JP7731676B2 - Powder manufacturing apparatus and powder manufacturing method - Google Patents

Description

This disclosure discloses a powder manufacturing apparatus and a powder manufacturing method.

One proposed electrode material for lithium-ion secondary batteries involves gradually adding a coating solution to an active material and then drying and solidifying the solution on a hot plate to form a coating layer on the surface of the active material (see, for example, Patent Document 1). This electrode material includes an electrolyte material that includes a sulfide layer containing a sulfide material and an oxide formed by oxidizing the sulfide material, and has an oxide layer located on the surface of the sulfide layer, and an active material with a coating layer. It is said that further improvements in the charge and discharge efficiency of batteries are desirable. Another proposed electrode material for lithium-ion secondary batteries involves creating a slurry from a solution containing a positive electrode active material, lithium, phosphoric acid, and a transition metal, which is then dried and heat-treated to form a lithium-transition metal-phosphate coating layer (see, for example, Patent Document 2). It is said that this electrode material can reduce the interfacial resistance between the positive electrode active material and the sulfide-based solid electrolyte. Additionally, as an electrode material for lithium-ion secondary batteries, for example, a cathode active material surface coated with a glass-based electrolyte using a tumbling flow method in which active material powder is vigorously stirred and thrown up and down in a chamber, and a coating liquid is sprayed onto the surface while the material is heated and dried (see, for example, Patent Document 3). This cathode active material can increase the capacity and charge/discharge efficiency of sulfide all-solid-state batteries.

Japanese Patent Application Laid-Open No. 2018-32621 Japanese Patent Application Laid-Open No. 2015-72772 JP 2016-39062 A

However, in the above-mentioned Patent Documents 1 and 2, the coating solution sinks due to gravity during static drying, which can lead to unevenness in the coating solution concentration and unevenness in the coating layer. Furthermore, in Patent Document 3, a uniform coating layer can be formed using the tumbling flow method, but forming a uniform coating layer requires slow processing over time, leaving a need for further improvements in processing efficiency.

The present disclosure has been made in consideration of these issues, and its primary objective is to provide a powder manufacturing apparatus and a powder manufacturing method that can form a more uniform functional material layer on the powder surface with more efficient processing.

After extensive research to achieve the above-mentioned objectives, the inventors discovered that by using a wet powder with a solids volume fraction within a predetermined range, wet enough to prevent the powder from becoming a slurry, and then performing one or more cyclone processes, a more efficient process can be performed, resulting in the formation of a more uniform functional material layer on the powder surface, leading to the completion of the invention disclosed in this specification.

That is, the powder manufacturing apparatus of the present disclosure is
A powder manufacturing apparatus for coating a surface of powder with a functional material,
a supply unit that stores wet powder obtained by wetting the powder with a liquid containing the functional material and supplies a fluid containing the wet powder and heated gas;
a first circulating portion connected to the supply portion and through which the fluid circulates;
one or more cyclone sections that cause the fluid supplied from the first circulation section to flow and remain there;
a collecting section connected to the cyclone section and configured to collect powder contained in the fluid after the fluid has accumulated;
It is equipped with the following.

The method for producing powder of the present disclosure includes:
A method for producing powder in which the surface of the powder is coated with a functional material, comprising the steps of:
a supplying step of supplying a fluid containing wet powder obtained by wetting the powder with a liquid containing the functional material and heated gas;
one or more cyclone steps in which the supplied fluid is passed through and then retained while flowing;
a collecting step of collecting powder contained in the fluid after the cyclone step;
It includes:

The powder production apparatus and powder production method disclosed herein are capable of forming a more uniform functional material layer on the powder surface through more efficient processing. The reasons for this effect are presumed to be, for example, as follows: Generally, in static drying, the liquid containing the functional material flows downward due to gravity, resulting in a thicker protective layer and a higher coverage rate for particles at the bottom, which can lead to uneven coverage. Furthermore, particles in areas with a higher concentration of the functional material-containing liquid tend to aggregate. On the other hand, in a method of air-flow drying of wet powder using a cyclone, the particles are introduced into the airflow while still wet with the liquid and are subjected to a disintegrating force caused by the centrifugal force generated by the cyclone, which causes the powder to dry while deagglomerating. In this way, the functional material-coated powder is less likely to aggregate, resulting in a more uniform particle size. Furthermore, the use of one or more such cyclones allows for sufficient drying and disintegration processes, which is presumed to more efficiently form a more uniform functional material layer on the powder surface.

