CN107546398A - A kind of ion-conductive membranes and its preparation and application with micro phase separation structure - Google Patents

Abstract

The present invention relates to a kind of ion-conductive membranes with micro phase separation structure, it is above raw material with one or more in hydrophilic polymer resin by one or both of hydrophobic polymer resin, after being dissolved in organic solvent, solvent flashing is prepared, aqueous favoring aggregation is induced in solvent volatilization process, so as to form the micro phase separation structure ion-conductive membranes with hydrophobic region and hydrophilic region；Wherein the mass ratio of the concentration of hydrophobic polymer resin and hydrophilic polymer resin is 0.5 5.Ion-conductive membranes technical process with micro phase separation structure is simple, and environmental friendly, Microphase Structure is controllable, easily realizes batch production, and the battery assembled with this has good capability retention and excellent battery performance.

Description

A kind of ion conduction membrane with microphase separation structure and its preparation and application

technical field

The invention relates to an ion conduction membrane for a liquid flow battery.

Background technique

Liquid flow battery is a new electrochemical energy storage technology. Compared with other energy storage technologies, it has the advantages of flexible system design, large storage capacity, free site selection, high energy conversion efficiency, deep discharge, safety and environmental protection, and low maintenance costs. It can be widely used in wind energy, solar energy and other renewable energy generation and energy storage, emergency power system, backup power station and power system peak shaving and valley filling. Vanadium flow battery (VFB) is considered to have a good application prospect due to its advantages of high safety, good stability, high efficiency, long life (lifetime > 15 years), and low cost.

The battery separator is an important part of the flow battery, which plays a role in blocking the positive and negative electrolytes and providing proton transport channels. The proton conductivity, chemical stability and ion selectivity of the membrane will directly affect the electrochemical performance and service life of the battery; therefore, the membrane is required to have a lower active material permeability (that is, a higher selectivity) and a lower Surface resistance (that is, high ionic conductivity), but also should have good chemical stability and low cost. At present, the membrane materials used at home and abroad are mainly Nafion membrane developed by DuPont Company of the United States. Nafion membrane has excellent performance in terms of electrochemical performance and service life. These membranes consist of a hydrophobic fluorocarbon backbone and hydrophilic sulfonic acid side chains. Due to its special structure, the hydrophobic skeleton and hydrophilic groups in the membrane have a microphase separation structure when it is applied in the battery, so that it has excellent proton conductivity. It is precisely because of the microphase structure of this fixed structure that it has disadvantages such as poor ion selectivity when used in batteries, especially in all-vanadium redox flow batteries; on the other hand, this type of membrane is expensive, which limits the membrane. industrial applications. Therefore, it is crucial to develop battery separators with high selectivity, high stability, and low cost. Due to the presence of ion-exchange groups in non-fluorine ion-exchange membranes, their chemical stability in all-vanadium redox flow batteries is insufficient to meet long-term use requirements.

Copolymeric polymers can often form complex structures of different scales and have a wide range of applications in the field of material technology. Multi-component polymers such as block or graft are composed of two or more chain segments with different properties. When the solubility parameters of the monomer segments differ greatly, resulting in incompatibility, there is a tendency for phase separation to occur; however, due to the chemical bonds between the different monomer segments, these copolymers cannot occur macroscopically. However, only some phase regions in the range of nanometer or micrometer scale can be formed. This kind of phase separation is called microphase separation, and the structure formed by this kind of microphase separation is called microphase separation structure. Generally, the preparation process of block copolymers with microphase separation structure is complicated, and a large amount of organic solvents are required, which is not conducive to the ecological environment, which limits its large-scale application to a certain extent.

Contents of the invention

The purpose of the present invention is to prepare an ion conduction membrane with a microphase separation structure, and to prepare ion conduction membranes with different microphase structures by controlling the preparation conditions, so that it has both excellent ion selectivity and ion conductivity, and provides a liquid The application of ion-conducting membranes with micro-phase separation structure for flow batteries in flow batteries, especially the application of such membranes in all-vanadium flow batteries.

To achieve the above object, the technical scheme adopted in the present invention is as follows:

An ion-conducting membrane with a microphase separation structure, which is made of one or more than two kinds of hydrophobic polymer resins and one or more than two kinds of hydrophilic polymer resins as raw materials, dissolved in an organic solvent, volatilized Prepared with a solvent, the hydrophilic phase is induced to aggregate during the solvent volatilization process, thereby forming a microphase-separated structure ion-conducting membrane with hydrophobic regions and hydrophilic regions;

Wherein the mass ratio of the hydrophobic polymer resin to the hydrophilic polymer resin is 0.5-5.

