Bromine-chromium flow battery electrolyte and flow battery

Abstract

The invention relates to the technical field of flow batteries, in particular to a bromine-chromium flow battery electrolyte and a flow battery. The electrolyte is composed of a basic electrolyte and an additive; the additive is an iodine elementary substance or an iodine-containing compound; the basic electrolyte comprises bromide ions, chromium ions and hydrogen ions; the molar concentration ratio of iodine to bromide ions in the electrolyte is (1: 8)-(1: 4), one or two of iodine elementary substances or iodide ions are used as additives, the bromide ions and the iodine elementary substances are complexed in the charging process to form I2nBr <-> to exist in the electrolyte, then the I2nBr <-> generates the bromine elementary substances through an electrochemical reaction, and the electrochemical reaction electrode potential (Egt) of I2nBr <->-Br2; the electrode potential (E = 1.0873 V vs.SHE) is higher than the electrode potential (E = 1.0873 V vs.SHE) of Br <->-> Br2, so that the energy density of the bromine-chromium flow battery is 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 electrolyte and a liquid flow battery. Background Art

[0002] With the booming economy, energy demand continues to rise, while the environmental challenges caused by the large-scale consumption of fossil energy are becoming increasingly severe. Against this backdrop, countries around the world have turned their attention to the large-scale development and utilization of renewable energy, viewing it as a core strategy to ensure energy security and promote sustainable development. However, the inherent intermittent and unstable nature of renewable energy such as wind and solar energy has set up obstacles to their direct and efficient application. To this end, 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 and high safety, and have excellent development prospects in the field of flow battery energy storage. However, the common bromine-chromium flow batteries still have problems such as low potential window and low energy density, which limit their further development. Summary of the invention

[0006] Based on the above technical problems, the present invention provides a bromine-chromium liquid flow battery electrolyte and a liquid flow battery.

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

[0008] In one aspect, the present invention provides a bromine-chromium flow battery electrolyte, the electrolyte comprising a basic electrolyte and an additive; the additive is iodine element or an iodine-containing compound;

[0009] The basic electrolyte contains bromide ions, chromium ions, and hydrogen ions;

[0010] In the electrolyte, the molar concentration ratio of iodine element to bromide ion is 1:8-1:4.

[0011] In the above technical solution, further, in the electrolyte, the concentration of iodine element is 0.01-3M.

[0012] In the above technical solution, further, the iodine-containing compound is one or more of hydrogen iodide, sodium iodide, chromium iodide, potassium iodide, lithium iodide, magnesium iodide, and zinc iodide.

[0013] In the above technical scheme, further, the chromium ions are derived from one or more of chromium bromide, chromium chloride, chromium iodide, chromium sulfate, and chromium nitrate; the bromide ions are derived from one of sodium bromide, potassium bromide, lithium bromide, ammonium bromide, magnesium bromide, zinc bromide, chromium bromide, and hydrogen bromide; and the hydrogen ions are derived from one or more of sulfuric acid, hydrochloric acid, hydrogen bromide, hydrogen iodide, and nitric acid.

[0014] In the above technical solution, further, the basic electrolyte also contains chloride ions.

[0015] In the above technical solution, further, the chloride ions are derived from one of sodium chloride, potassium chloride, lithium chloride, ammonium chloride, magnesium chloride, zinc chloride, chromium chloride and hydrogen chloride.

[0016] On the other hand, the present invention provides a bromine-chromium liquid flow battery, which is composed of 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 includes an end plate, an 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 the circulation pump I, and the negative electrode electrolyte storage tank is connected to the negative electrode of the battery module via the circulation pump II, and the positive electrode electrolyte and the negative electrode electrolyte are both the above-mentioned electrolytes.

[0017] In the above technical solution, further, the material of the electrodes is one of carbon felt, carbon cloth or carbon paper, preferably carbon felt.

[0018] In the above technical solution, further, the diaphragm is an ion exchange membrane, a porous membrane, preferably a Nafion212 membrane.

