Abstract:
An improved chemical composition and manufacturing process for a battery electrode are disclosed. This battery electrode may be later arranged in flowing electrolyte battery cells. Battery electrode material formulation may include a mixture of polypropylene, carbon black, graphite, bonding additives and other substances in different concentrations. The inclusion of graphite may reduce the amount of carbon black in the mixture, thereby reducing the swelling of the battery electrode in the presence of bromine. Moreover, material formulation may reduce warpage caused by the swelling of electrode material, and may additionally improve the performance and properties of flowing electrolyte batteries. An extrusion molding process may be employed in order to fabricate the disclosed battery electrode.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority as a continuation-in-part of U.S. Non-Provisional Patent Application Serial No. 13/591,802, filed on Aug. 22, 2012, which in turn claims priority from U.S. Provisional Patent Application Serial No. 61/526,145, filed on Aug. 22, 2011, the entirety of which are each expressly incorporated by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    This invention relates generally to flowing electrolyte battery systems, and more particularly, to material formulations for battery electrodes employed in flowing electrolyte batteries. 
         [0004]    2. Background Information 
         [0005]    The performance of electrochemical storage devices involves complex, interrelated physical and chemical processes between electrode materials and electrolytes. 
         [0006]    Flowing electrolyte batteries may include a stack of flow frame assemblies where electrodes and separators are bonded to the flow frames. There are flow channels in the frames designed to direct electrolyte flow over the anode and cathode side of each electrode. On one side of each electrode, a component of the electrolyte is deposited and consumed during each cycle, while the other side of the electrode may include a carbon felt to support the catholyte evolution and consumption reactions. 
         [0007]    There is a need for improvement in many aspects of the design of flowing electrolyte batteries, including materials and manufacturing processes. One of the key areas with room for improvement relates to the formulation of electrodes. 
         [0008]    Zinc-bromine batteries are an example of rechargeable batteries. Rechargeable batteries may have their energy content restored by being charged, however deterioration of the battery may occur on each charge-discharge cycle. The deterioration may occur due to the interaction between the electrolyte and the electrodes within the battery cell. Electrolyte causes the electrode material to degrade, thus decreasing the active surface of the electrode while increasing internal resistance and diminishing battery capacity. 
         [0009]    Other limitations of existing battery electrodes is the inefficient bond between the frame and the electrode, which causes failures in battery performance. Another drawback is the fact that solids content represents a considerable percentage of the material&#39;s formulation. Some solids tend to absorb present reagents; producing an expansion of the electrode in the frame, thus creating warpage, which negatively affects battery performance. By reducing the amount of solids in the formulation, development of warpage may be decreased, while also improving the bonding between the electrode and the frame. Moreover, larger amounts of solids in the formulation may also cause the electrode to be brittle, so it is necessary to add components capable of increasing flexibility and tensile strength of the electrodes. 
         [0010]    Therefore, battery electrodes currently employed in flow batteries have performance and durability limitations. Electrodes employed in flowing electrolyte batteries and other electrochemical devices need to have low electrical resistivity, high chemical stability, good mechanical properties, and for some applications low weight and volume. Additionally, electrodes should be resistant to deformation due to the presence of reagents, such as bromine, or any other product employed during battery operation. 
         [0011]    More efficient battery electrodes are key to the advancement of energy storage technology, thus there is a need for material formulations which may provide battery electrodes with good flex strength, high conductivity, and resistance to expansion due to reagent exposure. 
       BACKGROUND ART 
       [0012]    U.S. Pat. No. 4,125,680 Shropshire et al., Bipolar carbon-plastic electrode structure-containing multicell electrochemical device and method of making same (Aug. 18, 1977) 
         [0013]    Abstract A novel multicell electrochemical device having a plurality of bipolar carbon-plastic electrode structures and a novel method of making the device are described. A plurality of bipolar carbon-plastic electrode structures are formed by first molding thin conductive carbon-plastic sheets from heated mixtures of specified carbon and plastic, and then establishing frames of dielectric plastic material around the sheets and sealing the frames to the sheets so as to render the resulting structures liquid impermeable. A plurality of electrochemical cell elements in addition to the electrode structures, e.g. separators, spacers and the like, are also formed with dielectric plastic frames. The frames of both the electrode structures and the additional elements have projections on at least ne surface. The electrode structures and the additional elements are stacked to form a group of items in an electrochemically functional arrangement. The arrangement is such that the projection of each frame contacts a frame surface of the next item in the stack. The items in the stack are joined to one another, e.g. by heat welding or ultrasonic welding, at these areas of contact so as to form a multicell electrochemical device capable of holding liquid therein. 
