A negative electrolyte, a preparation method thereof and a zinc-bromine flow battery

Abstract

The application belongs to the technical field of electrochemical energy storage, and provides a negative electrolyte, a preparation method thereof and a zinc-bromine flow battery. The components of the negative electrolyte include zinc bromide, a supporting electrolyte, a negative electrode additive and water, the negative electrode additive includes malic acid, the concentrations of the zinc bromide, the supporting electrolyte and the malic acid in the negative electrolyte are 2.0-2.5 mol / L, 2.0-3.0 mol / L and 0.02-0.04 mol / L respectively. The zinc dendrite and hydrogen evolution reaction are effectively inhibited, and the synergistic improvement of coulombic efficiency, voltage efficiency and energy efficiency is realized. Therefore, by introducing malic acid into the negative electrolyte, the zinc dendrite and hydrogen evolution reaction in the zinc-bromine flow battery can be effectively inhibited, and the synergistic improvement of coulombic efficiency, voltage efficiency and energy efficiency is realized.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, specifically relating to a negative electrode electrolyte and its preparation method, and a zinc-bromine redox flow battery. Background Technology

[0002] With the increasing prominence of clean energy, the demand for energy storage technologies is becoming more diversified. Flow batteries, as a highly efficient and sustainable medium- to long-term energy storage technology, have attracted significant attention. Zinc-bromine flow batteries, due to their high energy density, low cost, and environmental friendliness, have become an important branch of flow batteries.

[0003] The negative electrode in zinc-bromine flow batteries faces a severe challenge—the formation of zinc dendrites and the hydrogen evolution reaction (HER). During zinc deposition, influenced by the microenvironment at the electrode-electrolyte interface, the reduced zinc tends to preferentially grow along a specific crystal orientation, ultimately forming a dendritic zinc dendrite structure. With continuous charge-discharge cycling, these zinc dendrites continue to grow in the kinetically dominant direction, significantly reducing the interfacial stability of the zinc-bromine flow battery. When the zinc dendrites grow to a critical size, their tips penetrate the separator, causing damage to the internal structure of the zinc-bromine flow battery and triggering a series of irreversible battery failure mechanisms. On the one hand, the bromine at the positive electrode shuttles through the punctured separator, greatly reducing the coulombic efficiency of the zinc-bromine flow battery and severely affecting its performance. On the other hand, contact between the zinc dendrites and the positive electrode can cause a short circuit, directly leading to battery failure, severely limiting the lifespan and stability of the zinc-bromine flow battery, becoming a key factor hindering its widespread application. The occurrence of the hydrogen evolution reaction can affect battery performance, safety, and economy from multiple dimensions. On the one hand, the hydrogen ions and water consumed by the hydrogen evolution reaction are irreversible and will generate hydroxide ions, which will trigger the zinc passivation layer. On the other hand, the hydrogen evolution reaction will cause the local pH of the electrode surface to rise, triggering a loose and porous zinc deposition layer and accelerating the growth of zinc dendrites. At the same time, the evolution of hydrogen will bring certain safety hazards to the zinc-bromine flow battery. Summary of the Invention

[0004] To address the issues of zinc dendrite formation and hydrogen evolution reaction at the negative electrode of existing zinc-bromine flow batteries, this invention provides a negative electrode electrolyte, its preparation method, and a zinc-bromine flow battery, effectively suppressing zinc dendrite formation and hydrogen evolution reaction, and achieving a synergistic improvement in coulombic efficiency, voltage efficiency, and energy efficiency.

[0005] This invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a negative electrode electrolyte, the components of which include: zinc bromide, supporting electrolyte, negative electrode additive and water, wherein the negative electrode additive includes malic acid; the concentrations of zinc bromide, supporting electrolyte and malic acid in the negative electrode electrolyte are 2.0-2.5 mol / L, 2.0-3.0 mol / L and 0.02-0.04 mol / L, respectively.

[0007] Preferably, the negative electrode additive also includes dipalmitoylphosphatidylcholine.

