This present disclosure relates to manufacture of electrochemical cells. More particularly, the present disclosure provides techniques, including a method and device, for a solid state battery device. Merely by way of example, the invention has been provided with use of lithium based battery cells, but it would be recognized that other battery cells made from materials such as zinc, silver and lead, nickel could be operated in the same or like fashion. Additionally, such batteries can be used for a variety of applications such as portable electronics (cell phones, personal digital assistants, radio players, music players, video cameras, and the like), tablet and laptop computers, power supplies for military use (communications, lighting, imaging, satellite, and the like), power supplies for aerospace applications (aero plane, satellites and micro air vehicles), power supplies for vehicle applications (hybrid electric vehicles, plug-in hybrid electric vehicles, fully electric vehicles, electric scooter, underwater vehicle, boat, ship, electric garden tractor, and electric ride on garden device), power supplies for remote control devices (unmanned aero drone, unmanned aero plane, an RC car), power supplies for a robotic appliances (robotic toys, robotic vacuum cleaner, robotic garden tools, robotic construction utility), power supplies for power tool (electric drill, electric mower, electric vacuum cleaner, electric metal working grinder, electric heat gun, electric press expansion tool, electric saw and cutters, electric sander and polisher, electric shear and nibbler, and routers), power supply for personal hygiene device (electric tooth brush, hand dryer and electric hair dryer), heater, cooler, chiller, fan, humidifier, power supplies for other applications (a global positioning system (GPS) device, a laser rangefinder, a flashlight, an electric street lighting, standby power supply, uninterrupted power supplies, and other portable and stationary electronic devices). The method and system for operation of such batteries are also applicable to cases in which the battery is not the only power supply in the system, and additional power is provided by a fuel cell, other batteries, an IC engine or other combustion devices, capacitors, solar cells, combinations thereof, and others.
Common electro-chemical cells often use liquid electrolytes. Such cells are typically used in many conventional applications. Alternative techniques for manufacturing electro-chemical cells include solid-state cells. Such solid state cells are generally in the experimental state, have been difficult to make, and have not been successfully produced in large scale. Although promising, solid state cells have not been achieved due to limitations in cell structures and manufacturing techniques. These and other limitations have been described throughout the present specification and more particularly below.
From the above, it is seen that techniques for improving the manufacture of solid state cells are highly desirable.
According to the present disclosure, techniques related to manufacture of electrochemical cells are provided. More particularly, the present disclosure provides techniques, including a method and device, for a solid state battery device. Merely by way of example, the invention has been provided with use of lithium based battery cells, but it would be recognized that other battery cells made from materials such as zinc, silver and lead, nickel could be operated in the same or like fashion. Additionally, such batteries can be used for a variety of applications such as portable electronics (cell phones, personal digital assistants, radio players, music players, video cameras, and the like), tablet and laptop computers, power supplies for military use (communications, lighting, imaging, satellite, and the like), power supplies for aerospace applications (aero plane, satellites and micro air vehicles), power supplies for vehicle applications (hybrid electric vehicles, plug-in hybrid electric vehicles, fully electric vehicles, electric scooter, underwater vehicle, boat, ship, electric garden tractor, and electric ride on garden device), power supplies for remote control devices (unmanned aero drone, unmanned aero plane, an RC car), power supplies for a robotic appliances (robotic toys, robotic vacuum cleaner, robotic garden tools, robotic construction utility), power supplies for power tool (electric drill, electric mower, electric vacuum cleaner, electric metal working grinder, electric heat gun, electric press expansion tool, electric saw and cutters, electric sander and polisher, electric shear and nibbler, and routers), power supply for personal hygiene device (electric tooth brush, hand dryer and electric hair dryer), heater, cooler, chiller, fan, humidifier, power supplies for other applications (a global positioning system (GPS) device, a laser rangefinder, a flashlight, an electric street lighting, standby power supply, uninterrupted power supplies, and other portable and stationary electronic devices). The method and system for operation of such batteries are also applicable to cases in which the battery is not the only power supply in the system, and additional power is provided by a fuel cell, other batteries, an IC engine or other combustion devices, capacitors, solar cells, combinations thereof, and others.