         [0014]    U.S. Pat. No. 4,379,814 Tsien et al., Sheet electrode for electrochemical systems (Apr. 12, 1983) 
         [0015]    Abstract: An electrochemical cell construction features a novel co-extruded plastic electrode in an interleaved construction with a novel integral separator-spacer. Also featured is a leak and impact resistant construction for preventing the spill of corrosive materials in the event of rupture. 
         [0016]    U.S. Pat. No. 4,496,637 Shimada et al., Electrode for flowcell (Dec. 22, 1983) 
         [0017]    Abstract: An electrode for an flowcell comprising electrode material made of carbon fiber having average &amp;It;002&amp;gt; spacing of quasi-graphite crystalline structure of not more than 3.70 .ANG., and the average C-axis size of crystallite of not less than 9.0 .ANG. and at least 3% by mole of oxygen atom bound to the fiber surface based on carbon atom, whereby the electrode has remarkable high electrical conductivity, current efficiency handling characteristics and hydrodynamic characteristics, and is adapted to flowcell. 
         [0018]    U.S. Pat. No. 5,591,532 Eidler et al, Zinc-bromine battery with non-flowing electrolyte (Jul. 7, 1995) 
         [0019]    Abstract: A battery including a plurality of bipolar electrodes and non-conductive separators, each having first and second surfaces. A carbon coating is applied on the first surface of each of the plurality of carbon plastic electrodes, and each separator is disposed in spaced, sandwich relation with respect to two of the plurality of electrodes. The electrodes and separators define a plurality of electrochemical cells, including a plurality of anodic half-cells, and a plurality of cathodic half-cells. A high surface area carbon material is disposed in, and completely fills, each cathodic half-cell, and an electrolyte is disposed in each half-cell. A spacer is disposed in each anodic half-cell. The spacer may be a mesh or screen made from polymeric material. The spacer may also be an aggregated glass mat. 
         [0020]    JP 07057740 Miyagawa et al., Electrode material of zinc-bromine battery (Mar. 3, 1995) 
         [0021]    Purpose: To provide an electrode material of zinc-bromine battery, which can prevent increase in the internal resistance while eliminating the warping caused by a swollen electrode material, and which can improve the service life and the reliability of the battery. 
         [0022]    Constitution: An electrode material to be arranged in the battery m in body of a zinc-bromine battery, comprises a four-component sheet form molding consisting of kneaded material, for which a predetermined composition ratio of carbon black, graphite and ion trapping agent are added to a high density polyethylene resin. The composition ratio of this electrode material is 45-49 wt. % of high density polyethylene resin, approximate 15 wt. % of carbon black, approximate 35 wt. % of graphite, and 1-5 wt. % of ion trapping agent. The ion trapping agent is of bismuth negative ion exchange type, and has acid resistance and alkali resistance and an inorganic ion exchanger, the form of which is selected among powder, paste and granular or tape all having heat resistance of not lower than 400° C. 
       SUMMARY 
       [0023]    According to various embodiments, a chemical composition and manufacturing process are provided for fabricating battery electrodes which may be used in flowing electrolyte batteries. Flowing electrolyte batteries may be used as means to store and transport energy. The disclosed chemical composition of battery electrodes may include a mixture of polypropylene, glass fiber, carbon fiber, graphite, carbon black, elastomer, among others. This mixture may be later extruded to form electrode sheets. 
         [0024]    According to an aspect of the present disclosure, the invention addresses the deficiencies in the prior art by providing a chemical composition of battery electrodes which may reduce warpage and degradation that may be present when electrodes come in contact with bromine. That is, by minimizing the amount of carbon black in the chemical composition and adding graphite instead, the swelling of the battery electrode in the presence of bromide may be minimized. As a result, zinc-bromine batteries integrating the disclosed battery electrodes may exhibit improved efficiency and longer life span. In addition, by reducing warpage in the battery electrode, the electrolyte flow distribution within the battery may be also improved, therefore increasing battery performance and stability. 
