PVDF-HFP / LLZO composite solid electrolyte membrane, preparation method and application of PVDF-HFP / LLZO composite solid electrolyte membrane in flexible electronic device

Abstract

The invention belongs to the technical field of new energy materials and lithium ion batteries, and relates to a PVDF-HFP / LLZO composite solid electrolyte membrane, a preparation method and application of the PVDF-HFP / LLZO composite solid electrolyte membrane in a flexible electronic device. The composite solid electrolyte membrane disclosed by the invention comprises a matrix formed by PVDF-HFP (Polyvinylidene Fluoride-Hexafluoropropylene) nanofibers and LLZO (Likelike Likelike Zinc Oxide) particles, and a three-dimensional network structure formed by crosslinking DVB (Divinylbenzene) in the matrix, wherein SDS (Sodium Dodecyl Sulfate) is adsorbed on the surfaces of the LLZO particles. A flexible fiber scaffold structure is constructed through an electrostatic spinning process, and sodium dodecyl sulfate (SDS) is introduced into a precursor to carry out interface regulation and control treatment on the surface of an inorganic filler LLZO, so that the dispersity and wettability of the inorganic filler LLZO in a polymer matrix are improved; meanwhile, divinylbenzene (DVB) is introduced as a cross-linking monomer, and in-situ construction of a three-dimensional network structure is realized under a heat treatment condition, so that the mechanical stability and ionic conductivity of the membrane material are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials and lithium-ion batteries, and relates to a PVDF-HFP / LLZO composite solid electrolyte membrane, a preparation method and application thereof in flexible electronic devices. Background Art

[0002] With the growing demand for high-energy-density and high-safety energy storage systems in areas such as electric vehicles, renewable energy grid integration, and portable electronic devices, solid-state lithium-ion batteries have become an important development direction for the next generation of energy storage devices due to their non-flammable liquid electrolytes, higher thermal stability, and excellent mechanical properties. However, current polymer-based solid-state electrolytes still face problems such as low ionic conductivity and poor interfacial stability at room temperature. In particular, during long cycles, debonding of the electrode / electrolyte interface and increased interfacial impedance are very likely to occur, seriously restricting their performance in practical applications.

[0003] Poly(vinyl fluoride)-hexafluoropropylene copolymer (PVDF-HFP) is widely used in polymer electrolyte systems due to its excellent chemical stability, electrical insulation and flexible processing properties. In order to improve its ion conductivity, high conductivity inorganic ceramic fillers such as cubic lithium lanthanum zirconium oxide (LLZO, Li7La3Zr2O 12 ), constructing a polymer-ceramic composite electrolyte structure. However, LLZO has poor surface wettability in a highly polar organic matrix, prone to agglomeration and delamination. This leads to discontinuous ion migration paths, thereby increasing interfacial impedance, affecting overall conductivity and interfacial stability. This has become one of the core challenges in optimizing composite solid-state electrolyte systems.

[0004] Furthermore, conventional polymer electrolytes are prone to structural deformation and channel collapse under mechanical stress or cyclic volume changes, making it difficult to maintain a stable lithium ion transport path. Therefore, there is an urgent need to construct a composite solid electrolyte material system that combines excellent interfacial wettability, a stable three-dimensional network structure, and high ionic conductivity. Summary of the Invention

[0005] The purpose of the present invention is to overcome the problems of easy agglomeration of inorganic fillers and poor interface compatibility in existing polymer-based solid electrolytes, as well as insufficient mechanical strength of the electrolyte membrane and structural instability during the cycle, and to provide a PVDF-HFP / LLZO composite solid electrolyte membrane with high ionic conductivity, excellent interface stability and good mechanical properties.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A method for preparing a composite solid electrolyte membrane, the method comprising the following steps:

[0008] S1. Preparing a composite precursor solution: dissolving or dispersing polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), LLZO ceramic filler, lithium salt, sodium dodecyl sulfate (SDS), cross-linking monomer divinylbenzene (DVB) and initiator in a solvent to obtain a composite precursor solution;

