Electrode for an energy storage device

Abstract

An electrode active layer is disclosed that includes a network of high aspect ratio carbon elements (e.g., carbon nanotubes, carbon nanotube bundles, graphene sheets, etc.) that provide a highly conductive scaffold that entangles or entangles the active material, thereby supporting the layer. 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, thereby improving the overall cohesion and mechanical stability of the active layer. The surface treatment forms only a thin (in some cases even monomolecular) layer on the network, thereby leaving large void spaces free of any bulk adhesive material and which can be filled, instead, with the active material. The resulting active layer can be formed with excellent mechanical stability, even under large thicknesses and high active material mass loadings.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit of and priority to U.S. Provisional Patent Application Serial No. 63 / 041,801, filed June 19, 2020; U.S. Provisional Patent Application Serial No. 62 / 954,771, filed December 30, 2019; U.S. Provisional Patent Application Serial No. 62 / 871,041, filed July 5, 2019; and U.S. Provisional Patent Application Serial No. 63 / 003,341, filed April 1, 2020, the entire contents of each of the foregoing references are incorporated herein by reference. BACKGROUND

[0003] Lithium batteries are used in a variety of products, including medical devices, electric cars, airplanes, and consumer products such as laptops, cell phones, and cameras. Because of their high energy density, high operating voltage, and low self-discharge, lithium-ion batteries have outpaced the secondary battery market and continue to find new uses in products and industries in development.

[0004] Generally, lithium-ion batteries (LIB or LiB) include 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 an anode active material or a cathode active material with a binder and a solvent to form a paste or slurry, which is then coated and dried on a current collector, such as aluminum or copper, to form a film on the current collector. The anode and cathode are then layered or wound before being housed in a pressurized outer casing containing the electrolyte material, all of which together form a lithium-ion battery.

[0005] In conventional electrodes, the binder has sufficient adhesion and chemical properties such that the film coated on the current collector will remain in contact with the current collector even when manipulated to fit into a pressurized battery casing. Since the film contains the electrode active material, if the film cannot maintain sufficient contact with the current collector, there can be significant interference with the electrochemical performance of the battery. Further, it is important to select a binder that is mechanically compatible with the electrode active material, such that it can withstand the degree of expansion and contraction of the electrode active material during charging and discharging of the battery.

[0006] Accordingly, binders such as cellulose 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 the volume in the electrode active layer that could otherwise be used to increase the mass loading of active material and decrease the electrical conductivity of the electrode. Also, the binder tends to electrochemically react with the electrolyte used in the battery, especially in high voltage, high current, and / or high temperature applications, resulting in degradation of the battery performance. SUMMARY

[0007] Applicants have recognized that electrodes can be constructed to exhibit superior mechanical stability without requiring bulk polymer binders. In one aspect, the present disclosure describes embodiments of an electrode active layer that includes a network of high aspect ratio carbon elements (e.g., carbon nanotubes, carbon nanotube bundles, graphene sheets, etc.) that provide a highly conductive scaffold that entangles or entangles the active material, thereby supporting the layer. As detailed 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 layer (e.g., a current collector layer), thereby improving the overall cohesion and mechanical stability of the active layer. The surface treatment forms only a thin (in some cases even monomolecular) layer on the network, leaving large void spaces free of any bulk adhesive material and thus can be filled alternatively with active material. The resulting active layer can be formed with superior mechanical stability even under large thicknesses and high active material mass loadings.

[0008] In another aspect, the present disclosure describes a method including: dispersing high aspect ratio carbon elements and a surface treatment material in a solvent to form an initial slurry, wherein the dispersing step results in 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.

[0009] Various embodiments can include any of the features or elements described herein, either individually or in any suitable combination. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a schematic of an electrode featuring an active material layer.

[0011] Figure 2 is a detailed illustration of an embodiment of an active material layer.

[0012] Figure 3 is a detailed illustration of another embodiment active material layer.

[0013] Figure 4 is an electron micrograph of an active material of the type described herein.

[0014] Figure 5 is a schematic of an energy storage battery.

[0015] Figure 6 is a flowchart showing a method of manufacturing Figure 1 an electrode.

[0016] Figure 7 shows a schematic of a pouch battery.

[0017] Figure 8 A summary of functional parameters for pouch cells for EV applications is shown.

[0018] Figure 9 A summary of functional parameters for pouch cells is shown.

[0019] Figure 10 Results of a comparative performance evaluation of a pouch cell featuring binder-free cathodes (left plot) and a pouch cell featuring binder-based cathodes (right plot) are shown.

[0020] Figure 11 Results of a comparative performance evaluation of a pouch cell featuring binder-free cathodes (upper trace) and a pouch cell featuring binder-based cathodes (lower trace) are shown.

[0021] Figure 12 is a schematic of a half-cell lithium battery device.

[0022] Figure 13 is a plot showing the potential (vs. Li / Li+ potential) vs. specific capacity of a binder-free cathode half-cell (solid trace) and a reference binder-based cathode half-cell (dashed trace) at different current densities.

[0023] Figure 14 is a plot showing the potential (vs. Li / Li+ potential) vs. volumetric capacity of a binder-free cathode half-cell (solid trace) and a reference binder-based cathode half-cell (dashed trace) at different current densities.

[0024] Figure 15 is a plot showing the volumetric capacity vs. current density of a binder-free cathode half-cell (upper trace) and a reference binder-based cathode half-cell (lower trace).

[0025] Figure 16 is a Nyquist plot generated from the electrochemical impedance spectra of several binder-free cathode half-cells (square, circle, and triangle marked traces) and a reference binder-based cathode half-cell. The binder-free cathode half-cells exhibit significantly superior performance to the reference cell. DETAILED DESCRIPTION

[0026] REFERENCE Figure 1 , an electrode 10 is shown that includes an active layer 100 disposed on a current collector 101. Some embodiments can include an optional adhesion layer 102 disposed between the active layer 101 and the current collector 102. In other embodiments, the adhesion layer 102 can be omitted.

[0027] The current collector 101 can be an electrically conductive layer, such as a metal foil. An optional adhesion layer 102 (which can be omitted in some embodiments) can be a layer of material that promotes adhesion between the current collector 102 and the active layer 100. Examples of suitable materials for the current collector 101 and optional adhesion layer 102 are described in International Patent Publication No. WO / 2018 / 102652, published June 7, 2018.

[0028] Electrode active layer

[0029] In some embodiments, the active layer 100 can include a three-dimensional network 200 of high aspect ratio carbon elements 201, defining interstitial spaces within the network 200. A plurality of active material particles 300 are disposed in the interstitial spaces within the network 200. Thus, the active material particles are entangled or enmeshed in the network 200, thereby improving cohesion of the active layer 100.

[0030] In some embodiments, a surface treatment 202 (not shown, refer to FIG. 2B) is applied to the surfaces of the high aspect ratio carbon elements 201 of the network 200. Figure 2 The surface treatment promotes adhesion between the high aspect ratio carbon elements and the active material particles 300. The surface treatment can also promote adhesion between the high aspect ratio carbon elements and the current collector 100 (also referred to herein as “the electrically conductive layer”) and / or the optional adhesion layer 102.

[0031] 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 greater than the size in a transverse dimension (“minor dimension”) of the element.

[0032] For example, in some embodiments, the high aspect ratio carbon elements 201 can include platelet- or sheet-like elements having two major dimensions and one minor dimension. For example, in some such embodiments, the length ratio of each of the major dimensions can be at least 5, 10, 100, 500, 1,000, 5,000, 10,000, or more times the length ratio of the minor dimension. Exemplary elements of this type include graphene sheets or flakes.

[0033] For example, in some embodiments, the high aspect ratio carbon elements 201 can include elongated rod- or fiber-like elements having one major dimension and two minor dimensions. For example, in some such embodiments, the length ratio of the major dimension can be at least 5, 10, 100, 500, 1,000, 5,000, 10,000, or more times the length ratio of each of the minor dimensions. Exemplary elements of this type include carbon nanotubes, bundles of carbon nanotubes, carbon nanorods, and carbon fibers.

[0034] In some embodiments, the high aspect ratio carbon elements 201 can include single-walled nanotubes (SWNTs), double-walled nanotubes (DWNTs), or multi-walled nanotubes (MWNTs), carbon nanorods, 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 materials. In some embodiments, the high aspect ratio carbon elements 201 can include graphene in the form of sheets, flakes, or curved flakes, and / or formed into high aspect ratio cones, rods, etc.

[0035] In some embodiments, the electrode active layer 100 can include little or no binder material of significant volume, leaving more space in the network 200 occupied by active material particles 300. For example, in some embodiments, the active layer 200 includes less than 10% by weight, less than 1% by weight, less than 0.1% by weight, less than 0.01% by weight, or less of a binder material (e.g., a polymeric or cellulose binder material) disposed in interstitial space.

[0036] For example, in some embodiments, the electrode active layer is free or substantially free of polymeric materials or any materials other than the active material 300, and the network 200 is composed of high aspect ratio carbon elements 201 and surface treatments 202 disposed thereon.

[0037] In some embodiments, the network 200 is primarily or even entirely composed of carbon. For example, in some embodiments, the network 200 is at least 90% carbon by weight, at least 95% carbon by weight, at least 96% carbon by weight, at least 97% carbon by weight, at least 98% carbon by weight, at least 99% carbon by weight, at least 99.5% carbon by weight, at least 99.9% carbon by weight, or more.

[0038] 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 both principal dimensions can be at least 0.1 pm, 0.5 pm, 1 pm, 5 pm, 10 pm, 50 pm, 100 pm, 200 pm, 300 pm, 400 pm, 500 pm, 600 pm, 7000 pm, 800 pm, 900 pm, 1,000 pm, or more. For example, in some embodiments, the size (e.g., average size, median size, or minimum size) of the elements 201 forming the network 200 can be in the range of 1 pm to 1,000 pm, or any sub-range thereof (such as 1 pm to 600 pm).

[0039] In some embodiments, the elements can be relatively uniform in size. For example, in some embodiments, more than 50%, 60%, 70%, 80%, 90%, 95%, 99%, or more of the elements 201 can have a size along one or both major dimensions that is within 10% of the average size of the elements 201 that make up the network 200.

[0040] Applicants have discovered that active layers 100 of the type herein can provide exemplary performance (e.g., high electrical conductivity, low electrical resistance, high voltage performance, and high energy and power density) even when the mass fraction of the elements 201 that make up the network 200 in the layer 100 is very low, thereby allowing for 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 of active material particles 300.

[0041] In some embodiments, the network 200 forms an interconnected network of high- conductivity paths for electrical current (e.g., electron or ion transport) through the active layer 100. For example, in some embodiments, high-conductivity junctions can occur at points where elements 201 of the network intersect with each other, or at points where they are close enough to allow quantum tunneling of charge carriers (e.g., electrons or ions) from one element to the next. While the elements 201 can constitute a relatively low mass fraction of the active layer (e.g., less than 10 wt%, 5 wt%, 4 wt%, 3 wt%, 2 wt%, 1 wt%, or less, in the range of 0.5 wt% to 10 wt% or any sub-range thereof, such as 1 wt% to 5.0 wt%), the interconnected network of high-conductivity paths formed in the network 200 can provide long conductive paths to facilitate electrical current flow within and through the active layer 100 (e.g., conductive paths on the order of the thickness of the active layer 100).

[0042] For example, in some embodiments, network 200 may include one or more structures of interconnect elements 201, wherein the total length of the structure along one or more dimensions is 2, 3, 4, 5, 10, 20, 50, 100, 500, 1,000, 10,000 or more times the average length of the constituent elements 201 constituting the structure. For example, in some embodiments, network 200 may include one or more structures of interconnect elements 200, wherein the total length of the structure is 2 to 10,000 times (or any subrange thereof) the average length of the constituent elements 201 constituting the structure. For example, in some embodiments, network 200 may include highly conductive paths with lengths greater than 100 μm, 500 μm, 1,000 μm, 10,000 μm or larger (e.g., in the range of 100 μm to 10,000 μm in any of its subranges).

[0043] As used herein, the term “highly conductive path” should be understood as a path formed by interconnect element 201, which has a higher conductivity than the active material particles embedded in network 200.