         [0025]    Yet, according to another aspect of the present disclosure, by employing the disclosed material formulation, nucleation of battery electrodes may be reduced, thus diminishing dendrite formation and branching between battery cells, which may translate into separator failure and internal leakage within the flowing electrolyte battery. 
         [0026]    In other embodiments, chemical composition of battery electrode may further include components such as, but not limited to, carbon nanotubes, carbon nano-fibers, graphene, micro-graphites, insert molding adhesion promoters, glass beads, talc, mica, coupling agents, stabilizing fillers, crystallinity promoters, anti-oxidants among others. 
         [0027]    Numerous other aspects, features and advantages of the present invention may be made apparent from the following detailed description taken together with the drawing figures. 
       LIST OF FIGURES 
       [0028]    Non-limiting embodiments of the present invention are described by way of example with reference to the accompanying figures which are schematic and are not intended to be drawn to scale. Unless indicated as representing the background art, the figures represent aspects of the invention. 
         [0029]      FIG. 1  shows a flowchart of a manufacturing method for battery electrodes, according to an embodiment. 
         [0030]      FIG. 2  depicts an illustrative embodiment of a battery electrode. 
         [0031]      FIG. 3  illustrates an embodiment of second extrusion process. 
         [0032]      FIG. 4  represents an illustrative embodiment of a battery cell stack. 
     
    
     DETAILED DESCRIPTION 
       [0033]    Disclosed herein is a composition for electrodes that may be employed in flowing electrolyte batteries, according to an embodiment. The present disclosure is hereby described in detail with reference to embodiments illustrated in the drawings, which form a part hereof. In the drawings, which are not necessarily to scale or to proportion, similar symbols typically identify similar components, unless context dictates otherwise. Other embodiments may be used and/or other changes may be made without departing from the spirit or scope of the present disclosure. The illustrative embodiments described in the detailed description are not meant to be limiting of the subject matter presented herein. 
       Definitions 
       [0034]    As used herein, “battery cell” may refer to an enclosure provided with at least a pair of electrodes and at least one inlet and one outlet configured to allow the flow of electrolyte through the enclosure. 
         [0035]    As used herein, “battery cell stack” may refer to one or more battery cells, placed between a pair of terminal electrodes or end caps, that share a common electrolyte path. 
         [0036]    As used herein, “flow battery” or “flowing electrolyte battery” may refer to an electrochemical device that includes at least one battery cell stack and is capable of storing energy. 
         [0037]    As used herein, “flow frame” may refer to a flow battery component that forms at least a portion of the enclosure of a battery cell, containing at least a portion of paths configured to control the flow of electrolyte through a battery cell stack. 
         [0038]    As used herein, “battery electrode” may refer to a structure inside the battery through which electric current is passed. 
         [0039]    As used herein “warpage” may refer to at least one distortion in a battery component. 
         [0040]    As used herein “bromine expansion” may refer to the expansion suffered by an electrode due to exposure to bromine. 
       DESCRIPTION OF DRAWINGS 
       [0041]    Disclosed herein is a material formulation and method for producing battery electrodes which, according to an embodiment, may be employed in the manufacturing of electrochemical devices such as flowing electrolyte batteries. 
         [0042]      FIG. 1  shows a flowchart of manufacturing method  100 , according to an embodiment. Manufacturing method  100  may start with formulation components  102  which may include polypropylene, glass fiber, graphite, carbon black, elastomers, and other additives. Formulation components  102  may be compounded in first extrusion process  104  to obtain pellets  106 . Subsequently, pellets  106  may pass through second extrusion process  108  in order to obtain electrode film  110 ; where electrode film  110  may exhibit a uniform thickness ranging from about 0.1 mm to about 4 mm, with 0.6 mm being preferred. Afterwards, electrode film  110  may pass through die cutting process  112  in order to form electrode sheets  114  within preferred dimensions. 
         [0043]    Following the process in  FIG. 1 , electrode sheets  114  may be coated with activation layer  116  which may include, in some embodiments, carbon and adhesives. Activation layer  116  may be pressed onto electrode sheet  114  to form a proper bond. Required pressure to bond activation layer  116  onto electrode sheet  114  may range from about 10 psi to about 200 psi, with 100 psi being preferred. Finally, in order to obtain smooth plastic surface for appropriate bonding with the flow frame of a flow battery, electrode sheets  114  coated with activation layer  116  may pass through edging process  118 , where a rubber blade may remove the carbon from all the perimeter of electrode sheet  114 . and forming battery electrode  120 . 