[0009] The solid solute of the composite precursor solution comprises: 50-62% PVDF-HFP, 10-30% LLZO, 3-6% lithium salt, 3-10% SDS, 20-30% DVB, and 0.05-3% initiator, based on the total mass of the solid solute as 100%;

[0010] S2. Electrospinning of SDS / DVB synergistically reinforced composite nanofiber membrane: electrospinning the composite precursor solution to obtain a composite nanofiber membrane;

[0011] S3, heat treatment: heat treating the composite nanofiber membrane at 60-120° C. to induce a cross-linking reaction of the DVB to form a three-dimensional network structure, thereby obtaining the composite solid electrolyte membrane;

[0012] S4. Performing hot pressing treatment on the composite solid electrolyte membrane at a temperature of 80-120° C. and a pressure of 3-8 MPa.

[0013] This invention uses an electrospinning process to construct a flexible fiber scaffold structure. Sodium dodecyl sulfate (SDS) is introduced into the precursor to perform interfacial treatment on the surface of the inorganic filler LLZO, improving its dispersibility and wettability within the polymer matrix. Divinylbenzene (DVB) is also introduced as a cross-linking monomer, and a three-dimensional network structure is constructed in situ under heat treatment conditions, significantly improving the mechanical stability and ionic conductivity of the membrane material. This composite solid electrolyte membrane exhibits excellent interfacial compatibility, electrochemical stability, and mechanical flexibility, effectively inhibiting lithium dendrite growth and enhancing the cycle life and safety of lithium-ion batteries.

[0014] Preferably, the solid solute of the composite precursor solution comprises: 50-55% PVDF-HFP, 10-12% LLZO, 3-6% lithium salt, 3-6% SDS, 20-30% DVB, and 1-2% initiator, based on the total mass of the solid solute as 100%.

[0015] Preferably, the LLZO is a high ion conductive cubic phase structure formed by element doping, and the doping element is selected from Al, Ga, Nb, Ta or a combination thereof;

[0016] The lithium salt is selected from one or more of the following lithium-based electrolyte compounds: lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiOTf), fluorophosphate lithium salts, lithium nitrate (LiNO3), lithium trifluoroacetate (LiTFA), lithium chloride (LiCl), lithium iodide (LiI), lithium bromide (LiBr) or fluoroalkylsulfonyl imide lithium salts.

[0017] As a preferred LLZO is lithium lanthanum zirconium oxide (Li7La3Zr2O 12 , LLZO); the initiator is ammonium persulfate (APS).

[0018] As the preferred process parameters of the electrospinning in S2, the voltage is 10-30 kV, the collection distance is 20-30 cm, the propulsion speed is 1.0-3.5 mL / h, the ambient humidity is ≤30%, and the temperature is 15-35 ° C. Further preferably, the electrospinning parameters are: voltage 12-18 kV, injection rate 0.8-1.5 mL / h, receiving distance 12-18 cm, and ambient temperature 20-25 ° C. The spinning environment temperature in S2 is 15-35 ° C and the humidity is less than 30% to ensure that the fibers are quickly solidified and formed during the electrospinning process, and to avoid fiber adhesion and structural unevenness caused by ambient water vapor.

[0019] As a preferred S3, the heat treatment includes: placing the composite nanofiber membrane obtained in S2 in a vacuum oven at 50-80°C and drying for more than 12 hours to completely remove residual solvent and unreacted monomers; placing the dried composite nanofiber membrane in a flat hot press and performing hot pressing treatment at 80-120°C and 3-8 MPa pressure for 5-10 minutes to densify the membrane and promote further cross-linking of DVB.

[0020] In S3, the composite nanofiber membrane obtained by electrospinning is dried and pretreated (preferably in a vacuum at 50-80 °C for ≥12 hours) to completely remove residual organic solvents such as DMF, prevent them from affecting the interfacial performance and subsequent stability of the electrolyte membrane, and prevent the collapse of the fiber membrane structure.

