A dynamically cross-linked ultra-thin polymer electrolyte membrane, a preparation method and application thereof
By using dynamically cross-linked ultrathin polymer electrolyte membranes, the mechanical and interfacial stability issues of ultrathin polymer electrolyte membranes during battery cycling were resolved, resulting in improved ionic conductivity and lithium-ion transference number, thus enhancing the electrochemical performance of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANKAI UNIV
- Filing Date
- 2026-07-03
- Publication Date
- 2026-07-31
AI Technical Summary
Existing ultrathin polymer electrolyte membranes lack sufficient mechanical and interfacial stability during battery cycling, leading to battery performance degradation.
A dynamic cross-linked ultrathin polymer electrolyte membrane is adopted, which forms a dynamic cross-linked network through a dynamic cross-linking agent. Combined with a high dielectric constant polymer fiber skeleton and boron nitride, a single-ion conduction mechanism is constructed to enhance mechanical stability and interfacial compatibility.
It achieves high ionic conductivity, high lithium-ion transference number, good mechanical stability and interfacial stability, and can be matched with high-voltage cathode materials to improve the electrochemical performance of batteries.
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Figure CN122494801A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid-state lithium metal battery technology, specifically relating to a dynamically cross-linked ultrathin polymer electrolyte membrane, its preparation method, and its application. Background Technology
[0002] Solid-state lithium metal batteries hold immense potential in terms of high safety and high energy density. The development of the electrolyte is crucial in solid-state lithium metal batteries, determining their future direction. Among various electrolyte types, ultrathin polymer electrolytes have attracted widespread attention due to their tunable structure, excellent processability, ability to significantly reduce the electrolyte's weight proportion in the battery, and ability to effectively shorten ion transport distance.
[0003] However, as the thickness decreases, the mechanical and interfacial stability of the polymer electrolyte membrane typically declines during battery cycling. During battery charging and discharging, the covalent bonds within the electrolyte undergo repeated movement and twisting, and the resulting localized damage easily accumulates, leading to battery performance degradation.
[0004] Therefore, there is an urgent need to develop a polymer electrolyte membrane that combines ultra-thin thickness, good mechanical and interfacial stability, and excellent ion transport performance. Summary of the Invention
[0005] To address the problems mentioned in the background section, the present invention aims to provide a dynamically cross-linked ultrathin polymer electrolyte membrane, its preparation method, and its applications. The dynamically cross-linked ultrathin polymer electrolyte membrane provided by the present invention has a thickness between 10 μm and 20 μm and exhibits high ionic conductivity, high lithium-ion transference number, high oxidation stability, good mechanical stability, and interfacial stability, enabling it to be matched with high-voltage cathode materials to achieve excellent electrochemical performance.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On the one hand, the present invention provides a dynamically cross-linked ultrathin polymer electrolyte membrane, wherein the raw materials of the dynamically cross-linked ultrathin polymer electrolyte membrane include: a dynamic cross-linking agent, a multi-arm cross-linking agent, a monofunctional monomer, an electrolyte, a photoinitiator, and a high dielectric constant polymer membrane composed of boron nitride. The dynamic crosslinking agent is , wherein R1 is selected from H or F, and R2 is selected from H or F; The electrolyte comprises lithium salt, 1,2-butenyl carbonate, and difluoroethylene carbonate. The high dielectric constant polymer used in the composite boron nitride high dielectric constant polymer film is selected from at least one of polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluoroethylene, and polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0007] Furthermore, the monofunctional monomer is selected from at least one of trifluoroethyl methacrylate, poly(ethylene glycol) methacrylate, and allyl borate pinacol ester, wherein the molecular weight of the poly(ethylene glycol) methacrylate is from 200 g / mol to 600 g / mol.
[0008] Further, the multi-arm crosslinking agent is selected from at least one of polyethylene glycol dimethacrylate, N,N-methylenebis(acrylamide), and triallyl isocyanurate, wherein the molecular weight of the polyethylene glycol dimethacrylate is from 200 g / mol to 700 g / mol; And / or, the photoinitiator is selected from at least one of 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; And / or, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, and lithium tetrafluoroborate, preferably lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, and lithium tetrafluoroborate.
[0009] Furthermore, the boron nitride used in the high dielectric constant polymer film of the composite boron nitride is hexagonal boron nitride nanosheets, and the boron nitride nanosheets have a diameter of 80 nm to 100 nm.
[0010] Furthermore, the high dielectric constant polymer film of the composite boron nitride is prepared using an electrospinning method.
