METHOD FOR PRODUCING AN ELECTRODE FOR AN ELECTROCHEMICAL CELL

Abstract

A method for producing an electrode for an electrochemical cell, the method comprising: providing a mixture containing an electroactive material, a binder, and a solvent; rolling the mixture into a film; forming a multilayer stack from the film; forming an electrode film precursor by performing a plurality of successive rolling operations, each rolling operation comprising rolling the multilayer stack through a first gap defined in a direction transverse to a plane of the multilayer stack, the plurality of successive rolling operations comprising: a first rolling operation in which the multilayer stack is in a first orientation with respect to a machine direction, and a second rolling operation in which the multilayer stack is in a second orientation with respect to the machine direction, the second orientation being different from the first orientation;Forming an electrode film by rolling the electrode film precursor through a second gap defined in direction, wherein the second gap is less than or equal to the first gap; and drying the electrode film to remove at least some of the solvent to form the electrode.

Description

INTRODUCTION The present invention relates to a method for producing an electrode for an electrochemical cell by rolling. High-energy-density electrochemical cells, such as lithium-ion batteries, can be used in a wide variety of consumer goods and vehicles, for example, in battery-electric or hybrid electric vehicles. Battery-powered vehicles are a promising transportation option, as technological advancements in battery performance and lifespan continue. From EP 1 239 528 A2, a method for producing a multilayer electrode is known, which allows for the simple production of an electrode or electrode composite unit optimized for the respective application. It is proposed that a first layer be rolled onto a substrate and at least one further functional layer be produced by spraying on a powder. In order to achieve thermal fixation of a layer by means of binders, in addition to mechanical fixation, it is advantageous if the layer is rolled on using one or more heated rollers. This also allows a sprayed layer, onto which a further layer is rolled, to be thermally fixed by the binders. Further details of the state of the art can be found in documents US 2018 / 0205064A1 and US 2016 / 0211505A1. SUMMARY This section contains a general summary of the invention. According to the invention, a method for manufacturing an electrode for an electrochemical cell is presented, characterized by the features of claim 1. The process comprises providing a mixture. The mixture contains an electroactive material, a binder, and a solvent. The process further comprises rolling the mixture to form a film. The process further comprises forming a multilayer stack from the film. The process further comprises forming an electrode film precursor by performing several successive rolling operations. Each rolling operation involves rolling the multilayer stack through a first gap defined in a direction transverse to a plane of the multilayer stack. The majority of successive rolling operations comprise a first and a second rolling operation. In the first rolling operation, the multilayer stack is in a first orientation with respect to a machine direction. In the second rolling operation, the multilayer stack is in a second orientation with respect to the machine direction.The second orientation differs from the first. The process further comprises the formation of an electrode film by rolling the electrode film precursor through a second, directionally defined gap. The second gap is smaller than or equal to the first gap. The process also comprises drying the electrode film to remove at least some of the solvent. In one aspect, the second orientation deviates from the first orientation by approximately 85-95°. In one aspect, the electroactive material has a knock density of less than or equal to approximately 1.3 g / cm3. In one aspect, the number of successive rolling processes ranges from 2 to 50. In one aspect, the second slit is smaller than the first slit. In one aspect, the second gap measures 20 µm - 2 mm. In one aspect, preparation involves forming a premix by mixing the electroactive material and a conductive filler. Preparation also includes forming the mixture by lump-mixing the premix, the binder, and the solvent. In one aspect, the provision involves forming the mixture by kneading the electroactive material, a conductive filler, the binder and the solvent. In one aspect, the process also includes coupling the electrode to a current collector after drying. In one aspect, coupling involves applying an electrically conductive adhesive between the electrode and the current collector. Coupling also includes hot lamination of the electrode to the current collector. In one aspect, hot lamination involves passing the electrode and current collector, with the electrically conductive adhesive in between, through a third, directionally defined gap. This third gap is larger than the second gap. In one aspect, coupling also includes preheating the electrode and the current collector before hot lamination. In one aspect, the current collector is a grid current collector. Coupling involves pressing the electrode onto the grid current collector. In one aspect, forming the electrode film involves applying the foil before rolling. Furthermore, an electrode for an electrochemical cell is described. The electrode contains an electroactive material, a binder, and a conductive filler. The electroactive material is present in an amount of 80–98 wt%. The electroactive material has a knock density of less than approximately 2 g / cm³. The binder is present in an amount of approximately 0.5–10 wt%. The conductive filler is present in an amount of approximately 0.5–15 wt%. The electrode is configured to exhibit a discharge capacity of approximately 0.5–50 mAh / cm² during the cyclic operation of an electrochemical cell containing the electrode. In one aspect, the electroactive material is a positive electroactive material. The positive electroactive material contains an olivine compound. In one aspect, the electroactive material comprises a lithium manganese iron phosphate. In several aspects, this disclosure provides an electrode arrangement. The electrode arrangement comprises an active material layer, a current collector, and an electrically conductive adhesive layer. The active material layer contains the electrode. The electrically conductive adhesive layer is located between the electrode and the current collector. In one aspect, the electrically conductive adhesive layer contains a polymer and a conductive filler. The weight ratio of the conductive filler to the polymer is in the range of approximately 0.1–50%. In several aspects, the present invention provides an electrode arrangement for an electrochemical cell. The electrode arrangement comprises two active material layers, a current collector, and two conductive adhesive layers. Each of the two active material layers has a thickness of approximately 20 µm to 2 mm. Each of the two active material layers has a porosity of approximately 25–65%. Each of the two active material layers contains lithium manganese iron phosphate, a binder, and a conductive filler. The lithium manganese iron phosphate is present in an amount of approximately 80–98 wt%. The binder is present in an amount of approximately 0.5–10 wt%. The conductive filler is present in an amount of approximately 0.5–15 wt%. The current collector is located between the two active material layers. Each of the conductive adhesive layers is located between the current collector and one of the two active material layers.Each active material layer is configured to have a discharge capacity of approximately 4 mAh / cm2 or greater during the cyclic operation of an electrochemical cell containing the electrode assembly. Further areas of application will become apparent from the description given here. The description and specific examples in this summary serve only for illustration. BRIEF DESCRIPTION OF THE DRAWINGS The drawings described here serve only to illustrate selected embodiments and not all possible implementations. Fig. 1 is a schematic representation of an electrochemical battery cell for the cyclic movement of lithium