System for battery electrode fabrication

Abstract

A system for battery electrode fabrication is provided. The system includes an assembly configured to receive and disperse powder particles onto a substrate to define a first coating thickness of the powder particles on the substrate. The system includes a pair of calender rollers configured to receive the substrate in-between to create a pattern of compressed and uncompressed areas in the uniform coating. The compressed areas define a second coating thickness dimensioned smaller than the first coating thickness.

Description

SYSTEM FOR BATTERY ELECTRODE FABRICATIONCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of a co-pending, commonly assigned U.S. Provisional Patent Application No. 63 / 612,875, which was filed on December 20, 2023. The entire content of the foregoing provisional application is incorporated herein by reference.BACKGROUND

[0002] A variety of batteries are available in the industry for different uses. Lithium- ion (Li-ion) batteries have generally become the predominant type of battery used in portable consumer electronics and electric vehicles. Fabrication of Li-ion batteries involves numerous steps, each of which can affect the quality of the battery itself, as well as the cost involved in manufacturing the battery. One conventional manufacturing process is referred to as “spreader roller coating” and generally includes the steps of passing dry powder on a substrate through spreading rollers to evenly spread the powder on the substrate surface, and subsequently passing the substrate through compaction rollers to densify and compress the powder onto the substrate surface. The compression and densification adheres the powder coating to the substrate. In such manufacturing steps, the entire substrate surface is coated with the powder, i.e., no uncoated strips or areas for tab welding. Such spreader roller coating technology is described in, e.g., International Patent Application No. PCT / US23 / 69175, which is incorporated herein by reference in its entirety.

[0003] Another conventional manufacturing process generally includes formation of an electrode slurry having an active material, a conductive additive, and a binder, mixed in an organic solvent, and the electrode slurry is applied to a metal foil material. Once applied to the foil material, the solvent is dried out or evaporated while the active electrode mixture remains attached to the metal foil material surface. In some instances, the solvent may be toxic and can necessitate additional steps for handling / discarding that increase the overall cost of the manufacturing process. The cost of removing the solvent from the coated material on the metal foil therefore involves an additional step that also increases the overall cost of the manufacturing process.

[0004] An alternative manufacturing technique used in the industry is electrostatic spray deposition (ESD), which is a solvent- free manufacturing process for electrode coating for Li-ion batteries. See, e.g., B. Ludwig et al., Solvent-Free Manufacturing ofElectrodes for Lithium-ion Batteries, Sci. Rep. 6, Article No. 23150, doi: 10.1038 / srep23150 (2016); M. Wang et al., The Influence of Polyvinylidene Fluoride (PVDF) Binder Properties on LiNi0.33Co0.33Mn0.33O2 (NMC) Electrodes Made by a Dry-Powder-Coating Process, J. Electrochem. Soc., Vol. 166, No. 10, A2151 (2019); H. Abe et al., Electrostatic Spray Deposition for Fabrication of Li-ion Batteries, Transactions of JWRI, Vol. 44, No. 2 (2015); and U.S. Patent No. 10,547,044). Rather than relying on a solvent mixture, the ESD process uses a powder of the active electrode mixture which is applied to the metal foil material. By removing the solvent from the mixture and the drying step from the manufacturing process, the overall process is simplified and becomes more economic, resulting in a viable alternative for large-scale manufacturing. In particular, the solvent-free electrode coating technology is an attractive alternative to traditional manufacturing since it can significantly reduce energy consumption in the manufacturing process and thus significantly reduce the manufacturing cost of batteries.

[0005] In electrode manufacturing, the concepts and fundamentals of web handling are important in generating an acceptable product that is within required specifications and of the correct geometry. This is equally true for the ESD process as it is for the conventional slurry cast process. A traditional dry powder ESD coating system typically includes a substrate or web which continuously passes through a coating chamber that applies an active material mixture coating on the web. The web then passes in-between and through calender rolls to densify the active material mixture coating on the web. The web is eventually rolled onto a core at the rewind station, ready to be slit and assembled into a Li- ion battery. The direction in which the web travels is commonly known in industry as the Machine Direction (MD), while the orthogonal axis is known as the Cross Direction (CD).

