Powder rolling unit

Abstract

This powder rolling unit comprises: a pair of rolling rolls (2a, 2b) that form a rolled sheet (5) by rolling a powder material (4); a hopper (1) that stores the powder material (4) above the pair of rolling rolls (2a, 2b); and a squeegee (3) that is disposed above the pair of rolling rolls (2a, 2b), that is disposed parallel with respect to the axial direction of each of the pair of rolling rolls (2a, 2b), and that vibrates at a frequency of 2-300 kHz.

Description

Powder Rolling Unit

[0001] The present disclosure relates to a powder rolling unit.

[0002] In recent years, dry coating methods, which directly form powder films, have been attracting attention as a method that can form powder layers with high performance and low environmental impact compared to wet coating methods, which disperse powder in a solvent and then apply the powder.The dry coating method suppresses material damage to the powder caused by the solvent, maintains high performance, does not require drying the solvent, and can obtain a powder layer that can significantly reduce energy consumption.

[0003] In a conventional dry powder film-forming method, for example, a powder-rolling apparatus is used to roll-form powder to produce a rolled sheet such as an electrode sheet from a powder containing an electrode active material.

[0004] For example, Patent Document 1 discloses a technique for obtaining a rolled sheet of powder by controlling the amount of powder supplied through a rolling section. Patent Document 1 describes that a hopper, which is a powder storage section, is divided into sections and the amount of powder stored in each section is controlled to adjust the thickness of the resulting rolled sheet in the width direction to be uniform.

[0005] Patent No. 5772427

[0006] In Patent Document 1, since the hopper is divided, it is difficult to make the basis weight uniform in the width direction of the obtained rolled sheet, and the basis weight varies. In addition, hopper bridging occurs in the nip region where the powder is rolled by the rolling rolls, and the basis weight also varies in the flow direction of the rolled sheet.

[0007] To improve this, it is necessary to improve the flow of the powder in the hopper. As a method for improving the flow of the powder in the hopper, a method of vibrating the hopper is known. However, it is difficult to vibrate a hopper that is in contact with a rolling roll, and there is a problem that the basis weight varies.

[0008] Therefore, the present disclosure provides a powder rolling unit that can suppress clogging of powder material due to hopper bridges or the like in the nip region and suppress variations in basis weight in the width direction and flow direction of the rolled sheet.

[0009] A powder rolling unit according to one aspect of the present disclosure includes a pair of rolling rolls that roll a powder material to form a rolled sheet, a hopper that stores the powder material above the pair of rolling rolls, and a squeegee that is disposed above the pair of rolling rolls and parallel to the axial directions of each of the pair of rolling rolls, and vibrates at a frequency of 2 kHz to 300 kHz.

[0010] According to the powder rolling unit according to one aspect of the present disclosure, it is possible to suppress blockage of the powder material in the nip region due to a hopper bridge or the like, and to suppress variations in basis weight in the width direction and flow direction of the rolled sheet.

[0011] FIG. 1 is a schematic diagram showing a powder rolling unit according to an embodiment of the present disclosure as viewed from the side. FIG. 2 is a schematic diagram showing a powder rolling unit according to an embodiment of the present disclosure as viewed from above. FIG. 3A is a schematic diagram showing how particles of powder material are uniformly supplied to a nip region by a squeegee according to an embodiment of the present disclosure. FIG. 3B is a schematic diagram showing the positional relationship between a pair of rolling rolls and a squeegee when the powder rolling unit according to an embodiment of the present disclosure is viewed from the side. FIG. 4A is a schematic diagram showing a powder rolling unit according to a first modification of the present disclosure as viewed from the side. FIG. 4B is a schematic diagram showing the positional relationship between a pair of rolling rolls, a squeegee, and a multi-stage squeegee when the powder rolling unit according to the first modification of the present disclosure is viewed from the side. FIG. 5 is a schematic diagram showing a powder rolling unit according to a second modification of the present disclosure as viewed from the side. FIG. 6 is a schematic diagram showing a powder rolling unit according to the second modification of the present disclosure as viewed from the side.

[0012] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, component placement positions, and connection configurations shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in independent claims are described as optional components.

[0013] In addition, each drawing is a schematic diagram in which emphasis, omission, or adjustment of proportions has been appropriately made to illustrate the present disclosure, and is not necessarily an exact illustration, and may differ from the actual shape, positional relationship, and proportion. In each drawing, the same reference numerals are used to denote substantially the same configurations, and duplicated explanations may be omitted or simplified.

[0014] Furthermore, in the following embodiments, expressions such as thickness direction or cylindrical shape are used. For example, thickness direction or cylindrical shape does not only mean a completely thickness direction or cylindrical shape, but also means a substantially thickness direction or cylindrical shape, i.e., a shape with an error of a few percent. Furthermore, thickness direction or cylindrical shape means a thickness direction or a cylindrical shape within the range in which the effects of the present disclosure can be achieved. The same applies to other expressions using "direction" and "shape."

[0015] (Summary) A powder rolling unit according to the present disclosure will be described below.

[0016] A powder rolling unit according to one aspect of the present disclosure applies vibration to the powder near the rolling rolls to improve the fluidity of the powder in the nip region, thereby preventing clogging of the powder and enabling uniformity of the basis weight of the resulting rolled sheet.

[0017] Such a powder rolling unit includes a hopper as a material supply section, a pair of rolling rolls, and a squeegee. The squeegee vibrates by ultrasonic waves and transmits the vibrations to the powder, thereby imparting fluidity to the powder. A plurality of squeegees may be provided within the hopper.

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0019] (Embodiment) Hereinafter, the present embodiment will be described with reference to FIGS.

[0020] 1 is a schematic side view of a powder rolling unit according to an embodiment of the present disclosure, showing a hopper 1, rolls 2a and 2b, a squeegee 3, powder material 4, and a resulting rolled sheet 5.

[0021] 2 is a schematic diagram showing a powder rolling unit according to an embodiment of the present disclosure as viewed from above, in which the axial direction of the squeegee 3 is indicated by an arrow and the standing wave caused by the vibration of the squeegee 3 is indicated by a two-dot chain line.

[0022] FIG. 3A is a schematic diagram illustrating particles of powder material 4 being uniformly delivered to a nip region by a squeegee 3 according to an embodiment of the present disclosure.

[0023] FIG. 3B is a schematic diagram showing the positional relationship between the pair of rolls 2 a and 2 b and the squeegee 3 when the powder rolling unit according to the embodiment of the present disclosure is viewed from the side.

[0024] 4A is a schematic diagram showing a powder rolling unit according to Modification 1 of the present disclosure as viewed from the side. In FIG. 4A, it is shown that the powder rolling unit of FIG. 1 is further provided with multi-stage squeegees 7a and 7b.

[0025] 4B is a schematic diagram showing the positional relationship between a pair of mill rolls 2a, 2b, the squeegee 3, and the multi-stage squeegees 7a, 7b when the powder rolling unit according to Modification 1 of the present disclosure is viewed from the side. In Fig. 4B, the arc tangent to or overlapping with the squeegee 3 as the axial center of the mill roll 2a, and the arc tangent to or overlapping with the squeegee 3 as the axial center of the mill roll 2b are respectively indicated by two-dot chain lines. In addition, the arc L1a + 50 mm from the surface of the mill roll 2a as the axial center of the mill roll 2a, and the arc L1b + 50 mm from the surface of the mill roll 2b as the axial center of the mill roll 2b are respectively indicated by one-dot chain lines. Furthermore, an arc indicating the range L1a or L1b from the surface of the squeegee 3 as the axial center of the squeegee 3 is indicated by a closely spaced dashed line, and an arc indicating a range within 50 mm further outward from the arc indicated by the narrow dashed line (L1a + 50 mm or L1b + 50 mm) is indicated by a widely spaced dashed line. Areas surrounded by two-dot chain lines, one-dot chain lines, narrow dashed lines, and widely spaced dashed lines are indicated by hatching. The axial center of the squeegee 3 may sometimes be simply referred to as the center of the squeegee 3. The axial centers of the rolling rolls 2a, 2b may sometimes be simply referred to as the centers of the rolling rolls 2a, 2b.

