A modified PEO electrolyte membrane and its preparation method

Abstract

This invention relates to the field of electrolyte membrane technology, specifically to a modified PEO electrolyte membrane and its preparation method. Using polyethylene oxide as a matrix, PEO and lithium salt are dissolved in acetonitrile to form a polymer electrolyte solution. A two-dimensional network polyethylene glycol, prepared from a polyethylene glycol reverse-phase suspension, is then added to obtain an organically modified electrolyte slurry. Lithium lanthanum zirconium tantalum oxide nanoparticles are then added, followed by ultrasonication and drying to obtain the modified PEO electrolyte membrane. The synergistic modification by the two-dimensional network polyethylene glycol and inorganic nanoparticles enhances the ion transport performance and interfacial stability of the electrolyte membrane.

Description

Technical Field

[0001] This invention relates to the field of electrolyte membrane technology, specifically to a modified PEO electrolyte membrane and its preparation method. Background Technology

[0002] Driven by the rapid development of electric vehicles, consumer electronics, and smart grids, the market demand for batteries with high energy density, rechargeability, and excellent safety is becoming increasingly urgent. Currently, while traditional liquid lithium-ion batteries (LIBs) are the mainstream technology in energy storage, their organic liquid electrolytes have significant drawbacks, including environmental unfriendliness, corrosivity, flammability, and thermal instability, which can lead to serious safety hazards. In contrast, solid-state battery technology, which replaces liquid electrolytes, not only significantly improves battery safety performance but also simplifies the overall battery structure. Among these, solid polymer electrolytes (SPEs) show broad application prospects in electrochemical energy storage devices such as rechargeable batteries, fuel cells, and supercapacitors. Solid-state electrolytes are a new type of electrolyte material formed by introducing lithium salts into traditional polymer electrolyte systems. These electrolytes possess elasticity, plasticity, and mechanical stability, can be processed without solvents, have simple preparation processes, and easily achieve tight electrode / electrolyte interface contact. Their flexible geometric adaptability, wide temperature range operation, and high energy density further enhance their significant potential in special applications such as flexible batteries and wearable electronic devices, providing an innovative path for developing high-safety solid-state lithium batteries. Among them, the polyethylene oxide (PEO)-based electrolyte system is a typical representative of polymer solid-state electrolytes. Polymer-based electrolytes have unique mechanical advantages, effectively adapting to volume changes in electrode materials during charging and discharging through elastic deformation and plastic deformation. However, the conductivity of pure PEO-based electrolytes at room temperature is typically only 10. -7 The S / cm range is insufficient to meet the needs of practical battery applications. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this application provides a modified PEO electrolyte membrane and its preparation method. Using PEO as a matrix, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is added, and the membrane is modified by adding two-dimensional network polyethylene glycol and lithium lanthanum zirconium tantalum oxide (LLZTO) nanoparticles to obtain a modified PEO electrolyte membrane. This improves the electrochemical window to adapt to high-voltage electrodes and extend cycle life, increases lithium-ion transport number and transport rate, and improves the interfacial stability with the electrode.

[0004] To achieve the above objectives, this application adopts the following technical solution:

[0005] In a first aspect, this application provides a modified PEO electrolyte membrane, wherein the modified PEO electrolyte membrane is prepared from a composite electrolyte slurry, the composite electrolyte slurry comprising an organic modified electrolyte slurry and inorganic nanoparticles; the inorganic nanoparticles are LLZTO nanoparticles; the organic modified electrolyte slurry is obtained by reacting a polymer electrolyte solution with a two-dimensional network polyethylene glycol; the polymer electrolyte solution comprises polyethylene oxide (PEO), lithium salt, and acetonitrile; the two-dimensional network polyethylene glycol is prepared from a polyethylene glycol (PEG) reverse suspension; the PEG reverse suspension is obtained by reacting hollow SiO2 microspheres, PEG, an emulsifier, and cyclohexane.

[0006] In one feasible implementation, the PEO includes an ethylene oxide unit (EO), and the EO and lithium ions (Li) in the lithium salt... + The molar ratio of PEO to acetonitrile is (10-20):1; the mass ratio of PEO to acetonitrile is 1:(14-20); the amount of two-dimensional network PEG is 5wt%-10wt% of PEO; the amount of inorganic nanoparticles added is 5wt%-10wt% of PEO; the mass-volume ratio of hollow SiO2 microspheres, PEG, emulsifier and cyclohexane is (3-3.5)g:(10-11.2)g:(0.55-0.62)g:(60-64)mL.

[0007] In one feasible implementation, the molecular weight of the PEO is 600,000, the molecular weight of the EO is 44; the lithium salt is lithium bis(trifluoromethanesulfonyl)imide; the particle size of the two-dimensional network PEG is 150-300 μm; the particle size of the hollow SiO2 microspheres is 2-5 μm; the molecular weight of the PEG is 1000 (i.e., PEG-1000); the emulsifier is polyethylene glycol 400 monostearate; and the thickness of the modified PEO electrolyte membrane is 180-240 μm.

[0008] Secondly, this application provides a method for preparing a modified PEO electrolyte membrane, comprising the following steps:

[0009] S1. Hollow SiO2 microspheres are activated to obtain pretreated hollow SiO2 microspheres; PEG is melted at a first set temperature, and an emulsifier is added and mixed to obtain a PEG mixture; cyclohexane is heated to a second set temperature and the PEG mixture is added dropwise, and a first ultrasonic treatment is performed. The pretreated hollow SiO2 microspheres are added and a first stirring is performed to obtain a PEG reverse suspension.

