A non-ionic ion-conducting membrane and its preparation and application

Abstract

The present invention discloses the application of a non-ionic ion-conducting membrane in an alkaline zinc-iron flow battery. This type of membrane is prepared by uniformly dissolving an organic polymer resin and a water-soluble polymer containing oxygen functional groups in an organic solvent and heating and drying the solvent at a certain temperature. The prepared membrane material is processed with a non-solvent to obtain a non-ionic ion-conducting membrane. During the non-solvent treatment process, a part of the water-soluble polymer containing oxygen functional groups dissolves in the non-solvent, forming a nano-scale pore structure, thereby promoting ion conduction; the water-soluble polymer containing oxygen functional groups wrapped by the water-insoluble polymer resin can further promote the conduction of charge-balanced ions in the membrane, thereby improving the ion conductivity of the membrane material. The designed and prepared non-ionic ion-conducting membrane has excellent battery performance in an alkaline zinc-iron flow battery.

Description

Technical Field

[0001] The present invention relates to an ion conducting membrane and preparation and application thereof, and in particular to application of the membrane in an alkaline zinc-iron liquid flow battery. Background Art

[0002] At present, actively promoting the transformation of energy structure and seizing the new round of technological and economic commanding heights has become a consensus among countries around the world, and the development and utilization model of the "distributed energy + energy storage" system has received widespread attention. my country attaches great importance to the development of distributed energy. In recent years, driven by relevant national policies and plans, the development of distributed energy has continued to accelerate. The state has approved 108 pilot demonstration projects, which have become a new feature of distributed energy development. Distributed energy will play a more important role in my country's energy production in the future, effectively improving resource utilization efficiency and alleviating environmental problems. It is estimated that by 2030, the scale of distributed energy development in my country will reach 350-570GWh, accounting for 11.5%-19.1% of the national installed power capacity. Therefore, distributed energy storage technology will have broad application prospects in the future. In addition, the development of distributed energy storage technology can reserve mature technology for the large-scale entry of photovoltaic power generation into thousands of households in the future, increase the penetration rate of new energy from 15% to 40%, effectively alleviate the capacity expansion of distribution networks, and save users' electricity bills.

[0003] At present, the more mature electrochemical energy storage technologies mainly include liquid flow batteries, lithium-ion batteries, lead-acid batteries, etc. Compared with other energy storage technologies, liquid flow battery technology has the advantages of safety, reliability, long life, and environmental friendliness. At present, liquid flow battery energy storage technology represented by all-vanadium liquid flow batteries has developed rapidly and is now in the stage of industrialization and promotion. Compared with other liquid flow battery technologies, all-vanadium liquid flow battery technology has the problems of high one-time investment and low energy density, and is more suitable for large-scale energy storage.

[0004] Zinc-iron flow batteries use abundant zinc and iron as active materials, with low cost (~$100 / kWh) and high open circuit voltage (1.74V), which is very suitable for application in distributed energy and home energy storage. Since GB.Adams et al. proposed the concept of zinc-iron flow batteries in 1979, compared with the all-vanadium flow batteries and zinc-bromine flow batteries currently in the demonstration application stage, zinc-iron flow batteries have not yet made significant breakthroughs. One of the reasons is that the commercialized perfluorosulfonic acid ion exchange membrane (trade name: ) The production process is complex and expensive (about $600-800 / m2), and the battery performance assembled with Nafion membrane is poor (the battery has a low current density at 35 mA cm -2Under the working current density, the coulombic efficiency is only 76%, which seriously affects the performance of the battery. The traditional anion exchange membrane has been proven to have poor alkali stability in alkaline fuel cells and cannot meet the needs of long-term operation in alkaline zinc-based flow batteries. Summary of the invention

