Electrodes for energy storage devices

Abstract

Disclosed herein is a device comprising an electrode active layer comprising: a network of high aspect ratio carbon elements defining void spaces within the network; a plurality of electrode active material particles disposed in the void spaces within the network and entrapped in the network; and a surface treatment on a surface of the high aspect ratio carbon elements that promotes adhesion between the high aspect ratio carbon elements and the active material particles.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 413,435, filed October 5, 2022, which is incorporated herein by reference in its entirety. [Background technology]

[0002] Lithium batteries are used in many products, including medical devices, electric vehicles, airplanes, and consumer products such as laptop computers, cell phones, and cameras. Due to their high energy density, high operating voltage, and low self-discharge, lithium-ion batteries have overtaken the secondary battery market and continue to find new applications in products and evolving industries.

[0003] Generally, a lithium ion battery ("LIB" or "LiB") includes an anode, a cathode, and an electrolyte material, such as an organic solvent containing a lithium salt. More specifically, the anode and cathode (collectively "electrodes") are formed by mixing either the anode or cathode active material with a binder and a solvent to form a paste or slurry, which is then coated onto a current collector, such as aluminum or copper, and dried to form a film on the current collector. The anode and cathode are then layered or coiled before being housed within a pressurized casing containing the electrolyte material, all of which together form the lithium ion battery.

[0004] Conventional electrodes use binders with sufficient adhesive and chemical properties to ensure that the film coated on the current collector maintains contact with the current collector, even when manipulated to fit into a pressurized battery casing. Because the film contains the electrode active material, if the film does not maintain sufficient contact with the current collector, it is likely to significantly interfere with the electrochemical performance of the battery. Furthermore, it has been important to select a binder that is mechanically compatible with the electrode active material so that it can withstand the degree of expansion and contraction of the electrode active material during battery charging and discharging.

[0005] Therefore, binders such as cellulosic binders or cross-linked polymer binders have been used to provide good mechanical properties. However, such binder materials have adverse effects. For example, a large portion of the binder fills a volume within the electrode active layer that could otherwise be used to increase the mass loading of the active material and reduce the conductivity of the electrode. Furthermore, binders tend to react electrochemically with the electrolyte used in the cell (especially in high-voltage, high-current, and / or high-temperature applications), resulting in degradation of the cell's performance. Summary of the Invention

[0006] Applicants have recognized that electrodes can be constructed to exhibit excellent mechanical stability without the need for bulk polymer binders. In one aspect, the present disclosure describes embodiments of electrode active layers comprising a network of high-aspect-ratio carbon elements (e.g., carbon nanotubes, carbon nanotube bundles, graphene flakes, etc.), which provide a highly conductive scaffold that surrounds or entangles the active material, thereby supporting the layer. As described in more detail below, a surface treatment can be applied to the high-aspect-ratio carbon elements to promote adhesion to the active material and any underlying electrode layers (e.g., current collector layers), thereby improving the overall cohesion and mechanical stability of the active layer. This surface treatment forms only a thin (possibly monomolecular) layer on the network, free of bulk binder material, leaving instead large void spaces that can be filled with active material. The resulting active layers can be formed with excellent mechanical stability, even at large thicknesses and high active material mass loadings.

[0007] In another aspect, the present disclosure describes a method that includes dispersing high aspect ratio carbon elements and a surface treatment material in a solvent to form an initial slurry, the dispersing step resulting in the formation of a surface treatment on the high aspect ratio carbon; mixing an active material into the first slurry to form a final slurry; coating the final slurry onto a substrate; and drying the final slurry to form an electrode active layer.

[0008] Various embodiments may include any of the features or elements described herein individually or in any suitable combination. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram of an electrode featuring an active material layer. [Figure 2] FIG. 2 is a detailed view of one embodiment of an active material layer. [Figure 3] FIG. 10 is an explanatory view of another embodiment of the active material layer. [Figure 4]1 is an electron micrograph of an active material of the type described herein. [Figure 5] FIG. 1 is a schematic diagram of an energy storage cell. [Figure 6] 2 is a flowchart illustrating a method for manufacturing the electrode of FIG. 1. [Figure 7] 1 shows a schematic diagram of a pouch cell battery. [Figure 8] 1 shows an overview of the performance parameters of pouch cell batteries for EV applications. [Figure 9] 1 shows an overview of the performance parameters of a pouch cell battery. [Figure 10] 1 shows the results of a comparative performance evaluation of a pouch cell battery featuring a binder-free cathode (top plot) and a pouch cell battery featuring a binder-based cathode (bottom plot). [Figure 11] 1 shows the results of a comparative performance evaluation of a pouch cell battery featuring a binder-free cathode (top trace) and a pouch cell battery featuring a binder-based cathode (bottom trace). [Figure 12] FIG. 1 is a schematic diagram of a half-cell lithium battery device. [Figure 13] 1 is a plot showing specific capacity versus potential (referenced to Li / Li+ potential) for a binder-free cathode half-cell (solid trace) and a reference binder-based cathode half-cell (dashed trace) at various current densities. [Figure 14] 1 is a plot showing potential (referenced to Li / Li+ potential) versus volumetric capacity for a binder-free cathode half-cell (solid trace) and a reference binder-based cathode half-cell (dashed trace) at various current densities. [Figure 15] 1 shows a plot of volumetric capacity versus current density for a binder-free cathode half-cell (top trace) and a reference binder-based cathode half-cell (bottom trace). [Figure 16]Figure 1 shows Nyquist plots obtained from electrochemical impedance spectroscopy for several binder-free cathode half-cells (traces marked with squares, circles, and triangles) and a reference binder-based cathode half-cell. The binder-free cathode half-cells show significantly better performance than the reference cells. [Figure 17] 1 shows the discharge capacity (Ah) for C / 10 and C / 3 cycles 1 and 2 at 25° C. for a battery cell containing an NCM91 cathode and a silicon-dominant anode. [Figure 18] 1 shows the discharge energy (Wh) for C / 10 and C / 3 cycles 1 and 2 at 25° C. for a battery cell containing an NCM91 cathode and a silicon-dominant anode. [Figure 19] 1 shows the initial C / 10 and C / 3 charge / discharge curves at 25° C. for an NCM91 cathode / silicon dominant anode battery cell. [Figure 20] 1 shows various discharge C-rate curves at 25° C. for an NCM91 cathode / silicon dominant anode battery cell. [Figure 21A] 1 shows the results of a discharge C-rate cycling test at 25° C. for an NCM91 cathode / silicon dominant anode battery cell. [Figure 21B] 1 shows the results of a discharge C-rate cycling test at 25° C. for an NCM91 cathode / silicon dominant anode battery cell. [Figure 22A] 1 shows the results of a charge C-rate cycling test at 25° C. for an NCM91 cathode / silicon dominant anode battery cell. [Figure 22B] 1 shows the results of a charge C-rate cycling test at 25° C. for an NCM91 cathode / silicon dominant anode battery cell. [Figure 23] 1 shows various charge C-rate curves at 25° C. for an NCM91 cathode / silicon dominant anode battery cell. [Figure 24] It is shown that under fast charging at 3.5C rate at 25°C, 80% state of charge (SOC) can be achieved in about 15 minutes of charging of the NCM91 cathode / silicon dominant anode battery cell. [Figure 25] We show that under C / 3 cycling in the range of 4.2 to 2.8 V (100% SOC to 5% SOC) at 25 °C, the NCM91 cathode / silicon-dominant anode battery cell achieves 400 cycles with a discharge capacity retention of approximately 91%. [Figure 26] We show that under 100% fast charging via 3.5C / 1C cycling in the range of 4.2 to 2.8V (100% SOC to 5% SOC) at 25°C, the NCM91 cathode / silicon-dominant anode battery cell achieves 400 cycles with approximately 86% discharge capacity retention. [Figure 27] 1 shows the direct current internal resistance (DCIR) for a range of state of charge (SOC) at 25° C. for an NCM91 cathode / silicon dominant anode battery cell. [Figure 28A] Dimensions of an NCM91 cathode / silicon dominant anode battery cell in the form of a pouch cell are shown. [Figure 28B] 1 shows the outside of the pouch cell. [Figure 29] 1 shows the dimensions of a battery cell containing a nickel-rich NMC cathode and a graphite-dominant anode in the form of a pouch cell. DETAILED DESCRIPTION OF THE INVENTION

[0010] Definitions and General Instructions Unless otherwise defined or clearly indicated otherwise by their usage herein, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0011] When introducing elements of the present invention or embodiments thereof, the articles "a," "an," and "the" are intended to mean that there are one or more elements. Similarly, the term "another," when used to introduce an element, is intended to mean one or more elements. The terms "comprising," "containing," "including," and "having" are intended to be inclusive so that one or more other elements may be present in addition to the listed element(s). As used herein, the term "exemplary" is not intended to imply a best or preferred example. Rather, the term "exemplary" refers to an exemplary embodiment that is one of many possible embodiments.

[0012] The terms "or" and "and / or" refer to two elements and mean "either or, or both, or," and when referring to more than two elements, mean "either, or, or, or combinations or all of them." As an example, the phrase "A or / and B" means "either A or B, or both A and B," and the phrase "A, B, or / and C" means "either A, B, or C, or any combination or all of them."

[0013] The term "about" or "approximately" refers to an acceptable error for a particular value as determined by one of ordinary skill in the art, which depends in part on how the value is measured or determined. In certain embodiments, the term "about" or "approximately" refers to within one standard deviation. In some embodiments, when a specific error limit (e.g., standard deviation for the mean value shown in a chart or table of data) is not stated, the term "about" or "approximately" refers to a range that encompasses the stated value, and a range that is included by rounding up or down from the stated value, taking into account significant digits. In certain embodiments, the term "about" or "approximately" refers to within 10% or 5% of the specified value. Whenever the term "about" or "approximately" precedes the first number in a series of two or more numbers or a series of two or more numerical ranges, the term "about" or "approximately" applies to each of the numbers in the series or numerical range.

[0014] In some embodiments, the term "substantially all" means at least about 90%, 95%, 96%, 97%, 98%, or 99%. In some embodiments, the term "substantially free" means less than about 10%, 5%, 4%, 3%, 2%, or 1% by weight, or less than about 1000 ppm, 500 ppm, 400 ppm, 300 ppm, 200 ppm, or 100 ppm.

[0015] Whenever the term "at least" or "greater than" precedes the first number in a series of two or more numbers, the term "at least" or "greater than" applies to every number in the series.

[0016] Whenever the term "less than or equal to" or "less than" precedes the first number in a series of two or more numbers, the term "less than or equal to" or "less than" applies to each and every number in the series.

[0017] Any functional language used in any claim appended hereto is not intended to be construed as invoking 35 U.S.C. 112(f) construction as "means-plus-function" language, unless specifically expressed as such by use of the term "means for" or "step for" in the claim.

[0018] Any terminology of orientation provided herein is for illustrative purposes only and is not intended to limit the invention. For example, the "top" layer may be referred to as the second layer, and the "bottom" layer may be referred to as the first layer. Other nomenclatures and arrangements may be used without limiting the teachings herein.

[0019] Although some chemicals may be described herein as providing a particular function(s), a given chemical may be useful for other purpose(s).

[0020] Various other components may be included or required to provide aspects of the teachings herein, for example, additional materials, combinations of materials, and / or omissions of materials may provide additional embodiments within the scope of the teachings herein.

[0021] Various modifications of the teachings herein may be implemented. In general, modifications may be designed according to the needs of a user, designer, manufacturer, or other similarly interested party. Modifications may be intended to meet specific criteria of performance deemed important by that party. Similarly, performance acceptability should be evaluated by the appropriate user, designer, manufacturer, or other similarly interested party.

[0022] The entire contents of each of the publications and patent applications cited herein are hereby incorporated by reference. In the event that any of the cited references conflicts with the present disclosure, the present disclosure shall control.

[0023] 1 shows an electrode 10 including an active layer 100 disposed on a current collector 101. Some embodiments may include an optional adhesion layer 102 disposed between the active layer 100 and the current collector 101. In other embodiments, the adhesion layer 102 may be omitted.

[0024] Current collector 101 may be a conductive layer such as a metal foil. Optional adhesive layer 102 (which may be omitted in some embodiments) may be a layer of material that promotes adhesion between current collector 101 and active layer 100. Examples of suitable materials for current collector 101 and optional adhesive layer 102 are described in International Patent Publication No. WO / 2018 / 102652, published June 7, 2018.

[0025] electrode active layer 2, in some embodiments, the active layer 100 may include a three-dimensional network 200 of high aspect ratio carbon elements 201 that define void spaces within the network 200. A plurality of active material particles 300 are disposed in the void spaces within the network 200, such that the active material particles are surrounded or entangled within the network 200, improving the cohesion of the active layer 100.

[0026] In some embodiments, a surface treatment 202 is applied onto the surfaces of the high aspect ratio carbon elements 201 of the network 200. The surface treatment promotes adhesion between the high aspect ratio carbon elements and the active material particles 300. The surface treatment may also promote adhesion between the high aspect ratio carbon elements and the current collector 101 (also referred to herein as the "conductive layer") and / or optional adhesion layer 102.

[0027] As used herein, the term "high aspect ratio carbon element" refers to a carbonaceous element having a size in one or more dimensions ("major dimension") that is significantly larger than the size of the element in its transverse dimension ("minor dimension").

[0028] For example, in some embodiments, the high aspect ratio carbon elements 201 may comprise flake- or plate-like elements having two major dimensions and one minor dimension. For example, in some such embodiments, the length of each of the major dimensions may be at least about 5, 10, 50, 100, 500, 1,000, 5,000, 10,000, or more times greater than the length of the minor dimension. Exemplary elements of this type include graphene sheets and flakes.

[0029] For example, in some embodiments, the high aspect ratio carbon elements 201 may comprise elongated rod- or fibrous elements having one major dimension and two minor dimensions. For example, in some such embodiments, the length of the major dimension may be at least about 5, 10, 50, 100, 500, 1,000, 5,000, 10,000, or more times greater than the length of each of the minor dimensions. Exemplary elements of this type include carbon nanotubes, carbon nanotube bundles, carbon nanorods, and carbon fibers.

[0030] In some embodiments, the high aspect ratio carbon elements 201 can comprise carbon nanotubes (CNTs, including single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs), and / or multi-walled nanotubes (MWNTs)), carbon nanorods, or carbon fibers, or mixtures thereof. In some embodiments, the high aspect ratio carbon elements 201 can be formed from interconnected bundles, clusters, or aggregates of CNTs or other high aspect ratio carbon elements or materials. In some embodiments, the high aspect ratio carbon elements 201 can comprise graphene in sheet, flake, or curved flake form, and / or can be formed into high aspect ratio cones, rods, etc.

[0031] In some embodiments, the electrode active layer 100 may contain little or no bulk binder material, leaving more space within the network 200 occupied by the active material particles 300. For example, in some embodiments, the active layer 100 contains less than about 10% by weight, less than about 5% by weight, less than about 1% by weight, less than about 0.1% by weight, less than about 0.01% by weight, or less than that, of binder material (e.g., polymeric or cellulosic binder material) disposed in the void spaces.