[0008] Furthermore, the concentration of dipalmitoylphosphatidylcholine in the negative electrode electrolyte is 0.01-0.03 mol / L.

[0009] Preferably, the supporting electrolyte is potassium chloride.

[0010] Secondly, the present invention provides a method for preparing the negative electrode electrolyte, wherein zinc bromide, supporting electrolyte and negative electrode additive are dissolved in water to obtain the negative electrode electrolyte.

[0011] Preferably, the method for preparing the negative electrode electrolyte specifically includes: dissolving zinc bromide in water to obtain a zinc bromide solution; dissolving a supporting electrolyte in the zinc bromide solution to obtain an electrolyte solution; and dissolving a negative electrode additive in the electrolyte solution to obtain the negative electrode electrolyte.

[0012] Thirdly, the present invention provides a zinc-bromine flow battery, comprising a positive electrode electrolyte and a negative electrode electrolyte as described above.

[0013] Preferably, in the zinc-bromine flow battery, the positive electrode electrolyte comprises zinc bromide, a supporting electrolyte, and 1-methyl-1-ethylpyrrolidine ammonium bromide.

[0014] Preferably, the zinc-bromine flow battery has a coulombic efficiency of 91.8%-95.8%, an energy efficiency of 76.65%-83.06%, and a voltage efficiency of 83.5%-86.7%.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] This invention incorporates malic acid into the negative electrode electrolyte. Malic acid has multiple coordination sites in its molecular structure, allowing it to form stable, soluble complexes with zinc ions. This complexation reduces the concentration of free zinc ions in the negative electrode electrolyte, thus slowing down the reduction rate of zinc ions on the negative electrode surface when used as a negative electrode electrolyte in zinc-bromine flow batteries. This prevents uneven zinc deposition, effectively reduces or even eliminates the formation of zinc dendrites, and improves the safety and reliability of the battery. Malic acid also has excellent buffering capacity, stabilizing pH and inhibiting hydrogen evolution reaction. Therefore, by introducing malic acid into the negative electrode electrolyte, this invention effectively inhibits the reaction between zinc dendrites and hydrogen evolution in zinc-bromine flow batteries, achieving a synergistic improvement in coulombic efficiency, voltage efficiency, and energy efficiency.

[0017] Furthermore, this invention introduces dipalmitoylphosphatidylcholine into the negative electrode electrolyte. Dipalmitoylphosphatidylcholine consists of a hydrophilic head group and two hydrophobic fatty acid chains. The head group is phosphocholine, which is hydrophilic, and the two fatty acid chains are palmitic acid, which is hydrophobic. This special molecular structure determines that dipalmitoylphosphatidylcholine will form a bilayer membrane structure in water, with the hydrophilic phosphocholine facing the aqueous phase and the hydrophobic fatty acid chains aggregating to form the interior of the membrane. The positively charged choline groups in the phosphocholine will preferentially adsorb onto the protruding, highly active sites on the negative electrode surface, forming a hydrophobic molecular layer barrier. This increases the energy barrier for the reduction of zinc ions to metallic zinc at the protruding sites, inhibiting the rapid growth of zinc at these sites. Meanwhile, in flat or recessed areas on the negative electrode surface, less dipalmitoylphosphatidylcholine is adsorbed, allowing zinc to deposit relatively easily. This forces zinc to grow laterally rather than perpendicularly to the negative electrode, guiding the formation of a dense, flat, dendrite-free deposition layer. This fundamentally inhibits zinc dendrite growth, avoiding the risk of membrane puncture and significantly improving the safety and reliability of the zinc-bromine flow battery. The dipalmitoylphosphatidylcholine molecular layer adsorbed on the negative electrode surface alters the double-layer structure and properties of the electrode / electrolyte interface, potentially affecting the zinc ion desolvation process and charge transfer rate. This results in more uniform zinc nucleation and a greater number of crystal nuclei, promoting uniform zinc deposition. The resulting flat zinc deposition layer dissolves more completely and reversibly during discharge, reducing the formation of "dead zinc" and thus improving the utilization rate of the active material zinc. This enhances the coulombic efficiency, voltage efficiency, and energy efficiency of the zinc-bromine flow battery. Detailed Implementation

[0018] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0019] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0020] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] The present invention provides a negative electrode electrolyte for a zinc-bromine flow battery, the components of which include: zinc bromide, supporting electrolyte, negative electrode additive and water, wherein the negative electrode additive includes malic acid.