In an example, the cathode material can be deposited so as to produce observable discontinuities, taking the form of any combination of poly disperse generalized cones, which may variously, with changes in inclination of the conical surface relative to the substrate, be platelets, cones, inverted cones or right circular cylinders, surface discontinuities which variously appear as fissures, continuous or discontinuous polyhedral elements, holes, cracks or other defects, additive, deposited layers, any of the aforementioned geometries, in combination with three-dimensional, irregular, deposited poly-hedral structures, among others. Of course, there can be other variations, modifications, and alternatives.
Benefits are achieved over conventional techniques. Depending upon the specific embodiment, one or more of these benefits may be achieved. In a preferred embodiment, the present disclosure provides a suitable solid state battery structure including barrier regions. Preferably, the cathode material is configured to provide improved power density for electrochemical cells. The present cathode material can be made using conventional process technology techniques. Of course, there can be other variations, modifications, and alternatives.
The present disclosure achieves these benefits and others in the context of known process technology. However, a further understanding of the nature and advantages of the present disclosure may be realized by reference to the latter portions of the specification and attached drawings.
The following diagrams are merely examples, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. It is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this process and scope of the appended claims.
Solid state batteries have been proven to have several advantages over conventional batteries using liquid electrolyte in lab settings. Safety is the foremost one. Solid state battery is intrinsically more stable than liquid electrolyte cells since it does not contain a liquid that causes undesirable reaction, resulting thermal runaway, and an explosion in the worst case. Solid state battery can store over 30% more energy for the same volume or over 50% more for the same mass than conventional batteries. Good cycle performance, more than 10,000 cycles, and a good high temperature stability also has been reported.
In the context of batteries, it is desired in some applications to be able to limit certain depth-of-discharge (DOD) ranges and depth-of-charge (DOC) ranges that are descriptive of the present battery condition, but that may not be directly measured. In the context of the battery systems, particularly those that need to operate for long period of time and cycles, as aggressively as possible without harming the battery life, for example, in hybrid electric vehicle batteries, laptop computer batteries, portable tool batteries, and the like, it is desired that information regarding state of charge is accurate and fast so one can further control the power/energy output of the batteries, determine if it is necessary to charge the batteries, and determine the health of batteries.
As an example, the use of estimation of parameters for a battery cell has been described in (Zhang et al. U.S. Pat. No. 8,190,384 B2), and assigned to Sakti3, Inc. of Ann Arbor, Mich., which is hereby incorporated by reference in its entirety. This state-of-charge range controlled approach enhances the cycle-ability of the solid-state battery without sacrificing the energy density of the cells/batteries. Although highly successful, the approach can still be improved. Further details of the present disclosure can be found throughout the present specification and more particularly below.
I. Battery Cells can be Represented with Arbitrary Precision Using an Equivalent Circuit Model (“ECM”) (e.g., EC-n, EC-n,m)
where E is the open circuit voltage of the battery cell, soc is the state of charge of the battery cell, iL is the load current applied associated with the application of the battery cell, ii is the current through the resistor Ri. ii is calculated by:
as a solution of the differential equation formulated through current balance:
where τi=RiCi and t is time.
For a solid state battery cell made of multiple cell stacks connected in parallel, each cell stack can be represented by a ECM model, which is shown as EC-n,1 in
For a solid state battery pack made of multiple cells connected in parallel, each cell can be represented by a ECM model, which is shown as EC-n,m in
For a solid state battery pack made of multiple cells connected in series, each cell can be represented by a ECM model, which is shown as EC-n,m in
For a solid state battery pack made of multiple cells configured in a mixture of series and parallel connection, each cell can be represented by an ECM model, which is shown as EC-n,m in
II.1 Capacity Retention and Functionally Graded Materials
In an example, the present disclosure describes the unexpected benefits of controlling state of charge in solid state battery cathodes with functionally graded properties. Functionally graded materials (FGM) can be characterized by the variation in composition and structure gradually over volume, resulting in corresponding changes in the properties of the material. As an example in
Lithium Escaping into Substrate (Specific Embodiment, Glass)
In a specific embodiment, the present disclosure provides a method of preventing loss of lithium ions into a non-active layers in a solid-state battery. In solid state batteries, lithium ions can diffuse through cathode, current collector, and reach a substrate because the thickness of current collector is in the order of microns or less unlike particulate based batteries where a cathode is coated and pressed on a thick metal foil of about 100 μm or thicker. When lithium ions reach a substrate, the ions may diffuse into the bulk of glass substrate, or react with polymer materials, making irreversible reactions.
