Mixture plate forming device

Abstract

A mixture plate molding device (1) is provided with: a storage unit (2) for a powdery electrode mixture (8); and a first molding roller (4) and a second molding roller (6) which are adjacent to each other with a predetermined interval therebetween, the electrode mixture (8) in the storage part (2) is carried on a first peripheral surface (4a) of the first molding roller (4) and a second peripheral surface (6a) of the second molding roller (6) and supplied to a gap between the two rollers, and the electrode mixture (8) is compressed into a plate shape to mold a mixture plate (10). The first peripheral surface (4a) has a first surface roughness, and the second peripheral surface (6a) has a second surface roughness greater than the first surface roughness. A region (R2) of the second peripheral surface (6a) in which the powdery electrode mixture (8) is carried is smaller than a region (R1) of the first peripheral surface (4a) in which the powdery electrode mixture (8) is carried.

Description

Technical Field

[0001] The present disclosure relates to a composite plate forming device. Background Art

[0002] Patent Document 1 describes a powder rolling device comprising a pair of rolling rollers and a hopper mounted above the rolling rollers. In this powder rolling device, composite particles containing an electrode active material, i.e., an electrode mixture, are introduced from the hopper between the rollers as the rolling rollers rotate. The pair of rolling rollers then roll the electrode mixture to form a rolled sheet, i.e., a mixture sheet.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2016-27573 Summary of the Invention

[0006] Technical problem to be solved by the invention

[0007] When a mixture plate is formed from an electrode mixture by a pair of rollers, it is desired to be able to stably form the mixture plate.

[0008] The present disclosure has been made in view of such circumstances, and one of its objects is to provide a technology for improving the molding stability of a composite plate.

[0009] Methods used to solve technical problems

[0010] One embodiment of the present disclosure is a composite plate forming device. The device includes: a storage portion for a powdered electrode mixture; and a first forming roller and a second forming roller, which are adjacent to each other at a predetermined interval. The first circumferential surface of the first forming roller and the second circumferential surface of the second forming roller carry the electrode mixture in the storage portion and supply it to the gap between the two rollers, compressing the electrode mixture into a plate shape to form a composite plate. The first circumferential surface has a first surface roughness. The second circumferential surface has a second surface roughness greater than the first surface roughness. The area of ​​the second circumferential surface that carries the powdered electrode mixture is smaller than the area of ​​the first circumferential surface that carries the powdered electrode mixture.

[0011] Optional combinations of the above-described constituting elements and modes in which the present disclosure is converted into methods, apparatuses, systems, etc. may also be effective as modes of the present disclosure.

[0012] Effects of the Invention

[0013] According to the present disclosure, it is possible to improve the molding stability of the composite plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the composite plate forming device according to the embodiment.

[0015] Figure 2 (A) and Figure 2 (B) is a diagram showing a modified example of the shielding member. DETAILED DESCRIPTION

[0016] Below, the present disclosure is described with reference to the accompanying drawings based on preferred embodiments. The embodiments do not limit the present disclosure but are illustrative, and all the features or combinations thereof described in the embodiments do not necessarily represent the essential content of the present disclosure. The same or equivalent components, parts, and processes shown in the drawings are marked with the same figure marks, and repeated descriptions are appropriately omitted. In addition, the scales or shapes of the various parts shown in the drawings are conveniently set for easy description, and are not interpreted as restrictive unless otherwise specified. In addition, when terms such as "first" and "second" are used in this specification or claims, unless otherwise specified, the terms do not indicate any order or importance, but are used to distinguish one configuration from other configurations. In addition, in the drawings, a part of unimportant components is omitted for display when describing the embodiments.

[0017] Figure 1 Schematic diagram of a composite plate forming apparatus 1 according to an embodiment. The composite plate forming apparatus 1 includes a storage unit 2, a first forming roller 4, and a second forming roller 6. The storage unit 2 is, for example, a well-known hopper, and stores a powdered or granular electrode mixture 8 serving as a raw material for the composite plate 10.

