A single-ion quasi-solid polymer electrolyte, a preparation method thereof and an application thereof

Abstract

The present invention provides a single-ion quasi-solid-state polymer electrolyte, a preparation method, and its application. The single-ion quasi-solid-state polymer electrolyte is prepared from a lithium-rich porous aromatic framework material (PAF material), a small molecule lithium salt, and a functional polymer. The present invention uses a monomer containing an imidazole structure to prepare a PAF material containing an imidazole structure, and then lithiates the PAF material containing an imidazole structure to obtain a lithium-rich PAF material. The lithium-rich PAF material is then solution-blended with a small molecule lithium salt and a functional polymer, and after soaking in a plasticizer, a single-ion quasi-solid-state polymer electrolyte is obtained, thereby improving the electrochemical performance and stability of the battery. At room temperature, the ionic conductivity of the single-ion quasi-solid-state polymer electrolyte obtained by the present invention is 2.06×10 ‑4 S cm ‑1 , the lithium ion transference number is ~0.76, and the electrochemical window can reach ~5.1V (vsLi + Therefore, the polymer electrolyte obtained by the present invention has good application prospects in the field of batteries.

Description

Technical Field

[0001] The present invention belongs to the field of polymer electrolytes, and in particular relates to a single-ion quasi-solid polymer electrolyte, a preparation method and applications thereof. Background Art

[0002] Lithium metal batteries (LMBs) are increasingly attracting attention due to their high energy density and ultra-low redox potential. However, the safety of liquid electrolytes and the performance degradation caused by dendrite growth and cathode electrochemistry have seriously hindered the practical application of LMBs. At the same time, the contradiction between high energy density and high safety needs to be resolved in practical applications. At present, quasi-solid-state polymer electrolytes (QSPE) have advantages in adaptability and safety to current battery technology and are considered to be a very promising solution. However, the quasi-solid-state polymer electrolytes currently prepared have the problem of low electrochemical stability, such as low lithium ion migration number, narrow electrochemical window, and low ionic conductivity. Therefore, how to obtain quasi-solid-state polymer electrolytes for lithium batteries with excellent electrochemical performance is a technical problem that needs to be solved urgently. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a single-ion quasi-solid polymer electrolyte, the preparation method of which comprises the following steps:

[0004] Step 1: Under nitrogen, 1,3,5-tris(4-ethynylphenyl)benzene and 4,7-dibromo-1H-benzimidazole are added to a solvent in a molar ratio of 1:1-3, and then tetrakis(triphenylphosphine)palladium and cuprous iodide are added; then, after a cycle of -196°C liquid nitrogen cooling-vacuuming-nitrogen filling-50°C heating and thawing, the mixture is reacted at 80-120°C for 40-55 hours, and vacuum dried at 40-60°C for 12-48 hours to obtain a PAF material containing an imidazole structure, wherein the mass ratio of 1,3,5-tris(4-ethynylphenyl)benzene:4,7-dibromo-1H-benzimidazole:tetrakis(triphenylphosphine)palladium:copper iodide is 1-5:1.5-5:0.1-1:0.1-1.5;

[0005] The solvent is one or any combination of n-hexane, N,N-dimethylformamide, acetone, triethylamine, and N-pyrrolidone;

[0006] Step 2: Under nitrogen protection, the imidazole structure-containing PAF material obtained in step 1 and the lithiated compound are mixed in a solvent, reacted at -30°C to 30°C for 48 to 60 hours, and then the product is filtered, washed with a solvent, and vacuum-dried at 60 to 80°C for 12 to 48 hours to obtain a lithium-rich PAF material;

[0007] The lithiated compound is one or any combination of n-butyl lithium, tert-butyl lithium, methyl lithium, and phenyl lithium; the mass ratio of the PAF material containing an imidazole structure to the lithiated compound is 0.1 to 1:1; the solvent is one or any combination of n-hexane, cyclohexane, heptane, or toluene;

[0008] Step 3: Under vacuum conditions, the lithium-rich PAF material and lithium salt obtained in step 2 are added to a solvent, stirred at 15-40°C for 20-30 hours, and then a functional polymer is added under normal pressure. After stirring at 15-40°C for 20-30 hours, the mixture is vacuum dried at 60-150°C for 6-15 hours to obtain a polymer electrolyte;

