High-stability neutral aqueous flow battery based on quaternary ammonium salinized biphenol derivative

Abstract

The invention belongs to the technical field of new energy materials, and particularly relates to a high-stability neutral aqueous flow battery based on a quaternary ammonium salinized biphenol derivative. The preparation method comprises the following steps: bridging biphenol and dimethylamine through a condensation reaction to obtain an intermediate, and further introducing a water-soluble quaternary ammonium salt group to obtain the quaternary ammonium salinized biphenol derivative. The solubility of the material in pure water is as high as 6.28 M, and the material has the advantages of high potential, good redox reversibility and fast reaction kinetics. The neutral aqueous flow battery with high stability and energy efficiency is obtained after assembling by taking the neutral aqueous flow battery as a catholyte, methyl viologen as an anolyte and a sodium chloride aqueous solution as an electrolyte. The discharge platform of the redox flow battery is 1.06 V, the discharge capacity is 12.86 mAh, after cyclic charge and discharge, the capacity fading rate of each circle is 0.02%, the coulombic efficiency is 98.49%, the energy efficiency reaches 90.21%, and the application prospect is wide.

Description

Technical Field

[0001] The invention belongs to the technical field of new energy materials, and specifically relates to a high-stability neutral aqueous liquid flow battery based on quaternary ammonium salt biphenol derivatives. Background Art

[0002] Aqueous organic flow batteries (AOFBs) use water-soluble organic molecules as active electrolytes for energy storage. The structure of organic molecules is highly tunable, and the properties of active materials can be customized through different chemical synthesis methods. Based on these advantages, aqueous organic flow batteries are considered to be one of the most promising low-cost, safe, and scalable electrochemical energy storage systems. In particular, neutral aqueous organic flow batteries can avoid the damage to equipment caused by conventional acidic and alkaline flow batteries and are suitable for a variety of long-term energy storage devices.

[0003] Active electrolytes are the most critical materials for energy storage, conversion and release in organic flow battery systems. The physical and chemical properties of water-soluble redox electrolyte molecules can directly determine the electrochemical properties of flow batteries, such as theoretical capacity and energy efficiency. First, the solubility of organic matter and the number of electrons involved in the redox reaction directly determine the capacity of organic flow batteries. Therefore, it is promising to develop organic matter with high solubility and multi-electron storage by adding organic chains with solubilizing functional groups to increase the solubility of organic matter. Secondly, the redox potential of organic matter can directly determine the voltage of aqueous organic flow batteries. Therefore, the design of electrolyte molecular structure has always been an important means to improve battery performance. At the same time, compared with traditional RFBs, due to the limitation of the narrow electrochemical window of aqueous electrolytes, the voltage of aqueous batteries is usually significantly lower than that of non-aqueous batteries, which is only about 1.23V. When the open circuit voltage exceeds the stable voltage window of the aqueous electrolyte, hydrogen or oxygen evolution reactions may occur in the aqueous solution. Therefore, the choice of active materials in aqueous electrolytes is usually limited, and the selection of suitable electroactive materials is crucial to determine the energy density of ARFBs.

[0004] In early studies, the most widely used conjugated carbonyl compounds in aqueous organic flow batteries are quinone and its derivatives. However, the solubility of quinone and its derivatives in water is generally low, resulting in the energy efficiency and density of the composed batteries being too low, which needs to be further improved. Summary of the invention

[0005] The object of the present invention is to provide a new type of quaternized biphenol derivative for the cathode of an aqueous organic liquid flow battery, wherein the biphenol unit is bridged with dimethylamine by a condensation reaction to obtain an intermediate, and then a water-soluble quaternary ammonium salt group is introduced to obtain a biphenol derivative. The derivative is an active electrode material with strong structural design and good redox reversibility. The organic material can be used as a cathode electrolyte for a liquid flow battery, can more effectively delocalize the free π electrons on the ring, and has a solubility of up to 6.28M in pure water. Electrochemical studies have shown that the redox reversibility of 2,5,2',5'-tetrakis(trimethylmethyleneammonium)-biphenol tetrachloride (DBTT) is affected by the pH value of the solution, and the redox potential is 0.56V (relative to the standard hydrogen electrode), with faster reaction kinetics, and it is used as a positive electrode material in a liquid flow battery, and is assembled with methyl viologen (MV) to obtain an aqueous liquid flow battery. Performance studies revealed that the coulombic efficiency of the 0.1M MV / / DBTT cell was 98.49% and the energy efficiency reached 90.21%.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] The quaternary ammonium salt biphenyl diphenol derivative used as cathode active electrolyte for aqueous organic liquid flow battery has the following chemical structure:

[0008]

[0009] wherein R is independently selected from (I) none, (II) -CH 2 -,(III)-SO 2 -,(IV)-C(CH 3 ) 2 -.

