Self-powered buckling Janus composite nanofiber membranes, methods of making and applications

Abstract

This invention relates to the field of fiber membrane technology, and particularly to a self-driven buckling Janus composite nanofiber membrane, its preparation method, and its applications. The preparation method involves using a layered electrospinning technique to prepare a bilayer membrane consisting of a primary nanofiber membrane I and a primary nanofiber membrane II. After calcination, the significant difference in thermal shrinkage properties between the two primary fiber membranes generates internal stress between them, which in turn drives the fiber membrane to spontaneously form a buckling structure. This invention transforms the difference in shrinkage properties, which easily leads to membrane defects in traditional preparation processes, into an effective driving force for constructing the microstructure, achieving an innovative utilization of process disadvantages. The Janus composite nanofiber membrane has a clear interface between the two layers and well-defined component partitioning, combining the excellent properties of both materials. The solid-state electrolyte for lithium batteries prepared using this Janus composite nanofiber membrane can effectively alleviate the problem of stress concentration, thereby stabilizing the interfacial contact between the electrode and the electrolyte.

Description

Technical Field

[0001] This invention relates to the field of fiber membrane technology, and more particularly to self-driven buckling Janus composite nanofiber membranes, their preparation methods, and applications. Background Technology

[0002] Janus composite fiber membranes are a novel type of functional porous membrane material characterized by asymmetric chemical composition, microstructure, or surface physicochemical properties on both sides. Leveraging the flexibility and ease of processing of organic polymer substrates, and combining the high-temperature resistance, antifouling properties, photoelectric response, and piezoelectric characteristics of inorganic nanomaterials, the resulting organic-inorganic Janus composite system can achieve multiple functions such as unidirectional moisture conduction, selective separation, intelligent sensing, and ion conduction. It has been widely applied in various technological fields including oily wastewater treatment, membrane distillation for seawater desalination, flexible electronic devices, energy storage membranes, and smart textiles.

[0003] Currently, several mature preparation processes have been developed for organic-inorganic Janus composite fiber membranes, with electrospinning technology becoming the mainstream method. Through processes such as coaxial spinning, parallel-axial spinning, layered step-by-step electrospinning, and single-sided coating modification, the pore size, porosity, and layered structure of the fiber membrane can be controlled and adjusted. The resulting nanofiber network porous structure ensures that the membrane material possesses a high specific surface area and excellent air and water permeability.

[0004] Meanwhile, existing technologies can use post-processing techniques such as interfacial polymerization, biomimetic mineralization, plasma modification, hydrothermal growth, and atomic layer deposition to load inorganic functional nanoparticles such as silica, titanium dioxide, zinc oxide, and barium titanate onto the surface of organic fiber matrices, endowing the fiber membranes with asymmetric functional properties such as hydrophilicity / oleophobicity, hydrophobicity / oleophobicity, piezoelectricity, and conductivity. However, existing organic-inorganic Janus composite fiber membrane technologies still face many technical challenges in practical applications and industrialization, as follows: I. Inorganic components mostly exist in particulate form, making it difficult to form a continuous network structure: In existing organic-inorganic Janus composite fiber membranes, the inorganic phase is mostly doped into the polymer fiber system in the form of nanoparticles, microparticles, or short-range dispersed phases. Although this doping method can enable the material to initially possess some of the characteristics of inorganic components, inorganic particles are prone to agglomeration in the spinning solution and local enrichment during fiber forming, making it difficult to form a continuous and interconnected inorganic network structure. As a result, the inorganic function can only be exerted in local areas of the material, resulting in poor structural integrity and uniformity.

[0005] Second, the components are randomly mixed and arranged, lacking a clear functional zoning structure design: Currently, most composite nanofiber membranes are prepared using a blending electrospinning method, in which organic and inorganic components are pre-mixed in the same spinning solution to obtain a composite fiber membrane with randomly distributed components. Although this process is simple to operate, the two components lack a clear hierarchical division and functional distinction in the spatial dimension, failing to take into account both the flexible support advantages of the organic matrix and the functional characteristics of the inorganic components.

[0006] Third, the membrane structure is predominantly flat, lacking active morphology control strategies based on material shrinkage differences. In existing electrospinning and heat treatment preparation systems, fiber membranes are mostly prepared as flat sheet structures. Phenomena such as membrane bending and uneven shrinkage during heat treatment are usually regarded as material structural instability defects and are avoided as much as possible.

[0007] Fourth, there is a lack of systematic construction of a synergistic structure between a continuous inorganic network and a flexible polymer skeleton: existing composite nanofiber membranes mostly focus on the introduction of inorganic components and the increase of inorganic content, focusing only on the optimization of a single function, without systematically solving the matching and synergistic problem between the continuity of the inorganic phase and the flexible support of the organic phase from the overall structural level.

[0008] Therefore, there is an urgent need to develop a new type of organic-inorganic Janus composite fiber membrane to solve the structural or performance defects existing in the current technology. Summary of the Invention

[0009] This invention aims to at least solve one of the technical problems existing in related technologies. Therefore, the first objective of this invention is to provide a method for preparing a self-driven buckling Janus composite nanofiber membrane; the second objective is to provide a self-driven buckling Janus composite nanofiber membrane; and the third objective is to provide applications of the self-driven buckling Janus composite nanofiber membrane.

[0010] To achieve the first objective, the technical solution adopted by this invention is as follows: The preparation method of self-driven buckling Janus composite nanofiber membrane includes: (a) Primary nanofiber membrane I and primary nanofiber membrane II were sequentially spun using electrospinning technology to obtain a primary composite nanofiber membrane; The spinning solution used to spin the nascent nanofiber membrane I is a polyamic acid spinning solution, and the spinning solution used to spin the nascent nanofiber membrane II is a precursor spinning solution containing a metal-citric acid complex. The nascent nanofiber membrane I and nascent nanofiber membrane II are laminated and composited during electrospinning. (b) The nascent composite nanofiber membrane is calcined to obtain a self-driven buckling Janus composite nanofiber membrane with a polyimide fiber layer and a metal oxide ceramic fiber layer.

