Working roller for rolling mill for forming film by thinning sheet of alkali metal or alloy thereof

Abstract

To ameliorate at least some of inconveniences present in the prior art.SOLUTION: Disclosed is a working roller for a rolling mill for forming a film by thinning a sheet of alkali metal or alloy thereof. The working roller has: a cylindrical center portion defining a central axis, the center portion having an outer surface defining a lamination surface; and first and second frustoconical portions extending from first and second ends of the center portion. When the central axis is straight, an angle between the outer surface of the center portion and an outer surface of each of the first and second frustoconical portions is less than 0.05 degrees. A width of the center portion is greater than a width of each of the first and second frustoconical portions. The width of the center portion is less than a sum of the widths of the first and second portions. A rolling mill having two such working rollers is also disclosed.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

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

[0003] Rechargeable batteries made from laminates of solid polymer electrolytes and thin film anodes and cathodes offer many advantages over traditional liquid electrolyte batteries, including smaller overall battery weight, higher specific energy, longer service life, and environmental compatibility by eliminating the risk of leaking toxic liquids into the environment.

[0004] The components of a solid polymer battery include a positive electrode, a negative electrode, and an insulating material capable of allowing ion conduction, such as a solid polymer electrolyte, sandwiched between the electrodes. The anode or negative electrode is typically 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 typically formed from a mixture of active materials, such as transition metal oxides, a conductive filler, usually carbon particles, an ion-conducting polymer electrolyte material, and a current collector, usually a thin sheet of aluminum. The composite cathode thin film is typically obtained by coating the current collector.

[0005] The production of thin films of lithium in the form of strips as wide as tens of centimeters or more, hundreds of meters long, and less than 100 microns thick, using fast and reliable processes faces significant technical challenges due to the extreme physical and chemical properties of this metal, such as chemical reactivity, malleability, low mechanical strength, rapid self-welding by contact alone, and strong adhesion to most solid materials.

[0006] Cold extrusion is used for the continuous production of sheets over 100 microns, a thickness generally adapted for the production of lithium batteries using liquid electrolytes. For smaller thicknesses, the membrane obtained by extrusion is then thinned between processing rollers made of a hard material.

[0007] In large-scale production processes, there are a number of challenges in achieving efficient thinning of high-density lithium to thicknesses that vary between 20 microns and 100 microns for the production of polymer electrolyte batteries.

[0008] The thinned lithium metal often reacts with and / or deforms with the processing rollers it contacts during the thinning process and adheres to the processing rollers. This problem can be solved by the use of lubricants such as those described in U.S. Patent Nos. 5,233,339; 5,399,623; and 5,433,663, each of which is incorporated by reference herein in its entirety. The lubricants contain additives that prevent the thin thin lithium film from reacting with or excessively adhering to the processing rollers and do not affect the electrochemistry of the resulting electrochemical cell. However, there is a need for proper and efficient application of lubricants during the thinning process.

[0009] The excessive ductility of lithium or its alloys allows only very small pulling tensions in the lithium film exiting the processing rollers, which must be precisely monitored and controlled to prevent rupture or tearing of the lithium film and the resulting costly interruptions in production.

[0010] Between 20 and 100 microns in thickness, it is difficult to thin a lithium or alloy film to a consistent thickness across the entire width of the film and across the extended length of the film. Thickness variations occur across the width of the thinned lithium film in conventional thinning processes, which promotes destruction of the lithium film during the thinning operation and results in a thinned lithium film that is less than suitable for electrochemical cells.

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

[0012] Thus, there is a need for a rolling mill adapted for reducing sheets of alkali metals or their alloys into films that addresses at least some of the above problems. There is also a need for alkali metal films produced by such mills that retain desirable properties across the width and length of the film. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] U.S. Pat. No. 5,837,401 [Patent Document 2] U.S. Patent No. 5,528,920 [Patent Document 3] U.S. Patent No. 6,019,801 Summary of the Invention [Problem to be solved by the invention]

[0014] It is an object of the present technology to remedy at least some of the disadvantages present in the prior art. [Means for solving the problem]

[0015] According to one aspect of the present technology, a rolling mill for thinning a sheet of an alkali metal or alloy thereof into a film is provided. The rolling mill includes a frame, a first work roller rotatably mounted to the frame, a second work roller rotatably mounted to the frame, the first work roller and the second work roller positioned to receive a sheet therebetween, at least two first actuators operably connected to opposite ends of the first work roller for bending the first work roller, and at least two second actuators operably connected to opposite ends of the second work roller for bending the second work roller. Each of the first work roller and the second work 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 and second frustum 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 frustum conical portions. 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 some embodiments of the present technology, the angle is less than 0.03 degrees.

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

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

[0019] In an embodiment of the present technology, for each of the first and second work rollers, the central portion, the first frusto-conical portion, and the second frusto-conical portion have a chrome coating.

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

[0021] In an embodiment 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 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 an embodiment of the present technology, for each of the first and second processing rollers, the first and second frusto-conical portions taper as they extend away from the central portion.

