Self-supporting electrode film for dry electrode manufacturing

Abstract

An apparatus for manufacturing electrodes for an energy storage device includes at least one laminator for simultaneously laminating two self-supporting electrode films on both sides of a current collector, and a pair of mill lines each operable to produce the two films and simultaneously feed the two films to the laminator. Each mill line may include at least one press including a work roll horizontally disposed for pressing a powder mixture into each of the films, and at least one press including a work roll (typically vertically disposed) for reducing the thickness of each of the films. The apparatus may include a mill line expansion module insertable into the mill line and having at least one additional press including a work roll for reducing the thickness of each of the films and controlling other major parameters. The films may have an elongation of less than 4% and a tensile strength of less than 250 kPa.

Description

Technical Field

[0001] Cross - References to Related Applications Not applicable

[0002] Description of Research and Development Funded by the Federal Government Not applicable

Background Art

[0003] 1. Technical Field

[0004] This disclosure generally relates to the manufacture of energy storage devices such as Li - ion batteries, and more specifically to dry processes for the manufacture of electrodes for energy storage devices.

[0005] 2. Related Art

[0006] There is an increasing demand for low-cost energy storage devices, and various methods for manufacturing electrodes have been proposed. Among these, there is a so-called "dry" process that can produce a self-supporting electrode film while avoiding the costs and drying times associated with solvents and aqueous solutions typically used in slurry coating and extrusion processes. After the self-supporting electrode film is produced, it is laminated onto a current collector to generate an electrode. Although there have been some attempts to devise a continuous process that performs both the generation of the self-supporting electrode film and the lamination of the self-supporting electrode film onto the current collector (see, for example, German Patent Application Publication No. DE 10 2017 208 220), the success of such processes has been limited, which is partly due to the difficulty of generating a uniform electrode film and handling it without breaking the self-supporting electrode film. This difficulty is particularly pronounced in the case of thinner electrode films or more inflexible electrode films made from materials such as battery active materials, including but not limited to lithium nickel manganese cobalt oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium iron phosphate (LFP), graphite, and silicon, which may be more difficult to work with than, for example, activated carbon. SUMMARY OF THE INVENTION

[0007] The present disclosure contemplates various apparatuses and methods for overcoming the above-mentioned drawbacks associated with the related art, as well as related products. One aspect of an embodiment of the present disclosure is an apparatus for manufacturing an electrode for an energy storage device. The apparatus may include at least one laminator for simultaneously laminating two self-standing electrode films on both sides of a current collector, and a pair of mill lines each operable to generate the two self-standing electrode films and simultaneously feed the two self-standing electrode films to the laminator. Each mill line may include at least one first press including a work roll horizontally disposed for pressing a powder mixture into each of the self-standing electrode films, and at least one second press including a work roll (typically vertically disposed) for reducing the thickness of each self-standing electrode film.

[0008] The apparatus may include a mill line expansion module. The mill line expansion module may be insertable into a mill line of the pair of mill lines and may have at least one additional second press including a work roll (typically vertically disposed) for reducing the thickness of each of the self-standing electrode films. Generally, the number of presses may be directly related to the final thickness, porosity, and density of the electrode film, and the mechanical strength of the corresponding film, such as breakage, elongation, and tensile strength, as well as the speed of the mill line. By employing a modular system rather than having a fixed number of presses, the apparatus can accommodate these parameters for various material types with different electrode specifications.

[0009] Each of the mill lines may include one or more conveyors arranged to support the respective self-standing electrode film when it is fed from at least one second press of the mill line to the laminator. The one or more conveyors may be arranged to support the respective self-standing electrode film when it is fed from a first one of the at least one second press of the mill line to a second one of the at least one second press of the mill line. The speed of the one or more conveyors between the at least one second press of the mill line and the laminator may be controlled to be different from the speed of the one or more conveyors between a first one of the at least one second press of the mill line and a second one of the at least one second press of the mill line. The one or more conveyors may be further arranged to support the respective self-standing electrode film when it is fed from the at least one first press of the mill line to the at least one second press. The speed of the conveyor between each stage, including between a first press and a first one of the second presses, between any adjacent second presses, and between the second press and the laminator, may be controlled to be different. Each of the mill lines may include one or more tension sensors arranged to measure the tension of the self-standing electrode film. The speed of the one or more conveyors of the mill line and / or the speed of the work roll of at least one second press of the mill line may be controlled based on the measured tension, for example, to prevent breakage of the film. The one or more conveyors may include at least one vacuum conveyor.

[0010] Another aspect of an embodiment of the present disclosure is a method of manufacturing an electrode for an energy storage device. The method includes providing the above-described apparatus, preparing a first powder mixture having an electrode active material and a fibrillatable binder, fibrillating the fibrillatable binder in the first powder mixture by subjecting the first powder mixture to a shearing force, pressing the first powder mixture into a first self-supporting electrode film using the at least one first press of the first milling line of the pair of milling lines, reducing the thickness of the first self-supporting electrode film using the at least one second press of the first milling line, and laminating the first self-supporting electrode film on a first side of a current collector using the at least one laminator.

[0011] The method may include preparing a second powder mixture having an electrode active material and a fibrillatable binder, fibrillating the fibrillatable binder in the second powder mixture by subjecting the second powder mixture to a shearing force, pressing the second powder mixture into a second self-supporting electrode film using the at least one first press of the second milling line of the pair of milling lines, reducing the thickness of the second self-supporting electrode film using the at least one second press of the second milling line, and laminating the second self-supporting electrode film on a second side of the current collector opposite the first side using the at least one laminator simultaneously with the laminating of the first self-supporting electrode film on the first side of the current collector.