[0011] A bilayer membrane consisting of nascent nanofiber membrane I and nascent nanofiber membrane II is prepared using a layered electrospinning technique. During the subsequent calcination process, the two nascent nanofiber membranes exhibit significant differences in shrinkage properties, generating internal stress between the layers and driving the spontaneous formation of a buckled structure. This invention transforms the difference in shrinkage properties, which easily leads to membrane defects in traditional preparation processes, into an effective driving force for the construction of a special morphology. After calcination, nascent nanofiber membrane I and nascent nanofiber membrane II respectively form a polyimide fiber layer and a metal oxide ceramic fiber layer. The two layers form a structure with a clear interface and well-defined component partitioning in space, combining the advantages of polyimide fibers (flexibility, high toughness, and radiation resistance) with the characteristics of metal oxide ceramic fibers (high temperature resistance, flame retardancy, high rigidity, and good thermal stability), thus achieving a differentiated combination of material properties. The membrane spontaneously forms a buckled three-dimensional morphology, which, compared to traditional planar fiber membranes, can construct multi-level pores and hollow structures, further enhancing its performance in heat insulation, buffering, coating, and filtration, and expanding the application scenarios of the material.

[0012] Furthermore, the volume ratio of the polyamic acid spinning solution to the precursor spinning solution containing the metal-citric acid complex is 3:7 to 8:2.

[0013] Furthermore, in the process of spinning nascent nanofiber membrane I using electrospinning technology, the parameter settings include: The spinning time is 1h to 3h, the extrusion rate of the polyamic acid spinning solution is 0.5mL / h to 1.0mL / h, and the rotation speed of the receiving roller is 1500r / min to 2500r / min; In the process of spinning nascent nanofiber membranes II using electrospinning technology, the parameter settings include: The spinning time is 1h to 3h, the extrusion rate of the precursor spinning solution containing the metal-citric acid complex is 0.5mL / h to 1.5mL / h, and the rotation speed of the receiving roller is 50r / min to 100r / min.

[0014] Furthermore, the preparation of the polyamic acid spinning solution includes: Pyromellitic dianhydride and diaminodiphenyl ether were added to organic solvent I and stirred until homogeneous to obtain the polyamic acid spinning solution. The molar ratio of pyromellitic dianhydride to diaminodiphenyl ether is 0.9:1 to 1.1:1, and the mass percentage concentration of the polyamic acid spinning solution is 25% to 30%. The preparation of precursor spinning solutions containing metal-citric acid complexes includes: The metal ion precursor and citric acid were added to organic solvent II, mixed evenly, and then a spinning aid was added and stirred evenly to obtain a precursor spinning solution containing a metal-citric acid complex. The molar ratio of the metal ion precursor to citric acid is 0.8:2 to 1.2:2, the mass percentage concentration of the precursor spinning solution containing the metal-citric acid complex is 10% to 20%, and the mass percentage concentration of the spinning aid is 15% to 20%.

[0015] Furthermore, both organic solvent I and organic solvent II are selected from N,N-dimethylformamide.

[0016] Furthermore, the metal ion precursor is selected from one or more of Ce(NO3)3·6H2O, Gd(NO3)3·6H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Cu(NO3)2·3H2O, and Zr(NO3)4·5H2O.

[0017] Furthermore, the spinning aid is selected from polyvinylpyrrolidone.

[0018] Furthermore, the calcination treatment is carried out at a temperature of 350℃~450℃ for a time of 2.5h~3.5h.

[0019] To achieve the second objective, the technical solution adopted by this invention is as follows: The self-driven buckling Janus composite nanofiber membrane is prepared using any one of the above-described methods and includes a polyimide fiber layer and a metal oxide ceramic fiber layer. The polyimide fiber layer is formed by calcining the nascent nanofiber membrane I, and the metal oxide ceramic fiber layer is formed by calcining the nascent nanofiber membrane II.

[0020] To achieve the third objective, the technical solution adopted by this invention is as follows: Application of self-driven buckling Janus composite nanofiber membrane: Preparation of solid electrolyte using the self-driven buckling Janus composite nanofiber membrane.

[0021] The above-described one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: This invention provides a self-driven buckling Janus composite nanofiber membrane, its preparation method, and its application. The preparation method utilizes layered electrospinning technology to fabricate a bilayer membrane composed of a nascent nanofiber membrane I and a nascent nanofiber membrane II. During subsequent calcination, the significant difference in thermal shrinkage properties between the two nascent fiber membranes generates interlayer internal stress, which in turn drives the fiber membrane to spontaneously form a self-curling structure. This invention transforms the difference in shrinkage properties, which easily leads to membrane defects in traditional preparation processes, into an effective driving force for constructing unique microstructures, achieving an innovative utilization of process disadvantages.

[0022] After high-temperature calcination and transformation, nascent nanofiber membranes I and II can respectively form a polyimide fiber layer and a metal oxide ceramic fiber layer. The two layers have a clear interface and well-defined component partitioning, fully integrating the excellent properties of both materials: retaining the advantages of polyimide fibers such as good flexibility, high toughness, and radiation resistance, while also possessing the characteristics of metal oxide ceramic fibers such as high temperature resistance, good flame retardancy, high rigidity, and excellent thermal stability, achieving differentiated complementarity and optimized combination of material properties. At the same time, the spontaneously formed three-dimensional curled morphology of the membrane, compared with traditional planar fiber membranes, can construct multi-level pores and hollow structures, effectively enhancing the comprehensive performance of the material in terms of heat insulation, buffering, coating, and filtration, and significantly broadening the application scenarios and scope of application of the material.

