Self-standing electrode films for dry electrode fabrication

Abstract

An apparatus for manufacturing an electrode for an energy storage device includes: at least one laminating machine for simultaneously laminating two free-standing electrode films on opposite sides of a current collector; and a pair of rolling lines operable to respectively produce two films and simultaneously feed the two films to the laminating machine. Each rolling line may have at least one press comprising horizontally arranged working rolls for pressing the powder mixture into a respective one of the films, and at least one press comprising working rolls (typically vertically arranged) for reducing the thickness of the respective film. The apparatus may include a rolling line extension module insertable into the rolling line and having at least one additional press including working rolls for reducing thickness and controlling other key parameters of the respective film. The film may have an elongation of less than 4% and a tensile strength of less than 250 kPa.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] not applicable

[0003] Notice: Federal Government Research / Development

[0004] not applicable Technical Field

[0005] The present disclosure relates generally to the manufacture of energy storage devices such as lithium-ion batteries, and more particularly to dry processes for manufacturing electrodes for energy storage devices. Background Art

[0006] As the demand for inexpensive energy storage devices increases, various methods have been proposed to make electrodes. Among them, there is a so-called "dry process" by which a free-standing electrode film can be made while avoiding the costs and drying times associated with solvents and aqueous solutions typically used in slurry coating and extrusion processes. After the free-standing electrode film is produced, it is laminated to a current collector to produce the electrode. Although there have been some attempts to design a continuous method for both producing a free-standing electrode film and laminating the free-standing electrode film to a current collector (see, for example, German Patent Application Publication No.

[0007] DE102017208220), but the success of this approach has been limited, in part, due to the difficulty in producing uniform electrode films and the difficulty in handling free-standing electrode films without damaging them. This challenge is particularly significant for thinner electrode films or for less flexible electrode films made from, for example, battery active materials, including but not limited to, for example, 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 handle than activated carbon. Summary of the invention

[0008] The present disclosure contemplates various apparatuses and methods and related products for overcoming the above-mentioned shortcomings associated with the prior art. One aspect of an embodiment of the present disclosure is an apparatus for manufacturing electrodes for energy storage devices. The apparatus may include: at least one laminator for laminating two self-supporting electrode films simultaneously on opposite sides of a current collector; and a pair of mill lines, which are operable to produce two self-supporting electrode films respectively and to feed the two self-supporting electrode films to the laminator simultaneously. Each rolling line may include at least one first press and at least one second press, at least one first press including horizontally arranged working rollers for pressing the powder mixture into a corresponding one of the self-supporting electrode films, and at least one second press including working rollers (usually arranged vertically) for reducing the thickness of the corresponding self-supporting electrode film.

[0009] The apparatus may include a rolling line extension module. The rolling line extension module may be inserted into a rolling line in a pair of rolling lines and may include at least one additional second press comprising working rolls (typically arranged vertically) for reducing the thickness of the corresponding self-supporting electrode film. Typically, the number of presses may be directly related to the final electrode film thickness, porosity and density and the corresponding film mechanical strength (such as elongation at break and tensile strength) and the speed of the rolling line. By adopting a modular system rather than having a fixed number of presses, the apparatus may customize these parameters for various material types with different electrode specifications.

[0010] Each rolling line may include one or more conveyors arranged to support the corresponding self-supporting electrode film when the corresponding self-supporting electrode film is supplied from at least one second press of the rolling line to the laminator. One or more conveyors may be arranged to support the corresponding self-supporting electrode film when the corresponding self-supporting electrode film is supplied from the first press of at least one second press of the rolling line to the second press of at least one second press. The speed of one or more conveyors between at least one second press of the rolling line and the laminator may be controlled to be different from the speed of one or more conveyors between the first press of at least one second press of the rolling line and the second press of at least one second press. One or more conveyors may be arranged to support the corresponding self-supporting electrode film when the corresponding self-supporting electrode film is supplied from at least one first press of the rolling line to at least one second press. The speed of the conveyor between each stage (including between the first press of the first press and the second press, between any adjacent second press, and between the second press and the laminator) may be controlled to be different. Each rolling line may include one or more tension sensors arranged to measure the tension of the self-supporting electrode film. The speed of one or more conveyors of the rolling line and / or the speed of the working rolls of at least one second press of the rolling line may be controlled based on the measured tension, for example to prevent film rupture. The one or more conveyors may include at least one vacuum conveyor.

[0011] Another aspect of an embodiment of the present disclosure is a method for manufacturing an electrode for an energy storage device. The method may include setting up the above-mentioned apparatus, preparing a first powder mixture including an electrode active material and a fibrillable binder, fibrillating the fibrillable binder in the first powder mixture by subjecting the first powder mixture to a shear force, pressing the first powder mixture into a first self-supporting electrode film using at least one first press of the first rolling line of the pair of rolling lines, reducing the thickness of the first self-supporting electrode film using at least one second press of the first rolling line, and laminating the first self-supporting electrode film on a first side of a current collector using at least one laminator.

[0012] The method may include preparing a second powder mixture including an electrode active material and a fibrillable binder, fibrillating the fibrillable binder in the second powder mixture by subjecting the second powder mixture to a shear force, pressing the second powder mixture into a second self-supporting electrode film using at least one first press of a second rolling line in the pair of rolling lines, reducing the thickness of the second self-supporting electrode film using at least one second press of the second rolling line, and laminating the second self-supporting electrode film on a second side of the current collector opposite to the first side using at least one laminator while laminating the first self-supporting electrode film on the first side of the current collector.

