Method for online recovery of performance of iron-chromium flow battery

Abstract

The invention discloses a method for recovering the performance of an iron-chromium flow battery on line, which comprises the following steps: completely discharging the iron-chromium flow battery to be recovered, and introducing the positive electrolyte of the iron-chromium flow battery into the battery negative electrode of an external balancing device; adding a hydrochloric acid solution into the positive electrode of the battery of the external balancing device; the external balancing device is operated, parameters of the external balancing device are set, charging reduction is carried out, and the reduced electrolyte is introduced into the positive electrode of the iron-chromium flow battery again; rare metal chloride is added into the negative electrolyte of the iron-chromium flow battery, and the surface of the negative electrolyte is covered with organic matter for sealing treatment. In order to solve the problem that the capacities of positive and negative electrolyte are greatly attenuated in the long-time operation process of a commercial iron-chromium flow battery, InCl3 is added to improve the ion activity and inhibit the capacity attenuation, and the positive electrolyte is introduced into an external balancing device and a hydrochloric acid solution to form a primary battery for charging and reducing Fe < 3 + >; and online performance recovery of the iron-chromium flow battery is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage, and more specifically, the present invention relates to a method for online recovery performance of an iron-chromium liquid flow battery. Background Art

[0002] Clean renewable energy such as wind and solar energy is urgently needed to increase its share in total electricity consumption, but its output is unstable. Iron-chromium liquid flow batteries provide an important solution for storing wind and solar energy with safety, stability and low cost. After comprehensively considering indicators such as energy density, efficiency, scale, cycle life and cost, liquid flow energy storage battery technology is considered the best choice in adapting to the new generation of power grids.

[0003] After long-term operation, a large amount of trivalent iron ions will accumulate in the positive electrode of the iron-chromium flow battery. In order to restore the capacity of the iron-chromium flow battery, the trivalent iron ions need to be reduced to divalent iron ions. In the existing technology, the byproduct hydrogen is used to continuously reduce the positive electrode electrolyte. The system itself has high requirements for technology and cost, and the system needs to be continuously maintained. The subsequent investment cost is huge, and technical innovation and solutions are urgently needed to overcome it. Summary of the invention

[0004] An object of the present invention is to solve at least the above problems and / or disadvantages and to provide at least the advantages which will be described hereinafter.

[0005] In order to achieve these purposes and other advantages of the present invention, a method for online recovery of performance of an iron-chromium flow battery is provided, characterized in that it comprises the following steps:

[0006] Step 1: Completely discharge the iron-chromium flow battery to be restored, open the valve of the positive electrolyte outlet, and introduce the positive electrolyte of the iron-chromium flow battery into the negative electrode of the battery of the external balancing device;

[0007] Step 2: Close the positive electrolyte outlet valve and add hydrochloric acid solution to the positive electrode of the battery in the external balancing device;

[0008] Step 3: Run the external balancing device, set the parameters of the external balancing device, perform charging and reduction, then open the valve of the positive electrode electrolyte inlet of the iron-chromium liquid flow battery, re-introduce the reduced electrolyte into the positive electrode of the iron-chromium liquid flow battery, and close the valve of the positive electrode electrolyte inlet of the iron-chromium liquid flow battery;

[0009] Step 4: Add rare metal chlorides to the negative electrode electrolyte of the iron-chromium liquid flow battery, and cover the surface of the negative electrode electrolyte with organic matter for sealing.

[0010] Preferably, in step 2, the concentration of the hydrochloric acid solution is 2-4 mol / L.

[0011] Preferably, in step 2, the volume of the added hydrochloric acid solution is equal to the volume of the introduced positive electrode electrolyte.

[0012] Preferably, in step three, the parameters of the external balancing device include: temperature, electrolyte flow rate and current density.

[0013] Preferably, the temperature is 40-70°C.

[0014] Preferably, the electrolyte flow rate is 30 to 60 cm 3 / s.

[0015] Preferably, the current density is 16-96 mA / cm 2 .

[0016] Preferably, in step 4, the rare metal chloride is InCl 3 The amount added is 0.3~0.6mol / L.

[0017] Preferably, in step 4, the organic matter is one or more of polyurethane and acrylate.

