Vanadium-manganese flow battery electrolyte and preparation and application thereof

Abstract

The invention discloses a vanadium-manganese flow battery electrolyte as well as preparation and application thereof. The electrolyte comprises a positive electrode electrolyte and a negative electrode electrolyte, the positive electrode electrolyte is an aqueous solution containing a first vanadium source, a manganese source, first acid radical ions, hydrogen ions and an additive, the negative electrode electrolyte is an aqueous solution containing a second vanadium source, second acid radical ions and hydrogen ions, and the additive comprises phenazine-(2, 2, 6-trimethyl-1, 3-pentanediol)-1, 2, 6-trimethyl-1, 3-pentanediol. The surfactant is selected from at least two of 1, 3-diyl) dioxodiacetic acid, perylene diimide, a cationic quaternary ammonium salt surfactant and triethanolamine or an isomer thereof. The preparation method comprises the following steps: dissolving a first vanadium source, a manganese source and inorganic acid in water, adding an additive, and fully stirring and uniformly mixing to obtain a positive electrode electrolyte; and dissolving a second vanadium source and inorganic acid in water, and electrolyzing to obtain the negative electrode electrolyte. The additive is introduced into the positive electrode electrolyte, so that disproportionation of positive electrode manganese can be effectively inhibited, and the stability of the electrolyte under a high-temperature condition is remarkably improved, so that the overall performance of the flow battery is optimized.

Description

Technical Field

[0001] The present invention relates to a battery electrolyte and its preparation and application, and in particular to a vanadium-manganese flow battery electrolyte and its preparation and application. Background Art

[0002] Traditional all-vanadium flow batteries have the following problems:

[0003] (1) Since expensive vanadium ions are used as active substances for both the positive and negative electrodes, the cost of the electrolyte is high. This disadvantage limits its application in the energy storage field.

[0004] (2) The solubility of vanadium ions is limited. If the concentration exceeds a certain range, pentavalent vanadium ions are prone to irreversible reactions and precipitate to form V2O5. Traditional vanadium electrolytes directly use vanadium pentoxide (V2O5) or vanadyl sulfate (VOSO4) as raw materials, but they are prone to form inert polyvanadates (such as V 10 O 28 6- ) in acidic solutions, resulting in limited solubility of vanadium ions. Therefore, the concentration of the electrolyte cannot be too high, which leads to a low energy density in the traditional all-vanadium flow battery system.

[0005] To improve the energy density and reduce the cost of all-vanadium flow batteries, other metal ion redox couples, such as the Mn 3+ / Mn 2+ redox couple, can be introduced into the electrolyte to obtain a manganese flow battery or a manganese-vanadium flow battery. However, Mn 3+ has a disproportionation problem. Oxidized Mn 3+ is prone to disproportionation side reactions to generate products such as MnO2, resulting in the accumulation of "dead manganese". The manganese disproportionation reaction will reduce the energy density, reversibility, and cycle stability of the battery because the MnO2 generated by disproportionation cannot fully participate in subsequent charge and discharge reactions, reducing the effective utilization rate of active substances.

[0006] How to introduce a manganese ion redox couple into the all-vanadium electrolyte and avoid manganese disproportionation has become an urgent problem to be solved. Summary of the Invention

[0007] Object of the Invention: The object of the present invention is to provide a vanadium-manganese flow battery electrolyte to solve the problems of low energy density and manganese disproportionation existing in existing flow batteries. The second object of the present invention is to propose a preparation method for a vanadium-manganese flow battery electrolyte to solve the problem of how to prepare a vanadium-manganese flow battery electrolyte. The third object of the present invention is to propose the application of the electrolyte in the preparation of a vanadium-manganese flow battery to solve the problem of how to prepare a vanadium-manganese flow battery.

[0008] Technical solution: An electrolyte for a vanadium-manganese flow battery according to the present invention includes a positive electrolyte and a negative electrolyte. The positive electrolyte is an aqueous solution containing a first vanadium source, a manganese source, a first acid radical ion, hydrogen ions, and an additive. The negative electrolyte is an aqueous solution containing a second vanadium source, a second acid radical ion, and hydrogen ions. The additive includes at least two of phenazine-(2,3-diyl)dioxydibutyric acid, phenazine-(2,3-diyl)dioxydiacetic acid, naphthalenediimide, perylenediimide, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, triethanolamine, or its isomers.