[0044] To avoid being bound by theory, in some embodiments, network 200 can be characterized as an electrically interconnected network of elements 201 exhibiting connectivity exceeding a percolation threshold. The percolation threshold is a mathematical concept related to percolation theory, which describes the form of long-range connectivity in a stochastic system. Below the threshold, there are no so-called "giant" connections on the order of the system size; above the threshold, giant connections on the order of the system size exist.

[0045] In some embodiments, the percolation threshold can be determined by increasing the mass fraction of element 201 in the active layer 100 while measuring the conductivity of the layer, while keeping all other properties of the layer constant. In some such cases, the threshold can be identified by the mass fraction of the layer whose conductivity increases sharply and / or the mass fraction of the layer whose conductivity increases slowly only with the addition of more element 201. Such behavior indicates the threshold required to form interconnect structures that provide conductive paths with lengths on the order of the size of the active layer 100.

[0046] Figure 2 A network 200 (e.g., a network located near several active material particles 300) is shown. Figure 1 A detailed view of the high aspect ratio carbon element 201 is shown. In the illustrated embodiment, 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 211 and a hydrophilic end 212, wherein the hydrophobic end is disposed near the surface of the carbon element 201 and the hydrophilic end 212 is disposed far from the surface.

[0047] In some embodiments in which the carbon elements 201 are hydrophobic (as is typically the case for nano-shaped carbon elements such as CNTs, CNT bundles, and graphene sheets), the hydrophobic end 211 of the surfactant elements 210 will be attracted to the carbon elements 201. Thus, in some embodiments, the surface treatment 202 can be a self-assembled layer. For example, as detailed below, in some embodiments, when the 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 due to electrostatic interactions between the elements 201 and 210 within the slurry.

[0048] In some embodiments, the surface treatment 202 can be a self-limiting layer. For example, as detailed below, in some embodiments, when the 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 due to electrostatic interactions between the elements 201 and 210 within the slurry. In some such embodiments, once a region of the surface of the elements 201 is covered with surfactant elements 210, additional surfactant elements 210 will not be attracted to that region. In some embodiments, once the surface of the elements 201 is covered with surfactant elements 202, other 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, ensuring that the layer is thin, e.g., a single molecule or a few molecules thick.

[0049] In some embodiments, the hydrophilic end 212 of at least a portion of the surfactant elements forms a bond with the active material particles 300. Thus, the surface treatment 202 can provide good adhesion between the elements 201 of the network 200 and the active material particles. In some embodiments, the bond can be a covalent bond or a non-covalent bond, e.g., a π-π bond, a hydrogen bond, an electrostatic bond, or a combination thereof.

[0050] For example, in some embodiments, the hydrophilic end 212 of the surfactant elements 210 has a first polarity charge, while the surface of the active material particles 300 carries a second polarity charge opposite the first polarity charge, and thus are attracted to each other.

[0051] For example, in some embodiments in which, during formation of the layer 100, the active material particles 300 are combined with the carbon elements 201 bearing the surface treatment 202 in a solvent (as described in more detail below), the outer surfaces of the active material particles 300 can be characterized by a zeta potential having an opposite sign to the zeta potential of the outer surfaces of the surface treatment 202, as is known in the art. Thus, in some such embodiments, the attractive force between the carbon elements 201 bearing the surface treatment 202 and the active material product 300 facilitates self-assembly of the structure, with the active material particles 300 becoming entangled with the carbon elements 201 of the network 200.

[0052] In some embodiments, the hydrophilic end 212 of at least a portion of the surfactant elements forms a bond with a current collector layer or an attachment layer underlying the active material layer 100. Thus, the surface treatment 202 can provide good adhesion between the elements 201 of the network 200 and such underlying layers. In some embodiments, the bond can be a covalent bond or a non-covalent bond, such as a pi-pi bond, a hydrogen bond, an electrostatic bond, or a combination thereof. In some embodiments, this arrangement provides superior mechanical stability of the electrode 10, as discussed in more detail below.

[0053] In various embodiments, the surfactant used to form the surface treatment 202 as described above can include any suitable material. For example, in some embodiments, the surfactant can include one or more of: cetyltrimethylammonium hexafluorophosphate (CTAP), cetyltrimethylammonium tetrafluoroborate (CTAB), cetyltrimethylammonium acetate, cetyltrimethylammonium nitrate, cocamidopropyl betaine, N-(cocoalkyl)-N,N,N-trimethylammonium methylsulfate, and cocamidopropyl betaine. Other suitable materials are described below.

[0054] In some embodiments, the surfactant layer 202 can be formed by dissolving a compound in a solvent such that the surfactant layer is formed from ions from the compound (e.g., in a self-limiting process as described above). In some such embodiments, the active layer 100 will then include residual counterions 214 of the surfactant ions that form the surface treatment 202.

[0055] In some embodiments, these surfactant counterions 214 are selected to be compatible for use in an electrochemical cell. For example, in some embodiments, the counterions are selected to not react or to react mildly with materials used in the cell, such as electrolytes, separators, housings, etc. For example, if an aluminum housing is used, the counterions can be selected to not react or to react mildly with the aluminum housing.

[0056] For example, in some embodiments, the residual counterion is free or substantially free of halogen groups. For example, in some embodiments, the residual counterion is free or substantially free of bromine.

[0057] In some embodiments, the residual counterion can be selected to be compatible with the electrolyte used in the energy storage cell that includes the active layer 200. For example, in some embodiments, the residual counterion can be the same kind of ion used in the electrolyte itself. For example, if the electrolyte includes a dissolved LiPF6salt, the electrolyte anion is PF6. In such cases, the surfactant can be selected to be, for example, CTA PF6, such that the surface treatment 202 is formed as a layer of anions from the CTA PF6, and the residual surfactant counterion is the PF6anion from the CTA PF6(hence matching the anion of the electrolyte).

[0058] In some embodiments, the surfactant material used can be soluble in a solvent that exhibits advantageous properties. For example, in some embodiments, the solvent can include water or an alcohol, such as methanol, ethanol, or 2-propanol (isopropyl alcohol, sometimes referred to as IPA), or a combination thereof. In some embodiments, the solvent can include one or more additives for further improving the properties of the solvent, for example, a low-boiling point additive, such as acetonitrile (ACN), deionized water, and tetrahydrofuran.

[0059] For example, if a low-boiling point solvent is used in the formation of the surface treatment 202, a thermal drying process (e.g., of the type described in more detail below) that is performed at a relatively low temperature can be used to quickly remove the solvent. As will be appreciated by those skilled in the art, this can improve the speed and / or cost of manufacture of the active layer 202.

[0060] 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 250°C, 225°C, 202°C, 200°C, 185°C, 180°C, 175°C, 150°C, 125°C, or lower, for example, less than or equal to 100°C.

[0061] In some embodiments, the solvent can exhibit other advantageous properties. In some embodiments, the solvent can have a low viscosity, such as a viscosity of less than or equal to 3.0 centipoise, 2.5 centipoise, 2.0 centipoise, 1.5 centipoise, or lower at 20°C. In some embodiments, the solvent can have a low surface tension, such as a surface tension of less than or equal to 40 mN / m, 35 mN / m, 30 mN / m, 25 mN / m, or lower at 20°C. In some embodiments, the solvent can have a low toxicity, for example, comparable to that of an alcohol, such as isopropyl alcohol.

[0062] Notably, this is in contrast to processes used to form conventional electrode active layers, which feature a bulk volume of binder material such as polyvinylidene fluoride or polyvinylidene difluoride (PVDF). Such bulk volumes of binder require caustic solvents that are typically characterized by a high boiling point. 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 a high-temperature drying process to remove the solvent. Moreover, NMP is expensive, requires a complex solvent recovery system, and is highly toxic, presenting serious safety concerns. In contrast, as described in further detail below, in various embodiments, the active layer 200 can be formed without the use of NMP or similar compounds such as pyrrolidone compounds.

[0063] While one example surface treatment 202 is described above, it should be appreciated that other treatments can also be used. For example, in various embodiments, the surface treatment 202 can be formed by functionalizing the high aspect ratio carbon elements 201 using any suitable technique described herein or known in the art. The functional groups applied to the elements 201 can be selected to promote adhesion between the active material particles 300 and the network 200. For example, in various embodiments, the functional groups can include carboxyl groups, hydroxyl groups, amine groups, silane groups, or combinations thereof.

[0064] As will be described in further detail below, in some embodiments, the functionalized carbon elements 201 are formed from a dried (e.g., lyophilized) aqueous dispersion that includes nano-shaped 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.

[0065] With reference to Figure 3 In some embodiments, the surface treatment 202 on the high aspect ratio carbon elements 201 includes a thin polymer layer disposed on the carbon elements that promotes adhesion of the active material to the network. In some such embodiments, the thin polymer layer includes a self-assembled and / or self-limiting polymer layer. In some embodiments, the thin polymer layer is bound to the active material, for example, through hydrogen bonding.

[0066] In some embodiments, the thin polymer layer can have a thickness in a direction normal to the outer surface of the carbon elements that is less than 3 times, 2 times, 1 time, 0.5 times, 0.1 times (or less) of the minor dimension of the elements 201.

[0067] In some embodiments, the thin polymer layer includes functional groups (e.g., pendant functional groups) that are bound to the active material, for example, through non-covalent bonds such as pi-pi bonds. In some such embodiments, the thin polymer layer can form a stable capping layer over at least a portion of the elements 201.

[0068] In some embodiments, a thin polymer layer on some of the elements 201 can be combined with the current collector 101 or the attachment layer 102 underneath the active layer 200. For example, in some embodiments, the thin polymer layer includes a side functional group that binds, e.g., through non-covalent bonding such as pi-pi bonding, to the surface of the current collector 101 or the attachment layer 102. In some such embodiments, the thin polymer layer can form a stable coating on at least a portion of the elements 201. In some embodiments, this arrangement provides superior mechanical stability of the electrode 10, as discussed in more detail below.

[0069] In some embodiments, the polymeric material is miscible in a solvent of the type described in the examples above. For example, in some embodiments, the polymeric material is miscible in a solvent that includes an alcohol such as methanol, ethanol, or 2-propanol (isopropyl alcohol, sometimes referred to as IPA), or a combination thereof. In some embodiments, the solvent can include one or more additives for further improving the solvent properties, e.g., a low-boiling point additive such as acetonitrile (ACN), deionized water, and tetrahydrofuran.

[0070] Suitable examples of materials that can be used to form the polymer layer include water-soluble polymers such as polyvinylpyrrolidone. Additional example materials are provided below.

[0071] In some embodiments, the polymeric material has a low molecular mass, e.g., less than or equal to 1,000,000 g / mol, 500,000 g / mol, 100,000 g / mol, 50,000 g / mol, 10,000 g / mol, 5,000 g / mol, 2,500 g / mol, or lower.

[0072] Note that the thin polymer layer described above is distinct in nature from the bulk polymer binder used in conventional electrodes. Rather than filling a large portion of the volume of the active layer 100, the thin polymer layer resides on the surface of the high-aspect-ratio carbon elements, leaving a vast majority of the interstitial space within the network 200 available for accommodating active material particles 300.

[0073] For example, in some embodiments, the thin polymer layer has a maximum thickness in a direction normal to the outer surface of the network that is less than or equal to 1, 0.5, 0.25, or less times the size of the carbon elements 201 along their secondary dimension. For example, in some embodiments, the thin polymer layer can be only a few molecules thick (e.g., less than or equal to 100, 50, 10, 5, 4, 3, 2, or even 1 molecule thick). Thus, in some embodiments, less than 10%, 5%, 1%, 0.1%, 0.01%, 0.001%, or less of the volume of the active layer 100 is filled with the thin polymer layer.

[0074] In yet another exemplary embodiment, the surface treatment 202 may be formed of a carbonaceous material layer produced by the pyrolysis of a polymeric material disposed on high aspect ratio carbon elements 201. This carbonaceous material layer (e.g., graphite or amorphous carbon) may adhere (e.g., via covalent bonds) to the active material particles 300 or otherwise promote adhesion to the active material particles. Examples of suitable pyrolysis techniques are described in U.S. Patent Application Serial No. 63 / 028982, filed May 22, 2020. A suitable polymeric material for use in this technique is polyacrylonitrile (PAN).

