Device for rolling a metal lithium ribbon

Abstract

A device for rolling a metal lithium strip, comprising a rolling zone (ZL), a feeding zone and a storage zone, the rolling zone comprising two cylinders (2.1, 2.2), the feeding zone comprising means for feeding a lithium strip (FL1) having a first thickness into the rolling zone, means for feeding two films interposed between the lithium strip having the first thickness and the cylinders (2.1, 2.2), the storage zone comprising means for collecting a lithium strip (FL1) having a second thickness. The lithium strip (FL1) having the second thickness is tensioned and a roller (20) ensures the separation of each film (FP1, FP2) from the surface of one of the cylinders (2.1, 2.2) in a separation zone, which exceeds the horizontal plane (PH) and is opposite the other cylinder, the horizontal plane passing through the rotation axis of the cylinders.

Description

Technical Field

[0001] This invention relates to an apparatus for rolling lithium metal strips. Background Technology

[0002] To date, lithium-ion technology has allowed for an energy density of 250 Wh / kg, which experts consider a small step forward. So-called "all-solid-state" technology appears to be the future of lithium-ion, especially with the use of metallic lithium at the anode. Indeed, this material boasts very high mass and volumetric energy densities, and if these technologies are developed, they could significantly increase the energy density of rechargeable batteries.

[0003] Therefore, one of the main concerns involves mastering the manufacturing process of lithium metal strips (which are currently widely used in lithium metal batteries) to limit energy density. Target thicknesses in the range of a few micrometers to tens of micrometers can be achieved through rolling mills.

[0004] Lithium metal is a ductile, viscous, and therefore highly fragile material, making the manufacture of strips tens of micrometers in diameter relatively complex. Therefore, it is necessary to optimize all rolling parameters to master the process and produce strips tens of micrometers in diameter.

[0005] Generally, the rollers are made of metal. To prevent lithium from adhering to the rollers, a polymer film is inserted between each roller and the metallic lithium. An example of such a manufacturing apparatus is described in document US3783666, in which an annular tape of polyethylene or polyvinyl chloride is wound around the rollers. This apparatus can manufacture metallic lithium films in the range of 250 micrometers.

[0006] Document EP0692831 describes an apparatus for rolling lithium strips that allows for thicknesses of tens of micrometers, but it requires the use of a rolling lubricant. Summary of the Invention

[0007] Therefore, the object of the present invention is to provide an apparatus for dry rolling of lithium metal strip, i.e., without the need for the input of any liquid lubricant.

[0008] The above objective is achieved by a rolling apparatus comprising: at least two rolls between which lithium metal is rolled; a device for supplying a thin film of lithium metal to the input end of a mill, the device being located upstream of the rolls; and a device for storing the thin film of lithium metal at the output end of the mill, the storage device being located downstream of the rolls. The apparatus applies tension to the lithium film at the output end of the mill, mechanically tautning the lithium film. The apparatus also includes a device for circulating two plastic films, the device being arranged to insert the plastic films between each roll and the lithium film, and to travel the films together with the lithium film.

[0009] The inventors have determined that when the separation angle between the film and the belt is within a specific range, it is possible to manufacture a lithium metal film with a second thickness (tens of micrometers) while simultaneously reducing or even suppressing the risk of film tearing, without the need for liquid lubricant. This angle range is achieved through the specific orientation of each plastic film downstream of the roller.

[0010] The specific orientation of the plastic film is such that the separation line between the plastic film and the lithium film lies in a region beyond a horizontal plane passing through the axis of rotation of the roller, which is in contact with the plastic film.

[0011] Without using lubricants that could contaminate metallic lithium, it is possible to obtain lithium films with a thickness of tens of micrometers (e.g., between 10 and 100 micrometers) that do not tear.

[0012] Advantageously, the separation line is located in the region between the horizontal plane and the vertical plane passing through the axis of rotation of the roller.

