Smoothing of the coating stack layer by induction heating

Abstract

A method for forming a smooth film stack layer for an energy storage device is disclosed herein. In one example, a method for smoothing the outer layer of a film stack for an energy storage device includes forming the outer layer on a current collector of the film stack and heating the outer layer by supplying energy to a heat source placed on the outer layer of the film stack. Heating the outer layer of the film stack causes reflow of the outer layer, thereby reducing defects on the surface of the outer layer.

Description

TECHNICAL FIELD

[0001] Field Embodiments of the present disclosure generally relate to methods and apparatus for processing substrates, and more specifically relate to smoothing of film stack layers by induction heating.

BACKGROUND ART

[0002] Substrate-Independent Direct Transfer (SIDT) is a method for prelithiating an anode in an energy storage device to improve the life cycle of a battery. In the SIDT method, lithium is first deposited on a support layer composed of one or more materials such as polyethylene terephthalate (PET), paper, or a combination thereof. The material on the support layer is directly transferred to the anode for prelithiation. The release layer enables lithium and other materials to be transferred from the support layer to the anode.

[0003] After SIDT, due to imperfections in processing equipment, defects may be imprinted on or within the lithium surface of the formed film stack, resulting in a rough lithium surface with undesirable defects. Such a rough lithium surface can be a site that serves as a source for crystal growth. These crystal growth sites are problematic because they are uncontrolled and can degrade the quality of lithium films for use in electrochemical devices. For example, defects on the lithium surface can lead to non-uniformity on the surface of the lithium film. As a result, as in other industries, the battery and capacitor industries require high-quality alkali metal films (e.g., Li films) that can be used for device integration, so SIDT has not been utilized.

[0004] There is a need to improve the quality of film stack layers for energy storage devices.

SUMMARY OF THE INVENTION

[0005] Embodiments of the present disclosure generally relate to methods and apparatus for processing substrates, and more specifically relate to smoothing of film stack layers by induction heating.

[0006] In one embodiment, a method for smoothing the outer layer of a coating stack of an energy storage device includes forming the outer layer on a current collector of the coating stack and heating the outer layer by supplying energy to a heat source placed on the outer layer of the coating stack. Heating the outer layer of the coating stack causes reflow of the outer layer, thereby reducing defects on the surface of the outer layer.

[0007] Embodiments may include one or more of the following: A heat source is configured to provide a temperature gradient smaller than the thickness of the outer layer of the film stack. The heat source is connected to a platform configured to move the heat source along the outer layer of the film stack. The method further includes operating the platform across the width of the film stack. The outer layer is an alkali metal-containing layer containing lithium or sodium. The current collector is the anode. The first film stack is formed by substrate-independent direct transfer. The heat source does not contact the film stack. The heat source is an induction heater. Reflow of the outer layer results in a surface roughness of about 6Ra to about 30Ra. The surface roughness is about 6Ra to about 12Ra.

[0008] In another embodiment, a method for smoothing the outer layer of a coating stack for an energy storage device includes forming the outer layer on a current collector of the coating stack and heating the surface of the outer layer by supplying energy to an induction heater positioned on the outer layer of the coating stack. The induction heater is configured to provide a temperature gradient smaller than the thickness of the outer layer of the coating stack. Furthermore, heating the surface of the outer layer causes reflow of the outer layer to reduce defects and forms a smoothed outer layer surface having a surface roughness of 6Ra to about 30Ra.

[0009] The embodiments may include one or more of the following: The outer layer is an alkali metal-containing layer. The alkali metal-containing layer contains lithium or sodium. The film stack is formed by substrate-independent direct transfer. The thickness of the outer layer of the film stack is about 1 micron to about 20 microns. The method further includes operating an induction heater placed on a platform over the entire film stack in a back-and-forth, overlapping pattern.

[0010] In yet another embodiment, a method for smoothing the outer layer of a film stack for an energy storage device includes forming the outer layer on a current collector of the film stack, operating a platform on which a heat source is located along the outer lithium layer of the film stack passing through a substrate-independent direct transfer system, and heating the surface of the outer layer by supplying energy to an induction heater located on the outer layer of the film stack and not in contact with the outer layer. The outer lithium layer is located on a current collector layer containing graphite or copper. The lithium layer has a surface roughness of less than 10 microns. The induction heater is configured to provide a temperature gradient smaller than the thickness of the outer lithium layer of the film stack. Furthermore, by heating the surface of the outer lithium layer, reflow of the outer lithium layer is induced, reducing defects on the surface of the outer lithium layer and forming a smoothed surface of the outer lithium layer having a surface roughness of 6Ra to about 12Ra.

[0011] In another embodiment, a non-temporary computer-readable medium stores instructions that, when executed by a processor, cause a process to perform the operation of the above-mentioned apparatus and / or method.

[0012] In yet another embodiment, a flexible substrate processing system is provided. The system includes a pickup hub, a supply hub, a calendering unit, and a heating unit. The calendering unit includes calender rollers and is located downstream of the supply hub and upstream of the pickup hub. The heating unit has an internal region. The pickup hub is configured to rotate and assist in transporting the flexible substrate through the internal region of the heating unit. The heating unit is located downstream of the supply hub and upstream of the pickup hub. The heating unit includes one or more heating sources configured to generate and direct thermal energy towards the flexible substrate as the flexible substrate is transported through the internal region of the heating unit.

