Bromine chromium flow battery

Abstract

The invention relates to the technical field of flow batteries, in particular to a bromine-chromium flow battery. A positive electrode electrolyte of the flow battery comprises a bromine-containing compound, a chromium salt, an inorganic acid and a complexing agent, a negative electrode electrolyte of the flow battery comprises a bromine-containing compound, a chromium salt and an inorganic acid, a negative electrode redox couple is Cr < 3 + > / Cr < 2 + >, a positive electrode redox couple is Br <-> / Br2, the complexing agent of the positive electrode electrolyte is one or a mixture of more of amino bromide, pyridyl bromide and tourmaline-based bromide. The bromine-chromium flow battery is high in stability and low in cost, the complexing agent is selected to be added into the positive electrode electrolyte, the situation that the battery performance is reduced due to the fact that bromine gas overflows and is separated out from the positive electrode electrolyte under the high-temperature condition is avoided, the bromine-chromium flow battery can run at the high temperature, and meanwhile the activity and stability of the bromine-chromium flow battery are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a bromine-chromium liquid flow battery. Background Art

[0002] With the development of economy, the demand for energy is increasing, and the environmental problems caused by the large consumption of fossil energy are becoming increasingly prominent. Large-scale utilization of renewable energy and realization of energy diversification have become important strategies for energy security and sustainable development in countries around the world. However, renewable energy such as wind energy and solar energy are discontinuous and unstable, making their direct use difficult. Therefore, the use of energy storage technology to achieve continuous supply of renewable energy has become the key to solving the above problems. Liquid flow batteries have become one of the most promising technologies in the large-scale energy storage market due to their flexible design (capacity and power are designed separately), good safety, and long design life.

[0003] At present, the more mature liquid flow systems include all-vanadium liquid flow batteries and iron-chromium liquid flow batteries. However, all-vanadium liquid flow batteries face high costs, which have a certain impact on commercial applications. In addition, the deactivation of chromium electrodes in the electrolyte of the iron-chromium liquid flow battery system leads to electrolyte deactivation, low efficiency, and easy hydrogen evolution. These problems need to be solved. Therefore, it is particularly important to develop new environmentally friendly and highly stable liquid flow batteries.

[0004] Bromine-chromium flow batteries use bromine and chromium, which are abundant in the earth's crust, as active materials. The electrolyte cost is low, and its potential window is large and its solubility is high, so its theoretical energy density is high. Therefore, bromine-chromium flow batteries are expected to become one of the preferred technologies for the new generation of large-scale energy storage technology. However, the main problem with bromine-chromium flow batteries at present is the overflow of bromine produced after the positive electrode is charged, which not only causes the capacity loss of the battery, but also causes corrosion of the core battery components such as the pump pipeline and reduces the battery life. In response to the above problems, patent CN 18507788 A discloses a bromine-chromium flow battery based on a high-concentration hydrogen bromide solution, which uses excess bromide ions to complex with bromide ions produced during the charging process to form polybromide ions that are stably present in the electrolyte. However, excess bromide ions will not only reduce the utilization rate of the battery electrolyte, but the volatility of high-concentration hydrogen bromide in the electrolyte will also cause the loss of the core components of the battery. Summary of the invention

[0005] Based on the above technical problems, the present invention provides a new type of bromine-chromium liquid flow battery, which has the characteristics of high electrode activity, low corrosion, long cycle life, stable performance, simple structure and manufacturing process.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A bromine-chromium liquid flow battery, the battery comprising a battery module, a positive electrode electrolyte storage tank, a negative electrode electrolyte storage tank, a circulation pump I, a circulation pump II, a positive electrode circulation pipeline, and a negative electrode circulation pipeline; the battery module is formed by one or more single batteries connected in series; the single battery comprises an electrode end plate, a bipolar plate, an electrode, a diaphragm, and an electrode frame; the positive electrode electrolyte storage tank is connected to the positive electrode of the battery module via the positive electrode circulation pipeline; the negative electrode electrolyte storage tank is connected to the negative electrode of the battery module via the negative electrode circulation pipeline; the positive electrode electrolyte comprises a bromine-containing compound, a chromium salt, an inorganic acid, and a complexing agent; the negative electrode electrolyte comprises a bromine-containing compound, a chromium salt, and an inorganic acid; the negative electrode redox couple is Cr 3+ / Cr 2+ , the positive electrode redox couple is Br - / Br2; the complexing agent is one or a mixture of amino bromide, pyridyl bromide and malinyl bromide.

