Working roller for a rolling mill for thinning a sheet of an alkali metal or its alloy into a film

Abstract

A processing roller for a rolling mill for thinning a sheet of an alkali metal or its alloy into a film is disclosed. The processing roller has a cylindrical central portion defining a central axis and having an outer surface defining a thinning surface, and first and second frusto-conical portions extending from first and second ends of the central portion. When the central axis is straight, the angle between the outer surface of the central portion and the outer surfaces of each of the first and second frusto-conical portions is less than 0.05 degrees. The width of the central portion is greater than the width of each of the first and second frusto-conical portions. The width of the central portion is less than the sum of the widths of the first and second portions. A rolling mill having two such processing rollers is also disclosed.

Description

Technical Field

[0001] Cross-reference This application claims the benefit of U.S. Provisional Patent Application No. 62 / 936,806, filed on November 18, 2019, U.S. Provisional Patent Application No. 62 / 936,809, filed on November 18, 2019, and U.S. Provisional Patent Application No. 62 / 936,814, filed on November 18, 2019, and the entire disclosures of all of them are incorporated herein by reference in their entirety.

[0002] The present technology relates to a processing roller for a rolling mill for thinning a sheet of an alkali metal or its alloy into a film, and a rolling mill having such a processing roller.

Background Art

[0003] Rechargeable batteries manufactured from a laminate of a solid polymer electrolyte and thin film anodes and cathodes exhibit many advantages over conventional liquid electrolyte batteries. These advantages include a smaller overall battery weight, a higher specific energy, a longer service life, and environmental compatibility due to the elimination of the risk of toxic liquids leaking into the environment.

[0004] The components of a solid polymer battery include a positive electrode, a negative electrode, and an insulating material capable of enabling ion conduction, such as a solid polymer electrolyte sandwiched between the electrodes. The anode or negative electrode is usually made from a lightweight metal film such as an alkali metal and its alloys such as lithium metal, lithium-aluminum alloy, etc. The composite cathode or positive electrode is usually formed from a mixture of active substances such as transition metal oxides, a conductive filler which is usually carbon particles, an ion-conductive polymer electrolyte material, and a current collector which is a thin sheet of aluminum. The composite cathode thin film is usually obtained by coating the current collector.

[0005] The production of thin films of lithium, in the form of strips of, for example, a width of 10 centimeters or more and lengths of hundreds of meters and with a thickness of less than 100 microns, using quickly reliable processes, faces significant technical difficulties due to the extreme physical and chemical properties of this metal, such as chemical reactivity, malleability, low mechanical strength, rapid self - fusion by contact only, and strong adhesion in most solid materials.

[0006] Cold extrusion is used for the continuous production of sheets of 100 microns or more in thickness. This thickness is generally suitable for the production of lithium batteries using liquid electrolytes. For smaller thicknesses, the film obtained by extrusion is then thinned between processing rollers made of hard materials.

[0007] In large - scale production processes, there are several difficulties in achieving efficient thinning of lithium to a thickness varying between 20 and 100 microns for the production of polymer electrolyte batteries.

[0008] Thinned lithium metal often reacts with and / or deforms and adheres to the processing rollers it contacts during the thinning process. This problem can be solved by the use of lubricants as described in Patent Document 1, Patent Document 2, and Patent Document 3, the entireties of each of these patents being incorporated herein by reference. The lubricant contains additives that prevent the thinned lithium film from reacting or from adhering excessively to the processing rollers and that do not affect the electrochemistry of the resulting electrochemical battery. However, there is a requirement for the proper and efficient application of the lubricant during the thinning process.

[0009] The excessive ductility of lithium or its alloys allows only a very small tensile stress in the lithium film exiting the processing rollers. Therefore, the tensile stress must be accurately monitored and controlled to prevent breakage or tearing of the lithium film and the resulting significant loss and interruption of production.

[0010] When the thickness is between 20 microns and 100 microns, it is difficult to thin a film of lithium or its alloy to a uniform thickness across the entire width and the extended length of the film. In a conventional thinning process, a change in thickness occurs across the width of the thinned lithium film, which promotes the breakage of the lithium film during the thinning operation and consequently provides a thinned lithium film that is not suitable for an electrochemical cell.

[0011] Processing rollers have conventionally been made from polyacetal, a hard plastic material that is compatible with lithium (i.e., does not react with lithium). However, for large-scale production, polyacetal rollers quickly wear out, requiring frequent replacement and disposal of the worn-out rollers, thereby significantly increasing costs. This makes the thinning manufacturing process economically difficult.

[0012] Accordingly, there is a need for a rolling mill adapted to thin a sheet of an alkali metal or its alloy into a film to address at least some of the above problems. There is also a need for an alkali metal film produced by such a rolling mill that maintains desirable properties across the width and length of the film.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0014] It is an object of the present technology to improve at least some of the disadvantages existing in the prior art.

Means for Solving the Problems

[0015] According to one aspect of the present technology, a rolling mill for thinning a sheet of an alkali metal or its alloy into a film is provided. The rolling mill includes a frame, a first processing roller rotatably provided on the frame, and a second processing roller rotatably provided on the frame. The first processing roller and the second processing roller are positioned to receive a sheet therebetween. At least two first actuators operably connected to both ends of the first processing roller to bend the first processing roller, and at least two second actuators operably connected to both ends of the second processing roller to bend the second processing roller. Each of the first processing roller and the second processing roller has a cylindrical central portion defining a central axis, the central portion having an outer surface defining a thinning surface, a first frustum portion extending from a first end of the central portion, and a second frustum portion extending from a second end of the central portion. When the central axis is straight, the angle between the outer surface of the central portion and the outer surface of each of the first frustum portion and the second frustum portion is less than 0.05 degrees. The width of the central portion is greater than the width of each of the first frustum portion and the second frustum portion. The width of the central portion is less than the sum of the width of the first portion and the width of the second portion.

[0016] In certain embodiments of the present technology, the angle is less than 0.03 degrees.

[0017] In certain embodiments of the present technology, the angle is less than 0.02 degrees.

[0018] In certain embodiments of the present technology, the angle is greater than 0.01 degrees.

[0019] In certain embodiments of the present technology, for each of the first processing roller and the second processing roller, the central portion, the first frustum portion, and the second frustum portion have a chromium coating.

[0020] In certain embodiments of the present technology, the chromium coating is a hard chromium coating.

[0021] In certain embodiments of the present technology, for each of the first processing roller and the second processing roller, the central portion, the first frustoconical portion, and the second frustoconical portion have a surface roughness in the range between Ra of 0.025 microns and Ra of 0.5 microns.