[0010] The specific names and structural formulas of the new quaternized biphenol derivatives used for the cathode of aqueous organic flow batteries are as follows:

[0011]

[0012] 2,5,2',5'-Tetrakis(trimethylmethyleneammonium)-biphenylenephenol tetrachloride (I)

[0013]

[0014] 2,5,2',5'-Tetrakis(trimethylmethyleneamine)-methylenediphenol tetrachloride(II)

[0015]

[0016] 2,5,2',5'-Tetrakis(trimethylmethyleneamine)-sulfonylbiphenol tetrachloride(III)

[0017]

[0018] 2,5,2',5'-Tetrakis(trimethylmethyleneamine)-isopropylbiphenyl tetrachloride (IV). The present invention also provides a preparation method of the quaternary ammonium salt biphenyl diphenol derivative, which comprises a hydrothermal reaction method and an ultrasonic reaction method.

[0019] The synthesis steps using the hydrothermal reaction method are as follows:

[0020] (1) Mix the biphenyl diphenol derivative, formaldehyde aqueous solution and dimethylamine, and add the mixture into a hydrothermal reactor for reaction. The reaction temperature is 100°C to 140°C, and the reaction time is 12 to 72 hours. After the reaction is completed, cool to room temperature, perform rotary evaporation on the reaction liquid, and vacuum dry the solid after rotary evaporation to obtain a yellow solid intermediate product. The drying temperature is 80°C and the time is 36 hours.

[0021] (2) The yellow solid intermediate product obtained in step (1) is dissolved in ethyl acetate, and an excess of methyl iodide is added. The reaction is stirred continuously at room temperature for 48 to 72 hours. After the reaction is completed, the solid is filtered and dried to obtain a light yellow solid. Ion exchange is performed, and the solid is rotary evaporated and vacuum dried to obtain a quaternary ammonium salt of biphenyl diphenol derivative. The drying temperature is 80° C. and the drying time is 24 hours.

[0022] The synthesis steps using the ultrasonic reaction method are as follows:

[0023] (1) Mix the biphenyl diphenol derivative, formaldehyde aqueous solution and dimethylamine, and add the mixture into an ultrasonic reaction container. The ultrasonic power of the ultrasonic device is 500W, the ultrasonic frequency is 20kHz, the reaction temperature is controlled at 50℃~55℃, the reaction time is 30~240min, and the reaction is paused for 10min every 30min. After the reaction is completed, cool to room temperature, perform rotary evaporation on the reaction liquid, and vacuum dry the solid after rotary evaporation at 80℃ for 36h to obtain a yellow solid intermediate product.

[0024] (2) The yellow solid intermediate product obtained in step (1) is dissolved in ethyl acetate, and an excess of methyl iodide is added. The reaction is stirred continuously at room temperature for 48 to 72 hours. After the reaction is completed, the solid is filtered and dried to obtain a light yellow solid. Ion exchange is performed, and the solid is rotary evaporated and vacuum dried at 80° C. for 24 hours to obtain a quaternary ammonium salt of biphenyl diphenol derivative.

[0025] The biphenol derivative is biphenol, methylene biphenol, sulfonyl biphenol or isopropyl biphenol. Meanwhile, the molar ratio of the biphenol derivative, formaldehyde aqueous solution (40% vol.) and dimethylamine is 1:5:4 to 1:6:6.

[0026] The molar ratio of the yellow solid intermediate product to methyl iodide in step (2) is 1:4 to 1:8.

[0027] The quaternary ammonium salted biphenol derivative is used as a cathode electrolyte of a liquid flow battery, and a suitable viologen derivative is selected as an anode electrolyte to form a neutral aqueous liquid flow battery.

