Patent Application
20210313578
N/A
Aspects of the present disclosure relate to energy generation and storage. More specifically, certain embodiments of the disclosure relate to a method and system for clay minerals as cathode, silicon anode, or separator additives in lithium-ion batteries.
Conventional approaches for battery electrodes may be costly, cumbersome, and/or inefficient—e.g., they may be complex and/or time consuming to implement, and may limit battery lifetime.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present disclosure as set forth in the remainder of the present application with reference to the drawings.
A system and/or method for clay minerals as cathode, silicon anode, or separator additives in lithium-ion batteries, substantially as shown in and/or described in connection with at least one of the figures, as set forth more completely in the claims.
These and other advantages, aspects and novel features of the present disclosure, as well as details of an illustrated embodiment thereof, will be more fully understood from the following description and drawings.
The development of portable electronic devices and electrification of transportation drive the need for high performance electrochemical energy storage. Small-scale (<100 Wh) to large-scale (>10 KWh) devices primarily use lithium-ion (Li-ion) batteries over other rechargeable battery chemistries due to their high-performance.
The anode 101 and cathode 105, along with the current collectors 107A and 107B, may comprise the electrodes, which may comprise plates or films within, or containing, an electrolyte material, where the plates may provide a physical barrier for containing the electrolyte as well as a conductive contact to external structures. In other embodiments, the anode/cathode plates are immersed in electrolyte while an outer casing provides electrolyte containment. The anode 101 and cathode are electrically coupled to the current collectors 107A and 1078, which comprise metal or other conductive material for providing electrical contact to the electrodes as well as physical support for the active material in forming electrodes.
The configuration shown in
In an example scenario, the battery 100 may comprise a solid, liquid, or gel electrolyte. The separator 103 preferably does not dissolve in typical battery electrolytes such as compositions that may comprise: Ethylene Carbonate (EC), Fluoroethylene Carbonate (FEC), di-fluoroethylene carbonate (DiFEC), trifluoropropylene carbonate (TFPC), vinyl carbonate (VC), Propylene Carbonate (PC), Dimethyl Carbonate (DMC), Ethyl Methyl Carbonate (EMC), Diethyl Carbonate (DEC), etc. with dissolved lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate monohydrate (LiAsF6), lithium perchlorate (LiClO4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium difluoro(oxalate)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), and lithium triflate (LiCF3SO3), lithium tetrafluorooxalato phosphate (LTFOP), lithium difluorophosphate (LiPO2F2), lithium pentafluoroethyltrifluoroborate (LiFAB), and lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI), lithium bis(2-fluoromalonato)borate (LiBFMB), lithium 4-pyridyl trimethyl borate (LPTB) and lithium 2-fluorophenol trimethyl borate (LFPTB), lithium catechol dimethyl borate (LiCDMB), etc.
The separator 103 may be wet or soaked with a liquid or gel electrolyte. In addition, in an example embodiment, the separator 103 does not melt below about 100 to 120° C., and exhibits sufficient mechanical properties for battery applications. A battery, in operation, can experience expansion and contraction of the anode and/or the cathode. In an example embodiment, the separator 103 can expand and contract by at least about 5 to 10% without failing, and may also be flexible.
The separator 103 may be sufficiently porous so that ions can pass through the separator once wet with, for example, a liquid or gel electrolyte. Alternatively (or additionally), the separator may absorb the electrolyte through a gelling or other process even without significant porosity. The porosity of the separator 103 is also generally not too porous to allow the anode 101 and cathode 105 to transfer electrons through the separator 103.
The anode 101 and cathode 105 comprise electrodes for the battery 100, providing electrical connections to the device for transfer of electrical charge in charge and discharge states. The anode 101 may comprise silicon, carbon, or combinations of these materials, for example. Typical anode electrodes comprise a carbon material that includes a current collector such as a copper sheet. Carbon is often used because it has excellent electrochemical properties and is also electrically conductive. Anode electrodes currently used in rechargeable lithium-ion cells typically have a specific capacity of approximately 200 milliamp hours per gram. Graphite, the active material used in most lithium ion battery anodes, has a theoretical energy density of 372 milliamp hours per gram (mAh/g). In comparison, silicon has a high theoretical capacity of 4200 mAh/g at high temperature and 3579 mAh/g at room temperature. In order to increase volumetric and gravimetric energy density of lithium-ion batteries, silicon may be used as the active material for the cathode or anode. Silicon anodes may be formed from silicon composites, with more than 50% silicon, for example.