[0023] Tensile stress-strain test results show that the introduction of the self-driven buckling Janus composite nanofiber membrane buckling structure can provide sufficient deformation space for the fiber membrane. When the material is subjected to external force, the load can be buffered by the gradual unfolding of the buckling structure unit, thereby reducing the risk of rapid material failure caused by local stress concentration. At the same time, the buckling structure enables the Janus composite nanofiber membrane to have progressive deformation characteristics, giving the Janus composite nanofiber membrane excellent tensile adaptability and overall structural stability.

[0024] The mechanical response and cyclic deformation stability test results show that the construction of the self-driven buckling Janus composite nanofiber membrane buckling structure enables the fiber membrane to achieve reversible energy dissipation during tensile deformation, avoiding the performance degradation caused by direct fiber fracture, and significantly improving the fatigue resistance and long-term reliability of the fiber membrane under dynamic service conditions.

[0025] Compression performance test results show that the self-driven buckling Janus composite nanofiber membrane buckling structure can effectively buffer and disperse external stress under pressure, significantly enhance the overall deformation resistance of the fiber membrane, and greatly improve the compressive strength and compaction resistance of the fiber membrane.

[0026] The solid electrolyte prepared based on this self-driven buckling Janus composite nanofiber membrane exhibits a smoother stress change curve and better cycle repeatability, indicating that the fiber membrane can effectively alleviate the stress concentration problem caused by battery electrode volume fluctuations, stabilize the interfacial contact state between the electrode and the electrolyte, and thus significantly improve the cycle stability and service life of the battery.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 The Fourier transform infrared spectra of the PAA nascent nanofiber membrane and the PI fiber membrane provided in Embodiment 1 of the present invention are shown.

[0030] Figure 2 This is a thermogravimetric analysis curve of the PAA nascent nanofiber membrane and the GDC precursor nascent nanofiber membrane provided in Example 2 of the present invention.

[0031] Figure 3 This is the X-ray diffraction pattern of the GDC nanofiber membrane provided in Example 2 of the present invention.

[0032] Figure 4 These are scanning electron microscope (SEM) images of the fiber membrane provided in Embodiment 6 of the present invention; wherein, image a is an SEM image of the GDC layer of the PAA / GDC precursor composite nascent nanofiber membrane, image b is an SEM image of the GDC layer of the Buck-PI / GDC Janus fiber membrane, image c is an SEM image of the PAA layer of the PAA / GDC precursor composite nascent nanofiber membrane, image d is an SEM image of the PI layer of the Buck-PI / GDC Janus fiber membrane, image e is a cross-sectional view of the Buck-PI / GDC Janus fiber membrane (scale bar is 150 μm), and image f is a partial magnified view of image e (scale bar is 50 μm).

[0033] Figure 5 This is the elemental energy spectrum (EDS) of the Buck-PI / GDC Janus fiber membrane provided in Embodiment 6 of the present invention.

[0034] Figure 6Figure 6 shows the physical images of the fiber membranes provided in Example 6 of the present invention; wherein, (a) is a physical image of the GDC precursor (GDC-pre) fiber membrane (prepared in Example 2) and the calcined GDC fiber membrane (prepared in Example 2), (b) is a physical image of the PAA fiber membrane and the calcined PI fiber membrane, and (c) is a physical image of the PAA layer and GDC precursor layer of the PAA / GDC precursor composite nascent nanofiber membrane and the PI layer and GDC layer of the Buck-PI / GDC Janus fiber membrane.

[0035] Figure 7 These are SEM images of the cross-section of the Buck-PI / GDC Janus fiber membrane provided in Examples 3 to 8 of the present invention.

[0036] Figure 8 These are SEM images of the surface of the GDC precursor fiber membrane provided in Embodiments 6, 9 and 10 of this invention.

[0037] Figure 9 These are SEM images of the surface and cross-section of the Janus composite nanofiber membrane provided in Examples 13 to 16 of this invention.

[0038] Figure 10 These are elemental distribution diagrams of the Janus composite nanofiber membranes provided in Examples 13 to 16 of this invention.

[0039] Figure 11 The tensile stress-strain test results are those of the PI fiber membrane provided in Example 1 and the Buck-PI / GDC Janus fiber membrane provided in Example 6 of the present invention; wherein, Figure a is a tensile stress-strain curve of the PI fiber membrane and the Buck-PI / GDC Janus fiber membrane, and Figure b is a real-time morphology diagram of the Buck-PI / GDC Janus fiber membrane during the stretching process.

[0040] Figure 12 The results show the mechanical response and cyclic deformation stability of the PI fiber membrane provided in Example 1 and the Buck-PI / GDC Janus fiber membrane provided in Example 6 of this invention. Figure a is the tensile stress-strain curve of the Buck-PI / GDC Janus fiber membrane, Figure b is the 40% strain cyclic performance curve of the Buck-PI / GDC Janus fiber membrane, Figure c is the tensile stress-strain curve of the PI fiber membrane, and Figure d is the 40% strain cyclic performance curve of the PI fiber membrane.

[0041] Figure 13 The graph shows the test results of the compression performance of the PI fiber membrane provided in Example 1 and the Buck-PI / GDC Janus fiber membrane provided in Example 6 of this invention.

[0042] Figure 14 This invention describes the internal stress changes of PEO, PI@PEO, and Buck-PI / GDC@PEO electrolyte assembled batteries during charge-discharge cycles. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. The following embodiments are used to illustrate this invention but should not be used to limit the scope of this invention.

