Method and apparatus for the dry, solvent free manufacture of electrodes using powders

Abstract

A method for dry manufacturing an electrode for an energy storage device includes (a) pre-calendering a solvent free dry powder on a substrate to decrease the porosity ε of the dry powder to a predetermined critical porosity εc. In addition, the method includes (b) calendering the dry powder on the substrate after (a) to further decrease the porosity ε of the dry powder from the predetermined critical porosity εc to a predetermined target porosity εt that is less than the predetermined critical porosity εc.

Description

2238-23501TAMUS 6523METHOD AND APPARATUS FOR THE DRY, SOLVENT FREE MANUFACTURE OF ELECTRODES USING POWDERSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. provisional patent application Serial No. 63 / 700,250 filed September 27, 2024, and entitled “Method and Apparatus for the Dry, Solvent Free Manufacture of Electrodes Using Powders," which is hereby incorporated herein by reference in its entirety for all purposes.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.BACKGROUND

[0003] The disclosure relates generally to methods and apparatus for dry manufacturing electrodes for energy storage devices such as batteries (e.g., lithium ion batteries, sodium ion batteries, solid state batteries, etc.). More specifically, the disclosure relates to methods and apparatus for dry manufacturing electrodes having reduced defects and improved quality.

[0004] Li-ion battery (LIB) production capacity is projected to grow significantly in the coming years. Consequently, it is anticipated that about a 4x increase of manufacturing capacity will need to be added over the next decade to meet the demand for Li-ion batteries. Argonne National Lab has estimated that the battery electrode manufacturing equipment alone may cost about $66 million for each 5 GWh plant. To build up 1 ,000 GWh of new capacity, 200 such plants need to be constructed.

[0005] The rapid growth in battery manufacturing imposes significant impacts on energy consumption and greenhouse gas emissions. For example, a current 5GWh Li-ion battery plant consumes about 565 GWh / year of electricity. In particular, conventional methods for manufacturing electrodes for Li-ion batteries utilize slurry casting techniques that require energy intensive drying, environmentally hazardous solvents, and a relatively large footprint.BRIEF SUMMARY OF THE DISCLOSURE2238-23501TAMUS 6523

[0006] Methods for dry manufacturing electrodes for energy storage devices are disclosed herein. In one embodiment, a method for dry manufacturing an electrode for an energy storage device comprises (a) pre-calendering a solvent free dry powder on a substrate to decrease the porosity E of the dry powder to a predetermined critical porosity EC. In addition, the method comprises (b) calendering the dry powder on the substrate after (a) to further decrease the porosity E of the dry powder from the predetermined critical porosity scto a predetermined target porosity stthat is less than the predetermined critical porosity EC.

[0007] Embodiments of systems for dry manufacturing electrodes for energy storage devices are disclosed herein. In one embodiment, a system for dry manufacturing an electrode for an energy storage device comprises a first pair of vertically-spaced precalendering rollers configured to apply a first compaction load to a solvent free dry powder on a substrate to decrease a porosity E of the dry powder to a predetermined critical porosity EC. In addition, the method comprises a pair of vertically-spaced calendering rollers spaced apart from the first pair of vertically-spaced pre-calendering rollers. The pair of vertically-spaced calendering rollers are configured to apply a second compaction load to the dry powder on the substrate to further decrease the porosity E of the dry powder from the predetermined critical porosity ECto a predetermined target porosity £t.

[0008] In another embodiment, a system for dry manufacturing an electrode for an energy storage device comprises a first pair of vertically-spaced pre-calendering rollers configured to apply a first compaction load to a solvent free dry powder on a substrate to decrease a porosity E of the dry powder to an intermediate porosity E,. In addition, the system comprises a second pair of vertically-spaced pre-calendering rollers positioned downstream of the first pair of vertically-spaced pre-calendering rollers relative to a feed direction of the substrate. The second pair of vertically- spaced pre-calendering rollers are configured to apply a second compaction load to the dry powder on the substrate to decrease the porosity E of the dry powder from the intermediate porosity £i to a predetermined critical porosity EC. Further, the system comprises a pair of vertically-spaced calendering rollers positioned downstream of the second pair of vertically-spaced pre-calendering rollers relative to the feed direction of the substrate. The pair of vertically-spaced calendering rollers are configured to apply a third compaction load to the dry powder on the substrate to further decrease the2238-23501TAMUS 6523 porosity e of the dry powder from the predetermined critical porosity ecto a predetermined target porosity £t.

[0009] Embodiments described herein comprise a combination of features and characteristics intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical characteristics of the disclosed embodiments in order that the detailed description that follows may be better understood. The various characteristics and features described above, as well as others, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes as the disclosed embodiments. It should also be realized that such equivalent constructions do not depart from the spirit and scope of the principles disclosed herein.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] For a detailed description of various exemplary embodiments, reference will now be made to the accompanying drawings in which:

[0011] FIG. 1 is a schematic side view of an embodiment of a system for drymanufacturing electrodes for energy storage devices in accordance with principles described herein;

[0012] FIG. 2A is a schematic view of an exemplary micro-particle and a plurality of exemplary nano-particles that can be used to form the dry powder of FIG. 1 ;

[0013] FIG. 2B is a schematic view of an exemplary nano-particle coated microparticle formed from the exemplary micro-particle and exemplary nano-particles of FIG2A;

[0014] FIG. 3 is a schematic view of an embodiment of a method for drymanufacturing electrodes for energy storage devices in accordance with principles described herein;

[0015] FIG. 4 is a schematic side view of an embodiment of a system for drymanufacturing electrodes for energy storage devices in accordance with principles described herein;

[0016] FIG. 5 is a graphical illustration of the compression pressure versus density obtained by confined uniaxial compression of 96N2P2C mixture (96 wt% NMC, 2 wt%2238-23501TAMUS 6523PVDF, and 2 wt% carbon) along with fitted results via modified Heckel model in accordance with Example 1 ;

[0017] FIG. 6 is a graphical illustration of the compression pressure versus porosity as obtained by confined uniaxial compression of 96N2P2C mixture (96 wt% NMC, 2 wt% PVDF, and 2 wt% carbon) along with fitted results via modified Heckel model in accordance with Example 1 .DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad applications, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

[0019] Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

[0020] Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints, and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary.

[0021] In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to... .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct engagement between the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a particular axis (e.g., central axis of a2238-23501TAMUS 6523 body or a port), while the terms “radial” and “radially” generally mean perpendicular to a particular axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. As used herein, the terms “approximately,” “about,” “substantially,” and the like mean within 10% (i.e., plus or minus 10%) of the recited value. Thus, for example, a recited angle of “about 80 degrees” refers to an angle ranging from 72 degrees to 88 degrees.

[0022] As described above, conventional methods for manufacturing electrodes for energy storage devices (e.g., Li-ion batteries, sodium ion batteries, all solid-state batteries, etc.) typically have high energy demands, rely on environmentally hazardous solvents, may require a relatively large footprint, and may not be scalable for large scale production. Dry electrode manufacturing offers a sustainable alternative to traditional solvent-based methods. Unlike solvent methods, which require hazardous solvents like N-Methyl-2-pyrrolidone (NMP) and energy-intensive drying processes, dry manufacturing methods eliminate solvents entirely, thereby reducing environmental impacts, production costs, and energy consumption. The dry manufacturing methods not only simplify manufacturing but also align with industry goals for greener, more efficient production processes while maintaining or even exceeding the mechanical and electrochemical performance of electrodes made by traditional wet solvent-based manufacturing methods. Accordingly, embodiments of systems and methods disclosed herein for manufacturing electrodes for energy storage devices are directed to solvent free (or “dry”) techniques that are environmentally friendly, and that offer the potential to reduce energy consumption and greenhouse gas emissions.