[0021] PVDF-HFP has a molecular weight of 10,000-20,000, which is conducive to forming a flexible and stable polymer support network while ensuring the ductility and film-forming properties of the electrolyte membrane.

[0022] The SDS is an anionic surfactant that can significantly reduce the interfacial tension between the LLZO particles and the PVDF-HFP matrix, thereby improving the dispersibility and interfacial compatibility of the ceramic filler in the composite material. The average particle size of the LLZO dispersion is ≤500 nm. The DVB is a small molecule monomer containing two vinyl functional groups. It has good cross-linking ability and can form a stable three-dimensional network structure under the action of a thermal initiator, thereby improving the dimensional stability and mechanical properties of the electrolyte membrane. The DVB used in S1 undergoes free radical cross-linking polymerization under heat treatment or hot pressing conditions under the initiation of APS to form a stable three-dimensional network structure, thereby improving the elongation at break (≥20%) and compressive strength (≥15 MPa) of the membrane and maintaining the integrity of the ion channel.

[0023] The hot pressing treatment described in S4 not only densifies the membrane, but also promotes the cross-linking of DVB molecules, improves the free volume control and flexibility of the polymer chain segments, and realizes the spatial optimization of the lithium ion conduction channel.

[0024] A composite solid electrolyte membrane prepared by the method described in the present invention comprises a matrix composed of PVDF-HFP nanofibers and LLZO particles, and a three-dimensional network structure formed by DVB cross-linking in the matrix; wherein SDS is adsorbed on the surface of the LLZO particles.

[0025] Preferably, the thickness of the membrane is 30-100 μm, and / or the ionic conductivity at room temperature is not less than 1×10 -4 S / cm.

[0026] The composite solid electrolyte membrane of the present invention presents a continuous and uniform LLZO ceramic dispersed phase on both the surface and cross section, with no obvious agglomeration defects at the interface, a membrane thickness of 30-100 μm, and an area density of 1-3 mg / cm 2 .

[0027] The composite solid electrolyte membrane of the present invention is suitable for all-solid-state lithium metal batteries and can achieve a lithium ion conductivity of ≥1×10 -4 S / cm, interface resistance ≤100 Ω·cm 2 , cycle stability ≥300 cycles.

[0028] An application of the composite solid electrolyte membrane of the present invention in a solid-state lithium-ion battery, an all-solid-state energy storage device or a flexible electronic device.

[0029] A lithium battery comprises the composite solid electrolyte membrane according to the present invention.

[0030] The present invention introduces the surfactant sodium dodecyl sulfate (SDS) into the polymer matrix to improve the organic-inorganic interface compatibility, and uses divinylbenzene (DVB) as a crosslinking agent to construct a stable three-dimensional crosslinked network, thereby significantly improving the ion conductivity, mechanical strength, and thermal stability of the electrolyte membrane. Compared with the existing technology, the present invention has the following advantages:

[0031] This invention innovatively combines SDS interface regulation with DVB in-situ crosslinking. SDS effectively improves the dispersion of LLZO in the PVDF-HFP matrix, reducing interfacial impedance; while the three-dimensional network formed by DVB crosslinking significantly enhances the mechanical strength and dimensional stability of the membrane. The two work synergistically to comprehensively improve the overall performance of the electrolyte.

[0032] The composite solid electrolyte membrane prepared by the present invention has high ionic conductivity (up to 25.22 mS cm at 50 ° C) -1 ), excellent interface stability (Li / / Li symmetric battery stable cycle for over 500h) and good rate and cycle performance, which can effectively inhibit the growth of lithium dendrites.