[0044] In the following examples, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0045] Example 1 The preparation of polyimide (PI) nanofiber membranes is as follows: pyromellitic dianhydride (PMDA) (2.92 g) and diaminodiphenyl ether (ODA) (2.68 g) are added to N,N-dimethylformamide (DMF) (14.4 g) solvent and stirred continuously until uniformly mixed to obtain a uniform polyamic acid (PAA) spinning solution. The polyamic acid spinning solution was loaded into a pipette, and nascent fiber membranes were prepared using electrospinning technology. The electrospinning process parameters were set as follows: spinning voltage 20kV, receiving distance 20cm, spinning solution extrusion rate 0.5mL / h, receiving roller speed 2000r / min, and continuous spinning time 2h, to obtain PAA nascent nanofiber membranes. The PAA nascent nanofiber membrane was placed in a muffle furnace and calcined at 400°C for 3 hours to obtain the PI fiber membrane.

[0046] Fourier transform infrared spectra of PAA nascent nanofiber membranes and PI fiber membranes, as shown Figure 1 As shown in the figure, it can be seen that the PAA nascent nanofiber membrane at 1718 cm⁻¹... -1 1659cm -1 1607cm -1 1545cm -1 and 1406cm -1 Characteristic absorption peaks appear nearby, corresponding to the vibrations of carboxyl groups, amide groups, and related functional groups in the polyamic acid structure; the PI fiber membrane obtained after imidization treatment shows an absorption peak at 1776 cm⁻¹. -1 and 1726cm-1 Absorption peaks for both asymmetric and symmetric stretching vibrations of the imide ring carbonyl group appear nearby, along with peaks at 1373 cm⁻¹. -1 and 725cm -1 The presence of characteristic absorption peaks of imide structure nearby, and the significant weakening or disappearance of related amyl acid characteristic peaks in PAA, indicate that PAA has been successfully converted into PI and the imidization reaction has proceeded fully.

[0047] Example 2 The preparation of gadolinium-doped cerium oxide (GDC) nanofiber membranes is as follows: Ce(NO3)3·6H2O (1.953 g), Gd(NO3)3·6H2O (0.2255 g) and citric acid (1.92 g) are added to N,N-dimethylformamide (DMF) (18 g) solvent and mixed evenly. Then, polyvinylpyrrolidone (PVP) (5 g) is added to the mixture and stirred continuously until homogeneous to obtain GDC precursor spinning solution. The GDC precursor spinning solution was loaded into a pipette, and nanofiber membranes were prepared by electrospinning. The electrospinning process parameters were as follows: spinning voltage 20kV, receiving distance 20cm, spinning solution extrusion rate 1.0mL / h, receiving roller speed 100r / min, and continuous spinning for 2h to obtain the GDC precursor nascent nanofiber membrane. The GDC precursor nascent nanofiber membrane was placed in a muffle furnace and calcined at 400°C for 3 hours to obtain the GDC nanofiber membrane.

[0048] Thermogravimetric analysis curves of PAA nascent nanofiber membrane (prepared in Example 1) and GDC precursor nascent nanofiber membrane are shown below. Figure 2 As shown in the figure, PAA exhibits slight mass loss in the low-temperature region, mainly due to adsorbed water, residual solvent, and the removal of small molecules during imidization. When the temperature rises to approximately 550℃ or higher, the sample undergoes significant decomposition, indicating that PAA conversion to PI has good thermal stability. The GDC precursor experiences rapid weight loss in the 100–150℃ range, primarily corresponding to the volatilization of water and residual solvent. Subsequent weight loss continues in the 200–400℃ range, attributable to the decomposition of organic components and complexes. The curve stabilizes around 400℃, indicating the basic formation of the inorganic GDC phase. Therefore, calcining the initial fiber membrane at 400℃ can simultaneously achieve the thermal imidization of PAA and the in-situ formation of the GDC inorganic ceramic phase, laying the foundation for the subsequent construction of Buck-PI / GDC Janus fiber membranes.

[0049] X-ray diffraction pattern of GDC nanofiber membrane, such as Figure 3As shown in the figure, the XRD diffraction peaks of the GDC nanofiber membrane match those of the standard card JCPDS No. 75-0106. The positions of the main diffraction peaks are consistent with the characteristic peaks of the GDC fluorite crystal structure, and no obvious impurity phase peaks were observed. This indicates that a GDC nanofiber membrane with a clear crystal phase and good crystallinity can be obtained by calcining at 400℃ for 3 hours.

[0050] Example 3 The preparation process of PAA / GDC composite nanofiber membrane (self-driven buckling Janus composite nanofiber membrane) is as follows: Preparation of PAA spinning solution: Add PMDA (2.92g) and ODA (2.68g) to DMF (14.4g) and stir until homogeneous to obtain PAA spinning solution; Preparation of GDC precursor spinning solution: Ce(NO3)3·6H2O (1.953g), Gd(NO3)3·6H2O (0.2255g) and citric acid (1.92g) were added to DMF (18g), mixed evenly, and then 5g of polyvinylpyrrolidone (PVP) was added and stirred until the system was homogeneous to obtain GDC precursor spinning solution; The PAA spinning solution and the GDC precursor spinning solution were separately placed in two pipettes. A layered electrospinning process was used to first spin a nascent nanofiber membrane I (PAA layer) on the same receiving substrate, and then spin a nascent nanofiber membrane II (GDC precursor layer) on it, forming a stacked structure with the PAA layer on the bottom and the GDC layer on the top. The spinning volume ratio of the two spinning solutions is V. PAA :V GDC =8:2 (i.e., the volume ratio of polyamic acid spinning solution to GDC precursor spinning solution is 8:2), and the electrospinning process parameters of PAA spinning solution are set as follows: spinning voltage 20kV, receiving distance 20cm, spinning solution extrusion rate 0.5mL / h, receiving roller speed 2000r / min, and continuous spinning time 2h. The electrospinning process parameters for the GDC precursor solution were set as follows: spinning voltage 20kV, receiving distance 20cm, spinning solution extrusion rate 1.0mL / h, receiving roller speed 100r / min, and continuous spinning time 2h. PAA spinning solution and GDC precursor spinning solution were spun in layers to obtain PAA / GDC precursor composite nascent nanofiber membrane. The composite nascent fiber membrane was then placed in a muffle furnace and calcined at 400℃ for 3 hours. After calcination, PAA / GDC composite nanofiber membrane (denoted as Buck-PI / GDC Janus fiber membrane) was obtained, which is a self-driven buckling Janus composite nanofiber membrane.