[0009] The solvent is one or any combination of N-pyrrolidone, N,N-dimethylformamide, acetone, and triethylamine; the lithium salt is one or any combination of lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiAsF6), lithium hexafluorophosphate (LiPF6), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI); the functional polymer is one or any combination of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polyvinyl alcohol (PVA); the mass ratio of the functional polymer, lithium-rich PAF material, and lithium salt is 1-25:1:1-10;

[0010] Step 4: Soaking the polymer electrolyte obtained in step 3 in a plasticizer for 10 minutes to 2 hours at room temperature to obtain a single-ion quasi-solid polymer electrolyte;

[0011] The plasticizer is one or any combination of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene glycol dimethyl ether (DME).

[0012] The present invention also provides application of the single-ion quasi-solid polymer electrolyte in lithium-ion batteries.

[0013] Beneficial effects of the present invention:

[0014] Compared with the prior art, the present invention provides the following advantages to the single-ion quasi-solid polymer electrolyte (SIQSPE) through the synergistic effect of raw materials, reaction ratio and process:

[0015] The main structure of the single-ion quasi-solid polymer electrolyte obtained by the present invention is a benzene ring, which is a highly stable rigid skeleton structure. It has the characteristics of being lithium-rich, having good compatibility with electrodes, good stability, safety, high specific surface area, and adjustable pores. The formation of a single-ion system through lithiation is beneficial to the quality control of lithium ions, and provides more transmission channels for lithium ions, thereby improving the transmission efficiency of lithium ions; in terms of improving Li + While increasing the content in PAF, the anions are fixed on the skeleton, and only lithium ions move in the system, promoting the dissociation and transmission of lithium ions, achieving efficient departure and rapid movement of lithium ions; increasing the number of lithium ion migration, reducing concentration polarization, and inhibiting the formation of lithium dendrites; and helping to increase the interaction area between the polymer electrolyte and the electrode material, reducing the interface impedance, and improving the lithium ion conductivity. The conductivity reaches 2.06×10 at room temperature. -4 S cm -1 , which is higher than the MOF-doped quasi-solid polymer electrolyte reported in the prior art (1.38×10 -4 S cm -1 (Chen Lining. Preparation of polymer / metal organic framework composite quasi-solid polymer electrolyte by photoinitiated in situ polymerization and research on its performance [D]. Hubei University, 2022.), which is much higher than the common pure PEO electrolyte (8×10 at 30°C). -6 S cm -1 )(Liu Y, Zhao Y, Lu W, et al. PEO based polymer in plastic crystal electrolytes for room temperature high-voltage lithium metal batteries[J]. Nano Energy, 2021, 88: 106205.) In addition, the single-ion quasi-solid polymer electrolyte obtained in the present invention has excellent cycle performance and rate performance. At 0.2C, its initial discharge capacity is 164 mAh g -1 , the specific capacity reaches 130mA h·g at 2C -1 , the specific capacity reaches 107mAh·g at 3C -1 The capacity retention rate after 100 cycles is 98.8-99.92%; after 300 cycles, the specific capacity is 151 mAh g -1 The capacity retention rate can still reach 92%; the coulombic efficiency is ≈100%, and the lithium ion transference number is 0.76, which is much higher than the lithium ion transference number of commercial PE / PP separator (~0.3).

[0016] The single-ion quasi-solid polymer electrolyte obtained in the present invention has a small activation energy of 0.142 eV, and has a lower lithium ion dissociation energy barrier; compared with the existing technology, the activation energy reported in the existing technology "A Single-Ion Conducting Borate Network Polymer as a Viable Quasi-Solid Electrolyte for Lithium Metal Batteries" (Journal: Adv. Mater. 2020, 32, 1905771; Author: Dong-Myeong Shin et al.) is 0.24 eV, which is much larger than the activation energy of the present invention. Therefore, the lithium ions of the present invention are more easily dissociated and moved inside the electrolyte.

[0017] In addition, the oxidation stability potential of the single-ion quasi-solid polymer electrolyte prepared by the present invention can be stabilized to 5.1V (vs Li + / Li), which is much higher than that of commercial PP separator (2.0-4.5V), and there is no oxidation leakage current, indicating that the single-ion quasi-solid-state polymer electrolyte prepared by the present invention has good electrochemical stability.

