A protonated metal organic framework composite solid-state polymer electrolyte for lithium metal batteries and a method of making the same

Abstract

This invention discloses a protonated metal-organic framework (MOF) composite solid polymer electrolyte for lithium metal batteries and its preparation method. The composite solid polymer electrolyte comprises vinyl oxide, lithium salt, and filler; the filler is a protonated amino-functionalized MOF. This invention introduces a protonated amino-functionalized MOF with protonated functional groups and a three-dimensional porous structure into a polyethylene oxide-lithium salt to construct a composite solid polymer electrolyte. This reduces the crystallinity of polyethylene oxide, promotes the dissociation of lithium salt, and improves lithium-ion conductivity and transference number. Simultaneously, it regulates the uniform deposition of lithium ions and forms a stable solid electrolyte interface, effectively suppressing lithium dendrites and improving the electrochemical stability and interfacial compatibility of the electrolyte. This invention pioneers a new strategy for modifying polyethylene oxide solid polymer electrolytes with protonated MOF fillers. The preparation process is simple and controllable, and the filler has good dispersibility, which is beneficial for the research and industrialization of high-safety, high-performance lithium metal batteries.

Description

Technical Field

[0001] This invention relates to the field of energy materials technology, and in particular to a protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries and its preparation method. Background Technology

[0002] Lithium metal batteries, due to their extremely high theoretical specific capacity and lowest electrochemical potential, are considered a core direction for breaking through the bottlenecks of existing energy storage technologies and realizing the next generation of high-energy-density electrochemical energy storage systems. Lithium metal batteries mainly consist of three parts: a positive electrode, a negative electrode, and an electrolyte. Among them, the electrolyte, as the core carrier for lithium-ion transport, plays a crucial role in charge transfer, interfacial compatibility, and safety performance of the battery.

[0003] Solid polymer electrolytes are a type of electrolyte system that combines the flexibility of polymers with the high safety of solid electrolytes. They effectively avoid the safety hazards of liquid electrolytes, such as flammability and leakage, and also have good compatibility with lithium metal anodes. Therefore, they have become an important technical path for achieving high-safety, long-cycle lithium metal batteries. Among various solid polymer electrolytes, vinyl oxide solid polymer electrolytes have received the most extensive research and attention due to their excellent solvation ability for lithium salts, good electrochemical stability, and simple preparation process. However, pure vinyl oxide solid polymer electrolytes have high crystallinity at room temperature, resulting in low lithium-ion conductivity; at the same time, their mechanical strength is insufficient, making it difficult to effectively suppress the growth and penetration of lithium dendrites; in addition, their interfacial compatibility with lithium metal anodes is poor. These problems seriously restrict the cycle stability and safety performance of lithium metal batteries.

[0004] In recent years, to improve the overall performance of vinyl oxide solid polymer electrolytes (PES), researchers have attempted to introduce inorganic ceramic particles, carbon materials, and unmodified metal-organic frameworks as fillers into PES to construct composite PES. These fillers can reduce the crystallinity of PES to some extent and improve ionic conductivity. However, existing filler systems still struggle to simultaneously achieve high lithium-ion transference numbers, stable electrode interfaces, and excellent long-cycle performance, and the suppression effect on lithium dendrites needs further improvement. Therefore, continuing to develop novel functionalized fillers to construct high-performance PES composite PES and achieve a synergistic improvement in ion transport performance and interface stability is a key focus and challenge in this field.

[0005] Currently, there are no reports on using protonated amino-functionalized metal-organic frameworks as fillers to modify polyoxyethylene solid polymer electrolytes, thereby achieving synergistic optimization of lithium-ion transport and lithium dendrite suppression. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries, using a protonated amino-functionalized metal-organic framework as a filler, to achieve synergistic optimization of lithium-ion transport and lithium dendrite suppression, thereby improving the electrochemical stability and interfacial compatibility of the electrolyte. Another objective of this invention is to provide a method for preparing the above-mentioned composite solid polymer electrolyte.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention provides a protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries, comprising vinyl polyethylene oxide, lithium salt, and filler; the filler is a protonated amino-functionalized metal-organic framework, with a mass fraction of 5-20 wt% in the composite solid polymer electrolyte; the protonated amino-functionalized metal-organic framework is a protonated UiO-66-NH2 with a three-dimensional porous structure and -NH3 on its surface. + It has a functional group and a positive Zeta potential.