[0051] Example 4 Compared with Example 3, this embodiment only changes the volume ratio of PAA spinning solution to GDC precursor spinning solution from 8:2 to 7:3, while the rest of the process is the same as in Example 3.

[0052] Example 5 Compared with Example 3, this embodiment only changes the volume ratio of PAA spinning solution to GDC precursor spinning solution from 8:2 to 6:4, while the rest of the process is the same as in Example 3.

[0053] Example 6 Compared with Example 3, this embodiment only changes the volume ratio of PAA spinning solution to GDC precursor spinning solution from 8:2 to 5:5, while the rest of the process is the same as in Example 3.

[0054] SEM images, EDS images, and physical images related to Buck-PI / GDC Janus fiber membranes are as follows: Figure 4 , Figure 5 and Figure 6 As shown.

[0055] Figure 4 Figure a shows a SEM image of the GDC layer in the PAA / GDC precursor composite nascent nanofiber membrane. The image reveals that the GDC precursor fibers have a continuous structure overall, with some fibers exhibiting a distinct strip-like morphology. Compared to ordinary cylindrical fibers, the strip-like fibers have a larger contact area with the adjacent PAA / PI layer, thus enhancing interfacial adhesion and stress transfer between the two layers. Figure b shows the SEM image of the GDC layer of the Buck-PI / GDC Janus fiber membrane. From this image, it can be seen that the GDC still has a complete fiber network structure at the microscopic level after calcination. Figure c shows the SEM image of the PAA layer of the PAA / GDC precursor composite nascent nanofiber membrane. From the figure, it can be seen that the PAA precursor fibers are continuous and have a smooth surface, indicating that they can provide a stable PI precursor framework. Figure d shows the SEM image of the PI layer of the Buck-PI / GDC Janus fiber membrane. From the image, it can be seen that: obvious wrinkled structure appears on the surface of the PI layer. This morphology can be attributed to the traction force and stress transmission effect caused by the violent shrinkage of the GDC layer during calcination; there is an interfacial adhesion and mechanical coupling effect between the GDC layer and the PI layer. The stress driving force generated by the shrinkage of the GDC layer is transmitted to the flexible PI layer, thereby inducing stress wrinkling and morphology reconstruction in the PI layer. Figure e is a cross-sectional view of the Buck-PI / GDC Janus fiber membrane (scale bar: 150 μm), and Figure f is a magnified view of a portion of Figure e (scale bar: 50 μm). From these two figures, it can be seen that the interface between the GDC layer and the PI layer is in continuous and tight contact, and no obvious large-scale delamination or interface voids or other defects were observed, indicating that there is excellent interfacial coupling between the two layers.

[0056] from Figure 5 It can be seen that Ce is mainly enriched in the GDC region, proving that the membrane still maintains a clear PI / GDC partitioning structure after calcination.

[0057] Figure 6 (a) Figure shows the physical images of the GDC precursor (GDC-pre) fiber membrane (prepared in Example 2) and the calcined GDC fiber membrane (prepared in Example 2). From the figure, it can be seen that the GDC precursor fiber membrane is obviously broken after calcination and it is difficult to maintain the complete self-supporting membrane morphology. This indicates that the GDC layer will generate strong shrinkage stress and structural damage tendency during the thermal conversion process. (b) The figure shows the actual images of the PAA fiber membrane and the calcined PI fiber membrane. The PAA fiber membrane (prepared in Example 1) can still maintain good overall integrity after being transformed into the PI fiber membrane (prepared in Example 1) by heat treatment. Therefore, the dehydration and cyclization volume shrinkage during the transformation of the PAA fiber membrane into the PI fiber membrane is not the main factor causing the large-scale morphological changes. (c) The figure shows the PAA layer, GDC precursor layer of PAA / GDC precursor composite nascent nanofiber membrane and the PI layer and GDC layer of Buck-PI / GDC Janus fiber membrane. From the figure, it can be seen that after GDC and PAA are made into a bilayer composite membrane, the PAA layer (which is subsequently formed into PI) can play a supporting role and constrain the GDC layer from cracking during heat treatment, thus successfully achieving the complete formation of GDC membrane.

[0058] Example 7 Compared with Example 3, this embodiment only changes the volume ratio of PAA spinning solution to GDC precursor spinning solution from 8:2 to 4:6, while the rest of the process is the same as in Example 3.

[0059] Example 8 Compared with Example 3, this embodiment only changes the volume ratio of PAA spinning solution to GDC precursor spinning solution from 8:2 to 3:7, while the rest of the process is the same as in Example 3.