[0009] In the present invention, a vanadium redox couple is introduced into the negative electrolyte part of the flow battery. By utilizing its excellent redox performance, efficient conversion between divalent vanadium ions and trivalent vanadium ions can be achieved. In addition, this vanadium-based energy storage medium is more stable than the manganese-based energy storage medium at the negative electrode in a manganese flow battery, and there is no disproportionation problem.

[0010] In the present invention, a vanadium redox couple, a manganese redox couple, and an additive are introduced into the positive electrolyte part of the flow battery. By utilizing the excellent redox performance of the manganese redox couple, compared with the positive vanadium electrolyte in a all-vanadium flow battery, the energy density of the battery can be significantly improved. In addition, compared with Mn at the positive electrode in a manganese flow battery 3+ is prone to disproportionation reaction to generate MnO2 with poor irreversible conductivity. By introducing chloride ions and other additives at the positive electrode, the disproportionation reaction of Mn is inhibited 3+ The Coulomb efficiency of manganese is improved, and no obvious black substance (manganese dioxide) is generated, realizing reversible Mn 2+ / Mn 3+ transformation. While ensuring the safe and stable operation of the battery, the energy density of the battery is increased. In addition, since the manganese redox couple is lower in price than the vanadium couple, the battery cost can be significantly reduced.

[0011] In the present invention, an additive composed of various organic compounds is added to the positive electrolyte. This additive can form a complex with Mn, increasing the energy barrier of the disproportionation reaction, reducing the reduction potential of the Mn 3+ / Mn 2+ redox couple, and stabilizing Mn in the trivalent state, making it not prone to disproportionation. In addition, the larger organic ligand wraps around Mn 3+ and can kinetically hinder the approach of Mn 3+ ions to undergo electron transfer, thereby inhibiting the disproportionation reaction.

[0012] Preferably, the first vanadium source and the second vanadium source are independently selected from at least one of V2O5, VO2, V2O3, (VO2)2SO4, VOSO4, VO2Cl, VOCl2, VCl3, VCl2; the manganese source includes at least one of MnCl2, MnCl3, MnSO4, Mn2(SO4)3, manganese glycinate.

[0013] More preferably, the first vanadium source and the second vanadium source are independently selected from at least one of V2O5, VO2, (VO2)2SO4, VOSO4, VOCl2.

[0014] Preferably, the first acid radical ion and the second acid radical ion are independently selected from SO4 2- or Cl - .

[0015] Preferably, the concentration of the manganese source in the positive electrolyte is 0.01 - 0.2 mol / L, the concentration of the first vanadium source is 1.0 - 3.0 mol / L, and the concentration of the second vanadium source in the negative electrolyte is 1.0 - 3.0 mol / L.

[0016] The second aspect of the present invention discloses a method for preparing the vanadium-manganese redox flow battery electrolyte, comprising the following steps:

[0017] (1) Dissolve the first vanadium source and an inorganic acid in water, stir well to dissolve to obtain a first solution, dissolve the manganese source in the first solution, and add an additive and stir well to mix evenly to obtain a positive electrolyte;

[0018] (2) Dissolve the second vanadium source and an inorganic acid in water to obtain a second solution, electrolyze the second solution, and take the negative solution after complete electrolysis to obtain a negative electrolyte.

[0019] Preferably, in step (1), the particle size of the insoluble solid in the additive is 5 - 100 μm, and the inorganic acid is sulfuric acid or hydrochloric acid with a final concentration of 1 - 3 M; in step (2), the inorganic acid is sulfuric acid or hydrochloric acid with a final concentration of 1 - 3 M.

[0020] Preferably, in step (1), the additive is composed of phenazine-(2,3-diyl)dioxodiacetic acid, perylene diimide, a cationic quaternary ammonium salt surfactant, and triethanolamine in a molar ratio of 1 - 5:0.1 - 2:10 - 50:0.01 - 0.5, and the cationic quaternary ammonium salt surfactant includes at least one of cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide.

[0021] Preferably, in step (1), the mass fraction of the additive in the positive electrolyte is 0.5 - 4%.

[0022] The third aspect of the present invention discloses the application of the above electrolyte in the preparation of a vanadium-manganese flow battery.

[0023] The working principle of the above vanadium-manganese flow battery is as follows:

[0024] Negative electrode: The negative electrode of this new type of flow battery consists of a vanadium-based energy storage medium and a sulfuric acid or hydrochloric acid solution. Working principle: During the charging process, trivalent vanadium ions are reduced to divalent vanadium ions; during the discharging process, divalent vanadium ions at the negative electrode are oxidized to trivalent vanadium ions. Through the function of the diaphragm, the products and intermediate products between the negative electrode and the positive electrode do not interfere with each other, ensuring the independent progress of the redox reaction of the vanadium energy storage medium.

