Method for manufacturing electrode layer

Abstract

An embodiment of the present invention is a method for manufacturing an electrode layer, the method comprising: a step (A) in which an electrode material containing an electrode active material, a conductive auxiliary agent, and an electrolyte solution and having a solid content concentration of 40-80 vol% is supplied onto a collector foil using a screw pump; and a step B for leveling the electrode material supplied onto the current collector foil and forming an electrode layer on the current collector foil, the screw pump being provided with: a cylindrical housing having a supply port for supplying the electrode material at one end and a discharge port for discharging the electrode material at the other end; a screw that is rotatably provided within the cylindrical frame and has a pitch region in which the thread pitch becomes narrower toward the downstream in the direction in which the electrode material is fed; and a shield disposed at the delivery port, the shield having a surface intersecting the axial direction of the screw and a through-hole penetrating the surface, the surface facing the downstream end surface of the screw blade of the screw in a non-contact manner, and the through-hole being provided at a position facing the downstream end surface.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an electrode layer. Background Technology

[0002] In recent years, from a safety perspective, research has been conducted on quasi-solid-state batteries that replace a portion of the electrolyte with a solid electrolyte. Furthermore, the manufacture of battery electrodes using powders containing electrode active materials typically includes a process of coating the powdered electrode material containing the electrode active material onto a support.

[0003] Regarding the manufacture of battery electrodes using powder, for example, it is disclosed that an electrode slurry premixed with a quasi-solid electroactive material is applied along the surface of a current collector using a doctor blade (for example, see Patent Document 1).

[0004] Furthermore, a technique is disclosed in which premixed electrode material is supplied to a cylindrical shape-holding member, and the electrode material compacted to the opening of the shape-holding member is discharged to a support, thereby producing an electrode molded body with excellent in-plane uniformity of mass distribution (for example, see Patent Document 2). A method for manufacturing an electrode for a lithium-ion battery is disclosed in which, after forming a powder layer by scraping powder containing electrode active material supplied on a substrate by a scraper roller, the substrate is conveyed in a vertical direction while the powder layer is compacted onto the substrate by a pair of stamping rollers to manufacture an electrode sheet (for example, see Patent Document 3).

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-533548

[0006] Patent Document 2: International Publication No. 2021 / 033689

[0007] Patent Document 3: International Publication No. 2016 / 111137 Summary of the Invention

[0008] The technical problem to be solved by the invention

[0009] In the manufacture of battery electrodes using powder, electrode layers are formed using pre-prepared electrode materials. However, the thickness of the electrode layer is prone to deviation, making it difficult to consistently produce electrode layers with good in-plane density uniformity. Nevertheless, from the viewpoint of battery performance, uniform material density in the in-plane direction is considered an important factor in the electrode layer, which is one of the main structures of a battery.

[0010] As with conventional techniques, film formation is typically performed after pre-mixing materials such as active substances and electrolytes. However, the pre-mixed materials are prone to containing air particles within the active substances and electrolytes. While this is less common in general dilution coatings, it becomes unavoidable in electrode layers containing a relatively large amount of powdered solid components, leading to air incorporation during manufacturing. In other words, depending on the method of supplying the pre-mixed materials, the density of the supplied materials can easily fluctuate, making it difficult to uniformly control the density of the produced electrode layer. Furthermore, when pressing a clay-like mixture (coating) prepared by mixing active substances and electrolytes to form a film, the pressure applied to the mixture is usually cumulative, resulting in uneven pressure applied at the start of pressing (initial) compared to the end of pressing (final). Consequently, it becomes difficult to achieve uniform material density in the in-plane direction of the produced electrode layer. Furthermore, similarly, when using a pre-mixed material of the desired composition, the pressure exerted on the mixed material (coating) above and below its gravitational direction (e.g., near the surface and bottom of the liquid when contained in a storage container) varies over time due to its own weight. The closer to the bottom, the more compacted the material becomes due to its own weight, thus easily leading to uneven density in the fabricated electrode layer. This is not limited to a single electrode layer; for example, it can be assumed that the same unevenness occurs between multiple electrode layers fabricated as a single sheet.

[0011] The present invention was made in view of the above circumstances.

[0012] One embodiment of the present invention aims to solve the problem of providing a method for manufacturing an electrode layer with high uniformity of material density.

[0013] means for solving technical problems

[0014] The specific methods used to solve the problem include the following.

[0015] <1> A method for manufacturing an electrode layer, comprising:

[0016] Step A involves using a screw pump to supply electrode material, comprising electrode active material, conductive additives, and electrolyte, with a solid content concentration of 40% to 80% by volume, onto the current collector foil; and

[0017] Step B involves leveling the electrode material supplied to the current collector foil and forming an electrode layer on the current collector foil.

[0018] The above-mentioned screw pump has the following features:

[0019] A cylindrical frame has a supply port for supplying electrode material at one end and an outlet for discharging electrode material at the other end.

[0020] The screw is rotatably disposed inside the aforementioned cylindrical frame and has a pitch region in which the thread pitch narrows as it moves downstream toward the direction of electrode material delivery; and

[0021] A shielding element is configured at the aforementioned outlet.

[0022] The aforementioned shielding member has a surface that intersects the axial direction of the aforementioned screw and a through hole that penetrates the aforementioned surface.

[0023] The aforementioned surface is positioned opposite the downstream end face of the screw blade of the aforementioned screw in a non-contact manner, and the aforementioned through hole is located opposite the aforementioned downstream end face.

[0024] <2> According to the method for manufacturing the electrode layer described in <1>, wherein,

[0025] The aforementioned shielding member supports one end of the downstream side of the shaft core of the aforementioned screw.

[0026] <3> The method for manufacturing the electrode layer according to <1> or <2>, wherein,

[0027] The clearance between the surface intersecting the aforementioned axis and the downstream end face of the aforementioned screw blade is less than 3 mm.

[0028] <4> The method for manufacturing the electrode layer according to any one of <1> to <3>, wherein,

[0029] The screw pump includes: a first screw pump; and a second screw pump connected to the first screw pump via piping, and having a smaller delivery capacity than the first screw pump. The first screw pump and the second screw pump each have the cylindrical frame, the screw, and the shielding member.

[0030] <5> The method for manufacturing the electrode layer according to any one of <1> to <4>, wherein,

[0031] The aforementioned shielding member has two or more of the aforementioned through holes, which are arranged at equal intervals along the circumference of the aforementioned screw.

[0032] <6> A method for manufacturing an electrode layer according to any one of <1> to <5>, wherein,

[0033] The thread pitch variation in the above-mentioned pitch region is more than 50%.

[0034] <7> A method for manufacturing an electrode layer according to any one of <1> to <6>, wherein,

[0035] In process A, the above-mentioned electrode active material, the above-mentioned conductive additive and the above-mentioned electrolyte are not premixed before being supplied to the above-mentioned screw pump.

[0036] Invention Effects

[0037] According to one embodiment of the present invention, a method for manufacturing an electrode layer with high uniformity of material density is provided. Attached Figure Description

[0038] Figure 1 This is a schematic diagram illustrating the process of manufacturing the electrode layer.

[0039] Figure 2 This is an enlarged schematic cross-sectional view showing the downstream side of the screw pump's discharge direction.

[0040] Figure 3 It is a schematic cross-sectional view used to illustrate the flow of electrode material when the electrode material is subjected to shear and pressure from the screw.

[0041] Figure 4 This is a schematic diagram showing the structure near the extrusion port of a conventional extruder.

[0042] Figure 5 This is a side view of an example of a screw.

[0043] Figure 6 Observation from the sending side Figure 2 A schematic top view of a screw pump. Detailed Implementation

[0044] The method for manufacturing the electrode layer according to the present invention will be described below. However, the present invention is not limited to the following embodiments, and can be implemented by appropriate modifications within the scope of the present invention.

[0045] In describing embodiments of the invention with reference to the accompanying drawings, descriptions of repeated constituent elements and symbols are sometimes omitted. Constituent elements represented by the same symbols in the drawings refer to the same constituent elements. The ratios of dimensions in the drawings do not necessarily represent the ratios of actual dimensions.

[0046] In this invention, the numerical range represented by "~" refers to the range encompassed by the values ​​recorded before and after "~" as lower and upper limits. Within the numerical range recorded in stages in this invention, the upper limit value recorded within a certain numerical range can be replaced with the upper limit value of another numerical range recorded in stages, and the lower limit value recorded within a certain numerical range can be replaced with the lower limit value of another numerical range recorded in stages. Within the numerical range recorded in stages in this invention, the upper or lower limit value recorded within a certain numerical range can also be replaced with the values ​​shown in the embodiments.

[0047] In this invention, a combination of two or more preferred methods is a more preferred method.

