Boron-based negative electrode electrolyte and organic redox flow battery including the same

Abstract

The present invention discloses an organoboron-based negative electrode electrolyte and an organic flow battery comprising the same. The organoboron-based negative electrode electrolyte includes an active molecule selected from the group consisting of a β-diketonate boron compound, a β-diamide boron compound, and a β-ketoate amide boron compound. The organic flow battery disclosed herein has the advantages of low cost, high energy density, and excellent battery performance.

Description

Technical Field

[0001] The present disclosure relates to the field of electrochemical technology, and in particular to using a novel boron-based organic compound as a negative electrode electrolyte and an organic liquid flow battery comprising the same. Background Art

[0002] In recent years, renewable energy sources, such as wind and solar power, have been recognized as alternative, clean power generation methods to meet growing electricity demand. However, due to the intermittent nature of renewable energy, weather-dependent, and time-varying characteristics, the supply of electricity and human needs require large-scale energy storage devices to coordinate. Among existing energy storage technologies, redox flow batteries offer advantages such as independent power and capacity, good scalability, and long cycle life as low-cost and safe energy storage devices. They can store solar and wind energy during peak periods and release it during valleys, thus enabling the integration of these renewable energy sources into smart integrated grids. A typical flow battery consists of a fluid storage tank, a battery reactor, and a peristaltic pump. The positive and negative active materials are stored in the fluid storage tank and driven by a pump to the battery stack. Redox reactions occur in the battery reactor, and electrons flow through the current collector to the external circuit.

[0003] The organic molecules currently under investigation for organic flow battery systems are structurally designable, allowing the addition of functional groups to optimize parameters such as the potential, solubility, and kinetic diffusion coefficient of electroactive organic compounds. In recent years, a growing body of research has focused on developing non-aqueous organic electroactive molecules with wider electrochemical windows. These include quinones, phenazines, TEMPOs, and ferrocenes, all of which exhibit excellent electrochemical performance. However, the reported molecules suffer from high synthesis costs and low battery energy density. Organoboron organic molecules, however, offer significant potential as active materials for negative electrode electrolytes, offering advantages such as low cost, low redox potential, and high solubility in organic solvents. Furthermore, the use of organoboron electroactive materials as negative electrode electrolytes in organic flow batteries has not been reported. Summary of the Invention

[0004] To solve the existing problems, the present disclosure provides a highly efficient and low-cost renewable energy storage system.

[0005] The present disclosure provides a boron-based negative electrode electrolyte, comprising:

[0006] Active molecules; wherein the active molecules are β-diketonate boron compounds, β-diamine boron compounds or β-ketoate amine boron compounds.

[0007] In the embodiments of the present disclosure, the active molecule is as shown in Formula I:

[0008]

[0009] wherein R, R1 and R2 each independently represent a hydrogen atom, an alkyl group or a phenyl group.

[0010] In the embodiments of the present disclosure, the alkyl group is a straight-chain or branched alkyl group, including: -CH3, -CH(CH3)2, -C(CH3)3; the phenyl group includes -C6H5.

[0011] In the embodiment of the present disclosure, R is H, and R1 and R2 are both -C(CH3)3.

[0012] In the embodiments of the present disclosure, the active molecule is as shown in Formula II:

[0013]

[0014] Among them, R1-R 10 Each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group or one of the following functional groups: -CH3, -CH(CH3)2, -OCH2CH2OCH3, -O(CH2CH2O) n CH3(n=1, 2, 3, 4), -O(CH2CH2O) n CH2CH3(n=1, 2, 3, 4), -O(CH2CH2O) n OH (n=1, 2, 3, 4); Ar and Ar' represent aromatic groups.

[0015] In the embodiments of the present disclosure, the active molecule is as shown in Formula III:

[0016]

[0017] Wherein, R1-R5 each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group or one of the following functional groups: -CH3, -CH(CH3)2, -OCH2CH2OCH3, -O(CH2CH2O) n CH3(n=1, 2, 3, 4), -O(CH2CH2O) n CH2CH3(n=1, 2, 3, 4), -O(CH2CH2O) n OH (n=1, 2, 3, 4); Ar represents an aryl group.

[0018] In the embodiment of the present disclosure, the alkyl group includes a linear or branched saturated or unsaturated C1-C 10 Alkyl, the alkoxy group includes a linear or branched saturated or unsaturated C1-C 10Alkoxy; the aryl is a monocyclic or polycyclic aryl, including: phenyl, naphthyl, azulenyl, anthracenyl, fluorenyl, pyrenyl, phenanthrenyl, biphenyl, biphenyl and terphenyl, or, the aryl is one or more saturated or unsaturated alkyl chains or C1-C 10 Alkoxy or heteroatom aryl, wherein the heteroatom includes a halogen atom, -SH, -SR, -NO, -CN, -OH, and an amino group.

[0019] In the embodiment of the present disclosure, R2, R4, R7, and R9 are all H, and R1, R5, R6, R 10 Both are -CH3, and both R3 and R8 are -CH3 or -OCH2CH2OCH3.

[0020] The present disclosure also provides an organic liquid flow battery, comprising the boron-based negative electrode electrolyte as described in any one of the above items.

[0021] In an embodiment of the present disclosure, the organic liquid flow battery further includes a positive electrode electrolyte; the positive electrode electrolyte includes a positive electrode electrolyte active substance; wherein the positive electrode electrolyte active substance is 2,5-di-tert-butyl-1-methoxy-4-[2′-methoxyethoxy]benzene.