[0025] During the charging process, a reduction reaction of the vanadium energy storage medium occurs:

[0026] V 3+ +e - →V 2+

[0027] During the discharging process, an oxidation reaction of the vanadium energy storage medium occurs:

[0028] V 2+ →V 3+ +e -

[0029] Positive electrode: The positive electrode of this new type of flow battery consists of a vanadium redox couple, a manganese redox couple, an additive, and a sulfuric acid or hydrochloric acid solution. Working principle: During the charging process, divalent manganese ions at the positive electrode are oxidized to trivalent manganese ions on the positive electrode carbon felt, and tetravalent vanadium ions are oxidized to pentavalent vanadium ions; during the discharging process, pentavalent vanadium ions at the positive electrode are reduced to tetravalent vanadium ions, and trivalent manganese ions are reduced to divalent manganese ions at the positive electrode. Through the function of the diaphragm, the products and intermediate products between the negative electrode and the positive electrode do not interfere with each other, ensuring the independent progress of the redox reaction of each redox couple.

[0030] During the charging process, an oxidation reaction of divalent manganese ions occurs to form trivalent manganese ions, and tetravalent vanadium ions are oxidized to pentavalent vanadium ions:

[0031] Mn 2+ →Mn 3+ +e - ,VO 2+ →VO2 + +e -

[0032] During the discharging process, a reduction reaction of trivalent manganese ions occurs to form divalent manganese ions, and pentavalent vanadium ions are reduced to tetravalent vanadium ions:

[0033] Mn 3+ +e - →Mn 2+, VO2 + +e - →VO 2+

[0034] Coupling system: Place the negative electrode containing a vanadium-based energy storage medium and the positive electrode containing a manganese redox couple and a vanadium redox couple in the same system. They are separated by a diaphragm to ensure that the reactions between the positive and negative electrodes proceed separately. Ensure that there is an external circuit connection between the two systems to ensure that this new flow battery system can be used for electrical energy storage and output.

[0035] Advantages: Compared with the prior art, the present invention has the following remarkable advantages:

[0036] By adding a vanadium redox couple to the negative electrode electrolyte of the flow battery and introducing a vanadium redox couple, a manganese redox couple, and an additive into the positive electrode electrolyte to form a new flow battery electrolyte, the present invention effectively reduces the battery cost, improves the battery energy density, and avoids the generation of Mn 3+ disproportionation.

[0037] By screening an additive composition that can effectively improve the stability of manganese in the positive electrode, the present invention can significantly reduce the manganese disproportionation reaction, ensure the safe and stable operation of the battery, and improve the energy density of the flow battery. At the same time, the existing vanadium ions in the positive electrode can also inhibit the disproportionation of manganese. A very small amount of manganese dioxide will be chemically reduced by vanadium ions and participate in the capacity contribution again, making the Coulomb efficiency of manganese close to 100%. Description of the Drawings

[0038] Figure 1 It is a schematic diagram of the discharging process of the manganese-vanadium flow battery in the present invention;

[0039] Figure 2 It is a schematic diagram of the charging process of the manganese-vanadium flow battery in the present invention. Detailed Embodiments

[0040] The technical solutions of the present invention will be further described below with reference to the drawings.

[0041] Example 1: The composition and preparation method of an electrolyte for a vanadium-manganese flow battery are as follows:

[0042] (1) Take phenazine-(2,3-diyl)dioxydiacetic acid powder and perylene diimide powder with a particle size of 5-25 μm for standby. Mix the phenazine-(2,3-diyl)dioxydiacetic acid powder, perylene diimide powder, cetyltrimethylammonium chloride, and triethanolamine according to a molar ratio of 3:1:30:0.25 to obtain an additive;

[0043] (2) Dissolve VOSO4 with a final concentration of 2.0 mol / L, MnSO4 with a final concentration of 0.1 mol / L, and sulfuric acid with a final concentration of 2 mol / L in water, and then add an additive at a mass fraction of 2%, and stir well to obtain the positive electrode electrolyte;

[0044] (3) Dissolve VOSO4 with a final concentration of 2.0 mol / L and sulfuric acid with a final concentration of 2 mol / L in water to obtain a second solution. Electrolyze the second solution using a gradient electrolysis mode, and electrolyze at current densities of 100 mA / cm 2 , 50 mA / cm 2 , 30 mA / cm 2 respectively. The cut-off condition is 2 V in all cases. After complete electrolysis, take the negative electrode solution as the negative electrode electrolyte.

