Vanadium battery electrolyte and preparation method thereof

Abstract

The invention relates to the technical field of vanadium batteries, and provides a vanadium battery electrolyte and a preparation method thereof.The preparation method comprises the steps that vanadium pentoxide, concentrated sulfuric acid and water are mixed and then heated, then acid ester is added, then boiling, cooling and filtering are conducted in sequence, and the vanadium battery electrolyte is obtained; the mass ratio of vanadium pentoxide to concentrated sulfuric acid is 1: (1.3-1.5); the mass ratio of the vanadium pentoxide to the acid ester is 1: (1.1-1.3); the acid ester comprises the following components in percentage by mass: 50-51% of oxalic acid, 4-5% of sodium sulfite and 45-46% of ethyl acetate. Compared with the traditional vanadium battery electrolyte, the use amount of the concentrated sulfuric acid and oxalic acid is greatly reduced, the obtained electrolyte is weakly acidic, the corrosivity and danger are greatly reduced, and the electrolyte is not easy to separate out and not easy to block a film in the charging and discharging process. In conclusion, compared with the traditional electrolyte, the vanadium battery electrolyte provided by the invention is safer, more environment-friendly and more efficient.

Description

Technical Field

[0001] This invention relates to the field of vanadium battery technology, and in particular to a vanadium battery electrolyte and its preparation method. Background Technology

[0002] A vanadium battery, also known as a vanadium redox flow battery, is a redox battery in which the active material is in a circulating liquid state. The electrolyte in a vanadium battery is the carrier for energy storage, and the concentration of the electrolyte determines the energy density of the vanadium battery.

[0003] Currently, the common preparation method for vanadium battery electrolytes is to use vanadium compounds such as V2O5 and NH4VO3 to undergo chemical or electrochemical reactions under certain conditions to produce vanadium in different valence states, which are then mixed with concentrated sulfuric acid to form an electrolyte.

[0004] Concentrated sulfuric acid is highly corrosive and oxidizing, and releases a large amount of acid mist when diluted. In the current technology for preparing vanadium battery electrolytes, a large amount of sulfuric acid is used, with a weight ratio of V2O5 to concentrated sulfuric acid of about 1:(6-7). The final vanadium electrolyte has a high sulfuric acid concentration, reaching about 8.5-10 mol / L, which is very acidic. During the production and processing, operators must not touch it with their hands or get it on their clothes. Due to the large size of the battery, the large area of ​​liquid acidic material also poses great safety hazards during transportation, operation, and maintenance. There are also significant safety and environmental issues in the later maintenance, repair, and electrolyte recycling and regeneration processes.

[0005] Furthermore, in the existing technology, oxalic acid is usually used as a reducing agent when preparing vanadium battery electrolyte. The amount of oxalic acid used is relatively large, and the weight ratio of V2O5 to oxalic acid is about 1:(2.5~3). This results in a large amount of oxalic acid residue in the electrolyte, which is easy to precipitate and cause membrane blockage during charging and discharging. Summary of the Invention

[0006] In view of this, the present invention provides a vanadium battery electrolyte and its preparation method. The vanadium battery electrolyte provided by the present invention greatly reduces the amount of sulfuric acid and oxalic acid used, significantly reduces the corrosiveness and hazard of the resulting electrolyte, and is less prone to membrane clogging during charging and discharging.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] A method for preparing a vanadium battery electrolyte includes the following steps:

[0009] Vanadium pentoxide, concentrated sulfuric acid and water are mixed and heated, then nitrite is added, followed by boiling, cooling and filtration to obtain the vanadium battery electrolyte.

[0010] The mass ratio of vanadium pentoxide to concentrated sulfuric acid is 1:(1.3-1.5);

[0011] The mass ratio of vanadium pentoxide to ester is 1:(1.1-1.3);

[0012] The ester comprises the following components by mass fraction: 50-51% oxalic acid, 4-5% sodium sulfite, and 45-46% ethyl acetate.