[0019] The present invention uses iodine (if it is an iodine-containing compound, iodine ions are oxidized to iodine during charging) and bromide ions to synthesize I2Br - , then I2Br - Oxidized to bromine, I2Br - →The electrochemical reaction electrode potential of Br2 is higher than that of Br - →Br2 electrode potential, thereby improving the energy density of bromine-chromium flow battery.

[0020] During charging, Cr in the negative electrolyte 3+ The ions are reduced to Cr at the negative electrode. 2+ Ions, iodine in the positive electrolyte (or iodine ions oxidized to iodine) and bromide ions complex to form I2Br - , then I2Br - Oxidized to bromine, bromine combines with the remaining bromide ions in the positive electrolyte to form Br3 - (If the base electrolyte contains chloride ions, the bromine element reacts with the remaining bromide ions and chloride ions in the positive electrolyte to form Br3 - and Br2Cl - );

[0021] The specific reactions are as follows:

[0022] 2I - -2e - →I2 E=0.5355V vs.SHE

[0023] nI2+Br - →I 2n Br -

[0024] 2I 2n Br - -2e - →2nI2+Br2 E>1.09V vs.SHE

[0025] During discharge, Br3 - (Br3 - and Br2Cl - ) undergoes an electrochemical reaction at the positive electrode to generate I2Br - Ion, I2Br - Reduced to generate iodide ions, which dissolve in the positive electrode electrolyte, Cr 2+ Oxidized to Cr at the negative electrode 3+ , and dissolved in the negative electrode electrolyte.

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

[0027] 1. The present invention uses one or both of iodine or iodide ions as additives, and during the charging process, bromide ions and iodine ions are complexed to form I 2n Br - Exists in the electrolyte, then I 2n Br - The electrochemical reaction generates bromine, I 2n Br - →The electrochemical reaction electrode potential of Br2 (E>1.09V vs.SHE) is higher than that of Br -→Br2 electrode potential (E = 1.0873V vs. SHE), thereby improving the energy density of bromine-chromium flow batteries;

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

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

[0030] Among them: 1. positive terminal plate, 2. negative terminal plate, 3. positive electrode, 4. negative electrode, 5. positive electrode frame, 6. negative electrode frame, 7. diaphragm, 8. circulation pump I, 9. circulation pump II, 10. positive electrolyte storage tank, 11. negative electrolyte storage tank. DETAILED DESCRIPTION

[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] like Figure 1 As shown, the present invention provides a bromine-chromium liquid flow battery, which consists of a battery module, a positive electrolyte storage tank 10, a negative electrolyte storage tank 11, a circulation pump I8, a circulation pump II9, and a circulation pipeline; the battery module includes an end plate (including a positive end plate 1 and a negative end plate 2), electrodes (including a positive electrode 3 and a negative electrode 4) and a diaphragm 7, the cavity between the positive electrode 3 and the diaphragm 7 is filled with a positive electrolyte, the cavity between the negative electrode 4 and the diaphragm 7 is filled with a negative electrolyte, the positive electrolyte storage tank 10 is connected to the positive electrode of the battery module through the circulation pump I8, and the negative electrolyte storage tank 11 is connected to the negative electrode of the battery module through the circulation pump II9.

[0033] The present invention is described in detail below with reference to embodiments.

[0034] Example 1

[0035] 1. Electrolyte configuration:

[0036] 30ml positive electrolyte, 30ml negative electrolyte. The positive and negative electrolytes have the same composition, consisting of a basic electrolyte and an additive. The additive is iodine. The electrolyte contains 1mol L -1 Chromium chloride, 4 mol L -1 Hydrogen bromide and 0.5 mol L -1 of iodine.

[0037] 2.Battery module assembly:

[0038] The structure of the flow battery system is as follows: Figure 1As shown, the battery module is assembled in sequence according to the positive electrode stainless steel end plate, the positive electrode carbon felt electrode (6cm×8cm), the separator (Nafion212), the negative electrode carbon felt electrode (6cm×8cm), and the negative electrode stainless steel end plate.

[0039] 3.Battery test:

[0040] Charge and discharge at 25°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 , operating voltage is 0.7V to 1.55V.

