A three-dimensional structure of oriented nanofiber coated cubic phase stone garnet type LLZO composite solid electrolyte and a preparation method thereof

Abstract

The application relates to the technical field of solid electrolyte preparation, in particular to a three-dimensional structure directional nanofiber coated cubic phase garnet type LLZO composite solid electrolyte and a preparation method thereof, and the preparation method comprises the following steps: S1. dispersing LLZO nanoparticles in N.N-dimethylformamide, and performing ultrasonic treatment to obtain an LLZO suspension; S2. adding a structure directional modification liquid to perform fixed electrospinning, and obtaining a nanofiber membrane; S3. drying the collected nanofiber membrane to obtain a highly oriented PAN coated LLZO particle nanofiber membrane; and S4. casting a modified interface compatibilizer on the highly oriented PAN coated LLZO particle nanofiber membrane, and performing vacuum drying to remove redundant solvents, and obtaining an LLZO composite solid electrolyte. Through the synergistic effect of the modified interface compatibilizer and the structure directional modification liquid, a continuous lithium ion high-speed transmission path is established, the interface side reaction is effectively inhibited, and the cycle stability and interface integrity of the composite solid battery are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte preparation technology, specifically to a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte and its preparation method. Background Technology

[0002] Lithium-ion batteries have been widely used in portable devices, electric vehicles, and energy storage systems due to their excellent energy density and cycle stability. However, their theoretical specific capacity is limited by the relatively low theoretical capacity of graphite anodes (372 mAh g⁻¹). -1 Due to safety concerns associated with liquid electrolytes (such as leakage, flammability, and dendrite puncture), existing lithium-ion batteries are gradually approaching their performance limits. To achieve higher energy density and safety, solid-state lithium metal batteries (SSLMBs) are considered a core technology for next-generation energy storage systems. These batteries use lithium metal as the negative electrode and a solid electrolyte instead of a flammable liquid electrolyte, potentially significantly improving energy density and safety. However, while traditional inorganic solid electrolytes (oxides and sulfides) possess excellent ionic conductivity and electrochemical stability, their rigid structure leads to poor interfacial contact, mechanical brittleness, and difficulties in large-scale processing, limiting their practical application. In contrast, polymer electrolytes exhibit unique advantages in solid-state batteries due to their excellent flexibility and interfacial compatibility. However, their low room-temperature ionic conductivity and limited mechanical strength also make them difficult to meet the stringent requirements of high-performance SSLMBs.

[0003] In recent years, composite solid-state electrolytes have fully integrated the advantages of inorganic ceramic electrolytes and polymer electrolytes. By introducing inorganic fillers or constructing ordered multiphase structures within a polymer matrix, they are expected to synergistically improve ionic conductivity, interfacial stability, and mechanical strength, becoming a key strategy for overcoming existing bottlenecks. Their performance advantages are mainly reflected in several aspects: Firstly, by controlling the crystal structure, optimizing the lithium-ion diffusion path, and enhancing interfacial compatibility, the ionic conductivity of the electrolyte can be significantly improved. Secondly, this multiphase fusion structure also endows the material with higher mechanical stability and durability, which is of great significance for suppressing lithium dendrite growth and extending battery cycle life. Furthermore, the composite design helps to broaden the electrochemical stability window of the electrolyte, supporting higher operating voltages, thereby improving the overall energy density of the battery.

[0004] Garnet-type oxide Li7La3Zr2O 12 (LLZO) has high ionic conductivity (10) -4 -10 -3With a high efficiency (S / cm) and a wide electrochemical stability window, it exhibits good interfacial stability with lithium metal anodes, making it a promising lithium-ion conductor oxide. Current technologies primarily improve the overall performance of composite solid-state electrolytes through methods such as introducing inorganic fillers, liquid additives, grafting organic polymers, and interface structure design. However, our understanding of lithium-ion transport mechanisms and interfacial reactions between different materials remains insufficient. Furthermore, the impact of the electrolyte on the lithium metal anode-cathode interface is rarely discussed, highlighting the current shortcomings in composite solid-state electrolyte research. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte and its preparation method. This invention forms a continuous and rapid lithium-ion conduction channel. The preparation process of this composite solid electrolyte includes: preparing a three-dimensional oriented PAN-(cubic phase) LLZO nanofiber membrane using a high-temperature solid-state method and electrospinning. The obtained PAN-(cubic phase) LLZO nanofiber membrane is then composited with PEO, which has excellent interfacial compatibility, to form a highly oriented composite solid electrolyte (CSE) with a three-dimensional structure. Within the PEO matrix, the highly oriented PAN-(cubic phase) LLZO nanofiber membrane provides a continuous and rapid lithium-ion transport channel. Simultaneously, the high ionic conductivity and good crystal structure of cubic LLZO are fully preserved, enabling the material to achieve a high conductivity of 1.6 × 10⁻⁶ ions at 30°C. -4 Scm -1 The ionic conductivity is high. Furthermore, the PAN-(cubic phase) LLZO nanofiber membrane forms a oriented continuous structure within the electrolyte, significantly enhancing the mechanical strength of the composite solid electrolyte, preventing breakage and deformation during use, and thus improving the battery's mechanical stability. In addition, the combination of PAN-(cubic phase) LLZO nanofibers and polyethylene oxide (PEO) combines the advantages of both polymers, inheriting the excellent interfacial compatibility between PEO and lithium metal and exhibiting the high ionic conductivity of PAN. This promotes rapid lithium-ion transport within the electrolyte, effectively mitigating non-uniform lithium-ion deposition during cycling, and enabling lithium metal to exhibit excellent stability during deposition / stripping, with a stable cycle time exceeding approximately 2000 hours.

