CN-122025692-A - High-ion-selectivity perfluorinated sulfonic acid ionic membrane for vanadium battery and preparation method and application thereof

CN122025692ACN 122025692 ACN122025692 ACN 122025692ACN-122025692-A

Abstract

The invention discloses a high-ion-selectivity perfluorinated sulfonic acid ionic membrane for a vanadium battery, and a preparation method and application thereof. Belonging to the technical field of electrochemical energy storage and functional polymer materials. The ionic membrane takes perfluorinated sulfonic acid resin as a matrix and contains functional core-shell hybrid filler and a double-interface cross-linked network. The filler core layer is a rich-OH and low-F MXene nano-sheet pretreated by mild etching, and the shell layer is an SNW-1 covalent organic framework with bimodal pore size distribution which grows in situ by a gradient heating method. The dual crosslinked network is cooperatively formed by a silane coupling agent chemically anchored to MXene and a flexible organic crosslinking agent. The membrane has high proton conductivity, extremely low vanadium ion permeability and high ion selectivity through the cooperation of the three components, and has excellent stability in strong acid accelerated aging, so that the key bottleneck of poor ion selectivity and insufficient long-term stability of the traditional perfluorinated sulfonic acid membrane is effectively solved.

Inventors

JIANG XINXI
ZHOU LI
LI HONGXIA
WAN WEI
LI XIAFENG
NI YUNTAO
LI XIANTAO
Xie Hongqian
LIU ZHIHAN
REN CHUAN
Hu Shidan

Assignees

贵州志喜科技有限公司

Dates

Publication Date: 20260512
Application Date: 20260205

Claims (10)