[0005] In order to solve the above problems, the present invention prepares a non-ionic ion conduction membrane. This type of membrane is prepared by uniformly dissolving an organic polymer resin and a water-soluble polymer containing oxygen functional groups in an organic solvent, and heating and drying the solvent at a certain temperature. The prepared membrane material is treated with a non-solvent to obtain a non-ionic ion conduction membrane. During the non-solvent treatment process, a part of the water-soluble polymer containing oxygen functional groups is dissolved in the non-solvent to form a nanoscale pore structure, thereby promoting the conduction of ions; the water-soluble polymer containing oxygen functional groups wrapped by the water-insoluble polymer resin can further promote the conduction of charge-balancing ions in the membrane, thereby improving the ion conductivity of the membrane material. The designed and prepared non-ionic ion conduction membrane has excellent alkali resistance and stability, and its performance can be effectively regulated according to the content and type of the water-soluble polymer containing oxygen functional groups, and has good battery performance in alkaline zinc-iron liquid flow batteries.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a non-ionic ion conducting membrane, the method for preparing the non-ionic ion conducting membrane is as follows:

[0008] The organic polymer resin raw material and the water-soluble polymer containing oxygen functional groups are dissolved in an organic solvent to form a uniform solution and then uniformly coated on a substrate; the organic polymer resin raw material is one or more of polyethersulfone, polysulfone, chloromethylated polysulfone, polyetherketone, and polyolefin; the water-soluble polymer containing oxygen functional groups is one or more of polyvinyl alcohol (PVA), polyethylene glycol (PEG), sodium polyacrylate, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and sulfonated polyetheretherketone;

[0009] The organic matter concentration in the prepared solution is 1wt% to 50wt%, preferably 15wt% to 30wt%; the ratio of the organic polymer resin to the water-soluble polymer containing oxygen functional groups is 7:3 to 3:7, preferably 5:5 to 4:6.

[0010] The organic solvent in step (1) is one or more of dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF);

[0011] The uniform solution is evenly coated on a flat substrate and dried at room temperature to 100° C. for 1 h to 100 h, wherein the temperature is preferably 50° C. to 70° C., and the drying time is preferably 3 h to 12 h.

[0012] The prepared membrane material is treated with a non-solvent for 12 hours to 100 hours to obtain a non-ionic ion conductive membrane, and the treatment time is preferably 12 hours to 48 hours;

[0013] The non-solvent is one or more of water and a mixed solution of water / alcohol; wherein the volume ratio of water / alcohol is 99.9:0.1 to 60:40, preferably 99.9:0.1 to 90:10; the alcohol is one or more of ethanol, methanol, isopropanol and glycerol;

[0014] The non-ionic ion conducting membrane is prepared by the above method;

[0015] The application of the non-ionic ion conductive membrane is: application in alkaline zinc-iron liquid flow batteries.

[0016] Beneficial results of the present invention:

[0017] 1. This type of membrane is prepared by blending an organic polymer resin without ion exchange groups with a water-soluble polymer resin containing oxygen functional groups and then drying it to form a membrane. The membrane material is treated with a non-solvent to obtain a non-ionic ion conductive membrane. During the non-solvent treatment, part of the water-soluble polymer resin containing oxygen functional groups will dissolve in the non-solvent to form a nano-scale pore structure, thereby promoting the conduction of ions; in addition, part of the water-soluble polymer resin containing oxygen functional groups is preserved in the membrane material because it is wrapped by the organic polymer resin insoluble in the non-solvent. The oxygen-containing functional groups in the water-soluble polymer resin react with K in the electrolyte in the alkaline zinc-iron flow battery. + Or Na + Combining with basic oxygen can achieve OH - Ion conduction can significantly improve the ion conductivity of membrane materials in alkaline zinc-iron systems.

[0018] 2. The non-ionic ion-conducting membrane prepared by the present invention can effectively avoid the problems existing in the conventional ion-conducting membrane containing anion exchange groups (the conventional anion exchange membrane has poor alkali resistance and stability, and the commercial perfluorosulfonic acid ion exchange membrane has low performance).

