Drum for electrode fabrication system

Abstract

A drum for a dry powder coating system is provided. The drum includes a body defining an outer surface and configured to rotate about a central longitudinal axis. The drum includes electrodes patterned and disposed on the outer surface of the body, and at least one voltage source connected to the electrodes and configured to provide a controlled voltage to the electrodes. The at least one voltage source is configured to provide the controlled voltage in the form of a first voltage to attract a powder material to the electrodes. The at least one voltage source is configured to provide the controlled voltage in the form of a second voltage to release the powder material from the electrodes and onto a surface.

Description

DRUM FOR ELECTRODE FABRICATION SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No. 63 / 662,484, filed on June 21, 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 spray 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 thedrying step from the manufacturing process, the overall process is simplified and becomes more economic, resulting in a viable alternative for large-scale manufacturing. In particular, the solvent-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 reduce the manufacturing cost of batteries.

[0004] In a conventional dry powder ESD coating system, a web (e.g., a grounded electrically conductive substrate) passes through a coating volume or region while the dry powder mixture is dispensed from a hopper. Some conventional systems include a distributer that includes pins or brushes which capture the powder mixture as the distributer passes under the hopper. As the distributer rotates away from the hopper and towards the web, the powder particles are removed mechanically via agitation, relative motion, or the like, resulting in powder falling off the pins or brushes. However, such distributers are unable to deposit a substantially equal and / or well dispersed amount of powder particles during each rotation and therefore cannot consistently deposit a uniform amount of powder particles onto the web. The dispensing from pins or brushes also results in an imprecise deposition of powder on the web surface. In some instances, the powder deposited may be clumpy, agglomerated, or otherwise of non-uniform volume (or packing) fraction.

[0005] In the manufacturing of unitary battery objects from powdered battery materials (which may include an active component, conductive component, binder component, and any other additive) it is desired to control the deposition of the various powdered battery materials to achieve a desired loading (mass per area), thickness, and pattern of the powdered battery materials on a substrate such as a metal foil (typically aluminum or copper). None of the industry techniques fully enable the manufacturing of battery electrodes with comparable quality and speed to state-of-the-art slurry-based manufacturing techniques. Enabling state-of-the-art performance generally requires high throughput with web speeds in excess of 100 m / min, controllable heights of deposited materials of between 10 and 500 um, and as-deposited porosities of between 20 and 50% (volume basis), among other characteristics. These requirements are not trivial to achieve.SUMMARY

[0006] In accordance with embodiments of the present disclosure, an exemplary drum for a dry powder coating system is provided, as well as a system and method of use of the drum. The drum includes a body defining an outer surface and configured to rotate abouta central longitudinal axis, and electrodes patterned and disposed on the outer surface of the body. The drum includes at least one voltage source connected to the electrodes and configured to provide a controlled voltage to the electrodes. The at least one voltage source is configured to provide the controlled voltage in the form of a first voltage to attract a powder material to the electrodes. The at least one voltage source is configured to provide the controlled voltage in the form of a second voltage to release the powder material from the electrodes and onto a surface.

[0007] The body can define a substantially cylindrical configuration. In some embodiments, the electrodes can include a first set of electrodes and a second set of electrodes. In such embodiments, the at least one voltage source can be configured to selectively provide the controlled voltage of a first potential to the first set of electrodes and a second potential to the second set of electrodes, and the first and second potentials are different. In some embodiments, the electrodes can be patterned in an interdigitated form such that electrodes alternate along the outer surface of the body with insulative material in-between respective electrodes. In the interdigitated form, the respective electrodes can extend axially from one end to an opposing end of the body in a direction parallel to the central longitudinal axis of the drum. In some embodiments, the drum can include a cover insulative material disposed over the electrodes and the insulative material. In the interdigitated form, the respective electrodes can extend linearly from one end to an opposing end of the body in a direction parallel to the central longitudinal axis.

[0008] In some embodiments, the electrodes can be patterned in an island form with multiple individual electrodes disposed in a spaced manner relative to each other on the outer surface of the body along a direction parallel to the central longitudinal axis. In some embodiments, each of the multiple individual electrodes can define a circular configuration. In some embodiments, each of the multiple individual electrodes can define a honeycomb configuration. In some embodiments, each of the multiple individual electrodes can define a square configuration, e.g., in a grid form separated by insulative material.

[0009] The first voltage can be an amount with a magnitude greater than zero. In some embodiments, the second voltage can be either an amount equal to zero to ground the electrodes or an amount different from the amount of the first voltage, to remove or reduce the electrostatic forces to release the powder material. In some embodiments, the second voltage can be different from the first voltage, but not necessarily zero (i.e., ground). The at least one voltage source can be configured to regulate the controlled voltageindependently for each of the electrodes. The powder material can include electrochemical active materials and binder materials.

[0010] In accordance with embodiments of the present disclosure, an exemplary dry powder coating fabrication system is provided. The system includes a powder feeding unit configured to receive a powder material, a weh including a coating surface, and a drum for depositing the powder material onto the coating surface. The drum includes a body defining an outer surface and configured to rotate about a central longitudinal axis, and electrodes patterned and disposed on the outer surface of the body. The drum includes at least one voltage source connected to the electrodes and configured to provide a controlled voltage to the electrodes. The at least one voltage source is configured to provide the controlled voltage in the form of a first voltage to attract the powder material to the electrodes. The at least one voltage source is configured to provide the controlled voltage in the form of a second voltage to release the powder material from the electrodes and onto the coating surface.

[0011] The drum is rotatably disposed relative to the powder feeding unit and the coating surface. The central longitudinal axis of the drum extends laterally across the coating surface. The at least one voltage source is configured to provide the controlled voltage in the form of the first voltage to attract the powder material to the electrodes when the outer surface of the body is rotated to face the powder feeding unit. The at least one voltage source is configured to provide the controlled voltage in the form of the second voltage to release the powder material from the electrodes and onto the coating surface when the outer surface of the body is rotated to face the powder feeding unit. The first voltage is an amount with a magnitude greater than zero, and the second voltage is either an amount equal to zero to ground the electrodes, or an amount different from the amount of the first voltage.

