Energy storage device with swellable electrodes

Abstract

An energy storage device comprising two electrodes and a separator located between the two electrodes for electrically separating them, wherein at least one of the electrodes comprises an active layer containing electrode active particles, conductive elements, and an electrolyte. The active layer is characterized by one or more of the following: the volume of the active layer in the presence of the electrolyte is at least 10%, preferably at least 20%, greater than the volume of the combination of electrode active particles and conductive elements in the absence of the electrolyte; the volume in use is at least 10%, preferably at least 20%, greater than the original volume; the conductive elements are in the form of a flexible network that can expand and / or compress; and the active layer contains a flexible binder that facilitates the expansion and contraction of the active layer.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims the benefits of U.S. Patent Application Publication No. 63 / 452,831, filed on 17 March 2023, which is incorporated herein by reference in its entirety.

[0002] (Field of invention) The present invention relates to energy storage devices, particularly ultracapacitors and lithium-ion batteries, and electrodes used therein. [Background technology]

[0003] Lithium batteries are used in a wide range of products, including medical devices, electric vehicles, airplanes, and consumer products such as laptop computers, mobile phones, and cameras. Due to their high energy density, high operating voltage, and low self-discharge, lithium-ion batteries have overtaken the rechargeable battery market and continue to find new applications in products and evolving industries.

[0004] Generally, a lithium-ion battery ("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, the "electrode") are formed by mixing either the anode active material or the cathode active material with a binder and a solvent to form a paste or slurry, which is then coated onto a current collector such as aluminum or copper and dried to form a film on the current collector. The anode and cathode are then layered or coiled before being housed in a pressurized casing containing the electrolyte material, and together they form a lithium-ion battery.

[0005] A problem experienced with some batteries is that the electrode material can expand and contract during charging and discharging. This can lead to a degradation in battery performance. Therefore, it is generally recommended to avoid electrode swelling.

[0006] Therefore, it is recommended that electrode swelling during charging and discharging can be reduced by using a combination of two binders having different glass transition temperatures and different degrees of swelling in the electrolyte. See U.S. Patent No. 10,566,627. [Overview of the project]

[0007] In a first embodiment, an energy storage device is disclosed herein, comprising an electrolyte, two electrodes, and a separator located between the two electrodes, wherein at least one of the two electrodes comprises an active layer containing active particles scattered within a network of carbon nanotubes, characterized by a volume increase in use of at least 10%, preferably at least 20%, compared to the original volume of the active layer.

[0008] Furthermore, this specification discloses an energy storage device comprising two electrodes and a separator located between the two electrodes for electrically separating them. At least one of the electrodes comprises an active layer comprising electrode active particles, conductive elements, and a first electrolyte, wherein the volume of the active layer in the presence of the electrolyte is at least 10%, preferably at least 20%, greater than the volume of the combination of electrode active particles and conductive elements in the absence of the electrolyte, the conductive elements are in the form of a flexible network that can be expanded and / or compressed, and the active layer comprises a flexible binder that facilitates the expansion and contraction of the active layer.

[0009] This specification also discloses a method for fabricating an energy storage device, comprising: providing a slurry containing a first conductive element and a first electrode active material in a liquid; forming a film of the slurry; and drying to remove the liquid to form a first electrode active layer precursor. The energy storage device is fabricated by: arranging the first electrode active layer precursor adjacent to a first side of a separator; arranging a second electrode adjacent to the side of the separator opposite to the first side; providing a first electrolyte to the first electrode active layer precursor to form a first active layer characterized by one or more of the following: the volume of the first active layer in the presence of the first electrolyte is at least 20% greater than the volume of the combination of the first electrode active particles and the first conductive element in the absence of the first electrolyte; the first conductive element is in the form of a flexible network that can expand and / or compress; and the active layer contains an optional flexible binder that facilitates the expansion and contraction of the active layer. [Brief explanation of the drawing]

