Patent Application
20210245302
The present invention relates to an epoch-making original sheet dividing method that enables an original sheet for producing an electrode sheet used in a lithium secondary battery, a lithium capacitor, an electric double layer capacitor, and the like, to be divided into a plurality of sections with a laser beam, while the original sheet is being moved, without dust during being cut and without occurrence of burrs at cut end faces, and a dividing mechanism and a dividing apparatus therefor.
Nonaqueous electrolytic solution secondary batteries typified by lithium ion secondary batteries have been used in small electric apparatuses such as mobile phones and personal computers and in various large electric components such as electrical storage devices of hybrid or electric vehicles, since these secondary batteries have the merit of having a high energy density. Electrode assemblies that are main internal structures of lithium ion secondary batteries include a wound type in which a separator and positive and negative electrode bands each having an active material applied to a metal foil are stacked and wound, and a lamination type in which separators and positive and negative electrode sheets each obtained by cutting an original sheet into a rectangular shape are alternately laminated. The above structures are also the same in lithium capacitors and electric double layer capacitors.
These electrode assemblies are configured according to the sizes of electric components to be used. Meanwhile, an original sheet that is a raw material for the electrode assemblies includes: an electrode portion in which a positive or negative active material is applied to one surface or both surfaces of a wide metal foil such as aluminum or copper over the substantially entire width, in the form of a band, and in a longitudinal direction in terms of productivity; and non-electrode portions (referred to as ear portions) that are provided at both sides of the electrode portion and in which no active material is applied. In general, the original sheet is wound in the form of a roll.
A conventional dividing apparatus slits a wide original sheet into a required width according to use, for example, with a slitter having a pair of upper and lower disc-shaped blades (Patent Literature 1).
However, when the conventional dividing apparatus slits, with the disc-shaped slitter blades, an original sheet on which a hard active material is applied, the cutting edges of the blades is gradually worn by the hard active material, so that sharp burrs easily occur at cut end faces, that is, on the surface of the original sheet, in the cutting direction. Regarding such a defect, the following problems have been pointed out.
When the above slit narrow original sheet is used to produce a wound type assembly in which a separator and positive and negative electrode bands are stacked and wound or a lamination type assembly in which separators and positive and negative electrode sheets each obtained by cutting an original sheet into a rectangular shape are alternately laminated, and the produced assembly is used as an electrode assembly of a secondary battery, the battery slightly and repeatedly expands and contracts, due to charging and discharging, to slightly and gradually increase the volume thereof. Thus, the burrs may repeatedly damage the separator, which is an insulating film, to cause flaws thereon to grow, or the burrs may grow, due to the above charging and discharging, to break through the separator to cause insulation breakdown, which causes trouble.
In addition to the above, in the case of cutting with blades, the conventional dividing apparatus requires periodical maintenance because of the wear as described above, and the apparatus has to be stopped for replacing the blades each time maintenance is performed, which becomes an obstacle to improvement of productivity.
As a solution to such problems, use of a laser beam has been proposed. In the case of cutting an original sheet by applying a laser beam to the original sheet while the original sheet is being moved, an irradiation spot of the laser beam moves on a cutting line. At the irradiation spot, the original sheet instantaneously melts in a small range. Then, when the irradiation spot has moved from one point on the cutting line to the next irradiation position, the previous melting portion instantaneously becomes solidified due to its heat being taken by the surroundings, so that the cut portion becomes rejoined. As a result, the original sheet is not sufficiently cut, and its appearance is similar to that in the case where the laser beam merely runs over the original sheet.
Therefore, in order to avoid the rejoining due to the solidification, the conventional dividing apparatus using a laser beam is configured to spray high-pressure assist air to the irradiation spot of the laser beam to instantaneously blow away the melting material (Non-Patent Literature 1).
Accordingly, in the case of laser cutting, in order to avoid the rejoining due to the solidification, the high-pressure assist air is sprayed to the irradiation spot of the laser beam to instantaneously blow away the melting material.
As described above, in the case of spraying the high-pressure assist air to the irradiation spot of the laser beam to instantaneously blow away the melting material, the blown-away melting material scatters as fine particles to the surrounding area to adhere to the original sheet. When the above electronic component is produced by using the original sheet to which the fine particles have adhered, the adhering particles break the separator of the assembly during use of the electronic component to cause insulation breakdown, causing the same trouble as with the burrs.
