Web coating method and ventilated cooling drum with integral electrostatic clamp - Patent Application 20070122997

Abstract

A rotatable drum is provided for supporting a substrate. The rotatable drum includes a curved drum surface for supporting the substrate. The curved drum surface includes a dielectric portion and an electrode coupled to a power source. The electrode is electrically coupled to the curved drum surface and is capable of chucking and dechucking the substrate from the curved drum surface at one or more circumferential segments of the curved drum surface.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The embodiments described herein relate generally to metal electrodes, and more specifically to lithium-containing anodes, and to apparatus and methods for fabricating high performance electrochemical devices, such as primary and secondary electrochemical devices, that include the lithium-containing electrodes described above. [Background technology]

[0002] Lithium (Li)-ion batteries have played a key role in the development of current generations of mobile devices, microelectronics, and electric vehicles. A typical Li-ion battery is made up of a positive electrode (cathode), a negative electrode (anode), an electrolyte that conducts ions, a porous separator (electrical insulator) between the two electrodes to keep them physically separated, and packaging.

[0003] Methods for depositing lithium on substrates, such as large flexible substrates, can be temperature-sensitive, potentially causing wrinkles and other defects. The substrate can be guided and supported on a rotatable coating drum with a curved drum surface. Vapor can be deposited on the substrate as it moves past one or more evaporation sources and onto the curved drum surface of the rotatable drum. The drum can be used to maintain and control the substrate temperature by using high pressure to cool and pressurize the backside of the substrate and maintain a uniform gap height between the substrate and the curved drum surface. For large thin-film substrates, lower pressures can be used due to grains, film stress, or misalignment that can cause wrinkles in the machine direction.

[0004] Therefore, there is a need for an apparatus and method for maintaining low pressure and enhanced substrate cooling to improve throughput. Summary of the Invention

[0005] In one aspect, a rotatable drum for supporting a substrate is provided. The rotatable drum supports the substrate and includes a curved drum surface including a dielectric portion. The rotatable drum further includes an electrode coupled to a power source, the electrode being electrically coupled to the curved drum surface and capable of chucking and dechucking the substrate from the curved drum surface at one or more circumferential segments of the curved drum surface.

[0006] Embodiments may include one or more of the following: The dielectric portion comprises a material selected from the group consisting of diamond-like carbon, aluminum oxide, boron nitride, polyimide, and combinations thereof. The electrode is a fixed electrode spaced radially inward from the curved drum surface and electrically coupled to the curved drum surface by a plurality of movable electrode spokes. The electrode includes a first hemisphere that is electrically grounded and a second hemisphere that is coupled to a power source. Each of the one or more circumferential segments includes at least one cooling channel and one or more gas passages extending from the inner surface of the circumferential segment to the curved drum surface. The dielectric portion of the curved drum surface includes a first polyimide layer, a patterned electrode disposed on the first polyimide layer, and a second polyimide layer disposed on the patterned electrode. The patterned electrode includes copper. The patterned electrode includes a plurality of mesas. The mesas are polygonal. The mesas are arranged in a row extending from one edge of the rotatable drum to the opposite edge of the rotatable drum. The rotatable drum further includes surface channels disposed between adjacent rows of the patterned electrodes. The rows alternate with a first row coupled to a power source and a second row coupled to a ground plane. The rotatable drum further includes heat sinks disposed radially inward from the curved drum surface and radially outward from the electrodes. A deposition apparatus includes a rotatable drum and an evaporation source configured to deposit a material onto a substrate disposed on the curved drum surface of the rotatable drum.

[0007] In another aspect, an electrode assembly for electrostatically chucking a substrate to a rotatable drum is provided, the electrode assembly including a first protective layer interfacing with the rotatable drum, an electrode disposed on the first protective layer, and a second protective layer disposed on the electrode and including a curved surface for supporting the substrate.

[0008] Embodiments may include one or more of the following: the first and second protective layers include aluminum oxide and the electrodes include aluminum or an alloy of aluminum; the electrodes are arranged in a plurality of rows extending substantially parallel to one another and extending from one edge of the rotatable drum to an opposite edge of the rotatable drum; the rows alternate with a first row coupled to power and a second row connected to ground, with a channel disposed between the rows.

[0009] In yet another aspect, a method of coating a substrate in a vacuum chamber is provided. The method includes transporting a substrate onto a curved surface of a rotatable drum, where the substrate is electrostatically chucked to at least a portion of the curved surface of the rotatable drum. The method further includes evaporating material in an evaporation crucible. The method further includes directing the evaporated material from the evaporation crucible to the substrate.

[0010] Embodiments may include one or more of the following: Transporting the substrate further includes holding the substrate on the curved surface of the rotatable drum such that a gap is formed between the substrate and the curved surface of the rotatable drum; The method further includes supplying a gas to the gap between the backside of the substrate and the curved surface of the rotatable drum; The substrate is transported in a machine direction extending from an entrance side to an exit side of the rotatable drum, and the substrate is chucked at the entrance side and dechucked at the exit side.

[0011] In another aspect, a non-transitory computer-readable medium stores instructions that, when executed by a processor, cause a process to perform the operations of the apparatus and / or methods described above.

