Non-aqueous redox flow battery

Abstract

A non-aqueous redox flow battery (RFB) comprising: - a positive compartment in which a positive electrode is placed and in which a non-aqueous liquid positive electrolyte flows; - a negative compartment in which a negative electrode is placed and in which a non-aqueous liquid negative electrolyte flows; - an ion exchange membrane placed between the positive compartment and the negative compartment; wherein: - the non-aqueous liquid positive electrolyte comprises a solution of copper trifluoromethanesulfonate or copper tetrafluoroborate complex [Cu(I) or Cu(II)] in at least one organic solvent; - the non-aqueous liquid negative electrolyte comprises a solution of at least one benzothiadiazole having general formula (I): wherein: - R1 and R2, equal to or different from each other, represent a hydrogen atom; or represent a linear or branched, saturated or unsaturated C1-C 20 alkyl radical, preferably C1-C 10 ; or represent a -O-R3 radical, wherein R3 is selected from a linear or branched, saturated or unsaturated C1-C 20 alkyl radical, preferably C1-C 10 , or R3 is selected from a -(CH2) n COOR4 radical, wherein R4 is selected from a linear or branched, saturated or unsaturated C1-C 20 alkyl radical, preferably C1-C 10 , n is an integer from 1 to 10, preferably from 1 to 8, or R3 is selected from a -(CH2) n OR4 radical, wherein R4 and n have the same meaning as above, or R3 is selected from a -(CH2CH2O) n R4 radical, wherein R4 and n have the same meaning as above, or R3 is selected from a -(CH2) n CN radical, wherein n has the same meaning as above, or R3 is selected from a -(CH2) n NR4R5 radical, wherein R4 and n have the same meaning as above and R5 is selected from a linear or branched, saturated or unsaturated C1-C 20 alkyl radical, preferably C1-C 10 , or R3 is selected from a -(CH2) n CONR4R5 radical, wherein R4, R5 and n have the same meaning as above, or R3 is selected from a -(CH2) n Si(R4)3 radical, wherein R4 and n have the same meaning as above, or R3 is selected from a -(CH2) nSi(OR4)3groups, wherein R4and n have the same meaning as above; provided that at least one of R1and R2is not hydrogen, and at least one of R1and R2is in the 2-position of the phenyl group. The nonaqueous redox flow battery (RFB) can be advantageously used in devices requiring medium to high power output (e.g., about 10 kW - 100 MW) for multiple hours (i.e., > 1 hour), for example, in devices for storing energy from a plant or alternative energy source (e.g., solar or wind) for later use (e.g., for domestic or industrial use, e.g., home or commercial) or for sale.

Description

Technical Field

[0001] This invention relates to non-aqueous redox flow batteries (RFB).

[0002] More specifically, the present invention relates to a non-aqueous redox flow battery (RFB) comprising: a positive electrode compartment in which a positive electrode is positioned and a non-aqueous liquid positive electrode electrolyte flows; a negative electrode compartment in which a negative electrode is positioned and a non-aqueous liquid negative electrode electrolyte flows; an ion exchange membrane located between the positive and negative electrode compartments; wherein: the non-aqueous liquid positive electrode electrolyte comprises a solution of copper trifluoromethanesulfonate or copper tetrafluoroborate complex [Cu(I) or Cu(II)] in at least one organic solvent; and the non-aqueous liquid negative electrode electrolyte comprises a solution of at least one benzothiadiazole having a specific general formula (I) provided below in at least one organic solvent.

[0003] The non-aqueous redox flow battery (RFB) can be advantageously used in devices that require medium to high power output (e.g., about 10kW-100MW) for several hours (i.e., >1 hour), such as for storing energy from a plant or alternative energy source (e.g., solar or wind power) for later use (e.g., for residential or industrial use, such as home or commercial) or for sale. Background Technology

[0004] Redox flow batteries (RFBs) are becoming an increasingly promising energy storage technology due to their flexibility and scalability, as well as their low environmental impact and safe operation. But most importantly, the separation between the energy that can be stored and the power that can be delivered distinguishes them from all other secondary batteries.

[0005] A redox flow battery (RFB) is a rechargeable battery in which an electrolyte solution containing one or more electroactive materials flows through an electrochemical cell, directly converting chemical energy into electrical energy. The electrochemical cell typically consists of a negative electrode compartment (or negative half-cell) and a positive electrode compartment (or positive half-cell) separated by an ion-exchange membrane. By storing these electrolytes in an external reservoir, the power component (i.e., the power output depending on the size and design of the electrochemical cell) and the energy component (i.e., the stored energy depending on the size of the external reservoir and the concentration of the electrolyte contained therein) are decoupled, resulting in significant gains in flexibility of application.

[0006] A typical characteristic of solutions of one or more electroactive substances is their high energy density, which depends on a variety of factors, such as the concentration of the electroactive substance in the solution, the number of electrons transferred to the positive or negative electrode compartment (or half-cell), and the reaction potential.

[0007] Most redox flow batteries (RFBs) use aqueous solutions of inorganic electrolytes. Recently, organic electrolytes have also been investigated, proving to be of interest due to their stability in redox cycles. These organic reagent-based RFBs are characterized by high energy density, minimal environmental impact (no use of heavy metals or corrosive solutions), and low cost. In fact, given the relatively high price and significant market volatility of vanadium, using organic reagents avoids the use of elements distributed in a few countries, thus allowing for market control. Furthermore, aqueous systems are limited by the small electrochemical stability window of water (approximately 1.2V). Therefore, much research is underway to develop flow batteries with non-aqueous systems, where the electrochemical window is much wider.

[0008] The fundamental characteristics of redox flow battery (RFB) operation involve the stability and solubility (>0.5-1M) of the active material in the electrolyte. Commonly used solvents are acetonitrile, propylene carbonate, ethylene carbonate, or mixtures thereof. Acetonitrile is the most commonly used solvent in cyclic voltammetry: in fact, despite its flammability and high volatility, it is a polar solvent capable of dissolving the supporting electrolyte and polar materials that can form in a redox flow battery (RFB), and also possesses a particularly wide electrochemical window (>5V). Propylene carbonate, ethylene carbonate, or mixtures thereof are of great interest due to their low flammability.

[0009] Since Singh P. reported the first redox flow battery (RFB) with a non-aqueous solvent in the "Journal of Power Sources" (1984), Vol. 11, pp. 135-142, many redox pairs have been tried, including metals [Ru(acac)3, Ru(bpy)3, Fe(ppy)3, V(acac)3, Mn(acac)3] and nonmetals (2,2,6,6-tetramethylpiperidine oxide (TEMPO), N-methylphthalimide, quinoxaline, anthraquinone, viologen, benzothiadiazole).

[0010] For example, the international patent application WO 2018 / 007991 representing the applicant relates to a non-aqueous redox flow battery (RFB), which includes:

[0011] - Positive electrode compartment, in which the positive electrode is placed and a non-aqueous liquid positive electrode electrolyte flows;

[0012] - Negative electrode compartment, in which the negative electrode is placed and the non-aqueous liquid negative electrode electrolyte flows;

[0013] - An ion exchange membrane placed between the positive and negative electrode compartments;

[0014] in:

[0015] -The non-aqueous liquid positive electrode electrolyte comprises a solution of copper trifluoromethanesulfonate or copper tetrafluoroborate complex [Cu(I) or Cu(II)] in at least one organic solvent;

[0016] - The non-aqueous liquid negative electrode electrolyte comprises a solution of at least one benzothiadiazole or its derivative in at least one organic solvent.

[0017] Preferably, the non-aqueous liquid negative electrode electrolyte comprises a solution of benzothiadiazole (1):

[0018]

[0019] It is said that the aforementioned non-aqueous redox flow battery (RFB) can be advantageously used in devices that require medium to high power output (e.g., about 100kW-100MW) for several hours (i.e., >1 hour), such as for storing energy from a plant or alternative energy source (e.g., solar or wind power) for later use (e.g., for home use) or for sale.