[0010] Here, we refer to the diagram, which is an exemplary embodiment, and similar elements are numbered similarly. [Figure 1] This is a cross-sectional view of an example of an energy storage device disclosed herein. [Figure 2a] This is a cross-sectional view of the energy storage device disclosed herein, showing the energy storage device before the expansion of the active layer. [Figure 2b] This is a cross-sectional view of the energy storage device disclosed herein, showing the energy storage device after the expansion of the active layer. [Figure 3] This is a schematic diagram of a portion of the active layer disclosed herein. [Modes for carrying out the invention]

[0011] While electrode swelling in lithium-ion energy storage devices such as batteries and / or ultracapacitors has generally been taught as a problem to be avoided, the present invention is based on the intentional and controlled expansion and / or compression of the electrode active layer. This expansion and / or compression can provide one or more of the following advantages: ensuring good contact between the electrode active layer and the current collector; ensuring good contact between the electrode active layer and the separator (or solid electrolyte in some embodiments); and providing a flexible (e.g., compressible and / or expandable) electrode structure that is highly tolerant of roughness on the separator (or solid electrolyte) and / or the electrode, and / or highly tolerant of changes in the size of individual components of the electrode, or the formation of gases in the energy storage device during use.

[0012] A more complete understanding of the components, processes, and apparatus disclosed herein can be obtained by referring to the accompanying drawings. These drawings are merely schematic representations based on convenience and ease of demonstration of the disclosure and are not intended to show the relative sizes and dimensions of the devices or their components, and / or to define or limit the scope of the exemplary embodiments. Certain terms are used in the following specification for clarity, but these terms are intended to refer only to specific structures of embodiments selected for illustrative purposes in the drawings and are not intended to define or limit the scope of the disclosure. In the drawings and the following specification, similar numerical designations should be understood to refer to components of similar function.

[0013] The energy storage device may include a housing that holds electrodes (anode and cathode), a separator between the electrodes to prevent direct electrical contact between the anode and the cathode, and an electrolyte for each electrode.

[0014] As shown in Figure 1, an example of a battery 100 (representing an energy storage device disclosed herein) includes a separator 106, a first active layer 110a adjacent to a first side of the separator 106, and a second active layer 110b adjacent to a second side of the separator 106. The battery may also include a first current collector 102a and / or a second current collector 102b adjacent to the first active layer 110a and the second active layer 110b, respectively.

[0015] The current collectors 102a and 102b may include metal (e.g., substantially pure metal or metal alloy, etc.). For example, the current collector may be in the form of a metal strip or metal foil such as aluminum foil or strip, aluminum alloy foil or strip, copper foil or strip, or copper alloy foil or strip. The current collector may have a thickness of 15 μm or less, 10 μm or less, 8 μm or less, or 5 μm or less. In some embodiments, the current collector may have a thickness of at least 3 μm at the same time. For example, the current collector 102 may have a thickness of 3 to 15 μm, or 6 μm and about 8 μm. As another example, the current collector 102 is aluminum foil or aluminum alloy foil with a thickness of 5 to 7 μm.

[0016] Either the first electrode, the second electrode, or both comprises an active layer that expands and / or contracts, as described herein.

[0017] The volume of the active layer can expand in the presence of an electrolyte and / or during use. For example, the volume of the active layer in the presence of an electrolyte, during use, or both, is at least 10%, or at least 20%, or at least 30% greater than the volume of the combination of electrode active particles and conductive elements without the presence of an electrolyte and / or before use, and up to 60% or 50% greater. FIG. 2a shows the active layer 110a before expansion. There is little contact between the active layer 110a and the current collector 102a, and between the active layer 110a and the separator 106. In contrast, after swelling as shown in FIG. 2b, there are many good contacts between the active layer 110a and both the current collector 102a and between the active layer 110a and the separator 106.

[0018] As another example, the active layer can be compliant (i.e., capable of expanding, compressing, or other shape changes in response to force). For example, at least one of the electrodes can include a conductive element in the form of a movable flexible network. Thus, since other components of the battery can expand (e.g., gas can be formed from the reaction), the flexible network can move to adapt to the space occupied by the other components. For example, the flexible network can move or compress as other components expand. Additionally, the flexible network can expand in the absence of pressure so that the active layer more fully fills the space between the current collector and the separator.