[0012] So that the above-recited features of the present disclosure may be understood in detail, a more particular description of the present disclosure briefly summarized above can be had by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings illustrate only exemplary embodiments and therefore should not be considered as limiting the scope thereof, as other equally effective embodiments may be recognized. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 shows a simplified cross-sectional view of one embodiment of an energy storage device incorporating an anode electrode structure according to some embodiments described herein. [Figure 2] FIG. 2 shows a cross-sectional view of one embodiment of a double-sided anode electrode structure according to some embodiments described herein. [Figure 3] FIG. 3 shows a simplified cross-sectional view of an evaporation source for depositing evaporated material on a substrate according to some embodiments described herein. [Figure 4] FIG. 4 shows a simplified cross-sectional view of a vapor deposition apparatus according to some embodiments described herein. [Figure 5A] FIG. 5A shows a schematic view of the deposition apparatus of FIG. 4 viewed along the axis of rotation of the rotatable drum according to some embodiments described herein. [Figure 5B] FIG. 5B illustrates a cross-sectional end view of a rotatable drum carrying a substrate according to some embodiments described herein. [Figure 6] FIG. 6 illustrates a cross-sectional view of a portion of a dielectric portion of a rotatable drum according to some embodiments described herein. [Figure 7] FIG. 7 illustrates a top view of a dielectric portion of a rotatable drum according to certain embodiments described herein. [Figure 8] FIG. 8 illustrates a cross-sectional end view of a dielectric portion coupled to a body of a drum according to some embodiments described herein. [Figure 9]FIG. 9 illustrates an interior view of a drum according to some embodiments described herein. [Figure 10] FIG. 10 shows a flow diagram illustrating a method for coating a substrate according to some embodiments described herein.

[0014] For ease of understanding, wherever possible, identical reference numerals have been used to designate identical elements 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 OF THE INVENTION

[0015] The present disclosure relates generally to metal electrodes, more specifically lithium-containing anodes, and to apparatus and methods for assembling high performance electrochemical devices, such as primary and secondary electrochemical devices, that include the lithium-containing electrodes described above.

[0016] A deposition system for coating a web substrate guided over a rotatable coating drum is referred to herein as a roll-to-roll (R2R) deposition system. As described herein, a flexible substrate can be considered to include, among other things, films, foils, webs, strips of plastic material, metal, paper, or other materials. Typically, terms such as "web," "foil," "strip," and "substrate" are used interchangeably.

[0017] Energy storage devices, such as Li-ion batteries, typically include a positive electrode (e.g., cathode) and a negative electrode (e.g., anode) separated by a polymer separator with a liquid electrolyte. Solid-state batteries also typically include a positive electrode and a negative electrode, but replace both the polymer separator and the liquid electrolyte with an ionically conductive material. Lithium is deposited on a substrate by evaporating molten lithium or lithium vapor onto a substrate, such as graphite-coated copper foil or copper foil. The substrate is maintained below a certain temperature while lithium is deposited on the front side of the substrate. Maintaining the temperature may include cooling the backside of the substrate by passing a gas between the drum surface supporting the substrate and the substrate. The deposition rate of lithium on the substrate is limited by the cooling rate of the backside of the substrate. The cooling gas is selected to be non-reactive with lithium. In some embodiments, the cooling gas can be or include argon, helium, or a combination thereof.

[0018] In addition to supplying cooling gas to the backside of the substrate, a uniform gap distance between the substrate and the drum surface is typically maintained. Traditional solutions for holding the substrate have included mechanical solutions, such as placing hold-down rollers around the drum to hold the substrate to the drum and applying gas to prevent the substrate from expanding and moving away from the drum as the substrate thermally expands. These solutions can result in edge damage and delamination. The use of electrostatic clamps has been found to hold the substrate to the drum and also maintain a uniform gap between the substrate and the drum surface.

[0019] FIG. 1 shows a simplified cross-sectional view of one embodiment of an energy storage device 100 incorporating an anode electrode structure 110 formed according to some embodiments described herein. The anode electrode structure 110 includes an anode film 170 having one or more protective film(s) 180 formed thereon. The energy storage device 100 may be a solid-state energy storage device or a lithium-ion based energy storage device. While the energy storage device 100 is shown as a planar structure, it can also be formed into a cylinder by rotating the stack, and other cell configurations, such as prismatic cells, button cells, or stacked electrode cells, can also be formed. The energy storage device 100 includes an anode electrode structure 110 and a cathode electrode structure 120, optionally with an electrolyte or polymer separator 130 disposed therebetween. The cathode electrode structure 120 includes a cathode current collector 140 and a cathode film 150.

[0020] In one or more embodiments, which may be combined with other embodiments, the one or more protective film(s) 180 include one or more ceramic materials. The ceramic material may be an oxide. In one embodiment, the one or more protective film(s) 180 may be made of, for example, aluminum oxide (Al2O3), aluminum oxynitride, aluminum nitride (AlN, aluminum deposited in a nitrogen environment), aluminum oxide hydroxide (AlO(OH)) (e.g., diaspore ((α-AlO(OH))), boehmite (γ-AlO(OH)), or accdalite (5Al2O3·H2O)), calcium carbonate (CaCO3), titanium dioxide (TiO2), SiS2, SiPO4, silicon oxide, or the like. Examples of suitable protective films include silicon dioxide (SiO), zirconium oxide (ZrO), hafnium oxide (HfO), MgO, TiO, TaO, NbO, LiAlO, BaTiO, boron nitride (BN), ion-conducting garnets, ion-conducting perovskites, ion-conducting antiperovskites, porous glass-ceramics, and the like, or combinations thereof. In certain embodiments, one or more protective film(s) 180 are deposited using evaporation techniques described herein.

[0021] In one or more embodiments that can be combined with other embodiments, each layer of the one or more protective film(s) 180 is a coating or individual film having a thickness in the range of about 1 nanometer to about 3,000 nanometers (e.g., in the range of about 10 nanometers to about 600 nanometers, in the range of about 50 nanometers to about 100 nanometers, in the range of about 50 nanometers to about 200 nanometers, in the range of about 100 nanometers to about 150 nanometers).

[0022] The cathode electrode structure 120 includes a cathode current collector 140 having a cathode film 150 formed thereon. It should be understood that the cathode electrode structure 120 may include other elements or films.