1. A high ion selectivity perfluorosulfonic acid ion membrane for a vanadium battery, the ion membrane comprising: A perfluorosulfonic acid polymer matrix; A functionalized core-shell hybrid filler uniformly dispersed in the perfluorinated sulfonic acid polymer matrix, the functionalized core-shell hybrid filler comprising: a) The nuclear layer is an MXene nano-sheet subjected to etching pretreatment, and the molar ratio of-F functional groups to-OH functional groups of the pretreated MXene nano-sheet is less than 0.5:1; b) The shell layer is an SNW-1 covalent organic framework layer which grows on the surface of the pretreated MXene nano-sheet in situ, wherein the SNW-1 covalent organic framework layer has bimodal pore size distribution and comprises inherent micropores of 0.5-0.8 nm and mesopores of 2-5 nm which are generated in situ in the SNW-1 covalent organic framework layer; A dual interface crosslinked network consisting of: i. A silane coupling agent, wherein one end of the silane coupling agent can form an Si-O-Ti covalent bond with an-OH group on the surface of MXene, and the other end of the silane coupling agent contains an amino group or an epoxy group which can interact with a perfluorinated sulfonic acid polymer matrix; Flexible organic crosslinking agent; Wherein the mass fraction of the functionalized core-shell hybrid filler in the ionic membrane is 0.5-5 wt%; The total mass fraction of the silane coupling agent and the flexible organic crosslinking agent is 0.1-1.5 wt%, and the mass ratio of the silane coupling agent to the flexible organic crosslinking agent is 1:0.2-1:1.
2. The ionic membrane of claim 1, wherein the silane coupling agent is gamma-aminopropyl triethoxysilane or gamma-glycidoxypropyl trimethoxysilane; the flexible organic cross-linking agent is polyethylene glycol diglycidyl ether.
3. The method for preparing the high ion selectivity perfluorosulfonic acid ion membrane for vanadium redox batteries according to any one of claims 1 or 2, comprising the steps of: (1) Mild etching pretreatment of MXene nanoplatelets: Dispersing Ti 3 AlC 2 MAX phase powder in a mixed etchant, stirring and reacting for 12-36 hours at 30-50 ℃, centrifuging and washing to be neutral after the reaction is finished to obtain a multi-layer MXene etching product with interlayer Al selectively etched, and carrying out low-power ultrasonic stripping on the multi-layer MXene etching product under a protective atmosphere to enable the multi-layer MXene etching product to be separated from the layers to obtain a single-layer or less-layer pretreated MXene nano-sheet dispersion liquid; (2) In situ growth of gradient bimodal pore size SNW-1 covalent organic framework layer: Mixing the dispersion liquid of the pretreated MXene nano-sheets obtained in the step (1) with 1,3, 5-trimethyl phloroglucinol, 1, 4-diaminobenzene and glacial acetic acid, and reacting by a gradient heating method to obtain an SNW-1 type covalent organic framework layer with bimodal pore size distribution, namely a core-shell hybrid filler of the MXene and the SNW-1 type covalent organic framework, which grows in situ on the surfaces of the pretreated MXene nano-sheets; The gradient heating method comprises reacting at 0-10deg.C for 2-6h, then heating to 60-80deg.C at a rate of 0.5-1 deg.C/min, and continuing reacting at this temperature for 20-40h; (3) Interface preliminary modification of hybrid filler: dispersing the core-shell hybrid filler obtained in the step (2) in absolute ethyl alcohol, adding a silane coupling agent, and carrying out reflux reaction for 4-8 hours at 60-80 ℃ to obtain the hybrid filler with the surface grafted with the silane coupling agent; (4) Preparing casting solution and performing interface secondary crosslinking: Dissolving the hybridized filler of the surface grafted silane coupling agent obtained in the step (3), the perfluorinated sulfonic acid resin solution and the flexible organic crosslinking agent in an organic solvent, and forming uniformly dispersed casting film liquid under the conditions of ultrasonic treatment and stirring; (5) Solution casting and in-situ curing molding: Casting the casting film obtained in the step (4) on a flat substrate, and carrying out gradient heating drying, namely, firstly drying for 2-4h at 40-60 ℃, then treating for 4-10h at 100-130 ℃, and finally carrying out heat treatment for 0.5-2h at 140-160 ℃ to obtain the high ion selectivity perfluorinated sulfonic acid ionic membrane.
4. The method of claim 3, wherein the mass to volume ratio of the Ti 3 AlC 2 MAX phase powder to the mixed etchant of step (1) is 1: 1 g:30-60 mL; The mixed etchant is concentrated hydrochloric acid and aqueous solution prepared with lithium fluoride, the final concentration of the concentrated hydrochloric acid in the mixed etchant is 6-9M, and the final concentration of the lithium fluoride is 0.5-2.0M; the low-power ultrasonic stripping process is that under the protection of argon or nitrogen, ultrasonic stripping treatment is carried out for 0.5-2h with the power of 50-150W.
5. The process according to claim 3, wherein the gradient heating in step (2) is performed by reacting at 5℃for 4 hours, then heating at 0.8℃/min to 70℃and maintaining at 70℃for 30 hours.
6. The method according to claim 3, wherein in the step (2), based on the mass of the MXene nanoplatelets contained in the pretreated MXene nanoplatelet dispersion, the addition amount of the 1,3, 5-trimethylphloroglucinol is 10-40 mmol/g, the molar ratio of the 1, 4-diaminobenzene to the 1,3, 5-trimethylphloroglucinol is 1.5-2.0:1, and the addition amount of the glacial acetic acid accounts for 3-8 vol% of the total volume of the reaction system.
7. The preparation method of claim 3, wherein the dispersion concentration of the core-shell hybrid material in the step (3) in absolute ethyl alcohol is 2-10 mg/mL, and the addition amount of the silane coupling agent is 5-20% of the mass of the core-shell hybrid material.
8. The method according to claim 3, wherein the organic solvent in the step (4) is at least one of N, N-dimethylformamide, N-dimethylacetamide and dimethylsulfoxide; The mass ratio of the hybrid filler of the surface grafting silane coupling agent to the dry weight of the perfluorinated sulfonic acid resin in the step (4) is 0.5-5:100, and the total solid content of the casting solution is 5-15 wt%.
9. An all-vanadium redox flow battery, characterized in that the high-ion-selectivity perfluorosulfonic acid ion membrane prepared by the method of any one of claims 1 or 2 or any one of claims 3 to 8 is used as a battery diaphragm.
10. The all-vanadium redox flow battery according to claim 9, wherein the battery has an average coulombic efficiency of not less than 99.0%, an average energy efficiency of not less than 90.0%, and a capacity retention rate of not less than 97% after 3000 charge-discharge cycles when subjected to a charge-discharge test at a current density of 150 mA cm -2 .