[0020] Zhang J. et al., in the Journal of Power Sources (2018), Vol. 397, pp. 214-222, described a non-aqueous redox flow battery (RFB) in which the cathode electrolyte (non-aqueous liquid cathode electrolyte) is a substituted dialkoxybenzene having formula (II):

[0021]

[0022] Furthermore, the anolyte (non-aqueous liquid negative electrode electrolyte) is a benzothiadiazole having formula (III):

[0023]

[0024] in:

[0025] -R4 = H, CN;

[0026] -R5 = H, CH3; CH3O; F

[0027] -R6 = H; CH3;

[0028] -R7 = H, CN,

[0029] Their stability and degradation due to redox reactions were investigated. However, Zhang J. et al. reported that even in the presence of the anolyte / cathode electrolyte pair exhibiting the highest chemical stability, the lifespan of such non-aqueous redox flow batteries (RFBs) is largely (but not exclusively) limited by parasitic reactions due to cross-contamination of reaction products between the compartments of the RFB. They also reported that, in many cases, the cycling performance of these RFBs appears to be strongly affected by poor membrane selectivity.

[0030] Zhao Y. et al., in "Accepted Manuscript" (Journal of Material Chemistry A) (2020), DOI:10.1039 / D0TA02214D, described the use of 2,1,3-benzothiadiazole (BzNSN) as a model anode electrolyte (non-aqueous liquid negative electrode electrolyte) in a non-aqueous redox flow battery ("RFB") to investigate the effects of various supporting electrolytes. Zhao Y. et al. observed that changing the composition of the supporting electrolyte altered the redox potential and electrochemical stability of 2,1,3-benzothiadiazole. Specifically, they observed that the redox potential of 2,1,3-benzothiadiazole became increasingly negative with increasing supporting electrolyte cation size, from -1.63 V to Ag / Ag. + and Li + The voltage becomes -1.82V for Ag / Ag + and larger cations such as K + And tetraethylammonium. Furthermore, the larger cation increases the electrochemical stability of the model compounds.

[0031] Huang J. et al. described a non-aqueous redox flow battery (RFB) in the Journal of Material Chemistry A (2018), Vol. 6, pp. 6251-6254, in which the cathode electrolyte (non-aqueous liquid cathode electrolyte) is a substituted dialkoxybenzene having formula (II):

[0032]

[0033] Furthermore, the anolyte (non-aqueous liquid negative electrode electrolyte) is a benzothiadiazole having formula (IV):

[0034]

[0035] The R values ​​were H, CH3, OCH3, F, and CF3. The stability and degradation due to redox reactions were investigated, particularly the lifetime of anionic radicals in acetonitrile. The difference between these lifetimes and the stability of the redox flow battery (RFB) indicated the presence of additional parasitic reactions.

[0036] As can be seen from the above, although benzothiadiazole and its derivatives are effective redox materials in non-aqueous redox flow batteries (RFBs), the high reactivity of the free radicals formed during the charging phase of such non-aqueous redox flow batteries (RFBs) makes the discharge operation difficult: in fact, the formed BTD free radicals tend to bind to the membrane located between the positive and negative electrode compartments, or to the graphite electrode present in the compartments, causing parasitic reactions.

[0037] Therefore, the problem facing the applicant is to find benzothiadiazole derivatives that do not have the above-mentioned disadvantages and thus enable the use of them in non-aqueous redox flow batteries (RFBs) to be more stable. Summary of the Invention

[0038] The applicant has now discovered that certain benzothiadiazole derivatives having the specific general formula (I) provided below exhibit good chemical stability during charge-discharge cycles in non-aqueous redox flow batteries (RFBs) using them, thus enabling greater stability of the RFBs. Furthermore, these benzothiadiazole derivatives possess very good electrochemical performance as determined by cyclic voltammetry, as well as high solubility in the organic solvents used (particularly acetonitrile and propylene carbonate). Moreover, these benzothiadiazole derivatives can provide excellent performance (i.e., high potential difference (E°) and high energy density (ρ) in the open circuit). e Non-aqueous redox flow battery (RFB).

[0039] Therefore, the object of the present invention is to provide a non-aqueous redox flow battery (RFB) comprising:

[0040] - Positive electrode compartment, in which the positive electrode is placed and a non-aqueous liquid positive electrode electrolyte flows;

[0041] - Negative electrode compartment, in which the negative electrode is placed and the non-aqueous liquid negative electrode electrolyte flows;

[0042] - An ion exchange membrane placed between the positive and negative electrode compartments;

[0043] in:

[0044] -The non-aqueous liquid positive electrode electrolyte comprises a solution of copper trifluoromethanesulfonate or copper tetrafluoroborate complex [Cu(I) or Cu(II)] in at least one organic solvent;

[0045] -The non-aqueous liquid negative electrode electrolyte comprises a solution of at least one benzothiadiazole having the general formula (I) in at least one organic solvent:

[0046]

[0047] in:

[0048] -R1 and R2 may be the same or different from each other, representing hydrogen atoms; or representing straight-chain or branched, saturated or unsaturated C1-C atoms. 20 Alkyl groups, preferably C1-C 10 ; or represents the -O-R3 group, where R3 is selected from straight-chain or branched, saturated or unsaturated C1-C groups. 20 Alkyl groups, preferably C1-C 10 Or R3 is selected from -(CH2). n The COOR4 group, wherein R4 is selected from straight-chain or branched, saturated or unsaturated C1-C groups. 20 Alkyl groups, preferably C1-C 10 n is an integer from 1 to 10, preferably from 1 to 8, or R3 is selected from -(CH2). n The OR4 group, wherein R4 and n have the same meaning as described above, or R3 is selected from -(CH2CH2O). n The R4 group, wherein R4 and n have the same meaning as described above, or R3 is selected from -(CH2). n The CN group, wherein n has the same meaning as above, or R3 is selected from -(CH2). n The NR4R5 group, wherein R4 and n have the same meaning as described above and R5 is selected from straight-chain or branched, saturated or unsaturated C1-C groups. 20 Alkyl groups, preferably C1-C 10 Or R3 is selected from -(CH2). n The CONR4R5 group, wherein R4, R5, and n have the same meaning as described above, or R3 is selected from -(CH2). n The Si(R4)3 group, wherein R4 and n have the same meaning as described above, or R3 is selected from -(CH2). n The Si(OR4)3 group, wherein R4 and n have the same meaning as described above;

[0049] The condition is that at least one of R1 and R2 is not hydrogen, and at least one of R1 and R2 is at the 2 position of the phenyl group.

[0050] For the purposes of this specification and the following claims, unless otherwise stated, the definition of a numerical range always includes the endpoint values.

[0051] For the purposes of this specification and the following claims, the term "comprising" also includes the terms "consisting substantially of" or "consisting of".

[0052] For the purposes of this specification and the following claims, the term "C1-C" is used. 20 "Alkyl" refers to a straight-chain or branched, saturated or unsaturated alkyl group having 1 to 20 carbon atoms. C1-C 20 Specific examples of alkyl groups are: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-decyl, and n-dodecyl. Detailed Implementation

[0053] According to a preferred embodiment of the present invention, the copper trifluoromethanesulfonate or copper tetrafluoroborate complex [Cu(I) or Cu(II)] can be selected from, for example: copper tetraacetonitrile trifluoromethanesulfonate (I) [Cu(NCCH3)4·CF3SO3], copper trifluoromethanesulfonate (II) [Cu(CF3SO3)2], copper tetraacetonitrile tetrafluoroborate (I) [Cu(NCCH3)4·BF4], or mixtures thereof.

[0054] According to a preferred embodiment of the present invention, in the general formula (I):

[0055] -R1 and R2 may be the same or different from each other, representing hydrogen atoms; or they may represent the -OR3 group, where R3 is selected from...

[0056] -(CH2) n The COOR4 group, wherein R4 is selected from straight-chain or branched, saturated or unsaturated C1-C groups. 20 Alkyl groups, preferably C1-C 10 n is an integer from 1 to 10, preferably from 1 to 8, or R3 is selected from -(CH2CH2O). n The R4 group, wherein R4 and n have the same meaning as described above; preferably they represent propoxycarbonylethoxy, methoxycarbonylethoxy, or methoxyethoxyacetoxy.

[0057] The condition is that at least one of R1 and R2 is not hydrogen, and at least one of R1 and R2 is at the 2 position of the phenyl group.

[0058] Specific examples of compounds having general formula (I) that can be used for the purposes of this invention are reported in Table 1.

[0059] Table 1

[0060]

[0061] It should be noted that, for the purposes of this invention, if a solution containing at least one benzothiadiazole having general formula (I) is electrochemically reduced from a solution of copper(II) trifluoromethanesulfonate complex [Cu(II)], the reduced form of benzothiadiazole having general formula (I) is obtained. - Then it is fed into the negative electrode compartment.

