Systems and methods for low cost redox flow batteries

Abstract

The present disclosure provides batteries with long duration or long life for energy storage applications. In one aspect, the present disclosure provides perylenediimide molecules that are water-soluble and can be used as energy storage materials. In operation, the perylenediimide molecules are oxidized in an anode chamber and the electrons released during oxidation flow to a cathode chamber where they reduce molecules in the cathode chamber. The perylenediimide molecules according to many embodiments are highly compatible with inexpensive and easy-to-process polymeric materials, thus allowing for a significant reduction in manufacturing costs.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to low cost redox flow batteries; and more particularly to redox flow batteries with mild aqueous electrolytes and low cost materials for battery components. BACKGROUND

[0002] In redox flow batteries, electrolyte solutions can be stored in reservoirs and pumped to pass through electrochemical cell units and back into the reservoirs. The number of cell units (cell unit stacks) can determine the power output (watts) of the system, while the size of the reservoirs can determine the energy (watt-hours). This engineering separation of power and energy is an advantage of flow batteries, enabling easy scaling. Vanadium oxide redox flow batteries use highly acidic electrolyte solutions, such as electrolytes containing sulfuric acid. In addition, vanadium itself is highly corrosive. Thus, the acidic and corrosive solution components of vanadium oxide redox flow batteries can require that cell unit manufacturing parts be composed of highly chemically resistant materials. For example, vanadium redox flow batteries can require fluorinated polymers as components of the flow battery. The manufacturing cost of these specialty materials can be high, particularly when scaling up flow battery production. There is a great need for redox flow batteries that are chemically stable for long periods of storage, have long electrolyte lifetimes, and are compatible with low cost and high-throughput manufacturable materials. In order to widely apply redox flow batteries, new flow battery systems can be needed that are compatible with low cost and batch producible materials. SUMMARY

[0003] Summarized here and described in detail below is a redox flow battery that is compatible with low cost and non-highly chemically resistant materials as various components of the battery. The redox flow battery according to many embodiments contains a neutral pH aqueous electrolyte solution. In several embodiments, the low cost and non-highly chemically resistant materials are stable under redox flow battery operating conditions for weeks and months. The mild electrolyte solution enables the use of non-highly chemically resistant materials in flow battery manufacturing, which can be scaled up, and the materials are readily available, have reduced cost, and use high-throughput manufacturing techniques.

[0004] In many embodiments, the electrolyte solution can contain water-soluble perylene diimide molecules for charge storage applications, and the aqueous solution is compatible with materials that are not designated as highly chemically resistant (i.e., non-highly chemically resistant materials). In several embodiments, the electrolyte solution can contain water-soluble perylene diimide molecules and water-soluble ferrocene molecules for charge storage applications, and the aqueous solution is compatible with materials that are not designated as highly chemically resistant. The term compatibility is defined as having little or no deleterious electrochemical or physical reactions between any component of the cell unit and the electrolyte solution that would impede long term or multi-year device lifetimes.

[0005] In many embodiments, a redox flow battery includes a first half-cell unit including an anolyte solution and a second half-cell unit including a catholyte solution. The anolyte solution can include, but is not limited to, a water-soluble perylene diimide molecule or a water-soluble perylene diimide derivative. The catholyte solution can include, but is not limited to, a water-soluble ferrocene molecule or a water-soluble ferrocene derivative. In several embodiments, one or more battery components can be made of a non-highly-chemically-resistant material. Examples of various battery components include, but are not limited to, electrodes, gaskets, flow frames, bipolar plates, membranes, seals, and tubing. Examples of low-cost non-highly-chemically-resistant materials include, but are not limited to, plastics, rubbers, elastomers, ceramics, glasses, metals, metal alloys, membranes, ion exchange membranes, size exclusion membranes, and any combination thereof. In some embodiments, battery components can be made of a non-fluorinated polymer. In several embodiments, the non-fluorinated polymer can include, but is not limited to, a polyolefin, a polyether, a polyketone, a polyamide, a polyurea, a natural rubber, or any combination thereof.

[0006] Many embodiments provide non-highly-chemically-resistant materials that are compatible with operating conditions of a redox flow battery at a range of states of charge (SOC) in cycling and long-term high SOC exposure tests. Examples of compatibility and non-highly-chemically-resistant materials include, but are not limited to, ethylene propylene diene rubber (EPDM), polychloroprene (Neoprene), polyamide (Nylon), polyether ether ketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate (sodium benzenesulfonate), sodium 4-toluenesulfonate (sodium toluenesulfonate), propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), EPDM polypropylene matrix elastomer (Santoprene). According to several embodiments, certain non-highly-chemically-resistant materials, such as 316 stainless steel, 6061 aluminum, and polysiloxane rubber (silicone), can not have the required compatibility with a redox flow battery.

[0007] In many embodiments, the battery can be a redox flow battery. In some embodiments, the redox flow battery has a capacity retention of greater than 99% over a period of at least two weeks. In some embodiments, the redox flow battery has a capacity retention of greater than 99.9% over a period of at least two weeks.

[0008] In certain embodiments, components of the flow battery can be made using various processes, including, but not limited to, melt processes, thermoforming processes, additive manufacturing processes, 3D printing processes, and any combination thereof. Examples of thermoforming processes include, but are not limited to, injection molding, blow molding, and extrusion. In several embodiments, the components can be made from materials including hydrocarbon plastics, elastomers, and / or rubbers, including, but not limited to, polyethylene, polypropylene, polycarbonate, polystyrene, polyoxymethylene, santoprene, EPDM, neoprene, PEEK, POM, PVC, PMMA, polyurethane, nylon, sodium benzene sulfonate, sodium toluene sulfonate, propylene carbonate, sulfolane, BUNA-N, natural latex rubber, latex, natural gum rubber, and any combination thereof.

[0009] In many embodiments, the reaction vessel (also referred to as a flow frame) that defines the interior of the half-cell of the battery can be made from at least one non-fluorinated polymer. Examples of non-fluorinated polymers include, but are not limited to, polyethylene, polypropylene, polymethylpentene (PMP), polybutene-1, PVC, polystyrene, PMMA, acrylonitrile butadiene styrene (ABS), nylon, POM, polycarbonate, PEEK, and any combination thereof. In some embodiments, the reaction vessel can be made from a copolymer derived from two or more of the above-mentioned polymers.

[0010] The bipolar plate of the half-cell that is in contact with the catholyte or anolyte solution can be made from graphite or a polymer composite. In some embodiments, the bipolar plate can be made from a resin-filled graphite composite. In certain embodiments, the polymer of the resin-filled graphite composite can be polyethylene or polypropylene. In some embodiments, the resin-filled graphite composite can be a thermoset resin, including, but not limited to, a phenol formaldehyde resin.

[0011] In several embodiments, the gasket in the half-cell that is in contact with the catholyte or anolyte solution can be made from a non-fluorinated elastomeric material. In some embodiments, the non-fluorinated elastomeric material is a non-highly-chemically-resistant rubber material, including, but not limited to, EPDM, santoprene, neoprene, butadiene-styrene (BUNA-S), BUNA-N, latex, trans-polyisoprene, silicone, or polyurethane.

[0012] In many embodiments, the redox flow battery may include supply lines and / or conduits located outside the half-cell units, which deliver anolyte solutions and catholyte solutions to a first half-cell unit and a second half-cell unit, respectively. According to several embodiments, the supply lines may be made of materials not specified as highly chemically resistant. In some embodiments, the supply lines may be made of non-fluorinated elastomer polymers. In various embodiments, the supply lines may be made of non-highly chemically resistant rubber materials, including (but not limited to) EPDM, santoprene, neoprene, BUNA-S, BUNA-N, latex, trans-isoprene, silicone, or polyurethane. In many embodiments, the supply lines may be made of rigid plastics, including (but not limited to) polyethylene, polypropylene, or polyvinyl chloride.

[0013] In some embodiments, the membrane in a redox flow battery can be made of an ion exchange membrane, including (but not limited to) anion exchange membranes. Several embodiments use a seldomium exchange membrane in the redox flow battery. TM Anion or cation exchange membranes and / or Selemion TM AMVN membrane and / or Selemion TM CMVN membrane. Selemion TM AMVN is a polystyrene-based anion exchange membrane that can contain various functional groups. Selemion TM CMVNs are polystyrene-based cation exchange membranes that can contain various functional groups. Some implementations use Fumasep. TM FAA-3-20 is used as the anion exchange membrane in the redox flow battery. Some embodiments use Fumasep™ FAA-3-50 as the anion exchange membrane in the redox flow battery. Some embodiments use Fumasep™ FAS-30 as the anion exchange membrane in the redox flow battery. Some embodiments use Fumasep™ FAM-PP as the anion exchange membrane in the redox flow battery. Some embodiments use Fumasep™ FAPQ-375-PP as the anion exchange membrane in the redox flow battery. Some embodiments use Fumasep™ FKS-PK-75 as the cation exchange membrane in the redox flow battery. Some embodiments use Fumasep™ FKS-50 as the cation exchange membrane in the redox flow battery. Some embodiments use Fumasep™ E620K as the cation exchange membrane in the redox flow battery. Fumasep TM FAA-3-30, Fumasep TM FAA-3-50, Fumasep TMFAS-30, Fumasep TM FAM-PP and Fumasep TM FAPQ-375-PP is an anion exchange membrane. Fumasep TM FKS-PK-75, Fumasep TM FKS-50 and Fumasep TM E620K is an anion exchange membrane. Fumasep TM Membranes are polyether ether ketone based membranes that can contain various functional groups.

[0014] Many embodiments provide for redox flow batteries to be compatible with functional groups, such as small molecules, including, but not limited to, sodium benzenesulfonate, sodium toluenesulfonate, propylene carbonate, sulfolane, and any combination thereof.

[0015] Some embodiments include a compound of Formula (I):

[0016] (I) or a salt thereof, wherein:

[0017] T is -(L-G) n -X;

[0018] T' is H, (Ci-C6)alkyl, or -(L-G) n -X;

[0019] L is -(C2-C5)-alkyl, optionally OH, OCH3, halogen substituted,

[0020]

[0021] each X is independently H, -(Ci-C 10 )alkyl, -(C2-C6)alkenyl, -(C2-C6)alkynyl, and -(C2-C6)alkoxy, each of which is unsubstituted or substituted with 1, 2, or 3 independently selected R 1 groups;

[0022] each R 1 is independently -OH, -0(Ci-C6)-alkyl, -0(Ci-C6)-alkyl-0(Ci-C6)-alkyl, -0(Ci-C6)-alkyl-0(Ci-C6)-alkyl-0(Ci-C6)alkyl, -[0(Ci-C6)-alkyl] p-O(C1-C6), -0(C=0)(C1-C6)alkyl, -0(C=0)0(C1-C6)alkyl, -0(C=0)OH, -0(C=0)NH2, -0(C=0)NH(C1-C6)alkyl, 0(C=0)N[(C1-C6)alkyl]2, -NH(C=0)(C1-C6)alkyl, N(C1-C6)alkyl(C=0)(C1-C6)alkyl, halogen, -CN, -N02, NH2, NH(C1-C6)alkyl, and N[(C1-C6)alkyl]2;

[0023] n = 2 to 8; and

[0024] p = 3 to 20.

[0025] In some embodiments, T and T' are each independently -(L-G) n -X.

[0026] In some embodiments, L is unsubstituted -(C2-C5)-alkyl.

[0027] In some embodiments, L is ethyl or propyl.

[0028] In some embodiments, n is 2, 3, or 4.

[0029] In some embodiments, G is .

[0030] In some embodiments, X is H, methyl, or -CH2CH2OH.

[0031] In some embodiments, each X is independently H or -(C1-C6)-alkyl.

[0032] In some embodiments, at least one X is -CH2CH2OH.

[0033] In some embodiments, the compound of formula (I) is:

[0034] ;

[0035] ;

[0036] ;

[0037] ;

[0038] ; or

[0039] .

[0040] Some embodiments include a compound of Formula (II):

[0041] (II)

[0042] wherein

[0043] each Y is independently -O-, -S-, or -NH-;

[0044] each q is independently 1 to 8; and

[0045] each X is independently H, -(Ci-C 10 alkyl, -(C2-C6)alkenyl, -(C2-C6)alkynyl, and -(Ci-C6)alkoxy, each of which is unsubstituted or substituted with 1, 2, or 3 independently selected R 1 groups;

[0046] each R 1 is independently -OH, -0(Ci-C6)-alkyl, -0(Ci-C6)-alkyl-0(Ci-C6)-alkyl, -0(Ci-C6)-alkyl-0(Ci-C6)-alkyl-0(Ci-C6)alkyl, -[0(Ci-C6)-alkyl] p -O(Ci-C6), -0(C=0)(Ci-C6)alkyl, -0(C=0)0(Ci-C6)alkyl, -0(C=0)OH, -0(C=0)NH2, -0(C=0)NH(Ci-C6)alkyl, 0(C=0)N[(Ci-C6)alkyl]2, -NH(C=0)(Ci-C6)alkyl, N(Ci-C6)alkyl(C=0)(Ci-C6)alkyl, halogen, -CN, -N02, NH2, NH(Ci-C6)alkyl, and N[(Ci-C6)alkyl]2; and

[0047] each V is a counterion.

[0048] In some embodiments, the compound of Formula (II) is:

[0049] .

[0050] Some embodiments include a compound of Formula (III):

[0051] (III)

[0052] wherein:

[0053] each X is independently H, -(Ci-C 10)-alkyl, -(C2-C6)alkenyl, -(C2-C6)alkynyl, and -(Ci-C6)alkoxy, each of which is unsubstituted or substituted with 1, 2, or 3 independently selected R 1

[0054] each R 1 is independently -OH, -0(Ci-C6)-alkyl, -0(Ci-C6)-alkyl-0(Ci-C6)-alkyl, -0(Ci-C6)-alkyl-0(Ci-C6)-alkyl-0(Ci-C6)alkyl, -[0(Ci-C6)-alkyl] p -O(Ci-C6), -0(C=0)(Ci-C6)alkyl, -0(C=0)0(Ci-C6)alkyl, -0(C=0)OH, -0(C=0)NH2, -0(C=0)NH(Ci-C6)alkyl, 0(C=0)N[(Ci-C6)alkyl]2, -NH(C=0)(Ci-C6)alkyl, N(Ci-C6)alkyl(C=0)(Ci-C6)alkyl, halogen, -CN, -N02, NH2, NH(Ci-C6)alkyl, and N[(Ci-C6)alkyl]2;

[0055] each s is independently 2 to 4;

[0056] each R is independently H, -CH2OH, -CH2CH2OH, -CH2CH2OCH2CH2OH, or -CH2CH2OCH2CH2O(C 1- 6)alkyl; and

[0057] each V - is a counterion.

[0058] In some embodiments, the compound of Formula (III) is:

[0059] ; or

[0060] .

[0061] Some embodiments include a compound of Formula (IV):

[0062] (IV)

[0063] wherein

[0064] R is , or .

[0065] In some embodiments, the compound of Formula (IV) is

[0066] ​ .

[0067] Some embodiments include a compound of Formula (V):

[0068] (V) or a salt thereof, wherein

[0069] L is -(Ci-C6)-alkyl;

[0070] each G is ;

[0071] A is a cation; and

[0072] n = 1 to 5.

[0073] In some embodiments, L is OH, OCH3, and halogen substituted.

[0074] In some embodiments, each A is lithium, sodium, potassium, or ammonium.

[0075] In some embodiments, each G is .

[0076] In some embodiments, each L is propyl.

[0077] In some embodiments, n is 2.

[0078] In some embodiments, the L-G n group has at least one chiral center.

[0079] In some embodiments, Formula (V) has at least one stereoisomer.

[0080] In some embodiments, the compound of Formula (V) is:

[0081] .

[0082] In some embodiments, the compound of Formula (V) is:

[0083] .

[0084] In some embodiments, the compound of Formula (V) is:

[0085] .

[0086] In some embodiments, the compound of Formula (V) is selected from the group consisting of:

[0087] and any combination thereof.

[0088] In some embodiments, A is lithium, sodium, potassium, or ammonium.

[0089] In some embodiments, the compound of formula (V) is:

[0090] .

[0091] Some implementations include compounds having a formula selected from the group consisting of:

[0092] ,

[0093] ,

[0094]

[0095]

[0096] ,

[0097] ,

[0098] ,

[0099] ,

[0100] ,

[0101] ,

[0102] ,and

[0103] .

[0104] Some embodiments include compounds of formula (VI):

[0105]

[0106] in:

[0107] L is -(C1-C 10 -alkyl, -(C1-C6)-alkenyl, -(C1-C6)-ynyl, -(C1-C6)-alkyl-O(C1-C6)-alkyl, -(C1-C6)-alkyl-O-(C=O)-(C1-C6)alkyl, -(C1-C6)-alkyl-(C=O)-O-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-NR 2-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2 -(C1-C6)alkyl or -(C1-C 10 )-alkyl-aryl;

[0108] L' is -H, -(C1-C 10 )-alkyl, -(C1-C6)-alkenyl, -(C1-C6)-alkynyl, -(C1-C6)-alkyl-O(C1-C6)-alkyl, -(C1-C6)-alkyl-O-(C=O)-(C1-C6)alkyl, -(C1-C6)-alkyl-(C=O)-O-(C1-C6)alkyl, -(C1-C6)alkyl-NH-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-NR 2 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2 -(C1-C6)alkyl or -(C1-C 10 )-alkyl-aryl;

[0109] G is selected from the group consisting of: ;

[0110] G is greater than or equal to 2;

[0111] A is Li, K, Na, or NH4; and

[0112] R 2 is -(C1-C 10 )-alkyl, -(C1-C6)-alkenyl, -(C1-C6)-alkynyl, -(C1-C 10 )-alkyl-aryl, -aryl, or -(C=O)-(C1-C6)-alkyl.

[0113] In some embodiments, L is substituted with at least one group selected from the group consisting of G, -OH, -OCH3, and -halogen.

[0114] In some embodiments, L' is substituted with at least one group selected from the group consisting of G, -OH, -OCH3, and -halogen.

[0115] In some embodiments, R 2 is substituted with at least one G.

[0116] In some embodiments, L-G n has at least one chiral center.

