Low temperature resistant electrolyte for flow battery and preparation method and zinc-bromine flow battery

Abstract

The application relates to the technical field of liquid flow batteries, and discloses a low-temperature-resistant liquid flow battery electrolyte, a preparation method thereof and a zinc-bromine liquid flow battery. The low-temperature-resistant liquid flow battery electrolyte comprises water, an electrolyte salt, a supporting electrolyte, a 2-phenyl benzopyran type cationic additive and an alcohol solvent. The 2-phenyl benzopyran type cationic additive has a double regulation function, can synchronously solve the problems of polybromide shuttling effect and zinc negative electrode irreversibility, and can construct a high-performance zinc-bromine liquid flow battery. The alcohol solvent has little influence on the electrolyte conductivity and viscosity, can reduce the freezing point of the electrolyte, and can improve the reaction kinetics of zinc under low-temperature conditions. The interaction between the alcohol solvent and the 2-phenyl benzopyran type cationic additive enables the zinc-bromine liquid flow battery to operate more stably and efficiently under low-temperature conditions, and solves the problem of low energy efficiency of the zinc-bromine liquid flow battery under low-temperature conditions in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of flow battery technology, and particularly relates to a low-temperature resistant flow battery electrolyte and its preparation method, as well as a zinc-bromine flow battery. Background Technology

[0002] Zinc-bromine flow batteries are high-efficiency energy storage systems based on the bromine-zinc redox reaction. They offer advantages such as high safety, low cost, and long cycle life (over 5000 cycles), and are widely used in grid-scale energy storage and renewable energy grid integration. Their working principle relies on the positive electrode Br2 / Br... - and negative electrode Zn 2+ In the redox reaction of Zn, the electrolyte (usually an aqueous solution of ZnBr2) plays a crucial role in ion conduction and dissolution of active substances.

[0003] However, the practical application of zinc-bromine flow batteries is limited by ambient temperature, especially in low-temperature environments below 0°C, where the physicochemical properties of the electrolyte undergo significant changes, leading to a sharp decline in battery performance. Traditional zinc-bromine flow battery electrolytes are aqueous solutions of zinc bromide, conductive support agents (such as potassium chloride, sodium chloride, ammonium chloride, and methanesulfonic acid), and complexing agents (such as 1-methyl-1-ethylpyrrolidine bromide and N-methyl-N-propylmorpholine bromide). The complexing agents complex with Br2 and polybrominated compounds generated at the positive electrode, forming dense, viscous, and immiscible oil-phase polybrominated complexes, resulting in water / oil phase separation. When the temperature is ≤-10°C, the oil phase crystallinity is >30%, and water / oil phase separation triggers localized solidification, reducing the bromide ion transport number by approximately 40%. Furthermore, the solidified material can clog the circulation lines, affecting battery stability.

[0004] To address the aforementioned issues, Chinese invention patent CN115775903B discloses a low-temperature resistant flow battery electrolyte and its application. Choline chloride is added as an additive to the electrolyte, which lowers the freezing point of the polybrominated complex, a charging product at the positive electrode of a zinc-bromine flow battery. Zinc-bromine flow batteries assembled using this electrolyte can achieve a charging rate of 40 mA / cm². 2 Current density at It operates stably for a long time at 10℃, and The battery maintains normal charge and discharge at 20°C, but its energy efficiency is low at low temperatures (the coulombic efficiency decays to 82.3% of the efficiency at room temperature at -20°C). Therefore, developing a high-performance low-temperature zinc-bromine flow battery electrolyte is crucial for further advancements in zinc-bromine flow battery technology. Summary of the Invention

[0005] To overcome the technical problem of low energy efficiency of zinc-bromine flow batteries under low temperature conditions in the prior art, the present invention aims to provide a low-temperature resistant flow battery electrolyte, a preparation method, and a zinc-bromine flow battery. This electrolyte can effectively capture bromine molecules and inhibit zinc dendrite formation while maintaining an aqueous solution state. It can maintain an aqueous solution state during charging and discharging in an environment of -20℃, so that the zinc-bromine flow battery can still maintain high energy efficiency under low temperature conditions, thus broadening the application scenarios of zinc-bromine flow batteries.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention provides a cryogenic flow battery electrolyte, comprising water, an electrolyte salt, a supporting electrolyte, a 2-phenylbenzopyran-type cationic additive, and an alcohol solvent; wherein the concentration of the 2-phenylbenzopyran-type cationic additive in the cryogenic flow battery electrolyte is 0.05-0.2 mol / L; and the mass of the alcohol solvent is 5%-10% of the sum of the mass of the alcohol solvent and the water.

