System for powder coating with rapid heating stage

Abstract

A system for powder coating is provided. The system includes a powder deposition unit configured to deposit powder particles onto a web. The system includes a calendering assembly configured to apply compression or compaction to the powder particles deposited onto the web. The system includes a rapid heating unit disposed upstream of the calendering assembly. The rapid heating unit is configured to heat the powder particles prior to calendering at the calendering assembly. Subsequent to heating of the powder particles, the powder particles are at least partially cooled prior to calendering at the calendering assembly.

Description

Attorney Docket No. 137174.00102SYSTEM FOR POWDER COATING WITH RAPID HEATING STAGECROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 699,578, filed on September 26, 2024. The entire content of the foregoing provisional application is incorporated herein by reference in its entirety.BACKGROUND

[0002] A variety of batteries are available in the industry for different uses. Lithium- ion (Li-ion) batteries have generally become the predominant type of battery used in portable consumer electronics and electric vehicles. Fabrication of Li-ion batteries involves numerous steps, each of which can affect the quality of the battery itself, as well as the cost involved in manufacturing the battery. A conventional manufacturing process generally includes formation of an electrode slurry having an active material, a conductive additive, and a binder, mixed in an organic solvent, and the electrode slurry is applied to a metal foil material. Once applied to the foil material, the solvent is dried out or evaporated while the active electrode mixture remains attached to the metal foil material surface. In some instances, the solvent may be toxic and can necessitate additional steps for handling / discarding that increase the overall cost of the manufacturing process. The cost of removing the solvent from the coated material on the metal foil therefore involves an additional step that also increases the overall cost of the manufacturing process.

[0003] An alternative manufacturing technique used in the industry is electrostatic deposition (ESD), which is a solvent-free manufacturing process for electrode coating for Li-ion batteries. (See, e.g., B. Ludwig et al., Solvent-Free Manufacturing of Electrodes for Lithium-ion Batteries, Sci. Rep. 6, Article No. 23150, doi: 10.1038 / srep23150 (2016); M. Wang et al., The Influence of Polyvinylidene Fluoride (PVDF) Binder Properties on LiNio.33Coo.33Mno.33O2 (NMC) Electrodes Made by a Dry-Powder-Coating Process, J. Electrochem. Soc., Vol. 166, No. 10, A2151 (2019); H. Abe et al., Electrostatic Spray Deposition for Fabrication of Li-ion Batteries, Transactions of JWRI, Vol. 44, No. 2 (2015); and U.S. Patent No. 10,547,044). Rather than relying on a solvent mixture, the ESD process uses a dry powder of the active electrode mixture which is applied to the metal foil material. By removing the solvent from the mixture and the drying step from the manufacturing process, the overall process is simplified and becomes more economical, resulting in a viable alternative for large-scale manufacturing. In particular, the solvent-1MEl\58064498.vlAttorney Docket No. 137174.00102 free electrode coating technology is an attractive alternative to traditional manufacturing since it can significantly reduce energy consumption in the manufacturing process and thus significantly reduces the manufacturing cost of batteries.

[0004] In a conventional continuous dry powder ESD coating system, a web (e.g., a grounded electrically conductive substrate) passes continuously through a coating chamber while the dry powder mixture is fluidized and pneumatically conveyed from a hopper to an electrostatic spray gun. The electrostatic spray gun electrostatically charges the powders using tribo-charging or corona charging, and sprays the charged powders onto the web where they are deposited.

[0005] Another conventional manufacturing process for coating of a web is referred to as “spreader roller coating”. A spreader roller coating system generally includes a reservoir that receives and dispenses powder particles onto a moving web. The web is passed through a pair of spreading rollers to spread and distribute the powder particles uniformly on the surface of the web to achieve a uniform coating on the web. The web is subsequently passed through a pair of calender rollers which compress and densify the powder particles. Such compression and densification causing the powder particles to adhere to each other and the web. Compression and densification performed by the calender rollers with or without heating promotes cohesion and adhesion of the powder particles to the web, and after such process, a dry electrode is produced. Such spreader roller coating technology is described in, e.g., International Patent Application No. PCT / US23 / 69175, which is incorporated herein by reference in its entirety.

[0006] In some instances, the ESD coating method and the spreading roller coating method can be used in conjunction where first an ESD coated layer is produced on the web and then is subsequently refined by a spreading roller (or vice versa), as is described in U.S. Provisional Patent Application No. 63 / 542,918, filed on October 6, 2023, which is incorporated herein by reference in its entirety.

[0007] In both ESD coating and spreader roller technology, the dry and loose powder layer deposited on the fast-moving web can be difficult to compress at the same speed using the conventional calendering assemblies due to lack of cohesive forces among powder particles, which can lead to powder layer separation, and various defects or an undesired surface finish. Further, by using conventional heated (e.g., 100° C or higher) calendering on the dry coated powder layer on a fast-moving web (e.g., greater than 5 m / min), it can be2MEl\58064498.vlAttorney Docket No. 137174.00102 difficult to achieve optimal adhesion between the coated layer and the current collector / sub strate .

[0008] With faster speeds of the moving web, the deposited powder coating receives less time in the heated calendering nip. As such, the binder in the dry coating experiences inadequate heating and thermal activation, resulting in poor mechanical strength of the electrode. In addition, high temperatures (e.g., over 100° C) for conventional calendering can lead to various textures and wrinkles on the calendered electrode surface due to uncontrolled thermal expansion and resulting stresses of the coating upon interacting (compression) with the heated calender roll surface. As such, improved surface finish and mechanical strength is desired during fast-moving web coating operations.SUMMARY

[0009] Embodiments of the present disclosure provide an exemplary system for powder coating including a rapid heating stage. In particular, the system provides for faster processing of dry powder with improved surface finish and mechanical strength of the final calendered electrode by introducing a rapid pre-heating (e.g., melting) stage before any compression / compaction step. The rapid pre-heating stage and the compression / compaction step can be followed by a post- annealing step that, in some embodiments, can be incorporated at the winding station of the electrode manufacturing line or completely offline. The process results in low (e.g., in some embodiments, room) temperature high-speed calendering of the dry electrodes with texture / defect-free smooth surface and improved mechanical strength.

[0010] In accordance with embodiments of the present disclosure, an exemplary system for powder coating including a rapid heating stage is provided. The system includes a powder deposition unit configured to deposit powder particles onto a web. The system includes a calendering assembly configured to apply compression or compaction to the powder particles deposited onto the web. The system includes a rapid heating unit disposed upstream of the calendering assembly. The rapid heating unit is configured to heat the powder particles prior to calendering at the calendering assembly. Subsequent to heating of the powder particles, the powder particles can be at least partially cooled prior to calendering at the calendering assembly.

