Electrodes for energy storage devices

Abstract

An electrode for an energy storage device is disclosed. The electrode includes an active layer including a network of high aspect ratio carbon elements defining voids within the network, a plurality of electrode active material particles disposed in the voids within the network and including silicon, and a polymer additive that is at least one of a polyolefin, a poly(acrylic acid), and a styrene butadiene rubber (SBR).

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Patent Application No. 63 / 290,284, filed December 16, 2021, which is incorporated by reference herein in its entirety. [Background technology]

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

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

[0004] Conventional electrodes use binders with sufficient adhesive and chemical properties so that the film coated on the current collector maintains contact with the current collector even when manipulated to fit into a pressurized battery casing. Since the film contains the electrode active material, significant interference with the electrochemical properties of the battery can occur if the film does not maintain sufficient contact with the current collector. Furthermore, it is important to select a binder that is mechanically compatible with the electrode active material(s) so that it can withstand the degree of expansion and contraction of the electrode active material(s) during charging and discharging of the battery. Therefore, binders such as cellulosic binders or cross-linked polymer binders have been used to provide good mechanical properties. However, in conventional electrodes, the binders selected generally require environmentally unfriendly or toxic solvents for processing.

[0005] Another area for improving the performance of energy storage devices for such electronic devices is the use of silicon-based anodes in LiBs. Although silicon exhibits excellent charge storage properties, it disadvantageously undergoes significant mechanical swelling when accepting a charge. This swelling can cause mechanical failure in the electrode, rendering it unsuitable for use.

[0006] Therefore, there is interest in using composite structures of carbon and silicon to provide high performance electrodes with suitable mechanical stability during charging and discharging processes. Consider, for example, International Patent Application No. PCT / US2019 / 013261, entitled "Silicon Micro-Reactors for Lithium Rechargeable Batteries," the entire contents of which are incorporated herein by reference. The '261 application discloses a process for making composite silicon carbon anodes. Another example is provided in U.S. Patent No. 10,340,520, entitled "Nanocomposite battery electrode particles with changing properties," issued on July 2, 2019, the entire contents of which are incorporated herein. The '520 patent discloses silicon containing carbon nanoshell particles for use in electrodes.

[0007] However, such approaches are often not amenable to rapid, low-cost manufacturing and may exhibit many other disadvantageous characteristics. For example, in some cases, electrodes made using these approaches may require the inclusion of polymer binders that reduce the performance of the electrode, making them unsuitable for use under operating conditions such as high voltages or temperatures.

[0008] The continuing need for increased power and energy in energy storage devices such as batteries and capacitors requires advances in the physics and chemistry of electrode technology to provide such improvements.

[0009] The following is a brief description of the drawings, in which like elements are numbered likewise, which are presented for the purpose of illustrating, and not for the purpose of limiting, the exemplary embodiments disclosed herein. [Brief description of the drawings]

[0010] [Figure 1A] 1A-1D are diagrams of electrodes according to various embodiments. [Figure 1B] 1A-1D are diagrams of electrodes according to various embodiments. [Figure 1C] 1A-1D are diagrams of electrodes according to various embodiments. [Diagram 2] 1A-1D are diagrams of electrodes according to various embodiments. [Diagram 3] 1A-1D are diagrams of electrodes according to various embodiments. [Figure 4] 1 is an example of an electron micrograph of an active layer according to various embodiments. [Diagram 5] FIG. 1 is a schematic diagram of an energy storage device. [Figure 6] 1 is a flowchart of a method for making an electrode according to various embodiments. [Figure 7] 1 shows a schematic diagram of a pouch cell battery. [Figure 8] 1 is a schematic cutaway diagram illustrating an embodiment of an energy storage device (ESD). [Figure 9] 9 is a schematic cutaway view illustrating an embodiment of a prior art storage cell of the energy storage device (ESD) of FIG. 8. [Figure 10] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 11] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 12] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 13] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 14] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 15] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 16] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 17] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 18] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 19] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 20] FIG. 1 is a schematic diagram illustrating aspects of an assembled energy storage cell in accordance with various embodiments. [Figure 21] FIG. 1 is a schematic diagram illustrating aspects of an assembled energy storage cell in accordance with various embodiments. [Figure 22] 1 is a chart illustrating the electrical performance of energy storage cells constructed in accordance with various embodiments. [Diagram 23] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 24] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Diagram 25] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 26] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 27] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 28] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Figure 29] 1 is a graph illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments. [Diagram 30] 1 is a chart illustrating the electrical performance of energy storage cells constructed in accordance with various embodiments. [Diagram 31] 1 is a graph illustrating the electrical performance of energy storage cells constructed in accordance with various embodiments. [Diagram 32] 1 is a chart illustrating the electrical performance of energy storage cells constructed in accordance with various embodiments. [Diagram 33] 1 is a chart illustrating the electrical performance of energy storage cells constructed in accordance with various embodiments. [Diagram 34] 1 is a graph illustrating the electrical performance of energy storage cells constructed in accordance with various embodiments. [Diagram 35] 1 is a graph illustrating the electrical performance of energy storage cells constructed in accordance with various embodiments. [Diagram 36] 1 is a graph illustrating the electrical performance of energy storage cells constructed in accordance with various embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The components, processes, and devices disclosed herein can be more fully understood by referring to the accompanying drawings. These figures are merely schematic diagrams for convenience and ease of demonstration of the present disclosure, and are therefore not intended to illustrate the relative sizes and dimensions of the devices or their components, and / or to define or limit the scope of the exemplary embodiments. Although specific terms are used in the following description for clarity, these terms are intended to refer only to the specific structures of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the present disclosure. It should be understood that in the drawings and the following description, like number designations refer to components of similar function.

[0012] Various embodiments provide an energy storage device with an anode having a relatively high loading of silicon particles. Silicon is relatively inexpensive and has a relatively high specific capacity. Therefore, silicon can be used to increase the capacity of the energy storage device. However, silicon expands / swells during the charging phase of the energy storage device. The swelling of silicon during the charging phase can cause mechanical stress on the anode. Various embodiments provide a robust network of carbon elements to provide strong mechanical support to maintain electrical connectivity and mechanical resilience throughout the entire charge / discharge cycle of the energy storage device.

[0013] Various embodiments provide electrodes including polymer additives that exhibit strong electrical performance and strong mechanical stability, facilitating safe and clean manufacturing processes and energy storage devices. Various embodiments provide electrodes that do not include (e.g., do not contain) polymer additives that are not soluble in one or more of water or alcohols, such as ethanol. In some embodiments, the electrode is substantially free of polymer additives that are not soluble in one or more of water or alcohols, such as ethanol. In some embodiments, the active layer of the electrode is free or substantially free of polymer additives that are not soluble in one or more of water or alcohols, such as ethanol. For example, any polymer additive to the electrode according to various embodiments is soluble in one or more of water and alcohol.

[0014] According to various embodiments, the electrode comprises an active layer. In some embodiments, the active layer comprises: (i) a network of high aspect ratio carbon elements, the network defining voids within the network; (ii) a plurality of electrode active material particles disposed in the voids within the network, the active material particles comprising silicon; and (iii) a polymer additive. In some embodiments, the silicon comprised in the active material particles comprises one or more of silicon oxide and microsilicon. In some embodiments, the polymer additive is water processable.

[0015] In some embodiments, the polymeric additive comprises one or more of a polyolefin, a poly(acrylic acid), and a styrene butadiene rubber (SBR). In some embodiments, the amount of polymeric material in the active layer is about 8% by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer is 8% or less by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer is about 10% by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer is 10% or less by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer is less than 12% by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer is less than 15% by weight of the active layer.

[0016] According to various embodiments, the active layer includes a polymer additive comprising a polyolefin. In some embodiments, the polyolefin has an average particle size of 1 μm or less. In some embodiments, the polyolefin includes an unsaturated hydrocarbon having 3-6 carbon atoms and at least one of a propylene component and a 1-butene component. In some embodiments, the polymer additive comprising a polyolefin is produced using a polyolefin resin including 50-98% by weight of an unsaturated hydrocarbon having 3-6 carbon atoms and 0.5-20% by weight of an unsaturated carboxylic acid unit. In some embodiments, the polyolefin includes an ethylene component. In some embodiments, the polyolefin includes (i) an unsaturated hydrocarbon having 3-6 carbon atoms and at least one of a propylene component and a 1-butene component, and (ii) an ethylene component. In some embodiments, the polyolefin includes a crosslinker and / or a tackifier. In some embodiments, the polyolefin includes at least one selected from the group consisting of maleic anhydride, acrylic acid, and methacrylic acid.

[0017] According to various embodiments, the electrode comprises an active layer. In some embodiments, the active layer comprises (i) a network of high aspect ratio carbon elements, the network defining voids within the network, (ii) a plurality of electrode active material particles disposed within the voids within the network, and (iii) a polymer additive. In some embodiments, the polymer additive comprises one or more of a polyolefin, a poly(acrylic acid), and a styrene butadiene rubber (SBR). In some embodiments, the silicon in the active material particles comprises one or more of silicon oxide and fine silicon. In some embodiments, the active layer comprises 20% to 95% by weight of silicon-based particles based on the weight of the active layer. In some embodiments, the active layer comprises 50% to 95% by weight of silicon-based particles based on the weight of the active layer. In some embodiments, the active layer comprises more than 75% by weight of silicon-based particles based on the weight of the active layer. In some embodiments, the active layer comprises more than 80% by weight of silicon-based particles based on the weight of the active layer. In some embodiments, the active layer comprises 20 wt% to 75 wt% silicon-based particles based on the weight of the active layer. In some embodiments, the active layer comprises more than 20 wt% silicon particles (e.g., fine silicon) based on the weight of the active layer. In some embodiments, the active layer comprises 20 wt% to 40 wt% silicon particles (e.g., fine silicon) based on the weight of the active layer. In some embodiments, the active layer comprises 30 wt% to 40 wt% silicon particles (e.g., fine silicon) based on the weight of the active layer. In some embodiments, the active layer comprises more than 50 wt% silicon oxide particles based on the weight of the active layer. In some embodiments, the active layer comprises 60 wt% to 70 wt% silicon oxide particles based on the weight of the active layer.

[0018] According to various embodiments, the active layer includes silicon-based particles. In some embodiments, the active layer includes both fine silicon particles and silicon oxide particles. In some embodiments, the active layer includes fine silicon particles and is substantially free of silicon oxide particles (e.g., the active layer does not include any silicon oxide particles). Silicon oxide particles do not appear to expand to the same extent as fine silicon (e.g., pure silicon). For example, the oxide layer around the silicon is large enough that the expansion of silicon in the silicon oxide generally does not significantly expand the silicon oxide too much. In contrast, fine silicon expands and contracts to a greater extent than silicon oxide, thereby making it more difficult to maintain the electrical and / or mechanical properties of the electrode (e.g., anode). For example, the expansion of fine silicon can destroy the electrical connections in the electrode (e.g., in the active layer) or the mechanical stability of the electrode. Various embodiments provide a network of high aspect ratio carbon elements that maintain electrical connections and mechanical support through charge-discharge cycles.

[0019] According to various embodiments, the electrode comprises an active layer. In some embodiments, the active layer comprises: (i) a network of high aspect ratio carbon elements, the network defining voids within the network; (ii) a plurality of electrode active material particles disposed in the voids within the network, the plurality of electrode active material particles comprising a plurality of silicon-based particles (e.g., fine silicon, silicon oxide, etc.); and (iii) a polymer additive. The polymer additive has a relatively high molecular weight. In some embodiments, the polymer additive has a molecular weight of at least 400,000 g / mol. In some embodiments, the polymer additive has a molecular weight of at least 1,000,000 g / mol. In some embodiments, the polymer additive has a molecular weight of at least 1,500,000 g / mol. In some embodiments, the polymer additive has a molecular weight of 700,000 g / mol to 1,500,000 g / mol. In some embodiments, the polymer additive has a molecular weight of 500,000 g / mol to 1,000,000 g / mol.

[0020] According to various embodiments, the electrode comprises an active layer. In some embodiments, the active layer comprises: (i) a network of high aspect ratio carbon elements, the network defining voids within the network; (ii) a plurality of electrode active material particles disposed in the voids within the network, the plurality of electrode active material particles comprising a plurality of silicon-based particles (e.g., fine silicon, silicon oxide, etc.); and (iii) a polymer additive. The polymer additive has a relatively high tensile strength. For example, the polymer additive comprises a polymer that is difficult to stretch. In some embodiments, the polymer additive has a relatively high tensile strength and is processable in water or alcohol. In some embodiments, the polymer additive has a relatively high tensile strength and is processable in water (e.g., is relatively easily processable using water). In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 20 MPa at about 10% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 30 MPa at about 10% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of 30 MPa to 35 MPa at about 10% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 10 MPa at about 20% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 20 MPa at about 20% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 25 MPa at about 20% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of between 25 MPa and 30 MPa at about 20% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 15 MPa at 5% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 18 MPa at 5% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 20 MPa at 5% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of between 15 MPa and 25 MPa at 5% strain. In some embodiments, the polymer additive comprises a polymer having an ultimate strength of greater than 20 MPa.In some embodiments, the polymer additive comprises a polymer having a maximum strength of greater than 25 MPa. In some embodiments, the polymer additive comprises a polymer having a maximum strength of greater than 30 MPa. In some embodiments, the polymer additive comprises a polymer having a maximum strength of 30 MPa to 35 MPa. In some embodiments, the polymer additive comprises a polymer having a maximum strength of about 33 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of greater than 5.5 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of greater than 7 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of greater than 7.5 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of about 8 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of 5.5 MPa to 10 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of 7 MPa to 10 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of 7 MPa to 8.5 MPa.

[0021] According to various embodiments, the electrode comprises an active layer. In some embodiments, the active layer comprises (i) a network of high aspect ratio carbon elements, the network defining voids within the network, (ii) a plurality of electrode active material particles disposed within the voids within the network, and (iii) a polymer additive. In some embodiments, the silicon contained in the active material particles comprises one or more of silicon oxide and fine silicon. In some embodiments, the polymer additive comprises one or more of polyolefin, poly(acrylic acid), and styrene butadiene rubber (SBR). In some embodiments, the network of high aspect ratio carbon elements defining voids within the network comprises a first set of carbon nanotubes and a second set of carbon nanotubes. In some embodiments, the network of high aspect ratio carbon elements further comprises a third set of carbon elements. The third set of carbon elements may comprise graphite. The first set of carbon nanotubes comprises a plurality of first carbon nanotubes or a plurality of bundles of first carbon nanotubes. The second set of carbon nanotubes includes a plurality of second carbon nanotubes or a plurality of bundles of second carbon nanotubes. The second set of carbon nanotubes has one or more properties different from the first set of carbon nanotubes. According to various embodiments, the first set of carbon nanotubes includes multi-walled nanotubes and the second set of carbon nanotubes includes single-walled nanotubes. As an example, the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes is about 2:1. In some embodiments, the multi-walled carbon nanotubes include an average diameter of 6 nm to 10 nm, an average wall thickness of 6 nm to 7 nm, and an average length of 13 microns to 17 microns. In some embodiments, the average length of the multi-walled carbon nanotubes is about 13 microns. In some embodiments, the average length of the multi-walled carbon nanotubes is about 15 microns. In some embodiments, the average length of the multi-walled carbon nanotubes is about 16 microns. In some embodiments, the single-walled carbon nanotubes include an average diameter of 1 nm to 2 nm, and an average length of about 5 microns.In some embodiments, the single-walled carbon nanotubes comprise an average diameter of 3 nm to 5 nm and an average length of 7 to 8 microns.

[0022] According to various embodiments, the network of high aspect ratio carbon elements in the active layer of the electrode includes a first set of carbon nanotubes and a second set of carbon nanotubes. The first set of carbon nanotubes includes a plurality of first carbon nanotubes or a plurality of bundles of the first carbon nanotubes. The second set of carbon nanotubes includes a plurality of second carbon nanotubes or a plurality of bundles of the second carbon nanotubes. The second set of carbon nanotubes has one or more properties different from the first set of carbon nanotubes. In some embodiments, the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes is about 2:1. In some embodiments, the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes is about 9:1. In some embodiments, the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes is at least 5:1. In some embodiments, the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes is at least 7:1.

[0023] In some embodiments, the network of high aspect ratio carbon elements further comprises a third set of carbon elements. The third set of carbon elements may comprise graphite. The graphite may be used to increase coulombic efficiency. Graphite is conductive and can eliminate swollen shapes. In some embodiments, the active layer of the electrode comprises at least 5% graphite by weight of the active layer. In some embodiments, the active layer of the electrode comprises about 5% graphite by weight of the active layer. In some embodiments, the active layer of the electrode comprises at least 10% graphite by weight of the active layer. In some embodiments, the active layer of the electrode comprises at least 15% graphite by weight of the active layer. In some embodiments, the active layer of the electrode comprises at least 20% graphite by weight of the active layer.