[0012] In accordance with embodiments of the present disclosure, an exemplary method of dry powder coating fabrication is provided. The method includes providing a powder material to a powder feeding unit disposed over a drum. The drum includes a body defining an outer surface, electrodes patterned and disposed on the outer surface of the body, and at least one voltage source connected to the electrodes. The method includes providing a controlled voltage to the electrodes with the at least one voltage source in the form of a first voltage to attract the powder material to the electrodes. The method includes providing the controlled voltage to the electrodes with the at least one voltage source in theform of a second voltage to release the powder material from the electrodes and onto a coating surface of a web.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] To assist those of skill in the art in making and using a drum for an electrode fabrication system, reference is made to the accompanying figures, wherein:

[0014] FIG. 1 is a diagrammatic view of an exemplary electrode fabrication system in accordance with embodiments of the present disclosure, including a drum.

[0015] FIG. 2 is a perspective view of a rotating drum used in an exemplary electrode fabrication system in accordance with embodiments of the present disclosure.

[0016] FIG. 3 is a diagrammatic cross-sectional view of a patterned electrode configuration on the surface of a drum of an exemplary electrode fabrication system in accordance with embodiments of the present disclosure.

[0017] FIGS. 4A, 4B, 4C and 4D are diagrammatic views of a patterned electrode configuration on the surface of a drum of an exemplary electrode fabrication system in accordance with embodiments of the present disclosure, including a linear pattern of electrodes (FIG. 4A), a circular island pattern of electrodes (FIG. 4B), a honeycomb island pattern of electrodes (FIG. 4C), and a square island pattern of electrodes (FIG. 4D).

[0018] FIG. 5 is a diagrammatic view of a voltage source connected to electrodes at one end of a drum of an exemplary electrode fabrication system in accordance with embodiments of the present disclosure.

[0019] FIG. 6 is a diagrammatic view of a voltage source connected to electrodes at an opposite end of a drum shown in FIG. 5

[0020] FIG. 7 is a diagrammatic view of a patterned electrode configuration used on a rotating drum of an exemplary electrode fabrication system in accordance with embodiments of the present disclosure.

[0021] FIG. 8 is a diagrammatic side view of a drum of an exemplary electrode fabrication system in accordance with embodiments of the present disclosure, the entire outer surface of the drum having a patten of electrodes.

[0022] FIG. 9 is a diagrammatic side view of a drum of an exemplary electrode fabrication system in accordance with embodiments of the present disclosure, the drum including segmented areas of patterned electrodes separated by intermediate segments.

[0023] FIG. 10 is a diagrammatic perspective view of the drum of FIG. 9.DETAILED DESCRIPTION

[0024] Electrostatic-based approaches are attractive for several reasons. Electrostatic forces can actuate fine particles (both conductive and insulative) in a directed manner based upon at least two of the charge of the fine particles, the direction of an electric field, the shape of an electric field (including curvature and / or non -uniformity), and / or the material properties of the powder particles, among others. Generally, electrostatic forces depend upon a property of the particles and a property of the field. By independently controlling each (the field and the particle), a strong degree of performance can be designed into and extracted from various electrostatics-based systems.

[0025] In some embodiments, a rotating drum of an electrode fabrication system is patterned with a blocking set of ordered electrodes. The blocking electrodes can block the flow of current to material (e.g., powder) on the surface of the electrodes. In some embodiments, a patterned electrode array can include a pair of electrodes covered with a material different than the electrodes, where the material can be an insulative material. In some embodiments, the ordered electrodes are arranged to provide a controlled voltage and an electrical ground in an alternating fashion. In some embodiments, the electrodes can be arranged to provide a controlled first voltage to a first set of electrodes, a second (different, non-zero) voltage to a second set of electrodes, with neither set of electrodes set to ground. In some embodiments, the electrodes may not be able to pass current to material which resides on the surface of the drum. For example, the electrodes can be covered by a material which opposes the passage of current, i.e., an insulative layer, from the electrodes to the powder. The thin insulative layer covering the electrodes can be, e.g., polytetrafluoroethylene (PTFE), KAPTON®, other polymer or ceramic film, TEFLON®, polyamide, polyimide, polyvinyl chloride, glass, or any other non-conductive material, to prevent passage of current and to prevent dielectric breakdown at high potentials. The insulative layer is configured to prevent the passage of current from the electrode to the outside surface of the drum (e.g., the powder).

[0026] In some embodiments, the electrodes can be patterned by including a first set or collection of electrodes appearing separate or spaced on the drum surface, but in electrical communication with each other, and a second set or collection of electrodes appearing separate or spaced on the drum surface, but in electrical communication with each other. In some embodiments, the patterning of electrodes can be an interdigitated electrode array, with a first potential applied to the first set of electrodes and a second (different) potentialapplied to the second set of electrodes. In some embodiments, the first or second potential can be ground potential. In some embodiments, the applied potential can vary depending upon the angular position of the electrodes on the drum, including a change in angular position of the electrodes as the drum is rotated relative to a reference position (or angle). Although two sets of electrodes are discussed, it should be understood that the drum can include two or more sets of electrodes and the voltage source can selectively apply substantially equal or different potentials to the multiple sets of electrodes. Thus, multiple electrical potentials can be applied to the sets of electrodes without shorting.