[0018] The electrode mixture 8 contains an electrode active material and a binding component. Furthermore, it may contain a conductive agent as needed. The binding component is a component that binds the electrode active materials together and includes at least one of a binding material (i.e., a binder) and a solvent. In a conventional lithium-ion secondary battery, the positive electrode of the electrode active material is lithium cobalt oxide or lithium iron phosphate, and the negative electrode is graphite, for example. The conductive agent is graphite, carbon black, acetylene black, etc.

[0019] Binders include polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF). When electrode mixture 8 is used for the negative electrode, examples of solvents include water, alcohols such as ethanol, N-methylpyrrolidone (NMP), toluene, dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). Furthermore, when electrode mixture 8 is used for the positive electrode, examples of solvents include amine solvents such as N,N-dimethylaminopropylamine and diethylenetriamine; ether solvents such as tetrahydrofuran; ketone solvents such as methyl ethyl ketone; ester solvents such as methyl acetate; and amide solvents such as dimethylacetamide and N-methyl-2-pyrrolidone.

[0020] As an example, the electrode mixture 8 has a binder content of 10% by mass or less relative to the total mass of the electrode mixture 8, which is a so-called dry electrode mixture. When the electrode mixture 8 is dry, the binder content is 5% by mass or less, or 3% by mass or less, or 0.1% by mass, or even substantially 0% relative to the total mass of the electrode mixture 8. By making the electrode mixture 8 dry, a drying oven for the mixture plate 10 can be omitted.

[0021] The first forming roller 4 and the second forming roller 6 are arranged at the powder outlet of the storage section 2. The first forming roller 4 and the second forming roller 6 are arranged so that a portion of each circumference is exposed to the storage space of the electrode mixture 8 in the storage section 2. In the following, the circumference of the first forming roller 4 is set as the first circumference 4a, and the circumference of the second forming roller 6 is set as the second circumference 6a. The first forming roller 4 and the second forming roller 6 are positioned in such a way that their respective rotation axes are parallel to each other, and are adjacent to each other at a predetermined interval. The second forming roller 6 is arranged on the downstream side of the conveying direction of the mixture plate 10 closer to the first forming roller 4.

[0022] The first forming roller 4 and the second forming roller 6 carry the electrode mixture 8 in the storage portion 2 on the first circumferential surface 4a and the second circumferential surface 6a and supply it to the gap between the two rollers. Therefore, the first forming roller 4 and the second forming roller 6 also function as feed rollers. The first forming roller 4 and the second forming roller 6 rotate in opposite directions to each other, compressing the electrode mixture 8 supplied to the gap into a plate shape. Thus, the mixture plate 10 is formed. The mixture plate 10 is continuously fed out from the gap between the first forming roller 4 and the second forming roller 6. Therefore, the mixture plate 10 is in the shape of a strip that is long in the transmission direction.

[0023] In addition, the first forming roller 4 and the second forming roller 6 of this embodiment have different surface roughnesses on each circumferential surface. Specifically, the first circumferential surface 4a has a first surface roughness, and the second circumferential surface 6a has a second surface roughness that is greater than the first surface roughness. The surface roughnesses of the first circumferential surface 4a and the second circumferential surface 6a are different, so that the formed composite plate 10 is stretched by a pair of forming rollers. In other words, the first forming roller 4 and the second forming roller 6 also function as stretching rollers. The composite plate 10 formed and stretched by the first forming roller 4 and the second forming roller 6 is supported by the second circumferential surface 6a having a greater surface roughness and is transported to the downstream side.

[0024] The "surface roughness" in this embodiment refers to the arithmetic mean roughness Ra specified in JIS B 0601 2001. The surface roughness is not limited to Ra and may also be other well-known indicators such as the maximum height roughness Rz. That is, for any of these roughness indicators, the roughness of the second circumferential surface 6a is greater than the roughness of the first circumferential surface 4a. Furthermore, in addition to setting the surface roughness of the second circumferential surface 6a to be greater than the surface roughness of the first circumferential surface 4a, the composite sheet 10 can be more easily stretched by setting the circumferential speed of the second forming roller 6 to be faster than the circumferential speed of the first forming roller 4.

