Electrode including capacitor material disposed on or intermingled with electroactive material and electrochemical cell including the same

A capacitor-assisted electrode for an electrochemical cell that cycles lithium ions is provided. The capacitor-assisted electrode may include at least two electroactive materials disposed on one or more surfaces of a current collector. A first electroactive material of the at least two electroactive materials may have a first reversible specific capacity and forms a first electroactive material having a first press density. A second electroactive material of the at least two electroactive materials has a second reversible specific capacity and forms a second electroactive material having a second press density. The second reversible specific capacity may be different from the first reversible specific capacity. The second press density may be different from the first press density. One or more capacitor materials may be disposed on or intermingled with one or more of the at least two electroactive materials.

The present disclosure relates to capacitor-assisted gradient electrodes, electrochemical cells including capacitor-assisted gradient electrodes, and methods of formation relating thereto.

Advanced energy storage devices and systems are in demand to satisfy energy and/or power requirements for a variety of products, including automotive products such as start-stop systems (e.g., 12V start-stop systems), battery-assisted systems, hybrid electric vehicles (“HEVs”), and electric vehicles (“EVs”). Typical lithium ion batteries include at least two electrodes and an electrolyte and/or separator. One of the two electrodes serves as a positive electrode or cathode and the other electrode serves as a negative electrode or anode. A separator and/or electrolyte may be disposed between the negative and positive electrodes. The electrolyte is suitable for conducting lithium ions between the electrodes and, like the two electrodes, may be in solid and/or liquid form and/or a hybrid thereof. In instances of solid-state batteries, which include solid-state electrodes and a solid-state electrolyte, the solid-state electrolyte may physically separate the electrodes so that a distinct separator is not required.

Conventional rechargeable lithium-ion batteries operate by reversibly passing lithium ions back and forth between the negative electrode and the positive electrode. For example, lithium ions may move from the positive electrode to the negative electrode during charging of the battery, and in the opposite direction when discharging the battery. Such lithium-ion batteries can reversibly supply power to an associated load device on demand. More specifically, electrical power can be supplied to a load device by the lithium-ion battery until the lithium content of the negative electrode is effectively depleted. The battery may then be recharged by passing a suitable direct electrical current in the opposite direction between the electrodes.

During discharge, the negative electrode may contain a comparatively high concentration of intercalated lithium, which is oxidized into lithium ions and electrons. Lithium ions may travel from the negative electrode to the positive electrode, for example, through the ionically conductive electrolyte solution contained within the pores of an interposed porous separator. Concurrently, electrons pass through an external circuit from the negative electrode to the positive electrode. Such lithium ions may be incorporated into the material of the positive electrode by an electrochemical reduction reaction. The battery may be recharged or regenerated after a partial or full discharge of its available capacity by an external power source, which reverses the electrochemical reactions that transpired during discharge.

In various instances, however, the lithium-ion battery may experience limited regeneration capabilities, for example as a result of lithium plating on one or more surfaces of the negative electrode, especially during high power and frequent regeneration processes. Some materials, such as hard carbon, may experience improved regeneration capabilities and minimal plating. However, such materials are costly. Accordingly, it would be desirable to develop high-performance electrode designs and methods that enhance intercalation and de-intercalation rates and high-power regeneration capabilities.

SUMMARY

In various aspects, the present disclosure provides a capacitor-assisted electrode for an electrochemical cell that cycles lithium ions. The capacitor-assisted electrode includes at least two electroactive materials disposed on one or more surfaces of a current collector. A first electroactive material of the at least two electroactive materials may have a first reversible specific capacity. A second electroactive material of the at least two electroactive materials may have a second reversible specific capacity. The second reversible specific capacity may be different from the first reversible specific capacity. One or more capacitor materials may be disposed on or intermingled with one or more of the at least two electroactive materials.

In one aspect, the first electroactive material may form a first electroactive material layer. The first electroactive material layer may be disposed adjacent to the one or more surfaces of the current collector. The first electroactive material layer may define a first exposed surface. The second electroactive material may form a second electroactive material layer. The second electroactive material layer may be disposed adjacent to the first exposed surface of the first electroactive material layer.

In one aspect, the first electroactive material layer may have a first press density and the second electroactive material layer may have a second press density. The second press density may be greater than the first press density.

In one aspect, the second reversible specific capacity may be greater than the first reversible specific capacity.

In one aspect, the second electroactive material layer may define a second exposed surface and the at least two electroactive materials may further include a third electroactive material having a third reversible specific capacity. The third electroactive material may forms a third electroactive material layer. The third electroactive material layer may be disposed adjacent to the second exposed surface of the second electroactive material layer.

In one aspect, the first electroactive material layer may have a first press density. The second electroactive material layer may have a second press density. The third electroactive material layer may have a third press density. The third press density may be less than or equal to the second press density. The second press density may be less than or equal to the first press density.

In one aspect, the first press density, the second press density, and the third press density may be each independently greater than or equal to about 2.0 g/cc to less than or equal to about 3.5 g/cc.

In one aspect, the first press density, the second press density, and the third press density may be each independently greater than or equal to about 1.0 g/cc to less than or equal to about 2.0 g/cc.

In one aspect, the third reversible specific capacity may be greater than the second reversible specific capacity. The second reversible specific capacity may be greater than the first reversible specific capacity.

In one aspect, the third reversible specific capacity may be the same as the second reversible specific capacity. The second and third reversible specific capacities may be greater than the first reversible specific capacity.

In one aspect, the second reversible specific capacity may be greater than the third reversible specific capacity. The first reversible specific capacity may be greater than the second reversible specific capacity.

In one aspect, the one or more capacitor materials may be intermingled with the third electroactive material to form the third electroactive material layer.

In one aspect, the one or more capacitor materials may form a capacitor material layer. The capacitor material layer may be disposed adjacent to a third exposed surface of the third electroactive material layer.

In various other aspects, the present disclosure provides an electrochemical cell that cycles lithium ions. The electrochemical cell that cycles lithium ions includes a first electrode comprising a first electroactive material and a second electrode. The second electrode may include a first layer disposed adjacent to a surface of a current collector; at least one additional layer disposed adjacent to a surface of the first layer; and one or more capacitor materials disposed adjacent to or intermingled with one or more of the first layer and the at least one additional layer. The first layer may have a first reversible specific capacity. The additional layer may have an additional reversible specific capacity that is different from the first reversible specific capacity. The first layer and the at least one additional layer may each include a respective electroactive material.

In one aspect, the at least one additional layer may include a second layer and a third layer. The second layer may be disposed adjacent to the surface of the first layer. The third layer may be disposed adjacent to a surface of the second layer. The second layer may have a second reversible specific capacity. The third layer may have a third reversible specific capacity. The third reversible specific capacity may be greater than the second reversible specific capacity. The second reversible specific capacity may be greater than the first reversible specific capacity.

In one aspect, the first layer may have a first press density. The second layer may have a second press density. The third layer may have a third press density. The second press density maybe greater than the third press density. The first press density may be greater than the second press density. The first layer may include greater than about 0 wt. % to less than or equal to about 100 wt. % of the first electroactive material. The second layer may include greater than about 0 wt. % to less than or equal to about 80 wt. % of a second electroactive material. The third layer may include greater than about 0 wt. % to less than or equal to about 50 wt. % of a third electroactive material.

In one aspect, the first, second, and third electroactive materials may be the same. The one or more capacitor materials may form a first capacitor layer adjacent to a surface of the third electroactive layer.

In one aspect, the one or more capacitor materials may be intermingled with the third layer.

In one aspect, the current collector may be a first current collector and the one or more capacitor materials may be first capacitor materials. The first electrode may include a second layer disposed adjacent to a surface of a second current collector; at least one second additional layer disposed adjacent to a surface of the second layer; and one or more second capacitor materials disposed adjacent or intermingled with one or more of the first layer and the at least one second additional layer. The second layer may have a second reversible specific capacity. The additional layer may have an additional reversible specific capacity that is different from the second reversible specific capacity. The second layer and the at least one second additional layer may each comprise a respective electroactive material.

DETAILED DESCRIPTION

The present technology pertains to capacitor-assisted gradient electrodes, electrochemical cells including capacitor-assisted gradient electrodes, and methods of formation relating thereto. For example, capacitor-material coatings or layers disposed on exposed surfaces of an electrode may absorb the regeneration current pulses, for example braking regeneration current during braking regeneration in battery electric vehicles (BEVs). Specific capacity and press density gradients may assist lithium deintercalation and intercalation in respective electrodes. Such electrodes and electrochemical cells integrate capacitors with lithium-ion batteries that may be used in, for example, automotive or other vehicles (e.g., motorcycles, boats), but may also be used in electrochemical cells used in a variety of other industries and applications, such as consumer electronic devices, by way of non-limiting example.

