Electrode manufacturing method and electrode manufacturing system

Abstract

A method for forming an electrode layer with uniform thickness and particle distribution is provided. A method for manufacturing a battery electrode includes mixing particles of an active electrode material, a conductive additive, and a binder to form a dry powder electrode material. The dry powder is then deposited onto a moving electrode current collector using a dry powder distribution device. The dry powder is a loose powder that is continuously injected from the distribution device onto a moving current collector, where the powder remains loose on the collector as it moves toward the compaction stage. After being injected onto the collector, the loose dry powder is uniformly spread across the width of the moving current collector web by one or more spreading devices, such as a smoothing roller and a conditioning roller. Finally, the dry powder is compressed using a calender configured to apply pressure and / or heat to the dry powder electrode material to activate the binder and form the battery electrode.

Description

[Technical Field]

[0001] The present invention relates to an electrode manufacturing process, and in particular to a dry powder electrode manufacturing process. [Background technology]

[0002] Batteries typically contain two electrode layers, an anode and a cathode, connected to conductive current collectors made of copper or aluminum. These layers contain either a cathode or anode active material mixed with one or more conductive materials and a binder to form a structure that easily charges and discharges during battery operation. The selection of active materials, binders, and conductive materials can vary depending on the desired chemistry, application, and manufacturing method.

[0003] A common approach to battery manufacturing employs a wet-coating process to form the electrode layer. In this process, electrode active material, conductive material, and binder are mixed in a solvent to form a slurry, which is then coated onto a conductive current collector. The coating layer is then dried to evaporate the solvent and densify the electrode structure. The most commonly used solvent is N-ethyl-2-pyrrolidone (NMP), which is toxic and must be recovered after evaporation and purified by distillation for further reuse. Both drying and solvent recovery require a large manufacturing footprint and energy consumption, resulting in high manufacturing costs.

[0004] Solvent-free approaches to forming electrode layers from dried active material powders have been proposed. These include the use of electrostatic deposition, which sprays the active material, conductive material, and binder onto a conductive current collector. The active material particles, conductive material, and binder particles are aerated or aerosolized by a pressurized gas stream. The gas stream passes the fluidized particles through an electrostatic applicator, where they are charged by an electric field and then deposited onto a grounded conductive current collector. Electrostatic forces adhere the charged particles to the grounded current collector, making the active material, conductive material, and binder easier to handle before compaction. However, electrostatic deposition tends to produce uneven layers due to electrostatic forces acting more on some particles than others, resulting in particle settling (e.g., uneven particle distribution along an axis perpendicular to the current collector surface). Gas streams, achieved using forced air, also tend to produce uneven surface thickness and unnatural settling of particles on the substrate, often characterized by waves or stripes across the surface of the layer. These non-uniformities cause uneven current distribution during battery charging and discharging across the layers, negatively impacting cycle life as current overwhelms areas of lower resistance. Also, because forced air is used to atomize the powder, this deposition technique raises containment and safety concerns.

[0005] Therefore, a solvent-free process for forming electrode layers with uniform thickness and particle distribution is desirable. Summary of the Invention

[0006] A method for manufacturing a battery electrode is disclosed. The method includes mixing dry particles of one or more electrode active materials, a conductive additive, and one or more binder materials to form a binder-coated dry powder electrode material. The binder-coated dry powder electrode material can be for a cathode or an anode. The dry powder electrode material is then deposited onto an electrode current collector substrate using a dry powder dispenser. In various examples, the dry powder electrode material is a loose powder that can be poured from the dispenser onto a moving current collector web in a roll-to-roll system. The dry powder electrode material remains loose on the current collector web after deposition as it moves toward a consolidation stage.

[0007] After being poured onto the current collector, the loose dry powder electrode material is spread evenly across the width of the moving current collector web by one or more spreaders. The one or more spreaders can include a doctor blade, one or more counter-rotating smoothing rollers, and one or more forward-rotating alignment rollers. Furthermore, in at least one embodiment, the one or more spreaders work in concert with the selected material on the moving current collector web to create and maintain a smooth, uniform loose powder layer that is sufficiently cohesive until compaction. Thus, the dry powder electrode material is compacted against the moving current collector web using a calender configured to apply at least one of pressure or heat to the dry powder electrode material to activate the binder and form a battery electrode.

[0008] The drawings illustrate, by way of example only, one or more embodiments in accordance with the present teachings. In the drawings, like reference numerals indicate the same or similar elements. Additionally, it should be understood that the drawings are not necessarily to scale. [Brief explanation of the drawings]

[0009] [Figure 1] 1 illustrates an example of a lithium metal cell for a battery, according to one or more embodiments. [Figure 2A] 1 shows an example of flowable dry powder electrode material particles according to one or more embodiments. [Figure 2B] 1 illustrates example morphologies of dry powder electrode material particles, according to various embodiments. [Figure 2C] 1 illustrates example morphologies of dry powder electrode material particles, according to various embodiments. [Figure 2D] 1 illustrates example morphologies of dry powder electrode material particles, according to various embodiments. [Figure 2E] 1 illustrates example morphologies of dry powder electrode material particles, according to various embodiments. [Figure 3A] 1 illustrates an example of a dry powder electrode manufacturing platform, according to one or more embodiments. [Figure 3B] 1 shows an example of a primer layer deposited on a surface of a current collector web, according to one or more embodiments. [Figure 3C] 1 illustrates an exemplary roughened surface of a dust collection web according to one or more embodiments. [Figure 3D] 1 illustrates an exemplary conditioning station according to one or more embodiments. [Figure 4A] 1 illustrates an exemplary double-sided dry powder electrode manufacturing platform according to one or more embodiments. [Figure 4B] 1 illustrates an exemplary double-sided electrode, according to various embodiments. [Figure 5] 1 illustrates an exemplary double-sided dry powder electrode manufacturing platform according to one or more embodiments. [Figure 6] 1 is a flowchart of a solventless method for manufacturing a battery electrode, according to various embodiments. [Figure 7A] 1 illustrates an exemplary post-consolidation morphology of a dry powder electrode according to a liquid phase embodiment. [Figure 7B] 10 illustrates another exemplary post-consolidation form of a dry powder electrode according to a liquid phase embodiment. [Figure 8] 1 illustrates an exemplary dry powder electrode manufacturing platform, according to one or more embodiments. [Figure 9A] 1 illustrates an exemplary curing process for patterned binder curing, according to various embodiments. [Figure 9B]1 illustrates an exemplary curing process for patterned binder curing, according to various embodiments. [Figure 10A] 1 illustrates an exemplary curing process for patterned binder curing, according to various embodiments. [Figure 10B] 10 illustrates another exemplary cheating process for patterned binder curing, according to various embodiments. [Figure 11A] 1 illustrates an exemplary monopolar battery configuration, according to one or more embodiments. [Figure 11B] 1 illustrates an exemplary bipolar battery configuration, according to one or more embodiments. [Figure 12] 1 shows a flowchart for a method of manufacturing a battery cell, according to various embodiments. [Figure 13] 1 illustrates an example process for forming a battery using a build platform battery configuration, according to one or more embodiments. [Figure 14] 10 illustrates another exemplary process for forming a battery using a build platform battery configuration, according to one or more embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the following detailed description, numerous specific details are set forth by way of example to provide a thorough understanding of the disclosed subject matter. However, upon reading this disclosure, it may become apparent to those skilled in the art that one or more of the disclosed aspects may be practiced without such details. Furthermore, the description of various embodiments according to the present disclosure may include reference to one or more known techniques or operations, and such references may be at a relatively high level to avoid obscuring various concepts, aspects, and features with details that are not specific to the present disclosure and are not necessary for a complete understanding of the present disclosure.

[0011] A method for manufacturing a battery electrode is disclosed. The method includes mixing dry particles of one or more electrode active materials, a conductive additive, and one or more binder materials to form a binder-coated dry powder electrode material. The binder-coated dry powder electrode material may be for a cathode or an anode. The dry powder electrode material is then deposited onto an electrode current collector substrate using a dry powder dispenser. In various examples, the dry powder electrode material is a loose powder that can be injected at a velocity or mass rate from the dispenser onto a moving current collector web in a roll-to-roll system. The dry powder electrode material remains loose on the current collector web after deposition as it moves toward the consolidation stage. As used herein, the term "loose" means that the dry powder electrode material is not maintained on the current collector web using a specific force, such as a vacuum or electrostatic force used in electrostatic deposition as described above.

[0012] After being poured onto the current collector, the loose dry powder electrode material is spread evenly across the width of the moving current collector web by one or more spreaders, which can include a doctor blade, one or more counter-rotating smoothing rollers, and one or more forward-rotating conditioning rollers.

[0013] Handling loose dry powder on a moving web before compression is challenging. Therefore, in various examples, the constituent materials of loose dry powder electrode materials are selected to achieve a balance between flowability and cohesiveness. The flowability of loose dry powder electrode materials is adjusted so that they can be easily poured from a dispensing device, but not so flowable that they scatter when struck by a moving web or are easily disturbed by the web's movement and associated vibrations. Furthermore, the electrode layer must be smooth and uniform in thickness after compression; materials that are too flowable will not compress sufficiently during calendering. Attempts to compress highly flowable materials with a calender often result in streaks in the direction of the moving web due to the flowable powder being pushed down against the current collector web by the calender or due to powder slippage. Conversely, if the loose dry powder electrode material is too cohesive, it will emerge from the powder dispenser in clumps and will not spread well or form a smooth, uniform layer during calendering or spreading (e.g., there will often be separation between individual clumps). Therefore, the constituent materials of the loose dry powder electrode material are selected to achieve a balance between flowability and cohesiveness.

[0014] However, flowability and cohesion are not the only constraints or challenges in designing loose, dry powder electrode materials. While a balance between flowability and cohesion is necessary to produce a uniform layer, these materials must also be able to deliver the target electrochemical properties for the desired battery performance. Therefore, powders designed to optimize the balance between flowability and cohesion in powder deposition do not necessarily deliver the type of electrochemical performance required for a suitable battery. For example, a relatively high concentration of binder in a loose, dry powder electrode material formed by mixing with high shear forces has been shown to provide an optimal balance of flowability and cohesion. The resulting morphology is a thick coating of binder around the flowable active electrode material particles. However, a relatively large amount of binder reduces the pore volume for sufficient electrolyte penetration, and a thick coating around the active electrode material inhibits ionic conduction. Furthermore, excess binder can close pores within the particle network or at least suboptimize the pore size distribution, a factor related to electrolyte uptake. Therefore, after several trials controlling each of these variables, the binder concentration and shear force of the mixer were reduced to form a powder coating layer that was sufficiently confined to the surface where the binder material adhered to the active material particles to allow sufficient electrolyte penetration. Ideally, the binder would be confined to the contact points of the active material particles. However, there is a large element of randomness in the location of the binder particles on the active material particles, and it was determined that a lower binder coverage around the active material particles would improve ionic conduction.