[0023] The current collectors 140, 160 on the cathode film 150 and anode film 170, respectively, can be the same or different electronic conductors. In certain embodiments, at least one of the current collectors 140, 160 is a flexible substrate. The flexible substrate can be or include one or more layers selected from plastic, polymeric material, metallized plastic, metal, paper, multilayers thereof, or combinations thereof. The flexible substrate can be or include a cast polypropylene ("CPP") film, a biaxially oriented polypropylene ("OPP") film, or a polyethylene terephthalate ("PET") film. Alternatively, the flexible substrate may be precoated paper, polypropylene (PP) film, polyethylene naphthalate (PEN) film, polylactic acid (PLA) film, polyimide (PI) film, poly(methyl methacrylate) (PMMA) film, cellulose triacetate (TAC) film, polypropylene (PP) film, polyethylene (PE) film, polycarbonate (PC) film, or PVC film. Examples of metals from which the current collectors 140 and 160 can be constructed include aluminum (Al), copper (Cu), zinc (Zn), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), stainless steel, clad materials, alloys thereof, and combinations thereof. In one or more embodiments that can be combined with other embodiments, at least one of the current collectors 140 and 160 is perforated. In one or more embodiments that can be combined with other embodiments, at least one of the current collectors 140 and 160 includes a polymer substrate (e.g., polyethylene terephthalate (“PET”)) coated with a metallic material. In one or more embodiments, which can be combined with other embodiments, anode current collector 160 is a polymer substrate (e.g., a PET film) coated with copper. In another embodiment, anode current collector 160 is a multi-metal layer on a polymer substrate. The multi-metal layer can be or include copper, chromium, nickel, alloys thereof, or any combination thereof.In one embodiment, the anode current collector 160 is a multilayer structure including a copper-nickel clad material. In one embodiment, the multilayer structure includes a first layer of nickel or chromium, a second layer of copper formed on the first layer, and a third layer including nickel, chromium, or both formed on the second layer. In one or more embodiments that can be combined with other embodiments, the anode current collector 160 is nickel coated with copper. In one or more embodiments that can be combined with other embodiments, the anode current collector 160 is graphite coated with copper. Furthermore, the current collector can be of any form factor (e.g., metal foil, sheet, or plate), shape, and micro / macro structure.

[0024] In one or more embodiments that can be combined with other embodiments, the cathode current collector 140 can be or can include aluminum. The cathode current collector 140 can be or can include aluminum deposited on a polymer substrate, such as a PET film. The cathode current collector 140 can have a thickness of less than 50 μm, more specifically 5 μm, or even more specifically 2 μm. The cathode current collector 140 can have a thickness of about 0.5 μm to about 20 μm, for example, about 1 μm to about 10 μm, about 2 μm to about 8 μm, or about 5 μm to about 10 μm. The anode current collector 160 can be or can include copper. The anode current collector 160 can be or can include stainless steel. In one or more embodiments that can be combined with other embodiments, the anode current collector 160 has a thickness of less than 50 μm, more specifically 5 μm or less, or even more specifically 2 μm or less. In one or more embodiments that can be combined with other embodiments, the anode current collector 160 has a thickness of about 0.5 μm to about 20 μm, for example, about 1 μm to about 10 μm, about 2 μm to about 8 μm, about 6 μm to about 12 μm, or about 5 μm to about 10 μm.

[0025] The cathode film 150, or cathode, may be any material compatible with the anode and may include an intercalation compound, an insertion compound, or an electrochemically active polymer.

[0026] The anode electrode structure 110 includes an anode current collector 160 having an anode film 170 formed thereon. The anode electrode structure 110 may further include one or more protective film(s) 180.

[0027] In one or more embodiments, which can be combined with other embodiments, the anode film 170 is composed of lithium metal, lithium metal foil, or lithium alloy foil (e.g., lithium aluminum alloy), or a mixture of lithium metal and / or lithium alloy with materials such as carbon (e.g., coke, graphite), nickel, copper, tin, indium, silicon, their oxides, or any combination thereof. The anode film 170 can be or include one or more lithium-containing intercalation compounds or lithium-containing insertion compounds. In certain embodiments, the anode film is a lithium metal film. In some embodiments in which the anode film 170 is or includes lithium metal, the lithium metal can be deposited using methods described herein.

[0028] In one or more embodiments, which can be combined with other embodiments, the anode film 170 can be or include graphite, silicon, or any combination thereof. The anode film 170 can be or include one or more carbonaceous materials, such as natural or synthetic graphite, partially graphitized or amorphous carbon, petroleum, coke, needle coke, and various interphases, silicon-containing graphite, silicon, nickel, copper, tin, indium, aluminum, silicon, oxides thereof, combinations thereof, or mixtures of lithium metal and / or lithium alloys with materials such as carbon, e.g., coke or graphite, nickel, copper, tin, indium, aluminum, silicon, oxides thereof, or combinations thereof. In one example, the anode film 170 can be or include silicon-graphite. In another example, the anode film 170 can be or include graphite.

[0029] In one or more embodiments, which can be combined with other embodiments in which anode film 170 is or includes graphite, silicon, or silicon, anode film 170 has a layer of lithium formed on the surface of anode film 170. The lithium metal layer can have a thickness of about 20 μm to about 50 μm. The lithium layer can be a prelithiated layer.

[0030] In one or more embodiments, which can be combined with other embodiments, the anode film 170 has a thickness of about 10 μm to about 200 μm, e.g., about 1 μm to about 100 μm, about 10 μm to about 30 μm, about 20 μm to about 30 μm, about 1 μm to about 20 μm, or about 50 μm to about 100 μm.

[0031] In one or more embodiments that can be combined with other embodiments, the polymer separator 130 is a porous polymeric ion-conducting polymer substrate. The porous polymer substrate can be a multilayer polymer substrate. In certain embodiments, the porous polymer substrate has a porosity in the range of about 20% to about 80% (e.g., in the range of about 28% to about 60%). The porous polymer substrate can have an average pore size in the range of about 0.02 μm to about 5 μm (e.g., about 0.08 μm to about 2 μm). In certain embodiments, the porous polymer substrate has a Gurley number in the range of about 15 seconds to about 150 seconds. The porous polymer substrate can be or include one or more polyolefin polymers. Examples of suitable polyolefin polymers include polypropylene, polyethylene, or a combination thereof. In one or more embodiments that can be combined with other embodiments, the porous polymer substrate is a polyolefin membrane. In one or more embodiments that can be combined with other embodiments, the polyolefin membrane is a polyethylene membrane or a polypropylene membrane.