[0028] The benefits of the present invention are as follows: the hydrothermal method and ultrasonic method, which are easy to scale up, are used to quaternize the biphenol derivatives, and the quaternized biphenol derivatives with a solubility of up to 6.28M in pure water are prepared, which have the advantages of high potential, good redox reversibility and fast reaction kinetics. It is used as a positive electrode material in liquid flow batteries, and assembled with methyl viologen (MV) to obtain a neutral aqueous liquid flow battery. Performance studies have revealed that the coulombic efficiency of the 0.1M MV / / DBTT battery is 98.49%, and the energy efficiency reaches 90.21%, which has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the CV diagram of the quaternary ammonium salt biphenol derivative prepared in Example 1 in a neutral NaCl solution.

[0030] Figure 2 This is a solubility test chart of the quaternary ammonium salt diphenol derivative prepared in Example 1 in a neutral NaCl solution.

[0031] Figure 3 The LSV diagram of the quaternary ammonium salt biphenyl diphenol derivative prepared in Example 1 at different rotation speeds in a neutral NaCl solution and the Levich diagram of the limiting current and the square root of the rotation speed.

[0032] Figure 4 The Koutecky'-Levich relationship diagram and Tafel relationship diagram of quaternary ammonium salt biphenyl diphenol derivatives in 1.5M NaCl solution.

[0033] Figure 5 This is the CV diagram of the quaternary ammonium salt biphenol derivative prepared in Example 2 in a neutral NaCl solution.

[0034] Figure 6 This is the CV diagram of the quaternary ammonium salt biphenol derivative prepared in Example 3 in a neutral NaCl solution.

[0035] Figure 7 This is the CV diagram of the quaternary ammonium salt biphenol derivative prepared in Example 4 in a neutral NaCl solution.

[0036] Figure 8 This is the CV diagram of the quaternary ammonium salt diphenol derivative prepared in Example 5 in a neutral NaCl solution.

[0037] Fig. 9 The charge and discharge curves of a neutral aqueous flow battery assembled with the quaternary ammonium salt biphenol derivative prepared in Example 1 as the positive electrode and methyl viologen as the negative electrode.

[0038] Fig.10 The graph shows the capacity retention rate and efficiency of a neutral aqueous flow battery assembled with the quaternary ammonium salt diphenol derivative prepared in Example 1 as the positive electrode and methyl viologen as the negative electrode after 100 cycles. DETAILED DESCRIPTION

[0039] The present invention is described in detail below with reference to specific embodiments.

[0040] Example 1

[0041]

[0042] 6.64 g (0.04 mol) of biphenyl, 18 mL of 40% formaldehyde solution and 29.40 mL (0.24 mol) of dimethylamine were mixed and added to a hydrothermal reactor, and reacted at 140° C. for 72 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the reaction solution was subjected to rotary evaporation. The solid after rotary evaporation was vacuum dried at 80° C. for 36 h, and the yellow solid obtained was tetramethylethyleneaminebiphenyl (TABP).

[0043] 3.46 g (7 mmol) of TABP was dissolved in 150 ml of ethyl acetate, and 56 mmol of iodomethane was added. The mixture was stirred at room temperature for 72 h. After the reaction was completed, the mixture was filtered and the filter cake was dried in a vacuum oven at 60° C. for 12 h to obtain a light yellow solid. The light yellow solid was ion exchanged, rotary evaporated and vacuum dried at 80° C. for 24 h to obtain 2,5,2',5'-tetrakis(trimethylmethyleneammonium)-biphenyldiphenol tetrachloride (light yellow solid, DBTT, 3.29 g, yield 83.9%).

[0044] Figure 1 This is the CV diagram of the quaternary ammonium salt biphenol derivative prepared in Example 1 in a neutral NaCl solution, and the equilibrium potential is 0.58V.

[0045] Figure 2This is a solubility test graph of the quaternary ammonium salt biphenyl diphenol derivative prepared in Example 1 in a neutral NaCl solution. The left figure is the UV absorption curve of DBTT at different solubilities in water, and the right figure is the fitting curve of DBTT concentration and absorbance. As can be seen from the left figure, the maximum absorbance of DBTT is at 280nm, and the linear equation obtained by fitting it with the concentration of DBTT is Y=0.01795X. Dissolve the DBTT prepared in Example 1 in water as much as possible, prepare a saturated aqueous solution of DBTT, and then take an appropriate amount of the solution and dilute it 300,000 times, measure the absorbance of the diluted solution at 280nm and bring it into the standard curve of DBTT, and obtain the solubility of DBTT in a neutral NaCl solution at room temperature as 6.28M.

