Porous ion-conducting membrane with pore size in gradient distribution, preparation and application

文档序号：702576 发布日期：2021-04-13 浏览：28次中文

阅读说明：本技术 一种孔径具有梯度分布的多孔离子传导膜及制备和应用 (Porous ion-conducting membrane with pore size in gradient distribution, preparation and application ) 是由袁治章李先锋张华民于 2019-10-11 设计创作，主要内容包括：本发明公开了一种孔径具有梯度分布的多孔离子传导膜在碱性锌铁液流电池中的应用。该类膜是以有机高分子树脂和可与酸反应生成气体的无机颗粒共混后,经过在酸溶液中相转化制备得到。成膜过程中,铸膜液溶剂与非溶剂交换形成孔结构,同时,非溶剂中的质子酸与进入铸膜液中后,与铸膜液中的无机颗粒反应生气气体,从而使得在成膜过程中生成孔径具有梯度分布的多孔离子传导膜。该类孔径具有梯度分布的多孔离子传导膜工艺过程简单,工艺环保,孔径及孔隙率可控,容易实现批量生产。与原有多孔膜相比,该类孔径具有梯度分布的多孔离子传导膜可通过控制无机颗粒含量、非溶剂中酸浓度控制孔结构,以此组装的液流电池具有很好的电池性能。(The invention discloses application of a porous ion-conducting membrane with gradient pore size distribution in an alkaline zinc-iron flow battery. The film is prepared by blending organic polymer resin and inorganic particles which can react with acid to generate gas and then carrying out phase conversion in an acid solution. In the film forming process, the solvent of the film casting solution and the non-solvent are exchanged to form a pore structure, and meanwhile, the protonic acid in the non-solvent reacts with the inorganic particles in the film casting solution to generate gas after entering the film casting solution, so that the porous ion conducting film with the pore diameter in gradient distribution is generated in the film forming process. The porous ion conduction membrane with the pore diameter in gradient distribution has the advantages of simple process, environment-friendly process, controllable pore diameter and porosity and easy realization of batch production. Compared with the original porous membrane, the porous ion conduction membrane with the pore diameter in gradient distribution can control the pore structure by controlling the content of inorganic particles and the concentration of acid in a non-solvent, so that the assembled flow battery has good battery performance.)

1. A porous ion-conducting membrane having a gradient distribution of pore sizes, characterized by: the porous ion-conducting membrane with the pore diameter in gradient distribution is prepared by mixing organic polymer resin serving as a raw material and inorganic particles capable of reacting with acid to generate gas, and immersing the mixture in an acid solution for phase conversion.

2. The porous ion-conducting membrane with a gradient of pore sizes according to claim 1, characterized in that:

the organic polymer resin is prepared by blending a first polymer material or a first polymer material and a second polymer material;

the first type of high polymer material is one or more than two of polysulfone, polyacrylonitrile, polyimide, polyether ketone, polytetrafluoroethylene, polyvinylidene fluoride, polybenzimidazole or polyvinyl pyridine;

the second polymer material is one or more of sulfonated polymer resin or quaternized polymer resin, polyvinylpyrrolidone and polyethylene glycol; the sulfonated high molecular resin or the quaternized high molecular resin is one or more than two of sulfonated polysulfone or quaternized polysulfone, sulfonated polyimide, sulfonated polyether ketone or quaternized polyether ketone, or sulfonated polybenzimidazole;

the mass content of the first polymer material in the organic polymer resin raw material is 100% (namely, the first polymer material can be completely composed) to 40%, preferably 95% to 65%.

3. The porous ion-conducting membrane with pore size gradient distribution according to claim 1, wherein the inorganic particles capable of reacting with acid to generate gas are one or more of lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, calcium carbonate, calcium bicarbonate, barium carbonate, barium bicarbonate and magnesium carbonate, and have a particle size of 1-80 nm.

4. A porous ion-conducting membrane with a gradient in pore size distribution according to claim 1, 2 or 3, characterized in that: the acid solution is one or more than two of hydrochloric acid solution, sulfuric acid solution and acetic acid solution; wherein the acid concentration is 1-30 wt%, preferably 5-20 wt%.

