EDGE TENSION OF ELECTRODE FOILS

Abstract

Aspects of the disclosure include a system for calendering electrodes that utilizes the edge tension of the electrode foil to reduce wrinkling during calendering, and a method of manufacturing electrodes using this system. An exemplary system includes a calendering module having a pair of calender rolls separated by a gap. The gap includes a distance selected to accommodate a current collector. The current collector includes an uncoated portion and a coated portion having an electrode active material having a first thickness thereon. The system includes an unwinding module upstream of the calendering module, a collector module downstream of the calendering module, and one or more idler rolls.An idler roll of the one or more idler rolls includes a collet having a second thickness selected based on the first thickness to span underlying portions of the current collector, the collet being aligned with the uncoated portion of the current collector.

Description

INTRODUCTION

[0001] The present disclosure relates to the manufacture of battery cells and, more particularly, to a system for calendering electrodes that utilizes the edge tension of the electrode foil to reduce wrinkling during calendering.

[0002] Electrodes are used in a variety of devices that store electrical energy, including primary (non-rechargeable) battery cells, secondary (rechargeable) battery cells, fuel cells, and capacitors. An ideal electrode must balance various electrical energy storage properties, such as energy density, power density, maximum charge rate, internal leakage current, equivalent series resistance (ESR), cycle stability, high electrical conductivity, and low tortuosity. Electrodes often include current collectors to complement or otherwise enhance these electrical energy storage properties. Current collectors can be added to achieve higher conductivity and increase the available contact area to minimize the interfacial contact resistance between the electrode and its terminal.

[0003] A current collector is typically a plate of conductive material to which the electrode active material is attached. Commonly used as current collectors for an electrode are aluminum foil, aluminum alloy, copper alloy, stainless steel, and titanium foil. For example, in some electrode manufacturing processes, a film containing activated carbon powder (i.e., the electrode active material) is attached to a thin aluminum or copper foil with an adhesive layer. To improve the quality of the interfacial bond between the film of electrode active material and the current collector, the combined film and current collector is processed in a pressure laminator, such as a calender. This process is commonly called calendering. Therefore, the manufacture of an electrode typically involves preparing a film of electrode active material and laminating this film onto a current collector. SUMMARY

[0004] In an exemplary embodiment, a system for calendering electrodes is provided for the production of electrodes that utilizes the edge tension of the electrode foil to reduce wrinkling during calendering. The roll-to-roll system includes a calendering module having a pair of calender rolls separated by a nip. The nip has a spacing selected to accommodate a current collector. The current collector has an uncoated portion and a coated portion having an electrode active material having a first thickness thereon. The system includes an unwinding module upstream of the calendering module, a collector module downstream of the calendering module, and one or more idler rolls disposed between the unwinding module and the collector module.An idler roll of the one or more idler rolls includes a collet having a second thickness selected based on the first thickness to span underlying portions of the current collector. The collet is aligned with the uncoated portion of the current collector.

[0005] In addition to one or more of the features described herein, in some embodiments, the calendering pressures encountered in the calendering module serve to correct the overvoltage applied to the uncoated portion of the current collector, thereby reducing wrinkling of the film after calendering.

[0006] In some embodiments, the clamping sleeve is attached to the respective idler roller of the one or more idler rollers by means of a press fitting and / or adhesive. In some embodiments, the clamping sleeve is attached to the respective idler roller of the one or more idler rollers with one or more set screws. In some embodiments, the clamping sleeve is attached to the respective idler roller of the one or more idler rollers with one or more leaf springs.

[0007] In some designs the clamping sleeve is conical.

[0008] In some embodiments, the collet includes a patterned texture having one or more protrusions, one or more depressions, or one or more grooves.

[0009] In some embodiments, a line speed and / or tensile force of the current collector is adjusted to adjust the overvoltage applied to the uncoated portion of the current collector.

[0010] In some embodiments, one or more dancer rolls are arranged between the unwind module and the collector module. In some embodiments, the tensile force of the current collector is adjusted by shifting a position of at least one of the one or more dancer rolls.

