A self-supporting brush-like polyionic liquid-based electrolyte membrane, a preparation method and application thereof

Abstract

The application relates to a self-supporting brush-shaped polyionic liquid-based electrolyte film and a preparation method and application thereof. The preparation method is as follows: (1) synthesizing 9-bromohexylcarbazole; (2) synthesizing p-toluenesulfonyl-modified polyethylene glycol; (3) synthesizing imidazole-modified polyethylene glycol by taking the p-toluenesulfonyl-modified polyethylene glycol in step (2) as raw material; (4) synthesizing carbazole-functionalized imidazole-based ionic liquid by taking the 9-bromohexylcarbazole in step (1) and the imidazole-modified polyethylene glycol in step (3) as raw material; (5) synthesizing TFSI-containing carbazole-functionalized imidazole-based ionic liquid by taking the carbazole-functionalized imidazole-based ionic liquid in step (4) as raw material; and (6) preparing the product of the application by taking the TFSI-containing carbazole-functionalized imidazole-based ionic liquid in step (5) as raw material. Compared with the prior art, the product prepared by the application has excellent film-forming property, low crystallinity and excellent ionic conductivity, and has a good application prospect in the field of lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a self-supporting brush-shaped polyionic liquid-based electrolyte membrane, its preparation method, and its application. Background Technology

[0002] Currently, human energy consumption is primarily based on fossil fuels (with losses as high as 60%), generating substantial amounts of carbon oxides. Reports indicate that traditional energy consumption accounts for up to 82% of carbon emissions, and energy demand growth between 2000 and 2040 is projected to reach the combined levels of the 20th century. With this ever-increasing energy demand, carbon emissions are incalculable. Although various renewable and clean energy sources (such as solar, wind, and nuclear power) have been developed and utilized, these new energy sources often suffer from unstable power generation voltages, severely impacting their utilization and recycling. Therefore, storing energy and ensuring continuous and stable output is crucial. Currently, lithium-ion batteries, due to their high energy density, high open-circuit voltage, adjustable output power, and fast charging / discharging speeds, serve as efficient energy intermediates connecting new energy sources and end-use applications, and will become a vital component in achieving the goal of "carbon neutrality."

[0003] During the charge and discharge process of lithium-ion batteries, influenced by factors such as traditional liquid electrolytes and the positive and negative electrodes, lithium ions tend to accumulate at the cathode, leading to concentration polarization and the formation of lithium dendrites. These dendrites can puncture the battery separator, causing internal short circuits and posing safety hazards. Polymer electrolytes can effectively mitigate lithium dendrite formation in this regard. Traditional solid-state polymer electrolytes are prepared by dissolving lithium salts and anions within a polymer matrix to achieve dual-ion conductivity, but the lithium-ion transference number is generally low. Ionic liquids possess advantages such as high electrochemical stability and low flammability. Using ionic liquids as the main component, single-lithium-ion conductive solid-state polymer electrolytes can be constructed. While maintaining safety and high efficiency, this promotes the dispersion of negative charges, solving the concentration gradient problem. Even at relatively high charge and discharge currents, the utilization rate of the active electrode material remains at approximately 100%, and the phenomenon of lithium dendrite formation is effectively suppressed. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing solid polymer electrolytes, such as low lithium-ion transference numbers, and to provide a self-supporting brush-shaped polyionic liquid-based electrolyte membrane, its preparation method, and its application.

[0005] This invention leverages the advantages of rapid and easy membrane fabrication through electrochemical polymerization. Using imidazole-based ionic liquids, a novel self-supporting brush-shaped polyionic liquid-based electrolyte membrane is prepared. Strong ionic interactions suppress the crystallinity of polyethylene glycol monomethyl ether, thereby improving the lithium-ion conductivity of the polymer. In lithium-ion battery applications, the self-supporting brush-shaped polymer electrolyte membrane exhibits excellent lithium-ion capacity and good stability.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a method for preparing a self-supporting brush-shaped polyionic liquid-based electrolyte membrane, comprising the following steps:

[0008] Synthesis of S1, 9-bromohexylcarbazole: Carbazole, potassium tert-butoxide, and anhydrous tetrahydrofuran were mixed in an inert gas environment and at room temperature, and then 1,6-dibromohexane was added dropwise for heating reaction. After the reaction was completed, rotary evaporation, extraction, drying and purification were performed in sequence to obtain 9-bromohexylcarbazole.

[0009] S2. Synthesis of p-toluenesulfonyl modified polyethylene glycol: Polyethylene glycol and p-toluenesulfonyl chloride were dissolved in dichloromethane solution. Potassium hydroxide was added under an inert gas environment and the reaction was continued with stirring. After the reaction was completed, the reaction was quenched, extracted and dried in sequence to obtain p-toluenesulfonyl modified polyethylene glycol.

[0010] S3. Synthesis of imidazole-modified polyethylene glycol: The p-toluenesulfonyl-modified polyethylene glycol obtained in step S2, imidazole, sodium hydroxide, and tetrahydrofuran were mixed and refluxed under an inert gas environment. After the reaction was completed, rotary evaporation, extraction, drying, and purification were performed sequentially to obtain imidazole-modified polyethylene glycol.