[0019] As another example, the active layer can include a flexible binder that forms a connecting structure that holds the active particles and conductive elements to form the active layer, while the flexibility of the binder allows movement (expansion or compression) of other components (particularly the conductive elements).

[0020] FIG. 3 shows an example of the active layer 110 disclosed herein, including active particles 112 dispersed among the conductive elements 114 in the form of a network. A binder 116 can be added to hold the elements in place. A flexible binder is preferred. For example, the binder may be an elastomer, or the binder may have a foamed structure.

[0021] In one embodiment, the flexible binder is preferably an elastomer. In another embodiment, the flexible binder may include a polymer that swells but does not completely dissolve in the electrolyte. Examples of elastomers are polysiloxane, polybutadiene, polyisoprene, styrene-butadiene rubber, poly(styrene)-block-poly(butadiene), poly(acrylonitrile)-block-poly(styrene)-block-poly(butadiene) (ABS), polychloroprene, epichlorohydrin rubber, polyacrylic rubber, silicone elastomer (polysiloxane), fluorosilicone elastomer, fluoroelastomer, perfluoroelastomer, polyether block amide (PEBA), chlorosulfonated polyethylene, ethylene propylene diene rubber (EPR), ethylene-vinyl acetate elastomer, etc., or combinations thereof.

[0022] Examples of polymers include polyacetal, polyacrylic acid, polycarbonate, polyalkyd, polystyrene, polyolefin, polyester, polyamide, polyaramid, polyamide-imide, polyarylate, polyurethane, epoxy, phenols, silicone, polyarylsulfone, polyethersulfone, polyphenylene sulfide, polysulfone, polyimide, polyetherimide, polytetrafluoroethylene, polyetherketone, polyetheretherketone, polyetherketoneketone, polybenzoxazole, polyoxadiazole, polybenzothiadinophenothiazine, polybenzothiazole, polypyradinoquinoxaline, polypyromelillimide, polygynoxaline, polybenzimidazole, polyoxyindole, Examples include lioxoisoindoline, polydioxoisoindoline, polytriazine, polypyridazine, polypiperazine, polypyridine, polypiperidine, polytriazole, polypyrazole, polycarborane, polyoxabicyclononane, polydibenzofuran, polyphthalide, polyacetal, polyanhydride, polyvinyl ether, polyvinyl thioether, polyvinyl alcohol, polyvinyl ketone, polyvinyl halide, polyvinyl nitrile, polyvinyl ester, polysulfonate, polysulfide, polythioester, polysulfone, polysulfonamide, polyurea, polyphosphazene, polysilazane, polypropylene, polyethylene, polyethylene terephthalate, polyvinylidene fluoride, polysiloxane, etc., or combinations thereof.

[0023] The conductive elements 114 may be separate elements that come into contact with each other to form a network, as shown in Figure 3, or they may be in the form of a mesh or web. The conductive elements include a conductive material. For example, the conductive elements may include carbon or metal.

[0024] For example, if the conductive elements are separate but in contact with each other, they may include high aspect ratio elements, preferably high aspect ratio carbon elements. The term “high aspect ratio element” refers to an element having a size in one or more dimensions (“long dimension”) that is significantly larger than the size of the element in the lateral dimension (“short dimension”). High aspect ratio carbon elements may include substantially cylindrical networks of carbon atoms. The conductive material may include carbon nanotubes or bundles of carbon nanotubes.

[0025] The network may be a permeable network capable of transmitting current between any two isolated points located on the surface of a solid active layer (which does not contain a solvent or electrolyte). In other words, current may be transmitted from one surface or end of the active layer to the opposite surface or end by physical contact between conductive elements in the electrode active layer or by electron hopping. The permeable network may include voids between high aspect ratio carbon elements that can contain or accommodate the electrode active material. The high aspect ratio conductive material can be substantially oriented in a direction substantially parallel to the current collector within the electrode active layer 110 to facilitate the conduction of current from one end to the other of the electrode while still maintaining less orientation throughout the thickness of the active layer.

