Flame Retardants For Battery Electrolytes

Abstract

This invention provides nonaqueous electrolyte solutions for lithium batteries. The nonaqueous electrolyte solutions comprise a liquid electrolyte medium; a lithium-containing salt; 4-bromomethyl-1,3-dioxolan-2-one, and at least one electrochemical additive.

Claims

1. A nonaqueous electrolyte solution for a lithium battery, which solution comprises i) a liquid electrolyte medium; ii) a lithium-containing salt; iii) 4-bromomethyl-1,3-dioxolan-2-one; and iv) at least one electrochemical additive I) selected from: a) unsaturated cyclic carbonates containing three to about six carbon atoms, b) fluorine-containing saturated cyclic carbonates containing three to about five carbon atoms and one to about four fluorine atoms, c) tris(trihydrocarbylsilyl) phosphites containing three to about nine carbon atoms, d) trihydrocarbyl phosphates containing three to about twelve carbon atoms, e) cyclic sultones containing three to about eight carbon atoms, f) saturated cyclic hydrocarbyl sulfites having a 5-membered or 6-membered ring and containing two to about six carbon atoms, g) saturated cyclic hydrocarbyl sulfates having a 5-membered or 6-membered ring and containing two to about six carbon atoms, h) cyclic dioxadithio polyoxide compounds having a 6-membered, 7-membered, or 8-membered ring and containing two to about six carbon atoms, i) another lithium-containing salt, and j) mixtures of any two or more of the foregoing; or II) selected from: at least one electrochemical additive selected from vinylene carbonate, 4-fluoro-ethylene carbonate, tris(trimethylsilyl)phosphite, triallyl phosphate, 1,3-propane sultone, 1,3-propene sultone, 1,3,2-dioxathiolane 2-oxide, 1,3,2-dioxathiolane 2,2-dioxide, 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide, lithium di(fluoro)(oxalato)borate, lithium bis(oxalato)borate, and mixtures of any two or more of these.

2. A solution as in claim 1 wherein the electrochemical additive in I) is selected from: a) unsaturated cyclic carbonates containing three to about four carbon atoms, b) fluorine-containing saturated cyclic carbonates containing three to about four carbon atoms and one to about two fluorine atoms, c) tris(trihydrocarbylsilyl) phosphites containing three to about six carbon atoms, d) trihydrocarbyl phosphates containing three to about nine carbon atoms, e) cyclic sultones containing three to about four carbon atoms, f) saturated cyclic hydrocarbyl sulfites having a 5-membered ring and containing two to about four carbon atoms, g) saturated cyclic hydrocarbyl sulfates having a 5-membered ring and containing two to about four carbon atoms, h) cyclic dioxadithio polyoxide compounds having a 6-membered or 7-membered ring and containing two to about four carbon atoms, i) another lithium-containing salt, and j) mixtures of any two or more of the foregoing.

3. A solution as in claim 1 the electrochemical additive in I) is selected from: a) an unsaturated cyclic carbonate in an amount of about 0.5 wt % to about 12 wt %, relative to the total weight of the nonaqueous electrolyte solution, b) a fluorine-containing saturated cyclic carbonate in an amount of about 0.5 wt % to about 8 wt %, relative to the total weight of the nonaqueous electrolyte solution, c) a tris(trihydrocarbylsilyl) phosphite in an amount of about 0.1 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, d) a trihydrocarbyl phosphate in an amount of about 0.5 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, e) a cyclic sultone in an amount of about 0.25 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, f) a cyclic sultone in an amount of about 1.5 wt % to about 12 wt %, relative to the total weight of the nonaqueous electrolyte solution, g) a saturated cyclic hydrocarbyl sulfite in an amount of about 0.5 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, h) a saturated cyclic hydrocarbyl sulfate in an amount of about 0.25 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, i) a cyclic dioxadithio polyoxide compound in an amount of about 0.5 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, j) another lithium-containing salt in an amount of about 0.5 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution, and k) mixtures of any two or more of the foregoing.