An exemplary and schematic illustration of an electrochemical cell (also referred to as the battery)20is shown inFIG.1. The battery20includes a negative electrode30, a positive electrode40, and a separator52disposed between the electrodes30,40. As shown, the negative electrode30and positive electrode40are capacitor-assisted electrodes in accordance with certain aspects of the present disclosure, in that they include both electroactive materials and capacitor materials, such that they function as a hybrid electrode and capacitor. Batteries may incorporate solid-state electrolytes, liquid electrolytes, or semi-solid/gel electrolytes. As shown inFIG.1, a separator52provides electrical separation and prevents physical contact between the electrodes30,40. For example, the separator52provides a minimal resistance path for internal passage of lithium ions, and in certain instances, related anions, during cycling of the lithium ions. In various aspects, the negative electrode30, positive electrode40, and/or the separator52may each include an electrolyte solution or system50.

Any appropriate electrolyte50, whether in solid, liquid, or gel form, capable of conducting lithium ions between the electrodes30,40, may be used in the battery20. For example, as shown inFIG.1, the electrolyte50may be a non-aqueous liquid electrolyte solution that includes a lithium salt dissolved in an organic solvent or a mixture of organic solvents. In certain variations, the separator52may be formed of a microporous insulating material, where liquid or semi-solid electrolyte can be imbibed into the pores. While not shown, in various aspects, the liquid electrolyte50and separator52may be substituted for solid-state electrolyte particles. For example, solid-state electrolyte particles may serve as both ion conductors (e.g., to transport lithium ions) and electrical insulators (e.g., to prevent charge or current from flowing from the negative electrode30to the positive electrode40). For example, the separator52may be defined by a plurality of solid-state electrolyte particles (not shown). In certain variations, solid-state electrolyte particles (not shown) may also be mixed with electroactive materials34,44present in the negative and positive electrodes30,40, respectively.

A negative electrode current collector32may be positioned at or near the negative electrode30, and a positive electrode current collector42may be positioned at or near the positive electrode40. The negative electrode current collector32and the positive electrode current collector42respectively collect and move free electrons to and from an external circuit22. For example, an interruptible external circuit22and a load device24may connect the negative electrode30(through the negative electrode current collector32) and the positive electrode40(through the positive electrode current collector42). The positive electrode current collector42may be a metal foil, metal grid or screen, or expanded metal comprising aluminum or any other appropriate electrically conductive material known to those of skill in the art. The negative electrode current collector32may be a metal foil, metal grid or screen, or expanded metal comprising copper or any other appropriate electrically conductive material known to those of skill in the art.

The battery20can generate an electric current during discharge by way of reversible electrochemical reactions that occur when the external circuit22is closed (to connect the negative electrode30and the positive electrode40) and the negative electrode30contains a relatively greater quantity of available lithium. The chemical potential difference between the positive electrode40and the negative electrode30drives electrons produced by the oxidation of inserted lithium at the negative electrode30through the external circuit22towards the positive electrode40. Lithium ions, which are also produced at the negative electrode30, are concurrently transferred through the separator52towards the positive electrode40. The electrons flow through the external circuit22and the lithium ions migrate across the separator52to the positive electrode40, where they may be reacted or intercalated. The electric current passing through the external circuit22can be harnessed and directed through the load device24until the available lithium in the negative electrode30is depleted and the capacity of the battery20is diminished.

The battery20can be charged or re-energized at any time by connecting an external power source (e.g., charging device) to the battery20to reverse the electrochemical reactions that occur during battery discharge. The connection of the external power source to the battery20compels the non-spontaneous oxidation of one or more metal elements at the positive electrode40to produce electrons and lithium ions. The electrons, which flow back towards the negative electrode30through the external circuit22, and the lithium ions, which move across the separator52back towards the negative electrode30, reduce at the negative electrode30and replenish it with lithium for consumption during the next battery discharge cycle. As such, each discharge and charge event is considered to be a cycle, where lithium ions are cycled between the positive electrode40and the negative electrode30.

The external power source that may be used to charge the battery20may vary depending on size, construction, and particular end-use of the battery20. Some notable and exemplary external power sources include, but are not limited to, AC power sources, such as an AC wall outlet and a motor vehicle alternator. In many battery20configurations, each of the negative electrode current collector32, the negative electrode30, the separator52, the positive electrode40, and the positive electrode current collector42are prepared as relatively thin layers (for example, from several microns to a millimeter or less in thickness) and assembled in layers connected in electrical parallel arrangement to provide a suitable electrical energy and power package. In various other instances, the battery20may include electrodes30,40that are connected in series.

Further, in certain aspects, the battery20may include a variety of other components that, while not depicted here, are nonetheless known to those of skill in the art. For instance, the battery20may include a casing, gasket, vents, terminal caps, and any other conventional components or materials that may be situated within the battery20, including between or around the negative electrode30, the positive electrode40, and/or the separator52, by way of non-limiting example. As noted above, the size and shape of the battery20may vary depending on the particular applications for which it is designed. Battery-powered vehicles, hybrid (for example start-stop, microhybrid, and mild-hybrid) internal combustion vehicles, and hand-held consumer electronic devices are three non-limiting examples where the battery20would most likely be designed to different size, capacity, and power-output specifications. The battery20may also be connected in series or parallel with other similar lithium-ion cells or batteries to produce a greater voltage output, energy, and power if it is required by the load device24.

Accordingly, the battery20can generate electric current to a load device24that can be operatively connected to the external circuit22. The load device24may be powered fully or partially by the electric current passing through the external circuit22when the lithium ion battery20is discharging. While the load device24may be any number of known electrically-powered devices, a few specific examples of power-consuming load devices include an electric motor for a hybrid vehicle or an all-electric vehicle, a laptop computer, a tablet computer, a cellular phone, and cordless power tools or appliances, by way of non-limiting example. The load device24may also be a power-generating apparatus that charges the battery20for purposes of storing energy.

With renewed reference toFIG.1, the negative and positive electrodes30,40and/or the separator52may each include an electrolyte solution or system50. As noted above, the electrolyte50may be a non-aqueous liquid electrolyte solution, which may include a lithium salt dissolved in an organic solvent or a mixture of organic solvents. Numerous conventional non-aqueous liquid electrolyte solutions may be employed in the battery20.

These and other similar lithium salts may be dissolved in a variety of organic solvents, including but not limited to various alkyl carbonates, such as cyclic carbonates (e.g., ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), fluoroethylene carbonate (FEC)), linear carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC)), aliphatic carboxylic esters (e.g., methyl formate, methyl acetate, methyl propionate), γ-lactones (e.g., γ-butyrolactone, γ-valerolactone), chain structure ethers (e.g., 1,2-dimethoxyethane (DME), 1-2-diethoxyethane, ethoxymethoxyethane), cyclic ethers (e.g., tetrahydrofuran, 2-methyltetrahydrofuran), 1,3-dioxolane (DOL)), sulfur compounds (e.g., sulfolane), and combinations thereof. In various aspects, the electrolyte50may include greater than or equal to 1 M to less than or equal to about 2 M concentration of the one or more lithium salts. In certain variations, for example when the electrolyte has a lithium concentration greater than about 2 M or ionic liquids, the electrolyte50may include one or more diluters, such as fluoroethylene carbonate (FEC) and/or hydrofluoroether (HFE).

In various aspects, as described above, the electrolyte50may be a solid-state electrolyte, where the particles form both the electrolyte50and the separator52. The solid-state electrolyte may include one or more solid-state electrolyte particles that may comprise one or more polymer-based components, oxide-based particles, sulfide-based particles, halide-based particles, borate-based particles, nitride-based particles, and hydride-based particles. Such a solid-state electrolyte may be disposed in a plurality of layers so as to define a three-dimensional structure. In various aspects, the polymer-based components may be intermingled with a lithium salt so as to act as a solid solvent. In certain variations, the polymer-based components may comprise one or more of polymer materials selected from the group consisting of: polyethylene glycol, polyethylene oxide (PEO), poly(p-phenylene oxide) (PPO), poly(methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP), polyvinyl chloride (PVC), and combinations thereof. In one variation, the one or more polymer materials may have an ionic conductivity equal to about 104S/cm.