[0009] Furthermore, the polyethylene oxide of this invention has a viscosity-average molecular weight ≤ 600,000; the EO units of the polyethylene oxide and the Li in the lithium salt... + The molar ratio is n(EO)∶n(Li) + The ratio of lithium salt to lithium trifluoromethanesulfonylimide is 12 to 16:1; the lithium salt is lithium bis(trifluoromethanesulfonylimide).

[0010] In the above scheme, the preparation method of the protonated amino-functionalized metal-organic framework filler of the present invention includes the following steps:

[0011] (1) Using a solvothermal method, zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide to obtain a mixed solution; the concentration of zirconium tetrachloride in the mixed solution was 0.036-0.054 mol / L, and the concentration of 2-aminoterephthalic acid was 1-1.3 times that of zirconium tetrachloride; the mixed solution was transferred to a high-pressure reactor for heating and reaction, and after the reaction was completed, it was cooled, centrifuged, washed, and vacuum dried to obtain amino-functionalized metal-organic framework crystals;

[0012] (2) The amino-functionalized metal-organic framework crystals are dispersed in an acid solution for protonation reaction. The concentration of the amino-functionalized metal-organic framework crystals in the acid solution is 8.3-12.5 g / L. After the reaction, the crystals are washed and vacuum dried to obtain the protonated amino-functionalized metal-organic framework filler.

[0013] Further, in step (1) of the present invention, the heating reaction temperature is 100–140°C, the reaction time is 12–48 h; the vacuum drying temperature is 40–80°C, the absolute pressure is 0.002–0.02 MPa, and the drying time is 12–36 h. In step (2), the acid solution is hydrochloric acid solution with a concentration of 0.01–0.05 mol / L; the protonation reaction temperature is 20–35°C, the reaction time is 12–36 h; the sample is washed with water until the pH is 6.5–7.0, and then washed with methanol 3–5 times; the vacuum drying temperature is 40–80°C, the absolute pressure is 0.002–0.02 MPa, and the drying time is 12–36 h.

[0014] Another objective of this invention is achieved through the following technical solution:

[0015] The preparation method of the protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries provided by the present invention is as follows: the lithium salt is dissolved in an organic solvent, the concentration of the lithium salt in the organic solvent is 14.4-34.5 g / L; then the protonated UiO-66-NH2 filler is added, and the filler is uniformly dispersed by ultrasonic treatment. Subsequently, polyethylene oxide is added, and the mixture is continuously stirred at room temperature to obtain a uniform slurry. Then, the mixture is cast into a film, and the solvent is removed by vacuum drying to obtain the protonated metal-organic framework composite solid polymer electrolyte membrane.

[0016] Furthermore, in the preparation method of the composite solid polymer electrolyte of the present invention, the organic solvent is acetonitrile; the ultrasonic treatment time is 10-40 min; the stirring time is 12-36 h; during vacuum drying, the drying temperature is 40-80℃, the absolute pressure is 0.002-0.02 MPa, and the drying time is 12-36 h.

[0017] The electrolyte obtained using the above-described method for preparing a protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries has an ionic conductivity of 2.8 × 10⁻⁶. -4 ~4.7×10 -4 S / cm, lithium-ion transference number is 0.20 to 0.55.

[0018] The present invention has the following beneficial effects:

[0019] (1) In this invention, a protonated amino-functionalized metal-organic framework with a three-dimensional porous structure and protonated functional groups is introduced as a filler into a polyethylene oxide-lithium salt matrix, which can exert the following synergistic effects: (a) The three-dimensional porous framework of the protonated amino-functionalized metal-organic framework can disrupt the crystalline arrangement of polyethylene oxide, reduce its crystallinity, and at the same time provide ordered lithium-ion transport channels, significantly improving the ionic conductivity and lithium-ion transference number of the electrolyte; (b) the -NH3 on the surface of the filler +The functional groups can adsorb lithium salt anions through electrostatic interaction, promote lithium salt dissociation, and regulate the uniform deposition of lithium ions on the surface of lithium metal anode, effectively inhibiting the growth of lithium dendrites; (c) The filler helps to form a stable solid electrolyte interface on the surface of lithium metal anode, improves the interfacial compatibility between electrolyte and lithium metal anode, thereby achieving long-term stable cycling; (d) The introduction of the filler can improve the thermal stability of polyoxyethylene electrolyte and enhance the safety of battery use under high temperature conditions.