[0015] Additionally, in at least one example, one or more spreaders operate in concert with the selected material on the moving current collector web to form and maintain a smooth, uniform loose powder layer that is sufficiently cohesive until compaction. In one example, the spreaders aid in maintaining cohesion at web speeds >5 meters / min. Thus, the dry powder electrode material is compacted against the moving current collector web using a calender configured to apply at least one of pressure or heat to the dry powder electrode material to activate the binder and form the battery electrode.

[0016] [Battery Overview] FIG. 1 illustrates an example of a lithium metal cell 100 for batteries according to the present disclosure. As used herein, "battery" refers to any structure in which chemical energy is converted into electricity and used as a power source. The terms "cell" and "battery" are generally interchangeable when referring to a single electrochemical cell, although the term "cell" can also be used to refer to a plurality or stack of electrically interconnected cells. The lithium battery 100 of FIG. 1 includes a cathode current collector 102, a cathode 104, a separator 106, an anode 108, and an anode current collector 110.

[0017] In various embodiments, the anode current collector 110 comprises a plate, sheet, foil, fabric, or the like formed of a suitable conductive material. Examples of materials that can be used to form the anode current collector 110 include carbon black, activated carbon, graphite, graphene, carbon fiber, and carbon nanotubes, copper, nickel, silver, carbon-polymer composites, metal-polymer composites, or combinations thereof. The anode current collector 110 can have any suitable thickness. In various embodiments, the anode current collector 110 has a thickness ranging from 1 to 50 microns. In one embodiment, the anode current collector 110 has a thickness of 8 microns. The anode current collector can serve as a substrate and mechanical support for the anode electrode.

[0018] The anode 108 is comprised of an active anode material bonded to an anode current collector 110. In various embodiments, the active anode material includes lithium, lithium powder, molten lithium, semi-liquid lithium, lithium titanium oxide, silicon, silicon oxide, hard carbon, and graphite, or a combination thereof. The anode 108 can have any suitable thickness. In various embodiments, the thickness of the anode 108 ranges from 3 microns to 600 microns. In one embodiment, the anode 108 includes a lithium metal anode having a thickness of 20 microns. In another embodiment, the anode 108 includes a graphite anode having a thickness of 70 microns. The anode 108 has an inner surface that contacts the anode current collector 110 and an inner surface that contacts the separator 106 when the cell 100 is assembled.

[0019] In one embodiment, the dry powder anode material for the anode 108 is formed by mixing an anode active material (e.g., graphite) with a conductive additive (e.g., conductive carbon) in a first mixing process. In this example, the graphite selected for the anode is pearl graphite for sufficient flowability, e.g., 93% by weight, with a D50 particle size in the range of 5-20 μm. The conductive carbon, in this example, is 1.5% by weight, with a D50 particle size in the range of 1 nm to <1 μm. A second mixing process is then performed to mix the graphite / conductive carbon mixture with a binder, such as PVDF. Any suitable mixing process can be used for the first and second mixing processes. The dry powder anode material is then deposited onto a positive electrode collector to the desired thickness and coverage. A compaction process is then performed to densify the powder and fuse the binder, as described later in this specification.

[0020] The cathode 104 is composed of a cathode active material adhered to a cathode current collector 102. In various embodiments, the cathode current collector 102 may be in the form of a plate, sheet, foil, cloth, or the like formed of a suitable conductive material. Examples of materials that may be used to form the cathode current collector 102 include carbon black, activated carbon, graphite, graphene, carbon fiber, carbon nanotubes, aluminum, nickel, silver, carbon-polymer composites, metal-polymer composites, or combinations thereof. The cathode current collector 102 may have any suitable thickness. In various embodiments, the cathode current collector 102 has a thickness ranging from 1 to 30 microns. In one embodiment, the cathode current collector 102 has a thickness of 12 microns. The cathode current collector can be used as a substrate and mechanical support for the cathode electrode.

[0021] The cathode electrode 104 is formed from a suitable cathode active material. Examples of cathode active materials include lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCMA), lithium nickel manganese cobalt oxide (NMC) and all variants thereof, lithium nickel manganese oxide (LMNO), lithium vanadium oxide (LVO), lithium iron disulfide, silver vanadium oxide, carbon monofluoride, copper oxide, sulfur, or combinations thereof. The cathode electrode can have any suitable thickness. In various embodiments, the cathode 104 has a thickness of 3 to 600 microns, depending on the desired load.

[0022] In one embodiment, the dry powder cathode material for the cathode 104 is formed using a mixing process that partially coats carbon and a binder (such as PVDF) onto the cathode active material particles. In one embodiment, 0.5 to 5% binder is used in the mixing process. However, higher concentrations of 12% have been used. The resulting composite cathode powder has better dry powder flowability compared to pure cathode powders such as NMC itself. This allows for dry powder deposition onto current collectors with controllable thickness. For this implementation, compaction (e.g., press or calender) at temperatures between 100°C and 250°C and pressures of 10-30 MPa was applied to activate the binder.

[0023] A separator 106 is disposed between the anode 108 and the cathode 104 to provide electronic insulation and thus prevent short circuits between the anode and cathode. While providing electronic insulation, the separator 106 must be an ionic conductor, allowing the transport of ions such as lithium and sodium ions. The separator 106 can be formed of any suitable electrolyte material, including a liquid electrolyte, a polymer composite electrolyte, a solid electrolyte, or a combination thereof. The separator 106 can have a thickness ranging from 5 to 100 microns. In various embodiments, the separator can be formed separately as a free-standing layer and then disposed between the anode and cathode. Alternatively, the separator can be formed directly on the anode or cathode.

[0024] In one embodiment, the separator 106 is a freestanding polymer film or membrane with a suitable porous structure that allows for the infusion of a liquid electrolyte to provide lithium ion conduction through the membrane. The membrane can have a thickness ranging from 5-50 microns, a pore size ranging from 30-150 nm, and a porosity ranging from 30%-80%. Materials used for the membrane can include polypropylene, polyethylene, other polyolefins, nylon, cellulose, glass fiber, polyimide, PVDF, and the like. Any suitable liquid electrolyte can be utilized and infused into the porous network of the membrane. The liquid electrolyte can include one or more lithium salts dissolved in one or more organic solvents, including various carbonates, ethers, ionic liquids, and combinations. Examples of lithium salts include lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, and the like. Examples of organic solvents for dissolving lithium salts include dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, dimethoxyethane, dioxolane, trimethyl phosphate, triethyl phosphate, tetrafluoropropyl ether, ionic liquids, and the like.

[0025] In another embodiment, the separator 106 is a ceramic layer formed on top of the anode or cathode. The ceramic layer can have a thickness, pore size, and porosity similar to those described above for the polymer membrane, which allows for the infusion of a liquid electrolyte to provide lithium ion conduction through the layer. Materials used for the ceramic layer can include aluminum oxide, silicon dioxide, titanium dioxide, zinc oxide, etc. The ceramic layer can be formed on top of the anode or cathode by any suitable deposition method, such as powder bed printing, inkjet or jet material printing, screen printing, or electrophotographic printing. For example, the ceramic layer can be formed on top of the anode or cathode using a dry powder of ceramic material precoated with a binder, similar to a dry anode or cathode material coated with the binder. In another embodiment, the separator 106 is a polymer-ceramic composite layer formed on top of the anode or cathode. In addition to the polymer and ceramic material, the composite layer can include a lithium salt to enhance ionic conductivity.

[0026] In a further embodiment, the separator 106 is a solid electrolyte layer formed on top of the anode or cathode. In this case, a liquid electrolyte is not required because the solid electrolyte can provide sufficient ionic conductivity. The solid electrolyte layer can have a thickness ranging from 5 to 50 microns and a porosity of less than 5%. Materials used for the solid electrolyte layer can include solid polymers such as polyethylene oxide, lithium lanthanum zirconium oxide and its variants, lithium aluminum germanium phosphate, and lithium sulfide. The solid electrolyte layer can be formed on the anode or cathode by any suitable deposition method, such as powder bed printing, inkjet or jet material printing, screen printing, or electrophotographic printing. In one embodiment, the solid electrolyte layer is formed on the anode or cathode with a dry powder of solid electrolyte material precoated with a binder.

[0027] [Dry Powder Engineering] As described herein, the anode electrode layer and the cathode electrode layer are each formed using a binder-coated dry powder electrode material manufacturing process. Therefore, the binder-coated dry powder electrode material used to manufacture the dry powder electrode layer is manufactured by dry-mixing particles of one or more active electrode materials, conductive additives, and one or more binder materials. As mentioned above, handling loose dry powder on a moving web before compaction is not easy, and the constituent materials of the loose dry powder electrode material are selected to achieve a balance between flowability and cohesiveness. The flowability of the loose dry powder electrode material is designed to allow these materials to be easily poured from a dispensing device, but not so flowable that the powder scatters when it hits the moving web or is easily disturbed by the web movement and associated vibrations. Furthermore, the loose dry powder electrode material cannot be too cohesive, or it will be dispensed as clumps and will not spread well. Therefore, the constituent materials of the loose dry powder electrode material are selected to achieve a balance between flowability and cohesiveness.

[0028] However, flowability and cohesion are not the only constraints. While a reasonable balance between flowability and cohesion is necessary to produce a uniform layer, these materials must also be able to provide the electrochemical properties for battery performance. Thus, powders designed for an optimal balance between flowability and cohesion in a powder deposition process will not necessarily yield the type of electrochemical performance required for a suitable battery.

[0029] For example, a relatively high concentration of binder in a loose dry powder electrode material has been shown to provide a balance of flowability and cohesion when mixed using relatively high shear forces. The resulting morphology is a thick coating of binder around the ideally flowable active electrode material particles. FIG. 2A shows an exemplary flowable dry powder electrode material particle 200 according to one or more embodiments. In this example, the dry powder electrode material particle 200 includes active material particles 202 and a thick binder layer 204. In one example, the thick binder layer 204 was fabricated by dry mixing the active material, 4% binder, and a conductive additive. The thick binder layer 204 coats the entire surface of the active material particles 202, promoting flowability. However, the thick binder layer 204 prevents sufficient electrolyte access to the active material particles 200, thus inhibiting ionic conduction. Furthermore, the electrode layer produced by the dry powder electrode material particles 200 tends to be dense, with the binder filling most of the interparticle space ideally occupied by the electrolyte.

