Metal-organic framework-polymer composite solid-state electrolyte and preparation method and application thereof

Abstract

The application relates to the technical field of composite solid electrolytes, in particular to a metal-organic framework-polymer composite solid electrolyte and a preparation method and application thereof, and comprises the following steps: adding a modified complexing system into anhydrous solvent to form a complexing solution, adding modified UiO-66 into the complexing solution to form a precursor slurry, performing polymerization under a nitrogen atmosphere to form a gel electrolyte film, shaping the polymerized gel electrolyte film, obtaining a composite solid electrolyte film, and soaking the composite solid electrolyte film in a lithium salt ethanol solution to obtain a metal-organic framework-polymer composite solid electrolyte film. The hydrophilic / lithiophilic group of the modified coupling agent is used for optimizing the adsorption and transmission of UiO-66 to Li + , the modified complexing system can improve the dissociation degree of lithium salt and the migration rate of Li + , the modified UiO-66 can realize the uniform distribution of Li + in the electrolyte, reduce the local current density, and inhibit the dendrite growth from the kinetic aspect.

Description

Technical Field

[0001] This invention relates to the field of composite solid electrolyte technology, specifically to metal-organic framework-polymer composite solid electrolytes, their preparation methods, and applications. Background Technology

[0002] Lithium metal batteries (LMBs) have become important candidate energy storage devices for meeting current societal energy demands due to their high energy density, good environmental compatibility, and high voltage characteristics, especially in the field of flexible electronic devices, where they have broad application prospects. However, current LMBs still face severe safety challenges. For example, lithium dendrites produced by lithium metal anodes can cause internal short circuits, leading to thermal runaway and other problems, which are not conducive to the development of flexible LMBs. On the other hand, LMBs integrated into flexible electronic devices face long-term bending deformation, which can induce fatigue cracks, delamination, or even fracture of the electrolyte in the device. To solve these problems, researchers have converted the internal liquid electrolyte into a polymerized solid electrolyte (SPE) because it has high toughness, is easy to prepare, and has high compatibility at the solid-solid interface. Currently, various polymers have been developed as electrolyte matrices, including polyethylene oxide (PEO), polysiloxane (PS), and polycarbonate (PC). However, these solid electrolytes composed of polymer matrices and lithium salts usually have low ionic conductivity and do not have high flexibility.

[0003] For high conductivity and heat resistance, metal-organic frameworks (MOFs) can be introduced to meet the requirements. Due to their combination of active sites, ion screening capabilities and easy preparation, they have become novel solid electrolyte materials. For example, ZIF-8 was introduced as a MOF material into the PEO-based electrolyte system. Its Lewis acid sites promoted the dissociation of lithium salts, thereby significantly improving the ionic conductivity.

[0004] MOFs are inorganic rigid materials with significantly different physicochemical properties from organic polymer matrices. Simple physical mixing can easily lead to gaps and phase separation at the interface, forming dead zones for lithium-ion transport, greatly increasing interfacial impedance and reducing ion conduction efficiency. At the same time, the interfacial bonding is not strong, and peeling and cracking can easily occur during battery cycling or mechanical deformation, disrupting the continuity of the ion transport network. Therefore, in response to the problems mentioned in the background art, those skilled in the art have proposed metal-organic framework-polymer composite solid electrolytes and their preparation methods and applications. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a metal-organic framework-polymer composite solid electrolyte, its preparation method and application, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing a metal-organic framework-polymer composite solid electrolyte includes the following steps:

[0008] S1. Add the modified complexing system to anhydrous solvent and stir for 1-1.5 h at 22-27℃ under a nitrogen atmosphere to form a complexing solution. Add the modified UiO-66 to the complexing solution and disperse for 40-50 min. Stir for 7-8 h at 40-45℃ to form a precursor slurry.

[0009] S2. The precursor slurry is cast into a polytetrafluoroethylene mold, vacuumed for 5-10 minutes, and then polymerized in a nitrogen atmosphere to form a gel electrolyte membrane. The polymerized gel electrolyte membrane, together with the mold, is heated to 60-70℃ and dried for 3-4 hours to solidify, thus obtaining a composite solid electrolyte membrane.

[0010] S3. Peel the composite solid electrolyte membrane from the polytetrafluoroethylene mold, immerse the composite solid electrolyte membrane in lithium salt ethanol solution for 10-15 min, take it out and vacuum dry it at 55-60℃ for 1.5-2 h to obtain metal-organic framework-polymer composite solid electrolyte membrane.

[0011] Modified UiO-66 is prepared through the following steps:

[0012] S11. Add UiO-66 to a mixed solvent of toluene and ethanol, and disperse it under a nitrogen atmosphere for 20-25 minutes to form a suspension;

[0013] S12. Add the modified coupling agent dropwise to the suspension. After the addition is complete, raise the temperature to 50-60℃ and continue stirring for 5-6 hours.