[0013] The embodiments may include one or more of the following: One or more heating sources include a first heat source and a second heat source, the first heat source being configured to direct thermal energy to a first portion of the internal region relative to a first side of the flexible substrate as the flexible substrate is transported through the internal region of the heating unit, and the second heat source being configured to direct thermal energy to a second portion of the internal region relative to a second side of the flexible substrate opposite to the first side as the flexible substrate is transported through the internal region of the heating unit. The heating unit is located downstream of the calendering unit and upstream of the pickup hub. One or more heating sources can melt, liquefy, and reflow an alkali metal-containing layer placed on top of the current collector layer without thermally affecting the current collector layer. One or more heating sources can heat lithium to or above a melting temperature of 181 degrees. One or more heating sources include induction heaters having a capacity of approximately 1,000 BTU / hour to approximately 50,000 BTU / hour. One or more heating sources are arranged on a movable platform. The movable platform is operable or scannable along the length of a flexible substrate, across the width of a flexible substrate, or along the length and width of a flexible substrate.

[0014] In yet another embodiment, a flexible substrate processing system for transferring a film from a substrate is provided. The system includes a heating unit and a system control device. The heating unit has an internal region. The heating unit includes one or more inductive heating sources configured to generate and direct thermal energy onto the flexible substrate as the flexible substrate is transported through the internal region of the heating unit. The system control device is configured to cause the processing system to perform a process. This process includes transporting a flexible carrier from a supply hub to a pickup hub, wherein the flexible carrier has an alkali metal-containing layer formed thereon; bringing the flexible carrier into contact with a flexible substrate, wherein the alkali metal-containing layer is in contact with the flexible substrate; separating the flexible carrier from the alkali metal-containing layer; and exposing the alkali metal-containing layer, which is placed on the flexible substrate, to thermal energy to heat the alkali metal-containing layer.

[0015] Embodiments may include one or more of the following: Exposure of the alkali metal-containing layer to thermal energy includes heating the surface of the alkali metal-containing layer by supplying energy to one or more induction heating sources positioned on the alkali metal-containing layer, the one or more induction heating sources configured to provide a temperature gradient smaller than the thickness of the alkali metal-containing layer. Heating the surface of the alkali metal-containing layer causes reflow of the alkali metal-containing layer, reducing defects and forming a smoothed surface of the alkali metal-containing layer having a surface roughness of 6Ra to about 30Ra. The alkali metal-containing layer contains lithium or sodium. The thickness of the alkali metal-containing layer is about 1 micron to about 20 microns. The process further includes operating one or more induction heating sources positioned on a platform in a back-and-forth, overlapping pattern over the entire alkali metal-containing layer positioned on a flexible substrate. The flexible carrier contains a polymer material, and the alkali metal-containing layer contains lithium. The flexible substrate includes a current collector substrate, an anode film, or an anode film formed on a current collector substrate. Bringing a flexible carrier into contact with a flexible substrate includes laminating an alkali metal-containing layer onto the flexible substrate.

[0016] In another embodiment, a non-temporary computer-readable medium stores instructions that, when executed by a processor, cause a process to perform the operation of the above-mentioned apparatus and / or method.

[0017] To allow for a more detailed understanding of the above-mentioned features of this disclosure, a more specific description of this disclosure, which is concisely summarized above, can be obtained by reference to embodiments, some of which are shown in the accompanying drawings. However, it should be noted that the accompanying drawings show only exemplary embodiments of this disclosure and should not be considered limiting its scope, as other equally valid embodiments may be permitted. [Brief explanation of the drawing]

[0018] [Figure 1]This is a schematic cross-sectional view of a coating stack according to at least one embodiment of the present disclosure. [Figure 2A] This flowchart shows a selected operation of a method for smoothing a film stack layer according to at least one embodiment of the present disclosure. [Figure 2B] This is a schematic cross-sectional view of a coating stack processed by the operation of the method shown in Figure 2A according to at least one embodiment of the present disclosure. [Figure 2C] This is a schematic cross-sectional view of a coating stack processed by the operation of the method shown in Figure 2A according to at least one embodiment of the present disclosure. [Figure 2D] This is a schematic cross-sectional view of a coating stack processed by the operation of the method shown in Figure 2A according to at least one embodiment of the present disclosure. [Figure 3] This is a side cross-sectional view of a flexible substrate processing system according to at least one embodiment of the present disclosure. [Figure 4] This is a side cross-sectional view of a heating unit included in the flexible substrate processing system of Figure 3 according to at least one embodiment of the present disclosure. [Modes for carrying out the invention]

[0019] For ease of understanding, the same reference numerals are used to indicate identical elements common to the figures, where possible. Elements and features of one embodiment can be usefully incorporated into other embodiments without further enumeration.

[0020] Embodiments of this disclosure generally relate to techniques for forming smooth film stack layers for energy storage devices. Film stacks described herein can have superior device performance compared to the prior art. Methods described herein are reproducible and can yield a uniform lithium layer. Furthermore, embodiments described herein can enable streamlined material handling and integration, as well as a longer storage life for lithium film stacks (e.g., lithium film rolls) than the prior art.

[0021] Although embodiments of the present disclosure are described with respect to lithium, it is contemplated that the embodiments described herein may also be applied to other materials such as other alkali metals (e.g., sodium).

[0022] Exemplary Film Stack Figure 1 shows a schematic cross-sectional view of one embodiment of a film stack 100. The film stack 100 may be or include a device or a portion of a device. The film stack 100 includes a current collector (CC) layer 102 having a bottom surface 102a and a top surface 102b. The film stack 100 further includes an alkali metal-containing layer 104 (e.g., a lithium-containing layer, a sodium-containing layer, a lithium alloy or a sodium alloy) having a bottom surface 104a disposed on the top surface 102b of the CC layer 102. The alkali metal-containing layer 104 further has a top surface 104b. In some embodiments, the film stack 100 includes non-alkali metals and alloys.

[0023] The top surface 104b may be smoothed to form the alkali metal-containing layer 104 having a substantially uniform thickness across the entire length of the substrate, resulting in a smooth and level alkali metal-containing layer 104. After the smoothing operation, the surface roughness (Ra) of the top surface may be about 6 Ra to about 30 Ra, for example about 6 Ra to about 12 Ra, which may exhibit a mirror-like finish.