[0062] The aforementioned electrolyte may include at least one supporting electrolyte. The supporting electrolyte maintains the charge balance between the electrolytes in the negative electrode compartment and the electrolytes in the positive electrode compartment, but does not participate in the reaction. Typically, the supporting electrolyte must be chemically inert over the considered potential range, must have high ionic conductivity to ensure low resistance to current, and must not impede electron exchange on the electrode surface.

[0063] According to one embodiment of the present invention, the electrolyte comprises at least one supporting electrolyte selected from the following: lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), methyl trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide [Li(CF3SO2)2N], tetraethylammonium tetrafluoroborate (TEABF4), tetrabutylammonium tetrafluoroborate (TBABF4), or mixtures thereof. Lithium tetrafluoroborate (LiBF4) and tetrabutylammonium tetrafluoroborate (TBABF4) are preferred.

[0064] According to a preferred embodiment of the present invention, the organic solvent may be selected from, for example, acetonitrile, dimethylacetamide, diethyl carbonate, dimethyl carbonate, γ-butyrolactone (GBL), propylene carbonate (PC), ethylene carbonate (EC), N-methyl-2-pyrrolidone (NMP), fluoroethylene carbonate, N,N-dimethylacetamide, or mixtures thereof. Acetonitrile and propylene carbonate (PC) are preferred.

[0065] It should be noted that, for the purposes of this invention, it is preferable to use the same solvent in the positive and negative electrode compartments to prevent possible diffusion problems through the ion exchange membrane and the resulting contamination between the two compartments.

[0066] It should also be noted that the copper trifluoromethanesulfonate or copper tetrafluoroborate complex [Cu(I) or Cu(II)] and the benzothiadiazole having general formula (I) have good solubility in the organic solvent used, i.e., a solubility of 0.05 M to 2 M, preferably 0.08 M to 1.5 M.

[0067] According to a preferred embodiment of the present invention, the ion exchange membrane may be selected from polymer membranes, for example:

[0068] - Ion exchange membranes, such as membranes based on styrene-divinylbenzene copolymers or chloromethylstyrene-divinylbenzene copolymers containing amino groups, membranes based on poly(ether ether ketone), membranes based on divinylbenzene-vinylpyridine copolymers containing quaternary pyridine groups, membranes based on aromatic polysulfone copolymers containing chloromethyl and amino groups, and membranes based on polytetrafluoroethylene (PTFE).

[0069] - Cation exchange membranes, such as membranes based on fluoropolymer copolymers based on tetrafluoroethylene sulfonate, membranes based on poly(ether ether ketone), membranes based on polysulfone, membranes based on polyethylene, membranes based on polypropylene, membranes based on ethylene-propylene copolymers, membranes based on polyimide, and membranes based on polyvinyl fluoride.

[0070] An anion exchange membrane that is advantageously suited for the purposes of this invention and is commercially available is Astom's. AMX, AHA ACS, Lanxess's Ionac MA3475, DuPont's Fumatech's FAA-3.

[0071] A commercially available cation exchange membrane that is advantageously suited for the purposes of this invention is Astom's. CMX, CIMS, DuPont

[0072] Preferably, the negative electrode may include at least one metal, such as platinum, copper, aluminum, nickel, or stainless steel; or at least one carbon-containing material, such as carbon black, activated carbon, amorphous carbon, graphite, graphene, or carbon nanostructure materials; or a mixture thereof. The negative electrode may be porous, grooved, or smooth.

[0073] Preferably, the positive electrode may include at least one metal, such as platinum, copper, aluminum, nickel, or stainless steel; or at least one carbon-containing material, such as carbon black, activated carbon, amorphous carbon, graphite, graphene, or carbon nanostructure materials; or a mixture thereof. The positive electrode may be porous, grooved, or smooth.

[0074] Some of the benzothiadiazoles listed above with general formula (I) are new.

[0075] Therefore, another object of the present invention is to provide benzothiadiazole having the general formula (Ia):

[0076]

[0077] in:

[0078] -R1 and R2 may be the same or different from each other, representing hydrogen atoms; or representing straight-chain or branched, saturated or unsaturated C1-C atoms. 20 Alkyl groups, preferably C1-C 10 ; or represents the -O-R3 group, where R3 is selected from -(CH2). n The COOR4 group, wherein R4 is selected from straight-chain or branched, saturated or unsaturated C1-C groups. 20 Alkyl groups, preferably C1-C 10 n is an integer from 1 to 10, preferably from 1 to 8, or R3 is selected from -(CH2). n The OR4 group, wherein R4 and n have the same meaning as described above, or R3 is selected from -(CH2CH2O). n The R4 group, wherein R4 and n have the same meaning as described above, or R3 is selected from -(CH2). n The CN group, wherein n has the same meaning as above, or R3 is selected from -(CH2). n The NR4R5 group, wherein R4 and n have the same meaning as described above and R5 is selected from straight-chain or branched, saturated or unsaturated C1-C groups. 20 Alkyl groups, preferably C1-C 10 Or R3 is selected from

[0079] -(CH2) n CONR4R5 group, wherein R4, R5 and n have the same meaning as described above, or R3 is selected from...

[0080] -(CH2) n The Si(R4)3 group, wherein R4 and n have the same meaning as described above, or R3 is selected from...

[0081] -(CH2) n The Si(OR4)3 group, wherein R4 and n have the same meaning as described above;

[0082] The condition is that at least one of R1 and R2 is not hydrogen, and at least one of R1 and R2 is at the 2 position of the phenyl group.

[0083] Benzothiadiazoles having the general formula (I) can be synthesized according to methods known in the art. In particular, compounds (2), (3) and (4) are synthesized from 2-hydroxyphenylboronic acid and 4,7-dibromobenzothiadiazole via the Suzuki reaction to give 4,7-bis(2-hydroxyphenyl)-benzothiadiazole: the Suzuki reaction has high selectivity, and the boric acid derivative is non-toxic, easy to handle and stable. Typically, the Suzuki reaction is catalyzed by a palladium-based catalyst, such as tetrakis(triphenylphosphine)palladium(II)[Pd(PPh3)4], 1,1'-bis(diphenylphosphine)ferrocene]palladium(II) dichloride[Pd(dppf)Cl2], tris(dibenzylideneacetone)-dipalladium(O) / tris(o-tolyl)phosphine[Pd2dba3 / P(o-tolyl)3]: in particular, tetrakis(triphenylphosphine)palladium(II)[Pd(PPh3)4] is used, for example, as reported by Ji C. et al. in "Dyes and Pigments" (2017), Vol. 140, pp. 203-211. The Suzuki reaction requires a basic environment, and the most commonly used bases for this purpose are: alkali metal carbonates (potassium, sodium, cesium), potassium acetate, potassium phosphate, potassium tert-butyl; in particular, potassium carbonate is used. The Suzuki reaction can be carried out in the presence of pure organic solvents or mixtures of these solvents, such as dioxane, toluene, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, water, ethanol, and isopropanol; in particular, it is carried out in the presence of dioxane and water. The Suzuki reaction is usually carried out in an inert atmosphere at a temperature of 70°C to 100°C; in particular, it is carried out at 80°C to 85°C.

[0084] The 4,7-bis(2-hydroxyphenyl)-benzothiadiazole obtained from the Suzuki reaction described above is converted to compounds (2), (3), and (4) via a known Williamson etherification reaction (as reported, for example, by Guy K. et al. in the Journal of Medicinal Chemistry (2009), Vol. 52, pp. 3892-3901), depending on whether it is reacted with ethyl 4-bromobutyrate to give compound (2), with ethyl 2-bromoacetate to give compound (3), or with 1-bromo-2-(2-methoxyethoxy)ethane to give compound (4). The Williamson etherification reaction is generally carried out in an alkaline environment (particularly in the presence of potassium carbonate) and in the presence of a dipolar aprotic solvent (particularly in the presence of dimethylformamide). The isolated products are purified by silica gel column chromatography in yields ranging from 80% to 95%.