[0026] The network may be flexible to allow movement of parts of the network in order to compensate for the expansion of other components of the active layer, or to expand in the absence of pressure to improve contact with the separator and, if used, with the current collector. In one example, the network may have spring properties that allow for compression and expansion of the active layer.

[0027] The conductive material may be present in the mixture in an amount of 0.1–1.3, 0.15–1.2, or 0.3–1 weight percent, based on the total weight of the mixture (the mixture includes the conductive material, electrode active material, binder material, and solvent). The conductive material may be present in the active layer in an amount of 0.2–3.5, 0.3–3, or 0.5–2 weight percent, based on the total weight of the solids in the active layer (the total weight of the solids does not include the solvent, but includes the conductive material, binder material, and electrode active material).

[0028] High aspect ratio carbon elements may be single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWNTs), or mixtures of both.

[0029] Single-walled carbon nanotubes can have an outer diameter of 0.5 to 5.0 nanometers, preferably 1.0 to 3.5 nanometers. Single-walled carbon nanotubes can have an aspect ratio (ratio of length to diameter) greater than about 2.0, preferably greater than 5.0, preferably greater than 10.0, greater than 50, and more preferably greater than 100. In exemplary embodiments, single-walled carbon nanotubes can have an average aspect ratio of 5 to 200.

[0030] Single-walled carbon nanotubes can have a length greater than 6 nanometers, preferably greater than 10 nanometers, preferably greater than 15 nanometers, preferably greater than 30 nanometers, preferably greater than 50 nanometers, more preferably greater than 100 nanometers, preferably greater than 1 micrometer, preferably greater than 5 micrometers, preferably greater than 10 micrometers, more preferably greater than 15 micrometers, and at least up to 200 micrometers. In an exemplary embodiment, single-walled carbon nanotubes can have an average length of 10 to 20 micrometers, preferably 20 to 15 micrometers.

[0031] Single-walled carbon nanotubes can be present in a mixture of conductive material, binder material, electrode active material, and solvent in an amount of 0.1 to 2 weight percent based on the total weight of the mixture. For example, the amount of single-walled nanotubes in the mixture may be 0.1 to 0.3 or 0.15 to 9.25 weight percent. As another example, the amount of single-walled nanotubes in the mixture may be 0.4 to 2 weight percent.

[0032] Single-walled carbon nanotubes can be present in the electrode active layer (solvent-free conductive material, binder material, and electrode active material) in an amount of 0.2 to 4 weight percent (W%) based on the total weight of the electrode active layer. For example, the amount of single-walled nanotubes in the electrode active layer may be 0.2 to 0.6 or 0.3 to 0.5 weight percent. As another example, the amount of single-walled nanotubes in the electrode active layer may be 0.5 to 4 weight percent.

[0033] The number of carbon layers in a multi-walled carbon nanotube can be 2 or more, 5 or more, 10 or more, or 50 or more. On average, a multi-walled carbon nanotube can contain 3 to 15 layers, 4 to 12 layers, 5 to 10 layers, or 6 to 8 layers.

[0034] The active layer 110 may contain multi-walled carbon nanotubes and single-walled carbon nanotubes. The layer containing multi-walled carbon nanotubes swells more than the layer containing only single-walled carbon nanotubes when wetted by the electrolyte in the energy storage device where the electrode 100 is located. For example, the layer having multi-walled carbon nanotubes may swell by at least 15%, at least 25%, or at least 50% more than the layer having single-walled carbon nanotubes when wetted by the electrolyte in the energy storage device where the electrode 100 is located. For example, the length of the multi-walled carbon nanotubes may expand by at least 15%, at least 25%, or at least 50% more than the length of the single-walled carbon nanotubes when wetted by the electrolyte. In another example, the multi-walled carbon nanotubes may swell by up to 50% when wetted (e.g., the length of the multi-walled carbon nanotubes increases by 50% after wetting by the electrolyte, and / or the diameter of the multi-walled carbon nanotubes increases by 50% after wetting).