FIG. 1 is an explanatory diagram showing an example of a powder manufacturing apparatus 10. FIG. 1 is a plan view of a powder manufacturing apparatus 10. 1 is a schematic diagram of a powder manufacturing apparatus 10 when wet powder is introduced. FIG. 10 is an explanatory diagram showing an example of another powder manufacturing apparatus 10B. FIG. 1 is an explanatory diagram showing an example of a known tumbling fluidization coating apparatus 110. Photograph showing the state in which the slurry of Comparative Example 1 adheres to the inside of the apparatus.

(Powder manufacturing equipment)
The powder manufacturing apparatus disclosed herein is an apparatus for coating the surface of powder with a functional material. The powder manufacturing apparatus includes a supply unit that accommodates wet powder obtained by wetting powder with a liquid containing a functional material and supplies a fluid containing the wet powder and heated gas; a first circulating unit connected to the supply unit and through which the fluid flows; one or more cyclone units that allow the fluid supplied from the first circulating unit to flow and accumulate; and a collecting unit connected to the cyclone units and collects the powder contained in the fluid after accumulation. The powder manufacturing apparatus may include one cyclone unit or two or more cyclone units. Below, a powder manufacturing apparatus including two cyclone units will be primarily described.

This embodiment will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of a powder manufacturing apparatus 10. FIG. 2 is a plan view of the powder manufacturing apparatus 10. FIG. 3 is a schematic diagram of wet powder being charged into the powder manufacturing apparatus 10. The powder manufacturing apparatus 10 is an apparatus that coats the surface of powder with a functional material. The powder is not particularly limited, but examples include those used as electrode materials for electricity storage devices. Examples of electrode materials include active material particles, solid electrolyte particles, conductive material particles, binder particles, and current collector particles. Examples of functional materials include protective materials that form protective layers, coating materials that form coating layers, conductive materials that impart conductivity, electrolyte materials that impart ionic conductivity, and binders that impart binding properties.

Examples of active materials include transition _{metal composite oxides having} the basic formula _{LixNiaCobMncO2} (where 0≦x≦1.2, 0≦a≦1, 0≦b≦1, 0≦c≦1, and a+ _b + _c = ₁ ) _{or LixNiaCobMncO4} (where 0≦x≦1.2, 0≦a≦1, 0≦b≦1, 0 _< c<1, and a+b+c=2), and lithium iron phosphate compounds having the basic formula _LiFePO4 . Examples of active materials include carbonaceous materials such as cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Examples of solid electrolytes include lisicon oxides, sulfides, perovskite oxides, garnet oxides, nasicon oxides, glass ceramics, and thiolicon solid electrolytes. Examples of conductive materials include graphite, such as natural graphite (scale graphite, flake graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fiber, and metals (copper, nickel, aluminum, silver, gold, etc.). Examples of binders include fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber, thermoplastic resins such as polypropylene and polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, and natural butyl rubber (NBR). Examples of protective materials include _LiNbO3 . Examples of liquids that wet the powder include water and organic solvents, with water being preferred. Examples of organic solvents include alcohol, acetone, chloroform, as well as N-methylpyrrolidone (NMP), dimethylformamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. For ease of explanation, the powder is active material particles of an electricity storage device, the functional material is a protective material for the active material, and the powder production apparatus 10 that forms a protective layer containing the protective material on the surface of the active material particles will be mainly described here.

The powder manufacturing apparatus 10 includes a supply unit 11, a first circulating unit 16, a first cyclone unit 21, a second circulating unit 22, a second cyclone unit 24, a collecting unit 25, a suction unit 27, and a control unit 28.