Pinholes in Current Collectors
In a specific embodiment, the present disclosure provides a method of preventing lithium diffusion through the pinholes in the current collector, which leads to the initial energy loss and capacity fade in solid state batteries. The method provides regulated cycling range, specifically limiting the state of charge that determines the number of lithium element per the stoichiometric cathode. The cells are operable at a state of charge between a lower bound to an upper bound. As an example, the state of charge lower bound ranges from 0.5% to 75%, and the state of charge upper bound range from 25% to 99.5%. Upon discharging, the lithium species moves into the cathode and start making contact of the current collector. The current collector below a certain thickness, for example 25 microns for aluminum film, made by high rate evaporation may contain a number of pinholes as shown in
The present disclosure limits regions where lithium can reach within a cathode to the vicinity of electrolyte away from the current collector, essentially preventing loss of lithium in a substrate. Lower diffusivity at a region close to current collectors prevents lithium diffusion through the cathode down to the current collectors. This functionally graded cathode material containing high diffusivity region near the electrolyte and low diffusivity region at the bottom adjacent to the current collector provides unique combination for both high power performance and capacity retention. That is, the lithium moves within specific spatial regions of the cathode, and is confined within such spatial regions, while staying away from regions, which can lead to diffusion into the bulk substrate or other regions. As one example, 95% of lithium ion will be confined within 95% of cathode thickness from the electrolyte-cathode interface toward the cathode current collector.
Anode Corrosion
In a specific embodiment, the present disclosure provides a method for preventing a solid-state battery device from lithium corrosion within the anode layer. The method includes regulating the depth-of-discharge, specifically the lower limit of cycling voltage, and preventing fully discharging of the solid-state batteries. Upon discharging, a portion of lithium anode layer intercalates into the cathode through the electrolyte, leaving some portion of lithium layer in the original region to maintain the conduction and diffusion path for the following cycles. If a solid state battery is fully or even overly discharged, which drives the significant portion of lithium within the anode into the cathode, the remaining lithium within the anode may become very thin and susceptible to corrosive chemical species of lithium such as oxygen, nitrogen, and water. The formations of lithium oxides, nitrides, and lithium hydroxides are irreversible and the lithium consumed in these reactions is not retrievable for further cycles (
The mechanism for preserving reactive lithium is the protection of lithium from corrosion by limitation of overdischarge. We determined that overdischarge results in lithium diffusion into the cathode current collector and into substrates for other inert layers. We further found that overcharge results in lithium diffusion into barrier or other layers designed to entrain lithium into the spatial region of the anode. As an example, such layers have been described in (Kim et al. U.S. Pat. App. No. 20120040233), and assigned to Sakti3, Inc. of Ann Arbor, Mich., which is hereby incorporated by reference in its entirety.
Lithium Anode Plating
In a specific embodiment, the present disclosure provides a prevention technique against the preferential lithium plating and the resulting energy loss of a solid-state battery device. Preferential lithium plating is referring to the non-uniform lithium diffusion across the electrolyte and anode interface, or local plating, when charging. This phenomenon leads to capacity drops in the following discharge cycles due to the loss of accessible lithium in some area within the anode layer as shown in the
Another issue with the lithium plating is the increase of impedance due to the discontinuity across the anode that provides diffusion and conduction path for the lithium ions and electrons. Such discontinuity creates an inhomogeneous distribution of lithium in the anode spatial region, which can result in reduced overall charge density over a homogenously distributed material. In some cases, this inhomogeneity could be sufficient to cause the anode regions to be unpercolated, namely sufficiently dispersed and unconnected such that there is not a domain spanning conductive path in the x-y plane.