[0022] In certain embodiments of the present technology, the range is between Ra of 0.05 microns and Ra of 0.3 microns.

[0023] In certain embodiments of the present technology, for each of the first processing roller and the second processing roller, the first frustoconical portion and the second frustoconical portion taper as they extend away from the central portion.

[0024] In certain embodiments of the present technology, for each of the first processing roller and the second processing roller, a first shoulder is defined between the central portion and the first frustoconical portion, and a second shoulder is defined between the central portion and the second frustoconical portion.

[0025] In certain embodiments of the present technology, for each of the first processing roller and the second processing roller, the first frustoconical portion tapers as it extends from its outer end towards the central portion, and the second frustoconical portion tapers as it extends from its outer end towards the central portion.

[0026] In certain embodiments of the present technology, a first backup roller is rotatably provided to the frame. The first backup roller is in contact with the first processing roller to apply pressure to the first processing roller. A second backup roller is rotatably provided to the frame, and the second backup roller is in contact with the second processing roller to apply pressure to the second processing roller.

[0027] According to another aspect of the present technology, a processing roller for a rolling mill for thinning a sheet of an alkali metal or its alloy into a film is provided. The processing roller has a cylindrical central portion defining a central axis, the central portion having an outer surface defining a thinning surface, a first frustum portion extending from a first end of the central portion, and a second frustum portion extending from a second end of the central portion. When the central axis is straight, the angle between the outer surface of the central portion and the outer surface of each of the first frustum portion and the second frustum portion is less than 0.05 degrees. The width of the central portion is greater than the width of each of the first frustum portion and the second frustum portion. The width of the central portion is less than the sum of the width of the first portion and the width of the second portion.

[0028] In certain embodiments of the present technology, the angle is less than 0.03 degrees.

[0029] In certain embodiments of the present technology, the angle is less than 0.02 degrees.

[0030] In certain embodiments of the present technology, the angle is greater than 0.01 degrees.

[0031] In certain embodiments of the present technology, the central portion, the first frustum portion, and the second frustum portion have a chromium coating.

[0032] In certain embodiments of the present technology, the chromium coating is a hard chromium coating.

[0033] In certain embodiments of the present technology, the central portion, the first frustum portion, and the second frustum portion have a surface roughness in the range between 0.025 microns Ra and 0.5 microns Ra.

[0034] In certain embodiments of the present technology, the range is between 0.05 microns Ra and 0.3 microns Ra.

[0035] In certain embodiments of the present technology, the first frustum portion and the second frustum portion taper as they extend away from the central portion.

[0036] In certain embodiments of the present technology, a first shoulder is defined between the central portion and the first frustoconical portion. A second shoulder is defined between the central portion and the second frustoconical portion.

[0037] In certain embodiments of the present technology, the first frustoconical portion tapers as it extends from its outer end towards the central portion. The second frustoconical portion tapers as it extends from its outer end towards the central portion.

[0038] For the purposes of the present application, surface roughness is expressed by the meter method and is specifically provided as the roughness average (Ra) expressed in microns, and angles are expressed in degrees (i.e., 360 degrees for a full rotation). For the purposes of the present application, hardness represents the resistance of a material (e.g., sheets and films) to local deformation where the deformation is introduced by either mechanical indentation or abrasion. For the purposes of the present application, tensile strength (TS) refers to the ability of such a material (e.g., sheets and films) to resist a load that attempts to elongate the material. Tensile strength is measured by the maximum stress that the material can withstand while being stretched or pulled before failure.

[0039] The term "about" is used in this specification, whether explicitly or not, and is meant to refer to the actual provided value, and also to refer to approximations to such a given value that are reasonably inferred based on ordinary technical skill, including equivalents and approximations due to experimental conditions and / or measurement conditions for such a provided value. For example, the term "about" in the context of a provided value or range refers to a value or range that is within 20% of the provided value or range, preferably within 15% of it, more preferably within 10% of it, more preferably within 9% of it, more preferably within 8% of it, more preferably within 7% of it, more preferably within 6% of it, and more preferably within 5% of it.

[0040] Embodiments of the present technology each have at least one of the above objects and / or aspects, and do not necessarily have all of them. It should be understood that certain aspects of the present technology arising from attempts to achieve the above-described objects may not satisfy this object and / or may satisfy other objects not explicitly proposed herein.

[0041] Additional and / or alternative features, aspects, and advantages of embodiments of the present technology will become apparent from the following description, the accompanying drawings, and the appended claims.

[0042] In addition to the present technology, the following description, used in conjunction with the accompanying drawings, is referenced for a better understanding of other aspects and further features of the present technology.

Brief Description of the Drawings

[0043]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 4C

Figure 5

Figure 6A

Figure 6B

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

DETAILED DESCRIPTION OF THE INVENTION

[0044] FIG. 1 schematically shows a rolling mill 10 and associated components adapted to produce a thin film 12 of lithium or a lithium alloy having a thickness of less than 100 microns from a pre-extruded sheet 14 of lithium or a lithium alloy having a thickness of about 100 to 500 microns. Embodiments of the present technology are described in connection with the production of a thin film 12 of lithium or a lithium alloy from a sheet 14 of lithium or a lithium alloy, although it is contemplated that at least some aspects of the present technology can be used for the production of thin films of other alkali metals or alkali metal alloys from sheets of other alkali metals or alkali metal alloys.

[0045] The rolling mill 10 has a main frame 16, a pair of working rollers 18a and 18b, a backup roller 20a that contacts and is adjacent to the working roller 18a, a backup roller 20b that contacts and is adjacent to the working roller 18b, a thinning lubricant dispensing unit 22 for dispensing a lubricant to the working roller 18b, and a thinning lubricant dispensing unit 200 for dispensing a lubricant to the working roller 18a. As can be seen, the working roller 18a is disposed below the working roller 18b. The working rollers 18a, 18b and the thinning lubricant dispensing units 22, 200 will be described in more detail later. The working rollers 18a, 18b and the backup rollers 20a, 20b are rotatably mounted on support frames 50 and 52 (FIG. 2) as will be described in more detail later.