[0022] In an embodiment of the present disclosure, the organic flow battery further comprises:

[0023] Organic solvents, including: acetonitrile, ethylene glycol dimethyl ether, propylene carbonate, dichloromethane, dimethyl sulfoxide, N-methylpyrrolidone;

[0024] Supporting electrolytes, including: tetraethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide), tetraethylammonium perfluoroalkylsulfonyl imide, and lithium perchlorate;

[0025] The isolation membrane comprises: polypropylene, polyethylene, polystyrene and polytetrafluoroethylene; wherein the isolation membrane is a porous film with a pore diameter of 5-200 nanometers;

[0026] Carbon electrodes, including: carbon felt, graphite felt, carbon cloth, carbon paper; wherein the carbon electrodes are porous electrodes with a fiber diameter of 1-20 microns and a porosity of 50-98%;

[0027] The bipolar plate includes: a graphite plate, a conductive plastic plate, and a conductive rubber plate; wherein the conductivity of the bipolar plate is 50-800mS / cm.

[0028] The technical solution disclosed in this disclosure has the following positive effects:

[0029] The present disclosure provides a non-aqueous redox flow battery system with high open circuit voltage and high energy density, wherein the negative electrode electrolyte active molecule has (1) extremely low redox potential; (2) high electrochemical stability; and (3) high solubility in acetonitrile. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The disclosed features, advantages and technical and industrial significance of exemplary embodiments will be described below with reference to the accompanying drawings, in which like reference numerals designate like elements.

[0031] Figure 1 Schematic diagram of the optional chemical structure of the boron-based negative electrode electrolyte active material according to the embodiment of the present disclosure.

[0032] Figure 2 Schematic diagram summarizing the cyclic voltammetry of β-diketonate boron esters according to embodiments of the present disclosure.

[0033] Figure 3 Schematic diagram of cyclic voltammetry of compound 1 according to an embodiment of the present disclosure.

[0034] Figure 4 Schematic diagram of cyclic voltammetry of compound 2 according to an embodiment of the present disclosure.

[0035] Figure 5 Schematic diagram of cyclic voltammetry of compound 3 according to an embodiment of the present disclosure.

[0036] Figure 6 Schematic diagram of cyclic voltammetry of compound 4 according to an embodiment of the present disclosure.

[0037] Figure 7 Schematic diagram of cyclic voltammetry of compound 5 according to an embodiment of the present disclosure.

[0038] Figure 8 Schematic diagram of cyclic voltammetry of compound 5 in the embodiment of the present disclosure at different scan rates.

[0039] Figure 9 Schematic diagram of the Randles-Sevcik structure of compound 5 of the present disclosure.

[0040] Figure 10 Schematic diagram of cyclic voltammetry of compound 5 / DBMMB dissolved in TEABF4 / MeCN according to an embodiment of the present disclosure.

[0041] Figure 11 Schematic diagram of the effect of current density on charge and discharge capacity in an embodiment of the present disclosure.

[0042] Figure 12 Schematic diagram showing the effect of current density on coulombic efficiency, voltage efficiency, and energy efficiency according to an embodiment of the present disclosure.

[0043] Figure 13 is a schematic diagram of the battery performance of an embodiment of the present disclosure.

[0044] Figure 14 Schematic diagram of cyclic voltammetry of compound 6 according to an embodiment of the present disclosure.

[0045] Figure 15 Schematic diagram of cyclic voltammetry of compound 7 according to the embodiment of the present disclosure.

[0046] Figure 16 Schematic diagram of cyclic voltammetry of compound 8 according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0047] The present disclosure will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present disclosure in a schematic manner.

[0048] A redox flow battery is a rechargeable, rechargeable secondary battery in which electrochemically active substances undergo reversible charge and discharge through a reversible redox reaction. A redox flow battery typically consists of several key components: an anode liquid tank, a cathode liquid tank, a battery pack, a separator, and a peristaltic pump. During charging, the active molecules in the anode electrolyte accept electrons for reduction, while the active molecules in the cathode electrolyte undergo oxidation. During discharge, the reduced active molecules in the cathode electrolyte lose electrons for oxidation, returning to their original active molecules in the cathode electrolyte. The oxidized active molecules in the cathode electrolyte undergo reduction, returning to their original active molecules in the cathode electrolyte. The separator, located in the center of the reaction cell, allows charged ions to pass through while preventing the two electrolytes from mixing.

[0049] In order to overcome the shortcomings of existing organic active molecules, such as high material cost and low battery energy density, the present disclosure proposes a boron-based redox anode electrolyte active material for redox flow batteries. Figure 1 and Figure 2 Schematic diagram of the chemical structure of a representative negative electrode electrolyte active material according to the embodiment of the present disclosure. The β-diketonate boron or its derivative used as the negative electrode electrolyte active material can be selected, for example, from the β-diketonate boron of general formula (I):

[0050]

[0051] Wherein, R, R1 and R2 may be the same or different and represent a hydrogen atom or the following straight chain (or branched) alkyl groups: -CH3, -CH(CH3)2 (e.g. i Pr), -C(CH3)3(such as t Bu), or phenyl (such as -C6H5). Preferably, R is H, R1 and R2 are both -C(CH3)3 (such ast Bu).