[0023] One step in the formation of an electrode from solvent-free, dry powder involves compressing and compacting the dry powder with rollers onto an underlying substrate (e.g., a current collector such as a metal foil) to enable the dry powder to adhere to the substrate to fabricate the electrode with a desired combination of porosity, mechanical integrity, and interfacial adhesion. In general, the process of compressing and compacting the dry powder onto an underlying substrate to form the electrode may be referred to herein as “calendering.” It has been discovered that dividing calendaring of the dry powder into one or more pre-calendering steps followed by a final calendaring step based on the porosity of the dry powder offers the potential to enhance the quality of the resulting electrode. As is known in the art, the term2238-23501TAMUS 6523“porosity” refers to the ratio of the volume of voids or empty spaces (pores) within a material to its total volume, typically expressed as a percentage or fraction.

[0024] Referring now to FIG. 1 , an embodiment of a system 100 for dry manufacturing electrodes for energy storage devices (e.g., Li-ion batteries, solid-state batteries, etc.) is shown. In this embodiment, system 100 produces a continuous sheet or layer of electrode material 101 from a solvent-free, dry powder 135 on a web or substrate 105. The electrode material 101 and substrate 105 can be cut as desired to produce a plurality of individual electrodes for use in energy storage devices. Accordingly, for purposes of clarity and further explanation, electrode material 101 may also be referred to herein as electrode 101. It is to be understood that powder 135 and electrode material 101 formed therefrom are “dry,” meaning neither includes any solvent.

[0025] In this embodiment, system 100 includes an unwinding or supply roller 110 and a winding or receiving roller 120 horizontally spaced from the supply roller 110. Supply roller 110 generally provides a continuous sheet of substrate 105 on which electrode 101 is formed with system 100. In general, substrate 105 can be unwound from supply roller 110, or provided by another roller (not shown) and passed over supply roller 110 to the remainder of system 100. Supply roller 110 rotates in a rotational direction 111 about a central axis 115 to supply substrate 105 in a generally horizontal feed direction 106 through system 100. As shown in the side view of FIG. 1 , rotational direction 111 is counterclockwise and feed direction 106 is to the left. In embodiments described herein, substrate 105 is fed from supply roller 110 and moved in feed direction 106 at a feed rate or speed greater than 0.0 m / min and less than or equal to 120.0 m / min. For purposes of clarity and further explanation, the terms “upstream” and “downstream” are used herein to refer to positions of different components of system 100 relative to feed direction 106.

[0026] Receiving roller 120 is downstream of supply roller 110 and generally receives the continuous sheet of substrate 105 and electrode 101 formed thereon. Substrate 105 and electrode 101 can be wound onto receiving roller 120, or passed over receiving roller 120 to another roller (not shown). Receiving roller 120 rotates in a rotational direction 121 about a central axis 125 to receive substrate 105 and electrode 101 along the generally horizontal feed direction 106. As shown in FIG. 1 , rotational direction 121 is counterclockwise, and thus, rotational directions 111 , 121 of supply roller 110 and receiving roller 120, respectively, are the same. As previously2238-23501TAMUS 6523 described, in embodiments described herein, substrate 105 is moved in feed direction106 at a feed rate or speed ranging greater than 0.0 m / min and less than or equal to 120.0 m / min, and thus, substrate 105 and electrode 101 formed thereon are received by receiving roller 120 at that same rate.

[0027] In embodiments described herein, substrate 105 comprises a conductive base107 in the form of a sheet of conductive material and a friction enhancing treatment108 applied to the upper surface of base 107. Surface treatment 108 offers the potential to improve performance of electrode 101 by enhancing adhesion and electrical conductance between electrode 101 and substrate 105. In general, base 107 can be a thin sheet of any suitable conductive material with electrochemical stability (e.g., little to no corrosion or dissolution in electrolyte under operating voltage) and mechanical properties sufficient for handling by system 100 without physical damage (e.g., can handle calendering, winding, cycling stresses, etc.). Cost, scalability, and density / weight may also be taken into consideration in assessing potential materials for base 107. Examples of suitable materials for base 107 include, without limitation, aluminum foil (e.g., 10.0 to 20.0 pm thickness), copper foil (e.g., 6.0 to 12.0 pm thickness), nickel foil, stainless steel foil, or titanium foil.

[0028] In general, friction enhancing treatment 108 on the surface of base 107 can be a material coating / layer or texture applied to the surface of base 107. In embodiments where friction enhancing treatment 108 is a coating, any suitable material for (i) increasing the coefficient of friction between the surface of substrate 105 and dry powder 135 and (ii) increasing the adhesion between electrode 101 and substrate 105 including, without limitation, a carbon coating or a polyvinylidene fluoride (PVDF) coating. In an embodiment, base 107 is aluminum foil and friction enhancing treatment 108 is carbon. In embodiments where friction enhancing treatment 108 is a texture applied to the surface of base 107, the texture can be any suitable texture for (i) increasing the coefficient of friction between the surface of substrate 105 and dry powder 135, (ii) increasing the adhesion between electrode 101 and substrate 105, and (iii) increasing the interaction between the surface of substrate 105 and dry powder 135 including, without limitation, a laser etched, induced texture, or the like. Although substrate 105 includes surface treatment 108 in this embodiment, in other embodiments, surface treatment 108 may not be provided.

[0029] Substrate 105 has a substantially uniform thickness T s measured perpendicularly between its upper and lower surfaces. In embodiments described2238-23501TAMUS 6523 herein, the thickness T105 of substrate 105 ranges from 1.0 m to 200.0 pm, and alternatively ranges from 1.0 pm to 30.0 pm. In addition, in this embodiment, substrate 105 has a uniform width measured perpendicular to feed direction 106 between the parallel, lateral sides or edges of substrate 105.

[0030] Referring still to FIG. 1 , in this embodiment, system 100 also includes a powder supply or delivery device 130, a pair of vertically arranged spreading rollers 160, 161 , a pair of vertically arranged pre-calendering rollers 170, 171 horizontally spaced from and downstream of spreading rollers 160, 161 , and a pair of vertically arranged calendering rollers 180, 181 horizontally spaced from and downstream of precalendering rollers 170, 171. Powder delivery device 130, spreading rollers 160, 161 , pre-calendering rollers 170, 171 , and calendering rollers 180, 181 are generally horizontally arranged side-by-side. More specifically, powder delivery device 130 is horizontally positioned between supply roller 110 and spreading rollers 160, 161 , spreading rollers 160, 161 are horizontally positioned between pre-calendering rollers 170, 171 and powder delivery device 130, pre-calendering rollers 170, 171 are horizontally positioned between spreading rollers 160, 161 and calendering rollers 180, 181 , and calendering rollers 180, 181 are horizontally positioned between precalendering rollers 170, 171 and receiving roller 120. Thus, powder delivery device 130 is downstream of supply roller 110, spreading rollers 160, 161 are downstream of powder delivery device 130, pre-calendering rollers 170, 171 are downstream of spreading rollers 160, 161 , and calendering rollers 180, 181 are downstream of precalendering rollers 170, 171. Although spreading rollers 160, 161 are included in system 100, in other embodiments, spreading rollers 160, 161 may not be included and / or a single, upper spreading roller may be included between powder delivery device 130 and pre-calendering rollers 170, 171.