[0045] Example 2: The composition and preparation method of an electrolyte for a vanadium-manganese flow battery are as follows:

[0046] (1) Prepare phenazine-(2,3-diyl)dioxydiacetic acid powder and perylene diimide powder with particle sizes in the range of 20 - 50 μm. Mix the phenazine-(2,3-diyl)dioxydiacetic acid powder, perylene diimide powder, dodecyltrimethylammonium chloride, and triethanolamine according to a molar ratio of 5:2:50:0.5 to obtain an additive;

[0047] (2) Dissolve VOCl2 with a final concentration of 3.0 mol / L, MnCl2 with a final concentration of 0.2 mol / L, and hydrochloric acid with a final concentration of 3 M in water, and then add an additive at a mass fraction of 4%, and stir well to obtain the positive electrode electrolyte;

[0048] (3) Dissolve VOCl2 with a final concentration of 3.0 mol / L and hydrochloric acid with a final concentration of 3 M in water to obtain a second solution. Electrolyze the second solution using a gradient electrolysis mode, and electrolyze at current densities of 100 mA / cm 2 , 50 mA / cm 2 , 30 mA / cm 2 respectively. The cut-off condition is 2 V in all cases. After complete electrolysis, take the negative electrode solution as the negative electrode electrolyte.

[0049] Example 3: The composition and preparation method of an electrolyte for a vanadium-manganese flow battery are as follows:

[0050] (1) Prepare phenazine-(2,3-diyl)dioxydiacetic acid powder and perylene diimide powder with particle sizes in the range of 50 - 100 μm. Mix the phenazine-(2,3-diyl)dioxydiacetic acid powder, perylene diimide powder, cetyltrimethylammonium bromide, and triethanolamine according to a molar ratio of 1:0.1:10:0.01 to obtain an additive;

[0051] (2) Dissolve V2O5 with a final concentration of 1.0 mol / L, Mn2(SO4)3 with a final concentration of 0.01 mol / L, and sulfuric acid with a final concentration of 1 M in water, and then add an additive according to a mass fraction of 0.5% and stir well to obtain the positive electrode electrolyte;

[0052] (3) Dissolve (VO2)2SO4 with a final concentration of 1.0 mol / L and sulfuric acid with a final concentration of 1 M in water to obtain a second solution. Electrolyze the second solution using a gradient electrolysis mode, and electrolyze at current densities of 100 mA / cm 2 , 50 mA / cm 2 , 30 mA / cm 2 respectively. The cut-off condition is 2 V in all cases. After complete electrolysis, take the negative electrode solution as the negative electrode electrolyte.

[0053] Example 4: The composition and preparation method of an electrolyte for a vanadium-manganese flow battery are as follows:

[0054] (1) Prepare phenazine-(2,3-diyl)dioxydiacetic acid powder and perylene diimide powder with particle sizes in the range of 10 - 40 μm. Mix the phenazine-(2,3-diyl)dioxydiacetic acid powder, perylene diimide powder, dodecyltrimethylammonium bromide, and triethanolamine according to a molar ratio of 4:2:25:0.2 to obtain an additive;

[0055] (2) Dissolve VO2 with a final concentration of 1.5 mol / L, manganese glycinate with a final concentration of 0.15 mol / L, and sulfuric acid with a final concentration of 2 M in water, and then add an additive according to a mass fraction of 1% and stir well to obtain the positive electrode electrolyte;

[0056] (3) Dissolve VOCl2 with a final concentration of 1.5 mol / L and sulfuric acid with a final concentration of 2 M in water to obtain a second solution. Electrolyze the second solution using a gradient electrolysis mode, and electrolyze at current densities of 100 mA / cm 2 , 50 mA / cm 2 , 30 mA / cm 2 respectively. The cut-off condition is 2 V in all cases. After complete electrolysis, take the negative electrode solution as the negative electrode electrolyte.

[0057] Comparative Example 1: The rest are the same as in Example 1, except that:

[0058] No additive is added to the positive electrode electrolyte.

[0059] Comparative Example 2: The rest are the same as in Example 1, except that:

[0060] The additive is only phenazine-(2,3-diyl)dioxydiacetic acid powder.

