PVDF-BFO@PDA composite solid-state electrolyte and preparation method and application thereof
By preparing BFO@PDA composite nanofibers and PVDF polymer matrix through electrospinning, the problems of low conductivity and insufficient mechanical strength of PVDF electrolyte were solved, achieving efficient ion transport and lithium dendrite suppression, thus expanding the application range of high voltage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 湖北皇恩烨新材料科技有限公司
- Filing Date
- 2026-05-26
- Publication Date
- 2026-07-31
AI Technical Summary
Existing polymer-based solid electrolytes such as PVDF suffer from low room-temperature ionic conductivity, insufficient mechanical strength, and a tendency to induce lithium dendrite growth. In contrast, inorganic ceramic materials such as BFO exhibit poor flexibility and are difficult to process. Furthermore, inorganic ceramic nanomaterials in composite materials tend to agglomerate, have uneven distribution, and poor interfacial compatibility, making it difficult to achieve high-performance industrial applications.
BFO@PDA composite nanofibers were prepared by electrospinning. By coating the surface of BFO nanofibers with a polydopamine layer, a core-shell structure of BFO@PDA composite nanofibers was formed. These nanofibers were then combined with a PVDF polymer matrix to prepare a PVDF-BFO@PDA composite solid electrolyte.
It improves the interfacial compatibility between inorganic and organic materials, constructs an efficient and continuous ion transport channel, enhances mechanical strength, inhibits lithium dendrite growth, improves room temperature ionic conductivity and long-cycle stability of the battery, and broadens the application range of high voltage.
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Figure CN122494792A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of solid electrolyte materials, specifically relating to a PVDF-BFO@PDA composite solid electrolyte, its preparation method, and its application. Background Technology
[0002] Solid electrolytes have great application potential in the field of lithium-ion batteries, but traditional polymer-based solid electrolytes such as PVDF have problems such as low room temperature ionic conductivity, insufficient mechanical strength and easy to induce lithium dendrite growth, which seriously affect their practical value. Ferroelectric ceramic materials such as bismuth ferrite (BFO) can theoretically enhance ion transport through ferroelectric spontaneous polarization effect and local electric field, but single inorganic ceramic materials have poor flexibility and are difficult to process.
[0003] Current reports on this type of composite solid electrolyte focus on direct particle filling or simple mixing methods. Due to the high surface energy of inorganic ceramic nanomaterials, their main drawback is that the filler is prone to agglomeration in the organic matrix, uneven distribution, and poor interfacial compatibility, resulting in serious interfacial defects. At the same time, it is difficult to achieve high-performance industrial applications. Summary of the Invention
[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a PVDF-BFO@PDA composite solid electrolyte, its preparation method and application, thereby solving the technical problems of poor interfacial compatibility, easy agglomeration and low room temperature ionic conductivity of solid electrolytes in the prior art.
[0005] To achieve the above-mentioned technical objectives, the present invention provides a PVDF-BFO@PDA composite solid electrolyte, comprising a polyvinylidene fluoride (PVDF) polymer matrix and BFO@PDA composite nanofibers uniformly dispersed in the matrix, wherein the filling ratio of the BFO@PDA composite nanofibers is 1-8 wt%; the BFO@PDA composite nanofibers are fillers with a core-shell structure, with perovskite-structured bismuth ferrite (BFO) nanofibers as the core and a polydopamine (PDA) layer coated on the surface.
[0006] Furthermore, the diameter of the BFO nanofibers is 100-500 nm, and the film thickness of the composite solid electrolyte is 50-100 μm.
[0007] Furthermore, the PVDF polymer matrix also contains a lithium salt, which is one or more of LiFSI, LiTFSI, LiClO4 or LiPF6.