In various aspects, the oxide-based particles may comprise one or more garnet ceramics, LISICON-type oxides, NASICON-type oxides, and Perovskite-type ceramics. For example, the one or more garnet ceramics may be selected from the group consisting of: Li6.5La3Zr1.75Te0.25O12, Li7La3Zr2O12, Li6.2Ga0.3La2.95Rb0.05Zr2O12, Li6.85La2.9Ca0.1Zr1.75Nb0.25O12, Li6.25Al0.25La3Zr2O12, L16.75La3Zr1.75Nb0.25O12, Li6.75La3Zr1.75Nb0.25O12, and combinations thereof. The one or more LISICON-type oxides may be selected from the group consisting of: Li14Zn(GeO4)4, Li3+x(P1−xSix)O4(where 0<x<1), Li3+xGexV1−xO4(where 0<x<1), and combinations thereof. The one or more NASICON-type oxides may be defined by LiMM′(PO4)3, where M and M′ are independently selected from Al, Ge, Ti, Sn, Hf, Zr, and La. For example, in certain variations, the one or more NASICON-type oxides may be selected from the group consisting of: Li1+xAlxGe2−x(PO4)3(LAGP) (where 0≤x≤2), Li1+xAlxTi2−x(PO4)3(LAGP) (where 0≤x≤2), Li1−xYxZr2−x(PO4)3(LYZP) (where 0≤X≤2), Li1.3Al0.3Ti1.7(PO4)3, LiTi2(PO4)3, LiGeTi2(PO4)3, LiGe2(PO4)3, LiHf2(PO4)3, and combinations thereof. The one or more Perovskite-type ceramics may be selected from the group consisting of: Li3.3La0.53TiO3, LiSr1.65Zr1.3Ta1.7O9, Li2x−ySr1−xTayZr1−yO3(where X=0.75y and 0.60<y<0.75), Li3/8Sr7/16Nb3/4Zr1/4O3, Li3xLa(2/3−x)TiO3(where 0<x<0.25), and combinations thereof. In one variation, the one or more oxide-based materials may have an ionic conductivity greater than or equal to about 10−5S/cm to less than or equal to about 10−1S/cm.

In various aspects, the sulfide-based particles may include one or more sulfide-based materials selected from the group consisting of: Li2S—P2S5, Li2S—P2S5-MSx(where M is Si, Ge, and Sn and 0≤x≤2), Li3.4Si0.4P0.6S4, Li10GeP2S11.7O0.3, Li9.6P3S12, Li7P3S11, Li9P3S9O3, Li10.35Si1.35P1.65S12, Li9.81Sn0.81P2.19S12, Li10(Si0.5Ge0.5)P2S12, Li(Ge0.5Sn0.5)P2S12, Li(Si0.5Sn0.5)PsS12, Li10GeP2S12(LGPS), Li6PS5X (where X is Cl, Br, or I), Li7P2S8I, Li10.35Ge1.35P1.65S12, Li3.25Ge0.25P0.75S4, Li10SnP2S12, Li10SiP2S12, Li9.54Si1.74P1.44S11.7Cl0.3, (1−X)P2S5−XLi2S (where 0.5≤x≤0.7), and combinations thereof. In one variation, the one or more sulfide-based materials may have an ionic conductivity greater than or equal to about 10−7S/cm to less than or equal to about 1 S/cm.

In various aspects, the halide-based particles may include one or more halide-based materials selected from the group consisting of: Li2CdCl4, Li2MgCl4, Li2CdI4, Li2ZnI4, Li3OCl, LiI, Li5ZnI4, Li3OCl1−xBrx(where 0<x<1), and combinations thereof. In one variation, the one or more halide-based materials may have an ionic conductivity greater than or equal to about 10−8S/cm to less than or equal to about 10−1S/cm.

In various aspects, the borate-based particles may include one or more borate-based materials selected from the group consisting of: Li2B4O7, Li2O—(B2O3)—(P2O5), and combinations thereof. In one variation, the one or more borate-based materials may have an ionic conductivity greater than or equal to about 10−7S/cm to less than or equal to about 10−2S/cm.

In various aspects, the nitride-based particles may include one or more nitride-based materials selected from the group consisting of: Li3N, Li7PN4, LiSi2N3, LiPON, and combinations thereof. In one variation, the one or more nitride-based materials may have an ionic conductivity greater than or equal to about 10−9S/cm to less than or equal to about 1 S/cm.

In various aspects, the hydride-based particles may include one or more hydride-based materials selected from the group consisting of: Li3AlH6, LiBH4, LiBH4—LiX (where X is one of Cl, Br, and I), LiNH2, Li2NH, LiBH4—LiNH2, and combinations thereof. In one variation, the one or more hydride-based materials may have an ionic conductivity greater than or equal to about 10−7S/cm to less than or equal to about 10−2S/cm.

In still further variations, the electrolyte50may be a quasi-solid electrolyte comprising a hybrid of the above detailed non-aqueous liquid electrolyte solution and solid-state electrolyte systems—for example including one or more ionic liquids and one or more metal oxide particles, such as aluminum oxide (Al2O3) and/or silicon dioxide (SiO2).

In various instances, the separator52may be a microporous polymeric separator including a polyolefin, including those made from a homopolymer (derived from a single monomer constituent) or a heteropolymer (derived from more than one monomer constituent), which may be either linear or branched. In certain aspects, the polyolefin may be polyethylene (PE), polypropylene (PP), or a blend of PE and PP, or multi-layered structured porous films of PE and/or PP. Commercially available polyolefin porous separator52membranes include CELGARD® 2500 (a monolayer polypropylene separator) and CELGARD® 2340 (a trilayer polypropylene/polyethylene/polypropylene separator) available from Celgard LLC.

When the separator52is a microporous polymeric separator, it may be a single layer or a multi-layer laminate. For example, in one embodiment, a single layer of the polyolefin may form the entire microporous polymer separator52. In other aspects, the separator52may be a fibrous membrane having an abundance of pores extending between the opposing surfaces and may have a thickness of less than a millimeter, for example. As another example, however, multiple discrete layers of similar or dissimilar polyolefins may be assembled to form the separator52.

Furthermore, the separator52may be mixed with a ceramic material or its surface may be coated in a ceramic material. For example, a ceramic coating may include alumina (Al2O3), silicon dioxide (SiO2), or combinations thereof. Various conventionally available polymers and commercial products for forming the separator52are contemplated, as well as the many manufacturing methods that may be employed to produce such a microporous polymer separator52.

The negative electrode30is formed from a lithium host material that is capable of functioning as a negative terminal of a lithium ion battery. For example, the negative electrode30may comprise a lithium host material (e.g., negative electroactive material) that is capable of functioning as a negative terminal of the battery20. In various aspects, the negative electrode30may be defined by a plurality of negative electroactive material particles34. Such negative electroactive material particles34may be disposed in one or more layers so as to define the three-dimensional structure of the negative electrode30. In certain variations, the negative electrode30may further include the electrolyte50, for example a plurality of electrolyte particles (not shown).

The negative electrode30may include a negative electroactive material that is lithium-based comprising, for example, a lithium metal and/or lithium alloy. In other variations, the negative electrode30may be a negative electroactive material that is silicon-based comprising silicon, for example, a silicon alloy, silicon oxide, or combinations thereof that may be further mixed, in certain instances, with graphite. In still other variations, the negative electrode30may include a negative electroactive material that is carbonaceous-based comprising one or more of graphite, graphene, carbon nanotubes (CNTs), and combinations thereof. In still further variations, the negative electrode30may comprise one or more lithium-accepting negative electroactive materials such as lithium titanium oxide (Li4Ti5O12), one or more transition metals (such as tin (Sn)), one or more metal oxides (such as vanadium oxide (V2O5), tin oxide (SnO), titanium dioxide (TiO2)), titanium niobium oxide (TixNbyOz, where 0≤x≤2, 0≤y≤24, and 0≤z≤64), metal alloys such as copper-tin alloy (Cu6Sn5), and one or more metal sulfides (such as iron sulfide (FeS)).

In various aspects, the negative electroactive materials in the negative electrode30may be optionally intermingled with one or more electrically conductive materials that provide an electron conductive path and/or at least one polymeric binder material that improves the structural integrity of the negative electrode30. For example, the negative electroactive material may be optionally intermingled with binders such as poly(tetrafluoroethylene) (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile butadiene rubber (NBR), styrene ethylene butylene styrene copolymer (SEBS), styrene butadiene styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, and combinations thereof. Electrically conductive materials may include carbon-based materials, powder nickel or other metal particles, or a conductive polymer. Carbon-based materials may include, for example, particles of carbon black, graphite, superP, acetylene black (such as KETCHEN™ black or DENKA™ black), carbon fibers and nanotubes, graphene, and the like. Examples of a conductive polymer include polyaniline, polythiophene, polyacetylene, polypyrrole, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, and the like.

The negative electrode30may include greater than or equal to about 50 wt. % to less than or equal to about 97 wt. % of the negative electroactive material, optionally greater than or equal to about 0 wt. % to less than or equal to about 60 wt. % of a solid-state electrolyte, optionally greater than or equal to about 0 wt. % to less than or equal to about 15 wt. % of electrically conductive materials, and optionally greater than or equal to about 0 wt. % to less than or equal to about 10 wt. % of a binder.