[0013] Another aspect of an embodiment of the present disclosure is a method for manufacturing an electrode for an energy storage device. The method may include preparing a first powder mixture including an electrode active material and a fibrillable binder, fibrillating the fibrillable binder in the first powder mixture by subjecting the first powder mixture to a shear force, preparing a second powder mixture including an electrode active material and a fibrillable binder, fibrillating the fibrillable binder in the second powder mixture by subjecting the second powder mixture to a shear force, and using a pair of rolling production lines to simultaneously produce a first self-supporting electrode film from the first powder mixture and a second self-supporting electrode film from the second powder mixture, each rolling production line includes at least one first press and at least one second press, the first press includes a horizontally arranged working roller for pressing the corresponding powder mixture into a corresponding self-supporting electrode film, and the second press includes a working roller (usually arranged vertically) for reducing the thickness of the corresponding self-supporting electrode film. The method may also include: continuously with the production of the first and second self-supporting electrode films, supplying the first and second self-supporting electrode films from the corresponding rolling production lines to a laminator and laminating the first and second self-supporting electrode films to opposite sides of the current collector.

[0014] The method may include using one or more conveyors to support the first self-supporting electrode film when the first self-supporting electrode film is fed from the corresponding rolling line to the laminating press. The method may include using one or more conveyors to support the first self-supporting electrode film when the first self-supporting electrode film is fed from the first press of at least one second press of the corresponding rolling line to the second press of at least one second press. The method may include controlling the speed of one or more conveyors between the corresponding rolling line and the laminating press to be different from the speed of one or more conveyors between the first press of at least one first press of the corresponding rolling line and the second press of at least one first press. The method may include using one or more conveyors to support the first self-supporting electrode film when the first self-supporting electrode film is fed from at least one first press of the corresponding rolling line to at least one second press. The method may include controlling the speed of the conveyor to be different between each stage, including between the first press of the first press and the second press, between any adjacent second presses, and between the second press and the laminating press. The method may include measuring the tension of the first free-standing electrode film and controlling the speed of one or more conveyors and / or the speed of the working rolls of at least one second press based on the measured tension, for example to prevent film rupture. The one or more conveyors may include at least one vacuum conveyor.

[0015] Another aspect of an embodiment of the present disclosure is a self-supporting electrode film. The self-supporting electrode film may include an electrode active material and a fibrillable binder. The longitudinal elongation percentage of the self-supporting electrode film may be less than 4%. The longitudinal elongation percentage of the self-supporting electrode film may be less than 2%. The longitudinal tensile strength of the self-supporting electrode film may be greater than 450 kPa. The porosity of the self-supporting electrode film may be less than 32%. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] These and other features and advantages of the various embodiments disclosed herein will be better understood with reference to the following description and accompanying drawings, in which like reference numerals refer to like parts throughout, and in which:

[0017] Figure 1 An apparatus for making an electrode for an energy storage device is shown;

[0018] Figure 2 shows a partial view of the plant, wherein a rolling line extension module is inserted into a rolling line of the plant;

[0019] Figure 3 An operation flow for manufacturing an electrode for an energy storage device is shown;

[0020] Figure 4 Shows Figure 3An exemplary sub-operation flow of step 330 in FIG.

[0021] Figure 5 shows the active material loading as a function of film thickness for an active dry NCM811 electrode; and

[0022] Figure 6 Shown is the C rate performance of the wet electrode relative to the active dry NCM811 electrode. DETAILED DESCRIPTION

[0023] The present disclosure covers various embodiments of apparatus, methods of manufacture, and intermediate and final products thereof for manufacturing electrodes for energy storage devices. The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of several currently contemplated embodiments and is not intended to represent the only form in which the disclosed invention may be developed or utilized. This specification sets forth functions and features in conjunction with the illustrated embodiments. However, it should be understood that the same or equivalent functions may be achieved by different embodiments, which are also intended to be covered within the scope of the present disclosure. It should also be understood that the use of relative terms such as first and second is used solely to distinguish one entity from another, without necessarily requiring or implying any actual such relationship or order between such entities.

[0024] Figure 1An apparatus 100 for manufacturing electrodes for energy storage devices, such as lithium-ion batteries, solid-state batteries, lithium-ion capacitors (LICs), or supercapacitors, is shown. The finished energy storage device may include one or more electrodes assembled by laminating a first self-supporting electrode film 10a and a second self-supporting electrode film 10b to opposite sides of a current collector 20, the current collector being a metal sheet such as aluminum in the case of cathode electrode films 10a, 10b, or a copper metal sheet in the case of anode electrode films 10a, 10b. The apparatus 100 may include at least one laminator 110, at least one laminator 110 for laminating two self-supporting electrode films 10a, 10b to opposite sides of a current collector 20 simultaneously. The laminator 110 may have working rollers 112-1, 112-2, which are arranged horizontally, for example, as shown in the figure, but vertical arrangement is also contemplated. The apparatus 100 may also include a pair of rolling lines 120a, 120b (e.g., arranged as two wings of the apparatus 100), which are operable to produce two self-supporting electrode films 10a, 10b, respectively, and simultaneously feed the two self-supporting electrode films to the laminator 110. The laminator 110 may then laminate the two self-supporting electrode films 10a, 10b on both sides of the current collector as the current collector 20 is unwound from the first reel 130, and then wind the current collector 20 together with the laminated films 10a, 10b on the second reel 140 (or alternatively send to a cutting machine). Thanks to the apparatus 100 and the associated methods described herein, free-standing electrode films 10a, 10b can be efficiently processed even in the following cases: relatively thin free-standing electrode films 10a, 10b (e.g., less than 200 μm or less than 100 μm) and / or electrode films formed of less flexible materials (e.g., battery active materials), such as NCM, NCA, LFP, graphite, and silicon, thereby allowing the production of a variety of energy storage devices for different purposes. In some embodiments, as described in more detail below, the apparatus 100 can have a modular design, thereby allowing the same apparatus 100 to be used to efficiently manufacture electrodes for energy storage devices with different specifications as needed.

