Composite additive, vanadium electrolyte and all-vanadium redox flow battery

Abstract

The present application belongs to the field of liquid flow battery, and particularly relates to a composite additive, a vanadium electrolyte and a full vanadium liquid flow battery. The composite additive of the present application comprises acetylacetone-based complexing agent and dispersant. The vanadium electrolyte comprising the composite additive of the present application can improve the high and low temperature stability of the vanadium electrolyte, and can improve the performance of the full vanadium liquid flow battery.

Description

Technical Field

[0001] This invention belongs to the field of flow batteries, specifically relating to a composite additive, vanadium electrolyte, and an all-vanadium flow battery. Background Technology

[0002] Vanadium electrolyte, as the key carrier for the conversion of chemical energy into electrical energy in vanadium redox flow batteries (VFBs), directly affects the capacity of the VFB due to its concentration and volume. Simultaneously, the electrochemical activity and stability of the vanadium electrolyte determine the reliability and stability of the VFB during operation. With the continuous development of the VFB field and the constant increase in current density, the requirements for vanadium electrolyte concentration are also increasing.

[0003] However, traditional vanadium electrolyte preparation technologies suffer from numerous problems, such as insufficient electrolyte activity, poor stability, and difficulty in increasing concentration. These issues severely limit the performance and application range of VFBs. Especially at high current densities, traditional vanadium electrolytes often fail to meet the battery's requirements for energy density and cycle stability, leading to decreased battery efficiency and shortened lifespan.

[0004] Therefore, there is an urgent need to develop a vanadium electrolyte with high activity and high stability. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a composite additive, a vanadium electrolyte, and a full vanadium redox flow battery. The composite additive of this invention comprises an acetylacetone-based complexing agent and a dispersant. The vanadium electrolyte containing the acetylacetone-based complexing agent and dispersant can improve the high and low temperature stability of the vanadium electrolyte and also act as a catalytic oxidant to enhance the performance of the full vanadium redox flow battery.

[0006] Specifically, the present invention provides a composite additive comprising an acetylacetone complexing agent and a dispersant.

[0007] In one or more embodiments, the acetylacetone-based complexing agent is selected from one or more of acetylacetone, vanadium acetylacetone, and vanadium acetylacetone oxyacetate.

[0008] In one or more embodiments, the dispersant is selected from one or more of methanol, ethanol, toluene, acetone and ethyl acetate.

[0009] In one or more embodiments, the mass ratio of the acetylacetone complexing agent to the dispersant is 1:(0.5-0.8).

[0010] This invention provides a vanadium electrolyte, which comprises vanadium ions, an acidic supporting electrolyte, and any composite additive of this invention.

[0011] In one or more embodiments, the content of the composite additive in the vanadium electrolyte is 0.01wt% to 1wt%.

[0012] In one or more embodiments, calculations are performed with the acidic supporting electrolyte being fully ionized, wherein the molar ratio of vanadium ions to hydrogen ions in the vanadium electrolyte is 1:(3-6).

[0013] In one or more embodiments, calculations are performed with the acidic supporting electrolyte being fully ionized, and the molar concentration ratio of vanadium ions to hydrogen ions in the vanadium electrolyte is 1:(4.3-4.6).

[0014] In one or more embodiments, the acidic supporting electrolyte is selected from one or more of sulfuric acid, hydrochloric acid, and methanesulfonic acid.

[0015] In one or more embodiments, the concentration of vanadium ions in the vanadium electrolyte is 1-3 mol / L.

[0016] In one or more embodiments, the concentration of vanadium ions in the vanadium electrolyte is 1.5-2.5 mol / L.