[0006] The electrode formed by the traditional ESD coating system generally results in at least one uncoated region along which conductive tabs can be welded to the electrode for incorporation of the electrode into a battery. However, the location of the uncoated region is typically limited due to the active material powder being applied to the web. For example, in conventional slurry cast electrode manufacturing, formation of these types of uncoated regions can be performed by controlling the deposition of the slurry onto the web using a slot die. In such conventional process, the slurry has adequate viscosity such that it can be precisely applied to the web in the desired coating region while avoiding the edge tab regions. A sharp edge between the active material and the edge tab is generally formed to reduce the risk of cathode-to-anode capacity mismatching which may lead to reducedcycle life or an internal short circuit. For the dry ESD process, however, the powders cannot be dispensed in such a controlled manner since the dry particles’ momentum and trajectory is easily altered by external forces, such as drag and / or electromagnetic fields. Due to the inherent process differences between wet slurry and dry powders, the slurry cast electrode manufacturing solution to the problem is not applicable. The desired location and number of uncoated regions in an ESD process is therefore limited.

[0007] Turning to the web converting industry as a whole does not provide readily available solutions to the limitations of the conventional slurry cast electrode manufacturing process or the conventional ESD process. There are several ways coatings are controlled or removed from a web. However, the aim of such conventional means is to control coating thickness and uniformity through either metering or using a blade. These options do not lend themselves to introducing or forming a pattern in the coating with varied thickness across the width of the web (e.g., uncoated areas formed in-between coated areas). Existing solutions in the industry are generally applied to aqueous or liquid-based coating material. Few web handling applications coat dry powder onto a moving web. The nature of dry powder introduces new challenges not met by slurry cast methods and the current web handling industry.SUMMARY

[0008] In accordance with embodiments of the present disclosure, an exemplary system for battery electrode fabrication is provided. The system provides a controlled means for forming uncoated regions or areas along the electrode for subsequent tab welding. The system allows the substrate to first be dry powder coated with the active powder particles, and relies on grooves in a calender roller to selectively create densified and non-densified areas of the powder particle coating. In particular, the calender roller includes grooves formed therein that pass over the powder particle coating without compressing the coating in specific areas or strips of the substrate. It should be understood that the location of the grooves can be selected based on the desired location of the uncoated areas for tab welding, with the groove location customizable based on end user specifications. The powder in the uncompressed areas can be easily removed after passage of the substrate through the calender roller using, e.g., a vacuum, or the like. The compressed areas of the powder remain attached to the substrate, thereby creating clear delineations of the coated and uncoated regions of the substrate.

[0009] In accordance with embodiments of the present disclosure, an exemplary system for battery electrode fabrication is provided. The system includes an assembly configured to receive and disperse powder particles onto a substrate to define a first coating thickness of the powder particles on the substrate. The system includes a pair of calender rollers configured to receive the substrate in-between to create a pattern of compressed and uncompressed areas in the uniform coating. The compressed areas define a second coating thickness dimensioned smaller than the first coating thickness. The system can operate as part of an ESD system, a spreader roller coating system, or both.

[0010] In some embodiments, the system can include a pair of spreading rollers disposed between the assembly and the pair of calender rollers (e.g., in a spreader roller coating system). The pair of spreading rollers can be configured to receive the substrate in-between to spread the powder particles along the substrate into a uniform coating having an intermediate coating thickness before passage of the substrate to the pair of calender rollers. The intermediate coating thickness can be dimensioned smaller than the first coating thickness and larger than the second coating thickness. The substrate defines a length extending between a proximal end and a distal end, and further defines a width transverse to the length. The uniform coating can define uniformity in the intermediate coating thickness along the width and the length of the substrate.

[0011] The uncompressed areas can be formed through either no compressive forces applied by the pair of calender rollers on the powder particles, or a minimal compressive force applied by the pair of calender rollers on the powder particles. The minimal compressive force is less than a compressive force applied by the pair of calender rollers on the powder particles to form the compressed areas.

[0012] At least one of the pair of calender rollers can include at least one circumferential groove formed therein. The at least one circumferential groove can be surrounded by uniform outer surfaces that define a diameter dimensioned greater than a diameter of the at least one circumferential groove. The at least one circumferential groove can include side edges and a central recessed area between the side edges. The central recessed area defines, e.g., an inwardly curved concave cross-section, an inwardly directed square cross-section, an inwardly directed rectangular cross-section, or the like.

[0013] During passage of the substrate through the pair of calender rollers, the at least one circumferential groove does not apply pressure or applies a minimal pressure to theuniform coating to create the uncompressed area in the uniform coating. During passage of the substrate through the pair of calender rollers, the uniform outer surfaces apply pressure to the uniform coating to create the compressed areas in the uniform coating. The pressure applied by the uniform outer surfaces is greater than the minimal pressure applied by the at least one circumferential groove. It should be understood that if pressure is applied on the powder particles at the grooves of the calender rollers, such pressure is only minimal and is significantly less than the pressure applied by the uniform outer surfaces of the calender roller for densifying and compressing the powder particles.

