A high-dielectric composite solid electrolyte with a flexible outer layer and a rigid inner layer, its preparation method and application

Abstract

This invention discloses a high-dielectric, externally flexible, internally rigid composite solid electrolyte, its preparation method, and its application. Inorganic oxide ceramic nanoparticles are added to a photosensitive resin to obtain solution A. A photoinitiator is added to solution A, followed by photopolymerization and 3D printing. After cleaning, a ceramic frame with a porous array structure is obtained. A block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonyl)imide are added to a solvent and stirred until homogeneous to obtain solution B. Barium titanate nanoparticles are added to solution B to obtain a polymer slurry, which is then cast into the ceramic frame and vacuum dried to obtain the high-dielectric, externally flexible, internally rigid composite solid electrolyte. This invention not only possesses good mechanical strength but also improves interfacial compatibility and reduces interfacial impedance. When applied to lithium metal batteries, it effectively promotes lithium salt dissociation, increases the concentration of freely moving lithium ions, improves ionic conductivity, and thus enhances the cycle performance of solid-state lithium metal batteries.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte technology, and in particular to a high-dielectric composite solid electrolyte with an outer flexible and inner rigid structure, its preparation method, and its application. Background Technology

[0002] With the rapid development of energy storage devices in new energy vehicles and mobile electronic products, the development of high-energy-density energy storage has become an inevitable trend. Lithium metal batteries have a high theoretical specific capacity (3860 mAh g). -1 With its low electrochemical potential (-3.04V vs. standard hydrogen electrode), it is considered one of the most promising next-generation high-energy-density battery systems. Due to the risks of electrolyte leakage and thermal runaway associated with liquid batteries, next-generation high-energy-density solid-state lithium metal batteries, combining high energy density and high safety, have become a research hotspot in the field of lithium metal batteries.

[0003] Solid electrolytes are the core component of solid-state batteries, mainly including polymer electrolytes, inorganic electrolytes, and composite electrolytes. Polymer electrolytes have advantages such as good electrode compatibility and ease of processing, but their ion transport performance and mechanical strength are relatively poor. Inorganic electrolytes, especially inorganic oxide ceramic electrolytes with wide electrochemical windows and good stability, have significant advantages in ionic conductivity and structural strength. However, ceramics are brittle, lack flexibility, are difficult to process, and struggle to alleviate interfacial stress caused by repeated changes in electrode volume, resulting in high interfacial resistance. Composite solid electrolytes, which combine polymers and ceramics, can leverage the advantages of both and have attracted widespread attention from researchers. Currently, most composite solid electrolyte preparation strategies involve mixing organic polymers with inorganic fillers. While this method achieves a balance between electrolyte ionic conductivity and electrode compatibility to some extent, there is still considerable room for improvement in interfacial compatibility and mechanical strength. Furthermore, the number of freely moving lithium ions is limited, and the ionic conductivity of the electrolyte still falls short of practical application requirements. Summary of the Invention

[0004] The purpose of this invention is to provide a high-dielectric, flexible-outer-rigid-inner composite solid electrolyte, its preparation method, and its application. The solid electrolyte not only has good mechanical strength but also excellent electrode interface compatibility. When applied to lithium metal batteries, it can effectively promote lithium salt dissociation, increase the concentration of freely moving lithium ions, improve ionic conductivity, and thus enhance the cycle performance of solid lithium metal batteries.

[0005] To achieve the above objectives, this invention provides a high-dielectric, externally flexible, internally rigid composite solid electrolyte, its preparation method, and its application, comprising the following steps:

[0006] S1. Add inorganic oxide ceramic nanoparticles with a volume fraction of 60-80 vol% to the photosensitive resin and stir until homogeneous to obtain mixed solution A.

[0007] S2. Add the photoinitiator to the mixed solution A in S1 at a mass ratio of 1:100 with the photosensitive resin, and stir evenly to obtain the printing paste.

[0008] S3. Place the printing paste from S2 onto the printing platform, and heat it under a UV laser with a power of 1000-3000 mW / cm². 2 Photopolymer 3D printing was performed at a scanning speed of 500-2000 mm / s and a scanning width of 0.03-0.07 mm. After cleaning, a ceramic frame with a porous array structure was obtained.