[0019] 3. The non-ionic ion-conducting membrane prepared by the present invention transmits charge-balancing ions through the mechanism of pore size screening conduction in the nanoscale pore structure and alkaline oxygen-conducting ions formed in the membrane. The synergistic effect of the two greatly improves the ion conductivity of the membrane, thereby significantly improving the voltage efficiency of the battery.

[0020] 4. The non-ionic ion conductive membrane prepared by the present invention broadens the preparation method of membrane materials for alkaline zinc-iron liquid flow batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 In Comparative Example 1, alkaline zinc-iron flow batteries assembled with Nafion membranes of different thicknesses were -2 Battery performance under working current density conditions;

[0022] Figure 2 In Comparative Example 2, the alkaline zinc-iron flow battery assembled with PES-PVP membrane was -2 The charge and discharge curves under the working current density conditions;

[0023] Figure 3 In Comparative Example 3, the alkaline zinc-iron flow battery assembled with PES-SPEEK membrane was -2 Performance diagram under working current density conditions;

[0024] Figure 4 (ac) IR and (d) NMR spectra of a non-ionic ion-conducting membrane prepared with polyethylene glycol (PEG) as a water-soluble polymer containing oxygen functional groups before and after water treatment (water treatment for 48 h);

[0025] Figure 5 Schematic diagram of the application of non-ionic ion-conducting membranes prepared with polyethylene glycol (PEG) as water-soluble polymers containing oxygen functional groups in alkaline zinc-iron flow batteries;

[0026] Figure 6 The application of membrane materials prepared by using polyethersulfone (PES) as the substrate and different contents of PEG as the water-soluble polymer containing oxygen functional groups in alkaline zinc-iron flow batteries. (a) Alkaline zinc-iron flow batteries assembled with non-ionic ion-conducting membranes with different PEG contents at 80 mA cm -2 (a) The battery performance diagram under the working current density conditions; (b) The charge and discharge curve corresponding to Figure (a); (c) The rate performance test of the alkaline zinc-iron liquid flow battery assembled with P52 membrane; (d) The SOC-OCV test of the alkaline zinc-iron liquid flow battery assembled with P52 membrane; (e) The polarization curve test of the alkaline zinc-iron liquid flow battery assembled with P52 membrane under different SOC conditions; (f) The polarization curve test of the alkaline zinc-iron liquid flow battery assembled with P52 membrane at 80mA cm -2 Cyclic performance test under working current density conditions;

[0027] Figure 7 The influence of the increase of PEG content in the casting solution on the number of nano-scale pores formed in the non-ionic ion-conducting membrane;

[0028] Figure 8 The alkali stability test of non-ionic ion conductive membrane was carried out by exposing P52 non-ionic ion conductive membrane to 6 mol L -1 After being treated in NaOH solution for 8 days, the alkaline zinc-iron flow battery assembled with it performed at 80 mA cm -2 Cyclic performance test under working current density conditions. DETAILED DESCRIPTION

[0029] The following examples use alkaline zinc-iron flow battery performance test conditions: carbon felt is used as the positive and negative electrodes, and the positive electrode electrolyte is 0.8 mol L -1 Na 4 Fe(CN) 6 +3mol L -1 KOH solution; the negative electrode electrolyte is 0.4 mol L -1 Na 2 Zn(OH) 4 +3mol L -1 NaOH solution; the volume of positive and negative electrolytes is 60 mL each; the battery adopts constant current charge and discharge mode at 80 mA cm -2 The battery was charged for 15 min under the current density condition, and the voltage was used as the cut-off condition during the discharge process. -2 The discharge was carried out to 0.1 V under the condition of current density.

[0030] The following examples are provided to further illustrate the present invention, but are not intended to limit the scope of the present invention.