[0008] The preparation method of the PVDF-BFO@PDA composite solid electrolyte as described above includes the following steps:
[0009] (1) Take a bismuth source and an iron source, add glacial acetic acid and water to form solution A; take polyvinylpyrrolidone (PVP) and add it to N,N-dimethylformamide (DMF) to form solution B; mix solution A and solution B, and obtain precursor fibers by electrospinning, controlling the spinning parameters as follows: voltage 12-18kV, receiving distance 10-20cm, injection rate 0.2-1.0mL / h; then slowly heat and calcine the precursor fibers to obtain one-dimensional BFO nanofibers;
[0010] (2) The obtained BFO nanofibers were dispersed in a weakly alkaline buffer solution containing dopamine and subjected to a self-polymerization coating reaction at room temperature. After washing and drying, BFO@PDA composite nanofibers were obtained.
[0011] (3) Take PVDF polymer and lithium salt as the main materials, add solvent to mix, heat and stir magnetically to dissolve to obtain PVDF solution;
[0012] (4) The BFO@PDA composite nanofibers were mixed with PVDF solution, ultrasonically dispersed, and then coated into a film by scraping. After drying, the PVDF-BFO@PDA composite solid electrolyte was obtained.
[0013] Further, in step (1), the specific process of slow heating and calcination is as follows: heating to 500-700℃ at a heating rate of 0.5-2℃ / min, and calcination time is 2-6h.
[0014] Further, in step (2), the weakly alkaline buffer is a Tris-HCl buffer with pH=8.0-9.0, and the concentration of dopamine is 1.0-3.0 g / L; the coating reaction time is 12-36 h.
[0015] Furthermore, in step (2), during the dissolution of PVDF polymer and lithium salt, the solvent is N,N-dimethylformamide (DMF); the mass ratio of PVDF polymer to lithium salt is (1-2):1; and the temperature for heating and magnetic stirring is 50-70℃.
[0016] Furthermore, in step (3), the BFO@PDA composite nanofibers account for 1-8% of the mass of the PVDF polymer; the ultrasonic dispersion time is 10-30 min.
[0017] Further, in step (3), after ultrasonic dispersion, magnetic stirring is continued for 10-15 hours; the drying treatment is carried out under vacuum conditions at 60-80℃ for 12-48 hours.
[0018] The above PVDF-BFO@PDA composite solid electrolyte is used as an electrolyte for all-solid-state lithium-ion batteries.
[0019] Compared with the prior art, the beneficial effects of the present invention include:
[0020] 1. This invention uses electrospinning combined with in-situ dopamine polymerization coating technology to prepare BFO@PDA composite nanofibers. The calcination adopts an extremely slow heating rate, which effectively prevents fiber collapse caused by the decomposition of template polymers. The prepared morphology is a highly uniform one-dimensional nano-network structure, which is conducive to large-scale industrial production.
[0021] 2. This invention coats the surface of BFO with a PDA layer, utilizing the abundant polar functional groups of PDA to act as a "bridge," greatly improving the interfacial compatibility between the inorganic filler and the organic PVDF matrix, solving the aggregation problem, and constructing an efficient and continuous ion transport channel.
[0022] 3. This invention introduces a mechanical reinforcement effect through the strong interaction between the fiber network structure and the PDA, achieving an organic unity of flexibility and high conductivity. The mechanical strength, as an important support, can effectively suppress the growth of lithium dendrites, greatly promoting the long-cycle stability and safety of the battery (symmetric batteries can cycle stably for more than 2000 hours).
[0023] 4. This invention broadens the application scope of solid electrolytes. The functional groups on the PDA surface help stabilize the high-voltage interface, enabling the composite solid electrolyte of this invention, when paired with the high-nickel ternary cathode material (NCM811), to maintain excellent cycle capacity retention under high voltage conditions, which has strong practical value.
[0024] 5. The research mechanism of this invention is that the external core-shell structure filler (BFO@PDA) enhances the internal ion migration pathway. The ferroelectric spontaneous polarization effect of BFO and the synergistic effect of the polar groups in PDA promote lithium salt dissociation, resulting in a significant improvement in lithium-ion transport efficiency (room temperature ionic conductivity reaches 8.04 × 10⁻⁶). -4 The electrochemical performance (S / cm) is significantly improved compared to that of a single polymer electrolyte. Attached Figure Description
[0025] Figure 1 This is a SEM image of the BFO nanofibers obtained in Example 1 of the present invention;
[0026] Figure 2 This is a comparison XRD pattern of pure BFO and BFO@PDA composite filler prepared in Example 1 of the present invention;
[0027] Figure 3 The impedance (EIS) spectrum of the PVDF-BFO@PDA composite solid electrolyte prepared in Example 1 of this invention;
[0028] Figure 4This is a long-cycle voltage-time curve of a Li / Li symmetric battery assembled with a PVDF-BFO@PDA composite solid electrolyte prepared in Example 1 of the present invention.