ions; Fig. 2 is a flowchart illustrating a method for producing an electrode by a rolling process according to various aspects of the present invention; Fig. 3 is a perspective view of a method for forming a film according to various aspects of the present invention; Fig. 4 is a perspective view of a stack according to various aspects of the present invention; Fig. 5 is a perspective view of a step in a method for forming an electrode film precursor according to various aspects of the present invention; Fig.Figure 6 is a perspective view of a further step of a method for forming an electrode film precursor according to various aspects of the present invention; Figure 7 is a perspective view of a method for forming an electrode film according to various aspects of the present invention; Figure 8 is a side view of a method for forming an electrode arrangement according to various aspects of the present invention; Figure 9 is a sectional view of the electrode arrangement formed according to the method of Figure 8; Figure 10 is a scanning electron microscope (SEM) image of an electrode arrangement according to various aspects of the present invention; Figure 11 is an SEM image of an electrode according to various aspects of the present invention; FigureFigure 12 is a graph of the specific capacity and voltage for an electrochemical half-button cell with one electrode according to various aspects of the present invention; and Figure 13 is a graph showing the discharge capacity for 25 cycles in an electrochemical half-button cell with one electrode according to various aspects of the present invention. The corresponding reference symbols designate corresponding parts in the different views of the drawings. DETAILED DESCRIPTION Exemplary embodiments are now described in more detail with reference to the attached drawings. The present technology relates to rechargeable lithium-ion batteries that can be used in vehicle applications. However, the present technology can also be used in other electrochemical devices that cyclically move lithium ions, e.g., in electronic handheld devices or energy storage systems (ESS). General function, structure and composition of the electrochemical cell An electrochemical cell generally contains a first electrode, such as a positive electrode or cathode, a second electrode, such as a negative electrode or anode, an electrolyte, and a separator. In a lithium-ion battery pack, electrochemical cells are often electrically connected in a stack to increase overall power. Lithium-ion electrochemical cells function by reversibly conducting lithium ions back and forth between the negative and positive electrodes. The separator and electrolyte can be positioned between the negative and positive electrodes. The electrolyte is suitable for conducting lithium ions and can be in liquid, gel, or solid form. Lithium ions move from the positive electrode to the negative electrode during charging and in the opposite direction during discharging. Each of the negative and positive electrodes within a stack is typically electrically connected to a current collector (e.g., a metal such as copper for the negative electrode and aluminum for the positive electrode). During battery operation, the current collectors belonging to the two electrodes are connected by an external circuit that allows the electron-generated current to flow between the negative and positive electrodes to compensate for the transport of lithium ions. The electrodes can generally be incorporated into various commercially available battery designs, such as prismatic cells, wound cylindrical cells, button cells, pouch cells, or other suitable cell shapes. The cells can comprise a single-electrode-per-polarity structure or a stacked structure with multiple positive and negative electrodes mounted in parallel and / or series electrical configurations. Specifically, the battery can include a stack of alternating positive and negative electrodes with separators between them. While the positive electroactive materials in batteries can be used for primary or single-use applications, the resulting batteries generally exhibit desirable cycle characteristics for secondary battery use through multiple cyclic uses of the cells. An exemplary schematic representation of a lithium-ion battery 20 is shown in Fig. 1. The lithium-ion battery 20 comprises a negative electrode 22, a positive electrode 24, and a porous separator 26 (e.g., a microporous or nanoporous polymeric separator) arranged between the negative and positive electrodes 22, 24. An electrolyte 30 is arranged between the negative and positive electrodes 22, 24 and in the pores of the porous separator 26. The electrolyte 30 can also be present in the negative electrode 22 and the positive electrode 24, e.g., in pores. A current collector 32 for the negative electrode can be positioned on or near the negative electrode 22. A current collector 34 for the positive electrode can be positioned on or near the positive electrode 24. Although not shown, the current collector 32 for the negative electrode and the current collector 34 for the positive electrode can be coated on one or both sides. In certain aspects, the current collectors can be coated on both sides with an electroactive material / electrode layer. The current collector 32 for the negative electrode and the current collector 34 for the positive electrode each collect free electrons and move them to and from an external circuit 40. The interruptible external circuit 40 includes a load device 42 and connects the negative electrode 22 (via the current collector 32 of the negative electrode) and the positive electrode 24 (via the current collector 34 of the positive electrode). The porous separator 26 acts as both an electrical insulator and a mechanical support. Specifically, the porous separator 26 is positioned between the negative electrode 22 and the positive electrode 24 to prevent or reduce physical contact and thus the occurrence of a short circuit. The porous separator 26 not only provides a physical barrier between the two electrodes 22 and 24, but can also provide a path of minimal resistance for the internal flow of lithium ions (and similar anions) during the lithium-ion cycle, thereby facilitating the operation of the lithium-ion battery 20. The lithium-ion battery 20 can generate an electric current during discharge through reversible electrochemical reactions that occur when the external circuit 40 is closed (to electrically connect the negative electrode 22 and the positive electrode 24) and when the negative electrode 22 contains a relatively larger amount of cyclically mobile lithium. The chemical potential difference between the positive electrode 24 and the negative electrode 22 drives the electrons generated by the oxidation of lithium (e.g., embedded / alloyed / plated lithium) at the negative electrode 22 through the external circuit 40 toward the positive electrode 24. Lithium ions, also generated at the negative electrode, are simultaneously transported through the electrolyte 30 and the porous separator 26 to the positive electrode 24.The electrons flow through the external circuit 40, and the lithium ions migrate through the porous separator 26 into the electrolyte 30 to be incorporated / alloyed / plated into a positive electroactive material of the positive electrode 24. The electric current flowing through the external circuit 40 can be utilized and passed through the load device 42 until the lithium in the negative electrode 22 is consumed and the capacity of the lithium-ion battery 20 has decreased. The lithium-ion battery 20 can be charged or recharged at any time by connecting an external power source (e.g., a charger) to it, in order to reverse the electrochemical reactions that occur during battery discharge. Connecting an external power source to the lithium-ion battery 20 forces the lithium ions at the positive electrode 24 to move back towards the negative electrode 22. The electrons flowing back to the negative electrode 22 through the external circuit 40 and the lithium ions carried back to the negative electrode 22 by the electrolyte 30 through the separator 26 combine at the negative electrode 22 and replenish it with stored lithium for use during the next battery discharge cycle.Therefore, each discharge and charge event is considered a cycle in which lithium ions are