[0012] Another aspect of embodiments of the present disclosure is a method of manufacturing an electrode for an energy storage device. The method includes preparing a first powder mixture having an electrode active material and a fibrillatable binder, fibrillating the fibrillatable binder in the first powder mixture by subjecting the first powder mixture to a shearing force, preparing a second powder mixture having an electrode active material and a fibrillatable binder, fibrillating the fibrillatable binder in the second powder mixture by subjecting the second powder mixture to a shearing force, and simultaneously generating a first self-standing electrode film from the first powder mixture and a second self-standing electrode film from the second powder mixture using a pair of mill lines, each of the mill lines including at least one first press including a work roll horizontally disposed for pressing the respective powder mixture into the respective self-standing electrode film, and at least one second press including a work roll (typically vertically disposed) for reducing the thickness of the respective self-standing electrode film. The method may further include, subsequent to the step of generating the first and second self-standing electrode films, feeding the first and second self-standing electrode films from the respective mill lines to a laminator and laminating the first and second self-standing electrode films on both sides of a current collector.

[0013] The method may comprise supporting the first self-standing electrode film using one or more conveyors when the first self-standing electrode film is fed from the respective mill lines to the laminator. The method may comprise supporting the first self-standing electrode film using one or more conveyors when the first self-standing electrode film is fed from the first of the at least one second press of the respective mill lines to the second of the at least one second press. The method may comprise controlling the speed of the one or more conveyors between the respective mill lines and the laminator to be different from the speed of the one or more conveyors between the first of the at least one first press of the respective mill lines and the second of the at least one first press. The method may comprise supporting the first self-standing electrode film using one or more conveyors when the first self-standing electrode film is fed from the at least one first press of the respective mill lines to the at least one second press. The method may comprise controlling the speed of the conveyor to be different between each stage, including between the first press and the first of the second presses, between any adjacent second presses, and between the second press and the laminator. The method may comprise measuring the tension of the first self-standing electrode film and controlling the speed of the one or more conveyors and / or the speed of the work roll of the at least one second press based on the measured tension, for example, to prevent breakage of the film. The one or more conveyors may include at least one vacuum conveyor.

[0014] Another aspect of an embodiment of the present disclosure is a self-standing electrode film. The self-standing electrode film may comprise an electrode active material and a fibrillatable binder. The elongation rate of the self-standing electrode film in the machine direction may be less than 4%. The elongation rate of the self-standing electrode film in the machine direction may be less than 2%. The tensile strength of the self-standing electrode film in the machine direction may be greater than 450 kPa. The porosity of the self-standing electrode film may be less than 32%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] These and other features and advantages of the various embodiments disclosed in this specification will be better understood with reference to the following description and drawings, in which like numerals refer to like parts throughout.

[0016]

Figure 1

[0017]

Figure 2

[0018]

Figure 3

[0019]

Figure 4

[0020]

Figure 5

[0021]

Figure 6

DETAILED DESCRIPTION OF THE INVENTION

[0022] The present disclosure encompasses apparatuses for manufacturing electrodes for energy storage devices, as well as manufacturing methods and various embodiments of intermediate and final products. In connection with the accompanying drawings, the detailed description set forth below is intended as a description of some presently contemplated embodiments and is not intended to represent the only form in which the disclosed invention may be developed or utilized. This description describes functions and features in relation to the illustrated embodiments. However, it is to be understood that the same or equivalent functions may be achieved by different embodiments that are equally intended to be encompassed within the scope of the present disclosure. It is further to be understood that the use of relational terms such as first and second is used simply to distinguish one entity from another without necessarily requiring or implying any actual such relationship or order between such entities.

[0023] FIG. 1 shows an apparatus 100 for manufacturing electrodes for energy storage devices such as lithium-ion batteries, solid-state batteries, lithium-ion capacitors (LICs), or ultracapacitors. The final energy storage device may comprise one or more electrodes assembled by laminating a first self-supporting electrode film 10a and a second self-supporting electrode film 10b on both sides of a current collector 20 such as an aluminum metal sheet in the case of the cathode electrode films 10a, 10b, or a copper metal sheet in the case of the anode electrode films 10a, 10b. The apparatus 100 may comprise at least one laminator 110 for simultaneously laminating two self-supporting electrode films 10a, 10b on both sides of the current collector 20. The laminator 110 may have, for example, work rolls 112-1, 112-2 arranged horizontally as shown, although a vertical arrangement is also contemplated. The apparatus 100 may further comprise a pair of mill lines 120a, 120b (e.g., arranged in the wings of the apparatus 100) operable to each generate two self-supporting electrode films 10a, 10b and feed them simultaneously to the laminator 110. The laminator 110 may then laminate the two self-supporting electrode films 10a, 10b on either side of the current collector 20 when unwound from a first spool 130 and then wound onto a second spool 140 (or alternatively sent to a cutter) together with the laminated films 10a, 10b. By the apparatus 100 and associated methods described herein, efficient handling of the relatively thin self-supporting electrode films 10a, 10b (e.g., less than 200 μm or less than 100 μm), and / or even those formed from less flexible materials (e.g., battery active materials) such as NCM, NCA, LFP, graphite, and silicon, which enable the manufacture of a wide variety of energy storage devices for different purposes, can be made possible. In some embodiments, as described in more detail below, the apparatus 100 may have a modular design that allows the same apparatus 100 to be used to efficiently manufacture electrodes for energy storage devices having different specifications as needed.