[0052] In the embodiment of the present disclosure, β-diamino boron or its derivatives can also be selected from β-diketonate boron having the general formula (II):

[0053]

[0054] Among them, R1-R 10 may be the same or different and represent a hydrogen atom, a halogen atom, or one of the following functional groups: -CH3, -CH(CH3)2 (e.g. i Pr), -OCH2CH2OCH3, -O(CH2CH2O) n CH3 (n can be 1, 2, 3, 4), -O (CH2CH2O) n CH2CH3 (n can be 1, 2, 3, 4), -O(CH2CH2O) n OH (n can be 1, 2, 3, 4), or selected from linear or branched, saturated or unsaturated C1-C 10 Alkyl or alkoxy. In the embodiments of the present disclosure, the aryl groups may be the same or different and represent monocyclic or polycyclic aryl groups. The aryl groups described herein include, but are not limited to, phenyl, naphthyl, azulenyl, anthracenyl, fluorenyl, pyrenyl, phenanthrenyl, biphenyl and terphenyl. Aryl also represents one or more aryl groups containing saturated or unsaturated alkyl chains, or saturated or unsaturated C1-C 10 Alkoxy, or other functional groups with heteroatoms, such as halogen atoms, -SH, -SR, -NO, -CN, -OH, amino or other heteroaryl groups. Preferably, R2, R4, R7, R9 are all H, R1, R3, R5, R6, R8, R 10 are all -CH3; or preferably R2, R4, R7, R9 are all H, R1, R5, R6, R 10 Both are -CH3, and R3 and R8 are -OCH2CH2OCH3.

[0055] The organic solvent used in these non-aqueous redox flow battery systems can be acetonitrile (MeCN), ethylene glycol dimethyl ether (DME), propylene carbonate, dichloromethane, dimethyl sulfoxide, N-methylpyrrolidone; preferably, the organic solvent is acetonitrile (MeCN).

[0056] The supporting electrolyte may be tetraethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, lithium bis(trifluoromethylsulfonylimide), tetraethylammonium tetrafluoromethylsulfonylimide, or lithium perchlorate; preferably, the supporting electrolyte is tetraethylammonium tetrafluoroborate.

[0057] The polymer porous membrane is selected from the following: polypropylene, polyethylene, polystyrene and polytetrafluoroethylene, wherein the pore size of the separator is between 5 and 200 nm. Preferably, the polymer porous membrane is polypropylene, and its pore size is about 64 nm.

[0058] The porous carbon electrode can be carbon felt, graphite felt, carbon cloth or carbon paper. The fiber diameter is about 1-20 μm and the porosity is 50-98%. Preferably, the porous carbon electrode is graphite felt, wherein the fiber has a wire diameter of about 10 μm, a density of about 1.39 g / cm 3 density and 93% porosity.

[0059] Compact carbon bipolar plates can be graphite, conductive plastic, or conductive rubber, with a conductivity of approximately 50-800 mS / cm. The plates may or may not have flow channels. Preferably, the dense carbon bipolar plates are graphite plates with engraved flow channels, with a conductivity of 320 mS / cm.

[0060] The operating principle of this non-aqueous organic flow battery is as follows: during charging, the redox-active molecules at the negative electrode gain electrons to generate reduced negatively charged free radical products, while the positive electrode electrolyte loses electrons to generate oxidized products. During discharge, the redox-active molecules at the negative electrode lose electrons, while the positive electrode electrolyte receives electrons and returns to its original state.

[0061] Synthesis of compound 1

[0062] 5mL (48.7mmol) of acetylacetone was dissolved in 20mL of toluene. 6mL (48.7mmol) of boron trifluoride etherate was added to the reaction mixture. The reaction flask was connected to a KOH scrubber and continuously supplied with N2. After heating the reaction mixture at 90°C for 18 hours, all solvents and unreacted starting materials were removed by vacuum distillation, and a light yellow solid was obtained as the desired product, compound 1. Yield: 6.82 grams, 95%.

[0063]

[0064] 1 H NMR (400MHz, CDCl3): δ6.01(s,1H),2.27(s,6H). 13 C NMR (100MHz, CDCl3): δ192.4, 101.9, 23.9. 11 B NMR (128 MHz, CDCl 3 ): δ 2.14.

[0065] Synthesis of compound 2

[0066] 1 mL (8.59 mmol) of 3-methyl-2,4-pentanedione was dissolved in 10 mL of toluene. 1.06 mL (8.59 mmol) of boron trifluoride etherate was added to the reaction mixture. The reaction flask was connected to a KOH scrubber and N2 was continuously supplied. After heating the reaction mixture at 50 ° C for 14 hours, all solvents and unreacted starting materials were removed by vacuum distillation, and a brown solid was obtained as the desired product, compound 2. Yield: 1.32 g, 95%.

[0067]

[0068] 1 H NMR (400MHz, CDCl3): δ2.31 (s, 6H), 1.93 (s, 3H). 13 C NMR (100MHz, CDCl3): δ190.4,107.2,22.8,11.9. 11 B NMR (128 MHz, CDCl 3 ): δ 1.74.

[0069] Synthesis of compound 3

[0070] 1 mL (9.34 mmol) of 2,6-dimethyl-3,5-heptanedione was dissolved in 10 mL of toluene. 1.15 mL (9.34 mmol) of boron trifluoride etherate was added to the reaction mixture. The reaction flask was connected to a KOH scrubber and N2 was continuously supplied. After heating the reaction mixture at 60 ° C for 16 hours, all solvents and unreacted starting materials were removed by vacuum distillation, and a light yellow oil was obtained as the desired product, compound 3. Yield: 1.2 g, 63%.

[0071]

[0072] 1 H NMR (400MHz, CDCl3): δ5.96 (s, 1H), 2.72 (septet, J = 6.8Hz, 2H), 1.26 (d, J = 6.8Hz, 12H). 13 C NMR (100MHz, CDCl3): δ200.1,96.4,36.4,19.2. 11 B NMR (128 MHz, CDCl 3 ): δ 2.44.