[0018] Preferably, in step 4, the amount of organic matter used is 10-20% of the total volume of the negative electrode electrolyte.

[0019] Preferably, in step 4, a composite additive is used to replace InCl 3 The preparation method of the composite additive is: InCl 3 and GaCl 3 Add deionized water in a molar ratio of 1:0.1-0.3, add hexadecyltrimethylammonium bromide after ultrasonic dispersion for 20-50 minutes, continue ultrasonic dispersion for 1-2 hours, let stand for 8-14 hours, and vacuum dry at 80-120°C for 12-36 hours to obtain a composite additive; wherein InCl 3 and GaCl 3 The ratio of total mass to deionized water volume is 1g:50~120mL, InCl 3 and GaCl 3 The mass ratio of the total mass to the mass ratio of hexadecyltrimethylammonium bromide is 1:0.1-0.5; the specific conditions of ultrasonic dispersion are: power 200-500W, frequency 50-70kHz, temperature 50-70℃.

[0020] The present invention has at least the following beneficial effects:

[0021] (1) The present invention uses hydrochloric acid solution as the positive electrode electrolyte and the positive electrode electrolyte of the iron-chromium flow battery as the negative electrode electrolyte, and forms an external balancing device with a single cell or a battery stack and a DC power supply to quickly reduce trivalent iron ions to divalent iron ions to achieve online performance recovery of the iron-chromium flow battery. The method has low cost, simple operation, low maintenance cost, and great application prospects;

[0022] (2) The present invention can effectively inhibit the hydrogen evolution side reaction and increase the activity of Cr ions with different valence states by adding a certain proportion of rare metal chloride to the negative electrode electrolyte of the iron-chromium liquid flow battery and adding organic matter to the surface of the negative electrode electrolyte, thereby reducing the capacity decay and significantly improving the battery performance.

[0023] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with embodiments so that those skilled in the art can implement the invention with reference to the description.

[0025] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0026] In the following embodiments, the external balancing device includes a battery and a DC power supply, a hydrochloric acid solution is added to the positive electrode of the battery, the positive electrode electrolyte of the iron-chromium liquid flow battery is introduced into the negative electrode of the battery, and the DC power supply is energized to the battery, thereby reducing the trivalent iron ions in the positive electrode electrolyte of the iron-chromium liquid flow battery to divalent iron ions, and at the same time, the chloride ions in the hydrochloric acid solution are oxidized to chlorine gas, and the reaction is as follows:

[0027]

[0028] Example 1

[0029] A method for online recovery of performance of an iron-chromium flow battery comprises the following steps:

[0030] Step 1: Completely discharge the iron-chromium flow battery to be restored, open the valve of the positive electrolyte outlet, and introduce the positive electrolyte in the positive electrode of the iron-chromium flow battery into the negative electrode of the battery of the external balancing device, wherein the molar ratio of iron ions, chromium ions, and hydrochloric acid in the positive electrolyte is 1:1:3;

[0031] Step 2: Close the positive electrolyte outlet valve and add an equal volume of 3 mol / L hydrochloric acid solution to the positive electrode of the battery in the external balancing device;

[0032] Step 3: Run the external balancing device, set the temperature of the external balancing device to 50°C and the electrolyte flow rate to 40cm 3 / s, current density is 40mA / cm 2 , and charge and restore; the charging process uses the coulometer method to accurately measure the amount of charge flowing through the battery during the charging process. A coulometer is connected in series in the charging circuit to monitor and accumulate the amount of electricity passed in real time. When charging is completed, the accumulated charge value can be approximately regarded as the capacity charged in the battery. When the capacity reaches 680mAh (20mL), it is fully recovered. The valve of the positive electrode electrolyte inlet of the iron-chromium liquid flow battery is opened, and the fully recovered electrolyte is reintroduced into the positive electrode of the iron-chromium liquid flow battery, and the valve of the positive electrode electrolyte inlet of the iron-chromium liquid flow battery is closed;

[0033] Step 4: Add InCl to the negative electrolyte of the iron-chromium flow battery 3 , so that InCl 3 The concentration in the negative electrode electrolyte is 0.6 mol / L, and the surface of the negative electrode electrolyte is covered with organic polyurethane for sealing treatment; the volume of the organic matter is 10% of the total volume of the negative electrode electrolyte, and the molar ratio of iron ions, chromium ions and hydrochloric acid in the negative electrode electrolyte is 1:1:3.