[0029] Figure 5 The graph shows the charge-discharge capacity and coulombic efficiency of the LFP / Li full cell assembled with the composite solid electrolyte prepared in Example 1 of this invention under long-term cycling.
[0030] Figure 6 The diagram shows the capacity and coulombic efficiency of the high-voltage NCM811 / Li full cell assembled with the composite solid electrolyte prepared in Example 1 of this invention under long-term cycling. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0032] This invention provides a method for preparing a PVDF-BFO@PDA composite solid electrolyte, comprising the following steps:
[0033] S1. Using bismuth and iron sources as precursors, glacial acetic acid and water are added as solvents to form solution A; polyvinylpyrrolidone (PVP) is added to N,N-dimethylformamide (DMF) to form solution B; solution A and solution B are mixed and stirred to form a stable precursor solution, and precursor fibers are obtained by electrospinning, controlling the spinning parameters as follows: voltage 12-18kV, receiving distance 10-20cm, and injection rate 0.2-1.0mL / h; then, the fibers are heated to 500-700℃ at a very slow heating rate for 2-6h to obtain one-dimensional BFO nanofibers; wherein, the BFO nanofibers are perovskite-structured ferroelectric ceramic fibers; S2. The BFO nanofibers are added to a weakly alkaline buffer solution containing dopamine, stirred at room temperature to carry out a self-polymerization reaction, washed and dried to obtain BFO@PDA composite nanofibers with a core-shell structure;
[0034] S3. Take PVDF polymer and lithium salt as the main materials, add solvent to mix, heat and magnetically stir to dissolve to obtain PVDF solution, wherein the lithium salt is one or more of LiFSI, LiTFSI, LiClO4 or LiPF6.
[0035] S4. The BFO@PDA composite nanofibers are mixed with PVDF solution, and the BFO@PDA composite nanofibers account for 1-8 wt% of the total weight of PVDF polymer after the composite. The mixed slurry is coated into a film by a blade coating method and then vacuum dried to obtain the PVDF-BFO@PDA composite solid electrolyte.
[0036] Preferably, in step S1, the molar ratio of bismuth source to iron source is Bi:Fe=1:1; the electrospinning process is carried out at room temperature, and the specific process of slow heating and calcination is as follows: first, dry at 80℃ for 12h, and then heat to the target temperature at a heating rate of 0.5-2℃ / min.
[0037] Preferably, in step S2, the weakly alkaline buffer is a 10mM Tris-HCl buffer with pH=8.0-9.0, and the concentration of dopamine is 1.0-3.0g / L; the coating reaction is carried out in an oxygen-containing environment with stirring at room temperature for 12-36h, and the drying conditions are drying in a vacuum oven at 60℃ for 12h.
[0038] Preferably, the preparation process of the PVDF solution in step S3 is as follows: take a certain mass of PVDF polymer and lithium salt, dissolve them in a polar organic solvent at a mass ratio of (1-2):1, and magnetically stir at 400-800 r / min at 50-70℃ for 10-15 h until completely dissolved, wherein the solvent is N,N-dimethylformamide (DMF).
[0039] More preferably, the diameter of the BFO nanofibers in step S1 is between 100-500 nm (observed under a scanning electron microscope).
[0040] Preferably, in step S4, the composite process of BFO@PDA composite nanofibers and PVDF solution is as follows: ultrasonic dispersion for 10-30 min, followed by magnetic stirring for 10-15 h; after coating into a film, drying at 60-80℃ under vacuum for 12-48 h.
[0041] A PVDF-BFO@PDA composite solid electrolyte is composed of a PVDF polymer matrix, a lithium salt, and BFO@PDA composite nanofibers uniformly dispersed in the matrix, wherein the filling ratio of the BFO@PDA composite nanofibers is 1-8 wt%.
