EP4677656A1

EP4677656A1 - Flexible substrate passivation

Info

Publication number: EP4677656A1
Application number: EP24771401.7A
Authority: EP
Inventors: Jean Delmas; Terry Bluck; Subramanya P. Herle; Jeffrey Aaron FOX; Visweswaren Sivaramakrishnan
Original assignee: Elevated Materials Germany GmbH
Current assignee: Elevated Materials Germany GmbH
Priority date: 2023-03-10
Filing date: 2024-03-05
Publication date: 2026-01-14
Also published as: JP2026508560A; WO2024191662A1; CN120917581A; KR20250159225A

Abstract

In one embodiment, a flexible substrate processing system is provided comprising: a pickup hub; a calendering unit comprising a first calender roller and a second calender roller; and a passivation unit having an interior volume, the pickup hub configured to rotate and assist in conveying a flexible substrate through the interior volume of the passivation unit after the flexible substrate passes between the first calender roller and the second calender roller, the passivation unit including one or more ultraviolet (UV) lamps configured to direct UV radiation towards the flexible substrate when the flexible substrate is conveyed through the interior volume of the passivation unit.

Description

FLEXIBLE SUBSTRATE PASSIVATION

BACKGROUND

[0001] Embodiments of the present disclosure generally relate to equipment and methods for passivating a layer on flexible substrate, such as passivating a lithium layer disposed on a flexible substrate used in a roll-to-rol I application.

Description of the Related Art

[0002] Flexible substrates can be used in the manufacture of electrodes for lithium- ion batteries. Different materials can be used for the anode of lithium-ion batteries, such as one or more of copper, silicon, and graphite. Prelithiation is a technique that adds lithium to an electrode (e.g., the anode) of a lithium-ion battery to prevent loss of lithium ions that act as charge carriers during use of the lithium-ion battery. Preventing this loss of lithium ions can improve the useful life of a lithium-ion battery by reducing performance loss that can occur with aging of the battery.

[0003] Although lithium can be deposited directly on a flexible substrate serving as the anode, this process can often be damaging to materials (e.g., copper) used as the anode. Thus, one method is to deposit a lithium film onto a flexible carrier (e.g., PET) and then transfer the lithium film from the flexible carrier to the flexible substrate serving as the anode.

[0004] Although prelithiation of flexible substrates serving as the anode can improve the performance of lithium-ion batteries, the prelithiated anodes have not fully solved the performance issues associated with loss of lithium ions. Accordingly, there is a need for improved methods and equipment that can further reduce the performance issues associated with loss of lithium ions in lithium-ion batteries.

SUMMARY

[0005] In one embodiment, a flexible substrate processing system is provided comprising: a pickup hub; a calendering unit comprising a first calender roller and a second calender roller; and a passivation unit having an interior volume, the pickup hub configured to rotate and assist in conveying a flexible substrate through the interior volume of the passivation unit after the flexible substrate passes between the first calender roller and the second calender roller, the passivation unit including one or more ultraviolet (UV) lamps configured to direct UV radiation towards the flexible substrate when the flexible substrate is conveyed through the interior volume of the passivation unit.

[0006] In another embodiment, a flexible substrate processing system is provided comprising: a pickup hub; a calendering unit comprising a first calender roller and a second calender roller; and a passivation unit having an interior volume, the pickup hub configured to rotate and assist in conveying a flexible substrate through the interior volume of the passivation unit after the flexible substrate passes between the first calender roller and the second calender roller, the passivation unit including one or more plasma-generating units configured to generate and provide a plasma to the interior volume of the passivation unit when the flexible substrate is conveyed through the interior volume of the passivation unit.

[0007] In another embodiment, a flexible substrate processing system is provided comprising: a pickup hub; a calendering unit comprising a first calender roller and a second calender roller; and a passivation unit having an interior volume, the pickup hub configured to rotate and assist in conveying a flexible substrate through the interior volume of the passivation unit after the flexible substrate passes between the first calender roller and the second calender roller, the passivation unit including one or more plasma-generating units configured to generate and provide a plasma to the interior volume of the passivation unit when the flexible substrate is conveyed through the interior volume of the passivation unit.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments.

[0009] Figure 1 shows a side cross-sectional view of a flexible substrate processing system, according to one embodiment. [0010] Figure 2A shows a side cross-sectional view of a first type of passivation unit shown in Figure 1 , according to one embodiment

[0011] Figure 2B shows a top schematic view of an alternative passivation unit, according to one embodiment

[0012] Figure 2C shows a side cross-sectional view of a second type of passivation unit shown in Figure 1 , according to one embodiment

[0013] Figure 3 is a process flow diagram of a method of transferring lithium films onto the flexible substrate and passivating the surfaces of these lithium films using the processing system of Figure 1 , according to one embodiment.

[0014] Figure 4 shows a side cross-sectional view of a flexible substrate processing system, according to another embodiment.

[0015] Figure 5 shows a side cross-sectional view of a flexible substrate processing system, according to another embodiment.

[0016] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

[0017] Embodiments of the present disclosure generally relate to flexible substrate processing systems that include one or more passivation units to treat a recently exposed surface of a film positioned on a flexible substrate. One exemplary use of the processing systems and methods provided in this disclosure include passivating a surface of a lithium film that can be used as part of an electrode in a lithium ionbattery. For example, a lithium film can be transferred from a flexible carrier (e.g., a polymer-based carrier) to a flexible substrate (e.g., a flexible copper substrate) by having the flexible carrier and the flexible substrate pass through a calendering unit and then peeling away the flexible carrier. Transferring the lithium film to the flexible substrate exposes a new surface of the lithium film to the surrounding environment when the flexible carrier is peeled away from the flexible substrate. This newly exposed surface can then be conveyed through a passivation unit with the flexible substrate to prevent reactions of the newly exposed surface with the ambient environment that can negatively affect the performance of the lithium film in a lithium- ion battery. For example, reactions between lithium and nitrogen can negatively affect the performance of using a lithium film on the anode of a lithium-ion battery.