[0006] This oriented three-dimensional network structure establishes a uniform and stable interface between the composite solid electrolyte and the electrode, effectively mitigating side reactions between the electrolyte and electrode materials, thereby significantly improving the interface stability of the battery. Based on this, the developed CSEs exhibit excellent cycling performance under high voltage conditions, maintaining 88.6% capacity retention after 1000 cycles at a charging voltage as high as 4.2V. This means that the highly oriented three-dimensional network structure further enhances the lithium-ion transport rate and cycle stability of all-solid-state lithium metal batteries (ASSLMBs).

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] Rapid lithium-ion conduction within composite solid-state electrolytes (SSEs) is not only related to the electrolyte itself, but its structure has become a key factor influencing ion transport kinetics. Traditionally, randomly dispersing inorganic particles within a polymer matrix leads to agglomeration, thus affecting lithium-ion transport. An effective design strategy is to uniformly anchor LLZO particles within ordered polymer fibers. Compared to randomly dispersed inorganic particles and disordered polymer fibers, this facilitates continuous and rapid lithium-ion conduction in the SSE. Furthermore, the mechanical properties of SSEs are crucial for their safety and cycle stability. SSEs must possess high mechanical properties to prevent lithium dendrite penetration and internal short circuits.

[0009] A method for preparing a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte includes the following preparation steps:

[0010] S1. By weight, 1.5-2 parts of LLZO nanoparticles are dispersed in 10-13 parts of NN-dimethylformamide, and ultrasonic treatment is carried out for 25-30 minutes at a frequency of 40kHz to obtain an LLZO suspension.

[0011] S2. Add 2-4 parts of structure-oriented modification liquid to the LLZO suspension, then transfer it to a 10mL syringe equipped with a No. 14 stainless steel needle, and perform fixed electrospinning to obtain a nanofiber membrane.

[0012] S3. The collected nanofiber membranes are dried in a vacuum drying oven at 55-60°C for 5-6 hours to completely remove residual solvent and obtain highly oriented PAN-coated LLZO nanofiber membranes.

[0013] S4. Cast 25-30 parts of modified interface compatibilizer into a nanofiber membrane of highly oriented PAN-coated LLZO particles. After it is fully wetted, vacuum dry at 55-60°C for 10-12 hours to remove excess solvent and obtain LLZO composite solid electrolyte.

[0014] The preparation of the structure-oriented modification liquid includes the following steps:

[0015] S21. By weight, dissolve 1-3 parts of polyacrylonitrile and 0.5-0.8 parts of thermoplastic polyurethane in 10-13 parts of N,N-dimethylformamide at 58-62℃ and stir at 400-500 r / min for 3-4 h.

[0016] S22. Add 0.1-0.2 parts of polymethyl methacrylate to the solution obtained in step S21, and stir at a low speed of 150-200 r / min for 50-60 min at 38-40℃ to avoid introducing air bubbles;

[0017] S23. Disperse 0.1-0.3 parts of nano-silica and 0.05-0.1 parts of KH-550 in 5-6 parts of ethanol by ultrasonication for 20-30 min. After drying, add the mixture obtained in step S22 and continue ultrasonic dispersion for 50-60 min. Let stand for 1-2 h to degas and obtain the structure-oriented modified liquid.

[0018] Preferably, the preparation of LLZO nanoparticles includes the following steps:

[0019] S11. By mass, add 2.9-3 parts of lanthanum oxide, 1.8-2 parts of lithium hydroxide, and 1.2-1.3 parts of zirconium oxide to a ball mill jar, inject anhydrous ethanol, and ball mill for 5-6 hours, then vacuum dry at 75-80℃ for 10-12 hours.

[0020] S12. The product obtained in step S11 is heated to 750-800℃ in a muffle furnace at a heating rate of 5℃ / min, held at that temperature for 5-6 hours, cooled to room temperature, and then ball-milled at a speed of 300-350r / min for 3-4 hours. The product is then passed through an 800-mesh sieve to obtain LLZO nanoparticles.

[0021] Preferably, the preparation of the modified interface compatibilizer includes the following steps:

[0022] S41. By weight, add 5-6 parts of polyethylene oxide and 20-23 parts of anhydrous acetonitrile to an argon glove box, and stir at 300-400 r / min for 1-2 hours at 58-60℃.

[0023] S42. Add 1.4-1.7 parts of lithium bis(trifluoromethanesulfonyl)imide, 0.05-0.08 parts of lithium hexafluorophosphate, and 0.05-0.1 parts of lithium nitrate to the solution obtained in step S41, and stir at 400-500 r / min for 10-12 h at 35-40℃ to obtain a preliminary modified solution;

[0024] S43. Add 0.1-0.3 parts of vinylene carbonate to the preliminary modified solution and stir for 50-60 min. Let it stand for 3-4 h to remove bubbles and obtain the modified interface compatibilizer.

[0025] Preferably, in step S2, a positive voltage of 18kV and a negative voltage of 2kV are applied to the fixed electrospinning, which is sprayed onto the aluminum foil collection substrate. The spinning distance is set to 15cm, the feeding rate is 1mL / h, and the collection drum speed is 1200rpm.

[0026] Preferably, the rotational speed of the planetary ball mill in step S11 is 250-300 r / min.

[0027] Preferably, the drying temperature in step S23 is 75-80℃.