[0011] S4. Preparation of carbazole-functionalized imidazole-based ionic liquid: 9-bromohexylcarbazole obtained in step S1 and imidazole-modified polyethylene glycol obtained in step S3 were dissolved in anhydrous acetonitrile and refluxed under an inert gas environment. After the reaction was completed, rotary evaporation, extraction and drying were performed in sequence to obtain carbazole-functionalized imidazole-based ionic liquid.

[0012] S5. Preparation of TFSI-containing carbazole-functionalized imidazole ionic liquid: The carbazole-functionalized imidazole ionic liquid obtained in step S4, lithium bis(trifluoromethanesulfonylimide), and anhydrous dichloromethane were heated and reacted in an inert gas environment. After the reaction was completed, rotary evaporation, extraction, and drying were performed sequentially to obtain TFSI-containing carbazole-functionalized imidazole ionic liquid.

[0013] S6. Preparation of self-supporting brush-shaped polyionic liquid-based electrolyte membrane: The TFSI-containing carbazole-functionalized imidazole ionic liquid and tetra-n-butylhexafluorophosphate obtained in step S5 were dissolved in a mixed solution of anhydrous dichloromethane and anhydrous acetonitrile. The resulting mixed solution was used as the electrolyte. Electrochemical polymerization was carried out by cyclic voltammetry using a standard three-electrode system connected to an electrochemical workstation to obtain a self-supporting brush-shaped polyionic liquid-based electrolyte membrane.

[0014] Further, in step S1, the molar ratio of carbazole, potassium tert-butoxide, and 1,6-dibromohexane is 1:1.2:1.2; the inert gas is selected from nitrogen or argon; the time for adding 1,6-dibromohexane is 1 hour; the temperature for heating the reaction is 50°C, and the heating time is 12 hours; the extraction process is set as follows: using saturated sodium chloride solution and dichloromethane as the extractant; the drying process is set as follows: drying with anhydrous sodium sulfate or vacuum drying; the purification process is set as follows: column chromatography separation and purification using a mixture of petroleum ether and dichloromethane as the eluent, wherein the volume ratio of petroleum ether to dichloromethane is 10:1.

[0015] Furthermore, in step S2, the molecular weight of polyethylene glycol is 200-750 (the structural formula of polyethylene glycol is HO(CH2CH2O)). n H, the molecular weight of polyethylene glycol is calculated based on n); the molar ratio of polyethylene glycol monomethyl ether, p-toluenesulfonyl chloride, and potassium hydroxide is 1:1.05:4; the inert gas is selected from nitrogen or argon; the stirring process is set as follows: temperature 0℃, time 5h; the quenching process is set as follows: quenching with water; the extraction process is set as follows: using saturated sodium chloride solution and dichloromethane as extractants; the drying process is set as follows: drying with anhydrous sodium sulfate or vacuum drying, wherein the vacuum drying temperature is 60℃ and the vacuum drying time is 12h.

[0016] Further, in step S3, the molar ratio of imidazole, sodium hydroxide, and p-toluenesulfonyl-modified polyethylene glycol is 2.28:2.15:1; the inert gas is selected from nitrogen or argon; the reflux reaction temperature is 70℃, and the reflux reaction time is 12h; the extraction process is set as follows: saturated sodium chloride solution and dichloromethane are used as extractants; the drying process is set as follows: drying with anhydrous sodium sulfate or vacuum drying; the purification process is set as follows: column chromatography separation and purification with dichloromethane as eluent.

[0017] Further, in step S4, the molar ratio of imidazole-modified polyethylene glycol to 9-bromohexylcarbazole is 1:1.2; the inert gas is selected from nitrogen or argon; the reflux reaction temperature is 86℃, and the reflux reaction time is 12h; the extraction process is set as follows: ethyl acetate and saturated sodium chloride are used as extractants; the drying process is set as follows: drying with anhydrous sodium sulfate or vacuum drying, wherein the vacuum drying temperature is 60℃, and the vacuum drying time is 12h.

[0018] Further, in step S5, the molar ratio of carbazole-functionalized imidazole ionic liquid to lithium bis(trifluoromethanesulfonyl)imide is 1:1; the inert gas is selected from nitrogen or argon; the heating temperature is 45°C and the heating time is 24 h; the extraction process is set as follows: saturated sodium chloride solution and dichloromethane are used as extractants; the drying process is set as follows: drying with anhydrous sodium sulfate or vacuum drying, wherein the vacuum drying temperature is 60°C and the vacuum drying time is 12 h.

[0019] Furthermore, in step S6, the molar ratio of the TFSI-containing carbazole-functionalized imidazole ionic liquid to tetrabutylammonium hexafluorophosphate is 1:100; the volume ratio of anhydrous dichloromethane to anhydrous acetonitrile in the mixed solution of anhydrous dichloromethane and anhydrous acetonitrile is 3:2.

[0020] Furthermore, in step S6, the standard three-electrode system uses Ag / Ag + The reference electrode is a conductive glass electrode, the working electrode is a platinum wire, and the counter electrode is a platinum wire. The voltage range for electrochemical polymerization is -0.4 to 1.6 V, and the scan rate is 100 mV / s. -1 .

