An additive, a zinc-bromine flow battery electrolyte, a preparation method thereof, and an application thereof

Abstract

The present invention belongs to the technical field of zinc-bromine flow batteries, and particularly relates to an additive, an electrolyte for zinc-bromine flow batteries, a preparation method thereof and an application. The additive is 1-(4-cyanophenethyl)-2-(trifluoromethyl)pyridinium bromide, and the electrolyte for zinc-bromine flow batteries comprises the additive, zinc bromide and potassium chloride. The additive of the present invention can greatly improve the cycle life and stability of the battery. The electrolyte for zinc-bromine flow batteries provided by the present invention has good wettability to the electrodes. It can not only reduce the diffusion of bromine and improve the Coulomb efficiency of the battery, but also form a stable electrolyte interface layer on the zinc negative electrode, induce the uniform deposition or dissolution of zinc ions in the zinc-bromine flow battery, effectively inhibit the growth of zinc dendrites on the zinc negative electrode in the zinc-bromine flow battery, and greatly improve the cycle life and stability of the zinc-bromine flow battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of zinc-bromine flow batteries, and particularly relates to an additive, an electrolyte for zinc-bromine flow batteries, a preparation method thereof, and applications thereof. Background Art

[0002] As a flow battery technology, zinc-bromine flow batteries have received attention in the field of large-scale energy storage technologies due to their great flexibility and strong scalability in system design. At the same time, rechargeable batteries with zinc-containing systems have long been considered competitive in large-scale energy storage system applications due to the high energy density and low cost of zinc; and zinc-bromine flow batteries have high application potential in fields such as power grid peak shaving, renewable energy power generation such as wind energy and solar energy, and electric vehicles.

[0003] For zinc-bromine flow batteries, the poor stability of the zinc negative electrode has been an important factor restricting the development of such batteries. During the charging process of the battery, it is difficult to control the dendritic growth of the zinc negative electrode, resulting in problems such as shedding and accumulation of zinc metal on the negative electrode during the discharging process, making the battery stability worse. During the discharging process of the battery, due to factors such as battery polarization and uneven zinc deposition, after each charge and discharge of the battery, the active substances generated during charging cannot be completely consumed, resulting in the accumulation of active substances and affecting the battery cycle performance.

[0004] As an important component of zinc-bromine flow batteries, the electrolyte plays a very important role in improving the interfacial stability of the zinc negative electrode and inhibiting the dendritic growth of the zinc negative electrode. Regulating the electrolyte composition is one of the simplest and most effective strategies for inhibiting the dendritic growth of the zinc negative electrode and improving the cycle performance of zinc-bromine flow batteries. Therefore, developing an electrolyte that can achieve high-reversible and stable cycling of zinc-bromine flow batteries has significant practical significance. Summary of the Invention

[0005] Aiming at the above problems, one of the purposes of the present invention is to provide an additive that can improve the cycle life and stability of zinc-bromine flow batteries.

[0006] Another purpose of the present invention is to provide an electrolyte for zinc-bromine flow batteries, which has good wettability to the electrode, can not only reduce the diffusion of bromine, improve the Coulomb efficiency of the battery, but also form a stable electrolyte interface layer on the zinc negative electrode, induce the uniform deposition or dissolution of zinc ions in the zinc-bromine flow battery, and effectively inhibit the dendritic growth of the zinc negative electrode in the zinc-bromine flow battery.

[0007] Another purpose of the present invention is to provide a preparation method for an electrolyte for zinc-bromine flow batteries, which is simple and easy to control.

[0008] Another purpose of the present invention is to provide a zinc-bromine flow battery that has good cycle life and stability.

[0009] To achieve one of the above purposes, the present invention is realized through the following technical solutions:

[0010] An electrolyte additive for a zinc-bromine flow battery, wherein the additive is 1-(4-cyanophenethyl)-2-(trifluoromethyl)pyridinium bromide, and the structural formula is as follows:

[0011]

[0012] To achieve the second of the above purposes, the present invention also provides a zinc-bromine flow battery electrolyte, which includes the above additive, zinc bromide, and potassium chloride.