4. A solution as in claim 1 wherein the electrochemical additive in I) is a saturated cyclic hydrocarbyl sulfate, a cyclic sultone, or another lithium-containing salt.

5. A solution as in claim 1 wherein the electrochemical additive in I) is a saturated cyclic hydrocarbyl sulfate in an amount of about 1 wt % to about 4 wt %, a cyclic sultone in an amount of about 0.5 wt % to about 4 wt %, a cyclic sultone in an amount of about 1.5 wt % to about 12 wt %, a tris(trihydrocarbylsilyl) phosphite in an amount of about 0.2 wt % to about 3 wt %, or another lithium-containing salt in an amount of about 1 wt % to about 4 wt %, each relative to the total weight of the nonaqueous electrolyte solution; or 1,3,2-dioxathiolane 2,2-dioxide, 1,3-propene sultone, 1,3-propane sultone, tris(trimethylsilyl)phosphite, lithium di(fluoro)(oxalato)borate, or lithium bis(oxalato)borate.

6. (canceled)

7. A solution as in claim 5 wherein each electrochemical additive is not used with other electrochemical additives.

8. A solution as in claim 1 wherein the electrochemical additive is a mixture of an unsaturated cyclic carbonate and a saturated cyclic hydrocarbyl sulfite, or a mixture of a cyclic sultone, a tris(trihydrocarbylsilyl) phosphite, and a cyclic dioxadithio polyoxide, optionally wherein the combined amount of the electrochemical additives in each mixture is about 0.25 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution.

9. (canceled)

10. A solution as in claim 1 wherein the 4-bromomethyl-1,3-dioxolan-2-one is in an amount of about 10 wt % or more bromine relative to the total weight of the solution, and/or wherein the liquid electrolyte medium is ethylene carbonate, ethyl methyl carbonate, or a mixture thereof, and/or wherein the lithium-containing salt is lithium hexafluorophosphate.

11. (canceled)

12. A solution as in claim 1 wherein the nonaqueous electrolyte solution further comprises vinylene carbonate in an amount of about 8 wt % to about 11 wt %, relative to the total weight of the nonaqueous electrolyte solution.

13. A nonaqueous lithium battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte solution as in claim 1.

14. (canceled)

15. A solution as in claim 14 wherein the electrochemical additive in II) is selected from: vinylene carbonate in an amount of about 0.5 wt % to about 3 wt %, relative to the total weight of the nonaqueous electrolyte solution; vinylene carbonate in an amount of about 8 wt % to about 11 wt %, relative to the total weight of the nonaqueous electrolyte solution; 4-fluoro-ethylene carbonate in an amount of about 1.5 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution; tris(trimethylsilyl) phosphite in an amount of about 0.2 wt % to about 3 wt %, relative to the total weight of the nonaqueous electrolyte solution; triallyl phosphate in an amount of about 1 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution; 1,3-propane sultone or 1,3-propene sultone in an amount of about 0.5 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; 1,3-propane sultone in an amount of about 1.5 wt % to about 12 wt %, relative to the total weight of the nonaqueous electrolyte solution; 1,3,2-dioxathiolane 2-oxide in an amount of about 1 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; 1,3,2-dioxathiolane 2,2-dioxide in an amount of about 1 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide in an amount of about 1 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; lithium di(fluoro)(oxalato)borate in an amount of about 1 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; lithium bis(oxalato)borate in an amount of about 1 wt % to about 4 wt %, relative to the total weight of the nonaqueous electrolyte solution; and mixtures of any two or more of these.

16. A solution as in claim 1 wherein the electrochemical additive in II) is selected from 1,3-propane sultone, 1,3-propene sultone, 1,3,2-dioxathiolane 2,2-dioxide, tris(trimethylsilyl)phosphite, lithium di(fluoro)(oxalato)borate, and lithium bis(oxalato)borate; or selected from 1,3-propane sultone in an amount of about 0.5 wt % to about 4 wt %, 1,3-propane sultone in an amount of about 1.5 wt % to about 12 wt %, 1,3-propene sultone in an amount of about 0.5 wt % to about 4 wt %, 1,3,2-dioxathiolane 2,2-dioxide, in an amount of about 1 wt % to about 4 wt %, lithium di(fluoro)(oxalato)borate in an amount of about 1 wt % to about 4 wt %, and lithium bis(oxalato)borate in an amount of about 1 wt % to about 4 wt %, each relative to the total weight of the nonaqueous electrolyte solution.

