Highly stable neutral aqueous flow battery based on quaternary ammonium saltified biphenol derivatives

Abstract

The application belongs to the technical field of new energy materials, and particularly relates to a high-stability neutral aqueous flow battery based on quaternary ammonium saltized biphenol derivative. Biphenol is bridged with dimethylamine through condensation reaction to obtain an intermediate, and then a water-soluble quaternary ammonium salt group is introduced to obtain a quaternary ammonium saltized biphenol derivative. The solubility of the material in pure water is as high as 6.28M, and the material has the advantages of high potential, good redox reversibility and fast reaction kinetics. With the material as cathode electrolyte, methyl viologen as anode electrolyte and sodium chloride aqueous solution as electrolyte, a neutral aqueous flow battery with high stability and energy efficiency is obtained after assembly. The discharge platform of the flow battery is 1.06V, the discharge capacity is 12.86mAh, the capacity attenuation rate of each cycle after cyclic charging and discharging 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 application belongs to the technical field of new energy materials, and particularly relates to a high-stability neutral aqueous flow battery based on quaternary ammonium saltized biphenol derivatives. BACKGROUND

[0002] Aqueous organic flow battery (AOFB) uses water-soluble organic molecules as active electrolyte for energy storage. The structure of organic molecules has high adjustability, and the properties of active materials can be customized through different chemical synthesis methods. Based on these advantages, aqueous organic flow battery is considered as one of the most promising low-cost, safe and large-scale electrochemical energy storage systems. Especially, neutral aqueous organic flow battery can avoid the damage of conventional acid and alkaline flow battery to equipment, and is suitable for various long-time energy storage devices.

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

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

[0005] The application aims to provide a new type of quaternary ammonium saltized biphenol derivative for a cathode of an aqueous organic flow battery, a biphenol unit is bridged with dimethylamine through 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 of a flow battery, can more effectively delocalize free π electrons on the ring, and has a solubility as high as 6.28 M in pure water. Electrochemical studies show that the redox reversibility of 2,5,2',5'-tetra(trimethyl methylene ammonium)-biphenol tetrachloride (DBTT) is affected by the pH value of the solution, the redox potential is 0.56 V (relative to the standard hydrogen electrode), and the reaction kinetics is fast. When the derivative is used as a positive electrode material and applied to a flow battery, a water-based flow battery is assembled by matching with methyl viologen (MV). Performance studies show that the coulombic efficiency of a 0.1M MV / / DBTT battery is 98.49%, and the energy efficiency reaches 90.21%.

[0006] In order to achieve the above-mentioned target, the application adopts the following technical solutions:

[0007] A quaternary ammonium saltized biphenol derivative for a cathode active electrolyte of an aqueous organic flow battery has the following chemical structure:

[0008]

[0009] wherein R is independently selected from (I) none, (II) -CH2-, (III) -SO2-, and (IV) -C(CH3)2-.

[0010] The specific name and structure of the new quaternary ammonium saltized biphenol derivative for a cathode of an aqueous organic flow battery are as follows:

[0011]

[0012] 2,5,2',5'-tetra(trimethyl methylene ammonium)-biphenol tetrachloride (I)

[0013]

[0014] 2,5,2',5'-tetra(trimethyl methylene ammonium)-biphenol tetrachloride (II)

[0015]

[0016] 2,5,2',5'-tetra(trimethyl methylene ammonium)-biphenol tetrachloride (III)

[0017]

[0018] 2,5,2',5'-tetra(trimethyl methylene amine)-isopropyl biphenol dichloride (IV).

[0019] The present application also provides a preparation method of the quaternary ammonium saltified biphenol derivative, which is a hydrothermal reaction method and an ultrasonic reaction method respectively.

[0020] The synthesis steps of the hydrothermal reaction method are as follows:

[0021] (1) The biphenol derivative, the formaldehyde aqueous solution and the dimethylamine are mixed, and the mixture is added into a hydrothermal reaction kettle for reaction. The reaction temperature is 100-140°C, and the reaction time is 12-72h. After the reaction is completed, the reaction solution is cooled to room temperature, and then rotary evaporation is performed on the reaction solution. The solid after rotary evaporation is vacuum dried at 80°C for 36h to obtain a yellow solid intermediate product.

