Bromine chromium flow battery system

Abstract

The invention relates to the technical field of flow batteries, in particular to a bromine-chromium flow battery system. According to the invention, one or more of hydrobromic acid, hydrochloric acid and hydroiodic acid are used as additives, and Br2 and the additives in the electrolyte are complexed to form Br2X <-> to exist in the electrolyte, so that battery performance reduction caused by overflow and precipitation of bromine gas in the positive electrolyte is avoided, and the efficiency of the bromine-chromium flow battery is improved; meanwhile, the flow battery system further relieves battery part aging caused by bromine overflow and capacity fading caused by bromine loss through the gas conveying device, so that the service life of the bromine-chromium flow battery is prolonged.

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 system. Background Art

[0002] The inherent intermittent and unstable nature of renewable energy such as wind and solar energy has set up obstacles for their direct and efficient application. Therefore, the introduction of energy storage technology has become the key to solving this problem, aiming to achieve a continuous and stable supply of renewable energy.

[0003] Among many energy storage technologies, flow batteries have become one of the preferred technologies in the field of large-scale energy storage due to their design flexibility (capacity and power can be optimized independently), excellent safety performance and long life design. At present, all-vanadium flow batteries, zinc-bromine flow batteries, sodium polysulfide bromine flow batteries, iron-chromium flow batteries and manganese-based flow batteries have shown a relatively mature development trend.

[0004] Despite this, all-vanadium flow batteries still face the challenges of high cost and strong acid corrosion of electrolytes; iron-chromium flow batteries have a reduced efficiency due to the deactivation of chromium pairs in the electrolyte, and there is hydrogen evolution, which affects their overall performance. In view of this, it is particularly important to develop a new type of flow battery system that is both environmentally friendly and highly stable. This is not only a demand for technological innovation, but also a necessary path to promote the transformation of the global energy structure and achieve green and sustainable development.

[0005] Bromine-chromium flow batteries have the advantages of low cost, high potential window, and high theoretical capacity, and have excellent development prospects in the field of flow battery energy storage. However, the common bromine-chromium flow batteries still have the problems of traditional bromine-based flow batteries, such as bromine overflow causing capacity decay, overpressure inside the positive electrode storage tank, and corrosion of battery core components. Summary of the invention

[0006] Based on the above technical problems, the present invention provides a bromine-chromium liquid flow battery system, which has the characteristics of long cycle life and simple structure and manufacturing process.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A bromine-chromium liquid flow battery system, the system comprising a battery module, a positive electrode electrolyte storage tank, a negative electrode electrolyte storage tank, a circulation pump I, a circulation pump II, and a circulation pipeline, the battery module is formed by one or more single batteries connected in series, the single battery comprises a positive electrode, a negative electrode and a diaphragm, the cavity between the positive electrode and the diaphragm is filled with a positive electrode electrolyte, the cavity between the negative electrode and the diaphragm is filled with a negative electrode electrolyte, the positive electrode electrolyte storage tank is connected to the positive electrode of the battery module via a positive electrode circulation pipeline, the negative electrode electrolyte storage tank is connected to the negative electrode of the battery module via a negative electrode circulation pipeline, the positive electrode electrolyte and the negative electrode electrolyte are both composed of a basic electrolyte and an additive, the basic electrolyte comprises bromide ions and chromium ions, the additive is HX, wherein X is one or more of Cl, Br, and I;

[0009] The negative electrode redox couple of the single cell is Cr 3+ / Cr 2+ , the positive electrode redox couple is Br - / Br2X - ;

[0010] The battery system further includes a gas delivery device, which includes a gas drainage pipe I, a gas drainage pipe II, a unidirectional flow fan, an air pressure sensor and an air pressure balance unit;

[0011] The air inlet of the unidirectional flow fan is connected to the negative electrode electrolyte storage tank through the gas drainage pipe I and is located above the negative electrode electrolyte level, and the air outlet of the unidirectional flow fan is connected to the positive electrode electrolyte storage tank through the gas drainage pipe I and is located above the positive electrode electrolyte level;

[0012] The positive electrode electrolyte storage tank is connected to the negative electrode electrolyte storage tank through a gas drainage pipe II, and one end of the gas drainage pipe II is located above the positive electrode electrolyte level, and the other end extends below the negative electrode electrolyte level;

[0013] The air pressure sensor is used to detect the gas pressure in the system;

[0014] The air pressure balance unit is used to maintain air pressure balance in the system.