[0018] The passivation unit can supply one or more gases (e.g., CO2) to form a passivation layer on the newly exposed surface of the lithium film, which prevents the negative reactions mentioned above from occurring, such as the reactions with nitrogen. As the passivation layer forms, the available locations for the lithium to react with ambient environment are consumed, and thus after the formation of the passivation layer is completed, the negative reactions between the lithium film and components (e.g., nitrogen) of the ambient environment are prevented or substantially reduced. In some embodiments, the passivation layers are also formed in a selflimiting manner, so that while the gases used to form the passivation layer can react with lithium to form the passivation layer, the gases do not continue to react with the passivation layer to increase the thickness of the passivation layer.

[0019] The passivation unit can include ultraviolet lamps or a plasma generator to increase the rate of these passivation reactions between the one or more supplied gases (e.g., CO2) and the newly exposed surface of the lithium film. Although the following disclosure mainly describes passivating a recently exposed surface of a lithium film formed on a flexible substrate, the benefits of this disclosure can be applied for passivating recently exposed surfaces of other films, such as films of other alkali metals or alloys including an alkali metal, transferred to any type of flexible substrate. More generally, the benefits can particularly apply to situations when new surfaces of films formed of highly reactive materials, such as lithium, are exposed.

[0020] Figure 1 shows a side cross-sectional view of a flexible substrate processing system 100, according to one embodiment. The processing system 100 includes equipment for transferring lithium films on a first flexible carrier 110 and a second flexible carrier 120 to each side of a flexible substrate 130, so that the flexible substrate 130 with the lithium films can be used as an electrode (e.g., anode) in a lithium-ion battery. The processing system 100 includes a calendering unit 140 to transfer the lithium films on the flexible carriers 110, 120 to the flexible substrate 130. The processing system 100 further includes either a passivation unit 200A or a passivation unit 200C for passivating the newly exposed surfaces of the lithium films transferred onto the flexible substrate 130. Additional detail on the passivating unit 200A is described in reference to Figure 2A below. Additional detail on the passivating unit 200C is described in reference to Figure 2C below.

[0021] The processing system 100 includes a first flexible carrier supply hub 115. A supply roll 111 of the first flexible carrier 110 is positioned on the first flexible carrier supply hub 115. In some embodiments, the first flexible carrier 110 can be formed of a polymer material, such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), or combinations thereof. A lithium film (not shown in Figure 1 ) is positioned on the lower side 110L of the first flexible carrier 110, so that this lithium film faces an upper surface 130U of the flexible substrate 130 as the first flexible carrier 110 and the flexible substrate 130 are conveyed through the calendering unit 140. This lithium film is shown as the lithium film 201 in Figures 2A and 2C after being transferred to the flexible substrate 130. The upper surface 130U of the flexible substrate 130 is on an opposite side relative to a lower surface 130L of the flexible substrate 130. The upper surface 130U is also referred to as the first surface or the first side of the flexible substrate 130 while the lower surface is also referred to as the second surface or the second side of the flexible substrate 130.

[0022] The processing system 100 includes a second flexible carrier supply hub 125. A supply roll 121 of the second flexible carrier 120 is positioned on the second flexible carrier supply hub 125. In some embodiments, the second flexible carrier 120 can be formed of a same material (e.g., PET) as the first flexible carrier 110. A lithium film (not shown in Figure 1 ) is positioned on the upper side 120U of the second flexible carrier 120, so that this lithium film faces the lower surface 130L of the flexible substrate 130 as the second flexible carrier 120 and the flexible substrate 130 are conveyed through the calendering unit 140. This lithium film is shown as the lithium film 202 in Figures 2A and 2C after being transferred to the flexible substrate 130.

[0023] In some embodiments, the lithium films on the first carrier 110 and the second carrier 120 can be formed of lithium metal, another alkali metals or an alloy including an alkali metal.

[0024] The processing system 100 includes a flexible substrate supply hub 135. A supply roll 131 of the flexible substrate 130 is positioned on the flexible substrate supply hub 135. In some embodiments, the flexible substrate 130 can be formed of one or more of copper, graphite, silicon, silicon graphite, silicon oxide graphite, silicon, metalized plastic, or other materials.

[0025] The processing system 100 further includes the calendering unit 140. The calendering unit 140 includes a first calender roller 141 and a second calender roller 142. The first flexible carrier 110, the second flexible carrier 120, and the flexible substrate 130 are arranged to be conveyed along a path that extends between the first calender roller 141 and the second calender roller 142. The flexible substrate 130 is positioned between the first flexible carrier 110 and the second flexible carrier 120 when the first flexible carrier 110, the second flexible carrier 120, and the flexible substrate 130 are conveyed between the first calender roller 141 and the second calender roller 142. The calender rollers 141 , 142 exert a high amount of pressure on the carriers 110, 120 and the flexible substrate 130 that causes the lithium film on each of the carriers 110, 120 to be transferred to the flexible substrate 130. In some embodiments, a release layer is disposed on each of the flexible carriers 110, 120 between the corresponding flexible carrier 110, 120 and the lithium film on that flexible carrier. In some embodiments, the release layer can be formed of siloxane.

[0026] The processing system 100 includes a first flexible carrier pickup hub 116. A pickup roll 112 of the first flexible carrier 110 is positioned on the first flexible carrier pickup hub 116. The lithium film is no longer on the first flexible carrier 110 when the first flexible carrier 110 is wound onto the first flexible carrier pickup hub 116 because the lithium film previously on the first flexible carrier 110 is transferred onto the flexible substrate 130 by the calendering unit 140.

[0027] The processing system 100 includes a second flexible carrier pickup hub 126. A pickup roll 122 of the second flexible carrier 120 is positioned on the second flexible carrier pickup hub 126. The lithium film is no longer on the second flexible carrier 120 when the second flexible carrier 120 is wound onto the second flexible carrier pickup hub 126 because the lithium film previously on the second flexible carrier 120 is transferred onto the flexible substrate 130 by the calendering unit 140.