[0060] SEM images of the cross-sections of the Buck-PI / GDC Janus fiber membranes prepared in Examples 3 to 8 are shown below. Figure 7As shown in the figure, the cross-sectional morphology of Buck-PI / GDC Janus fiber membranes prepared with different spinning solution ratios was characterized by scanning electron microscopy (SEM) to investigate the control mechanism of the spinning solution ratio on the microstructure construction and interlayer interface structure formation behavior of the fiber membrane. The comprehensive characterization results show that both excessively low and excessively high GDC precursor content fail to achieve the synergistic matching of uniform dispersion of GDC inorganic components, continuous buckling fiber structure formation, and stable Janus asymmetric interface. When the proportion of GDC precursor is too low, the uniformity of inorganic phase dispersion within the fiber is poor, and the structural driving force generated by the drying shrinkage of the inorganic layer is insufficient, resulting in a significant decrease in the overall structural continuity and integrity of the final fiber membrane. If the GDC precursor content is too high, fiber adhesion problems easily occur during spinning, and the characteristic buckling porous structure of the fiber is destroyed. When the spinning solution ratio is adjusted to 5:5, a clearly defined asymmetric two-phase structure can be observed in the cross-section of the resulting Janus fiber membrane. The inorganic functional layer maintains a smooth surface after shrinkage, while the organic support layer undergoes directional bending under the pull of the inorganic layer, forming a regularly arranged buckled microstructure. Simultaneously, the interface between the inorganic functional layer and the organic support layer is tightly bonded, without obvious interlayer delamination, delamination collapse, or other defects. These results confirm that a 5:5 spinning solution ratio achieves optimal synergistic balance in terms of uniform dispersion of inorganic functional components, construction of the Janus asymmetric structure, and interlayer interface stability. Therefore, this invention determines 5:5 as the optimal preparation ratio for Buck-PI / GDC Janus fiber membranes. Janus fiber membranes prepared under this ratio possess advantages such as structural integrity, stable interlayer interface bonding, and uniform and controllable microstructure.

[0061] Example 9 Compared with Example 6, this embodiment only adjusts the extrusion rate of the GDC precursor spinning solution from 1.0 mL / h to 0.5 mL / h, while the rest of the process is the same as in Example 6.

[0062] Example 10 Compared with Example 6, this embodiment only adjusts the extrusion rate of the GDC precursor spinning solution from 1.0 mL / h to 1.5 mL / h, while the rest of the process is the same as in Example 6.

[0063] Example 11 Compared with Example 6, this embodiment only adjusts the spinning time of both PAA spinning solution and GDC precursor spinning solution from 2h to 1h, while the rest of the process is the same as in Example 6.

[0064] As spinning parameters change, the proportion of ribbon fibers in the fiber network also changes. Compared to ordinary linear fibers, ribbon fibers have a larger fiber width and overlap area, which increases the effective contact area between fibers, thereby improving interfiber adhesion and providing a continuous path for stress transfer within the fiber network during subsequent heat treatment or structural shrinkage. When the proportion of ribbon fibers is low, the fibers are mainly in a thin, linear structure, with point or small-area contact between fibers, resulting in relatively weak interfiber adhesion. This makes it difficult for the stress generated by the shrinkage of the inorganic GDC layer to be uniformly transferred within the fiber membrane, which is not conducive to the formation of a continuous and regular buckling structure in the organic layer. With the optimization of spinning parameters and an appropriate increase in the proportion of ribbon fibers, the overlap area between fibers increases, and the connection stability of the fiber network is enhanced. This facilitates the more effective transfer of stress generated by the shrinkage of the inorganic GDC layer to the organic layer, thereby promoting the formation of a stable and regular buckling morphology in the Janus fiber membrane. However, when the proportion of strip fibers is too high, the excessively large fiber contact area can easily lead to local fiber adhesion, which may restrict the coordinated deformation of fibers under stress, causing stress concentration or local structural defects, which is detrimental to the uniform construction of the buckling structure. Therefore, by adjusting the spinning parameters to control the proportion of strip fibers, it is possible to effectively regulate the adhesion between fibers and the stress transmission capacity within the membrane, thereby achieving the control of the buckling structure formation process of Janus fiber membranes.

[0065] SEM images of the surface of the GDC precursor fiber membranes provided in Examples 6, 9, and 10 are shown below. Figure 8 As shown in the figure, it can be seen that the GDC precursor fiber strip provided in Example 6 can ensure that the fiber network has sufficient adhesion stability and stress transmission continuity, and can also avoid buckling structure damage caused by excessive adhesion, thus providing an important foundation for obtaining a structurally stable and morphologically regular Janus fiber membrane.

[0066] Example 12 Compared with Example 6, this embodiment only adjusts the spinning time of both PAA spinning solution and GDC precursor spinning solution from 2h to 3h, while the rest of the process is the same as in Example 6.

[0067] Example 13 Compared with Example 6, this embodiment replaces Ce(NO3)3·6H2O (1.953g) and Gd(NO3)3·6H2O (0.2255g) with Fe(NO3)3·9H2O (2.02g), and the rest of the process is the same as in Example 6.

[0068] Example 14 Compared with Example 6, this embodiment replaces Ce(NO3)3·6H2O (1.953g) and Gd(NO3)3·6H2O (0.2255g) with Co(NO3)2·6H2O (1.46g), and the rest of the process is the same as in Example 6.

[0069] Example 15 Compared with Example 6, this embodiment replaces Ce(NO3)3·6H2O (1.953g) and Gd(NO3)3·6H2O (0.2255g) with Cu(NO3)2·3H2O (1.21g), and the rest of the process is the same as in Example 6.

[0070] Example 16 Compared with Example 6, this embodiment replaces Ce(NO3)3·6H2O (1.953g) and Gd(NO3)3·6H2O (0.2255g) with Zr(NO3)4·5H2O (2.15g), and the rest of the process is the same as in Example 6.

[0071] SEM images of the surface and cross-section of the Janus composite nanofiber membranes provided in Examples 13 to 16 are shown below. Figure 9 As shown in the figure, it can be seen that when different inorganic oxide precursors are used to prepare fiber membranes, the resulting fiber membranes can all form clear buckling morphology and asymmetric Janus structure; the fiber layer is continuous and intact as a whole, the buckling units are arranged relatively regularly, and the inorganic layer and organic layer are tightly bonded at the cross section, with no obvious delamination or peeling phenomenon observed.