[0015] In the above technical solution, further, the concentration of bromide ions in the basic electrolyte is 0.1 to 3 mol·dm -3 , the concentration of chromium ions in the basic electrolyte is 0.1~3 mol·dm -3 The concentration of the additive in the positive and negative electrolytes is 0.1 to 6 mol·dm -3 .

[0016] In the above technical solution, further, the air pressure sensor and the air pressure balance unit are both connected to the gas drainage tube II.

[0017] In the above technical solution, further, the air pressure balance unit includes a gas storage bottle and a valve;

[0018] The gas storage cylinder is used for storing inert gas.

[0019] In the above technical solution, further, the operating temperature of the battery module is 25-50°C.

[0020] In the above technical solution, further, the positive electrode and the negative electrode both adopt metal materials with plate-like structure or porous structure, or carbon materials, and the carbon materials include carbon cloth, carbon paper, and carbon felt.

[0021] In the above technical solution, further, the diaphragm is an ion exchange membrane or a porous membrane.

[0022] 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 - The ions are oxidized to Br2 at the positive electrode, and Br2 complexes with the supporting electrolyte in the electrolyte to form Br2X - Exists in the electrolyte, and the remaining unreacted Br2 remains in the positive electrode electrolyte storage tank; 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, Br2X - Reduction to Br at the positive electrode - The ions return to the positive electrode electrolyte storage tank through circulation pump I. The Br2 remaining in the positive electrode storage tank exists in the form of bromine vapor and continues to accumulate as the cycle proceeds.

[0023] In the above technical scheme, further, during the operation of the bromine-chromium liquid flow battery, when the air pressure sensor detects that the internal pressure of the system exceeds 10% of the system working pressure, the unidirectional flow fan is turned on, and the gas in the negative electrolyte storage tank enters the positive electrolyte storage tank, forming a positive pressure in the positive electrolyte storage tank, and at the same time, the residual bromine vapor above the positive electrolyte storage tank enters the negative electrolyte, so that the bromine vapor and the negative electrolyte react chemically; when the air pressure sensor detects that the internal pressure of the system is lower than 80% of the system working pressure, the gas balance unit is used to maintain the system pressure balance.

[0024] The reaction equation after bromine vapor Br2 enters the negative electrode electrolyte is as follows:

[0025] Br2+2Cr 2+ →Br- +2Cr 3+

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The present invention uses one or more of hydrobromic acid, hydrochloric acid and hydroiodic acid as additives, and Br2 is complexed with the additives in the electrolyte to form Br2X - It exists in the electrolyte, preventing the battery performance from deteriorating due to the overflow and precipitation of bromine gas from the positive electrode electrolyte, thereby improving the efficiency of the bromine-chromium flow battery; at the same time, the flow battery system further alleviates the aging of battery components caused by bromine overflow and the capacity attenuation caused by bromine loss through the gas transmission device, thereby improving the life of the bromine-chromium flow battery;

[0028] 2. The electrolyte components of the bromine-chromium liquid flow battery of the present invention are simple, and the liquid flow battery system has a simple structure, low preparation cost, and simple manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the overall structure of the bromine-chromium liquid flow battery system of the present invention;

[0030] Figure 2 A schematic diagram of a local structure of a bromine-chromium liquid flow battery system of the present invention;

[0031] Figure 3 This is a schematic diagram of the structure of the air pressure balance unit of the present invention;

[0032] Among them: 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, 10. gas transmission device, 11. air pressure sensor, 12. air pressure balance unit, 13. unidirectional flow fan, 14. gas storage bottle, 15. valve. DETAILED DESCRIPTION

[0033] 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.