[0022] (2) The yellow solid intermediate product obtained in step (1) is dissolved in ethyl acetate, and excess iodomethane is added. The reaction is continuously stirred at room temperature, and the stirring time is 48-72h. After the reaction is completed, the reaction solution is filtered and dried to obtain a light yellow solid. Ion exchange is performed, and then rotary evaporation and vacuum drying are performed at 80°C for 24h to obtain the quaternary ammonium saltified biphenol derivative.

[0023] The synthesis steps of the ultrasonic reaction method are as follows:

[0024] (1) The biphenol derivative, the formaldehyde aqueous solution and the dimethylamine are mixed, and the mixture is added 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°C, and the reaction time is 30-240min. The reaction is paused for 10min every 30min. After the reaction is completed, the reaction solution is cooled to room temperature, and then rotary evaporation is performed on the reaction solution. The solid after rotary evaporation is vacuum dried at 80°C for 36h to obtain a yellow solid intermediate product.

[0025] (2) The yellow solid intermediate product obtained in step (1) is dissolved in ethyl acetate, and excess iodomethane is added. The reaction is continuously stirred at room temperature, and the stirring time is 48-72h. After the reaction is completed, the reaction solution is filtered and dried to obtain a light yellow solid. Ion exchange is performed, and then rotary evaporation and vacuum drying are performed at 80°C for 24h to obtain the quaternary ammonium saltified biphenol derivative.

[0026] The biphenol derivative is biphenol, methylene biphenol, sulfonyl biphenol or isopropyl biphenol. Meanwhile, the molar ratio of the biphenol derivative, the formaldehyde aqueous solution (40%vol.) and the dimethylamine is 1:5:4-1:6:6.

[0027] The molar ratio of the yellow solid intermediate product and iodomethane in step (2) is 1:4 to 1:8.

[0028] The quaternized biphenyl derivative was used as the cathode electrolyte of the flow battery, and a suitable viologen derivative was selected as the anode electrolyte to form a neutral aqueous flow battery.

[0029] The advantages of this invention are: Quaternization of biphenyl derivatives is achieved using hydrothermal and ultrasonic methods, which are easily mass-producible, respectively. This yields quaternized biphenyl derivatives with a solubility of up to 6.28 M in pure water, exhibiting advantages such as high potential, good redox reversibility, and fast reaction kinetics. These derivatives are then used as cathode materials in flow batteries, and when combined with methyl viologen (MV), a neutral aqueous flow battery is obtained. Performance studies reveal that the 0.1 M MV / / DBTT battery has a coulombic efficiency of 98.49% and an energy efficiency of 90.21%, demonstrating broad application prospects. Attached Figure Description

[0030] Figure 1 The CV diagram shows the quaternary ammonium biphenyl derivative prepared in Example 1 in neutral NaCl solution.

[0031] Figure 2 The graph shows the solubility of the quaternized biphenyl derivative prepared in Example 1 in neutral NaCl solution.

[0032] Figure 3 The LSV plots and Levich plots of limiting current versus the square root of rotation speed for the quaternized biphenyl derivative prepared in Example 1 in neutral NaCl solution at different rotation speeds are shown.

[0033] Figure 4 The Koutecky-Levich and Tafel plots are shown for quaternized biphenyl derivatives in 1.5 M NaCl solution.

[0034] Figure 5 The CV diagram shows the quaternary ammonium biphenyl derivative prepared in Example 2 in neutral NaCl solution.

[0035] Figure 6 The CV diagram shows the quaternary ammonium biphenyl derivative prepared in Example 3 in neutral NaCl solution.

[0036] Figure 7 The CV diagram shows the quaternary ammonium biphenyl derivative prepared in Example 4 in neutral NaCl solution.

[0037] Figure 8 The CV diagram shows the quaternary ammonium biphenyl derivative prepared in Example 5 in neutral NaCl solution.

[0038] Figure 9 The charge-discharge curves are of a commercially available neutral aqueous flow battery assembled with methyl viologen as the negative electrode, using the quaternized biphenyl derivative prepared in Example 1 as the positive electrode.

[0039] Figure 10 The graph shows the capacity retention and efficiency of a commercially available neutral aqueous flow battery assembled with methyl viologen as the negative electrode, using the quaternized biphenyl derivative prepared in Example 1 as the positive electrode, after 100 cycles. Detailed Implementation

[0040] The present invention will now be described in detail with reference to specific embodiments.