5. The porous ion-conducting membrane with a gradient of pore sizes according to claim 1, characterized in that: the porous ion conduction membrane consists of a skin layer and a macroporous support layer, wherein the thickness of the skin layer is 30nm-5 μm, and the thickness of the macroporous support layer is 40-200 μm, preferably 60-120 μm; the pore diameter of the macroporous support layer is 1-50 um, preferably 2-20 um, and the porosity of the porous ion conduction membrane is 20-95%, preferably 75-90%;

the pore diameters of pores distributed on the surface of the skin layer in the direction of the macroporous support layer are gradually increased, and the pores comprise small pores, medium pores and large pores;

the size of the macropores in the skin layer of the porous ion conduction membrane is 1.0-5 mu m; the size of the mesopore is 30 nm-less than 1.0 μm; the size of the small hole is 0.1nm to less than 30 nm; preferred ranges are: the size of the macropores is 2.5-4 mu m; the size of the mesopore is 0.2-0.5 μm; the size of the small hole is 0.5-2 nm.

6. A process for the preparation of a porous ion-conducting membrane having a gradient of pore sizes according to any one of claims 1 to 5, characterized in that:

the porous ion-conducting membrane with the pore diameter having gradient distribution is prepared by the following steps:

(1) dispersing inorganic particles which are dissolved in organic polymer resin and can react with acid to generate gas in an organic solvent, fully stirring and dispersing for 20-60 h, preferably 30-40 h at the temperature of 20-60 ℃ to prepare a blending solution; wherein the concentration of the organic polymer resin is 10-40 wt%, preferably 25-35%; the inorganic particles which can react with acid to generate gas are 20 to 100 weight percent of the content of the polymer resin, preferably 40 to 70 weight percent;

(2) pouring the blending solution prepared in the step (1) on a non-woven fabric substrate or directly on a glass plate, volatilizing the solvent for 0-60 seconds, preferably 0-40 seconds, then wholly soaking the blending solution in an acid solution to completely react inorganic particles, and preparing a porous ion-conducting membrane with pore size in gradient distribution at the temperature of 10-50 ℃; the thickness of the film is 40 to 200 μm.

7. The process for preparing a porous ion-conducting membrane having a pore size gradient according to claim 6, wherein:

the organic solvent is one or more than two of DMSO, DMAC, NMP and DMF.

Then the whole body is immersed into acid solution for 20 s-10 min to make the inorganic particles completely react.

8. Use of a porous ion-conducting membrane having a gradient pore size distribution according to any one of claims 1 to 5, wherein: the electrolyte is used in flow batteries including, but not limited to, all-vanadium flow batteries, zinc-iron flow batteries, zinc-bromine flow batteries, zinc-iodine flow batteries, and the like.

Technical Field

The invention relates to a porous ion-conducting membrane material with gradient pore size distribution, in particular to a preparation method of the membrane and application of the membrane in a flow battery.

Background

The flow battery energy storage technology has the characteristics of environmental friendliness, high safety, flexible design, long cycle life and the like, and is very suitable for application in the fields of distributed energy sources and large-scale energy storage. As a key material for flow batteries, the physicochemical properties and cost of ion-conducting membranes directly impact the performance and cost of the battery system. A commercial perfluorosulfonic acid ion exchange membrane (trade name:) The production process is complex and expensive (about $ 600-^-2The coulomb efficiency of the battery is only 76%) under the condition of working current density, and the performance of the flow battery is seriously influenced. The non-fluorine ion exchange membrane has the characteristics of low cost and high selectivity, but due to the introduction of ion exchange groups, the ion exchange membrane has poor oxidation stability in a flow battery system with strong acid and strong oxidation performance, such as an all-vanadium flow battery system, so that the requirement of long-time operation of the battery cannot be met. The porous ion-conducting membrane can effectively realize sieving conduction between the active substance and the charge balance ions by a pore size sieving principle. Conventional porous icms are then prepared by submerged phase inversion, which generally results in porous icms having an asymmetric structure: namely a macroporous support layer and a selective compact skin layer. The selectivity of such porous ion-conducting membranes is typically provided by a dense skin layer. The compact skin layer can endow the prepared porous ion-conducting membrane with high ion selectivity, but can reduce the ion conductivity; the compact skin layer structure can be adjusted by adjusting film forming parameters, such as coagulation bath composition, solid content of casting solution and the like, the method can effectively improve the ionic conductivity of the film, but can obviously reduce the ionic selectivity of the film, namely, the porous ionic conduction film prepared by the traditional phase inversion method has a 'trade-off' effect. Is composed ofThe invention solves the key scientific problems, and discloses a porous ion-conducting membrane with the pore size in gradient distribution, which can effectively solve the problem of 'trade-off' existing between ion selectivity and ion conductivity of the traditional porous ion-conducting membrane, thereby greatly improving the efficiency of a flow battery.

