Molecular design of electroactive species and materials processing methods in organic redox flow batteries

Abstract

A composition of matter useful as a posolyte or negolyte in a redox flow battery, including a compound comprising a first electroactive moiety and one or more solubilizing moieties each connected to the first electroactive moiety directly or via linker moieties, wherein the linker moieties, when present each comprise carbon and could contain at least one of hydrogen, oxygen, nitrogen, sulfur, or silicon.

Description

[0001] MOLECULAR DESIGN OF ELECTROACTIVE SPECIES AND MATERIALS PROCESSING METHODS IN ORGANIC REDOX FLOW BATTERIES

[0002] CROSS REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit under 35 U.S.C. Section 119(e) of co- pending and commonly-assigned U.S. provisional patent application Serial No. 63 / 579.890 filed August 31, 2023, by Nathan Daniel Kirchhofer and Zachary David Rengert entitled ‘ MOLECULAR DESIGN OF ELECTRO ACTIVE SPECIES AND MATERIALS PROCESSING METHODS IN ORGANIC REDOX FLOW BATTERIES,’' which application is incorporated by reference herein.

[0004] BACKGROUND OF THE INVENTION

[0005] 1. Field of the invention:

[0006] The present invention relates to electroactive materials and methods of making the same.

[0007] 2. Description of related art

[0008] Electroactive materials are useful for a variety of applications including, but not limited to, batteries. Battery technologies have proven to be a viable power source in the new ‘‘green” economy. Redox flow batteries have applications in residential to large scale long-duration energy storage for, e.g., single-home, business, microgrid scale, grid scale, voltage regulation, peak shaving, and more. What is needed, however, are electroactive materials for redox flow batteries that improve the cost, energy density, and stability of the flow battery.

[0009] SUMMARY OF THE INVENTION: The present disclosure describes a composition of matter useful as a positive or negative electrolyte, known as a posolyte or negolyte, in a redox flow battery, comprising a compound comprising a first electroactive moiety, one or more linker moieties, and one or more solubilizing moieties each connected to the first electroactive moiety via a different one of the linker moieties, wherein the linker moieties each may comprise carbon and could contain at least one of oxygen, nitrogen, hydrogen, silicon, or sulfur. In one or more embodiments, the invention provides new chemistries of carbon-based small molecules for charge storage in the cathode and anode of the electrochemical cells of a rechargeable redox flow battery. Redox flow batteries have applications in residential to large scale long-duration energy storage for, e.g., single- home, business, microgrid scale, grid scale, voltage regulation, peak shaving, and more. The invention describes new chemistries for the cathode and anode chambers that are independent from one another and provide improved electrochemical performance regardless of the presence of the other. The invention describes new processing methods for electroactive materials that improve their performance in the applications described herein. Some embodiments described herein therefore improve the voltage, solubility, stability, as well as other physical optoelectronic properties of the electroactive materials, and decrease the cost of building the resulting electrochemical cell. Some embodiments described also decrease the cost of materials synthesis and result in a lower overall cost of the resulting redox flow battery. Illustrative embodiments include, but are not limited to, the following. 1. A composition of matter useful as a posolyte or negolyte in a redox flow battery, comprising: a compound comprising a first electroactive moiety and one or more solubilizing moieties each connected to the first electroactive moiety directly or via a linker moiety, wherein the linker moieties, when present each comprise at least one of carbon, hydrogen, oxygen, nitrogen, sulfur, or silicon. 2. The composition of matter of clause 1, wherein: the compound comprises one or more second electroactive moieties connected to the first electroactive moiety, each of the second electroactive moieties connected to the first electroactive moiety via a different one of the linker moieties, and the second electroactive moieties enhance an electroactivity, including a redox potential and / or an electrochemical reversibility, of the first electroactive moiety as an electron donor or an electron acceptor in a redox reaction of the redox flow battery.

[0010] 3. The composition of matter of any of the clauses 1-2, wherein the compound comprises one or more aromatic rings, comprising the first electroactive moiety, covalently bonded to pendant groups comprising the linker moieties and the solubilizing moieties.

[0011] 4. The composition of matter of clause 1, wherein the compound compnses a posolyte comprising a ferrocene or maleimide comprising the first electroactive moiety.

[0012] 5. The composition of matter of clause 1, wherein the compound comprises a heterocyclic aromatic ring comprising a heteroatom and the first electroactive moiety, wherein the linker moiety is bonded to the heteroatom.

[0013] 6. The composition of matter of clause 1, wherein the compound comprises an aromatic compound comprising: a first ring covalently bonded to a first pendant group comprising a first one of the linker moieties bonded to a first one of the solubilizing moieties; a second ring covalently bonded to a second pendant group comprising a second one of the linker moieties bonded to a second one of the solubilizing moieties.

[0014] 7. The composition of matter of any of the clauses 1-6, wherein the linker moiety comprises 1, 2. 3. 4, or 5 of the carbon atoms, or a chain comprising 2-5 carbon atoms, wherein the length of the chain is tuned as a trade-off between increasing the electroactivity of the first electroactive moiety and increasing solubility of the compound in a solvent of the redox flow' battery'. 8. The composition of matter of any of the clauses 1-7, wherein the solubilizing moieties each comprise an ion covalently bonded to one of the linker moieties and a counterion for the ion.

[0015] 9. The composition of matter of any of the clauses 1-8. further comprising a water or an organic solvent combined with the solubilizing moieties, wherein one or more of the solubilizing moieties comprise a zwitterion covalently bonded to one of the linker moieties.

[0016] 10. The composition of matter of clause 8 or 9, wherein: the ion comprises at least one of -OSO3‘, -SO?', -PO42', -PO4H', -PO32', -PO3H' , -COT, -OR, -O', -alkyd, -COR, or -COOR, PFs’, BF3‘ . -SO2NSO2X'. -NSO2X' where R is H or alkyl and X is H, CF3. CF2CF?, phenyl, alkyl, pentafluorophenyl; and the counterion comprises at least one of Na+, K+, Li+, NH4+, NR4+, or Cs+, methylammonium CH3NH3+, ethylammonium (C2H5)NH.- . alkylammonium, formamidinium NH2(CH)NH2+, guanidinium C(NH2).? . imidazolium C3N2H5 . hydrazinium H2N-NHs+azetidinium (CH2)3NH2+, dimethylammonium (CH3)2NH2+, tetramethylammonium (CH3)4N+, phenylammonium CeHsNHs , pyridinium, arylammonium, heteroarylammonium, triazolium. sulfonylimide where R is H or alkyl or a combination thereof; or the ion comprises at least one of a halide, -OH, -OR, -O', -NR2, -NR.3 . -OSO.?' , -S03', -PO42', -PO4H-. -PO32; -PO3H; -COT, -alkyl, -COR, or -COOR; and the counterion comprises at least one of Na+, K+, Li+, NH4+. NR4+, or Cs+, methylammonium CH?NH3. ethylammonium (C2H5)NH?+, alkylammonium, formamidinium NH2(CH)NH2+, guanidinium C(NH2).? . imidazolium C.?N2H5+, hydrazinium H2N-NHs+azetidinium (CH2)sNH2+, dimethylammonium (CHs)2NH2+, tetramethylammonium (CHs)4N+, phenylammonium CTFTNH? . pyridinium, arylammonium, heteroarylammonium, triazolium. sulfonylimide where R is H or alkyl. 11. The composition of matter of clauses 1-3 or 5-10, wherein the compound comprises a negolyte comprising an isoindigo compound comprising the first electroactive moiety.

[0017] 12. The composition of clause 11, wherein the isoindigo compound comprises (E)-[3,3'-biindolinyhdene]-2,2'-dione.

[0018] 13. The composition of clause 11 or 12 wherein the solubilizing moieties are at least one of the 5,5’ positions, the 6,6' positions, the 1,1 ’ positions, the 4,4’ positions, or the 7,7’ positions on the isoindigo compound.

[0019] 14. A composition of matter useful as a posolyte or negolyte in a redox flow battery, comprising: a compound comprising the structure: wherein:

[0020] XI. X2. X3, X4, X5 are each independently an ion,

[0021] Yl, Y2, Y3, Y4, Y5 are each independently a counterion for the ion, the ion is an anion or a cation, and

[0022] XI -Yl, X2-Y2, X3-Y3, X4-Y4, and X5-Y5 each comprise a solubilizing group.

[0023] 15. A composition of matter useful as a posolyte or negolyte in a redox flow battery (or comprising the composition of matter of clause 1), comprising the structure of Fig. 1 wherein the solubilizing moiety comprises an organic compounds (e.g., alky l, alkyl chain, or equivalent) configured for solubility in an organic / nonaqueous solvent, wherein the composition of matter is optionally combined with the solvent.

[0024] 16. The composition of matter of clause 14 or 15. wherein:

[0025] Xi and X2 are each independently -OSCh", -SCh", -PCh2', -PChH’, -PCh2’, - POsH', -COT, -OR, -O', -alkyl, -COR, or -COOR, or an alkoxy, where R is H or alky l;

[0026] Y 1 and Y2 are each independently a counter cation to Xi and X2. respectively and are Na+, K+, Li+, NH4+, NR4+. or Cs+. where R is H or alkyl;

[0027] X3-X6 are each independently a halide, H, -OH, -OR, -O', -NR2, -NR.Y, -

[0028] OSOs', -SO3', -PO42', -PO4H; -PO32; -POsH', -COT, -alkyl, -COR, or -COOR; and

[0029] Y3-Y6 are independently a counter cation to X3- Xe, respectively and are Na+, K+, Li+. NH4+, NR4+, or Cs+, where R is H or alkyl.

[0030] 17. The composition of matter of any of the clauses 14-17, wherein

[0031] Xi and X2 are each independently an alkoxy, such as but not limited to, - RO(A)', -ROR(A)' where A is alky l;

[0032] Y 1 and Y2 are each independently a counter cation to Xi and X2. respectively and are Na+, K+, Li+, NH4+, NR4+. or Cs+. where R is H or alkyl;

[0033] X3-X6 are each independently a halide, -OH, -OR, -O', -NR2, -NR3T -OSO3', -

[0034] SOs', -PO42', -PO4H; -PO32; -PO3H; -COT, -alkyl, -COR, or -COOR; and

[0035] Y3-Y6 are independently a counter cation to X3- Xe, respectively and are Na+, K+, Li+. NH4+, NR4+, or Cs+, where R is H or alkyl.

[0036] 18. A composition of matter useful as a negolyte in a redox flow battery, comprising: a compound having the structure:

[0037] wherein:

[0038] Zi and Z2 are each independently a C1-C10 alky l chain, -(CH2CH2O)n-, C1-C5- Pentose, Ci-Ce-hexose. a fumarate, a succinate, or an aspartate, where n=l-12; X1-X10 are independently an ion, such as -OSO3’, -SO3‘, -PCh2-, -POrH', -PO32'

[0039] , -PO3H; -COy, or -Alkyl, -COR, -C(O)R, Halide, -OH, -OR, -O’, -NR2, -C(O)NR2, - NR3+, or -C(O)OR, where R is H or alkyl; -O-(Si(CHs)2-O)n-SiOR where R = (CH2)nR’ or Si(CH3)2R’ where R’ = -NR?