[0008] Optionally, the 2-phenylbenzopyran-type cationic additive is a 2-phenylbenzopyran-type cationic compound with the following structural formula:

[0009]

[0010] Among them, R1, R2, R3 and the three R4s contain at least four -OH groups, and the rest are -H or -OCH3.

[0011] Optionally, the 2-phenylbenzopyran-type cationic additive is one of delphinidin, geranium pigment, and cornflower pigment.

[0012] Optionally, the electrolyte salt is zinc bromide.

[0013] Optionally, the concentration of zinc bromide in the electrolyte of the low-temperature flow battery is 2-2.5 mol / L.

[0014] Optionally, the supporting electrolyte is one or two of potassium chloride, sodium chloride, and ammonium chloride.

[0015] Optionally, the concentration of the supporting electrolyte in the low-temperature flow battery electrolyte is 1.0-2.0 mol / L.

[0016] Optionally, the alcohol solvent is one or two of ethylene glycol, 1,2-propanediol, methanol, glycerol, and 2-propanol.

[0017] A method for preparing a low-temperature resistant flow battery electrolyte as described above includes the following steps:

[0018] Water and an alcohol solvent are mixed thoroughly to obtain an alcohol solution;

[0019] An electrolyte salt, a supporting electrolyte, and a 2-phenylbenzopyran-type cationic additive are mixed to form a mixture;

[0020] Add an alcohol solution to the mixture and stir until homogeneous to obtain a low-temperature flow battery electrolyte.

[0021] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and the aforementioned low-temperature resistant flow battery electrolyte; the positive electrode, negative electrode, and separator are all immersed in the low-temperature resistant flow battery electrolyte, and the positive electrode and negative electrode are physically separated by the separator.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention provides a low-temperature resistant flow battery electrolyte, comprising water, an electrolyte salt, a supporting electrolyte, a 2-phenylbenzopyran-type cationic additive, and an alcohol solvent. The 2-phenylbenzopyran-type cationic additive possesses a dual regulatory function, simultaneously addressing the polybrominator shuttle effect and the irreversibility of the zinc anode, thus constructing a high-performance zinc-bromine flow battery. On one hand, under acidic conditions (the electrode solution in a zinc-bromine flow battery is acidic), the 2-phenylbenzopyran-type cationic additive undergoes protonation by combining with hydrogen ions, generating a positive electrostatic potential. This allows bromide ions and polybrominators to be stably adsorbed on the positive electrode side, effectively suppressing the bromine shuttle effect. Furthermore, it maintains the electrolyte in a homogeneous aqueous solution state after bromine capture, avoiding localized solidification caused by phase separation, thereby significantly increasing the bromine redox reaction rate. On the other hand, the polar hydroxyl functional groups in the molecular structure of the 2-phenylbenzopyran-type cationic additive can form a hydrogen bond network with water molecules, optimizing the coordination environment of zinc ions, improving the reversibility of zinc deposition / dissolution, and inhibiting zinc dendrite growth. Therefore, the 2-phenylbenzopyran-type cationic additive in this invention allows the electrolyte to remain in an aqueous solution state during charge and discharge, enabling bromine to participate in the positive electrode redox reaction without undergoing a complexation / dissociation process. This ensures the stability of the zinc-bromine flow battery while maintaining high energy efficiency even at low temperatures. The alcohol solvent used not only has minimal impact on the electrolyte's conductivity and viscosity but also lowers its freezing point. Simultaneously, the hydroxyl groups (-OH) of the alcohol form hydrogen bonds with H₂O, weakening the [Zn(H₂O)₆] group. 2+The coordination structure lowers the desolventization activation energy of zinc, thereby reducing the energy barrier for zinc deposition, enhancing the reaction kinetics of zinc under low-temperature conditions, slowing down zinc dendrite formation, and enabling the zinc-bromine flow battery to maintain high efficiency at low temperatures. The interaction between the alcohol solvent and the 2-phenylbenzopyran-type cationic additives allows the zinc-bromine flow battery to operate more stably and efficiently at low temperatures, providing a reliable solution for large-scale, long-term energy storage applications. This expands the application of zinc-bromine flow batteries in large-scale, long-term energy storage fields such as wind and solar energy storage and grid peak shaving, demonstrating significant commercial value and social benefits.