[0021] The second technical solution of the present invention is to provide a self-supporting brush-shaped polyionic liquid-based electrolyte membrane, based on the preparation method described in one of the above technical solutions.

[0022] The third technical solution of the present invention is to provide an application of the self-supporting brush-shaped polyionic liquid-based electrolyte membrane as described in the second technical solution above, wherein the self-supporting brush-shaped polyionic liquid-based electrolyte membrane is used as a solid polymer electrolyte in lithium-ion batteries.

[0023] Further, the preparation method of the lithium-ion battery includes the following steps: cutting the self-supporting brush-shaped polyionic liquid-based electrolyte membrane to obtain a self-supporting brush-shaped polyionic liquid-based electrolyte membrane with a size of 19 mm and a thickness of 110 μm, drying it in a vacuum oven at a temperature of 60°C for 12 hours, and then transferring it to a glove box for assembling the lithium-ion battery. In a glove box filled with argon atmosphere, the positive electrode sheet, the self-supporting brush-shaped polyionic liquid-based electrolyte membrane, the negative electrode sheet, the spring sheet, and the gasket are placed sequentially into the positive electrode shell, the negative electrode sheet is covered, and it is placed in a press for encapsulation and forming. The positive electrode sheet is a LiFePO4 electrode sheet with a composition of LiFePO4:Super P:PVDF = 8:1:1 by mass and a size of 12 mm, and the negative electrode sheet is a lithium sheet with a size of 16 mm.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) This invention uses carbazole as a backbone and prepares a self-supporting brush-shaped polyionic liquid-based electrolyte membrane by electrochemical polymerization. Furthermore, ether bonds and imidazole cations are modified onto the side chains of polycarbazole, which, while binding anions, inhibits the crystallization behavior of polyethylene glycol monomethyl ether and helps Li + The membrane moves between chain segments, exhibiting excellent ionic conductivity. Electrochemical test data show that the self-supporting brush-shaped polyionic liquid-based electrolyte membrane prepared in this invention has an initial capacity of 139-171.6 mAh g⁻¹ under 200 cycles at 0.5C. -1 The capacity utilization rate is 89.2-92.2%.

[0026] (2) The self-supporting brush-shaped polyionic liquid-based electrolyte membrane prepared by the present invention has excellent moldability and low crystallinity, and can provide a lithium-ion coordinated polyether structure for lithium-ion transport, and has good application prospects in the field of lithium batteries. Attached Figure Description

[0027] Figure 1 This is a synthetic route diagram for a self-supporting brush-shaped polyionic liquid-based electrolyte membrane.

[0028] Figure 2 This is the 1H NMR spectrum of Cz-Br.

[0029] Figure 3 This is the carbon NMR spectrum of Cz-Br.

[0030] Figure 4 The image shows the 1H NMR spectrum of OTs-PEG-200.

[0031] Figure 5 The 1H NMR spectrum of Im-PEG-200

[0032] Figure 6 The image shows the carbon NMR spectrum of Im-PEG-200.

[0033] Figure 7 The 1H NMR spectrum of Cz-IL-200-Br.

[0034] Figure 8 Rate performance diagrams of the polymer electrolyte membranes prepared in Examples 1-3: a) PCz-IL-200-TFSI; b) PCz-IL-550-TFSI; c) PCz-IL-750-TFSI; d) PEO.

[0035] Figure 9 The following are long-cycle performance diagrams of the polymer electrolyte membranes prepared in Examples 1-3: a) PCz-IL-200-TFSI; b) PCz-IL-550-TFSI; c) PCz-IL-750-TFSI; d) PEO. Detailed Implementation

[0036] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0037] Unless otherwise specified, the raw materials or processing techniques used in the following embodiments and comparative examples are all conventional commercially available raw materials or conventional processing techniques in the art.

[0038] Commercial pure PEO: M w =6×10 5 Brand: Aladdin Reagents; Product Number: P101341.

[0039] The following are the test methods for each embodiment:

[0040] (1) Compositional characterization of intermediate products:

[0041] The proton and carbon NMR spectra of Cz-Br, OTs-PEG-X, Im-PEG-X, and Cz-IL-X-Br were determined using an AVANCEⅢHD 500Hz NMR spectrometer.

[0042] (2) Electrochemical performance characterization of PCz-IL-X-TFSI polymer electrolyte membrane:

[0043] The rate and long-cycle rate performance of button cells were determined using a LAND-CT2001A battery charge-discharge tester at a test temperature of 60℃.

[0044] Example 1:

[0045] A method for preparing a self-supporting brush-shaped polyionic liquid-based electrolyte membrane includes the following steps:

[0046] (1) Weigh 5 g (29.94 mmol) of carbazole and 4.03 g (35.93 mmol) of potassium tert-butoxide into a 250 mL three-necked flask, add 100 mL of tetrahydrofuran, and stir for 30 min at room temperature under argon atmosphere. Weigh 8.77 g (35.93 mmol) of 1,6-dibromohexane and slowly add it dropwise to the mixture over 1 h using a constant pressure dropping funnel. After the addition is complete, heat to 50 °C and react for 12 h. After the reaction is complete, remove the organic solvent by rotary evaporation. Add a certain amount of saturated sodium chloride solution and dichloromethane for extraction. Add anhydrous sodium sulfate to the extracted organic phase and dry. After filtration, remove the organic solvent by rotary evaporation. Use a mixture of PE:CH2Cl2 (v:v = 10:1) as the eluent for column chromatography to obtain Cz-Br. The 1H and 1C NMR spectra of Cz-Br are shown below. Figure 2 and Figure 3 .

