Neutral zinc-iron flow battery and preparation method of negative electrode electrolyte of neutral zinc-iron flow battery

Abstract

The invention discloses a neutral zinc-iron flow battery and a preparation method of a negative electrode electrolyte of the neutral zinc-iron flow battery, and relates to the technical field of neutral zinc-iron flow batteries. The neutral zinc-iron flow battery comprises a positive electrode electrolyte and a negative electrode electrolyte, the positive electrode electrolyte comprises Na4Fe (CN) 6, KCl, Na4Fe (CN) and KCl, the negative electrode electrolyte comprises Zn < 2 + >, KCl and D-aspartic acid, the pH value of the negative electrode electrolyte is adjusted to 5-6 through one or two alkalis in stronger ammonia water or a sodium hydroxide solution, the molar concentration ratio of Zn < 2 + > to KCl is 1: 3, the molar concentration ratio of D-aspartic acid to D-aspartic acid is 1: 1, and the molar concentration ratio of D-aspartic acid to D-aspartic acid is 1: 1. The molar concentration ratio of Zn < 2 + > to D-aspartic acid ranges from 4 to 8, and the concentration of Zn < 2 + > ranges from 0.5 mol / L to 1 mol / L. According to the invention, D-aspartic acid is added into the negative electrode electrolyte of the neutral zinc-iron flow battery, so that the precipitation of reaction between zinc ions and the positive electrode electrolyte is reduced, the problem that zinc dendrites and zinc ions shuttle to the positive electrode due to non-uniform zinc deposition of the neutral zinc-iron flow battery is solved, and the cycle life and the surface capacity of battery operation are greatly optimized.

Description

Technical Field

[0001] The present invention relates to the technical field of neutral zinc-iron liquid flow batteries, and in particular to a neutral zinc-iron liquid flow battery and a method for preparing a negative electrode electrolyte thereof. Background Art

[0002] Neutral zinc-iron flow batteries (Zn-Fe) utilize abundant zinc and iron as active materials. They offer advantages such as low electrolyte cost, high energy density, and environmental friendliness, holding great promise for distributed, long-duration energy storage. Zinc / ferrocyanide batteries were first designed in 1978. Compared to all-vanadium flow batteries and zinc-bromine flow batteries, which are currently in the demonstration phase, alkaline Zn-Fe flow batteries have yet to achieve significant breakthroughs. A key technical bottleneck lies in the uneven deposition of zinc ions at the negative electrode during charge and discharge in neutral Zn-Fe flow batteries or stacks, which can easily form zinc dendrites and increase the production of irreversible zinc, thereby reducing reversible capacity. The deposited zinc is susceptible to hydrogen evolution corrosion with active water molecules in the desolvated shell, reducing coulombic efficiency and battery capacity. Furthermore, Zn ions diffuse to the positive electrode side and form precipitation with Fe(CN)64-, increasing the irreversible nature of the battery reaction. These issues reduce battery or stack stability and significantly increase maintenance costs.

[0003] The prior art discloses a neutral zinc-iron flow battery, which uses Fe(CN)6 4- 、High concentration salt solution (3moL -1 ) as the positive electrode electrolyte, ZnCl2, high concentration salt solution (3moL -1 ) as the negative electrode electrolyte, the battery system has better enhanced the battery performance by adding nicotinamide (NAM) additive, showing a high power density (185 mW cm −2 ), long cycle stability (400 cycles, 120 hours), enhanced resistance to self-discharge (capacity retention rate of 98.9% within 12 hours), and excellent battery efficiency (50 mA cm −2 energy efficiency is 70%).