[0026] Fig. 5 is a schematic diagram showing a powder rolling unit according to Modification 2 of the present disclosure as viewed from the side. Fig. 5 shows that the powder rolling unit of Fig. 1 further includes a blockage-opening mechanism 8 arranged parallel to the rolls 2a and 2b.

[0027] Fig. 6 is a schematic diagram showing a powder rolling unit according to Modification 2 of the present disclosure as viewed from the side. Fig. 6 shows that the powder rolling unit in Fig. 1 further includes a blockage-opening mechanism 8 arranged perpendicular to the rolls 2a and 2b.

[0028] [Powder Rolling Unit] (Functional Configuration of Powder Rolling Unit) As shown in Figures 1 and 2, the powder rolling unit includes a hopper 1 and a squeegee 3 arranged inside the hopper 1. The hopper 1 stores a powder material 4 made of powder above a pair of rolling rolls 2a, 2b and serves to supply the powder material 4 to the rolling rolls 2a, 2b. The squeegee 3 serves to apply vibrations to the powder material 4 stored inside the hopper 1, thereby constantly supplying the powder material 4 to the rolling rolls 2a, 2b so as not to clog the rolling rolls 2a, 2b. In this embodiment, the pair of rolling rolls 2a, 2b may be simply referred to as rolling rolls 2a, 2b.

[0029] The powder material 4 supplied to the rolling rolls 2a and 2b at a constant rate is rolled at the compression point where the distance between the surface of the rolling roll 2a and the surface of the rolling roll 2b is shortest. Therefore, a rolled sheet 5 made of the powder material 4 rolled by the rolling rolls 2a and 2b at the compression point can be obtained.

[0030] The squeegee 3 is desirably positioned parallel to the rolls 2a and 2b when viewed in the thickness direction of the rolled sheet 5. This is because if the squeegee 3 is not positioned parallel to the rolls 2a and 2b, the distance from one end of the squeegee 3 to the compression point will be different from the distance from the other end of the squeegee 3 to the compression point. This will result in variations in the basis weight at one end of the resulting rolled sheet 5 and the basis weight at the other end of the rolled sheet 5. In this embodiment, the squeegee 3 is positioned parallel to the rolls 2a and 2b when viewed in the thickness direction of the rolled sheet 5. This makes it possible to prevent variations in the basis weight at one end of the rolled sheet 5 and the basis weight at the other end of the rolled sheet 5.

[0031] Furthermore, it is desirable that the squeegee 3 be positioned parallel to the rolls 2a and 2b when viewed along the flow direction of the rolled sheet 5. This is because, if they are not positioned parallel, the distance from the center of the squeegee 3 to the compression point will be different from the distance from the end of the squeegee 3 to the compression point, resulting in variations in the basis weight of the central portion of the rolled sheet 5 and the basis weight of the end of the rolled sheet 5. In this embodiment, the squeegee 3 is positioned parallel to the rolls 2a and 2b when viewed along the flow direction of the rolled sheet 5. This prevents variations in the basis weight of the central portion of the rolled sheet 5 and the basis weight of the end of the rolled sheet 5. Note that in this embodiment, "parallel" does not only mean perfectly parallel, but also means substantially parallel, i.e., includes an error of about a few percent.

[0032] The squeegee 3 vibrates at a frequency of 2 kHz to 300 kHz. By using a vibrator 6 that vibrates at a frequency of 2 kHz to 300 kHz, the squeegee 3 can be vibrated efficiently. To impart fluidity to powder with a particle diameter of 0.005 μm to 500 μm, a high-frequency vibration of 2 kHz to 300 kHz is required. This is because low-frequency vibrations below 2 kHz result in an insufficient number of vibrations for the powder, making it impossible to impart sufficient fluidity. High-frequency vibrations above 300 kHz result in significant vibration attenuation as the vibrations propagate through the powder, making it impossible to impart sufficient fluidity to the powder. In this embodiment, the squeegee 3 vibrates at a frequency of 2 kHz to 300 kHz. Therefore, the squeegee 3 can impart sufficient fluidity to the powder.

[0033] 1 and 3A, the squeegee 3 is in contact with the powder material 4, so when the squeegee 3 vibrates, the vibration of the squeegee 3 is transmitted to the powder material 4. The vibration of the powder material 4 reduces the frictional resistance between the powder particles (between the particles) of the powder material 4, improving the fluidity of the powder. In other words, the vibration of the squeegee 3 improves the fluidity of the powder material 4, making it possible to supply the powder material 4 consistently to the compression point.

[0034] For example, powder material 4 present on the rolling rolls 2a and 2b moves in the rotational direction of the rolling rolls 2a and 2b. At this time, the powder constituting the powder material 4 is not aligned and exists in a disordered manner. The squeegee 3 is arranged with a certain gap between it and the rolling rolls 2a and 2b and vibrates. The squeegee 3 aligns the powder constituting the powder material 4 by passing the powder material 4 between the rolling rolls 2a and 2b and the squeegee 3 before it reaches the compression point. By aligning the powder constituting the powder material 4, the filling rate of the powder material 4 supplied to the compression point can be controlled, and the variation in the basis weight of the rolled sheet 5 can be reduced. Conversely, if the squeegee 3 does not vibrate, the powder material 4 is not subjected to vibration from the squeegee 3, and therefore the fluidity of the powder material 4 is not improved, and clogging of the powder material 4 may occur as the powder material 4 passes through the squeegee 3. Even if clogging of the powder material 4 does not occur, the filling rate of the powder material 4 cannot be controlled, and it is difficult to reduce the variation in the basis weight of the rolled sheet 5.

[0035] The squeegee 3 only needs to vibrate in at least one direction among the thickness direction of the rolled sheet 5, the width direction of the rolled sheet 5, and the flow direction of the rolled sheet 5. When focusing on the movement of each particle constituting the powder material 4, since each particle is surrounded by and in contact with adjacent particles on all sides, vibrating in each direction can reduce the coefficient of friction with the particles in contact in each direction. This makes it possible to improve the fluidity of the powder material 4. When the squeegee 3 vibrates in two or more directions, it is possible to further improve the fluidity of the powder material 4.

[0036] (Distance Between Squeegee 3 and Rollers 2a and 2b) Next, the distance between the squeegee 3 and the rollers 2a and 2b will be described.

[0037] 1 and 3B, the squeegee 3 has the role of improving the fluidity of the powder material 4 in the nip region between the rolls 2a and 2b, and is therefore preferably located as close to the rolls 2a and 2b as possible. In this embodiment, at least a portion of the squeegee 3 may be disposed between the rolls 2a and 2b. In other words, at least a portion of the squeegee 3 may be disposed in the nip region. Needless to say, the squeegee 3 is disposed so as not to come into contact with the rolls 2a and 2b.

