WO2024085749A1 - A non-aqueous redox flow battery - Google Patents

A non-aqueous redox flow battery Download PDF

Info

Publication number
WO2024085749A1
WO2024085749A1 PCT/NL2023/050533 NL2023050533W WO2024085749A1 WO 2024085749 A1 WO2024085749 A1 WO 2024085749A1 NL 2023050533 W NL2023050533 W NL 2023050533W WO 2024085749 A1 WO2024085749 A1 WO 2024085749A1
Authority
WO
WIPO (PCT)
Prior art keywords
hydrocarbyl group
carbon atoms
cyclic
substituted
branched
Prior art date
Application number
PCT/NL2023/050533
Other languages
French (fr)
Inventor
Nicolas DAUB
René Albert Johan Janssen
Nico Jacob Leroy VAN RIJSWIJK
Original Assignee
Technische Universiteit Eindhoven
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Technische Universiteit Eindhoven filed Critical Technische Universiteit Eindhoven
Publication of WO2024085749A1 publication Critical patent/WO2024085749A1/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • H01M8/184—Regeneration by electrochemical means
    • H01M8/188—Regeneration by electrochemical means by recharging of redox couples containing fluids; Redox flow type batteries
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C25/00—Compounds containing at least one halogen atom bound to a six-membered aromatic ring
    • C07C25/02—Monocyclic aromatic halogenated hydrocarbons
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C255/00—Carboxylic acid nitriles
    • C07C255/49—Carboxylic acid nitriles having cyano groups bound to carbon atoms of six-membered aromatic rings of a carbon skeleton
    • C07C255/57—Carboxylic acid nitriles having cyano groups bound to carbon atoms of six-membered aromatic rings of a carbon skeleton containing cyano groups and carboxyl groups, other than cyano groups, bound to the carbon skeleton
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C63/00—Compounds having carboxyl groups bound to a carbon atoms of six-membered aromatic rings
    • C07C63/04—Monocyclic monocarboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C69/00—Esters of carboxylic acids; Esters of carbonic or haloformic acids
    • C07C69/76—Esters of carboxylic acids having a carboxyl group bound to a carbon atom of a six-membered aromatic ring
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
    • C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
    • C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
    • C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D213/78—Carbon atoms having three bonds to hetero atoms, with at the most one bond to halogen, e.g. ester or nitrile radicals
    • C07D213/84—Nitriles
    • C07D213/85—Nitriles in position 3
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • a non-aqueous redox flow battery TECHNICAL FIELD The present invention relates to a battery, specifically to a non- aqueous redox flow battery.
  • the invention further relates to a method of operating such a battery.
  • BACKGROUND In a world where climate neutrality is the goal, green energy sources are essential. More than half of the produced green energy comes from wind and solar power. In order to overcome their intermittency, energy storage applications are inevitable.
  • Redox flow batteries (RFBs) are very promising storage systems in the transition towards renewable energy sources.
  • a redox flow battery generally comprises a negative electrode immersed in a liquid negative electrolyte, a positive electrode immersed in a liquid positive electrolyte, and an ion-permeable separator (e.g., a porous membrane, film, sheet, or panel as well as ion-exchange membranes) between the negative and the positive electrolyte.
  • an electrolyte salt e.g., a lithium, sodium, or organic salt
  • a strong acid or base e.g., NaOH, KOH, HCl or H 2 SO 4
  • a redox reactant e.g.
  • an electrochemically stable organic solvent They can be broadly classified in aqueous and non-aqueous systems.
  • aqueous RFBs the voltage and hence energy density is limited by the water electrolysis potential (usually between 1.15 and 1.55V).
  • the used electrolytes are in most of the cases highly corrosive (operate at pH 0 or 14).
  • Non-aqueous systems operate with organic solvents, which allow for a much broader potential window (up to three times higher) compared to water. Combination of organic solvents with organic redox active materials could pave the way for all carbon-based RFBs with superior energy densities compared to aqueous systems.
  • US10424806B2 discloses a non-aqueous redox flow battery wherein the redox reactant of the positive electrolyte is a dialkoxybenzene compound, and the redox reactant of the negative electrolyte is a viologen compound or a dipyridyl ketone.
  • US10535891 B2 discloses a redox flow battery comprising a two- electron, redox active, bridged, multi-cyclic compound (“TRBMC”) that comprises a non-aromatic, bridged cyclic portion fused to an aromatic cyclic portion.
  • TRBMC redox active, bridged, multi-cyclic compound
  • each redox reactant is selected from an organic compound comprising a conjugated unsaturated moiety, a boron cluster compound, and a combination thereof.
  • the organic redox reactant of the positive electrolyte is selected to have a higher redox potential than the redox reactant of the negative electrolyte.
  • an organic solvent can be used that can withstand higher potentials, but finding redox active compounds that offer a combination of higher redox potentials, high stability in charged form, and high solubility remains a challenge.
  • the present invention therefore relates in a first aspect to a battery comprising a liquid electrolyte, the liquid electrolyte comprising: a compound selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV):
  • R 1 and R 2 and/or R 3 and R 4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group, or R 1 , R 2 , R 3 , R 4 and R 5 represent independent from each other H; CN; halogen; NO 2 ; NR 6 2; N 2 R 6 ; COR 6 ; linear, branched or cyclic hydrocarbyl group independently selected from alkyl; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms.
  • R 6 represents H or a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1- 18 carbon atoms, wherein A- represents an anion.
  • the present invention relates to a method of manufacturing a battery according to the first aspect, the method comprising: - immersing a negative electrode in a first non-aqueous liquid electrolyte; - immersing a positive electrode in a second non-aqueous liquid electrolyte; - interposing a semi-permeable separator between the negative and positive electrodes; wherein the first non-aqueous liquid electrolyte comprises the liquid electrolyte as described for the first aspect.
  • the present invention relates to a method of operating a battery according to the first aspect of the present invention. The method comprises: providing the battery according to the first aspect.
  • the present invention relates to a compound according to formula (I).
  • R 2 and R 4 are H.
  • R 1 is CN; COR 6 ; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms.
  • R 3 is COOR 7 , wherein R 7 represents linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms.
  • the present invention relates to a method of manufacturing said compound. Embodiments of the first aspect are applicably correspondingly to the second, third, fourth and fifth aspect according to the present invention.
  • Figure 1 shows a schematic representation of the working principle of a redox flow battery according to one example according to the present invention.
  • Figure 2A shows the normalized discharge capacity of static, coin cell cycling, up to 3000 cycles.
  • Figure 2B shows the normalized discharge capacity of static, coin cell cycling, up to 10000 cycles.
  • Figure 2C shows the normalized discharge capacity of static, coin cell cycling at higher concentration, up to 1000 cycles.
  • Figure 2D shows the normalized discharge capacity of static, coin cell cycling up to 500 cycles.
  • Figure 2E shows the normalized discharge capacity of static, coin cell cycling at a concentration of 50 mM with various catholytes, up to 1000 cycles.
  • Figure 2F shows the normalized discharge capacity of static, coin cell cycling of the most promising anolyte/catholytes combinations, up to 20000 cycles.
  • Figure 3 shows the volumetric capacity versus the cycle number of flow battery cycling for an example according to the present invention.
  • Figure 4A shows volumetric capacity versus cycle number of flow battery cycling for another example according to the present invention.
  • Figure 4B shows a voltage versus capacity profile for the example of Fig.4A.
  • Figure 5A shows volumetric capacity versus cycle number of flow battery cycling for another example according to the present invention.
  • Figure 5B shows a voltage versus capacity profile for the example of Fig.5A.
  • the invention relates in a first aspect to a battery comprising a liquid electrolyte comprising a compound selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV).
  • This compound is able to take up an electron.
  • this compound would be defined as the anolyte.
  • the liquid electrolyte comprises comprises two or more compounds selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV).
  • said compounds have a similar redox potential.
  • the redox potentials of said two or more compounds differ less than 200 mV.
  • the liquid electrolyte comprises a compound selected from the group consisting of formula (I), formula (II) and formula (IV).
  • R 1 and R 2 and/or R 3 and R 4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group.
  • the ring depicted in the formula forms a fused ring system with a ring formed by R 1 and R 2 and/or R 3 and R 4 .
  • the substituent(s), when present, may be branched or unbranched.
  • R 1 and R 2 as well as R 3 and R 4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group.
