A positive electrolyte of aqueous organic flow battery and application thereof

Abstract

This invention discloses a positive electrode electrolyte for an aqueous organic flow battery and its application. By adding 0.1~3.0 wt% of an additive with moderate oxidizing power to a positive electrode electrolyte containing piperidine oxygen radical derivatives, the content of hydroxylamine in the electrolyte is effectively reduced, the influence of hydroxylamine on battery performance is weakened, and the stability and capacity utilization of the aqueous organic flow battery are improved. The additives described in this invention are easy to obtain and require small amounts, making them suitable for large-scale applications.

Description

Technical Field

[0001] This invention belongs to the field of energy storage flow battery technology, specifically relating to a positive electrode electrolyte for an aqueous organic flow battery and its application. Background Technology

[0002] In recent years, new energy sources such as wind and solar power have developed rapidly, but their further market penetration has been limited due to their instability and uncontrollability. Therefore, large-scale energy storage technology has emerged. Among various electrochemical energy storage technologies, flow battery technology has received widespread attention due to its ability to independently design energy and power. Although the most mature vanadium-based flow battery has achieved a certain degree of commercialization, its low energy density, narrow operating temperature threshold, and high vanadium cost limit its further development. Addressing the problems of vanadium-based flow batteries, aqueous organic flow batteries have developed rapidly, with wide-ranging raw material sources, highly tunable molecular structures, and mild operating environments. Among many organic compounds with redox electrochemical activity, 2,2,6,6-tetramethylpiperidine oxygen radical derivatives have high electrode potential, high solubility, and excellent electrochemical reversibility and stability, making them one of the preferred positive electrode active materials for organic flow batteries. In industrial production, the hydroxylamine byproduct generated during piperidine oxidation is difficult to completely remove. Figure 1 As shown, during battery charging, hydroxylamine can lose two electrons to form an ammonium ion derivative. However, during discharge, due to the slow kinetics of the conversion reaction between piperidine oxygen radicals and hydroxylamine, it is difficult for the piperidine oxygen radicals to return to the hydroxylamine state. Therefore, the presence of hydroxylamine results in low coulombic efficiency in the first charge cycle and reduced effective electrolyte utilization. On the other hand, during the first charge cycle, the conversion of hydroxylamine to piperidine oxygen radicals releases hydrogen ions, causing the solution pH to become acidic. Figure 2 As shown, under acidic conditions, piperidine oxygen radicals undergo a disproportionation reaction to generate hydroxylamine and the corresponding ammonium oxo ions. Since hydroxylamine is not utilized during battery discharge, the apparent capacity of the battery decays rapidly. One way to remove hydroxylamine is to add alkali to adjust the pH to near neutral after the first charge cycle. However, under actual conditions, ammonium oxo ions and the substituents on the piperidine ring (often quaternary ammonium ions) also exhibit acidity in aqueous solution. Furthermore, ammonium oxo ions react with hydroxide ions. Therefore, this method is unlikely to fundamentally solve the impact of the presence of hydroxylamine on battery capacity utilization and cycle stability. Summary of the Invention

[0003] To address the aforementioned problems, this invention discloses a positive electrode electrolyte for an aqueous organic flow battery and its application.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: A positive electrode electrolyte for an aqueous organic flow battery, the positive electrode electrolyte comprising an active substance 2,2,6,6-tetramethylpiperidine oxygen radical derivative, a supporting electrolyte, water, and an additive, wherein the additive is an additive with moderate oxidizing power, capable of oxidizing hydroxylamine to piperidine oxygen radical without further oxidation; the additive with moderate oxidizing power includes any one of hydrogen peroxide, peracetic acid, hypochlorous acid, sodium hypochlorite, sodium percarbonate, sodium perborate, and potassium perborate; the supporting electrolyte includes any one of sodium chloride, potassium chloride, aluminum chloride, magnesium chloride, ammonium chloride, tetramethylammonium chloride, and tetraethylammonium chloride.

[0005] Furthermore, the additive with moderate oxidizing power is preferably sodium hypochlorite.

[0006] Furthermore, the sodium hypochlorite comprises either a solid or an aqueous solution, and its effective molar amount does not exceed the content of hydroxylamine in the electrolyte.

[0007] Further, the amount of sodium hypochlorite solid added is 0.1~3.0 wt%; the concentration of sodium hypochlorite solution is 0.5~1.5 mol / L, and the amount of sodium hypochlorite solution added is 1~30% of the volume of the electrolyte.

[0008] Furthermore, the preferred amount of sodium hypochlorite solid added is 0.075g, 0.15g, or 2g; the preferred concentration of the sodium hypochlorite aqueous solution is 0.946mol / L, and the preferred volume is 6.8ml.

[0009] Furthermore, the concentration of the 2,2,6,6-tetramethylpiperidine oxygen radical derivative in the positive electrode electrolyte is 1.0~2.0 mol / L.