[0072] Elemental distribution diagrams of the Janus composite nanofiber membranes provided in Examples 13 to 16 are as follows: Figure 10 As shown in the figure, it can be seen that Fe, Co, Cu and Zr elements can all be detected in the corresponding fiber membrane samples and are effectively distributed in the fiber membrane structure; at the same time, C element mainly corresponds to the organic component region, indicating that different inorganic oxide components can co-construct a stable Janus layered structure with the organic fiber layer.

[0073] Example 17 The preparation of a polyethylene oxide (PEO) solid electrolyte film is as follows: PEO (2.0 g) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) (1.0 g) are added to acetonitrile (25 mL) and stirred evenly to obtain a PEO-LiTFSI mixed solution; the PEO-LiTFSI mixed solution is uniformly coated onto the surface of a polytetrafluoroethylene (PTFE) sheet, and then the PTFE sheet coated with the liquid film is transferred to a constant temperature oven and dried at 50 °C for 12 h to obtain the PEO solid electrolyte.

[0074] Example 18 Compared with Example 17, this embodiment combines a PI fiber membrane with PEO to prepare a PI@PEO composite solid electrolyte, while the rest of the process is the same as in Example 17.

[0075] Example 19 Compared with Example 17, this embodiment combines the self-driven buckling Janus composite nanofiber membrane prepared in Example 6 with PEO to prepare Buck-PI / GDC@PEO solid electrolyte, and the rest of the process is the same as in Example 17.

[0076] Detection example I. Investigate the influence of buckling structure on the tensile deformation capacity and mechanical stability of fiber membranes.

[0077] The tensile stress-strain test results of the PI fiber membrane (prepared in Example 1) and the Buck-PI / GDC Janus fiber membrane (prepared in Example 6) are as follows: Figure 11 As shown; Figure a shows the tensile stress-strain curves of the PI fiber membrane and the Buck-PI / GDC Janus fiber membrane. The figure reveals that the PI fiber membrane exhibits a rapid increase in stress with strain during stretching, with a relatively small fracture strain, demonstrating high rigidity but limited deformation capacity. In contrast, the Buck-PI / GDC Janus fiber membrane shows a more gradual stress increase during stretching and can withstand greater tensile deformation, indicating better flexibility and ductility. This difference suggests that the introduction of buckling structures provides additional deformation space for the fiber membrane. Under external forces, the gradual unfolding of buckling units achieves load buffering, thereby reducing the risk of rapid failure caused by localized stress concentration.

[0078] Figure b shows the real-time morphology of the Buck-PI / GDC Janus fiber membrane during the stretching process. As can be seen from the figure, the Buck-PI / GDC Janus fiber membrane can maintain good overall continuity during continuous stretching. The test sample gradually stretches as the stretching time increases until it finally breaks. This result shows that the PI / GDC Janus fiber membrane does not break instantaneously under external force, but can achieve gradual deformation by relying on its pre-constructed buckling structure, exhibiting good tensile adaptability and structural stability.

[0079] II. Investigate the mechanical response and cyclic deformation stability of the fiber membrane during the stretching process.

[0080] The results of the mechanical response and cyclic deformation stability measurements of the PI fiber membrane (prepared in Example 1) and the Buck-PI / GDC Janus fiber membrane (prepared in Example 6) are as follows: Figure 12 As shown; Figure a shows the tensile stress-strain curve of the Buck-PI / GDC Janus fiber membrane. From this figure, it can be seen that the Buck-PI / GDC Janus fiber membrane can withstand tensile strain up to 200%, and during the multi-gradient strain cyclic loading process from 40% to 200%, the residual strain after unloading is extremely low, showing excellent reversible deformation and shape recovery ability. Figure b shows the cyclic performance curve of Buck-PI / GDC Janus fiber membrane at 40% strain. From the figure, it can be seen that in the continuous cyclic loading test at 40% strain, the stress-strain hysteresis loop of Buck-PI / GDC Janus fiber membrane remains stable after multiple cycles, the energy dissipation drops rapidly to a low level without significant fluctuation, and there is no significant degradation in mechanical properties. Figure c shows the tensile stress-strain curve of the PI fiber membrane. The PI fiber membrane exhibits significant plastic deformation at 50% strain, with large residual strain after unloading. Furthermore, it shows high energy dissipation and a continuous decay of peak stress during cyclic loading, leading to irreversible structural damage. This indicates that the buckling structure enables reversible energy dissipation during the stretching process, avoiding performance degradation caused by direct fiber fracture and significantly improving the fatigue resistance and long-term reliability of the fiber membrane under dynamic service conditions. Figure d shows the cyclic performance curve of PI fiber membrane at 40% strain. From the figure, it can be seen that as the number of cycles increases, the hysteresis loop area shrinks significantly, and plastic damage accumulates after repeated stretching, resulting in severe irreversible deformation. PI fiber membrane lacks a reversible dynamic interface, and after repeated stretching, the polymer chains undergo permanent slippage, the fiber structure is irreversibly damaged, and the cycle durability is poor.

[0081] III. Compression performance tests of PI fiber membrane (prepared in Example 1) and Buck-PI / GDC Janus fiber membrane (prepared in Example 6) were conducted, and the results are as follows: Figure 13As shown in the figure, the Buck-PI / GDC Janus fiber membrane exhibits significantly higher stress levels and compressive moduli than the control group PI fiber membrane under different strain conditions ranging from 20% to 80%. These results indicate that the buckling structure can provide stress buffering and dispersion during compression, effectively enhancing the overall deformation resistance of the fiber membrane and significantly improving its compressive strength and compaction resistance. While the PI fiber membrane can deform to some extent under compressive load, the compressive load is primarily borne by the fiber network itself, thus its stress buffering capacity during compression is relatively limited. Furthermore, compared to the PI fiber membrane, the Buck-PI / GDC Janus fiber membrane exhibits less residual deformation after cyclic compression and achieves a higher proportion of elastic recovery after unloading, demonstrating superior structural stability and fatigue resistance. It maintains the integrity of its mechanical properties and microstructure after multiple large deformation cycles. This characteristic stems from the fact that the Buck-PI / GDC Janus fiber membrane can disperse loads through the deformation of its buckling structure during compression, providing reliable mechanical support for its application in flexible deformation and complex stress conditions.