[0024] In some embodiments, an optional high-purity passivation layer may be disposed on the top surface 104b of the alkali metal-containing layer 104 to protect the alkali metal-containing layer 104 from undesirable reactions that may affect the performance of the film stack, for example, when the film stack 100 is used as a battery (or a portion of a battery).

[0025] The film stack 100 can be used in energy storage devices such as batteries. For example, the energy storage device may include an anode and the film stack 100 disposed over the anode.

[0026] Exemplary Method Embodiments described herein also relate to methods for forming one or more smooth alkali metal-containing layers. Generally, in some embodiments, the smoothing and / or planarizing methods described herein include heating the surface of the alkali metal-containing layer to reflow the surface material of the alkali metal-containing layer.

[0027] The alkali metal-containing layer may be part of a film stack, such as one fabricated by substrate-independent direct transfer (SIDT). SIDT is a method for forming an electrode device stack by transferring one or more layers, including an alkali metal layer, such as a lithium metal layer, to a receiving substrate, such as a current collector, in embodiments where the lithium metal functions as an anode or functions to pre-lithify (or pre-sodium) an anode material already formed on the current collector. Examples of alkali metals include alkali metals such as lithium metal, sodium, potassium, rubidium, cesium, francium, alloys containing alkali metals, or combinations thereof. The already formed anode material may include, but is not limited to, graphite, silicon, silicon-graphite, silicon oxide-graphite, silicon, tin, hard carbon, metal oxides, or combinations thereof. Alloys containing alkali metals may include alloys of alkali metals and anode material. The current collector may include, or may be, metallized plastic, copper, or a combination thereof. In the SIDT method, alkali metals are formed on a carrier substrate composed of one or more materials, such as a polymer substrate, for example polyethylene terephthalate (PET), paper, or a combination thereof. The material formed on the carrier substrate is directly transferred to a receiving substrate. The receiving substrate may include, or may be, a current collector, a current collector having the formed anode material on top, a metallized plastic substrate, a separator, or a metallized plastic substrate having the formed alkali metal on top. A release layer may be formed between the alkali metal layer and the carrier substrate. The release layer allows for the transfer of the alkali metal and other materials from the carrier substrate to the receiving substrate.

[0028] After SIDT, defects may be imprinted on the lithium surface of the formed film stack due to imperfections on the processing material and / or processing equipment, such as PET, the release layer, or the rollers, resulting in a rough lithium surface with undesirable defects. Such rough lithium surfaces can be sources of crystal growth. These crystal growth locations are problematic because they are uncontrolled and can degrade the quality of the desired lithium film for use in electrochemical devices. In other words, defects on the lithium surface can lead to non-uniformity of the lithium film. Consequently, as in other industries, SIDT is not utilized in the battery and capacitor industry, which requires high-quality alkali metal films (e.g., Li films) that can be used for device integration. However, since SIDT can enable deposition on larger substrates and higher throughput, its use in such industries may be beneficial. Furthermore, general-purpose plastic substrates are widely available and recyclable. Additional advantages include streamlining production regardless of customer substrate and electrode pattern requirements, good Li edge control through lamination, and the construction of thin film layers of the device stack necessary to enhance functionality, preferably under reduced pressure before SIDT, as well as the use of the same deposition system to enable the highest quality contact surfaces. In contrast, methods of depositing lithium by evaporation, molten lithium slot die, and molten lithium hot roll transfer, as with other methods, can be problematic for most substrates because thermal exposure during deposition causes warping. SIDT transfer eliminates all thermal problems associated with the actual substrate.

[0029] As described herein, post-SIDT smoothing operations can achieve, for example, improved quality of metal films for superior device performance.

[0030] Figure 2A is a flowchart showing selected operations of Method 200 for forming a smooth film stack layer (e.g., alkali metal-containing layer 104) according to at least one embodiment of the present disclosure. Figures 2B–2D show schematic cross-sectional views of a film stack 260 processed by the operations of Method 200 in Figure 2A according to at least one embodiment of the present disclosure.

[0031] Method 200 may be a continuous process in which the film stack 100 moves continuously so that the film stack 260 is continuously smoothed.

[0032] Method 200 begins with a coating stack 260, which may include a rough top surface 104b having defects 208 (such as pinholes), as shown in Figure 2B. In some embodiments, the coating stack 260 undergoes a cleaning operation (not shown) to remove harmful substances from the top surface 104b. As shown in Figure 2C, in operation 205, heat is applied to the coating stack 260 to melt and reflow the top surface 104b of the alkali metal-containing layer 104. The alkali metal-containing layer 104 is located on the top surface 102b of the CC layer 102. As shown in Figure 2B, initially, the top surface 104b is rough and uneven. For example, after the SIDT operation, the top surface 104b may exhibit defects 208 (such as pinholes) etched from the PET, the release layer, and / or the rollers. In some cases, the surface roughness (Ra) of the upper surface 104b may be at most about 10 μm, or less than about 9 μm, e.g., less than about 8 μm, e.g., less than 7 μm, e.g., less than 6 μm, e.g., less than 5 μm. In some embodiments, pinholes may substantially extend into the alkali metal-containing layer 104. In some embodiments, the thickness of the alkali metal-containing layer 104 varies along the width of the substrate from about 1 micron (um) to about 120 μm, e.g., from about 1 μm to about 100 μm.

[0033] The heating process of operation 205 may include performing an adjustable heat treatment 254 on the coating stack 260 using a heat source 252 to form the coating stack 100. The term “adjustable” means that the thermal energy supplied to the coating stack can be manipulated. For example, by supplying greater or less power to the heater, or by moving the position of the heater closer to and / or further away from the coating stack along its length and width. As shown in Figure 2C, the transitional coating stack 270 is undergoing the heating operation 205. Here, defects 208 and / or roughness on the top surface 104b are softened, partially liquefied, and reflowed by gravity to produce a uniform top surface 104b of the alkali metal-containing layer 104.