[0024] In an embodiment 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 frustum portion, and a second shoulder is defined between the central portion and the second frustum portion.

[0025] In one embodiment of the present technology, for each of the first processing roller and the second processing roller, the first frustum portion tapers as it extends from its outer end toward the central portion, and the second frustum portion tapers as it extends from its outer end toward the central portion.

[0026] In an embodiment of the present technology, a first backup roller is rotatably mounted to the frame, the first backup roller contacting the first processing roller to apply pressure to the first processing roller, and a second backup roller is rotatably mounted to the frame, the second backup roller contacting 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 alloy thereof into a film is provided. The processing roller has a cylindrical central portion defining a central axis and having an outer surface defining a thinning surface, a first frustoconical portion extending from a first end of the central portion, and a second frustoconical portion extending from a second end of the central portion. 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 frustoconical portion and the second frustoconical portion is less than 0.05 degrees. The width of the central portion is greater than the width of each of the first frustoconical portion and the second frustoconical 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 some embodiments of the present technology, the angle is less than 0.03 degrees.

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

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

[0031] In an embodiment of the present technology, the central portion, the first frusto-conical portion, and the second frusto-conical portion have a chrome coating.

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

[0033] In an embodiment of the present technology, the central portion, the first frusto-conical portion, and the second frusto-conical portion have a surface roughness in the range between Ra of 0.025 microns and Ra of 0.5 microns.

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

[0035] In an embodiment of the present technology, the first frusto-conical portion and the second frusto-conical portion taper as they extend away from the central portion.

[0036] In an embodiment of the present technology, a first shoulder is defined between the central portion and the first frusto-conical portion, and a second shoulder is defined between the central portion and the second frusto-conical portion.

[0037] In an embodiment of the present technology, the first frusto-conical portion tapers as it extends from its outer end towards the central portion, and the second frusto-conical portion tapers as it extends from its outer end towards the central portion.

[0038] For the purposes of this application, surface roughness is provided in terms of roughness average (Ra), expressed in metric units, specifically expressed in microns, and angles expressed in degrees (i.e., 360 degrees for a complete revolution). For the purposes of this application, hardness describes the resistance of materials (e.g., sheets and films) to localized deformation, where the deformation is introduced by either mechanical indentation or abrasion. For the purposes of this application, tensile strength (TS) refers to the ability of materials (e.g., sheets and films) to resist loads tending to elongate such materials. Tensile strength is measured by the maximum stress that a material can withstand while being stretched or pulled before breaking.

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

[0040] Embodiments of the present technology each have at least one of the above-mentioned objects and / or aspects, but not necessarily all of them. It should be understood that certain aspects of the present technology that arise from attempts to achieve the above-mentioned objects may not meet that object and / or may meet other objects not expressly 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] For a better understanding of the present technology, as well as other aspects and further features thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which: [Brief description of the drawings]

[0043] [Figure 1] FIG. 1 is a schematic cross-sectional side view of a rolling mill and associated components for reducing a sheet of lithium or lithium alloy into a thin film. [Diagram 2] FIG. 2 is a schematic side elevational view showing the main components of the rolling mill of FIG. 1 that allow control of the thickness and shape of the thinned lithium or lithium alloy film. [Diagram 3] FIG. 3 is a schematic front elevational view of the major components of the rolling mill of FIG. 2. [Figure 4A] 3 is a schematic front elevational view of the backup rollers and work rollers of the rolling mill of FIG. 2 shown in different arrangements, with the angle of the frustoconical portion of the work roller and the degree of bending of the work roller exaggerated for illustrative purposes. [Figure 4B] 3 is a schematic front elevational view of the backup rollers and work rollers of the rolling mill of FIG. 2 shown in different arrangements, with the angle of the frustoconical portion of the work roller and the degree of bending of the work roller exaggerated for illustrative purposes. [Figure 4C]3 is a schematic front elevational view of the backup rollers and work rollers of the rolling mill of FIG. 2 shown in different arrangements, with the angle of the frustoconical portion of the work roller and the degree of bending of the work roller exaggerated for illustrative purposes. [Diagram 5] FIG. 3 is a front elevational view of one work roller of the rolling mill of FIG. 2. [Figure 6A] 6 is an enlarged view of area 6 of FIG. 5 according to one embodiment of the roller of FIG. 5. [Figure 6B] 6 is an enlarged view of area 6 of FIG. 5 according to another embodiment of the roller of FIG. 5. [Figure 7] FIG. 3 is a schematic cross-sectional profile of a sheet of lithium or lithium alloy fed to the rolling mill of FIG. 2. [Figure 8] FIG. 2 is a perspective view of a thinning lubricant dispensing unit for lubricating the upper work rollers of the rolling mill of FIG. 1. [Figure 9] FIG. 2 is a perspective view of a thinning lubricant dispensing unit for lubricating the lower work rollers of the rolling mill of FIG. 1. [Figure 10] FIG. 10 is a top plan view of the thinning lubricant dispensing unit of FIG. [Figure 11] FIG. 10 is a front elevational view of the thinning lubricant dispensing unit of FIG. [Figure 12] 12 is a cross-sectional view of the thinning lubricant dispensing unit of FIG. 9 taken through line 12-12 of FIG. 10. [Figure 13] FIG. 13 is an enlarged view of a portion 13 of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] 1 illustrates generally a rolling mill 10 and associated components adapted to produce thin lithium or lithium alloy films 12 less than 100 microns thick from pre-extruded lithium or lithium alloy sheets 14 having a thickness of approximately 100-500 microns. Although embodiments of the present technique are described in connection with the production of thin lithium or lithium alloy films 12 from lithium or lithium alloy sheets 14, it is contemplated that at least some aspects of the present technique may be used for the production of other alkali metal or alkali metal alloy thin films from sheets of the other alkali metals or alkali metal alloys.