[0034] Example 2

[0035] A method for online recovery of performance of an iron-chromium flow battery comprises the following steps:

[0036] Step 1: Completely discharge the iron-chromium flow battery to be restored, open the valve of the positive electrolyte outlet, and introduce the positive electrolyte in the positive electrode of the iron-chromium flow battery into the negative electrode of the battery of the external balancing device, wherein the molar ratio of iron ions, chromium ions, and hydrochloric acid in the positive electrolyte is 1.2:1.4:2;

[0037] Step 2: Close the positive electrolyte outlet valve and add an equal volume of 2.4 mol / L hydrochloric acid solution to the positive electrode of the battery in the external balancing device;

[0038] Step 3: Run the external balancing device, set the temperature of the external balancing device to 60°C and the electrolyte flow rate to 50cm 3 / s, current density is 50mA / cm 2 , and charge and restore; when the capacity reaches 700mAh (20mL) for full recovery, open the valve of the positive electrode electrolyte inlet of the iron-chromium flow battery, re-introduce the fully recovered electrolyte into the positive electrode of the iron-chromium flow battery, and close the valve of the positive electrode electrolyte inlet of the iron-chromium flow battery;

[0039] Step 4: Add InCl to the negative electrolyte of the iron-chromium flow battery 3 , so that InCl3 The concentration in the negative electrode electrolyte is 0.8 mol / L, and the surface of the negative electrode electrolyte is covered with organic polyurethane for sealing treatment; the volume of the organic matter is 15% of the total volume of the negative electrode electrolyte, and the molar ratio of iron ions, chromium ions, and hydrochloric acid in the negative electrode electrolyte is 1.2:1.4:2.

[0040] Example 3

[0041] A method for online recovery of performance of an iron-chromium flow battery comprises the following steps:

[0042] Step 1: Completely discharge the iron-chromium flow battery to be restored, open the valve of the positive electrolyte outlet, and introduce the positive electrolyte in the positive electrode of the iron-chromium flow battery into the negative electrode of the battery of the external balancing device, wherein the molar ratio of iron ions, chromium ions, and hydrochloric acid in the positive electrolyte is 1:1:3;

[0043] Step 2: Close the positive electrolyte outlet valve and add an equal volume of 2.5 mol / L hydrochloric acid solution to the positive electrode of the battery in the external balancing device;

[0044] Step 3: Run the external balancing device, set the temperature of the external balancing device to 40°C and the electrolyte flow rate to 40cm 3 / s, current density is 40mA / cm 2 , and charge and restore; when the capacity reaches 690mAh (20mL), it is fully recovered, open the valve of the positive electrode electrolyte inlet of the iron-chromium liquid flow battery, re-introduce the fully recovered electrolyte into the positive electrode of the iron-chromium liquid flow battery, and close the valve of the positive electrode electrolyte inlet of the iron-chromium liquid flow battery;

[0045] Step 4: Add InCl to the negative electrolyte of the iron-chromium flow battery 3 , so that InCl 3 The concentration in the negative electrode electrolyte is 0.7 mol / L, and the surface of the negative electrode electrolyte is covered with organic polyurethane for sealing treatment; the volume of the organic matter is 14% of the total volume of the negative electrode electrolyte, and the molar ratio of iron ions, chromium ions and hydrochloric acid in the negative electrode electrolyte is 1:1:3.

[0046] The data of the performance of the iron-chromium flow battery of Examples 1 to 3 before and after the recovery are shown in Table 1. It can be seen that, through the method of the present invention, the capacity and coulombic efficiency of the iron-chromium flow battery are significantly improved, and its electrochemical performance is effectively recovered.