[0028] The processing system 100 includes a flexible substrate pickup hub 136. A pickup roll 132 of the flexible substrate 130 is positioned on the flexible substrate pickup hub 136. The flexible substrate 130 includes a lithium film on each of the upper surface 130U and the lower surface 130L of the flexible substrate 130. These lithium films are transferred from the respective carriers 110, 120 onto the flexible substrate 130 by the calendering unit 140.

[0029] The processing system 100 further includes a plurality of rollers 181-188. In some embodiments, each of the rollers 181-188 can be passive rollers. The rollers 181-188 can assist in applying proper tension to and assist in changing the direction of the flexible carriers 110, 120 and the flexible substrate 130 during the movement of each of the carriers 110, 120 and the flexible substrate 130 through the different portions of the processing system 100. Some of the rollers 181-188 can also assist in moving the carriers 110, 120 closer to or further away from the flexible substrate 130. For example, the second and third rollers 182, 183 assist in bringing the carriers 110, 120 into contact with the flexible substrate 130 before the carriers 110, 120 and the flexible substrate 130 are conveyed through the calendering unit 140. Additionally, the fourth and fifth rollers 184, 185 provide a location at which tension can be applied to the carriers 110, 120 to peel these carriers 110, 120 away from the flexible substrate 130. In some embodiments, one or more of the rollers 181-188 can instead be a bar, such as metal bar, that can apply tension to the carrier or flexible substrate during the movement of the carrier or flexible substrate.

[0030] In some embodiments, the passivation unit 200A, 200C is placed within a short distance from the rollers 184, 185 to reduce the duration of the time from when the surfaces of the lithium films are exposed by the peeling away of the flexible carriers 110, 120 to when the newly exposed surfaces of the lithium films are passivated by the corresponding passivation unit 200A, 200C. In some embodiments, the corresponding passivation unit 200A, 200C can be positioned within two feet of the rollers 184, 185, such as within one foot, such as within six inches of the rollers 184, 185. Similarly, in some embodiments, the corresponding passivation unit 200A, 200C can be positioned within two feet of the calender rollers 141 , 142, such as within one foot, such as within six inches of the rollers 141 , 142.

[0031] Furthermore, in some embodiments the rollers 184, 185 can be positioned in a controlled atmosphere, such as an atmosphere including no nitrogen, an atmosphere of inert gas without any significant amount of other gases, or an atmosphere including one or more gases provided to the interior volume of the passivation unit 200A, 200C, such as carbon dioxide without any gases known to negatively affect the performance of the lithium films, such as nitrogen. In one embodiment, the rollers 184, 185 and the corresponding passivation unit 200A ,200C are housed in a same enclosure that has a controlled atmosphere as described above, so that there is no exposure of the newly exposed lithium surfaces to an uncontrolled atmosphere, such as an atmosphere including nitrogen. In some embodiments, each portion of the processing system 100 is in a controlled atmosphere, such as an environment including no nitrogen.

[0032] The processing system 100 can further include actuators (not shown) configured to rotate each of the hubs 115, 116, 125, 126, 135, 136, so that the carriers 110, 120 and the flexible substrate 130 can be conveyed from the corresponding supply hub 115, 125, 135, through the calendering unit 140, and to the corresponding pick hub 116, 126, 136. The processing system 100 can further include one or more actuators (not shown) to rotate the calender rollers 141 , 142 of the calendering unit

140. The rotational speed of the actuators can be adjusted to control the speed at which the flexible substrate 130 and flexible carriers 110, 120 are conveyed through the processing system 100.

[0033] In the processing system 100, the flexible substrate 130 is conveyed along a path from the supply roll 131 that is supported by the supply hub 135, past the first roller 181 , between the second and third rollers 182, 183, between the calender rollers

141 , 142, between the fourth and fifth rollers 184, 185, through the passivation unit 200A, 200C, past the eighth roller 188, and to the pickup roll 132 around the pickup 136. The pickup hub 136 is configured to rotate and assist in conveying the flexible substrate through the interior volume of the corresponding passivation unit 200A, 200C after the flexible substrate 130 passes between the first calender roller 141 and the second calender roller 142. Similarly, the pickup hubs 116, 126 are configured to rotate and assist in conveying the flexible carriers along paths between the supply hubs 115, 125 and the pickup hubs 116, 126.

[0001] The processing system 100 can also include a controller 105 for controlling processes performed by the processing system 100. The controller 105 can be any type of controller used in an industrial setting, such as a programmable logic controller (PLC). The controller 105 includes a processor 107, a memory 106, and input/output (I/O) circuits 108. The controller 105 can further include one or more of the following components (not shown), such as one or more power supplies, clocks, communication components (e.g., network interface card), and user interfaces typically found in controllers for semiconductor equipment.

[0034] The memory 106 can include non-transitory memory. The non-transitory memory can be used to store the programs and settings described below. The memory 106 can include one or more readily available types of memory, such as read only memory (ROM) (e.g., electrically erasable programmable read-only memory (EEPROM), flash memory, floppy disk, hard disk, or random access memory (RAM) (e.g., non-volatile random access memory (NVRAM).

[0035] The processor 107 is configured to execute various programs stored in the memory 106, such as a program configured to execute the method 3000 described below in reference to Figure 3. During execution of these programs, the controller 105 can communicate to I/O devices through the I/O circuits 108. For example, during execution of these programs and communication through the I/O circuits 108, the controller 105 can control outputs (e.g., the actuators connected to the different hubs and the calendering unit 140). The memory 106 can further include various operational settings used to control the processing system 100. For example, the settings can include speed settings for the actuators connected to the hubs as well as settings to control the passivation units 200A, 200C described below.