Disclosure of Invention

The invention aims to prepare a porous ion-conducting membrane with pore size gradient distribution, and provides a porous ion-conducting membrane with pore size gradient distribution for a flow battery.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the porous ion conducting membrane with the pore diameter in gradient distribution is prepared by mixing organic polymer resin serving as a raw material and inorganic particles capable of reacting with acid to generate gas, and immersing the mixture in an acid solution for phase conversion.

The organic polymer resin is prepared by blending a first polymer material or a first polymer material and a second polymer material;

the mass content of the first polymer material in the organic polymer resin raw material is 100% (namely, the first polymer material can be completely composed) to 40%, preferably 95% to 65%.

The porous ion conducting membrane with the pore diameter in gradient distribution can react with acid to generate gas, and the inorganic particles are one or more than two of lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, calcium carbonate, calcium bicarbonate, barium carbonate, barium bicarbonate and magnesium carbonate, and the particle size is 1-80 nm.

The acid solution is one or more than two of hydrochloric acid solution, sulfuric acid solution and acetic acid solution; wherein the acid concentration is 1-30 wt%, preferably 5-20 wt%.

The porous ion conduction membrane consists of a skin layer and a macroporous support layer, wherein the thickness of the skin layer is 30nm-5 μm, and the thickness of the macroporous support layer is 40-200 μm, preferably 60-120 μm; the pore diameter of the macroporous support layer is 1-50 um, preferably 2-20 um, and the porosity of the porous ion conduction membrane is 20-95%, preferably 75-90%.

The pore diameters of pores distributed on the surface of the skin layer in the direction of the macroporous support layer are gradually increased, and the pores comprise small pores, medium pores and large pores;

The porous ion-conducting membrane with the pore diameter having gradient distribution is prepared by the following steps:

The organic solvent is one or more than two of DMSO, DMAC, NMP and DMF.

Then the whole body is immersed into acid solution for 20 s-10 min to make the inorganic particles completely react.

The electrolyte is used in flow batteries including, but not limited to, all-vanadium flow batteries, zinc-iron flow batteries, zinc-bromine flow batteries, zinc-iodine flow batteries, and the like.

The invention has the following beneficial results:

1. the porous ion-conducting membrane with the pore diameter in gradient distribution, which is prepared by the invention, is applied to a flow battery, adopts an in-situ bubble pore-forming method, utilizes inorganic particles which can react with acid to generate gas to react with the acid concentration in a coagulating bath in situ to generate bubbles, and generates nano-scale pores in the process of membrane formation; meanwhile, in the film forming process, the solvent and the non-solvent are exchanged to form macropores, and finally the porous ion conduction film with the pore diameter having gradient distribution is obtained, so that the selectivity and the ionic conductivity of the film are effectively improved, and better battery performance is obtained; the pore size distribution and the porosity of the membrane can be effectively controlled by changing the content of inorganic particles which can react with acid to generate gas and the concentration of acid in the coagulating bath.

2. The prepared porous ion-conducting membrane with the gradient distribution of the pore diameter can effectively intercept active substances with larger molecular size and allow charge balance ions to freely pass through; the mesopores can further realize the selective separation of active substances and charge balance ions and realize secondary screening, thereby endowing the prepared membrane with high ion selectivity and ion conduction; the macropores mainly support the mesopores and the micropores, and meanwhile, the macropores can effectively fill supporting electrolyte of the flow battery, so that charge balance ions have high ion conduction capability in the membrane.

3. The porous ion-conducting membrane with the pore diameter having gradient distribution, prepared by the invention, can regulate and control the ion selection selectivity and ion conductivity of the membrane by changing the content of inorganic particles capable of reacting with acid to generate gas and the acid concentration in a coagulating bath.