[0025] The composite sheet forming apparatus 1 of this embodiment includes a stretching roller 12 located downstream of the second forming roller 6 in the conveying direction of the composite sheet 10. The stretching roller 12 is positioned so that its rotation axis is parallel to the rotation axis of the second forming roller 6 and is adjacent to the second forming roller 6 at a predetermined distance. The composite sheet 10 passes through the gap between the second forming roller 6 and the stretching roller 12. The second forming roller 6 and the stretching roller 12 can rotate in opposite directions with the composite sheet 10 sandwiched therebetween, thereby conveying the composite sheet 10.

[0026] In addition, the second forming roller 6 and the stretching roller 12 rotate at different peripheral speeds. Specifically, the peripheral speed of the stretching roller 12 is faster than the peripheral speed of the second forming roller 6. Alternatively, the second forming roller 6 and the stretching roller 12 have different surface roughnesses on their respective peripheral surfaces. Specifically, the surface roughness of the peripheral surface of the stretching roller 12 (hereinafter referred to as the third peripheral surface 12a) is greater than the second surface roughness. Due to at least one of the difference in peripheral speed and the difference in surface roughness, the composite sheet 10 passing through the gap between the stretching roller 12 and the second forming roller 6 is stretched.

[0027] The composite sheet 10 is transferred to the stretching roller 12 at a position where the second forming roller 6 faces the stretching roller 12, supported by the third circumferential surface 12a, and transported downstream. Furthermore, one or more stretching rollers 12 may be arranged downstream of the stretching roller 12 adjacent to the second forming roller 6. Furthermore, a transport roller having only a transport function and no stretching function may be provided. Furthermore, a laminating roller may be provided to transport a substrate such as a current collector plate and to laminate the composite sheet 10 onto the substrate.

[0028] The interval between the first forming roller 4 and the second forming roller 6 is determined according to the predetermined supply amount of the electrode mixture 8. Therefore, after the electrode mixture 8 exceeding the set amount is introduced into the gap, the torque required for the rotation of each forming roller may exceed the assumed value. At this time, the rotation of each forming roller is suppressed, and the forming and stretching of the mixture plate 10 may become difficult. In addition, when the peripheral speed of the second forming roller 6 slows down, the ratio of the peripheral speed of the second forming roller 6 to the peripheral speed of the stretching roller 12 deviates from the design range, and it may be difficult to stretch and transmit the mixture plate 10. In addition, when the peripheral speed of the second forming roller 6 is slower than the peripheral speed of the first forming roller 4, it may be difficult to transfer the mixture plate 10 to the second peripheral surface 6a.

[0029] The amount of electrode mixture 8 introduced into the gap between a pair of forming rollers from the storage portion 2 by the first circumferential surface 4a and the second circumferential surface 6a usually changes from time to time. In particular, in the present embodiment, since the forming and stretching of the compound plate 10 is also implemented by a pair of forming rollers, the surface roughness of the second circumferential surface 6a is set to be larger than the surface roughness of the first circumferential surface 4a. When the surface roughness is increased, the amount of electrode mixture 8 introduced into the gap increases. When the amount of electrode mixture 8 introduced increases, the amplitude of change in the amount introduced may also become larger. In the case where the interval between the forming rollers is determined to be larger based on the estimation of the increased amplitude of change, the increase in torque caused by the increase in the amount introduced can be avoided, but when the amount introduced decreases, the forming of the compound plate 10 may become difficult. Therefore, the forming stability of the compound plate 10 may be reduced.

[0030] In this regard, in the present embodiment, the region R2 of the second circumferential surface 6a that carries the powdered electrode mixture 8, i.e., the unformed electrode mixture 8, is smaller than the region R1 of the first circumferential surface 4a that carries the powdered electrode mixture 8. In other words, the portion of the second circumferential surface 6a that is exposed in the storage space for the electrode mixture 8 is smaller than the portion of the first circumferential surface 4a that is exposed in the storage space. As an example, the end portion on the upstream side of the rotation direction of the forming roller in the regions R1 and R2 is the boundary between the portion in contact with the electrode mixture 8 and the portion that is not in contact. In addition, the end portion on the downstream side is the portion that is closest to the first circumferential surface 4a and the second circumferential surface 6a.