[0048] Furthermore, regarding the amount of each component in the composition described in this specification, in the case where multiple substances equivalent to each component are present in the composition, unless otherwise specified, the amount refers to the total amount of the multiple substances present in the composition.

[0049] In this specification, the term "process" includes not only independent processes, but also processes that can not be clearly distinguished from other processes, as long as the intended purpose of the process can be achieved.

[0050] In this manual, "mass%" and "weight%" have the same meaning, and "parts by mass" and "parts by weight" have the same meaning.

[0051] Furthermore, "total solids content" refers to the total mass of the components after removing the solvent from all the components of the composition. The term "solids content" can refer to either a solid or a liquid at 25°C.

[0052] The method for manufacturing the electrode layer of the present invention includes: step A (hereinafter also referred to as step A), using a screw pump to supply electrode material comprising electrode active material, conductive additive and electrolyte and having a solid component concentration of 40 vol% to 80 vol% to a current collector foil; and step B (hereinafter also referred to as step B), leveling the electrode material supplied to the current collector foil and forming an electrode layer on the current collector foil. Other steps may be included as needed.

[0053] In the electrode layer manufacturing method of the present invention, the screw pump comprises: a cylindrical frame having a supply port for supplying electrode material at one end and a discharge port for discharging electrode material at the other end; a screw rotatably disposed within the cylindrical frame and having a pitch region in which the thread pitch narrows as it moves downstream in the electrode material discharging direction; and a shielding member disposed at the discharge port of the cylindrical frame. The shielding member then has a surface (hereinafter also referred to as the "shielding surface") intersecting the axial direction of the screw and a through hole penetrating the shielding surface. The shielding surface faces the downstream end face of the screw blades in a non-contact manner, and the through hole is disposed at a position facing the downstream end face.

[0054] As an electrode layer used in quasi-solid-state batteries, when fabricating an electrode layer containing electrode active material, conductive additive, and electrolyte with a high solid content concentration of 40% or more on a current collector foil, from the viewpoint of improving the performance of quasi-solid-state batteries, it is desirable to establish a technique that can control the material density of the fabricated electrode layer to a uniform state and can stably homogenize the material density in the in-plane direction of the electrode layer. Furthermore, this is not limited to homogenization within a single electrode layer, but also applies to homogenization of the material density between electrode layers when multiple electrode layers are fabricated as a single sheet.

[0055] In conventional methods, when a clay-like mixture (coating) prepared by mixing active materials and electrolytes is press-fed to form a film, the pressure on the mixture is usually applied cumulatively. Therefore, the pressure applied at the start and end of the pressing process is uneven. Furthermore, when the mixture is contained in a storage container, the surface and bottom of the mixture experience different pressures due to their own weight over time, resulting in uneven pressure applied above and below the mixture in the direction of gravity. That is, the mixture becomes locally compacted near the bottom due to its own weight. As a result, the material density in the formed electrode layer tends to become uneven, making it difficult to achieve uniform material density. This is especially noticeable when using pre-mixed electrode materials.

[0056] In view of the above situation, in this invention, a specific screw pump is selected that can supply electrode material obtained by mixing and compacting materials onto the current collector foil. That is, the components of the electrode material are not necessarily pre-mixed, but the electrode material obtained by mixing and compacting the components of the electrode material in the screw pump is supplied onto the current collector foil. Specifically, the electrode material obtained by supplying the components of the electrode material to the screw pump and mixing them, and by applying pressure and compacting the electrode material while applying shear within the screw pump, is supplied onto the current collector foil. As a result, when the electrode material is flattened to form an electrode layer in the next step, the air mixed into the electrode layer can be suppressed to a smaller extent, and the material density in the in-plane direction can be set to a uniform and high state, thereby obtaining an electrode layer with excellent material density uniformity. The electrode layer is long and has a large area (e.g., 500 mm). 2 ~700mm 2 This is effective in the case of [missing information]. Furthermore, the uniformity of material density between electrode layers is also improved, for example, when multiple electrode layers are fabricated as a single sheet.

[0057] <Process A>

[0058] In step A of the electrode layer manufacturing method of the present invention, an electrode material comprising an electrode active substance, a conductive additive and an electrolyte, and having a solid component concentration of 40% to 80% by volume, is supplied to the current collector foil using a screw pump.

[0059] In process A, the electrode material supplied has a solid content concentration of 40% to 80% by volume, which is typically high for film-forming materials used, for example, in coating processes. Therefore, when forming a film on a current collector foil, this electrode material has the property of being difficult to directly produce an electrode layer of the desired thickness; for example, it is manufactured by leveling it using a tool such as a scraper. The electrode layer is the part that affects the performance of the battery; if the density of the material on which the electrode layer is formed changes, the battery performance is also prone to change. In this invention, in order to uniformly control the density state of the material on which the electrode layer is formed, a specific screw pump is used to supply the electrode material to the current collector foil.

[0060] The concentration of solid components in the electrode material is not limited as long as it is within the above-mentioned range, but from the viewpoint of battery performance, a higher concentration is preferred, preferably exceeding 50% by volume and below 80% by volume, and more preferably 60% to 80% by volume. Here, the concentration of solid components in the electrode material is calculated based on the composition ratio of each component contained in the electrode material and the specific gravity of these components.

[0061] Here, for reference Figure 1 Let's illustrate one example of process A. Figure 1 This is a schematic diagram illustrating the process of manufacturing the electrode layer.

[0062] exist Figure 1 The electrode layer manufacturing apparatus 100 is shown. The electrode layer manufacturing apparatus 100 consists of a supply unit A and a film-forming unit B. The supply unit A of the electrode layer manufacturing apparatus 100 includes: a first screw pump 10; and a second screw pump 20, connected to the first screw pump 10 via a connecting pipe 16. The first screw pump 10 includes at least: a cylindrical frame; a screw disposed inside the cylindrical frame; and a shielding member disposed at the outlet of the cylindrical frame. A feeding hopper 12 is installed at one end of the cylindrical frame, capable of supplying electrode material to the first screw pump 10. The second screw pump 20 is a small pump with a smaller discharge capacity than the first screw pump 10, and uses screws of different sizes to deliver electrode material in stages. This minimizes the further compaction of the electrode material and reduces fluctuations that easily occur during discharge according to each screw pitch. A tray 50 for conveying the current collector foil 35 in the direction of electrode material discharge from the second screw pump 20 is arranged. In the film-forming section B downstream of the conveying direction of the tray 50, a scraper 30 for forming electrode material and a piezoelectric scraper 40 for adjusting the thickness of the electrode material formed into a constant shape are arranged sequentially along the arrow direction.

[0063] If electrode material is fed into the feeding hopper 12 of the electrode layer manufacturing apparatus 100, electrode material 14 is supplied to the first screw pump 10. If the screw installed in the cylindrical frame of the first screw pump 10 is started and begins to rotate, the electrode material 14 passes through the rotating screw blades 2b (see reference). Figure 5 The electrode material 14 is then fed towards the other end of the cylindrical frame, which has a feed outlet. The electrode material 14 is then fed from the feed outlet at the other end of the cylindrical frame to the connecting pipe 16, and supplied to the second screw pump 20 via the connecting pipe 16. One end of the connecting pipe is connected to one end of the cylindrical frame of the second screw pump 20. If the screw installed in the cylindrical frame of the second screw pump 20 is started and begins to rotate, the electrode material 14 is fed towards the other end of the cylindrical frame, which has a feed outlet, via the rotating screw blades. The electrode material 14 is then fed from the feed outlet at the other end of the cylindrical frame and supplied to the current collector foil 35 on the tray 50. The electrode material is supplied continuously or intermittently in a rope-like shape through a through hole provided in a shielding member located at the other end (feed outlet) of the cylindrical frame.

[0064] Next, we move on to process B. Details about process B will be described later.

[0065] Next, the screw pump will be explained.

[0066] The screw pump of this invention comprises at least: a cylindrical frame; a screw disposed inside the cylindrical frame; and a shielding member disposed at the outlet of the cylindrical frame. The screw pump mixes electrode material supplied from a feed port at one end of the cylindrical frame towards the other end along the length of the cylindrical frame by rotating the screw. As the electrode material approaches the other end, it is subjected to shearing and pressure from the surface of the screw blades and the inner wall of the cylindrical frame in a pitch region where the thread pitch narrows. Thus, the electrode material is compacted.

[0067] For the same reason, the screw preferably has the following structure: a conveyor section with equally spaced thread pitch is provided on the upstream side in the length direction, and a compaction extrusion section with a thread pitch narrower than that of the conveyor section is provided on the downstream side of the conveyor section.

[0068] An example of a screw pump is shown below. Figure 2 . Figure 2 This is an enlarged schematic cross-sectional view showing the downstream side of the screw pump's discharge direction.