[0073] Synthesis of compound 4

[0074] 130 mg (0.764 mmol) or 2,2,6-trimethylheptane-3,5-dione was dissolved in 5 mL of toluene. 1.15 mL (0.764 mmol) of boron trifluoride etherate was added to the reaction mixture. The reaction flask was connected to a KOH scrubber and continuously supplied with N2. After heating the reaction mixture at 50 ° C for 14 hours, all solvents and unreacted starting materials were removed by vacuum distillation, and a light yellow oil was obtained as the desired product compound 4. Yield: 128 mg, 77%.

[0075]

[0076] 1 H NMR (400MHz, CDCl3): δ6.04 (s, 1H), 2.72 (septet, J = 6.8Hz, 2H), 1.27 (s, 9H), 1.25 (d, J = 6.8Hz, 6H). 13 C NMR (100MHz, CDCl3): δ202.1,200.3,94.8,39.4,36.6,27.2,19.2. 11 B NMR (128 MHz, CDCl 3 ): δ 2.48.

[0077] Synthesis of compound 5:

[0078] Boron trifluoride etherate (0.592 ml, 4.79 mmol, 1 equivalent) was added to a solution of 2,2,6,6-tetramethyl-3,5-heptanedione (1 ml, 4.79 mmol, 1 equivalent) dissolved in toluene (10 ml). The reaction flask was connected to a KOH scrubber and N2 was continuously supplied. The mixture was heated at 50 ° C for 15 hours. After removing the solvent and unreacted starting materials by vacuum distillation, the resulting white solid was tBuBF2 (890 mg, 80%) compound. 1 H NMR (400MHz, CDCl3): δ6.14 (s, 1H), 1.28 (s, 18H). 13 CNMR (100MHz, CDCl3): δ202.4,92.9,39.6,27.3. 11 B NMR (128MHz, CDCl3): δ2.66.

[0079] Compound 6: 4,6-di-tert-butyl-2,2-difluoro-1,3-diphenyl-1,2-dihydro-1,3λ 4 ,2λ 4 -Synthesis of diazaborane

[0080]

[0081] 6mL (65.7mmol) of aniline and 10.2mL (69.7mmol) of triethylamine were dissolved in 150mL of tetrahydrofuran. 8.5mL of trimethylacetyl chloride (69.0mmol) was added dropwise to the reaction mixture at 0°C and then stirred at room temperature for 3 hours. The white precipitate was filtered to obtain a filtrate. After vacuum drying and washing with hexane, a white solid, i.e., the amide product N-phenylpivalamide, was obtained. Yield: 11.36 grams (98%). 5g (28.2mmol) of N-phenylpivalamide was suspended in 10.3mL (141.2mmol) of thionyl chloride. The reaction flask was connected to a KOH scrubber, N2 was continuously supplied, and heated at 70°C for 2 hours. All solvents were then removed under vacuum, and the desired product was extracted with hexane to obtain a yellow oil in the form of N-phenylpivalamide chloride. Yield: 5.432 grams (99%). 2 g (10.22 mmol) of N-phenylpivalyl chloride was dissolved in 8 mL of diethyl ether. 15.7 mL (20.44 mmol) of 1.3 M methyl lithium was slowly added to diethyl ether at -78 °C, and the mixture was stirred at room temperature under N2 for 5 hours, then carefully quenched with ice and water and extracted with diethyl ether. After removing the solvent in vacuo, the resulting oil was purified by vacuum distillation to obtain a colorless oil as 3,3-dimethyl-N-phenylbutane-2-imine. Yield: 1.4 g (78%). 0.5 g (2.85 mmol) of 3,3-dimethyl-N-phenylbutane-2-imine and 0.436 mL (2.91 mmol) of N,N,N',N'-tetramethylethylenediamine were dissolved in 6 mL of hexane. 1.82 mL (2.91 mmol) of 1.6 M n-butyl lithium in hexane was then slowly added at -78 °C. The mixture was stirred at room temperature overnight, and then 0.558 g (2.85 mmol) of N-phenylpivaloyl chloride was added dropwise in 5 mL of hexane. After the reaction flask was refluxed for 3 hours, the desired product was extracted with ether and water. The organic layer was obtained and then dried by adding anhydrous magnesium sulfate and vacuum dried, and then used as a reactant in the next step without further purification. 0.36 g (1.08 mmol) of the reactant (2,2,6,6-tetramethyl-N 3 , N 5 -diphenylheptane-3,5-diimine) was dissolved in 5 mL of toluene. 0.133 mL (1.08 mmol) of boron trifluoride etherate was added to the reaction mixture. The reaction flask was connected to a KOH scrubber and continuously supplied with N2. After heating the reaction mixture at 50 ° C for 12 hours, all solvents and unreacted starting materials were removed by vacuum distillation, and the white solid was further purified by column chromatography to obtain the desired product compound 6 as a white solid. Yield: 80 mg, 19%.

[0082]

[0083] 1 H NMR (400MHz, CDCl3): δ7.31(m,6H),7.18(m,4H),5.98(s,1H),1.14(s,18H). 11 BNMR (128MHz,CDCl3):δ2.02(t). 19 F NMR (376MHz, CDCl3): δ-138.1.

