A composite membrane material for aqueous organic liquid flow battery with wide pH adaptability and its preparation and application

Abstract

The present invention discloses a membrane material for aqueous organic liquid flow batteries with wide pH adaptability and its preparation and application. The membrane material is a montmorillonite material with suitable interlayer spacing and charge characteristics composited onto a porous membrane matrix. The montmorillonite layer with charge characteristics is negatively charged in an alkaline medium, and has a significant charge repulsion effect on the active substances in the alkaline organic liquid flow battery system, giving the membrane material high ion selectivity; in an acidic medium, the cations between the montmorillonite layers are replaced by protons and have high proton conductivity. At the same time, after the interlayer cations are replaced by protons, the interlayer spacing is improved, which can effectively regulate the selectivity of the active substances in the acid-base organic liquid flow battery system. The prepared composite membrane material has a wide pH adaptability, has good performance in organic liquid flow battery systems of different pH, and can give the battery high battery performance.

Description

Technical Field

[0001] The present invention relates to a composite membrane material for an aqueous organic liquid flow battery with wide pH adaptability and a preparation method and application thereof, and in particular to an application of the composite membrane material in an aqueous organic liquid flow battery system. Background Art

[0002] Liquid flow battery energy storage technology has the advantages of safety, reliability, long life and high efficiency, and has become one of the preferred technologies for large-scale energy storage. All-vanadium liquid flow battery is one of the most mature liquid flow battery technologies currently developed, but due to the influence of vanadium resources and prices, the cost of this battery is relatively high; in addition, the open circuit voltage of all-vanadium liquid flow battery is relatively low (1.2V) and the concentration of active substances is low, which makes the energy density of this battery low. Therefore, the development of a new generation of low-cost, high-energy-density liquid flow battery system has become a current research hotspot. Among the many new liquid flow battery systems, the aqueous organic liquid flow battery system has the advantages of rich organic redox couple resources, easy structure and properties to regulate, and has received widespread attention in liquid flow batteries in recent years, such as quinone-based liquid flow battery system, phenazine-based liquid flow battery system, TEMPO-type liquid flow battery system and viologen-type liquid flow battery system. As a key core component common to aqueous organic liquid flow batteries, the ion conduction membrane plays a role in blocking the mutual connection of positive and negative active substances and transferring charge-balancing ions to form a battery circuit. Therefore, the ion conduction membrane is required to have the following characteristics: ① high ion selectivity to reduce the mutual penetration of positive and negative active substances to reduce battery capacity decay; ② high ion conductivity to reduce battery voltage loss; ③ low cost and high stability (alkali stability, oxidation stability) to facilitate large-scale production and application; ④ excellent resistance to organic pollution to ensure efficient and stable operation of the battery.

[0003] At present, the research on ion-conducting membranes for aqueous organic flow batteries is very limited, and there are few types of ion-conducting membranes available for use (Table 1). ) has become the preferred membrane material for aqueous organic flow batteries due to its excellent stability. However, the production process of perfluorosulfonic acid cation conductive membrane is complicated and expensive (about 600-800 US dollars / square meter), which restricts the further development of aqueous organic flow batteries; in addition, the perfluorosulfonic acid cation conductive membrane (Nafion) has a large membrane resistance in the alkaline aqueous organic flow battery system, resulting in low battery performance. In addition, in the aqueous organic flow battery environment, the stability of non-fluorinated ion exchange membranes is poor. For example, the quaternary ammonium groups on non-fluorinated anion exchange membranes will undergo Hoffman elimination and nucleophilic substitution reactions, resulting in poor stability of this type of membrane, which cannot meet the needs of long-term operation in aqueous organic flow batteries. Therefore, the design and development of high-performance, low-cost membrane materials is a key bottleneck technology for promoting the practical application of aqueous organic flow batteries.