[0013] Preferably, the molar ratio of the additive to zinc bromide is 0.2 - 0.3:1.

[0014] Preferably, the molar ratio of zinc bromide to potassium chloride is 0.8 - 1:1.

[0015] Preferably, the concentration of potassium chloride in the zinc-bromine flow battery electrolyte is 2 - 5 mol / L.

[0016] Preferably, the concentration of zinc bromide in the zinc-bromine flow battery electrolyte is 2 - 4 mol / L.

[0017] To achieve the third of the above purposes, the present invention also provides a preparation method for a zinc-bromine flow battery electrolyte, which includes the following steps:

[0018] 1) Add the additive to the mixed aqueous solution of zinc bromide and potassium chloride and mix evenly;

[0019] 2) Filter the solution to obtain the zinc-bromine flow battery electrolyte.

[0020] As a possible implementation manner, further, in step 2), a 0.22 - 0.45 μm filter membrane is used to filter the solution.

[0021] To achieve the fourth of the above purposes, the present invention also provides a zinc-bromine flow battery, which includes a positive electrode, a negative electrode, an ion exchange membrane, and the above zinc-bromine flow battery electrolyte.

[0022] Preferably, the positive electrode selects a graphite electrode, the negative electrode selects a zinc electrode, and the ion exchange membrane selects a PE diaphragm with a pore size of 0.05 - 0.2 μm.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The additive of the present invention can greatly improve the cycle life and stability of the battery.

[0025] The zinc-bromine flow battery electrolyte provided by the present invention has good wettability to the electrodes. It can not only reduce the diffusion of bromine and improve the Coulomb efficiency of the battery, but also form a stable electrolyte interface layer on the zinc negative electrode, induce the uniform deposition or dissolution of zinc ions in the zinc-bromine flow battery, effectively inhibit the dendrite growth of the zinc negative electrode in the zinc-bromine flow battery, and greatly improve the cycle life and stability of the zinc-bromine flow battery.

[0026] The zinc-bromine flow battery of the present invention has good cycle life and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a charge-discharge cycle performance test chart of the zinc-bromine flow battery assembled for Examples 1-4 and Comparative Examples 2-5 at 20 mA / g. DETAILED DESCRIPTION OF THE INVENTION

[0028] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] The present invention discloses an additive for a zinc-bromine flow battery. The additive is 1-(4-cyanophenethyl)-2-(trifluoromethyl)pyridinium bromide, and its structural formula is as follows:

[0030]

[0031] The present invention also provides a zinc-bromine flow battery electrolyte, and its preparation method is as follows:

[0032] Add the additive to the mixed aqueous solution of zinc bromide and potassium chloride and mix evenly; filter the solution with a 0.22 μm filter membrane to obtain the zinc-bromine flow battery electrolyte. Among them, the molar ratio of the additive to zinc bromide is 0.2-0.3:1; the molar ratio of zinc bromide to potassium chloride is 0.8-1:1.

[0033] In the zinc-bromine flow battery electrolyte, the concentration of potassium chloride is 2-5 mol / L, and the concentration of zinc bromide is 2-4 mol / L.

[0034] The present invention further provides a zinc-bromine flow battery, including a positive electrode, a negative electrode, an ion exchange membrane, and the above-mentioned zinc-bromine flow battery electrolyte. Among them, the positive electrode is a graphite electrode, the negative electrode is a zinc electrode, and the ion exchange membrane is a PE diaphragm with a pore size of 0.1 μm.

[0035] Example 1

[0036] 1) Add 1-(4-cyanophenethyl)-2-(trifluoromethyl)pyridinium bromide to the mixed aqueous solution of zinc bromide and potassium chloride and mix evenly. The concentration of zinc bromide in the mixed aqueous solution is 2 mol / L, the concentration of potassium chloride is 2 mol / L, and the molar ratio of 1-(4-cyanophenethyl)-2-(trifluoromethyl)pyridinium bromide to zinc bromide is 0.25:1;

[0037] 2) Filter the solution through a 0.22 μm filter membrane to obtain the electrolyte of the zinc-bromine flow battery.