[0017] This invention provides an all-vanadium redox flow battery comprising any of the vanadium electrolytes described in this invention.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects: the acetylacetone complexing agent in the vanadium electrolyte of the present invention has a good complexing and dispersing effect on vanadium ions of various valence states. The dispersant promotes the further dispersion of the complex in the vanadium electrolyte system, effectively increases the high and low temperature stability of the vanadium electrolyte, inhibits the transmembrane migration behavior of vanadium ions, and at the same time, the generated acetylacetone vanadium / vanadium oxide has a catalytic oxidation effect, effectively improving the electrochemical activity of the vanadium electrolyte during the charging and discharging process. Detailed Implementation

[0019] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0020] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0021] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0022] In this document, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0023] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0024] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0025] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0026] The composite additive of this invention comprises an acetylacetone-based complexing agent and a dispersant. Improving the stability of vanadium electrolytes cannot be achieved with only an acetylacetone-based complexing agent and no dispersant, or with only a dispersant and no acetylacetone-based complexing agent. This invention improves the stability of vanadium electrolytes through the synergistic effect of the acetylacetone-based complexing agent and the dispersant, thereby improving the three main efficiencies and charge / discharge energy of the vanadium redox flow battery.

[0027] In this invention, the acetylacetone-based complexing agent can be one or more selected from acetylacetone, vanadium acetylacetone, and vanadium acetylacetone oxide. In this invention, the dispersant can be one or more selected from methanol, ethanol, toluene, acetone, and ethyl acetate. In this invention, selecting the above-mentioned acetylacetone-based complexing agent and dispersant can synergistically improve the stability of the vanadium electrolyte and enhance the three major efficiencies and charge / discharge energy of the vanadium redox flow battery.

[0028] In this invention, the mass ratio of acetylacetone-based complexing agent to dispersant can be 1:(0.5-0.8), for example, 1:0.5, 1:0.6, 1:0.7, or 1:0.8. Controlling the mass ratio of acetylacetone-based complexing agent to dispersant in the composite additive within this invention is beneficial for improving the stability of the vanadium electrolyte and enhancing the three main efficiencies and charge / discharge energy of the vanadium redox flow battery.

[0029] The vanadium electrolyte of this invention comprises vanadium ions, an acidic supporting electrolyte, and the composite additive of this invention. The content of the composite additive in the vanadium electrolyte of this invention can be 0.01wt% to 1wt%, for example, 0.01wt%, 0.03wt%, 0.05wt%, 0.07wt%, 0.09wt%, 0.1wt%, 0.3wt%, 0.5wt%, 0.7wt%, 0.9wt%, or 1wt%. In this invention, allowing the content of the composite additive to be between 0.01wt% and 1wt% is beneficial for improving the stability of the vanadium electrolyte and enhancing the three main efficiencies and charge / discharge energy of the vanadium redox flow battery.

[0030] In this invention, the acidic supporting electrolyte can be one or more selected from sulfuric acid, hydrochloric acid, and methanesulfonic acid. In this invention, based on the complete ionization of the acidic supporting electrolyte, the molar ratio of vanadium ions to hydrogen ions in the vanadium electrolyte can be 1:(3-6), preferably 1:(4.3-4.6), for example 1:4.3, 1:4.4, 1:4.5, and 1:4.6.

[0031] In this invention, the acidic supporting electrolyte can be sulfuric acid or hydrochloric acid. In the corresponding vanadium 3.5 valence electrolyte, the sulfate concentration can be between 2-5 mol / L, and the chloride ion concentration can be between 3-6 mol / L. During use, the concentrations of both can be dynamically adjusted according to the hydrogen ion concentration.

[0032] In this invention, the acidic supporting electrolyte can be sulfuric acid and methanesulfonic acid. In the corresponding 3.5 valence vanadium electrolyte, the sulfate concentration can be between 2-5 mol / L, and the methanesulfonic acid concentration can be between 0.1-2 mol / L. During use, the concentrations of both can be dynamically adjusted according to the hydrogen ion concentration. In the vanadium electrolyte of this invention, the vanadium ion concentration can be 1-3 mol / L, preferably 1.5-2.5 mol / L, for example 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, and 2.5 mol / L. This invention provides a full vanadium redox flow battery incorporating the vanadium electrolyte of this invention.