[0013] Preferably, the heating temperature is 60-70°C.

[0014] Preferably, the mass ratio of vanadium pentoxide to water is 1:5.5 to 6.5.

[0015] Preferably, the boiling time is based on V in the mixing system. 5+ Restore all to V 4+ As the standard.

[0016] Preferably, the mass ratio of vanadium pentoxide to concentrated sulfuric acid is 1:1.5; and the mass ratio of vanadium pentoxide to ester is 1:1.2.

[0017] Preferably, the ester comprises the following components by mass fraction: 50% oxalic acid, 5% sodium sulfite, and 45% ethyl acetate.

[0018] Preferably, the purity of the vanadium pentoxide is 99.99% or higher; and the mass concentration of the concentrated sulfuric acid is 98% or higher.

[0019] Preferably, after adding the ester, the mixture is stirred at 60-70°C for 30 minutes, and then heated to boiling.

[0020] The present invention also provides a vanadium battery electrolyte prepared by the preparation method described above, wherein the components of the vanadium battery electrolyte include VOSO4, H2SO4, Na2SO4, H2C2O4 and water.

[0021] Preferably, the concentration of VOSO4 in the vanadium battery electrolyte is 1.3 to 1.5 mol / L; and the pH value of the vanadium battery electrolyte is 4 to 5.

[0022] This invention provides a method for preparing a vanadium battery electrolyte, comprising the following steps: mixing vanadium pentoxide, concentrated sulfuric acid, and water and heating, then adding an ester, followed by boiling, cooling, and filtering to obtain the vanadium battery electrolyte; the mass ratio of vanadium pentoxide to concentrated sulfuric acid is 1:(1.3-1.5); the mass ratio of vanadium pentoxide to ester is 1:(1.1-1.3); the ester comprises the following components by mass fraction: oxalic acid 50-51%, sodium sulfite 4-5%, and ethyl acetate 45-46%; this invention uses oxalic acid and sodium sulfite as reducing agents and ethyl acetate as a stabilizer to prepare the vanadium battery electrolyte. Compared with traditional vanadium battery electrolytes, the amount of concentrated sulfuric acid used in this invention is greatly reduced, and the resulting electrolyte is weakly acidic (pH value 4-5), greatly reducing corrosiveness and hazard; furthermore, compared with traditional vanadium battery electrolytes, the amount of oxalic acid used in this invention is also greatly reduced, making it less prone to precipitation and membrane blockage during charging and discharging. In summary, the vanadium battery electrolyte provided by this invention is safer, more environmentally friendly, and more efficient than traditional electrolytes.

[0023] The results of the examples show that the vanadium battery electrolyte of the present invention completed more than 3200 charge-discharge cycles. During the charge-discharge process, the electrolyte did not crystallize or precipitate, and no blockage phenomenon was found in the ion membrane. The electrolyte exhibited a high concentration with an energy density of 15-40 Wh / L, a charge-discharge efficiency of over 93%, and a discharge energy of 10.93 Wh. Furthermore, the electrolyte has a wide temperature range and can adapt to environments from -5 to 50°C. Attached Figure Description

[0024] Figure 1 The test results show the charge and discharge efficiency of the all-vanadium redox flow battery using the electrolyte of this invention.

[0025] Figure 2 The current collector plate inside the fuel cell stack is corroded by the highly acidic vanadium battery electrolyte;

[0026] Figure 3 The ion exchange membranes of the vanadium redox flow battery (left) using the electrolyte of this invention and the control group (right) after completing charge-discharge cycles. Detailed Implementation

[0027] This invention provides a method for preparing a vanadium battery electrolyte, comprising the following steps:

[0028] Vanadium pentoxide, concentrated sulfuric acid and water are mixed and heated, then nitrite is added, followed by boiling, cooling and filtration to obtain the vanadium battery electrolyte.