The hydrophobic polymer resin is polyethersulfone, polysulfone, polyether ketone, polytetrafluoroethylene, polyvinylidene fluoride or polystyrene; the hydrophilic polymer resin is sulfonated polysulfone, sulfonated Polyimides, sulfonated polyetherketones, sulfonated polybenzimidazoles, polyvinylpyrrolidone or polyethylene glycol.

Wherein, the phase separation structure is a layered structure, a co-continuous structure, a spherical structure or a columnar structure.

The ion-conducting membrane with a microphase separation structure is prepared by the following steps:

(1) Dissolve the hydrophobic polymer resin and the hydrophilic polymer resin in an organic solvent, and fully stir at a temperature of 20-100°C for 20-60 hours to make a blended uniform solution; wherein the hydrophobic polymer resin and the hydrophilic polymer resin The mass ratio of the water-based polymer resin is between 0.5-5; the mass concentration of the hydrophobic polymer resin and the hydrophilic polymer resin in the organic solvent is 10-50%.

(2) Pour the blended solution prepared in step (1) onto a non-woven fabric substrate or directly onto a glass plate, volatilize the solvent for 0 to 60 seconds, and then evaporate the solvent to dryness at a temperature of 40 to 200°C to form a film; the solvent volatilizes The aggregation of the hydrophilic phase is induced to obtain a membrane with a microphase separation structure; the thickness of the membrane is between 20 and 500 μm.

The organic solvent is dimethyl sulfoxide (DMSO), N,N'-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), N,N'-dimethylformamide (DMF) , tetrahydrofuran (THF) in one or two or more.

The ion-conducting membrane with micro-phase separation structure is used in a liquid flow battery.

The flow battery includes an all-vanadium flow battery, a zinc/cerium flow battery, a vanadium/bromine flow battery or an iron/chromium flow battery.

Beneficial results of the present invention

1. The blending method used in the present invention is to obtain a homogeneous casting solution by blending the hydrophobic high molecular polymer and the hydrophilic high molecular polymer uniformly in an organic solvent, and the casting solution is evenly coated on Evaporate the solvent to form a film on a non-woven fabric or a clean glass plate. During the solvent evaporation process, the solvent induces the aggregation of the hydrophilic polymer resin so that the mixture undergoes microphase separation. The prepared ion-conducting membrane with micro-phase separation structure is applied in the flow battery, and the ion-conducting membrane with different micro-phase structures is prepared by controlling the preparation conditions, so that it has both excellent ion selectivity and ion conductivity, providing a The application of ion-conducting membranes with micro-phase separation structure for flow batteries in flow batteries, especially the application of such membranes in all-vanadium flow batteries.

2. The ion-conducting membrane with a microphase separation structure prepared by the present invention has an adjustable microphase structure and is easy to realize mass production.

3. The blending method used in the present invention prepares the ion-conducting membrane with a microphase separation structure, only needs to use an aqueous solution of ion-exchange resin and a cleaning solvent, and the preparation process is clean and environmentally friendly.

4. The present invention can realize the controllability of the battery efficiency and capacity of the redox flow battery, especially the all-vanadium redox flow battery.

Description of drawings

The SEM image of the surface and cross-section of the microphase ion-conducting membrane prepared in Fig. 1 Example 1

(a: SEM image of the surface of the film facing the air side; b: enlarged surface image of the white dotted line in Figure a; c: SEM image of the surface of the film facing the glass plate side; d: cross-sectional SEM image of the prepared film).

Figure 2 The surface resistance of the ion-conducting membrane with microphase separation structure and the Nafion115 membrane prepared under different conditions are obtained by the two-electrode AC impedance test (Solartron Electrochemical System). The specific test method is as follows: first, place the membrane in 0.5molL ^{- 1} Fully soak in sulfuric acid aqueous solution for 24 hours; then place the membrane in a test cell filled with 0.5mol L ^-1 dilute sulfuric acid, use a graphite plate with a fixed electrode spacing as an electrode, and use an AC impedance meter to scan in the range of 1kHZ-1MHZ, The measured resistance was r ₁ ; finally, the film was taken out, and the resistance of the blank sample was measured by AC impedance again as r ₂ . The effective area S of the membrane is 1 cm ² , and the calculation formula of surface resistance is: r=(r ₁ −r ₂ )xS.

