Device for rolling a metal lithium band

Abstract

A device for manufacturing a lithium band including a rolling area including two rolling cylinders, a feed-in area including a device for feeding in the rolling area with a lithium band with a first thickness, a device for feeding in two films interposed between the lithium band with a first thickness and a rolling cylinder, and a storage area including a device for collecting a lithium band having a second thickness. The lithium band with a second thickness is tensioned and rolls ensure a separation of each film off the surface of one of the rolling cylinders in a separation area located beyond a horizontal plane passing through the axis of rotation of the rolling cylinder and located opposite to the other rolling cylinder.

Claims

1. A device for rolling a metal lithium band, the device comprising: at least two rolling cylinders, located in a rolling area, between which the metal lithium band, having a first thickness, passes, each rolling cylinder rotating about an axis of rotation, first means for feeding, into the rolling area, the metal lithium band with the first thickness, second means for feeding, into the rolling area, two plastic material films so that each plastic material film is interposed between the metal lithium band and one of the rolling cylinders, the first and second means for feeding each including a roller, and means for collecting the metal lithium band in a storage area, the metal lithium band having a second thickness smaller than the first thickness after passing through the at least two rolling cylinders, wherein the device further includes at least one roller configured to tension the metal lithium band, and separation means including a roller, for each plastic material film, configured to separate each plastic material film off a surface of one rolling cylinder of the at least two rolling cylinders in the storage area side in a separation area located beyond a horizontal plane passing through the axis of rotation of the one rolling cylinder, and located opposite another of the at least two rolling cylinders, said separation area including said horizontal plane.

2. The rolling device according to claim 1, wherein the at least one roller configured to tension the metal lithium band is configured to apply a tension per unit surface area of the cross-section of the film with a second thickness between 1 N/mm.sup.2 and 1.4 N/mm.sup.2.

3. The rolling device according to claim 1, further comprising means for applying a tension to the plastic material films at least in the storage area, said means for applying the tension being configured to apply a tension per unit width of the plastic material films between 0.1 N/mm and 0.6 N/mm.

4. The rolling device according to claim 1, wherein each roller of the separation means has an axis of rotation that is parallel to that of the associated rolling cylinder of the at least two rolling cylinders and whose axis of rotation is located in the separation area.

5. The rolling device according to claim 4, wherein position of each roller of the separation means is modifiable.

6. The rolling device according to claim 1, wherein the plastic material films include a silicone coating at least over a face to be in contact with the metal lithium band.

7. The rolling device according to claim 1, wherein the plastic material films are made of poly(ethylene terephthalate).

8. The rolling device according to claim 1, wherein the plastic material films are in a form of endless belts, a tension of the plastic material films being set by a tensioner roll.

9. The rolling device according to claim 1, further comprising a spindle around which the lithium metal band having the second thickness is wound, and at least one roller configured to simultaneously wind a plastic material film so as to avoid sticking of the lithium metal band on itself.

10. The rolling device according to claim 1, further comprising two actuators configured to drive in rotation each of the at least two rolling cylinders separately, and control circuitry configured to control the two actuators so that the at least two rolling cylinders rotate at different speeds.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will be better understood based on the following description and the appended drawings wherein:

(2) FIG. 1 is a schematic representation of a device for rolling a lithium film by a rolling process,

(3) FIG. 2 is a detail view of a device for rolling a metal lithium film according to one embodiment,

(4) FIG. 3 is a detail view of a device for rolling a metal lithium film according to another embodiment.

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

(5) In FIG. 1, is shown a device for rolling a lithium film, also called band, including an area ZL for rolling the lithium, an area ZA for feeding in lithium upstream of the rolling area ZL, an area ZS for storing the lithium downstream of the rolling area ZL.

(6) In the present application, the upstream-downstream direction should be understood from the feed-in area towards the storage area.

(7) In the present application, the expressions lithium film and metal lithium film refer to a film made of lithium or of a lithium alloy, comprising for example and without limitation magnesium and/or aluminium . . . .

(8) The rolling area includes at least two rolling cylinders 2.1, 2.2 opposite each other, the opposing external surfaces of the cylinders being separated by the desired thickness of the lithium film. Several pairs of rolling cylinders disposed one after another from upstream to downstream may be implemented for example to progressively lower the thickness of the lithium film. The rolling cylinders are driven in rotation by actuators, such as electric motors.

(9) The plane in which the lithium film runs between the two rolling cylinders will be called rolling plane.