cyclically moved between the positive electrode 24 and the negative electrode 22. The external power source that can be used to charge the lithium-ion battery 20 can vary depending on the size, design, and specific end application of the lithium-ion battery 20. Some notable and exemplary external power sources include AC power sources, such as an AC wall outlet or a vehicle alternator. A converter can also be used to convert AC to DC for charging the battery 20. In many configurations of the lithium-ion battery, the current collector 32 for the negative electrode, the negative electrode 22, the separator 26, the positive electrode 24, and the current collector 34 for the positive electrode are each manufactured as relatively thin layers (e.g., from a few micrometers to one millimeter or less thick) and assembled in electrically series-connected or parallel layers to obtain a suitable electrical energy and power package. Furthermore, the lithium-ion battery 20 may, in certain aspects, contain a variety of other components, which, although not shown here, are nevertheless known to those skilled in the art. For example, the lithium-ion battery 20 may contain a casing, seals, terminal caps, tabs, battery terminals, and any other conventional components or materials that may be found within the battery 20, among others.between or around the negative electrode 22, the positive electrode 24, and / or the separator 26. As mentioned above, the size and shape of the lithium-ion battery 20 can vary depending on the specific applications for which it is designed. Battery-powered vehicles and portable consumer electronics devices are two examples where the lithium-ion battery 20 is most likely to be designed to different size, capacity, and power specifications. The lithium-ion battery 20 can also be connected in series or parallel with other similar lithium-ion cells or batteries to produce a higher output voltage, energy, and / or power if required by the load device 42. Accordingly, the lithium-ion battery 20 can generate an electric current for the load device 42, which can be operationally connected to the external circuit 40. While the load device 42 can be any number of known electrically powered devices, some specific examples of power-consuming load devices include an electric motor for a hybrid or all-electric vehicle, a laptop computer, a tablet computer, a mobile phone, and cordless power tools or devices. The load device 42 can also be a power-generating device that charges the lithium-ion battery 20 for energy storage purposes. In certain other variations, the electrochemical cell can be a supercapacitor, for example, a lithium-ion-based supercapacitor. electrolyte Any suitable electrolyte 30, whether in solid, liquid, or gel form, capable of conducting lithium ions between the negative electrode 22 and the positive electrode 24, can be used in the lithium-ion battery 20. In certain aspects, the electrolyte 30 can be a non-aqueous liquid electrolyte solution containing one or more lithium salts dissolved in an organic solvent or a mixture of organic solvents. Numerous non-aqueous liquid solutions containing electrolyte 30 can be used in the lithium-ion battery 20. In certain variations, the electrolyte 30 can contain an aqueous solvent (i.e., a water-based solvent) or a hybrid solvent (e.g., an organic solvent with at least 1 wt% water). Suitable lithium salts generally have inert anions. Examples of lithium salts that can be dissolved in an organic solvent to form the non-aqueous liquid electrolyte solution are lithium hexafluorophosphate (LiPF6); lithium perchlorate (LiClO4); lithium tetrachloroaluminate (LiAlCl4); lithium iodide (LiI); lithium bromide (LiBr); lithium thiocyanate (LiSCN); lithium tetrafluoroborate (LiBF4); lithium difluorooxalatoborate (LiBF2(C2O4)) (LiODFB); lithium tetraphenylborate (LiB(C6H5)4); lithium bis(oxalate)borate (LiB(C2O4)2) (LiBOB); lithium tetrafluorooxalate phosphate (LiPF4(C2O4)) (LiFOP); lithium nitrate (LiNO3); lithium hexafluoroarsenate (LiAsF6); and lithium trifluoromethanesulfonate (LiCF3SO3). Lithium bis(trifluoromethanesulfonimide) (LITFSI) (LiN(CF3SO2)2); lithium fluorosulfonylimide (LIN(FSO2)2) (LiFSI) and combinations thereof. In certain variations, electrolyte 30 can contain a concentration of 1.2 M of the lithium salts. These lithium salts can be dissolved in a variety of organic solvents, such as organic ethers or organic carbonates. Organic ethers can include dimethyl ethers, glymes (glycol dimethyl ether or dimethoxyethane (DME, e.g., 1,2-dimethoxyethane)), diglymes (diethylene glycol dimethyl ether or bis(2-methoxyethyl) ether), triglymes (tri(ethylene glycol) dimethyl ether), ethers with additional chain structures, such as 1,2-diethoxyethane, ethoxymethoxyethane, 1,3-dimethoxypropane (DMP), cyclic ethers, such as tetrahydrofuran, 2-methyltetrahydrofuran, and combinations thereof. In certain variations, the organic ether compound is selected from the group consisting of: tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, dimethoxyethane (DME), diglyme (diethylene glycol dimethyl ether), triglyme (tri(ethylene glycol) dimethyl ether), 1,3-dimethoxypropane (DMP), and combinations thereof. Carbonate-based solvents can include various alkyl carbonates, such as...Cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate) and acyclic carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC)). Ether-based solvents include cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane) and chain ethers (e.g., 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane). In various embodiments, suitable solvents can be selected in addition to those described above from propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, dimethyl sulfoxide, acetonitrile, nitromethane and mixtures thereof. If the electrolyte is a solid electrolyte, it may contain a composition selected from the group consisting of: LiTi2(PO4)3, LiGe2(PO4)3, Li7La3Zr2O12, Li3xLa2 / 3-xTiO3, Li3PO4, Li3N, Li4GeS4, Li10GeP2S12, Li2S-P2S5, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li3OCl, Li2,99Ba0,005ClO or any combination thereof. Porous separator Separator 26 can, in certain variations, comprise a microporous polymeric separator containing a polyolefin, including those made from a homopolymer (derived from a single monomer component) or a heteropolymer (derived from more than one monomer component), which may be either linear or branched. In certain aspects, the polyolefin may be polyethylene (PE), polypropylene (PP), a blend of PE and PP, or multilayer structured porous films of PE and / or PP. Commercially available membranes for the porous polyolefin separator 26 include CELGARD® 2500 (a single-layer polypropylene separator) and CELGARD® 2340 (a three-layer polypropylene / polyethylene / polypropylene separator), available from CELGARD LLC. If the porous separator 26 is a microporous polymeric separator, it can be a single layer or a multilayer laminate. For example, in one embodiment, a single layer of the polyolefin can form the entire microporous polymeric separator 26. In other embodiments, the separator 26 can be a fibrous membrane with numerous pores extending between the opposing surfaces and can, for example, have a thickness of less than one millimeter. As another example, however, several discrete layers of similar or dissimilar polyolefins can be assembled to form the microporous polymeric separator 26. The microporous polymeric separator 26 can also contain other polymers, such as, alternatively or additionally to the polyolefin, such as...Polyethylene terephthalate (PET), polyvinylidene fluoride (PVdF), polyamide (nylons), polyurethanes, polycarbonates, polyesters, polyether ether ketones (PEEK), polyether sulfones (PES), polyimides (PI), polyamide-imides, polyethers, polyoxymethylene (e.g. acetal), polybutylene terephthalate, polyethylene naphthenate, polybutene, polymethylpentene, Polyolefin copolymers, acrylonitrile-butadiene-styrene copolymers (ABS), polystyrene copolymers, polymethyl methacrylate (PMMA), polysiloxane polymers (e.g. polydimethylsiloxane (PDMS)), polybenzimidazole (PBI), polybenzoxazole (PBO), polyphenylenes, polyarylene ether ketones, polyperfluorocyclobutanes, polyvinylidene fluoride copolymers (e.g PVdF-hexafluoropropylene or (PVdF-HFP)), and polyvinylidene fluoride terpolymers, Polyvinyl fluoride, liquid crystalline polymers (e.g. VECTRAN™ (Hoechst AG, Germany) and ZENITE® (DuPont, Wilmington, DE)), polyaramides, polyphenylene oxide, cellulose-containing materials, meso-porous silica or a combination thereof. Furthermore, the porous separator 26 can be mixed with a ceramic material or its surface can be coated with a ceramic material. For example, a ceramic coating can contain aluminum oxide (Al₂O₃), silicon dioxide (SiO₂), or combinations thereof. Various commercially available polymers and products for the manufacture of the separator 26 are considered, as are the many manufacturing processes that can be used to produce such a microporous polymer separator 26. solid electrolyte In various aspects, the porous separator 26 and the electrolyte 30 can be replaced by a solid electrolyte (SSE) that functions as both an electrolyte and a separator. The SSE can be positioned between a positive and a negative electrode. The SSE facilitates the transfer of lithium ions while mechanically separating and electrically isolating the negative and positive electrodes 22, 24 from each other. For example, SSEs may contain LiTi2(PO4)3, Li1,3Al0,3Ti1,7(PO4)3(LATP), LiGe2(PO4)3, Li7La3Zr2O12, Li3xLa2 / 3-xTiO3, Li3PO4, Li3N, Li4GeS4, Li10GeP2S12, Li2S-P2S5, Li6PS5Cl, Li6PS5Br, Li6PS5I, Li3OCl, Li2,99Ba0,005ClO or combinations thereof. Power collectors The negative and positive electrodes 22, 24 are generally connected to the respective negative and positive electrode current collectors 32, 34 to facilitate the flow of electrons between the electrode and the external circuit 40. The current collectors 32, 34 are electrically conductive and may contain metal, such as a metal foil, a metal grid or screen, or expanded metal. Expanded metal current collectors refer to metal grids with a greater thickness, allowing a larger amount of electrode material to be placed within the metal grid. Examples of electrically conductive materials include copper, nickel, aluminum, stainless steel, titanium, alloys thereof, or combinations thereof. The current collector 34 of the positive electrode can be made of aluminum or another suitable electrically conductive material known to those skilled in the art. The current collector 32 for the negative electrode can be made of copper or another suitable electrically conductive material known to those skilled in the art. Current collectors of the negative electrode generally do not contain aluminum, since aluminum reacts with lithium, causing large volume expansion and contraction. These drastic volume changes can lead to breakage and / or pulverization of the current collector. Positive & negative electrodes The positive electrode 24 can be formed from or contain a lithium-based active material capable of undergoing sufficient lithium insertion and removal, alloying and dealloying, or plating and stripping while serving as the positive terminal of the lithium-ion battery 20. The positive electrode 24 can contain a positive electroactive material. Positive electroactive materials can contain one or more transition metal cations, such as manganese (Mn), nickel (Ni), cobalt (Co), chromium (Cr), iron (Fe), vanadium (V), and combinations thereof. In certain variations, however, the positive electrode 24 is essentially free of selected metal cations, such as nickel (Ni) and cobalt (Co). Two exemplary common classes of electroactive materials that can be used to form the positive electrode 24 are layered lithium transition metal oxides and spinel-phase lithium transition metal oxides. For example, in certain cases, the positive electrode 24 can contain a spinel-like transition metal oxide, such as lithium manganese oxide (Li(1+x)Mn(2-x)O4), where x is typically < 0.15, including LiMn2O4(LMO) and lithium manganese nickel oxide LiMn1,5Ni0,5O4(LMNO). In other cases, the positive electrode 24 can contain layered materials such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), a lithium nickel manganese cobalt oxide (Li(NiNiO2)O2, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1 and x + y + z = 1) (e.g.LiNi0.6Mn0.2Co0.2O2, LiNi0.7Mn0.2Co0.1O2, LiNi0.8Mn0.1Co0.1O2, and / or LiMn0.33Ni0.33Co0.33O2), or a lithium nickel cobalt metal oxide (LiNi(1-xy)CoxMyO2, where 0 < x < 1, 0 < y < 1 and M can be Al, Mg, Mn, or the like). Other known lithium transition metal compounds such as lithium iron phosphate (LiFePO4), lithium iron fluorophosphate (Li2FePO4F), or lithium manganese iron phosphate (e.g., LiMnFePO4) can also be used. In certain aspects, the positive electrode 24 can contain an electroactive material containing manganese, such as lithium manganese oxide. (Li(1+x)Mn(2-x)O4) and / or a lithium manganese nickel mixed oxide (LiMn(2-x)NixO4), where 0 ≤ x ≤ 1. In a lithium-sulfur battery, the positive electrodes can have elemental sulfur as the active material or a sulfur-containing active material. The positive electroactive materials can be powder compositions. These materials can be mixed with an optional electrically conductive material (e.g., electrically conductive particles) and a polymeric binder. The binder can both hold the positive electroactive material together and impart ionic conductivity to the positive electrode. The negative electrode 22 can contain a negative electroactive material as a lithium host material, which can function as the negative terminal of the lithium-ion battery 20. Common negative electroactive materials include lithium inlay materials or alloy host materials. Such materials can include carbon-based materials such as lithium-graphite inlay compounds, lithium-silicon compounds, lithium-tin alloys, or lithium titanate Li4+xTi5O12, where 0 ≤ x ≤ 3, as in Li4Ti5O12(LTO). In certain aspects, the negative electrode 22 can contain lithium, and in certain variations, metallic lithium, as well as the lithium-ion battery 20. The negative electrode 22 can be a lithium metal electrode (LME). The lithium-ion battery 20 can be a lithium metal battery or cell. Metallic lithium for use in the negative electrode of a rechargeable battery has several potential advantages, including the highest theoretical capacity and the lowest electrochemical potential. Thus, batteries with lithium metal anodes can have a higher energy density, which can potentially double the storage capacity, so that the battery might be only half the size but still last the same amount of time as other lithium-ion batteries. In certain variations, the negative electrode 22 may optionally contain an electrically conductive material as well as one or more polymeric binder materials to structurally hold the lithium material together. Some electroactive materials, such as lithium manganese iron phosphates (e.g., LiMnFePO4) (LMFPs), are capable of high energy density and long lifetimes. However, these materials can exhibit properties such as a large specific surface area, high porosity, and low knock density, which present certain challenges. For example, materials with low knock density can be difficult to incorporate into wet coating processes because the particles of the electroactive material tend to separate, resulting in low energy density. Furthermore, materials with a large surface area and / or low knock density, such as LMFPs, can absorb a large amount of solvent, leading to a non-flowing slurry with low solids content. Additionally, electrodes made with these materials using wet coating processes may be prone to cracking after drying. Method for manufacturing an electrode In various aspects, the present invention provides a method for producing an electrode. The method generally comprises providing a mixture containing an electroactive material, a binder, and a solvent. In certain aspects, the electroactive material has a knock density of less than about 2 g / cm³, optionally less than about 1.3 g / cm³, or optionally less than about 1 g / cm³. The method further comprises rolling the mixture into a film and forming a multilayer stack from the film. The method also comprises forming an electrode film precursor by rolling the stack through a first gap. The rolling is carried out at least twice, the stack being in a first orientation with respect to a machine direction during a first rolling operation and in a second orientation different from the first during a second rolling operation.The process further comprises forming an electrode film by rolling the electrode film precursor through a second gap that is smaller than