[0027] Various considerations can be made when designing or configuring the pattern of electrodes on the drum. Such considerations can include, e.g., width of the electrodes, spacing between electrodes, ability to control the electrical potential on individual electrodes (such that adjacent electrodes can exhibit different voltages), ability to provide voltage signals to individual electrodes based upon the angular position of the electrodes as the drum is rotated (for example, all electrodes in a lower angular sector may be held at a first potential, while other electrodes are held at a second / diff erent potential).|0028 | In some embodiments, the electrode width can be larger than the particle size (typically the diameter, such as an average diameter), such that the electrode width may be a minimum of about 2 to 10 times the diameter of the electrodes. In some embodiments, the width of the electrodes may be comparable to the diameter of the powder particles (such as an average particle diameter). In some embodiments, the spacing of the electrodes may be chosen similar to the spacing of the electrode width. For example, the spacing between electrodes, which are 1 mm in width, may be between about 0.5 and 1.5 mm. In some embodiments, the width between the electrodes can be less than the width of the electrodes. In some embodiments, the spacing between the electrodes may be large as compared to the width of the electrodes. For example, electrodes of 1 mm width may be spaced at a distance of 2 mm. In some embodiments, the electrodes may be thin and widely spaced. For example, the electrodes may exhibit a width of between about 100 um and 1 mm, and spaced a distance of between 1 mm and 5 mm. However, it should be understood that the dimensional examples provided herein are non-limiting examples. In some embodiments, voltages can be selected based upon a combination of the desired electrostatic force, geometry of a fringe electric field (generated in part by the geometry and spacing of the electrodes), and the dielectric properties of any material which forms at least a portion of the blocking electrode (such as an insulation, for example). In some embodiments, it may be desired that the blocking electrodes remain blocking electrodes during operation of thedrum system, and this requires that dielectric breakdown and passage of current is prevented (or avoided) during charging and discharging of the electrodes.

[0029] The patterned drum is rotated to contact a supply of powder for coating in one radial position of the drum. The powder is attached to the drum via electrostatic forces created by the electrodes, and the drum is rotated to bring the coated regions away from the powder supply and towards the web surface. Once the coated region of the drum rotates to bring the powder opposite an object to be coated (e.g., a moving web), the electric field is modulated (e.g., grounded) to release the powder from the drum surface and deposit the powder on the object to be coated. The field encouraging the attachment may be an oscillatory field (high voltage and over a range of frequencies), and the electrode voltage encouraging detachment may be a zero field or a DC field at high potential.

[0030] In some embodiments, the drum can be segmented into various radial sections. The radial sections can be fixed in space, such that as the drum is rotated, different regions located on the drum will enter and exit the radial sections. A first drum segment can be a powder pickup segment, a second drum segment can be a powder transport segment, and a third drum segment can be a powder ejection or transfer segment. Any adjacent pair of segments can be separated by an additional segment (e.g., an intermediate segment) to account for the transition between segments.

[0031] For example, FIG. 8 shows a side view of a drum 700 rotating in a direction 702. The drum 700 includes an outer surface 704 having a pattern of electrodes 706 that uniformly cover the outer surface 704. In particular, rather than a segmented structure, the drum 700 includes a continuous pattern of electrodes 706 that extends radially around the entire (or substantially entire) outer surface 704 of the drum 700. In contrast, FIGS. 9 and 10 show side and perspective views of a drum 800 rotating along direction 802 about its longitudinal axis 804. The outer surface 806 of the drum 800 includes patterned electrodes 814 which may in some embodiments be isolated, and in some embodiments may only be connected by commutating segments (elements 808, 810, 812). The elements 808, 810, 812 remain fixed while the drum 800 rotates. The patterned electrodes 814 may be configured to conduct electricity along their length (in the axial direction of the drum 800). According to some embodiments, the patterned electrodes 814 may not exhibit a connection along the circumference of the drum 800, such that if a first electrode in the pattern of electrodes 814 is supplied a voltage VI, an adjacent electrode to the first electrode (such as a second electrode) may be set to a second voltage V2, and no current may pass between the first and second electrodes 814 even as they are held at potentials VI and V2,respectively, where VI and V2 may be different voltages. Although illustrated as having three elements 808, 810, 812, it should be understood any number of two or more elements could be used. The elements 808, 810, 812 are separated by intermediate sections 816, 818, 820. In some embodiments, the sections 816, 818, 820 can electrically separate or insulate the elements 808, 810, 812 from each other. The sections 816, 818, 820 can be dimensioned equally or can be of different radial and angular dimensions. The electrodes 814 of the segments 808, 810, 812 can be selectively regulated to have substantially equal voltages, or can have different voltages. The surface of the drum 800 can thereby be customized for the desired usage of the drum 800.

[0032] In some embodiments, electrodes 814 extending axially along a surface of a drum 800 may be segmented (including additional segmentation) such that a portion or first segment of the electrodes 814 may be electrically controlled (e.g., with a set voltage, for example) from a first axial location of a drum 800, and a second segment of the electrodes 814 may be controlled from a second axial location of a drum 800. For example, a first location may be one end of a drum 800 and a second location may be an end of the drum 800 opposite the first location. As a further example, the first and second locations may be adjacent, with electrical connections between and among the electrodes 814 and control locations (such as commutators, for example) separated with electrically insulative materials.

[0033] In some embodiments, the drum can be commutated to permit application of voltage on the drum at different positions on the drum as the drum is rotated (see, e.g., FIGS. 5 and 6). Since there may be more than one electrode on the drum (as in the case when the electrodes are interdigitated), a first set of electrodes can contact a voltage source on a first end of the drum, while a second set of electrodes can contact a voltage source on a second end of the drum. The electrodes on the first and second ends of the drum can be further segmented (e.g., on the circumference, for example) to permit the application of different voltages to the interdigitated electrodes as the drum is rotated.

[0034] FIG. 1 is a diagrammatic view of a battery electrode fabrication system 100. The system 100 includes a rolling element, e.g., a drum 110, below a hopper 120 that feeds powder 108 to the top or upward facing radial surface of the drum 1 10. The hopper 120 can be referred to as a powder feeding unit. In some embodiments, the drum 110 and hopper 120 may be oriented at a different angle or orientation relative to each other, and the powder 108 is fed to the radial surface of the drum 110 facing or located adjacent to the dispensing opening of the hopper 120. The powder 108 can include, e.g., an anode material,a cathode material, a binder material, combinations thereof, or the like.