[0035] Multiwalled carbon nanotubes can have an outer diameter of 2.0–50 nanometers, 5.0–40 nanometers, or 6–10 nanometers. Multiwalled carbon nanotubes can have a length greater than 10 nanometers, greater than 15 nanometers, greater than 30 nanometers, greater than 50 nanometers, greater than 100 nanometers, greater than 500 nanometers, greater than 1 micrometer, greater than 5 micrometers, greater than 10 micrometers, or greater than 15 micrometers. At the same time, multiwalled carbon nanotubes can have an average length of up to 25 micrometers or up to 20 micrometers. In exemplary embodiments, multiwalled carbon nanotubes have an average length of 10–20 micrometers, or 20–15 micrometers. Multiwalled carbon nanotubes can have an aspect ratio (ratio of length to diameter) greater than 5.0, greater than 10.0, greater than 50, greater than 100, or greater than 500.

[0036] The electrodes contain multilayer carbon nanotubes that may be relatively longer compared to those contained in electrodes of related technologies. The use of relatively longer multilayer carbon nanotubes in electrodes has been found to have beneficial mechanical and / or electrical properties. For example, multilayer carbon nanotubes provide relatively good output at low densities. As another example, shorter multilayer carbon nanotubes generally do not swell (e.g., expand) as much as longer multilayer carbon nanotubes. Therefore, the use of shorter multilayer carbon nanotubes loses (or reduces) some of the beneficial properties associated with the swelling of carbon nanotubes. As an extreme example, carbon black does not swell because it is simply carbon particles without the entanglement exhibited by sets of multilayer carbon nanotubes. An indicator that a certain amount of multilayer carbon nanotubes has a length exceeding a threshold length and therefore has sufficient swelling properties is observed during the calendering process, and a relatively large amount of pressure or effort to calender the slurry in relation to its application to foil indicates that the collective swelling (e.g., average swelling) of multilayer carbon nanotubes in the active layer meets a certain performance threshold. However, multi-walled carbon nanotubes are generally difficult to process.

[0037] The processing of multi-walled carbon nanotubes related to the preparation / formation of the active layer and / or electrode is milder than the process for electrodes in related technologies. Therefore, processes according to various embodiments maintain longer multi-walled carbon nanotubes (e.g., fewer multi-walled carbon nanotubes are fractured, fragmented, or destroyed). 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 multi-walled carbon nanotubes in electrodes of related technologies. According to various embodiments, the length distribution of the set of multi-walled carbon nanotubes is distorted relative to the nominal length of the multi-walled carbon nanotubes. As an example, the nominal length of the multi-walled carbon nanotubes is approximately 16 microns. For example, the multi-walled carbon nanotubes are processed and / or applied in a manner that reduces or minimizes the fracture or destruction of the multi-walled carbon nanotubes. The length of multi-walled carbon nanotubes in a network of high-aspect-ratio carbon elements is generally the nominal length of the multi-walled carbon nanotubes, or such lengths tend to be more distorted relative to 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 their 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 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 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.

[0038] According to various embodiments, the length distribution of a set of multi-walled carbon nanotubes is distorted relative to the nominal length of the multi-walled carbon nanotubes. For example, multi-walled carbon nanotubes are processed and / or applied in a manner that reduces or minimizes the fragmentation or fracture of the multi-walled carbon nanotubes. The length of multi-walled carbon nanotubes in a network of high aspect ratio carbon elements is generally the nominal length of the multi-walled carbon nanotube, or the length of such multi-walled carbon nanotubes tends to be more distorted relative to the nominal length.

[0039] 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 their nominal length (e.g., 13.4 micrometers to about 15 micrometers). 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 micrometers. 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 micrometers. 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 their nominal length (e.g., 13.4 micrometers to about 15 micrometers). 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 micrometers. 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 micrometers.

[0040] Multiwalled carbon nanotubes may be present in a mixture (the mixture comprising a conductive material, an electrode active material, a binder material, and a solvent) in an amount of 0.3 to 1.0 weight percent, preferably 0.4 to 0.9 weight percent, based on the total weight of the mixture. Multiwalled carbon nanotubes may also be present in a solid anode active layer (the solid active layer, without a solvent, comprising a conductive material, a binder material, and an electrode active material) in an amount of 0.8 to 2.6 weight percent, preferably 1.0 to 1.8 weight percent, based on the total weight of the solid anode active material.