[0038] Specifically, the radius of the squeegee 3 is defined as rs. The distance between the rolling roll 2a and the squeegee 3, which is the shortest distance between the surfaces when a straight line is drawn between the center of the rolling roll 2a and the center of the squeegee 3, is defined as L1a. The distance between the rolling roll 2b and the squeegee 3, which is the shortest distance between the surfaces when a straight line is drawn between the center of the rolling roll 2b and the center of the squeegee 3, is defined as L1b. The distance at the compression point where the distance between the rolling rolls 2a and 2b is shortest (the distance between compressions), that is, the shortest distance between the rolling rolls 2a and 2b at the compression point, is defined as Lr. Distances L1a and L1b are examples of distance L.

[0039] In this case, it is desirable that at least one of the distances L1a and L1b is equal to or greater than the distance Lr and equal to or less than Lr+50 mm. That is, it is desirable that the shortest distance L1a between the surface of the squeegee 3 and the surface of the rolling roll 2a is equal to or greater than Lr and equal to or less than Lr+50 mm, and that the shortest distance L1b between the surface of the squeegee 3 and the surface of the rolling roll 2b is equal to or greater than Lr and equal to or less than Lr+50 mm.

[0040] When at least one of the distances L1a and L1b is equal to or less than Lr+50 mm, the powder particles aligned by vibration can maintain that alignment up to the nip region, preventing variations in the basis weight of the rolled sheet 5. Here, the nip region is the region between the rolling roll 2a and the rolling roll 2b.

[0041] Furthermore, at least one of the distances L1a and L1b is greater than Lr. When at least one of the distances L1a and L1b is greater than Lr, the amount of powder material 4 supplied to the nip region is sufficient, and the desired rolled sheet 5 can be obtained. The distances L1a and L1b do not necessarily have to be the same. Therefore, it is sufficient that the squeegee 3 is positioned relative to the rolling roll 2a within a range where either Lr≦L1a≦Lr+50 mm or Lr≦L1a<Lr+50 mm holds. It is also sufficient that the squeegee 3 is positioned relative to the rolling roll 2b within a range where either Lr≦L1b≦Lr+50 mm or Lr≦L1b<Lr+50 mm holds.

[0042] Furthermore, with regard to the position of the squeegee 3 in the thickness direction of the obtained rolled sheet 5, the distance between the center of the squeegee 3 and the center between the rolling rolls 2a and 2b, i.e., the distance between the center of the squeegee 3 and the compression point, is desirably Lr / 2+rs or less. In other words, it is desirable that the squeegee 3 be located above the rolling rolls 2a and 2b so as to overlap both of them. This range, with the distance L1a or L1b being appropriate, allows the powder material 4 with sufficient powder alignment to be supplied to the nip region, preventing variation in the basis weight of the rolled sheet 5.

[0043] (Material and Shape of Squeegee 3) Next, the material and shape of the squeegee 3 will be described.

[0044] The squeegee 3 is formed of, for example, a metal material. By using a metal material for the squeegee 3, high-frequency waves propagate through the squeegee 3 without significant attenuation. High-frequency waves with short wavelengths tend to attenuate easily, but metal materials have the property of easily transmitting waves, so a squeegee 3 made of a metal material can suppress the attenuation of high-frequency waves. As a result, the vibration state is uniform throughout the squeegee 3, suppressing variations in the basis weight in the width direction of the rolled sheet 5.

[0045] Examples of metal materials that can be used include stainless steel, titanium, aluminum, copper, iron, and nickel. In particular, stainless steel or titanium is preferred as the metal material because it has high corrosion resistance and is resistant to rust. Titanium is also preferred as the metal material because it is easily vibrated by light ultrasonic waves.

[0046] The squeegee 3 may be made of a material other than a metal material. For example, the squeegee 3 may be made of a resin material or a ceramic material, or may be made of a composite member that selectively uses two or more materials from among a metal material, a resin material, and a ceramic material.

[0047] Furthermore, the shape of the squeegee 3 is desirably cylindrical in order to uniformly vibrate the surrounding powder material 4. For example, the shape of the squeegee 3 is a long cylinder extending along a predetermined direction. In this case, the diameter of the squeegee 3 is desirably 2 mm or more and 30 mm or less. When the diameter of the squeegee 3 is 30 mm or less, the squeegee 3 vibrates easily and can impart sufficient fluidity to the powder material 4. When the diameter is 2 mm or more, the squeegee 3 is sufficiently thick and is less likely to deform, and can impart sufficient fluidity to the powder material 4.

[0048] (Amplitude of Squeegee 3) Next, the amplitude of the squeegee 3 will be described.

[0049] It is desirable that the squeegee 3 vibrates in at least one of the width direction of the resulting rolled sheet 5, the thickness direction of the rolled sheet 5, and the length direction of the rolled sheet 5. If the squeegee 3 vibrates in two or more of the above three directions, it is possible to further improve the fluidity of the powder material 4. In particular, in the case of a cylindrical squeegee 3, it is desirable that the squeegee 3 vibrates in at least one of the thickness direction or flow direction of the rolled sheet 5 in order to efficiently transmit vibrations to the powder material 4 surrounding the squeegee 3. In this case, it is possible to further improve the fluidity of the powder material 4.

[0050] Furthermore, it is desirable that the amplitude of the squeegee 3 is 0.1 μm or more in at least one of the three directions. If the amplitude is 0.1 μm or more, sufficient fluidity can be imparted to the powder material 4. From the viewpoint of improving the fluidity of the powder material 4, it is desirable that the amplitude of the squeegee 3 is as large as possible, and therefore the amplitude of the squeegee 3 may be amplified to a practically feasible extent.

[0051] Furthermore, as shown by the two-dot chain line in Fig. 2, the squeegee 3 usually vibrates due to a standing wave. In other words, when the squeegee 3 vibrates, there are vibration antinodes where the amplitude increases and vibration nodes where the amplitude decreases. In order to transmit the vibration of the squeegee 3 to the powder material 4 without attenuation, it is desirable to position the wall surface of the hopper 1 in Fig. 2 at the vibration node.

[0052] (Frequency at which the squeegee 3 is vibrated) Next, the frequency at which the squeegee 3 is vibrated will be described.

[0053] As shown in Figures 1 and 2, the squeegee 3 is vibrated by a vibrator 6 connected to the squeegee 3. At this time, the squeegee 3 vibrates naturally at a frequency of 2 kHz to 300 kHz due to the vibrator 6. That is, the squeegee 3 vibrates at a high frequency near the ultrasonic band. Specifically, when the powder material 4 supplied to the hopper 1 passes between the rolling rolls 2a, 2b and the squeegee 3 (between the rolling roll 2a and the squeegee 3 and between the rolling roll 2b and the squeegee 3), the vibration of the squeegee 3 is transmitted to the powder material 4, thereby increasing the fluidity of the powder material 4. As a result, clogging is suppressed when the powder material 4 passes through the gap between the rolling rolls 2a, 2b and the squeegee 3.

[0054] This is because the squeegee 3 vibrates at a high frequency, so that the powder material 4 in contact with the squeegee 3 is less susceptible to frictional resistance due to powder pressure. This increases the fluidity of the powder material 4 in contact with the squeegee 3, thereby suppressing retention and aggregation of the powder material 4.

[0055] Furthermore, for the powder material 4 located near the squeegee 3, the vibration of the squeegee 3 reduces the frictional force between adjacent powder particles, increasing the fluidity and thereby suppressing aggregation of the powder material 4.

[0056] The fluidity of the powder material 4 tends to increase as the vibration frequency of the squeegee 3 increases. Therefore, if the squeegee 3 is vibrated at a frequency of 2 kHz or higher, which is a high frequency region near the ultrasonic band, the fluidity of the powder material 4 can be sufficiently increased. However, since the vibration tends to attenuate as the frequency increases, it becomes more difficult for the vibration of the squeegee 3 to propagate through the powder material 4. However, if the frequency is 300 kHz or lower, the fluidity of the powder material 4 can be sufficiently increased.