[0082] IV. The internal stress changes of PEO (prepared in Example 17), PI@PEO (prepared in Example 18), and Buck-PI / GDC@PEO (prepared in Example 19) electrolyte-assembled batteries during charge-discharge cycles were investigated, and the results are as follows: Figure 14 As shown in the figure, all three electrolyte systems exhibit periodic stress changes corresponding to the charge-discharge process. The PEO electrolyte system shows a certain stress accumulation effect; the PI@PEO electrolyte system exhibits larger stress fluctuations, indicating a strong stress response within the battery. The Buck-PI / GDC@PEO electrolyte system shows a smoother stress change and better repeatability of stress changes during cycling, indicating that this composite electrolyte system can effectively alleviate stress concentration caused by electrode volume changes, improve the contact stability of the electrode / electrolyte interface, and thus contribute to improving the battery's cycle stability and lifespan.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a self-driven buckling Janus composite nanofiber membrane, characterized in that, include: (a) Primary nanofiber membrane I and primary nanofiber membrane II were sequentially spun using electrospinning technology to obtain a primary composite nanofiber membrane; The spinning solution used to spin the nascent nanofiber membrane I is a polyamic acid spinning solution, and the spinning solution used to spin the nascent nanofiber membrane II is a precursor spinning solution containing a metal-citric acid complex. The nascent nanofiber membrane I and nascent nanofiber membrane II are stacked and composited during the electrospinning process; (b) The nascent composite nanofiber membrane is calcined to obtain a self-driven buckling Janus composite nanofiber membrane with a polyimide fiber layer and a metal oxide ceramic fiber layer.

2. The method for preparing the self-driven buckling Janus composite nanofiber membrane as described in claim 1, characterized in that, The volume ratio of the polyamic acid spinning solution to the precursor spinning solution containing the metal-citric acid complex is 3:7 to 8:

2.

3. The method for preparing the self-driven buckling Janus composite nanofiber membrane as described in claim 1, characterized in that, In the process of spinning nascent nanofiber membrane I using electrospinning technology, the parameter settings include: The spinning time is 1h to 3h, the extrusion rate of the polyamic acid spinning solution is 0.5mL / h to 1.0mL / h, and the rotation speed of the receiving roller is 1500r / min to 2500r / min; In the process of spinning nascent nanofiber membranes II using electrospinning technology, the parameter settings include: The spinning time is 1h to 3h, the extrusion rate of the precursor spinning solution containing the metal-citric acid complex is 0.5mL / h to 1.5mL / h, and the rotation speed of the receiving roller is 50r / min to 100r / min.

4. The method for preparing the self-driven buckling Janus composite nanofiber membrane as described in claim 1, characterized in that, The preparation of the polyamic acid spinning solution includes: Pyromellitic dianhydride and diaminodiphenyl ether were added to organic solvent I and stirred until homogeneous to obtain the polyamic acid spinning solution. The molar ratio of pyromellitic dianhydride to diaminodiphenyl ether is 0.9:1 to 1.1:1, and the mass percentage concentration of the polyamic acid spinning solution is 25% to 30%. The preparation of precursor spinning solutions containing metal-citric acid complexes includes: The metal ion precursor and citric acid were added to organic solvent II, mixed evenly, and then a spinning aid was added and stirred evenly to obtain a precursor spinning solution containing a metal-citric acid complex. The molar ratio of the metal ion precursor to citric acid is 0.8:2 to 1.2:2, the mass percentage concentration of the precursor spinning solution containing the metal-citric acid complex is 10% to 20%, and the mass percentage concentration of the spinning aid is 15% to 20%.

5. The method for preparing the self-driven buckling Janus composite nanofiber membrane as described in claim 4, characterized in that, Both organic solvent I and organic solvent II are selected from N,N-dimethylformamide.

6. The method for preparing the self-driven buckling Janus composite nanofiber membrane as described in claim 4, characterized in that, The metal ion precursor is selected from one or more of Ce(NO3)3·6H2O, Gd(NO3)3·6H2O, Fe(NO3)3·9H2O, Co(NO3)2·6H2O, Cu(NO3)2·3H2O and Zr(NO3)4·5H2O.

7. The method for preparing the self-driven buckling Janus composite nanofiber membrane as described in claim 4, characterized in that, The spinning aid is selected from polyvinylpyrrolidone.

8. The method for preparing the self-driven buckling Janus composite nanofiber membrane as described in claim 1, characterized in that, The calcination temperature is 350℃~450℃, and the time is 2.5h~3.5h.

9. A self-driven buckling Janus composite nanofiber membrane, characterized in that, The self-driven buckling Janus composite nanofiber membrane is prepared using the preparation method according to any one of claims 1 to 8, comprising a polyimide fiber layer and a metal oxide ceramic fiber layer, wherein the polyimide fiber layer is transformed from the nascent nanofiber membrane I by calcination, and the metal oxide ceramic fiber layer is transformed from the nascent nanofiber membrane II by calcination.

10. The application of self-driven buckling Janus composite nanofiber membranes, characterized in that, Solid electrolytes were prepared using the self-driven buckling Janus composite nanofiber membrane as described in claim 9.

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