[0117] In some embodiments, the compound has at least one stereoisomer.

[0118] In some embodiments, the compound of Formula (VI) is:

[0119] .

[0120] In some embodiments, the compound of Formula (VI) is:

[0121] .

[0122] In some embodiments, the compound of Formula (VI) is:

[0123] .

[0124] In some embodiments, the compound of Formula (VI) is selected from the group consisting of:

[0125] and any combination thereof.

[0126] In some embodiments, the compound of Formula (VI) is:

[0127] .

[0128] Some embodiments include a redox flow battery comprising: a first half-cell unit containing a first aqueous solution, the first aqueous solution comprising a first electrode and an anode electrolyte; wherein the anode electrolyte comprises a perylene diimide compound; a second half-cell unit containing a second electrode and a second aqueous solution, the second aqueous solution comprising a cathode electrolyte; and a separator between the first half-cell unit and the second half-cell unit; wherein an interior surface of the first half-cell unit in contact with the first aqueous solution and an interior surface of the second half-cell unit in contact with the second aqueous solution comprise one or more non-highly-chemically-resistant materials.

[0129] In some embodiments, the non-highly-chemically-resistant material is a polymer.

[0130] In some embodiments, the polymer is a non-fluorinated polymer.

[0131] In some embodiments, the non-fluorinated polymer is selected from the group consisting of: a polyolefin, a polyether, a polyketone, a polyamide, a polyurea, a natural rubber, and combinations thereof.

[0132] In some embodiments, the non-fluorinated polymer is a copolymer of two or more polymers selected from the group consisting of: a polyolefin, a polyether, a polyketone, a polyamide, a polyurea, and a natural rubber.

[0133] In some embodiments, the non-fluorinated polymer is selected from the group consisting of ethylene propylene terpolymer (EPDM), polychloroprene (Neoprene), polyamide (Nylon), polyether ether ketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate (Sodium Benzenesulfonate), sodium 4-toluenesulfonate (Sodium Toluene Sulfonate), propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), EPDM polypropylene matrix elastomer (Santoprene), and combinations thereof.

[0134] In some embodiments, the non-fluorinated polymer is a copolymer of two or more polymers selected from the group consisting of ethylene propylene terpolymer (EPDM), polychloroprene (Neoprene), polyamide (Nylon), polyether ether ketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate (Sodium Benzenesulfonate), sodium 4-toluenesulfonate (Sodium Toluene Sulfonate), propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), and EPDM polypropylene matrix elastomer (Santoprene).

[0135] In some embodiments, the first half-cell unit includes a first bipolar plate and the second half-cell unit includes a second bipolar plate, wherein the first bipolar plate comprises a composite of graphite and a polymer.

[0136] In some embodiments, the composite is a resin-filled graphite.

[0137] In some embodiments, the first bipolar plate material comprises graphite in a thermoset resin matrix.

[0138] In some embodiments, the polymer of the composite is polyethylene or polypropylene.

[0139] Some embodiments further include a gasket separating the reaction vessel from the first bipolar plate, wherein the gasket comprises a non-highly-chemically-resistant elastomer material.

[0140] In some embodiments, the non-highly-chemically-resistant elastomer material is a non-fluorinated elastomer material.

[0141] In some embodiments, the non-highly chemically resistant elastomeric material is selected from the group consisting of ethylene propylene diene rubber (EPDM), polychloroprene (Neoprene), polyamide (Nylon), polyether ether ketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate (Sodium Benzenesulfonate), sodium 4-toluenesulfonate (Sodium Toluene Sulfonate), propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), EPDM polypropylene matrix elastomer (Santoprene), and combinations thereof.

[0142] In some embodiments, the separator includes an ion exchange membrane.

[0143] In some embodiments, the ion exchange membrane includes a non-fluorinated polymer.

[0144] In some embodiments, wherein the ion exchange membrane is a polystyrene-based ion exchange membrane.

[0145] Some embodiments further include a supply line external to the first half-cell unit for supplying anode electrolyte to the first half-cell unit, wherein the supply line comprises a non-highly chemically resistant elastomeric material.

[0146] In some embodiments, the non-highly chemically resistant elastomeric material is a non-fluorinated elastomeric polymer.

[0147] In some embodiments, the non-highly chemically resistant elastomeric material is selected from the group consisting of ethylene propylene diene rubber (EPDM), polychloroprene (Neoprene), polyamide (Nylon), polyether ether ketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate (Sodium Benzenesulfonate), sodium 4-toluenesulfonate (Sodium Toluene Sulfonate), propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), EPDM polypropylene matrix elastomer (Santoprene), and combinations thereof.

[0148] In some embodiments, the perylene diimide compound has the formula (I):

[0149] (I) or a salt thereof, wherein:

[0150] T is -(L-G) n -X;

[0151] T' is H, (Ci-C6)alkyl, or -(L-G) n -X;

[0152] L is -(C2-C5)-alkyl, optionally substituted with OH, OCH3, halogen,

[0153]

[0154] each X is independently H, -(Ci-C 10 alkyl, -(C2-C6)alkenyl, -(C2-C6)alkynyl, and -(C2-C6)alkoxy, each of which is unsubstituted or substituted with 1, 2, or 3 independently selected R 1 groups;

[0155] each R 1 is independently -OH, -0(Ci-C6)-alkyl, -0(Ci-C6)-alkyl-0(Ci-C6)-alkyl, -0(Ci-C6)-alkyl-0(Ci-C6)-alkyl-0(Ci-C6)alkyl, -[0(Ci-C6)-alkyl] p -O(Ci-C6), -0(C=0)(Ci-C6)alkyl, -0(C=0)0(Ci-C6)alkyl, -0(C=0)OH, -0(C=0)NH2, -0(C=0)NH(Ci-C6)alkyl, 0(C=0)N[(Ci-C6)alkyl]2, -NH(C=0)(Ci-C6)alkyl, N(Ci-C6)alkyl(C=0)(Ci-C6)alkyl, halogen, -CN, -N02, NH2, NH(Ci-C6)alkyl, and N[(Ci-C6)alkyl]2;

[0156] n = 2 to 8; and

[0157] p = 3 to 20;

[0158] In some embodiments, the perylene diimide compound has formula (II):

[0159] (II)

[0160] wherein

[0161] each Y is independently -0-, -S-, or -NH-;

[0162] each q is independently 1 to 8; and

[0163] each X is independently H, -(Ci-C 10 alkyl, -(C2-C6)alkenyl, -(C2-C6)alkynyl, and -(C2-C6)alkoxy, each of which is unsubstituted or substituted with 1, 2, or 3 independently selected R 1 groups;

[0164] each R1 Independently, it can be -OH, -O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl-O(C1-C6)alkyl, or -[O(C1-C6)-alkyl] p -O(C1-C6), -O(C=O)(C1-C6)alkyl, -O(C=O)O(C1-C6)alkyl, -O(C=O)OH, -O(C=O)NH2, -O(C=O)NH(C1-C6)alkyl, O(C=O)N[(C1-C6)alkyl]2, -NH(C=O)(C1-C6)alkyl, N(C1-C6)alkyl(C=O)(C1-C6)alkyl, halogen, -CN, -NO2, NH2, NH(C1-C6)alkyl and N[(C1-C6)alkyl]2; and

[0165] Each V represents a balanced ion.

[0166] In some embodiments, the perylene diimide compound has formula (III):

[0167] (III)

[0168] in:

[0169] Each X is independently H, -(C1-C 10 -alkyl, -(C2-C6)alkenyl, -(C2-C6)ynyl, and -(C1-C6)alkoxy, each being unsubstituted or having one, two, or three independently selected R... 1 Group-substituted;

[0170] Each R 1 Independently, it can be -OH, -O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl-O(C1-C6)alkyl, or -[O(C1-C6)-alkyl] p -O(C1-C6), -O(C=O)(C1-C6)alkyl, -O(C=O)O(C1-C6)alkyl, -O(C=O)OH, -O(C=O)NH2, -O(C=O)NH(C1-C6)alkyl, O(C=O)N[(C1-C6)alkyl]2, -NH(C=O)(C1-C6)alkyl, N(C1-C6)alkyl(C=O)(C1-C6)alkyl, halogen, -CN, -NO2, NH2, NH(C1-C6)alkyl and N[(C1-C6)alkyl]2;

[0171] Each s is independently 2 to 4;

[0172] each R is independently H, -CH2OH, -CH2CH2OH, -CH2CH2OCH2CH2OH, or -CH2CH2OCH2CH2O(C 1- 6) alkyl; and

[0173] each V - is a counterion.

[0174] In some embodiments, the perylene diimide compound has formula (IV):

[0175] (IV)

[0176] wherein

[0177] R is , or .

[0178] In some embodiments, the perylene diimide compound has formula (V):

[0179] (V) or a salt thereof, wherein

[0180] L is -(Ci-C6)-alkyl;

[0181] each G is ;

[0182] A is a cation; and

[0183] n = 1 to 5.

[0184] In some embodiments, the catholyte comprises a ferrocene compound.

[0185] In some embodiments, the ferrocene compound has a formula selected from the group consisting of:

[0186] ,

[0187] ,

[0188]

[0189]

[0190] ,

[0191] ,

[0192] ,

[0193] ,

[0194] ,

[0195] ,

[0196] ,and

[0197] .

[0198] In some embodiments, the ferrocene compound has formula (VI):

[0199]

[0200] in:

[0201] L is -(C1-C 10 -alkyl, -(C1-C6)-alkenyl, -(C1-C6)-ynyl, -(C1-C6)-alkyl-O(C1-C6)-alkyl, -(C1-C6)-alkyl-O-(C=O)-(C1-C6)alkyl, -(C1-C6)-alkyl-(C=O)-O-(C1-C6)alkyl, -(C1-C6)alkyl-NH-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-NR 2 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2 -(C1-C6)alkyl or -(C1-C6)alkyl 10 alkyl-aryl;

[0202] L' represents -H, -(C1-C 10 -alkyl, -(C1-C6)-alkenyl, -(C1-C6)-ynyl, -(C1-C6)-alkyl-O(C1-C6)-alkyl, -(C1-C6)-alkyl-O-(C=O)-(C1-C6)alkyl, -(C1-C6)-alkyl-(C=O)-O-(C1-C6)alkyl, -(C1-C6)alkyl-NH-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-NR 2 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2 -(C1-C6)alkyl or -(C1-C6)alkyl 10 )-alkyl-aryl;

[0203] G can choose from the following groups: ;

[0204] G is greater than or equal to 2;

[0205] A is Li, K, Na, or NH4; and

[0206] R 2 -(C1-C 10 )-alkyl, -(C1-C6)-alkenyl, -(C1-C6)-alkynyl, -(C1-C 10 )-alkyl-aryl, -aryl, or -(C=0)-(C1-C6)-alkyl.

[0207] Additional implementations and features naturally fall within the scope of the disclosed subject matter, and can be better understood by reference to the following description, taken in conjunction with the accompanying drawings. Further understanding can be facilitated by reference to the drawings, in which: BRIEF DESCRIPTION OF DRAWINGS

[0208] The description will be more fully understood with reference to the following figures, which are presented as exemplary embodiments of the application and should not be construed as a complete recitation of the scope of the application, wherein:

[0209] FIG. 1 illustrates a redox flow battery having components made from low cost materials, according to an embodiment of the application.

[0210] FIG. 2 illustrates a prototype of a redox flow battery, according to an embodiment of the application.

[0211] FIGS. 3A and 3B illustrate H-cell components and an assembled H-cell, according to an embodiment of the application.

[0212] FIG. 4A illustrates the capacity of H-cell cycle testing using nylon, according to an embodiment of the application.

[0213] FIG. 4B illustrates the capacity of H-cell cycle testing using 316 stainless steel, according to an embodiment of the application.

[0214] FIG. 5 illustrates a schematic of an H-cell cycle process, according to an embodiment of the application.

[0215] FIGS. 6A-6C illustrate HPLC results of EPDM in high state of charge exposure testing, according to an embodiment of the application.

[0216] FIG. 7 illustrates the coulombic efficiency of a 10 mAh flow cell, according to an embodiment of the application.

[0217] Figure 8A shows the capacity retention of a redox flow battery manufactured using a polypropylene flow frame in contact with the electrolyte solution according to an embodiment of the present invention after 14 days of cycling.

[0218] Figure 8B shows the coulombic efficiency of a redox flow battery manufactured using a polypropylene flow frame in contact with the electrolyte solution according to an embodiment of the present invention after 14 days of cycling.

[0219] Figure 9 illustrates the cycling of glutamic acid-PDI and dipropanesulfonate ferrocene according to one embodiment of the present invention.

[0220] Figure 10 illustrates the cycling of glutamic acid-PDI and glutamic acid-ferrocene according to one embodiment of the present invention. Detailed Implementation

[0221] Referring now to the accompanying drawings, a redox flow battery comprising low-cost and non-highly chemically resistant components and a mild electrolyte is described.

[0222] Vanadium redox flow batteries are robust systems due to the long lifespan of their electrolytes. However, the high system cost hinders their commercialization and adoption. These costs primarily stem from the cell components, as vanadium formulations are highly corrosive. Conventional vanadium redox flow batteries contain solutions dissolved in sulfuric acid (H2O) with a pH less than 1. + HSO4 - SO4 2- V in ions 2+ / V 3+ and VO 2+ / VO2 + Highly oxidizing electrolytes for ions. The highly acidic and corrosive environment of vanadium redox flow batteries necessitates polymer backbone fluorination to achieve high chemical resistance due to the higher binding energy of the CF bond compared to the CH bond. Fluorinated materials can be very expensive in device components due to their complex synthesis leading to high material costs and difficulty in manufacturing. For example, polytetrafluoroethylene (PTFE), also known as Teflon, requires special processing techniques and is shaped into parts via compression molding and machining because this polymer cannot melt or flow.

[0223] Conventional vanadium redox flow batteries can require fluorinated elastomers (e.g., PTFE) as soft materials, isomolded graphite as bipolar plates, fluorinated Nafion membranes as ion exchange membranes, and fluorinated rubbers for cell fabrication. Due to poor manufacturability of these materials, such as lack of a melting point that enables injection molding or thermoforming, such fabrication is often difficult and time consuming. Replacing these highly chemically resistant materials with less expensive and easily manufactured plastics and rubbers would greatly increase the ability to high-throughput fabricate these cells to take advantage of the scalable architecture of decoupled power and energy. Attempts to replace pyrolized, high resistance graphite bipolar plates in vanadium systems with plastic-filled composites have shown rapid degradation of the parts and poor cell performance. (See, e.g., Liu, H.; et al., Corrosion behavior of a bipolar plate of carbon-polyethylene composite in a vanadium redox flow battery. RSC Advances 2015, 5 (8), 5928-5932; the disclosure of which is incorporated herein by reference.)

[0224] Organic molecules used as charge carriers can enable a range of organic solvents and / or aqueous solutions to be in a non-corrosive range at near neutral pH levels. However, due to the high instability of organic radicals, which are the species generated when storing charge in organic molecules, organic redox flow batteries have not shown long-term molecular stability. The instability of most organic radicals caused by chemical events that consume, quench, or degrade the active materials in the electrolyte are evidenced in the short time life of organic redox flow batteries. Chemical events include, but are not limited to, reactions of neutral or active charge carrying species with materials used to construct the device itself. Additionally, cell fabrication materials degrade through contact with electrolyte formulations, also leading to shortened life as the mechanical and chemical properties of the materials change, leading to brittleness, leaks, or other unsatisfactory performance. Radical species generated in organic redox flow batteries can be highly reactive radical reducing and oxidizing agents and can react with many functional groups present in less expensive and less chemically resistant materials, which can include olefins, esters, C-H bonds, and / or amides. Conventional vanadium redox flow batteries are assembled from: 1) highly chemically resistant materials, such as (but not limited to) fluorinated polymers, PTFE (Teflon), PVDF (Viton), Nafion, Kalrez, etc.; 2) non-reactive minerals, such as (but not limited to) glass, graphite, and carbon felt; 3) other chemically resistant materials and any coatings that increase chemical resistance; and 4) chemically resistant separators, such as fluorinated membranes.

[0225] Many embodiments provide electrolyte formulations for redox flow batteries that contain stable radicals. The stable radicals from the electrolyte formulations according to several embodiments cannot oxidize or reduce cell fabrication materials. In some embodiments, the electrolyte formulations can be dissolved in aqueous solutions with neutral pH (pH ranging from about 5.5 to about 8.5), which would allow the use of less expensive plastics as well as natural and synthetic rubbers that can be easily melt, injection molded, and processed on high-throughput equipment. Several embodiments can reduce the cost of cell fabrication by eliminating corrosive solvents and reactive radical species. Plastics (e.g., polyolefins such as polypropylene and polyethylene) can be synthesized from natural gas and petroleum. Many embodiments can reduce the cost of redox flow batteries by reducing the manufacturing and raw material costs through the use of non-highly-chemically-resistant materials for various components of the battery system.

[0226] Many embodiments provide long-duration and / or long-life redox flow batteries for energy storage applications. In some embodiments, water-soluble perylene diimide molecules or perylene diimide-based molecules can be used as energy storage materials. In operation, in the anode chamber, molecules containing a neutral perylene diimide core are reduced during charging to store energy, and then the reduced form can be oxidized during discharging to release energy. Correspondingly, in the cathode chamber, during charging, electrons can be released from the charge storage material during oxidation to store energy, and the charge storage material can then be reduced during discharging to release energy. Several embodiments employ ferrocene or ferrocene-based molecules as the cathode charge storage material. In many embodiments, the perylene diimide molecules, perylene diimide-based molecules, ferrocene molecules, and ferrocene-based molecules can be compatible with inexpensive and easily processed polymeric materials, thus allowing for the fabrication of less expensive redox flow batteries.