In an example scenario, the anode 101 and cathode 105 store the ion used for separation of charge, such as lithium. In this example, the electrolyte carries positively charged lithium ions from the anode 101 to the cathode 105 in discharge mode, as shown in
While the battery 100 is discharging and providing an electric current, the anode 101 releases lithium ions to the cathode 105 via the separator 103, generating a flow of electrons from one side to the other via the coupled load 109. When the battery is being charged, the opposite happens where lithium ions are released by the cathode 105 and received by the anode 101.
The materials selected for the anode 101 and cathode 105 are important for the reliability and energy density possible for the battery 100. The energy, power, cost, and safety of current Li-ion batteries need to be improved in order to, for example, compete with internal combustion engine (ICE) technology and allow for the widespread adoption of electric vehicles (EVs). High energy density, high power density, and improved safety of lithium-ion batteries are achieved with the development of high-capacity and high-voltage cathodes, high-capacity anodes and functionally non-flammable electrolytes with high voltage stability and interfacial compatibility with electrodes. In addition, materials with low toxicity are beneficial as battery materials to reduce process cost and promote consumer safety.
The performance of electrochemical electrodes, while dependent on many factors, is largely dependent on the robustness of electrical contact between electrode particles, as well as between the current collector and the electrode particles. The electrical conductivity of silicon anode electrodes may be manipulated by incorporating conductive additives with different morphological properties. Carbon black (SuperP), vapor grown carbon fibers (VGCF), graphite, graphene, etc., and/or a mixture of these have previously been incorporated separately into the anode electrode resulting in improved performance of the anode. The synergistic interactions between the two carbon materials may facilitate electrical contact throughout the large volume changes of the silicon anode during charge and discharge.
State-of-the-art lithium-ion batteries typically employ a graphite-dominant anode as an intercalation material for lithium. Silicon-dominant anodes, however, offer improvements compared to graphite-dominant Li-ion batteries. Silicon exhibits both higher gravimetric (3579 mAh/g vs. 372 mAh/g for graphite) and volumetric capacities (2194 mAh/L vs. 890 mAh/L for graphite). In addition, silicon-based anodes have a lithiation/delithiation voltage plateau at about 0.3-0.4V vs. Li/Li+, which allows it to maintain an open circuit potential that avoids undesirable Li plating and dendrite formation. While silicon shows excellent electrochemical activity, achieving a stable cycle life for silicon-based anodes is challenging due to silicon's large volume changes during lithiation and delithiation. Silicon regions may lose electrical contact from the anode as large volume changes coupled with its low electrical conductivity separate the silicon from surrounding materials in the anode.
In addition, the large silicon volume changes exacerbate solid electrolyte interphase (SEI) formation, which can further lead to electrical isolation and, thus, capacity loss. Expansion and shrinkage of silicon particles upon charge-discharge cycling causes pulverization of silicon particles, which increases their specific surface area. As the silicon surface area changes and increases during cycling, SEI repeatedly breaks apart and reforms. The SEI thus continually builds up around the pulverizing silicon regions during cycling into a thick electronic and ionic insulating layer. This accumulating SEI increases the impedance of the electrode and reduces the electrode electrochemical reactivity, which is detrimental to cycle life.
Among all the potential cathode active materials, Ni-rich NCA (Nickel cobalt aluminum oxide) and NCM (Nickel Cobalt Manganese Oxide) are considered to be most promising. Ni-rich NCA or NCM cathodes show excellent thermodynamic stability and specific capacity as high as 200 mAh/g. Although NCA or NCM are best known for long-term stability and high energy density, they have also been shown to be problematic due to poor cycle stability and low electronic conductivity.
It is generally believed that the capacity of the cathode materials is one of the major limiting factors for the energy density of Li-ion batteries. Therefore, Ni-rich cathode materials (such as NCA, NCM) and Li-rich layered oxide cathode materials have been considered and explored as the possible future choices because of their high specific capacity and low cost. These materials are especially useful if they can be coupled with high capacity and low-voltage anode materials, such as Si. However, these cathode materials have some fundamental challenges, such as irreversible phase transition from hexagonal through cubic to rock salt structure, mechanical cracking of the secondary particle structure, electrolyte depletion that is often accompanied by impedance increase and volumetric swelling of the batteries, as well as gelation of cathode slurry in the slurry-making process.
