the sodium hydroxide aqueous solution was 10 mass%, the spraying time of 33.3 kg of the aqueous solution was 35 minutes, and the average temperature within the layer of the infusible coal during the addition of the aqueous solution was 98° C.

Example 5
Impregnated coal was obtained by the same procedure as in Example 3, except that the average particle size _Dv50 of the infusible coal was 9.1 μm, the _Dv90 was 21.0 μm, the spraying time of 16.7 kg of a 20 mass% sodium hydroxide aqueous solution was 82 minutes, and the average temperature within the infusible coal layer during the addition of the aqueous solution was 130°C.

(Comparative Example 1)
The same reaction vessel and infusible carbon were used as in Example 1. 6.0 kg of infusible carbon was placed in the reaction vessel, nitrogen gas was introduced from the bottom of the reaction vessel at 2 L/min, and 6.0 kg of a 20% by mass aqueous sodium hydroxide solution was added all at once while rotating the stirring blade at 150 rpm, and thoroughly mixed to form a slurry. The temperature of the slurry was 35°C.

Next, superheated steam was introduced into the outer jacket of the reaction vessel, the external temperature was heated to 135-150°C, and the water was removed while maintaining the internal pressure of the reaction vessel at a gauge pressure of -0.03 MPa to -0.06 MPa. As the water evaporated, the slurry viscosity increased, and the resistance of the stirring blades increased. As a result, the stirring blades stopped, making it difficult to continue the experiment.

(Comparative Example 2)
The same reaction vessel as in Example 2 was used. The same infusible coal as in Example 1 was used, except that the average particle size _DV50 of the infusible coal was 7.1 μm and the _DV90 was 17.0 μm. 30 kg of infusible coal was placed in the reaction vessel, and while rotating the stirring blade at 130 rpm, 66.7 kg of a 5% by mass aqueous sodium hydroxide solution was added to the reaction vessel over a period of 5 minutes to form a slurry. The temperature of the infusible coal slurry at the time of adding the aqueous solution was 35° C.

Next, the gauge pressure was reduced to -0.02 MPa, superheated steam was introduced into the outer jacket of the reaction vessel, and the external temperature was heated to 140-150°C to evaporate the water. After the slurry changed into lumps, the chopper was rotated at 1800 rpm to crush the lumps while drying the impregnated coal, and it was confirmed that the temperature inside the layer had risen to 130°C. The internal pressure of the reaction vessel was then returned to normal pressure, and the superheated steam introduced into the jacket of the reaction vessel was switched to water for cooling, yielding impregnated coal.

The impregnation conditions and test results in the above-mentioned Examples and Comparative Examples are shown in Table 1, and the test conditions such as the stirring speed are shown in Table 2. Note that "-" in the column of the particle diameter _DV90 of the NaOH-impregnated carbon in Table 1 and the column of the average temperature in the layer in Table 2 indicates that the measurement was not possible.

As shown in Table 1, in Examples 1 to 5 included in the scope of the present invention, the moisture content of the alkali-impregnated carbon precursor during the impregnation process was 20 mass% or less, so the alkali impregnation process proceeded without passing through a slurry state, and the alkali compound was impregnated and the moisture was removed. The particle size expansion rate of the obtained alkali-impregnated carbon precursor was in the range of 1.0 to 1.1, and it was confirmed that the shape of the carbon precursor before impregnation was almost maintained. Therefore, the alkali-impregnated carbon precursors of Examples 1 to 5 were useful in that they could be subjected to the firing process without being subjected to a crushing process. In addition, according to the measured impregnation rate, it was confirmed that an alkali-impregnated carbon precursor with an impregnation efficiency of 99% or more was obtained in Examples 1 to 4, and an alkali-impregnated carbon precursor with an impregnation efficiency of 60% was obtained in Example 5.

In contrast, in both Comparative Example 1 and Comparative Example 2, the moisture content during impregnation exceeded 20% by mass, and the alkali impregnation process proceeded in a slurry state. In Comparative Example 1, the amount of water added was small, so as the moisture evaporated, the slurry viscosity increased, and the output capacity of the motor attached to the stirrer was insufficient, making mixing by stirring difficult. In Comparative Example 2, stirring could be continued by increasing the motor output capacity of the stirrer, but the alkali impregnated carbon precursor obtained after removing the moisture had a large particle size expansion rate and was in a lumpy form. Therefore, it was necessary to subject the alkali impregnated carbon precursor to a pulverization process to obtain a particle size suitable for the firing process.

REFERENCE SIGNS LIST 1 Reaction vessel 2 Side surface 3 Bottom surface 4 Side wall 5 Bottom wall 6 Top lid 7 Supply port for carbon precursor 8 Discharge port for treated material 9 Observation window 10 Gas inlet 11 Gas pressure gauge 12 Replacement gas 13 Carbon precursor 14 Temperature measuring device 15 Support 20 Heating medium (heat medium)
21 Heating medium supply port 22 Heating medium flow path 23 Heating medium discharge port 24 Temperature measuring device on heat medium inlet side 25 Temperature measuring device on heat medium discharge side 30 Stirring means (stirrer)
Reference Signs List 31 Rotating shaft 32 Agitating blade 33 Motor 34 Tip of agitating blade 35 Lower end of agitating blade 36 Agitating flow 40 Chopper 41 Rotating shaft 42 Chopper blade 43 Motor 50 Alkaline aqueous solution 51 Spray nozzle 52 Supply pipe for alkaline aqueous solution 53 Weight scale 54 Storage container for alkaline aqueous solution 55 Pressure measuring device 56 Pressurizing air 57 Temperature measuring device 60 Bag filter 61 Backwash gas introduction pipe 62 Gas exhaust pipe 63 Exhaust gas

Claims (8)

Stirring and heating the carbon precursor in a reaction vessel;
adding an alkaline aqueous solution containing an alkali metal compound to the carbon precursor being stirred, and removing moisture from the alkaline aqueous solution to obtain an alkali-impregnated carbon precursor in which the alkali metal compound is impregnated into the carbon precursor,
the water content of the alkali-impregnated carbon precursor in the reaction vessel is 20 mass% or less,
The water content is the water content at a point in time when 80 mass % of the total amount of the alkaline aqueous solution added has been added. The method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery according to claim 1, wherein the alkaline aqueous solution has a concentration of the alkali metal compound of 40 mass % or less. A method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery as described in claim 1 or 2, wherein the carbon precursor being stirred has an average temperature within the particle layer of 70 to 125°C. A method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the water addition rate (kg/h/kg-C) at which water in the alkaline aqueous solution is added per 1 kg of the carbon precursor being stirred is 0.1 or more and 10.0 or less. The method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the reaction vessel is provided with a supply port for introducing the carbon precursor into the reaction vessel, a discharge port for removing the alkali-impregnated carbon precursor from the reaction vessel, a heating means for heating the carbon precursor, a stirring means for stirring the carbon precursor, and an adding means for adding the alkali aqueous solution to the carbon precursor. A method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the carbon precursor is derived from petroleum-based pitch, coal-based pitch, or a mixture thereof. 7. The method for producing an alkali-impregnated carbon precursor for a non-aqueous electrolyte secondary battery according to claim 1, wherein the alkali-impregnated carbon precursor has a particle diameter _DV90 corresponding to a cumulative 90% by volume of 150 μm or less. A method for producing a carbonaceous material for a non-aqueous electrolyte secondary battery, comprising: carrying out a heat treatment at 800° C. to 1500° C. in an inert atmosphere using the alkali-impregnated carbon precursor according to any one of claims 1 to 7 to produce a carbonaceous material.

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