The supply unit 11 is a unit that stores wet powder obtained by wetting a powder with a liquid containing a functional material and supplies a fluid (hereinafter simply referred to as a fluid) containing the wet powder and heated gas. In the powder production apparatus 10, by using flash drying, the process from powder input to collection can be completed in a short time (e.g., less than one second). The supply unit 11 includes a storage unit 12, a heating unit 13, and a constant volume feeder. The storage unit 12 is a container that stores the wet powder. For example, the storage unit 12 may store and supply wet powder with a solid volume fraction greater than 40% by volume. In the range of 40% by volume or less, dilatancy occurs or the powder becomes a slurry state, resulting in a loss of particle fluidity, making flash drying unsuitable for this apparatus. On the other hand, there is no particular upper limit on the volume percentage. The wet powder is not a liquid such as a slurry, but rather a powder that contains liquid but has voids and maintains powder fluidity. This wet powder may be, for example, a powder in the pendular range. The heating section 13 is a heater that heats the gas flowing through the apparatus. Examples of the gas to be heated include air, nitrogen, and rare gases, and the gas is selected depending on the object to be treated. The constant volume feeder is a device that supplies a fixed amount of wet powder from the storage section 12 to the first flow section 16. The supply section 11 may supply gas heated to a temperature range of 100°C or higher and 230°C or lower. The supply section 11 may also supply gas at a rate of 0.5 ^m3 /min or higher, more preferably 0.8 ^m3 /min or higher and 7.5 ^m3 /min or lower. The supply conditions of the supply section 11 may be selected appropriately depending on the object to be treated.

The first circulating section 16 is a unit connected to the supply section 11 and the first cyclone section 21 and through which fluid flows. The first circulating section 16 includes a mixing section 17 connected to the supply section 11 and having a larger volume than the first cyclone section 21, and a circulation pipe 18 connecting the mixing section 17 and the first cyclone section 21. The mixing section 17 is a portion through which the heated gas and wet powder supplied from the supply section 11 flow downward and mix. It is a cylinder with a larger diameter than the first cyclone section 21. The first circulating section 16 may not include the mixing section 17 and the supply section 11 may be directly connected to the circulation pipe 18. However, from the perspective of further mixing the heated gas and wet powder and increasing their movement speed, it is preferable to have the mixing section 17 connected. The mixing section 17 may have a diameter similar to that of the circulation pipe 18. The first circulating section 16 may have a length at least twice the total length L of the first cyclone section 21. The relatively long first flow section 16 allows the heated gas and wet powder to be thoroughly mixed before reaching the first cyclone section 21.

The first cyclone section 21 is a unit that dries wet particles by causing the fluid to flow and accumulate in a vortex or spiral shape, and also performs a process that breaks down the powder particles by causing them to collide with each other, preventing particle aggregation. In the first cyclone section 21, the powder is rotated in the cyclone while flying, thereby increasing the flight distance and improving drying efficiency. The first cyclone section 21 has a cylindrical main body with the first flow section 16 located at the top, and a tapered section connected to the bottom of the main body, whose inner diameter decreases downward.

The second circulating section 22 is a circulating pipe that is connected to the first cyclone section 21 and the second cyclone section 24 and circulates the fluid that has accumulated in the first cyclone section 21. This second circulating section 22 includes a U-shaped pipe connected to an outlet formed at the bottom of the first cyclone section 21, a vertical pipe that guides the fluid upward, and a horizontal pipe that guides the fluid horizontally. The horizontal pipe is connected perpendicular to the second cyclone section 24. If the second circulating section 22 is made relatively long, it is possible to ensure a longer drying time.

The second cyclone section 24 is a unit connected to the second flow section 22 and performs a process of retaining the fluid while it flows. The upper part of the second cyclone section 24 is connected to the filter 26, and the suction section 27 is connected downstream of the filter 26. A collection section 25 for capturing powder is also provided below the second cyclone section 24. In this second cyclone section 24, the gas flow flows to the downstream filter 26, and the powder falls downward under its own weight. Therefore, the second cyclone section 24 has the function of separating the coated powder from the gas flow with high yield. Similar to the first cyclone section 21, the second cyclone section 24 retains the fluid while flowing it in a vortex or spiral shape, drying the wet particles, and also has the function of crushing the powder particles by colliding with each other, thereby suppressing particle aggregation. The second cyclone section 24 comprises a cylindrical main body with the second flow section 22 disposed at the top, and a tapered section connected to the bottom of the main body, the inner diameter of which decreases downward.

The collection unit 25 is connected to the second cyclone unit 24 and is a container that collects powder contained in the fluid after it has accumulated in the second cyclone unit 24. The collection unit 25 is removably disposed in the second cyclone unit 24. The filter 26 prevents the powder from being sucked into the suction unit 27, which is disposed downstream of the filter 26. The gas flowing out from the filter 26 enters the suction unit 27, where it is dried via a dehumidifier (not shown), and is sent back to the heating unit 13. The suction unit 27 reduces the pressure within the system to allow the gas to circulate, and may be, for example, a vacuum pump, suction pump, or aspirator.