[0047] (2) Weigh 1.000 g (5 mmol) of polyethylene glycol (M = 200) and 1.001 g (5.25 mmol) of p-toluenesulfonyl chloride and dissolve them in 50 mL of dichloromethane solution. Under nitrogen and an ice bath (0 °C), slowly add 1.112 g (19.99 mmol) of ground potassium hydroxide and stir for 5 h at this temperature. After the reaction is complete, quench with water. Extract the resulting mixed solution with saturated sodium chloride and dichloromethane. Dry the organic phase obtained by extraction with anhydrous sodium sulfate, filter, remove the organic solvent by rotary evaporation, and dry under vacuum at 60 °C for 12 h to obtain OTs-PEG-200. The 1H NMR spectrum of OTs-PEG-200 is shown below. Figure 4 .

[0048] (3) Weigh 2.06 g (30.28 mmol) imidazole and 1.14 g (28.56 mmol) sodium hydroxide into a 100 mL three-necked flask, add 5 mL of deionized water, stir until the imidazole is completely dissolved, then add 4.70 g (13.28 mmol) OTs-PEG-200 and 50 mL of tetrahydrofuran under nitrogen atmosphere and reflux at 70 °C for 12 h. After the reaction, remove the organic solvent by rotary evaporation, add a certain amount of saturated sodium chloride solution and dichloromethane for extraction, add anhydrous sodium sulfate to the extracted organic phase for drying, filter, remove the organic solvent by rotary evaporation, and perform column chromatography separation and purification using dichloromethane as eluent to obtain Im-PEG-200. The 1H and 1C NMR spectra of Im-PEG-200 are shown below. Figure 5 and Figure 6 .

[0049] (4) Weigh 0.78 g (3.31 mmol) Im-PEG-200 and 1.31 g (3.97 mmol) Cz-Br into a 100 mL three-necked flask, add 50 mL of anhydrous acetonitrile, and reflux at 86 °C for 12 h. After the reaction is complete, remove the organic solvent by rotary evaporation, extract with a certain amount of ethyl acetate and saturated sodium chloride solution, dry the organic phase with anhydrous sodium sulfate, filter, remove the organic solvent by rotary evaporation, and dry under vacuum at 60 °C for 12 h to obtain Cz-IL-200-Br. The 1H NMR spectrum of Cz-IL-200-Br is shown in [reference needed]. Figure 7 .

[0050] (5) Weigh 1 g (1.3 mmol) of Cz-IL-200-Br and 371 mg (1.3 mmol) of LiTFSI into a 100 mL three-necked flask, add 50 mL of anhydrous dichloromethane, and heat at 45 °C for 24 h. After the reaction is complete, the resulting mixed solution is extracted with saturated sodium chloride and dichloromethane. The organic phase obtained by extraction is dried with anhydrous sodium sulfate, filtered, and the organic solvent is removed by rotary evaporation. The solution is then dried under vacuum at 60 °C for 12 h to obtain Cz-IL-200-TFSI.

[0051] (6) Weigh 20 mg (0.024 mmol) of Cz-IL-200-TFSI and 930.33 mg (2.4 mmol) of tetrabutylammonium hexafluorophosphate and dissolve them in a mixed solution of 24 mL of anhydrous dichloromethane and 16 mL of anhydrous acetonitrile. Electrochemical polymerization was carried out using cyclic voltammetry with a standard three-electrode system connected to an electrochemical workstation. In the standard three-electrode system, Ag / Ag + The reference electrode is a conductive glass electrode, the working electrode is a platinum wire, and the counter electrode is a platinum wire. The voltage range for electrochemical polymerization is -0.4 to 1.6 V, and the scan rate is 100 mV / s. -1 The self-supporting brush-shaped polyionic liquid-based electrolyte membrane PCz-IL-200-TFSI was finally obtained.

[0052] The preparation method of lithium-ion batteries includes the following steps:

[0053] (1) PCz-IL-200-TFSI was cut into electrolyte membranes with a diameter of 19 mm and a thickness of 110 μm using a punching machine, and dried in a vacuum oven at 60 °C for 12 h before being transferred to a glove box for later use.

[0054] (2) Under an argon atmosphere in a glove box, the positive electrode, electrolyte membrane, negative electrode, spring sheet, and gasket were sequentially placed into the positive electrode shell, and the negative electrode was placed on top. The shell was then sealed in a press. The positive electrode was a LiFePO4 electrode with a mass ratio of LiFePO4:Super P:PVDF = 8:1:1 and a size of 12 mm. The negative electrode was a lithium sheet with a size of 16 mm. Electrochemical performance tests were then performed.

[0055] like Figure 8 As shown in Figure a, the discharge specific capacity of PCz-IL-200-TFSI at 0.5, 1, 2, 3, 5, and 0.1C are 140, 136, 130, 128, 119, and 133 mAh g, respectively. -1 Compared with commercially available pure PEO polymer electrolyte membranes ( Figure 8 d) In comparison, the PCz-IL-200-TFSI prepared in this embodiment can effectively improve the specific capacity of lithium-ion batteries, and the lithium-ion batteries still have a high discharge specific capacity after returning from a high rate to a low rate.