[0032] In one or more embodiments, which can be combined with other embodiments, the porous polymer substrate has a thickness in the range of about 1 μm to about 50 μm, e.g., in the range of about 3 μm to about 25 μm, in the range of about 7 μm to about 12 μm, or in the range of about 14 μm to about 18 μm.

[0033] 2 shows a cross-sectional view of one embodiment of a double-sided anode electrode structure 210 formed in accordance with one or more embodiments described herein. The double-sided anode electrode structure 210 includes an anode current collector 160 having anode films 170a, 170b (collectively 170) formed on either side of the anode current collector 160. The double-sided anode electrode structure 210 further includes one or more protective film(s) 180a, 180b (collectively 180) formed on the anode films 170a, 170b, respectively.

[0034] 3 shows a schematic cross-sectional view of an evaporation source 300 for depositing evaporated material on a substrate 310 according to some embodiments described herein. The substrate 310 may be supported by a substrate support 313, e.g., the surface of a drum. The evaporation source 300 includes an evaporation crucible 330 for heating the source material 312 to a temperature higher than the evaporation or sublimation temperature of the source material 312 so that the source material 312 evaporates. The source material 312 can be a solid or liquid source material. The evaporation crucible 330 defines an interior volume 331 that acts as a material reservoir for containing the source material 312 in a solid and / or liquid state, and a first heater 335 for heating the interior volume 331 of the evaporation crucible 330 so that the source material 312 evaporates. For example, the source material 312 may be a metal, e.g., an alkali metal such as lithium or sodium, and the first heater 335 may be configured to heat the interior volume 331 of the evaporation crucible 330 to a temperature of about 600°C or higher, particularly about 700°C or higher, or about 800°C or higher.

[0035] The evaporation source 300 further includes a vapor distributor 320 having a plurality of nozzles 321 for directing evaporated material in the evaporation crucible 330 toward the substrate 310 so that a coating 311 is deposited on the substrate 310. The vapor distributor 320 may include an interior volume 323 in fluid communication with the interior volume 331 of the evaporation crucible 330 such that the evaporated material can flow from the interior volume 331 of the evaporation crucible 330 through a vapor conduit 340 and into the interior volume 323 of the vapor distributor 320, for example, along a linear connecting tube or passageway. The plurality of nozzles 321 may be configured to direct the evaporated material from the interior volume 323 of the vapor distributor 320 toward the substrate 310.

[0036] In some embodiments, the vapor distributor 320 may be a vapor distribution showerhead having multiple nozzles 321 arranged in a one- or two-dimensional pattern to direct the vaporized material toward the substrate 310 .

[0037] Evaporation crucible 330 is fluidly connected to vapor distributor 320 via a vapor conduit 340 that extends from evaporation crucible 330 to vapor distributor 320 in a conduit length direction A. During evaporation, vapor distributor 320 is typically provided at a second temperature higher than the first temperature within evaporation crucible 330 to prevent condensation of material on the interior wall surfaces of vapor distributor 320.

[0038] The evaporation source 300 may further include a first heater 335 for heating and evaporating the raw material 312 in the internal volume 331 of the evaporation crucible 330 and a second heater 325 for heating the internal volume 323 of the vapor distributor 320. The first heater 335 and the second heater 325 may be independently controlled. For example, the first heater 335 may be configured to heat the evaporation crucible 330 to a first temperature, and the second heater 325 may be configured to heat the vapor distributor 320 to a second temperature different from the first temperature, particularly a second temperature higher than the first temperature. During deposition, the internal volume 323 of the vapor distributor 320 is typically at a higher temperature than the internal volume 331 of the evaporation crucible 330 to prevent condensation of the evaporated material on the inner wall of the vapor distributor 320. On the other hand, most of the internal volume 331 of the evaporation crucible 330 should be maintained at a temperature near the evaporation temperature of the raw material 312, for example, slightly lower or slightly higher than the evaporation temperature, so that the raw material 312 can be evaporated little by little at a time at a predetermined evaporation rate.

[0039] The evaporation source 300 may further include a system controller 336 for controlling various aspects of the evaporation source and deposition apparatus. The system controller 336 facilitates control and automation of the evaporation source and deposition apparatus and may include a central processing unit (CPU), memory, and support circuits (or I / O). Software instructions and data may be coded and stored in the memory to instruct the CPU. The system controller 336 may communicate with one or more of the components of the deposition apparatus, for example, via a system bus. A program (or computer instructions) readable by the system controller 336 determines which tasks can be performed on the substrate. In some embodiments, the program is software readable by the system controller 336 and may include code for monitoring chamber conditions, including independent temperature control of one or more evaporation sources 300. While only a single system controller is shown, it should be understood that multiple system controllers may be used in the embodiments described herein.

[0040] Figure 4 shows a simplified cross-sectional view of a vapor deposition apparatus 400 according to some embodiments of the present disclosure. Figure 5A shows a simplified view of the vapor deposition apparatus 400 of Figure 4, viewed along the axis of rotation of a rotatable drum 410. The vapor deposition apparatus 400 may include a vapor deposition source 300 or several vapor deposition sources according to any of the embodiments described herein, such as the vapor deposition source 300 described with respect to Figure 3.

[0041] The deposition apparatus 400 includes a substrate support that is a rotatable drum 410 having a curved drum surface 411 for supporting the substrate 310 during deposition. Multiple nozzles 321 of the evaporation source 300 are directed toward the curved drum surface 411, and the deposition apparatus 400 is configured so that the substrate 310 on the curved drum surface 411 passes through the evaporation source 300. In some embodiments, several evaporation sources 300 described herein may be arranged one after the other in a circumferential direction T around the rotatable drum 410 so that the substrate 310 can be subsequently coated by several evaporation sources 300. Different coating materials can be deposited on the substrate 310, or one thicker coating layer of the same coating material can be deposited on the substrate 310 by the evaporation sources 300.