[0011] In another exemplary embodiment, a method for manufacturing electrodes is provided. The method includes providing a calender module having a pair of calender rolls separated by a gap. The gap includes a distance selected to accommodate a current collector. The current collector includes an uncoated portion and a coated portion having an electrode active material having a first thickness thereon. The method includes providing an unwind module upstream of the calender module, a collector module downstream of the calender module, and one or more idler rolls disposed between the unwind module and the collector module. An idler roll of the one or more idler rolls includes a clamp sleeve having a second thickness selected based on the first thickness to span underlying portions of the current collector.The clamping sleeve is aligned with the uncoated section of the current collector.

[0012] In addition to one or more of the features described herein, in some embodiments, the calendering pressures encountered in the calendering module serve to correct the overvoltage applied to the uncoated portion of the current collector, thereby reducing wrinkling of the film after calendering.

[0013] In some embodiments, the clamping sleeve is attached to the respective idler roller of the one or more idler rollers by means of a press fitting and / or adhesive. In some embodiments, the clamping sleeve is attached to the respective idler roller of the one or more idler rollers with one or more set screws. In some embodiments, the clamping sleeve is attached to the respective idler roller of the one or more idler rollers with one or more leaf springs.

[0014] In some embodiments, an additional idler roller of the one or more idler rollers is positioned over the coated portion of the current collector. The additional idler roller may include an additional collet having a diameter 1 to 4 micrometers larger than the diameter of the additional idler roller.

[0015] In some embodiments, the collet includes a patterned texture having one or more protrusions, one or more depressions, or one or more grooves.

[0016] In some embodiments, a line speed and / or tensile force of the current collector is adjusted to adjust the overvoltage applied to the uncoated portion of the current collector.

[0017] In some embodiments, one or more dancer rolls are arranged between the unwind module and the collector module. In some embodiments, the tensile force of the current collector is adjusted by shifting a position of at least one of the one or more dancer rolls. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Further features, advantages and details are listed only as examples in the following detailed description, which refers to the drawings. Fig. 1 is a vehicle constructed in accordance with one or more embodiments; Fig. 2 is an exemplary configuration of a system for calendering electrodes in accordance with one or more embodiments; Fig. Figure 3A is an exemplary embodiment of an idler roller of the system for calendering electrodes from Fig. 2 according to one or more embodiments; Fig. 3B, Fig. 3C and Fig. 3D show exemplary assembly designs of the clamping sleeves of the idler roller from Fig. 3A according to one or more embodiments; Fig. 4A is an exemplary embodiment of an idler roller of the system for calendering electrodes from Fig. 2 according to one or more embodiments; Fig. 4B, Fig. 4C, Fig. 4D and Fig. 4E show exemplary profile designs of the clamping sleeves of the idler roller made of Fig. 4A according to one or more embodiments; and Fig. 5 is a flowchart according to one or more embodiments. DETAILED DESCRIPTION

[0019] The following description is merely exemplary and is not intended to limit the present disclosure, its application, or uses. It should be understood that throughout the drawings, corresponding reference characters designate like or corresponding parts and features.

[0020] Electrodes often include current collectors to complement or otherwise enhance the electrical energy storage properties of the integrated end device (e.g., a battery). A current collector typically comprises a film of conductive material (e.g., aluminum foil, copper foil, etc.) to which an electrode active material is attached. To improve the quality of the interfacial bond between the film of electrode active material and the current collector, the combined film and current collector are processed in a pressure laminator. Therefore, the fabrication of an electrode typically involves fabricating a film of electrode active material and laminating this film to a current collector (the so-called calendering process).

[0021] Calendering can be broadly defined as the compression of a dried electrode (usually resulting from the coating and drying of an electrode slurry) to reduce its porosity, improve particle contact, and increase energy or power density. Conventional calendering processes have been used to improve various aspects of battery technology, such as providing higher specific conductivity, larger contact areas, and lower contact resistance in the electrode. However, several challenges exist in optimizing the calendering process.

[0022] One such challenge, for example, is that calendering electrodes (e.g., cathodes) onto current collector substrates (e.g., foil substrates such as aluminum, stainless steel, and titanium) results in wrinkling when lower porosity is desired. Wrinkling (also known as uneven stretching) occurs at the interface between the coated sections of the current collector (i.e., the sections with pressed electrode films) and the uncoated sections (i.e., the uncoated sections of the current collector) and is caused by the different material properties and thicknesses of the electrode and substrate materials. These defects worsen as the resulting porosity decreases, meaning that electrodes with relatively low porosity are inherently more affected by wrinkling.

