Zinc-bromine static battery aqueous electrolyte, zinc-bromine static battery and application of zinc-bromine static battery

Abstract

The invention discloses a zinc-bromine static battery aqueous electrolyte, a zinc-bromine static battery and application thereof, and relates to the technical field of battery energy storage. The zinc-bromine static battery aqueous electrolyte comprises zinc bromide, non-halogen anion zinc salt, cyclodextrin and derivatives thereof, and water. When the aqueous electrolyte is used for preparing the zinc-bromine static battery, zinc ions in high-concentration non-halogen anion zinc salt can be combined with free Br <-> to form zinc-bromine complex ions, high-concentration cyclodextrin and derivatives thereof can be combined with free Br <-> to form clathrate compounds, and the zinc ions and the cyclodextrin are matched with each other and have a synergistic effect, so that the free Br <-> in the electrolyte is efficiently reduced, and the zinc-bromine static battery is prepared. Therefore, the self-discharge performance of the zinc-bromine static battery is effectively improved. The zinc-bromine static battery can be applied to the field of large-scale energy storage.

Description

Technical Field

[0001] The invention relates to the technical field of battery energy storage, and in particular to a zinc-bromine static battery aqueous electrolyte, a zinc-bromine static battery and applications thereof. Background Art

[0002] Relying on Zn 2+ The aqueous zinc-bromine static battery, which uses the Br / Zn (negative electrode) and Br2 / Brˉ (positive electrode) electrode pair reactions, has gradually become a rising star in the field of large-scale energy storage with its breakthrough cost advantage, intrinsic safety, and high theoretical energy density (435Wh / kg). However, in the temperature range of tens of degrees below zero to tens of degrees above zero, the battery always has the defect of excessive self-discharge: the free Brˉ in the electrolyte reacts with the positive electrode charging product Br2 to form Br3ˉ, which will dissolve and penetrate into the negative electrode and react chemically with Zn, resulting in severe self-discharge, which cannot meet the application requirements of energy storage devices. Therefore, the development of a new aqueous electrolyte that can efficiently reduce free Brˉ has important industrial application value.

[0003] In the prior art, patent CN 116742092 A discloses a homogeneous electrolyte for the positive electrode of a zinc-bromine flow battery. The patent uses cyclodextrin derivatives (methylated cyclodextrin, hydroxyethyl cyclodextrin, hydroxypropyl cyclodextrin, carboxymethyl cyclodextrin, sulfate cyclodextrin, sulfonate cyclodextrin, phosphate cyclodextrin) as bromine complexes to obtain a zinc-bromine flow battery with excellent CE, VE and EE. Patent CN 118431529 A discloses the application of a bromine capture agent based on supramolecular assembly in a zinc-bromine flow battery. The patent uses cyclodextrin and its derivatives as bromine capture agents to effectively improve the coulombic efficiency of the battery. The above patents all use cyclodextrin or its derivatives as bromine complexing agents (capturing agents) to improve the relevant performance of zinc-bromine flow batteries. However, the applicant found during the relevant research that in zinc-bromine static batteries, after adding cyclodextrin or its derivatives to the electrolyte alone, there will still be a large amount of free Brˉ (taking 1 mol / L zinc bromide aqueous solution as an example, the free Brˉ concentration exceeds 0.5 mol / L), resulting in the inability to effectively improve the self-discharge performance. Therefore, it is necessary to propose a new strategy that can effectively reduce free Brˉ in response to the self-discharge requirements of zinc-bromine static batteries. Summary of the invention

[0004] In view of the above shortcomings, the present invention provides a zinc-bromine static battery aqueous electrolyte, a zinc-bromine static battery and its application, which solves the problem that the concentration of free Brˉ in the aqueous zinc-bromine static battery electrolyte is high, resulting in excessive self-discharge of the battery. The present invention effectively reduces the free Brˉ in the electrolyte by adding two bromide ion binders, namely, non-halogen anion zinc salt and cyclodextrin and its derivatives, to the electrolyte, thereby effectively improving the self-discharge performance of the zinc-bromine static battery. The specific technical scheme is as follows:

[0005] A zinc-bromine static battery aqueous electrolyte comprises zinc bromide, non-halogen anion zinc salt, cyclodextrin and its derivatives and water.