[0042] Preferably, the composite solid electrolyte prepared by this invention has a film thickness of 50-100 μm and a room temperature ionic conductivity of 10⁻⁻⁻⁶. 4 S / cm or higher.
[0043] An application of a PVDF-BFO@PDA composite solid electrolyte preparation method in the field of all-solid-state lithium-ion batteries, specifically in the preparation of high-performance, high-voltage stable solid electrolyte membranes.
[0044] An all-solid-state lithium-ion battery system includes the aforementioned PVDF-BFO@PDA composite solid-state electrolyte. The ferroelectric effect of BFO fibers and the synergistic effect of PDA polar functional groups drive the ion transport path, further promoting lithium salt dissociation, improving lithium-ion migration efficiency and interface stability, and thus utilizing the composite structure to enhance the battery's cycle performance and safety.
[0045] This invention uses BFO@PDA composite nanofibers to fill a PVDF matrix. The in-situ polymerized PDA layer solves the defect of easy agglomeration of inorganic fillers, forming a uniform fiber network structure, constructing continuous high-speed ion transport channels and local electric fields, and can prepare highly efficient composite solid electrolytes.
[0046] PVDF-BFO@PDA composite solid electrolyte possesses excellent ionic conductivity, high-voltage interface stability, and mechanical strength, and is mainly used in lithium-ion batteries, flexible electronic devices, and high-safety energy storage. PVDF-BFO@PDA composite solid electrolyte can organically combine polymer flexibility, ceramic ferroelectric effect, and PDA surface modification to exert a strong synergistic effect, further promoting ionic conductivity and effectively inhibiting lithium dendrite growth. It not only overcomes the shortcomings of single materials, but also greatly expands the application range of solid electrolytes in high-voltage systems such as high-nickel ternary batteries.
[0047] The present invention will be further described in detail below through specific embodiments.
[0048] Example 1
[0049] This embodiment describes a method for preparing a PVDF-BFO@PDA composite solid electrolyte, the steps of which are as follows:
[0050] S1. Bismuth nitrate and ferric nitrate were added to glacial acetic acid and water in a molar ratio of Bi:Fe = 1:1 to form solution A; PVP was added to DMF to form solution B; the two solutions were mixed and stirred to form a stable precursor; precursor fibers were prepared by electrospinning with the following parameters: voltage 15kV, receiving distance 15cm, and injection rate 0.5mL / h; the fibers were first dried at 80℃ for 12h, and then calcined at 600℃ for 4h at a very slow heating rate of 1℃ / min to obtain one-dimensional BFO nanofibers.
[0051] S2. Take 0.5g of the above BFO nanofibers and add them to a Tris-HCl buffer solution containing 10mM and pH 8.5. Add dopamine hydrochloride (concentration 2.0g / L), seal and punch holes at room temperature to maintain slow oxygen exchange, stir magnetically for 24h, centrifuge and wash, and dry in a vacuum oven at 60℃ for 12h to obtain BFO@PDA composite nanofibers.
[0052] S3. Weigh 0.75g of PVDF polymer and 0.5g of LiFSI (i.e., mass ratio 3:2) as the main material, add solvent (6ml of DMF) and mix. Stir magnetically at 600r / min for 12h at 60℃ to dissolve and obtain PVDF solution.
[0053] S4. Add the BFO@PDA composite nanofibers to the PVDF solution and disperse them by ultrasonication for 20 min to break up the agglomeration. Then continue to stir magnetically for 12 h. After the composite, the BFO@PDA composite nanofibers account for 4 wt% (0.03 g) of the total weight of PVDF. Coat the mixed slurry into a film with a doctor blade and dry it at 60 °C under vacuum for 24 h to obtain the PVDF-BFO@PDA composite solid electrolyte (thickness of about 60 μm).
[0054] Figure 1 The image shown is a SEM image of the BFO nanofibers prepared in this embodiment, which has a continuous and uniform one-dimensional long-range morphology.