[0014] The powder particles on the substrate in the compressed areas are bonded together to form a first coating layer and the first coating layer is adhered to the substrate. The powder particles on the substrate in the uncompressed areas are not bonded together to form a second coating layer and the second coating layer is not adhered to the substrate. In some embodiments, the system can include powder removal assembly configured to remove the powder particles in the uncompressed areas of the uniform coating to expose uncoated areas of the substrate. The powder removal assembly includes a vacuum configured to remove the powder particles in the uncompressed areas as the substrate passes through or under the powder removal assembly.

[0015] A thickness of the powder particles in the uncompressed areas can be dimensioned greater than the second coating thickness or equal to the first coating thickness. The compressed areas in the uniform coating define densified areas of the powder coating on the substrate.

[0016] In accordance with embodiments of the present disclosure, an exemplary system for battery electrode fabrication is provided. The system includes an assembly configured to receive and disperse powder particles onto the substrate to define a first coating thickness of the powder particles on the substrate. The system includes a pair of spreading rollers configured to receive the substrate in-between to spread the powder particles along the substrate into a uniform coating having an intermediate coating thickness. The intermediate coating thickness is dimensioned smaller than the first coating thickness. The system includes a pair of calender rollers configured to receive the substrate in-between to create a pattern of compressed and uncompressed areas in the uniform coating. The compressed areas define a second coating thickness dimensioned smaller than the intermediate coating thickness.

[0017] In accordance with embodiments of the present disclosure, an exemplary method of battery electrode fabrication is provided. The method includes dispersing powder particles onto a substrate to define a first coating thickness of the powder particles on the substrate. The method includes passing the substrate between a pair of calender rollers to create a pattern of compressed and uncompressed areas in the uniform coating. The compressed areas define a second coating thickness dimensioned smaller than the first coating thickness.

[0018] The powder particles on the substrate in the compressed areas are bonded together to form a first coating layer and the first coating layer is adhered to the substrate. The powder particles on the substrate in the uncompressed areas are not bonded together to form a second coating layer and the second coating layer is not adhered to the substrate. The method can include passing the substrate through or under a powder removal assembly to remove the powder particles in the uncompressed areas of the uniform coating to expose uncoated areas of the substrate.

[0019] In accordance with embodiments of the present disclosure, an exemplary method of battery electrode fabrication is provided. The method includes dispersing powder particles onto a substrate to define a first coating thickness of the powder particles on the substrate. The method includes passing the substrate between a pair of spreading rollers to spread the powder particles along the substrate into a uniform coating having an intermediate coating thickness. The intermediate coating thickness is dimensioned smaller than the first coating thickness. The method includes passing the substrate between a pair of calender rollers to create a pattern of compressed and uncompressed areas in the uniform coating. The compressed areas define a second coating thickness dimensioned smaller than the intermediate coating thickness.

[0020] In accordance with embodiments of the present disclosure, an exemplary system for battery electrode fabrication is provided. The system includes an assembly configured to receive and disperse powder particles onto a substrate to define a first coating thickness of the powder particles on the substrate. The system includes a pair of spreading rollers configured to receive the substrate in-between to spread the powder particles along the substrate into a uniform coating having a second coating thickness. The second coating thickness is dimensioned smaller than the first coating thickness. The system includes a pair of calender rollers configured to receive the substrate in-between to create a pattern of compressed and uncompressed areas in the uniform coating, the compressed areas definea third coating thickness dimensioned smaller than the second coating thickness.

[0021] The substrate defines a length extending between a proximal end and a distal end, and further defines a width transverse to the length. The uniform coating defines uniformity in the second coating thickness along the width and the length of the substrate. At least one of the pair of calender rollers can include at least one circumferential groove formed therein. The at least one circumferential groove can be surrounded by uniform outer surfaces that define a diameter dimensioned greater than a diameter of the at least one circumferential groove. The at least one circumferential groove can include side edges and a central recessed area between the side edges. In some embodiments, the central recessed area can define an inwardly curved or concave cross-section. In some embodiments, the central recessed area can define an inwardly directed square or rectangular cross-section.

[0022] During passage of the substrate through the pair of calender rollers, the at least one circumferential groove does not apply pressure to the uniform coating to create at least one uncompressed area in the uniform coating. During passage of the substrate through the pair of calender rollers, the uniform outer surfaces apply pressure to the uniform coating to create the compressed areas in the uniform coating. The powder particles in the compressed areas can be adhered to the substrate, and the powder particles in the uncompressed areas are not adhered to the substrate.