[0011] The web can be a moving web traveling at a speed of greater than about 5 m / min through the calendering assembly. The powder particles can include an anode, a cathode,3MEl\58064498.vlAttorney Docket No. 137174.00102 and a binder material. In some embodiments, the binder can be a thermal plastic polymer material. The rapid heating unit can be configured to heat the powder particles to a threshold temperature at or near a melting temperature of the binder material to activate the binder material. In some embodiments, the rapid heating unit can be configured to heat the powder particles to a threshold temperature during a first period of time, maintain the powder particles at the threshold temperature for a second period of time, and at least partially cool the powder particles from the threshold temperature for a third period of time. In such embodiments, the second period of time can be equal to or less than about one second. Activating the binder material can increase coating cohesive and adhesive strengths between the powder particles and the web.

[0012] In some embodiments, the rapid heating unit can be configured to apply heating to the powder particles for about one second or less. In some embodiments, the rapid heating unit can be configured to apply heating to the powder particles for less than hundreds of a millisecond.

[0013] In some embodiments, the rapid heating unit can include at least one of a hot plate, an infrared source, combinations thereof, or the like. In some embodiments, the rapid heating unit can include at least one of a first heat source disposed over the web, a second heat source disposed below the web, or both. In some embodiments, the first heat source can be configured to apply heat to the powder particles through radiative means. In some embodiments, the second heat source can be configured to apply heat to the powder particles through conductive means through the web.

[0014] The system can include a cooling stage disposed between and separating the rapid heating unit and the calendering assembly. In the cooling stage, the powder particles can be at least partially cooled prior to calendering at the calendering assembly. The rapid heating unit can be configured to heat the powder particles to a temperature at or above a binder melting temperature of the powder particles. The system can include a postcalendering rapid heating unit disposed downstream of the calendering assembly. The postcalendering rapid heating unit can be configured to heat calendered powder particles to a threshold temperature at or near a melting temperature of the binder material.

[0015] In some embodiments, the system can include an annealing enclosure downstream of the calendering assembly. The annealing enclosure can be in line with the web at the coating assembly, or can be disposed offline from the coating assembly. The4MEl\58064498.vlAttorney Docket No. 137174.00102 annealing enclosure can be configured to maintain heating of the web after calendering at a controlled temperature.

[0016] In some embodiments, the system can include a sensor disposed downstream of the rapid heating unit and configured to detect a characteristic of the powder particles prior to calendering. The system can include a controller in communication with the sensor and configured to adjust operation of the rapid heating unit based on the detected characteristic of the powder particles after rapid heating.

[0017] In accordance with embodiments of the present disclosure, an exemplary system for powder coating is provided. The system includes a powder deposition unit configured to deposit powder particles onto a moving web. The system includes a calendering assembly configured to apply compression or compaction to the powder particles deposited onto the moving web. The system includes a first rapid heating unit disposed upstream of the calendering assembly. The system includes a second heating unit disposed downstream of the calendering assembly. The first and second heating units are configured to heat the powder particles prior to and post calendering, respectively. Subsequent to heating of the powder particles at the first rapid heating unit, the powder particles can be at least partially cooled prior to calendering at the calendering assembly.

[0018] In accordance with embodiments of the present disclosure, an exemplary method of powder coating is provided. The method includes depositing powder particles onto a web with a powder deposition unit. The method includes applying heat to the powder particles with a rapid heating unit disposed upstream of a calendering assembly. The method includes at least partially cooling the powder particles prior to entry of the powder particles into the calendering assembly. The method includes passing the heated web through the calendering assembly.

[0019] In accordance with embodiments of the present disclosure, an exemplary system for powder coating is provided. The system includes a powder deposition unit configured to deposit powder particles onto a web. The system includes a calendering assembly configured to apply compression or compaction to the powder particles deposited on the web. The system includes a rapid heating unit disposed downstream of the calendering assembly. The rapid heating unit is configured to heat the powder particles after calendering at the calendering assembly.5MEl\58064498.vlAttorney Docket No. 137174.00102

[0020] In some embodiments, the web can be a moving web traveling at a speed of greater than about 5 m / min through the calendering assembly. The powder particles can include an anode, a cathode, and a binder material. In some embodiments, the binder can be a thermal plastic polymer material. The rapid heating unit can be configured to heat the powder particles to a threshold temperature at or near a melting temperature of the binder material to activate the binder material. In some embodiments, the rapid heating unit can be configured to heat the powder particles to a threshold temperature during a first period of time, maintain the powder particles at the threshold temperature for a second period of time, and at least partially cool the powder particles from the threshold temperature for a third period of time. In some embodiments, the second period of time can be equal to or less than about one second.

[0021] Activating the binder material can increase coating cohesive and adhesive strengths between the powder particles and the web. In some embodiments, the rapid heating unit can be configured to apply heating to the powder particles for about one second or less. In some embodiments, the rapid heating unit can include at least one of a hot plate or an infrared source. In some embodiments, the rapid heating unit can include at least one of a first heat source disposed over the web, a second heat source disposed below the web, or both. In some embodiments, the first heat source can be configured to apply heat to the powder particles through at least one of (i) radiative means or (ii) conductive means through the web.

[0022] In some embodiments, the system can include a cooling stage disposed at or downstream of the rapid heating unit. In the cooling stage, the powder particles can be at least partially cooled after heating by the rapid heating unit. In some embodiments, an upstream rapid heating unit can be disposed upstream of the calendering assembly. The upstream rapid heating unit can be configured to heat the powder particles prior to calendering at the calendering assembly and, subsequent to heating of the powder particles, the powder particles can be at least partially cooled prior to calendering at the calendering assembly.

[0023] In some embodiments, the system can include an annealing enclosure downstream of the calendering assembly and the rapid heating unit. The annealing enclosure can be configured to maintain heating of the web after calendering and after the rapid heating unit at a controlled temperature. In some embodiments, the system can include a sensor disposed downstream of the rapid heating unit and configured to detect a6MEl\58064498.vlAttorney Docket No. 137174.00102 characteristic of the powder particles after heating by the rapid heating unit. In some embodiments, the system can include a controller in communication with the sensor and configured to adjust operation of the rapid heating unit based on the detected characteristic of the powder particles after heating by the rapid heating unit.

[0024] In accordance with embodiments of the present disclosure, an exemplary method of powder coating is provided. The method includes depositing powder particles onto a web with a powder deposition unit. The method includes passing the web and the powder particles through a calendering assembly. The method includes applying heat to the powder particles with a rapid heating unit disposed downstream of the calendering assembly. In some embodiments, the method can include at least partially cooling the powder particles after heating of the powder particles at the rapid heating unit.

[0025] Any combination and / or permutation of embodiments is envisioned. Other objects and features will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the present disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To assist those of skill in the art in making and using the system for powder coating with rapid heating stage, reference is made to the accompanying figures, wherein:

[0027] FIG. 1 is a diagrammatic side view of an exemplary system for powder coating in accordance with embodiments of the present disclosure.

[0028] FIG. 2 is a diagrammatic side view of an exemplary system for powder coating with rapid heating stages in accordance with embodiments of the present disclosure.