[0034] The heating process of operation 205 may be a continuous process in which the film stack 260 moves continuously so that the film stack 100 is continuously generated. In some embodiments, the film stack 260 moves continuously under a stationary heat source 252. In some embodiments, the heat source 252 is mounted on a movable platform that can scan the upper surface 104b of the alkali metal-containing layer 104 over the entire width of the film stack. The platform is configured to deliver thermal energy to the alkali metal-containing layer 104. In other embodiments, the heat source 252 is configured to scan the upper surface 104b of the alkali metal-containing layer 104 in an overlapping pattern over a predetermined front-to-back distance along the length of the moving film stack 270. The coating stack 260 can pass through the heat source 252 at coating processing speeds of approximately 0.1 meters / min (m / min) to approximately 100 m / min, for example, approximately 2 m / min to approximately 90 m / min, for example, approximately 1 m / min to approximately 75 m / min, approximately 1 m / min to approximately 50 m / min, for example, approximately 1 m / min to approximately 25 m / min, for example, approximately 1 m / min to approximately 10 m / min, for example, approximately 2 m / min to approximately 8 m / min, for example, approximately 3 m / min to approximately 6 m / min.

[0035] The heating process of operation 205 can be performed inline as the substrate passes under an exposed heat source 252. The exposed heat source can be defined as being accessible for maintenance without requiring a production stoppage. In some embodiments, the heating process is performed within a housed heating chamber configured to perform the heating operation, such as a cleaning chamber having heating capabilities. The heating process of operation 205 can utilize a heater capable of melting, liquefying, and reflowing the alkali metal-containing layer 104 without thermally affecting the CC layer 102. In some embodiments, for example, the heater can heat the lithium to or beyond a melting temperature of 181 degrees Celsius, e.g., approximately 160 to 250 degrees Celsius, e.g., approximately 170 to 230 degrees Celsius, e.g., approximately 180 to 220 degrees Celsius, e.g., approximately 200 to 210 degrees Celsius. Furthermore, the heater can also adjust the heating rate to accommodate dynamic heating rate fluctuations. For example, the heater may allow for a higher heating rate for faster film stacking rates and a lower heating rate for slower film stacking rates. For example, the heating process may be carried out by a non-contact induction heater having a capacity of about 1,000 BTU / hour to about 50,000 BTU / hour. In other embodiments, a resistance heater, a graphite-based resistance heater, or a radiation source heater such as a xenon lamp may be used to soften, liquefy, and / or reflow only the alkali metal-containing layer 104. In some embodiments, the heater may be mounted on a roller that contacts the film stack as the flexible substrate is being processed. The heated roller can provide the passing substrate with enough heat to enable reflow and thus smooth the top surface 104b.

[0036] The heat treatment process of operation 205 can be performed for a duration of less than approximately 10 minutes (min), for example less than approximately 5 minutes, for example less than approximately 2 minutes, for example less than approximately 1 minute, for example less than approximately 30 seconds (s), for example less than approximately 20 seconds, for example less than approximately 10 seconds, or for a duration of approximately 1 second to approximately 30 seconds, for example approximately 5 seconds to approximately 20 seconds, although other values ​​are also possible. By adjusting the duration of the heat treatment process, the processing rate and the heating rate of the heater can be further adjusted. Any of the aforementioned figures can be used alone to describe the open-end range or in combination to describe the closed-end range.

[0037] In some embodiments, the heat treatment may include a radio frequency (RF) power supply to power, for example, an induction heater. The RF power supply may provide alternating current (AC) power used to power the heater for processing the film stack 270. The RF power supply may be set to a frequency range of about 400 kilohertz (kHz) to about 20 megahertz (MHz), for example, about 1 MHz to about 13.56 MHz, or for example, about 1 MHz to about 5 MHz, but other values ​​are also possible. Any of the aforementioned figures may be used alone to describe the open-end range or in combination to describe the closed-end range.

[0038] The heat treatment in operation 205 is configured to heat the alkali metal-containing layer 104 without thermally affecting the CC layer 102. For example, the heat source 252 provides a temperature gradient within the alkali metal-containing layer 104. However, in various embodiments, the temperature gradient does not penetrate substantially beyond the thickness of the alkali metal-containing layer 104. In some embodiments, the top surface 104b is hot, but the contact surface between the bottom surface 104a and the top surface 102b of the CC layer 102 is not significantly affected by the heat treatment. In various embodiments, the following formula can be used to configure a temperature gradient to a depth less than or equal to the thickness of the alkali metal-containing layer 104. TIFF2026534158000002.tif7170 formula, D = Depth (in centimeters (cm)) ρ=material resistivity (ohm-cm) μ = relative magnetic permeability of the material f = AC field frequency (Hertz (Hz)) Equation (1) relates the material properties to the applied heat delivered to a specific depth. Thus, dynamic thermal control can be configured to target a specific depth so that the alkali metal-containing layer 104 softens and reflows, thereby providing a smoothing operation 210, while the CC layer 102 remains undamaged by the heat. For example, the thickness of the alkali metal-containing layer 104 can be about 1 micron to about 20 microns, and therefore the depth can be set to less than the thickness of the alkali metal-containing layer 104.

[0039] Method 200 further includes smoothing the surface (e.g., the top surface 104b) of the alkali metal-containing layer 104 in operation 210. Figure 2D shows the film stack 100 obtained after the film stack 270 of Figure 2C has undergone operation 210, as shown in Figure 2C. Here, surface smoothing may include active or passive reflow of the top surface 104b to close and / or reduce defects 208 present on the film stack 260. Furthermore, smoothing the film stack 260 reduces, for example, the crystal growth of lithium crystals, thereby extending the life of the film stack 100, resulting in more long-term storage options and improved performance of electronic devices such as batteries.