[0040] Y1-Y10 are independently an endcap group or counter-cation to X1-X10 and are Na+, K+, Li+, NHC, NRZ, or Cs+, where R is H or alkyl; and

[0041] Z1-X1-Y1, Z2-X2-Y2, X3-Y3, X4-Y4, X5-Y5, X6-Y6JX7-Y7, X8-Y8, X9-Y9, and / or X10-Y10 each comprise a solubilizing group.

[0042] 19. A composition of matter useful as posolyte or a negolyte. comprising a malemide of the structure:

[0043] sidechains in any of the examples 1-18.

[0044] 20. The composition of matter for any of the clauses 1-19 configured as a posolyte or negolyte for use in a redox flow battery.

[0045] 21. The composition of matter of clause 20, wherein the redox flow battery further comprises: a first tank storing a first liquid comprising a first redox active compound; a second tank storing a second liquid (bulk liquid or ionic liquid or a solution) comprising a second redox active compound; and an electrochemical cell comprising: a first half cell comprising the first liquid connected to a first electrode; a second half cell comprising the second liquid connected to a second electrode; and a boundary separating the first half cell and the second half cell; and a system comprising conduits and pumps circulating the first liquid between the first tank and the first half cell and the second liquid between the second tank and the second half cell; and wherein at least one of: the first redox active compound comprises the composition of matter of any of the clauses having the first electroactive moiety having the redox potential associated with a posolyte, or the second redox active compound comprises the composition of matter of any of the clauses having the first electroactive moiety having the redox potential associated with a negolyte. 22. The composition of matter of clause 21, wherein the redox flow battery further comprises an electrical circuit comprising a load connected to the first electrode and the second electrode, wherein during discharging of the redox flow battery: the second redox active compound is oxidized to release electrons through the second electrode into the circuit; and the first redox active compound is reduced upon receiving the electrons from the circuit through the first electrode. 23. The composition of matter of any of the clauses 20-22, further comprising: at least one of the first liquid or the second liquid further comprising one or more additives in solution with the liquids or as a constitutive part of the liquid and the additives comprising one or more electrochemically inert salts that at least: increase a first solubility of the first redox active compound in the first liquid or a second solubility of the second redox compound in the second liquid, respectively, or increase a conductivity of the first liquid or the second liquid, or decrease a probability of an hydrogen evolution reaction in the second half- cell. 24. The composition of matter of clause 22 or 23, wherein the additives comprise an electrolyte comprising a sodium salt (such as NaCl, NaBr, NaI, NaOH, NaHCO3, Na2CO3, etc.), a potassium salt (such as KCl, KBr, KI, KOH, KHCO3, K2CO3, etc.), an ammonium salt (such as NH4CI, NH4OH, NH4OAC, NH iBr. NH4H2PO4, NH4F, NH4PF6, etc.), and / or an ionic liquid (such as LiPFe, LiTFSI, EMIM-TFSI, TEA-TFSI, TBA-PFe, etc ).

[0046] 25. The composition of matter of clause 22 or clause 23 or clause 24, wherein: the additives comprise an electrolyte comprising a salt mixture comprised of the potassium salt, the ammonium salt, and the ionic liquid in a X:Y :Z molar ratio, respectively, where x=0-100, y=0-100, z=0-100, or the electrolyte comprises a salt mixture comprised of the sodium salt, the ammonium salt, and the ionic liquid in a X:Y :Z molar ratio, respectively, where x=0- 100, y =0-100, z=0-100.

[0047] 26. The composition of matter of any of the clauses 23-25, wherein the additives comprise a hydrotrope.

[0048] 27. The composition of matter of any of the clauses 1-26, wherein the solubilizing groups in the posolyte or the negolyte increase a solubility of the posolyte or the negolyte in the first liquid or the second liquid, respectively.

[0049] 28. The composition of matter of clause 27, further comprising the first liquid or the second liquid comprising a polar solvent.

[0050] 29. The composition of matter of clause 27, wherein the first liquid and the second liquid comprise or consist essentially of water.

[0051] 30. The composition of matter of any of the clauses 1-29, wherein the solubilizing moieties each comprise a siloxane or a hydroxy group.

[0052] 31. A composition of matter useful as a posolyte or negolyte in a redox flow battery, or the composition of matter of clause 1, wherein the compound comprises one of the following structures:

[0053] where X is Na+, Ka+, or NH4+or one of the following and R is H, CHs.t-Bu, alkyl, Ph, CF? or, CF2CF3, 32. A composition of matter useful as a posolyte or negolyte in a redox flow battery, or the composition of matter of clause 1, wherein the compound comprises: Where n is an integer.

[0054] 33. The composition of matter of any of the clauses 1-32, wherein the solubilizing moieties render the composition soluble in oil and / or immiscible in water. A composition of matter useful as a posolyte or negolyte in a redox flow battery, or the composition of matter of clause 1, comprising the compound of the structure:

[0055] 35. A composition of matter useful as a posolyte or negolyte in a redox flow battery, or the composition of matter of clause 1, comprising the compound of the structure: or where R is and R is H, CHs,t-Bu, Ph, CF3 or CF2CF3 .

[0056] 36. A composition of mater useful as a posolyte or negolyte in a redox flow batery or the composition of mater of clause 1 , wherein the compound has the structure: Where R is H, CH3. t-Bu, Ph, CF3or CF2CF3.

[0057] 37. A composition of matter useful as a posolyte or negolyte in a redox flow battery or the composition of matter of clause 1, wherein the compound has the structu

[0058] Where R is H, CH3, t-Bu, Ph, CF3or CF2CF3.

[0059] 38. A composition of matter useful as a posolyte or negolyte in a redox flow battery or the composition of matter of clause 1, wherein the compound comprises one of the following structures:

[0060]

[0061] 39. The composition of mater of any of the clauses 1-38, wherein the solubilizing moiety has a composition selected to tune at least one of a redox potential or solubility of the compound in the first liquid or the second liquid.

[0062] 40. The composition of matter of clause 39, wherein the solubility is tuned such that the compound is soluble in the first liquid but immiscible in the second liquid or vice versa.

[0063] 41. The composition of mater of clause 39 or 40, wherein the redox potential is tuned such that the compound has the redox potential of the posolyte or negolyte useful in the flow batery. 42. A composition of matter useful as a posolyte or negolyte in a redox flow battery or the composition of matter of clause L comprising the compound of the structure: or or

[0064] Where R is H, CH3, t-Bu, Ph, CF3or CF2CF3.

[0065] 43. A composition of matter useful as a posolyte or negolyte in a redox flow battery, comprising: a compound comprising the structure:

[0066] Linker moiety Solubilizing moiety wherein the solubilizing moiety comprises an organic compound configured for solubility in an organic or nonaqueous solvent, and wherein the composition of matter is optionally combined with the solvent.

[0067] 44. A composition of matter useful as a posolyte or negolyte in a redox flow battery, comprising the electroactive moiety combined with the solubilizing moiety and the linker moiety, the solubilizing moiety in combination the linker moiety having the structure:

[0068] A non-aqueous material used as a water-immiscible solvent combined with either a posolyte or negolyte comprising the composition of matter of clause 1 useful in a flow battery, the non-aqueous material comprising one of the following structures:

[0069] Where n and m are integers The composition of matter of any of the clauses 1-45, wherein the solubilizing moiety is a 1 -hydroxy ethyl or bistriflimide (TFSI). 47. An electrolyte useful in a flow battery comprising an oil or non-aqueous non- organic composition of matter combined with an electroactive moiety linked with a linker to a solubilizing moiety.

[0070] 48. The electrolyte of clause 47 wherein the non-aqueous non-organic composition of matter comprises the structure: or or

[0071]

[0072] BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee

[0074] Referring now to the drawings in which like reference numbers represent corresponding parts throughout:

[0075] Fig. 1 illustrates a structure of a composition of matter according to one or more embodiments described herein.

[0076] Fig. 2A. An example Markush structure of a ferrocene material.

[0077] Fig. 2B. Synthetic entry’ to l,l'-bis(hydroxymethyl)ferrocene.

[0078] Fig 2C. Sulfonation of l.r-bis(hydroxymethyl)ferrocene and ion exchange.

[0079] Figure 2D. Sulfonamidation of 1 J ’-bis(sulfonyl)ferrocene

[0080] Figure 2E. Synthesis of ferrocene disulfonate and ferrocene disulfonamidate derivatives containing longer linkers with an oxygen atom

[0081] Figure 2F. Synthetic entry to bis-oligodimethylsiloxane ferrocene.

[0082] Figure 2G. Synthesis of alkyl trimethylammonium functionalized maleimide and ion exchange.

[0083] Figure 2H. More generic synthesis of maleimide with charged solubilizing group

[0084] Figure 21. Maleimide-diene adduct formation and thermally activated retro diels alder.

[0085] Figure 3. Cyclic voltammetry’ of typical ferrocene and maleimide derivatives to show their redox potentials when dissolved in water at neutral pH with appropriate supporting electrolyte.

[0086] Figure 4A. Markush structure of isoindigo.

[0087] Figure 4B and 4C illustrate example water soluble isoindigo synthesis. Figure 4D. Characteristic double redox peak for a difunctionalized isoindigo in dimethylformamide solvent relative to a silver reference electrode.

[0088] Figure 4E. Redox potential of N,N’-dihexyl isoindigo in DMF with 100 mM TBAF supporting electrolyte relative to unmodified ferrocene as a reference.

[0089] Fig. 5A illustrates example compositions used as a posolyte and negolyte in a flow battery.

[0090] Fig. 5B and 5C are UV-Vis spectra of the compositions in Fig. 5A.

[0091] Figure 5D are Example charge / discharge at low concentration (30 mL total at 0.675 Ah / L) for the battery comprising the compositions in Fig. 5A.

[0092] Fig. 5E illustrates a redox flow battery utilizing the posolyte and / or negolyte described herein.

[0093] Fig. 6. Flowchart illustrating a method of making a composition of matter.

[0094] Fig. 7 illustrates further example compositions used as negolyte in a flow battery where the negolyte is non-aqueous.

[0095] Fig. 8A-8B illustrate example functionalizations to generate compositions used as negolyte in a flow battery', pictured for one bipyridine but valid for others, where Fig. 8A is example of zwitterionic attachment and Fig. 8B of carbon-carbon attachment.

[0096] Fig. 9 illustrates further example compositions used as posolyte in a flow battery, where R is typically H, CEE or an electron withdrawing group, especially a perfluorinated chain.

[0097] .Fig. 10A illustrates further compositions used as a posolyte in a flow battery where the posolyte is non-aqueous.

[0098] Fig. 10B illustrates further compositions used as a posolyte in a flow battery'.

[0099] Fig. 11A illustrates examples of cyclic voltammetry to confirm the electroactivity and characterize the redox potential of the illustrated compositions used as a posolyte at a variety of pH values.

[0100] Fig. 11B illustrates examples of cyclic voltammetry' to confirm the electroactivity' and characterize the impacts of chemical structure on the redox potential of the illustrated compositions used as a posolyte for both aqueous and non- aqueous embodiments.