[0029] FIG. 3 is a diagrammatic side view of an exemplary system for powder coating with rapid heating stages in accordance with embodiments of the present disclosure, and an offline heating enclosure.

[0030] FIG. 4 is a graph showing a rapid heating stage, a holding stage, and a cooling stage performed by an exemplary system for powder coating in accordance with embodiments of the present disclosure.7MEl\58064498.vlAttorney Docket No. 137174.00102DETAILED DESCRIPTION

[0031] An exemplary system for powder coating is provided. The system includes a rapid heating stage disposed prior to a calendering assembly. The rapid heating stage applies heat to the powder particles deposited on the web to induce a morphological change in the binder material, which enables enough cohesive strength of the loose powder for high-speed processing during the calendering stage. The rapid heating stage can be followed by an air cooling stage prior to calendering. In some embodiments, the system can include a secondary rapid heating stage disposed after the calendering process to raise the temperature of the powder coating above the binder melting temperature. In some embodiments, downstream of the calendering assembly, the system can include a heated enclosure for winding and storage of the coated electrode. The heated enclosure can control the holding temperature and cooling rate for the electrode. Operation of the system ensures an improved surface finish and mechanical strength of the resulting electrode.

[0032] In some embodiments, the system can include a feedback control loop including one or more sensors configured to detect the characteristics of the powder particles after the rapid heating stage (whether before or after calendering). In some embodiments, the sensors can detect the degree or level of melting of the binder material. The sensors can be in communication with a controller. Based on the received signals from the sensors, the controller can regulate operation of the rapid heating unit(s) to achieve the desired melting level of the binder material for optimal calendering operation, surface finish, and mechanical strength.

[0033] FIG. 1 is a diagrammatic view of an exemplary system 100 for powder coating for purposes of battery electrode fabrication (hereinafter “system 100”). The system 100 can be used to manufacture a coated substrate usable in, e.g., Li-ion batteries, solid state batteries, or the like. The system 100 can be incorporated into a containment enclosure (e.g., a containment chamber, a coating chamber, or the like) for deposition of the powder coating onto a substrate or web 102, e.g., a continuously moving substrate or web 102. It should be understood that the enclosure or coating chamber includes a housing / structure positioned at least partially over the components illustrated in FIG. 1. The web 102 includes a top surface 104 configured to be coated, and an opposing bottom surface. In some embodiments, both surfaces of the web 104 can be coated. The powder coating includes at least a cathode material or an anode material, e.g., for rechargeable lithium batteries, or the like. In some embodiments, a binder material can be included in the powder8MEl\58064498.vlAttorney Docket No. 137174.00102 coating mixture. In some embodiments, polyvinylidene fluoride (PVDF) (e.g., a polymer binder) can be used in the powder mixture. However, it should be understood that any thermal plastic polymer material can be used in the powder mixture.

[0034] Materials used for the web may be selected for a variety of reasons, including, but not limited to, a range or minimum amount of electrical conductivity, an ability to form the material in a thin sheet (e.g., in the range between about 5 and about 20 microns inclusive, for example), a density of the material, an electrochemical compatibility of the material with the active material, the voltage range over which the active material must operate, cost, or the like, for example. According to some embodiments, the web material may include a metal (such as copper, an alloy of copper, aluminum, an alloy of aluminum, titanium, an alloy of titanium, or the like), a conductive polymer (such as poly (pyrrole), poly(acetylene), poly(vinylene), poly (thiophene), poly (aniline), poly(phenylene sulfide), or the like), a composite of a polymer (conductive or not) and a metal (where a non- conductive polymer may include at least one of an olefinic polymer, a poly (propylene), a poly (ethylene), a poly(styrene), a poly (aery lie), a fluorinated polymer (such as a poly(vinylidene fluoride), or a poly(tetrafluoroethylene), for example), a thermoset polymer, or a thermoplastic polymer, for example. According to some embodiments, a web may also include a laminate structure including a metal and a polymer, for example.

[0035] At a starting point or upstream side, the system 100 includes a roller or spool 106 from which an uncoated web 102 is fed through the coating chamber. The spool 106 can maintain tension on the web 102 as it passes through the system 100 in combination with one or more rollers (omitted for clarity). The web 102 travels in a web direction 108 as it leaves the spool 106, and passes through or under a powder deposition unit 110. Conventional slurry systems can operate at a web speed of about 50-100 m / min. However, for processing (compaction) of dry loose powder on a moving web without any rapid heating unit, it can be difficult to operate anywhere above 5 m / min as the deposited loose powder tends to exhibit various surface defects, including separation of layers. The rapid heading provided by the exemplary system allows for processing (compaction) of dry loose powder on a web moving at 5 m / min or greater (and in some instances, 20 m / min or greater) without the surface defects typically seen in conventional systems. The deposition unit 110 can be any type of dry powder coating assembly known in the industry, such as ESD coating, spreader roller coating, or the like. For example, the deposition unit 110 can include a reservoir that receives a mixture of the powder particles for dispersion onto the9MEl\58064498.vlAttorney Docket No. 137174.00102 web 102.

[0036] In some embodiments, the deposition unit 110 can include one or more powder dispersion systems, e.g., nozzles, rollers, dispensing tubes, mechanical feeders, electrostatic powder feeders, dispersion based on gravimetric or volumetric meter basis, vibratory and / or acoustic dispersion systems, or the like, and any one or combination of the following charging mechanisms, e.g., corona discharge (positive or negative), tribocharging, direct conduction charging, induction charging, dielectric barrier discharges, other non-thermal plasmas, or the like. In some embodiments, deposition unit 110 can include one or more features of those disclosed in International Patent Application No. PCT / US23 / 26276, filed on June 27, 2023; International Patent Application No. PCT / US23 / 82635, filed on December 6, 2023; and International Patent Application No. PCT / US24 / 18424, filed on March 4, 2024, each of which is incorporated herein by reference. In some embodiments, the deposition unit 110 can include one or more scattering rollers, one or more spreader rollers, and one or more calendering rollers.

[0037] Downstream of the deposition unit 110, the system 100 includes a conditioning assembly 112 with one or more pairs of rollers (e.g., rollers 114, 116, 118, 120, 122, 124) disposed above and below the web 102. The conditioning assembly 112 can alter the powder particles deposited onto the web 102 by, e.g., spreading, smoothening, compaction, combinations thereof, or the like. The conditioning assembly 112 ensures uniformity in the powder coating layer on the web 102.

[0038] After the powder particles have been conditioned, the web 102 moves further downstream to a calendering assembly 126 in which compaction of the powder particles onto the top surface 104 of the web 102 is performed (with or without heat). Although only a single pair of calendering rollers 128, 130 is shown in FIG. 1, it should be understood that one or more pairs of calendering rollers could be used for compaction of the powder particle coating. In some embodiments, heat can be applied before, during and / or after the compaction steps.