[0020] (2) This invention pioneers a new strategy for modifying polyoxyethylene solid polymer electrolytes with protonated metal-organic framework fillers. The preparation process is simple and controllable, the filler has good dispersibility, and the resulting electrolyte has an ionic conductivity of 2.8 × 10⁻⁶ at 60 °C. -4 ~4.7×10 -4 The S / cm ratio and lithium-ion transference number range from 0.20 to 0.55. Furthermore, it exhibits excellent lithium dendrite suppression, which is beneficial for the research and industrialization of high-safety, high-performance solid-state lithium metal battery technology. Attached Figure Description

[0021] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0022] Figure 1 These are images of the appearance of the protonated metal-organic framework composite solid polymer electrolyte prepared according to Example 1 of this invention.

[0023] Figure 2 These are impedance spectra of the protonated metal-organic framework composite solid polymer electrolyte prepared in Example 1 of this invention at different temperatures.

[0024] Figure 3 This is the DC polarization curve of the protonated metal-organic framework composite solid polymer electrolyte prepared in Example 1 of the present invention;

[0025] Figure 4 The Li||Li symmetric battery assembled from the protonated metal-organic framework composite solid polymer electrolyte prepared in Example 1 of this invention operates at 0.1 mA cm⁻¹. −2 Constant current charge-discharge curves at current density;

[0026] Figure 5 The output shows the charge-discharge cycle performance curves of the LFP||Li full cell assembled from the protonated metal-organic framework composite solid polymer electrolyte prepared in Example 1 of this invention. Detailed Implementation

[0027] Example 1:

[0028] 1. This embodiment discloses a protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries, comprising vinyl polyethylene oxide, lithium salt, and filler; wherein the filler is a protonated amino-functionalized metal-organic framework, with a mass fraction of 10 wt% in the composite solid polymer electrolyte; the protonated amino-functionalized metal-organic framework is a protonated UiO-66-NH2 with a three-dimensional porous structure and -NH3 on its surface. + It has functional groups and a positive Zeta potential. The viscosity-average molecular weight of polyethylene oxide is 600,000; the EO units of polyethylene oxide react with Li in lithium salts. + The molar ratio is n(EO)∶n(Li⁺)=14∶1; the lithium salt is lithium bis(trifluoromethanesulfonylimide).

[0029] The preparation method of the above-mentioned protonated amino-functionalized metal-organic framework filler comprises the following steps:

[0030] (1) Using the solvothermal method, zirconium tetrachloride (0.50 g, 2.14 mmol) and 2-aminoterephthalic acid (0.39 g, 2.14 mmol) were weighed and placed in a beaker. 50 mL of N,N-dimethylformamide solvent was added and stirred vigorously to dissolve it completely. The mixture was then transferred to a stainless steel high-pressure reactor with a polytetrafluoroethylene liner and placed in an oven. The temperature was raised to 120 °C and heated for 24 h. After naturally cooling to room temperature, the reaction product crystals were collected by centrifugation and washed three times each with N,N-dimethylformamide and methanol. The obtained solid was dried in a vacuum drying oven at 60 °C and an absolute pressure of 0.01 MPa for 24 h to obtain UiO-66-NH2 crystals.

[0031] (2) Weigh the above UiO-66-NH2 crystals and place them in a beaker. Add a hydrochloric acid solution with a concentration of 0.01 mol / L. The concentration of UiO-66-NH2 crystals in the hydrochloric acid solution is 10 g / L. Stir continuously at 25℃ for 24 h to complete the amino protonation reaction. Then wash the product with deionized water until the pH of the system is 6.8. Wash it three times with methanol. Finally, dry it in a vacuum drying oven at 60℃ and an absolute pressure of 0.01 MPa for 24 h to obtain the protonated UiO-66-NH2 filler.