[0034] like Figure 1As shown, the present invention provides a bromine-chromium liquid flow battery system, which consists of a battery module, a positive electrolyte storage tank 8, a negative electrolyte storage tank 9, a circulation pump I6, a circulation pump II, and a circulation pipeline. The battery module is composed of one or more single batteries connected in series. The single battery includes a positive terminal plate 1, a positive electrode 3, a diaphragm 5, a negative electrode 4, and a negative terminal plate 2. The cavity between the positive electrode 3 and the diaphragm 5 is filled with a positive electrolyte, and the cavity between the negative electrode 4 and the diaphragm 5 is filled with a negative electrolyte. The positive electrolyte storage tank 8 is connected to the positive electrode of the battery module through the positive circulation pipeline, and the negative electrolyte storage tank 9 is connected to the negative electrode of the battery module through the negative circulation pipeline.

[0035] Both the positive and negative electrolytes are composed of a basic electrolyte and an additive. The basic electrolyte contains bromide ions and chromium ions, and the additive is HX, where X is one or more of Cl, Br, and I. The negative electrode redox couple of the single cell is Cr 3+ / Cr 2+ , the positive electrode redox couple is Br - / Br2X - ;

[0036] The system further includes a gas delivery device 10, which includes a gas drainage pipe I, a gas drainage pipe II, a unidirectional flow fan 13, a gas pressure sensor 11 and a gas pressure balance unit 12;

[0037] The air inlet of the unidirectional flow fan 13 is connected to the negative electrode electrolyte storage tank 9 through the gas drainage pipe I and is located above the negative electrode electrolyte level. The air outlet of the unidirectional flow fan 13 is connected to the positive electrode electrolyte storage tank 8 through the gas drainage pipe I and is located above the positive electrode electrolyte level.

[0038] The positive electrode electrolyte storage tank 8 is connected to the negative electrode electrolyte storage tank 9 through a gas drainage tube II, and one end of the gas drainage tube is located above the positive electrode electrolyte level, and the other end extends below the negative electrode electrolyte level;

[0039] The air pressure sensor 11 is used to detect the gas pressure in the system. The air pressure balance unit 12 is used to maintain the air pressure balance in the system. The air pressure balance unit 12 includes a gas storage bottle 14 and a valve 15. The gas storage bottle 14 is used to store inert gas.

[0040] During charging, the positive electrode electrolyte is transported from the positive electrode electrolyte storage tank 8 to the positive electrode via the circulation pump I6, and the negative electrode electrolyte is transported from the negative electrode electrolyte storage tank 9 to the negative electrode via the circulation pump II. 3+ The ions are reduced to Cr at the negative electrode. 2+ Ion, Br - The ions are oxidized to Br2 at the positive electrode, and Br2 complexes with the supporting electrolyte in the electrolyte to form Br2X -Exists in the electrolyte, and the remaining unreacted Br2 remains in the positive electrode electrolyte storage tank 8; during discharge, Cr 2+ The ions are oxidized to Cr at the negative electrode. 3+ ions, return to the negative electrode electrolyte storage tank 9 through the circulation pump II, Br2X - Reduction to Br at the positive electrode - The ions return to the positive electrode electrolyte storage tank 8 through the circulation pump I6. The Br2 remaining in the positive electrode storage tank exists in the form of bromine vapor and continues to accumulate as the cycle proceeds.

[0041] During the operation of the bromine-chromium liquid flow battery, when the air pressure sensor 11 detects that the internal pressure of the system exceeds 10% of the system working pressure, the unidirectional flow fan 13 is turned on, and the gas in the negative electrolyte storage tank 9 enters the positive electrolyte storage tank 8, forming a positive pressure in the positive electrolyte storage tank 8. At the same time, the residual bromine vapor above the positive electrolyte storage tank 8 enters the negative electrolyte under the action of the positive pressure, causing the bromine vapor to react chemically with the negative electrolyte; when the air pressure sensor 11 detects that the internal pressure of the system is lower than 80% of the system working pressure, the gas balance unit is used to maintain the system air pressure balance.

[0042] The reaction equation after bromine vapor Br2 enters the negative electrode electrolyte is as follows:

[0043] Br2+2Cr 2+ →Br - +2Cr 3+

[0044] The present invention is described in detail below with reference to embodiments.

