Efficient solid electrolyte membrane and preparation method thereof

Abstract

The invention discloses an efficient solid electrolyte membrane and a preparation method thereof, and belongs to the field of polyion liquid. The preparation method comprises the following steps: synthesizing polyepichlorohydrin of which the main chain has a chiral structure through ring-opening polymerization, then exchanging the polyepichlorohydrin with aminoimidazole to synthesize chiral polyion liquid of which the end group contains amino, and forming a micron column structure by the polyion liquid in a solution through a crystallization driving assembly method during film formation. The polyionic liquid shows more excellent conductivity than common polyionic liquid. The electrolyte membrane has the advantages that the electrolyte membrane has relatively high ionic conductivity, the ionic conductivity is increased along with the increase of the temperature, the electrolyte membrane serving as the polyion liquid electrolyte membrane has the potential of being applied to a solid-state lithium battery, and in addition, compared with a traditional organic electrolyte and a traditional polyion liquid electrolyte membrane, the preparation is more environment-friendly and high in safety.

Description

Technical Field

[0001] The present invention belongs to the field of polyionic liquids and specifically relates to a high-efficiency solid electrolyte membrane and a preparation method thereof. Background Art

[0002] Solid polymer electrolyte (SPE), also known as ion-conducting polymer. The most widely studied polymer electrolyte at home and abroad is polyethylene oxide (PEO) polymer electrolyte, but due to the crystallinity of PEO, its room temperature ionic conductivity is very low, about 10 −7 ~10 −8 S / cm. In previous studies, it was found that inhibiting the crystallization of polymer chains and copolymerization and cross-linking are effective ways to improve electrolyte conductivity. In this study, we found that the method of preparing chiral polyionic liquids, because the introduction of chirality in the main chain structure promotes the obvious limitation of the crystallization of the main chain of polyionic liquids, but at the same time, through the crystallization cold-driven method, the amino part of the polymer side chain will partially form assembled crystals, thereby inducing the polymer to form a micron columnar structure. The prepared polyionic liquid solid film exhibits very high conductivity. In fact, the regulation of this polymer structure is an effective method to regulate the conductivity of polyionic liquids. On the one hand, it can be assembled in environmentally friendly solvents, and the crystallization is also limited to a certain nanometer size range, thereby forming a columnar high conductivity polymer. Summary of the invention

[0003] In order to solve the above technical problems, the present invention adopts a preparation method of a highly efficient and green solid electrolyte membrane.

[0004] The present invention provides a polyionic liquid, the structural formula of the polyionic liquid is: .

[0005] The invention provides a method for preparing a polyionic liquid, comprising the following steps: using D or L-epichlorohydrin as a raw material, synthesizing a polyepichlorohydrin with a chiral structure in the main chain through ring-opening polymerization, then exchanging the polyepichlorohydrin with aminoimidazole to synthesize a chiral polyionic liquid with an amino group at the end group, namely the polyionic liquid.

[0006] Furthermore, the polyionic liquid can be cooled in a polar solvent to induce crystallization to form a columnar structure.

[0007] Furthermore, the polyionic liquid has excellent electrical conductivity.

[0008] The present invention provides a method for preparing a high-efficiency solid electrolyte membrane, which adopts the polyionic liquid described in claim 1 and then prepares the high-efficiency solid electrolyte membrane through a crystallization-driven self-assembly method.

[0009] The method further specifically comprises the following steps:

[0010] Chiral polyepichlorohydrin PECH was synthesized by using D or L-epichlorohydrin as the raw material in anhydrous 1,2-dichloroethane-anhydrous ethanol system with anhydrous tin tetrachloride as the initiator and trifluoroacetic acid as the catalyzer. Then, PECH was reacted with aminoimidazole to prepare a counterion of Cl - The polyionic liquid was then further prepared by ion exchange with NTF2 - The solid electrolyte membrane is prepared by a method of preparing a polyionic liquid containing counter ions, dissolving the polyionic liquid in a polar solvent, heating the solvent to a temperature above 60° C., and cooling the solvent for crystallization.

