All-vanadium redox flow battery electrolyte based on bromo-hydrochloric acid group and application of all-vanadium redox flow battery electrolyte

Abstract

The invention relates to the technical field of redox flow batteries, in particular to an all-vanadium redox flow battery electrolyte based on bromo-hydrochloric acid and application of the all-vanadium redox flow battery electrolyte. The electrolyte comprises vanadium ions, hydrogen ions, bromide ions and chloride ions, wherein the molar concentration ratio of the chloride ions to the bromide ions is greater than or equal to 2; and the volume ratio of the positive electrode electrolyte to the negative electrode electrolyte is (0.5-0.95): 1. According to the electrolyte disclosed by the invention, on the basis of fully utilizing the capacity provided by vanadium, the capacity provided by bromine is effectively utilized through participation of bromine ions in an electrochemical reaction, so that the capacity of the all-vanadium redox flow battery is improved, and meanwhile, the energy cost is reduced; the electrolyte can improve the high-temperature stability of the all-vanadium redox flow battery.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to a bromine-based hydrochloric acid-based all-vanadium liquid flow battery electrolyte and applications thereof. 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 more and more 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.

[0003] 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. However, due to the solubility of active substances and the number of electron transfers, the energy density of liquid flow batteries is usually low, making their material costs relatively high. Taking the all-vanadium liquid flow battery with an all-sulfuric acid system as an example, its vanadium ion concentration can only reach about 1.7M, resulting in a theoretical energy density of only 45Ah / L; the hydrochloric acid and sulfuric acid mixed acid system can increase the concentration of active vanadium ions to about 2.4M, which can increase the theoretical energy density to 64Ah / L. The main cost of vanadium electrolyte comes from the vanadium element, but the increase in vanadium ion concentration will significantly increase the cost of the electrolyte, and the energy cost has not decreased. Summary of the invention

[0004] The purpose of the present invention is to provide a bromine-based hydrochloric acid-based all-vanadium redox flow battery electrolyte and its application. Bromine ions have high solubility and excellent electrochemical activity. Compared with vanadium, bromine is less expensive, and Br2 / Br - The electrode potential and VO2 + / VO 2+ So the introduction of bromide ions into the cathode electrolyte can increase the capacity of the all-vanadium flow battery under the same cut-off potential conditions and reduce the capacity cost. However, bromine has problems with corrosiveness, volatility and diffusivity, and requires the addition of a chelating agent to stabilize it. The excess chloride ions in mixed-acid or all-hydrochloric acid-based all-vanadium flow batteries can act as chelating agents for bromine to stabilize the overflow of bromine. At the same time, the presence of bromine can inhibit the chlorine evolution problem of hydrochloric acid-based all-vanadium flow batteries under high charge conditions. And the presence of bromine can improve the high temperature resistance of all-vanadium flow batteries.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] On the one hand, the present invention provides a bromine-hydrochloric acid-based all-vanadium liquid flow battery electrolyte, characterized in that: the electrolyte contains vanadium ions, hydrogen ions, bromide ions, and chloride ions, wherein the molar concentration ratio of chloride ions to bromide ions is ≥2; the volume ratio of the positive electrode electrolyte to the negative electrode electrolyte is (0.5-0.95):1.

[0007] Based on the above scheme, preferably, the electrolyte further contains sulfate ions.

[0008] Based on the above scheme, preferably, the bromide ions are derived from at least one of hydrobromic acid, sodium bromide, potassium bromide, zinc bromide, ammonium bromide, and vanadium bromide; the chloride ions are derived from at least one of hydrochloric acid, sodium chloride, potassium chloride, zinc chloride, ammonium chloride, and vanadium chloride; and the hydrogen ions are derived from at least one of hydrobromic acid, hydrochloric acid, and sulfuric acid.

[0009] Based on the above scheme, preferably, the sulfate ion is derived from at least one of sulfuric acid, sodium sulfate, potassium sulfate, zinc sulfate, ammonium sulfate, vanadium sulfate, and vanadyl sulfate.

[0010] Based on the above scheme, preferably, the concentration of vanadium ions in the electrolyte is 0.5mol / L~3.5mol / L; the concentration of bromide ions in the electrolyte is 0.1mol / L~6mol / L; the concentration of chloride ions in the electrolyte is 3mol / L~9mol / L, and the concentration of hydrogen ions in the electrolyte is 1mol / L~10mol / L.