  • Suitable examples of an optionally substituted cyclic group are an optionally substituted cycloalkane group, cycloheteroalkane group, cycloalkene group and cycloheteroalkene group.
  • the optionally substituted cyclic group is a cycloalkane group.
  • R 1 , R 2 , R 3 , R 4 and R 5 represent independent from each other H; CN; halogen; NR 6 2; COR 6 ; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-10 carbon atoms, preferably from 1-5 carbon atoms;
  • R 1 , R 2 , R 3 , R 4 and R 5 represent independent from each other H; CN; COR 6 ; linear or branched hydrocarbyl group independently selected from alkyl, alkoxy and alkoxycarbonyl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted
  • R 1 is not H.
  • R 3 is also not H.
  • at least one of R 1 and R 3 is branched.
  • R 1 and R 3 are independently chosen from CH 3 , C 2 H 5 , C 3 H 7 , C 4 H 9 , tert-butyl, COOCH 3 , COOC 2 H 5 , COOC 3 H 7 , COOC 4 H 9 and COOC(CH 3 ) 3 .
  • R 3 may be the same or different from R 1 , preferably R 3 is different from R 1 .
  • the presence and nature of substituents allow for adjustability of the stability, solubility and redox potential of the compound. When R 3 and R 1 are different, this asymmetry allows for finetuning of redox potential and a higher solubility.
  • the compound is according to formula (III), there is an anion present. This anion must be electrochemically inert in the potential window in which the battery is operated.
  • the compound is selected from formula (I), (II) or (IV).
  • the liquid electrolyte comprises a compound according to one of the following formulas:
  • the liquid electrolyte comprises a compound according to one of the following formulas: In an embodiment, the liquid electrolyte comprises a compound according to one of the following formulas: preferably wherein the compound is according to any one of formulas (1) – (13), more preferably according to any one of formulas (1) – (12). In a preferred embodiment, the liquid electrolyte comprises a compound according to one of the following formulas:
  • the battery further comprises a solvent that is electrochemically stable in a wide potential range, preferably between -3V to +2V, such as between -2.5V to + 1.5V vs ferrocene/ferrocenium (Fc/Fc + ), wherein the solvent is acetonitrile; an ether-based solvent, preferably dimethoxyethane; diethyl carbitol, dimethylformamide or a mixture thereof.
  • the battery further comprises one or more electrolyte salts and a counter ion, wherein the one or more electrolyte salts has a solubility of >0.5 M in the solvent.
  • the one or more electrolyte salt is a quaternary ammonium or imidazolium.
  • the counter ion is chosen from the group of PF 6 -, BF 4 -, N(SO 2 CF 3 ) 2 - (TFSI), CF 3 SO 3 - (FSI), CH 3 SO 3 - or CH 3 C 6 H 4 SO 3 - (OTs) and diethyl phosphate.
  • the battery is a redox flow battery. In a specific embodiment, the battery is a non-aqueous redox flow battery.
  • the invention relates in a first aspect to a battery comprising a compound according to one of the formulas (I)-(IV).
  • this compound serves as the anolyte.
  • this compound is often described as material to store electrons, or as material for the anode.
  • the battery further comprises a material for the cathode (in certain types of batteries such as in redox flow batteries called a catholyte).
  • This catholyte may for instance be chosen from 2,5-di-tert-butyl-1,4-bis(2- methoxyethoxy)benzene (DBBB), 1,4-di-tert-butyl-2-methoxy-5-(2-(2- methoxyethoxy)ethoxy)benzene (DBMMB) as well as 1,4-di-tert-butyl-2,5-bis(2,2,2- trifluoroethoxy)benzene compounds.
  • DBBB 2,5-di-tert-butyl-1,4-bis(2- methoxyethoxy)benzene
  • DBMMB 1,4-di-tert-butyl-2-methoxy-5-(2-(2- methoxyethoxy)ethoxy)benzene (DBMMB) as well as 1,4-di-tert-butyl-2,5-bis(2,2,2- trifluoroethoxy)benzene compounds.
  • catholytes are 10-[2-(2- methoxyethoxy)ethyl]-10H-phenothiazine (MEEPT) and other phenothiazines, N- (ferrocenylmethyl)-N,N-dimethylethanaminium bis-(trifluoromethanesulfonyl)imide (Fc1N112-TFSI) and other ferrocenium derivatives as well as carbazole derivatives (e.g. 1,3,6,8-tetra-tert-butyl-2-ethylhexyl-carbazole, Cbz1).
  • the catholyte preferably has a high oxidation potential, stability and solubility.
  • a redox flow battery 1 The working principle of a redox flow battery 1 is shown in Fig. 1.
  • electrons 3 are released via an oxidation reaction from a high chemical potential state on the anode side 5 of the battery 1.
  • the electrons 3 move through the external circuit 7 and provide the electrical energy.
  • the electrons 3 are accepted via a reduction reaction at a lower chemical potential state on the cathode side 9 of the battery 1.
  • charge neutrality ions move through a membrane 11 inside the cell while on each side 5, 9 the side’s 5,9 respective liquid is circulated in the side’s 5,9 own respective space 13, 15.
  • the voltage, or electromotive force, generated in each cell 17 of the battery 1 is determined by the total difference in chemical potential between the chemical states of the active materials (anolyte and catholyte) on the two sides 5, 9 of the battery 1.
  • the voltage is dependent on the chemical species involved in the reactions as well as the number of cells 17 arranged in series. When charging the battery, this process will take place in a reverse manner.
  • the terms “deep reduction potential”, “high cell voltage”, “high stability in charged form” and “high solubility” may be seen as relative terms, but in the context of this invention they may be defined as follows.
  • a deep reduction potential can be defined as a reduction potential of or deeper than -1.5 V vs Fc/Fc + , preferably of or deeper than -2 V, more preferably of or deeper than -3 V.
  • High stability may be defined as at least 1000 cycles for cyclability (for instance with at least 50% retention of charge- discharge capacity) and at most 10% per month self-discharge.
  • High solubility determines together with the cell voltage the energy density of the battery. For example, with a cell voltage of 2.75 V (with DBBB or DBMMB catholyte), a solubility of 0.7 M would outperform vanadium RFBs in terms of energy density.
  • the present invention further relates to a method of manufacturing a non-aqueous redox flow battery, the method comprising: - immersing a negative electrode in a first non-aqueous liquid electrolyte; - immersing a positive electrode in a second non-aqueous liquid electrolyte; - interposing a semi-permeable separator between the negative and positive electrodes; wherein the first non-aqueous liquid electrolyte comprises a compound selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV): wherein R 1 and R 2 and/or R 3 and R 4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group, or wherein R 1 , R 2 , R 3 , R 4 and R 5 represent independent from each other H; CN; halogen; NO 2 ; NR 6 2; N 2 R 6 ; COR 6 ; linear, branched or cyclic hydrocarbyl group independently selected from
  • the second electrolyte is the liquid electrolyte that is comprised in the battery according to the present invention.
  • the present invention relates further to a method of operating a battery according to the present invention, the method comprising providing the battery according to the first aspect.
  • the present invention also relates to a compound according to formula (I). In this compound, R 2 and R 4 are H.
  • R 1 is CN; COR 6 ; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms.
  • R 3 is COOR 7 , wherein R 7 represents linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms.
  • R 1 and R 7 (which is the ester substituent) have as first (viewed from the depicted structure) atom a carbon atom.
  • R 1 is selected from CH 3 , CH 2 CH 3 , C 3 H 7 , C 4 H 9 , tertbutyl
  • COOCH 3 and R 7 is selected from CH 3 , CH 2 CH 3 , C 3 H 7 , C 4 H 9 and C(CH 3 ) 3
  • thus R 3 is selected from COOCH 3 , COO CH 2 CH 3 , COOC 3 H 7 , COOC 4 H 9 and COOC(CH 3 ) 3 ).
  • R 1 is methyl
  • R 7 is CH 3 or CH 2 CH 3 (thus R 3 is COOCH 3 or COOCH 2 CH 3 ).
  • the compounds of this embodiment are thus methyl 2,5- dicyano-4-methylbenzoate and ethyl 2,5-dicyano-4-methylbenzoate, and have the following formulas: .
  • the present invention relates also to a method of manufacturing the above-described compounds according to formula (I). In an embodiment, this method comprises the provision of a mixture of para-substituted dibromo derivative and copper cyanide.
  • Molecules 1 - 3 can all be synthesized with basic chemistry knowledge from cheap benzene derivatives.
  • 2,5-Di-tert-butylterephthalonitrile 7 1,4-Dibromo-2,5-di-tert- butylbenzene (350 mg, 1.01 mmol) was dissolved in anhydrous DMF (0.2 M), copper cyanide (198 mg, 2.21 mmol) added, and the mixture stirred under reflux for two days. After cooling down, the mixture was poured into 10% aqueous ammonia and extracted 3 times with DCM. The combined organic phase was washed twice with demineralized water, dried over MgSO 4 and concentrated under vacuo. The crude mixture was recrystallized from heptane to yield 176 mg of molecule 7 as white crystals (73%).
  • the aqueous phase was extracted twice with DCM and the combined organic phase washed with demineralized water, dried over MgSO 4 and concentrated under vacuo resulting in a colorless oil.
  • the crude mixture was analyzed by NMR and revealed a mixture of 0.99 g (48%) of 2,5-dibromo- 4-tert-butyltoluene and 0.75 g (37%) of unwanted 2,6-dibromo-4-tert-butyltoluene. It was not possible to separate both products by either column chromatography or distillation.
  • 2-tert-Butyl-5-methylterephthalonitrile 8 A mixture of 2,5- Dibromo-4-tert-butyltoluene (56.5%) and 2,6-Dibromo-4-tert-butyltoluene (43.5%) (500 mg, 1.63 mmol) was dissolved in anhydrous NMP (0.3 M), copper cyanide (293 mg, 3.27 mmol) added, and the mixture heated in the microwave for 20 minutes. After cooling down, the mixture was poured into 10% aqueous ammonia and extracted 3 times with DCM. The combined organic phase was washed twice with demineralized water, dried over MgSO 4 and concentrated under vacuo to yield a brown oil.