[0009] S4. A block copolymer of polyvinylidene fluoride and polytetrafluoroethylene (the block copolymer contains 80 w.t. of polyvinylidene fluoride and 20 w.t. of polytetrafluoroethylene, purchased from Daikin Fluorochemicals Co., Ltd.) and lithium bis(trifluoromethanesulfonylimide) are added to a solvent at a mass ratio of 3.5-5.5:1 and stirred until homogeneous to obtain mixed solution B.

[0010] S5. Add barium titanate nanoparticles to solution B in S4. The barium titanate nanoparticles are 5-20 wt% of a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene. After mixing evenly, a polymer slurry is obtained.

[0011] S6. The polymer slurry in S5 is poured into the ceramic frame in S3, with a mass ratio of polymer slurry to ceramic frame of 5-7.5:5-2.5. Then, it is vacuum dried at 50-70℃ for 24-48h to obtain a high-dielectric, flexible-outer-rigid-inner composite solid electrolyte.

[0012] Preferably, in S1, the inorganic oxide ceramic nanoparticles are lithium aluminum germanium phosphate (Li... 1.5 AI 0.5 Ge 1.5 (PO4)3) Ceramic nanoparticles (refer to "Li 1.5 AI 0.5 Ge 1.5 Preparation and performance study of (PO4)3 solid electrolyte and its battery.

[0013] Preferably, in S1, the photosensitive resin is at least one of ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate, and butyl acrylate.

[0014] Preferably, in S2, the photoinitiator is one or more of 2-hydroxy-2-methyl-1-phenylpropanone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2-methyl-1-(4-methylthiophenyl)-2-morpholin-1-propanone.

[0015] Preferably, in S4, the solvent is at least one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0016] Preferably, in S4, the mass ratio of the solvent to the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene is 10-15:1.

[0017] The composite solid electrolyte obtained by the above-mentioned high-dielectric flexible-outer-rigid-inner composite solid electrolyte has an inner layer of porous array structure inorganic oxide ceramic electrolyte framework and an outer layer of flexible block polymer electrolyte.

[0018] Applications of the above-mentioned composite solid electrolyte: This composite solid electrolyte is used in the preparation of lithium metal batteries.

[0019] Therefore, the beneficial effects of the present invention are as follows:

[0020] 1. By combining photopolymerization 3D printing technology and slurry casting, a composite solid electrolyte with a flexible outer structure and a rigid inner structure can be obtained. The inorganic oxide ceramic framework of the inner layer serves as a skeleton support, providing good mechanical strength for the composite electrolyte and effectively inhibiting lithium dendrite growth. The outer layer has a high viscoelastic polyvinylidene fluoride and polytetrafluoroethylene block copolymer to achieve stable and tight interfacial contact, improving electrolyte / electrode interface compatibility and cycle stability.

[0021] 2. Introducing barium titanate nanoparticles as functional fillers into the composite electrolyte system, due to their high dielectric constant, will generate a built-in reverse electric field when placed in an electric field, thereby effectively promoting the dissociation of lithium salt, increasing the concentration of freely moving lithium ions, increasing ionic conductivity, and thus improving the ion transport capability of solid-state lithium metal batteries.

[0022] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope image of the porous array inorganic oxide ceramic framework prepared in Example 1 of the present invention;

[0024] Figure 2 This is a scanning electron microscope image of the high-dielectric, externally flexible, internally rigid composite solid electrolyte prepared in Example 1 of this invention;

[0025] Figure 3 This is a scanning electron microscope image of the high-dielectric integrated composite solid electrolyte prepared in Comparative Example 1 of the present invention;

[0026] Figure 4The AC impedance spectra of the high dielectric external flexible internal rigid composite solid electrolyte prepared in Example 4 of the present invention, the high dielectric integrated composite solid electrolyte obtained in Comparative Example 1, and the lithium lanthanum titanate-based high dielectric external flexible internal rigid composite solid electrolyte obtained in Comparative Example 3 are shown.