[0010] Furthermore, the supporting electrolyte is preferably sodium chloride.

[0011] Furthermore, the concentration of the supporting electrolyte is 0~1.0 mol / L.

[0012] Furthermore, the water is deionized water.

[0013] Furthermore, the present invention also provides the application of the above-mentioned positive electrode electrolyte in an aqueous organic flow battery.

[0014] The beneficial effects of this invention are as follows: (1) The additive used in this invention can convert hydroxylamine into piperidine oxygen free radicals, which can be utilized in the battery charge-discharge cycle, thereby improving the battery capacity utilization rate. (2) The additives used in this invention reduce the hydroxylamine content in the positive electrode electrolyte, making the battery operation more stable; (3) The additives of the present invention are low in cost and simple in process, and are one of the most effective methods to improve battery capacity utilization. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the interconversion between piperidine oxygen free radicals and hydroxylamine during the charging and discharging process; Figure 2 This is a schematic diagram of the disproportionation reaction of piperidine oxygen free radicals under acidic conditions; Figure 3 The battery pack charge-discharge test diagrams for Comparative Example 1 and Examples 1-4 of this invention are shown. Detailed Implementation

[0016] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0017] Example 1 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 0.075 g of industrial-grade sodium hypochlorite solid to the positive electrode electrolyte and stir to dissolve. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0018] Battery pack charge / discharge test diagram as shown below Figure 3 As shown.

[0019] Example 2 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 0.075 g of industrial-grade sodium hypochlorite solid to the positive electrode electrolyte and sonicate for 30 min. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0020] Battery pack charge / discharge test diagram as shown below Figure 3 As shown.

[0021] Example 3 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 0.15 g of industrial-grade sodium hypochlorite solid to the positive electrode electrolyte and sonicate for 30 min. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0022] Battery pack charge / discharge test diagram as shown below Figure 3 As shown.

[0023] Example 4 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add the clear solution obtained by dissolving 2 g of industrial-grade sodium hypochlorite solid in water and filtering out insoluble matter to the positive electrode electrolyte. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0024] Battery pack charge / discharge test diagram as shown below Figure 3 As shown.

[0025] Example 5 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 6.8 ml of 0.946 mol / L sodium hypochlorite solution to the positive electrode electrolyte and sonicate for 30 min. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0026] Example 6 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 6.8 ml of 0.946 mol / L sodium hypochlorite solution to the positive electrode electrolyte, stir, and let stand for 30 min. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0027] Example 7 Prepare 80 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 6.8 ml of 0.946 mol / L sodium hypochlorite solution to the positive electrode electrolyte, stir, and let stand for 30 min. Prepare 80 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0028] Example 8 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylquaternary ammonium)piperidine oxygen free radical chloride as the positive electrode active material and 1.0 mol / L sodium chloride as the supporting electrolyte, and test its conductivity. Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylquaternary ammonium)piperidine oxygen free radical chloride as the positive electrode active material and 1.0 mol / L potassium chloride as the supporting electrolyte, and test its conductivity. Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylquaternary ammonium)piperidine oxygen free radical chloride as the positive electrode active material and 1.0 mol / L aluminum chloride as the supporting electrolyte, and test its conductivity. Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylquaternary ammonium)piperidine oxygen free radical chloride as the positive electrode active material and 1.0 mol / L magnesium chloride as the supporting electrolyte, and test its conductivity. Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylquaternary ammonium)piperidine oxygen free radical chloride as the positive electrode active material and 1.0 mol / L ammonium chloride as the supporting electrolyte, and test its conductivity. Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylquaternary ammonium)piperidine oxygen free radical chloride as the positive electrode active material and 1.0 mol / L tetramethylammonium chloride as the supporting electrolyte, and test its conductivity. Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylquaternary ammonium)piperidine oxygen free radical chloride as the positive electrode active material and 1.0 mol / L tetraethylammonium chloride as the supporting electrolyte, and test its conductivity.

[0029] Example 9

[0030] Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 2 g of 1 mol / L hydrogen peroxide solution to the positive electrode electrolyte. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0031] Example 10 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 2 g of 1 mol / L peracetic acid solution to the positive electrode electrolyte. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0032] Example 11 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 2 g of 1 mol / L hypochlorous acid solution to the positive electrode electrolyte. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0033] Example 12 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 2 g of sodium percarbonate solid to the positive electrode electrolyte. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0034] Example 13 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 2 g of sodium perborate solid to the positive electrode electrolyte. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0035] Example 14 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Add 2 g of potassium perborate solid to the positive electrode electrolyte. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0036] Comparative Example 1 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Prepare 20 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, a 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0037] Battery pack charge / discharge test diagram as shown below Figure 3 As shown.