This point also applies to the case of suction. When the original sheet is perforated with the laser beam, air is immediately sucked from the hole toward a suction hole at the back side of the original sheet. At this time, the material that is melted during cutting is entrained in the air and sucked into the suction hole. However, an external force in the suction direction is momentarily applied to the melting material at start of the suction, so that part of the material scatters as fine dust to the surrounding area to adhere to the original sheet, causing the above trouble.
[PTL 1] Japanese Laid-Open Utility Model Publication No. 7-37595
[PTL 2] Japanese Laid-Open Patent Publication No. 2007-14993
[NPL 1] http://www.monozukuri.org/mono/db-dmrc/laser-cut/kiso/
In the invention of cited literature 2, a focal length or the effective aperture of a condensing lens is set to a predetermined condition, and an original sheet that is being continuously fed is cut with a laser beam. However, as described above, the original sheet cannot be cut only with the laser beam. Thus, assist gas has to be used as disclosed in Non-Patent Literature 1. With this method, cutting dust scatters to the surrounding area as described above.
An object of the present invention is to provide a method that enables an original sheet to be divided without scattering cutting dust, unlike such conventional art, and a dividing mechanism and a dividing apparatus therefor.
An invention method recited in claim 1 is an original sheet dividing method for cutting an original sheet 1 having an active material layer applied to at least one surface of a long metal foil 4, with a laser beam L in a longitudinal direction, the original sheet dividing method including:
The above case includes a case where the moving direction of the other original sheet 1t agrees with the moving direction of the original sheet 1 before division and only the moving direction of the one divided original sheet 1s is caused to be upward or downward relative to the moving direction of the other original sheet 1t, and a case where the one divided original sheet 1s is moved upward relative to the moving direction of the original sheet 1 before division and the other original sheet 1t is moved downward relative to the moving direction of the original sheet 1 before division. A separation angle θ occurs between the original sheets 1s and 1t.
Accordingly, a maintenance-free continuous operation is enabled to be performed, and the original sheet 1 can be assuredly divided at a high speed into a plurality of the narrow original sheets 1s and 1t with the laser beam L without occurrence of burrs at cut faces and without scattering cutting dust to the surrounding area.
In the invention method recited in claim 2, in claim 1, the original sheet 1 is cut while the laser beam L is caused to reciprocate along a running direction of the original sheet 1.
While the laser beam L moves in the same direction as the original sheet 1, the relative moving speed of the laser beam L to the original sheet 1 decreases, so that irradiation energy per unit time increases. As a result, the original sheet 1 is cut deeply.
On the other hand, while the laser beam L moves in a direction opposite to that of the original sheet 1, the relative moving speed of the laser beam L to the original sheet 1 increases, so that the irradiation energy per unit time decreases. Accordingly, a melting material adhering to a cut portion is heated by the laser beam L to be rounded, and the cut portion is finished with a clean cut face. In this case, output of the laser beam L is adjusted such that the original sheet 1 is divided as a result of a plurality of times of reciprocation of the laser beam L.
In the invention method recited in claim 3, in claim 1 or 2,
By using the separating member 40, assured division is enabled.
An invention recited in claim 4 is an original sheet dividing mechanism 110 for cutting a running original sheet 1 having an active material layer applied to at least one surface of a long metal foil 4, with a laser beam L in a longitudinal direction, the original sheet dividing mechanism 110 including:
Here, the separating member 40 includes two members, that is, a member configured to raise (press down) only the one divided original sheet 1s (1t) as shown in
An invention recited in claim 5 is an original sheet dividing mechanism 110 for cutting a running original sheet 1 having an active material layer applied to at least one surface of a long metal foil 4, with a laser beam L in a longitudinal direction, the original sheet dividing mechanism 110 including:
In this case, as shown in
In the invention recited in claim 6, the separating member 40 of claim 4 or 5 is provided so as to move toward and away from the irradiation point P. Accordingly, the separation angle θ of the divided original sheets 1s and 1t adjacent to each other at the irradiation point P can be adjusted.