[0033] The present invention adopts the process of electrospinning combined with heat treatment / hot pressing to prepare all functional components into a precursor solution in a one-step method. The process is simple, and it is easy to achieve uniform compounding of the components. The cross-linking and densification processes are easy to control, and are suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a small-magnification SEM morphology image of the nanofiber membrane obtained in Supplementary Example 1;

[0035] Figure 2 This is a high-magnification SEM morphology image of the nanofiber membrane obtained in Supplementary Example 1;

[0036] Figure 3 is the EIS spectrum of the composite solid electrolyte obtained in Supplementary Example 3;

[0037] Figure 4 This is the long cycle curve of the composite solid electrolyte obtained in Supplementary Example 4 in a Li / / Li symmetric battery;

[0038] Figure 5 This is the Tafel test of the composite solid electrolyte obtained in Supplementary Example 5 in a Li / / Li symmetric battery;

[0039] Figure 6 This is a long cycle test of the solid electrolyte obtained in Supplementary Example 6 in a full battery;

[0040] Figure 7 3 is the stress-strain diagram of the solid electrolyte obtained in Example 1. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described in detail below through specific examples. It should be understood that the implementation of the present invention is not limited to the following examples, and any form of modification and / or change made to the present invention will fall within the scope of protection of the present invention.

[0042] In the present invention, unless otherwise specified, all parts and percentages are by weight, and the equipment and raw materials used are commercially available or commonly used in the art. The methods in the following examples are all conventional methods in the art unless otherwise specified.

[0043] Unless otherwise specified, the reagents used in the following examples can be purchased from conventional biochemical reagent stores.

[0044] Lithium bis(trifluoromethanesulfonyl)imide, LiTFSI, was purchased from Aladdin Reagent (Shanghai) Co., Ltd.;

[0045] Lithium lanthanum zirconium oxide (Li7La3Zr2O 12 , LLZO) was purchased from Shenzhen Huaxin New Materials Technology Co., Ltd.

[0046] Example 1: A method for preparing a composite solid electrolyte fiber membrane based on the synergistic effect of SDS interface optimization and DVB structure enhancement, the specific steps are as follows:

[0047] S1. Preparation of spinning solution: weigh 1g of PVDF-HFP, LLZO (Li7La3Zr2O 12 ) and 0.1g of LiTFSI were added to 8mL of N,N-dimethylformamide (DMF) solvent. 0.1g of sodium dodecyl sulfate (SDS) was also added as a surfactant to improve the dispersion of LLZO in the polymer solution and its interfacial wettability with the substrate. The mixture was placed in a constant-temperature magnetic stirring apparatus and stirred continuously at 40°C for at least 12 hours until the solution was uniformly mixed and clear, obtaining spinning solution ①.

[0048] S2. Slowly add 0.5 mL of DVB as a cross-linking monomer to the spinning solution ①, and at the same time add 0.02 g of thermal initiator (ammonium persulfate APS). Continue stirring at 30°C for more than 6 hours to ensure that the cross-linking components are fully dissolved and evenly dispersed in the system to obtain a composite precursor solution with cross-linking potential.

[0049] S3. Electrospinning: The above solution was loaded into a syringe and the nanofiber membrane was prepared using an electrospinning device. The process parameters were controlled as follows: voltage 14 kV, collection distance 25 cm, propulsion speed 2.0 mL / h, ambient humidity ≤ 30%, and temperature 30°C. The resulting fibers were uniformly deposited on a rotating drum current collector, forming a continuous, dense nanofiber membrane.

[0050] S4. The resulting fiber membrane was peeled from the current collector and dried in a vacuum drying oven at 60°C for 12 hours to remove residual solvent. It was then heat treated at 80°C for 4 hours to complete the DVB cross-linking reaction, resulting in a structurally stable composite solid electrolyte membrane with excellent performance. This membrane was named SDPH-DVB.

[0051] S5. Place the dried composite nanofiber membrane in a flat-plate hot press and perform hot pressing treatment at 110°C and 5 MPa pressure for 10 minutes to densify the membrane and promote further cross-linking of DVB, thereby constructing a stable three-dimensional cross-linked network structure and forming a solid electrolyte membrane with good mechanical properties and ionic conductivity.