[0030] Therefore, after several tests to isolate these variables, the binder concentration and shear force in the dry mixer were reduced to produce active material particles with partial binder coverage or binder dispersion. These tests were performed using PVDF as the binder, resulting in a sufficiently limited surface area for the PVDF to adhere to the active material particles during binder activation, while still allowing sufficient electrolyte penetration throughout the electrode layer.

[0031] FIG. 2B illustrates an example morphology of a dry powder electrode material particle 220 according to various embodiments. In this embodiment, the dry powder electrode material particle 220 includes spherical active material particles 222, such as cathode active material NMC, having a partial binder coating 224. Similarly, FIG. 2D illustrates an example morphology of a dry powder electrode material particle 240 according to various embodiments. In this embodiment, the dry powder electrode material particle 240 includes amorphous active material particles 242, such as cathode active material LFP, having a partial binder coating 244.

[0032] In one embodiment, the partial binder coating 224 was fabricated by dry-mixing the active material, 2% PVDF, and conductive additive under relatively low shear. The low shear and low binder concentration applied to the active material particles resulted in a partial binder coating, but the shear was still great enough to deform the binder particles and cause them to coalesce, giving them the appearance of molten wax. In one embodiment, X-ray photoelectron spectroscopy (XPS) analysis revealed that the partial binder coating 224 covered approximately 60-70% of the surface of the active material particles 222. Thus, the dry powder electrode material particles 220 do not flow as well as the dry powder electrode material particles 200, yet possess excellent electrochemical properties. For example, the partial binder coating 224 sufficiently confines the PVDF to the surface of the active material particles after compression and binder activation, providing sufficient space (voids, cavities, etc.) between the active material particles within the electrode layer for electrolyte penetration.

[0033] FIG. 2C illustrates an example morphology of a dry powder electrode material particle 230 according to various embodiments. In this example, the dry powder electrode material particle 230 includes spherical active material particles 232, such as cathode active material NMC, having a porous binder coating 234. Similarly, FIG. 2E illustrates an example morphology of a dry powder electrode material particle 250 according to various embodiments. In this example, the dry powder electrode material particle 250 includes amorphous active material particles 252, such as cathode active material LFP, having a porous binder coating 254.

[0034] The porous binder coating 234 is a matrix of nano-PVDF particles 236 (200-500 nm in diameter). In one embodiment, the matrix can appear as a fluffy dusting of nano-PVDF particles 236, ranging from areas uncoated on the surface of the active material particles 232 to areas the thickness of several nano-PVDF particles 236. In one embodiment, the adjective "fluffy" is used to characterize the porous, rigid, sponge-like layer consisting of many nano-PVDF particles 236 attached to each other surrounding the active material particles 232. In one embodiment, the porous binder coating 234 was fabricated by dry-mixing the active material, 2% nano-PVDF, and conductive additive at even lower shear compared to Figure 2B. XPS analysis of these particles revealed that the binder surface coverage of the active material particles 232 was 70-90%, which is higher than that of the active material particles 220 described above in Figure 2B. Although this particular test was performed with nano-PVDF, the scope of the present disclosure should not be construed as being limited to PVDF, and other binder particles may also be used.

[0035] 2A-2B , the high shear forces exerted during particle mixing at least partially deform the binder, molding it onto the surfaces of the active material particles (202, 222). Conversely, the relatively low shear forces exerted during mixing of the dry powder electrode material particles 230 cause the nano-PVDF particles 236 to adhere to the surfaces of the active material particles 230 and to each other (forming a three-dimensional matrix of particles) without complete deformation. This adhesion without complete deformation results in the porous matrix layer of the porous binder coating 234 described above. The porous binder coating 234 thus exhibits increased friction, with a Hausner ratio of approximately 1.38-1.45. Therefore, the dry powder electrode material particles 230 do not flow as easily as the dry powder electrode material particles (202, 222), but still have excellent electrochemical properties.

[0036] As shown in Figure 2C, the porous binder coating 234 also sufficiently confines the PVDF to the surface adhesion of the active material particles after compression and binder activation, providing sufficient space (voids, cavities, etc.) between the active material particles in the electrode layer for electrolyte penetration, as will be described in more detail with reference to Figures 7A-7B. Furthermore, the resulting morphology, its porosity, and the extent of the binder layer, in one embodiment, results in increased ionic conductivity due to capillary forces that facilitate electrolyte penetration and access to the active material particles 232.

[0037] In one embodiment, a small amount of solvent can be added during the mixing process as a processing aid. The solvent is then removed at a later stage or immediately after the mixing process. This results in improved binding efficiency as a result of modifying the shape and structure of the binder. The solvent can be removed by gentle heating (80-160°C), which "locks in" the modified structure of the binder and produces a dry active material powder. This dry active material powder can then be deposited onto a current collector as described elsewhere herein.

[0038] The dry powder used to fabricate the dry powder electrode layer can be manufactured using any suitable thermoplastic binder composition other than PVDF binder. To achieve an optimal balance between dry powder flowability and cohesion for producing a uniform layer, a hybrid binder composition can be used. In one example, the hybrid binder composition can include a thermoplastic binder and a thermosetting binder. In another example, the hybrid binder composition can include a thermoplastic binder and a UV-curable binder. In another example, the hybrid binder composition can include a thermosetting binder and a UV-curable binder. In another example, the hybrid binder composition can include two or more UV-curable compositions, each cured by UV radiation of a different wavelength. In yet another example, the hybrid binder composition can include one or more B-staged binder compositions that are partially cured, i.e., in a B-stage state. In various embodiments, one or more components of the hybrid binder composition can be selectively cured or partially cured to adjust the flowability and cohesion of the dry powder during the dry powder mixing process described above or the dry powder electrode fabrication process described below.

[0039] [Dry powder electrode manufacturing system] 3A illustrates a dry powder electrode manufacturing platform 300 according to one or more embodiments. The platform 300 includes a moving current collector web 302, a first web roller 304, a powder deposition station 306, a smoothing station 314, a conditioning station 316, a first calender 318, a second calender 320, and a second web roller 324.

[0040] In various embodiments, platform 300 is a roll-to-roll manufacturing system, in this example, where a fabrication substrate or current collector web 302 is unwound by a first roller 304 and, after the electrode layer is completed, is unwound by a second web roller 324. The final product of platform 300 is a roll of electrode (i.e., either a cathode or an anode).

[0041] Thus, the first web roller 304 unwinds the current collector web 302, and a powder dispensing device 308 at the powder deposition station 306 deposits or pours the dry powder electrode material 310 onto the moving current collector web 302. As discussed above, the dry powder electrode material 310 is flowable enough to be poured from the powder dispensing device 308 and cohesive enough not to spill over the sides of the current collector web 302. However, it is a loose powder that remains loose on the moving current collector web 302 after deposition.

[0042] In one embodiment, the moving current collector web 302 is designed to accept a spreadable powder, promoting cohesion and facilitating spreading of the deposited dry powder electrode material 310. Figure 3B shows a primer layer 330 deposited on the surface of the current collector web 302, according to one or more embodiments. In addition to enhancing adhesion between the active material and the current collector, the roughness of the primer can be tailored and utilized to improve dry deposition of the electrode powder on the current collector. The primer layer 330 can include a polymer binder and an electronically conductive material, such as carbon black, graphite, carbon nanotubes, graphene, or a conductive polymer. The primer layer can have a thickness ranging from 1 to 30 microns and a surface roughness ranging from 0.2 to 0.5 microns (Ra) and 1 to 3 microns (Rz). In another example, Figure 3C shows a roughened surface 340 of the current collector web 302, according to one or more embodiments. The roughened surface 340 can be mechanically roughened using, for example, sandpaper or chemical etching. In each of these examples, the properties of the surface treatment are selected for their ability to increase friction between the deposited dry powder electrode material 310 and the moving current collector web 302. The roughened surface 340 can have a surface roughness of Ra in the range of 0.5 to 1 micron and Rz in the range of 2 to 5 microns.

[0043] The powder deposition station 306 further includes a gauge or spreader 312, such as a doctor blade or smoothing roller (i.e., a counterclockwise rotating roller), configured to perform the initial spreading of the dry powder electrode material 310 and set the height of the initial powder layer. After the initial spreading, the moving current collector web 302 transports the dry powder electrode material 310 to a smoothing station 314, which, in one embodiment, includes one or more smoothing rollers. Once poured onto the current collector web 302, the dry powder electrode material 310 is a loose pile of powder of relatively variable thickness that may or may not cover the width of the current collector web 302. Furthermore, this loose pile of powder may contain other surface imperfections, such as spots, valleys, and holes, after being poured and initially spread. It is important to remove these imperfections and non-uniformities. Layer imperfections and other non-uniformities, such as uneven thickness, in battery electrodes must be removed because they lead to reduced battery performance and cycle life. Thus, one or more smoothing rollers redistribute some of the powder to level the dry powder electrode material 310, fill in holes, or otherwise remove non-uniformities.

[0044] After the smoothing station 314, the moving current collector web 302 transports the dry powder electrode material 310 to a conditioning station 316, which in this example includes one or more smoothing rollers. As discussed above, the dry powder electrode material 310 is a free-flowing powder that is not suited to being moved, transported, or vibrated as it is conveyed down the moving web. Furthermore, it is important that the dry powder electrode material 310 layer be sufficiently dense and uniform for battery performance. Furthermore, the dry powder electrode material 310 layer must reach a dense and uniform final compaction stage. Therefore, in various embodiments, measures are taken to maintain the dry powder electrode material 310's handleability and reasonable cohesion before it is compressed into an electrode in a calendaring process.

[0045] The figure shows a conditioning station 316 according to one or more embodiments. In this example, the conditioning station 316 includes a first roller 352, a second roller 354, and a third roller 356. These rollers can be conditioning rollers, smoothing rollers, or a combination of both. The smoothing rollers are counter-rotating rollers that rotate backward (i.e., relative to the direction of the moving web, as indicated by the arrows in FIG. 3D) and generally smooth the powder layer by redistributing some of the powder and arranging the particles more efficiently. This backfills any irregularities or unevenness within the layer. The conditioning rollers are forward-rotating rollers that rotate in the direction of the moving web (i.e., forward) and effectively operate to compact or densify the dry powder electrode material 310 layer. In one embodiment, each conditioning roller imparts between 3-7% compression to the powder layer, although greater compression from these rollers is possible. Both the smoothing rollers and the conditioning rollers aid in eliminating void space between particles. Conditioning rollers achieve this primarily through weak or gentle compression, while smoothing rollers achieve it primarily by organizing the particles more efficiently relative to one another. This handleability can be achieved by any form of physical or chemical adhesion or interparticle bonding to the primer layer, including, but not limited to, thermal activation of the binder or heat, sintering of polymer particles, chemical reaction of the binder with air humidity, surface tension-induced bonding forces from exposure to liquids or vapors in the form of water, volatile solutions, or solvents, ultraviolet or microwave initiation of photosensitive radicals in the form of monomers or polymers, or Brownian sedimentation of small particles between the interstitial spaces of the powder particles.

