Composite film resistant to oxidation corrosion of vanadium battery electrolyte and preparation method of composite film

Abstract

The invention discloses a preparation method of a vanadium battery electrolyte oxidation corrosion resistant composite membrane, which comprises the following steps: S1, uniformly dispersing graphene oxide nanosheets on the surface of an SPEEK (sulfonated polyether ether ketone) matrix by using sulfonated polyether ether ketone as a substrate to obtain an SPEEK / GO (graphene oxide) substrate; s2, treating the SPEEK / GO substrate in oxygen plasma treatment equipment, and ultrasonically cleaning the SPEEK / GO substrate with isopropanol for 10-20 minutes; s3, dissolving polybenzimidazole in N, N-dimethylacetamide (the concentration is 3-5wt%), and magnetically stirring until the polybenzimidazole is completely dissolved; the preparation method comprises the following steps: adding TiO2 nanoparticles (the particle size is 20-25nm, and the TiO2 nanoparticles are pretreated by a silane coupling agent KH-570) according to the mass ratio of 15-20%, ultrasonically dispersing and carrying out ice bath to obtain PBI-TiO2 dispersion liquid; s4, the SPEEK / GO substrate treated in the step S1 is vertically immersed in PBI-TiO2 dispersion liquid, the final coating thickness is 1.5 + / -0.2 [mu] m, and a pretreated film is obtained; and S5, carrying out hot pressing on the pretreated membrane by using a hot press, and then carrying out gradient cooling to room temperature to obtain the final composite membrane. The vanadium battery is better in vanadium resistance and corrosion resistance and suitable for high-power-density vanadium batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of vanadium battery composite membranes, and particularly to a composite membrane resistant to oxidation corrosion of vanadium battery electrolyte and a preparation method thereof. Background Art

[0002] The vanadium battery, also known as the all-vanadium redox flow battery (Vanadium Redox Battery, abbreviated as VRB), is a redox battery with active substances in a circulating liquid state, and is also a relatively advanced and widely commercialized flow battery. The vanadium battery uses the different chemical potentials of vanadium ions in different oxidation states to store energy. During operation, the positive and negative electrolyte solutions enter the positive and negative electrode units of the stack from the positive and negative electrolyte storage tanks through circulation pumps respectively, and then return to the positive and negative electrolyte storage tanks through pipelines respectively to complete the cycle. Inside the stack, the active substances of the positive and negative electrolyte solutions both undergo electrochemical reactions on the electrodes. During the reaction process, only the valence state changes and no phase transformation occurs. The positive and negative electrolyte solutions are separated by an ion exchange membrane and exchange charges.

[0003] The vanadium battery composite membrane is a key component in the vanadium battery, used to separate the positive and negative half-cells and prevent the cross-mixing of ions with different valence states. The performance of the composite membrane largely determines the performance and lifespan of the vanadium battery. As one of the key materials of the vanadium battery, the composite membrane needs to have high ion selectivity, low vanadium ion permeability, good chemical stability, and electrochemical performance. The electrolyte of the vanadium battery is usually a vanadium ion solution containing sulfuric acid. The positive electrode is mainly VO2+, and the negative electrode is V2+ / V3+. These ions will undergo redox reactions during the charge and discharge process. Especially on the positive electrode side, the vanadium ions in the high oxidation state (such as VO2+) cause oxidation corrosion to the composite membrane material.

[0004] In recent years, remarkable progress has been made in the research on vanadium battery composite membranes. For example, low-cost and high-performance Nafion / TiO2 nanotube composite membranes and Nafion / graphene oxide composite membranes have been developed. These composite membranes show excellent performance in reducing vanadium ion permeability, improving ion selectivity, and battery energy efficiency. In addition, new composite membrane materials such as sulfonated polyether ether ketone (SPEEK) / lignin composite membranes have also been successfully applied to flow batteries and shown good application prospects. However, the existing preparation process of the composite membrane has not been optimized to prepare a composite membrane with better oxidation corrosion resistance. Summary of the Invention

[0005] The present invention aims to provide a composite membrane resistant to oxidation corrosion of vanadium battery electrolyte and a preparation method thereof, and optimize the preparation process of the composite membrane to prepare a composite membrane with better oxidation corrosion resistance.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A preparation method for an electrolyte oxidation corrosion-resistant vanadium battery, comprising the following steps:

[0008] S1. Using sulfonated polyether ether ketone (SPEEK) as a substrate, uniformly dispersing graphene oxide (GO) nanosheets on the surface of the SPEEK matrix to obtain a SPEEK / GO substrate;

[0009] S2. Placing the SPEEK / GO substrate in an oxygen plasma treatment device (power 50 - 70 W, oxygen flow rate 20 - 30 sccm), treating for 3 - 5 minutes, and ultrasonically cleaning with isopropanol for 10 - 20 minutes;

[0010] S3. Dissolving polybenzimidazole (PBI) in N,N-dimethylacetamide (DMAc) (concentration 3 - 5 wt%), magnetically stirring until completely dissolved; adding TiO2 nanoparticles (particle size 20 - 25 nm, pretreated with silane coupling agent KH-570), with a mass ratio of 15 - 20% (relative to PBI), ultrasonically dispersing and performing an ice bath to obtain a PBI-TiO2 dispersion;

[0011] S4. Vertically immersing the SPEEK / GO substrate treated in S1 into the PBI-TiO2 dispersion (immersion time 30 - 40 seconds), with a pulling speed of 0.5 - 1 mm / s, controlling the environmental temperature and humidity < 30%, and the temperature at 20 - 25°C; repeating the immersion-pulling 3 - 5 times, with an interval of 10 - 15 minutes each time, and finally obtaining a pretreatment film with a coating thickness of 1.5 ± 0.2 μm;

[0012] S5. Thermally pressing the pretreatment film with a hot press, then gradually cooling to room temperature, immersing the pretreatment film in a 1 - 2 wt% aqueous glutaraldehyde (GA) solution (pH = 3 - 4, 60 - 70°C, 1 - 1.5 hours), and then irradiating the surface of the coating with ultraviolet light (365 nm) for 30 - 50 minutes to obtain the final composite film.

[0013] The working principle and beneficial effects of the present invention:

[0014] First, sulfonated polyether ether ketone (SPEEK) in S1 has excellent proton conductivity and chemical stability, and is an ideal base material for vanadium battery electrolytes. Graphene oxide (GO) nanosheets are introduced through physical dispersion. Its abundant oxygen-containing functional groups (such as hydroxyl groups and carboxyl groups) can enhance the surface activity of the substrate, while improving the mechanical strength and barrier properties, forming a composite substrate with both high proton conductivity and mechanical strength. The introduction of GO can enhance the antioxidant corrosion ability; in S2, oxygen plasma (50 - 70 W, O2 flow rate 20 - 30 sccm) bombards the substrate surface through high-energy particles, etching impurities and introducing polar functional groups (such as hydroxyl groups and carboxyl groups), improving surface hydrophilicity. Isopropyl alcohol ultrasonic cleaning further removes surface residues, strengthens the surface activity of the substrate, promotes the uniform adhesion of the subsequent PBI-TiO2 coating, and reduces interface defects; in S3, benzimidazole (PBI) is dissolved in DMAc to form a viscous solution, serving as the film-forming matrix of the coating. Its high-temperature resistance and chemical inertness can improve the stability of the composite membrane. TiO2 nanoparticles (pretreated with KH-570) are combined with PBI through a silane coupling agent, enhancing the mechanical strength and corrosion resistance of the coating. Ultrasonic dispersion and ice bath inhibit particle agglomeration to ensure uniform distribution (particle size standard deviation < 10%); in S4, the coating thickness is controlled by vertical dipping and pulling (0.5 - 1 mm / s), repeated 3 - 5 times to form a uniform and dense PBI-TiO2 layer. A low-temperature and low-humidity environment (temperature 20 - 25 °C, humidity < 30%) reduces the solvent evaporation rate, avoids film layer cracking, and obtains a uniform coating with a thickness of 1.5 ± 0.2 μm, with high thickness controllability and no macroscopic defects on the surface. In S5, hot pressing enhances the denseness of the film layer, and gradient cooling (rate 2 °C / min) reduces thermal stress, avoiding film layer warping or cracking. Under acidic conditions (pH = 3 - 4), glutaraldehyde reacts with the amino groups of PBI to form a three-dimensional network structure, improving the chemical stability and mechanical strength of the membrane. 365 nm ultraviolet light initiates the reaction of residual functional groups on the coating surface (such as free radical cross-linking), further curing the film layer. The cross-linked composite membrane has excellent corrosion resistance (such as resistance to H + and VO2 + erosion) and long-term stability.