[0024] This invention provides a method for preparing a low-temperature resistant flow battery electrolyte as described above. The method involves mixing water and an alcohol solvent to obtain an alcohol solution; then adding the alcohol solution to a mixture of an electrolyte salt, a supporting electrolyte, and a 2-phenylbenzopyran-type cationic additive, and adjusting the volume to obtain the low-temperature resistant flow battery electrolyte. The preparation method is simple, requiring no complex equipment or harsh reaction conditions. Furthermore, the prepared low-temperature resistant flow battery electrolyte enables zinc-bromine flow batteries prepared using it to achieve an energy efficiency of over 95% of the energy efficiency at room temperature under -20°C conditions, thus realizing high-efficiency energy storage over a wide temperature range.

[0025] The present invention also provides a zinc-bromine flow battery, comprising a positive electrode, a negative electrode, a separator, and the aforementioned low-temperature resistant flow battery electrolyte. The zinc-bromine flow battery can still achieve an energy efficiency of over 95% at room temperature even at a low temperature of -20°C, exhibiting excellent low-temperature performance and high energy efficiency at low temperatures. It can operate efficiently and stably over a wide temperature range, providing reliable energy storage support for the power grid, effectively responding to fluctuations in power demand and sudden events, and improving the stability and resilience of the power grid. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the preparation method of the low-temperature resistant flow battery electrolyte of the present invention. Detailed Implementation

[0027] To facilitate understanding of the present invention, the present invention will be described more fully below through embodiments.

[0028] This invention provides a low-temperature resistant flow battery electrolyte, comprising water, electrolyte salt, supporting electrolyte, 2-phenylbenzopyran-type cationic additive, and alcohol solvent.

[0029] The electrolyte salt is zinc bromide, and the concentration of zinc bromide in the electrolyte of the low-temperature flow battery is 2-2.5 mol / L;

[0030] The supporting electrolyte is one or two of potassium chloride, sodium chloride and ammonium chloride, and the concentration of the supporting electrolyte in the low-temperature flow battery electrolyte is 1.0-2.0 mol / L;

[0031] The 2-phenylbenzopyran-type cationic additive is a 2-phenylbenzopyran-type cationic compound with the following structural formula:

[0032]

[0033] Among them, R1, R2, R3 and the three R4s contain at least four -OH groups, and the rest are -H or -OCH3;

[0034] Preferably, the 2-phenylbenzopyran-type cationic additive is one of delphinidin, geranium pigment, and cornflower pigment, and the concentration of the 2-phenylbenzopyran-type cationic additive in the low-temperature flow battery electrolyte is 0.05-0.2 mol / L;

[0035] The structure of delphinidin is shown below:

[0036] ;

[0037] The structure of geranium pigment is shown below:

[0038] ;

[0039] The structure of cornflower pigment is shown below:

[0040] ;

[0041] The alcohol solvent is one or two of ethylene glycol, 1,2-propanediol, methanol, glycerol and 2-propanol, and the alcohol solvent accounts for 5%-10% of the total solvent (the sum of alcohol solvent and water) by mass.