or equal to the first gap. The process also includes drying the electrode film to remove at least some of the solvent. In certain aspects, the process can be considered a "rolling process". The manufacturing process can promote the formation of a three-dimensional (3D) binder-bonding network (see, for example, Fig. 11 and accompanying discussion). This 3D binder-bonding network can increase the contact between the electroactive particles and facilitate the formation of an electrode with lower porosity. The resulting electrode can exhibit a higher energy density and active material loading than an electrode with similar materials produced by a wet coating process. In certain aspects, the electrode is configured to have a discharge capacity of approximately 4 mAh / cm² or greater during the cycle of an electrochemical cell containing the electrode. The electrode can be described as a "thick electrode." With reference to Fig. 2, a method for producing an electrode according to various aspects of the present invention is provided. The method generally comprises providing a mixture at 110, forming a film at 114, forming a multilayer stack at 118, forming an electrode film precursor at 122, forming an electrode film at 126, and forming an electrode at 130. In certain aspects, the method also comprises producing an electrode assembly at 134. In certain aspects, the method also comprises assembling an electrochemical cell at 138. In certain other aspects, a method according to the various aspects of the present invention may comprise only some of the steps, such as 110, 114, 126, 130, and 134. Each of the steps is described in more detail below. Providing a mixture In process 110, the procedure involves providing a mixture. This mixture generally contains an electroactive material, a binder, and a solvent. In certain aspects, the mixture also contains a conductive filler. The mixture can contain 80–98% electroactive material, 0.5–15% conductive filler, and 0.5–10% binder, based on dry weight. In various aspects, preparing the mixture involves forming it. The mixture can be formed in a one-stage or a two-stage process. The one-stage process for forming a mixture can involve kneading the electroactive material, the conductive filler, and the binder together with the solvent. This one-stage process can be carried out using a commercially available kneading machine. The two-stage process for forming the mixture generally involves creating a premix by blending the electroactive material and the conductive filler, followed by forming the mixture through the clumping of the premix, binder, and solvent. This two-stage process can be carried out using commercially available equipment, such as a planetary mixer, a bowl mixer, an extruder, or any combination thereof. The tap density (also called "tapped density") is an increased bulk density that is achieved after mechanically tapping a container, e.g. a measuring cylinder, containing a powder sample of the electroactive material, after a defined time. In certain aspects, the electroactive material has a knock density of less than approximately 3 g / cm3 (e.g., less than or equal to approximately 2.8 g / cm3, less than or equal to approximately 2.5 g / cm3, less than or equal to approximately 2 g / cm3, less than or equal to approximately 1.5 g / cm3, less than or equal to approximately 1.4 g / cm3, less than or equal to approximately 1.3 g / cm3, less than or equal to approximately 1.2 g / cm3, less than or equal to approximately 1.1 g / cm3, less than or equal to approximately 1 g / cm3, less than or equal to approximately 0.9 g / cm3, less than or equal to approximately 0.8 g / cm3, less than or equal to approximately 0.7 g / cm3, less than or equal to approximately 0.6 g / cm3, less than or equal to approximately 0.5 g / cm3). The electroactive material comprises either a positive electroactive material or a negative electroactive material. In certain aspects, the positive electroactive material includes an olivine compound, a rock salt layered oxide, a spinel, a tavorite, a borate, a silicate, an organic compound, other types of positive electrode materials (such as those described in the discussion of Fig. 1), or any combination thereof. The olivine compound may, for example, include LiV₂(PO₄)₃, LiFePO₄(LFP), LiCoPO₄, and / or a lithium manganese iron phosphate (LMFP). LMFPs may include, for example, LiMnFePO₄ and / or LiMnxFe₁-xPO₄, where 0 ≤ x ≤ 1. Examples of LiMnxFe1-xPO4, with 0 ≤ x ≤ 1, include LiMn0.7Fe0.3PO4, LiMn0.6Fe0.4PO4, LiMn0.8Fe0.2PO4, and LiMn0.75Fe0.25PO4, to name a few. The rock salt layered oxide can include LiNixMnyCo1-x-yO2, LiNixMn1-xO2, Li1+xMO2, (e.g.,Examples include LiCoO₂, LiNiO₂, LiMnO₂, and / or LiNi0.5Mn0.5O₂), a lithium nickel manganese cobalt oxide (NMC) (e.g., NMC 111, NMC 523, NMC 622, NMC 721, and / or NMC 811), and / or a lithium nickel cobalt aluminum oxide (NCA), to name a few. The spinel may, for example, comprise LiMn₂O₄ and / or LiNi0.5Mn1.5O₄. The tavorite compound may, for example, comprise LiVPO₄F. The borate compound may, for example, comprise LiFeBO₃, LiCoBO₃, and / or LiMnBO₃. The silicate compound may, for example, comprise Li₂FeSiO₄, Li₂MnSiO₄, and / or LiMnSiO₄F. The organic compound can contain, for example, dilithium (2,5-dilithiooxy) terephthalate and / or polyimide. Another example of a positive electroactive material is a sulfur-containing material, such as sulfur. In one example, the positive electroactive material contains one or more olivine compounds and has a knock density of less than approximately 2 g / cm³, optionally less than approximately 1.3 g / cm³, or optionally less than approximately 1 g / cm³. Some positive electroactive materials, such as olivine compounds, rock salt layered oxides, and / or spinels, may be coated and / or doped. Dopants may include magnesium (Mg), aluminum (Al), yttrium (Y), scandium (Sc), and similar materials. For example, the positive electroactive material may contain one or more of the following materials: LiMn0.7Mg0.05Fe0.25PO4, LiMn0.75Al0.05Fe0.2PO4, LiMn0.75Al0.03Fe0.22PO4, LiMn0.75Al0.03Fe0.22PO4, LiMn0.7Al0.02Fe0.28PO4, LiMn0.7Mg0.02Al0.03Fe0.25PO4, and the like. In certain aspects, a positive electroactive material containing an LMFP compound may be doped with approximately 10 wt% of one or more dopants. In certain aspects, the negatively electroactive material comprises a carbon-containing material, a tin-containing material, lithium titanium oxide, a metal oxide, a metal sulfide, a silicon-containing material, or any combination thereof. The carbon-containing material may, for example, contain carbon nanotubes, graphite, and / or graphene. The tin-containing material may, for example, contain tin and / or a tin alloy. The lithium titanium oxide may, for example, contain Li₄Ti₅O₁₂. The metal oxide may, for example, contain V₂O₅, SnO₂, and / or Co₃O₄. The metal sulfide may, for example, contain FeS. The silicon-containing material may contain silicon, a silicon alloy, and / or silicon graphite. In certain aspects, the conductive filler includes carbon-based materials, a metal (e.g., metal wire), a metal oxide, and / or a conductive polymer. Carbon-based materials can include, for example, graphite, carbon black (e.g., KETJEN carbon black, DENKA carbon black, SUPER-P (SP), and / or acetylene carbon black), and / or carbon fibers (e.g., vapor-deposited carbon fibers (VGCF)). Conductive metal particles can include nickel, gold, silver, copper, and / or aluminum. Examples of a conductive polymer are polyaniline, polythiophene, polyacetylene, and / or polypyrrole. An example of a metal oxide is RuO₂. In certain aspects, mixtures of electrically conductive materials can also be used. In certain aspects, the binder contains a polymer configured to undergo fibrillation within a temperature range or under shear stress. The binder may include polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), styrene-butadiene rubber (SBR), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene (ECTFEC), polyvinyl fluoride (PVF), perfluoroalkoxyalkanes (PFA), fluorinated ethylene propylene (FEP), a polymer of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride (THV), polychlorotrifluoroethylene (PCTFE), or any combination thereof. In certain aspects, the binder includes an aqueous polymer dispersion, such as an aqueous PTFE dispersion. In certain aspects, the