4. The porous ion-conducting membrane with the pore diameter in gradient distribution, prepared by the invention, has rich pore structure and adjustable pore diameter, and is easy to realize mass production.

5. The porous ion-conducting membrane with the pore diameter distributed in a gradient manner, which is prepared by the invention, only needs to use the dilute acid solution of the high polymer resin, and the preparation process is clean and environment-friendly.

6. The invention widens the variety and application range of membrane materials for the flow battery, is particularly suitable for being applied to the zinc-iron flow battery, and improves the charge balance ions (H) of the porous membrane on the basis of keeping the ion conductivity of the porous membrane⁺，Na⁺，K⁺，OH^-) And positive and negative electrode active material ions (e.g. vanadium ion, Zn (OH))₄ ^2-、Fe(CN)₆ ^4-/Fe(CN)₆ ^3-Etc.) are selected.

7. The invention can realize the controllability of the performance of the flow battery.

Drawings

Figure 1SEM morphology characterization: (a) solid content 35%, Polyethersulfone (PES): polyvinylpyrrolidone (PVP) ═ 85: 15 (mass ratio) in 10 wt% hydrochloric acid solution, and performing phase inversion to obtain a membrane (P-I membrane for short) with SEM image of cross section skin layer; (b) solid content 35%, Polyethersulfone (PES): polyvinylpyrrolidone (PVP) ═ 85: 15 (mass ratio) of the dispersion (containing 1.2g of sodium hydrogencarbonate) in a 10 wt% hydrochloric acid solution, and a SEM photograph of the cross-sectional skin layer of the membrane prepared by the phase inversion method (referred to as P-P membrane).

Fig. 2TEM topography characterization: (a) high resolution TEM image of P-I film; (b) high resolution TEM images of P-P films.

FIG. 3 alkaline zinc-iron flow battery assembled by using P-I film at 80mA cm^-2And (5) testing the cycle performance under the working current density condition.

FIG. 4 alkaline zinc-iron flow battery assembled by using P-P film at 80mA cm^-2And (5) testing the cycle performance under the working current density condition.

FIG. 5 shows the rate performance of the alkaline zinc-iron flow battery assembled by using the P-P film.

Detailed Description

The cycle performance test conditions of the alkaline zinc-iron flow battery are as follows: the positive and negative electrodes are made of carbon feltThe electrode and the positive electrode electrolyte are 0.8mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.4mol/L Zn (OH)₄ ^2-+3mol/L OH^-A solution; the volumes of the positive electrolyte and the negative electrolyte are respectively 60 mL; the battery adopts a constant current charging and discharging mode and is at 80mA cm^-2Under the condition of current density of (1), charging for 15min, and then cutting off the voltage to 80mA cm^-2Is discharged to 0.1V under the current density condition of (1).

The alkaline zinc-iron redox flow battery multiplying power performance test conditions are as follows: the positive electrode and the negative electrode both adopt carbon felts as electrodes, and the electrolyte of the positive electrode is 0.8mol/L Fe (CN)₆ ^4-+3mol/L OH^-A solution; the negative electrode electrolyte is 0.4mol/L Zn (OH)₄ ^2-+3mol/L OH^-A solution; the volumes of the positive electrolyte and the negative electrolyte are respectively 60 mL; the battery adopts a constant current charge-discharge mode at 40-120mA cm^-2Under the condition of current density of (1), charging to the same capacity, and then cutting off the voltage to 40-120mA cm^-2Is discharged to 0.1V under the current density condition of (1).

The following examples are further illustrative of the present invention and are not intended to limit the scope of the present invention.