[0031] Powder delivery device 130 generally feeds or delivers a dry powder 135 that is used to form electrode 101 on substrate 105. In particular, powder delivery device 130 deposits a continuous layer 139 of dry powder 135 onto the upper surface of substrate 105, which carries and moves layer 139 of dry powder 135 in feed direction 106 through system 100. In this embodiment, powder delivery device 130 includes a powder feeder 131 and a powder de-lumping device 134 positioned below powder feeder 131. In general, powder feeder 131 can be any suitable device for controllably feeding a dry powder such as a volumetric feeder (e.g., as screw feeder), a vibratory feeder, a gravimetric feeder (e.g., as loss-in-weight feeders), a hopper-based gravity2238-23501TAMUS 6523 feeder, or the like. Powder feeder 131 deposits layer 139 of dry powder 135 onto the upper surface of substrate 105, which carries and moves dry powder 135 in feed direction 106 through the remainder of system 100. For most electrode manufacturing operations, the mass feed rate of dry powder 135 onto substrate 105 by powder delivery system 130 is greater than 0.0 gram / s and less than or equal to 300.0 gram / s per 100 mm of width W105 of substrate 105.

[0032] De-lumping device 134 is positioned between powder feeder 131 and substrate 105 to break-up any clumps in dry powder 135 before it is deposited onto substrate 105. In this embodiment, de-lumping device 134 is an ultrasonic sieve, and more specifically, an ultrasonic sieve that vibrates at a frequency of 33-37 kHz and has a sieve mesh size ranging from 200 pm to 40 pm. Thus, dry powder 135 exits powder feeder 131 and passes through de-lumping device 134, which breaks up any clumps of dry powder 135 before dry powder 135 is deposited on substrate 105. As shown in FIG. 1 and described in more detail below, spreading rollers 160, 161 spread the deposited layer 139 of dry powder 135 on substrate 105, whereas pre-calendering rollers 170, 171 and calendering rollers 180, 181 compress and compact the deposited layer 139 of dry powder 135 to form electrode 101 on substrate 105. More specifically, and as will be described in more detail below, pre-calendering rollers 170, 171 compress and compact the deposited layer 139 of dry powder 135 to a predetermined threshold or critical porosity £c, and then calendaring rollers 180, 181 compress and compact the deposited layer 139 of dry powder 135 from the predetermined critical porosity ECto a final or target porosity £tto form electrode 101 . For purposes of clarity and further explanation, the layer 139 of dry powder 135 spread on substrate by spreading rollers 160, 161 may also be referred to herein as “spread” layer 139 of dry powder 135, the spread layer 139 of dry powder 135 compressed and compacted by pre-calendering rollers 170, 171 may also be referred to herein as “precalendered” layer 139 of dry powder 135, and the pre-calendered layer 139 of dry powder 135 that is further compressed and compacted by calendering rollers 180, 181 may also be referred to as “calendered” layer 139 of dry powder 135. Calendered layer 139 of dry powder 135 defines electrode 101 on substrate 105.

[0033] In embodiments in which electrode 101 is manufactured for use in Li-ion batteries, dry powder 135 includes an active material, a binder, and a conductive additive (each in a powder form). Optionally, one or more solid-state electrolytes (also in a powder form) can be included in dry powder 135 when electrode 101 is2238-23501TAMUS 6523 manufactured for use in solid-state Li-ion batteries. Regardless of whether electrode 101 is manufactured for use in a Li-ion battery or an all-solid-state battery, dry powder 135 comprises at least 70 wt% active material and less than 30 wt% other components. The active material can include, without limitation, cathode materials such as lithium transition metal oxides, lithium transition metal sulfides, lithium transition metal phosphates (e.g., lithium nickel-cobalt-manganese oxide (NMC), lithium iron phosphate (LFP), lithium cobalt oxide (LCO)), sodium manganese oxide, sodium cobalt phosphate, sodium nickel phosphate, sodium iron phosphate, sodium manganese phosphate, sodium iron hexacyanoferrate, sodium manganese hexacyanoferrate, or combinations thereof; and anode materials such as graphite, carbonaceous anode materials (e.g., graphite, graphene, disordered carbon, and the like), lithium transition metal oxides, Si-based composites, or combinations thereof. The binder can include, without limitation, a thermoplastic polymer such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), poly(vinyl alcohol) (PVA), polyethylene oxide (PEO), poly(methyl methacrylate) (PMMA), styrenebutadiene rubber (SBR), polyurethanes, ethylene vinyl acetate (EVA), acrylic polymers, polyethylene (PE), other thermoplastic polymer, or combinations thereof. The conductive additive can include, without limitation, one or more of carbon black (CB), nanoparticles, nanowires, nanotubes (e.g., carbon nanotubes (CNT)), carbon fibers, graphene, nanosilica, nanoalumina, or the like. The one or more solid-state electrolytes can include, without limitation, solid polymer electrolyte PEO / LiTFSI, lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanate (LLTO), LisInCh, LiePSsCI, silica nanofillers, AI2O3 nanofillers, LLZO nanofillers, or combinations thereof. In some embodiments, the solid-state electrolyte can function as a binder, in which case the binder may be described as comprising a solid-state electrolyte. In some embodiments, the solid-state electrolyte can function as an active material, in which case the active material may be described as comprising a solid-state electrolyte.

[0034] In some embodiments, dry powder 135 comprises a plurality of micro-particles at least partially coated in a plurality of nano-particles (i.e., each micro-particle is at least partially coated in a plurality of nano-particles). As used herein, the term “microparticle” refers to a single, individual particle, which may comprise, without limitation, a single crystal particle, a polycrystal particle, a partial crystalline particle, a composite particle, or an aggregate or agglomeration of a plurality of smaller particles (e.g., a2238-23501TAMUS 6523 plurality of smaller single crystal particles, a plurality of polycrystal particles, a particle of an amorphous material, a plurality of nano-particles, or combinations thereof), having a size (e.g., diameter or average diameter) greater than or equal to 1.0 pm; and the term “nano-particle” refers to a single, individual particle, which may comprise, without limitation, a single crystal particle, a polycrystal particle, a particle of an amorphous material, or a partial crystalline particle having a size (e.g., diameter or average diameter) less than 1.0 pm. Thus, in embodiments where dry powder 135 comprises a plurality of micro-particles at least partially coated in a plurality of nanoparticles, the micro-particles in dry powder 135 have sizes that are preferably at least 10x the size of the nano-particles. For example, referring briefly to FIG. 2A, a single micro-particle 190 comprising a first material (e.g., an active material), a first plurality of nano-particles 191 comprising a second material (e.g., conductive additive), and a second plurality of nano-particles 192 comprising a third material (e.g., binder) are shown. The micro-particle 190 has a size that is at least 10x the size of the first plurality of nano-particles 191 and the second plurality of nano-particles 192. In FIG. 2B, the micro-particle 190 is shown coated in the nano-particles 191 and the nanoparticles 192 to form one exemplary nano-particles coated micro-particle 193. A plurality of such nano-particle coated micro-particles 193 can be used as dry powder 135.