Figure 3 vanadium permeability of ion-conducting membranes with microphase separation structures and Nafion115 membranes prepared under different conditions;

The solution composition of the left permeation cell of the vanadium permeation test device is 80mL 3mol L ^-1 VOSO ₄ +3mol L ^-1 H ₂ SO ₄ solution, and the solution composition of the right permeation cell is 80mL 3molL ^-1 MgSO ₄ +3mol L ^-1 H ₂ SO ₄ , where MgSO ₄ is used to balance the ionic strength of the solutions on both sides to reduce water migration caused by osmotic pressure, and the effective area of the membrane is 9cm ² . In order to avoid concentration polarization at the liquid/membrane interface, the solutions on both sides were continuously stirred during the test. Take out 3mL sample solution from the right osmosis cell every 24h, and supplement the same volume of vanadium solution at the same time. The concentration of VO ²⁺ in the sample solution was measured by UV-Vis spectrophotometer.

Figure 4 shows the single-cell performance of ion-conducting membranes with microphase separation structures and Nafion115 membranes prepared under different conditions under the condition of 80mA cm ^-2 .

Fig. 5 Cycle stability of polyethersulfone ion-conducting membrane with microphase separation structure under the conditions of 80mA cm ^-2 and 120mAcm ^-2 .

Figure 6 The capacity stability of polyethersulfone ion-conducting membrane with microphase separation structure and Nafion 115 membrane under the condition of 80mA cm ^-2 .

detailed description

The following examples are to further illustrate the present invention, but not to limit the scope of the present invention.

comparative example

14.9184g of polyethersulfone (PES) was dissolved in 45.0593g of DMAC, stirred for 48 hours, and the formed polymer solution was spread on a glass plate, and then the glass plate was transferred to a 50°C hot stage for heating for 48 hours, and then cooled at room temperature. The glass plate was placed in a water bath to obtain a homogeneous polyethersulfone membrane.

The all-vanadium redox flow battery was assembled by using the prepared polyethersulfone membrane and the commercialized Nafion 115 membrane, in which the catalytic layer was activated carbon felt, the bipolar plate was graphite plate, the effective area of the membrane was 48cm ² , and the current density was 80mA.cm ^-2 , the vanadium ion concentration in the electrolyte is 1.50mol L ^-1 , and the H ₂ SO ₄ concentration is 3mol L ^-1 . Since there is no phase separation structure in the polyethersulfone membrane, the ion transport resistance is relatively large, and the assembled flow battery cannot be charged and discharged normally; the coulombic efficiency of the all-vanadium redox flow battery assembled with the commercial Nafion 115 membrane is 93.38%, and the voltage efficiency is 88.30%, energy efficiency is 82.45%.

Example 1

1.6087g polyethersulfone, 0.4028g sulfonated polyether ether ketone and 1.0029g polyethylene glycol were dissolved in 8.0655g DMAC, stirred for 24 hours, and the polymer solution formed was spread on a glass plate, and then the glass plate was transferred to Heating on a hot stage at 50°C for 48 hours, during the process of solvent volatilization, induce phase separation of the hydrophilic phase sulfonated polyetheretherketone, polyethylene glycol and hydrophobic phase polyethersulfone, and obtain a polyethersulfone membrane with a microphase separation structure (Figure 1) , after cooling at room temperature, place the glass plate in a water tank with a film thickness of 22 μm. An all-vanadium redox flow battery was assembled using the prepared ion-conducting membrane with a microphase separation structure, in which the catalytic layer was activated carbon felt, the bipolar plate was a graphite plate, the effective area of the membrane was 48cm ² , and the current density was 80mA.cm ^-2 . The vanadium ion concentration in the solution is 1.50mol L ^-1 , and the H ₂ SO ₄ concentration is 3mol L ^-1 . The assembled flow battery has a coulombic efficiency of 91.09%, a voltage efficiency of 90.08%, and an energy efficiency of 82.05% (Fig. 3).