[0024] According to various embodiments, the electrode comprises an active layer. In some embodiments, the active layer comprises: (i) a network of high aspect ratio carbon elements, the network defining voids within the network; (ii) a plurality of electrode active material particles disposed in the voids within the network; and (iii) a polymer additive that is soluble in at least one of (a) water and (b) alcohol. The network of high aspect ratio carbon elements defining voids within the network may comprise a set of multi-walled carbon nanotubes. According to various embodiments, the distribution of lengths of the set of multi-walled carbon nanotubes is biased toward the nominal length of the multi-walled carbon nanotubes. For example, the multi-walled carbon nanotubes are processed and / or applied in a manner that reduces or minimizes the crushing or breaking of the multi-walled carbon nanotubes. The length of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements is generally the nominal length of the multi-walled carbon nanotubes, or the lengths of such multi-walled carbon nanotubes tend to be more biased toward the nominal length. In some embodiments, at least 75% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements are within 10% of the nominal length (e.g., 13.4 microns to about 15 microns). In some embodiments, at least 75% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements have a length of at least 12 microns. In some embodiments, at least 75% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements have a length of at least 13 microns. In some embodiments, at least 50% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements are within 10% of the nominal length (e.g., 13.4 microns to about 15 microns). In some embodiments, at least 50% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements have a length of at least 12 microns. In some embodiments, at least 50% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements have a length of at least 13 microns.

[0025] According to various embodiments, the electrode comprises an active layer. In some embodiments, the active layer comprises (i) a network of high aspect ratio carbon elements, the network defining voids within the network, (ii) a plurality of electrode active material particles disposed in the voids within the network, and (iii) a polymer additive that is soluble in water or alcohol, the active layer exhibiting an adhesion to the electrode foil of at least 75 N / m. In some embodiments, the active layer exhibits an adhesion to the electrode foil of at least 90 N / m. In some embodiments, the active layer exhibits an adhesion to the electrode foil of at least 100 N / m. In some embodiments, the active layer exhibits an adhesion to the electrode foil of about 100 N / m. In some embodiments, the active layer exhibits an adhesion to the electrode foil of at least 125 N / m. In some embodiments, the active layer exhibits an adhesion to the electrode foil of at least 150 N / m. The network of high aspect ratio carbon elements may comprise multi-walled carbon nanotubes. The adhesion of the active layer to the foil of the electrode may be determined according to the peel test described herein. In some embodiments, the foil comprises copper and / or a copper alloy. According to various embodiments, the foil is coated on both sides (e.g., on opposite sides). Coating the foil on both sides can prevent the foil from folding during the drying process of drying the active layer (e.g., after the active layer is applied to the foil). For example, drying of the active layer can cause the active layer to shrink, and the shrinkage can apply a force to the foil to cause it to fold / crunch accordingly. To help prevent the foil from crumpling, a thicker foil may be selected, or the foil is coated on opposite sides. In some embodiments, the foil (e.g., foil thickness) is determined at least in part based on a tensile strength sufficient to withstand the force applied to the foil by the shrinkage of the active layer during the drying process and / or the force caused during the charge / discharge cycle (e.g., the force caused by the expansion / contraction of silicon during charge / discharge). In an embodiment, the foil has a thickness of less than 10 micrometers. In an embodiment, the foil has a thickness of less than 8 micrometers. In an embodiment, the foil has a thickness of less than 7 micrometers. In an embodiment, the foil has a thickness of less than 6 micrometers.In an embodiment, the foil has a thickness of less than 5 micrometers. In an embodiment, the foil has a thickness of about 6 micrometers.

[0026] According to various embodiments, the electrode comprises an active layer. In some embodiments, the active layer comprises (i) a network of high aspect ratio carbon elements, the network defining voids within the network, (ii) a plurality of electrode active material particles disposed in the voids within the network, and (iii) a polymer additive that is soluble in water or alcohol, wherein the active layer does not exhibit cracks when the electrode is wound around a mandrel having a diameter of at least 6 mm. The network of high aspect ratio carbon elements may comprise multi-walled carbon nanotubes. In some embodiments, the observation that the active layer does not exhibit any cracks within the active layer is determined based on human observation of the active layer, such as the surface of the active layer. In some embodiments, the human observation of the active layer is performed using analysis of the electrode under a microscope. An example of a test for determining whether the active layer exhibits cracks includes winding a sample electrode around a set of mandrels (e.g., from smallest diameter to largest diameter), opening the sample electrode and observing the crack condition on the front and back, and repeating with increasing mandrel thickness until no cracks are observed.

[0027] According to various embodiments, the electrode comprises an active layer. In some embodiments, the active layer comprises (i) a network of high aspect ratio carbon elements, the network defining voids within the network, (ii) a plurality of electrode active material particles disposed in the voids within the network, and (iii) a polymer additive processable in water or alcohol, the active layer exhibiting less than 50% swelling when wetted with an electrolyte. The polymer additive may be soluble in water or alcohol. In some embodiments, the active layer exhibits less than 40% swelling when wetted with an electrolyte. In some embodiments, the active layer exhibits less than 30% swelling when wetted with an electrolyte. In some embodiments, the active layer exhibits less than 10% swelling when wetted with an electrolyte. In some embodiments, the active layer exhibits less than 10% swelling when wetted with an electrolyte. In some embodiments, the active layer exhibits between 5% and 20% swelling when wetted with an electrolyte. In some embodiments, the active layer exhibits between 5% and 15% swelling when wetted with an electrolyte. In some embodiments, the active layer exhibits a 5% to 10% expansion when wetted with an electrolyte. The network of high aspect ratio carbon elements may include multi-walled carbon nanotubes.

[0028] As used herein, "peel test" refers to a 90-degree peel test. A sample (e.g., an electrode with an active layer attached to a foil) having a size of 2.54 cm x 10 cm is used. The test procedure for the peel test includes: (i) cutting a double-sided cathode electrode sample to a size of 10 cm x 2.54 cm; (ii) placing double-sided tape on one side and attaching it to the metal plate of the tester, fixing one end of the Scotch transparent tape by a clamp, and attaching the other end flat to the electrode surface at a 90-degree angle; (iii) setting the system to zero, i.e., setting the transfer mode to "cycle mode"; (iv) opening a test file named "sw-1x-v3" and selecting "com5" from the setup menu; (v) clicking "clear all data" in the left menu list, setting "set sampling rate" to 0.2 seconds, starting the tester and simultaneously selecting "sample continuously"; (vi) selecting "stop sampling" in the left menu list, stopping the tester, and saving the file.

[0029] As used herein, the term "high aspect ratio carbon element" refers to a carbonaceous element having a size in one or more dimensions (the "major dimension") that is significantly larger than the size of the element in the transverse dimension (the "minor dimension").

[0030] According to various embodiments, the electrode comprises an active layer. In some embodiments, the active layer comprises: (i) a network of high aspect ratio carbon elements, the network defining voids within the network; (ii) a plurality of electrode active material particles disposed in the voids within the network, the active material particles comprising silicon; and (iii) a polymer additive, the polymer additive comprising a polymeric material as described in U.S. Pat. No. 8,124,277, the entire disclosure of which is incorporated herein by reference for all purposes. In some embodiments, the silicon contained in the active material particles comprises one or more of silicon oxide and finely divided silicon. In some embodiments, the active material particles may comprise one or more of graphite, hard carbon, activated carbon, nanoform carbon, silicon, silicon oxide, and carbon-encapsulated silicon nanoparticles. In some embodiments, the active layer of the electrode may be intercalated with lithium, for example, using prelithiation methods known in the art.

[0031] 1A is a diagram of an electrode according to various embodiments. In the example shown, an electrode 100 is provided. According to various embodiments, the electrode 100 comprises a current collector 102 and an active layer 106. The electrode 100 may optionally include an adhesion layer 104. By way of example, the adhesion layer 104 includes a material that promotes adhesion between the current collector 102 and the active layer 106.

[0032] In some embodiments, the current collector 102 is a conductive layer. For example, the current collector 102 may be a metal, a metal alloy, or the like. As another example, the current collector 102 is a metal foil. In some embodiments, the current collector 102 is an aluminum foil or an aluminum alloy foil. In some embodiments, the current collector 102 is a copper foil or a copper alloy foil. The current collector 102 has a thickness of less than 15 μm. The current collector 102 has a thickness of less than 10 μm. The current collector 102 has a thickness of less than 8 μm. The current collector 102 has a thickness of less than 5 μm. The current collector 102 has a thickness of less than 15 μm. In some preferred embodiments, the current collector 102 has a thickness of about 6 μm to about 8 μm. In some preferred embodiments, the current collector 102 has a thickness of about 5 μm to about 8 μm. In some embodiments, the current collector 102 is an aluminum foil or an aluminum alloy foil, and the current collector 102 has a thickness of about 6 μm. In some embodiments, the electrodes comprise a foil provided with active layers on opposite sides.

[0033] In some embodiments, the active layer 106 can include a three-dimensional network of high aspect ratio carbon elements 108 that define voids within the network. A plurality of active material particles 110 are disposed within the voids within the network. The active material particles 110 are thus entangled or intertwined with the network, thereby improving the cohesion of the active layer 106. In some embodiments, the three-dimensional network of high aspect ratio carbon elements 108 provides mechanical support for the active material particles 110.

[0034] According to various embodiments, the three-dimensional network of high aspect ratio carbon elements 108 includes one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, a set of carbon nanotubes having a small number of walls (e.g., less than six walls), a set of carbon nanotubes having a large number of walls (e.g., more than six walls), carbon nanostructures, fragments of single-walled carbon nanotubes, fragments of multi-walled carbon nanotubes, fragments of carbon nanostructures, carbon black, etc. Various other high aspect ratio carbon elements may be implemented. The three-dimensional network of high aspect ratio carbon elements 108 maintains electrical connections between the high aspect ratio carbon elements (e.g., carbon nanotubes) during charging and discharging cycles of the electrode. For example, the three-dimensional network of high aspect ratio carbon elements 108 maintains electrical connections between the high aspect ratio carbon elements (e.g., carbon nanotubes) when silicon particles included in the active layer expand and / or contract during charging and discharging cycles. Multi-walled carbon nanotubes (or carbon nanotubes with multiple walls) provide good bonding or coating of silicon particles, such as silicon oxide, when the silicon expands (e.g., silicon particles can expand about 300%). Single-walled carbon nanotubes (or carbon nanotubes with fewer walls) can expand with the silicon as it expands during charge / discharge cycles, and therefore such carbon nanotubes generally do not reduce energy transfer.

[0035] According to various embodiments, the active layer 106 (e.g., a three-dimensional network of high aspect ratio carbon elements 108) includes multi-walled carbon nanotubes or sets of carbon nanotubes having multiple walls (e.g., more than five walls, or walls having five layers, etc.). In some embodiments, the amount of multi-walled carbon nanotubes (or sets of multi-walled carbon nanotubes) included in the active layer 106 is between 2% and 5% by weight of the active layer. In some embodiments, the amount of multi-walled carbon nanotubes (or sets of multi-walled carbon nanotubes) included in the active layer 106 is between 3% and 5% by weight of the active layer. In some embodiments, the amount of multi-walled carbon nanotubes (or sets of multi-walled carbon nanotubes) included in the active layer 106 is between 3.75% and 5% by weight of the active layer. In some embodiments, the amount of multi-walled carbon nanotubes (or sets of multi-walled carbon nanotubes) included in the active layer 106 is about 4% by weight of the active layer.

[0036] The active layer 106 has an average thickness between 10 microns and 200 microns. In some embodiments, the active layer 106 has an average thickness between 15 microns and 50 microns. In some embodiments, the active layer 106 has an average thickness between 10 microns and 25 microns. In some embodiments, the active layer 106 has an average thickness of about 100 microns. In some embodiments, the active layer 106 has an average thickness of about 50 microns. In some embodiments, the active layer 106 has an average thickness between 25 microns and 50 microns. Generally, the active layer swells when wetted by an electrolyte. One example for measuring the amount of swelling (e.g., expansion at least in the thickness direction) may include obtaining a sample electrode with a 1 inch diameter, such as by punching a sample from a larger sheet of electrodes with a 1 inch diameter round punch, measuring and recording the thickness of the active layer, placing the sample electrode in a coin cell case, injecting the sample electrolyte into the coin cell case, allowing the sample (e.g., with electrolyte injected) to sit for 1 hour, measuring and recording the thickness after 1 hour, then placing the electrode (soaked in electrolyte) in a drying chamber, covering it with a metal tray for 48 hours, and measuring and recording the thickness of the electrode after 48 hours. According to various embodiments, the volume of the active layer 106 expands (e.g., swells) by less than 10% when wetted with electrolyte. For example, the thickness of the active layer 106 after being wetted with electrolyte is less than 110% of the thickness of the active layer 106 without electrolyte. According to various embodiments, the volume of the active layer 106 expands (e.g., swells) by less than 20% when wetted with electrolyte. For example, the thickness of the active layer 106 after being wetted with electrolyte is less than 120% of the thickness of the active layer 106 without the electrolyte.

[0037] According to various embodiments, when the active layer 106 includes multi-walled carbon nanotubes and single-walled carbon nanotubes, the multi-walled carbon nanotubes swell more than single-walled carbon nanotubes when wetted with an electrolyte in an energy storage device in which the electrode 100 is included. In some embodiments, the multi-walled carbon nanotubes swell at least 15% more than single-walled carbon nanotubes when wetted with an electrolyte in an energy storage device in which the electrode 100 is included. For example, the length of the multi-walled carbon nanotubes expands at least 15% more than the length of single-walled carbon nanotubes when wetted with an electrolyte. In some embodiments, the multi-walled carbon nanotubes swell at least 25% more than single-walled carbon nanotubes when wetted with an electrolyte in an energy storage device in which the electrode 100 is included. For example, the length of the multi-walled carbon nanotubes expands at least 25% more than the length of single-walled carbon nanotubes when wetted with an electrolyte. In some embodiments, the multi-walled carbon nanotubes swell at least 50% more than single-walled carbon nanotubes when wetted with an electrolyte in an energy storage device in which the electrode 100 is included. For example, the length of a multi-walled carbon nanotube expands when wetted with an electrolyte by at least 50% more than the length of a single-walled carbon nanotube, hi some embodiments, the multi-walled carbon nanotube swells up to 50% upon wetting (e.g., the length of the multi-walled carbon nanotube is 50% greater after wetting with an electrolyte and / or the diameter of the multi-walled carbon nanotube is 50% greater after wetting, etc.).

[0038] According to various embodiments, the three-dimensional network of the high aspect ratio carbon elements 108 includes carbon nanotubes, where the carbon nanotubes are only multi-walled carbon nanotubes and / or carbon nanotube fragments. For example, the three-dimensional network of the high aspect ratio carbon elements 108 does not include single-walled carbon nanotubes or single-walled carbon nanotube fragments. According to various embodiments, the three-dimensional network of the high aspect ratio carbon elements 108 includes at least 99% carbon by weight. In some embodiments, the three-dimensional network of the high aspect ratio carbon elements 108 includes a network of electrically interconnected carbon elements that exhibits connectivity above the percolation threshold, and the network defines one or more highly conductive pathways having a length of more than 100 μm. In some embodiments, the three-dimensional network of the high aspect ratio carbon elements 108 maintains electrical connectivity when the silicon particles included in the active layer expand or contract during the charge-discharge cycle of the electrode 100.

[0039] According to various embodiments, the network of high aspect ratio carbon elements defines voids within the network, and the network of high aspect ratio carbon elements includes a first set of carbon nanotubes and a second set of carbon nanotubes. In some embodiments, the first set of carbon nanotubes includes a plurality of first carbon nanotubes or a plurality of bundles of first carbon nanotubes, and the second set of carbon nanotubes includes a plurality of second carbon nanotubes or a plurality of bundles of second carbon nanotubes. The second set of carbon nanotubes has one or more properties different from the first set of carbon nanotubes. For example, the second set of carbon nanotubes has a number of layers (e.g., walls) different from the number of layers (e.g., walls) of the first set of carbon nanotubes. In some embodiments, the first set of carbon nanotubes includes multi-walled carbon nanotubes. In some embodiments, the second set of carbon nanotubes includes single-walled carbon nanotubes. For example, the network of high aspect ratio carbon elements includes a set of multi-walled carbon nanotubes and a set of single-walled carbon nanotubes. The set of multi-walled carbon nanotubes may comprise fragments of multi-walled carbon nanotubes and / or the set of single-walled carbon nanotubes may comprise fragments of multi-walled carbon nanotubes. According to various embodiments, the active layer comprises more multi-walled carbon nanotubes by weight than single-walled carbon nanotubes. In some embodiments, the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes in the active layer is about 1.5:1. In some embodiments, the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes in the active layer is at least 1.5:1. In some embodiments, the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes in the active layer is about 2:1. In some embodiments, the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes in the active layer is at least 5:1.In some embodiments, the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes in the active layer is about 9:1.