[0011] Further, the mass ratio of the dynamic crosslinking agent, multi-arm crosslinking agent, monofunctional monomer, and electrolyte is (1~5):(1~5):(5~15):(75~90), and the amount of photoinitiator added is 1%~5% of the total mass of the dynamic crosslinking agent, multi-arm crosslinking agent, and monofunctional monomer; The molar ratio of lithium salt, 1,2-butenyl carbonate, and difluoroethylene carbonate in the electrolyte is 1:(2~2.7):(0.3~1). The mass ratio of boron nitride to high dielectric constant polymer in the composite boron nitride polymer film is (0.5~2):15.
[0012] Furthermore, the thickness of the dynamically cross-linked ultrathin polymer electrolyte membrane is 10 μm to 20 μm, and the thickness of the composite boron nitride high dielectric constant polymer membrane is 5 μm to 15 μm.
[0013] On the other hand, the present invention provides a method for preparing any of the above-described dynamically cross-linked ultrathin polymer electrolyte membranes, comprising the following steps: S1: A high dielectric constant polymer is dissolved in a solvent to form a high dielectric constant polymer solution. Then, boron nitride is uniformly dispersed in the high dielectric constant polymer solution to obtain an electrospinning precursor solution. The electrospinning precursor solution is used to obtain a nanofiber membrane by electrospinning. Then, the membrane is dried and rolled to obtain a high dielectric constant polymer membrane with boron nitride composite. S2: Mix dynamic crosslinking agent, multi-arm crosslinking agent, monofunctional monomer, electrolyte and photoinitiator to obtain polymerization precursor solution; S3: The polymerization precursor liquid described in S2 is coated on the high dielectric constant polymer film of composite boron nitride described in S1, and then photo-initiated polymerization is performed to prepare a dynamically cross-linked ultrathin polymer electrolyte film. or S1: Mix dynamic crosslinking agent, multi-arm crosslinking agent, monofunctional monomer, electrolyte and photoinitiator to obtain polymerization precursor solution; S2: Dissolve a high dielectric constant polymer in a solvent to form a high dielectric constant polymer solution, then uniformly disperse boron nitride in the high dielectric constant polymer solution to obtain an electrospinning precursor solution, and obtain a nanofiber membrane by electrospinning the electrospinning precursor solution, and then obtain a high dielectric constant polymer membrane with boron nitride composite by drying and rolling. S3: The polymerization precursor liquid described in S1 is coated on the high dielectric constant polymer film of composite boron nitride described in S2, and then photo-initiated polymerization is performed to prepare a dynamically cross-linked ultrathin polymer electrolyte film.
[0014] Furthermore, the solvent includes one of N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and acetone.
[0015] Furthermore, the mass ratio of the high dielectric constant polymer to the solvent in the high dielectric constant polymer solution is (1~2):(8~9).
[0016] Furthermore, the electrospinning process parameters are as follows: electrostatic voltage of 18kV~25kV, spinning distance of 10cm~20cm, electrospinning precursor liquid flow rate of 0.2mL / h~0.6mL / h, and receiving cylinder rotation speed of 500rpm~1500rpm.
[0017] Furthermore, the drying temperature is 50℃~80℃, and the drying time is 24h~48h.
[0018] Furthermore, the rolling process is carried out at a temperature of room temperature to 60°C.
[0019] Furthermore, the light source for the photo-initiated polymerization is 365nm ultraviolet light, and the photo-initiated polymerization time is 10min~20min.
[0020] On the other hand, the present invention provides an application of any of the above-described dynamic cross-linked ultrathin polymer electrolyte membranes or the dynamic cross-linked ultrathin polymer electrolyte membranes prepared by the above-described preparation methods in solid-state lithium metal batteries.
[0021] In another aspect, the present invention provides a solid-state lithium metal battery, comprising any of the dynamically cross-linked ultrathin polymer electrolyte membranes described above or dynamically cross-linked ultrathin polymer electrolyte membranes prepared by the preparation methods described above.