[0010] S2. The PEG reverse suspension is placed in a gradient temperature and frozen while being stirred for the second time to obtain a frozen sample. The frozen sample is then freeze-dried to obtain a freeze-dried product. The freeze-dried product is then soaked in an alkaline solution for treatment, washed until neutral, dried, and ground to obtain a two-dimensional network PEG.

[0011] S3. Dissolve PEO and lithium salt in acetonitrile to obtain a polymer electrolyte solution; add the two-dimensional network PEG to the polymer electrolyte solution and perform a third stirring to obtain an organic modified electrolyte slurry;

[0012] S4. Add inorganic nanoparticles to the organic modified electrolyte slurry, perform a second ultrasonic treatment to obtain a composite electrolyte slurry, and dry the composite electrolyte slurry to obtain the modified PEO electrolyte membrane.

[0013] Cyclohexane is a poor solvent for PEG-1000. As the continuous phase, it receives the PEG mixture, while molten PEG-1000 forms the dispersed phase. In this system, polyethylene glycol 400 monostearate provides emulsification. The long-chain alkyl group of stearic acid in the PEG-400 monostearate molecule acts as a hydrophobic chain, anchoring cyclohexane. The hydrophilic PEG segments are compatible with PEG-1000. Under ultrasonication, PEG-1000 forms uniform droplets at the micron level. The reversed-phase system prevents the dissolution of PEG-1000. Pretreated hollow SiO2 microspheres have a density close to that of cyclohexane and are uniformly dispersed in the droplet gaps, forming a bidispersion system. Utilizing a vertical temperature gradient of -20℃ at the top to 0℃ at the bottom, cyclohexane (freezing point 6.5℃) undergoes directional crystallization: ice crystals grow directionally from the low-temperature region (top) to the high-temperature region (bottom), forming parallel, sheet-like ice crystal templates. Due to the difference in interfacial tension between PEG-1000 droplets and the ice crystals, they are pushed into the gaps between the ice crystals and accumulate directionally as the ice crystals grow, forming a continuous network structure. Magnetic stirring inhibits the sedimentation of SiO2 microspheres, ensuring they are uniformly embedded within the PEG-1000 network, providing a template for subsequent secondary pores. During freeze-drying, the cyclohexane ice... Crystal sublimation leaves a network of pores, forming the main framework of the two-dimensional structure. At this time, hollow SiO2 microspheres form physical sites between the networks. After etching with 5% NaOH solution (SiO2 + 2NaOH = Na2SiO3 + H2O), pores that penetrate the network structure are left, forming a porous network. Freeze-drying at -45℃ avoids softening of PEG-1000 and maintains the network skeleton. The freeze-dried network block forms a rigid skeleton due to the intermolecular forces of PEG-1000. After grinding, 0.15-0.3mm particles are retained, and the network porous characteristics are completely preserved.

[0014] PEO and LiTFSI (lithium bis(trifluoromethanesulfonylimide)) are soluble in acetonitrile. The ether oxygen bond (-O-) of PEO reacts with Li... +Coordination forms a solvated sheath, and the high polarity of acetonitrile promotes the dissociation of lithium salt, forming a homogeneous polymer-ion system. After the addition of two-dimensional network PEG, the ether chains of PEG interact with the PEO backbone through hydrogen bonds. The porous network of the two-dimensional network structure is Li + It provides additional transport channels while inhibiting PEO crystallization; LLZTO nanoparticles are uniformly dispersed after ultrasonic treatment, and their high dielectric constant can weaken the interaction between PEO and Li. + Coordination of Li promotes + Dissociation; simultaneously, oxygen vacancies on the LLZTO surface can act as Li + Transport sites are established, transport pathways are constructed, and the slurry forms a continuous membrane structure after vacuum drying. The flexible chains of PEO and the two-dimensional network of PEG and LLZTO nanoparticles form a mechanical interlock, enhancing the mechanical strength of the membrane. Simultaneously, the porous structure and inorganic particles jointly enhance the Li... + Electrical conductivity.

[0015] In one feasible implementation, the activation treatment in S1 includes: mixing the hollow SiO2 microspheres with anhydrous ethanol at a solid-liquid ratio of 1:15, ultrasonically dispersing at 280-300W for 25-35 minutes, and vacuum drying to obtain pretreated hollow SiO2 microspheres.

[0016] By utilizing the polarity of ethanol to form hydrogen bonds with the hydroxyl groups on the surface of SiO2, microsphere aggregation is broken and dispersibility is improved.

[0017] In one feasible implementation, the first set temperature in S1 is 60-65℃, the second set temperature is 40-45℃, the dropping rate is 1-1.5mL / min, the power of the first ultrasonic treatment is 400-450W, the time is 18-22min, and the first stirring time is 25-35min.

[0018] In one feasible implementation, the gradient temperature of S2 is -20°C to 0°C, the rotation speed of the second stirring is 50-80 rpm, and the freezing time is 40-60 min.

[0019] In one feasible implementation, the freeze-drying parameters in S2 are -45℃, 0.08mbar, and freeze-drying time of 22-24h; the alkaline solution is 5% NaOH solution; and the soaking time is 1.5-2h.