[0028] Preferably, the frequency of ultrasonic dispersion in step S23 is 40 kHz.

[0029] Preferably, the stirring in step S43 is carried out under light-protected conditions, and the rotation speed is 200-300 r / min.

[0030] A three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte was prepared by the above-described method.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. This invention utilizes the synergistic effect of modified interface compatibilizers and structure-oriented modifying liquids to form a highly oriented PAN-TPU nanofiber framework, uniformly anchoring LLZO particles within the fibers to form a three-dimensional oriented network. This provides mechanical support and establishes a continuous high-speed lithium-ion transport path. Simultaneously, it effectively suppresses interfacial side reactions, significantly improving the cycle stability and interfacial integrity of the composite solid-state battery.

[0033] 2. The three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte prepared by this invention can achieve high safety, long life and wide temperature range all-solid-state lithium metal batteries in the field of lithium metal batteries. It is suitable for continuous production and provides key technical support for industrialization. Attached Figure Description

[0034] Figure 1 This is a process flow diagram for preparing the LLZO composite solid electrolyte of the present invention;

[0035] Figure 2 This is a SEM image of the LLZO suspension obtained in Example 1 of the present invention;

[0036] Figure 3This is a SEM image of the highly oriented PAN-coated LLZO nanofiber membrane obtained in Example 1 of the present invention.

[0037] Figure 4 This is a TEM image of the LLZO nanoparticles obtained in Example 1 of the present invention;

[0038] Figure 5 EDX image of the LLZO composite solid electrolyte obtained in Example 1 of this invention;

[0039] Figure 6 The XRD pattern of LLZO nanoparticles obtained in Example 1 of this invention;

[0040] Figure 7 XPS spectra of LLZO nanoparticles obtained in Example 1 of this invention and their corresponding lithium (Li), lanthanum (La), and zirconium (Zr) elements;

[0041] Figure 8 Thermogravimetric analysis (TGA) curves of the randomly dispersed composite solid electrolyte membrane (r-PPZO) obtained in Comparative Example 2, the disordered composite solid electrolyte membrane (d-PPZO) obtained in Comparative Example 1, and the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1 are shown.

[0042] Figure 9 The stress-strain curves are shown for the randomly dispersed composite solid electrolyte membrane (r-PPZO) obtained in Comparative Example 2, the disordered composite solid electrolyte membrane (d-PPZO) obtained in Comparative Example 1, and the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1.

[0043] Figure 10 The image shows the contact angle test result of the LLZO composite solid electrolyte obtained in Example 1 of this invention.

[0044] Figure 11 Linear scanning voltammetry curves of the randomly dispersed composite solid electrolyte membrane (r-PPZO) obtained in Comparative Example 2, the disordered composite solid electrolyte membrane (d-PPZO) obtained in Comparative Example 1, and the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1.

[0045] Figure 12 The graph shows the lithium-ion transference number curves obtained from the current change over time and impedance spectrum of the randomly dispersed composite solid electrolyte membrane (r-PPZO) before and after polarization in Comparative Example 2 of this invention.

[0046] Figure 13The graph shows the lithium-ion transference number curves obtained from the current change over time and impedance spectrum of the disordered composite solid electrolyte membrane (d-PPZO) before and after polarization in Comparative Example 1 of this invention.

[0047] Figure 14 The graph shows the lithium-ion transference number curves obtained from the current change over time and impedance spectrum of the LLZO composite solid electrolyte (o-PPZO) before and after polarization obtained in Example 1 of this invention.

[0048] Figure 15 For 60℃ and 0.1mAcm -2 Schematic diagram of the cycle performance of lithium metal symmetric batteries using the randomly dispersed composite solid electrolyte membrane (r-PPZO) obtained in Comparative Example 2, the disordered composite solid electrolyte membrane (d-PPZO) obtained in Comparative Example 1, and the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1 at the current density of the present invention.

[0049] Figure 16 This is a schematic diagram of the cycle performance of a lithium symmetric battery assembled with the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1 of the present invention.

[0050] Figure 17 This is a schematic diagram of the cycle performance of a lithium symmetric battery assembled from the randomly dispersed composite solid electrolyte membrane (r-PPZO) obtained in Comparative Example 2 of the present invention.

[0051] Figure 18 This is a schematic diagram of the cycle performance of a lithium symmetric battery assembled from the disordered composite solid electrolyte membrane (d-PPZO) obtained in Comparative Example 1 of the present invention.

[0052] Figure 19 For 60℃ and 0.1mAcm -2 A schematic diagram of the cycle performance of a lithium metal symmetric battery using the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1 of this invention at a current density;

[0053] Figure 20 For 30℃ and 1mAcm -2 A schematic diagram of the cycle performance of a lithium metal symmetric battery using the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1 of this invention at a current density. Detailed Implementation

[0054] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0055] Please see Figure 1-20 The present invention provides a technical solution:

[0056] Example 1

[0057] A method for preparing a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte:

[0058] Before preparing the LLZO composite solid electrolyte, LLZO nanoparticles, a structure-oriented modified liquid, and a modified interfacial compatibilizer are first prepared:

[0059] The preparation of LLZO nanoparticles includes the following steps:

[0060] S11. Add 2.9g of lanthanum oxide, 1.8g of lithium hydroxide and 1.2g of zirconium oxide to a ball mill jar, inject anhydrous ethanol, and ball mill at 250r / min for 5h, then vacuum dry at 75℃ for 10h.