[0004] Although the battery achieved good performance, it showed a low areal capacity (3.33 mAh / cm -2 ) and a shorter cycle life. This is partly due to the slow instantaneous nucleation rate of zinc ions by NAM molecules and the thin adsorption layer of NAM molecules, which makes hydrogen evolution corrosion still susceptible to occur. Furthermore, the zinc ions, after complexing with NAM, remain relatively small, migrating through the separator material to the positive electrode and reacting with ferrocyanide / ferrocyanide ions to form a precipitate. Therefore, it is necessary to screen for a new additive with a multifunctional specific group to effectively improve the surface capacity and cycle life of neutral new iron flow batteries from the electrolyte side. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a neutral zinc-iron liquid flow battery and a method for preparing a negative electrode electrolyte thereof, which solves the problems raised in the above-mentioned background technology.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A neutral zinc-iron liquid flow battery, the neutral zinc-iron liquid flow battery comprising: a positive electrode electrolyte and a negative electrode electrolyte;

[0007] The positive electrode electrolyte includes: Na4Fe(CN)6 and KCl;

[0008] The Na4Fe(CN) and KCl, Na + With K + The molar concentration ratio is 4:3, Fe(CN)6 4- With Cl - The molar concentration ratio range is 1 to 4, Fe(CN)6 4- The concentration is 0.5mol / L~0.7mol / L;

[0009] The negative electrode electrolyte includes: Zn 2+ , KCl and D-aspartic acid;

[0010] The negative electrode electrolyte is adjusted to pH 5-6 by one or two alkalis selected from concentrated ammonia or sodium hydroxide solution. 2+ The molar concentration ratio of Zn to KCl is 1:3. 2+ The molar concentration ratio of Zn to D-aspartic acid is 4 to 8, and the Zn 2+ The concentration is 0.5mol / L~1mol / L.

[0011] A further improvement of the technical solution of the present invention is that in the negative electrode electrolyte, Zn 2 Derived from any one of zinc chloride, zinc nitrate, zinc acetate, zinc phosphate, zinc trifluoromethanesulfonate, zinc tetrafluoroborate, zinc hexafluorophosphate, zinc bis(oxaloyl)borate, zinc bromide, and zinc perchlorate.

[0012] A further improvement of the technical solution of the present invention is that the neutral zinc-iron flow battery has a high surface capacity and a long cycle life, wherein the high surface capacity is 20 mAh / cm -2 , the cycle life is 500 stable cycles.

[0013] The present invention also provides a method for preparing a negative electrode electrolyte of a neutral zinc-iron flow battery, the method comprising

[0014] S1, after mixing the zinc precursor and potassium chloride, adding deionized water, stirring at 20-40 ° C for 0.1 hour to prepare a uniform colorless solution, then adding D-aspartic acid additive, adding deionized water, stirring at 30-60 ° C for 0.1-1 hour to obtain the negative electrode electrolyte;

[0015] A further improvement of the technical solution of the present invention is that the method further includes: S2, mixing the zinc precursor and potassium chloride, adding deionized water, and stirring at 20-40 ° C for 0.1 hour to prepare a uniform colorless solution, then adding D-aspartic acid additive, adding deionized water, and heating at 50 ° C for 10 minutes by microwave method to obtain the negative electrode electrolyte

[0016] Beneficial effects

[0017] Compared with the prior art, the beneficial effects of the present invention are: by adding D-aspartic acid to the negative electrode electrolyte of the neutral zinc-iron liquid flow battery, the zinc ion nucleation rate is increased, the precipitation of zinc ions reacting with the positive electrode electrolyte is reduced, and the problem of zinc dendrites and zinc ion shuttle to the positive electrode caused by uneven zinc deposition in the neutral zinc-iron liquid flow battery is effectively suppressed, thereby greatly optimizing the cycle life and surface capacity of the battery operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a test graph showing the effect of different D-aspartic acid concentrations on the cycling performance of a neutral zinc-iron flow battery at the same current density in Example 1 of the present invention;

[0019] Figure 2 This is a test graph showing the effect of different D-aspartic acid concentrations on the cycling performance of a neutral zinc-iron flow battery at the same current density in Example 2 of the present invention;