[0006] Preferably, the non-halogen anion zinc salt is at least one of zinc trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonyl)imide, zinc acetate, zinc sulfate, zinc nitrate, zinc nitrite, zinc chlorate, zinc bromate, zinc perchlorate, zinc permanganate, zinc formate, zinc gluconate, zinc fluorosilicate, zinc fluoroborate, and zinc pivalate; more preferably, the non-halogen anion zinc salt is at least one of zinc trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonyl)imide, zinc acetate, zinc sulfate, zinc nitrate, and zinc perchlorate.

[0007] Preferably, the cyclodextrin and its derivatives are at least one of α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, hydroxypropyl-α-cyclodextrin, hydroxypropyl-β-cyclodextrin, hydroxypropyl-γ-cyclodextrin, hydroxyethyl-β-cyclodextrin, methyl-β-cyclodextrin, hydroxybutyl-β-cyclodextrin, carboxymethyl-β-cyclodextrin, β-cyclodextrin sodium sulfate, β-cyclodextrin sodium sulfonate, and β-cyclodextrin sodium phosphate; more preferably, the cyclodextrin and its derivatives are at least one of α-cyclodextrin, γ-cyclodextrin, hydroxypropyl-α-cyclodextrin, hydroxypropyl-β-cyclodextrin, hydroxypropyl-γ-cyclodextrin, and hydroxyethyl-β-cyclodextrin.

[0008] Preferably, the concentration of zinc bromide is 0.5 to 5 mol / L, and more preferably, the concentration of zinc bromide is 1 to 3 mol / L.

[0009] Preferably, the concentration of the non-halogen anion zinc salt is 0.5 to 15 mol / L, and more preferably, the concentration of the non-halogen anion zinc salt is 2 to 10 mol / L.

[0010] Preferably, the concentration of the cyclodextrin and its derivatives is 0.05-2 mol / L, and more preferably, the concentration of the cyclodextrin and its derivatives is 0.1-1 mol / L.

[0011] The present invention also provides a zinc-bromine static battery, comprising a positive electrode, a negative electrode, a diaphragm and the zinc-bromine static battery aqueous electrolyte; the negative electrode is a commercially available zinc foil, and the diaphragm is a commercially available microporous diaphragm.

[0012] The preparation method of the positive electrode of the zinc-bromine static battery is as follows: firstly, activated carbon, XC-72 conductive carbon and polytetrafluoroethylene are uniformly mixed in a mass ratio of 90:5:5, isopropyl alcohol is added to prepare the slurry, and then the slurry is pressed into a thin sheet by a stainless steel rolling machine, and vacuum dried at 120° C., and finally the thin sheet is cut into a suitable size to obtain the battery positive electrode.

[0013] The present invention also provides an application of the zinc-bromine static battery, which is used in the field of large-scale energy storage.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention combines non-halogen anion zinc salt with cyclodextrin and its derivatives for the aqueous electrolyte of zinc-bromine static battery for the first time, solving the problem that the free Brˉ concentration in the aqueous zinc-bromine static battery electrolyte is high, resulting in excessive self-discharge of the battery. Among them, the zinc ions in the high-concentration non-halogen anion zinc salt can combine with free Brˉ to form zinc-bromine complex ions, and the high-concentration cyclodextrin and its derivatives can combine with free Brˉ to form inclusion compounds. The two cooperate with each other, synergistically enhance the effect, and efficiently reduce the free Brˉ in the electrolyte, thereby effectively improving the self-discharge performance of the zinc-bromine static battery. DETAILED DESCRIPTION

[0016] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0017] Example 1

[0018] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0019] Zinc bromide, zinc trifluoromethanesulfonate, and hydroxypropyl-α-cyclodextrin are dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 1.5 mol / L, the concentration of zinc trifluoromethanesulfonate is 5 mol / L, and the concentration of hydroxypropyl-α-cyclodextrin is 0.3 mol / L.