17. (canceled)

18. A solution as in claim 16 wherein each electrochemical additive is not used with other electrochemical additives.

19. A solution as in claim 1 wherein the electrochemical additive in II) is selected from A) a mixture of vinylene carbonate and 1,3,2-dioxathiolane 2-oxide, B) a mixture of vinylene carbonate and 1,3-propane sultone, and C) a mixture of 1,3-propene sultone, tris(trimethylsilyl)phosphite, and 1,3,2-dioxathiolane 2,2-dioxide, optionally wherein the combined amount of the electrochemical additives in each mixture is about 0.25 wt % to about 5 wt %, relative to the total weight of the nonaqueous electrolyte solution.

20-23. (canceled)

24. A process for producing a nonaqueous electrolyte solution for a lithium battery, which process comprises combining components comprising: i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) 4-bromomethyl-1,3-dioxolan-2-one; and iv) at least one electrochemical additive I) selected from: a) unsaturated cyclic carbonates containing three to about six carbon atoms, b) fluorine-containing saturated cyclic carbonates containing three to about five carbon atoms and one to about four fluorine atoms, c) tris(trihydrocarbylsilyl) phosphites containing three to about nine carbon atoms, d) trihydrocarbyl phosphates containing three to about twelve carbon atoms, e) cyclic sultones containing three to about eight carbon atoms, f) saturated cyclic hydrocarbyl sulfites having a 5-membered or 6-membered ring and containing two to about six carbon atoms, g) saturated cyclic hydrocarbyl sulfates having a 5-membered or 6-membered ring and containing two to about six carbon atoms, h) cyclic dioxadithio polyoxide compounds having a 6-membered, 7-membered, or 8-membered ring and containing two to about six carbon atoms, i) another lithium-containing salt, and j) mixtures of any two or more of the foregoing; or II) selected from: at least one electrochemical additive selected from vinylene carbonate, 4-fluoro-ethylene carbonate, tris(trimethylsilyl)phosphite, triallyl phosphate, 1,3-propane sultone, 1,3-propene sultone, 1,3,2-dioxathiolane 2-oxide, 1,3,2-dioxathiolane 2,2-dioxide, 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide, lithium di(fluoro)(oxalato)borate, lithium bis(oxalato)borate, and mixtures of any two or more of these.

25. (canceled)

26. A nonaqueous electrolyte solution for a lithium battery, which solution comprises i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) 4-bromomethyl-1,3-dioxolan-2-one.

27. A solution as in claim 26 wherein the 4-bromomethyl-1,3-dioxolan-2-one is in an amount of about 10 wt % or more bromine relative to the total weight of the solution; and/or the liquid electrolyte medium is ethylene carbonate, ethyl methyl carbonate, or a mixture thereof, and/or wherein the lithium-containing salt is lithium hexafluorophosphate.

28. (canceled)

29. A nonaqueous lithium battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte solution as in claim 26.

30. A process for producing a nonaqueous electrolyte solution for a lithium battery, which process comprises combining components comprising: i) a liquid electrolyte medium; ii) a lithium-containing salt; and iii) 4-bromomethyl-1,3-dioxolan-2-one.

31. A process as in claim 30 wherein the 4-bromomethyl-1,3-dioxolan-2-one is in an amount of about 10 wt % or more bromine relative to the total weight of the solution; and/or wherein the liquid electrolyte medium is ethylene carbonate, ethyl methyl carbonate, or a mixture thereof, and/or wherein the lithium-containing salt is lithium hexafluorophosphate or lithium bis(oxalato)borate.