[0056] For the long-cycle performance of PCz-IL-200-TFSI, see [link to PCz-IL-200-TFSI documentation]. Figure 9 a. At 0.5C, the initial discharge specific capacity of PCz-IL-200-TFSI is 139 mAh g. -1 After 200 cycles, the discharge specific capacity is 128.1 mAh g. -1 Superior performance compared to commercially available pure PEO polymer electrolytes. Figure 9 d). In addition, it retains 92.2% of its capacity, demonstrating excellent electrochemical stability.

[0057] Example 2:

[0058] (1) Weigh 5 g (29.94 mmol) of carbazole and 4.03 g (35.93 mmol) of potassium tert-butoxide into a 250 mL three-necked flask, add 100 mL of tetrahydrofuran and stir for 30 min at room temperature under argon atmosphere. Weigh 8.77 g (35.93 mmol) of 1,6-dibromohexane and slowly add it dropwise to the above mixture over 1 h using a constant pressure dropping funnel. After the addition is complete, heat to 50 °C and react for 12 h. After the reaction is complete, remove the organic solvent by rotary evaporation. Add a certain amount of saturated sodium chloride solution and dichloromethane for extraction. Add anhydrous sodium sulfate to the organic phase obtained by extraction and dry. After filtration, remove the organic solvent by rotary evaporation. Use a mixture of PE:CH2Cl2 (v:v = 10:1) as the eluent for column chromatography separation and purification to obtain Cz-Br.

[0059] (2) Weigh 2.750 g (5 mmol) of polyethylene glycol (M = 550) and 1.001 g (5.25 mmol) of p-toluenesulfonyl chloride and dissolve them in 50 mL of dichloromethane solution. Under nitrogen and ice bath conditions (0 °C), slowly add 1.112 g (19.99 mmol) of ground potassium hydroxide and stir at this temperature for 5 h. After the reaction is completed, add water to quench the reaction. Extract the resulting mixed solution with saturated sodium chloride and dichloromethane. Add anhydrous sodium sulfate to the organic phase obtained by extraction and dry it. After filtration, remove the organic solvent by rotary evaporation and dry it under vacuum at 60 °C for 12 h to obtain OTs-PEG-550.

[0060] (3) Weigh 2.06 g (30.28 mmol) imidazole and 1.14 g (28.56 mmol) sodium hydroxide into a 100 mL three-necked flask, add 5 mL of deionized water, stir until the imidazole is completely dissolved, add 9.35 g (13.28 mmol) OTs-PEG-550 and 50 mL of tetrahydrofuran under nitrogen atmosphere and reflux reaction. The reflux reaction temperature is 70 °C and the reflux reaction time is 12 h. After the reaction is completed, remove the organic solvent by rotary evaporation, add a certain amount of saturated sodium chloride solution and dichloromethane for extraction, add anhydrous sodium sulfate to the organic phase obtained by extraction and dry, filter and remove the organic solvent by rotary evaporation, and perform column chromatography separation and purification with dichloromethane as eluent to obtain Im-PEG-550.

[0061] (4) Weigh 1.94 g (3.31 mmol) Im-PEG-550 and 1.31 g (3.97 mmol) Cz-Br into a 100 mL three-necked flask, add 50 mL of anhydrous acetonitrile, and reflux at 86 °C for 12 h. After the reaction is complete, remove the organic solvent by rotary evaporation, extract with a certain amount of ethyl acetate and saturated sodium chloride solution, dry the organic phase with anhydrous sodium sulfate, filter, remove the organic solvent by rotary evaporation, and dry under vacuum at 60 °C for 12 h to obtain Cz-IL-550-Br.

[0062] (5) Weigh 1.19 g (1.3 mmol) of Cz-IL-550-Br and 371 mg (1.3 mmol) of LiTFSI into a 100 mL three-necked flask, add 50 mL of anhydrous dichloromethane, and heat at 45 °C for 24 h. After the reaction is complete, the resulting mixed solution is extracted with saturated sodium chloride and dichloromethane. Anhydrous sodium sulfate is added to the organic layer obtained by extraction and dried. After filtration, the organic solvent is removed by rotary evaporation and dried under vacuum at 60 °C for 12 h to obtain Cz-IL-550-TFSI.

[0063] (6) Weigh 28.4 mg (0.024 mmol) of Cz-IL-550-TFSI and 930.33 mg (2.4 mmol) of tetra-n-butylhexafluorophosphate and dissolve them in a mixed solution of 24 mL of anhydrous dichloromethane and 16 mL of anhydrous acetonitrile. Electrochemical polymerization was carried out using cyclic voltammetry with a standard three-electrode system connected to an electrochemical workstation. In the standard three-electrode system, Ag / Ag + The reference electrode is a conductive glass electrode, the working electrode is a platinum wire electrode, and the counter electrode is a platinum wire electrode. The voltage range for electrochemical polymerization is -0.4 to 1.6 V, and the scan rate is 100 mV / s. -1 Ultimately, a self-supporting brush-shaped polyionic liquid-based electrolyte membrane, PCz-IL-550-TFSI, was obtained.