[0035] In general, the sizes of the various components in dry powder 135 (e.g., active material, binder, conductive additive, solid-state electrolytes, etc.) can range from nanometers (e.g., nano-particles) to tens of microns (e.g., micro-particles). For example, the active materials may have sizes ranging from 0.5 pm to 40 pm, whereas the conductive additives and some of the solid polymer electrolyte (e.g., nanofillers) can have sizes less than 1 pm. In general, any one or more of the individual components in dry powder 135 (e.g., active material, binder, conductive additive, solid- state electrolytes, etc.) can serve as and define the micro-particles, and any one or more of the individual components in dry powder 135 (e.g., active material, binder, conductive additive, solid-state electrolytes, etc.) can serve as and define the nanoparticles. For example, in FIGS. 2A and 2B, the micro-particle 190 may comprise an active material, the first plurality of nano-particles 191 may comprise conductive additives, and the second plurality of nano-particles 192 may comprise binder.

[0036] In some embodiments, each micro-particle (e.g., each micro-particle 190) preferably has a size ranging from 1.0 pm to 30.0 pm and each nano-particle2238-23501TAMUS 6523 preferably has a size ranging from 1.0 nm to 500.0 nm to advantageously enhance flowability of dry powder 135. In general, the nano-particle coated micro-particles forming dry powder 135 can be prepared by any suitable means known in the art (e.g., intensive dry mixing) and then added to powder feeder 131 for controlled deposition on substrate 105.

[0037] In addition to the active material, the binder, the conductive additive, and other optional components described above (e.g., solid-state electrolytes for solid-state Li- ion batteries), the dry powder 135 can optionally include other types of nano-particles as functional additives to fine-tune particular aspects of battery performance such as safety, energy density, integrity, rate performance, and cycle life. For instance, TiC>2 nano-particles can be added in graphite (micro-particle) anode to improve rate capability and thermal stability. Further, particles or units of nanomaterials such as nanowires and / or nanotubes can be used in conjunction with nano-particles or as an alternative to nano-particles to coat the micro-particles to achieve similar effects. Examples of such other nanomaterials include hollow nano-particles, core-shell nanoparticles, nano-dots, nano-tubes, nano-rods, nano-wires, nano-sheets, (graphene quantum dots, silicon nano-wires, carbon nano-tubes, silicon nano-tubes, nano-sized carbon fiber, mesoporous carbon, graphene, etc.). Any such particles or units of nanomaterials preferably have at least one dimension less than 1.0 pm, and more preferably at least one dimension less than 100 nm.

[0038] As previously described, in some embodiments, dry powder 135 comprises a plurality of nano-particle coated micro-particles 193. However, in other embodiments, dry powder 135 may comprise a mixture of other types of particles other than nanoparticle coated micro-particles 193.

[0039] Referring again to FIG. 1 , in this embodiment, spreading rollers 160 161 uniformly spread layer 139 of dry powder 135 deposited on the upper surface of substrate 105, then pre-calendering rollers 170, 171 compress and compact the spread layer 139 of dry powder 135 deposited on the upper surface of substrate 105, and then calendering rollers 180, 181 further compress and compact pre-calendered layer 139 of dry powder 135 to form electrode 101. Thus, in embodiments described herein, spreading rollers 160, 161 generally function to spread layer 139 of dry powder 135 but do not compact or compress layer 139, and further, do not facilitate adhesion of layer 139 of dry powder 135 to substrate 105; whereas pre-calendering rollers 170, 171 and calendering rollers 180, 181 function to compress and compact layer 139 of2238-23501TAMUS 6523 dry powder 135 and facilitate adhesion of layer 139 of dry powder 135 to substrate 105. Accordingly, pre-calendering rollers 170, 171 and calendering rollers 180, 181 may also be referred to herein as “compaction” rollers.

[0040] In this embodiment, spreading rollers 160, 161 are vertically arranged one- above-the-other, and thus, may be described as an upper roller 160 and a lower roller 161. Each roller 160, 161 has a central axis 165 about which it may rotate, and a radially outer cylindrical surface 162. In this embodiment, spreading rollers 160, 161 are positioned such that central axes 165 are disposed in a common vertical plane. Consequently, the uppermost portion of outer surface 162 of lower roller 161 is directly, vertically opposed to the lowermost potion of outer surface 162 of upper roller 160. The lower portion of upper roller 160 directly contacts and spreads dry powder 135 on substrate 105, while the upper portion of lower roller 161 directly contacts and supports the lower surface of substrate 105. In general, upper roller 160 can rotate in a direction 166 about axis 165 (counterclockwise in FIG. 1), rotate in a direction 166’ about axis 165 that is opposite direction 166 (clockwise in FIG. 1 ), or not rotate about axis 165. Lower roller 161 rotates in direction 166 about its axis 165 (counterclockwise in FIG. 1 ). In this embodiment, lower spreading roller 161 rotates at a uniform rotational speed, and upper spreading roller 160 (if it rotates) also rotates at a uniform speed. In embodiments described herein, the rotational speed of lower spreading roller 161 (and upper spreading roller 160 if it rotates) is preferably ranges from 0.1 to 600.0 RPM. In some embodiments, both spreading rollers 160, 161 have the same rotational speed, however, in other embodiments, the rotational speeds of spreading rollers 160, 161 can be different.

[0041] Spreading rollers 160, 161 are vertically-spaced apart a sufficient distance to provide a gap Gsmeasured vertically from the upper surface of substrate 105 to the lowermost portion of outer surface 162 of upper roller 160. Thus, the vertical distance between spreading rollers 160, 161 is equal to the thickness Tws plus gap Gs. It should be appreciated that gap Gsdefines the vertical thickness to which layer 139 of dry powder 135 is spread on substrate 105 by spreading rollers 160, 161. In embodiments described herein, gap Gs, and hence the vertical thickness of spread layer 139 of dry powder 135 after passing between spreading rollers 160, 161 , ranges from 0.00 to 3,000.00 pm, and alternatively ranges from 20.00 pm to 500.00 pm.

[0042] In embodiments described herein, outer cylindrical surface 162 of upper spreading roller 160 that directly contacts dry powder 135 is preferably a low friction2238-23501TAMUS 6523 surface to reduce friction between spreading roller 160 and dry powder 135. The low friction surface preferably exhibits an average surface roughness Ra less than 0.05 pm, and alternatively less than 0.02 pm. In general, the low friction surface can be defined by a surface treatment or a coating. Examples of surface treatments and coatings include, without limitation, a polished surface, a carbide coating, a ceramic coating, chrome-plating, a PTFE coating, and a graphite coating (or the entire roller 160 can be made of a graphite material). The material selected for the outer cylindrical surface 162 of spreading roller 170 that directly contacts dry powder 135 is preferably selected to reduce and / or prevent electrostatic charging or attachment of dry powder 135. Examples of suitable materials include conductive materials such as steel or chrome, which are preferably grounded.