[0031] Comparative Example 1

[0032] The comparative example of the present invention is a perfluorosulfonic acid ion exchange membrane. The alkaline zinc-iron liquid flow battery is assembled using Nafion 212 with a thickness of 50 μm. -2 Under the working current density condition, the electrochemical performance was tested. The test results are as follows Figure 1 As shown. It can be seen that the perfluorosulfonic acid ion exchange membrane has excellent ion selectivity in the alkaline zinc-iron flow battery, and its coulombic efficiency is close to 100%, while the voltage efficiency of the battery is low, only 82.95%. This is mainly because the interaction between the perfluororesin skeleton and the side chain sulfonic acid groups of the perfluorosulfonic acid ion exchange membrane is strong, resulting in the side chain sulfonic acid groups and the cations (K + Or Na + ) has a weak binding energy, K + Or Na + The resistance to permeation of the membrane through the mechanism of ion exchange transfer is relatively large, which makes the ion conductivity of the perfluorosulfonic acid ion exchange membrane low in the alkaline system, resulting in a low voltage efficiency of the battery.

[0033] Comparative Example 2

[0034] Polyethersulfone (PES) was used as the substrate and water-soluble polyvinylpyrrolidone (PVP) was used as the regulator. In the solution, the total mass fraction of PES and PVP was 25wt%, and the mass ratio of PES:PVP was 50:50. It was dissolved in DMAC solvent to form a homogeneous solution. The above solution was evenly coated on a clean glass plate, dried at 50°C for 12 hours, and then the glass cup was transferred to deionized water and soaked for 30 hours. Part of the PVP dissolved in water to form nano-scale pores (pore size distribution range 0.1nm~0.6nm, porosity 40%), and part of the PVP was wrapped by PES and remained in the matrix. The alkaline zinc-iron liquid flow battery was assembled with the membrane material prepared above, and the battery was operated at 40mA cm -2 The battery was charged and discharged under the working current density. Due to the large resistance of the membrane material, the battery could not be charged and discharged normally ( Figure 2 ), it can be seen that the composite membrane prepared by PVP is used in alkaline zinc-iron flow batteries, the ion conductivity is extremely low and normal charging and discharging cannot be guaranteed. This may be because although the resin is a water-soluble polymer resin, it does not contain ion-conducting groups.

[0035] Comparative Example 3

[0036] Polyethersulfone (PES) was used as the substrate and sulfonated polyetheretherketone (SPEEK) was used as the regulator. In the solution, the total mass fraction of PES and SPEEK was 25wt%, and the mass ratio of PES:SPEEK was 50:50. They were dissolved in DMAC solvent to form a homogeneous solution. The above solution was evenly coated on a clean glass plate, dried at 50°C for 12h, and then the glass cup was transferred to deionized water and soaked for 30h. The alkaline zinc-iron liquid flow battery was assembled with the membrane material prepared above, and the flow rate was 80mA cm -2 The battery was charged and discharged under the working current density condition. The results are as follows Figure 3 As shown in Figure 2, SPEEK is insoluble in water and cannot form nanoscale pore structures in the membrane, resulting in a large resistance. When used in alkaline zinc-iron flow batteries, the battery is at 80 mA cm -2 Under the working current density conditions, the coulomb efficiency is 98.44% and the voltage efficiency is 79.06%.

[0037] Comparative Example 4

[0038] Polyethersulfone (PES) was used as the substrate and PEG10000 (number average molecular weight: 10000) was used as the regulator. In the solution, the total mass fraction of PES and PEG was 25wt%, and the mass ratio of PES:PEG10000 was 50:50. The solution was dissolved in DMAC solvent to form a solution. The above solution was evenly coated on a clean glass plate, dried at 50°C for 12 hours, and then the above glass cup was transferred to deionized water and soaked for 30 hours to obtain the desired membrane with a porosity of 28% and a pore size of 10-13nm. The alkaline zinc-iron liquid flow battery was assembled with the membrane material prepared above. The battery was operated at 80mA cm -2 Under the working current density conditions, the Coulomb efficiency is 81.67% and the voltage efficiency is 91.17%.