[0014] S13. After the reaction is complete, the suspension is naturally cooled to room temperature, and stirring is continued for 10-20 minutes to obtain modified UiO-66;

[0015] The modified coupling agent is prepared through the following steps:

[0016] Add KH570 and PEG200 to anhydrous toluene and stir for 10-15 min under a nitrogen atmosphere. Add p-toluenesulfonic acid and hydroquinone, stir until homogeneous, and reflux at 60-70℃ for 5-6 h. After the reaction is complete, cool to room temperature to obtain the reaction solution. Purify the reaction solution by rinsing to remove p-toluenesulfonic acid, hydroquinone, and unreacted PEG200. Collect the filtrate and evaporate it for 1-1.5 h to obtain the modified coupling agent.

[0017] Furthermore, the modified complex system in step S1 is prepared through the following steps:

[0018] S101. Under a nitrogen atmosphere at room temperature, polyethylene glycol diacrylate, polyethylene glycol monoacrylate and trimethylolpropane triacrylate are mixed to obtain a mixture. PEG200 is added to the mixture. While maintaining a nitrogen atmosphere, the mixture is heated to 40-45℃ and stirred for 20-30 minutes to obtain a ternary monomer mixture.

[0019] S102. Add anhydrous acetonitrile to the ternary monomer mixture, stir for 10-20 min and adjust the viscosity to 50-80 mPa·s. Purify the ternary monomer mixture after viscosity adjustment and collect the filtrate to obtain the modified monomer system.

[0020] S103. Add the pretreated lithium salt to the modified monomer system and stir under a nitrogen atmosphere for 25-30 minutes to form a modified complex system.

[0021] Furthermore, the pretreated lithium salt in step S103 is obtained through the following steps:

[0022] LiTFSI and ethylene carbonate were mixed at a mass ratio of (9-10):1 and dried under vacuum at 50-60℃ for 1-2 hours to obtain pretreated lithium salt.

[0023] Furthermore, in step S1, the mass ratio of the modified complex system to the modified UiO-66 and the anhydrous solvent is 100:(5-15):(60-80), in step S3, the mass ratio of the composite solid electrolyte membrane to the lithium salt ethanol solution is 1:(5-10), and the mass ratio of ethanol to LiTFSI in the lithium salt ethanol solution is 100:(0.8-1.2).

[0024] Furthermore, in steps S11 and S12, the mass ratio of UiO-66 to the modified coupling agent is 100:(5-8), and the mass ratio of UiO-66 to the mixed solvent of toluene and ethanol is 1:(20-30), wherein the mass ratio of toluene to ethanol is (3-4):1.

[0025] Furthermore, in steps S101, S102, and S103, the mass ratio of polyethylene glycol diacrylate, polyethylene glycol monoacrylate, and trimethylolpropane triacrylate is (69.7-79.2):(9.95-19.8):1; the mass ratio of the mixture to PEG200 and anhydrous acetonitrile is 100:(5-10):(100-130); and the mass ratio of the modified monomer system to the pretreated lithium salt is 100:(15-25).

[0026] Furthermore, in the preparation step of the modified coupling agent, the mass ratio of KH570 to PEG200 is (2-3):1, and the mass ratio of the total amount of KH570 and PEG200 to anhydrous toluene, p-toluenesulfonic acid and hydroquinone is 100:(150-200):(1-2):(0.5-1).

[0027] Furthermore, the metal-organic framework-polymer composite solid electrolyte was prepared according to the preparation method described above.

[0028] Furthermore, the application of metal-organic framework-polymer composite solid electrolytes in lithium metal batteries.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. This invention optimizes the hydrophilic / lithophilic groups of the coupling agent UiO-66 for Li + The adsorption and transport of lithium salts by modified complexing systems can enhance the dissociation of lithium salts and Li. + The migration rate, combined with the lithium-conducting effect of modified UiO-66, enables the internal Li-ionization of the electrolyte. + The uniform distribution of the current density reduces the local current density, thereby suppressing dendrite growth from a dynamic perspective.

[0031] 2. This invention, by modifying the structural synergy of the ternary monomers in the complex system, balances the flexibility and cross-linking strength of the polymer matrix, avoiding the problems of being flexible but not strong or strong but brittle caused by a single monomer. This allows the electrolyte membrane to withstand repeated bending and deformation of flexible electronic devices. The modified complex system enhances the lithium salt dissociation degree, and the modified UiO-66 provides highly efficient Li... + The transport channels, together with the other two, enable the composite solid electrolyte to have excellent ion conduction capabilities. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the preparation process of the metal-organic framework-polymer composite solid electrolyte in this invention;

[0033] Figure 2 This is a schematic diagram of the preparation process of modified UiO-66 in this invention;

[0034] Figure 3 This is a schematic diagram of the preparation process of the modified complexing system in this invention;

[0035] Figure 4 Scanning electron microscope image of modified UiO-66;

[0036] Figure 5 Scanning electron microscope image of a metal-organic framework-polymer composite solid electrolyte membrane;

[0037] Figure 6 The XRD patterns of the metal-organic framework-polymer composite solid electrolyte membranes in Examples 1, 2, and 3 are shown.