[0046] As mentioned above, steps are taken to maintain easy handling and adequate cohesion of the dry powder electrode material 310. This includes ensuring that the powder bed is smooth and uniform in width across and along the length of the current collector web 302. In one embodiment, these steps include a combination of smoothing rollers and conditioning rollers. However, different powder characteristics combined with desired web speeds may require more or less smoothing rollers and / or conditioning rollers. In this example, the moving current collector web 302 transports the dry powder electrode material 310 to a first roller 352 for conditioning. In this example, the first roller 352 performs a first compression on the dry powder electrode material 310 layer, reducing its thickness from a first thickness 350 to a second thickness 354. Thus, the dry powder electrode material 310 is then transported to a second roller 356, another conditioning roller, which performs a second compression on the layer, reducing its thickness from the second thickness 354 to a third thickness 358.

[0047] Finally, in this example, the dry powder electrode material 310 layer is conveyed to a third smoothing roller 360, which further reduces the layer thickness from a third thickness 358 to a fourth thickness 362. While the example described with reference to FIG. 3D shows two conditioning rollers and one smoothing roller, the three rollers can be all conditioning rollers or any permutation of conditioning and smoothing rollers, depending on the powder characteristics and web speed requirements. Furthermore, the number of rollers is adjustable (i.e., more than or less than three rollers) depending on the powder characteristics and web speed requirements. Thus, the result of the conditioning station 316 is a smooth, uniform loose powder layer conditioned for final compaction and binder activation. Thus, the one or more conditioning rollers of the conditioning station 316 help densify the loose powder layer to help maintain its cohesiveness as the moving current collector web 302 is moved and vibrated prior to compaction. Although the powder bed remains loose on the moving current collector web 302 until final compression by one or more calenders, the void space between the particles of the dry powder electrode material 310 layer is reduced, thereby increasing the internal friction between the individual particles and forming a weaker, internally locked particle network that is better suited to compression.

[0048] Furthermore, depending on the characteristics of the dry powder electrode material 310, it can be difficult to obtain a smooth, uniform electrode layer when fully compressing a loose powder layer without a single calender and conditioning. In these instances, the resulting compressed layer often contains areas of greater and lesser compression, characteristic of a wave or crosshatch pattern. Therefore, in various embodiments, the loose powder layer benefits from conditioning and / or incremental compression, where each compression stage provides additional compression to the powder layer.

[0049] After conditioning, the layer of dry powder electrode material 310 is compressed by a first calender 318 and then a second calender 320 to produce an electrode layer 322, according to one or more embodiments. In one embodiment, the pressure applied to the layer of dry powder electrode material 310 by the first calender 318 and the second calender 320 is greater than the pressure applied by the conditioning station 316 and is configured to target an electrode layer porosity of 20-40%, which is comparable to or less than the porosity of conventional wet-cast electrodes. These porosities are achieved by a calender pressure of 10-30 MPa. Additionally, at least one of the first calender 318 and the second calender 320 is heated to activate the binder in the dry powder electrode material 310 and produce the electrode layer 322. In one embodiment, at least one of the first calender 318 and the second calender 320 is heated to a temperature between 150-210°C. In one embodiment, a first temperature is used for the upper or top calender roller (e.g., 150-210°C), and a second temperature is used for the lower or bottom calender (e.g., 90-160°C). Thus, in this embodiment, the electrode layer 322 on the moving current collector web 302 is then unwound into a roll by a second web roller 324. In some embodiments, after conditioning, the dry powder electrode material layer 310 is compressed by a single calender. In other embodiments, after conditioning, the dry powder electrode material layer 310 is compressed by three or more calenders.

[0050] The dry powder electrode manufacturing platform 300 may include additional features or process steps to improve the handleability and cohesion of the dry powder electrode material layer 310 and to address other issues, such as powder adhesion, splitting, or breakage of the dry powder electrode material to the calendering rollers, which can result in unacceptable defects and non-uniform part production of the dry powder electrode. To address these issues, in one embodiment, a lubricant or wetting agent may be applied to the dry powder electrode material layer 310 to enhance the cohesion of the dry powder electrode material layer prior to compaction by the calendering rollers. For example, a lubrication station may be included between the conditioning station 316 and the calender 318. In one embodiment, the lubrication station provides water-generated steam to improve the cohesion of the dry powder electrode material layer, prevent sticking and / or splitting of the dry powder electrode material, and help provide uniform compaction. Any suitable lubricant, including organic materials (e.g., organic solvents) and other materials added to the water, may be used to improve the cohesion and uniform compaction of the dry powder electrode material. The amount of lubricant applied to the dry powder electrode material may be less than 10% by weight, preferably less than 5% by weight. In some embodiments, a lubricant can be added to the dry powder electrode material during the dry powder manufacturing process. In certain examples, one or more B-stage binders are included in the dry powder electrode material, and the B-stage binders are partially cured and function as the lubricant. In other examples, the lubricant can function as an activator to activate binder curing.

[0051] Additionally, the dry powder electrode manufacturing platform 300 can use heat separate from the calenders to improve the handleability and cohesion of the dry powder electrode material layer 310 traveling over the current collector web 302. For example, heat can be applied directly to the current collector web, from below, to the dry powder electrode material layer 310, or some combination thereof. Additionally, the application of heat and binder activation can be completely separate from the calenders (i.e., one or more calenders apply pressure only), or the dry powder electrode manufacturing platform 300 can apply heat in addition to applying a heated calender.

[0052] In various embodiments, the dry powder electrode manufacturing platform 300 can include a curing station between the conditioning station 316 and the calender 318. When a hybrid binder including one or more of a thermoplastic binder, a thermosetting binder, and a UV-curable binder is used, one or more components of the hybrid binder can be selectively cured or partially cured by the curing station to improve the cohesion and handling of the dry powder electrode material layer 310 prior to compression by the calenders 318 and 320.

[0053] 4A shows a double-sided dry powder electrode manufacturing platform 400 according to one or more embodiments. The platform 400 includes a moving current collector web 402, an unwinding web roller 404, a first powder deposition station 406, a first smoothing station 414, a first conditioning station 416, a first compression roller 418, a turn roller 422 for flipping the web 402, a second powder deposition station 424, a second smoothing station 432, a second conditioning station 434, a second compression roller 436, a first calender 438, a second calender 440, and an unwinding web roller 446.

[0054] 3A-3D, platform 400 is a roll-to-roll manufacturing system. However, in this example, current collector web 402 is unwound by unwind roller 404, a first electrode layer is deposited on a first side of current collector web 402, current collector web 402 is rotated downward using turn roller 422 and then returned to horizontal, positioning the second side of current collector web 402 facing upward. A second electrode is then deposited on the second side, and after the second electrode layer is completed, current collector web 402 is unwound by unwind roller 446, producing a double-sided electrode as further described above with respect to FIG. 4B.

[0055] Thus, the unwind roller 404 unwinds the current collector web 402, and a powder dispensing device 408 at the powder deposition station 406 pours the first dry powder electrode material 410 onto the moving current collector web 402. As described above with respect to FIG. 3A , the first dry powder electrode material 410 is transported to a first smoothing station 414 and then to a first conditioning station 416 before undergoing a first densification by a first compression roller 418 to produce a partially compressed first layer 420. In this example, the first compression roller 418 may be a light pressure calender or one or more conditioning rollers to which heat is applied to partially activate the binder in the first dry powder electrode material 410 so that the partially compressed first layer 420 has sufficient cohesion to create a flip without separation. Thus, the partially compressed first layer 420 is not fully compressed at this stage because the partially compressed first layer 420 then undergoes a second, full compression when the second dry powder electrode material 428 is fully compressed. Thus, at this stage, the partially compressed first layer 420 is only partially compressed, with full compression being performed later when both the first dry powder electrode material 410 and the second dry powder electrode material 428 are simultaneously calendered.

[0056] The partially compressed first layer 420 turns downward around a first turn roller 422, as shown in FIG. 4A, and then turns back horizontally around a second turn roller 422, revealing the uncoated bottom side of the moving current collector web 402. As described above, the moving current collector web 402 eventually reaches a second powder dispenser 426 at a powder deposition station 424, where a second dry powder electrode material 428 is poured onto the inverted bottom side of the moving current collector web 402. The second dry powder electrode material 428 is then transported to a second smoothing station 432 and then to a second conditioning station 434 before undergoing densification by a second compression roller 436. In one embodiment, the second compression roller applies a similar treatment to the second dry powder electrode material 428 performed on the first dry powder electrode material 410 by the first compression roller 418 to balance the compression of the two layers before final compression.

[0057] In one embodiment, the moving current collector web 402 includes a primer layer on each side, and the first and second compression rollers 418, 436 apply heat in a manner that does not melt the primer on the opposite side. In one embodiment, the first and second compression rollers 418, 436 are calenders. Thus, the first and second compression rollers 418, 436 each have an upper and lower roller, where the upper roller applies a first temperature (e.g., 150-210°C) to activate the binder, and the lower roller applies a second temperature (e.g., 90-160°C). Referring to FIG. 4A, in one embodiment, the moving current collector web 402 includes a primer layer onto which the first dry powder electrode material 410 is deposited. Additionally, the bottom side of the moving current collector web 402 includes a second primer layer, and it is undesirable to melt or activate the primer without powder already deposited thereon. Therefore, to apply less heat to the bottom primer layer, the bottom roller is set at a lower temperature than the top roller. This process can be similarly applied with respect to the second compression roller 436, but in this case the compressed first layer 420 is on the bottom side of the moving current collector web 402.

[0058] Finally, according to one or more embodiments, the two layers are simultaneously compressed using a first calender 438 and a second calender 440. As described above, at least one of the first calender 438 or the second calender 440 applies heat to each layer to activate the binder in the dry powder electrode materials 410 and 428, respectively, to produce respective electrode layers 442 and 444 on either side of the current collector web 402. In one embodiment, at least one of the first calender 438 or the second calender 440 is heated to a temperature between 150 and 210 degrees Celsius. The electrode layers 442 and 444 on the moving current collector web 402 are then rewound into a double-sided electrode roll by an unwind web roller 446.