[0040] In related art energy storage devices, the network of carbon elements includes fragmented carbon nanotubes, such as fragmented multi-walled carbon nanotubes. Related art processes for manufacturing electrodes are. For example, the fragmented multi-walled carbon nanotubes included in related art electrodes generally have an average length that is significantly shorter than the nominal length of the multi-walled carbon nanotubes (e.g., the length of the multi-walled carbon nanotubes before they are input into a process for manufacturing an electrode, such as a process for creating an active layer or a process for depositing an active layer on a current collector). The fragmented multi-walled carbon nanotubes included in related art electrodes generally have an average length that is less than half the nominal length of the multi-walled carbon nanotubes. The fragmented multi-walled carbon nanotubes included in related art electrodes generally have an average length that is less than one-third the nominal length of the multi-walled carbon nanotubes. The processes for preparing multi-walled carbon nanotubes or the processes for preparing / manufacturing / applying active layers for related art electrodes do not treat the multi-walled carbon nanotubes gently, causing them to break down or shatter. Longer multi-walled carbon nanotubes may generally provide better mechanical support for the active material particles in the active layer. For example, longer multi-walled carbon nanotubes provide better mechanical support for the active material particles as they expand / contract during charge / discharge cycling (e.g., the active material particles are better entangled between the relatively long multi-walled carbon nanotubes). In addition, longer multi-walled carbon nanotubes may form a longer interconnected network of highly conductive pathways formed within the network, providing long conductive paths (e.g., conductive paths on the order of the thickness of an active layer, such as active layer 106 of electrode 100 of FIG. 1A) to facilitate current flow within and through the active layer.

[0041] According to various embodiments, the electrodes include multi-walled carbon nanotubes that are relatively long compared to those included in related art electrodes. It has been found that the use of relatively long multi-walled carbon nanotubes in the electrodes provides beneficial mechanical and / or electrical properties. For example, multi-walled carbon nanotubes provide relatively good power output at low density. As another example, shorter multi-walled carbon nanotubes generally do not swell (e.g., expand) as much as longer multi-walled carbon nanotubes. Thus, using shorter multi-walled carbon nanotubes loses (or reduces) some of the beneficial properties associated with carbon nanotube swelling. As an extreme example, carbon black does not exhibit swelling because it is simply a particle of carbon that does not have the entanglement exhibited by a set of multi-walled carbon nanotubes. That a certain amount of multi-walled carbon nanotubes have a length above a threshold length and therefore sufficient swelling properties is indicated by observations during the calendering process, i.e., the relatively high pressure or effort to calender the slurry in conjunction with application to the foil indicates that the collective swelling (e.g., average swelling) of the multi-walled carbon nanotubes in the active layer meets a certain performance threshold. However, multi-walled carbon nanotubes are generally difficult to process. Processing of multi-walled carbon nanotubes in connection with the creation / formation of the active layer and / or electrode is gentler than processing of related art electrodes. Thus, the process according to various embodiments preserves longer multi-walled carbon nanotubes (e.g., fewer multi-walled carbon nanotubes are crushed, fragmented, broken, etc.). In some embodiments, the active layer of the electrode includes a set of multi-walled carbon nanotubes having an average length longer than the average length of the multi-walled carbon nanotubes in the related art electrodes. According to various embodiments, the length distribution of the set of multi-walled carbon nanotubes is biased toward the nominal length of the multi-walled carbon nanotubes. In one example, the nominal length of the multi-walled carbon nanotubes is about 16 microns. For example, the multi-walled carbon nanotubes are processed and / or applied in a manner that reduces or minimizes the crushing or breaking of the multi-walled carbon nanotubes.The length of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements is generally the nominal length of the multi-walled carbon nanotubes, or the lengths of such multi-walled carbon nanotubes tend to be more biased toward the nominal length. In some embodiments, at least 75% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements are within 10% of the nominal length (e.g., 13.4 microns to about 15 microns). In some embodiments, at least 75% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements have a length of at least 12 microns. In some embodiments, at least 75% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements have a length of at least 13 microns. In some embodiments, at least 50% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements are within 10% of the nominal length (e.g., 13.4 microns to about 15 microns). In some embodiments, at least 50% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements have a length of at least 12 microns. In some embodiments, at least 50% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements have a length of at least 8 microns. In some embodiments, at least 50% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements have a length of at least 13 microns. In some embodiments, at least 50% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements are within 50% of their nominal length (e.g., 13.4 microns to about 15 microns). In some embodiments, at least 50% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements are within 60% of their nominal length (e.g., 13.4 microns to about 15 microns). In some embodiments, at least 50% of the multi-walled carbon nanotubes in the network of high aspect ratio carbon elements are within 75% of their nominal length (e.g., 13.4 microns to about 15 microns).In some embodiments, the amount of multi-walled carbon nanotubes having a length less than half their nominal length is less than 50% by weight of the active layer. In some embodiments, the amount of multi-walled carbon nanotubes having a length less than half their nominal length is less than 30% by weight of the active layer. In some embodiments, the amount of multi-walled carbon nanotubes having a length less than half their nominal length is less than 25% by weight of the active layer.

[0042] The multi-walled carbon nanotubes included in the electrode exhibit, on average, a higher aspect ratio, including a longer length, than the multi-walled carbon nanotubes of related art electrodes. A slurry having a high viscosity is prepared and is exposed to relatively low shear forces during processing. Thus, the aspect ratio of the multi-walled carbon nanotubes is maintained. In some embodiments, at least a subset of the multi-walled carbon nanotubes included in the active layer are branched carbon nanotubes. In some embodiments, at least a subset of the multi-walled carbon nanotubes included in the active layer are branched, interdigitated, entangled, and / or share a common wall. Characterization of the multi-walled carbon nanotubes can be obtained using a scanning electron microscope (SEM). According to various embodiments, the multi-walled carbon nanotubes include an average length of at least 5 microns. In some embodiments, the multi-walled carbon nanotubes include an average length of at least 10 microns. In some embodiments, the multi-walled carbon nanotubes include an average length of between 10 microns and 15 microns. According to various embodiments, the multi-walled carbon nanotubes include an average diameter of between 6 nm and 15 nm. In some embodiments, the multi-walled carbon nanotubes include an average diameter of between 6 nm and 10 nm. According to various embodiments, the multi-walled carbon nanotubes include an average of 3 to 15 walls. In some embodiments, the multi-walled carbon nanotubes include an average of 3 to 15 walls. In some embodiments, the multi-walled carbon nanotubes include an average of 5 to 10 walls. In some embodiments, the multi-walled carbon nanotubes include an average of 6 to 7 walls. In some embodiments, the multi-walled carbon nanotubes include an average of at least 6 walls. In some embodiments, the multi-walled carbon nanotubes (e.g., a set of multi-walled carbon nanotubes) include an average aspect ratio of at least 100. In some embodiments, the multi-walled carbon nanotubes include an average aspect ratio of 200 to 1000. In some embodiments, the high aspect ratio carbon elements may include flake or plate shaped elements having two major dimensions and one minor dimension.For example, in some such embodiments, the ratio of the length of each of the major dimensions may be at least 5 times, 10 times, 100 times, 500 times, 1,000 times, 5,000 times, 10,000 times, or more, the length of the minor dimension.

[0043] According to various embodiments, the electrode comprises particles of silicon-based active material. In some embodiments, the electrode comprises at least one electrode active material selected from the group consisting of silicon (e.g., finely divided silicon), silicon oxide (e.g., SiOx), SiOx powder (Shin-Etsu 7131). Various other silicon-based particles may be implemented. In some embodiments, the active material comprises one or more of graphite, hard carbon, activated carbon, nanoform carbon, silicon, silicon oxide, and carbon-encapsulated silicon nanoparticles.

[0044] According to various embodiments, the plurality of active material particles 110 comprises finely divided silicon.

[0045] The active layer 106 includes a relatively large amount of active material particles. In some embodiments, the active layer 106 includes at least 50.0% active material particles by weight of the active layer. In some embodiments, the active layer 106 includes 70.0%-90.0% active material particles by weight of the active layer. In some embodiments, the active layer 106 includes more than 80% active material particles by weight of the active layer.

[0046] According to various embodiments, the active layer 106 includes a polymer additive. The polymer additive may provide mechanical support to at least a subset of the plurality of active material particles 110 and / or at least a portion of the three-dimensional network of high aspect ratio carbon elements 108. For example, the polymer additive may bond or adhere to the active material particles or carbon elements such as carbon nanotubes (e.g., multi-walled carbon nanotubes and / or single-walled carbon nanotubes). According to various embodiments, electrochemically stable polymers are found to have beneficial properties as polymer additives to the active layer 106. The polymer additive may be selected as a polymer that is completely soluble or highly soluble in a solvent used to process the electrode 100. For example, the polymer additive is soluble or highly soluble in water or an alcohol such as ethanol. In some embodiments, the polymer additive is processable in water.

[0047] According to various embodiments, the polymer additive has a relatively high tensile strength. For example, the polymer additive comprises a polymer that is difficult to stretch. In some embodiments, the polymer additive has a relatively high tensile strength and is processable in water or alcohol. In some embodiments, the polymer additive has a relatively high tensile strength and is processable in water (e.g., relatively easily processable using water). In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 20 MPa at about 10% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 30 MPa at about 10% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of 30 MPa to 35 MPa at about 10% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 10 MPa at about 20% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 20 MPa at about 20% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 25 MPa at about 20% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of 25 MPa to 30 MPa at about 20% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 15 MPa at 5% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 18 MPa at 5% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of greater than 20 MPa at 5% strain. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of 15 MPa to 25 MPa at 5% strain. In some embodiments, the polymer additive comprises a polymer having a maximum strength of greater than 20 MPa. In some embodiments, the polymer additive comprises a polymer having a maximum strength of greater than 25 MPa. In some embodiments, the polymer additive comprises a polymer having a maximum strength of greater than 30 MPa. In some embodiments, the polymer additive comprises a polymer having a maximum strength of 30 MPa to 35 MPa. In some embodiments, the polymer additive comprises a polymer having a maximum strength of about 33 MPa.In some embodiments, the polymer additive comprises a polymer having a Young's modulus greater than 5.5 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus greater than 7 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus greater than 7.5 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of about 8 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus between 5.5 MPa and 10 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus between 7 MPa and 10 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus between 7 MPa and 8.5 MPa.

[0048] In some embodiments, the polymer additive comprises one or more of a polyolefin, a poly(acrylic acid), and a styrene butadiene rubber (SBR). In some embodiments, the polymer additive comprises an AquaCharge binder.

[0049] According to various embodiments, the electrode comprises 89 wt% Wacker fine silicon + 1 wt% pre-dispersed single-walled carbon nanotube NeoCarbonix ethanolic suspension + 10 wt% AquaCharge binder (10 wt% aqueous solution). AQUACHARGE is a trade name for an aqueous binder for electrodes developed using water-soluble resin technology. AQUACHARGE is manufactured by Sumitomo Seika Chemicals Co., Ltd., Hyogo Prefecture, Japan. A similar example is provided in U.S. Patent No. 8,124,277, entitled "Binder for electrode formation, slurry for electrode formation using the binder, electrode using the slurry, rechargeable battery using the electrode, and capacitor using the electrode," which is incorporated herein by reference in its entirety. Further examples include polyacrylic acid (PAA), which is a synthetic polymer of acrylic acid, sodium polyacrylate, which is the sodium salt of polyacrylic acid, and the like.

[0050] Related art electrodes generally use polymer binders that are soluble only in toxic or environmentally unfriendly solvents. Polymer binders are used to disperse, adhere, and bind particles and allow them to survive in harsh environments. Energy storage device batteries can gradually lose capacity over cycling and hundreds or thousands of charge / discharges. Polymer binders can help maintain the capacity of the energy storage device over its operating life.

[0051] According to various embodiments, the electrode 100 and / or active layer 106 does not include (e.g., does not contain) a polymer additive that is not processable or soluble in one or more of water or an alcohol, such as ethanol. In some embodiments, the electrode is substantially free of a polymer additive that is not processable or soluble in one or more of water or an alcohol, such as ethanol. In some embodiments, the electrode 100 and / or active layer 106 of the electrode 100 is not included or substantially free of a polymer additive that is not soluble in one or more of water or an alcohol, such as ethanol. For example, any polymer additive to the electrode 100 according to various embodiments is soluble in one or more of water and an alcohol (e.g., methanol, ethanol, etc.).

[0052] The polymer additive may be selected based at least in part on its response to a particular electrolyte used in an energy storage device including electrode 100. In some embodiments, a polymer additive having a relatively high (e.g., very high) molecular weight is selected because such a polymer additive is generally resistant to the solvent. For example, a polymer additive having a high molecular weight will not dissolve in the solvent, while a polymer having a low molecular weight will become sludgy. In some embodiments, the polymer additive is selected as a polymer that does not soften (e.g., softens below a flexibility threshold) when mixed with the electrolyte. In some embodiments, the polymer additive is selected as a polymer that does not substantially expand (e.g., does not swell or expand above a predetermined swelling threshold) when wetted / mixed with the electrolyte used in the energy storage device.

[0053] The active layer 106 may include a polymer additive that is processable or soluble in water and / or alcohol, such as ethanol. In some embodiments, the polymer additive has a relatively high molecular weight. For example, the polymer additive has a molecular weight greater than 200 g / mol. In some embodiments, the polymer additive has a molecular weight greater than 400,000 g / mol. In some embodiments, the polymer additive has a molecular weight greater than 500,000 g / mol. In some embodiments, the polymer additive has a molecular weight greater than 1,000,000 g / mol. In some embodiments, the polymer additive has a molecular weight between 500,000 g / mol and 1,500,000 g / mol.

[0054] The polymer additive is 1.0 g / cm 3 ~2.5g / cm 3 In some embodiments, the polymer additive may have a specific gravity of 1.135 g / cm 3 In some embodiments, the polymer additive has a specific gravity of greater than 1.20 g / cm 3 The specific gravity of the polymer additive may be measured according to ASTM D792 test method.

[0055] The polymer additive may have a specific heat of 1.5 J / g°C at 23°C to 3.5 J / g°C at 23°C. In some embodiments, the polymer additive has a specific heat of greater than 2.0 J / g°C at 23°C. In some embodiments, the polymer additive has a specific heat of greater than 2.2 J / g°C at 23°C. In some embodiments, the polymer additive has a specific heat of about 2.4 J / g°C at 23°C. The specific heat of the polymer additive may be measured based on DSC measurements.

[0056] The polymer additive may have a tensile strength of 4 MPa to 100 MPa when the polymer additive is dry. As an example, the polymer additive has a tensile strength of 4 MPa to 70 MPa when the polymer additive is dry. In some embodiments, the polymer additive has a tensile strength of less than 70 MPa when measured when the polymer additive is dry. In some embodiments, the polymer additive has a tensile strength of less than 50 MPa when measured when the polymer additive is dry. In some embodiments, the polymer additive comprises a polymer that exhibits a stress of 15 MPa to 25 MPa at 5% strain. In some embodiments, the polymer additive comprises a polymer that has a maximum strength of greater than 20 MPa. In some embodiments, the polymer additive comprises a polymer that has a maximum strength of greater than 25 MPa. In some embodiments, the polymer additive comprises a polymer that has a maximum strength of greater than 30 MPa. In some embodiments, the polymer additive comprises a polymer that has a maximum strength of 30 MPa to 35 MPa. In some embodiments, the polymer additive comprises a polymer that has a maximum strength of about 33 MPa. In some embodiments, the polymer additive comprises a polymer that has a Young's modulus of greater than 5.5 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus greater than 7 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus greater than 7.5 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of about 8 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of 5.5 MPa to 10 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of 7 MPa to 10 MPa. In some embodiments, the polymer additive comprises a polymer having a Young's modulus of 7 MPa to 8.5 MPa. The tensile strength of the polymer additive may be measured according to the ASTM D638 test method.

[0057] The polymer additive has a yield point elongation of greater than 4%. As an example, the polymer additive has a yield point elongation of greater than 4% and less than 50% when measured when the polymer additive is dry. In some embodiments, the polymer additive has a yield point elongation of greater than 5% when measured when the polymer additive is dry. In some embodiments, the polymer additive has a yield point elongation of greater than 10% when measured when the polymer additive is dry. In some embodiments, the polymer additive has a yield point elongation of greater than 20% when measured when the polymer additive is dry. In some embodiments, the polymer additive has a yield point elongation of greater than 25% when measured when the polymer additive is dry. In some embodiments, the polymer additive has a yield point elongation of 20% to 30% when measured when the polymer additive is dry. The yield point elongation of the polymer additive may be measured according to the ASTM D638 test method.

[0058] According to various embodiments, the active layer 106 includes a polymer additive selected from the family of polyamides, or modified polyamides or derivatives of polyamides. The polymer additive is soluble in water or alcohol, such as ethanol. In some embodiments, the polymer additive has a relatively high molecular weight. The polymer additive may be at least partially disposed within at least one void defined by the network of high aspect ratio carbon elements. In some embodiments, the polymer additive acts as a polymer binder. Upon cooling a mixture of the polymer additive and ethyl cellosolve, the polymer additive may exhibit gelation. As an example, the polymer additive may be completely soluble in each of water, ethylene glycol, benzyl alcohol, acetic acid, and isobutanol. As an example, the polymer additive is completely soluble in N-methylpyrrolidone. The solubility of the polymer additive may be measured by adding 10 g of the polymer additive to 100 ml of a particular solvent, stirring the mixture at 80° C. for about 3 hours, cooling the mixture to room temperature after stirring, and then observing the mixture.