[0020] In one feasible implementation, the third stirring time described in S3 is 12-24 hours.

[0021] In one feasible implementation scenario, the duration of the second ultrasonic treatment in S4 is 1-1.5 hours.

[0022] Beneficial technical effects:

[0023] This invention uses PEO matrix as the solid electrolyte base polymer and modifies PEG with LLZTO nanoparticles as inorganic fillers and two-dimensional network PEG. Through the abundant pore structure of LLZTO nanoparticles and two-dimensional network PEG, more Li is provided. + Transmission path, thereby shortening Li + The increased transport path ensures uniform flux, reduces the risk of lithium dendrite puncture, and extends the cycle life of the electrolyte membrane. Simultaneously, the increased conduction path and shortened transport distance improve the ionic conductivity and reduce electrolyte impedance. Furthermore, the two-dimensional network PEG lowers the HOMO and LUMO energy levels of the PEG electrolyte, resulting in a lower transport barrier for Li+ and increased lithium-ion transport rate. The low HOMO and LUMO energy levels of the polymer electrolyte also allow for the formation of a stable SEI interface with the high-voltage cathode electrode, thereby improving the electrochemical stability of the modified PEO electrolyte membrane. The modified PEO electrolyte membrane of this invention, through the synergistic effect of two-dimensional network PEG, LLZTO, and PEO polymers, increases the lithium-ion transport pathway, enhances ionic conductivity, broadens the electrochemical window of solid-state batteries, and improves the lithium-ion transference number. The prepared electrolyte membrane exhibits high ionic conductivity, excellent cycle stability, and a wider electrochemical stability window, making it suitable for the design and production of flexible batteries and contributing to improved safety performance of lithium-ion batteries. Attached Figure Description

[0024] Figure 1 This is a photograph of the modified PEO electrolyte membrane prepared in Example 1.

[0025] Figure 2 A 200 μm scanning electron microscope image of the surface of the modified PEO electrolyte membrane prepared in Example 1;

[0026] Figure 3 A 10 μm scanning electron microscope image of the surface of the modified PEO electrolyte membrane prepared in Example 1;

[0027] Figure 4 A 200 μm scanning electron microscope image of the surface of the modified PEO electrolyte membrane prepared in Comparative Example 1;

[0028] Figure 5 A 200 μm scanning electron microscope image of the surface of the modified PEO electrolyte membrane prepared in Comparative Example 3;

[0029] Figure 6 This is a 200 μm scanning electron microscope image of the cross-section of the modified PEO electrolyte membrane prepared in Example 1.

[0030] Figure 7 The image shows the polarization curve of the modified PEO electrolyte membrane prepared in Example 1.

[0031] Figure 8 The image shows a comparison of the impedance curves of the modified PEO electrolyte membrane prepared in Example 1 before and after polarization.

[0032] Figure 9 Impedance diagrams of the modified PEO electrolyte membrane prepared in Example 1 at different temperatures.

[0033] Figure 10 The specific capacity-voltage curves of the modified PEO electrolyte membrane prepared in Example 1 at different times are shown.

[0034] Figure 11 The graph shows a comparison of the conductivity of the modified PEO electrolyte membranes prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0035] Figure 12 Comparative graphs show the electrochemical window test results of the modified PEO electrolyte membranes prepared in Example 1, Comparative Example 1, and Comparative Example 2.

[0036] Figure 13 The XRD patterns are of the modified PEO electrolyte membranes prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3.

[0037] Figure 14 This is a 1mm scanning electron microscope image of the two-dimensional network PEG prepared in Example 1. Detailed Implementation

[0038] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the application will be further described in detail below with reference to embodiments. However, this should not be construed as limiting the scope of this application to the following examples. All other embodiments obtained by those skilled in the art without creative effort without departing from the above-described methodological spirit of this application are within the scope of protection of this application.

[0039] In this application, the terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0040] The singular forms “for,” “or,” “a,” “any,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0042] The following will describe in detail, with reference to different embodiments, a modified PEO electrolyte membrane and its preparation method provided in this application.

[0043] The LLZTO nanoparticles used in the examples are Li 6.4 La3Zr 1.4 Ta 0.6 O 12 .

[0044] Example 1

[0045] A method for preparing a modified PEO electrolyte membrane includes the following steps:

[0046] 1. Mix 3g of hollow SiO2 microspheres with anhydrous ethanol at a solid-liquid ratio of 1:15, disperse by ultrasonication at 280W for 35min, and vacuum dry at 60℃ for 2h to obtain pretreated hollow SiO2 microspheres; melt 10g of PEG-1000 in a water bath at 60℃, add 0.55g of polyethylene glycol 400 monostearate, and stir to dissolve to obtain a PEG mixture; preheat 60mL of cyclohexane to 40℃, pour into a three-necked flask, add the PEG mixture dropwise to the three-necked flask at a dropping rate of 1mL / min, sonicate at 400W for 22min, add the pretreated SiO2 microspheres to the three-necked flask, and continue stirring for 25min to obtain a PEG reversed-phase suspension;

[0047] 2. The PEG reverse suspension was injected into a cylindrical mold with a diameter of 5 cm and a height of 12 cm. The bottom of the mold was made of copper plate and immersed in an ice-water bath. The stainless steel cover plate at the top of the mold was in contact with an aluminum tray containing a dry ice-ethanol mixture (-20℃). The mold was wrapped with 5 mm thick polyurethane foam to form a temperature gradient from -20℃ at the top to 0℃ at the bottom. A magnetic stir bar was placed at the bottom of the mold and stirred at 50 rpm. The mixture was frozen for 40 min to obtain a frozen sample. The frozen sample was transferred to a freeze dryer and freeze-dried at -45℃ and 0.08 mbar for 22 h to obtain a freeze-dried product. The freeze-dried product was soaked in 5% NaOH solution for 1.5 h, washed with deionized water until neutral, dried, ground, and sieved to obtain two-dimensional network PEG with a particle size between 150-300 μm.