[0101] Fig. 12A-12B illustrate examples of differential pulse voltammetry and cyclic voltammetry to further confirm the electroactivity and characterize the impacts of chemical structure on the redox potential of the illustrated compositions used as a posolyte in a flow battery.

[0102] Fig. 13A illustrates an example nuclear magnetic resonance (NMR) spectrum to confirm the synthesis and purification of illustrated composition used as a posolyte in a redox flow battery.

[0103] Fig. 13B illustrates an example NMR spectrum to confirm the synthesis and purification of the illustrated composition used as a posolyte in a redox flow batten'.

[0104] Fig. 13C illustrates an example NMR spectrum to confirm the synthesis and purification of the illustrated composition used as a posolyte in a redox flow battery.

[0105] Fig 13D illustrates an example NMR spectrum to confirm the synthesis and purification of illustrated composition used as a posolyte in a redox flow battery.

[0106] Fig. 14 illustrates an example composition of a non-aqueous material used as a water-immiscible solvent for either posolyte or negolyte.

[0107] DETAILED DESCRIPTION

[0108] In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.

[0109] Technical Description

[0110] The present invention provides electroactive materials having novel chemistries for use in an electrochemical device such as, but not limited, to, an electrical storage device such as an electrical fuel cell or half-cell capable of storing or releasing electrical energy in an electrochemical cell by converting a chemical potential to an electric potential through electron transfer reactions at the surface of an electrode. In various embodiments, the new chemistries described by the invention afford electroactive materials that are soluble in. or partially soluble in or suspended in, a solvent, that is preferably water, more preferably an electrically conductive solution of electrolyte in water, most preferably a solution containing one or more salts dissolved in water. The solvent could also be a different liquid that is organic or silicon-based, that is preferably immiscible with water, more preferably a solution of electrolyte in this water-immiscible liquid, most preferably a solution containing one or more salts dissolved in the water-immiscible fluid.

[0111] Fig. 1 illustrates a typical composition of matter according to embodiments described herein comprises a compound comprising a first electroactive moiety, one or more organic linker moieties, and one or more solubilizing moieties each connected to the first electroactive moiety via a different one of the linker moieties. The electroactive moiety, linker moieties, and solubilizing group(s) are chosen to tune the solubility, redox potential, intermolecular interactions, and synthetic access of the final resulting molecule.

[0112] The composition of matter can be embodied in many ways as illustrated by the following examples.

[0113] First Example: Posolyte

[0114] (a) Ferrocene

[0115] An example posolyte, or electron donor during charge or electron acceptor during discharge, comprises a ferrocene (e.g. biscyclopentadienyl iron) core that is functionalized on both rings in the 1 and 1’ positions. Importantly, this new derivative having novel chemistry may be functionalized with methylene or methoxy groups in the 1, 1 ’ positions that a) afford a synthetically accessible position for attaching solubilizing groups and b) do not disturb the electronic structure of the ferrocene ring through resonance or pi-orbital overlap, but instead modify the electronic structure of the ferrocene group through inductive effects. This is an important distinction to prior art because previous efforts have focused on attachment of solubilizing groups directly to the ferrocene ring, which results in undesired intramolecular interactions of solubilizing groups with the electronic structure of the cyclopentadienyl ligand or the unfdled d-orbital of Iron itself. Functionalizing directly to the ferrocene group also decreases the solubility' of the molecule by increasing intramolecular interactions and decreasing intermolecular interactions concomitantly. The inclusion of two solubilizing groups through functionalization at the 1,1 ’-methylene positions serves an additional purpose of greatly improving the solubility of the molecule in polar solvents such as water and aqueous electrolyte solutions compared to a monofunctionalized ferrocene core. Additionally, the counter ion choice influences solubility in polar solvents, with “soft” ions affording higher solubility. Cations such as but not limited to ammonium, tetraalkyl ammonium, tetrafluoroborate, or cesium represent suitable choices.

[0116] Fig. 2A illustrates an example structure of a ferrocene material wherein: Xi and X2 are independently -OSOs’. -SCh’, -PO42’, -PO4FF, -POs2’, -POsFF, - CO2’. -OR, -O’. -Alkyl. -COR, or -COOR; where R is H or alkyl;

[0117] Y1 and Y2 are independently a counter cation to XI and X2 and are Na+, K+, Li+, NH4+, NR4+, or Cs+; where R is H or alkyl;

[0118] X3-X6 are independently a Halide, -H, -OH, -OR, -O’, -NR2, -NRs+, -OSDs’, - SO3’, -PO42’, -PO4H’. -PO32’, -PO3H , -CO2 , -Alkyl, -COR, or -COOR; and

[0119] Y3-Y6 are independently a counter cation to X3-X6 respectively and are Na+, K+, Li+, NH4+, NR4+, or Cs+; where R is H or alkyl.

[0120] Depending on the electron withdrawing character of the solubilizing groups and the dielectric constant of the solvent used, the oxidation potential of these ferrocene derivatives can range from 0.05-0.25 V vs. Fc / Fc+. Depending on the solvent used, these materials ty pically display a fully reversible oxidation wave, which are sometimes quasi-reversible in poor (e.g. non-polar) solvents where they are sparingly soluble. The diffusion coefficient of these materials can range from 10'8- 10'3cm2 / s.

[0121] Depending on the ferrocene derivative used and the nature and concentration of the supporting electrolyte, the solubility of the ferrocene derivatives varies between 0.1 - 5 M. Stable suspensions of the ferrocene derivatives can also readily be made and these suspensions show similar electrochemical characteristics to homogeneous solutions.

[0122] Another important aspect of the present invention that is illustrated in Figure 2B-F is the synthetic pathway that allows for the synthesis of the ferrocene materials. l,l’-ferrocenedicarboxaldehyde is readily afforded directly from ferrocene, and the reduction of the aldehydes with sodium borohydride affords 1,1’- bis(hydroxymethyl)ferrocene, as illustrated in Fig. 2B.

[0123] The desired solubilizing groups can easily be introduced in a one or two step procedure, depending on the solubilizing group desired. In one embodiment, shown in Fig 2C, sulfonation of l,l’-bis(hydroxymethyl)ferrocene can be accomplished by reaction with sulfuric acid or by reaction with chlorosulfonic acid. Reaction with the appropriate ion exchange medium then affords the bis-sulfonate salt. In a different embodiment shown in Fig 2D, prior to ion exchange, l,l’-bis(sulfonyl)ferrocene can be reacted further with oxalyl chloride and a sulfonamide of the form R-SO2-NH2 to afford a l,l’-bis(sulfonyhmide)ferrocene. Reaction with the appropriate ion exchange medium then affords the bis-sulfonate salt, as illustrated in Fig. 2C.

[0124] Sulfonate and sulfonamide moieties and the corresponding exchanged counterions are important because they provide novel functionalization of the ferrocene redox moiety for use in redox flow batteries, and the ion exchange procedure alters the solubility and intermolecular interactions that have direct consequence on the energy capacity and lifetime performance of a redox flow battery. The length of the linker also affects the solubility of the molecule.

[0125] In another embodiment shown in Fig. 2E, l,l ’-bis(hydroxymethyl)ferrocene can be functionalized with 1,3 -Propane sultone to afford a disubstituted ferrocene that has longer linkers that contain oxygen atoms. The position of the oxygen atom 1 carbon atom away from the ferrocene electroactive moiety allows it to affect the redox potential of the ferrocene. The longer linkers should serve to increase solubility because the longer chains can sample more solvent conformations to allow the molecule to solvate. This atomic conformation is a unique embodiment of this invention for application in redox flow batteries.

[0126] In another embodiment, phosphonation can be accomplished by reaction with diphenylphosphoryl chloride and subsequent reduction of the phenyl protecting groups with hydrogen to afford the free bis-phosphonic acid ester. Reaction with the appropriate ion exchange medium then affords the bis-phosphonate ester salt.

[0127] In another embodiment shown in Fig. 2F, cyclic oligo dimethylsiloxane is reacted with l,l '-bis(hydroxymethyl)ferrocene to afford a bis-oligodimethylsiloxane ferrocene that is soluble in poly(dimethylsiloxane) oils that are immiscible with water and very safe. This results in a unique embodiment of the invention that would allow for operation of a redox flow battery' without a membrane when such a functionalized ferrocene as the posolyte is paired with an aqueous-soluble negolyte material to complete a full cell.

[0128] (b) Mai eimide

[0129] In another example, the electroactive material comprises a functionalized maleimide as illustrated in Fig 2H. This provides a unique embodiment of the invention because functionalized maleimide has not been used as a flow battery component nor functionalized for that purpose.

[0130] In a further embodiment shown in Fig. 21, the thermally activated retro diels alder in step 2 of Fig 2F provides a unique strategy to protect the redox active moiety from electrochemistry or separate it from maleimide molecules that have already been electrochemically reacted. Specifically, maleimide is a good dienophile so will readily react with dienes (e.g. substituted furan as shown) to form an adduct as shown in the second chemical structure of Fig 2G, and this compound is not electrochemically active; however, once heated above -100C this adduct returns to its constitutive parts of mal eimide and diene (e.g. furan) where the malemide is again electrochemically addressable.

[0131] Fig. 3 illustrates the current v. voltage performance of a typical ferrocene and maleimide materials measured with cyclic voltammetry in water-based electrolyte solutions, indicating an oxidation potential in a range of 0.2-0.65 V vs. the Ag / AgCl reference electrode at neutral pH.

[0132] Second Example: Negolvte

[0133] An example negolyte or electron acceptor during charge or electron donor during discharge comprises an Isoindigo motif (e.g. (E)-[3,3'-biindolinylidene]-2,2'- dione) that can be functionalized with solubilizing groups at several positions. The 5.5’ and 6,6’ positions offer the most facile synthetic access for attaching solubilizing groups, however the 1,1 ’ positions are of utility as well. Additionally, the 4,4’ and the 7,7' positions represent potential locations for attachment of solubilizing groups, however they are harder to access synthetically. The inclusion of two solubilizing groups at the 6.6’ positions serves the purpose of affording solubility of the molecule in polar solvents such as water and aqueous electrolyte solutions. More solubilizing groups can be added to any of the aforementioned locations (i.e. 1,1 ’ and / or 4,4’ and / or 5,5’ and / or 6,6’ and / or 7,7’) to improve solubility of the molecule in polar solvents at the expense of increased molecular weight and molecular complexity. Additionally, the counter ion choice is another factor that influences solubility in polar solvents, with “soft” ions affording higher solubility. Cations such as ammonium, tetraalkylammonium, tetrafluoroborate, or cesium represent suitable choices.