  • Diethyl 2,5-dicyanoterephthalate 9 A mixture of diethyl 2,5- dibromoterephthalate (2 g, 5.26 mmol) and copper cyanide (1.04 g, 11.58 mmol) was dissolved in DMSO (0.5 M) and the mixture heated for 3 h at 120 °C. After cooling down, the precipitate was filtered off, and the filtrate poured into 10% aqueous ammonia. The solids were filtered off again. Both solids were washed with DCM, the solvents combined and washed twice with demineralized water. After drying over MgSO 4 and concentration under vacuo beige solids remained.
  • Dibutyl 2,5-dicyanoterephthalate 10 A mixture of dibutyl-2,5- dibromoterephthalate (1.4 g, 3.21 mmol) and copper cyanide (0.63 g, 7.06 mmol) was dissolved in DMSO (0.5 M) and the mixture heated for 3 h at 120 °C.
  • Methyl 2,5-dicyano-4-methylbenzoate 11 A mixture of Ethyl 2,5- dibromo-4-methylbenzoate (1.14 g, 3.70 mmol) and copper cyanide (0.73 g, 8.14 mmol) was dissolved in DMSO (0.5 M) and the mixture heated for 2 h at 130 °C. After cooling down, the mixture was poured into 10% aqueous ammonia and extracted twice with DCM. The combined organic phase was washed twice with demineralized water.
  • Ethyl 2,5-dicyano-4-methylbenzoate 12 A mixture of Ethyl 2,5- dibromo-4-methylbenzoate (0.174 g, 0.54 mmol) and copper cyanide (0.11 g, 1.19 mmol) was dissolved in DMSO (0.5 M) and the mixture heated for 1 h at 120 °C and 1 h at 130 °C. After cooling down, the mixture was poured into 10% aqueous ammonia and extracted twice with DCM. The combined organic phase was washed twice with demineralized water. After drying over MgSO 4 and concentration under vacuo a brown solid remained.
  • Redox reaction in the battery application with electrolyte salt included The following reactions take place in the battery application with electrolyte salt included: Charging: Reduction: Anolyte + e ⁇ ⁇ Anolyte ⁇ Oxidation: Catholyte ⁇ Catholyte + + e ⁇ Discharging: Oxidation: Anolyte ⁇ ⁇ Anolyte + e ⁇ Reduction: Catholyte + + e ⁇ ⁇ Catholyte This depicts the redox processes happening while charging and discharging in the battery. While charging, the anolyte takes up an additional electron. On the catholyte side, another molecule gets oxidized, which means an electron gets removed.
  • the positive part of the electrolyte salt in this case tetrabutylammonium, moves towards the anolyte side and its negative part, the hexafluorophosphate, to the catholyte side.
  • the opposite process takes place.
  • 4 mL of 5 mM solutions of molecule 3 respectively 7 with 200 mM electrolyte salt (TBAPF 6 ) in acetonitrile get loaded on each side of an H-cell.
  • TAPF 6 200 mM electrolyte salt
  • a biologic VSP potentiostat a current is applied and the working side negatively charged. After full charging, the solution is removed and filled into a screw-capped glass vial.
  • Samples for absorption measurements were prepared in a 0.2 mm pathlength quartz cuvette in the glove box but measured outside the glove box at different points in time. While the at the core positions unprotected molecule 3 lost its charge completely after 10 days, the charged solution of molecule 7 still contained 31% of its initial charge after 43 days.
  • CV measurements prior to charging and after storing for 43 days were performed and revealed a similar state-of-charge (SoC) after 43 days of 27%, determined via the open-circuit voltage.
  • SoC state-of-charge
  • the maximum power density for both systems could not be determined as the potentiostat limited the current to 0.157 A/cm 2 . Extrapolation suggests a very high maximum power density of about 0.39 W/cm 2 at a current density of 0.27 A/cm 2 . Also, the performance of the molecule 9/MEEPT-system was evaluated and suggested an extrapolated maximum power density of about 0.142 W/cm 2 at a current density of 0.176 A/cm 2 .
  • Figure 2A shows static, coin cell cycling of 45 or 50 mM of molecule 3 (full squares and diamonds), 7 (half squares and half diamonds), 8 (stars), respectively 12 (circles), and 50 or 55 mM DBBB in 200 mM TBAPF 6 /acetonitrile if not differently indicated. Only every 50 th cycle is shown for better clarity.
  • Figure 2B shows static, coin cell cycling of 50 mM of molecule 7 and 8 with 50 mM DBBB in 200 mM TBAPF 6 /acetonitrile. Only every 200 th cycle is shown for better clarity.
  • Figure 2C shows static, coin cell cycling at high a concentration of 500 mM of molecule 7 and 350 mM of 8 with 550 mM DBMMB in 750 mM TBAPF 6 /acetonitrile, respectively 385 and 525 mM. Only every 20 th cycle is shown for better clarity.
  • Figure 2D shows static, coin cell cycling of molecule 11 at a concentration of 50 mM in 200 mM TBAPF 6 /acetonitrile. Only every 10 th cycle is shown for better clarity.
  • Figure 2E and 2F show static, coin cell cycling of molecule 9 at a concentration of 50 mM with various catholytes at 50 mM in 200 mM TBAPF 6 /acetonitrile.
  • Figure 3 shows the volumetric capacity versus cycle number of flow battery cycling of a mixed solution of 50 mM of molecule 7 with 55 mM DBBB and 200 mM TBAPF 6 in acetonitrile using a porous Daramic 175 separator.
  • the very soluble molecule 3 was paired with DBMMB.
  • a 0.5 M battery was run for 50 cycles as a demonstration ( Figure 4A and 4B). Further optimization has to be done for a better performance.
  • the 50 mM flow battery cycling of molecule 7 shows very promising results. Charging was performed with a constant current of 30 mA/cm 2 , with a voltaic cutoff at 3.1 V.
  • Discharging was performed at a constant current of -30 mA/cm 2 with a voltaic cutoff at 1.5 V. Very high average coulombic and energy efficiencies of 93.4% and 79% were achieved.
  • the battery’s capacity retention stayed very steady after an initial capacity drop between cycle 50 and 150.
  • the fast capacity drop within the first 150 cycles can be attributed to transport phenomena.
  • about 1.25 mL have been transferred from anolyte to catholyte reservoir including active compounds and electrolyte salt. Analyzing both reservoirs after 500 cycles by cyclic voltammetry revealed that at least 73% of molecule 7 remained in the anolyte reservoir and 80% in the catholyte reservoir, showing an excellent stability of the molecule itself.
  • the decay from cycle 200 to 500 is about -0.06%/cycle which correlates with a decay of about 0.05%/cycle taking the capacity retention of 73% determined by CV.
  • the system of molecule 9/MEEPT was evaluated in a flow battery at a concentration of 50 mM in 200 mM TBAPF 6 in acetonitrile ( Figure 5A and 5B). Thereby, no detectable decay could be determined by the discharge capacity nor cyclic voltammetry with a microelectrode after 100 cycles.
  • Table 2 shows a comparison of molecules 6, 7 and 9 (numbers indicated in brackets in the first column) according to the present invention with anolytes from literature. Table 2: Comparison with literature.
  • Figure 4A shows volumetric capacity versus cycle number of flow battery cycling of a mixed solution of 500 mM of molecule 3 with 550 mM DBBB and 750 mM TBAPF 6 in acetonitrile using a porous Daramic 175 separator.
  • Figure 4B shows the charging and discharging voltages in dependance of their SoC (expressed via capacity) for cycle number 1 and 25. The upper lines represent the charging and the lower ones the discharging. The curves reveal relatively high average discharge voltages of 2.43 and 2.33 V for cycle 1, respectively 25, as well as a slight overcharge in the first cycle which can be attributed to active material crossing over through the porous separator.
  • the 500 mM flow battery cycling shows very promising results.
  • Molecule 3 exhibits at least a high solubility of 500 mM in all SoCs in the 0.75 M TBAPF 6 /acetonitrile mixture.
  • Charging was performed with a constant current of 50 mA/cm 2 , followed by a constant voltage at 2.95 V with a cutoff threshold of 15 mA/cm 2 .
  • Discharging was performed almost fully at a constant current of -50 mA/cm 2 with a very short voltaic hold at 1 V (threshold 6 mA/cm 2 ). Energy efficiencies of 55 to 63% were achieved. This could be increased by charging and discharging slower.
  • the battery’s capacity retention might be limited due to unwanted reaction of the anolyte with the catholyte (both are present in both reservoirs in a mixed flow battery) or solvent or electrolyte salt.
  • Sterically more protected derivatives, such as molecules 7 and 8 will mitigate side reaction as well as self-discharge, which could be proven for molecule 7 in UV-vis-NIR as well as coin cell and flow battery cycling experiments.
  • Another very promising possibility to increase the stability is alternating the solvent/electrolyte salt mixture.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Electrochemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Sustainable Energy (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The present invention relates to a battery comprising a liquid electrolyte, the liquid electrolyte comprising a compound selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV), wherein R1 and R2 and/or R3 and R4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group, or wherein R1, R2, R3, R4 and R5 represent independent from each other H; CN; halogen; NO2; NR6 2; N2R6; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein R6 represents H or a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein A" is an anion. The present invention further relates to a method of manufacturing such a battery, and to a method of operating such a battery. The present invention further relates to a compound according to formula (I) wherein R2 and R4 are H; wherein R1 is CN; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein R3 is COOR7, wherein R7 represents linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms. The present invention further relates to a method of manufacturing said compound.