[0045] Example 1

[0046] 1. Electrolyte configuration:

[0047] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide, the additive is hydrogen chloride; in the positive and negative electrolytes, the concentration of the additive is 0.1 mol dm -3 .

[0048] 2.Battery assembly:

[0049] The structure of the flow battery system is as follows: Figure 1As shown, a gas transfer device 10 is installed between the positive and negative electrolyte storage tanks 9, and the single cell is assembled in sequence according to the positive terminal plate 1, the positive bipolar plate, the positive carbon felt electrode (6cm×8cm), the ion conductive membrane (Nafion212), the negative carbon felt electrode (6cm×8cm), the negative bipolar plate, and the negative terminal plate 2.

[0050] 3.Battery test:

[0051] Charge and discharge at 25°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0052] Example 2

[0053] 1. Electrolyte configuration:

[0054] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide, the additive is hydrogen chloride; the concentration of the additive in the positive and negative electrolytes is 1 mol dm -3 .

[0055] 2.Battery assembly:

[0056] The structure of the liquid flow battery system is the same as that of Example 1.

[0057] 3.Battery test:

[0058] Charge and discharge at 25°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0059] Example 3

[0060] 1. Electrolyte configuration:

[0061] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide, the additive is hydrogen chloride; the concentration of the additive in the positive and negative electrolytes is 3 mol dm -3 .

[0062] 2.Battery assembly:

[0063] The structure of the liquid flow battery system is the same as that of Example 1.

[0064] 3.Battery test:

[0065] Charge and discharge at 25°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0066] Example 4

[0067] 1. Electrolyte configuration:

[0068] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide, the additive is hydrogen chloride; the concentration of the additive in the positive and negative electrolytes is 6 mol dm -3 .

[0069] 2.Battery assembly:

[0070] The structure of the liquid flow battery system is the same as that of Example 1.

[0071] 3.Battery test:

[0072] Charge and discharge at 25°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0073] Example 5

[0074] 1. Electrolyte configuration:

[0075] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide, the additive is hydrogen iodide; the concentration of the additive in the positive and negative electrolytes is 3 mol dm -3 .

[0076] 2.Battery assembly:

[0077] The structure of the liquid flow battery system is the same as that of Example 1.

[0078] 3.Battery test:

[0079] Charge and discharge at 25°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0080] Example 6

[0081] 1. Electrolyte configuration:

[0082] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide, the additive is hydrogen bromide; in the positive and negative electrolytes, the concentration of the additive is 3 mol dm -3 .

[0083] 2.Battery assembly:

[0084] The structure of the liquid flow battery system is the same as that of Example 1.

[0085] 3.Battery test:

[0086] Charge and discharge at 25°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0087] Example 7

[0088] 1. Electrolyte configuration:

[0089] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide, the additive is hydrogen chloride; the concentration of the additive in the positive and negative electrolytes is 3 mol dm -3 .

[0090] 2.Battery assembly:

[0091] The structure of the liquid flow battery system is the same as that of Example 1.

[0092] 3.Battery test:

[0093] Charge and discharge at 30°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0094] Example 8

[0095] 1. Electrolyte configuration:

[0096] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm-3 Hydrogen bromide, the additive is hydrogen chloride; the concentration of the additive in the positive and negative electrolytes is 3 mol dm -3 2.Battery assembly:

[0097] The structure of the liquid flow battery system is the same as that of Example 1.

[0098] 3.Battery test:

[0099] Charge and discharge at 40°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0100] Example 9

[0101] 1. Electrolyte configuration:

[0102] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide, the additive is hydrogen chloride; the concentration of the additive in the positive and negative electrolytes is 3 mol dm -3 2.Battery assembly:

[0103] The structure of the liquid flow battery system is the same as that of Example 1.

[0104] 3.Battery test:

[0105] Charge and discharge at 50°C, electrolyte flow rate 50ml / min, charge and discharge current density 100mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0106] Comparative Example 1

[0107] 1. Electrolyte configuration:

[0108] 30ml positive electrolyte, 30ml negative electrolyte, both positive and negative electrolytes are basic electrolytes, containing 1moldm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide.