[0027] Figure 5 The high-dielectric, externally flexible and internally rigid composite solid electrolyte prepared in Example 4 of this invention and the externally flexible and internally rigid composite solid electrolyte obtained in Comparative Example 2 are charge-discharge test curves at 0.5C. Detailed Implementation

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] The present invention will be explained in more detail through the following embodiments. The purpose of disclosing the present invention is to protect all changes and modifications within the scope of the present invention. The present invention is not limited to the following embodiments.

[0030] Example 1

[0031] S1. Add 60 vol% (v / v) of lithium aluminum germanium phosphate ceramic nanoparticles to ethoxylated trimethylolpropane triacrylate and stir until homogeneous to obtain mixed solution A.

[0032] S2. Add 2-hydroxy-2-methyl-1-phenylpropanone to the mixed solution A in S1 at a mass ratio of 1:100 with ethoxylated trimethylolpropane triacrylate, and stir until homogeneous to obtain the printing paste.

[0033] S3. Place the printing paste from S2 onto the printing platform, and heat it under a UV laser with a power of 1000mW / cm². 2 Photopolymer 3D printing was performed at a scanning speed of 500 mm / s and a scanning width of 0.03 mm. After cleaning, a ceramic frame with a porous array structure was obtained.

[0034] S4. Add the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonylimide) at a mass ratio of 3.5:1 to N-methylpyrrolidone, and stir until homogeneous to obtain mixed solution B.

[0035] The mass ratio of N-methylpyrrolidone to the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene is 10:1.

[0036] S5. Add barium titanate nanoparticles to solution B in S4. The barium titanate nanoparticles are 5 wt% of a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene. After mixing evenly, a polymer slurry is obtained.

[0037] S6. The polymer slurry in S5 is poured into the ceramic frame in S3, with a mass ratio of polymer slurry to ceramic frame of 5:5. Then, it is vacuum dried at 50°C for 48 hours to obtain a high-dielectric, flexible-outer-rigid-inner composite solid electrolyte.

[0038] like Figure 1 As shown, the porous array composite solid electrolyte has a uniformly distributed pore structure, which can serve as a framework for the composite electrolyte, providing ample space for filling the polymer electrolyte slurry. Figure 2 As shown, the composite solid electrolyte obtained in this embodiment has a relatively flat and uniform surface morphology.

[0039] Example 2

[0040] S1. Add 70 vol% (v / v) of lithium aluminum germanium phosphate ceramic nanoparticles to polyethylene glycol diacrylate and stir until homogeneous to obtain mixed solution A.

[0041] S2. Add phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide to the mixed solution A in S1 at a mass ratio of 1:100 to polyethylene glycol diacrylate, and stir evenly to obtain the printing paste.

[0042] S3. Place the printing paste from S2 onto the printing platform, and heat it under a UV laser with a power of 1500mW / cm². 2 At a scanning speed of 1000 mm / s and a scanning width of 0.04 mm, photopolymerization 3D printing was performed, and after cleaning, a ceramic frame with a porous array structure was obtained.

[0043] S4. Add the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonylimide) at a mass ratio of 4:1 to N,N-dimethylformamide, and stir until homogeneous to obtain mixed solution B.

[0044] The mass ratio of N,N-dimethylformamide and the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene is 11:1.

[0045] S5. Add barium titanate nanoparticles to solution B in S4. The barium titanate nanoparticles are 10 wt% of a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene. After mixing evenly, a polymer slurry is obtained.

[0046] S6. The polymer slurry in S5 is poured into the ceramic frame in S3, with a mass ratio of polymer slurry to ceramic frame of 6:4. Then, it is vacuum dried at 55°C for 40 hours to obtain a high-dielectric, flexible-outer-rigid-inner composite solid electrolyte.

[0047] Example 3

[0048] S1. Add 75 vol% (v / v) of lithium aluminum germanium phosphate ceramic nanoparticles to butyl acrylate and stir until homogeneous to obtain mixed solution A.

[0049] S2. Add 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone to the mixed solution A in S1 at a mass ratio of 1:100 with butyl acrylate, and stir until homogeneous to obtain the printing paste.