In various aspects, the negative electrode30further includes one or more first capacitor materials36disposed on, or in certain aspects, intermingled with the negative electroactive material particles34. For example, as seen inFIG.1, the negative electrode30may have a first region or layer31comprising the negative electroactive material particles34and a second region or layer37comprising the one or more first capacitor materials36. In certain aspects, the first region or layer31may be disposed on a surface33of the negative electrode current collector32. The first region or layer31may define an exposed surface35. The second region or layer37may be disposed on the exposed surface35. For example, the second layer37comprising the one or more first capacitor materials36may have a thickness greater than or equal to about 10 nm to less than or equal to about 1 mm, and in certain aspects, optionally greater than or equal to about 100 nm to less than or equal to about 200 μm; and the first layer31may have a thickness greater than or equal to about 1 μm to less than or equal to about 2000 μm.

While not shown, as appreciated by those of skill in the art, the first layer31and second layer37may not form discrete layers, but rather may have intermingled particles with different concentrations of the negative electroactive materials34and the one or more first capacitor materials36, such that a gradient of distinct particles may be formed within the negative electrode30. For example, where a concentration of the negative electroactive material particles34is highest adjacent to the surface33of the negative electrode current collector32and the first capacitor material particles36have a concentration that is greatest adjacent to the separator52. Various embodiments of such gradients are further described below, by way of example.

The first capacitor material36may include one or more capacitor materials such as one or more metal oxides (MO, where M is one of cobalt (Co), ruthenium (Ru), niobium (Nb), iridium (Ir), manganese (Mn), chromium (Cr), tantalum (Ta), vanadium (V), and molybdenum (Mo) and 0.5≤x≤3.5), for example one or more metal oxides selected from cobalt oxide (Co3O4), manganese oxide (MnO2), iridium oxide (IrO2), niobium pentoxide (Nb2O5), ruthenium oxide (RuO2), tantalum pentoxide (Ta2O5), tin oxide (SnO2), and vanadium oxide (V2O5); metal sulfides, for example one or more metal sulfides selected from titanium disulfide (TiS2), copper sulfide (CuS), and iron sulfide (FeS); carbon-based materials, for example one or more carbonaceous materials selected from activated carbon, graphene, graphite, rnesoporous carbon, macroporous carbon, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon aero gels, and activated carbon fiber cloth; and polymer-based materials, for example one or more polymer selected from polyaniline, polyacetylene, poly(3,4-ethylenedioxythiophene), and poly(3,4-ethylenedioxythiophene), poly(4-styrenesulfonate).

In various aspects, the negative electrode30may include greater than or equal to about 50 wt. % to less than or equal to about 97 wt. % of the negative electroactive material, optionally greater than or equal to about 0 wt. % to less than or equal to about 60 wt. % of a solid-state electrolyte; optionally greater than or equal to about 0 wt. % to less than or equal to about 15 wt. % of electrically conductive materials, optionally greater than or equal to about 0 wt. % to less than or equal to about 10 wt. % of a binder, and optionally greater than or equal to about 0 wt. % to less than or equal to about 10 wt. % of the first capacitor material particles36. Integration of such first capacitor material particles36may improve the pulsed high power capability, such as reaeration performance, of the battery20.

The positive electrode40comprises a lithium-based positive electroactive material that is capable of undergoing lithium intercalation and deintercalation, alloying and dealloying, or plating and stripping, while functioning as a positive terminal of the capacitor battery20. In various aspects, the positive electrode40may be defined by a plurality of electroactive material particles44. Such positive electroactive material particles44may be disposed in one or more layers so as to define the three-dimensional structure of the positive electrode40. In certain variations, the positive electrode40may further include the electrolyte50, for example a plurality of electrolyte particles (not shown).

The positive electrode40may be one of a layered-oxide cathode, a spinel cathode, an olivine cathode, a tavorite cathode, a borate cathode, and a silicate cathode. For example, layered-oxide cathodes (e.g., rock salt layered oxides) comprise one or more lithium-based positive electroactive materials selected from LiNixMnyCo1−x−yO2(where 0≤x≤1 and 0≤y≤1), LiNixMn1−xO2(where 0≤x≤1), Li1+xMO2(where M is one of Mn, Ni, Co, and Al and 0≤x≤1) (for example LiCoO2(LCO), LiNiO2, LiMnO2, LiNi0.5Mn0.5O2, NMC111, NMC523, NMC622, NMC721, NMC811, NMC165, NMC174, NCA). Spinel cathodes comprise one or more lithium-based positive electroactive materials selected from LiMn2O4(LMO) and LiNi0.5Mn1.5O4. Olivine-type cathodes comprise one or more lithium-based positive electroactive material such as LiV2(PO4)3, LiFePO4, LiCoPO4, and LiMnPO4. Tavorite-type cathodes comprise lithium-based positive electroactive materials such as LiVPO4F. Borate-type cathodes comprise, for example, one or more lithium-based positive electroactive materials selected from LiFeBO3, LiCoBO3, and LiMnBO3. Silicate-type cathodes comprise, for example, one or more lithium-based positive electroactive materials selected from Li2FeSiO4, Li2MnSiO4, and LiMnSiO4F. In still further variations, the positive electrode40may comprise one or more other lithium-based positive electroactive materials, such as one or more of dilithium (2,5-dilithiooxy)terephthalate. In various aspects, the positive electroactive material may be optionally coated (for example by LiNbO3and/or Al2O3) and/or may be doped (for example by magnesium (Mg), zirconium (Zr), and/or fluorine (F)).

In various aspects, the positive electrode40may be optionally intermingled with one or more electrically conductive materials that provide an electron conductive path and/or at least one polymeric binder material that improves the structural integrity of the positive electrode40. For example, the positive electrode40may be optionally intermingled with binders such as poly(tetrafluoroethylene) (PTFE), polyvinylidene fluoride (PVDF), nitrile butadiene rubber (NBR), styrene ethylene butylene styrene copolymer (SEBS), styrene butadiene styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, and combinations thereof. Electrically conductive materials may include carbon-based materials, powder nickel or other metal particles, or a conductive polymer. Carbon-based materials may include, for example, particles of carbon black, graphite, acetylene black (such as KETCHEN™ black or DENKA™ black), carbon fibers and nanotubes, graphene, and the like. Examples of a conductive polymer include polyaniline, polythiophene, polyacetylene, polypyrrole, and the like.

The positive electrode40may include greater than or equal to about 50 wt. % to less than or equal to about 97 wt. % of the positive electroactive material, optionally greater than or equal to about 0 wt. % to less than or equal to about 60 wt. % of a solid-state electrolyte, optionally greater than or equal to about 0 wt. % to less than or equal to about 15 wt. % of electrically conductive materials, and optionally greater than or equal to about 0 wt. % to less than or equal to about 10 wt. % of a binder. For example, in certain aspects, the positive electrode40may include about 95 wt. % of the positive electroactive material, about 3 wt. % of the electrically conductive materials, and about 2 wt. % of the binder.

In various aspects, the positive electrode40further includes one or more second capacitor materials disposed on, or in certain aspects, intermingled with, the positive electroactive material particles44. For example, as seen inFIG.1, the positive electrode40may have a first region or layer41comprising the positive electroactive material particles44and a second region or layer47comprising the one or more second capacitor materials46. In certain aspects, the first region or layer41may be disposed on a surface43of the positive electrode current collector42. The first region or layer41may define an exposed surface45. The second region or layer47may be disposed on the exposed surface45. For example, the second layer47comprising the one or more second capacitor materials46may have a thickness greater than or equal to about 10 nm to less than or equal to about 1 mm, and in certain aspects, optionally greater than or equal to about 200 nm to less than or equal to about 200 μm; and the second layer47may have a thickness greater than or equal to about 1 μm to less than or equal to about 2000 μm.

While not shown, as appreciated by those of skill in the art, the first layer41and the second layer47may not form discrete layers, but rather may have intermingled particles with different concentrations of the positive electroactive materials44and the one or more second capacitor materials46, such that a gradient of distinct particles may be formed within the positive electrode40. For example, where a concentration of the positive electroactive materials44is highest adjacent to the surface43of the positive electrode current collector42and the particles comprising the second capacitor materials46have a concentration that is greatest adjacent to the separator52. Various embodiments of such gradients are further described below, by way of example.