[0032] For example, in some embodiments, the electrode active layer does not include, or is substantially free of, binder or polymer materials, or any materials other than the active material 300, the network 200 comprised of high aspect ratio carbon elements 201, and any surface treatments 202 disposed thereon.

[0033] In some embodiments, network 200 is composed mostly or entirely of carbon. For example, in some embodiments, network 200 is at least about 90% by weight carbon, at least about 95% by weight carbon, at least about 96% by weight carbon, at least about 97% by weight carbon, at least about 98% by weight carbon, at least about 99% by weight carbon, at least about 99.5% by weight carbon, at least about 99.9% by weight carbon, or more.

[0034] In some embodiments, the size (e.g., average size, median size, or minimum size) of the high aspect ratio carbon elements 201 forming the network 200 along one or two major dimensions may be at least about 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, 1,000 μm, or more. For example, in some embodiments, the size (e.g., average size, median size, or smallest size) of the high aspect ratio carbon elements 201 forming the network 200 may be in the range of about 1 μm to about 1,000 μm, or any subrange thereof, such as about 1-600 μm, 1-100 μm, 100-200 μm, 200-300 μm, 300-400 μm, 400-500 μm, or 500-600 μm.

[0035] In some embodiments, the size of the high aspect ratio carbon elements 201 can be relatively uniform. For example, in some embodiments, about 50%, 60%, 70%, 80%, 90%, 95%, 99% or more of the elements 201 may have a size along one or two major dimensions that is within about 10% of the average size of the elements 201 that make up the network 200.

[0036] The inventors have found that active layers 100 of the type herein can provide exemplary performance (e.g., high conductivity, low resistance, high voltage capability, and high energy and power density) even when the mass fraction of high aspect ratio carbon elements 201 comprising the network 200 within the layer 100 is very low, thereby enabling high mass loading of active material particles 300. For example, in some embodiments, the active layer 100 can be at least about 50 wt% (weight percent), 60 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 99.5 wt%, or more active material particles 300.

[0037] In some embodiments, network 200 forms an interconnected network of highly conductive pathways for current flow (e.g., electron or ion transport) through active layer 100. For example, in some embodiments, highly conductive junctions can occur at points where high aspect ratio carbon elements 201 of the network cross one another or where they are sufficiently close to one another to allow quantum tunneling of charge carriers (e.g., electrons or ions) from one element to the next. Although elements 201 can constitute a relatively low mass fraction of the active layer (e.g., less than about 10 wt%, less than 5 wt%, less than 4 wt%, less than 3 wt%, less than 2 wt%, less than 1 wt% or less, or in the range of about 0.5 wt% to about 10 wt%, or any subrange thereof, such as about 0.5 or 1 wt% to about 5 wt%), the interconnected network of highly conductive pathways formed within network 200 can provide long conductive pathways (e.g., conductive pathways on the order of the thickness of active layer 100) that facilitate current flow in and through active layer 100.

[0038] For example, in some embodiments, network 200 may include one or more structures of interconnection elements 201, the structures having an overall length along one or more dimensions that is about 2, 3, 4, 5, 10, 20, 50, 100, 500, 1,000, 10,000, or more times longer than the average length of the components 201 that comprise the structure. For example, in some embodiments, network 200 may include one or more structures of interconnection elements 201, the structures having an overall length in the range of about 2 to about 10,000 times (or any subrange thereof) the average length of the components 201 that comprise the structure. For example, in some embodiments, network 200 can include highly conductive pathways having lengths greater than about 100 μm, 500 μm, 1,000 μm, 10,000 μm, or greater, e.g., about 100 μm to 10,000 μm, or any subrange thereof, e.g., about 100 to 1000 μm, 1000 to 2000 μm, 2000 to 3000 μm, 3000-4000 μm, 4000 to 5000 μm, 5000 to 6000 μm, 6000 to 7000 μm, 7000-8000 μm, 8000 to 9000 μm, or 9000 to 10,000 μm.

[0039] As used herein, the term "highly conductive pathway" should be understood as a pathway formed by interconnection elements 201 that has a higher conductivity than the conductivity of the active material particles trapped in network 200.

[0040] Without being bound by theory, in some embodiments, network 200 can be characterized as an electrically interconnected network of elements 201 that exhibit connectivity above a percolation threshold. The percolation threshold is a mathematical concept related to percolation theory, which is the formation of long-range connectivity in random systems. Below the threshold, so-called "giant" connected components on the order of the system size do not exist. Above that, there exist giant elements on the order of the system size.

[0041] In some embodiments, the percolation threshold can be determined by increasing the mass fraction of element 201 in active layer 100 while measuring the conductivity of the layer and holding all other properties of the layer constant. In some such cases, the threshold can be identified by the mass fraction at which the conductivity of the layer increases sharply and / or the mass fraction above which the conductivity of the layer increases only slowly with the addition of more element 201. Such behavior indicates that the threshold necessary for the formation of interconnect structures that provide conductive pathways with lengths on the order of the size of active layer 100 has been exceeded.

[0042] Figure 2 shows a high aspect ratio carbon element 201 (shown in Figure 1) of network 200 in proximity to several active material particles 300. In the embodiment shown in Figure 2, the surface treatment 202 on element 201 is a surfactant layer bonded to the outer layer of the surface of element 201. As shown, the surfactant layer includes a plurality of surfactant elements 210, each having a hydrophobic end or tail 211 and a hydrophilic end or head 212, with the hydrophobic end or tail 211 disposed proximal to the surface of carbon element 201 and the hydrophilic end or head 212 disposed distal to the surface of carbon element 201.

[0043] In some embodiments where the carbon elements 201 are hydrophobic (as is typically the case for nanomorphic carbon elements such as CNTs, CNT bundles, and graphene flakes), the hydrophobic ends or tails 211 of the surfactant elements 210 are attracted to the carbon elements 201. Thus, in some embodiments, the surface treatment 202 may be a self-assembled layer. For example, as described in more detail below, in some embodiments, when the carbon elements 201 are mixed with the surfactant elements 210 in a solvent to form a slurry, the surface treatment 202 layer self-assembles on the surface of the carbon elements 201 due to electrostatic interactions between the carbon elements 201 and the surfactant elements 210 in the slurry.

[0044] In some embodiments, the surface treatment 202 may be a self-limiting layer. For example, as described in more detail below, in some embodiments, when the carbon element 201 is mixed with the surfactant element 210 in a solvent to form a slurry, the surface treatment 202 layer self-assembles on the surface of the carbon element 201 due to electrostatic interactions between the elements 201 and 210 in the slurry. In some such embodiments, once an area on the surface of the carbon element 201 is covered with the surfactant element 210, additional surfactant elements 210 are not attracted to that area. In some embodiments, once the surface of the carbon element 201 is covered with the surfactant element 210, additional surfactant elements are repelled from the layer, resulting in a self-limiting process. For example, in some embodiments, the surface treatment 202 can form in a self-limiting process, thereby ensuring that the layer is thin, e.g., only a single molecule or a few molecules thick.

[0045] In some embodiments, at least some of the hydrophilic ends or heads 212 of the surfactant elements 210 form covalent or non-covalent bonds or interact with the active material particles 300. Thus, the surface treatment 202 can provide good adhesion between the high aspect ratio carbon elements 201 of the network 200 and the active material particles 300. In some embodiments, the bond may be a covalent bond or a non-covalent bond such as a π-π bond, hydrogen bond, electrostatic bond, or a combination thereof, or the interaction may be a van der Waals interaction.

[0046] For example, in some embodiments, the hydrophilic end or head 212 of the surface-active element 210 has a polar charge of a first polarity, while the surface of the active material particles 300 carries a polar charge of a second polarity opposite to the first polarity, and thus the two are attracted to each other.

[0047] For example, in some embodiments (as described in more detail below) in which active material particles 300 are combined with carbon elements 201 having surface treatments 202 in a solvent during formation of active layer 100, the outer surfaces of active material particles 300 may be characterized by a zeta potential (as known in the art) having an opposite sign to the zeta potential of the outer surface of surface treatment 202. Thus, in some such embodiments, the attraction between carbon elements 201 having surface treatments 202 and active material particles 300 promotes self-assembly of a structure in which active material particles 300 are entangled with carbon elements 201 of network 200.

[0048] In some embodiments, at least some hydrophilic ends or heads 212 of surface-active elements 210 form covalent or non-covalent bonds or interact with current collector or adhesion layers underlying active material layer 100. Thus, surface treatment 202 can provide good adhesion between high-aspect-ratio carbon elements 201 of network 200 and such underlying layers. In some embodiments, the bonds may be covalent or non-covalent, such as π-π bonds, hydrogen bonds, electrostatic bonds, or combinations thereof, or the interactions may be van der Waals interactions. In some embodiments, this arrangement provides excellent mechanical stability of electrode 10, as described below.

[0049] In some embodiments, the surfactant used to form the above-described surface treatment 202 may include any suitable material. For example, in some embodiments, the surfactant may include one or more of hexadecyltrimethylammonium hexafluorophosphate (CTAP), hexadecyltrimethylammonium tetrafluoroborate (CTAB), hexadecyltrimethylammonium acetate, hexadecyltrimethylammonium nitrate, hexamidopropyl betaine, N-(cocoalkyl)-N,N,N-trimethylammonium methyl sulfate, and cocamidopropyl betaine. Additional suitable surfactants and materials are described below.

[0050] In some embodiments, the surfactant layer 202 may be formed by dissolving a compound in a solvent (e.g., in a self-limiting process as described above) such that the surfactant layer is formed from ions from the compound. In some such embodiments, the active layer 100 may include residual counterions 214 to the surfactant ions that form the surface treatment 202.

[0051] In some embodiments, the surfactant counterion 214 is selected to be compatible for use in an electrochemical cell. For example, in some embodiments, the counterion is selected to be non-reactive or mildly reactive with materials used in the cell, such as the electrolyte, separator, housing, etc. For example, if an aluminum housing is used, the counterion may be selected to be non-reactive or mildly reactive with the aluminum housing.

[0052] For example, in some embodiments, the residual counterions are free or substantially free of halide groups. For example, in some embodiments, the residual counterions are free or substantially free of bromine / bromide.

[0053] In some embodiments, the residual counterions may be selected to be compatible with the electrolyte used in the energy storage cell that includes active layer 100. For example, in some embodiments, the residual counterions may be the same species as the ions used in the electrolyte itself. For example, if the electrolyte includes a dissolved LiPF salt, the electrolyte anion is PF. In such a case, the surfactant may be selected as, for example, CTA PF, such that surface treatment 202 forms as a layer of anions from CTA PF, while the remaining surfactant counterions are PF anions from CTA PF (and thus match the anions of the electrolyte).

[0054] In some embodiments, the surfactant used may be soluble in a solvent that exhibits advantageous properties. For example, in some embodiments, the solvent may include water and / or an alcohol, such as methanol, ethanol, or 2-propanol (sometimes referred to as isopropyl alcohol, IPA), or a combination thereof. In some embodiments, the solvent may include one or more additives used to further improve the solvent's properties, such as low-boiling additives, such as acetonitrile (ACN), deionized water, and tetrahydrofuran.

[0055] For example, if a low boiling point solvent is used to form the surface treatment 202, the solvent can be quickly removed using a thermal drying process (e.g., of the type described in more detail below) that is performed at a relatively low temperature. As will be appreciated by those skilled in the art, this can improve the speed and / or cost of manufacturing the active layer 100.

[0056] For example, in some embodiments, the surface treatment 202 is formed from a material that is soluble in a solvent having a boiling point of less than about 250°C, less than 225°C, less than 202°C, less than 200°C, less than 185°C, less than 180°C, less than 175°C, less than 150°C, less than 125°C, less than 100°C, or less, e.g., less than or equal to about 100°C.

[0057] In some embodiments, the solvent may exhibit other advantageous properties. In some embodiments, the solvent may have a low viscosity, such as a viscosity of about 3.0 centipoise, 2.5 centipoise, 2.0 centipoise, 1.5 centipoise, 1.0 centipoise or less at about 20° C. In some embodiments, the solvent may have a low surface tension, such as a surface tension of about 40 mN / m, 35 mN / m, 30 mN / m, 25 mN / m, 20 mN / m or less at about 20° C. In some embodiments, the solvent may have low toxicity, for example, toxicity comparable to that of an alcohol, such as isopropyl alcohol.

[0058] The present disclosure contrasts particularly with processes used to form conventional electrode active layers, which feature bulk binder materials such as polyvinylidene fluoride or polyvinylidene difluoride (PVDF). Such bulk binders often require aggressive solvents characterized by high boiling points. One such example is N-methyl-2-pyrrolidone (NMP). The use of NMP (or other pyrrolidone-based solvents) as a solvent requires the use of high-temperature drying processes to remove the solvent. Furthermore, NMP is expensive, requires complex solvent recovery systems, and is highly toxic, posing significant safety concerns. In contrast, as described in more detail below, in some embodiments, the active layer 100 may be formed without the use of NMP or similar compounds, such as pyrrolidone-based compounds.

[0059] While exemplary embodiments of surface treatment 202 are described above, it is understood that other treatments may be used. For example, in some embodiments, surface treatment 202 may be formed by functionalizing high aspect ratio carbon elements 201 using any suitable technique described herein or known in the art. The functional groups applied to elements 201 may be selected to promote adhesion between active material particles 300 and network 200. For example, in some embodiments, the functional groups may include carboxyl groups, carbonyl groups, ester groups, hydroxyl groups, thiol groups, amine groups, silane groups, phosphate groups, or combinations thereof.

[0060] As described in more detail below, in some embodiments, the functionalized carbon elements 201 are formed from a dried (e.g., freeze-dried) aqueous dispersion that includes nanoform carbon and a functionalizing material, such as a surfactant. In some such embodiments, the aqueous dispersion is substantially free of materials that would damage the carbon elements 201, such as acids.

[0061] 3, in some embodiments, the surface treatment 202 of the high aspect ratio carbon elements 201 comprises a thin polymer layer disposed on the carbon elements, which promotes adhesion of the active material to the network. In some such embodiments, the thin polymer layer comprises a self-assembled and / or self-limiting polymer layer. In some embodiments, the thin polymer layer bonds to or interacts with the active material via, for example, hydrogen bonding and / or van der Waals forces.

[0062] In some embodiments, the thin polymer layer may have a thickness perpendicular to the outer surface of the carbon element that is less than about 3 times, less than 2 times, less than 1 time, less than 0.5 times, less than 0.1 times, or less than the short dimension of the carbon element 201.

[0063] In some embodiments, the thin polymer layer includes functional groups (e.g., side chain functional groups such as aromatic groups, carboxyl groups, carbonyl groups, ester groups, hydroxyl groups, thiol groups, amine groups, silane groups, phosphate groups, or combinations thereof) that bond to the active material via non-covalent bonds, such as, for example, π-π bonds, hydrogen bonds, electrostatic bonds, or ionic bonds. In some such embodiments, the thin polymer layer can form a stable coating layer over at least a portion of the carbon element 201.