[0085] Compounds (5), (6), and (7) were synthesized from the corresponding methoxy derivatives prepared by a Suzuki reaction from 4,7-dibromobenzothiadiazole and the corresponding dimethoxyphenylboronic acid, in a manner similar to the Suzuki reaction between 2-hydroxyphenylboronic acid and 4,7-dibromobenzothiadiazole reported above. It is known in the literature, such as in, for example, Petronzi C. et al., “European Journal of Medicinal Chemistry” (2011), Vol. 46, pp. 488-496, that methoxy ethers can be demethylated to provide the corresponding hydroxyl groups by reacting with boron tribromide (commercially available as a 1M dichloromethane solution). Specifically, 4,7-di(2,6-hydroxyphenyl)-benzothiadiazole is obtained from 4,7-di(2,6-dimethoxyphenyl)-benzothiadiazole, 4,7-di(2,5-dihydroxyphenyl)-benzothiadiazole is obtained from 4,7-di(2,4-dihydroxyphenyl)-benzothiadiazole, and 4,7-di(2,4-dihydroxyphenyl)-benzothiadiazole is obtained from 4,7-di(2,4-dimethoxyphenyl)-benzothiadiazole. The corresponding compounds (5), (6), and (7) are obtained by reacting these dihydroxyphenylbenzothiadiazole derivatives with ethyl 4-bromobutyrate under alkaline conditions via the Williamson reaction.

[0086] Alternatively, benzothiadiazoles having the general formula (I) can be synthesized via micellar synthesis, as described, for example, by Beverina L. et al. in “Organic Letters” (2017), Vol. 19, pp. 654-657. In this regard, for example, with respect to compound (2), 2-(propoxycarbonylethoxy)-1-bromobenzene was used as the starting material and reacted with pinacol benzothiadiazole-4,7-diboron ester in a solvent consisting of a 90% aqueous solution containing 2% Kolliphor and 10% toluene, in the presence of [1,1′-bis(di-tert-butylphosphino)ferrocene-dichloro-palladium(II)[Pd(dtbpf)Cl2] as a catalyst, in an alkaline environment prepared from triethylamine (micelle synthesis). Product (2) was obtained after elution on a silica gel column in 90% yield. The advantages of this reaction are considerable: i) it reduces the use of toxic solvents, with water being the primary solvent; ii) it reduces reaction time; iii) it lowers the reaction temperature; and iv) it increases the yield. Similarly, this synthetic route has been used to prepare compound (7). In this paper, micellar synthesis also enables the use of an environmentally friendly method to obtain the desired product in high yield.

[0087] Now, we will refer to the following reports regarding... Figure 1 The present invention will be described in more detail with reference to the implementation scheme.

[0088] In particular, Figure 1 An embodiment of the non-aqueous redox flow battery (RFB) according to the present invention is schematically illustrated. In this respect, the non-aqueous redox flow battery (RFB) (1) includes: a positive electrode compartment (6a) in which a positive electrode (6) is placed, and a non-aqueous liquid positive electrode electrolyte (…). Figure 1 (Not shown) flows in the positive electrode compartment; negative electrode compartment (8a), in which a negative electrode (8) is placed, non-aqueous liquid negative electrode electrolyte ( Figure 1 (Not shown) flows in the negative electrode compartment; an ion exchange membrane (7) is placed between the positive electrode compartment (6a) and the negative electrode compartment (8a).

[0089] The positive electrode compartment (6a) is connected to a reservoir (2) containing a non-aqueous liquid positive electrode electrolyte via an inlet pipe (3), a pump (4a) (e.g., a peristaltic pump), and an outlet pipe (5), thereby allowing the supply and discharge of the non-aqueous liquid positive electrode electrolyte during operating cycles (i.e., during the charge-discharge phase), the non-aqueous liquid positive electrode electrolyte comprising a solution of copper trifluoromethanesulfonate or copper tetrafluoroborate complex [Cu(I) or Cu(II)] in at least one organic solvent.

[0090] The negative electrode compartment (8a) is connected to a reservoir (12) containing a non-aqueous liquid negative electrode electrolyte via an inlet pipe (11) and a pump (4b) (e.g., a peristaltic pump) and an outlet pipe (10), thereby allowing the supply and discharge of the non-aqueous liquid negative electrode electrolyte during operating cycles (i.e., during the charge-discharge phase), the non-aqueous liquid negative electrode electrolyte comprising a solution of at least one benzothiadiazole having general formula (I) in at least one organic solvent.

[0091] The voltmeter (9) is connected to the positive terminal (6) and the negative terminal (8).

[0092] During the charging phase of the non-aqueous redox flow battery (RFB) (1), a potential difference is applied between the positive and negative electrodes using a voltmeter (9), while a non-aqueous liquid positive electrode electrolyte is supplied from the positive electrode electrolyte reservoir (2) to the positive electrode compartment (6a) via a pump (4a), and a non-aqueous liquid negative electrode electrolyte is supplied from the negative electrode electrolyte reservoir (12) to the negative electrode compartment (8a) via a pump (4b). The non-aqueous liquid positive electrode electrolyte present in the positive electrode compartment (6a) undergoes an oxidation reaction at the positive electrode (6), while the non-aqueous liquid negative electrode electrolyte present in the negative electrode compartment (8a) undergoes a reduction reaction at the negative electrode (8). Ions participating in the above oxidation and reduction reactions flow through the ion exchange membrane (7) in opposite directions to balance the charge. During the discharging phase of the non-aqueous redox flow battery (RFB) (1), a reverse reaction occurs. The above charging and discharging phases can be summarized as follows:

[0093] negative electrode:

[0094] positive electrode:

[0095] Battery:

[0096] in:

[0097] - "carica": charging;

[0098] -“scarica”: discharge;

[0099] -BTD = benzothiadiazole (I) having the general formula (I);

[0100] -Cu = Copper;

[0101] -e - =Electron.

[0102] During the operating cycle (i.e., during the charge-discharge phase), non-aqueous liquid positive electrode electrolyte and non-aqueous liquid negative electrode electrolyte are continuously pumped into the positive and negative electrode compartments, respectively, to continuously supply the positive and negative electrode compartments.

[0103] The energy stored in a non-aqueous redox flow battery (RFB) (1) can be directly used for the operation of devices plugged into the battery, or it can be transferred to the grid during peak electricity demand to supplement the power supply. AC / DC converter ( Figure 1 (Not shown) can optionally be used to facilitate the transfer of energy to and from an AC power supply network.

[0104] The present invention will be further illustrated by the following embodiments. These embodiments are for illustrative purposes only and do not limit the present invention.

[0105] Example 1

[0106] Synthesis of 4,7-bis[2-(methoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (3)]

[0107]

[0108] Synthesis of 4,7-bis(2-hydroxyphenyl)-benzothiadiazole

[0109]

[0110] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at room temperature (25 °C), the following substances were added sequentially to a solution of 0.08 M 4,7-dibromobenzothiadiazole (Aldrich) (990 mg; 3.37 mmol) in dioxane (Aldrich): 2-hydroxyphenylboronic acid (Aldrich) (2 g; 9.1 mmol), potassium carbonate (K₂CO₃) (Aldrich) (3.7 g; 27 mmol), and distilled water (12 ml). After removing oxygen from the reaction environment through three vacuum / nitrogen cycles, tetrakis(triphenylphosphine)palladium(II)[Pd(PPh₃)₄](Aldrich) (200 mg; 0.17 mmol) was added. The flask was then immersed in an oil bath preheated to 85 °C and placed at that temperature with stirring for 20 hours. Then, distilled water (50 ml) was added and all substances were extracted with diethyl ether (Aldrich) (3 × 100 ml). The resulting organic phases were combined, washed with saturated sodium chloride aqueous solution (Aldrich) until neutral, and dehydrated with sodium sulfate (Aldrich). After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column [eluting solvent: heptane (Aldrich) / dichloromethane (Aldrich) / ethyl acetate (Aldrich), gradient from 91 / 6 / 3 to 82 / 12 / 6 to 70 / 20 / 10], to give 986 mg of 4,7-bis(2-hydroxyphenyl)-benzothiadiazole (yield = 91%).

[0111] Synthesis of 4,7-bis[2-(methoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (3)]

[0112]

[0113] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at room temperature (25 °C), potassium carbonate (K₂CO₃) (Aldrich) (276 mg; 2 mmol) was added to a solution of 0.05 M 4,7-bis(2-hydroxyphenyl)-benzothiadiazole (157.22 mg; 0.49 mmol) in N,N-dimethylformamide (DMF) (Aldrich) with stirring. After 5 minutes, ethyl 2-bromoacetate (Aldrich) (220 μl; 334 mg; 2 mmol) was added. The flask was then immersed in an oil bath preheated to 80 °C and left to stand at that temperature with stirring for 12 hours. Distilled water (100 ml) was then added, and all substances were extracted with diethyl ether (Aldrich) (3 × 100 ml). The resulting organic phases were combined, washed with a saturated aqueous sodium chloride solution (Aldrich) until neutral, and dehydrated with sodium sulfate (Aldrich). After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column [eluting solvent: heptane (Aldrich) / dichloromethane (Aldrich) / ethyl acetate (Aldrich), gradient from 91 / 6 / 3 to 82 / 12 / 6], to give 229 mg of 4,7-bis[2-(methoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (3) (yield = 95%).

