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

Abstract

The invention discloses a preparation method and application of an alkaline zinc-based flow battery electrolyte, and the preparation method comprises the following steps: dissolving a hydroxide solid in deionized water to obtain an alkaline aqueous solution; dissolving a zinc oxide solid in the alkaline aqueous solution obtained in the step (I) to obtain an alkaline aqueous solution containing zincate; and finally, sugar alcohol and chloromethane are dissolved in the alkaline aqueous solution containing the zincate obtained in the step (II), and the alkaline electrolyte is obtained. According to the invention, sugar alcohol and chloromethane with different concentrations are introduced into the alkaline electrolyte containing the zinc salt, so that the double electric layers and solvation structure of the zinc negative electrode are regulated and controlled, and the zinc negative electrode is effectively inhibited from being in a strong alkaline state (pHgt; 14) the problems of self-corrosion and hydrogen evolution side reaction under the condition are solved; the alkaline electrolyte has good zinc compatibility, high stability and fast reaction kinetics, and shows huge potential in development and application of alkaline zinc-based flow batteries.

Description

Technical Field

[0001] This application belongs to the field of flow batteries, and particularly relates to a preparation method and application of an electrolyte for an alkaline zinc-based flow battery. Background Art

[0002] The gradual development of renewable energy and the rapid development of devices such as portable electronic devices and new energy vehicles have put forward higher and more urgent requirements for the future energy storage market. Since lithium-ion batteries have become mature and are approaching their theoretical energy density limit, it is crucial to develop safe, reliable, and cost-effective next-generation energy storage technologies. Alkaline zinc-based flow batteries are one of the promising candidates for next-generation energy storage technologies due to their low cost, high theoretical energy density, and high safety.

[0003] Different from all-flow batteries, there is a solid-liquid phase transition process, namely zinc deposition and stripping, during the redox process of the negative electrode of alkaline zinc-based flow batteries. Therefore, serious problems of morphological stability and chemical stability are faced. In alkaline electrolytes, especially in strongly alkaline electrolytes with pH>14, a large number of hydroxide ions exist and continuously corrode the zinc negative electrode, resulting in problems such as loss of active substances and electrode passivation. At the same time, zinc ions exist in the form of zincates in the alkaline system, 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 alkaline zinc-based flow batteries is severely limited, specifically manifested as low Coulomb efficiency and short cycle life. Therefore, it is crucial to regulate the electrolyte environment (such as the double-layer components and solvation structure) to control the reaction kinetics and cycle stability of the zinc negative electrode for a long time, but it is still extremely challenging at present. Summary of the Invention

[0004] The present invention is proposed to overcome the disadvantages existing in the prior art, and its purpose is to provide a preparation method and application of an electrolyte for an alkaline zinc-based flow battery.

[0005] The present invention is achieved through the following technical solutions:

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

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

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

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

[0010] In the above technical solution, 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 mol / L to 6 mol / L.

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

[0012] In the above technical solution, 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 mol / L to 0.8 mol / L.

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

[0014] In the above technical solution, the mixing temperature of steps (I) to (II) is 20 °C to 40 °C.

[0015] In the above technical solution, the pH of the alkaline electrolyte is 14 to 14.8.

[0016] An alkaline zinc-based flow battery electrolyte is prepared by the foregoing method.

[0017] An application of an alkaline zinc-based flow battery electrolyte prepared by the foregoing method in an alkaline zinc-based flow battery, wherein the alkaline zinc-based flow battery electrolyte is used as the negative electrode electrolyte of the alkaline zinc-based flow battery.

[0018] An alkaline zinc-based flow battery, wherein the negative electrode electrolyte of the alkaline zinc-based flow battery is prepared by the foregoing method.

[0019] The beneficial effects of the present invention are:

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

[0021] Figure 1 For Examples 1 to 12 at 80 mA / cm2 Coulombic efficiency after deposition of 40 mAh / cm 2 followed by standing for 0 - 5 h;

[0022] Figure 2 For Comparative Examples 1 - 4, Coulombic efficiency after deposition of 40 mAh / cm 2 followed by standing for 0 - 5 h at 80 mA / cm; 2 For Comparative Examples 5 - 7, Coulombic efficiency after deposition of 40 mAh / cm

[0023] Figure 3 followed by standing for 0 - 5 h at 80 mA / cm; 2 For Comparative Example 8, Coulombic efficiency after deposition of 40 mAh / cm 2 followed by standing for 0 - 5 h at 80 mA / cm;

[0024] Figure 4 For Examples 1 - 12 and Comparative Examples 1 - 8, cycle life of symmetric cell tests conducted at 80 mA / cm 2 For those of ordinary skill in the art, without creative efforts, other related drawings can be obtained based on the above drawings. 2 For those of ordinary skill in the art, without creative efforts, other related drawings can be obtained based on the above drawings.