[0059] Because the polymer additive provides mechanical support for the electrode 100 (e.g., provides mechanical support for the active material particles and / or carbon elements), the polymer additive is selected such that the polymer additive has a glass transition temperature that is generally outside the operating temperature of the energy storage device. In some embodiments, the polymer additive has a glass transition temperature less than 0° C. In some embodiments, the polymer additive has a glass transition temperature less than −10° C. In some embodiments, the polymer additive has a glass transition temperature less than −25° C. In some embodiments, the polymer additive has a glass transition temperature less than −30° C. In some embodiments, the polymer additive has a glass transition temperature less than −40° C. In some embodiments, the polymer additive has a glass transition temperature less than −45° C. In some embodiments, the polymer additive has a glass transition temperature between −50° C. and −40° C. The glass transition temperature of the polymer additive may be measured based on DSC measurements.

[0060] According to various embodiments, the polymer additive has a 5% weight loss temperature of 375° C. to 400° C. In some embodiments, the polymer additive has a 5% weight loss temperature of about 385° C. The polymer additive may be selected such that an aqueous solution of the polymer additive and at least one of water and an alcohol exhibits a viscosity of at least 60 Pa·s at a concentration of about 50% by weight of the polymer additive.

[0061] The active layer 106 may include less than 5% of the polymer additive by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer 106 is about 8% by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer 106 is 8% or less by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer 106 is about 10% by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer 106 is 10% or less by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer 106 is less than 12% by weight of the active layer. In some embodiments, the amount of polymeric material in the active layer 106 is less than 15% by weight of the active layer.

[0062] Examples of polymer additives are polyolefins, poly(acrylic acid), styrene butadiene rubber (SBR), polyethylene oxide (PEO), polyethers, derivatives of poly(ethylene glycol) (PEG), fluorine-containing polymers, in particular poly(vinylidene difluoride) (PVDF), polyurethane (PU), polytetrafluoroethylene (PTFE), alginates (Alg), regenerated DNA / Alg, Alg-catechol, PAA-catechol, carboxymethyl chitosan, guar gum, agarose, konjac glucomannan, carboxymethylated gellan gum, PDA-PAA-PEO, pectin / PAA, partially retinized PAA and Nafion, sequence-defined peptoids, PMDOPA, branched PAA, NaPAA-g-CMC, CS-g-PAAN. a, PVA-g-PAA, GC-g-LiPAA, PVDF-g-PAA, branched PAA-PEG, CS-g-PANI, hyperbranched β-cyclodextrin, double helix natural xanthan gum, Li-Nafion, PAA / CMC, crosslinked PAA / PVA, glycerol crosslinked PEDOT:PSS, MAH crosslinked corn starch, MAH crosslinked CMC, crosslinked natural GG polymer, crosslinked chitosan, CS-CG+GA, crosslinked dextrin, crosslinked CMC-PEG, crosslinked hyperbranched PEI, crosslinked PAM hydrogel, crosslinked PU elastomer, crosslinked PVA-PEI, TMM functionalized PVA network, polyamide (e.g., nylon), functionalized polyamide, PEO copolymers and polyamide-containing polymers, self-healing polymers, self-healing PAU-g-PEG, Ca-Upy supramolecular self-healing polymers, self-healing PAU-g-PEG ... 2+ Crosslinked SA hydrogel, (Fe 3+ ) Crosslinking (PANa 0.8 Fe y ), Sn 4+ Cross-linked PEDOT:PSS, PAA-PEG-PBI, cross-linked CMC-CPAM, metal polymer, Si@Fe 3+-PDA-PAA, β-CDp / 6AD, slide-ring PR-PAA, conductive PFFOMB, PEG-grafted PFP, PF-COONa, PFPQ-COONa, pyrene-based (PPyE), pyrene-based (PPyMAA), pyrene-based (PPyMADMA), PANI, FA-doped PEDOT:PSS, stretchable conductive adhesive, poly(phenanthrenequinone), cyclized PAN, PAA-P(HEA-co-DMA), PEDOT:PSS / PEO / PEI, PAA / PVA+elastic gel polymer electrolyte, PAA+BFPU, hybrids of PU and poly(acrylic acid) (PAA), copolymers of any subset of the above, and the like. Zhao, YM., et al. 2021, "Various other polymers may be implemented as the polymeric additive," InfoMat, Vol. 3, Issue 5, p. 460-501 (hereinafter "Zhao") provides a description of various polymers that may be implemented as polymeric additives. Zhao is incorporated herein in its entirety for all purposes.

[0063] In some embodiments, a surface treatment 202 (not shown, see FIG. 2) is applied on the surface of the high aspect ratio carbon elements 108 of the network. The surface treatment promotes adhesion between the high aspect ratio carbon elements and the active material particles 110. The surface treatment may also promote adhesion between the high aspect ratio carbon elements and the current collector 102 (also referred to herein as the "conductive layer"), the optional adhesion layer 104, and / or at least a subset of the active material particles 110. The surface treatment may include a surfactant layer coupled to the high aspect ratio carbon elements 108, the surfactant layer including a plurality of surfactant elements each having a hydrophobic end and a hydrophilic end, the hydrophobic end disposed proximal to one surface of the high aspect ratio carbon elements 108 and the hydrophilic end disposed distal to said one surface of the high aspect ratio carbon elements 108. In some embodiments, the surface treatment 202 includes at least a portion of a polymer additive. In some embodiments, the surface treatment includes a material that is soluble in a solvent having a boiling point less than 202° C. In some embodiments, the surface treatment comprises a material that is soluble in a solvent having a boiling point below 185°C.

[0064] In some embodiments, the surface treatment 202 may form a layer of carbonaceous material resulting from pyrolysis of a polymeric material disposed on the high aspect ratio carbon elements. This layer of carbonaceous material (e.g., graphitic or amorphous carbon) may attach (e.g., via covalent bonds) or otherwise promote adhesion to the active material particles. An example of a suitable pyrolysis technique is described in U.S. Patent Application No. 63 / 028,982, filed May 22, 2020. One polymeric material suitable for use in this technique is polyacrylonitrile (PAN).

[0065] According to various embodiments, the active layer 106 includes a dispersant. The dispersant may be selected based on its compatibility with water and / or alcohol, such as ethanol. In some embodiments, the dispersant is a water-soluble polymer. In some embodiments, the dispersant is an alcohol-soluble polymer. In some embodiments, the dispersant is a polymer processable in water or alcohol. In some embodiments, the dispersant corresponds to or includes polyvinylpyrrolidone (PVP). The PVP used in the dispersant may be a PVP having a relatively high molecular weight.

[0066] According to various embodiments, the active layer 106 comprises about 25% dispersant by weight of the active layer 106. In some embodiments, the amount of dispersant in the active layer 106 is between 10% and 50% by weight of the active layer 106. In some embodiments, the amount of dispersant in the active layer 106 is between 15% and 40% by weight of the active layer 106. In some embodiments, the amount of dispersant in the active layer 106 is between 20% and 30% by weight of the active layer 106.

[0067] 1B is a diagram of an electrode according to various embodiments. In the example shown, an electrode 125 is provided. According to various embodiments, the electrode 125 comprises a current collector 128 and an active layer 132. The electrode 125 may optionally include an adhesion layer 130. By way of example, the adhesion layer 130 includes a material that promotes adhesion between the current collector 128 and the active layer 132. In some embodiments, the current collector 128 corresponds to (or is similar to) the current collector 102 of FIG. 1A.

[0068] In some embodiments, active layer 132 corresponds to (or is similar to) current active layer 106 of Figure 1A. According to various embodiments, the active layer of the electrode includes a set of multi-walled carbon nanotubes (e.g., shown at 134, shown in solid lines) and a set of single-walled carbon nanotubes (e.g., shown at 136, shown in dotted lines). In some embodiments, the average aspect ratio of the set of multi-walled carbon nanotubes is greater than the average aspect ratio of the set of single-walled carbon nanotubes.

[0069] According to various embodiments, active layer 132 (including multi-walled carbon nanotubes and single-walled carbon nanotubes) comprises 0.25% to 4% by weight of the active layer. In some embodiments, active layer 132 comprises 0.01% to 2% by weight of the active layer. In some embodiments, active layer 136 comprises 0.5% to 1.5% by weight of the active layer. According to various embodiments, the activity of the multi-walled carbon nanotubes in active layer 132 is The weight ratio of the active layer of multi-walled carbon nanotubes in active layer 132 to the single-walled carbon nanotubes in active layer 132 is about 2:1. In some embodiments, the weight ratio of the active layer of multi-walled carbon nanotubes in active layer 132 to the single-walled carbon nanotubes in active layer 132 is about 5:1. In some embodiments, the weight ratio of the active layer of multi-walled carbon nanotubes in active layer 132 to the single-walled carbon nanotubes in active layer 132 is about 9:1. In some embodiments, the weight ratio of the active layer of multi-walled carbon nanotubes in active layer 132 to the single-walled carbon nanotubes in active layer 132 is at least 7:1.

[0070] In some embodiments, the amount of multi-walled carbon nanotubes in active layer 132 is 0.25% to 5% by weight of the active layer. In some embodiments, the amount of single-walled carbon nanotubes in active layer 132 is 0.01% to 2% by weight of the active layer. In some embodiments, the amount of multi-walled carbon nanotubes in active layer 132 is 3% to 6% by weight of the active layer. In some embodiments, the amount of multi-walled carbon nanotubes in active layer 132 is 3% to 5% by weight of the active layer. In some embodiments, the amount of multi-walled carbon nanotubes in active layer 132 is 4% to 5% by weight of the active layer. In some embodiments, the amount of multi-walled carbon nanotubes in active layer 132 is about 4% by weight of the active layer.

[0071] In some embodiments, the active layer 132 includes additional graphite. Graphite may be used to increase coulombic efficiency. Graphite is conductive and can eliminate swollen shapes. In some embodiments, the active layer 132 of the electrode includes at least 5% graphite by weight of the active layer 132. In some embodiments, the active layer 132 of the electrode includes between 4% and 7% graphite by weight of the active layer 132. In some embodiments, the active layer 132 of the electrode includes about 5% graphite by weight of the active layer 132. In some embodiments, the active layer 132 of the electrode includes at least 10% graphite by weight of the active layer 132. In some embodiments, the active layer 132 of the electrode includes at least 15% graphite by weight of the active layer 132. In some embodiments, the active layer 132 includes at least 20% graphite by weight of the active layer 132.

[0072] The single-walled carbon nanotubes included in the electrode exhibit, on average, a longer length than the single-walled carbon nanotubes of related art electrodes. A slurry having a high viscosity is prepared and is subjected to relatively low shear forces during processing. The multi-walled carbon nanotubes can be characterized using a scanning electron microscope (SEM). According to various embodiments, the single-walled carbon nanotubes include a length range of 1 nm to 34 nm. The average length of the single-walled carbon nanotubes may be 7 to 8 microns. In some embodiments, the single-walled carbon nanotubes include an average diameter of 1 nm to 2 nm and an average length of about 5 microns. In some embodiments, the single-walled carbon nanotubes include an average diameter of 3 nm to 5 nm and an average length of at least 200 microns. In some embodiments, the single-walled carbon nanotubes include an average diameter of 3 nm to 5 nm and an average length of 7 to 8 microns. In some embodiments, the single-walled carbon nanotubes include an average diameter of 5 nm to 6 nm and an average length of 7 to 8 microns. In some embodiments, the single-walled carbon nanotubes include, on average, one or two walls.

[0073] 1C is a diagram of an electrode according to various embodiments. In the illustrated example, the active layer of the electrode 150 includes functionalized carbon elements. As an example, the functionalized carbon elements may be obtained at least in part based on subjecting high aspect ratio carbon elements 108 (e.g., sets of multi-walled carbon nanotubes and / or sets of single-walled carbon nanotubes, etc.) of the active layer 106 of the electrode 100 shown in FIG. 1A to a surface treatment.

[0074] In some embodiments, the functionalized carbon elements are formed from a dried (e.g., freeze-dried) aqueous dispersion that includes nanoform carbon and a functionalizing material, such as a surfactant, In some such embodiments, the aqueous dispersion is substantially free of materials that damage the carbon elements, such as acids.

[0075] In some embodiments, the surface treatment of the high aspect ratio carbon elements comprises 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 comprises a self-assembled and / or self-limiting polymer layer. In some embodiments, the thin polymer layer bonds to the active material, for example, via hydrogen bonding.

[0076] In some embodiments, the thin polymer layer may have a thickness perpendicular to the outer surface of the carbon element that is less than 3, 2, 1, 0.5, 0.1 times (or less) the minor dimension of the element.

[0077] In some embodiments, the thin polymer layer includes functional groups (e.g., pendant functional groups) that bond to the active material through non-covalent bonds, such as π-π bonds, In some such embodiments, the thin polymer layer can form a stable coating layer over at least a portion of the carbon element.

[0078] In some embodiments, the thin polymer layer on some of the elements may be bonded to a current collector or adhesive layer disposed above and below the active layer containing the energy storage (i.e., active) material. For example, in some embodiments, the thin polymer layer includes side functional groups that bond to the surface of the current collector or adhesive layer via non-covalent bonds, such as π-π bonds. In some such embodiments, the thin polymer layer may form a stable coating layer on at least a portion of the elements. In some embodiments, this arrangement provides excellent mechanical stability of the electrode.

[0079] 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 may include one or more additives used to further improve the properties of the solvent, such as low boiling additives, such as acetonitrile (ACN), deionized water, and tetrahydrofuran. In this example, the mixture is formed in a solvent that does not include NMP.

[0080] In yet another exemplary embodiment, the surface treatment may be formed from a layer of carbonaceous material resulting from pyrolysis of a polymeric material disposed on the high aspect ratio carbon element. This layer of carbonaceous material (e.g., graphitic or amorphous carbon) may attach (e.g., via covalent bonds) to or otherwise promote adhesion with the active material particles. An example of a suitable pyrolysis technique is described in U.S. Patent Application No. 63 / 028,982, filed May 22, 2020, which is incorporated herein in its entirety for all purposes. One suitable polymeric material for use in this technique is polyacrylonitrile (PAN).

[0081] According to various embodiments, the active layer 106 includes a dispersant. The dispersant may be selected based on its compatibility with water and / or alcohol, such as ethanol. In some embodiments, the dispersant is a water-soluble polymer. In some embodiments, the dispersant corresponds to or includes polyvinylpyrrolidone (PVP). The PVP used in the dispersant may be a PVP having a relatively high molecular weight.

[0082] Dispersants and additives may be added to the mixture. An example of a dispersant is PVP. Polyvinylpyrrolidone (PVP), commonly also called "polyvidone" or "povidone", is a water-soluble polymer made from the monomer N-vinylpyrrolidone. In general, dispersants function as emulsifiers and disintegrants for solution polymerization, as well as surfactants, reducing agents, shape control agents, and dispersants in nanoparticle synthesis and their self-assembly. Another example of a dispersant includes AQUACHARGE, a trade name for an aqueous binder for electrodes developed by applying water-soluble resin technology. AQUACHARGE is manufactured by Sumitomo Seika Chemicals Co., Ltd., Hyogo Prefecture. A similar example is provided in U.S. Patent No. 8,124,277, entitled "Binder for electrode formation, slurry for electrode formation using the binder, electrode using the slurry, rechargeable battery using the electrode, and capacitor using the electrode", which is incorporated herein by reference in its entirety. Further examples include polyacrylic acid (PAA), a synthetic polymer of acrylic acid, sodium polyacrylate, a sodium salt of polyacrylic acid, and the like. [Table 1] [Table 2]

[0083] 2 is a diagram of an electrode according to various embodiments. In the example shown, a detailed view of a high aspect ratio carbon element 201 of a network 200 (as shown in FIGS. 1A and 1B) is provided, located near several active material particles 300. In the embodiment shown, the surface treatment 202 on the element 201 is a surfactant layer bonded to the outer layer of the surface of the element 201. As shown, the surfactant layer comprises a plurality of surfactant elements 210, each having a hydrophobic end 211 and a hydrophilic end 212, the hydrophobic end disposed proximal to the surface of the carbon element 201 and the hydrophilic end 212 disposed distal to the surface.

[0084] In some embodiments where the carbon element 201 is hydrophobic (as is typically the case for nanoform carbon elements such as CNTs, CNT bundles, and graphene flakes), the hydrophobic end 211 of the surfactant element 210 will be attracted to the carbon element 201. Thus, in some embodiments, the surface treatment 202 may be a self-assembled layer. For example, as described in more detail below, in some embodiments, when the carbon element 201 is mixed with the surfactant element 210 in a solvent to form a slurry, the surface treatment 202 layer self-assembles on the surface due to electrostatic interactions between the elements 201 and 210 in the slurry.

[0085] In some embodiments, the surface treatment 202 is applied onto the surface of the high aspect ratio carbon elements of the three-dimensional network (e.g., high aspect ratio carbon elements 108 of the electrode 100 of FIG. 1A). The surface treatment promotes adhesion between the high aspect ratio carbon elements and the active material particles 300 (e.g., active material particles 110 of the electrode 100 of FIG. 1A). The surface treatment may also promote adhesion between the high aspect ratio carbon elements and a current collector (also referred to herein as a "conductive layer"), such as current collector 102 of the electrode 100 of FIG. 1A, and / or an optional adhesion layer (e.g., adhesion layer 104 of the electrode 100 of FIG. 1A).