[0041] In examples where both multi-walled and single-walled carbon nanotubes are used, the ratio of the weight of multi-walled carbon nanotubes to the weight of single-walled carbon nanotubes in the mixture or solid active material layer may be at least 2:1.

[0042] In one example, a three-dimensional network of high aspect ratio carbon elements 108 contains carbon nanotubes, and these carbon nanotubes are multi-walled carbon nanotubes and / or fragments of such carbon nanotubes.

[0043] In another example, multi-walled carbon nanotubes are present in a mixture or solid anode active material layer in an amount that is at least twice the amount of single-walled carbon nanotubes, based on the weight of the conductive material.

[0044] A three-dimensional network of high aspect ratio carbon elements 108 can contain at least 99% by weight of carbon.

[0045] A three-dimensional network of high aspect ratio carbon elements 108 may include an electrically interconnected network of carbon elements exhibiting connectivity above a penetration threshold, where the network defines one or more highly conductive paths having a length greater than 100 μm. The penetration threshold is a threshold that provides a conductive network where conductive elements are in contact with each other and measured across any two points on any surface of the network.

[0046] The active layer contains active particles dispersed in a network of conductive elements. The active particles contain an active material, which is typically different at the anode and cathode.

[0047] For example, the anode active material may include silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), titanium (Ti), nickel (Ni), cobalt (Co), cadmium (Cd); alloys of these, or two or more of these, or alloys of these with other elements; oxides, carbides, nitrides, sulfides, phosphides, selenides, and tellurides of these metals, and mixtures thereof or lithium-containing composites; salts and hydroxides of Sn; lithium titanate, lithium manganate, lithium aluminate, lithium-containing titanium oxide, lithium transition metal oxides; pre-lithified versions thereof; Li, Li alloys, or surface-stabilized Li particles having at least 60 wt% lithium; or combinations thereof. The active material may include graphite instead of, or in addition to, the anode active material. As an example, the anode active material may include silicon oxide and / or silicon carbonate. Such an anode active material containing silicon dioxide or silicon carbon dioxide may further contain graphite.

[0048] For example, the cathode active material may include lithium cobalt oxide (LCO, sometimes referred to as "lithium cobaltate" or "lithium cobaltite"). Examples of LCO formulations include LiCoO2, lithium nickel manganese cobalt (NMC, with variations of LiNiMnCo), lithium manganese oxide (LiMn2O4, Li2MnO3, etc., or LMO with variations of combinations thereof), and lithium titanate (LTO, one variation of which is Li4Ti5O 12), lithium iron phosphate (LFP, one variant is LiFePO4), lithium nickel cobalt aluminum oxide (and its variant as NCA), and other similar materials. Other variants of the foregoing may be included.

[0049] When NMC is used as the active material, nickel-rich NMC can be used. For example, a variant of NMC is LiNi x Mn y Co (1-x-y) O2, where x is about 0.7 or more, 0.75, 0.80, 0.85 or more, y is 0.1 or more, 0.15, 0.2, or 0.25, and x + y is less than 1. For example, NMC811 with x being about 0.8 and y being about 0.1 can be used. Alternatively, the active material can include lithium nickel manganese cobalt oxide (LiNi x Mn y Co z O2). Variants of this formula that can be used in the active material layer include NMC111 (detailed below), NMC532 (LiNi 0.5 Mn 0.3 Co 0.2 O2), NMC622 (LiNi 0.6 Mn 0.2 Co 0.2 O2), or combinations thereof.