[0048] 3. PEO, LiTFSI and acetonitrile with a molecular weight of 600,000 were mixed. The molar ratio of EO to LiTFSI was 14:1 and the mass ratio of PEO to acetonitrile was 1:19. The mixture was stirred until completely dissolved to obtain a polymer electrolyte solution. Two-dimensional network PEG was added to the polymer electrolyte solution. The mass of the two-dimensional network PEG was 7 wt% of PEO. The mixture was stirred for 24 h to obtain an organic modified electrolyte slurry.

[0049] 4. Add LLZTO nanoparticles (5 wt% of PEO mass) to the organic-modified electrolyte slurry, and sonicate for 1 hour to obtain a composite electrolyte slurry; cast the composite electrolyte slurry into a polytetrafluoroethylene mold and vacuum dry at 60°C for 24 hours to obtain the desired product. Figure 1The modified PEO electrolyte membrane shown has a thickness of 220 μm.

[0050] Example 2

[0051] A method for preparing a modified PEO electrolyte membrane includes the following steps:

[0052] 1. 3.5 g of hollow SiO2 microspheres were mixed with anhydrous ethanol at a solid-liquid ratio of 1:15, ultrasonically dispersed at 300 W for 25 min, and vacuum dried at 60 °C for 2 h to obtain pretreated hollow SiO2 microspheres; 11.2 g of PEG-1000 was melted in a water bath at 65 °C, and 0.62 g of polyethylene glycol 400 monostearate was added and stirred to dissolve to obtain a PEG mixture; 64 mL of cyclohexane was preheated to 45 °C and poured into a three-necked flask, and the PEG mixture was added dropwise to the three-necked flask at a dropping rate of 1.5 mL / min. After ultrasonication at 450 W for 18 min, the pretreated SiO2 microspheres were added to the three-necked flask, and stirring was continued for 35 min to obtain a PEG reversed-phase suspension;

[0053] 2. The PEG reverse suspension was injected into a cylindrical mold with a diameter of 5 cm and a height of 12 cm. The bottom of the mold was made of copper plate and immersed in an ice-water bath. The stainless steel cover plate at the top of the mold was in contact with an aluminum tray containing a dry ice-ethanol mixture (-20℃). The mold was wrapped with 5 mm thick polyurethane foam to form a temperature gradient from -20℃ at the top to 0℃ at the bottom. A magnetic stir bar was placed at the bottom of the mold and stirred at 80 rpm. The mixture was frozen for 60 min to obtain a frozen sample. The frozen sample was transferred to a freeze dryer and freeze-dried at -45℃ and 0.08 mbar for 24 h to obtain a freeze-dried product. The freeze-dried product was soaked in 5% NaOH solution for 1.5 h, washed with deionized water until neutral, dried, ground, and sieved to obtain two-dimensional network PEG with a particle size between 150-300 μm.

[0054] 3. PEO, LiTFSI and acetonitrile with a molecular weight of 600,000 were mixed. The molar ratio of EO to LiTFSI was 10:1 and the mass ratio of PEO to acetonitrile was 1:20. The mixture was stirred until completely dissolved to obtain a polymer electrolyte solution. Two-dimensional network PEG was added to the polymer electrolyte solution. The mass of the two-dimensional network PEG was 5 wt% of PEO. The mixture was stirred for 12 h to obtain an organic modified electrolyte slurry.

[0055] 4. Add LLZTO nanoparticles to the organic modified electrolyte slurry, the mass of the LLZTO nanoparticles being 7wt% of the mass of PEO, and sonicate for 1.5h to obtain a composite electrolyte slurry; cast the composite electrolyte slurry into a polytetrafluoroethylene mold and vacuum dry at 60℃ for 24h to obtain a modified PEO electrolyte membrane with a thickness of 180μm.

[0056] Example 3

[0057] A method for preparing a modified PEO electrolyte membrane includes the following steps:

[0058] 1. 3.2 g of hollow SiO2 microspheres were mixed with anhydrous ethanol at a solid-liquid ratio of 1:15, ultrasonically dispersed at 290 W for 30 min, and vacuum dried at 60 °C for 2 h to obtain pretreated hollow SiO2 microspheres; 10.6 g of PEG-1000 was melted in a water bath at 65 °C, and 0.58 g of polyethylene glycol 400 monostearate was added and stirred to dissolve to obtain a PEG mixture; 62 mL of cyclohexane was preheated to 40 °C and poured into a three-necked flask, and the PEG mixture was added dropwise to the three-necked flask at a dropping rate of 1.5 mL / min. After ultrasonication at 450 W for 20 min, the pretreated SiO2 microspheres were added to the three-necked flask, and stirring was continued for 30 min to obtain a PEG reversed-phase suspension;

