Preparation method and application of alkaline zinc-based flow battery electrolyte

Abstract

The application discloses a preparation method and application of an alkaline zinc-based flow battery electrolyte, and comprises the following steps: firstly, dissolving a hydroxide solid in deionized water to obtain an alkaline aqueous solution; secondly, dissolving a zinc oxide solid in the alkaline aqueous solution obtained in the step (I) to obtain an alkaline aqueous solution containing a zincate; and finally, dissolving a sugar alcohol and a chloromethane in the alkaline aqueous solution containing the zincate obtained in the step (II) to obtain an alkaline electrolyte. By introducing different concentrations of the sugar alcohol and the chloromethane into the alkaline electrolyte containing the zincate, the double electric layer and the solvation structure of the zinc negative electrode are regulated, the self-corrosion and the hydrogen evolution side reaction problems of the zinc negative electrode under the strong alkaline (pH>14) condition are effectively inhibited, the alkaline electrolyte has good zinc compatibility, high stability and relatively fast reaction kinetics, and has great potential in the development and application of the alkaline zinc-based flow battery.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of flow batteries, and particularly relates to a preparation method and application of an alkaline zinc-based flow battery electrolyte. BACKGROUND

[0002] The gradual development of renewable energy and the rapid development of portable electronic devices, new energy vehicles and other equipment have put forward higher and more urgent requirements for the future energy storage market. Since lithium ion batteries have been mature and are close to their theoretical energy density limit, it is crucial to develop a safe and reliable next-generation energy storage technology with cost-effectiveness. Alkaline zinc-based flow batteries are one of the favorable candidates for the next-generation energy storage technology due to their low cost, high theoretical energy density and high safety.

[0003] Unlike all-flow batteries, the negative electrode of the alkaline zinc-based flow battery undergoes a solid-liquid phase transition process during the redox process, i.e., zinc deposition and stripping, and thus faces serious problems of morphology stability and chemical stability. In alkaline electrolyte, especially in strong alkaline electrolyte with pH>14, a large number of hydroxyl ions exist and continuously corrode the zinc negative electrode, resulting in problems such as active material loss and electrode passivation. At the same time, zinc ions exist in the form of zincate in alkaline systems, and their solubility is generally low, resulting in problems such as slow kinetics and side reactions. Affected by the above problems, the actual performance of the alkaline zinc-based flow battery is severely limited, specifically in the form of low coulombic efficiency and short cycle life. Therefore, it is crucial to control the electrolyte environment (such as the double-layer composition and solvation structure), and to control the reaction kinetics and cycle stability of the zinc negative electrode for a long time, but it is still extremely challenging. SUMMARY

[0004] The present application is proposed to overcome the shortcomings in the prior art, and aims to provide a preparation method and application of an alkaline zinc-based flow battery electrolyte.

[0005] The present application is realized by the following technical solutions:

[0006] A preparation method of an alkaline zinc-based flow battery electrolyte, comprising the following steps:

[0007] (I) dissolving a hydroxide solid in deionized water to obtain an alkaline aqueous solution;

[0008] (II) dissolving a zinc oxide solid in the alkaline aqueous solution obtained in step (I) to obtain an alkaline aqueous solution containing zincate;

[0009] (III) dissolving a sugar alcohol and a chloromethane in the alkaline aqueous solution containing zincate obtained in step (II) to obtain an alkaline electrolyte.

[0010] In the technical scheme, the hydroxide is at least one of lithium hydroxide, sodium hydroxide or potassium hydroxide, and the concentration of the hydroxide in the alkaline aqueous solution is 1-6 mol / L.

[0011] In the technical scheme, the zinc oxide is nano-zinc oxide, the zincate is formed by dissolving the zinc oxide in the alkaline aqueous solution, and the concentration of the zincate in the alkaline aqueous solution containing the zincate is 0.02-0.2 mol / L.

[0012] In the technical scheme, the sugar alcohol is at least one of erythritol, xylitol, sorbitol or mannitol, and the concentration of the sugar alcohol in the alkaline electrolyte is 0.01-0.8 mol / L.

[0013] In the technical scheme, the methyl chloride is at least one of methyl chloride, dichloromethane or trichloromethane, and the concentration of the methyl chloride in the alkaline electrolyte is 0.01-0.2 mol / L.

[0014] In the technical scheme, the mixing temperature of the steps (I)-(II) is 20-40℃.