[0050] In one embodiment, the active material used in both electrodes (anode and / or cathode) may also include a nickel-rich combination of nickel, manganese, and cobalt. Lithium nickel manganese cobalt oxide (LiNiMnCoO2), abbreviated as NMC, provides the high overall performance, excellent specific energy, and lowest self-heating rate of all mainstream cathode powders. NMC powder may contain 20–40 wt% nickel, 20–40 wt% manganese, and 20–40 wt% cobalt, based on the total weight of the NMC blend. While the term “NMC powder” can refer to various blends, it is preferable to use a blend containing 33 wt% nickel, 33 wt% manganese, and 33 wt% cobalt. This blend, sometimes referred to as 1-1-1 (NMC111), is useful for applications using frequent cycles (automotive, energy storage) due to the reduced material cost resulting from a lower cobalt content and the nickel-rich combination of nickel, manganese, and cobalt (NMC). NMC powder may contain 20–40 wt% nickel, 20–40 wt% manganese, and 20–40 wt% cobalt, based on the total weight of the NMC blend. While the term “NMC powder” can refer to various blends, it is preferable to use a blend containing 33 wt% nickel, 33 wt% manganese, and 33 wt% cobalt. This blend, sometimes referred to as 1-1-1, is useful for applications with frequent cycles (automotive, energy storage) due to the reduced material cost resulting from its lower cobalt content. Lithium nickel manganese cobalt oxide (LiNiMnCoO2) provides the high overall performance, excellent specific energy, and lowest self-heating rate of all mainstream cathode powders.

[0051] As disclosed herein, the active material may be located within a network of high-aspect-ratio active materials present in the electrode active layer. The active material may be present in the mixture used to form the electrode in an amount of 35 to 75% by weight, preferably 40 to 70% by weight, based on the total weight of the electrode mixture (a mixture used to produce the electrode active layer containing an electrode polymer binder material, electrode active material, conductive material, and solvent). The electrode active material may be present in the (solvent-free) electrode active layer in an amount of 95 to 98.5% by weight, based on the total weight of the cathode active layer.

[0052] The active layer may also contain a binder. The binder can promote the cohesiveness of other components of the active layer and / or hold the active particles and conductive elements in their relative positions and shapes. The binder may be a polymer or may contain a polymer as a main component. The binder may contain a single polymer that may be a homopolymer or copolymer. Since the active layer disclosed herein is mobile (expands, contracts, etc.), the binder may, advantageously, be a flexible polymer material such as an elastomer or polymer foam. As another example, the binder may be characterized by softening in an electrolyte.

[0053] The binder can also promote the dispersion of active particles and conductive elements (in the case of particulate foam) in the slurry during the production of the active layer. The binder can also promote the adhesion of the active layer to adjacent layers within the battery. The binder may include, for example, cellulosic polymers or acrylic polymers.

[0054] The active layer 110 disclosed herein includes an electrolyte. The electrolyte facilitates the transport of ions between the cathode and the anode. The electrolyte may include a salt in an organic solvent. In certain cases, the organic solvent may be selected to soften the binder. Examples of salts that may be used as electrolytes include lithium hexafluoride phosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetraborate (LiBF4), lithium hexafluorarsenate (LiAsF6), lithium hexafluorosilicate (LiSiF6), and lithium tetraphenylborate (LiB(C6H5)4). Examples of organic solvents include ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, methyl formate, methyl acrylate, methyl butyrate, and ethyl acetate.

[0055] The separator 106 prevents direct electrical contact between the two electrodes but allows ions to pass from one electrode to the other. The separator may include, for example, a polymer film. In a specific example, the separator may include a single-layer or multilayer polymer film comprising one or more polyolefin layers. For example, a film made of a laminate of polyethylene and polypropylene can be used. The separator may have a rough surface, and compliance and / or expansion of the active layer, as described herein, can promote good contact between the active layer and the separator.

[0056] The energy storage devices disclosed herein can be manufactured by mixing a conductive material, an electrode active material, and an optional binder with a liquid to form a slurry. The slurry can be formed into a film and dried to remove the liquid to form an electrode active layer precursor. The energy storage device can then be assembled by placing the electrode active layer precursor adjacent to the first side of a separator, placing a second electrode adjacent to the opposite side of the separator, and providing a first electrolyte to the first electrode active layer precursor to form a first active layer. In one embodiment, the combination of electrodes and separator is placed in a housing before the electrolyte is provided.

[0057] When an electrode with an active layer comes into contact with an electrolyte, it expands, thereby improving contact with the current collector and separator. This improves electrical conductivity.