[0064] The preparation method of lithium-ion batteries includes the following steps:

[0065] (1) PCz-IL-200-TFSI was cut into electrolyte membranes with a diameter of 19 mm and a thickness of 110 μm using a punching machine, and then dried in a vacuum oven at 60 °C for 12 h before being transferred to a glove box for later use.

[0066] (2) Under an argon atmosphere in a glove box, the positive electrode, electrolyte membrane, negative electrode, spring sheet, and gasket were sequentially placed into the positive electrode shell, and the negative electrode was placed on top. The shell was then sealed in a press. The positive electrode was a LiFePO4 electrode with a mass ratio of LiFePO4:Super P:PVDF = 8:1:1 and a size of 12 mm. The negative electrode was a lithium sheet with a size of 16 mm. Electrochemical performance tests were then performed.

[0067] like Figure 8 As shown in b, the discharge specific capacity of PCz-IL-550-TFSI at 0.5, 1, 2, 3, 5, and 0.1C are 168, 163, 162, 159, 148, and 168 mAh, respectively. -1 Compared with commercially available pure PEO polymer electrolyte membranes ( Figure 8 d) In comparison, the PCz-IL-550-TFSI prepared in this embodiment can effectively improve the specific capacity of lithium-ion batteries, and the lithium-ion batteries still have a high discharge specific capacity after returning from a high rate to a low rate.

[0068] The long-cycle performance of PCz-IL-550-TFSI is as follows: Figure 9 As shown in b, the initial discharge specific capacity of the PCz-IL-550-TFSI is 171.6 mAh g. -1 After 200 cycles, the discharge specific capacity is 149.6 mAh g. -1 The capacity retention rate was 87.2%, which is superior to the performance of commercially available pure PEO polymer electrolytes. Figure 9 d).

[0069] Example 3:

[0070] (1) Weigh 5 g (29.94 mmol) of carbazole and 4.03 g (35.93 mmol) of potassium tert-butoxide into a 250 mL three-necked flask, add 100 mL of tetrahydrofuran and stir for 30 min at room temperature under argon atmosphere. Weigh 8.77 g (35.93 mmol) of 1,6-dibromohexane and slowly add it dropwise to the above mixture over 1 h using a constant pressure dropping funnel. After the addition is complete, heat to 50 °C and react for 12 h. After the reaction is complete, remove the organic solvent by rotary evaporation. Add a certain amount of saturated sodium chloride solution and dichloromethane for extraction. Add anhydrous sodium sulfate to the organic phase obtained by extraction and dry. After filtration, remove the organic solvent by rotary evaporation. Use a mixture of PE:CH2Cl2 (v:v = 10:1) as the eluent for column chromatography separation and purification to obtain Cz-Br.

[0071] (2) Weigh 3.750 g (5 mmol) of polyethylene glycol (M = 750) and 1.001 g (5.25 mmol) of p-toluenesulfonyl chloride and dissolve them in 50 mL of dichloromethane solution. Under nitrogen and ice bath conditions (0 °C), slowly add 1.112 g (19.99 mmol) of ground potassium hydroxide and stir at this temperature for 5 h. After the reaction is completed, add water to quench the reaction. Extract the resulting mixed solution with saturated sodium chloride and dichloromethane. Add anhydrous sodium sulfate to the organic phase obtained by extraction and dry it. After filtration, remove the organic solvent by rotary evaporation and dry it under vacuum at 60 °C for 12 h to obtain OTs-PEG-750.

[0072] (3) Weigh 2.06 g (30.28 mmol) imidazole and 1.14 g (28.56 mmol) sodium hydroxide into a 100 mL three-necked flask, add 5 mL of deionized water, stir until the imidazole is completely dissolved, add 12.01 g (13.28 mmol) OTs-PEG-750 and 60 mL of tetrahydrofuran under nitrogen atmosphere and reflux reaction. The reflux reaction temperature is 70 °C and the reflux reaction time is 12 h. After the reaction is completed, remove the organic solvent by rotary evaporation, add a certain amount of saturated sodium chloride solution and dichloromethane for extraction, add anhydrous sodium sulfate to the organic layer obtained by extraction and dry, filter and remove the organic solvent by rotary evaporation, and perform column chromatography separation and purification with dichloromethane as eluent to obtain Im-PEG-750.

[0073] (4) Weigh 2.60 g (3.31 mmol) Im-PEG-750 and 1.31 g (3.97 mmol) Cz-Br into a 100 mL three-necked flask, add 50 mL of anhydrous acetonitrile, and reflux at 86 °C for 12 h. After the reaction is complete, remove the organic solvent by rotary evaporation, extract with a certain amount of ethyl acetate and saturated sodium chloride solution, dry the organic phase with anhydrous sodium sulfate, filter, remove the organic solvent by rotary evaporation, and dry under vacuum at 60 °C for 12 h to obtain Cz-IL-750-Br.