[0039] Example 1

[0040] With polyethersulfone (PES) as the substrate and oxygen-containing water-soluble polyethylene glycol 400 (PEG-400) as the regulator, the mass fraction of PES and PEG in the solution is 25wt%, and the mass ratio of PES:PEG is 50:50; 48:52; 45:55 (referred to as P50, P52, and P55, respectively). Dissolved in DMAC solvent to form a homogeneous solution, the above solution is evenly coated on a clean glass plate, dried at 70°C for 12 hours, and then the above glass cup is transferred to deionized water and soaked for 30 hours. Part of PEG is dissolved in water to form nano-scale pores, and part of PEG is wrapped by PES and remains in the matrix. To confirm this conclusion, P52 was selected as the research object, and the structure of its membrane before and after soaking in water was characterized. Figure 4 The infrared and nuclear magnetic spectra of P52 membrane before and after soaking in water are shown in Figure 1. Figure 4 ac) It can be seen that before and after soaking in water, the PEG in the membrane is at 2870 cm -1 (PEG-CH 2 - symmetrical stretching vibration peak) and 1166cm -1 (PEG-CH 2 –O–CH 2 – vibration peak) are present, indicating the presence of PEG in the membrane after soaking in water. Figure 4 d) The presence of PEG in the membrane after soaking in water was further confirmed (chemical shifts at 3.40ppm, 3.41ppm and 3.42ppm are characteristic peaks of methylene on PEG). After soaking in water, the characteristic absorption peak intensity of PEG on infrared and nuclear magnetic resonance decreased, indicating that after soaking in water, part of PEG dissolved in water, and the dissolved PEG can form nanoscale pores (pore size distribution range 0.1nm ~ 2nm, porosity 43-51%) in the membrane, thereby facilitating the transfer of ions in the membrane. The membrane material prepared above was used to assemble an alkaline zinc-iron liquid flow battery ( Figure 5 ), at 80 mA cm-2 The battery is charged and discharged under the working current density condition. The battery performance is as follows Figure 6 As shown in Figure 2, as the PEG content in the solution increases, more PEG is dissolved and more nanoscale pores are formed ( Figure 7 ), which helps the transfer of charge-balancing ions in the membrane. The alkaline zinc-iron flow battery assembled with P50 has a coulombic efficiency of 98.75% and a voltage efficiency of 83.52%, the alkaline zinc-iron flow battery assembled with P52 has a coulombic efficiency of 99.26% and a voltage efficiency of 87.46%, and the alkaline zinc-iron flow battery assembled with P55 has a coulombic efficiency of 95.99% and a voltage efficiency of 91.72%. At the same time, the PEG content remaining in the membrane also increases accordingly. The oxygen on the PEG is alkaline in an alkaline system and helps OH - Under the synergistic effect of the two, the conductivity of the membrane material gradually increases, and the voltage efficiency of the alkaline zinc-iron flow battery cell assembled with it also gradually increases ( Figure 6 a and b). Figure 6 c is the rate performance test of the alkaline zinc-iron flow battery assembled with P52. Even at 120 mA cm -2 Under the working current density condition, the energy efficiency of the battery can still be maintained above 80%, showing excellent rate performance. Figure 6 d) and better rate performance ( Figure 6 c), the alkaline zinc-iron flow battery assembled with P52 membrane has a higher power density ( Figure 6 d). Alkaline zinc-iron flow battery assembled with P52 at 80 mA cm -2 Under the working current density conditions, the battery operates stably for more than 150 cycles and its performance remains stable, showing good stability.

[0041] In order to verify the alkali stability of the designed non-ionic ion conducting membrane, the P52 membrane was placed in 6 mol L -1 The samples were treated in NaOH solution for 8 days, and then used to assemble alkaline zinc-iron flow battery cells and perform cycle performance tests. The test results are shown in Figure 8 The battery ran stably for 120 cycles and its performance remained stable, indicating that this non-ionic ion conductive membrane has excellent alkali resistance and stability and has good application prospects in alkaline zinc-iron liquid flow battery systems.