[0055] Figure 2 The image shows a comparison of XRD patterns between pure BFO and BFO@PDA composite nanofibers in this embodiment, demonstrating that the pure phase perovskite structure was not damaged before and after coating.
[0056] Figure 3 The image shows the electrochemical impedance spectroscopy (EIS) spectrum of the PVDF-BFO@PDA composite solid electrolyte in this embodiment. Calculations show that its room-temperature ionic conductivity is as high as 8.04 × 10⁻⁻⁻⁶. 4 S / cm.
[0057] Example 2
[0058] This embodiment describes a method for preparing a PVDF-BFO@PDA composite solid electrolyte, the steps of which are as follows:
[0059] S1. The electrospinning and slow heating calcination steps are the same as in Example 1 to obtain BFO nanofibers;
[0060] S2, the PDA coating step is the same as in Example 1, to obtain BFO@PDA composite nanofibers;
[0061] S3. Weigh 0.75g of PVDF polymer and 0.5g of LiFSI as the main materials, add solvent (6ml of DMF) and mix. Stir magnetically at 60℃ for 12h to dissolve and obtain PVDF solution.
[0062] S4. Add the BFO@PDA composite nanofibers to the PVDF solution and disperse them by ultrasonication for 20 min, followed by magnetic stirring for 12 h. After the composite, the BFO@PDA composite nanofibers account for 2 wt% (0.015 g) of the total weight of PVDF. Coat the mixed slurry into a film and dry it at 60 °C under vacuum for 24 h to obtain the PVDF-BFO@PDA composite solid electrolyte.
[0063] Example 3
[0064] This embodiment describes a method for preparing a PVDF-BFO@PDA composite solid electrolyte, the steps of which are as follows:
[0065] S1. The electrospinning and slow heating calcination steps are the same as in Example 1 to obtain BFO nanofibers;
[0066] S2, the PDA coating step is the same as in Example 1, to obtain BFO@PDA composite nanofibers;
[0067] S3. Weigh 0.75g of PVDF polymer and 0.5g of LiFSI as the main materials, add solvent (6ml of DMF) and mix. Stir magnetically at 60℃ for 12h to dissolve and obtain PVDF solution.
[0068] S4. Add the BFO@PDA composite nanofibers to the PVDF solution and disperse them by ultrasonication for 20 min, followed by magnetic stirring for 12 h. After the composite, the BFO@PDA composite nanofibers account for 6 wt% (0.045 g) of the total weight of PVDF. Coat the mixed slurry into a film and dry it at 60 °C under vacuum for 24 h to obtain the PVDF-BFO@PDA composite solid electrolyte.
[0069] The specific preparation examples of the PVDF-BFO@PDA composite solid electrolyte provided by this invention are listed in Table 1.
[0070] Table 1 examines the selection of the weight percentage of BFO@PDA composite fiber in PVDF in step S4 (labeled A), the selection of lithium salt type in step S3 (labeled B), and the selection of calcination heating rate in step S1 (labeled C).
[0071] Table 1. Parameter selection and weight percentage in various embodiments of the invention.
[0072] Example A (filler percentage) B (Lithium salt type) C (heating rate) Example 1 4% LiFSI 1℃ / min Example 2 2% LiFSI 1℃ / min Example 3 6% LiFSI 1℃ / min Example 4 8% LiFSI 1℃ / min Example 5 4% LiTFSI 1℃ / min Example 6 4% LiClO4 1℃ / min Example 7 4% LiPF6 1℃ / min Example 8 2% LiTFSI 1℃ / min Example 9 6% LiTFSI 1℃ / min Example 10 8% LiTFSI 1℃ / min Example 11 2% LiFSI 0.5℃ Example 12 4% LiFSI 0.5℃ Example 13 6% LiFSI 0.5℃ Example 14 2% LiFSI 2℃ / min Example 15 4% LiFSI 2℃ / min Example 16 6% LiFSI 2℃ / min Example 17 2% LiClO4 1℃ / min Example 18 6% LiClO4 1℃ / min
[0073] Figure 4 , Figure 5 and Figure 6The figures show the long-cycle performance of the symmetric battery, LFP / Li full battery, and NCM811 / Li full battery assembled with the composite solid electrolyte prepared in Example 1 of this invention. They demonstrate that the solid electrolyte of this invention effectively suppresses lithium dendrite growth while possessing excellent high-voltage cycling stability and superior interfacial compatibility.