[0057] As a result, even when using powder material 4 with low fluidity and a particle size of 500 μm or less, the vibrating squeegee 3 allows the powder material 4 to pass through the gap between the rolling rolls 2 a, 2 b and the squeegee 3 without stagnation or agglomeration. This makes it possible to regulate the film thickness and filling rate of the powder material 4. As a result, a rolled sheet 5 with little variation in basis weight can be obtained.

[0058] (Vibrator 6) Next, the vibrator 6 will be described.

[0059] The squeegee 3 is provided with a vibrator 6. When the vibrator 6 vibrates, the vibration is transmitted to the squeegee 3, causing the squeegee 3 to vibrate.

[0060] The vibrator 6 has a plurality of piezoelectric bodies and electrodes provided on the end surfaces of each of the plurality of piezoelectric bodies. In the vibrator 6, each of the plurality of piezoelectric bodies is sandwiched between electrodes. In other words, the vibrator 6 has a sandwich structure of piezoelectric bodies and electrodes. For example, the number of piezoelectric bodies is an even number, such as two, four, or six. The electrodes are thin metal plates made of, for example, copper, phosphor bronze, or the like.

[0061] The piezoelectric material may be, for example, a lead zirconate titanate (PbTiO ３ -PbZrO ３ PZT-based, commonly known as PZT), and barium titanate (BaTiO ３ As the piezoelectric material, for example, quartz crystal and LiNbO ３ Alternatively, a piezoelectric single crystal such as the above may be used.

[0062] When the piezoelectric body is made of piezoelectric ceramics (for example, PZT), each piezoelectric body has a thickness of approximately 2 mm to 5 mm.

[0063] Furthermore, the vibrator 6 has a sandwich structure in which a piezoelectric body is sandwiched between a metal front plate and a metal backing plate, and a Langevin type vibrator whose overall length is half the wavelength is preferred because it has high output and high reliability.

[0064] Specifically, the Langevin vibrator has a structure in which a metal front plate and a metal backing plate are arranged on either side of a piezoelectric body such as PZT and are fastened together with bolts. The metal front plate and the metal backing plate are made of duralumin. The bolts are made of steel, titanium alloy, or the like. A screw hole for connection is formed in the center of the metal front plate, and the squeegee 3 is inserted into the screw hole and fastened, firmly connecting the vibrator 6 and the squeegee 3. This allows the vibration generated by the vibrator 6 to be transmitted to the squeegee 3. At this time, a horn that amplifies the amplitude or a horn that disperses the direction of vibration may be connected between the vibrator 6 and the squeegee 3.

[0065] The vibrator 6 is a vibrator that excites waves. A positive charge and a negative charge are applied to the thin metal plates provided on both end surfaces of the piezoelectric body of the vibrator 6, respectively. This converts electrical energy into mechanical energy. The conversion of the electrical signal into mechanical vibration causes the vibrator 6 to vibrate at a high frequency. This vibration is propagated to the squeegee 3.

[0066] When the vibrator 6 is long, it is preferable that the polarization direction of the piezoelectric material such as PZT coincides with the longitudinal direction of each vibrator 6 so that the vibrator 6 has a structure that expands and contracts in the longitudinal direction of each vibrator 6. In this case, the vibration direction of the vibrator 6 is the longitudinal direction of the vibrator 6, making it easier to control the vibration direction of the generated vibration.

[0067] (Rolling Rolls 2a, 2b) Next, the rolling rolls 2a, 2b will be described.

[0068] The powder material 4, whose fluidity has been improved by the vibration of the squeegee 3, is supplied to the nip region of the rolling rolls 2a and 2b, where it is compressed and stretched. At this time, the shortest distance between the rolling rolls 2a and 2b, which is the compression point, determines the thickness of the rolled sheet 5. The distance between the rolling rolls 2a and 2b is determined by the thickness of the rolled sheet 5. It is desirable that the distance between the rolling rolls 2a and 2b be 2 mm or less. When using a powder material 4 with a powder particle diameter of 500 μm or less, if the distance between the rolling rolls 2a and 2b is 2 mm or less, the compressive force on the powder material 4 is sufficient, the powder material 4 can be sufficiently rolled, and the desired rolled sheet 5 can be obtained.

[0069] The obtained rolled sheet 5 may be passed through the gap between the rolls 2 a and 2 b multiple times. Alternatively, the rolled sheet 5 may be stretched one or more times by using rolls 2 a and 2 b having roll diameters, peripheral speeds, gaps, etc. different from those of the rolls 2 a and 2 b.

[0070] The rolling rolls 2 a and 2 b have a predetermined diameter, for example, 100 mm to 200 mm. In this case, the rolling rolls 2 a and 2 b may be heated to heat-press the powder material 4 with the rolling rolls 2 a and 2 b, or the rolled sheet 5 may be heat-pressed with the rolling rolls 2 a and 2 b.

[0071] (Modification 1) Next, Modification 1 of the present embodiment will be described with reference to FIGS. 4A and 4B.

[0072] The powder rolling unit in this modified example differs from the powder rolling unit in the above embodiment in that it further includes multi-stage squeegees 7a and 7b. In this modified example, the same components as those in the powder rolling unit in the above embodiment are denoted by the same reference numerals and their description will be omitted where appropriate, and only the parts that differ from the powder rolling unit in the above embodiment will be described in detail.

[0073] The powder rolling unit includes multi-stage squeegees 7a, 7b each having a columnar shape such as a cylindrical shape and rotatably arranged in a hopper 1. The multi-stage squeegees 7a, 7b can gently pre-crush the powder material 4 so that the powder material 4 does not clog between the rolling rolls 2a, 2b and the squeegee 3. From the viewpoint of pre-crushing the powder material 4 uniformly, it is desirable that the multi-stage squeegees 7a, 7b be arranged in the hopper 1 so as to be parallel to the rolling rolls 2a, 2b. In other words, the multi-stage squeegees 7a, 7b are arranged in the hopper 1 so that the axial direction of the multi-stage squeegees 7a, 7b is parallel to the axial direction of the rolling rolls 2a, 2b.

[0074] The multi-stage squeegees 7a, 7b can gently break down the powder material 4 between the rolling rolls 2a, 2b and the squeegee 3 in advance. That is, the multi-stage squeegee 7a can break down the powder material 4 between the rolling roll 2a and the squeegee 3, and the multi-stage squeegee 7b can break down the powder material 4 between the rolling roll 2b and the squeegee 3. Here, the shortest distance between the surface of the multi-stage squeegee 7a and the surface of the squeegee 3 is defined as L3a, the shortest distance between the surface of the multi-stage squeegee 7b and the surface of the squeegee 3 is defined as L3b, the shortest distance between the surface of the multi-stage squeegee 7a and the surface of the rolling roll 2a is defined as L4a, and the shortest distance between the surface of the multi-stage squeegee 7b and the surface of the rolling roll 2b is defined as L4b.

[0075] In this case, it is desirable that the multi-stage squeegee 7a be positioned at a position that satisfies L1a≦L3a≦L1a+50 mm and L1a≦L4a≦L1a+50 mm. It is also desirable that the multi-stage squeegee 7b be positioned at a position that satisfies L1b≦L3b≦L1b+50 mm and L1b<L4b≦L1b+50 mm. In other words, the hatched areas surrounded by the two-dot chain line, the one-dot chain line, the narrow dashed line, and the wide dashed line in FIG. 4B are shown as areas where the multi-stage squeegees 7a and 7b can be positioned. It is sufficient that at least a portion of the multi-stage squeegees 7a and 7b overlap the hatched areas. It goes without saying that the multi-stage squeegees 7a and 7b are positioned so as not to come into contact with the rolling rolls 2a and 2b and the squeegee 3.