[0038] 3) Assemble a zinc-bromine flow battery with this electrolyte. In the zinc-bromine flow battery, the positive electrode uses a graphite electrode, the negative electrode uses a zinc electrode, and the ion exchange membrane uses a PE diaphragm with a pore size of 0.1 μm.

[0039] Example 2

[0040] 1) Add 1-(4-cyanophenethyl)-2-(trifluoromethyl)pyridinium bromide to the mixed aqueous solution of zinc bromide and potassium chloride and mix evenly. The concentration of zinc bromide in the mixed aqueous solution is 3 mol / L, the concentration of potassium chloride is 3 mol / L, and the molar ratio of 1-(4-cyanophenethyl)-2-(trifluoromethyl)pyridinium bromide to zinc bromide is 0.2:1;

[0041] 2) Filter the solution through a 0.22 μm filter membrane to obtain the electrolyte of the zinc-bromine flow battery.

[0042] 3) Assemble a zinc-bromine flow battery with this electrolyte. In the zinc-bromine flow battery, the positive electrode uses a graphite electrode, the negative electrode uses a zinc electrode, and the ion exchange membrane uses a PE diaphragm with a pore size of 0.1 μm.

[0043] Example 3

[0044] 1) Add 1-(4-cyanophenethyl)-2-(trifluoromethyl)pyridinium bromide to the mixed aqueous solution of zinc bromide and potassium chloride and mix evenly. The concentration of zinc bromide in the mixed aqueous solution is 4 mol / L, the concentration of potassium chloride is 4 mol / L, and the molar ratio of 1-(4-cyanophenethyl)-2-(trifluoromethyl)pyridinium bromide to zinc bromide is 0.3:1;

[0045] 2) Filter the solution through a 0.22 μm filter membrane to obtain the electrolyte of the zinc-bromine flow battery.

[0046] 3) Assemble a zinc-bromine flow battery with this electrolyte. In the zinc-bromine flow battery, the positive electrode uses a graphite electrode, the negative electrode uses a zinc electrode, and the ion exchange membrane uses a PE diaphragm with a pore size of 0.1 μm.

[0047] Example 4

[0048] 1) Add 1-(4-cyanophenyl)ethyl-2-(trifluoromethyl)pyridinium bromide to the mixed aqueous solution of zinc bromide and potassium chloride and mix evenly. The concentration of zinc bromide in the mixed aqueous solution is 4 mol / L, the concentration of potassium chloride is 5 mol / L, and the molar ratio of 1-(4-cyanophenyl)ethyl-2-(trifluoromethyl)pyridinium bromide to zinc bromide is 0.25:1;

[0049] 2) Filter the solution through a 0.22 μm filter membrane to obtain the electrolyte of the zinc-bromine flow battery.

[0050] 3) Assemble a zinc-bromine flow battery with this electrolyte. In the zinc-bromine flow battery, a graphite electrode is selected as the positive electrode, a zinc electrode is selected as the negative electrode, and a PE diaphragm with a pore size of 0.1 μm is selected as the ion exchange membrane.

[0051] Comparative Example 1

[0052] 1) Filter the mixed aqueous solution of zinc bromide and potassium chloride through a 0.22 μm filter membrane to obtain the electrolyte of the zinc-bromine flow battery; the concentration of zinc bromide in the electrolyte of the zinc-bromine flow battery is 2 mol / L, and the concentration of potassium chloride is 2 mol / L.

[0053] 2) Assemble a zinc-bromine flow battery with this electrolyte. In the zinc-bromine flow battery, a graphite electrode is selected as the positive electrode, a zinc electrode is selected as the negative electrode, and a PE diaphragm with a pore size of 0.1 μm is selected as the ion exchange membrane.