[0042] Example 2

[0043] Polyethersulfone (PES) was used as the substrate, and oxygen-containing water-soluble polyvinyl alcohol (PVA, number average molecular weight: 5000) was used as the regulator. In the solution, the mass fraction of PES and PVA was 25wt%, and the mass ratio of PES:PVA was 50:50. It was dissolved in DMAC solvent to form a homogeneous solution. The above solution was evenly coated on a clean glass plate, dried at 50°C for 12 hours, and then the glass cup was transferred to deionized water and soaked for 30 hours. Part of the PVA dissolved in water to form nano-scale pores (pore size distribution range of 0.1-3nm, porosity of 45%), and part of the PVA was wrapped by PES and remained in the matrix. The alkaline zinc-iron liquid flow battery was assembled with the membrane material prepared above, and the battery was operated at 80mA cm -2 The battery was charged and discharged under the working current density condition, and the battery coulomb efficiency was 98.79% and the voltage efficiency was 86.72%.

[0044] Example 3

[0045] Polyethersulfone (PES) was used as the substrate, and oxygen-containing water-soluble polyvinyl alcohol (PVA, number average molecular weight: 5000) was used as the regulator. In the solution, the mass fraction of PES and PVA was 25wt%, and the mass ratio of PES:PVA was 60:40. It was dissolved in DMAC solvent to form a homogeneous solution. The above solution was evenly coated on a clean glass plate, dried at 50°C for 12 hours, and then the glass cup was transferred to deionized water and soaked for 30 hours. Part of the PVA dissolved in water to form nano-scale pores (pore size distribution range of 0.1-1nm, porosity of 35%), and part of the PVA was wrapped by PES and remained in the matrix. The alkaline zinc-iron liquid flow battery was assembled with the membrane material prepared above, and the battery was operated at 80mA cm -2 The battery was charged and discharged under working current density conditions, and the battery coulomb efficiency was 97.17% and the voltage efficiency was 72.28%.

[0046] Example 4

[0047] Polyethersulfone (PES) was used as the substrate, and oxygen-containing water-soluble polyvinyl alcohol (PVA, number average molecular weight 5000) was used as the regulator. In the solution, the mass fraction of PES and PVA was 25wt%, and the mass ratio of PES:PVA was 50:50. It was dissolved in DMAC solvent to form a homogeneous solution. The above solution was evenly coated on a clean glass plate, dried at 50°C for 12 hours, and then the glass cup was transferred to a mixed solution of deionized water and ethanol and soaked for 30 hours (the volume ratio of water to ethanol was 99:1). Part of the PVA dissolved in the mixed solution to form nanoscale pores (pore size distribution range 0.1-3nm, porosity 44%), and part of the PVA was wrapped by PES and remained in the matrix. The membrane material prepared above was used to assemble an alkaline zinc-iron liquid flow battery, and at 80mA cm -2The battery was charged and discharged under working current density conditions, and the battery coulomb efficiency was 99.26% and the voltage efficiency was 87.16%.

[0048] Example 5

[0049] Polyethersulfone (PES) was used as the substrate, and oxygen-containing water-soluble polyvinyl alcohol (PVA number average molecular weight 5000) was used as the regulator. In the solution, the mass fraction of PES and PVA was 25wt%, and the mass ratio of PES:PVA was 30:70. It was dissolved in DMAC solvent to form a homogeneous solution. The above solution was evenly coated on a clean glass plate, dried at 50°C for 12 hours, and then the glass cup was transferred to a mixed solution of deionized water and ethanol and soaked for 30 hours (the volume ratio of water to ethanol was 99:1). Part of the PVA dissolved in the mixed solution to form nanoscale pores (pore size distribution range 0.3-5nm, porosity 62%), and part of the PVA was wrapped by PES and remained in the matrix. The alkaline zinc-iron liquid flow battery was assembled with the membrane material prepared above, and the battery was operated at 80mA cm -2 The battery was charged and discharged under working current density conditions, and the battery coulomb efficiency was 82.14% and the voltage efficiency was 91.17%.