[0025] The dry powder mixture 12a, 12b used to produce the free-standing electrode films 10a, 10b may have various formulations and may be produced according to various methods, depending on the specific application of the energy storage device to be fabricated. Some exemplary dry powder formulations and methods that can be used to produce 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 these U.S. applications being incorporated herein by reference in its entirety. Typically, since the first and second free-standing electrode films 10a, 10b will be arranged on the same current collector 20 by the apparatus 100, the two dry powder mixtures 12a, 12b will be formulated and produced in the same manner (and thus may in fact be separated, for example, from the same production batch).

[0026] Each of the rolling lines 120a, 120b may include at least one first press 122a, 122b for pressing one of the powder mixtures 12a, 12b into a corresponding self-supporting electrode film 10a, 10b. Referring to the rolling line 120a as an example (in the case of the rolling line 120b, the letter "b" is used instead of the equivalent reference numeral "a"), the first press 122a may include working rollers 123a-1, 123a-2 arranged horizontally as shown, so that the powder mixture 12a can be poured on top of the working rollers 123a-1, 123a-2 (e.g., from the powder feed conveyor 13a) and the powder mixture 12a emerges from the bottom of the working rollers 123a-1, 123a-2 in the form of a continuous film that has been subjected to pressure and heat from the working rollers 123a-1, 123a-2. To this end, the working rollers 123a-1, 123a-2 of the first press 122a can have an elevated surface temperature (e.g., greater than 70°C). Advantageously, the working rollers 123a-1, 123a-2 can be controlled to rotate at the same speed as each other, wherein the gap between the working rollers 123a-1, 123a-2 can be freely adjusted to influence the film density and porosity required for a specific material and application. In this regard, it should be noted that it may be unnecessary for the first press 122a to generate a shearing effect by the operation of the working rollers 123a-1, 123a-2 with different speeds, especially in the case where the powder mixture 12a has been produced by one of the above-mentioned exemplary methods, in which the powder mixture 12a has been subjected to shear forces, for example, using a jet mill.

[0027] Each of the rolling lines 120a, 120b may also include at least one second press 124a, 124b for reducing the thickness of the corresponding self-supporting electrode film 10a, 10b. Referring again to the rolling line 120a as an example, the second press 124a may include working rolls 125a-1, 125a-2 that are typically (although not necessarily) arranged vertically as shown. Similar to the working rolls 123a-1, 123a-2 of the first press 122a, the working rolls 125a-1, 125a-2 of the second press 124a may have an elevated surface temperature (e.g., greater than 70°C) and may be controlled to rotate at the same speed as each other, wherein the gap between the working rolls 125a-1, 125a-2 may be freely adjusted as needed. Although Figure 1Only a single second press 124a is shown, but it is contemplated that any number of second presses 124a may be arranged in a row, each of which further reduces the thickness of the self-supporting electrode film 10a by applying heat and pressure (e.g., for each second press 124a, the working rollers 125a-1, 125a-2 are in contact with the film 10a, and the gap between the working rollers 125a-1, 125a-2 becomes successively smaller) until the desired film thickness is achieved for a given application. As described in more detail below with respect to the modular aspects of the apparatus 100, for each rolling line 120a, 120b, it is most advantageous to include only a single second press 124a, 124b as part of the infrastructure of the apparatus 100 (where the apparatus 100 may be used as Figure 2 One or more rolling line expansion modules 150 are shown as expansions) to best accommodate production runs using only a single second press 124a, 124b in each of the rolling lines 120a, 120b, such as when relatively thick self-supporting electrode films 10a, 10b are produced. Along the same production line, it is contemplated that in some embodiments, the infrastructure of each of the rolling lines 120a, 120b may include only one or more first presses 122a, 122b without any second presses 124a, 124b.