[0020] Figure 3 This is a test graph showing the effect of different D-aspartic acid concentrations on the cycling performance of a neutral zinc-iron flow battery at the same current density according to Example 3 of the present invention;

[0021] Figure 4 In Example 4 of the present invention, the neutral zinc-iron flow battery 0.09 mol·L -1 Cycling performance diagram of D-aspartic acid at different current densities;

[0022] Figure 5 In Example 5 of the present invention, the neutral zinc-iron flow battery 0.09 mol·L -1 Cycling performance diagram of D-aspartic acid at different current densities;

[0023] Figure 6 In Example 6 of the present invention, the neutral zinc-iron flow battery 0.09 mol·L -1Cycling performance diagram of D-aspartic acid at different current densities;

[0024] Figure 7 Example 7 of the present invention at 50 mA / cm -2 、10mAh / cm -2 At a current density of 0.09 mol L -1 Cycling performance diagram of D-aspartate neutral zinc-iron flow battery;

[0025] Figure 8 The neutral zinc-iron flow battery of Example 8 of the present invention is 10 mAh / cm -2 Rate performance diagram;

[0026] Figure 9 For comparative example 1 at 20 mAh / cm -2 Long cycle performance diagram of additive-free neutral zinc-iron flow battery at surface capacity;

[0027] Figure 10 For comparative example 2 at 10 mAh / cm -2 Long cycle performance diagram of additive-free neutral zinc-iron flow battery at surface capacity;

[0028] Figure 11 For comparative example 3, the neutral zinc-iron flow battery without additives was tested at 10 mAh / cm -2 Rate performance diagram under area capacity. DETAILED DESCRIPTION

[0029] Various exemplary embodiments, features, and aspects of the present application will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0030] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0031] In addition, numerous specific details are provided in the following specific examples to better illustrate the present application. Those skilled in the art will appreciate that the present application can be practiced without certain specific details. In some instances, methods, means, and components well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present application.

[0032] The present invention provides a neutral zinc-iron liquid flow battery, which comprises: a positive electrode electrolyte and a negative electrode electrolyte;

[0033] The positive electrode electrolyte includes: Na4Fe(CN)6 and KCl;

[0034] The Na4Fe(CN) and KCl, Na + With K + The molar concentration ratio is 4:3, Fe(CN)6 4- With Cl - The molar concentration ratio range is 1 to 4, Fe(CN)6 4- The concentration is 0.5mol / L~0.7mol / L;

[0035] The negative electrode electrolyte includes: Zn 2+ , KCl and D-aspartic acid;

[0036] The negative electrode electrolyte is adjusted to pH 5-6 by one or two alkalis selected from concentrated ammonia or sodium hydroxide solution. 2+ The molar concentration ratio of Zn to KCl is 1:3. 2+ The molar concentration ratio of Zn to D-aspartic acid is 4 to 8, and the Zn 2+ The concentration is 0.5mol / L~1mol / L.

[0037] In the negative electrode electrolyte, Zn 2 Derived from any one of zinc chloride, zinc nitrate, zinc acetate, zinc phosphate, zinc trifluoromethanesulfonate, zinc tetrafluoroborate, zinc hexafluorophosphate, zinc bis(oxaloyl)borate, zinc bromide, and zinc perchlorate.

[0038] The neutral zinc-iron flow battery has a high areal capacity and a long cycle life, wherein the high areal capacity is 20 mAh / cm -2 , the cycle life is 500 stable cycles.

[0039] The present invention also provides a method for preparing a negative electrolyte for a neutral zinc-iron flow battery, the method comprising:

[0040] S1. After mixing the zinc precursor and potassium chloride, deionized water is added, and the mixture is stirred at 20-40°C for 0.1 hour to prepare a uniform colorless solution. D-aspartic acid additive is then added, and deionized water is added, and the mixture is stirred at 30-60°C for 0.1-1 hour to obtain the negative electrode electrolyte.