[0008] In the above technical solution, further, the bromine-containing compound is one or more of potassium bromide, sodium bromide, lithium bromide, chromium bromide, and hydrobromic acid;

[0009] The chromium salt is one or more of chromium chloride, chromium bromide, chromium iodide, chromium sulfate, chromium nitrate, and chromium phosphate;

[0010] The inorganic acid is one of hydrochloric acid and hydrobromic acid.

[0011] In the above technical solution, further, the amino bromide is N-methyl-N, N-bis(2-hydroxyethyl)-1-propylamine bromide (PMDA);

[0012] The pyridyl bromide is one or both of 1-ethylpyridine-1-bromide ([C2Py]Br) and 1-hexylpyridine-1-bromide ([C6Py]Br);

[0013] The malein bromide is one or both of 4-methylethylmorpholine bromide (MEM-Br) and quaternary ammonium 4-methylpropylmorpholine bromide (MPM-Br).

[0014] In the above technical solution, further, during charging, the positive electrode electrolyte is transported from the positive electrode electrolyte storage tank to the positive electrode via a circulation pump I, and the negative electrode electrolyte is transported from the negative electrode electrolyte storage tank to the negative electrode via a circulation pump II, Cr 3+ The ions are reduced to Cr at the negative electrode. 2+ Ion, Br - Ions are oxidized to Br2 at the positive electrode; during discharge, Cr 2+ The ions are oxidized to Cr at the negative electrode. 3+ ions, return to the negative electrode electrolyte storage tank through circulation pump II, and Br2 is reduced to Br at the positive electrode. -The ions return to the positive electrode electrolyte storage tank through circulation pump I.

[0015] In the above technical solution, further, in the positive electrode electrolyte, the concentration of bromide ions is 0.1 to 6 mol / L, the concentration of chromium ions is 0.1 to 3 mol / L, the concentration of acid is 0.1 to 6 mol / L, and the concentration of complexing agent is 0.1 to 1 mol / L;

[0016] In the negative electrode electrolyte, the concentration of bromide ions is 0.1 to 6 mol / L, the concentration of chromium ions is 0.1 to 3 mol / L, and the concentration of acid is 0.1 to 6 mol / L.

[0017] In the above technical solution, further, the operating temperature of the liquid flow battery is 25-70°C.

[0018] In the above technical solution, further, both the positive electrode and the negative electrode are made of metal or carbon material with a plate structure or a porous structure, and the carbon material includes carbon cloth, carbon paper or carbon felt.

[0019] In the above technical solution, further, the diaphragm is an ion exchange membrane or a porous membrane.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention selects organic complexing agents such as amine bromide, pyridyl bromide, and malinyl bromide as positive electrode electrolyte additives. Through the strong coordination effect between organic bromide molecules and bromine element, the battery performance degradation caused by the overflow and precipitation of bromine gas from the positive electrode electrolyte under high temperature conditions is avoided, so that the bromine-chromium flow battery can be operated at high temperature, while the activity and stability of the bromine-chromium flow battery are improved.

[0022] 2. The present invention uses a bromine electrode pair and a chromium electrode pair to not only provide a new type of battery system, but also improve the complex structure of bromide ions to chromium ions in water, so the cycle life and battery performance of the battery are also improved.

[0023] 3. The bromine-chromium liquid flow battery of the present invention has a simple structure, and the electrolyte is easy to obtain and has low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of a bromine-chromium liquid flow battery;

[0025] In the figure: 1, positive terminal plate, 2, negative terminal plate, 3, positive electrode, 4, negative electrode, 5, diaphragm, 6, circulation pump I, 7, circulation pump II, 8, positive electrolyte storage tank, 9, negative electrolyte storage tank;

[0026] Figure 2 The bromine-chromium redox flow battery of Example 1-5 is at 40 mA / cm2 Performance under current density conditions;

[0027] Figure 3 The bromine-chromium redox flow battery of Examples 6-8 and Comparative Example 2 at 40 mA / cm 2 Performance under current density conditions;

[0028] Figure 4 The bromine-chromium redox flow battery of Examples 9-11 is at 40 mA / cm 2 Performance under current density conditions;

[0029] Figure 5 The bromine-chromium flow battery of Comparative Example 1, Example 4, and Example 12 is 40 mA / cm 2 performance under current density conditions. DETAILED DESCRIPTION

[0030] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0031] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments, but the scope of the present invention is not limited thereto.