[0004] Table 1 Performance comparison of aqueous organic flow batteries assembled using different membrane materials

[0005]

[0006] Summary of the invention

[0007] Montmorillonite is a typical 2:1 layered aluminosilicate structure, that is, each structural unit consists of two SiO 2 Tetrahedron, with an Al 2 O 3 The structural units are arranged periodically to form montmorillonite layers. 4+ Easy to be Al 3+ Substitution, part of the Al in the alumina octahedral layer 3+ Easily affected by Mg 2+ 、Zn 2+ , Ca 2+ Plasma substitution will cause the internal charge of the MMT structure unit to be unbalanced and negatively charged. + , Ca 2+ Mg 2+Various cations, such as hydrated cations, can be exchanged with cations in the solution to achieve controllable interlayer spacing. In order to solve the above problems, the present invention prepares a composite membrane based on a montmorillonite composite layer. This type of membrane material is a montmorillonite material with suitable interlayer spacing and charge characteristics composited onto a porous membrane matrix. The montmorillonite layer with charge characteristics is negatively charged in an alkaline medium, and has an obvious charge repulsion effect on the active substances in the alkaline organic liquid flow battery system, giving the membrane material high ion selectivity; in an acidic medium, the cations between the montmorillonite layers are replaced by protons and have a high proton conductivity. At the same time, after the interlayer cations are replaced by protons, the interlayer spacing is improved, which can effectively regulate the selectivity of the active substances in the acid-base organic liquid flow battery system. The prepared composite membrane material has a wide pH adaptability, has good performance in organic liquid flow battery systems of different pH, and can give the battery high battery performance. To achieve the above purpose, the technical scheme adopted by the present invention is as follows:

[0008] The present invention provides a composite membrane, comprising a porous ion conductive membrane base membrane and a montmorillonite layer composited with the surface of the base membrane;

[0009] The loading of montmorillonite on the porous ion conducting membrane substrate is 0.5-4 mg cm -2 , preferably 1-3 mg cm -2 .

[0010] Furthermore, in the above technical solution, the thickness of the montmorillonite layer is 1 to 10 μm.

[0011] Furthermore, in the above technical solution, montmorillonite includes but is not limited to hydrogen type and sodium type. The base film material of the porous ion conducting membrane is a polymer resin.

[0012] The present invention further provides a method for preparing the composite film, comprising the following steps:

[0013] (1) Using polymer resin as raw material, a porous ion conductive membrane base film is prepared by a phase conversion method;

[0014] (2) compounding a dispersion containing montmorillonite onto the porous ion conductive membrane substrate in step (1);

[0015] The dispersion in step (2) is composed of a polymer binder, montmorillonite, and a solvent, wherein the mass ratio of the polymer binder to the montmorillonite is 0.5:9.5 to 3:7, the solid content of the polymer binder and the montmorillonite in the dispersion is 1 to 40 wt %; the loading of the montmorillonite on the porous ion conductive membrane substrate is 0.5 to 4 mg cm -2 .

[0016] Furthermore, in the above technical solution, in the step (2), the mass ratio of the polymer binder to the montmorillonite is 1:9 to 2:8, the solid content of the polymer binder and the montmorillonite in the dispersion is 5 to 10 wt%; the loading of the montmorillonite on the porous ion conductive membrane substrate is 1 to 3 mg cm -2 ;

[0017] The polymer binder is one or two or more of Nafion solution, PVDF, SPEEK, PBI, PES, PSF, PAN, etc.;

[0018] Furthermore, in the above technical solution, in step (2), the composite method includes spraying, spin coating, filtration, gel adhesion and other methods.

[0019] The present invention provides the use of the composite membrane as a separator for an aqueous organic liquid flow battery, with the side with the montmorillonite composite layer facing the organic redox electrode side of the battery.

[0020] Furthermore, in the above technical solution, the aqueous organic liquid flow battery includes an alkaline system liquid flow battery based on quinone redox couples and an acidic system liquid flow battery based on phenazine redox couples.

[0021] Furthermore, in the above technical solution, the supporting electrolyte of the alkaline system flow battery based on quinone redox couple contains 0.1 to 2 mol L -1 OH - solution (pH 13-14.3); the supporting electrolyte of the acidic system flow battery based on the phenazine redox couple contains 0.1-5 mol L -1 H + Solution (pH -0.7 to 1).

[0022] The present invention provides an aqueous organic liquid flow battery, wherein the diaphragm thereof is the composite membrane, which is a composite membrane material for an aqueous organic liquid flow battery having wide pH adaptability.