[0046] Before the roll 24 of the wound and extruded sheet 14 of lithium or lithium alloy reaches the processing rollers 18a and 18b, it is disposed on a feed roller 26 equipped with a drive motor control unit (not shown) adapted to control the tension of the lithium sheet 14. The sheet 14 passes through a series of free rollers 28 to an encoder roller 41 that measures the exact speed of the advancing sheet 14, and meanders to a tension roller 43 equipped with a load cell adapted to accurately measure the tension in the sheet 14 entering the thinning device 10. The load cell of the tension roller 43 can be electronically connected to the control unit of the drive motor of the roll 24 to automatically adjust the tension exerted on the sheet 14. Next, the sheet 14 is fed into a straightener 30, which quickly winds the sheet 14 through a series of closely packed rollers 32. The series of rollers 32 has the effect of ensuring that the sheet 14 is fed straight into the central portion of the processing rollers 18a and 18b without the lateral bending and winding movement that is harmful to the thinning process by eliminating the lateral displacement of the sheet 14 and preventing the zigzag movement of the sheet 14. Therefore, the sheet 14 is fed into the processing rollers 18a and 18b at a fixed position between the rollers 18a and 18b.

[0047] At the inlet of the rolling mill 10, the lubricant dispensing units 22 and 200 discharge an appropriate amount of a thinning lubricant compatible with lithium onto the working surfaces of the respective processing rollers 18a and 18b upstream of the thinning region so that the sheet 14 is thinned by the appropriately lubricated processing rollers 18a and 18b, thereby preventing the unwanted adhesion of the thinned film 12 to either of the processing rollers 18a and 18b. One suitable lubricant is described in Patent Documents 1 and 3, the entirety of which are incorporated herein by reference. In one embodiment, the lubricant is based on toluene, hexane, and polyoxyethylene distereate and is used in sufficient amounts for each of the processing rollers 18a and 18b to prevent excessive adhesion of the thinned film 12 to either of the processing rollers 18a and 18b.

[0048] The sheet 14 passes between two processing rollers 18a and 18b, where the thickness of the sheet 14 is reduced from about 100 to 500 microns to about 20 to 100 microns according to the desired final thickness of the film 12. Pressure is applied to the processing rollers 18a and 18b by the backup rollers 20a and 20b, and the processing rollers 18a and 18b further exert on the sheet 14 sufficient pressure to reduce the thickness of the sheet 14 and deform the sheet 14 into the film 12. The thinning pressure is applied through the backup rollers 20a and 20b instead of being directly applied to the processing rollers 18a and 18b to help avoid undesirable bending of the processing rollers 18a and 18b that would be reflected in the shape and thickness of the film 12. As will be explained later, the surface roughness of the processing rollers 18a and 18b needs to be minimal to produce a high-quality thin film 12. The pressure applied to the processing rollers 18a and 18b by the backup rollers 20a and 20b is evenly distributed over the surfaces of the respective rollers 18a and 18b, thereby leaving the shape of the processing rollers 18a and 18b undisturbed. However, if the processing rollers 18a and 18b are sufficiently rigid, the necessary pressure required to reduce the thickness of the sheet 14 and deform the sheet 14 into the film 12 may be directly applied by the processing rollers 18a and 18b without using the backup rollers. The use of multiple backup rollers to apply uniform pressure to each of the processing rollers 18a and 18b is also being considered. For example, two pairs of backup rollers may be positioned on either side of the processing rollers 18a and 18b.

[0049] The thinned film 12 is pulled through an optical heat-resistant system 36 that measures the uniformity of the surface of the film 12 and also detects pores in the film 12 or cracks along the edges of the film 12. The optical system can also be used to measure the thickness of the film 12. The controlled pull is applied to the film 12 by a driven winding roller 38 to ensure that the film 12 is properly wound. Before reaching the winding roller 38, the thinned film 12 meanders under a controlled pull through a series of rollers. The first of these rollers is a tension roller 45 equipped with a load cell adapted to accurately measure the tension in the thinned film 12 exiting the rolling mill 10. The load cell of the tension roller 45 can be electronically connected to the control unit of the drive motor of the winding roller 38 to automatically adjust the tension exerted on the film 12. Next, the film 12 passes over an encoder roller 47 that measures the exact speed of the advancing film 12. Next, the film 12 passes through a series of free rollers 34 that lead to the winding roller 38.

[0050] A thin insulating film 90, such as a polypropylene film, is also wound around the winding roller 38 to separate the layers of the film 12 so that the films 12 do not adhere to each other. The insulating film 90 is pulled from a roll 92 by the winding roller 38. From the roll 92, the insulating film 90 passes over a tension roller 94 before reaching the roller 38. The tension roller 94 is equipped with a load cell adapted to accurately measure the tension in the insulating film 90. This tension measurement is used to control the tension exerted on the film 12 by the winding roller 38 because the tension exerted by the winding roller 38 is divided between the film 12 and the insulating film 90.

[0051] Encoder rollers 41 and 47 measure the speed of the sheet 14 entering the rolling mill 10 and the speed of the thinned film 12 exiting the rolling mill 10, respectively. The relationship between the entry speed of the sheet 14 and the exit speed of the thinned film 12 is directly proportional to the thickness reduction from the initial sheet 14 to the film 12. Thereby, the thickness of the thinned film 12 can be mathematically determined when the thickness of the initial sheet 14 is known. Thus, the thickness of the thinned film 12 is controlled and verified through the speed difference of the speeds measured by the encoder rollers 41 and 47. It is also contemplated that the thickness of the thinned film 12 can be controlled and verified to be different.

[0052] In one embodiment, the thinning process is performed in an anhydrous atmosphere containing less than 1% relative humidity to prevent an undesired chemical reaction of the lithium film 12 with water particles that would render the lithium film 12 unsuitable for use in an electrochemical cell.

[0053] Referring now to FIGS. 2 and 3, the main components of the rolling mill 10 that enable control of the thickness and shape of the film 12 to be thinned are described. It should be understood that the illustrated rolling mill 10 is one exemplary embodiment of a rolling mill adapted to control the shape and thickness of the thinned film 12 and that other embodiments are contemplated. For example, the support members and the frame may have different configurations and various hydraulic system configurations may be used.

[0054] Backup rollers 20a and 20b are each rotatably provided in bearings of support frames 50 and 52. The support frame 52 is slidably provided on the vertical member of the main frame 16 through any suitable means such as a slide passage or a bearing. The support frame 50 is fixedly provided on the vertical member of the main frame 16. Therefore, the support frame 52 can move in the vertical direction. The processing rollers 18a and 18b are each driven by an electric or hydraulic motor (not shown). The processing rollers 18a and 18b drive the backup rollers 20a and 20b by friction. A pair of hydraulic linear actuators 66 are provided on the horizontal member above the main frame 16. The hydraulic actuators are connected to the support frame 52. The hydraulic linear actuator 66 controls the up and down movement of the support frame 52 and controls the pressure applied to the processing rollers 18a and 18b. The processing rollers 18a and 18b are each rotatably provided in support members 54 and 56. The support members 54 and 56 are each operably connected to the support frames 50 and 52. The end portions 58 and 59 of the support member 54 are operably connected to the support frame 50 via a pair of hydraulic linear actuators 60 and 61, and the end portions 62 and 63 of the support member 56 are operably connected to the support frame 52 via a pair of hydraulic linear actuators 64 and 65.