[0018] 2. The single-ion quasi-solid polymer electrolyte of the present invention has a simple preparation method, a wide range of raw materials, conventional instruments, and is easy to use. It has good application prospects in the field of lithium-ion batteries and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the infrared spectrum of PAF-220-1 obtained in Example 1 of the present invention;

[0020] Figure 2 This is a cycle performance curve of a battery assembled with the single-ion quasi-solid polymer electrolyte PAF-220-SIQSPE-20 obtained in Example 1 of the present invention;

[0021] Figure 3 This is a rate performance curve of the PAF-220-SIQSPE-20 obtained in Example 1 of the present invention after being assembled into a battery;

[0022] Figure 4 This is the AC impedance spectrum of the PAF-220-SIQSPE-20 obtained in Example 1 of the present invention after being assembled into a battery;

[0023] Figure 5 This is a diagram of the AC impedance spectrum fitted with the Arrhenius equation after the PAF-220-SIQSPE-20 obtained in Example 1 of the present invention is assembled into a battery;

[0024] Figure 6This is an electrochemical window test curve diagram of the PAF-220-SIQSPE-20 obtained in Example 1 of the present invention after being assembled into a battery. DETAILED DESCRIPTION

[0025] Example

[0026] The present invention is further described below through specific examples. These examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0027] Example 1

[0028] (1) Under nitrogen purge, 1,3,5-tris(4-ethynylphenyl)benzene (0.23 g, 0.60 mmol) and 4,7-dibromo-1H-benzimidazole (0.25 g, 0.90 mmol) were added to a round-bottom flask, followed by 15 mL of DMF and 15 mL of triethylamine. Tetrakis(triphenylphosphine)palladium (0.15 g, 0.13 mmol) and CuI (0.05 g, 0.26 mmol) were then added. After three cycles of cooling at -196°C with liquid nitrogen, vacuuming, and heating and thawing at -50°C with nitrogen, the reaction system was refluxed at 100°C for 48 h. After the reaction was completed, the mixture was filtered and vacuum-dried at 60°C for 24 h to obtain brownish-yellow powder PAF-220-1. Under nitrogen protection, 200 mg of the obtained PAF-220 was added to 10 mL of anhydrous n-hexane and stirred for 10 min. Add 3 mL of 1.6 mol L -1 A solution of n-butyl lithium in n-hexane was stirred for 2 h, and the mixed solution was transferred to room temperature and stirred for 48 h. The solid was filtered, washed with n-hexane, and dried at 60 ° C for 24 h to obtain PAF-220-1-Li, whose structure is as follows:

[0029] Structure of PAF-220-1-Li

[0030] (2) 26.6 mg of PAF-220-1-Li and 40 mg of LiTFSI prepared in step (1) were added to N-methylpyrrolidone under vacuum conditions and stirred at room temperature for 24 h. Then, 106.4 mg of PVDF-HFP was added under normal pressure and stirred at room temperature for 24 h. The mixed solution was dropped onto a glass plate and then vacuum dried at 120°C for 12 h to obtain a polymer electrolyte. The obtained polymer electrolyte was cut into discs with a diameter of 16 mm and soaked in plasticizer EC / PC (v / v=1:1) at room temperature for 1 h to obtain a single-ion quasi-solid-state polymer electrolyte PAF-220-SIQSPE-20, wherein the mass of PAF-220-1-Li accounts for 20% of the total mass of PAF-220-1-Li and PVDF-HFP.

[0031] Example 2

[0032] (1) Under nitrogen purge, 1,3,5-tris(4-ethynylphenyl)benzene (0.34 g, 0.90 mmol) and 4,7-dibromo-1H-benzimidazole (0.25 g, 0.90 mmol) were added to a round-bottom flask, followed by 15 mL of DMF and 15 mL of triethylamine. Tetrakis(triphenylphosphine)palladium (0.23 g, 0.20 mmol) and CuI (0.08 g, 0.40 mmol) were then added. After three cycles of cooling at -196°C with liquid nitrogen, vacuuming, and heating and thawing at -50°C with nitrogen, the reaction system was refluxed at 100°C for 48 h. After the reaction was completed, the mixture was filtered and vacuum-dried at 60°C for 24 h to obtain brown-yellow powder PAF-220-2. Under nitrogen protection, 200 mg of the obtained PAF-220-2 was added to 10 mL of anhydrous n-hexane and stirred for 10 min. Add 4.8 mL of 1.6 mol L -1 A n-hexane solution of tert-butyl lithium was stirred for 2 h; the mixed solution was transferred to room temperature and stirred for 48 h, the solid was filtered, washed with n-hexane, and dried at 60 ° C for 24 h to obtain PAF-220-2-Li.