[0050] The preparation process of Example 6-7 is the same as that of Example 5, and the differences therefrom are shown in the table below.

[0051] The preparation process of Comparative Example 5-6 is the same as that of Example 5, and the differences therefrom are shown in the table below.

[0052]

[0053]

[0054] It can be seen from the implementation data of the above-mentioned Examples 1-7 and Comparative Examples 1-6 that the non-ionic ion conductive membrane prepared by the present invention has good performance in alkaline zinc-iron flow batteries and can effectively regulate battery performance. By regulating the type of water-soluble polymer resin containing oxygen functional groups in the non-ionic ion conductive membrane, higher battery performance can also be achieved. When the content of water-soluble polymer resin containing oxygen functional groups in the membrane material is reduced, its resistance is large, which will lead to low voltage efficiency in alkaline zinc-iron flow batteries. When the content of water-soluble polymer resin containing oxygen functional groups in the membrane material is high, the water-soluble polymer resin dissolves to form more pores, the membrane material swells severely, and the coulomb efficiency of the battery assembled therewith is low; the content of water-soluble polymer resin containing oxygen functional groups in the membrane material is too low, the membrane resistance of the prepared membrane material is large, and the battery cannot be charged and discharged normally. The content ratio of the two is a mass ratio of organic polymer resin without ion exchange groups to water-soluble polymer resin containing oxygen functional groups of 7:3 to 3:7, preferably 5:5 to 4:6.

[0055] During the film formation process, when the water content in the non-solvent is low, the water-soluble polymer resin containing oxygen functional groups in the film cannot be dissolved well, the membrane has fewer pores, the membrane resistance is large, which is not conducive to the transfer of ions in the membrane, and the performance of the battery assembled with it is low. The appropriate volume ratio of water and alcohol is 99.9:0.1 to 60:40.

[0056] Comparative Example 4 selects PEG with a molecular weight of 10,000 as the water-soluble polymer resin. From the battery performance test results, the coulombic efficiency is only 81.67%. This is probably because as the molecular weight of the water-soluble polymer resin increases, the solubility of the resin in the organic solvent becomes worse, and the aggregation of PEG is serious during the film formation process. During the non-solvent treatment process, the aggregated PEG dissolves in the film to form a large uneven pore structure, thereby reducing the ion selectivity of the membrane material. Therefore, for different types of water-soluble polymer resins, an appropriate molecular weight range is also necessary.