[0028] As newer energy storage device applications begin to require electrodes made of thinner self-supporting electrode films 10a, 10b, and as the possibilities for active materials grow to include materials that produce less flexible and more fragile self-supporting electrode films 10a, 10b, conventional roll-to-roll processing devices and methods may be insufficient to handle the self-supporting electrode films 10a, 10b without breakage. Therefore, in order to better support the self-supporting electrode films 10a, 10b as each of the self-supporting electrode films 10a, 10b passes through the corresponding rolling lines 120a, 120b toward the laminator 110 (thereafter the self-supporting electrode films 10a, 10b will be fully supported by the more robust current collector 20 and will no longer be self-supporting), it is envisioned that each of the rolling lines 120a, 120b may include one or more conveyors 126a, 126b, such as vacuum conveyors. Referring to the rolling line 120a as an example, one or more conveyors 126a may be arranged to support the self-supporting electrode film 10a at any of a variety of positions, including, for example, i) when the self-supporting electrode film 10a is fed from the second press 124a of the rolling line 120a to the laminator 110, ii) when the self-supporting electrode film 10a is fed from the first press of the second press 124a to the second press of the second press 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 each conveyor 126a may be controlled according to the thickness and tension of the self-supporting electrode film 10a at each specific position, which may be determined by the arrangement of the presses 122a, 124a and their roller speeds, and the arrangement of the downstream laminator 110 and its roller speeds. For example, the speed of the conveyor 126a between the second press 124a and the laminator 110 can be controlled to be different from the speed of the conveyor between the consecutive second presses 124a, and the speed of the conveyor 126a between the second press 124a and the laminator 110 can in turn be different from the speed of the conveyor between the first press 122a and the second press 124a. In fact, the speed of the conveyor 126a can be controlled in a cascade manner, wherein the final laminator speed 110 determines the speed at each upstream position of each of the rolling lines 120a, 120b. As feedback to the control process, each of the rolling lines 120a, 120b can include one or more tension sensors 128a, 128b arranged to measure the tension on the self-supporting electrode membrane 10a, 10b. Load cells or other proximity sensors can be used to maintain optimal tension control by adjusting the rotation speed of the conveyor and the work rolls.The variable speed and / or speed ratio of one or more conveyors 126a, 126b can be controlled so that the speeds between presses are appropriately matched based on the tension measured using any of a variety of algorithms including machine learning models, thereby allowing the lamination speed to remain constant and preventing rupture of the films 10a, 10b.

[0029] Figure 2 A partial view of the device 100 is shown, wherein the rolling line extension module 150 is inserted into the rolling line 120a of the device 100. The rolling line extension module 150 may include at least one additional second press 154a for reducing the thickness of the corresponding self-supporting electrode film 10a, 10b (in this case, the electrode film 10a shown). As shown, for example, the rolling line 120a of the basic device 100 may include a single second press 124a, and the rolling line extension module 150 may introduce one or more additional second presses 154a (as shown, two additional second presses 154a). For example, the additional second press 154a can be inserted into the rolling line 120a just in front of the second press 124a of the basic device 100. (Note that in the case where the rolling line 120a does not include the second press 124a, the additional second press 154a introduced by the rolling line extension module 150 can be the only thickness reduction press of the device 100). Figure 2 The dashed arrows in FIG. 1 show a possible insertion process, wherein the first press 122a is moved away from the laminator 110 (at Figure 2 and the rolling line extension module 150 is placed into the resulting space (in Figure 2 ), wherein the dashed line shows the rolling line extension module 150 before being inserted into the rolling line 120a.

[0030] Similar to each of the second presses 124a, 124b of the corresponding rolling line 120a of the base equipment 100, each additional second press 154a introduced by the rolling line extension module 150 may include working rolls 155a-1, 155a-2 that are typically (although not necessarily) arranged vertically as shown. The working rolls 155a-1, 155a-2 of each additional second press 154a may have an elevated surface temperature (e.g., greater than 70°C) and may be controlled to rotate at the same speed as each other, wherein the gap between the working rolls 155a-1, 155a-2 may be freely adjusted as needed. It is conceivable that the rolling line extension module 150 may also include one or more additional conveyors 156a that may be inserted between the conveyors 126a of the rolling line 120a as shown. The rolling line extension module 150 may further include one or more additional tension sensors 158a, which are arranged to measure the tension when the self-supporting electrode film 10a passes through (e.g., before or after) the additional second press 154a of the rolling line extension module 150. The additional conveyor 156a and the additional tension sensor 158a may be connected to the same speed control system as the conveyor 126a and tension sensor 128a of the base equipment 100. It should be noted that the rolling line extension module 150 can be symmetrically designed to be inserted into the rolling line 120b instead of the rolling line 120a as shown (and in this case, the letter "b" can be used instead of the equivalent reference numeral of "a", although not shown separately).

[0031] With the aid of the rolling line extension module 150, the same device 100 can be easily customized for different production runs with different specifications for the energy storage devices to be produced. A manufacturer of energy storage devices manufactured using relatively thick self-supporting electrode films 10a, 10b can use only the basic device 100 without a rolling line extension module 150 or only a single rolling line extension module 150 in each of the rolling lines 120a, 120b, while a manufacturer who needs to produce thinner self-supporting electrode films 10a, 10b can insert several rolling line extension modules 150 (or, in some cases, a rolling line extension module 150 with a greater number of additional second presses 154a, 154b, although standardized rolling line extension modules 150 may be preferred). The same device 100 can meet the needs of both manufacturers, allowing efficient production and use of the device 100 and the rolling line extension module 150. Without a modular design, it would be necessary to either i) sell and produce a variety of different sizes of apparatus 100, or custom manufacture the apparatus 100 for each manufacturer (with associated inefficiencies and costs in either case), or ii) produce only the largest possible apparatus 100 with the largest possible number of second presses 124a, 124b that could be used. In the latter case, the apparatus 100 may become unreasonably expensive in terms of purchase price for manufacturers who do not need to reduce the thickness of the self-supporting electrode films 10a, 10b too much, and in terms of the personnel required to maintain and inspect and operate such a large apparatus 100. In addition, any unused second press 124a, 124b in a given run increases the risk of damaging the self-supporting electrode films 10a, 10b on the way to the laminator 110, reducing the yield of the run and making a large number of unused second presses 124a, 124b a burden on the manufacturer.