[0022] This invention introduces malic acid as a negative electrode additive. On the one hand, the molecular structure of malic acid has multiple coordination sites, which can form stable and soluble complexes with zinc ions. The complexation effect reduces the concentration of free zinc ions in the negative electrode electrolyte, thereby slowing down the reduction rate of zinc ions on the negative electrode surface, avoiding uneven zinc deposition, and promoting the formation of a denser and more uniform zinc deposition layer, effectively reducing or even eliminating the formation of zinc dendrites. On the other hand, malic acid promotes the deposition of zinc into a uniform deposition layer. During discharge, the zinc in the zinc deposition layer can be oxidized into zinc ions more quickly and completely and return to the electrolyte, which improves the coulombic efficiency of the battery. Furthermore, malic acid also has good buffering capacity, stabilizes pH value, inhibits hydrogen evolution reaction, and improves the coulombic efficiency, voltage efficiency, and energy efficiency of zinc-bromine flow batteries.

[0023] In the negative electrode electrolyte of this invention, the concentrations of zinc bromide, supporting electrolyte, and malic acid are 2.0-2.5 mol / L, 2.0-3.0 mol / L, and 0.02-0.04 mol / L, respectively. Specifically, the concentration of zinc bromide can be 2.0 mol / L, 2.2 mol / L, 2.5 mol / L, etc.; the concentration of supporting electrolyte can be 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, etc.; and the concentration of malic acid can be 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, etc. The concentration of malic acid has a certain influence on the performance of the zinc-bromine flow battery. Within the 0.02-0.04 mol / L range specified in this invention, as the concentration of malic acid increases, the coulombic efficiency, voltage efficiency, and energy efficiency of the zinc-bromine flow battery all gradually increase.

[0024] To further improve the performance of the zinc-bromine flow battery, the negative electrode additive in the negative electrode electrolyte of this invention may further include dipalmitoylphosphatidylcholine. The hydrophilic choline groups in dipalmitoylphosphatidylcholine preferentially adsorb onto the protruding, highly active sites on the zinc negative electrode surface. This modification strategy guides zinc towards directional deposition, inhibits zinc dendrite growth, avoids the risk of membrane puncture, and effectively improves the stability of the zinc-bromine flow battery. Simultaneously, the dipalmitoylphosphatidylcholine molecular layer adsorbed on the negative electrode surface can alter the double-layer structure and properties of the electrode / electrolyte interface, resulting in more uniform zinc nucleation and a greater number of crystal nuclei, thereby promoting uniform zinc deposition. A smooth zinc deposition layer can dissolve more completely and reversibly during discharge, reducing the formation of "dead zinc" and thus improving the utilization rate of active materials.

[0025] In the negative electrode electrolyte of this invention, the concentration of dipalmitoylphosphatidylcholine is 0.01-0.03 mol / L, specifically, for example, 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, etc. The concentration of dipalmitoylphosphatidylcholine also has a certain impact on the performance of the zinc-bromine flow battery. Within the 0.01-0.03 mol / L range specified in this invention, as the concentration of dipalmitoylphosphatidylcholine increases, the coulombic efficiency, voltage efficiency, and energy efficiency of the zinc-bromine flow battery all gradually increase.

[0026] In some specific embodiments of the present invention, the supporting electrolyte in the negative electrode electrolyte is potassium chloride.

[0027] The negative electrode electrolyte of the present invention can be prepared by a simple method, namely, by dissolving zinc bromide, supporting electrolyte and additives in water.

[0028] In specific implementation, the method for preparing the negative electrode electrolyte of the present invention specifically includes: dissolving zinc bromide in water to obtain a zinc bromide solution; dissolving a supporting electrolyte in the zinc bromide solution to obtain an electrolyte solution; and dissolving a negative electrode additive in the electrolyte solution to obtain the negative electrode electrolyte.