[0038] Figure 7 The rate performance test curve of the battery prepared in Example 1 at 60°C;

[0039] Figure 8 To obtain the rate performance test curve of the battery at 60℃ for Comparative Example 1;

[0040] Figure 9 To obtain the rate performance test curve of the battery at 60℃ for Comparative Example 2;

[0041] Figure 10 To obtain the rate performance test curve of the battery at 60℃ for Comparative Example 3;

[0042] Figure 11 The cycle performance test curve of the battery prepared in Example 1 at 60°C is shown.

[0043] Figure 12 To obtain the cycle performance test curve of the battery at 60℃ for Comparative Example 1;

[0044] Figure 13 To obtain the cycle performance test curve of the battery at 60℃ for Comparative Example 2;

[0045] Figure 14 To obtain the cycle performance test curve of the battery at 60℃ for Comparative Example 3. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0047] Please see Figures 1-14 The present invention provides a technical solution:

[0048] Example 1:

[0049] A method for preparing a metal-organic framework-polymer composite solid electrolyte includes the following steps:

[0050] Preparation of modified UiO-66:

[0051] S11. Take 100g of UiO-66 and add it to a toluene-ethanol mixed solvent (total mass 2000g, i.e. 1500g of toluene and 500g of ethanol), and disperse it under a nitrogen atmosphere at 25℃ for 20min to form a suspension.

[0052] S12. Add 66.67g KH570 (γ-methacryloyloxypropyltrimethoxysilane) and 33.33g PEG200 (polyethylene glycol 200) to 150g anhydrous toluene. Stir at 25℃ under a nitrogen atmosphere for 10min. Add 1g p-toluenesulfonic acid and 0.5g hydroquinone. After stirring evenly, reflux at 60℃ for 5h. After the reaction is completed, cool to 25℃. Purify the reaction solution by rinsing to remove impurities. Collect the filtrate. Evaporate the filtrate for 1h to obtain the modified coupling agent. Add 5g of the modified coupling agent dropwise to the suspension. After the addition is completed, heat to 50℃ and continue stirring for 5h.

[0053] S13. After the reaction is complete, allow it to cool naturally to 25°C, and continue stirring for 10 minutes to obtain modified UiO-66.

[0054] Preparation of modified complexation system:

[0055] S101. Mix 86.42g of polyethylene glycol diacrylate, 12.34g of polyethylene glycol monoacrylate and 1.24g of trimethylolpropane triacrylate at 25°C under a nitrogen atmosphere to obtain a mixture. Add 5g of PEG200 to the mixture, maintain the nitrogen atmosphere, heat to 40°C and stir for 20min to obtain a ternary monomer mixture.

[0056] S102. Add 100g of anhydrous acetonitrile to the ternary monomer mixture, stir for 10min and adjust the viscosity to 50mPa·s. Purify the ternary monomer mixture after viscosity adjustment and collect the filtrate to obtain the modified monomer system.

[0057] S103. Mix 90g LiTFSI (lithium bis(trifluoromethanesulfonyl)imide) with 10g ethylene carbonate and dry under vacuum at 50℃ for 1h to obtain a pretreated lithium salt. Add 15g of the pretreated lithium salt to 100g of the modified monomer system and stir at 25℃ under a nitrogen atmosphere for 25min to form a modified complex system.

[0058] Preparation of composite solid electrolyte membranes:

[0059] S1. Add 100g of modified complex system to 60g of anhydrous solvent, stir for 1h at 22℃ under nitrogen atmosphere to form complex solution, add 5g of modified UiO-66 to complex solution and disperse for 40min, stir at 40℃ for 7h to form precursor slurry;

[0060] S2. The precursor slurry is cast into a polytetrafluoroethylene mold, vacuumed for 5 minutes, and then polymerized in a nitrogen atmosphere at 25°C to form a gel electrolyte membrane. The polymerized gel electrolyte membrane, together with the mold, is heated to 60°C and dried for 3 hours to solidify, thus obtaining a composite solid electrolyte membrane.

[0061] S3. Add 0.8g LiTFSI to 100g ethanol and stir to dissolve to obtain a lithium salt ethanol solution. Soak 10g of the composite solid electrolyte membrane in 50g of lithium salt ethanol solution for 10min. After taking it out, vacuum dry it at 55℃ for 1.5h to obtain a metal-organic framework-polymer composite solid electrolyte membrane.