[0227] Anolyte solutions according to many embodiments can include water-soluble perylene diimide (PDI) molecules. The highly conjugated, electron-poor core of a PDI readily and reversibly reduces to accept two electrons. In several embodiments, perylene diimides with functionality at one or both imide nitrogen atoms can be synthesized from perylene tetracarboxylic dianhydride (PDI) by condensation with a primary amine. Organic, water-soluble, polymeric, and liquid crystalline perylene diimides have been developed in which the choice of functional groups on one or both nitrogen atoms are covalently bound to groups that can alter the properties of the perylene diimide. The inventors have found that while these molecular modifications can alter certain perylene diimide properties, these modifications do not significantly affect the charge storage stability of the perylene diimide. The electron and frontier molecular orbital density for the perylene diimide core is concentrated in the aromatic backbone, meaning that the redox properties of N-functionalized perylene diimides can be the same in terms of energy level, reversibility, and stability in solution regardless of how modified. Thus, this molecular modification does not affect charge storage stability.

[0228] In several embodiments, perylene diimide molecules used as anolytes can include a perylene diimide redox core covalently bound to a solubilizing group. In certain embodiments, the perylene diimide core can be solubilized by attachment of an ionic scaffold. Any common ionic group can be used to solubilize the perylene diimide core, including but not limited to ammonium ions, carboxylates, phosphonates, sulfonates, imidazoliums, pyridiniums, and thiazoliums. In various embodiments, one or both nitrogen atoms of the perylene diimide core can be covalently bound to a quaternized aminoalkyl group. In some embodiments, one or both nitrogen atoms of the perylene diimide core can be covalently bound to a carboxylate group.

[0229] In many embodiments, perylene diimide molecules can be highly stable in their charged and / or uncharged states. Perylene diimides according to several embodiments exhibit stability in their 2-electron reduced state when present in high concentrations in aqueous media. In some embodiments, perylene diimide molecules are compatible with both ion exchange and size exclusion membranes.

[0230] Many embodiments provide that the perylenediimide molecules are water soluble. In certain embodiments, the anolyte solution can comprise a perylenediimide compound dissolved in water without comprising an additional solvent. The perylenediimide compound can be dissolved in, but is not limited to, water, tap water, ground water, well water, filtered water, or deionized water. It can be readily appreciated that any of a variety of water sources can be suitably used in accordance with the requirements of a particular application in accordance with various embodiments of the present application. A filtration process can be performed prior to use to filter out any unwanted constituents. As can be readily appreciated, any of a variety of filtered waters and / or a variety of water filtration processes can be suitably used in accordance with the requirements of a particular application in accordance with various embodiments of the present application. In some embodiments, the anolyte solution can comprise a co- electrolyte including, but not limited to, NaCl, KC1, NH4C1, Na2S04, MgC12, or mixtures thereof. In certain embodiments, the anolyte solution can comprise a cosolvent to increase the solubility of the perylenediimide compound in the aqueous solution. Examples of cosolvents include, but are not limited to, methanol, propylene carbonate, and ethylene glycol.

[0231] The perylenediimide molecules in accordance with several embodiments can be chemically stable over a range of pH levels. In some embodiments, the anolyte solution can be prepared with an acidic, neutral, or basic aqueous medium. In various embodiments, the anolyte solution can be prepared at a neutral pH (pH of about 7) or a pH of about 6 to about 8; or a pH of about 6.5 to about 7.5. Several embodiments prepare the anolyte solution in a basic medium. In such embodiments, the pH of the anolyte solution can vary between about 7.5 to about 10. Many embodiments prepare the anolyte solution in an acidic medium, wherein the pH of the anolyte solution ranges from about 4 to about 6.5; or from about 5 to about 6.5.

[0232] In many embodiments, the catholyte solution can be prepared in an acidic, neutral, or basic medium. In several embodiments, the catholyte solution can be prepared at a neutral pH (pH of about 7); or a pH of about 6 to about 8; or a pH of about 6.5 to about 7.5. Some embodiments prepare the catholyte solution in a basic medium, wherein the pH of the catholyte solution is about 7.5 to about 10. In various embodiments, the catholyte solution can be prepared in an acidic medium, wherein the pH of the catholyte solution ranges from about 4 to about 6.5; or from about 5 to about 6.5.

[0233] In some embodiments, the pH of both the anolyte and catholyte solutions can be neutral or near neutral (pH range of about 5.5 to about 8.5). In several embodiments, the anolyte and catholyte solutions can be prepared using tap water.

[0234] In various embodiments, the perylene diimide compounds can have the structure of Formula (I) or salts thereof:

[0235] (I)

[0236] wherein:

[0237] T is -(L-G) n -X;

[0238] T' is H, C 1-6 alkyl or -(L-G) n -X;

[0239] L is -(C2-C5)-alkyl, optionally substituted with OH, OCH3, halogen;

[0240] ;

[0241] each X is independently H, -(C1-C 10 )alkyl, -(C2-C6)alkenyl, -(C2-C6)alkynyl, and -(C2-C6)alkoxy, each of which is unsubstituted or substituted with 1, 2, or 3 independently selected R 1 groups;

[0242] each R 1 is independently -OH, -0(C1-C6)-alkyl, -0(C1-C6)-alkyl-0(C1-C6)-alkyl, -0(C1-C6)-alkyl-0(C1-C6)-alkyl-0(C1-C6)alkyl, -[0(C1-C6)-alkyl] p -O(C1-C6), -0(C=0)(C1-C6)alkyl, -0(C=0)0(C1-C6)alkyl, -0(C=0)OH, -0(C=0)NH2, -0(C=0)NH(C1-C6)alkyl, 0(C=0)N[(C1-C6)alkyl]2, -NH(C=0)(C1-C6)alkyl, N(C1-C6)alkyl(C=0)(C1-C6)alkyl, halogen, -CN, -N02, NH2, NH(C1-C6)alkyl, and N[(C1-C6)alkyl]2;

[0243] n = 2 to 8; and

[0244] p = 3 to 20.

[0245] In the compounds of Formula (I), each L-G group of variable T can be the same or different. In some embodiments, if n is equal to 2, each L can be ethyl. In certain embodiments, a first L group can be ethyl and a second L group can be propyl. According to some embodiments, the G groups of variable T can be the same or different. In some embodiments, if n is equal to 2, each G group of L-G can be an ammonium group. In several embodiments, a first G group can be an ammonium group and a second G group can be a pyridine group.

[0246] In some embodiments, the perylene diimide molecules of Formula (I) are symmetrical (i.e., T = T'). In certain embodiments, the perylene diimide molecules are asymmetrical (i.e., T and T' are not equal).

[0247] In several embodiments, the perylene diimide molecules of Formula (I) each L of L-G is ethyl or propyl.

[0248] In some embodiments, the perylene diimide molecules are compounds of Formula (I) wherein n can be 2. In several embodiments, the perylene diimide molecules are compounds of Formula (I) wherein n can be 3. In certain embodiments, the perylene diimide molecules are compounds of Formula (I) wherein n can be 4.

[0249] In many embodiments, the perylene diimide molecules of Formula (I) wherein L can be unsubstituted -(C2-C5)-alkyl. In certain embodiments, L can be unsubstituted ethyl. In some embodiments, L can be unsubstituted propyl.

[0250] In some embodiments, the perylene diimide molecules of Formula (I) wherein G can be In several embodiments, each X can be H. In various embodiments, each X can be methyl. In certain embodiments, one X can be H and at least one other X can be methyl. In certain embodiments, at least one X can be -CH2CH2OH.

[0251] In some embodiments, the perylene diimide molecules of Formula (I) wherein each X can be independently H or -(C1-C6)-alkyl.

[0252] In many embodiments, the perylene diimide molecules of Formula (I) wherein at least one X can be -(C1-C6)-alkyl-OH. In some embodiments, at least one X can be -CH3CH2OH.

[0253] In many embodiments, the compounds of Formula (I) have the following structure:

[0254]

[0255] In some embodiments, the compound of formula (I) has the following structure:

[0256]

[0257] In some embodiments, the compound of formula (I) has the following structure:

[0258]

[0259] In several embodiments, the compound of formula (I) has the following structure:

[0260]

[0261] In many embodiments, the compound of formula (I) has the following structure:

[0262]

[0263] In some embodiments, the compound of formula (I) has the following structure:

[0264]

[0265] In several embodiments, the perylene diimide compound has the structure of formula (II):

[0266]

[0267] in:

[0268] Each Y is independently -O-, -S-, or -NH-;

[0269] Each q is independently 1 to 8;

[0270] Each X is independently H, -(C1-C 10 -alkyl, -(C2-C6)alkenyl, -(C2-C6)ynyl, and -(C1-C6)alkoxy, each of which is unsubstituted or represented by one, two, or three independently chosen R groups. 1 Group-substituted;

[0271] Each R 1 Independently, it can be -OH, -O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl-O(C1-C6)alkyl, or -[O(C1-C6)-alkyl] p-O(C1-C6), -0(C=0)(C1-C6)alkyl, -0(C=0)0(C1-C6)alkyl, -0(C=0)OH, -0(C=0)NH2, -0(C=0)NH(C1-C6)alkyl, 0(C=0)N[(C1-C6)alkyl]2, -NH(C=0)(C1-C6)alkyl, N(C1-C6)alkyl(C=0)(C1-C6)alkyl, halogen, -CN, -N02, NH2, NH(C1-C6)alkyl, and N[(C1-C6)alkyl]2;

[0272] each V is a counterion.

[0273] In some embodiments, the compound of formula (II) has the following structure:

[0274]

[0275] In various embodiments, the perylene diimide compound has the structure of formula (III):

[0276] (III)

[0277] wherein:

[0278] each X is independently H, -(C1-C 10 )alkyl, -(C2-C6)alkenyl, -(C2-C6)alkynyl, and -(C1-C6)alkoxy, each of which is unsubstituted or substituted with 1, 2, or 3 independently selected R 1 groups;

[0279] each R 1 is independently -OH, -0(C1-C6)-alkyl, -0(C1-C6)-alkyl-0(C1-C6)-alkyl, -0(C1-C6)-alkyl-0(C1-C6)-alkyl-0(C1-C6)alkyl, -[0(C1-C6)-alkyl] p -O(C1-C6), -0(C=0)(C1-C6)alkyl, -0(C=0)0(C1-C6)alkyl, -0(C=0)OH, -0(C=0)NH2, -0(C=0)NH(C1-C6)alkyl, 0(C=0)N[(C1-C6)alkyl]2, -NH(C=0)(C1-C6)alkyl, N(C1-C6)alkyl(C=0)(C1-C6)alkyl, halogen, -CN, -N02, NH2, NH(C1-C6)alkyl, and N[(C1-C6)alkyl]2;

[0280] each s is independently 2 to 4;

[0281] each R is independently H, -CH2OH, -CH2CH2OH, -CH2CH2OCH2CH2OH, or -CH2CH2OCH2CH2O(C 1- C6)alkyl; and

[0282] each V is a counterion.

[0283] In several embodiments, the compound of formula (III) has the structure:

[0284]

[0285] In some embodiments, the compound of formula (III) has the structure:

[0286]

[0287] In certain embodiments, the perylene diimide compound has the structure of formula (IV):

[0288] (IV)

[0289] In some embodiments, the compound of formula (IV) has the structure:

[0290] .

[0291] In some embodiments, the perylene diimide compound has the structure of formula (V) or a salt thereof:

[0292] (V)

[0293] wherein:

[0294] each L is independently -(Ci-C6)-alkyl, optionally substituted with OH, OCH3, and halogen;

[0295] each G can be independently selected from ;

[0296] A is a cation; and

[0297] n = 1 to 5.

[0298] In certain embodiments, A in formula (V) can be lithium, sodium, potassium, or ammonium.

[0299] In some embodiments, G in formula (V) can be .

[0300] In several embodiments, L in formula (V) can be propyl.

[0301] In certain embodiments, n in formula (V) can be 2.

[0302] In certain embodiments, L-G n The group can have one or more chiral centers. If so, the resulting compound of Formula (V) can have several stereoisomers. In some embodiments, the compound can be a single stereoisomer. In other embodiments, the compound can be a mixture of two or more stereoisomers in any proportion. The mixture can include each stereoisomer of the compound, or the mixture can not include one or more stereoisomers. If chirality is not indicated at a stereocenter, the compound can consist of any mixture of stereoisomers.

[0303] In many embodiments, the compound of Formula (V) can be:

[0304] .

[0305] In certain embodiments, the compound of Formula (V) can be:

[0306]

[0307] In certain embodiments, the compound of Formula (V) can be:

[0308]

[0309] In certain embodiments, the compound of Formula (V) can be any mixture of the following stereoisomers:

[0310]

[0311] In certain embodiments, the compound of Formula (V) can be:

[0312]

[0313] A redox flow battery according to many embodiments can include a catholyte solution in the cathode chamber. In some embodiments, the catholyte solution comprises a water-soluble redox active organic molecule. In certain embodiments, the redox active component of the catholyte can include, but is not limited to, TEMPO, ferrocyanide, iodine, or other catholyte materials.

[0314] In some embodiments, the redox active component of the catholyte solution is a water-soluble ferrocene-based compound. In certain embodiments, the ferrocene core can be solubilized by attachment of an ionic scaffold. In several embodiments, the scaffold can contain an ammonium ion. In various embodiments, the scaffold can contain a carboxylate ion. In some embodiments, the scaffold can contain a sulfonate ion. Any common ionic group can be used to solubilize the ferrocene core, including, but not limited to, carboxylate, phosphonate, sulfonate, imidazolium, pyridinium, and thiazolium.

[0315] In various embodiments, the ferrocene-based molecule has one of the following structures:

[0316]

[0317]

[0318]

[0319]

[0320]

[0321]

[0322]

[0323]

[0324] In some embodiments, the ferrocene compound has the structure of Formula (VI):

[0325] (VI)

[0326] wherein:

[0327] L is -(C1-C 10 )-alkyl, -(C1-C6)-alkenyl, -(C1-C6)-alkynyl, -(C1-C6)-alkyl-O(C1-C6)-alkyl, -(C1-C6)-alkyl-O-(C=O)-(C1-C6)alkyl, -(C1-C6)-alkyl-(C=O)-O-(C1-C6)alkyl, -(C1-C6)alkyl-NH-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-NR 2 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2-(C1-C6)alkyl, -(C1-C6)alkenyl, -(C1-C6)alkynyl, -(C1-C6)alkyl-O(C1-C6)alkyl, -(C1-C6)alkyl-O-(C=O)-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-O-(C1-C6)alkyl, -(C1-C6)alkyl-NH-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-NR 10 -alkyl-aryl, each optionally substituted with one, two or more G, -OH, -OCH3, -halogen;

[0328] L' is -H, -(C1-C 10 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2 -(C1-C6)alkyl, -(C1-C 10 -alkyl-aryl, each optionally substituted with one, two or more G, -OH, -OCH3, -halogen;

[0329] Each G can be independently selected from :

[0330] The number of G is greater than or equal to 2;

[0331] A is Li, K, Na or NH4; and

[0332] R 2 is -(C1-C 10 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 10 -alkyl-aryl, -aryl or -(C=O)-(C1-C6)-alkyl, and can be optionally substituted with one or more G.

[0333] In certain embodiments, L-G n groups can have one or more chiral centers. If this is the case, the resulting compound of formula (VI) can have several stereoisomers. In some embodiments, the compound can be a single stereoisomer. In other embodiments, the compound can be a mixture of two or more stereoisomers in any proportion. The mixture can include each stereoisomer of the compound, or the mixture can exclude one or more stereoisomers. If chirality is not indicated at a stereocenter, the compound can consist of any mixture of stereoisomers.

[0334] In certain embodiments, the compound of formula (VI) can be:

[0335]

[0336] In certain embodiments, the compound of formula (VI) can be:

[0337]

[0338] In certain embodiments, the compound of formula (VI) can be:

[0339]

[0340] In certain embodiments, the compound of formula (VI) can be any mixture of the following stereoisomers:

[0341]

[0342] In certain embodiments, the compound of formula (VI) can be:

[0343]

[0344] In certain embodiments, the anolyte and / or catholyte solution can contain a co- electrolyte. In several embodiments, a co-electrolyte can not be necessary in the anolyte and / or catholyte solution. Any co-electrolyte including, but not limited to, inorganic salts and organic salts can be used. Representative inorganic salts include, but are not limited to, NaCl, KC1, LiCl, NaBr, KBr, LiBr, Nal, KI, Lil, MgCl2, CaCl2, MgBr2, CaBr2, MgI2, and CaI2, NH4CI, NH4Br, and NH4I. Representative organic salts include, but are not limited to, alkylammonium chlorides, alkylammonium bromides, alkylammonium iodides, sodium toluenesulfonate, and sodium benzenesulfonate. In some embodiments, the solution can also contain a co-solvent including, but not limited to, sulfolane or propylene carbonate.

[0345] Many embodiments provide a redox flow battery comprising the aqueous anolyte and catholyte solutions described above. The anolyte and catholyte solutions can be pumped through a conduit into a half-cell unit where they undergo an electrochemical reaction. The anolyte and catholyte solutions are cycled through the half-cell unit in repeated charge and discharge cycles. The materials used to make the battery need to be compatible with the anolyte and catholyte solutions to ensure long life of the battery. Redox flow batteries made from common materials according to several embodiments can be manufactured at low cost without compromising the life of the battery. In certain embodiments, the materials can be manufactured using techniques including, but not limited to, a melt process, a thermoforming process, injection molding, blow molding, extrusion, additive manufacturing, or 3D printing. In several embodiments, the materials used to make the battery comprise non-fluorinated polymers designated as non-highly chemically resistant. In some embodiments, the materials used to make the battery can be made from commonly occurring hydrocarbon plastics and rubbers. In multiple embodiments, the materials used to make the battery can be polyethers (e.g., PEEK or POM), polynitriles (e.g., ABS or BUNA-N), polyolefins (e.g., EPDM or santoprene rubber or neoprene rubber), or latex or ABS, polyhalides (e.g., PVC), polyureas (e.g., polyurethanes), polycarbonates (e.g., polycarbonates), amides (e.g., nylons), and polyaromatics (e.g., polystyrene or BUNA-S).

