Preparation method of ionic membrane for all-vanadium redox flow battery

Abstract

The invention belongs to the field of flow batteries, and particularly relates to a preparation method of an ionic membrane for an all-vanadium flow battery, the structure of a polybenzimidazole membrane is relaxed at room temperature by adopting a simple acid protonation pre-swelling and ion exchange strategy, a proton transmission channel is widened, and the ionic conductivity of the polybenzimidazole membrane is improved. The all-vanadium redox flow battery assembled by adopting the polybenzimidazole membrane prepared by the invention shows excellent battery performance. The method is simple to operate, mild in reaction environment and suitable for large-scale production, and has a very good application prospect.

Description

Technical Field

[0001] The invention belongs to the field of liquid flow batteries, and in particular relates to a method for preparing an ion membrane for an all-vanadium liquid flow battery. Background Art

[0002] Renewable energy replacing traditional fossil energy is very important for achieving the beautiful vision of carbon neutrality. However, the intermittent and uncertain nature of renewable energy such as wind and solar energy leads to fluctuations in the power grid, so efficient energy storage technology is urgently needed to improve energy utilization. Liquid flow battery energy storage technology is considered to be a very promising large-scale energy storage technology because of its green, safe, long cycle life, flexible structural design and high energy conversion efficiency.

[0003] Polybenzimidazole has excellent mechanical stability and chemical stability due to hydrogen bonds and π-π conjugation in the molecular chain, and is a very promising ion membrane material for flow batteries. However, since protons need enough space to transfer, the densely packed molecular chains of polybenzimidazole membranes lead to poor proton conductivity. Therefore, an effective treatment method is needed to relax the structure of the membrane, broaden the proton transport channel of the membrane, and improve the ionic conductivity of polybenzimidazole. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for preparing an ion membrane for an all-vanadium liquid flow battery.

[0005] The technical solution of the present invention is: A method for preparing an ion membrane for an all-vanadium liquid flow battery comprises the following steps: Step 1, dissolving polybenzimidazole solid powder in a highly polar aprotic solvent to form a resin solution with a solid content of 12-18 wt%; Step 2: Smear the resin solution obtained in step 1 on a glass plate, and then heat-treat it in an oven at 80-120° C. for 4-6 hours to remove the solvent and obtain a film; Step 3, treating the membrane obtained in step 2 in an acid solution for 6 to 10 hours, wherein the acid solution is one or more of phosphoric acid, acetic acid or hydrochloric acid, and the concentration is 0.5 to 1 mol / L; Step 4: Treat the membrane obtained in step 3 in a metal salt solution for 12 hours to obtain an ion membrane for all-vanadium redox flow battery. The metal salt solution is Cu 2+ 、Ni 2+ 、Zn 2 +、Cr 3+ or Fe 3+ An aqueous solution with a concentration of 0.1~0.5mol / L.

[0006] Furthermore, in the above-mentioned method for preparing an ion membrane for an all-vanadium redox flow battery, the highly polar aprotic solvent in step 1 is one or more of acetone, dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide.

[0007] Advantages and beneficial effects of the present invention: The present invention relaxes the structure of the polybenzimidazole membrane through a simple acid treatment and ion exchange method, broadens the proton transmission channel, and improves the ion conductivity of the polybenzimidazole membrane. The all-vanadium liquid flow battery assembled with the polybenzimidazole membrane prepared by the method exhibits excellent battery performance. The method is simple to operate, has a mild reaction environment, is suitable for large-scale production, and exhibits very good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Schematic diagram of the mechanism of relaxing the polybenzimidazole membrane structure. DETAILED DESCRIPTION

[0009] The specific implementation modes of the present invention are further described in detail below in conjunction with examples and comparative examples. The following examples are used to illustrate the present invention but cannot be used to limit the scope of the present invention.

[0010] In the following examples and comparative examples, the battery models all adopt all-vanadium liquid flow batteries, and the positive and negative electrodes are both 4×7 cm in size. 2 Carbon felt is used as electrode material, bipolar plate is used as current collector, membrane is polybenzimidazole membrane, thickness is 50 microns, peristaltic pump flow rate is 150mlmin -1 , the positive and negative electrolytes are 1.65 molL -1 V 3.5+ +3molL -1 H2SO4, the volume of positive and negative electrolytes is 80ml; the charge and discharge cut-off voltage is 1.55~1.0V.

[0011] Example 1

[0012] The present embodiment provides a method for preparing an ion membrane for an all-vanadium liquid flow battery, which specifically comprises the following steps: First, the polybenzimidazole solid powder was dissolved in dimethyl sulfoxide to form a resin solution with a solid content of 15wt%; then the resin solution was scraped onto a glass plate, and then heat-treated in an oven at 100°C for 5 hours to remove the solvent to obtain a film; then the film was treated in a phosphoric acid solution for 10 hours; finally, the obtained film was treated in a 0.4mol / LCuCl2 solution for 12 hours; the proton conductivity of the polybenzimidazole film prepared in this embodiment was 60mAcm -1 It is assembled in an all-vanadium flow battery and can -2 、150mAcm -2、200mAcm -2 At the current density, the battery voltage efficiency is 93.5%, 86.4% and 81.7% respectively.