[0024] Depending on the specific use of the energy storage device to be manufactured, the dry powder mixtures 12a, 12b used to produce the self-supporting electrode films 10a, 10b may have various formulations and may be produced according to various methods. Some exemplary dry powder formulations and methods that can be used to produce the dry powder mixtures 12a, 12b are described in the inventor's own patents and patent applications, including U.S. Patent No. 10,069,131 entitled "Electrode for Energy Storage Devices and Method of Making Same", U.S. Patent Application Publication No. 2020 / 0388822 entitled "Dry Electrode Manufacture by Temperature Activation Method", U.S. Patent Application Publication No. 2022 / 0077453 entitled "Dry Electrode Manufacture with Lubricated Active Material Mixture", U.S. Patent Application No. 17 / 097,200 entitled "Dry Electrode Manufacture with Composite Binder", and U.S. Patent Application No. 17 / 492,458 entitled "Dry Electrode Manufacture for Solid State Energy Storage Devices", the entire disclosure of each of which is hereby incorporated by reference in its entirety. Typically, since the first and second self-supporting electrode films 10a, 10b will be disposed on the same current collector 20 by the device 100, both dry powder mixtures 12a, 12b will be formulated and produced in the same manner (and thus, in practice, may be split, for example, from the same manufacturing batch).

[0025] Each of the mill lines 120a, 120b may comprise at least one first press 122a, 122b for pressing one of the powder mixtures 12a, 12b onto the respective self-supporting electrode films 10a, 10b. Referring by way of example to the mill line 120a (in the case of the mill line 120b, equivalent reference numerals use the letter "b" instead of "a"), the first press 122a is such that the powder mixture 12a is poured (e.g., from the powder feed conveyor 13a) onto the upper parts of the work rolls 123a-1, 123a-2 and is discharged from the bottom thereof in the form of a continuous film subjected to pressure and heat by the work rolls 123a-1, 123a-2, and may include the work rolls 123a-1, 123a-2 arranged horizontally as shown. For this purpose, the work rolls 123a-1, 123a-2 of the first press 122a may have an elevated surface temperature (e.g., higher than 70°C). Advantageously, the work rolls 123a-1, 123a-2 are controlled to rotate at the same speed relative to each other so as to affect the film density and porosity as desired for a specific material and application, with the gap between the work rolls 123a-1, 123a-2 being freely adjustable. In this regard, it should be noted that, in particular, when the powder mixture 12a is produced by one of the exemplary methodologies referred to above, where the powder mixture 12a has already been subjected to shear forces, for example using a jet mill, it may not be necessary for the first press 122a to produce a shearing effect by the operation of work rolls 123a-1, 123a-2 having different speeds.

[0026] Each of the mill lines 120a, 120b may further include at least one second press 124a, 124b for reducing the thickness of the respective self-supporting electrode films 10a, 10b. Referring again to the mill line 120a as an example, the second press 124a may include work rolls 125a-1, 125a-2 that are typically (but not necessarily) vertically disposed as shown. Similar to the work rolls 123a-1, 123a-2 of the first press 122a, the work rolls 125a-1, 125a-2 of the second press 124a may have an elevated surface temperature (e.g., higher than 70° C.) and may be controlled to rotate at the same speed relative to each other with the gap between the work rolls 125a-1, 125a-2 being freely adjustable as desired. Although only a single second press 124a is shown in FIG. 1, any number of second presses 124a may be provided in series such that each further reduces the thickness of the self-supporting electrode film 10a (e.g., the work rolls 125a-1, 125a-2 in contact with the film 10a and the gap between the work rolls 125a-1, 125a-2 continuously decreases for each second press 124a) through the application of heat and pressure until the desired film thickness for a given application is achieved. In order to best fit manufacturing operations that use only a single second press 124a, 124b in each mill line 120a, 120b, such as when producing relatively thick self-supporting electrode films 10a, 10b, each mill line 120a, 120b may most advantageously include only a single second press 124a, 124b as part of the infrastructure of the apparatus 100 (as shown in FIG. 2, the apparatus 100 is expandable using one or more mill line expansion modules 150). Along the same line, in some implementations, it is contemplated that the infrastructure of each mill line 120a, 120b may include no second presses 124a, 124b and may include only one or more first presses 122a, 122b.