[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention relates to a dynamically cross-linked ultrathin polymer electrolyte membrane. By employing a dynamic cross-linking agent to form a dynamic cross-linking network, the membrane gains self-healing capabilities, thus enhancing its mechanical stability. A high-dielectric-constant polymer fiber framework promotes lithium salt dissociation. Boron nitride and borate ester groups are used to construct a single-ion conduction mechanism, enhancing lithium metal interfacial compatibility. This dynamically cross-linked ultrathin polymer electrolyte membrane exhibits high ionic conductivity, high lithium-ion transference number, high oxidation stability, good mechanical stability, and interfacial stability, enabling it to be matched with high-voltage cathode materials to achieve excellent electrochemical performance. Attached Figure Description
[0023] Figure 1 This is a scanning electron microscope image of the high dielectric constant polymer film of boron nitride composite prepared in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of the present invention; Figure 3 This is a digital photograph of the thickness of the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of the present invention; Figure 4 The stress-strain curve of the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of this invention is shown. Figure 5 This is a graph showing the ionic conductivity of the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of this invention. Figure 6 Linear scan voltammogram of the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of this invention; Figure 7 The graph shows the lithium-ion transference number test results of the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of this invention. Figure 8The cycling performance diagram of a symmetrical battery with lithium metal as the two electrodes, using the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of the present invention; Figure 9 The cycling performance diagram of a battery using the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of the present invention, with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode; Figure 10 The cycling performance diagram of a battery using the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of the present invention, with lithium nickel cobalt manganese oxide (NCM811) as the positive electrode and lithium metal as the negative electrode; Figure 11 The cycling performance diagram of a battery using the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of the present invention, with lithium cobalt oxide as the positive electrode and lithium metal as the negative electrode; Figure 12 The cycling performance diagram of a symmetrical battery with lithium metal as the two electrodes, using the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 2 of the present invention; Figure 13 The cycling performance diagram of a battery using the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 2 of the present invention, with lithium iron phosphate as the positive electrode and lithium metal as the negative electrode; Figure 14 Cyclic performance diagram of a symmetrical battery with lithium metal as the two electrodes, using the polymer electrolyte membrane prepared by Comparative Example 1 of the present invention; Figure 15 The cycling performance diagram of a battery with lithium nickel cobalt manganese oxide (NCM811) as the positive electrode and lithium metal as the negative electrode is shown for the polymer electrolyte membrane prepared using Comparative Example 1 of the present invention. Figure 16 The graph shows the cycle performance of a battery using the polymer electrolyte membrane prepared in Comparative Example 2 of this invention, with lithium nickel cobalt manganese oxide (NCM811) as the positive electrode and lithium metal as the negative electrode. Detailed Implementation
[0024] To better understand the content of this invention, the following detailed description is provided in conjunction with specific implementation methods. However, the scope of protection of this invention is not limited to the following embodiments.
[0025] In this invention, all equipment and raw materials can be purchased from the market or are commonly used in this industry.
[0026] Example 1 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and boron nitride composite. The electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the high dielectric constant polymer film is hexagonal boron nitride nanosheets with a diameter of 80 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0027] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 1,4-Phenylated boric acid (6 mmol) and 1-thioglycerol (13 mmol) were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0028] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: electrostatic voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at room temperature to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 13μm.
[0029] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone was used to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and electrolyte is 3:4:8:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate was 3%. The polymerization precursor solution was coated onto a high dielectric constant polymer film composed of boron nitride and photo-initiated polymerization was carried out under 365 nm ultraviolet light for 15 min to obtain a dynamically cross-linked ultrathin polymer electrolyte film with a film thickness of 16 μm.
[0030] The high dielectric constant polymer film of the prepared boron nitride composite was scanned by electron microscopy, and the results are as follows: Figure 1 As shown. From Figure 1 As can be seen from the scanning electron microscope, the high dielectric constant polymer film of boron nitride composite has a uniformly distributed fibrous structure, proving its successful preparation.
[0031] The prepared dynamically cross-linked ultrathin polymer electrolyte membrane was scanned by electron microscopy, and the results are as follows: Figure 2 As shown. From Figure 2 It can be seen that the fiber skeleton was uniformly filled after polymerization, proving that a uniform electrolyte membrane was successfully prepared.
[0032] The thickness of the prepared dynamically cross-linked ultrathin polymer electrolyte membrane was tested, and the results are as follows: Figure 3 As shown. From Figure 3 It can be seen that a thinner electrolyte membrane with a thickness of 16 μm helps to achieve a higher energy density.
[0033] Stress-strain tests were performed on the prepared dynamically cross-linked ultrathin polymer electrolyte membrane, and the results are as follows: Figure 4 As shown. From Figure 4 It can be seen that the dynamically cross-linked ultrathin polymer electrolyte membrane exhibits excellent mechanical strength and flexibility, with a tensile strength of 13 MPa and a maximum strain of nearly 50%, which can meet the requirements of battery use.
[0034] The ionic conductivity of the prepared dynamically cross-linked ultrathin polymer electrolyte membrane was calculated by electrochemical impedance spectroscopy, and the results are as follows: Figure 5 As shown. From Figure 5 It can be seen that the dynamically cross-linked ultrathin polymer electrolyte membrane exhibits a strength of 1.1 × 10⁻⁶ at 25 °C. -3 S cm -1 Its high ionic conductivity enables the battery to achieve good charge and discharge capacity.
