Iron-chromium flow battery electrolyte containing double-halogen-based compound and application of iron-chromium flow battery electrolyte

Abstract

The invention relates to the technical field of redox flow batteries, in particular to an iron-chromium redox flow battery electrolyte containing a double-halogen-based compound and application of the iron-chromium redox flow battery electrolyte. The electrolyte contains iron ions, chromium ions, hydrogen ions, a compound containing a chlorine element and a compound containing a bromine element, the concentration of the chlorine ions in the electrolyte is 0.1 mol / L-14 mol / L, the concentration of the bromine ions in the electrolyte is 0.1 mol / L-14 mol / L, and the molar ratio of the bromine ions to the chlorine ions is (1: 80)-(80: 1). The electrolyte used in the invention can effectively reduce the capacity fading of the iron-chromium flow battery and prolong the service life of the battery. The complexing structure of chromium is improved by introducing double halogen ions of bromide ions and chloride ions, so that the structure is more stable, the capacity fading speed is reduced, and the electrocouple activity of chromium ions is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid flow batteries, and in particular to an iron-chromium liquid flow battery electrolyte containing a dihalogen-based compound and an application 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 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] As a key component of iron-chromium flow battery, the electrolyte determines the performance and stability of the battery to a large extent. 3+ 、Cr(H2O)5Cl 2+ 、Cr(H2O)4Cl2 + Three complex structures, Cr(H2O)6 3+ Inactive. The deactivation of the Fe-Cr flow battery electrolyte is due to Cl - The complex structure is unstable and easy to fall off, resulting in Cr(H2O)6 3+ The amount of inactive substances increases. Therefore, improving the stability of the complex structure of chromium in the negative electrode electrolyte of the iron-chromium flow battery is crucial to extending the battery cycle life. Summary of the invention

[0004] The object of the present invention is to provide an iron-chromium flow battery electrolyte containing a dihalogen compound and its application, wherein the electrolyte can reduce the capacity attenuation of the iron-chromium flow battery and improve the chromium-electrode activity of the iron-chromium flow battery, thereby achieving the purpose of efficient and stable operation of the iron-chromium flow battery.

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

[0006] On the one hand, the present invention provides an iron-chromium liquid flow battery electrolyte containing a dihalogen-based compound, wherein the electrolyte contains iron ions, chromium ions, hydrogen ions, compounds containing chlorine elements, and compounds containing bromine elements, wherein the chloride ion concentration in the electrolyte is 0.1 mol / L to 14 mol / L, the bromide ion concentration is 0.1 mol / L to 14 mol / L, and the molar ratio of bromide ions to chloride ions is (1:80) to (80:1).

[0007] In the above technical scheme, further, the compound containing bromine element is one or more of LiBr, NaBr, KBr, HBr, FeBr3, FeBr2, CrBr3, CrBr2, and NH4Br.

[0008] In the above technical scheme, further, the compound containing chlorine element is one or more of LiCl, NaCl, KCl, HCl, FeCl3, FeCl2, CrCl3, CrCl2, and NH4Cl.

[0009] In the above technical solution, further, in the electrolyte, the concentration of iron ions is 0.5 mol / L to 3 mol / L, the concentration of chromium ions is 0.5 mol / L to 3 mol / L, and the concentration of hydrogen ions is 1.5 mol / L to 6 mol / L.

[0010] In the above technical solution, further, the iron ion is Fe 3+ and / or Fe 2+ .

[0011] In the above technical solution, further, the chromium ion is Cr 3+ Cr 2+ 、CrO4 2- CrO2 - and Cr2O7 2- One or more of the .

[0012] Another aspect of the present invention provides an application of the above-mentioned iron-chromium liquid flow battery electrolyte containing a dihalogen-based compound, wherein the electrolyte is used as a positive electrode and a negative electrode electrolyte in an iron-chromium liquid flow battery.

[0013] The beneficial effects of the present invention are:

[0014] 1) The electrolyte used in the present invention can effectively reduce the capacity decay of the iron-chromium flow battery and extend the battery life. This is due to the introduction of bromide ions to improve the complex structure of chromium, making the structure more stable and reducing the capacity decay rate.

[0015] 2) The electrolyte used in the present invention can effectively enhance the activity of the negative electrode chromium ion couple in the iron-chromium liquid flow battery and improve the battery performance.

[0016] 3) The electrolyte of the present invention is easy to obtain and has low cost, and can ensure the long-term efficient and stable operation of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of an iron-chromium flow battery;

[0018] In the figure: 1, positive terminal plate, 2, negative terminal plate, 3, positive electrode, 4, negative electrode, 5, ion conduction membrane, 6, circulation pump I, 7, circulation pump II, 8, positive electrode electrolyte storage tank, 9, negative electrode electrolyte storage tank;

[0019] Figure 2 The cyclic voltammetry curves of the electrolytes of Example 1 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0020] 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.

[0021] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained through commercial channels or prepared according to conventional methods well known to those skilled in the art.