[0023] While there are several approaches to reducing wrinkling, each has drawbacks. For example, the naive approach is to increase the target porosity, which will proportionally reduce wrinkling but also reduce electrode conductivity. Another approach is to completely cover the substrate so that there is no interface where wrinkling can occur. The drawback of this is that the uncoated foil sections of the current collector (i.e., the sections not covered by the electrode active material) are ideal for use as battery terminals, and simply removing the uncoated foil sections will reduce battery efficiency.

[0024] This disclosure presents a novel electrode calendering system that utilizes the edge tension of the electrode film to reduce wrinkling during calendering, and a method for manufacturing electrodes using this system. Rather than increasing the desired porosity or removing (or reducing) the uncoated film portions of an electrode, the electrode calendering system described herein is designed to intentionally overtension the film during the roll-to-roll drawing process. The film edge pressures created during the calendering process serve to correct (reverse, undo, etc.) this overtension (rather than create new wrinkles), thereby reducing film wrinkling after calendering. In short, the film edge overtension results in local stretching, which is accommodated by calendering.Although the term "pre-tensioning" primarily refers to over-tensioning, where the film edge is pre-tensioned before calendering, in some embodiments, the film edge can be over-tensioned after calendering to the extent of what is known as post-tensioning. Over-tensioning of the film edge can be achieved by attaching tension sleeves to the idler (or draw) roll(s) before or after the calender rolls, by tensioning the electrodes by controlling the dancer roll(s) and the line speed, or by a combination of both.

[0025] The use of a system for calendering electrodes with a film-edge tensioning measure according to one or more embodiments offers several technical advantages over previous embodiments. The modified electrode manufacturing system and associated method described herein can be used, in particular, to produce electrodes with no (or greatly reduced) wrinkling and with relatively improved elongation. Batteries manufactured from electrodes without wrinkles and with more uniform elongation offer a number of improved battery properties, as these defects compromise the integrity of the electrodes (e.g., wrinkles can lead to poor adhesion between the coated electrode film and the current collector, resulting in areas of relatively weak bonding that are prone to delamination or delamination).increase electrical resistance (wrinkles and thickness variations can create gaps or areas of reduced contact between the electrode material and the current collector, which can impede electron flow), increase deterioration and reduce lifetime (electrodes with wrinkles and / or uneven stretching can be subjected to increased stress and strain during charge / discharge cycling due to uneven mechanical properties, which can lead to accelerated deterioration, cracking, or even electrode failure), increase thermal instability (wrinkles can trap electrolyte and impede heat dissipation, resulting in local hotspots that can degrade the electrolyte), and reduce capacity and energy density (wrinkle formation and stretching defects can lead to uneven thickness distribution across the entire electrode surface),and these non-uniformities can lead to lower utilization of the active material, lower capacity, and lower battery energy density. Further advantages are possible. For example, existing roll-to-roll processes can be relatively easily modified to reduce wrinkles by incorporating collets and / or adjusting line speed and dancer roll positions, without requiring redesign of the main roll / calender roll. The reduction of wrinkles and stretch defects described herein also eliminates the need to anneal and stiffen the foil, as well as to introduce grooves into the current collector—both techniques typically used to reduce defects but known to weaken the foil. Furthermore, the annealing and foil stiffening steps are energy-intensive and expensive.

[0026] A vehicle according to an exemplary embodiment is shown in Fig. 1, the vehicle 100 is generally designated 100. The vehicle 100 is illustrated in the form of an automobile having a body 102. The body 102 includes a passenger compartment 104 in which a steering wheel, front seats, and rear seats (not separately identified) are disposed. Disposed within the body 102 are a number of components, including, for example, an electric motor 106 (shown by projection under the front hood). The electric motor 106 is shown for illustration and discussion only. It is to be understood that the configuration, location, size, arrangement, etc., of the electric motor 106 are not to be considered particularly limited, and that all such configurations (including configurations having multiple motors) are within the intended scope of this disclosure.