[0134] Fig. 4A illustrates an example structure of the Isoindigo material, wherein: Zi and Z2 are each independently a C1-C10 alkyl chain, -(CH2CH2O)n-, C1-C5- Pentose, Ci-Ce-hexose, a fumarate, a succinate, or an aspartate, where n=l-12; Xi-Xio are independently an ion, such as -OSCh’, -SCh', -PCh2', -PO iIT. -PCh2' , -PO3H; -CO / , or -Alkyl, -COR, -C(O)R, Halide, -OH, -OR, -O’, -NR2, -C(O)NR2, - NRs+, or -C(O)OR. where R is H or alkyl; -O-(Si(CH3)2-O)n-SiOR where R = (CH2)nR’ or Si(CH3)2R' where R’ = -NR3+

[0135] Y1-Y10 are independently an endcap group or counter-cation to X1-X10 and are Na+, K+, Li+, NH4+, NRC, or Cs+, where R is H or alkyd;

[0136] Z1-X1-Y1, Z2-X2-Y2, X3-Y3, X4-Y4, X5-Y5, X6-Y6, X7-Y7, Xs-Ys, X9-Y9, and / or X10-Y10 each comprise a solubilizing group.

[0137] Fig. 4B and 4C illustrate water soluble isoindigo synthesis.

[0138] Isoindigo derivatives display two reduction potentials in most solvents as show n in Figure 4D. Depending on the electron withdrawing character of the solubilizing groups and the dielectric constant of the solvent used, the first (lower energy) reduction potential of these isoindigo derivatives can range from -1.2 to -0.5 V vs. Fc / Fc+and the second reduction potential can be from -1.0 to -1.7 V vs. Fc / Fc+. Depending on the solvent used these materials typically display a fully reversible oxidation wave, which are sometimes quasi-reversible or irreversible in poor (e.g. non-polar) solvents where they are sparingly soluble. The diffusion coefficient of these materials can range from 10'8- 10'3cm2 / s.

[0139] Depending on the isoindigo derivative used and the nature and concentration of the supporting electrolyte, the solubility of the isoindigo derivatives varies between 0. 1 - 5 M. Stable suspensions of the isoindigo derivatives can also readily be made and these suspensions show similar electrochemical characteristics to homogeneous solutions.

[0140] The solubilizing groups on the isoindigo core can be introduced before or after the construction of the isoindigo unit, depending on the nature of the solubilizing group. Isoindigo can be directly sulfonated using sulfuric acid at benzene ring in positions 4,4’ and / or 5,5’ and / or 6,6’ and / or 7,7’ depending on the conditions used. Typically the 6,6’ positions are favored and are the most desirable from the perspective of the resulting electronic structure of the material after introduction of the sulfonate groups. Functionalization at the N,N-1,1’ positions can also be done before or after the formation of the Isoindigo unit, however, it is most conveniently done after the isoindigo unit is formed. For the N,N-1,1’ positions, direct functionalization is not synthetically possible and therefore a small alkyl chain, or similar solubilizing group, between 1 -10 carbon units is used to attach the solubilizing group in a way that affords a stable molecule.

[0141] N,N'-dihexyl isoindigo is soluble in Acetonitrile with TBAF as supporting electrolyte. Under these conditions, as shown in Fig. 4E, N,N'-dihexyl isoindigo shows quasi-reversibility at a redox potential that is approximately 1.2 V negative of ferrocene in solution as a reference.

[0142] Third Example: Device Operation and Performance of a Redox Flow Battery Fig. 5D and Fig. 5E show example battery performance for a battery using the composition in Fig. 5A as posolyte and negolyte.

[0143] Fig. 5F illustrates a redox flow battery 500 comprising the negolyte and / or posolyte described herein. The flow battery comprises a first tank 502 storing a first liquid 504 (e.g., a bulk liquid or ionic liquid or a solution) comprising a first redox active compound; a second tank 506 storing a second liquid 508 (e.g., bulk liquid or ionic liquid or a solution) comprising a second redox active compound; and an electrochemical cell 510.

[0144] As illustrated in Fig 5E, the electrochemical cell comprises a first half cell 512 comprising the first liquid connected to a first electrode 514; a second half cell 516 comprising the second liquid connected to a second electrode 518; and a boundary 520 (membrane or phase boundary' between two immiscible fluids such as water and poly(dimethylsiloxane) oil) separating the first half cell and the second half cell.

[0145] The flow battery further comprises a system of conduits 522 and pumps 524 circulating the first liquid between the first tank and the first half cell and the second liquid between the second tank and the second half cell. The first redox active compound comprises a posolyte electroactive moiety (having the redox potential associated with a posolyte) and the second redox active compound comprises the negolyte electroactive moiety (having the redox potential associated with a negolyte).

[0146] Fig. 5E further illustrates the flow battery further comprises an electrical circuit 526 comprising a load 528 connected to the first electrode and the second electrode, wherein during discharging of the redox flow battery:

[0147] (1) the second redox active compound is oxidized to release electrons through the second electrode into the circuit; and

[0148] (2) the first redox active compound is reduced upon receiving the electrons from the circuit through the first electrode.

[0149] The device may use carbon felt electrodes, but other electrode types may be used, which are electronically connected to an end plate on either side of the electrochemical cell, which may be gold plated or made of another suitable material. A solution of the redox active species for each side of the half cell is held into the exterior tank and pumped into the electrochemical cell at an appropriate rate. The solution then travels through a flow plate that is pre-patterened with a serpentine flow, interdigitated flow, or other suitable flow design. An ion-exchange membrane is utilized and is comprised of one of the following materials: Nafion, a size-exclusion membrane, Fumasep, Selemion, etc.

[0150] In another embodiment, the positive side of the redox flow battery utilizes potassium ferrocyanide and the negative side of the flow battery utilizes the Class 2 derivatives. The device may use carbon felt electrodes, but other electrode types may be used, which are electronically connected to an end plate on either side of the electrochemical cell, which may be gold plated or made of another suitable material. A solution of the redox active species for each side of the half cell is held in the exterior tank and pumped into the electrochemical cell at an appropriate rate. The solution then travels through a flow plate that is pre-patterened with a serpentine flow, interdigitated flow, or other suitable flow design. An ion-exchange membrane is utilized and is comprised of one of the following materials: Nafion, a size-exclusion membrane, etc.

[0151] The device may use carbon felt electrodes, but other electrode types may be used, which are electronically connected to an end plate on either side of the electrochemical cell, which may be gold plated or made of another suitable material. A solution of the redox active species for each side of the half cell is held in the exterior tank and pumped into the electrochemical cell at an appropriate rate. The solution then travels through a flow plate that is prepatterened with a serpentine flow, interdigitated flow, or other suitable flow design. An ion-exchange membrane is utilized and is comprised of one of the following materials: Nafion, a size-exclusion membrane, etc.

[0152] Fourth Example: Supporting Additives

[0153] The electroactive materials described herein can be combined with various additives that enhance electroactive performance.

[0154] In one example, at least one of the first liquid or the second liquid of the redox flow battery may further comprise additives that comprise one or more electrochemically inert salts that at least: increase a first solubility of the first redox active compound in the first liquid or a second solubility of the second redox compound in the second liquid, respectively, or increase a conductivity of the first liquid or the second liquid, or decrease a probability' of a hydrogen evolution reaction in the second half-cell, or serve an additional function.

[0155] Such example additives include, but are not limited to, electrolytes, hydrotropes, or other additives, in solution with the liquid or as a constitutive part of the bulk liquid). (a) Example Electrolyte

[0156] The nature of the electrochemically inert supporting electrolyte in one embodiment is a sodium salt (Such as NaCl, NaBr, Nal, NaOH, NaHCCE, Na2COs. etc.), a potassium salt (Such as KC1, KBr, KI, KOH. KHCO3. K2CO3. etc.), an ammonium salt (such as NH4CI, NH4OH, NH4OAC, NHtBr, NH4H2PO4, NH4F, NH4PF6, etc.), and / or an ionic liquid (such as LiPFe, LiTFSI, EMIM-TFSI, TEA- TFSI. TBA-PFs, Siloxane salt, etc.). In another embodiment, any salt suitable to increase the conductivity of the solution may be used.

[0157] In one embodiment, the salt mixture is comprised of a potassium salt, an ammonium salt, and an ionic liquid in a 4:2: 1 molar ratio, respectively.

[0158] In another embodiment, the salt mixture is comprised of a sodium salt, an ammonium salt, and an ionic liquid in a 4:2: 1 molar ratio, respectively.

[0159] In another embodiment, the salt mixture is comprised of a potassium salt, an ammonium salt, and an ionic liquid in a 2:2: 1 molar ratio, respectively.

[0160] In another embodiment, the salt mixture is comprised of a sodium salt, an ammonium salt, and an ionic liquid in a 2:2: 1 molar ratio, respectively.

[0161] In another embodiment, the salt mixture is comprised of a potassium salt, an ammonium salt, and an ionic liquid in a 1 : 1 : 1 molar ratio, respectively.

[0162] In another embodiment, the salt mixture is comprised of a sodium salt, an ammonium salt, and an ionic liquid in a 1 : 1 : 1 molar ratio, respectively.

[0163] In another embodiment, the salt mixture is comprised of a potassium salt, an ammonium salt, and an ionic liquid in a X:Y:Z molar ratio, respectively. Where x=0- 100, y=0-100, 2=0-100.

[0164] In another embodiment, the salt mixture is comprised of a sodium salt, an ammonium salt, and an ionic liquid in a X:Y:Z molar ratio, respectively. Where x=0- 100, y=0-100, z=0-100.

[0165] (b) Example Hydrotropes p-toluenesulfonic acid (p-TsOH), 2-naphthalenesulfonic acid (2-NpOH), and anthraquinone-2-sulfonic acid (AQS), urea, tosylate, cumenesulfonate, xylenesulfonate, nicotinamide

[0166] (c) Other Example Additives

[0167] Citric acid, EDTA, or other chelating or complexing agents

[0168] Fifth Example: Process Steps

[0169] Method of making

[0170] Fig. 6 is a flowchart illustrating a method of making a composition of matter according to one or more embodiments described herein.

[0171] Block 600 represents selecting and obtaining a first electroactive moiety.

[0172] Block 602 represents connecting one or more solubilizing moieties to the first electroactive moiety directly or via a different linker moieties, wherein the linker moieties (when present) each comprise carbon and hydrogen and could contain at least one of oxygen, nitrogen, or sulfur.

[0173] In one example, a method of synthesizing a composition of matter useful as a posolyte in a redox flow battery, comprises: reacting a ferrocene comprising an aldehyde under conditions wherein the aldehyde is reduced in a presence of sodium borohydride so as to form l,l ’-bis(hydroxymethyl)ferrocene; and attaching solubilizing groups to the methylene groups of the l,l’-bis(hydroxymethyl)ferrocene; and so that the composition of matter useful as a posolyte is made. In one or more examples, the attaching comprises sulfonation of the 1,1’- bis(hydroxymethyl)ferrocene by reaction with sulfuric acid or by reaction with chlorosulfonic acid. In another example, the attaching comprises phosphonation of the l.r-bis(hydroxymethyl)ferrocene by reaction with diphenylphosphoryl chloride to form an intermediary compound and subsequent reduction of the phenyl protecting groups in the intermediary compound with hydrogen to afford a second intermediary7comprising a free bis-phosphonic acid ester; and reaction of the second intermediary compound with an appropriate ion exchange medium so as to afford a bis- phosphonate ester salt attached to the l,l’-bis(hydroxymethyl)ferrocene.