[0011] Based on the above scheme, preferably, the concentration of sulfate ions in the electrolyte is 0.1 mol / L to 4 mol / L.

[0012] On the other hand, the present invention provides a bromine-based hydrochloric acid-based all-vanadium liquid flow battery, which includes end plates, electrodes and diaphragms. The cavity between the positive electrode and the diaphragm is filled with a positive electrode electrolyte, and the cavity between the negative electrode and the diaphragm is filled with a negative electrode electrolyte. The positive electrode electrolyte and the negative electrode electrolyte are both the above-mentioned electrolytes.

[0013] Based on the above scheme, preferably, the electrode is activated carbon felt or graphite felt; the diaphragm is any one of perfluorosulfonic acid membrane, porous polyolefin membrane, sulfonated polyetheretherketone membrane, and polybenzimidazole membrane; the end plate is an acid-corrosion-resistant metal plate, including any one of aluminum alloy plate and stainless steel plate, preferably a stainless steel plate; the electrolyte circulates between the cavity and the electrolyte storage tank through a magnetic centrifugal pump or a peristaltic pump to construct a bromine-based hydrochloric acid-based all-vanadium liquid flow battery.

[0014] The above-mentioned bromine-based hydrochloric acid-based all-vanadium liquid flow battery adopts one of the charging modes of constant current, constant current plus constant voltage, constant power, and constant power plus constant voltage for charging and discharging. The specific charging process is as follows:

[0015] first step:

[0016] VO 2+ +H2O→VO2 + +2H + +e - E=0.991V

[0017] Step 2:

[0018] 2Br - →Br2+2e - E=1.04V

[0019] Step 3:

[0020] Br2+Cl - →Br2Cl -

[0021] Compared with the existing technology, the beneficial effects of the present invention are:

[0022] 1) The electrolyte of the present invention not only fully utilizes the capacity provided by vanadium, but also effectively utilizes the capacity provided by bromine by the participation of bromide ions in electrochemical reactions, thereby increasing the capacity of the all-vanadium redox flow battery and reducing energy costs;

[0023] 2) Due to the synergistic effect of bromide ions, chloride ions and vanadium ions, the electrolyte of the present invention improves the stability of the water and structure of pentavalent vanadium ions, thereby improving the high temperature stability of the all-vanadium redox flow battery;

[0024] 3) Due to the presence of a large amount of chloride ions, the electrolyte of the present invention can effectively complex bromine in the presence of bromine so that it can be stably present in the electrolyte, thereby improving the stability of bromine in the solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure of the all-vanadium liquid flow battery of the present invention;

[0026] 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. DETAILED DESCRIPTION

[0027] 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.

[0028] An all-vanadium liquid flow battery, the structure of which is as follows Figure 1As 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, and the single battery is composed of a positive terminal plate 1, a negative terminal plate 2, a positive electrode 3, a negative electrode 4, and a diaphragm 5; 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.

[0029] Comparative Example 1

[0030] 1. Electrolyte configuration:

[0031] The positive electrode electrolyte is 30 ml and the negative electrode electrolyte is 33 ml. The positive electrode electrolyte contains 1.65 mol / L 3.5-valent vanadium sulfate and 3 mol / L sulfuric acid. The negative electrode electrolyte has the same composition as the positive electrode electrolyte.

[0032] 2.Battery assembly:

[0033] like Figure 1 As shown, the battery is assembled in sequence including a positive stainless steel end plate, a positive bipolar plate (7.5 cm×9.5 cm), a positive carbon felt electrode (6 cm×8 cm), a separator (Nafion212), a negative carbon felt electrode (6 cm×8 cm), a negative bipolar plate (7.5 cm×9.5 cm), and a negative stainless steel end plate.

[0034] 3.Battery test:

[0035] 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 1V to 1.55V.

[0036] Comparative Example 2

[0037] 1. Electrolyte configuration:

[0038] The positive electrolyte is 30 ml and the negative electrolyte is 33 ml. The positive electrolyte contains 1.65 mol / L 3.5-valent vanadium sulfate and 3 mol / L sulfuric acid. The negative electrolyte has the same composition as the positive electrolyte.

[0039] 2.Battery assembly:

[0040] Same as Comparative Example 1.

[0041] 3.Battery test:

[0042] Charge and discharge at 43°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2, operating voltage is 1V to 1.55V.