[0042] The 2-phenylbenzopyran-type cationic additive in the electrolyte of this low-temperature flow battery, under acidic conditions (the electrode solution of the zinc-bromine flow battery is acidic), combines with hydrogen ions and undergoes protonation, generating a positive electrostatic potential. This allows bromide ions and polybrominates to be stably adsorbed on the positive electrode side, effectively suppressing the bromine shuttle effect, preventing the loss of active materials and the degradation of battery performance, and ensuring the stable progress of the internal reaction of the zinc-bromine flow battery. Simultaneously, the 2-phenylbenzopyran-type cationic additive, after capturing bromine, maintains the electrolyte in a homogeneous aqueous solution state, avoiding the localized solidification problem caused by water / oil phase separation in traditional electrolytes. The alcohol solvent used not only has minimal impact on the electrolyte conductivity and viscosity but also lowers the electrolyte's freezing point, enabling the zinc-bromine flow battery to operate at lower temperatures and expanding its application temperature range. Furthermore, the hydroxyl groups of the alcohol solvent form hydrogen bonds with water, weakening the [Zn(H₂O)₆] group. 2+ The coordination structure lowers the desolventization activation energy of zinc, thereby reducing the energy barrier for zinc deposition. This improves the reaction kinetics of zinc at low temperatures, slows down zinc dendrite formation, and further ensures the stable operation of the zinc anode at low temperatures, enabling the zinc-bromine flow battery to maintain high efficiency at low temperatures. It is evident that the interaction between the alcohol solvent and the 2-phenylbenzopyran-type cationic additives jointly improves the low-temperature stability and energy efficiency of the zinc-bromine flow battery, enabling it to operate more stably and efficiently in low-temperature environments, providing a reliable solution for large-scale, long-term energy storage applications.

[0043] See Figure 1 The present invention also provides a method for preparing a low-temperature resistant flow battery electrolyte, comprising the following steps:

[0044] S1: Stir water and alcohol solvent until well mixed to obtain an alcohol solution;

[0045] S2: Mix the electrolyte salt, supporting electrolyte, and 2-phenylbenzopyran-type cationic additive to form a mixture;

[0046] S3: Add alcohol solution to the mixture and stir until homogeneous to obtain low-temperature flow battery electrolyte;

[0047] The resulting low-temperature flow battery electrolyte contains an electrolyte salt concentration of 2-2.5 mol / L, a supporting electrolyte concentration of 1.0-2.0 mol / L, a 2-phenylbenzopyran-type cationic additive concentration of 0.05-0.2 mol / L, and an alcohol solvent accounting for 5%-10% of the total solvent (the sum of alcohol solvent and water).

[0048] The electrolyte salt is zinc bromide;

[0049] The supporting electrolyte is one or two of potassium chloride, sodium chloride and ammonium chloride;

[0050] The 2-phenylbenzopyran-type cationic additive is a 2-phenylbenzopyran-type cationic compound with the following structural formula:

[0051]

[0052] Among them, R1, R2, R3 and the three R4s contain at least four -OH groups, and the rest are -H or -OCH3;

[0053] Preferably, the 2-phenylbenzopyran-type cationic additive is one of delphinidin, geranium pigment, and cornflower pigment;

[0054] The alcohol solvent is one or two of ethylene glycol, 1,2-propanediol, methanol, glycerol, and 2-propanol.

[0055] This method is simple, requires no complex equipment or harsh reaction conditions, and the prepared low-temperature resistant flow battery electrolyte enables the zinc-bromine flow battery prepared using it to achieve an energy efficiency of more than 95% of the energy efficiency at room temperature under -20℃ conditions, thus realizing high-efficiency energy storage over a wide temperature range.

[0056] The present invention also provides a zinc-bromine flow battery, comprising a positive electrode, a negative electrode, a separator, and the aforementioned low-temperature resistant flow battery electrolyte; the positive electrode, the negative electrode, and the separator are all immersed in the low-temperature resistant flow battery electrolyte, and the positive electrode and the negative electrode are physically isolated by the separator.

[0057] Preferably, the positive electrode of the zinc-bromine flow battery is prepared by the following process:

[0058] Porous carbon material and binder Nafion were applied to a substrate (9cm) at a ratio of 9:1. 2 On carbon felt or bipolar plates, the loading is 2 mg / cm³. 2 The preferred positive electrode substrate is carbon felt;

[0059] The porous carbon material includes microporous and mesoporous carbon materials. Preferably, the porous carbon material includes one or more of activated carbon, carbon nanotubes, and graphene.