[0025] Figure 5 For those of ordinary skill in the art, without creative efforts, other related drawings can be obtained based on the above drawings. 2 For those of ordinary skill in the art, without creative efforts, other related drawings can be obtained based on the above drawings.

[0026] For those of ordinary skill in the art, without creative efforts, other related drawings can be obtained based on the above drawings. Specific Embodiments

[0027] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings of the specification and through specific embodiments.

[0028] Example 1

[0029] A preparation method and application of an alkaline zinc - based flow battery electrolyte, specifically:

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

[0031] (2) Add nano - zinc oxide powder to the alkaline aqueous solution and stir to dissolve at room temperature. The zinc oxide dissolves to form zincate, obtaining an alkaline aqueous solution containing zincate, and the concentration of zincate in the alkaline aqueous solution containing zincate is 0.2 mol / L;

[0032] (3) Add sorbitol and dichloromethane to the zincate in the alkaline aqueous solution containing zincate to obtain an alkaline electrolyte. The concentration of sorbitol in the alkaline electrolyte is 0.2 mol / L, and the concentration of dichloromethane is 0.1 mol / L;

[0033] (4) Assemble a single-flow zinc symmetric battery and a flow zinc half-cell using the above electrolyte, and test the performance of the battery at a current density of 80 mA / cm 2 ; the fixed amount of single charge is 40 mAh / cm 2 ; Assembly method: The zinc electrode uses a zinc foil with a thickness of 0.1 mm, the counter electrode uses a graphite felt with a thickness of 3 mm, the Nafion 117 membrane is an ion-conducting membrane, and the electrolytes for both the positive and negative electrodes are 40 mL;

[0034] (5) Assemble a single-flow zinc-nickel battery using the above electrolyte, and test the performance of the battery at a current density of 80 mA / cm 2 ; Assembly method: The negative electrode uses a zinc foil with a thickness of 0.1 mm, the positive electrode uses nickel hydroxide foam with a thickness of 3 mm, the Nafion 117 membrane is an ion-conducting membrane, and the electrolytes for both the positive and negative electrodes are 40 mL.

[0035] Examples 2 to 12 were obtained by changing the types of sugar alcohols and chloromethanes, and the rest were the same as in Example 1. The types of sugar alcohols and chloromethanes in Examples 2 to 12 are shown in Table 1 below.

[0036] Table 1: Types of sugar alcohols and chloromethanes in Examples 2 to 12

[0037]

[0038]

[0039] Through Figure 1 Analysis shows that: The single-flow symmetric battery assembled with this negative electrolyte can operate stably for more than 100 hours, and the overpotential is less than 50 mV, proving that this 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 shows that: After standing for 0 to 5 hours, the Coulomb efficiency > 85%, the loss of deposited zinc is 5%, and the loss of static zinc is 2% per hour, proving that this electrolyte can effectively inhibit the self-corrosion and side reactions of the zinc negative electrode, and can achieve reversible deposition and stripping of zinc in a strong alkaline environment.

[0041] Comparative Example 1

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

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

[0044] (2) Add nano-zinc oxide powder to Solution A. The zinc oxide dissolves to form zincate with a concentration of 0.2 mol / L. Stir and dissolve at room temperature to obtain Solution B;

[0045] (3) Add sorbitol to Solution B. The concentration of sorbitol after dissolution is 0.2 mol / L to obtain Electrolyte Comparative Example 1.

[0046] Change sorbitol to erythritol, xylitol, and mannitol respectively to obtain Comparative Examples 2-4, and the rest are the same as Comparative Example 1.

[0047] Comparative Example 5

[0048] A method for preparing an alkaline electrolyte and the application of the alkaline electrolyte in an alkaline zinc-based flow battery are specifically as follows:

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

[0050] (2) Add nano-zinc oxide powder to Solution A. The zinc oxide dissolves to form zincate with a concentration of 0.2 mol / L. Stir and dissolve at room temperature to obtain Solution B;

[0051] (3) Add dichloromethane to Solution B. The concentration of dichloromethane after dissolution is 0.1 mol / L to obtain Electrolyte Comparative Example 5.

[0052] Change dichloromethane to chloromethane and trichloromethane respectively to obtain Comparative Examples 6 and 7, and the rest are the same as Comparative Example 5.

[0053] Comparative Example 8

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

[0055] (2) Add nano-zinc oxide powder to Solution A. The zinc oxide dissolves to form zincate with a concentration of 0.2 mol / L. Stir and dissolve at room temperature to obtain the electrolyte.