[0027] The electric motor 106 is powered by a battery pack 108 (shown by projection near the rear of the vehicle 100). The battery pack 108 is shown for illustration and discussion only. It is understood that the configuration, location, size, arrangement, etc., of the battery pack 108 are not to be considered particularly limited, and that all such configurations (including split configurations) are within the scope of this disclosure. Moreover, while the present disclosure is primarily discussed in the context of a battery pack 108 configured for the electric motor 106 of the vehicle 100, the aspects described herein may similarly be incorporated into any system (vehicle, building, or otherwise) having one or more energy storage systems (e.g.,one or more battery packs or modules), and all such configurations and applications are within the intended scope of this disclosure.

[0028] As explained in more detail below, the battery pack 108 includes one or more cells with electrodes having improved edge quality (i.e., uniform stretch and fewer or no wrinkles). In some embodiments, a system for calendering electrodes is modified by incorporating clamp sleeves on the idler (or draw) roll(s) before or after the calender rolls, or by tensioning the electrodes by controlling the dancer roll(s) and the line speed, or by a combination of both (see Fig. 2). The clamping sleeves can be mounted using a number of mounting techniques (see Fig. 3A, Fig. 3B, Fig. 3C, and Fig. 3D). The design of the shape and profile of the clamping sleeves can be customized for further optimization (see Fig. 4A, Fig. 4B, Fig. 4C, Fig. 4D, and Fig. 4E).

[0029] Fig. 2 shows an exemplary embodiment of a system 200 for calendering electrodes according to one or more embodiments. As shown in Fig. 2, the electrode calendering system 200 may include a coated current collector 202 (itself comprised of a current collector foil and an electrode coating, not separately identified) that is fed from an unwind module 204 to a collector module 206 via a series of idler rolls 208 (also referred to as pull rolls or positioning rolls). The number and position of the idler rolls 208 are for illustrative purposes only and are not to be considered particularly limiting.

[0030] The idler rolls 208 guide the coated current collector 202 between a pair of calender rolls 210 (also referred to as a top roll press and a bottom roll press) of a calender module 212 (also referred to as a roll press system) for calendering. In some embodiments, the electrode calendering system 200 includes an infeed module 214 disposed between the unwind module 204 and the calender module 212. In some embodiments, the electrode calendering system 200 includes an outfeed module 216 disposed between the calender module 212 and the collector module 206. In some embodiments, the electrode calendering system 200 may include a thickness gauge module 218 disposed before or after the calender module 212 (as shown).

[0031] In some embodiments, the infeed module 214 and / or the outfeed module 216 include one or more dancer rolls 220. The dancer rolls 220 can be translated vertically and / or horizontally (e.g., by springs, levers, cams, and / or pneumatics) to change the travel length of the coated current collector 202, thereby changing the voltage applied to the coated current collector 202. It should be understood that the electrode calendering system 200 has been simplified for clarity and simplicity. The electrode calendering system 200 may include any number of additional rolls (e.g., guide rolls, positioning rolls, dancer rolls, etc.) and other roll-to-roll equipment (e.g., monitoring devices such as high-speed cameras, film guiding and tracking systems, support structures such as a steel frame, etc.), and all such configurations are within the intended scope of this disclosure.

[0032] In some embodiments, the coated current collector 202 comprises a current collector coated with an electrode active material (see Fig. 3A). Without particular limitation, the electrode active material may (depending on the requirements of a particular application) include, for example, various cathode or anode materials such as activated carbon powder, nickel manganese cobalt oxide (NMC), lithium iron phosphate (LFP), nickel cobalt aluminum oxide (NCA), nickel cobalt manganese aluminum oxide (NCMA), lithium manganese iron phosphate (LMFP), lithium and manganese rich (LMR) cathode or anode material, lithium manganese oxide (LMO), graphite, silicon, silicon-graphite composites, tin, tin oxide (SnO2), lithium titanate (Li4Ti5O 12 , LTO), sulfur and lithium-sulfur (Li-S) composites, lithium metal (Li) and / or lithium alloys such as lithium antimony (Li-Sb), lithium aluminum (Li-Al) and lithium germanium (Li-Ge) and the like.