[0041] The method further comprises:

[0042] S2. After mixing the zinc precursor and potassium chloride, deionized water was added, and the mixture was stirred at 20-40° C. for 0.1 hour to prepare a uniform colorless solution. D-aspartic acid additive was then added, deionized water was added, and the mixture was heated at 50° C. for 10 minutes using a microwave method to obtain the negative electrode electrolyte.

[0043] The present invention will be described in detail below with reference to the examples, and further described below with reference to the specific examples. The raw materials used in the following examples are all commercially available conventional products.

[0044] The following examples and comparative examples are composed of neutral zinc-iron flow batteries:

[0045] Among them, the composition of the positive electrode electrolyte includes: 0.5mol·L -1 Na4Fe (CN)6,3mol·L -1 KCl, the volume of positive and negative electrolytes is 20 mL each;

[0046] The negative electrode electrolyte composition includes: 0.4 mol·L -1 Zn 2+ 、3mol·L -1 KCl, different concentrations of D-aspartic acid additives.

[0047] Both positive and negative electrodes are 9cm 2 It is a porous carbon felt electrode, a graphite plate is used as a current collector, and the ion conductive membrane is Nafion117.

[0048] The preparation method of the negative electrode electrolyte in the following examples is as follows: zinc chloride and potassium chloride are mixed and then added and stirred thoroughly for 0.1 hour to form a uniform colorless solution, D-aspartic acid additive is then added, deionized water is added, and deionized water is added at 20-40°C, and stirred thoroughly at 30-60°C for 0.1-1 hour to obtain the negative electrode electrolyte;

[0049] The following examples and comparative examples are assembled in the following order: positive terminal plate, PFTE plate, copper current collector, graphite current collector, gasket, positive electrode 3×3cm 2 Carbon felt, Nafion117 membrane, negative electrode 3×3cm 2 Carbon felt, gasket, graphite current collector, copper current collector, PFTE plate, negative terminal plate.

[0050] Example 1: This example prepares 0.5 mol·L -1 ZnCl2 +3mol·L -1 KCl + 0.06M D-aspartic acid negative electrolyte, 0.5 mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20mL each of positive and negative electrolytes, assemble the battery; the battery adopts constant current charge and discharge mode, at 40mA / cm -2The constant current charge was carried out for 30 min under the current density of 40 mA / cm -2 The battery was discharged to 0.1V under the condition of current density.

[0051] Example 2: This example prepares 0.5 mol·L -1 ZnCl2 +3mol·L -1 KCl + 0.09M D-aspartic acid negative electrolyte, 0.5 mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20 mL each of positive and negative electrolytes, assembled the battery; the battery was charged and discharged in constant current mode at 40 mA / cm -2 The constant current charge was carried out for 30 min under the current density of 40 mA / cm -2 The battery was discharged to 0.1V under the condition of current density.

[0052] Example 3, this example prepares 0.5 mol·L -1 ZnCl2 +3mol·L -1 KCl + 0.12M D-aspartic acid negative electrolyte, 0.5 mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20 mL each of positive and negative electrolytes, assembled the battery; the battery was charged and discharged in constant current mode at 40 mA / cm -2 The constant current charge was carried out for 30 min under the current density of 40 mA / cm -2 The battery was discharged to 0.1V under the condition of current density.

[0053] Example 4: This example prepares 0.5 mol·L -1 ZnCl2 +3mol·L -1 KCl + 0.09M D-aspartic acid negative electrolyte, 0.5 mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20 mL each of positive and negative electrolytes, assembled the battery; the battery was charged and discharged in constant current mode at 40 mA / cm -2 The constant current charge was carried out for 30 min under the current density of 40 mA / cm-2 The battery was discharged to 0.1V under the condition of current density.

[0054] Example 5: This example prepares 0.5 mol·L -1 ZnCl2 +3mol·L -1 KCl + 0.09M D-aspartic acid negative electrolyte, 0.5 mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20 mL each of positive and negative electrolytes, assembled the battery; the battery was charged and discharged in constant current mode at 30 mA / cm -2 The constant current charge was carried out for 30 min under the current density of 30 mA / cm -2 The battery was discharged to 0.1V under the condition of current density.