[0033] (2) 20.0 mg of PAF-220-2-Li and 30 mg of LiFSI prepared in step (1) were added to N-methylpyrrolidone under vacuum conditions and stirred at room temperature for 24 h. Then, 113.0 mg of PVDF-HFP was added under normal pressure and stirred at room temperature for 24 h. The mixed solution was dropped onto a glass plate and then vacuum dried at 120°C for 12 h to obtain a polymer electrolyte. The obtained polymer electrolyte was cut into discs with a diameter of 16 mm and immersed in plasticizer EC / DMC (v / v=2:1) at room temperature for 1 h to obtain a single-ion quasi-solid-state polymer electrolyte PAF-220-SIQSPE-15, in which the mass of PAF-220-2-Li accounted for 15% of the total mass of PAF-220-2-Li and PVDF-HFP.

[0034] Example 3

[0035] (1) Under nitrogen purge, 1,3,5-tris(4-ethynylphenyl)benzene (0.23 g, 0.60 mmol) and 4,7-dibromo-1H-benzimidazole (0.33 g, 1.20 mmol) were added to a round-bottom flask, followed by 15 mL of DMF and 15 mL of triethylamine. Tetrakis(triphenylphosphine)palladium (0.23 g, 0.20 mmol) and CuI (0.08 g, 0.40 mmol) were then added. After three cycles of cooling at -196°C with liquid nitrogen, vacuuming, and heating and thawing at -50°C with nitrogen, the reaction system was refluxed at 100°C for 48 h. After the reaction was completed, the mixture was filtered and vacuum-dried at 60°C for 24 h to obtain brown-yellow powder PAF-220-3. Under nitrogen protection, 200 mg of the obtained PAF-220-3 was added to 16 mL of anhydrous n-hexane and stirred for 10 min. Add 3.9 mL, 1.6 mol L -1 A n-hexane solution of tert-butyl lithium was stirred for 2 h, and the mixed solution was transferred to room temperature and stirred for 48 h. The solid was filtered, washed with n-hexane, and dried at 60 °C for 24 h to obtain PAF-220-3-Li.

[0036] (2) 13.3 mg of PAF-220-3-Li and 30 mg of LiPF6 prepared in step (1) were added to N-methylpyrrolidone under vacuum conditions and stirred at room temperature for 24 h. Then, 119.7 mg of PVDF-HFP was added under normal pressure and stirred at room temperature for 24 h. The mixed solution was dropped onto a glass plate and then vacuum dried at 120°C for 12 h to obtain a polymer electrolyte. The obtained polymer electrolyte was cut into 16 mm diameter discs and soaked in plasticizer EMC / PC (v / v = 1:1) at room temperature for 1 h to obtain a single-ion quasi-solid-state polymer electrolyte PAF-220-SIQSPE-10, in which the mass of PAF-220-3-Li accounted for 10% of the total mass of PAF-220-3-Li and PVDF-HFP.

[0037] Example 4

[0038] (1) Under nitrogen purge, 1,3,5-tris(4-ethynylphenyl)benzene (0.23 g, 0.60 mmol) and 4,7-dibromo-1H-benzimidazole (0.42 g, 1.50 mmol) were added to a round-bottom flask, followed by 20 mL of DMF and 20 mL of triethylamine. Tetrakis(triphenylphosphine)palladium (0.30 g, 0.26 mmol) and CuI (0.1 g, 0.52 mmol) were then added. After three cycles of cooling at -196°C with liquid nitrogen, vacuuming, and heating and thawing at -50°C with nitrogen, the reaction system was refluxed at 100°C for 48 h. After the reaction was completed, the mixture was filtered and vacuum-dried at 60°C for 24 h to obtain brownish-yellow powder PAF-220-4. Under nitrogen protection, 200 mg of the obtained PAF-220-4 was added to 10 mL of anhydrous n-hexane and stirred for 10 min. Add 3 mL of 1.6 mol L -1 A solution of n-butyl lithium in n-hexane was stirred for 2 h, and the mixed solution was transferred to room temperature and stirred for 48 h. The solid was filtered, washed with n-hexane, and dried at 60 °C for 24 h to obtain PAF-220-4-Li.