Claims

1. Application of a non-ionic ion-conducting membrane in alkaline zinc-iron flow batteries, Features: The non-ionic ion conductive membrane is prepared by preparing a homogeneous mixed solution of an organic polymer resin raw material without ion exchange groups and a water-soluble polymer resin containing oxygen functional groups in an organic solvent, and then drying to form a membrane, and then treating the organic polymer resin without ion exchange groups in a non-solvent to obtain a non-ionic conductive membrane; the organic polymer resin raw material without ion exchange groups is one or more of polyether sulfone, polysulfone, chloromethylated polysulfone, polyether ketone, and polyolefin; the water-soluble polymer containing oxygen functional groups is one or more of polyvinyl alcohol (PVA), polyethylene glycol (PEG), sodium polyacrylate, carboxymethyl cellulose, methyl cellulose, and hydroxyethyl cellulose; the positive electrode electrolyte of the alkaline zinc-iron liquid flow battery is Fe(CN) 6 4- The negative electrode electrolyte is Zn(OH) 4 2- The alkaline aqueous solution is NaOH or / and KOH solution; the total mass concentration of the organic polymer resin raw material without ion exchange groups and the water-soluble polymer resin containing oxygen functional groups in the solution is 1 wt%~50 wt%; the porosity range is 30%~70%, the pore size distribution range is 0.1 nm~8 nm, The non-ionic conductive membrane is prepared by the following steps: 1) blending an organic polymer resin raw material without ion exchange groups and a water-soluble polymer resin containing oxygen functional groups in a desired mass ratio and dissolving the mixture in an organic solvent to form a homogeneous solution; 2) The above solution is evenly coated on the substrate and dried at room temperature -100 °C for 1-100 h to form a film; 3) immersing the dried membrane in step 2) together with the substrate in a non-solvent for a treatment time of 12 h to 100 h to obtain the desired non-ionic conductive membrane; During the non-solvent treatment process, some water-soluble polymer resins containing oxygen functional groups will dissolve in the non-solvent to form a nanoscale pore structure, thereby promoting ion conduction; in addition, some water-soluble polymer resins containing oxygen functional groups are preserved in the membrane material because they are wrapped by organic polymer resins that are insoluble in the non-solvent. The oxygen-containing functional groups in the water-soluble polymer resin react with K in the electrolyte in the alkaline zinc-iron flow battery. + Or Na + Combining with basic oxygen can achieve OH - Ion conduction.

2. The use according to claim 1, Features: The mass ratio of the organic polymer resin without ion exchange groups to the water-soluble polymer resin containing oxygen functional groups is 7:3~3:7; the number average molecular weight of polyvinyl alcohol is 2000~130000, the number average molecular weight of polyethylene glycol is 200~5000, the number average molecular weight of sodium polyacrylate is 800~200000, the number average molecular weight of carboxymethyl cellulose is 178~170000, the number average molecular weight of methyl cellulose is 40000~180000, and the number average molecular weight of hydroxyethyl cellulose is 30000~200000.

3. The use according to claim 1, Features: The total mass concentration of the organic polymer resin raw material without ion exchange groups and the water-soluble polymer resin containing oxygen functional groups in the solution is 15 wt%~30 wt%, the porosity range is 50%~70%, and the pore size distribution range is 0.5-5nm; the mass ratio of the organic polymer resin without ion exchange groups to the water-soluble polymer resin containing oxygen functional groups is 5:5~4:

6.

4. The use according to claim 1, Features: The total mass concentration of the organic polymer resin raw material without ion exchange groups and the water-soluble polymer resin containing oxygen functional groups in the solution is 16 wt%~28wt%.

5. The use according to claim 1, Features: The organic solvent in step 1) is one or more of dimethyl sulfoxide (DMSO), N,N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF).

6. The use according to claim 1, Features: The drying in step 2) is performed at room temperature-100°C for 1-100 h.

7. The use according to claim 1, Features: In the step 2), the drying temperature is 50° C. to 70° C. and the drying time is 3 h to 12 h.

8. The use according to claim 1, Features: The non-solvent treatment time of step 3) is 12 h to 48 h; The non-solvent is one of water and a mixed solution of water / alcohol; wherein the volume ratio of water to alcohol in the mixed solution is 99.9:0.1-60:40; and the alcohol is one or more of ethanol, methanol, isopropanol and glycerol.

9. The use according to claim 1, Features: The non-solvent treatment time of step 3) is 24 h to 36 h; The non-solvent is one of water and a mixed solution of water / alcohol; wherein the volume ratio of water to alcohol in the mixed solution is 99.9:0.1-90:

10.

10. The use according to claim 1, It is characterized in that Positive electrolyte Fe(CN) 6 4- The active substance is one or more of Na4Fe(CN)6, Na4Fe(CN)6, Na4Fe(CN)6, K4Fe(CN)6, K4Fe(CN)6+NaOH, K4Fe(CN)6, Na4Fe(CN)6, and K4Fe(CN)6.

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