The particles comprising the second capacitor material46may be the same or different from the particles comprising the first capacitor materials36. For example, the particles comprising the second capacitor material46include one or more capacitor materials such as one or more metal oxides (MO, where M is one of cobalt (Co), ruthenium (Ru), niobium (Nb), iridium (Ir), manganese (Mn), chromium (Cr), tantalum (Ta), vanadium (V), and molybdenum (Mo) and 0.5≤x≤3.5), for example one or more metal oxides selected from cobalt oxide (Co3O4), manganese oxide (MnO2), iridium oxide (IrO2), niobium pentoxide (Nb2O5), ruthenium oxide (RuO2), tantalum pentoxide (Ta2O5), tin oxide (SnO2), and vanadium oxide (V2O5); metal sulfides, for example one or more metal sulfides selected from titanium disulfide (TiS2), copper sulfide (CuS), and iron sulfide (FeS); carbon-based materials, for example one or more carbonaceous materials selected from activated carbon, graphene, graphite, rnesoporous carbon, macroporous carbon, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon aerogels, and activated carbon fiber cloth; and polymer-based materials, for example one or more polymer selected from polyaniline, polyacetylene, poly(3,4-ethylenedioxythiophene), and poly(3,4-ethylenedioxythiophene), poly(4-styrenesulfonate).

The positive electrode40may include greater than or equal to about 50 wt. % to less than or equal to about 97 wt. % of the positive electroactive material44, optionally greater than or equal to about 0 wt. % to less than or equal to about 60 wt. % of a solid-state electrolyte, optionally greater than or equal to about 0 wt. % to less than or equal to about 15 wt. % of electrically conductive materials, optionally greater than or equal to about 0 wt. % to less than or equal to about 10 wt. % of a binder, and optionally greater than or equal to about 0 wt. % to less than or equal to about 10 wt. % of the second capacitor materials46.

In accordance with various aspects of the present disclosure, one or more of the negative and positive electrodes30,40illustrated inFIG.1may have a gradient structure comprising one or more electroactive material layers having varying concentrations of one or more electroactive materials, for example as illustrated inFIGS.2A-2D.FIGS.2A-2Dare exemplary and schematic illustrations of capacity-assisted gradient electrodes.

The electrode200illustrated inFIG.2Aincludes at least two electroactive materials202,204disposed in electrical communication with a current collector210. For example, the electrode200may include greater than or equal to about 20 wt. % to less than or equal to about 100 wt. %, and in certain aspects, optionally greater than or equal to about 40 wt. % to less than or equal to about 80 wt. %, of a first electroactive material202; and greater than about 0 wt. % to less than or equal to about 80 wt. %, and in certain aspects, optionally greater than or equal to about 20 wt. % to less than or equal to about 60 wt. %, of a second electroactive material204.

In various aspects, the at least two electroactive materials202,204may be disposed on or adjacent one or more surfaces of the current collector210. For example, as illustrated, the at least two electroactive materials202,204may be disposed on or adjacent a first surface211of the current collector210. The skilled artisan will appreciate that in various aspects, the at least two electroactive materials202,204may be further disposed on or adjacent one or more other surfaces of the current collector210. For example, on or adjacent a second surface that opposes or is parallel with the first surface211of the current collector210.

The first electroactive material202may form a first electroactive material layer212, and the second electroactive material204may form a second electroactive material layer214. The first electroactive material layer212may be disposed on or near the current collector210. The second electroactive material layer214may be disposed on or near an exposed surface of the first electroactive material layer212. The first electroactive material layer212may have a first press density, and the second electroactive material layer214may have a second press density. In certain instances, the first press density may be greater than the second press density.

For example, in the instance of positive electrodes, the first press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 3 g/cc to less than or equal to about 3.5 g/cc. The second press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 2.8 g/cc to less than or equal to about 3.3 g/cc. In the instance of negative electrodes, the first press density may be greater than or equal to about 1 g/cc to less than or equal to about 2 g/cc, and in certain aspects, optionally greater than or equal to about 1.6 g/cc to less than or equal to about 1.9 g/cc. The second press density may be greater than or equal to about 1 g/cc to less than or equal to about 2 g/cc, and in certain aspects, optionally greater than or equal to about 1.5 g/cc to less than or equal to about 1.8 g/cc.

Such a density differential may increase the availability of lithium transfer channels within the electrode200, as well as improve the lithium transfer diffusion rate, decrease lithium content deviation, for example in the cathode during fast charging and/or high power braking regeneration processes, and enhance the durability of a battery or pack including the electrode200.

In various aspects, the first and second electroactive materials202,204may each comprise one or more positive electroactive materials, for example to form a layered-oxide cathode, a spinel cathode, an olivine cathode, a tavorite cathode, a borate cathode, and a silicate cathode. In certain aspects, the one or more positive electroactive materials may be independently selected from the group consisting of: LiNixMnyCo1−x−yO2(where 0≤x≤1 and 0≤y≤1), LiNixMn1−xO2(where 0≤x≤1), Li1+xMO2(where M is one of Mn, Ni, Co, and Al and 0≤x≤1) (for example LiCoO2(LCO), LiNiO2, LiMnO2, LiNi0.5Mn0.5O2, NMC111, NMC523, NMC622, NMC721, NMC811, NMC165, NMC174, NCA), LiMn2O4(LMO), LiNi0.5Mn1.5O4, LiV2(PO4)3, LiFePO4, LiCoPO4, LiMnPO4, LiVPO4F, LiFeBO3, LiCoBO3, LiMnBO3, Li2FeSiO4, Li2MnSiO4, LiMnSiO4F, dilithium (2,5-dilithiooxy)terephthalate, polyimide, and combinations thereof.

In various other aspects, the first and second electroactive materials202,204may each comprise one or more negative electroactive materials independently selected from the group consisting of: lithium, lithium metal, silicon, silicon oxide, graphite, graphene, carbon nanotubes titanium oxide (Li4Ti5O12), tin (Sn), tin oxide (SnO2), tin alloy (Cu6Sn5), vanadium oxide (V2O5), titanium dioxide (TiO2), titanium niobium oxide (TixNbyOz, where 0≤x≤2, 0≤y≤24, and 0≤z≤64), iron sulfide (FeS), and combinations thereof.

In each instance, the first electroactive material202may have a first average reversible specific capacity, and the second electroactive material204may have a second average reversible specific capacity. In various instances, the first average reversible specific capacity may be greater than the second average reversible specific capacity. For example, by way of non-limiting example, the first electroactive material202may comprise a nickel manganese cobalt oxide (NMC), such as NMC532 and/or NMC165, and the second electroactive material204may comprise a distinct NMC, such as NMC 721, where NMC 532 has a first specific capacity of about 160 mAh/g and NMC 721 has a second specific capacity of about 184 mAh/g. In another non-limiting example, the first electroactive material202may comprise graphite and the second electroactive material204may comprise graphite in combination with silica, wherein graphite has a first specific capacity of about 350 mAh/g and the graphite-silica combination has a second specific capacity of about 440 mAh/g.

In various aspects, similar to electrodes30,40illustrated inFIG.1, electrode200may further include one or more capacitor materials220disposed on, or in certain aspects, intermingled with, the at least two electroactive materials202,204. For example, the electrode200may comprise greater than or equal to about 0 wt. % to less than or equal to about 10 wt. %, and in certain aspects, optionally greater than or equal to about 0.01 wt. % to less than or equal to about 1 wt. %, of the one or more capacitor materials220. In various aspects, as illustrated, the one or more capacitor materials220may be disposed on or near an exposed surface of the second electroactive material layer214so as to form a capacitor material layer216. The capacitor material layer216may have a thickness greater than or equal to about 10 nm to less than or equal to about 1 mm, and in certain aspects, optionally greater than or equal to about 50 nm to less than or equal to about 20 μm. In certain instances, the capacitor material layer216may comprise greater than or equal to about 5 wt. % to less than or equal to about 97 wt. % of the one or more capacitor materials220, optionally greater than or equal to about 0 wt. % to less than or equal to about 15 wt. % of a conductive material, and optionally greater than or equal to about 0 wt. % to less than or equal to about 40 wt. % of a binder.

The one or more capacitor materials220include one or more metal oxides (MOX, where M is one of cobalt (Co), ruthenium (Ru), niobium (Nb), iridium (Ir), manganese (Mn), chromium (Cr), tantalum (Ta), vanadium (V), and molybdenum (Mo) and 0.5≤x≤3.5), for example one or more metal oxides selected from cobalt oxide (Co3O4), manganese oxide (MnO2), iridium oxide (IrO2), niobium pentoxide (Nb2O5), ruthenium oxide (RuO2), tantalum pentoxide (Ta2O5), tin oxide (SnO2), and vanadium oxide (V2O5); metal sulfides, for example one or more metal sulfides selected from titanium disulfide (TiS2), copper sulfide (CuS), and iron sulfide (FeS); carbon-based materials, for example one or more carbonaceous materials selected from activated carbon, graphene, graphite, mesoporous carbon, macroporous carbon, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon aerogels, and activated carbon fiber cloth; and polymer-based materials, for example one or more polymer selected from polyaniline, polyacetylene, poly(3,4-ethylenedioxythiophene), and poly(3,4-ethylenedioxythiophene), poly(4-styrenesulfonate).