[0075] In various embodiments, the active material particles 300 may include any active material suitable for use in energy storage devices, including metal oxides such as lithium metal oxides. For example, the active material particles 300 may include lithium cobalt oxide (LCO, sometimes called "lithium cobaltate" or "lithium cobaltite"), a chemical compound with one possible variant of the chemical formula LiCoO2; lithium nickel manganese cobalt oxide (NMC, having the variant LiNiMnCo); lithium manganese oxide (LMO, having LiMn2O4, Li2MnO3, and other variants); lithium nickel cobalt aluminum oxide (LiNiCoAlO2 and its variants such as NCA); and lithium titanate oxide (LTO, one of which has the variant Li4Ti5O). 12 ); lithium iron phosphate oxide (LFP, one variant of which is LiFePO4), lithium nickel cobalt aluminum oxide (and its variants such as NCA), and other similar materials. Other variants of the foregoing may be included.

[0076] In some embodiments where NMC is used as the active material, nickel-rich NMC can be used. For example, in some embodiments, a variant of NMC may be LiNi. x Mn y Co 1-x-y , where x is equal to or greater than about 0.7, 0.75, 0.80, 0.85 or greater. In some embodiments, so-called NMC811 may be used, where in the foregoing formula, x is about 0.8 and y is about 0.1.

[0077] In some embodiments, the active material includes other forms of lithium nickel manganese cobalt oxide (LiNi). x Mn y Co2O2). For example, common variants include, but are not limited to: NMC111(LiNi). 0.33 Mn 0.33 Co 0.33 O2), NMC 532(LiNi) 0.5 Mn 0.3Co 0.2 O2), NMC 622 (LiNi 0.6 Mn 0.2 Co 0.2 O2); and other variants can be used.

[0078] In some embodiments, for example, where the electrode is used as an anode, the active material can include graphite, hard carbon, activated carbon, nanocarbon, silicon, silicon oxide, carbon-encapsulated silicon nanoparticles. In some such embodiments, the active layer 100 can be intercalated with lithium, for example, using prelithiation methods known in the art.

[0079] In some embodiments, the techniques described herein can allow the active layer 100 to be made of a majority of material in the active layer, for example, greater than 75%, 80%, 85%, 90%, 95%, 99%, 99.5%, 99.8% or more by weight, 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 can have such a foregoing substantial amount of active material and a large thickness (e.g., greater than 50 pm, 100 pm, 150 pm, 200 pm or more), while still exhibiting excellent mechanical properties (e.g., no delamination during operation in an energy storage device of the type described herein).

[0080] The active material particles 201 in the active layer 100 can be characterized by a median particle size in the range of, for example, 0.1 pm and 50 pm, or any sub-range thereof. The active material particles 201 in the active layer 100 can be characterized by a particle size distribution of a unimodal, bimodal, or multimodal particle size distribution. The active material particles 201 can have a specific surface area in the range of 0.1 square meters per gram (m 2 / g) and 100 square meters per gram (m 2 / g), or any sub-range thereof.

[0081] In some embodiments, the active layer 100 can have a mass loading of active material particles 300 of, for example, at least 20 mg / cm 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 more.

[0082] Referring to Figure 4FIG. 2, shows an electron micrograph of an exemplary active material layer of the type described herein. The tendrillar, high aspect ratio carbon elements 201 (formed from CNT bundles) are clearly shown as entangling the active material particles 300. Note that there is no bulk polymeric material occupying space within the layer.

[0083] Energy storage battery

[0084] Referring Figure 5 FIG. 2, shows an energy storage battery 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, 502 can be of the type described herein.

[0085] In some embodiments, the energy storage battery 500 can be a battery, such as a lithium ion battery. In some such embodiments, the electrolyte can be a lithium salt dissolved in a solvent, for example a lithium salt of the type described in Qi Li, Juner Chen, Lei Fan, Xueqian Kong, Yingying Lu, “Progress in electrolytes for rechargeable Li-based batteries and beyond,” Green Energy & Environment, Vol. 1, Issue 1, pp. 18-42, the entire contents of which are incorporated herein by reference.

[0086] In some such embodiments, the energy storage battery can have an operating voltage in the range of 1.0 V to 5.0 V, or any sub-range thereof, such as 2.3 V to 4.3 V.

[0087] In some such embodiments, the energy storage battery 500 can have an operating temperature range including -40 °C to 100 °C, or any sub-range thereof, such as -10 °C to 60 °C.

[0088] In some such embodiments, the energy storage battery 500 can have a gravimetric energy density of at least 100 Wh / kg, 200 Wh / kg, 300 Wh / kg, 400 Wh / kg, 500 Wh / kg, 1000 Wh / kg, or more.

[0089] In some such embodiments, the energy storage battery 500 can have a volumetric energy density of at least 200 Wh / L, 400 Wh / L, 600 Wh / L, 800 Wh / L, 1,000 Wh / L, 1,500 Wh / L, 2,000 Wh / L, or more.

[0090] In some such embodiments, the energy storage battery 500 can have a C-rate in the range of 0.1 to 50.

[0091] In some such embodiments, the energy storage battery 500 can have a cycle life of at least 1,000, 1500, 2,000, 2,500, 3,000, 3,500, 4,000, or more charge-discharge cycles.

[0092] In some embodiments, the energy storage battery 500 can be a lithium-ion capacitor of the type described in U.S. Patent Application Serial No. 63 / 021492, filed May 8, 2020, the entire contents of which are hereby incorporated by reference.

[0093] In some such embodiments, the energy storage battery 500 can have an operating temperature range including -60°C to 100°C, or any sub-range thereof, such as -40°C to 85°C.

[0094] In some such embodiments, the energy storage battery 500 can have a gravimetric energy density of at least 10 Wh / kg, 15 Wh / kg, 20 Wh / kg, 30 Wh / kg, 40 Wh / kg, 50 Wh / kg, or more.

[0095] In some such embodiments, the energy storage battery 500 can have a volumetric energy density of at least 20 Wh / L, 30 Wh / L, 40 Wh / L, 50 Wh / L, 60 Wh / L, 70 Wh / L, 80 Wh / L, or more.

[0096] In some such embodiments, the energy storage battery 500 can have a gravimetric power density of at least 5 kW / kg, 7.5 W / kg, 10 kW / kg, 12.5 kW / kg, 14 kW / kg, 15 kW / kg, or more.

[0097] In some such embodiments, the energy storage battery 500 can have a volumetric power density of at least 10 kW / L, 15 kW / L, 20 kW / L, 22.5 kW / L, 25 kW / L, 28 kW / L, 30 kW / L, or more.

[0098] In some such embodiments, the energy storage battery 500 can have a C-rate in the range of 0.1 to 50.

[0099] In some such embodiments, the energy storage battery 500 can have a cycle life of at least 100,000, 500,000, 1,000,000, or more charge-discharge cycles.

[0100] Manufacturing method

[0101] Any suitable manufacturing process can be used to manufacture the electrode 10 featuring the active layer 100 described herein. As will be appreciated by those skilled in the art, in some embodiments, the electrode 10 can be manufactured using a wet coating technique of the type described in International Patent Publication No. WO / 2018 / 102652, published June 7, 2018, further in view of the teachings described herein.

[0102] Referring to Figure 6 In some embodiments, the active layer 100 of the electrode 10 can be formed using the method 1000. In step 1001, the high aspect ratio carbon elements 201 and a surface treatment material (e.g., a surfactant or polymeric material described herein) are combined with a solvent (of the type described herein) to form an initial slurry.

[0103] In step 1002, the initial slurry is treated to ensure good dispersion of the solid material in the slurry. In some embodiments, the treatment includes introducing mechanical energy into the mixture of the solvent and the solid material (e.g., using an ultrasonic generator, which can also sometimes be referred to as an “ultrasonic disrupter”) or other suitable mixing equipment (e.g., a high shear mixer). In some embodiments, the mechanical energy introduced into the mixture is at least 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 the mixture can be in a range of 0.4 kWh / kg to 1.0 kWh / kg, or any sub-range thereof, such as 0.4 kWh / kg to 0.6 kWh / kg.

[0104] In some embodiments, an ultrasonic bath mixer can be used. In other embodiments, a probe sonicator can be used. Probe sonication can be significantly more powerful and effective than ultrasonic baths used for nanoparticle applications. The high shear forces generated by ultrasonic cavitation have the ability to break up particle agglomerates and result in smaller and more uniform particle sizes. Among other things, the ultrasonic treatment can result in a stable and uniform suspension of the solids in the slurry. Generally, this results in dispersion, de-agglomeration, and other breakdown of the solids. An example of a probe sonication equipment includes the Q Series probe sonicators available from QSonica LLC, Newington, CT. Another example includes the Branson Digital SFX-450 ultrasonic generator commercially available from Thomas Scientific, Swedesboro, NJ.

[0105] However, in some embodiments, the local properties 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 overcome by using a setup with a continuous flow cell and proper mixing. That is, with such a setup, mixing of the slurry will achieve a reasonably uniform dispersion.

[0106] In some embodiments, the initial slurry, once processed, will have a viscosity in the range of 5,000 cps to 25,000 cps, or any sub-range thereof, such as 6,000 cps to 19,000 cps.

[0107] In step 1003, the surface treatment 202 can be formed, in whole or in part, on the high aspect ratio carbon elements 201 in the initial slurry. In some embodiments, at this stage, the surface treatment 202 can self-assemble as described above with reference to Figure 2 and Figure 3 The resulting surface treatment 201 can include functional groups or other features that can facilitate adhesion between the high aspect ratio carbon elements 201 and the active material particles 300 as described in the additional steps below.

[0108] In step 1004, active material particles 300 can be combined with the initial slurry to form a final slurry that includes the active material particles 300 and the high aspect ratio carbon elements 201 on which the surface treatment 202 is formed.

[0109] In some embodiments, the active material 300 can be added directly to the initial slurry. In other embodiments, the active material 300 can first be dispersed in a solvent (e.g., using techniques described above with respect to the initial solvent) to form an active material slurry. This active material slurry can then be combined with the initial slurry to form the final slurry.

[0110] 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 can be used. In some embodiments, this processing can use techniques described above with reference to step 1002. In some embodiments, a planetary mixer can be used, such as a multi-shaft (e.g., tri-shaft or multi-shaft) planetary mixer. In some such embodiments, the planetary mixer can have multiple blades, such as two or more mixing blades and one or more (e.g., two, three, or more) dispersing blades, such as disc dispersing blades.

[0111] In some embodiments, during this step 1005, the matrix 200 that entangles the active material 300 can self-assemble, in whole or in part, as described above with reference to Figure 2 and Figure 3The surface treatment 202 and the active material 300 interact in a self-assembly process. The details of the self-assembly process are described in greater detail below. In some embodiments, the interaction between the surface treatment 202 and the active material 300 facilitates the self-assembly process.

[0112] In some embodiments, the final slurry, once processed, will have a viscosity in the range of 1,000 cps to 10,000 cps, or any sub-range thereof, such as 2,500 cps to 6,000 cps.

[0113] In step 1006, the active layer 100 is formed from the final slurry. In some embodiments, the final slurry can be directly wet cast onto the current collector conductive layer 101 (or optional attachment layer 102) and dried. For example, the casting can be by application of at least one of heat and vacuum until substantially all of the solvent and any other liquid is removed, thereby forming the active layer 100. In some such embodiments, it can be desirable to protect portions of the underlying layers. For example, it can be desirable to protect the underside of the conductive layer 101 where the electrode 10 is intended for double-sided operation. The protection can include, for example, protection from the solvent by masking certain areas, or providing a drain to direct the solvent away.

[0114] In other embodiments, the final slurry can be at least partially dried elsewhere and then transferred to the attachment layer 102 or conductive layer 101 using any suitable technique (e.g., roll-to-roll layer application) to form the active layer 100. In some embodiments, the wet combined slurry can be placed onto an intermediate material having a suitable surface and dried to form the layer (i.e., the active layer 100). Although any material having a suitable surface can be used as the intermediate material, exemplary intermediate materials include PTFE due to its properties that facilitate subsequent removal from the surface. In some embodiments, the designated layer is formed in a press to provide a layer exhibiting the desired thickness, area, and density.