Description

High-ion-selectivity perfluorinated sulfonic acid ionic membrane for vanadium battery and preparation method and application thereof Technical Field The invention relates to the technical field of electrochemical energy storage and functional polymer materials, in particular to a high-ion-selectivity perfluorinated sulfonic acid ionic membrane for a vanadium battery, and a preparation method and application thereof. Background All-Vanadium Redox Flow Battery (VRFB) has the advantages of high safety, long cycle life, independent design of power and capacity and the like, and has a great application prospect in the field of large-scale energy storage. The ion exchange membrane is used as one of the core components of VRFB and is used for conducting protons to close a circuit and blocking the double tasks of cross permeation of vanadium ions in positive and negative electrolyte. Thus, the ion selectivity (ratio of proton conductivity to vanadium ion permeability) of the membrane is a key indicator in determining the coulombic efficiency, energy efficiency and lifetime of the cell. Currently, commercial perfluorosulfonic acid (PFSA) membranes (e.g., nafion series) are widely studied for their excellent chemical stability and higher proton conductivity. However, the ion transport channel size (typically 3-5 nm) formed by ion clusters inside the PFSA membrane is much larger than the size of hydrated protons (about 0.24 nm) and hydrated vanadium ions (V n+, >0.6 nm), resulting in extremely weak sizing capability for vanadium ions, causing serious cross-contamination of vanadium ions. This not only results in a cell with a coulombic efficiency generally lower than 90%, but also results in an imbalance of active materials and capacity fading, forming an inherent contradiction in which proton conductivity and ion selectivity are difficult to combine. To improve the ion selectivity of PFSA membranes, researchers have mainly adopted two strategies, blend modification and composite membranes. Among them, the introduction of covalent organic framework materials with regular nanopores as molecular sieve packing is a research hotspot in recent years. For example, in the prior art, it has been reported that SNW-1 type COF is grown in situ on the surface of Graphene Oxide (GO) and is composited with PFSA to enhance selectivity. Another study has grown SNW-1 COF in situ on the surface of two-dimensional MXene nanoplatelets and used in Sulfonated Polyetheretherketone (SPEEK) membranes to aid proton conduction and increase ion diffusion pathways using the hydrophilicity and lamellar structure of MXene. However, in the development of PFSA-based composite films for high-performance, long-life VRFB applications, the above prior art still faces the following difficult-to-surmount bottlenecks: The filler is fragile with the matrix interface, and the compatibility of the strongly polar hybrid filler (such as MXene/COF) and the hydrophobic PFSA matrix is poor, so that the interface is easy to have defects due to physical blending. In a strong acid and strong oxidizing environment for a long time, the interface is extremely easy to debond, a non-selective ion leakage channel is formed, and the performance is rapidly declined. The proton conduction network is discontinuous, namely a high-efficiency proton exchange bridge is lacking between proton conduction sites (such as-OH) on the surfaces of MXene and other fillers and a sulfonate ion cluster network of PFSA, the proton cross-interface transmission resistance is high, and the proton conduction advantage of the fillers cannot be effectively converted into macroscopic membrane performance. Mass transfer limitations of a single microporous structure-conventional COFs have only micropores (< 2 nm), which can effectively screen vanadium ions, but also cause steric hindrance and diffusion limitation on the transmission of hydrated protons, especially become bottlenecks restricting proton conduction when pursuing high current densities, and are difficult to truly break the "conductivity-selectivity trade-off. The intrinsic surface properties of MXene are disadvantageous in that the MXene surface prepared by the traditional hydrofluoric acid etching method is rich in hydrophobic-F groups, so that the proton affinity is weak, and uniform nucleation growth of COF and interface bonding with a polymer are not facilitated. Therefore, the PFSA-based composite membrane capable of fundamentally and cooperatively solving the problems of interface compatibility, proton transmission continuity and multi-scale ion screening is developed, and has great significance for promoting the commercialization process of VRFB technology. Disclosure of Invention In view of the above, the invention develops a high ion selectivity perfluorinated sulfonic acid ionic membrane for a vanadium battery, and a preparation method and application thereof, which successfully improves the conductivity of the ionic membrane, red