[0040] Exemplary processing chamber Embodiments of the present disclosure generally relate to a flexible substrate processing system comprising one or more heating units for processing the recently exposed surface of a coating disposed on a flexible substrate. One exemplary use of the processing method provided in the present disclosure involves heating the surface of a lithium coating that can be used as part of the electrodes of a lithium-ion battery. For example, a lithium coating can be transferred from a flexible carrier (e.g., a polymer-based carrier) to a flexible substrate (e.g., a flexible copper substrate) by passing a flexible carrier and a flexible substrate through a calendering unit and then peeling off the flexible carrier. When the lithium coating is transferred to the flexible substrate, a new surface of the lithium coating is exposed to the surrounding environment when the flexible carrier is peeled off the flexible substrate. This newly exposed surface may be rough, uneven, and contain defects from the processing, which can adversely affect the performance of the lithium coating in a lithium-ion battery. For example, an uneven surface of the lithium layer can adversely affect the performance of using the lithium coating on the anode of a lithium-ion battery.

[0041] Figure 3 shows a side cross-sectional view of a flexible substrate processing system 300 according to at least one embodiment of the present disclosure. The processing system 300 includes equipment for transferring lithium films on a first flexible carrier 310 and a second flexible carrier 320 to both sides of a flexible substrate 330, so that the flexible substrate 330 having the lithium films can be used as an electrode (e.g., anode) of a lithium-ion battery. The processing system 300 includes a calendering unit 340 for transferring the lithium films on the flexible carriers 310 and 320 to the flexible substrate 330. The processing system 300 further includes a heating unit 400 for smoothing the upper surface of the lithium films before they are transferred to the flexible substrate 330.

[0042] The processing system 300 includes a first flexible carrier supply hub 315. The supply roll 311 for the first flexible carrier 310 is located on the first flexible carrier supply hub 315. In some embodiments, the first flexible carrier 310 can be formed from a polymer material such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), or a combination thereof. A lithium film (not shown in Figure 3) is located on the underside 310L of the first flexible carrier 310, so that as the first flexible carrier 310 and the flexible substrate 330 are transported through the calendering section 340, this lithium film faces the upper surface 330U of the flexible substrate 330. After being transferred to the flexible substrate 330, this lithium film is shown as lithium film 401 in Figure 4. The upper surface 330U of the flexible substrate 330 is on the opposite side from the lower surface 330L of the flexible substrate 330. The upper surface 330U is also referred to as the first surface or first side of the flexible substrate 330, and the lower surface is also referred to as the second surface or second side of the flexible substrate 330.

[0043] The processing system 300 includes a second flexible carrier supply hub 325. The supply roll 321 for the second flexible carrier 320 is located on the second flexible carrier supply hub 325. In some embodiments, the second flexible carrier 320 can be formed from the same material as the first flexible carrier 310 (e.g., PET). A lithium film (not shown in Figure 3) is located on the upper side 320U of the second flexible carrier 320, so that as the second flexible carrier 320 and the flexible substrate 330 are transported through the calendering section 340, this lithium film faces the lower surface 330L of the flexible substrate 330. After being transferred to the flexible substrate 330, this lithium film is shown as lithium film 402 in Figure 4.

[0044] In some embodiments, the lithium coatings on the first flexible carrier 310 and the second flexible carrier 320 can be formed from lithium metal, another alkali metal, or an alloy containing an alkali metal.

[0045] The processing system 300 includes a flexible substrate supply hub 335. A feed roll 331 for the flexible substrate 330 is located on the flexible substrate supply hub 335. In some embodiments, the flexible substrate 330 can be formed from one or more of the following materials: copper, graphite, silicon, silicon-graphite, silicon oxide-graphite, silicon, metallized plastic, or other materials.

[0046] The processing system 300 further includes a calendering unit 340. The calendering unit 340 includes a first calender roller 341 and a second calender roller 342. The first flexible carrier 310, the second flexible carrier 320, and the flexible substrate 330 are arranged to be conveyed along a path extending between the first calender roller 341 and the second calender roller 342. When the first flexible carrier 310, the second flexible carrier 320, and the flexible substrate 330 are conveyed between the first calender roller 341 and the second calender roller 342, the flexible substrate 330 is positioned between the first flexible carrier 310 and the second flexible carrier 320. Calender rollers 341 and 342 apply significant pressure to the flexible carriers 310 and 320 and the flexible substrate 330, transferring the lithium film on each of the flexible carriers 310 and 320 to the flexible substrate 330. In some embodiments, a release layer is placed on each of the flexible carriers 310 and 320, and the release layer is located between the corresponding flexible carriers 310 and 320 and the lithium film on them. In some embodiments, the release layer can be formed of siloxane.

[0047] The processing system 300 includes a first flexible carrier pickup hub 316. The pickup roll 312 of the first flexible carrier 310 is located on the first flexible carrier pickup hub 316. When the first flexible carrier 310 is wound onto the first flexible carrier pickup hub 316, the lithium film that was previously on the first flexible carrier 310 is transferred to the flexible substrate 330 by the calendering unit 340, so the lithium film is no longer on the first flexible carrier 310.

[0048] The processing system 300 includes a second flexible carrier pickup hub 326. The pickup roll 322 of the second flexible carrier 320 is located on the second flexible carrier pickup hub 326. When the second flexible carrier 320 is wound onto the second flexible carrier pickup hub 326, the lithium film that was previously on the second flexible carrier 320 is transferred to the flexible substrate 330 by the calendering unit 340, so the lithium film is no longer on the second flexible carrier 320.