The control unit 28 is configured as a controller centered around a CPU (not shown) and controls the entire device. This control unit 28 is electrically connected to the supply unit 11 and other components, receives signals from the supply unit 11, and outputs control signals to the supply unit 11.

Since wet powder containing voids is dried, the coverage rate may not exceed the specified value, but this coverage rate and the thickness of the coating layer can be adjusted by the number of coats. The number of coats can be selected appropriately depending on the coverage rate and the thickness of the coating layer, and may be, for example, three or more times, five or more times, or ten or fewer times.

In the powder manufacturing apparatus 10, the heating unit 13 is disposed in the supply unit 11, but a heating unit for heating the fluid may also be provided in one or more of the first circulating unit 16, first cyclone unit 21, second circulating unit 22, and second cyclone unit 24. The heating unit may be disposed anywhere within the apparatus as appropriate depending on the temperature of the fluid. Note that if the heating unit 13 is provided only in the supply unit 11, the apparatus configuration can be simplified.

Here, the operation of the powder manufacturing apparatus 10 will be described. First, an operator prepares a wet powder by wetting the powder with a liquid containing the functional material to a solid volume fraction in a range where dilatancy or a slurry state does not occur, for example, greater than 40% by volume, and places the wet powder in the supply unit 11. Next, the operator inputs processing conditions, such as the gas supply rate, heating temperature, and wet powder supply rate, into the control unit 28 and initiates the process. The control unit 28 controls the supply unit 11 and other components according to the set processing conditions. Figure 3 is a schematic diagram of the wet powder being introduced into the powder manufacturing apparatus 10. The fluid containing the wet powder and heated gas supplied from the supply unit 11 flows through the mixing unit 17 and the flow pipe 18 and enters the first cyclone unit 21. The fluid flows and stagnates in the first cyclone unit 21 in a vortex pattern, where the agglomerated powder is crushed and dried. The powder that reaches the bottom of the first cyclone section 21 flows into the second cyclone section 24 via the second flow section 22. The fluid flows in a vortex and remains in the second cyclone section 24, and the dried powder falls downward to be collected in the collection section 25.

(Method for producing powder)
The powder manufacturing method disclosed herein is a method for manufacturing powder in which the surface of the powder is coated with a functional material, and includes a supplying step of supplying a fluid containing a wet powder obtained by wetting the powder with a liquid containing the functional material and a heated gas, one or more cyclone steps of circulating the supplied fluid and then causing the fluid to flow and remain, and a collecting step of collecting the powder contained in the fluid after the cyclone step. This manufacturing method may include one cyclone step or two or more cyclone steps. Below, we will first mainly describe a powder manufacturing method that performs a first cyclone step and a second cyclone step.

The powder manufacturing method disclosed herein is a method for manufacturing powder whose surface is coated with a functional material. This manufacturing method includes a supplying step, a first cyclone step, a second cyclone step, and a collecting step. This manufacturing method may be performed by the powder manufacturing apparatus 10 described above. This manufacturing method may also include a wet powder manufacturing step in which the powder is wetted with a liquid containing the functional material to produce a wet powder. In this wet powder manufacturing step, the powder may be wetted with a liquid containing the functional material to produce a wet powder whose solid volume fraction is above the range in which dilatancy does not occur, for example, greater than 40% by volume.

(Supply process)
In the supplying step, a fluid containing a wet powder obtained by wetting a powder with a liquid containing a functional material and a heated gas is supplied. In this step, a wet powder having a solid volume fraction of more than 40% by volume may be supplied. Furthermore, the solid volume fraction of the wet powder may be equal to or greater than the range in which dilatancy does not occur, depending on the properties of the powder, or may be in a range greater than 40% by volume. In addition to the functional material and powder, the processing conditions described for the powder production apparatus above can be used as appropriate. In this step, the gas may be supplied at a temperature in the range of 100°C to 230°C. In this step, a fluid may be supplied at a rate of 0.5 ^m3 /min or more, more preferably 0.8 ^m3 /min to 7.5 ^m3 /min.