[0027] As new energy storage device applications begin to require electrodes made from thinner self-supporting electrode films 10a, 10b, and as the potential active materials come to include materials that produce self-supporting electrode films 10a, 10b that are less flexible and more breakable, conventional roll-to-roll processing apparatuses and methods can become inappropriate for handling the self-supporting electrode films 10a, 10b without breakage. Thus, each self-supporting electrode film 10a, 10b is better supported as it passes through its respective mill line 120a, 120b towards the laminator 110 (subsequently, the self-supporting electrode films 10a, 10b will be supported by the more robust current collector 20 and will no longer be self-supporting). For this purpose, it is contemplated that each mill line 120a, 120b may comprise one or more conveyors 126a, 126b, such as a vacuum conveyor. Referring to mill line 120a as an example, one or more conveyors 126a may be arranged to support the self-supporting electrode film 10a at any of various positions, including, for example, i) when the self-supporting electrode film 10a is fed from the second press 124a of the mill line 120a to the laminator 110, ii) when the self-supporting electrode film 10a is fed from the first of the second presses 124a to the second of the second presses 124a, and / or iii) when the self-supporting electrode film 10a is fed from the first press 122a to the second press 124a. The speed of the conveyor 126a may be controlled according to the thickness and tension of the self-supporting electrode film 10a at each particular position, which may be determined by the arrangement of the presses 122a, 124a and their roller speeds, as well as that of the laminator 110 of the granules. For example, the speed of the conveyor 126a between the second press 124a and the laminator 110 may be controlled to be different from the speed of the conveyor between subsequent second presses 124a, which in turn may be different from the speed of the conveyor between the first press 122a and the second press 124a. In practice, the speed of the conveyor 126a may be controlled in a cascading manner where the final laminator speed 110 determines the speeds at each upstream position of each mill line 120a, 120b.As feedback to the control process, each mill line 120a, 120b may include one or more tension sensors 128a, 128b arranged to measure the tension on the self-supporting electrode films 10a, 10b. A load cell or other proximity sensor may be employed to maintain optimal tension control by adjusting the rotational speeds of the conveyor and the work roll. In order to keep the lamination speed constant and prevent the films 10a, 10b from breaking, the variable speeds and / or speed ratios of one or more conveyors 126a, 126b may be controlled such that the speeds between the presses are appropriately matched based on the tension measured using any of a variety of algorithms including a machine learning model.

[0028] Figure 2 shows a partial view of an apparatus 100 in which a mill line extension module 150 is inserted into its mill line 120a. The mill line extension module 150 may include at least one additional second press 154a for reducing the thickness of each self-supporting electrode film 10a, 10b (in this case, the electrode film 10a as shown). As shown, for example, the mill line 120a of the base apparatus 100 may include a single second press 124a, and the mill line extension module 150 may introduce one or more additional second presses 154a (two additional second presses 154a as shown). The additional second press 154a - may be insertable into the mill line 120a, for example, immediately before the second press 124a of the base apparatus 100. (Note that if the mill line 120a does not include a second press 124a, the additional second press 154a introduced by the mill line extension module 150 may be the only thickness-reducing press of the apparatus 100.) The dashed arrow in Figure 2 shows one possible insertion procedure, where the first press 122a is moved away from the laminator 110 (towards the left in Figure 2), and the mill line extension module 150 is inserted into the created space (above in Figure 2), and the phantom line shows the mill line extension module 150 before being inserted into the mill line 120a.

[0029] Similar to each of the second presses 124a, 124b of each mill line 120a of the base device 100, each additional second press 154a introduced by the mill line extension module 150 may include work rolls 155a-1, 155a-2 that are typically (but not necessarily) vertically arranged as shown. The work rolls 155a-1, 155a-2 of each additional second press 154a may have an elevated surface temperature (e.g., higher than 70 °C) and may be controlled to rotate at the same speed relative to each other with the gap between the work rolls 155a-1, 155a-2 being freely adjustable as desired. The mill line extension module 150 is contemplated to further include one or more additional conveyors 156a that can be inserted between the conveyors 126a of the mill line 120a as shown. The mill line extension module 150 may further include one or more additional tension sensors 158a arranged to measure the tension on the self-supporting electrode film 10a as it passes through the additional second press 154a of the mill line extension module 150 (e.g., before and after). The additional conveyor 156a and the additional tension sensor 158a may be connected to the same speed control system as the conveyor 126a and the tension sensor 128a of the base device 100. It should be noted that the mill line extension module 150 may be symmetrically designed for insertion into the mill line 120b instead of the mill line 120a as shown (and equivalent reference numerals using the letter "b" instead of "a" may be referred to in this case, but are not shown separately).

[0030] The mill line expansion module 150 enables the same apparatus 100 to be easily customized for different manufacturing operations with different specifications for the energy storage devices to be produced. Manufacturers of energy storage devices made using relatively thick self-supporting electrode films 10a, 10b may use only the base apparatus 100 without the mill line expansion module 150 on each mill line 120a, 120b, or with only a single mill line expansion module 150, while manufacturers who need to produce thinner self-supporting electrode films 10a, 10b may insert several mill line expansion modules 150 (or in some cases, mill line expansion modules 150 having a greater number of additional second presses 154a, 154b, although standard mill line expansion modules 150 may be preferred). The same apparatus 100 can meet the needs of both manufacturers, enabling efficient manufacture and use of the apparatus 100 and the mill line expansion module 150. Without the module design, either i) marketing and producing different sizes of the apparatus 100, or custom-building the apparatus 100 for each manufacturer (both cases being associated with inefficiency and cost), or ii) producing only the largest possible apparatus 100 having the maximum number of second presses 124a, 124b that can be used, would be necessary. In the latter case, the apparatus 100 can be prohibitively expensive for manufacturers who do not need to reduce the thickness of the self-supporting electrode films 10a, 10b very much, both in terms of the purchase price and also in terms of the maintenance of such a large apparatus 100 and the personnel required to monitor and operate it. Also, since it is on the path up to the laminator 110, the risk of damaging the self-supporting electrode films 10a, 10b by any unused second presses 124a, 124b in a given operation increases, the yield of the operation decreases, and the large number of unused second presses 124a, 124b becomes a liability for the manufacturer.