[0011] Further, the specific synthetic route is: .

[0012] The present invention provides a high-efficiency solid electrolyte membrane, which is prepared by the above method.

[0013] Furthermore, the electrolyte membrane has high ionic conductivity, which increases with increasing temperature.

[0014] The present invention also provides a solid-state lithium battery made by using the above-mentioned high-efficiency solid electrolyte membrane.

[0015] A polyionic liquid prepared by the present invention has the following advantages:

[0016] Based on the high viscosity and low conductivity of polyionic liquids, we prepared a polyionic liquid with a main chain of chiral PEO and a side chain containing some aminoimidazole, and formed a polymer film with a columnar structure by cooling crystallization in a polar solvent. The film has excellent ionic conductivity, which increases with increasing temperature. As a high-efficiency solid electrolyte membrane, it has the potential to be used in solid-state lithium batteries. In addition, compared with traditional organic electrolytes, the high-efficiency solid electrolyte membrane prepared by polyionic liquids is more environmentally friendly and more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the columnar structure formed by the chiral polyionic liquid in Example 4 under cold crystallization. DETAILED DESCRIPTION

[0018] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention. Example 1 Synthesis of Chiral Polyepichlorohydrin

[0019] 0.05 mmolSnCl4 and 20 mL of anhydrous 1,2-dichloroethane-10 mL of anhydrous ethanol were added to 1 mmolD-epichlorohydrin respectively, and polymerization was initiated under vacuum conditions to synthesize chiral polyepichlorohydrin with a molecular weight of 500. Example 2 Polyepichlorohydrin linked to aminoimidazole

[0020] Pre-dry 1 mmol chiral PECH (number average molecular weight 500), 100 mL Shrek bottle and magnet in a vacuum drying oven and cool naturally, weigh a certain amount of PECH and add it to the flask, place the flask in a heating mantle for baking, vacuumize and bake, then replace the gas in the flask with argon, repeat vacuum-filling argon 3-4 times, heat the flask evenly to remove the residual solvent in PECH until there are no bubbles, at which time PECH is yellow and transparent, and finally remove the heating mantle under argon filling conditions. Stir and add 0.9 mmol 4-aminoimidazole to the flask at room temperature, continue stirring for 20 min after the addition is complete, transfer the flask to an 80°C oil bath, stir magnetically for 10 h, and the mixed solution is orange. After the reaction is completed, the reaction product is dissolved in anhydrous ethanol and transferred to a 250 ml conical flask, and precipitated in ether several times until the supernatant is not UV-sensitive by TLC to remove the unattached aminoimidazole, and the volatile solvent is removed by rotary evaporation, and the product is vacuum dried at 40°C for 24 h to obtain the final product PIL, which is a white, slightly sticky solid. Example 3 Anion replacement in polyionic liquids

[0021] Take a certain amount of polymer in a 50 mL flask, add water to dissolve it, stir magnetically at room temperature, weigh NaNTF2 and dissolve it in water, and after the addition is complete, transfer the flask to a 40°C oil bath and stir for 48 hours. After the reaction is completed, transfer the mixed solution obtained from the experiment to a dialysis bag, dialyze the mixed solution in deionized water to wash away small molecules, and use silver nitrate solution to check until there is no white precipitate in the eluate, which proves that the product has been washed clean. Finally, use a freeze dryer to freeze-dry to remove the water in the mixed solution to obtain a polyionic liquid after anion replacement. Example 4

[0022] 1 mg of the polyionic liquid prepared in Example 3 was dissolved in 1 mL of ethanol, and then heated to 60°C, then cooled to room temperature and left to stand for 24 h to obtain a polymer with a columnar structure. Figure 1 Transmission diagram showing the columnar structure formed by the chiral polyionic liquid in Example 4 under cold crystallization. Example 5 Conductivity test

[0023] The polyionic liquid obtained in Example 4 was prepared into a 1 mm polymer film in a mold, and then taken out and cut into a circular electrolyte membrane with a diameter of 16 mm, and loaded into a button battery. The lithium-ion battery model used in this article is a CR2025 button battery. The polyionic liquid electrolyte membrane was sandwiched between the LiFePO4 positive electrode and the lithium sheet, and its conductivity was tested.