[0041] Example 2

[0042] 1. Electrolyte configuration:

[0043] 30ml positive electrolyte, 30ml negative electrolyte. The positive and negative electrolytes have the same composition, consisting of a basic electrolyte and an additive. The additive is iodine. The electrolyte contains 1mol L -1 Chromium chloride, 4 mol L -1 Hydrogen bromide and 0.75 mol L -1 of iodine.

[0044] 2.Battery module assembly:

[0045] The assembly method is the same as that of Example 1.

[0046] 3.Battery test:

[0047] Charge and discharge at 25°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 , operating voltage is 0.7V to 1.55V.

[0048] Example 3

[0049] 1. Electrolyte configuration:

[0050] 30ml positive electrolyte, 30ml negative electrolyte. The positive and negative electrolytes have the same composition, consisting of a basic electrolyte and an additive. The additive is iodine. The electrolyte contains 1mol L -1 Chromium chloride, 4 mol L -1 Hydrogen bromide and 1 mol L -1 of iodine.

[0051] 2.Battery module assembly:

[0052] The assembly method is the same as that of Example 1.

[0053] 3.Battery test:

[0054] Charge and discharge at 25°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 , operating voltage is 0.7V to 1.55V.

[0055] Example 4

[0056] 1. Electrolyte configuration:

[0057] 30ml positive electrolyte, 30ml negative electrolyte. The positive and negative electrolytes have the same composition, consisting of a basic electrolyte and an additive. The additive is potassium iodide. The electrolyte contains 2mol L -1 Chromium chloride, 4 mol L -1 Hydrogen bromide, 4 mol L -1 Hydrochloric acid and 1 mol L -1 of iodine.

[0058] 2.Battery module assembly:

[0059] The assembly method is the same as that of Example 1.

[0060] 3.Battery test:

[0061] Charge and discharge at 25°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 , operating voltage is 0.7V to 1.55V.

[0062] Example 5

[0063] 1. Electrolyte configuration:

[0064] 30ml positive electrolyte, 30ml negative electrolyte. The positive and negative electrolytes have the same composition, consisting of a basic electrolyte and an additive. The additive is hydrogen iodide. The electrolyte contains 2mol L -1 Chromium chloride, 4 mol L -1 Hydrogen bromide, 4 mol L -1 Hydrochloric acid and 1 mol L -1 of iodine.

[0065] 2.Battery module assembly:

[0066] The assembly method is the same as that of Example 1.

[0067] 3.Battery test:

[0068] Charge and discharge at 25°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 , operating voltage is 0.7V to 1.55V.

[0069] Example 6

[0070] 1. Electrolyte configuration:

[0071] 30ml positive electrolyte, 30ml negative electrolyte. The positive and negative electrolytes have the same composition, consisting of a basic electrolyte and an additive. The additive is iodine. The electrolyte contains 1mol L -1 Chromium bromide, 4 mol L -1 Hydrogen bromide and 1 mol L -1 of iodine.

[0072] 2.Battery module assembly:

[0073] The assembly method is the same as that of Example 1.

[0074] 3.Battery test:

[0075] Charge and discharge at 25°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 , operating voltage is 0.7V to 1.55V.

[0076] Comparative Example 1

[0077] 1. Electrolyte configuration:

[0078] 30ml positive electrolyte, 30ml negative electrolyte, both positive and negative electrolytes are basic electrolytes, containing 1molL -1 Chromium chloride, 4 mol L -1 Hydrogen bromide.

[0079] 2.Battery assembly:

[0080] The assembly method is the same as that of Example 1.

[0081] 3.Battery test:

[0082] Charge and discharge at 25°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 . The operating voltage is 0.7V to 1.55V.

[0083] Comparative Example 2

[0084] 1. Electrolyte configuration:

[0085] 30ml positive electrolyte, 30ml negative electrolyte, both positive and negative electrolytes are basic electrolytes, containing 2molL -1 Chromium chloride, 4 mol L -1 Hydrogen bromide, 4 mol L -1 Hydrogen chloride.