[0055] During operation, the thinning rate is set by the speeds of the processing rollers 18a and 18b. The pressure P required to reduce the film 12 to the desired thickness is adjusted through a hydraulic valve that controls the hydraulic linear actuator 66. The backup roller 20b transmits the pressure P to the processing roller 18b. Once the desired pressure P is set, the final shape of the thinned film 12 is finely tuned by adjusting the fluid pressure to each of the hydraulic linear actuators 60, 61, 64, and 65, as will be described in more detail later, thereby adjusting the forces exerted on the support members 54 and 56 by each of the hydraulic linear actuators 60, 61, 64, and 65. The hydraulic linear actuators 60, 61, 64, 65, and 66 may be replaced by other types of actuators, such as electric actuators, that can generate sufficient force. In an alternative embodiment, an additional hydraulic linear actuator is connected between the support members 54, 56. In such an embodiment, the hydraulic linear actuators 60, 61, 64, 65, and 66 are used to push the support members 54, 56 towards each other, and the additional hydraulic linear actuator is used to push the support members 54, 56 towards each other.

[0056] During the thinning process, heat accumulates in the processing rollers 18a and 18b through the friction generated on the thinning surface due to the effect of slightly expanding the processing rollers 18a and 18b. The expansion of the processing rollers 18a and 18b at a few microns in the thinning region is sufficient to produce a film 12 of non-uniform thickness that is inappropriate for the thin film electrochemical cell. To alleviate this problem and help ensure a film 12 of uniform thickness, the central portions 100 (FIG. 4A) of the expanded processing rollers 18a and 18b are adjusted by bending the processing rollers 18a and 18b to straighten the central portion 100 and produce a uniform thickness lithium film 12. This control process will be described later in relation to FIGS. 4A-4C. It should be noted that the shapes of the processing rollers 18a and 18b shown in FIGS. 4A-4C are greatly exaggerated for clarity, and the tapering of the end portions of the processing rollers 18a, 18b, and the bending profile represent a deviation of only a few microns from a completely linear profile, so it should be understood that they are not actually visible to the naked eye.

[0057] FIG. 4A shows the processing rollers 18a and 18b in the neutral position. The backup rollers 20a and 20b apply a pressure P sufficient to reduce the thickness of the sheet 14 to the desired thickness of the film 12 to the processing rollers 18a and 18b, but no lateral force is applied to the support members 54 and 56 of the processing rollers 18a, 18b.

[0058] In FIG. 4B, backup rollers 20a and 20b still apply a pressure P sufficient to reduce the thickness of the sheet 14 to the desired thickness of the film 12 to the processing rollers 18a and 18b. However, due to thermal expansion, the central portions of the processing rollers 18a and 18b are expanding through the accumulation of heat generated by the friction of the central portion 100 in contact with the sheet 14. To counteract this thermal expansion that has deformed the processing rollers 18a and 18b, a laterally directed force Fx oriented inward is applied to the support members 54 and 56. The lateral force Fx bends the processing rollers 18a and 18b slightly outward, thereby flattening the central portion 100 as depicted in FIG. 4B. The outer edges of the processing rollers 18a and 18b are bent inward to straighten the central portion 100. Thus, the resulting thinned film 12 is flat and has a uniform thickness. The thermal expansion of the processing rollers 18a, 18b is somewhat weakened by the application of a thinning lubricant to the processing rollers 18a, 18b. It is also being considered that additional means for cooling the processing rollers 18a, 18b can be used to help weaken the thermal expansion of the processing rollers 18a, 18b.

[0059] When the edges of the thinned sheet 14 are thicker than the central portion of the sheet 14, in order to thin the film 12 having a uniform thickness across the width of the film 12, a greater pressure is applied by the processing rollers 18a and 18b to the outer edges of the sheet 14 and thus to the outer edges of the central portion 100. To do so, the same lateral force Fx is applied to the support members 54 and 56, thereby slightly bending the outer edges of the processing rollers 18a and 18b inwardly to apply a greater pressure to the edges rather than the central portion of the sheet 14. As a result, the thinned film 12 has a uniform thickness across its width. As heat accumulates in the processing rollers 18a and 18b through friction with the central portion 100 in contact with the sheet 14, the central portions of the processing rollers 18a and 18b expand slightly. To counteract this thermal expansion that slightly increases the diameter of the central portions of the processing rollers 18a and 18b, the lateral force Fx is proportionally decreased to keep the central portion 100 straight so that the resulting thinned film 12 pixels have a uniform thickness across their entire width.

[0060] At that time, the central portion of the sheet 14 to be thinned may be thicker than its edges. In order to thin the film 12 having a uniform thickness across the width of the film 12, a greater pressure needs to be applied by the processing rollers 18a and 18b to the central portion of the sheet 14 and thus to the central portion of the central portion 100. As shown in FIG. 4C, to do so, a laterally directed force Fy oriented outwardly is applied to the support members 54 and 56. The lateral force Fy slightly bends the central portions of the processing rollers 18a and 18b inwardly and pushes the central portion of the central portion 100 inwardly, thereby applying a greater pressure to the central portion of the sheet 14 and thinning the film 12 having a uniform thickness across the entire width of the film 12.

[0061] In a certain situation, the heat generated by the friction of the central portion 100 in contact with the sheet 14 accumulates in the outer portions of the facing surfaces of the processing rollers 18a and 18b, expands these outer portions, and creates a small gap in the central portion of the central portion 100. To counteract this thermal expansion, a laterally directed outward force Fy is applied to the support members 54 and 56 of the processing rollers 18a and 18b. The lateral force Fy slightly bends the central portion of the central portion 100 and straightens the central portion 100. The contour of the central portion 100 of the processing rollers 18a and 18b is bent back to a straight line such that the resulting thinned film 12 is flat and has a uniform thickness throughout its entire width.

[0062] Only the symmetrical adjustment of the processing rollers 18a and 18b is shown in FIGS. 4B and 4C, but since the support members 54 and 56 are independent of each other, other adjustments are possible. For example, if the processing rollers 18a and 18b expand more on one side than the other, the left or right support members 54 and 56 may have a force Fx or Fy that exceeds the force Fx or Fy of the support members 54 and 56 on the opposite side so that a large number of fine adjustments are possible.