Stress and Peeling Layers
In a specific embodiment, the present disclosure provides a method of restraining the stress within individual films and multilayers. Previously described cycling of solid state batteries causes significant intercalation-induced stresses by transporting lithium species between cathode and anode layers. This may result in film cracking and peeling, especially in combination with lithium corrosion and/or undesired lithium diffusion into the current collector and substrate. Fracture, or crack on the cell layers due to high film stress causes discontinuity, short circuits, and current leakage, which leads to low energy density and short cycle life. Examples of stress-induced film cracks and interlayer fractures are shown in
The present disclosure provides a method of regulating the state of charge to reduce the intercalation induced strain and stress during cycling, and thus prevent cracking and peeling of battery among solid state battery layers. State of charge regulation governs the state of stress because state of charge determines the state of intercalation stress in the battery cell. In one example, overdischarge would result in no material remaining in the anode spatial region, resulting in a zero stress boundary between the electrolyte and the anode spatial regions. This in turn could result in cracking or other damages to the electrolyte because the presence of the anode layer provides a cohesive force on the electrolyte during the operation of the cell. In another example, overdischarge of the cell could result in formation of one or more lithium rich layers in the cathode spatial region, which results in changed stress on the boundaries of the cathode spatial region. In another example, overdischarge leading to a concentration of anode material in the cathode current collector could alter the stress of the current collector on the surface of the cathode resulting in irreversible cracking or other damage including delamination. Any of these phenomena, for example, damage to an electrode or electrolyte, or loss of electrical contact between any layers would results in reduced energy density of the cell.
Controlling state-of-charge (SOC) while cycling the solid state battery cells has unexpected benefits. These benefits are further explained by the underpinning physical mechanisms explained as follows.
Because solid state batteries have much higher energy densities than conventional batteries, these batteries are capable of delivering very high energy density even cycled at limited SOC (not full SOC range).
Because solid state batteries have much higher energy densities than conventional batteries, these batteries are capable of delivering very high energy density even cycled at limited SOC (not full SOC range). For a specific high power application using such batteries, the application device can operate longer time using such batteries.
Battery material properties can also be adjusted by tuning processing parameters, such as background gas types, background gas partial pressure, and substrate temperature. As an example, increasing gas pressure will result in decrease in mass density and increase in diffusivity. As another example, by changing the gas type, we can change the concentration of different species in the film composition.
Because solid state batteries have much higher energy densities than conventional batteries, these batteries are capable of delivering very high energy density even cycled at limited SOC (not full SOC range). For a specific wearable device application using such batteries,
Battery material properties can also be adjusted by tuning processing parameters.
1. Capacity Loss
2. Functional Graded Material
3. Discharge Curve Comparison
EXAMPLE 1: building multiple stack solid state batteries by winding: As an example, the present invention provides a method of using a flexible material that has a thickness in the range between 0.1 and 100 μm as the substrate for the solid state batteries. The flexible material can be selected from polymer film, such as PET, PEN, or metal foils, such as copper, aluminum. The deposited layers that comprise solid state batteries on the flexible substrate, then can be wound into a cylindrical shape or wound then compressed into a prismatic shape.
EXAMPLE 2: building multiple stack solid state batteries by z-folding: As an example, the present invention provides a method of using a flexible substrate that can be a part of solid state batteries. As shown in
EXAMPLE 3: building multiple stack solid state batteries by iterative deposition process: As an example, the present invention provides a method of building multiple stack solid state batteries by moving a substrate through a number of deposition processes. By repeating a sequence of processes by N times, the solid state battery device 2500 has N number of stacks as shown in the schematic diagram in
EXAMPLE 4 vacuum cleaner,
EXAMPLE 5 robotic appliance,
EXAMPLE 6 electric scooter,
EXAMPLE 7 aero drone,
EXAMPLE 8 garden tool,