[0086] 2.Battery assembly:

[0087] The assembly method is the same as that of Example 1.

[0088] 3.Battery test:

[0089] Charge and discharge at 25°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 . The operating voltage is 0.7V to 1.55V.

[0090] The battery performances of Examples 1-6 and Comparative Example 1 are shown in Table 1.

[0091] Table 1

[0092] Group Temperature / ℃ CE / % VE / % EE / % Average voltage / V Discharge capacity / Wh L Comparative Example 1 25 97.21 83.12 80.8 1.28 29.16 Comparative Example 2 25 97.51 82.95 80.56 1.28 57.99 Example 1 25 97.25 83.61 81.31 1.38 31.47 Example 2 25 97.52 83.88 81.80 1.42 32.45 Example 3 25 97.01 83.53 81.03 1.45 33.22 Example 4 25 97.11 83.01 80.61 1.45 65.99 Example 5 25 97.51 83.42 81.34 1.46 67.17 Example 6 25 97.61 83.93 81.92 1.43 33.03

[0093] The battery performance of Comparative Example 1 and Examples 1-3 is shown in Table 1. With the introduction of the iodine elemental additive in the electrolyte, the average discharge voltage of the battery is significantly increased, thereby increasing the battery discharge capacity. The results of Examples 1-3 show that with the increase in the concentration of the iodine elemental additive in the electrolyte, the average discharge voltage of the battery is significantly increased, thereby increasing the battery discharge capacity.

[0094] The battery performance of Comparative Example 2 and Examples 4-5 is shown in Table 1. When potassium iodide, an additive, is introduced into the bromine-chromium flow battery, the average discharge voltage of the battery is significantly increased, thereby increasing the discharge capacity of the battery. The results of Examples 4 and 5 show that when the additive is changed to hydrogen iodide of the same concentration, the battery efficiency is significantly improved, and the average battery voltage is also significantly improved.

[0095] The test results of Example 3 and Example 6 show that when the electrolyte contains only bromide ions, the average discharge voltage of the bromine electrode pair can also be increased, thereby increasing the discharge capacity.

[0096] 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 flow battery electrolyte, characterized in that: The electrolyte is composed of a basic electrolyte and an additive; the additive is iodine element or an iodine-containing compound; The basic electrolyte contains bromide ions, chromium ions, and hydrogen ions; The molar concentration ratio of iodine element to bromide ion in the electrolyte is 1:8-1:

4.

2. The electrolyte according to claim 1, characterized in that: In the electrolyte, the concentration of iodine element is 0.01-3M.

3. The electrolyte according to claim 1, characterized in that: The iodine-containing compound is one or more of hydrogen iodide, sodium iodide, chromium iodide, potassium iodide, lithium iodide, magnesium iodide and zinc iodide.

4. The electrolyte according to claim 1, characterized in that: The chromium ions are derived from one or more of chromium bromide, chromium chloride, chromium iodide, chromium sulfate, and chromium nitrate; the bromide ions are derived from one of sodium bromide, potassium bromide, lithium bromide, ammonium bromide, magnesium bromide, zinc bromide, chromium bromide, and hydrogen bromide; and the hydrogen ions are derived from one or more of sulfuric acid, hydrochloric acid, hydrogen bromide, hydrogen iodide, and nitric acid.

5. The bromine-chromium redox flow battery electrolyte according to claim 1, characterized in that: The basic electrolyte also contains chloride ions.

6. The electrolyte according to claim 5, characterized in that: The chloride ions are derived from one of sodium chloride, potassium chloride, lithium chloride, ammonium chloride, magnesium chloride, zinc chloride, chromium chloride and hydrogen chloride.

7. A bromine-chromium liquid flow battery, comprising 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 comprises an end plate, an electrode and a diaphragm, the cavity between the positive electrode and the diaphragm is filled with a positive electrolyte, 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 via the circulation pump I, and the negative electrolyte storage tank is connected to the negative electrode of the battery module via the circulation pump II, characterized in that: The positive electrode electrolyte and the negative electrode electrolyte are both the electrolytes according to any one of claims 1 to 6.

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