[0059] The double-sided dry powder electrode manufacturing platform 400 can include additional features or process steps to improve the handleability and cohesion of the dry powder electrode material layer 410 and address other issues, such as powder buildup on the calender rollers, splitting or breaking of the dry powder electrode material, and other issues that may result in unacceptable defects and uneven part production of the dry powder electrode. For example, lubricants and hybrid binders can be used to enhance the handleability and cohesion of the dry powder electrode material. In one embodiment, a lubrication station can be included between the conditioning station 416 and the calender 418, where the lubrication station applies a lubricant, such as steam generated from water, to the dry powder electrode material layer 410 to improve the cohesion of the first layer 420 and prevent breakage of the first layer during flipping through the turn rollers 422. Alternatively, the double-sided dry powder electrode manufacturing platform 400 can include a curing station between the conditioning station 416 and the calender 418. If a hybrid binder including one or more of a thermoplastic binder, a thermosetting binder, and a UV-curable binder is used, one or more of the components of the hybrid binder can be selectively cured or partially cured by a curing station to improve the cohesion and handling of the first dry powder electrode material layer 420 and prevent fracture of the first layer during flipping through the turn rollers 422. Lubrication and curing stations can be included between the conditioning station 434 and the calender 436 to improve the cohesion and handling of the second dry powder electrode material layer 428 prior to compression by the calenders 436, 438, and 440.

[0060] The final product of platform 400 is a roll of double-sided electrode (i.e., either a double-sided cathode or a double-sided anode, or a bipolar electrode having one anode and the other cathode), as shown in Figure 4B. Figure 4B shows a double-sided electrode 450 according to various embodiments. In this example, double-sided electrode 450 includes a first electrode 442 corresponding to first dry powder electrode material 410 / 420 and a second electrode 440 corresponding to second dry powder electrode material 428.

[0061] 5 illustrates a double-sided dry powder electrode manufacturing platform 500 according to one or more embodiments. The platform 500 includes a moving carrier substrate 502, a substrate unwind roller 504, a first powder deposition station 506, a first conditioning station 512, a current collector unwind roller 514, a second powder deposition station 518, a second conditioning station 524, a first calender 526, a second calender 528, a substrate unwind roller 532, and an electrode unwind roller 536.

[0062] In this example, a substrate unwind roller 504 unwinds a moving carrier substrate 502, such as Mylar or aluminum (i.e., no surface treatment or primer), onto which a first powder deposition station 506 deposits a first dry powder electrode material 510. The first dry powder electrode material 510 is then transported through a smoothing and / or conditioning station 512 to condition the powder layer before compaction, as described above. However, unlike the previous example, a current collector web 516 is unwound by the current collector unwind roller 514 over the conditioned first dry powder electrode material 510 layer, forming a stack 520 consisting of the carrier substrate 502, the first dry powder electrode material 510, and the current collector web 516. Accordingly, a second dry powder electrode material 522 is deposited onto the current collector web 516 by a second powder deposition station 518 and is subjected to a smoothing and / or conditioning station 524, as described above. Although not shown in FIG. 5, the platform 500 may further include rollers between the current collector unwind roller 514 and the second powder deposition station 518 for aligning and tensioning the current collector web 516 .

[0063] At this point, prior to final compaction by the first and second calenders 526 and 528, the pre-calendered electrode is a stack including a bottom carrier substrate 502, a first loose layer of electrode material (i.e., first dry powder electrode material 510), a current collector web 516 on the first loose layer, and a second loose layer of electrode material (i.e., second dry powder electrode material 522). Thus, according to one or more embodiments, the first and second calenders 526 and 528 are used to simultaneously compact two layers. As described above, at least one of the first and second calenders 526 and 528 applies heat to each layer to activate the binders in the dry powder electrode materials 510 and 522, respectively, to produce respective electrode layers 530 and 534 on either side of the current collector web 516. In one embodiment, at least one of the first and second calenders 526 and 528 is heated to a temperature between 150 and 210 degrees Celsius.

[0064] Additionally, as described above, the upper and lower rollers of the first calender 526 or the second calender 528 can be provided with different temperatures. For example, a lower lower roller temperature can facilitate removal of the carrier substrate 502. Finally, the carrier substrate 502 is separated from the electrode layer 534 and unwound by substrate unwind rollers 532, and the electrode layers 530 and 534 on either side of the current collector web 516 are unwound into a double-sided electrode roll by electrode unwind rollers 536.

[0065] [Manufacturing method for dry powder electrodes] 6 is a flowchart of a method 600 for solventless manufacturing of a battery electrode according to various embodiments. Alternative embodiments may include more, fewer, or different steps than those shown in FIG. 6, and the steps may be performed in a different order than those shown in FIG.

[0066] In this method, anode or cathode active material particles, one or more conductive additives, and one or more binder materials are mixed (602) to form a dry powder electrode material. In one embodiment, the one or more binder materials include 0.5-2% PVDF mixed with the active material particles and conductive additives. In another embodiment, 2-4% PVDF is used. In one embodiment, the active material particles and one or more binder materials are dry mixed to achieve a partial coating of PVDF on the active material particles of between 50 and 85%. Furthermore, the dry particles are mixed for a period and with sufficient shear to adhere 70-100% of the fine binder particles to the surfaces of the active material particles, achieving a D50 of 7-12 μm and a Hausner ratio of between 1.3-1.45.

[0067] The dry powder electrode material is deposited onto the moving current collector web using a dry powder dispensing device (604). The dry powder electrode material is a loose powder that remains loose on the moving current collector web after being deposited. In one embodiment, the moving current collector includes a primer layer or roughened surface to increase friction between the current collector and the deposited powder, enhancing deposition and powder spreading.

[0068] The deposited loose dry powder electrode material is then spread evenly (606) onto the moving current collector web using one or more spreading devices to achieve a uniform loose dry powder electrode layer. The one or more spreading devices include a smoothing roller and a conditioning roller to form a smooth, uniform, and relatively cohesive powder layer as the layer moves and vibrates the current collector web. In one embodiment, the one or more conditioning rollers each reduce the layer thickness by gentle compaction, resulting in a layer compaction of 3-7%.

[0069] The uniform loose dry powder electrode layer is consolidated (608) against the current collector web using one or more calenders configured to apply at least one of pressure or heat to the loose dry powder electrode material to activate the one or more binder materials and form a battery electrode. The loose dry powder electrode material remains loose until consolidated by the one or more calenders. In one embodiment, after the one or more calenders apply a pressure of 10-30 MPa to the loose dry powder electrode material, the battery electrode has a porosity of between 20-35%.

[0070] [Electrode characteristics] FIG. 7A shows an example post-formation morphology of a dry powder electrode 700 according to various embodiments. In this example, the dry powder electrode 700 includes active material particles 702 held in place by an activated binder 704 after calendering. As described herein, calendering further refers to the application of heat (e.g., 130-210°C) sufficient to activate or fuse the binder described with respect to FIGS. 2B-2E to produce the activated binder 704. FIG. 7A further shows a porous structure including cavities 706, which are represented as spaces or voids within the particle network of the electrode 700. In this example, the active material particles 702 are spherical particles, such as NMC.

[0071] 7B shows an example of the post-formation form of a dry powder electrode 750 according to various embodiments. In this example, the dry powder electrode 750 includes active material particles 752 held in place by an active binder 754 and cavities 756 after calendaring. In this example, the active material particles 752 are amorphous particles, such as LFP. In one embodiment, the dry powder electrodes 700 and 750 are manufactured using any of the platforms 300, 400, or 500 described above.

[0072] In both examples, the active binder 704 and the active binder 754 are confined to the surface of the respective active material particles and do not penetrate into the cavities 706 and 756, respectively. These cavities are not found in processes using PTFE or wet-cast PVDF. In contrast, PTFE fiberizes, and these fibers penetrate into the spaces between the active material particles, inhibiting electrolyte penetration. Similarly, wet-cast PVDF using NMP completely crystallizes the PVDF, filling the spaces between the active material particles with a rigid, sponge-like structure that inhibits electrolyte penetration. The function of the binder is to hold the particles in place and form a cohesive layer; therefore, ideally, the binder is confined to the contact points between particles in the post-calendered electrode. Confining the binder to the contact points ensures (or at least greatly facilitates) sufficient electrolyte penetration into the electrode layer.

[0073] There are several factors that can drive the morphology of dry powder electrode 700 and dry powder electrode 750. One factor is the appropriate amount of binder. The binder must be sufficient to ensure adequate particle-to-particle adhesion, but not so much that it fills unnecessary interparticle volume. Another factor is the particle size of the binder. Small particles may not clump together as easily as larger aggregates upon melting, allowing the binder to maintain surface adhesion (i.e., prevent the binder from filling the interparticle cavities). Another factor is mixing intensity or shear force. The shear force must be strong enough to bond the binder particles to the active material particle surfaces, but not so strong that they deform and fuse together, completely coating the particle surfaces. Another factor is calendar pressure and heat. Too much pressure will cause the structure to collapse. Thus, the resulting morphology of dry powder electrode 700 and dry powder electrode 750, in one embodiment, is a porous structure that increases ionic conductivity due to capillary forces that facilitate electrolyte penetration and access to the active material particles 702 and 752.

[0074] [System for additive manufacturing of batteries] FIG. 8 illustrates an example additive manufacturing (or 3D printing) platform 800 for producing batteries using dry powder electrodes, according to one or more embodiments. Platform 800 includes a substrate transport system 802, a dry powder deposition station 804, a spreading station 806, a compaction station 808, a pattern hardening station 810, a cutting station 812, a transfer system 814, and a build station 816. Substrate transport system 802 is used to transport substrates (i.e., anode or cathode collectors) as needed from station to station within system 800. Transport system 802 can be configured to transport substrates through the system in any suitable manner. In some embodiments, the transport system includes a conveyor system that transports substrate units 818 from station to station within the system. In other embodiments, the substrate is provided as a continuous sheet that is unwound from and rewound onto a roll.

[0075] The dry powder deposition station 804 includes the necessary equipment for depositing the dry powder onto the substrate, such as a hopper 820 for holding the dry powder and a dispensing unit 822 configured to form a powder bed 824 on the substrate 818 with a desired thickness and coverage. In various embodiments, the dry powder deposition station 804 includes a binder-jet three-dimensional printing system, although any suitable device or mechanism capable of depositing powder according to desired specifications can be used. The dispensing device 822 and / or the substrate 818 are movable relative to one another so that the dispensing device 822 can make one or more passes over the substrate / powder bed to deposit one or more layers of dry powder electrodes on the substrate / powder bed to achieve the desired thickness and / or coverage. The spreading station 806 includes a spreader 826 configured to evenly spread the dry powder 824 on or across the substrate 818. In some embodiments, the spreader includes a counter-rotating roller. In other embodiments, the spreader can include a blade or similar type of device. Any suitable type of spreader can be used.