32. (canceled)

Description

EXAMPLE 1

[0071] Nonaqueous electrolyte solutions containing 4-bromomethyl-1,3-dioxolan-2-one, prepared as described above, were subjected to the modified UL-94 test described above. Results are summarized in Table 1 below; as noted above, the reported numbers are an average value from three runs.

TABLE-US-00001 TABLE 1 Flame retardant Bromine wt % in wt % in Time to Flame retardant soln. soln. Result extinguish 4- 25 11 flame 24 s bromomethyl-1, retardant 3-dioxolan- 2-one

EXAMPLE 2

[0072] Additional flammability testing of nonaqueous electrolyte solutions was performed at Sandia National Laboratories. In these thermal abuse tests, a closer approximation was made to the conditions under which electrolytes in abuse conditions need to exhibit non-flammable properties, in particular a cell that is venting in combination with an ignition source. The tests were conducted by filling an 18650-sized battery cell with approximately 5 mL of the nonaqueous electrolyte solution, crimping the cell with a typical cell header assembly, and heating the electrolyte-containing cell at a fixed rate of 5° C./min with a spark-wire ignition source at a fixed position roughly 2 inches above the cell header. At about 200° C., the battery cell began venting, the hot electrolyte solution became aerosolized, and was exposed to the spark-wire ignition source. Each sample was monitored for ignition; non-ignition was considered to pass the test, while ignition of the sample failed the test.

[0073] One sample was a nonaqueous electrolyte solution without a flame retardant, and contained 1.2 M LiPF.sub.6 in ethylene carbonate/ethyl methyl carbonate (wt ratio 3:7). The rest of the samples contained the desired amount of flame retardant in the electrolyte solution. Results are summarized in Table 2 below. A flame duration of zero (non-ignition) is best, and a short flame duration is better than a longer one. In the results below, the shorter flame durations as compared to the electrolyte solution indicate that the flame retardant significantly reduced the flame duration.

TABLE-US-00002 TABLE 2 Flame retardant Bromine Flame Chemical Name in soln. in soln. Result duration.sup.2 Electrolyte soln..sup.1 0 0 Fail ~117 s 4-bromomethyl- 25 wt % 11 wt % Pass 0 1,3-dioxolan- 2-one 4-bromomethyl- 25 wt % 11 wt % Fail  ~9 s 1,3-dioxolan- 2-one .sup.1Comparative run. .sup.2Approximate time of flame duration after ignition.

EXAMPLE 3

[0074] Tests of some flame retardants in coin cells were also carried out. Coin cells were assembled using nonaqueous electrolyte solutions containing the desired amount of flame retardant. The coin cells were then subjected to electrochemical cycling of CCCV charging to 4.2 V at C/5, with a current cutoff of C/50 in the CV portion, and CC discharge at C/5 to 3.0 V.

[0075] One sample was a nonaqueous electrolyte solution without a flame retardant, and contained 1.2 M LiPF.sub.6 in ethylene carbonate/ethyl methyl carbonate (wt ratio 3:7). The rest of the samples contained the desired amount of flame retardant in the electrolyte solution; some solutions also contained an electrochemical additive in addition to the flame retardant. Results are summarized in Tables 3A-3D below; the error range in the Coulombic efficiencies is about 0.5% to about 1.0%. Results reported in Tables 3A-3C are averages from multiple cells except where noted; “multiple cells” usually means two or three cells.

TABLE-US-00003 TABLE 3A Coulombic Flame efficiency retardant Bromine 1st 10th Chemical Name in soln. in soln. cycle cycle Electrolyte soln..sup.1 0 0 81.8%  99.6% 4-bromomethyl-  8 wt % 3.5 wt % 63.8%  99.6% 1,3-dioxolan- 2-one 4-bromomethyl- 25 wt %  11 wt % 45.5%  95.7% 1,3-dioxolan- 2-one 4-bromomethyl- 25 wt %  11 wt % 43.0% 100.7% 1,3-dioxolan- 2-one.sup.2 .sup.1Comparative run. .sup.2Prepared by combining 0.2M LiPF.sub.6•in 4-bromomethyl-1,3-dioxolan-2-one with the plain electrolyte solution for a final concentration of 1.02M LiPF.sub.6.