[0041] Example 1

[0042]

[0043] 6.64 g (0.04 mol) of biphenyl hydrochloride, 18 mL of 40% formaldehyde aqueous solution, and 29.40 mL (0.24 mol) of dimethylamine were sequentially added to a hydrothermal reactor and reacted at 140 °C for 72 h. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was rotary evaporated. The solid obtained after rotary evaporation was vacuum dried at 80 °C for 36 h to obtain a yellow solid, which was tetramethylethyleneamine biphenyl hydrochloride (TABP).

[0044] 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 drying oven at 60 °C for 12 h to obtain a pale yellow solid. The pale yellow solid was subjected to ion exchange, rotary evaporation, and vacuum drying at 80 °C for 24 h to obtain 2,5,2',5'-tetra(trimethylmethyleneammonium)-biphenyltetrachloride (pale yellow solid, DBTT, 3.29 g, yield 83.9%).

[0045] Figure 1 The CV diagram for the quaternized biphenyl derivative prepared in Example 1 in neutral NaCl solution shows an equilibrium potential of 0.58 V.

[0046] Figure 2The graph shows the solubility test results of the quaternized biphenyl derivative prepared in Example 1 in neutral NaCl solution. The left graph shows the UV absorbance curves of DBTT at different solubilities in water, and the right graph shows the fitting curve of DBTT concentration versus absorbance. As can be seen from the left graph, the maximum absorbance of DBTT is at 280 nm, and the linear equation obtained by fitting it with the concentration of DBTT is Y = 0.01795X. DBTT prepared in Example 1 was dissolved in water as much as possible to prepare a saturated aqueous solution of DBTT. Then, an appropriate amount of the solution was diluted 300,000 times, and the absorbance of the diluted solution at 280 nm was measured and substituted into the standard curve of DBTT. The solubility of DBTT in neutral NaCl solution at room temperature was found to be 6.28 M.

[0047] Figure 3 The LSV plots and Levich plots of the limiting current versus the square root of the rotational speed for the quaternized biphenyl derivative prepared in Example 1 in neutral NaCl solution at different rotational speeds are shown. Fitting the two plots yields Y = 3.42X + 10.95, and the diffusion coefficient D is calculated to be 2.64 × 10⁻⁶. -6 cm 2 s -1 .

[0048] Figure 4 To select current data at different overpotentials on the LSV curve, the Koutecky-Levich relationship of the quaternized biphenyl derivative in 1.5M NaCl solution was obtained, and then the Tafel relationship was further derived. Based on the Butler-Volmer equation, the α value of the quaternized biphenyl derivative was calculated to be 0.43, and the kinetic equilibrium constant k was determined to be k. 0 1.46x10 - 3 cms -1 This indicates that the quaternized biphenyl derivatives have relatively fast kinetics.

[0049] Example 2

[0050]

[0051] 6.64 g (0.04 mol) of biphenyl hydroquinone, 18 mL (0.24 mol) of 40% formaldehyde aqueous solution, and 29.40 mL (0.24 mol) of dimethylamine were sequentially added to an ultrasonic reaction vessel. The ultrasonic power of the device was 500 W, the ultrasonic frequency was 20 kHz, the reaction temperature was controlled at 55 °C, and the reaction time was 240 min, with a 10 min pause every 30 min. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was rotary evaporated. The solid obtained by rotary evaporation was then vacuum dried to obtain a yellow solid intermediate product. The drying temperature was 80 °C, and the time was 36 h. The resulting yellow solid was tetramethylethyleneamine biphenyl hydroquinone (TABP).

[0052] 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 complete, the mixture was filtered, and the filter cake was dried in a vacuum drying oven at 60 °C for 12 h to obtain a pale yellow solid. The pale yellow solid was subjected to ion exchange, rotary evaporation, and vacuum drying at 80 °C for 24 h to obtain 2,5,2',5'-tetra(trimethylmethyleneammonium)-biphenyl tetrachloride (pale yellow solid, DBTT, 3.65 g, yield 93.1%). Following the method of Example 1, the solubility of the quaternized biphenyl derivative prepared in Example 2 in neutral NaCl solution was determined to be 6.14 M.

[0053] Figure 5 The CV curve for the quaternized biphenyl derivative prepared in Example 2 in neutral NaCl solution shows an equilibrium potential of 0.62 V.