[0049] The processing system 300 includes a flexible substrate pickup hub 336. The pickup roll 332 of the flexible substrate 330 is located on the flexible substrate pickup hub 336. The flexible substrate 330 includes lithium films on its upper surface 330U and lower surface 330L, respectively. These lithium films are transferred from each flexible carrier 310, 320 onto the flexible substrate 330 by the calendering unit 340.

[0050] The processing system 300 further includes a plurality of rollers 381-388. In some embodiments, each of the rollers 381-388 may be a passive roller. The rollers 381-388 can help apply appropriate tension to the flexible carriers 310, 320 and the flexible substrate 330 and help change their orientation as each of the flexible carriers 310, 320 and the flexible substrate 330 moves through different parts of the processing system 300. Some of the rollers 381-388 can also help move the flexible carriers 310, 320 closer to or further away from the flexible substrate 330. For example, second and third rollers 382, ​​383 help bring the flexible carriers 310, 320 into contact with the flexible substrate 330 before the flexible carriers 310, 320 and the flexible substrate 330 are transported through the calendering unit 340. Furthermore, the fourth and fifth rollers 384 and 385 provide positions from which tension can be applied to the flexible carriers 310 and 320 in order to separate them from the flexible substrate 330. In some embodiments, one or more of the rollers 381 to 388 may instead be bars, such as metal bars, that can apply tension to the carrier or flexible substrate while the carrier or flexible substrate is moving.

[0051] In some embodiments, the heating unit 400 is positioned within a short distance of the rollers 384 and 385 to increase the duration of the smoothing process after heating the flexible substrate. In some embodiments, the corresponding heating unit 400 can be positioned within 2 feet of the rollers 384 and 385, for example, within 1 foot, or within 6 inches of the rollers 384 and 385. Similarly, in some embodiments, the corresponding heating unit 400 can be positioned within 2 feet of the calender rollers 341 and 342, for example, within 1 foot, or within 6 inches of the rollers 341 and 342.

[0052] The processing system 300 may further include actuators (not shown) configured to rotate each hub 315, 316, 325, 326, 335, 336, thereby allowing the flexible carriers 310, 320 and flexible substrates 330 to be transported from the corresponding supply hubs 315, 325, 335 through the calendering unit 340 to the corresponding pick hubs 316, 326, 336. The processing system 300 may further include one or more actuators (not shown) for rotating the calender rollers 341, 342 of the calendering unit 340. The rotational speed of the actuators can be adjusted to control the speed at which the flexible substrates 330 and flexible carriers 310, 320 are transported through the processing system 300.

[0053] In the processing system 300, the flexible substrate 330 is transported along a path from a supply roll 331 supported by a supply hub 335, through a first roller 381, between the second roller 382 and the third roller 383, between the calender rollers 341 and 342, between the fourth roller 384 and the fifth roller 385, through the heating unit 400, through the eighth roller 388, and to a pickup roll 332 around a pickup 336. The flexible substrate pickup hub 336 is configured to rotate to assist in the transport of the flexible substrate 330 through the corresponding internal region of the heating unit 400 after it has passed between the first calender roller 341 and the second calender roller 342. Similarly, the pickup hubs 316 and 326 are configured to rotate to assist in the transport of the flexible carrier along a path between the flexible carrier supply hubs 315 and 325 and the pickup hubs 316 and 326.

[0054] The processing system 300 may also include a control device 305 for controlling the processes performed by the processing system 300. The control device 305 can be any type of control device used in an industrial environment, such as a programmable logic controller (PLC). The control device 305 includes a processor 307, memory 306, and input / output (I / O) circuitry 308. The control device 305 may further include one or more components (not shown) such as one or more power supplies, clocks, communication components (e.g., a network interface card), and user interfaces, which are typically found in control devices for semiconductor equipment.

[0055] Memory 306 may include non-temporary memory. Non-temporary memory can be used to store programs and settings, as described later. Memory 306 may 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)).

[0056] The processor 307 is configured to execute various programs stored in the memory 306, such as programs configured to perform the methods described herein. While these programs are running, the control unit 305 can communicate with I / O devices via the I / O circuit 308. For example, while these programs are running and while communicating via the I / O circuit 308, the control unit 305 can control outputs (e.g., actuators connected to different hubs and calendering units 340). The memory 306 may further include various operating settings used to control the processing system 300. For example, the settings may include speed settings for actuators connected to the hubs and settings for controlling the heating unit 400, which will be described later.

[0057] Figure 4 shows a side cross-sectional view of a heating unit 400 included in the flexible substrate processing system of Figure 3 according to at least one embodiment of the present disclosure. In Figure 4, the upper lithium film 401 (first lithium film) is located on the upper surface 330U of the flexible substrate 330, and the lower lithium film 402 (second lithium film) is located on the lower surface 330L of the flexible substrate 330. The flexible substrate 330 and the lithium films 401 and 402 can be transported in direction D toward the flexible substrate pickup hub 336 (see Figure 3) through the heating unit 400. The upper lithium film 401 has an outer surface 403. The lower lithium film 402 has an outer surface 404. At the point when the first flexible carrier 310 and the second flexible carrier 320 are conveyed through the calendering unit 340 and, after passing through rollers 384 and 385, are peeled off from the flexible substrate 330 (see Figure 3), the outer surfaces 403 and 404 may be rough surfaces 412 and / or may contain defects 208.

[0058] The heating unit 400 includes a plurality of heating sources, e.g., 452U and 452L, configured to heat the lithium coatings 401 and 402 as the flexible substrate 330 is transported in direction D. The heating sources 452U and 452L are positioned on movable platforms 410 and 411. Each movable platform 410 and 411 may be movable independently or synchronously with respect to each other. Although the movable platforms 410 and 411 are shown to be operable (or scannable) along the length of the flexible substrate 330, they may also be operable across the width of the flexible substrate 330. As shown, the movable platforms 410 and 411 move in directions B and F over a predetermined distance to facilitate proper heat treatment of the lithium coatings 401 and 402.