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

[0046] A roll 24 of wound extruded lithium or lithium alloy sheet 14 is placed on a feed roller 26 with a drive motor control unit (not shown) adapted to control the tension on the lithium sheet 14 before reaching processing rollers 18a and 18b. The sheet 14 snakes through a series of free rollers 28 to an encoder roller 41 that measures the exact speed of the advancing sheet 14, and onto a tension roller 43 equipped with a load cell adapted to accurately measure the tension on the sheet 14 as it enters the thinning apparatus 10. The load cell of tension roller 43 may be electronically linked to the control unit of the drive motor of roll 24 to automatically adjust the tension exerted on the sheet 14. The sheet 14 is then fed into a straightener 30 which quickly winds the sheet 14 through a series of closely packed rollers 32 which serve to eliminate lateral displacement of the sheet 14 and prevent zigzag motion of the sheet 14, thereby ensuring that the sheet 14 is fed straight into the center of the processing rollers 18a and 18b without lateral meandering motion that would be detrimental to the thinning process. The sheet 14 is then fed into the processing rollers 18a and 18b at a fixed position between the rollers 18a, 18b.

[0047] At the inlet of the rolling mill 10, lubricant dispensing units 22 and 200 dispense a lithium-compatible thinning lubricant in a suitable amount onto the working surface of each of the work rollers 18a and 18b upstream of the thinning region so that the sheet 14 is thinned on the properly lubricated work rollers 18a and 18b, thereby preventing undesirable adhesion of the thinned film 12 to either of the work rollers 18a, 18b. One suitable lubricant is described in U.S. Patent Nos. 5,399,623 and 5,433,363, which are incorporated by reference herein in their entireties. In one embodiment, the lubricant is based on toluene, hexane, and polyoxyethylene distereate and is used on each of the work rollers 18a and 18b in a sufficient amount to prevent excessive adhesion of the thinned film 12 to either of the work 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 100-500 microns to about 20-100 microns, depending on 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, which exert sufficient pressure on the sheet 14 to further reduce the thickness of the sheet 14 and transform the sheet 14 into the film 12. The thinning pressure is applied through the backup rollers 20a and 20b, instead of directly to the processing rollers 18a and 18b, to help avoid undesirable bending of the processing rollers 18a and 18b, which 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 by the backup rollers 20a and 20b to the processing rollers 18a and 18b is uniformly distributed on the surface of each roller 18a and 18b, thereby leaving 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 to transform the sheet 14 into the membrane 12 may be applied directly by the processing rollers 18a and 18b without the use of a backup roller. It is also contemplated that multiple backup rollers may be used to apply uniform pressure to each of the processing rollers 18a and 18b. 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 thermal resistance system 36 that measures the surface uniformity of the film 12 and also detects holes 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. A controlled tension is applied to the film 12 by a driven wrapping roller 38 to ensure that the film 12 is properly wrapped. Before reaching the wrapping roller 38, the thinned film 12 snakes under a controlled tension 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 on the thinned film 12 exiting the rolling mill 10. The load cell of the tension roller 45 can be electronically linked to a control unit of the drive motor of the wrapping roller 38 to automatically adjust the tension exerted on the film 12. The film 12 then passes over an encoder roller 47 that measures the exact speed of the advancing film 12. The film 12 then passes through a series of free rollers 34 that lead to the wrapping roller 38.

[0050] A thin insulating film 90, such as a polypropylene film, is also wrapped around the winding roller 38 to separate the layers of the film 12 so that the film 12 does not stick to one another. 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 tensioning roller 94 before reaching the roller 38. The tensioning 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 by the winding roller 38 on the film 12, since the tension exerted by the winding roller 38 is shared between the film 12 and the insulating film 90.

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

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

[0053] 2 and 3, the main components of the rolling mill 10 are described that allow for control of the thickness and shape of the thinned film 12. It should be understood that the rolling mill 10 shown 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 frame may have different configurations, and various hydraulic system configurations may be used.