[0032] Along the same production line, manufacturers producing a variety of different products are better served by the modular device 100, which can allow manufacturers to increase or decrease the number of presses by attaching or removing the rolling line extension module 150 as needed. The device 100 can be used for some operations with several rolling line extension modules 150, and for other operations with few or no rolling line extension modules 150, thereby reducing the relevant costs of these operations in terms of personnel and output. As another possibility, it is conceivable that the rolling line extension module 150 can be used as a replacement when the press 154a, 154b of another rolling line extension module 150 needs to be repaired. It is not necessary to shut down the entire production line before repairing the damaged pressing station, but the rolling line extension module 150 in question can be simply replaced with a new rolling line extension module 150. In this way, the manufacturing process can continue after only a moment's delay. Even when the manufacturing process is ongoing, the damaged rolling line extension module 150 can be repaired without significantly interrupting production.

[0033] Figure 3 The operation flow for manufacturing an electrode of an energy storage device according to the disclosed innovation is shown. In particular, Figure 3 The operation process can be used Figure 1 and Figure 2The process may be performed by the apparatus 100 described above. The process may begin with producing a first mixture 12a and a second powder mixture 12b (step 310) and fibrillating the binder contained in the powder mixtures 12a, 12b (step 320). For example, as described in the inventor's own patents and patent applications incorporated by reference above, the powder mixtures 12a, 12b may include at least one type of fibrillable binder, such as polytetrafluoroethylene (PTFE), polyvinyl pyrrolidone (PVP), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyethylene (PE) or carboxymethyl cellulose (CMC), or a combination of the above binders or copolymers, in addition to at least one type of electrode active material (e.g., lithium metal oxide in the case of the cathode, or graphite or silicon in the case of the anode). The fibrillable binders are characterized by their soft, pliable consistency, and in particular, the ability to stretch, lengthen and thin to present a fibrous state when the fibrillable binder is subjected to shear forces. Due to the use of one or more fibrillable binders, which can be further chemically or thermally activated to increase their flexibility as described in the inventor's patents and patent applications, the powder mixture can be pressed into a self-supporting film without breaking and without excessive use of toxic and expensive solvents, such as N-methylpyrrolidone (NMP). The binder can be fibrillated by subjecting the powder mixture 12a, 12b to shear forces, for example using a kitchen blender, an industrial blender, a coffee grinder, a grain grinder, a high-speed mixer, a cyclone paint mixer, a rotary mixer, a planetary mixer, a high shear disperser (such as Admix Rotosolver), a high shear granulator (such as Diosna P1-6), a high shear micronizer (such as a jet mill), a high shear emulsifier, a high shear mixer (such as Ross Megashear mixer) or an acoustic mixer. As described above, the powder mixture 12a, 12b can actually be separated from the same production batch. In this regard, it should be noted that step 310 and step 320 may be combined, or equivalently, step 310 may encompass producing the first and second powder mixtures 12a, 12b without separating them (ie, producing enough powder mixture for both rolling lines 120a, 120b).

[0034] Figure 4 The operational flow may continue using a pair of rolling lines 120a, 120b (such as Figure 1 and Figure 2 The rolling line) simultaneously produces a first self-supporting electrode film 10a and a second self-supporting electrode film 10b from the powder mixture 12a, 12b (step 330). Figure 4An exemplary sub-operation flow for this step is shown, which may begin by inserting one or more rolling line extension modules 150 into the rolling lines 120a, 120b as needed to achieve specific specifications (e.g., thickness, density and porosity, as well as mechanical strength, such as film tensile strength and elongation) for each self-supporting electrode film 10a, 10b of the electrode to be manufactured (step 410). In the case where the rolling lines 120a, 120b of the apparatus 100 have been expanded accordingly, Figure 4 The sub-operation process can continue to use the corresponding first press 122a, 122b to press the powder mixture 12a, 12b into the corresponding self-supporting electrode film 10a, 10b (step 420), use the conveyor 126a, 126b to support the self-supporting electrode film 10a, 10b when the self-supporting electrode film 10a, 10b passes through the rolling production line 120a, 120b (step 430), and use any second press 124a, 124b that is part of the basic equipment 100 plus any additional second press 154a, 154b added by the rolling production line expansion module 150 to reduce the thickness of the corresponding self-supporting electrode film 10a, 10b (step 440). Due to the innovative design of the apparatus 100 , two free-standing electrode films 10 a , 10 b can be produced simultaneously and appropriately thinned, thereby allowing the two free-standing electrode films 10 a , 10 b to be subsequently fed to the laminator 110 and laminated simultaneously onto the current collector 20 .