[0039] (2) 33.3 mg of PAF-220-4-Li and 30 mg of LiClO4 prepared in step (1) were added to N-methylpyrrolidone under vacuum conditions and stirred at room temperature for 24 h. Then, 99.7 mg of PVDF-HFP was added under normal pressure and stirred at room temperature for 24 h. The mixed solution was dropwise added to a glass plate and then vacuum dried at 120°C for 12 h to obtain a polymer electrolyte. The obtained polymer electrolyte was cut into 16 mm diameter discs and soaked in a plasticizer EMC / DME (v / v = 2:1) at room temperature for 1 h to obtain a single-ion quasi-solid-state polymer electrolyte PAF-220-SIQSPE-25, in which the mass of PAF-220-4-Li accounted for 25% of the total mass of PAF-220-4-Li and PVDF-HFP.

[0040] Comparative Example 1 (Single-ion Quasi-solid Polymer Electrolyte)

[0041] Article Title: Single-Ion Conducting Borate Network Polymer as a Viable Quasi-Solid Electrolyte for Lithium Metal Batteries

[0042] Journal: Adv. Mater. 2020, 32, 1905771

[0043] Authors: Dong-Myeong Shin, Jonathan E. Bachman, Mercedes K. Taylor, et al.

[0044] Methods: In the presence of n-butyl lithium, tetrakis (4- (chloromethyl) -2.3.5.6 tetrafluorophenyl) lithium borate and cis-2-butene-1,4-diol were polymerized to obtain a non-porous anionic network polymer with tetraphenylborate anion nodes. The polymer was dispersed in N, N-dimethylformamide and then ultrasonicated. The suspension was drop-cast onto a polydimethylsiloxane substrate or mixed with a free radical initiator 2,2′-azobis (2-methylpropionitrile) and then drop-cast. The sample was heated at 70 ° C for 12 h to completely evaporate the N, N-dimethylformamide, and then a free-standing single-ion quasi-solid-state polymer electrolyte was obtained. The ionic conductivity of the polymer electrolyte membrane at room temperature was 1.5×10 -4 S cm -1 , Li + The activation energy of the transmission is 0.24eV, and the electrochemical window is 4.5V (vs.Li + / Li).

[0045] The ionic conductivity of the single-ion quasi-solid polymer electrolyte in Comparative Example 1 is 1.5×10 -4 S cm -1 The single-ion quasi-solid polymer electrolyte PAF-220-SIQSPE-20 prepared in Example 1 of the present invention has a high ionic conductivity of 2.06×10 -4 S cm -1 , the activation energy is 0.142 eV, which is lower than the activation energy disclosed in Comparative Example 1, so Li + The movement of ions requires a lower energy barrier and is easier to dissociate and move in the electrolyte, resulting in a higher Li + At the same time, the oxidation stability potential of PAF-220-SIQSPE-20 prepared in Example 1 can be stabilized to 5.1V (vs Li + / Li), and without any oxidation leakage current, which is higher than the electrochemical window of the quasi-solid polymer electrolyte in Comparative Example 1 (4.5V (vs.Li + / Li)), indicating that the single-ion quasi-solid-state polymer electrolyte prepared by the present invention has excellent electrochemical stability.

[0046] manual Figure 1 Infrared testing

[0047] PAF-220-1 was tested with infrared spectrum. The test results are as follows: Figure 1 As shown in the figure, it can be seen that the -1The peaks appearing at 1450 cm-1 are the characteristic peaks of ≡CC of PAF-220-1, indicating the conversion of alkyne hydrogen to alkyne carbon. -1 , 1500cm -1 , 1584cm -1 The C=C characteristic peak on the benzene ring appears at 702cm -1 , 807cm -1 , 877cm -1 The characteristic peak of CH out-of-plane bending vibration appears at , indicating that PAF-220-1 was successfully synthesized.