[0054] Backup rollers 20a and 20b are rotatably mounted on bearings in support frames 50 and 52, respectively. Support frame 52 is slidably mounted to the vertical member of main frame 16 through any suitable means, such as slideways or bearings. Support frame 50 is fixedly mounted to the vertical member of main frame 16, so that support frame 52 can move vertically. Processing rollers 18a and 18b are each driven by an electric or hydraulic motor (not shown). Processing rollers 18a, 18b drive backup rollers 20a and 20b by friction. A pair of hydraulic linear actuators 66 are mounted on the upper horizontal member of main frame 16. The hydraulic actuators are connected to support frame 52. The hydraulic linear actuators 66 control the up and down movement of support frame 52 as well as the pressure applied to processing rollers 18a and 18b. Processing rollers 18a and 18b are rotatably mounted on support members 54 and 56, respectively. Support members 54 and 56 are operably coupled to support frames 50 and 52, respectively. End portions 58 and 59 of support member 54 are operably connected to support frame 50 via a pair of hydraulic linear actuators 60 and 61, and end portions 62 and 63 of support member 56 are operably connected to support frame 52 via a pair of hydraulic linear actuators 64 and 65.

[0055] During operation, the speed of thinning is set by the speed of processing rollers 18a and 18b. The pressure P required to reduce film 12 to the desired thickness is regulated through a hydraulic valve controlling hydraulic linear actuator 66. Backup roller 20b transmits pressure P to processing roller 18b. Once the desired pressure P is set, the final shape of thinned film 12 is finely tuned by adjusting the fluid pressure to each of hydraulic linear actuators 60, 61, 64, and 65, and thereby the force exerted by each of hydraulic linear actuators 60, 61, 64, and 65 on support members 54 and 56, as described in more detail below. Hydraulic linear actuators 60, 61, 64, 65, and 66 may be replaced by other types of actuators capable of generating sufficient force, such as electric actuators. In an alternative embodiment, additional hydraulic linear actuators are connected between support members 54, 56. In such an embodiment, hydraulic linear actuators 60, 61, 64, 65, and 66 are used to urge support members 54, 56 toward one another, and additional hydraulic linear actuators are used to urge support members 54, 56 toward one another.

[0056] During the thinning process, heat accumulates on the processing rollers 18a and 18b through friction generated at the thinning surface by the effect of slightly expanding the processing rollers 18a and 18b. Expansion of the processing rollers 18a, 18b by a few microns in the thinning area is sufficient to produce a film 12 of non-uniform thickness that is unsuitable for a thin film electrochemical cell. To alleviate this problem and help ensure a film 12 of uniform thickness, the central portion 100 (FIG. 4A) of the expanded processing rollers 18a and 18b is adjusted by bending the processing rollers 18a and 18b to straighten the central portion 100 and produce a lithium film 12 of uniform thickness. This control process is described below in connection with FIGS. 4A-4C. It should be noted that the shapes of processing rollers 18a and 18b shown in Figures 4A-4C have been greatly exaggerated for clarity, and it should be understood that the tapering and bending profiles of the end portions of processing rollers 18a, 18b represent deviations of only a few microns from a perfectly linear profile and are therefore not actually visible to the naked eye.

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

[0058] In FIG. 4B, the backup rollers 20a and 20b still apply a pressure P to the processing rollers 18a and 18b sufficient to reduce the thickness of the sheet 14 to the desired thickness of the film 12. However, due to thermal expansion, the central portions of the processing rollers 18a and 18b expand through the accumulation of heat generated by the friction of the central portions 100 in contact with the sheet 14. To counteract this thermal expansion, which has deformed the processing rollers 18a and 18b, an inwardly directed lateral force Fx 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 portions 100 as depicted in FIG. 4B. The outer edges of the processing rollers 18a and 18b are bent inward to straighten the central portions 100. The resulting thinned film 12 is therefore flat and has a uniform thickness. The thermal expansion of the processing rollers 18a, 18b is counteracted somewhat by the application of a thinning lubricant to the processing rollers 18a, 18b. It is also contemplated that additional means for cooling the processing rollers 18a, 18b may be used to help counteract the thermal expansion of the processing rollers 18a, 18b.

[0059] When the edges of the sheet 14 being thinned are thicker than the central portion of the sheet 14, in order to thin the film 12 to a uniform thickness across its width, a greater pressure is applied by the processing rollers 18a and 18b to the outer edges of the sheet 14, and therefore 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 bending the outer edges of the processing rollers 18a and 18b slightly inwardly, applying a greater pressure to the edges than to the central portion of the sheet 14. As a result, the thinned film 12 has a uniform thickness across its width. As heat builds up in the processing rollers 18a and 18b through friction of the central portion 100 in contact with the sheet 14, the central portions of the processing rollers 18a and 18b expand slightly. To offset this thermal expansion, which causes the diameter of the central portions of the processing rollers 18a and 18b to increase slightly, the lateral force Fx is proportionally reduced to keep the central portions 100 straight so that the resulting thinned film 12 pixel has a uniform thickness throughout its entire width.

[0060] The central portion of the thinned sheet 14 may then be thicker than its edges. In order to thin the film 12 with a uniform thickness throughout its width, a greater pressure needs to be applied to the central portion of the sheet 14 by the processing rollers 18a and 18b, and thus to the central portion of the central portion 100. To do so, as shown in FIG. 4C, an outwardly directed lateral force Fy is applied to the support members 54 and 56. The lateral force Fy causes the central portions of the processing rollers 18a and 18b to bend slightly inwardly and push 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 with a uniform thickness throughout its entire width.