[0114] Example 2

[0115] Synthesis of 4,7-bis[2-(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (2)]

[0116]

[0117] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at room temperature (25 °C), potassium carbonate (K₂CO₃) (Aldrich) (972 mg; 7.03 mmol) was added to a 0.2 M solution of 4,7-bis(2-hydroxyphenyl)-benzothiadiazole (986 mg; 3.06 mmol) in N,N-dimethylformamide (DMF) (Aldrich) with stirring. After 5 minutes, ethyl 4-bromobutyrate (Aldrich) (970 μl; 1322 mg; 6.73 mmol) was added. The flask was then immersed in an oil bath preheated to 80 °C and left at that temperature with stirring for 12 hours. Then, distilled water (100 ml) was added and all substances were extracted with ethyl acetate (Aldrich) (3 × 100 ml). The resulting organic phases were combined, washed with saturated sodium chloride aqueous solution (Aldrich) until neutral, and dehydrated with sodium sulfate (Aldrich). After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column [eluting agent: heptane (Aldrich) / ethyl acetate (Aldrich), gradient from 80 / 20 to 70 / 30] to give 1300 mg of 4,7-bis[2-(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (2) (yield = 80%)].

[0118] Example 3

[0119] Synthesis of 4,7-bis[2-(2-(2-methoxyethoxy)ethoxy)phenyl]-benzothiadiazole [compound (4)]

[0120]

[0121] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at room temperature (25 °C), potassium carbonate (K₂CO₃) (Aldrich) (334 mg; 2.42 mmol) was added to a solution of 0.08 M 4,7-bis(2-hydroxyphenyl)-benzothiadiazole (260 mg; 0.81 mmol) in N,N-dimethylformamide (DMF) (Aldrich). After 5 minutes, 1-bromo-2-(2-methoxyethoxy)ethane (Aldrich) (323 μl; 440 mg; 2.42 mmol) was added. The flask was then immersed in an oil bath preheated to 80 °C and left at that temperature for 12 hours. Then, distilled water (50 ml) was added and all substances were extracted with ethyl acetate (Aldrich) (3 × 50 ml). The resulting organic phases were combined, washed with saturated sodium chloride aqueous solution (Aldrich) until neutral, and dehydrated with sodium sulfate (Aldrich). After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column [eluting agent: heptane (Aldrich) / ethyl acetate (Aldrich), gradient from 80 / 20 to 70 / 30 to 60 / 40] to give 340 mg of 4,7-bis[2-(2-(2-methoxyethoxy)ethoxy)phenyl]-benzothiadiazole [compound (4) (yield = 80%)].

[0122] Example 4

[0123] Synthesis of 4,7-bis[2,6-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (5)]

[0124] Synthesis of 4,7-bis(2,6-dimethoxyphenyl)-benzothiadiazole

[0125]

[0126] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at room temperature (25 °C), the following substances were added sequentially to a solution of 0.08 M 4,7-dibromobenzothiadiazole (Aldrich) (500 mg; 1.7 mmol) in dioxane (Aldrich): 2,6-dimethoxyphenylboronic acid (Aldrich) (1000 mg; 4.6 mmol), potassium carbonate (K₂CO₃) (Aldrich) (1.88 g; 13.6 mmol), and distilled water (7 ml). After removing oxygen from the reaction environment through three vacuum / nitrogen cycles, tetrakis(triphenylphosphine)palladium(II)[Pd(PPh₃)₄](Aldrich) (100 mg; 0.086 mmol) was added. The flask was then immersed in an oil bath preheated to 85 °C and placed at that temperature with stirring for 20 hours. Then, distilled water (50 ml) was added and all substances were extracted with ether (Aldrich) (3 × 50 ml). The resulting organic phases were combined, washed with distilled water until neutral, and dehydrated with sodium sulfate (Aldrich). After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column [eluting agent: heptane (Aldrich) / dichloromethane (Aldrich), gradient from 100 / 0 to 95 / 5 to 90 / 10 to 85 / 15] to give 460 mg of 4,7-bis(2,6-dimethoxyphenyl)-benzothiadiazole (yield = 66%).

[0127] Synthesis of 4,7-bis(2,6-dihydroxyphenyl)-benzothiadiazole

[0128]

[0129] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at -78 °C, with stirring, slowly add dropwise a solution of 1 M boron tribromide (BBr3) (Aldrich) in anhydrous dichloromethane (CH2Cl2) (Aldrich) (16 ml; 16 mmol) to a solution of 0.09 M 4,7-bis(2,6-dimethoxyphenyl)-benzothiadiazole (Aldrich) (439 mg; 1.07 mmol) obtained as described above in anhydrous dichloromethane (CH2Cl2) (Aldrich): allowing the temperature to rise slowly and spontaneously to room temperature (25 °C). After cooling the mixture to -78 °C, slowly add dropwise ethanol (Aldrich) (25 ml). The temperature was then restored to room temperature (25°C), and the solvent was removed by vacuum distillation. Distilled water (50 ml) was added, and all substances were extracted with ethyl acetate (Aldrich) (3 × 50 ml). The resulting organic phases were combined, washed with sodium chloride aqueous solution (Aldrich) until neutral, and dehydrated with sodium sulfate (Aldrich). The residue was purified by elution on a silica gel column (eluting agent: heptane (Aldrich) / ethyl acetate (Aldrich), ratio 60 / 40 v / v) to give 289.4 mg of 4,7-bis(2,6-dihydroxyphenyl)-benzothiadiazole (yield = 77%).

[0130] Synthesis of 4,7-bis[2,6-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (5)]

[0131]

[0132] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at room temperature (25 °C), potassium carbonate (K₂CO₃) (Aldrich) (959 mg; 4.9 mmol) was added to a solution of 0.05 M 4,7-bis(2,6-dihydroxyphenyl)-benzothiadiazole (289.4 mg; 0.82 mmol) in N,N-dimethylformamide (DMF) (Aldrich) with stirring. After 5 minutes, ethyl 4-bromobutyrate (Aldrich) (704 μl; 1322 mg; 4.9 mmol) was added. The flask was then immersed in an oil bath preheated to 80 °C and left to stand at that temperature with stirring for 12 hours. Distilled water (50 ml) was then added, and all substances were extracted with ethyl acetate (Aldrich) (3 × 50 ml). The resulting organic phases were combined, washed with distilled water until neutral, and dehydrated with sodium sulfate (Aldrich). After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column (eluting agent: heptane (Aldrich) / ethyl acetate (Aldrich), ratio 70 / 30 v / v) to give 380 mg of 4,7-bis[2,6-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (5) (yield = 57%)].

[0133] Example 5

[0134] Synthesis of 4,7-bis[2,5-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (6)]

[0135] Synthesis of 4,7-bis(2,5-dimethoxyphenyl)-benzothiadiazole

[0136]

[0137] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at room temperature (25 °C), the following substances were added sequentially to a solution of 0.08 M 4,7-dibromobenzothiadiazole (Aldrich) (700 mg; 2.4 mmol) in dioxane (Aldrich): 2,5-dimethoxyphenylboronic acid (Aldrich) (1180 mg; 6.5 mmol), potassium carbonate (K₂CO₃) (Aldrich) (2.65 g; 19.2 mmol), and distilled water (10 ml). After removing oxygen from the reaction environment through three vacuum / nitrogen cycles, tetrakis(triphenylphosphine)palladium(II)[Pd(PPh₃)₄](Aldrich) (140 mg; 0.121 mmol) was added. The flask was then immersed in an oil bath preheated to 85 °C and placed at that temperature with stirring for 20 hours. Then, distilled water (100 ml) was added and all substances were extracted with diethyl ether (Aldrich) (3 × 100 ml). The resulting organic phases were combined, washed with distilled water until neutral, and dehydrated with sodium sulfate. After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column (eluting agent: heptane (Aldrich) / dichloromethane (Aldrich), gradient from 100 / 0 to 95 / 5 to 90 / 10 to 85 / 15) to give 880 mg of 4,7-bis(2,5-dimethoxyphenyl)-benzothiadiazole (yield = 90%).