[0042] As shown generally in FIGS. 4 and 5A, the evaporation source 300 includes an evaporation crucible 330 for evaporating material, a vapor distributor 320 having a plurality of nozzles 321 for directing the evaporated material toward a substrate 310 supported on a rotatable drum 410, and a vapor conduit 340 extending in a conduit length direction "A" from the evaporation crucible 330 to the vapor distributor 320 and providing a fluid connection between the evaporation crucible 330 and the vapor distributor 320. At least one or all of the nozzles in the plurality of nozzles 321 may have a nozzle axis extending in or essentially parallel to the conduit length direction "A." As shown in FIG. 4, the conduit length direction "A" may essentially correspond to a radial direction of the rotatable drum 410.

[0043] In one or more embodiments, which may be combined with other embodiments described herein, the multiple nozzles 321 may be arranged in multiple nozzle rows extending in a column direction "L" or may be arranged adjacent to one another in a circumferential direction "T", where the column direction "L" may essentially correspond to the axial direction of the rotatable drum 410. Thus, the vapor distributor 320 provides an area showerhead having multiple nozzles arranged in a two-dimensional array to reduce the heat load per area on the substrate 310 supported on the curved drum surface 411.

[0044] As shown in FIG. 5A, three, four, or more evaporation sources 300A-300C described herein may be arranged one after the other in a circumferential direction "T" around a rotatable drum 410. Each evaporation source 300A-300C may define a coating window on the curved drum surface 411 extending over an angular range (a) of 10° to 45°. The conduit lengths "A" of adjacent evaporation sources 300 may each encompass an angle of 10° to 45°. Thus, the curved drum surface 411 of the rotatable drum 410 is well suited for deposition onto flexible substrates, such as metal foils or plastic substrates, where a relatively low heat load per substrate area can be maintained while maintaining a high deposition rate, thereby reducing substrate damage.

[0045] In one or more embodiments, which can be combined with other embodiments described herein, the evaporation sources 300A-300C further include an edge exclusion shield 430 extending from the evaporation source 300 toward the curved drum surface 411. Referring to Figure 4, the edge exclusion shield 430 may include edge exclusion portions 431 for masking areas of the substrate 310 that are not to be coated, for example, for masking side edge regions of the substrate 310 that are to be left free of coating material. For example, the edge exclusion portions 431 may be configured to mask two opposing side edges of the substrate 310.

[0046] The edge exclusion portion 431 may extend in a circumferential direction "T" along the curved drum surface 411 of the rotatable drum 410, following the curvature of the curved drum surface 411. Thus, the width "D" of the gap between the curved drum surface 411 and the edge exclusion portion 431 may be kept small (e.g., 2 mm or less) and essentially constant along the circumferential direction T, such that edge exclusion accuracy may be improved and sharp, well-defined coating layer edges may be deposited on the substrate.

[0047] As used herein, the circumferential direction "T" may be understood as the direction along the circumference of the rotatable drum 410, corresponding to the direction of movement of the curved drum surface 411 as the rotatable drum 410 rotates about its axis. The circumferential direction "T" corresponds to the substrate transport direction as the substrate 310 passes the evaporation source 300 on the curved drum surface 411. In some embodiments, the rotatable drum 410 may have a diameter ranging from about 300 mm to about 1400 mm or more. Reliably shielding the vapor 315 downstream of the multiple nozzles 321 to confine the vapor 315 within the vapor propagation volume 432 and provide a precisely defined, sharp coating edge is particularly challenging when a flexible substrate moving over the curved drum surface 411 is being coated because the vapor propagation volume 432 and coating window may have a complex shape in this case. The embodiments described herein enable reliable and accurate edge exclusion and material shielding, even in deposition apparatus configured to coat a web substrate disposed on the curved drum surface 411. Specifically, the edge exclusion shield 430 may at least partially surround a vapor propagation volume 432 downstream of the multiple nozzles 321, may confine the vapor 315 within the vapor propagation volume 432, and may provide precise edge exclusion via the edge exclusion portion 431.

[0048] In one or more embodiments, which can be combined with other embodiments described herein, a heating device may be provided to actively or passively heat the edge exclusion shield 430. For example, the edge exclusion shield 430 may be heated to a temperature higher than the condensation temperature of the evaporated material to reduce or prevent material condensation on the edge exclusion shield 430. This can reduce cleaning effort and improve the quality of the coating layer edge. For example, during deposition, the edge exclusion shield 430 may be heated to a temperature of approximately 500°C or higher.

[0049] The edge exclusion shield 430 does not contact the rotatable drum 410 so that a substrate supported on the rotatable drum 410 can pass through the evaporation source 300 and pass through the edge exclusion shield 430 during deposition.

[0050] The deposition apparatus 400 may be a roll-to-roll deposition system for coating flexible substrates, such as foils or plastic substrates. The substrate 310 to be coated may have a thickness of 50 μm or less, particularly 20 μm or less, or even 6 μm or less. For example, metal foils, flexible metal-coated foils, polymer substrates, or flexible polymer substrates may be coated in the deposition apparatus 400. In some embodiments, the substrate 310 is a thin copper foil or thin aluminum foil having a thickness of less than 30 μm, for example, 6 μm or less. The substrate 310 may also be a thin metal foil (e.g., copper foil) or polymer substrate (e.g., PET substrate) coated with graphite, silicon, silicon oxide, or any combination thereof, for example, with a thickness of 150 μm or less, particularly 100 μm or less, or even 50 μm or less. According to some embodiments, the web may further include graphite, silicon, silicon oxide, or any combination thereof. For example, a layer comprising graphite, silicon, silicon oxide, or any combination thereof may be prelithiated with lithium.

[0051] In a roll-to-roll deposition system, the substrate 310 may be unwound from a storage spool, at least one or more layers of material may be deposited on the substrate 310 while the substrate 310 is guided over the curved drum surface 411 of a rotatable drum 410, and the coated substrate may be wound onto a take-up spool after deposition and / or may be coated in a further deposition apparatus.