[0069] Figure 2The screw pump 1 shown includes at least: a cylindrical frame 4; a screw 2 disposed inside the cylindrical frame 4; and a shielding member 8 disposed at the outlet 6 of the cylindrical frame 4. The shielding member 8 has a shielding surface 8a intersecting the axial direction of the screw 2 and a through hole 3 penetrating the shielding surface 8a. The shielding surface 8a faces the downstream end face 2a of the screw blade in a non-contact manner, and the through hole 3 is located opposite the downstream end face 2a. Furthermore, the shielding member 8 is supported by abutting against one end of the screw 2 on the downstream side (electrode material delivery direction) of the shaft.

[0070] Screw pump 1 delivers electrode material in the direction of the arrow through the rotation of screw 2. Near the downstream outlet 6, the downstream end face 2a of screw 2 repeatedly passes through the through hole 3 as the screw rotates. If the electrode material is guided by the screw blades and simultaneously introduced to the vicinity of outlet 6, then... Figure 3 As shown, the electrode material 14 is fed out to the outside through the through hole 3, which is subjected to shear force and pressure from the downstream end face 2a and the inner wall surface of the screw 2 and is not blocked by the shielding member 8.

[0071] Here, an extruder with a conventional screw is shown. Figure 4 .

[0072] In the case of a conventional extruder 200, such as Figure 4 As shown, the device comprises a cylindrical frame and a screw, but has an extrusion port at the end of a structure where the cross-sectional area of ​​the section perpendicular to the axial direction in the extrusion direction within the cylindrical frame gradually decreases; that is, when viewed in a cross-section parallel to the length direction, the inner wall surface is inclined and the height and width become narrower. In other words, there is no shielding member in the extrusion direction within the cylindrical frame to prevent the extrusion of the compound, and therefore it does not have a surface that intersects the axial direction of the screw. Therefore, in the extruder 200, only mixing is performed, and it is not possible to prepare the electrode material while mixing, as in the electrode layer manufacturing method of the present invention, and to apply pressure and compaction to the prepared electrode material while applying shear before feeding it onto the current collector foil. As a result, the electrode layer formed by leveling the electrode material in the next process has difficulty in achieving uniform material density due to the large amount of air mixed in, making it difficult to form an electrode layer with high material density uniformity.

[0073] In the screw pump of this invention, it is preferable to have a conductivity meter for measuring the conductivity of the electrode material located inside (e.g., on the inner wall surface) at the other end of the cylindrical frame (the end in the direction of electrode material delivery). Regarding the electrode material, an electrolyte and active material are pre-mixed, thus allowing for the measurement of resistance at a desired density state and monitoring of the state of the electrode material (e.g., changes in conductivity accompanying flow). Examples of conductivity meters include conductivity probes and conductivity sensors.

[0074] -Cylindrical frame-

[0075] The cylindrical frame has a supply port for supplying electrode material at one end and an outlet for discharging electrode material at the other end. "Cylindrical" includes not only cases where the frame itself is cylindrical in shape, but also cases where, even if the frame is not cylindrical in shape, it has a cylindrical chamber inside (cylindrical inner chamber) and is formed into a cylindrical shape when viewed from the screw.

[0076] There are no restrictions on the supply port, as long as it is a structure capable of receiving electrode material and supplying it into the cylindrical frame. For example, a container (hopper, etc.) in the shape of an inverted cone or an inverted quadrangular pyramid can be installed at the supply port.

[0077] There are no restrictions on the outlet, as long as it is a structure that allows the prepared electrode material to be removed to the outside.

[0078] In step A of the present invention, it is preferable to feed the electrode material components, which include electrode active material, conductive additive and electrolyte, into the supply port of the cylindrical frame without pre-mixing, and to directly supply each component of the electrode material (electrode active material, conductive additive and electrolyte, etc.) to the screw pump.

[0079] -Screw-

[0080] The screw is rotatably mounted within the aforementioned cylindrical frame.

[0081] The screw has a solid shaft and screw blades formed by winding around the shaft along its length. Regarding the screw, the size of the screw blades is not limited as long as it can rotate within a cylindrical frame.

[0082] Regarding the positional relationship between the screw and the cylindrical frame, the shortest distance between the screw blades and the inner wall of the cylindrical frame is preferably 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less. By keeping the shortest distance to 10 mm or less, shear and pressure can be stably applied to the electrode material, resulting in more uniform compaction of the material density.

[0083] In addition, the lower limit of the shortest distance can be set to 0.01mm.

[0084] The screw has a pitch region where the thread pitch narrows as it moves downstream in the direction of electrode material delivery. The thread pitch is the distance between a screw blade located on a line parallel to the screw's axis and its adjacent blade.

[0085] Figure 5 This is a side view of an example of a screw. Figure 5The screw 2 shown has: a conveyor section (i) with equally spaced thread pitches on its upstream side in the longitudinal direction; and a compaction extrusion section (ii) with a thread pitch narrower than that of the conveyor section (i) on its downstream side. Thus, electrode material is primarily conveyed in the conveyor section (i), and in the subsequent compaction extrusion section (ii), the thread pitch is reduced to shear the electrode material while simultaneously applying pressure for compaction.

[0086] The thread pitch is preferably set such that the thread pitch L1 of the conveyor section (i) and the thread pitch L2 of the compaction extrusion section (ii) satisfy the relationship L1 > L2. Furthermore, the thread pitch of the compaction extrusion section can be different in stages. For example, it can be set such that when the thread pitch narrows in the first half L2a and the second half L2b (L2a > L2b) of the compaction extrusion section, the overall thread pitch satisfies the relationship L1 > L2a > L2b. It is not limited to two stages; it can also narrow in three stages. Moreover, the thread pitch can be set such that the relationship L1 > L2 is satisfied, and the thread pitch L2 decreases in the compaction extrusion section.

[0087] Reducing the screw thread pitch increases the flow velocity of the continuous phase, thereby increasing the shear force of the continuous phase. Conversely, increasing the thread pitch decreases the flow velocity of the continuous phase, thereby reducing the shear force of the continuous phase.

[0088] The preferred range for the thread pitch of the screw blade is 1 mm to 50 mm, and more preferably 2 mm to 20 mm.

[0089] In the pitch region where the thread pitch narrows as it moves downstream toward the electrode material feeding direction, the thread pitch variation from the widest pitch to the narrowest pitch is preferably 30% or more, more preferably 50% or more. If the thread pitch variation ratio is 30% or more, it is easier to impart shear and pressure to the electrode material, which can further improve the uniformity of material density.

[0090] The clearance between the screw blades and the inner wall of the cylindrical frame is preferably 0.5 mm or less, more preferably 0.4 mm or less. If the clearance is 0.5 mm or less, it is easier to apply shear and pressure to the electrode material. This allows for further compaction of the electrode material.

[0091] The clearance between the screw blade and the inner wall of the cylindrical frame is the absolute value of the difference between the outermost diameter of the screw blade and the inner diameter of the cylindrical frame.

[0092] By thickening the screw shaft, increasing the outermost diameter of the screw blades, or reducing the inner diameter of the cylindrical frame, the clearance between the screw blades and the inner wall of the cylindrical frame can be reduced.

[0093] There are no particular limitations on the thickness of the screw blades, but it is preferably in the range of 0.1 mm to 5 mm, and more preferably in the range of 0.3 mm to 2 mm.

[0094] -Shielding components-

[0095] A shielding element is disposed at the feed outlet of the cylindrical frame. The shielding element has a surface (shielding surface) that intersects the axial direction of the screw and a through hole that penetrates the shielding surface. The shielding surface is opposed to the downstream end face of the screw blade in a non-contact manner, and the through hole is located opposite the downstream end face.

[0096] By placing a shielding member at the outlet of the cylindrical frame, outward feeding of the electrode material at its feeding end is blocked. Only the electrode material that can be fed out through the through hole provided in the shielding member is compacted and fed out under predetermined shear and pressure. As a result, electrode material with less air mixing and increased density of solid material is supplied to the current collector foil.

[0097] The shielding member has a shielding surface that intersects the axial direction of the screw. Regarding the shielding surface, it can be selected within a range that prevents the electrode material fed downstream of the cylindrical frame via the screw from being easily discharged to the outside. From the viewpoint of effectively performing the above function, the angle formed by the axial direction and the shielding surface is an acute angle θ, preferably in the range of 70°≤θ≤90°, more preferably in the range of 80°≤θ≤90°, even more preferably in the range of 85°≤θ≤90°, and particularly preferably a surface orthogonal to the axial direction of the screw. "Orthogonal to the axial direction" means that the angle formed by the axial direction and the shielding surface is 90° or an angle with a maximum deviation from 90° of 2°.