From the cathode side, a number of strategies may be utilized to overcome these issues, such as cation doping for stabilizing the cathode material lattice structure, surface coating for protecting cathode particles from parasitic reactions with the electrolyte components, synthesizing concentration-gradient or core-shell structures with high Ni content core for stabilizing the material's surface chemistry, as well as using electrolyte additives for chemically trapping released oxygen.
Without negative impacts on the anode, electrolyte, and the battery manufacturing procedures or design, incorporating a cathode additive is an efficient, cost-effective and practically feasible strategy to overcome the issues with layered cathode materials and to improve the full cell performance.
Commercial Li-ion batteries are based on graphite anode layered metal oxide cathodes, particularly Ni-rich LiMO2 (M—Ni, Co, Mn). Layered Li[NixCoy(Al or Mn)1-x-y]O2 (Al=NCA or Mn=NCM) materials have been the most promising cathode materials used for EVs, as evidenced by an automobile manufacturer adopting an NCA cathode, Li[Ni0.8Co0.15Al0.05]O2 (NCM811), in its current model cars. High Ni content cathodes (NCM and NCA) that can provide high capacity (180-200 mAh/g) have become the fastest developing commercial cathode for EVs in recent years. However, their thermal instability on de-lithiation due to the presence of the high-valance Ni raises safety concerns for Li-ion cells. These cathodes also have some issues with metal dissolution which this disclosure addresses/solves. Compared to Ni-rich cathodes, olivine LiFePO4 electrodes are significantly more stable to lithium extraction, but their low capacities (100-150 mAh/g) limit their use in EVs.
In addition, the nominal upper cutoff voltage of layered structures is ˜4.0-4.2 V. An increase in the upper cutoff voltage of such materials results in the higher capacity fade of the cathode. Thus, new and improved cathode materials with modified chemical compositions or novel additives that can suppress inherent instability of layered Ni-rich cathode materials are desired to meet the ever-growing demand for high energy density, long cycle life, and cost-effective Li-ion batteries.
Although Ni-rich NCM or NCA are promising cathode materials for high energy density Li-ion batteries because of their high capacity and low cost, charging the NCM or NCA cathode to high potentials not only triggers oxygen evolution but also causes oxidative decomposition of the electrolyte solvents which finally lead to serious capacity degradation. To overcome these problems, a number of strategies may be utilized, including cationic doping for stabilizing the lattice structure, surface coating for protecting particles from reacting with the electrolyte components, synthesizing concentration-gradients, core-shell materials with high Ni content core, and using electrolyte additives, for example.
The surface modification of a cathode active material can greatly affect battery performance because the electrochemical reaction takes place at the interface of the electrochemically active materials and the electrolyte. The protective effects of these surface coatings are typically attributed to the scavenging of HF, limiting transition metal dissolution, altering the composition of the solid electrolyte interface on the positive electrode, and the physical blockage of electrolyte components from reaching the electroactive material surface. However, these treatments need additional precipitating (or washing) and heating processes, leading to an increase in the cost of battery manufacture.
In order to simplify the treatment process, in this disclosure a small amount of clay minerals is dispersed into the normal cathode-coating slurry to prepare clay mineral-containing cathodes for Si-dominant anode-based Li-ion batteries. Clay is a finely-grained natural rock or soil material that combines one or more clay minerals with possible traces of quartz (SiO2), metal oxides (Al2O3, MgO, etc.) and organic matter. The presence of the clay minerals may provide the following benefits: (i) serves as a chemically stable and mechanically strong interphase, which minimizes the reductive reaction of carbonate electrolytes and other solvents, and suppresses the direct contact between cathode electrodes or cathode powders and other solvents, and therefore may enhance electrochemical stability; (ii) helps modify the cathode electrolyte interphase (CEI) layer composition and improve the CEI stability on the surface of cathodes or cathode powders, which permits effective surface passivation of the cathode, increase CEI robustness and structural stability of the cathodes; (iii) helps reduce the impedance built-up throughout cycling; (iv) helps reduce the dissolution of transition metal ions from the cathode side; (v) consumes HF using the containing metal oxide; (vi) acts as a rheology additive in the electrode coating slurry and as a lithium-ion conducting additive, (vii) depresses the severe aggregation of cathode powders, and (viii) helps improve the thermal stability. Therefore, the presence of clay minerals provides substantial benefits to Li-ion battery cathodes and contributes to electrochemical performance improvements.