[0048] manual Figure 2 Cyclic performance test

[0049] Using lithium iron phosphate (LFP) as the positive electrode material, 8g LFP, 1g acetylene black and 1g PVDF were dissolved in 5mL of organic solvent NMP and evenly blended to prepare a viscous slurry. The mixed slurry was then evenly spread on aluminum foil with a spatula to obtain aluminum foil loaded with positive electrode material. After drying, it was cut into discs with a diameter of 12mm using a punch and vacuum dried at 120°C for 24h. After the positive electrode sheet was prepared, in a glove box filled with argon atmosphere (H2O <0.5ppm, O2 <0.5ppm), a lithium iron phosphate composite electrode was used as the positive electrode and a metal lithium sheet was used as the negative electrode. The PAF-220-SIQSPE-20 prepared in Example 1 was used to seal and assemble a 2025 button cell. Within the voltage window of 3.0 to 4.3V. The rate performance and cycle performance of the lithium battery were tested using the Xinwei battery testing system. The cycle performance test results of the battery assembled using PAF-220-SIQSPE-20 are as follows: Figure 2 As shown, at 0.2C, its reversible specific capacity is 164mAh·g -1 After 100 cycles, the capacity retention rate is 99.92%, and after 300 cycles, the capacity retention rate can still reach 92%, and the coulombic efficiency is ≈100%. This shows that the single-ion quasi-solid polymer electrolyte PAF-220-SIQSPE-20 has good cycling stability.

[0050] After 100 cycles, the capacity retention rates of the polymer electrolytes obtained in Examples 2-4 were ∼99.8%, ∼99.6% and ∼99.2%, respectively.

[0051] manual Figure 3 Rate performance test

[0052] from Figure 3As can be seen from the figure, when the current gradually increases from 0.1C to 3C, the discharge capacity of the battery assembled by PAF-220-SIQSPE-20 decreases, but still maintains excellent rate performance. At 0.1, 0.2, 2 and 3C, the capacity is 166, 164, 130 and 107 mAh g, respectively. -1 The coulombic efficiency is basically maintained at 100%, and the capacity returns to 164 mAh g after recovering to 0.2C. -1 , indicating that it has good rate performance.

[0053] manual Figure 4 Ionic conductivity test

[0054] The AC impedance method is used to measure the ionic conductivity of single-ion quasi-solid-state polymer electrolytes and its relationship with temperature. PAF-220-SIQSPE-20 is sandwiched between two stainless steel discs with a diameter of 16 mm to assemble into a "SS / PAF-220-SIQSPE-20 / SS" sandwich battery structure, and the impedance is measured at intervals of 10°C in the temperature range of 20 to 90°C. In order to achieve thermal equilibrium, the battery needs to be placed at a specific temperature for 1 hour before the test. In order to analyze the temperature dependence of the electrolyte ionic conductivity, a curve is drawn between the logarithm of the electrolyte ionic conductivity and the inverse of the absolute temperature, such as Figure 4 As shown. P4000 was used to apply a small amplitude (oscillation voltage of 5mV) sinusoidal AC signal to the test system, with a scanning frequency of 1MHz to 1Hz, to measure the AC impedance spectrum. The test results are shown as follows: Figure 4 The intersection of the impedance spectrum and the real axis in the high frequency region is the bulk impedance R of the electrolyte. b The electrical conductivity is calculated using formula (1):

[0055]

[0056] Where, l represents the thickness of the single-ion quasi-solid polymer electrolyte (cm), R b represents the bulk impedance of the single-ion quasi-solid polymer electrolyte (Ω), and S represents the actual effective contact area between the electrolyte and the steel sheet (cm 2 ).

[0057] from Figure 4 The calculated ionic conductivity of PAF-220-SIQSPE-20 prepared in Example 1 is 2.06×10 - 4 S cm -1The material contains abundant polar functional groups, which not only enable it to interact with lithium ions, facilitating the control of lithium salt content in the PAF pores, but also prepares single-ion lithium salts by fixing imidazolium anions on the skeleton, which facilitates the dissociation, movement and uniform transmission of lithium ions, improving their transmission efficiency, reducing interfacial impedance, inhibiting the formation of lithium dendrites, and improving the battery's cycle stability and rate performance.