[0035] The dry battery electrode materials can include one or more various powdered materials, non-limiting examples of which are provided herein. In some embodiments, the powdered materials can include binders (such as PVDF), conductive components (such as carbon black), and at least one active material (such as NCM622, NCM811, among other active materials). These powdered materials are often fine - that is, the materials may range from nanometer to micrometer in size (typically diameter). For example, binder materials (such as PVDF) and conductive materials (such as carbon black) may be as small as 100 nm, and active materials (such as NCM622) may range in size (e.g., the mean of a volume- weighted distribution) of between 2 and 10 um, inclusive. The fine size of these various materials promotes surface forces (such as capillarity, van der Waals, electrostatic, or the like) over other forces (e.g., gravitational, shear forces owing to imposed motion, or the like), resulting in cohesive behavior of assemblages of the particles. In some embodiments, the various powder particles may exhibit a variety of properties, including electrical properties, such as electrical conductivity (or resistivity).

[0036] In some embodiments, the powder 108 particles can be a composite including active materials and binder materials. In some embodiments, electric conductive materials can be added into the composite powder particle mixture. In some embodiments, the weight ratio of active material (relative to the remainder of other components / materials) in the powder particles can be about, e.g., 1-100% inclusive, 70-90% inclusive, 80-90% inclusive, 90-100% inclusive, or the like. In some embodiments, the weight ratio of active materials can be at least, e.g., 70%, 80%, 90%, or the like, with the remainder including other components / materials. In some embodiments, the other components / materials can be powder materials other than active powder materials in the mixture. In some embodiments, the other components / materials can include, e.g., binder materials (such as polymer binder materials, for example), conductive materials (such as conductive carbonbased or carbon-containing materials, for example), combinations thereof, or the like. In some embodiments, the weight ratio of active material (relative to the remainder of other components / materials) in the powder particles can be, e.g., more than 70%, or the like.

[0037] In some embodiments, the powder 108 particles can include composite particles, where a first set of particles is attached, adhered, bound, or otherwise stuck onto a second set of particles. In such embodiments, each of the first set of particles is dimensioned smaller than each of the second set of particles. In some embodiments, thesmaller particle size can be less than about 1 um, and the bigger particle size can be larger than about 1 um. In some embodiments, the first and second sets of particles can be characterized by an average particle size using, e.g., a volume-based average, or the like. In some embodiments, the first and second sets of particles can exhibit average particle sizes different by between a factor of, e.g., 10 and 100 inclusive, 50 and 200 inclusive, 100 and 500 inclusive, 200 and 2,000 inclusive, greater than a factor of 2,000, or the like. By way of a non-limiting example, an average diameter of the smaller of the two sets of particles can be about 1 nanometer and the larger of the two sets of particles can be about 5 micrometers, for a factor of 5,000. In some embodiments, the bigger particles can be active materials, e.g., cathode materials for a battery, anode materials for a battery, combinations thereof, or the like. In some embodiments, the smaller particles can be, e.g., polymer binder materials, a mixture of binder and conductive materials, combinations thereof, or the like. In some embodiments, the weight ratio of active material (relative to binder, conductive materials and / or other non-active materials) in the powder can be about, e.g., 1-100% inclusive, or the like. In some embodiments, the weight ratio of active material (relative to binder, conductive materials and / or other non-active materials) in the powder can be, e.g., more than 70%, or the like. In some embodiments, the weight ratio of active material (relative to binder, conductive materials and / or other non-active materials) in the powder can be about, e.g., 50-100% inclusive, 60-100% inclusive, 70-100% inclusive, 80-100% inclusive, 90-100% inclusive, 95-100% inclusive, 96-97% inclusive, or the like. In some embodiments, higher percentages (by weight) of the active materials can be used, since the volumetric and gravimetric energy density of the battery (among other performance metrics) are improved when greater amounts of active material are included.

[0038] In some embodiments, the active materials in a rechargeable battery or a lithium ion battery can include cathode materials (such as, e.g., lithium metal oxide), cathode materials (such as, e.g., NCM (Lithium Nickel Cobalt Manganese Oxide), LMO (Lithium Manganese Oxide), NCA (Lithium Nickel Cobalt Aluminum Oxide), LCO (Lithium Cobalt Oxide), lithium polyanion type cathode materials (such as, e.g., LFP (Lithium Iron Phosphate), LiMnxFei.xPO4, Li2FeSiO4), and / or anode materials (e.g., based on carbonaceous anode materials, graphite, Si, Si-based composites, SiOx, lithium alloyable materials, or lithium transition metal oxide anode materials). In a sodium-ion battery, the active materials can include cathode materials (including, e.g., sodium transition metaloxide, such as Naz / aFei / zMni / zCh, sodium polyanion materials, such as NaiMnSiCh, Prussian Blue Analogues), cathode materials (such as, e.g., Na2MnFe(CN)6), and / or anode materials (including, e.g., carbonaceous anode, sodium alloyable materials, sodium transition metal oxide, or Prussian Blue Analogues anode materials). In some embodiments, the active materials in the powder particle mixture can include, e.g., solid electrolyte materials, including Li dnCk, and LLZO materials, or the like.

[0039] In some embodiments, the binder materials can include polymeric materials (such as, e.g., PVDF (polyvinylidene fluoride), PTFE (Polytetrafluoroethylene), PEO (Polyethylene oxide), or PMMA (Poly(methyl methacrylate)), SBR (Polystyrene butadiene rubber binder), CMC (Carboxy methyl cellulose binder), or PAA (Polyacrylic acid), or polyolefins, which are electrical insulators), or the like. In some embodiments, the binder materials can be polymer electrolytes (such as, e.g., PEO / lithium triflate polymer electrolyte, or the like). In some embodiments, the binder can be solid state electrolyte composites (including, e.g., inorganic solid electrolytes and polymeric binders, polymer electrolyte binders or organic binders, such as Li dnCk, / PMMA composite, LLZO / polymer electrolyte composite, or the like).

[0040] In some embodiments, the conductive materials can include, e.g., carbon black (CB), carbon nanotubes, graphene, conductive polymer materials, or inorganic conductive materials, which are electrically conductive. In some embodiments, functional additives can be included in the composite electrode. In such embodiments, the functional additives can be, e.g., silica, alumina, zirconium oxide, combinations thereof, or the like.