(10) The feed-in area ZA includes a dispenser 4 of a metal lithium film FL1 with a first thickness e1. For example, the film is obtained by extrusion and as for example a thickness in the range of 200 ?m. The film is wound on the dispenser. Rolls and guides generally implemented in rolling mills ensure guidance of the film FL1 with a first thickness up to the rolling area ZL.

(11) The feed-in area ZA also includes a dispenser 6 of a first plastic material film FP1, a portion of the film FP1 being intended to be interposed between the rolling cylinder 2.1 and the lithium film FL1 with a first thickness and to be in contact with the rolling cylinder 2. The feed-in area ZA also includes a dispenser 8 of a second plastic material film FP2, the film FP2 being intended to be interposed between the rolling cylinder 2.2 and the lithium film FL1 with a first thickness. Rolls and guides may be implemented to guide the plastic material films FP1 and FP2 up to the rolling area.

(12) Each plastic material film FP1, FP2 is associated to a rolling cylinder 2.1, 2.2 respectively. The storage area ZS includes a spindle 10 on which the metal lithium film FL1 with a second thickness smaller than the first thickness is wound, a spindle 12 on which the plastic material film FP1 is wound and a spindle 14 on which the plastic material film FP2 is wound. Rolls and guides may be implemented to guide the lithium films FL1 with a second thickness, the plastic material films FP1 and FP2 from the rolling area towards their storage spindle.

(13) The dispensers and the spindles are driven in rotation by actuators, such as electric motors.

(14) The elements of the feed-in area and of the storage area, in particular the dispenser 4 and the dispensers 6, 8 and the spindles 12, 14, are controlled so that the lithium film at the input of the rolling mill and the plastic material films FP1, FP2 have close or equal speeds of displacement. The speed of the spindle 10 of the lithium film at the output of the rolling mill is different from the speed of the dispensers 4, 6 and 8 and of the spindles 12, 14.

(15) The axes of the spindles, rolls, cylinders are parallel to each other and normal to the direction of displacement of the films.

(16) Advantageously, a plastic material film is wound at the same time as the film FL1 with a second thickness on the spindle 10 so that the windings of the film FL1 with a second thickness are separated by a plastic material film, for example made of polypropylene.

(17) As example for a lithium film comprised between 60 mm and 100 mm, the tightening force exerted on the lithium strip by the rolling cylinders is for example comprise between 10 kN and 23 kN. For example, this force is exerted by the rolling cylinder 2.1.

(18) In FIG. 2, is shown a detail view of a device D1 for manufacturing a metal lithium film according to a first embodiment.

(19) In addition to the elements of the device of FIG. 1, the device D1 comprises separation means 16 allowing setting the separation area between the film FP1 and the external surface of its associated rolling cylinder 2.1, and separation means allowing setting the separation area between the film FP2 and its associated rolling cylinder 2.2.

(20) The means for separating the films FP1, FP2 being similar or identical, only the means 16 will be described in detail.

(21) The separation area is materialised by a separation line LS1 that is formed by a generatrix of the rolling cylinder. In FIG. 2, this line is symbolised by a point.

(22) Indeed, the inventors have determined that by setting the position of the separation line in a given area, a lithium film FL1 with a second thickness with a thickness of a few tens of ?m, for example between 50 ?m and 30 ?m, could be obtained while limiting the risks of tearing of the film FL1 with a second thickness, and without the need for bringing in liquid at the level of the rolling cylinders.

(23) The inventors have determined that a separation line lying in an area located above a horizontal plane PH passing through the axis of rotation X1 of the rolling cylinder 2.1 allowed facilitating the detachment between the plastic material film and the lithium film, thereby substantially reducing the risk of tearing of a lithium film FL1 with a second thickness with a thickness of a few tens of ?m. The horizontal plane PH is parallel to the rolling plane.

(24) Advantageously, the area is also delimited by a vertical plane PV passing through the axis of rotation of the rolling cylinder 2.1. Preferably, the separation line is located in an area delimited between a plane directed at 45? with respect to the vertical plane and the vertical plane in the counterclockwise direction.

(25) In the represented example and advantageously, the means 16 include a roll 20 disposed between the rolling cylinder 2.1 and the spindle 12 on which the plastic material film FP1 is wound, and whose axis of rotation X2 and in the horizontal plane PH. The roll 20 is disposed on the route of the film FP1 between the rolling cylinder and the spindle 12 so that the separation line LS1 is in the plane PH. It is considered that the separation line LS1 and the axis of rotation of the roll 20 are substantially in the same plane containing the axis of rotation of the rolling cylinder.

(26) The plastic material film FP1 runs between the rolling cylinder 2.1 and the roll 20.