[0015] In some embodiments, GO is dispersed in an HNO3 solution and refluxed at 80 °C for 6 to 8 hours. KH-550 (γ-aminopropyltriethoxysilane) is dissolved in an ethanol / water mixture, and the pH is adjusted to 4 - 5, followed by stirring at 60 °C for 2 to 3 hours. The pretreated GO is dispersed in absolute ethanol (at a concentration of 1 - 2 mg / mL) and ultrasonicated for 1 hour to ensure uniform dispersion. The hydrolyzed KH-550 solution is added at 10 - 15% of the mass of GO, and the reaction is stirred under nitrogen protection. After centrifugal washing, KH-GO is dried in vacuo and uniformly dispersed on the surface of the SPEEK matrix. The HNO3 reflux oxidation increases the carboxyl content on the surface of GO, improving its dispersibility and reactivity. The KH-550-modified silane coupling agent enhances the interfacial bonding force between GO and the SPEEK matrix through chemical bonding, reducing interfacial defects, and enabling KH-GO to be uniformly dispersed in the SPEEK matrix, forming a composite structure with strong interfacial bonding.

[0016] In some embodiments, 0.1 wt% polyethylene glycol (PEG-400) is added as a leveling agent when PBI is dissolved in S2. As a leveling agent, it avoids the appearance of pinholes during the coating in S4.

[0017] In some embodiments, the rate of gradient cooling to room temperature is 2 °C.

[0018] In some embodiments, when TiO2 is dispersed in S3, the standard deviation of the particle size distribution is ensured to be < 10%. Detailed implementation manners

[0019] The following is a further detailed description through specific implementation manners:

[0020] Example 1: A preparation method of an electrolyte oxidation corrosion resistant vanadium battery, comprising the following steps: S1. Using sulfonated polyether ether ketone (SPEEK) as a substrate, uniformly dispersing graphene oxide (GO) nanosheets on the surface of the SPEEK matrix to obtain a SPEEK / GO substrate; S2. Placing the SPEEK / GO substrate in an oxygen plasma treatment device (power 60 W, oxygen flow rate 20 sccm), treating for 3 minutes, and ultrasonically cleaning with isopropanol for 10 minutes; S3. Dissolving polybenzimidazole (PBI) in N,N-dimethylacetamide (DMAc) (concentration 3 wt%), magnetically stirring until completely dissolved; adding TiO2 nanoparticles (particle size 20 nm, pretreated with silane coupling agent KH-570), with a mass ratio of 15% (relative to PBI), ultrasonically dispersing and performing an ice bath to obtain a PBI-TiO2 dispersion; S4. Vertically immersing the SPEEK / GO substrate treated in S1 into the PBI-TiO2 dispersion (immersion time 30 seconds), with a pulling speed of 0.5 mm / s, controlling the environmental temperature and humidity <30%, and the temperature at 20°C; repeating the immersion-pulling 3 times, with an interval of 10 minutes each time, and finally obtaining a pretreatment film with a coating thickness of 1.5 μm; S5. Thermally pressing the pretreatment film with a hot press, then cooling to room temperature at a gradient (rate 2°C), immersing the pretreatment film in a 1 wt% aqueous glutaraldehyde (GA) solution (pH = 3, 60°C, 1 hour), and then irradiating the surface of the coating with ultraviolet light (365 nm) for 30 minutes to obtain the final composite film.

[0021] Example 2: A preparation method of an electrolyte oxidation corrosion resistant vanadium battery, comprising the following steps: S1. Using sulfonated polyether ether ketone (SPEEK) as a substrate, dispersing GO in a 3 mol / L HNO3 solution, refluxing at 80°C for 6 hours, dissolving KH-550 (γ-aminopropyltriethoxysilane) in an ethanol / water mixture, adjusting the pH to 4, and stirring at 60°C for 2 hours; dispersing the pretreated GO in absolute ethanol (concentration 1 mg / mL), and ultrasonically treating for 1 hour to ensure uniform dispersion; adding the hydrolyzed KH-550 solution according to 10% of the mass of GO, stirring and reacting under nitrogen protection, centrifuging and washing, and then vacuum drying KH-GO, and uniformly dispersing KH-GO on the surface of the SPEEK matrix to obtain a SPEEK / GO substrate;