[0060] The negative electrode of the zinc-bromine flow battery is 9cm. 2 Carbon felt or bipolar plate, with the same substrate material as the positive electrode;

[0061] The diaphragm is selected from microporous membranes and Nafion membranes, preferably microporous membranes;

[0062] This zinc-bromine flow battery maintains an energy efficiency of over 95% at room temperature even at -20°C, demonstrating excellent low-temperature performance and high energy efficiency. It can operate efficiently and stably over a wide temperature range, providing reliable energy storage support for the power grid, effectively addressing fluctuations in power demand and unexpected events, and improving the stability and resilience of the power grid.

[0063] Example 1

[0064] A method for preparing a low-temperature resistant flow battery electrolyte, comprising:

[0065] Place 95g of deionized water and 5g of ethylene glycol in a beaker, stir and mix well to obtain an ethylene glycol solution;

[0066] Weigh out 56.3g of zinc bromide, 14.9g of potassium chloride, and 1.4g of delphinidin, add ethylene glycol solution to make up to 100ml, and obtain the electrolyte for a low-temperature flow battery; wherein the concentration of zinc bromide is 2.5mol / L, the concentration of potassium chloride is 2mol / L, and the concentration of delphinidin is 0.05mol / L.

[0067] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above.

[0068] The zinc-bromine flow battery assembly process is as follows:

[0069] Porous carbon material and binder Nafion were coated onto a 9cm layer at a mass ratio of 9:1. 2 On carbon felt (5mm thick), the loading was 2 mg / cm³. 2 A zinc-bromine flow battery is obtained by using a carbon felt as the positive electrode and a microporous membrane as the separator, and loading a low-temperature resistant flow electrolyte into the positive and negative electrode storage tanks, with 50 ml of electrolyte in each tank, forming a reflux.

[0070] Example 2

[0071] A method for preparing a low-temperature resistant flow battery electrolyte, comprising:

[0072] Place 92g of deionized water and 8g of ethylene glycol in a beaker, stir and mix well to obtain an ethylene glycol solution;

[0073] Weigh out 51.8g of zinc bromide, 7.5g of potassium chloride, and 5.7g of delphinidin, add ethylene glycol solution to make up to 100ml to obtain the electrolyte for a low-temperature flow battery; wherein the concentration of zinc bromide is 2.3mol / L, the concentration of potassium chloride is 1mol / L, and the concentration of delphinidin is 0.2mol / L.

[0074] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0075] Example 3

[0076] A method for preparing a low-temperature resistant flow battery electrolyte, comprising:

[0077] Place 92g of deionized water and 8g of ethylene glycol in a beaker, stir and mix well to obtain an ethylene glycol solution;

[0078] Weigh out 45g of zinc bromide, 11.2g of potassium chloride and 2.9g of delphinidin, add ethylene glycol solution to make up to 100ml to obtain the electrolyte for a low-temperature flow battery; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L and the concentration of delphinidin is 0.1mol / L.

[0079] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0080] Example 4

[0081] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0082] Place 95g of deionized water and 5g of ethylene glycol in a beaker, stir and mix well to obtain an ethylene glycol solution;

[0083] Weigh out 45g of zinc bromide, 11.2g of potassium chloride and 5.7g of delphinidin, add ethylene glycol solution to make up to 100ml to obtain the electrolyte for a low-temperature flow battery; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L and the concentration of delphinidin is 0.2mol / L.

[0084] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0085] Example 5

[0086] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0087] Place 92g of deionized water and 8g of ethylene glycol in a beaker, stir and mix well to obtain an ethylene glycol solution;

[0088] Weigh out 45g of zinc bromide, 11.2g of potassium chloride and 5.7g of delphinidin, add ethylene glycol solution to make up to 100ml to obtain the electrolyte for a low-temperature flow battery; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L and the concentration of delphinidin is 0.2mol / L.