[0059] 2. The PEG reverse suspension was injected into a cylindrical mold with a diameter of 5cm and a height of 12cm. The bottom of the mold was made of copper plate and immersed in an ice-water bath. The stainless steel cover plate at the top of the mold was in contact with an aluminum tray containing a dry ice-ethanol mixture (-20℃). The mold was wrapped with 5mm thick polyurethane foam to form a temperature gradient from -20℃ at the top to 0℃ at the bottom. A magnetic stir bar was placed at the bottom of the mold and stirred at 60rpm. The mixture was frozen for 50min to obtain a frozen sample. The frozen sample was transferred to a freeze dryer and freeze-dried at -45℃ and 0.08mbar for 23h to obtain a freeze-dried product. The freeze-dried product was soaked in 5% NaOH solution for 2h, washed with deionized water until neutral, dried, ground, and sieved to obtain two-dimensional network PEG with a particle size between 150-300μm.

[0060] 3. PEO, LiTFSI and acetonitrile with a molecular weight of 600,000 were mixed. The molar ratio of EO to LiTFSI was 18:1 and the mass ratio of PEO to acetonitrile was 1:15. The mixture was stirred until completely dissolved to obtain a polymer electrolyte solution. Two-dimensional network PEG was added to the polymer electrolyte solution. The mass of the two-dimensional network PEG was 7 wt% of PEO. The mixture was stirred for 18 h to obtain an organic modified electrolyte slurry.

[0061] 4. Add LLZTO nanoparticles to the organic modified electrolyte slurry, the mass of the LLZTO nanoparticles being 10wt% of the mass of PEO, and sonicate for 1 hour to obtain a composite electrolyte slurry; cast the composite electrolyte slurry into a polytetrafluoroethylene mold and vacuum dry at 60℃ for 24 hours to obtain a modified PEO electrolyte membrane with a thickness of 230μm.

[0062] Example 4

[0063] A method for preparing a modified PEO electrolyte membrane includes the following steps:

[0064] 1. Mix 3g of hollow SiO2 microspheres with anhydrous ethanol at a solid-liquid ratio of 1:15, disperse by ultrasonication at 300W for 35min, and vacuum dry at 60℃ for 2h to obtain pretreated hollow SiO2 microspheres; melt 10g of PEG-1000 in a water bath at 60℃, add 0.55g of polyethylene glycol 400 monostearate, and stir to dissolve to obtain a PEG mixture; preheat 60mL of cyclohexane to 45℃, pour into a three-necked flask, add the PEG mixture dropwise to the three-necked flask at a dropping rate of 1mL / min, sonicate at 450W for 22min, add the pretreated SiO2 microspheres to the three-necked flask, and continue stirring for 30min to obtain a PEG reversed-phase suspension;

[0065] 2. The PEG reverse suspension was injected into a cylindrical mold with a diameter of 5 cm and a height of 12 cm. The bottom of the mold was made of copper plate and immersed in an ice-water bath. The stainless steel cover plate at the top of the mold was in contact with an aluminum plate containing a dry ice-ethanol mixture (-20℃). The mold was wrapped with 5 mm thick polyurethane foam to form a temperature gradient from -20℃ at the top to 0℃ at the bottom. A magnetic stir bar was placed at the bottom of the mold and stirred at 70 rpm. The mold was frozen for 60 min to obtain a frozen sample. The frozen sample was transferred to a freeze dryer and freeze-dried at -45℃ and 0.08 mbar for 24 h to obtain a freeze-dried product. The freeze-dried product was soaked in 5% NaOH solution for 2 h, washed with deionized water until neutral, dried, ground, and sieved to obtain two-dimensional network PEG with a particle size between 150-300 μm.

[0066] 3. PEO, LiTFSI and acetonitrile with a molecular weight of 600,000 were mixed, with a molar ratio of EO:LiTFSI of 20:1 and a mass ratio of PEO to acetonitrile of 1:14. The mixture was stirred until completely dissolved to obtain a polymer electrolyte solution. Two-dimensional network PEG was added to the polymer electrolyte solution, with the mass of the two-dimensional network PEG being 10 wt% of PEO. The mixture was stirred for 24 h to obtain an organic modified electrolyte slurry.

[0067] 4. Add LLZTO nanoparticles to the organic modified electrolyte slurry, the mass of the LLZTO nanoparticles being 10wt% of the mass of PEO, and sonicate for 1 hour to obtain a composite electrolyte slurry; cast the composite electrolyte slurry into a polytetrafluoroethylene mold and vacuum dry at 60℃ for 24 hours to obtain a modified PEO electrolyte membrane with a thickness of 240μm.

[0068] Comparative Example 1

[0069] A method for preparing a modified PEO electrolyte membrane, with the same steps and parameters as in Example 1, except that two-dimensional network PEG is not used, and LLZTO nanoparticles are directly added to the polymer electrolyte solution and ultrasonically treated for 1 hour to obtain a composite electrolyte slurry.

[0070] Comparative Example 2

[0071] A method for preparing a modified PEO electrolyte membrane, with the same steps and parameters as in Example 1, except that LLZTO nanoparticles are not added, and the organic modified electrolyte slurry is directly cast into a polytetrafluoroethylene mold and dried to obtain the modified PEO electrolyte membrane.