[0061] S12. The product obtained in step S11 is heated to 750°C in a muffle furnace at a heating rate of 5°C / min, held at that temperature for 5 hours, cooled to room temperature, and then ball-milled at a speed of 300 r / min for 3 hours. The product is then passed through an 800-mesh sieve to obtain LLZO nanoparticles.

[0062] The preparation of the structure-oriented modification liquid includes the following steps:

[0063] S21. Dissolve 1g of polyacrylonitrile and 0.5g of thermoplastic polyurethane in 10g of N,N-dimethylformamide at 58℃ and stir at 400r / min for 3h.

[0064] S22. Add 0.1g of polymethyl methacrylate to the solution obtained in step S21, and stir at a low speed of 150r / min for 50min at 38℃ to avoid introducing air bubbles;

[0065] S23. Disperse 0.1g of nano-silica and 0.05g of KH-550 in 5ml of ethanol at a frequency of 40kHz for 20min, dry at 75℃, add the mixture obtained in step S22, continue to disperse by ultrasonication for 50min, and let stand for 1h to degas and obtain the structure-oriented modified liquid.

[0066] The preparation of modified interface compatibilizers includes the following steps:

[0067] S41. Add 5g of polyethylene oxide and 20g of anhydrous acetonitrile to an argon glove box, and stir at 300r / min for 1h at 58℃.

[0068] S42. Add 1.4g of lithium bis(trifluoromethanesulfonyl)imide, 0.05g of lithium hexafluorophosphate, and 0.05g of lithium nitrate to the solution obtained in step S41, and stir at 400r / min for 10h at 35℃ to obtain a preliminary modified solution.

[0069] S43. Add 0.1g of vinylene carbonate to the preliminary modified solution, stir at 200r / min for 50min under light-protected conditions, and let stand for 3h to remove bubbles to obtain the modified interface compatibilizer;

[0070] S1. 1.5g LLZO nanoparticles were dispersed in 10g N,N-dimethylformamide and subjected to ultrasonic treatment at a frequency of 40kHz for 25min to obtain an LLZO suspension;

[0071] S2. Add 2g of structure-oriented modification liquid to the LLZO suspension, then transfer it to a 10mL syringe equipped with a No. 14 stainless steel needle, and perform fixed electrospinning (apply a positive voltage of 18kV and a negative voltage of 2kV, spray onto the aluminum foil collection substrate, set the spinning distance to 15cm, the feeding rate to 1mL / h, and the collection drum speed to 1200rpm) to obtain a nanofiber membrane;

[0072] S3. The collected nanofiber membranes were dried in a vacuum drying oven at 55°C for 5 hours to completely remove residual solvent and obtain highly oriented PAN-coated LLZO nanofiber membranes.

[0073] S4. 25g of modified interface compatibilizer was cast onto a nanofiber membrane of highly oriented PAN-coated LLZO particles. After it was fully wetted, it was vacuum dried at 55°C for 10h to remove excess solvent and obtain LLZO composite solid electrolyte. This embodiment was further named o-PPZO.

[0074] Example 2

[0075] A method for preparing a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte:

[0076] Before preparing the LLZO composite solid electrolyte, LLZO nanoparticles, a structure-oriented modified liquid, and a modified interfacial compatibilizer are first prepared:

[0077] The preparation of LLZO nanoparticles includes the following steps:

[0078] S11. Add 3g of lanthanum oxide, 2g of lithium hydroxide, and 1.3g of zirconium oxide to a ball mill jar, inject anhydrous ethanol, and ball mill at 300r / min for 6h, then vacuum dry at 80℃ for 12h.

[0079] S12. The product obtained in step S11 is heated to 800°C in a muffle furnace at a heating rate of 5°C / min, held at that temperature for 6 hours, cooled to room temperature, and then ball-milled at a speed of 350 r / min for 4 hours. The product is then passed through an 800-mesh sieve to obtain LLZO nanoparticles.

[0080] The preparation of the structure-oriented modification liquid includes the following steps:

[0081] S21. Dissolve 3g of polyacrylonitrile and 0.8g of thermoplastic polyurethane in 13g of N,N-dimethylformamide at 62℃ and stir at 500r / min for 4h.

[0082] S22. Add 0.2g of polymethyl methacrylate to the solution obtained in step S21, and stir at a low speed of 200r / min for 60min at 40℃ to avoid introducing air bubbles;

[0083] S23. Disperse 0.3g of nano-silica and 0.1g of KH-550 in 6ml of ethanol at a frequency of 40kHz for 30min, dry at 80℃, add the mixture obtained in step S22, continue to disperse by ultrasonication for 60min, and let stand for 2h to degas and obtain the structure-oriented modified liquid.

[0084] The preparation of modified interface compatibilizers includes the following steps:

[0085] S41. Add 6g of polyethylene oxide and 23g of anhydrous acetonitrile to an argon glove box and stir at 400r / min for 2h at 60℃.

[0086] S42. Add 1.7g of lithium bis(trifluoromethanesulfonyl)imide, 0.08g of lithium hexafluorophosphate, and 0.1g of lithium nitrate to the solution obtained in step S41, and stir at 500r / min for 12h at 40℃ to obtain a preliminary modified solution.