In the invention recited in claim 7, the separating member 40 of claim 4 or 5 is composed of a roller configured to rotate in contact with the divided original sheets 1s and 1t.
In the invention recited in claim 8, the separating member 40 of claim 4 or 5 is composed of a plate member having a cross-section parallel to a running direction of the original sheet 1, the cross-section having a thickness that gradually decreases as distance to an irradiation point P side decreases.
An invention recited in claim 9 is an original sheet dividing apparatus 100 for cutting a running original sheet 1 having an active material layer applied to at least one surface of a long metal foil 4, with a laser beam L in a longitudinal direction, the original sheet dividing apparatus 100 including:
According to the present invention, the original sheet can be cut while being conveyed, and a continuous operation can be enabled to be performed without occurrence of burrs at cut end faces, without scattering cutting dust, and without time and effort for component replacement.
Hereinafter, the present invention will be described by means of illustrated embodiments. As shown in
An applied original sheet 1 in
The metal foil 4 is, for example, a copper foil or an aluminum foil. The electrode paste contains an active material, a binder, and a solvent, etc. Examples of the active material include a positive electrode active material and a negative electrode active material.
The positive electrode active material contains, for example, a composite oxide, metal lithium, and sulfur, etc.
The negative electrode active material includes, for example, various carbons, an alkali metal such as lithium and sodium, a metal compound, a metal oxide of SiOx, and a boron-added carbon.
As the binder, a resin such as fluorine-containing resin, thermoplastic resin, and imide resin is used.
The original sheet supply portion 10 includes a feed-side servomotor 11 that is a feeding side, an original sheet feed shaft 12 connected to the feed-side servomotor 11, and an original sheet support stand (not shown). The original sheet 1 that is in the form of a roll and is suspended by the original sheet support stand is mounted to the original sheet feed shaft 12 and fed by the feed-side servomotor 11.
Next to the original sheet supply portion 10, the feed-side rollers 20a to 20n are installed. The feed-side rollers 20a to 20n convey the original sheet 1 fed from the original sheet supply portion 10 while keeping the original sheet 1 horizontal, and a roller 20d is incorporated in the middle as a publicly-known original sheet-side dancing roller for adjusting the tension of the original sheet 1 being fed. At the rearmost end of the feed-side rollers 20a to 20n, a pair of upper and lower feed-side rollers 20m and 20n are installed and serve to hold the sent original sheet 1 therebetween from above and below and send the original sheet 1 to a division region for the next process while keeping the original sheet 1 horizontal.
The downstream side of the feed-side rollers 20m and 20n at the rearmost end is the division region for the original sheet 1, and the laser emission device 30 is installed directly above the division region. In the drawing, the single laser emission device 30 is depicted, but a plurality of laser emission devices (not shown) can be installed according to the number of sections into which the original sheet 1 is to be divided. The laser emission device 30 divides the original sheet 1 merely into two sections, and thus a laser beam L thereof only needs to be fixed. However, the laser emission device 30 may be a galvano type laser emission device capable of moving the laser beam L as described later.
In the drawings, an irradiation point of the laser emission device 30 is shown by P. The irradiation point P is set to be close to and immediately rearward of the upper feed-side roller 20m at the rearmost end. The laser beam L may be emitted in a single mode, but a second-fourth harmonic laser (green laser), a picosecond laser, and a femtosecond laser, etc., which have higher output, may be used for reducing thermal effects on the active material.
To assuredly separate the original sheets 1s and 1t from each other, it is important that a portion melted at the irradiation point P is separated before becoming rejoined. For this, it is important that, at the downstream side of the irradiation point P, a moving direction of the one divided original sheet 1s is caused to be upward or downward relative to a moving direction of the other original sheet 1t and the divided original sheets 1s and 1t adjacent to each other at the irradiation point P are vertically separated from each other.
The above case includes a case (
The separating member 40 may not be used for the vertical separation, and the divided original sheets 1s and 1t may be taken up such that conveying directions of the original sheets 1s and 1t are displaced vertically relative to each other. However, by using the separating member 40 that will be described next, the original sheets 1s and 1t can be assuredly separated from each other.