[0063] The adjustment of the shape of the central portion 100 in combination with the accurate measurement of a suitable measuring device such as the optical heat-resistant system 36 can produce a high-quality thinned film 12 with a thickness in the range of 20 to 100 microns that exhibits a substantially constant thickness throughout the entire length and width in the rolling mill 10.

[0064] The adjustment of the contour and thickness of the thinned film 12 is carried out by an operator on-site who finely tunes the pressure applied by the backup rollers 20a and 20b and the pressure applied to the support members 54 and 56, or this task is electronically performed by connecting the measurement readings and an actuator that controls the various pressures and forces of the backup rollers 20a, 20b and the processing rollers 18a, 18b to a computer that provides real-time adjustment of these parameters.

[0065] Referring now to FIGS. 5 to 6B, the processing roller 18a will be described in more detail. In the present embodiment, the processing roller 18b is the same as the processing roller 18a, and therefore the processing roller 18b will not be separately described herein. The possibility that the processing roller 18b may be partially different from the processing roller 18a is being considered.

[0066] As previously mentioned, the processing roller 18a has a central portion 100. The central portion 100 is a cylindrical central portion 100. The outer surface 102 of the central portion 100 defines a thinning surface that rolls across the sheet 14 during the thinning process. Thereby, the central portion 100 has a width W1 that is slightly wider than the width W2 (FIG. 7) of the sheet 14 to be thinned. The central portion 100 defines the central axis 104 of the processing roller 18a.

[0067] The frustoconical portions 106 extend from the ends of the central portion 100. The frustoconical portions 106 are mirror images of each other. In FIG. 5, the outer surface 110 of the frustoconical portion 106 does not appear to taper. This is because the taper angle is very small and not visible to the naked eye. This angle is exaggerated in FIGS. 6A and 6B, which show two different embodiments of the processing roller 18a and will be described later. Each frustoconical portion 106 has a width W3. The width W1 of the central portion 100 is greater than the width W3 of each frustoconical portion 106. The width W1 of the central portion 100 is less than the sum of the widths W3 of both frustoconical portions 106 (i.e., W1 < W3 + W3). In one embodiment, the width W1 is between 125 mm and 210 mm, and the width W3 is between 65 mm and 110 mm.

[0068] In one embodiment shown in FIG. 6A, the frustoconical portion 106 tapers as it extends away from the central portion 100. This embodiment is the one shown in FIGS. 4A - 4C where the tapering was exaggerated. In this embodiment, a shoulder 108 is defined between the central portion 100 and each frustoconical portion 106 (shown for one frustoconical portion in FIG. 6A). In some embodiments, the shoulder 108 has a height H1 less than 0.05 mm. In some embodiments, the height H1 is less than 0.02 mm. It has been considered that the shoulder 108 may be omitted. When the central axis 104 is straight (i.e., when the processing roller 18a is in the neutral position as in FIG. 4A), the angle A between the outer surface 102 of the central portion 100 and the outer surface 110 of the frustoconical portion 106 is less than 0.05 degrees. In some embodiments, the angle A is less than 0.03 degrees. In some embodiments, the angle A is less than 0.02 degrees. In some embodiments, the angle A is less than 0.02 degrees but greater than 0.01 degrees. In some embodiments, the central portion 100 has a diameter D1 between 70 mm and 90 mm. In some embodiments, the difference between the minimum diameter D2 and the maximum diameter D3 of each frustoconical portion 106 is between 0.03 mm and 0.17 mm. The profiles of the processing rollers 18a and 18b according to this embodiment facilitate the bending of the processing rollers 18a and 18b by providing a free zone 84 (FIG. 4A) between the frustoconical portions 106 and a free zone 85 (FIG. 4A) between the frustoconical portions 106 and the backup rollers 20a and 20b so that the ends of the processing rollers 18a and 18b can be moved to bend the central portion 100 as desired. The free zone 84 can also discharge excess thinning lubricant laterally during the thinning process. The processing roller 18a of the embodiment shown in FIG. 6A can be used with sheets 14 having many different profiles thanks to the adjustments that can be made in the rolling mill 10 (as detailed in relation to FIGS. 4A - 4C), but this embodiment of the processing roller 18a is particularly well-suited for thinning a sheet 14 extruded at a central portion 112 having a height H2 (FIG. 7) less than the height H3 of the lateral portion 114 (FIG. 7) of the sheet 14. Again, in FIG. 7, the heights H2 and H3 do not appear as a difference because the difference is not visible to the naked eye.In one embodiment, the height H2 is less than 15 microns smaller than the height H3.

[0069] In other embodiments shown in FIG. 6B, each frustoconical portion 106 tapers as it extends from its outer end towards the central portion 100 (i.e., D2 is greater than D3). When the central axis 104 is straight (i.e., when the processing roller 18a is in the neutral position), the angle B between the outer surface 102 of the central portion 100 and the outer surface 110 of the frustoconical portion 106 is less than 0.05 degrees. In one embodiment, the angle B is less than 0.03 degrees. In one embodiment, the angle B is less than 0.02 degrees. In one embodiment, the angle B is less than 0.02 degrees but greater than 0.01 degrees. In one embodiment, the central portion 100 has a diameter D1 between 70 mm and 90 mm. In one embodiment, the difference between the maximum diameter D2 and the minimum diameter D3 of each frustoconical portion 106 is between 0.03 mm and 0.17 mm. The processing roller 18a of the embodiment shown in FIG. 6B can be used with sheets 14 having many different profiles thanks to the adjustments that can be made in the rolling mill 10 (as detailed in connection with FIGS. 4A - 4C), but this embodiment of the processing roller 18a is particularly well-suited for thinning a sheet 14 extruded with a central portion 112 having a height H2 (FIG. 7) greater than the height H3 of the lateral portion 114 (FIG. 7) of the sheet 14. In one embodiment, the height H2 is less than 15 microns greater than the height H3.

[0070] Returning to FIG. 5, the processing roller 18a has support shafts 116, 118 extending from the ends of the frustoconical portion 106. The support shafts 116, 118 are received in bearings (not shown) for rotatably mounting the processing roller 18a to the support member 54 (or to the support member 56 for the processing roller 18b). The support shaft 118 has an extension 120 adapted for connection to a motor for driving the processing roller 18b. The portions 100, 106 and the support shafts 116, 118 are integrally formed.