[0087] S43. Add 0.3g of vinylene carbonate to the preliminary modified solution, stir at 300r / min for 60min under light-protected conditions, and let stand for 4h to remove bubbles to obtain the modified interface compatibilizer;

[0088] S1. Disperse 2g of LLZO nanoparticles in 13g of N,N-dimethylformamide and sonicate for 30min at a frequency of 40kHz to obtain an LLZO suspension;

[0089] S2. Add 4g of structure-oriented modification liquid to the LLZO suspension, then transfer it to a 10mL syringe equipped with a No. 14 stainless steel needle, and perform fixed electrospinning (apply a positive voltage of 18kV and a negative voltage of 2kV, spray onto the aluminum foil collection substrate, set the spinning distance to 15cm, the feed rate to 1mL / h, and the collection drum speed to 1200rpm) to obtain a nanofiber membrane;

[0090] S3. The collected nanofiber membranes were dried in a vacuum drying oven at 60°C for 6 hours to completely remove residual solvent and obtain highly oriented PAN-coated LLZO nanofiber membranes.

[0091] S4. Cast 30g of modified interface compatibilizer onto a nanofiber membrane of highly oriented PAN-coated LLZO particles. After it is fully wetted, vacuum dry at 60°C for 12h to remove excess solvent and obtain LLZO composite solid electrolyte.

[0092] Example 3

[0093] A method for preparing a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte:

[0094] Before preparing the LLZO composite solid electrolyte, LLZO nanoparticles, a structure-oriented modified liquid, and a modified interfacial compatibilizer are first prepared:

[0095] The preparation of LLZO nanoparticles includes the following steps:

[0096] S11. Add 2.92g of lanthanum oxide, 1.85g of lithium hydroxide and 1.23g of zirconium oxide to a ball mill jar, inject anhydrous ethanol, and ball mill at 270r / min for 5.5h, then vacuum dry at 77℃ for 11h.

[0097] S12. The product obtained in step S11 is heated to 770°C in a muffle furnace at a heating rate of 5°C / min, held at that temperature for 5.5h, cooled to room temperature, and then ball-milled at a speed of 320r / min for 3.5h. The product is then passed through an 800-mesh sieve to obtain LLZO nanoparticles.

[0098] The preparation of the structure-oriented modification liquid includes the following steps:

[0099] S21. Dissolve 1.5g of polyacrylonitrile and 0.6g of thermoplastic polyurethane in 11g of N,N-dimethylformamide at 60℃ and stir at 420r / min for 3.5h.

[0100] S22. Add 0.12g of polymethyl methacrylate to the solution obtained in step S21, and stir at a low speed of 170r / min for 52min at 39℃ to avoid introducing air bubbles;

[0101] S23. Disperse 0.15g of nano-silica and 0.06g of KH-550 in 5.5ml of ethanol at a frequency of 40kHz for 22min, dry at 77℃, add the mixture obtained in step S22, continue to disperse by ultrasonication for 52min, and let stand for 1.5h to degas and obtain the structure-oriented modified liquid.

[0102] The preparation of modified interface compatibilizers includes the following steps:

[0103] S41. Add 5.5g polyethylene oxide and 21g anhydrous acetonitrile to an argon glove box and stir at 320r / min for 1.5h at 59℃.

[0104] S42. Add 1.5g of lithium bis(trifluoromethanesulfonyl)imide, 0.06g of lithium hexafluorophosphate, and 0.06g of lithium nitrate to the solution obtained in step S41, and stir at 420r / min for 11h at 36℃ to obtain a preliminary modified solution.

[0105] S43. Add 0.15g of vinylene carbonate to the preliminary modified solution, stir at 220r / min for 52min under light-protected conditions, and let stand for 3.5h to remove bubbles to obtain the modified interface compatibilizer;

[0106] S1. 1.6g of LLZO nanoparticles were dispersed in 11g of N,N-dimethylformamide and subjected to ultrasonic treatment at a frequency of 40kHz for 26min to obtain an LLZO suspension;

[0107] S2. Add 2.5g of structure-oriented modification liquid to the LLZO suspension, then transfer it to a 10mL syringe equipped with a No. 14 stainless steel needle, and perform fixed electrospinning (apply a positive voltage of 18kV and a negative voltage of 2kV, spray onto an aluminum foil collection substrate, set the spinning distance to 15cm, the feed rate to 1mL / h, and the collection drum speed to 1200rpm) to obtain a nanofiber membrane;

[0108] S3. The collected nanofiber membrane was dried in a vacuum drying oven at 56°C for 5.5 h to completely remove residual solvent and obtain a nanofiber membrane with highly oriented PAN-coated LLZO particles.

[0109] S4. 26g of modified interface compatibilizer was cast onto a nanofiber membrane of highly oriented PAN-coated LLZO particles. After it was fully wetted, it was vacuum dried at 56°C for 11h to remove excess solvent and obtain LLZO composite solid electrolyte.

[0110] Example 4

[0111] A method for preparing a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte:

[0112] Before preparing the LLZO composite solid electrolyte, LLZO nanoparticles, a structure-oriented modified liquid, and a modified interfacial compatibilizer are first prepared:

[0113] The preparation of LLZO nanoparticles includes the following steps:

[0114] S11. Add 2.97g of lanthanum oxide, 1.95g of lithium hydroxide, and 1.26g of zirconium oxide to a ball mill jar, inject anhydrous ethanol, and ball mill at 280r / min for 5.5h, then vacuum dry at 78℃ for 11.5h.

[0115] S12. The product obtained in step S11 is heated to 780°C in a muffle furnace at a heating rate of 5°C / min, held at that temperature for 5.5h, cooled to room temperature, and then ball-milled at a speed of 340r / min for 3.5h. The product is then passed through an 800-mesh sieve to obtain LLZO nanoparticles.

[0116] The preparation of the structure-oriented modification liquid includes the following steps:

[0117] S21. Dissolve 2.5g of polyacrylonitrile and 0.7g of thermoplastic polyurethane in 12g of N,N-dimethylformamide at 61℃ and stir at 450r / min for 3.5h.