[0072] Comparative Example 3

[0073] A method for preparing a modified PEO electrolyte membrane, with the same steps and parameters as in Example 1, except that LLZTO nanoparticles and two-dimensional network PEG are not added, and the PEO-LiTFSI solution is directly cast into a polytetrafluoroethylene mold and dried to obtain the modified PEO electrolyte membrane.

[0074] Performance testing:

[0075] The modified PEO electrolyte membranes prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to the following performance tests:

[0076] Ion conductivity test:

[0077] Electrochemical impedance spectroscopy (EIS) is a testing method that applies a small-amplitude sinusoidal voltage (or current) perturbation signal to a system. Because the amplitude of the applied electrical signal perturbation is very small, it has little effect on the system and is therefore widely used in electrochemical research. This invention uses EIS testing to obtain the bulk impedance value of a modified PEO electrolyte membrane, and then calculates the ionic conductivity of the modified PEO electrolyte membrane. The sample is clamped between two stainless steel blocking electrodes, and a small-amplitude sinusoidal AC voltage with continuously varying frequency is applied. The change in response current with the input voltage is measured, thus obtaining the change in the impedance value of the modified PEO electrolyte membrane with frequency.

[0078] The formula for calculating ionic conductivity σ is:

[0079] σ = L / (R·S)

[0080] Where L is the thickness of the modified PEO electrolyte membrane, measured by a micrometer, in cm; R is the bulk impedance of the modified PEO electrolyte membrane, which in this experiment is taken as the abscissa impedance value at the intersection of the high-frequency region and the straight line in the EIS spectrum, in Ω; and S is the area of ​​the modified PEO electrolyte membrane, in cm². 2 .

[0081] After assembling the double stainless steel (SS) blocking electrode, it was placed in a 60℃ oven for 24 hours and then left at room temperature for 24 hours to ensure good contact between the solid electrolyte membrane and the electrode, reducing the influence of interfacial impedance on the test results. The test temperature range was 30–80℃, with a temperature increase of 10℃, and each temperature stage was held for at least 1 hour. The voltage frequency range was 0.1–10. 6 Hz, voltage amplitude is 10mV.

[0082] Electrochemical window testing:

[0083] The electrochemical stability window (ESW) refers to the stable voltage range within which a solid electrolyte does not react during charging and discharging. In this experiment, the test procedure involved scanning from the open-circuit potential to 6V at a scan rate of 0.01 mV·s. -1 .

[0084] Table 1 Performance test results of modified PEO electrolyte membrane

[0085] Ionic conductivity (S / cm) Electrochemical window (V) Example 1 <![CDATA[6.737×10 -5 ]]> 5.01 Example 2 <![CDATA[6.521×10 -5 ]]> 4.95 Example 3 <![CDATA[6.604×10 -5 ]]> 4.89 Example 4 <![CDATA[6.597×10 -5 ]]> 4.96 Comparative Example 1 <![CDATA[1.230×10 -5 ]]> 4.53 Comparative Example 2 <![CDATA[2.328×10 -5 ]]> 4.84 Comparative Example 3 <![CDATA[8.624×10 -7 ]]> 3.98

[0086] As shown in Table 1, the ionic conductivity of the modified PEO electrolyte membranes prepared in Examples 1-4 of this invention is 6.521 × 10⁻⁶. -5 -6.737×10 -5 The electrochemical window is 4.89-5.01 V, exhibiting stability. The modified PEO electrolyte membranes prepared in Comparative Examples 1-3 have an ionic conductivity of 8.624 × 10⁻⁶ S / cm. -7 -2.328×10 -5 The S / cm electrochemical window is 3.98-4.84V, which is significantly lower than that of the example.

[0087] Comparative Example 1, without the use of two-dimensional network PEG, had an ionic conductivity of only 1.230 × 10⁻⁶. -5 With an electrochemical window reduced to 4.53 V and a S / cm, the two-dimensional network PEG exhibits a high dielectric constant, which can weaken the interaction between PEO and Li through electrostatics. + The coordination effect of Li promotes the dissociation of LiTFSI, and its porous structure is Li + The critical pathway for rapid migration. Without addition, PEO molecular chains are tightly packed, while Li... + Migration is limited to the ether-oxygen bonds (-O-) in the amorphous regions of PEO, resulting in a few and tortuous transport paths and a significant decrease in conductivity. Simultaneously, the two-dimensional network PEG interacts with PEO through intermolecular hydrogen bonds, inhibiting PEO crystallization. In Comparative Example 1, the increased crystallinity of PEO and decreased proportion of amorphous regions hindered Li… +Migration. On the other hand, the network structure of two-dimensional PEG can buffer the stress at the electrode / electrolyte interface. Without its addition, side reactions are prone to occur at the interface, leading to a narrowing of the electrochemical window.

[0088] Comparative Example 2, without the addition of LLZTO nanoparticles, directly cast and dried the organic-modified electrolyte slurry to obtain a modified PEO electrolyte membrane with an ionic conductivity of 2.328 × 10⁻⁶. -5 With an S / cm ratio and an electrochemical window of 4.84 V, the oxygen vacancies on the surface of LLZTO nanoparticles can act as Li... + Temporary adsorption / desorption sites form a cooperative transport network; without addition, Li + Strong coordination with PEO leads to a decrease in free ion concentration and a decrease in conductivity, and Li + Migration relies solely on PEO chain segment movement, resulting in an increased migration energy barrier: LLZTO nanoparticles can inhibit the oxidative decomposition of PEO at high voltages. Without the addition, the electrolyte membrane is prone to oxidation above 4.8V, leading to a narrowing of the electrochemical window.