The separating member 40 may be any member as long as the member vertically separates the original sheets 1s and 1t from each other before a melting material that is melted by the laser beam L at the irradiation point P becomes solidified, thereby preventing rejoining. In later-described examples, a roller or a sliding plate is used. As a matter of course, the separating member 40 is not limited to the roller and the sliding plate as long as the separating member 40 performs the above operation. The separating member 40 is movable toward and away from the irradiation point P so as to be able to change a division angle θ of the divided left and right original sheets 1s and 1t that are separated by the separating member 40.
In the former case, as shown in
In
The left separating roller 40a is configured to be brought into contact with the lower surface of the divided original sheet 1s to raise the divided original sheet 1s. Meanwhile, the right separating roller 40b is configured to be brought into contact with the upper surface of the divided original sheet 1t to press down the divided original sheet 1s. The illustrated separating rollers 40a and 40b are coaxial with each other, and rotate in contact with the divided original sheets 1s and 1t, respectively. Thus, the separating rollers 40a and 40b rotate in the moving direction of the divided original sheets 1s and 1t. The separating rollers 40a and 40b are provided so as to be rotatable in directions opposite to each other.
The illustrated separating rollers 40a and 40b are coaxial with each other. However, as a matter of course, the separating rollers 40a and 40b are not limited thereto, and may be mounted on different shafts so as to be rotatable in directions opposite to each other.
In the case where the number of the divided sections is equal to or larger than 3, adjacent separating rollers are set alternately such that one of the separating rollers raises the divided original sheet and the other separating roller presses down the divided original sheet so as to form a division angle θ between the adjacent divided original sheets. The plate-like separating member 40 in
The reception-side rollers 50a to 50n are provided at the downstream side of the separating rollers 40a and 40b. The reception-side rollers 50a to 50n send the divided original sheets 1s and 1t to the original sheet take-up portion 60 while keeping the divided original sheets 1s and 1t horizontal.
In the case where the divided original sheets 1s and 1t are raised and pressed down by the same amount by the separating rollers 40a and 40b as shown in
In the case where, as shown in
A take-up-side dancing roller is not installed as one of the illustrated reception-side rollers 50a to 50n in the drawing, but may be provided as necessary.
The original sheet take-up portion 60 is installed subsequent to the reception-side rollers 50a to 50n, and the divided original sheets 1s and 1t are taken up on a take-up shaft 62. A take-up servomotor 61 is connected to the take-up shaft 62 and rotates in synchronization with the feeding servomotor 11.
Next, operation of a first embodiment of the apparatus 100 will be described. The original sheet 1 is mounted on the original sheet feed shaft 12 as shown in
When the apparatus 100 is actuated in this state, the feed-side servomotor 11 operates to feed the original sheet 1 at a predetermined speed. At the same time, the take-up servomotor 61 rotates in synchronization with the feed-side servomotor 11, so that the divided original sheets 1s and 1t are taken up.
In the division region, the laser beam L is emitted from the laser emission device 30 toward the original sheet 1, and the active material and the metal foil 4 of the original sheet 1 instantaneously melt at the irradiation point P. In the present invention, during emission of the laser beam L, assist gas is not sprayed toward the irradiation point P as in the conventional art, and thus the melting material is not blown away and stays at the irradiation point P.
Since the original sheet 1 is continuously fed, the irradiation point P linearly moves in accordance with the movement of the original sheet 1. Owing to the action of the pair of left and right separating rollers 40a and 40b described above, the adjacent divided left and right original sheets 1s and 1t are vertically separated from each other at the irradiation point P simultaneously with the melting. Thus, even when the melting material staying at the irradiation point P becomes solidified at the next moment at which the irradiation point P moves, the melting material cannot become rejoined, and remains at cut end faces and becomes solidified. As a result, the original sheets 1s and 1t are assuredly separated from each other. In addition, at this time, the cut ends are formed by fusion cutting, and the melting material becomes solidified at the cut ends in a round shape due to its surface tension as described above. Accordingly, burrs, which occur as a result of cutting with a blade, do not occur. When the melting material is blown away by assist gas as in the conventional art, the melting material that remains at the cut end faces is pulled by the blown-away melting material and remains as sharp thorns like icicles. However, in the present invention, such a phenomenon does not occur.