[0032] A bromine-chromium flow battery having a structure as follows Figure 1 As shown, it is composed of a battery module, a positive electrolyte storage tank 8, a negative electrolyte storage tank 9, a circulation pump I6, a circulation pump II7, a positive circulation pipeline and a negative circulation pipeline. The battery module is composed of one or more single batteries connected in series. The single battery is composed of electrode end plates (including positive end plates 1 and negative end plates 2), bipolar plates, electrodes (including positive electrodes 3 and negative electrodes 4), diaphragms 5, and electrode frames; the positive electrolyte storage tank 8 is connected to the positive electrode 3 of the battery module through the positive circulation pipeline, and the negative electrolyte storage tank 9 is connected to the negative electrode 4 of the battery module through the negative circulation pipeline. The negative electrode redox couple of the battery is Cr 3+ / Cr 2+ , the positive electrode redox couple is Br - / Br2. During charging, the positive electrode electrolyte and the negative electrode electrolyte are respectively transported to the positive electrode and the negative electrode from the positive electrode electrolyte storage tank 8 and the negative electrode electrolyte storage tank 9 via the circulation pump I6 and the circulation pump II7, respectively. 3+ The ions are reduced to Cr at the negative electrode. 2+ Ion, Br - Ions are oxidized to Br2 at the positive electrode; during discharge, Cr 2+ The ions are oxidized to Cr at the negative electrode. 3+ ions, and return to the negative electrode electrolyte storage tank 9 via the circulation pump II 7; Br2 is reduced to Br at the positive electrode -The ions return to the positive electrode electrolyte storage tank 8 via the circulation pump I6.

[0033] The positive electrode electrolyte includes a bromine-containing compound, a chromium salt, an inorganic acid and a complexing agent, wherein the concentration of bromide ions is 0.1 to 3 mol / L, the concentration of chromium ions is 0.1 to 3 mol / L, the concentration of acid is 0.1 to 6 mol / L, and the concentration of the complexing agent is 0.1 to 1 mol / L.

[0034] The negative electrode electrolyte includes a bromine-containing compound, a chromium salt and an inorganic acid, wherein the concentration of bromide ions is 0.1 to 3 mol / L, the concentration of chromium ions is 0.1 to 3 mol / L, and the concentration of the acid is 0.1 to 6 mol / L.

[0035] The operating temperature of flow batteries is 25-70°C.

[0036] The positive electrode 3 and the negative electrode 4 are both made of metal or carbon materials with plate-like or porous structures, and the carbon materials include carbon cloth, carbon paper, and carbon felt;

[0037] The diaphragm is an ion exchange membrane (Nafion 212).

[0038] Example 1

[0039] 1. Electrolyte configuration:

[0040] The positive electrode electrolyte is 30 ml, and the negative electrode electrolyte is 30 ml. The positive electrode electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide, 3 mol / L hydrochloric acid and 0.1 mol / L PMDA, and the negative electrode electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide and 3 mol / L hydrochloric acid.

[0041] 2.Battery assembly:

[0042] The single cell is assembled in the following order: positive electrode stainless steel end plate 1, positive electrode bipolar plate, positive electrode carbon felt electrode (6cm×8cm), separator 5 (Nafion212), negative electrode carbon felt electrode (6cm×8cm), negative electrode bipolar plate, and negative electrode stainless steel end plate 2.

[0043] 3.Battery test:

[0044] Charge and discharge at 45°C, electrolyte flow rate of 50 ml / min, constant current charge and discharge, charge and discharge current density of 40 mA cm -2 , the operating voltage is 0.7V to 1.5V.

[0045] Example 2

[0046] 1. Electrolyte configuration:

[0047] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide, 3 mol / L hydrochloric acid and 0.3 mol / L PMDA, and the negative electrolyte contains 1 mol / L chromium chloride, 1 mol / L chromium bromide, 3 mol / L sodium bromide and 3 mol / L hydrochloric acid.

[0048] 2.Battery assembly:

[0049] Same as Example 1.

[0050] 3.Battery test:

[0051] Charge and discharge at 45°C, electrolyte flow rate of 50 ml / min, constant current charge and discharge, charge and discharge current density of 40 mA cm -2 , the operating voltage is 0.7V to 1.5V.