[0061] Comparative Example 3: The rest are the same as in Example 1, except that:

[0062] The additive is only perylene diimide powder.

[0063] Comparative Example 4: The rest are the same as in Example 1, except that:

[0064] The additive is only cetyltrimethylammonium chloride.

[0065] Comparative Example 5: The rest are the same as in Example 1, except that:

[0066] The additive is only triethanolamine.

[0067] Comparative Example 6: The rest are the same as in Example 1, except that:

[0068] The additive is only phenazine-(2,3-diyl)dioxydibutyric acid.

[0069] Comparative Example 7: The rest are the same as in Example 1, except that:

[0070] The additive is only 2,3-diaminophenazine.

[0071] Comparative Example 8: The rest are the same as in Example 1, except that:

[0072] The additive is only polyaniline powder.

[0073] Comparative Example 9: The rest are the same as in Example 1, except that:

[0074] Phenazine-(2,3-diyl)dioxydiacetic acid powder is not added to the additive.

[0075] Comparative Example 10: The rest are the same as in Example 1, except that:

[0076] Perylene diimide powder is not added to the additive.

[0077] Comparative Example 11: The rest are the same as in Example 1, except that:

[0078] Cetyltrimethylammonium chloride is not added to the additive.

[0079] Comparative Example 12: The rest are the same as in Example 1, except that:

[0080] Triethanolamine is not added to the additive.

[0081] Comparative Example 13: The rest are the same as in Example 1, except that:

[0082] Phenazine-(2,3-diyl)dioxydiacetic acid powder is replaced with phenazine-(2,3-diyl)dioxydibutyric acid.

[0083] Comparative Example 14: The rest is the same as in Example 1, except that:

[0084] The perylene diimide powder is replaced with naphthalene diimide powder.

[0085] Comparative Example 15: The rest is the same as in Example 1, except that:

[0086] Triethanolamine is replaced with ethyldiethanolamine.

[0087] Comparative Example 16: The rest is the same as in Example 1, except that:

[0088] MnSO4 is replaced with VOSO4;

[0089] Flow batteries were assembled by conventional assembly methods using the electrolytes prepared in Examples 1-4 and Comparative Examples 1-16 respectively. The structure of the flow battery is as Figure 1 and Figure 2 shown. Equal volumes of the positive electrolyte and the negative electrolyte were respectively filled into the positive and negative liquid tanks. The positive electrolyte and the negative electrolyte were separated by a diaphragm. Carbon felt electrodes were inserted into the positive electrolyte and the negative electrolyte respectively to obtain a flow battery.

[0090] After the above flow battery was charged and discharged 100 times, the energy density of the flow battery was measured. After measurement, the positive electrolyte was centrifuged to obtain a precipitate. The precipitate was wet-digested with a mixed acid of nitric acid and perchloric acid (1:9), and then the manganese element was quantified by flame atomic absorption spectrometry. The disproportionation rate of the manganese element was calculated using the following formula:

[0091] Disproportionation rate of manganese element = (total weight of manganese element in the precipitate / total weight of initial manganese element in the positive electrolyte) × 100%;

[0092] The results are as follows:

[0093] Table 1 Energy density and manganese disproportionation rate of different flow batteries

[0094] Group Manganese disproportionation rate (%) Energy density (Wh / L) Example 1 0.06 25.13 Example 2 0.09 25.22 Example 3 0.14 24.87 Example 4 0.17 24.41 Comparative Example 1 4.93 21.34 Comparative Example 2 5.19 22.21 Comparative Example 3 4.24 22.45 Comparative Example 4 4.76 22.91 Comparative Example 5 5.55 21.51 Comparative Example 6 3.26 21.74 Comparative Example 7 4.73 22.32 Comparative Example 8 5.04 22.48 Comparative Example 9 4.68 22.88 Comparative Example 10 3.17 21.76 Comparative Example 11 4.61 21.65 Comparative Example 12 4.23 22.19 Comparative Example 13 3.48 22.33 Comparative Example 14 3.02 21.97 Comparative Example 15 1.17 22.53 Comparative Example 16 - 22.51