[0084] Compound 7: 4,6-di-tert-butyl-2,2-difluoro-1,3-dimethyl-1,2-dihydro-1,3λ 4 ,2λ 4 Synthesis of diazaboronic acid

[0085]

[0086] 9.23 mL (65.7 mmol) of 2.4,6-trimethylaniline and 9.71 mL (69.7 mmol) of triethylamine were dissolved in 150 mL of tetrahydrofuran. 8.5 mL of trimethylacetyl chloride (69.0 mmol) was added dropwise to the reaction mixture at 0°C and then refluxed for 2 hours. The white precipitate was filtered to obtain a filtrate. After vacuum drying and washing with hexane, a white solid amide product, N-triacylpivalamide, was obtained. Yield: 14 g (97%). 10 g (45.6 mmol) of N-triacylpivalamide was suspended in 16.6 mL (228 mmol) of thionyl chloride. The reaction flask was connected to a KOH scrubber, N2 was continuously supplied, and heated at 70°C for 3 hours. All solvents were then removed under vacuum, and the desired product was extracted with hexane to obtain a light yellow oil, N-triacylpivalamide chloride. Yield: 10.77 g (99%). 3.5 g (14.7 mmol) of N-mesityl neopentylamine chloride was dissolved in 14 mL of diethyl ether. 34 mL (44.2 mmol) of 1.3 M methyl lithium in diethyl ether was slowly added at -78°C, and the mixture was stirred at room temperature under N2 for 2 hours, then carefully quenched with ice and water and extracted with diethyl ether. After removing the solvent in vacuo, the resulting oil was purified by vacuum distillation to obtain a colorless oil, N-mesityl-3,3-dimethylbutane-2-imine. Yield: 2.56 g (80%). 0.5 g (2.3 mmol) of N-mesityl-3,3-dimethylbutane-2-imine and 0.379 mL (2.53 mmol) of N,N,N',N'-tetramethylethylenediamine were dissolved in 3 mL of hexane. 1.87 mL (2.99 mmol) of 1.6 M n-butyl lithium in hexane was then slowly added at -78°C. The mixture was stirred at room temperature overnight, and then 0.547 g (2.3 mmol) of N-triacyl neoglutamine chloride was added dropwise in 4 mL of hexane. After the reaction flask was refluxed for 2 hours, the desired product was extracted with ether and water. The organic layer was obtained, and then anhydrous magnesium sulfate was added for drying and vacuum drying. The mixture was recrystallized in refluxing hexane to obtain N- 3 , N 5 -dimethyl-2,2,6,6-tetramethylheptane-3,5-diimine. Yield: 650 mg (68%). 100 mg N 3 , N 5-Dimethyl-2,2,6,6-tetramethylheptane-3,5-diimine (0.24 mmol) was dissolved in 7 mL of toluene. 0.1 mL of triethylamine (0.72 mmol) was slowly added at room temperature and stirred at the same temperature for 30 minutes. 0.177 mL (1.43 mmol) of boron trifluoride ether was added to the reaction mixture. The reaction flask was connected to a KOH scrubber and N2 was continuously supplied. After heating the reaction mixture at 100 ° C for 15 hours, 1 mL of water was added to stop the reaction, and the product was extracted with toluene, washed with water several times, and purified by column chromatography to obtain compound 7 in the form of a light yellow solid. Yield: 102 mg, 91%.

[0087]

[0088] 1 H NMR (400MHz, CDCl3): δ6.78(s,4H),5.89(s,1H),2.22(s,6H),2.21(s,12H),1.13(s,18H). 11 B NMR (128MHz, CDCl3): δ2.19(t). 19 F NMR (376MHz, CDCl3): δ-139.9.

[0089] Compound 8: 4,6-di-tert-butyl-1,3-bis(2,6-diisopropylphenyl)-2,2-difluoro-1,2-dihydro-1,3λ 4 ,2λ 4 Synthesis of diazaboronic acid

[0090]

[0091] 12.4mL (65.7mmol) 2.6-diisopropylaniline and 9.71mL (69.7mmol) triethylamine were dissolved in 150mL tetrahydrofuran. 8.5mL trimethylacetyl chloride (69.0mmol) was added dropwise to the reaction mixture at 0°C and then refluxed for 2 hours. The white precipitate was filtered to obtain a filtrate, and the precipitate was then extracted twice with tetrahydrofuran. After vacuum drying and washing with hexane, a white solid amide product N-(2,6-diisopropylphenyl) pivalamide was obtained. Yield: 12.2 grams (70%). 10g (38.3mmol) of N-(2,6-diisopropylphenyl) pivalamide was suspended in 13.9mL (191.3mmol) thionyl chloride. The reaction flask was connected to a KOH scrubber, N2 was continuously supplied, and heated at 70°C for 3 hours. All solvents were then removed under vacuum, and the desired product was extracted with hexane to obtain a yellow oil in the form of N-(2,6-diisopropylphenyl)pivalylamine chloride. Yield: 10.65 g (99%). 3.0 g (10.72 mmol) of N-(2,6-diisopropylphenyl)pivalylamine chloride was dissolved in 10 mL of ether. 24.7 mL (32.2 mmol) of 1.3 M methyl lithium in ether was slowly added at -78 ° C., and the mixture was stirred at room temperature under N2 for 5 hours, then carefully quenched with ice and water, and extracted with ether. After removing the solvent under vacuum, the resulting oil was purified by vacuum distillation to obtain a colorless oil, N-(2,6-diisopropylphenyl)-3,3-dimethylbutane-2-imine. Yield: 2.1 g (76%). 0.5 g (1.93 mmol) of N-(2,6-diisopropylphenyl)-3,3-dimethylbutane-2-imine and 0.318 mL (2.12 mmol) of N, N, N', N'-tetramethylethylenediamine were dissolved in 3 mL of hexane. Then 1.57 mL (2.51 mmol) of hexane containing 1.6 M n-butyl lithium was slowly added at -78 ° C. The mixture was stirred at room temperature overnight, and then 0.539 g (1.93 mmol) of N-(2,6-diisopropylphenyl) neopentylamine chloride was added dropwise in 3 mL of hexane. After the reaction flask was refluxed for 2 hours, the desired product was extracted with ether and water. The organic layer was obtained, and then anhydrous magnesium sulfate was added for drying and vacuum drying. The mixture was recrystallized in refluxing hexane and stored at -30 ° C overnight, and then washed with cold pentane to obtain N 3 , N 5 Bis(2,6-diisopropylphenyl)-2,2,6,6-tetramethylheptane-3,5-diimine was obtained as a white solid. Yield: 698 mg (72%). 80 mg N 3 , N 5Di(2,6-diisopropylphenyl)-2,2,6,6-tetramethylheptane-3,5-diimine (0.16 mmol) was dissolved in 5 mL of toluene. 0.111 mL of triethylamine (0.796 mmol) was slowly added at room temperature and stirred at the same temperature for 30 minutes. 0.196 mL (1.59 mmol) of boron trifluoride ether was added to the reaction mixture at 0 ° C. The reaction flask was connected to a KOH scrubber and N2 was continuously supplied. After heating the reaction mixture at 100 ° C for 24 hours, 1 mL of water was added to stop the reaction, and the product was extracted with toluene, washed several times with water, and purified by column chromatography to obtain compound 8 in the form of a light yellow solid. Yield: 10.5 mg, 12%.

