Additive, zinc-bromine flow battery electrolyte, and preparation method and application of zinc-bromine flow battery electrolyte

Abstract

The invention belongs to the technical field of zinc-bromine flow batteries, and particularly relates to an additive, a zinc-bromine flow battery electrolyte and a preparation method and application of the zinc-bromine flow battery electrolyte, the additive is 1-p-cyanophenyl-2-trifluoromethylpyridine bromide, and the zinc-bromine flow battery electrolyte comprises the additive, zinc bromide and potassium chloride. The additive disclosed by the invention can greatly prolong the cycle life and improve the stability of the battery. The zinc-bromine flow battery electrolyte provided by the invention has good wettability to an electrode, not only can reduce diffusion of bromine and improve coulombic efficiency of the battery, but also can form a stable electrolyte interface layer on a zinc negative electrode to induce uniform deposition or dissolution of zinc ions in the zinc-bromine flow battery, so that the zinc-bromine flow battery is more stable in performance. The growth of zinc negative electrode dendrites in the zinc-bromine flow battery is effectively inhibited, and the cycle life and the stability of the zinc-bromine flow battery are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of zinc-bromine liquid flow batteries, and in particular relates to an additive, a zinc-bromine liquid flow battery electrolyte, and a preparation method and application thereof. Background Art

[0002] As a type of liquid flow battery technology, zinc-bromine flow battery has attracted attention in the field of large-scale energy storage technology due to its great flexibility and strong scalability in system design. At the same time, rechargeable batteries containing zinc 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 the fields of power grid peak regulation, renewable energy generation such as wind and solar energy, and electric vehicles.

[0003] For zinc-bromine flow batteries, the poor stability of the zinc negative electrode has always been an important factor restricting the development of this type of battery. During the battery charging process, the dendrite growth of the zinc negative electrode is difficult to control, resulting in the shedding and accumulation of the negative electrode zinc element during the discharge process, which makes the battery stability worse. During the battery discharge process, due to factors such as battery polarization and uneven zinc deposition, the active substances generated by the battery after each charge and discharge cannot be completely consumed, resulting in the accumulation of active substances, 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 dendrite growth of the zinc negative electrode. Regulating the electrolyte composition is one of the simplest and most effective strategies to inhibit the dendrite growth of the zinc negative electrode and improve the cycle performance of zinc-bromine flow batteries. Therefore, it is of great practical significance to develop an electrolyte that can achieve highly reversible and stable cycling of zinc-bromine flow batteries. Summary of the invention

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

[0006] The second object of the present invention is to provide a zinc-bromine flow battery electrolyte, which has good wettability to electrodes, can not only reduce the diffusion of bromine and improve the coulombic efficiency of the battery, but also can form a stable electrolyte interface layer on the zinc negative electrode, induce uniform deposition or dissolution of zinc ions in the zinc-bromine flow battery, and effectively inhibit the growth of zinc negative electrode dendrites in the zinc-bromine flow battery.

[0007] The third object of the present invention is to provide a method for preparing a zinc-bromine flow battery electrolyte, which is simple and easy to control.

[0008] A fourth object of the present invention is to provide a zinc-bromine flow battery having good cycle life and stability.

[0009] To achieve one of the above purposes, the present invention is implemented through the following technical solutions: An electrolyte additive for zinc-bromine flow battery, the additive is 1-p-cyanophenethyl-2-trifluoromethylpyridinium bromide, and the structural formula is as follows:

[0010] To achieve the second of the above objectives, the present invention also provides a zinc-bromine flow battery electrolyte, comprising the above additives, zinc bromide, and potassium chloride.

[0011] Preferably, the molar ratio of the additive to zinc bromide is 0.2-0.3:1.

[0012] Preferably, the molar ratio of zinc bromide to potassium chloride is 0.8-1:1.

[0013] Preferably, the concentration of potassium chloride in the zinc-bromine flow battery electrolyte is 2-5 mol / L.

[0014] Preferably, the concentration of zinc bromide in the zinc-bromine flow battery electrolyte is 2-4 mol / L.

[0015] To achieve the third of the above objectives, the present invention also provides a method for preparing a zinc-bromine flow battery electrolyte, comprising the following steps: 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.

[0016] As a possible implementation, further, in step 2), the solution is filtered using a 0.22-0.45 μm filter membrane.

[0017] To achieve the fourth objective above, the present invention further provides a zinc-bromine flow battery, comprising a positive electrode, a negative electrode, an ion exchange membrane and the above-mentioned zinc-bromine flow battery electrolyte.

[0018] Preferably, the positive electrode is a graphite electrode, the negative electrode is a zinc electrode, and the ion exchange membrane is a PE membrane with a pore size of 0.05-0.2 um.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: The additive of the present invention can greatly improve the cycle life and stability of the battery.