[0071] As previously mentioned, the thinning lubricant dispensed onto the processing rollers 18a and 18b helps prevent the adhesion of the film 12 to the processing rollers 18a, 18b such that the film 12 exits the processing rollers 18a, 18b in a straight line. The use of the lubricant enables the thinning of lithium and lithium alloys with processing rollers 18a, 18b made of materials that would not normally be suitable for adhesion to lithium. The lubricant negates this constraint. For large-scale production, therefore, the processing rollers 18a, 18b are preferably made from a durable, hard material such as steel, stainless steel, and even ceramics. In one embodiment, the steel or stainless steel rollers 18a, 18b have a thin chromium coating for additional hardness. The chromium coating is applied at least to the central portion 100 and the frustoconical portion 106 of the processing rollers 18a, 18b. In one embodiment, the chromium coating is a hard chromium coating. In order to provide the desired surface finish to the film 12 and to allow some adhesion of the thinning lubricant to the processing rollers 18a, 18b, in one embodiment, the outer surface 102 of the central portion 100 and the outer surface 110 of the frustoconical portion 106 have a surface roughness in the range between 0.025 microns Ra and 0.5 microns Ra. In other embodiments, the surface roughness is in the range between 0.05 microns Ra and 0.30 microns Ra.

[0072] Referring now to FIG. 8, the thinning lubricant dispensing unit 22 will be described in more detail. The thinning lubricant dispensing unit 22 includes four nozzles 150 provided on the rail 152. It is contemplated that the thinning lubricant dispensing unit 22 may have five or more or three or fewer nozzles 150. The thinning lubricant is supplied to a passage (not shown) inside the rail 152 via the suction connector 154. The suction connector 154 is fluidly connected to a pump (not shown) that supplies the lubricant from a lubricant reservoir (not shown) holding the thinning lubricant to the suction connector 154. The four nozzles 150 are in fluid communication with the passage inside the rail 152. As can be seen in FIG. 1, the thinning lubricant dispensing unit 22 is disposed upstream of the thinning region and is spaced apart from the processing roller 18b. The thinning lubricant dispensing unit 22 is disposed above the central axis 104 of the processing roller 18b and is inclined such that the nozzles 150 continuously spray the thinning lubricant onto the thinning surface of the processing roller 18b. The spray from the nozzles 150 covers an area slightly wider than the thinning surface.

[0073] Each nozzle 150 has a nozzle body 156, a filter, a nozzle head 158, and a nut 160. The nozzle body 156 is screwed into the rail 152. The filter is disposed inside the nozzle body 156. The nozzle head 158 defines a spray opening 162 and is disposed at the end of the nozzle body 156. The nut 160 is disposed on the nozzle body 156 and is screwed onto the nozzle body 156 to hold the nozzle head 158 and the filter in place.

[0074] Referring to FIGS. 9 to 13 here, the thinning lubricant dispensing unit 200 will be described. In the present embodiment, the thinning lubricant dispensing unit 200 is made of a single product of an antistatic acetal copolymer. For example, it is considered that other types of materials such as polyamide, polypropylene, polyethylene, acrylonitrile butadiene styrene, polyethylene terephthalate, polystyrene, thermoplastic polyurethane, poly(methyl methacrylate), polyvinyl chloride, brass, and aluminum may be used. Other materials are also being considered. It is also being considered that the thinning lubricant dispensing unit 200 can be made of a plurality of parts bonded or otherwise connected to each other.

[0075] The thinning lubricant dispensing unit 200 has a dispensing unit body 202. Each rear corner portion of the dispensing unit body 202 defines two openings 206. A fixture (not shown) is received in the opening 206 to attach the dispensing unit body 202 to the frame 16 of the rolling mill 10 at a position between the processing roller 18a and the straightener 30. The dispensing unit body 202 defines a laterally extending wall 208. A single lubricant passage 210 is defined in the dispensing unit body 202 as best seen in FIG. 12. The lubricant passage 210 has an inlet (not shown) defined in the rear wall 214 of the dispensing unit body 202 and an outlet 216 defined in the laterally extending wall 208. As can be seen, the outlet 216 is laterally centered in the laterally extending wall 208 and is disposed at the bottom of the wall 208. It is being considered that a plurality of lubricant passages 210 may be defined in the dispensing unit body 202 with the outlets of these passages at different positions along the laterally extending wall 208. It is also being considered that at least some of these plurality of lubricant passages 210 may have a common inlet.

[0076] Two side walls 218 extend forward from the laterally extending wall 208. As can be seen in FIG. 10, the side walls 218 are parallel to each other. As can be seen in FIG. 12, the front end 220 of the side wall 218 is inclined obliquely from the vertical so as not to interfere with the processing roller 18a.

[0077] The thinning lubricant dispensing unit 200 also has a shelf portion 222. The shelf portion 222 is connected to the lower end of the laterally extending wall 208 and extends forward from the bottom. The shelf portion 222 is also connected to the lower ends of the side walls 218 and extends therebetween. The shelf portion 222, the side walls 218, and the laterally extending wall 208 together define a recess 224 having an open side in front of the thinning lubricant dispensing unit 200. The shelf portion 222 has a front edge 226 that contacts the thinning surface of the processing roller 18a at a position below the vertical direction of the central axis 104 of the processing roller 18a, as can be seen in FIG. 12. The front edge 226 has a width W4 (FIG. 10) that is greater than the width W1 of the thinning surface of the processing roller 18a in order to help ensure that the thinning lubricant is applied over the entire width of the thinning surface.

[0078] Referring to FIG. 13, the shelf portion 222 has an inclined portion 228 that extends upwardly and rearwardly toward a wall 208 that extends laterally from a front edge 226. The angle 230 between the inclined portion 228 and the front edge 226 is arcuate. In some embodiments, the inclined portion 228 extends at an angle C between 5 degrees and 25 degrees from horizontal. In some embodiments, the angle C is between 10 degrees and 20 degrees from horizontal. The shelf portion 222 also has a generally horizontal portion 232 that extends between the inclined portion 228 and the laterally extending wall 208. The portion 232 is horizontal when viewed from the side (i.e., as viewed in FIGS. 12 and 13). However, when viewed from the front of the portion 232 (i.e., as viewed in FIG. 11), the portion 232 is slightly inclined downwardly on both sides of its lateral center, such that the lateral center thereof corresponds to the apex of the portion 232. In some embodiments, the angle D (FIG. 11) between the surfaces on both sides of the lateral center of the portion 232 is greater than 180 degrees but less than 185 degrees, and in some embodiments, less than 182 degrees. It is also contemplated that the portion 232 may be flat (i.e., the angle D is 180 degrees) when viewed from the front of the portion 232 (i.e., as viewed in FIG. 11). As can be seen in FIGS. 11 and 12, the outlet 216 of the lubricant passage 210 is aligned laterally with the apex of the portion 232, and the lower portion of the outlet 216 is vertically aligned with the upper portion of a portion 232 of the adjacent shelf portion 222 thereat. The possibility of omitting the portion 232 and the possibility of the inclined portion 228 extending to the laterally extending wall 208 from the front edge 226 are being considered.