Description

TITLE A non-aqueous redox flow battery TECHNICAL FIELD The present invention relates to a battery, specifically to a non- aqueous redox flow battery. The invention further relates to a method of operating such a battery. BACKGROUND In a world where climate neutrality is the goal, green energy sources are essential. More than half of the produced green energy comes from wind and solar power. In order to overcome their intermittency, energy storage applications are inevitable. Redox flow batteries (RFBs) are very promising storage systems in the transition towards renewable energy sources. A redox flow battery generally comprises a negative electrode immersed in a liquid negative electrolyte, a positive electrode immersed in a liquid positive electrolyte, and an ion-permeable separator (e.g., a porous membrane, film, sheet, or panel as well as ion-exchange membranes) between the negative and the positive electrolyte. During charging and discharging, the electrolytes are circulated over their respective electrodes. The electrolytes each comprise either an electrolyte salt (e.g., a lithium, sodium, or organic salt) or a strong acid or base (e.g., NaOH, KOH, HCl or H2SO4), a redox reactant, and optionally a solvent (e.g. an electrochemically stable organic solvent). They can be broadly classified in aqueous and non-aqueous systems. In aqueous RFBs, the voltage and hence energy density is limited by the water electrolysis potential (usually between 1.15 and 1.55V). Furthermore, the used electrolytes are in most of the cases highly corrosive (operate at pH 0 or 14). Non-aqueous systems operate with organic solvents, which allow for a much broader potential window (up to three times higher) compared to water. Combination of organic solvents with organic redox active materials could pave the way for all carbon-based RFBs with superior energy densities compared to aqueous systems. US10424806B2 discloses a non-aqueous redox flow battery wherein the redox reactant of the positive electrolyte is a dialkoxybenzene compound, and the redox reactant of the negative electrolyte is a viologen compound or a dipyridyl ketone.
US10535891 B2 discloses a redox flow battery comprising a two- electron, redox active, bridged, multi-cyclic compound (“TRBMC”) that comprises a non-aromatic, bridged cyclic portion fused to an aromatic cyclic portion.
US9300000B2 discloses a non-aqueous redox flow battery wherein each redox reactant is selected from an organic compound comprising a conjugated unsaturated moiety, a boron cluster compound, and a combination thereof. The organic redox reactant of the positive electrolyte is selected to have a higher redox potential than the redox reactant of the negative electrolyte.
In non-aqueous flow batteries an organic solvent can be used that can withstand higher potentials, but finding redox active compounds that offer a combination of higher redox potentials, high stability in charged form, and high solubility remains a challenge.
In addition, the currently used organic molecules, however, become more and more complex as they have to fulfill several requirements, e.g. regarding high solubility and stability, as well as high redox potentials and multi-electron redox events to increase capacitance. In general, implementing all these functionalities results in an undesirable higher molecular weight. Moreover, the synthetic complexity of the molecules tends to increase which reduces the feasibility for a large-scale application.
Therefore, there is a need for a redox flow battery that combines high redox potentials, high stability in charged form, and high solubility.
SUMMARY
The present invention therefore relates in a first aspect to a battery comprising a liquid electrolyte, the liquid electrolyte comprising: a compound selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV):
Figure imgf000005_0001
In these formulas, R1 and R2 and/or R3 and R4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group, or R1, R2, R3, R4 and R5 represent independent from each other H; CN; halogen; NO2; NR6 2; N2R6; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms. R6 represents H or a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1- 18 carbon atoms, wherein A- represents an anion. In a second aspect, the present invention relates to a method of manufacturing a battery according to the first aspect, the method comprising: - immersing a negative electrode in a first non-aqueous liquid electrolyte; - immersing a positive electrode in a second non-aqueous liquid electrolyte; - interposing a semi-permeable separator between the negative and positive electrodes; wherein the first non-aqueous liquid electrolyte comprises the liquid electrolyte as described for the first aspect. In a third aspect, the present invention relates to a method of operating a battery according to the first aspect of the present invention. The method comprises: providing the battery according to the first aspect. In a fourth aspect, the present invention relates to a compound according to formula (I). In this compound, R2 and R4 are H. In this compound, R1 is CN; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms. In this compound, R3 is COOR7, wherein R7 represents linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms. In a fifth aspect, the present invention relates to a method of manufacturing said compound. Embodiments of the first aspect are applicably correspondingly to the second, third, fourth and fifth aspect according to the present invention. BRIEF DESCRIPTION OF DRAWINGS The present invention is described hereinafter with reference to the accompanying drawings in which embodiments of the present invention are shown and in which like reference numbers indicate the same or similar elements. Figure 1 shows a schematic representation of the working principle of a redox flow battery according to one example according to the present invention. Figure 2A shows the normalized discharge capacity of static, coin cell cycling, up to 3000 cycles. Figure 2B shows the normalized discharge capacity of static, coin cell cycling, up to 10000 cycles. Figure 2C shows the normalized discharge capacity of static, coin cell cycling at higher concentration, up to 1000 cycles. Figure 2D shows the normalized discharge capacity of static, coin cell cycling up to 500 cycles. Figure 2E shows the normalized discharge capacity of static, coin cell cycling at a concentration of 50 mM with various catholytes, up to 1000 cycles. Figure 2F shows the normalized discharge capacity of static, coin cell cycling of the most promising anolyte/catholytes combinations, up to 20000 cycles. Figure 3 shows the volumetric capacity versus the cycle number of flow battery cycling for an example according to the present invention. Figure 4A shows volumetric capacity versus cycle number of flow battery cycling for another example according to the present invention. Figure 4B shows a voltage versus capacity profile for the example of Fig.4A. Figure 5A shows volumetric capacity versus cycle number of flow battery cycling for another example according to the present invention. Figure 5B shows a voltage versus capacity profile for the example of Fig.5A. DESCRIPTION It is an object of the present invention to provide an improved non- aqueous redox flow battery. It is a further object of the present invention to provide a non-aqueous redox flow battery with deep reduction potential anolytes and ultimately a high cell voltage and/or high stability in charged form, and/or high solubility. It is a further object of the present invention to provide a non-aqueous redox flow battery that combines deep reduction potential anolytes and ultimately a high cell voltage, high stability in charged form, and high solubility. It is a further object of the present invention to provide deep reduction potential anolytes for non-aqueous redox flow batteries of which the organic molecules are relatively easy to synthesize. As stated above, the invention relates in a first aspect to a battery comprising a liquid electrolyte comprising a compound selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV). This compound is able to take up an electron. In some types of batteries, such as in redox flow batteries, this compound would be defined as the anolyte. In an embodiment, the liquid electrolyte comprises comprises two or more compounds selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV). When there are two or more of such compounds, preferably said compounds have a similar redox potential. For example, the redox potentials of said two or more compounds differ less than 200 mV. The presence of two or more of such compounds will lead to a similar or higher solubility than when the liquid electrolyte comprises one of such compounds. In an embodiment, the liquid electrolyte comprises a compound selected from the group consisting of formula (I), formula (II) and formula (IV). In an embodiment, R1 and R2 and/or R3 and R4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group. In other words, the ring depicted in the formula forms a fused ring system with a ring formed by R1 and R2 and/or R3 and R4. The substituent(s), when present, may be branched or unbranched. In an embodiment, R1 and R2 as well as R3 and R4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group. Suitable examples of an optionally substituted cyclic group are an optionally substituted cycloalkane group, cycloheteroalkane group, cycloalkene group and cycloheteroalkene group. In an embodiment, the optionally substituted cyclic group is a cycloalkane group. In an embodiment of the first aspect according to the present invention, R1, R2, R3, R4 and R5 represent independent from each other H; CN; halogen; NR6 2; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-10 carbon atoms, preferably from 1-5 carbon atoms; In an embodiment of the first aspect according to the present invention, R1, R2, R3, R4 and R5 represent independent from each other H; CN; COR6; linear or branched hydrocarbyl group independently selected from alkyl, alkoxy and alkoxycarbonyl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-10 carbon atoms, preferably from 1-5 carbon atoms; In an embodiment of the first aspect according to the present invention, R6 represents H or a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-10 carbon atoms, preferably from 1-5 carbon atoms. In an embodiment of the first aspect according to the present invention, at least one of R1 of R2 and at least one of R3 and R4 is H, preferably wherein R2 = R4 = H. In an embodiment of the first aspect according to the present invention, R1 is not H. In an embodiment of this, R3 is also not H. In an embodiment, at least one of R1 and R3 is branched. In an embodiment, R1 and R3 are independently chosen from CH3, C2H5, C3H7, C4H9, tert-butyl, COOCH3, COOC2H5, COOC3H7, COOC4H9 and COOC(CH3)3. R3 may be the same or different from R1, preferably R3 is different from R1. The presence and nature of substituents allow for adjustability of the stability, solubility and redox potential of the compound. When R3 and R1 are different, this asymmetry allows for finetuning of redox potential and a higher solubility. When the compound is according to formula (III), there is an anion present. This anion must be electrochemically inert in the potential window in which the battery is operated. Examples of suitable anions include PF6-, BF4-, N(SO2CF3)2- (TFSI), CF3SO3- (FSI), CH3SO3-, CH3C6H4SO3- (OTs) or diethyl phosphate. In an embodiment, the compound is selected from formula (I), (II) or (IV). In an embodiment, the liquid electrolyte comprises a compound according to one of the following formulas:
Figure imgf000009_0001
Figure imgf000010_0001
In an embodiment, the liquid electrolyte comprises a compound according to one of the following formulas:
Figure imgf000011_0001
In an embodiment, the liquid electrolyte comprises a compound according to one of the following formulas:
Figure imgf000012_0001
preferably wherein the compound is according to any one of formulas (1) – (13), more preferably according to any one of formulas (1) – (12). In a preferred embodiment, the liquid electrolyte comprises a compound according to one of the following formulas:
Figure imgf000013_0001
Without wishing to be bound by theory, the inventors believe that, while compounds with formulas (I)-(IV) provide deep reduction potentials, a careful selection of the side groups R1, R2, R3, R4 and R5 will impart stability in the neutral and reduced states on these compounds in combination with high solubility in organic electrolytes via a proper choice of R1, R2, R3, R4 and R5, via an increase and differentiation in length, branching, and bulkiness of the side groups. In this respect the inventors believe that combinations of branched-linear or branched-branched, and linear side groups, as well as ester groups of different lengths are particular successful for enhancing solubility. In an embodiment of the first aspect according to the present invention, the battery further comprises a solvent that is electrochemically stable in a wide potential range, preferably between -3V to +2V, such as between -2.5V to + 1.5V vs ferrocene/ferrocenium (Fc/Fc+), wherein the solvent is acetonitrile; an ether-based solvent, preferably dimethoxyethane; diethyl carbitol, dimethylformamide or a mixture thereof. In an embodiment of the first aspect according to the present invention, the battery further comprises one or more electrolyte salts and a counter ion, wherein the one or more electrolyte salts has a solubility of >0.5 M in the solvent. In a specific embodiment, the one or more electrolyte salt is a quaternary ammonium or imidazolium. In a specific embodiment, the counter ion is chosen from the group of PF6-, BF4-, N(SO2CF3)2- (TFSI), CF3SO3- (FSI), CH3SO3- or CH3C6H4SO3- (OTs) and diethyl phosphate. In an embodiment of the first aspect according to the present invention, the battery is a redox flow battery. In a specific embodiment, the battery is a non-aqueous redox flow battery. As stated above, the invention relates in a first aspect to a battery comprising a compound according to one of the formulas (I)-(IV). When the battery is a redox flow battery, this compound serves as the anolyte. In other types of batteries, such as lithium ion or lead acid batteries, this compound is often described as material to store electrons, or as material for the anode. In an embodiment, the battery further comprises a material for the cathode (in certain types of batteries such as in redox flow batteries called a catholyte). This catholyte may for instance be chosen from 2,5-di-tert-butyl-1,4-bis(2- methoxyethoxy)benzene (DBBB), 1,4-di-tert-butyl-2-methoxy-5-(2-(2- methoxyethoxy)ethoxy)benzene (DBMMB) as well as 1,4-di-tert-butyl-2,5-bis(2,2,2- trifluoroethoxy)benzene compounds. Other suitable catholytes are 10-[2-(2- methoxyethoxy)ethyl]-10H-phenothiazine (MEEPT) and other phenothiazines, N- (ferrocenylmethyl)-N,N-dimethylethanaminium bis-(trifluoromethanesulfonyl)imide (Fc1N112-TFSI) and other ferrocenium derivatives as well as carbazole derivatives (e.g. 1,3,6,8-tetra-tert-butyl-2-ethylhexyl-carbazole, Cbz1). The catholyte preferably has a high oxidation potential, stability and solubility. The working principle of a redox flow battery 1 is shown in Fig. 1. During discharging of the battery 1, electrons 3 are released via an oxidation reaction from a high chemical potential state on the anode side 5 of the battery 1. The electrons 3 move through the external circuit 7 and provide the electrical energy. Then, the electrons 3 are accepted via a reduction reaction at a lower chemical potential state on the cathode side 9 of the battery 1. To compensate charge neutrality ions move through a membrane 11 inside the cell while on each side 5, 9 the side’s 5,9 respective liquid is circulated in the side’s 5,9 own respective space 13, 15. The voltage, or electromotive force, generated in each cell 17 of the battery 1 is determined by the total difference in chemical potential between the chemical states of the active materials (anolyte and catholyte) on the two sides 5, 9 of the battery 1. The voltage is dependent on the chemical species involved in the reactions as well as the number of cells 17 arranged in series. When charging the battery, this process will take place in a reverse manner. With the present invention, at least one of the objects is achieved. The terms “deep reduction potential”, “high cell voltage”, “high stability in charged form” and “high solubility” may be seen as relative terms, but in the context of this invention they may be defined as follows. A deep reduction potential can be defined as a reduction potential of or deeper than -1.5 V vs Fc/Fc+, preferably of or deeper than -2 V, more preferably of or deeper than -3 V. High stability may be defined as at least 1000 cycles for cyclability (for instance with at least 50% retention of charge- discharge capacity) and at most 10% per month self-discharge. High solubility determines together with the cell voltage the energy density of the battery. For example, with a cell voltage of 2.75 V (with DBBB or DBMMB catholyte), a solubility of 0.7 M would outperform vanadium RFBs in terms of energy density. The present invention further relates to a method of manufacturing a non-aqueous redox flow battery, the method comprising: - immersing a negative electrode in a first non-aqueous liquid electrolyte; - immersing a positive electrode in a second non-aqueous liquid electrolyte; - interposing a semi-permeable separator between the negative and positive electrodes; wherein the first non-aqueous liquid electrolyte comprises a compound selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV):
Figure imgf000015_0001
wherein R1 and R2 and/or R3 and R4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group, or wherein R1, R2, R3, R4 and R5 represent independent from each other H; CN; halogen; NO2; NR6 2; N2R6; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein R6 represents H or a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein A- represents an anion. In other terms, the second electrolyte is the liquid electrolyte that is comprised in the battery according to the present invention. The present invention relates further to a method of operating a battery according to the present invention, the method comprising providing the battery according to the first aspect. The present invention also relates to a compound according to formula (I). In this compound, R2 and R4 are H. In this compound, R1 is CN; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms. In this compound, R3 is COOR7, wherein R7 represents linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms. To clarify, the compound described above is according to the following formula:
Figure imgf000016_0001
Both R1 and R7 (which is the ester substituent) have as first (viewed from the depicted structure) atom a carbon atom. Further in the chain there may be heteroatoms such as oxygen or nitrogen present (such as when the R-group is CN or COR6). In an embodiment, R1 is selected from CH3, CH2CH3, C3H7, C4H9, tertbutyl, COOCH3 and R7 is selected from CH3, CH2CH3, C3H7, C4H9 and C(CH3)3 (thus R3 is selected from COOCH3, COO CH2CH3, COOC3H7, COOC4H9 and COOC(CH3)3). In an embodiment, R1 is methyl, and R7 is CH3 or CH2CH3 (thus R3 is COOCH3 or COOCH2CH3). The compounds of this embodiment are thus methyl 2,5- dicyano-4-methylbenzoate and ethyl 2,5-dicyano-4-methylbenzoate, and have the following formulas:
Figure imgf000017_0001
. The present invention relates also to a method of manufacturing the above-described compounds according to formula (I). In an embodiment, this method comprises the provision of a mixture of para-substituted dibromo derivative and copper cyanide. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope thereof. The scope of the present invention is defined by the appended claims. One or more of the objects of the invention are achieved by the appended claims. EXAMPLES
The present invention is further elucidated based on the Examples below which are illustrative only and not considered limiting to the present invention.
If for a reported value no specific method of measurement is explicitly mentioned, it can be assumed that the same method of measurement is used as described elsewhere in the present description.
Synthesis of dicyanobenzenes
Synthesis routes of several dicyanobenzenes are as follows, and further elaborated below.
Figure imgf000018_0001
Figure imgf000019_0001
Molecules 1 - 3 can all be synthesized with basic chemistry knowledge from cheap benzene derivatives.
2-Ethylterephthalonitrile 3: 1 ,4-Dibromo-2-ethylbenzene (500 mg,