[0020] Example 2

[0021] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0022] Zinc bromide, zinc trifluoromethanesulfonate, and hydroxypropyl-β-cyclodextrin are dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 1.5 mol / L, the concentration of zinc trifluoromethanesulfonate is 5 mol / L, and the concentration of hydroxypropyl-β-cyclodextrin is 0.3 mol / L.

[0023] Example 3

[0024] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0025] Zinc bromide, zinc bis(trifluoromethanesulfonyl)imide, and γ-cyclodextrin are dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 2 mol / L, the concentration of zinc bis(trifluoromethanesulfonyl)imide is 4 mol / L, and the concentration of γ-cyclodextrin is 0.4 mol / L.

[0026] Example 4

[0027] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0028] Zinc bromide, zinc perchlorate, and hydroxyethyl-β-cyclodextrin are dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 2.5 mol / L, the concentration of zinc perchlorate is 7 mol / L, and the concentration of hydroxyethyl-β-cyclodextrin is 0.7 mol / L.

[0029] Example 5

[0030] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0031] Zinc bromide, zinc acetate and hydroxypropyl-γ-cyclodextrin are dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 1 mol / L, the concentration of zinc acetate is 2 mol / L, and the concentration of hydroxypropyl-γ-cyclodextrin is 0.1 mol / L.

[0032] Example 6

[0033] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0034] Zinc bromide, zinc sulfate, and hydroxypropyl-α-cyclodextrin are dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 3 mol / L, the concentration of zinc sulfate is 10 mol / L, and the concentration of hydroxypropyl-α-cyclodextrin is 1 mol / L.

[0035] Example 7

[0036] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0037] Zinc bromide, zinc nitrate and α-cyclodextrin are dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 2 mol / L, the concentration of zinc nitrate is 4 mol / L, and the concentration of α-cyclodextrin is 0.3 mol / L.

[0038] Comparative Example 1

[0039] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0040] Zinc bromide is dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 1.5 mol / L.

[0041] Comparative Example 2

[0042] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0043] Zinc bromide and hydroxypropyl-α-cyclodextrin are dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 1.5 mol / L, and the concentration of hydroxypropyl-α-cyclodextrin is 0.3 mol / L.

[0044] Comparative Example 3

[0045] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0046] Zinc bromide and hydroxypropyl-β-cyclodextrin are dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 1.5 mol / L, and the concentration of hydroxypropyl-β-cyclodextrin is 0.3 mol / L.

[0047] Comparative Example 4

[0048] Preparation of aqueous electrolyte for zinc-bromine static battery:

[0049] Zinc bromide and zinc trifluoromethanesulfonate are dissolved in deionized water to obtain an aqueous electrolyte, wherein the concentration of zinc bromide is 1.5 mol / L, and the concentration of zinc trifluoromethanesulfonate is 5 mol / L.

[0050] The electrolytes prepared in the above embodiments and comparative examples are respectively used to prepare zinc-bromine static batteries, and the batteries include a positive electrode, a negative electrode (commercially available zinc foil), a diaphragm (commercially available microporous diaphragm) and an aqueous electrolyte. The preparation method of the positive electrode is: firstly, activated carbon, XC-72 conductive carbon and polytetrafluoroethylene are uniformly mixed according to a mass ratio of 90:5:5, and then isopropanol is added to prepare the slurry, and then the slurry is pressed into a thin sheet by a stainless steel film rolling machine, and vacuum dried at 120°C, and finally the thin sheet is cut into a suitable size to obtain the positive electrode of the battery.

[0051] Performance Test:

[0052] (1) The zinc-bromine static batteries of each embodiment and each comparative example were subjected to electrochemical tests to examine their self-discharge performance. The experimental conditions were:

[0053] The test temperature was selected at three different temperatures: -10, 25, and 50°C; the current density for charging and discharging was the same, both 10 mA / cm 2 The charge cut-off voltage is 1.8 V, and the discharge cut-off voltage is 0.6 V. For the self-discharge performance, the discharge energy retention rate of the battery is compared after charging to the cut-off voltage and standing for 3 days.