[0079] A laterally extending groove 234 is defined in the inclined portion 228 of the shelf portion 222. As best seen in FIG. 10, the ends of the groove 234 are spaced from the side wall 218. The groove 234 is spaced from the front edge 226 of the shelf portion 222. As can be seen in FIG. 13, the groove 234 is closer to the front edge 226 than a portion 232 of the shelf portion 222.

[0080] Referring to FIG. 12, the inlet of the lubricant passage 210 is fluidly connected to a pump 236, and the pump 236 itself is fluidly connected to a lubricant reservoir 238. The lubricant reservoir 238 holds the thinning lubricant therein. It is contemplated that the lubricant reservoir 238 may also be used to supply the thinning lubricant to the thinning lubricant dispensing unit 22 described above. The pump 236 pumps the thinning fluid from the lubricant reservoir 238 to the lubricant passage 210. From the outlet 216 of the lubricant passage 210, the lubricant flows forwardly and laterally (due to the angle D) along a portion 232 of the shelf. Next, the lubricant flows downward along the inclined portion 228. A portion of the lubricant flows into grooves 234 that help ensure uniform distribution of the lubricant across the width of the shelf 222. Next, the lubricant flows to the leading edge 226 that contacts the thinning surface of the processing roller 18a. The upwardly moving thinning surface of the processing roller 18a picks up the lubricant, and the lubricant effectively coats the thinning surface that contacts the sheet 14.

[0081] In certain embodiments, the film of an alkali metal or alkali metal alloy of the present technology is a thinned lithium film or a thinned lithium alloy film obtained using a rolling mill and processing rollers as defined herein.

[0082] Lithium alloys that may be used to prepare the film of the present technology include, but are not limited to, lithium-silicon, lithium-aluminum, lithium-magnesium, lithium-strontium, lithium-barium, and the like.

[0083] The film of lithium or lithium alloy of the present technology contains an amount of metal element. The addition of the metal element to the film of lithium or lithium alloy can reduce the overall thickness of the film and improve the overall mechanical strength of the film. In one example, the metal element is present in the film of lithium or lithium alloy in an amount that improves the mechanical strength throughout the width, thickness, and length of the film.

[0084] The metal elements that can be used in the preparation of the lithium or lithium alloy film of the present technology are preferably conductive. It is understood that the presence of the metal element should not prevent the conductivity of the lithium or lithium alloy film. For example, aluminum is a metal element that can be used in the film of lithium or lithium alloy. In one example, aluminum is present in the film in an amount in the range of from about 3000 ppm to about 10000 ppm, from about 3000 ppm to about 9000 ppm, from about 3000 ppm to about 8000 ppm, from about 3000 ppm to about 7000 ppm, from about 3000 ppm to about 6000 ppm, or from about 3000 ppm to about 5000 ppm. In one example, aluminum is present in the film in an amount of 3000 ppm or more.

[0085] In one example, the lithium or lithium alloy film of the present technology has a hardness measured by a Shore indentation hardness tester (Shore A scale) in the range of from about 50 to about 85, from about 60 to about 80, from about 60 to about 75, from about 50 to about 70, from about 60 to about 75, from about 65 to about 75, from about 66 to about 70, or from about 66 to about 69. In one example, the hardness is at least 65. In another example, the hardness is at least about 66. In one example, the hardness is uniform throughout the lithium or lithium alloy film.

[0086] The lithium film obtained by the technology defined in this specification has a width (corresponding to the distance from one edge of the thin film to the other edge) in the range of from about 140 mm to about 200 mm, from about 150 mm to about 200 mm, from about 160 mm to about 180 mm, from about 160 mm to about 175 mm, from about 160 mm to about 170 mm, or from about 160 mm to about 165 mm, and has a thickness in the range of from about 20 microns to about 100 microns, from about 20 microns to about 90 microns, from about 20 microns to about 75 microns, from about 20 microns to about 50 microns, or from about 20 microns to about 30 microns. The thickness of the lithium or lithium alloy film is uniform throughout the width of the film. The thickness that is uniform throughout the width of the film encompasses a thickness variation of about ±2 microns.

[0087] In some embodiments, the lithium or lithium alloy film obtained by the technology defined in this specification has a thickness-to-width ratio (t / w) that is between about 1x10 -4 and about 7x10 -4 . In one example, this t / w is maintained throughout the length of the film.

[0088] Specifically, the technology can maintain the width, thickness, and hardness of the lithium or lithium alloy film over the length of the stretched film. For example, the lithium or lithium alloy film of the technology maintains its width, thickness, and hardness over at least about 15000 meters, over at least about 10000 meters, over at least about 9000 meters, over at least 8000 meters, over at least about 7000 meters, over at least about 6000 meters, over at least about 5000 meters, over at least about 4000 meters, over at least about 3000 meters, over at least about 2000 meters, or over at least about 1000 meters.

[0089] (Example) The following examples are provided to illustrate the implementation of various embodiments of the present technology. These examples are not intended to limit or define the entire scope of the present technology. It should be understood that the present technology is not limited to the specific embodiments described and illustrated herein, but includes all changes and modifications within the scope of the present disclosure as defined in the appended embodiments.

[0090] (Example 1) Production of a Thinned Lithium Alloy Film (3000 ppm) The thinned lithium film was prepared using a rolling mill equipped with a processing roller as defined herein. The resulting lithium film had a width of 170 mm, a thickness of 60 microns, and an aluminum content of 3000 ppm. The hardness of the film was evaluated using a Shore indentation hardness tester (PTC model 320 - A scale). The results are presented in Table 1.

[0091] [Table 1]

[0092] (Example 2) Production of a Thinned Lithium Alloy Film (5000 ppm) The thinned lithium film was prepared using a rolling mill equipped with a processing roller as defined herein. The resulting lithium film had a width of 170 mm, a thickness of 60 microns, and an aluminum content of 5000 ppm. The hardness of the film was evaluated using a Shore indentation hardness tester (PTC model 320 - A scale). The results are presented in Table 2.

[0093] [Table 2]

[0094] (Example 3) Evaluate the Tensile Strength of a Thinned Lithium Alloy Film (3000 ppm) The thinned lithium-aluminum film was prepared using a rolling mill equipped with processing rollers as defined herein. The lithium film had a width of 170 mm, a thickness of 60 microns, and an aluminum content of 3000 ppm. The tensile strength of the lithium film was evaluated using 25 kN of Testometric M500. The results are presented in Table 3 (Table 3).