[0074] (5) Weigh 1.45 g (1.3 mmol) of Cz-IL-750-Br and 371 mg (1.3 mmol) of LiTFSI into a 100 mL three-necked flask, add 50 mL of anhydrous dichloromethane, and heat at 45 °C for 24 h. After the reaction is complete, the resulting mixed solution is extracted with saturated sodium chloride and dichloromethane. Anhydrous sodium sulfate is added to the extracted organic phase for drying. After filtration, the organic solvent is removed by rotary evaporation, and the solution is dried under vacuum at 60 °C for 12 h to obtain Cz-IL-750-TFSI.

[0075] (6) Weigh 33.2 mg (0.024 mmol) of Cz-IL-750-TFSI and 930.33 mg (2.4 mmol) of tetrabutylammonium hexafluorophosphate and dissolve them in a mixed solution of 24 mL of anhydrous dichloromethane and 16 mL of anhydrous acetonitrile. Electrochemical polymerization was carried out using cyclic voltammetry with a standard three-electrode system connected to an electrochemical workstation. In the standard three-electrode system, Ag / Ag + The reference electrode is a conductive glass electrode, the working electrode is a platinum wire, and the counter electrode is a platinum wire. The voltage range for electrochemical polymerization is -0.4 to 1.6 V, and the scan rate is 100 mV / s. -1 Finally, a self-supporting brush-shaped polyionic liquid-based electrolyte membrane PCz-IL-750-TFSI was obtained.

[0076] The preparation method of lithium-ion batteries includes the following steps:

[0077] (1) PCz-IL-200-TFSI was cut into electrolyte membranes with a diameter of 19 mm and a thickness of 110 μm using a punching machine, and dried in a vacuum oven at 60 °C for 12 h before being transferred to a glove box for later use.

[0078] (2) Under an argon atmosphere in a glove box, the positive electrode, electrolyte membrane, negative electrode, spring sheet, and gasket were sequentially placed into the positive electrode shell, and the negative electrode was placed on top. The shell was then sealed in a press. The positive electrode was a LiFePO4 electrode with a mass ratio of LiFePO4:Super P:PVDF = 8:1:1 and a size of 12 mm. The negative electrode was a lithium sheet with a size of 16 mm. Electrochemical performance tests were then performed.

[0079] like Figure 8 As shown in c, the discharge specific capacity of PCz-IL-750-TFSI at 0.5, 1, 2, 3, 5, and 0.1C are 153, 150, 142, 139, 128, and 51 mAh g, respectively. -1 Compared with commercially available pure PEO polymer electrolyte membranes ( Figure 8 d) In comparison, the PCz-IL-750-TFSI prepared in this embodiment can effectively improve the specific capacity of lithium-ion batteries, and the lithium-ion batteries still have a high discharge specific capacity after returning from a high rate to a low rate.

[0080] The long-cycle performance of PCz-IL-750-TFSI is as follows: Figure 9 As shown in c, the initial discharge specific capacity of PCz-IL-750-TFSI is 153.9 mAh g. -1 After 200 cycles, the discharge specific capacity is 137.3 mAh g. -1 The capacity retention rate was 89.2%, which is superior to the performance of commercially available pure PEO polymer electrolytes. Figure 9 d).

[0081] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a self-supporting brush-shaped polyionic liquid-based electrolyte membrane, characterized in that, Includes the following steps: Synthesis of S1, 9-bromohexylcarbazole: Carbazole, potassium tert-butoxide, and anhydrous tetrahydrofuran were mixed in an inert gas environment and at room temperature, and then 1,6-dibromohexane was added dropwise for heating reaction. After the reaction was completed, rotary evaporation, extraction, drying and purification were performed in sequence to obtain 9-bromohexylcarbazole. S2. Synthesis of p-toluenesulfonyl modified polyethylene glycol: Polyethylene glycol and p-toluenesulfonyl chloride were dissolved in dichloromethane solution. Potassium hydroxide was added under an inert gas environment and the reaction was continued with stirring. After the reaction was completed, the reaction was quenched, extracted and dried in sequence to obtain p-toluenesulfonyl modified polyethylene glycol. S3. Synthesis of imidazole-modified polyethylene glycol: The p-toluenesulfonyl-modified polyethylene glycol obtained in step S2, imidazole, sodium hydroxide, and tetrahydrofuran were mixed and refluxed under an inert gas environment. After the reaction was completed, rotary evaporation, extraction, drying, and purification were performed sequentially to obtain imidazole-modified polyethylene glycol. S4. Preparation of carbazole-functionalized imidazole-based ionic liquid: 9-bromohexylcarbazole obtained in step S1 and imidazole-modified polyethylene glycol obtained in step S3 were dissolved in anhydrous acetonitrile and refluxed under an inert gas environment. After the reaction was completed, rotary evaporation, extraction and drying were performed in sequence to obtain carbazole-functionalized imidazole-based ionic liquid. S5. Preparation of TFSI-containing carbazole-functionalized imidazole ionic liquid: The carbazole-functionalized imidazole ionic liquid obtained in step S4, lithium bis(trifluoromethanesulfonylimide), and anhydrous dichloromethane were heated and reacted in an inert gas environment. After the reaction was completed, rotary evaporation, extraction, and drying were performed sequentially to obtain TFSI-containing carbazole-functionalized imidazole ionic liquid. S6. Preparation of self-supporting brush-shaped polyionic liquid-based electrolyte membrane: The TFSI-containing carbazole-functionalized imidazole ionic liquid and tetra-n-butylhexafluorophosphate obtained in step S5 were dissolved in a mixed solution of anhydrous dichloromethane and anhydrous acetonitrile. The resulting mixed solution was used as the electrolyte. Electrochemical polymerization was carried out by cyclic voltammetry using a standard three-electrode system connected to an electrochemical workstation to obtain a self-supporting brush-shaped polyionic liquid-based electrolyte membrane.