[0035] The prepared dynamically cross-linked ultrathin polymer electrolyte membrane was tested by linear sweep voltammetry, and the results are as follows: Figure 6 As shown. From Figure 6It can be seen that the oxidation stability potential of the dynamically cross-linked ultrathin polymer electrolyte membrane can reach 5.6V, which can be matched with positive electrodes with high working potential (such as lithium nickel cobalt manganese oxide NCM811 and lithium cobalt oxide LCO).
[0036] The lithium-ion transference number of the prepared dynamically cross-linked ultrathin polymer electrolyte membrane was measured and calculated using time / current testing and impedance testing before and after polarization. The results are as follows: Figure 7 As shown. From Figure 7 It can be seen that the dynamically cross-linked ultrathin polymer electrolyte membrane exhibits a high lithium-ion transference number of 0.91, indicating that the electrolyte membrane effectively achieves the binding effect of anions, realizing the effects of single-ion conduction and suppression of concentration polarization, which helps the battery achieve high-rate performance.
[0037] Cyclic testing was performed on a symmetrical battery with lithium metal as both electrodes (the battery used the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of this invention). The cyclic test results are as follows: Figure 8 As shown. From Figure 8 As can be seen from this, the battery operates at 0.2 mA cm -2 0.2mAh cm -2 The stable cycling of more than 1300 hours under the specified conditions demonstrates the good stability of the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 to lithium metal.
[0038] A battery using lithium iron phosphate (LFP) as the positive electrode and lithium metal as the negative electrode (this battery uses the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of this invention) was subjected to cycle testing, and the cycle test results are as follows: Figure 9 As shown. From Figure 9 As can be seen, this battery can stably cycle for over 1800 times at a 0.5C rate, with a maximum discharge specific capacity of 147mAh g. -1 With a capacity retention rate of 81% and a coulombic efficiency of over 99%, it demonstrates promising prospects for practical applications.
[0039] A battery using lithium nickel cobalt manganese oxide (NCM811) as the positive electrode and lithium metal as the negative electrode (this battery uses the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of this invention) was subjected to cycle testing, and the cycle test results are as follows: Figure 10 As shown. From Figure 10 As can be seen, the discharge specific capacity is as high as 188 mAh g at 0.5C. 1 It maintains a stable cycle of 600 revolutions, with a coulomb efficiency of over 99% and a capacity retention rate of 80%.
[0040] A battery using lithium cobalt oxide (LCO) as the positive electrode and lithium metal as the negative electrode (this battery uses the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 of this invention) was subjected to cycle testing, and the cycle test results are as follows: Figure 11 As shown. From Figure 11 As can be seen, at a maximum charging cutoff voltage of 4.6V and a charge / discharge rate of 0.5C, the discharge specific capacity reaches as high as 203mAh g. 1 It maintains a stable cycle of 200 times with a capacity retention rate of 76%.
[0041] The above results demonstrate that the lithium metal battery assembled from the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 1 can still achieve excellent capacity performance and cycle stability for high-voltage cathodes.
[0042] Example 2 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and boron nitride composite. The electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the high dielectric constant polymer film is hexagonal boron nitride nanosheets with a diameter of 100 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0043] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 6 mmol of 2,5-difluoro-1,4-phenyldiboronic acid and 13 mmol of 1-thioglycerol were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0044] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: static voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at room temperature to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 12μm.
[0045] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone was used to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and electrolyte is 3:4:8:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate was 3%. The polymerization precursor solution was coated onto a high dielectric constant polymer film composed of boron nitride and photo-initiated polymerization was carried out under 365 nm ultraviolet light for 15 min to obtain a dynamically cross-linked ultrathin polymer electrolyte film with a film thickness of 15 μm.
[0046] Cyclic testing was performed on a symmetrical battery with lithium metal as both electrodes (the battery used the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 2 of this invention). The cyclic test results are as follows: Figure 12 As shown. From Figure 12 As can be seen from this, the battery operates at 0.2 mA cm -2 0.2mAh cm -2 The stable cycling of more than 500 hours under the specified conditions demonstrates the good stability of the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 2 for lithium metal.
[0047] A battery using lithium iron phosphate (LFP) as the positive electrode and lithium metal as the negative electrode (this battery uses the dynamically cross-linked ultrathin polymer electrolyte membrane prepared in Example 2 of this invention) was subjected to cycle testing, and the cycle test results are as follows: Figure 13 As shown. From Figure 13As can be seen, this battery can stably cycle for more than 180 times at a 1C rate, with a maximum discharge specific capacity of 136mAh g. -1 The capacity retention rate is 100%.
[0048] The above results demonstrate that the lithium metal battery assembled from the ultrathin polymer solid electrolyte membrane prepared in Example 2 can still achieve excellent performance.