[0052] Example 3

[0053] 1. Electrolyte configuration:

[0054] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide, 3 mol / L hydrochloric acid and 0.5 mol / L PMDA, and the negative electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide and 3 mol / L hydrochloric acid.

[0055] 2.Battery assembly:

[0056] Same as Example 1.

[0057] 3.Battery test:

[0058] Charge and discharge at 45°C, electrolyte flow rate of 50 ml / min, constant current charge and discharge, charge and discharge current density of 40 mA cm -2 , the operating voltage is 0.7V to 1.5V.

[0059] Example 4

[0060] 1. Electrolyte configuration:

[0061] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide, 3 mol / L hydrochloric acid and 0.8 mol / L PMDA, and the negative electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide and 3 mol / L hydrochloric acid.

[0062] 2.Battery assembly:

[0063] Same as Example 1.

[0064] 3.Battery test:

[0065] Charge and discharge at 45°C, electrolyte flow rate of 50 ml / min, constant current charge and discharge, charge and discharge current density of 40 mA cm -2 , the operating voltage is 0.7V to 1.5V.

[0066] Example 5

[0067] 1. Electrolyte configuration:

[0068] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide, 3 mol / L hydrochloric acid and 1 mol / L PMDA, and the negative electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide and 3 mol / L hydrochloric acid.

[0069] 2.Battery assembly:

[0070] Same as Example 1.

[0071] 3.Battery test:

[0072] Charge and discharge at 45°C, electrolyte flow rate of 50 ml / min, constant current charge and discharge, charge and discharge current density of 40 mA cm -2 , the operating voltage is 0.7V to 1.5V.

[0073] The battery performance of Examples 1-5 is as follows Figure 2 As shown in the figure, with the increase of PMDA concentration in the electrolyte, the battery coulombic efficiency, voltage efficiency and energy efficiency first increase and then decrease. This is because higher concentrations of PMDA can complex more bromine and reduce the overflow of bromine gas, thereby improving the performance of the battery. When the concentration is too high, PMDA is an organic solution, which has a certain effect on the viscosity of the electrolyte, increases its ohmic polarization and reduces the battery efficiency.

[0074] Example 6

[0075] 1. Electrolyte configuration:

[0076] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L chromium chloride, 3 mol / L sodium bromide, 3 mol / L hydrobromic acid and 0.5 mol / L PMDA, and the negative electrolyte contains 1 mol / L chromium chloride, 3 mol / L sodium bromide and 3 mol / L hydrobromic acid.

[0077] 2.Battery assembly:

[0078] Same as Example 1.

[0079] 3.Battery test:

[0080] Charge and discharge at 20°C, electrolyte flow rate of 50 ml / min, constant current charge and discharge, charge and discharge current density of 40 mA cm -2 . The operating voltage is 0.7V to 1.5V.

[0081] Example 7

[0082] 1. Electrolyte configuration:

[0083] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L chromium chloride, 3 mol / L sodium bromide, 3 mol / L hydrobromic acid and 0.5 mol / L PMDA, and the negative electrolyte contains 1 mol / L chromium chloride, 3 mol / L sodium bromide and 3 mol / L hydrobromic acid.

[0084] 2.Battery assembly:

[0085] Same as Example 1.

[0086] 3.Battery test:

[0087] Charge and discharge at 45°C, electrolyte flow rate of 50 ml / min, constant current charge and discharge, charge and discharge current density of 40 mA cm -2 , the operating voltage is 0.7V to 1.5V.

[0088] Example 8

[0089] 1. Electrolyte configuration:

[0090] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L chromium chloride, 3 mol / L sodium bromide, 3 mol / L hydrobromic acid and 0.5 mol / L PMDA, and the negative electrolyte contains 1 mol / L chromium chloride, 3 mol / L sodium bromide and 3 mol / L hydrobromic acid.

[0091] 2. Battery Assembly:

[0092] Same as Example 1.

[0093] 3.Battery test:

[0094] Charge and discharge at 70°C, electrolyte flow rate of 50 ml / min, constant current charge and discharge, charge and discharge current density of 40 mA cm -2 , the operating voltage is 0.7V to 1.5V.