Comparative example 1

PES/PVP is used as a base material, and the PES/PVP is dissolved in a DMAC solvent to obtain a blending solution with the mass concentration of 35%, wherein the mass ratio of PES to PVP is 85: and 15, pouring the blended solution on a clean and flat glass plate, volatilizing the solvent for 10s under the humidity condition of 20 percent, and then soaking the whole into a 10wt percent hydrochloric acid solution to prepare a porous ion conduction membrane, namely a P-I membrane for short at 25 ℃. And characterizing the micro-morphology of the sample. As can be seen from the SEM image of FIG. 1a, the cross-sectional skin structure of the prepared P-I film is a more compact structure; further characterization of the skin microstructure by TEM (fig. 2a) shows that the skin microstructure of the P-I film appears to be non-porous, consistent with the SEM structure of fig. 1 a. The prepared P-I membrane is adopted to assemble the alkaline zinc-iron flow battery, the performance of the alkaline zinc-iron flow battery is tested (figure 3), and the alkaline zinc-iron flow battery assembled by the alkaline zinc-iron flow battery can be seen to be 80mA cm^-2The voltage efficiency of the cell is low, only 8About 5 percent. Meanwhile, along with the circulation, the efficiency fluctuation of the battery is large, the voltage efficiency of the battery is attenuated to about 78% in the later stage, and the coulomb efficiency of the battery is 98%.

Comparative example 2

PES/PVP is used as a base material, the PES/PVP and nano calcium carbonate are dissolved in a DMAC solvent together to obtain a blending solution with the mass concentration of 35%, wherein the mass ratio of PES to PVP is 85: and 15, pouring the blended solution on a clean and flat glass plate, volatilizing the solvent for 10s under the humidity condition of 20 percent, and then soaking the whole into a 10wt percent hydrochloric acid solution to prepare a porous ion conduction membrane, namely a P-I membrane for short at 25 ℃. And characterizing the micro-morphology of the sample. As can be seen from SEM images of the section and the surface of the membrane skin layer, the prepared P-I membrane has a uniform-aperture 80-100nm nanoscale pores and a single and discontinuous pore diameter; the alkaline zinc-iron flow battery assembled by the electrolyte is 80mA cm^-2Under the condition of working current density, the battery continuously and stably runs for more than 100 cycles, the initial voltage efficiency of the battery is 86 percent, along with the cycle, the voltage efficiency is about 72 percent, the coulomb efficiency of the battery is 90 percent,

compared with the examples, the comparative example 2 uses the conventional pore-forming agent to form pores on the surface of the membrane, the particle size is fixed, the formed pores are single and discontinuous, the pore diameter of the surface can be formed compared with the ion conductivity of the dense layer (the comparative example 1), so the initial voltage efficiency can be improved, but the pore diameter is isolated and has no continuity penetration, so the voltage efficiency is different from the examples, and simultaneously the selective permeability of ions is reduced due to the pore size, so the coulombic efficiency is relatively reduced, and the problem that the voltage efficiency and the coulombic efficiency are mutually contradictory is well solved.

Example 1

PES/PVP is used as a base material, and the PES/PVP is dissolved in a DMAC solvent to obtain a blending solution with the mass concentration of 35%, wherein the mass ratio of PES to PVP is 85: 15, after the solution is completely dissolved, adding 1.2g of sodium bicarbonate (accounting for 43 percent of the polymer resin and having the particle size of 5-15nm), and uniformly stirring and dispersing; pouring the blended solution into a clean and flat containerVolatilizing the solvent for 10s under the humidity condition of 20% on a glass plate, then immersing the whole into a 10 wt% hydrochloric acid solution for 3min, and preparing a porous ion-conducting membrane, namely a P-P membrane for short at 25 ℃. And characterizing the micro-morphology of the sample. As can be seen from the SEM image of FIG. 1b, the cross-sectional skin structure of the prepared P-P film is a clear pore structure; meanwhile, the pore diameter has obvious gradient distribution, the distribution from small pores, middle pores to large pores is changed, and the size of the middle pore is 298nm, 127nm and 46 nm; the pore size is 27nm and 19nm (the macroporous structure cannot be shown in the figure (the sizes of the macropores of the skin layer and the macroporous support layer are 2.6-3 mu m) because of SEM results under higher magnification), the thickness of the skin layer is about 500nm, the thickness of the macroporous support layer is about 100 mu m, and the porosity of the membrane is 70-85%. Further characterization of the cortical microstructure by TEM (fig. 2b) reveals that the cortical microstructure of the P-P membrane exhibits a pore structure with a distinct gradient of pore size, consistent with the SEM structure of fig. 1 b. The prepared P-P membrane is adopted to assemble the alkaline zinc-iron flow battery, the performance of the alkaline zinc-iron flow battery is tested (figure 4), and the alkaline zinc-iron flow battery assembled by the P-P membrane can be seen to be 80mA cm^-2Under the condition of working current density, the battery continuously and stably runs for more than 120 cycles, the performance is not obviously attenuated, the initial voltage efficiency of the battery is 89%, and along with the circulation, the voltage efficiency is always kept about 85% and is far higher than the performance of the alkaline zinc-iron flow battery assembled by a P-I film. The improvement of the performance mainly comes from the fact that in the film forming process, hydrochloric acid in a coagulating bath and sodium bicarbonate in a casting solution react in situ to generate carbon dioxide bubbles, the bubbles are generated and broken at the skin layer of the film at the initial stage of film forming, so that a pore structure with gradient distribution is formed, and the special pore structure distribution is helpful for charge balance ions to pass through the ion conducting film, so that high ion conductivity is given to the ion conducting film.