[0031] In this way, the contact area between the second circumferential surface 6a and the unformed electrode mixture 8 is made smaller than the contact area between the first circumferential surface 4a and the unformed electrode mixture 8, so that the degree of increase in the amount of electrode mixture 8 introduced based on the second circumferential surface 6a can be suppressed by increasing the surface roughness of the second circumferential surface 6a. As a result, the variation range of the amount of electrode mixture 8 introduced can be reduced. As a result, the forming stability of the composite plate 10 can be improved. As an example, the size of the region R2 can be adjusted so that the amount of electrode mixture 8 introduced into the first circumferential surface 4a per rotation of the first forming roller 4 or per unit time is equal to the amount of electrode mixture 8 introduced into the second circumferential surface 6a per rotation of the second forming roller 6 or per unit time.

[0032] In this embodiment, the region R2 is set to be smaller than the region R1 by providing a shielding member 14 in the storage section 2. The shielding member 14 is arranged in the storage section 2 to shield a portion of the second circumferential surface 6a exposed in the storage section 2 from the electrode mixture 8. As an example, the shielding member 14 is a partition inserted into the storage space for the electrode mixture 8. At this time, the storage space is divided by the shielding member 14 into a first space 2a located above the first forming roller 4 and a second space 2b located above the second forming roller 6. Furthermore, the electrode mixture 8 is accommodated only in the first space 2a. Thus, the shielding member 14 exists between the electrode mixture 8 accommodated in the first space 2a and a portion of the second circumferential surface 6a, and the region R2 is smaller than the region R1.

[0033] In addition, as an example, the shielding member 14 is arranged in a manner that extends vertically directly above the gap between a pair of forming rollers, that is, it is arranged in a manner that is equidistant from the rotation center of each forming roller. Preferably, the lower end of the shielding member 14, that is, the end 14a on the side close to the gap between the forming rollers, is located above the rotation center 6c of the second forming roller 6 and below the upper end of the second circumferential surface 6a. A portion of the electrode mixture 8 contained in the first space 2a is carried in the area R1 of the first circumferential surface 4a and is introduced into the gap between the pair of forming rollers. In addition, a portion of the electrode mixture 8 contained in the first space 2a is carried in the area R2 of the second circumferential surface 6a below the end 14a of the shielding member 14 and is introduced into the gap between the pair of forming rollers.

[0034] The inventors of the present invention conducted molding tests of a composite plate 10 using the composite plate molding apparatus 1 of the present embodiment (Example) and molding tests of a composite plate 10 using a conventional composite plate molding apparatus without a shielding member 14 (Comparative Example). In the Example, the end 14a of the shielding member 14 was configured so that the setting height d was 33%. The setting height d was calculated using the equation d = D / R × 100 [%], where the radius of the second molding roller 6 is R and the height distance from the rotation center 6c to the end 14a is D.

[0035] In the comparative example, the amount of electrode mixture 8 fed into the storage portion 2 is set to 50 g, 100 g, and 200 g. When set in this way, at any amount fed, at least one of the following conditions may occur: the torque required for rotating the forming roller is higher than the maximum output of the motor that rotates the forming roller, or the compound plate 10 cannot be transferred to the second circumferential surface 6a. On the other hand, in the embodiment, the amount fed is set to 200 g, and there is no situation where the required torque is higher than the maximum output of the motor, and the transfer of the compound plate 10 to the second circumferential surface 6a can be implemented without any problem. Therefore, according to the compound plate forming device 1 of this embodiment, it is confirmed that the forming stability of the compound plate 10 is improved. In addition, the inventors of the present invention have confirmed that the effect of improving the forming stability is also obtained in cases where the height d is set to other than 33%.