[0074] Comparative Example 1
[0075] The only difference from Example 1 is that the proportion of BFO@PDA composite nanofibers in the total weight of PVDF in step S4 is adjusted to 0 wt% (i.e., no BFO@PDA composite filler is added), while the other steps and conditions are the same as in Example 1.
[0076] Morphological observation and comparison revealed that the pure PVDF polymer electrolyte had numerous pores on its surface, poor density, and obvious structural defects. In contrast, the PVDF-BFO@PDA composite electrolyte prepared in Example 1 showed a significant reduction in the number of pores, a decrease in pore depth, and a marked reduction in surface undulation. The introduction of the PDA layer greatly improved the inorganic-organic interface compatibility and further optimized the density and structural uniformity of the membrane.
[0077] Comparative Example 2
[0078] The only difference from Example 1 is that in step S4, pure BFO nanofibers that have not been coated in step S2 are added (the amount added is the same as 4wt%), while the other steps and conditions are the same as in Example 1.
[0079] Because they are not coated with PDA, the single inorganic BFO nanofibers have high surface energy and are prone to agglomeration in the organic PVDF polymer matrix, leading to interface defects and microcracks. Their ionic conductivity and cycling stability are significantly lower than those in Example 1.
[0080] Application Example 1
[0081] The composite solid electrolyte prepared according to this invention was subjected to application testing.
[0082] The prepared composite solid electrolytes were subjected to ionic conductivity tests and all-solid-state lithium-ion battery performance evaluations. Electrochemical impedance spectroscopy (EIS) and constant current charge-discharge methods were used for the tests. The assembled batteries included Li | composite electrolyte | Li symmetric cells, Li | composite electrolyte | LiFePO4 structures, and high-voltage Li | composite electrolyte | NCM811 structures. The thickness of the composite electrolyte film was 50-100 μm. The test conditions were carried out at room temperature (25℃).
[0083] Tests showed that Example 1 exhibited a room-temperature ionic conductivity as high as 8.04 × 10⁻⁶. -4 S / cm, Figure 4The Li / Li symmetric cell demonstrates extremely stable cycling for over 2000 hours at 0.1 mA cm⁻². Figure 5 The LiFePO4 / PVDF-BFO@PDA / Li full cell showed a capacity retention of 91.7% after 100 cycles at a current density of 0.5C. Figure 6 The high-voltage NCM811 / PVDF-BFO@PDA / Li battery maintains an extremely high specific capacity after 200 cycles at 0.2C, with a capacity retention rate as high as 92.5%. In contrast, the capacity decay under single polymer conditions is faster and polarization is more severe. This indicates that the PVDF-BFO@PDA composite solid electrolyte of this invention can organically combine the flexibility of polymer, the ferroelectric effect of ceramics and the polar functional groups of PDA to exert a synergistic effect, further promoting ion conduction, stabilizing the high-voltage interface and inhibiting lithium dendrite growth.
[0084] Compared with the prior art, the present invention provides a PVDF-BFO@PDA composite solid electrolyte and its preparation method, comprising the following steps: preparing one-dimensional BFO nanofibers by electrospinning combined with extremely slow heating and calcination technology; in-situ polymerizing and coating a PDA layer on the surface of the BFO nanofibers to obtain pure-phase core-shell structured fibers; combining the BFO@PDA composite nanofibers with a PVDF solution by a blade coating method to obtain the composite solid electrolyte; the mass percentage of the composite BFO@PDA nanofibers to the total weight percentage of PVDF is 1-8 wt%; and vacuum drying the mixed membrane to obtain the PVDF-BFO@PDA composite solid electrolyte.
[0085] This invention modifies BFO fibers by in-situ dopamine polymerization and then composites them with PVDF. This solves the problem of easy agglomeration of inorganic fillers, improves the uniformity of the fiber network and interfacial compatibility, greatly enhances the ionic conductivity of the composite electrolyte, strengthens the migration and long-range high-speed transport of lithium ions at the interface, and fully utilizes the ferroelectric effect, the synergistic effect of polar groups and polymer matrix to construct a more efficient, safe and high-pressure resistant solid electrolyte material.