[0174] In another example, a method of making a composition of matter useful as a negolyte in a redox flow battery, comprises attaching solubilizing groups to an isoindigo core via: sulfonation using sulfuric acid at benzene ring in positions 4,4’ and / or 5,5’ and / or 6,6’ and / or 7,7’ , or attaching an alkyl chain between 1-10 carbon units in length.

[0175] In some embodiments, compositional selections are made by balancing desired solubility, redox potential, intermolecular interactions, and manufacturability / cost. These properties often are tied together because solubilizing moieties and linkers afford solubility, but affect redox potential and intermolecular interactions (by virtue of their covalent bonding through-space interactions with their own molecule and adjacent molecules) and impart cost through the steps required to manufacture. In one or more embodiments, for redox potential, it may be desirable for the posolyte redox potential to be as high as possible without having kinetic competition with oxygen evolution from electrochemical water splitting, and it may be desirable for the negolyte redox potential to be as low' as possible without having kinetic competition with hydrogen evolution from electrochemical water splitting. Some solubilizing moieties require hydrotropes (which are discussed herein) that can affect pH, or require higher or lower pH, which can also affect the redox potential of the molecules.

[0176] In some examples, same sign valence of the charges on the solubilizing moieties helps with intermolecular interactions because like charges repel, for example positive repels positive and negative repels negative, and coulombically disfavoring interactions in this way mitigates dimerization and other failure modes of the molecules.

[0177] In some embodiments, it may be desirable to reduce the number of reaction steps to a minimum as w ell as using the cheapest starting materials, while keeping desired solubility in redox potential, and intermolecular interactions in mind, sen es to enhance manufacturability and lower cost. In some embodiments, it may be desirable to compromise on redox potential or solubility if cost could be lowered substantially.

[0178] In one embodiment, a method for synthesizing a composition of matter comprises identifying a solubilizing moiety for solubilizing (aiding or facilitating solubility) of the electroactive moiety in the first liquid or second liquid used in the flow battery. The next step comprises covalently attaching the solubilizing moiety at one or more attachment locations on the electroactive moiety (using covalent bonds) with a spacing from the electroactive moiety (e.g., using an appropriate linker length and / or composition) such that the resulting compound is soluble in the first or second liquid to form an at least 0.1 molar (or greater) concentration of the compound in the first or second liquid. The spacing and number of attachment points / locations is further tuned or selected such that a redox potential of the compound in the first or second liquid is in the desired range for the compound acting as a posolyte or a negolyte in combination with the first liquid or the second liquid. The redox potential is kept below a level at which the redox potential would cause electrochemical splitting (e.g., in the case of water as the solvent, splitting into H and OH ions, or H2 gas or O2 gas).

[0179] In another embodiment, a method for synthesizing a composition of matter comprises selecting, from the literature of known solubilizing moi eties or functional groups, a solubilizing moiety or functional group that is known to be soluble (and / or facilitate solubility of an electroactive moiety) in a known solvent selected as the first liquid or second liquid in the flow battery. The next step comprises covalently attaching the solubilizing moiety at one or more attachment locations on the electroactive moiety (using covalent bonds) with a spacing from the electroactive moiety (e.g., using an appropriate linker length and / or composition) such that the resulting compound is soluble in the first or second liquid to form an at least 0.1 molar (or greater) concentration of the compound in the first or second liquid. The spacing and number of attachment points is further tuned or selected such that a redox potential of the compound in the first or second liquid is in the desired range for the compound acting as a posolyte or a negolyte in combination with the first liquid or the second liquid. The redox potential is kept below a level at which the redox potential would cause electrochemical splitting (e.g., in the case of water as the solvent, splitting into H and OH ions, or H2 gas or O2 gas).

[0180] In one embodiment, the first liquid or the second liquid is an oil-based solvent, or a non-aqueous non-organic viscous fluid (immiscible in water or an aqueous solvent) and the solubilizing moiety comprises constituent moi eties (e.g., a compound comprising silicon covalently bonded to oxygen and not containing C-C bonds) of the nonaqueous non-organic viscous fluid so as to facilitate solubility of the electroactive moiety in the non-aqueous non-organic viscous fluid. Such oil based or non-aqueous non-organic fluids are useful as the, e.g.. first liquid in a flow battery example where the second liquid is an aqueous (e.g.. water) and further where the posolyte (negolyte) is soluble in the first liquid (but not the second liquid) and the negolyte (posolyte) is soluble in the second liquid but is not soluble in the first fluid. In this way, a barrierless boundary between the first liquid and the second fluid in the electrochemical cell by virtue of the first liquid and the second liquid being immiscible.

[0181] Block 604 represents the end result, a composition of matter useful as a posolyte or a negolyte.

[0182] Illustrative embodiments of the composition of matter include, but are not limited to, the following examples.

[0183] 1. A composition of matter useful as a posolyte or negolyte in a redox flow battery, comprising: a compound comprising a first electroactive moiety and one or more solubilizing moieties each connected to the first electroactive moiety directly or via a linker moiety , wherein the linker moiety, when present, is an alkyl chain or oligo dimethyl siloxane chain, or more broadly each comprise one or more carbon atoms and / or at least one of hydrogen, oxygen, nitrogen, sulfur, or silicon or a plurality of those atoms.

[0184] 2. The composition of matter of example 1. wherein: the compound comprises one or more second electroactive moieties connected to the first electroactive moiety, each of the second electroactive moieties connected to the first electroactive moiety via a different one of the linker moieties, and the second electroactive moieties enhance an electroactivity, including a redox potential and / or an electrochemical reversibility, of the first electroactive moiety as an electron donor or an electron acceptor in a redox reaction of the redox flow battery.

[0185] 3. The composition of matter of any of the examples 1-2, wherein the compound comprises one or more aromatic rings, comprising the first electroactive moiety, covalently bonded to pendant groups comprising the linker moieties and the solubilizing moieties.

[0186] 4. The composition of matter of any the examples 1-2, wherein the compound comprises a posolyte comprising a ferrocene or maleimide comprising the first electroactive moiety.

[0187] 5. The composition of matter of example 1, wherein the compound comprises a heterocyclic aromatic ring comprising a heteroatom and the first electroactive moiety, wherein the linker moiety is bonded to the heteroatom.

[0188] 6. The composition of matter of example 1 , wherein the compound comprises an aromatic compound comprising: a first ring covalently bonded to a first pendant group comprising a first one of the linker moieties bonded to a first one of the solubilizing moieties; a second ring covalently bonded to a second pendant group comprising a second one of the linker moieties bonded to a second one of the solubilizing moieties.

[0189] 7. The composition of matter of any of the examples, wherein the linker moiety comprises 1 , 2, 3, 4, or 5 of the carbon atoms, or a chain comprising 2-5 carbon atoms, wherein the length of the chain is tuned as a trade-off between increasing the electroactivity of the first electroactive moiety and increasing solubility of the compound in a solvent of the redox flow batten'.

[0190] 8. The composition of matter of any of the examples 1-7, wherein the solubilizing moieties each comprise an ion covalently bonded to one of the linker moieties and a counterion for the ion.

[0191] 9. The composition of matter of example 8, wherein: the ion comprises at least one of -OSCh’, -SCh’, -PO42’, -POrH’. -PCh2’, -PChH’ , -CO2, -OR, -O’, -alkyl, -COR, -COOR, or where R is H or alkyd and the counterion comprises at least one of Na+, K+, Li+, NH4+, NR4+, or Cs, where R is H or alkyl; or the ion comprises at least one of a halide, -OH, -OR, -O’, -NR2, -NR3 . -OSOs’ , -SO3’, -PO42', -PO4H; -PO32; -PO3H; -COT, -alkyl, -COR, or -COOR; and the counterion comprises at least one of Na+, K+, Li+, NH4 . NR4+, or Cs+, where R is H or alkyl.

[0192] 10. The composition of matter of example 8, wherein the ion comprises: an ionic liquid like ion, a bis-sulfonamide modified with electron withdrawing groups X = O, CF3, CF2CF3, Phenyl, methyl. Pentafluorophenyl, e.g., SO2NSO2X, where X is CF3, CF2CF3, Phenyl, methyl, Pentafluorophenyl), or a sulfonamide modified with electron withdrawing groups X = O, CF3, CF2CF3, phenyl, methyl, pentafluorophenyl, and R = H or alky l, e.g., NSO3X, SO2NSO3X, where X = O, CF3, CF2CF3, phenyl, methyl, pentafluorophenyl, and R = H or alkyl, or

[0193] -BF3, or R-PFs.

[0194] 11. The composition of matter of example 8 or 10, wherein the counterion comprises an organic cation such as, but not limited to, an imidazolium, a pryidinium, or a tertiary ammonium, or a quaternary ammonium.

[0195] 12. The composition of matter of examples 1 -3 or 5-8, wherein the compound comprises a negolyte comprising an isoindigo compound comprising the first electroactive moiety. 13. The composition of example 12, wherein the isoindigo compound comprises (E)-[3,3'-biindolinylidene]-2,2'-dione.

[0196] 14. The composition of example 12 wherein the solubilizing moieties are at least one of the 5,5’ positions, the 6.6’ positions, the 1,1 ’ positions, the 4,4’ positions, or the 7,7’ positions on the isoindigo compound.

[0197] 15. A composition of matter useful as a posolyte or negolyte in a redox flow battery', comprising: a compound comprising the structure: wherein:

[0198] XI, X2, X3, X4, X5 are each independently an ion,

[0199] Yl, Y2. Y3, Y4, Y5 are each independently a counterion for the ion, the ion is an anion or a cation, and

[0200] XI -Yl, X2-Y2, X3-Y3, X4-Y4, and X5-Y5 each comprise a solubilizing group.

[0201] Xi and X2 are independently -OSOs’. -Sth', -PO42, -PO4H’, -PCh2’, -POsH". - COT, -OR, -O’, -Alkyl, -COR, or -COOR; where R is H or alkyl;

[0202] Yl and Y2 are independently a counter cation to XI and X2 and are Na+, K+, Li+, NH4+, NR4+, or Cs+; where R is H or alkyl;

[0203] X3-X6 are independently a Halide. -H. -OH. -OR, -O’, -NR2, -NRs+, -OSOs’, - SO3’. -PO42". -PO4H’. -PO32", -PO3H’, -COT. -Alkyl. -COR, or -COOR; and

[0204] Y3-Y6 are independently a counter cation to X3-X6 respectively and are Na+, K+, Li+, NH4+, NR4+, or Cs+; where R is H or alkyl. 16. A composition of matter useful as a posolyte or negolyte in a redox flow batten', comprising: a compound comprising the structure:

[0205] Linker moiety Solubilizing moiety wherein the solubilizing moiety comprises organic compounds (e.g., alkyl, alkyl chain, siloxane or equivalent) configured for sol ubil ity in an organic / nonaqueous solvent, wherein the composition of matter is optionally combined with the solvent.