EXAMPLE 9 garden tractor,
EXAMPLE 10 hair dryer,
EXAMPLE 11 smartphone,
EXAMPLE 13 laptop/tablet,
EXAMPLE 13 electric vehicle,
In one specific embodiment, cathode material of current invention comprise amorphous or crystalline lithiated or non-lithiated transition metal oxide and lithiated transition metal phosphate, wherein the metal is in Groups 3 to 12 in the periodic table, including but not limited to lithium manganese oxide, lithium nickel oxide, lithium cobalt oxide, lithium nickel-cobalt-manganese oxide, lithium nickel-cobalt-aluminum oxide, lithium copper-manganese oxide, lithium iron-manganese oxide, lithium nickel-manganese oxide, lithium cobalt-manganese oxide, lithium nickel-manganese oxide, lithium aluminum-cobalt oxide, lithium iron phosphate, lithium manganese phosphate, lithium nickel phosphate, lithium cobalt phosphate, vanadium oxide, magnesium oxide, sodium oxide, sulfur, metal (Mg, La) doped lithium metal oxides, such as magnesium doped lithium nickel oxide, lanthanum doped lithium manganese oxide, lanthanum doped lithium cobalt oxide. Electrolyte materials of current invention includes, but not limited to, lithiated oxynitride phosphorus (LIPON), poly(ethylene oxide) (PEO), lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium sodium niobium oxide, lithium aluminum silicon oxide, lithium phosphate, lithium thiophosphate, lithium aluminum germanium phosphate, lithium aluminum titanium phosphate, LISICON (lithium super ionic conductor, generally described by LixM1-yM′yO4 (M=Si, Ge, and M′=P, Al, Zn, Ga, Sb)), thio-LISICON (lithium super ionic conductor, generally described by LixM1-yM′yS4 (M=Si, Ge, and M′=P, Al, Zn, Ga, Sb)), lithium ion conducting argyrodites (Li6PS5X (X═Cl, Br, I)), with ionic conductivity ranging from 10−5 to 10−1 S/m. Anode materials of current invention comprises of amorphous or crystalline lithiated or non-lithiated transition metal oxide, including but not limited to lithium titanium oxide, germanium oxide, or graphite, lithium, silicon, antimony, bismuth, indium, tin nitride, or lithium alloys, including but not limited to lithium magnesium alloy, lithium aluminum alloy, lithium tin alloy, lithium tin aluminum alloy. Substrate materials of current invention comprises a polymer material, a polyethylene terephthalate (PET), PEN, a glass, an alumina, a silicon, an insulation coated metals, an anodized metals or a mica. The first barrier layer materials of current invention comprise at least oxides, nitride, and phosphate of metal in Groups 4, 10, 11, 13 and 14 of the periodic table, and wherein the barrier layer material comprises a LixPOy where x+y<=7. The second barrier layer of current invention comprises an acrylate, acrylic ester and other polymers.
In an embodiment, the present invention provides a multi-layered solid-state battery device comprising: an equivalent circuit numbered from 1 through N associated with, respectively, a plurality of solid state battery cells numbered from 1 through N, each of the solid state battery cells comprising a first current collector overlying the substrate member, a cathode device overlying the first current collector, an electrolyte device overlying the cathode, an anode device overlying the electrolyte device, and a second current collector overlying the anode device, each of the plurality of solid state battery cells being operable at a state of charge between a lower bound to an upper bound; an energy density of greater than 50 watt hour per liter and greater characterizing the plurality of solid state battery cells; and a plurality of collimated pillar structures characterizing each of the cathode devices, each of the plurality of collimated pillar structures comprising an amorphous cathode material.
In a specific embodiment, the state of charge lower bound ranges from 0.5% to 75%, wherein the state of charge upper bound ranging from 25% to 99.5%. The cathode device can be characterized by an amorphous or crystalline structure. The cathode device can have a thickness ranging from 0.05 to 200 microns; and the anode device has a thickness ranging from 0.02 to 200 microns. The region of the cathode device can include a thickness ranging from about 0.05 to about 200 microns. The region can be substantially amorphous in characteristic. The anode device can include metal film. The plurality of battery cells can be wound or stacked.
In a specific embodiment, the solid state battery device can include a substrate made of at least one of a glass structure, a conductive structure, a metal structure, a ceramic structure, a plastic or polymer structure, or a semiconductor structure, or one or more active layers may comprise the substrate layer. The device can include a termination which is configured in a parallel or a serial arrangement using either a self-terminated or post-terminated connector configuration. The device can include a local conductivity characterizing the region of the cathode device and a bulk conductivity characterizing the cathode device.