[0098] The shielding component has a through hole penetrating the shielding surface. The through hole is selectively located at the opening of the feed port of the cylindrical frame, through which electrode material is fed out. Regarding the through hole, the shielding component has at least one, and the number of through holes can be two or more, three or more, or four or more, depending on the size and thickness of the manufactured electrode layer, the manufacturing speed of the electrode layer, the size of the shielding component, and the through hole. The upper limit for the number of through holes can be set to 12. The preferred number of through holes is 3 to 8.

[0099] The shape of the through hole is not particularly limited; for example, it can be any of a circle, ellipse, or rectangle. The diameter of the through hole can be selected based on the thickness of the electrode material fed in a rope-like or similar elongated shape, preferably 1mm to 30mm, more preferably 2mm to 25mm, and even more preferably 2mm or more but less than 10mm. If the diameter is within the above range, the electrode material can be easily leveled in step B, making it easier to fabricate an electrode layer of the desired thickness. When using a small pump with a reduced discharge volume, the size of the through hole is preferably smaller than the diameter of the upstream pump. This allows for the supply of a finer and easier-to-coat electrode. The size of the through hole can also be appropriately designed according to the size of the screw blades. It is preferably smaller than the radius from the axis of the screw blade to the end of the blade (i.e., the radius of the screw).

[0100] The diameter of a through hole refers to the maximum diameter of the hole.

[0101] The shielding surface is positioned opposite the downstream end face of the screw blades in a non-contact manner. By opposing the screw without contacting the shielding surface, shear and pressure can be effectively applied to the electrode material. For the same reason, the clearance between the shielding surface and the downstream end face of the screw blades is preferably 3 mm or less, more preferably 1.5 mm or less. If the clearance is 3 mm or less, shear and pressure can be applied to the electrode material more effectively. This further improves the compaction of the electrode material. Furthermore, the lower limit of the clearance can be set to 0.01 mm.

[0102] refer to Figure 2 The clearance is explained. For example... Figure 2 As shown, clearance refers to the shortest distance s1 between the shielding surface 8a of the shielding member 8 and the downstream end face 2a of the screw blade of the screw 2. Figure 4 The clearance s2 in the conventional extruder 200 shown can be any shape that forms a narrower extrusion orifice than the barrel portion where the screw is disposed, and is extruded. It is different from the clearance s1 of the screw pump in this invention in that it does not assume that shearing is imparted.

[0103] The through hole is positioned opposite the downstream end face. The downstream end face refers to the lowest face of the screw blade in the direction of electrode material delivery, for example, in... Figure 2 In the case of the screw pump shown, the face is represented by the symbol 2a. "Opposite position" refers to the position in the shielding member that faces the downstream end face, through which electrode material is delivered from the through hole by the downstream end face opposing the through hole at this position.

[0104] The shielding member preferably has two or more through holes, and these two or more through holes are arranged at equal intervals along the circumference of the screw. That is, it is preferable to arrange the through holes in the circumference of the screw to preferentially feed out electrode material with high density uniformity that has been fluidized and compacted by shearing based on the screw blades. For example, such as Figure 6 As shown, the shielding member 8 can also have three through holes, and these three through holes are arranged at equal intervals (i.e., at the vertices of an equilateral triangle) along the circumference of the screw. In this case, the downstream end face of the screw 2 sequentially reaches the positions of the three through holes 3 as the screw rotates, thereby moving along the rotation direction of the screw (in the direction of rotation). Figure 6 (In the counter-clockwise direction) the electrode material is sequentially delivered from the three through holes that arrive in sequence.

[0105] in addition, Figure 6 Observation from the sending side Figure 2 A schematic top view of a screw pump.

[0106] The shielding element is preferably shaped at one end of the shaft supporting the screw (downstream of the electrode material feeding direction). This configuration distinguishes it from conventional extruder screws.

[0107] Screw pumps can be used individually or in combination via piping. When using multiple screw pumps, screw pumps of different sizes can be combined.

[0108] In this invention, a first screw pump and a smaller second screw pump can be combined. The smaller second screw pump is connected to the first screw pump via piping and has a smaller delivery capacity than the first screw pump. "Smaller" refers to a smaller capacity for accommodating electrode material, resulting in a relatively smaller delivery capacity of electrode material per unit time via screw rotation. Preferably, both the first and second screw pumps have a cylindrical frame, a screw, and a shielding element.

[0109] (Current collector foil)

[0110] Current collector foil includes current collector foil used for positive or negative current collectors.

[0111] Examples of positive current collectors include aluminum, aluminum alloys, stainless steel, nickel, and titanium. Aluminum or aluminum alloys are preferred. Alternatively, the positive current collector may be aluminum with a coating layer on its surface containing one or more of the following: carbon, nickel, titanium, silver, gold, platinum, and vanadium oxide.

[0112] Examples of negative electrode current collectors include aluminum, copper, copper alloys, stainless steel, nickel, and titanium. The negative electrode current collector is preferably aluminum, copper, copper alloys, or stainless steel, and more preferably copper or copper alloys. The negative electrode current collector may also be copper or stainless steel with a coating layer on its surface containing one or more of carbon, nickel, titanium, silver, and lithium.

[0113] As current collector foils, aluminum foil (including aluminum foil with the aforementioned coating layer on its surface) and copper foil (including copper foil with the aforementioned coating layer on its surface) are preferred. Aluminum foil is typically used as the positive current collector. Copper foil is typically used as the negative current collector.

[0114] Furthermore, a resin film can be placed in the current collector foil as a support material.

[0115] Resin films can be cited as supporting materials. Examples of resin films include polyethylene terephthalate (PET) film, polypropylene (PP) film, polyethylene (PE) film, cyclic olefin polymer (COP, COC) film, triacetyl cellulose (TAC) film, polyimide (PI) film, and polyamide (PA) film.

[0116] Furthermore, as an example of a support material, a release material can also be cited. Examples of release materials include release paper (e.g., release paper manufactured by LINTEC Corporation), films with release layers, and papers with release layers, among which release paper is preferred.

[0117] Next, the components of the electrode material will be explained.

[0118] Electrode materials include at least electrode active materials, conductive additives, and electrolytes, and may include other components as needed.

[0119] (Electrode active material)

[0120] Electrode active materials are substances capable of intercalating and releasing ions of metallic elements belonging to Group 1 or Group 2 of the periodic table. Electrode active materials are included in the solid component.

[0121] Examples of electrode active materials include positive electrode active materials and negative electrode active materials.

[0122] -Positive electrode active material-

[0123] There are no restrictions on the active material used as the positive electrode; any known active material used in positive electrodes can be used. Preferably, the active material is one capable of reversibly inserting and releasing lithium ions.

[0124] Specifically, examples of positive electrode active materials include transition metal oxides and elements capable of complexing with lithium (e.g., sulfur). Among these, transition metal oxides are preferred as positive electrode active materials.

[0125] The transition metal oxide is preferably a transition metal oxide containing at least one transition metal element (hereinafter referred to as "element Ma") selected from the group consisting of Co (cobalt), Ni (nickel), Fe (iron), Mn (manganese), Cu (copper) and V (vanadium).

[0126] When the transition metal oxide contains Li and the element Ma, the molar ratio of Li to Ma (Li / Ma) is preferably 0.3 to 2.2.

[0127] Furthermore, the transition metal oxide may also contain at least one transition metal element selected from the group consisting of Group 1 elements (excluding lithium), Group 2 elements, Al (aluminum), Ga (gallium), In (indium), Ge (germanium), Sn (tin), Pb (lead), Sb (antimony), Bi (bismuth), Si (silicon), P (phosphorus), and B (boron) (hereinafter referred to as "element Mb"). The content of element Mb relative to the amount of element Ma is preferably 0 mol% to 30 mol%.

[0128] Examples of transition metal oxides include transition metal oxides with layered rock salt-type structures, transition metal oxides with spinel-type structures, lithium-containing transition metal phosphate compounds, lithium-containing transition metal halophosphate compounds, and lithium-containing transition metal silicate compounds.

[0129] Examples of transition metal oxides with a layered rock-salt structure include LiCoO2 (lithium cobalt oxide [LCO]), LiNi2O2 (lithium nickel oxide), and LiNi 0.85 Co 0.10 Al 0.05 O2 (lithium nickel cobalt aluminum oxide [NCA]), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (lithium nickel manganese cobalt oxide [NMC]) and LiNi 0.5 Mn 0.5 O2 (lithium manganese nickel oxide).

[0130] Examples of transition metal oxides with spinel-type structures include LiCoMnO4, Li2FeMn3O8, Li2CuMn3O8, Li2CrMn3O8, and Li2NiMn3O8.

