Electrolyte membrane for concentration cell and preparation method thereof

Abstract

The invention discloses an electrolyte membrane for a concentration cell and a preparation method of the electrolyte membrane. The preparation method comprises the following steps: synthesizing a sulfonated polyether-ether-ketone polymer; the sulfonated polyether-ether-ketone polymer is used for preparing a sulfonated polyether-ether-ketone membrane, namely an electrolyte membrane, through a solvent pouring method, and the electrolyte membrane is used as a concentration difference battery electrolyte membrane, so that the battery power density can reach more than 5W / m < 2 >. The concentration cell electrolyte membrane is simple in preparation method, excellent in electricity generation performance and good in mechanical performance, and has practical application potential.

Description

Technical Field

[0001] The present invention belongs to the preparation technology of electrolyte membranes for concentration cells, and particularly to a method for preparing an electrolyte membrane for a concentration cell with high output power. Background Art

[0002] With the depletion of traditional fossil fuels and the threat of global climate change, the demand for sustainable and renewable energy by humans is increasing continuously. In recent years, the energy stored in salinity gradient solutions has been regarded as a promising renewable energy source. Among them, reverse electrodialysis (RED) is a process that uses ion exchange membranes (IEMs) and concentration differences to generate electrical energy. It is a variant of electrodialysis technology. By reversing the flow direction of normal electrodialysis, ions in the solution move from the high-concentration region to the low-concentration region under specific conditions, thereby generating a potential difference. Therefore, this technology can generate electrical energy using salinity gradients.

[0003] Currently, most of the research on reverse electrodialysis focuses on inorganic materials such as the monolayer MoS2 nanoporous membrane of nanomaterials in Document 1 (Nature 536 (2016) 197 - 200), organic materials such as the polymer carbon nitride membrane in Document 2 (Angew Chem Int Ed Engl 57 (2018) 10123 - 10126), composite materials such as MXene / ANF in Document 3 (Nat Commun 20 (2019) 2920), and soft matter materials. Although these works have made progress in basic research and provided theoretical guidance for selective membranes in osmotic energy conversion, the progress of materials is still hindered by complex preparation processes and insufficient mechanical properties, restricting the large-scale use of salinity gradient power generation. Therefore, it is necessary to construct membranes with desired properties and easy synthesis. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing an electrolyte membrane for a concentration cell with high output power by adopting a simple polymer synthesis and solvent casting membrane preparation strategy.

[0005] In the first aspect, the present invention provides a method for preparing an electrolyte membrane, and the steps are as follows:

[0006] Synthesize sulfonated polyether ether ketone polymer;

[0007] Prepare a sulfonated polyether ether ketone membrane by solvent casting using the sulfonated polyether ether ketone polymer, which is the electrolyte membrane.

[0008] Preferably, the sulfonated polyether ether ketone polymer is synthesized from concentrated sulfuric acid and polyether ether ketone, and its structural formula is;

[0009]

[0010] Wherein, x is the sulfonation degree, which is controlled to be 0.54 - 0.65.

[0011] Specifically, the dosage ratio of the polyether ether ketone to concentrated sulfuric acid (98%) is 5 g : 95 mL.

[0012] Preferably, the sulfonated polyether ether ketone membrane is prepared from the sulfonated polyether ether ketone polymer by the solvent casting method. The specific steps are as follows: Dissolve the sulfonated polyether ether ketone polymer in N,N-dimethylacetamide, then pour the solution into a casting dish and dry it to obtain a sulfonated polyether ether ketone membrane with a thickness of about 60 μm.

[0013] In a second aspect, the present invention provides an electrolyte membrane prepared by the method described in the first aspect.

[0014] In a third aspect, the present invention provides an electrolyte membrane prepared by the method described in the first aspect as a concentration cell electrolyte membrane, and the power density of the battery can reach more than 5 W / m 2 of the above.

[0015] Compared with the prior art, the present invention has the following remarkable advantages:

[0016] (1) A simple method for preparing a concentration cell electrolyte membrane with a relatively high output power is provided. Through the polymer synthesis and solvent casting method preparation process, the concentration cell electrolyte membrane can reach a relatively high output power.

[0017] (2) Compared with the prior art, it has the advantages of simple polymer synthesis and film preparation process, and good mechanical properties of the prepared concentration cell electrolyte membrane.

[0018] (3) Other similar concentration cell electrolyte membranes can be prepared simultaneously in the same way, meeting the needs of relevant fields, especially the field of conversion from osmotic energy to electrical energy, and having the potential for practical industrial applications.

[0019] The present invention will be further described in detail below with reference to the accompanying drawings. Description of the Drawings

[0020] Figure 1 It is the output power density curve of the concentration cell electrolyte membranes of Examples 2, 3, and 4 of the present invention.

[0021] Figure 2 It is the output power density curve of the SPEEK-8 membrane of Example 4 of the present invention under different concentration gradients. Detailed Embodiments

[0022] In order to make the objectives and technical solutions of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those with ordinary skills in the technical field to which the present invention belongs.

[0023] The following embodiments are further explanations of the present invention, rather than limiting the scope of the present invention.

[0024] Abbreviation explanations in the embodiments:

[0025] SPEEK: Sulfonated poly(ether ether ketone)s

[0026] DMAc: N,N’-dimethylacetamide

[0027] The expression method of the concentration difference battery electrolyte membrane with high output power is SPEEK-x membrane, where SPEEK represents sulfonated polyether ether ketone polymer; x represents the reaction time (h) for synthesizing sulfonated polyether ether ketone.