[0029] The mass ratio of vanadium pentoxide to concentrated sulfuric acid is 1:(1.3-1.5);

[0030] The mass ratio of vanadium pentoxide to ester is 1:(1.1-1.3);

[0031] The ester comprises the following components by mass fraction: 50-51% oxalic acid, 4-5% sodium sulfite, and 45-46% ethyl acetate.

[0032] In this invention, the purity of vanadium pentoxide is preferably 99.99% or higher; the mass concentration of concentrated sulfuric acid is preferably 98% or higher; the mass ratio of vanadium pentoxide to concentrated sulfuric acid is preferably 1:1.5; the mass ratio of vanadium pentoxide to ester is preferably 1:1.2; the ester preferably comprises the following components by mass fraction: 50% oxalic acid, 5% sodium sulfite, and 45% ethyl acetate; this invention does not have special requirements for the preparation method of the ester, and oxalic acid, sodium sulfite, and ethyl acetate can be mixed according to the above ratio.

[0033] In this invention, the mass ratio of vanadium pentoxide to water is preferably 1:5.5 to 6.5, and more preferably 1:6.

[0034] In this invention, the heating temperature is preferably 60-70°C.

[0035] In this invention, it is preferable to first mix vanadium pentoxide, concentrated sulfuric acid and water and heat to 60-70°C, then add vanadium ester, stir at 60-70°C for 30 minutes, and then heat to boiling.

[0036] In this invention, the boiling time is expressed as V in the mixing system. 5+ Restore all to V 4+ For the sake of accuracy, in a specific embodiment of the present invention, it is preferred to treat V in the mixed system. 5+ Conduct testing, wait for no V 5+ Upon detection, boiling can be stopped. After boiling, the resulting product is cooled and then subjected to oil-water separation and filtration. In this invention, the ethyl acetate is used as a stabilizer during the reduction process and is separated out during the oil-water separation process after the reduction is completed.

[0037] This invention also provides a vanadium battery electrolyte prepared by the method described above. The vanadium battery electrolyte comprises VOSO4, H2SO4, Na2SO4, H2C2O4, and water. The concentration of VOSO4 in the vanadium battery electrolyte is preferably 1.3–1.5 mol / L, more preferably 1.4–1.5 mol / L. The total concentration of sulfate in the vanadium battery electrolyte is preferably 2.3–2.6 mol / L. The pH value of the vanadium battery electrolyte is preferably 4–5. The vanadium battery electrolyte provided by this invention is weakly acidic, has low corrosiveness and hazard, and is safer and more environmentally friendly than traditional electrolytes.

[0038] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0039] The V2O5 used in the examples had a purity of 99.99%, and the concentrated sulfuric acid had a concentration of 98%.

[0040] Example 1

[0041] V2O5 and concentrated sulfuric acid were added to the reactor at a weight ratio of 1:1.5, followed by the addition of purified water (V2O5 to water weight ratio of 1:6). The mixture was heated to 60°C, and then the ester was added. The weight ratio of V2O5 to the ester was 1:1.2. The ester was composed of the following components by mass fraction: oxalic acid 50%, sodium sulfite 5%, and ethyl acetate 45%.

[0042] After adding the ester, stir at 60°C for 30 minutes, then heat to boiling until V... 5+ Restore all to V 4+ After cooling and filtration, a vanadium battery electrolyte was obtained. The concentration of VOSO4 in the electrolyte was 240 g / L (molar concentration of 1.47 mol / L), the total concentration of sulfate was 2.3 mol / L, and the pH value of the electrolyte was 5.

[0043] Test case

[0044] The electrolyte prepared in Example 1 was applied to a vanadium redox flow battery and tested for 6 months. A conventional strongly acidic vanadium battery electrolyte was used as a control group. The conventional strongly acidic vanadium battery electrolyte contained 1.47 mol / L VOSO4 and 4.2 mol / L H2SO4. The test conditions were: constant current charging at 10A; constant voltage charging at 1.6V; and constant power discharging at 10W.