[0043] Referring still to FIG. 1 , pre-calendering rollers 170, 171 are vertically arranged one-above-the-other, and thus, may be described as an upper roller 170 and a lower roller 171. Each roller 170, 171 has a central axis 175 about which it rotates, and a radially outer cylindrical surface 172. In this embodiment, pre-calendering rollers 170, 171 are positioned such that central axes 175 are disposed in a common vertical plane. However, in other embodiments, the central axes of the pre-calendering rollers (e.g., central axes 175 of pre-calendering rollers 170, 171) may not lie in a common vertical plane. Consequently, the uppermost portion of outer surface 172 of lower roller 171 is directly, vertically opposed the lowermost potion of outer surface 172 of upper roller 170. The lower portion of upper roller 170 directly contacts, compresses, and compacts spread layer 139 of dry powder 135 on substrate 105 to begin formation of electrode 101 on substrate 105, while the upper portion of lower roller 171 directly contacts and supports the lower surface of substrate 105. In this embodiment, precalendering rollers 170, 171 , and in particular upper roller 170, compacts and compresses spread layer 139 of dry powder 135 to the pre-determined critical porosity £cof the dry powder 135, which will be described in more detail below.

[0044] In general, upper roller 170 can rotate in a direction 176 about axis 175 (counterclockwise in FIG. 1 ) or rotate in a direction 176’ about axis 175 that is opposite direction 176 (clockwise in FIG. 1 ). For most applications, upper roller 170 rotates in direction 176’ such that it moves in the same direction as feed direction 106 proximal substrate 105 and dry powder 135. Lower roller 171 rotates in direction 176 about its axis 175 (counterclockwise in FIG. 1 ) such that it moves in the same direction as feed direction 106 proximal substrate 105. Thus, in most applications, rotational directions2238-23501TAMUS 6523176’, 176 of pre-calendering rollers 170, 171 , respectively, are opposite to each other. In embodiments described herein, the rotational speed of each pre-calendering roller 170, 171 preferably ranges from 0.1 to 600.0 RPM. In some embodiments, both precalendering rollers 170, 171 have the same rotational speed, however, in other embodiments, the rotational speeds of pre-calendering rollers 170, 171 can be different.

[0045] In embodiments described herein, pre-calendering rollers 170, 171 apply a compaction load of up to about 3.5 tons / cm to compress dry powder 135 (along a line contact between roller 170 and dry powder 135), and more preferably apply a compaction load ranging from 0.01 to 1.5 tons / cm to compress spread layer 139 of dry powder 135 (along a line contact between roller 170 and dry powder 135).

[0046] Pre-calendering rollers 170, 171 are vertically-spaced apart a sufficient distance to provide a gap Gpcmeasured vertically from the upper surface of substrate 105 to the lowermost portion of outer surface 172 of upper roller 170. Thus, the vertical distance between pre-calendering rollers 170, 171 is equal to the thickness T s plus gap Gpc. It should be appreciated that gap Gpcdefines the vertical thickness to which spread layer 139 of dry powder 135 is compressed and compacted on substrate 105 by pre-calendering rollers 170, 171. In embodiments described herein, gap Gpc, and hence the vertical thickness of dry powder 135 after passing between pre-calendering rollers 170, 171 , ranges from 0.0 to 3,000.0 pm, and alternatively ranges from 0.0 pm to 500.0 pm. As pre-calendering rollers 170, 171 compress and compact spread layer 139 of dry powder 135 downstream of spreading rollers 160, 161 , gap Gpcis less than gap Gs. The ratio of gaps Gs / Gpc preferably ranges from 1.2 to 10.0. As previously noted and will be described in more detail below, in embodiments described herein, pre-calendering rollers 170, 171 compress and compact spread layer 139 such that the porosity E of spread layer 139 decreases to a predetermined critical porosity EC. Thus, the gap Gpc and the ratio of gaps Gs / Gpc are preferably set to yield the predetermined critical porosity Ec of layer 139 of dry powder 135.

[0047] Referring still to FIG. 1 , in this embodiment, calendering rollers 180, 181 are vertically arranged one-above-the-other, and thus, may be described as an upper roller 180 and a lower roller 181. Each roller 180, 181 has a central axis 185 about which it rotates, and a radially outer cylindrical surface 182. In this embodiment, calendering rollers 180, 181 are positioned such that central axes 185 are disposed in a common vertical plane. However, in other embodiments, the central axes of the2238-23501TAMUS 6523 calendering rollers (e.g., central axes 185 of calendering rollers 180, 181) may not lie in a common vertical plane. Consequently, the uppermost portion of outer surface 182 of lower roller 181 is directly, vertically opposed the lowermost potion of outer surface 182 of upper roller 180. The lower portion of upper roller 180 directly contacts, and further compresses and compacts pre-calendered layer 139 on substrate 105 to form calendered layer 139 of dry powder 135, which defines electrode 101. In other words, the calendered layer 139 resulting from compression and compaction by calendering rollers 180, 181 completes the formation of electrode 101 on substrate 105. During formation of electrode 101 on substrate 105, the upper portion of lower roller 181 directly contacts and supports the lower surface of substrate 105. In this embodiment, calendering rollers 180, 181 , and in particular upper roller 180, compacts and compresses pre-calendered layer 139 of dry powder 135 to the pre-determined target porosity et, which will be described in more detail below.

[0048] In general, upper roller 180 can rotate in a direction 186 about axis 185 (counterclockwise in FIG. 1 ) or rotate in a direction 186’ about axis 185 that is opposite direction 186 (clockwise in FIG. 1 ). For most applications, upper roller 180 rotates in direction 186’ such that it moves in the same direction as feed direction 106 proximal substrate 105 and dry powder 135. Lower roller 181 rotates in direction 186 about its axis 185 (counterclockwise in FIG. 1 ) such that it moves in the same direction as feed direction 106 proximal substrate 105. Thus, in most applications, rotational directions 186’, 186 of calendering rollers 180, 181 , respectively, are opposite to each other. In embodiments described herein, the rotational speed of each calendering roller 180, 181 preferably ranges from 0.1 to 600.0 RPM. In some embodiments, both calendering rollers 180, 181 have the same rotational speed, however, in other embodiments, the rotational speeds of calendering rollers 180, 181 can be different.

[0049] In embodiments described herein, calendering rollers 180, 181 apply a compaction load of up to about 3.5 tons / cm to compress dry powder 135 (along a line contact between roller 180 and dry powder 135), and more preferably apply a compaction load ranging from 0.01 to 1.5 tons / cm to compress dry powder 135 (along a line contact between roller 180 and dry powder 135).

[0050] Calendering rollers 180, 181 are vertically-spaced apart a sufficient distance to provide a gap Gcmeasured vertically from the upper surface of substrate 105 to the lowermost portion of outer surface 182 of upper roller 180. Thus, the vertical distance between calendering rollers 180, 181 is equal to the thickness T s plus gap Gc. It2238-23501TAMUS 6523 should be appreciated that gap Gcdefines the vertical thickness to which dry powder 135 is compacted on substrate 105 by calendering rollers 180, 181 to form electrode 101 . Thus, gap Gcdefines the thickness of electrode 101. In embodiments described herein, gap Gc, and hence the vertical thickness of dry powder 135 after passing between calendering rollers 180, 181 , ranges from 0.0 pm to 3,000.0 pm, and alternatively ranges from 0.0 pm to 500.0 pm. As calendering rollers 180, 181 compress and compact pre-calendered layer 139 downstream of pre-calendering rollers 170, 171 , gap Gcis less than gap Gpc. The ratio of gaps Gpc / Gc preferably ranges from 1.00 to 100.00. As previously noted and will be described in more detail below, in embodiments described herein, calendering rollers 180, 181 compress and compact pre-calendered layer 139 such that the porosity £ of pre-calendered layer 139 decreases to a predetermined target porosity £t. Thus, the gap Gc and the ratio of gaps Gpc / Gc are preferably set to yield the predetermined target porosity etof layer 139 of dry powder 135.