[0092]

[0093] 1 H NMR (400MHz, CDCl3): δ7.21(t,2H),7.07(d,4H),5.69(s,1H),3.12(sep,4H),1.28(d,12H),1.22(d,12H),1.13(s,18H). 11 B NMR(128MHz, CDCl3): δ2.50(t). 19 F NMR (376MHz, CDCl3): δ-127.5.

[0094] Cyclic voltammetry test

[0095] Weigh 0.01 mmol of β-diketonate boron, β-diamine boron, β-ketoate amine boron, or their derivatives and dissolve them in 5 ml of 0.5 mol / L tetraethylammonium tetrafluoroborate (TEABF4) in anhydrous acetonitrile. Stir the solution to a homogeneous concentration of 2 mmol / L under a nitrogen atmosphere. Cyclic voltammetry was performed using a three-electrode system with silver nitrate / silver as the reference electrode, a platinum rod electrode as the counter electrode, and a glassy carbon electrode as the working electrode. The scan rate was 100 mV / s.

[0096] See Figures 3 to 7 , Figures 3 to 7Schematic diagram of cyclic voltammetry of compounds 1-5 of the examples of the present disclosure. The examples of the present disclosure first studied the redox reversibility of the smallest diketonate boron analog 1. In MeCN / TBABF4, the reduction of 1 showed a completely irreversible redox couple. Next, the effect of the R'-group on the redox reversibility was studied by adding another methyl group to 1. However, similar to 1, irreversible redox was observed for 2, with no reoxidation current, indicating that the generated radical anion is unstable and substitution on the R'-group may not improve the redox reversibility. These results prompted us to focus on the relationship between the volume of the R-group and redox reversibility. It is hypothesized that the use of bulky R-groups may increase reversibility by enhancing the steric hindrance of the reduced radical anion. As expected, the isopropyl derivative 3 and the asymmetric compound 4 showed a significant improvement in redox reversibility. Unfortunately, despite being liquid and miscible in organic solvents such as MeCN, they are still quasi-reversible. The symmetric di-tert-butyl species 5 was quasi-reversible at -1.83V (vs Ag / Ag + ) showed reversible redox signal.

[0097] Weigh 0.01 mmol of β-diketonate boron, β-diamine boron, β-ketoate amine boron, or their derivatives and dissolve them in 5 ml of 0.5 mol / L tetraethylammonium tetrafluoroborate in anhydrous acetonitrile. Stir the solution to a homogeneous concentration of 2 mmol / L under a nitrogen atmosphere. Cyclic voltammetry was performed using a three-electrode system with silver nitrate / silver as the reference electrode, a platinum column electrode as the counter electrode, and a glassy carbon electrode as the working electrode. Scan rates were 20 mV / s, 50 mV / s, 100 mV / s, 200, and 500 mV / s.

[0098] See Figures 8 to 10 , Figure 8 is a schematic diagram of cyclic voltammetry of compound 5 of the present disclosure at different scan rates, Figure 9 is a Randles-Sevcik structure diagram of the reduction wave and oxidation wave of compound 5 in the embodiment of the present disclosure, Figure 10 The cyclic voltammogram of a 2 mM mixture of 5 and DBMMB in 0.5 MTEABF4 / MeCN at a scan rate of 100 mV / s shows that the redox reaction of 5 is diffusion controlled.

[0099] Redox flow battery rate performance testing

[0100] In a glove box, 1.6 mmol of β-diketonate boron, β-diamine boron, β-ketoate amine boron, or their derivatives were weighed as the negative electrolyte active molecule and dissolved in 16 mL of a 0.5 mol / L tetraethylammonium tetrafluoroborate solution in anhydrous acetonitrile. The molar concentration was 0.1 mol / L, and the solution was shaken to form a homogeneous solution. Then, 472 mg of 2,5-di-tert-butyl-1-methoxy-4-[2′-methoxyethoxy]benzene (DBMMB) was weighed as the positive electrolyte and added to the previously prepared homogeneous solution. The molar concentration was 0.1 mol / L. The battery was then assembled into a sandwich configuration in the following order: first phenolic plate, first aluminum end plate, first gold-plated copper current collector, first graphite plate, first electrode, first polytetrafluoroethylene gasket, and first polymer microporous membrane. This was followed by a second polytetrafluoroethylene gasket, second electrode, second graphite plate, second gold-plated copper current collector, second aluminum end plate, and second phenolic resin. The prepared 16 mL mixed electrolyte solution was divided into two equal portions (8 mL each) and injected into two closed electrolyte storage tanks. The inlet and outlet of the storage tanks with flow pumps were then connected to the inlet and outlet of the positive and negative flow fields of the battery, and the electrolyte was circulated at a flow rate of 40 mL / min using a peristaltic pump.