[0346] In some embodiments, at least one of the materials used to make the battery is polyethylene. In several embodiments, at least one of the materials used to make the battery is polypropylene. In certain embodiments, at least one of the materials used to make the battery is polycarbonate. In several embodiments, at least one of the materials used to make the battery is propylene carbonate. In many embodiments, at least one of the materials used to make the battery is polyoxomethylene. In some embodiments, at least one of the materials used to make the battery is EPDM. In various embodiments, at least one of the materials used to make the battery is polyurethane. In several embodiments, at least one of the materials used to make the battery is nylon. In some embodiments, at least one of the materials used to make the battery is PVC. In certain embodiments, at least one of the materials used to make the battery is latex or natural latex rubber. In several embodiments, at least one of the materials used to make the battery is gutta-percha rubber. In various embodiments, at least one of the materials used to make the battery is santoprene rubber or santoprene. In several embodiments, at least one of the materials used to make the battery is PMMA. In some embodiments, at least one of the materials used to make the battery is Neoprene. In certain embodiments, at least one of the materials used to make the battery is PEEK. In several embodiments, at least one of the materials used to make the battery is sodium benzenesulfonate. In some embodiments, at least one of the materials used to make the battery is sodium toluenesulfonate. In various embodiments, at least one of the materials used to make the battery is BUNA-N.

[0347] The polymers can contain additional additives such as plasticizers, colorants, fillers, and stabilizers that are embedded in the material to adjust properties. For example, common additives in polyethylene and PVC can include phthalates and adipates. The perylene diimide anode electrolytes according to many embodiments are compatible with common plasticizers, colorants, fillers.

[0348] Redox flow battery

[0349] A unit cell of a redox flow battery can include two half-cells. One of the two half-cells can be a cathode half-cell, and the other can be an anode half-cell. A catholyte (or catholyte) can be pumped into the cathode half-cell, and an anolyte (or anolyte) can be pumped into the anode half-cell. The cathode and anode half-cells can be connected with a membrane for ion transport. The half-cells of the battery include various components, including but not limited to electrodes, gaskets, flow plates, bipolar plates, and membranes. According to several embodiments, any or all of the components of the half-cells can be made from non-fluorinated polymers that are not specified as highly chemically resistant. In many embodiments, the redox flow battery can include at least one unit cell; or at least 2 unit cells; or at least 5 unit cells; or at least 10 unit cells; or at least 15 unit cells; or at least 20 unit cells; or at least 25 unit cells; or at least 30 unit cells; or at least 50 unit cells; or at least 100 unit cells; or at least 150 unit cells.

[0350] In many embodiments, a redox flow battery can include a first half-cell comprising an anolyte solution and a second half-cell comprising a catholyte solution, wherein the anolyte solution includes water-soluble perylene diimide molecules, and wherein one or more battery components (e.g., electrodes, gaskets, liquid flow frames, bipolar plates, membranes) are made from materials that are not specified as highly chemically resistant. The redox flow battery cell can be constructed from at least one hard material for liquid flow frames, hard tubing connections, and electrolyte reservoirs; at least one soft material for seals and hoses; and a hard conductive material for flow fields, conductive porous electrodes, and membranes. In some embodiments, the battery components can be made from non-fluorinated polymers. In several embodiments, the non-fluorinated polymers can be polyolefins, polyethers, polyketones, polyamides, polyureas, natural rubbers, or combinations thereof.

[0351] The flow frame of a redox flow battery is the reaction vessel where charging and discharging occurs. The flow frame contains a porous electrode and is exposed to the active electrolyte as it flows. In certain embodiments, the reaction vessel (flow frame) that defines the interior of a half-cell of a battery can be made of at least one non-fluorinated polymer. Examples of non-fluorinated polymers that can be used to make the flow frame include, but are not limited to, polyethylene, polypropylene, PMP, polybutene-1, PVC, polystyrene, PMMA, ABS, nylon, POM, polycarbonate, nylon, PEEK, or combinations thereof. In some embodiments, the reaction vessel can be made of a copolymer derived from two or more of the above-mentioned polymers. In various embodiments, the flow frame can be made of titanium. In various embodiments, the flow frame can be made of a metal alloy comprising titanium. In several embodiments, the flow frame can be made of stainless steel.

[0352] The bipolar plate of a redox flow battery is in direct contact with the electrolyte solution and collects the current while separating the cell units within the battery stack. The bipolar plate should exhibit high chemical and mechanical stability, high electrical conductivity, and impermeability to prevent leakage. Vanadium redox flow batteries conventionally use isostatic graphite bipolar plates because they have good chemical stability in addition to electrical conductivity. However, isostatic graphite plates are expensive to process and are prone to cracking and leaking due to the fact that graphite is brittle and has high porosity. The perylenediimide anolyte electrolyte according to some embodiments allows for the use of carbon-polymer composites or graphite-resin blends to make the bipolar plates. In certain embodiments, the bipolar plates in the anolyte half-cell, or the bipolar plates in both the anolyte half-cell and the catholyte half-cell, can be made of extruded graphite. In several embodiments, the bipolar plates in the half-cell containing the anolyte, or the bipolar plates in both the anolyte half-cell and the catholyte half-cell, can be made of a graphite / polymer composite. The graphite / polymer composite can be injection molded or bulk molded. In certain embodiments, the graphite / polymer composite is a resin-filled graphite. In various embodiments, the polymer of the graphite / polymer composite is polyethylene or polypropylene.

[0353] The gasket is a rubber seal placed between each layer of a half-cell (e.g., between the flow frame and the bipolar plate). In many embodiments, the gasket in contact with the electrolyte solution in the anolyte half-cell, or in both the anolyte half-cell and the catholyte half-cell, can comprise a non-fluorinated elastomeric material. In some embodiments, the non-fluorinated elastomeric material can be a non-highly-chemically-resistant rubber material including, but not limited to, EPDM, santoprene, neoprene, BUNA-S, BUNA-N, latex, trans-polyisoprene, PUR, and polyurethane.

[0354] The membrane in a redox flow battery separates the anode side and the cathode side. The membrane should prevent the crossover of active species of each half-cell and should have high ionic conductivity, low area resistance, and good chemical stability. In several embodiments, the membrane can be an ion exchange membrane or a size exclusion membrane. In some embodiments, the membrane can be made from a non-fluorinated polymer. In various embodiments, the membrane can be made from a hydrocarbon polymer including, but not limited to, polyethylene, polypropylene, polystyrene. These hydrocarbon membranes include non-fluorinated charge conducting groups including, but not limited to, aminated polystyrene, sulfonated polystyrene, and sulfonated polyether ketone.

[0355] In many embodiments, the membrane frame of a redox flow battery can be made from a non-fluorinated polymer. In several embodiments, the membrane frame can be made from a non-fluorinated polymer including, but not limited to, polyethylene, polypropylene, PMP, polybutene-1, PVC, polystyrene, PMMA, ABS, nylon, POM, polycarbonate, PEEK, or combinations thereof. In some embodiments, the membrane frame can be made from a copolymer derived from two or more of the above-mentioned polymers.

[0356] A redox flow battery can include supply lines and / or pipes external to the anode and cathode that supply electrolyte to the battery and carry electrolyte back to storage tanks. In several embodiments, the supply lines of a redox flow battery can be manufactured from a non-highly chemically resistant material. In certain embodiments, the supply lines can be constructed from a non-fluorinated polymer. In some embodiments, the supply lines can be made from a non-fluorinated elastomeric material. In various embodiments, the non-fluorinated elastomeric material can be a non-highly chemically resistant rubber material including, but not limited to, EPDM, santoprene, neoprene, BUNA-S, BUNA-N, latex, trans-polyisoprene, PUR, and polyurethane.

[0357] A redox flow battery can include supply manifolds and electrolyte storage tanks to supply electrolyte. In many embodiments, the supply manifolds and / or electrolyte storage tanks can be made from at least one non-fluorinated polymer. Examples of non-fluorinated polymers that can be used to manufacture the flow frame include, but are not limited to, polyethylene, polypropylene, PMP, polybutene-1, PVC, polystyrene, PMMA, ABS, nylon, POM, polycarbonate, nylon, PEEK, or combinations thereof. In some embodiments, the supply manifolds and / or electrolyte storage tanks can be made from a copolymer derived from two or more of the above-mentioned polymers.

[0358] In redox flow batteries, the number of cells (cell stack) can determine the power output (watts) of the system, while the electrolyte can be contained in tanks, the size of which can determine the energy (watt-hours). This engineering separation of power and energy can be an advantage that makes redox flow batteries easy to scale up. FIG. 1 shows a schematic of a redox flow battery cell with non-highly chemically resistant materials, according to an embodiment. The redox flow battery cell is connected to a catholyte tank and an anolyte tank. The flow battery cell contains a bipolar plate 101, a flow frame 102, a porous electrode 103, a membrane and membrane frame 104, and a gasket (sealing layer) 105. Electrolyte (anolyte or catholyte) solution can flow through flow inlets in the charge-collecting plate (in a single cell) or bipolar plate (in a cell stack). The plate can be engraved with flow fields that help distribute the electrolyte as it diffuses into the carbon felt electrode. The electrode is contained within a non-conductive flow frame 102. The flow frame 102 can be a chamber in which the electrolyte can be charged and discharged. The flow frame 102 is separated from the other half of the cell by an ionically conductive membrane 104 that allows charged ions to pass through but retains electrolyte molecules. The electrolyte is then allowed to diffuse out of the electrode and exit from flow outlets 107 on the opposite side of the charge-collecting plate or bipolar plate 101. The two half-cells can be pressed into contact with each layer sealed by a gasket 105 that prevents leaks.

[0359] In a conventional vanadium redox flow battery, the bipolar plate can be made of isostatic graphite; the flow frame can be made of PTFE; the porous electrode can be made of carbon felt; the membrane can be made of Nafion TM ; the membrane frame can be made of PTFE; and the gasket (sealing layer) can be made of Viton rubber.

[0360] A redox flow battery according to many embodiments employs perylene diimide-based molecules for charge storage in the anolyte, such that the cell can be made with non-fluorinated and low-cost materials. In several embodiments, the bipolar plate 101 can be made of resin-filled graphite composites; the flow frame 102 can be made of polypropylene; the porous electrode can be made of carbon felt; the membrane 104 can be made of Selemion TMThe gaskets 105 can be made of Santoprene. Polypropylene is a ubiquitous melt-formable thermoplastic. Polypropylene is inexpensive, can be produced in large quantities, and has a higher hardness than polyethylene. In certain embodiments, the backsheet, flow frame, hose connection, and / or electrolyte reservoir can be constructed of polypropylene. Santoprene is a thermoplastic vulcanizate that contains EPDM rubber encapsulated in a polypropylene matrix. The addition of polypropylene in this material lowers the cost compared to pure EPDM, and also enables Santoprene to be melted and worked like a thermoplastic. Santoprene is commonly used as a component of seals, hoses, and flexible connections. According to some embodiments, Santoprene can be used for seals and flexible tubing. Impregnated graphite is less expensive than pyrolytic grade required for corrosive vanadium redox flow batteries. Selemion TM AMVN can be used as an ion exchange membrane. Selemion TM AMVN is a water desalination membrane that is stable in mild and pH neutral electrolytes. These materials significantly reduce the cost of each of these components. Many embodiments show that the cost associated with manufacturing the components of a redox flow battery is significantly lower than the manufacturing cost of a redox flow battery made with conventional vanadium redox flow battery materials.

[0361] Figure 2 shows the parts of a redox flow battery cell and the assembled redox flow battery cell according to an embodiment of the present application. The end plates (a) can be made of aluminum, bolted together, and provide a sealing pressure to the cell as a press. The cell backsheet (b) can be composed of polypropylene and serves as an insulating layer between the charge collection plate and the metal press, while also providing a surface to connect the fluid inlet and outlet (via polypropylene barb connectors). Between this layer and the charge collection plate is a flat Santoprene seal (c). Due to the corrosive nature of the cell media, the seal in conventional vanadium systems is made of a fluorinated elastomer (such as PFA or Viton). Many embodiments use an inexpensive Santoprene seal in the redox flow battery. The charge collection plate (d) is engraved with flow fields and drilled with inlet and outlet holes for supply. Resin impregnated graphite can be used for the bipolar plate or charge collection plate. Resin impregnated graphite is liquid tight and is less expensive than high grade isopressed graphite, where the resin would be degraded by the acidic electrolyte. The charge collection plate is separated from the flow frame by another Santoprene gasket (e). The flow frame can be composed of polypropylene and has voids in which carbon felt electrodes (g) are placed. These components make up one half of the cell, which is separated from the other half by a membrane (h). Selemion TMAMVN, a polystyrene-based film, can be used as the film. The second half of the cell is a mirror image of the first half, and the configuration of the cell is shown in FIG. 2. The total cell area (1 inch circle) can be about 5 cm 2 ; or less than about 5 cm 2 ; or greater than about 5 cm 2 ; about 5 cm 2 to about 100 cm 2 ; greater than about 100 cm 2 ; about 100 cm 2 to about 500 cm 2 ; about 500 cm 2 to about 1500 cm 2 ; greater than about 1500 cm 2 . All tubing of the cell supplied via centrifugal pumps can be made of a polymer, including but not limited to PVC, and the electrolyte supply reservoirs can be made of plastic, polymer, or glass.

[0362] Redox flow battery performance

[0363] The perylene diimides disclosed herein provide stability to long-life redox flow batteries. The ferrocenes disclosed herein provide stability to long-life redox flow batteries. As used herein, the term “long-life” refers to a battery having a stable capacity retention over repeated charge cycles or over time. In some embodiments, the redox flow battery can have a lifetime of at least 5 years; or at least 10 years; or at least 20 years; or at least 50 years; or a lifetime of 5 to 50 years; or a lifetime of 5 to 50 years; or a lifetime of 20 to 50 years.

[0364] Coulombic efficiency is a direct measure of molecular stability in organic flow batteries. Coulombic efficiency is the ratio of the number of electrons released from the battery to the number of electrons input. For example, if a battery releases 99 electrons out of 100 electrons charged into the device in a given cycle, its coulombic efficiency is 99%. This can be a direct measure of molecular stability in organic flow batteries. Electrons can be lost in various ways besides molecular breakdown, such as through solution leakage from the battery cell or cross-permeation of active species across the membrane. However, molecular breakdown manifests as a loss of coulombic efficiency. While not all losses of coulombic efficiency are due to molecular breakdown, they do lead to a decrease in efficiency. If leakage is the cause of the loss, the molecule may be more stable than the coulombic efficiency suggests. On the other hand, the molecule's stability may not be lower than the coulombic efficiency suggests. Any molecular breakdown will result in a decrease in coulombic efficiency. An example of such breakdown can be when organic free radicals on a charged molecule are quenched by a destructive chemical event, such as dimerization of two free radicals and the formation of permanent bonds or solvent attack. A coulombic efficiency indicating a 500-year lifespan may have molecular stability of 750 years, but may not have molecular stability of less than 500 years as indicated by the coulombic efficiency.

[0365] In many embodiments, the redox flow battery comprising a stable and water-soluble perylene diimide anode electrolyte and a stable and water-soluble ferrocene exhibits high coulombic efficiency at neutral pH (pH about 7) or near-neutral pH levels (pH about 6 to about 8; or pH about 5.5 to about 8.5). In several embodiments, the coulombic efficiency of the redox flow battery can be at least 98% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles. In some embodiments, the coulombic efficiency can be at least 98.5% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles. In some embodiments, the coulombic efficiency is at least 99% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles. In several embodiments, the coulombic efficiency is at least 99.5% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles. In some embodiments, the coulombic efficiency is at least 99.6% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles. In some embodiments, the coulombic efficiency is at least 99.7% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles. In many embodiments, the coulombic efficiency is at least 99.9% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles. In some embodiments, the coulombic efficiency is about 100% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles. In several embodiments, the coulombic efficiency is from about 98.5% to about 99.5% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles. In some embodiments, the coulombic efficiency is from about 99% to about 99.5% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles. In several embodiments, the coulombic efficiency is about 99.5% to about 99.9% after at least about 200 charge / discharge cycles; or after at least 380 charge / discharge cycles.

[0366] The high coulombic efficiency of redox flow batteries according to many embodiments results in long lifetimes for the charge storage species within the battery. In some embodiments, the half-life of the species in the battery (i.e., the time required for the battery to lose half of its charge storage capacity due to molecular degradation) can be greater than about 10 years. In some embodiments, the half-life of the charge storage material used in the redox flow battery can be greater than about 20 years. In some embodiments, the half-life of the charge storage material used in the redox flow battery can be greater than about 50 years. In some embodiments, the half-life of the charge storage material used in the redox flow battery can be greater than about 70 years. In some embodiments, the half-life of the charge storage material used in the redox flow battery can be greater than about 100 years. In various embodiments, the half-life of the charge storage material used in the redox flow battery can be greater than about 200 years. In many embodiments, the half-life of the charge storage material used in the redox flow battery can be greater than about 500 years. In some embodiments, the half-life of the charge storage material used in the redox flow battery can be greater than about 1,000 years. In several embodiments, the half-life of the charge storage material for the redox flow battery can be greater than about 2,000 years. In some embodiments, the half-life of the charge storage material for the redox flow battery can be greater than about 3,000 years. In some embodiments, the half-life of the storage material of the redox flow battery of this disclosure can be greater than about 5,000 years. In many embodiments, the half-life of the charge storage material for the redox flow battery is about 50 years to about 100 years. In some embodiments, the half-life of the charge storage material for the redox flow battery is about 100 years to about 500 years. In various embodiments, the half-life of the charge storage material for the redox flow battery is about 500 years to about 1,000 years. In some embodiments, the half-life of the charge storage material for the redox flow battery is about 1,000 years to about 2,000 years. In several embodiments, the half-life of the charge storage material for the redox flow battery is about 2,000 years to about 3,000 years. In some embodiments, the half-life of the charge storage material used in the redox flow battery is from about 2,000 years to about 5,000 years.