[0049] Example 3 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of polyethylene glycol dimethacrylate (molecular weight 330 g / mol), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a composite boron nitride polymer film. The electrolyte includes lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the composite boron nitride high dielectric constant polymer film is hexagonal boron nitride nanosheets with a sheet diameter of 80 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0050] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 1,4-Phenylated boric acid (6 mmol) and 1-thioglycerol (13 mmol) were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0051] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: electrostatic voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at 60℃ to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 14μm.
[0052] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of polyethylene glycol dimethacrylate, trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone is used to obtain a polymerization precursor solution. The mass ratio of polyethylene glycol dimethacrylate, trifluoroethyl methacrylate, and electrolyte is 3:4:8:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of polyethylene glycol dimethacrylate and trifluoroethyl methacrylate is 3%. The polymerization precursor solution is coated onto a high dielectric constant polymer film composed of boron nitride and photo-initiated polymerization is carried out by irradiation under 365 nm ultraviolet light for 15 min to obtain a dynamically cross-linked ultrathin polymer electrolyte film with a film thickness of 16 μm.
[0053] Example 4 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of N,N-methylenebis(acrylamide), poly(ethylene glycol) methacrylate (molecular weight 330 g / mol), electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a composite boron nitride polymer film. The electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the composite boron nitride high dielectric constant polymer film is hexagonal boron nitride nanosheets with a sheet diameter of 80 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0054] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 1,4-Phenylated boric acid (6 mmol) and 1-thioglycerol (13 mmol) were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0055] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: static voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at room temperature to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 15μm.
[0056] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of N,N-methylenebis(acrylamide), poly(ethylene glycol) methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone was used to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), poly(ethylene glycol) methacrylate, and electrolyte is 3:4:8:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of N,N-methylenebis(acrylamide) and poly(ethylene glycol) methacrylate was 3%. The polymerization precursor solution was coated onto a high dielectric constant polymer film composed of boron nitride and photo-initiated polymerization was carried out under 365 nm ultraviolet light for 15 min to obtain a dynamically cross-linked ultrathin polymer electrolyte film with a film thickness of 18 μm.
[0057] Example 5 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and boron nitride composite. The electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the high dielectric constant polymer film is hexagonal boron nitride nanosheets with a diameter of 90 nm, and the high dielectric constant polymer is polyvinylidene fluoride-hexafluoropropylene.
[0058] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 1,4-Phenylated boric acid (6 mmol) and 1-thioglycerol (13 mmol) were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0059] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: electrostatic voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at room temperature to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 14μm.
[0060] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone was used to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and electrolyte is 3:4:8:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate was 3%. The polymerization precursor solution was coated onto a high dielectric constant polymer film composed of boron nitride and photo-initiated polymerization was carried out under 365 nm ultraviolet light for 15 min to obtain a dynamically cross-linked ultrathin polymer electrolyte film with a film thickness of 16 μm.
[0061] Example 6 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a composite boron nitride. The electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the composite boron nitride high dielectric constant polymer film is hexagonal boron nitride nanosheets with a diameter of 80 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene.
[0062] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 1,4-Phenylated boric acid (6 mmol) and 1-thioglycerol (13 mmol) were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0063] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: electrostatic voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at room temperature to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 15μm.
[0064] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone was used to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and electrolyte is 3:4:8:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate was 3%. The polymerization precursor solution was coated onto a high dielectric constant polymer film composed of boron nitride and photo-initiated polymerization was carried out under 365 nm ultraviolet light for 15 min to obtain a dynamically cross-linked ultrathin polymer electrolyte film with a film thickness of 18 μm.
[0065] Example 7 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and boron nitride composite. The electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the high dielectric constant polymer film is hexagonal boron nitride nanosheets with a diameter of 80 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0066] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 1,4-Phenylated boric acid (6 mmol) and 1-thioglycerol (13 mmol) were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0067] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: static voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at room temperature to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 15μm.
[0068] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone was used to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and electrolyte is 1:4:10:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate was 3%. The polymerization precursor solution was coated onto a high dielectric constant polymer film composed of boron nitride and photo-initiated polymerization was carried out under 365 nm ultraviolet light for 15 min to obtain a dynamically cross-linked ultrathin polymer electrolyte film with a film thickness of 18 μm.
[0069] Example 8 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and boron nitride composite. The electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the high dielectric constant polymer film is hexagonal boron nitride nanosheets with a diameter of 80 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0070] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 1,4-Phenylated boric acid (6 mmol) and 1-thioglycerol (13 mmol) were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0071] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: static voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at room temperature to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 15μm.