[0076] This further improves the fluidity of the powder material 4, and makes it possible to obtain a rolled sheet 5 with less variation in basis weight.

[0077] (Modification 2) Next, Modification 2 of the present embodiment will be described with reference to FIGS. 5 and 6. FIG.

[0078] The powder rolling unit in this modified example differs from the powder rolling unit in the above embodiment in that it further includes multi-stage squeegees 7a and 7b. In this modified example, the same components as those in the powder rolling unit in the above embodiment are denoted by the same reference numerals and their description will be omitted where appropriate, and only the parts that differ from the powder rolling unit in the above embodiment will be described in detail.

[0079] The powder rolling unit in this modified example differs from the powder rolling unit in the above embodiment in that it is further provided with a blocking and crushing mechanism 8. In this modified example, the same components as those in the powder rolling unit in the above embodiment are denoted by the same reference numerals and explanations thereof are omitted as appropriate, and only the parts that differ from the powder rolling unit in the above embodiment will be described in detail.

[0080] The powder rolling unit has a columnar shape such as a cylindrical shape, and includes a blocking and crushing mechanism 8 rotatably disposed in the hopper 1 .

[0081] This plug-opening and crushing mechanism 8 can gently crush the powder material 4 in advance so that the powder material 4 does not clog between the mill rolls 2a, 2b and the squeegee 3. The plug-opening and crushing mechanism 8 may be arranged in the hopper 1 so as to be parallel to the mill rolls 2a, 2b as shown in Fig. 5. In other words, the plug-opening and crushing mechanism 8 may be arranged in the hopper 1 so that the axial direction of the plug-opening and crushing mechanism 8 is parallel to the axial direction of the mill rolls 2a, 2b.

[0082] The blocked-cell crushing mechanism 8 may also be disposed at right angles to the rolls 2a and 2b as shown in Fig. 6. In other words, the blocked-cell crushing mechanism 8 may be disposed in the hopper 1 so that the axial direction of the blocked-cell crushing mechanism 8 and the axial direction of the rolls 2a and 2b are perpendicular to each other.

[0083] The blockage disintegration mechanism 8 may be disposed at any angle relative to the rolls 2a and 2b.

[0084] From the viewpoint of uniformly pre-crushing the powder material 4, it is desirable that the blocking / crushing mechanism 8 be disposed parallel to or perpendicular to the rolling rolls 2a and 2b.

[0085] The clog-disintegrating mechanism 8 has a rotating shaft 8a and convex claws 8b arranged on the rotation surface of the shaft 8a. The claws 8b protrude radially from the rotation surface of the shaft 8a. The clog-disintegrating mechanism 8 rotates to agitate the powder material 4 in advance to prevent clogging of the powder material 4 between the rolling rolls 2a, 2b and the squeegee 3, thereby gently disintegrating the powder material 4. This further improves the fluidity of the powder material 4, allowing for the production of a rolled sheet 5 with little variation in basis weight.

[0086] (Method of Supplying Powder Material 4) Next, a method of supplying powder material 4 to the powder rolling unit will be described.

[0087] The powder material 4 is supplied to a hopper 1. The hopper 1 temporarily stores the powder material 4 and continuously supplies the powder material 4 to the nip region of the rolling rolls 2a and 2b. The powder material 4 may be supplied to the hopper 1 by intermittently supplying the powder material 4 to the nip region of the rolling rolls 2a and 2b, or by continuously supplying the powder material 4 to the nip region of the rolling rolls 2a and 2b using a known constant-volume supply device such as a screw feeder or a vibrating feeder. From the viewpoint of maintaining a constant powder pressure generated between the rolling rolls 2a and 2b and the squeegee 3, it is desirable to continuously supply the powder material 4 to the nip region of the rolling rolls 2a and 2b using a constant-volume supply device such as a screw feeder or a vibrating feeder. This allows the powder pressure generated between the rolling rolls 2a and 2b and the squeegee 3 to be maintained constant, resulting in a rolled sheet 5 with little variation in basis weight.

[0088] (Particle diameter of powder) Next, the particle diameter of the powder material 4 will be described.

[0089] The particle diameter (D50) of the powder in the powder material 4 is preferably, for example, 0.005 μm or more and 500 μm or less. In this case, the smaller the particle diameter (D50) of the powder, the more likely the fluidity of the powder material 4 is to decrease, but the vibration of the squeegee 3 improves the fluidity of the powder material 4. Therefore, retention and aggregation are suppressed in the powder material 4, and the powder particles are aligned and arranged. Therefore, the powder material 4 is in a high-quality state with little variation in basis weight.

[0090] Here, the particle diameter (D50) is a volume-based median diameter calculated from the particle size distribution measured by a laser diffraction / scattering method, etc. This particle diameter (D50) can be measured using a commercially available laser analysis / scattering particle size distribution measuring device.

[0091] Here, the basis weight is a value expressed as the amount of powder per unit area in weight, and the unit of basis weight is, for example, g / cm ２ It is shown as follows.

[0092] Furthermore, the powder may contain only one type of powder, or may contain two or more types of powder. Furthermore, the powder material 4 may be granulated powder obtained by compacting a predetermined amount of powder to enlarge it. The powder material 4 may be any powdery substance. In other words, the raw materials of the powder material 4, the composition of the powder material 4, and the particle shape of the powder material 4 are not particularly limited. In this embodiment, the powder material 4 is a particle group containing a positive electrode active material used in a lithium-ion secondary battery.

[0093] [Manufacturing Method] Next, a method for manufacturing the rolled sheet 5 with less variation in basis weight by using a powder rolling unit will be described.

[0094] The manufacturing method includes supplying powder material 4 to a hopper 1 (powder supplying step), supplying the powder material 4 with the powder aligned to a nip region by passing the powder material 4 between rolling rolls 2a, 2b and a squeegee 3 (powder alignment step), and rolling the powder material 4 by the rolling rolls 2a, 2b to obtain a rolled sheet 5 (powder rolling step).

[0095] First, the powder material 4 is prepared. The raw material of the powder material 4 is not particularly limited, but for example, a particle group containing an active material may be used. When a particle group containing an active material is used, the active material is mixed with appropriate additives (for example, a binder, a conductive material, etc.) to prepare the powder material 4. Examples of the mixing method include a method using a mortar, a ball mill, a mixer, etc. In particular, a method of mixing powders without using a solvent, etc. is preferred because it does not cause material deterioration.

[0096] Next, in the powder supplying step, the powder material 4 is supplied to the hopper 1. The powder material 4 may be supplied to the hopper 1 intermittently, or may be supplied continuously using a known constant volume supplying device such as a screw feeder or a vibrating feeder.

[0097] In the powder alignment process, a squeegee 3 is used to supply the powder material 4 with aligned powder to the nip region. That is, in the powder alignment process, the squeegee 3 controls the supply amount and degree of crushing of the powder material 4 supplied to the nip region. At this time, the squeegee 3 vibrates at a frequency of 2 kHz to 300 kHz. The squeegee 3 resonates (natural vibration) with a sinusoidal standing wave. The squeegee 3 vibrates in at least one direction among the thickness direction, width direction, and length direction of the resulting rolled sheet 5. This can enhance the fluidity of the powder material 4. Furthermore, when the squeegee 3 vibrates in multiple directions, the fluidity of the powder material 4 can be further enhanced.