[0095] The battery performance of Examples 6-8 and Comparative Example 2 is as follows: Figure 3As shown in the figure, as the temperature of the battery increases during charge and discharge, the battery coulombic efficiency, voltage efficiency and energy efficiency first increase and then drop sharply. This is because the reaction activity of the electrode pair will be increased when the charge and discharge temperature is just starting to increase. At the same time, high temperature has a recovery effect on the deactivation of the chromium electrode pair, which will improve the performance of the battery. When the temperature is higher than 70°C, the complexing agent PMDA will no longer be able to complex bromine, and a large amount of bromine gas overflow will cause irreversible damage to the battery performance. Therefore, the efficiency of the battery drops sharply at 80°C.

[0096] Example 9

[0097] 1. Electrolyte configuration:

[0098] 30 ml of positive electrolyte and 30 ml of negative electrolyte, wherein the positive electrolyte contains 1 mol / L chromium chloride, 3 mol / L hydrogen bromide, and 0.4 mol / L [C2Py] Br, and the negative electrolyte contains 1 mol / L chromium chloride, 1 mol / L hydrogen bromide, and 2 mol / L hydrochloric acid.

[0099] 2.Battery assembly:

[0100] Same as Example 1.

[0101] 3.Battery test:

[0102] Charge and discharge at 45°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 40mAcm 2 , the operating voltage is 0.7V to 1.5V.

[0103] Example 10

[0104] 1. Electrolyte configuration:

[0105] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L chromium chloride, 3 mol / L hydrogen bromide and 0.4 mol / L [C2Py] Br, and the negative electrolyte contains 1 mol / L chromium chloride, 2 mol / L hydrogen bromide and 1 mol / L hydrochloric acid.

[0106] 2.Battery assembly:

[0107] Same as Example 1.

[0108] 3.Battery test:

[0109] Charge and discharge at 45°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 40mAcm 2 , the operating voltage is 0.7V to 1.5V.

[0110] Embodiment 11

[0111] 1. Electrolyte configuration:

[0112] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L chromium chloride, 3 mol / L hydrogen bromide and 0.4 mol / L [C2Py] Br, and the negative electrolyte contains 1 mol / L chromium chloride and 3 mol / L hydrogen bromide.

[0113] 2.Battery assembly:

[0114] Same as Example 1.

[0115] 3.Battery test:

[0116] Charge and discharge at 45°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 40mAcm 2 , the operating voltage is 0.7V to 1.5V.

[0117] The battery performance of Examples 9-11 is as follows Figure 4 As shown in the figure, as the concentration of bromide ions in the negative electrode electrolyte increases, the coulombic efficiency and energy efficiency of the battery are improved. This is because bromide ions have a certain effect on chromium. Compared with the original water structure of chromium ions, the water structure of chromium and bromine is more stable, which is helpful to improve the battery performance.

[0118] Example 12

[0119] 1. Electrolyte configuration:

[0120] The positive electrode electrolyte is 30 ml, and the negative electrode electrolyte is 30 ml. The positive electrode electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide, 3 mol / L hydrochloric acid, and 0.8 mol / L MEM-Br. The negative electrode electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide, and 3 mol / L hydrochloric acid.

[0121] 2.Battery assembly:

[0122] Same as Example 1.

[0123] 3.Battery test:

[0124] Charge and discharge at 45°C, electrolyte flow rate of 50 ml / min, constant current charge and discharge, charge and discharge current density of 40 mA cm -2 , the operating voltage is 0.7V to 1.5V.

[0125] The battery data of Example 4, Example 12 and Comparative Example 1 are as follows: Figure 5As shown, the experiment shows that with the introduction of additives, the coulombic efficiency, voltage efficiency and energy efficiency of the battery are improved. This is because the introduction of PMDA and MEM-Br can complex bromine, reduce the overflow of bromine vapor and thus improve the performance of the battery.

[0126] Comparative Example 1

[0127] 1. Electrolyte configuration:

[0128] The positive electrode electrolyte is 30 ml, and the negative electrode electrolyte is 30 ml. The positive electrode electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide, and 3 mol / L hydrochloric acid, and the negative electrode electrolyte contains 1 mol / L chromium bromide, 3 mol / L sodium bromide, and 3 mol / L hydrochloric acid.

[0129] 2.Battery assembly:

[0130] Same as Example 1.

[0131] 3.Battery test:

[0132] Charge and discharge at 45°C, electrolyte flow rate of 50 ml / min, constant current charge and discharge, charge and discharge current density of 40 mA cm -2 , the operating voltage is 0.7V to 1.5V.