[0072] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone was used to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and electrolyte is 2:3:15:80, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate was 3%. The polymerization precursor solution was coated onto a high dielectric constant polymer film composed of boron nitride and photo-initiated polymerization was carried out under 365 nm ultraviolet light for 15 min to obtain a dynamically cross-linked ultrathin polymer electrolyte film with a film thickness of 20 μm.
[0073] Example 9 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and boron nitride composite. The electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the high dielectric constant polymer film is hexagonal boron nitride nanosheets with a diameter of 100 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0074] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 1,4-Phenylated boric acid (6 mmol) and 1-thioglycerol (13 mmol) were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0075] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.1g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: electrostatic voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at room temperature to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 15μm.
[0076] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone was used to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and electrolyte is 3:4:8:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate was 3%. The polymerization precursor solution was coated onto a high dielectric constant polymer film composed of boron nitride and photo-initiated polymerization was carried out under 365 nm ultraviolet light for 15 min to obtain a dynamically cross-linked ultrathin polymer electrolyte film with a film thickness of 18 μm.
[0077] Example 10 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and boron nitride composite. The electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the high dielectric constant polymer film is hexagonal boron nitride nanosheets with a diameter of 80 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0078] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 1,4-Phenylated boric acid (6 mmol) and 1-thioglycerol (13 mmol) were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0079] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: electrostatic voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at 60℃ to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 13μm.
[0080] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate and difluoroethylene carbonate were mixed in a molar ratio of 0.7:0.1:0.2:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone was used to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and electrolyte is 3:4:8:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate was 3%. The polymerization precursor solution was coated onto a high dielectric constant polymer film composed of boron nitride and photo-initiated polymerization was carried out under 365 nm ultraviolet light for 15 min to obtain a dynamically cross-linked ultrathin polymer electrolyte film with a film thickness of 18 μm.
[0081] Example 11 Dynamically cross-linked ultrathin polymer electrolyte membrane: its raw materials include dynamic cross-linking agents. The high dielectric constant polymer film consists of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and boron nitride composite. The electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate. The boron nitride used in the high dielectric constant polymer film is hexagonal boron nitride nanosheets with a diameter of 80 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0082] The preparation method of dynamically cross-linked ultrathin polymer electrolyte membrane is as follows: (1) Synthesis: 6 mmol of 2,5-difluoro-1,4-phenyldiboronic acid and 13 mmol of 1-thioglycerol were weighed and placed in a round-bottom flask containing 25 mL of tetrahydrofuran. The mixture was stirred at room temperature for 1 h until all compounds were completely dissolved. Anhydrous magnesium sulfate was added to the round-bottom flask, and the reaction was stirred at room temperature for 24 h. The anhydrous magnesium sulfate was then removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was washed and purified with heptane and filtered. The washing process was repeated 3–5 times. Finally, the purified white solid product was dried in a vacuum oven at 40 °C for 24 h to obtain... .
[0083] (2) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: electrostatic voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at room temperature to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 14μm.
[0084] (3) Preparation of dynamically cross-linked ultrathin polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte solution. A mixture of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone was used to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and electrolyte is 4:4:12:80, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone is... The total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate was 3%. The polymerization precursor solution was coated onto a high dielectric constant polymer film of boron nitride composite and photoinitiated by irradiation under 365 nm ultraviolet light for 15 min to obtain a dynamically crosslinked ultrathin polymer electrolyte film with a film thickness of 18 μm.
[0085] Comparative Example 1 Polymer electrolyte membrane: Its raw materials include N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone; the electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate and difluoroethylene carbonate.
[0086] The polymer electrolyte membrane was prepared as follows: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 hours to prepare the electrolyte. N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, the electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and the electrolyte was 7:8:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone was 3% of the total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate. The polymerization precursor solution was coated onto a regular polypropylene membrane and photo-initiated polymerization was carried out by irradiation under 365nm ultraviolet light for 15 min to obtain a polymer electrolyte membrane with a thickness of 25μm.
[0087] Cyclic testing was performed on a symmetrical battery with lithium metal as both electrodes (the battery used the polymer electrolyte membrane prepared in Comparative Example 1 of this invention). The cyclic test results are as follows: Figure 14 As shown. From Figure 14 As can be seen from this, the battery operates at 0.2 mA cm -2 0.2mAh cm -2 Under the given conditions, it could only cycle for less than 200 hours, indicating that the polymer electrolyte membrane prepared in Comparative Example 1 had poor stability against lithium metal.
[0088] A battery using lithium nickel cobalt manganese oxide (NCM811) as the positive electrode and lithium metal as the negative electrode (this battery uses the polymer electrolyte membrane prepared in Comparative Example 1 of this invention) was subjected to cycle testing, and the cycle test results are as follows: Figure 15 As shown. From Figure 15 As can be seen, the discharge specific capacity is low at 0.5C, only 173 mAh g. -1 Furthermore, after 600 cycles, the capacity retention rate is only 30%.