[0052] The substrate 310 is held on the curved drum surface 411 using an electrostatic chuck integrated into the rotatable drum 410. Depending on the type or material of the substrate, the electrostatic chuck can be integrated into the rotatable drum 410 in various embodiments, such as the configurations shown in Figure 5B, or Figures 6 and 7, or Figures 8 and 9.

[0053] FIG. 5B shows a cross-sectional end view of a rotatable drum 500 carrying a substrate 310. The rotatable drum 500 guides the substrate 310 with the aid of multiple rollers 503. The rotatable drum 500 has a drum shaft 502 at the center of the rotatable drum 500. An electrode 504 at least partially surrounds the drum shaft 502. In some embodiments, the electrode 504 is a powered electrode that completely surrounds the drum shaft 502, referred to herein as having a monopolar configuration. In some embodiments, the electrode 504 includes a first hemisphere 514A and a second hemisphere 514B. In some embodiments, DC power of about −1300 V to about −1200 V is supplied to the electrode 504 from a power supply 501. The first hemisphere 514A is powered and the second hemisphere 514B is grounded, referred to herein as having a bipolar configuration. The first hemisphere 514A and the second hemisphere 514B can be electrically isolated using dielectric isolators 520A-B. In some embodiments, the electrode 504 is fixed and electrically coupled to the curved surface 518 of the rotatable drum 500.

[0054] The electrode 504 is electrically coupled to the curved surface 518 by a plurality of movable electrode spokes 506 that extend from the electrode 504 to the curved surface 518. In some embodiments, the spokes 506 penetrate the body 512 of the rotatable drum 500. The spokes 506 are electrically insulated from the body 512 of the rotatable drum 500 by dielectric isolators 508. The spokes 506 are electrically coupled to the electrode 504 at connections 510, which can be made or broken depending on the desired chucking or dechucking. The body 512 of the rotatable drum 500 is a metal, such as stainless steel, or a copper-containing material. The body 512 of the rotatable drum 500 is water-cooled and includes a plurality of gas channels 516. The plurality of gas channels 516 form a heat sink to maintain a substrate temperature below about 200°C, for example, between about 60°C and about 180°C, for example, between about 100°C and about 160°C, for example, between about 120°C and about 140°C. In some embodiments, the substrate is copper and has a thickness of about 4 μm to about 6 μm. Without being bound by theory, it is believed that thin substrates are more susceptible to thermal expansion, which can result in substrate defects. Substrates for use in battery anodes often use polymer binders that can melt, degrade, or lose their binding properties when exposed to high temperatures, such as hot lithium. It has been discovered that by efficiently maintaining substrate temperature using the apparatus and methods provided herein, throughput can be increased without affecting substrate properties.

[0055] The body 512 is surrounded by a dielectric portion 519, such as a dielectric coating, such as a spray coating. The dielectric portion 519 can be implemented in a variety of ways depending on the attributes of the substrate held on the rotatable drum 500. In some embodiments, the dielectric portion 519 includes a patterned electrode structure thereon. In some embodiments, the dielectric portion 519 includes diamond-like carbon, aluminum oxide, boron nitride, polyimide, or a combination thereof.

[0056] FIG. 6 shows a cross-sectional view of a portion of a dielectric portion 600 that can be used as the dielectric portion 519 of FIG. 5B. The dielectric portion 600 includes a base layer 602, such as a copper-containing layer, a first protective layer 604A disposed on the base layer 602, a second protective layer 604B disposed on the first protective layer 604A, and a patterned electrode 700 (shown, for example, in FIG. 7) including a plurality of mesa structures 606 formed on the second protective layer 604B. A third protective layer 604C is formed on the plurality of mesa structures 606, and the substrate 310 can be supported on the third protective layer 604C. Each of the protective layers 604A, 604B, and 604C can independently be an adhesion layer, such as one or more polyimide layers. In one or more examples, the first protective layer 604A can be or include a first polyimide layer, the second protective layer 604B can be or include a second polyimide layer, and the third protective layer 604C can be or include a third polyimide layer. In some embodiments, the protective layers 604A-604C can be or include aluminum oxide, and the patterned electrode 700, e.g., the mesa structure 606, can be or include an aluminum-containing material, such as aluminum or an alloy of aluminum. In some embodiments, the patterned electrode 700 covers the entire surface of the drum surface.

[0057] In some embodiments, the mesa structure 606 includes a mesa height "M" of about 100 μm to about 300 μm, e.g., about 120 μm to about 200 μm. In some embodiments, the stack height "H1" of the first protective layer 604A, the second protective layer 604B, and the third protective layer 604C together with the mesa structure 606 can be about 100 μm to about 400 μm, e.g., about 200 μm to about 250 μm. Referring to FIG. 7, in some embodiments, a channel 706 is formed between adjacent mesa structures 606. Referring to FIG. 6, in some embodiments, the channel 706 formed between adjacent mesa structures 606 has a height "H3" of about 100 μm to about 300 μm. In some embodiments, the gap height "H2" between the substrate 310 and the surface 608 of the protective layer 604C is between about 0.5 μm and 10 μm, such as between about 1 μm and about 8 μm, for example between about 2 μm and about 6 μm.

[0058] FIG. 7 shows a top view of the dielectric portion 600. Multiple mesa structures 606 can be arranged in columns 702, 704. Each mesa structure 606 in each column is connected in series (e.g., via connections 708) and can be connected to a power source 710 or a ground plane. In some embodiments, each powered column 702 alternates with a grounded column 704. The alternation of powered and grounded electrode columns is referred to herein as having a bipolar configuration and allows for the support of substrates made from a variety of different materials, such as paper and plastic, e.g., PET. Alternatively, all columns 702, 704 can be powered and the substrate is a ground foil, which is referred to herein as having a monopolar configuration. Each column of mesa structures 606 is separated by a channel 706 that allows gas to flow between the mesa structures 606. The gas can flow substantially parallel to the surface 608 of the dielectric portion 600, allowing for a gap between the surface 608 and the backside of the substrate 310, e.g., a gap defined by "H2." In some embodiments, the electrodes are elongated, continuous strips extending from one edge of the dielectric portion 600 to the opposite edge, instead of mesa structures 606. Each electrode strip can be powered in a monopolar configuration or alternately powered and grounded in a bipolar configuration. In some embodiments, argon is supplied through gas nozzles parallel to the surface of the drum to maintain the gap. The nozzles have a diameter of about 200 μm to about 1000 μm, e.g., about 300 μm to about 500 μm.