[0051] As previously described, substrate 105 may have a friction enhancing treatment 108 to increase a coefficient of friction P105-135 between substrate 105 and dry powder 135. In some embodiments, outer surface 182 of upper calendering roller 180 may include a friction reducing treatment to decrease the coefficient of friction P180-135 between outer surface 182 of upper calendering roller 180 and dry powder 135. Notwithstanding the option of providing substrate 105 with a surface treatment and / or providing outer surface 182 of upper roller 180 with a surface treatment, in embodiments described herein, the coefficient of friction P105-135 between substrate 105 and dry powder 135 is relatively high and the coefficient of friction P180-135 between outer surface 182 of upper roller 180 and dry powder 135 is relatively low to enhance adhesion between substrate 105 and dry powder 135.

[0052] Referring now to FIG. 3, an embodiment of a method 200 for manufacturing electrode 101 on substrate 105 is shown. Method 200 is performed with system 100 previously described and shown in FIG. 1 , and thus, will be described with reference to system 100.

[0053] In this embodiment, method 200 begins in block 201 in which dry powder 135 is prepared. As described above, dry powder 135 comprises a plurality of nano-particle coated micro-particles (e.g., nano-particle coated micro-particles 193) and is “dry” (i.e., does not include any solvent and is not prepared using any solvent). Next, in block 202, powder feeder 131 of powder delivery device 130 is loaded with dry powder 135,2238-23501TAMUS 6523 and in block 203, substrate 105 is moved in feed direction 106 via rollers 110, 120. Moving now to block 204, dry powder 135 is deposited on substrate 105 as layer 139 via powder delivery device 130. As previously described, dry powder 135 passes from powder feeder 131 through de-lumping device 134 in route to substrate 105 to break up any clumps in dry powder 135 before it lands on substrate 105. Substrate 105 (moving in feed direction 106) transports layer 139 of dry powder 135 through the remainder of system 100. In particular, substrate 105 transports dry powder 135 in feed direction 106 from powder delivery device 130 to spreading rollers 160, 161 , then from spreading rollers 160, 161 to pre-calendering rollers 170, 171 , then from precalendering rollers 170, 171 to calendering rollers 180, 181 , and then from calendering rollers 180, 181 to receiving roller 120. During the transport of dry powder 135 through system 100, substrate 105 is vertically supported by rollers 161 , 171 , 181. In particular, at block 205, upper spreading roller 160 spreads layer 139 of dry powder 135 on substrate 105 such that the resulting spread layer 139 has a substantially uniform thickness equal to the gap Gs. Next, in block 206, pre-calendering rollers 170, 171 , and in particular upper pre-calendering roller 170, compress and compact the spread layer 139 of dry powder 135 on substrate 105 to the pre-determined critical porosity scof dry powder 135. The resulting pre-calendered layer 139 has a uniform thickness equal to gap Gpc, which is less than gap Gs. Then, in block 207, calendering rollers 180, 181 , and in particular upper calendering roller 180, further compress and compact the pre-calendered layer 139 of dry powder 135 on substrate 105 to the predetermined target porosity et. The resulting calendered layer 139 has a uniform thickness equal to gap Gc, which is less than gap Gpc, and forms electrode 101 on substrate 105. Electrode 101 disposed and adhered to substrate 105 then passes onto receiving roller 120. It is to be understood that process 200 occurs in a continuous manner such that electrode 101 is continuously formed on substrate 105.

[0054] The sequential pre-calendering of spread layer 139 of dry powder 135 on substrate 105 in block 206 and subsequent calendering of the pre-calendered layer 139 of dry powder 135 on substrate 105 in block 207 of process 200 as described offers the potential to improve the quality of the resulting electrode 101 . For example, improper calendering of dry powder 135, whether performed in a single step or in multiple steps, may result in undesirable defects in the resulting electrode 101 including delamination, textures, patterns or high nonuniformity. Namely, it has been discovered that the porosity e of the pre-calendered layer 139 of dry powder 1352238-23501TAMUS 6523 resulting from block 206, which is then further compacted to the target porosity Et in block 207 impacts the quality of the produced electrode 101. More specifically, in embodiments described herein, compression and compacting of spread layer 139 of dry powder 135 to form electrode 101 is precisely done in multiple sequential steps - a pre-calendering block 206 and a calendering block 207, each subsequent step further decreasing the porosity E of layer 139 of dry powder 135. It should be appreciated that the density p of layer 139 of dry powder 135 generally increases as it is compressed and the porosity E decreases (i.e., porosity E and density p are inversely related). The sequential steps are preferably performed such that spread layer 139 of dry powder 135 is compressed and compacted to a predetermined critical porosity EC, and then further compressed and compacted to a predetermined final or target porosity st. In other words, spread layer 139 of dry powder 135 is “pre-calendered” to the predetermined critical porosity EC(i.e., compressed and compacted to the predetermined critical porosity EC) before the pre-calendered layer 139 of dry powder 135 is “calendered” to the target porosity Et (i.e., compressed and compacted to the target porosity st). For example, as shown in process 200 and described above, layer 139 of dry powder 135 is pre-calendered (compressed and compacted) to the predetermined critical porosity ECby pre-calendering rollers 170, 171 (and in particular upper pre-calendering roller 170) in block 206, and then calendered (further compressed and compacted) to the predetermined target porosity ECby calendering rollers 180, 181 (and in particular upper calendering roller 180). Accordingly, the term “pre-calender” and variants thereof (e.g., “pre-calendering” and “pre-calendered”) may be used herein to describe the process or steps performed (and associated device(s) for doing same) to compress and compact the layer of dry powder (e.g., spread layer 139 of dry powder 135) to the predetermined critical porosity EC, and the term “calender” and variants thereof (e.g., “calendering” and “calendered”) without the prefix “pre-“ may be used herein to describe the process or steps performed (and associated device(s) for doing same) to further compress and compact the layer of dry powder (e.g., pre-calendered layer 139 of dry powder 135) from the predetermined critical porosity ECto the predetermined target porosity £t.

[0055] The predetermined critical porosity ECis the threshold porosity at which the dry powder (e.g., dry powder 135) begins to gain rigidity and deform as a unitary and monolithic body. Before reaching the predetermined critical porosity EC(i.e., when the porosity s is greater than the predetermined critical porosity sc), the individual particles2238-23501TAMUS 6523 in the dry powder (e.g., nano-particle coated micro-particle 193 in dry powder 135) are generally free to move and re-arrange relative to each other and the substrate (e.g., substrate 105). However, at or below the critical porosity £c(i.e., when the porosity E is less than the predetermined critical porosity EC), the individual particles in the dry powder are generally not free to move and re-arrange relative to each other or substrate 105, and thus, can remain sufficiently intact and adhered to the substrate such that the substrate and adhered layer of dry powder compressed thereon can be handled in a vertical orientation without movement or re-arrangement relative to each other. Without being limited by this or any particular theory, as the individual particles in the dry powder are generally free to move and re-arrange relative to each other and the substrate when the porosity E of the dry powder is above the predetermined critical porosity EC, when the porosity of the dry powder is greater than the predetermined threshold porosity ECupon performance of the final calendering step (e.g., block 207), undesirable defects (e.g., delamination, textures, patterns or high nonuniformity) can result in the produced electrode (e.g., electrode 101 ). Accordingly, as described above, in embodiments described herein, the dry powder is pre-calendered to the predetermined critical porosity EC(e.g., block 206), and then calendered to the target porosity EC(e.g., block 207).