[0101] See Figure 11 and Figure 12 , Figure 11 The charge and discharge performance of the assembled battery using β-diketonate boron (5) as the negative electrode electrolyte active molecule and DBMMB as the positive electrode electrolyte active molecule is shown. Figure 12 The effect of current density on coulombic efficiency (CE), voltage efficiency (VE) and energy efficiency (EE) of the disclosed embodiments is shown. 2 、30mA / cm 2 , 40mA / cm 2 and 50mA / cm 2 The rate performance is tested at different current densities to understand the 2 Up to 50mA / cm 2 For every 10mA / cm 2 The capacity changes. Figure 11 and 12 As shown, the coulombic efficiency is from 20mA / cm 2 60% of the time when the 2 This indicates that under different currents, the active substances shuttle less between the two sides of the membrane and the electrochemical reversibility of the active molecules is good. In addition, due to the increase in overpotential between the charge / discharge process, the voltage efficiency drops from 92% to 80%. From the study of the rate performance of the battery, the embodiment of this disclosure selects 40mA / cm 2The current density of is taken as the optimal current density for long-term charge and discharge cycles.

[0102] Long-cycle testing of redox flow batteries

[0103] In a glove box, 1.6 mmol of β-diketonate boron (5) was weighed and dissolved in 16 mL of a 0.5 mol / L tetraethylammonium tetrafluoroborate anhydrous acetonitrile solution. The molar concentration was 0.1 mol / L, and the mixture was shaken to form a homogeneous solution. Then 472 mg of 2,5-di-tert-butyl-1-methoxy-4-[2′-methoxyethoxy]benzene (DBMMB) was weighed as the positive electrolyte and added to the previously prepared homogeneous solution. In this 16 mL mixed electrolyte solution, the molar concentration of the positive electrolyte and the negative electrolyte was 0.1 mol / L. The battery was then assembled in the following order to form a sandwich shape: a first phenolic plate, a first aluminum end plate, a first gold-plated copper current collector, a first graphite plate, a first electrode, a first polytetrafluoroethylene gasket, and a first polymer microporous membrane, and a second polytetrafluoroethylene gasket, a second electrode, a second graphite plate, a second gold-plated copper current collector, a second aluminum end plate, and a second phenolic resin were stacked. The prepared 16 mL mixed electrolyte solution was divided into two equal portions (8 mL each) and injected into two closed electrolyte storage tanks. The inlet and outlet of the storage tanks with flow pumps were then connected to the inlet and outlet of the positive and negative flow fields of the battery, and the circulation was driven by a peristaltic pump at a flow rate of 40 mL / min.

[0104] See Figure 13 , Figure 13 The stability, efficiency, and capacity of 0.1 M 5 / DBMMB dissolved in 0.5 M TEABF4 / MeCN are shown. Figure 13 The cycling performance of a flow battery using β-diketonate boron (5) as the negative electrode electrolyte active molecule and DBMMB as the positive electrode electrolyte active molecule, such as charge / discharge capacity and efficiency, is shown. The flow battery achieved stable efficiency (CE 80%, EE 68%, VE 85% in the first 80 cycles). However, a gradual capacity decay was observed after 80 cycles, with a capacity retention rate of 50%, corresponding to a capacity retention rate of 99.4% per cycle. Overall, the disclosed embodiments confirm that organic boron-based compounds may be negative electrode electrolyte active molecules that achieve high solubility, have high electrochemical stability, low redox potential and high energy density, and provide important insights for the future development of boron-based redox-active electrolytes in organic flow battery technology.

[0105] See Figure 14 , Figure 14 Schematic diagram of cyclic voltammetry of compound 6 according to an embodiment of the present disclosure. Figure 14Compound 6: 4,6-di-tert-butyl-2,2-difluoro-1,3-diphenyl-1,2-dihydro-1,3λ 4 ,2λ 4 -Diazaborane shows about -2.2V (vs Ag / Ag + )'s redox potential.

[0106] See Figure 15 , Figure 15 Schematic diagram of cyclic voltammetry of compound 7 according to the embodiment of the present disclosure. Figure 15 Compound 7: 4,6-di-tert-butyl-2,2-difluoro-1,3-dimethyl-1,2-dihydro-1,3λ 4 ,2λ 4 -diazaborates show a potential of approximately -2.5 V (vs Ag / Ag + ) has an extremely low redox potential.

[0107] See Figure 16 , Figure 16 Schematic diagram of cyclic voltammetry of compound 8 according to an embodiment of the present disclosure. Figure 16 Compound 8: 4,6-di-tert-butyl-1,3-bis(2,6-diisopropylphenyl)-2,2-difluoro-1,2-dihydro-1,3λ 4 ,2λ 4 -diazaboronic acid showed about -2.45V (vs Ag / Ag + ) has an extremely low redox potential.