1.89 mmol) was dissolved in anhydrous N-methyl-2-pyrrolidone (NMP) (0.75 M), copper cyanide (339 mg, 3.79 mmol) added, and the mixture stirred under reflux overnight. After cooling down, the mixture was poured into 10% aqueous ammonia and extracted 3 times with dichloromethane (DCM). The combined organic phase was twice washed with demineralized water, dried over MgSO4 and concentrated under vacuo. The crude mixture was recrystallized from heptane to yield 163 mg of molecule 3 as white crystals (55%). 1H NMR (400 MHz, Chloroform-d) δ 7.73 (d, 1H), 7.64 (s, 1H), 7.59 (dd, 1H), 2.94 (q, 2H), 1.34 (t, 3H). The synthesis of molecule 5 has been described in US009603848B2. 2,5-Diethylterephthalonitrile 6: 1,4-Dibromo-2,5-di-ethylbenzene (300 mg, 1.03 mmol) was dissolved in anhydrous DMF (0.2 M), copper cyanide (202 mg, 2.26 mmol) added, and the mixture stirred under reflux overnight. After cooling down, the mixture was poured into 10% aqueous ammonia and extracted 3 times with DCM. The combined organic phase was twice washed with demineralized water, dried over MgSO4 and concentrated under vacuo. The crude mixture was recrystallized from heptane to yield 141 mg of molecule 6 as white crystals (75%). 2,5-Dibromo-1,4-di-tert-butylbenzene: 1,4-Di-tert-butylbenzene (1 g, 5.25 mmol) was dissolved in chloroform (0.5 M) and cooled to 0°C. Bromine (0.54 mL, 10.51 mmol) and iodine (0.133 g, 0.53 mmol) were added, and the mixture stirred for two days. After pouring slowly into 20% aqueous sodium hydroxide the solution discolored and the organic phase was separated. The aqueous phase was extracted 2 times with DCM and the combined organic phase washed with demineralized water, dried over MgSO4 and concentrated under vacuo. The crude mixture was recrystallized from heptane to yield 0.82 g of 1,4-dibromo-2,5-di-tert-butylbenzene as white crystals (45%). %).1H NMR (400 MHz, Chloroform-d) δ 7.58 (s, 2H), 1.48 (s, 18H). An analysis of the crude mixture revealed the presence of 48% of 1-bromo-2,5-di-tert- butylbenzene. 2,5-Di-tert-butylterephthalonitrile 7: 1,4-Dibromo-2,5-di-tert- butylbenzene (350 mg, 1.01 mmol) was dissolved in anhydrous DMF (0.2 M), copper cyanide (198 mg, 2.21 mmol) added, and the mixture stirred under reflux for two days. After cooling down, the mixture was poured into 10% aqueous ammonia and extracted 3 times with DCM. The combined organic phase was washed twice with demineralized water, dried over MgSO4 and concentrated under vacuo. The crude mixture was recrystallized from heptane to yield 176 mg of molecule 7 as white crystals (73%).1H NMR (400 MHz, Chloroform-d) δ 7.74 (s, 2H), 1.52 (s, 18H). 2,5-Dibromo-4-tert-butyltoluene: 4-tert-Butyl-toluene (1 g, 6.75 mmol) was mixed with chloroform (1 M) and cooled to 0°C. Bromine (0.78 mL, 15.18 mmol) and iodine (0.171 g, 0.67 mmol) were added, and the mixture stirred for two days. After pouring slowly into 20% aqueous sodium hydroxide the solution discolored and the organic phase was separated. The aqueous phase was extracted twice with DCM and the combined organic phase washed with demineralized water, dried over MgSO4 and concentrated under vacuo resulting in a colorless oil. The crude mixture was analyzed by NMR and revealed a mixture of 0.99 g (48%) of 2,5-dibromo- 4-tert-butyltoluene and 0.75 g (37%) of unwanted 2,6-dibromo-4-tert-butyltoluene. It was not possible to separate both products by either column chromatography or distillation. 1H NMR of 2,5-dibromo-4-tert-butyltoluene (400 MHz, Chloroform-d) δ 7.54 (s, 1H), 7.45 (s, 1H), 2.31 (s, 3H), 1.48 (s, 9H).1H NMR of 2,6-dibromo-4-tert- butyltoluene (400 MHz, Chloroform-d) δ 7.49 (s, 2H), 2.53 (s, 3H), 1.28 (s, 9H). 2-tert-Butyl-5-methylterephthalonitrile 8: A mixture of 2,5- Dibromo-4-tert-butyltoluene (56.5%) and 2,6-Dibromo-4-tert-butyltoluene (43.5%) (500 mg, 1.63 mmol) was dissolved in anhydrous NMP (0.3 M), copper cyanide (293 mg, 3.27 mmol) added, and the mixture heated in the microwave for 20 minutes. After cooling down, the mixture was poured into 10% aqueous ammonia and extracted 3 times with DCM. The combined organic phase was washed twice with demineralized water, dried over MgSO4 and concentrated under vacuo to yield a brown oil. Column chromatography in heptane/DCM (starting with 10:1) yielded 103 mg of molecule 8 (31.8%). 1H NMR (400 MHz, Chloroform-d) δ 7.68 (s, 1H), 7.62 (s, 1H), 2.54 (s, 3H), 1.51 (s, 9H). As a side product, 69 mg of 2-tert-butyl-5-methyl-1,4-dicyanobenzene (21.2%) could be isolated. 1H NMR (400 MHz, Chloroform-d) δ 7.81 (s, 2H), 2.72 (s, 3H), 1.33 (s, 9H). Diethyl 2,5-dicyanoterephthalate 9: A mixture of diethyl 2,5- dibromoterephthalate (2 g, 5.26 mmol) and copper cyanide (1.04 g, 11.58 mmol) was dissolved in DMSO (0.5 M) and the mixture heated for 3 h at 120 °C. After cooling down, the precipitate was filtered off, and the filtrate poured into 10% aqueous ammonia. The solids were filtered off again. Both solids were washed with DCM, the solvents combined and washed twice with demineralized water. After drying over MgSO4 and concentration under vacuo beige solids remained. Recrystallization in heptane/ethyl acetate yielded 1.33 g of molecule 9 (93%). 1H NMR (400 MHz, Chloroform-d) δ 8.54 (s, 2H), 4.54 (q, J = 7.15 Hz, 4H), 1.49 (t, J = 7.15 Hz, 6H). Dibutyl 2,5-dibromoterephthalate: A mixture of 2,5- dibromoterephthalic acid (2 g, 6.17 mmol) and thionyl chloride (1.5 M) was refluxed for 4 h. After evaporation of the thionyl chloride, the residue was dissolved in anhydrous THF (1.5 M), 1-butanol (3 mL, 32.72 mmol) and the mixture stirred at room temperature overnight.50 mL of DCM were added, and the mixture washed four times with demineralized water. After drying over MgSO4 and concentration under vacuo a white gel-like compound remained (52%, 1.4 g). 1H NMR (400 MHz, Chloroform-d) δ 8.01 (s, 2H), 4.37 (q, J = 6.62 Hz, 4H), 1.77 (quintet, J = 6.87 Hz, 4H), 1.46 (dt, J = 14.57, 7.39 Hz, 4H), 1.77 (t, J = 7.38 Hz, 6H). Dibutyl 2,5-dicyanoterephthalate 10: A mixture of dibutyl-2,5- dibromoterephthalate (1.4 g, 3.21 mmol) and copper cyanide (0.63 g, 7.06 mmol) was dissolved in DMSO (0.5 M) and the mixture heated for 3 h at 120 °C. After cooling down, the precipitate was filtered off, and the filtrate poured into 10% aqueous ammonia. The solids were filtered off again. Both solids were washed with DCM, the solvents combined and washed twice with demineralized water. After drying over MgSO4 and concentration under vacuo a beige solid remained. Recrystallization in heptane/ethyl acetate yielded 0.66 g of molecule 10 (63%). 1H NMR (400 MHz, Chloroform-d) δ 8.53 (s, 2H), 4.48 (t, J = 6.65 Hz, 4H), 1.83 (quintet, J = 6.85 Hz, 4H), 1.49 (dt, J = 14.61, 7.33 Hz, 4H), 1.00 (t, J = 7.36 Hz, 6H). 2,5-Bromo-4-methylbenzoic acid: 1,4-Dibromo-2,5- dimethylbenzene (2.61 g, 9.89 mmol) was dissolved in water/nitric acid (55/45%, 0.5 M) and the mixture heated for 6 h at 130 °C in a pressure-tight microwave vial and the pressure released by a needle. The mixture was cooled to 120 °C and stirred for an additional 16 h. After cooling down to 80°C, the pressure was released and the precipitate filtered hot and washed with water. After drying at 70 °C under vacuo, 2.21 g of a white solid of 2,5-dibromo-4-methylbenzoic acid remained (76%). 1H NMR (400 MHz, DMSO-d6) δ 13.56 (br s, 1H), 7.93 (s, 1H), 7.76 (s, 1H), 2.37 (s, 3H). Methyl 2,5-dibromo-4-methylbenzoate: 2,5-Dibromo-4- methylbenzoic acid (1.11 g, 3.78 mmol) was dissolved in thionyl chloride (7.6 mL) and refluxed for 3 h. After evaporation of the thionyl chloride, ethanol (7.6 mL) was added at 0°C and mixture stirred overnight. Concentration under vacuo led to a white powder, 1.14 g of methyl 2,5-dibromo-4-methylbenzoate (98%). 1H NMR (400 MHz, Chloroform-d) δ 8.01 (s, 1H), 7.54 (s, 1H), 3.92 (s, 3H), 2.41 (s, 3H). Methyl 2,5-dicyano-4-methylbenzoate 11: A mixture of Ethyl 2,5- dibromo-4-methylbenzoate (1.14 g, 3.70 mmol) and copper cyanide (0.73 g, 8.14 mmol) was dissolved in DMSO (0.5 M) and the mixture heated for 2 h at 130 °C. After cooling down, the mixture was poured into 10% aqueous ammonia and extracted twice with DCM. The combined organic phase was washed twice with demineralized water. After drying over MgSO4 and concentration under vacuo a brown solid remained. Recrystallization in heptane/ethyl acetate yielded 0.49 g of beige/yellowish crystals, which turned out to be a mixture between singly and doubly cyanated product. Column chromatography in heptane/DCM (starting with pure heptane, going up to 67% DCM) yielded 0.07 g of molecule 11 (9%). 1H NMR (400 MHz, Chloroform-d) δ 8.37 (s, 1H), 7.78 (s, 1H), 4.03 (s, 3H), 2.67 (s, 3H). 13C NMR (100 MHz, Chloroform-d) δ 162.75, 147.05, 136.30, 135.02, 117.18, 116.59, 116.05, 115.61, 53.33, 20.57. Ethyl 2,5-dibromo-4-methylbenzoate: 2,5-Dibromo-4- methylbenzoic acid (0.49 g, 1.65 mmol) was dissolved in thionyl chloride (10 mL) and refluxed for 3 h. After evaporation of the thionyl chloride, ethanol (20 mL) was added at 0°C and mixture stirred overnight. After adding water and DCM, the organic phase was separated and twice washed with demineralized water. Drying over MgSO4 and concentration under vacuo led to a dark brown liquid/oil. Column chromatography in heptane/DCM (starting with pure heptane, going up to 33% DCM) yielded 0.174 g of ethyl 2,5-dibromo-4-methylbenzoate (26%). 1H NMR (400 MHz, Chloroform-d) δ 7.98 (s, 1H), 7.53 (s, 1H), 4.39 (q, 2H), 1.40 (t, 3H). Ethyl 2,5-dicyano-4-methylbenzoate 12: A mixture of Ethyl 2,5- dibromo-4-methylbenzoate (0.174 g, 0.54 mmol) and copper cyanide (0.11 g, 1.19 mmol) was dissolved in DMSO (0.5 M) and the mixture heated for 1 h at 120 °C and 1 h at 130 °C. After cooling down, the mixture was poured into 10% aqueous ammonia and extracted twice with DCM. The combined organic phase was washed twice with demineralized water. After drying over MgSO4 and concentration under vacuo a brown solid remained. Recrystallization in heptane/ethyl acetate yielded 0.11 g of beige/yellowish crystals, which turned out to be a mixture between singly and doubly cyanated product. Column chromatography in heptane/DCM (starting with pure heptane, going up to 67% DCM) yielded 0.024 g of molecule 12 (21%). 1H NMR (400 MHz, Chloroform-d) δ 8.36 (s, 1H), 7.77 (s, 1H), 4.48 (q, 2H), 1.45 (t, 3H). Cyclic voltammetry Cyclic voltammetry is a technique used to investigate oxidation and reduction processes of redox-active compounds. By applying a potential sweep in alternating directions, peaks emerge which indicate at which potential oxidation and/or reduction processes occur. In the ideal case their shape follows the Nernst equation and peak separation, and height can be used to determine diffusion coefficients and homogenous electron transfer rates. Cyclic voltammograms of the molecules 1-17 at a concentration of 5 mM in various solvents and electrolyte salts were recorded with a scan rate of 100 mV s−1 and shown in Table 1. In Table 1, the following abbreviations are used: can = acetonitrile, DMF = dimethylformamide, PhCN = benzonitrile, Pyr = pyridine, DME = dimethoxyethane, TBAPF6 = tetrabutylammonium hexafluorophosphate, TEATFSI = tetraethylammonium bis(trifluoromethanesulfonyl)imide, KTFSI = potassium bis(trifluoromethanesulfonyl)imide. Table 1: Reduction potentials vs Fc/Fc+ and solubilities (if determined) of compounds 1-18.