[0028] Example 1: Synthesis of sulfonated polyether ether ketone with different sulfonation degrees

[0029] Put 5 g of polyether ether ketone and 95 mL of concentrated sulfuric acid (98%) into a flask and react at 45°C for 6, 7, and 8 h respectively to form a brown solution, and then pour it into ice water to produce a pink polymer. Wash the polymer with ultrapure water several times until the pH of the mixture becomes 7, and then dry it at 60°C for 12 h. The obtained product is SPEEK-x (x = 6, 7, 8), and its sulfonation degree and ion exchange capacity vary with the reaction time (6, 7, 8 h) as shown in Table 1:

[0030] Table 1 Sulfonation degree and ion exchange capacity of sulfonated polyether ether ketone with different reaction times

[0031]

[0032] Example 2: Preparation of SPEEK-6 membrane

[0033] 1.2 g of dry SPEEK-6 was dissolved in 30 mL of DMAc. After filtration through a Zhong's funnel, the solution was sonicated to remove bubbles, and then the solution was evenly poured into a casting dish and dried at 80 °C under normal pressure for 10 h, and then taken out after drying at 120 °C under normal pressure for 2 h to obtain a SPEEK-6 membrane with a thickness of about 60 μm.

[0034] Example 3: Preparation of SPEEK-7 membrane

[0035] Similar to the preparation method of the SPEEK-6 membrane in Example 2, the difference is that SPEEK-7 was used.

[0036] Example 4: Preparation of SPEEK-8 membrane

[0037] Similar to the preparation method of the SPEEK-6 membrane in Example 2, the difference is that SPEEK-8 was used.

[0038] Application example: Output power density test

[0039] The output power densities of the concentration difference cell electrolyte membranes prepared in Examples 2, 3, and 4 were tested respectively. The specific process was as follows: A two-compartment reverse electrodialysis device was used. The two compartments were a concentrated compartment and a dilute compartment. The electrodes were Ag|AgCl (during the reverse electrodialysis experiment, the Ag|AgCl electrode participated in the electrochemical reaction, so the electrode needed to be electroplated to ensure electrochemical stability. The method was as follows. A pair of silver electrodes were polished with sandpaper and used as the cathode and anode and placed in 1 M KCl, and electroplating was carried out through an externally applied DC power supply), and the effective membrane area was 0.0314 mm 2 . 0.1, 0.5, and 1 M potassium chloride solutions were placed in the concentrated compartment respectively, and 0.01 M potassium chloride solution was placed in the dilute compartment to form concentration gradient solutions of 10, 50, and 100 times. To avoid solution leakage, the membrane and the compartment were sealed with gaskets. The effective membrane area was controlled by a laser-drilled PI membrane, and its center was a circle with a radius of 0.1 mm. During the test, the Ag|AgCl electrodes were connected to both sides of the load resistor, and a picoammeter was used to measure the voltage value on both sides of the load resistor. By adjusting the size of the load resistor, the voltage on both sides was recorded, and then the curve of the output power density changing with the load resistor was calculated.

[0040] The test results were respectively Figure 1 , Figure 2 listed. Figure 1 The results showed that the higher the degree of sulfonation of the polymer, the higher the output power density of the membrane. Among them, the output power density of SPEEK-8 was the highest, which was 6.24 W / m 2 , and it could effectively convert osmotic energy into electrical energy to meet the needs of commercial benchmarks. Figure 2The results show that the higher the concentration gradient, the higher the output power density of the membrane. Therefore, a higher concentration gradient should be selected in practical applications.

[0041] Table 2 Mechanical strength of SPEEK-x membranes (x = 6, 7, 8)

[0042]

[0043]

[0044] Table 2 shows the mechanical strength of the concentration difference battery electrolyte membranes in Examples 2, 3, and 4 of the present invention. The results show that although the lower the degree of sulfonation of the polymer, the better the mechanical properties, the SPEEK membranes all exhibit excellent mechanical strength.

Claims

1. A method for preparing an electrolyte membrane, characterized in that, The steps are as follows: Synthesize sulfonated polyether ether ketone polymer; Prepare a sulfonated polyether ether ketone membrane by a solvent casting method using the sulfonated polyether ether ketone polymer, which is the electrolyte membrane.

2. The method according to claim 1, wherein The sulfonated polyether ether ketone polymer is synthesized from concentrated sulfuric acid and polyether ether ketone, and its structural formula is; In the formula, x is the sulfonation degree, which is controlled to be 0.54 - 0.

65.

3. The method according to claim 2, characterized in that, The dosage ratio of the polyether ether ketone to the concentrated sulfuric acid is 5g:95mL.

4. The method according to claim 1, wherein Prepare a sulfonated polyether ether ketone membrane by a solvent casting method using the sulfonated polyether ether ketone polymer. The specific steps are: dissolve the sulfonated polyether ether ketone polymer in N,N-dimethylacetamide, then pour the solution into a casting dish and dry it to obtain the sulfonated polyether ether ketone membrane.

5. An electrolyte membrane prepared by the method according to any one of claims 1 - 4.

6. An electrolyte membrane prepared by the method according to any one of claims 1-4 is used as an electrolyte membrane of a concentration cell, and the electrolyte membrane achieves a cell power density of more than 5 W / m 2 2.

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