(27) Alternatively, the spindle 12 and the rolls and guides of the plastic material film FP1 in the storage area are disposed with respect to the rolling cylinder 2.1 so that the separation line LS1 is in the plane PH.

(28) The implementation of a roll 20 allows setting the position of the line LS1 more accurately.

(29) For example, the distance separating the surface of the rolling cylinder and the surface of the roll is comprised between 1 mm and 4 mm.

(30) The lithium film FL1 with a second thickness is kept under mechanical tension. Preferably, a specific tension is between 1 N/mm.sup.2 of lithium film section and 1.4 N/mm.sup.2 of lithium film section is applied. A specific tension in the range of 1 N/mm.sup.2 is preferably applied to a pure or almost pure lithium film, and a specific tension in the range of 1.4 N/mm.sup.2 is preferably applied to a lithium alloy film.

(31) For example, for a lithium film having a section of 3 mm.sup.2 (for example 60 mm wide and 50 ?m thick), the applied force is comprised between 3 N (for a specific tension of 1 N/mm.sup.2) and 4.2 N (for a specific tension of 1.4 N/mm.sup.2).

(32) The mechanical tension applied to the plastic material films FP1 and FP2 downstream of the rolling area depends on the width of the films. Preferably, the specific tension is comprised between 0.1 N/mm and 0.6 N/mm, preferably this tension is comprised between 0.2 N/mm and 0.3 N/mm, which facilitates even more the detachment and contributes to the suppression of the apparition of tearing of the lithium film FL1 with a second thickness.

(33) For example, the tension of the film FL1 with a second thickness and the tensions of the plastic material films downstream of the rolling area are set by adjusting the speed and the torque of motors.

(34) Quite advantageously, the plastic material films include, at least over a face intended to come into contact with the lithium film, a silicone coating reducing the risks of sticking between the lithium and the plastic material film. For example, the coating has a thickness of 100 nm.

(35) Silicone has the advantage of leaving no residue after rolling. Indeed, no silicone trace has been detected on the film FL1 with a second thickness.

(36) For example, the plastic material films are made of poly(ethylene terephthalate) covered with a solid silicone layer, for example of a few tens of nanometres, over at least one face. For example, the thickness of the plastic material films is comprised between 15 ?m and 100 ?m.

(37) Advantageously, the roll 20 has a modifiable position with respect to the rolling cylinder in particular its angular position, allowing adapting the device easily to the manufacture of films with different thicknesses while limiting the risks of tearing.

(38) Alternatively, the plastic material films consist of closed loops forming endless belts, which allows avoiding having to manage the plastic material film length remaining in the feed-in area. For example, the tension of the plastic material films is set by means of a tensioner roll.

(39) The invention allows reaching lithium film thicknesses of 30 ?m without any tearing. In contrast, it has been noticed that by placing the roll 20 underneath the horizontal plane PH, films having at least a thickness of 60 ?m were torn.

(40) In FIG. 3, is shown another example of a device for rolling a lithium film which differs from that of FIG. 2, in that the separation line of the plastic material film and of the associated rolling cylinder is located substantially in a vertical plane passing through the axis of rotation of the rolling cylinder.

(41) In the represented example and advantageously, the means 116 include a roll 120 which is disposed between the rolling cylinder 2.1 and the spindle 12 on which the plastic material film FP1 is wound, and whose axis of rotation X102 is in the vertical plane PV. The roll 120 is disposed on the route of the film FP1 between the rolling cylinder and the spindle 12 so that the separation line LS101 is substantially in the plane PV. It is considered that the separation line LS101 and the axis of rotation of the roll 120 are substantially in the same plane containing the axis of rotation of the rolling cylinder.

(42) The separation line of each of the plastic material films could be located beyond the vertical plane when considering the counterclockwise direction. The location of the separation line could depend on the relative arrangement of the different elements of the rolling device and on the available space.

(43) In the examples of FIGS. 2 and 3, the positionings of the separation rolls for the two plastic material films are symmetrical with respect to the rolling plane.

(44) Alternatively, their positioning could be asymmetrical, and the separation lines could also be located asymmetrically with respect to the rolling plane.

(45) Also, different means for setting the location of the separation line between the plastic material film and the associated rolling cylinder could be different between the plastic material films.

(46) In a particularly advantageous operating mode, the actuators of each of the rolling cylinders are driven independently of each other so as to make them rotate at different speeds, in order to create a speed difference between them, which allows promoting sticking of the lithium film on the upper or lower plastic film.

(47) Preferably, the difference between the speed V1 of the upper rolling cylinder 2.1 and the speed V2 of the lower rolling cylinder 2.2 is comprised between:
?30%?(V2?V1)/V1?30%.