[0031] Manufacturers that produce various different products along the same line are better served by the modular apparatus 100, whereby the manufacturer may be able to increase or decrease the number of presses by attaching or removing the mill line expansion module 150 as needed. The apparatus 100 may be used with some mill line expansion modules 150 for some operations and with fewer or no mill line expansion modules 150 for other operations, thereby reducing the associated costs of these operations in terms of personnel and yield. As another possibility, it is contemplated that the mill line expansion module 150 may be used as a replacement in the event that the presses 154a, 154b of another mill line expansion module 150 require repair. Instead of waiting for the damaged press station to be repaired and shutting down the entire production line, the problematic mill line expansion module 150 can simply be replaced with a new mill line expansion module 150. In this way, the manufacturing process can resume after only a temporary delay. The damaged mill line expansion module 150 can be repaired without significantly interrupting production, even while the manufacturing process is underway.

[0032] Figure 3 shows an operation flow for manufacturing an electrode for an energy storage device according to the disclosed innovation. In particular, the operation flow of Figure 3 may be executed using the apparatus 100 described in connection with Figures 1 and 2. The operation flow may begin by preparing first and second powder mixtures 12a, 12b (step 310) and fibrillating the binders contained in the powder mixtures 12a, 12b (step 320). For example, as described in the inventors' own patents and patent applications incorporated by reference above, the powder mixtures 12a, 12b may include, in addition to at least one type of electrode active material (e.g., lithium metal oxide for a cathode or graphite or silicon for an anode), at least one type of fibrillatable binder, such as polytetrafluoroethylene (PTFE), polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyethylene (PE), or carboxymethylcellulose (CMC), or a combination of the above binders or copolymers. Fibrillatable binders may be characterized by their soft, flexible toughness and, in particular, their ability to stretch, assuming a fibrous state that becomes longer and thinner when subjected to shear forces. By using one or more fibrillatable binders that may be further chemically or thermally activated to enhance their flexibility, as described in the inventors' patents and patent applications, the powder mixture may be pressed into a self-standing film without breaking and without excessive use of toxic and expensive solvents such as N-Methylpyrrolidone (NMP).The binder can fibrillate the powder mixtures 12a, 12b by subjecting them to shear forces, for example, using a high-shear disperser such as a kitchen blender, an industrial blender, a coffee grinder, a grain mill grinder, a high-speed mixer, a cyclone paint mixer, a rotary mixer, a planetary mixer, an Admix Rotosolver, a high-shear granulator such as a Diosna P1-6, a high-shear micronizer such as a jet mill, a high-shear emulsifier, a high-shear mixer such as a Ross Megashear mixer, or a soundproof mixer. As described above, the powder mixtures 12a, 12b may, in practice, be divided from the same production batch. In this regard, it should be noted that steps 310 and 320 may be combined, or equivalently, step 310 may include preparing a sufficient amount of powder mixture for preparing the first and second powder mixtures 12a, 12b without separating them (i.e., two mill lines 120a, 120b).

[0033] The operation flow of FIG. 4 can continue with simultaneously generating the first and second self-standing electrode films 10a, 10b from the powder mixtures 12a, 12b using a pair of mill lines 120a, 120b such as those described in relation to FIGS. 1 and 2 (step 330). FIG. 4 shows an exemplary sub-operation flow at this stage, which may begin by inserting one or more mill line expansion modules 150 into the mill lines 120a, 120b as needed (step 410) to achieve the specific specifications of the respective self-standing electrode films 10a, 10b for the electrodes to be manufactured (e.g., thickness, density, and porosity, and mechanical strength such as the tensile strength and elongation of the film). With the mill lines 120a, 120b of the apparatus 100 appropriately expanded, the sub-operation flow of FIG. 4 proceeds to pressing the powder mixtures 12a, 12b into the respective self-standing electrode films 10a, 10b using the respective first presses 122a, 122b (step 420), supporting the self-standing electrode films 10a, 10b as they pass through the mill lines 120a, 120b using the conveyors 126a, 126b (step 430), and reducing the thickness of the respective self-standing electrode films 10a, 10b using any second presses 124a, 124b that are part of the base apparatus 100 and any additional second presses 154a, 154b added by the mill line expansion modules 150 (step 440). Due to the innovative design of the apparatus 100, the two self-standing electrode films 10a, 10b can be generated and appropriately thinned simultaneously, thereby enabling subsequent feeding to the laminator 110 and simultaneous lamination onto the current collector 20.

[0034] In particular, referring again to FIG. 3, the operation flow may proceed to feeding the first and second self-supporting electrode films 10a, 10b from their respective mill lines 120a, 120b to the laminator 110 (step 340). This may be done while continuing to support the self-supporting electrode films 10a, 10b on appropriately speed-controlled conveyors 126a, 126b, thereby minimizing the possibility of breakage at the thinnest, lowest breaking strength, or most fragile positions of the films 10a, 10b. In this regard, the operation flow may further include measuring the tension of the self-supporting electrode films 10a, 10b at one or more positions using tension sensors 128a, 128b, 158a, 158b (step 350), and, in particular, appropriately controlling the speed of the mill line as described above by adjusting the speed of conveyors 126a, 126b, 156a, 156b (step 360) and / or the rotational speed of the work rolls. When the self-supporting electrode films 10a, 10b exit their respective mill lines 120a, 120b, the laminator 110 may laminate them on both sides of the current collector 20, which in some cases may be pre-treated by chemical etching, coated with a conductive binder layer, or both (step 370). The completed electrodes may be wound around the second spool 140 or cut by a cutting machine. By using a pair of mill lines 120a, 120b to simultaneously produce the self-supporting electrode films 10a, 10b and feeding the self-supporting electrode films 10a, 10b to the laminator 110 in a continuous process (in particular, when the mill lines 120a, 120b are arranged as the upstream wings of a separate central press functioning as the laminator 110), the disclosed manufacturing process can proceed at twice the speed of a process that uses the same single mill line to produce both films. In such a process, between the formation of the films and the lamination on the current collector, a separate laminator machine must be loaded with two rolls of the produced active material film and one roll of the current collector, and as a result, the final electrode lamination speed is at most half the speed of the mill line. The disclosed apparatus 100 enables a speed that is twice that of such a multi-step process.