[0036] Figure 2A shows a side cross-sectional view of the passivation unit 200A shown in Figure 1 , according to one embodiment. In Figure 2A, an upper lithium film 201 (first lithium film) is positioned on the upper surface 130U of the flexible substrate 130, and a lower lithium film 202 (second lithium film) is positioned on the lower surface 130L of the flexible substrate 130. The flexible substrate 130 and the lithium films 201 , 202 can be conveyed in a direction D through the passivation unit 200A and towards the pickup hub 136 (see Figure 1 ). The upper lithium film 201 includes an outer surface 203. The lower lithium film 202 includes an outer surface 204. The outer surfaces 203, 204 become exposed when the first flexible carrier 110 and the second flexible carrier 120 are peeled away from the flexible substrate 130 after being conveyed through the calendering unit 140 and passing the rollers 184, 185 (see Figure 1). [0037] The newly exposed surfaces 203, 204 of the lithium films 201 , 202 can begin to react with the surrounding environment, for example by reacting with nitrogen in the atmosphere if the environment is not a controlled atmosphere as described above. These reactions with nitrogen reduce the benefits of prelithiating an electrode (e.g., an anode) for a lithium-ion battery. To address this problem, one or more different gases (e.g., CO2) are supplied to the passivating units 200A (Figure 2A), 200C (Figure 2C) to passivate these newly exposed surfaces 203, 204. These one or more different gases (e.g., CO2) undergo passivation reactions with the lithium on the surfaces 203, 204, which passivates these surfaces 203, 204 to prevent or substantially reduce further undesirable reactions of the lithium films 201 , 202 with components (e.g., nitrogen) in an uncontrolled atmosphere.

[0038] In some embodiments, carbon dioxide (CO2) is provided to the corresponding passivating units 200A, 200C along with one or more of argon (Ar), hydrogen (H2), oxygen (O2), and water vapor to form a passivation layer of lithium carbonate (IJ2CO3). In other embodiments, sulfur hexafluoride (SFe) is provided to the corresponding passivating units 200A, 200C along with one or more of argon (Ar), hydrogen (H2), oxygen (O2), and water vapor to form a passivation layer of lithium fluoride (LiF) or lithium sulfur hexafluoride (LixSFe). Other gases that can be used to form passivation layers on a lithium surface include carbon monoxide (CO), carbon tetrafluoride (CF4), ammonia (NH3) as well as other oxide, fluoride, and chloride gases. The thickness of the passivation layers formed on the lithium surfaces can be from about 1 nm to about 1000 nm, such as from about 10 nm to about 500 nm. In some embodiments, the lithium films 201 , 202 can have a thickness from about 1 micron to about 100 micron, such as about 10 micron.

[0039] The passivation unit 200A includes a housing 215 disposed around an interior volume 208. The housing 215 includes an upper portion 215U and a lower housing 215L. The flexible substrate 130 with the lithium films 201 , 202 is conveyed through the interior volume 208 as the flexible substrate 130 is moved towards the pickup hub 136. The interior volume 208 includes an upper volume 208U above the flexible substrate 130 and a lower volume 208L below the flexible substrate 130.

[0040] In some embodiments, the passivation unit 200A further includes a plurality of seals 251-254. The seals 251-254 can be formed of a compressible material. The seals 251-254 can be used to maintain a separate environment in the interior volume 208 relative to the environment surrounding the passivation unit 200A. For example, the interior volume 208 can have different concentrations of gases as well as a different temperature and/or pressure relative to the environment surrounding the passivation unit 200A.

[0041] In some embodiments, the seals 251-254 can be omitted and pressure differentials between the interior volume 208 and the surrounding environment can be used. For example, in one embodiment, the pressure in the interior volume 208 is higher than a pressure of the surrounding environment, so that nitrogen and other undesirable gases do not enter the interior volume 208 of the passivation unit 200A. In some embodiments, an air knife, for example using an inert gas or other gas (e.g., CO2), can be used at the entrance and exit to the interior volume to prevent mixing of gases in the interior volume 208 with gases in the surrounding environment.

[0042] The first seal 251 is positioned between the upper housing 215U and the flexible substrate 130 at the entrance to the interior volume 208 of the passivation unit 200A. The second seal 252 is positioned between the lower housing 215L and the flexible substrate 130 at the entrance to the interior volume 208 of the passivation unit 200A. The third seal 253 is positioned between the upper housing 215U and the flexible substrate 130 at the exit from the interior volume 208 of the passivation unit 200A. The fourth seal 254 is positioned between the lower housing 215L and the flexible substrate 130 at the exit from the interior volume 208 of the passivation unit 200A. In some embodiments, the upper housing 215U or the lower housing 215L can be configured to move, for example in a vertical direction, so that it can be easier position a new flexible substrate 130 in the interior volume 208 as well as to adjust the pressure of the seals 251-254 on the flexible substrate 130 or distance between the seals 251-254 and the flexible substrate 130 during processing.

[0043] The upper housing 215U includes a gas inlet port 231 U near the entrance to the upper volume 208U and a gas outlet port 241 U near the exit from the upper volume 208U. The lower housing 215L includes a gas inlet port 231 L near the entrance to the lower volume 208L and a gas outlet port 241 L near the exit from the lower volume 208L. The gas inlet ports 231 U, 231 L can be connected to gas sources 230A, 230B. In some embodiments, the gas sources 230A, 230B can be a single gas source. The gas outlet ports 241 U, 241 L can be connected to exhaust pumps 240A, 240B. In some embodiments, the exhaust pumps 240A, 240B can be a single exhaust pump.

[0044] The passivation unit 200A further includes a plurality of ultraviolet (UV) lamps 210. Five UV lamps 210 are positioned in the upper housing 215U. Five UV lamps 210 are positioned in the lower housing 215L. Each of the UV lamps 210 can be connected to an electrical power supply (not shown) and electrical power to the UV lamps 210 can be controlled by the controller 105 (Figure 1 ). The passivation unit 200A includes an upper window 260U positioned between the UV lamps 210 in the upper housing 215U and the upper interior volume 208U. The passivation unit 200 includes a lower window 260L positioned between the UV lamps 210 in the lower housing 215L and the lower interior volume 208L. The windows 260U, 260L can be formed of a UV-transparent material, such as quartz. In some embodiments, the UV lamps 210 can be positioned in the corresponding interior volumes 208U, 208L.