[0035] In particular, returning a reference Figure 3, the operational flow may continue by feeding the first self-supporting electrode film 10a and the second self-supporting electrode film 10b from the respective rolling lines 120a, 120b to the laminator 110 (step 340). Of particular note, this may be done while continuing to support the self-supporting electrode films 10a, 10b on the conveyors 126a, 126b whose speeds are appropriately controlled, thereby minimizing the likelihood of fracture of the films 10a, 10b at their thinnest, lowest fracture strength or most vulnerable locations. In this regard, the operational flow may also include measuring the tension of each self-supporting electrode film 10a, 10b at one or more locations using tension sensors 128a, 128b, 158a, 158b (step 350), and controlling the rolling line speed accordingly as described above, in particular by adjusting the speed of the conveyors 126a, 126b, 156a, 156b (step 360) and / or the rotational speed of the work rolls. When the self-supporting electrode films 10a, 10b leave the respective rolling lines 120a, 120b, the laminator 110 can laminate the self-supporting electrode films 10a, 10b to opposite sides of the current collector 20 (step 370), in some cases, the current collector 20 can be pre-treated with chemical etching, coated with a conductive adhesive layer, or both pre-treated with chemical etching and coated with a conductive adhesive layer. The completed electrode can be wound on a second reel 140 or cut by a cutter. By using a pair of rolling lines 120a, 120b to simultaneously produce the self-supporting electrode films 10a, 10b, and in a continuous process (especially when the rolling lines 120a, 120b are arranged to serve as the upstream wings of different central presses of the laminator 110), the disclosed manufacturing process can be carried out at a speed exceeding twice the speed of a process for producing two films using the same single rolling line. In a process where two films are produced using the same single rolling line, a separate laminator must be loaded with two rolls of produced active material film and one roll of current collector, where the current collector is between the films formed and laminated on the current collector, so that the final electrode lamination speed is at most half the speed of the rolling line. The disclosed apparatus 100 is capable of achieving twice the speed of this multi-step process.

[0036] Exemplary data for free-standing electrode films 10a, 10b made from three different active materials are provided in Table 1 below.

[0037] Table 1

[0038]

[0039] In order to produce each membrane group to a specified thickness ("Membrane Group" column), the disclosed apparatus 100 can be equipped with a suitable number of presses ("Number of Presses" column). In this regard, the number of presses shown in Table 1 (for which the data ranges from 1 to 15) should be understood to refer to all presses in a given rolling line 120a, including both the first press 122a and the second press 124a, as well as any additional second presses 154a added using one or more rolling line expansion modules 150. For example, a 250 μm NCM cathode membrane group can be produced using an apparatus 100 having a single first press 122a and no second press 124a in a rolling line 120a for producing membranes (number of presses = 1), while a 65 μm NCM cathode membrane group can be produced using the same apparatus 100 having a single first press 122a in the rolling line 120a but having fourteen additional second presses 154a added by the rolling line expansion modules 150 (number of presses = 15). Table 1 shows average thicknesses (column "Average Thickness"), which are examples corresponding to actual measured thicknesses of each membrane group in practice.

[0040] The last five columns of Table 1 show exemplary data for such a membrane, in which it can be seen that the tensile strength and membrane density of the membrane increase as the membrane is thinned and vary from material to material, while the elongation percentage of the membrane (maximum machine direction elongation before breaking) and the membrane porosity decrease as the membrane is thinned and also vary from material to material. The elongation percentage (elongation) can be determined by a tensile test (where the machine direction can refer to the tensile direction in which the membrane is elongated by the operation of the working rolls). An exemplary tensile test can measure the stretching distance before a 2.5 cm wide × 10 cm long (machine direction) membrane strip breaks under an initial tension of, for example, 5 gf. In particular, it is noted that NCM cathode membranes and graphite anode membranes are more difficult to handle than activated carbon membranes due to the significantly less flexibility (and therefore lower elongation percentage) of the NCM cathode membranes and graphite anode membranes. It can be seen that this difficulty becomes more pronounced for thinner membranes. With the aid of the apparatus 100 and the associated processes described herein, it is contemplated that a variety of self-supporting electrode films 10a, 10b can be successfully and efficiently produced on the same apparatus 100. For example, the self-supporting electrode films 10a, 10b can be made of various materials including NCM, graphite, or activated carbon, and can have a thickness from 300 μm to 50 μm or less. For each run of the apparatus 100, the rolling line 120a, 120b can be equipped accordingly for the desired thickness or other parameters, and can be expanded as needed by inserting a rolling line expansion module 150 to increase the number of presses for thickness reduction. In addition, due to the innovative design of the apparatus 100, preferably including conveyors 126a, 126b, 156a, 156b to support the fragile film as it passes through the rolling line 120a, 120b before being laminated to the current collector 20, it is expected that the resulting self-supporting electrode film 10a, 10b can have a tensile strength from 40kPa up to greater than 100kPa, greater than 450kPa or even greater than 600kPa (in the case of NCM or graphite), or greater than 1100kPa for very thin graphite anode films. At the same time, the longitudinal elongation percentage can be in the range of 10% to less than 4% or even less than 2%, sometimes as low as 0.50% or even 0.20% (in the case of NCM or graphite). Without the innovation of the disclosed apparatus 100 and related processes, effective processing of such fragile self-supporting electrode films 10a, 10b would not be achieved.

[0041] Typically, it is expected that a self-supporting film having a tensile strength greater than 100 kPa and a percent elongation of less than 10% in the longitudinal direction may require a unique tension control design to achieve a high-speed production process. The use of the expected conveyors 126a, 126b, 156a, 156b combined with strategically placed sensors 128a, 128b (sometimes using multiple measurement methods) along the axis of the self-supporting film can provide the necessary control to handle sensitive battery active material electrode films 10a, 10b. The difficulty in producing dry battery electrodes with self-supporting films comes from the inherent brittleness of the active materials, which makes conventional web processing methods impossible. The disclosed apparatus 100 and method can overcome these difficulties by using conveyors 126a, 126b, 156a, 156b to support and transport the self-supporting electrode films 10a, 10b through each pressing station in an automatic self-threading process.