[0138] Synthesis of 4,7-bis(2,5-dihydroxyphenyl)-benzothiadiazole

[0139]

[0140] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at -78 °C, with stirring, slowly add dropwise a 1 M solution of boron tribromide (BBr3) in anhydrous dichloromethane (CH2Cl2) (Aldrich) (27 ml; 27 mmol) obtained as described above to a solution of 0.09 M 4,7-bis(2,5-dimethoxyphenyl)-benzothiadiazole (Aldrich) (738 mg; 1.8 mmol) in anhydrous dichloromethane (CH2Cl2) (Aldrich): allow the temperature to rise slowly and spontaneously to room temperature (25 °C). After cooling the mixture to -78 °C, slowly add ethanol (25 ml). The temperature was then restored to room temperature (25°C), and the solvent was removed by vacuum distillation. Distilled water (50 ml) was added, and all substances were extracted with ethyl acetate (Aldrich) (3 × 50 ml). The resulting organic phases were combined, washed with sodium chloride aqueous solution (Aldrich) until neutral, and dehydrated with sodium sulfate. The residue was purified by elution on a silica gel column (eluting agent: heptane (Aldrich) / ethyl acetate (Aldrich), ratio 60 / 40 v / v) to give 557.4 mg of 4,7-bis(2,5-dihydroxyphenyl)-benzothiadiazole (yield = 87.2%).

[0141] Synthesis of 4,7-bis[2,5-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (6)]

[0142]

[0143] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at room temperature (25 °C), potassium carbonate (K₂CO₃) (Aldrich) (1300 mg; 9.4 mmol) was added to a solution of 0.1 M 4,7-bis(2,5-dihydroxyphenyl)-benzothiadiazole (557.4 mg; 1.57 mmol) in N,N-dimethylformamide (DMF) (Aldrich) with stirring. After 5 minutes, ethyl 4-bromobutyrate (1.35 ml; 1322 mg; 9.4 mmol) was added. The flask was then immersed in an oil bath preheated to 85 °C and left to stand at that temperature with stirring for 12 hours. Distilled water (50 ml) was then added, and all substances were extracted with ethyl acetate (Aldrich) (3 × 50 ml). The resulting organic phases were combined, washed with distilled water until neutral, and dehydrated with sodium sulfate. After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column (eluting agent: heptane (Aldrich) / ethyl acetate (Aldrich), ratio 70 / 30 v / v) to give 888 mg of 4,7-bis[2,5-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (6) (yield = 70%)].

[0144] Example 6

[0145] Synthesis of 4,7-bis[2,4-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (7)]

[0146] Synthesis of 4,7-bis(2,4-dimethoxyphenyl)-benzothiadiazole

[0147]

[0148] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at room temperature (25 °C), the following substances were added sequentially to a solution of 0.08 M 4,7-dibromobenzothiadiazole (Aldrich) (705 mg; 2.4 mmol) in dioxane (Aldrich): 2,4-dimethoxyphenylboronic acid (Aldrich) (1170 mg; 6.43 mmol), potassium carbonate (K₂CO₃) (Aldrich) (6.5 g; 19.2 mmol), and distilled water (10 ml). After removing oxygen from the reaction environment through three vacuum / nitrogen cycles, tetrakis(triphenylphosphine)palladium(II)[Pd(PPh₃)₄](Aldrich) (140 mg; 0.121 mmol) was added. The flask was then immersed in an oil bath preheated to 85 °C and placed at that temperature with stirring for 20 hours. Then, distilled water (50 ml) was added and all substances were extracted with diethyl ether (Aldrich) (3 × 50 ml). The resulting organic phases were combined, washed with distilled water until neutral, and dehydrated with sodium sulfate (Aldrich). After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column (eluting agent: heptane (Aldrich) / dichloromethane (Aldrich), gradient from 100 / 0 to 95 / 5 to 90 / 10 to 85 / 15 to 80 / 20 to 70 / 30) to give 832 mg of 4,7-bis(2,4-dimethoxyphenyl)-benzothiadiazole (yield = 85%).

[0149] Synthesis of 4,7-bis(2,4-dihydroxyphenyl)-benzothiadiazole

[0150]

[0151] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at -78 °C, with stirring, slowly add dropwise a solution of 1 M boron tribromide (BBr3) (Aldrich) in anhydrous dichloromethane (CH2Cl2) (Aldrich) (12 ml; 12 mmol) to a solution of 0.09 M 4,7-bis(2,4-dimethoxyphenyl)-benzothiadiazole (Aldrich) (330 mg; 0.8 mmol) obtained as described above in anhydrous dichloromethane (CH2Cl2) (Aldrich): allowing the temperature to rise slowly and spontaneously to room temperature (25 °C). After cooling the mixture to -78 °C, slowly add dropwise ethanol (Aldrich) (25 ml). The temperature was then restored to room temperature (25°C), and the solvent was removed by vacuum distillation. Distilled water (50 ml) was added, and all substances were extracted with ethyl acetate (Aldrich) (3 × 50 ml). The resulting organic phases were combined, washed with sodium chloride aqueous solution (Aldrich) until neutral, and dehydrated with sodium sulfate (Aldrich). The resulting residue was purified by elution on a silica gel column (eluting agent: heptane (Aldrich) / ethyl acetate (Aldrich), ratio 60 / 40 v / v) to give 270 mg of 4,7-bis(2,4-dihydroxyphenyl)-benzothiadiazole (yield = 95%).

[0152] Synthesis of 4,7-bis[2,4-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (7)]

[0153]

[0154] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under an inert atmosphere and at room temperature (25 °C), potassium carbonate (K₂CO₃) (Aldrich) (626 mg; 4.54 mmol) was added to a solution of 0.076 M of 4,7-bis(2,4-dihydroxyphenyl)-benzothiadiazole (268 mg; 0.76 mmol) in N,N-dimethylformamide (DMF) (Aldrich) with stirring. After 5 minutes, ethyl 4-bromobutyrate (Aldrich) (652 μl; 889 mg; 4.54 mmol) was added. The flask was then immersed in an oil bath preheated to 80 °C and left to stand at that temperature with stirring for 12 hours. Distilled water (50 ml) was then added, and all substances were extracted with ethyl acetate (Aldrich) (3 × 50 ml). The resulting organic phases were combined, washed with distilled water until neutral, and dehydrated with sodium sulfate (Aldrich). After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column (eluting agent: heptane (Aldrich) / ethyl acetate (Aldrich), ratio 70 / 30 v / v) to give 490 mg of 4,7-bis[2,4-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (7) (yield = 80%)].

[0155] Example 7

[0156] Synthesis of 4,7-bis[2-(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (2)] - Suzuki- Micellar Synthesis

[0157]

[0158] “acqua” = water

[0159] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under the presence of air and at room temperature (25 °C), 2-(propoxycarbonylethoxy)-1-bromobenzene (Aldrich) (1000 mg, 3.5 mmol), 4,7-benzothiadiazole diborate pinacol ester (Aldrich) (630 mg, 1.62 mmol), and [1,1'-bis(di-tert-butylphosphine)ferrocene]palladium(II) dichloride [Pd(dtbpf)Cl2] (Aldrich) (24 mg, 0.037 mmol) were added to 4.5 ml of [amount not specified in the original text]. Triethylamine (TEA) (Aldrich) (1022 mg, 1.4 mL, 10 mmol) was added to a suspension of a 9:1 (v / v) mixture of EL (2 wt% solution in deionized water) and toluene (Aldrich). The resulting reaction mixture was heated to 70 °C and maintained at that temperature for 15 minutes with stirring. Then, distilled water (50 mL) was added and all substances were extracted with ethyl acetate (Aldrich) (3 × 50 mL). The resulting organic phases were combined, washed with distilled water until neutral, and dehydrated with sodium sulfate (Aldrich). After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column (eluting agent: heptane (Aldrich) / ethyl acetate (Aldrich), ratio 80 / 20 v / v) to give 797.8 mg of 4,7-bis[2-(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (2) (yield = 90%)].