[0045] The UV lamps 210 in the upper housing 215U can direct UV energy into the upper volume 208U to increase the rate of the passivation reactions between the upper lithium film 201 and the one or more gases (e.g., CO2) supplied to the upper interior volume 208U from the gas source 230A. Similarly, the UV lamps 210 in the lower housing 215L can direct UV energy into the lower volume 208L to increase the rate of the passivation reactions between the lower lithium film 202 and the one or more gases (e.g., CO2) supplied to the lower interior volume 208L from the gas source 230B. The increased rate of passivation reactions on the exposed lithium surfaces 203, 204 provided by the UV energy enables a sufficient portion of the surfaces 203, 204 to be effectively passivated before the flexible substrate 130 exits the passivation unit 200A. In some embodiments, the UV lamps 210 can emit UV radiation having a wavelength from about 100 nm to about 270 nm, such as from about 185 nm to about 254 nm. Wavelengths within these ranges can dissociate gases supplied to the passivation unit 200A. For example, UV radiation within these wavelengths can split carbon dioxide (CO2) into CO and O, which can be more reactive than the originally supplied CO2. Similarly, these wavelengths can split water (H2O) into H and OH, and oxygen (O2) into O and O3, which can also be more reactive than the originally supplied water vapor or oxygen. [0046] Figure 2B shows a top schematic view of an alternative passivation unit 200A’, according to one embodiment. The passivation unit 200A’ is the same as the passivation unit 200A except that the passivation unit 200A’ includes a different arrangement of components for supplying and exhausting one or more gases to and from the interior volumes 208U, 208L. Figure 2B illustrates the arrangement of these components in the XY-plane. The following describes the locations of these components in the Z-direction. With additional reference to Figure 2A, the lamps 210 are located in the housing 215U while the flexible substrate 130, the gas supply lines 232 and the exhaust lines 242 are located in the upper interior volume 208U.

[0047] Although Figure 2B is described as a top view with components for supplying and exhausting gases to and from the upper interior volume 208U of Figure 2A, the description is also applicable to a bottom view of the lower interior volume 208L. The upper housing 215U is shown as transparent so that the relative location of the different components can be shown. The flexible substrate 130 is shown as dashed inside the passivation unit 200A’ to indicate that the flexible substrate 130 extends below the supply and exhaust lines and below the UV lamps 210.

[0048] The passivation unit 200A’ includes supply gas lines 232 that are disposed along three sides of the interior volume 208U to supply one or more gases (e.g., CO2) from the gas source 230A to the interior volume 208U at the entrance to the interior volume 208U as well as along the sides of the flexible substrate 130 as the flexible substrate 130 moves towards the exit of the interior volume 208. The supply gas lines 232 include a plurality of perforations 235 configured to supply the one or more gases to different locations in the upper interior volume 208U. In some embodiments, the supply gas lines 232 can further include sections extending in the Y-direction in regions 211 between the UV lamps 210, so that the one or more gases can be supplied to the upper interior volume 208U at these locations as well. Furthermore, although only a single row of perforations 235 is shown, in some embodiments, the gas lines 232 can include perforations 235 at different locations in the Z-direction as well. For example, in some embodiments, the gas lines 232 can include sections having a showerhead arrangement with perforations 235 arranged across an XZ plane or a YZ plane with the perforations arranged across most of the available space in that plane in the Z-direction (e.g., from the top of the interior volume 208 to the bottom of the interior volume 208). Furthermore, in some embodiments, the perforations 235 can be oriented in a downward direction towards the flexible substrate 130.

[0049] The passivation unit 200A’ further includes exhaust gas lines 242 that extend across a region near the exit from the upper interior volume 208U. The exhaust gas lines 242 include a plurality of perforations 245 configured to exhaust the one or more gases across the width of the flexible substrate 130 in the Y-direction near the exit from the upper interior volume 208U.

[0050] Figure 2C shows a side cross-sectional view of the passivation unit 200C shown in Figure 1 , according to one embodiment. The passivation unit 200C is the same as the passivation unit 200A except that the passivation unit 200C is configured to supply a plasma P into the interior volumes instead of UV energy to increase the rate of the intended reactions between the lithium film and the plasma species (e.g., radicals of CO2).

[0051] The housing and interior volumes of the passivation unit 200C are different (e.g., different shape and/or size) than the housing 215 and interior volume 208 of the passivation unit 200A described above. The passivation unit 200C includes an upper housing 285U and a lower housing 285L. The passivation unit 200C includes an upper interior volume 288U and a lower interior volume 288L. The upper interior volume 288U is between the upper housing 285U and the upper side of the flexible substrate 130. The lower interior volume 288L is between the lower housing 285L and the lower side of the flexible substrate 130.

[0052] The passivation unit 200C can include a plurality of plasma-generating units 270 that can each generate a capacitively coupled plasma. Although five plasmagenerating units 270 are shown in the upper housing 285U and the lower housing 285L, other embodiments may include more or less plasma-generating units 270. Furthermore, the plasma-generating units 270 are one example of providing a plasma to the interior volume that includes the flexible substrate 130 and many other types of plasma-generating units can be used, such as different types of capacitively coupled plasma-generating units (e.g., different arrangements of electrodes and/or power sources other than RF energy, such as microwave energy) or inductively coupled plasma-generating units. In other embodiments, a remote plasma source can be used to supply plasma to the interior volume that includes the flexible substrate 130. [0053] The plasma-generating units 270 are each configured to generate a plasma P of one or more gases (e.g., CO2) supplied from the gas sources 230A, 230B. Each plasma-generating unit 270 includes a first electrode 271 , a second electrode 272, a connecting plate 273, and an interior volume 275. The first electrode 271 of each plasma-generating unit 270 can be connected to one of the radio frequency (RF) power sources 265A, 265B. The second electrode 272 of each plasma-generating unit 270 can be connected to electrical ground. Only one connection between the electrodes 271 , 272 is shown on either side of the flexible substrate 130 in order to not clutter the drawing. In some embodiments, the electrodes 271 , 272 can be spaced apart from each other in the X-direction by about 0.25 mm to about 10 mm, such as by about 0.5 mm to about 5 mm, such as by about 1 mm. In some embodiments, the ends of the electrodes 271 , 272 closest to the flexible substrate 130 can be spaced apart from the flexible substrate 130 by about 1 mm to about 10 mm, such as by about 4 mm.