[0033] The present invention will be described below by way of specific embodiments. It should be understood that these embodiments are merely illustrative and are not intended to limit the scope of the invention. The methods, reagents, and materials used in the embodiments are conventional methods, reagents, and materials in the art, unless otherwise stated. The raw material compounds in the embodiments are all commercially available.

[0034] Example 1

[0035] In this embodiment, a composite additive was prepared with a mass ratio of acetylacetone vanadium oxide and acetone of 1:0.5. The composite additive was added to the sulfuric acid-based electrolyte and allowed to dissolve completely to obtain a vanadium electrolyte with a composite additive content of 0.05 wt%. The concentration of vanadium ions (3.5 valence) was 1.7 mol / L and the concentration of hydrogen ions was 7.31 mol / L.

[0036] Example 2

[0037] The other conditions in this embodiment are the same as in Embodiment 1, except that the content of the composite additive in this embodiment is 0.5 wt%.

[0038] Example 3

[0039] The other conditions in this embodiment are the same as in embodiment 1, except that the content of the composite additive in this embodiment is 1 wt%.

[0040] Example 4

[0041] In this embodiment, a composite additive was prepared according to a mass ratio of vanadium acetylacetonate to acetone of 1:0.8. The composite additive was added to a sulfuric acid / hydrochloric acid-based electrolyte and allowed to dissolve completely to obtain a vanadium electrolyte with a composite additive content of 0.07 wt%. The concentration of vanadium ions (3.5 valence) was 2.2 mol / L, the concentration of hydrogen ions was 10 mol / L, the concentration of sulfate ions was 2 mol / L, and the concentration of chloride ions was 6 mol / L.

[0042] Example 5

[0043] The other conditions in this embodiment are the same as in embodiment 4, except that the content of the composite additive in this embodiment is 0.7 wt%.

[0044] Example 6

[0045] In this embodiment, a composite additive was prepared according to a mass ratio of acetylacetone vanadium oxide and acetone of 1:0.8. The composite additive was added to a sulfuric acid / methanesulfonic acid-based electrolyte and allowed to dissolve completely to obtain a vanadium electrolyte with a composite additive content of 0.05 wt%. The concentration of vanadium ions (3.5 valence) was 2 mol / L, the concentration of hydrogen ions was 9.6 mol / L, the concentration of sulfate ions was 4.5 mol / L, and the concentration of methanesulfonic acid was 0.6 mol / L.

[0046] Comparative Example 1

[0047] The conditions for this comparative example are the same as those for Example 1, except that the composite additive in this comparative example contains only vanadium acetylacetonate.

[0048] Comparative Example 2

[0049] The conditions for this comparative example are the same as those for Example 4, except that the composite additive in this comparative example contains only acetone.

[0050] Comparative Example 3

[0051] The conditions for this comparative example are the same as those for Example 1, except that the composite additive in this comparative example contains only acetone.

[0052] Comparative Example 4

[0053] The conditions for this comparative example are the same as those for Example 4, except that the composite additive in this comparative example contains only vanadium acetylacetonate.

[0054] Comparative Example 5

[0055] The conditions for this comparative example are the same as those for Example 1, except that the ratio of acetylacetone vanadium oxide to acetone in the composite additive of this comparative example is 1:0.4.

[0056] Comparative Example 6

[0057] The conditions for this comparative example are the same as those for Example 1, except that the amount of the composite additive added in this comparative example is 1.1 wt%.

[0058] Blank Group 1

[0059] The other conditions for this blank group are the same as those for Example 1, except that this blank group does not contain composite additives.

[0060] Blank Group 2

[0061] The other conditions for this blank group are the same as those for Example 4, except that this blank group does not contain composite additives.

[0062] Blank Group 3

[0063] The other conditions for this blank group are the same as those for Example 6, except that this blank group does not contain composite additives.