Moreover, since the melting material remains at the cut ends in a round shape, cutting dust, which occurs in the case of using assist gas, does not occur.
Since the original sheet 1 is continuously fed, the original sheet 1 is continuously divided as long as the laser beam L is emitted. The divided original sheets 1s and 1t are taken up on the take-up shaft 62 as described above. At this time, a dancing roller may be provided as one of the reception-side rollers 50a to 50n for tension adjustment, although not shown.
Next, a second embodiment will be described (
Meanwhile, a right portion of the separating member 40 is configured to be brought into sliding contact with the upper surface of the divided right original sheet 1t to press down the divided original sheet 1s. This portion is a pressing-down portion 40b. The separating member 40 is movable toward and away from the irradiation point P so as to be able to change the division angle θ of the divided left and right original sheets 1s and 1t. Since the separating member 40 is brought into sliding contact with the divided original sheets 1s and 1t as described above, the separating member 40 is preferably a hard resin having a low coefficient of friction (e.g., tetrafluoroethylene resin). The separating member 40 is provided so as to cover the entire length of the original sheet 1, but may be shorter than the width of the original sheet 1 as long as the separating member 40 does not impede feeding of the original sheet 1.
Next, a third embodiment of the present invention will be described with reference to
Next, another method for dividing the original sheet 1 of the present invention will be described with reference to
Then, when the active material layer of the lower surface portion 1d is melted, the left and right original sheets 1s and 1t are pulled vertically to be separated due to movement of the original sheet 1 toward the separating member 40, simultaneously with the melting, before rejoining of the melting material, so that the original sheet 1 is assuredly cut.
Here, the laser beam L reciprocates along the moving direction of the original sheet 1 with the angle α. When the laser beam L reciprocates at a constant angular velocity (the running speed on the original sheet 1 is also substantially the same speed), while the laser beam L moves in the same direction as the moving direction of the original sheet 1, the relative speed of the laser beam L to the original sheet 1 is decreased by the moving speed of the original sheet 1, and energy inputted by the applied laser beam L increases, so that the original sheet 1 is fusion-cut thin; and, on the other hand, while the laser beam L moves in a direction opposite to the moving direction of the original sheet 1, the relative speed of the laser beam L to the original sheet 1 is increased by an amount corresponding to the movement of the original sheet 1, and the energy inputted by the applied laser beam L decreases, so that the melting material is heated and shaped to be rounded. Accordingly, cleaner cut faces can be obtained.
The output of the laser emission device 30 can be freely changed by a program. Thus, it is possible to make the output for the active material layer different from that for the metal foil 4, and it is possible to cause the laser beam L to run on the cutting line in zigzag or while drawing a loop, although not shown. This point is applicable to the case where the laser beam L is not caused to reciprocate along the moving direction of the original sheet 1 as described above. That is, the laser beam L can be caused to zigzag or draw a loop by swinging the laser beam L laterally relative to the irradiation point P. Accordingly, the melting width of the irradiation point P can be increased.
As described above, by vertically spreading the melted original sheet 1 at the irradiation point P of the laser beam L, rejoining at the time of solidification of the melting material can be physically avoided, and the original sheet 1 can be assuredly divided while running.
1 original sheet
1
a active material layer (electrode portion)
1
b ear portion
1
d lower surface portion
1
s,
1
t divided original sheet
1
u front surface portion
4 metal foil
5 tab
10 original sheet supply portion
11 feeding servomotor
12 original sheet feed shaft
20
a to 20n feed-side roller
20
d original sheet-side dancing roller
30 laser emission device
40 separating member
40
a,
40
a′ raising-side member (roller, portion, large-diameter portion)
40
b pressing-side member (roller, portion, small-diameter portion)
40
c holding roller
50
a to 50n reception-side roller
60 original sheet take-up portion
61 take-up servomotor
62 take-up shaft
100 original sheet dividing apparatus
110 dividing mechanism
L laser beam
P irradiation point
θ separation angle
α oscillation angle of laser beam
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2016/000042 | 1/6/2016 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 20200276670 A1 | Sep 2020 | US |