[0033] Likewise, the current collector (also referred to as a sheet or uncoated foil) is not particularly limited but can comprise, for example, a sheet of conductive metal such as aluminum foil, stainless steel, and titanium foil. Other materials are possible, such as semi-metals (e.g., tin, graphite), alloys of the metals and / or semi-metals, conductive two-dimensional wire mesh, conductive three-dimensional wire mesh, conductive foam, and the like.

[0034] In some embodiments, the calender rolls 210 are arranged to apply pressure to the coated current collector 202. This process, referred to as calendering, is intended to improve the density, uniformity, and overall performance of the resulting pressed electrode (not separately identified) by pressing and compacting an electrode material onto a portion of a current collector. The calender rolls 210 may be made of a durable material, such as steel, and manufactured with precision surfaces (e.g., with tolerances of less than 10 micrometers) to ensure uniform pressure distribution. In some embodiments, a gap between the calender rolls 210 may be adjusted by moving (e.g., hydraulically) one or both calender rolls 210 to control the amount of applied pressure.

[0035] In some embodiments, the electrode calendering system 200 includes several control parameters, such as a roll temperature (top and / or bottom), a calender pressure, a gap distance, and a line speed. In some embodiments, the roll temperature is up to 150 degrees Celsius, the pressure is up to 10 MPa, and the line speed is 110 meters per minute, although other calendering configurations are within the intended scope of this disclosure. In some embodiments, the gap between the calender rolls 210 can be adjusted (hydraulically or otherwise) to the desired thickness of the pressed electrode.

[0036] In some embodiments, a line speed and / or a tensile force of the electrode calendering system 200 is adjusted to achieve a predetermined overvoltage of the coated current collector 202. In some embodiments, the predetermined overvoltage is an overvoltage empirically known (e.g., from previous runs of the roll-to-roll process) or simulatively predicted (e.g., through finite element analysis (FEA)) to obtain a wrinkle-free pressed electrode after calendering. Note that the line speed and / or the tensile force required to obtain a wrinkle-free pressed electrode (after calendering) varies depending on the loading (e.g., milligrams per square centimeter) and density of the electrode material, the material chosen for the current collector, and the desired thickness of the pressed electrode.The line speed and / or tensile force may also vary due to additional factors, particularly electrode formulation, surface roughness, tensile properties, and the like.

[0037] The tensile force of the electrode calendering system 200 can be adjusted by vertically and / or horizontally translating one or more dancer rolls 220, as discussed herein. For example, in some embodiments, the line speed of the electrode calendering system 200 is 10 m / s and the tensile force of the electrode calendering system 200 is 22 kg, although the tensile force and line speed may vary depending on the requirements of the actual configuration (e.g., electrode thickness, composition, etc.). All such configurations are within the intended scope of this disclosure. In some embodiments, the degree of deformation (prestress) can be observed (i.e., empirically verified) for a range of tensile force and line speed combinations for a known electrode configuration.

[0038] Fig. Figure 3A shows an exemplary embodiment of an idler roller 208 of the system 200 for calendering electrodes from Fig. 2 according to one or more embodiments. As in Fig. 3A, the idler roller 208 (which itself may be one or more of the idler rollers 208 in Fig. 2) may include one or more collets 302. In some embodiments, the additional thickness of the collets 302 on the idler roll 208 serves to span underlying portions of the coated current collector 202.

[0039] In some embodiments, the coated current collector 202 comprises one or more uncoated film sections 304 and one or more coated sections 306, and the clamping sleeves 302 are positioned to align with the uncoated film sections 304. In this way, the clamping sleeves 302 can be used to span the uncoated film sections 304 of the coated current collector 202. Advantageously, this span of the uncoated film sections 304 of the coated current collector 202 is fully or partially restored during the calendering process (see Fig. 2), since during calendering, asymmetric stresses are naturally exerted on the uncoated film sections 304 and the coated sections 306 of the coated current collector 202.