[0131] Examples of lithium-containing transition metal phosphate compounds include olivine-type iron phosphates (e.g., LiFePO4 and Li3Fe2(PO4)3), iron pyrophosphates (e.g., LiFeP2O7), cobalt phosphates (e.g., LiCoPO4), and monoclinic NASICON-type vanadium phosphates (e.g., Li3V2(PO4)3 (lithium vanadium phosphate)).

[0132] Examples of lithium-containing transition metal halophosphates include iron fluorophosphates (e.g., Li₂FePO₄F), manganese fluorophosphates (e.g., Li₂MnPO₄F), and cobalt fluorophosphates (e.g., Li₂CoPO₄F).

[0133] Examples of lithium-containing transition metal silicate compounds include Li2FeSiO4, Li2MnSiO4, and Li2CoSiO4.

[0134] The transition metal oxide is preferably a transition metal oxide with a layered rock salt structure, more preferably selected from LiCoO2 (lithium cobalt oxide [LCO]) and LiNi. 0.85 Co 0.10 Al 0.05 O2 (lithium nickel cobalt aluminum oxide [NCA]) and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 At least one compound from the group consisting of O2 (lithium nickel manganese cobalt oxide [NMC]).

[0135] The positive electrode active material can be a commercially available product or a synthetic product manufactured by known methods (e.g., calcination). For example, the positive electrode active material obtained by calcination can be cleaned with water, acidic aqueous solutions, alkaline aqueous solutions, or organic solvents.

[0136] Furthermore, the active material of the positive electrode can have a carbon film on its surface.

[0137] The shape of the positive electrode active material is not limited, but from an operational point of view, it is preferred to be particulate.

[0138] The volume average particle size of the positive electrode active material is not limited, and can be set to, for example, 0.1 μm to 50 μm. The volume average particle size of the positive electrode active material is preferably 0.3 μm to 40 μm, and more preferably 0.5 μm to 30 μm.

[0139] By having a volume average particle size of 0.3 μm or more for the positive electrode active material, splashing of the positive electrode active material during operation can be suppressed. By having a volume average particle size of 40 μm or less for the positive electrode active material, the thickness of the electrode layer can be easily adjusted, and voids generated during the molding process can be suppressed.

[0140] The volume average particle size of the active material in the positive electrode was determined using the following method.

[0141] A dispersion containing less than 0.1% by mass of the positive electrode active material was prepared by mixing the positive electrode active material with a solvent (e.g., pure water, ethanol, heptane, octane, toluene, or xylene). The dispersion, irradiated with ultrasound at 1 kHz for 10 minutes, was used as the test sample. Using a laser diffraction / scattering particle size distribution measuring device (e.g., LA-960 manufactured by HORIBA, Ltd.), 50 data readings were performed at 25°C, and the volume average particle size was determined based on the volume frequency particle size distribution. A quartz cuvette was used for the measurement. The above determination was performed using five samples, and the average of the measured values ​​was taken as the volume average particle size of the positive electrode active material. For other detailed conditions, refer to "JIS Z 8828:2013" as needed.

[0142] Methods for adjusting the particle size of the positive electrode active material include, for example, using a pulverizer, a crusher, or a classifier. Furthermore, the well-known milling method can be used to adjust the particle size of the positive electrode active material.

[0143] The active material of the positive electrode can be used alone or in combination with two or more.

[0144] Furthermore, even when using a single positive electrode active material, positive electrode active materials with different particle sizes can be used in combination.

[0145] The content of positive electrode active material relative to the total volume of electrode material is preferably 30% to 60% by volume, more preferably 35% to 55% by volume, and even more preferably 40% to 50% by volume.

[0146] In the method for manufacturing the electrode layer according to the present invention, it is preferable to determine the amount of active material used in the positive electrode so that the content in the electrode layer is within the above-mentioned range.

[0147] -Negative electrode active material-

[0148] There are no restrictions on the active material used as the negative electrode; any known active material used in negative electrodes can be utilized. Preferably, the active material is one capable of reversibly inserting and releasing lithium ions.

[0149] Examples of active materials for the negative electrode include carbonaceous materials, metal oxides (e.g., tin oxide), silicon oxide, metal composite oxides, lithium monomers, lithium alloys (e.g., lithium-aluminum alloys), and metals capable of forming alloys with lithium (e.g., Sn, Si, and In). From a reliability standpoint, carbonaceous materials or lithium composite oxides are preferred as active materials for the negative electrode.

[0150] Carbonaceous materials are materials that are essentially composed of carbon.

[0151] Examples of carbonaceous materials include petroleum pitch, carbon black (e.g., acetylene black), graphite (e.g., natural graphite and artificial graphite (e.g., vapor-grown graphite)), hard carbon, and carbonaceous materials made by calcining synthetic resins (e.g., polyacrylonitrile (PAN) and furfuryl alcohol resin). Examples of carbonaceous materials also include carbon fibers (e.g., polyacrylonitrile-based carbon fibers, cellulose-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, dehydrated PVA (polyvinyl alcohol)-based carbon fibers, lignin carbon fibers, glassy carbon fibers, and activated carbon fibers). Examples of graphite include mesophase microspheres, graphite whiskers, and planar graphite.

[0152] In this invention, "flat" refers to a shape having two main planes facing opposite directions.

[0153] As a metal composite oxide, a metal composite oxide capable of encapsulating and releasing lithium is preferred.

[0154] From the viewpoint of high current density charge and discharge characteristics, metal composite oxides capable of encapsulating and releasing lithium preferably contain at least one element selected from the group consisting of titanium and lithium.

[0155] Metal oxides and metal composite oxides are particularly preferred to be amorphous oxides.

[0156] Metal oxides and metal complex oxides are preferably chalcogenides. Chalcogenides are the reaction products of metallic elements with elements in Group 16 of the periodic table.

[0157] Among the compounds consisting of amorphous oxides and chalcogenides, amorphous oxides and chalcogenides of half-metallic elements are preferred, and oxides and chalcogenides of at least one element selected from the group consisting of elements selected from groups 13 to 15 of the periodic table, Al, Ga, Si, Sn, Ge, Pb, Sb and Bi are more preferred.

[0158] Furthermore, it is preferable that the negative electrode active material also contains titanium. From the viewpoint of small volume change during lithium ion encapsulation and release, excellent rapid charge-discharge characteristics, and the ability to improve the lifespan of lithium-ion secondary batteries by suppressing electrode degradation, the negative electrode active material containing titanium is preferably Li4Ti5O. 12 (Lithium titanate [LTO]).

[0159] The negative electrode active material can be a commercially available product or a synthetic product manufactured by known methods (e.g., calcination). For example, negative electrode active materials obtained by calcination can be cleaned with water, acidic aqueous solutions, alkaline aqueous solutions, or organic solvents.

[0160] The active material for the negative electrode can be obtained, for example, as CGB20 (Nippon Graphite Industries Co., Ltd.).

[0161] The composition of the active material of the negative electrode was determined using inductively coupled plasma (ICP) emission spectroscopy.

[0162] The shape of the active material of the negative electrode is not limited, but from the viewpoint of ease of operation and easy management of uniformity during mass production, particulate form is preferred.

[0163] The volume average particle size of the active material of the negative electrode is preferably 0.1 μm to 60 μm, more preferably 0.3 μm to 50 μm, and especially preferably 0.5 μm to 40 μm.

[0164] The volume average particle size of the active material of the negative electrode was determined by a method based on the above-described method for determining the volume average particle size of the active material of the positive electrode.

[0165] As a method for adjusting the particle size of the active material of the negative electrode, for example, the use of a pulverizer or a classifier can be cited.

[0166] The active material of the negative electrode can be used alone or in combination with two or more.

[0167] Furthermore, even when using a single negative electrode active material, negative electrode active materials with different particle sizes can be used in combination.

[0168] The content of the negative electrode active material relative to the total volume of the electrode material is preferably 30% to 60% by volume, more preferably 35% to 57% by volume, and even more preferably 45% to 55% by volume.

[0169] In the method for manufacturing the electrode layer according to the present invention, it is preferable to determine the amount of active material used in the negative electrode to make the content in the electrode layer within the above-mentioned range.

[0170] The surfaces of the positive electrode active material and the negative electrode active material can be coated with a surface coating agent, respectively. Examples of surface coating agents include metal oxides containing Ti, Nb, Ta, W, Zr, Si, or Li. Examples of such metal oxides include spinel titanate, tantalum oxides, niobium oxides, and lithium niobate compounds.

[0171] (Conductive additive)

[0172] From the viewpoint of improving the electronic conductivity of electrode active materials, electrode materials include conductive additives. There are no restrictions on the type of conductive additive used; known conductive additives can be employed.

[0173] Conductive additives are included in the solid components.