[0054] (2) The battery performance test results are shown in Table 1:

[0055] Table 1 Battery performance test results of the embodiment and the comparative example

[0056]

[0057] (3) The results show that:

[0058] The electrolyte of the embodiment contains two bromide ion binders. At different test temperatures, the static discharge energy retention rate of the battery containing the electrolyte of the two bromide ion binders is much greater than that of the comparative example, indicating that the embodiment has lower self-discharge than the comparative example.

[0059] From the data of Example 1, Example 2, Comparative Example 2, Comparative Example 3, and Comparative Example 4, it can be seen that the complexing performance of free Brˉ when non-halogen anion zinc salt is added alone or cyclodextrin and its derivatives are added alone to the electrolyte is much lower than the effect of adding both at the same time, and the effects of Example 1 and Example 2 are also better than the sum of the effects of adding both alone, which means that non-halogen anion zinc salt and cyclodextrin and its derivatives have a synergistic enhancing effect on the complexing of bromide ions, can efficiently reduce free Brˉ in the electrolyte, thereby effectively improving the self-discharge performance of the zinc-bromine static battery.

[0060] In summary, the present invention combines non-halogen anion zinc salt with cyclodextrin and its derivatives for the first time in the aqueous electrolyte of zinc-bromine static battery, which solves the problem that the free Brˉ concentration in the aqueous electrolyte of zinc-bromine static battery is high, resulting in excessive self-discharge of the battery. Among them, the zinc ions in the high-concentration non-halogen anion zinc salt can combine with free Brˉ to form zinc-bromine complex ions, and the high-concentration cyclodextrin and its derivatives can combine with free Brˉ to form inclusion complexes. The two cooperate with each other, synergistically enhance the effect, and efficiently reduce the free Brˉ in the electrolyte, thereby effectively improving the self-discharge performance of zinc-bromine static battery.

[0061] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A zinc-bromine static battery aqueous electrolyte, characterized in that: include: Zinc bromide, zinc salts of non-halogen anions, cyclodextrins and their derivatives, and water.

2. The aqueous electrolyte for a zinc-bromine static battery according to claim 1, characterized in that: The non-halogen anion zinc salt is at least one of zinc trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonyl)imide, zinc acetate, zinc sulfate, zinc nitrate, zinc nitrite, zinc chlorate, zinc bromate, zinc perchlorate, zinc permanganate, zinc formate, zinc gluconate, zinc fluorosilicate, zinc fluoroborate, and zinc pivalate.

3. The aqueous electrolyte for zinc-bromine static battery according to claim 1, characterized in that: The cyclodextrin and its derivatives are at least one of α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, hydroxypropyl-α-cyclodextrin, hydroxypropyl-β-cyclodextrin, hydroxypropyl-γ-cyclodextrin, hydroxyethyl-β-cyclodextrin, methyl-β-cyclodextrin, hydroxybutyl-β-cyclodextrin, carboxymethyl-β-cyclodextrin, β-cyclodextrin sodium sulfate, β-cyclodextrin sodium sulfonate, and β-cyclodextrin sodium phosphate.

4. The aqueous electrolyte for zinc-bromine static battery according to claim 1, characterized in that: The concentration of the zinc bromide is 0.5-5 mol / L.

5. The aqueous electrolyte for zinc-bromine static battery according to claim 1, characterized in that: The concentration of the non-halogen anion zinc salt is 0.5-15 mol / L.

6. The aqueous electrolyte for zinc-bromine static battery according to claim 1, characterized in that: The concentration of the cyclodextrin and its derivatives is 0.05-2 mol / L.

7. A zinc-bromine static battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and an aqueous electrolyte of a zinc-bromine static battery as claimed in any one of claims 1 to 6.

8. The use of a zinc-bromine static battery as claimed in claim 7, characterized in that: The application is in the field of large-scale energy storage.

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