[0029] In this invention, the order of adding each component in the negative electrode electrolyte does not affect the performance of the electrolyte. Therefore, the negative electrode electrolyte can also be prepared according to other feeding orders. For example, the electrolyte can be dissolved in water first, then zinc bromide can be added, and then the negative electrode additive can be added.

[0030] Based on the negative electrode electrolyte described above, the present invention provides a zinc-bromine flow battery, that is, using the negative electrode electrolyte described above as the negative electrode electrolyte of the zinc-bromine flow battery.

[0031] The positive electrode electrolyte in the zinc-bromine flow battery of the present invention may include zinc bromide, supporting electrolyte, and 1-methyl-1-ethylpyrrolidine ammonium bromide.

[0032] Because this invention introduces malic acid and dipalmitoylphosphatidylcholine as binary additives, their synergistic effect can effectively inhibit the reaction between zinc dendrites and hydrogen evolution, thereby achieving a synergistic improvement in coulombic efficiency, voltage efficiency, and energy efficiency. Specifically, the coulombic efficiency of the zinc-bromine flow battery described in this invention is 91.8%-95.8%, the energy efficiency is 76.65%-83.06%, and the voltage efficiency is 83.5%-86.7%.

[0033] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments do not constitute a limitation on the present invention. The key components of the negative electrode electrolyte in each embodiment and comparative example are shown in Table 1.

[0034] Table 1. Composition of key components in the negative electrode electrolytes of Examples 1-8 and Comparative Example 1

[0035]

[0036] The specific preparation process of the negative electrode electrolytes in Examples 1-8 and Comparative Example 1 is as follows. In Examples 1-8 and Comparative Example 1 below, the molar concentrations of zinc bromide, potassium chloride, malic acid, and dipalmitoylphosphatidylcholine all refer to the molar concentrations in the prepared negative electrode electrolytes.

[0037] Example 1

[0038] A method for preparing a negative electrode electrolyte for a zinc-bromine flow battery, comprising:

[0039] S1: Accurately weigh 49.54g zinc bromide (2.2mol / L), 22.37g potassium chloride (3.0mol / L), and 0.268g malic acid (0.02mol / L).

[0040] S2: Mix zinc bromide with deionized water and stir until completely dissolved;

[0041] S3: Add potassium chloride to the solution prepared in S2 and stir until completely dissolved;

[0042] S4: Add malic acid to the solution prepared in S3 and stir until completely dissolved;

[0043] S5: The solution prepared in S4 is diluted to 100 mL with deionized water to obtain the negative electrode electrolyte of the present invention.

[0044] Example 2

[0045] A method for preparing a negative electrode electrolyte for a zinc-bromine flow battery, comprising:

[0046] S1: Accurately weigh 49.54g zinc bromide (2.2mol / L), 22.37g potassium chloride (3.0mol / L), and 0.536g malic acid (0.04mol / L).

[0047] S2: Mix zinc bromide with deionized water and stir until completely dissolved;

[0048] S3: Add potassium chloride to the solution prepared in S2 and stir until completely dissolved;

[0049] S4: Add malic acid to the solution prepared in S3 and stir until completely dissolved;

[0050] S5: The solution prepared in S4 is diluted to 100 mL with deionized water to obtain the negative electrode electrolyte of the present invention.

[0051] Example 3

[0052] A method for preparing a negative electrode electrolyte for a zinc-bromine flow battery, comprising:

[0053] S1: Accurately weigh 49.54g zinc bromide (2.2mol / L), 22.37g potassium chloride (3.0mol / L), and 0.805g malic acid (0.06mol / L).

[0054] S2: Mix zinc bromide with deionized water and stir until completely dissolved;

[0055] S3: Add potassium chloride to the solution prepared in S2 and stir until completely dissolved;

[0056] S4: Add malic acid to the solution prepared in S3 and stir until completely dissolved;

[0057] S5: The solution prepared in S4 is diluted to 100 mL with deionized water to obtain the negative electrode electrolyte of the present invention.