[0059] As shown in the embodiment of Figure 4, the rough surface 412 and / or defects 208 are located on or within the lithium films 401, 402. The smooth surface 420 is the surface obtained after heat-treating the lithium films 401, 402 to soften the lithium, uniformly leveling it, and producing a smooth surface.

[0060] The embodiments and all functional operations described herein can be performed by digital electronic circuits, or by computer software, firmware, or hardware, or a combination thereof, including the structural means and structural equivalents disclosed herein. The embodiments described herein can be performed as one or more non-temporary computer program products, i.e., one or more computer programs tangibly embodied in a machine-readable storage device for execution by or control of the operation of a data processing device, such as a programmable processor, a computer, or a plurality of processors or computers.

[0061] The processes and logic flows described herein can be executed by one or more programmable processors that run one or more computer programs so that their functions are performed by manipulating input data to produce outputs. The processes and logic flows can also be executed by dedicated logic circuits, such as FPGAs (Field-Programmable Gate Arrays) or ASICs (Application-Specific Integrated Circuits), and the devices can also be implemented as dedicated logic circuits.

[0062] Embodiments of this disclosure generally relate to coating stacks for electronic devices and methods for forming coating stacks. The coating stacks described herein can have superior device performance compared to the prior art. The methods described herein are reproducible and can produce a uniform passivation layer. Furthermore, the embodiments described herein can enable, for example, streamlined material handling and integration, and a longer shelf life for passivation coating stacks (passivation coating rolls) than the prior art.

[0063] As is evident from the above general description and specific embodiments, while the forms of embodiments have been illustrated and described, various modifications can be made without departing from the spirit and scope of this disclosure. Therefore, this disclosure is not intended to be limited thereto. Similarly, the term “comprising” is considered to be synonymous with the term “including.” Similarly, whenever a composition, process operation, multiple process operations, element, or group of elements precedes the transitional phrase “comprising,” the same composition or group of elements is also intended, where the transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “Is” precedes a composition, process operation, multiple process operations, element, or enumeration of elements, and vice versa. For example, the terms “comprising,” “consisting essentially of,” and “consisting of” are understood to also include combinations of elements enumerated before the term.

[0064] For the purposes of this disclosure, unless otherwise specified, all numerical values ​​in the detailed descriptions and claims of this specification are qualified with values ​​indicated "about" or "approximately," taking into account the experimental errors and variability expected by those skilled in the art. For brevity, only specific ranges are explicitly disclosed in this specification. However, to enumerate ranges not explicitly enumerated, a range from any lower limit can be combined with any upper limit, and similarly, to enumerate ranges not explicitly enumerated, a range from any lower limit can be combined with any other lower limit, and similarly, a range from any upper limit can be combined with any other upper limit to enumerate ranges not explicitly enumerated. For example, the enumeration of numerical ranges 1 to 5 includes subranges 1 to 4, 1.5 to 4.5, and 1 to 2, as well as other subranges. As another example, the enumeration of numerical ranges 1 to 5, such as 2 to 4, includes subranges 1 to 4 and 2 to 5, as well as other subranges. Furthermore, ranges include all points or individual values ​​between their endpoints, even if not explicitly enumerated. For example, the enumeration of the numerical range 1 to 5 includes the digits 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5, just like any other number. Therefore, every point or individual value can function as a lower or upper limit in combination with any other point or individual value, or any other lower or upper limit, to enumerate a range that is not explicitly enumerated.

[0065] As used herein, the indefinite articles "a" or "an" mean "at least one" unless otherwise specified or the context clearly indicates otherwise. For example, a "layer" includes a layer that includes one, two, or more layers unless otherwise specified or the context clearly indicates that it includes only one layer.

[0066] While the foregoing applies to aspects of the present disclosure, other and further aspects of the present disclosure can be devised without departing from its basic scope, the scope of which is determined by the following claims.

Claims

1. A method for smoothing the outer layer of a coating stack of an energy storage device, Forming an outer layer on the current collector of the film stack, By supplying energy to a heat source placed on the outer layer of the coating stack, the outer layer is heated. A method comprising heating the outer layer of a coating stack to induce reflow of the outer layer and reduce defects on the outer layer surface.

2. The method according to claim 1, wherein the heat source is configured to provide a temperature gradient smaller than the thickness of the outer layer of the coating stack.

3. The method according to claim 1, wherein the heat source is connected to a platform configured to move the heat source along the outer layer of the coating stack.

4. The method according to claim 3, further comprising operating a platform across the width of a film stack.

5. The method according to claim 1, wherein the outer layer is an alkali metal-containing layer containing lithium or sodium.

6. The method according to claim 1, wherein the current collector is the anode.

7. The method according to claim 1, wherein the first film stack is formed by substrate-independent direct transfer.

8. The method according to claim 1, wherein the heat source does not come into contact with the coating stack.

9. The method according to claim 1, wherein the heat source is an induction heater.

10. The method according to claim 1, wherein the reflow of the outer layer results in a surface roughness of about 6 Ra to about 30 Ra.

11. The method according to claim 10, wherein the surface roughness is about 6Ra to about 12Ra.

12. A non-temporary computer-readable medium that stores instructions, and when an instruction is executed by a processor, the processor performs the operation according to claim 1.

13. A method for smoothing the outer layer of a coating stack for an energy storage device, Forming an outer layer on the current collector of the film stack, The process involves supplying energy to an induction heater placed on the outer layer of a coating stack to heat the surface of the outer layer, wherein the induction heater is configured to provide a temperature gradient smaller than the thickness of the outer layer of the coating stack, and also involves supplying power to the induction heater. A method comprising heating the surface of the outer layer to induce reflow of the outer layer, thereby reducing defects and forming a smoothed outer layer surface having a surface roughness of 6Ra to about 30Ra.