FIG. 5 is a graph of a rate capability test of an alkaline zinc-iron flow battery assembled using a P-P membrane. It can be seen that the current density is 40-120mA cm^-2The coulomb efficiency of the battery is always kept above 98 percent even at 120mA cm^-2Under the current density condition of (2), the voltage efficiency of the battery can still be kept above 82%, and the table showsShowing excellent rate performance.

Example 2

Example 3

Example 4

PES/SPEEK (sulfonated polyether ether ketone, sulfonation degree: 0.81) is used as a base material, and the PES/SPEEK is dissolved in a DMAC solvent to obtain a blending solution with the mass concentration of 30%, wherein the mass ratio of the PES to the SPEEK is 92: 8, after the solution is completely dissolved, adding 1.0g of calcium carbonate (accounting for 38 percent of the polymer resin), and uniformly stirring and dispersing; pouring the blended solution on a clean and flat glass plate, volatilizing the solvent for 10s under the condition of 20% humidity, then wholly immersing the blended solution in 15 wt% hydrochloric acid solution, and preparing a porous ion conduction membrane with gradient distribution of pore diameter at 25 ℃, wherein the size of a large pore is 3.1-3.6 mu m; the size of the mesopore is 242 nm-258 nm; the size of the small hole is 1.0-1.5 nm, the thickness of the skin layer is about 500nm, the thickness of the macroporous support layer is about 100um, and the porosity of the membrane is 50-70%. . The alkaline zinc-iron flow battery assembled by the electrolyte is 80mA cm^-2Under the condition of working current density, the coulomb efficiency of the battery can reach 98.78%, the voltage efficiency can reach 88.27%, the battery continuously and stably runs for 114 cycles, and the performance is kept stable.

Example 5

PES/SPEEK (sulfonated polyether ether ketone, sulfonation degree: 0.81) is used as a base material, and the PES/SPEEK is dissolved in a DMAC solvent to obtain a blending solution with the mass concentration of 30%, wherein the mass ratio of the PES to the SPEEK is 92: 8, after the solution is completely dissolved, adding 0.4g of calcium carbonate (accounting for 22 percent of the polymer resin), and uniformly stirring and dispersing; pouring the blended solution on a clean and flat glass plate, volatilizing the solvent for 10s under the condition of 20% humidity, then wholly immersing the blended solution in 15 wt% hydrochloric acid solution, and preparing a porous ion conduction membrane with gradient distribution of pore diameter at 25 ℃, wherein the size of a large pore is 2.5-4 mu m; the size of the mesopore is 256 nm-276 nm; smallThe pore size is 1.0-1.5 nm, the thickness of the skin layer is about 500nm, the thickness of the macroporous support layer is about 100um, and the porosity of the membrane is 20-45%. . The alkaline zinc-iron flow battery assembled by the electrolyte is 80mA cm^-2Under the condition of working current density, the coulombic efficiency of the battery can reach 88.37%, the voltage efficiency is only 81.93%, and the battery efficiency is low.