[0046] Figure 3 The LSV plot of the quaternary ammonium salt biphenyl diphenol derivative prepared in Example 1 at different rotation speeds in a neutral NaCl solution and the Levich plot of the limiting current and the square root of the rotation speed are shown in Figure 1. The two are fitted to obtain Y = 3.42X + 10.95, and its diffusion coefficient D is calculated to be 2.64×10 -6 cm 2 s -1 .

[0047] Figure 4 In order to select the current data at different overpotentials on the LSV curve, the Koutecky'-Levich relationship diagram of the quaternary ammonium salt biphenol derivative in 1.5M NaCl solution was obtained, and then the Tafel relationship diagram was further obtained. According to the Butler-Volmer equation, the α of the quaternary ammonium salt biphenol derivative was calculated to be 0.43 and the kinetic equilibrium constant k 0 1.46x10 -3 cm s -1 , indicating that the quaternary ammonium salt of diphenol derivatives has faster kinetics.

[0048] Example 2

[0049]

[0050] 6.64g (0.04mol) of biphenyl, 18mL (0.24mol) of 40% formaldehyde aqueous solution and 29.40mL (0.24mol) of dimethylamine were mixed and added to an ultrasonic reaction container. The ultrasonic power of the ultrasonic device was 500W, the ultrasonic frequency was 20kHz, the reaction temperature was controlled at 55°C, the reaction time was 240min, and the reaction was paused for 10min every 30min. After the reaction was completed, it was cooled to room temperature, and the reaction solution was rotary evaporated. The solid after rotary evaporation was vacuum dried to obtain a yellow solid intermediate product. The drying temperature was 80°C and the time was 36h. The yellow solid obtained was tetramethylethyleneamine biphenyl (TABP).

[0051] 3.46g (7mmol) TABP was dissolved in 150ml ethyl acetate, 56mmol iodomethane was added, and the mixture was stirred at room temperature for 72h. After the reaction was completed, the mixture was filtered and dried in a vacuum oven at 60℃ for 12h to obtain a light yellow solid. The light yellow solid was ion exchanged, rotary evaporated and vacuum dried at 80℃ for 24h to obtain 2,5,2',5'-tetrakis(trimethylmethyleneammonium)-biphenyldiphenol tetrachloride (light yellow solid, DBTT, 3.65g, yield 93.1%). The solubility of the quaternary ammonium salt biphenyldiphenol derivative prepared in Example 2 in a neutral NaCl solution was measured to be 6.14M.

[0052] Figure 5 This is the CV diagram of the quaternary ammonium salt biphenol derivative prepared in Example 2 in a neutral NaCl solution, and the equilibrium potential is 0.62V.

[0053] Example 3

[0054]

[0055] 8 g (0.04 mol) of methylenediphenol, 18 mL (0.24 mol) of 40% formaldehyde aqueous solution and 29.40 mL (0.24 mol) of dimethylamine were mixed and added to a hydrothermal reactor, and reacted at 140°C for 72 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the reaction solution was subjected to rotary evaporation. The solid after rotary evaporation was vacuum dried at 80°C for 36 hours, and the yellow solid obtained was tetramethylethyleneamine methylenediphenol.

[0056] 3.72g (10mmol) of the intermediate product was dissolved in 150ml of ethyl acetate, 40mmol of iodomethane was added, and the mixture was stirred at room temperature for 72h. After the reaction was completed, suction filtration was performed, and the filter cake was placed in a 60°C vacuum drying oven and dried for 12h to obtain a yellow solid. The yellow solid was ion exchanged, rotary evaporated and vacuum dried at 80°C for 24h to obtain 2,5,2',5'-tetrakis (trimethylmethyleneamine)-methylenediphenol tetrachloride (yellow solid, yield 81.5%). The solubility of the quaternary ammonium salt diphenol derivative prepared in Example 3 in a neutral NaCl solution was measured to be 5.26M using the same method as in Example 1.

[0057] Figure 6 This is the CV diagram of the quaternary ammonium salt biphenol derivative prepared in Example 3 in a neutral NaCl solution, and the equilibrium potential is 0.60V.