2. The method for preparing a self-supporting brush-shaped polyionic liquid-based electrolyte membrane according to claim 1, characterized in that, In step S1, the molar ratio of carbazole, potassium tert-butoxide, and 1,6-dibromohexane is 1:1.2:1.2; the inert gas is selected from nitrogen or argon; the time for adding 1,6-dibromohexane is 1 hour; the reaction temperature is 50°C and the reaction time is 12 hours; the extraction process is set as follows: saturated sodium chloride solution and dichloromethane are used as the extractant; the drying process is set as follows: drying with anhydrous sodium sulfate or vacuum drying; the purification process is set as follows: column chromatography separation and purification is performed using a mixture of petroleum ether and dichloromethane as the eluent, wherein the volume ratio of petroleum ether to dichloromethane is 10:

1.

3. The method for preparing a self-supporting brush-shaped polyionic liquid-based electrolyte membrane according to claim 1, characterized in that, In step S2, the molecular weight of polyethylene glycol is 200-750; the molar ratio of polyethylene glycol monomethyl ether, p-toluenesulfonyl chloride, and potassium hydroxide is 1:1.05:4; the inert gas is selected from nitrogen or argon; the stirring process is set as follows: temperature 0℃, time 5h; the quenching process is set as follows: quenching by adding water; the extraction process is set as follows: using saturated sodium chloride solution and dichloromethane as extractants; the drying process is set as follows: drying by adding anhydrous sodium sulfate or vacuum drying, wherein the vacuum drying temperature is 60℃ and the vacuum drying time is 12h.

4. The method for preparing a self-supporting brush-shaped polyionic liquid-based electrolyte membrane according to claim 1, characterized in that, In step S3, the molar ratio of imidazole, sodium hydroxide, and p-toluenesulfonyl-modified polyethylene glycol is 2.28:2.15:1; the inert gas is selected from nitrogen or argon; the reflux reaction temperature is 70℃, and the reflux reaction time is 12h; the extraction process is set as follows: saturated sodium chloride solution and dichloromethane are used as extractants; the drying process is set as follows: drying with anhydrous sodium sulfate or vacuum drying; the purification process is set as follows: column chromatography separation and purification with dichloromethane as eluent.

5. The method for preparing a self-supporting brush-shaped polyionic liquid-based electrolyte membrane according to claim 1, characterized in that, In step S4, the molar ratio of imidazole-modified polyethylene glycol to 9-bromohexylcarbazole is 1:1.2; the inert gas is selected from nitrogen or argon; the reflux reaction temperature is 86℃ and the reflux reaction time is 12h; the extraction process is set as follows: ethyl acetate and saturated sodium chloride are used as extractants; the drying process is set as follows: drying with anhydrous sodium sulfate or vacuum drying, wherein the vacuum drying temperature is 60℃ and the vacuum drying time is 12h.

6. The method for preparing a self-supporting brush-shaped polyionic liquid-based electrolyte membrane according to claim 1, characterized in that, In step S5, the molar ratio of carbazole-functionalized imidazole ionic liquid to lithium bis(trifluoromethanesulfonyl)imide is 1:1; the inert gas is selected from nitrogen or argon; the heating temperature is 45℃ and the heating time is 24h; the extraction process is set as follows: saturated sodium chloride solution and dichloromethane are used as extractants; the drying process is set as follows: drying with anhydrous sodium sulfate or vacuum drying, wherein the vacuum drying temperature is 60℃ and the vacuum drying time is 12h.

7. The method for preparing a self-supporting brush-shaped polyionic liquid-based electrolyte membrane according to claim 1, characterized in that, In step S6, the molar ratio of the TFSI-containing carbazole-functionalized imidazole ionic liquid to tetrabutylammonium hexafluorophosphate is 1:100; the volume ratio of anhydrous dichloromethane to anhydrous acetonitrile in the mixed solution of anhydrous dichloromethane and anhydrous acetonitrile is 3:

2.

8. The method for preparing a self-supporting brush-shaped polyionic liquid-based electrolyte membrane according to claim 1, characterized in that, In step S6, the standard three-electrode system uses Ag / Ag + The reference electrode is a conductive glass electrode, the working electrode is a platinum wire, and the counter electrode is a platinum wire. The voltage range for electrochemical polymerization is -0.4 to 1.6 V, and the scan rate is 100 mV / s. -1 .

9. A self-supporting brush-shaped polyionic liquid-based electrolyte membrane, characterized in that, Based on the preparation method according to any one of claims 1-8.

10. An application of the self-supporting brush-shaped polyionic liquid-based electrolyte membrane as described in claim 9, characterized in that, The self-supporting brush-shaped polyionic liquid-based electrolyte membrane is used as a solid polymer electrolyte in lithium-ion batteries.

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