         [0044]      FIG. 2  depicts an illustrative embodiment of battery electrode  120  obtained from manufacturing method  100 . As seen in  FIG. 2 , battery electrode  120  may include electrode sheet  114  coated with activation layer  116 , along with edged perimeter  202  formed during edging process  118 . Bonding between battery electrode  120  and frame may be improved by removing activation layer  116  as edged perimeter  202  may have a good probability of achieving a suitable bonding with the frame. 
         [0045]    The dimensions of battery electrode  120  depicted in  FIG. 2  may vary according to the size and application of the flowing electrolyte battery that may integrate battery electrode  120 . 
         [0046]    Formulation Components  102   
         [0047]    Chemical formulation of battery electrodes  120  may include formulation components  102  such as polypropylene, glass fiber, carbon fiber, graphite, carbon black, elastomers and other additives. Two types of polypropylene compounds may be employed: 1) polypropylene with low Melt Flow Index (MFI) and 2) polypropylene with high MFI. Low MFI polypropylene is required to achieve an extrusion grade material while improving the dispersion of carbon fillers, which may increase the conductivity of battery electrode  120 . High MFI polypropylene is employed in order to improve molding process of battery electrode  120 . Low MFI polypropylene may have a MFI between 1 and 10 gm/10 min at 230° C., 2.16 Kg, while high MFI polypropylene may have a MFI between 10 and 130 gm/10 min at 230° C., 2.16 Kg. Suitable suppliers for high MFI polypropylene and low MFI polypropylene may include Himont Inc. 
         [0048]    Carbon black may be added in the mixture of formulation components  102  in order to improve the electrical conductivity of battery electrodes  120 . Suitable suppliers for carbon black may include Akzo Chemie America. Carbon black tends to swell in the presence of bromine, producing an expansion of battery electrode  120 . As such, in order to reduce the expansion in battery electrode  120 , graphite may be used as one of the formulation components  102 . The addition of a suitable amount of graphite may allow a reduction in the amount of carbon black needed in the formulation. Graphite may also provide stability and conductivity to battery electrode  120 . Graphite may be purchased from SGL and Timcal. 
         [0049]    Carbon fiber may be also added to formulation components  102  to increase conductivity of battery electrode  120 . Suitable suppliers for carbon fiber may include Akzo Chemie America. To enhance the strength of the resultant battery electrode  120 , formulation components  102  may also include glass fiber which may add stability and resistance to bromine and thermal expansion. Glass fiber may be purchase from Owens Corning. 
         [0050]    Furthermore, bonding additives may be added to formulation components  102  to enhance bonding properties and improve insert molding process during the fabrication of flowing electrolyte batteries that may integrate battery electrode  120 . In some embodiments, a polyolefin elastomer may be employed as bonding additive. A suitable polyolefin elastomer may be ethylene octene copolymer which may be provided by Dow Chemical. Ethylene octene copolymer increases the mobility and miscibility of polypropylene resulting in greater cohesion between battery electrode  120  and the frame in which battery electrode  120  may be placed. 
         [0051]    According to an embodiment formulation components  102  may include low MFI polypropylene in concentrations ranging from about 35% wt to about 65% wt; high MFI polypropylene in concentrations ranging from about 5% wt to about 1.5% wt; glass fiber in concentrations from about 3% wt to about 10% wt; carbon fiber in concentrations from about 2% wt to about 10% wt; graphite in concentrations from about 5% wt to about 15% wt; carbon black in concentrations from about 7% wt to about 20% wt; and polyolefin elastomer in concentrations ranging from about 2% wt to about 10% wt. 
         [0052]    In other embodiments formulation components  102  may also include carbon nanotubes, carbon nanofibers, graphene, micro-graphites, insert molding adhesion promoter glass beads, talc, mica, coupling agents, stabilizing fillers, crystallinity promoters and anti-oxidants in varied concentrations. 