[0056] Perform performance tests on Examples 1-12 and Comparative Examples 1-8. 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 to 12, it was found that when sugar alcohol and chloromethane were added to the electrolyte simultaneously, the zinc negative electrode exhibited good performance: a relatively long cycle life, all exceeding 90 hours; a relatively high initial Coulombic efficiency, ranging from 92% to 96%; and a relatively small loss of Coulombic efficiency with standing. After standing for 5 hours, there was still 84 - 86%. Comparing with Comparative Examples 1 to 4, it was found that when sugar alcohol was added to the electrolyte but chloromethane was not, the cycle life of the zinc negative electrode was relatively short, only 40 - 50 hours, the initial Coulombic efficiency was only 83 - 86%, and it decreased to 67 - 70% after standing for 5 hours. Comparing with Comparative Examples 5 to 7, it was found that when chloromethane was added to the electrolyte but sugar alcohol was not, the cycle life of the electrolyte was relatively short, only 40 - 50 hours, the initial Coulombic efficiency was only 87 - 90%, and it decreased to 57 - 60% after standing for 5 hours. Comparing with Comparative Example 8, it was found that when neither sugar alcohol nor chloromethane was added, the cycle life was only 20 hours, and the initial Coulombic efficiency and the Coulombic efficiency after standing for 5 hours were only 80.5% and 49.6% respectively. Analyzing Comparative Examples 1 to 4 and Comparative Example 8, it can be seen that after adding sugar alcohol to the electrolyte, the initial Coulombic efficiency increased by about 3 - 5%, and the Coulombic efficiency after standing for 5 hours increased by 18 - 20%. This shows that the addition of sugar alcohol adsorbed on the surface of the zinc negative electrode, slowed down the self-corrosion of the zinc negative electrode, and thus improved its electrochemical performance. Analyzing Comparative Examples 5 to 7 and Comparative Example 8, it can be seen that after adding chloromethane to the electrolyte, the initial Coulombic efficiency increased by about 7 - 9%. This shows that the addition of chloromethane optimized the solvation structure of zincate, inhibited the occurrence of side reactions of the zinc negative electrode, and thus improved its performance. Analyzing Examples 1 to 12 and Comparative Example 8, it can be seen that when sugar alcohol and chloromethane are added together, the self-corrosion and side reactions of the zinc negative electrode can be inhibited simultaneously, which is the key to significantly improving the stability of the zinc negative electrode.

[0060] The present invention proposes a novel negative electrode electrolyte, in which hydroxide is used as a supporting electrolyte, zinc oxide is used as a zincate source, sugar alcohol and chloromethane are used as additives to stabilize the zinc negative electrode and improve the Coulombic efficiency; this negative electrode electrolyte can effectively inhibit the growth of zinc dendrites and the occurrence of side reactions, improve the Coulombic efficiency and cycle stability of the negative electrode, and provide new ideas for the development of a long-term energy storage system with high safety and high stability; the electrolyte preparation method of the present invention has a simple and easy implementation process, realizes the stable regulation of the double electric layer of the negative electrode and the solvation structure of zinc ions, and broadens the feasibility of zinc-based flow batteries in a strongly alkaline (pH > 14) environment.

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

[0062] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing an alkaline zinc-based flow battery electrolyte, characterized in that: The following steps are involved: (I) dissolving a hydroxide solid in deionized water to obtain an alkaline aqueous solution; (II) dissolving zinc oxide solid in the alkaline aqueous solution obtained in step (I) to obtain an alkaline aqueous solution containing zincate; (III) Dissolving sugar alcohol and methyl chloride in the alkaline aqueous solution containing zincate obtained in step (II) to obtain an alkaline electrolyte.

2. The method for preparing an alkaline zinc-based flow battery electrolyte according to claim 1, characterized in that: 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 mol / L to 6 mol / L.

3. The method for preparing an 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; and the zincate concentration in the alkaline aqueous solution containing the zincate is 0.02 mol / L to 0.2 mol / L.

4. The method for preparing an alkaline zinc-based flow battery electrolyte according to claim 1, characterized in that: 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 mol / L to 0.8 mol / L.

5. The method for preparing an alkaline zinc-based flow battery electrolyte according to claim 1, characterized in that: The methyl chloride is at least one of monochloromethane, dichloromethane or chloroform, and the concentration of the methyl chloride in the alkaline electrolyte is 0.01 mol / L to 0.2 mol / L.

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

7. The method for preparing an 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 according to any one of claims 1 to 7.

9. An 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 liquid flow battery electrolyte is used as the negative electrode electrolyte of the alkaline zinc-based liquid flow battery.

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

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