[0040] The number of collets 302 can be adjusted depending on the number of uncoated foil sections 304 of the coated current collector 202. For example, with single- or double-sided coating, a pair of collets 302 can be positioned to cover the two exposed edges of the coated current collector 202. With track coating (as shown), any number of collets 302 can be positioned to accommodate any number of coating tracks (e.g., three tracks, although 4, 5, 10 tracks, etc. are also possible). In some embodiments, the number of collets 302 can be greater than the number of uncoated foil sections 304 of the coated current collector 202. In particular, one or more additional collets 302 can be positioned, for example, to prevent warping of the electrode track (of the coated current collector 202).In some embodiments, three collets 302 can be positioned such that a center collet is applied over the coated portions 306 of the coated current collector 202. In this case, a diameter of the center collets (and all other collets of the collets 302) can be several micrometers (e.g., 1 to 4 micrometers) larger than the pull roller (e.g., the idler rollers 208), allowing the center collets to exert additional pulling force on the respective area of the coated current collector 202. In this way, overall distortion of the electrode track can be reduced.

[0041] Fig. 3B, Fig. 3C and Fig. 3D show exemplary assembly configurations of the clamping sleeves 302 of the idler roller 208 from Fig. 3A according to one or more embodiments. Fig. 3B shows an assembly using a press fitting and / or adhesive. Fig. 3C shows an assembly using adjusting screw(s). Fig. 3D shows an assembly using leaf spring(s). Regardless of the design, the clamping sleeves 302 can be dynamically adjusted in some embodiments. This can be achieved, for example, through smart materials, adjustable elliptical springs, expansion of the sleeves by heating or cooling the sleeves, etc.

[0042] As in Fig. As shown in Figure 3B, the clamping sleeves 302 can be attached to the idler roller 208 using a press fitting and / or adhesive 308. The press fitting and / or adhesive 308 is not particularly limited but can be selected, for example, depending on the material, thickness, and / or other properties of the clamping sleeves 302 and / or the idler roller 208. The press fitting and / or adhesive 308 can, for example, comprise a polyurethane blend for metal-polymer applications.

[0043] As in Fig. 3C, the clamping sleeves 302 may be secured to the idler roller 208 with one or more set screws 310. The number and type of set screws 310 are not to be considered particularly limited, and all such configurations are within the intended scope of this disclosure.

[0044] As in Fig. As shown in Figure 3D, the clamping sleeves 302 can be secured to the idler roller 208 with one or more leaf springs 312. The number and type of leaf springs 312 are not particularly limited, and all such configurations are within the intended scope of this disclosure. Advantageously, the clamping sleeves 302 can be dynamically adjusted in this configuration by adjusting the tension in the leaf springs 312.

[0045] Fig. Figure 4A shows an exemplary embodiment of an idler roller 208 of the system 200 for calendering electrodes from Fig. 2 according to one or more embodiments. Fig. 4B, Fig. 4C, Fig. 4D and Fig. 4E show exemplary profile designs of the clamping sleeve 302 in the detailed view 400 of Fig. 4A according to one or more embodiments.

[0046] Fig. Figure 4B shows a relatively rapid taper 402 of the collet 302. A relatively rapid taper is defined herein as a taper that is completed within less than 20 percent or 10 percent of the width of the collet 302. In this way, the collet 302 provides a flat profile suitable for applications requiring uniform electrode coating thickness.

[0047] Fig. 4C shows a relatively slow taper 404 of the collet 302. A relatively slow taper is defined herein as a taper that occurs across at least 50 percent, 60 percent, 75 percent, 90 percent, or 100 percent (as shown) of the width of the collet 302. In this manner, the collet 302 provides a concave (or alternatively, a convex) profile suitable for applications where the thickness of the electrode coating increases (or decreases) across the width of the coated current collector 202.

[0048] Fig. 4D shows a clamping sleeve 302 with a patterned texture 406 instead of a smooth texture as in Fig. 4B and Fig. 4C. The patterned texture 406 may include any number of protrusions and / or depressions arranged in any desired configuration, and all such configurations are within the intended scope of this disclosure. In some embodiments, the patterned texture 406 is evenly distributed (within the tool limits) across the collet 302. In some embodiments, the patterned texture 406 is asymmetrically distributed across the collet 302. For example, the number, size, position, spacing, and / or orientation of the protrusions and / or depressions of the patterned texture 406 may vary across the collet 302 to achieve any desired span geometry, and all such configurations are within the intended scope of this disclosure.