[0059] FIG. 8 illustrates a cross-sectional end view of a dielectric portion 600 coupled to a drum body according to some embodiments described herein. The dielectric portion 600 can be coupled to a drum body 800 as shown in the cross-sectional end view illustrated in FIG. 8. The rotatable drum body 800 can include a plurality of segments 802, such as one or more circumferential segments. The plurality of segments 802 can include gas channels 810, such as cooling channels, for cooling. In some embodiments, the drum has a diameter of about 200 mm to about 700 mm, e.g., about 300 mm to about 600 mm, e.g., about 400 mm to about 500 mm. In some embodiments, the body 800 can include about 10 to about 40 segments, e.g., about 22 to about 32 segments. The segment arc angle 804 of the plurality of segments 802 can be about 10 degrees to about 40 degrees, e.g., about 15 degrees to about 20 degrees, depending on the number of segments. In some embodiments, the body 800 can include gas nozzles 808 that extend from an inner surface 814 of the body 800 to an outer surface 816 of the body 800. Figure 9 shows an interior view of the gas channels 810 and gas nozzles 808 of the segment 802.

[0060] FIG. 10 is a flow diagram illustrating a method 1000 of coating a substrate according to certain embodiments described herein.

[0061] In operation 1002, a substrate, e.g., substrate 310, is transported over a curved surface of a rotatable drum, e.g., curved surface 518 of rotatable drum 500. In some embodiments, the substrate is held on the curved surface using a low tensile pressure, e.g., about 20 N / m or less, e.g., about 5 N / m to about 15 N / m, e.g., about 10 N / m to about 12 N / m. The tensile pressure allows for a uniform gap between the substrate and the curved surface before clamping the substrate. The gap has a variation of about 75 μm or less. The rotatable drum includes one or more electrodes such that the substrate is electrostatically chucked to at least a portion of the curved surface of the rotatable drum. After applying electrostatic clamping, the gap variation is reduced to about 10 μm or less.

[0062] In operation 1004, a material is evaporated in an evaporation crucible. For example, a metal such as lithium is evaporated in an evaporation crucible, such as evaporation crucible 330. The evaporation crucible may be heated to a first temperature of about 500°C or higher, for example, between about 600°C and about 1200°C, for example, between about 700°C and about 1000°C.

[0063] In operation 1006, evaporated material is directed from the evaporation crucible to a substrate. As the evaporated material is directed to the substrate, the substrate is held on the curved surface of the rotatable drum such that a gap is formed between the substrate and the curved surface of the rotatable drum. A gas, such as a non-reactive gas such as argon, is supplied to the gap between the backside of the substrate and the curved surface of the rotatable drum. In some embodiments, the gap is between about 0.5 μm and 10 μm, e.g., between about 1 μm and about 8 μm, e.g., between about 2 μm and about 6 μm. As the evaporated material is deposited on the substrate, the substrate is continuously transported in a machine direction extending from the entrance side to the exit side of the rotatable drum. The substrate is chucked at the entrance side and dechucked at the exit side to release the substrate from the drum surface.

[0064] In some embodiments, the substrate is a flexible substrate that is supported on a curved drum surface of a rotatable drum during deposition. Specifically, the substrate may pass through multiple nozzles that deposit material onto the substrate on the curved drum surface of the rotatable drum.

[0065] The substrate may be a flexible foil, particularly a flexible metal foil, more particularly a copper foil or copper-carrying foil, such as a foil coated with copper on one or both sides. The substrate may have a thickness of 50 μm or less, particularly 20 μm or less, for example about 8 μm. In some embodiments, the substrate may be a thin copper foil having a thickness in the range of 20 μm or less.

[0066] According to some embodiments, which can be combined with other embodiments described herein, a battery anode is fabricated, wherein the flexible substrate comprises or consists of a polymer, copper, or a copper alloy. According to some embodiments, the web may further comprise graphite, silicon, silicon oxide, or any combination thereof. For example, the layer comprising graphite, silicon, and / or silicon oxide may be prelithiated with lithium.

[0067] Deposition of metals, such as lithium, onto flexible substrates, such as copper substrates, by evaporation may be used to fabricate batteries, such as Li batteries. For example, a lithium layer may be deposited onto a thin flexible substrate to fabricate the anode of the battery. After assembling the anode layer stack and the cathode layer stack, optionally with an electrolyte and / or separator therebetween, the fabricated layer arrangement may be rolled or otherwise laminated to fabricate the Li battery.

[0068] The foregoing embodiments of the present disclosure have many advantages, including enabling improved deposition onto flexible substrates. The rotatable drum can rotate during deposition to expose different areas of the substrate to the deposition environment while maintaining a uniform gap height across the web, thereby improving heat transfer across the substrate. Electrostatic clamping resists "blowout" or "web slippage" at high gap pressures and maximizes the heat transfer coefficient, allowing for web coating at low thermal budgets, e.g., below 80 degrees Celsius, and improving throughput. However, the present disclosure does not require that all advantageous features and benefits be incorporated into all embodiments of the present disclosure.

[0069] In the Summary and Detailed Description, as well as in the claims and accompanying drawings, reference is made to specific features (including method operations) of the present disclosure. It should be understood that the disclosure herein includes all possible combinations of such specific features. For example, if a specific feature is disclosed in the context of a particular aspect, embodiment, or example of the present disclosure, or in the context of a particular claim, that feature can also be used in combination with and / or in the context of other specific aspects and embodiments of the present disclosure, and generally in the present disclosure, to the extent possible.