[0064] Test Example 1

[0065] Vanadium electrolyte stability test: The vanadium electrolytes prepared in Examples 1-6 and Comparative Examples 1-6 were charged and discharged sequentially to obtain divalent, trivalent, tetravalent and pentavalent vanadium electrolytes, respectively. The stable existence time of divalent and trivalent vanadium electrolytes at -10℃ and the stable existence time of tetravalent and pentavalent vanadium electrolytes at 45℃ were tested.

[0066] The deposition times of divalent, trivalent, tetravalent, and pentavalent vanadium electrolytes in blank group 1, Examples 1-3, Comparative Examples 1, 3, and 5-6 under low and high temperature conditions are shown in Table 1; the deposition times of divalent, trivalent, tetravalent, and pentavalent vanadium electrolytes in blank group 2, Examples 4-5, Comparative Examples 2, and 4 under low and high temperature conditions are shown in Table 2; the deposition times of divalent, trivalent, tetravalent, and pentavalent vanadium electrolytes in blank group 3 and Example 6 under low and high temperature conditions are shown in Table 3.

[0067] Table 1: Stable time of divalent, trivalent, tetravalent, and pentavalent vanadium electrolytes in blank group 1, Examples 1-3, Comparative Examples 1, 3, and 5-6

[0068]

[0069] (Note: d represents the number of days)

[0070] Table 2: Stable time of divalent, trivalent, tetravalent and pentavalent vanadium electrolytes in blank group 2, Examples 4-5, Comparative Examples 2 and 4

[0071]

[0072] (Note: d represents the number of days)

[0073] Table 3: Stable time of divalent, trivalent, tetravalent, and pentavalent vanadium electrolytes in blank group 3 and Example 6

[0074]

[0075] (Note: d represents the number of days)

[0076] Table 1 shows that the composite additive increased the high and low temperature stability of the vanadium electrolyte using sulfuric acid as the electrolyte. Examples 1-3, Comparative Example 6, and Blank Group 1 show that within the range of 0.01 wt% to 1 wt%, the stability of the vanadium electrolyte increased with the increase of the amount of composite additive. However, when the amount of composite additive increased to 1.1 wt%, exceeding the range of 0.01 wt% to 1 wt%, the stability of the vanadium electrolyte decreased. In Comparative Example 1, the composite additive only contained an acetylacetone complexing agent and no dispersant, resulting in poor stability of the corresponding vanadium electrolyte. In Comparative Example 3, the composite additive only contained a dispersant and no acetylacetone complexing agent, resulting in poor stability of the corresponding vanadium electrolyte. Therefore, based on Comparative Examples 1, 3, and Blank Group 1, neither having an acetylacetone complexing agent without a dispersant nor having only a dispersant without an acetylacetone complexing agent can improve the stability of the vanadium electrolyte. In Comparative Example 5, the mass ratio of acetylacetone complexing agent to dispersant in the composite additive was 1:0.4, resulting in poor stability of the vanadium electrolyte. Therefore, as can be seen from Example 1, Comparative Example 5, and Blank Group 1, controlling the mass ratio of acetylacetone complexing agent to dispersant in the composite additive between 1:(0.5-0.8) is beneficial to improving the stability of the vanadium electrolyte.

[0077] Table 2 shows that the composite additives improved the high and low temperature stability of the vanadium electrolyte using sulfuric acid / hydrochloric acid as the electrolyte. In Comparative Example 4, the composite additives only contained acetylacetone complexing agents and no dispersants, resulting in poor stability of the vanadium electrolyte. In Comparative Example 2, the composite additives only contained dispersants and no acetylacetone complexing agents, resulting in poor stability of the vanadium electrolyte. Therefore, based on Comparative Examples 2, 4, and Blank Group 2, it can be seen that neither having only acetylacetone complexing agents without dispersants nor having only dispersants without acetylacetone complexing agents can improve the stability of the vanadium electrolyte.

[0078] As shown in Table 3, the composite additives increased the high and low temperature stability of the vanadium electrolyte using sulfuric acid / methanesulfonic acid as the electrolyte.