[0062] Example 2:

[0063] A method for preparing a metal-organic framework-polymer composite solid electrolyte includes the following steps:

[0064] Preparation of modified UiO-66:

[0065] S11. Take 100g of UiO-66 and add it to a toluene-ethanol mixed solvent (total mass 2500g, i.e. 2000g toluene and 500g ethanol), and disperse it at 25℃ under a nitrogen atmosphere for 22.5min to form a suspension.

[0066] S12. Add 71.43g KH570 and 28.57g PEG200 to 175g anhydrous toluene, stir for 10min at 25℃ under a nitrogen atmosphere, add 1.5g p-toluenesulfonic acid and 0.75g hydroquinone, stir evenly, and reflux at 65℃ for 5.5h. After the reaction is completed, cool to 25℃, purify the reaction solution by rinsing to remove impurities, collect the filtrate, evaporate the filtrate for 1.2h to obtain the modified coupling agent, add 6.5g of the modified coupling agent dropwise to the suspension, and after the addition is completed, heat to 55℃ and continue stirring for 5.5h.

[0067] S13. After the reaction is complete, allow it to cool naturally to 25°C, and continue stirring for 15 minutes to obtain modified UiO-66.

[0068] Preparation of modified complexation system:

[0069] S101. Mix 74.45g of polyethylene glycol diacrylate, 14.88g of polyethylene glycol monoacrylate and 1g of trimethylolpropane triacrylate under a nitrogen atmosphere at 25°C to obtain a mixture. Add 7.5g of PEG200 to the mixture, maintain the nitrogen atmosphere, heat to 42°C and stir for 25 minutes to obtain a ternary monomer mixture.

[0070] S102. Add 115g of anhydrous acetonitrile to the ternary monomer mixture, stir for 15min and adjust the viscosity to 65mPa·s. Purify the ternary monomer mixture after viscosity adjustment and collect the filtrate to obtain the modified monomer system.

[0071] S103. Mix 95g LiTFSI with 10g ethylene carbonate and dry under vacuum at 55℃ for 1.5h to obtain pretreated lithium salt. Add 20g of pretreated lithium salt to 100g modified monomer system and stir at 25℃ under nitrogen atmosphere for 27min to form modified complex system.

[0072] Preparation of composite solid electrolyte membranes:

[0073] S1. Add 100g of modified complex system to 70g of anhydrous solvent, stir for 1.2h at 24℃ under nitrogen atmosphere to form complex solution, add 10g of modified UiO-66 to complex solution and disperse for 45min, stir at 42℃ for 7.5h to form precursor slurry;

[0074] S2. The precursor slurry is cast into a polytetrafluoroethylene mold, vacuumed for 7 minutes, and then polymerized in a nitrogen atmosphere at 25°C to form a gel electrolyte membrane. The polymerized gel electrolyte membrane, together with the mold, is heated to 65°C and dried for 3.5 hours to solidify, thus obtaining a composite solid electrolyte membrane.

[0075] S3. Add 1g LiTFSI to 100g ethanol and stir to dissolve to obtain a lithium salt ethanol solution. Soak 10g of the composite solid electrolyte membrane in 75g of lithium salt ethanol solution for 12min. After taking it out, vacuum dry it at 57℃ for 1.7h to obtain a metal-organic framework-polymer composite solid electrolyte membrane.

[0076] Example 3:

[0077] A method for preparing a metal-organic framework-polymer composite solid electrolyte includes the following steps:

[0078] Preparation of modified UiO-66:

[0079] S11. Take 100g of UiO-66 and add it to a toluene-ethanol mixed solvent (total mass 3000g, i.e. 2400g toluene and 600g ethanol), and disperse it at 25℃ under a nitrogen atmosphere for 25min to form a suspension.

[0080] S12. Add 75g KH570 and 25g PEG200 to 200g anhydrous toluene, stir for 10min under a nitrogen atmosphere at 25℃, add 2g p-toluenesulfonic acid and 1g hydroquinone, stir evenly, and reflux at 70℃ for 6h. After the reaction is completed, cool to 25℃, purify the reaction solution by rinsing to remove impurities, collect the filtrate, evaporate the filtrate for 1.5h to obtain the modified coupling agent, add 8g of the modified coupling agent dropwise to the suspension, and after the addition is completed, heat to 60℃ and continue stirring for 6h.

[0081] S13. After the reaction is complete, let it cool naturally to 25°C, and continue stirring for 20 minutes to obtain modified UiO-66.

[0082] Preparation of modified complexation system:

[0083] S101. Mix 79.2g of polyethylene glycol diacrylate, 19.8g of polyethylene glycol monoacrylate and 1g of trimethylolpropane triacrylate at 25°C under a nitrogen atmosphere to obtain a mixture. Add 10g of PEG200 to the mixture, maintain the nitrogen atmosphere, heat to 45°C and stir for 30 minutes to obtain a ternary monomer mixture.