[0133] Comparative Example 2

[0134] 1. Electrolyte configuration:

[0135] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L chromium chloride, 3 mol / L sodium bromide, 3 mol / L hydrobromic acid and 0.5 mol / L PMDA, and the negative electrolyte contains 1 mol / L chromium chloride, 3 mol / L sodium bromide and 3 mol / L hydrobromic acid.

[0136] 2.Battery assembly:

[0137] Same as Example 1.

[0138] 3.Battery test:

[0139] Charge and discharge at 80℃, electrolyte flow rate 50ml / min, constant current charge and discharge, charge and discharge current density 40mAcm 2 , the operating voltage is 0.7V to 1.5V.

[0140] The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation methods. The protection scope of the present invention shall be subject to the scope defined in the claims. Other different forms of changes or modifications may be made based on the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A bromine-chromium liquid flow battery, the battery comprising a battery module, a positive electrode electrolyte storage tank, a negative electrode electrolyte storage tank, a circulation pump I, a circulation pump II, a positive electrode circulation pipeline, and a negative electrode circulation pipeline, the battery module is composed of one or more single cells connected in series, the single cell comprises an electrode end plate, a bipolar plate, an electrode, a diaphragm, and an electrode frame, the positive electrode electrolyte storage tank is connected to the positive electrode of the battery module via the positive electrode circulation pipeline, and the negative electrode electrolyte storage tank is connected to the negative electrode of the battery module via the negative electrode circulation pipeline, characterized in that: The positive electrode electrolyte includes a bromine-containing compound, a chromium salt, an inorganic acid and a complexing agent, and the negative electrode electrolyte includes a bromine-containing compound, a chromium salt and an inorganic acid. The negative electrode redox couple is Cr 3+ / Cr 2+ , the positive electrode redox couple is Br - / Br2; The complexing agent is one or a mixture of amino bromide, pyridyl bromide and malinyl bromide.

2. The bromine-chromium redox flow battery according to claim 1, characterized in that: The bromine-containing compound is one or more of potassium bromide, sodium bromide, lithium bromide, chromium bromide, and hydrobromic acid; The chromium salt is one or more of chromium chloride, chromium bromide, chromium iodide, chromium sulfate, chromium nitrate, and chromium phosphate; The inorganic acid is one of hydrochloric acid and hydrobromic acid.

3. The bromine-chromium redox flow battery according to claim 1, characterized in that: The amino bromide is N-methyl-N, N-bis(2-hydroxyethyl)-1-propylamine bromide; the pyridyl bromide is one or both of 1-ethylpyridine-1-bromide and 1-hexylpyridine-1-bromide; the maltyl bromide is one or both of 4-methylethylmorpholine bromide and quaternary amine 4-methylpropylmorpholine bromide.

4. The bromine-chromium redox flow battery according to claim 1, characterized in that: During charging, the positive electrode electrolyte is transported from the positive electrode electrolyte storage tank to the positive electrode via circulation pump I, and the negative electrode electrolyte is transported from the negative electrode electrolyte storage tank to the negative electrode via circulation pump II. 3+ The ions are reduced to Cr at the negative electrode. 2+ Ion, Br - Ions are oxidized to Br2 at the positive electrode; during discharge, Cr 2+ The ions are oxidized to Cr at the negative electrode. 3+ ions, return to the negative electrode electrolyte storage tank through circulation pump II, and Br2 is reduced to Br at the positive electrode. - The ions return to the positive electrode electrolyte storage tank through circulation pump I.

5. The bromine-chromium redox flow battery according to claim 1, characterized in that: In the positive electrode electrolyte, the concentration of bromide ions is 0.1 to 6 mol / L, the concentration of chromium ions is 0.1 to 3 mol / L, the concentration of acid is 0.1 to 6 mol / L, and the concentration of complexing agent is 0.1 to 1 mol / L; In the negative electrode electrolyte, the concentration of bromide ions is 0.1-6 mol / L, the concentration of chromium ions is 0.1-3 mol / L, and the concentration of acid is 0.1-6 mol / L.

6. The bromine-chromium redox flow battery according to claim 1, characterized in that: The operating temperature of the liquid flow battery is 25-70°C.

7. The bromine-chromium redox flow battery according to claim 1, characterized in that: The positive electrode and the negative electrode both adopt metal or carbon materials with plate-like structure or porous structure, and the carbon material includes carbon cloth, carbon paper or carbon felt.

8. The bromine-chromium redox flow battery according to claim 1, characterized in that: The diaphragm is an ion exchange membrane or a porous membrane.

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