[0023] Beneficial results of the present invention:

[0024] 1. The composite membrane material based on the montmorillonite composite layer prepared by the present invention can simultaneously obtain high battery performance in organic liquid flow battery systems of acidic and alkaline media;

[0025] 2. The composite membrane material based on the montmorillonite composite layer prepared by the present invention is negatively charged in an alkaline medium, has a significant charge repulsion effect on the active substances in the alkaline organic flow battery system, and gives the membrane material higher ion selectivity;

[0026] 3. The composite membrane material based on the montmorillonite composite layer prepared by the present invention has high proton conductivity after the cations between the montmorillonite layers are replaced by protons in an acidic medium. At the same time, after the cations between the layers are replaced by protons, the interlayer spacing is improved, which can effectively regulate the selectivity of active substances in the organic liquid flow battery system of the acidic system;

[0027] 4. The composite membrane material based on the montmorillonite composite layer prepared by the present invention has excellent anti-pollution ability to organic redox couples due to the charge characteristics and controllable interlayer spacing of the montmorillonite composite layer, thereby giving the battery high cycle stability;

[0028] 5. The composite membrane material based on the montmorillonite composite layer prepared by the present invention broadens the application scope of membrane materials for aqueous organic liquid flow batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 XRD spectra of montmorillonite (MMT) and montmorillonite with sodium ions as interlayer cations (Na-MMT);

[0030] Figure 2 a, b, and c are TEM images of MMT, respectively; d, e, and f are TEM images of Na–MMT, respectively;

[0031] Figure 3 is the potential value of Na-MMT in ultrapure water;

[0032] Figure 4 a and b are the surface morphology images of PES-based membranes at different magnifications; c and d are the surface morphology images of sodium ion-type montmorillonite composite ion-conducting membranes;

[0033] Figure 5 a and b are cross-sectional morphology images of PES-based membranes at different magnifications; and c and d are cross-sectional morphology images of sodium ion-type montmorillonite composite ion-conducting membranes;

[0034] Figure 6 Alkaline Alizarin Red-Iron flow battery assembled with PM membrane and Na-MMT-M membrane at 40 mA cm -2 Capacity retention rate under working current density conditions. DETAILED DESCRIPTION

[0035] Alkaline Alizarin Red-Iron Liquid Flow Battery Performance Test: Both the positive and negative electrodes use carbon felt as electrodes, and the positive electrode electrolyte is 0.2 mol L -1 Na 4 Fe(CN) 6 +1mol L -1 KOH solution; the negative electrode electrolyte is 0.1 mol L -1Alizarin Red + 1.2 mol L -1 KOH solution; the volume of positive and negative electrolytes is 10 mL each; the battery adopts constant current charge and discharge mode, and the working current density is: 40 mA cm -2 ; The battery charge and discharge cut-off voltages are 1.7V and 0.4V.

[0036] Acidic vanadium-methylene blue flow battery performance test: Both positive and negative electrodes use carbon felt as electrodes, 15mL 0.1molL -1 MB+3mol L -1 H 2 SO 4 As the positive electrolyte, 20 mL of 1.5 mol L -1 V 2+ +3mol L -1 H 2 SO 4 As the negative electrode electrolyte; the battery adopts constant current charge and discharge mode, and the working current density is: 40mA cm -2 ;The battery charge and discharge cut-off voltages are 1.3V and 0.3V.

[0037] Figure 1 The analytical grade montmorillonite K-10 (denoted by MMT) purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. and the treated montmorillonite K-10 powder was placed in 0.5 mol L -1 H 2 SO 4 The solution was treated for 24 h to convert the cations between the MMT layers into the intermediate hydrogen ion montmorillonite (H-MMT) to achieve complete protonation. The prepared H-MMT was then placed in 1 mol L -1 H-MMT was converted into sodium ion montmorillonite (Na-MMT) by treating in NaOH solution for 24h. XRD spectrum of montmorillonite K-10. Compared with the initial MMT structure, the crystal phase of H-MMT and Na-MMT did not change significantly after acid and alkali treatment, indicating that montmorillonite has good acid and alkali stability. For the original MMT, due to the highly variable size and distribution of interlayer cations, it has an unclear weak peak near 5.8°. After interlayer cation exchange, the peak intensity of Na-MMT is enhanced, indicating that the interlayer cations are transformed from disordered to ordered structure.