[0049] Fig. 4E shows a clamping sleeve 302 with a series of grooves 408 distributed throughout the clamping sleeve 302. The number, size, position, spacing, and / or orientation of the grooves 408 may be varied as desired to achieve any desired span geometry, and all such configurations are within the intended scope of this disclosure.

[0050] The exemplary designs of the clamping sleeves 302 according to Fig. 4B, Fig. 4C, Fig. 4D and Fig. 4E are illustrated as having substantially the same width, but this is for clarity only. The clamping sleeves 302 of the idler rollers 208 need not be the same width. Also, the clamping sleeves 302 need not have the same thickness and / or taper, and all such configurations are within the intended scope of this disclosure. Furthermore, any taper may be symmetrical or limited to a single side (e.g., outer edge, inner edge) of the clamping sleeves 302.

[0051] In some embodiments, a thickness of the collets 302 is selected for a particular application to achieve a predetermined overvoltage of the coated current collector 202. In some embodiments, the predetermined overvoltage is an empirically known (e.g., from previous runs of the roll-to-roll process) or simulated (e.g., through finite element analysis (FEA)) overvoltage to obtain a wrinkle-free pressed electrode after calendering. It should be noted that the thickness required to obtain a wrinkle-free pressed electrode (after calendering) varies depending on the loading (e.g., milligrams per square centimeter) and density of the electrode material, the material chosen for the current collector, and the desired thickness of the pressed electrode. Furthermore, the strip thickness can be selected based on a number of design and / or target parameters, such as:Flexural strength, stress, elongation, electrode thickness, and / or yield strength. Strip thickness may also vary due to additional factors, including electrode formulation, surface roughness, tensile properties, and the like. In some embodiments, for example, collets 302 may be manufactured with a thickness of 50 to 100 micrometers, e.g., 70 micrometers, although other thicknesses are within the intended scope of this disclosure. In some embodiments, collets 302 may be placed over idler rolls 208 by wrapping material over idler rolls 208. In some embodiments, collets 302 are wrapped over idler rolls 208 with a wrap angle of greater than 90 degrees.

[0052] The clamping sleeves 302 can be made of a material with known elasticity, which is selected depending on the intended calendering pressures. The clamping sleeves 302 can be made, for example, of metals such as aluminum, stainless steel, steel alloys, etc., without particular limitation, or of polymers and / or elastomers such as silicone blended with a polymer such as polypropene, thermoplastic polymers such as polyethylene terephthalate (PET) and polyvinylidene fluoride (PVDF), polyethylene (PE), including low-density polyethylene (LDPE) and high-density polyethylene (HDPE), polytetrafluoroethylene (PTFE), polyamides such as nylon, synthetic rubbers such as neoprene, hybrid materials with glass fibers, silicon oxide, etc., polymeric and metal laminates with rubber, and the like.

[0053] With reference now to Fig. 5 generally illustrates a flowchart 500 for manufacturing electrodes using an electrode calendering system that utilizes the edge tension of the electrode foil to reduce wrinkling during calendering, according to one embodiment. The flowchart 500 is described with reference to Fig. 1-4E and may include further steps described in Fig. 5 are not shown. The Fig. Although the blocks shown in Figure 5 are presented in a specific order, they can also be rearranged, subdivided and / or combined.

[0054] In block 502, the method includes providing a calender module having a pair of calender rolls separated by a gap. The gap has a spacing selected to accommodate a current collector. The current collector has an uncoated portion and a coated portion having an electrode active material having a first thickness thereon.

[0055] In block 504, the method includes providing an unwinding module upstream of the calendering module. In block 506, the method includes providing a collector module downstream of the calendering module.

[0056] At block 508, the method includes providing one or more idler rolls disposed between the unwind module and the collector module. In some embodiments, one of the one or more idler rolls includes a collet having a second thickness. In some embodiments, the second thickness is selected based on the first thickness to span underlying portions of the current collector. In some embodiments, the collet is aligned with the uncoated portion of the current collector (i.e., spans the uncoated portions).

[0057] In some embodiments, the calendering pressures encountered in the calendering module serve to correct the overvoltage applied to the uncoated portion of the current collector, thereby reducing wrinkling of the film after calendering.