[0039] In some embodiments, the compressive force applied by the calendering assembly 126 to form the coating layer can be about, e.g., 10-4000 N / mm inclusive, 10- 3900 N / mm inclusive, 10-3800 N / mm inclusive, 10-3700 N / mm inclusive, 10-3600 N / mm inclusive, 10-3500 N / mm inclusive, 10-3400 N / mm inclusive, 10-3300 N / mm inclusive, 10-3200 N / mm inclusive, 10-3100 N / mm inclusive, 10-3000 N / mm inclusive, 10-290010MEl\58064498.vlAttorney Docket No. 137174.00102N / mm inclusive, 10-2800 N / mm inclusive, 10-2700 N / mm inclusive, 10-2600 N / mm inclusive, 10-2500 N / mm inclusive, 10-2400 N / mm inclusive, 10-2300 N / mm inclusive, 10-2200 N / mm inclusive, 10-2100 N / mm inclusive, 10-2000 N / mm inclusive, 10-1900 N / mm inclusive, 10-1800 N / mm inclusive, 10-1700 N / mm inclusive, 10-1600 N / mm inclusive, 10-1500 N / mm inclusive, 10-1400 N / mm inclusive, 10-1300 N / mm inclusive, 10-1200 N / mm inclusive, 10-1100 N / mm inclusive, 10-1000 N / mm inclusive, 10-900 N / mm inclusive, 10-800 N / mm inclusive, 10-700 N / mm inclusive, 10-600 N / mm inclusive, 10-500 N / mm inclusive, 10-400 N / mm inclusive, 10-300 N / mm inclusive, 10-200 N / mm inclusive, 10-100 N / mm inclusive, 10-50 N / mm inclusive, 10-20 N / mm inclusive, 20-4000 N / mm inclusive, 30-4000 N / mm inclusive, 40-4000 N / mm inclusive, 50-4000 N / mm inclusive, 100-4000 N / mm inclusive, 200-4000 N / mm inclusive, 300-4000 N / mm inclusive, 400-4000 N / mm inclusive, 500-4000 N / mm inclusive, 600-4000 N / mm inclusive, 700-4000 N / mm inclusive, 800-4000 N / mm inclusive, 900-4000 N / mm inclusive, 1000-4000 N / mm inclusive, 1100-4000 N / mm inclusive, 1200-4000 N / mm inclusive, 1300-4000 N / mm inclusive, 1400-4000 N / mm inclusive, 1500-4000 N / mm inclusive, 1600-4000 N / mm inclusive, 1700-4000 N / mm inclusive, 1800-4000 N / mm inclusive, 1900-4000 N / mm inclusive, 2000-4000 N / mm inclusive, 2100-4000 N / mm inclusive, 2200-4000 N / mm inclusive, 2300-4000 N / mm inclusive, 2400-4000 N / mm inclusive, 2500-4000 N / mm inclusive, 2600-4000 N / mm inclusive, 2700-4000 N / mm inclusive, 2800-4000 N / mm inclusive, 2900-4000 N / mm inclusive, 3000-4000 N / mm inclusive, 3100-4000 N / mm inclusive, 3200-4000 N / mm inclusive, 3300-4000 N / mm inclusive, 3400-4000 N / mm inclusive, 3500-4000 N / mm inclusive, 3600-4000 N / mm inclusive, 3700-4000 N / mm inclusive, 3800-4000 N / mm inclusive, 3900-4000 N / mm inclusive, 20-1500 N / mm inclusive, 20-1000 N / mm inclusive, 20-500 N / mm inclusive, 20- 300 N / mm inclusive, 1000-3000 N / mm inclusive, 1500-2500 N / mm inclusive, 10 N / mm, 20 N / mm, 30 N / mm, 40 N / mm, 50 N / mm, 60 N / mm, 70 N / mm, 80 N / mm, 90 N / mm, 100 N / mm, 200 N / mm, 300 N / mm, 400 N / mm, 500 N / mm, 600 N / mm, 700 N / mm, 800 N / mm, 900 N / mm, 1000 N / mm, 1100 N / mm, 1200 N / mm, 1300 N / mm, 1400 N / mm, 1500 N / mm, 1600 N / mm, 1700 N / mm, 1800 N / mm, 1900 N / mm, 2000 N / mm, 2100 N / mm, 2200 N / mm, 2300 N / mm, 2400 N / mm, 2500 N / mm, 2600 N / mm, 2700 N / mm, 2800 N / mm, 2900 N / mm, 3000 N / mm, 3100 N / mm, 3200 N / mm, 3300 N / mm, 3400 N / mm, 3500 N / mm, 3600 N / mm, 3700 N / mm, 3800 N / mm, 3900 N / mm, 4000 N / mm, or the like, depending on the desired thickness, the type of powder particles used, or the like. After compression by the calendering unit 126, the web 102 can be fed to a distal end of the system 100 (e.g., the11MEl\58064498.vlAttorney Docket No. 137174.00102 downstream end) at which the web 102 is collected at a roller and / or spool 132.

[0040] FIG. 2 is a diagrammatic view of an exemplary system 100 including one or more rapid heating or preheating stages. The powder deposition unit 110 releases or deposits loose powder particles as an initial layer 140 on the top surface 104 of the web 102. In some embodiments, the calendering assembly 126 can include two pairs of rollers (e.g., rollers 142, 144 and rollers 146, 148), each configured to apply compression / compaction to the powder particles. For example, the rollers 142, 144 can apply a first level of compression / compaction to the initial layer 140, resulting in a thinner secondary layer 150, and the rollers 146, 148 can apply a second level of compression / compaction to the secondary layer 150 to achieve a final layer 152. The secondary layer 150 defines a thickness dimensioned smaller than the initial layer 140, and the final layer 152 defines a thickness dimensioned smaller than the secondary layer 150. It should be understood that multiple calendering rollers could be used to achieve the final layer 152.

[0041] The system 100 can include a first rapid heating or preheating unit 154 disposed between the conditioning assembly 112 and the calendering assembly 126. The unit 154 is therefore disposed upstream of the calendering assembly 126. The unit 154 can include a heating source 156 disposed over the top of the web 102 to apply heat to the powder particles through radiative means, a heating source 148 disposed below the web 102 to apply heat to the powder particles through conduction, or both. Both radiative and conductive heating through the top / bottom heating sources, respectively, may necessitate longer areas under / in contact with the web 102 and / or powder as the web 102 speed increases to raise in order to raise the coating surface temperature above the binder melting temperature. Therefore, the contact or adjacently positioned surface area of the heating sources can be adjusted or designed based on the intended speed of the web 102 to ensure sufficient heating can be applied as the speed is increased. In some embodiments, the heating sources can be configured to raise the coating surface temperature above the binder melting temperature by about, e.g., l-50°C inclusive, l-40°C inclusive, l-30°C inclusive, l-20°C inclusive, l-10°C inclusive, 1-5°C inclusive, 5-50°C inclusive, 10-50°C inclusive, 20-50°C inclusive, 30-50°C inclusive, 40-50°C inclusive, 10-40°C inclusive, 20-30°C inclusive, 1°C, 5°C, 10°C, 20°C, 30°C, 40°C, 50°C, or the like. The unit 154 is spaced from the initial stage of the calendering assembly 126 by a distance 159, which allows for cooling of the preheated powder particle coating prior to entry into the calendering assembly 126.12MEl\58064498.vlAttorney Docket No. 137174.00102The unit 154 is therefore not intended to function as a preheating stage prior to entry into the calendering assembly 126, and instead is intended to activate the binder of the coating layer to increase the overall mechanical strength of the coating layer prior to calendering. Cooling of the coating layer is therefore permitted between the unit 154 and the calendering assembly 126. In some embodiments, cooling can be performed by air cooling with passage of the web 102 through the ambient air. In some embodiments, the system 100 can include an air cooling unit 160, e.g., a fan, or the like, configured to apply air flow to the powder coating layer 140.