[0038] Comparative Example 2 Prepare 80 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen radical chloride as the positive electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Prepare 80 ml of negative electrode electrolyte, using 1.0 mol / L N,N'-dimethyl-4,4'-bipyridine dichloride as the negative electrode active material and 1.0 mol / L NaCl as the supporting electrolyte. Use 4 mm thick carbon felt, a 3 mm spacing between the membrane plates, and an active area of ​​5 cm². 2 The above electrolyte was tested using an anion exchange membrane. The test procedure was as follows: (1) Charge with a constant current of 200mA and a charging cutoff voltage of 1.5V; charge with a constant voltage of 1.5V and a cutoff current of 10mA; discharge with a constant current of 200mA and a discharge cutoff voltage of 0.9V. (2) Constant current 500mA charging, charging cut-off voltage is 1.5V, constant voltage charging, cut-off voltage is 10mA; constant current 500mA discharging, discharging cut-off voltage is 0.9V; (3) Repeat step (2) 50 times.

[0039] Comparative Example 3 Prepare 20 ml of positive electrode electrolyte, using 1.0 mol / L 2,2,6,6-tetramethyl-4-(N,N,N-trimethylammonium)piperidine oxygen free radical chloride as the positive electrode active material, without adding supporting electrolyte, and test its conductivity; Table 1 shows that adding sodium hypochlorite to the positive electrode electrolyte can convert hydroxylamine into piperidine oxygen radicals, which then participate in the battery's charge-discharge cycle, thus reducing the hydroxylamine content and improving the electrolyte utilization rate. On the other hand, Figure 3 Battery charge-discharge cycle data indicate that the addition of sodium hypochlorite promotes the operational stability of the battery.

[0040] As shown in Table 2, adding supporting electrolytes to a 1 mol / L positive electrode electrolyte can effectively improve the conductivity of the electrolyte. Among them, sodium chloride and ammonium chloride have the best effect. Considering that ammonium chloride is irritating to the skin and mucous membranes and can cause liver and kidney damage, sodium chloride, which is healthy, harmless and readily available, was chosen as the supporting electrolyte.

[0041] As shown in Table 3, adding an oxidant with moderate oxidizing power to the 1 mol / L positive electrode electrolyte can effectively reduce the hydroxylamine content in the electrolyte. Sodium hypochlorite has the best effect and has the least impact on the battery charge and discharge efficiency. Therefore, sodium hypochlorite is the preferred additive.

[0042] .

[0043] .

[0044] .

[0045] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A positive electrolyte for aqueous organic flow batteries, characterized in that: The positive electrode electrolyte comprises an active substance, 2,2,6,6-tetramethylpiperidine oxygen radical derivative, a supporting electrolyte, water, and additives. The additives are moderately oxidizing agents capable of oxidizing hydroxylamine to piperidine oxygen radicals without further oxidation. The moderately oxidizing additives include any one of hydrogen peroxide, peracetic acid, hypochlorous acid, sodium hypochlorite, sodium percarbonate, sodium perborate, and potassium perborate. The supporting electrolyte includes any one of sodium chloride, potassium chloride, aluminum chloride, magnesium chloride, ammonium chloride, tetramethylammonium chloride, and tetraethylammonium chloride.

2. The positive electrode electrolyte of an aqueous organic flow battery as described in claim 1, characterized in that: The additive with moderate oxidizing power is preferably sodium hypochlorite.

3. The positive electrode electrolyte of an aqueous organic flow battery as described in claim 1, characterized in that: The sodium hypochlorite comprises either a solid or an aqueous solution, and its effective molar amount does not exceed the content of hydroxylamine in the electrolyte.

4. The positive electrode electrolyte of an aqueous organic flow battery as described in claim 3, characterized in that: When the sodium hypochlorite is in solid form, the amount added is 0.1~3.0 wt%; when the sodium hypochlorite is in aqueous solution form, the concentration of the aqueous solution is 0.5~1.5 mol / L, and the amount of the aqueous solution added is 1~30% of the volume of the electrolyte.

5. The positive electrode electrolyte of an aqueous organic flow battery as described in claim 4, characterized in that: When the sodium hypochlorite is a solid, the amount of solid added is any one of 0.075g, 0.15g, or 2g; when the sodium hypochlorite is an aqueous solution, the concentration of the aqueous solution is 0.946mol / L and the volume is 6.8ml.

6. The positive electrode electrolyte of an aqueous organic flow battery as described in claim 1, characterized in that: The concentration of the 2,2,6,6-tetramethylpiperidine oxygen radical derivative in the positive electrode electrolyte is 1.0~2.0 mol / L.

7. The positive electrode electrolyte of an aqueous organic flow battery as described in claim 1, characterized in that: The concentration of the supporting electrolyte is 0~1.0 mol / L.

8. The positive electrode electrolyte of an aqueous organic flow battery as described in claim 1, characterized in that: The supporting electrolyte is preferably sodium chloride.

9. The positive electrode electrolyte of an aqueous organic flow battery according to any one of claims 1-7, characterized in that: The positive electrode electrolyte is used in aqueous organic flow batteries.

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