binder includes an organic polymer latex. In certain aspects, the binder is NMP-based. In certain aspects, the solvent includes an organic solvent. The organic solvent may, for example, include an alcohol (e.g., isopropanol) and / or a ketone. Forming and foil In step 114, the process comprises forming a film from the mixture. In certain aspects, step 114 can be described as a "pre-rolling step". With reference to Fig. 3, an illustration of the process for forming a film according to various aspects of the present invention is shown. The process involves rolling the mixture, which may be in the form of a multitude of lumps 210, through a pair of first rollers 214 to form a film 218. The first rollers 214 discharge the film 218 in a machine direction (MD) 222. In certain aspects, the first rollers 214 define a pre-roll gap 226 between themselves. The pre-roll gap 226 is defined in a direction transverse to a plane of the film 218. The pre-roll gap 226 can be in a range of 150 µm - 5 mm (e.g. 150 - 250 µm, 250 - 500 µm, 500 µm - 1 mm, 500 - 750 µm, 750 µm - 1 mm, 1 - 3 mm, 1 - 2 mm, 2 - 3 mm, 3 - 5 mm, 3 - 4 mm or 4 - 5 mm). Stacking Returning to Fig. 2: At 118, the process includes the formation of a stack from the foil. As shown in Fig. 4, the film 218 is formed into a multi-layered stack 240. The film 218 can be formed into the stack 240 by winding, forming a Z-shape, or otherwise combining it. In certain aspects, the stack 240 is formed when the sheet is dispensed from the first rolls 214. The stack 240 defines an axis 244. In certain aspects, the axis 244 can run substantially parallel to the machine direction 222 (Fig. 3). The stack 240 can comprise approximately 2 - 100 layers (e.g. 2 - 10, 10 - 50, 10 - 25, 10 - 15, 15 - 25, 25 - 50, 50 - 100, 50 - 75, 75 - 100, 100 - 200, 100 - 150 or 150 - 200). Formation of an electrode film precursor Returning to Fig. 2: At 122, the process comprises the formation of an electrode film precursor from the stack. In certain aspects, the formation of the electrode film precursor can be described as the “main rolling process.” The forming of the electrode film precursor generally involves carrying out a plurality of successive rolling steps (or “rolling operations”) and changing the orientation of the stack between at least some of the rolling steps. The stack is rolled in at least two different orientations. Accordingly, the plurality of rolling steps includes at least a first rolling step (Fig. 5) and a second rolling step (Fig. 6). With reference to Fig. 5, a first rolling step according to various aspects of the present invention is illustrated. In the first rolling step, the stack 240 is rolled by a pair of second rolls 260. The pair of second rolls 260 defines a first or main rolling gap 264 between them. The first gap 264 is defined in a direction transverse to a plane of the stack 240 (i.e., parallel to the pre-rolling gap 226). The first gap 264 can be 150 µm to 5 mm (e.g., 150–250 µm, 250–500 µm, 500 µm–1 mm, 500–750 µm, 750 µm–1 mm, 1–3 mm, 1–2 mm, 2–3 mm, 3–5 mm, 3–4 mm, or 4–5 mm). The binder distribution can be more uniform with a larger first gap 264. In certain aspects, the first gap 264 is smaller than or equal to the pre-rolling gap 226 (Fig. 3). For example, the pre-rolling gap 226 and the first gap 264 can be the same. In certain aspects, each of the rolling steps in the main rolling process is carried out at the first gap 264.In certain aspects, the same rolling machine and the same rollers can be used to form the film 218 ( Fig. 3) and the electrode film precursor 268. The stack 240 is arranged in a first orientation with respect to the machine direction 222. In one example, as shown, the first orientation is essentially perpendicular to the machine direction 222 (i.e., a pulling direction). In another example, the first orientation is essentially parallel to the machine direction 222. Figure 6 illustrates a second rolling step according to various aspects of the present invention. The second rolling step comprises rolling the stack 240 (Figure 5) by the pair of second rollers 260 in a second orientation with respect to the machine direction 222 to form an electrode film precursor 268. The second orientation differs from the first orientation. In one example, as shown, the second orientation is substantially parallel to the machine direction 222. In another example, the second orientation is substantially perpendicular to the machine direction 222. In certain other aspects, the first and second orientations may differ from the machine and train directions. The second orientation can generally deviate from the first orientation by approximately 45–135° (e.g., 45–90°, 45–55°, 55–65°, 65–75°, 70–110°, 75–85°, 80–100°, 85–95°, 90–135°, 95–105°, 105–115°, 115–125°, or 125–135°). In certain aspects, the second orientation deviates from the first orientation by 80–100°. For example, if the first and second orientations correspond to the machine and train directions, the first and second orientations will be approximately 90° apart. In various aspects, the multitude of rolling steps can include rolling the stack of 240 in more than two different orientations (e.g., three different orientations or four different orientations). The formation of the electrode film precursor 268 involves performing at least the first rolling step with the stack 240 in the first orientation (Fig. 5) and the second rolling step with the stack 240 in the second orientation (Fig. 6). However, the formation of the electrode film precursor 268 can also include additional rolling steps, such as repeating the first and second rolling steps and / or performing additional rolling steps with different stack orientations. In certain aspects, the number of rolling steps ranges from 2 to 50 (e.g., 2 to 40, 2 to 25, 2 to 10, 2 to 6, 3 to 5, 4 to 10, 10 to 25, 10 to 15, 15 to 25, 25 to 50, 25 to 35, or 35 to 50). In one example, stack 240 is rolled or rolled alternately in the first and second orientations (e.g., first-second-first-second, etc.). However, stack 240 can also be rolled in different orientation patterns (e.g.,first-first-second-second or first-second-first-first-second). Performing the successive rolling steps can facilitate the formation of a 3D binder compound network, as described below in the discussion of Fig. 11. Formation of an electrode film Returning to Fig. 2: At 126, the process includes the formation of an electrode film from the electrode film precursor. In certain aspects, the forming of the electrode film can be described as the "final rolling step". With reference to Fig. 7, a pair of third rolls 280 is provided, defining a second or final roll gap 284 between them. The method comprises rolling the electrode film precursor 268 between the pair of third rolls 280 to form an electrode film 288. In certain aspects, the forming of the electrode film can be carried out on the same rolling machine as the forming of the film and / or the forming of the electrode film precursor. The electrode film precursor 268 can be in the first orientation, the second orientation (as shown), or another orientation with respect to the machine direction 222. The second gap 284 is defined in a direction transverse to a plane of the electrode film precursor 268 (i.e., parallel to the pre-roll gap 226 and the first gap 264). The second gap 284 is smaller than or equal to the first gap 264 (Fig. 5). In certain aspects, the second gap 284 is smaller than the first gap 264. The second gap 284 can be 20 µm to 2 mm (e.g., 20–500 µm, 20–100 µm, 100–250 µm, 250–500 µm, 500 µm to 1 mm, 500–750 µm, 750 µm to 1 mm, 1–2 mm, 1–1.5 mm, or 1.5–2 mm). The second gap 284 is essentially identical to a desired electrode film thickness. In certain aspects, the formation of the electrode film 288 optionally involves applying the electrode film precursor to a substrate 292 prior to rolling. The substrate 292 can be a PET film. The PET film can, for example, have a thickness of approximately 10 µm. Applying the electrode film precursor 288 to the substrate 292 prior to rolling increases the tensile strength when the electrode film precursor 288 and the substrate 292 are rolled together. This increased tensile strength allows the rolling process to be carried out at a higher speed. In certain aspects, the electrode film 288 can be wound around a core 296 as it emerges from the third rolls 280 