[0035] Exemplary data for the self-supporting electrode films 10a, 10b made from three different active materials are provided in Table 1 below.

[0036] Table 1

Table 1

[0037] To generate each film group of a specified thickness (the "film group" column), the disclosed apparatus 100 may comprise a suitable number of presses (the "number of presses" column). In this regard, the number of presses shown in Table 1 (in this data in the range of 1 to 15) is to be understood to refer to all presses in a given mill line 120a, including the first press 122a and the second press 124a, as well as any additional second presses 154a added using one or more mill line extension modules 150. For example, the 250 μm NCM cathode film group (number of presses = 1) can be generated using an apparatus 100 having a single first press 122a in the mill line 120a used to generate the film and no second press 124a, while the 65 μm NCM cathode film group (number of presses = 15) can be generated using the same apparatus 100 having a single first press 122a in the mill line 120a and 14 additional second presses 154a added by the mill line extension module 150. Table 1 shows the average thickness (the "average thickness" column) exemplifying the actually measured thickness corresponding to each film group in practice.

[0038] The last five columns of Table 1 show exemplary data for such membranes, where the tensile strength and membrane density of the membranes increase for thinner membranes and vary for different materials, while the elongation (maximum machine direction elongation before breakage) and porosity of the membranes decrease for thinner membranes and similarly vary for each material. The elongation can be determined by a tensile test (where the machine direction can refer to the pulling direction in which the membrane is stretched by the operation of the work roll). An exemplary tensile test can measure the distance the strip of membrane of 2.5 cm width and 10 cm length (machine direction) is pulled before breakage, for example, with an initial tension of 5 gf. It should be noted that the NCM cathode and graphite anode membranes are more difficult to work with than the activated carbon membranes, especially because their flexibility is significantly lower (and thus they have a lower elongation). As can be seen, the difficulty is even more pronounced for thinner membranes. It is contemplated that the apparatus 100 and associated processes described herein can successfully and efficiently produce a wide variety of self - standing electrode membranes 10a, 10b in the same apparatus 100. For example, the self - standing electrode membranes 10a, 10b can be made of various materials including NCM graphite or activated carbon and can have a thickness ranging from a maximum of 300 μm to a minimum of 50 μm or thinner. For each operation of the apparatus 100, the mill lines 120a, 120b can be adjusted as appropriate for the desired thickness or other parameters and can be expanded as needed by inserting a mill line expansion module 150 to increase the number of thickness reduction presses. Also, due to the innovative design of the apparatus 100 preferably including conveyors 126a, 126b, 156a, 156b to support the fragile membranes 10a, 10b as they pass through the mill lines 120a, 120b, the resulting self - standing electrode membranes 10a, 10b can be contemplated to have a tensile strength in the range of from 40 kPa to more than 100 kPa, more than 450 kPa, or even more than 600 kPa (for NCM or graphite), or more than 1100 kPa for very thin graphite anode membranes.At the same time, the elongation rate in the machine direction can range from 10% to as low as less than 4%, or even less than 2%, and sometimes 0.50% or even 0.20% (in the case of NCM or graphite). Efficient handling of such fragile self-standing electrode membranes 10a, 10b would not be achievable without the disclosed innovations of the apparatus 100 and the associated processes.

[0039] Generally, self-standing membranes having a tensile strength higher than 100 kPa and an elongation rate of less than 10% along the machine direction are contemplated to require a unique tension control design to enable a high-speed manufacturing process. The use of the contemplated conveyors 126a, 126b, 156a, 156b in combination with sensors 128a, 128b strategically placed along the self-standing membrane (sometimes using multiple measurement methods) can provide the control necessary to handle the sensitive battery active material electrode membranes 10a, 10b. The difficulty in creating dry battery electrodes in self-standing membranes is due to the inherently brittle nature of the active materials that renders conventional web handling methods impossible. The disclosed apparatus 100 and method can overcome these difficulties by using conveyors 126a, 126b, 156a, 156b to support the self-standing electrode membranes 10a, 10b and transport them through each press station in an automated self-screwing process.