[0109] 2.Battery assembly:

[0110] The structure of the liquid flow battery system is similar to that of Example 1, except that it does not contain a gas transmission device. The single cell is sequentially provided with a positive terminal plate 1, a positive bipolar plate, a positive carbon felt electrode (6×8 cm 2 )、ion conductive membrane (Nafion212), negative carbon felt electrode (6×8cm 2), the negative bipolar plate and the negative end plate 2 are assembled.

[0111] 3.Battery test:

[0112] Charge and discharge at 25°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 . The operating voltage is 0.7V to 1.4V.

[0113] Comparative Example 2

[0114] 1. Electrolyte configuration:

[0115] 30ml positive electrolyte, 30ml negative electrolyte, both positive and negative electrolytes are basic electrolytes, containing 1moldm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide.

[0116] 2.Battery assembly:

[0117] The structure of the liquid flow battery system is the same as that of Example 1.

[0118] 3.Battery test:

[0119] Charge and discharge at 25°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0120] Comparative Example 3

[0121] 1. Electrolyte configuration:

[0122] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide, the additive is hydrogen chloride; the concentration of the additive in the positive and negative electrolytes is 3 mol dm -3 2.Battery assembly:

[0123] The structure of the liquid flow battery system is the same as that of Example 1.

[0124] 3.Battery test:

[0125] Charge and discharge at 60°C, electrolyte flow rate 50ml / min, charge and discharge current density 100mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0126] Comparative Example 4

[0127] 1. Electrolyte configuration:

[0128] 30ml positive electrolyte, 30ml negative electrolyte, the positive and negative electrolytes are composed of basic electrolyte and additives, the basic electrolyte contains 1mol dm -3 Chromium chloride, 3 mol dm -3 Hydrogen bromide, the additive is hydrogen chloride; the concentration of the additive in the positive and negative electrolytes is 3 mol dm -3 .

[0129] 2.Battery assembly:

[0130] The structure of the liquid flow battery system is the same as that of Comparative Example 1.

[0131] 3.Battery test:

[0132] Charge and discharge at 25°C, electrolyte flow rate of 50 ml / min, charge and discharge current density of 100 mA cm -2 , the operating voltage is 0.7V to 1.4V.

[0133] The battery performances of Examples 1-9 and Comparative Examples 1-4 are shown in Table 1.

[0134] Table 1

[0135]

[0136]

[0137] The battery performances of Comparative Examples 1 and 2 are shown in Table 1. When a gas transfer device is introduced into the bromine-chromium flow battery, the capacity attenuation problem caused by bromine overflow is effectively solved, and the battery cycle performance is effectively improved.

[0138] The battery performance of Examples 1-4 is shown in Table 1. As the concentration of hydrogen chloride additive in the electrolyte increases, the battery coulomb efficiency and energy efficiency gradually increase and then stabilize, while the voltage efficiency remains basically unchanged. This is because a higher concentration of hydrogen chloride can complex more bromine to reduce the overflow of bromine gas, thereby improving the performance of the battery. Example 3, Example 5-6 As the halogen element changes, the coulomb efficiency obtained by the same concentration of hydrogen chloride, hydrogen bromide, and hydrogen iodide additives gradually increases, mainly due to the different complexing forces with Br2.

[0139] The battery performances of Example 3 and Comparative Example 4 are shown in Table 1. When additives are introduced into the bromine-chromium flow battery to improve the bromine overflow problem, the battery efficiency is effectively improved.

[0140] The battery performance of Examples 7-9 is shown in Table 1. As the temperature of the battery increases during charge and discharge, the battery coulombic efficiency, voltage efficiency and energy efficiency first increase and then decrease. This is because the initial increase in charge and discharge temperature will increase the reaction activity of the electrode pair, and high temperature has a recovery effect on the deactivation of the chromium electrode pair, which will improve the performance of the battery. However, when the temperature of Comparative Example 3 is higher than 60°C, the ability of the additive to complex bromine is weakened, and a large amount of bromine gas overflows, causing irreversible damage to the battery performance, and the efficiency of the battery drops sharply.