[0054] The connecting plate 273 extends between the first electrode 271 and the second electrode 272 of each plasma-generating unit 270. The connecting plate 273 can be formed of or coated by a dielectric material. Furthermore, in some embodiments, the electrodes 271 , 272 can be coated by a dielectric material. Additionally, each plasma-generating unit 270 can also include plates extending in the X-direction (not visible in Figure 2C), so that the interior volume 275 is enclosed around four sides. In some embodiments, these additional plates extending in the X- direction can be formed of or coated by a dielectric material while in other embodiments these additional plates extending in the X-direction can be a pair of electrodes similar to the electrodes 271 , 272.

[0055] The plasma P generated by the plasma-generating units then flows from the interior volume 275 of each plasma-generating unit 270 towards the flexible substrate 130, so that the plasma species (e.g., radicals of CO2) can react with the corresponding lithium film 201 , 202 on either side of the flexible substrate 130. The plasma P increases the rate of the passivation reactions on the exposed lithium surfaces 203, 204, so that a sufficient portion of the surfaces 203, 204 can be effectively passivated before the flexible substrate 130 exits the passivation unit 200C. [0056] Although the passivation units 200A, 200C are generally described as passivating surfaces of a lithium film, the passivation units 200A, 200C can also be used to passivate surfaces of other films, such as films formed of different alkali metals or films formed of alloys including at least one alkali metal.

[0057] Figure 3 is a process flow diagram of a method 3000 of transferring lithium films onto the 130 flexible substrate and passivating the surfaces of these lithium films using the processing system 100 of Figure 1 , according to one embodiment. The passivation of the lithium films can be performed using the passivation unit 200A of Figure 2A or the passivation unit 200C of Figure 2C. With reference to Figures 1 , 2A- 2C, and 3, the method 3000 is described.

[0058] The method begins at block 3002. At block 3002, the processing system 100 begins to convey sections of the flexible carriers 110, 120 and the flexible substrate 130 from the corresponding supply hubs 115, 125, 135 towards the calendering unit 140.

[0059] At block 3004, the lithium films 201 , 202 are transferred from flexible carriers 110, 120 to the flexible substrate 130 by the calendering unit 140. The first lithium film 201 is transferred from the first flexible carrier 110 to the upper surface 130U of the flexible substrate 130 by the calendering unit 140. The second lithium film 202 is transferred from the second flexible carrier 120 to the lower surface 130L of the flexible substrate 130 by the calendering unit 140.

[0060] At block 3006, the flexible carriers 110, 120 are peeled away from the flexible substrate 130 as the flexible carriers 110, 120 are conveyed past the rollers 184, 185 as shown in Figure 1. In some embodiments, a release layer is disposed on each of the flexible carriers 110, 120 to aid in the release of the lithium films 201 , 202 from each flexible carrier 110, 120. Each of the flexible carriers 110, 120 is then conveyed to the respective pickup hub 116, 126.

[0061] At block 3008, the flexible substrate 130 and the newly transferred lithium films 201 , 202 are conveyed into one of the passivation units 200A, 200C, and the newly exposed surfaces 203, 204 of these lithium films 201 , 202 are passivated in the corresponding passivation unit 200A, 200C. [0062] In one embodiment of block 3008 using the passivation unit 200A (Figure 2A), one or more gases (e.g., CO2) are supplied into the upper interior volume 208U and the lower interior volume 208L from the one or more gas sources 230A, 230B. UV energy is directed into interior volumes 208U, 208L to increase the rate of the passivation reactions between the lithium films 201 , 202 and the gases activated by the UV energy. The activated gas energized by the UV energy from the UV lamps 210 effectively passivates the lithium films 201 , 202 on the flexible substrate 130 by the time these films 201 , 202 and the flexible substrate 130 exit the passivation unit 200B.

[0063] In another embodiment of block 3008 using the passivation unit 200C (Figure 2C), one or more gases (e.g., CO2) are supplied into the interior volume 275 of each of the plasma-generating units 270. RF power is supplied from the corresponding RF power source 265A, 265B to the electrodes 271 , 272 of each of the plasma-generating units 270 to generate the plasma P in the interior volume 275 in each of the plasma-generating units 270. The plasma P including plasma species (e.g., CO2 ions and radicals) then flows towards the corresponding lithium films 201 , 202 and reacts with the lithium to passivate the respective surfaces 203, 204. The plasma effectively passivates the lithium films 201 , 202 on the flexible substrate 130 by the time these films 201 , 202 and the flexible substrate 130 exit the passivation unit 200C.

[0064] At block 3010, the passivated lithium films 201 , 202 on the flexible substrate 130 are conveyed to the pickup hub 136. Because the surfaces 203, 204 of the lithium films 201 , 202 on the flexible substrate 130 have been passivated, the lithium films 201 , 202 can remain exposed to an ambient environment, for example including nitrogen, for substantially longer durations without significantly effecting the performance of the lithium films for eventual use as part of an electrode (e.g., anode) in a lithium-ion battery compared to otherwise similar lithium films not having passivated surfaces. Furthermore, the passivation of the lithium films 201 , 202 improves the performance of the lithium films 201 , 202 when the lithium films 201 , 202 are used as part of an electrode (e.g., anode) of a lithium-ion battery.

[0065] Figure 4 shows a side cross-sectional view of a flexible substrate processing system 400, according to one embodiment. The flexible substrate processing system 400 is the same as the flexible substrate processing system 100 of Figure 1 except that the flexible substrate processing system 400 includes one of the passivation units 200A, 200C as part of a flexible substrate pickup unit 430. The pickup unit 430 includes the same flexible substrate pickup hub 136 as flexible substrate processing system 100 (Figure 1 ). The pickup hub 136 winds the flexible substrate roll 132 around the pickup hub 136 after the flexible substrate is conveyed through the passivation unit 200A, 200C. The pickup unit 430 includes a roller 488 to assist in applying proper tension to the flexible substrate 130 as the flexible substrate 130 is wound around the pickup hub 136.