[0042] Advantageously, the multiple pressing design of the apparatus 100 can allow for greater flexibility in customizing final electrode properties (such as thickness uniformity, density, and porosity) compared to other dry electrodes produced with or without free-standing membranes. As shown in Table 1 above, for example, the membrane density can be selected as desired (e.g., between 3.02 g / cc and 3.40 g / cc for NCM cathodes, or between 1.21 g / cc and 1.71 g / cc for graphite anodes), and the membrane porosity can also be selected as desired (e.g., between 25.9% and 34.2% for NCM cathodes, or between 23.5% and 46.0% for graphite anodes), and low porosity (e.g., less than 32%) can be achieved due to the use of the apparatus 100 to effectively process the fragile free-standing electrode membranes 10a, 10b. In general, dry battery electrode technology requires the ability to control the loading, porosity, and uniformity of the active material layer. Other dry battery electrode processing technologies cannot precisely control these parameters. For example, dry spray or dry deposition electrode processes that do not produce self-supporting films may be limited in the ability to control thickness uniformity because the powder is located on top of the current collector and cannot flow in multiple axes during pressing. In addition, density and porosity may be limited by the amount of powder that can be applied to the current collector before pressing and the pressing force that can be used without damaging the current collector. The disclosed innovative technology can meet all of these requirements by using multiple pressing stations working in series to simultaneously produce self-supporting electrode films 10a, 10b for both sides of the current collector 20. In addition, the thickness reduction pressing station of the system is set to a modular construction (using a freely insertable rolling line expansion module 150) instead of a fixed number of presses, allowing customization based on different material types such as anode materials or customized cathode materials.

[0043] Figure 5The active material loading of an active dry NCM811 electrode (Ni:Co:Mn ratio 8:1:1) is shown as a function of film thickness. As shown, the degree of active material loading (expressed as discharge capacity per unit area (mAh / cm 2 )) 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, for example, less than 6 mAh / cm 2 The discharge capacity per unit area of ​​​​the film is generally suitable as a drop-in technology for high power density applications (such as electric vehicles (EV)). At the same time, electrodes made of thicker films (e.g., greater than 80μm) may exhibit, for example, greater than 6mAh / cm 2 The discharge capacity per unit area is generally applicable to high energy density applications such as energy storage systems (ESS). Using conventional methods, this wide range of applications requires different manufacturing equipment dedicated to each application, resulting in high costs and inefficiencies for manufacturers. In contrast, embodiments of the apparatus 100 described herein can advantageously allow the production of a variety of electrodes using the same apparatus 100, wherein the thickness and other parameters of the self-supporting films 10a, 10b can be freely selected by modifying the number of presses 124a, 124b, 154a, 154b for thickness reduction using a rolling line extension module 150, for example, allowing batteries for EVs, ESSs, and other applications to be manufactured at relatively low cost and high efficiency.

[0044] Figure 6 The C rate performance of a wet electrode relative to an active dry NCM811 electrode (ADE) is shown. An active dry electrode may refer to, for example, an electrode produced by an active dry process as described herein and incorporated herein by reference, while an intended wet electrode (WET REF) may be manufactured by, for example, a conventional slurry coating process. It can be seen that the performance of the electrode at a given C rate (expressed as a discharge capacity retention rate (%)) may depend on the thickness of the active dry electrode film, with thinner ADE films (e.g., 54 μm) showing better performance at higher C rates than thicker ADE films (e.g., 78 μm) or wet electrodes. Therefore, depending on the desired C rate of the battery to be produced, the manufacturer may wish to be able to freely adjust the thickness of the electrode film, which is not easy to do and is generally not possible using conventional manufacturing equipment. However, according to embodiments of the apparatus 100 described herein, the thickness of the self-supporting membranes 10a, 10b may be customized as required by the desired C rate or other parameters of the energy storage device to be produced.

[0045] In the above embodiment, it is described how to use the apparatus 100 to produce a double-sided electrode by running two rolling lines 120a, 120b simultaneously and laminating two self-supporting electrode films 10a, 10b to opposite sides of the current collector 20. However, the method described herein is not limited to using the apparatus 100 in this manner. For example, in order to produce a single-sided electrode, a single rolling line 120a of the apparatus 100 can be run, and the laminator 110 only laminates a single self-supporting electrode film 10a on the current collector 20. It should also be recognized that the working rollers 112-1, 112-2 of the laminator 110, the working rollers 123a-1, 123a-2, 125a-1, 125a-2 of the rolling line 120a, the working rollers 155a-1, 155a-2 of the rolling line extension module 150, and any corresponding working rollers arranged relative to the rolling line 120b can be supported by one or more support rollers, such as 4HI, 6HI or multi-roller configurations.

[0046] The above description is given by way of example and not limitation. Based on the above disclosure, those skilled in the art can design variations within the scope and spirit of the invention disclosed herein. In addition, the various features of the embodiments disclosed herein can be used alone or in different combinations from each other, and are not intended to be limited to the specific combinations described herein. Therefore, the scope of the claims is not limited by the embodiments shown.

Claims

1. An apparatus for manufacturing an electrode for an energy storage device, the apparatus comprising: at least one laminator for laminating two free-standing electrode films simultaneously on opposite sides of a current collector; as well as a pair of rolling lines operable to respectively produce the two self-supporting electrode films and to simultaneously feed the two self-supporting electrode films to the laminator, each of the rolling lines comprising: at least one first press including horizontally arranged work rolls for pressing the powder mixture into a respective one of said free-standing electrode films; as well as At least one second press including work rolls for reducing the thickness of the respective free-standing electrode film.