[0058] Example 4

[0059]

[0060] 10 g (0.04 mol) of sulfonyl biphenol, 15 mL (0.20 mol) of 40% formaldehyde aqueous solution and 19.60 mL (0.16 mol) of dimethylamine were mixed and added to a hydrothermal reactor, and reacted at 100°C for 12 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and the reaction solution was subjected to rotary evaporation. The solid after rotary evaporation was vacuum dried at 80°C for 36 hours, and the yellow solid obtained was tetramethylethyleneamine sulfonyl biphenol.

[0061] 4.42 g (10 mmol) of the intermediate product was dissolved in 150 ml of ethyl acetate, 40 mmol of iodomethane was added, and the mixture was stirred at room temperature for 72 h. After the reaction was completed, the mixture was filtered and the filter cake was placed in a vacuum drying oven at 60° C. and dried for 12 h to obtain a light yellow solid. The light yellow solid was ion exchanged, rotary evaporated and vacuum dried at 80° C. for 24 h to obtain 2,5,2',5'-tetrakis(trimethylmethyleneamine)-sulfobiphenol tetrachloride (light yellow solid, yield 71.6%).

[0062] The solubility of the quaternary ammonium salt diphenol derivative prepared in Example 4 in a neutral NaCl solution was measured to be 4.96M using the same method as in Example 1.

[0063] Figure 7 This is the CV diagram of the quaternary ammonium salt biphenol derivative prepared in Example 4 in a neutral NaCl solution, and the equilibrium potential is 0.51V.

[0064] Example 5

[0065]

[0066] 10g (0.04mol) sulfonyl biphenol, 15mL (0.20mol) 40% formaldehyde aqueous solution and 19.60mL (0.16mol) dimethylamine were mixed and added to an ultrasonic reaction container. The ultrasonic power of the ultrasonic device was 500W, the ultrasonic frequency was 20kHz, the reaction temperature was controlled at 50°C, and the reaction time was 30min. After the reaction was completed, it was cooled to room temperature, the reaction solution was subjected to rotary evaporation, and the solid after rotary evaporation was vacuum dried to obtain a light yellow solid intermediate product. The drying temperature was 80°C and the time was 36h. The yellow solid obtained was tetramethylethyleneamine biphenol (TABP).

[0067] 4.42 g (10 mmol) of the intermediate product was dissolved in 150 ml of ethyl acetate, 40 mmol of iodomethane was added, and the mixture was stirred at room temperature for 72 h. After the reaction was completed, the mixture was filtered and the filter cake was dried in a vacuum oven at 60° C. for 12 h to obtain a light yellow solid. The light yellow solid was ion exchanged, rotary evaporated and vacuum dried at 80° C. for 24 h to obtain 2,5,2',5'-tetrakis(trimethylmethyleneamine)-sulfobiphenol tetrachloride (light yellow solid, yield 87.1%).

[0068] The same method as in Example 1 was used to measure the solubility of the quaternary ammonium salt biphenol derivative prepared in Example 5 in a neutral NaCl solution to be 5.02 M.

[0069] Figure 8 This is the CV diagram of the quaternary ammonium salt biphenol derivative prepared in Example 5 in a neutral NaCl solution, and the equilibrium potential is 0.61V.

[0070] Example 6

[0071]

[0072] 9.13 g (0.04 mol) of isopropyl biphenol, 15 mL (0.20 mol) of 40% formaldehyde aqueous solution and 24.50 mL (0.20 mol) of dimethylamine were mixed and added to a hydrothermal reactor in sequence, and reacted at 120° C. for 24 h. After the reaction was completed, the reaction solution was cooled to room temperature, and the reaction solution was subjected to rotary evaporation. The solid after rotary evaporation was vacuum dried at 80° C. for 36 h, and the yellow solid obtained was tetramethylethyleneamine isopropyl biphenol.

[0073] 3.2 g (8 mmol) of the intermediate product was dissolved in 150 ml of ethyl acetate, 48 mmol of iodomethane was added, and the mixture was stirred at room temperature for 72 h. After the reaction was completed, the mixture was filtered and the filter cake was dried in a vacuum oven at 60° C. for 12 h to obtain a light yellow solid. The light yellow solid was ion exchanged, rotary evaporated and vacuum dried at 80° C. for 24 h to obtain 2,5,2',5'-tetrakis(trimethylmethyleneamine)-isopropylbiphenyldiphenol tetrachloride (yellowish brown solid, yield 81.2%).