(First cyclone process)
In the first cyclone process, the supplied fluid is circulated and then retained while flowing. In this process, the fluid can be made to flow in a vortex or spiral shape by flowing the fluid perpendicularly to the cylinder. In this process, the wet particles are dried and the powder particles are crushed by colliding with each other, thereby suppressing particle aggregation.

(Second cyclone process)
In the second cyclone process, the fluid from the first cyclone process is passed through and then retained while flowing. This process separates the dried powder from the gas flow. In this process, the fluid is introduced perpendicular to the cylinder, allowing the fluid to flow in a vortex or spiral shape.

(Collection process)
The collection step involves carrying out a process for collecting powder contained in the fluid after the second cyclone step. This process may involve collecting powder that has been separated from the gas flow in the second cyclone process and fallen down.

In this manufacturing method, the series of coating processes, including the supply process, first cyclone process, second cyclone process, and collection process, described above, may be repeated multiple times. By performing the coating process multiple times, the coverage of the functional material layer on the powder surface can be further increased. The number of times this coating process is performed can be determined depending on the coverage.

The powder production apparatus 10 and powder production method of this embodiment, described in detail above, enable more efficient processing and the formation of a more uniform functional material layer on the powder surface. The reason for this effect is presumed to be, for example, as follows: Generally, in static drying, the liquid containing the functional material flows downward due to gravity, resulting in a thicker protective layer and a higher coverage rate for particles at the bottom, which can lead to uneven coverage. Furthermore, particles in areas with a higher concentration of the functional material-containing liquid tend to aggregate. On the other hand, in a method of air-flow drying of wet powder using a cyclone, the particles are introduced into the airflow while still wet with the liquid and are subjected to a disintegrating force caused by the centrifugal force generated by the cyclone, which causes the powder to dry while deagglomerating. In this way, the functional material-coated powder is less likely to aggregate and has a uniform particle size. Furthermore, the use of multiple cyclones allows for sufficient drying and disintegration processes, presumably resulting in a more efficient and uniform functional material layer being formed on the powder surface.

It goes without saying that the present disclosure is in no way limited to the above-described embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.

For example, while the above-described embodiment describes a powder manufacturing apparatus 10 equipped with two cyclone sections, this is not particularly limited, and a powder manufacturing apparatus 10B equipped with one first cyclone section 21 may also be used, as shown in FIG. 4. FIG. 4 is an explanatory diagram showing an example of another powder manufacturing apparatus 10B. In this powder manufacturing apparatus 10B, a collection section 25, a filter 26, and a suction section 27 are connected to the first cyclone section 21. In this way, even an apparatus equipped with one cyclone section can form a more uniform functional material layer on the powder surface with more efficient processing.

In the above-described embodiment, a powder manufacturing method that performs two cyclone processes has been described, but this is not particularly limited, and a powder manufacturing method that performs only one cyclone process may also be used. In this way, even in a method that performs one cyclone process, a more uniform functional material layer can be formed on the powder surface with more efficient processing.

Below, we will explain an example in which a powder production apparatus according to the present disclosure was specifically fabricated and a powder production method was carried out using this powder production apparatus.

First, the powder production apparatus 10 shown in Figure 1 and the powder production apparatus 10B shown in Figure 4 were fabricated. In the fabricated powder production apparatus 10, the volume of the storage section 12 was 1 L, the total length of the first flow section 16 was 80 cm, the length L of the first cyclone section 21 was 40 cm and its volume was 0.4 L, the total length of the second flow section 22 was 45 cm, and the length of the second cyclone section 24 was 30 cm and its volume was 0.2 L. There are no restrictions on the size of each component as long as the configuration is not changed.

Example 1
20 g of _Li1.14 ( _{Ni0.34Co0.34Mn0.31} ) _O2 (also referred to _as NCM) was placed in a mixer container as the positive _electrode active material. A predetermined amount of a coating solution containing _LiNbO3 as a protective material was added to the positive electrode active material powder so that the solid volume fraction was 54.9% by volume, and the mixture was stirred with a spoon. The process of stirring with the mixer and scraping off any residue from the wall was repeated three times to obtain a wet powder. The prepared wet powder sample was introduced in small amounts from the top of the powder production apparatus 10B (Figure 4) and subjected to airflow drying. Air heated to 220°C was circulated at 0.6 ^m3 /min, and the wet powder was supplied at a supply rate of 120 g/min, with a total mass of 20 g (powder only). This series of coating treatments, consisting of the wetting treatment and the airflow drying treatment, was repeated three times to obtain an active material powder (coated powder) having a protective layer formed thereon, which was designated as Example 1. The time from the introduction of the sample to drying and collection was 0.2 minutes per drying treatment.