[0032] 2. The preparation method of the protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries in this embodiment is as follows:

[0033] Lithium bis(trifluoromethanesulfonyl)imide (0.23 g, 0.80 mmol) was dissolved in 8 mL of acetonitrile solvent. The protonated UiO-66-NH2 filler was added, and the mixture was sonicated for 30 min to ensure uniform dispersion. Polyethylene oxide was then added, and the mixture was stirred continuously at room temperature for 24 h to obtain a homogeneous slurry. The slurry was poured into a polytetrafluoroethylene mold, smoothed with a scraper, and allowed to dry naturally at room temperature for 4 h to form a film. The film was then transferred to a vacuum drying oven and dried at 60 °C and 0.01 MPa absolute pressure for 24 h to remove residual solvent. After removal from the mold, the film was peeled off to obtain an electrolyte membrane with a thickness of approximately 100 μm. This membrane was then punched into discs with a diameter of 16 mm and stored in an argon-atmospheric glove box for later use. This yielded an electrolyte membrane with an ionic conductivity of 4.7 × 10⁻⁶ at 60 °C. -4 A protonated metal-organic framework composite solid polymer electrolyte with a S / cm and a lithium-ion transference number of 0.55.

[0034] Example 2:

[0035] 1. This embodiment discloses a protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries, comprising vinyl polyethylene oxide, lithium salt, and filler; wherein the filler is a protonated amino-functionalized metal-organic framework, with a mass fraction of 5 wt% in the composite solid polymer electrolyte; the protonated amino-functionalized metal-organic framework is a protonated UiO-66-NH2 with a three-dimensional porous structure and -NH3 on its surface. + It has functional groups and a positive Zeta potential. The viscosity-average molecular weight of polyethylene oxide is 600,000; the EO units of polyethylene oxide react with Li in lithium salts. + The molar ratio is n(EO)∶n(Li⁺)=12∶1; the lithium salt is lithium bis(trifluoromethanesulfonylimide).

[0036] The preparation method of the above-mentioned protonated amino-functionalized metal-organic framework filler comprises the following steps:

[0037] (1) Using the solvothermal method, zirconium tetrachloride (0.50 g, 2.14 mmol) and 2-aminoterephthalic acid (0.47 g, 2.57 mmol) were weighed and placed in a beaker. 50 mL of N,N-dimethylformamide solvent was added and stirred vigorously to dissolve it completely. The mixture was then transferred to a stainless steel high-pressure reactor with a polytetrafluoroethylene liner, placed in an oven, heated to 100 °C and heated for 48 h. After naturally cooling to room temperature, the reaction product crystals were collected by centrifugation and washed three times each with N,N-dimethylformamide and methanol. The obtained solid was dried in a vacuum drying oven at 50 °C and an absolute pressure of 0.01 MPa for 36 h to obtain UiO-66-NH2 crystals.

[0038] (2) Weigh the above UiO-66-NH2 crystals and place them in a beaker. Add a hydrochloric acid solution with a concentration of 0.01 mol / L. The concentration of UiO-66-NH2 crystals in the hydrochloric acid solution is 10 g / L. Stir continuously at 30℃ for 12 h to complete the amino protonation reaction. Then wash the product with deionized water until the pH of the system is 6.9. Wash it three times with methanol. Finally, dry it in a vacuum drying oven at 50℃ and an absolute pressure of 0.01 MPa for 36 h to obtain the protonated UiO-66-NH2 filler.

[0039] 2. The preparation method of the protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries in this embodiment is as follows:

[0040] Lithium bis(trifluoromethanesulfonyl)imide (0.23 g, 0.80 mmol) was dissolved in 8 mL of acetonitrile solvent. The protonated UiO-66-NH2 filler was added, and the mixture was sonicated for 30 min to ensure uniform dispersion. Polyethylene oxide was then added, and the mixture was stirred continuously at room temperature for 12 h to obtain a homogeneous slurry. The slurry was poured into a polytetrafluoroethylene mold, smoothed with a scraper, and allowed to dry naturally at room temperature for 4 h. It was then transferred to a vacuum drying oven and dried at 40 °C and 0.01 MPa absolute pressure for 36 h to remove residual solvent. After removing the slurry from the mold, an electrolyte membrane with a thickness of approximately 100 μm was obtained. This membrane was then punched into discs with a diameter of 16 mm and stored in an argon-atmospheric glove box for later use. This yielded an electrolyte membrane with an ionic conductivity of 4.2 × 10⁻⁶ at 60 °C. -4 A protonated metal-organic framework composite solid polymer electrolyte with a S / cm and a lithium-ion transference number of 0.38.