Example 6

PES/SPEEK (sulfonated polyether ether ketone, sulfonation degree: 0.81) is used as a base material, and the PES/SPEEK is dissolved in a DMAC solvent to obtain a blending solution with the mass concentration of 30%, wherein the mass ratio of the PES to the SPEEK is 92: 8, after the solution is completely dissolved, adding 2.6g of calcium carbonate (accounting for 92 percent of the polymer resin), and uniformly stirring and dispersing; pouring the blended solution on a clean and flat glass plate, volatilizing the solvent for 10s under the condition of 20% humidity, then wholly immersing the blended solution in 15 wt% hydrochloric acid solution, and preparing a porous ion conduction membrane with gradient distribution of pore diameter at 25 ℃, wherein the size of a large pore is 6.4-8.6 mu m; the mesopore size is 677 nm-726 nm; the pore size is 12 nm-21 nm, the thickness of the cortex layer is about 500nm, the thickness of the macroporous support layer is about 100um, and the porosity of the membrane is 80-85%. The alkaline zinc-iron flow battery assembled by the electrolyte is 80mA cm^-2Under the condition of working current density, the coulombic efficiency of the battery is only 85.35%, the voltage efficiency can reach 90.66%, and the energy efficiency of the battery is only 77.38%.

Example 7

PES/PEG (polyethylene glycol) is used as a base material, and the PES/PEG is dissolved in a DMAC solvent to obtain a blending solution with the mass concentration of 30%, wherein the mass ratio of the PES to the PEG is 80: 20, after the solution is completely dissolved, adding 1.4g of sodium bicarbonate (accounting for 52 percent of the polymer resin), and uniformly stirring and dispersing; pouring the blended solution on a clean and flat glass plate, volatilizing the solvent for 10s under the condition of 20% humidity, then wholly immersing the blended solution in 10 wt% sulfuric acid solution, and preparing a porous ion-conducting membrane with the thickness of 90 mu m and the pore diameter of gradient distribution at 25 ℃, wherein the size of a large pore is 3.2-3.6 mu m; the mesopore size is 387nm to 432 nm; the pore size is 1.5 nm-1.8 nm, the thickness of the cortex is about 500nm, the thickness of the macroporous supporting layer is about 100um, and the porosity of the membrane is 70% [ up to six ]85 percent. The alkaline zinc-iron flow battery assembled by the electrolyte is 80mA cm^-2Under the condition of working current density, the coulombic efficiency of the battery can reach 96.13%, the voltage efficiency can reach 91.24%, the battery continuously and stably runs for 67 cycles, and the performance is kept stable.

Example 8

PES/PEG (polyethylene glycol) is used as a base material, and the PES/PEG is dissolved in a DMAC solvent to obtain a blending solution with the mass concentration of 30%, wherein the mass ratio of the PES to the PEG is 80: 20, after the solution is completely dissolved, adding 1.4g of sodium bicarbonate (accounting for 52 percent of the polymer resin), and uniformly stirring and dispersing; pouring the blended solution on a clean and flat glass plate, volatilizing the solvent for 10s under the condition of 20% humidity, and then immersing the whole into a 1 wt% sulfuric acid solution to prepare a porous ion-conducting membrane with the thickness of 90 μm and the pore diameter having gradient distribution at 25 ℃, wherein the preferable range is as follows: the size of the macropores is 1.6-2.3 mu m; the size of the mesopore is 125 nm-190 nm; the pore size is 0.3 nm-0.6 nm, the thickness of the skin layer is about 500nm, the thickness of the macroporous support layer is about 100um, and the porosity of the membrane is 70-85%. The alkaline zinc-iron flow battery assembled by the electrolyte is 80mA cm^-2Under the condition of working current density, because the concentration of acid in the coagulating bath is lower, the reaction rate with particles in the casting solution is lower, and the reaction rate with acid to generate other products is lower than the curing rate of the casting solution, the discontinuous holes of the small hole layer are more, the coulombic efficiency of the battery can reach 99.08 percent, and the voltage efficiency is only 80.16 percent.