[0040] Advantageously, the multiple press designs of apparatus 100 can allow for higher flexibility in matching the final electrode characteristics such as thickness uniformity, density, and porosity, compared to other dry process electrodes produced with or without a self-standing membrane. As shown in Table 1 above, by way of example, the membrane density may be selected as desired (e.g., between 3.02 g / cc and 3.40 g / cc for an NCM cathode, or between 1.21 g / cc and 1.71 g / cc for a graphite anode), and similarly, the membrane porosity may be selected as desired (e.g., between 25.9% and 34.2% for an NCM cathode, or between 23.5% and 46.0% for a graphite anode). Through the efficient handling of the brittle self-standing electrode membranes 10a, 10b using apparatus 100, a low porosity (e.g., less than 32%) can be achieved. Generally, dry battery electrode technology requires the ability to control the loading, porosity, and uniformity of the active material layer. Other dry battery electrode process technologies are not capable of precisely matching the control of these parameters. For example, dry spray or dry deposition electrode processes that do not produce a self-standing membrane may have limited ability to control thickness uniformity because the powder is resting on top of the current collector and cannot flow in multiple axes during pressing. Also, the density and porosity may be limited by the amount of powder that can be applied to the current collector prior to pressing and the limitations on the pressing force that can be used without damaging the current collector. The disclosed innovation can address all of these requirements by using multiple press stations that cooperate to simultaneously produce self-standing electrode membranes 10a, 10b on both sides of the current collector 20. Further, having a thickness reduction press station in the system in a modular configuration (employing freely insertable mill line expansion modules 150) rather than a fixed number of presses allows for customization based on different material types such as anode materials or custom cathode materials.

[0041] Figure 5 shows the active material loading as a function of the film thickness of an activated dry NCM811 electrode (having a nickel:cobalt:manganese ratio of 8:1:1). As shown, the discharge capacity per unit area (mAh / cm2 ) The degree of loading of the active material represented as can be determined at least in part by the film thickness (μm). Electrodes made from thinner films (e.g., less than 90 μm) may exhibit a discharge capacity per unit area of less than, for example, 6 mAh / cm 2 and may typically be suitable as a drop-in technology for applications with high power density such as electric vehicles (EVs). On the other hand, electrodes made from thicker films (e.g., greater than 80 μm) may exhibit a discharge capacity per unit area of greater than, for example, 6 mAh / cm 2 and may typically be suitable for applications with high energy density such as energy storage systems (ESSs). Using conventional methods, such a wide range of applications requires different manufacturing equipment specialized for each application, which results in significant costs and inefficiencies for manufacturers. In contrast, embodiments of the apparatus 100 described herein advantageously enable a wide variety of electrodes to be produced using the same apparatus 100, and the thickness and other parameters of the self-supporting films 10a, 10b can be freely selected by modifying the number of thickness reduction presses 124a, 124b, 154a, 154b using the mill line expansion module 150, thereby enabling the manufacture of batteries for, for example, EVs, ESSs, and other applications at relatively low cost and high efficiency.

[0042] Figure 6 shows the C-rate performance of a wet-activated dry NCM811 electrode (ADE). The activated dry electrode can refer to, for example, one generated by an activation dry method as described herein and incorporated by reference, while the intended wet electrode (WET REF) can be made, for example, by a conventional slurry coating method. As can be seen, the performance of the electrode at a given C-rate, expressed as the discharge capacity retention rate (%), can depend on the thickness of the activated dry electrode film, and a thinner ADE film (e.g., 54 μm) exhibits better performance at higher C-rates than a thicker ADE film (e.g., 78 μm) or the wet electrode. Therefore, depending on the desired C-rate of the battery to be produced, a manufacturer may desire to be able to freely adjust the thickness of the electrode film, but this is not easily achievable and is often not possible using conventional manufacturing equipment. However, according to embodiments of the apparatus 100 described herein, the thickness of the self-supporting films 10a, 10b can be customizable as needed for the desired C-rate or other parameters of the energy storage device to be produced.

[0043] In the above example, it was described how the apparatus 100 can be used to generate a double-sided electrode by operating both of the milling lines 120a, 120b simultaneously and laminating two self-supporting electrode films 10a, 10b on both sides of the current collector 20. However, the process described herein is not intended to be limited to using the apparatus 100 in this manner. For example, to generate an electrode on one side, a single milling line 120a of the apparatus 100 may be operated, and the laminator 110 may laminate only a single self-supporting electrode film 10a on the current collector 20. Also, it should be understood that any of the work rolls 112-1, 112-2 of the laminator 110, the work rolls 123a-1, 123a-2, 125a-1, 125a-2 of the milling line 120a, the work rolls 155a-1, 155a-2 of the milling line extension module 150, and any corresponding work rolls provided in relation to the milling line 120b may be supported by one or more backing rolls such as a 4HI, 6HI, or cluster roll configuration.

[0044] The above description is provided by way of example and not limitation. Given the above disclosure, those skilled in the art will be able to devise variations within the spirit and scope of the invention disclosed herein. Further, the various features of the embodiments disclosed herein can be used alone or in various combinations with each other and are not intended to be limited to the specific combinations described herein. Thus, the scope of the claims is not limited by the exemplary embodiments shown.

Claims

1. An apparatus for manufacturing electrodes for an energy storage device, the apparatus comprising: at least one laminator for simultaneously laminating two self-supporting electrode films on both sides of a current collector; and a pair of mill lines each operable to produce the two self-supporting electrode films and simultaneously feed the two self-supporting electrode films to the laminator, each of the mill lines comprising: at least one first press including a work roll horizontally disposed for pressing a powder mixture into one of each of the self-supporting electrode films; and at least one second press including a work roll for reducing the thickness of each of the self-supporting electrode films having an apparatus.

2. The apparatus according to claim 1, further comprising a mill line extension module, the mill line extension module being insertable into a mill line of the pair of mill lines and having at least one additional second press including a work roll for reducing the thickness of each of the self-supporting electrode films.