[0086] In some embodiments, the surface treatment 202 may be a self-limiting layer. For example, as described in more detail below, in some embodiments, when the element 201 is mixed with the surfactant element 210 in a solvent to form a slurry, the surface treatment 202 layer self-assembles on the surface due to electrostatic interactions between the elements 201 and 210 in the slurry. In some such embodiments, once an area of ​​the surface of the element 201 is covered with the surfactant element 210, additional surfactant elements 210 will not be attracted to that area. In some embodiments, once the surface of the element 201 is covered with the surfactant element 202, additional elements are repelled from the layer, resulting in a self-limiting process. For example, in some embodiments, the surface treatment 202 may form in a self-limiting process, thereby ensuring that the layer is thin, e.g., a single molecule or a few molecules thick.

[0087] In some embodiments, at least some of the hydrophilic ends 212 of the surfactant elements form bonds with the active material particles 300. Thus, the surface treatment 202 may provide good adhesion between the elements 201 of the network 200 and the active material particles. In some embodiments, the bonds may be covalent bonds or non-covalent bonds such as π-π bonds, hydrogen bonds, electrostatic bonds, or combinations thereof.

[0088] For example, in some embodiments, the hydrophilic ends 212 of the surfactant elements 210 have a polar charge of a first polarity, while the surfaces of the active material particles 300 have a polar charge of a second polarity opposite to that of the first polarity, and are therefore attracted to each other.

[0089] For example, in some embodiments where active material particles 300 are combined in a solvent with carbon elements 201 bearing surface treatment 202 (as described in more detail below) during formation of layer 100, the outer surface of active material particles 300 may be characterized by a zeta potential having an opposite sign to the zeta potential of the outer surface of surface treatment 202 (as known in the art). Thus, in some such embodiments, the attraction between carbon elements 201 bearing surface treatment 202 and active material product 300 promotes self-organization of the active material particles 300 into an entangled structure with carbon elements 201 of network 200.

[0090] In some embodiments, the hydrophilic ends 212 of at least some of the surfactant elements form bonds with current collector or adhesion layers underlying the active material layer 100. Thus, the surface treatment 202 may provide good adhesion between the elements 201 of the network 200 and such underlying layers. In some embodiments, the bonds may be covalent or non-covalent bonds such as π-π bonds, hydrogen bonds, electrostatic bonds, or combinations thereof. In some embodiments, this arrangement provides excellent mechanical stability of the electrode 10, as discussed in more detail below.

[0091] In various embodiments, the surfactant used to form the above-mentioned surface treatment 202 may include any suitable material. For example, in some embodiments, the surfactant may include one or more of the following: hexadecyltrimethylammonium hexafluorophosphate (CTAP), hexadecyltrimethylammonium tetrafluoroborate (CTAB), hexadecyltrimethylammonium acetate, hexadecyltrimethylammonium nitrate, hocamidopropyl betaine, N-(cocoalkyl)-N,N,N-trimethylammonium methyl sulfate, and cocamidopropyl betaine. Additional suitable materials are described below.

[0092] In some embodiments, the surfactant layer 202 may be formed by dissolving a compound in a solvent such that a layer of surfactant 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 counter ions 214 to the surfactant ions that form the surface treatment 202.

[0093] 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 be non-reactive or mildly reactive with materials used in the cell, such as the electrolyte, separator, housing, etc. For example, if an aluminum housing is used, the counterions may be selected to be non-reactive or mildly reactive with the aluminum housing.

[0094] For example, in some embodiments, the residual counterions are free or substantially free of halide groups. For example, in some embodiments, the residual counterions are free or substantially free of bromine groups.

[0095] In some embodiments, the residual counterions may be selected to be compatible with the electrolyte used in the energy storage cell containing the active layer 200. For example, in some embodiments, the residual counterions may be the same species of ions used in the electrolyte itself. For example, if the electrolyte includes a dissolved Li PF6 salt, the electrolyte anion is PF6. In such a case, the surfactant may be selected, for example, CTA PF6, such that the surface treatment 202 is formed as a layer of anions from CTA PF6, while the residual surfactant counterions are PF6 anions from CTA PF6 (and thus match the anions of the electrolyte).

[0096] In some embodiments, the surfactant material used may be soluble in a solvent that exhibits advantageous properties. For example, in some embodiments, the solvent may include water or an alcohol, such as methanol, ethanol, or 2-propanol (sometimes referred to as isopropyl alcohol, IPA), or a combination thereof. In some embodiments, the solvent may include one or more additives used to further improve the properties of the solvent, such as low-boiling additives, such as acetonitrile (ACN), deionized water, and tetrahydrofuran.

[0097] For example, if a low boiling point solvent is used to form the surface treatment 202, the solvent may be quickly removed using a thermal drying process (e.g., of the type described in more detail below) carried out at a relatively low temperature. As will be appreciated by those skilled in the art, this may improve the speed and / or cost of manufacture of the active layer 202.

[0098] 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 less, such as 100°C or less.

[0099] In some embodiments, the solvent may exhibit other advantageous properties. In some embodiments, the solvent may have a low viscosity, such as a viscosity at 20° C. of 3.0 centipoise or less, 2.5 centipoise, 2.0 centipoise, 1.5 centipoise, or less. In some embodiments, the solvent may have a low surface tension, such as a surface tension at 20° C. of 40 mN / m or less, 35 mN / m, 30 mN / m, 25 mN / m or less. In some embodiments, the solvent may have low toxicity, for example, toxicity comparable to that of alcohol, such as isopropyl alcohol.

[0100] Notably, this is in contrast to processes used to form conventional electrode active layers that feature bulk binder materials such as polyvinylidene fluoride or polyvinylidene difluoride (PVDF). Such bulk binders require aggressive solvents, often characterized by high boiling points. One such example is n-methyl-2-pyrrolidone (NMP). The use of NMP (or other pyrrolidone-based solvents) as a solvent requires the use of high temperature drying processes to remove the solvent. Furthermore, NMP is expensive, requires complex solvent recovery systems, and is highly toxic, posing significant safety hazards. In contrast, as described in more detail below, in various embodiments, the active layer 200 can be formed without the use of NMP or similar compounds such as pyrrolidone compounds.

[0101] While one class of exemplary surface treatments 202 are described above, it is understood that other treatments may be used. For example, in various embodiments, surface treatment 202 may be formed by functionalizing high aspect ratio carbon elements 201 using any suitable technique described herein or known in the art. The functional groups applied to elements 201 may be selected to promote adhesion between active material particles 300 and network 200. For example, in various embodiments, the functional groups may include carboxyl groups, hydroxyl groups, amine groups, silane groups, or combinations thereof.

[0102] As described in more detail below, in some embodiments, the functionalized carbon elements 201 are formed from a dried (e.g., freeze-dried) aqueous dispersion comprising nanoform carbon and a functionalizing material, such as a surfactant. In some such embodiments, the aqueous dispersion is substantially free of materials that would damage the carbon elements 201, such as acids.

[0103] FIG. 3 is a diagram of electrodes according to various embodiments.

[0104] 3, in some embodiments, the surface treatment 202 on the high aspect ratio carbon element 201 includes polymer particles disposed on the carbon element that promote adhesion of the active material to the network. In some such embodiments, the polymer particles include a self-assembled and / or self-limiting polymer layer. In some embodiments, the polymer particles bond to the active material, for example, via hydrogen bonding.

[0105] In some embodiments, the polymer particles include functional groups (e.g., pendant functional groups) that bond to the active material via non-covalent bonds, such as π-π bonds, In some such embodiments, the polymer particles can form a stable coating layer over at least a portion of element 201.

[0106] In some embodiments, the polymer particles on some of the elements 201 may bond to the current collector 101 or adhesion layer 102 underlying the active layer 200. For example, in some embodiments, the polymer particles include pendant functional groups that bond to the surface of the current collector 101 or adhesion layer 102 via non-covalent bonds, such as π-π bonds. In some such embodiments, the polymer particles may form a stable coating layer over at least a portion of the elements 201. In some embodiments, this arrangement provides excellent mechanical stability of the electrode 10, as discussed in more detail below.

[0107] 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 may include one or more additives that are used to further improve the properties of the solvent, such as low-boiling additives, such as acetonitrile (ACN), deionized water, and tetrahydrofuran.

[0108] Suitable examples of materials that may be used for the polymer particles include water-soluble polymers such as polyvinylpyrrolidone.

[0109] FIG. 4 is an example of an electron microscope image of an active layer according to various embodiments.

[0110] Referring to Figure 4, an electron microscope photograph of an exemplary active material layer of the type described herein is shown. The vine-like, high aspect ratio carbon elements (formed from CNT bundles) are clearly shown intertwined with the active material particles. In some embodiments, the active layer is free of bulky polymeric materials that occupy space within the layer.

[0111] FIG. 5 is a schematic diagram of an energy storage device.

[0112] 5, there is shown an energy storage cell 500 including a first electrode 501, a second electrode 502, a permeable separator 503 disposed between the first electrode 501 and the second electrode 502, and an electrolyte 504 that wets the first and second electrodes. Either or both of the electrodes 501, 502 can be of a type described herein.

[0113] In some embodiments, the energy storage cell 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, 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, Volume 1, Issue 1, Pages 18-42, which is incorporated herein by reference in its entirety.

[0114] In some such embodiments, the energy storage cell may have an operating voltage in the range of 1.0V to 5.0V, or any subrange therein, for example, 2.3V to 4.3V.

[0115] In some such embodiments, the energy storage cell 500 may have an operating temperature range including -40°C to 100°C, or any sub-range thereof, such as -10°C to 60°C.

[0116] In some such embodiments, the energy storage cell 500 may 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.

[0117] In some such embodiments, the energy storage cell 500 may 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.

[0118] In some such embodiments, the energy storage cell 500 may have a C-rate in the range of 0.1-50.

[0119] In some such embodiments, the energy storage cell 500 may 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.

[0120] In some embodiments, the energy storage cell 500 may be a lithium ion capacitor of the type described in U.S. Patent Application No. 63 / 021492, filed May 8, 2020, the entire contents of which are incorporated herein by reference.

[0121] In some such embodiments, the energy storage cell 500 may have an operating temperature range including -60°C to 100°C, or any sub-range thereof, such as -40°C to 85°C.

[0122] In some such embodiments, the energy storage cell 500 may 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.

[0123] In some such embodiments, the energy storage cell 500 may 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.

[0124] In some such embodiments, the energy storage cell 500 may have a gravimetric power density of at least 5 kW / kg, 7.5 kW / kg, 10 kW / kg, 12.5 kW / kg, 14 kW / kg, 15 kW / kg, or more.

[0125] In some such embodiments, the energy storage cell 500 may 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.

[0126] In some such embodiments, the energy storage cell 500 may have a C-rate in the range of 1.0-100.

[0127] In some such embodiments, the energy storage cell 500 may have a cycle life of at least 100,000, 500,000, 1,000,000 or more charge / discharge cycles.

[0128] Manufacturing method Electrode 100 including active layer 106 of FIG. 1A and electrode 125 including active layer 132 of FIG. 1B as described herein may be fabricated using any suitable manufacturing process. As will be appreciated by one of ordinary skill in the art, in some embodiments, electrode 10 may be fabricated using wet coating techniques of the type described in International Patent Publication No. WO 2018 / 102652, published June 7, 2018, with further consideration of the teachings described herein.

[0129] 6 is a flow chart of a method for making an electrode according to various embodiments. A description of process 600 is provided with respect to electrode 100 of FIG. 1A. Process 600 may similarly be implemented in connection with the manufacture of electrodes according to various embodiments disclosed herein, including electrode 125 of FIG. 1B.

[0130] 6, in some embodiments, the active layer of an electrode (e.g., 106 of electrode 100) may be formed using process 600. The manufacture or processing of the active layer and / or electrode is further described in U.S. Patent Application No. PCT / US2021 / 53519, filed October 5, 2021, which is incorporated by reference herein in its entirety for all purposes.

[0131] At 610, the high aspect ratio carbon elements 201 and a surface treatment material (eg, a surfactant or polymeric material described herein) are combined with a solvent (of the type described herein) to form an initial slurry.

[0132] At 620, the initial slurry is treated to ensure good dispersion of the solid materials in the slurry. In some embodiments, this treatment involves introducing mechanical energy to the mixture of solvent and solid materials (e.g., using a sonicator, sometimes also referred to as a "sonifier") or other suitable mixing device (e.g., a high shear mixer). In some embodiments, the mechanical energy introduced to 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 to the mixture per kilogram of mixture may be in the range of 0.4 kWh / kg to 1.0 kWh / kg, or any subrange therein, such as 0.4 kWh / kg to 0.6 kWh / kg.

[0133] In some embodiments, an ultrasonic bath mixer may be used. In other embodiments, a probe sonicator may be used. Probe sonication may be significantly more powerful and effective compared to ultrasonic baths for nanoparticle applications. The high shear forces generated by ultrasonic cavitation have the ability to break down particle agglomerates, resulting in smaller, more uniform particle sizes. Among other things, sonication results in a stable, homogenous suspension of solids in a slurry. Generally, this results in dispersion, deagglomeration, and other breakdown of solids. An example of a probe sonicator includes the Q Series Probe Sonicator available from QSonica LLC of Newtown, Connecticut. Another example includes the Branson Digital SFX-450 Sonicator available from Thomas Scientific of Swedesboro, New Jersey.

[0134] However, in some embodiments, the localization of each probe within the probe assembly may result in non-uniform mixing and suspension. For example, this may be the case for large samples. This can be overcome by using a device with a continuous flow cell and appropriate mixing. For example, such a device can achieve a reasonably uniform dispersion when mixing a slurry.

[0135] 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 subrange therein, such as, for example, 6,000 cps to 19,000 cps.

[0136] At 630, the surface treatment 202 may be fully or partially formed on the high aspect ratio carbon elements 201 in the initial slurry. In some embodiments, at this stage, the surface treatment 202 may self-assemble, as described in detail above with reference to Figures 2 and 3. The resulting surface treatment 201 may include functional groups or other features that may promote adhesion between the high aspect ratio carbon elements 201 and the active material particles 300, as described in further steps below.

[0137] At 640, the active material particles 300 may be combined with the initial slurry to form a final slurry containing the active material particles 300 with the high aspect ratio carbon elements 201 having the surface treatment 202 formed thereon.

[0138] In some embodiments, active material 300 may be added directly to the initial slurry. In other embodiments, active material 300 may first be dispersed in a solvent (e.g., using the techniques described above for the initial solvent) to form an active material slurry. This active material slurry can then be mixed with the initial slurry to form the final slurry.

[0139] At 650, the final slurry is processed to ensure good dispersion of the solid materials in the final slurry. In various embodiments, any suitable mixing process known in the art may be used. In some embodiments, this processing may use the techniques described above with respect to 620. In some embodiments, a planetary mixer may be used, such as a multi-shaft (e.g., three or more shafts) planetary mixer. In some such embodiments, the planetary mixer may feature multiple blades, e.g., two or more mixing blades and one or more (e.g., two, three, or more) dispersion blades, such as a disk dispersion blade.

[0140] In some embodiments, during 650, the matrix 200 entangled with the active material 300 may fully or partially self-assemble, as described in detail above with respect to Figures 2 and 3. In some embodiments, an interaction between the surface treatment 202 and the active material 300 facilitates the self-assembly process.

[0141] 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 subrange therein, such as, for example, in the range of 2,500 cps to 6,000 cps.

[0142] At 660, the active layer 106 is formed from the final slurry. In some embodiments, the final slurry can be poured wet directly onto the current collector conductive layer 102 (or optional adhesive layer 104) and dried. By way of example, pouring can be done by applying at least one of heat and vacuum until substantially all of the solvent and any other liquids are removed, thereby forming the active layer 106. In some such embodiments, it may be desirable to protect various portions of the underlying layers. For example, if the electrode 100 is intended for double-sided operation, it may be desirable to protect the underside of the conductive layer 102. Protection may include, for example, protection from the solvent by masking certain areas or providing a drain to drain the solvent.

[0143] In other embodiments, the final slurry may be at least partially dried elsewhere using any suitable technique (e.g., roll-to-roll layer application) and then transferred onto the adhesive layer 104 or conductive layer 102 to form the active layer 106. In some embodiments, the wetted mixed slurry may be placed onto an intermediate material having a suitable surface and dried to form a layer (e.g., active layer 106). While any material having a suitable surface may be used as the intermediate material, an exemplary intermediate material includes PTFE, as its properties facilitate its subsequent removal from the surface. In some embodiments, the designated layer is formed in a press to provide a layer exhibiting a desired thickness, area, and density.

[0144] In some embodiments, the final slurry may be formed into a sheet and coated onto the adhesive layer 104 or the conductive layer 102, as appropriate. For example, in some embodiments, the final slurry may be applied through a slot die to control the thickness of the applied layer. In other embodiments, the slurry may be applied and then leveled to the desired thickness using, for example, a doctor blade. A variety of other techniques may be used to apply the slurry. For example, coating techniques may include, but are not limited to, comma coating, comma reverse coating, doctor blade coating, slot die coating, direct gravure coating, air doctor coating (air knife), chamber doctor coating, offset gravure coating, one roll kiss coating, reverse kiss coating with a small diameter gravure roll, bar coating, three reverse roll coating (top feed), three reverse roll coating (fountain die), reverse roll coating, and the like.