[0054] Comparative Example 2

[0055] 1) Add 1-phenylethyl-2-methylpyridinium bromide to the mixed aqueous solution of zinc bromide and potassium chloride and mix evenly. The concentration of zinc bromide in the mixed aqueous solution is 2 mol / L, the concentration of potassium chloride is 2 mol / L, and the molar ratio of 1-phenylethyl-2-methylpyridinium bromide to zinc bromide is 0.25:1; among them, the structural formula of 1-phenylethyl-2-methylpyridinium bromide is as follows:

[0056]

[0057] 2) Filter the solution through a 0.22 μm filter membrane to obtain the electrolyte of the zinc-bromine flow battery.

[0058] 3) Assemble a zinc-bromine flow battery with this electrolyte. In the zinc-bromine flow battery, a graphite electrode is selected as the positive electrode, a zinc electrode is selected as the negative electrode, and a PE diaphragm with a pore size of 0.1 μm is selected as the ion exchange membrane.

[0059] Comparative Example 3

[0060] 1) Add 1-(4-cyanophenyl)ethyl-2-methylpyridinium bromide to an aqueous mixed solution of zinc bromide and potassium chloride and mix well. The concentration of zinc bromide in the aqueous mixed solution is 3 mol / L, the concentration of potassium chloride is 3 mol / L, and the molar ratio of 1-(4-cyanophenyl)ethyl-2-(trifluoromethyl)pyridinium bromide to zinc bromide is 0.2:1. Among them, the structural formula of 1-(4-cyanophenyl)ethyl-2-methylpyridinium bromide is as follows:

[0061]

[0062] 2) Filter the solution through a 0.22 μm filter membrane to obtain the electrolyte for the zinc-bromine flow battery.

[0063] 3) Assemble a zinc-bromine flow battery with this electrolyte. In the zinc-bromine flow battery, a graphite electrode is selected as the positive electrode, a zinc electrode is selected as the negative electrode, and a PE diaphragm with a pore size of 0.1 μm is selected as the ion exchange membrane.

[0064] Comparative Example 4

[0065] 1) Add 1-phenethyl-2-(trifluoromethyl)pyridinium bromide to an aqueous mixed solution of zinc bromide and potassium chloride and mix well. The concentration of zinc bromide in the aqueous mixed solution is 4 mol / L, the concentration of potassium chloride is 4 mol / L, and the molar ratio of 1-(4-cyanophenyl)ethyl-2-(trifluoromethyl)pyridinium bromide to zinc bromide is 0.3:1. Among them, the structural formula of 1-phenethyl-2-(trifluoromethyl)pyridinium bromide is as follows:

[0066]

[0067] 2) Filter the solution through a 0.22 μm filter membrane to obtain the electrolyte for the zinc-bromine flow battery.

[0068] 3) Assemble a zinc-bromine flow battery with this electrolyte. In the zinc-bromine flow battery, a graphite electrode is selected as the positive electrode, a zinc electrode is selected as the negative electrode, and a PE diaphragm with a pore size of 0.1 μm is selected as the ion exchange membrane.

[0069] Comparative Example 5

[0070] 1) Add N-methyl-N-ethylpyrrolidinium bromide (MEP) to an aqueous mixed solution of zinc bromide and potassium chloride and mix well. The concentration of zinc bromide in the aqueous mixed solution is 4 mol / L, the concentration of potassium chloride is 5 mol / L, and the molar ratio of MEP to zinc bromide is 0.25:1.

[0071] 2) Filter the solution through a 0.22 μm filter membrane to obtain the electrolyte for the zinc-bromine flow battery.

[0072] 3) Assemble a zinc-bromine flow battery with this electrolyte. In the zinc-bromine flow battery, a graphite electrode is selected as the positive electrode, a zinc electrode is selected as the negative electrode, and a PE diaphragm with a pore size of 0.1 μm is selected as the ion exchange membrane.