In a specific embodiment, the cathode device is made from a material selected from lithiated or non-lithiated transition metal oxide and lithiated transition metal phosphate, wherein the metal is in Groups 3 to 12 in the periodic table, including but not limited to lithium manganese oxide, lithium nickel oxide, lithium cobalt oxide, lithium nickel-cobalt-manganese oxide, lithium nickel-cobalt-aluminum oxide, lithium copper-manganese oxide, lithium iron-manganese oxide, lithium nickel-manganese oxide, lithium cobalt-manganese oxide, lithium nickel-manganese oxide, lithium aluminum-cobalt oxide, lithium iron phosphate, lithium manganese phosphate, lithium nickel phosphate, lithium cobalt phosphate, vanadium oxide, magnesium oxide, sodium oxide, sulfur, metal (Mg, La) doped lithium metal oxides, such as magnesium doped lithium nickel oxide, lanthanum doped lithium manganese oxide, lanthanum doped lithium cobalt oxide.
In a specific embodiment, the anode device is made of a material selected from lithiated or non-lithiated transition metal oxide, including but not limited to lithium titanium oxide, germanium oxide, or graphite, lithium, silicon, antimony, bismuth, indium, tin nitride, or lithium alloys, including but not limited to lithium magnesium alloy, lithium aluminum alloy, lithium tin alloy, lithium tin aluminum alloy.
In a specific embodiment, the electrolyte device is selected from lithiated oxynitride phosphorus (LIPON), poly(ethylene oxide) (PEO), lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide, lithium sodium niobium oxide, lithium aluminum silicon oxide, lithium phosphate, lithium thiophosphate, lithium aluminum germanium phosphate, lithium aluminum titanium phosphate, LISICON (lithium super ionic conductor, generally described by LixM1-yM′yO4 (M=Si, Ge, and M′=P, Al, Zn, Ga, Sb)), thio-LISICON (lithium super ionic conductor, generally described by LixM1-yM′yS4 (M=Si, Ge, and M′=P, Al, Zn, Ga, Sb)), lithium ion conducting argyrodites (Li6PS5X (X═Cl, Br, I)), with ionic conductivity ranging from 10−5 to 10−1 S/m.
In a specific embodiment, each pair of the plurality of solid state battery cells comprises a bonding material in between. The cathode device can be characterized by a material comprising a plurality of pillar-like structures, each of which extends along a direction of the thickness, and substantially normal to a plane of the thickness of material and surface region. The cathode device can include a plurality of pillar structures, each of the pillar structure having a base region and an upper region, each of the pillar structures comprising a plurality of smaller particle-like structures, each of the smaller particle like structures being configured within each of the pillar structures. The cathode device can include a plurality of pillar structures, each of the pillar structure having a base region and an upper region, each of the pillar structures comprising a plurality of particle-like structures, each of the particle like structures being configured within each of the pillar structures, each pair of pillar structures having a plurality of irregularly-shaped polyhedral structures provided between the pair of pillar structures.
In an embodiment, the present invention provides a solid-state battery apparatus comprising: a plurality of battery cell devices, each of the devices having an anode device, an electrolyte device, and a cathode device; an equivalent circuit (EC) numbered from 1 through N characterizing the plurality of battery cells devices; a state of charge characterizing the plurality of battery cell devices; and a resistor, capacitor, or other electrical parameters provided in the equivalent circuit.
In a specific embodiment, the apparatus can include an appliance coupled to the plurality of battery cells, whereupon the application is selected from at least one of or more of at least a smartphone, a cell phones, personal digital assistants, radio players, music players, video cameras, tablet and laptop computers, military communications, military lighting, military imaging, satellite, aero-plane, satellites, micro air vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, fully electric vehicles, electric scooter, underwater vehicle, boat, ship, electric garden tractor, and electric ride on garden device, unmanned aero drone, unmanned aero-plane, an RC car, robotic toys, robotic vacuum cleaner, robotic garden tools, robotic construction utility, robotic alert system, robotic aging care unit, robotic kid care unit, electric drill, electric mower, electric vacuum cleaner, electric metal working grinder, electric heat gun, electric press expansion tool, electric saw and cutters, electric sander and polisher, electric shear and nibbler, electric routers, an electric tooth brush, an electric hair dryer, an electric hand dryer, a global positioning system (GPS) device, a laser rangefinder, a flashlight, an electric street lighting, standby power supply, uninterrupted power supplies, and other portable and stationary electronic devices
While the above is a full description of the specific embodiments, various modifications, alternative constructions and equivalents may be used. Therefore, the above description and illustrations should not be taken as limiting the scope of the present disclosure which is defined by the appended claims.