[0084] S102. Add 130g of anhydrous acetonitrile to the ternary monomer mixture, stir for 20min and adjust the viscosity to 80mPa·s. Purify the ternary monomer mixture after viscosity adjustment and collect the filtrate to obtain the modified monomer system.

[0085] S103. Mix 100g LiTFSI with 10g ethylene carbonate and dry under vacuum at 60℃ for 2h to obtain pretreated lithium salt. Add 25g of pretreated lithium salt to 100g modified monomer system and stir at 25℃ under nitrogen atmosphere for 30min to form modified complex system.

[0086] Preparation of composite solid electrolyte membranes:

[0087] S1. Add 100g of modified complex system to 80g of anhydrous solvent, stir for 1.5h at 27℃ under nitrogen atmosphere to form complex solution, add 15g of modified UiO-66 to complex solution and disperse for 50min, stir at 45℃ for 8h to form precursor slurry;

[0088] S2. The precursor slurry is cast into a polytetrafluoroethylene mold, vacuumed for 10 minutes, and then polymerized in a nitrogen atmosphere at 25°C to form a gel electrolyte membrane. The polymerized gel electrolyte membrane, together with the mold, is heated to 70°C and dried for 4 hours to solidify, thus obtaining a composite solid electrolyte membrane.

[0089] S3. Add 1.2g LiTFSI to 100g ethanol and stir to dissolve to obtain a lithium salt ethanol solution. Soak 10g of the composite solid electrolyte membrane in 100g of lithium salt ethanol solution for 15min. After taking it out, vacuum dry it at 60℃ for 2h to obtain a metal-organic framework-polymer composite solid electrolyte membrane.

[0090] Comparative Example 1

[0091] Comparative Example 1 differs from Example 1 in that the modified UiO-66 is replaced with conventional UiO-66, and the remaining steps are exactly the same as in Example 1.

[0092] Comparative Example 2

[0093] Comparative Example 2 differs from Example 1 in that the modified complexing system is replaced with polyethylene glycol diacrylate, while the remaining steps are exactly the same as in Example 1.

[0094] Comparative Example 3

[0095] Comparative Example 3 differs from Example 1 in that the modified coupling agent is replaced with KH570 coupling agent, and the remaining steps are exactly the same as in Example 1.

[0096] Six different metal-organic framework-polymer composite solid electrolyte membranes were prepared using Examples 1-3 and Comparative Examples 1-3. The metal-organic framework-polymer composite solid electrolyte membranes were cut into 16mm diameter discs and sandwiched between two 0.5mm thick lithium sheets to form a Li / / electrolyte membrane / / Li battery. The batteries were tested at 60°C using a constant current charge-discharge mode with a current density of 1mA / cm². 2 Charge / discharge capacity 1mAh / cm 2 For a single period of 1 hour, the battery was cycled until the battery impedance suddenly increased or the voltage fluctuated drastically. The stable cycle life of the battery was recorded. Within the voltage range of 2.5-4.2V, constant current charge and discharge tests were performed sequentially at rates of 0.1C, 0.2C, 0.5C, 1C, and 2C. Each rate was cycled 5 times. The first discharge specific capacity of the battery at each rate was recorded. The capacity retention capability at high rates was analyzed with 0.1C rate as the benchmark. The specific test results are shown in Table 1 below.

[0097] Table 1

[0098]

[0099] As shown in Table 1, the metal-organic framework-polymer composite solid electrolyte of the present invention (Examples 1-3) is superior to the comparative examples 1-3 without the complete modification scheme in terms of core performance, which fully verifies the effectiveness of the modification design. The cycle life of Examples 1-3 is all above 850h, with the highest being 896h of Example 2, while the cycle life of the comparative examples 1-3 is only 283-320h. In terms of the first discharge specific capacity at 0.1C, the examples are stable at 162-168mAh / g, while the comparative examples are 148-156mAh / g, demonstrating better ion transport and interface compatibility. In terms of capacity retention after 200 cycles, the examples reach 92.6%-93.4%, while the comparative examples are only 71%-76.1%, and the anti-degradation ability is greatly improved.