[0055] Example 6: This example prepares 0.5 mol·L -1 ZnCl2 +3mol·L -1 KCl + 0.09M D-aspartic acid negative electrolyte, 0.5 mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20 mL each of positive and negative electrolytes, assembled the battery; the battery was charged and discharged in constant current mode at 50 mA / cm -2 The constant current charge was carried out for 30 min under the current density of 50 mA / cm -2 The battery was discharged to 0.1V under the condition of current density.

[0056] Example 7, this example prepares 0.5 mol·L -1 ZnCl2 +3mol·L -1 KCl + 0.09M D-aspartic acid negative electrolyte, 0.5 mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20 mL each of positive and negative electrolytes, assembled the battery; the battery was charged and discharged in constant current mode at 50 mA / cm -2 The constant current charge was carried out for 12 min under the current density of 50 mA / cm -2 The battery was discharged to 0.1V under the condition of current density.

[0057] Example 8, this example prepares 0.5 mol·L -1 ZnCl2 +3mol·L -1 KCl + 0.09M D-aspartic acid negative electrolyte, 0.5 mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20 mL each of positive and negative electrolytes, assemble the battery; the battery adopts constant current charge and discharge mode, and the charge surface capacity is set to 10 mAh / cm -2 , at 40~70mA / cm -2 The batteries were charged at constant current at different current densities and discharged at constant current to 0.1V.

[0058] Comparative Example 1: 0.5 mol·L -1 ZnCl2 +3mol·L -1 KCl negative electrolyte, 0.5 mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20 mL each of positive and negative electrolytes, assembled the battery; the battery was charged and discharged in constant current mode at 50 mA / cm -2 The constant current charge was carried out for 30 min under the current density of 50 mA / cm -2 The battery was discharged to 0.1V under the condition of current density.

[0059] Comparative Example 2: 0.5 mol·L -1 ZnCl2 + 3mol KCl negative electrode electrolyte, 0.5mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20 mL each of positive and negative electrolytes, assembled the battery; the battery was charged and discharged in constant current mode at 50 mA / cm -2 The constant current charge was carried out for 12 min under the current density of 50 mA / cm -2 The battery was discharged to 0.1V under the condition of current density.

[0060] Comparative Example 3: 0.5 mol·L -1ZnCl2 +3mol·L -1 KCl negative electrolyte, 0.5 mol·L -1 Na4Fe (CN)6+2mol·L -1 KCl positive electrolyte, positive and negative electrodes are carbon felt (effective area 9cm 2 ), 20 mL each of positive and negative electrolytes, assemble the battery; the battery adopts constant current charge and discharge mode, set at 10 mAh / cm -2 The constant current charging was carried out under different current density conditions, 50mA / cm -2 The battery was discharged to 0.1V under the condition of current density.

[0061] In order to determine the effect of different concentrations of D-aspartic acid on the cycle performance of neutral zinc-iron flow battery, the current density was kept the same and the concentration of D-aspartic acid was changed. Figure 1-3 As shown;

[0062] To determine the cycling performance of the neutral zinc-iron flow battery at different current densities when the D-aspartic acid concentration is the same, the D-aspartic acid concentration is controlled to 0.09 mol·L -1 , change the current density, as shown in the attached Figure 4-6 As shown;

[0063] To determine the neutral zinc-iron flow battery at 50 mA / cm -2 Current density, 10 mAh / cm -2 Under, containing 0.09 mol·L -1 The cycling performance of D-aspartic acid was controlled at a current density of 50 mA / cm -2 、10mAh / cm -2 , D-aspartic acid concentration was 0.09 mol·L -1 , the results are attached Figure 7 As shown;

[0064] To determine the neutral zinc-iron flow battery at 10 mAh / cm -2 Therefore, the test results of Example 8 are shown in the attached figure. Figure 8 As shown;

[0065] For the convenience of comparison, the comparative example 1 was -2 The long cycle performance test of the neutral zinc-iron flow battery without additives at the surface capacity, the comparative example 2 at 10 mAh / cm -2 The neutral zinc-iron flow battery without additives was tested for long cycle at 10 mAh / cm -2The rate performance test was carried out under the surface capacity, and the results are as follows Figure 9 、 10 , as shown in 11.