[0042] Various modes of heating can be used in the unit 154, either individually or in combination, with the heating sources intended to heat at least a portion of the powder during processing. The heating modes may include, e.g., conduction, convection, radiation, combinations thereof, or the like. In some embodiments, the heating sources can be used for heating and / or preheating.

[0043] In some embodiments, heating sources using conduction can include systems where an object, such as a surface, roller, plate, or other structure, is configured to touch a portion of a conveying web along a surface of the web which is not coated with powder. Direct contact on a powder-coated surface of the web may disturb the powder and this behavior may be undesirable in certain embodiments. Thus, the object makes contact with an uncoated area of the web to prevent disruption of the powder coating.

[0044] In some embodiments, a roller may be used to contact and heat the conveying web via conduction. The roller may be of a large diameter (e.g., in excess of 100 mm, 200 mm, or the like) with a wrap angle sufficient to provide a length over which the conveying web and powder may be heated. As used herein, wrap angle refers to an angle measuring the arc of engagement of a web / foil on the surface of a roller. For example, a wrap angle of X degrees on a roller of diameter D will result in a wrap, or length of engagement, along the direction of web travel of L=2*7t*X / 360*D. For a web speed vw, this will result in an engagement of L / vw. In some embodiments, multiple rollers may be used in series during the heating stage.

[0045] In some embodiments, heating sources using convection may include systems using natural and / or forced convection. Natural convection systems may include heating surfaces (such as heated plates, heated rods, heated meshes, heated porous plates, heated pins, or the like) closely spaced and, in some instances touching, if the convection heating13MEl\58064498.vlAttorney Docket No. 137174.00102 process is desired to be supplemented by a conduction heating process. By closely spacing the heated surface and the web, preferably with the uncoated surface of the web above a heated surface, the heated surface transmits heat to any fluid intervening between the heated surface and the web, and the (now) heated fluid ascends toward the web to be heated and transfers heat to the web, raising the temperature of the web and the coating thereon.

[0046] In some embodiments, heating systems may use forced convection. In such embodiments, a liquid is heated and directed toward an object to be heated using a forcing apparatus. In some embodiments, the liquid heated can be, e.g., air or another gas, liquids and liquid-containing streams (such as aerosols), or the like. The object to be heated can be, e.g., a web and powder thereon. In some embodiments, the forcing apparatus can be, e.g., a fan, blower, or other mechanism designed to impart momentum to the fluid stream in the act of directing the fluid stream toward the object to be heated. In some embodiments, a convection apparatus can include a fan, blower, pump, or other displacement apparatus including at least an infeed and a discharge end, with the discharge end directed toward a heat exchanger to permit the heating of a fluid exiting the discharge end. In some embodiments, a heat exchanger can include a heated filament or a series of filaments (such as a resistance wire), a heated tube or a series of tubes, a heated pipe or a series of pipes, a heated fin or a series of fins, a heated plate or a series of plates, or any other surface across, through, over, around, beside, or otherwise adjacent to which a fluid may pass and heat prior to interacting with a conveying web and powder thereon. In some embodiments, the flow of fluid corresponding to the fluid which performs the forced convective heating may be directed to an underside (e.g., an uncoated side) of a conveying web carrying an amount of battery electrode powder.

[0047] In some embodiments, radiative heating can be used to heat at least a portion of the web and powder coating. In some embodiments, a heating system can include a radiative heater. A radiative heater can provide a source of infrared radiation directed toward the surface of the web and / or powder. A radiative heater may be directed to address, or otherwise shine upon, a full width of the web and / or powder residing on the web. In some embodiments, a first radiative heater can be configured to address a first surface of the web, such as an underside of the web, and a second radiative heater can be configured to address a second surface of the web, such as a top surface of the web. In some embodiments, a top surface of the web may be coated with an amount of battery electrode powder. In some embodiments, an underside of the web may be uncoated, coated with a14MEl\58064498.vlAttorney Docket No. 137174.00102 primer layer (such as an adhesive interface layer, or the like), or may be coated with an amount of battery electrode powder which has been at least partially compressed upon the surface of the conveying web.

[0048] In some embodiments, a temperature of a heater may be below, at, or above a target temperature for a heating process. In some embodiments, a heating system can be segmented, arranged, or otherwise configured to provide a heating profile to the conveying web, such that a temperature experienced by a surface of the web or coating varies along the direction of travel of the web. For example, and in the case of a conduction heating process with a series of rollers, a first heated roller may be heated to a first temperature and may first interact with a portion of a conveying web, and a second heated roller may be heated to a second temperature and may interact with a conveying web after the first heated roller. In some embodiments, the first and second temperatures may be the same or different.

[0049] In some embodiments, it may be desirable to provide a heating profile to a conveying web and battery electrode powder. A heating profile can include a first ramp from a first temperature to a plateau temperature over a first duration of time, a hold at the plateau temperature for a second duration of time, and a ramp down from a plateau temperature to a third temperature, the ramp down occurring over a third duration of time. Any combination of ramp up events, hold events, and ramp down events can be used. In some embodiments, a heating profile can include a ramp up in temperature and a ramp down in temperature, without a hold (e.g., without a plateau temperature period).

[0050] In some embodiments, the various heating modes discussed here may be used to also cool at least a portion of the powder during processing. For example, in some embodiments, it may be desirable to heat, hold, and then cool a conveying web and coated battery electrode powder.

[0051] In some embodiments, the system 100 can include a downstream or secondary heating unit 162 disposed downstream of the calendering assembly 126 and upstream of the spool 132. The unit 162 can include a heating source 164 disposed over the top of the web 102 to apply heat to the powder particle layer 152 through radiative means, a heating source 166 disposed below the web 102 to apply heat to the powder particle layer 152 through conduction, or both. The heating sources disposed downstream of the calendering assembly 126 can similarly be designed to provide sufficient contact (direct or indirect) for15MEl\58064498.vlAttorney Docket No. 137174.00102 heating the layer 152 depending on the speed of the web 102. The unit 162 is configured to heat the layer 152 around or above the binder melting temperature, e.g., l-50°C inclusive above the binder melting temperature. In some embodiments, cooling of the web 102 after the unit 162 can be a maximum of 10°C / min to ensure the raised electrode temperature is not cooled below the set holding temperature of the enclosure 168.