[0054] Example 3

[0055]

[0056] 8 g (0.04 mol) of methylene biphenyl phenol, 18 mL (0.24 mol) of 40% formaldehyde aqueous solution, and 29.40 mL (0.24 mol) of dimethylamine were sequentially added to a hydrothermal reactor and reacted at 140 °C for 72 h. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was rotary evaporated. The solid obtained after rotary evaporation was vacuum dried at 80 °C for 36 h to obtain a yellow solid, which was tetramethylethyleneamine methylene biphenyl phenol.

[0057] 3.72 g (10 mmol) of the intermediate product was dissolved in 150 mL of ethyl acetate, and 40 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 drying oven at 60 °C for 12 h to obtain a yellow solid. The yellow solid was subjected to ion exchange, rotary evaporation, and vacuum drying at 80 °C for 24 h to obtain 2,5,2',5'-tetra(trimethylmethyleneamine)-methylenebiphenyl tetrachloride (yellow solid, yield 81.5%). Following the method of Example 1, the solubility of the quaternized biphenyl derivative prepared in Example 3 in neutral NaCl solution was determined to be 5.26 M.

[0058] Figure 6 The CV curve for the quaternized biphenyl derivative prepared in Example 3 in neutral NaCl solution shows an equilibrium potential of 0.60 V.

[0059] Example 4

[0060]

[0061] 10 g (0.04 mol) of sulfonylbiphenyl, 15 mL (0.20 mol) of 40% formaldehyde aqueous solution, and 19.60 mL (0.16 mol) of dimethylamine were sequentially added to a hydrothermal reactor and reacted at 100 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was rotary evaporated. The solid obtained after rotary evaporation was vacuum dried at 80 °C for 36 h to obtain a yellow solid, which was tetramethylethyleneamine sulfonylbiphenyl.

[0062] 4.42 g (10 mmol) of the intermediate product was dissolved in 150 mL of ethyl acetate, and 40 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 drying oven at 60 °C for 12 h to obtain a pale yellow solid. The pale yellow solid was subjected to ion exchange, rotary evaporation, and vacuum drying at 80 °C for 24 h to obtain 2,5,2',5'-tetra(trimethylmethyleneamine)-sulfonylbiphenyl tetrachloride (pale yellow solid, yield 71.6%).

[0063] Using the same method as in Example 1, the solubility of the quaternized biphenyl derivative prepared in Example 4 in neutral NaCl solution was measured to be 4.96 M.

[0064] Figure 7 The CV curve for the quaternized biphenyl derivative prepared in Example 4 in neutral NaCl solution shows an equilibrium potential of 0.51 V.

[0065] Example 5

[0066]

[0067] 10 g (0.04 mol) of sulfonylbiphenylhydrazine, 15 mL (0.20 mol) of 40% formaldehyde aqueous solution, and 19.60 mL (0.16 mol) of dimethylamine were sequentially added to an ultrasonic reaction vessel. The ultrasonic power of the device was 500 W, the ultrasonic frequency was 20 kHz, the reaction temperature was controlled at 50 °C, and the reaction time was 30 min. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was rotary evaporated. The solid obtained after rotary evaporation was dried under vacuum to obtain a pale yellow solid intermediate product. The drying temperature was 80 °C, and the time was 36 h. The resulting yellow solid was tetramethylethyleneamine biphenylhydrazine (TABP).

[0068] 4.42 g (10 mmol) of the intermediate product was dissolved in 150 mL of ethyl acetate, and 40 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 drying oven at 60 °C for 12 h to obtain a pale yellow solid. The pale yellow solid was subjected to ion exchange, rotary evaporation, and vacuum drying at 80 °C for 24 h to obtain 2,5,2',5'-tetra(trimethylmethyleneamine)-sulfonylbiphenyl tetrachloride (pale yellow solid, yield 87.1%).

[0069] Using the same method as in Example 1, the solubility of the quaternized biphenyl derivative prepared in Example 5 in neutral NaCl solution was measured to be 5.02 M.

[0070] Figure 8 The CV curve for the quaternized biphenyl derivative prepared in Example 5 in neutral NaCl solution shows an equilibrium potential of 0.61 V.