[0058] Example 4

[0059] A method for preparing a negative electrode electrolyte for a zinc-bromine flow battery, comprising:

[0060] S1: Accurately weigh 49.54g zinc bromide (2.2mol / L), 22.37g potassium chloride (3.0mol / L), 0.805g malic acid (0.06mol / L), and 0.734g dipalmitoylphosphatidylcholine (0.01mol / L).

[0061] S2: Mix zinc bromide with deionized water and stir until completely dissolved;

[0062] S3: Add potassium chloride to the solution prepared in S2 and stir until completely dissolved;

[0063] S4: Add malic acid and dipalmitoylphosphatidylcholine to the solution prepared in S3 and stir until completely dissolved;

[0064] S5: The solution prepared in S4 is diluted to 100 mL with deionized water to obtain the negative electrode electrolyte of the present invention.

[0065] Example 5

[0066] A method for preparing a negative electrode electrolyte for a zinc-bromine flow battery, comprising:

[0067] S1: Accurately weigh 49.54g zinc bromide (2.2mol / L), 22.37g potassium chloride (3.0mol / L), 0.805g malic acid (0.06mol / L), and 1.468g dipalmitoylphosphatidylcholine (0.02mol / L).

[0068] S2: Mix zinc bromide with deionized water and stir until completely dissolved;

[0069] S3: Add potassium chloride to the solution prepared in S2 and stir until completely dissolved;

[0070] S4: Add malic acid and dipalmitoylphosphatidylcholine to the solution prepared in S3 and stir until completely dissolved;

[0071] S5: The solution prepared in S4 is diluted to 100 mL with deionized water to obtain the negative electrode electrolyte of the present invention.

[0072] Example 6

[0073] A method for preparing a negative electrode electrolyte for a zinc-bromine flow battery, comprising:

[0074] S1: Accurately weigh 49.54g zinc bromide (2.2mol / L), 22.37g potassium chloride (3.0mol / L), 0.805g malic acid (0.06mol / L), and 2.20g dipalmitoylphosphatidylcholine (0.03mol / L).

[0075] S2: Mix zinc bromide with deionized water and stir until completely dissolved;

[0076] S3: Add potassium chloride to the solution prepared in S2 and stir until completely dissolved;

[0077] S4: Add malic acid and dipalmitoylphosphatidylcholine to the solution prepared in S3 and stir until completely dissolved;

[0078] S5: The solution prepared in S4 is diluted to 100 mL with deionized water to obtain the negative electrode electrolyte of the present invention.

[0079] Example 7

[0080] A method for preparing a negative electrode electrolyte for a zinc-bromine flow battery, comprising:

[0081] S1: Accurately weigh 45.04g zinc bromide (2.0mol / L), 14.91g potassium chloride (2.0mol / L), 0.268g malic acid (0.02mol / L), and 0.734g dipalmitoylphosphatidylcholine (0.01mol / L).

[0082] S2: Mix zinc bromide with deionized water and stir until completely dissolved;

[0083] S3: Add potassium chloride to the solution prepared in S2 and stir until completely dissolved;

[0084] S4: Add malic acid and dipalmitoylphosphatidylcholine to the solution prepared in S3 and stir until completely dissolved;

[0085] S5: The solution prepared in S4 is diluted to 100 mL with deionized water to obtain the negative electrode electrolyte of the present invention.

[0086] Example 8

[0087] A method for preparing a negative electrode electrolyte for a zinc-bromine flow battery, comprising:

[0088] S1: Accurately weigh 56.30g zinc bromide (2.5mol / L), 18.64g potassium chloride (2.5mol / L), 0.805g malic acid (0.06mol / L), and 2.202g dipalmitoylphosphatidylcholine (0.03mol / L).

[0089] S2: Mix zinc bromide with deionized water and stir until completely dissolved;

[0090] S3: Add potassium chloride to the solution prepared in S2 and stir until completely dissolved;

[0091] S4: Add malic acid and dipalmitoylphosphatidylcholine to the solution prepared in S3 and stir until completely dissolved;

[0092] S5: The solution prepared in S4 is diluted to 100 mL with deionized water to obtain the negative electrode electrolyte of the present invention.