[0015] In the technical scheme, the pH of the alkaline electrolyte is 14-14.8.

[0016] The application provides a preparation method of an alkaline zinc-based flow battery electrolyte.

[0017] The application provides an application of the alkaline zinc-based flow battery electrolyte prepared by the method in an alkaline zinc-based flow battery, and the alkaline zinc-based flow battery electrolyte is used as a negative electrolyte of the alkaline zinc-based flow battery.

[0018] The application provides an alkaline zinc-based flow battery, and a negative electrolyte of the alkaline zinc-based flow battery is prepared by the method.

[0019] The application has the following beneficial effects:

[0020] The application provides a preparation method and application of an alkaline zinc-based flow battery electrolyte, the prepared alkaline electrolyte realizes reversible deposition and stripping of a zinc negative electrode in a strong alkaline environment (pH>14), and realizes a high-performance novel flow battery system in a strong alkaline environment (pH>14); the additive added in the alkaline electrolyte can effectively inhibit self-corrosion of the zinc negative electrode, effectively improve Coulomb efficiency and cycle stability of the alkaline zinc-based flow battery, effectively accelerate reaction kinetics of zinc, and effectively inhibit growth of dendrites and occurrence of side reactions. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 For examples 1-12, the current density is 80 mA / cm2 Under deposition 40 mAh / cm 2 Coulombic efficiency after standing for 0-5 h;

[0022] Figure 2 For Comparative Examples 1-4, 80 mA / cm 2 Under deposition 40 mAh / cm 2 Coulombic efficiency after standing for 0-5 h;

[0023] Figure 3 For Comparative Examples 5-7, 80 mA / cm 2 Under deposition 40 mAh / cm 2 Coulombic efficiency after standing for 0-5 h;

[0024] Figure 4 For Comparative Example 8, 80 mA / cm 2 Under deposition 40 mAh / cm 2 Coulombic efficiency after standing for 0-5 h;

[0025] Figure 5 For Examples 1-12 and Comparative Examples 1-8, 80 mA / cm 2 Cycle life for symmetric cell testing.

[0026] For those skilled in the art, other related drawings can be obtained from the above drawings without creative labor. DETAILED DESCRIPTION

[0027] In order for those skilled in the art to better understand the technical solutions of the present application, the technical solutions of the present application will be further described below in combination with the drawings of the specification and through specific embodiments.

[0028] Example 1

[0029] The application relates to a preparation method and application of an alkaline zinc-based flow battery electrolyte, and particularly relates to the following technical scheme.

[0030] (1) A sodium hydroxide aqueous solution with a concentration of 4 mol / L is prepared to obtain an alkaline aqueous solution;

[0031] (2) Nano-zinc oxide powder is added into the alkaline aqueous solution, and the zinc oxide is dissolved to form zincate under stirring at room temperature, so that an alkaline aqueous solution containing zincate is obtained, wherein the concentration of the zincate in the alkaline aqueous solution containing zincate is 0.2 mol / L;

[0032] (3) Sorbitol and dichloromethane are added into the alkaline aqueous solution containing zincate, so that an alkaline electrolyte is obtained, wherein the concentration of the sorbitol in the alkaline electrolyte is 0.2 mol / L, and the concentration of the dichloromethane in the alkaline electrolyte is 0.1 mol / L;

[0033] (4) Assembled single flow zinc symmetric battery and flow zinc half-cell with the above electrolyte, and tested the performance of the battery at a current density of 80 mA / cm 2 , and the single charge capacity was fixed at 40 mAh / cm 2 ; the assembly method: the zinc electrode used a zinc foil with a thickness of 0.1 mm, the counter electrode used a graphite felt with a thickness of 3 mm, Nafion 117 membrane was used as the ion conducting membrane, and the electrolyte of the positive and negative electrodes was 40 mL;

[0034] (5) Assembled single flow zinc-nickel battery with the above electrolyte, and tested the performance of the battery at a current density of 80 mA / cm 2 ; the assembly method: the negative electrode used a zinc foil with a thickness of 0.1 mm, the positive electrode used a nickel hydroxide foam with a thickness of 3 mm, Nafion 117 membrane was used as the ion conducting membrane, and the electrolyte of the positive and negative electrodes was 40 mL.

[0035] Examples 2-12 were obtained by changing the type of sugar alcohol and the type of chloromethane, and the rest was the same as Example 1. The type of sugar alcohol and the type of chloromethane in Examples 2-12 are shown in Table 1 below.