[0061] In some circumstances, heat generated by friction of central portion 100 in contact with sheet 14 builds up at the outer portions of the facing surfaces of work rollers 18a and 18b, causing them to expand and opening a small gap in the center of central portion 100. To counteract this thermal expansion, an outwardly directed lateral force Fy is applied to support members 54 and 56 of work rollers 18a and 18b. The lateral force Fy bends the center portion of central portion 100 slightly, straightening central portion 100. The contour of central portion 100 of work rollers 18a, 18b is bent back to a straight line so that the resulting thinned web 12 is flat and has a uniform thickness throughout its entire width.

[0062] 4B and 4C, other adjustments are possible because the support members 54 and 56 are independent of each other. For example, if the processing rollers 18a, 18b expand more on one side than the other, the left or right support member 54, 56 may have a force Fx or Fy that exceeds the force Fx or Fy of the support member 54, 56 on the opposite side, allowing for multiple fine tuning adjustments.

[0063] Controlling the shape of the central portion 100, combined with precise measurements from an appropriate measurement device such as the optical thermal resistance system 36, enables the rolling mill 10 to produce high quality thinned films 12 in the thickness range of 20 to 100 microns that exhibit a nearly constant thickness throughout their entire length and width.

[0064] Adjustment of the contour and thickness of the thinned film 12 is performed by an on-site operator 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 performed electronically by linking measurement readings and actuators that control the various pressures and forces of the backup rollers 20a, 20b and 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 frusto-conical portions 106 taper as they extend away from the central portion 100. This embodiment was shown in FIGS. 4A-4C where the taper was exaggerated. In this embodiment, a shoulder 108 is defined between the central portion 100 and each of the frusto-conical portions 106 (one frusto-conical portion is shown 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 is contemplated that the shoulder 108 may be omitted. When the central axis 104 is straight (i.e., when the processing roller 18a is in a 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 frusto-conical portion 106 is less than 0.05 degrees. In some embodiments, the angle A is less than 0.03 degrees. In some embodiments, angle A is less than 0.02 degrees. In some embodiments, angle A is less than 0.02 degrees but greater than 0.01 degrees. In some embodiments, 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 contour of processing rollers 18a and 18b according to this embodiment facilitates bending of processing rollers 18a and 18b by providing free zones 84 (FIG. 4A) between frustoconical portions 106 and free zones 85 (FIG. 4A) between frustoconical portions 106 and backup rollers 20a and 20b such that the ends of processing rollers 18a and 18b can be moved to bend central portion 100 as desired. Free zones 84 also allow excess thinning lubricant to drain laterally during the thinning process. Although the embodiment of processing roller 18a shown in Figure 6A can be used with sheets 14 having many different contours, thanks to adjustments that can be made in rolling mill 10 (as described in detail in connection with Figures 4A-4C), this embodiment of processing roller 18a is particularly well adapted for thinning an extruded sheet 14 at a central portion 112 having a height H2 (Figure 7) that is less than the height H3 of side portions 114 (Figure 7) of sheet 14. Again, in Figure 7, the heights H2 and H3 do not appear to be different because the difference is not visible to the naked eye.In one embodiment, height H2 is less than 15 microns less than height H3.

[0069] In another embodiment shown in FIG. 6B, each frustum portion 106 tapers as it extends from its outer end toward 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 a neutral position), the angle B between the outer surface 102 of the central portion 100 and the outer surface 110 of the frustum portion 106 is less than 0.05 degrees. In some embodiments, the angle B is less than 0.03 degrees. In some embodiments, the angle B is less than 0.02 degrees. In some embodiments, the angle B 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 maximum diameter D2 and the minimum diameter D3 of each frustum portion 106 is between 0.03 mm and 0.17 mm. Although the embodiment of processing roller 18a shown in Figure 6B can be used with sheets 14 having many different contours because of adjustments that can be made in rolling mill 10 (as described in detail in connection with Figures 4A-4C), this embodiment of processing roller 18a is particularly well adapted for thinning an extruded sheet 14 at a central portion 112 having a height H2 (Figure 7) that is greater than height H3 of side portions 114 (Figure 7) of sheet 14. In one embodiment, height H2 is less than 15 microns greater than height H3.

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

[0071] As mentioned above, the thinning lubricant dispensed on the processing rollers 18a and 18b helps prevent adhesion of the lithium film 12 to the processing rollers 18a, 18b so that the film 12 exits the processing rollers 18a, 18b in a straight line. The use of the lubricant allows lithium and lithium alloys to be thinned on processing rollers 18a, 18b made from materials that are not normally suitable for adhesion to lithium. The lubricant negates this constraint. Therefore, for large scale production, the processing rollers 18a, 18b are preferably made from durable, hard materials such as steel, stainless steel, or even ceramic. In one embodiment, the steel or stainless steel rollers 18a, 18b have a thin chrome coating for additional hardness. The chrome coating is applied to at least the central portion 100 and the frustum portion 106 of the processing rollers 18a, 18b. In one embodiment, the chrome coating is a hard chrome coating. To provide a desired surface finish to the membrane 12 and to allow for 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 frusto-conical portion 106 have a surface roughness in the range of between 0.025 microns Ra and 0.5 microns Ra. In other embodiments, the surface roughness is in the range of between 0.05 microns Ra and 0.30 microns Ra.