[0022] The structure of iron-chromium flow battery is 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), 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.

[0023] Comparative Example 1

[0024] 1. Electrolyte configuration:

[0025] 30ml of positive electrolyte and 30ml of negative electrolyte, wherein the positive electrolyte contains 1mol / L ferrous chloride, 1mol / L chromium chloride and 3mol / L hydrochloric acid, and the negative electrolyte is the same as the positive electrolyte.

[0026] 2.Battery assembly:

[0027] according to Figure 1 The battery structure shown in the figure is composed of a positive stainless steel end plate, a positive carbon felt electrode (6×8cm 2 )、ion conductive membrane (Nafion212), negative carbon felt electrode (6×8cm 2 ) and the negative electrode stainless steel end plate are assembled.

[0028] 3.Battery test:

[0029] Charge and discharge at 65°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 1.2V.

[0030] Comparative Example 2

[0031] 1. Electrolyte configuration:

[0032] The positive electrolyte is 30 ml and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L ferrous bromide, 1 mol / L chromium bromide and 3 mol / L HBr. The negative electrolyte is the same as the positive electrolyte.

[0033] 2.Battery assembly:

[0034] Same as Comparative Example 1.

[0035] 3.Battery test:

[0036] Charge and discharge at 65°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 1.2V.

[0037] Example 1

[0038] 1. Electrolyte configuration:

[0039] 30ml of positive electrolyte and 30ml of negative electrolyte, wherein the positive electrolyte contains 1mol / L ferrous chloride, 1mol / L chromium chloride, 3mol / L hydrochloric acid and 0.1mol / L KBr, and the negative electrolyte is the same as the positive electrolyte.

[0040] 2.Battery assembly:

[0041] according to Figure 1 The battery structure shown in the figure is composed of a positive stainless steel end plate, a positive carbon felt electrode (6×8cm 2 )、ion conductive membrane (Nafion212), negative carbon felt electrode (6×8cm 2 ) and the negative electrode stainless steel end plate are assembled.

[0042] 3.Battery test:

[0043] Charge and discharge at 65°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 1.2V.

[0044] Example 2

[0045] 1. Electrolyte configuration:

[0046] 30ml of positive electrolyte and 30ml of negative electrolyte, wherein the positive electrolyte contains 1mol / L ferrous chloride, 1mol / L chromium chloride, 3mol / L hydrochloric acid and 0.5mol / L KBr, and the negative electrolyte is the same as the positive electrolyte.

[0047] 2.Battery assembly:

[0048] Same as Example 1.

[0049] 3.Battery test:

[0050] Charge and discharge at 65°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 1.2V.

[0051] Example 3

[0052] 1. Electrolyte configuration:

[0053] 30ml of positive electrolyte and 30ml of negative electrolyte, wherein the positive electrolyte contains 1mol / L ferrous chloride, 1mol / L chromium chloride, 3mol / L hydrochloric acid and 1mol / L KBr, and the negative electrolyte is the same as the positive electrolyte.

[0054] 2.Battery assembly:

[0055] Same as Example 1.

[0056] 3.Battery test:

[0057] Charge and discharge at 65°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 1.2V.

[0058] Example 4

[0059] 1. Electrolyte configuration:

[0060] 30ml of positive electrolyte and 30ml of negative electrolyte, wherein the positive electrolyte contains 1mol / L ferrous chloride, 1mol / L chromium chloride, 3mol / L hydrochloric acid and 1mol / L HBr, and the negative electrolyte is the same as the positive electrolyte.

[0061] 2.Battery assembly:

[0062] Same as Example 1.

[0063] 3.Battery test:

[0064] Charge and discharge at 65°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 1.2V.

[0065] Example 5

[0066] 1. Electrolyte configuration:

[0067] 30ml of positive electrolyte and 30ml of negative electrolyte, wherein the positive electrolyte contains 1mol / L ferrous chloride, 1mol / L chromium chloride, 3mol / L hydrochloric acid and 3mol / L HBr, and the negative electrolyte is the same as the positive electrolyte.

[0068] 2.Battery assembly:

[0069] Same as Example 1.

[0070] 3.Battery test:

[0071] Charge and discharge at 65°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 1.2V.

[0072] Example 6

[0073] 1. Electrolyte configuration:

[0074] 30ml of positive electrolyte and 30ml of negative electrolyte, wherein the positive electrolyte contains 1mol / L ferrous chloride, 1mol / L chromium chloride and 6mol / L HBr, and the negative electrolyte is the same as the positive electrolyte.

[0075] 2.Battery assembly:

[0076] Same as Example 1.

[0077] 3.Battery test:

[0078] Charge and discharge at 65°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 1.2V.

[0079] Example 7

[0080] 1. Electrolyte configuration:

[0081] The positive electrolyte is 30 ml, and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L ferrous chloride, 1 mol / L chromium chloride, 6 mol / L HBr and 8 mol / L KBr. The negative electrolyte is the same as the positive electrolyte.