[0174] Examples of conductive additives include graphite (e.g., natural and artificial graphite), carbon black (e.g., acetylene black, Ketjen black, and furnace black), amorphous carbon (e.g., needle coke), carbon fibers (e.g., vapor-grown carbon fibers and carbon nanotubes), other carbonaceous materials (e.g., graphene and fullerene), metal powders (e.g., copper and nickel powders), metal fibers (e.g., copper and nickel fibers), and conductive polymers (e.g., polyaniline, polypyrrole, polythiophene, polyacetylene, and polyphenylene derivatives).

[0175] Conductive additives can be used alone or in combination with two or more.

[0176] The content of conductive additive relative to the total volume of electrode material is preferably 0.05 vol% to 5 vol%, more preferably 0.1 vol% to 4 vol%, and even more preferably 0.5 vol% to 3 vol%.

[0177] In the method for manufacturing the electrode layer according to the present invention, it is preferable to determine the amount of conductive additive used so that the content of the conductive additive in the electrode layer is within the above-mentioned range.

[0178] (Electrolyte)

[0179] The electrode material includes an electrolyte. There are no particular limitations on the electrolyte; known electrolytes can be used. Examples of electrolytes include those comprising an electrolyte and a solvent. Specific examples of electrolytes include those comprising a lithium salt compound as the electrolyte and a carbonate compound as the solvent.

[0180] Examples of lithium salt compounds include lithium hexafluorophosphate. The electrolyte may contain a single lithium salt compound or two or more lithium salt compounds.

[0181] Examples of carbonate compounds include chain carbonate compounds such as ethyl methyl carbonate (also known as EMC), dimethyl carbonate (also known as DMC), and diethyl carbonate (DEC), and cyclic carbonate compounds such as ethylene carbonate (also known as EC) and propylene carbonate (also known as PC). The electrolyte may contain a single carbonate compound, or it may contain two or more carbonate compounds, or it may combine one or more chain carbonate compounds and one or more cyclic carbonate compounds.

[0182] As the electrolyte contained in the electrolyte, known inorganic solid electrolytes can also be used, for example.

[0183] Ionic liquids can be used as components of electrolytes, for example. Ionic liquids can be used as both electrolytes and solvents.

[0184] The electrolyte content relative to the total volume of the electrode material is preferably 70% by volume or less, but can also be 50% by volume or less, or even 40% by volume or less. The lower limit of the electrolyte content relative to the total volume of the electrode material is not limited and can be 20% by volume or more, or 30% by volume or more.

[0185] The electrolyte content relative to the total volume of the electrode material is preferably 30% to 50% by volume, for example.

[0186] (solvent)

[0187] In electrode materials, the liquid component may contain solvents other than those included as components of the electrolyte (hereinafter also referred to as "solvents").

[0188] Examples of solvents include alcohol solvents, ether solvents, amide solvents, amino solvents, ketone solvents, aromatic solvents, aliphatic solvents, and nitrile solvents.

[0189] The boiling point of the solvent is preferably 50°C or higher at normal pressure (i.e., one atmosphere), more preferably 70°C or higher. The upper limit of the boiling point of the solvent is preferably 250°C or lower at normal pressure (i.e., one atmosphere), more preferably 220°C or lower.

[0190] Solvents can be used alone or in combination with two or more.

[0191] The content of liquid components (i.e., electrolyte and solvent) relative to the total volume of the electrode material is preferably 70% by volume or less, but may also be 50% by volume or less, or even 40% by volume or less. The lower limit of the content of liquid components relative to the total volume of the electrode material is not limited, and may be 20% by volume or more, or 30% by volume or more.

[0192] The liquid content relative to the total volume of the electrode material is preferably 30% to 50% by volume.

[0193] Furthermore, the liquid component contained in the electrode material, i.e., the component in the electrode layer that is liquid at 25°C, is preferably liquid even at -10°C, and more preferably liquid even at -20°C. That is, the component in the electrode layer that is liquid at 25°C is preferably a component that does not solidify at -10°C, and more preferably a component that does not solidify even at -20°C.

[0194] (Other ingredients)

[0195] In addition to the components mentioned above, electrode materials may also contain inorganic solid electrolytes, binders, dispersants, and other additives.

[0196] From the viewpoint of increasing energy density, the electrode material preferably has a low content of binder (also known as resin component), preferably less than 1% by mass, and especially preferably none (0% by mass).

[0197] In addition to resin components, adhesives also contain components known as rheology modifiers and dispersants, such as fluorinated resins, hydrocarbon thermoplastic resins, acrylic resins, and urethane resins.

[0198] As a dispersant, known dispersants capable of dispersing the object to be dispersed can be cited.

[0199] As other additives, known additives that can be added to the electrode can be utilized.

[0200] ~Preparation of Electrode Materials~

[0201] Electrode materials can be prepared, for example, by mixing electrode active materials, conductive additives, electrolytes, and, as needed, inorganic solid electrolytes and other components. Examples of mixing methods include using ball mills, bead mills, planetary mixers, blade mixers, roller mills, kneaders, or disc mills.

[0202] ~Electrode material supply~

[0203] There are no restrictions on the method of supplying electrode material, as long as it is supplied to the screw pump; any suitable method can be selected. The supply of electrode material to the screw pump can be intermittent or continuous. The amount of electrode material supplied can be appropriately selected based on the size and thickness of the electrode layer being manufactured.

[0204] <Process B>

[0205] In step B of the electrode layer manufacturing method of the present invention, the electrode material supplied to the current collector foil in step A is leveled and an electrode layer is formed on the current collector foil.

[0206] In step B, the electrode material supplied to the current collector foil in step A is flattened and shaped into layers to form an electrode layer. The electrode material supplied in step A has a rope-like shape because it is fed out through the through holes. If the shielding member has multiple (e.g., 3) through holes, a number (e.g., 3) of rope-like electrode material corresponding to the number of through holes is supplied to the current collector foil.

[0207] Here, for reference Figure 1 Let's illustrate one example of process B. Figure 1 This is a schematic diagram illustrating the process of manufacturing the electrode layer.

[0208] Figure 1The electrode layer manufacturing apparatus 100 shown comprises a supply unit A and a film-forming unit B. In the film-forming unit B, a scraper 30 and a piezoelectric scraper 40 are arranged sequentially along the direction of the arrow. The current collector 35 moves together with the tray 50, which moves along the direction of the arrow, and the electrode material supplied to the current collector foil 35 in the supply unit A is formed into a layer by the fixedly arranged scraper 30. Then, the thickness of the layered electrode material is adjusted by the piezoelectric scraper 40 to manufacture the desired electrode layer 37.

[0209] As a method for leveling electrode materials, limiting components such as scrapers and rollers can be used.

[0210] The limiting component can vibrate when in contact with the electrode material.

[0211] A scraper is a flat, plate-shaped component. The shape, size, and material of the contact portion that comes into contact with the electrode material can be appropriately selected based on the type of electrode material (type of active electrode material, concentration of solid components, composition of the electrolyte (viscosity, surface tension), etc.) and the size and thickness of the manufactured electrode layer.

[0212] Preferably, the contact portion of the scraper with the electrode material is not prone to electrode material adhesion; for example, preferably, at least the contact portion of the scraper exhibits release properties. The scraper can be, for example, a resin scraper (fluoropolymers such as polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK), etc.), a metal scraper (stainless steel, aluminum, iron, hard alloy, etc.), or a ceramic scraper. Furthermore, from the viewpoint of imparting release properties to the surface of the contact portion of the scraper, the scraper can have a surface layer exhibiting release properties (e.g., a surface layer containing fluoropolymers, a surface layer containing silicon particles and resin). Moreover, from the viewpoint of improving the wear resistance of the scraper, a high-hardness coating such as titanium oxide, titanium nitride (TiN), or tungsten carbide can be formed on the metal or ceramic scraper body.

[0213] When flattening electrode material to manufacture an electrode layer, by moving a limiting member (e.g., a scraper) relative to the current collector foil, the electrode material supplied to the current collector foil can be formed into a layer of a predetermined thickness on the current collector foil. Thus, an electrode layer is formed. The relative movement can be such that the limiting member (e.g., a scraper) moves relative to the fixed current collector foil in one direction, or that the current collector foil moves relative to the limiting member (e.g., a scraper), or that the current collector foil and the limiting member (e.g., a scraper) move in different directions or in the same direction at different speeds. From the viewpoint of continuously manufacturing electrode layers, it is preferable to use a long strip of current collector foil, and to flatten the electrode material by conveying and moving the long strip of current collector foil relative to the fixed limiting member (e.g., a scraper).

[0214] Furthermore, when using a scraper, limiting components that restrict the width of the electrode material can be provided at both ends of the scraper in the width direction, and the thickness and width of the electrode material can be limited simultaneously or at different times (i.e., time difference).