[0043] Comparative Example 3

[0044] 1. Electrolyte configuration:

[0045] The positive electrode electrolyte is 30 ml and the negative electrode electrolyte is 33 ml. The positive electrode electrolyte contains 1.65 mol / L 3.5-valent vanadium sulfate, 3 mol / L sulfuric acid, and 0.165 mol / L hydrogen bromide. The negative electrode electrolyte has the same composition as the positive electrode electrolyte.

[0046] 2.Battery assembly:

[0047] Same as Comparative Example 1.

[0048] 3.Battery test:

[0049] 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 1V to 1.55V.

[0050] Comparative Example 4

[0051] 1. Electrolyte configuration:

[0052] The positive electrode electrolyte is 30 ml and the negative electrode electrolyte is 33 ml. The positive electrode electrolyte contains 1.65 mol / L 3.5-valent vanadium sulfate, 2.835 mol / L sulfuric acid, 0.165 mol / L hydrochloric acid, and 0.165 mol / L hydrogen bromide. The negative electrode electrolyte has the same composition as the positive electrode electrolyte.

[0053] 2.Battery assembly:

[0054] Same as Comparative Example 1.

[0055] 3.Battery test:

[0056] 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 1V to 1.55V.

[0057] Comparative Example 5

[0058] 1. Electrolyte configuration:

[0059] The positive electrode electrolyte is 30 ml, and the negative electrode electrolyte is 30 ml. The positive electrode electrolyte contains 1.65 mol / L 3.5-valent vanadium sulfate, 3 mol / L hydrochloric acid, and 0.165 mol / L hydrogen bromide. The negative electrode electrolyte has the same composition as the positive electrode electrolyte.

[0060] 2.Battery assembly:

[0061] Same as Comparative Example 1.

[0062] 3.Battery test:

[0063] 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 1V to 1.55V.

[0064] Example 1

[0065] 1. Electrolyte configuration:

[0066] The positive electrode electrolyte is 30 ml and the negative electrode electrolyte is 33 ml. The positive electrode electrolyte contains 1.65 mol / L 3.5-valent vanadium sulfate, 3 mol / L hydrochloric acid, and 0.165 mol / L hydrogen bromide. The negative electrode electrolyte has the same composition as the positive electrode electrolyte.

[0067] 2.Battery assembly:

[0068] Same as Comparative Example 1.

[0069] 3.Battery test:

[0070] 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 1V to 1.55V.

[0071] Example 2

[0072] The positive electrode electrolyte is 30 ml and the negative electrode electrolyte is 33 ml. The positive electrode electrolyte contains 1.65 mol / L 3.5-valent vanadium sulfate, 3 mol / L hydrochloric acid, and 0.165 mol / L hydrogen bromide. The negative electrode electrolyte has the same composition as the positive electrode electrolyte.

[0073] 2.Battery assembly:

[0074] Same as Comparative Example 1.

[0075] 3.Battery test:

[0076] Charge and discharge at 43°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 , operating voltage is 1V to 1.55V.

[0077] Example 3

[0078] The positive electrode electrolyte is 30 ml and the negative electrode electrolyte is 33 ml. The positive electrode electrolyte contains 2.4 mol / L 3.5-valent vanadium chloride, 3 mol / L hydrochloric acid, and 0.24 mol / L hydrogen bromide. The negative electrode electrolyte has the same composition as the positive electrode electrolyte.

[0079] 2.Battery assembly:

[0080] Same as Comparative Example 1.

[0081] 3.Battery test:

[0082] Charge and discharge at 43°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 , operating voltage is 1V to 1.55V.

[0083] Example 4

[0084] The positive electrode electrolyte is 30 ml and the negative electrode electrolyte is 60 ml. The positive electrode electrolyte contains 2.4 mol / L 3.5-valent vanadium chloride, 3 mol / L hydrochloric acid, and 2.4 mol / L hydrogen bromide. The negative electrode electrolyte has the same composition as the positive electrode electrolyte.

[0085] 2.Battery assembly:

[0086] Same as Comparative Example 1.

[0087] 3.Battery test:

[0088] Charge and discharge at 43°C, electrolyte flow rate of 50ml / min, constant current charge and discharge, charge and discharge current density of 100mAcm -2 . The operating voltage is 1V to 1.55V.

[0089] The performance test results of the batteries assembled in Examples 1-4 and Comparative Examples 1-5 are shown in Table 1.