[0020] The zinc-bromine liquid flow battery electrolyte provided by the present invention has good wettability to electrodes, which can not only reduce the diffusion of bromine and improve the coulombic efficiency of the battery, but also form a stable electrolyte interface layer on the zinc negative electrode, induce uniform deposition or dissolution of zinc ions in the zinc-bromine liquid flow battery, effectively inhibit the growth of zinc negative electrode dendrites in the zinc-bromine liquid flow battery, and greatly improve the cycle life and stability of the zinc-bromine liquid flow battery.

[0021] The zinc-bromine liquid flow battery of the present invention has good cycle life and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a test chart of the 20mA / g charge-discharge cycle performance of the zinc-bromine flow battery assembled in Examples 1-4 and Comparative Examples 2-5. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] The present invention discloses an additive for zinc-bromine liquid flow battery, wherein the additive is 1-p-cyanophenethyl-2-trifluoromethylpyridinium bromide, and the structural formula thereof is as follows:

[0025] The present invention also provides a zinc-bromine flow battery electrolyte, and the preparation method thereof is as follows: Add the additive to the mixed aqueous solution of zinc bromide and potassium chloride and mix them evenly; filter the solution with a 0.22 μm filter membrane to obtain a zinc-bromine flow battery electrolyte, wherein the molar ratio of the additive to zinc bromide is 0.2-0.3:1; and the molar ratio of zinc bromide to potassium chloride is 0.8-1:1.

[0026] 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.

[0027] The present invention further provides a zinc-bromine flow battery, comprising a positive electrode, a negative electrode, an ion exchange membrane and the above zinc-bromine flow battery electrolyte, wherein 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 um.

[0028] Example 1 1) Add 1-p-cyanophenethyl-2-trifluoromethylpyridinium bromide to a mixed aqueous solution of zinc bromide and potassium chloride and mix them 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-p-cyanophenethyl-2-trifluoromethylpyridinium bromide to zinc bromide is 0.25:1; 2) The solution was filtered through a 0.22 μm filter membrane to obtain a zinc-bromine flow battery electrolyte.

[0029] 3) Use the electrolyte to assemble a zinc-bromine flow battery. In the zinc-bromine flow battery, a graphite electrode is used as the positive electrode, a zinc electrode is used as the negative electrode, and a PE diaphragm with a pore size of 0.1um is used as the ion exchange membrane.

[0030] Example 2 1) Add 1-p-cyanophenethyl-2-trifluoromethylpyridinium bromide to a mixed aqueous solution of zinc bromide and potassium chloride and mix them 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-p-cyanophenethyl-2-trifluoromethylpyridinium bromide to zinc bromide is 0.2:1; 2) The solution was filtered through a 0.22 μm filter membrane to obtain a zinc-bromine flow battery electrolyte.

[0031] 3) Use the electrolyte to assemble a zinc-bromine flow battery. In the zinc-bromine flow battery, a graphite electrode is used as the positive electrode, a zinc electrode is used as the negative electrode, and a PE diaphragm with a pore size of 0.1um is used as the ion exchange membrane.

[0032] Example 3 1) Add 1-p-cyanophenethyl-2-trifluoromethylpyridinium bromide to a mixed aqueous solution of zinc bromide and potassium chloride and mix them 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-p-cyanophenethyl-2-trifluoromethylpyridinium bromide to zinc bromide is 0.3:1; 2) The solution was filtered through a 0.22 μm filter membrane to obtain a zinc-bromine flow battery electrolyte.

[0033] 3) Use the electrolyte to assemble a zinc-bromine flow battery. In the zinc-bromine flow battery, a graphite electrode is used as the positive electrode, a zinc electrode is used as the negative electrode, and a PE diaphragm with a pore size of 0.1um is used as the ion exchange membrane.

[0034] Example 4 1) Add 1-p-cyanophenethyl-2-trifluoromethylpyridinium bromide to a mixed aqueous solution of zinc bromide and potassium chloride and mix them 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-p-cyanophenethyl-2-trifluoromethylpyridinium bromide to zinc bromide is 0.25:1; 2) The solution was filtered through a 0.22 μm filter membrane to obtain a zinc-bromine flow battery electrolyte.

[0035] 3) Use the electrolyte to assemble a zinc-bromine flow battery. In the zinc-bromine flow battery, a graphite electrode is used as the positive electrode, a zinc electrode is used as the negative electrode, and a PE diaphragm with a pore size of 0.1um is used as the ion exchange membrane.

[0036] Comparative Example 1 1) A mixed aqueous solution of zinc bromide and potassium chloride is filtered through a 0.22 μm filter membrane to obtain a zinc-bromine flow battery electrolyte; the zinc bromide concentration in the zinc-bromine flow battery electrolyte is 2 mol / L, and the potassium chloride concentration is 2 mol / L.

[0037] 2) Use the electrolyte to assemble a zinc-bromine flow battery. In the zinc-bromine flow battery, a graphite electrode is used as the positive electrode, a zinc electrode is used as the negative electrode, and a PE diaphragm with a pore size of 0.1um is used as the ion exchange membrane.