[0367] The performance of a redox flow battery can be measured by its capacity retention. A sufficient battery life is ensured if the redox flow battery loses minimal charge storage capacity during multiple charge / discharge cycles. Redox flow batteries according to many embodiments lose negligible charge storage capacity over multiple charge / discharge cycles. In some embodiments, the redox flow battery loses less than about 2% of its charge storage capacity after about 300 full charge / discharge cycles; or after about 380 full charge / discharge cycles. In several embodiments, the redox flow battery loses less than about 1% of its charge storage capacity after about 300 full charge / discharge cycles; or after about 380 full charge / discharge cycles. In some embodiments, the redox flow battery loses less than about 0.5% of its charge storage capacity after about 300 full charge / discharge cycles; or after about 380 full charge / discharge cycles. In various embodiments, after approximately 300 full charge / discharge cycles; or after approximately 380 full charge / discharge cycles, the redox flow battery loses less than approximately 0.25% of its charge storage capacity. In several embodiments, after approximately 300 full charge / discharge cycles; or after approximately 380 full charge / discharge cycles, the redox flow battery loses less than approximately 0.1% of its charge storage capacity. In some embodiments, after approximately 300 full charge / discharge cycles; or after approximately 380 full charge / discharge cycles, the redox flow battery loses less than approximately 0.05% of its charge storage capacity. In several embodiments, after approximately 300 full charge / discharge cycles; or after approximately 380 full charge / discharge cycles, the redox flow battery loses less than approximately 0.03% of its charge storage capacity. In some embodiments, after approximately 300 full charge / discharge cycles; or after approximately 380 full charge / discharge cycles, the redox flow battery loses less than approximately 0.01% of its charge storage capacity. In some embodiments, after about 300 full charge / discharge cycles; or after about 380 full charge / discharge cycles, the redox flow battery loses about 0.05% to about 0.1% of its charge storage capacity. In several embodiments, after about 300 full charge / discharge cycles; or after about 380 full charge / discharge cycles, the redox flow battery loses about 0.03% to about 0.1% of its charge storage capacity. In some embodiments, after about 300 full charge / discharge cycles; or after about 380 full charge / discharge cycles, the redox flow battery loses about 0.01% to about 0.05% of its charge storage capacity.

[0368] Many embodiments demonstrate that redox flow batteries lose very little charge storage capacity during operation. In some embodiments, the redox flow battery loses less than about 2% of its charge storage capacity per year. In several embodiments, the redox flow battery loses less than about 1% of its charge storage capacity per year. In some embodiments, the redox flow battery loses less than about 0.5% of its charge storage capacity per year. In some embodiments, the redox flow battery loses less than about 0.25% of its charge storage capacity per year. In some embodiments, the redox flow battery loses less than about 0.1% of its charge storage capacity per year. In several embodiments, the redox flow battery loses less than about 0.05% of its charge storage capacity per year. In some embodiments, the redox flow battery loses less than about 0.03% of its charge storage capacity per year. In some embodiments, the redox flow battery loses less than about 0.01% of its charge storage capacity per year. In various embodiments, the redox flow battery loses about 0.05% to about 0.1% of its charge storage capacity per year. In some embodiments, the redox flow battery loses approximately 0.03% to approximately 1% of its charge storage capacity per year. In various embodiments, the redox flow battery loses approximately 0.01% to approximately 0.05% of its charge storage capacity per year.

[0369] Exemplary Implementation

[0370] The following embodiments are provided to provide a complete disclosure and description of how to prepare and use the invention to those skilled in the art, and are not intended to limit the scope of what the inventors consider to be their invention, nor to represent that the following experiments are all or only the experiments performed. Efforts have been made to ensure the accuracy of the figures used (e.g., quantities, temperatures, etc.), but some experimental errors and biases should be taken into account.

[0371] Example 1 : Non-highly chemically resistant materials

[0372] Many embodiments utilize readily available and common plastic and rubber materials manufactured in redox flow batteries. Due to the mild operating conditions of the battery (e.g., neutral electrolyte solution and non-corrosive redox molecules), a variety of plastics, rubbers, and small molecules are compatible with redox flow batteries. Examples of plastics compatible with redox flow batteries include (but are not limited to) nylon, PEEK, POM, PVC, PE, PMMA, and PP. Plastic materials according to some embodiments can be used to construct wetting parts, such as flow frames, supply manifolds, and electrolyte reservoirs. Examples of flexible materials (rubbers and elastomers) include (but are not limited to) EPDM, Neoprene, silicone, BUNA-N, latex, PUR, and Santoprene. Flexible materials according to several embodiments can be used for seals, piping, and other components of the battery system requiring flexibility. Examples of metals include (but are not limited to) 316 stainless steel, 6061 aluminum, Hastelloy, and Grade 2 titanium. Some embodiments provide small molecules compatible with redox flow batteries, including (but not limited to) sodium benzenesulfonate, sodium toluenesulfonate, propylene carbonate, and sulfolane. Stability tests can be performed by adding small molecules to electrolyte solutions at concentrations many times higher than those of charge-carrying molecules. These small molecules represent functional groups of interest in high-concentration stress tests to verify that the electrolyte does not interact with certain types of structures. Sodium benzenesulfonate (in the form of an aromatic sulfonate salt) represents grafting onto Selemion. TM Functional groups on the polystyrene backbone of the AMVN anion exchange membrane. Adding sodium benzenesulfonate in total excess can determine whether aryl sulfonates present in or leached from the anion exchange membrane have inherent stability issues. Sodium toluenesulfonate, with an added structural motif of benzyl carbon (methyl group), is used as a water-soluble stability test at this position, and can undergo radical-promoted reactions under certain conditions. Propylene carbonate and sulfolane are non-volatile solvents with viscosity-reducing properties. The chemical structure of the material is shown in Table 1. The stability of the material in H-type battery cell cycling tests and high SOC exposure tests is described below.

[0373] Table 1. Chemical structure and chemical formula of non-high chemical resistance materials.

[0374]

[0375]

[0376] Example 2. H-cell experiments with non-highly chemically resistant materials

[0377] Many implementations employ redox flow battery cells including (but not limited to) H-type battery cells, testing the compatibility of the electrolyte solution in both charged and uncharged states with the battery cell manufacturing materials by exposing the materials to the materials within a membrane-transferred glass H-type battery cell. The battery cell manufacturing materials are placed within a half-cell of the H-type battery cell for compatibility analysis. This static battery cell experimental setup allows for precise measurement of coulombic efficiency to analyze the electrochemical and physical compatibility of the charged electrolyte solution with the battery cell manufacturing materials. High coulombic efficiency indicates that electrons entering the organic charge storage electrolyte during charging return during discharge, meaning that the electrolyte, although in a charged state, does not undergo electrochemical or physical reactions with the battery cell manufacturing materials to quench the charge. Furthermore, this static battery cell experiment allows for sampling of the H-type battery cell by removing small samples over time for high-performance liquid chromatography analysis. This analysis reveals new molecular species generated by the reaction of the charged electrolyte with various materials within the battery cell. The absence or slow generation of new molecular species indicates compatibility.

[0378] A glass H-type battery cell with a theoretical capacity of 1 mAh can be used for material stability testing. Figure 3A shows the various components of the H-type battery cell. Figure 3B shows the assembled H-type battery cell. The H-type battery cell includes two glass chambers, a metal clamp, a membrane, two carbon felt electrodes connected to a battery circulator via platinum wire, two PTFE stir bar, two Viton O-rings, and two spacer caps. To assemble the H-type battery cell, the two glass chambers are connected and held in place by the metal clamp, with the membrane secured between the two halves to separate the sides. One side is the anode half, and the other side is the cathode half. The membrane can be sealed with two Viton O-rings (one on each side of the membrane). A PTFE-coated stir bar can be placed in each glass chamber of the H-type battery cell. A thin platinum wire can be inserted through the spacer cap to connect an external load to the carbon felt electrode, which is secured to the end of the wire by the spacer cap. A spacer cap can then be placed at the anode and cathode. An empty H-type battery cell without electrodes can be assembled outside a glove box. Empty H-type cell units can be purged and backfilled in a nitrogen atmosphere at least three times in the anteroom before being transferred to a glove box. Felt electrodes can be attached to platinum wires at the anode and cathode, and the cell units are filled with deoxygenated anolyte and cathode electrolyte solutions.

[0379] The anolyte and cathode electrolyte solutions are used as the electrolytes at the anode and cathode, respectively, in an H-type battery cell. According to many embodiments, the anolyte can be perylene diimide (PDI) and / or any perylene diimide. According to several embodiments, the cathode electrolyte can be ferrocene and / or any ferrocene derivative. For H-type battery cell testing, some embodiments use PDI-tetraammonium-Cl4 in the anolyte half-cell and ferrocene-diammonium-Cl2 in the cathode half-cell. As will be readily understood, according to various embodiments of the invention, any form of PDI derivative can be used in the anolyte, and any form of ferrocene derivative can be used in the cathode electrolyte, provided it is suitable for the requirements of the specific application. The electrolytes can be dissolved in about 1M sodium chloride for electrochemical stability testing. The molar number of anolyte and cathode electrolyte molecules present can be controlled to achieve a desired capacity of 1 mAh. During charge-discharge cycles, each molecule of PDI-tetraammonium-Cl4 accepts and provides two electrons, while each molecule of ferrocene-diammonium-Cl2 accepts and provides only one electron. Therefore, the molar concentration of PDI-tetraammonium-Cl4 in the H-cell is half the molar concentration of ferrocene-diammonium-Cl2. TM Anion exchange membranes (AMVNs) can be used in H-cell cells. TM AMVN is a polystyrene-based ion-exchange membrane. In cycling tests, the materials used to construct the H-type battery cells (e.g., glass, Viton, PTFE, platinum, and carbon) did not show any adverse interactions with the electrolyte.

[0380] For compatibility testing of H-cell cells, approximately 7 mL of anolyte and catholyte are provided on the anode and cathode sides, respectively. After the H-cell cell is equipped with rod electrodes and filled with electrolyte in the glove box, it can be connected to the battery testing system. Before cycling, the H-cell cell can be placed on a magnetic stirrer. The operating temperature of the H-cell cell is approximately 30°C to approximately 38°C. The capacity of the H-cell cell may vary slightly between different tests and depends on the electrolyte refresh rate (or the rotation speed of the stir bar), electrode position, and operating temperature.

[0381] The H-type battery cell testing method includes constant current and constant voltage schemes. The H-type battery cell can first be left to rest for approximately 10 seconds, then charged at a constant current of approximately 0.25 mA (corresponding to a charging rate of approximately 0.25C). Once the voltage reaches approximately 1V, it is left to rest for another 30 seconds. Next, a constant voltage of approximately 1V can be applied for charging until the charging current drops to approximately 0.05 mA (corresponding to a charging rate of approximately 0.05C). Afterward, the H-type battery cell can be fully charged and left to rest at its open-circuit voltage for approximately 30 seconds. A two-step current discharge method can also be used. The H-type battery cell is discharged at a constant current of approximately 0.25 mA until its voltage drops to approximately 0.1V, and then discharged at a lower rate until the discharge current is below approximately 0.05 mA. When the first charge-discharge cycle is completed, the same test scheme can be continuously applied to subsequent cycles.

[0382] After establishing a baseline for several cycles, the charge-discharge cycle test is paused. The two spacer caps are opened, and a small piece of material is placed into each of the two chambers of the H-type battery cell. The spacer caps are then returned to their original positions. The charge-discharge cycle test of the H-type battery cell can then resume. Cyclic testing can continue for at least two weeks. During the test, coulombic efficiency and capacity are monitored. Depending on the implementation, if a coulombic efficiency higher than 99.9% cannot be maintained, the material is considered incompatible with the electrolyte.

[0383] H-cell cycle tests according to many embodiments demonstrated compatibility of various materials during several-cycle battery runs, with an average coulombic efficiency exceeding approximately 99.9%. This material compatibility provides a wide range of feasible options for structural components of the battery system. Examples of compatible rigid materials include, but are not limited to, nylon, PEEK, POM, PVC, PE, PMMA, and PP. Compatible materials enable the realization of low-cost redox flow batteries that are easy to manufacture. Materials including, but not limited to, nylon, PE, and PP can be provided as 3D printing filaments, which will enable rapid prototyping of components such as liquid supply manifolds and flow frames. Examples of compatible soft materials include, but are not limited to, EPDM, Neoprene, BUNA-N, natural latex rubber, PUR, and Santoprene. Soft materials can be used for flexible parts of redox flow batteries, including, but not limited to, tubing and seals. However, according to many embodiments, not all tested materials are compatible with redox flow batteries. In some embodiments, silicone exhibited a coulombic efficiency of approximately 99.89% during H-cell cell testing. The coulombic efficiency of silicones in redox flow batteries is less than the desired 99.9%, making it possible that silicones may not be stable enough to provide the expected lifetime of at least 20 years. Examples of compatible small molecules include (but are not limited to) sodium benzenesulfonate, sodium toluenesulfonate, propylene carbonate, and sulfolane. The stability of sodium benzenesulfonate and sodium toluenesulfonate indicates that Selemion... TM The aryl sulfonic acid in the AMVN membrane has no negative impact on the stability of the cycled battery. Furthermore, the stability of sodium toluenesulfonate indicates the stability of the benzylmethyl group, which is commonly used as a motif. Cosolvents can be added to the electrolyte formulation to improve solution properties such as viscosity, solubility, and volatility. Examples of compatible cosolvents include (but are not limited to) propylene carbonate and sulfolane. The compatibility of propylene carbonate with redox flow batteries generally indicates the overall compatibility of the carbonate portion and means that polycarbonate plastics and other carbonate-containing molecules can be stable. Some implementations show that metals (e.g., 316 stainless steel and 6061 aluminum) may be insufficient for the wetting portion of redox flow batteries. These alloys contain various transition metals and elements that can be electrochemically oxidized and reduced. Once the battery is charged, electrons may migrate from redox molecules in the electrolyte to these metallic materials and lead to degradation. Several embodiments may use compatible plastic or rubber materials, including (but not limited to) nylon, PEEK, POM, PVC, PE, PMMA, PP, EPDM, Neoprene, BUNA-N, latex, Santoprene, polyurethane, and any combination thereof, to coat any metallic material used in redox flow batteries.

[0384] Figure 4A shows the cycle test results of an H-type battery cell using nylon according to an embodiment of the present invention. Figure 4A shows that the H-type battery cell using nylon has a coulombic efficiency of approximately 99.95% after approximately 19.9 days of cycling. With an average coulombic efficiency of approximately 99.95% over approximately 20 days, the discharge capacity (orange line) and charge capacity (blue line) are uniform in each cycle after the addition of nylon to the battery cell. As shown in Figure 4A, the capacity of the battery cell remains flat, indicating that there is no detectable nylon degradation under the operating conditions of a redox flow battery.

[0385] Figure 4B shows the cycle test results of an H-type battery cell using 316 stainless steel according to an embodiment of the present invention. Figure 4B shows that the H-type battery cell using 316 stainless steel has a coulombic efficiency of approximately 99.32% after approximately 12.9 days of cycling. The coulombic efficiency of the steel test is approximately 99.32%, and the capacity decreases significantly. The capacity loss of 316 stainless steel in the redox flow battery shown in Figure 4B may be due to discharge into the steel, chemical reactions between the electrolyte and the steel, and / or adsorption of active species into the steel. When the battery capacity decreases to below 99.9% efficiency, the redox flow battery in contact with the electrolyte solution may become less stable.

[0386] The results of H-cell cycle tests on the exemplary materials are summarized in Table 2. If the coulombic efficiency is equal to or greater than approximately 99.9% after at least 14 days of H-cell testing, the material is considered stable. If the coulombic efficiency is less than approximately 99.9% after at least 14 days of H-cell testing, the material is considered unstable.

[0387] Table 2. Cyclic test results of H-type battery cells.

[0388]

[0389] Example 3. High-charge state exposure test

[0390] For materials that pass the H-cell cycle test, a high SOC exposure test can be performed to test compatibility with a fully charged electrolyte over an extended period. For the high SOC test, the H-cell can be charged to 100% state of charge. The cycle can then be stopped, and the fully charged anolyte and catholyte can be transferred to separate vials. An additional vial containing approximately 1.0 M NaCl aqueous solution can be used as a reference. A small piece of material can be placed in each of these three vials, in significant excess (by mass) compared to the electrolyte molecules present in solution. Small samples can be collected from these three vials and periodically analyzed by HPLC to monitor chemical changes caused by the exposure of charged species to the test material. The NaCl control can be used to monitor the leaching of any components from the material into the brine, as these components may continue to interact with the electrolyte. Furthermore, both electrolytes exhibit color changes upon discharge, providing a rapid, qualitative measurement of stability. The high SOC test does not require a battery cycler, leaving a cycler channel for H-cell experiments and parallel workflows. Figure 5 illustrates the process of testing a combined H-type battery cell with high SOC exposure for a given material.

[0391] The stability and therefore practicality of each material that showed positive results in the H-type battery cell cycling test (Table 2) can be further explored using high SOC exposure tests. These tests are performed by storing the test material in contact with a charged electrolyte for a duration of approximately 133 days. The test results indicate that the timescale of interactions may be longer than that of the initial cycling test. Any interactions detrimental to battery life, such as chemical reactions between electrolyte molecules and the material, or chemical reactions between electrolyte molecules and leachates or decomposition products dissolved from the material into the solution, will necessarily result in the presence of new chemical species in the solution that will be detected by HPLC. Furthermore, even harmless precipitates and decomposition products of materials in contact with brine are readily detectable. If no new chemical products are detected in the anolyte or catholyte solution, and no significant leachings or decomposition products are observed in the brine control experiment, it can be concluded that no chemical decomposition occurred during the test time of contact with the material. During the high SOC test, a small amount of electrolyte, approximately 15 mg, is present in hundreds of milligrams of the test material (e.g., plastics and / or rubber).

[0392] High SOC testing can be performed concurrently with H-cell testing. For example, polystyrene and polycarbonate can be tested by charging the H-cell to 100% SOC and dispensing the electrolyte into vials for placing and storing the materials. Table 3 summarizes the results of high SOC exposure tests using PDI-tetraammonium-Cl4 (PDI-XL-2), ferrocene-diammonium-Cl2 (Fc-XL-2), and NaCl controls. Materials that showed compatibility in H-cell testing also showed positive results in exposure testing. Furthermore, no species exceeding the noise level was detected by leaching from the materials into pure brine.

[0393] Table 3. Results of high SOC exposure tests.

[0394]

[0395] * Indicates materials tested after charging to 100% without extending the cycle time.