[0095]

Table 3

[0096] (Example 4) Evaluate the tensile strength of the thinned lithium alloy film (5000 ppm) The thinned lithium-aluminum film was prepared using a rolling mill equipped with processing rollers as defined herein. The lithium film had a width of 170 mm, a thickness of 60 microns, and an aluminum content of 5000 ppm. The tensile strength of the lithium film was evaluated using 25 kN of Testometric M500. The results are presented in Table 4 (Table 4).

[0097]

Table 4

[0098] Changes and improvements to the foregoing embodiments of the present technology may be apparent to those skilled in the art. The foregoing description is intended to be illustrative rather than limiting. Accordingly, the scope of the present technology is intended to be limited only by the scope of the appended claims.

Description of Reference Numerals

[0099] 10 Rolling mill, thinning device 12 Thin film of lithium or lithium alloy 14 Sheet of lithium or lithium alloy 16 Main frame 18a, 18b Processing rollers Backup rollers 20a and 20b Lubricant dispensing unit 22 for thinning Roll 24 Feed roller 26 Free roller 28 Free roller 34 Heat-resistant refraction system 36 Winding roller 38 Encoder roller 41 Tension rollers 43 and 45 Encoder roller 47 Support frames 50 and 52 Support members 54 and 56 End portions 58, 59, 62, and 63 Hydraulic linear actuators 60, 61, 64, 65, and 66 Free zones 84 and 85 Insulating film 90 Roll 92 Tension roller 94 Central portion 100 Outer surface of the central portion 100 of the sheet 102 Central axis 104 Frustum portion 106 Shoulder 108 Outer surface of the frustum portion 106 of the sheet 110 Central portion of the sheet 14 of the sheet 112 Side portion of the sheet 14 of the sheet 114 Support shafts 116 and 118 Extension portion 120 Nozzle 150 Rail 152 Suction connector 154 Nozzle body 156 Nozzle head 158 Nut 160 Spray opening 162 Lubricant dispensing unit 200 for thinning Dispensing unit body 202 Opening 206 Wall extending in the horizontal direction 208 Lubricant passage 210 Rear wall 214 Outlet 216 218 Side wall 220 Front end 222 Shelf part 224 Recess 226 Leading edge 228 Diagonal part 230 Corner 232 Generally horizontal part 234 Groove 236 Pump 238 Lubricant storage part Angle between outer surfaces 102 and 110 of A and B C Angle of diagonal part 228 D Angle D1 Diameter of central part 100 D2, D3 Minimum or maximum diameter of frustum part 106 Fx Lateral force Fy Lateral force H1 Height of shoulder 108 H2 Height of central part 112 H3 Height of lateral part 114 W1 Width of central part 100 W2 Width of sheet 14 W3 Width of frustum part 106

Claims

1. A rolling mill for thinning a sheet of an alkali metal or its alloy into a film, wherein the rolling mill comprises: A frame; A first processing roller rotatably mounted on the frame; A second processing roller rotatably mounted on the frame, wherein the first processing roller and the second processing roller are positioned to receive the sheet therebetween; At least two first actuators operably connected to both ends of the first processing roller for bending the first processing roller; At least two second actuators operably connected to both ends of the second processing roller for bending the second processing roller; And Each of the first processing roller and the second processing roller comprises: A cylindrical central portion defining a central axis and having an outer surface defining a thinning surface; A first frustum portion extending from a first end of the central portion; A second frustum portion extending from a second end of the central portion; And When the central axis is straight, an angle between the outer surface of the central portion and the outer surfaces of each of the first frustum portion and the second frustum portion is less than 0.05 degrees; A width of the central portion is greater than a width of each of the first frustum portion and the second frustum portion; The width of the central portion is less than a sum of the width of the first frustum portion and the width of the second frustum portion; For each of the first processing roller and the second processing roller, the first frustum portion and the second frustum portion taper as they extend away from the central portion; For each of the first processing roller and the second processing roller, a first shoulder is defined between the central portion and the first frustum portion, and a second shoulder is defined between the central portion and the second frustum portion. Rolling mill.

2. The rolling mill according to claim 1, wherein the angle is less than 0.03 degrees.

3. The rolling mill according to claim 2, wherein the angle is less than 0.02 degrees.

4. The rolling mill according to claim 3, wherein the angle is greater than 0.01 degrees.

5. The rolling mill according to any one of claims 1 to 4, wherein for each of the first processing roller and the second processing roller, the central portion, the first frustum portion, and the second frustum portion have a chromium coating.

6. The rolling mill according to any one of claims 1 to 5, wherein for each of the first processing roller and the second processing roller, the central portion, the first frustum portion, and the second frustum portion have a surface roughness in the range between Ra of 0.025 microns and Ra of 0.5 microns.

7. The rolling mill according to claim 6, wherein the range is between Ra of 0.05 microns and Ra of 0.3 microns.

8. A first backup roller rotatably mounted on the frame and in contact with the first processing roller to apply pressure to the first processing roller, and a first backup roller; A second backup roller rotatably mounted on the frame and in contact with the second processing roller to apply pressure to the second processing roller, and a second backup roller The rolling mill according to any one of claims 1 to 7, further comprising:

9. A processing roller for a rolling mill for thinning a sheet of an alkali metal or an alloy thereof into a film, wherein the processing roller has: a cylindrical central portion defining a central axis, the central portion having an outer surface defining a thinning surface; a first frustum portion extending from a first end of the central portion; a second frustum portion extending from a second end of the central portion; and comprising: when the central axis is straight, an angle between the outer surface of the central portion and the outer surfaces of each of the first frustum portion and the second frustum portion is less than 0.05 degrees; a width of the central portion is greater than a width of each of the first frustum portion and the second frustum portion; the width of the central portion is less than a sum of the width of the first frustum portion and the width of the second frustum portion; the first frustum portion and the second frustum portion taper as they extend away from the central portion; a first shoulder is defined between the central portion and the first frustum portion, and a second shoulder is defined between the central portion and the second frustum portion; a processing roller.

10. The processing roller according to claim 9, wherein the angle is less than 0.03 degrees.

11. The processing roller according to claim 10, wherein the angle is less than 0.02 degrees.

12. The processing roller according to claim 11, wherein the angle is greater than 0.01 degrees.

13. The processing roller according to any one of claims 9 to 12, wherein the central portion, the first frustum portion, and the second frustum portion have a chromium coating.

14. The central portion, the first frustoconical portion, and the second frustoconical portion have a surface roughness in the range between Ra of 0.025 microns and Ra of 0.5 microns, the processing roller according to any one of claims 9 to 13.

15. The range is between Ra of 0.05 microns and Ra of 0.3 microns, the processing roller according to claim 14.

Images