[0064] In some embodiments, the thin polymer layer on some of the carbon elements 201 may bond to the current collector 101 or adhesion layer 102 underlying the active layer 100. For example, in some embodiments, the thin polymer layer includes side-chain functional groups (e.g., aromatic groups, carboxyl groups, carbonyl groups, ester groups, hydroxyl groups, thiol groups, amine groups, silane groups, phosphate groups, or combinations thereof) that bond to the surface of the current collector 101 or adhesion layer 102 via non-covalent bonds, such as π-π bonds, hydrogen bonds, electrostatic bonds, or ionic bonds. In some such embodiments, the thin polymer layer can form a stable coating layer on at least some of the carbon elements 201. In some embodiments, this configuration provides excellent mechanical stability of the electrode 10, as described in more detail below.

[0065] In some embodiments, the polymeric material is miscible in the types of solvents described in the examples above. For example, in some embodiments, the polymeric material is miscible in a solvent containing an alcohol, such as methanol, ethanol, or 2-propanol (isopropyl alcohol), or a combination thereof. In some embodiments, the solvent may contain one or more additives used to further improve the properties of the solvent, such as, for example, low-boiling additives such as acetonitrile, deionized water, and tetrahydrofuran.

[0066] Suitable examples of materials that can be used to form the polymer layer include water-soluble polymers such as polyvinylpyrrolidone. Further exemplary materials are provided below.

[0067] In some embodiments, the polymeric material has a low molecular weight, for example, about 1,000,000 g / mol or less, 500,000 g / mol or less, 100,000 g / mol or less, 50,000 g / mol or less, 10,000 g / mol or less, 5,000 g / mol or less, 2,500 g / mol or less.

[0068] The thin polymer layer described above is qualitatively different from the bulk polymer binders used in conventional electrodes: rather than filling a significant portion of the volume of the active layer 100, the thin polymer layer resides on the surface of the high aspect ratio carbon elements 201, leaving most of the void space within the network 200 available to hold the active material particles 300.

[0069] For example, in some embodiments, the thin polymer layer has a maximum thickness perpendicular to the outer surface of the network that is about 1 or less, 0.5 or less, 0.25 or less, or 0.1 or less times the size along the minor dimension of the carbon elements 201. For example, in some embodiments, the thin polymer layer may be only a few molecules thick (e.g., about 100, 50, 10, 5, 4, 3, 2, or 1 molecule thick or less). Thus, in some embodiments, less than about 10%, 5%, 1%, 0.1%, 0.01%, or 0.001% of the volume of the active layer 100 is occupied by the thin polymer layer.

[0070] In further embodiments, surface treatment 202 may form a layer of carbonaceous material resulting from pyrolysis of a polymeric material disposed on high aspect ratio carbon elements 201. This layer of carbonaceous material (e.g., graphite or amorphous carbon) may adhere to active material particles 300 (e.g., via covalent or non-covalent bonds or van der Waals forces) or may promote adhesion to active material particles 110 in a separate manner. Examples of suitable pyrolysis techniques are described in U.S. Patent Application No. 63 / 028982, filed May 22, 2020. One suitable polymeric material for use in this technique is polyacrylonitrile (PAN).

[0071] In some embodiments, the active material particles 300 may comprise any active material suitable for use in an energy storage device, including, for example, a metal oxide such as lithium metal oxide for the active layer of a cathode. For example, the active material particles 300 of the active layer of a cathode may be, for example, lithium cobalt oxide (LCO, sometimes called "lithium cobaltate" or "lithium cobaltite," a chemical compound in which one possible formulation is LiCoO), lithium nickel manganese cobalt oxide (NMC, variants of which include LiNi x Mn y Co 1-x-y O2, where x + y + (1 - xy) = 1.0, for example, LiNi 0.33 Mn 0.33 Co 0.33 O2[NMC111], LiNi 0.5 Mn 0.3 Co 0.2 O2[NMC532], LiNi 0.6 Mn 0.2 Co 0.2 O2[NMC622] and LiNi 0.7 Mn 0.2 Co 0.1 O2 [NMC721]) Lithium Manganese Nickel Oxide (LNMO, one variant is LiNi 0.5 Mn 1.5 O4), lithium manganese oxide (LMO, modified formulas include LiMnO2, LiMn2O4, Li2MnO3, etc.), lithium nickel cobalt aluminum oxide (NCA, modified formula LiNi x Co y Al z O2, where x+y+z=1.0, e.g., LiNi 0.8 Co 0.15 Al 0.05 O2 and LiNi 0.84 Co 0.12 Al 0.04 O2), lithium titanate oxide (LTO, one variant is Li4Ti5O 12 (LiFePO4), Lithium Iron Phosphate (LFP, LiFePO4), and other similar materials. Other variations of the foregoing may also be included.

[0072] In some embodiments where NMC is used as the active material, nickel-dominant or nickel-rich NMC may be used. For example, in some embodiments, a variant of nickel-rich NMC is LiNi x Mn y Co 1-x-y O2, where x is about 0.7, 0.75, 0.8, 0.85, 0.9, or greater, including NMC721 and NMC811. In some embodiments, so-called NMC811 (LiNi 0.8 Mn 0.1 Co 0.1 O2) may be used, where x is about 0.8 and y is about 0.1. For nickel-predominant NMCs, in some embodiments, x in the above formula is at least 0.5, which includes NMC532 and NMC622. Similarly, in some embodiments, the general formula LiNi x Co y Al z In O, nickel-predominant NCAs with x≧0.5 or nickel-rich NCAs with x≧about 0.7, 0.75, 0.8, 0.85, or 0.9 can be used as cathode active materials. Examples of nickel-rich NCAs are LiNi 0.888 Co 0.097 Al 0.015 O2(NCA90). Nickel-rich NMC or NCA contains less cobalt, an expensive metal, and therefore is less costly. Additionally, increasing the nickel content increases the voltage and therefore the amount of energy that can be stored in the battery.

[0073] In some embodiments, the active material may be other forms of lithium nickel manganese cobalt oxide (e.g., LiNi x Mn y Co z O2). For example, NMC111 (LiNi 0.33 Mn 0.33 Co 0.33 O2), NMC532(LiNi 0.5 Mn 0.3 Co 0.2O2), NMC622(LiNi 0.6 Mn 0.2 Co 0.2 Common variants such as α- and β-glucan may also be used.

[0074] In some embodiments, for example, when the electrode is used as an anode, the active material may include graphite, hard carbon, activated carbon, nanoform carbon, silicon, silicon oxide, carbon-encapsulated silicon nanoparticles, or combinations thereof. In some such embodiments, the active layer 100 may be intercalated with lithium using, for example, prelithiation methods known in the art.

[0075] In some embodiments, the techniques described herein may enable the active layer 100 to be composed of a high percentage of active material in the active layer (e.g., greater than about 75%, 80%, 85%, 90%, 95%, 99%, 99.5%, 99.8%, or more by weight of active material) while still exhibiting excellent mechanical properties (e.g., no delamination during operation in an energy storage device of the type described herein). For example, in some embodiments, the active layer may have a high percentage of active material and a large thickness (e.g., greater than about 50 μm, 100 μm, 150 μm, 200 μm, or more) and still exhibit excellent mechanical properties (e.g., no delamination during operation in an energy storage device of the type described herein).

[0076] The active material particles 300 in the active layer 100 can be characterized by a median particle size (e.g., diameter) in the range of, for example, about 0.1 μm to about 50 μm, or any subrange thereof, such as about 0.1-1 μm, 1-10 μm, 10-20 μm, 20-30 μm, 30-40 μm, or 40-50 μm. The active material particles 300 in the active layer 100 can be characterized by a particle size distribution that is unimodal, bimodal, or multimodal particle size distribution. The active material particles 300 can be characterized by a median particle size (e.g., diameter) in the range of, for example, about 0.1 μm to about 50 μm, or any subrange thereof, such as about 0.1-1 μm, 1-10 μm, 10-20 μm, 20-30 μm, 30-40 μm, or 40-50 μm. 2 / g, 1-25m 2 / g, 25-50m 2 / g, 50-75m 2 / g or 75-100m 2 / g, approximately 0.1m 2 / g~about 100m 2 / g or any subrange thereof.

[0077] In some embodiments, the active layer 100 has a surface area of ​​at least about 20 mg / cm, for example. 2 , 30 mg / cm 2 , 40 mg / cm 2 , 50 mg / cm 2 , 60 mg / cm 2 , 70 mg / cm 2 , 80 mg / cm 2 , 90 mg / cm 2 , 100 mg / cm 2 , or greater, mass loading of active material particles 300.

[0078] 4 shows an electron micrograph of an exemplary active layer of the type described herein. Tendrils of high aspect ratio carbon elements 201 (formed from CNT bundles) surround active material particles 300. Bulky polymer material does not occupy space within the active layer.

[0079] Energy Storage Cell 5 shows an energy storage cell 500 including a first electrode 501, a second electrode 502, a permeable separator 503 disposed between the first electrode 501 and the second electrode 502, and an electrolyte 504 wetting the first and second electrodes. One or both of the electrodes 501 and 502 may be of the type described herein.

[0080] In some embodiments, the energy storage cell 500 may be a battery, such as a lithium-ion battery. In some such embodiments, the electrolyte may be a lithium salt dissolved in a solvent of the type described, for example, in Qi Li, Juner Chen, Lei Fan, Xueqian Kong, Yingying Lu, Progress in electrolytes for rechargeable Li-based batteries and beyond, Green Energy & Environment, Volume 1, Issue 1, Pages 18-42, the entire contents of which are incorporated herein by reference.

[0081] In some such embodiments, the energy storage cell may have an operating voltage in the range of about 1.0 V to about 5.0 V, or any subrange thereof, such as about 2.3 V to 4.3 V, 1.0 V to 3.0 V, or 3.0 V to 5.0 V, or at least about 2.0 V, 2.5 V, 3.0 V, 3.5 V, or 4.0 V.

[0082] In some such embodiments, the energy storage cell 500 comprises about - 40℃ to about 100℃ or 150℃, or about - 10℃ to about 100℃ or 150℃, or about - It may have an operating temperature range of 10°C to about 60°C or any subrange thereof, such as at least about 50°C, 60°C, 80°C or 100°C.

[0083] In some such embodiments, the energy storage cell 500 may have a gravimetric energy density of at least about 100 Wh / kg, 200 Wh / kg, 300 Wh / kg, 400 Wh / kg, 500 Wh / kg, 1000 Wh / kg, or more.

[0084] In some such embodiments, the energy storage cell 500 may have a volumetric energy density of at least about 200 Wh / L, 400 Wh / L, 600 Wh / L, 800 Wh / L, 1000 Wh / L, 1500 Wh / L, 2000 Wh / L, or more.

[0085] In some such embodiments, the energy storage cell 500 can have a C-rate in the range of about 0.1 to about 50, or any subrange thereof, such as about 1 to 10, 10 to 30, or 30 to 50, or a C-rate of at least about 1, 2, 5, 10, 20, or 30.

[0086] In some such embodiments, the energy storage cell 500 can have a cycle life of at least about 1000, 1500, 2000, 2500, 3000, 3500, 4000, 5000, or more charge / discharge cycles.

[0087] In some embodiments, energy storage cell 500 may be a lithium ion capacitor of the type described in U.S. Provisional Patent Application No. 63 / 021,492, filed May 8, 2020, which is incorporated herein by reference.

[0088] In some such embodiments, the energy storage cell may have an operating voltage in the range of about 2.0V to about 5.0V, or any subrange thereof, such as about 2.0V to 4.0V, or at least about 2.0V, 2.5V, 3.0V, 3.5V, or 4.0V.

[0089] In some such embodiments, the energy storage cell 500 comprises about - 60℃ to about 100℃ or 150℃, or about - 40℃ to approximately 100℃ or 150℃, or approximately - It may have an operating temperature range of any subrange thereof, such as 40°C to about 85°C, or an operating temperature of at least about 60°C, 80°C, or 100°C.

[0090] In some such embodiments, the energy storage cell 500 may have a gravimetric energy density of at least about 10 Wh / kg, 15 Wh / kg, 20 Wh / kg, 30 Wh / kg, 40 Wh / kg, 50 Wh / kg, 100 Wh / kg, or more.

[0091] In some such embodiments, the energy storage cell 500 may have a volumetric energy density of at least about 20 Wh / L, 30 Wh / L, 40 Wh / L, 50 Wh / L, 60 Wh / L, 70 Wh / L, 80 Wh / L, 100 Wh / L, 150 Wh / L, 200 Wh / L, or more.

[0092] In some such embodiments, the energy storage cell 500 can have a gravimetric power density of at least about 5 kW / kg, 7.5 kW / kg, 10 kW / kg, 12.5 kW / kg, 14 kW / kg, 15 kW / kg, 20 kW / kg, 30 kW / kg, 40 kW / kg, 50 kW / kg, or more.

[0093] In some such embodiments, the energy storage cell 500 may have a volumetric power density of at least about 10 kW / L, 15 kW / L, 20 kW / L, 22.5 kW / L, 25 kW / L, 28 kW / L, 30 kW / L, 50 kW / L, 100 kW / L, or more.

[0094] In some such embodiments, the energy storage cell 500 can have a C-rate in the range of about 1.0 to about 100, or any subrange thereof, such as about 1 to 25, 25 to 50, 50 to 75, or 75 to 100, or a C-rate of at least about 10, 20, 30, 40, or 50.

[0095] In some such embodiments, the energy storage cell 500 may have a cycle life of at least about 100,000, 500,000, 1,000,000, or more charge / discharge cycles.

[0096] Manufacturing method Electrode 10 including active layer 100 described herein can be fabricated using any suitable manufacturing process. As will be appreciated by those skilled in the art, in some embodiments, electrode 10 may be fabricated using wet coating techniques of the type described in International Patent Publication No. WO 2018 / 102652 A1, further in view of the disclosure herein.

[0097] 6 outlines an exemplary method 1000 for forming the active layer 100 of the electrode 10. In step 1001, high aspect ratio carbon elements 201 and a surface treatment material (e.g., a surfactant or polymeric material as described herein) are combined with a solvent (of the type described herein) to form an initial slurry.

[0098] At 1002, the initial slurry is treated to ensure good dispersion of the solid materials in the slurry. In some embodiments, this treatment involves introducing mechanical energy into the mixture of solvent and solid materials (e.g., using an ultrasonicator, sometimes called a "sonifier") or other suitable mixing device (e.g., a high-shear mixer). In some embodiments, the mechanical energy introduced into the mixture is at least about 0.4 kilowatt-hours per kilogram (kWh / kg), 0.5 kWh / kg, 0.6 kWh / kg, 0.7 kWh / kg, 0.8 kWh / kg, 0.9 kWh / kg, 1.0 kWh / kg, or more. For example, the mechanical energy introduced into the mixture per kilogram of mixture can be in the range of about 0.4 kWh / kg to about 1.0 kWh / kg, or any subrange thereof, such as about 0.4 kWh / kg to about 0.6 kWh / kg.