[0089] The above results demonstrate that the lithium metal battery assembled from the polymer electrolyte membrane prepared in Comparative Example 1 has poor performance.
[0090] Comparative Example 2 Polymer electrolyte membrane: Its raw materials include N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and a high dielectric constant polymer membrane with composite boron nitride; the electrolyte includes lithium bis(trifluoromethanesulfonylimide), lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate; the boron nitride used in the high dielectric constant polymer membrane with composite boron nitride is hexagonal boron nitride nanosheets with a sheet diameter of 80 nm, and the high dielectric constant polymer is polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
[0091] The preparation method of polymer electrolyte membrane is as follows: (1) Preparation of high dielectric constant polymer film of composite boron nitride: 1.5g of polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene was dissolved in 8.5g of N,N-dimethylformamide solvent, and then 0.05g of hexagonal boron nitride nanosheets were added. The mixture was stirred at room temperature for 24h to obtain a uniformly dispersed electrospinning precursor solution. The electrospinning precursor solution was spun into a nanofiber membrane under the following conditions: static voltage of 20kV, spinning distance of 15cm, electrospinning precursor solution flow rate of 0.4mL / h, and receiving cylinder rotation speed of 1000rpm. The membrane was then vacuum dried at 80℃ for 24h and rolled at room temperature to obtain a high dielectric constant polymer film of composite boron nitride with a thickness of 13μm.
[0092] (2) Preparation of polymer electrolyte membrane: Lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium tetrafluoroborate, 1,2-butenyl carbonate, and difluoroethylene carbonate were mixed in a molar ratio of 0.8:0.1:0.1:2.7:0.3 and stirred at room temperature for 24 h to prepare an electrolyte. N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, electrolyte, and 2-hydroxy-2-methyl-1-phenyl-1-propanone were mixed to obtain a polymerization precursor solution. The mass ratio of N,N-methylenebis(acrylamide), trifluoroethyl methacrylate, and electrolyte was 7:8:85, and the mass of 2-hydroxy-2-methyl-1-phenyl-1-propanone was 3% of the total mass of N,N-methylenebis(acrylamide) and trifluoroethyl methacrylate. The polymerization precursor solution was coated onto a high dielectric constant polymer film of boron nitride composite and photo-initiated polymerization was carried out under 365nm ultraviolet light for 15 min to obtain a polymer electrolyte film with a thickness of 25μm.
[0093] A battery using lithium nickel cobalt manganese oxide (NCM811) as the positive electrode and lithium metal as the negative electrode (this battery uses the polymer electrolyte membrane prepared in Comparative Example 2 of this invention) was subjected to cycle testing, and the cycle test results are as follows: Figure 16 As shown. From Figure 16 As can be seen, the discharge specific capacity is low at 0.5C, only 178 mAh g.-1 Furthermore, after 600 cycles, the capacity retention rate is only 69%.
[0094] The above results demonstrate that the lithium metal battery assembled from the polymer electrolyte membrane prepared in Comparative Example 2 has poor performance.
[0095] In summary, the dynamically cross-linked ultrathin polymer electrolyte membrane of this invention achieves excellent performance in lithium metal batteries. The constructed dynamic covalent cross-linked network not only endows the electrolyte membrane with self-healing ability through borate ester bond rearrangement to repair mechanical damage to the electrolyte membrane during cycling, but also binds anions through Lewis acid-base interactions, inducing uniform lithium deposition. The introduction of a polymer fiber skeleton with a high dielectric constant facilitates the full dissociation of lithium salts. The introduced boron nitride inorganic nanofiller can enhance the mechanical strength of the electrolyte membrane while binding anions through Lewis acid-base interactions, thereby improving the stability of the electrolyte membrane for lithium metal.
[0096] The above description is only a specific embodiment of the present invention and not all embodiments. Any equivalent modifications made by those skilled in the art to the technical solutions of the present invention by reading the present invention specification shall be covered by the claims of the present invention.
Claims
1. A dynamically cross-linked ultrathin polymer electrolyte membrane, characterized in that, The raw materials for the dynamically crosslinked ultrathin polymer electrolyte membrane include: dynamic crosslinking agent, multi-arm crosslinking agent, monofunctional monomer, electrolyte, photoinitiator, and high dielectric constant polymer membrane with composite boron nitride. The dynamic crosslinking agent is , wherein R1 is selected from H or F, and R2 is selected from H or F; The electrolyte includes lithium salt, 1,2-butenyl carbonate and difluoroethylene carbonate. The high dielectric constant polymer used in the composite boron nitride high dielectric constant polymer film is selected from at least one of polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trifluoroethylene, and polyvinylidene fluoride-trifluoroethylene-trifluorochloroethylene.