[0215] When leveling the electrode material, vibration can be applied to the limiting component (e.g., a scraper). Vibration can be imparted, for example, by a vibrator. By propagating the vibration to the electrode material and applying shear force, at least at the contact area between the electrode material and the limiting component (e.g., the scraper), a decrease in viscosity and an increase in flowability can occur. As a result, the surface morphology of the manufactured electrode layer is smooth, and an electrode layer with minimal thickness deviation can be obtained.

[0216] (Electrode layer)

[0217] The electrode layer comprises electrode active materials, conductive additives, and electrolyte. Depending on the requirements, it may also include inorganic solid electrolytes and other components. Details regarding each component are as described above and therefore omitted here.

[0218] The thickness of the electrode layer is preferably 100 μm to 1000 μm, more preferably 200 μm to 600 μm. The thickness of the electrode layer is set as the arithmetic mean of the thicknesses at any three locations measured by cross-sectional observation. A known microscope (e.g., a scanning electron microscope) can be used for cross-sectional observation.

[0219] <Other Processes>

[0220] The method for manufacturing the electrode layer of the present invention may include other steps besides those described above.

[0221] Other processes include, for example, pressing the electrode layer, and transferring the electrode layer from the release paper to the current collector when release paper is used as a support material.

[0222] (The process of applying pressure to the electrode layer)

[0223] By including a process of pressurizing the electrode layer, the density of the electrode material can be further increased, and the in-plane uniformity of density and thickness can be further improved.

[0224] Examples of pressure-applying mechanisms include pressure rollers and stamping presses.

[0225] The pressure applied when pressurizing the electrode material is preferably 0.01 MPa to 100 MPa, more preferably 0.1 MPa to 50 MPa, and especially preferably 0.2 MPa to 10 MPa.

[0226] Regarding pressurization, multiple pressurization mechanisms (such as pressurization roller pairs) can be used to pressurize the electrode layer in stages. By using multiple pressurization mechanisms to pressurize the electrode layer in stages, the density and thickness uniformity of the electrode material can be further improved. For example, by using multiple pressurization roller pairs that are adjusted to progressively narrow the gap between the rollers, the electrode material film can be pressurized in stages.

[0227] Preferredly, pressurization is performed by moving the pressurizing mechanism relative to the electrode layer. "Moving the pressurizing mechanism relative to the electrode layer" includes moving the pressurizing mechanism relative to the electrode layer in one direction, moving the electrode layer relative to the pressurizing mechanism in one direction, and moving the pressurizing mechanism and the electrode layer in different directions or moving them in the same direction at different speeds. Preferably, the electrode layer moves relative to the pressurizing mechanism in one direction.

[0228] Examples of mechanisms for moving the electrode layer include belt conveyors, linear sliding guides, and cross roller conveyors.

[0229] Furthermore, from the viewpoint of improving formability, pressure can be applied, for example, to the electrode layer heated to 30°C to 100°C.

[0230] Example

[0231] The present invention will now be described in more detail through embodiments. However, the present invention is not limited to the following embodiments as long as it does not depart from its spirit.

[0232] <Example 1>

[0233] (Preparation of current collector foil)

[0234] Positive current collector foil (S1): Aluminum foil (average thickness: 20μm, Ra: 0.5μm, EAA-218D, carbon-coated product manufactured by Korea JCC Co., Ltd.)

[0235] Negative electrode current collector foil (S2): Copper foil (average thickness: 10μm, Ra: 0.55μm, manufactured by Nippon Denkai, Ltd.)

[0236] In addition, the Ra of the current collector mentioned above refers to the arithmetic mean roughness Ra on the surface of the electrode layer.

[0237] (Preparation of the apparatus)

[0238] Prepared with Figure 1 Manufacturing equipment constructed in the same manner.

[0239] Specifically, one first screw pump 10 and three second screw pumps 20 are prepared, and the three second screw pumps are connected to the first screw pump via piping 16. The piping 16 connected to the first screw pump branches in three directions to connect to the three second screw pumps. The first screw pump 10 has a cylindrical frame 4, which has a hopper 12 (supply port) for supplying electrode material at one end and an outlet 6 for discharging electrode material at the other end. The second screw pump 20 has a cylindrical frame 4, which has a piping 16 (supply port) for supplying electrode material at one end and an outlet 6 for discharging electrode material at the other end. The inner diameter of the piping 16 is set to φ10mm. Each of the cylindrical frames in the first screw pump 10 and the second screw pump 20 has a screw 2 inside, and both are rotatable. Furthermore, as... Figure 5 As shown, each screw has a pitch region including a conveyor section (i) and a compaction extrusion section (ii), and the thread pitch narrows as it moves downstream toward the electrode material feeding direction. The pitch variation from the widest pitch to the narrowest pitch is 50%.

[0240] Furthermore, a shielding member 8 with a circular cross-section discharge port (through hole) 3 is provided at the outlet 6 of each of the second screw pumps 20. For example... Figure 2 As shown, one end of the screw shaft on the downstream side is supported by a shield 48. Figure 6 As shown, three discharge holes 3 are arranged at equal intervals along the circumference. The diameter of the discharge port 3 is set to φ6mm. The clearance s1 between the shielding surface 8a and the downstream end face 2a of the screw blade in the second screw pump is set to 1mm. Furthermore, in the second screw pump 20, the shortest distance between the screw blade and the inner wall surface of the cylindrical frame is 0.5mm.

[0241] Stainless steel scraper is used as scraper 30, and piezoelectric scraper 40 is arranged downstream of scraper 30.

[0242] (Fabrication of the electrode layer)

[0243] After mixing 13.4g of LiPF6 (electrolyte) into a mixture of 45g ethylene carbonate (EC), 10g propylene carbonate (PC), and 45g diethyl carbonate (DEC), 2.3g of vinylene carbonate (VC) was further mixed in. 64g of the resulting 115.7g mixture was taken out and used as electrolyte X1.

[0244] Preparation and Figure 1 Similarly, the manufacturing apparatus 100 supplies positive electrode material to a strip of current collector foil 35 that is disposed on a movable tray 50 and conveyed, thereby producing an electrode layer 37.

[0245] Specifically, in the supply unit A equipped with a screw pump, 174g of positive electrode active material (ferric phosphate: "LFP NCO M121" manufactured by Aleees), 2g of conductive additive (Ketjenblack: "CARBON ECP600JD" manufactured by Lion Specialty Chemicals Co., Ltd.), and electrolyte X1 are respectively added as electrode material 14 into the feed hopper 12 of the manufacturing apparatus, thereby supplying electrode material 14 to the first screw pump 10. The screw installed in the cylindrical frame of the first screw pump 10 is started and rotated to mix the components of the electrode material 14 and deliver it out, and then it is delivered to the three connecting pipes 16 through the outlet, thereby supplying electrode material 14 to the three second screw pumps 20 respectively. The screws of the three second screw pumps 20 are rotated to transport the electrode material 14 downstream of each second screw pump 20. While the electrode material is further subjected to shearing and pressure in each second screw pump, it is delivered from the outlet of each second screw pump and supplied to the positive electrode current collector foil (S1) 35 that moves through the tray 50 (process A).

[0246] The supplied positive electrode material is Bingham fluid with a yield value of 50 kPa, and the volume ratio of solid to liquid components is 48:52.

[0247] Next, in film-forming section B, where scrapers 30 and piezoelectric scrapers 40 are arranged sequentially along the arrow direction, the positive electrode current collector 35 is moved along the arrow direction by the tray 50, thereby causing the electrode material 14 to be formed into a layer by the fixedly arranged scraper 30. Then, by further conveying the positive electrode current collector foil 35 through the piezoelectric scraper 40, the thickness of the layered electrode material is adjusted, and an electrode layer with a thickness of 325 μm is produced (step B).

[0248] <Example 2>

[0249] A manufacturing apparatus configured in the same manner as the apparatus prepared in Example 1 was prepared. Furthermore, an electrolyte X1 (64 g) was prepared, which was the same electrolyte used in the positive electrode material prepared in Example 1.

[0250] Using the same manufacturing apparatus as in Example 1, in the supply section A equipped with a screw pump, a conductive additive (carbon black: "C-NERGY SUPER C45" manufactured by Imerys Graphite & Carbon), a negative electrode active material ("MESOPHASE GRAPHITE POWDER A (MGP-A)" manufactured by ChinaSteel Chemical Corporation), and electrolyte X1 were respectively added as electrode material 14 into the feed hopper 12 of the manufacturing apparatus, thereby supplying electrode material 14 to the first screw pump 10. The ratio of conductive additive to negative electrode active material was set to 2.7:63.4 by mass (= conductive additive: negative electrode active material). Furthermore, 64 g of electrolyte X1 was added relative to the total amount of conductive additive and negative electrode active material (159 g).