[0056] Although the process of pre-calendering the dry powder 135 to the predetermined critical porosity ECand then calendering the pre-calendered dry powder 135 from the predetermined critical porosity ECto the predetermined final target porosity £thas been described in connection with system 100 previously described and shown in FIG. 1 , it should be appreciated that such process can be performed by other systems and devices. In addition, although system 100 and process 200 as previously described include a single pre-calendering step (i.e., block 206) performed by a single pair of pre-calendaring rollers 180, 181 before the final calendering step (block 207), it should be appreciated that multiple pre-calendering steps performed by a plurality of sequential spaced pre-calendering rollers or pairs of rollers can be performed prior to the calendering step with the understanding that the precalendering steps are performed until the layer of dry powder (e.g., layer 139 of dry powder 135) reaches the predetermined critical porosity EC, and then the subsequent calendering step is performed to reduce the porosity E of the layer of dry powder from the predetermined critical porosity ECto the predetermined target porosity £t. For example, FIG. 4 illustrates an embodiment of a system 100’ for dry manufacturing2238-23501TAMUS 6523 electrodes for energy storage devices in accordance with the principles described herein, which is the same as system 100 and functions in the same manner as system 100 previously described with the exception that system 100’ includes two sequentially spaced pairs of pre-calendering rollers 170, 171 that collectively reduce the porosity E of the spread layer 139 of dry powder 135 to the predetermined critical porosity EC. In particular, the first pair of pre-calendering rollers 170, 171 relative to feed direction 106 (right pair of pre-calendering rollers 170, 171 ), pre-calender the spread layer 139 of dry powder to decrease the porosity E of the dry powder 135 to an intermediate porosity si that is greater than the predetermined critical porosity EC, and then second pair of pre-calendering rollers 170, 171 relative to feed direction 106 (left pair of precalendering rollers 170, 171 ), pre-calender the spread layer 139 of dry powder to further decrease the porosity E of the dry powder 135 to from the intermediate porosity £i to the predetermined critical porosity EC.

[0057] In general, the predetermined critical porosity ECfor any given dry powder (e.g., dry powder 135) used to form an electrode (e.g., electrode 101 ) in accordance with embodiments described herein can be determined (e.g., calculated, estimated, etc.) by any suitable technique known in the art. One exemplary technique to determine the predetermined critical porosity ECfor any given dry powder is via a graph illustrating the porosity of the dry powder (expressed as a %) versus the compression pressure applied to the dry powder as described in Example 1 below. To summarize, in such graph-based technique, the porosity E of the dry powder initially decreases sharply (relatively steep slope) as the compression pressure increases up to the critical porosity ECdue to the individual particles in the dry powder being free to move and rearrange themselves relative to each other. However, as the compression pressure continues to increase beyond the critical porosity EC, the porosity E of the dry powder decreases very gradually (a more gradual and less steep slow as compared to the slope below the critical porosity EC) due to the individual particles in the dry powder being unable to move or rearrange themselves relative to each other. Thus, the critical porosity ECis the porosity E along the porosity versus compression pressure graph where the slope abruptly changes from relatively steep to relatively gradual. Without being limited by this or any particular theory, the relatively gradual decrease in the porosity E of the dry powder as the compression pressure increases above the critical porosity ECdespite the inability of the particles of the dry powder to move and rearrange themselves relative to each other may be due to a variety of reasons2238-23501TAMUS 6523 including plastic deformation of individual particles (e.g., micro-particles 190, nanoparticles 191 , 192) within the dry powder. For most compositions of dry powder (e.g., dry powder 135) for use in manufacturing electrodes (e.g., electrode 101 ), the predetermined critical porosity ECranges from 35% to 45%. The predetermined target porosity £t, as dictated by the application of the electrode and customer requirements, typically ranges from 15% to 20%.

[0058] In the manner described, embodiments of systems (e.g., systems 100, 100’) and methods (e.g., method 200) described herein can be used to dry manufacture electrodes for energy storage devices such as batteries (e.g., lithium ion batteries, solid state batteries, etc.). Such embodiments offer the potential to reduce defects in, and hence improve the quality of, the produced electrodes as compared to conventional systems and methods, and are applicable to a wide range of electrode compositions. In addition, the use of “dry” powder to form electrodes in accordance with embodiments described herein can reduce manufacturing costs, manufacturing equipment footprint, and energy consumption by eliminating the need for solvent drying and recovery.EXAMPLES

[0059] The subject matter having been generally described, the following examples are given as particular aspects of the disclosure and are included to demonstrate the practice and advantages thereof, as well as aspects and features of the presently disclosed subject matter. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventors to function well in the practice of the present subject matter, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific aspects which are disclosed and still obtain a like or similar result without departing from the scope of the instant disclosure. It is understood that the examples are given by way of illustration and are not intended to limit the specification of the claims to follow in any manner.EXAMPLE 1

[0060] Mixtures of dry powders for forming electrodes in accordance with principles disclosed herein were prepared. Specific weight ratios of active materials (NMC) and additives (carbon and PVDF binders) were mixed in a mixing container. The resulting mixtures of dry powders comprised microparticles coated with nanoparticles as2238-23501TAMUS 6523 previously described. The microparticles 190 had sizes in the range of 1 .0 to 20.0 pm to enhance flowability and compaction characteristics.

[0061] To characterize the compaction characteristics of each of the mixtures of the dry powders, an Instron 5984 Universal Testing Machine available from Instron Corp, of Norwood, MA, USA, was utilized. In particular, a 1.0 g sample of each mixture of dry powder was loaded into a cylindrical cavity within a die with a diameter of 1 .27 cm for uniaxial pressure compaction measurement. The dry powder was confined within the cylindrical cavity, and compression pressure was applied in a uniaxial direction by a piston. Prior to the compaction process, the dry powders were tapped after loading into the die. During compression of each sample of each mixture of dry powder, the piston was moved at a speed of 1.0 mm / min until a target pressure of 100 MPa was reached. Compression pressure and powder density p curves were obtained for each measurement. The powder density p during compression was calculated based on the die volume at various compression pressures and the mass loaded. The relative density p / p of each sample of each mixture of dry powder was calculated as the ratio of the in-die density p at the applied compression pressure to the theoretical true density of the powder p~, and porosity were calculated according to Equation (1 ) as follows:The true densityof each sample of the compacted mixture of dry powder was obtained by Equation (2) as follows:Wherein, Wi, W2, and W3 represent the weight percentage of the active material NMC, the PVDF binder, and the carbon, respectively, within each mixture of dry powder. Similarly, pi, p2, and ps denote the densities of the active material NMC, PVDF binder, and carbon, respectively, within each mixture of dry powder.

[0062] The measured density versus compression pressure relationship (or porosity and compression pressure) were fitted by the modified Heckel equation shown in Equation (3) as follows:2238-23501TAMUS 6523wherein, a represents the compression pressure, and C is a constant indicating the deformability of the dry powder under investigation. In general, a higher C value indicates greater plasticity. The constant C can be determined from the testing described in this example.