[0089] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0090] Example 6

[0091] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0092] Place 90g of deionized water and 10g of ethylene glycol in a beaker, stir and mix well to obtain an ethylene glycol solution;

[0093] Weigh out 45g of zinc bromide, 11.2g of potassium chloride and 5.7g of delphinidin, add ethylene glycol solution to make up to 100ml to obtain the electrolyte for a low-temperature flow battery; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L and the concentration of delphinidin is 0.2mol / L.

[0094] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0095] Example 7

[0096] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0097] Place 92g of deionized water and 8g of 1,2-propanediol in a beaker, stir and mix well to obtain a 1,2-propanediol solution;

[0098] Weigh 45g of zinc bromide, 11.2g of potassium chloride, and 5.7g of delphinidin into a beaker, add 1,2-propanediol solution to make up to 100ml, and obtain the low-temperature flow battery electrolyte; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L, and the concentration of delphinidin is 0.2mol / L.

[0099] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0100] Example 8

[0101] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0102] Place 92g of deionized water and 8g of methanol in a beaker, stir and mix well to obtain a methanol solution;

[0103] Weigh 45g of zinc bromide, 11.2g of potassium chloride, and 5.7g of delphinidin, add them to methanol solution and bring the volume to 100ml to obtain a low-temperature flow battery electrolyte; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L, and the concentration of delphinidin is 0.2mol / L.

[0104] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0105] Example 9

[0106] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0107] Place 92g of deionized water and 8g of glycerin in a beaker, stir and mix well to obtain a glycerin solution;

[0108] Weigh out 45g of zinc bromide, 11.2g of potassium chloride and 5.7g of delphinidin, add glycerol solution to make up to 100ml to obtain the electrolyte for a low-temperature flow battery; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L and the concentration of delphinidin is 0.2mol / L.

[0109] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0110] Example 10

[0111] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0112] Place 92g of deionized water and 8g of 2-propanol in a beaker, stir and mix well to obtain a 2-propanol solution;

[0113] Weigh out 45g of zinc bromide, 11.2g of potassium chloride and 5.7g of delphinidin, add 2-propanol solution and make up to 100ml to obtain the electrolyte for a low-temperature flow battery; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L and the concentration of delphinidin is 0.2mol / L.

[0114] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0115] Example 11

[0116] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0117] Place 90g of deionized water and 10g of ethylene glycol in a beaker and stir to mix evenly to obtain an ethylene glycol solution.

[0118] Weigh out 45g of zinc bromide, 11.2g of potassium chloride and 6.1g of geranium pigment, add ethylene glycol solution to make up to 100ml to obtain the electrolyte for a low-temperature flow battery; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L and the concentration of geranium pigment is 0.2mol / L.

[0119] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0120] Example 12

[0121] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0122] Place 90g of deionized water and 10g of 1,2-propanediol in a beaker, stir and mix well to obtain a 1,2-propanediol solution;

[0123] Weigh out 45g of zinc bromide, 11.2g of potassium chloride and 6.1g of geranium pigment, add 1,2-propanediol solution to make up to 100ml, stir well to obtain the low-temperature flow battery electrolyte; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L and the concentration of geranium pigment is 0.2mol / L.

[0124] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0125] Example 13

[0126] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0127] Place 92g of deionized water and 8g of methanol in a beaker, stir and mix well to obtain a methanol solution;

[0128] Weigh out 51.8 g of zinc bromide, 7.5 g of potassium chloride, and 6.8 g of cornflower pigment, add methanol solution to make up to 100 ml, and obtain the low-temperature flow battery electrolyte; wherein the concentration of zinc bromide is 2.3 mol / L, the concentration of potassium chloride is 1.0 mol / L, and the concentration of cornflower pigment is 0.2 mol / L.

[0129] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0130] Example 14

[0131] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0132] Place 92g of deionized water and 8g of methanol in a beaker, stir and mix well to obtain a methanol solution;

[0133] Weigh out 51.8 g of zinc bromide, 5.8 g of sodium chloride, and 6.8 g of cornflower pigment, add methanol solution and make up to 100 ml to obtain a low-temperature flow battery electrolyte; wherein the concentration of zinc bromide is 2.3 mol / L, the concentration of sodium chloride is 1.0 mol / L, and the concentration of cornflower pigment is 0.2 mol / L.