[0036] In this embodiment, the shielding member 14 is positioned directly above the gap between the pair of forming rollers. However, the placement of the shielding member 14 is not limited to this and may be offset toward either forming roller. Furthermore, when the shielding member 14 is a spacer, its thickness can be adjusted appropriately. Preferably, the thickness of the shielding member 14 can also be adjusted to a thickness that does not deform under the weight of the electrode mixture 8 contained in the first space 2a.

[0037] Furthermore, the shielding member 14 may include the following modified examples. Figure 2 (A) and Figure 2 (B) is a diagram showing a modified example of the shielding member 14. That is, for example, Figure 2 As shown in (A), the shielding member 14 may also be tilted. Preferably, the shielding member 14 is tilted so that the upper end thereof tilts toward the second forming roller 6. In this case, the volume of the first space 2a can be increased, thereby increasing the capacity of the electrode mixture 8 in the reservoir 2. Alternatively, the enlargement of the first space 2a to ensure sufficient capacity for the electrode mixture 8 can be suppressed.

[0038] In addition, if Figure 2 As shown in (B), the shielding member 14 may also be curved along the second circumferential surface 6a. In this case, the second space 2b can be substantially omitted. This further increases the capacity of the electrode mixture 8 in the reservoir 2. Alternatively, the need to enlarge the first space 2a to ensure sufficient capacity for the electrode mixture 8 can be further suppressed.

[0039] The surface of the shielding member 14 preferably has a third surface roughness that is lower than the first surface roughness. In particular, the surface exposed in the first space 2a and in contact with the electrode mixture 8 preferably has the third surface roughness. This prevents the electrode mixture 8 from adhering to the shielding member 14. Consequently, the molding stability of the mixture plate 10 can be further improved.

[0040] Furthermore, in this embodiment, region R2 is made smaller than region R1 by shielding the electrode mixture 8 from the second circumferential surface 6a by the shielding member 14. However, region R2 can also be made smaller than region R1 without using the shielding member 14. For example, region R2 can be made smaller than region R1 by using a reservoir 2 that does not have the second space 2b and only has the first space 2a occupying the storage space for the electrode mixture 8, that is, a reservoir 2 whose outline reaches the position of the shielding member 14. When the shielding member 14 is used, an existing hopper can be utilized as the reservoir 2. Therefore, the cost reduction required for implementing this embodiment can be achieved.

[0041] As described above, in the composite plate forming apparatus 1 of this embodiment, the first circumferential surface 4a of the first forming roller 4 has a first surface roughness, and the second circumferential surface 6a of the second forming roller 6 has a second surface roughness greater than the first surface roughness. Furthermore, the region R2 of the second circumferential surface 6a that supports the powdered electrode mixture 8, i.e., the electrode mixture 8 before being formed into the composite plate 10, is smaller than the region R1 of the first circumferential surface 4a that supports the powdered electrode mixture 8. This reduces the variation in the amount of electrode mixture 8 supplied to the gap between the pair of forming rollers, thereby improving the forming stability of the composite plate 10.

[0042] In particular, when the electrode mixture 8 is a dry electrode mixture, that is, when the binder component is 10% or less by mass, the fluidity is lower than when the electrode mixture is a wet electrode mixture, that is, when the binder component is greater than 10% by mass. As a result, when the amount of electrode mixture 8 introduced increases, the load applied to each forming roller is likely to be excessive. Therefore, the composite plate forming device 1 of this embodiment can function particularly effectively when the electrode mixture 8 is dry. In addition, when the electrode mixture 8 is wet, this embodiment can achieve improved forming stability of the composite plate 10.

[0043] The above is a detailed description of the embodiments of the present disclosure. The aforementioned embodiments only show specific examples when implementing the present disclosure. The contents of the embodiments do not limit the technical scope of the present disclosure, and various design changes such as changes, additions, and deletions of constituent elements can be made without departing from the scope of the idea of ​​the present disclosure as defined in the claims. The new embodiment with design changes has the effects of the combined embodiment and the deformation. In the aforementioned embodiments, the contents that can be subjected to such design changes are emphasized by expressions such as "in this embodiment" and "in this embodiment", and design changes are allowed even if there are no such expressions. Any combination of the constituent elements included in each embodiment is also valid as a scheme of the present disclosure. The hatching marked on the cross section of the accompanying drawings does not limit the material of the object marked with the hatching.