[0066] In the accompanying drawings, Efficency represents battery cycle performance, Capacity represents battery capacity, Cycle number represents the cycle test, Coulombic efficiency represents Coulombic efficiency, and Energy efficiency represents energy efficiency.

[0067] From the test experiments in the above figure, it can be seen that the present application increases the zinc ion nucleation rate and reduces the precipitation of zinc ions reacting with the positive electrode electrolyte by adding D-aspartic acid to the negative electrode electrolyte of the neutral zinc-iron liquid flow battery, effectively suppressing the problems of zinc dendrites and zinc ion shuttling to the positive electrode caused by uneven zinc deposition in the neutral zinc-iron liquid flow battery, thereby greatly optimizing the cycle life and surface capacity of the battery operation.

[0068] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0069] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A neutral zinc-iron flow battery, characterized in that: The neutral zinc-iron flow battery comprises: a positive electrode electrolyte and a negative electrode electrolyte; the positive electrode electrolyte comprises: Na4Fe(CN)6, KCl; Na4Fe(CN)6 and KCl + With K + The molar concentration ratio is 4:3, Fe(CN)6 4- With Cl - The molar concentration ratio range is 1 to 4, Fe(CN)6 4- The concentration is 0.5mol / L to 0.7mol / L; the negative electrode electrolyte comprises: Zn 2+ , KCl and D-aspartic acid; the negative electrode electrolyte is adjusted to pH 5 to 6 by one or two alkalis in concentrated ammonia or sodium hydroxide solution, the Zn 2+ The molar concentration ratio of Zn to KCl is 1:

3. 2+ The molar concentration ratio of Zn to D-aspartic acid is 4 to 8, and the Zn 2+ The concentration is 0.5mol / L~1mol / L.

2. A neutral zinc-iron flow battery according to claim 1, characterized in that: In the negative electrode electrolyte, Zn 2 Derived from any one of zinc chloride, zinc nitrate, zinc acetate, zinc phosphate, zinc trifluoromethanesulfonate, zinc tetrafluoroborate, zinc hexafluorophosphate, zinc bis(oxalatoborate), zinc bromide, and zinc perchlorate.

3. A neutral zinc-iron flow battery according to claim 1, characterized in that: The neutral zinc-iron flow battery has a high areal capacity and a long cycle life, wherein the high areal capacity is 20 mAh / cm -2 , the cycle life is 500 stable cycles.

4. A method for preparing a negative electrode electrolyte for a neutral zinc-iron liquid flow battery, which is applied to the preparation of a negative electrode electrolyte for a neutral zinc-iron liquid flow battery according to any one of claims 1 to 3, characterized in that: The method comprises: S1, mixing a zinc precursor with potassium chloride, adding deionized water, and fully stirring at 20-40°C for 0.1 hour to prepare a uniform colorless solution, then adding D-aspartic acid additive, adding deionized water, and fully stirring at 30-60°C for 0.1-1 hour to obtain the negative electrode electrolyte.

5. The method for preparing a negative electrolyte for a neutral zinc-iron flow battery according to claim 4, characterized in that: The method further includes: S2, mixing the zinc precursor and potassium chloride, adding deionized water, and fully stirring at 20-40°C for 0.1 hour to prepare a uniform colorless solution, then adding D-aspartic acid additive, adding deionized water, and heating at 50°C for 10 minutes using a microwave method to obtain the negative electrode electrolyte.

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