[0082] 2.Battery assembly:

[0083] Same as Example 1.

[0084] 3.Battery test:

[0085] Charge and discharge at 65°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 1.2V.

[0086] Example 8

[0087] 1. Electrolyte configuration:

[0088] 30ml of positive electrolyte and 30ml of negative electrolyte, wherein the positive electrolyte contains 1mol / L ferrous bromide, 1mol / L chromium bromide, 3mol / L HBr and 0.1mol / L HCl, and the negative electrolyte is the same as the positive electrolyte.

[0089] 2.Battery assembly:

[0090] Same as Example 1.

[0091] 3.Battery test:

[0092] Charge and discharge at 65°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 1.2V.

[0093] Example 9

[0094] 1. Electrolyte configuration:

[0095] The positive electrolyte is 30 ml, and the negative electrolyte is 30 ml. The positive electrolyte contains 1 mol / L ferrous bromide, 1 mol / L chromium bromide, 3 mol / L HBr and 0.5 mol / L HCl. The negative electrolyte is the same as the positive electrolyte.

[0096] 2.Battery assembly:

[0097] Same as Example 1.

[0098] 3.Battery test:

[0099] Charge and discharge at 65°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 1.2V.

[0100] Table 1 Battery performance of comparative examples 1-2 and embodiments 1-9

[0101]

[0102] The battery performance of Comparative Example 1 and Examples 1-7 is shown in Table 1. As the concentration of bromide ions increases, the battery capacity decays and the capacity decay rate slows down. By further increasing the bromine-chlorine ratio, the battery decay is further controlled, but the battery efficiency is reduced to a certain extent.

[0103] from Figure 2 From the cyclic voltammetry curves in the figure, it can be found that when bromide ions are introduced into the chlorine-based iron-chromium flow battery, the reversibility of the electrochemical reaction of the chromium electrode can be improved, thereby reducing the decay rate of the iron-chromium flow battery. This is mainly because the hydration structure of chromium is transformed from the hydration structure of chromium chloride to the hydration structure of chromium chlorobromide, thereby improving its stability. The structure is more stable and not easily deactivated in the electrolyte, thereby slowing down the decay rate of the electrolyte and making the battery run more stably. Further increasing the bromine-chlorine ratio can further control the battery decay, but the battery efficiency is reduced to a certain extent.

[0104] The battery performances of Comparative Examples 1-2 and Examples 8-9 are shown in Table 1. After all the chloride ions in the electrolyte were replaced with bromide ions, the battery decay rate was further improved, but the battery efficiency was significantly reduced. When chloride ions were introduced into the bromide system iron-chromium flow battery, the battery efficiency was further improved without significantly deteriorating the battery decay.

[0105] The above experimental results show that by regulating the ratio of chloride ions, bromide ions and halide ions in the electrolyte, a high-efficiency and low-attenuation-rate iron-chromium flow battery can be achieved.

[0106] 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 by 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. An iron-chromium flow battery electrolyte containing a dihalogen compound, characterized in that: The electrolyte contains iron ions, chromium ions, hydrogen ions, compounds containing chlorine elements and compounds containing bromine elements, wherein the concentration of chloride ions in the electrolyte is 0.1 mol / L to 14 mol / L, the concentration of bromide ions is 0.1 mol / L to 14 mol / L, and the molar ratio of bromide ions to chloride ions is (1:80) to (80:1).

2. The iron-chromium flow battery electrolyte containing a dihalogen compound according to claim 1, characterized in that: The compound containing bromine element is one or more of LiBr, NaBr, KBr, HBr, FeBr3, FeBr2, CrBr3, CrBr2, and NH4Br.

3. The iron-chromium flow battery electrolyte containing a dihalogen compound according to claim 1, characterized in that: The chlorine-containing compound is one or more of LiCl, NaCl, KCl, HCl, FeCl3, FeCl2, CrCl3, CrCl2, and NH4Cl.

4. The iron-chromium flow battery electrolyte containing a dihalogen compound according to claim 1, characterized in that: In the electrolyte, the concentration of iron ions is 0.5 mol / L to 3 mol / L, the concentration of chromium ions is 0.5 mol / L to 3 mol / L, and the concentration of hydrogen ions is 1.5 mol / L to 6 mol / L.

5. The iron-chromium flow battery electrolyte containing a dihalogen compound according to claim 1, characterized in that: The iron ion is Fe 3+ and / or Fe 2+ .

6. The iron-chromium flow battery electrolyte containing a dihalogen compound according to claim 1, characterized in that: The chromium ion is Cr 3+ Cr 2+ 、CrO4 2- CrO2 - and Cr2O7 2- One or more of the .

7. An application of an iron-chromium flow battery electrolyte containing a dihalogen compound according to any one of claims 1 to 6, characterized in that: The electrolyte is used as positive electrode and negative electrode electrolyte in an iron-chromium liquid flow battery.

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