[0038] In order to further study the stability of montmorillonite, MMT and Na-MMT before and after treatment were characterized by TEM. Figure 2 TEM spectra of MMT and Na-MMT. Figure 2 a and Figure 2 d are the surface morphologies of MMT and Na-MMT, respectively. It can be seen that the two are similar in size. Figure 2 b, 2c, 2e and 2f are high-magnification TEM images of MMT and Na-MMT. It can be seen that the microstructure of montmorillonite before and after acid and alkali treatment is basically the same, showing a regular structure with multiple layers arranged closely, which further proves that the structure of MMT does not change significantly after acid and alkali treatment. This shows that MMT can exist stably in a wide pH medium and is expected to be applied to aqueous organic flow batteries in different acid and alkali systems.

[0039] In order to study the surface charge characteristics of montmorillonite, the treated montmorillonite sample Na-MMT was dispersed in ultrapure water and its surface potential value was tested. Figure 3 The Zata potential diagram of Na-MMT shows that the Zata potential of Na-MMT is about -29mV, indicating that the charge on the surface of Na-MMT is negative. Negatively charged montmorillonite has a good repulsive effect on negatively charged organic redox pairs. At the same time, the controllable interlayer spacing has a good selectivity for larger-sized organic redox pairs and has a good anti-pollution ability for organic redox pairs.

[0040] Preparation of composite membrane materials:

[0041] (1) Preparation of porous ion-conducting membrane base film:

[0042] The polymer polyethersulfone (PES) and sulfonated polyetheretherketone (SPEEK) (as a pore-adjusting agent to adjust the structure of the polyethersulfone-based membrane) are dissolved in N,N-dimethylacetamide (DMAc) to obtain a PES-SPEEK casting solution with a solid content of 35wt%, wherein the mass of SPEEK accounts for 8wt% of the total mass of PES-SPEEK. After stirring evenly and standing for degassing, the above solution is uniformly poured onto a clean and flat glass plate. Under the condition that the humidity is not higher than 10%, a 200μm thick scraper is used to scrape out a smooth film. After that, the glass plate with the film is immersed in water, and the PES-SPEEK ion conductive membrane will automatically fall off. The membrane thickness is ~110μm, expressed in PM.

[0043] (2) Montmorillonite composite to porous ion-conducting membrane base film:

[0044] After MMT or the H-MMT or Na-MMT (H-MMT) obtained above is immersed in an alkaline solution, H + The cations in the alkaline solution will be replaced by Na-MMT or K-MMT) and evenly dispersed in 1wt% Nafion solution (the mass ratio of Na-MMT powder (g) to 1wt% Nafion binder (g) (calculated by the mass of Nafion resin) is 8:2), and then the above suspension is evenly dispersed in ultrasound for 3 hours. 2The carrier gas is sprayed at a pressure of 0.4 MPa, and it is evenly sprayed on one side of the PM substrate with a spray gun to obtain a montmorillonite-composite polyethersulfone composite ion conductive membrane.

[0045] Using the method in (2), the loading of Na-MMT on PM was 1.2 mg cm -2 The composite membrane material is represented by Na-MMT-M; the loading of Na-MMT on PM is 0.6 mg cm -2 The composite membrane material is represented by Na-MMT-M1; the loading of Na-MMT on PM is 3.8 mg cm -2 The composite membrane material is represented by Na-MMT-M2; the loading of MMT on PM is 1.3 mg cm -2 The composite membrane material is represented by MMT-M; the loading of H-MMT on PM is 1.3 mg cm -2 The composite membrane material is represented by H-MMT-M;

[0046] Figure 4 The surface morphology of the prepared polyethersulfone-based membrane PM and montmorillonite composite ion-conducting membrane Na-MMT-M. It can be seen that the surface of the PM-based membrane ( Figure 4 a, 4b) presents a smooth and dense structure. After Na-MMT is compounded onto the PM surface, the dense surface is evenly covered by montmorillonite ( Figure 4 c, 4d), the Na-MMT on the membrane surface is stacked in a layered form.