14. The method according to claim 13, wherein the outer layer is an alkali metal-containing layer.

15. The method according to claim 14, wherein the alkali metal-containing layer contains lithium or sodium.

16. The method according to claim 13, wherein the film stack is formed by substrate-independent direct transfer.

17. The method according to claim 13, wherein the thickness of the outer layer of the coating stack is approximately 1 micron to approximately 20 microns.

18. The method according to claim 13, further comprising operating induction heaters positioned on the platform in a front-to-back and overlapping pattern across the entire coating stack.

19. A non-temporary computer-readable medium that stores instructions, and when an instruction is executed by a processor, the processor performs the operation according to claim 13.

20. A method for smoothing the outer layer of a coating stack for an energy storage device, Forming an outer layer on the current collector of the film stack, The method involves operating a platform on which a heat source is located along the outer lithium layer of a film stack passing through a substrate-independent direct transfer system, wherein the outer lithium layer is located on a current collector layer containing graphite or copper, and the lithium layer has a surface roughness of less than 10 microns. The method involves supplying energy to an induction heater positioned on the outer layer of a coating stack and not in contact with the outer layer, thereby heating the surface of the outer layer, wherein the induction heater is configured to provide a temperature gradient smaller than the thickness of the outer lithium layer of the coating stack, and by heating the surface of the outer lithium layer, reflow of the outer lithium layer is caused, reducing defects on the surface of the outer lithium layer and forming a smooth surface of the outer lithium layer, and powering the induction heater. Methods that include...

21. Pickup hub and Supply hub, A calendering unit comprising one or more calender rollers, located downstream of the supply hub and upstream of the pickup hub, A heating unit having an internal region, wherein a pickup hub is configured to rotate and assist in transporting a flexible substrate through the internal region of the heating unit, the heating unit is positioned downstream of a supply hub and upstream of a pickup hub, and includes one or more heating sources configured to generate and direct thermal energy towards the flexible substrate as the flexible substrate is transported through the internal region of the heating unit. A flexible substrate processing system including [the specified element].

22. A flexible substrate processing system according to claim 21, wherein one or more heating sources include a first heat source and a second heat source, the first heat source being positioned to guide thermal energy to a first portion of the internal region relative to a first side of the flexible substrate as the flexible substrate is transported through the internal region of the heating unit, and the second heat source being positioned to guide thermal energy to a second portion of the internal region relative to a second side of the flexible substrate opposite to the first side as the flexible substrate is transported through the internal region of the heating unit.

23. The flexible substrate processing system according to claim 21, wherein the heating unit is positioned downstream of the calendering unit and upstream of the pickup hub.

24. The flexible substrate processing system according to claim 21, wherein one or more heat sources can melt, liquefy, and reflow an alkali metal-containing layer placed on a current collector layer without thermally affecting the current collector layer.

25. The flexible substrate processing system according to claim 21, wherein one or more heat sources can heat lithium to or above a melting temperature of 181 degrees.

26. The flexible substrate processing system according to claim 21, wherein one or more heating sources include induction heaters having a capacity of about 1,000 BTU / hour to about 50,000 BTU / hour.

27. The flexible substrate processing system according to claim 21, wherein one or more heating sources are arranged on a movable platform.

28. The flexible substrate processing system according to claim 27, wherein the movable platform is operable or scannable along the length of the flexible substrate, across the width of the flexible substrate, or along the length of the flexible substrate and across the width of the flexible substrate.

29. A flexible substrate processing system for transferring a film from a substrate, A heating unit having an internal region, The heating unit includes one or more induction heating sources configured to generate and direct thermal energy towards the flexible substrate as the flexible substrate is transported through the internal region of the heating unit. Heating unit and A system control device for transporting a flexible carrier from a supply hub to a pickup hub, wherein the flexible carrier has an alkali metal-containing layer formed thereon. The method involves bringing a flexible carrier into contact with a flexible substrate, wherein the alkali metal-containing layer is in contact with the flexible substrate, and the method involves bringing a flexible carrier into contact with a flexible substrate. Separating the flexible carrier from the alkali metal-containing layer, and Heating an alkali metal-containing layer placed on a flexible substrate by exposing it to thermal energy. A system control device configured to cause a processing system to execute a process including the following: A flexible substrate processing system including [the specified element].

30. The flexible substrate processing system according to claim 29, wherein exposing the alkali metal-containing layer to thermal energy includes supplying energy to one or more induction heating sources disposed on the alkali metal-containing layer to heat the surface of the alkali metal-containing layer, and the one or more induction heating sources are configured to provide a temperature gradient smaller than the thickness of the alkali metal-containing layer.

31. The flexible substrate processing system according to claim 30, wherein heating the surface of the alkali metal-containing layer causes reflow of the alkali metal-containing layer, thereby reducing defects and forming a smoothed surface of the alkali metal-containing layer having a surface roughness of 6Ra to about 30Ra.

32. The flexible substrate processing system according to claim 29, wherein the alkali metal-containing layer contains lithium or sodium.

33. The flexible substrate processing system according to claim 29, wherein the thickness of the alkali metal-containing layer is approximately 1 micron to approximately 20 microns.

34. The flexible substrate processing system according to claim 29, further comprising the process of operating one or more induction heating sources positioned on a platform in a back-and-forth, overlapping pattern over the entire alkali metal-containing layer positioned on a flexible substrate.

35. The flexible substrate processing system according to claim 29, wherein the flexible carrier comprises a polymer material and the alkali metal-containing layer comprises lithium.

36. The flexible substrate processing system according to claim 29, wherein the flexible substrate includes a current collector substrate, an anode film, or an anode film formed on a current collector substrate.

37. The flexible substrate processing system according to claim 29, wherein contacting the flexible carrier with the flexible substrate includes laminating an alkali metal-containing layer onto the flexible substrate.

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