[0118] S22. Add 0.16g of polymethyl methacrylate to the solution obtained in step S21, and stir at a low speed of 180r / min for 58min at 39℃ to avoid introducing air bubbles;

[0119] S23. Disperse 0.25g of nano-silica and 0.08g of KH-550 in 5.6ml of ethanol at a frequency of 40kHz for 28min, dry at 78℃, add the mixture obtained in step S22, continue to disperse by ultrasonication for 58min, and let stand for 1.5h to degas and obtain the structure-oriented modified liquid.

[0120] The preparation of modified interface compatibilizers includes the following steps:

[0121] S41. Add 5.5g polyethylene oxide and 22g anhydrous acetonitrile to an argon glove box and stir at 380r / min for 1.5h at 59℃.

[0122] S42. Add 1.6g of lithium bis(trifluoromethanesulfonyl)imide, 0.07g of lithium hexafluorophosphate, and 0.08g of lithium nitrate to the solution obtained in step S41, and stir at 480r / min for 11.5h at 38℃ to obtain a preliminary modified solution.

[0123] S43. Add 0.25g of vinylene carbonate to the preliminary modified solution, stir at 280r / min for 58min under light-protected conditions, and let stand for 3.5h to degas to obtain the modified interface compatibilizer;

[0124] S1. 1.8 g of LLZO nanoparticles were dispersed in 12.5 g of N,N-dimethylformamide and subjected to ultrasonic treatment at a frequency of 40 kHz for 28 min to obtain an LLZO suspension;

[0125] S2. Add 3.5g of structure-oriented modification liquid to the LLZO suspension, and then transfer it to a 10mL syringe equipped with a No. 14 stainless steel needle for fixed electrospinning (apply a positive voltage of 18kV and a negative voltage of 2kV, spray onto an aluminum foil collection substrate, set the spinning distance to 15cm, the feed rate to 1mL / h, and the collection drum speed to 1200rpm) to obtain a nanofiber membrane;

[0126] S3. The collected nanofiber membrane was dried in a vacuum drying oven at 58°C for 5.5 h to completely remove residual solvent and obtain a nanofiber membrane with highly oriented PAN-coated LLZO particles.

[0127] S4. 28g of modified interface compatibilizer was cast onto a nanofiber membrane of highly oriented PAN-coated LLZO particles. After it was fully wetted, it was vacuum dried at 58°C for 11.5h to remove excess solvent and obtain LLZO composite solid electrolyte.

[0128] Comparative Example 1

[0129] The only difference between Comparative Example 1 and Example 1 is that the fixed electrospinning in step S2 is replaced with moving electrospinning, and the collecting drum speed is set to 300 rpm. The remaining steps are exactly the same in Comparative Example 1 and Example 1. The product obtained is a disordered composite solid electrolyte membrane, and this comparative example is further named d-PPZO.

[0130] Comparative Example 2

[0131] In this comparative example, the preparation methods of LLZO nanoparticles, structure-oriented modification liquid, and modified interface compatibilizer are the same as those in Example 1.

[0132] 1.5g of LLZO nanoparticles were mixed with 2g of structure-oriented modification liquid and 25g of modified interface compatibilizer. After ultrasonic treatment at a frequency of 40kHz for 25min, the mixture was vacuum dried at 55℃ for 10h to obtain a randomly dispersed composite solid electrolyte membrane. This comparative example was further named r-PPZO.

[0133] Performance testing:

[0134] Scanning electron microscopy was used to observe the LLZO suspension and the highly oriented PAN-coated LLZO nanofiber membrane obtained in Example 1 of this invention. Figure 2 SEM image of the LLZO suspension obtained in Example 1 of this invention, and attached... Figure 3 SEM image of the highly oriented PAN-coated LLZO nanofiber membrane obtained in Example 1 of this invention. (See attached image.) Figure 2-3 It can be seen that the LLZO fibers coated with the structure-oriented modified liquid are uniformly distributed, proving that the electrospinning process has been successfully optimized, thus producing highly oriented nanofibers, which is beneficial for promoting rapid ion transport within them. (Appendix) Figure 4 The image shown is a TEM image of the LLZO nanoparticles obtained in Example 1 of this invention. It can be seen that a single LLZO nanoparticle is approximately 10-20 nm in size. Figure 5 The image shows the EDX curve of the LLZO composite solid electrolyte obtained in Example 1 of this invention. The curve confirms the uniform distribution of La, Zr, Al, and O elements, which is crucial for maximizing the energy / power density of the battery. (See attached image.) Figure 6 The XRD pattern and attached XRD pattern of LLZO nanoparticles obtained in Example 1 of this invention Figure 7 XPS spectra of the LLZO nanoparticles obtained in Example 1 of this invention and their corresponding lithium (Li), lanthanum (La), and zirconium (Zr) elements (where the horizontal axis represents binding energy in eV and the vertical axis represents intensity in au) successfully confirmed the preparation of LLZO nanoparticles via a solid-state method. This indicates that they possess a cubic garnet structure, and all diffraction peaks of the LLZO composite solid electrolyte were observed, meaning that the high ionic conductivity and favorable crystal structure of the LLZO composite solid electrolyte were fully preserved during its formation. Simultaneously, the crystallinity of the LLZO composite solid electrolyte was significantly reduced, which is beneficial for the rapid transport of lithium ions within it.