[0041] Both dielectric (materials opposing the passage of current) and conductive (materials opposing the formation of an electric field and admitting the passage of current) powder particles may interact with electromagnetic fields in ways to cause attraction and / or adhesion of powder particles to electrodes applying an electromagnetic field. For example, the application of a voltage to a pair of electrodes configured in an interdigitated array which are also blocking (e.g., covered by a layer of dielectric material configured with the field to block the passage of current) may polarize matter including the powder particles displacing charge on an atomic level within the particles to generate net attractive forces between the electrode applying the voltage and the particles sensing the applied voltage via charge displacement. Such attraction is known in the art for both conductive and dielectric materials.

[0042] The drum 110 rotates along its central longitudinal axis 102 (e.g., cylindrical axis) in a radial direction 124. Electrodes 112 are disposed on the outer surface 104 of the drum 110. The electrodes 112 are disposed around the circumference of the drum 110 in a spaced manner (e.g., a substantially equal radial distribution pattern). In particular, the electrodes 112 are spaced from each other such that the sections 106 of the outer surface of the drum 110 are exposed between the electrodes 112. In some embodiments, the sections 106 can include an insulative or dielectric material. In some embodiments, the insulative or dielectric material can be coated onto the exposed areas of the surface 104 between the electrodes 112. This spacing prevents shorting of the electrodes 112 when a voltage is applied to them. Each of the electrodes 112 is connected to a voltage source 119 such that voltage can be selectively applied and removed from the respective electrodes 112.

[0043] Below the drum 110 is a foil web 116 that is actuated by, e.g., rollers, to move continuously under the drum 110. As the drum 110 spins about its axis 102, groups of electrodes 1 12 are sequentially disposed adjacent to the hopper 120 such that powder 108 is available for deposition onto the drum 110 surface (or, according to some embodiments, uptake onto the drum 110 surface). Including at least when the electrodes 112 are disposed adjacent to the dispensing opening of the hopper 120, the voltage source applies a voltage to those specific electrodes 112 to attract powder 108 from the hopper 120 onto the electrodes 112 by electrostatic forces. The voltage is maintained to these electrodes 112 as the drum 110 rotates along a direction 124 and until a predetermined angular zone, sector, or distance 114 of the drum 110 is disposed above or near the surface of the web 116. In some embodiments, the angular sector 114 can be, e.g., between 45 and 90 degrees inclusive, up to 120 degrees, between 15 and 45 degrees inclusive, or between 2 and 15 degrees inclusive. In some embodiments, the voltage applied to the electrodes 112 carrying the powder 108 can be gradually increased as the drum 110 rotates towards the web 116 to increase the attraction to the electrodes 112, thereby ensuring that the powder 108 remains attached to the drum 110 until release of the powder 108 is desired (e.g., avoiding or reducing detachment of powder 108 due to gravity, or the like).

[0044] The fingers of the interdigitated electrode 112 array may range in size from 1 to 5 mm inclusive, or from 5 to 10 mm inclusive, or from 0.1 to 1 mm inclusive, for the width of the electrodes 112. In certain embodiments, the spacing between the electrodes 112 may be identical to the electrode 112 size. In some embodiments, the spacing between the electrodes 112 may range between 1 / 1 Oth or 10 times the electrode 112 size. The distancecan be measured along the circumference along the roller’s surface. The spacing is the distance between electrodes 112 along the circumference. The height of the electrodes 112 (distance perpendicular to the surface of the drum radius) may take a variety of values, since only a conductive path along the electrodes 112 is required. The height of the electrodes may be in a range of about 1 um to 1 mm, or about 1 mm to 10 mm, or any other thickness from which an electrode material may be fabricated to permit the passage of current along the electrode.

[0045] Decreasing the spacing between the electrodes 1 12 increases the pickup surface area of powder 108 particles (relative to the total area of the electrode 112 array), whereas increasing the spacing between the electrodes 112 decreases the pickup surface area of powder 108 particles, according to some embodiments. In some embodiments, the level of voltage applied to the electrodes 112 can be varied depending on the size of the spacing between the electrodes 112. Once the electrodes 112 are rotated to be within the angular sector 114, the voltage is perturbed, modified, grounded, or otherwise changed to remove, reduce, perturb or affect the electrostatic forces from the electrodes 112 sufficient to at least decrease the adhesive forces between the electrodes 112 and powder 108 relative to detachment forces (such as gravity, for example) or otherwise impose an ejection force from the electrode 112 toward the web 116, thereby allowing the powder 108 to drop from the electrodes 112 and be deposited onto the surface of the web 116.

[0046] In some embodiments, the system 100 can include means 117 for assisting with removal of at least some of the powder 108 from the drum 110 for dispersing powder 108 on the web 116. In some embodiments, it may be desirable to utilize mechanical means 117 of particle removal from the drum 110 coupled with electrostatic capture and conveyance of particles onto the drum 110. For example, and according to certain embodiments, particles may be captured by the drum 110 from the hopper 120 using the electrostatic techniques described herein, and the drum 110 is rotated to engage recently captured powder 108 on the drum 110 surface with a brushing element (such as a spinning cylindrical brush with axis parallel to the drum 110), a vibrating brush with vibrational excitation in a direction parallel to the axis 102 of the drum 110, or other relative motion of a brushing element sufficient to dislodge powder 108 particles from the surface of the drum 110. In some embodiments, mechanical methods of particle removal may be performed on angular sectors of the drum 110 where the voltage of the electrodes 112 has been set to ground or other potential different than voltage conditions causing the initial attachment of powder 108 particles to the electrodes 112 patterned on the drum 110.

[0047] In some embodiments, an airflow may be used as the means 117 to assist with powder 108 particle removal from the drum 110. An airflow can be established by blowing a stream of gas toward the drum 110 surface. The blowing stream of gas can be targeted toward regions of the drum 110, which are regions of close approach relative to a web 116 or current collector. In some embodiments, a suction may be applied instead of (or in addition to) a blowing stream of gas. The suction can direct a flow of gas toward a low pressure source located near the points of closest approach between the drum 110 and the web 1 16. In some embodiments, the suction can be applied downstream of the drum 110 (e.g., a distance away from the drum 110 along the direction of travel of the web 116). In some embodiments, the suction can be applied upstream of the drum 110 (e.g., a distance away from the drum 110 opposite the direction of travel of the web 116).