to form an electrode film roll 300. Alternatively, the electrode film roll 300 can also be formed in a separate process. Drying the electrode film Returning to Fig. 2: At 130, the process involves drying the electrode film. The electrode film is dried to remove at least some of the solvent. In certain aspects, drying removes substantially all of the solvent. Drying can be carried out in commercially available drying machines or chambers. Drying can be performed after the formation of the electrode film at 126. In certain aspects, drying is performed before or after the electrode film 288 is wound onto the core 296. In certain other aspects, drying is performed after the formation of the electrode array at 134 and before the assembly of the electrochemical cell at 138. In certain aspects, the process can include several drying steps, e.g., at several points in the process. Forming an electrode arrangement In document 134, the method comprises the formation of an electrode arrangement. The electrode arrangement generally comprises a current collector and at least one electrode film layer. In certain aspects, the electrode arrangement comprises two electrode layers between which the current collector is arranged. The current collector can be in the form of a foil, a wire mesh, or a meshed foil. The current collector is formed from a conductive material, as described in the discussion of Fig. 1. The forming of the electrode assembly can involve a lamination process and / or a pressing process. The forming process can be carried out on a roller machine (Fig. 8) or on mounting plates. With reference to Fig. 8, a method for forming an electrode arrangement 310 in a lamination process according to various aspects of the present invention is described. In certain aspects, the current collector 314 has the form of a film. The current collector 314 can be provided on a current collector roll 318. The electrode film 288 is provided on the electrode film roll 300. In certain aspects, two electrode film rolls 300 are provided to form a double-sided electrode arrangement 310. The current collector 314 can be arranged between the electrode films 288. The current collector 314 and the two electrode films 288 are rolled together between a pair of fourth rolls 322, which have a third or laminating gap 326 between them. The third gap 326 is defined in a direction transverse to the current collector 314 and the electrode films 288 (i.e., parallel to the pre-rolling gap 226, the first gap 264, and the second gap 284). The third gap 326 is larger than the second gap 284 (Fig. 7). In certain aspects, the third gap 326 is the sum of the thicknesses of the current collector 314 and the two electrode films 288. In other aspects, the third gap 326 can be smaller than the sum of the thicknesses to achieve a desired electrode density. In certain aspects, the electrode arrangement 310 is wound onto a core 330 after rolling to form an electrode arrangement roll 334. The electrode films 288 can be coupled to the current collector 314 via an electrically conductive adhesive 338. The conductive adhesive 338 can be applied to both sides of the current collector 314 via nozzles 342 in front of the fourth rollers 322. In certain other aspects, the conductive adhesive 338 is applied to the electrode films 288 or to both the electrode films 288 and the current collector 314. The conductive adhesive 338 can be applied by in-line coating, as shown, and / or the current collector 314 and / or the electrode films 288 can be pre-coated. Conductive adhesive 338 generally contains a polymer and a conductive component. The polymer is generally solvent-resistant and offers good adhesion. Specific polymer types include epoxy, polyimide, PAA, polyester, vinyl esters, and thermoplastic polymers (e.g., polyvinylidene fluoride (PVDF), polyamide, silicone, and / or acrylic). The conductive filler may include carbon materials (e.g., carbon black, such as SP, graphene, carbon nanotubes, and / or carbon nanofibers) and / or metal powders (e.g., silver, aluminum, and / or nickel). The weight ratio of conductive filler to polymer can be approximately 0.1–50% (e.g., 0.1–1%, 0.1–0.5%, 0.5–1%, 1–5%, 5–25%, 5–10%, 10–20%, 20–30%, 25–50%, 30–40%, or 40–50%). In certain applications, the solids content of the conductive adhesive can be approximately 5% by weight.In one example, the conductive adhesive 338 contains SP and PAA in a weight ratio of approximately 1 / 3. In another example, the conductive adhesive 338 contains single-walled carbon nanotubes (SWCNTs) and PVDF in a weight ratio of approximately 0.2%. In certain aspects, the lamination process can be a hot lamination process. The hot lamination process can be carried out at a lamination temperature that is higher than the glass transition temperature of the polymer in the conductive adhesive 338 (e.g., approximately 29 °C for PTFE) and lower than the polymer's melting point. In certain aspects, the lamination temperature is 50–350 °C (e.g., 50–100 °C, 100–150 °C, 150–200 °C, 200–250 °C, 250–300 °C, or 300–350 °C). In certain aspects, the lamination process includes preheating the electrode film 288 and / or the current collector 314 before rolling. As mentioned above, forming the electrode array can additionally or alternatively involve a pressing process. Specifically, the electrode film can be pressed onto the current collector. Depending on the specific application, the current collector can be a grid or a meshed foil current collector. The pressing process can be a hot pressing process. An electrode array with a grid current collector can be free of electrically conductive adhesive. Therefore, the electrode film can be in direct contact with the current collector. Assembly of an electrochemical cell Returning to Fig. 2: At 138, the method can further comprise the formation of an electrochemical cell according to known methods. The electrochemical cell can contain a positive and / or negative electrode arrangement, which has been prepared according to various aspects of the present invention. The electrochemical cell can also contain an electrolyte and a separator, as described above in the discussion of Fig. 1. electrode In various aspects, the present invention provides an electrode for use in an electrochemical cell. The electrode contains an electroactive material, a binder, and a conductive filler. The electroactive material can have a knock density of 3 g / cm³ (e.g., less than or equal to approximately 2.8 g / cm³, less than or equal to approximately 2.5 g / cm³, less than or equal to approximately 2 g / cm³, less than or equal to approximately 1.5 g / cm³, less than or equal to approximately 1.4 g / cm³, less than or equal to approximately 1.3 g / cm³, less than or equal to approximately 1.2 g / cm³, less than or equal to approximately 1.1 g / cm³, less than or equal to approximately 1 g / cm³, less than or equal to approximately 0.9 g / cm³, less than or equal to approximately 0.8 g / cm³, less than or equal to approximately 0.7 g / cm³, less than or equal to approximately 0.6 g / cm³, less than or equal to approximately 0.5 g / cm³). In one example, the electroactive material has a knock density of less than or equal to approximately 2 g / cm³.In another example, the electroactive material has a knock density of less than or equal to approximately 1.3 g / cm³. In yet another example, the electroactive material has a knock density of less than or equal to approximately 1 g / cm³. In certain aspects, the electroactive material contains LMFP. The electrode is configured to have a discharge capacity of approximately 0.5–50 mAh / cm² (e.g., 0.5–10 mAh / cm², 0.5–2.5 mAh / cm², 2.5–7.5 mAh / cm², 2.5–5 mAh / cm², 5–10 mAh / cm², 10–20 mAh / cm², 20–30 mAh / cm², 30–40 mAh / cm², or 40–50 mAh / cm²) during the cyclic operation of an electrochemical cell containing the electrode. In certain aspects, the discharge capacity of each active material layer is greater than approximately 4 mAh / cm2 (e.g., greater than or equal to approximately 4.5 mAh / cm2, greater than or equal to approximately 5 mAh / cm2, greater than or equal to approximately 5.1 mAh / cm2, 5.2 mAh / cm2, 5.3 mAh / cm2, 5.4 mAh / cm2 or 5.5 mAh / cm2).In various aspects, the present invention provides an electrode arrangement comprising one or more layers of the electrode (“electrode layers”) and a current collector. With