[0099] In some embodiments, an ultrasonic bath mixer may be used. In other embodiments, a probe sonicator may be used. Probe sonication can be significantly more powerful and effective when compared to an ultrasonic bath for nanoparticle applications. The high shear forces generated by ultrasonic cavitation have the ability to break down particle agglomerates, resulting in smaller, more uniform particle sizes. Among other things, sonication can result in a stable and homogeneous suspension of solids in a slurry. Generally, this results in dispersion and deagglomeration and other breakdown of solids. An example of a probe sonication device is the Q Series Probe Sonicator available from QSonica LLC (Newtown, Connecticut). Another example is the Branson Digital SFX-450 sonicator available from Thomas Scientific (Swedesboro, New Jersey).

[0100] However, the localized nature of each probe within the probe assembly can result in non-uniform mixing and suspension. This can be the case, for example, with large samples. This can be addressed by using a setup with a continuous flow cell and appropriate mixing. In such a setup, the mixing of the slurry achieves a reasonably uniform dispersion.

[0101] In some embodiments, the initial slurry, once processed, has a viscosity in the range of about 5,000 cps to about 25,000 cps, or any subrange thereof, for example, from about 6,000 cps to about 19,000 cps.

[0102] In step 1003, the surface treatment 202 may be completely or partially formed on the high aspect ratio carbon elements 201 in the initial slurry. In some embodiments, at this stage, the surface treatment 202 may self-assemble as described above with reference to Figures 2 and 3. The resulting surface treatment 202 may include functional groups or other features that may promote adhesion between the high aspect ratio carbon elements 201 and the active material particles 300, as described in further steps below.

[0103] In step 1004, the active material particles 300 may be combined with the initial slurry to form a final slurry containing the active material particles 300 with the high aspect ratio carbon elements 201 having the surface treatment 202 formed thereon.

[0104] In some embodiments, the active material 300 may be added directly to the initial slurry. In other embodiments, the active material 300 may first be dispersed in a solvent (e.g., using the techniques described above for the initial solvent) to form the active material slurry. The active material slurry can then be combined with the initial slurry to form the final slurry.

[0105] In step 1005, the final slurry is processed to ensure good dispersion of the solid materials in the final slurry. In various embodiments, any suitable mixing process known in the art may be used. In some embodiments, processing of the final slurry may use the techniques described above with respect to step 1002. In some embodiments, a planetary mixer, such as a multi-shaft (e.g., three or more) planetary mixer, may be used. In some such embodiments, the planetary mixer may feature multiple blades, for example, two or more mixing blades and one or more (e.g., two, three, or more) dispersion blades, such as a disk dispersion blade.

[0106] In step 1005, in some embodiments, the matrix 200 surrounding the active material 300 may fully or partially self-assemble, as described above with reference to Figures 2 and 3. In some embodiments, an interaction between the surface treatment 202 and the active material 300 facilitates the self-assembly process.

[0107] In some embodiments, the final slurry, once processed, has a viscosity in the range of about 1,000 cps to about 10,000 cps, or any subrange thereof, for example, 2,500 cps to 6000 cps.

[0108] In step 1006, the active layer 100 is formed from the final slurry. In some embodiments, the final slurry may be wet cast directly onto the current collector conductive layer 101 (or optional adhesive layer 102) and dried. As an example, casting may form the active layer 100 by applying heat and / or vacuum until substantially all of the solvent and any other liquids are removed. In some such embodiments, it may be desirable to protect various portions of the underlying layer(s). For example, if the electrode 10 is intended for double-sided operation, it may be desirable to protect the underside of the conductive layer 101. Protection may include, for example, protecting from the solvent by masking certain areas or providing a drain for removing the solvent.

[0109] In other embodiments, the final slurry can be at least partially dried elsewhere using any suitable technique (e.g., roll-to-roll layer application) and then transferred onto the conductive layer 101 or optional adhesive layer 102 to form the active layer 100. In some embodiments, the wet mixed slurry can be placed onto an intermediate material having a suitable surface and dried to form a layer (e.g., active layer 100). While any material having a suitable surface can be used as the intermediate material, an exemplary intermediate material is PTFE because its properties facilitate its subsequent removal from the surface. In some embodiments, the specified layer is formed in a press to provide a layer exhibiting a desired thickness, area, and density.

[0110] In some embodiments, the final slurry may be formed into a sheet and coated onto the conductive layer 101 or adhesive layer 102, as appropriate. For example, in some embodiments, the final slurry may be applied through a slot die to control the thickness of the applied layer. In other embodiments, the slurry may be applied and then leveled to the desired thickness using, for example, a doctor blade. Various other techniques can be used to apply the slurry. For example, coating techniques include, but are not limited to, comma coating, comma reverse coating, doctor blade coating, slot die coating, direct gravure coating, air doctor coating (air knife), chamber doctor coating, offset gravure coating, one-roll kiss coating, reverse kiss coating with a small diameter gravure roll, bar coating, three-reverse roll coating (top feed), three-reverse roll coating (fountain die), reverse roll coating, and the like.

[0111] The viscosity of the final slurry can vary depending on the application technique. For example, for comma coating, the viscosity can range from about 1,000 cps to about 200,000 cps. Lip die coating provides a coating with a slurry exhibiting a viscosity of about 500 cps to about 300,000 cps. Reverse kiss coating provides a coating with a slurry exhibiting a viscosity of about 5 cps to 1,000 cps. In some applications, each layer can be formed in multiple passes.

[0112] In some embodiments, the active layer 100 formed from the final slurry may be compressed (e.g., using a calendering device) before or after being applied to the current collector. In some embodiments, the slurry may be partially or completely dried (e.g., by applying heat, vacuum, or a combination thereof) before or during the compression process. For example, in some embodiments, the active layer may be compressed to a final thickness (e.g., in a direction perpendicular to the current collector layer 101) that is less than about 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, or less than its pre-compression thickness.

[0113] In some embodiments, if a partially dried layer is formed during the coating or pressing process, the layer may then be completely dried (e.g., by applying heat, vacuum, or a combination thereof), in some embodiments, substantially all of the solvent is removed from active layer 100.

[0114] In some embodiments, the solvent used to form the slurry is recovered and recycled into the slurry making process.

[0115] In some embodiments, the active layers may be compressed to, for example, break down some of the constituent high aspect ratio carbon elements or other carbonaceous materials and increase the surface area of ​​each layer. In some embodiments, the compression process may increase adhesion between layers, the ion transport rate within the layer(s), or the surface area of ​​the layer(s), or any combination or all of these. In some embodiments, compression may be applied before or after each layer is applied or formed to electrode 10.

[0116] In some embodiments, in which calendering is used to compress the active layer 100, the calendering apparatus may be set with a gap spacing equal to less than about 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, or less than the pre-compression thickness of the layer (e.g., set at about 33% of the pre-compression thickness of the layer). The calender rolls can be configured to provide a suitable pressure, for example, greater than about 1, 1.5, 2, or 2.5 tons per cm of roll length. In some embodiments, the compressed active layer can have a density in the range of about 1 g / cc to less than 10 g / cc, or any subrange thereof, such as less than 2.5 g / cc to less than 4.0 g / cc. In some embodiments, the calendering process can be carried out at a temperature in the range of about 20° C. to about 140° C., or any subrange thereof, such as about 50-100° C. or 50-75° C. In some embodiments, the active layer can be preheated prior to calendering, for example, at a temperature in the range of about 20°C to about 100°C, or any subrange thereof, such as 50 to 75°C.

[0117] Once the electrode 10 is assembled, it can be used to assemble an energy storage device. Assembly of the energy storage device may follow conventional steps used to assemble an electrode with a separator and place it into a housing, such as a canister or pouch, or may include additional steps to add electrolyte and seal the housing.

[0118] In some embodiments, the process 1000 may include any of the following features (individually or in any suitable combination):

[0119] In some embodiments, the initial slurry has a solids content in the range of about 0.1% to 20.0% by weight, or any subrange thereof, such as about 1 to 20% by weight or 5 to 15% by weight. In some embodiments, the final slurry has a solids content in the range of about 10.0% to 80% by weight, or any subrange thereof, such as about 40 to 80% by weight or 40 to 60% by weight.

[0120] In some embodiments, the solvent used may be any of those described herein with respect to forming surface treatment 202. In some embodiments, the surfactant used to form surface treatment 202 may be soluble in a solvent that exhibits advantageous properties. For example, in some embodiments, the solvent may include water and / or an alcohol, such as methanol, ethanol, or 2-propanol (isopropyl alcohol), or a combination thereof. In some embodiments, the solvent may include one or more additives used to further improve the properties of the solvent, for example, low-boiling additives such as acetonitrile, deionized water, and tetrahydrofuran.

[0121] In some embodiments, when a low boiling point solvent is used, the solvent can be quickly removed using a thermal drying process carried out at a relatively low temperature, which can improve the speed and / or cost of manufacturing the electrode 10. For example, in some embodiments, the solvent may have a boiling point of less than about 250°C, 225°C, 202°C, 200°C, 185°C, 180°C, 175°C, 150°C, 125°C, 100°C, or less, e.g., 100°C or less.

[0122] In some embodiments, the solvent may exhibit other advantageous properties. In some embodiments, the solvent may have a low viscosity, such as a viscosity of about 3.0 centipoise, 2.5 centipoise, 2.0 centipoise, 1.5 centipoise, 1.0 centipoise or less at about 20° C. In some embodiments, the solvent may have a low surface tension, such as a surface tension of about 40 mN / m, 35 mN / m, 30 mN / m, 25 mN / m, 20 mN / m or less at about 20° C. In some embodiments, the solvent may have low toxicity, for example, toxicity comparable to that of an alcohol, such as isopropyl alcohol.

[0123] In some embodiments, during formation of the active layer, the material forming the surface treatment may be dissolved in a solvent that is substantially free of pyrrolidone compounds. In some embodiments, the solvent is substantially free of N-methyl-2-pyrrolidone.

[0124] In some embodiments, the surface treatment 202 is formed from a material that includes a surfactant of the type described herein.

[0125] In some embodiments, dispersing the high aspect ratio carbon elements and the surface treatment material in a solvent to form an initial slurry includes applying a force to the agglomerated carbon elements to slide the elements away from each other along a direction transverse to the minor axes of the elements. In some embodiments, techniques for forming such a dispersion may be adapted from those disclosed in International Patent Publication No. WO 2018 / 102652 A1, in further view of the disclosures herein.

[0126] In some embodiments, the high-aspect ratio carbon elements 201 can be functionalized prior to forming a slurry used to form electrode 10. For example, in one aspect, a method is disclosed that includes dispersing the high-aspect ratio carbon elements 201 and a surface treatment material in an aqueous solvent to form an initial slurry, where the dispersing step forms a surface treatment on the high-aspect ratio carbon elements, and drying the initial slurry to remove substantially all of the water to obtain a dry powder of the surface-treated high-aspect ratio carbon elements. In some embodiments, the dry powder may be combined with, for example, a solvent and a slurry of active material to form a final slurry of the type described above with reference to method 1000.

[0127] In some embodiments, drying the initial slurry comprises lyophilizing (freeze-drying) the initial slurry. In some embodiments, the aqueous solvent and the initial slurry are substantially free of substances that are damaging to the high-aspect ratio carbon elements. In some embodiments, the aqueous solvent and the initial slurry are substantially free of acids. In some embodiments, the initial slurry consists essentially of the high-aspect ratio carbon elements, the surface treatment material, and water.

[0128] Some embodiments further include dispersing a dry powder of the high aspect ratio carbon elements in a solvent with a surface treatment material and adding an active material to form a secondary slurry, coating the secondary slurry on a substrate, and drying the secondary slurry to form an electrode active layer. In some embodiments, the preceding steps may be performed using techniques adapted from those disclosed in International Patent Publication No. WO / 2018 / 102652 A1, further in view of the disclosures herein.

[0129] In some embodiments, the final slurry may include a polymer additive, such as polyacrylic acid (PAA), poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), polyacrylonitrile (PAN), polyisoprene (PIpr), polyaniline (PANi), polyethylene (PE), polyimide (PI), polystyrene (PS), polyurethane (PU), polyvinyl butyral (PVB), and polyvinylpyrrolidone (PVP). In some embodiments, the active layer may be treated by applying heat to pyrolyze the additive, such that a surface treatment 202 may be formed on the layer of carbonaceous material resulting from the pyrolysis of the polymer additive. This layer of carbonaceous material (e.g., graphite or amorphous carbon) may adhere to or interact with the active material particles 300 (e.g., via covalent or non-covalent bonds) or otherwise promote adhesion thereto. The heat treatment may be applied by any suitable means, such as by application of a laser beam. Examples of suitable pyrolysis techniques are described in U.S. Provisional Application No. 63 / 028,982, filed May 22, 2020.

[0130] surfactants The above-described technique involves the use of surfactants to form a surface treatment 202 on the high aspect ratio carbon elements (e.g., nanotubes) 201 to promote adhesion with the active material particles 300. While several suitable surfactants have been described, it is understood that other surfactants may be used, including:

[0131] Surfactants are molecules or groups of molecules with surface activity, including wetting agents, dispersants, emulsifiers, detergents, and foaming agents. Various surfactants can be used in preparing the surface treatment agents described herein. Typically, the surfactants used contain a lipophilic, nonpolar hydrocarbon group and a polar functional hydrophilic group. The polar functional group can be, for example, a carboxylic acid, carboxylate, ester, amine, amide, imide, hydroxyl, ether, nitrile, phosphate, sulfate, or sulfonic acid. Surfactants can be used alone or in combination. Thus, surfactant combinations can include anionic, cationic, nonionic, zwitterionic, amphoteric, and / or ampholytic surfactants, so long as there is a net positive or negative charge in the head region of the surfactant molecule group or the head region of the surfactant is hydrophilic. In some cases, a single negatively or positively charged surfactant can be used in preparing the electrode composition of the present invention.

[0132] The surfactants used in preparing the electrode composition of the present invention may be anionic, including, but not limited to, sulfonic acids such as alkyl sulfonic acids, alkyl benzene sulfonic acids, alpha olefin sulfonic acids, paraffin sulfonic acids, and alkyl ester sulfonic acids; sulfates such as alkyl sulfates, alkyl alkoxy sulfates, and alkyl alkoxylated sulfates; phosphates such as monoalkyl phosphates and dialkyl phosphates; phosphonates; carboxylates such as fatty acids, alkyl alkoxycarboxylates, sarcosinates, isethionates, and taurates. Specific examples of carboxylates include sodium oleate, sodium cocoyl isethionate, sodium methyl oleoyl taurate, sodium laureth carboxylate, sodium trideceth carboxylate, sodium lauryl sarcosinate, lauroyl sarcosine, and cocoyl sarcosine. Specific examples of sulfates include sodium dodecyl sulfate (SDS), sodium lauryl sulfate, sodium laureth sulfate, sodium trideceth sulfate, sodium tridecyl sulfate, sodium cosyl sulfate, and sodium lauric acid monoglyceride sulfate.