[0048] The electrodes 112 can have a voltage between the adjacent electrodes 112 which creates the electrostatic forces to capture powder 108 particles at the top radial or angular distance of the drum 1 10 (e.g., under the dispensing opening of the hopper 120) and the voltage is reduced when the electrodes 112 reach the bottom of their travel adjacent to the web 116 (e.g., the radial distance 114) thus releasing the powder 108 towards and onto the web 116. The electrodes 112 have an applied voltage that changes with the radial position of the outer surface of the drum 110. The electrodes 112 can be patterned on the outer surface of the drum 110 in a variety of configurations. In some embodiments, the electrodes 112 can be, e.g., interdigitated, patterned as islands (with circular, hexagon, square, or any other shape), combinations thereof, or the like. Although not illustrated, it should be understood that the system 100 can include, e.g., a charging assembly for charging the powder particles, calendering rollers to densify and compress the powder particles onto the surface of the web without heat, and other components of an ESD system (such as the system discussed in PCT Patent Application No. PCT / US24 / 60663, filed on December 18, 2024, which is incorporated herein by reference in its entirety).

[0049] FIG. 2 shows a rotating drum 200 used in a battery electrode fabrication system 100. The drum 200 generally defines cylindrical configuration with a planar outer surface on which electrodes can be positioned for attraction of powder particles to the drum 200. The drum 200 includes two substantially flat opposing ends 202, 204, and defines an axial direction 220 extending parallel to a central longitudinal axis 210. The drum 200 is actuated to rotate in a direction 124 about its axis 210. As discussed herein, the outer surface of the drum 200 can include a variety of pattern of electrodes which can be selectively actuatedto form electrostatic forces, thereby attracting powder particles to the electrodes. As the drum 200 rotates over the web within a predetermined radial distance, the voltage applied to the electrodes can be changed (e.g., grounded or otherwise varied) to allow the powder particles to drop onto the web surface. By using such electrodes on the surface of the drum 200, a uniform amount of powder particles can be captured at each rotation of the drum 200, resulting in uniform deposition of the powder particles on the web.

[0050] FIG. 3 shows the arrangement of electrodes 212 on the surface of the drum 216. In particular, FIG. 3 is a diagrammatic cross-sectional view of the drum 216 if the drum 216 outer surface was rolled out into a flat configuration for purposes of discussion only. However, it should be understood that the diagrammatic view of FIG. 3 is representative of the cylindrical, curved outer surface of the drum 216 with the pattern of electrodes 212. Electrodes 212 are distributed along the surface of the drum 212 in a spaced manner with sections of insulative material 214 disposed in-between to avoid shortage of the electrodes 212. The electrodes 212 and insulative material 214 therefore alternate. Although illustrated as having an equal width, it should be understood that the width of the electrodes 212 as compared to the insulative material 214 can be different to achieve the desired powder attachment surface area for each electrode 212. Further, although illustrated as flat (e.g., parallel top surface to the drum 216), in some embodiments, the electrodes 212 can include peaked or pointed configurations (e.g., similar to FIG. 1).

[0051] In some embodiments, all electrodes 212 can be connected to a single voltage source such that voltage can be selectively applied, reduced and / or removed from the electrodes 212 to attract the powder particles to the electrodes 212. In some embodiments, one group of alternating electrodes 212 can be connected to a first voltage source 218, and another group of alternating electrodes 212 can be connected to a second voltage source 230. The electrodes 212 connected to the voltage source 218 can be a first set of electrodes, and the electrodes 212 connected to the voltage source 230 can be a second set of electrodes not interconnected with the first set of electrodes 212. The first and second set of electrodes 212 can therefore be actuated independently, and within the sets of electrodes 212, the electrodes 212 can be independently actuated by the respective voltage source 218, 230. In some embodiments, the voltage potential applied by the first and second voltage sources 218, 230, can be the same or different.

[0052] In some embodiments, the arrangement of electrodes 212 can include an insulative material 232 (e.g., a cover insulative material) disposed above and fully coveringeach of the electrodes 212, as well as the insulative material 214. For example, above the electrodes 212 and co-planar insulative material 214, a further insulative material 232 or layer can be provided to block the passage of current from the electrodes 212 to any conductive material residing above the electrodes 212, and to any powder particles on the electrodes 212. The insulative material 232 can be any insulative material sufficient to withstand and prevent dielectric breakdown and current conduction under the operating conditions specified herein, including, e.g., polymeric materials (fluorinated polymers, poly(tetrafluoroethylene), TEFLON®, polyimide, polyamide, KAPTOP®), inorganic materials (glass, ceramics, metallic oxides, nitrides, carbides), or the like.

[0053] FIGS. 4A, 4B, 4C and 4D are diagrammatic views of different patterns of electrodes 212 on the surface of the drum 200. In particular, FIG. 4A shows an alternating, interdigitated pattern of electrodes 212, FIG. 4B shows a circular island pattern of electrodes 212, FIG. 4C shows a honeycomb or hexagonal pattern of electrodes 212, and FIG. 4D shows a square grid island pattern of electrodes 212. The voltage connections illustrated in FIG. 3 can be used for any of the electrode 212 patterns of FIGS. 4A-D. In some embodiments, using an island arrangement for the electrodes 212 (as compared to a linear arrangement) can allow for imparting of different arrangements of powder when the powder is transferred to the moving web. As noted above, the electrodes 212 can be connected to respective voltage sources and can thereby be part of different sets or groups of electrodes 212 independently actuated relative to each other.

[0054] In some embodiments, the island arrangement of electrodes 212 can be used to generate more random and, once dislodged, finely dispersed patterns of deposited powders, the distribution of which can randomize during transit from the electrostatic drum 200 to the web onto which the powders deposit. Rotational speed of the rotating drum may be adjusted to deliver powder with higher or lower density. Embodiments are not limited to specific voltages for specific drum electrodes 212. Each of the sets of electrodes 212 represented in these embodiments can be individually excited by different voltages that may change as a function of drum position.