[0073] Performance Test

[0074] The zinc-bromine flow batteries assembled with Examples 1-4 and Comparative Examples 1-5 were subjected to charge-discharge cycle tests at a current density of 20 mA / g, and the test results are as follows:

[0075] The first-cycle discharge capacity of the zinc-bromine flow battery assembled with Comparative Example 1 was 238 mAh / g, and the first-cycle Coulombic efficiency was 72%; after 200 cycles, the battery discharge capacity was 136 mAh / g, and the Coulombic efficiency decreased to 53.1%.

[0076] The charge-discharge cycle performance tests of the zinc-bromine flow batteries assembled with Examples 1-4 and Comparative Examples 2-5 at 20 mA / g are as shown in the appendix Figure 1 As shown. It can be seen from the figure that the first-cycle discharge capacity of the zinc-bromine flow batteries assembled with Examples 1-4 was 264 mAh / g. After 200 cycles, the battery discharge capacity remained basically unchanged, and the Coulombic efficiency reached more than 98%, which was significantly better than the zinc-bromine flow batteries assembled with Comparative Documents 1-5.

[0077] In addition, by comparing the test data of Comparative Examples 2-4 and Examples 1-3, it can be seen that the addition of p-cyano in phenethyl and trifluoromethyl in pyridine can effectively improve the Coulombic efficiency of the zinc-bromine flow battery. This is because the addition of p-cyano in phenethyl and trifluoromethyl in pyridine can improve the binding effect between bromide and bromide ions, thereby reducing the diffusion of bromine, and thus effectively improving the Coulombic efficiency of the zinc-bromine flow battery.

[0078] From the above test results, it can be seen that by using the electrolyte provided by the present invention, the Coulombic efficiency of the battery can be effectively improved, and the cycle life and stability of the zinc-bromine flow battery can be greatly improved.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An additive, characterized in that: The additive is used in the electrolyte of zinc-bromine liquid flow battery, and the additive is 1-p-cyanophenethyl-2-trifluoromethylpyridinium bromide, and the structural formula is as follows: 。 2. A zinc-bromine flow battery electrolyte, characterized in that: The invention comprises the additive 1-p-cyanophenethyl-2-trifluoromethylpyridinium bromide, zinc bromide and potassium chloride as claimed in claim 1.

3. The zinc-bromine flow battery electrolyte according to claim 2, characterized in that: The molar ratio of the additive to zinc bromide is 0.2-0.3:

1.

4. The zinc-bromine flow battery electrolyte according to claim 2, characterized in that: The molar ratio of zinc bromide to potassium chloride is 0.8-1:

1.

5. The zinc-bromine flow battery electrolyte according to claim 2, characterized in that: The concentration of potassium chloride in the zinc-bromine flow battery electrolyte is 2-5 mol / L.

6. The zinc-bromine flow battery electrolyte according to claim 2, characterized in that: The concentration of zinc bromide in the zinc-bromine flow battery electrolyte is 2-4 mol / L.

7. A method for preparing a zinc-bromine flow battery electrolyte as claimed in any one of claims 2 to 6, characterized in that: The steps include: 1) Add the additive to the mixed aqueous solution of zinc bromide and potassium chloride and mix well; 2) The solution is filtered to obtain the zinc-bromine flow battery electrolyte.

8. The method for preparing a zinc-bromine flow battery electrolyte according to claim 7, characterized in that: In step 2), the solution is filtered using a 0.22-0.45 μm filter membrane.

9. A zinc-bromine flow battery, characterized in that: The invention comprises a positive electrode, a negative electrode, an ion exchange membrane and a zinc-bromine flow battery electrolyte as claimed in any one of claims 2 to 6.

10. The zinc-bromine flow battery according to claim 9, characterized in that: The positive electrode is a graphite electrode, the negative electrode is a zinc electrode, and the ion exchange membrane is a PE diaphragm with a pore size of 0.05-0.2um.

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