[0100] Comparative Example 1, using unmodified UiO-66, exhibits poor interfacial compatibility with the polymer matrix, leading to easy aggregation and discontinuous ion conduction channels. This results in a significant decrease in dendrite suppression ability, with all performance indicators falling far below those of the examples. Comparative Example 2, a single polyethylene glycol diacrylate system, lacks the structural synergistic effect of ternary monomers, resulting in a simple crosslinking network, low mechanical strength, and the worst ion dissociation and transport capabilities, making it the lowest performing group. Comparative Example 3 uses pure KH570 coupling agent without PEG200-modified hydrophilic / lithophilic groups. The interfacial bonding between UiO-66 and the polymer matrix is ​​weak, and interfacial peeling easily occurs during cycling, resulting in significantly inferior performance compared to the example groups. Due to the lack of certain modification steps, the comparative examples suffer from problems such as interfacial peeling, discontinuous ion conduction channels, and insufficient dendrite suppression, leading to a significant decline in performance. This demonstrates that the modification scheme of the present invention can effectively solve the core pain points of conventional solid electrolytes.

[0101] Figure 4 The image shows a scanning electron microscope image of modified UiO-66. The crystals in the central region of the image exhibit a regular octahedral structure with sharp edges and clear crystal faces, which is a hallmark of UiO-66 material. This indicates that the modification process did not destroy its basic crystal framework. Some small deposits and slight roughness can be observed on some crystal surfaces, which is direct evidence that the modified coupling agent was successfully grafted onto the UiO-66 surface. The overall crystal form remains intact, indicating that the modification conditions were properly controlled and did not lead to crystal structure collapse or amorphization.

[0102] Figure 5This is a scanning electron microscope image of a metal-organic framework-polymer composite solid electrolyte membrane. The image shows a typical porous, wrinkled, interpenetrating network structure, composed of numerous nanoscale ribbon-like units interwoven and stacked. The internal pores are abundant and well-connected, with pore sizes mostly in the tens to hundreds of nanometers range. This porous structure with high specific surface area is beneficial for lithium salt dissociation and ion transport. The overall structure is uniformly distributed, and no obvious large-sized aggregates or phase separation defects were observed, indicating that the modified UiO-66 filler is well dispersed in the polymer matrix. The abundant pores and interpenetrating network structure provide a continuous transport path for lithium ions, which helps to improve the ionic conductivity of the electrolyte. The interwoven network structure can effectively improve the mechanical strength and deformation resistance of the membrane, which is crucial for the cycle stability of solid-state batteries. The uniform structure indicates that there is a good interfacial bond between the MOF filler and the polymer matrix, reducing interfacial impedance and improving battery performance.

[0103] Figure 6 The XRD patterns of the metal-organic framework-polymer composite solid electrolyte membranes in Examples 1, 2, and 3 are shown. All three curves show a broad diffraction peak near 2θ≈18°, without any sharp, strong diffraction peaks. This indicates that the modified UiO-66 exists in a highly dispersed form in the polymer matrix and does not form obvious crystalline aggregates. The composite membrane as a whole is mainly amorphous / semi-crystalline. The peak shapes and positions of the three curves are basically consistent, indicating that the main structure of the composite membranes (polymer matrix + modified UiO-66) in different examples has similar crystal phase characteristics. The modification process did not change the core structure of the composite membrane, but only optimized the dispersibility and interfacial bonding by adjusting the parameters.

[0104] Figure 7 The rate performance test curve of the battery prepared in Example 1 at 60°C is shown. At 0.1C, the battery exhibits the highest discharge specific capacity, approaching 162 mAh / g, indicating sufficient ion transport and high utilization of active materials at low rates. As the rate increases to 0.2C, 0.5C, 1C, and 2C, the discharge specific capacity gradually decreases, reaching approximately 130 mAh / g at 2C. This reflects the limitations of ion transport and reaction kinetics at high rates. At low rates (0.1C, 0.2C, 0.5C), the voltage plateau is relatively stable with minimal polarization, indicating low internal impedance and low Li... + Transmission is smooth; at high rates (1C, 2C), the voltage plateau shifts significantly downward, and polarization increases substantially. This is because at high current densities, Li... + The transport rate at the electrolyte and electrode interface cannot keep up with the reaction demand, resulting in increased energy loss.

[0105] Figure 8To obtain the rate performance test curve of the battery at 60°C for Comparative Example 1, at 0.1C, the discharge specific capacity was approximately 156 mAh / g, significantly lower than that of Example 1. At the 2C high rate, the specific capacity was only approximately 80 mAh / g, far lower than that of Example 1, and the capacity decay was greater. This indicates that the utilization rate of active material and the ion transport capability at high rates of Comparative Example 1 are weaker than those of Example 1. The voltage plateaus at all rates are shorter, and the voltage plateau shifts more significantly at high rates (1C, 2C), indicating a significant increase in polarization and a steeper voltage curve descent. This reflects the higher internal impedance of Comparative Example 1 and the presence of Li + The transport resistance is greater at the electrolyte and electrode interface, and the reaction kinetics are limited at high current densities.