[0115] In some embodiments, the final slurry can be formed into a sheet and applied to the attachment layer 102 or conductive layer 101 as appropriate. For example, in some embodiments, the final slurry can be applied through a slot die to control the thickness of the layer applied. In other embodiments, the slurry can be applied and then leveled to the desired thickness, for example, using a doctor blade. A variety of other techniques can be used to apply the slurry. For example, the coating techniques can 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); in-mold doctor blade coating; offset gravure coating; kiss roll coating; reverse kiss roll coating with small diameter gravure roll; rod coating; three-roll coating (top feed); three-roll coating (jet die); reverse roll coating; and others.

[0116] The viscosity of the final slurry can vary depending on the application technique. For example, for comma coating, the viscosity can range between about 1,000 cps to about 200,000 cps. Lip die coating provides for coating with a slurry exhibiting a viscosity of about 500 cps to about 300,000 cps. Reverse kiss coating provides for coating with a slurry exhibiting a viscosity of about 5 cps to 1,000 cps. In some applications, the respective layer can be formed by multiple passes.

[0117] In some embodiments, the active layer 100 formed from the final slurry can be compressed (e.g., using a calendering device) before or after being applied to the electrode 10. In some embodiments, the slurry can be partially or fully 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 can be compressed to a final thickness (e.g., in a direction normal to the current collector layer 101) that is less than 90%, 80%, 70%, 50%, 40%, 30%, 20%, 10%, or less of its pre-compression thickness.

[0118] In various embodiments, when a partially dried layer is formed during the coating or compression process, the layer can subsequently be fully dried (e.g., by applying heat, vacuum, or a combination thereof). In some embodiments, substantially all of the solvent is removed from the active layer 100.

[0119] In some embodiments, the solvent used to form the slurry is recovered and recycled into the slurry manufacturing process.

[0120] In some embodiments, the active layer can be compressed, for example, to break apart a portion of the high aspect ratio carbon elements or other carbonaceous material that make up the layer, thereby increasing the surface area of the respective layer. In some embodiments, this compression process can increase one or more of the adhesion between layers, the rate of ion transport within the layer, and the surface area of the layer. In various embodiments, the compression can be applied before or after the respective layer is applied to or formed on the electrode 10.

[0121] In some embodiments in which calendering is used to compress the active layer 100, the calendering device can be set to have a nip spacing equal to or less than 90%, 80%, 70%, 50%, 40%, 30%, 20%, 10% or less of the pre-compression thickness of the layer (e.g., set to about 33% of the pre-compression thickness of the layer). The calendering rollers can be configured to provide a suitable pressure, e.g., greater than 1 ton / cm of roller length, greater than 1.5 tons / cm of roller length, greater than 2.0 tons / cm of roller length, greater than 2.5 tons / cm of roller length, or greater. In some embodiments, the active layer after compression will have a density in the range of 1 g / cc to 10 g / cc, or any sub-range thereof, e.g., 2.5 g / cc to 4.0 g / cc. In some embodiments, the calendering process can be carried out at a temperature in the range of 20 °C to 140 °C, or any sub-range thereof. In some embodiments, the active layer can be pre-heated prior to calendering, e.g., at a temperature in the range of 20 °C to 100 °C, or any sub-range thereof.

[0122] Once the electrode 10 is assembled, the electrode 100 can be used to assemble an energy storage device 10. Assembly of the energy storage device 10 can follow conventional steps for assembling electrodes with separators and placing them within a housing such as a can or pouch, and can also include additional steps for electrolyte addition and housing sealing.

[0123] In various embodiments, the process 1000 can include any of the following features, alone or in any suitable combination.

[0124] In some embodiments, the initial slurry has a solids content in the range of 0.1%-20.0% by weight (or any sub-range thereof). In some embodiments, the final slurry has a solids content in the range of 10.0%-80% by weight (or any sub-range thereof).

[0125] In various embodiments, the solvent used can be any of those described herein with respect to formation of the surface treatment 202. In some embodiments, the surfactant material used to form the surface treatment 202 is soluble in a solvent that exhibits advantageous properties. For example, in some embodiments, the solvent can include water or an alcohol, such as methanol, ethanol, or 2-propanol (isopropyl alcohol, sometimes referred to as IPA), or combinations thereof. In some embodiments, the solvent can include one or more additives for further improving solvent properties, e.g., a low-boiling point additive such as acetonitrile (ACN), deionized water, and tetrahydrofuran.

[0126] In some embodiments, if a low boiling point solvent is used, a thermal drying process performed at a relatively low temperature can be used to quickly remove the solvent. As will be appreciated by those skilled in the art, this can improve the speed and / or cost of manufacture of the electrode 10. For example, in some embodiments, the solvent can have a boiling point that is less than 250°C, 225°C, 202°C, 200°C, 185°C, 180°C, 175°C, 150°C, 125°C, or less, such as less than or equal to 100°C.

[0127] In some embodiments, the solvent can exhibit other advantageous properties. In some embodiments, the solvent can have a low viscosity, such as a viscosity that is less than or equal to 3.0 centipoise, 2.5 centipoise, 2.0 centipoise, 1.5 centipoise, or less at 20°C. In some embodiments, the solvent can have a low surface tension, such as a surface tension that is less than or equal to 40 mN / m, 35 mN / m, 30 mN / m, 25 mN / m, or less at 20°C. In some embodiments, the solvent can have low toxicity, for example, comparable to that of an alcohol such as isopropanol.

[0128] In some embodiments, during formation of the active layer, the material forming the surface treatment can be dissolved in a solvent that is substantially free of a pyrrolidone compound. In some embodiments, the solvent is substantially free of n-methyl-2-pyrrolidone.

[0129] In some embodiments, the surface treatment 201 is formed from a material that includes a surfactant of the type described herein.

[0130] 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 aggregated carbon elements to cause the elements to slide apart from one another along a direction transverse to the short axis of the elements. In some embodiments, techniques for forming such dispersions can be adapted from those disclosed in International Patent Publication No. WO / 2018 / 102652, published June 7, 2018, in view of the teachings described herein.

[0131] In some embodiments, the high aspect ratio carbon elements 201 can be functionalized prior to forming a slurry for forming the electrode 10. For example, in one aspect, a method is disclosed that includes: dispersing high aspect ratio carbon elements 201 and a surface treatment material in an aqueous solvent to form an initial slurry, wherein the dispersing step results in formation of a surface treatment on the high aspect ratio carbon; drying the initial slurry to remove substantially all moisture, resulting in a dried powder of high aspect ratio carbon having a surface treatment thereon. In some embodiments, the dried powder can be combined with a slurry of, for example, a solvent and an active material, to form a final solvent of the type described above with reference to the method 1000.

[0132] In some embodiments, drying the initial slurry includes freeze-drying (lyophilizing) 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 acid. In some embodiments, the initial slurry consists essentially of the high aspect ratio carbon elements, the surface treatment material, and water.

[0133] Some embodiments further include dispersing the dry powder of high aspect ratio carbon with a surface treatment in a solvent and adding an active material to form a second slurry; coating the second slurry onto a substrate; and drying the second slurry to form an electrode active layer. In some embodiments, the foregoing steps can be performed using techniques disclosed in International Patent Publication No. WO / 2018 / 102652, published June 7, 2018, in view of the teachings described herein.

[0134] In some embodiments, the final slurry can include a polymeric additive, such as polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), polyacrylonitrile (PAN), polyisoprene (PIpr), polyaniline (PANi), polyethylene (PE), polyimide (PI), polystyrene (PS), polyurethane (PU), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP). In some embodiments, the active layer can be treated by applying heat to pyrolyze the additive, such that the surface treatment 202 can form a layer of carbonaceous material resulting from pyrolysis of the polymeric additive. This layer of carbonaceous material (e.g., graphite or amorphous carbon) can adhere (e.g., through covalent bonds) to the active material particles 300 or otherwise facilitate adhesion with the active material particles. The heat treatment can be performed by any suitable means, such as by applying a laser beam. Examples of suitable pyrolysis techniques are described in U.S. Patent Application Serial No. 63 / 028,982, filed May 22, 2020.

[0135] Surfactant

[0136] The above-described techniques include forming a surface treatment 202 on the high aspect ratio carbon nanotubes 201 using a surfactant in order to facilitate adhesion with the active material particles 300. While several suitably advantageous surfactants have been described, it will be appreciated that other surfactant materials can be used, including the following materials.

[0137] Surfactants are molecules or groups of molecules with surface activity, including wetting agents, dispersants, emulsifiers, detergents, and foaming agents. A variety of surfactants can be used to make the surface treatments described herein. Typically, the surfactants used contain a lipophilic, nonpolar hydrocarbon group and a polar functional hydrophilic group. The polar functional group can be a carboxylate, ester, amine, amide, imide, hydroxyl, ether, nitrile, phosphate, sulfate, or sulfonate. Surfactants can be used individually or in combination. Thus, combinations of surfactants can include anionic, cationic, nonionic, zwitterionic, amphoteric, and ampholytic surfactants, as long as there is a net positive or negative charge in the head region of the population of surfactant molecules. In some cases, a single negatively or positively charged surfactant is used in the preparation of the electrode compositions.

[0138] The surfactants used to make the electrode compositions can be anionic, including but not limited to sulfonates such as alkyl sulfonates, alkylbenzene sulfonates, alpha-olefin sulfonates, paraffin sulfonates, and alkyl ester sulfonates; sulfates such as alkyl sulfates, alkylalkoxy sulfates, and alkylalkylated sulfates; phosphates such as monoalkyl phosphates and dialkyl phosphates; phosphonates; carboxylates such as fatty acids, alkylalkoxy carboxylates, sarcosinates, isethionates, and taurinates. Specific examples of carboxylates are sodium oleate, sodium cocoyl isethionate, sodium methyl oleyl taurinate, sodium laureth carboxylate, sodium tridecyl 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 cocoyl sulfate, and sodium lauryl mono glyceride sulfate.

[0139] Suitable sulfonate-type surfactants include, but are not limited to, alkyl sulfonates, aryl sulfonates, monoalkyl and dialkyl sulfosuccinates, and monoalkyl and dialkyl sulfosuccinamates. Each alkyl group independently contains from about 2 to 20 carbons, and can also be ethoxylated with up to about 8, preferably up to about 6, average, e.g., 2, 3, or 4, units of ethylene oxide per alkyl group. Illustrative examples of alkyl and aryl sulfonates are sodium tridecyl benzene sulfonate (STBS) and sodium dodecyl benzene sulfonate (SDBS).

[0140] Illustrative examples of sulfosuccinates include, but are not limited to, dimethicone copolyol sulfosuccinate, dipentysulfosuccinate, didecyl ester sulfosuccinate, dicyclohexyl sulfosuccinate, diheptyl sulfosuccinate, dihexyl sulfosuccinate, diisobutyl sulfosuccinate, dioctyl sulfosuccinate, C12-15 parent sulfosuccinate, cetyl alcohol sulfosuccinate, coco polyglucose sulfosuccinate, cocoacyl glutpatum-10 sulfosuccinate, deceth-5 sulfosuccinate, deceth-6 sulfosuccinate, dithiodiglycol sulfosuccinylundecanoate, hydrogenated cottonseed glycerides sulfosuccinate, isodecyl sulfosuccinate, isostearyl alcohol sulfosuccinate, lanolin alcohol polyether-5 sulfosuccinate, lauryl ether sulfosuccinate, lauryl ether-12 sulfosuccinate, lauryl ether-6 sulfosuccinate, lauryl ether-9 sulfosuccinate, lauryl sulfosuccinate, myreth-10 sulfosuccinate, oleyl alcohol polyether-3 sulfosuccinate, oleyl alcohol polyether sulfosuccinate, PEG-10 lauryl alcohol citrate sulfosuccinate, sitosereth-14 sulfosuccinate, stearoyl sulfosuccinate, tallow, tridecyl sulfosuccinate, ditridecyl sulfosuccinate, diglycol ricinoleth sulfosuccinate, bis(l,3-bis-methylbutyl) sulfosuccinate, and silicone copolyol sulfosuccinate.