[0145] The viscosity of the final slurry may vary depending on the application technique. For example, for comma coating, the viscosity may range from about 1,000 cps to about 200,000 cps. Lip die coating provides coatings with slurries exhibiting viscosities of about 500 cps to about 300,000 cps. Reverse kiss coating provides coatings with slurries exhibiting viscosities of about 5 cps to 1,000 cps. In some applications, each layer may be formed in multiple passes.

[0146] In some embodiments, the active layer 106 formed from the final slurry may be compressed (e.g., using a calendaring apparatus) before or after it is applied to the electrode 100. In some embodiments, the slurry may be partially or completely dried (e.g., by application of heat, vacuum, or a combination thereof) before or during the compression process. For example, in some embodiments, the active layer may be compressed (e.g., in a direction perpendicular to the current collector layer 102) to a final thickness that is less than 90%, 80%, 70%, 50%, 40%, 30%, 20%, 10% or less of its pre-compression thickness.

[0147] In various embodiments, if a partially dried layer is formed during the coating or pressing process, the layer may then be fully dried (e.g., by application of heat, vacuum, or a combination thereof). In some embodiments, substantially all of the solvent is removed from the active layer 106.

[0148] In some embodiments, the solvent used to form the slurry is recovered and recycled into the slurry manufacturing process.

[0149] In some embodiments, the active layer 106 may be compressed, for example, to break down some of the constituent high aspect ratio carbon elements or other carbonaceous materials and increase the surface area of ​​each layer. In some embodiments, this compression process may increase one or more of the adhesion between the layers, the rate of ion transport within the layers, and the surface area of ​​the layers. In various embodiments, compression may be applied before or after each layer is applied to or formed on the electrode 100.

[0150] In some embodiments where calendaring is used to compress the active layer 106, the calendaring equipment may be set with a gap spacing equal to less than 90%, 80%, 70%, 50%, 40%, 30%, 20%, 10% or less of the pre-compressed thickness of the layer (e.g., set at about 33% of the pre-compressed thickness of the layer). The calendar rolls may be configured to provide a suitable pressure, for example, greater than 1 ton per cm of roll length, greater than 1.5 ton per cm of roll length, greater than 2.0 ton per cm of roll length, greater than 2.5 ton per cm of roll length, or more. 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 subrange therein, for example, 2.5 g / cc to 4.0 g / cc. In some embodiments, the calendaring process may be carried out at a temperature in the range of 20° C. to 140° C., or any subrange therein. In some embodiments, the active layer 106 can be preheated prior to calendering, for example at a temperature in the range of 20° C. to 100° C., or any subrange thereof.

[0151] Once the electrode 100 is assembled, an energy storage device can be assembled using the electrode 100. Assembly of the energy storage device can follow the conventional steps used to assemble an electrode with a separator and place it into a housing, such as a canister or pouch, and can further include additional steps for adding electrolyte and sealing the housing.

[0152] In various embodiments, the process 600 may include any of the following features (individually or in any suitable combination).

[0153] In some embodiments, the initial slurry has a solids content in the range of 0.1% to 20.0% by weight (or any subrange thereof), in some embodiments, the final slurry has a solids content in the range of 10.0% to 80% by weight (or any subrange thereof).

[0154] In various embodiments, the solvent used may be any of the solvents described herein with respect to forming the surface treatment 202. In some embodiments, the surfactant material used to form the surface treatment 202 may be soluble in a solvent that exhibits advantageous properties. For example, in some embodiments, the solvent may include water or an alcohol, such as methanol, ethanol, or 2-propanol (sometimes referred to as isopropyl alcohol, IPA), or a combination thereof. In some embodiments, the solvent may include one or more additives used to further improve the properties of the solvent, for example, low boiling additives such as acetonitrile (ACN), deionized water, and tetrahydrofuran.

[0155] In some embodiments, when a low boiling point solvent is used, the solvent may be quickly removed using a thermal drying process carried out at a relatively low temperature. As will be appreciated by one of ordinary skill in the art, this may improve the speed and / or cost of manufacturing the electrode 100. For example, in some embodiments, the solvent may have 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 less, such as 100° C. or less.

[0156] In some embodiments, the solvent may exhibit other advantageous properties. In some embodiments, the solvent may have a low viscosity, such as a viscosity at 20° C. of 3.0 centipoise or less, 2.5 centipoise, 2.0 centipoise, 1.5 centipoise, or less. In some embodiments, the solvent may have a low surface tension, such as a surface tension at 20° C. of 40 mN / m or less, 35 mN / m, 30 mN / m, 25 mN / m or less. In some embodiments, the solvent may have low toxicity, for example, toxicity comparable to that of alcohol, such as isopropyl alcohol.

[0157] In some embodiments, during the formation of the active layer, the material forming the surface treatment can be dissolved in a solvent that is substantially free of pyrrolidone compounds. In some embodiments, the solvent is substantially free of n-methyl-2-pyrrolidone.

[0158] In some embodiments, the surface treatment 201 is formed from a material that includes a surfactant of the type described herein.

[0159] 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 slide the elements apart along a direction perpendicular to the minor axis of the elements. In some embodiments, techniques for forming such dispersions may be adapted from those disclosed in International Patent Publication No. WO 2018 / 102652, published June 7, 2018, which is incorporated herein in its entirety for all purposes, with further consideration of the teachings described herein.

[0160] In some embodiments, the high aspect ratio carbon elements 201 may be functionalized prior to forming a slurry used to form the electrode 100. For example, in one aspect, a method is disclosed that includes dispersing the high aspect ratio carbon elements 201 and a surface treatment material in an aqueous solvent to form an initial slurry, where the dispersing step results in the formation of a surface treatment on the high aspect ratio carbon, and drying the initial slurry to remove substantially all of the water to produce a dry powder of high aspect ratio carbon having a surface treatment thereon. In some embodiments, the dry powder may be combined with, for example, a solvent and active material slurry to form a final slurry of the type described above with respect to method 600.

[0161] In some embodiments, drying the initial slurry comprises lyophilizing (freeze-drying) the initial slurry. In some embodiments, the aqueous solvent and the initial slurry are substantially free of materials that are damaging to the high aspect ratio carbon elements. In some embodiments, the aqueous solvent and the initial slurry are substantially free of acids. In some embodiments, the initial slurry consists essentially of the high aspect ratio carbon elements, the surface treatment material, and water.

[0162] Some embodiments further include dispersing the dry powder of high aspect ratio carbon in a solvent with a surface treatment and adding and active material to form a secondary slurry, coating the secondary slurry on a substrate, and drying the secondary slurry to form an electrode active layer. In some embodiments, the foregoing steps may be carried out using techniques adapted from those disclosed in International Patent Publication No. WO 2018 / 102652, published June 7, 2018, further taking into account the teachings described herein.

[0163] In some embodiments, the final slurry may include a polymer additive, such as polyacrylic acid (PAA), poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), polyacrylonitrile (PAN), polyisoprene (PIpr), polyaniline (PANi), polyethylene (PE), polyimide (PI), polystyrene (PS), polyurethane (PU), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), and the like. In some embodiments, the active layer may be treated by applying heat to pyrolyze the additive, such that the surface treatment 202 may form a layer of carbonaceous material resulting from the pyrolysis of the polymer additive. This layer of carbonaceous material (e.g., graphite or amorphous carbon) may adhere (e.g., via covalent bonds) to the active material particles 300 or may otherwise promote adhesion with the active material particles 300. The heat treatment may be applied by any suitable means, such as by application of a laser beam. Examples of suitable pyrolysis techniques are described in U.S. Patent Application No. 63 / 028982, filed May 22, 2020, which is incorporated herein in its entirety for all purposes.

[0164] Surfactants The techniques described above involve the use of surfactants for the surface treatment 202 on the high aspect ratio carbon nanotubes 201 to promote adhesion with the active material particles 300. Although several advantageously suitable surfactants are described, it should be understood that other surfactant materials may be used, including:

[0165] A surfactant is a molecule or group of molecules that has surface activity, such as a wetting agent, dispersant, emulsifier, detergent, and foaming agent. A variety of surfactants can be used in the preparation surface treatment as described herein. Typically, the surfactants used contain a lipophilic non-polar 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 alone or in combination. Thus, surfactant combinations can include anionic, cationic, nonionic, zwitterionic, amphoteric, and ampholytic surfactants, so 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 composition.

[0166] The surfactants used in the preparation of the electrode composition may be anionic, including but not limited to sulfonates such as alkyl sulfonates, alkyl benzene sulfonates, alpha olefin sulfonates, paraffin sulfonates, and alkyl ester sulfonates, sulfates such as alkyl sulfates, alkyl alkoxy sulfates, and alkyl alkoxylated sulfates, phosphates such as monoalkyl phosphates and dialkyl phosphates, phosphonates, fatty acids, alkyl alkoxy carboxylates, carboxylates such as sarcosinates, isethionates, and taurates. Specific examples of carboxylates are sodium oleate, sodium cocoyl isethionate, sodium methyl oleoyl taurate, sodium laureth carboxylate, sodium trideceth carboxylate, sodium lauryl sarcosinate, lauroyl sarcosine, and cocoyl sarcosinate. Specific examples of sulfates include sodium dodecyl sulfate (SDS), sodium lauryl sulfate, sodium laureth sulfate, sodium trideceth sulfate, sodium tridecyl sulfate, sodium cocyl sulfate, and sodium lauric monoglyceride sulfate.

[0167] Suitable sulfonate surfactants include, but are not limited to, alkyl sulfonates, aryl sulfonates, monoalkyl and dialkyl sulfosuccinates, and monoalkyl and dialkyl sulfosuccinamate salts. Each alkyl group independently contains about 2-20 carbons and may be ethoxylated with up to about 8 units, preferably up to about 6 units, for example, an average of 2, 3, or 4 units of ethylene oxide per alkyl group. Illustrative examples of alkyl and aryl sulfonates are sodium tridecylbenzene sulfonate (STBS) and sodium dodecylbenzene sulfonate (SDBS).

[0168] Illustrative examples of sulfosuccinates include, but are not limited to, dimethicone copolyol sulfosuccinate, diamyl sulfosuccinate, dicapryl sulfosuccinate, dicyclohexyl sulfosuccinate, diheptyl sulfosuccinate, dihexyl sulfosuccinate, diisobutyl sulfosuccinate, dioctyl sulfosuccinate, C12-15 pareth sulfosuccinate, cetearyl sulfosuccinate, cocopolyglucose sulfosuccinate, cocoyl butyl gluceth-10 sulfosuccinate, deceth-5 sulfosuccinate, deceth-6 sulfosuccinate, dihydroxyethyl sulfosuccinyl undecylenate, hydrogenated cottonseed glyceride sulfosuccinate, isodecyl sulfosuccinate. , isostearyl sulfosuccinate, laneth-5 sulfosuccinate, laureth sulfosuccinate, laureth-12 sulfosuccinate, laureth-6 sulfosuccinate, laureth-9 sulfosuccinate, lauryl sulfosuccinate, nonoxynol-10 sulfosuccinate, oleth-3 sulfosuccinate, oleyl sulfosuccinate, PEG-10 lauryl citrate sulfosuccinate, citrate-14 sulfosuccinate, stearyl sulfosuccinate, tallow, tridecyl sulfosuccinate, ditridecyl sulfosuccinate, bisglycol lysinosulfosuccinate, di(1,3-dimethylbutyl) sulfosuccinate, and silicone copolyol sulfosuccinate.

[0169] Illustrative examples of sulfosuccinates include, but are not limited to, lauramide-MEA sulfosuccinate, oleamide PEG-2 sulfosuccinate, cocamide MIPA-sulfosuccinate, cocamide PEG-3 sulfosuccinate, isostearamide MEA-sulfosuccinate, isostearamide MIPA-sulfosuccinate, lauramide MEA-sulfosuccinate, lauramide PEG-2 sulfosuccinate, lauramide PEG-5 sulfosuccinate, myristamide MEA-sulfosuccinate, oleamide MEA-sulfosuccinate, oleamide PIPA-sulfosuccinate, oleamide PEG-2 sulfosuccinate, palmitamide PEG-2 sulfosuccinate, palmitoleamide PEG-2 sulfosuccinate, PEG-4 cocamide MIPA-sulfosuccinate, ricinoleamide MEA-sulfosuccinate, stearamide MEA-sulfosuccinate, stearyl sulfosuccinate, talamide MEA-sulfosuccinate, tallow sulfosuccinate, tallowamide MEA-sulfosuccinate, undecylenamide MEA-sulfosuccinate, undecylenamide PEG-2 sulfosuccinate, wheat germ amide MEA-sulfosuccinate, and wheat germ amide PEG-2 sulfosuccinate.

[0170] Some examples of commercially available sulfonates are AEROSOL® OT-S, AEROSOL® OT-MSO, AEROSOL® TR70% (Cytec Inc., West Paterson, NJ), NaSul CA-HT3 (King Industries, Norwalk, Conn.), and C500 (Crompton Co., West Hill, Ontario, Canada). AEROSOL® OT-S is sodium dioctyl sulfosuccinate in petroleum fractions. AEROSOL® OT-MSO also contains sodium dioctyl sulfosuccinate. AEROSOL® TR70% is sodium bistridecyl sulfosuccinate in a mixture of ethanol and water. NaSul CA-HT3 is a calcium dinonyl naphthalene sulfonate / carboxylate complex. C500 is an oil-soluble calcium sulfonate.

[0171] Alkyl or alkyl group refers 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 or alicyclic or carbocyclic groups) (e.g., cyclopropyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, etc.), branched-chain alkyl groups (e.g., isopropyl, tert-butyl, sec-butyl, isobutyl, etc.), and alkyl substituted alkyl groups (e.g., alkyl substituted cycloalkyl groups and cycloalkyl substituted alkyl groups).

[0172] Alkyl can include both unsubstituted and substituted alkyls. Substituted alkyl refers to an alkyl group having substituents replacing one or more hydrogens on one or more carbons of the hydrocarbon backbone. Such substituents may include alkenyl, alkynyl, halogeno, hydroxyl, alkylcarbonyloxy, arylcarbonyloxy, alkoxycarbonyloxy, aryloxy, aryloxycarbonyloxy, carboxylate, alkylcarbonyl, arylcarbonyl, alkoxycarbonyl, aminocarbonyl, alkylaminocarbonyl, dialkylaminocarbonyl, alkylthiocarbonyl, alkoxyl, phosphate, phosphonate, phosphinato, cyano, amino (including alkylamino, dialkylamino, arylamino, diarylamino, and alkylarylamino), acylamino (including alkylcarbonylamino, arylcarbonylamino, carbamoyl, and ureido), imino, sulfhydryl, alkylthio, arylthio, thiocarboxylate, sulfate, alkylsulfinyl, sulfonate, sulfamoyl, sulfonamido, nitro, trifluoromethyl, cyano, azido, heterocyclic, alkylaryl, or aromatic (including heteroaromatic) groups.

[0173] In some embodiments, the substituted alkyl may include a heterocyclic group. A heterocyclic group includes a closed ring structure similar to a carbocyclic group, in which one or more of the carbon atoms in the ring is an element other than carbon, such as nitrogen, sulfur, or oxygen. A heterocyclic group may be saturated or unsaturated. Exemplary heterocyclic groups include aziridine, ethylene oxide (epoxide, oxirane), thiirane (episulfide), dioxirane, azetidine, oxetane, thietane, dioxetane, dithietane, dithiete, azolidine, pyrrolidine, pyrroline, oxolane, dihydrofuran, and furan.

[0174] In the case of anionic surfactants, the counterion is typically sodium, but can alternatively be potassium, lithium, calcium, magnesium, ammonium, amines (primary, secondary, tertiary, or quaternary), or other organic bases. Exemplary amines include isopropylamine, ethanolamine, diethanolamine, and triethanolamine. Mixtures of the above cations can also be used.

[0175] The surfactant used in the preparation of the material may be cationic. Such cationic surfactants include, but are not limited to, pyridinium-containing compounds and primary, secondary, tertiary, or quaternary organic amines. In the case of cationic surfactants, the counterion may be, for example, chloride, bromide, methosulfate, ethosulfate, lactate, saccharinate, acetate, and phosphate. Examples of cationic amines include polyethoxylated oleyl / stearylamine, ethoxylated tallow amine, cocoalkylamine, oleylamine, and tallow alkylamine, and mixtures thereof.

[0176] Examples of quaternary amines with a single long chain alkyl group are cetyltrimethylammonium bromide (CTAB), benzyldodecyldimethylammonium bromide (BddaBr), benzyldimethylhexadecylammonium chloride (BdhaCl), dodecyltrimethylammonium bromide, myristyltrimethylammonium bromide, stearyldimethylbenzylammonium chloride, oleyldimethylbenzylammonium chloride, lauryltrimethylammonium methosulfate (also known as cocotrimonium methosulfate), cetyldimethylhydroxyethylammonium dihydrogen phosphate, bassuamidopropylkonium chloride, cocotrimonium chloride, distearyldimonium chloride, wheat germ amidopropalkonium chloride, stearyl octyidimonium methosulfate, and the like. methosulfate), isostearuminopropanol chloride, dihydroxypropyl PEG-5 linoleate ammonium chloride, PEG-2 stearmonium chloride, behentrimonium chloride, dicetyldimonium chloride, tallowtrimonium chloride, and behenamidopropyl ethyldimonium ethosulfate.