[0063] A representative density versus compression pressure curve for the powder mixture 96N2P2C (96 wt% NMC, 2 wt% PVDF and 2 wt% carbon) is shown in FIG. 5. As shown in FIG. 5, the initial density p, measured approximately -2.36 ± 0.012 g / cm3, which closely resembled the tap density. As compression pressure increased to around -5 MPa, the density p swiftly increased to -2.7-2.8 g / cm3. Beyond this point, the density p increase was more gradual. Accordingly, the compression process could be delineated into two stages: a low-pressure stage (< 5MPa) and a high pressure stage (>5 MPa). Without being limited by this or any particular theory, the pronounced increase in density p observed as the compression pressure increased to 5 MPa could be attributed to particle movements and rearrangements, leading to enhanced packing density. Conversely, the gradual increase in density p as the compression pressure increased above 5 MPa could be attributed to the plastic deformation of the carbon and binder (PVDF) additives surrounding the NMC particles, as well as the plastic deformation of NMC particles themselves.

[0064] The density p versus compression pressure relationships for the powder mixture 96N2P2C (96 wt% NMC, 2 wt% PVDF and 2 wt% carbon) were fitted with the modified Heckel model as shown in FIG. 6, which illustrates the porosity versus compression pressure for the powder mixture 96N2P2C. The fitting revealed the powder mixture 96N2P2C had a critical porosity £c, which represented the porosity £ of the sample of the powder mixture at which movement and rearrangement of the particles within the powder mixture relative to each other had substantially ceased. Consequently, the critical porosity £calso represented a critical state where the powder mixture began to gain rigidity and strength, and hence, began to behave and deform as a single monolithic body. The critical porosity £cfor the powder mixture 96N2P2C, which occurred at the porosity £ in FIG. 6 where the slope abruptly changed from2238-23501TAMUS 6523 steep to gradual, was 42.7 ± 0.19%. As previously described, for most different types of powder mixtures used for the dry, solvent-free manufacture of electrodes, the critical porosities ecranged from 35% to 45%.

[0065] Referring still to FIG. 6, the compression of the powder mixture 96N2P2C could be divided into a pre-calendering phase up to the critical porosity EC, which occurred at compression pressures from 0.0 to about 3.0 MPa and a calendering phase above the critical porosity £c, which occurred at compression pressures greater than 3.0 MPa. For other, different types of powder mixtures, the pre-calendering phase may occur up to a range of different compression pressure such as 0.0 MPa to about 5 MPa, 0.0 MPa to about 10 MPa, or 0.0 MPa to about 20 MPa; and the calendering phase may occur above a range of different pressures such as greater than 5.0 MPa, greater than 10.0 MPa, or greater than 20.0 MPa.

[0066] While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1 ), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.

Claims

1. 2238-23501TAMUS 6523CLAIMSWhat is claimed is:

1. A method for dry manufacturing an electrode for an energy storage device, the method comprising:(a) pre-calendering a solvent free dry powder on a substrate to decrease the porosity £ of the dry powder to a predetermined critical porosity £c; and(b) calendering the dry powder on the substrate after (a) to further decrease the porosity £ of the dry powder from the predetermined critical porosity £cto a predetermined target porosity £t that is less than the predetermined critical porosity £c.

2. The method of claim 1 , wherein the predetermined critical porosity ECranges from 35% to 45%.

3. The method of claim 2, wherein the predetermined target porosity £tranges from 15% to 20%.

4. The method of claim 1 , further comprising determining the predetermined critical porosity £cof the dry powder before (a).

5. The method of claim 4, wherein determining the predetermined critical porosity £cof the dry powder comprises identifying a change in a slope along a porosity versus compression pressure curve for the dry powder.

6. The method of claim 1 , wherein the dry powder comprises a plurality of nanoparticle coated micro-particles.

7. The method of claim 1 , wherein (a) comprises applying a first compaction load to the dry powder to compress the dry powder on the substrate, and wherein (b) comprises applying a second compaction to the dry powder to further compress the dry powder on the substrate, wherein each compaction load ranges from 0.01 tons / cm to 3.5 tons / cm.2238-23501TAMUS 65238. The method of claim 1 , further comprising depositing a dry powder onto a surface of a substrate moving in a feed direction before (a).

9. The method of claim 8, wherein (a) comprises moving the dry powder on the substrate in the feed direction under one or more sequential pre-calendering rollers, and wherein (b) comprises moving the dry powder on the substrate in the feed direction under a calendering roller.

10. The method of claim 9, further comprising spreading the dry powder on the substrate to a substantially uniform thickness before (a).11 . The method of claim 1 , wherein (a) comprises:(a1 ) pre-calendering the dry powder on the substrate to decrease the porosity E of the dry powder to an intermediate porosity E, that is greater than the predetermined critical porosity EC; and(a2) pre-calendering the dry powder on the substrate after (a1 ) to decrease the porosity E of the dry powder from the first porosity E1 to the predetermined critical porosity EC.

12. A system for dry manufacturing an electrode for an energy storage device, the system comprising: a first pair of vertically-spaced pre-calendering rollers configured to apply a first compaction load to a solvent free dry powder on a substrate to decrease a porosity E of the dry powder to a predetermined critical porosity EC; and a pair of vertically-spaced calendering rollers spaced apart from the first pair of vertically-spaced pre-calendering rollers, wherein the pair of vertically- spaced calendering rollers are configured to apply a second compaction load to the dry powder on the substrate to further decrease the porosity E of the dry powder from the predetermined critical porosity scto a predetermined target porosity £t.

13. The system of claim 12, wherein the predetermined critical porosity ECranges from 35% to 45% and the predetermined target porosity stranges from 15% to 20%.2238-23501TAMUS 652314. The system of claim 13, wherein the dry powder comprises a plurality of nanoparticle coated micro-particles.

15. The system of claim 13, wherein the first compaction load is less than 3.5 tons / cm and the second compaction load is less than 3.5 tons / cm.

16. The system of claim 15, wherein each compaction load ranges from 0.01 to 1 .5 tons / cm.

17. The system of claim 12, further comprising a spreading roller upstream of the first pair of vertically-spaced pre-calendering rollers relative to a feed direction of the substrate, wherein the spreading roller is configured to spread the dry powder on the substrate and not compact the dry powder on the substrate.

18. The system of claim 17, further comprising a powder delivery device configured to deposit the dry powder onto the substrate upstream of the spreading roller relative to the feed direction.

19. A system for dry manufacturing an electrode for an energy storage device, the system comprising: a first pair of vertically-spaced pre-calendering rollers configured to apply a first compaction load to a solvent free dry powder on a substrate to decrease a porosity £ of the dry powder to an intermediate porosity £,; a second pair of vertically-spaced pre-calendering rollers positioned downstream of the first pair of vertically-spaced pre-calendering rollers relative to a feed direction of the substrate, wherein the second pair of vertically-spaced pre-calendering rollers are configured to apply a second compaction load to the dry powder on the substrate to decrease the porosity £ of the dry powder from the intermediate porosity £i to a predetermined critical porosity £c; a pair of vertically-spaced calendering rollers positioned downstream of the second pair of vertically-spaced pre-calendering rollers relative to the feed direction of the substrate, wherein the pair of vertically-spaced calendering rollers are configured to apply a third compaction load to the2238-23501TAMUS 6523 dry powder on the substrate to further decrease the porosity E of the dry powder from the predetermined critical porosity ECto a predetermined target porosity et.

20. The system of claim 19, wherein the predetermined critical porosity ECranges from 35% to 45% and the predetermined target porosity Et ranges from 15% to 20%.

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