[0013] Preferably, the specific tension applied to the plastic film is between 0.1 N / mm and 0.6 N / mm, and more preferably, it is between 0.2 N / mm and 0.3 N / mm. Applying this specific tension (which is associated with the orientation of one or more plastic films relative to one or more rolling rolls) facilitates separation between the plastic film and the lithium film having a second thickness.

[0014] For example, the specific orientation of each plastic film is obtained by a roller whose axis of rotation is parallel to the axis of rotation of the roller, and the plastic film travels between the rollers.

[0015] Advantageously, the plastic film includes a silicone coating.

[0016] One objective of this application is an apparatus for rolling lithium metal strip, comprising a rolling region, a supply region, and a storage region. The rolling region includes at least two rollers, and a lithium strip having a first thickness is used to travel between the at least two rollers, each of the rollers rotating about a rotation axis. The supply region includes: means for supplying the lithium strip having the first thickness into the rolling region; and means for supplying two plastic films such that each plastic film is inserted between the lithium strip having the first thickness and a roller referred to as an associated roller. The storage region includes means for collecting lithium strip having a second thickness, the second thickness being less than the first thickness. The apparatus further includes means for tensioning the lithium strip having the second thickness and means configured to ensure that each plastic film is separated from the surface of one of the rollers on the storage region side, in a separation region, the separation region extending beyond a horizontal plane and opposite to another roller, the horizontal plane passing through the rotation axis of the rollers, the separation region including the horizontal plane (PH).

[0017] Preferably, the device for applying tension to the lithium strip having a second thickness is configured such that the tension applied to each unit surface area of ​​the cross-section of the film having a second thickness is between 1 N / mm² and 1.4 N / mm².

[0018] Preferably, the rolling apparatus includes a device configured to apply tension to a plastic film located at least in the storage area, the device being configured to apply a tension of between 0.1 N / mm and 0.6 N / mm per unit width of the plastic film.

[0019] Advantageously, for each plastic film, the separating device includes a roller whose axis of rotation is parallel to the axis of rotation of the associated roller, and the axis of rotation of the roller is located within the separating region.

[0020] Advantageously, the position of the roller in the separation area is changeable.

[0021] The plastic film includes a silicone coating on at least the surface that comes into contact with lithium.

[0022] For example, plastic films are made of polyethylene terephthalate.

[0023] The plastic film is in the form of an annular belt, and the tension of the annular belt is set by a tensioner roller.

[0024] According to another feature, the rolling apparatus includes in the storage area: a mandrel wound with a lithium strip having a second thickness; and a device for simultaneously winding a plastic film to prevent the lithium strip having the second thickness from adhering to the plastic film itself.

[0025] According to another feature, the rolling apparatus includes: two actuators for rotatably driving each roll respectively; and a control unit configured to control the two actuators to rotate the two rolls at different speeds (V1, V1). Attached Figure Description

[0026] The invention will be better understood based on the following description and accompanying drawings, in which:

[0027] Figure 1 This is a schematic diagram of an apparatus used to roll lithium thin films using a rolling process.

[0028] Figure 2 This is a detailed view of an apparatus for rolling a thin film of lithium metal according to one embodiment.

[0029] Figure 3 This is a detailed view of an apparatus for rolling a thin film of metallic lithium according to another embodiment. Detailed Implementation

[0030] exist Figure 1 The image shows an apparatus for rolling lithium films (also known as strips), including a region ZL for rolling lithium, a region ZA for supplying lithium upstream of the rolling region ZL, and a region ZS for storing lithium downstream of the rolling region ZL.

[0031] In this application, the upstream-downstream direction should be understood as from the supply area toward the storage area.

[0032] In this application, the terms "lithium thin film" and "metallic lithium thin film" refer to thin films made of lithium or lithium alloys, including, for example, but not limited to, magnesium and / or aluminum.

[0033] The rolling zone includes at least two opposing rollers 2.1, 2.2, whose opposing outer surfaces are separated by a lithium film of desired thickness. For example, several pairs of rollers may be arranged sequentially from upstream to downstream to gradually reduce the thickness of the lithium film. The rollers are rotated by an actuator such as an electric motor.