[0023] In some embodiments, the system can include a powder removal assembly configured to remove the powder particles in the uncompressed areas of the uniform coating to expose uncoated areas of the substrate. In some embodiments, the powder removal assembly can include a vacuum configured to remove the powder particles in the uncompressed areas as the substrate passes through or under the powder removal assembly. A thickness of the powder particles in the uncompressed areas can be dimensioned greater than the third coating thickness. The compressed areas in the uniform coating can define densified areas of the powder coating on the substrate.

[0024] In accordance with embodiments of the present disclosure, an exemplary system for battery electrode fabrication is provided. The system includes a substrate configured to move from a proximal end to a distal end of a containment enclosure. The system includes an assembly configured to receive and disperse powder particles onto the substrate to define a first coating thickness of the powder particles on the substrate. The system includes a pair of spreading rollers configured to receive the substrate in-between to spread the powderparticles along the substrate into a uniform coating having a second coating thickness. The second coating thickness is dimensioned smaller than the first coating thickness. The system includes a pair of calender rollers configured to receive the substrate in-between to create a pattern of compressed and uncompressed areas in the uniform coating. The compressed areas define a third coating thickness dimensioned smaller than the second coating thickness. A thickness of the powder particles in the uncompressed areas can be dimensioned greater than the third coating thickness.

[0025] In accordance with embodiments of the present disclosure, an exemplary method of battery electrode fabrication. The method includes dispersing powder particles onto a substrate to define a first coating thickness of the powder particles on the substrate. The method includes passing the substrate between a pair of spreading rollers to spread the powder particles along the substrate into a uniform coating having a second coating thickness. The second coating thickness is dimensioned smaller than the first coating thickness. The method includes passing the substrate between a pair of calender rollers to create a pattern of compressed and uncompressed areas in the uniform coating. The compressed areas define a third coating thickness dimensioned smaller than the second coating thickness.

[0026] The powder particles in the compressed areas are adhered to the substrate. The powder particles in the uncompressed areas are not adhered to the substrate. The method can include passing the substrate through or under a powder removal assembly to remove the powder particles in the uncompressed areas of the uniform coating to expose uncoated areas of the substrate.

[0027] Any combination and / or permutation of embodiments is envisioned. Other objects and features will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed as an illustration only and not as a definition of the limits of the present disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To assist those of skill in the art in making and using the system for battery electrode fabrication with uncoated areas, reference is made to the accompanying figures, wherein:

[0029] FIG. 1 is a diagrammatic view of an exemplary system for battery electrode fabrication with uncoated areas in accordance with embodiments of the present disclosure.

[0030] FIG. 2 is a diagrammatic view of calender rollers of an exemplary system for battery electrode fabrication with uncoated areas of FIG. 1.

[0031] FIG. 3 is a diagrammatic view of a powder coated substrate before calendaring by an exemplary system for battery electrode fabrication with uncoated areas of FIG. 1.

[0032] FIG. 4 is a diagrammatic view of a powder coated substrate after calendaring by an exemplary system for battery electrode fabrication with uncoated areas of FIG. 1.

[0033] FIG. 5 is a diagrammatic view of a powder coated substrate after removal of uncompressed powder by an exemplary system for battery electrode fabrication with uncoated areas of FIG. 1.DETAILED DESCRIPTION

[0034] FIG. 1 is a diagrammatic view of an exemplary system 100 for battery electrode fabrication (hereinafter “system 100”). The system 100 can be used to manufacture a coated substrate with selective uncoated regions / areas usable in, e.g., Li-ion batteries, solid state batteries, or the like. In some embodiments, the system 100 can be used for spreader roller coating electrode manufacturing. In some embodiments, the system 100 can be used for ESD electrode manufacturing. The system 100 can be incorporated into an containment enclosure (e.g., a containment chamber) for deposition of the powder coating onto a substrate or web 102, e.g., a continuously moving substrate or web 102. The web 102 includes a top surface 104 on which the powder coating is applied. The powder coating includes at least a cathode material or an anode material, e.g., for rechargeable lithium batteries, or the like. In some embodiments, the bottom surface of the web 102 can also receive the powder coating either concurrently with the top surface or subsequent to the top surface being coated. Rollers 106, 108 can be positioned on opposite proximal and distal ends of the web 102 and suspend the web 102 as it passes through the containment enclosure. The rollers 106, 108 can rotate in a combined manner to maintain the continuous movement of the web 102 through the containment enclosure in a web direction 110.