In an example embodiment, Kaolin group minerals, which include dickite, nacrite, kaolinite and halloysite, and the trioctahedral minerals antigorite, chamosite, chrysotile, and cronstedite may be used as cathode additives for NCM811 cathode-based Li-ion full cells. Kaolinite is a clay mineral, part of the group of industrial minerals with the chemical composition Al2Si2O6(OH)4. It is a layered silicate mineral, with one tetrahedral sheet of silica (SiO4) linked through oxygen atoms to one octahedral sheet of alumina (AlO6) octahedral. The primary structural unit of the Kaolin group is a layer composed of one octahedral sheet condensed with one tetrahedral sheet. In the dioctahedral minerals the octahedral site are occupied by aluminum; in the trioctahedral minerals these sites are occupied by magnesium and iron. Kaolinite and halloysite comprise single-layer structures.
In another example scenario, Kaoline-serpentine group clay minerals may be utilized as cathode additives for NCM811 cathodes-based Li-ion full cells. These materials form hydrous magnesium iron phyllosilicate ((Mg,Fe)3Si2O5(OH)4) minerals.
In yet another example, the following materials may be utilized as cathode additives in NCM cathode-based cells: 1) smectite group clay minerals, which include dioctahedral smectites such as montmorillonite, nontronite and nicbeidellite, and trioctahedral smectites such as saponite; 2) the Illite group clay mineral, which includes clay-micas; 3) chlorite group clay minerals, which include a wide variety of similar minerals with considerable chemical variation; 4) other 2:1 clay types such as sepiolite or attapulgite.
These materials may be utilized as cathode additives for NCM811 or other NCM cathodes-based Li-ion full cells, such as NCM9 0.5 0.5, NCM622, NCM532, NCM433, NCM442, NCM111, NCMA, and others. Furthermore, the additives disclosed here may be utilized in NCA, LCO, LMO, Li-rich xLi2MnO3.(1−x)LiNiaCobMncO2, (LiNi1−xMxO2, Mn=Co, Mn, and Al), Li-rich layered oxides (LiNi1+xM1−xO2, Mn=Co, Mn, and Ni), high-voltage spinel oxides (LiNi0.5Mn1.5O4), high-voltage polyanionic compounds (phosphates, sulfates, silicates, etc.) cathode-based Li-ion full cells.
Furthermore, these clay minerals may be utilized as additives in Si-dominant anode-based Li-ion full cells with different cathodes, and may comprise direct coated Si-dominant anodes or other Si anode-based Li-ion full cells with different cathodes. Finally, the clay minerals may be utilized to modify separators to prepare different types of functional separators for Li-ion batteries and Li-metal batteries.
In step 201, the raw electrode active material may be mixed using a binder/resin (such as PI, PAI), solvent, and conductive carbon. For example, for the cathode, Super P/VGCF (1:1 by weight), or other types carbon materials, such as graphite, graphene, carbon nanotube, etc., may be dispersed in binder solution (mixture of NMP and PVDF) for 0.5 to 2 minutes at 1500-2500 rpm. NCA cathode material powder may be added to the mixture along with NMP solvent, then dispersed for another 1-3 minutes at 1500-2500 rpm to achieve a slurry viscosity within 2000-4000 cP (total solid content of about 48%). A clay-based additive may be mixed in with the slurry at this point, or may be added at a later stage in the process. A similar process may be utilized to mix the active material slurry for the anode, where a binder/resin, conductive carbon, and silicon may be utilized, for example.
In step 203, a slurry may be coated on a copper foil at a loading of 3-6 mg/cm2 (with 13-20% solvent content) for the anode and on an aluminum foil at a loading of, e.g., 15-35 mg/cm2 for the cathode. The coated foil may undergo drying in step 205 resulting in less than 13-20% residual solvent content. In another example scenario, a clay-based additive may be incorporated by dipping the coated foil in a solution with the desired additive.
In step 207, an optional calendering process may be utilized where a series of hard pressure rollers may be used to finish the film/substrate into a smoother and denser sheet of material.