[0071] Example 6

[0072]

[0073] 9.13 g (0.04 mol) of isopropylbiphenyl, 15 mL (0.20 mol) of 40% formaldehyde aqueous solution, and 24.50 mL (0.20 mol) of dimethylamine were sequentially added to a hydrothermal reactor and reacted at 120 °C for 24 h. After the reaction was completed, the mixture was cooled to room temperature, and the reaction solution was rotary evaporated. The solid obtained after rotary evaporation was vacuum dried at 80 °C for 36 h to obtain a yellow solid, which was tetramethylethyleneamine isopropylbiphenyl.

[0074] 3.2 g (8 mmol) of the intermediate product was dissolved in 150 mL of ethyl acetate, and 48 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 drying oven at 60 °C for 12 h to obtain a pale yellow solid. The pale yellow solid was subjected to ion exchange, rotary evaporation, and vacuum drying at 80 °C for 24 h to obtain 2,5,2',5'-tetra(trimethylmethyleneamine)-isopropylbiphenyl tetrachloride (yellowish-brown solid, yield 81.2%).

[0075] Using the same method as in Example 1, the solubility of the quaternized biphenyl derivative prepared in Example 6 in neutral NaCl solution was measured to be 4.78 M, and the equilibrium potential was 0.56 V.

[0076] Example 7

[0077] Using the quaternized biphenyl derivative prepared in Example 1 as the positive electrode, commercial methyl viologen as the negative electrode, and NaCl aqueous solution as the electrolyte, a neutral aqueous flow battery was assembled, and its electrochemical performance was tested.

[0078] The specific assembly process is as follows:

[0079] (1) Electrode pretreatment

[0080] First, cut the carbon paper (or carbon felt) into 5cm pieces. 2 The carbon paper (or carbon felt) is shaped into a square and then immersed in isopropanol solution for ultrasonic cleaning (5 minutes each time, 6 times in total, to remove as many surface impurities as possible). After cleaning, it is dried in a forced-air drying oven. Then, it is placed in a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid (3:1 volume ratio) and heated in a water bath at 50°C for 5 hours. After cooling to room temperature, the carbon paper (or carbon felt) is removed, the mixed acid solution is recovered, and it is washed multiple times with ultrapure water until the pH of the washing solution is neutral. Finally, the treated carbon paper (or carbon felt) is stored in a beaker containing ultrapure water. Throughout the process, the carbon paper (or carbon felt) is kept completely submerged.

[0081] (2) Treatment of the diaphragm

[0082] Treatment of AEM membrane: After removing the waterproof protective film from the cut AEM membrane, immerse it in 1M NaCl solution. Change the solution every 24 hours, and after three changes, store it in 1M NaCl.

[0083] DSV membrane treatment: Remove the waterproof protective film from the cut DSV membrane and immerse it in ultrapure water.

[0084] (3) Preparation of electrolyte solution

[0085] A 1.5M NaCl aqueous solution was used as the supporting electrolyte.

[0086] (4) Battery assembly

[0087] The flow battery test cell is equipped with serpentine flow channel graphite plates on both sides, serving as flow channels for the electrolyte on both sides. Carbon felt (paper) is used directly as the anode and cathode, with each electrode having a geometric area of ​​5 cm². 2 The battery separator is sandwiched between the anode and cathode materials. During assembly, the components are assembled sequentially from left to right and secured with screws to form the flow battery test cell. To prevent leakage, silicone rubber gaskets are used to seal any gaps in the battery. After assembly, electrolyte solution is added to the reservoirs on both sides of the battery and pumped at a rate of 60 mL / min using a peristaltic pump (BT-600EA). -1 The flow rate maintains the electrolyte solution circulating between the storage tank and the battery system mold.

[0088] Figure 9 The chart shows the charge-discharge curves of a commercially available neutral aqueous flow battery assembled with methyl viologen as the negative electrode, using the quaternized biphenyl derivative prepared in Example 1 as the positive electrode. The discharge plateau is 0.95V, the discharge capacity is 11.36mAh, and the coulombic efficiency is 98.49%. This represents a utilization rate of 84.8% relative to the theoretical capacity of 13.4mAh.

[0089] Figure 10 The graph shows the capacity retention and efficiency of a commercially available neutral aqueous flow battery assembled with methyl viologen as the negative electrode, using the quaternized biphenyl derivative prepared in Example 1 as the positive 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%.