[0093] Comparative Example 1

[0094] A method for preparing a negative electrode electrolyte for a zinc-bromine flow battery, comprising:

[0095] S1: Accurately weigh 49.54g zinc bromide (2.2mol / L) and 22.37g potassium chloride (3.0mol / L).

[0096] S2: Mix zinc bromide with deionized water and stir until completely dissolved;

[0097] S3: Add potassium chloride to the solution prepared in S2 and stir until completely dissolved;

[0098] S4: The solution prepared in S3 is diluted to 100 mL with deionized water to obtain the negative electrode electrolyte.

[0099] To test the performance of the negative electrode electrolytes in Examples 1-8 and Comparative Example 1, a zinc-bromine flow battery was assembled with the negative electrode electrolyte and a positive electrode electrolyte consisting of 2.0 mol / L zinc bromide, 1.5 mol / L potassium chloride, and 0.4 mol / L 1-methyl-1-ethylpyrrolidine ammonium bromide. The zinc-bromine flow battery was a single-flow battery, with the negative electrode electrolyte remaining stationary and the positive electrode electrolyte flowing. Both the positive and negative electrode materials were carbon felt, and the separator was a Daramic porous membrane. The test current density was 20 mA cm⁻¹. 2 The zinc-bromine flow battery was used as the test object for electrochemical performance testing. The test results of energy efficiency, voltage efficiency and coulombic efficiency are shown in Table 2.

[0100] Table 2 Performance test results of zinc-bromine flow batteries with negative electrode electrolytes in Examples 1-8 and Comparative Example 1

[0101]

[0102] Table 2 shows the performance test results of the negative electrode electrolytes prepared in Examples 1-8 and Comparative Example 1 in zinc-bromine flow batteries. As shown in Table 2, the test results of the zinc-bromine flow batteries based on the negative electrode electrolytes prepared according to this invention are as follows: coulombic efficiency 91.8%-95.8%, energy efficiency 76.65%-83.06%, and voltage efficiency 83.5%-86.7%. Comparing Examples 1-3, it can be seen that as the concentration of malic acid in the negative electrode electrolyte increases, the coulombic efficiency, energy efficiency, and voltage efficiency of the zinc-bromine flow battery all improve. Furthermore, compared with the negative electrode electrolyte of Comparative Example 1 without malic acid, the coulombic efficiency, energy efficiency, and voltage efficiency of the zinc-bromine flow batteries corresponding to the negative electrode electrolytes with added malic acid in Examples 1-3 of this invention are all improved to a certain extent. This indicates that the introduction of malic acid can significantly improve the coulombic efficiency, voltage efficiency, and energy efficiency of the zinc-bromine flow battery. The possible reasons are analyzed as follows.

[0103] Malic acid is a dicarboxylic acid containing a hydroxyl group and multiple coordination sites in its molecular structure. As a negative electrode additive, malic acid can form stable, soluble complexes with zinc ions. This complexation reduces the concentration of free zinc ions in the negative electrode electrolyte, thereby slowing down the reduction rate of zinc ions on the negative electrode surface. This promotes the formation of a dense, smooth zinc deposition layer, rather than disordered zinc dendrites that easily puncture the separator. Malic acid also has good buffering capacity, stabilizes pH, inhibits hydrogen evolution reaction, and improves the coulombic efficiency, voltage efficiency, and energy efficiency of zinc-bromine flow batteries.

[0104] Comparing Examples 3 and 4-6, it can be seen that the coulombic efficiency, energy efficiency, and voltage efficiency of the zinc-bromine flow battery are further improved after introducing dipalmitoylphosphatidylcholine into the negative electrode electrolyte. Furthermore, as the concentration of dipalmitoylphosphatidylcholine in the negative electrode electrolyte increases, the coulombic efficiency, energy efficiency, and voltage efficiency of the zinc-bromine flow battery all gradually increase. This indicates that the introduction of dipalmitoylphosphatidylcholine can significantly improve the coulombic efficiency, voltage efficiency, and energy efficiency of the zinc-bromine flow battery. Possible reasons are analyzed below.