[0034] The plane in which the lithium film travels between the two rollers will be called the "rolling plane".

[0035] The supply zone ZA includes a distributor 4 for a thin lithium metal film FL1 with a first thickness e1. For example, the film is obtained by extrusion, and its thickness is, for example, in the range of 200 micrometers. The film is wound around the distributor. Rollers and guide members, typically used in rolling mills, ensure that the film FL1 with the first thickness is guided into the rolling zone ZL.

[0036] The supply area ZA also includes a distributor 6 for a first plastic film FP1, a portion of which is inserted between roller 2.1 and a lithium film FL1 of a first thickness and contacts roller 2. The supply area ZA also includes a distributor 8 for a second plastic film FP2, which is inserted between roller 2.2 and the lithium film FL1 of the first thickness. Rollers and guide members are used to guide the plastic films FP1 and FP2 into the rolling area.

[0037] Each plastic film FP1, FP2 is associated with rollers 2.1 and 2.2, respectively.

[0038] Storage area ZS includes mandrels 10, 12, and 14. A lithium metal film FL1 with a second thickness less than a first thickness is wound on mandrel 10, a plastic film FP1 is wound on mandrel 12, and a plastic film FP2 is wound on mandrel 14. Rollers and guide members can be used to guide the lithium film FL1, plastic films FP1 and FP2 with the second thickness from the rolling area toward their storage mandrels.

[0039] The distributor and spindle are driven to rotate by an actuator such as an electric motor.

[0040] The components in the supply and storage areas (particularly distributors 4, 6, and 8, and spindles 12 and 14) are controlled such that the lithium film and plastic films FP1 and FP at the mill input have approximately or equal displacement speeds. The speed of the lithium film spindle 10 at the mill output is different from the speeds of distributors 4, 6, and 8, and spindles 12 and 14.

[0041] The axes of the mandrel, roller, and cylinder are parallel to each other and perpendicular to the direction of film displacement.

[0042] Advantageously, the plastic film and the film FL1 having a second thickness are simultaneously wound on the mandrel 10, such that the roll of the film FL1 having a second thickness is separated by a plastic film, for example, made of polypropylene.

[0043] For example, for a lithium film between 60 mm and 100 mm, the clamping force applied to the lithium strip by the roller is, for example, between 10 kN and 23 kN. For example, this force is applied by roller 2.1.

[0044] Figure 2 The image shows a detailed view of an apparatus D1 for manufacturing a thin film of lithium metal according to a first embodiment.

[0045] Apart from Figure 1 In addition to the components of the device, the device D1 also includes: a separation device 16 that enables the separation region to be formed between the outer surface of the film FP1 and the associated roller 2.1, and a separation device that enables the separation region to be formed between the film FP2 and the associated roller 2.2.

[0046] The devices used to separate thin films FP1 and FP2 are similar or the same; only device 16 is described in detail here.

[0047] The separation zone is achieved through a separation line LS1 formed by the generatrix of the rollers. Figure 2 In this context, the line is represented by a single point.

[0048] In fact, the inventors have determined that by setting the position of the separation line within a given area, it is possible to obtain a lithium film FL1 with a second thickness (which is tens of micrometers, for example, between 50 and 30 micrometers), while limiting the risk of tearing of the film FL1 with the second thickness, and without introducing liquid at the roller.

[0049] The inventors have determined that the separation line located above the horizontal plane PH, which lies on the axis of rotation X1 passing through the roller 2.1, facilitates the separation between the plastic film and the lithium film, thereby significantly reducing the risk of tearing of the second-thickness lithium film FL1, which has a thickness of several tens of micrometers. The horizontal plane PH is parallel to the rolling plane.

[0050] Advantageously, the region is also defined by a vertical plane PV passing through the axis of rotation of roller 2.1. Preferably, the separation line is located in the region between a plane at 45° relative to the vertical plane and the vertical plane in a counterclockwise direction.