[0022] S2. Place the SPEEK / GO substrate in an oxygen plasma treatment device (power 60 W, oxygen flow rate 20 sccm), treat for 3 minutes, and ultrasonically clean with isopropanol for 10 minutes; S3. Dissolve polybenzimidazole (PBI) in N,N-dimethylacetamide (DMAc) (concentration 3 wt%), and stir magnetically until completely dissolved; add TiO2 nanoparticles (particle size 20 nm, pretreated with silane coupling agent KH-570), with a mass ratio of 15% (relative to PBI), ultrasonically disperse and perform an ice bath to obtain a PBI-TiO2 dispersion; S4. Vertically immerse the SPEEK / GO substrate treated in S1 into the PBI-TiO2 dispersion (immersion time 30 seconds), with a pulling speed of 0.5 mm / s, control the environmental temperature and humidity < 30%, and the temperature is 20 °C; repeat the immersion-pulling 3 times, with an interval of 10 minutes each time, and the final coating thickness is 1.5 μm to obtain a pretreated membrane; S5. Thermally press the pretreated membrane with a hot press, then cool down to room temperature at a gradient (rate 2 °C), immerse the pretreated membrane in a 1 wt% glutaraldehyde (GA) aqueous solution (pH = 3, 60 °C, 1 hour), and then irradiate the coating surface with ultraviolet light (365 nm) for 30 minutes to obtain the final composite membrane.

[0023] Blank control group 1: Nafion117 membrane, pretreat with 3% H2O2, deionized water, and 0.5 M H2SO4 by boiling for 1 hour each, and wash with deionized water until neutral.

[0024] Blank control group 2: Only SPEEK is formed into a film, without GO and PBI-TiO2 modification.

[0025] Blank control group 3: A composite membrane prepared by referring to the preparation method of the SPEEK / GO / TiO2 composite ion-selective membrane selected within the nano-intercalation of the prior art CN110350223B.

[0026] Performance test: (1) Proton conductivity test: Use an electrochemical workstation to measure the proton conductivity of the membrane in 0.5 M H2SO4 by the alternating current impedance method (EIS). Formula: σ = R / A * L, where L is the membrane thickness, R is the resistance, and A is the electrode area; (2) Vanadium ion permeability test: Use a two-chamber diffusion cell, with 1.5 M VOSO4 (acidified with H2SO4 to pH = 2) on one side and 1.5 M MgSO4 (equilibrated osmotic pressure) on the other side, sample at regular intervals, and measure the VO 2 + concentration by a UV-visible spectrophotometer (UV-Vis, λ = 760 nm) to calculate the permeability. (3) Long-term corrosion resistance test: Immerse the membrane in a vanadium battery electrolyte (1.5 M VOSO4 + 3 M H2SO4), accelerate corrosion at 60 °C for 72 hours, and measure the mass loss rate. (4) Mechanical property test: Use a universal material testing machine to measure the tensile strength (ASTM D882 standard). The following experimental data are obtained:

[0027]

[0028] From the above data, it can be seen that: (1) The composite membranes of Examples 1 and 2 (35.2 / 33.8 mS / cm) are significantly higher than that of Method 3 of the blank control group (28.4 mS / cm), but lower than Nafion 117 (85.6 mS / cm). The reason is that the solution casting method of the blank control group 3 results in a lower dispersion uniformity of GO / TiO2 and a larger membrane thickness (60 μm vs. 1.5 μm), which hinders proton migration. (2) The vanadium-blocking performance of the composite membranes of Examples 1 and 2 is optimal (1.2×10 -7 cm 2 / min), followed by that of the blank control group 3 (2.8×10 -7 ), but still better than that of Nafion 117 (8.7×10 -7 ). The reason is that the dip-coating method of this application forms a denser PBI-TiO2 coating, while the GO / TiO2 intercalation structure of the blank control group 3 has a weaker physical barrier effect on vanadium ions. (3) The mass loss rate of the composite membranes of Examples 1 and 2 is the lowest (2.1%), and that of the method of the blank control group 3 is 5.6%, indicating that ultraviolet curing crosslinking is more effective than simple hot pressing (blank control group 3) in improving chemical stability and significantly enhancing corrosion resistance. (4) The tensile strength of the composite membranes of Example 1 and Example 2 (45.6 MPa) is better than that of the blank control group 3 (38.2 MPa) because the synergistic strengthening effect of PBI and GO is more significant.