[0206] 17. The composition of matter of example 15, wherein:

[0207] Xi and X2 are each independently -OSCh', -SOs', -PCh2', -POrH', -PO?2'. - PChH", -CO2', -OR, -O', -alkyd, -COR, or -COOR, or an alkoxy, where R is H or alkyl;

[0208] Yi and Y2 are each independently a counter cation to Xi and X2. respectively and are Na+, K+, Li+. NH4+, NR4+. or Cs+. where R is H or alkyl;

[0209] X3-X6 are each independently a halide, H, -OH, -OR, -O', -NR2, -NR< . - OSOs', -SO3; -PO42; -PO4H; -PO32; -POsH-, -COT, -alkyl, -COR, or -COOR; and

[0210] Y3-Y6 are independently a counter cation to X3- Xs, respectively and are Na+, K+, Li+. NH4+, NR4+, or Cs+, where R is H or alkyl.

[0211] 18. The composition of matter of example 15, wherein

[0212] Xi and X2 are each independently an alkoxy, such as but not limited to, - RO(A)' or -ROR(A)' where A is an anionic group;

[0213] Yi and Y2 are each independently a counter cation to Xi and X2. respectively and are Na+, K+, Li+, NH4+, NR4+, or Cs+, where R is H or alkyl; X3-X6 are each independently a halide, -OH, -OR, -O', -NR2, -NRs+, -OSOs', - SO3; -PO42; -PO4H; -PO32; -PO3H; -CO2', -alkyl, -COR, or -COOR; and

[0214] Y3-Y6 are independently a counter cation to X3- Xs, respectively and are Na+, K+. Li+. NH4+, NR4+. or Cs+, where R is H or alkyl.

[0215] 18. A composition of matter useful as posolyte or a negolyte, comprising a malemide of the structure: sidechains in any of the examples 1-15, 17, or 18.

[0216] 19. A composition of matter useful as a negolyte in a redox flow battery, compnsing: a compound having the structure:

[0217] w Z1 and Z2 are each independently a C1-C10 alkyl chain, -(CH2CH2O)n-, C1-C5- Pentose, C1-C6-hexose, a fumarate, a succinate, or an aspartate, where n=1-12; X1-X10are independently an ion, such as -OSO3-, -SO3-, -PO42-, -PO4H-, -PO32-, -PO3H-, -CO2-, or -alkyl, -aryl, -COR, -C(O)R, Halide, -OH, -OR, -O-, -NR2, - C(O)NR2, -NR3+, or -C(O)OR, where R is H or alkyl; -O-(Si(CH3)2-O)n-SiOR where R = (CH2)nR’ or Si(CH3)2R’ where R’ = -NR3+Y1-Y10are independently an endcap group or counter-cation to X1-X10and are Na+, K+, Li+, NH4+, NR4+, or Cs+, where R is H or alkyl; and Z1-X1-Y1, Z2-X2-Y2, X3-Y3,X4-Y4,X5-Y5,X6-Y6,X7-Y7,X8-Y8,X9-Y9,and / or X10-Y10 each comprise a solubilizing group. Block 606 represents optionally combining the composition of matter with one or more additives or other components. Block 608 represents configuring the composition of matter for an application. Example applications include, but are not limited to, the following. 20. A redox flow battery comprising the negolyte and / or posolyte of any of the examples 1-19. 21. The composition of matter of example 19, wherein the redox flow battery further comprises: a first tank storing a first liquid comprising a first redox active compound; a second tank storing a second liquid (bulk liquid or ionic liquid or a solution) comprising a second redox active compound; and an electrochemical cell comprising: a first half cell comprising the first liquid connected to a first electrode; a second half cell comprising the second liquid connected to a second electrode; and a boundary separating the first half cell and the second half cell; and a system comprising conduits and pumps circulating the first liquid between the first tank and the first half cell and the second liquid between the second tank and the second half cell; and wherein at least one of: the first redox active compound comprises the composition of matter of any of the examples having the first electroactive moiety having the redox potential associated with a posolyte, or the second redox active compound comprises the composition of matter of any of the examples having the first electroactive moiety having the redox potential associated with anegolyte.

[0218] 22. The composition of matter of example 20 or 21, wherein the redox flow battery further comprises an electrical circuit comprising a load connected to the first electrode and the second electrode, wherein during discharging of the redox flow battery: the second redox active compound is oxidized to release electrons through the second electrode into the circuit; and the first redox active compound is reduced upon receiving the electrons from the circuit through the first electrode.

[0219] 23. The composition of matter of any of the examples 20-22, further comprising: at least one of the first liquid or the second liquid further comprising one or more additives in solution with the liquids or as a constitutive part of the liquid and the additives comprising one or more electrochemically inert salts that at least: increase a first solubility of the first redox active compound in the first liquid or a second solubility of the second redox compound in the second liquid, respectively, or increase a conductivity of the first liquid or the second liquid, or decrease a probability of an hydrogen evolution reaction in the second half- cell.

[0220] 24. The composition of matter of example 23, wherein the additives comprise an electrolyte comprising a sodium salt (such as NaCL NaBr, Nal, NaOH, NaHCCh, Na2CCh, etc.), a potassium salt (such as KC1, KBr, KI, KOH, KHCO3, K2CO3, etc.), an ammonium salt (such as NH4CI, NH4OH, NH4OAC, NTEBr, NH4H2PO4, NH4F, NH4PF6, etc.), and / or an ionic liquid (such as LiPFe. LiTFSI, EMIM-TFS1. TEA-TFS1, TBA-PF6. etc ).

[0221] 25. The composition of matter of example 23 or example 24, wherein: the additives comprise an electrolyte comprising a salt mixture comprised of the potassium salt, the ammonium salt, and the ionic liquid in a X:Y :Z molar ratio, respectively, where x=0-100, y=0-100, z=0-100, or the electrolyte comprises a salt mixture comprised of the sodium salt, the ammonium salt, and the ionic liquid in a X:Y :Z molar ratio, respectively, where x=0- 100, y =0-100, z=0-100.

[0222] 26. The composition of matter of example 23, wherein the additives comprise a hydrotrope.

[0223] 27. The composition of matter of any of the examples 1-25, wherein the solubilizing groups in the posolyte or the negolyte increase a solubility of the posolyte or the negolyte in the first liquid or the second liquid, respectively.

[0224] 28. The composition of matter of any of the examples 1-26, further comprising the first liquid or the second liquid comprising a polar solvent. 29. The composition of matter of any of the examples 1-28, further comprising the first liquid and / or the second liquid comprise or consist essentially of water.

[0225] 30. In one or more examples 1-29, the redox flow battery utilizes two electroactive molecules, one on each side of the electrochemical cell, that form a redox system. The positive side of the electrochemical cell is comprised of an electroactive material dissolved in water which contains a supporting electrolyte, a flow frame which is in electrical contact with the positive electrode, a porous conductive current collector that is in electrical contact with both the flow frame and the solution of electrolyte material, an electrolyte reservoir that holds the above mentioned solution of the electrolyte material, and a pump to flow the electrolyte solution into the electrochemical cell via the flow frame. The negative side of the electrochemical cell is comprised of an electroactive material dissolved in water which contains a supporting electrolyte, a flow frame which is in electrical contact with the negative electrode, a piece of graphite felt that is in electrical contact with the flow frame, an electrolyte reservoir that holds the above mentioned solution of the electrolyte material, and a pump to flow the electrolyte solution into the electrochemical cell via the flow frame. The two sides of the electrochemical cell are separated by an ion exchange membrane that allows the crossing of small ions for charge compensation but does not allow the crossing of electroactive materials. The two sides of the electrochemical cell are also connected electrically from the two electrodes to two sides of an electrical load or power source to form a circuit and are discharged / charged through these electrical connections. During a charge / discharge cycle the solutions of electroactive materials are independently flowed through each half cell at an appropriate flow rate. The electroactive material used in the positive side of the battery, i.e. the posolyte, has the formula shown in figure 2. The electroactive material used in the negative side of the battery, i.e. the negolyte, has the formula shown in figure 4. 31. The composition of matter of any of the examples 1-30, wherein the solubilizing moi eties (e.g., comprising siloxane or dihexyl groups or other alkyl or aryl functionalities) enable solubility in oil and / or immiscibility in water and are optionally selected for having a higher redox potential. 32. The composition of matter of any of the applicable examples, wherein the solubilizing moieties each comprise a siloxane or a hydroxy group.

[0226] 33. The composition of matter of any of the applicable examples 1-31, comprising one of the following structures: or

[0227] R~ H. CH3, t-Bu, Ph, CF3SCF2CF3 or or

[0228] 34. The composition of matter of any of the examples 1-33 wherein both the first liquid and the second liquid solutions are aqueous and the posolyte and negolyte can be soluble in the aqueous solutions.

[0229] 35. The composition of matter of any of the examples 1-33 wherein the first or the second liquid is based on a non-aqueous solvent that is immiscible with water and one of the posolyte or negolyte is selected to be soluble in the first or the second liquid based on the non-aqueous solvent, while the other of the first or the second liquid is aqueous and the other of the posolyte or negolyte is soluble in the one of the first or the second liquid that is aqueous.

[0230] 36. The composition of matter of any of the applicable 1-35 examples wherein the solubilizing moieties are siloxane for solubility in an oil of the same character (e.g., polydimethylsiloxane / PDMS oils).

[0231] 37. The composition of matter of any of the applicable examples 1-36, wherein the redox potential (of the electroactive moiety comprising a ferrocene molecule) is tuned with the linker part of the functionalization (methyl group + ether oxygen off of the alpha carbon).

[0232] 38. The composition of matter of any of the applicable examples 1-36, wherein the solubilizing moieties render the composition soluble in oil and / or immiscible in water.

[0233] 39. The composition of matter useful as a posolyte or negolyte in a redox flow battery, or the composition of matter any of the applicable examples 1-38, comprising the compound of the structure: 40. A composition of matter useful as a posolyte or negolyte in a redox flow battery, or the composition of matter of any of the applicable examples 1-38, comprising the compound of the structure: or or or where R is and R is H, CH3, t-Bu, Ph, CF3 or CF2CF3 .

[0234] 41. A composition of matter useful as a posolyte or negolyte in a redox flow battery, or the composition of matter of any of applicable examples 1- 39 , wherein the compound has the structure: Where R is H, CH3. t-Bu. Ph. CF3or CF2CF3.

[0235] 42. A composition of mater useful as a posolyte or negolyte in a redox flow batery, or the composition of mater of any of the applicable examples 1-39, wherein the compound has the structure:

[0236] Where R is H, CH3, t-Bu, Ph, CF3or CF2CF3.

[0237] 43. A composition of mater useful as a posolyte or negolyte in a redox flow batery, or the composition of mater of any of the examples 1-39, wherein the

[0238] compound comprises one of the following structures:

[0239] 44. The composition of matter of any of the examples 1-43, wherein the solubilizing moiety has a composition selected to tune at least one of a redox potential or solubility' of the compound in the first liquid or the second liquid.

[0240] 45. The composition of matter of example 44, wherein the solubility is tuned such that the compound is soluble in the first liquid but immiscible in the second liquid or vice versa. 46. The composition of matter of example 44 or 45, wherein the redox potential is tuned such that the compound has the redox potential of the posolyte or negolyte useful in the flow battery.