[0072] Turning now to FIG. 8, the thinning lubricant dispensing unit 22 will be described in more detail. The thinning lubricant dispensing unit 22 comprises four nozzles 150 mounted on a rail 152. It is contemplated that the thinning lubricant dispensing unit 22 may have more than four or less than three nozzles 150. Thinning lubricant is supplied to a passageway (not shown) within the rail 152 via a suction connector 154. The suction connector 154 is fluidly connected to a pump (not shown) that supplies lubricant from a lubricant reservoir (not shown) that holds the thinning lubricant to the suction connector 154. The four nozzles 150 are in fluid communication with the passageway within the rail 152. As can be seen in FIG. 1, the thinning lubricant dispensing unit 22 is positioned upstream of the thinning region and spaced apart from the processing roller 18b. The thinning lubricant dispensing unit 22 is positioned above the central axis 104 of the processing roller 18b and is angled so that the nozzle 150 continuously sprays the thinning lubricant onto the thinning surface of the processing roller 18b. The spray from the nozzle 150 covers an area slightly larger 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 threads onto the rail 152. The filter is disposed within 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 threads onto the nozzle body 156 to hold the nozzle head 158 and filter in place.

[0074] 9-13, the thinning lubricant dispensing unit 200 will be described. In this embodiment, the thinning lubricant dispensing unit 200 is made from a single piece of static dissipative acetal copolymer. It is contemplated that other types of materials may be used, such as, for example, polyamide, polypropylene, polyethylene, acrylonitrile butadiene styrene, polyethylene terephthalate, polystyrene, thermoplastic polyurethane, poly(methyl methacrylate), polyvinyl chloride, brass, and aluminum. Other materials are also contemplated. It is also contemplated that the thinning lubricant dispensing unit 200 may be made from multiple pieces bonded or otherwise connected to one another.

[0075] The thinning lubricant dispensing unit 200 includes a dispensing unit body 202. Each rear corner portion of the dispensing unit body 202 defines two openings 206. Fasteners (not shown) are received in the openings 206 for fastening the dispensing unit body 202 to the frame 16 of the rolling mill 10 at a location between the processing rollers 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 a 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 located at the bottom of the wall 208. It is contemplated that multiple lubricant passages 210 may be defined in dispensing unit body 202 with outlets of the passages at different locations along laterally extending wall 208. It is also contemplated that at least some of the multiple lubricant passages 210 may have a common inlet.

[0076] Two side walls 218 extend forwardly from the transversely extending wall 208. As can be seen in Figure 10, the side walls 218 are parallel to one another. As can be seen in Figure 12, the front ends 220 of the side walls 218 are angled from the vertical so as not to interfere with the processing rollers 18a.

[0077] The thinning lubricant dispensing unit 200 also has a shelf 222. The shelf 222 is connected to the lower end of the laterally extending wall 208 and extends forward from the bottom. The shelf 222 is also connected to the lower end of the side wall 218 and extends between them. The shelf 222, the side wall 218, and the laterally extending wall 208 together define a recess 224 having an open side at the front of the thinning lubricant dispensing unit 200. The shelf 222 has a leading edge 226 that abuts the thinning surface of the processing roller 18a at a location vertically below the central axis 104 of the processing roller 18a, as seen in FIG. 12. The leading edge 226 has a width W4 (FIG. 10) that is greater than the width W1 of the thinning surface of the processing roller 18a to help ensure that the thinning lubricant is applied across the entire width of the thinning surface.

[0078] 13, the shelf 222 has an angled portion 228 that extends upwardly and rearwardly from a leading edge 226 toward the laterally extending wall 208. An angle 230 between the angled portion 228 and the leading edge 226 is arcuate. In some embodiments, the angled portion 228 extends at an angle C between 5 degrees and 25 degrees from the horizontal. In some embodiments, the angle C is between 10 degrees and 20 degrees from the horizontal. The shelf 222 also has a generally horizontal portion 232 that extends between the angled portion 228 and the laterally extending wall 208. The portion 232 is horizontal when viewed from the side (i.e., when viewed as viewed in FIGS. 12 and 13). However, when viewed from the front of the portion 232 (i.e., when viewed as viewed in FIG. 11), the portion 232 slopes slightly downwardly on either side of its lateral center, such that its lateral center corresponds to the apex of the portion 232. In some embodiments, the angle D (FIG. 11) between the surfaces on either side 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., angle D is 180 degrees) when viewed from the front of the portion 232 (i.e., when viewed as viewed in FIG. 11). As can be seen in FIGS. 11 and 12, the outlet 216 of the lubricant passage 210 is laterally aligned with the apex of the portion 232, and the bottom of the outlet 216 is vertically aligned with the top of the portion 232 of the shelf 222 adjacent thereto. It is contemplated that the portion 232 may be omitted and that the angled portion 228 may extend from the leading edge 226 to the laterally extending wall 208.