[0251] The screw 2, located within the cylindrical frame of the first screw pump 10, is activated and rotated to mix the components of the electrode material 14 and simultaneously deliver it. The mixture is then discharged through the outlet to three connecting pipes 16, thereby supplying the electrode material 14 to the three second screw pumps 20. The screws 2 of the three second screw pumps 20 are rotated, transporting the electrode material 14 downstream of each second screw pump 20. In each second screw pump, the electrode material is further subjected to shearing and pressure while being discharged from the outlet of each second screw pump and supplied to the negative electrode current collector foil (S2) 35, which moves via the tray 50 (step A).

[0252] The supplied negative electrode material is Bingham fluid with a yield value of 30 kPa, and the volume ratio of solid to liquid components is 52:48.

[0253] Next, in film-forming section B, where scraper 30 and piezoelectric scraper 40 are arranged sequentially along the arrow direction, the negative electrode current collector 35 is moved along the arrow direction by tray 50, thereby causing the electrode material 14 to be formed into a layer by the fixedly arranged scraper 30. Then, by further conveying the negative electrode current collector foil 35 through the piezoelectric scraper 40, the thickness of the layered electrode material is adjusted, and an electrode layer with a thickness of 335 μm is produced (step B).

[0254] <Example 3>

[0255] Using the same positive electrode material as in Example 1, without using the second screw pump 20, the material was supplied to the positive current collector foil 35 from the piping 16 (with an inner diameter φ of 10 mm) connected to the first screw pump 10 (step A). ​​Otherwise, the electrode layer was fabricated in the same manner as in Example 1.

[0256] <Example 4>

[0257] The same positive electrode material as in Example 1 was used, and the number of second screw pumps was changed from 3 to 5. The number of branches of the piping 16 connected to the first screw pump 10 was changed from 3 to 5. The five second screw pumps (each with a discharge port diameter of 6 mm) were connected. Otherwise, the electrode layer was fabricated in the same manner as in Example 1.

[0258] <Example 5>

[0259] Using the same positive electrode material as in Example 1, and having previously been mixed by stirring at 1500 rpm (revolutions per minute) for 30 seconds with Awatori Rentaro (manufactured by THINKY CORPORATION), the material was fed into the first screw pump 10. Otherwise, the electrode layer was fabricated in the same manner as in Example 1.

[0260] <Example 6>

[0261] The same negative electrode material as in Example 2 was used, and the material that had been mixed by stirring at 1500 rpm for 30 seconds with Awatori Rentaro (manufactured by THINKY CORPORATION) was fed into the first screw pump 10. Otherwise, the electrode layer was made in the same manner as in Example 2.

[0262] <Example 7>

[0263] In Example 1, the aperture (diameter) of the outlet 3 of the second screw pump 20 was changed from φ6mm to 10mm. Otherwise, the electrode layer was fabricated in the same manner as in Example 1.

[0264] <Example 8>

[0265] In Example 1, the clearance s1 between the shielding surface 8a and the downstream end face 2a of the screw blade in the second screw pump was changed from 1 mm to 3 mm. Otherwise, the electrode layer was fabricated in the same manner as in Example 1.

[0266] <Comparative Example 1>

[0267] Using the same positive electrode material as in Example 1, and without using a screw pump, the material was first stirred at 1500 rpm for 30 seconds using Awatori Rentaro (manufactured by THINKY CORPORATION) and then directly fed onto the positive current collector foil (S1) 35 (step A). ​​Otherwise, the electrode layer was fabricated in the same manner as in Example 1.

[0268] (evaluate)

[0269] (1) Thickness evaluation

[0270] The thickness distribution of the fabricated electrode layer was measured using a laser displacement meter and evaluated according to the following criteria. The measurement was performed downstream of the piezoelectric scraper 40.

[0271] <Standard>

[0272] A: Below 3%

[0273] B: More than 3% but less than 5%

[0274] C: More than 5% but less than 10%

[0275] D: More than 10%

[0276] (2) Surface morphology evaluation

[0277] An inspection camera was installed downstream of the piezoelectric scraper 40, and the frequency of exposure (defects) of the current collector foil was detected. Of the six electrode layers with an area of ​​210 mm × 150 mm that were continuously fabricated, the first electrode layer was not evaluated; instead, the remaining five electrode layers were evaluated according to the following criteria.

[0278] <Standard>

[0279] A: The defect count is 0.

[0280] B: The defect count is more than 1 but less than 5.

[0281] C: The defect count is 5 or more but less than 10.

[0282] D: The defect count is 10 or higher.

[0283] [Table 1]

[0284]

[0285] In addition, the details of the abbreviations in Table 1 are as follows.

[0286] Orifice diameter: Diameter of outlet 3 of the second screw pump

[0287] Number of piping branches: The number of branches that the piping connected to the first screw pump branches off to connect to the second screw pump.

[0288] Clearance s1: The shortest distance between the shielding surface 8a and the downstream end face 2a of the screw blade in the second screw pump.

[0289] As shown in Table 1, it can be seen that the electrode layers of each embodiment have good thickness and surface morphology, and the material density in the electrode layers is highly uniform. In contrast, in Comparative Example 1, which is supplied to the current collector foil by mixing with a mixer without using a screw pump, the thickness distribution is large and the material density is uneven, and multiple defects of exposed current collector foil are confirmed on the entire surface.

[0290] Furthermore, a comparison of Examples 1 and 2 with Examples 5 and 6 clearly demonstrates that the uniformity of material density is superior when the components are directly supplied to the screw pump without pre-mixing before being added (Examples 1 and 2) compared to the pre-mixing method (Examples 5 and 6). As for the screw pump structure, a multi-stage structure using a first screw pump and a second screw pump is preferred; increasing the number of second-stage second screw pumps from three to five further improves uniformity.

[0291] Regarding the outlet aperture, the uniformity was improved in Example 1 with φ6mm compared to Example 7 with φ10mm. Furthermore, regarding the clearance s1, the uniformity was further improved in Example 1 with 1mm compared to Example 8 with 3mm.

[0292] 1-Screw pump, 2-Screw, 2a-Downstream end face of screw blade, 2b-Screw blade, 3-Through hole, 4-Cylindrical frame, 6-Outlet, 8-Shielding component, 8a-Shielding surface, 10-First screw pump, 12-Hopper, 14-Electrode material, 16-Connecting piping, 20-Second screw pump, 30-Scraper, 35-Current collector foil, 37-Electrode layer, 40-Piezoelectric scraper, 50-Pattern, 100-Electrode layer manufacturing apparatus, 200-Conventional extruder, A-Feeding section, B-Film forming section, s1, s2-Clearance, i-Conveyor section, ii-Compacting extrusion section.

[0293] All disclosures in Japanese Patent Application No. 2023-065941, filed on April 13, 2023, are incorporated herein by reference.

[0294] All documents, patent applications and technical standards described herein are incorporated herein by reference to the same extent as those specifically and separately described therein.

Claims

1. A method for manufacturing an electrode layer, comprising: Step A involves using a screw pump to supply electrode material, comprising electrode active material, conductive additives, and electrolyte, with a solid content concentration of 40% to 80% by volume, onto the current collector foil; and Step B involves leveling the electrode material supplied to the current collector foil to form an electrode layer on the current collector foil. The screw pump has the following features: A cylindrical frame having a supply port for supplying electrode material at one end and an outlet for discharging electrode material at the other end; A screw, rotatably disposed inside the cylindrical frame, and having a pitch region in which the thread pitch narrows as it moves downstream toward the direction of electrode material feeding; and A shielding element, which is disposed at the outlet, The shielding member has a surface that intersects the axial direction of the screw and a through hole that penetrates the surface. The surface is positioned opposite the downstream end face of the screw blade in a non-contact manner, and the through hole is located opposite the downstream end face.

2. The method for manufacturing the electrode layer according to claim 1, wherein, The shielding member supports one end of the downstream side of the screw shaft.

3. The method for manufacturing the electrode layer according to claim 1 or 2, wherein, The clearance between the surface intersecting the axial direction and the downstream end face of the screw blade is less than 3 mm.

4. The method for manufacturing the electrode layer according to claim 1 or 2, wherein, The screw pump includes: a first screw pump; and a second screw pump connected to the first screw pump via piping, and having a smaller delivery capacity than the first screw pump. The first screw pump and the second screw pump each have the cylindrical frame, the screw, and the shielding member.

5. The method for manufacturing the electrode layer according to claim 1 or 2, wherein, The shielding member has two or more through holes, which are arranged at equal intervals along the circumference of the screw.

6. The method for manufacturing the electrode layer according to claim 1 or 2, wherein, The thread pitch in the pitch region varies by more than 50%.

7. The method for manufacturing the electrode layer according to claim 1 or 2, wherein, In process A, the electrode active material, the conductive additive, and the electrolyte are not premixed before being supplied to the screw pump.

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