reference to Fig. 9, an electrode arrangement 410 is provided according to various aspects of the present invention. The electrode arrangement 410 comprises a current collector 414, two electrode layers 418, and two conductive adhesive layers 422. In certain other aspects, the electrode arrangement 410 comprises the current collector 414 and a single electrode film layer 418. The current collector 414 is arranged between the two electrode layers 418. Each conductive adhesive layer 422 is arranged between the current collector 414 and a corresponding electrode layer 418. In certain aspects, each electrode layer 418 contains an electroactive material, a conductive filler, and a binder. The electroactive material can be present at 80–98 wt% (e.g., 80–85%, 85–90%, 90–95%, or 95–98%). The conductive filler can be present at 0.5–15 wt% (e.g., 0.5–5%, 5–10%, or 10–15%). The binder can be present at 0.5–10 wt% (e.g., 0.5–2.5%, 2.5–5%, or 5–10%). In certain aspects, each electrode layer 418 defines a first thickness 426 of 20 µm - 2 mm (e.g. 20 - 500 µm, 20 - 100 µm, 100 - 250 µm, 250 - 500 µm, 500 µm - 1 mm, 500 - 750 µm, 750 µm - 1 mm, 1 - 2 mm, 1 - 1.5 mm or 1.5 - 2 mm). The current collector 414 defines a second thickness 430 of 4 - 40 µm (e.g. 4 - 10 µm, 4 - 5 µm, 5 - 10 µm, 10 - 25 µm, 10 - 20 µm, 20 - 40 µm, 20 - 30 µm or 30 - 40 µm). The conductive adhesive layers 422 each define a third thickness 434 of 0.5–20 µm (e.g., 0.5–5 µm, 0.5–1 µm, 1–10 µm, 1–5 µm, 5–10 µm, 10–20 µm, 10–15 µm, 15–20 µm). In certain aspects, each electrode layer 418 defines a porosity of 25–65% (e.g., 25–30%, 30–35%, 35–40%, 40–45%, 45–50%, 50–55%, 55–60%, or 60–65%). In various aspects, the present invention provides an electrochemical cell that includes the electrode arrangement 410. Example 1 Referring to Figures 10-11, an electrode arrangement 510 is provided according to various aspects of the present invention. The electrode arrangement 510 comprises an electrode layer 514, a current collector 518, and an electrically conductive adhesive layer 520. The electrode layer 514 has a first thickness of 276 µm. The current collector 518 has a second thickness 526 of 20 µm. The electrode layer 514 has a discharge capacity of approximately 5.5 mAh / cm² during the cycle operation of an electrochemical cell with the electrode arrangement 510 at a rate of C / 10. The electrode layer 514 contains an electroactive material 544, a conductive filler, and a binder 552. Specifically, the electrode layer 514 contains LMFP as the electroactive material 544, SP and VGCF as conductive fillers, as well as PTFE and the binder 552. The LMFP is present at approximately 89 wt%, the SP at approximately 4 wt%, the VGCF at approximately 2 wt%, and the PTFE at approximately 5 wt%. The current collector 518 contains aluminum foil. A scale bar 554 is 2 µm. The binder 552 forms a 3D binder-connection network with a plurality of non-parallel polymer strands. In particular, at least a portion of the polymer strands extends substantially parallel to the current collector 518 in a first direction, and at least another portion of the polymer strands extends substantially parallel to the current collector 518 in a different second direction. The first and second directions may differ by a similar amount as the first and second orientations (see discussion of Fig. 5-6). In certain aspects, another portion of the polymer strands may extend substantially perpendicular to the current collector 518 (i.e., parallel to a thickness direction 558 of the electrode arrangement 510). The 3D binder compound network can form a net-like structure. This network can facilitate increased contact between electroactive particles and the formation of an electrode with lower porosity compared to an electrode with binder strands extending essentially in one or two directions. Thus, the resulting electrode can exhibit a higher energy density and active material loading than an electrode with similar materials formed by a wet coating process. In certain aspects, the formation of the electrode precursor in step 122 (Fig. 2) can facilitate the formation of the 3D binder compound network. In contrast, an electrode formed by rolling in a single orientation may have binder strands extending essentially in a single direction or plane. Example 2 An LMFP-based electrode arrangement is provided according to various aspects of the present invention. The LMFP-based electrode arrangement has essentially the same composition and thickness as the electrode arrangement 510 from Example 1. An electrochemical cell comprises the electrode arrangement, a lithium metal counter electrode, and an electrolyte with 1.2 M LiPF6in DMC / EC / EMC (1:1:1 by volume). The electrochemical cell is operated cyclically at a rate of C / 10. Figure 12 shows a graph depicting an initial cycle of the electrochemical cell. The x-axis (610) represents the specific capacity in mAh / g, and the y-axis (614) represents the voltage in V. The electrochemical cell exhibits an efficiency of approximately 92% in the first cycle. Example 3 First and second electrochemical cells are provided according to various aspects of the present invention. The two electrochemical cells have essentially the same components, compositions, and dimensions as the electrochemical cell from Example 2. Each of the first and second electrodes is operated cyclically in a half-button cell with a C-rate of C / 5. The voltage is in the range of 2.5–4.3 V. Referring to Fig. 13, a graph is shown depicting the cycle performance of the first and second electrochemical cells. An x-axis 640 represents the number of cycles. A y-axis 644 represents the discharge capacity in mAh / cm². A first curve 648 represents the discharge capacity of the first electrochemical cell. A second curve 652 represents the discharge capacity of the second electrochemical cell.

Claims

A method for producing an electrode for an electrochemical cell, the method comprising: providing a mixture containing an electroactive material, a binder, and a solvent; rolling the mixture into a film; forming a multilayer stack from the film; forming an electrode film precursor by performing a plurality of successive rolling operations, each rolling operation comprising rolling the multilayer stack through a first gap defined in a direction transverse to a plane of the multilayer stack, the plurality of successive rolling operations comprising: a first rolling operation in which the multilayer stack is in a first orientation with respect to a machine direction, and a second rolling operation in which the multilayer stack is in a second orientation with respect to the machine direction, the second orientation being different from the first orientation;Forming an electrode film by rolling the electrode film precursor through a second gap defined in direction, wherein the second gap is less than or equal to the first gap; and drying the electrode film to remove at least some of the solvent to form the electrode. Method according to claim 1, wherein the second orientation differs from the first orientation by 85-95°. Method according to one of the preceding claims, wherein the electroactive material has a knock density of less than or equal to 1.3 g / cm3. Method according to one of the preceding claims, wherein the plurality of successive rolling operations comprises 2 - 50 rolling operations. Method according to one of the preceding claims, wherein the second gap is smaller than the first gap. Method according to one of the preceding claims, wherein the second gap is 20 µm - 2 mm. Method according to one of the preceding claims, further comprising: coupling the electrode to a current collector after drying. Method according to claim 7, wherein the coupling comprises: the arrangement of an electrically conductive adhesive between the electrode and the current collector, and the hot lamination of the electrode onto the current collector. The method of claim 8, wherein the hot lamination comprises passing the electrode and the current collector with the electrically conductive adhesive between them through a third gap which is defined in direction, wherein the third gap is larger than the second gap. Method according to claim 8, wherein the coupling further comprises preheating the electrode and the current collector prior to hot lamination.

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