Example 9

PES/PEG (polyethylene glycol) is used as a base material, and the PES/PEG is dissolved in a DMAC solvent to obtain a blending solution with the mass concentration of 30%, wherein the mass ratio of the PES to the PEG is 80: 20, after the solution is completely dissolved, adding 1.4g of sodium bicarbonate (accounting for 52 percent of the polymer resin), and uniformly stirring and dispersing; pouring the blended solution on a clean and flat glass plate, volatilizing the solvent for 10s under the condition of 20% humidity, then wholly immersing the blended solution in 30 wt% sulfuric acid solution, and preparing a porous ion-conducting membrane with the thickness of 90 mu m and the pore diameter of gradient distribution at 25 ℃, wherein the size of a large pore is 4.5-4.8 mu m; the size of the mesopore is 634 nm-688 nm; small pore size of 23-28 nm, cortex thickness of 500nm, and large poreThe thickness of the supporting layer is about 100um, and the porosity of the membrane is 70-85%. The alkaline zinc-iron flow battery assembled by the electrolyte is 80mA cm^-2Under the condition of working current density, because the concentration of acid in the coagulating bath is higher, the reaction rate with particles in the casting solution is higher, the reaction rate with the acid to generate other bubbles is higher than the solidification rate of the casting solution, the generated bubbles are disturbed in the uncured casting solution to generate more continuous mesoporous layers, the coulombic efficiency of the battery is only 86.72%, and the voltage efficiency is as high as 92.26%.

Example 10

PES/PEG (polyethylene glycol) is used as a base material, and the PES/PEG is dissolved in a DMAC solvent to obtain a blending solution with the mass concentration of 30%, wherein the mass ratio of the PES to the PEG is 80: 20, after the solution is completely dissolved, adding 1.4g of sodium bicarbonate (accounting for 52 percent of the polymer resin), and uniformly stirring and dispersing; pouring the blended solution on a clean and flat glass plate, volatilizing the solvent for 10s under the condition of 20% humidity, then wholly immersing the blended solution in 10 wt% sulfuric acid solution, and preparing a porous ion-conducting membrane with the thickness of 45 mu m and the pore diameter of gradient distribution at 25 ℃, wherein the size of a large pore is 4.1-4.6 mu m; the mesopore size is 712 nm-824 nm; the pore size is 25 nm-28 nm, the thickness of the cortex is about 500nm, the thickness of the macroporous support layer is about 100um, and the porosity of the membrane is 70-85%. The alkaline zinc-iron flow battery assembled by the electrolyte is 80mA cm^-2Under the condition of working current density, the coulombic efficiency of the battery is only 83.19% due to the thin thickness of the film, the voltage efficiency reaches up to 91.77%, and the mechanical strength of the film is weak due to the thin thickness of the film, so that the film is easily pierced by zinc dendrites deposited by a negative electrode, the battery is short-circuited and failed, and the capacity of the battery is sharply reduced when the battery runs for about 35 cycles.

Example 11

PES/PEG (polyethylene glycol) is used as a base material, and the PES/PEG is dissolved in a DMAC solvent to obtain a blending solution with the mass concentration of 30%, wherein the mass ratio of the PES to the PEG is 80: 20, after the solution is completely dissolved, adding 1.4g of sodium bicarbonate (accounting for 52 percent of the polymer resin), and uniformly stirring and dispersing; pouring the above blended solution on a clean flat glass plate, volatilizing the solvent for 10s under the condition of 20% humidity, and then soaking the whole bodyAdding the mixture into 10 wt% sulfuric acid solution, and preparing a porous ion-conducting membrane with the thickness of 160 mu m and the pore diameter of gradient distribution at 25 ℃, wherein the size of a large pore is 1.1-1.4 mu m; the size of the mesopore is 87 nm-110 nm; the pore size is 0.2 nm-0.4 nm, the thickness of the skin layer is about 500nm, the thickness of the macroporous support layer is about 100um, and the porosity of the membrane is 70-85%. The alkaline zinc-iron flow battery assembled by the electrolyte is 80mA cm^-2Under the condition of working current density, the film thickness is thick, the film resistance is large, and the coulomb efficiency of the battery is only 85.48% (when the alkaline zinc-iron flow battery adopts a constant-capacitance charging mode, the discharge is a voltage cut-off condition, and the resistance of the film is large, the discharge voltage is mostly consumed on the film resistance, so the voltage of the battery quickly reaches the cut-off voltage, and the coulomb of the battery is low), and the voltage efficiency is only 78.86%.

Example 12

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Porous ion-conducting membrane with pore size in gradient distribution, preparation and application

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