Example 2

7.4592g of polyethersulfone, 7.5062g of polyvinylpyrrolidone (PVP) was dissolved in 45.1121g of DMAC, stirred for 48 hours, the formed polymer solution was spread on a glass plate, and then the glass plate was transferred to a 50°C hot stage and heated for 48 Hours, PVP phase separation was induced during the solvent volatilization process, and a polyethersulfone membrane (PES) with a microphase separation structure was obtained. After cooling at room temperature, the glass plate was placed in a water tank, and the membrane thickness was 55 μm. An all-vanadium redox flow battery was assembled using the prepared ion-conducting membrane with a microphase separation structure, in which the catalytic layer was activated carbon felt, the bipolar plate was a graphite plate, the effective area of the membrane was 48cm ² , and the current density was 80mA.cm ^-2 . The vanadium ion concentration in the solution is 1.50mol L ^-1 , and the H ₂ SO ₄ concentration is 3mol L ^-1 . The assembled flow battery has a coulombic efficiency of 99.09%, a voltage efficiency of 89.55%, and an energy efficiency of 88.74% (Fig. 4), and the performance of the battery has not declined significantly after more than 8,000 cycles, showing excellent stability (Fig. 5 ). Compared with Nafion 115 membrane, the single cell assembled with polyethersulfone ion-conducting membrane with microphase separation structure has excellent capacity retention (Figure 6).

Example 3

3.0396g polysulfone (PSF), 3.1204g polyethersulfone (PES) and 6.003g polyvinyl alcohol 6000 (PEG-6000) were dissolved in 42.6982g DMAC, stirred for 48 hours to form a polymer solution, spread on a glass plate , and then transfer the glass plate to a 50°C hot stage for heating for 48 hours, induce PEG-6000 phase separation during the solvent volatilization process, and obtain a polysulfone/polyethersulfone membrane (PSF for short) with a microphase separation structure. After cooling at room temperature, the The glass plate was placed in a water tank with a film thickness of 52 μm. An all-vanadium redox flow battery was assembled using the prepared ion-conducting membrane with a microphase separation structure, in which the catalytic layer was activated carbon felt, the bipolar plate was a graphite plate, the effective area of the membrane was 48cm ² , and the current density was 80mA.cm ^-2 . The vanadium ion concentration in the solution is 1.50mol L ^-1 , and the H ₂ SO ₄ concentration is 3mol L ^-1 . The assembled flow battery has a coulombic efficiency of 98.87%, a voltage efficiency of 91.14%, and an energy efficiency of 90.11% (Fig. 4).

Example 4

6.3019g polysulfone (PSF), 4.8015g polyvinylpyrrolidone (PVP) was dissolved in 48.0144g DMAC, stirred for 48 hours, the formed polymer solution was spread on a glass plate, and then the glass plate was transferred to a 50°C hot stage Heating for 48 hours, PVP phase separation was induced during the solvent volatilization process, and a polysulfone membrane with a microphase separation structure was obtained. After cooling at room temperature, the glass plate was placed in a water tank, and the membrane thickness was 42 μm. An all-vanadium redox flow battery was assembled using the prepared ion-conducting membrane with a microphase separation structure, in which the catalytic layer was activated carbon felt, the bipolar plate was a graphite plate, the effective area of the membrane was 48cm ² , and the current density was 80mA.cm ^-2 . The vanadium ion concentration in the solution is 1.50mol L ^-1 , and the H ₂ SO ₄ concentration is 3mol L ^-1 . The assembled flow battery has a coulombic efficiency of 99.36%, a voltage efficiency of 88.66%, and an energy efficiency of 88.10% (Fig. 4).

Example 5

7.2048g polyvinylidene fluoride (PVDF), 4.8015g polyvinylpyrrolidone (PVP) was dissolved in 45.3598g DMAC, stirred for 48 hours, and the polymer solution formed was spread on a glass plate, and then the glass plate was transferred to 50 ℃ heat Heating on the stage for 48 hours, PVP phase separation was induced during the solvent volatilization process, and a polyvinylidene fluoride film (PVDF for short) with a microphase separation structure was obtained. After cooling at room temperature, the glass plate was placed in a water tank, and the film thickness was 45 μm. An all-vanadium redox flow battery was assembled using the prepared ion-conducting membrane with a microphase separation structure, in which the catalytic layer was activated carbon felt, the bipolar plate was a graphite plate, the effective area of the membrane was 48cm ² , and the current density was 80mA.cm ^-2 . The concentration of vanadium ions in the liquid is 1.50mol L ^-1 , and the concentration of H ₂ SO ₄ is 3molL ^-1 . The assembled flow battery has a coulombic efficiency of 97.62%, a voltage efficiency of 89.39%, and an energy efficiency of 87.26%.

It can be seen from the topography image of the microphase separation structure prepared in Figure 1 that the surface of the membrane facing the air side (Figure 1a and b) has a more obvious microphase separation structure, mainly because the water vapor in the air can further induce Separation of hydrophilic and hydrophobic phases, thereby forming membranes with structures with different degrees of microphase separation.