[0044] The embodiment can also be determined by the items described below.

[0045] [First item]

[0046] A composite plate forming device (1) comprising:

[0047] a storage portion (2) for a powdered electrode mixture (8), and

[0048] The first forming roller (4) and the second forming roller (6) are adjacent to each other at a predetermined interval, and the electrode mixture (8) in the storage portion (2) is carried on the first circumferential surface (4a) of the first forming roller (4) and the second circumferential surface (6a) of the second forming roller (6) and supplied to the gap between the two rollers, thereby compressing the electrode mixture (8) into a plate shape to form a mixture plate (10);

[0049] The first peripheral surface (4a) has a first surface roughness,

[0050] The second peripheral surface (6a) has a second surface roughness greater than the first surface roughness,

[0051] The area (R2) of the second peripheral surface (6a) carrying the powdered electrode mixture (8) is smaller than the area (R1) of the first peripheral surface (4a) carrying the powdered electrode mixture (8).

[0052] [Second Item]

[0053] The composite plate forming device (1) as described in the first item,

[0054] The electrode mixture (8) contains an electrode active material and a binder component, and the content of the binder component is 10% by mass or less relative to the total mass of the electrode mixture (8).

[0055] [Third Item]

[0056] The composite sheet forming device (1) as described in the first item or the second item,

[0057] A shielding member (14) is also provided for shielding a portion of the second peripheral surface (6a) exposed in the storage portion (2) from the electrode mixture (8) in the storage portion (2).

[0058] [Fourth Item]

[0059] The composite plate forming device (1) as described in the third item,

[0060] The surface of the shielding member (14) has a third surface roughness that is lower than the first surface roughness.

[0061] [Fifth Item]

[0062] The composite sheet forming device (1) as described in any one of the first to fourth items,

[0063] The second forming roller (6) supports and transports the composite plate (10) with a second circumferential surface (6a).

[0064] The composite sheet forming device (1) further comprises a stretching roller (12) which is adjacent to the second forming roller (6) at a predetermined interval and stretches the composite sheet (10) passing through the gap between the composite sheet and the second forming roller (6).

[0065] Industrial applicability

[0066] The present disclosure can be utilized in a composite plate forming device.

[0067] Description of Reference Numerals

[0068] 1. Mixture plate forming device, 2. Accumulation unit, 4. First forming roller, 4a. First peripheral surface, 6. Second forming roller, 6a. Second peripheral surface, 8. Electrode mixture, 10. Mixture plate, 12. Stretching roller, 14. Shielding member.

Claims

1. A composite plate forming device comprising: A storage area for powdered electrode mixture, and The first and second forming rollers are adjacent to each other with a predetermined interval therebetween, and the electrode mixture in the reservoir is supported on a first circumferential surface of the first forming roller and a second circumferential surface of the second forming roller and supplied to a gap between the two rollers, thereby compressing the electrode mixture into a plate shape to form a mixture plate. The first peripheral surface has a first surface roughness, The second peripheral surface has a second surface roughness greater than the first surface roughness, The area of ​​the second peripheral surface supporting the powdered electrode mixture is smaller than the area of ​​the first peripheral surface supporting the powdered electrode mixture.

2. The composite plate forming device according to claim 1, The electrode mixture contains an electrode active material and a binding component, and the content of the binding component is 10% by mass or less relative to the total mass of the electrode mixture.

3. The composite plate forming device according to claim 1 or 2, A shielding member is provided that shields a portion of the second peripheral surface exposed in the reservoir from the electrode mixture in the reservoir.

4. The composite plate forming device according to claim 3, The surface of the shielding member has a third surface roughness that is lower than the first surface roughness.

5. The composite plate forming device according to claim 1 or 2, The second forming roller supports and transports the composite plate with the second circumferential surface. The composite sheet forming device includes a stretching roller adjacent to the second forming roller with a predetermined interval therebetween, and stretching the composite sheet passing through the gap between the second forming roller and the composite sheet.

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