2. The dynamically cross-linked ultrathin polymer electrolyte membrane according to claim 1, characterized in that, The monofunctional monomer is selected from at least one of trifluoroethyl methacrylate, poly(ethylene glycol) methacrylate, and allyl borate pinacol ester, wherein the molecular weight of the poly(ethylene glycol) methacrylate is from 200 g / mol to 600 g / mol.
3. The dynamically cross-linked ultrathin polymer electrolyte membrane according to claim 1, characterized in that, The multi-arm crosslinking agent is selected from at least one of polyethylene glycol dimethacrylate, N,N-methylenebis(acrylamide), and triallyl isocyanurate, wherein the molecular weight of the polyethylene glycol dimethacrylate is from 200 g / mol to 700 g / mol; And / or, the photoinitiator is selected from at least one of 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; And / or, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorooxalateborate, and lithium tetrafluoroborate.
4. The dynamically cross-linked ultrathin polymer electrolyte membrane according to claim 1, characterized in that, The high dielectric constant polymer film of the composite boron nitride uses hexagonal boron nitride nanosheets with a sheet diameter of 80 nm to 100 nm.
5. The dynamically cross-linked ultrathin polymer electrolyte membrane according to claim 1, characterized in that, The high dielectric constant polymer film of boron nitride composite was prepared by electrospinning.
6. The dynamically cross-linked ultrathin polymer electrolyte membrane according to claim 1, characterized in that, The mass ratio of the dynamic crosslinking agent, multi-arm crosslinking agent, monofunctional monomer, and electrolyte is (1~5):(1~5):(5~15):(75~90), and the amount of photoinitiator added is 1%~5% of the total mass of the dynamic crosslinking agent, multi-arm crosslinking agent, and monofunctional monomer. The molar ratio of lithium salt, 1,2-butenyl carbonate, and difluoroethylene carbonate in the electrolyte is 1:(2~2.7):(0.3~1). The mass ratio of boron nitride to high dielectric constant polymer in the composite boron nitride polymer film is (0.5~2):
15.
7. The dynamically cross-linked ultrathin polymer electrolyte membrane according to claim 1, characterized in that, The thickness of the dynamically cross-linked ultrathin polymer electrolyte membrane is 10 μm to 20 μm, and the thickness of the composite boron nitride high dielectric constant polymer membrane is 5 μm to 15 μm.
8. The method for preparing the dynamically cross-linked ultrathin polymer electrolyte membrane according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: A high dielectric constant polymer is dissolved in a solvent to form a high dielectric constant polymer solution. Then, boron nitride is uniformly dispersed in the high dielectric constant polymer solution to obtain an electrospinning precursor solution. The electrospinning precursor solution is used to obtain a nanofiber membrane by electrospinning. Then, the membrane is dried and rolled to obtain a high dielectric constant polymer membrane with boron nitride composite. S2: Mix dynamic crosslinking agent, multi-arm crosslinking agent, monofunctional monomer, electrolyte and photoinitiator to obtain polymerization precursor solution; S3: The polymerization precursor liquid described in S2 is coated on the high dielectric constant polymer film of composite boron nitride described in S1, and then photo-initiated polymerization is performed to prepare a dynamically cross-linked ultrathin polymer electrolyte film. or S1: Mix dynamic crosslinking agent, multi-arm crosslinking agent, monofunctional monomer, electrolyte and photoinitiator to obtain polymerization precursor solution; S2: Dissolve a high dielectric constant polymer in a solvent to form a high dielectric constant polymer solution, then uniformly disperse boron nitride in the high dielectric constant polymer solution to obtain an electrospinning precursor solution, and obtain a nanofiber membrane by electrospinning the electrospinning precursor solution, and then obtain a high dielectric constant polymer membrane with boron nitride composite by drying and rolling. S3: The polymerization precursor liquid described in S1 is coated on the high dielectric constant polymer film of composite boron nitride described in S2, and then photo-initiated polymerization is performed to prepare a dynamically cross-linked ultrathin polymer electrolyte film.
9. The application of the dynamically cross-linked ultrathin polymer electrolyte membrane according to any one of claims 1 to 7 or the dynamically cross-linked ultrathin polymer electrolyte membrane prepared by the preparation method according to claim 8 in solid-state lithium metal batteries.
10. A solid-state lithium metal battery, characterized in that, This includes the dynamically cross-linked ultrathin polymer electrolyte membrane according to any one of claims 1 to 7 or the dynamically cross-linked ultrathin polymer electrolyte membrane prepared by the preparation method according to claim 8.