[0024] As the temperature gradually increases, the ionic conductivity of the solid polyelectrolyte membrane increases. At 30°C, its ionic conductivity is 2.10×10 -3 S.cm -1 When we raise the temperature to 100°C, the ionic conductivity is 2.3 S.cm -1 , significantly improving the conductivity. As the temperature gradually increases, the ionic conductivity of the polyionic liquid electrolyte membrane shows a trend of gradually increasing. In addition, under conditions close to high temperature of 100°C, the ionic conductivity of the membrane shows ideal performance. Example 6

[0025] 0.05 mmolSnCl4 and 20 mL of anhydrous 1,2-dichloroethane-10 mL of anhydrous ethanol were added to 1 mmolD-epichlorohydrin respectively, and polymerization was initiated under vacuum conditions to synthesize chiral polyepichlorohydrin with a molecular weight of 1000.

[0026] The steps of Examples 2, 3 and 4 were followed to obtain a polyionic liquid with a molecular weight of 1000 after anion replacement, and its conductivity was measured in the same manner as in Example 5.

[0027] As the temperature gradually increases, the ionic conductivity of the solid polyelectrolyte membrane increases. At 30°C, its ionic conductivity is 3.13×10 -3 S.cm -1 When we raise the temperature to 100°C, the ionic conductivity is 2.48S.cm -1 , which is significantly improved by more than one order of magnitude. As the temperature gradually increases, the ionic conductivity of the polyionic liquid electrolyte membrane shows a trend of gradually increasing.

Claims

1. A polyionic liquid, characterized in that The structural formula of the polyionic liquid is: 。 2. The method for preparing a polyionic liquid according to claim 1, characterized in that: The method comprises the following steps: using D or L-epichlorohydrin as a raw material, synthesizing a polyepichlorohydrin with a chiral structure in the main chain through ring-opening polymerization, and then exchanging the polyepichlorohydrin with aminoimidazole to synthesize a chiral polyionic liquid with an amino group at the end group, namely the polyionic liquid.

3. The method for preparing a polyionic liquid according to claim 1, characterized in that: The polyionic liquid can be cooled in a polar solvent to induce crystallization to form a columnar structure.

4. The method for preparing a polyionic liquid according to claim 1, characterized in that: The polyionic liquid has excellent electrical conductivity.

5. A method for preparing a high-efficiency solid electrolyte membrane, characterized in that: The high-efficiency solid electrolyte membrane is prepared by using the polyionic liquid described in claim 1 and then by a crystallization-driven self-assembly method.

6. The method for preparing a high-efficiency solid electrolyte membrane according to claim 5, characterized in that: The specific steps include: Chiral polyepichlorohydrin PECH was synthesized by using D or L-epichlorohydrin as the raw material in anhydrous 1,2-dichloroethane-anhydrous ethanol system with anhydrous tin tetrachloride as the initiator and trifluoroacetic acid as the catalyzer. Then, PECH was reacted with aminoimidazole to prepare a counterion of Cl - The polyionic liquid was then further prepared by ion exchange with NTF2 - The solid electrolyte membrane is prepared by a method of preparing a polyionic liquid containing counter ions, dissolving the polyionic liquid in a polar solvent, heating the solvent to a temperature above 60° C., and cooling the solvent for crystallization.

7. The method for preparing a high-efficiency solid electrolyte membrane according to claim 6, characterized in that: The specific synthetic route is: 。 8. A high-efficiency solid electrolyte membrane, characterized in that: Prepared by the method according to any one of claims 1 to 3.

9. A high-efficiency solid electrolyte membrane according to claim 8, characterized in that: The electrolyte membrane has high ionic conductivity, which increases with increasing temperature.

10. A solid-state lithium battery made using the high-efficiency solid electrolyte membrane according to claim 8.

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