[0079] A laterally extending groove 234 is defined in angled portion 228 of shelf 222. As best seen in FIGURE 10, an end of groove 234 is spaced from sidewall 218. Groove 234 is spaced from leading edge 226 of shelf 222. As can be seen in FIGURE 13, groove 234 is closer to leading edge 226 than portion 232 of shelf 222.

[0080] 12, the inlet of the lubricant passage 210 is fluidly connected to a pump 236, which is itself fluidly connected to a lubricant reservoir 238. The lubricant reservoir 238 holds thinning lubricant therein. It is contemplated that the lubricant reservoir 238 may also be used to supply thinning lubricant to the thinning lubricant dispensing unit 22 described above. The pump 236 pumps thinning fluid from the lubricant reservoir 238 into the lubricant passage 210. From the outlet 216 of the lubricant passage 210, the lubricant flows forward and laterally (due to angle D) along a portion 232 of the shelf. The lubricant then flows downward along the angled portion 228. A portion of the lubricant flows into a groove 234 that helps ensure an even distribution of the lubricant across the width of the shelf 222. The lubricant then flows to a leading edge 226 that makes contact with the thinning surface of the processing roller 18a. The upwardly moving thinning surface of processing roller 18 a picks up the lubricant, which effectively coats the thinning surface in contact with sheet 14 .

[0081] In an embodiment, the alkali metal or alkali metal alloy film 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 membranes 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 lithium or lithium alloy film of the present technology includes an amount of a metal element. The addition of the metal element to the lithium or lithium alloy film can reduce the overall thickness of the film and improve the overall mechanical strength of the film. In some examples, the metal element is present in the lithium or lithium alloy film in an amount that improves the mechanical strength throughout the width, thickness, and length of the film.

[0084] The metal element that can be used in the preparation of the lithium or lithium alloy film of the present technology is preferably conductive. It is understood that the presence of the metal element should not hinder the conductivity of the lithium or lithium alloy film. For example, aluminum is a metal element that can be used in the lithium or lithium alloy film. In some examples, aluminum is present in the film in an amount ranging 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 some examples, aluminum is present in the film in an amount that is 3000 ppm or more.

[0085] In certain examples, the lithium or lithium alloy films of the present technology have a hardness, as measured by Shore hardness scale (Shore A scale), ranging from about 50 to about 85, between about 60 to about 80, between about 60 to about 75, between about 50 to about 70, between about 60 to about 75, between about 65 to about 75, between about 66 to about 70, or between about 66 to about 69. In some examples, the hardness is at least 65. In some other examples, the hardness is at least about 66. In some examples, the hardness is uniform throughout the lithium or lithium alloy film.

[0086] The lithium films obtained by the techniques defined herein have widths (corresponding to the distance from one edge of the thin film to the other) ranging from about 140 mm to about 200 mm, about 150 mm to about 200 mm, about 160 mm to about 180 mm, about 160 mm to about 175 mm, about 160 mm to about 170 mm, or about 160 mm to about 165 mm, and have thicknesses ranging from about 20 microns to about 100 microns, about 20 microns to about 90 microns, about 20 microns to about 75 microns, about 20 microns to about 50 microns, or 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 uniform thickness throughout the width of the film encompasses a thickness variation of about ±2 microns.

[0087] In some embodiments, the lithium or lithium alloy films obtained by the techniques defined herein have a thickness to width ratio (t / w) that is between about 1×10 and about 7×10, and in some instances, this t / w is maintained throughout the length of the film.

[0088] Specifically, the present 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 present technology maintains its width, thickness, and hardness over at least about 15,000 meters, at least about 10,000 meters, at least about 9,000 meters, at least 8,000 meters, at least 7,000 meters, at least 6,000 meters, at least 5,000 meters, at least 4,000 meters, at least 3,000 meters, at least 2,000 meters, or at least 1,000 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 modifications and variations that fall within the scope of the present disclosure as defined in the accompanying embodiments.

[0090] Example 1 Production of thin lithium alloy films (3000ppm) A thinned lithium film was prepared using a rolling mill with textured rollers 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 hardness tester (PTC Model 320-A scale). The results are presented in Table 1.

[0091] [Table 1]

[0092] Example 2 Production of thin lithium alloy films (5000ppm) A thinned lithium film was prepared using a rolling mill with textured rollers 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 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 thinned lithium alloy films (3000ppm) A thinned lithium-aluminum film was prepared using a rolling mill with textured 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 a Testometric M500 at 25 kN. The results are presented in Table 3.

[0095] [Table 3]

[0096] Example 4 Evaluate the tensile strength of thinned lithium alloy films (5000ppm) A thinned lithium-aluminum film was prepared using a rolling mill 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 a Testometric M500 at 25 kN. The results are presented in Table 4.