[0058] In some embodiments, the clamping sleeve is attached to the respective idler roller of the one or more idler rollers by means of a press fitting and / or adhesive. In some embodiments, the clamping sleeve is attached to the respective idler roller of the one or more idler rollers with one or more set screws. In some embodiments, the clamping sleeve is attached to the respective idler roller of the one or more idler rollers with one or more leaf springs.

[0059] In some designs the clamping sleeve is conical.

[0060] In some embodiments, the collet comprises a patterned texture with one or more projections (see Fig. 4D), one or more depressions (see Fig. 4D) or one or more grooves (see Fig. 4E).

[0061] In some embodiments, a line speed and / or tensile force of the current collector is adjusted to adjust the overvoltage applied to the uncoated portion of the current collector.

[0062] In some embodiments, the method includes providing one or more dancer rolls disposed between the unwind module and the collector module. In some embodiments, the tensile force of the current collector is adjusted by shifting a position of at least one of the one or more dancer rolls.

[0063] The terms "a" and "an" do not represent a quantity limitation, but indicate that at least one of the mentioned items is present. Unless the context clearly indicates otherwise, the term "or" stands for "and / or." When the description refers to "an aspect," this means that a particular element described in connection with the aspect (e.g., a feature, structure, step, or property) is included in at least one of the aspects described herein and may, but is not required to, appear in other aspects. It should also be noted that the described elements may be combined in any suitable way in the different aspects.

[0064] When an element such as a layer, film, region, or substrate is described as being "on" another element, it may be directly on top of the other element, or there may be intervening elements. In contrast, when an element is described as being "directly on" another element, there are no intervening elements.

[0065] Unless otherwise indicated herein, all examination standards are the most recent standard in effect on the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the examination standard appears.

[0066] Unless otherwise specified, all technical and scientific terms used herein have the meaning commonly attributed to such terms to one of ordinary skill in the art to which this disclosure belongs.

[0067] Although the above disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes may be made and equivalent elements may be substituted without departing from its scope. Furthermore, many changes may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Therefore, the present disclosure is not intended to be limited to the specifically disclosed embodiments, but is intended to include all embodiments falling within its scope.

Claims

[1] A roll-to-roll system for the production of electrodes, the system comprising: a calender module comprising a pair of calender rolls separated by a gap, the gap comprising a distance selected to accommodate a current collector, the current collector comprising an uncoated portion and a coated portion having an electrode active material having a first thickness thereon; an unwinding module located upstream of the calendering module; a collector module located downstream of the calender module; and one or more idler rollers arranged between the unwinding module and the collector module; wherein an idler roll of the one or more idler rolls comprises a collet having a second thickness selected based on the first thickness to span underlying portions of the current collector, the collet being aligned with the uncoated portion of the current collector. [2] The roll-to-roll system of claim 1, wherein the calendering pressures occurring at the calendering module serve to correct the over-tension applied to the uncoated portion of the current collector, thereby reducing wrinkling of the film after calendering. [3] Roll-to-roll system according to claim 1, wherein the clamping sleeve is attached to a respective idler roller of the one or more idler rollers by means of a press fitting and / or an adhesive. [4] Roll-to-roll system according to claim 1, wherein the clamping sleeve is fastened to the respective idler roller of the one or more idler rollers by one or more set screws. [5] Roll-to-roll system according to claim 1, wherein the clamping sleeve is attached to a respective one of the one or more idler rollers by means of one or more leaf springs. [6] Roll-to-roll system according to claim 1, wherein the clamping sleeve is conical. [7] The roll-to-roll system of claim 1, wherein the collet comprises a patterned texture having one or more projections, one or more depressions, or one or more grooves. [8] The roll-to-roll system of claim 1, wherein a line speed and / or tensile force of the current collector is adjusted to adjust the overvoltage applied to the uncoated portion of the current collector. [9] The roll-to-roll system of claim 8, further comprising one or more dancer rolls disposed between the unwind module and the collector module. [10] A roll-to-roll system according to claim 9, wherein the tensile force of the current collector is adjusted by shifting a position of at least one of the one or more dancer rolls.

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