[0089] Comparative Example 3, without the addition of two-dimensional network PEG and LLZTO nanoparticles, had an ionic conductivity of 8.624 × 10⁻⁶. -7 The S / cm electrochemical window is 3.98V, which is significantly narrowed. In the pure PEO-LiTFSI system, PEO molecular chains easily form ordered crystalline regions, while Li... + It can only migrate in a small number of amorphous regions, lacking both the porous channels of two-dimensional network PEG and the inorganic transport sites of LLZTO. + Migration relies entirely on the thermal motion of PEO segments, resulting in extremely low efficiency and conductivity close to the intrinsic value of pure PEO-based electrolytes.

[0090] like Figures 2-5 As shown in the comparison of SEM images of the modified PEO electrolyte membranes prepared in Example 1, Comparative Example 1, and Comparative Example 3, it can be seen that under a 200 μm SEM, the surface of the electrolyte membrane in Comparative Example 3 is uneven and exhibits a certain degree of crystallization. This is because PEO has the characteristic of being prone to crystallization, while the ion insertion and extraction of the electrolyte mainly occur in the non-crystalline region. This crystallization phenomenon is also the reason for the low room temperature conductivity of pure PEO solid electrolyte. In contrast, the surface smoothness of the modified PEO electrolyte membrane prepared in Comparative Example 1 is improved compared to Comparative Example 3 under a 200 μm SEM, with LLZTO nanoparticles evenly and randomly distributed within it, which is beneficial for interfacial contact with the electrodes. However, its surface is still uneven. After adding two-dimensional network PEG in Example 1, the membrane has a higher degree of smoothness, which is conducive to better ion exchange with the positive and negative electrodes.

[0091] like Figure 6The SEM cross-sectional image of the modified PEO electrolyte membrane prepared in Example 1 shows that the modified PEO electrolyte membrane prepared in Example 1 also has high flatness inside.

[0092] like Figure 7 , Figure 8 As shown, the polarization curve of the modified PEO electrolyte membrane prepared in Example 1 and the impedance curves before and after polarization show that the lithium-ion transference number of the button battery prepared by the modified PEO electrolyte membrane is 0.626, which is much higher than that of conventional PEO-based solid electrolyte (the lithium-ion transference number of the unmodified PEO-based solid electrolyte battery is about 0.16).

[0093] like Figure 9 As shown in the figure, the impedance diagrams of the modified PEO electrolyte membrane prepared in Example 1 of the present invention at different temperatures show that the solid-state battery prepared with the modified PEO electrolyte membrane prepared in Example 1 exhibits excellent conductivity at 30℃-80℃, and the conductivity can reach 6×10 at 60℃. -4 S / cm 2 .

[0094] like Figure 10 As shown in the figure, the specific capacity-voltage curves of the modified PEO electrolyte membrane prepared in Example 1 of this invention at different time intervals show that, in the electrochemical test with a charging cutoff voltage of 4.2V, the initial charging capacity is 156.81 mAh / g, the discharge capacity is 156.67 mAh / g, and the charge-discharge efficiency is 99.91%. After 20 cycles, the discharge capacity is 146.93 mAh / g, and the charge-discharge efficiency is 99.61%, exhibiting excellent cycling performance. After 50 cycles, the discharge capacity is 130.01 mAh / g, and the charge-discharge efficiency is 98.75%. This indicates that the introduction of two-dimensional network PEG effectively improves the cycling performance of the modified PEO electrolyte membrane.

[0095] like Figure 11 As shown in the graphs, the ionic conductivity of the modified PEO electrolyte membranes prepared in Examples 1, 1, and 2 of this invention increases with increasing temperature, indicating that the modified PEO electrolyte membranes exhibit temperature dependence. Compared to Comparative Example 1, which is simply doped with LLZTO, the coin cells assembled from the electrolyte membrane modified with two-dimensional network PEG alone in Comparative Example 2 and the electrolyte membrane synergistically modified with LLZTO and two-dimensional network PEG in Example 1 all show significantly improved ionic conductivity. Among them, the coin cell assembled from the modified PEO electrolyte membrane in Example 1 shows the highest improvement in ionic conductivity.

[0096] like Figure 12As shown, the modified PEO electrolyte membrane prepared in Example 1 of this invention has an electrochemical window of 5.01V, the electrochemical window of Comparative Example 1 reaches 4.5V, and the electrochemical window of 4.8V can be achieved by simply doping with two-dimensional network PEG. The electrochemical window refers to the stable voltage range within which a solid electrolyte does not react during charging and discharging. The figure illustrates that this invention can significantly improve the electrochemical stability of PEO-based solid electrolytes, providing possibilities for matching high-voltage cathodes in the future.

[0097] like Figure 13 As shown in the XRD patterns of the modified PEO electrolyte membranes prepared in Examples 1, 1, 2, and 3 of this invention, compared to the comparative examples, the intensity of the characteristic PEO crystallization peaks at 19.5° and 23.7° was significantly reduced in Example 1 after the simultaneous addition of LLZTO and two-dimensional network PEG. According to the characterization results, the peak intensity of Example 1 was even lower, indicating that the effects of LLZTO and two-dimensional network PEG on reducing the crystallinity of PEO-based solid electrolytes can be synergistically enhanced.