[0055] With respect to FIG. 4A, the electrodes 212 extend linearly in a direction parallel to the axial direction 220. In such embodiments, the electrodes 212 can extend from and between the opposing ends 202, 204 of the drum 200 (see FIG. 2). In some embodiments, the electrodes 212 can each extend circumferentially around the drum 200. In some embodiments, the electrodes 212 can be segmented along the linear orcircumferential direction. The pattern of electrodes 212 includes an alternating insulative material 214 in-between the respective adjacent electrodes 212. The width of each insulative material 214 can be dimensioned less than the width of the electrodes 212 to increase the overall surface area of the electrodes 212 covering the drum 200 surface. The alternating pattern of interdigitated electrodes 212 therefore covers the entire outer surface of the drum 200.

[0056] With respect to FIG. 4B, an island pattern of electrodes 212 is used on the surface of the drum 200. Each electrode 212 is substantially circular and is surrounded by insulative material 214 to separate the respective adjacent electrodes 212 from each other. In some embodiments, each row of circular electrodes 212 (e.g., rows along direction 220) can be substantially aligned with each other such that electrodes 212 are positioned in respective columns. In some embodiments, the rows of electrodes 212 can be offset from each other in an alternating manner such that every other row of electrodes 212 is aligned in respective columns.

[0057] With respect to FIG. 4C, an island pattern of electrodes 212 is used on the surface of the drum 200. Each electrode 212 is substantially hexagonal or honeycomb in shape, and is surrounded by insulative material 214 to separate the respective adjacent electrodes 212 from each other. The electrodes 212 are substantially aligned with each other in columns that extend perpendicularly to the axial direction 220. The shape of the electrodes 212 allows electrodes 212 to be positioned closer to each other and in a tighter group, while still avoiding shorting with the insulative material 214, thereby covering more surface area of the drum 200 (as compared to the circular electrodes of FIG 4B).

[0058] With respect to FIG. 4D, an island pattern of electrodes 212 is used on the surface of the drum 200. Each electrode 212 is substantially square in shape, and is surrounded by insulative material 214 to separate the respective adjacent electrodes 212 from each other. In some embodiments, rectangular shaped electrodes could be used in a similar arrangement. Similar to the hexagonal electrodes 212 of FIG. 4C, the square electrodes 212 can be positioned closer to each other while still being separated by the insulative material 214, allowing for greater surface area coverage of the drum 200. The electrodes 212 of FIG. 4D are aligned in both columns and rows.

[0059] Each of the electrodes 212 in FIGS. 4A-4D can be connected to a respective voltage source, as illustrated in FIG. 3. This allows each electrode 212 (or groups ofelectrodes 212) to be selectively actuated to attract powder particles with electrostatic forces when in a predetermined radial position relative to the web (e.g., adjacent to the dispensing opening of the hopper). The electrodes 212 are actuated to maintain the electrostatic forces as the drum 200 rotates, thereby maintaining the electrostatically confined particles on the surface of the drum 200. When the drum 200 rotates to a predetermined radial position or window adjacent to, facing the web or approaching the web, the voltage source can be removed or reduced to drop the powder particles from the electrodes 212 onto the web. In some embodiments, such voltage change or drop can be performed by contact of the edge of the drum 200 with a grounding material 121 (see, e.g., FIG. 1). For example, as the drum 200 rotates against the grounding material 121 in the predetermined radial position, the electrodes 212 are grounded and release the powder particles from the drum 200 surface.

[0060] In some embodiments, the electrodes 212 can be selectively sent a potential from the voltage source along a single row or column of electrodes 212. For example, in some embodiments, the potential can be sent to electrodes 212 in a row along the axial direction 220 of FIG. 4D. In some embodiments, the potential can be sent to electrodes 212 in a column perpendicular to the axial direction 220. In some embodiments, the electrodes 212 can extend up to the ends 202, 204. In some embodiments, the electrodes 212 can extend a distance offset from the ends 202, 204 of the drum 200. Thus, the surface of the drum 200 covered by the electrodes 212 along the direction 220 can be less than the distance between ends 202, 204. The shortened configuration of the electrodes 212 can be used in instances where the web is shorter than the drum 200, for example, and / or when the commutation of the electrodes 212 is performed at or near the edges of the drum 200.

[0061] With reference to FIGS. 4C and 4D, in some embodiments, one set of electrodes 212 can be held at one potential, and another set of electrodes 212 can be held at another potential. For example, the electrodes 212 along line 422 can be set to a potential VI by a first voltage source, and the electrodes 212 along the line 424 can be set to a potential V2 by a second voltage source, with the alternating potentials in a direction perpendicular to the axial direction 220. In some embodiments, a similar alternating potential pattern can be applied to electrodes 212 in groups extending parallel to the axial direction 220. In some embodiments, the potential can be applied diagonally relative to the axial direction 220 in an alternating manner. For example, the electrodes 212 along diagonal line 428 can be set to a potential VI by a first voltage source, and the electrodes 212 along diagonal line 426can be set to potential V2 by a second voltage source. These lines 422, 424, 426, 428 are patterns that show the patterns of excitation of the electrodes 212. The pattern of electrodes 212 as well as patterns of excitation may be repeated all over the surface of the rolling element or the drum 200. These patterns may be selectively repeated for all of the islanded electrodes 212. Electrode 212 may be selectively set to ground or set to a different potential. The system therefore provides for customization and adjustment of the potential applied to the electrodes 212 depending on the operational parameters needed for the system.