[0035] The system 100 includes a chamber 112 configured to receive and dispense the powder particles 1 14 onto the top surface 104 of the web 102 (e.g., an assembly of a powder storage chamber and a dispensing / dispersing mechanism, or the like). In spreader rollercoating systems, the chamber 112 can be used to dispense the powder particles 114 onto the web 102 for subsequent spreading by spreading rollers 116, 118. In ESD systems, the chamber 112 can use any known means for dispensing and / or dispersing the powder particles 114 onto the web 102, e.g., spray nozzles, distribution pipes, scattering rollers, combinations thereof, or the like. The system 100 includes a pair of spreading rollers 116, 118 positioned downstream or distally from the chamber 112. One spreading roller 116 is positioned adjacent to the top surface 104 of the web 102, and the other spreading roller 118 is positioned adjacent to the opposing bottom surface of the web 102, thereby sandwiching the web 102 between the rollers 116, 118. The spreading rollers 116, 118 rotate in opposite directions to feed the web 102 along the web direction 110.

[0036] As illustrated in FIG. 1, the initial coating of the powder particles 114 creates a coating layer of a first thickness, i.e., the largest thickness, as measured from the top surface 104 of the web 102 to the top of the coating layer. In some embodiments, the initial coating layer can be centrally positioned under the chamber 112 without covering the entire surface 104 of the web 102, e.g., a mound of powder, or the like. The web 102 moves continuously towards and between the spreading rollers 116, 118. As the web 102 passes between the spreading rollers 116, 118, the powder coating layer is distributed along the top surface 104 of the web 102 to generate a uniform or substantially uniform coating. This uniform coating defines a second thickness 120 which is dimensioned smaller than the first thickness. The spreading rollers 116, 118 ensure that the powder coating is redistributed or spread over the web 102 to achieve the uniform coating along the entire top surface 104 of the web 102. Thus, after passage of the web 102 through the spreading rollers 116, 118, the thickness 120 of the powder coating is uniform when viewed transversely across the web 102. At this stage of the process, the powder coating can cover the entire top surface 104 of the web 102 with no uncoated areas formed. The powder coating also defines a substantially uniform thickness 120 with a minimum thickness variation along the width and length of the web 102.

[0037] The web 102 is continuously moved to pass between a pair of calender rollers 122, 124 disposed downstream or distally from the spreading rollers 1 16, 1 18. One calender roller 122 is positioned adjacent to the top surface 104 of the web 102, and the other calender roller 124 is positioned adjacent to the opposing bottom surface of the web 102, thereby sandwiching the web 102 between the rollers 122, 124. The calender rollers 122, 124 rotate in opposite directions to feed the web 102 along the direction 110. Thecalender rollers 122, 124 are configured to further compress and densify the powder coating to achieve a predetermined third thickness 126, i.e., the thinnest thickness. The third thickness 126 is therefore dimensioned smaller than the second thickness 120. The densification step of the calender rollers 122, 124 can be performed with or without heat. Prior to densification, the powder coating sits on the web 102 without adhering to the web 102. After densification with the calender rollers 122, 124, the powder coating is adhered to the web 102 and powder particles 114 in the coating layer are bonded together via a binder material in the coating layer and / or mechanical force between the coating layer and the web 102 due to the compressive forces applied to the powder coating.

[0038] Conventional calender rollers define a flat, cylindrical surface to ensure that uniform pressure is applied onto the powder coating across the entire width of the web 102 for densification. In contrast, the system 100 relies on one or more grooves formed in at least one of the calender rollers 122, 124 to selectively create pressure for densification in only some areas of the powder coating. For example, if only the top surface 104 of the web 102 is being coated, only the top calender roller 122 includes the grooves formed therein. Alternatively, if only the bottom surface of the web 102 was being coated, only the bottom calender roller 124 would include the grooves formed therein. If both surfaces of the web 102 were being coated, both calender rollers 122, 124 could have grooves formed therein.

[0039] The number and location of grooves in the calender rollers 122, 124 can be determined based on the desired specifications of the end user. The grooves define areas where no pressure or less pressure is applied by the calender rollers 122, 124, thereby creating uncompressed strips or areas of the powder coating along the web 102. The remaining area of the calender rollers 122, 124 provides pressure on the powder coating and adheres the compressed powder coating to the web 102. The uncompressed powder coating can be easily removed by a powder removal assembly 128, e.g., a vacuum, or the like, to expose the top surface 104 of the web 102 and create uncoated strips or areas. The third coating thickness 126 is therefore formed in only the compressed areas, while the uncompressed areas remain at a thicker dimension (e.g., the second coating thickness 120, or the like).