[0133] Suitable sulfonic acid surfactants include, but are not limited to, alkyl sulfonic acids, aryl sulfonic acids, monoalkyl and dialkyl sulfosuccinates, and monoalkyl and dialkyl sulfosuccinamates. Each alkyl group independently contains about 2 to 20 carbon atoms and may be ethoxylated with an average of up to about 8 units, preferably up to about 6 units, e.g., 2, 3, or 4 units, of ethylene oxide per alkyl group. Illustrative examples of alkyl and aryl sulfonic acids are sodium tridecylbenzene sulfonate (STBS) and sodium dodecylbenzene sulfonate (SDBS).

[0134] Illustrative examples of sulfosuccinates include dimethicone copolyol sulfosuccinate, diamyl sulfosuccinate, dicapryl sulfosuccinate, dicyclohexyl sulfosuccinate, diheptyl sulfosuccinate, dihexyl sulfosuccinate, diisobutyl sulfosuccinate, dioctyl sulfosuccinate, C12-15 pareth sulfosuccinate, cetearyl sulfosuccinate, cocopolyglucose sulfosuccinate, cocoyl butyl gluceth-10 sulfosuccinate, deceth-5 sulfosuccinate, deceth-6 sulfosuccinate, dihydroxyethyl sulfosuccinyl undecylenate, hydrogenated cottonseed glyceride sulfosuccinate, isodecyl sulfosuccinate, isostearyl sulfosuccinate, lauric acid ... Examples of sulfosuccinates include, but are not limited to, nes-5 sulfosuccinate, laureth sulfosuccinate, laureth-12 sulfosuccinate, laureth-6 sulfosuccinate, laureth-9 sulfosuccinate, lauryl sulfosuccinate, nonoxynol-10 sulfosuccinate, oleth-3 sulfosuccinate, oleyl sulfosuccinate, PEG-10 lauryl citrate sulfosuccinate, sitosereth-14 sulfosuccinate, stearyl sulfosuccinate, tallow, tridecyl sulfosuccinate, ditridecyl sulfosuccinate, bisglycol ricino sulfosuccinate, di(1,3-dimethylbutyl) sulfosuccinate, and silicone copolyol sulfosuccinate.

[0135] Illustrative examples of sulfosuccinamates include lauramide-MEA sulfosuccinate, oleamide PEG-2 sulfosuccinate, cocamide MIPA-sulfosuccinate, cocamide PEG-3 sulfosuccinate, isostearamido MEA-sulfosuccinate, isostearamido MIPA-sulfosuccinate, lauramide MEA-sulfosuccinate, lauramide PEG-2 sulfosuccinate, lauramide PEG-5 sulfosuccinate, myristamide MEA-sulfosuccinate, oleamide MEA-sulfosuccinate, oleamide PIPA-sulfosuccinate, oleamide PEG-2 sulfosuccinate, and palmitate. Examples of sulfosuccinates include, but are not limited to, mitamide PEG-2 sulfosuccinate, palmitoleamido PEG-2 sulfosuccinate, PEG-4 cocamide MIPA-sulfosuccinate, ricinoleamide MEA-sulfosuccinate, stearamide MEA-sulfosuccinate, stearyl sulfosuccinamate, tallamido MEA-sulfosuccinate, tallow sulfosuccinamate, tallowamide MEA-sulfosuccinate, undecylenamide MEA-sulfosuccinate, undecylenamide PEG-2 sulfosuccinate, wheat germ amide MEA-sulfosuccinate, and wheat germ amide PEG-2 sulfosuccinate.

[0136] Some examples of commercially available sulfonic acids are AEROSOL® OT-S, AEROSOL® OT-MSO, AEROSOL® TR70% (Cytec Inc., West Paterson, New Jersey), NaSul CA-HT3 (King Industries, Norwalk, Connecticut), and C500 (Crompton Co., West Hill, Ontario, Canada). AEROSOL® OT-S is dioctyl sodium sulfosuccinate in petroleum distillates. AEROSOL® OT-MSO also contains dioctyl sodium sulfosuccinate. AEROSOL® TR70% is bistridecyl sodium sulfosuccinate in a mixture of ethanol and water. NaSul CA-HT3 is a dinonylnaphthalene sulfonic acid / calcium carboxylate complex. C500 is an oil-soluble calcium sulfonate.

[0137] Alkyl group refers to saturated hydrocarbon groups having one or more carbon atoms, including straight-chain alkyl groups (e.g., methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, etc.), cyclic alkyl groups (or cycloalkyl or alicyclic or carbocyclic groups) (e.g., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, etc.), branched-chain alkyl groups (e.g., isopropyl, tert-butyl, sec-butyl, isobutyl, etc.), and alkyl-substituted alkyl groups (e.g., alkyl-substituted cycloalkyl groups and cycloalkyl-substituted alkyl groups).

[0138] Alkyl can be unsubstituted or substituted. Substituted alkyl refers to an alkyl having one or more substituents replacing one or more hydrogen atoms on one or more carbon atoms of the hydrocarbon backbone. Such substituents may include, for example, alkenyl, alkynyl, halogeno (halo), hydroxyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate, phosphonato, phosphinato, cyano, amino (including alkylamino, dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyl, and ureido), imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfate, alkylsulfinyl, sulfonate, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido, heterocyclic, alkylaryl, or aromatic (including heteroaromatic) groups.

[0139] In some embodiments, the substituted alkyl can include a heterocyclic group. A heterocyclic group includes a closed ring structure similar to a carbocyclic group in which one or more of the carbon atoms in the ring is a heteroatom other than carbon, such as nitrogen, sulfur, or oxygen. A heterocyclic group can be saturated or unsaturated. Exemplary heterocyclic groups include aziridine, ethylene oxide (epoxide, oxirane), thiirane (episulfide), dioxirane, azetidine, oxetane, thietane, dioxetane, dithietane, dithiete, azolidine, pyrrolidine, pyrroline, oxolane, dihydrofuran, and furan.

[0140] For anionic surfactants, counterion is typically sodium, but can alternatively be, for example, potassium, lithium, calcium, magnesium, ammonium, amine (primary, secondary, tertiary or quaternary) or other organic base.Exemplary amines include isopropylamine, ethanolamine, diethanolamine and triethanolamine.Mixtures of the above cations can also be used.

[0141] The surfactants used in preparing the materials of the present invention can be cationic. Such cationic surfactants include, but are not limited to, pyridinium-containing compounds and primary, secondary, tertiary, or quaternary organic amines. In the case of cationic surfactants, the counterion can be, for example, chloride, bromide, methosulfate, ethosulfate, lactate, saccharinate, acetate, or phosphate. Examples of cationic amines include polyethoxylated oleyl / stearylamine, ethoxylated tallow amine, cocoalkylamine, oleylamine, and tallow alkylamine, and mixtures thereof.

[0142] Examples of quaternary amines with one long alkyl group are cetyltrimethylammonium bromide (CTAB), benzyldodecyldimethylammonium bromide (BddaBr), benzyldimethylhexadecylammonium chloride (BdhACl), dodecyltrimethylammonium bromide, myristyltrimethylammonium bromide, stearyldimethylbenzylammonium chloride, oleyldimethylbenzylammonium chloride, lauryltrimethylammonium methosulfate (also known as cocotrimonium methosulfate), cetyldimethylhydroxyethylammonium bromide, and methyl ammonium chloride. The following are the additives: methylhydrogen phosphate, bassuamidopropylkonium chloride, cocotrimonium chloride, distearyldimonium chloride, wheat germamidopropalkonium chloride, stearyl octyldimonium methosulfate, isostearaminopropalkonium chloride, dihydroxypropyl PEG-5 linoleammonium chloride, PEG-2 stearmonium chloride, behentrimonium chloride, dicetyldimonium chloride, tallowtrimonium chloride, and behenamidopropylethyldimonium ethosulfate.

[0143] Examples of quaternary amines with two long alkyl groups are didodecyldimethylammonium bromide (DDAB), distearyldimonium chloride, dicetyldimonium chloride, stearyloctyldimonium methosulfate, dihydrogenated palmoylethyl hydroxyethylmonium methosulfate, dipalmitoylethyl hydroxyethylmonium methosulfate, dioleoylethyl hydroxyethylmonium methosulfate, and hydroxypropylbisstearyldimonium chloride.

[0144] Quaternary ammonium compounds of imidazoline derivatives include, for example, isostearyl benzylimidonium chloride, cocoyl benzyl hydroxyethylimidazolinium chloride, cocoyl hydroxyethylimidazolinium PG-chloride phosphate, and stearyl hydroxyethylimidonium chloride.Other heterocyclic quaternary ammonium compounds such as dodecylpyridinium chloride, amprolium (AH), and benzethonium hydrochloride (BH) can also be used.

[0145] Surfactants used in preparing the materials of the present invention can be nonionic and include, but are not limited to, polyalkylene oxide carboxylic acid esters, fatty acid esters, fatty alcohols, ethoxylated fatty alcohols, poloxamers, alkanolamides, alkoxylated alkanolamides, polyethylene glycol monoalkyl ethers, and alkyl polysaccharides. Polyalkylene oxide carboxylic acid esters have one or two carboxylic acid ester moieties, each containing about 8 to 20 carbon atoms, and a polyalkylene oxide moiety containing about 5 to 200 alkylene oxide units. Ethoxylated fatty alcohols contain an ethylene oxide moiety containing about 5 to 150 ethylene oxide units and a fatty alcohol moiety containing about 6 to about 30 carbon atoms. The fatty alcohol moiety can be cyclic, straight-chain, or branched, and saturated or unsaturated. Some examples of ethoxylated fatty alcohols include ethylene glycol ethers of oleic alcohol, steareth alcohol, lauryl alcohol, and isocetyl alcohol. Poloxamers are ethylene oxide and propylene oxide block copolymers having about 15 to about 100 moles of ethylene oxide. Alkyl polysaccharide ("APS") surfactants (e.g., alkyl polyglycosides) contain a hydrophobic group having about 6 to about 30 carbon atoms and a polysaccharide (e.g., polyglycoside) as the hydrophilic group. An example of a commercially available nonionic surfactant is FOA-5 (Octel Starreon LLC., Littleton, Colorado).

[0146] Specific examples of suitable nonionic surfactants include alkanolamides such as cocamide diethanolamide ("DEA"), cocamide monoethanolamide ("MEA"), cocamide monoisopropanolamide ("MIPA"), PEG-5 cocamide MEA, lauramide DEA, and lauramide MEA; alkylamine oxides such as lauramine oxide, cocamine oxide, cocamidopropylamine oxide, and lauramidopropylamine oxide; sorbitan laurate, sorbitan distearate; fatty acids or fatty acid esters such as lauric acid, isostearic acid, and PEG-150 distearate; fatty alcohols or ethoxylated fatty alcohols such as lauryl alcohol; alkyl polyglucosides such as decyl glucoside, lauryl glucoside, and coco glucoside.

[0147] The surfactants used in preparing the materials of the present invention may be zwitterionic, possessing both positive and negative charges on the same molecule. The positively charged group may be, for example, a quaternary ammonium, phosphonium, or sulfonium group, while the negatively charged group may be, for example, a carboxylate, sulfonic acid, sulfate, phosphate, or phosphonate group. As with other classes of surfactants, the hydrophobic portion may contain one or more long, linear, cyclic, or branched aliphatic chains of approximately 8 to 18 carbon atoms. Specific examples of zwitterionic surfactants include alkyl betaines such as cocodimethyl carboxylmethyl betaine, lauryl dimethyl carboxymethyl betaine, lauryl dimethyl alpha carboxyethyl betaine, cetyl dimethyl carboxymethyl betaine, lauryl bis-(2-hydroxyethyl) carboxymethyl betaine, stearyl bis-(2-hydroxypropyl) carboxymethyl betaine, oleyl dimethyl gamma carboxypropyl betaine, and lauryl bis-(2-hydroxypropyl) alpha carboxyethyl betaine, amidopropyl betaines, and alkyl sultaines such as cocodimethyl sulfopropyl betaine, stearyl dimethyl sulfopropyl betaine, lauryl dimethyl sulfoethyl betaine, lauryl bis-(2-hydroxyethyl) sulfopropyl betaine, and alkyl amidopropyl hydroxysultaines.

[0148] The surfactant used in preparing the material of the present invention can be amphoteric.Examples of suitable amphoteric surfactants include alkylamphocarboxyglycinate and alkylamphocarboxypropionate, alkylamphodipropionate, alkylamphodiacetate, alkylamphoglycinate, and alkylamphopropionate, as well as ammonium or substituted ammonium salts of alkyliminopropionate, alkyliminodipropionate, and alkylamphopropylsulfonic acid.Specific examples include cocoamphoacetate, cocoamphopropionate, cocoamphodiacetate, lauroamphoacetate, lauroamphodiacetate, lauroamphodipropionate, lauroamphodiacetate, cocoamphopropylsulfonic acid, caproamphodiacetate, caproamphoacetate, caproamphodipropionate, and stearoamphoacetate.

[0149] Surfactants used in making the materials of the present invention may be polymers such as N-substituted polyisobutenyl succinimides and succinates, alkyl methacrylate vinylpyrrolidinone copolymers, alkyl methacrylate-dialkylaminoethyl methacrylate copolymers, alkyl methacrylate polyethylene glycol methacrylate copolymers, polystearamides, and polyethyleneimines.

[0150] The surfactant used in preparing the material may be a polysorbate-type nonionic surfactant, such as polyoxyethylene (20) sorbitan monolaurate (polysorbate 20), polyoxyethylene (20) sorbitan monopalmitate (polysorbate 40), polyoxyethylene (20) sorbitan monostearate (polysorbate 60), or polyoxyethylene (20) sorbitan monooleate (polysorbate 80).

[0151] The surfactants used in preparing the materials of the present invention can be oil-based dispersants, including, for example, alkyl succinimides, succinic acid esters, high molecular weight amines, and Mannich bases and phosphoric acid derivatives. Some specific examples are polyisobutenyl succinimide-polyethylene polyamine, polyisobutenyl succinic acid ester, polyisobutenyl hydroxybenzyl-polyethylene polyamine, and bis-hydroxypropyl phosphate.

[0152] The surfactants used in preparing the materials of the present invention may be a combination of two or more surfactants of the same type selected from the group consisting of anionic, cationic, nonionic, zwitterionic, amphoteric, and ampholytic surfactants. Suitable examples of combinations of two or more surfactants of the same type include, but are not limited to, a mixture of two anionic surfactants, a mixture of three anionic surfactants, a mixture of four anionic surfactants, a mixture of two cationic surfactants, a mixture of three cationic surfactants, a mixture of four cationic surfactants, a mixture of two nonionic surfactants, a mixture of three nonionic surfactants, a mixture of four nonionic surfactants, a mixture of two zwitterionic surfactants, a mixture of three zwitterionic surfactants, a mixture of four zwitterionic surfactants, a mixture of two amphoteric surfactants, a mixture of three amphoteric surfactants, a mixture of four amphoteric surfactants, a mixture of two ampholytic surfactants, a mixture of three amphoteric surfactants, and a mixture of four amphoteric surfactants.