Example 2
20 g of _Li1.14 ( _{Ni0.34Co0.34Mn0.31} ) _O2 (also referred to _as NCM) was placed in a mixer container as the positive _electrode active material. A predetermined amount of a coating solution containing _LiNbO3 as a protective material was added to the positive electrode active material powder so that the solid volume fraction was 49.5% by volume, and the mixture was stirred with a spoon. The process of stirring with the mixer and scraping off any residue from the wall was repeated three times to obtain a wet powder. The prepared wet powder sample was introduced in small amounts from the top of the powder production apparatus 10 (Figures 1 and 2) and subjected to airflow drying. Air heated to 220°C was circulated at 0.6 ^m3 /min, and the wet powder was supplied at a supply rate of 120 g/min, with a total mass of 20 g (powder only). The time from sample introduction to drying and collection was 0.21 minutes. The coated powder having the protective layer formed thereon obtained by this series of treatments was designated as Example 2.

Example 3
20 g of NCM was placed in a mixer container, and a predetermined amount of coating liquid containing _LiNbO3 was added so that the solid volume fraction was 49.5% by volume, and the mixture was stirred with a spoon. The mixture was stirred in the mixer, and any residue on the wall was scraped off. This process was repeated three times to prepare a wet powder sample. The prepared wet powder sample was introduced little by little from the top of the coating dryer and air-dried. The coated powder obtained by repeating this series of coating processes, consisting of wetting and air-drying, three times was designated Example 3.

(Comparative Example 1)
30 g of NCM was placed in a beaker, and a predetermined amount of coating liquid containing _LiNbO3 was added so that the solid volume fraction was 40.5% by volume. The mixture was stirred with a spoon to obtain a slurry sample. The prepared slurry sample was introduced little by little from the top of the powder production apparatus 10 and air-dried. The air-drying conditions were the same as in Example 1. The obtained coated powder was designated Comparative Example 1.

(Comparative Example 2)
A protective layer-forming active material powder was prepared using a tumbling fluidized coating apparatus 110 shown in FIG. 5 . FIG. 5 is an explanatory diagram showing an example of a known tumbling fluidized coating apparatus 110. The tumbling fluidized coating apparatus 110 includes a supply unit 111, a discharge unit 112, a stirring unit 113, a chamber 114, and a heater 115. This tumbling fluidized coating apparatus 110 supplies powder from the lower supply unit 111, and when the powder stirred by the stirring unit 113 is blown up into the upper chamber 114, a coating liquid is discharged from the discharge unit 112 and dried using the heater 115 provided above the chamber 114. 1000 g of NCM was loaded into the tumbling fluidized coating apparatus 110 and coated for 80 minutes while spraying 720 g of a coating liquid containing LiNbO ₃ . The resulting coated powder was designated Comparative Example 2.

(Comparative Example 3)
20 g of NCM was placed in a mixer container, and a predetermined amount of coating liquid containing _LiNbO3 was added so that the solid volume fraction was 49.5% by volume, followed by stirring with a spoon. The process of stirring with the mixer and scraping off any residue on the wall was repeated three times to prepare a wet powder sample. This powder was spread in a petri dish, and the dish was heated in a muffle furnace from 80°C to 200°C over 30 minutes, then held at 200°C for 1 hour to dry. The powder was then crushed appropriately with a spatula and collected. The resulting coated powder was designated Comparative Example 3.

(Comparative Example 4)
20 g of NCM was placed in a mixer container, and a predetermined amount of coating liquid containing _LiNbO3 was added so that the solid volume fraction was 49.5% by volume. The mixture was then stirred with a spoon. This process of stirring with the mixer and scraping off any residue on the wall was repeated three times to prepare a wet powder sample. The powder was spread in a petri dish, and the dish was heated in a muffle furnace from 80°C to 200°C over 30 minutes, then held at 200°C for 1 hour to dry. The powder was then crushed with a spatula and collected. The coated powder obtained by repeating this series of coating processes, from wetting to drying in a muffle furnace, three times was designated Comparative Example 4.