[0135] Appendix Figure 8The thermogravimetric analysis (TGA) curves of the randomly dispersed composite solid electrolyte membrane (r-PPZO) obtained in Comparative Example 2, the disordered composite solid electrolyte membrane (d-PPZO) obtained in Comparative Example 1, and the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1 are shown. The figures indicate that the LLZO nanoparticle content is approximately 15%, and the weight loss initiation temperature of o-PPZO is approximately 300℃, significantly improving the thermal stability of o-PPZO. When r-PPZO, d-PPZO, and o-PPZO were heated, o-PPZO remained intact throughout the heating process, while r-PPZO and d-PPZO melted and deformed. Besides thermal stability, mechanical properties are also crucial for composite solid electrolytes. o-PPZO exhibits excellent tensile strength and flexibility; a 0.07g electrolyte membrane can withstand 200g, while r-PPZO and d-PPZO showed significant tensile deformation, further demonstrating the technical effect of the modified interface compatibilizer. (Appendix) Figure 9 The stress-strain curves of the randomly dispersed composite solid electrolyte membrane (r-PPZO) obtained in Comparative Example 2, the disordered composite solid electrolyte membrane (d-PPZO) obtained in Comparative Example 1, and the LLZO composite solid electrolyte membrane (o-PPZO) obtained in Example 1 are shown. o-PPZO can withstand 91 MPa, further confirming that the highly oriented fiber structure significantly improves the mechanical properties of o-PPZO. This is crucial for maintaining the mechanical stability of the electrolyte and preventing its deformation, thereby significantly suppressing the formation of lithium dendrites. Furthermore, o-PPZO also exhibits excellent interfacial contact performance, through the attachment of… Figure 10 The contact angle test diagram of the LLZO composite solid electrolyte obtained in Example 1 of this invention shows that o-PPZO has a rapid wetting ability, which drops rapidly to 0° after 5s. Compared with d-PPZO and r-PPZO, o-PPZO has excellent interfacial compatibility with lithium metal.

[0136] The electrochemical stability window is a key factor determining battery energy output and durability. Linear sweep voltammetry (LSV) curves visually demonstrate the electrochemical stability window of composite solid electrolytes. (See attached image) Figure 11 Linear sweep voltammetry curves are shown for the randomly dispersed composite solid electrolyte membrane (r-PPZO) obtained in Comparative Example 2, the disordered composite solid electrolyte membrane (d-PPZO) obtained in Comparative Example 1, and the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1. Figure 12 The figures show the lithium-ion transference number curves obtained from the current versus time and impedance spectra of the randomly dispersed composite solid electrolyte membrane (r-PPZO) obtained in Comparative Example 2 of this invention before and after polarization; (See attached figures). Figure 13The graph shows the lithium-ion transference number curves obtained from the impedance spectrum and the current change over time before and after polarization of the disordered composite solid electrolyte membrane (d-PPZO) obtained in Comparative Example 1 of this invention; (See attached graph). Figure 14 This is a graph showing the lithium-ion transference number (LTN) curves obtained from the impedance spectrum and the current change over time before and after polarization of the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1 of this invention. (See attached graph.) Figure 11-14 It can be seen that the current of r-PPZO begins to rise at 4.9V, indicating that the electrolyte begins to decompose. In contrast, d-PPZO and o-PPZO, which contain fibrous structures, maintain a stable current up to 5.3V, demonstrating their excellent electrochemical stability. The lithium-ion transference number of o-PPZO was obtained by recording the current changes over time and impedance spectra before and after polarization. The lithium-ion transference number of r-PPZO was 0.53, while the lithium-ion transference number of d-PPZO increased to 0.67 after the introduction of the fibrous framework. Due to the highly oriented fibrous structure inside o-PPZO, lithium-ion transport is accelerated, resulting in a lithium-ion transference number as high as 0.75.

[0137] Furthermore, lithium-symmetric cells of r-PPZO, d-PPZO, and o-PPZO were assembled in the experiment to evaluate their ability to suppress lithium dendrites at 0.1 mA cm⁻¹. -1 Under these conditions, the Li / o-PPZO / Li battery exhibited exceptionally long cycle stability during deposition / stripping, achieving stable operation for 2000 hours. In contrast, r-PPZO and d-PPZO cells showed significant voltage fluctuations during operation, experiencing internal short circuits at 800 and 1000 hours, respectively. Figure 15-20 The diagrams show the cycle performance of lithium-ion symmetric batteries assembled using the LLZO composite solid electrolyte (o-PPZO) obtained in Example 1, the randomly dispersed composite solid electrolyte membrane (r-PPZO) obtained in Comparative Example 2, and the disordered composite solid electrolyte membrane (d-PPZO) obtained in Comparative Example 1, under different temperature and current density conditions. The diagrams show that even after more than 2000 hours of cycling, the polarization voltage remains below 130 mV, indicating that the highly oriented fiber skeleton enables the Li-ion battery to achieve optimal performance. + It diffuses uniformly and rapidly within its interior. It is noteworthy that even at a depth of up to 2 mA cm⁻¹... -1 At high current densities, o-PPZO can maintain a uniform lithium plating and delithiation process, while r-PPZO and d-PPZO show relatively poor lithium plating / delithiation rates at high current densities, with rates at 1.8 mA cm⁻¹ being lower. -1 and 1.5mA cm -1An anomaly was observed. By comparing the polarization voltage at different lithium plating / delithiation rates, it was clearly observed that the highly oriented o-PPZO electrolyte significantly improved its lithium-ion transport rate and ability to suppress lithium dendrites. Furthermore, o-PPZO exhibited an effect at up to 1 mA cm⁻¹. -1 It can operate stably for over 1000 hours even at high current densities. To further investigate the tolerance of o-PPZO to high current densities, a critical current density test was conducted at 30℃. It was observed that the highly oriented fiber network significantly improves its tolerance, with o-PPZO reaching a critical current density of 1.8 mA / cm². -1 While r-PPZO and d-PPZO were at 0.8 mAcm⁻¹ -1 and 0.5 mA cm -1 A short circuit occurred. Based on the ultra-high CCD value at 30℃, the Li / o-PPZO / Li battery achieved a 1mA cm⁻¹ flow rate at 30℃. -1 It can operate stably for over 800 hours at current densities (see attached). Figures 19-20 This demonstrates that the highly oriented fiber network can construct a uniform and rapid lithium-ion transport channel, thereby enabling o-PPZO to exhibit ultra-high cycle stability and showing great application potential in composite solid electrolytes. Furthermore, compared with traditional composite solid electrolytes, the o-PPZO designed in this invention has significant advantages in improving lithium metal stability.