2. The equipment according to claim 1 also includes a rolling line extension module, which can be inserted into the rolling line of the pair of rolling lines and includes at least one additional second press, and the at least one additional second press includes a working roller for reducing the thickness of the corresponding self-supporting electrode film.

3. The device according to claim 1, wherein: Each of the rolling lines further comprises one or more conveyors arranged to support the respective self-supporting electrode film as it is fed from the at least one second press of the rolling line to the laminator.

4. The device according to claim 3, wherein: The one or more conveyors are also arranged to support the respective self-supporting electrode film as it is fed from a first press of the at least one second press to a second press of the at least one second press of the rolling line.

5. The device according to claim 4, wherein: The speed of the one or more conveyors between the at least one second press in the rolling line and the laminating machine is controlled to be different from the speed of the one or more conveyors between the first press in the at least one second press in the rolling line and the second press in the at least one second press.

6. The device according to claim 4, wherein: The one or more conveyors are further arranged to support the respective self-supporting electrode film as it is fed from the at least one first press to the at least one second press of the rolling line.

7. The device according to claim 3, wherein: Each of the rolling lines further comprises one or more tension sensors arranged to measure the tension of the free-standing electrode film, the speed of the one or more conveyors of the rolling line being controlled based on the measured tension.

8. The device according to claim 7, wherein: The tension measured by the one or more tension sensors of each rolling line is also used to control the speed of the working rolls of the at least one second press of the rolling line.

9. The device according to claim 3, wherein: The one or more conveyors include at least one vacuum conveyor.

10. The device according to claim 1, wherein: The working rolls of the at least one second press are arranged vertically.

11. A method for manufacturing an electrode for an energy storage device, the method comprising: Providing the device according to claim 1; preparing a first powder mixture including an electrode active material and a fibrillable binder; fibrillating the fibrillable binder in the first powder mixture by subjecting the first powder mixture to shear forces; pressing the first powder mixture into a first free-standing electrode film using at least one first press of a first rolling line of a pair of rolling lines; reducing the thickness of the first free-standing electrode film using at least one second press in the first rolling line; and The first free-standing electrode film is laminated to a first side of a current collector using at least one laminator.

12. The method according to claim 11, further comprising: preparing a second powder mixture including an electrode active material and a fibrillable binder; fibrillating the fibrillable binder in the second powder mix by subjecting the second powder mix to shear forces; pressing the second powder mixture into a second self-supporting electrode film using at least one first pressing machine of a second rolling line of the pair of rolling lines; reducing the thickness of the second free-standing electrode film using at least one second press in the second rolling line; and Simultaneously with the laminating the first free-standing electrode film to the first side of the current collector, the second free-standing electrode film is laminated to a second side of the current collector opposite to the first side using the at least one laminator.

13. A method for manufacturing an electrode for an energy storage device, the method comprising: preparing a first powder mixture including an electrode active material and a fibrillable binder; fibrillating the fibrillable binder in the first powder mixture by subjecting the first powder mixture to shear forces; preparing a second powder mixture including an electrode active material and a fibrillable binder; fibrillating the fibrillable binder in the second powder mix by subjecting the second powder mix to shear forces; using a pair of rolling lines to simultaneously produce a first self-supporting electrode film from the first powder mixture and a second self-supporting electrode film from the second powder mixture, each of the rolling lines comprising at least one first press and at least one second press, the at least one first press comprising horizontally arranged working rolls for pressing the corresponding powder mixture into the corresponding self-supporting electrode film, the at least one second press comprising working rolls for reducing the thickness of the corresponding self-supporting electrode film; and, Continuously with the production of the first and second self-supporting electrode films, the first and second self-supporting electrode films are supplied from respective rolling lines to a laminator and laminated to opposite sides of a current collector.

14. The method of claim 13, further comprising using one or more conveyors to support the first self-supporting electrode film as it is fed from a corresponding rolling line to the laminator.

15. The method according to claim 14 further includes using the one or more conveyors to support the first self-supporting electrode film when the first self-supporting electrode film is supplied from the first press of the at least one second press of the corresponding rolling production line to the second press of the at least one second press.

16. The method according to claim 15 further includes controlling the speed of one or more conveyors between the corresponding rolling line and the laminating machine to be different from the speed of the one or more conveyors between the first press of the at least one first press of the corresponding rolling line and the second press of the at least one first press.

17. The method of claim 15, further comprising supporting the first self-supporting electrode film using the one or more conveyors as the first self-supporting electrode film is fed from the at least one first press to the at least one second press of the corresponding rolling line.

18. The method of claim 14, further comprising measuring tension in the first free-standing electrode film and controlling a speed of the one or more conveyors based on the measured tension.

19. The method of claim 18, further comprising controlling the speed of the work rolls 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 working rolls of the at least one second press are arranged vertically.

22. A self-supporting electrode membrane comprising: Electrode active materials; as well as Fibrillable binder, Wherein, the longitudinal elongation percentage of the self-supporting electrode film is less than 4%.

23. The self-supporting electrode membrane according to claim 22, wherein: The longitudinal elongation percentage of the self-supporting electrode film is less than 2%.

24. The self-supporting electrode membrane according to claim 22, wherein: The longitudinal tensile strength of the self-supporting electrode membrane is greater than 100 kPa.

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

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