[0086] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.
Claims
1. A PVDF-BFO@PDA composite solid-state electrolyte, characterized in that: The product comprises a polyvinylidene fluoride (PVDF) polymer matrix and BFO@PDA composite nanofibers uniformly dispersed in the matrix, wherein the filling ratio of BFO@PDA composite nanofibers is 1-8 wt%; the BFO@PDA composite nanofibers are fillers with a core-shell structure, with perovskite-structured bismuth ferrite (BFO) nanofibers as the core and a polydopamine (PDA) layer coated on the surface.
2. The PVDF-BFO@PDA composite solid-state electrolyte according to claim 1, characterized in that: The diameter of the BFO nanofibers is 100-500 nm, and the thickness of the composite solid electrolyte film is 50-100 μm. 3.The PVDF-BFO@ PDA composite solid-state electrolyte of claim 1, wherein: The PVDF polymer matrix also contains a lithium salt, which is one or more of LiFSI, LiTFSI, LiClO4 or LiPF6.
4. The preparation method of the PVDF-BFO@PDA composite solid electrolyte according to any one of claims 1-3, characterized in that: Includes the following steps: (1) Take a bismuth source and an iron source, add glacial acetic acid and water to form solution A; take polyvinylpyrrolidone (PVP) and add it to N,N-dimethylformamide (DMF) to form solution B; mix solution A and solution B, and obtain precursor fibers by electrospinning, controlling the spinning parameters as follows: voltage 12-18kV, receiving distance 10-20cm, injection rate 0.2-1.0mL / h; then slowly heat and calcine the precursor fibers to obtain one-dimensional BFO nanofibers; (2) The obtained BFO nanofibers were dispersed in a weakly alkaline buffer solution containing dopamine and subjected to a self-polymerization coating reaction at room temperature. After washing and drying, BFO@PDA composite nanofibers were obtained. (3) Take PVDF polymer and lithium salt as the main materials, add solvent to mix, heat and stir magnetically to dissolve to obtain PVDF solution; (4) The BFO@PDA composite nanofibers were mixed with PVDF solution, ultrasonically dispersed, and then coated into a film by scraping. After drying, the PVDF-BFO@PDA composite solid electrolyte was obtained.
5. The preparation method of the PVDF-BFO@PDA composite solid electrolyte according to claim 4, characterized in that: In step (1), the specific process of slow heating and calcination is as follows: heating to 500-700℃ at a heating rate of 0.5-2℃ / min, and calcination time is 2-6h.
6. The preparation method of the PVDF-BFO@PDA composite solid electrolyte according to claim 4, characterized in that: In step (2), the weakly alkaline buffer is a Tris-HCl buffer with pH=8.0-9.0, and the concentration of dopamine is 1.0-3.0 g / L; the coating reaction time is 12-36 h.
7. The preparation method of the PVDF-BFO@PDA composite solid electrolyte according to claim 4, characterized in that: In step (2), during the dissolution of PVDF polymer and lithium salt, the solvent is N,N-dimethylformamide (DMF); the mass ratio of PVDF polymer to lithium salt is (1-2):1; and the temperature for heating and magnetic stirring is 50-70℃.
8. The preparation method of the PVDF-BFO@PDA composite solid electrolyte according to claim 4, characterized in that: In step (3), the BFO@PDA composite nanofibers account for 1-8% of the mass of the PVDF polymer; the ultrasonic dispersion time is 10-30 min.
9. The preparation method of the PVDF-BFO@PDA composite solid electrolyte according to claim 4, characterized in that: In step (3), after ultrasonic dispersion, magnetic stirring is continued for 10-15 hours; the drying process is carried out under vacuum at 60-80℃ for 12-48 hours.
10. The application of the PVDF-BFO@PDA composite solid electrolyte as described in any one of claims 1-3 as an electrolyte for all-solid-state lithium-ion batteries.