[0066] In some embodiments, the flexible substrate pickup unit 430 can include an enclosure 431. In some of these embodiments, the enclosure 431 can operate at a higher pressure than the surrounding environment to prevent gases (e.g., nitrogen) from the atmosphere, which can have a negative effect on the lithium films 201 , 202 (see e.g., Figure 2A) from interacting with the lithium films 201 , 202 in the enclosure 431. In some of these embodiments, the enclosure 431 can be pressurized with inert gases (e.g., argon) or gases known not to negatively affect the performance of the lithium films, such as oxygen and carbon dioxide. The entrance to the enclosure 431 can be directly after the flexible carriers 110, 120 are peeled away to reduce the amount of time that the surfaces of the lithium films 201 , 202 (see Figure 2A) are exposed before entering the controlled environment of the enclosure 431. In some embodiments, the interior of the enclosure 431 can also be temperature controlled to control the temperature of the flexible substrate 130 and the roll 132. In some embodiments, the hub 136 can be temperature controlled to maintain the roll 132 of flexible substrate at a specified temperature. Including one of the passivation unit 200A, 200C as part of one the flexible substrate pickup unit 430 can make it easier to add a passivation unit to existing equipment.

[0067] In the processing system 400, the flexible substrate 130 is conveyed along a path from the supply roll 131 that is supported by the supply hub 135, past the first roller 181 , between the second and third rollers 182, 183, between the calender rollers 141 , 142, between the fourth and fifth rollers 184, 185, through the passivation unit 200A, 200C, past the eighth roller 488, and to the pickup roll 132 around the pickup 136. In some embodiments, the passivation unit 200A, 200C can also be positioned between the roller 488 and the pickup hub 136. [0068] Figure 5 shows a side cross-sectional view of a flexible substrate processing system 500, according to one embodiment. The flexible substrate processing system 500 is the same as the flexible substrate processing system 100 of Figure 1 except that the flexible substrate processing system 500 includes three passivation units 200Ai, 2OOA2, and 200C instead of only one of the passivation units 200A, 200C. The following provides an exemplary arrangement for the three passivation units, but other arrangements can also be used, such as placing the passivation unit 200C before one or more of the other passivation units 2OOA1, 2OOA2.

[0069] The first and second passivation units 2OOA1, 2OOA2 are each one of the passivation units 200A (see Figures 2A, 2B) that can direct UV energy into the interior volumes 208U, 208L. The first passivation unit 2OOA1 can be used to clean the lithium films 201 , 202. For example, after the lithium films 201 , 202 are peeled away from the flexible carriers 110, 120 some residual material (e.g., hydrocarbon material) from the flexible carriers 110, 120 or elsewhere can remain on the surfaces 203, 204 of the lithium films 201 , 202. The passivation unit 2OOA1 can direct UV energy from the UV lamps 210 at an inert gas (e.g., argon) in the corresponding interior volumes 208U, 208L to activate to inert gas to assist in removing this residual material. The inert gas can be supplied from the one or more gas sources 230A, 230B.

[0070] The second passivation unit 2OOA2 can used to form a passivation layer on the lithium films 201 , 202. The second passivation unit 2OOA2 can direct UV energy from the UV lamps 210 at one or more reactive gases (e.g., CO2) in the interior volumes 208U, 208L to activate the one or more reactive gases. The activation of these one or more gases by the UV energy increases the rate at which the gases react with the lithium films 201 , 202 to form the passivation layer. The one or more reactive gases can be supplied from the one or more sources 230A, 230B.

[0071] The third passivation unit 200C can be used to form an additional passivation layer on the lithium films 201 , 202 or to increase the thickness of the passivation layer started by the second passivation unit 2OOA2. With reference to Figure 2C, the third passivation unit 200C is configured to generate a plasma P from one or more gases supplied from the one or more gas source 230A, 230B to the interior volumes 275 of the plasma-generating units 270. The plasma P including plasma species (e.g., CO2 ions and radicals) then flows towards the corresponding lithium films 201 , 202 and reacts with lithium to further passivate the lithium films 201 , 202.

[0072] By using the three passivation units 200Ai, 2OOA2, 200C in the processing system 500, a more effective passivation layer can be formed on the lithium films. For example, the first passivation unit 2OOA1 can remove residual materials that may not otherwise be removed by the other passivation units. These residual materials could eventually flake off and expose unpassivated lithium which could then undergo undesirable reactions, for example with nitrogen that would negatively affect the performance of the lithium films when used as part of an anode in a lithium-ion battery. Furthermore, in some embodiments using the two passivation units 2OOA2, 200C can form a more effective passivation layer or two passivation layers that have improved passivation properties compared to a single passivation layer formed by only one of the passivation units 2OOA2, 200C. For example, in one embodiment a first gas (e.g., CO2) can be supplied to the passivation unit 2OOA2 and a second gas (e.g., CF4) can be supplied to the passivation unit 200C. As another example, the plasma P formed by the passivation unit 200C may be better at filling in small voids in the passivation layer formed by the passivation unit 2OOA2. Thus, the passivation unit 200C that is configured to generate the plasma P can be used to fill in remaining voids in the passivation layer formed by the second passivation unit 2OOA2.

[0073] In the processing system 500, the flexible substrate 130 is conveyed along a path from the supply roll 131 that is supported by the supply hub 135, past the first roller 181 , between the second and third rollers 182, 183, between the calender rollers 141 , 142, between the fourth and fifth rollers 184, 185, through the passivation unit 200Ai, through the passivation unit 2OOA2, through the passivation unit 200C, past the eighth roller 188, and to the pickup roll 132 around the pickup 136.

[0074] While the foregoing is directed to examples of the present disclosure, other and further examples of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is:

1 . A flexible substrate processing system comprising: a pickup hub; a calendering unit comprising a first calender roller and a second calender roller; and a passivation unit having an interior volume, the pickup hub configured to rotate and assist in conveying a flexible substrate through the interior volume of the passivation unit after the flexible substrate passes between the first calender roller and the second calender roller, the passivation unit including one or more ultraviolet (UV) lamps configured to direct UV radiation towards the flexible substrate when the flexible substrate is conveyed through the interior volume of the passivation unit.