[0013] Example 2

[0014] The present embodiment provides a method for preparing an ion membrane for an all-vanadium liquid flow battery, which specifically comprises the following steps: First, the polybenzimidazole solid powder was dissolved in N,N-dimethylformamide to form a resin solution with a solid content of 12 wt%; then the resin solution was scraped onto a glass plate, and then heat-treated in an oven at 120°C for 6 hours to remove the solvent to obtain a film; then the film was treated in a hydrochloric acid solution for 6 hours; finally, the obtained film was treated in a 0.1 mol / L ZnCl2 solution for 12 hours; the proton conductivity of the polybenzimidazole film prepared in this embodiment was 58 mA cm -1 , assembled into an all-vanadium flow battery, at 80 mA cm -2 、150mAcm -2 、200mAcm -2 At the current density, the battery voltage efficiency is 93%, 85.7% and 80.9% respectively.

[0015] Example 3

[0016] The present embodiment provides a method for preparing an ion membrane for an all-vanadium liquid flow battery, which specifically comprises the following steps: First, the polybenzimidazole solid powder was dissolved in N,N-dimethylacetamide to form a resin solution with a solid content of 18wt%; then the resin solution was scraped onto a glass plate, and then heat-treated in an oven at 80°C for 4 hours to remove the solvent to obtain a film; then the film was treated in a hydrochloric acid solution for 10 hours; finally, the obtained film was treated in a 0.1mol / LFeCl3 solution for 12 hours; the proton conductivity of the polybenzimidazole film prepared in this embodiment was 62mAcm -1 , assembled into an all-vanadium flow battery, at 80 mA cm -2 、150mAcm -2 、200mAcm -2 At the current density, the battery voltage efficiency is 93.9%, 87% and 82.5% respectively.

[0017] Comparative Example 1 This comparative example provides a method for preparing an ion membrane for an all-vanadium liquid flow battery, which specifically comprises the following steps: First, the polybenzimidazole solid powder was dissolved in N,N-dimethylacetamide to form a resin solution with a solid content of 18wt%; then the resin solution was scraped onto a glass plate, and then heat-treated in an oven at 120°C for 4 hours to remove the solvent to obtain a film; the proton conductivity of the polybenzimidazole film prepared in this comparative example was 18mAcm -1 , assembled into an all-vanadium flow battery, at 80 mA cm -2 、150mAcm -2 、200mAcm -2 At the current density, the battery voltage efficiency is 89%, 82% and 75% respectively.

[0018] The above examples and comparative examples show that the polybenzimidazole membrane of the present invention is pre-swollen by acid protonation, and then the protons are exchanged by metal ions with larger ionic radius, which successfully relaxes the structure of the membrane and broadens the proton transmission channel. Figure 1 As shown, it is a schematic diagram of the mechanism of relaxing the polybenzimidazole membrane structure. Thanks to the characteristics of the polybenzimidazole membrane with a relaxed structure, the proton conductivity of the membrane is effectively improved, thereby improving the battery performance.

[0019] All the above embodiments only express the implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. Any form of equivalent replacement or equivalent transformation is within the protection scope of the present invention.

Claims

1. A method for preparing an ion membrane for an all-vanadium redox flow battery, characterized in that: The following steps are involved: Step 1, dissolving polybenzimidazole solid powder in a highly polar aprotic solvent to form a resin solution with a solid content of 12-18 wt %; Step 2: Scrape the resin solution obtained in step 1 onto a glass plate, and then heat-treat it in an oven at 80-120° C. for 4-6 hours to remove the solvent and obtain a film; Step 3, treating the membrane obtained in step 2 in an acid solution for 6 to 10 hours; the acid solution is one or more of phosphoric acid, acetic acid or hydrochloric acid, with a concentration of 0.5 to 1 mol / L; Step 4: Treat the membrane obtained in step 3 in a metal salt solution for 12 hours to obtain an ion membrane for all-vanadium redox flow battery. The metal salt solution is Cu 2+ 、Ni 2+ 、Zn 2 +、Cr 3+ or Fe 3+ An aqueous solution with a concentration of 0.1~0.5mol / L.

2. The method for preparing an ion membrane for an all-vanadium redox flow battery according to claim 1, characterized in that: The highly polar aprotic solvent in step 1 is one or more of acetone, dimethyl sulfoxide, N,N-dimethylformamide or N,N-dimethylacetamide.

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