[0062] In some embodiments, the voltages applied to the electrodes 212 may be modulated. In some embodiments, the voltage may be one magnitude at the top of its travel while capturing powder particles and may be a different voltage (such as ground or reduced) when the electrode reaches the bottom of its travel to release powder to be deposited onto the foil web. In some embodiments, the voltage can be increased during rotation of the drum to maintain the powder attracted to the electrodes 212 and avoid detachment due to, e.g., gravity, or the like. Such commutation can therefore be used to modulate the potential on the rotating roller. In some embodiments, contact pads can be extended on opposite sides of the drum 200 to contact with the brushes or pads (or a shoe) to apply specific potentials based upon the angular position of the drum 200 as it rotates relative to the hopper and the web. This would allow for particles to be attracted to the electrodes 212, and for particles to be selectively released from the electrodes 212 to be deposited onto the web. In some embodiments, voltage source excitations may produce traveling waves through the electrodes 212 timed for self-commutation.

[0063] FIG. 5 is a diagrammatic view of voltage sources 510, 512 connected to electrodes on one end 202 of the rotating drum 200 such that the above-referenced commutation can take place. FIG. 6 is a diagrammatic view of voltage sources 610, 612 connected to electrodes on the opposite end 204 of the drum 200 of FIG. 5. As illustrated in FIGS. 5 and 6, when the angular position of the drum 200 is facing away from the web, a first potential can be applied by voltage sources 510, 612. When the angular position of the drum 200 faces the web and release of powder particles is needed, a second potential can be applied by voltage sources 512, 610.

[0064] FIG. 7 is a diagrammatic view of electrodes used on the rotating drum 200. The drum 200 can include different sets of electrodes that stretch across the axial direction 220 of the drum 200 from opposing ends 202, 204. For example, electrodes 710, 712, 714, 716, 718 can extend from one end towards an opposing end, leaving a gap in-between, andelectrodes 720, 722, 724, 726, 728 can extend from the opposite end in-between the electrodes 710, 712, 714, 716, 718 (with grounded material in-between). These electrodes 710-728 can thereby be interdigitated with each other. In some embodiments, the electrodes 710-728 can be set to different voltages and can be commutated selectively.

[0065] 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.

Claims

CLAIMS:

1. A drum for a dry powder coating system, the drum comprising: a body defining an outer surface and configured to rotate about a central longitudinal axis; electrodes patterned and disposed on the outer surface of the body; and at least one voltage source connected to the electrodes and configured to provide a controlled voltage to the electrodes; wherein the at least one voltage source is configured to provide the controlled voltage in the form of a first voltage to attract a powder material to the electrodes; and wherein the at least one voltage source is configured to provide the controlled voltage in the form of a second voltage to release the powder material from the electrodes and onto a surface.

2. The drum of claim 1 , wherein the electrodes include a first set of electrodes and a second set of electrodes, wherein the at least one voltage source is configured to selectively provide the controlled voltage of a first potential to the first set of electrodes and a second potential to the second set of electrodes, and wherein the first and second potentials are different.

3. The drum of claim 1, wherein the electrodes are patterned in an interdigitated form such that electrodes alternate along the outer surface of the body with insulative material in-between respective electrodes.

4. The drum of claim 1 , comprising a cover insulative material disposed over the electrodes and the insulative material.

5. The drum of claim 3, wherein in the interdigitated form, the respective electrodes extend linearly from one end to an opposing end of the body in a direction parallel to the central longitudinal axis of the drum.

6. The drum of claim 1 , wherein the electrodes are patterned in an island form with multiple individual electrodes disposed in a spaced manner relative to each other on the outer surface of the body along a direction parallel to the central longitudinal axis.

7. The drum of claim 6, wherein each of the multiple individual electrodes defines a circular configuration.

8. The drum of claim 6, wherein each of the multiple individual electrodes defines a honeycomb configuration.

9. The drum of claim 6, wherein each of the multiple individual electrodes defines a square configuration.

10. The drum of claim 1, wherein the first voltage is an amount with a magnitude greater than zero.

11. The drum of claim 1 , wherein the second voltage is either an amount equal to zero to ground the electrodes or an amount different from the amount of the first voltage.

12. The drum of claim 1, wherein the at least one voltage source is configured to regulate the controlled voltage independently for each of the electrodes.

13. The drum of claim 1, wherein the powder material includes electrochemical active materials and binder materials.

14. A dry powder coating fabrication system, comprising: a powder feeding unit configured to receive a powder material; a web including a coating surface; and a drum for depositing the powder material onto the coating surface, the drum including: a body defining an outer surface and configured to rotate about a central longitudinal axis; electrodes patterned and disposed on the outer surface of the body; and at least one voltage source connected to the electrodes and configured to provide a controlled voltage to the electrodes; wherein the at least one voltage source is configured to provide the controlled voltage in the form of a first voltage to attract the powder material to the electrodes; andwherein the at least one voltage source is configured to provide the controlled voltage in the form of a second voltage to release the powder material from the electrodes and onto the coating surface.

15. The dry powder coating fabrication system of claim 14, wherein the drum is rotatably disposed relative to the powder feeding unit and the coating surface.

16. The dry powder coating fabrication system of claim 14, wherein the central longitudinal axis of the drum extends laterally across the coating surface.

17. The dry powder coating fabrication system of claim 14, wherein the at least one voltage source is configured to provide the controlled voltage in the form of the first voltage to attract the powder material to the electrodes when the outer surface of the body is rotated to face the powder feeding unit.

18. The dry powder coating fabrication system of claim 14, wherein the at least one voltage source is configured to provide the controlled voltage in the form of the second voltage to release the powder material from the electrodes and onto the coating surface when the outer surface of the body is rotated to face the powder feeding unit.

19. The dry powder coating fabrication system of claim 14, wherein the first voltage is an amount with a magnitude greater than zero, and the second voltage is either an amount equal to zero to ground the electrodes or an amount different from the amount of the first voltage.

20. A method of dry powder coating fabrication, comprising: providing a powder material to a powder feeding unit disposed over a drum, the drum including (i) a body defining an outer surface, (ii) electrodes patterned and disposed on the outer surface of the body, and (iii) at least one voltage source connected to the electrodes; providing a controlled voltage to the electrodes with the at least one voltage source in the form of a first voltage to attract the powder material to the electrodes; andproviding the controlled voltage to the electrodes with the at least one voltage source in the form of a second voltage to release the powder material from the electrodes and onto a coating surface of a web.

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