[0396] All test materials were subjected to HPLC analysis. Figures 6A to 6C show the HPLC results of high SOC exposure tests over time for PDI-tetraammonium-Cl4, ferrocene-diammonium-Cl2, and NaCl controls after exposure to EPDM rubber and subsequent settling, according to one embodiment of the present invention. Figure 6A shows the HPLC results of high SOC exposure tests over time for PDI-tetraammonium-Cl4 in contact with EPDM rubber. Figure 6B shows the HPLC results of high SOC exposure tests over time for ferrocene-diammonium-Cl2 in contact with EPDM rubber. Figure 6C shows the HPLC results of high SOC exposure tests over time for NaCl in contact with EPDM rubber. Since the samples were diluted to a concentration suitable for HPLC, the total peak absorbance may introduce some variations; therefore, the chromatograms were normalized to the maximum peak height of the sample with the strongest absorbance at the detection wavelength. Since minute variations in temperature and concentration subtly affect retention time, time normalization was also performed to align the maximum values ​​of the product peaks for PDI-tetraammonium-Cl4 and ferrocene-diammonium-Cl2. To more directly compare the concentrations of any extracts and electrolyte molecules in the brine blank control, brine data were presented on the same scale as ferrocene-diammonium-Cl2 data. All chromatograms were performed on a C-18 reversed-phase column, and elution conditions for PDI-tetraammonium-Cl4 and ferrocene-diammonium-Cl2 were developed separately. For the brine control experiments, the method used for ferrocene-diammonium-Cl2 was employed. Some HPLC spectra contained solvent front artifacts, which appeared as peaks with short retention times and randomly varying intensities. These signals are a result of changes in the UV absorption of the carrier solvent at injection time and do not correspond to any chemical species present in the analyte.

[0397] For PDI-tetraammonium-Cl4, the HPLC chromatogram remained unchanged after prolonged exposure to EPDM (approximately 19 weeks). The small peak 601, visible at approximately 1.8 minutes, is the injected solvent front and, unlike genuine impurities or decomposition products, its intensity varies randomly between samples rather than increasing over time. The broad peak and tailing shape are typical characteristics of PDI molecules and are attributed to aggregation in solution.

[0398] Following exposure to EPDM, positive results were also obtained for ferrocene-diammonium-Cl2. The earliest elution peak (similar to the earliest elution peak of PDI-tetraammonium-Cl4) is the solvent front of the injection and varies considerably between samples, independent of concentration or time. Uncharged ferrocene-diammonium-Cl2 in brine also exhibits this peak at 602. This is likely due to the solvent front elution of the column and trace products in brine. NaCl mixed with polar ferrocene-diammonium-Cl2 initially eluted very rapidly on the reversed-phase column. After the NaCl was washed away and co-eluted with some ferrocene-diammonium-Cl2, the remaining ferrocene-diammonium-Cl2 remained on the column and eluted as a single peak at approximately 8 minutes. A small, sharp visible signal was also observed at approximately 18 minutes. This signal did not increase over time and was also observed in brine not exposed to any test material, indicating that it is a systematic artifact present in the HPLC column and all samples. Since this peak appears in the absence of ferrocene-diammonium-Cl2, it is not a decomposition product. It can be seen that no new product is formed.

[0399] Example 4. Redox flow battery cell performance

[0400] The compatible materials used to construct the redox flow battery showed no signs of degradation, and the flow battery cell exhibited an average coulombic efficiency of approximately 100% after approximately 20 days of testing. According to several embodiments, the electrolyte supply reservoir of the flow battery cell can be filled with PDI-tetraammonium-Cl4 and ferrocene-diammonium-Cl2, respectively, as the anode and cathode electrolytes. The flow rate can be set to approximately 10 mL / min, and the battery can be cycled similarly to the stability test of an H-type battery cell.

[0401] Figure 7 illustrates cycling data from a 10mAh flow battery cell according to one embodiment of the invention. Initially, inconsistent pumping caused a slight delay in data collection, but after equilibration, electrolyte supply was maintained and cycling testing began. The flow battery cell cycled for approximately 20 days and approximately 380 cycles. This long-term cycling test in Figure 7 shows a coulombic efficiency above 99.9%. The average coulombic efficiency is approximately 100%.

[0402] Example 5: Batteries made from non-highly chemically resistant materials

[0403] A flow battery cell was constructed, comprising two non-porous resin-filled graphite bipolar plates in contact with graphite felt, separated by a Fumasep FAPQ anion exchange membrane. The chambers containing the electrodes and graphite felt were constructed of polypropylene, with these layers sealed with Santoprene rubber (polypropylene / EPDM elastomer). Inlets and outlets were drilled into the graphite plates to allow electrolyte solution to flow into and out of the two chambers separated by the membrane. The rigid fixtures and tubing were constructed of polypropylene, while the tubing for delivering the electrolyte was made of Santoprene rubber. Fluid flow was supplied by a peristaltic pump that compressed the Santoprene rubber tubing. The electrolytes were each dissolved at 0.5 M in 5 mL of a 1.0 M NaCl aqueous solution and stored in a glass tank. The chemical structures of the anolyte (PDI-tetraammonium-Cl4) and catholyte (ferrocene-diammonium-Cl2) molecules are shown below. The solution was pumped through the flow battery cell at a rate sufficient for charging and discharging. The battery cell was continuously charged and discharged for 14 days, exhibiting a 97% capacity retention and a 99.99% total coulombic efficiency, as shown in Figures 8A and 8B, respectively. This example demonstrates the stability of the electrolyte solution in contact with these non-highly chemically resistant materials.

[0404]

[0405] Example 6: Compatibility of perylene diimide molecules in two electron reduction states with non-highly chemically resistant materials

[0406] In a battery similar to that of Example 5, the anolyte was brought to a high state of charge on one side of a glass H-type cell equipped with a carbon felt electrode and a platinum current collector. The anolyte solution was separated from the cathode electrolyte by a Selemion ion-exchange membrane. After charging, the anolyte material was removed from the electrochemical cell, and aliquots of the solution were placed in glass sample vials and contacted with samples of different materials such that the total mass of each material was much greater than the total mass of the charged electrolyte molecules in the sample. Under high charge, the anolyte was deep purple, while the uncharged anolyte was bright red. This color difference provided a direct way to determine the relative state of charge of any anolyte solution. After five months of contact, the anolyte samples in contact with polypropylene, polyurethane, polyethylene, and Santoprene rubber, as well as the control sample containing only the anolyte solution, all remained purple, indicating that free radical species were not quenched or incompletely quenched, and confirming the stability of the anolyte solutions in contact with these materials.

[0407] Example 7: HPLC experiments to assess chemical stability

[0408] In this embodiment, the compatibility of the battery materials was evaluated using high-performance liquid chromatography (HPLC). After contact in a neutral or charged state, the chromatographic traces of the electrolyte solution indicated minimal or no degradation of the material into the solvent, and minimal or no degradation of the electrolyte into new chemical species. The tested materials included: ABS, BUNA-N, EPDM, latex, Neoprene, nylon, polyethylene, PEEK, polycarbonate, polypropylene, polystyrene, POM, polyurethane, PVC, Santoprene, silicone, and titanium. A summary of material compatibility is shown in Table 3.

[0409] HPLC testing was performed using a similar procedure. An exemplary immersion experiment was conducted by separately mixing anolyte and catholyte solutions containing neutral pH water, NaCl auxiliary electrolyte, and their respective PDI-tetraammonium-Cl4 and ferrocene-diammonium-Cl2 solutions. A portion of these solutions was placed in a separate vial, and approximately 50 mg of the test material was introduced into each vial. An additional 1 mAh portion of these solutions was placed in an H-type battery cell with a Selemion AMV membrane and fully charged. Once charged, the anolyte and catholyte solutions were placed in separate vials, and approximately 50 mg of the test material was introduced into each vial. A control solution of neutral pH water and NaCl was placed in a separate vial, and approximately 50 mg of the test material was added to each vial. The solutions were stored in an airless glove box, and samples were taken weekly. Aliquots from all vials were injected into the HPLC instrument for purity analysis to confirm the chemical compatibility of the test material with the charged anolyte and catholyte solutions, the neutral anolyte and catholyte solutions, and the control solution. Chromatographic trace amounts of ferrocene and perylene diimide were recorded after 14 weeks of exposure for analysis.

[0410] Small molecule testing. Sodium benzenesulfonate is in the form of an aromatic sodium sulfonate salt, representing grafting to Selemion. TM Functional groups on the polystyrene backbone of the AMVN membrane. Adding sodium benzenesulfonate in total excess will allow us to determine whether there are inherent stability issues in the presence of aryl sulfonates in or from our membrane. Sodium toluenesulfonate has an added structural motif of benzyl carbon (methyl group) and is used as a water solubility test for stability at this position; sodium toluenesulfonate is known to undergo radical-promoted reactions under certain conditions. Propylene carbonate and sulfolane are non-volatile solvents with viscosity-reducing properties.

[0411] Example 8: Synthesis of water-soluble perylene diimide redox-active compounds

[0412] The synthetic procedure for obtaining perylene diimide is described below.

[0413]

[0414] PTCDA (2.35 g, 6 mmol) was suspended in dimethylacetamide (20 mL) and stirred. N,N-dimethyldipropyltriamine (1.96 g, 2.22 mL, 12.3 mmol) was added and the solution was heated to 120 °C. The solution was maintained at 120 °C for 12 hours and then cooled to ambient temperature. The reactants were poured into EtOAc (100 mL) and stirred vigorously. The precipitated solid was collected by filtration, washed with EtOAc, and dried under high vacuum to give the product as a deep purple / red solid (2.5 g, 3.7 mmol, 62%). 1H NMR: (CDCl3, 300 MHz) δ 1.67 (tt, J = 7.1 Hz, 7.1 Hz, 4H), 1.97 (tt, J= 6.8 Hz, 6.8 Hz, 4H), 2.21 (s, 12H), 2.32 (t, J = 7.4 Hz, 4H), 2.71 (dt, J =18.2 Hz, 7 Hz, 8H), 4.23 (t, J = 6.8 Hz, 4H), 8.13 (d, J = 7.2 Hz, 4H), 8.35 (d, J = 7.8 Hz, 4H).

[0415]

[0416] Tetramine PDI (1.35 g, 2 mmol) and potassium carbonate (0.829 g, 6 mmol) were suspended in methanol (20 mL). Methyl toluenesulfonate (4.47 g, 3.62 mL, 24 mmol) was added, and the reaction mixture was heated to 55 °C overnight. The reaction mixture was cooled to ambient temperature, diluted with methanol (20 mL), and filtered to remove the white solid. The filtrate was concentrated and dried by rotary evaporator and dissolved in a minimal amount of methanol. Acetone was added, precipitating a red solid from the solution. The solid was separated by filtration and dried under vacuum at 55 °C to give a dark red solid (2.05 g, 1.41 mmol, 71%). 1H NMR: (D2O, 300 MHz) δ 2.17(s, 12H, OTs-), 2.43 – 2.25 (m, 8H), 3.14 (s, 18H), 3.22 (s, 12H), 3.38 (m,4H), 3.47 (m, 4H), 3.62 (m, 4H), 4.12 (m, 4H), 7.29 – 7.10 (bs, 4H), 7.17 (d,J = 8.2 Hz, 8H, OTs-), 7.51 (d, J = 8.2 Hz, 8H, OTs-), 7.69 (bs, 4H).

[0417]

[0418] Tetraammonium toluenesulfonate (PDI) (2.90 g, 2 mmol) was dissolved in concentrated HCl (20 mL). The resulting mixture was heated to 85 °C for 24 hours. The reaction mixture was cooled to ambient temperature and diluted with isopropanol (60 mL) with vigorous stirring. The precipitate solution was collected by filtration, washed with isopropanol, and dried under vacuum at 70 °C to give the product as a red / black solid (1.6 g, 1.77 mmol, 88%). ¹H NMR: (D₂O, 300 MHz) δ 2.71 – 2.12 (bm, 8H), 3.90 – 2.99 (bm, 42H), 4.21 (bs, 4H), 8.39 – 6.96 (bm, 8H).

[0419]

[0420] Glutamic acid and PTCDA were suspended in DMSO. Potassium tribasic phosphate was added with stirring, and the solution was heated to 120°C. The reaction mixture was stirred for 18 hours and then cooled to ambient temperature. 1M HCl was added, and the precipitated solid was filtered to give the product as a purple / black solid (100%, based on recovered starting material).

[0421]

[0422] Aspartic acid (2.93 g, 22 mmol) and PTCDA (3.92 g, 10 mmol) were suspended in ethylene glycol. Potassium tribasic phosphate (9.9 g, 46 mmol) was added, and the resulting solution was heated to 140 °C for 12 hours. The reaction mixture was cooled to ambient temperature and poured into 1 M HCl (aq) (50 mL). The precipitate was collected by filtration, washed with water, and dried under vacuum at 55 °C to give the product as a purple solid (1.914 g, 3.07 mmol, 31%). ¹H NMR: (D₆-DMSO, 300 MHz) δ 2.85 (dd, J = 16.6 Hz, 4.5 Hz, 2H), 3.42 (m, 2H), 6.08 – 6.01 (m, 2H), 8.43 – 7.67 (bm, 8H).

[0423] Example 9: Synthesis of water-soluble ferrocenyl redox-active compounds

[0424]

[0425] 4-Chlorobutylferrocene

[0426] Ferrocene (50 g, 269 mmol, 1.1 equivalents) was added to a 3 L, 3-necked round-bottom flask equipped with a stir bar, a feeding funnel, and a gas outlet leading to a bubbler filled with a saturated NaHCO3 aqueous solution. The apparatus was purged with dry nitrogen. Dichloromethane (600 mL) was added and stirred to dissolve the ferrocene. The mixture was cooled to 0 °C in an ice-water bath. In a separate round-bottom flask equipped with a stir bar, aluminum chloride (35.9 g, 269 mmol, 1.1 equivalents) was added and the flask was purged with dry nitrogen. Dichloromethane (600 mL) was added and stirred to suspend the aluminum chloride. 4-Chlorobutyryl chloride (34.4 g, 245.5 mmol, 1.0 equivalents) was added dropwise to the aluminum chloride suspension and stirred until the aluminum chloride stopped dissolving. The undissolved aluminum chloride from the acid-chloride mixture was decanted into the feeding funnel of the reaction apparatus. The solution was slowly added to the ferrocene solution in the reaction vessel at 0°C, taking care not to heat the mixture above 10°C. The mixture was then stirred for 3 hours while the bath was slowly warmed to ambient temperature. The vessel was then cooled back to 0°C. In a separate flask, sodium borohydride (18.5 g, 489 mmol, 2.0 equivalent) was combined with diethylene glycol dimethyl ether (70 mL) and dichloromethane (20 mL) under a nitrogen atmosphere. This mixture was transferred to the feeding funnel of the reaction vessel and added dropwise to the reaction mixture. The reaction mixture was stirred at ambient temperature for 18 hours. The reaction was quenched at 0°C by adding 1 M ammonium chloride aqueous solution (100 mL), followed by water (100 mL) and saturated potassium sodium tartrate aqueous solution (400 mL). After the gas escape ceased, the organic layer was collected, and the aqueous layer was extracted with dichloromethane (washed 3 times, 100 mL each time) to remove the solvent from the combined organic layers. The resulting liquid was dissolved in 500 mL of hexane. The hexane layer was washed with water (8 washes, 200 mL each) to remove diethylene glycol dimethyl ether and dried by shaking with a saturated aqueous sodium chloride solution. The organic layer was further dried over solid magnesium sulfate (100 g), filtered, and the solvent was removed to give the desired product as an orange oil (60 g, 88%). ¹H NMR (300 MHz, chloroform-d) δ(ppm) 4.11 (overlap, 9H), 3.58 (t, J = 7.0 Hz, 2H), 2.40 (t, J = 7.8 Hz, 2H), 1.84 (dt, J = 6.8, 7.8, 2H), 1.71 (dt, J = 6.8, 7.0, 2H).

[0427]

[0428] N-[3-(dimethylamino)propyl]-N,N-dimethylferrocenebutyryl ammonium chloride

[0429] 4-Chloroprene (75 g, 276.6 mmol, 1.0 equivalent), N,N,N',N'-tetramethyl-1,3-propanediamine (105 g, 814 mmol, 3 equivalent), and acetonitrile (500 mL) were combined in a round-bottom flask and heated to 60 °C for 12 hours. The mixture was cooled and washed with hexane (5 washes, 150 mL each), retaining the acetonitrile layer. The combined hexane layer was evaporated to give an orange liquid, to which N,N,N',N'-tetramethyl-1,3-propanediamine (50 g, 388 mmol, 1.43 equivalent) and acetonitrile (250 mL) were added in a round-bottom flask, and the mixture was heated to 60 °C for 12 hours. After cooling, the acetonitrile solution was washed with hexane (5 washes, 150 mL each), and the acetonitrile layer was combined with the retained layer from the previous step. The solvent was removed from the merged layers to obtain an orange oil, which was ultrasonically ground with ether (200 mL). The ether was decanted, and the volatiles were further removed under vacuum to give a very viscous orange oil (97 g, 88%). ¹H NMR (300 MHz, chloroform-d) δ (ppm): 4.08 (overlap, 9H), 3.53 (overlap, 4H), 3.40 (s, 6H), 2.44 (t, J = 7.9, 2H), 2.36 (t, J = 6.0, 2H), 2.19 (s, 6H), 1.83 (m, 2H), 1.70 (m, 2H), 1.58 (m, 2H).

[0430]

[0431] N,N,N,N2,N2-Pentamethyl-N2-ferrocene-butyl-1,3-propanediammonium dichloride

[0432] N-[3-(dimethylamino)propyl]]-N,N-dimethylferrocene butyryl ammonium chloride (97 g, 238 mmol, 1.0 equivalent) was dissolved in methanol (1000 mL). Iodomethane (101 g, 715.3 mmol, 3.0 equivalent) was slowly added via syringe, and the mixture was stirred at ambient temperature for 12 hours. The solvent and unreacted iodomethane were removed under reduced pressure, and the residue was dissolved in water (200 mL) and stirred with Amberlite IRA-400 ion exchange resin beads (200 cm3) for 1 hour. The resin was then filtered off, and the solution was passed through an Amberlite IRA-400 ion exchange resin bead column (500 cm3) using water as the eluent. Water was removed from the resulting solution to give a very viscous orange oil that crystallized upon standing (94.4 g, 87%). ¹H NMR (300 MHz, heavy water) δ (ppm) 4.20 (overlapping 9H), 3.34 (overlapping, 6H), 3.16 (s, 9H), 3.09 (s, 6H), 2.42 (t, J = 7.0, 2H), 2.27 (m, 2H), 1.76 (m, 2H), 1.55 (m, 2H).