[0097] [Table 4]

[0098] Modifications and improvements to the above-described embodiments of the technology may become apparent to those skilled in the art. The foregoing description is intended to be illustrative and not limiting. Accordingly, the scope of the technology is intended to be limited only by the scope of the appended claims. [Explanation of symbols]

[0099] 10 Rolling mill, thinning equipment 12 Thin film of lithium or lithium alloy 14 Lithium or lithium alloy sheet 16 Main Frame 18a, 18b Processing roller 20a, 20b Backup rollers 22 Thinning lubricant dispensing unit 24 rolls 26 Feed roller 28 Free Roller 34 Free Roller 36 Heat-resistant refraction system 38 Winding roller 41 Encoder roller 43, 45 Pulling roller 47 Encoder roller 50, 52 Support frame 54, 56 Support member 58, 59, 62, 63 End part 60, 61, 64, 65, 66 Hydraulic Linear Actuators 84, 85 Free Band 90 Insulating Film 92 rolls 94 Pulling roller 100 central part 102 Outer surface of central portion 100 104 Center axis 106 Cone frustum 108 Shoulder 110 Outer surface of the truncated cone portion 106 112 Center part of sheet 14 114 Side portion of seat 14 116, 118 Support shaft 120 Extension 150 nozzles 152 Rail 154 Intake connector 156 Nozzle body 158 Nozzle Head 160 Nut 162 Spray opening 200 Thinning Lubricant Dispensing Unit 202 Dispensing unit body 206 Aperture 208 Horizontal Wall 210 Lubricant passage 214 Back wall 216 Exit 218 Side wall 220 front end 222 Shelf 224 Recess 226 Leading Edge 228 Diagonal Part 230 angle 232 Generally horizontal parts 234 Groove 236 Pump 238 Lubricant reservoir A, B Angle between outer surface 102 and outer surface 110 C Angle of the diagonal part 228 D angle D1 Diameter of central part 100 D2, D3 The minimum or maximum diameter of the truncated cone portion 106 Fx lateral force Fy lateral force H1 Height of shoulder 108 H2 Height of central part 112 H3 Height of side part 114 W1 Width of central part 100 W2 Sheet 14 width W3 Width of the truncated cone part 106

Claims

1. 1. A rolling mill for reducing a sheet of an alkali metal or alloy thereof into a film, the rolling mill comprising: A frame, a first processing roller rotatably mounted to the frame; a second work roller rotatably mounted to the frame, the first work roller and the second work roller positioned to receive the sheet therebetween; and at least two first actuators operatively connected to opposite ends of the first working roller for bending the first working roller; at least two second actuators operatively connected to opposite ends of the second working roller for bending the second working roller; Equipped with 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 reduced surface; a first frusto-conical portion extending from a first end of the central portion; a second frusto-conical portion extending from a second end of the central portion; and Equipped with when the central axis is straight, an angle between the outer surface of the central portion and an outer surface of each of the first frusto-conical portion and the second frusto-conical portion is less than 0.05 degrees; a width of the central portion is greater than a width of each of the first frusto-conical portion and the second frusto-conical 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; For each of the first processing roller and the second processing roller, the first frusto-conical portion tapers as it extends from its outer end toward the central portion; the second frusto-conical portion tapers as it extends from its outer end toward the central portion; Rolling machine.

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

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

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

5. 5. The rolling mill of claim 1, wherein for each of the first and second work rollers, the central portion, the first frusto-conical portion, and the second frusto-conical portion have a chrome coating.

6. 6. The rolling mill of claim 1, wherein for each of the first and second work rollers, the central portion, the first frusto-conical portion, and the second frusto-conical portion have a surface roughness in the range between 0.025 microns Ra and 0.5 microns Ra.

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

8. a first backup roller rotatably mounted to the frame and in contact with the first processing roller to apply pressure to the first processing roller; a second backup roller rotatably mounted to the frame and in contact with the second work roller to apply pressure to the second work roller; The rolling mill of claim 1 , further comprising:

9. 1. A processing roller for a rolling mill for reducing a sheet of an alkali metal or alloy thereof into a film, the processing roller comprising: a cylindrical central portion defining a central axis, the central portion having an outer surface defining a reduced surface; a first frusto-conical portion extending from a first end of the central portion; a second frusto-conical portion extending from a second end of the central portion; and Equipped with when the central axis is straight, an angle between the outer surface of the central portion and an outer surface of each of the first frusto-conical portion and the second frusto-conical portion is less than 0.05 degrees; a width of the central portion is greater than a width of each of the first frusto-conical portion and the second frusto-conical 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; the first frusto-conical portion tapers as it extends from its outer end toward the central portion; the second frusto-conical portion tapers as it extends from its outer end toward the central portion; Processing roller.

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

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

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

13. 13. The processing roller of claim 9, wherein the central portion, the first frusto-conical portion, and the second frusto-conical portion have a chrome coating.

14. 14. The processing roller of claim 9, wherein the central portion, the first frusto-conical portion, and the second frusto-conical portion have a surface roughness in the range of between 0.025 microns Ra and 0.5 microns Ra.

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

Images