[0052] Supplementary Example 1: Surface morphology characteristics of SDPH-DVB composite solid electrolyte membrane

[0053] In order to characterize the microstructure and morphology of the SDPH-DVB composite solid electrolyte membrane after drying, scanning electron microscopy (SEM) analysis was performed. Figure 1 and Figure 2 The results showed that the prepared nanofibers presented a continuous, uniform, and highly oriented three-dimensional network structure, with fiber diameters mainly distributed between 300-600 nm, and the overall arrangement was dense without obvious breaks. LLZO inorganic particles were evenly embedded in the polymer fibers without obvious agglomeration, indicating that the SDS surfactant effectively improved their dispersibility and interfacial compatibility. Further observations revealed that the introduction of the DVB crosslinker caused adhesion and fusion between the fibers, forming an enhanced physical crosslinked network, especially at the intersection of the fibers, which exhibited dense skeleton characteristics. This three-dimensional crosslinked structure helps to improve the mechanical strength of the membrane and the stability of the fiber structure, laying the foundation for the subsequent realization of efficient lithium ion transport and the optimization of the comprehensive performance of solid electrolyte membranes.

[0054] Supplementary Example 2: Mechanical Properties of SDPH-DVB Composite Solid Electrolyte Membrane

[0055] In order to evaluate the mechanical robustness and flexibility of the prepared SDPH-DVB composite solid electrolyte membrane in practical applications, tensile tests were carried out to obtain stress-strain curves to characterize its key mechanical properties such as fracture strength, elongation at break, and elastic modulus. The experimental conditions are as follows: a standard tensile tester (such as Instron 3345) was used, and the stretching rate was set to 5 mm min -1 The specimens were cut into rectangular shapes (typical size: 10 mm × 50 mm) with a thickness of approximately 50–70 μm. The test environment was room temperature (25°C) and relative humidity <30%.

[0056] The results are as follows Figure 7 As shown, the composite solid electrolyte membrane has good mechanical strength and flexibility.

[0057] S1 and S2 can also be prepared using the following procedure: 1g PVDF-HFP, 0.2g LLZO, 0.1g LiTFSI, 0.1g SDS, 0.5mL DVB, and 0.02g APS are added all at once to 8mL DMF solvent. Magnetic stirring is performed at 40°C for 18 hours until all components are completely dissolved or evenly dispersed, directly obtaining a composite precursor solution suitable for electrospinning. Testing has shown that the performance of the composite solid electrolyte fiber membranes obtained using this one-step method is comparable, making it a simpler method.

[0058] Example 2: A method for preparing a stainless steel symmetrical battery. The specific steps of the method are as follows:

[0059] Take out the solid electrolyte in Example 1, stack the negative electrode battery shell, spring, gasket, solid electrolyte, gasket, positive electrode battery shell in sequence, and use a hydraulic press to package them. The pressure of the hydraulic press is 50 kg cm -2 , a stainless steel symmetrical battery was prepared.

[0060] Supplementary Example 3: Electrochemical Performance Test of SDPH-DVB Composite Solid Electrolyte

[0061] The stainless steel symmetrical battery prepared in Example 2 was subjected to EIS test by an electrochemical workstation, wherein the frequency range is generally 10mHZ-10KHZ and the amplitude is 5mV. Figure 3 As shown in the figure, the Nyquist plot was obtained, and the SDPH-DVB solid electrolyte showed a thermal conductivity of 25.22 mS cm at 50 °C through fitting calculation. -1 This high ionic conductivity indicates that the SDPH-DVB composite solid electrolyte has better ion transport ability.

[0062] Example 3: A method for preparing a lithium symmetrical battery, the specific steps of the method are as follows:

[0063] Take out the solid electrolyte in Example 1, stack the negative battery shell, spring, gasket, lithium sheet, solid electrolyte, lithium sheet, gasket, positive battery shell in sequence, and use a hydraulic press to package them. The pressure of the hydraulic press is 50 kg cm -2 , a lithium symmetric battery was prepared.

[0064] Supplementary Example 4: Cycling Performance of Li / / Li Symmetrical Cells

[0065] like Figure 4 The Li / / Li symmetric cell exhibits ultralong cycling stability of over 500 h without voltage polarization fluctuation, which indicates that the SDPH-DVB composite solid electrolyte has excellent ionic conductivity and interfacial stability.