TABLE-US-00004 TABLE 3B Addi- Coulombic Flame tive efficiency retardant 1 in 1st 10th Chemical Name in soln. soln. cycle cycle 4-bromomethyl-1,3- 25 wt %  0 37.1% 99.2% dioxolan-2-one.sup.1,2 4-bromomethyl-1, 8 wt % 1 wt % 51.5% 99.6% 3-dioxolan-2-one + vinylene carbonate 4-bromomethyl-1, 8 wt % 2 wt % 59.8%  100% 3-dioxolan-2-one + vinylene carbonate 4-bromomethyl-1, 8 wt % 10 60.7% 99.8% 3-dioxolan-2-one + wt % vinylene carbonate 4-bromomethyl-1, 8 wt % 2 wt % 52.5% 97.2% 3-dioxolan-2-one + 4-fluoro-ethylene carbonate 4-bromomethyl-1, 8 wt % 2 wt % 64.8% 98.4% 3-dioxolan-2-one + tris(trimethylsilyl)phosphite 4-bromomethyl-1, 8 wt % 2 wt % 71.3% 98.0% 3-dioxolan-2-one + 1,3,2-dioxathiolane 2,2-dioxide 4-bromomethyl-1, 8 wt % 2 wt % 63.8% 99.8% 3-dioxolan-2-one + 1,5,2,4-dioxadithiane 2,2,4,4-tetroxide 4-bromomethyl-1, 8 wt % 2 wt % 62.6% 99.5% 3-dioxolan-2-one + triallyl phosphate 4-bromomethyl-1, 8 wt % 2 wt % 69.6% 99.5% 3-dioxolan-2-one + 1,3-propene sultone 4-bromomethyl-1, 8 wt % 2 wt % 66.1% 99.6% 3-dioxolan-2-one + 1,3-propane sultone 4-bromomethyl-1, 25 wt %  2 wt % 50.3% 99.0% 3-dioxolan-2-one + 1,3-propane sultone.sup.3 4-bromomethyl-1, 25 wt %  6 wt % 39.5% 95.6% 3-dioxolan-2-one + 1,3-propane sultone.sup.3 4-bromomethyl-1, 25 wt %  10 31.4% 97.0% 3-dioxolan-2-one + wt % 1,3-propane sultone.sup.3 4-bromomethyl-1, 8 wt % 2 wt % 74.6% 99.8% 3-dioxolan-2-one + lithium di(fluoro) (oxalato)borate.sup.1 4-bromomethyl-1, 8 wt % 2 wt % 67.4% 99.3% 3-dioxolan-2-one + lithium bis(oxalato)borate 4-bromomethyl-1, 25 wt %  2 wt % 48.2% 96.8% 3-dioxolan-2-one + vinylene carbonate.sup.3 4-bromomethyl-1, 25 wt %  2 wt % 43.9% 99.7% 3-dioxolan-2-one + vinylene carbonate.sup.3 .sup.1Data is from single best-performing cell. 2Prepared by combining 4-bromomethyl-1,3-dioxolan-2-one (25 wt %), ethylene carbonate (5 wt %), methyl ethyl carbonate (70 wt %), and LiPF.sub.6 (1.02M); this was a partial electrolyte replacement test. .sup.3Prepared by combining 0.2M LiPF.sub.6•in 4-bromomethyl-1,3-dioxolan-2-one with the plain electrolyte solution for a final concentration of 1.02M LiPF.sub.6, prior to the addition of vinylene carbonate.