2. The flexible substrate processing system of claim 1 , wherein the passivation unit further comprises one or more gas inlets configured to direct gas towards the flexible substrate when the flexible substrate is conveyed through the interior volume of the passivation unit.

3. The flexible substrate processing system of claim 2, wherein the one or more gas inlets includes a first gas inlet and a second gas inlet, the first gas inlet is configured to direct gas to a first portion of the interior volume on a first side of the flexible substrate when the flexible substrate is conveyed through the interior volume of the passivation unit, and the second gas inlet is configured to direct gas to a second portion of the interior volume on a second side of the flexible substrate opposite to the first side when the flexible substrate is conveyed through the interior volume of the passivation unit.

4. The flexible substrate processing system of claim 3, wherein the one or more UV lamps includes a first UV lamp and a second UV lamp, the first UV lamp is configured to direct UV energy at the first portion of the interior volume on the first side of the flexible substrate when the flexible substrate is conveyed through the interior volume of the passivation unit, and the second UV lamp is configured to direct UV energy at the second portion of the interior volume on the second side of the flexible substrate when the flexible substrate is conveyed through the interior volume of the passivation unit.

5. The flexible substrate processing system of claim 1 , wherein the one or more UV lamps includes a first UV lamp and a second UV lamp, the first UV lamp is configured to direct UV energy at a first portion of the interior volume on a first side of the flexible substrate when the flexible substrate is conveyed through the interior volume of the passivation unit, and the second UV lamp is configured to direct UV energy at a second portion of the interior volume on a second side of the flexible substrate opposite to the first side when the flexible substrate is conveyed through the interior volume of the passivation unit.

6. The flexible substrate processing system of claim 1 , further comprising a first roller positioned between the calendering unit and the passivation unit, wherein the first roller is configured to assist in peeling a first flexible carrier away from the flexible substrate before the flexible substrate enters the passivation unit.

7. The flexible substrate processing system of claim 6, further comprising a second roller positioned between the calendering unit and the passivation unit, wherein the second roller is configured to assist in peeling a second flexible carrier away from the flexible substrate before the flexible substrate enters the passivation unit.

8. The flexible substrate processing system of claim 6, wherein the passivation unit is positioned less than one foot from the first roller.

9. The flexible substrate processing system of claim 1 , wherein the passivation unit is positioned less than one foot from the calendering unit.

10. A flexible substrate processing system comprising: a pickup hub; a calendering unit comprising a first calender roller and a second calender roller; and a passivation unit having an interior volume, the pickup hub configured to rotate and assist in conveying a flexible substrate through the interior volume of the passivation unit after the flexible substrate passes between the first calender roller and the second calender roller, the passivation unit including one or more plasmagenerating units configured to generate and provide a plasma to the interior volume of the passivation unit when the flexible substrate is conveyed through the interior volume of the passivation unit.

11. The flexible substrate processing system of claim 10, wherein the plasmagenerating unit comprises a first electrode and a second electrode.

12. The flexible substrate processing system of claim 11 , wherein the first electrode is coupled to a radio frequency power source and the second electrode is coupled to an electrical ground.

13. The flexible substrate processing system of claim 10, wherein the one or more plasma-generating units includes a first plasma-generating unit and a second plasma-generating unit, the first plasma-generating unit is configured to direct plasma generated by the first plasma-generating unit to a first portion of the interior volume on the first side of the flexible substrate when the flexible substrate is conveyed through the interior volume of the passivation unit, and the second plasma-generating unit is configured to direct plasma generated by the second plasma-generating unit to a second portion of the interior volume on the second side of the flexible substrate when the flexible substrate is conveyed through the interior volume of the passivation unit.

14. The flexible substrate processing system of claim 10, further comprising a first roller positioned between the calendering unit and the passivation unit, wherein the first roller is configured to assist in peeling a first flexible carrier away from the flexible substrate before the flexible substrate enters the passivation unit.

15. The flexible substrate processing system of claim 14, further comprising a second roller positioned between the calendering unit and the passivation unit, wherein the second roller is configured to assist in peeling a second flexible carrier away from the flexible substrate before the flexible substrate enters the passivation unit.

16. The flexible substrate processing system of claim 14, wherein the passivation unit is positioned less than one foot from the first roller.

17. The flexible substrate processing system of claim 10, wherein the passivation unit is positioned less than one foot from the calendering unit.

18. A flexible substrate processing system comprising: a pickup hub; a calendering unit comprising a first calender roller and a second calender roller; a first passivation unit having an interior volume, the pickup hub configured to rotate and assist in conveying a flexible substrate through the interior volume of the first passivation unit after the flexible substrate passes between the first calender roller and the second calender roller, the first passivation unit including one or more ultraviolet (UV) lamps configured to direct UV radiation towards the flexible substrate when the flexible substrate is conveyed through the interior volume of the first passivation unit; and a second passivation unit having an interior volume, the pickup hub configured to rotate and assist in conveying the flexible substrate through the interior volume of the second passivation unit after the flexible substrate passes between the first calender roller and the second calender roller, the passivation unit including one or more plasma-generating units configured to generate and provide a plasma to the interior volume of the second passivation unit when the flexible substrate is conveyed through the interior volume of the second passivation unit.

19. The flexible substrate processing system of claim 18, wherein the pickup hub is configured to assist in conveying the flexible substrate along a path from the calendering unit through the interior volume of the first passivation unit, through the interior volume of the second passivation unit, and to the pickup hub, and the first passivation unit is located between calendering unit and the second passivation unit on the path.

20. The flexible substrate processing system of claim 18, further comprising a third passivation unit having an interior volume, the pickup hub configured to rotate and assist in conveying a flexible substrate through the interior volume of the third passivation unit after the flexible substrate exits the interior volume of the first passivation unit, the third passivation unit including one or more ultraviolet (UV) lamps configured to direct UV radiation towards the flexible substrate when the flexible substrate is conveyed through the interior volume of the third passivation unit, wherein the first passivation unit is coupled to a first gas source configured to supply one or more inert gases to the interior volume of the first passivation unit, and the third passivation unit is coupled to a second gas source configured to supply one or more reactive gases to the interior volume of the third passivation unit.