[0040] FIG. 2 is a diagrammatic view of calender rollers 122, 124 of the system 100. The bottom calender rollers 124 defines a uniform outer surface 130 such that the roller 124 has a substantially uniform outer diameter. In contrast, the top calender roller 122 includes circumferential grooves 132 formed therein. Each groove 132 includes opposingside edges 134, 136 that define the limits or starting points of the groove 132, and a central area 138 that defines an inwardly curved or recessed section. In some embodiments, the central area 138 can have a concave or curved cross-section. In some embodiments, the central area 138 can have a linear (e.g., square, rectangular, triangular, or the like) crosssection. The remaining surfaces 140 of the roller 122 define a uniform outer surface that can substantially match the outer diameter of the surface 130 of the roller 124. The diameter of the grooves 132 is therefore dimensioned smaller than the diameter of the surfaces 140 of the roller 122.

[0041] When the calender rollers 122, 124 pass over the web 102, the surfaces 130, 140 of the rollers 122 compress the web 102 and the powder coating. The sections of the roller 122 with the grooves 132 do not provide a compressive force on the powder coating. The mechanical strength between powder particles 114, the coating layer and the web 102 should be sufficiently high that the densified areas are not affected during the subsequent powder removal process. In some embodiments, the compressive force range can be about, e.g., 10-2000 N / mm or higher, inclusive, 10-1900 N / mm inclusive, 10-1800 N / mm inclusive, 10-1700 N / mm inclusive, 10-1600 N / mm inclusive, 10-1500 N / mm inclusive, 10-1400 N / mm inclusive, 10-1300 N / mm inclusive, 10-1200 N / mm inclusive, 10-1100 N / mm inclusive, 10-1000 N / mm inclusive, 10-900 N / mm inclusive, 10-800 N / mm inclusive, 10-700 N / mm inclusive, 10-600 N / mm inclusive, 10-500 N / mm inclusive, 10- 400 N / mm inclusive, 10-300 N / mm inclusive, 10-200 N / mm inclusive, 10-100 N / mm inclusive, 10-50 N / mm inclusive, 10-20 N / mm inclusive, 20-2000 N / mm inclusive, 30- 2000 N / mm inclusive, 40-2000 N / mm inclusive, 50-2000 N / mm inclusive, 100-2000 N / mm inclusive, 200-2000 N / mm inclusive, 300-2000 N / mm inclusive, 400-2000 N / mm inclusive, 500-2000 N / mm inclusive, 600-2000 N / mm inclusive, 700-2000 N / mm inclusive, 800-2000 N / mm inclusive, 900-2000 N / mm inclusive, 1000-2000 N / mm inclusive, 1100-2000 N / mm inclusive, 1200-2000 N / mm inclusive, 1300-2000 N / mm inclusive, 1400-2000 N / mm inclusive, 1500-2000 N / mm inclusive, 1600-2000 N / mm inclusive, 1700-2000 N / mm inclusive, 1800-2000 N / mm inclusive, 1900-2000 N / mm inclusive, 20-1500 N / mm inclusive, 20-1000 N / mm inclusive, 20-500 N / mm inclusive, 20- 300 N / mm inclusive, 10 N / mm, 20 N / mm, 30 N / mm, 40 N / mm, 50 N / mm, 60 N / mm, 70 N / mm, 80 N / mm, 90 N / mm, 100 N / mm, 200 N / mm, 300 N / mm, 400 N / mm, 500 N / mm, 600 N / mm, 700 N / mm, 800 N / mm, 900 N / mm, 1000 N / mm, 1100 N / mm, 1200 N / mm,1300 N / mm, 1400 N / mm, 1500 N / mm, 1600 N / mm, 1700 N / mm, 1800 N / mm, 1900 N / mm, 2000 N / mm or above, or the like.