[0047] Table 1

[0048]

[0049] Example 4

[0050] In this embodiment, in step 4, a composite additive is used to replace InCl 3 The remaining steps are the same as those in Example 1; the preparation method of the composite additive is: InCl 3 and GaCl 3 The mixture was added into deionized water at a molar ratio of 1:0.2, and ultrasonically dispersed at 60°C, 55kHz, and 300W for 30 minutes, and then hexadecyltrimethylammonium bromide was added. The mixture was ultrasonically dispersed at 60°C, 55kHz, and 300W for 1 hour, and then allowed to stand for 12 hours. The mixture was vacuum dried at 100°C for 24 hours to obtain a composite additive. Among them, InCl 3 and GaCl 3 The ratio of total mass to deionized water volume is 1g:80mL, InCl 3 and GaCl 3 The mass ratio of the total mass to hexadecyltrimethylammonium bromide is 1:0.3.

[0051] In this embodiment, InCl 3 and GaCl 3 The composite additive is used to prepare the raw material, which is beneficial to improve the hydrogen evolution overpotential of the electrolyte and slow down the capacity decay; at the same time, hexadecyltrimethylammonium bromide can be used as a surfactant to promote the uniform dispersion of the raw material and improve the electrochemical performance of the electrolyte. Adding the composite additive of the present invention to the negative electrode electrolyte can further reduce the amount of hydrogen evolution of the negative electrode electrolyte, improve the efficiency of the battery, and improve the electrochemical performance of the battery.

[0052] Example 5

[0053] In this embodiment, when preparing the composite additive, hexadecyltrimethylammonium bromide is not added, and the remaining steps are the same as those in Embodiment 4.

[0054] The data of the performance of the iron-chromium flow batteries of Examples 1, 4-5 before and after recovery are shown in Table 2. It can be seen that compared with Example 1, the batteries of Examples 4-5 with the addition of the composite additive have a greater improvement in coulombic efficiency after recovery than before recovery, and the capacity attenuation rate is lower after 200 constant current charge and discharge cycles.

[0055] Table 2

[0056]

[0057] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A method for online performance recovery of an iron-chromium flow battery, characterized in that: The following steps are involved: Step 1: Completely discharge the iron-chromium flow battery to be restored, open the valve of the positive electrolyte outlet, and introduce the positive electrolyte of the iron-chromium flow battery into the negative electrode of the battery of the external balancing device; Step 2: Close the positive electrolyte outlet valve and add hydrochloric acid solution to the positive electrode of the battery in the external balancing device; Step 3: Run the external balancing device, set the parameters of the external balancing device, perform charging and reduction, then open the valve of the positive electrode electrolyte inlet of the iron-chromium liquid flow battery, re-introduce the reduced electrolyte into the positive electrode of the iron-chromium liquid flow battery, and close the valve of the positive electrode electrolyte inlet of the iron-chromium liquid flow battery; Step 4: Add rare metal chlorides to the negative electrode electrolyte of the iron-chromium liquid flow battery, and cover the surface of the negative electrode electrolyte with organic matter for sealing.

2. A method for online recovery of performance of an iron-chromium flow battery as claimed in claim 1, characterized in that: In the step 2, the concentration of the hydrochloric acid solution is 2-4 mol / L.

3. The method for online recovery of performance of an iron-chromium flow battery according to claim 1, characterized in that: In the step 2, the volume of the added hydrochloric acid solution is equal to the volume of the introduced positive electrode electrolyte.

4. The method for online recovery of performance of an iron-chromium flow battery according to claim 1, characterized in that: In step three, the parameters of the external balancing device include: temperature, electrolyte flow rate and current density.

5. A method for online performance recovery of an iron-chromium flow battery as claimed in claim 4, characterized in that: The temperature is 40-70°C.

6. A method for online performance recovery of an iron-chromium flow battery as claimed in claim 4, characterized in that: The electrolyte flow rate is 30-60 cm 3 / s.

7. A method for online performance recovery of an iron-chromium flow battery as claimed in claim 4, characterized in that: The current density is 16-96 mA / cm 2 .

8. The method for online recovery of performance of an iron-chromium flow battery according to claim 1, characterized in that: In the step 4, the rare metal chloride is InCl3, and the addition amount thereof is 0.3-0.6 mol / L.

9. The method for online recovery of performance of an iron-chromium flow battery according to claim 1, characterized in that: In the step 4, the organic matter is one or more of polyurethane and acrylate.

10. The method for online recovery of performance of an iron-chromium flow battery according to claim 1, characterized in that: In the step 4, the amount of organic matter used is 10-20% of the total volume of the negative electrode electrolyte.

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