(Calculation of coverage)
The coverage of the coated powder was determined by performing surface elemental analysis of the obtained coated powder by X-ray photoelectron spectroscopy (XPS: PHI X-tool manufactured by ULVAC-PHI), and calculating the coverage by applying the detected intensity values of C1S, O1S, Nb3d, Mn2p3, Co2p3, Ni2p3, etc. to the following formula (1):

(Measurement of particle diameter D90)
The particle size (μm) of the powder after coating treatment was determined as the particle size D90 showing 90% of the cumulative distribution using a laser diffraction/scattering measuring device (Aerotrac II manufactured by Microtrac Bell).

(Results and Discussion)
Table 1 summarizes the conditions for Examples 1 to 3 and Comparative Examples 1 to 4, such as the drying method, powder state, number of coatings, and wetting and drying treatment times. Table 2 also summarizes the coverage and particle size for Examples 1 to 3 and Comparative Examples 1 to 4. Examples 1 to 3 and Comparative Examples 1, 3, and 4 represent the results of a manufacturing method in which the wetting and drying processes are separated. Comparative Example 2 represents the results of a manufacturing method in which the wetting and drying processes are integrated. In Example 1, a wet powder with a solid volume fraction of 54.9% by volume was dried using a powder manufacturing apparatus with a single cyclone coating dryer (Figure 4). In Examples 2 and 3, a wet powder with a solid volume fraction of 49.5% by volume was dried using a powder manufacturing apparatus with a double cyclone coating dryer (Figure 1). As in Example 3, it was found that when the coating process was repeated multiple times, the coverage could be further increased with a high yield. Furthermore, the results for Example 1 were similar to those for Examples 2 and 3. In Comparative Example 1, the same powder production equipment as in Example 2 was used. However, because the powder used as raw material was in the form of a slurry with a low solids volume fraction, as shown in Figure 6, the slurry adhered to the inner wall of the glass cylinder, taking a long time to dry. Furthermore, the yield was low due to the remaining particles adhering to the beaker and spoon. Figure 6 is a photograph of the slurry from Comparative Example 1 adhering to the inside of the equipment. In Comparative Example 2, the powder was produced using a tumbling fluidized coating device, but the coverage and particle size were similar to those of Examples 2 and 3. On the other hand, Comparative Example 2 was produced using a batch processing device for powder (1 kg), and the size of the fluidized kiln alone was 70 cm high. Furthermore, when the processing volume is increased, for example, in an equipment for processing 25 kg, the height of the fluidized kiln alone is 2.2 m, making the equipment larger and the processing time longer. In Comparative Examples 3 and 4, static drying was used, but the drying time was long, the coverage was low, and particles aggregated.

As described above, while the tumbling fluidized coating apparatus required time and space to form a functional layer on the powder surface, the powder production apparatus 10, 10B of the present disclosure was found to enable shortening of processing time and downsizing of the apparatus. The powder production apparatus 10, 10B used airflow drying, which significantly reduced the processing time from powder input to collection of the coated powder, compared to other apparatuses. Furthermore, the use of a constant volume feeder enabled continuous powder input, enabling continuous coating. Because continuous processing was possible, large quantities could be processed. Furthermore, the powder production apparatus 10, 10B was found to produce coated particles with a high coverage rate, uniformity, and suppressed particle aggregation. Furthermore, the thickness of the coating layer could be adjusted by changing the number of coatings. In addition, tests other than those described above have shown that the preferred conditions for producing the wet powder and for air drying are a solid volume fraction of more than 40% by volume, a drying air temperature of 100°C or higher and 230°C or lower at the inlet, and an air volume of 0.5 ^m3 /min or higher, more preferably 0.8 ^m3 /min or higher and 7.5 ^m3 /min or lower.

Coating powder surfaces with protective layers or functional materials is an extremely useful technique for protecting the powder and providing new functions. It is widely used in many technical fields that involve powders, such as battery materials and magnetic materials. Positive electrode active materials in all-solid-state lithium-ion secondary batteries, for example, pose a challenge: repeated charge and discharge can cause a reaction between the active material and the solid electrolyte, resulting in a decline in output characteristics. Therefore, coating the active material surface with a protective layer of lithium-ion conductive metal oxide effectively reduces this reaction resistance. If a protective layer can be uniformly applied to the active material while suppressing agglomeration of the coated powder, it is possible to suppress deterioration of the positive electrode and extend the battery's life. In this example, a powder production device consisting of a single-cyclone or double-cyclone coating dryer was used to coat active materials for lithium-ion secondary batteries as an example. However, this technology has broad applicability and can also be used to coat other powder surfaces with different materials uniformly, suppress particle agglomeration, and quickly and efficiently.