[0241] 47. The composition of matter of example 1, comprising the compound of the structure: or or or Where R is H, CH3, t-Bu, Ph, CF3or CF2CF3.

[0242] 48. A composition of matter useful as a posolyte or negolyte in a redox flow battery (e.g., of any of the examples 1-46). comprising: a compound comprising the structure:

[0243] Linker moiety Solubilizing moiety wherein the solubilizing moiety comprises an organic compound configured for solubility in an organic or nonaqueous solvent, and wherein the composition of matter is optionally combined with the solvent.

[0244] 49. The composition of matter of any of the examples 1-48 useful as a posolyte or negolyte in a redox flow battery, comprising the electroactive moiety combined with the solubilizing moiety and the linker moiety, the solubilizing moiety in combination the linker moiety having the structure:

[0245] The composition of matter of example 49 further combined with a counterion. A non-aqueous material used as a water-immiscible solvent combined with either a posolyte or negolyte comprising the composition of matter of any of the examples 1-50 useful in a flow battery’, the non-aqueous material comprising one of the following structures:

[0246] and wherein counterions may optionally be present. 52. An electrolyte comprising the non-aqueous material of example 50.

[0247] 53. A aqueous or nonaqueous medium or liquid or electrolyte comprising the composition of matter of any of the examples 1-52 comprising a solvent for the composition of matter of examples 1-51 in combination with the composition of matter / compound, wherein the combination of the solvent and the composition of matter form an electrolyte (posoyte or negolyte or catholyte or anolyte) useful in a flow battery.

[0248] Sixth Example: Additional Derivative Posolvtes and Negolvtes

[0249] The functional groups can be modified to tune solubility and / or redox potential.

[0250] Fig. 7 shows some siloxane derivatives of isoindigo useful as a posolyte or negolyte according to one or more embodiments of the invention.

[0251] Fig. 8 shows some zwitterionic and carbon-carbon covalent attachments of bis(R-sulfonimide) solubilizing groups to bipyridine redox cores, useful as a posolyte or negolyte according to one or more embodiments of the invention. Notably the addition of linker may be made to any of the bipyridine cores although 4-4 bipyridine is pictured.

[0252] Fig. 8 illustrates sulfonate and sulfonimide functionalization of maleimide useful as a posolyte or negolyte according to one or more embodiments of the invention.

[0253] Fig. 10A-10B illustrate 1,1’ -bis(l -hydroxy ethyl) and siloxane funcitonalization of ferrocene useful as a posolyte or negolyte according to one or more embodiments.

[0254] Seventh Example: Electrochemical Response of Derivative Posolvtes or Negolvtes The electroactive materials described herein show different electrochemical responses depending on the nature of the linker and solubilizing moieties appended to the redox cores, which can be used to enhance or control electroactive performance.

[0255] In one example, at least one of the posolyte or negolyte. as embodied in a first liquid or second liquid of a redox flow battery, may be analyzed with electrochemical techniques such as cyclic voltammetry' or differential pulse voltammetry to discern the redox potential of the redox active compound in the respective posolyte or negolyte to determine that a certain moiety: increases or decreases a first redox potential of a first redox active compound in a first posolyte or negolyte composition, or increases or decreases a second redox potential of a second redox active compound in a second posolyte or negolyte composition, or increases or decreases the electron transfer rate or diffusion kinetics of a redox active molecule in a posolyte or negolyte composition, or serves an additional function

[0256] Figure 11 A illustrates a cyclic voltammetry' measurement that shows the redox potential change afforded from the 1-hydroxyethyl and dimethylsulfonate functionalizations of ferrocene, and also shows that it is generally pH-independent.

[0257] Figure 11B illustrates a cyclic voltammetry measurement that shows the redox potential change afforded from the 1-hydroxyethyl and variety' of siloxane functionalizations of ferrocene, indicating a change of more than 0.5V from the presence of the branched methylene unit on the linker containing

[0258] Figure 12 illustrates a differential pulse voltammetry' measurement that shows the redox potential change afforded from dimethylsulfonate, 1,1 ’-bis(l -hydroxy ethyl), and bis(methoxylpropylsulfonate) functionalizations of ferrocene, resulting in nuanced control of redox potential

[0259] Eighth example: figure 13A-D, NMRs Figures 13A-D are Nuclear Magnetic Resonance spectra which demonstrate the resonances associated with several ferrocene compositions in Fig. 10A.

[0260] Ninth Example: modification of polvdimethylsiloxane oil Figure 14 illustrates modification of poly dimethylsiloxane oil as a solvent for at least one of the posolyte or negolyte as described herein and useful as a first liquid or second liquid of the redox flow battery described herein. Modification can impact the solvation properties, latent ionic conductivity of the solvent, and solvent viscosity'

[0261] Tenth Example: Redox Potential as a function of linker length and number of solubilizing groups

[0262] The data in table 1 shows that increasing the distance of the solubilizing group from the redox core decreases the redox potential of the posolyte (ferrocene), and that adding 2 solubilizing groups also increases the redox potential of the posolyte.

[0263] Other data (see Fig. 2 in [1], and [2-6]) shows that increasing the distance between the solubilizing groups and the electroactive core increases the solubility and increasing the number of solubilizing groups increases the solubility. However, for the solubilizing groups in [1,2,3] increasing the distance from the electroactive core to the solubilizing groups decreases the redox potential.

[0264] Thus, the data show there is a tradeoff between solubility and redox potential. Solubility and redox potential can be measured as a function of linker length and the linker length can be tuned to select solubility and redox potential for the desired application (posolyte or negolyte) and type of potential.

[0265] Example applications

[0266] Embodiments of the composition of matter described herein can be used in a variety of applications including, but not limited to, batteries, redox flow batteries, electrochemical devices, energy storage systems, fuel cells, flow cells, supercapacitors, microbial fuel cells, reverse microbial fuel cells, microbiological electrochemical devices, biological sensors, biological imaging, metabolic engineering, fluorescence microscopy, membrane intercalating molecules, xenobiotics, protein prosthetics, and antibiotics.

[0267] Advantages and improvements

[0268] The present invention solved one or more problems with prior art by increasing the solubility of the electroactive materials, increasing the stability of the electroactive materials over many charge / discharge cycles, and increasing the operation voltage of the resulting device.

[0269] The formula of the two electroactive materials, show n in figures 1 and 2, have improvement over prior art in that they are highly soluble in water and aqueous solutions containing electrochemically inert supporting electrolyte, and thus improve the energy density of the resulting flow battery. Improving the energy density' of the flow battery is a crucial metric that paves the way to a commercially viable product. Additionally, the two electroactive materials are found to have improved stability over thousands of charge / dis charge cycles compared to prior art, a metric that allows the resulting battery to have a large operational lifetime and thus decreases the overall cost of the flow battery due to an extended product lifetime.

[0270] The use of specific blends of electrochemically inert supporting electrolyte improves on prior art in that they concomitantly increase the electrical conductivity of the solution, increase the solubility of the electroactive materials, and suppress possible water splitting on both sides of the electrochemical cell. The increase in electrical conductivity of the solution decreases the internal resistance of the cell and improves the overall energy efficiency of the flow battery. The increase in solubility of the electroactive materials by using specific blends of supporting electrolyte increases the energy density of the battery. The suppression of water splitting in the electrochemical cell increases the energy’ efficiency of the cell, increases the operational voltage of the cell, and suppresses the formation of gaseous byproducts in the electrolyte reservoirs containing the bulk volume of the electroactive solutions.

[0271] References

[0272] The following references are incorporated by reference herein.

[0273] [1] Chen et al, ChemSusChem 2021, 14, 1295-1301; doi.org / 10. 1002 / cssc.202002467

[0274] [2] Hu et al, J. Am. Chem. Soc. 2017, 139, 1207-12; doi.org / 10. 1021 / jacs.6bl0984

[0275] [3] Yu et al, En. Stor. Mat. 2020, 29, 216-22; doi.org / 10. 1016 / j.ensm.2020.04.020

[0276] [4] Xavier et al, Chem. Commun., 2022, 58, 4196-4199; doi.org / 10. 1039 / D2CC00424K

[0277] [5] Yao et al, Appl. Ener. Mater. 2021. 4, 8052-58; doi.org / 10. 1021 / acsaem. 1 cOl 363

[0278] [6] Zhao et al, Appl. Ener. Mater. 2020, 3, 10270-77; doi.org / 10. 1021 / acsaem.0c02259 Conclusion

[0279] This concludes the description of the preferred embodiment of the present invention. The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.

Claims

WHAT IS CLAIMED IS:

1. A composition of matter useful as a posolyte or negolyte in a redox flow battery, comprising: a compound comprising a first electroactive moiety and one or more solubilizing moieties each connected to the first electroactive moiety directly or via a linker moiety, wherein the linker moieties. when present each comprise at least one of carbon, hydrogen, oxygen, nitrogen, sulfur, or silicon.

2. The composition of matter of claim 1, wherein: the compound comprises one or more second electroactive moieties connected to the first electroactive moiety, each of the second electroactive moieties connected to the first electroactive moiety via a different one of the linker moieties, and the second electroactive moieties enhance an electroactivity, including a redox potential and / or an electrochemical reversibility, of the first electroactive moiety as an electron donor or an electron acceptor in a redox reaction of the redox flow battery.

3. The composition of matter of claim 1, wherein the compound comprises one or more aromatic rings, comprising the first electroactive moiety’, covalently bonded to pendant groups comprising the linker moieties and the solubilizing moieties.

4. The composition of matter of claim 1, wherein the compound comprises a posolyte comprising a ferrocene or maleimide comprising the first electroactive moiety.

5. The composition of matter of claim 1 , wherein the compound comprises a heterocyclic aromatic ring comprising a heteroatom and the first electroactive moiety, wherein the linker moiety is bonded to the heteroatom.

6. The composition of matter of claim 1, wherein the compound comprises an aromatic compound comprising: a first ring covalently bonded to a first pendant group comprising a first one of the linker moieties bonded to a first one of the solubilizing moieties; a second ring covalently bonded to a second pendant group comprising a second one of the linker moieties bonded to a second one of the solubilizing moieties.

7. The composition of matter of claim 1, wherein the linker moiety comprises 1, 2, 3, 4, or 5 of the carbon atoms, or a chain comprising 2-5 carbon atoms, wherein the length of the chain is tuned as a trade-off between increasing the electroactivity of the first electroactive moiety and increasing solubility of the compound in a solvent of the redox flow battery.

8. The composition of matter of claim 1, wherein the solubilizing moieties each comprise an ion covalently bonded to one of the linker moieties and a counterion for the ion.

9. The composition of matter of claim 1, further comprising a water or an organic solvent combined with the solubilizing moieties, wherein one or more of the solubilizing moieties comprise a zwitterion covalently bonded to one of the linker moieties.