[0052] In particular, in some embodiments, the system 100 can include a heating enclosure 168 disposed at least partially around the spool 132, e.g., a winding station for the calendered web 102. The enclosure 168 can be regulated to maintain a holding temperature and / or cooling rate for the electrode after the heating steps performed by the heating unit 162. Cooling of the electrode or web 102 can therefore be performed in a regulated and controlled rate manner. In some embodiments, cooling of the electrode or web 102 in the enclosure 168 can be in the range of about, e.g., 10-100°C / min, or the like. In some embodiments, the heating enclosure 168 can be disposed downstream or offline relative to the web 102 coating chamber on a winding roll or spool 178, as illustrated in FIG. 3. The calendered and winded roll of the electrode can therefore be post-processed in the offline heating enclosure 168 which heats and anneals the roll of electrode inside the enclosure 168 to improve its mechanical strength. In such embodiments, the sensor 172 can be responsible for detecting conditions of the web 102 after the calendering assembly 126.

[0053] The heating unit 154 is configured to apply a rapid heating to the powder particles in the layer 140. The term “rapid heating” or “rapid preheating” discussed herein refers to heating of the powder coating / layer at a rate fast enough to reach and / or exceed the binder melting temperature during the speed of the web 102. Therefore, the unit for rapid heating can be dimensioned and designed to ensure such heating level of the binder material is reached based on the speed of the web 102. In some embodiments, the time the web 102 spends within, underneath or between the heating unit components can be extended by increasing the length of the unit along the web direction to ensure sufficient time for heating is provided due to the speed of the web 102. In some embodiments, as discussed herein, rapid heating refers to less than one second or hundreds of milliseconds of heating applied to the layer 140. The heating unit 162 can operate under the same rapid heating conditions, while also allowing for partial cooling of the powder layer prior to the enclosure 168.16MEl\58064498.vlAttorney Docket No. 137174.00102

[0054] In some embodiments, “rapid heating” can involve a heating rate anywhere from about 20°C / sec up to about 200°C / sec. In some embodiments, for battery fabrication in which material is deposited on a web, the deposited coating layer can be compressed with the application of heat and pressure. The rapid heating of the coating layer, if heated to or above its binder melt temperature, promotes coating cohesive and adhesive (with the web) strengths against shear forces. Rapid heating is not an auxiliary heating for calendering (compression); rather, it is a way to provide the coating layer enough mechanical strength to survive the high shear in the calendering nip. Thus, rather than a pre-heating for the calendering stage, rapid heating focuses on activation of the binder of the coating layer for an increase in the mechanical strength of the coating layer.

[0055] In some embodiments, rapid heating can include heating of a thickness of powder (such as a portion of a powder layer deposited on a conveying web) such that the limit to the rate at which the temperature changes at locations within the deposited layer is based upon heat transfer mechanisms internal to the deposited layer. For example, a rate of heat transfer within the layer may be based upon a thermally-conductive process with a time constant ti, and a heating mode external to the surface may have a time constant t2. In some embodiments, the heating may be considered “rapid” when the time constant ti>t2, meaning that the physical process of transferring heat within the porous material throttles the change in temperature at the boundary of the material. Moreover, this condition may also require that a heating apparatus providing heat to a surface (or boundary) of a powder to be heated is capable of maintaining a flux of heat sufficient to maintain a time constant t2 or, similarly, a rate of heating r2=l / 22.

[0056] In some embodiments, rapid heating can be dependent on the time required to raise the temperature of the coating near or before the binder melt temperature by the application of the heating mode with respect to the speed of the moving web. The rapid heating of the battery electrode material should allow sufficient heating up to the threshold temperature in the deposited coating layer for successful compression at web speeds of greater than 5 m / min. For example, if conduction mode of heat is applied to the coating layer after deposition via, e.g., a hot plate or heated idler roller, then the time required to raise the temperature of the coating layer near or above the binder melt temperature would be dependent on the thermal conductivity of the coating material and the current collector, physical properties of the coating and the current collection (such as thickness, density, or the like), heat exposure time for the coating, and the temperature difference of the heat17MEl\58064498.vlAttorney Docket No. 137174.00102 source and the coating layer itself. For battery electrode material on a moving web, the deposited coating layer can achieve near or above the binder melt temperature within about, e.g., 1 second, or the like, via conduction or radiation heat transfer modes.

[0057] The rapid pre-heating (e.g., melting) step is enough to induce desired morphological changes in the PVDF binder (or any thermal plastic polymer material) that enables enough cohesive strength of the loose powder for high-speed processing. The preheating step performed by the heating unit 154 can be incorporated before any calendering step (at a distance 159 from the calendering assembly 126 for at least one second of air cooling) of the electrode manufacturing line. Hence, rapid heating of PVDF binder with the heating unit 154 prior to calendering promotes smaller crystallite sizes with increased beta phase content percentage, which is responsible for improved cohesive strength of the loose powder particle layer 140. The improved cohesive strength of the powder particles allows for high-speed compression steps to be performed in the calendering nip or the calendering assembly 126 with defect-free and smooth surface finish. Inclusion of the heating unit 154 therefore optimizes and significantly improves the resulting surface finish and mechanical strength of the electrode. In particular, as noted herein, the rapid heating stage is not intended as a pre-heating stage prior to calendering, and instead is intended for activation of the binder in the coating layer to improve the surface finish and increase the mechanical strength of the coating layer prior to calendering.

[0058] FIG. 4 is a graph showing an example of different stages performed by the exemplary system 100 for powder coating during the exemplary process. Initially, the powder coating (and the web) can be maintained at an input temperature 200 (e.g., room temperature, or the like). During the rapid heating stage 202, the temperature is increased to a predetermined threshold temperature during a period of time (e.g., raised to 160°C within 1 second, or the like). Once the powder coating reaches the predetermined threshold temperature, at a holding stage 204, the powder coating is maintained at the threshold temperature for a period of time (e.g., about 1 second or less). Next, at a cooling stage 206, the powder coating temperature is reduced to an output temperature 208 and the powder coating proceeds to calendering at the output temperature 208. In some embodiments, the output temperature 208 can be greater than the input temperature 200. However, it is understood based on FIG. 4 that the output temperature 208 is closer to the input temperature 200 than the threshold temperature at the holding stage 204.18MEl\58064498.vlAttorney Docket No. 137174.00102

[0059] Thus, as shown in FIG. 4, the temperature achieved by the coating during rapid heating does not need to be maintained throughout the calendering process when the web moves into the calendering nip. The coating can be allowed to cool down from the near or above binder melt temperature within, e.g., about 1 second, or the like, after such temperature is achieved. Hence, the calendering roll surface temperature does not need to be at an elevated temperature for processing the coating at faster web speeds.