[0433]

[0434] 1,1'-Bis(3-chloropropyl)ferrocene

[0435] Add ferrocene (10.0 g, 53.4 mmol, 1.00 equivalent) to a 1 L three-necked round-bottom flask equipped with a stir bar, a feeding funnel, a reflux condenser, and a gas outlet leading to a bubbler filled with a saturated NaHCO3 aqueous solution. Purge the apparatus with dry nitrogen. Add dichloromethane (100 mL) and stir to dissolve the ferrocene. Cool the mixture to 0 °C in an ice-water bath. In a separate round-bottom flask equipped with a stir bar, add aluminum trichloride (18.0 g, 134 mmol, 2.50 equivalent) and purge the flask with dry nitrogen. Add dichloromethane (100 mL) and stir to suspend the aluminum trichloride. Add 3-chloropropionyl chloride (17.0 g, 134 mmol, 2.50 equivalent) dropwise to the aluminum trichloride suspension and stir until the aluminum trichloride stops dissolving. Undissolved aluminum trichloride from the acid-chloride mixture was decanted into the feeding funnel of the reaction apparatus. This solution was slowly added to the ferrocene solution in the reaction vessel at 0°C, taking care not to heat the mixture above 10°C. The mixture was then heated under reflux for 16 hours. The vessel was cooled back to 0°C. In a separate flask, sodium borohydride (8.00 g, 214 mmol, 4.00 equivalents) was combined with diethylene glycol dimethyl ether (40 mL) and dichloromethane (20 mL) under a nitrogen atmosphere. This mixture was transferred to the feeding funnel of the reaction vessel and added dropwise to the reaction mixture. The reaction mixture was stirred at ambient temperature for 18 hours. The reaction was quenched at 0°C by adding 1 M ammonium chloride aqueous solution (100 mL), followed by water (100 mL) and a saturated potassium sodium tartrate aqueous solution (100 mL). After the gas escape ceased, the organic layer was collected, and the aqueous layer was extracted with dichloromethane (washed 3 times, 50 mL each time). The solvent was removed from the combined organic layers, and the resulting liquid was dissolved in 200 mL of hexane. The hexane layer was washed with water (washed 8 times, 200 mL each time) to remove diethylene glycol dimethyl ether and dried by shaking with a saturated aqueous sodium chloride solution. The organic layer was further dried over solid magnesium sulfate (50 g), filtered, and the solvent was removed to give the desired product X as an orange oil (13 g, 72%). ¹H NMR (300 MHz, chloroform-d) δ(ppm) 4.10 (overlap, 8H), 3.58 (t, J = 6.2 Hz, 4H), 2.50 (t, J = 7.1 Hz, 4H), 1.98 (tt, J = 6.2 Hz, 7.1 Hz, 4H).

[0436]

[0437] Potassium 1,1'-bis(propyl-3-sulfonic acid)ferrocene

[0438] 1,1'-bis(3-chloropropyl)ferrocene (1.5 g, 4.4 mmol, 1.0 equivalent), potassium sulfite (8.4 g, 53 mmol, 12 equivalent), and water (100 mL) were added to a 250 mL round-bottom flask equipped with a condenser. The mixture was heated under reflux for 4 days, during which time the immiscible ferrocene starting material slowly disappeared as it was converted to the water-soluble product. The mixture was cooled and extracted with ethyl acetate (3 washes, 200 mL) to remove the starting material. Water was removed from the aqueous layer and methanol (100 mL) was added. The mixture was filtered, and methanol was removed by distillation. The resulting yellow solid was washed with a large amount of isopropanol to remove acetate. After drying, a yellow powdery product (1.2 g, 54%) was obtained. ¹H NMR (300 MHz, heavy water) δ (ppm) 4.06 (overlap, 8H), 2.84 (t, J = 7.8 Hz, 4H), 2.40 (t, J = 7.6 Hz, 4H), 1.98 (tt, J = 7.8 Hz, 7.6 Hz, 4H).

[0439]

[0440] Ferrocene butanecarboxylic acid (1.00 g, 3.67 mmol) and N-hydroxysuccinimide (0.423 g, 3.67 mmol) were dissolved in DCM (18.5 mL), and the resulting mixture was stirred at ambient temperature. EDC (0.733 g, 4.04 mmol) was added, and the mixture was stirred overnight at ambient temperature. Triethylamine (2.02 g, 2.78 mL, 20 mmol) was added to a solution of glutamic acid (1.08 g, 7.3 mmol) in isopropanol (10 mL). After the glutamic acid was dissolved, a crude solution of ferrocene N-hydroxysuccinimide activated ester was added to the glutamic acid mixture. The resulting mixture was stirred at ambient temperature for 12 hours, and then heated to 90 °C for 12 hours. The reaction mixture was quenched by adding 1 M NaOH and washed with ethyl acetate. The aqueous layer was acidified with 1 M HCl and extracted with ethyl acetate. The ethyl acetate layer was washed with 0.01 M NaOH, and the washings were discarded. The organic layers were then extracted with two portions of 0.1M NaOH. The aqueous extracts were combined, acidified with 1M HCl, and extracted with EtOAc. The organic extracts were washed with water and brine, dried over magnesium sulfate, filtered, and concentrated to give the product as a yellow solid (0.200 g, 0.5 mmol, 14%). 1HNMR: (d-DMSO, 300 MHz) δ 1.83 – 1.63 (m, 4H), 2.03 – 1.90 (m, 1H), 2.14 (t, J= 7.2 Hz, 2H), 2.32 – 2.23 (m, 4H), 4.05 – 4.01 (m, 1H), 4.08 (d, J = 1.3 Hz, 2H), 4.1 (s, 5H), 4.21 (dt, J = 8.5 Hz, 5.0 Hz, 1H), 8.08 (d, J = 7.5 Hz, 1H).

[0441]

[0442] Synthesis of N-(4-ferrocene-butyryl)-L-glutamic acid. 4-ferrocene-butyric acid (68.0 g, 250 mmol, 1.0 equivalent) was added to a 1 L round-bottom flask. A DCM (125 mL) and a stir bar were also added. Under positive pressure of N2 (g) and vigorous stirring, oxaloyl chloride (23.6 mL, 275 mmol, 23.6 mL, 1.20 equivalent) was slowly added dropwise, carefully allowing gas to escape. The dark brown solution was stirred at 25 °C until gas escape slowed (approximately 5 minutes). The reactants were then further heated to 40 °C and allowed to react for 1 hour. The solvent was removed by rotary evaporation.

[0443] A solution of L-glutamate monohydrate (143 g, 763 mmol, 3.05 equivalents), sodium hydroxide (30.0 g, 750 mol, 3.0 equivalents), and water (68 mL) was prepared at 100 °C. Once all solids were dissolved, the previously prepared ferrocene chloride was rapidly added to the stirred glutamate solution. During the addition of the acid chloride, the formation of a brown precipitate was observed. Approximately 50 mL of additional water was added to aid stirring of the reactants. The reactants were allowed to react at 100 °C for approximately 5 min. The reactants were cooled to room temperature and water was added to completely dissolve all solids. NaCl(s) was added to completely saturate the aqueous solution. The resulting aqueous solution was titrated to pH 5.8 with HCl (6 M). Impurities were extracted with MeCN (4 × 200 mL). The resulting aqueous layer was further titrated to pH 3 with HCl (6 M). The product was extracted from the aqueous layer using MeCN until the resulting aqueous layer was blue (3 × approximately 200 mL). Add approximately 200 mL of silica and approximately 200 mL of anhydrous sodium sulfate to the acetonitrile solution. Stir the acetonitrile slurry at room temperature for 30 minutes. Filter the slurry through a porous glass filter and collect the acetonitrile solution. Concentrate the dark red solution by rotary evaporation. Further concentrate the resulting dark red oily substance under vacuum to give a dark yellow-brown solid (53.8 g, 113 mmol, 45% yield, 84% purity).

[0444]

[0445] Synthesis of N-butyryl-4-ferrocene-iminodiacetic acid. Ferrocene butyric acid (10 g, 0.037 mol) was dissolved in DCM (50 mL), and a few drops of DMF were added. Oxaloyl chloride (5.13 g, 3.47 mL, 0.40 mol) was added dropwise over 5 minutes, and the resulting mixture was stirred for 45 minutes. The solvent was removed by rotary evaporator to give a red oily product. A solution of iminodiacetic acid (9.78 g, 0.074 mol) in 6 M NaOH (24 mL) was diluted with acetone (12 mL). The solution was diluted with water until the mixture became homogeneous (30 mL). The iminodiacetic acid solution and pure acid chloride were simultaneously pushed through a static mixer, and the resulting reaction mixture was stirred for 20 minutes. The reaction mixture was diluted to 150 mL. The pH was adjusted to 4.9 with 2 M HCl, and the solution was extracted with two portions of DCM. The organic layer was discarded. The aqueous layer was adjusted to pH 2.8 with 6 M HCl, and a solid precipitated under vigorous stirring. The solid was collected by filtration and washed more than twice with water, 0.1M HCl, and water. The solid was dried to obtain the product, which was a grayish-yellow solid (7.74 g, 0.02 mol, 54%).

[0446] 1H NMR: (d-DMSO, 500 MHz) δ 1.72 – 1.65 (m, 2H), 2.29 – 2.24 (m, 4H), 3.96 (s, 1H), 4.03 (t, J = 1.75 Hz, 2H), 4.075 (t, J = 1.8 Hz, 1H), 4.11 (s,5H), 4.1 (s, 5H), 4.14-4.12 (bs, 2H).

[0447] Example 10: H-cell experiments showing stability of anionic water-soluble perylene diimide and ferrocene electrolyte solutions ​

[0448] These experiments demonstrate that the disclosed anionic electrolyte solution is compatible in both charged and uncharged states. This static battery cell experimental setup allows for precise measurement of coulombic efficiency to analyze the electrochemical and physical compatibility of the charged electrolyte solution with the battery cell manufacturing materials. High coulombic efficiency indicates that electrons entering the organic charge storage electrolyte during charging return during discharge, meaning that the electrolyte does not undergo electrochemical or physical reactions with anything (including the battery cell manufacturing materials) in the charged state to quench the charge.

[0449] An exemplary 1mAh H-type battery cell was fabricated using glutamate-PDI in the anode electrolyte half-cell unit and ferrocene dipropylsulfonate in the cathode electrolyte half-cell unit. The structures of these molecules are shown below. The cycling of glutamate-PDI and ferrocene dipropylsulfonate is illustrated in Figure 9. The battery cell includes glass, and the membrane is Selemion. TM CMV. Each half-cell was mixed with a PTFE stirring rod, and the electrodes were carbon felt. Coulombic efficiency was measured over a set of cycles. An average coulombic efficiency of >99.9% was observed after 10 to 40 cycles, indicating that both the anolyte and catholyte solutions were stable due to minimal electrochemical or physical degradation under charged conditions. Capacity also remained stable.

[0450]

[0451] An exemplary 1mAh H-type battery cell was fabricated using glutamate-PDI in the anolyte half-cell cell and glutamate-ferrocene amide in the cathode half-cell cell. The structures of these molecules are shown below. Cycling of glutamate-PDI and ferrocene dipropylsulfonate is shown in Figure 10. The battery cell comprises glass, with a Selemion CMV membrane. Each half-cell cell was mixed with a PTFE stirring rod, and the electrodes were carbon felt. Coulombic efficiency was measured for a set of cycles. Cycles 10 to 40 showed an average coulombic efficiency of 99.9%, indicating that both the anolyte and cathode electrolyte solutions were stable due to minimal electrochemical or physical degradation under charged conditions. The capacity also remained stable.

[0452]

[0453] Example

[0454] Example 1: A redox flow battery, comprising: a first half-cell unit containing a first aqueous solution, the first aqueous solution including a first electrode and an anode electrolyte, wherein the anode electrolyte includes a perylene diimide compound; a second half-cell unit containing a second electrode and a second aqueous solution containing a cathode electrolyte; and a separator between the first half-cell unit and the second half-cell unit; wherein the internal surfaces of the first half-cell unit in contact with the first aqueous solution and the internal surfaces of the second half-cell unit in contact with the second aqueous solution comprise one or more non-highly chemically resistant materials.

[0455] Example 2: The redox flow battery of Example 1, wherein the non-fluorinated polymer is selected from the group consisting of: polyolefins, polyethers, polyketones, polyamides, polyureas, natural rubber, and combinations thereof.

[0456] Example 3: Redox flow battery of Example 1 or 2, wherein the non-fluorinated polymer is a copolymer of two or more polymers selected from the group consisting of: polyolefins, polyethers, polyketones, polyamides, polyureas and natural rubber.

[0457] Example 4: A redox flow battery of Example 1, 2, or 3, wherein the non-fluorinated polymer is selected from the group consisting of: ethylene propylene diene monomer (EPDM), polychloroprene (Neoprene), polyamide (nylon), polyetheretherketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate, sodium 4-toluenesulfonate, propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), EPDM polypropylene matrix elastomer (Santoprene), and combinations thereof.

[0458] Example 5: A redox flow battery of any of Examples 1 to 4, wherein the non-fluorinated polymer is a copolymer of two or more polymers selected from the group consisting of: ethylene propylene diene monomer (EPDM), polychloroprene (Neoprene), polyamide (nylon), polyetheretherketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate, sodium 4-toluenesulfonate, propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), and EPDM polypropylene matrix elastomer (Santoprene).

[0459] Example 6: A redox flow battery of any of Examples 1 to 5, wherein the first half-cell unit includes a first bipolar plate, the second half-cell unit includes a second bipolar plate, and the first bipolar plate comprises a composite material of graphite and polymer.

[0460] Example 7: A redox flow battery of any of Examples 1 to 6, wherein the composite material is resin-filled graphite; or graphite in a thermosetting resin matrix.

[0461] Example 8: A redox flow battery of any of Examples 1 to 7, wherein the polymer of the composite material is polyethylene or polypropylene.

[0462] Example 9: The redox flow battery of any of Examples 1 to 8 further includes a gasket separating the reaction vessel from the first bipolar plate, wherein the gasket comprises a non-highly chemically resistant elastomer material; wherein the non-highly chemically resistant elastomer material is selected from the group consisting of: ethylene propylene diene monomer (EPDM), polychloroprene (Neoprene), polyamide (nylon), polyetheretherketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate, sodium 4-toluenesulfonate, propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), EPDM polypropylene matrix elastomer (Santoprene), and combinations thereof.

[0463] Example 10: A redox flow battery of any of Examples 1 to 9, wherein the separator comprises a polystyrene-based ion exchange membrane.

[0464] Example 11: The redox flow battery of any of Examples 1 to 10 further includes a supply line located outside the first half-cell unit for supplying the anode electrolyte to the first half-cell unit, wherein the supply line comprises a non-highly chemically resistant elastomer material; wherein the non-highly chemically resistant elastomer material is selected from the group consisting of: ethylene propylene diene monomer (EPDM), polychloroprene (Neoprene), polyamide (nylon), polyetheretherketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate, sodium 4-toluenesulfonate, propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), EPDM polypropylene matrix elastomer (Santoprene), and combinations thereof.

[0465] Example 12: A redox flow battery of any one of Examples 1 to 11, wherein the perylene diimide compound has formula (I):

[0466] (I) or its salt, wherein:

[0467] T is -(LG) n -X;

[0468] T' can be H, (C1-C6) alkyl, or -(LG). n -X;

[0469] L is a -(C2-C5)-alkyl group, and can optionally be OH, OCH3, or a halogen.

[0470]

[0471] Each X is independently H, -(C1-C 10 alkyl, -(C2-C6)alkenyl, -(C2-C6)ynyl, and -(C2-C6)alkoxy, each being unsubstituted or represented by one, two, or three independently chosen R groups. 1 Group-substituted;

[0472] Each R 1 Independently, it can be -OH, -O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl-O(C1-C6)alkyl, or -[O(C1-C6)-alkyl] p-O(C1-C6), -O(C=O)(C1-C6)alkyl, -O(C=O)O(C1-C6)alkyl, -O(C=O)OH, -O(C=O)NH2, -O(C=O)NH(C1-C6)alkyl, O(C=O)N[(C1-C6)alkyl]2, -NH(C=O)(C1-C6)alkyl, N(C1-C6)alkyl(C=O)(C1-C6)alkyl, halogen, -CN, -NO2, NH2, NH(C1-C6)alkyl and N[(C1-C6)alkyl]2;

[0473] n = 2 to 8; and

[0474] p=3 to 20.

[0475] Example 13: A redox flow battery of any one of Examples 1 to 12, wherein T and T' are each independently -(LG). n -X.

[0476] Example 14: A redox flow battery of any of Examples 1 to 13, wherein L is selected from the group consisting of unsubstituted -(C2-C5)-alkyl, ethyl and propyl.

[0477] Example 15: A redox flow battery of any one of Examples 1 to 14, wherein n is 2, 3 or 4.

[0478] Example 16: A redox flow battery of any one of Examples 1 to 15, wherein G is Where X is H, methyl, -CH2CH2OH or -(C1-C6)-alkyl.

[0479] Example 17: A redox flow battery of any one of Examples 1 to 16, wherein the compound of formula (I) is:

[0480] ;

[0481] ;

[0482] ;

[0483] ;

[0484] ;or

[0485] .