[0108] The boron-based negative electrode electrolyte active molecules proposed in this disclosure are used in organic non-aqueous flow batteries. These batteries utilize β-diketonate boron molecules with high solubility, good electrochemical reversibility, and chemical stability, β-diamine boron molecules with extremely low redox potential, or β-ketoate urethane boron molecules as the negative electrode electrolyte active material, and DBMMB or other organic positive electrolytes as the positive electrode electrolyte active molecule. This results in an organic non-aqueous flow battery with low cost, high energy density, and excellent battery performance.

[0109] It should be understood that the specific embodiments described above are only used to explain the present disclosure and are not used to limit the present disclosure. Obvious changes or modifications derived from the spirit of the present disclosure are still within the scope of protection of the present disclosure.

[0110] Throughout this specification, references to "exemplary embodiment," "preferred embodiment," "one embodiment," etc., mean that a specific feature, structure, or characteristic described with respect to that embodiment is included in at least one embodiment of the present disclosure. The appearance of these terms in different places in this specification does not necessarily refer to the same embodiment. Furthermore, when specific features, structures, or characteristics are described with respect to any embodiment / embodiments, it should be understood that those skilled in the art can also implement such features, structures, or characteristics in other embodiments of the present disclosure.

[0111] The embodiments of the present disclosure are described in detail above. However, aspects of the present disclosure are not limited to the above embodiments. Various modifications and substitutions can be applied to the above embodiments without departing from the scope of the present disclosure.

Claims

1. A boron-based negative electrode electrolyte comprising: redox-active molecules; The redox active molecule is shown in Formula I: wherein R, R1 and R2 each independently represent a hydrogen atom, an alkyl group or a phenyl group; or The redox active molecule is shown in Formula II: Among them, R1-R 10 Each independently represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group; Ar and Ar' represent an aryl group; or The redox active molecule is shown in Formula III: Wherein, R1-R5 each independently represents a hydrogen atom, a halogen atom, an alkyl group, or an alkoxy group; Ar represents an aryl group.

2. The boron-based negative electrode electrolyte according to claim 1, characterized in that In Formula I, the alkyl group is a straight chain or branched chain alkyl group, including: -CH3, -CH(CH3)2, -C(CH3)3; the phenyl group includes -C6H5.

3. The boron-based negative electrode electrolyte according to claim 1, characterized in that In Formula I, R is H, and R1 and R2 are both -C(CH3)3.

4. The boron-based negative electrode electrolyte according to claim 1, characterized in that In formula II and formula III, the alkyl group includes a linear or branched saturated or unsaturated C1-C 10 Alkyl, the alkoxy group includes a linear or branched saturated or unsaturated C1-C 10 Alkoxy; the aryl is a monocyclic or polycyclic aryl, including: phenyl, naphthyl, azulenyl, anthracenyl, fluorenyl, pyrenyl, phenanthrenyl, biphenyl, biphenyl and terphenyl, or, the aryl is one or more saturated or unsaturated alkyl chains or C1-C 10 Alkoxy or heteroatom aryl, wherein the heteroatom includes a halogen atom, -SH, -SR, -NO, -CN, -OH, and an amino group.

5. The boron-based negative electrode electrolyte according to claim 1, characterized in that: In Formula II and Formula III, R2, R4, R7, and R9 are all H, and R1, R5, R6, and R 10 Both are -CH3, and both R3 and R8 are -CH3 or -OCH2CH2OCH3.

6. The boron-based negative electrode electrolyte according to claim 1, characterized in that In Formula II, R1-R 10 Each independently represents one of the following functional groups: -CH3, -CH(CH3)2, -OCH2CH2OCH3, -O(CH2CH2O) n CH3(n=1, 2, 3, 4), -O(CH2CH2O) n CH2CH3(n=1, 2, 3, 4), -O(CH2CH2O) n OH (n = 1, 2, 3, 4).

7. The boron-based negative electrode electrolyte according to claim 1, characterized in that In formula III, R1-R5 each independently represent one of the following functional groups: -CH3, -CH(CH3)2, -OCH2CH2OCH3, -O(CH2CH2O) n CH3(n=1, 2, 3, 4), -O(CH2CH2O) n CH2CH3(n=1, 2, 3, 4), -O(CH2CH2O) n OH (n = 1, 2, 3, 4).

8. An organic liquid flow battery comprising the boron-based negative electrode electrolyte according to any one of claims 1 to 7.

9. The organic flow battery according to claim 8, characterized in that The organic liquid flow battery further includes a positive electrode electrolyte; the positive electrode electrolyte includes a positive electrode electrolyte active material; wherein the positive electrode electrolyte active material is 2,5-di-tert-butyl-1-methoxy-4-[2′-methoxyethoxy]benzene.

10. The organic flow battery according to claim 8, wherein The organic flow battery further comprises: Organic solvents, including: acetonitrile, ethylene glycol dimethyl ether, propylene carbonate, dichloromethane, dimethyl sulfoxide, N-methylpyrrolidone; Supporting electrolytes, including: tetraethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, tetrabutylammonium hexafluorophosphate, tetrabutylammonium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl imide), tetraethylammonium perfluoroalkylsulfonyl imide, and lithium perchlorate; The isolation membrane comprises: polypropylene, polyethylene, polystyrene and polytetrafluoroethylene; wherein the isolation membrane is a porous film with a pore diameter of 5-200 nanometers; Carbon electrodes, including: carbon felt, graphite felt, carbon cloth, carbon paper; wherein the carbon electrodes are porous electrodes with a fiber diameter of 1-20 microns and a porosity of 50-98%; The bipolar plate includes: a graphite plate, a conductive plastic plate, and a conductive rubber plate; wherein the conductivity of the bipolar plate is 50-800mS / cm.

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