[0050] S3. Place the printing paste from S2 onto the printing platform, and heat it under a UV laser with a power of 2000mW / cm². 2 Photopolymer 3D printing was performed at a scanning speed of 1500 mm / s and a scanning width of 0.05 mm. After cleaning, a ceramic frame with a porous array structure was obtained.

[0051] S4. Add the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonylimide) at a mass ratio of 4.5:1 to N,N-dimethylacetamide, and stir until homogeneous to obtain mixed solution B.

[0052] The mass ratio of N,N-dimethylacetamide and the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene is 13:1.

[0053] S5. Add barium titanate nanoparticles to solution B in S4. The barium titanate nanoparticles are 15 wt% of a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene. After mixing evenly, a polymer slurry is obtained.

[0054] S6. The polymer slurry in S5 is poured into the ceramic frame in S3, with a mass ratio of polymer slurry to ceramic frame of 7:3. Then, it is vacuum dried at 60°C for 32 hours to obtain a high-dielectric, flexible-outer-rigid-inner composite solid electrolyte.

[0055] Example 4

[0056] S1. Add 80 vol% of lithium aluminum germanium phosphate ceramic nanoparticles to ethoxylated trimethylolpropane triacrylate and stir until homogeneous to obtain mixed solution A.

[0057] S2. Add 2-hydroxy-2-methyl-1-phenylpropanone to the mixed solution A in S1 at a mass ratio of 1:100 with ethoxylated trimethylolpropane triacrylate, and stir until homogeneous to obtain the printing paste.

[0058] S3. Place the printing paste from S2 onto the printing platform, and heat it under a UV laser with a power of 3000mW / cm². 2 At a scanning speed of 2000 mm / s and a scanning width of 0.07 mm, photopolymerization 3D printing was performed, and after cleaning, a ceramic frame with a porous array structure was obtained.

[0059] S4. Add the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonylimide) at a mass ratio of 5.5:1 to N-methylpyrrolidone, and stir until homogeneous to obtain mixed solution B.

[0060] The mass ratio of N-methylpyrrolidone to the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene is 15:1.

[0061] S5. Add barium titanate nanoparticles to solution B in S4. The barium titanate nanoparticles are 20 wt% of a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene. After mixing evenly, a polymer slurry is obtained.

[0062] S6. The polymer slurry in S5 is poured into the ceramic frame in S3, with a mass ratio of polymer slurry to ceramic frame of 7.5:2.5. Then, it is vacuum dried at 70°C for 24 hours to obtain a high-dielectric, flexible-outer-rigid-inner composite solid electrolyte.

[0063] Comparative Example 1

[0064] S1. Add the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonylimide) at a mass ratio of 5.5:1 to N-methylpyrrolidone, and stir until homogeneous to obtain mixed solution A.

[0065] The mass ratio of N-methylpyrrolidone to the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene is 15:1.

[0066] S2. Add barium titanate nanoparticles to solution A in S1. The barium titanate nanoparticles are 20 wt% of a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene. After mixing evenly, a polymer slurry is obtained.

[0067] S3. Add lithium germanium aluminum phosphate ceramic nanoparticles to the polymer slurry in S2. The lithium germanium aluminum phosphate ceramic nanoparticles are 20 wt% of a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene. After mixing evenly, an electrolyte slurry is obtained.

[0068] S4. The electrolyte mixture from S3 is poured into a polytetrafluoroethylene mold and then vacuum dried at 70°C for 24 hours to obtain a high-dielectric integrated composite solid electrolyte.

[0069] like Figure 3 As shown, the composite solid electrolyte prepared in this comparative example has some ceramic nanoparticle protrusions on its surface, and its overall balance is poor.

[0070] Comparative Example 2

[0071] S1. Add 80 vol% of lithium aluminum germanium phosphate ceramic nanoparticles to ethoxylated trimethylolpropane triacrylate and stir until homogeneous to obtain mixed solution A.

[0072] S2. Add 2-hydroxy-2-methyl-1-phenylpropanone to the mixed solution A in S1 at a mass ratio of 1:100 with ethoxylated trimethylolpropane triacrylate, and stir until homogeneous to obtain the printing paste.