[0038] Comparative Example 2 1) Add 1-phenethyl-2-methylpyridinium bromide to a mixed aqueous solution of zinc bromide and potassium chloride and mix them 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-phenethyl-2-methylpyridinium bromide to zinc bromide is 0.25:1; wherein the structural formula of 1-phenethyl-2-methylpyridinium bromide is as follows:

[0039] 2) The solution was filtered through a 0.22 μm filter membrane to obtain a zinc-bromine flow battery electrolyte.

[0040] 3) Use the electrolyte to assemble a zinc-bromine flow battery. In the zinc-bromine flow battery, a graphite electrode is used as the positive electrode, a zinc electrode is used as the negative electrode, and a PE diaphragm with a pore size of 0.1um is used as the ion exchange membrane.

[0041] Comparative Example 3 1) Add 1-p-cyanophenethyl 2-methylpyridinium bromide to a mixed aqueous solution of zinc bromide and potassium chloride and mix them 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-p-cyanophenethyl-2-trifluoromethylpyridinium bromide to zinc bromide is 0.2:1; wherein the structural formula of 1-p-cyanophenethyl 2-methylpyridinium bromide is as follows:

[0042] 2) The solution was filtered through a 0.22 μm filter membrane to obtain a zinc-bromine flow battery electrolyte.

[0043] 3) Use the electrolyte to assemble a zinc-bromine flow battery. In the zinc-bromine flow battery, a graphite electrode is used as the positive electrode, a zinc electrode is used as the negative electrode, and a PE diaphragm with a pore size of 0.1um is used as the ion exchange membrane.

[0044] Comparative Example 4 1) Add 1-phenethyl-2-trifluoromethylpyridinium bromide to a mixed aqueous solution of zinc bromide and potassium chloride and mix them 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-p-cyanophenethyl-2-trifluoromethylpyridinium bromide to zinc bromide is 0.3:1; wherein the structural formula of 1-phenethyl-2-trifluoromethylpyridinium bromide is as follows:

[0045] 2) The solution was filtered through a 0.22 μm filter membrane to obtain a zinc-bromine flow battery electrolyte.

[0046] 3) Use the electrolyte to assemble a zinc-bromine flow battery. In the zinc-bromine flow battery, a graphite electrode is used as the positive electrode, a zinc electrode is used as the negative electrode, and a PE diaphragm with a pore size of 0.1um is used as the ion exchange membrane.

[0047] Comparative Example 5 1) Add N-methyl-N-ethylpyrrolidine bromide (MEP) to a mixed aqueous solution of zinc bromide and potassium chloride and mix them 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 MEP to zinc bromide is 0.25:1; 2) The solution was filtered through a 0.22 μm filter membrane to obtain a zinc-bromine flow battery electrolyte.

[0048] 3) Use the electrolyte to assemble a zinc-bromine flow battery. In the zinc-bromine flow battery, a graphite electrode is used as the positive electrode, a zinc electrode is used as the negative electrode, and a PE diaphragm with a pore size of 0.1um is used as the ion exchange membrane.

[0049] Performance Testing The zinc-bromine flow batteries assembled in Examples 1-4 and Comparative Examples 1-5 were subjected to charge and discharge cycle tests at a current density of 20 mA / g. The test results are as follows: The zinc-bromine flow battery assembled in Comparative Example 1 had a first-cycle discharge capacity of 238 mAh / g and a first-cycle coulombic efficiency of 72%. After 200 cycles, the battery discharge capacity was 136 mAh / g and the coulombic efficiency dropped to 53.1%.

[0050] The 20 mA / g charge-discharge cycle performance test of the zinc-bromine flow battery assembled in Examples 1-4 and Comparative Examples 2-5 is shown in the attached Figure 1As shown in the figure, the first cycle discharge capacity of the zinc-bromine flow battery assembled in Example 1-4 is 264 mAh / g. After 200 cycles, the battery discharge capacity remains basically unchanged, and the coulombic efficiency is more than 98%, which is significantly better than the zinc-bromine flow battery assembled in Comparative Documents 1-5.

[0051] In addition, by comparing the test data of Comparative Examples 2-4 and Examples 1-3, it can be seen that the addition of the para-cyano group in phenethyl and the trifluoromethyl group in pyridine can effectively improve the coulombic efficiency of the zinc-bromine flow battery. This is because the addition of the para-cyano group in phenethyl and the trifluoromethyl group in pyridine can enhance the binding effect of bromide and bromide ions, thereby reducing the diffusion of bromine, thereby effectively improving the coulombic efficiency of the zinc-bromine flow battery.

[0052] It can be seen from the above test results that the use of the electrolyte provided by the present invention can effectively improve the coulombic efficiency of the battery and greatly enhance the cycle life and stability of the zinc-bromine flow battery.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions 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: Contains the additive as claimed in claim 1, zinc bromide and potassium chloride.

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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