[0153] Thin polymer layer material The above-described techniques involve the use of polymers to form surface treatments 202 on high aspect ratio carbon elements (e.g., nanotubes) 201 to promote adhesion with active material particles 300. While several suitable polymers have been described, it is understood that other polymers may be used, including:

[0154] The polymer used to prepare the materials of the present invention can be a polymeric material, such as a water-processable polymeric material. In some embodiments, any of the following polymers (and combinations thereof) can be used: polyacrylic acid (PAA), poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), polyacrylonitrile (PAN), polyisoprene (PiPr), polyaniline (PANi), polyethylene (PE), polyimide (PI), polystyrene (PS), polyurethane (PU), polyvinyl butyral (PVB), and polyvinylpyrrolidone (PVP). Another exemplary polymeric material is fluorine acrylic hybrid latex (TRD202A) available from JSR Corporation.

[0155] Representative Embodiments The following embodiments are presented for the purpose of illustrating the present disclosure. 1. An energy storage cell comprising an electrode active layer, the electrode active layer comprising: a network of high aspect ratio carbon elements defining void spaces within the network; a plurality of electrode active material particles disposed in void spaces within the network and captured by the network; a surface treatment on the surface of the high aspect ratio carbon element, the surface treatment promoting adhesion between the high aspect ratio carbon element and the active material particles; An energy storage cell comprising: 2. An energy storage cell as described in embodiment 1, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and one minor dimension, and the ratio of the length of each of the major dimensions to the length of the minor dimension is at least 10 times. 3. An energy storage cell as described in embodiment 1, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, the ratio of the length of the major dimension being at least 10 times the length of each of the minor dimensions. 4. The energy storage cell of embodiment 1, wherein the high aspect ratio carbon elements comprise carbon nanotubes or carbon nanotube bundles. 5. The energy storage cell of embodiment 1, wherein the high aspect ratio carbon elements comprise graphene flakes. 6. The energy storage cell of embodiment 1, wherein the electrode active layer contains less than 10 wt. % of a polymer binder disposed in the void space. 7. The energy storage cell of embodiment 1, wherein the electrode active layer contains less than 1 wt. % of a polymer binder disposed in the void space. 8. The energy storage cell of embodiment 1, wherein the electrode active layer is substantially free of polymeric materials other than the surface treatment. 9. The energy storage cell of embodiment 1, wherein the electrode active layer is substantially free of polymeric materials. 10. The energy storage cell of embodiment 1, wherein the surface treatment comprises a material soluble in a solvent having a boiling point less than 202°C. 11. The energy storage cell of embodiment 1, wherein the surface treatment comprises a material soluble in a solvent having a boiling point less than 185°C. 12. The energy storage cell of embodiment 1, wherein during the formation of the active layer, the material forming the surface treatment is dissolved in a solvent having a boiling point below 202°C. 13. The energy storage cell of embodiment 1, wherein during the formation of the active layer, the material forming the surface treatment is dissolved in a solvent having a boiling point below 185°C. 14. The energy storage cell of embodiment 1, wherein during the formation of the active layer, the material forming the surface treatment is dissolved in a solvent comprising isopropyl alcohol. 15. The energy storage cell of embodiment 1, wherein during the formation of the active layer, the material forming the surface treatment is dissolved in a solvent that is substantially free of pyrrolidone compounds. 16. The energy storage cell of embodiment 1, wherein the active material particles comprise lithium metal oxide. 17. The energy storage cell of embodiment 16, wherein the lithium metal oxide is lithium cobalt oxide, lithium nickel manganese cobalt oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanate oxide, or lithium iron phosphate oxide. 18. Lithium cobalt oxide is LiCoO2, lithium nickel manganese cobalt oxide is LiNiMnCo, lithium manganese oxide is LiMn2O4 or Li2MnO3, lithium nickel cobalt aluminum oxide is LiNiCoAlO2, and lithium titanate oxide is Li4Ti5O 12 and the lithium iron phosphate oxide is LiFePO4. 19. LiNiMnCo is LiNi x Mn y Co 1-x-y 19. The energy storage cell of embodiment 18, wherein x is greater than or equal to about 0.7 and y is about 0.1. 20. LiNiMnCo is LiNi 0.33 Mn 0.33 Co 0.33 O2, LiNi 0.5 Mn 0.3 Co 0.2 O2 or LiNi 0.6 Mn 0.2 Co 0.2 19. The energy storage cell of embodiment 18, wherein the energy storage cell is O2. 21. An energy storage cell as described in embodiment 1, wherein the network is at least 99 weight percent carbon and exhibits electrical connectivity above the percolation threshold, and the network defines one or more highly conductive pathways having a length greater than 100 μm. 22. The energy storage cell of embodiment 1, wherein the surface treatment includes a surfactant forming a surfactant layer bonded to the carbon element, the surfactant elements each having a hydrophobic end and a hydrophilic end, the hydrophobic end positioned proximate the surface of the carbon element and the hydrophilic end positioned distal to the surface of the carbon element. 23. The energy storage cell of embodiment 22, wherein the surfactant is an ionic surfactant compound comprising at least one selected from the group consisting of hexadecyltrimethylammonium tetrafluoroborate, hexadecyltrimethylammonium tetrafluoroborate, N-(cocoalkyl)-N,N,N-trimethylammonium methyl sulfate, cocamidopropyl betaine hexadecyltrimethylammonium acetate, and hexadecyltrimethylammonium nitrate. 24. The energy storage cell of embodiment 22, wherein the surfactant provides functional groups that promote adhesion of the active material particles to the network. 25. An energy storage device comprising an electrode, an active layer comprising an active material and nanocarbon, the active layer being substantially free of polyvinylidene fluoride / difluoride (PVDF) and N-methyl-2-pyrrolidone (NMP); A current collector; 1. An energy storage device comprising: 26. The energy storage device of embodiment 25, wherein the nanocarbon has a high aspect ratio. 27. The energy storage device of embodiment 25 or 26, wherein the nanocarbon is selected from carbon nanotubes, graphene (e.g., graphene flakes), graphene oxide, exfoliated graphite nanoplatelets, carbon nanoparticles, carbon powder, activated carbon, carbon black, carbon nanofibers, carbon nanohorns, carbon nanoonions, fullerenes, carbon aerogels, and any combination thereof. 28. The energy storage device of embodiment 27, wherein the nanocarbon comprises carbon nanotubes (CNTs), such as single-walled CNTs, double-walled CNTs, or multi-walled CNTs, or any combination thereof. 29. The energy storage device of any one of embodiments 25 to 28, wherein the nanocarbon has a surface treatment. 30. The energy storage device of embodiment 29, wherein the surface treatment improves adhesion between the nanocarbon and the active material and between the active layer and the current collector. 31. The energy storage device of any one of embodiments 25 to 30, wherein the active layer further comprises a polymer additive, a polymer or a surfactant, or any combination thereof. 32. The energy storage device of embodiment 31, wherein the polymer additive, polymer or surfactant, or any combination thereof, provides a surface treatment to the nanocarbon. 33. The energy storage device of any one of embodiments 25-32, wherein the electrode is a cathode. 34. The energy storage device of embodiment 33, wherein the active material comprises lithium iron phosphate, or a lithium metal oxide such as lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, or lithium titanate oxide, or any combination thereof. 35. The energy storage device of embodiment 34, wherein the active material comprises a nickel-rich lithium nickel manganese cobalt oxide, such as NMC721, NMC811, or NMC91. 36. The energy storage device of any one of embodiments 33-35, wherein the active layer of the cathode comprises about 90-99 wt. % nickel-rich lithium nickel manganese cobalt oxide, about 0.5-5% nanocarbon, and about 0.5-5% polymer additive, polymer, or surfactant, or any combination thereof. 37. The energy storage device of any one of embodiments 33-36, wherein the current collector comprises aluminum foil. 38. The energy storage device of any one of embodiments 25-37, wherein the electrode is an anode. 39. The energy storage device of embodiment 38, wherein the active material comprises silicon, silicon oxide, a silicon composite (e.g., a silicon / graphite composite), or graphite, or any combination thereof. 40. The energy storage device of embodiment 39, wherein the active material comprises silicon as the predominant element by weight. 41. The energy storage device of any one of embodiments 38-40, wherein the active layer of the anode comprises about 60-90% by weight of silicon or / and silicon composite (e.g., silicon / graphite composite), about 5-20% graphite, about 1-5% nanocarbon, and about 5-20% polymer additive, polymer or surfactant, or any combination thereof. 42. The energy storage device of any one of embodiments 38-41, wherein the current collector comprises copper foil. 43. The energy storage device of any one of embodiments 25-42, further comprising an electrolyte comprising one or more salts and one or more organic solvents. 44. The energy storage device of embodiment 43, wherein the electrolyte comprises one or more lithium salts, such as LiPF6 or / and lithium bis(fluorosulfonyl)imide (LiFSI), and one or more carbonate solvents, such as one or more linear carbonate solvents selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). 45. The energy storage device of embodiment 43 or 44, wherein the electrolyte further comprises one or more additives, such as one or more cyclic carbonates selected from ethylene carbonate (EC), fluoroethylene carbonate (FEC), vinylethylene carbonate (VEC), vinylene carbonate (VC), and propylene carbonate (PC). 46. (a) has a specific energy of at least about 330 Wh / kg; (b) has a gravimetric energy density of at least about 330 Wh / kg; (c) a volumetric energy density of at least about 850 Wh / L; (d) having a capacity of at least about 50 Ah; (e) having an internal resistance of about 40 mΩ or less; (f) Charge to 80% charge within approximately 15 minutes, (g) an operating voltage range of at least about 4.0 to 2.5 V; or (h) has a cycle life of at least about 750 charge / discharge cycles; or (i) any combination or all of the above; 46. ​​The energy storage device of any one of embodiments 25 to 45, wherein 47. The energy storage device of any one of embodiments 25-46, which is a battery cell or battery. [Example]

[0156] The following non-limiting examples further illustrate the application of the teachings of the present disclosure. In some embodiments of the following examples, the term "binder-free" or "binder-less" electrode refers to an electrode of the type described in detail above, characterized by a 3D matrix or scaffold of high aspect ratio carbon elements (e.g., nanotubes) with a surface treatment that promotes adhesion of the active material to the matrix or scaffold without the need for a bulk polymer binder such as PVDF.

[0157] As used in the following examples, the term C-rate refers to a measure of the rate at which a battery is discharged relative to its maximum capacity. A 1C rate means that the discharge current will discharge the entire battery in 1 hour. For a battery with a capacity of 100 ampere-hours, this is equivalent to a discharge current of 100 amperes.

[0158] Example 1. Battery cell for electric vehicles The following battery cell is suitable for use in electric vehicles ("EVs"). This cell combines cathode and anode technologies of the type described herein for use in EV applications, for example. Important high-level advantages include lower manufacturing costs, higher energy density, excellent power density, and wide temperature range operation. These advantages result from the present method for manufacturing battery electrodes, which eliminates the use of PVDF polymer binders and toxic solvents such as N-methyl-2-pyrrolidone (NMP). The result is substantial performance advantages in range, charge rate, and acceleration for end users, and a cheaper, less capital-intensive, and safer manufacturing process for battery manufacturers.

[0159] The teachings herein provide a technology platform for fabricating electrodes for energy storage that may offer advantages such as reduced manufacturing costs and resulting $ / kWh of LIBs, increased energy density by combining a cathode with a thick coating and a high-capacity anode featuring high-performance active materials such as Si or SiOx, and fast charging. The teachings herein provide a scalable technology for improving power density in energy storage by removing traditional polymer binders from active material coatings or layers.

[0160] Conventional electrodes for LiBs are fabricated by mixing active material, conductive additives, and a polymer binder in a slurry. Conventional cathodes are fabricated using an NMP-based slurry and a PVDF polymer binder. These binders have very high molecular weights and promote the aggregation of active material particles and their adhesion to the current collector foil through two main mechanisms: 1) entanglement promoted by long polymer chains, and 2) hydrogen bonding between the polymer, active material, and current collector. However, polymer binder-based methods present significant drawbacks in performance, power density, energy density, and manufacturing costs.

[0161] The teachings herein provide electrodes that lack a PVDF binder in the cathode and other conventional binders in the anode. Instead, as detailed above, a 3D carbon scaffold or matrix holds the active material particles together to form a cohesive layer that is also strongly attached to the metal current collector. Such active material structures are created during slurry preparation, followed by a roll-to-roll ("R2R") coating and drying process. One of the key advantages of this technology is its scalability and "drop-in" nature, as it is compatible with conventional electrode manufacturing processes.

[0162] The 3D carbon matrix is ​​formed during slurry preparation using the techniques described herein. High-aspect ratio carbon materials (e.g., nanotubes) are appropriately dispersed and chemically functionalized, for example, using a two-step slurry preparation process (such as the type described above with reference to Figure 6). The chemical functionalization is designed to form organized self-assembled structures with the surfaces of active material particles, such as NMC particles for use in the cathode, or silicon ("Si") or silicon oxide ("SiOx") particles in the case of the anode. The slurry thus formed can be based on alcohol solvent(s) for the cathode and water for the anode; such solvents are very easily evaporated and handled during the manufacturing process. Electrostatic interactions promote the self-assembled structure in the slurry, and after the drying process, bonding between the carbon matrix with the thus-formed active material particles and the surface of the current collector is promoted by the surface treatment (e.g., functional groups on the matrix) as well as the strong entanglement of the active material in the carbon matrix.

[0163] As will be appreciated by those skilled in the art, the mechanical properties of the electrode can be easily modified depending on the application and mass loading requirements by tuning the surface functionalization versus the entanglement effect.

[0164] After coating and drying, the electrode undergoes a calendering process to control the density and porosity of the active material. Densities of approximately 3.5 g / cc or higher and porosities of approximately 20% or higher can be achieved for NMC cathode electrodes. Depending on the mass loading and LIB cell requirements, the porosity can be optimized. For SiOx / Si anodes, the porosity is specifically controlled to accommodate the expansion of the active material during the lithiation process.

[0165] In some typical applications, the teachings herein can provide a $ / kWh reduction of up to about 20%. By using advantageous solvents that evaporate easily, electrode throughput is higher, and more importantly, energy consumption from long dryers is significantly reduced. If alcohol or other solvent mixtures are used instead of NMP, the solvent recovery system is also greatly simplified.

[0166] The teachings herein provide a 3D carbon matrix that dramatically increases electrode conductivity by approximately 10 to 100 times compared to electrodes using conventional binders such as PVDF, enabling rapid charging at the battery level. This technology enables thick electrode coatings in the cathode, up to approximately 150 μm (or more) per side of the current collector. The solvent(s) used in the slurry, combined with the strong 3D carbon matrix, are designed to achieve a thick wet coating without cracking during the drying process. A thick cathode with a high-capacity anode enables a substantial jump in energy density, reaching approximately 400 Wh / kg or more.