[0134] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0135] Example 15

[0136] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0137] Place 95g of deionized water and 5g of 2-propanol in a beaker and stir to mix evenly to obtain a 2-propanol solution.

[0138] Weigh out 56.3g of zinc bromide, 14.9g of potassium chloride, and 1.4g of delphinidin, add 2-propanol solution to make up to 100ml to obtain the electrolyte for a low-temperature flow battery; wherein the concentration of zinc bromide is 2.5mol / L, the concentration of potassium chloride is 2.0mol / L, and the concentration of delphinidin is 0.05mol / L.

[0139] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0140] Example 16

[0141] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0142] Place 95g of deionized water and 5g of 2-propanol in a beaker and stir to mix evenly to obtain a 2-propanol solution.

[0143] Weigh out 56.3g of zinc bromide, 10.7g of ammonium chloride and 1.4g of delphinidin, add 2-propanol solution and make up to 100ml to obtain the low-temperature flow battery electrolyte; wherein the concentration of zinc bromide is 2.5mol / L, the concentration of ammonium chloride is 2.0mol / L and the concentration of delphinidin is 0.05mol / L.

[0144] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0145] Example 17

[0146] A method for preparing a low-temperature resistant zinc-bromine flow battery electrolyte, comprising:

[0147] Place 92g of deionized water and 8g of ethylene glycol in a beaker, stir and mix well to obtain an ethylene glycol solution;

[0148] Weigh out 45g of zinc bromide, 7.5g of potassium chloride, 2.9g of sodium chloride, and 5.7g of delphinidin, add ethylene glycol solution to make up to 100ml to obtain the low-temperature flow battery electrolyte; wherein the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1mol / L, the concentration of sodium chloride is 0.5mol / L, and the concentration of delphinidin is 0.2mol / L.

[0149] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0150] Comparative Example 1

[0151] Except for the absence of the co-solvent ethylene glycol, the types and proportions of the electrolyte, supporting electrolyte, and 2-phenylbenzopyran-type cationic additives added in Comparative Example 1 are the same as those in Example 3. The preparation method of the electrolyte provided in Comparative Example 1 includes the following steps:

[0152] Weigh out 45g of zinc bromide, 11.2g of potassium chloride, and 2.9g of delphinidin, add deionized water to a final volume of 100ml to obtain the electrolyte; the concentration of zinc bromide is 2.0mol / L, the concentration of potassium chloride is 1.5mol / L, and the concentration of delphinidin is 0.1mol / L.

[0153] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and an electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0154] Comparative Example 2

[0155] Except for the absence of 2-phenylbenzopyran-type cationic additives, the types and proportions of electrolytes, supporting electrolytes, and alcohol solvents added in Comparative Example 2 and Example 6 are the same. The electrolyte preparation method includes the following steps:

[0156] Place 90g of deionized water and 10g of ethylene glycol in a beaker, stir and mix well to obtain an ethylene glycol solution;

[0157] Weigh 45g of zinc bromide and 11.2g of potassium chloride, add ethylene glycol solution to make up to 100ml to obtain the electrolyte; wherein the concentration of zinc bromide is 2.0mol / L and the concentration of potassium chloride is 1.5mol / L.

[0158] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0159] Comparative Example 3

[0160] Except for the absence of 2-phenylbenzopyran-type cationic additives and alcohol solvents, the types and proportions of electrolytes and supporting electrolytes added in Comparative Example 3 and Example 6 are the same. The electrolyte preparation method includes the following steps:

[0161] Weigh 45g of zinc bromide and 11.2g of potassium chloride, add deionized water to a final volume of 100ml to obtain the electrolyte; wherein the concentration of zinc bromide is 2.0mol / L and the concentration of potassium chloride is 1.5mol / L.

[0162] A zinc-bromine flow battery includes a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described above. The assembly process of the zinc-bromine flow battery is the same as in Example 1.