In step 209, the active material may be pyrolyzed by heating to 500-1200° C. such that carbon precursors are partially or completely converted into glassy carbon. Pyrolysis can be done either in roll form or after punching in step 211. If done in roll form, the punching is done after the pyrolysis process. The punched electrode may then be sandwiched with a separator and cathode with electrolyte to form a cell. In step 213, the cell may be subjected to a formation process, comprising initial charge and discharge steps to lithiate the anode, with some residual lithium remaining and cell testing to determine performance.
This process is shown in the flow diagram of
In step 303, the slurry may be coated on a polymer substrate, such as polyethylene terephthalate (PET), polypropylene (PP), or Mylar. The slurry may be coated on the PET/PP/Mylar film at a loading of 3-6 mg/cm2 (with 13-20% solvent content) for the anode and 15-35 mg/cm2 for the cathode, and then dried to remove a portion of the solvent in step 305. In another example scenario, a clay-based additive may be incorporated by dipping the green layer coated substrate in a solution with the desired additive. An optional calendering process may be utilized where a series of hard pressure rollers may be used to finish the film/substrate into a smoothed and denser sheet of material.
In step 307, the green film may then be removed from the PET, where the active material may be peeled off the polymer substrate, the peeling process being optional for a polypropylene (PP) substrate, since PP can leave ˜2% char residue upon pyrolysis. The peeling may be followed by a cure and pyrolysis step 309 where the film may be cut into sheets, and vacuum dried using a two-stage process (100-140° C. for 14-16 hours, 200-240° C. for 4-6 hours). The dry film may be thermally treated at 1000-1300° C. to convert the polymer matrix into carbon.
In step 311, the pyrolyzed material may be flat press or roll press laminated on the current collector, where for aluminum foil for the cathode and copper foil for the anode may be pre-coated with polyamide-imide with a nominal loading of 0.35-0.75 mg/cm2 (applied as a 5-7 wt % varnish in NMP, dried 10-20 hour at 100-140° C. under vacuum). In flat press lamination, the active material composite film may be laminated to the coated aluminum or copper using a heated hydraulic press (30-70 seconds, 250-350° C., and 3000-5000 psi), thereby forming the finished composite electrode. In another embodiment, the pyrolyzed material may be roll-press laminated to the current collector. In yet another example scenario, a clay-based additive may be incorporated by dipping the coated foil in a solution with the desired additive.
In step 313, the electrodes may then be sandwiched with a separator and electrolyte to form a cell. The cell may be subjected to a formation process, comprising initial charge and discharge steps to lithiate the anode, with some residual lithium remaining, and testing to assess cell performance.
In this example, the NCM811 control cathode cell is represented by the dotted lines while the solid lines represent a 1 wt % Halloysite-containing NCM811 cathode cell. The electrolyte formulation used may comprise 1.2 M LiPF6 in FEC/EMC (3/7 wt %). The control cathodes may comprise ˜92 wt % NCM811, 4 wt % Super P and 4 wt % PVDF5130, and may be coated on 15 μm Al foil. The average loading may be 15-25 mg/cm2. The 1 wt % Halloysite-containing NCM811 cathodes may comprise ˜91 wt % NCM811, 1 wt % Halloysite, 4 wt % Super P and 4 wt % PVDF5130, and may also be coated on 15 μm Al foil with a similar loading with control. The CV measurements may be in the voltage range of 2-4.3 V at a scan rate of 0.2 mV s−1.
Capacity retention is shown in
The long-term cycling programs include: (i) At the 1st cycle, charge at 0.33 C to 4.2 V until 0.05 C, rest 5 minutes, discharge at 0.33 C to 3.1 V, rest 5 minutes; and (ii) from the 2nd cycle, Charge at 1 C to 4.2 V until 0.05 C, rest 5 minutes, discharge at 0.5 C to 3.1 V, rest 5 minutes. But after every 100 cycles, the test conditions in the 1st cycle may be repeated.