[0029] In summary, the preparation method of this application has more advantages in terms of oxidation and corrosion resistance and vanadium-blocking performance. The blank control group 3 and the blank control group 1 have potential in terms of process simplification and need to be further optimized to balance performance and cost. This application has better vanadium-blocking and corrosion resistance and is suitable for high-power density vanadium batteries.

Claims

1. A method for preparing a composite membrane resistant to oxidation corrosion of vanadium battery electrolyte, characterized in that, It includes the following steps: S1. Using sulfonated polyether ether ketone (SPEEK) as the substrate, uniformly dispersing graphene oxide (GO) nanosheets on the surface of the SPEEK matrix to obtain the SPEEK / GO substrate; S2. Placing the SPEEK / GO substrate in an oxygen plasma treatment device (power 50 - 70 W, oxygen flow rate 20 - 30 sccm), treating for 3 - 5 minutes, and ultrasonically cleaning with isopropanol for 10 - 20 minutes; S3. Dissolving polybenzimidazole (PBI) in N,N-dimethylacetamide (DMAc) (concentration 3 - 5 wt%), magnetically stirring until completely dissolved; adding TiO2 nanoparticles (particle size 20 - 25 nm, pretreated with silane coupling agent KH-570), with a mass ratio of 15 - 20% (relative to PBI), ultrasonically dispersing and performing an ice bath to obtain the PBI-TiO2 dispersion. S4. Vertically immersing the SPEEK / GO substrate treated in S1 into the PBI-TiO2 dispersion (immersion time 30 - 40 seconds), with a pulling speed of 0.5 - 1 mm / s, controlling the environmental temperature and humidity < 30%, and the temperature at 20 - 25°C; repeating the immersion-pulling 3 - 5 times, with an interval of 10 - 15 minutes each time, and finally obtaining a pretreatment film with a coating thickness of 1.5 ± 0.2 μm; S5. Thermally pressing the pretreatment film with a hot press, and then gradually cooling to room temperature. Immerse the pretreatment film in a 1 - 2 wt% aqueous glutaraldehyde (GA) solution (pH = 3 - 4, at 60 - 70°C for 1 - 1.5 hours), and then irradiate the surface of the coating with ultraviolet light (365 nm) for 30 - 50 minutes to obtain the final composite film.

2. The method for preparing a composite membrane resistant to oxidation corrosion of a vanadium battery electrolyte according to claim 1, characterized in that: Disperse GO in the HNO3 solution, reflux at 80°C for 6 - 8 hours. Dissolve KH-550 (γ-aminopropyltriethoxysilane) in the ethanol / water mixture, adjust the pH to 4 - 5, and stir at 60°C for 2 - 3 hours; Disperse the pretreated GO in anhydrous ethanol (concentration 1 - 2 mg / mL), and ultrasonically treat for 1 hour to ensure uniform dispersion; Add the hydrolyzed KH-550 solution according to 10 - 15% of the mass of GO, stir and react under nitrogen protection, centrifuge and wash, and then vacuum dry KH-GO, and uniformly disperse KH-GO on the surface of the SPEEK matrix.

3. The preparation method of the composite film resistant to oxidation corrosion of vanadium battery electrolyte according to claim 2, characterized in that: Add 0.1 wt% polyethylene glycol (PEG-400) as a leveling agent when dissolving PBI in S2.

4. The preparation method of the composite film resistant to oxidation corrosion of vanadium battery electrolyte according to any one of claims 1 to 3, characterized in that: The rate of gradually cooling to room temperature is 2°C.

5. The preparation method of the composite film resistant to oxidation corrosion of vanadium battery electrolyte according to claim 4, characterized in that: When dispersing TiO2 in S3, ensure that the standard deviation of the particle size distribution < 10%.

6. A composite film resistant to oxidation corrosion of vanadium battery electrolyte, prepared by the preparation method according to any one of claims 1 - 5.

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