[0051] In the example shown, and advantageously, device 16 includes a roller 20 disposed between roller 2.1 and mandrel 12 wound with plastic film FP1, the axis of rotation X2 of said roller lying in the horizontal plane PH. Roller 20 is positioned on the path of travel of film FP1 between roller and mandrel 12, such that separation line LS1 lies in plane PH. It can be considered that the separation line LS1 and the axis of rotation of roller 20 are substantially located in the same plane containing the axis of rotation of roller.

[0052] The plastic film FP1 travels between roller 2.1 and roller 20.

[0053] Alternatively, the mandrel 12 of the plastic film FP1 in the storage area, as well as the rollers and guide members, are arranged relative to the roller 2.1 such that the separation line LS1 is located in the plane PH.

[0054] Roller 20 enables more accurate setting of the position of line LS1.

[0055] For example, the distance between the surface of the roller and the surface of the roller is between 1 mm and 4 mm.

[0056] The lithium film FL1, having a second thickness, is held under mechanical tension. Preferably, the applied specific tension is between 1 N / mm² lithium film cross-section and 1.4 N / mm² lithium film cross-section. A specific tension in the range of 1 N / mm² is preferably applied on pure lithium or near-pure lithium films, and a specific tension in the range of 1.4 N / mm² is preferably applied on lithium alloy films.

[0057] For example, for a lithium film with a cross-section of 3 square millimeters (e.g., 60 millimeters wide and 50 micrometers thick), the applied force is between 3 Newtons (specific tensile strength of 1 Newton per square millimeter) and 4.2 Newtons (specific tensile strength of 1.4 Newtons per square millimeter).

[0058] The mechanical tension applied to the plastic films FP1 and FP2 downstream of the rolling zone depends on the width of the film. Preferably, the specific tension is between 0.1 N / mm² and 0.6 N / mm², and more preferably, between 0.2 N / mm² and 0.3 N / mm², which is more conducive to separation and helps to suppress the occurrence of tearing of the lithium film FL1 with a second thickness.

[0059] For example, the tension of the film FL1 with a second thickness and the tension of the plastic film downstream of the rolling zone can be set by adjusting the speed and torque of the motor.

[0060] Advantageously, the plastic film includes a silicone coating on at least the surface that comes into contact with the lithium film, which reduces the risk of adhesion between the lithium and the plastic film. For example, the coating thickness is 100 nanometers.

[0061] Silicone has the advantage of leaving no residue after rolling. Indeed, no traces of silicone were detected on the second-thickness film FL1.

[0062] For example, the plastic film is made of polyethylene terephthalate, which has a solid silicone layer, for example, tens of nanometers thick, coated on at least one surface. For example, the thickness of the plastic film is between 15 micrometers and 100 micrometers.

[0063] Advantageously, the roller 20 has a variable position (especially its angular position) relative to the roller, which makes the device easily adaptable to the manufacture of films of different thicknesses while limiting the risk of tearing.

[0064] Alternatively, the plastic film consists of closed loops forming an annular belt, which makes it possible to avoid having to manage the length of the plastic film remaining in the supply area. For example, the tension of the plastic film is set by a tensioner roller.

[0065] This invention enables the achievement of lithium film thicknesses of 30 micrometers without any tearing. In contrast, it has been noted that films with a thickness of at least 60 micrometers are torn when the roller 20 is placed below the horizontal plane PH.

[0066] exist Figure 3 The image shows another example of an apparatus for rolling lithium films, which is similar to... Figure 2 The difference is that the separation line between the plastic film and the associated roller is essentially located in a vertical plane passing through the axis of rotation of the roller.

[0067] In the example shown, and advantageously, device 116 includes a roller 120 disposed between roller 2.1 and mandrel 12 wound with plastic film FP1, the axis of rotation of said roller X102 lying in a vertical plane PV. Roller 120 is positioned on the path of travel of film FP1 between roller and mandrel 12 such that separation line LS101 lies substantially in plane PV. It can be considered that separation line LS101 and the axis of rotation of roller 120 are substantially in the same plane containing the axis of rotation of roller.