[0041] Example 3:

[0042] 1. This embodiment discloses a protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries, comprising vinyl polyethylene oxide, lithium salt, and filler; wherein the filler is a protonated amino-functionalized metal-organic framework, with a mass fraction of 15 wt% in the composite solid polymer electrolyte; the protonated amino-functionalized metal-organic framework is a protonated UiO-66-NH2 with a three-dimensional porous structure and -NH3 on its surface. + It has functional groups and a positive Zeta potential. The viscosity-average molecular weight of polyethylene oxide is 600,000; according to the molar ratio of EO units in polyethylene oxide to Li in lithium salts... + = 16:1; the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

[0043] The preparation method of the above-mentioned protonated amino-functionalized metal-organic framework filler comprises the following steps:

[0044] (1) Using the solvothermal method, zirconium tetrachloride (0.50 g, 2.14 mmol) and 2-aminoterephthalic acid (0.50 g, 2.78 mmol) were weighed and placed in a beaker. 50 mL of N,N-dimethylformamide solvent was added and stirred vigorously to dissolve it completely. The mixture was then transferred to a stainless steel high-pressure reactor with a polytetrafluoroethylene liner, placed in an oven, heated to 140 °C and heated for 12 h. After naturally cooling to room temperature, the reaction product crystals were collected by centrifugation and washed three times each with N,N-dimethylformamide and methanol. The obtained solid was dried in a vacuum drying oven at 80 °C and an absolute pressure of 0.01 MPa for 12 h to obtain UiO-66-NH2 crystals.

[0045] (2) Weigh the above UiO-66-NH2 crystals and place them in a beaker. Add a hydrochloric acid solution with a concentration of 0.05 mol / L. The concentration of UiO-66-NH2 crystals in the hydrochloric acid solution is 10 g / L. Stir continuously at 35℃ for 36 h to complete the amino protonation reaction. Then wash the product with deionized water until the pH of the system is 7.0. Wash it with methanol 5 times. Finally, dry it in a vacuum drying oven at 80℃ and an absolute pressure of 0.01 MPa for 12 h to obtain the protonated UiO-66-NH2 filler.

[0046] 2. The preparation method of the protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries in this embodiment is as follows:

[0047] Lithium bis(trifluoromethanesulfonyl)imide (0.23 g, 0.80 mmol) was dissolved in 8 mL of acetonitrile solvent. The protonated UiO-66-NH2 filler was added, and the mixture was sonicated for 40 min to ensure uniform dispersion. Polyethylene oxide was then added, and the mixture was stirred continuously at room temperature for 36 h to obtain a homogeneous slurry. The slurry was poured into a polytetrafluoroethylene mold, smoothed with a scraper, and allowed to dry naturally at room temperature for 4 h. It was then transferred to a vacuum drying oven and dried at 80 °C and 0.01 MPa absolute pressure for 12 h to remove residual solvent. After removal from the mold, the membrane was peeled off to obtain an electrolyte membrane with a thickness of approximately 100 μm. This membrane was then punched into discs with a diameter of 16 mm and stored in an argon-atmospheric glove box for later use. This yielded an electrolyte membrane with an ionic conductivity of 3.9 × 10⁻⁶ at 60 °C. -4 A protonated metal-organic framework composite solid polymer electrolyte with a S / cm and a lithium-ion transference number of 0.31.

[0048] The protonated metal-organic framework composite solid polymer electrolyte membrane prepared using the method described in Example 1 of this invention is as follows: Figure 1 As shown, the ionic conductivity at 60℃ is 4.7 × 10⁻⁶. -4 S / cm ( Figure 2 ), Li +The migration count is 0.55 ( Figure 3 In an argon-atmospheric glove box, using lithium iron phosphate electrodes as the positive electrode and lithium metal foil as the negative electrode, a protonated metal-organic framework composite solid polymer electrolyte membrane was used to assemble a battery. The assembled Li||Li symmetric battery achieved an ultra-long cycle life exceeding 3200 hours. Figure 4 The assembled LFP||Li full cell still maintains a high capacity retention of 92.2% after 300 cycles. Figure 5 The above results indicate that the protonated metal-organic framework composite solid polymer electrolyte prepared in the embodiments of the present invention is suitable for lithium metal batteries.