[0047] Figure 5 The cross-sectional morphology of PM and Na-MMT-M ion conducting membranes. It can be seen from the figure that the PM cross-sectional morphology is an asymmetric structure, consisting of a cortex and a finger-like macroporous support layer ( Figure 5 a, 5b). After the sodium ion montmorillonite is compounded onto the surface of the PM base film, a Na-MMT layer with a thickness of about 5 μm is formed ( Figure 5 c, 5d), the interlayer cations are easily exchanged with the charge-balancing ions in the solution, which can ensure that the charge-balancing ions quickly pass through the montmorillonite layer, thereby ensuring the high ionic conductivity of Na-MMT-M.

[0048] The following examples are provided to further illustrate the present invention, but not to limit the scope of the present invention. In assembling a battery, the above-obtained material is used as a separator, with the side with the montmorillonite composite layer facing the organic redox couple side of the battery.

[0049] Comparative Example 1

[0050] Alkaline Alizarin Red-Iron flow battery assembled with PM at 40 mA cm -2Under the working current density, the battery coulombic efficiency (CE) is 97.16%, the voltage efficiency (VE) is 89.47%, and the battery capacity retention rate is only 74.46% after 11 cycles ( Figure 6 ).

[0051] Example 1

[0052] Alkaline Alizarin Red-Iron flow battery assembled with Na-MMT-M at 40 mA cm -2 Under the working current density conditions, the battery coulombic efficiency (CE) is 98.95%, the voltage efficiency (VE) is 88.87%, and the capacity retention rate of the battery remains at 79.08% after 86 cycles. The battery has been running stably for more than 200 cycles and its efficiency remains stable.

[0053] Comparative Example 2

[0054] PM-assembled acidic vanadium-methylene blue flow battery at 40 mA cm -2 Under the working current density, the battery coulombic efficiency (CE) is 94.32%, the voltage efficiency (VE) is 89.26%, and the battery capacity retention rate is only 68.16% after 15 cycles. After disassembling the battery, it was found that the membrane surface adsorbed a lot of blue methylene blue active substances, indicating that the membrane was seriously polluted.

[0055] Example 2

[0056] Acidic vanadium-methylene blue flow battery assembled with Na-MMT-M has a high conductivity at 40 mA cm -2 Under the working current density, the battery coulombic efficiency (CE) increased to 98.79%, the voltage efficiency (VE) was 89.77%, and the battery capacity retention rate remained at 82.15% at 92 cycles, and the battery performance was significantly improved. After disassembling the battery, it was found that the blue color on the membrane surface was lighter, indicating that less methylene blue active substances were adsorbed, and the membrane pollution problem was well improved.

[0057] Example 3

[0058] Acidic vanadium-methylene blue flow battery assembled with Na-MMT-M1 at 40 mA cm -2 Under the working current density conditions, the battery coulombic efficiency (CE) increased to 95.65%, the voltage efficiency (VE) was 89.69%, and the capacity retention rate was 72.39% after 56 cycles. The battery performance was improved compared with the battery assembled with PM membrane.

[0059] Example 4

[0060] Acidic vanadium-methylene blue flow battery assembled with Na-MMT-M2 at 40 mA cm -2Under the working current density conditions, the battery coulombic efficiency (CE) increased to 99.21%, the voltage efficiency (VE) was 83.17%, and the capacity retention rate of the battery was 83.27% at 77 cycles. The battery performance was improved compared with the battery assembled with PM membrane, but due to the increase in the thickness of the montmorillonite layer, the membrane resistance increased and the battery voltage efficiency was significantly reduced.

[0061] Example 5

[0062] The acidic vanadium-methylene blue flow battery was assembled with MMT-M. The MMT interlayer cations on MMT-M were easily absorbed by H in the battery system. + Replacement to form H-MMT-M. At 40 mA cm -2 Under the working current density, the battery coulombic efficiency (CE) increased to 98.82%, the voltage efficiency (VE) was 88.69%, and the battery capacity retention rate remained at 81.21% after 100 cycles, and the battery performance was significantly improved. After disassembling the battery, it was found that the blue color on the membrane surface was lighter, indicating that less methylene blue active substances were adsorbed, and the membrane pollution problem was well improved.