Figure imgf000024_0001
Figure imgf000025_0001
Redox reaction in the battery application with electrolyte salt included The following reactions take place in the battery application with electrolyte salt included: Charging: Reduction: Anolyte + e− → Anolyte− Oxidation: Catholyte → Catholyte+ + e− Discharging: Oxidation: Anolyte− → Anolyte + e− Reduction: Catholyte+ + e− → Catholyte This depicts the redox processes happening while charging and discharging in the battery. While charging, the anolyte takes up an additional electron. On the catholyte side, another molecule gets oxidized, which means an electron gets removed. In order to balance the charges, the positive part of the electrolyte salt, in this case tetrabutylammonium, moves towards the anolyte side and its negative part, the hexafluorophosphate, to the catholyte side. Upon discharging the opposite process takes place. In a nitrogen-filled glove box 4 mL of 5 mM solutions of molecule 3 respectively 7 with 200 mM electrolyte salt (TBAPF6) in acetonitrile get loaded on each side of an H-cell. With a biologic VSP potentiostat a current is applied and the working side negatively charged. After full charging, the solution is removed and filled into a screw-capped glass vial. Samples for absorption measurements were prepared in a 0.2 mm pathlength quartz cuvette in the glove box but measured outside the glove box at different points in time. While the at the core positions unprotected molecule 3 lost its charge completely after 10 days, the charged solution of molecule 7 still contained 31% of its initial charge after 43 days. CV measurements prior to charging and after storing for 43 days were performed and revealed a similar state-of-charge (SoC) after 43 days of 27%, determined via the open-circuit voltage. A comparison of the peak heights for the reduction implies that 18% of the material has been degraded, which could be another hint towards unwanted reactions of the active material with impurities. Also, the capacity retention of molecule 9 has been evaluated and showed promising results of more than 80% retention after being stored in its reduced state for 20 days. The 50 mM battery cycling of molecule 3 with a commonly used catholyte shows a retention of 73% after 100 cycles. In a real application, the battery might not always get fully charged which is why the charging to various states-of- charge was tested and showed similar retention of 74% after 100 cycles. A 3.22 V battery with molecule 6 and a high oxidation potential catholyte, presented in ACS Appl. Mater. Interfaces 2022, 14, 28834, showed a retention of 61% after 100 cycles. All batteries showed high energy efficiencies of over 70%. Depolarization measurements of a flow batteries of a mixed solution of 50 mM of molecule 3 with 55 mM DBBB and 200 mM TBAPF6 in acetonitrile as well 200 mM of molecule 3 with 220 mM DBBB and 400 mM TBAPF6 in acetonitrile at 100% SoC have been performed. In both cases a porous Daramic 175 separator has been used. The two measurements revealed almost identical results and higher achievable power densities than a 100 mM MV/TEMPOL and a 1.67 M Vanadium flow battery, shown in J. Noack et al., Energies 2016, 9, 627, due to the more than doubled voltage of the molecule 3/DBBB-system. The maximum power density for both systems could not be determined as the potentiostat limited the current to 0.157 A/cm2. Extrapolation suggests a very high maximum power density of about 0.39 W/cm2 at a current density of 0.27 A/cm2. Also, the performance of the molecule 9/MEEPT-system was evaluated and suggested an extrapolated maximum power density of about 0.142 W/cm2 at a current density of 0.176 A/cm2. Figure 2A shows static, coin cell cycling of 45 or 50 mM of molecule 3 (full squares and diamonds), 7 (half squares and half diamonds), 8 (stars), respectively 12 (circles), and 50 or 55 mM DBBB in 200 mM TBAPF6/acetonitrile if not differently indicated. Only every 50th cycle is shown for better clarity. Figure 2B shows static, coin cell cycling of 50 mM of molecule 7 and 8 with 50 mM DBBB in 200 mM TBAPF6/acetonitrile. Only every 200th cycle is shown for better clarity. Figure 2C shows static, coin cell cycling at high a concentration of 500 mM of molecule 7 and 350 mM of 8 with 550 mM DBMMB in 750 mM TBAPF6/acetonitrile, respectively 385 and 525 mM. Only every 20th cycle is shown for better clarity. Figure 2D shows static, coin cell cycling of molecule 11 at a concentration of 50 mM in 200 mM TBAPF6/acetonitrile. Only every 10th cycle is shown for better clarity. Figure 2E and 2F show static, coin cell cycling of molecule 9 at a concentration of 50 mM with various catholytes at 50 mM in 200 mM TBAPF6/acetonitrile. Only every 20th cycle is shown for better clarity. Even though, coin cells are a static system, the charge-discharge behavior of redox active molecules can be evaluated without wasting large amounts of materials. Thereby, the cycling of the molecules 7 and 8 showed almost an order of magnitude better stability than the one of molecule 3, while molecule 9 exhibited almost two orders of magnitude higher stability than 3. The superior cycling performance of molecule 7, 8 and 9 could be demonstrated over 10,000 cycles. The molecule 9/MEEPT system could even be demonstrated over 20,000 cycles with a loss of only 9% of its initial discharge capacity. Figure 3 shows the volumetric capacity versus cycle number of flow battery cycling of a mixed solution of 50 mM of molecule 7 with 55 mM DBBB and 200 mM TBAPF6 in acetonitrile using a porous Daramic 175 separator. To prove the possibility to operate dicyanobenzene flow batteries also at higher concentration, the very soluble molecule 3 was paired with DBMMB. A 0.5 M battery was run for 50 cycles as a demonstration (Figure 4A and 4B). Further optimization has to be done for a better performance. The 50 mM flow battery cycling of molecule 7 shows very promising results. Charging was performed with a constant current of 30 mA/cm2, with a voltaic cutoff at 3.1 V. Discharging was performed at a constant current of -30 mA/cm2 with a voltaic cutoff at 1.5 V. Very high average coulombic and energy efficiencies of 93.4% and 79% were achieved. The battery’s capacity retention stayed very steady after an initial capacity drop between cycle 50 and 150. The fast capacity drop within the first 150 cycles can be attributed to transport phenomena. After these cycles, about 1.25 mL have been transferred from anolyte to catholyte reservoir including active compounds and electrolyte salt. Analyzing both reservoirs after 500 cycles by cyclic voltammetry revealed that at least 73% of molecule 7 remained in the anolyte reservoir and 80% in the catholyte reservoir, showing an excellent stability of the molecule itself. The decay from cycle 200 to 500 is about -0.06%/cycle which correlates with a decay of about 0.05%/cycle taking the capacity retention of 73% determined by CV. Furthermore, the system of molecule 9/MEEPT was evaluated in a flow battery at a concentration of 50 mM in 200 mM TBAPF6 in acetonitrile (Figure 5A and 5B). Thereby, no detectable decay could be determined by the discharge capacity nor cyclic voltammetry with a microelectrode after 100 cycles. Table 2 shows a comparison of molecules 6, 7 and 9 (numbers indicated in brackets in the first column) according to the present invention with anolytes from literature. Table 2: Comparison with literature.
Figure imgf000028_0001
Figure imgf000029_0001
Figure imgf000030_0001
Figure 4A shows volumetric capacity versus cycle number of flow battery cycling of a mixed solution of 500 mM of molecule 3 with 550 mM DBBB and 750 mM TBAPF6 in acetonitrile using a porous Daramic 175 separator. Figure 4B shows the charging and discharging voltages in dependance of their SoC (expressed via capacity) for cycle number 1 and 25. The upper lines represent the charging and the lower ones the discharging. The curves reveal relatively high average discharge voltages of 2.43 and 2.33 V for cycle 1, respectively 25, as well as a slight overcharge in the first cycle which can be attributed to active material crossing over through the porous separator. The 500 mM flow battery cycling shows very promising results. Molecule 3 exhibits at least a high solubility of 500 mM in all SoCs in the 0.75 M TBAPF6/acetonitrile mixture. Charging was performed with a constant current of 50 mA/cm2, followed by a constant voltage at 2.95 V with a cutoff threshold of 15 mA/cm2. Discharging was performed almost fully at a constant current of -50 mA/cm2 with a very short voltaic hold at 1 V (threshold 6 mA/cm2). Energy efficiencies of 55 to 63% were achieved. This could be increased by charging and discharging slower. The battery’s capacity retention might be limited due to unwanted reaction of the anolyte with the catholyte (both are present in both reservoirs in a mixed flow battery) or solvent or electrolyte salt. Sterically more protected derivatives, such as molecules 7 and 8, will mitigate side reaction as well as self-discharge, which could be proven for molecule 7 in UV-vis-NIR as well as coin cell and flow battery cycling experiments. Another very promising possibility to increase the stability is alternating the solvent/electrolyte salt mixture. List of cited documents I ACS Appl. Energy Mat.2019, 2, 2364 II RSC Adv.2019, 9, 13128 III Int. J. Electrochem. Sci.2018, 13, 6676 IV Int. J. Hydrogen Energy 2017, 42, 17488 V J. Power Sources 2020, 445, 227330 VI ChemElectroChem 2022, 9, e202200483 VII ACS Energy Lett.2017, 2, 1156 VIII J. Am. Chem. Soc.2019, 141, 15301 IX Angew. Chem.2019, 131, 7119 X ACS Energy Lett.2016, 1, 705 XI ACS Appl. Energy Mater.2021, 4, 9248 XII Nat. Commun.2020, 11, 3843 XIII Angew. Chem. Int. Ed.2015, 54, 8684