For example only, in instances where the first electroactive material202may comprise a lithium nickel manganese cobalt oxide (NMC), such as NMC532 and the second electroactive material204may comprise a distinct NMC, such as NMC 721, such as detailed above, the one or more capacitor materials220may comprise (single walled) carbon nanotubes. Further, for example only, in instances where the first electroactive material202comprises graphite and the second electroactive material204comprises graphite in combination with silica, also detailed above, the one or more capacitor materials2200may comprise graphene. Integration of the one or more capacitor materials220in combination with the specific capacity gradient of the electroactive materials improves safe, fast-charging capabilities, increases the uniformity of lithium distribution across the electrode200, and avoids or decreases dendrite formation.

The electrode230, illustrated inFIG.2B, includes at least three electroactive materials232,234,236disposed in electrical communication with a current collector240. For example, the electrode230may comprise greater than or equal to about 20 wt. % to less than or equal to about 100 wt. %, and, in certain aspects, optionally greater than or equal to about 30 wt. % to less than or equal to about 80 wt. %, of a first electroactive material232; greater than about 0 wt. % to less than or equal to about 80 wt. %, and in certain aspects, optionally greater than or equal to about 20 wt. % to less than or equal to about 70 wt. %, of a second electroactive material234; and greater than about 0 wt. % to less than or equal to about 50 wt. %, and in certain aspects, optionally greater than or equal to about 20 wt. % to less than or equal to about 50 wt. %, of a third electroactive material236.

In various aspects, the at least three electroactive materials232,234,236may be disposed on or adjacent one or more surfaces of the current collector240. For example, as illustrated the at least three electroactive materials232,234,236may be disposed on or adjacent a first surface241of the current collector240. The skilled artisan will appreciate that in various aspects, the at least three electroactive materials232,234,236may be further disposed on or adjacent one or more other surfaces of the current collector210. For example, on or adjacent a second surface that opposes or is parallel with the first surface241.

The first electroactive material232may form a first electroactive material layer242, the second electroactive material234may form a second electroactive material layer244, and the third electroactive material236may form a third electroactive material layer246. The first electroactive material layer242may be disposed on or near the current collector240. The second electroactive material layer244may be disposed on or near a first exposed surface of the first electroactive material layer242, and the third electroactive material layer246may be disposed on or near a first exposed surface of the second electroactive material layer244.

The first electroactive material layer242may have a first press density, the second electroactive material layer244may have a second press density, and the third electroactive material layer246may have a third press density. In certain instances, the first press density may be greater than the second press density and the second press density may be greater than the third press density.

For example, in the instance of positive electrodes, the first press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 3 g/cc to less than or equal to about 3.5 g/cc. For example, in certain aspects, the first press density may be about 3.46 g/cc. The second press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 2.9 g/cc to less than or equal to about 3.3 g/cc. For example, in certain aspects, the second press density may be about 3.28 g/cc. The third press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 2.8 g/cc to less than or equal to about 3.3 g/cc. For example, in certain aspects, the third press density may be about 3.1 g/cc.

In the instance of negative electrodes, the first press density may be greater than or equal to about 1 g/cc to less than or equal to about 2 g/cc, and in certain aspects, optionally greater than or equal to about 1.6 g/cc to less than or equal to about 1.9 g/cc. The second press density may be greater than or equal to about 1 g/cc to less than or equal to about 2 g/cc, and in certain aspects, optionally greater than or equal to about 1.5 g/cc to less than or equal to about 1.8 g/cc. The third press density may be greater than or equal to about 1 g/cc to less than or equal to about 2 g/cc, and in certain aspects, optionally greater than or equal to about 1.5 g/cc to less than or equal to about 1.7 g/cc.

In various other aspects, the first, second, and third electroactive materials232,234, and236may each comprise one or more negative electroactive materials independently selected from the group consisting of: lithium, lithium metal, silicon, silicon oxide, graphite, graphene, carbon nanotubes, titanium oxide (Li4Ti5O12), tin (Sn), tin oxide (SnO2), tin alloy (Cu6Sn5), vanadium oxide (V2O5), titanium dioxide (TiO2), titanium niobium oxide (TixNbyOz, where 0≤x≤2, 0≤y≤24, and 0≤z≤64), iron sulfide (FeS), and combinations thereof.

In each instance, the first electroactive material232may have a first average reversible specific capacity, the second electroactive material234may have a second average reversible specific capacity, and the third electroactive material236may have a third average reversible specific capacity. In various instances, the first average reversible specific capacity may be greater than the second average reversible specific capacity, and the second average reversible specific capacity may be greater than the third average reversible specific capacity. For example, by way of non-limiting example, the first electroactive material232may comprise a lithium nickel manganese cobalt oxide (NMC), such as NMC 523, the second electroactive material234may comprise a distinct NMC, such as NMC 622, and the third electroactive material236may comprise yet another distinct NMC, such as NMC 721, where NMC 523 has a first specific capacity of about 160 mAh/g, NMC 622 has a second specific capacity of about 175 mAh/g, and NMC 721 has a third specific capacity of about 184 mAh/g. In another non-limiting example, the first, second, and third electroactive materials232,234,236may comprise graphite having different specific capacities. For example, the first electroactive material232may have a first specific capacity of about 320 mAh/g, the second electroactive material234may have a second specific capacity of about 340 mAh/g, and the third electroactive material236may have a third specific capacity of about 350 mAh/g.

In various aspects, similar to electrodes30,40illustrated inFIG.1and electrode200illustrated inFIG.2A, electrode230may further include one or more capacitor materials250disposed on, or in certain aspects, intermingled with, the at least three electroactive materials232,234,236. For example, electrode230may comprise greater than or equal to about 0 wt. % to less than or equal to about 10 wt. %, and in certain aspects, optionally greater than or equal to about 0.01 wt. % to less than or equal to about 1 wt. %, of the one or more capacitor materials250. In various aspects, as illustrated, the one or more capacitor materials250may be disposed on or near an exposed surface of the third electroactive material layer246so as to form a capacitor material layer248. The capacitor material layer248may have a thickness greater than or equal to about 10 nm to less than or equal to about 1 mm, and in certain aspects, optionally greater than or equal to about 100 nm to less than or equal to about 20 μm.

In various aspects, the one or more capacitor materials250include one or more metal oxides (MO, where M is one of cobalt (Co), ruthenium (Ru), niobium (Nb), iridium (Ir), manganese (Mn), chromium (Cr), tantalum (Ta), vanadium (V), and molybdenum (Mo) and 0.5≤x≤3.5), for example one or more metal oxides selected from cobalt oxide (Co3O4), manganese oxide (MnO2), iridium oxide (IrO2), niobium pentoxide (Nb2O5), ruthenium oxide (RuO2), tantalum pentoxide (Ta2O5), tin oxide (SnO2), and vanadium oxide (V2O5); metal sulfides, for example one or more metal sulfides selected from titanium disulfide (TiS2), copper sulfide (CuS), and iron sulfide (FeS); carbon-based materials, for example one or more carbonaceous materials selected from activated carbon, graphene, graphite, mesoporous carbon, macroporous carbon, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon aerogels, and activated carbon fiber cloth; and polymer-based materials, for example one or more polymer selected from polyaniline, polyacetylene, poly(3,4-ethylenedioxythiophene), and poly(3,4-ethylenedioxythiophene), poly(4-styrenesulfonate).

For example only, in instances where the first electroactive material232comprises a nickel manganese cobalt (NMC), such as NMC 532, the second electroactive material234comprises a distinct NMC, such as NMC 622, and the third electroactive material236comprises yet another distinct NMC, such as NMC 721, such as detailed above, the one or more capacitor materials250may comprise one or more of activated carbon, (single walled) carbon nanotubes, and graphene. Further, for example only, in instances where the first, second, and third electroactive materials232,234,236may comprise graphite having a different specific capacities, also detailed above, the one or more capacitor materials250may comprise one or more of ruthenium oxide (RuO2) and graphene.

The electrode260illustrated inFIG.2Cincludes at least three electroactive materials262,264,266having different specific capacities disposed in electrical communication with a current collector270. For example, the electrode260may comprise greater than or equal to about 20 wt. % to less than or equal to about 100 wt. %, and in certain aspects, optionally greater than or equal to about 40 wt. % to less than or equal to about 80 wt. %, of a first electroactive material262; greater than about 0 wt. % to less than or equal to about 80 wt. %, and in certain aspects, optionally greater than or equal to about 20 wt. % to less than or equal to about 80 wt. %, of a second electroactive material264; and greater than or equal to about 0 wt. % to less than or equal to about 50 wt. %, and in certain aspects, optionally greater than or equal to about 20 wt. % to less than or equal to about 50 wt. %, of a third electroactive material266.