[0177] Examples of quaternary amines with two long chain alkyl groups are didodecyldimethylammonium bromide (DDAB), distearyldimonium chloride, dicetyldimonium chloride, stearyloctyldimonium methosulfate, dihydrogenated palmoylethyl hydroxyethylmonium methosulfate, dipalmitoylethyl hydroxyethylmonium methosulfate, dioleoylethyl hydroxyethylmonium methosulfate, and hydroxypropylbisstearyldimonium chloride.

[0178] Quaternary ammonium compounds of imidazoline derivatives include, for example, isostearyl benzylimidonium chloride, cocoyl benzyl hydroxyethyl imidazolinium chloride, cocoyl hydroxyethyl imidazolinium PG-chloride phosphate, and stearyl hydroxyethyl imidazolinium chloride.Other heterocyclic quaternary ammonium compounds such as dodecyl pyridinium chloride, amprolium hydrochloride (AH), and benzethonium hydrochloride (BH) can also be used.

[0179] The surfactants used in the preparation of the material may be non-ionic and include, but are not limited to, polyalkylene oxide carboxylates, fatty acid esters, fatty acid alcohols, ethoxylated fatty alcohols, poloxamers, alkanolamides, alkoxylated alkanolamides, polyethylene glycol monoalkyl ethers, and alkyl polysaccharides. The polyalkylene oxide carboxylates have one or two carboxylate moieties, each having about 8-20 carbons, and a polyalkylene oxide moiety containing about 5-200 alkylene oxide units. The ethoxylated fatty alcohols contain an ethylene oxide moiety containing about 5-150 ethylene oxide units and a fatty alcohol moiety having about 6 to about 30 carbons. The fatty alcohol moiety may be cyclic, linear, or branched, and may be saturated or unsaturated. Some examples of ethoxylated fatty alcohols include ethylene glycol ethers of oleic alcohol, steareth alcohol, lauryl alcohol, and isocetyl alcohol. Poloxamers are ethylene oxide and propylene oxide block copolymers having about 15 to about 100 moles of ethylene oxide. Alkyl polysaccharide ("APS") surfactants (e.g., alkyl polyglycosides) contain a hydrophobic group having about 6 to about 30 carbons and a polysaccharide (e.g., polyglycoside) as the hydrophilic group. An example of a commercially available nonionic surfactant is FOA-5 (Octel Starreon LLC., Littleton, Colo.).

[0180] Specific examples of suitable nonionic surfactants include alkanolamides such as cocamide diethanolamide ("DEA"), cocamide monoethanolamide ("MEA"), cocamide monoisopropanolamide ("MIPA"), PEG-5 cocamide MEA, lauramide DEA, and lauramide MEA; alkylamine oxides such as lauramine oxide, cocamine oxide, cocamidopropylamine oxide, and lauramidopropylamine oxide; fatty acids or fatty acid esters such as sorbitan laurate, sorbitan distearate, lauric acid, isostearic acid, and PEG-150 distearate; fatty alcohols or ethoxylated fatty alcohols such as lauryl alcohol; alkyl polyglucosides such as decyl glucoside, lauryl glucoside, and coco glucoside.

[0181] The surfactants used in the preparation of the present materials may be zwitterionic, having both formal positive and negative charges on the same molecule. The positively charged group may be a quaternary ammonium, phosphonium, or sulfonium, while the negatively charged group may be a carboxylate, sulfonate, sulfate, phosphate, or phosphonate. As with other classes of surfactants, the hydrophobic portion may contain one or more long linear, cyclic, or branched aliphatic chains of about 8 to 18 carbon atoms. Specific examples of zwitterionic surfactants include alkyl betaines such as cocodimethyl carboxymethyl betaine, lauryl dimethyl carboxymethyl betaine, lauryl dimethyl alpha carboxymethyl betaine, cetyl dimethyl carboxymethyl betaine, lauryl bis-(2-hydroxyethyl) carboxymethyl betaine, stearyl bis-(2-hydroxypropyl) carboxymethyl betaine, oleyl dimethyl gamma-carboxypropyl betaine, and lauryl bis-(2-hydroxypropyl) alpha carboxy-ethyl betaine, amidopropyl betaine, and cocodimethyl sulfopropyl betaine, stearyidimethyl sulfopropyl betaine, lauryl dimethyl sulfoethyl betaine, lauryl bis-(2-hydroxyethyl) sulfopropyl betaine, and alkyl amidopropyl sulfohydroxysultaine.

[0182] The surfactant used in the preparation of the material can be amphoteric.Examples of suitable amphoteric surfactants include ammonium or substituted ammonium salts of alkylamphocarboxyglycinates and alkylamphocarboxypropionates, alkylamphodipropionates, alkylamphodiacetates, alkylamphoglycinates, and alkylamphopropionates, as well as alkyliminopropionates, alkyliminodipropionates, and alkylamphopropylsulfonates.Specific examples are cocoamphoacetate, cocoamphopropionate, cocoamphodiacetate, lauroamphoacetate, lauroamphodiacetate, lauroamphodipropionate, lauroamphodiacetate, cocoamphopropylsulfonate, caproamphodiacetate, caproamphoacetate, caproamphodipropionate, and stearicamphoacetate.

[0183] Surfactants used in the preparation of the material can be polymers such as N-substituted polyisobutenyl succinimides and succinates, alkyl methacrylate vinylpyrrolidinone copolymers, alkyl methacrylate-dialkylaminoethyl methacrylate copolymers, alkyl methacrylate polyethylene glycol methacrylate copolymers, polystearamides, and polyethyleneimines.

[0184] The surfactant used in the preparation of the material can 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).

[0185] The surfactants used in the preparation of the material can be oil-based dispersants, including alkyl succinimides, succinate esters, high molecular weight amines, and Mannich bases and phosphoric acid derivatives. Some specific examples are polyisobutenyl succinimide-polyethylene polyamines, polyisobutenyl succinate esters, polyisobutenyl hydroxybenzyl-polyethylene polyamines, and bis-hydroxypropyl phosphates.

[0186] The surfactants used in the preparation of the material can be a combination of two or more surfactants of the same or different types selected from the group consisting of anionic, cationic, nonionic, zwitterionic, amphoteric and ampholytic surfactants. Suitable examples of combinations of two or more surfactants of the same type include, but are not limited to, a mixture of two anionic surfactants, a mixture of three anionic surfactants, a mixture of four anionic surfactants, a mixture of two cationic surfactants, a mixture of three cationic surfactants, a mixture of four cationic surfactants, a mixture of two nonionic surfactants, a mixture of three nonionic surfactants, a mixture of four nonionic surfactants, a mixture of two zwitterionic surfactants, a mixture of three zwitterionic surfactants, a mixture of four zwitterionic surfactants, a mixture of two amphoteric surfactants, a mixture of three amphoteric surfactants, a mixture of four amphoteric surfactants, a mixture of two ampholytic ionic surfactants, a mixture of three ampholytic ionic surfactants, and a mixture of four ampholytic ionic surfactants.

[0187] Polymer particles The techniques described above involve the use of polymers to form surface treatments 201 on high aspect ratio carbon nanotubes to promote adhesion with active material particles 300. Although several advantageously suitable polymers are described, it should be understood that other polymeric materials may be used, including:

[0188] The polymers used in the preparation of the material can be polymeric materials such as water-processable and / or alcohol-processable polymeric materials. In various embodiments, any of the following polymers (and combinations thereof) can be used: polyacrylic acid (PAA), poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), polyacrylonitrile (PAN), polyisoprene (PIpr), polyaniline (PANi), polyethylene (PE), polyimide (PI), polystyrene (PS), polyurethane (PU), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP). In some embodiments. Another exemplary polymeric material is Fluoroacrylic Hybrid Latex (TRD202A), supplied by JSR Corporation.

[0189] FIG. 7 shows a schematic diagram of a pouch cell battery.

[0190] According to various embodiments, the teachings herein provide electrodes that do not have a PVDF binder in the cathode or other conventional binders in the anode. Instead, as detailed above, a 3D carbon scaffold or matrix holds the active material particles together to form a cohesive layer that also adheres strongly to the metal current collector. Such an active material structure is created during the slurry preparation and the subsequent roll-to-roll ("R2R") coating and drying process. One of the main advantages of the technology is its scalability and "drop-in" nature, since various embodiments are compatible with conventional electrode manufacturing processes.

[0191] The 3D carbon matrix is ​​formed during slurry preparation using the techniques described herein, where the high aspect ratio carbon material is appropriately dispersed and chemically functionalized, for example, using a two-step slurry preparation process (such as the type described above with reference to process 600 in FIG. 6). The chemical functionalization is designed to form organized self-assembled structures with the surface of the active material particles, such as, for example, NMC particles for use in the cathode, or silicon particles ("Si") or silicon oxide ("SiOx") particles in the case of the anode. The slurries thus formed can be based on water and / or alcohol solvents for the cathode and water for the anode, such solvents being highly evaporative and easy to handle during the manufacturing process. Electrostatic interactions promote the self-assembled structure within the slurry, and after the drying process, the bond between the carbon matrix containing the so-formed active material particles and the surface of the current collector is promoted by the surface treatment (e.g., functional groups on the matrix) and the strong entanglement of the active material in the carbon matrix.

[0192] As will be appreciated by one of ordinary skill in the art, the mechanical properties of the electrodes can be easily modified by tuning the surface functionalization versus the entanglement effect depending on the application and mass loading requirements.

[0193] After coating and drying, the electrode undergoes a calendaring process to control the density and porosity of the active material. For NMC cathode electrodes, densities of 3.5 g / cc or more and porosities of 20% or more can be achieved. Depending on the mass loading and the requirements of the LIB cell, the porosity can be optimized. For SiOx / Si anodes, the porosity is specifically controlled to accommodate the active material expansion during the lithiation process.

[0194] In some typical applications, the teachings herein can result in up to a 20% reduction in $ / kWh. The use of a benign solvent that evaporates easily allows for higher electrode throughput and, more importantly, significantly reduces energy consumption due to long drying times. Traditional NMP recovery systems are also significantly simplified when alcohol or other solvent mixtures are used.

[0195] The teachings herein provide a 3D matrix that dramatically improves the electrode conductivity by 10-100 times compared to electrodes using traditional binders such as PVDF, thereby enabling fast charging at the battery level. This technology allows for thick electrode coatings of up to 150um per side (or more) of the current collector. The solvents used in the slurry in combination with the strong 3D carbon matrix are designed to provide a thick wet coating without cracking during the drying step. The thick cathode, along with the high capacity anode, allows for a substantial jump in energy density reaching 400Wh / kg or more.

[0196] Fast charging is achieved by combining a high capacity anode that is lithiated through an alloying process (Si / SiOx) and by reducing the overall impedance of the cell when the anode is combined with a cathode as described herein. The teachings herein provide fast charging by having a highly conductive electrode, specifically a highly conductive cathode electrode.

[0197] An exemplary embodiment includes a Li-ion battery energy storage device in a pouch cell format that combines a Ni-rich NMC active material in the cathode with a blend of SiOx and graphite active material in the anode, both of which are fabricated using the 3D carbon matrix process described herein.

[0198] A schematic of an electrode arrangement pouch cell device is shown in Figure 7. As shown, a double-sided cathode 700 using a cathode layer 760 (e.g., an active layer according to various embodiments disclosed herein) on opposite sides of an aluminum foil current collector 710 is disposed between two single-sided anodes 720 and 730, each having an anode layer 740 and 750 (e.g., an active layer comprising a network of carbon elements as disclosed herein) disposed on a copper foil current collector. The electrodes are separated by a permeable separator material (not shown) that is wetted with an electrolyte (not shown). This arrangement can be contained within a pouch cell of a type well known in the art.

[0199] These devices may feature high mass loading of Ni-rich NMC cathode electrode and its manufacturing method, i.e., mass loading = 20-30mg / cm2, specific capacity > 210mAh / g. SiOx / graphite anode (SiOx content = about 20 wt%) based electrode and its material synthesis and manufacturing method: mass loading 8-14mg / cm2, reversible specific capacity ≥ 550mAh / g. In particular, long life performance of SiOx / graphite anode based Li-ion based electrolyte of battery: -30 to 60℃. High energy, high power density, and long cycle life Ni-rich NMC cathode / SiOx+graphite / carbon+ based Li-ion battery pouch cell: capacity ≥ 5Ah, specific energy ≥ 300Wh / kg, energy density ≥ 800Wh / L, and cycle life over 500 cycles under 1C rate charge / discharge, and ultra-high power fast charge / discharge C rate (up to 5C rate) capability.

[0200] FIG. 8 is a schematic cutaway view illustrating an embodiment of an energy storage device (ESD).

[0201] In general, the examples of energy storage devices (ESDs) disclosed herein are exemplary, i.e., the energy storage devices (ESDs) are not limited to the embodiments of the present disclosure.

[0202] More specific examples of energy storage devices (ESDs) include supercapacitors such as double layer capacitors (devices that store charge electrostatically), pseudocapacitors (devices that store charge electrochemically), and hybrid capacitors (devices that store charge electrostatically and electrochemically). In general, electrostatic double layer capacitors (EDLCs) use carbon electrodes or derivatives with electrostatic double layer capacitance much larger than the electrochemical pseudocapacitance, achieving separation of charge in a Helmholtz double layer at the interface between the surface of the conductive electrode and the electrolyte. In general, electrochemical pseudocapacitors use metal oxide or conducting polymer electrodes that have a large amount of electrochemical pseudocapacitance in addition to the double layer capacitance. The pseudocapacitance is achieved by faradaic electronic charge transfer through redox reactions, intercalation or electrosorption. Hybrid capacitors such as lithium ion capacitors use electrodes with different characteristics: one exhibits mainly electrostatic capacitance, the other mainly electrochemical capacitance.

[0203] Other examples of energy storage devices (ESDs) include rechargeable, storage, or secondary batteries, which are types of electric cells that can be charged, discharged to a load, and recharged multiple times. During charging, the positive electrode active material is oxidized to produce electrons, and the negative electrode material is reduced to consume electrons. These electrons constitute the flow of electric current from the external circuit. Generally, an electrolyte acts as a buffer for the internal ion flow between the electrodes (e.g., the anode and cathode). The charge and discharge rates of a battery are often discussed by referring to the "C" rate of current. The C rate is the rate at which the battery would theoretically be fully charged or discharged in one hour. The "depth of discharge" (DOD) is usually expressed as a percentage of the nominal ampere-hour capacity. For example, zero percent (0%) DOD means there is no discharge.

[0204] 8 shows a cross section of an energy storage device (ESD) 810. The energy storage device (ESD) 810 includes a housing 811. The housing 811 has two terminals 800 disposed on its exterior. The terminals 800 provide an internal electrical connection to a storage cell 812 contained within the housing 811 and an external electrical connection to an external device, such as a load or charging device (not shown).

[0205] FIG. 9 is a schematic cutaway view illustrating an embodiment of a prior art storage cell of the energy storage device (ESD) of FIG.

[0206] A cutaway portion of the storage cell 12 is shown in FIG. 9. As shown in this figure, the storage cell 912 includes a multi-layer roll of energy storage material. That is, sheets or strips of energy storage material are wound together in a roll format. The roll of energy storage material includes opposing electrodes referred to as an "anode 930" and a "cathode 940." The anode 930 and cathode 940 are separated by a separator 950. Although not shown, included as part of the storage cell 912 is an electrolyte. Generally, the electrolyte permeates or wets the cathode 940 and anode 930 and facilitates the movement of ions within the storage cell 912. According to various embodiments, the cathode 940 corresponds to or is similar to the electrode 100 of FIG. 1A or the electrode 125 of FIG. 1B. In some embodiments, the cathode 940 corresponds to an electrode including a network of high aspect ratio carbon elements as disclosed herein and / or a polymer additive as disclosed herein.

[0207] 10-19 are graphs illustrating aspects of the electrical performance of energy storage cells constructed in accordance with various embodiments.

[0208] FIG. 10 is a graph showing the C-rate of a half cell constructed according to the teachings herein. The half cell contained an areal loading of NCM active material that was 22.5 mg / cm2. In this example, the "best process" curve represents a binder-free electrode manufactured according to the teachings herein. The "old process" curve represents a binder-free electrode manufactured without these surfactants and dispersants disclosed herein. The "PVDF" curve represents the performance of a cell using an electrode manufactured by the prior art. In this example, the half cell was a pouch cell construction. The initial specific and C-Rate test results are provided in the table below. The size of the working electrode was 45×45 mm and the Li counter electrode was 46×46 mm. The electrolyte was 1 M LiPF6 in EC / DMC (1 / 1 volume ratio) + 1% VC. [Table 3]

[0209] Figure 11 shows the results of testing the full pouch cell. In this example, the cathode was Ni-rich NMC, 45 x 45 mm, and the anode was a graphite electrode, 46 x 46 mm. The electrolyte was 1M LiPF6 in EC / DMC (1 / 1 volume ratio) + 1% VC. N / P ratio = about 1.1. It can be seen that the HPPC resistance is much lower compared to the conventional PVDF process. As shown in the figure, the lower charging resistance in the cathode according to the teachings herein results in improved performance at 10 percent state of charge. Figure 13 shows that the cathode made according to the teachings herein has improved cycling stability.