[0167] Fast charging is achieved by combining a high capacity anode that is lithiated through an alloying process (e.g., Si / SiOx) and by reducing the overall impedance of the cell when combining the anode and cathode as described herein. The teachings herein provide fast charging by having highly conductive electrodes, particularly highly conductive cathode electrodes.

[0168] One exemplary embodiment includes a pouch cell format Li-ion battery energy storage device that combines a Ni-rich NMC active material in the cathode and a SiOx and graphite blend active material in the anode, where both the anode and cathode are fabricated using the 3D carbon matrix process as described herein.

[0169] A schematic diagram of the electrode arrangement for a pouch cell device is shown in Figure 7. As shown, a double-sided cathode, using polymer binder-free cathode active layers on opposite sides of an aluminum foil current collector, is positioned between two single-sided anodes, each having a polymer binder-free anode active layer disposed on a copper foil current collector. The electrodes are separated by a permeable separator material (not shown) and wetted by the electrolyte (not shown). This arrangement can be housed within a pouch cell of the type known in the art.

[0170] These devices can feature high mass-loading Ni-rich NMC cathode electrodes and their fabrication methods: mass loading = 20-30 mg / cm 2 , specific capacity >210mAh / g. SiOx / graphite anode (SiOx content = ca. 20 wt%) based electrodes and their material synthesis and manufacturing method: mass loading 8-14mg / cm 2 , reversible specific capacity ≥ 550mAh / g. Long-life performance of SiOx / graphite anode-based Li-ion-based electrolytes, especially for batteries: -30 to 60°C. High-energy, high-power density, and long-cycle life Ni-rich NMC cathode / SiOx+graphite / carbon+ Li-ion battery pouch cells: capacity ≥ 5Ah, specific energy ≥ 300Wh / kg, energy density ≥ 800Wh / L, cycle life of over 500 cycles under 1C rate charge / discharge, and ultra-high-power fast charge / discharge C rate (up to 5C rate). An overview of the performance parameters of this type of pouch cell is summarized in Figure 8.

[0171] Example 2. Comparative Performance of NMC811 Lithium-ion Battery As detailed above, the teachings herein provide electrodes constructed using advanced 3D, high-aspect ratio carbon bonded structures that eliminate the need for polymer binders and provide greater power output, energy density (e.g., through thicker electrodes and higher mass loading of active material), and performance in extreme environments compared to conventional battery electrode designs. High-performance Li-ion battery energy storage devices are designed and fabricated using optimized capacity ratio designs for binder-free cathode / anode electrodes, anode electrode prelithiation, and wide operating temperature electrolytes (e.g., -30 to 60°C), as well as optimized test formation processes.

[0172] As described herein, electrodes are fabricated by completely eliminating high-molecular-weight polymers, such as PVDF, and toxic NMP solvent from the active material layer. This dramatically improves LiB performance while reducing manufacturing costs and capital expenditures associated with mixing, coating and drying, NMP solvent recovery, and calendaring. In electrode embodiments, a 3D nanoscopic carbon matrix serves as a mechanical scaffold for the electrode active material, mimicking the entanglement of polymer chains. Covalent and non-covalent bonds also exist between the surfaces of high-aspect-ratio carbon elements (e.g., nanotubes), the active material, and the current collector, promoting adhesion and cohesion. However, in contrast to polymers, the 3D nanoscopic carbon matrix is ​​highly conductive, enabling very high power (high C-rate). This scaffold structure is also more suitable for fabricating thick electrode active materials, a powerful method for increasing the energy density of thick-electrode batteries.

[0173] In this example, a binder-free cathode was fabricated and incorporated into a Li-ion battery (LIB) according to the teachings of the present disclosure, featuring NMC811 as the active material. The battery featured a conventional graphite anode known in the art. The cell was constructed as described above with reference to FIG. 7, using the parameters summarized in FIG. 9. A conventional electrolyte consisting of 1 M LiPF6 in a solvent mixture of ethylene carbonate and dimethyl carbonate with 1 wt. % vinyl carbonate additive was used. For comparison, an otherwise identical cell was fabricated using a PVDF binder-based cathode. The battery performance was compared as described below, demonstrating a clear advantage of the binder-free cathode battery.

[0174] As can be seen from the results shown in Figure 10, binder-free cells can reach specific energies as high as 320 Wh / kg based on a 20 Ah battery cell design and graphite anode with a cycle life of over 2000 cycles under a 2C rate charge / discharge. In comparison, conventional binder-based cathode cells can only achieve specific energies of 100-250 Wh / kg at the cell level.

[0175] The binder-free cathode cell exhibits ultra-high power fast charge / discharge C rates up to 5C rates, with a capacity retention of >50%. Figure 10 shows a comparison of the charge / discharge curves at various C rates for the binder-free cathode cell (top) and the conventional binder-based cathode cell (bottom). The charge / discharge curve of the binder-free cathode cell shows a capacity retention of over 60% for combined charge / discharge at a 5C rate. Therefore, separate discharge or charge shows even higher capacity retention. In the described example, a conventional graphite anode is used. Initial experimental results show that a 10C charge rate is achievable when a Si-dominant anode is combined with the NMC811 cathode used in this example.

[0176] Figure 11 shows a comparison of the cycle life of the above cells. The cells were repeatedly cycled between voltages of 2.75 V and 4.2 V at 25°C, and the discharge capacities were recorded. The binder-free cathode cell exhibits a life of over 2000 cycles with less than 20% discharge capacity loss. In contrast, the binder-based cathode cell experiences a discharge capacity loss of over 20% after only about 1000 cycles.

[0177] Example 3. Comparison of pouch half-cells Binder-free cathode electrodes of the type described herein can advantageously achieve high mass loadings, e.g., about 45 mg / cm per side of NMC811 active material. 2 This example presents experimental results showing the performance of an electrode without such a high mass loading binder compared to a control electrode featuring a PVDF binder and NMC811 active material.

[0178] For comparison purposes, half-cells of the type shown in Figure 12 were constructed using a single-sided cathode (either binder-free or a binder-based control) and lithium foil on a copper substrate as the battery counter electrode. The half-cells were subjected to charge rate testing under various current densities, and the results are summarized below.

[0179] 13 is a plot showing specific capacity versus potential (referenced to Li / Li potential) for a binder-free cathode half-cell (solid trace) and a reference binder-based cathode half-cell (dashed trace) at various current densities. At all current densities (and therefore at all C-rates), the binder-free cathode half-cell shows better performance (as indicated by the relative rightward shift of the traces).

[0180] 14 is a plot showing potential (referenced to Li / Li potential) versus volumetric capacity for a binder-free cathode half-cell (solid trace) and a reference binder-based cathode half-cell (dashed trace) at various current densities. At all current densities (and therefore at all C-rates), the binder-free cathode half-cell shows better performance (as indicated by the relative rightward shift of the traces).

[0181] Figure 15 shows a plot of volumetric capacity versus current density for a binder-free cathode half-cell (top trace) and a reference binder-based cathode half-cell (bottom trace). At all current densities (and therefore at all C-rates), the binder-free cathode half-cell exhibits better performance, with the relative performance gap widening at higher C-rates.

[0182] Figure 16 shows Nyquist plots obtained from electrochemical impedance spectroscopy for the three binder-free cathode half-cells (square, circle, and up-pointing triangle) and the reference binder-based cathode half-cell. The binder-free cathode half-cell shows significantly better performance than the reference half-cell.

[0183] Current density is 0.5mA / cm 2 to 10mA / cm 2 (1.2C rate), the discharge capacity retention of the binder-free NMC811 electrode was the same at 45 mg / cm for both electrodes compared to the PVDF binder-based control NMC811 electrode. 2 It can be seen from the figure that the C-rate tests under various current densities are presented as a relative comparison between the conventional PVDF binder-based cathode and the binder-free cathode, and do not reflect the absolute C-rate performance in a full-cell configuration, such as that presented in Examples 1 and 2 above.

[0184] Example 4. Battery Cell with PVDF-Free / NMP-Free Electrodes In some embodiments, a battery cell includes a PVDF-free / NMP-free, nickel-predominant or nickel-rich NMC cathode or cathodes. Nickel-predominant NMC and nickel-rich NMC are described above. In certain embodiments, the cathode, e.g., the cathode active layer, includes, by weight / mass, about 98.75% NCM91, about 0.5% nanocarbon, and about 0.75% polymer additive. The term "NCM91" is used interchangeably with the term "NMC91." NCM91 contains about 91% nickel. In certain embodiments, the cathode active layer includes, by weight / mass, about 0.5% carbon nanotubes (CNTs). The CNTs can form a CNT network and conductive pathways through and across the active layer. The CNT network surrounds or entangles metal oxide particles, thereby enhancing cohesion within and structural integrity of the active layer. The polymer additive(s) can function as a binder and / or provide a surface treatment of the nanocarbon(s) (e.g., CNTs) as described above, which improves adhesion between the active layer materials and to the current collector, thus eliminating the need for an adhesive layer between the active layer and the current collector. In some embodiments, the cathode includes a current collector (also referred to as a conductive layer) comprising one or more layers of aluminum (Al) foil. In certain embodiments, the thickness of each layer of aluminum foil, or the total thickness of the aluminum foil layer(s), is about 8-15 μm or about 10-12 μm.

[0185] In some embodiments, the battery cell includes a silicon-dominant anode or a silicon-rich anode, or multiple anodes. In some embodiments, the active layer of a silicon-dominant anode contains more than 50% silicon by weight / mass, and the active layer of a silicon-rich anode contains at least about 70%, 75%, 80%, 85%, or 90% silicon by weight / mass. In certain embodiments, the anode, such as the active layer of the anode, includes, by weight / mass, about 80% Si—C (silicon / carbon composite, such as a silicon / graphite composite), about 7% graphite, about 3% nanocarbon(s), and about 10% polymer(s). In certain embodiments, the anode active layer includes about 3% CNTs by weight / mass. The CNTs can form a CNT network and conductive pathways through and across the active layer. The polymer(s) can act as a binder and / or provide a surface treatment of the nanocarbon(s) (e.g., CNTs) as described above, which improves adhesion between the active layer materials and to the current collector, thus eliminating the need for an adhesive layer between the active layer and the current collector. In some embodiments, the anode includes a current collector comprising one or more layers of copper (Cu) foil. In particular embodiments, the thickness of each layer of copper foil, or the total thickness of the copper foil layer(s), is about 4-10 μm or about 6-8 μm.

[0186] Examples of nanocarbon(s) that can comprise the cathode or anode (e.g., the active layer thereof) include, but are not limited to, carbon nanotubes (including single-walled CNTs, double-walled CNTs, and multi-walled CNTs), graphene (e.g., graphene flakes), graphene oxide, exfoliated graphite nanoplatelets, carbon nanoparticles, carbon powder, activated carbon, carbon black, carbon nanofibers, carbon nanohorns, carbon nano-onions, fullerenes, carbon aerogels, and any combination thereof. In some embodiments, the nanocarbon comprises a high aspect ratio nanocarbon. In particular embodiments, the nanocarbon(s) comprise carbon nanotubes, whether single-walled CNTs, double-walled CNTs, or / and multi-walled CNTs.

[0187] Non-limiting examples of polymer additive(s) that can comprise the cathode or anode (e.g., the active layer thereof) include polyacrylic acid, poly(vinyl alcohol), poly(vinyl acetate), polyacrylonitrile, polyisoprene, polyaniline, polyethylene, polyimide, polystyrene, polyurethane, polyvinyl butyral, and polyvinylpyrrolidone, and any combination thereof.

[0188] Non-limiting examples of the polymer(s) that can comprise the cathode or anode (e.g., the active layer thereof) include polyacrylic acid, poly(vinyl alcohol), poly(vinyl acetate), polyacrylonitrile, polyisoprene, polyaniline, polyethylene, polyimide, polystyrene, polyurethane, polyvinyl butyral, polyvinylpyrrolidone, fluorine acrylic hybrid latex (TRD202A, JSR Corporation), and any combination thereof.

[0189] The battery cell includes an ion-permeable separator that physically separates the cathode and anode to prevent short circuits. In some embodiments, the separator includes one or more polymers and / or one or more ceramics. Non-limiting examples of polymer(s) that can comprise the separator include polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polyamide, polyetheretherketone (PEEK), and any combination thereof, and examples of such ceramic(s) include Al2O3 and / or SiO2. In some embodiments, the separator is a microporous ceramic-coated polyolefin membrane. In certain embodiments, the separator includes a membrane composed of PE and / or PP and a ceramic coating on one or both sides of the membrane. In certain embodiments, the membrane composed of PE and / or PP has a thickness of about 9 μm, and the ceramic coating on one or both sides of the membrane has a thickness of about 3 μm.

[0190] The battery cell further includes an electrolyte that fills the void spaces within the electrodes and between the electrodes and the separator. The electrolyte can include one or more ionic liquids, one or more salts, or one or more organic solvents, or any combination or all thereof. WO 2013 / 126915 A1 and corresponding U.S. Patent Application Publication No. 2014 / 0042988 A1 disclose exemplary electrolytes, both of which are incorporated herein by reference in their entireties. In some embodiments, the electrolyte includes one or two salts (e.g., one or two lithium salts, such as one or two selected from LiPF, LiPO, F, and lithium bis(fluorosulfonyl)imide [LiFSI]) and one or two organic solvents (e.g., one or two carbonate solvents, such as one or two selected from cyclic carbonates (e.g., ethylene carbonate [EC], fluoroethylene carbonate [FEC], vinyl ethylene carbonate [VEC], vinylene carbonate [VC], and propylene carbonate [PC]) and linear carbonates (e.g., dimethyl carbonate [DMC], diethyl carbonate [DEC], and ethyl methyl carbonate [EMC]). In further embodiments, the electrolyte comprises one or two carbonate solvents (e.g., one or two linear carbonates) as solvent(s) and one or two different carbonate solvents (e.g., one or two cyclic carbonates) as additive(s). In certain embodiments, the electrolyte comprises LiFSI and LiPF6 as lithium salts, one or two carbonate solvents (e.g., one or two linear carbonates selected from DMC, DEC, and EMC) as solvent(s), one or two different carbonate solvents (e.g., one or two cyclic carbonates, such as one or two selected from FEC, VEC, and VC) as additive(s), and optionally one or two additional additives (e.g., organosilicon-2 additives, cyclic sulfate-2 additives, or nitrile-based additives, or any combination thereof). The additive(s) can improve the electrochemical performance and properties of the electrode(s), such as the cathode.In certain embodiments, the concentration of the LiFSI / LiPF6 lithium salt blend in the electrolyte is about 1-1.5M, or about 1.2M.

[0191] Table 1 lists the electrochemical performance and characteristic values ​​of battery cells including an NCM91 cathode and a silicon-dominant anode in the form of a pouch cell. In initial capacity and energy density determinations, the battery cells demonstrated discharge capacities of ≥ 4.5 Ah, specific energy of ≥ 330 Wh / kg, and energy densities of ≥ 880 Wh / L at the beginning of life and at 25°C, based on total measured weight and total volume. In addition to superior electrochemical performance and characteristics, the battery cells achieve approximately 15% cost savings in $ / kWh compared to conventional battery cells, based in part on the higher energy density and lower cost of manufacturing NMP-free electrodes.