10. The composition of matter of claim 8, wherein: the ion comprises at least one of -OSO3‘, -SO3‘, -PO42’, -PO4H', -PO32', -PO3H‘ , -COT. -OR. -O’, -alkyl, -COR, or -COOR, PFf, BF3’ , -SO2NSO2X; -NSO2X’ where R is H or alkyl and X is H, CF3, CF2CF3, phenyl, alkyl, pentafluorophenyl; and the counterion comprises at least one of Na+, K+, Li+, NH4+, NR4+, or Cs+, methylammonium CH3NH3+, ethylammonium (C2H5)NH3+, alkylammonium,formamidinium NH2(CH)NH2+, guanidinium C(NH2)s+, imidazolium C3N2H5 . hydrazinium H2N-NH3 azetidinium (CH2)3NH2+, dimethylammonium (CHs)2NH2+, tetramethylammonium (CHs)4N+, phenylammonium CeHsNHs4, pyridinium, arylammonium, heteroarylammonium, triazolium. sulfonylimide where R is H or alkyl or a combination thereof; or the ion comprises at least one of a halide, -OH, -OR, -O’, -NR2, -NRs+, -OSO.v , -SO3’, -PO42', -PO4H’. -PO32; -PO3H; -COT, -alkyl, -COR, or -COOR; and the counterion comprises at least one of Na+, K+, Li+, NH4+. NR4+, or Cs+, methylammonium CH3NH3+, ethylammonium (C2H5)NH3+, alkylammonium, formamidinium NH2(CH)NH2+, guanidinium CTNHT)? . imidazolium C3N2H5 . hydrazinium H2N-NH3 azetidinium (CfbfNFb . dimethylammonium (CHs)2NH2+, tetramethylammonium (CHs)4N+, phenylammonium CTFENHT . pyridinium, arylammonium, heteroarylammonium, triazolium. sulfonylimide where R is H or alkyl.

11. The composition of matter of claim 1, wherein the compound comprises a negolyte comprising an isoindigo compound comprising the first electroactive moiety.

12. The composition of claim 11, wherein the isoindigo compound comprises (E)-[3,3'-biindolinylidene]-2,2'-dione.

13. The composition of claim 11 or 12 wherein the solubilizing moi eties are at least one of the 5,5’ positions, the 6,6’ positions, the 1,1’ positions, the 4,4’ positions, or the 7,7’ positions on the isoindigo compound.

14. A composition of matter useful as a posolyte or negolyte in a redox flow battery, comprising: a compound comprising the structure:wherein:XI, X2, X3, X4, X5 are each independently an ion,Yl, Y2. Y3, Y4, Y5 are each independently a counterion for the ion, the ion is an anion or a cation, andXl-Yl, X2-Y2, X3-Y3, X4-Y4, and X5-Y5 each comprise a solubilizing group.

15. A composition of matter useful as a posolyte or negolyte in a redox flow battery, comprising the structure of Fig. 1 wherein the solubilizing moiety comprises an organic compounds configured for solubility in an organic / nonaqueous solvent, wherein the composition of matter is optionally combined with the solvent.

16. The composition of matter of claim 14, wherein:Xi and X2 are each independently -OSCh', -SCh’, -PO42', -PChH’, -PCh2’, - POsH’, -CO2; -OR, -O’, -alkyl, -COR, or -COOR, or an alkoxy, where R is H or alkyl;Yi and Y2 are each independently a counter cation to Xi and X2, respectively and are Na+, K+, Li+, NH4+, NR4+, or Cs+, where R is H or alkyl;X3-X6 are each independently a halide, H, -OH, -OR, -O’, -NR2, -NR4 . - OSOs’, -SOs’, -PO42’. -PO4H’, -PO32; -POsH’, -COf, -alkyl, -COR, or -COOR; andY3-Y6 are independently a counter cation to X3- Xs, respectively and are Na+, K+, Li+, NH4+, NR4+, or Cs+, where R is H or alky l.

17. The composition of matter of claim 14, whereinXi and X2 are each independently an alkoxy, such as but not limited to, - RO(A)', -ROR(A)' where A is alky l;Yi and Y2 are each independently a counter cation to Xi and X2. respectively and are Na+, K+, Li+, NH4+, NR4+. or Cs+. where R is H or alkyl;X3-X6 are each independently a halide, -OH, -OR, -O', -NR2, -NRs+, -OSOs', - SOs', -PO42', -PO4H; -PO32; -PO3H; -COT, -alkyl, -COR, or -COOR; andY3-Y6 are independently a counter cation to X3- Xs, respectively and are Na+, K+, Li+. NH4+, NR4+, or Cs+, where R is H or alkyl.

18. A composition of matter useful as a negolyte in a redox flow battery, comprising: a compound having the structure:wherein:Zi and Z2 are each independently a C1-C10 alkyl chain, -(CH2CH2O)n-, C1-C5- Pentose, Ci-Cs-hexose, a fumarate, a succinate, or an aspartate, where n=l-12;Xi-Xio are independently an ion, such as -OSCh’, -SCh", -PCh2', -PChH", -PCh2' , -PO3H; -CO / , or -Alkyl, -COR, -C(O)R, Halide, -OH, -OR, -O’, -NR2, -C(O)NR2, - NRs+, or -C(O)OR. where R is H or alkyl; -O-(Si(CH3)2-O)n-SiOR where R = (CH2)nR’ or Si(CH3)2R' where R’ = -NR3+Y i-Y 10 are independently an endcap group or counter-cation to X1-X10 and areNa+, K+, Li+, NH4+, NRC, or Cs+, where R is H or alkyd; andZ1-X1-Y1, Z2-X2-Y2, X3-Y3, X4-Y4, X5-Y5, X6-Y6, X7-Y7, Xs-Ys, X9-Y9, and / or X10-Y10 each comprise a solubilizing group.

19. A composition of matter useful as posolyte or a negolyte, comprising a malemide of the structure:sidechains in any of the examples 1-18.

20. The composition of matter of claim 1 configured as a posolyte or negolyte for use in a redox flow batten- .

21. The composition of matter of claim 20, wherein the redox flow battery further comprises: a first tank storing a first liquid comprising a first redox active compound; a second tank storing a second liquid (bulk liquid or ionic liquid or a solution) comprising a second redox active compound; and an electrochemical cell comprising: a first half cell comprising the first liquid connected to a first electrode; a second half cell comprising the second liquid connected to a second electrode; and a boundary separating the first half cell and the second half cell; and a system comprising conduits and pumps circulating the first liquid between the first tank and the first half cell and the second liquid between the second tank and the second half cell; and wherein at least one of: the first redox active compound comprises the composition of matter of any of the claims having the first electroactive moiety having the redox potential associated with a posolyte, or the second redox active compound comprises the composition of matter of any of the claims having the first electroactive moiety having the redox potential associated with a negolyte.

22. The composition of matter of claim 21, wherein the redox flow battery- further comprises an electrical circuit comprising a load connected to the first electrode and the second electrode, wherein during discharging of the redox flow battery:the second redox active compound is oxidized to release electrons through the second electrode into the circuit; and the first redox active compound is reduced upon receiving the electrons from the circuit through the first electrode.

23. The composition of matter of claim 21, further comprising: at least one of the first liquid or the second liquid further comprising one or more additives in solution with the liquids or as a constitutive part of the liquid and the additives comprising one or more electrochemically inert salts that at least: increase a first solubility of the first redox active compound in the first liquid or a second solubility of the second redox compound in the second liquid, respectively, or increase a conductivity of the first liquid or the second liquid, or decrease a probability of an hydrogen evolution reaction in the second half- cell.

24. The composition of matter of claim 23. wherein the additives comprise an electrolyte comprising a sodium salt, a potassium salt, an ammonium salt, and / or an ionic liquid.

25. The composition of matter of claim 23. wherein: the additives comprise an electrolyte comprising a salt mixture comprised of the potassium salt, the ammonium salt, and the ionic liquid in a X:Y :Z molar ratio, respectively, where x=0-100, y=0-100, z=0-100, or the electrolyte comprises a salt mixture comprised of the sodium salt, the ammonium salt, and the ionic liquid in aX:Y:Z molar ratio, respectively, where x=0- 100, y =0-100, z=0-100.

26. The composition of matter of claim 23, wherein the additives comprise a hydrotrope.

27. The composition of matter of claim 1 or 21, wherein the solubilizing groups in the posolyte or the negolyte increase a solubility of the posolyte or the negolyte in a first liquid or the second liquid, respectively .

28. The composition of matter of claim 27. further comprising the first liquid or the second liquid comprising a polar solvent.

29. The composition of matter of claim 27, wherein the first liquid and the second liquid comprise or consist essentially of water.

30. The composition of matter of claim 1, wherein the solubilizing moieties each comprise a siloxane or a hydroxy group.

31. The composition of matter of claim 1, wherein the compound comprises one of the following structures:where X is Na+, Ka+, or NH4+or one of the followingand R is H, CHs,t-Bu, alkyl, Ph, CF3 or, CF2CF3,32. The composition of matter of claim 1, wherein the compound comprises:

33. The composition of matter of any of the claims, wherein the solubilizing moieties render the composition soluble in oil and / or immiscible in water.

34. The composition of matter of claim 1, comprising the compound of the structure:

35. The composition of matter of claim 1, comprising the compound of the structure:orororwhere R is and R is H, CHs,t-Bu, Ph, CF3 or CF2CF3 .

36. The composition of mater of claim 1, wherein the compound has the structure:Where R is H, CH3, t-Bu. Ph. CF3or CF2CF3.

37. The composition of matter of claim 1, wherein the compound has the structure:Where R is H, CH3. t-Bu, Ph, CF3or CF2CF3.

38. The composition of matter of claim 1, wherein the compound comprises one of the following structures:

39. The composition of mater of claim 1, wherein the solubilizing moiety has a composition selected to tune at least one of a redox potential or solubility of the compound in the first liquid or the second liquid.

40. The composition of mater of claim 39, wherein the solubility is tuned such that the compound is soluble in the first liquid but immiscible in the second liquid or vice versa.

41. The composition of matter of claim 39, wherein the redox potential is tuned such that the compound has the redox potential of the posolyte or negolyte useful in the flow battery.

42. The composition of matter of claim 1, comprising the compound of the structure:orororororWhere R is H, CH3, t-Bu, Ph, CF3or CF2CF3.

43. A composition of mater useful as a posolyte or negolyte in a redox flow batery, comprising: a compound comprising the structure:Linker moiety Solubilizing moietywherein the solubilizing moiety comprises an organic compound configured for solubility in an organic or nonaqueous solvent, and wherein the composition of mater is optionally combined with the solvent.

44. A composition of mater useful as a posolyte or negolyte in a redox flow batery, comprising the electroactive moiety combined with the solubilizing moiety and the linker moiety, the solubilizing moiety in combination the linker moiety having the structure:

45. A non-aqueous material used as a water-immiscible solvent combined with either a posolyte or negolyte comprising the composition of matter of claim 1 useful in a flow battery, the non-aqueous material comprising one of the following structures:or46. The composition of matter of claim 1, wherein the solubilizing moiety is a 1- hydroxyethyl or bistriflimide (TFSI).

47. An electrolyte useful in a flow battery comprising an oil or non-aqueous non- organic composition of matter combined with an electroactive moiety linked with a linker to a solubilizing moiety.

48. The electrolyte of claim 47 wherein the non-aqueous non-organic composition of matter comprises the structure:or

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