In various aspects, the at least three electroactive materials262,264,266may be disposed on or adjacent one or more surfaces of the current collector270. For example, as illustrated, the at least three electroactive materials262,264,266may be disposed on or adjacent a first surface271of the current collector270. The skilled artisan will appreciate that in various aspects, the at least three electroactive materials262,264,266may be further disposed on or adjacent one or more other surfaces of the current collector270. For example, on or adjacent a second surface that opposes or is parallel with the first surface271of the current collector270.

The first electroactive material262may form a first electroactive layer272having a first press density. The first electroactive layer272may be disposed on or near the current collector270. The second electroactive material264may form a second electroactive layer274having a second press density. The second electroactive layer274may be disposed on or near a first exposed surface of the first electroactive layer272. The third electroactive material266may form a third electroactive layer276having a third press density. The third electroactive layer276may be disposed on or near a second exposed surface of the second electroactive layer274.

In various aspects, the second and third electroactive layers274,276may each comprise one or more of the first, second, and third electroactive materials262,264,266. In certain aspects, the first electroactive layer272has a first average reversible specific capacity, the second electroactive layer274has a second average reversible specific capacity, and the third electroactive layer276has a third average reversible specific capacity. The second average reversible specific capacity may be greater than the third average reversible specific capacity. The first average reversible specific capacity may be greater than the second average reversible specific capacity.

In various aspects, electrode260may further include one or more capacitor materials280disposed on, or in certain aspects, intermingled with, one or more of the at least three electroactive materials262,264,266. For example, as illustrated, the one or more capacitor materials280may be disposed on or near an exposed surface of the third electroactive material layer276so as to form a capacitor material layer278.

The one or more capacitor materials280include one or more metal oxides (MOX, where M is one of cobalt (Co), ruthenium (Ru), niobium (Nb), iridium (Ir), manganese (Mn), chromium (Cr), tantalum (Ta), vanadium (V), and molybdenum (Mo) and 0.5≤x≤3.5), for example one or more metal oxides selected from cobalt oxide (Co3O4), manganese oxide (MnO2), iridium oxide (IrO2), niobium pentoxide (Nb2O5), ruthenium oxide (RuO2), tantalum pentoxide (Ta2O5), tin oxide (SnO2), and vanadium oxide (V2O5); metal sulfides, for example one or more metal sulfides selected from titanium disulfide (TiS2), copper sulfide (CuS), and iron sulfide (FeS); carbon-based materials, for example one or more carbonaceous materials selected from activated carbon, graphene, graphite, mesoporous carbon, macroporous carbon, single-walled carbon nanotubes, multi walled carbon nanotubes, carbon aerogels, and activated carbon fiber cloth: and polymer-based materials, for example one or more polymer selected from polyaniline, polyacetylene, poly(3,4-ethylenedioxythiophene), and poly(3,4-ethylenedioxythiophene), poly(4-styrenesulfonate).

In various instances, as illustrated inFIG.2D, the one or more capacitor materials310may be intermingled with a third electroactive material layer306furthest from the current collector. Electrode290includes at least three electroactive materials292,294,296having different specific capacities disposed in electrical communication with a current collector300. For example, the at least three electroactive materials292,294,296may be disposed on or adjacent a first surface301of the current collector300.

A first electroactive material292may form a first electroactive material layer302having a first press density. A second electroactive material294may form a second electroactive material layer304having a second press density. A third electroactive material296may form a third electroactive material layer306having a third press density. The first electroactive material layer302may be disposed on or near the current collector300. The second electroactive material layer304may be disposed on or near a first exposed surface of the first electroactive material layer302, and the third electroactive material layer306may be disposed on or near a first exposed surface of the second electroactive material layer304. In certain instances, the first press density may be greater than the second press density and the second press density may be greater than the third press density.

In various aspects, the embodiments shown are representative, but not necessarily limiting, of capacitor-assisted gradient electrodes and/or electrochemical cells, including capacitor-assisted gradient electrodes in accordance with the present teachings. Electrode gradients and/or capacitor materials may be employed in a variety of other design configurations to provide electrochemical cells having improved regeneration. As such, the skilled artisan will appreciate that the features detailed with respect to the battery20illustrated inFIG.1and/or the electrodes200,230,260, and290illustrated inFIGS.2A-2Dmay apply to various other electrochemical devices and structures, including, for example, in cells having additional layers and/or electrodes and/or composites. Further, the skilled artisan will appreciate that details illustrated inFIGS.1and2A-2Dalso extend to various stacked and/or wound rolled configurations. For example, in various aspects, an electrochemical cell may integrate one or more capacitor materials into one or both of a positive and negative electrode. For example, the one or more capacitor materials may be incorporated into a positive electrode (and not a negative electrode) so as to reduce degradation in the event of high charge rates, which can be particularly accommodating in the instances of silicon-containing negative electrodes. For example,FIG.3illustrates an example battery400where both the electrodes430,440comprise gradient structures and one or more capacitor materials464,466.

Battery400includes a negative electrode430, a positive electrode440, and a separator452disposed between the electrodes430,440. The negative and positive electrodes430,440and/or the separator452may each include an electrolyte solution or system450. A negative electrode current collector432may be positioned at or near the negative electrode430, and a positive electrode current collector442may be positioned at or near the positive electrode440. The negative electrode current collector432and the positive electrode current collector442respectively collect and move free electrons to and from an external circuit422. For example, an interruptible external circuit422and a load device424may connect the negative electrode430(through the negative electrode current collector432) and the positive electrode440(through the positive electrode current collector442).

In various aspects, the negative electrode430may include at least three electroactive materials434,436,438disposed in electrical communication with a current collector432. For example, the at least three electroactive materials434,436,438may be disposed on or adjacent a first surface of the current collector432. The negative electrode430may comprise greater than or equal to about 20 wt. % to less than or equal to about 100 wt. %, and, in certain aspects, optionally greater than or equal to about 30 wt. % to less than or equal to about 80 wt. %, of a first electroactive material434; greater than about 0 wt. % to less than or equal to about 80 wt. %, and in certain aspects, optionally greater than or equal to about 20 wt. % to less than or equal to about 70 wt. %, of a second electroactive material436; and greater than about 0 wt. % to less than or equal to about 50 wt. %, and in certain aspects, optionally greater than or equal to about 20 wt. % to less than or equal to about 50 wt. %, of a third electroactive material438. The at least three electroactive materials434,436,438may each be independently selected from the group consisting of: lithium, lithium metal, silicon, silicon oxide, graphite, graphene, carbon nanotubes titanium oxide (Li4Ti5O12), tin (Sn), tin oxide (SnO2), tin alloy (Cu6Sn5), vanadium oxide (V2O5), titanium dioxide (TiO2), titanium niobium oxide (TixNbyOz, where 0≤x≤2, 0≤y≤24, and 0≤z≤64), iron sulfide (FeS), and combinations thereof.

In various aspects, the first electroactive material434may have a first average reversible specific capacity, the second electroactive material436may have a second average reversible specific capacity, and the third electroactive material438may have a third average reversible specific capacity. In various instances, the first average reversible specific capacity may be greater than the second average reversible specific capacity, and the second average reversible specific capacity may be greater than the third average reversible specific capacity. In certain aspects, the first electroactive material434may form a first electroactive material layer435, the second electroactive material436may form a second electroactive material layer437, and the third electroactive material438may form a third electroactive material layer439. The first electroactive material layer435may be disposed on or near the negative electrode current collector432. The second electroactive material layer437may be disposed on or near a first exposed surface of the first electroactive material layer435, and the third electroactive material layer439may be disposed on or near a first exposed surface of the second electroactive material layer437.

The first electroactive material layer435may have a first press density, the second electroactive material layer437may have a second press density, and the third electroactive material layer439may have a third press density. In certain instances, the first press density may be greater than the second press density and the second press density may be greater than the third press density.

For example, in the instance of positive electrodes, the first press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 3 g/cc to less than or equal to about 3.5 g/cc. The second press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 2.9 g/cc to less than or equal to about 3.3 g/cc. The third press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 2.8 g/cc to less than or equal to about 3.3 g/cc.

In the instance of negative electrodes, the first press density may be greater than or equal to about 1 g/cc to less than or equal to about 2 g/cc, and in certain aspects, optionally greater than or equal to about 1.6 g/cc to less than or equal to about 1.9 g/cc. The second press density may be greater than or equal to about 1 g/cc to less than or equal to about 2 g/cc, and in certain aspects, optionally greater than or equal to about 1.5 Wee to less than or equal to about 1.8 g/cc. The third press density may be greater than or equal to about 1 g/cc to less than or equal to about 2 g/cc, and in certain aspects, optionally greater than or equal to about 1.5 g/cc to less than or equal to about 1.7 g/cc.