[0141] Illustrative examples of sulfosuccinamates include, but are not limited to, lauramidyl-MEA sulfosuccinamate, oleamidyl PEG-2 sulfosuccinamate, cocamidyl MIPA-sulfosuccinamate, cocamidyl PEG-3 sulfosuccinamate, isostearamidyl MEA-sulfosuccinamate, isostearamidyl MIPA-sulfosuccinamate, lauramidyl MEA-sulfosuccinamate, lauramidyl PEG-2 sulfosuccinamate, lauramidyl PEG-5 sulfosuccinamate, myristamidyl MEA-sulfosuccinamate, oleamidyl MEA-sulfosuccinamate, oleamidyl PIPA-sulfosuccinamate, oleamidyl PEG-2 sulfosuccinamate, palmitamidyl PEG-2 sulfosuccinamate, palmityolamidyl PEG-2 sulfosuccinamate, PEG-4 cocamidyl MIPA-sulfosuccinamate, ricinamidyl MEA-sulfosuccinamate, stearamidyl MEA-sulfosuccinamate, stearamidyl sulfosuccinamate, tallamidyl MEA-sulfosuccinamate, tallowamidyl MEA-sulfosuccinamate, undecylenamidyl MEA-sulfosuccinamate, undecylenamidyl PEG-2 sulfosuccinamate, wheat germamidyl MEA-sulfosuccinamate, and wheat germamidyl PEG-2 sulfosuccinamate.

[0142] Some examples of commercially available sulfonates are OT-S OT-MSO, TR70% (Cytec Inc., West Paterson, New Jersey), NaSul CA-HT3 (King Industries, Norwalk, Connecticut), and C500 (Crompton Co., West Hills, Ontario, Canada). OT-S is sodium dioctyl sulfosuccinate, a petroleum fraction. OT-MSO also contains sodium dioctyl sulfosuccinate. TR70% is sodium didecyl sulfosuccinate in a mixture of ethanol and water. NaSul CA-HT3 is a calcium nonylnaphthalene sulfonate / calcium carboxylate complex. C500 is an oil-soluble calcium sulfonate.

[0143] Alkyl or alkyl groups refer to saturated hydrocarbons 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, alicyclic, or carbocyclic groups) (e.g., cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, etc.), branched 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).

[0144] Alkyl groups can include unsubstituted alkyl groups and substituted alkyl groups. A substituted alkyl group is an alkyl group having a substituent that replaces one or more hydrogen atoms on one or more carbons of the hydrocarbon backbone. Such substituents may include alkenyl, alkynyl, halogen, hydroxyl, alkyl carbonyloxy, aryl carbonyloxy, alkoxy carbonyloxy, aryloxy, aryloxy carbonyloxy, carboxyl, alkyl carbonyl, aryl carbonyl, alkoxy carbonyl, amino carbonyl, alkyl amino carbonyl, dialkyl amino carbonyl, alkyl thioamino, alkoxy, phosphate, phosphono, phosphonite, cyano, amino (including alkylamino, dialkylamino, arylamino, diarylamino and alkylarylamino), acylamino (including alkyl carbonylamino, aryl carbonylamino, carbamoyl and urea), imino, mercapto, alkylthio, arylthio, thiocarboxylic acid ester, sulfate, alkyl sulfinyl, sulfonate, sulfonyl, sulfonamide, nitro, trifluoromethyl, cyano, azide, heterocyclic, alkyl acyl or aromatic (including heteroaromatic) groups.

[0145] In some embodiments, substituted alkyl groups can include heterocyclic groups. Heterocyclic groups include closed ring structures analogous to carbocyclic groups, in which one or more of the carbon atoms in the ring is an element other than carbon, such as nitrogen, sulfur, or oxygen. Heterocyclic groups can be saturated or unsaturated. Exemplary heterocyclic groups include aziridine, ethylene oxide (epoxide, oxirane), ethylene sulfide (episulfide), dioxirane, azetidine, oxetane, thietane, dioxetane, dithietane, dithietene, pyrrolidine, tetrahydropyrrole, pyrroline, oxolane, dihydrofuran, and furan.

[0146] For anionic surfactants, the counterion is typically sodium, but can alternatively be 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.

[0147] The surfactant used to make the materials of the present application can be cationic. Such cationic surfactants include, but are not limited to, pyridinium-containing compounds, as well as primary, secondary, tertiary, or quaternary organic amines. For cationic surfactants, the counterion can be, for example, chloride, bromide, methyl sulfate, ethanol sulfate, lactate, saccharinate, acetate, and phosphate. Examples of cationic amines include polyethoxylated oleyl / stearic amine, ethoxylated tallow amine, coconut alkyl amine, oleyl amine, and tallow alkyl amine, as well as mixtures thereof.

[0148] Examples of quaternary amines with a single long alkyl group are cetyltrimethylammonium bromide (CTAB), benzyldodecyldimethylammonium bromide (BddaBr), benzyldimethylcetyl ammonium chloride (BdhaCl), dodecyltrimethylammonium bromide, myristyltrimethylammonium bromide, stearyldimethylbenzylammonium chloride, oleyldimethylbenzylammonium chloride, dodecyltrimethylammonium methylsulfate (also known as cocoyl methyl sulfate hydrogen), cetyl-dimethylhydroxyethylammonium dihydrogen phosphate, basu palmitoyl amido propyl dimethyl benzyl ammonium chloride, cocotrimethylammonium chloride, dioctadecyl dimethylammonium chloride, maltamido propyl dimethyl benzyl ammonium chloride, octyldimethylstearylammonium methyl sulfate, isooctadecylamidopropyl dimethyl benzyl ammonium chloride, dihydroxypropyl PEG-5 linoleammonium chloride, PEG-2 octadecyldimethylammonium chloride, behenyltrimethylammonium chloride, dioctadecyl dimethylammonium chloride, tallowtrimethylammonium chloride, and behenamidopropylethyldimethylammonium ethyl sulfate.

[0149] Examples of quaternary amines having two long alkyl groups are didodecyldimethylammonium bromide (DDAB), distearyldimethylammonium chloride, dicetyl dimethylammonium chloride, stearyloctyl dimethyl methosulfate, dimyristyl ethyl hydroxyethyl methyl ammonium methyl sulfate, dipalmitoyl ethyl hydroxyethyl methyl ammonium methyl sulfate, dioleoyl ethyl hydroxyethyl methyl ammonium methyl sulfate, and hydroxypropyl bisiostearyl dimonium chloride.

[0150] Quaternary ammonium compounds of imidazoline derivatives include, for example, isotridecylbenzylimidazoline hydrochloride, cocobenzyl hydroxyethyl imidazoline hydrochloride, cocoyl hydroxyethyl imidazoline PG-hydrochloride phosphate, and octadecyl hydroxyethyl imidazoline hydrochloride. Other heterocyclic quaternary ammonium compounds can also be used, such as dodecylpyridinium chloride, ammonium hippurate (AH), and benzethonium chloride (BH).

[0151] Surfactants used to make the materials of the present application can be nonionic, including but not limited to polyalkylene oxide carboxylate, fatty acid ester, fatty alcohol, ethoxylated fatty alcohol, poloxamer, alkanolamide, alkoxylated alkanolamide, polyethylene glycol monoalkyl ether, and alkylpolysaccharide. Polyalkylene oxide carboxylate has one or two carboxylate moieties each having about 8 to 20 carbons and a polyoxyalkylene moiety comprising about 5 to 200 alkylene oxide units. Ethoxylated fatty alcohol comprises an ethylene oxide moiety containing about 5 to 150 ethylene oxide units and a fatty alcohol moiety having about 6 to about 30 carbons. The fatty alcohol moiety can be cyclic, straight-chain or branched, saturated or unsaturated. Some examples of ethoxylated fatty alcohols include glycol ethers of oleyl alcohol, stearyl alcohol, lauryl alcohol, and isacetyl alcohol. Poloxamers are ethylene oxide and propylene oxide block copolymers having about 15 to about 100 moles of ethylene oxide. Alkylpolysaccharide (“APS”) surfactants (e.g., alkyl polyglycosides) comprise a hydrophobic group with about 6 to about 30 carbons and a polysaccharide (e.g., polyglycoside) as a hydrophilic group. An example of a commercial nonionic surfactant is FOA-5 (Octel Starreon LLC. Company, Littleton, Colorado).

[0152] Specific examples of suitable nonionic surfactants include alkanolamides such as cocamido diethanolamide (“DEA”), cocamido monoethanolamide (“MEA”), cocamido mono isopropanolamide (“MIPA”), PEG-5 cocamide MEA, lauramide DEA, and lauramide MEA; alkylamine oxides such as laurylamine oxide, cocamine oxide, cocamidopropylamine oxide, and laurylaminopropylamine oxide; sorbitan laurate, sorbitan distearate, fatty acid or fatty acid ester such as lauric acid, isostearic acid, and PEG-150 distearate; fatty alcohol or ethoxylated fatty alcohol such as lauryl alcohol; alkylpolysaccharide such as alkyl glucoside, lauryl glucoside, and cocoyl glucoside.

[0153] The surfactant used to make the material of the present application can be zwitterionic, having a formal positive charge and a negative charge on the same molecule. The positive charge group can be quaternary ammonium, phosphonium, or sulfonium, while the negative charge group can be carboxylate, sulfonate, sulfate, phosphate, or phosphonate. Similar to other classes of surfactants, the hydrophobic portion can comprise one or more long, straight, cyclic, or branched aliphatic chains of about 8 to 18 carbon atoms. Specific examples of zwitterionic surfactants include alkyl betaines, such as coco dimethyl carboxymethyl betaine, lauryl dimethyl carboxymethyl betaine, lauryl dimethyl alpha-carboxyethyl betaine, cetyl dimethyl carboxymethyl betaine, lauryl bis-(2-hydroxypropyl) carboxymethyl betaine, stearyl bis-(2-hydroxypropyl) carboxymethyl betaine, oleyl dimethyl gamma-carboxypropyl betaine, and lauryl bis-(2-hydroxypropyl) alpha-carboxyethyl betaine, amidopropyl betaine; and alkyl sulfobetaines, such as coco dimethyl sulfopropyl betaine, stearyl dimethyl sulfopropyl betaine, lauryl dimethyl sulfoethyl betaine, lauryl bis-(2-hydroxyethyl) sulfopropyl betaine, and alkyl amidopropyl hydroxysultaine.

[0154] The surfactant used to make the material of the present application can be amphoteric. Examples of suitable amphoteric surfactants include ammonium or substituted ammonium salts of alkyl amphocarboxyglycinates and alkyl amphocarboxypropionates, alkyl amphodipropionates, alkyl amphodiacetates, alkyl amphoglycinates, and alkyl amphopropionates, as well as alkyl iminodipropionates, alkyl iminodiacetates, and alkyl amphopropyl sulfonates. Specific examples are cocoamphoacetate, cocoamphopropionate, cocoamphodiacetate, laurylamphoacetate, laurylamphodiacetate, laurylamphodipropionate, lauryl amphodiacetate, cocoamphopropyl sulfonate, hexadecyl amphodipropionate, hexadecyl amphoacetate, hexadecyl amphodipropionate, and cocoamphoacetate.

[0155] The surfactant used to make the material of the present application can also be a polymer, such as N-substituted polyisobutenyl succinimides and succinates, alkyl methacrylate vinyl pyrrolidone copolymer, alkyl methacrylate-dimethylaminoethyl methacrylate copolymer, alkyl methacrylate polyethylene glycol methacrylate copolymer, polyoxystearamide, and polyethyleneimine.

[0156] The surfactant used to make the material of the present application can also 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).

[0157] The surfactant used to make the material of the present invention can be an oil-based dispersant, which includes alkyl succinimides, succinates, high molecular weight amines, and Mannich base and phosphoric acid derivatives. Some specific examples are polyisobutenyl succinimide-polyethylene polyamine, polyisobutenyl succinate, polyisobutenyl hydroxybenzyl-polyethylene polyamine, and bis-hydroxypropyl phosphate.

[0158] The surfactant used to make the material of the present invention can be a combination of two or more surfactants of the same or different types selected from 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 ampholytic surfactants, and a mixture of four ampholytic surfactants.

[0159] Thin polymeric layer material

[0160] The above techniques include the use of polymers to form a surface treatment 201 on the high aspect ratio carbon nanotubes in order to promote adhesion to the active material particles 300. While several advantageously suitable polymers have been described, it will be appreciated that other polymeric materials can be used, including the following materials.