[0074] Using the same method as in Example 1, the solubility of the quaternary ammonium salt diphenol derivative prepared in Example 6 in a neutral NaCl solution was measured to be 4.78 M, and the equilibrium potential was 0.56 V.

[0075] Example 7

[0076] The quaternary ammonium salt biphenyl diphenol derivative prepared in Example 1 was used as the positive electrode, commercial methyl viologen was used as the negative electrode, and NaCl aqueous solution was used as the electrolyte to assemble a neutral aqueous flow battery, and its electrochemical performance was tested.

[0077] The specific assembly process is as follows:

[0078] (1) Electrode pretreatment

[0079] First, cut the carbon paper (or carbon felt) into 5cm 2 The carbon paper (or carbon felt) is then placed in an isopropanol solution for ultrasonic cleaning (5 minutes each time, 6 times, to remove surface impurities as much as possible). After the cleaning, it is dried in a blast drying oven, and then placed in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1. After heating in a 50°C water bath for 5 hours, it is cooled to room temperature, the carbon paper (or carbon felt) is taken out, the mixed acid solution is recovered, and it is washed with ultrapure water several times until the pH of the washing liquid is neutral. Finally, the treated carbon paper (or carbon felt) is stored in a beaker filled with ultrapure water. The carbon paper (or carbon felt) is kept completely immersed throughout the process.

[0080] (2) Treatment of diaphragm

[0081] Treatment of AEM membrane: After removing the waterproof protective film from the cut AEM membrane, soak it in 1M NaCl solution, change the solution every 24 hours, and store it in 1M NaCl after three changes.

[0082] Treatment of DSV membrane: Remove the waterproof protective film from the cut DSV membrane and soak it in ultrapure water.

[0083] (3) Preparation of electrolyte solution

[0084] The electrolyte used 1.5 M NaCl aqueous solution as the supporting electrolyte.

[0085] (4) Battery assembly

[0086] The two sides of the flow battery test cell are equipped with serpentine flow channel graphite plates, which are used as the flow channels for the electrolyte on both sides. Carbon felt (paper) is directly used as the anode and cathode, and the geometric area of ​​both electrodes is 5cm 2 . The battery separator is sandwiched between the anode and cathode materials of the battery. During assembly, assemble from left to right in sequence and fix with screws to obtain a flow battery test cell. At the same time, to prevent liquid leakage, a silicone rubber gasket is used to seal the battery gap. After the battery is assembled, add electrolyte solution to the liquid storage tanks on both sides of the battery and use a peristaltic pump (BT-600EA) at 60mL min -1 The flow rate maintains the electrolyte solution circulating between the storage tank and the battery system mold.

[0087] Fig. 9The charge and discharge curve of the neutral aqueous flow battery assembled with the quaternary ammonium salt biphenyl diphenol derivative prepared in Example 1 as the positive electrode and commercial methyl viologen as the negative electrode. The discharge platform is 0.95V, the discharge capacity is 11.36mAh, and the coulomb efficiency is 98.49%. Relative to the theoretical capacity of 13.4mAh, the utilization rate can reach 84.8%.

[0088] Fig.10 The capacity retention rate and efficiency diagram of the neutral aqueous flow battery assembled with the quaternary ammonium salt biphenyl diphenol derivative prepared in Example 1 as the positive electrode and commercial methyl viologen as the negative electrode after 100 cycles. The capacity decay rate per cycle is 0.07%, the coulombic efficiency is 98.41%, and the energy efficiency reaches 90.21%.

[0089] Example 8

[0090] The quaternary ammonium salt biphenyl diphenol derivative prepared in Example 2 was used as the positive electrode, commercial methyl viologen was used as the negative electrode, and NaCl aqueous solution was used as the electrolyte to assemble a neutral aqueous flow battery to test its electrochemical performance. The specific assembly process is the same as that in Example 8. The discharge platform is 1.06V, the discharge capacity is 12.86mAh, and the utilization rate can reach 95.97% relative to the theoretical capacity of 13.4mAh. After cyclic charge and discharge, the capacity decay rate per cycle is 0.02%, the coulomb efficiency is 98.22%, and the energy efficiency reaches 89.66%.