[0036] Table 1: Type of sugar alcohol and type of chloromethane in Examples 2-12

[0037]

[0038]

[0039] Through Figure 1 analysis, it can be seen that the single flow symmetric battery assembled using the negative electrolyte can be stably operated for more than 100 hours, and the overpotential is less than 50 mV, which proves that the electrolyte has excellent compatibility and stability, and improves the stability of the negative electrode of the alkaline zinc-based flow battery.

[0040] Through Figure 2 analysis, it can be seen that after standing for 0-5 hours, the coulombic efficiency is > 85%, the loss of deposited zinc is 5%, and the loss of standing zinc is 2% per hour, which proves that the electrolyte can effectively inhibit the self-corrosion and side reactions of the zinc negative electrode, and can realize the reversible deposition and stripping of zinc in a strong alkali environment.

[0041] Comparative Example 1

[0042] A preparation method of an alkaline electrolyte and application of the alkaline electrolyte in an alkaline zinc-based flow battery, specifically:

[0043] (1) A sodium hydroxide aqueous solution with a concentration of 4 mol / L was prepared to obtain solution A;

[0044] (2) Add nano zinc oxide powder to solution A, and dissolve the zinc oxide to form zincate with a concentration of 0.2 mol / L, and stir and dissolve at room temperature to obtain solution B;

[0045] (3) Add sorbitol to solution B, and dissolve the sorbitol to obtain an electrolyte comparative example 1 with a concentration of 0.2 mol / L.

[0046] Change the sorbitol to erythritol, xylitol, and mannitol to obtain comparative examples 2-4, respectively, and the rest is the same as comparative example 1.

[0047] Comparative example 5

[0048] A preparation method of an alkaline electrolyte and application of the alkaline electrolyte in a zinc-based alkaline flow battery, specifically:

[0049] (1) Prepare a sodium hydroxide aqueous solution with a concentration of 4 mol / L to obtain solution A;

[0050] (2) Add nano zinc oxide powder to solution A, and dissolve the zinc oxide to form zincate with a concentration of 0.2 mol / L, and stir and dissolve at room temperature to obtain solution B;

[0051] (3) Add dichloromethane to solution B, and dissolve the dichloromethane to obtain an electrolyte comparative example 5 with a concentration of 0.1 mol / L.

[0052] Change the dichloromethane to monochloromethane and trichloromethane to obtain comparative examples 6 and 7, respectively, and the rest is the same as comparative example 5.

[0053] Comparative example 8

[0054] (1) Prepare a sodium hydroxide aqueous solution with a concentration of 4 mol / L to obtain solution A;

[0055] (2) Add nano zinc oxide powder to solution A, and dissolve the zinc oxide to form zincate with a concentration of 0.2 mol / L, and stir and dissolve at room temperature to obtain an electrolyte.

[0056] Performance tests are performed on comparative examples 1-8 and examples 1-12, and the performance test results are shown in Table 2 and Figures 2 to 4 .

[0057] Table 2: Performance summary of examples 1-12 and comparative examples 1-8

[0058]

[0059] By analyzing examples 1-12, it is found that when sugar alcohol and chloromethane are added in the electrolyte at the same time, the zinc negative electrode exhibits good performance: the cycle life is longer, all more than 90 hours; the initial coulombic efficiency is higher, between 92%-96%; the coulombic efficiency loss with standing is smaller, still 84-86% after standing for 5 hours. By comparing with comparative examples 1-4, it is found that when the electrolyte is added with sugar alcohol but not chloromethane, the cycle life of the zinc negative electrode is shorter, only 40-50 hours, the initial coulombic efficiency is only 83-86%, and the loss is 67-70% after standing for 5 hours. By comparing with comparative examples 5-7, it is found that when the electrolyte is added with chloromethane but not sugar alcohol, the cycle life of the electrolyte is shorter, only 40-50 hours, the initial coulombic efficiency is only 87-90%, and the loss is 57-60% after standing for 5 hours. By comparing with comparative example 8, it is found that when neither sugar alcohol nor chloromethane is added, the cycle life is only 20 hours, and the initial coulombic efficiency and the coulombic efficiency after standing for 5 hours are only 80.5% and 49.6%. By analyzing comparative examples 1-4 and 8, it is found that after the electrolyte is added with sugar alcohol, the initial coulombic efficiency is increased by about 3-5%, and the coulombic efficiency after standing for 5 hours is increased by 18-20%, which shows that the addition of sugar alcohol is adsorbed on the surface of the zinc negative electrode, slows down the self-corrosion of the zinc negative electrode, and thus improves the electrochemical performance. By analyzing comparative examples 5-7 and 8, it is found that after the electrolyte is added with chloromethane, the initial coulombic efficiency is increased by about 7-9%, which shows that the addition of chloromethane optimizes the solvation structure of zincate, inhibits the occurrence of side reactions of the zinc negative electrode, and thus improves the performance. By analyzing examples 1-12 and comparative example 8, it is found that when sugar alcohol and chloromethane are added together, the self-corrosion and side reactions of the zinc negative electrode can be inhibited at the same time, which is the key to greatly improving the stability of the zinc negative electrode.