[0066] Supplementary Example 5: Electrochemical Performance of Li / / Li Symmetric Cells

[0067] To further study the interfacial reaction kinetics of the SDPH-DVB composite solid electrolyte in a lithium symmetric half-cell, a Tafel test was performed on the Li|SDPH-DVB|Li structure. The test was completed using an electrochemical workstation such as ZahnerZennium. The test was carried out at a constant temperature (room temperature) with a scanning voltage range of ±0.3 V (vs. Li + / Li), with a scan rate of 1 mV s -1 The resulting curve is Figure 5 shown.

[0068] from Figure 5 It can be observed that the Tafel curve shows a typical trend of symmetrical change of logarithmic current density (Log i) with voltage, indicating that lithium ions have good reversible lithium insertion / extraction behavior at the electrode / electrolyte interface. By extrapolating the linear range of the curve, the exchange current density (j0) of the system is obtained to be 3.9 μA cm -2 The exchange current density, j0, is an important parameter reflecting interfacial kinetic activity. A higher value indicates lower resistance to lithium ion reaction at the interface and lower interfacial polarization. The j0 in this system is significantly higher than that of conventional PEO electrolytes, indicating that the SDPH-DVB composite electrolyte possesses excellent interfacial ion transport properties and low interfacial impedance.

[0069] Example 4: A method for preparing a fully symmetrical battery, the specific steps of the method are as follows:

[0070] The positive electrode active material is commercial LFP powder, which is prepared into a composite electrode containing a conductive agent and a binder, and the surface capacity is controlled at 1.2-1.5 mAh cm -2; The negative electrode is a metal lithium sheet; the electrolyte membrane thickness is about 50-70 μm.

[0071] Supplementary Example 6: Long Cycle Test of Fully Symmetrical Batteries

[0072] In order to verify the cycle stability and interface compatibility of the SDPH-DVB composite solid electrolyte membrane in practical applications, an all-solid-state lithium battery (LFP|SDPH-DVB|Li) with LiFePO4 (LFP) as the positive electrode and metallic lithium as the negative electrode was assembled, and a constant current long-cycle charge-discharge test was carried out at room temperature.

[0073] The test conditions are as follows: initial activation is carried out at 0.05 C for 3 cycles; from the cycle performance diagram ( Figure 6 ) shows that the solid-state full battery maintained a capacity retention rate of >98% after over 100 constant-current charge-discharge cycles, demonstrating exceptional long-term cycling stability. Furthermore, the Coulombic efficiency consistently remained above 99.5%, indicating minimal side reactions and slow interfacial impedance growth during cycling. The developed SDPH-DVB composite solid-state electrolyte membrane exhibited excellent cycling stability and electrochemical compatibility in the full-battery system.

[0074] This invention introduces the surfactant sodium dodecyl sulfate (SDS) into the PVDF-HFP / LLZO composite system to manipulate the interface of the LLZO particles. This reduces the interfacial tension between the LLZO nanoparticles, prevents agglomeration of the inorganic filler in the polymer matrix, and effectively improves its uniform dispersion and interfacial wettability, thereby optimizing the overall microstructure of the composite membrane. Divinylbenzene (DVB) is introduced as a crosslinker, leveraging its chemical crosslinking properties to in situ construct a three-dimensional network framework within the material, enhancing the mechanical strength and structural stability of the electrolyte membrane while simultaneously inhibiting the free motion of polymer segments, thereby improving thermal stability and mechanical strength. This method achieves synergistic interface and structural manipulation, significantly enhancing the overall performance of the composite solid-state electrolyte membrane. The PVDF-HFP matrix material combines a good electrochemical stability window with flexibility. Combined with the high ionic conductivity of LLZO, the composite membrane maintains high electrical conductivity while exhibiting excellent deformation adaptability, making it suitable for flexible energy storage devices. The synergistic effect of SDS and DVB forms a three-dimensional cross-linked network structure, which significantly enhances the mechanical strength, thermal stability and dimensional stability of the polymer matrix, and effectively inhibits the deformation, swelling and mechanical failure of the electrolyte membrane during operation.