[0105] Dipalmitoylphosphatidylcholine consists of a hydrophilic head group and two hydrophobic fatty acid chains. The head group is phosphocholine, and the positively charged choline group and negatively charged phosphate group in phosphocholine give dipalmitoylphosphatidylcholine its hydrophilicity. The two fatty acid chains are palmitic acid, which is hydrophobic. This unique molecular structure determines that dipalmitoylphosphatidylcholine forms a bilayer structure in water, with the hydrophilic phosphocholine facing the aqueous phase and the hydrophobic fatty acid chains aggregating to form the interior of the membrane.

[0106] In this process, positively charged choline groups preferentially adsorb onto the protruding, highly active sites on the negative electrode surface. This adsorption forms a dynamic, hydrophobic molecular barrier, increasing the energy barrier for the reduction of zinc ions to metallic zinc at these protruding sites and inhibiting the rapid growth of zinc at these sites. Simultaneously, in flat or recessed areas of the negative electrode surface, less dipalmitoylphosphatidylcholine is adsorbed, allowing zinc to deposit relatively easily. This forces zinc ions to grow laterally rather than perpendicularly to the negative electrode, thus guiding the formation of a dense, flat, dendrite-free zinc deposition layer. By fundamentally inhibiting zinc dendrite growth, the risk of separator puncture is avoided, significantly improving the safety and reliability of the battery.

[0107] The dipalmitoylphosphatidylcholine molecular layer adsorbed on the negative electrode surface alters the electric double layer structure and properties at the electrode / electrolyte interface, potentially affecting the zinc ion desolvation process and charge transfer rate. This results in more uniform zinc nucleation and a greater number of crystal nuclei, thus promoting uniform zinc deposition. The resulting smooth zinc deposition layer dissolves more completely and reversibly during discharge, reducing the formation of "dead zinc" and improving the utilization rate of the active material zinc. This, in turn, enhances the coulombic efficiency, voltage efficiency, and energy efficiency of the zinc-bromine flow battery.

[0108] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of this invention.

Claims

1. A negative electrode electrolyte, characterized in that, The negative electrode electrolyte comprises: zinc bromide, supporting electrolyte, negative electrode additive, and water. The negative electrode additive includes malic acid and dipalmitoylphosphatidylcholine. The supporting electrolyte is potassium chloride. The concentrations of zinc bromide, supporting electrolyte, and malic acid in the negative electrode electrolyte are 2.0-2.5 mol / L, 2.0-3.0 mol / L, and 0.02-0.04 mol / L, respectively.

2. The negative electrode electrolyte according to claim 1, characterized in that, The concentration of dipalmitoylphosphatidylcholine in the negative electrode electrolyte is 0.01-0.03 mol / L.

3. The method for preparing the negative electrode electrolyte according to any one of claims 1-2, characterized in that, Zinc bromide, supporting electrolyte, and negative electrode additive are dissolved in water to obtain the negative electrode electrolyte.

4. The method for preparing the negative electrode electrolyte according to claim 3, characterized in that, include: Zinc bromide is dissolved in water to obtain a zinc bromide solution; The supporting electrolyte is dissolved in a zinc bromide solution to obtain an electrolyte solution; the negative electrode additive is dissolved in the electrolyte solution to obtain the negative electrode electrolyte.

5. A zinc-bromine flow battery, characterized in that, It includes the positive electrode electrolyte and the negative electrode electrolyte as described in any one of claims 1-2.

6. The zinc-bromine flow battery according to claim 5, characterized in that, The positive electrode electrolyte comprises zinc bromide, supporting electrolyte, and 1-methyl-1-ethylpyrrolidine ammonium bromide.

7. The zinc-bromine flow battery according to claim 5, characterized in that, The zinc-bromine flow battery has a coulombic efficiency of 91.8%-95.8%, an energy efficiency of 76.65%-83.06%, and a voltage efficiency of 83.5%-86.7%.

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