         [0053]    Formation of Pellets  106   
         [0054]    According to an embodiment, manufacturing method  100  for battery electrodes  120  may include first extrusion process  104  where formulation components  102  such as, but not limited to, high MFI polypropylene (PP), low MFI polypropylene and carbon black may be mixed to form a first mixture. Subsequently, first mixture may be blended in an internal mixer at a blade speed of about 200 rpm, at a temperature ranging from about 300° F. to about 500° F. Graphite may be slowly added to first mixture with the remaining formulation components  102  to obtain a pre-compounded mixture. The resulting pre-compounded mixture may be extruded into pellets  106 . Suitable temperature for first extrusion process  104  of pellets  106  may vary from about 300° F. to about 500° F., while clamping pressure applied during first extrusion process  104  molding may vary from about 20 psi to about 70 psi. 
         [0055]    Second Extrusion Process  108   
         [0056]      FIG. 3  illustrates an embodiment of second extrusion process  108  where pellets  106  may be supplied to hopper  302  and melted in heated chamber  304  which contains rotating screw  306 . Suitable temperature for heated chamber  304  may range from about 300° F. to about 500° F., with 400° F. being preferred, After heated chamber  304 , melted pellets  308  are obtained. Subsequently, melted pellets  308  may go through cooling chamber  310  which may operate at a temperature between 250° F. and 450° F., with 350° F. being preferred. Subsequently, melted pellets  308  may go through extruder  312  to obtain electrode film  110  having a uniform thickness. Extruder  312  may exert a pressure of about 50 psi. 
         [0057]    After second extrusion process  108 , electrode film  110  may undergo die cutting process  112  in order to obtain rectangular electrode sheets  114  of varied dimensions depending on the specifications needed for the flowing electrolyte batteries. 
         [0058]    Manufacturing Techniques for Coating Activation Layer  116  onto Electrode Sheet  114   
         [0059]    There may be three techniques that can be employed for the application of activation layer  116  onto electrode sheet  114 . 
         [0060]    In one embodiment, conductive glue may be applied onto one surface of electrode sheet  114  by means of a porous roller. Subsequently, electrode sheet  114  may be immediately immersed in a fluidized bed of granular activated carbon. Afterwards, electrode sheet  114  may be dried and then pressed at temperatures ranging from about 290° F. to about 400° F., with 320° F. being preferred. 
         [0061]    In other embodiment, activation layer  116  in sheet form may be applied to electrode sheet  114  in a laminating process during second extrusion process  108 . Depending on the type of activation layer  116  employed, the process may require a transfer sheet for providing stability during the transfer process. Activation layers  116  in sheet form may include paper, felt, gas diffusion layers, among others. 
         [0062]    In another embodiment activation layer  116  may be placed or glued, by means of a porous roller, on electrode sheet  114  and then may be pressed under pressure and heat. Pressure may range from about 10 psi to about 200 psi, with 100 psi being preferred; while temperature may range from about 290° F. to about 400° F., 320° F. being preferred. This process partially submerges activation layer  116  into electrode sheet  114 , thus creating a permanent mechanical bond. 
         [0063]    After coating process of activation layer  116 , electrode sheet  114  may undergo edging process  118  where a rubber blade may be employed in order to remove activation layer / 16  from the perimeter of electrode sheet  114  and prepare electrode sheet  114  for bonding with the frame of a flowing electrolyte battery. The amount of activation layer  116  removed from electrode sheet  114  during edging process  118  may depend on the surface dimensions and bonding properties of the frame in which battery electrode  120  may be bonded. 
         [0064]    Battery Electrode  120  Properties 
         [0065]    Battery electrodes  120  manufactured employing the disclosed formulation components  102  and manufacturing method  100  may have a melt flow index ranging from about 0 gm/10 min at 230° C. 5 Kg to about 5 gm/10 min at 230° C. 5 Kg. 
         [0066]    Electrical performance of battery electrode  120  may include a bulk resistivity ranging between 0 Ω·cm and 5 Ω·cm; and a surface resistivity in ranges from 1 Ω·cm 2  to 15 Ω·cm 2 . 