[0098] Next, in the powder rolling process, roll pressing is performed using rolling rolls 2a and 2b. The powder material 4, whose powder has been aligned by the vibration of the squeegee 3, is compressed from the nip region with the supply amount controlled by the vibration of the squeegee 3. As a result, a rolled sheet 5 is formed by compressing the powder material 4, whose powder has been aligned by the squeegee 3.

[0099] As described above, in the method for manufacturing the rolled sheet 5, the powder supplying step, the powder aligning step, and the powder rolling step are performed in this order to form the rolled sheet 5 made of the powder material 4. Such a rolled sheet 5 can be used in an energy device. For example, when a particle group containing an active material is used as the powder material 4, an electrode sheet for an energy device can be manufactured.

[0100] The fabricated energy device can have an electrode sheet with little variation in basis weight, in which the powder material 4 is fluidized and directly coated. Therefore, according to the manufacturing method of the rolled sheet 5, the powder material 4 is directly coated without dispersing the powder material 4 in a solvent or the like, coating it, and drying it. This prevents material degradation due to the solvent and enables high-capacity energy devices. It also prevents the use of solvents and the increased costs associated with drying the solvent. Furthermore, it reduces the large amount of energy consumed in the drying process, resulting in a manufacturing method with a low environmental impact. Meanwhile, when the basis weight of the rolled sheet 5 is highly uniform, the quality of the electrode in the energy device can be improved, and high-capacity energy devices with good quality can be manufactured at low cost.

[0101] (Rolled Sheet 5) Next, the rolled sheet 5 formed using the powder rolling unit will be described.

[0102] The rolled sheet 5 according to this embodiment is used, for example, in an energy device. The formed rolled sheet 5 has a film thickness of 30 μm or more. The rolled sheet 5 contains powder composed of at least one type of particulate material. The concentration of the solvent contained in the powder layer is 50 ppm or less. The powder layer has a small variation in basis weight.

[0103] This allows for the formation of a rolled sheet 5 with little variation in basis weight and suppressed deterioration due to the solvent. Furthermore, since drying of the solvent is not required, the energy consumed for drying the solvent can be reduced, thereby suppressing the environmental impact and preventing an increase in manufacturing costs. Therefore, by using such a powder layer in an energy device, the capacity and quality of the energy device can be increased, the environmental impact can be reduced, and low costs can be achieved.

[0104] The rolled sheet 5 of this embodiment can be used in, for example, a lithium ion secondary battery.

[0105] Hereinafter, the use of the rolled sheet 5 in a lithium ion secondary battery will be described in detail.

[0106] The rolled sheet 5 is used, for example, in combination with a known current collector as an electrode (positive electrode or negative electrode) of a lithium ion secondary battery. Such an electrode includes a current collector and the rolled sheet 5.

[0107] The electrode may further include another layer located between the current collector and the rolled sheet 5. The other layer may be, for example, a connection layer made of a conductive carbon material or the like.

[0108] The thickness of the rolled sheet 5 is 30 μm or more. There is no particular upper limit to the thickness of the rolled sheet 5, but the thickness of the rolled sheet 5 is, for example, 2000 μm or less.

[0109] The rolled sheet 5 also contains a powder material 4 made up of at least one type of particulate material.

[0110] The concentration of the solvent contained in the rolled sheet 5 is 50 ppm or less. In other words, the powder layer is substantially free of solvent. Here, "substantially free of solvent" means that the powder layer is completely free of solvent, or that the solvent is unavoidably contained at 50 ppm or less as an impurity or the like. The solvent concentration is a concentration based on weight. In any region on the surface of the rolled sheet 5, the variation in the powder layer basis weight is, for example, 8% or less.

[0111] The basis weight can be measured, for example, by the following method.

[0112] First, the rolled sheet 5 is punched into circles or polygons of a given size, and the weight of the punched rolled sheet 5 is measured. The basis weight can be determined by dividing this weight by the area of ​​the punched circle or polygon.

[0113] The variation in basis weight is measured, for example, by the following method.

[0114] First, an arbitrary region on the surface of the powder layer in a planar view is selected. This region may be a central region on the surface of the powder layer, or may be a region including the edge of the powder layer. Then, within this region, for example, five or more circular or polygonal shapes of arbitrary size are punched out, and the basis weight is measured using the above-described method. Nine or more punched out locations may be used to increase the accuracy of the variation measurement. The basis weight variation is calculated by dividing the difference (more specifically, the absolute value of the difference) between the average basis weight of all punched locations and the basis weight of the punched location with the largest difference from the average by the average. In other words, a basis weight variation of 8% or less means that the difference from the average basis weight at any punched location is 8% or less of the average.

[0115] Furthermore, the rolled sheet 5 is produced, for example, through a coating process that is substantially free of solvent. This allows the rolled sheet 5 to be formed without being substantially free of solvent. As a result, the rolled sheet 5 is not damaged by the solvent. This prevents deterioration of the rolled sheet 5 and reduces variation in the basis weight of the powder material 4 in the rolled sheet 5, making it possible to form a powder layer for a large, high-capacity energy device that has high capacity and excellent quality.

[0116] The rolled sheet 5 can also be used for the positive electrode, negative electrode, etc. of an energy device such as a lithium ion secondary battery.

[0117] When the rolled sheet 5 is used for a positive electrode, for example, the rolled sheet 5 containing the powder material 4 is a positive electrode mixture layer. That is, the positive electrode mixture layer is used in combination with a positive electrode current collector. The powder material 4 in the positive electrode mixture layer contains a positive electrode active material as at least one type of particulate material. When the rolled sheet 5 is used for a negative electrode, for example, the rolled sheet 5 containing the powder material 4 is a negative electrode mixture layer. That is, the negative electrode mixture layer is used in combination with a negative electrode current collector. The powder material 4 in the negative electrode mixture layer contains a negative electrode active material as at least one type of particulate material.

[0118] The concentration of the solvent contained in the positive electrode mixture layer and the negative electrode mixture layer is 50 ppm or less. That is, the positive electrode mixture layer and the negative electrode mixture layer are substantially free of solvent. Here, "substantially free of solvent" means that these layers are completely free of solvent and that these layers unavoidably contain 50 ppm or less of solvent as impurities or the like.

[0119] The solvent is, for example, an organic solvent. The method for measuring the solvent is not particularly limited, and can be measured using, for example, gas chromatography, mass variation analysis, etc. Examples of organic solvents include nonpolar organic solvents such as heptane, xylene, and toluene, polar organic solvents such as tertiary amine solvents, ether solvents, thiol solvents, and ester solvents, as well as combinations thereof. Examples of tertiary amine solvents include triethylamine, tributylamine, and triamylamine. Examples of ether solvents include tetrahydrofuran and cyclopentyl methyl ether. Examples of thiol solvents include ethane mercaptan. Examples of ester solvents include butyl butyrate, ethyl acetate, and butyl acetate.

[0120] Next, the materials used in the positive electrode mixture layer and the negative electrode mixture layer will be described in detail.

[0121] The positive electrode active material is a substance in which metal ions such as lithium (Li) are inserted into or extracted from the crystal structure at a potential higher than that of the negative electrode, and oxidation or reduction occurs along with the insertion or extraction of the metal ions such as lithium. The type of the positive electrode active material is appropriately selected, and examples thereof include oxide active materials.