[0076] The compaction station 808 is configured to apply a predetermined amount of pressure and / or heat to the powder bed / substrate to achieve desired properties of the deposited powder electrode, such as density, thickness, porosity, etc. In various embodiments, the compaction station 808 can include at least one roller 828, i.e., a calender roller, made of a hardened metal material configured as a cylindrical tube. In various embodiments, one or more pairs of calender rollers can be used to form a nip through which the powder / substrate is fed. Each pair of calender rollers can be configured to apply the same or different amounts of pressure and / or heat to the powder / substrate. For example, one pair of calender rollers can be configured as a hot calender that applies heat above a predetermined temperature (e.g., 100-210°C) to the powder / substrate, while a second pair of calender rollers can be configured as a cold calender that applies a lower temperature (e.g., 10-80°C) to the powder / substrate.

[0077] The pattern curing station 810 is configured to perform a prescribed binder curing process to form the printed pattern, i.e., patterned electrodes such as patterned anodes and cathodes. The pattern curing station includes one or more curing devices 830 for curing the binder. The type of device depends on the type of binder used with the powder. Examples of curing devices that can be used include a heating device for curing a thermosetting binder, an ultraviolet (UV) light device for curing a UV-curable binder, etc. The prescribed binder curing to form the printed pattern can be achieved using various pattern formation mechanisms, as further shown in Figures 9A-10B.

[0078] Once the deposition, spreading, compression, and prescribed binder curing processes are complete, the printed pattern is fed to a cutting station 812, which singulates the printed pattern into one or more individual battery components 832, such as patterned anodes and cathodes, of predetermined sizes and shapes that can be used for assembly of battery stacks in the build station 816. Any suitable cutting device or method can be used to form the electrode / collector components 832.

[0079] The transfer system 814 transfers the printing pattern (e.g., patterned anodes and cathodes) to the build station 816. The transfer system 814 includes a transfer device that can be configured to transfer the printing pattern onto a stack of printing pattern layers previously transferred to the build platform. The transfer device can include any suitable type of mechanism for removing electrode components and transferring the components to the build station, such as a pickup assembly, a vacuum device, an adhesive device, a translation device, etc. The build station has a work surface on which cell components can be stacked to form a battery cell and on which multiple cells can be stacked to form a battery. In various embodiments, the build station can include a substrate, a carrier substrate, an assembly plate, a conveyor belt, or a transport print platform, as examples.

[0080] [Additional manufacturing considerations] This disclosure provides a 3D printing apparatus and methodology that can be used for any additive manufacturing process based on powder bed printing or binder jetting 3D printing. The proposed 3D printing apparatus and methodology enables solvent-free powder bed printing using dry powder pre-coated with a binder. This disclosure eliminates the process steps of binder deposition and subsequent drying, solvent recovery, and / or disposal, thus significantly simplifying the binder jetting 3D printing process, increasing printing throughput, and lowering manufacturing costs.

[0081] In one embodiment, solvent-free powder bed printing involves process steps including (a) depositing a binder-coated powder onto a powder bed or substrate, (b) optionally further densifying the deposited layer through a compaction mechanism, (c) forming a printed pattern through predetermined binder curing, and (d) transferring the printed pattern to a build station or build platform, eliminating the process steps of binder deposition and subsequent drying and solvent recovery in traditional binder-jetting 3D printing. In some embodiments, further processing can be performed on the printed pattern layer prior to transfer.

[0082] In some embodiments, the binder-coated powder can include one or more organic binders or inorganic binders, or a combination thereof. The organic binder can include either a thermosetting composition or a photocurable composition, or a combination thereof. In some embodiments, the organic binder includes a thermosetting or heat-curable composition that can be applied as a liquid and cured or hardened when heated to bind the particles. The thermosetting composition can be any binder composition known in the art, such as various resin binders containing monomers, polymers, and curing agents (also known as hardeners or crosslinkers). In some embodiments, the organic binder includes a UV-curable composition that can be applied as a liquid and hardened or hardened when exposed to UV radiation. The UV-curable composition can be any composition known in the art, such as various UV-curable resins containing monomers, oligomers, and photoinitiators. In some embodiments, the organic binder can be a hybrid thermal and UV-curable binder that includes both a thermosetting and a UV-curable composition. In some embodiments, the organic binder can include two or more UV-curable compositions, each cured by UV radiation of a different wavelength. In some embodiments, the organic binder can include one or more B-staged binder compositions that are partially cured, i.e., B-staged. In some embodiments, the organic binder includes a thermoplastic composition that can melt when heated and harden when cooled to bind particles together. In some embodiments, the binder can remain as part of the printing process after printing. In other embodiments, the binder, e.g., the organic binder, can be removed from the printed object by pyrolysis during a post-printing process, e.g., sintering. In some embodiments, the binder can include a ceramic precursor, such as a polycarbosilane or polysiloxane, that can be thermally reacted to become part of the printed object during a post-printing process, e.g., sintering.In some embodiments, the binder-coated powder can include one or more of the binders described above, where the surface of the binder-coated powder is partially covered by the binder. In some embodiments, the binder-coated powder can include one or more of the binders described above, where the surface of the binder-coated powder is completely covered by the binder.

[0083] In various embodiments, the binder-coated powder can be produced by any of a variety of particle coating techniques, including, but not limited to, dry mixing, solvent evaporation, spray coating, including spray drying and spray congealing, air suspension coating (also known as fluidized bed coating), pan coating, centrifugal extrusion, and multi-orifice centrifugal processes.

[0084] In one embodiment, the binder-coated powder is prepared by dry powder blending. For example, the binder-coated dry powder material used to form the dry powder electrode layer can be prepared by dry blending particles of one or more electrode active materials, a conductive material, and one or more binder materials, such as PVDF.

[0085] In another embodiment, the powder is first formulated into a dispersion, slurry, or ink, collectively referred to as a liquid dispersion, containing solid particles of powder, solvent, binder, dispersant, and optionally other additives. The liquid dispersion is then processed by various solvent removal techniques to form the binder-coated powder. For example, solvent removal can be achieved using a liquid extraction device, as described in recently issued U.S. Patent No. 11,260,581 (incorporated herein by reference), in which the solvent is removed using one or more techniques of pressure differential, pressure plate, pressure cuff, vacuum, or by using a semipermeable membrane. Alternatively, if a low-boiling or fast-drying solvent is used in the liquid dispersion, heat can be applied by the liquid extraction device to extract the solvent by evaporation. In another example, solvent removal can be achieved using a spray drying system (spray dryer), in which the liquid dispersion is atomized into a spray of small droplets by pumping the liquid dispersion through a spray nozzle into a heated section of the spray dryer, where the solvent in the dispersion is evaporated to produce a dry binder-coated powder.

[0086] In another embodiment, the powder is formulated into a liquid dispersion with a molten binder, for example, a binder comprising a thermoplastic composition. The liquid dispersion with the molten binder is atomized into a spray of droplets by pumping the liquid dispersion through a spray nozzle into a cooled section of a spray congealing system, where the molten binder hardens to yield a dry binder-coated powder.

[0087] In another embodiment, binder-coated powders are produced using air suspension coating, also known as fluidized bed coating, in which solid particles of powder are suspended by an upward flow of air in a heated coating chamber, where a liquid binder is sprayed into the chamber through a nozzle and deposited as a thin layer on the surface of the suspended particles, resulting in a dry binder-coated powder. The coating chamber may also be configured with cooled air as the powder is coated with the molten binder, as in a spray-congealing system.

[0088] In some embodiments, binder-coated powders can contain particles of a single size or multiple sizes, and the multiple sizes may be a single distribution, a bimodal distribution, or a multimodal distribution. A series of binder-coated powders can be produced using powders containing particles of different sizes and distributions to achieve optimal printing results. For example, binder-coated powders can contain both large particles that provide the necessary printability and small particles that fill gaps or cavities formed between the large particles, thereby increasing particle packing density and resulting in a higher density in the final printed object after post-printing processes, such as sintering. Sintering can also be improved by using fine powders containing smaller particles. However, fine powders containing smaller particles (e.g., less than 5 μm) have poor flowability and are typically difficult to print by binder jet printing. To address this issue, the small particles of fine powders can be agglomerated into larger particles (e.g., 10-75 μm) using the binder coating processes described above, such as spray coating or fluidized bed coating.

[0089] In some embodiments, the binder-coated powder can be deposited onto a powder bed or substrate by a binder jet 3D printing system. In some embodiments, after powder deposition, a compression mechanism can be activated to further increase the packing density of the printed layer. For example, a calender roller can be used to compress the printed powder layer, thereby achieving a higher packing density.

[0090] After the binder-coated powder deposition and compression process, a predetermined binder cure or binder pattern cure is performed to form the print pattern. The defined binder cure to form the print pattern can be achieved using a variety of pattern formation mechanisms.

[0091] In some embodiments, a patterned heater including a printed pattern can be used to selectively cure patterned areas of deposited powder including either a thermosetting binder or a thermoplastic binder to form the printed pattern. The patterned heater can be formed on a substrate located below the printed powder, as shown in FIG. 9A. FIG. 9A illustrates an exemplary curing process 900 for binder pattern curing according to various embodiments. In this example, a binder-coated powder layer 902 is deposited on a patterned heater substrate 904 including non-patterned areas 906 and patterned areas 908. Furthermore, FIG. 9B illustrates an exemplary curing process 950 for binder pattern curing according to various embodiments. In this example, a binder-coated powder layer 954 is deposited on a substrate 956, and a patterned heater 952 (including non-patterned areas 958 and patterned areas 960) is positioned on or above the binder-coated powder layer 954. Patterning resolution can be improved by increasing the temperature difference between the patterned areas (908, 960), which are heated to harden the binder, and the non-patterned areas (906, 958), which are cooled to prevent binder hardening, and the non-patterned areas (906, 958) are removed before transferring the printed pattern to a build station or build platform.

[0092] In some embodiments, an infrared patterning mask can be used to selectively cure patterned areas of deposited powder comprising either a thermosetting binder or a thermoplastic binder to form a printed pattern, as shown in FIG. 10A . FIG. 10A illustrates an exemplary curing process 1000 for binder pattern curing, according to various embodiments. FIG. 10A illustrates binder coated powder 1002 deposited on a substrate 1004 with a patterning mask 1006 (including non-patterned areas 1008 and patterned areas 1010) positioned between the binder coated powder 1002 and an infrared radiation source 1012. The patterning mask 1006 can be formed using an infrared insulation or barrier material, where the patterned areas 1010 of the mask 1006 are open to allow infrared radiation to pass through, and the non-patterned areas 1008 of the mask 1006 include an infrared insulation or barrier material that blocks infrared radiation.