[0210] Another pouch cell was constructed for testing. In this embodiment, the cathode was Ni-rich NMC with a mass loading of 28-30 mg / cm2, 45×45 mm, and the anode was a combination of graphite / SiOx (45%SiOx) electrodes with a mass loading of 8-9 mg / cm2, 46×46 mm. The electrolyte was 1.1 M LiPF6 in PC:FEC:EMC:DEC=20:10:50:20. N / P ratio=about 1.04-1.10. Both NMC cathode and 45%SiOx anode electrode fabrication processes were used with the processes described herein, using hybrid surfactants and dispersants combined with a 3D nanocarbon matrix (e.g., NX electrodes). The full cell specific energy of the Li-ion battery was about 332 Wh / kg at 90% pouch cell packaging efficiency, and 351 Wh / kg when the packaging efficiency was increased to 95%. The energy density was about 808Wh / L for a pouch cell packaging efficiency of 90% and a pouch cell volume expansion of 10%, and the energy density was about 853Wh / L for a pouch cell packaging efficiency of 95% and a pouch cell volume expansion of 10%. The initial first cycle charge specific capacity of the cathode and anode based on the claimed electrode manufacturing process was about 228mAh / g and 852mAh / g, and the initial first cycle discharge specific capacity of the cathode and anode based on the claimed electrode manufacturing process was about 210mAh / g and 750mAh / g. In this example, the LiB full cell capacity is an initial charge capacity of 240mAh and an initial discharge capacity of 216mAh from 4.2V to 2.5V under constant current charge and discharge at 0.1C rate. The initial coulombic efficiency is about 90%. Aspects of this data and electrical performance of this cell are described in Figures 15-19.

[0211] Exemplary properties of cells using the resulting electrodes are shown in the table below: Additionally, the exemplary cells did not exhibit any cracks or stresses as would typically occur in several physical tests. [Table 4]

[0212] FIG. 20 illustrates an exemplary battery cell using an example electrode (e.g., an NX electrode) disclosed herein. The battery cell dimensions were approximately 46.5 mm×48.5 mm×7.14 mm. The battery cell illustrated in FIG. 20 corresponds to a 1.5-3.5 Ah battery cell. The illustrated battery cell (e.g., with an NX NMC811 electrode) exhibited a first cycle charge specific capacity of over 210 mAh / g and an areal capacity of substantially 5.6 mAh / cm2.

[0213] FIG. 21 illustrates an exemplary battery cell using an example electrode (e.g., an NX electrode, such as an electrode comprising a 3D nanocarbon matrix) disclosed herein. The battery cell was approximately 62 mm×107 mm×5.4 mm. The battery cell illustrated in FIG. 21 corresponds to a 9.0-12.0 Ah battery cell. The illustrated battery cell (e.g., having an NX NMC811 electrode) exhibited a first cycle charge specific capacity of greater than 1116 mAh / g, and an areal capacity of substantially 6.5 mAh / cm2.

[0214] FIG. 22 shows a chart of the characteristics of various examples of battery cells (e.g., pouch cells). The dimensions of the battery cells were approximately 46 mm×46 mm×3 mm. The battery cell package efficiency is approximately 86% for 9 layers of NMC811 cathode and 10 layers of Si anode (e.g., 1.5 Ah cell), but for larger pouch cells >5 Ah with more stack layers, the cell package efficiency may increase to 95% efficiency. The results show that the Si anode (5.5-5.0 mg / cm2) can improve the specific energy and energy density by at least 30% compared to a graphite anode electrode (16 mg / cm2 matching 24 mg / cm2 NX NMC811 cathode) with the same small pouch cell format and number of layers.

[0215] 23 shows a graph comparing the performance of battery cells with cathodes according to various embodiments compared to a control battery cell with a conventional PVDF cathode. As shown in FIG. 23, the use of a cathode with a 3D nanocarbon matrix (e.g., NX NMC811) reduces resistance by at least 20%.

[0216] 24 shows a chart comparing the performance of battery cells with cathodes according to various embodiments compared to a control battery cell with a conventional PVDF cathode. As shown in FIG. 24, the use of a cathode with a 3D nanocarbon matrix (e.g., NX NMC811) reduces resistance by at least 20%.

[0217] FIG. 25 shows a graph comparing the performance of battery cells with cathodes according to various embodiments compared to a control battery cell with a conventional PVDF cathode. The battery cells compared in FIG. 25 are 1.5 Ah cells with NX Si-C anode electrodes (e.g., electrodes with 3D nanocarbon matrix) and are measured following 1C1C cycles from 4.2 to 2.8V. As shown in FIG. 25, the use of a cathode with a 3D nanocarbon matrix (e.g., NX NMC811) has a greater discharge density, and the difference in discharge density increases as the number of cycles increases. After 250 cycles, the battery cells according to various embodiments (e.g., battery cells with cathodes including 3D nanocarbon matrix) have a discharge capacity of at least 1275 mAh, preferably at least 1375 mAh. After 250 cycles, the battery cells according to various embodiments (e.g., battery cells with cathodes including 3D nanocarbon matrix) have a discharge capacity of about 10% greater than the control battery cell (e.g., battery cells with cathodes including PVDF).

[0218] FIG. 26 shows a graph illustrating the performance of a battery cell including electrodes according to various embodiments. The battery cell measured in FIG. 26 includes a NX Si-C anode electrode (e.g., an electrode having a 3D nanocarbon matrix), a cathode according to various embodiments (e.g., a cathode having a 3D nanocarbon matrix), and is a 1.5 Ah cell measured following 1C1C cycles from 4.2 to 2.8 V. As shown in FIG. 26, the battery cell including the cathode having a 3D nanocarbon matrix (e.g., NX NMC811) has a discharge capacity retention of about 82.7% after 500 cycles. The battery cell including the cathode having a 3D nanocarbon matrix (e.g., NX NMC811) has a discharge capacity that decreases by less than 300 mAh after 500 cycles.

[0219] FIG. 27 shows a graph illustrating the performance of a battery cell with electrodes according to various embodiments. FIG. 27 provides a graph of fast charge cycle performance. The battery cell measured in FIG. 27 is a 1.5 Ah cell (e.g., pouch cell) with a NX Si-C anode electrode (e.g., an electrode with a 3D nanocarbon matrix), a cathode according to various embodiments (e.g., a cathode with a 3D nanocarbon matrix), and is measured according to 1C / 1C (3 cycles) + 3.5C (CCCV 15 min) / 1C (1 cycle) every 4 cycles over a voltage range of 4.2 to 2.8V. As shown in FIG. 27, the battery cell with the cathode with a 3D nanocarbon matrix (e.g., NX NMC811) has a discharge capacity retention of at least 87% after 500 cycles. In some embodiments, the battery cell with the cathode with a 3D nanocarbon matrix (e.g., NX NMC811) has a discharge capacity retention of 87% to 88% after 500 cycles. A battery cell with a cathode having a 3D nanocarbon matrix (eg, NX NMC811) has a discharge capacity that decreases by less than 300 mAh after 270 cycles.

[0220] FIG. 28 shows a graph illustrating the performance of a battery cell with electrodes according to various embodiments. FIG. 28 provides a graph of discharge energy versus cycling. The battery cell measured in FIG. 28 includes a NX Si-C anode electrode (e.g., an electrode with a 3D nanocarbon matrix), a cathode according to various embodiments (e.g., a cathode with a 3D nanocarbon matrix), a load of 5.6 mAh / cm2, and a cathode density of 3.5 g / cc, and is measured according to 1C / 1C cycles over a voltage range of 4.2 to 3.0 V. As shown in FIG. 28, the battery cell with the cathode with a 3D nanocarbon matrix (e.g., NX NMC811) has a discharge capacity retention of at least 70% after 600 cycles, preferably at least 80% after 600 cycles. In some embodiments, the battery cell including the cathode with a 3D nanocarbon matrix (e.g., NX NMC811) has a discharge capacity retention of about 70% after 1000 cycles. In some embodiments, battery cells with cathodes having a 3D nanocarbon matrix (e.g., NX NMC811) have 80%-90% discharge capacity retention after 600 cycles.

[0221] FIG. 29 shows a graph illustrating the performance of a battery cell with electrodes according to various embodiments. FIG. 29 provides a graph of capacity versus storage time. For example, the battery cells were measured according to a SOC100 calendar life test at 50 degrees Celsius. The battery cell measured in FIG. 29 is a 1.5 Ah pouch battery cell with a NX Si-C anode electrode (e.g., an electrode with a 3D nanocarbon matrix), a cathode (e.g., a cathode with a 3D nanocarbon matrix) according to various embodiments. As shown in FIG. 29, the battery cell with the cathode with a 3D nanocarbon matrix (e.g., NX NMC811) has at least 95% capacity retention after 21 days. In some embodiments, the battery cell with the cathode with a 3D nanocarbon matrix (e.g., NX NMC811) has at least about 95% capacity retention after 28 days. In some embodiments, the battery cell with the cathode including a 3D nanocarbon matrix (e.g., NX NMC811) has at least about 96% capacity retention after 28 days. In some embodiments, battery cells with cathodes having a 3D nanocarbon matrix (e.g., NX NMC811) have capacity retention after 28 days that is at least 1% better than a control 1.5 Ah pouch battery cell with a PVDF cathode.

[0222] Figures 30 and 31 show the performance of a battery cell comprising electrodes according to various embodiments of the present application. The battery cell whose performance is provided in Figures 30 and 31 is a pouch cell with dimensions of 46.5mm x 46.5mm x 7.14mm and a cathode comprising a 3D nanocarbon matrix (e.g., NX NMC811). Figure 30 provides a chart showing the cell capacity design, specific energy, and energy density. Figure 31 provides a graph of cell voltage versus capacity.

[0223] Figure 32 shows the weight distribution of a battery cell according to various embodiments. The battery cell whose weight distribution is measured in Figure 32 is a 3.4 Ah pouch cell with a cathode comprising a 3D nanocarbon matrix (e.g., NX NMC811).

[0224] FIG. 33 and FIG. 34 show the performance of a battery cell comprising electrodes according to various embodiments of the present application. The battery cells whose performance is provided in FIG. 33 and FIG. 34 are pouch cells with dimensions of 62 mm×107 mm and 5.4 mm and a cathode comprising a 3D nanocarbon matrix (e.g., NX NMC811). FIG. 33 provides a chart showing the cell capacity design, specific energy, and energy density. FIG. 34 provides a graph of capacity versus DST cycle number. According to various embodiments, the battery cell comprises a specific energy of 315 Wh / kg or more, an energy density of 820 Wh / L or more, and a cell capacity of 9 Ah. The battery cell according to various embodiments exhibits a DST cycle stability of at least about 70% at 1000 cycles, at least 92.5% at 225 cycles, and / or greater than 90% at 300 cycles.

[0225] 35 and 36 show charts of the performance of battery cells with electrodes according to various embodiments of the present application. As shown in FIG. 36, a battery cell according to various embodiments (e.g., a 9 Ah pouch cell with a cathode including a 3D nanocarbon matrix) exhibits less than 10% volume expansion from 0% to 100% charge. In some embodiments, such a battery cell exhibits less than 9% volume expansion from 0% to 100% charge. In some embodiments, such a battery cell exhibits approximately 8.8% volume expansion from 0% to 100% charge.

[0226] Various other components may be included or required to provide aspects of the teachings herein. For example, additional materials, combinations of materials, and / or omissions of materials may be used to provide additional embodiments that are within the scope of the teachings herein. Various modifications of the teachings herein may be implemented. In general, the modifications may be designed according to the needs of a user, designer, manufacturer, or other similar party. The modifications may be intended to meet particular performance criteria that the party considers important.

[0227] No accompanying claim or claim element should be construed as invoking 35 U.S.C. §112(f) unless the words "means for" or "step for" are expressly used in a particular claim.

[0228] When introducing elements of the invention or an embodiment(s) thereof, the articles "a," "an," and "the" are intended to mean that there are one or more elements. Similarly, the adjective "another," when used to introduce an element, is intended to mean one or more elements. The terms "including" and "having" are intended to be inclusive such that there may be additional elements other than the listed elements. As used herein, the term "exemplary" is not intended to mean a superordinate example. Rather, "exemplary" refers to an example embodiment that is one of many possible embodiments.

[0229] The following examples are merely illustrative of the various aspects disclosed herein and are not intended to limit the scope of the present invention. Unless otherwise stated, all examples were based on simulations.

[0230] In general, the present disclosure may alternatively comprise, consist of, or consist essentially of any suitable components disclosed herein.

Claims

1. An electrode, An active layer, a network of high aspect ratio carbon elements defining voids within said network; a plurality of electrode active material particles comprising silicon, the electrode active material particles being disposed in the voids within the network; and a polymer additive that is at least one of a polyolefin, a poly(acrylic acid), and a styrene butadiene rubber (SBR).

2. 2. The electrode of claim 1, wherein the silicon contained in the electrode active material particles is in the form of SiO.

3. The electrode according to claim 1 , wherein the silicon contained in the electrode active material is fine silicon.

4. 10. The electrode of claim 1, wherein the silicon contained in the electrode active material is greater than 50% by weight of the active layer.

5. 10. The electrode of claim 1, wherein the silicon contained in the electrode active material is at least 80% by weight of the active layer.

6. the network of high aspect ratio carbon elements comprises a mesh of carbon nanotubes; 10. The electrode of claim 1, wherein the mesh of carbon nanotubes maintains electrical connectivity between at least a subset of the carbon nanotubes contained in the mesh during expansion of the silicon.

7. the network of high aspect ratio carbon elements comprises a mesh of carbon nanotubes; 10. The electrode of claim 1, wherein the mesh of carbon nanotubes maintains electrical connectivity between at least a subset of the carbon nanotubes contained in the mesh during charging and discharging of a battery in which the electrode is included.

8. the network of high aspect ratio carbon elements is a first set of carbon nanotubes comprising a plurality of first carbon nanotubes or a plurality of bundles of first carbon nanotubes; a second set of carbon nanotubes, the second set of carbon nanotubes comprises a plurality of second carbon nanotubes or a plurality of bundles of second carbon nanotubes; 10. The electrode of claim 1, comprising: a second set of carbon nanotubes, the second set of carbon nanotubes having one or more properties different from the first set of carbon nanotubes.

9. The electrode of claim 8 , wherein the first set of carbon nanotubes comprises multi-walled nanotubes.

10. The electrode of claim 8 , wherein the second set of carbon nanotubes comprises single-walled nanotubes.

11. the first set of carbon nanotubes comprises multi-walled carbon nanotubes; the second set of carbon nanotubes comprises single-walled carbon nanotubes; 9. The electrode of claim 8, wherein the weight ratio of the first set of carbon nanotubes to the second set of carbon nanotubes is about 2:

1.

12. 9. The electrode of claim 8, wherein the first set of carbon nanotubes and the second set of carbon nanotubes form a mesh, the mesh maintaining electrical connectivity between the carbon nanotubes contained in the mesh during charging and discharging of a battery in which the electrode is included.

13. 9. The electrode of claim 8, wherein the average thickness of the multi-walled carbon nanotubes increases by less than 10% after being wetted with an electrolyte.

14. 9. The electrode of claim 8, wherein a first average aspect ratio of the first set of carbon nanotubes is greater than a second average aspect ratio of the second set of carbon nanotubes.

15. 9. The electrode of claim 8, wherein the first set of carbon nanotubes has an average aspect ratio of at least 100 microns.

16. the network of high aspect ratio carbon elements is a first set of carbon nanotubes comprising a plurality of first carbon nanotubes or a plurality of bundles of first carbon nanotubes; a second set of carbon nanotubes, the second set of carbon nanotubes comprises a plurality of second carbon nanotubes or a plurality of bundles of second carbon nanotubes; a second set of carbon nanotubes, the second set of carbon nanotubes having one or more properties different from the first set of carbon nanotubes; and graphite particles.

17. 17. The electrode of claim 16, wherein the network of high aspect ratio carbon elements comprises about 5% graphite by weight of the active layer.

18. the first set of carbon nanotubes comprises multi-walled carbon nanotubes; the second set of carbon nanotubes comprises single-walled carbon nanotubes; 17. The electrode of claim 16, wherein the network of high aspect ratio carbon elements is about 2% by weight single-walled carbon nanotubes.

19. the first set of carbon nanotubes comprises multi-walled carbon nanotubes; the second set of carbon nanotubes comprises single-walled carbon nanotubes; 17. The electrode of claim 16, wherein the network of high aspect ratio carbon elements is about 0.5% single-walled carbon nanotubes by weight of the active layer.

20. the first set of carbon nanotubes comprises multi-walled carbon nanotubes; the second set of carbon nanotubes comprises single-walled carbon nanotubes; 17. The electrode of claim 16, wherein the network of high aspect ratio carbon elements is less than or equal to about 2% by weight of the active layer of single-walled carbon nanotubes.

Images