[0163] The zinc-bromine flow batteries prepared in Examples 1-17 and Comparative Examples 1-3 were subjected to charge-discharge tests at 25°C and -20°C, respectively. The test conditions were: current density 20 mA / cm². 2 The charging time was 4 hours, the discharge cutoff voltage was 0.5V, and the positive and negative electrolytes were 50 ml (the same conditions were used for testing the battery performance in both the example and comparative examples). The coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) of the zinc-bromine flow battery were tested. When testing the performance of the zinc-bromine flow battery at -20℃, the battery was placed in a high and low temperature chamber for 6 hours before the charge and discharge test. The test results are shown in the table below:

[0164]

[0165] As shown in the table above, the zinc-bromine flow electrolyte prepared in this invention has a coulombic efficiency of 93.6%-97.8%, a voltage efficiency of 69.7%-80.3%, and an energy efficiency of 74.1%-84.4% at room temperature. This is similar to Comparative Example 1, but significantly better than Comparative Examples 2 and 3. This indicates that adding 2-phenylbenzopyran-type cationic additives to the electrolyte can effectively improve the performance of the zinc-bromine flow battery. At -20℃, the coulombic efficiency is 80.6%-90.9%, the voltage efficiency is 57.8%-71.0%, and the energy efficiency is 62.5%-78.5%. In contrast, Comparative Examples 1 and 3, which did not contain alcohol solvents, could not operate at -20℃, indicating that adding alcohol solvents to the electrolyte can effectively improve the low-temperature performance of the zinc-bromine flow battery.

[0166] Comparing Examples 4, 5, and 6, when the alcohol solvent ratio is in the range of 5wt%-10wt%, the energy efficiency retention rate at low temperature (compared to room temperature) shows a trend of first increasing and then remaining unchanged as the alcohol solvent ratio increases. However, the coulombic efficiency, voltage efficiency, and energy efficiency at room temperature show a trend of first increasing and then decreasing. The overall performance is optimal when the alcohol solvent ratio is 8wt%.

[0167] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0168] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Claims

1. A low-temperature resistant flow battery electrolyte, characterized in that, The electrolyte comprises water, an electrolyte salt, a supporting electrolyte, a 2-phenylbenzopyran-type cationic additive, and an alcohol solvent; wherein the concentration of the 2-phenylbenzopyran-type cationic additive in the low-temperature flow battery electrolyte is 0.05-0.2 mol / L; the alcohol solvent is one or two of ethylene glycol, 1,2-propanediol, methanol, glycerol, and 2-propanol, and the mass of the alcohol solvent is 5%-10% of the sum of the mass of the alcohol solvent and water; the 2-phenylbenzopyran-type cationic additive is a 2-phenylbenzopyran-type cationic compound with the following structural formula: Among them, R1, R2, R3 and the three R4s contain at least four -OH groups, and the rest are -H or -OCH3; the 2-phenylbenzopyran-type cationic additive is one of delphinidin, geranium pigment and cornflower pigment; the electrolyte salt is zinc bromide, and the concentration of zinc bromide in the low-temperature flow battery electrolyte is 2-2.5 mol / L; the supporting electrolyte is one or two of potassium chloride, sodium chloride and ammonium chloride, and the concentration of the supporting electrolyte in the low-temperature flow battery electrolyte is 1.0-2.0 mol / L.

2. A method for preparing a low-temperature resistant flow battery electrolyte as described in claim 1, characterized in that, Includes the following steps: Water and an alcohol solvent are mixed thoroughly to obtain an alcohol solution; An electrolyte salt, a supporting electrolyte, and a 2-phenylbenzopyran-type cationic additive are mixed to form a mixture; Add an alcohol solution to the mixture and stir until homogeneous to obtain a low-temperature flow battery electrolyte.

3. A zinc-bromine flow battery, comprising a positive electrode, a negative electrode, a separator, and a low-temperature resistant flow battery electrolyte as described in claim 1; wherein the positive electrode, the negative electrode, and the separator are all immersed in the low-temperature resistant flow battery electrolyte, and the positive electrode and the negative electrode are physically isolated by the separator.

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