[0060] The heating requirement can be dependent on the types and properties of binder materials used in the coating. Typically, the heating requirement threshold can be highly sensitive to the melt temperature of the binder. The coating material exposed to the threshold heating temperature can only be processed (compressed) at web speeds of greater than 5 m / min. For example, for HSV900 PVDF binder material having a melt temperature of about 168°C used for battery cathode manufacturing, the threshold heating temperature has been determined to be about 165°C-170°C, inclusive. This means that if any part of the coated material does not reach this threshold surface temperature, the coating layer cannot be processed at web speeds greater than 5 m / min in the calendering nip for compression. As another example of the PVDF binder with more amorphous phase due to presence of copolymers, such as Hexafluoropropylene (HFP) having a binder melt temperature of about 153 °C, the threshold heating temperature has been determined to be about 135°C-140°C, inclusive.

[0061] Both threshold temperatures for the mentioned binder types have been determined to be near or the same as the binder melt temperature, which allows for successful processing at faster web speeds for calendering. A threshold temperature may be defined as the temperature achieved by the coated material below which the coated material cannot be compressed at web speeds of greater than 1 m / min without any layer separation or other defects. Table 1, below, provides the threshold temperature with respect to the melt temperature for two different binder types which have been described in the examples above.Table 1: Threshold Temperature for Binder Materials19MEl\58064498.vlAttorney Docket No. 137174.00102

[0062] In some embodiments, a heating process may be performed to at least modify a cohesive property of the powder and powder- web interface. The heating process may cause a binder within a battery electrode powder to melt, soften, wet, or otherwise interact differently with other particles within the battery electrode powder, as compared to a battery electrode powder in which heat is not applied (e.g., at room temperature). For example, a resistance of the battery electrode powder to shearing may be greater when the battery electrode powder is heated. Such an increase in cohesion may also be reflected in an angle of repose of the battery electrode powder (static or dynamic), for example.

[0063] In the exemplary system 100, after the final calendering is performed at the calendering assembly 126, a rapid melting of the binder can be performed with the heating unit 162. In particular, the heating unit 162 applies rapid heating to the layer 152 to raise the temperature near or above the binder melting temperature. In some embodiments, the heating unit 162 operations can be substantially similar to those described for the heating unit 154. Thus, the heating unit 162 can be used to rapidly heat the powder coating layer 152 after the calendering stage to activate the binder in the powder particle mixture. In some embodiments, the post-calendering rapid heating can be performed in a similar manner as pre-calendering rapid heating, but with different purposes. The pre-calendering rapid heating can be intended to allow faster processing of the coated layer in the calendering nip, whereas the post-calendering rapid heating can be intended to improve mechanical properties of the calendered electrode. In some embodiments, both of the precalendering and post-calendering rapid heating can be incorporated separately or together in the electrode manufacturing lines to achieve the intended goals. After rapid heating with the unit 162, the system 100 allows for lower temperature annealing, which ensures improved chain mobility and lower degree of entanglement in the PVDF chain (although similar results can be performed with other binder materials). The annealing and cooling stage can be performed at the enclosure 168. A controlled annealing temperature and time at the enclosure 168 can aid in the improved flexibility of the final electrode.

[0064] The post- annealing step does not limit the processing speed of the dry electrode manufacturing, as it is incorporated at the winding station or the spool 132 downstream of the previous processing steps performed by the system 100. The electrode can therefore be post-treated at the enclosure 168 completely offline (see, e.g., FIG. 3). Thus, owing to significant intermolecular interaction (re-organization), the post-annealed electrode shows improved adhesion and mechanical performance.20MEl\58064498.vlAttorney Docket No. 137174.00102

[0065] In some embodiments, the heating source 156, 158, 164, 166 can be in the form of, e.g., a hot plate, an IR heating panel, combinations thereof, or the like. During experimentation, the hot plate was used to heat the deposited loose powder layer before calendering above the binder melting temperature by conduction mode and rapid cooling was achieved by ambient air cooling. Through the rapid heating (e.g., less than 1 second) cycle, a fast compression speed at the calendering assembly 126 was achieved without any layer separation and no defect was realized. In some embodiments, the rapid heating by the unit 154 can be achieved by using infrared (IR) radiative heating that can heat the loose powder layer temperature to the binder melting temperature in a milliseconds timescale, allowing successful compression steps at about a, e.g., 15 m / min web line speed.

[0066] In some embodiments, a hot plate was used at unit 162 to raise the temperature for about 1 second of a final calendered electrode above the binder melting temperature to ensure complete erasing of the thermal memory performed prior to unit 162. A second hot plate was used to anneal the immediately heated electrode (from the first hot plate) at a holding temperature of about, e.g., 140° C (higher than the crystallization temp of 128° C) for about 5 minutes. A 180-degree Peel Test revealed that the post-processed electrode achieved 3x to 5x higher peel strength as compared to the low / room temperature calendered electrode.

[0067] In some embodiments, the rapid heating of the final calendered electrode on a fast-moving web (e.g., greater than about 5 m / min) was achieved by using IR radiative heating at unit 162 that raised the densified coating temperature above the binder melt temperature in a milliseconds timescale. The step was followed by an annealing enclosure 168 at a desired holding temperature for a fixed amount of time to facilitate the crystallization of the binder for improved mechanical strength. The rapid heating stage prior to calendering, in addition to the post-calendering rapid heating and subsequent annealing stages, therefore resulted in reduced defects and increased mechanical strength of the resulting electrode.

[0068] In some embodiments, the system 100 can include a feedback loop formed by sensors 170, 172 and a processor or controller 174 in communication with the sensors 170, 172, the heating units 154, 162, and the enclosure 168. The sensors 170 172 can be positioned over the web 102 and are configured to detect one or more characteristics of the powder coating on the web 102 surface, e.g., binder melting level, cooling level, coating temperature, duration of the elevated temperature, or the like. In some embodiments,21MEl\58064498.vlAttorney Docket No. 137174.00102 melting of the binder can be inferred based on the coating temperature and the duration of the elevated temperature. Based on the detected characteristics, signals from the sensors 170, 172 can be transmitted to the controller 174 which, in turn, regulates operation of the heating units 156, 162, the enclosure 168, and / or the cooling unit 160 (if any). For example, the sensor 170 can detect characteristics of the layer 140 after passage through rapid heating at the unit 154 and / or during the cooling phase at distance 159, and the sensor 170 can detect characteristics of the layer 152 after passage through rapid heating at the unit 162 and / or during annealing at enclosure 168. Based on the detected characteristics, the controller 174 can operate or adjust the respective heating and / or cooling stages to ensure optimal results are achieved.