[0160] Example 8

[0161] Synthesis of 4,7-bis[2,4-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (7)] Suzuki - Micellar Synthesis

[0162]

[0163] In a 100 ml round-bottom flask equipped with a mechanical stirrer, thermometer, and coolant, under the presence of air and at room temperature (25 °C), 2,4-(propoxycarbonylethoxy)-1-bromobenzene (Aldrich) (2400 mg, 5.8 mmol), 4,7-benzothiadiazole diboronic acid pinacol ester (Aldrich) (1028 mg, 2.6 mmol), and [1,1'-bis(di-tert-butylphosphine)ferrocene]palladium(II) dichloride [Pd(dtbpf)Cl2] (Aldrich) (42 mg, 0.064 mmol) were added to a 4 ml container of [aluminum dichloride]. Triethylamine (Aldrich) (1752 mg, 2.4 ml, 17.3 mmol) was added to a suspension of EL (2 wt% solution in deionized water) and toluene (Aldrich) in a 9:1 (v / v) ratio: The resulting reaction mixture was heated to 70 °C and maintained at that temperature for 15 minutes with stirring.

[0164] Then, distilled water (100 ml) was added and all substances were extracted with ethyl acetate (Aldrich) (3 × 100 ml). The resulting organic phases were combined, washed with distilled water until neutral, and dehydrated with sodium sulfate (Aldrich). After removing the solvent by vacuum distillation, the residue was purified by elution on a silica gel column (eluting agent: heptane (Aldrich) / ethyl acetate (Aldrich), gradient from 80 / 20 to 70 / 30 to 65 / 35) to give 2140 mg of 4,7-bis[2,4-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (7)] (yield = 100%).

[0165] Example 9

[0166] Cyclic voltammetry measurement

[0167] Cyclic voltammetry was performed in a half-cell with a three-electrode configuration: a glassy carbon working electrode, a platinum counter electrode, and a silver / silver chloride (Ag / AgCl) reference electrode. Redox potential E°' Ox / Red From the positive peak (E) pf ) and return peak (E pr The position of ) is obtained:

[0168]

[0169] And relative to the solvent inter-ferrocene / ferrocene salt (Fc / Fc) + Normalize these values.

[0170] Evaluations were performed on an Autolab PGSTAT 128N analyzer at scan rates of 10, 20, 50, 70, 100, and 200 mV / s. All evaluations were performed in triplicate at room temperature (25°C). Solutions containing the following were used for this purpose:

[0171] -Benzothiadiazole(1)(Aldrich)(5×10 -3 M) and tetrabutylammonium tetrafluoroborate (TBABF4)

[0172] (Aldrich) (0.1M) in acetonitrile (Aldrich) solution (non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) (BTD);

[0173] -Benzothiadiazole(1)(Aldrich)(5×10 -3 M) and tetrabutylammonium tetrafluoroborate (TBABF4)

[0174] (Aldrich) (0.1M) in a solution of propylene carbonate (Aldrich) (non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) (BTD);

[0175] -4,7-Bis[2-(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (2) obtained in Example 7] (5×10 -3 A solution of 0.1 M tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) and 0.1 M tetrabutylammonium tetrafluoroborate (Aldrich) in acetonitrile (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) (BTD);

[0176] -4,7-Bis[2-(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (2) obtained in Example 7] (5×10 -3 A solution of 0.1 M tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) and 0.1 M tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) in propylene carbonate (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD] (2)];

[0178] -4,7-Bis[2-(methoxycarbonylethoxy)phenyl]-benzothiadiazole [the compound obtained in Example 1]

[0179] (3)](5×10 -3 A solution of tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in acetonitrile (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD(3)];

[0180] -4,7-Bis[2-(methoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (3) obtained in Example 1] (5×10 -3 A solution of 0.1 M tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) and 0.1 M tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) in propylene carbonate (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD] (3)];

[0182] -4,7-Bis[2-(2-(2-methoxyethoxy)ethoxy)phenyl]-benzothiadiazole [compound (4) obtained in Example 3] (5×10 -3 A solution of tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in acetonitrile (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD(4)];

[0183] -4,7-Bis[2-(2-(2-methoxyethoxy)ethoxy)phenyl]-benzothiadiazole [compound (4) obtained in Example 3] (5×10 -3A solution of tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in propylene carbonate (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD(4)];

[0184] -4,7-bis[2,6-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (5) obtained in Example 4] (5 × 10 -3 M) and tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in acetonitrile (Aldrich) (non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD(5)]; -4,7-bis[2,6-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (5) obtained in Example 4] (5×10 -3 A solution of tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in propylene carbonate (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD(5)];

[0185] -4,7-bis[2,5-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (6) obtained in Example 5] (5 × 10 -3 M) and tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in acetonitrile (Aldrich) (non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD(6)]; -4,7-bis[2,5-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (6) obtained in Example 5] (5×10 -3 A solution of tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in propylene carbonate (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD(6)];

[0186] -4,7-bis[2,4-bis(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (7) obtained in Example 8] (5 × 10 -3 A solution of tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in acetonitrile (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD(7)]; a solution of tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in propylene carbonate (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) [BTD(7)];

[0187] -Copper(II)trifluoromethanesulfonate[Cu(CF3SO3)2](Aldrich)(5×10 -4 A solution of 0.1 M tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) and 0.1 M tetrabutylammonium tetrafluoroborate (Aldrich) in acetonitrile (Aldrich) (a non-aqueous liquid positive electrode electrolyte in the positive electrode compartment) (copper trifluoromethanesulfonate);

[0188] -Copper tetrafluoroborate tetraacetonitrile (I)[Cu(NCCH3)4·BF4](Aldrich)(5×10⁻⁶) -4 A solution of copper tetrafluoroborate (I) in acetonitrile (Aldrich) and tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in acetonitrile (Aldrich) (a non-aqueous liquid positive electrode electrolyte in the positive electrode compartment);

[0189] -Copper tetraacetonitrile trifluoromethanesulfonate (I) [Cu(NCCH3)4·CF3SO3](Aldrich)(5×10 -4 A solution of tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in propylene carbonate (Aldrich) (a non-aqueous liquid positive electrode electrolyte in the positive electrode compartment) [Cu(I)];

[0190] The obtained values ​​are reported in Table 2.

[0191] Table 2

[0192]

[0193] Figure 2-8 The horizontal axis displays the measured potential (E) in volts (V), and the vertical axis displays the potential in amperes / cm². 2 (A·cm -2 The current density measured by the meter (J) is shown in the cyclic voltammograms obtained from the above [BTD and compounds (2)-(7)] in acetonitrile and propylene carbonate solutions at a scan rate of 200 mV / s.

[0194] For example, considering an acetonitrile solution of compound (2), it can be seen that a high potential difference (E°) of 2.53V is obtained in the open circuit, which is calculated according to the following formula:

[0195] E°=(E°1)–(E°2)

[0196] in:

[0197] -(E°1) is the redox potential of (copper trifluoromethanesulfonate) calculated as described above, and is equal to 0.62 Vvs(Fc / Fc). + );

[0198] -(E°2) is the redox potential of the different solutions calculated as described above and reported in Table 2 (Example 2 equals -1.91).

[0199] Example 10

[0200] Stability testing in cyclic voltammetry

[0201] Stability tests were performed using the same electrochemical cells as in Example 9.

[0202] Therefore, a solution containing the following was used:

[0203] -4,7-Bis[2-(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (2) obtained in Example 2 or 7] (1×10 -3 A solution of tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) (0.1M) in acetonitrile (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment).

[0204] Figure 9 [The horizontal axis shows the potential (E) measured in volts (V), and the vertical axis shows the current intensity (i) measured in amperes (A)] shows 150 consecutive redox cycles performed on the above-mentioned 4,7-bis[2-(propoxycarbonylethoxy)phenyl]-benzothiadiazole solution [compound (2) obtained in Example 7]: it can be seen that the cycles are recapitulated, which means that no material is deposited on the electrode due to parasitic or polymerization reactions, and the free radicals formed are stable.

[0205] Example 11

[0206] Non-aqueous redox flow battery (RFB) charge / discharge test [electrolyte: 4,7-bis[2-(propoxycarbonylethyl)] [Oxy)phenyl]-benzothiadiazole [compound (2)] and acetonitrile solution of copper tetrafluoroborate (I)]

[0207] Charge-discharge tests were conducted using an electrochemical cell with a surface area of ​​approximately 0.07 cm². 2 The surface area between the two platinum electrodes (Methrohm) is approximately 0.8 cm². 2 of The membrane (DuPont). The electrochemical cell is then assembled and sealed in a container containing argon (Ar) gas.