[0122] The positive electrode active material in this embodiment may be, for example, lithium transition metal oxide particles containing a transition metal element such as Co, Mn, or Ni. ｘ CoO ２ , Li ｘ NiO ２ , Li ｘ MnO ２ , Li ｘ Co ｙ Ni １－ｙ O ２ , Li ｘ Co ｙ M １－ｙ O ｚ , Li ｘ Ni １－ｙ M ｙ O ｚ , Li ｘ Mn ２ O ４ , Li ｘ Mn ２－ｙ M ｙ O ４ , LiMPO ４ , Li ２ MPO ４ F (M: at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B, 0<x≦1.2, 0<y≦0.9, 2.0≦z≦2.3). These may be used alone or in combination of two or more. In terms of increasing the capacity of a lithium ion secondary battery, the positive electrode active material particles are preferably Li ｘ NiO ２ , Li ｘ Co ｙ Ni １－ｙ O ２ , Li ｘ Ni １－ｙ M ｙ O ｚ It is preferable that the lithium-nickel composite oxide particles contain lithium-nickel composite oxide particles such as (M; at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B; 0<x≦1.2, 0<y≦0.9, 2.0≦z≦2.3).

[0123] Examples of the shape of the positive electrode active material include particulates. When the positive electrode active material is particulate, the particle diameter of the positive electrode active material is, for example, in the range of 0.05 μm to 30 μm, and may be in the range of 1 μm to 15 μm. If the particle diameter of the positive electrode active material is 0.05 μm or more, handling tends to be improved. On the other hand, if the particle diameter is 30 μm or less, using an active material with a small particle size increases the surface area, making it easier to obtain a high-capacity positive electrode. Note that the particle diameter of the material contained in the positive electrode mixture layer or the negative electrode mixture layer in this specification is, for example, the above-mentioned D50.

[0124] The negative electrode active material is a substance in which metal ions such as lithium are inserted into or extracted from the crystalline structure at a potential lower than that of the positive electrode, and which undergoes oxidation or reduction as the metal ions such as lithium are inserted or extracted.

[0125] Examples of the negative electrode active material in this embodiment include lithium alloys such as metallic lithium, lithium-aluminum alloys, lithium-lead alloys, lithium-silicon alloys, and lithium-tin alloys; carbon materials such as graphite, coke, and organic sintered bodies; and SnO ２ , SnO, TiO ２ These may be used alone or in combination of two or more. Furthermore, as the negative electrode active material, a composite in which the above-mentioned negative electrode active materials are appropriately mixed may also be used.

[0126] The particle size of the negative electrode active material is, for example, 30 μm or less. By using an active material with a small particle size, the surface area is increased, and a high capacity can be achieved.

[0127] Next, the positive electrode current collector and the negative electrode current collector will be described in detail.

[0128] The positive electrode in this embodiment includes a positive electrode current collector made of, for example, a metal foil. The positive electrode current collector may be, for example, a foil, plate, or mesh-like material made of aluminum, gold, platinum, zinc, copper, stainless steel (SUS), nickel, tin, titanium, or an alloy of two or more of these metals. The thickness and shape of the positive electrode current collector may be appropriately selected depending on the application of the positive electrode.

[0129] The negative electrode in this embodiment includes a negative electrode current collector made of, for example, a metal foil. The negative electrode current collector may be, for example, a foil, plate, or mesh-like material made of stainless steel, gold, platinum, zinc, copper, nickel, titanium, tin, or an alloy of two or more of these metals. The thickness and shape of the negative electrode current collector may be selected as appropriate depending on the application of the negative electrode.

[0130] (Operation and Effect) Hereinafter, the operation and effect of the powder rolling unit in this embodiment will be described.

[0131] As described above, the powder rolling unit of Technology 1 in this embodiment includes a pair of rolling rolls 2a, 2b that rolls the powder material 4 to form a rolled sheet 5, a hopper 1 that stores the powder material 4 above the pair of rolling rolls 2a, 2b, and a squeegee 3 that is arranged above the pair of rolling rolls 2a, 2b and parallel to the axial directions of the pair of rolling rolls 2a, 2b, and vibrates at a frequency of 2 kHz to 300 kHz.

[0132] This allows the squeegee 3 to vibrate the powder material 4 stored inside the hopper 1. This allows the powder material 4 to be supplied to the mill rolls 2a, 2b at a constant rate (uniform powder supply amount) so that the powder material 4 is not blocked by the mill rolls 2a, 2b. This improves the fluidity of the powder material 4 near the nip region inside the hopper 1.

[0133] Furthermore, since the squeegee 3 is positioned parallel to the rolling rolls 2a, 2b, the distance from one end of the squeegee 3 to the compression point is the same as the distance from the other end of the squeegee 3 to the compression point, making it less likely that differences due to variations will occur between the basis weight at one end of the resulting rolled sheet 5 and the basis weight at the other end of the rolled sheet 5.

[0134] Therefore, according to this embodiment, clogging of the powder material 4 by a hopper bridge or the like in the nip region can be suppressed, and variations in basis weight in the width direction and flow direction of the rolled sheet 5 can be suppressed. As a result, a rolled sheet 5 with a uniform basis weight can be obtained. In particular, according to this embodiment, it is possible to obtain a desired rolled sheet 5, and therefore a decrease in yield can be suppressed.

[0135] Furthermore, the powder rolling unit of Technology 2 in this embodiment is the powder rolling unit described in Technology 1. In this case, when the distance between the pair of rolls 2 a, 2 b at the compression point where the distance is shortest is Lr and the radius of the squeegee 3 is rs, the shortest distance between the surface of the squeegee 3 and the surface of at least one of the pair of rolls 2 a, 2 b is Lr or more and Lr + 50 mm or less, and the distance between the axial center of the squeegee 3 in the thickness direction of the rolled sheet 5 and the compression point is Lr / 2 + rs or less.

[0136] According to this, even if powder material 4 with poorly aligned powder is supplied to the nip region, the powder will be aligned by the vibration of the squeegee 3, thereby suppressing variations in basis weight in the width direction and flow direction of the rolled sheet 5.

[0137] Furthermore, the powder rolling unit of Technique 3 in this embodiment is the powder rolling unit described in Technique 1 or 2. In this case, the distance between the pair of rolling rolls 2a, 2b is 2 mm or less.

[0138] According to this, even when a powder material 4 having a particle diameter of 500 μm or less is used, sufficient compressive force can be applied to the powder material 4, so that the powder material 4 can be sufficiently rolled and the desired rolled sheet 5 can be obtained.

[0139] Furthermore, the powder rolling unit of Technique 4 in this embodiment is the powder rolling unit according to any one of Techniques 1 to 3. In this case, the diameter of the squeegee 3 is 2 mm or more and 30 mm or less.

[0140] For example, when the diameter of the squeegee 3 is 30 mm or less, the squeegee 3 vibrates easily and can impart sufficient fluidity to the powder material 4. When the diameter is 2 mm or more, the squeegee 3 is sufficiently thick and is less likely to deform, and can impart sufficient fluidity to the powder material 4.

[0141] According to this embodiment, the vibration of the squeegee 3 is transmitted to the powder material 4, so that the powder material 4 can be given sufficient fluidity.

[0142] Furthermore, the powder rolling unit of Technology 5 in this embodiment is the powder rolling unit described in any one of Technologies 1 to 4. In this case, the squeegee 3 has an amplitude of 0.1 μm or more in at least one direction among the width direction of the rolled sheet 5, the thickness direction of the rolled sheet 5, and the length direction of the rolled sheet 5.

[0143] According to this, from the viewpoint of improving the fluidity of the powder material 4, it is desirable that the amplitude of the squeegee 3 is as large as possible, and therefore, sufficient fluidity can be imparted to the powder material 4.

[0144] Further, the powder rolling unit of Technology 6 in this embodiment is the powder rolling unit described in any one of Technologies 1 to 5. In this case, the wall surface of the hopper 1 is arranged at the node portion of the standing wave of the squeegee 3.