[0058] All ranges disclosed herein include endpoints, which can be combined independently of each other (for example, the range “up to 25% by weight, or more specifically, 5% to 20% by weight” includes the endpoints and all intermediate values ​​of the range “5% to 25% by weight”, etc.). Furthermore, the upper and lower limits described may be combined to form a range (for example, “at least 1 or at least 2% by weight” and “up to 10 or 5% by weight” may be combined as the range “1 to 10% by weight”, or “1 to 5% by weight”, or “2 to 10% by weight”, or “2 to 5% by weight”).

[0059] This disclosure may, alternatively, include, consist of, or essentially consist of any suitable components disclosed herein. This disclosure may, additionally or alternatively, be formulated to lack, or substantially contain, any components, materials, ingredients, adjuvants, or species used in prior art compositions or not otherwise necessary for achieving the functions and / or purposes of this disclosure.

[0060] All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, if any terminology in this application conflicts with or is inconsistent with any terminology in any of the incorporated references, the terminology from this application shall prevail over the conflicting terminology from the incorporated references.

[0061] Unless otherwise indicated herein, all test standards are the most current standards in effect as of the filing date of this application, or, if priority is claimed, the filing date of the earliest priority application in which the test standard appears.

Claims

1. An energy storage device comprising two electrodes and a separator located between the two electrodes for electrically separating them, wherein at least one of the electrodes comprises an active layer containing electrode active particles, conductive elements, and a first electrolyte, the active layer being characterized by one or more of the following: the volume of the active layer in the presence of the electrolyte is at least 10%, preferably at least 20%, greater than the volume of the combined electrode active particles and conductive elements in the absence of the electrolyte; the conductive elements are in the form of a flexible network that can expand and / or compress; and the active layer contains a flexible binder that facilitates the expansion and contraction of the active layer.

2. The energy storage device according to claim 1, wherein the conductive element includes a web of high aspect ratio conductive elements.

3. The energy storage device according to claim 2, wherein the high aspect ratio conductive element includes carbon nanotubes.

4. The energy storage device according to claim 1, wherein the conductive element is a mesh.

5. The energy storage device according to any one of claims 1 to 4, wherein the active layer comprises the flexible binder.

6. The energy storage device according to claim 4, wherein the flexible binder is a foam.

7. The energy storage device according to claim 4, wherein the flexible binder is softened by the solvent of the electrolyte but does not dissolve in the solvent of the electrolyte.

8. The energy storage device according to any one of claims 1 to 7, wherein the flexible network behaves as a spring.

9. An energy storage device comprising two electrodes and a separator located between the two electrodes, wherein at least one of the two electrodes contains active particles, a conductive element, and an electrolyte, and is characterized in that its volume in use is at least 10%, preferably at least 20%, larger than its original volume.

10. The energy storage device according to any one of claims 1 to 9, wherein the active layer has a volume in use of 30 to 60% of the volume of the active layer precursor, which includes the electrode active particles contained within the network of conductive elements.

11. The energy storage device according to any one of claims 1 to 10, wherein the electrolyte comprises a salt in an organic solvent, the active layer comprises a binder, and the binder is softened by the organic solvent but not dissolved by the organic solvent.

12. A method for fabricating an energy storage device, To provide a slurry containing a conductive element, electrode-active particles, and an optional binder in a liquid. Forming a film of the slurry, The liquid is removed by drying to form an electrode active layer precursor, The energy storage device is assembled by arranging the electrode active layer precursor adjacent to the first side of the separator. The second electrode is placed adjacent to the opposite side of the separator, A method comprising providing an electrolyte to the electrode active layer precursor to form a first active layer.

13. The method according to claim 12, wherein the electrode activation precursor, the separator, and the second electrode are arranged in the housing before the electrolyte is provided.

14. The method according to claim 12 or 13, characterized in that the active layer is characterized by one or more of the following: the volume of the first active layer in the presence of the first electrolyte is at least 10%, preferably at least 20%, greater than the volume of the combination of the first electrode active particles and the first conductive element in the absence of the first electrolyte; the first conductive element is in the form of a flexible network that can be expanded and / or compressed; and the active layer contains a flexible binder that facilitates the expansion and contraction of the active layer.

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