It can be seen from the surface resistance test in Figure 2 that the surface resistance of the ion-conducting membrane with a microphase separation structure is lower than that of the Nafion 115 membrane, so this type of membrane should be used in flow batteries, especially in all-vanadium flow batteries. With high ionic conductivity, single cells assembled with this type are expected to obtain high voltage efficiency.

Figure 3 Vanadium permeation test shows that the vanadium ion permeation rate of the ion-conducting membrane with microphase separation structure is much lower than that of Nafion 115 membrane, so this type of membrane is used in flow batteries, especially all-vanadium Flow batteries should have high ion selectivity, and single cells assembled with this type are expected to obtain high Coulombic efficiency.

It can be seen from Figure 4 that due to the special microphase separation structure in the membrane, compared with the Nafion115 membrane, the single cell assembled with the ion conduction membrane with the microphase separation structure has excellent performance under the condition of 80mA cm ^-2 battery performance.

It can be seen from the battery cycle stability test in Figure 5 that the polyethersulfone ion-conducting membrane with a microphase separation structure has excellent stability in the all-vanadium redox flow battery.

It can be seen from Figure 6 that compared with the Nafion 115 membrane, under the condition of 80mA cm ^-2 , the single cell assembled with the polyethersulfone ion-conducting membrane with microphase separation structure has excellent capacity retention.

Claims (7)

1. An ion-conducting membrane with a micro-phase separation structure, characterized in that: one or more of the hydrophobic polymer resins and one or more of the hydrophilic polymer resins are raw materials, dissolved It is prepared by volatilizing the solvent after the organic solvent, and the hydrophilic phase is induced to aggregate during the solvent volatilization process, thereby forming an ion-conducting membrane with a microphase separation structure with hydrophobic regions and hydrophilic regions; Wherein the mass ratio of the hydrophobic polymer resin to the hydrophilic polymer resin is 0.5-5. 2. The ion-conducting membrane with microphase separation structure according to claim 1, characterized in that: said hydrophobic polymer resin is polyethersulfone, polysulfones, polyetherketones, polytetrafluoroethylene, One or more of polyvinylidene fluoride or polystyrene; the hydrophilic polymer resin is sulfonated polysulfone, sulfonated polyimide, sulfonated polyether ketone, sulfonated polybenzimidazole, poly One or more of vinylpyrrolidone or polyethylene glycol. 3. The preparation method of an ion-conducting membrane with a microphase-separated structure according to claim 1, wherein, said phase-separated structure is one of a layered structure, a co-continuous structure, a spherical structure or a columnar structure. species or two or more. 4. a method for preparing an ion-conducting membrane with a microphase separation structure described in claim 1, 2 or 3, characterized in that: The ion-conducting membrane with a microphase separation structure is prepared by the following steps: (1) Dissolve the hydrophobic polymer resin and the hydrophilic polymer resin in an organic solvent, and fully stir at a temperature of 20-100°C for 20-60 hours to make a blended uniform solution; wherein the hydrophobic polymer resin and the hydrophilic polymer resin The mass ratio of water-based polymer resin is between 0.5-5; (2) Pour the blended solution prepared in step (1) onto a non-woven fabric substrate or directly onto a glass plate, volatilize the solvent for 0 to 60 seconds, and then evaporate the solvent to dryness at a temperature of 40 to 200°C to form a film; the solvent volatilizes The aggregation of the hydrophilic phase is induced to obtain a membrane with a microphase separation structure; the thickness of the membrane is between 20 and 500 μm. 5. according to the preparation method of the ion-conducting membrane with microphase separation structure described in claim 4, it is characterized in that: described organic solvent is dimethylsulfoxide (DMSO), N,N'-dimethylacetamide One or more of (DMAC), N-methylpyrrolidone (NMP), N,N'-dimethylformamide (DMF), tetrahydrofuran (THF); hydrophobic polymer resin and high hydrophilicity The mass concentration of the molecular resin in the organic solvent is 10-50%. 6. An application of the ion-conducting membrane with a micro-phase separation structure according to any one of claims 1-3, characterized in that: the ion-conducting membrane with a micro-phase separation structure is used in a flow battery. 7. The application according to claim 6, wherein the flow battery includes an all-vanadium flow battery, a zinc/cerium flow battery, a vanadium/bromine flow battery or an iron/chromium flow battery.