[0075] The above examples show that the composite solid electrolyte membrane prepared by the present invention has excellent comprehensive performance and can meet the application requirements of high-performance solid-state lithium batteries.

Claims

1. A method for preparing a composite solid electrolyte membrane, characterized in that The method comprises the following steps: S1. Preparing a composite precursor solution: dissolving or dispersing polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), LLZO ceramic filler, lithium salt, sodium dodecyl sulfate (SDS), cross-linking monomer divinylbenzene (DVB) and initiator in a solvent to obtain a composite precursor solution; The solid solute of the composite precursor solution comprises: 50-62% PVDF-HFP, 10-30% LLZO, 3-6% lithium salt, 3-10% SDS, 20-30% DVB, and 0.05-3% initiator, based on the total mass of the solid solute as 100%; S2. Electrospinning of SDS / DVB synergistically reinforced composite nanofiber membrane: electrospinning the composite precursor solution to obtain a composite nanofiber membrane; S3, heat treatment: heat treating the composite nanofiber membrane at 60-120° C. to induce a cross-linking reaction of the DVB to form a three-dimensional network structure, thereby obtaining the composite solid electrolyte membrane; S4. Performing hot pressing treatment on the composite solid electrolyte membrane at a temperature of 80-120° C. and a pressure of 3-8 MPa.

2. The preparation method according to claim 1, wherein: The solid solute of the composite precursor solution comprises: 50-55% PVDF-HFP, 10-12% LLZO, 3-6% lithium salt, 3-6% SDS, 20-30% DVB, and 1-2% initiator, based on the total mass of the solid solute being 100%.

3. The preparation method according to claim 1, wherein: The LLZO is a high ion conductive cubic phase structure formed by element doping, and the doping element is selected from Al, Ga, Nb, Ta or a combination thereof; The lithium salt is selected from one or more of the following lithium-based electrolyte compounds: lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiOTf), fluorophosphate lithium salts, lithium nitrate (LiNO3), lithium trifluoroacetate (LiTFA), lithium chloride (LiCl), lithium iodide (LiI), lithium bromide (LiBr) or fluoroalkylsulfonyl imide lithium salts.

4. The preparation method according to claim 1, wherein: LLZO is lithium lanthanum zirconium oxide (Li7La3Zr2O 12 , LLZO); the initiator is ammonium persulfate (APS).

5. The preparation method according to claim 1, wherein: The electrospinning process parameters described in S2 are: voltage of 10-30 kV, collection distance of 20-30 cm, propulsion speed of 1.0-3.5 mL / h, ambient humidity ≤30%, and temperature of 15-35 °C.

6. The preparation method according to claim 1, wherein: S3. Heat treatment includes: The composite nanofiber membrane obtained in S2 was placed in a vacuum oven at 50-80°C and dried for more than 12 hours to completely remove the residual solvent and unreacted monomers; The dried composite nanofiber membrane is placed in a flat-plate hot press and hot-pressed for 5-10 minutes at 80-120°C and 3-8 MPa pressure to densify the membrane and promote further cross-linking of DVB.

7. A composite solid electrolyte membrane prepared by the method according to any one of claims 1 to 6, characterized in that: The invention comprises a matrix composed of PVDF-HFP nanofibers and LLZO particles, and a three-dimensional network structure formed by cross-linking DVB in the matrix; wherein SDS is adsorbed on the surface of the LLZO particles.

8. The composite solid electrolyte membrane according to claim 7, characterized in that The thickness of the membrane is 30-100 μm, and / or the ionic conductivity at room temperature is not less than 1×10 -4 S / cm.

9. Use of the composite solid electrolyte membrane according to claim 1 in a solid-state lithium-ion battery, an all-solid-state energy storage device or a flexible electronic device.

10. A lithium battery, characterized in that: Comprising the composite solid electrolyte membrane as claimed in claim 7.

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