[0192] [Table 1]

[0193] For the NCM91 cathode / silicon dominant anode battery cell, Figure 17 shows the discharge capacity (Ah) and Figure 18 shows the discharge energy (Wh) for C / 10 and C / 3 cycles 1 and 2 at 25°C. Figure 19 shows the initial C / 10 and C / 3 charge / discharge curves at 25°C. In Figure 19, "CCCV" indicates constant current constant voltage, and "CC" indicates constant current. Figure 20 shows various discharge C-rate curves at 25°C. All discharge C / 3, C / 2, 1C, 2C, 3C, and 4C rate curves show a stable trend. The discharge 4C rate capacity and retention for the first three cycles of C / 3 rate discharge are 5.8 mAh / cm. 2 Even for electrodes with higher loadings, the recovery rate is about 60%. Figures 21A and 21B show the results of discharge C-rate cycling tests at 25°C. The tests show a stable trend for all discharge rates: C / 3, C / 2, 1C, 2C, 3C, and 4C.

[0194] For the NCM91 cathode / silicon dominant anode battery cell, Figures 22A and 22B show the results of a charge C-rate cycling test at 25°C. In Figures 22A and 22B, "CC region" refers to the constant current charging region before reaching the constant voltage charging region. The test shows a stable trend for all C / 3, C / 2, 1C, 2C, 3C, and 3.5C CC region charge capacities. The 3.5C rate CC region charge capacity retention for the first three cycles of C / 3 CC charging is about 56%. Figure 23 shows various charge C-rate curves at 25°C. All charge C / 3, C / 2, 1C, 2C, 3C, and 3.5C rate curves show a stable trend. Figure 24 shows a 5.8 mAh / cm2 charge capacity at 3.5C rate under CCCV at 25°C. 2 Even with electrodes with high loads, 80% state of charge (SOC) can be achieved in approximately 15 minutes of charging. These figures demonstrate that the battery cell exhibits high charge / discharge rate capabilities.

[0195] Regarding the cycle life of the NCM91 cathode / silicon-dominant anode battery cell, Figure 25 shows that under C / 3 cycling in the range of 4.2 to 2.8 V (100% SOC to 5% SOC) at 25°C, the battery cell achieves 400 cycles with approximately 91% discharge capacity retention. Figure 26 shows that under 100% fast charging via 3.5 C / 1 C cycling in the range of 4.2 to 2.8 V (100% SOC to 5% SOC) at 25°C, the battery cell achieves 400 cycles with approximately 86% discharge capacity retention. Figure 27 shows the hybrid power pulse characterization (HPPC) direct current internal resistance (DCIR) over a range of state of charge (SOC) at 25°C. The battery cell has a low HPPC DCIR of approximately 39 mΩ at 50% SOC. DCIR may be a proxy for equivalent series resistance (ESR).

[0196] Table 2 lists the physical parameters for an embodiment of an NCM91 cathode / silicon dominant anode battery cell in the form of a pouch cell. As is evident from Table 2, the pouch cell is small and lightweight. FIG. 28A shows the dimensions of the pouch cell, and FIG. 28B shows the exterior of the pouch cell. Given the pouch cell's excellent electrochemical performance and properties, compactness, and light weight, the pouch cells can be stacked in layers to form modules that comprise lithium-ion batteries for electric vehicles.

[0197] [Table 2]

[0198] In another embodiment, the battery cell includes a PVDF-free / NMP-free nickel-rich NMC cathode having ingredients and compositions similar to those described above for the NCM91 cathode / silicon-dominant anode battery cell, except that a different nickel-rich NMC may be used. The nickel-rich NMC is described above. The active layer of the anode includes, by weight / mass, about 30-40% (e.g., about 40%) silicon / graphite composite, about 51.5% graphite, about 1.5% nanocarbon (e.g., carbon nanotubes), and about 7% polymer. The battery cell includes a separator and electrolyte similar to those of the NCM91 cathode / silicon-dominant anode battery cell. The battery cell can include, for example, 27 anodes and 28 cathodes. The battery cell has a capacity of about 50 Ah and an energy density of about 350 Wh / kg. An embodiment of the battery cell in the form of a pouch has the dimensions shown in Figure 29, a thickness of 7.7 mm, and a weight of 0.515 kg. The pouch cell can be used to form a lithium ion battery for an electric vehicle.

[0199] A battery cell including a PVDF-free / NMP-free electrode (e.g., cathode) can also contain other cathode materials and / or other anode materials. For example, the cathode, e.g., the active layer of the cathode, can include manganese, NMC (whether or not nickel-rich, e.g., NMC622, NMC721, or MMC811), NCA (whether or not nickel-rich, e.g., NCA90), LCO, LFP, or solid catholyte. Materials that an anode, such as the active layer of an anode, can include, but are not limited to, silicon (whether or not silicon-predominant), microsilicone, silicon oxide, silicon composites (e.g., silicon / carbon composites, such as silicon / graphite composites), or graphite, or any combination thereof. As a non-limiting example, a battery cell can include a lithium iron phosphate (LFP) cathode and a silicon-predominant anode, providing a current density of about 4.5 mAh / cm for use in electric vehicles. 2 or greater, a capacity of about 60 Ah or greater, a gravimetric energy density in the range of about 220-240 Wh / kg, and a volumetric energy density in the range of about 540-560 Wh / L.

[0200] The battery cell may be any battery type. For example, the battery may be a lithium-ion battery including a PVDF-free / NMP-free cathode, an anode containing graphite or / and silicon (whether silicon-predominant or not), and a liquid electrolyte. As another example, the battery may be a solid-state battery (e.g., a solid-state lithium-ion battery) including a PVDF-free / NMP-free cathode, a lithium metal anode or a silicon-predominant anode, and a solid electrolyte. Lithium and silicon can store more energy in less volume and mass than graphite. The solid electrolyte may include, for example, a polymer or / and ceramic and may also function as a separator. Solid electrolytes are typically non-flammable, while liquid electrolytes may contain flammable organic solvent(s). As a further example, the battery may be an anodeless battery including a PVDF-free / NMP-free cathode or catholyte, a current collector (e.g., a metal foil such as copper foil), and a solid or liquid electrolyte. A solid anodeless battery includes a solid electrolyte or catholyte. The catholyte combines the cathode material and solid electrolyte to form a single layer. Each battery type can include multiple cathodes and multiple anodes, optionally with different numbers of cathodes and anodes. The process for making a cathode for a lithium-ion battery (e.g., a PVDF-free / NMP-free cathode) is similar to the process for making a cathode for a solid-state battery or a cathode or catholyte for an anodeless battery.

[0201] The battery cells can be used in a variety of applications, for example, to form batteries (e.g., lithium-ion batteries) for use in electric vehicles, laptop computers, tablets, smartphones and other mobile devices, and electrical appliances.

[0202] The battery cells can have any suitable shape depending on their intended use. For example, the battery cells can have a cylindrical or prismatic shape, or can be in the form of a pouch, flat pack, or coin.

[0203] Example 5. Electrode Fabrication Cathodes, including PVDF-free / NMP-free cathodes, and anodes can be manufactured according to the methods disclosed in U.S. Patent Application Publication No. 2023 / 0238509 A1, which is incorporated herein by reference in its entirety. In some embodiments, a method for manufacturing an electrode for an energy storage device (e.g., a battery or ultracapacitor) comprises: heating a mixture of solvent(s) and material(s) for use as an energy storage medium; adding an active material to the mixture; adding a dispersant to the mixture to provide a slurry; coating the slurry onto a current collector; and calendering the coating of the slurry on a current collector to provide an electrode.

[0204] In some embodiments, the method further includes partially or completely drying the coated current collector, such as by exposing the coated current collector to heat and / or vacuum, before calendering the partially or completely dried coated current collector.

[0205] In some embodiments, the method further comprises sintering the coating of the slurry on the current collector.

[0206] In some embodiments, the energy storage material comprises a nanocarbon, such as a carbon nanotube. In some embodiments, the active material comprises a metal oxide (e.g., a lithium metal oxide such as NMC) or LFP for the cathode active layer. In further embodiments, the active material comprises silicon, a silicon composite (e.g., silicon / graphite), silicon oxide, or graphite, or any combination thereof, for the anode active layer.

[0207] Solvents that can be used to form the mixture include, but are not limited to, alcohols (e.g., methanol, ethanol, or isopropyl alcohol), acetonitrile, tetrahydrofuran, deionized water, and any combination thereof. The use of a solvent with a low boiling point facilitates drying of the electrode active layer. In certain embodiments, the solvent for fabricating a cathode (e.g., an NMC cathode) is or includes ethanol. In other embodiments, the solvent for fabricating an LFP cathode is or includes deionized water. In some embodiments, the solvent for fabricating an anode (e.g., a silicon-dominant anode) is or includes water and ethanol (e.g., ≦about 10% ethanol by weight or volume). The solvent(s) do not include NMP, which is toxic and difficult to recycle, making the fabrication process more environmentally friendly, significantly increasing throughput, and reducing cost and energy consumption.

[0208] Dispersants generally function as emulsifiers and disintegrants (e.g., in solution polymerization), and may also function as surfactants and shape control agents in nanoparticle formation and self-assembly. Examples of dispersion media include, but are not limited to, polyvinylpyrrolidone (PVP, a water-soluble polymer), polyacrylic acid, sodium polyacrylate, and AQUACHARGE (a trade name for an aqueous binder for electrodes sold by Sumitomo Seika Chemicals Co., Ltd., Hyogo Prefecture, Japan).

[0209] Polymer additive(s), polymer(s), or surfactant(s) may also be added to the mixture, such as in the dispersant addition step, to enhance adhesion of the materials in the active layer to each other and between the active layer and the current collector. The polymer additive(s) or polymer(s) do not include PVDF.

[0210] Instead of coating the current collector with the final slurry, the final slurry may be formed into a sheet and then coated directly onto the current collector or onto any intermediate layer, such as an adhesive layer, on the current collector.

[0211] Other aspects of the electrode manufacturing method are described in detail in the section entitled "Method of Manufacturing."

[0212] While the present invention has been described with reference to several embodiments, those skilled in the art will recognize that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the invention. For example, in some embodiments, one of the layers described above may have multiple layers therein. Additionally, modifications in adapting a particular device, component, or material to the present disclosure may be made without departing from the essential scope of the disclosure. Therefore, the present invention is not limited to the specific embodiments and examples disclosed herein; rather, the present invention includes all variations, modifications, and equivalents thereof, as well as all embodiments falling within the scope of the appended claims.

Claims

1. 1. An energy storage device comprising an electrode, an active layer comprising an active material and nanocarbon, the active layer being substantially free of polyvinylidene fluoride / difluoride (PVDF) and N-methyl-2-pyrrolidone (NMP); A current collector; 1. An energy storage device comprising:

2. 10. The energy storage device of claim 1, wherein the nanocarbon has a high aspect ratio.

3. 3. The energy storage device of claim 1, wherein the nanocarbon is selected from carbon nanotubes, graphene (e.g., graphene flakes), graphene oxide, exfoliated graphite nanoplatelets, carbon nanoparticles, carbon powder, activated carbon, carbon black, carbon nanofibers, carbon nanohorns, carbon nano-onions, fullerenes, carbon aerogels, and any combination thereof.

4. 4. The energy storage device of claim 3, wherein the nanocarbon comprises a carbon nanotube (CNT), such as a single-walled CNT, a double-walled CNT, or a multi-walled CNT, or any combination thereof.

5. The energy storage device according to any one of claims 1 to 4, wherein the nanocarbon has a surface treatment.

6. The energy storage device of claim 5 , wherein the surface treatment improves adhesion between the nanocarbon and the active material and between the active layer and the current collector.

7. The energy storage device of claim 1 , wherein the active layer further comprises a polymer additive, a polymer or a surfactant, or any combination thereof.

8. 8. The energy storage device of claim 7, wherein the polymer additive, the polymer, or the surfactant, or any combination thereof, provides a surface treatment to the nanocarbon.

9. The energy storage device according to any one of claims 1 to 8, wherein the electrode is a cathode.

10. 10. The energy storage device of claim 9, wherein the active material comprises lithium iron phosphate or a lithium metal oxide such as lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, or lithium titanate oxide, or any combination thereof.

11. 11. The energy storage device of claim 10, wherein the active material comprises a nickel-rich lithium nickel manganese cobalt oxide such as NMC721, NMC811, or NMC91.

12. 12. The energy storage device of claim 9, wherein the active layer of the cathode comprises about 90-99 wt. % nickel-rich lithium nickel manganese cobalt oxide, about 0.5-5% of the nanocarbon, and about 0.5-5% of a polymer additive, polymer, or surfactant, or any combination thereof.

13. The energy storage device according to any one of claims 9 to 12, wherein the current collector comprises aluminum foil.

14. The energy storage device according to any one of claims 1 to 13, wherein the electrode is an anode.

15. 15. The energy storage device of claim 14, wherein the active material comprises silicon, silicon oxide, a silicon composite (e.g., a silicon / graphite composite), or graphite, or any combination thereof.

16. 16. The energy storage device of claim 15, wherein the active material comprises silicon as the predominant element by weight.

17. 17. The energy storage device of any one of claims 14 to 16, wherein the active layer of the anode comprises about 60-90 wt% silicon or / and silicon composite (e.g., silicon / graphite composite), about 5-20% graphite, about 1-5% of the nanocarbon, and about 5-20% polymer additive, polymer or surfactant, or any combination thereof.

18. The energy storage device according to any one of claims 14 to 17, wherein the current collector comprises copper foil.

19. 19. The energy storage device of any one of claims 1 to 18, further comprising an electrolyte comprising one or more salts and one or more organic solvents.

20. The electrolyte is LiPF ６ or / and one or more lithium salts such as lithium bis(fluorosulfonyl)imide (LiFSI), and one or more carbonate solvents such as one or more linear carbonate solvents selected from dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

21. 21. The energy storage device of claim 19 or 20, wherein the electrolyte further comprises one or more additives such as one or more cyclic carbonates selected from ethylene carbonate, fluoroethylene carbonate, vinylethylene carbonate, vinylene carbonate, and propylene carbonate.

22. (a) has a specific energy of at least about 330 Wh / kg; (b) has a gravimetric energy density of at least about 330 Wh / kg; (c) having a volumetric energy density of at least about 850 Wh / L; (d) having a capacity of at least about 50 Ah; (e) having an internal resistance of about 40 mΩ or less; (f) charging to an 80% charge stage within approximately 15 minutes; (g) having an operating voltage range of at least about 4.0 to 2.5 V; or (h) has a cycle life of at least about 750 charge / discharge cycles; or (i) any combination or all of the above; 46. ​​The energy storage device of any one of embodiments 25-45, wherein

23. 23. The energy storage device according to any one of claims 1 to 22, which is a battery cell or a battery.

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