[0073] S3. Place the printing paste from S2 onto the printing platform, and heat it under a UV laser with a power of 3000mW / cm². 2 At a scanning speed of 2000 mm / s and a scanning width of 0.07 mm, photopolymerization 3D printing was performed, and after cleaning, a ceramic frame with a porous array structure was obtained.

[0074] S4. Add the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonylimide) at a mass ratio of 5.5:1 to N-methylpyrrolidone, and stir evenly to obtain a polymer slurry.

[0075] The mass ratio of N-methylpyrrolidone to the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene is 15:1.

[0076] S5. The polymer slurry in S4 is poured into the ceramic frame in S3. The mass ratio of polymer slurry to ceramic frame is 7.5:2.5. Then, it is vacuum dried at 70°C for 24 hours to obtain a flexible-on-the-outer, rigid-on-the-inner composite solid electrolyte.

[0077] Comparative Example 3

[0078] S1. Add 80 vol% lanthanum lithium titanate ceramic nanoparticles to ethoxylated trimethylolpropane triacrylate and stir until homogeneous to obtain mixed solution A.

[0079] S2. Add 2-hydroxy-2-methyl-1-phenylpropanone to the mixed solution A in S1 at a mass ratio of 1:100 with ethoxylated trimethylolpropane triacrylate, and stir until homogeneous to obtain the printing paste.

[0080] S3. Place the printing paste from S2 onto the printing platform, and heat it under a UV laser with a power of 3000mW / cm². 2 At a scanning speed of 2000 mm / s and a scanning width of 0.07 mm, photopolymerization 3D printing was performed, and after cleaning, a ceramic frame with a porous array structure was obtained.

[0081] S4. Add the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonylimide) at a mass ratio of 5.5:1 to N-methylpyrrolidone, and stir until homogeneous to obtain mixed solution B.

[0082] The mass ratio of N-methylpyrrolidone to the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene is 15:1.

[0083] S5. Add barium titanate nanoparticles to solution B in S4. The barium titanate nanoparticles are 20 wt% of a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene. After mixing evenly, a polymer slurry is obtained.

[0084] S6. The polymer slurry in S5 is poured into the ceramic frame in S3, with a mass ratio of polymer slurry to ceramic frame of 7.5:2.5. Then, it is vacuum dried at 70°C for 24 hours to obtain a high-dielectric, flexible-outer-rigid composite solid electrolyte based on lithium lanthanum titanate.

[0085] Performance tests of the composite solid electrolytes prepared in each embodiment:

[0086] The high-dielectric, flexible-outer-rigid composite solid electrolyte (all with a thickness of 200 μm) obtained in Example 4 was assembled with lithium iron phosphate cathode slurry and lithium metal anode to form CR2032 battery one.

[0087] The high-dielectric integrated composite solid electrolytes obtained from Comparative Examples 1 and 3, the lithium lanthanum titanate-based high-dielectric flexible-inner-rigid composite solid electrolytes, and the lithium iron phosphate cathode slurry and lithium metal anode were respectively assembled into CR2032 battery II and CR2032 battery V.

[0088] The high-dielectric, flexible-outer-rigid composite solid electrolyte obtained in Example 4 was assembled with a lithium metal anode to form a CR2032 symmetrical battery.

[0089] The externally flexible and internally rigid composite solid electrolyte obtained in Comparative Example 2 was assembled with a lithium metal anode to form a CR2032 symmetrical battery.

[0090] AC impedance measurements were performed on two CR2032 symmetrical cells, CR2032 I and CR2032 symmetrical cells II, using a Bio-Logic VSP electrochemical workstation. The test frequency range was 0.1–200 kHz. The results are as follows: Figure 4 As shown, the interfacial impedance of the high-dielectric integrated composite solid electrolyte of Comparative Example 1 is 413Ω, while the interfacial impedance of the lithium lanthanum titanate-based high-dielectric flexible-inner-rigid composite solid electrolyte of Comparative Example 3 is 376Ω. In contrast, the high-dielectric flexible-inner-rigid composite solid electrolyte of Example 4 exhibits a lower interfacial impedance of 128Ω. This may be due to the Ti in the lithium lanthanum titanate. 4+ It will be reduced to Ti when in contact with the lithium metal anode. 3+ This leads to the formation of high-impedance compounds at the interface, resulting in a significant increase in interface resistance.