[0138] 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 three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte, characterized in that, The preparation method includes the following steps: S1. By weight, 1.5-2 parts of LLZO nanoparticles are dispersed in 10-13 parts of NN-dimethylformamide, and ultrasonic treatment is carried out for 25-30 minutes at a frequency of 40kHz to obtain an LLZO suspension. S2. Add 2-4 parts of structure-oriented modification liquid to the LLZO suspension, then transfer it to a 10mL syringe equipped with a No. 14 stainless steel needle, and perform fixed electrospinning to obtain a nanofiber membrane. S3. The collected nanofiber membranes are dried in a vacuum drying oven at 55-60°C for 5-6 hours to completely remove residual solvent and obtain highly oriented PAN-coated LLZO nanofiber membranes. S4. Cast 25-30 parts of modified interface compatibilizer into a nanofiber membrane of highly oriented PAN-coated LLZO particles. After it is fully wetted, vacuum dry at 55-60°C for 10-12 hours to remove excess solvent and obtain LLZO composite solid electrolyte. The preparation method of the structure-oriented modified liquid includes the following steps: S21. By weight, dissolve 1-3 parts of polyacrylonitrile and 0.5-0.8 parts of thermoplastic polyurethane in 10-13 parts of N,N-dimethylformamide at 58-62℃ and stir at 400-500 r / min for 3-4 h. S22. Add 0.1-0.2 parts of polymethyl methacrylate to the solution obtained in step S21, and stir at a low speed of 150-200 r / min for 50-60 min at 38-40℃ to avoid introducing air bubbles; S23. Disperse 0.1-0.3 parts of nano-silica and 0.05-0.1 parts of KH-550 in 5-6 parts of ethanol by ultrasonication for 20-30 min, dry, add the mixture obtained in step S22, continue ultrasonic dispersion for 50-60 min, and let stand for 1-2 h to degas and obtain the structure-oriented modified liquid. The preparation of the LLZO nanoparticles includes the following steps: S11. By mass, add 2.9-3 parts of lanthanum oxide, 1.8-2 parts of lithium hydroxide, and 1.2-1.3 parts of zirconium oxide to a ball mill jar, inject anhydrous ethanol, and ball mill for 5-6 hours, then vacuum dry at 75-80℃ for 10-12 hours. S12. The product obtained in step S11 is heated to 750-800℃ in a muffle furnace at a heating rate of 5℃ / min, held at that temperature for 5-6h, cooled to room temperature, and then ball-milled at a speed of 300-350r / min for 3-4h. The product is then passed through an 800-mesh sieve to obtain LLZO nanoparticles. The preparation of the modified interface compatibilizer includes the following steps: S41. By weight, add 5-6 parts of polyethylene oxide and 20-23 parts of anhydrous acetonitrile to an argon glove box, and stir at 300-400 r / min for 1-2 hours at 58-60℃. S42. Add 1.4-1.7 parts of lithium bis(trifluoromethanesulfonyl)imide, 0.05-0.08 parts of lithium hexafluorophosphate, and 0.05-0.1 parts of lithium nitrate to the solution obtained in step S41, and stir at 400-500 r / min for 10-12 h at 35-40℃ to obtain a preliminary modified solution; S43. Add 0.1-0.3 parts of vinylene carbonate to the preliminary modified solution and stir for 50-60 min. Let it stand for 3-4 h to remove bubbles and obtain the modified interface compatibilizer.

2. The method for preparing a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte according to claim 1, characterized in that, In step S2, a positive voltage of 18kV and a negative voltage of 2kV are applied to the stationary electrospinning process, and the spinneret is sprayed onto the aluminum foil collection substrate. The spinning distance is set to 15cm, the feed rate is 1mL / h, and the collection drum speed is 1200rpm.

3. The method for preparing a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte according to claim 1, characterized in that, In step S11, the rotation speed of the planetary ball mill is 250-300 r / min.

4. The method for preparing a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte according to claim 1, characterized in that, The drying temperature in step S23 is 75-80℃.

5. The method for preparing a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte according to claim 1, characterized in that, In step S23, the frequency of ultrasonic dispersion is 40 kHz.

6. The method for preparing a three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte according to claim 1, characterized in that, In step S43, the stirring is carried out under light-protected conditions, and the speed is 200-300 r / min.

7. A three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte, characterized in that, The three-dimensional oriented nanofiber-coated cubic garnet-type LLZO composite solid electrolyte is prepared by the preparation method described in any one of claims 1-6.

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