[0208] Therefore, a solution containing the following was used:

[0209] -4,7-Bis[2-(propoxycarbonylethoxy)phenyl]-benzothiadiazole [compound (2) obtained in Example 7]: (1×10 -3A solution of 0.1 M tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) in acetonitrile (Aldrich) (a non-aqueous liquid negative electrode electrolyte in the negative electrode compartment) was degassed with argon (Ar) and electrolyzed to obtain the reduced form of benzothiadiazole [(BTD(2)· - )];

[0210] -Copper tetrafluoroborate tetraacetonitrile (I)[Cu(NCCH3)4·BF4](1×10 -3 A solution of 0.1M tetrabutylammonium tetrafluoroborate (TBABF4) (Aldrich) and 0.1M tetrabutylammonium tetrafluoroborate (Aldrich) in acetonitrile (Aldrich) (a non-aqueous liquid positive electrode electrolyte in the positive electrode compartment) (copper trifluoromethanesulfonate) was degassed with argon (Ar).

[0211] Introduce 6 ml of the above solution into the respective compartments.

[0212] The tests were conducted at room temperature (25°C) using an Autolab PGSTAT 128N (Metrohom) potentiostat / galvanometer.

[0213] Charge and discharge profiles were performed to evaluate the performance of the electrolyte in the battery. A charging potential of 2.5V and a discharging potential of 0.5V were applied, and the test was conducted in constant potential mode. Each potential was applied for 240 seconds.

[0214] Figure 10 [The horizontal axis shows the time measured in seconds (t / s); the vertical axis shows the current intensity (i) measured in amperes (A)] shows the obtained charge / discharge curves. During the discharge process, electrons are drawn from the negative electrode [(BTD(2)· - When the current flows towards the positive electrode (Cu), it has a negative sign. Conversely, during charging, the current has a positive sign. The current intensity is stable, thus both substances are characterized by good stability during redox cycles.

Claims

1. Non-aqueous redox flow battery (RFB) comprising: - a positive compartment in which a positive electrode is placed and in which a non-aqueous liquid positive electrolyte flows; - a negative compartment in which a negative electrode is placed and in which a non-aqueous liquid negative electrolyte flows; - an ion exchange membrane placed between the positive compartment and the negative compartment; wherein: - the non-aqueous liquid positive electrolyte comprises a solution of copper trifluoromethanesulfonate or copper tetrafluoroborate complex [Cu(I) or Cu(II)] in at least one organic solvent; - the non-aqueous liquid negative electrolyte comprises a solution of at least one benzothiadiazole having general formula (I) in at least one organic solvent: wherein: - R1and R2, equal to or different from each other, represent a hydrogen atom; or represent a linear or branched, saturated or unsaturated C1-C 20 alkyl group; or represent an -O-R3group, wherein R3is selected from a linear or branched, saturated or unsaturated C1-C 20 alkyl group, or R3is selected from a -(CH2) n COOR4group, wherein R4is selected from a linear or branched, saturated or unsaturated C1-C 20 alkyl group, n is an integer from 1 to 10, or R3is selected from a -(CH2) n OR4group, wherein R4and n have the same meaning as above, or R3is selected from a -(CH2CH2O) n R4group, wherein R4and n have the same meaning as above, or R3is selected from a -(CH2) n CN group, wherein n has the same meaning as above, or R3is selected from a -(CH2) n NR4R5group, wherein R4and n have the same meaning as above and R5is selected from a linear or branched, saturated or unsaturated C1-C 20 alkyl group, or R3is selected from -(CH2) n a group -CONR4R5, wherein R4, R5and n have the same meaning as above, or R3is selected from -(CH2) n Si(R4)3group, wherein R4and n have the same meaning as above, or R3is selected from -(CH2) n Si(OR4)3group, wherein R4and n have the same meaning as above; with the proviso that at least one of R1 and R2 is not hydrogen and at least one of R1 and R2 is in the 2 position of the phenyl group.

2. Non-aqueous redox flow battery (RFB) according to claim 1, wherein the copper trifluoromethanesulfonate or copper tetrafluoroborate complex [Cu(I) or Cu(II)] is selected from: copper(I) trifluoro-methanesulfonate tetraacetonitrile [Cu(NCCH3)4.CF3SO3], copper(II) trifluoro-methanesulfonate [Cu(CF3SO3)2], copper(I) tetrafluoro-borate tetraacetonitrile [Cu(NCCH3)4.BF4], or mixtures thereof.

3. Non-aqueous redox flow battery (RFB) according to claim 1 or 2, wherein in the general formula (I): - R1 and R2, equal to or different from each other, represent a hydrogen atom; or represent a group -OR3, wherein R3 is selected from -(CH2) n COOR4group, wherein R4is selected from linear or branched, saturated or unsaturated C1-C 20 alkyl, n is an integer from 1 to 10, or R3is selected from -(CH2CH20) n R4groups, wherein R4and n have the same meaning as above; with the proviso that at least one of R1 and R2 is not hydrogen and at least one of R1 and R2 is in the 2 position of the phenyl group.

4. Non-aqueous redox flow battery (RFB) according to claim 3, wherein in the general formula (I): - R1 and R2, equal to or different from each other, represent a propyloxycarbonyl ethyloxy group, a methoxycarbonyl ethyloxy group, a methoxyethyloxy acetyloxy group.

5. Non-aqueous redox flow battery (RFB) according to claim 1, wherein the aforesaid electrolyte comprises at least one supporting electrolyte selected from lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), methyl trifluoromethanesulfonate (LiCF3SO3), lithium bis(trifluoromethanesulfonyl)imide [Li(CF3SO2)2N], tetraethylammonium tetrafluoroborate (TEABF4), tetrabutylammonium tetrafluoroborate (TBABF4), or mixtures thereof.

6. Non-aqueous redox flow battery (RFB) according to claim 5, wherein the at least one supporting electrolyte is selected from lithium tetrafluoroborate (LiBF4), tetrabutylammonium tetrafluoroborate (TBABF4).

7. The non-aqueous redox flow battery (RFB) according to claim 1, wherein the organic solvent is selected from acetonitrile, dimethylacetamide, diethyl carbonate, dimethyl carbonate, gamma-butyrolactone (GBL), propylene carbonate (PC), ethylene carbonate (EC), N-methyl-2-pyrrolidone (NMP), fluoroethylene carbonate, N,N-dimethylacetamide or mixtures thereof.

8. The non-aqueous redox flow battery (RFB) according to claim 7, wherein the organic solvent is selected from acetonitrile, propylene carbonate (PC).

9. The non-aqueous redox flow battery (RFB) according to claim 1, wherein the ion exchange membrane is selected from a polymeric membrane selected from: - an ion exchange membrane selected from a film based on a styrene-divinylbenzene copolymer containing amino groups or a chloromethylstyrene-divinylbenzene copolymer, a film based on poly(ether ether ketone), a film based on a divinylbenzene-vinylpyridine copolymer containing quaternary pyridine groups, a film based on an aromatic polysulfone copolymer containing chloromethyl and amino groups, a film based on polytetrafluoroethylene (PTFE); - a cation exchange membrane selected from a film based on a tetrafluoroethylene sulfonate-based fluoropolymer copolymer, a film based on poly(ether ether ketone), a film based on polysulfone, a film based on polyethylene, a film based on polypropylene, a film based on an ethylene-propylene copolymer, a film based on polyimide, a film based on polyvinyl fluoride.

10. Benzothiadiazole for use as an anolyte in a non-aqueous redox flow battery (RFB) having the general formula (la): wherein: with the proviso that at least one of R1 and R2 is not hydrogen and at least one of R1 and R2 is in the 2-position of the phenyl group. - R1and R2, equal to or different from each other, represent a hydrogen atom or a linear or branched, saturated or unsaturated alkyl group C1-C 20 ; or a group -O-R3in which R3is selected from a linear or branched, saturated or unsaturated alkyl group C1-C 20 ; or R3is selected from a group -(CH2) n COOR4in which R4is selected from a linear or branched, saturated or unsaturated alkyl group C1-C 20 , n is an integer from 1 to 10, or R3is selected from a group -(CH2) n OR4in which R4and n have the same meaning as above, or R3is selected from a group -(CH2CH2O) n R4in which R4and n have the same meaning as above, or R3is selected from a group -(CH2) n CN in which n has the same meaning as above, or R3is selected from a group -(CH2) n NR4R5in which R4and n have the same meaning as above and R5is selected from a linear or branched, saturated or unsaturated alkyl group C1-C 20 , or R3is selected from a group -(CH2) n CONR4R5in which R4, R5and n have the same meaning as above, or R3is selected from a group -(CH2) n Si(R4)3in which R4and n have the same meaning as above, or R3is selected from a group -(CH2) n Si(OR4)3in which R4and n have the same meaning as above; ​

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