[0068] When considering a counter-clockwise direction, the separation line of each plastic film can extend beyond the vertical plane. The location of the separation line depends on the relative arrangement of the different components of the rolling mill and the available space.

[0069] exist Figure 2 and Figure 3 In the example, the positions of the separating rollers for the two plastic films are symmetrical about the rolling plane.

[0070] Alternatively, their positions can be asymmetrical, and the separation lines can also be arranged asymmetrically with respect to the rolling plane.

[0071] Furthermore, the different devices used to position the separation line between the plastic film and the associated roller may also differ.

[0072] In a particularly advantageous operating mode, the actuators of each roller are driven independently of each other so that they rotate at different speeds, thereby creating a speed difference between them, which facilitates the adhesion of the lithium film to the upper or lower plastic film.

[0073] Preferably, the difference between the speed V1 of the upper roller 2.1 and the speed V2 of the lower roller 2.2 is between -30% and (V2-V1) / V1, which is less than 30%.

Claims

1. A rolling apparatus for rolling lithium metal strip, comprising a rolling zone (ZL), a feeding zone (ZA), and a storage zone, the rolling zone comprising at least two rollers (2.1, 2.2), a lithium strip (FL1) having a first thickness for traveling between the at least two rollers, each of the rollers (2.1, 2.2) rotating about a rotation axis, the feeding zone comprising: Device for feeding lithium strip (FL1) of a first thickness into the rolling region; Devices for supplying two plastic films, such that each plastic film is inserted between a lithium strip of a first thickness and rollers (2.1, 2.2) referred to as associated rollers, wherein the storage area includes devices for collecting a lithium strip (FL1) of a second thickness less than the first thickness, wherein the rolling apparatus further includes devices for tensioning the lithium strip of the second thickness and separation devices configured to ensure that the surface of each plastic film (FP1, FP2) is separated from one of the rollers (2.1, 2.2) on the storage area (ZS) side, in a separation area, the separation area extending beyond a horizontal plane (PH) and opposite to another roller, the horizontal plane passing through the axis of rotation of the roller, the separation area including the horizontal plane (PH).

2. The rolling apparatus according to claim 1, wherein, The device for applying tension to the lithium strip having a second thickness is configured such that the tension applied to each unit surface area of ​​the cross-section of the lithium strip having a second thickness is between 1 N / mm² and 1.4 N / mm².

3. The rolling apparatus according to claim 1 or 2, comprising a device configured to apply tension to a plastic film at least located in the storage region, the device being configured such that the tension applied to each unit width of the plastic film is between 0.1 N / mm and 0.6 N / mm.

4. The rolling apparatus according to claim 1 or 2, wherein, For each plastic film, the separating device includes rollers (20, 120) whose rotation axes (X2, X102) are parallel to the rotation axes of the associated rollers (2.1, 2.2), and whose rotation axes (X2, X102) are located within the separating region.

5. The rolling apparatus according to claim 4, wherein, The position of the roller in the separation zone is changeable.

6. The rolling apparatus according to claim 1 or 2, wherein, The plastic films (FP1, FP2) include a silicone coating on at least the surface used for contact with lithium.

7. The rolling apparatus according to claim 1 or 2, wherein, The plastic films (FP1, FP2) are made of polyethylene terephthalate.

8. The rolling apparatus according to claim 1 or 2, wherein, The plastic films (FP1, FP2) are in the form of annular belts, and the tension of the annular belts is set by tensioner rollers.

9. The rolling apparatus according to claim 1 or 2, comprising the following in the storage area: A mandrel wound with a lithium strip of a second thickness; And a device for simultaneously winding a plastic film to prevent a lithium strip with a second thickness from adhering to the plastic film itself.

10. The rolling apparatus according to claim 1 or 2, comprising: Two actuators are used to drive each roller to rotate independently; A control unit is configured to control the two actuators to cause the two rollers to rotate at different speeds.

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