[0091] Using a CT-4000 Newway battery analyzer, constant current charge-discharge tests were performed on CR2032 battery three and CR2032 battery four within a voltage range of 2.5-3.8V. The results are as follows. Figure 5 As shown, the initial discharge specific capacity of the externally flexible and internally rigid composite solid electrolyte of Comparative Example 2CR2032 battery four is 146.8 mA h / g, and the capacity retention rate after 100 cycles is 52.1%, with a coulombic efficiency of 96.5%. In contrast, the high-dielectric externally flexible and internally rigid composite solid electrolyte of Example 4CR2032 symmetric battery three has an initial discharge specific capacity of 164.6 mA h / g, and after 100 cycles, it has a high capacity retention rate (93.6%) and a stable coulombic efficiency of 99.0%, demonstrating excellent cycle stability.

[0092] 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a high-dielectric, externally flexible, internally rigid composite solid electrolyte, characterized in that: Includes the following steps, S1. Add inorganic oxide ceramic nanoparticles with a volume fraction of 60-80 vol% to the photosensitive resin and stir until homogeneous to obtain mixed solution A. S2. Add the photoinitiator to the mixed solution A in S1 at a mass ratio of 0.5-2:100 to the photosensitive resin, and stir evenly to obtain the printing paste; S3. Place the printing paste from S2 onto the printing platform, and heat it under a UV laser with a power of 1000-3000 mW / cm². 2 Photopolymer 3D printing was performed at a scanning speed of 500-2000 mm / s and a scanning width of 0.03-0.07 mm. After cleaning, a ceramic frame with a porous array structure was obtained. S4. Add the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonylimide) at a mass ratio of 3.5-5.5:1 to the solvent and stir until homogeneous to obtain mixed solution B. S5. Add barium titanate nanoparticles to solution B in S4. The barium titanate nanoparticles are 5-20 wt% of a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene. After mixing evenly, a polymer slurry is obtained. S6. The polymer slurry in S5 is poured into the ceramic frame in S3, with a mass ratio of polymer slurry to ceramic frame of 5-7.5:5-2.

5. Then, it is vacuum dried at 50-70℃ for 24-48h to obtain a high-dielectric, flexible-outer-rigid-inner composite solid electrolyte.

2. The method for preparing a high-dielectric, externally flexible, internally rigid composite solid electrolyte according to claim 1, characterized in that: In S1, the inorganic oxide ceramic nanoparticles are lithium aluminum germanium phosphate ceramic nanoparticles.

3. The method for preparing a high-dielectric, externally flexible, internally rigid composite solid electrolyte according to claim 1 or 2, characterized in that: In S1, the photosensitive resin is at least one of ethoxylated trimethylolpropane triacrylate, polyethylene glycol diacrylate, and butyl acrylate.

4. The method for preparing a high-dielectric, externally flexible, internally rigid composite solid electrolyte according to claim 1 or 2, characterized in that: In S2, the photoinitiator is one or more of 2-hydroxy-2-methyl-1-phenylpropanone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2-methyl-1-(4-methylthiophenyl)-2-morpholin-1-propanone.

5. The method for preparing a high-dielectric, externally flexible, internally rigid composite solid electrolyte according to claim 1 or 2, characterized in that: In S4, the solvent is at least one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

6. The method for preparing a high-dielectric, externally flexible, internally rigid composite solid electrolyte according to claim 1 or 2, characterized in that: In S4, the mass ratio of the solvent to the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene is 10-15:

1.

7. The composite solid electrolyte obtained by the preparation method of the high-dielectric externally flexible and internally rigid composite solid electrolyte according to any one of claims 1-6, characterized in that: The inner layer of the composite solid electrolyte is a porous array structure of inorganic oxide ceramic electrolyte framework, and the outer layer is a flexible block polymer electrolyte.

8. The application of the composite solid electrolyte according to claim 7, characterized in that: This composite solid electrolyte is used in the preparation of lithium metal batteries.

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