[0069] While exemplary embodiments have been described herein, it is expressly noted that these embodiments should not be construed as limiting, but rather that additions and modifications to what is expressly described herein also are included within the scope of the invention. Moreover, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations are not made express herein, without departing from the spirit and scope of the invention.22MEl\58064498.vl

Claims

Attorney Docket No. 137174.00102CLAIMS:

1. A system for powder coating, comprising: a powder deposition unit configured to deposit powder particles onto a web; a calendering assembly configured to apply compression or compaction to the powder particles deposited onto the web; and a rapid heating unit disposed upstream of the calendering assembly; wherein the rapid heating unit is configured to heat the powder particles prior to calendering at the calendering assembly; and wherein subsequent to heating of the powder particles, the powder particles are at least partially cooled prior to calendering at the calendering assembly.

2. The system of claim 1, wherein the web is a moving web traveling at a speed of greater than 5 m / min through the calendering assembly.

3. The system of claim 1, wherein the powder particles include an anode, a cathode, and a binder material.

4. The system of claim 3, wherein the binder is a thermal plastic polymer material.

5. The system of claim 3, wherein the rapid heating unit is configured to heat the powder particles to a threshold temperature at or near a melting temperature of the binder material to activate the binder material.

6. The system of claim 5, wherein the rapid heating unit is configured to heat the powder particles to a threshold temperature during a first period of time, maintain the powder particles at the threshold temperature for a second period of time, and at least partially cool the powder particles from the threshold temperature for a third period of time.

7. The system of claim 6, wherein the second period of time is equal to or less than one second.

8. The system of claim 5, wherein activating the binder material increases coating cohesive and adhesive strengths between the powder particles and the web.

9. The system of claim 1, wherein the rapid heating unit is configured to apply heating to the powder particles for one second or less.23MEl\58064498.vlAttorney Docket No. 137174.0010210. The system of claim 1, wherein the rapid heating unit includes at least one of a hot plate or an infrared source.

11. The system of claim 1, wherein the rapid heating unit includes at least one of a first heat source disposed over the web, a second heat source disposed below the web, or both.

12. The system of claim 11, wherein the first heat source is configured to apply heat to the powder particles through at least one of (i) radiative means or (ii) conductive means through the web.

13. The system of claim 1, comprising a cooling stage disposed between and separating the rapid heating unit and the calendering assembly, wherein in the cooling stage, the powder particles are at least partially cooled prior to calendering at the calendering assembly.

14. The system of claim 1, comprising a post-calendering rapid heating unit disposed downstream of the calendering assembly.

15. The system of claim 14, wherein the post-calendering rapid heating unit is configured to heat calendered powder particles to a threshold temperature at or near a melting temperature of the binder material.

16. The system of claim 1, comprising an annealing enclosure downstream of the calendering assembly.

17. The system of claim 16, wherein the annealing enclosure is configured to maintain heating of the web after calendering at a controlled temperature.

18. The system of claim 1, comprising a sensor disposed downstream of the rapid heating unit and configured to detect a characteristic of the powder particles prior to calendering, and comprising a controller in communication with the sensor and configured to adjust operation of the rapid heating unit based on the detected characteristic of the powder particles after rapid heating.24MEl\58064498.vlAttorney Docket No. 137174.0010219. A system for powder coating, comprising: a powder deposition unit configured to deposit powder particles onto a moving web; a calendering assembly configured to apply compression or compaction to the powder particles deposited onto the moving web; a first rapid heating unit disposed upstream of the calendering assembly; and a second heating unit disposed downstream of the calendering assembly; wherein the first and second heating units are configured to heat the powder particles prior to and post calendering, respectively; and wherein subsequent to heating of the powder particles at the first rapid heating unit, the powder particles are at least partially cooled prior to calendering at the calendering assembly.

20. A method of powder coating, comprising: depositing powder particles onto a web with a powder deposition unit; applying heat to the powder particles with a rapid heating unit disposed upstream of a calendering assembly; at least partially cooling the powder particles prior to entry of the powder particles into the calendering assembly; and passing the heated web through the calendering assembly.

21. A system for powder coating, comprising: a powder deposition unit configured to deposit powder particles onto a web; a calendering assembly configured to apply compression or compaction to the powder particles deposited on the web; and a rapid heating unit disposed downstream of the calendering assembly; wherein the rapid heating unit is configured to heat the powder particles after calendering at the calendering assembly.

22. The system of claim 21, wherein the web is a moving web traveling at a speed of greater than 5 m / min through the calendering assembly.

23. The system of claim 21, wherein the powder particles include an anode, a cathode, and a binder material.

24. The system of claim 23, wherein the binder is a thermal plastic polymer material.25MEl\58064498.vlAttorney Docket No. 137174.0010225. The system of claim 23, wherein the rapid heating unit is configured to heat the powder particles to a threshold temperature at or near a melting temperature of the binder material to activate the binder material.

26. The system of claim 25, wherein the rapid heating unit is configured to heat the powder particles to a threshold temperature during a first period of time, maintain the powder particles at the threshold temperature for a second period of time, and at least partially cool the powder particles from the threshold temperature for a third period of time.

27. The system of claim 26, wherein the second period of time is equal to or less than one second.

28. The system of claim 25, wherein activating the binder material increases coating cohesive and adhesive strengths between the powder particles and the web.

29. The system of claim 21, wherein the rapid heating unit is configured to apply heating to the powder particles for one second or less.

30. The system of claim 21, wherein the rapid heating unit includes at least one of a hot plate or an infrared source.

31. The system of claim 21, wherein the rapid heating unit includes at least one of a first heat source disposed over the web, a second heat source disposed below the web, or both.

32. The system of claim 31, wherein the first heat source is configured to apply heat to the powder particles through at least one of (i) radiative means or (ii) conductive means through the web.

33. The system of claim 21, comprising a cooling stage disposed at or downstream of the rapid heating unit, wherein in the cooling stage, the powder particles are at least partially cooled after heating by the rapid heating unit.

34. The system of claim 21, comprising an upstream rapid heating unit disposed upstream of the calendering assembly.

35. The system of claim 34, wherein the upstream rapid heating unit is configured to26MEl\58064498.vlAttorney Docket No. 137174.00102 heat the powder particles prior to calendering at the calendering assembly and, subsequent to heating of the powder particles, the powder particles are at least partially cooled prior to calendering at the calendering assembly.

36. The system of claim 21, comprising an annealing enclosure downstream of the calendering assembly and the rapid heating unit.

37. The system of claim 36, wherein the annealing enclosure is configured to maintain heating of the web after calendering and after the rapid heating unit at a controlled temperature.

38. The system of claim 21, comprising a sensor disposed downstream of the rapid heating unit and configured to detect a characteristic of the powder particles after heating by the rapid heating unit, and comprising a controller in communication with the sensor and configured to adjust operation of the rapid heating unit based on the detected characteristic of the powder particles after heating by the rapid heating unit.

39. A method of powder coating, comprising: depositing powder particles onto a web with a powder deposition unit; passing the web and the powder particles through a calendering assembly; and applying heat to the powder particles with a rapid heating unit disposed downstream of the calendering assembly.

40. The method of claim 39, comprising at least partially cooling the powder particles after heating of the powder particles at the rapid heating unit.27MEl\58064498.vl

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