[0058] manual Figure 5 Arrhenius equation diagram;

[0059] Depend on Figure 5 It can be seen that the logarithmic value of the ionic conductivity of PAF-220-SIQSPE-20 prepared in Example 1 increases linearly with temperature, and the fitting curve of logσ and 1000 / T conforms to the Arrhenius equation. Calculation shows that the activation energy is 0.142 eV. The low activation energy indicates that it has a low lithium ion dissociation energy barrier, making it easier for lithium ions to dissociate and move within the electrolyte, resulting in a higher lithium ion conductivity of 2.06×10 -4 S cm -1 .

[0060] manual Figure 6 Electrochemical window test curve.

[0061] Linear sweep voltammetry (LSV) was used to measure the electrochemical stability window of the single-ion quasi-solid polymer electrolyte prepared in Example 1. A steel sheet (SS) was used as the working electrode, a lithium metal sheet was used as the reference electrode, and the single-ion quasi-solid polymer electrolyte was used as the electrolyte separator to assemble a "SS / PAF-220-SIQSPE-20 / Li" cell. The electrochemical stability was measured using an electrochemical workstation (P400). The scan rate was 1 mV·s -1 , the scanning range is 2.6~5.4V(vs.Li + / Li), the test temperature is 20℃. The test results are as follows Figure 6 shown.

[0062] Linear sweep voltammetry can determine the electrochemical stability window of a material. Figure 6 As can be seen from the figure, the oxidation stability potential of PAF-220-SIQSPE-20 prepared in Example 1 can be stabilized to 5.1 V (vs Li + / Li), and there is no oxidation leakage current, which shows that the single-ion quasi-solid-state polymer electrolyte prepared by the present invention has excellent electrochemical stability.

[0063] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions are not to be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A single-ion quasi-solid polymer electrolyte, characterized in that Its preparation method comprises the following steps: Step 1: Under nitrogen, 1,3,5-tris(4-ethynylphenyl)benzene and 4,7-dibromo-1H-benzimidazole are added to a solvent in a molar ratio of 1:1-3, and then tetrakis(triphenylphosphine)palladium and cuprous iodide are added; then, after a cycle of -196°C liquid nitrogen cooling-vacuuming-nitrogen filling-50°C heating and thawing, the mixture is reacted at 80-120°C for 40-55 hours, and vacuum dried at 40-60°C for 12-48 hours to obtain a PAF material containing an imidazole structure, wherein the mass ratio of 1,3,5-tris(4-ethynylphenyl)benzene:4,7-dibromo-1H-benzimidazole:tetrakis(triphenylphosphine)palladium:copper iodide is 1-5:1.5-5:0.1-1:0.1-1.5; The solvent is one or any combination of n-hexane, N,N-dimethylformamide, acetone, triethylamine, and N-pyrrolidone; Step 2: Under nitrogen protection, the imidazole structure-containing PAF material obtained in step 1 and the lithiated compound are mixed in a solvent, reacted at -30°C to 30°C for 48 to 60 hours, and then the product is filtered, washed with a solvent, and vacuum-dried at 60 to 80°C for 12 to 48 hours to obtain a lithium-rich PAF material; The lithiated compound is one or any combination of n-butyl lithium, tert-butyl lithium, methyl lithium, and phenyl lithium; the mass ratio of the PAF material containing an imidazole structure to the lithiated compound is 0.1 to 1:1; the solvent is one or any combination of n-hexane, cyclohexane, heptane, or toluene; Step 3: Under vacuum conditions, the lithium-rich PAF material and lithium salt obtained in step 2 are added to a solvent, stirred at 15-40°C for 20-30 hours, and then a functional polymer is added under normal pressure. After stirring at 15-40°C for 20-30 hours, the mixture is vacuum dried at 60-150°C for 6-15 hours to obtain a polymer electrolyte; The solvent is one or any combination of N-pyrrolidone, N,N-dimethylformamide, acetone, and triethylamine; the lithium salt is one or any combination of lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI); the functional polymer is one or any combination of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and polyvinyl alcohol (PVA); the mass ratio of the functional polymer, lithium-rich PAF material, and lithium salt is 1-25:1:1-10; Step 4: Soaking the polymer electrolyte obtained in step 3 in a plasticizer for 10 minutes to 2 hours at room temperature to obtain a single-ion quasi-solid polymer electrolyte; The plasticizer is one or any combination of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and ethylene glycol dimethyl ether (DME).

2. Application of a single-ion quasi-solid polymer electrolyte in lithium-ion batteries.

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