TABLE-US-00005 TABLE 3C Coulombic Flame Additive Additive efficiency retardant 1 2 1st 10th Chemical Name in soln. in soln. in soln. cycle cycle 4-bromomethyl-1,  8 wt %   2 wt % 1 wt % 62.8% 99.6% 3-dioxolan-2-one + vinylene carbonate + 1,2-ethylene sulfite.sup.1 4-bromomethyl-1,  8 wt % 0.5 wt % 0.25 63.5% 99.5% 3-dioxolan-2-one + wt %; 1,3-propene sultone + 0.25 tris(trimethylsilyl) wt %.sup.2 phosphite + 1,3,2- dioxathiolane 2,2- dioxide 4-bromomethyl-1, 25 wt %   1 wt % 1 wt % 47.9% 98.7% 3-dioxolan-2-one + vinylene carbonate + 1,3-propane sultone.sup.3 .sup.1Ethylene sulfite is electrochemical additive 2 at 1 wt %. .sup.2The second electrochemical additive (tris(trimethylsilyl)phosphite) and third electrochemical additive (1,3,2-dioxathiolane 2,2-dioxide) are each present at 0.25 wt %. .sup.3Prepared by combining 0.2M LiPF.sub.6•in 4-bromomethyl-1,3-dioxolan-2-one with the plain electrolyte solution for a final concentration of 1.02M LiPF.sub.6, prior to the addition of the additives.

[0076] Some flame retardants were tested in coin cells to 100 cycles; results are reported in Table 3D below. Data for each flame retardant below is reported from the single best-performing cell.

TABLE-US-00006 TABLE 3D Capacity Coulombic fade Flame efficiency 2nd to retardant Additive 2nd 100th 100th Chemical name in soln. in soln. cycle cycle cycle Electrolyte soln..sup.1 0 0 99.8% 100.3%  3.6% 4-bromomethyl-1,  8 wt % 0 97.7% 100.6%  9.3% 3-dioxolan-2-one 4-bromomethyl-1, 25 wt % 2 wt % 98.2%  99.3% 33.7% 3-dioxolan-2-one + vinylene carbonate.sup.2 4-bromomethyl-1, 25 wt % 2 wt % 98.7%  99.6% 18.6% 3-dioxolan-2-one + 1,3-propane sultone.sup.2 .sup.1Comparative run. .sup.2Prepared by combining 0.2M LiPF.sub.6•in 4-bromomethyl-1,3-dioxolan-2-one with the plain electrolyte solution for a final concentration of 1.02M LiPF.sub.6, prior to the addition of the additive.

[0077] Components referred to by chemical name or formula anywhere in the specification or claims hereof, whether referred to in the singular or plural, are identified as they exist prior to coming into contact with another substance referred to by chemical name or chemical type (e.g., another component, a solvent, or etc.). It matters not what chemical changes, transformations and/or reactions, if any, take place in the resulting mixture or solution as such changes, transformations, and/or reactions are the natural result of bringing the specified components together under the conditions called for pursuant to this disclosure. Thus the components are identified as ingredients to be brought together in connection with performing a desired operation or in forming a desired composition. Also, even though the claims hereinafter may refer to substances, components and/or ingredients in the present tense (“comprises”, “is”, etc.), the reference is to the substance, component or ingredient as it existed at the time just before it was first contacted, blended or mixed with one or more other substances, components and/or ingredients in accordance with the present disclosure. The fact that a substance, component or ingredient may have lost its original identity through a chemical reaction or transformation during the course of contacting, blending or mixing operations, if conducted in accordance with this disclosure and with ordinary skill of a chemist, is thus of no practical concern.

[0078] The invention may comprise, consist, or consist essentially of the materials and/or procedures recited herein.

[0079] As used herein, the term “about” modifying the quantity of an ingredient in the compositions of the invention or employed in the methods of the invention refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or use solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients employed to make the compositions or carry out the methods; and the like. The term about also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term “about”, the claims include equivalents to the quantities.

[0080] Except as may be expressly otherwise indicated, the article “a” or “an” if and as used herein is not intended to limit, and should not be construed as limiting, the description or a claim to a single element to which the article refers. Rather, the article “a” or “an” if and as used herein is intended to cover one or more such elements, unless the text expressly indicates otherwise.

[0081] This invention is susceptible to considerable variation in its practice. Therefore the foregoing description is not intended to limit, and should not be construed as limiting, the invention to the particular exemplifications presented hereinabove.