[0161] The polymer used to make the inventive material can be a polymeric material, such as a water processable polymeric material. In various embodiments, any one of the following polymers (and combinations thereof) can be used: polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), polyacrylonitrile (PAN), polyisoprene (PIpr), polyaniline (PANi), polyethylene (PE), polyimide (PI), polystyrene (PS), polyurethane (PU), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP). In some embodiments, another exemplary polymeric material is a fluorinated acrylic hybrid latex (TRD202A) and is provided by JSR Corporation.

[0162] Example

[0163] The following non-limiting examples further describe the application of the teachings of the present disclosure. In the examples below, the term “adhesive-free” or “without adhesive” electrodes refers to the type of electrodes described in detail above, characterized by a 3D matrix or scaffold of high aspect ratio carbon, with a surface treatment thereon that promotes adhesion of the active material to the scaffold without the need for a bulk polymer adhesive, such as PVDF.

[0164] As used hereinafter, 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 would discharge the entire battery in 1 hour. For a battery with a capacity of 100 Amp-hrs, this equates to a discharge current of 100 Amps.

[0165] Example 1 - Electric vehicle battery

[0166] The following battery is suitable for use in electric vehicles (“EV”). The battery incorporates the type of cathode and anode technology described herein for use in, for example, EV applications. The primary benefit advantages include lower manufacturing costs, higher energy density, superior power density, and wider temperature range operation. These benefits stem from the method of making the battery electrodes described herein, which eliminates the use of PVDF polymer adhesives and toxic solvents such as N-methyl-2-pyrrolidone (NMP). As a result, the end user has significant performance advantages in terms of range, charging speed, and acceleration, with a manufacturing process that is less costly, less capital intensive, and safer for the battery producer.

[0167] The teachings herein provide a technology platform for manufacturing electrodes for energy storage that can exhibit the following advantages: reduction in manufacturing cost and reduction in $ / kWh of the resulting LIB, increase in energy density obtained by combining a cathode with thick coating and a high capacity anode featuring high performance active materials such as Si or SiOx, fast charging. The teachings herein provide an scalable technology to improve power density in energy storage by removing conventional polymer binders from the active material coating.

[0168] Conventional electrodes for LiB are manufactured by mixing active materials, conductive additives, and polymer binders in a slurry. Conventional cathodes are manufactured using NMP based slurries and PVDF polymer binders. These binders have very high molecular weight and promote adhesion of active material particles and adherence to the current collector foil through two main mechanisms: 1) entanglement promoted by long polymer chains, and 2) hydrogen bonding between polymer, active material, and current collector. However, the polymer binder based approach has significant drawbacks in performance: power density, energy density, and manufacturing cost.

[0169] The teachings herein provide electrodes without PVDF binders in the cathode or other conventional binders in the anode. Instead, as described above, the 3D carbon scaffold or matrix holds the active material particles together to form a cohesive layer that is also firmly attached to the metal current collector. Such active material structures are created during slurry preparation and subsequently during roll-to-roll (“R2R”) coating and drying processes. One of the main advantages of this technology is its scalability and “drop-in” nature as it is compatible with conventional electrode manufacturing processes.

[0170] The 3D carbon matrix is formed during slurry preparation using the technology described herein: high aspect ratio carbon materials are suitably dispersed and chemically functionalized using, for example, a two-step slurry preparation process such as the type described above with reference to Figure 6 Chemical functionalization is designed to form organized self-assembly structures with the surface of active material particles, for example NMC particles for use in the cathode or silicon (“Si”) or silicon oxide (“SiOx”) particles in the case of the anode. The slurries so formed can be based on alcohol solvents for the cathode and water for the anode, and such solvents are very easy to evaporate and handle during the manufacturing process. Electrostatic interactions promote self-organization structures in the slurry and, after the drying process, the binding between the carbon matrix with active material particles so formed and the surface of the current collector is promoted through surface treatments (e.g., functional groups on the matrix) as well as strong entanglement of the active material in the carbon matrix.

[0171] As will be appreciated by those skilled in the art, the mechanical properties of the electrode can be easily changed by tuning the surface functionalization with the wrapping effect according to the application and mass loading requirements.

[0172] After coating and drying, the electrodes undergo a calendering step to control the density and porosity of the active material. In NMC cathode electrodes, a density of 3.5 g / cc or higher and a porosity of 20% or higher can be achieved. The porosity can be optimized according to the mass loading and LIB battery requirements. As for SiOx / Si anodes, the porosity is specially controlled to accommodate the swelling of the active material during the lithiation process.

[0173] In some typical applications, the teachings herein can provide up to 20% reduction in terms of $ / kWh. By using friendly solvents that evaporate easily, the electrode throughput is higher and, more importantly, the energy consumption from long dryers is significantly reduced. The conventional NMP recovery system is also greatly simplified when using alcohol or other solvent mixtures.

[0174] The teachings herein provide a 3D matrix that significantly increases the electrode conductivity by 10x to 100x compared to electrodes using conventional binders such as PVDF, which enables fast charging at the battery level. With this technology, thick electrode coatings in cathodes up to 150um per side (or more) of the current collector are possible. The solvents used in the slurry combined with the robust 3D carbon matrix are designed to achieve thick wet coatings without cracking during the drying step. Thick cathodes with high capacity anodes enable a significant boost in energy density up to 400 Wh / kg or higher.

[0175] Fast charging is achieved by combining high capacity anodes that are lithiated through the alloying process (Si / SiOx) and by reducing the total impedance of the battery when combining the anode and cathode as described herein. The teachings herein provide fast charging by having high conductive electrodes, and in particular high conductive cathode electrodes.

[0176] One exemplary embodiment includes a Li-ion battery energy storage device in the form of a pouch cell that combines a rich Ni NMC active material in the cathode and a SiOx and graphite mixture active material in the anode, where both the anode and cathode are made using the 3D carbon matrix process described herein.

[0177] Figure 7A schematic of the electrode arrangement of the soft pack battery device is shown in FIG. 1. As shown, a double-sided cathode using a polymer binder-free cathode layer on opposite sides of an aluminum foil current collector is disposed between two single-sided anodes, each having a polymer binder-free anode layer disposed on a copper foil current collector. The electrodes are separated by a permeable separator material (not shown) wetted with an electrolyte (not shown). This arrangement can be housed in a soft pack battery of the type well known in the art.

[0178] These devices can feature high mass loaded Ni-rich NMC cathode electrodes and methods of making them: mass loading = 20-30 mg / cm 2 , specific capacity > 210 mAh / g. SiOx / graphite anode (SiOx content ~ 20 wt.%) based electrodes and their material synthesis and manufacturing methods: mass loading 8-14 mg / cm 2 , reversible specific capacity > 550 mAh / g. Specifically, long life performance of SiOx / graphite anode based Li-ion based electrolytes: Ni-rich NMC cathode / SiOx+graphite / carbon+Li-ion based battery soft pack: capacity > 5 Ah, specific energy > 300 Wh / kg, energy density > 800 Wh / L, cycle life > 500 cycles at 1C rate charge-discharge, and ultra-high power fast charge-discharge C-rate (up to 5C rate) capability from -30 to 60 °C. Figure 8 A summary of the performance parameters of this type of soft pack battery is summarized in FIG. 2.

[0179] Example 2 - Comparative performance NMC811 lithium ion battery

[0180] As detailed above, the teachings herein provide electrodes configured with advanced 3D high aspect ratio carbon binding structures that eliminate the need for polymer binders, providing higher power, energy density (e.g., through thicker electrodes and higher active material mass loading), and performance in extreme environments compared to traditional battery electrode designs. High performance Li-ion battery energy storage devices are designed and manufactured with optimized capacity ratio designs of polymer binder-free cathode / anode electrodes, anode electrode pre-lithiation, and wide operating temperature electrolytes (e.g., -30 to 60 °C), and optimized testing formation processes.

[0181] As described herein, electrodes are manufactured by complete removal of high molecular weight polymers such as PVDF and toxic NMP solvent from the active material layer. This greatly improves LiB performance while reducing the cost of manufacturing as well as capital expenditure associated with mixing, coating and drying, NMP solvent recovery and calendaring. In embodiments of the electrode, the 3D nanoscale carbon matrix acts as a mechanical scaffold for the electrode active material and mimics polymer chain entanglement. Chemical bonds also exist between the surface of the carbon, the active material and the current collector, thereby facilitating adhesion and cohesion. However, in contrast to polymers, the 3D nanoscale carbon matrix is very conductive, which enables very high power (high C rates) to be achieved. This scaffold structure is also more amenable to producing thick electrode active materials, which is a powerful route to increasing the energy density of LiB batteries.

[0182] In this example, binderless cathodes were produced in accordance with the teachings of the present disclosure featuring NMC811 as the active material and incorporated in Li-ion batteries (LIBs). The batteries featured conventional type graphite anodes known in the art. The batteries were constructed as described above with reference to Figure 9 The parameters summarized in Table 1 were used. As a comparison, another identical battery was produced using a PVDF binder-based cathode. The performance of the batteries was compared as described below, showing the clear advantage of the binderless cathode battery. Figure 7 As shown by the results summarized in Table 1, the binderless battery can achieve a specific energy of up to 320 Wh / kg based on a 20 Ah battery design and a cycle life of over 2,000 cycles at 2C rate charge / discharge for a graphite anode. In comparison, the conventional binder-based cathode battery can only achieve 100-250 Wh / kg in specific energy at the battery level.

[0183] Figure 10 The binderless cathode battery exhibits ultra-high power fast charge-discharge C rates up to 5C rate with >50% capacity retention.

[0184] A comparison of the charge-discharge curves at different C rates is shown for the binderless cathode battery (left) and the conventional binder-based cathode battery (right). The binderless cathode battery charge-discharge curve shows over 60% capacity retention for the combined charge-discharge at 5C rate. Thus, the discharge or charge alone would exhibit even higher capacity retention. Note that in the example, the initial experimental results show that a 10C charge rate can be achieved when a Si-based anode is combined with the NMC811 cathode used in this example, using a conventional graphite anode. Figure 10

[0185] Figure 11 ​​A comparison of the cycle life of the above batteries is shown. At 25 °C, the batteries were cycled repeatedly between voltages of 2.75 V and 4.2 V, and the discharge capacity was recorded. The binder-free cathode battery exhibited a lifetime of greater than 2,000 cycles with less than 20% loss in discharge capacity. In comparison, the binder-based cathode battery experienced more than 20% loss in discharge capacity after only about 1,000 cycles.

[0186] Example Example 3 - Soft Pack Half Cell Comparison

[0187] Binder-free cathode electrodes of the type described herein can advantageously enable high mass loading, for example, 45 mg / cm2of NMC811 active material per side 2 of the mass loading is possible. The present example sets forth experimental results showing the performance of a material high mass loading binder-free electrode compared to a control electrode featuring a PVDF binder and NMC811 active material.

[0188] For comparison, Figure 12 Half cells of the type shown in Example 3 were constructed using a cathode on one side (either binder-free or binder-based control) and lithium foil on a copper substrate as the counter electrode for the battery. The half cells were subjected to charge rate testing at various current densities, and the results are summarized below.

[0189] Figure 13 is a plot showing the potential (vs. Li / Li+potential) versus specific capacity of a binder-free cathode half cell (solid trace) and a reference binder-based cathode half cell (dashed trace) at different current densities. At all current densities (and thus at all C-rates), the binder-free cathode half cell shows better performance (as indicated by the relative rightward shift of the trace).

[0190] Figure 14 is a plot showing the potential (vs. Li / Li+potential) versus volumetric capacity of a binder-free cathode half cell (solid trace) and a reference binder-based cathode half cell (dashed trace) at different current densities. At all current densities (and thus at all C-rates), the binder-free cathode half cell shows better performance (as indicated by the relative rightward shift of the trace).

[0191] Figure 15 is a plot showing the volumetric capacity versus current density of a binder-free cathode half cell (upper trace) and a reference binder-based cathode half cell (lower trace). At all current densities (and thus at all C-rates), the binder-free cathode half cell shows better performance, with the relative performance gap widening at higher C-rates.

[0192] Figure 16 Nyquist plots generated from electrochemical impedance spectroscopy of several binderless cathode half-cells (square, circular, and triangular labeled traces) and a reference binder-based cathode half-cell are shown. The binderless cathode half-cells exhibit significantly superior performance to the reference cell.