Claims

1. A protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries, comprising vinyl polyoxide, lithium salt, and filler; characterized in that: The filler is a protonated amino-functionalized metal-organic framework, with a mass fraction of 5–20 wt% in the composite solid polymer electrolyte; the protonated amino-functionalized metal-organic framework is a protonated UiO-66-NH2 with a three-dimensional porous structure and -NH3 on its surface. + It has a functional group and a positive Zeta potential.

2. The protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries according to claim 1, characterized in that: The polyethylene oxide has a viscosity-average molecular weight ≤ 600,000; the EO units of the polyethylene oxide and the Li in the lithium salt + The molar ratio is n(EO)∶n(Li) + The ratio of lithium salt to lithium trifluoromethanesulfonylimide is 12 to 16:1; the lithium salt is lithium bis(trifluoromethanesulfonylimide).

3. The protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries according to claim 1, characterized in that: The preparation method of the protonated amino-functionalized metal-organic framework filler includes the following steps: (1) Using a solvothermal method, zirconium tetrachloride and 2-aminoterephthalic acid were dissolved in N,N-dimethylformamide to obtain a mixed solution; the concentration of zirconium tetrachloride in the mixed solution was 0.036-0.054 mol / L, and the concentration of 2-aminoterephthalic acid was 1-1.3 times that of zirconium tetrachloride; the mixed solution was transferred to a high-pressure reactor for heating and reaction, and after the reaction was completed, it was cooled, centrifuged, washed, and vacuum dried to obtain amino-functionalized metal-organic framework crystals; (2) The amino-functionalized metal-organic framework crystals are dispersed in an acid solution for protonation reaction. The concentration of the amino-functionalized metal-organic framework crystals in the acid solution is 8.3-12.5 g / L. After the reaction, the crystals are washed and vacuum dried to obtain the protonated amino-functionalized metal-organic framework filler.

4. The protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries according to claim 3, characterized in that: In step (1), the heating reaction temperature is 100-140℃ and the reaction time is 12-48h; the vacuum drying temperature is 40-80℃, the absolute pressure is 0.002-0.02MPa, and the drying time is 12-36h.

5. The protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries according to claim 3, characterized in that: In step (2), the acid solution is hydrochloric acid solution with a concentration of 0.01–0.05 mol / L; the protonation reaction temperature is 20–35℃, and the reaction time is 12–36 h; the sample is washed with water until the pH is 6.5–7.0, and then washed with methanol 3–5 times; the vacuum drying temperature is 40–80℃, the absolute pressure is 0.002–0.02 MPa, and the drying time is 12–36 h.

6. The method for preparing the protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries according to any one of claims 1-5, characterized in that: The lithium salt is dissolved in an organic solvent with a concentration of 14.4–34.5 g / L. Then, the protonated UiO-66-NH2 filler is added, and the filler is ultrasonically treated to ensure uniform dispersion. Subsequently, polyethylene oxide is added, and the mixture is continuously stirred at room temperature to obtain a uniform slurry. The slurry is then cast into a film, and the solvent is removed by vacuum drying to obtain the protonated metal-organic framework composite solid polymer electrolyte membrane.

7. The method for preparing the protonated metal-organic framework composite solid polymer electrolyte for lithium metal batteries according to claim 6, characterized in that: The organic solvent is acetonitrile; the ultrasonic treatment time is 10–40 min; the stirring time is 12–36 h; during vacuum drying, the drying temperature is 40–80 °C, the absolute pressure is 0.002–0.02 MPa, and the drying time is 12–36 h.

8. The electrolyte obtained by the preparation method according to any one of claims 6-7, characterized in that: The electrolyte has an ionic conductivity of 2.8 × 10⁻⁶. -4 ~4.7×10 -4 S / cm, lithium-ion transference number is 0.20 to 0.55.

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