[0106] Figure 9 To obtain the rate performance test curve of the battery at 60°C for Comparative Example 2, at a rate of 0.1C, the discharge specific capacity was only about 148 mAh / g, which was much lower than that of Example 1. At a high rate of 2C, the specific capacity dropped sharply to about 78 mAh / g, and the capacity retention rate was only about 53% of that at 0.1C, which was much lower than that of Example 1. This indicates that the utilization rate of active material and the ion transport capability at high rates of Comparative Example 2 are significantly weaker than those of Example 1.

[0107] Figure 10 To obtain the rate performance test curve of the battery prepared for Comparative Example 3 at 60°C, at a rate of 0.1C, the discharge specific capacity was approximately 153 mAh / g, which was lower than that of Example 1 and slightly higher than that of Comparative Example 2. At a high rate of 2C, the specific capacity was approximately 72 mAh / g, but much lower than that of Example 1. The capacity retention rate was approximately 47% of that at 0.1C, and there was still a significant decay. This indicates that the utilization rate of active material and the ion transport capability at high rates of Comparative Example 3 are still far inferior to those of the fully modified Example 1.

[0108] Figure 11 The cycle performance test curve of the battery prepared in Example 1 at 60°C shows that the discharge specific capacity is the highest in the first cycle, about 162 mAh / g. As the number of cycles increases, the specific capacity gradually decreases. After 200 cycles, the discharge specific capacity is about 150 mAh / g, and the capacity retention rate is about 92.6%. The capacity decay rate is relatively slow, indicating that the battery has good utilization of active materials and structural stability during cycling, and there is no drastic performance drop. The voltage plateau is relatively stable at each cycle number, and the voltage curves of different cycles are small, indicating that the internal polarization of the battery does not change much during cycling and the interface stability is good. Even after 200 cycles, the voltage plateau remains clear and there is no obvious voltage drop, which reflects the effective control of interface stability by the modified electrolyte.

[0109] Figure 12To obtain the cycle performance test curve of the battery at 60°C for Comparative Example 1, the discharge specific capacity of the first cycle was approximately 155 mAh / g. As the number of cycles increased, the specific capacity decreased rapidly, and after 200 cycles, the discharge specific capacity was only about 118 mAh / g, with a capacity retention rate of approximately 76.1%, far lower than the 92.6% of Example 1. The capacity decay rate was significantly faster, indicating that the battery had poor utilization of active materials and structural stability during cycling, and more severe interfacial side reactions and impedance accumulation. Comparative Example 1 used unmodified UiO-66, and the MOF particles were prone to agglomeration, resulting in poor interfacial compatibility with the polymer matrix, leading to discontinuous ion transport channels and aggravated interfacial side reactions. This directly caused its cycle stability to be far worse than that of Example 1, confirming the key role of the modified UiO-66+ modified complex system in improving battery cycle life.

[0110] Figure 13 To obtain the cycle performance test curve of the battery at 60°C for Comparative Example 2, the discharge specific capacity of the battery in the first cycle was about 140 mAh / g. As the number of cycles increased, the specific capacity dropped sharply. After 200 cycles, the discharge specific capacity was only about 100 mAh / g, with a capacity retention rate of 71%, which was much lower than 92.6% in Example 1, and also significantly lower than Comparative Example 1 and Comparative Example 3. Comparative Example 2 used a single polyethylene glycol diacrylate as the matrix, which lacked the structural synergistic effect of ternary monomers, resulting in a single crosslinking network, low mechanical strength, and poor lithium salt dissociation efficiency. This directly caused discontinuous ion transport channels and aggravated interfacial side reactions, making its cycle stability the worst among all groups. This also confirms the key role of the modified complex system in improving the cycle life of the battery.

[0111] Figure 14 To obtain the cycle performance test curve of the battery at 60°C for Comparative Example 3, the discharge specific capacity of the first cycle was approximately 129 mAh / g. As the number of cycles increased, the specific capacity gradually decreased, and after 200 cycles, the discharge specific capacity was approximately 97 mAh / g, with a capacity retention rate of approximately 75%. Comparative Example 3 used pure KH570 coupling agent, which lacked the hydrophilic / lithophilic groups brought by PEG200 modification. This resulted in weak interfacial bonding between UiO-66 and the polymer matrix, making it prone to interfacial delamination during cycling and easy interruption of ion transport channels. Therefore, although its cycle stability was better than that of Comparative Example 2, it was still far inferior to that of Example 1. This also confirms the key role of the "KH570-PEG200 composite coupling agent" in improving the cycle life of the battery.