[0141] 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 system, the system consists of a battery module, a positive electrolyte storage tank, a negative electrolyte storage tank, a circulation pump I, a circulation pump II, and a circulation pipeline. The battery module is composed of one or more single batteries connected in series. The single battery includes a positive electrode, a negative electrode and a diaphragm. The cavity between the positive electrode and the diaphragm is filled with a positive electrolyte, and the cavity between the negative electrode and the diaphragm is filled with a negative electrolyte. The positive electrolyte storage tank is connected to the positive electrode of the battery module through the positive circulation pipeline, and the negative electrolyte storage tank is connected to the negative electrode of the battery module through the negative circulation pipeline. The characteristics are: The positive electrode electrolyte and the negative electrode electrolyte are both composed of a basic electrolyte and an additive, the basic electrolyte contains bromide ions and chromium ions, and the additive is HX, wherein X is one or more of Cl, Br, and I; The negative electrode redox couple of the single cell is Cr 3+ / Cr 2+ , the positive electrode redox couple is Br - / Br2X - ; The battery system further includes a gas delivery device, which includes a gas drainage pipe I, a gas drainage pipe II, a unidirectional flow fan, an air pressure sensor and an air pressure balance unit; The air inlet of the unidirectional flow fan is connected to the negative electrode electrolyte storage tank through the gas drainage pipe I and is located above the negative electrode electrolyte level, and the air outlet of the unidirectional flow fan is connected to the positive electrode electrolyte storage tank through the gas drainage pipe I and is located above the positive electrode electrolyte level; The positive electrode electrolyte storage tank is connected to the negative electrode electrolyte storage tank through a gas drainage pipe II, and one end of the gas drainage pipe II is located above the positive electrode electrolyte level, and the other end extends below the negative electrode electrolyte level; The air pressure sensor is used to detect the gas pressure in the system; The air pressure balance unit is used to maintain air pressure balance in the system.

2. The bromine-chromium liquid flow battery system according to claim 1, characterized in that: The concentration of bromide ions in the basic electrolyte is 0.1 to 3 mol·dm -3 , the concentration of chromium ions in the basic electrolyte is 0.1~3 mol·dm -3 The concentration of the additive in the positive and negative electrolytes is 0.1 to 6 mol·dm -3 .

3. The bromine-chromium liquid flow battery system according to claim 1, characterized in that: The air pressure sensor and the air pressure balance unit are both connected to the gas drainage pipe II.

4. The bromine-chromium liquid flow battery system according to claim 1, characterized in that: The air pressure balance unit includes a gas storage bottle and a valve; The gas storage cylinder is used for storing inert gas.

5. The bromine-chromium liquid flow battery system according to claim 1, characterized in that: The operating temperature of the battery module is 25-50°C.

6. The bromine-chromium liquid flow battery system 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 - The ions are oxidized to Br2 at the positive electrode, and Br2 complexes with the supporting electrolyte in the electrolyte to form Br2X - Exists in the electrolyte, and the remaining unreacted Br2 remains in the positive electrode electrolyte storage tank; 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, Br2X - Reduction to Br at the positive electrode - The ions return to the positive electrode electrolyte storage tank through circulation pump I. The Br2 remaining in the positive electrode storage tank exists in the form of bromine vapor and continues to accumulate as the cycle proceeds.

7. The bromine-chromium liquid flow battery system according to claim 1, characterized in that: During the operation of the bromine-chromium liquid flow battery, when the air pressure sensor detects that the internal pressure of the system exceeds 10% of the system working pressure, the unidirectional flow fan is turned on, and the gas in the negative electrolyte storage tank enters the positive electrolyte storage tank, forming a positive pressure in the positive electrolyte storage tank. At the same time, the residual bromine vapor above the positive electrolyte storage tank enters the negative electrolyte, causing the bromine vapor to react chemically with the negative electrolyte; when the air pressure sensor detects that the internal pressure of the system is lower than 80% of the system working pressure, the gas balance unit is used to maintain the system air pressure balance.

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