In various aspects, similar to electrodes30,40illustrated inFIG.1, negative electrode430may further include one or more capacitor materials464disposed on, or in certain aspects, intermingled with, the at least three electroactive materials434,436,438. For example, negative electrode430may comprise greater than or equal to about 0 wt. % to less than or equal to about 10 wt. %, and in certain aspects, optionally greater than or equal to about 0.01 wt. % to less than or equal to about 1 wt. %, of the one or more capacitor materials464.

The one or more capacitor materials464include one or more metal oxides (MOX, where M is one of cobalt (Co), ruthenium (Ru), niobium (Nb), iridium (Ir), manganese (Mn), chromium (Cr), tantalum (Ta), vanadium (V), and molybdenum (Mo) and 0.5≤x≤3.5), for example one or more metal oxides selected from cobalt oxide (Co3O4), manganese oxide (MnO2), iridium oxide (IrO2), niobium pentoxide (Nb2O5), ruthenium oxide (RuO2), tantalum pentoxide (Ta2O5), tin oxide (SnO2), and vanadium oxide (V2O5); metal sulfides, for example one or more metal sulfides selected from titanium disulfide (TiS2), copper sulfide (CuS), and iron sulfide (FeS); carbon-based materials, for example one or more carbonaceous materials selected from activated carbon, graphene, graphite, mesoporous carbon, macroporous carbon, single-walled carbon nanotubes, multi-wailed carbon nanotubes, carbon aerogels, and activated carbon fiber cloth; and polymer-based materials, for example one or more polymer selected from polyaniline, polyacetylene, poly(3,4-ethylenedioxythiophene), and poly(3,4-ethylenedioxythiophene), poly(4-styrenesulfonate).

In various aspects, as illustrated, the one or more capacitor materials464may be disposed on or near an exposed surface of the third electroactive material layer439so as to form a capacitor material layer431. The capacitor material layer431may have a thickness greater than or equal to about 10 nm to less than or equal to about 1 mm, and in certain aspects, optionally greater than or equal to about 100 nm to less than or equal to about 20 μm.

In various aspects, the positive electrode440may include at least three electroactive materials444,446,448disposed in electrical communication with a current collector442. For example, the at least three electroactive materials444,446,448may be disposed on or adjacent a first surface of the current collector442. The positive electrode440may comprise greater than or equal to about 20 wt. % to less than or equal to about 100 wt. %, and, in certain aspects, optionally greater than or equal to about 30 wt. % to less than or equal to about 80 wt. %, of a first electroactive material444; greater than about 0 wt. % to less than or equal to about 80 wt. %, and in certain aspects, optionally greater than or equal to about 20 wt. % to less than or equal to about 70 wt. %, of a second electroactive material446; and greater than about 0 wt. % to less than or equal to about 50 wt. %, and in certain aspects, optionally greater than or equal to about 10 wt. % to less than or equal to about 50 wt. %, of a third electroactive material448. The at least three electroactive materials444,446,448may each be independently selected from the group consisting of: LiNixMnyCo1−x−yO2(where 0≤x≤1 and 0≤y≤1), LiNixMn1−xO2(where 0≤x≤1), Li1+xMO2(where M is one of Mn, Ni, Co, and Al and 0≤x≤1) (for example LiCoO2(LCO), LiNiO2, LiMnO2, LiNi0.5Mn0.5O2, NMC111, NMC523, NMC622, NMC721, NMC811, NMC165, NMC174, NCA), LiMn2O4(LMO), LiNi0.5Mn1.5O4, LiV2(PO4)3, LiFePO4, LiCoPO4, LiMnPO4, LiWO4F, LiFeBO3, LiCoBO3, LiMnBO3, Li2FeSiO4, Li2MnSiO4, LiMnSiO4F, and combinations thereof.

In various aspects, the first electroactive material444may have a first average reversible specific capacity, the second electroactive material446may have a second average reversible specific capacity, and the third electroactive material448may have a third average reversible specific capacity. In various instances, the first average reversible specific capacity may be less than the second average reversible specific capacity, and the second average reversible specific capacity may be less than the third average reversible specific capacity. In certain aspects, the first electroactive material444may form a first electroactive material layer445, the second electroactive material446may form a second electroactive material layer447, and the third electroactive material448may form a third electroactive material layer449. The first electroactive material layer445may be disposed on or near the positive electrode current collector442. The second electroactive material layer447may be disposed on or near a first exposed surface of the first electroactive material layer445, and the third electroactive material layer449may be disposed on or near a first exposed surface of the second electroactive material layer447.

The first electroactive material layer445may have a first press density, the second electroactive material layer447may have a second press density, and the third electroactive material layer449may have a third press density. In certain instances, the first press density may be greater than the second press density and the second press density may be greater than the third press density. For example, the first press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 3 g/cc to less than or equal to about 3.5 g/cc. The second press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 2.9 g/cc to less than or equal to about 3.3 g/cc. The third press density may be greater than or equal to about 2 g/cc to less than or equal to about 3.5 g/cc, and in certain aspects, optionally greater than or equal to about 2.8 g/cc to less than or equal to about 3.3 g/cc.

In various aspects, similar to electrodes30,40illustrated inFIG.1, positive electrode440may further include one or more capacitor materials466disposed on, or in certain aspects, intermingled with, the at least three electroactive materials444,446,448. For example, positive electrode440may comprise greater than or equal to about 0 wt. % to less than or equal to about 10 wt. %, and in certain aspects, optionally greater than or equal to about 0.01 wt. % to less than or equal to about 1 wt. %, of the one or more capacitor materials466. The one or more capacitor materials466include one or more metal oxides (MO, where M is one of cobalt (Co), ruthenium (Ru), niobium (Nb), iridium (Ir), manganese (Mn), chromium (Cr), tantalum (Ta), vanadium (V), and molybdenum (Mo) and 0.5≤x≤3.5), for example one or more metal oxides selected from cobalt oxide (Co3O4), manganese oxide (MnO2), iridium oxide (IrO2), niobium pentoxide (Nb2O5), ruthenium oxide (RuO2), tantalum pentoxide (Ta2O5), tin oxide (SnO2), and vanadium oxide (V2O5); metal sulfides, for example one or more metal sulfides selected from titanium disulfide (TiS2), copper sulfide (CuS), and iron sulfide (FeS); carbon-based materials, for example one or more carbonaceous materials selected from activated carbon, graphene, graphite, mesoporous carbon, macroporous carbon, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon aerogels, and activated carbon fiber cloth; and polymer-based materials, for example one or more polymer selected from polyaniline, polyacetylene, poly(3,4-ethylenedioxythiophene), and poly(3,4-ethylenedioxythiophene), poly(4-styrenesulfonate).

In various aspects, as illustrated, the one or more capacitor materials466may be disposed on or near an exposed surface of the third electroactive material layer449so as to form a capacitor material layer451. The capacitor material layer451may have a thickness greater than or equal to about 10 nm to less than or equal to about 1 mm, and in certain aspects, optionally greater than or equal to about 100 nm to less than or equal to about 20 μm.

The skilled artisan will understand that in various aspects battery400may have various other structures, including, for example, in cells having additional layers and/or electrodes and/or composites, as well as positive and negative electrodes having various other layered densities and charge capacities.

In various aspects, the present disclosure provides a method of forming a capacity-assisted gradient electrode, such as the capacity-assisted gradient electrodes200,230,260,290illustrated inFIGS.2A-2D. The method includes disposing one or more first electroactive materials on an exposed surface of a current collector. For example, in various instances, the one or more first electroactive materials may be disposed using, for example, a die-coating process of a dry powder pressing process. In certain aspects, the one or more capacitor materials are included with the one or more first electroactive materials. The method may include drying the one or more disposed first electroactive materials and/or capacitor materials, for example by heating the one or more disposed first electroactive materials to a temperature greater than or equal to about 100° C. to less than or equal to about 300° C. for a time period greater than or equal to about 1 minute to less than or equal to about 60 minutes. Pressing may then be applied to the one or more disposed first electroactive materials to densify a first electroactive material layer.

The method may further include disposing, for example using a die-coating process, one or more second electroactive materials on an exposed surface of the first electroactive material layer. In certain aspects, the one or more capacitor materials are included with the one or more second electroactive materials. The method may include drying the one or more disposed second electroactive materials, for example by heating the one or more disposed first electroactive materials to a temperature greater than to equal to about 100° C. to less than or equal to about 300° C. for a time period greater than or equal to about 1 minute to less than or equal to about 60 minutes. Pressing may then be applied to the one or more disposed second electroactive materials to densify a second electroactive material layer. In certain aspects, one or more capacitor materials may be disposed on one or more exposed surfaces of the one or more first electroactive materials and/or the one or more second electroactive materials. The skilled artisan will appreciate that various numbers of disposing, heating, and pressing steps may be performed to obtain the desired electrode configuration.