[0090] Example 8

[0091] Using the quaternized biphenyl derivative prepared in Example 2 as the positive electrode, commercially available methyl viologen as the negative electrode, and NaCl aqueous solution as the electrolyte, a neutral aqueous flow battery was assembled, and its electrochemical performance was tested. The specific assembly process was the same as in Example 7. The discharge plateau was 1.06V, and the discharge capacity was 12.86mAh, achieving a utilization rate of 95.97% relative to the theoretical capacity of 13.4mAh. After cyclic charge-discharge, the capacity decay rate per cycle was 0.02%, the coulombic efficiency was 98.22%, and the energy efficiency reached 89.66%.

[0092] Example 9

[0093] Using the quaternized biphenyl derivative prepared in Example 3 as the positive electrode, commercially available methyl viologen as the negative electrode, and NaCl aqueous solution as the electrolyte, a neutral aqueous flow battery was assembled, and its electrochemical performance was tested. The specific assembly process was the same as in Example 8. The discharge plateau was 1.02V, and the discharge capacity was 11.21mAh, representing a utilization rate of 83.66% relative to the theoretical capacity of 13.4mAh. After cyclic charge-discharge, the capacity decay rate per cycle was 0.11%, the coulombic efficiency was 97.39%, and the energy efficiency reached 89.03%.

Claims

1. A quaternized biphenyl derivative, characterized in that: The chemical structural formulas of the derivatives are shown below:

2. The method for preparing quaternized biphenyl derivatives according to claim 1, characterized in that, The derivative is prepared by either hydrothermal reaction or ultrasonic reaction.

3. The method for preparing quaternized biphenyl derivatives according to claim 2, characterized in that, The steps of the hydrothermal reaction method are as follows: (1) Biphenyl hydrochloride derivative, formaldehyde aqueous solution and dimethylamine were mixed and added to a hydrothermal reactor for reaction. After the reaction was completed, the mixture was cooled to room temperature and the reaction solution was rotary evaporated. The solid after rotary evaporation was dried under vacuum to obtain a yellow solid intermediate product. (2) Dissolve the yellow solid intermediate obtained in step (1) in ethyl acetate, add iodomethane, stir the reaction at room temperature, filter and dry after the reaction is completed to obtain a pale yellow solid; perform ion exchange, rotary evaporate and vacuum dry to obtain quaternized biphenyl derivative.

4. The method for preparing quaternized biphenyl derivatives according to claim 2, characterized in that, The steps of the ultrasonic reaction method are as follows: (1) Mix biphenyl derivative, formaldehyde aqueous solution and dimethylamine. Add the mixture to an ultrasonic reaction vessel. After the reaction is completed, cool to room temperature and rotary evaporate the reaction solution. Dry the solid after rotary evaporation under vacuum to obtain a yellow solid intermediate product. (2) Dissolve the yellow solid intermediate obtained in step (1) in ethyl acetate, add iodomethane, stir the reaction at room temperature, filter and dry after the reaction is completed to obtain a pale yellow solid; perform ion exchange, rotary evaporate and vacuum dry to obtain quaternized biphenyl derivative.

5. The method for preparing quaternized biphenyl derivatives according to claim 3, characterized in that, In step (1), the reaction temperature is 100℃~140℃ and the reaction time is 12~72h; the drying temperature is 80℃ and the time is 36h.

6. The method for preparing quaternized biphenyl derivatives according to claim 4, 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℃~55℃, the reaction time is 30~240min, and the reaction is paused for 10min every 30min; the drying temperature is 80℃ and the time is 36h.

7. The method for preparing quaternized biphenyl derivatives according to claim 3 or 4, characterized in that, Bisphenol derivatives include: biphenol, methylene biphenol, sulfonyl biphenol, or isopropyl biphenol; the molar ratio of biphenol derivatives, formaldehyde, and dimethylamine is 1:5:4 to 1:6:

6.

8. The method for preparing quaternized biphenyl derivatives according to claim 3 or 4, characterized in that, In step (2), the molar ratio of the yellow solid intermediate product to iodomethane is 1:4 to 1:8; the stirring time is 48 to 72 h; the drying temperature is 80 °C and the time is 24 h.

9. An application of the quaternized biphenyl derivative according to claim 1, characterized in that, The quaternized biphenyl derivative is used as the cathode electrolyte in a neutral aqueous flow battery.

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