[0095] In the results of Table 1, in Comparative Example 1, due to the absence of additives, the manganese disproportionation rate increased significantly, indicating that the direct introduction of the manganese ion redox couple into the positive electrolyte would result in a serious manganese disproportionation reaction, thereby reducing the energy density of the battery. In Comparative Examples 2-8, the use of a single organic active substance could not effectively inhibit the occurrence of the manganese disproportionation reaction. Therefore, the manganese disproportionation rates of Comparative Examples 2-8 were close to or exceeded that of Comparative Example 1, and were significantly higher than that of Example 1. The manganese disproportionation rates of Comparative Examples 9-15 were also significantly higher than that of Example 1, indicating that the efficient inhibition of the manganese disproportionation reaction by the additives relied on the synergistic effect of phenazine-(2,3-diyl)dioxydiacetic acid powder, perylene diimide powder, cetyltrimethylammonium chloride, and triethanolamine. The absence or replacement of any one of the components could not effectively inhibit the manganese disproportionation reaction, thereby leading to a decrease in the energy density of the battery. From the comparison between Comparative Example 16 and Example 1, it can be seen that after solving the manganese disproportionation problem, the successful introduction of the manganese ion redox couple can significantly improve the energy density of the vanadium flow battery, and its electrochemical performance is significantly better than that of the all-vanadium flow battery.

Claims

1. A vanadium-manganese redox flow battery electrolyte, characterized in that, It includes a positive electrolyte and a negative electrolyte. The positive electrolyte is an aqueous solution containing a first vanadium source, a manganese source, a first acid radical ion, hydrogen ions and an additive. The negative electrolyte is an aqueous solution containing a second vanadium source, a second acid radical ion and hydrogen ions. The additive includes at least two of phenazine-(2,3-diyl)dioxydibutyric acid, phenazine-(2,3-diyl)dioxydiacetic acid, naphthalenediimide, perylenediimide, cetyltrimethylammonium chloride, cetyltrimethylammonium bromide, dodecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, triethanolamine or its isomers.

2. The vanadium-manganese redox flow battery electrolyte according to claim 1, wherein, The first vanadium source and the second vanadium source are independently selected from at least one of V2O5, VO2, V2O3, (VO2)2SO4, VOSO4, VO2Cl, VOCl2, VCl3, VCl2; the manganese source includes at least one of MnCl2, MnCl3, MnSO4, Mn2(SO4)3, manganese glycinate.

3. The vanadium-manganese flow battery electrolyte according to claim 2, wherein The first vanadium source and the second vanadium source are independently selected from at least one of V2O5, VO2, (VO2)2SO4, VOSO4, VOCl2.

4. The vanadium-manganese flow battery electrolyte according to claim 1, characterized in that, The first acid radical ion and the second acid radical ion are independently selected from SO4 2- or Cl - .

5. The vanadium-manganese redox flow battery electrolyte according to claim 1, wherein In the positive electrolyte, the concentration of the manganese source is 0.01 - 0.2 mol / L, the concentration of the first vanadium source is 1.0 - 3.0 mol / L, and in the negative electrolyte, the concentration of the second vanadium source is 1.0 - 3.0 mol / L.

6. The preparation method of the vanadium-manganese redox flow battery electrolyte according to any one of claims 1-5, characterized in that, It includes the following steps: (1) Dissolve the first vanadium source and an inorganic acid in water, stir well to dissolve to obtain a first solution, dissolve the manganese source in the first solution, and add the additive and stir well to mix evenly to obtain the positive electrolyte; (2) Dissolve the second vanadium source and an inorganic acid in water to obtain a second solution, electrolyze the second solution, and take the negative solution after complete electrolysis to obtain the negative electrolyte.

7. The preparation method of the vanadium-manganese redox flow battery electrolyte according to claim 6, wherein In step (1), the particle size of the insoluble solid in the additive is 5 - 100 μm, and the inorganic acid is sulfuric acid or hydrochloric acid with a final concentration of 1 - 3 M; in step (2), the inorganic acid is sulfuric acid or hydrochloric acid with a final concentration of 1 - 3 M.

8. The preparation method of the vanadium-manganese redox flow battery electrolyte according to claim 6, characterized in that, In step (1), the additive is composed of phenazine-(2,3-diyl)dioxydiacetic acid, perylenediimide, a cationic quaternary ammonium salt surfactant and triethanolamine with a molar ratio of 1 - 5:0.1 - 2:10 - 50:0.01 - 0.

5.

9. The preparation method of the vanadium-manganese redox flow battery electrolyte according to claim 6, wherein, In step (1), the mass fraction of the additive in the positive electrolyte is 0.5 - 4%.

10. Use of the electrolyte according to any one of claims 1 - 5 in the preparation of a vanadium-manganese flow battery.

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