[0093] In some embodiments, to further improve patterning accuracy, a laser melting mechanism can be implemented to form a printed pattern on a deposited powder that includes a thermoplastic binder, where a laser beam can be programmed to precisely melt the binder in the pattern area of ​​the deposited powder, forming the printed pattern as the molten binder hardens or solidifies during cooling.

[0094] In some embodiments, a photopatterning mask can be used to selectively cure patterned areas of a deposited powder comprising a photocurable binder composition, such as a UV-curable binder composition, as shown in FIG. 10B. FIG. 10B illustrates an exemplary curing process 1050 for binder pattern curing according to various embodiments. FIG. 10B illustrates binder coated powder 1052 deposited on a substrate 1054 with a patterned mask 1056 (including non-patterned areas 1058 and patterned areas 1060) positioned between the binder coated powder 1052 and a UV radiation source 1062. Similar to photopatterning masks used in photolithography, the patterned areas 1060 of the mask 1056 are open or transparent to allow light to pass through, while the non-patterned areas 1058 of the mask comprise an opaque material that does not allow light to pass through.

[0095] In some embodiments, the defined or patterned binder cure is controlled such that one or more binder compositions in the deposited powder are partially cured, i.e., B-staged. The presence of a B-staged binder in the printed pattern has the potential advantage of ensuring adequate adhesion between the patterned layers when the printed patterns are assembled into a stack at a build station.

[0096] In some embodiments, a defined binder cure is performed on patterned areas of deposited powder that include a hybrid binder that includes both a thermosetting composition and a UV-curable composition, where only the thermosetting binder composition is cured to form the printed pattern and the UV-curable binder composition is later cured to provide adhesion between the patterned layers during assembly into a stack of printed patterned layers. Alternatively, the UV-curable binder composition is cured to form the printed pattern and the thermosetting binder composition is later cured to provide adhesion between the patterned layers during assembly into a stack of printed patterned layers.

[0097] In some embodiments, a defined binder cure is performed on a patterned area of ​​deposited powder that includes a binder comprising two or more UV-curable compositions, each cured by UV radiation of a different wavelength from the others: a first UV-curable binder composition is cured at a first UV wavelength to form the printed pattern, and a second UV-curable binder composition is later cured at a second UV wavelength to provide adhesion between the patterned layers during assembly of the printed patterned layers into a stack.

[0098] In a further embodiment, after the binder-coated powder deposition and compaction process, an unpatterned cure is performed on the deposited powder layer to completely cure or partially cure the deposited powder layer, and the cured powder layer is then cut into a desired pattern that can be used for assembly of a stack in a build station.

[0099] In various embodiments, 3D printing apparatus and methodologies enabling solvent-free powder bed printing using dry powders pre-coated with binders according to the present disclosure can be used to form battery cells containing multiple layers of various functional materials. As shown in Figures 11A and 11B, the battery cell includes an anode, a cathode, and one or more layers of separator interconnecting the anode and cathode. In some embodiments, as shown in Figure 11A, the anode 1104 and cathode 1108 can be formed in a monopolar configuration, with the anode 1104 formed on one or both sides of an anode current collector 1102 and the cathode 1108 formed on one or both sides of a cathode current collector 1110. A separator 1106 is sandwiched between the monopolar anode 1104 and cathode 1108 to form a battery cell building repeat unit or sub-cell. The battery subcells are then stacked together and electrically connected in parallel via external current collector tabs or terminals (1120, 1118) to form the battery cell 1100. The battery cell can include a hermetic seal, enclosure, encapsulation, case, or casing, including a bottom seal 1112, a top seal 1116, and a sidewall seal 1114.

[0100] 11B, the anode 1104 and cathode 1108 can be formed in a bipolar configuration, with the anode 1104 formed on one side of a common bipolar current collector 1120 and the cathode 1108 formed on the other side to form a bipolar electrode repeat unit. The bipolar electrode repeat units are stacked with the anode side of the bipolar repeat unit facing the cathode side of the next adjacent bipolar repeat unit, and with a separator disposed between the anode and cathode, to form a multilayer bipolar battery cell 1100′, where the subcells including the anode 1104, cathode 1108, and separator 1120 interconnecting the anode and cathode are electrically connected in series without the use of external current collector tabs.

[0101] FIG. 12 shows a flowchart of a method 1200 for manufacturing a battery cell according to various embodiments. In FIG. 12, the method begins at step 1, where a bottom seal (e.g., 1112 in FIGS. 11A and 11B ) or enclosure is formed by printing or depositing a layer of dry powder of seal material pre-coated with a binder. In step 2, an anode current collector (e.g., 1102 in FIG. 11A ) is formed on the bottom seal using a dry powder of anode current collector material pre-coated with a binder. In step 3, an anode material layer (e.g., 1104 in FIG. 11A ) is formed on the anode current collector using a dry powder of anode material pre-coated with a binder. In step 4, a separator (e.g., 1106 in FIG. 11A ) is formed on the anode material layer using a dry powder of separator material pre-coated with a binder. In step 5, a cathode material layer (e.g., 1108 in FIG. 11A) is formed on the electrolyte separator using a dry powder of cathode material pre-coated with a binder. In step 6, a cathode current collector layer (e.g., 1110 in FIG. 11A) is formed on the cathode material layer using a dry powder of cathode current collector material pre-coated with a binder. In step 7, a cathode material layer is formed on the cathode current collector using a dry powder of cathode material pre-coated with a binder. In step 8, a separator is formed on the cathode material layer using a dry powder of separator material pre-coated with a binder. In step 9, an anode material layer is formed on the electrolyte separator using a dry powder of anode material pre-coated with a binder. The method continues by repeating steps 2 through 9 until the desired number of layers of the battery cell is reached. In step 11, the top seal (eg, 1116 in Figures 11A and 11B) or enclosure is formed by depositing a layer of dry powder of seal material that has been pre-coated with a binder.

[0102] In some embodiments, battery cells including multiple functional layers of anodes, cathodes, and separators interconnecting the anodes and cathodes may be fabricated directly on a build platform, build station, or support structure, or even on a substrate disposed on the build platform. Figure 13 illustrates a process 1300 in which a bottom seal is formed directly on a build platform 1302 by depositing a layer of dry powder of seal material pre-coated with a binder. An anode current collector is then formed on top of the bottom seal using a dry powder of anode current collector material pre-coated with a binder. The fabrication process continues with the deposition of layers of anode material, separator, cathode material, cathode current collector, etc., until the desired number of layers for the battery cell is reached.

[0103] Alternatively, Figure 14 shows a process 1400 in which each of the seal, anode current collector, anode material, separator, cathode material, and cathode current collector layers are formed separately in different print modules 1404 and then transferred to a build platform 1402 where the battery cell is assembled. For example, each of the functional layers includes a printed pattern formed by a solventless powder bed printing process in a specific print module (or station), as shown in Figures 8, 9A-10B. The printed patterns are then transferred to the build platform and stacked together according to the process flow shown in Figure 12.

[0104] In various embodiments, the seal, anode current collector, anode material, separator, cathode material, and cathode current collector layers may be formed by a solventless powder bed printing process at different printing speeds depending on the specific requirements of the material, layer thickness, and layer packing density. For example, the cathode material layer is typically thicker than the other layers, requiring more printing passes or operations, and therefore may be formed at a slower speed. Therefore, to speed up the printing process, an additional printing module for printing the cathode material is required. As another example, it may take more time to complete the transfer, alignment, and lamination of the layers on the build platform. In this case, an additional build platform is required. For mass production, multiple printing modules for printing the seal, anode current collector, anode material, separator, cathode material, and cathode current collector layers are arranged with multiple build platforms so that the printing speeds of each layer are synchronized with each other and with the speed of the build platform to achieve optimal speed or throughput of the entire process.

[0105] In some embodiments, battery cells including multiple functional layers—anode, cathode, and separator interconnecting the anode and cathode—can be fabricated by a hybrid process, where some of the layers—seal, anode current collector, anode material, separator, cathode material, and cathode current collector—can be formed by a solventless powder bed printing process, while other layers can be formed by alternative methods. For example, the anode or cathode current collector, which is typically much thinner than the anode or cathode, can be formed by inkjet or jetted material printing. Alternatively, the anode or cathode current collector can be formed using conventional copper or aluminum foil that is cut into a predetermined pattern, transferred to a build platform, and laminated with the other layers of the battery cell by a pick-and-place process. Lithium metal anodes can be formed by solventless powder bed printing using dry lithium powder pre-coated with a binder according to the present disclosure. Lithium anodes can be formed using conventional lithium foil that is cut into a predetermined pattern, transferred to a build platform, and laminated with the other layers of the battery cell by a pick-and-place process.

[0106] In various embodiments, a lithium-ion battery includes one or more battery cells, each battery cell including an anode, a cathode, and multiple repeating functional layers of separator interconnecting the anode and cathode. In some embodiments, the anode includes an anode active material selected from the group consisting of lithium, lithium powder, molten lithium, semi-liquid lithium, lithium titanium oxide, silicon, silicon oxide, and graphite, or a combination thereof. The cathode includes a separator material selected from the group consisting of lithium cobalt oxide (LCO), lithium manganese oxide (LMO), lithium iron phosphate (LFP), lithium nickel manganese cobalt (NMC), lithium nickel cobalt aluminum oxide (NCA), lithium nickel manganese oxide (LNMO), lithium vanadium oxide (LVO), lithium iron disulfide, silver vanadium oxide, carbon monofluoride, copper oxide, sulfur, or a combination thereof. The separator material may be selected from a polymer, a polymer gel, a solid electrolyte including a ceramic electrolyte, a polymer-ceramic composite, or a combination thereof. The separator material may be impregnated with a liquid electrolyte to enhance ionic conductivity and provide a suitable interface to the anode and cathode. Each battery cell may also include an anode current collector, a cathode current collector, and an airtight seal. The anode or cathode current collector may comprise an electronically conductive material selected from the group consisting of carbon materials, metals, semiconductors, conductive polymers, and polymer composites. For example, the anode current collector material may be selected from the group consisting of carbon black, activated carbon, graphite, graphene, carbon fibers, and carbon nanotubes, copper, nickel, silver, carbon-polymer composites, metal-polymer composites, or combinations thereof. The cathode current collector material may be selected from the group consisting of carbon black, activated carbon, graphite, graphene, carbon fibers, and carbon nanotubes, aluminum, nickel, silver, carbon-polymer composites, metal-polymer composites, or combinations thereof. The seal comprises a material selected from the group consisting of plastic, epoxy, polymer, polymer composite, glass, metal, ceramic, or a combination thereof.In some embodiments, the seal can include either a heat-curable composition or a light-curable (eg, UV-curable) composition, or a combination thereof.