Claims

CLAIMS 1. A battery comprising a liquid electrolyte, the liquid electrolyte comprising: a compound selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV):
Figure imgf000032_0001
wherein R1 andR2 and/or R3 and R4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group wherein R1, R2, R3, R4 and R5 represent independent from each other H; CN; halogen; NO2; N2; N2R6; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein R6 represents H or a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein A- represents an anion.
2. The battery according to claim 1, wherein R1 and R2 and/or R3 and R4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group, or wherein R1, R2, R3, R4 and R5 represent independent from each other H; CN; halogen; N2; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-10 carbon atoms, preferably from 1-6 carbon atoms.
3. The battery according to claim 1 or 2, wherein R1, R2, R3, R4 and R5 represent independent from each other H; CN; COR6; linear or branched hydrocarbyl group independently selected from alkyl, alkoxy and alkoxycarbonyl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-10 carbon atoms, preferably from 1- 6 carbon atoms.
4. The battery according to any of the preceding claims, wherein R6 represents H or a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-10 carbon atoms, preferably from 1-6 carbon atoms.
5. The battery according to any of the preceding claims, wherein at least one of R1 of R2 and at least one of R3 and R4 is H, preferably wherein R2 = R4 = H.
6. The battery according to any of the preceding claims, wherein R1 is not H.
7. The battery according to claim 6, wherein R3 is not H.
8. The battery according to claim 7, wherein at least one of R1 and R3 is branched, preferably wherein R3 is different from R1.
9. The battery according to claim 7, wherein at least one of R1 and R3 is branched, preferably wherein R3 = R1.
10. The battery according to claim 8 or 9, wherein R1 and R3 are independently chosen from CH3, C2H5, C3H7, C4H9, tertbutyl, COOCH3, COOC2H5, COOC3H7, COOC4H9 and COOC(CH3)3.
11. The battery according to claim 7, wherein R1 and R2 and/or R3 and R4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group, preferably wherein R1 and R2 as well as R3 and R4 together with the aromatic carbon atoms to which they are attached form a cycloalkane group, preferably a substituted cycloalkane group.
12. The battery according to claim 9 or 10, comprising a compound according to one of the following formulas:
Figure imgf000034_0001
Figure imgf000035_0002
13. The battery according to claim 12, comprising a compound according to one of the following formulas:
Figure imgf000035_0001
14. The battery according to any of the preceding claims, further comprising a solvent that is electrochemically stable in a wide potential range, preferably between -3 V to +2 V, such as between -2.5 V to +1.5 V vs ferrocene/ferrocenium (Fc/Fc+), wherein the solvent is acetonitrile; an ether-based solvent, preferably dimethoxyethane, diethyl carbitol, dimethylformamide or a mixture thereof.
15. The battery according to any of the preceding claims, further comprising one or more electrolyte salts and a counter ion, wherein the one or more electrolyte salts has a solubility of >0.5 M in the solvent, preferably wherein the one or more electrolyte salt is a quaternary ammonium or imidazolium, and preferably wherein the counter ion is chosen from the group of PF6-, BF4-, N(SO2CF3)2- (TFSI),CF3SO3- (FSI), CH3SO3-, CH3C6H4SO3- (OTs) and diethyl phosphate.
16. The battery according to any of the preceding claims, further comprising a material for the cathode selected from 2,5-di-tert-butyl-1,4-bis(2- methoxyethoxy)benzene (DBBB), 1,4-di-tert-butyl-2-methoxy-5-(2-(2- methoxyethoxy)ethoxy)benzene (DBMMB), 1,4-di-tert-butyl-2,5-bis(2,2,2- trifluoroethoxy)benzene, 10-[2-(2-methoxyethoxy)ethyl]-10H-phenothiazine (MEEPT), N-(ferrocenylmethyl)-N,N-dimethylethanaminium bis-(trifluoromethanesulfonyl)imide (Fc1N112-TFSI), and 1,3,6,8-tetra-tert-butyl-2-ethylhexyl-carbazole (Cbz1).
17. The battery according to any one of claims 1-16, wherein the battery is a redox flow battery.
18. The battery according to claim 17, wherein the battery is a non- aqueous redox flow battery.
19. Method of manufacturing a non-aqueous redox flow battery according to claim 18, the method comprising: - immersing a negative electrode in a first non-aqueous liquid electrolyte; - immersing a positive electrode in a second non-aqueous liquid electrolyte; - interposing a semi-permeable separator between the negative and positive electrodes; wherein the first non-aqueous liquid electrolyte comprises a compound selected from the group consisting of formula (I), formula (II), formula (III) and formula (IV):
Figure imgf000037_0001
wherein R1 and R2 and/or R3 and R4 together with the aromatic carbon atoms to which they are attached form an optionally substituted cyclic group, or wherein R1, R2, R3, R4 and R5 represent independent from each other H; CN; halogen; NO2; NR6 2; N2R6; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein R6 represents H or a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein A- represents an anion.
20. A method of operating a battery, the method comprising providing the battery according to any of claims 1-18.
21. Compound according to formula (I):
Figure imgf000038_0001
wherein R2 and R4 are H; wherein R1 is CN; COR6; linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein R3 is COOR7, wherein R7 represents linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, cyclic alkane, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms; wherein R6 represents H or a linear, branched or cyclic hydrocarbyl group independently selected from alkyl, alkenyl, aryl, aralkyl, alkoxy, alkoxycarbonyl or alkylaryl groups, and one or more combinations thereof; wherein said hydrocarbyl group may be substituted or unsubstituted, may contain one or more heteroatoms and has from 1-18 carbon atoms.
22. Compound according to claim 21, wherein R1 is selected from CH3, CH2CH3, C3H7, C4H9, tertbutyl, COOCH3 and R7 is selected from CH3, CH2CH3, C3H7, C4H9 and C(CH3)3.
23. Compound according to claim 21 or 22, wherein R1 is methyl, and R7 is CH3 or CH2CH3.
24. Method of manufacturing a compound according to claim 21-23.
25. Method according to claim 24, comprising the provision of a mixture of para-substituted dibromo derivative and copper cyanide.
PCT/NL2023/050533 2022-10-20 2023-10-12 A non-aqueous redox flow battery WO2024085749A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL2033363 2022-10-20
NL2033363 2022-10-20

Publications (1)

Publication Number Publication Date
WO2024085749A1 true WO2024085749A1 (en) 2024-04-25

Family

ID=84359568

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/NL2023/050533 WO2024085749A1 (en) 2022-10-20 2023-10-12 A non-aqueous redox flow battery

Country Status (1)

Country Link
WO (1) WO2024085749A1 (en)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05234617A (en) * 1992-02-19 1993-09-10 Ricoh Co Ltd Advanced secondary battery
US9300000B2 (en) 2012-02-28 2016-03-29 Uchicago Argonne, Llc Organic non-aqueous cation-based redox flow batteries
US9603848B2 (en) 2007-06-08 2017-03-28 Senomyx, Inc. Modulation of chemosensory receptors and ligands associated therewith
US10424806B2 (en) 2012-02-28 2019-09-24 Uchicago Argonne, Llc Organic non-aqueous cation-based redox flow batteries
US10535891B2 (en) 2017-08-11 2020-01-14 Uchicago Argonne, Llc Two-electron redox catholyte for redox flow batteries
US10727545B1 (en) * 2019-04-12 2020-07-28 Ses Holdings Pte. Ltd. Methods of charging secondary lithium metal batteries to reactive dead lithium with redox shuttling additives and battery control systems incorporating the same
WO2022174550A1 (en) * 2021-02-20 2022-08-25 宁德新能源科技有限公司 Electrochemical device and electronic device comprising same

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05234617A (en) * 1992-02-19 1993-09-10 Ricoh Co Ltd Advanced secondary battery
US9603848B2 (en) 2007-06-08 2017-03-28 Senomyx, Inc. Modulation of chemosensory receptors and ligands associated therewith
US9300000B2 (en) 2012-02-28 2016-03-29 Uchicago Argonne, Llc Organic non-aqueous cation-based redox flow batteries
US10424806B2 (en) 2012-02-28 2019-09-24 Uchicago Argonne, Llc Organic non-aqueous cation-based redox flow batteries
US10535891B2 (en) 2017-08-11 2020-01-14 Uchicago Argonne, Llc Two-electron redox catholyte for redox flow batteries
US10727545B1 (en) * 2019-04-12 2020-07-28 Ses Holdings Pte. Ltd. Methods of charging secondary lithium metal batteries to reactive dead lithium with redox shuttling additives and battery control systems incorporating the same
WO2022174550A1 (en) * 2021-02-20 2022-08-25 宁德新能源科技有限公司 Electrochemical device and electronic device comprising same

Non-Patent Citations (15)

* Cited by examiner, † Cited by third party
Title
COLEMAN GEORGE H ET AL: "T H E J O U R N A L O F Organic Chemistry Volume 24", THE JOURNAL OF ORGANIC CHEMISTRY, vol. 24, 1 June 1959 (1959-06-01), XP093113199 *
I ACS APPL. ENERGY MAT, vol. 2, 2019, pages 2364
II RSC ADV, vol. 9, 2019, pages 13128
III INT. J. ELECTROCHEM. SCI, vol. 13, 2018, pages 6676
IV INT. J. HYDROGEN ENERGY, vol. 42, 2017, pages 17488
IX ANGEW. CHEM, vol. 131, 2019, pages 7119
J. NOACK ET AL., ENERGIES, vol. 9, 2016, pages 627
V J. POWER SOURCES, vol. 445, 2020, pages 227330
VI CHEMELECTROCHEM, vol. 9, 2022, pages e202200483
VII ACS ENERGY LETT., vol. 2, 2017, pages 1156
VIII J. AM. CHEM. SOC, vol. 141, 2019, pages 15301
X ACS ENERGY LETT, vol. 1, 2016, pages 705
XI ACS APPL. ENERGY MATER, vol. 4, 2021, pages 9248
XII, NAT. COMMUN., vol. 11, 2020, pages 3843
XIII ANGEW. CHEM. INT. ED., vol. 54, 2015, pages 8684

Similar Documents

Publication Publication Date Title
EP2925768B1 (en) Cobaltcomplex salts
WO2014082706A1 (en) Cobalt complexes with tricyanoborate or dicyanoborate counter-anions for electrochemical or optoelectronic devices
EP2883881A1 (en) Cobaltcomplex salts and mixtures of Cobaltcomplex salts for use in DSSC
KR102651144B1 (en) Phenazine-based compound, electrolyte for redox flow battery comprising the same and redox flow battery
Yoshizawa-Fujita et al. A new Lewis-base ionic liquid comprising a mono-charged diamine structure: A highly stable electrolyte for lithium electrochemistry
CN105742077A (en) Power storage device, lithium-ion secondary battery, electric double layer capacitor and lithium-ion capacitor
KR20120135067A (en) Ionic liquid and power storage device including the same
Chai et al. Biphasic, membrane-free Zn/phenothiazine battery: effects of hydrophobicity of redox materials on cyclability
JP2017043774A (en) Use of specific polymer as charge storage body
Yan et al. Benzotriazoles as low-potential anolytes for non-aqueous redox flow batteries
Duvva et al. Hexyl dithiafulvalene (HDT)-substituted carbazole (CBZ) D–π–A based sensitizers for dye-sensitized solar cells
Chen et al. Polyethylene glycol modified tetrathiafulvalene for high energy density non-aqueous catholyte of hybrid redox flow batteries
US11094964B2 (en) Rechargeable electrochemical cell
Kurimoto et al. Four-electron transfer tandem tetracyanoquinodimethane for cathode-active material in lithium secondary battery
WO2024085749A1 (en) A non-aqueous redox flow battery
Mansha et al. Recent Developments on Electroactive Organic Electrolytes for Non‐Aqueous Redox Flow Batteries: Current Status, Challenges, and Prospects
CN114456195B (en) Conjugated fusion bipolar redox active molecule and preparation method and application thereof
Zhang et al. Panchromatic cross-conjugated π-bridge NIR dyes for DSCs
US10103402B2 (en) Liquid phenothiazine catholytes for non-aqueous redox flow batteries
Zhen et al. Coupling Tetraalkylammonium and Ethylene Glycol Ether Side Chain To Enable Highly Soluble Anthraquinone-Based Ionic Species for Nonaqueous Redox Flow Battery
KR20170077902A (en) Novel compound and solar cell including the same
US10637099B2 (en) Annulated tetra-substituted hydroquinone ether-based redox shuttle additives for lithium-ion batteries
US11569513B1 (en) Redox flow battery carrier molecule
KR101833125B1 (en) Novel compound comprising ferrocene and solar cell including the same
Mao Synthesis and Characterization of Novel P-conjugated Molecules for Organic Redox-flow Batteries