[0193] As can be seen from the plots, the discharge capacity retention of the binderless NMC811 electrodes have much higher values when the current density is increased from 0.5 to 10 mA / cm 2 (1.2C rate) compared to the binder-based PVDF control NMC811 electrode, even though both electrodes have the same 45 mg / cm 2 of mass loading. Note that this C-rate testing at different current densities is presented as a relative comparison between conventional binder-based PVDF cathodes and binderless cathodes, and does not reflect absolute C-rate performance in a full cell configuration, such as shown in Examples 1 and 2 above.

[0194] Conclusion

[0195] Any directional terminology used herein is for purposes of orientation only and is not intended to limit the present application. For example, a "top" layer can also be referred to as a second layer, and a "bottom" layer can also be referred to as a first layer. Other terminology and arrangements can be used without limiting the teachings herein.

[0196] Various other components can be included and called upon to provide aspects of the teachings herein. For example, additional materials, combinations of materials, and / or omissions of materials can be utilized to provide additional embodiments within the scope of the teachings herein.

[0197] Various modifications can be made to the teachings herein. Typically, modifications will be made in light of user, designer, manufacturer, or other similar considerations. Such modifications can be made in the design, arrangement, and / or other aspects of the teachings herein. Similarly, the acceptability of performance can be assessed by the appropriate user, designer, manufacturer, or other similar party.

[0198] While some chemicals can be listed herein as providing a certain function, a given chemical can be used for other purposes.

[0199] When introducing elements of the present application or the embodiments thereof, the articles "a," "an," and "the" are intended to mean that there are one or more of the elements. Similarly, the term "another" is intended to mean one or more. The terms "including," "comprising," and "having" are intended to be inclusive and are meant to indicate that there can be additional elements. As used herein, the term "exemplary" is intended to mean an example and is not intended to indicate the superiority or inferiority of the example over another example. Each of the publications and patent applications mentioned above are hereby incorporated by reference in their entirety. In the event of any conflict between any of the above publications and the present disclosure, the present disclosure shall control.

[0200] Note that, unless otherwise expressly specified herein, use of the expressions "a" or "an" or "the" preceding an element or intervention are intended to be interpreted as including one or more elements of that element or intervention. For example, the expression "a feature" is intended to mean one or more features. Also, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, elements, components, and / or groups thereof.

[0201] While the application has been described with reference to example embodiments, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the application. For example, in some embodiments, one of the aforementioned layers can include multiple layers therein. In addition, many modifications can be made to adapt a particular instrument, situation or material to the teachings of the application without departing from the essential scope thereof. Therefore, it is intended that the application not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this application but that the application will include all embodiments falling within the scope of the appended claims.

Claims

1. A device comprising an electrode active layer, the electrode active layer comprising: a network of high aspect ratio carbon elements, the network of high aspect ratio carbon elements defining interstitial spaces within the network; wherein high aspect ratio is defined by a ratio of a major dimension to a minor dimension of the carbon elements of at least 5; a plurality of electrode active material particles disposed in the interstitial spaces within the network and entangled in the network; and a surface treatment on a surface of the high aspect ratio carbon elements, the surface treatment promoting adhesion between the high aspect ratio carbon elements and the plurality of electrode active material particles; wherein the electrode active layer contains less than 10% by weight of a polymeric binder disposed in the interstitial spaces; wherein the high aspect ratio carbon elements comprise at least one of carbon nanotubes and carbon nanotube bundles; wherein the network is at least 99% by weight carbon and comprises an electrically interconnected network of carbon elements exhibiting connectivity beyond a percolation threshold, and wherein the network defines one or more high conductive pathways having a length greater than 100 pm; wherein the surface treatment comprises a layer of surfactant disposed on the carbon elements, wherein the layer of surfactant is bound to the high aspect ratio carbon elements and comprises a plurality of surfactant elements each having a hydrophobic end and a hydrophilic end, wherein the hydrophobic end is disposed proximal to a surface of the high aspect ratio carbon elements and the hydrophilic end is disposed distal to the surface of the high aspect ratio carbon elements; wherein the surface treatment further comprises a thin polymer layer disposed on the high aspect ratio carbon elements, the thin polymer layer promoting adhesion of the plurality of electrode active material particles to the network, wherein the thin polymer layer comprises a self-assembled polymer; and wherein the plurality of electrode active material particles comprise lithium metal oxides.

2. The device of claim 1, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 10 times a length ratio of the minor dimension.

3. The device of claim 1, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 100 times a length ratio of the minor dimension.

4. The device of claim 1, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 1,000 times a length ratio of the minor dimension.

5. The device of claim 1, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 10,0000 times a length ratio of the minor dimension.

6. The device of claim 1, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein the length ratio of the major dimension is at least 10 times the length ratio of each of the minor dimensions.

7. The device of claim 1, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein the length ratio of the major dimension is at least 100 times the length ratio of each of the minor dimensions.

8. The device of claim 1, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein the length ratio of the major dimension is at least 1,000 times the length ratio of each of the minor dimensions.

9. The device of claim 1, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein the length ratio of the major dimension is at least 10,000 times the length ratio of each of the minor dimensions.

10. The device of claim 1, wherein the high aspect ratio carbon elements comprise carbon nanotubes or bundles of carbon nanotubes.

11. The device of claim 1, wherein the high aspect ratio carbon elements comprise graphene sheets.

12. The device of claim 1, wherein the electrode active layer contains less than 1% by weight of polymeric binder disposed in the interstitial space.

13. The device of claim 1, wherein the electrode active layer is substantially free of polymeric materials other than the surface treatment.

14. The device of claim 1, wherein the electrode active layer is substantially free of polymeric materials.

15. The device of claim 1, wherein the surface treatment comprises a material that is soluble in a solvent having a boiling point less than 202°C.

16. The device of claim 1, wherein the surface treatment comprises a material that is soluble in a solvent having a boiling point less than 185°C.

17. The device of claim 1, wherein during formation of the active layer, a material that forms the surface treatment is dissolved in a solvent having a boiling point less than 202°C.

18. The device of claim 1, wherein during formation of the active layer, a material that forms the surface treatment is dissolved in a solvent having a boiling point less than 185°C.

19. The device of claim 1, wherein during formation of the active layer, a material that forms the surface treatment is dissolved in a solvent comprising isopropyl alcohol.

20. The device of claim 1, wherein during formation of the active layer, a material that forms the surface treatment is dissolved in a solvent that is substantially free of n-methyl-2-pyrrolidone.

21. The device of claim 1, wherein during formation of the active layer, a material that forms the surface treatment is dissolved in a solvent that is substantially free of pyrrolidone compounds.

22. The device of claim 1, wherein the network is at least 99.9% by weight carbon.

23. The device of claim 1, wherein the pathway comprises a length greater than 1,000 pm.

24. The device of claim 1, wherein the pathway comprises a length greater than 10,000 pm.

25. The device of claim 1, wherein the network comprises one or more structures formed from carbon elements, the structures comprising a total length that is at least ten times a length of a largest dimension of the carbon elements.

26. The device of claim 1, wherein the network comprises one or more structures formed from carbon elements, the structures comprising a total length that is at least 100 times a length of a largest dimension of the carbon elements.

27. The device of claim 1, wherein the network comprises one or more structures formed from carbon elements, the structures comprising a total length that is at least 1,000 times a length of a largest dimension of the carbon elements.

28. The device of claim 1, wherein the hydrophilic end of at least a portion of the surfactant elements forms a bond with the plurality of electrode active material particles.

29. The device of claim 28, wherein the bond comprises an ionic bond.

30. The device of claim 28, wherein the bond comprises a covalent bond.

31. The device of claim 28, wherein the bond comprises at least one from a list consisting of: a pi-pi bond, a hydrogen bond, and an electrostatic bond.

32. The device of claim 1, wherein: the hydrophilic end of each of the surfactant elements has a polar charge of a first polarity; and the plurality of electrode active material particles carry a polar charge of a second polarity that is opposite the polar charge of the first polarity.

33. The device of claim 1, wherein the surfactant layer comprises a water-soluble surfactant.

34. The device of claim 1, wherein the surfactant layer comprises ions from hexadecyltrimethylammonium hexafluorophosphate.

35. The device of claim 1, wherein the surfactant layer comprises ions of at least one from a list consisting of: hexadecyltrimethylammonium tetrafluoroborate, N-(cocoalkyl)-N,N,N-trimethylammonium methylsulfate, cocamidopropyl betaine, hexadecyltrimethylammonium acetate, and hexadecyltrimethylammonium nitrate.

36. The device of claim 1, wherein the surfactant layer comprises a surfactant ionic layer formed by dissolving an ionic compound in a solvent.

37. The device of claim 36, wherein the active layer comprises residual counterions of the surfactant ions formed by dissolving an ionic surfactant compound in a solvent.

38. The device of claim 37, wherein the counterions are compatible for use in an electrochemical cell.

39. The device of claim 38, wherein the counterions are substantially free of halogen groups.

40. The device of any one of claims 37-39, wherein the residual counterions are substantially free of bromine.

41. The device of claim 40, wherein the ionic surfactant compound comprises at least one selected from the list consisting of: cetyltrimethylammonium hexafluorophosphate, cetyltrimethylammonium tetrafluoroborate, N-(cocoalkyl)-N,N,N-trimethylammonium methylsulfate, cocamidopropyl betaine, cetyltrimethylammonium acetate, and cetyltrimethylammonium nitrate.

42. The device of claim 1, wherein the carbon elements are functionalized.

43. The device of claim 42, wherein the carbon elements are functionalized with a surfactant material.

44. The device of claim 42 or 43, wherein the carbon elements are functionalized with a functional group that promotes adhesion of the plurality of electrode active material particles to the network.

45. The device of claim 44, wherein the functional group comprises at least one from the list consisting of: a carboxyl group, a hydroxyl group, an amine group, and a silane group.

46. The device of claim 42, wherein functionalized carbon elements are formed from a dried aqueous dispersion comprising nano-shaped carbon and a surfactant.

47. The device of claim 46, wherein the functionalized carbon elements are formed from a lyophilized aqueous dispersion comprising nano-shaped carbon and a surfactant.

48. The device of claim 46 or 47, wherein the aqueous dispersion is substantially free of acid.

49. The device of claim 1, wherein the thin polymer layer comprises a self-assembled polymer.

50. The device of claim 1, wherein the thin polymer layer is bound to the plurality of electrode active material particles through hydrogen bonding.

51. The device of claim 1, wherein the thin polymer layer has a maximum thickness in a direction normal to an outer surface of the network of less than or equal to 50 nm.

52. The device of claim 1, wherein the thin polymer layer has a maximum thickness in a direction normal to an outer surface of the network of less than or equal to 10 nm.

53. The device of claim 1, wherein the thin polymer layer has a maximum thickness in a direction normal to an outer surface of the network of less than or equal to 1 nm.

54. The device of claim 1, wherein less than 1% by volume of the interstitial space defined by the network is filled with the thin polymer layer.

55. The device of claim 1, wherein less than 0.1% by volume of the interstitial space defined by the network is filled with the thin polymer layer.

56. The device of claim 1, wherein less than 0.01% by volume of the interstitial space defined by the network is filled with the thin polymer layer.

57. The device of claim 1, wherein the surface treatment comprises a layer of carbonaceous material formed from a pyrolized polymeric material.

58. The device of claim 57, wherein the layer of carbonaceous material formed from a pyrolized polymeric material promotes adhesion of the plurality of electrode active material particles to the network.

59. The device of claim 1, wherein the plurality of electrode active material particles are entangled in the network.

60. The device of claim 1, wherein the surface treatment promotes adhesion of the active material layer and a current collector layer.

61. The device of claim 60, wherein the surface treatment comprises a functional group that bonds with the current collector layer.

62. The device of claim 61, wherein the functional group bonds with the current collector layer through a non-covalent bond.

63. The device of claim 61, wherein the functional group bonds with the current collector layer using at least one selected from a list consisting of: a pi-pi bond, a hydrogen bond, and an ionic bond.

64. The device of any one of claims 60 to 63, wherein the current collector layer comprises a metal foil.

65. The device of any one of claims 60 to 63, wherein the active material layer has a thickness of at least 200 pm in a direction normal to the current collector.