         [0067]    Mechanical tests on battery electrode  120  may reveal a tensile strength between 3500 psi and 6000 psi; a tensile modulus between 500000 psi and 800000 psi; a tensile elongation ranging from about 1.0% to about 5.0%; flexural strength of about 9000 psi; a tensile strength reduction due to bromine exposure ranging from about 0% to about 10%; a tensile modulus reduction due to bromine exposure between 0% and 20%; a flexural modulus ranging from about 150000 psi to about 750000 psi; and a bromine expansion between 0.0% and 1.5%. 
         [0068]      FIG. 4  represents an illustrative embodiment of battery cell stack  400  for zinc-bromine batteries. Battery cell stack  400  may include micro-porous separators  402 , flow frames  404 , half-cell spacers  406  and battery electrodes  120 . In order to assemble battery cell stack  400 , a pair of micro-porous separators  402  which are previously bonded to flow frame  404  may be placed between two flow frames  404  containing a pair of battery electrodes  120  each. Subsequently, half-cell spacer  406  is placed between flow frames  404  containing micro-porous separators  402  and flow frames  404  containing battery electrodes  120 . Half-cell spacers  406  may be employed in order to maintain a constant cell gap and prevent the contact between battery electrode  120  and micro-porous separator  402 , thus allowing a constant electrolyte flow throughout the flow channels (not shown in  FIG. 4 ) of flow frames  404 . Zinc-bromine batteries are useful transportable means for energy storage, and may include a series of battery cell stacks  400  depending on the power capacity of the battery. 
       EXAMPLES 
       [0069]    Example #1 is an embodiment of battery electrode  120  where battery electrode  120  may exhibit the following properties: a melt flow index of fess than 1 gm/10 min at 230° C. 5 Kg, a bulk resistivity of 0.8 Ω·cm, a surface resistivity of 3.5 Ω·cm 2 , a tensile strength of 4800 psi, a tensile modulus of 660000 psi, a tensile elongation of 2.5%, a flexural strength of 9000 psi, a tensile strength reduction due to bromine exposure of less than 5%, tensile modulus reduction due to bromine exposure of less than 10%, a flexural modulus of 600000 psi, and a bromine expansion of 0.5%. In order to obtain these properties, battery electrode  120  may be manufactured using formulation components  102  containing 53% wt low MFI polypropylene, 10% wt high MFI polypropylene, 5% wt glass fiber, 5% wt carbon fiber, 10% wt graphite, 12% wt carbon black and 5% wt polyolefin elastomer. 
         [0070]    Example #2 is an embodiment of battery electrode  120  where battery electrode  120  may exhibit the following properties: a melt flow index of than 1 gm/10 min at 230° C. 5 Kg, a bulk resistivity of 2.3 Ω·cm, a surface resistivity of 10 Ω·cm 2 , a tensile strength of 4300 psi, a tensile modulus of 450000 psi, a tensile elongation of 2.2%, a flexural strength of 8600 psi, a tensile strength reduction due to bromine exposure of less than 10%, tensile modulus reduction due to bromine exposure of less than 10%, a flexural modulus of 450000 psi, and a bromine expansion of 0.5%. In order to obtain these properties, battery electrode  120  may be manufactured using formulation components  102  containing 50% wt low WWI polypropylene, 10% wt high MFI polypropylene, 5% wt glass fiber, 5% wt carbon fiber, 13% wt graphite, 10% wt carbon black and 7% wt polyolefin elastomer. 
         [0071]    Example #3 is an embodiment of battery electrode  120  where battery electrode  120  may exhibit the following properties: a melt flow index of than 1 gm/10 min at 230° C. 5 Kg, a bulk resistivity of 1.5 Ω·cm, a surface resistivity of 9 Ω·cm 2 , a tensile strength of 4300 psi, a tensile modulus of 480000 psi, a tensile elongation of 3.6%, a flexural strength of 8200 psi, a tensile strength reduction due to bromine exposure of less than 10%, tensile modulus reduction due to bromine exposure of less than 10%, a flexural modulus of 530000 psi, and a bromine expansion of 0.5%. In order to obtain these properties, battery electrode  120  may be manufactured using formulation components  102  containing 50% wt low MFI polypropylene, 10% wt high MFI polypropylene, 5% wt glass fiber, 10% wt carbon fiber, 10% wt graphite, 10% wt carbon black and 5% wt polyolefin elastomer. 
         [0072]    While various aspects and embodiments have been disclosed herein, other aspects and embodiments may be contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.