[0063] Example 6

[0064] Acidic vanadium-methylene blue flow battery assembled with H-MMT-M has a high conductivity at 40 mA cm -2 Under the working current density, the battery coulombic efficiency (CE) increased to 98.63%, the voltage efficiency (VE) was 89.12%, and the battery capacity retention rate remained at 83.19% at 91 cycles, and the battery performance was significantly improved. After disassembling the battery, it was found that the blue color on the membrane surface was lighter, indicating that less methylene blue active substances were adsorbed, and the membrane pollution problem was well improved.

[0065] Example 5

[0066] Alkaline Alizarin Red-Iron flow battery assembled with MMT-M at 40 mA cm -2 Under the working current density conditions, the battery coulombic efficiency (CE) is 99.23%, the voltage efficiency (VE) is 88.32%, and the capacity retention rate of the battery remains at 80.44% after 90 cycles. The battery operates stably for more than 200 cycles and its efficiency remains stable.

[0067] Example 6

[0068] Alkaline Alizarin Red-Iron flow battery assembled with H-MMT-M at 40 mA cm -2Under the working current density conditions, the battery coulombic efficiency (CE) is 99.39%, the voltage efficiency (VE) is 88.67%, and the capacity retention rate of the battery remains at 81.32% after 112 cycles. The battery has been running stably for more than 170 cycles and the efficiency remains stable.

Claims

1. Application of a composite membrane as a separator for an aqueous organic liquid flow battery, characterized in that: The side with the montmorillonite composite layer is directed toward the organic redox couple side of the battery; The composite membrane comprises a porous ion-conducting membrane base membrane and a montmorillonite layer composited with the surface of the base membrane; The loading of montmorillonite on the porous ion conducting membrane substrate is 0.5-4 mg cm -2 ; The aqueous organic liquid flow battery includes an alkaline system liquid flow battery based on quinone redox couples and an acidic system liquid flow battery based on phenazine redox couples.

2. The use according to claim 1, characterized in that: The thickness of the montmorillonite layer is 1 to 10 μm.

3. The use according to claim 1, characterized in that: The porous ion-conducting membrane base film is made of polymer resin; the loading amount of montmorillonite on the porous ion-conducting membrane base film is 1 to 3 mg cm -2 .

4. The use according to any one of claims 1 to 3, characterized in that: The method for preparing the composite film comprises the following steps: (1) Using polymer resin as raw material, a porous ion conductive membrane base film is prepared by a phase conversion method; (2) Compounding the dispersion containing montmorillonite onto the porous ion conductive membrane substrate in step (1); the compounding method includes spraying, spin coating, suction filtration, and gel adhesion; The dispersion in step (2) is composed of a polymer binder, montmorillonite, and a solvent, wherein the mass ratio of the polymer binder to the montmorillonite is 0.5:9.5 to 3:7, the solid content of the polymer binder and the montmorillonite in the dispersion is 1 to 40 wt %; the loading of the montmorillonite on the porous ion conductive membrane substrate is 0.5 to 4 mg cm -2 .

5. The use according to claim 4, characterized in that: In the step (2), the mass ratio of the polymer binder to the montmorillonite is 1:9 to 2:8, the solid content of the polymer binder and the montmorillonite in the dispersion is 5 to 10 wt%; the loading of the montmorillonite on the porous ion conductive membrane substrate is 1 to 3 mg cm -2 ; The polymer binder is one or two or more of Nafion solution, PVDF, SPEEK, PBI, PES, PSF and PAN.

6. The use according to claim 4, characterized in that: The composite method described in step (2) includes spraying, spin coating, filtration, and gel adhesion methods.

7. The use according to claim 1, characterized in that: The supporting electrolyte of the alkaline system flow battery based on quinone redox couple is 0.1 to 2 mol L -1 OH - Solution; the acidic system flow battery supporting electrolyte based on phenazine redox couple contains 0.1 to 5 mol L -1 H + Solution.

Images