66. The device of any one of claims 60 to 63, wherein the active material layer has a thickness of at least 300 pm in a direction normal to the current collector.

67. The device of any one of claims 60 to 63, wherein the active material layer has a thickness of at least 400 pm in a direction normal to the current collector.

68. An energy storage cell, comprising: a first electrode comprising an active material layer; a second electrode; a permeable separator disposed between the first electrode and the second electrode; and an electrolyte wetting the first electrode and the second electrode; wherein at least one of the first electrode or the second electrode comprises: a current collector; disposed on the current collector is an electrode active layer; the electrode active layer comprises: a network of high aspect ratio carbon elements defining interstitial spaces within the network; wherein the network of high aspect ratio carbon elements comprises elongated rod-like or fiber-like elements having one major dimension and two minor dimensions, and wherein the length ratio of the major dimension is at least 5 times or more than the length ratio of each of the minor dimensions; a plurality of electrode active material particles disposed in the interstitial spaces within the network and entangled in the network; and a surface treatment on surfaces of the high aspect ratio carbon elements, the surface treatment promoting adhesion between the high aspect ratio carbon elements and the plurality of electrode active material particles; wherein the surface treatment comprises a surfactant; and wherein the surfactant is an ionic surfactant compound comprising at least one selected from a list consisting of: cetyltrimethylammonium hexafluorophosphate, cetyltrimethylammonium tetrafluoroborate, cocamidopropyl betaine, cetyltrimethylammonium acetate, and cetyltrimethylammonium nitrate.

69. A method of forming an electrode active layer, comprising: ​ dispersing high aspect ratio carbon elements and a surface treatment material in a solvent to form an initial slurry, wherein the dispersing step results in a surface treatment forming on the high aspect ratio carbon; mixing an active material into the first slurry to form a final slurry; applying the final slurry to a substrate; and drying the final slurry to form an electrode active layer; wherein the electrode active layer comprises: a network of high aspect ratio carbon elements defining interstitial spaces within the network; wherein high aspect ratio is defined by a ratio of a major dimension to a minor dimension of the carbon elements of at least 5; a plurality of electrode active material particles disposed in the interstitial spaces within the network and entangled 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 plurality of electrode active material particles; wherein the electrode active layer contains less than 10% by weight of a polymeric binder disposed in the interstitial spaces; wherein the high aspect ratio carbon elements comprise at least one of carbon nanotubes and carbon nanotube bundles; wherein the network is at least 99% by weight carbon and comprises an electrically interconnected network of carbon elements exhibiting connectivity beyond a percolation threshold, and wherein the network defines one or more high conductive pathways having a length greater than 100 pm; wherein the surface treatment comprises a layer of surfactant disposed on the carbon elements, wherein the layer of surfactant is bound to the high aspect ratio carbon elements and comprises a plurality of surfactant elements each having a hydrophobic end and a hydrophilic end, wherein the hydrophobic end is disposed proximal to a surface of the high aspect ratio carbon elements and the hydrophilic end is disposed distal to the surface of the high aspect ratio carbon elements; wherein the surface treatment further comprises a thin polymer layer disposed on the high aspect ratio carbon elements that promotes adhesion of the plurality of electrode active material particles to the network, wherein the thin polymer layer comprises a self-assembled polymer; and wherein the plurality of electrode active material particles comprise lithium metal oxides.

70. The method of claim 69, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 10 times a length ratio of the minor dimension.

71. The method of claim 69, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 100 times a length ratio of the minor dimension.

72. The method of claim 69, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 1,000 times a length ratio of the minor dimension.

73. The method of claim 69, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and one minor dimension, wherein the length ratio of each of the major dimensions is at least 10,000 times the length ratio of the minor dimension.

74. The method of claim 69, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein the length ratio of the major dimension is at least 10 times the length ratio of each of the minor dimensions.

75. The method of claim 69, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein the length ratio of the major dimension is at least 100 times the length ratio of each of the minor dimensions.

76. The method of claim 69, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein the length ratio of the major dimension is at least 1,000 times the length ratio of each of the minor dimensions.

77. The method of claim 69, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein the length ratio of the major dimension is at least 10,000 times the length ratio of each of the minor dimensions.

78. The method of claim 69, wherein the high aspect ratio carbon elements comprise carbon nanotubes or bundles of carbon nanotubes.

79. The method of claim 69, wherein the high aspect ratio carbon elements comprise graphene sheets.

80. The method of claim 69, wherein the initial slurry has a solids content in the range of 0.1% - 20.0% by weight.

81. The method of claim 69, wherein the final slurry has a solids content in the range of 10.0% - 80% by weight.

82. The method of claim 69, wherein the solvent has a boiling point below 202 °C.

83. The method of claim 69, wherein the solvent has a boiling point below 185 °C.

84. The method of claim 69, wherein the solvent has a boiling point below 125 °C.

85. The method of claim 69, wherein the solvent has a boiling point below or equal to 100 °C.

86. The method of claim 69, wherein the solvent comprises at least one from the list consisting of: methanol, ethanol, 2-propanol, and water.

87. The method of claim 69, wherein during formation of the active layer, a material forming the surface treatment is dissolved in a solvent that is substantially free of a pyrrolidinone compound.

88. The method of claim 69, wherein the solvent is substantially free of n-methyl-2-pyrrolidinone.

89. The method of claim 69, wherein the surfactant layer is substantially free of halogen groups.

90. The method of claim 89, wherein the surfactant layer is substantially free of bromine.

91. The method of claim 69, wherein the surface treatment is a self-assembled layer.

92. The method of claim 69, further comprising forming a bond between the hydrophobic end of at least a portion of the surfactant elements and the plurality of electrode active material particles.

93. The method of claim 92, wherein the bond comprises an ionic bond.

94. The method of claim 92, wherein the bond comprises a covalent bond.

95. The method of claim 92, wherein the bond comprises at least one from the list consisting of: a π-π bond, a hydrogen bond, and an electrostatic bond.

96. The method of claim 69, wherein: the hydrophilic end of each of the surfactant elements has a polar charge of a first polarity; the plurality of electrode active material particles carry a polar charge of a second polarity opposite the first polarity of the polar charge.

97. The method of claim 69, wherein the surfactant layer comprises at least one selected from the list consisting of: hexadecyltrimethylammonium hexafluorophosphate, hexadecyltrimethylammonium tetrafluoroborate, N-(Cocoalkyl)-N,N,N-trimethylammonium methylsulfate, cocamidopropyl betaine, hexadecyltrimethylammonium acetate, and hexadecyltrimethylammonium nitrate.

98. The method of claim 69, wherein dispersing high aspect ratio carbon elements and surface treatment material in a solvent to form an initial slurry comprises applying a force to the aggregated carbon elements to cause the elements to slide apart from one another along a direction transverse to the short axis of the elements.

99. The method of claim 69, comprising drying the final slurry at a temperature below 202 °C.

100. The method of claim 69, comprising drying the final slurry at a temperature below 185 °C.

101. The method of claim 69, comprising drying the final slurry at a temperature below 125 °C.

102. The method of claim 69, comprising drying the final slurry at a temperature below or equal to 100 °C.

103. The method of claim 69, further comprising calendering the active layer to promote adhesion between the plurality of electrode active material particles and the network.

104. A method of forming an electrode active layer, comprising: dispersing high aspect ratio carbon elements and surface treatment material in an aqueous solvent to form an initial slurry, wherein the dispersing step results in a surface treatment on the high aspect ratio carbon; drying the initial slurry to remove substantially all water, resulting in a dried powder of the high aspect ratio carbon having the surface treatment thereon; dispersing the dried powder of the high aspect ratio carbon having the surface treatment in a second solvent and adding an active material to form a second slurry; applying the second slurry to a substrate; and drying the second slurry to form an electrode active layer; wherein the electrode active layer comprises: ​ a network of high aspect ratio carbon elements, the network of high aspect ratio carbon elements defining void spaces within the network; wherein high aspect ratio is defined by a ratio of a major dimension to a minor dimension of the carbon elements of at least 5; a plurality of electrode active material particles disposed in the void spaces within the network and intertangled in the network; and a surface treatment on a surface of the high aspect ratio carbon elements, the surface treatment promoting adhesion between the high aspect ratio carbon elements and the plurality of electrode active material particles; wherein the electrode active layer comprises less than 10% by weight of a polymeric binder disposed in the void spaces; wherein the high aspect ratio carbon elements comprise at least one of carbon nanotubes and carbon nanotube bundles; wherein the network is at least 99% by weight carbon and comprises an electrically interconnected network of carbon elements exhibiting connectivity beyond a percolation threshold, and wherein the network defines one or more high conductive pathways having a length greater than 100 pm; wherein the surface treatment comprises a layer of surfactant disposed on the carbon elements, wherein the layer of surfactant is bound to the high aspect ratio carbon elements and comprises a plurality of surfactant elements each having a hydrophobic end and a hydrophilic end, wherein the hydrophobic end is disposed proximal to a surface of the high aspect ratio carbon elements and the hydrophilic end is disposed distal to the surface of the high aspect ratio carbon elements; wherein the surface treatment further comprises a thin polymer layer disposed on the high aspect ratio carbon elements, the thin polymer layer promoting adhesion of the plurality of electrode active material particles to the network, wherein the thin polymer layer comprises a self-assembled polymer; and wherein the plurality of electrode active material particles comprise lithium metal oxides.

105. The method of claim 104, wherein drying the initial slurry comprises lyophilizing the initial slurry.

106. The method of claim 104 or 105, wherein the aqueous solvent and initial slurry are substantially free of substances that are damaging to the high aspect ratio carbon elements.

107. The method of claim 106, wherein the aqueous solvent and initial slurry are substantially free of acids.

108. The method of claim 107, wherein the initial slurry consists essentially of the high aspect ratio carbon elements, the surface treatment material, and water.

109. The method of claim 104, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 10 times a length ratio of the minor dimension.

110. The method of claim 104, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 100 times a length ratio of the minor dimension.

111. The method of claim 104, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 1,000 times a length ratio of the minor dimension.

112. The method of claim 104, wherein the high aspect ratio carbon elements comprise elements each having two major dimensions and a minor dimension, wherein a length ratio of each of the major dimensions is at least 10,000 times a length ratio of the minor dimension.

113. The method of claim 104, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein a length ratio of the major dimension is at least 10 times a length ratio of each of the minor dimensions.

114. The method of claim 104, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein a length ratio of the major dimension is at least 100 times a length ratio of each of the minor dimensions.

115. The method of claim 104, wherein the high aspect ratio carbon elements comprise elements each having one major dimension and two minor dimensions, wherein a length ratio of the major dimension is at least 1,000 times a length ratio of each of the minor dimensions.

116. The method of claim 104, wherein the high aspect ratio carbon elements comprise carbon nanotubes or bundles of carbon nanotubes.

117. The method of claim 104, wherein the high aspect ratio carbon elements comprise graphene sheets.

118. The method of claim 104, wherein the solvent has a boiling point below 202 °C.

119. The method of claim 104, wherein the solvent has a boiling point below 185 °C.

120. The method of claim 104, wherein the solvent has a boiling point below 125 °C.

121. The method of claim 104, wherein the solvent has a boiling point below or equal to 100 °C.

122. The method of claim 104, wherein the second solvent comprises at least one from the list consisting of: methanol, ethanol, 2-propanol, and water.

123. The method of claim 104, wherein the second solvent is substantially free of a pyrrolidone compound.

124. The method of claim 104, wherein the second solvent is substantially free of n-methyl-2-pyrrolidone.

125. The method of claim 104, wherein the surfactant layer is substantially free of halogen groups.

126. The method of claim 125, wherein the surfactant layer is substantially free of bromine.

127. The method of claim 104, wherein the surfactant layer is a self-assembled layer.

128. The method of claim 104, comprising drying the second slurry at a temperature below 202 °C.

129. The method of claim 104, comprising drying the second paste at a temperature below 185 °C.

130. The method of claim 104, comprising drying the second paste at a temperature below 125 °C.

131. The method of claim 104, comprising drying the second paste at a temperature below or equal to 100 °C.

132. The method of claim 104, further comprising calendering the active layer to promote adhesion.

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