[0486] Example 18: A redox flow battery of any of Examples 1 to 17, wherein the perylene diimide compound has formula (II):

[0487] (II)

[0488] in

[0489] Each Y is independently -O-, -S-, or -NH-;

[0490] Each q is independently 1 to 8; and

[0491] Each X is independently H, -(C1-C 10 -alkyl, -(C2-C6)alkenyl, -(C2-C6)ynyl, and -(C1-C6)alkoxy, each being unsubstituted or represented by one, two, or three independently chosen R groups. 1 Group-substituted;

[0492] Each R 1 Independently, it can be -OH, -O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl-O(C1-C6)alkyl, or -[O(C1-C6)-alkyl] p -O(C1-C6), -O(C=O)(C1-C6)alkyl, -O(C=O)O(C1-C6)alkyl, -O(C=O)OH, -O(C=O)NH2, -O(C=O)NH(C1-C6)alkyl, O(C=O)N[(C1-C6)alkyl]2, -NH(C=O)(C1-C6)alkyl, N(C1-C6)alkyl(C=O)(C1-C6)alkyl, halogen, -CN, -NO2, NH2, NH(C1-C6)alkyl and N[(C1-C6)alkyl]2; and

[0493] Each V represents a balanced ion.

[0494] Example 19: A redox flow battery of any of Examples 1 to 18, wherein the perylene diimide compound has formula (III):

[0495] (III)

[0496] in:

[0497] Each X is independently H, -(C1-C 10 -alkyl, -(C2-C6)alkenyl, -(C2-C6)ynyl, and -(C1-C6)alkoxy, each being unsubstituted or represented by one, two, or three independently chosen R groups. 1 Group-substituted;

[0498] Each R 1Independently, it can be -OH, -O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl-O(C1-C6)alkyl, or -[O(C1-C6)-alkyl] p -O(C1-C6), -O(C=O)(C1-C6)alkyl, -O(C=O)O(C1-C6)alkyl, -O(C=O)OH, -O(C=O)NH2, -O(C=O)NH(C1-C6)alkyl, O(C=O)N[(C1-C6)alkyl]2, -NH(C=O)(C1-C6)alkyl, N(C1-C6)alkyl(C=O)(C1-C6)alkyl, halogen, -CN, -NO2, NH2, NH(C1-C6)alkyl and N[(C1-C6)alkyl]2;

[0499] Each s is independently 2 to 4;

[0500] Each R is independently H, -CH2OH, -CH2CH2OH, -CH2CH2OCH2CH2OH, or -CH2CH2OCH2CH2O(C 1- 6) Alkyl groups; and

[0501] Each V - These are balanced ions.

[0502] Example 20: A redox flow battery of any one of Examples 1 to 19, wherein the compound of formula (III) is:

[0503] ;or

[0504] .

[0505] Example 21: A redox flow battery of any of Examples 1 to 20, wherein the perylene diimide compound has formula (IV):

[0506] (IV)

[0507] in

[0508] R is , or .

[0509] Example 22: A redox flow battery of any of Examples 1 to 21, wherein the perylene diimide compound has the formula (V):

[0510] (V) or its salt, wherein

[0511] L stands for -(C1-C6)-alkyl;

[0512] Each G is ;

[0513] A is a cation; and

[0514] n = 1 to 5.

[0515] Example 23: A redox flow battery of any of Examples 1 to 22, wherein L is substituted with OH, OCH3 and halogen; wherein A is lithium, sodium, potassium or ammonium.

[0516] Example 24: A redox flow battery of any one of Examples 1 to 23, wherein LG n The group has at least one chiral center.

[0517] Example 25: A redox flow battery of any of Examples 1 to 24, wherein the compound of formula (V) is selected from the group consisting of:

[0518] , ,or .

[0519] Example 26: A redox flow battery of any one of Examples 1 to 25, wherein A is lithium, sodium, potassium or ammonium.

[0520] Example 27: A redox flow battery of any of Examples 1 to 26, wherein the cathode electrolyte comprises a second compound having a ferrocene moiety, wherein the second compound has a formula selected from the group consisting of:

[0521] ,

[0522] ,

[0523] ,

[0524]

[0525] ,

[0526] ,

[0527] ,

[0528] ,

[0529] ,

[0530] ,

[0531] ,and

[0532] .

[0533] Example 28: A redox flow battery of any of Examples 1 to 27, wherein the cathode electrolyte comprises a second compound having a ferrocene moiety, wherein the second compound has the formula (VI):

[0534]

[0535] in:

[0536] L is -(C1-C 10 -alkyl, -(C1-C6)-alkenyl, -(C1-C6)-ynyl, -(C1-C6)-alkyl-O(C1-C6)-alkyl, -(C1-C6)-alkyl-O-(C=O)-(C1-C6)alkyl, -(C1-C6)-alkyl-(C=O)-O-(C1-C6)alkyl, -(C1-C6)alkyl-NH-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-NR 2 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2 -(C1-C6)alkyl or -(C1-C6)alkyl 10 )-alkyl-aryl;

[0537] L' represents -H, -(C1-C 10 -alkyl, -(C1-C6)-alkenyl, -(C1-C6)-ynyl, -(C1-C6)-alkyl-O(C1-C6)-alkyl, -(C1-C6)-alkyl-O-(C=O)-(C1-C6)alkyl, -(C1-C6)-alkyl-(C=O)-O-(C1-C6)alkyl, -(C1-C6)alkyl-NH-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-NR 2 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2 -(C1-C6)alkyl or -(C1-C6)alkyl 10 )-alkyl-aryl;

[0538] G can choose from the following groups: ;

[0539] G is greater than or equal to 2;

[0540] A is Li, K, Na, or NH4; and

[0541] R 2 -(C1-C 10 -alkyl, -(C1-C6)-alkenyl, -(C1-C6)-ynyl, -(C1-C6)-alkynyl 10 -alkyl-aryl, -aryl, or -(C=O)-(C1-C6)-alkyl.

[0542] Example 29: A redox flow battery of any one of Examples 1 to 28, wherein L is substituted with at least one group selected from the group consisting of: G, -OH, -OCH3, and -halogen; wherein L' is substituted with at least one group selected from the group consisting of: G, -OH, -OCH3, and -halogen; wherein R 2 It is replaced by at least one G.

[0543] Example 30: A redox flow battery of any of Examples 1 to 29, wherein the compound of formula (VI) is

[0544] , ,

[0545] ,or .

[0546] Principle of Equivalence

[0547] As can be inferred from the above discussion, the above concepts can be implemented in various arrangements according to embodiments of the invention. Therefore, although the invention has been described in certain specific aspects, many additional modifications and variations will be apparent to those skilled in the art. Thus, it should be understood that the invention can be practiced in ways other than those specifically described. Therefore, embodiments of the invention should be considered illustrative rather than restrictive in all respects.

[0548] As used herein, unless the context clearly indicates otherwise, the singular terms “a,” “an,” and “the” can include plural references. Referring to an object in the singular is not intended to mean “one and only one,” but rather “one or more” unless explicitly stated otherwise.

[0549] As used herein, the terms “approximately” and “about” are used to describe and indicate small variations. When used in conjunction with an event or situation, these terms can refer to a situation where the event or situation occurred precisely or very approximately. When used in conjunction with a numerical value, the term can refer to a range of variation less than or equal to ±10% of that value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%.

[0550] In addition, quantities, ratios, and other numerical values ​​may sometimes be presented in range form in this document. It should be understood that such range format is used for convenience and brevity, and should be flexibly interpreted to include not only the numerical values ​​explicitly specified as range boundaries, but also all individual numerical values ​​or subranges covered within that range, as if each numerical value and subrange were explicitly specified. For example, ratios in the range of about 1 to about 200 should be understood to include the explicitly listed boundaries of about 1 and about 200, but also individual ratios such as about 2, about 3, and about 4, and subranges such as about 10 to about 50, about 20 to about 100, etc.

Claims

1. A redox flow battery, comprising: A first half-cell unit includes a first aqueous solution, the first aqueous solution including a first electrode and an anode electrolyte, wherein the anode electrolyte includes a perylene diimide compound; A second half-cell unit includes a second electrode and a second aqueous solution, the second aqueous solution containing a cathode electrolyte; and A separator is located between the first half-cell cell and the second half-cell cell; The inner surfaces of the first half-cell unit in contact with the first aqueous solution and the inner surfaces of the second half-cell unit in contact with the second aqueous solution contain one or more non-highly chemically resistant materials.

2. The redox flow battery according to claim 1, wherein the non-fluorinated polymer is selected from the group consisting of: polyolefins, polyethers, polyketones, polyamides, polyureas, natural rubber, and combinations thereof.

3. The redox flow battery according to claim 1, wherein the non-fluorinated polymer is a copolymer of two or more polymers selected from the group consisting of: polyolefins, polyethers, polyketones, polyamides, polyureas, and natural rubber.

4. The redox flow battery according to claim 1, wherein the non-fluorinated polymer is selected from the group consisting of: ethylene propylene diene monomer (EPDM), polychloroprene (Neoprene), polyamide (nylon), polyetheretherketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate, sodium 4-toluenesulfonate, propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), EPDM polypropylene matrix elastomer (Santoprene), and combinations thereof.

5. The redox flow battery according to claim 1, wherein the non-fluorinated polymer is a copolymer of two or more polymers selected from the group consisting of: ethylene propylene diene monomer (EPDM), polychloroprene (Neoprene), polyamide (nylon), polyetheretherketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate, sodium 4-toluenesulfonate, propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), and EPDM polypropylene matrix elastomer (Santoprene).

6. The redox flow battery according to claim 1, wherein the first half-cell unit includes a first bipolar plate, and the second half-cell unit includes a second bipolar plate, wherein the first bipolar plate comprises a composite material of graphite and polymer.

7. The redox flow battery according to claim 6, wherein the composite material is resin-filled graphite; or graphite in a thermosetting resin matrix.

8. The redox flow battery according to claim 6, wherein the polymer of the composite material is polyethylene or polypropylene.

9. The redox flow battery according to claim 1, further comprising a gasket separating the reaction vessel from the first bipolar plate, wherein the gasket comprises a non-highly chemically resistant elastomer material; wherein the non-highly chemically resistant elastomer material is selected from the group consisting of: ethylene propylene diene monomer (EPDM), polychloroprene (Neoprene), polyamide (nylon), polyetheretherketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate, sodium 4-toluenesulfonate, propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), EPDM polypropylene matrix elastomer (Santoprene), and combinations thereof.

10. The redox flow battery of claim 1, wherein the separator comprises a polystyrene-based ion exchange membrane.

11. The redox flow battery according to claim 1, further comprising a supply line located outside the first half-cell unit for supplying the anode electrolyte to the first half-cell unit, wherein the supply line comprises a non-highly chemically resistant elastomer material; wherein the non-highly chemically resistant elastomer material is selected from the group consisting of: ethylene propylene diene monomer (EPDM), polychloroprene (Neoprene), polyamide (nylon), polyetheretherketone (PEEK), polyoxymethylene (POM), polyvinyl chloride (PVC), sodium benzenesulfonate, sodium 4-toluenesulfonate, propylene carbonate, sulfolane, acrylonitrile butadiene rubber (BUNA-N), natural latex rubber, polyethylene (PE), polymethyl methacrylate (PMMA), polypropylene (PP), polyurethane (PUR), EPDM polypropylene matrix elastomer (Santoprene), and combinations thereof.

12. The redox flow battery according to claim 1, wherein the perylene diimide compound has formula (I) or a salt thereof: (I) in: T is -(LG) n -X; T' can be H, (C1-C6) alkyl, or -(LG). n -X; L is a -(C2-C5)-alkyl group, which may optionally be substituted with OH, OCH3, or a halogen. Each X is independently H, -(C1-C 10 alkyl, -(C2-C6)alkenyl, -(C2-C6)ynyl, and -(C1-C6)alkoxy, each being unsubstituted or having one, two, or three independently selected R... 1 Group-substituted; Each R 1 Independently, it can be -OH, -O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl-O(C1-C6)alkyl, or -[O(C1-C6)-alkyl] p -O(C1-C6), -O(C=O)(C1-C6)alkyl, -O(C=O)O(C1-C6)alkyl, -O(C=O)OH, -O(C=O)NH2, -O(C=O)NH(C1-C6)alkyl, O(C=O)N[(C1-C6)alkyl]2, -NH(C=O)(C1-C6)alkyl, N(C1-C6)alkyl(C=O)(C1-C6)alkyl, halogen, -CN, -NO2, NH2, NH(C1-C6)alkyl and N[(C1-C6)alkyl]2; n = 2 to 8; and p=3 to 20.

13. The redox flow battery according to claim 12, wherein T and T' are each independently -(LG). n -X.

14. The redox flow battery according to claim 12, wherein L is selected from the group consisting of unsubstituted -(C2-C5)-alkyl, ethyl and propyl.

15. The redox flow battery according to claim 12, wherein n is 2, 3 or 4.

16. The redox flow battery according to claim 12, wherein G is... Where X is H, methyl, -CH2CH2OH or -(C1-C6)-alkyl.

17. The redox flow battery according to claim 12, wherein the compound of formula (I) is: ； ； ； ； ;or 。 18. The redox flow battery according to claim 1, wherein the perylene diimide compound has formula (II): (II) in: Each Y is independently -O-, -S-, or -NH-; Each q is independently 1 to 8; and Each X is independently H, -(C1-C 10 -alkyl, -(C2-C6)alkenyl, -(C2-C6)ynyl, and -(C1-C6)alkoxy, each being unsubstituted or having one, two, or three independently selected R... 1 Group-substituted; Each R 1 Independently, it can be -OH, -O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl-O(C1-C6)alkyl, or -[O(C1-C6)-alkyl] p -O(C1-C6), -O(C=O)(C1-C6)alkyl, -O(C=O)O(C1-C6)alkyl, -O(C=O)OH, -O(C=O)NH2, -O(C=O)NH(C1-C6)alkyl, O(C=O)N[(C1-C6)alkyl]2, -NH(C=O)(C1-C6)alkyl, N(C1-C6)alkyl(C=O)(C1-C6)alkyl, halogen, -CN, -NO2, NH2, NH(C1-C6)alkyl and N[(C1-C6)alkyl]2; and Each V represents a balanced ion.

19. The redox flow battery according to claim 1, wherein the perylene diimide compound has formula (III): (III) in: Each X is independently H, -(C1-C 10 -alkyl, -(C2-C6)alkenyl, -(C2-C6)ynyl, and -(C1-C6)alkoxy, each being unsubstituted or having one, two, or three independently selected R... 1 Group-substituted; Each R 1 Independently, it can be -OH, -O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl, -O(C1-C6)-alkyl-O(C1-C6)-alkyl-O(C1-C6)alkyl, or -[O(C1-C6)-alkyl] p -O(C1-C6), -O(C=O)(C1-C6)alkyl, -O(C=O)O(C1-C6)alkyl, -O(C=O)OH, -O(C=O)NH2, -O(C=O)NH(C1-C6)alkyl, O(C=O)N[(C1-C6)alkyl]2, -NH(C=O)(C1-C6)alkyl, N(C1-C6)alkyl(C=O)(C1-C6)alkyl, halogen, -CN, -NO2, NH2, NH(C1-C6)alkyl and N[(C1-C6)alkyl]2; Each s is independently 2 to 4; Each R is independently H, -CH2OH, -CH2CH2OH, -CH2CH2OCH2CH2OH, or -CH2CH2OCH2CH2O(C 1- 6) Alkyl groups; and Each V - These are balanced ions.

20. The compound according to claim 13, wherein the compound of formula (III) is: ;or 。 21. The redox flow battery according to claim 1, wherein the perylene diimide compound has formula (IV): (IV) in: R is , or .

22. The redox flow battery according to claim 1, wherein the perylene diimide compound has formula (V) or a salt thereof: （V） in: L stands for -(C1-C6)-alkyl; Each G is ; A is a cation; and n = 1 to 5.

23. The redox flow battery according to claim 22, wherein L is substituted with OH, OCH3 and halogen; wherein each A is lithium, sodium, potassium or ammonium.

24. The redox flow battery according to claim 22, wherein LG n The group has at least one chiral center.

25. The redox flow battery according to claim 22, wherein the compound of formula (V) is selected from the group consisting of: , or 。 26. The redox flow battery according to claim 25, wherein A is lithium, sodium, potassium or ammonium.

27. The redox flow battery of claim 1, wherein the cathode electrolyte comprises a second compound having a ferrocene moiety, wherein the second compound has a formula selected from the group consisting of: 、 、 、 、 、 、 、 、 、 ,as well as 。 28. The redox flow battery of claim 1, wherein the cathode electrolyte comprises a second compound having a ferrocene moiety, wherein the second compound has the formula (VI): in: L is -(C1-C 10 -alkyl, -(C1-C6)-alkenyl, -(C1-C6)-ynyl, -(C1-C6)-alkyl-O(C1-C6)-alkyl, -(C1-C6)-alkyl-O-(C=O)-(C1-C6)alkyl, -(C1-C6)-alkyl-(C=O)-O-(C1-C6)alkyl, -(C1-C6)alkyl-NH-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-NR 2 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2 -(C1-C6)alkyl or -(C1-C6)alkyl 10 )-alkyl-aryl; L' represents -H, -(C1-C 10 -alkyl, -(C1-C6)-alkenyl, -(C1-C6)-ynyl, -(C1-C6)-alkyl-O(C1-C6)-alkyl, -(C1-C6)-alkyl-O-(C=O)-(C1-C6)alkyl, -(C1-C6)-alkyl-(C=O)-O-(C1-C6)alkyl, -(C1-C6)alkyl-NH-(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-NR 2 -(C=O)(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NH-(C1-C6)alkyl, -(C1-C6)alkyl-(C=O)-NR 2 -(C1-C6)alkyl or -(C1-C6)alkyl 10 )-alkyl-aryl; G chooses from the following groups. ; G is greater than or equal to 2; A is Li, K, Na, or NH4; and R 2 -(C1-C 10 -alkyl, -(C1-C6)-alkenyl, -(C1-C6)-ynyl, -(C1-C6)-alkynyl 10 -alkyl-aryl, -aryl, or -(C=O)-(C1-C6)-alkyl.

29. The redox flow battery according to claim 28, wherein L is substituted by at least one group selected from the group consisting of: G, -OH, -OCH3, and -halogen; wherein L' is substituted by at least one group selected from the group consisting of: G, -OH, -OCH3, and -halogen; wherein R 2 It is replaced by at least one G.

30. The redox flow battery according to claim 28, wherein the compound of formula (VI) is: , , or .

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