[0098] like Figure 14 As shown, the two-dimensional network PEG prepared in Example 1 of the present invention has a distinct porous network structure.

[0099] In summary, the modified PEO electrolyte membrane prepared by this invention has high ionic conductivity, chemical stability, and a wider electrochemical stability window, making it suitable for the design and production of flexible batteries and beneficial for improving the electrochemical and safety performance of lithium-ion batteries.

[0100] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0101] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A modified PEO electrolyte membrane, characterized in that, The modified PEO electrolyte membrane is prepared from a composite electrolyte slurry, which comprises an organic modified electrolyte slurry and inorganic nanoparticles. The inorganic nanoparticles are lithium lanthanum zirconium tantalum oxide nanoparticles. The organic modified electrolyte slurry is obtained by reacting a polymer electrolyte solution with a two-dimensional network polyethylene glycol. The polymer electrolyte solution comprises polyethylene oxide, lithium salt, and acetonitrile. The two-dimensional network polyethylene glycol is prepared from a polyethylene glycol reverse-phase suspension. The polyethylene glycol reverse-phase suspension is obtained by reacting hollow SiO2 microspheres, polyethylene glycol, emulsifier, and cyclohexane. The preparation method of the two-dimensional network polyethylene glycol includes: Hollow SiO2 microspheres are activated to obtain pretreated hollow SiO2 microspheres; polyethylene glycol is melted at a first set temperature, and an emulsifier is added and mixed to obtain a polyethylene glycol mixture; cyclohexane is heated to a second set temperature and the polyethylene glycol mixture is added dropwise, followed by a first ultrasonic treatment, and then the pretreated hollow SiO2 microspheres are added and stirred for the first time to obtain a polyethylene glycol reverse suspension; The polyethylene glycol reverse suspension was frozen at a gradient temperature while being stirred a second time to obtain a frozen sample. The frozen sample was then freeze-dried to obtain a freeze-dried product. The freeze-dried product was then soaked in an alkaline solution for treatment, washed until neutral, dried, and ground to obtain a two-dimensional network polyethylene glycol.

2. The modified PEO electrolyte membrane according to claim 1, characterized in that, The polyethylene oxide comprises ethylene oxide units, and the molar ratio of the ethylene oxide units to lithium ions in the lithium salt is (10-20):1; the mass ratio of the polyethylene oxide to acetonitrile is 1:(14-20); the amount of the two-dimensional network polyethylene glycol is 5wt%-10wt% of the polyethylene oxide; the amount of inorganic nanoparticles added is 5wt%-10wt% of the polyethylene oxide; the mass-volume ratio of the hollow SiO2 microspheres, polyethylene glycol, emulsifier, and cyclohexane is (3-3.5)g:(10-11.2)g:(0.55-0.62)g:(60-64)mL.

3. The modified PEO electrolyte membrane according to claim 2, characterized in that, The polyethylene oxide has a molecular weight of 600,000, and the ethylene oxide unit has a molecular weight of 44; the lithium salt is lithium bis(trifluoromethanesulfonyl)imide; the two-dimensional network polyethylene glycol has a particle size of 150-300 μm; the hollow SiO2 microspheres have a particle size of 2-5 μm; the polyethylene glycol has a molecular weight of 1000; the emulsifier is polyethylene glycol 400 monostearate; and the modified PEO electrolyte membrane has a thickness of 180-240 μm.

4. The modified PEO electrolyte membrane according to claim 1, characterized in that, The activation treatment includes: mixing the hollow SiO2 microspheres with anhydrous ethanol at a solid-liquid ratio of 1:15, ultrasonically dispersing at 280-300W for 25-35 minutes, and vacuum drying to obtain pretreated hollow SiO2 microspheres.

5. The modified PEO electrolyte membrane according to claim 1, characterized in that, The first set temperature is 60-65℃, the second set temperature is 40-45℃, the dropping rate is 1-1.5mL / min, the power of the first ultrasonic treatment is 400-450W, the time is 18-22min, and the first stirring time is 25-35min.

6. The modified PEO electrolyte membrane according to claim 1, characterized in that, The gradient temperature is -20℃ to 0℃, the second stirring speed is 50-80 rpm, and the freezing time is 40-60 min.

7. The method for preparing a modified PEO electrolyte membrane according to claim 1, characterized in that, The freeze-drying parameters are -45℃, 0.08mbar, and freeze-drying time of 22-24h; the alkaline solution is 5% NaOH solution; and the soaking time is 1.5-2h.

8. A method for preparing a modified PEO electrolyte membrane as described in any one of claims 1-7, characterized in that, Includes the following steps: S1. Dissolve polyethylene oxide and lithium salt in acetonitrile to obtain a polymer electrolyte solution; add the two-dimensional network polyethylene glycol to the polymer electrolyte solution and perform a third stirring to obtain an organic modified electrolyte slurry; S2. Inorganic nanoparticles are added to the organic modified electrolyte slurry, and a second ultrasonic treatment is performed to obtain a composite electrolyte slurry. The composite electrolyte slurry is dried to obtain the modified PEO electrolyte membrane.

9. The method for preparing a modified PEO electrolyte membrane according to claim 8, characterized in that, The third stirring time mentioned in S1 is 12-24 hours.

10. The method for preparing a modified PEO electrolyte membrane according to claim 8, characterized in that, The duration of the second ultrasonic treatment in S2 is 1-1.5 hours.

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