Cyclic voltammetry (CV) curves of Si-dominant anode//NCM811 cathode full cells. The dotted lines represent an NCM811 control cathode cell and the solid lines represent a 1 wt % Kaolinite-containing NCM811 cathode cell. The electrolyte formulation may comprise 1.2 M LiPF6 in FEC/EMC (3/7 wt %). The Si-dominant anodes may comprise about 80 wt % Si, 5 wt % graphite and 15 wt % glassy carbon (from resin) and be laminated on 15 μm Cu foil. The average loading may be 2-5 mg/cm2. The control cathodes may comprise ˜92 wt % NCM811, 4 wt % Super P and 4 wt % PVDF5130, and may be coated on 15 μm Al foil. The average loading is ˜25-30 mg/cm2. The 1 wt % Kaolinite-containing NCM811 cathodes contain about 91 wt % NCM811, 1 wt % Kaolinite, 4 wt % Super P and 4 wt % PVDF5130, and are also coated on 15 μm Al foil with a similar loading with control. The CV measurements may be carried out in the voltage range of 2-4.3 V at a scan rate of 0.2 mV s−1.
In an example embodiment, the cathode clay additives disclosed above may be utilized to improve cycle performance for NCM cathode-based (including NCM, 433, NCM442, NCM811, NCM622, NCM532, NCM111, etc.) full cells with different Si anodes. In another example embodiment, the clay cathode additives disclosed above may be utilized to improve cycle performance for NCA cathode-based full cells with different Si anodes.
In yet another example embodiment, the cathode clay additives disclosed above may be utilized to improve cycle performance for LCO cathode-based full cells with different Si anodes, LiMn2O4 (LMO)-based cathodes with different Si anodes, Li-rich, xLi2MnO3.(1−x)LiNiaCobMncO2 cathode-based full cells with different Si anodes, Ni-rich layered oxides (LiNi1-xMxO2, Mn=Co, Mn, and Al)-based Li-ion full cells with different Si anodes, Li-rich layered oxides (LiNi1+xM1−xO2, Mn=Co, Mn, and Ni)-based Li-ion full cells with different Si anodes, high-voltage spinel oxides (LiNi0.5Mn1.5O4) cathode Li-ion full cells with different Si anodes, and high-voltage polyanionic compounds (phosphates, sulfates, silicates, etc.) cathode-based Li-ion full cells with different Si anodes.
Furthermore, the clay additives disclosed above may be incorporated with different anodes including graphite, graphene, or combinations thereof. The electrode may comprise graphene and other types of hard/soft carbon in combination with Si and layered Si materials.
In an example embodiment of the disclosure, a method and system are described for clay minerals as cathode, anode, or separator additives in lithium-ion batteries. The battery may comprise an anode, an electrolyte, and a cathode, wherein the cathode comprises an active material and a clay additive. The active material may comprise one or more of: nickel cobalt aluminum oxide (NCA), nickel cobalt manganese oxide (NCM), NCMA, lithium iron phosphate (LFP), lithium cobalt oxide (LCO), and lithium manganese oxide (LMO), Ni-rich layered oxides LiNi1−xMxO2 where M=Co, Mn, or Al, Li-rich xLi2MnO3(1−x)LiNiaCobMncO2, Li-rich layered oxides LiNi1+xM1−xO2 where M=Co, Mn, or Ni, and spinel oxides LiNi0.5Mn1.5O4.
The clay additive may comprise a Kaolin group clay mineral, where the Kaolin group clay mineral comprises Kaolinite or Halloysite. The clay additive may comprise one or more of: a Smectite group clay mineral, an Illite group clay mineral, and a Chlorite group clay material. The anode may comprise graphite and/or graphene. The anode may comprise an active material that comprises between 50% to 95% silicon. The battery may comprise a lithium ion battery. The electrolyte may comprise a liquid, solid, or gel.
As utilized herein, “and/or” means any one or more of the items in the list joined by “and/or”. As an example, “x and/or y” means any element of the three-element set {(x), (y), (x, y)}. In other words, “x and/or y” means “one or both of x and y”. As another example, “x, y, and/or z” means any element of the seven-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means “one or more of x, y and z”. As utilized herein, the term “exemplary” means serving as a non-limiting example, instance, or illustration. As utilized herein, the terms “e.g.,” and “for example” set off lists of one or more non-limiting examples, instances, or illustrations. As utilized herein, a battery, circuitry or a device is “operable” to perform a function whenever the battery, circuitry or device comprises the necessary hardware and code (if any is necessary) or other elements to perform the function, regardless of whether performance of the function is disabled or not enabled (e.g., by a user-configurable setting, factory trim, configuration, etc.).
While the present invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the present invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from its scope. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed, but that the present invention will include all embodiments falling within the scope of the appended claims.