[0107] According to another aspect of the present disclosure, a solvent-free powder bed 3D printing system is provided. The printing system includes a powder deposition apparatus configured to deposit a solvent-free, binder-coated powder (as described above) onto a substrate or powder bed. The powder deposition apparatus may be configured to deposit one powder at a time at a desired thickness. In some embodiments, the powder deposition apparatus and / or the substrate / powder bed are movable relative to each other so that the powder deposition apparatus can make one or more passes over the powder bed to deposit one or more layers of binder-coated powder onto the substrate / powder bed. The printing system also includes a pattern-curing unit configured to selectively cure the binder-coated powder to form a printed pattern using the above-described curing schemes, such as a patterned heater, an infrared patterning mask, a photographic patterning mask, or laser curing.

[0108] In some embodiments, the pattern-curing unit is configured to selectively cure only the heat-curable binder composition of a binder that includes both a heat-curable composition and a UV-curable composition to form the printed pattern, and the UV-curable binder composition is later cured to provide adhesion between the patterned layers during assembly of the printed pattern layers into a stack. In some embodiments, the pattern-curing unit is configured to selectively cure only the UV-curable binder composition of a binder that includes both a heat-curable composition and a UV-curable composition to form the printed pattern, and the heat-curable binder composition is later cured to provide adhesion between the patterned layers during assembly of the printed pattern layers into a stack. In some embodiments, the pattern-curing unit is configured to selectively cure only a first UV-curable composition of the binder to form the printed pattern, and the binder includes two or more UV-curable compositions, each composition cured by UV radiation of a different wavelength from the others. A first UV-curable binder composition is cured at a first UV wavelength, and a second UV-curable binder composition is later cured to provide adhesion between the patterned layers during assembly of the printed patterned layers into a stack.

[0109] In some embodiments, the printing system can include a compaction device for applying a predetermined amount of pressure to the binder-coated powder deposited on the substrate / powder bed to compact the powder to a predetermined density. In some embodiments, the compaction device can include at least one roller made of a hardened metal material designed as a cylindrical tube. The printing system can also include a build platform and a transfer device. The build platform has an upper surface with a longitudinal axis extending in the longitudinal direction. In some embodiments, the build platform can include, for example, a substrate, a carrier substrate, an assembly plate, a conveyor belt, or a transport printing platform. The transfer device is configured to transfer the printed pattern from the substrate / powder bed to the build platform. The transfer device can be configured to transfer the printed pattern to a stack of printed pattern layers previously transferred to the build platform. The transfer device can include any suitable type of mechanism for removing the printed pattern from the substrate / powder bed and transferring it to the build platform, such as a pickup assembly, a vacuum device, an adhesive device, a translation device, etc.

[0110] While various embodiments have been described, the descriptions are intended to be illustrative, not limiting, and it is understood that many more embodiments and implementations are possible that are within the scope of the embodiments. While many possible combinations of features are shown in the accompanying figures and discussed in this detailed description, many other combinations of the disclosed features are possible. Unless specifically limited, any feature of any embodiment can be used in combination with or substituted for any other feature or element in any other embodiment. Thus, it is understood that any of the features shown and / or discussed in this disclosure can be implemented together in any suitable combination. Therefore, the present embodiments should not be limited except in light of the appended claims and their equivalents. Various modifications and variations may be made within the scope of the appended claims.

[0111] While the above describes what is believed to be the best mode and / or other embodiments, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be embodied in various forms and embodiments, and that the teachings may be applied to numerous applications, only a few of which are described herein. It is intended that the following claims claim all such applications, modifications, and variations that fall within the true scope of the present teachings.

[0112] Unless otherwise indicated, all measurements, values, ratings, positions, dimensions, sizes, and other specifications set forth in this specification, including the following claims, are approximate rather than exact and are intended to have a reasonable range consistent with the function to which they relate and those customary in the art to which they pertain.

[0113] The scope of protection is limited only by the scope of the claims which follow. That scope is intended, and should be interpreted, as broadly as possible consistent with the ordinary meaning of the language used in the claims when interpreted in light of this specification and the following prosecution history, to encompass all structural and functional equivalents. Nonetheless, no claim is intended, and should be interpreted, to encompass subject matter that does not meet the requirements of 35 U.S.C. §§ 101, 102, or 103. Any unintended inclusion of such subject matter is hereby disclaimed.

[0114] Except as set forth immediately above, nothing described or illustrated is intended to, or should be construed to, cause any element, step, feature, object, benefit, advantage, or equivalent, whether claimed or not, to be offered to the public.

[0115] Terms and expressions used herein will be understood to have the ordinary meanings ascribed to such terms and expressions with respect to their respective fields of study and research, unless a specific meaning is otherwise stated herein. Relationship terms such as "first" and "second" are used solely to distinguish one entity or act from another and do not necessarily require or imply an actual relationship or order between such entities or acts. The terms "comprises," "comprising," or other variations are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements, but may include other elements not expressly listed or inherent in such process, method, article, or apparatus. An element preceded by "a" or "an" does not, without further constraints, exclude the presence of additional identical elements in a process, method, article, or apparatus that includes that element.

[0116] The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Furthermore, in the foregoing Detailed Description, it will be noted that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the claims require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Accordingly, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as separately claimed subject matter.

Claims

1. 1. A method for producing a dry powder electrode for a lithium ion battery, comprising: dry-mixing active material particles, one or more conductive additives, and one or more binder materials to form a dry powder electrode material; depositing a dry powder electrode material onto the moving current collector web using a dry powder dispensing device, the dry powder electrode material being a loose powder that remains loose on the moving current collector web after being deposited; and uniformly spreading the deposited free dry powder electrode material on the moving current collector web using one or more spreaders to achieve a uniform free dry powder electrode layer; and compressing the uniform loose dry powder electrode layer against a current collector web using one or more calenders configured to apply at least one of pressure or heat to the loose dry powder electrode material to activate the one or more binder materials and form a battery electrode, wherein the loose dry powder electrode material remains loose until compressed.

2. 10. The method of claim 1, wherein the one or more binder materials of the battery electrode are surface deposits of active material particles after application of heat.

3. 3. The method of claim 2, wherein the surface deposition of the one or more binder materials forms a porous structure between active material particles configured to increase electrolyte penetration and ionic conduction of the battery electrode.

4. 3. The method of claim 2, wherein the dry powder electrode material comprises 0.5-2% polyvinylidene fluoride (PVDF).

5. 5. The method of claim 4, wherein the partial coating of PVDF results in partial crystallization of the PVDF within the battery electrode after application of heat.

6. 5. The method of claim 4, wherein the active material particles and one or more binder materials are dry mixed to achieve a partial coating of PVDF on the active material particles, the partial coating being an average coverage of PVDF on the active material particles that is between 50 and 85%.

7. 10. The method of claim 1, further comprising applying a first compression to the uniform loose dry powder electrode layer with a first conditioning roller to effect a first reduction of the uniform loose dry powder electrode layer from a first height to a second height.

8. 10. The method of claim 7, further comprising applying a second compression to the uniform loose dry powder electrode layer using a second conditioning roller to effect a second reduction of the second height of the uniform loose dry powder electrode layer to a third height.

9. To uniformly spread the deposited free dry powder electrode material, 10. The method of claim 8, comprising using at least one smoothing roller to redistribute at least a portion of the dry powder electrode material along the layer to remove non-uniformities.

10. 10. The method of claim 1, wherein the dry particles are mixed for a period and with sufficient shear to adhere 70 to 100% of the fine binder particles onto the surface of the active material to achieve an average particle size of 7 to 12 μm.

11. 10. The method of claim 1, wherein the moving current collector web further comprises a primer layer configured to receive the dry powder electrode material and increase friction between the moving current collector web and the dry powder electrode material.

12. 10. The method of claim 1, wherein the moving current collector web includes a surface treatment configured to receive the dry powder electrode material and increase friction between the moving current collector web and the dry powder electrode material.

13. 10. The method of claim 1, wherein the battery electrode has a porosity of between 20 and 40% after the loose dry powder electrode layer is compressed against the current collector web.

14. 1. A system for producing dry powder electrodes for lithium ion batteries, comprising: a powder deposition station configured to deposit a dry powder electrode material onto a moving current collector web using a dry powder dispensing device, the dry powder electrode material being a dry mixture of active material particles, one or more conductive additives, and one or more binder materials, the dry powder electrode material being a loose powder that remains loose on the moving current collector web after being deposited; and one or more spreaders configured to evenly spread the loose dry powder electrode material deposited on the moving current collector web to achieve a uniform loose dry powder electrode layer; one or more conditioning rollers configured to reduce the thickness of the loose dry powder electrode material deposited on the moving current collector web prior to compaction; and one or more calenders configured to apply at least one of pressure or heat to the free dry powder electrode material to compress the free dry powder electrode layer against the current collector web and activate the one or more binder materials to form a battery electrode, wherein the free dry powder electrode material remains in a free state until compressed.

15. 15. The system of claim 14, wherein the one or more binder materials of the battery electrode are surface deposits of the active material particles after application of heat.

16. 16. The system of claim 15, wherein the surface deposition of the one or more binder materials forms a porous structure between the active material particles configured to increase electrolyte penetration and ionic conduction in the battery electrode.

17. 16. The system of claim 15, wherein the dry powder electrode material comprises 0.5-2% polyvinylidene fluoride (PVDF).

18. 20. The system of claim 17, wherein the partial coating of PVDF results in partial crystallization of the PVDF in the battery electrode after application of heat.

19. 20. The system of claim 17, wherein the active material particles and one or more binder materials are dry mixed to achieve a partial coating of PVDF on the active material particles, the partial coating being an average coverage of PVDF on the active material particles that is between 50 and 85%.

20. the one or more conditioning rollers include at least a first conditioning roller and a second conditioning roller; The first and second conditioning rollers applying a first compression to the deposited loose dry powder electrode layer using a first conditioning roller to reduce the thickness from a first layer thickness to a second layer thickness; 15. The system of claim 14, configured to apply a second compression to the deposited loose dry powder electrode layer using a second conditioning roller to reduce the thickness from the second layer thickness to a third layer thickness.

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