3. The apparatus according to claim 1, wherein each of the mill lines further comprises one or more conveyors arranged to support each of the self-supporting electrode films when it is fed from the at least one second press of the mill line to the laminator.

4. The apparatus according to claim 3, wherein the one or more conveyors are further arranged to support each of the self-supporting electrode films when it is fed from a first one of the at least one second presses of the mill line to a second one of the at least one second presses of the mill line.

5. The apparatus according to claim 4, wherein the speed of the one or more conveyors between the at least one second press of the mill line and the laminator is controlled to be different from the speed of the one or more conveyors between a first one and a second one of the at least one second presses of the mill line.

6. The apparatus according to claim 4, wherein the one or more conveyors are further arranged to support each of the self-supporting electrode films when it is fed from the at least one first press of the mill line to the at least one second press.

7. Each of the mill lines further has one or more tension sensors arranged to measure the tension of the self-supporting electrode film, and the speed of the one or more conveyors of the mill line is controlled based on the measured tension. The apparatus according to claim 3.

8. The tension measured by the one or more tension sensors of each mill line is further used to control the speed of the work roll of the at least one second press of the mill line. The apparatus according to claim 7.

9. The one or more conveyors include at least one vacuum conveyor. The apparatus according to claim 3.

10. The work roll of the at least one second press is arranged vertically. The apparatus according to claim 1.

11. A method for manufacturing an electrode for an energy storage device, the method comprising: providing the apparatus according to claim 1; preparing a first powder mixture having an electrode active material and a fibrillatable binder; fibrillating the fibrillatable binder in the first powder mixture by subjecting the first powder mixture to a shearing force; pressing the first powder mixture into a first self-supporting electrode film using the at least one first press of the first mill line of the pair of mill lines; reducing the thickness of the first self-supporting electrode film using the at least one second press of the first mill line; and laminating the first self-supporting electrode film on a first side of a current collector using the at least one laminator A method comprising.

12. preparing a second powder mixture having an electrode active material and a fibrillatable binder; fibrillating the fibrillatable binder in the second powder mixture by subjecting the second powder mixture to a shearing force; pressing the second powder mixture into a second self-supporting electrode film using the at least one first press of the second mill line of the pair of mill lines; reducing the thickness of the second self-supporting electrode film using the at least one second press of the second mill line; and Simultaneously with the lamination of the first self-supporting electrode film on the first side of the current collector, using the at least one laminator, laminating the second self-supporting electrode film on the second side of the current collector opposite the first side The method according to claim 11, further comprising. **Claim 13** A method of manufacturing an electrode for an energy storage device, the method comprising: Preparing a first powder mixture having an electrode active material and a fibrillatable binder; Fibrillating the fibrillatable binder in the first powder mixture by subjecting the first powder mixture to a shearing force; Preparing a second powder mixture having an electrode active material and a fibrillatable binder; Fibrillating the fibrillatable binder in the second powder mixture by subjecting the second powder mixture to a shearing force; Simultaneously generating a first self-supporting electrode film from the first powder mixture and a second self-supporting electrode film from the second powder mixture using a pair of mill lines, each of the mill lines comprising at least one first press including a work roll arranged horizontally for pressing the respective powder mixture into the respective self-supporting electrode film, and at least one second press including a work roll for reducing the thickness of the respective self-supporting electrode film; and Continuing with the step of generating the first self-supporting electrode film and the second self-supporting electrode film, feeding the first self-supporting electrode film and the second self-supporting electrode film from the respective mill lines to a laminator, and laminating the first self-supporting electrode film and the second self-supporting electrode film on both sides of a current collector A method comprising. **Claim 14** The method according to claim 13, further comprising supporting the first self-supporting electrode film using one or more conveyors when the first self-supporting electrode film is fed from the respective mill line to the laminator. **Claim 15** The method according to claim 14, further comprising supporting the first self-supporting electrode film using one or more conveyors when the first self-supporting electrode film is fed from the first of the at least one second press of the respective mill line to the second of the at least one second press of the respective mill line. **Claim 16** The method according to claim 15, further comprising the step of controlling the speed of the one or more conveyors between each of the mill lines and the laminator to be different from the speed of the one or more conveyors between the first of the at least one first press of each of the mill lines and the second of the at least one first press.

17. The method according to claim 15, further comprising the step of supporting the first self-supporting electrode film using the one or more conveyors when the first self-supporting electrode film is fed from the at least one first press of each of the mill lines to the at least one second press.

18. The method according to claim 14, further comprising the step of measuring the tension of the first self-supporting electrode film and controlling the speed of the one or more conveyors based on the measured tension.

19. The method according to claim 18, further comprising the step of controlling the speed of the work roll of the at least one second press based on the measured tension.

20. The method according to claim 14, wherein the one or more conveyors include at least one vacuum conveyor.

21. The method according to claim 13, wherein the work roll of the at least one second press is vertically arranged.

22. A self-supporting electrode film, comprising: an electrode active material; and a fibrillatable binder wherein the elongation rate in the machine direction of the self-supporting electrode film is less than 4%.

23. The self-supporting electrode film according to claim 22, wherein the elongation rate in the machine direction of the self-supporting electrode film is less than 2%.

24. The self-supporting electrode film according to claim 22, wherein the tensile strength in the machine direction of the self-supporting electrode film is greater than 100 kPa.

25. The self-supporting electrode film according to claim 22, wherein the porosity of the self-supporting electrode film is less than 32%.

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