[0145] This allows the wall surface of the hopper 1 to be positioned at the node of the vibration, so that the vibration of the squeegee 3 can be transmitted to the powder material 4 without being attenuated.

[0146] Furthermore, the powder rolling unit of Technology 7 in this embodiment is the powder rolling unit according to any one of Technologies 1 to 6. In this case, it further includes a blockage-opening mechanism 8 disposed in the hopper 1 above the squeegee 3. The blockage-opening mechanism 8 has a rotating shaft 8a and convex claws 8b disposed on the rotation surface of the shaft 8a.

[0147] According to this, the clog-disintegration mechanism 8 can rotate to agitate the powder material 4 in advance so as to prevent clogging of the powder material 4 between the rolling rolls 2a, 2b and the squeegee 3. Since the powder material 4 can be gently disintegrated, the fluidity of the powder material 4 can be further improved, and a rolled sheet 5 with little variation in basis weight can be obtained.

[0148] Furthermore, the powder rolling unit of Technology 8 in this embodiment is the powder rolling unit described in any one of Technologies 1 to 7. In this case, the powder rolling unit further includes two or more multi-stage squeegees 7a and 7b arranged above the squeegee 3.

[0149] According to this, the multi-stage squeegees 7a, 7b can gently crush the powder material 4 beforehand between the rolling rolls 2a, 2b and the squeegee 3. This can further improve the fluidity of the powder material 4, and can provide a rolled sheet 5 with little variation in basis weight.

[0150] The powder rolling unit of Technology 9 in this embodiment is the powder rolling unit described in Technology 8. In this case, the squeegee 3 and the two or more multi-stage squeegees 7a, 7b have an amplitude of 0.1 μm or more in at least one direction among the width direction of the rolled sheet 5, the thickness direction of the rolled sheet 5, and the length direction of the rolled sheet 5.

[0151] According to this, from the viewpoint of improving the fluidity of the powder material 4, it is desirable to have a larger amplitude of the squeegee 3 and two or more multi-stage squeegees 7a, 7b, so that the powder material 4 can be given sufficient fluidity.

[0152] Furthermore, the powder rolling unit of Technology 10 in this embodiment is the powder rolling unit described in Technology 8 or 9. In this case, when the distances between the surface of the squeegee 3 and each of the surfaces of the pair of rolling rolls 2a, 2b are L4a and L4b, the distances L3a and L3b between the surfaces of the multistage squeegees 7a and 7b and the surface of the squeegee 3 are L1a or more and L1a + 50 mm or less, and L1b or more and L1b + 50 mm or less, and the distances L4a and L4b between the surfaces of the multistage squeegees 7a and 7b and each of the surfaces of the pair of rolling rolls 2a and 2b are L1a or more and L1a + 50 mm or less, and L1b or more and L1b + 50 mm or less.

[0153] This allows the powder particles aligned by the vibration of the squeegee 3 and the two or more multi-stage squeegees 7a, 7b to maintain their alignment up to the nip region, thereby further improving the fluidity of the powder material 4 and producing a rolled sheet 5 with little variation in basis weight.

[0154] Furthermore, the powder rolling unit of Technology 11 in this embodiment is the powder rolling unit described in Technology 9. In this case, when the distances between the surface of the squeegee 3 and each of the surfaces of the pair of rolling rolls 2a, 2b are L4a and L4b, the distances L3a and L3b between the surfaces of the multistage squeegees 7a and 7b and the surface of the squeegee 3 are L1a or more and L1a + 50 mm or less, and L1b or more and L1b + 50 mm or less, and the distances L4a and L4b between the surfaces of the multistage squeegees 7a and 7b and each of the surfaces of the pair of rolling rolls 2a and 2b are L1a or more and L1a + 50 mm or less, and L1b or more and L1b + 50 mm or less.

[0155] This allows the powder particles aligned by the vibration of the squeegee 3 and the two or more multi-stage squeegees 7a, 7b to maintain their alignment up to the nip region, thereby further improving the fluidity of the powder material 4 and producing a rolled sheet 5 with little variation in basis weight.

[0156] (Other Embodiments) While the powder rolling unit according to the present disclosure has been described above based on the embodiments, the present disclosure is not limited to these embodiments. As long as they do not deviate from the gist of the present disclosure, various modifications that a person skilled in the art can conceive of to the embodiments and other forms constructed by combining some of the components of the embodiments are also included in the scope of the present disclosure.

[0157] The powder rolling unit of the present disclosure forms a uniform powder layer without using a solvent, and can be applied to applications such as a mixture layer for a high-quality lithium-ion secondary battery.

[0158] REFERENCE SIGNS LIST 1 Hopper 2a, 2b Rolling roll 3 Squeegee 4 Powder material 5 Rolled sheet 6 Oscillator 7a, 7b Multi-stage squeegee 8 Blockage release mechanism 8a Shaft 8b Claw portion

Claims

1. A powder rolling unit comprising: a pair of rolling rolls for rolling a powder material to form a rolled sheet; a hopper for storing the powder material above the pair of rolling rolls; and a squeegee disposed above the pair of rolling rolls and parallel to the axial direction of each of the pair of rolling rolls, and vibrating at a frequency of 2 kHz to 300 kHz.

2. A powder rolling unit as described in claim 1, wherein, when the distance between the pair of rolling rolls at the compression point where the distance between them is the shortest is Lr and the radius of the squeegee is rs, the shortest distance between the surface of the squeegee and the surface of at least one of the pair of rolling rolls is Lr or more and Lr + 50 mm or less, and the distance between the axial center of the squeegee in the thickness direction of the rolled sheet and the compression point is Lr / 2 + rs or less.

3. The powder rolling unit according to claim 1 or 2, wherein the distance between the pair of rolling rolls is 2 mm or less.

4. The powder rolling unit according to claim 1 or 2, wherein the diameter of the squeegee is 2 mm or more and 30 mm or less.

5. A powder rolling unit according to claim 1 or 2, wherein the squeegee has an amplitude of 0.1 μm or more in at least one of the width direction, thickness direction and length direction of the rolled sheet.

6. The powder rolling unit according to claim 1 or 2, wherein a wall surface of the hopper is disposed at a node portion of the standing wave of the squeegee.

7. A powder rolling unit as claimed in claim 1 or 2, further comprising a plug-dislodging mechanism disposed in the hopper above the squeegee, the plug-dislodging mechanism having a rotating shaft and a convex claw portion disposed on the rotating surface of the shaft.

8. The powder rolling unit according to claim 1 or 2, further comprising two or more multi-stage squeegees arranged above the squeegee.

9. The powder rolling unit according to claim 8, wherein the squeegee and the two or more multi-stage squeegees have an amplitude of 0.1 μm or more in at least one of the width direction of the rolled sheet, the thickness direction of the rolled sheet, and the length direction of the rolled sheet.

10. A powder rolling unit as described in claim 8, wherein, when the distance between the surface of the squeegee and each surface of a pair of the rolling rolls is L, the distance between the surface of the multi-stage squeegee and the surface of the squeegee is not less than L and not more than L + 50 mm, and the distance between the surface of the multi-stage squeegee and each surface of the pair of the rolling rolls is not less than L and not more than L + 50 mm.

11. A powder rolling unit as described in claim 9, wherein, when the distance between the surface of the squeegee and each surface of a pair of the rolling rolls is L, the distance between the surface of the multi-stage squeegee and the surface of the squeegee is not less than L and not more than L + 50 mm, and the distance between the surface of the multi-stage squeegee and each surface of the pair of the rolling rolls is not less than L and not more than L + 50 mm.