[0042] In particular, the roller 124 still provides a force on the bottom of the web 102, while the grooves 132 provide areas of clearance for the powder coating to avoid compressing the powder coating onto the web 102. Thus, compressive forces are not applied uniformly along the entire width of the web 102, and instead the compressive forces are selectively applied only in areas without grooves 132. In some embodiments, no compressive force is applied in the areas of the grooves 132. In some embodiments, only a minimal compressive force is applied that is insufficient to adhere the powder coating to the web 102, i.e., a significantly smaller compressive force than the force applied by the surfaces 130, 140. The maximum compression force applied to the coating layer should be sufficient to allow the subsequent powder removal process to selectively remove the powder particles 114 in the uncompressed areas without affecting the densified / compressed areas. In some embodiments, if a compressive force is applied at the grooves 132, such force can be in the range of about, e.g., 0-5 N / mm inclusive, 1-5 N / mm inclusive, 2-5 N / mm inclusive, 3-5 N / mm inclusive, 4-5 N / mm inclusive, 0-4 N / mm inclusive, 0-3 N / mm inclusive, 0-2 N / mm inclusive, 0-1 N / mm inclusive, 1-4 N / mm inclusive, 2-4 N / mm inclusive, 2-3 N / mm inclusive, 0 N / mm, 1 N / mm, 2 N / mm, 3 N / mm, 4 N / mm, 5 N / mm, or the like. Thus, as used herein, the term “uncompressed” refers to areas that either receive no compressive forces or receive only minimal compressive forces at the grooves 132, as compared to the significantly greater compressive forces provided by the non-grooved areas of the rollers 122, 124.

[0043] FIG. 2 illustrates calender rollers 122, 124 used for creating a pattern of uncoated areas on only one side of the web 102. It should be understood that both rollers 122, 124 could include the grooves 132, and the position of the grooves 132 could differ between the rollers 122, 124 depending on the specifications of the user. The powder in the uncompressed areas has a weak interaction with the web 102, while powder in the compressed areas is adhered to the web 102. After the calender rollers 122, 124, the web 102 moves under or through a powder removal assembly 127 which sucks or otherwise removes the powder from the uncompressed areas to generate the uncoated strips or areas on the web 102. The configuration of the calender rollers 122, 124 can therefore be used to selectively and accurately create uncoated areas on the web 102.

[0044] FIG. 3 is a diagrammatic top view of the web 102 with a powder coating 142 prior to passage through the calender rollers 122, 124. The powder coating 142 covers the entire top surface of the web 102 in a uniform or substantially uniform layer created by the spreading rollers 116, 118.

[0045] FIG. 4 is a diagrammatic top view of the web 102 after passage of the web 102 through the calender rollers 122, 124. The grooves 132 in the calender rollers 122 do not compress the powder coating 142 in specific areas, which results in uncompressed strips 144 along the length of the web 102. The remaining surface 140 of the roller 122 compresses the powder coating 142 between the strips 144 and creates densified areas 146 of the powder coating 142. The densified areas 146 are adhered to the web 102, while the uncompressed strips 144 only sit on the web 102 surface. The densified areas 146 define a smaller thickness than the uncompressed strips 144, as measured from the web 102 surface. The uncompressed strips 144 can be formed anywhere along the surface of the web 102, e.g., along one or both sides, between the side edges of the web 102, combinations thereof, or the like, depending on the specifications of the user.

[0046] FIG. 5 is a diagrammatic top view of the web 102 after passage of the web 102 through the powder removal assembly 127. The powder coating in the uncompressed strips 144 is easily removed from the web 102 surface to create uncoated strips or areas 148 along the length of the web 102. The densified areas 146 remain unaffected after passage through or under the powder removal assembly 127 due to the adherence of the powder coating to the web 102. The system 100 is therefore capable of creating clean and accurate delineations of coated and uncoated areas on the web 102. The web 102 can subsequently be passed for further processing steps and the uncoated areas 148 can be used for tab welding.

[0047] While exemplary embodiments have been described herein, it is expressly noted that these embodiments should not be construed as limiting, but rather that additions and modifications to what is expressly described herein also are included within the scope of the invention. Moreover, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations, even if such combinations or permutations are not made express herein, without departing from the spirit and scope of the invention.

Claims

CLAIMS:

1. A system for battery electrode fabrication, the system comprising: an assembly configured to receive and disperse powder particles onto a substrate to define a first coating thickness of the powder particles on the substrate; and a pair of calender rollers configured to receive the substrate in-between to create a pattern of compressed and uncompressed areas in the uniform coating, wherein the compressed areas define a second coating thickness dimensioned smaller than the first coating thickness.

2. The system of claim 1, comprising a pair of spreading rollers disposed between the assembly and the pair of calender rollers, wherein the pair of spreading rollers are configured to receive the substrate in-between to spread the powder particles along the substrate into a uniform coating having an intermediate coating thickness before passage of the substrate to the pair of calender rollers.