[0090] Table 1

[0091]

[0092]

[0093] From the comparison of the battery performance of Comparative Example 1, Comparative Example 3 and Example 1, it can be seen that only introducing bromide ions into the electrolyte will cause the bromide ions to overflow and thus lead to a decrease in battery performance. When chloride ions are introduced into the electrolyte, due to the complexation between chloride ions and bromine element, the bromine element can be stably present in the electrolyte, thereby improving the capacity of the battery.

[0094] By comparing Comparative Example 2 with Example 2, it can be seen that when the electrolyte temperature is raised to 43°C, the electrolyte into which chloride ions and bromide ions are introduced can stabilize pentavalent vanadium ions and prevent them from overflowing. At the same time, the battery efficiency and capacity are significantly improved at high temperature.

[0095] It can be seen from Example 3 that the vanadium ion concentration in the bromine-based hydrochloric acid-based all-vanadium liquid flow battery can reach 2.4 mol / L, and the battery capacity is significantly improved through the synergistic effect of bromide ions, chloride ions and vanadium ions.

[0096] It can be seen from Example 4 that in a bromine-based hydrochloric acid-based all-vanadium liquid flow battery, the vanadium ion concentration can reach 2.4 mol / L, and the bromide ion concentration can also be increased to 2.4 mol / L. Through the synergistic effect of bromide ions, chloride ions and vanadium ions, the battery capacity is significantly improved.

[0097] By comparing Comparative Example 4 with Example 1, it can be seen that when the molar concentration ratio of chlorine to bromine in the bromine-based hydrochloric acid-based all-vanadium liquid flow battery exceeds 2, the battery coulombic efficiency is significantly improved, and the reversibility of the bromine electrode pair is significantly improved.

[0098] By comparing Comparative Example 5 with Example 1, it can be seen that under the premise of the same electrolyte composition and the same positive electrode electrolyte volume, by increasing the volume of the negative electrode electrolyte, the partial capacity of bromine in the positive electrode electrolyte can be fully utilized, thereby effectively improving the battery capacity of the bromine-based hydrochloric acid-based all-vanadium redox flow battery.

[0099] 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-based hydrochloric acid-based all-vanadium redox flow battery electrolyte, characterized in that: The electrolyte includes vanadium ions, hydrogen ions, bromide ions, and chloride ions, wherein the molar concentration ratio of chloride ions to bromide ions is ≥2; and the volume ratio of the positive electrode electrolyte to the negative electrode electrolyte is (0.5-0.95):

1.

2. The bromine-based hydrochloric acid-based all-vanadium redox flow battery electrolyte according to claim 1, characterized in that: The electrolyte also includes sulfate ions.

3. The bromine-based hydrochloric acid-based all-vanadium redox flow battery electrolyte according to claim 1, characterized in that: The bromide ions are derived from at least one of hydrobromic acid, sodium bromide, potassium bromide, zinc bromide, ammonium bromide, and vanadium bromide; the chloride ions are derived from at least one of hydrochloric acid, sodium chloride, potassium chloride, zinc chloride, ammonium chloride, and vanadium chloride; and the hydrogen ions are derived from at least one of hydrobromic acid, hydrochloric acid, and sulfuric acid.

4. The bromine-based hydrochloric acid-based all-vanadium redox flow battery electrolyte according to claim 2, characterized in that: The sulfate ion is derived from at least one of sulfuric acid, sodium sulfate, potassium sulfate, zinc sulfate, ammonium sulfate, vanadium sulfate, and vanadyl sulfate.

5. The bromine-based hydrochloric acid-based all-vanadium redox flow battery electrolyte according to claim 1, characterized in that: The concentration of the vanadium ions in the electrolyte is 0.5 mol / L to 3.5 mol / L; the concentration of the bromide ions in the electrolyte is 0.1 mol / L to 6 mol / L; the concentration of the chloride ions in the electrolyte is 3 mol / L to 9 mol / L, and the concentration of the hydrogen ions in the electrolyte is 1 mol / L to 10 mol / L.

6. The bromine-based hydrochloric acid-based all-vanadium redox flow battery electrolyte according to claim 2, characterized in that: The concentration of the sulfate ions in the electrolyte is 0.1 mol / L to 4 mol / L.

7. A bromine-based hydrochloric acid-based all-vanadium redox flow battery, the battery comprising end plates, electrodes and diaphragms, 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, 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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