[0045] The results show that during the test, the vanadium redox flow battery using the electrolyte of this invention completed more than 3,200 charge-discharge cycles. During the test, there was no crystallization or precipitation of the electrolyte, no blockage of the ion membrane was found, the electrolyte had a high concentration, an energy density of 15-40 Wh / L, a charge-discharge efficiency of over 93%, a discharge energy of 10.93 Wh, and a wide temperature range, which can adapt to environments from -5 to 50℃.

[0046] Figure 1 The test results of the charge and discharge efficiency of the all-vanadium redox flow battery using the electrolyte of this invention are based on... Figure 1 It can be seen that the vanadium battery electrolyte of the present invention exhibits good charge-discharge effect during the charge-discharge process.

[0047] Midway through the experiment (after approximately 50 cycles, with a runtime of about 200 hours), the control group stack exhibited slight electrolyte leakage. Upon disassembly, significant corrosion marks were found on the internal structure. Figure 2 This is a current collector plate inside the fuel cell stack that has been corroded by the highly acidic vanadium battery electrolyte.

[0048] The vanadium redox flow battery using the electrolyte of this invention exhibits no crystallization, precipitation, or sedimentation of the electrolyte at a discharge energy of 10.93Wh, and the ion membrane is also free from blockage, whereas the control group showed these blockage phenomena. Figure 3 The ion-exchange membranes of the vanadium redox flow battery (left) and the control group (right) after completing charge-discharge cycles are shown below. Figure 3 It can be seen that in the vanadium redox flow battery using the electrolyte of this invention, the ion membrane was not blocked, while the ion membrane of the control group was blocked, indicating that precipitation occurred in the strongly acidic vanadium battery electrolyte during charge-discharge cycles.

[0049] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a vanadium battery electrolyte, characterized in that, Includes the following steps: Vanadium pentoxide, concentrated sulfuric acid and water are mixed and heated, then nitrite is added, followed by boiling, cooling and filtration to obtain the vanadium battery electrolyte. The mass ratio of vanadium pentoxide to concentrated sulfuric acid is 1:(1.3-1.5); The mass ratio of vanadium pentoxide to ester is 1:(1.1-1.3); The ester comprises the following components by mass fraction: 50-51% oxalic acid, 4-5% sodium sulfite, and 45-46% ethyl acetate.

2. The preparation method according to claim 1, characterized in that, The heating temperature is 60–70°C.

3. The preparation method according to claim 1, characterized in that, The mass ratio of vanadium pentoxide to water is 1:5.5 to 6.

5.

4. The preparation method according to claim 1, characterized in that, The boiling time is based on V in the mixing system. 5+ Restore all to V 4+ As the standard.

5. The preparation method according to claim 1, characterized in that, The mass ratio of vanadium pentoxide to concentrated sulfuric acid is 1:1.5; the mass ratio of vanadium pentoxide to ester is 1:1.

2.

6. The preparation method according to claim 1, characterized in that, The ester comprises the following components by mass fraction: 50% oxalic acid, 5% sodium sulfite, and 45% ethyl acetate.

7. The preparation method according to claim 1, characterized in that, The purity of the vanadium pentoxide is above 99.99%; the mass concentration of the concentrated sulfuric acid is above 98%.

8. The preparation method according to claim 1, characterized in that, After adding the ester, stir at 60-70°C for 30 minutes, and then heat to boiling.

9. The vanadium battery electrolyte prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The vanadium battery electrolyte comprises VOSO4, H2SO4, Na2SO4, H2C2O4, and water.

10. The vanadium battery electrolyte according to claim 9, characterized in that, The concentration of VOSO4 in the vanadium battery electrolyte is 1.3–1.5 mol / L; the pH value of the vanadium battery electrolyte is 4–5.

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