[0070] The embodiments and all functional operations described herein can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structural means disclosed herein and their structural equivalents, or in combinations thereof. The embodiments described herein can be implemented as one or more non-transitory computer program products, i.e., one or more computer programs tangibly embodied in a machine-readable storage device for execution by or to control the operation of a data processing device, e.g., a programmable processor, a computer, or multiple processors or computers.

[0071] The processes and logic flows described herein may be performed by one or more programmable processors executing one or more computer programs to perform functions by manipulating input data and generating output. The processes and logic flows may also be performed by, and an apparatus may also be implemented as, special purpose logic circuitry, such as, for example, an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0072] The term "data processing apparatus" encompasses all apparatus, devices, and machines for processing data, including, by way of example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, an apparatus may include code that creates the execution environment for the computer program in question, such as code constituting processor firmware, a protocol stack, a database management system, an operating system, or one or more combinations thereof. Processors suitable for the execution of computer programs include, by way of example, both general-purpose and special-purpose microprocessors, and any one or more processors of any kind of digital computer.

[0073] Computer-readable media suitable for storing computer program instructions and data include, by way of example, all forms of non-volatile memory, media, and memory devices, including semiconductor memory devices such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

[0074] The term "comprises" and its grammatical equivalents are used herein to mean that other elements, ingredients, operations, etc. are optionally present. For example, an article "comprising" (or "comprises") elements A, B, and C can consist of (i.e., contain only) elements A, B, and C, or it can include elements A, B, and C as well as one or more other elements. Furthermore, whenever a composition, element, or group of elements is preceded by the transitional phrase "comprising" or its grammatical equivalent, it is understood that the same composition or group of elements may also be preceded by the transitional phrase "consisting essentially of," "consisting of," "selected from the group consisting of," or "is," and vice versa.

[0075] When reference is made herein to a method including two or more defined actions, the defined actions may be performed in any order or simultaneously (unless the context excludes that possibility), and the method may include one or more other actions that are performed before any of the defined actions, between two of the defined actions, or after all of the defined actions (unless the context excludes that possibility).

[0076] While the above is directed to exemplary embodiments, other and further embodiments may be devised without departing from the basic scope thereof, which scope is determined by the claims that follow.

Claims

1. a rotatable drum for supporting a substrate, a curved drum surface supporting the substrate and including a dielectric portion; an electrode coupled to a power source; wherein the electrode is electrically coupled to the curved drum surface and is capable of chucking and dechucking the substrate from the curved drum surface at one or more circumferential segments of the curved drum surface. Rotatable drum.

2. The rotatable drum of claim 1 , wherein the dielectric portion comprises a material selected from the group consisting of diamond-like carbon, aluminum oxide, boron nitride, polyimide, and combinations thereof.

3. 2. The rotatable drum of claim 1, wherein the electrode is a fixed electrode spaced radially inward from the curved drum surface and electrically coupled to the curved drum surface by a plurality of movable electrode spokes.

4. The rotatable drum of claim 1 , wherein the electrode includes a first hemisphere that is electrically grounded and a second hemisphere that is coupled to a power source.

5. The rotatable drum of claim 1 , wherein each of the one or more circumferential segments includes at least one cooling channel and one or more gas passages extending from an inner surface of the circumferential segment to the curved drum surface.

6. the dielectric portion of the curved drum surface, a first polyimide layer; a patterned electrode disposed on the first polyimide layer; a second polyimide layer disposed over the patterned electrodes; 10. The rotatable drum of claim 1, comprising:

7. The rotatable drum of claim 6 , wherein the patterned electrode comprises copper.

8. The rotatable drum of claim 6 , wherein the patterned electrode comprises a plurality of mesas.

9. 9. The rotatable drum of claim 8, wherein the mesas are polygonal.

10. 9. The rotatable drum of claim 8, wherein the mesas are arranged in a row extending from one edge of the rotatable drum to an opposite edge of the rotatable drum.

11. 9. The rotatable drum of claim 8, further comprising surface channels disposed between adjacent rows of the patterned electrodes, the rows alternating between first rows coupled to a power source and second rows coupled to a ground plane.

12. The rotatable drum of claim 1 further comprising a heat sink disposed radially inward from the curved drum surface and radially outward from the electrode.

13. A rotatable drum according to claim 1; an evaporation source configured to deposit material onto a substrate disposed on the curved drum surface of the rotatable drum; A deposition apparatus comprising:

14. 1. An electrode assembly for electrostatically chucking a substrate to a rotatable drum, comprising: a first protective layer interfacing with the rotatable drum; an electrode disposed on the first protective layer; a second protective layer disposed over the electrode and including a curved surface for supporting the substrate; an electrode assembly comprising:

15. 15. The electrode assembly of claim 14, wherein the first and second protective layers comprise aluminum oxide and the electrode comprises aluminum or an alloy of aluminum.

16. 15. The electrode assembly of claim 14, wherein the electrodes are arranged in a plurality of rows extending substantially parallel to one another and extending from one edge of the rotatable drum to an opposite edge of the rotatable drum.

17. 17. The rotatable drum of claim 16, wherein the rows alternate with a first row coupled to power and a second row grounded, with a channel disposed between the rows.

18. 1. A method for coating a substrate in a vacuum chamber, comprising: transporting a substrate over a curved surface of a rotatable drum, the substrate being electrostatically chucked to at least a portion of the curved surface of the rotatable drum; evaporating a material in an evaporation crucible; and directing evaporated material from the evaporation crucible to the substrate; A method comprising:

19. 20. The method of claim 18, wherein transporting the substrate further comprises holding the substrate on the curved surface of the rotatable drum such that a gap is formed between the substrate and the curved surface of the rotatable drum.

20. 20. The method of claim 19, further comprising supplying a gas to a gap between the backside of the substrate and the curved surface of the rotatable drum.

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