[0112] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a metal-organic framework-polymer composite solid electrolyte, characterized in that, Includes the following steps: S1. Add the modified complexing system to anhydrous solvent and stir for 1-1.5 h at 22-27℃ under a nitrogen atmosphere to form a complexing solution. Add the modified UiO-66 to the complexing solution and disperse for 40-50 min. Stir for 7-8 h at 40-45℃ to form a precursor slurry. S2. The precursor slurry is cast into a polytetrafluoroethylene mold, vacuumed for 5-10 minutes, and then polymerized in a nitrogen atmosphere to form a gel electrolyte membrane. The polymerized gel electrolyte membrane, together with the mold, is heated to 60-70℃ and dried for 3-4 hours to solidify, thus obtaining a composite solid electrolyte membrane. S3. Peel the composite solid electrolyte membrane from the polytetrafluoroethylene mold, immerse the composite solid electrolyte membrane in lithium salt ethanol solution for 10-15 min, take it out and vacuum dry it at 55-60℃ for 1.5-2 h to obtain metal-organic framework-polymer composite solid electrolyte membrane. Modified UiO-66 is prepared through the following steps: S11. Add UiO-66 to a mixed solvent of toluene and ethanol, and disperse it under a nitrogen atmosphere for 20-25 minutes to form a suspension; S12. Add the modified coupling agent dropwise to the suspension. After the addition is complete, raise the temperature to 50-60℃ and continue stirring for 5-6 hours. S13. After the reaction is complete, the suspension is naturally cooled to room temperature, and stirring is continued for 10-20 minutes to obtain modified UiO-66; The modified coupling agent is prepared through the following steps: Add KH570 and PEG200 to anhydrous toluene and stir for 10-15 min under a nitrogen atmosphere. Add p-toluenesulfonic acid and hydroquinone and stir until homogeneous. Reflux at 60-70℃ for 5-6 h. After the reaction is complete, cool to room temperature to obtain the reaction solution. Purify the reaction solution by rinsing to remove p-toluenesulfonic acid, hydroquinone, and unreacted PEG200. Collect the filtrate and evaporate it for 1-1.5 h to obtain the modified coupling agent. The modified complex system in step S1 is prepared through the following steps: S101. Under a nitrogen atmosphere at room temperature, polyethylene glycol diacrylate, polyethylene glycol monoacrylate and trimethylolpropane triacrylate are mixed to obtain a mixture. PEG200 is added to the mixture. While maintaining a nitrogen atmosphere, the mixture is heated to 40-45℃ and stirred for 20-30 minutes to obtain a ternary monomer mixture. S102. Add anhydrous acetonitrile to the ternary monomer mixture, stir for 10-20 min and adjust the viscosity to 50-80 mPa·s. Purify the ternary monomer mixture after viscosity adjustment and collect the filtrate to obtain the modified monomer system. S103. Add the pretreated lithium salt to the modified monomer system and stir under a nitrogen atmosphere for 25-30 minutes to form a modified complex system. The pretreated lithium salt in step S103 is obtained through the following steps: LiTFSI and ethylene carbonate were mixed at a mass ratio of (9-10):1 and dried under vacuum at 50-60℃ for 1-2 hours to obtain pretreated lithium salt.

2. The method for preparing the metal-organic framework-polymer composite solid electrolyte according to claim 1, characterized in that, In step S1, the mass ratio of the modified complex system to the modified UiO-66 and the anhydrous solvent is 100:(5-15):(60-80). In step S3, the mass ratio of the composite solid electrolyte membrane to the lithium salt ethanol solution is 1:(5-10). In the lithium salt ethanol solution, the mass ratio of ethanol to LiTFSI is 100:(0.8-1.2).

3. The method for preparing the metal-organic framework-polymer composite solid electrolyte according to claim 1, characterized in that, In steps S11 and S12, the mass ratio of UiO-66 to the modified coupling agent is 100:(5-8), and the mass ratio of UiO-66 to the mixed solvent of toluene and ethanol is 1:(20-30), wherein the mass ratio of toluene to ethanol is (3-4):

1.

4. The method for preparing the metal-organic framework-polymer composite solid electrolyte according to claim 1, characterized in that, In steps S101, S102, and S103, the mass ratio of polyethylene glycol diacrylate, polyethylene glycol monoacrylate, and trimethylolpropane triacrylate is (69.7-79.2):(9.95-19.8):1; the mass ratio of the mixture to PEG200 and anhydrous acetonitrile is 100:(5-10):(100-130); and the mass ratio of the modified monomer system to the pretreated lithium salt is 100:(15-25).

5. The method for preparing the metal-organic framework-polymer composite solid electrolyte according to claim 1, characterized in that, In the preparation steps of the modified coupling agent, the mass ratio of KH570 to PEG200 is (2-3):1, and the mass ratio of the total amount of KH570 and PEG200 to anhydrous toluene, p-toluenesulfonic acid and hydroquinone is 100:(150-200):(1-2):(0.5-1).

6. A metal-organic framework-polymer composite solid electrolyte, characterized in that, It is prepared according to the preparation method described in any one of claims 1-5.

7. The application of the metal-organic framework-polymer composite solid electrolyte according to claim 6 in lithium metal batteries.

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