3. The system of claim 2, wherein the intermediate coating thickness is dimensioned smaller than the first coating thickness and larger than the second coating thickness.

4. The system of claim 2, wherein the substrate defines a length extending between a proximal end and a distal end, and further defines a width transverse to the length, and wherein the uniform coating defines uniformity in the intermediate coating thickness along the width and the length of the substrate.

5. The system of claim 1, wherein the uncompressed areas are formed through either (i) no compressive forces applied by the pair of calender rollers on the powder particles, or (ii) a minimal compressive force applied by the pair of calender rollers on the powder particles, wherein the minimal compressive force is less than a compressive force applied by the pair of calender rollers on the powder particles to form the compressed areas.

6. The system of claim 1, wherein at least one of the pair of calender rollers includes at least one circumferential groove formed therein.

7. The system of claim 6, wherein the at least one circumferential groove issurrounded by uniform outer surfaces that define a diameter dimensioned greater than a diameter of the at least one circumferential groove.

8. The system of claim 6, wherein the at least one circumferential groove includes side edges and a central recessed area between the side edges.

9. The system of claim 8, wherein the central recessed area defines an inwardly curved concave cross-section, an inwardly directed square cross-section, or an inwardly directed rectangular cross-section.

10. The system of claim 6, wherein during passage of the substrate through the pair of calender rollers, the at least one circumferential groove does not apply pressure or applies a minimal pressure to the uniform coating to create the uncompressed area in the uniform coating.

11. The system of claim 10, wherein during passage of the substrate through the pair of calender rollers, the uniform outer surfaces apply pressure to the uniform coating to create the compressed areas in the uniform coating, and wherein the pressure applied by the uniform outer surfaces is greater than the minimal pressure applied by the at least one circumferential groove.

12. The system of claim 1, wherein the powder particles on the substrate in the compressed areas are bonded together to form a first coating layer and the first coating layer is adhered to the substrate, and wherein the powder particles on the substrate in the uncompressed areas are not bonded together to form a second coating layer and the second coating layer is not adhered to the substrate.

13. The system of claim 1, comprising a powder removal assembly configured to remove the powder particles in the uncompressed areas of the uniform coating to expose uncoated areas of the substrate.

14. The system of claim 13, wherein the powder removal assembly includes a vacuum configured to remove the powder particles in the uncompressed areas as the substrate passes through or under the powder removal assembly.

15. The system of claim 1, wherein: a thickness of the powder particles in the uncompressed areas is dimensionedgreater than the second coating thickness or equal to the first coating thickness; or the compressed areas in the uniform coating define densified areas of the powder coating on the substrate.

16. A system for battery electrode fabrication, the system comprising: an assembly configured to receive and disperse powder particles onto the substrate to define a first coating thickness of the powder particles on the substrate; a pair of spreading rollers configured to receive the substrate in-between to spread the powder particles along the substrate into a uniform coating having an intermediate coating thickness, wherein the intermediate coating thickness is dimensioned smaller than the first coating thickness; and a pair of calender rollers configured to receive the substrate in-between to create a pattern of compressed and uncompressed areas in the uniform coating, wherein the compressed areas define a second coating thickness dimensioned smaller than the intermediate coating thickness.

17. A method of battery electrode fabrication, comprising: dispersing powder particles onto a substrate to define a first coating thickness of the powder particles on the substrate; and passing the substrate between a pair of calender rollers to create a pattern of compressed and uncompressed areas in the uniform coating, wherein the compressed areas define a second coating thickness dimensioned smaller than the first coating thickness.

18. The method of claim 17, wherein the powder particles on the substrate in the compressed areas are bonded together to form a first coating layer and the first coating layer is adhered to the substrate, and wherein the powder particles on the substrate in the uncompressed areas are not bonded together to form a second coating layer and the second coating layer is not adhered to the substrate.

19. The method of claim 17, comprising passing the substrate through or under a powder removal assembly to remove the powder particles in the uncompressed areas of the uniform coating to expose uncoated areas of the substrate.

0. A method of battery electrode fabrication, comprising: dispersing powder particles onto a substrate to define a first coating thickness of the powder particles on the substrate; passing the substrate between a pair of spreading rollers to spread the powder particles along the substrate into a uniform coating having an intermediate coating thickness, wherein the intermediate coating thickness is dimensioned smaller than the first coating thickness; and passing the substrate between a pair of calender rollers to create a pattern of compressed and uncompressed areas in the uniform coating, wherein the compressed areas define a second coating thickness dimensioned smaller than the intermediate coating thickness.

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