It goes without saying that the present disclosure is in no way limited to the above-described examples, and can be implemented in various forms as long as they fall within the technical scope of the present disclosure.

This disclosure is applicable to the battery technology field.

10, 10B Powder manufacturing apparatus, 11 Supply section, 12 Storage section, 13 Heating section, 16 First circulation section, 17 Mixing section, 18 Circulation pipe, 21 First cyclone section, 22 Second circulation section, 24 Second cyclone section, 25 Collection section, 26 Filter, 27 Suction section, 28 Control section, 110 Tumbling fluidized coating device, 111 Supply section, 112 Discharge section, 113 Stirring section, 114 Chamber, 115 Heater, L Overall length.

Claims (12)

A powder manufacturing apparatus for coating a surface of powder with a functional material,
a supply unit that stores wet powder obtained by wetting the powder with a liquid containing the functional material and supplies a fluid containing the wet powder and heated gas;
a first circulating portion connected to the supply portion and circulating the fluid without stagnation ;
a heating section disposed upstream of the first flow section in a fluid flow direction and configured to heat the fluid;
one or more cyclone sections that cause the fluid supplied from the first circulation section to flow and remain there;
a collecting section connected to the cyclone section and configured to collect powder contained in the fluid after the fluid has accumulated;
A powder manufacturing device equipped with the above. the cyclone unit includes a first cyclone unit and a second cyclone unit,
the first cyclone portion connected to the first flow portion and causing the fluid to flow and accumulate;
a second circulating section connected to the first cyclone section and through which the fluid circulates after stagnation;
the second cyclone portion connected to the second flow portion and causing the fluid to flow and accumulate;
the collection unit connected to the second cyclone unit;
The powder manufacturing apparatus according to claim 1 , The powder manufacturing apparatus of claim 2, wherein the first circulation section includes a mixing section connected to the supply section and having a larger volume than the first cyclone section, and a circulation pipe connecting the mixing section and the first cyclone section. The powder manufacturing apparatus according to any one of claims 1 to 3, wherein the supply unit stores and supplies the wet powder having a solid volume fraction greater than 40% by volume. The powder manufacturing apparatus according to any one of claims 1 to 4, wherein the supply unit supplies the gas at a temperature in the range of 100°C or higher and 230°C or lower. 6. The powder manufacturing apparatus according to claim 1, wherein the supply unit supplies the fluid in a range of 0.5 m ³ /min to 7.5 ^{m 3} /min. The powder manufacturing apparatus according to any one of claims 1 to 6, wherein the powder is active material particles of an electricity storage device, the functional material is a protective material for the active material, and a protective layer containing the protective material is formed on the surface of the active material particles. A method for producing powder in which the surface of the powder is coated with a functional material, comprising the steps of:
a supplying step of supplying a fluid containing wet powder obtained by wetting the powder with a liquid containing the functional material and a gas heated by a heating unit that heats the fluid ;
a first circulating step of circulating the fluid supplied in the supplying step without allowing it to stagnate;
one or more cyclone steps in which the supplied fluid is passed through and then retained while flowing;
a collecting step of collecting powder contained in the fluid after the cyclone step;
A method for producing a powder comprising: The cyclone process includes:
a first cyclone step in which the supplied fluid is circulated and then retained while flowing;
The method for producing powder according to claim 8, further comprising a second cyclone step of circulating the fluid after the first cyclone step and then retaining the fluid while it flows. The method for producing powder described in claim 8 or 9, wherein the supplying step supplies the wet powder with a solid volume fraction greater than 40% by volume. The method for producing powder described in any one of claims 8 to 10, wherein the gas is supplied at a temperature in the range of 100°C or higher and 230°C or lower in the supplying step. The method for producing powder according to any one of claims 8 to 11, wherein the fluid is supplied in the supply step at a rate in the range of 0.5 m ³ /min to 7.5 ^{m 3} /min.