[0091] Example 9

[0092] The quaternary ammonium salt biphenyl diphenol derivative prepared in Example 3 was used as the positive electrode, commercial methyl viologen was used as the negative electrode, and NaCl aqueous solution was used as the electrolyte to assemble a neutral aqueous flow battery to test its electrochemical performance. The specific assembly process is the same as that in Example 8. The discharge platform is 1.02V, the discharge capacity is 11.21mAh, and the utilization rate can reach 83.66% relative to the theoretical capacity of 13.4mAh. After cyclic charge and discharge, the capacity decay rate per cycle is 0.11%, the coulomb efficiency is 97.39%, and the energy efficiency reaches 89.03%.

Claims

1. A quaternary ammonium salt biphenol derivative, characterized in that: The chemical structural formula of the derivative is shown below: wherein R is independently selected from (I) none, (II) -CH2-, (III) -SO2-, and (IV) -C(CH3)2-.

2. The quaternary ammonium salt biphenol derivative according to claim 1, characterized in that: The chemical structural formulas of the derivatives are shown below:

3. The quaternary ammonium salt biphenol derivative according to claim 1, characterized in that: The preparation method of the derivative is: hydrothermal reaction method or ultrasonic reaction method.

4. The quaternary ammonium salt biphenol derivative according to claim 3, characterized in that: The steps of the hydrothermal reaction method are as follows: (1) mixing a biphenol derivative, a formaldehyde aqueous solution and dimethylamine, adding the mixture to a hydrothermal reactor for reaction, cooling to room temperature after the reaction, performing rotary evaporation on the reaction solution, and vacuum drying the solid after rotary evaporation to obtain a yellow solid intermediate product; (2) dissolving the yellow solid intermediate product obtained in step (1) in ethyl acetate, adding iodomethane, stirring and reacting at room temperature, and filtering and drying after the reaction to obtain a light yellow solid; performing ion exchange, rotary evaporation and vacuum drying to obtain a quaternary ammonium salt biphenyl diphenol derivative.

5. The quaternary ammonium salt biphenol derivative according to claim 3, characterized in that: The steps of the ultrasonic reaction method are as follows: (1) mixing a biphenol derivative, a formaldehyde aqueous solution and dimethylamine, adding the mixture into an ultrasonic reaction vessel, cooling to room temperature after the reaction is completed, performing rotary evaporation on the reaction solution, and vacuum drying the solid after rotary evaporation to obtain a yellow solid intermediate product; (2) dissolving the yellow solid intermediate product obtained in step (1) in ethyl acetate, adding iodomethane, stirring and reacting at room temperature, and filtering and drying after the reaction to obtain a light yellow solid; performing ion exchange, rotary evaporation and vacuum drying to obtain a quaternary ammonium salt biphenyl diphenol derivative.

6. The quaternary ammonium salt biphenol derivative according to claim 4, characterized in that: In step (1), the reaction temperature is 100° C. to 140° C., and the reaction time is 12 to 72 h; the drying temperature is 80° C., and the time is 36 h.

7. The quaternary ammonium salt biphenol derivative according to claim 5, characterized in that: In step (1), the ultrasonic power of the ultrasonic device is 500W, the ultrasonic frequency is 20kHz, the reaction temperature is 50°C to 55°C, the reaction time is 30 to 240min, and a 10min pause is performed every 30min; the drying temperature is 80°C and the time is 36h.

8. The quaternary ammonium salt biphenol derivative according to claim 4 or 5, characterized in that: The biphenol derivative is: biphenol, methylene biphenol, sulfonyl biphenol or isopropyl biphenol; the molar ratio of the biphenol derivative, formaldehyde and dimethylamine is 1:5:4 to 1:6:

6.

9. The quaternary ammonium salt biphenol derivative according to claim 4 or 5, characterized in that: In step (2), the molar ratio of the yellow solid intermediate product to methyl iodide is 1:4 to 1:8; the stirring time is 48 to 72 hours; the drying temperature is 80° C. and the drying time is 24 hours.

10. An application of the quaternary ammonium salt biphenol derivative according to claim 1, characterized in that: The quaternized biphenol derivative is used as a cathode electrolyte for a neutral aqueous liquid flow battery.

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