[0060] The present application proposes a new type of negative electrolyte, in which hydroxide is used as a supporting electrolyte, zinc oxide is used as a source of zincate, and sugar alcohol and chloromethane are used as additives to stabilize the zinc negative electrode and improve the coulombic efficiency; the negative electrolyte can effectively inhibit the growth of zinc dendrites and the occurrence of side reactions, improve the negative coulombic efficiency and cycle stability, and provide a new idea for developing a long-acting energy storage system with high safety and stability; the electrolyte configuration method of the present application is simple and easy to implement, realizes the stable regulation and control of the double electric layer of the negative electrode and the solvation structure of zinc ions, and widens the feasibility of zinc-based flow batteries in a strong alkaline (pH>14) environment.

[0061] It should be noted that the examples in the present application and the features in the examples can be combined with each other without conflict.

[0062] The applicant states that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing an alkaline zinc-based flow battery electrolyte, characterized in that: Includes the following steps: (I) Dissolve the hydroxide solid in deionized water to obtain an alkaline aqueous solution; The hydroxide is at least one of lithium hydroxide, sodium hydroxide, or potassium hydroxide; (II) Dissolve solid zinc oxide in the alkaline aqueous solution obtained in step (I) to obtain an alkaline aqueous solution containing zincate; (III) Dissolve sugar alcohol and chloromethane in the alkaline aqueous solution containing zincate obtained in step (II) to obtain an alkaline electrolyte; The sugar alcohol is at least one of erythritol, xylitol, sorbitol or mannitol; The chloromethane is at least one of chloromethane, dichloromethane, or trichloromethane.

2. The method for preparing the alkaline zinc-based flow battery electrolyte according to claim 1, characterized in that: The concentration of hydroxide in the alkaline aqueous solution is 1 mol / L to 6 mol / L.

3. The method for preparing the alkaline zinc-based flow battery electrolyte according to claim 1, characterized in that: The zinc oxide is nano zinc oxide; the zincate is formed by dissolving zinc oxide in an alkaline aqueous solution; the concentration of zincate in the alkaline aqueous solution containing zincate is 0.02 mol / L to 0.2 mol / L.

4. The method for preparing the alkaline zinc-based flow battery electrolyte according to claim 1, characterized in that: The concentration of sugar alcohol in the alkaline electrolyte is 0.01 mol / L to 0.8 mol / L.

5. The method for preparing the alkaline zinc-based flow battery electrolyte according to claim 1, characterized in that: The concentration of chloromethane in the alkaline electrolyte is 0.01 mol / L to 0.2 mol / L.

6. The method for preparing the alkaline zinc-based flow battery electrolyte according to claim 1, characterized in that: The mixing temperature in steps (I) to (II) is 20 ℃ to 40 ℃.

7. The method for preparing the alkaline zinc-based flow battery electrolyte according to claim 1, characterized in that: The pH of the alkaline electrolyte is 14 to 14.

8.

8. An alkaline zinc-based flow battery electrolyte, characterized in that: Prepared by the method described in any one of claims 1 to 7.

9. The application of an alkaline zinc-based flow battery electrolyte prepared by the method according to any one of claims 1 to 7, characterized in that: The alkaline zinc-based flow battery electrolyte serves as the negative electrode electrolyte in the alkaline zinc-based flow battery.

10. An alkaline zinc-based flow battery, characterized in that: The negative electrode electrolyte of the alkaline zinc-based flow battery is prepared by the method described in any one of claims 1 to 7.

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