[0079] Test Example 2

[0080] Charge-discharge test: The vanadium 3,5-valent electrolytes prepared in Examples 1, 4, Comparative Examples 1, 2, 3, and 4, as well as blank group 1 and blank group 2, had an effective area of ​​48 cm². 2 A carbon felt with a compression ratio of 20% was used to assemble an all-vanadium redox flow battery. The charge / discharge range was controlled between 1-1.55V and 160mA / cm. 2At different current densities, the charge-discharge capacity and three efficiencies of vanadium redox flow batteries assembled with vanadium electrolytes prepared in Examples 1, 4, 1, 2, 3, 4, 1 (blank), and 2 (blank) were tested during 100 cycles. Table 4 shows the charge-discharge capacity (charging capacity and discharging capacity) and three efficiencies (energy efficiency, voltage efficiency, and charge-discharge efficiency) of vanadium redox flow batteries assembled with vanadium electrolytes prepared in Blank 1, Example 1, 1, and 3 during the 5th cycle of 100 cycles. Table 5 shows the charge-discharge capacity and three efficiencies of vanadium redox flow batteries assembled with vanadium electrolytes prepared in Blank 2, Example 4, 2, and 4 during the 5th cycle of 100 cycles.

[0081] Table 4: Charge-discharge capacity and three major efficiencies of all-vanadium redox flow batteries assembled with vanadium electrolytes prepared in blank group 1, example 1, comparative example 1 and comparative example 3 during 100 cycles.

[0082]

[0083] Table 5: Charge-discharge capacity and three major efficiencies of all-vanadium redox flow batteries assembled with vanadium electrolytes prepared in blank group 2, example 4, comparative example 2 and comparative example 4 during 100 cycles.

[0084]

[0085] As shown in Table 4, the charge / discharge capacity and overall efficiencies of the vanadium redox flow batteries corresponding to Comparative Example 1, Comparative Example 3, and Blank Group 1 are all lower than those of Example 1. As shown in Table 5, the charge / discharge capacity and overall efficiencies of the vanadium redox flow batteries corresponding to Comparative Example 2, Comparative Example 4, and Blank Group 2 are all lower than those of Example 4. In summary, this invention improves the overall efficiencies and charge / discharge capacity of the vanadium redox flow battery.

Claims

1. A vanadium electrolyte, characterized in that, The vanadium electrolyte contains vanadium ions, an acidic supporting electrolyte, and a composite additive; the composite additive contains an acetylacetone complexing agent and a dispersant; the dispersant is selected from one or more of methanol, ethanol, toluene, acetone, and ethyl acetate; the mass ratio of the acetylacetone complexing agent to the dispersant is 1:(0.5-0.8); the content of the composite additive in the vanadium electrolyte is 0.01wt%~1wt%.

2. The vanadium electrolyte as described in claim 1, characterized in that, The acetylacetone-based complexing agent is selected from one or more of acetylacetone, vanadium acetylacetone, and vanadium acetylacetone oxide.

3. The vanadium electrolyte as described in claim 1, characterized in that, Calculations based on the complete ionization of the acidic supporting electrolyte show that the molar ratio of vanadium ions to hydrogen ions in the vanadium electrolyte is 1:(3-6).

4. The vanadium electrolyte as described in claim 3, characterized in that, Calculations based on the complete ionization of the acidic supporting electrolyte show that the molar concentration ratio of vanadium ions to hydrogen ions in the vanadium electrolyte is 1:(4.3-4.6).

5. The vanadium electrolyte as described in claim 1, characterized in that, The acidic supporting electrolyte is selected from one or more of sulfuric acid, hydrochloric acid, and methanesulfonic acid.

6. The vanadium electrolyte as described in claim 1, characterized in that, In the vanadium electrolyte, the concentration of vanadium ions is 1-3 mol / L.

7. The vanadium electrolyte as described in claim 6, characterized in that, In the vanadium electrolyte, the concentration of vanadium ions is 1.5-2.5 mol / L.

8. A full vanadium redox flow battery comprising the vanadium electrolyte according to any one of claims 1-7.

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