High-dielectric external-flexible internal-rigid composite solid electrolyte and preparation method and application thereof

Abstract

The invention discloses a high-dielectric external-flexible internal-rigid composite solid electrolyte and a preparation method and application thereof. The preparation method comprises the following steps: adding inorganic oxide ceramic nanoparticles into photosensitive resin to obtain a solution A; adding a photoinitiator into the mixed solution A, carrying out photocuring 3D printing, and cleaning to obtain a ceramic frame with a porous array structure; adding a segmented copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis (trifluoromethane sulfonimide) into a solvent, and uniformly stirring to obtain a mixed solution B; adding barium titanate nanoparticles into the solution B to obtain polymer slurry, pouring the polymer slurry into a ceramic frame, and performing vacuum drying to obtain the high-dielectric outer-flexible inner-rigid composite solid electrolyte. The composite material has good mechanical strength, interface compatibility is improved, interface impedance is reduced, lithium salt dissociation can be effectively promoted when the composite material is applied to the lithium metal battery, the concentration of free moving lithium ions is increased, the ionic conductivity is improved, and then the cycle performance of the solid-state lithium metal battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolytes, and particularly to a high-dielectric flexible exterior and rigid interior composite solid electrolyte, a preparation method thereof, and an application thereof. Background Art

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

[0003] Solid electrolytes are the core components of solid-state batteries, mainly including polymer electrolytes, inorganic electrolytes, and composite electrolytes. Polymer electrolytes have advantages such as good electrode compatibility and easy processing, but their ion transport performance and mechanical strength are poor. Inorganic electrolytes, especially inorganic oxide ceramic electrolytes with a wide electrochemical window and good stability, are the main representatives, and have obvious advantages in ion conductivity and structural strength. However, ceramics are brittle, have poor flexibility, are not easy to process, and it is difficult to relieve the interfacial stress generated by the repeated volume change of the electrode, and the interfacial resistance is large. The composite solid electrolyte prepared by combining polymers and ceramics can give play to the advantages of both, and has received extensive attention from research scholars. At present, the preparation strategy of most composite solid electrolytes is to mix organic polymers and inorganic fillers. Although this method achieves a certain degree of balance between the ionic conductivity of the electrolyte and electrode compatibility, there is still great room for improvement in its interfacial compatibility and mechanical strength, and the number of freely moving lithium ions is limited, and the ionic conductivity of the electrolyte still has a gap with the actual application requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-dielectric flexible exterior and rigid interior composite solid electrolyte, a preparation method thereof, and an application thereof. The solid electrolyte not only has good mechanical strength, but also has excellent electrode interface compatibility. When applied to a lithium metal battery, it can effectively promote the dissociation of lithium salts, increase the concentration of freely moving lithium ions, improve the ionic conductivity, and further improve the cycling performance of the solid-state lithium metal battery.

[0005] To achieve the above object, the present invention provides a high-dielectric flexible exterior and rigid interior composite solid electrolyte, a preparation method thereof, and an application thereof, including the following steps,

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

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

[0008] S3. Place the printing paste in S2 on a printing platform, and perform photocuring 3D printing under an ultraviolet laser power of 1000 - 3000 mW / cm 2 , 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 is obtained.

[0009] S4. Add a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene (the content of polyvinylidene fluoride in the block copolymer is 80 w.t.%, the content of polytetrafluoroethylene is 20 w.t.%, purchased from Daikin Fluorochemicals Co., Ltd.) and lithium bis(trifluoromethanesulfonyl)imide to a solvent at a mass ratio of 3.5 - 5.5:1, and stir evenly to obtain a mixed solution B.

[0010] S5. Add barium titanate nanoparticles to the solution B in S4. The barium titanate nanoparticles are 5 - 20 wt% of the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene, and stir evenly to obtain a polymer paste.

[0011] S6. Pour the polymer paste in S5 into the ceramic frame in S3. The mass ratio of the polymer paste to the ceramic frame is 5 - 7.5:5 - 2.5, and then perform vacuum drying at 50 - 70 °C for 24 - 48 h to obtain a high - dielectric flexible - inside - rigid - outside 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 "Preparation and Properties Research of Li 1.5 AI 0.5 Ge 1.5 (PO4)3 Solid - State Electrolytes and Their Batteries").

[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 - phenylpropan - 1 - one, phenylbis(2,4,6 - trimethylbenzoyl)phosphine oxide, and 2 - methyl - 1 - (4 - methylthiophenyl) - 2 - morpholinopropan - 1 - one.

[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 preparation method of the above high-dielectric flexible inside and rigid outside composite solid electrolyte: the inner layer of the composite solid electrolyte is a porous array structure inorganic oxide ceramic electrolyte framework, and the outer layer is a flexible block polymer electrolyte.

[0018] The application of the above composite solid electrolyte: The composite solid electrolyte is applied to the preparation of a lithium metal battery.

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

[0020] 1. By combining the photocuring 3D printing technology and the slurry casting method, a composite solid electrolyte with a flexible outside and rigid inside structure can be obtained. The inorganic oxide ceramic framework in the inner layer acts as a skeleton support, providing good mechanical strength for the composite electrolyte, effectively inhibiting the growth of lithium dendrites. The outer layer of the highly viscoelastic block copolymer of polyvinylidene fluoride and polytetrafluoroethylene realizes stable and tight interfacial contact, improving the electrolyte / electrode interfacial compatibility and cycle stability.

[0021] 2. Barium titanate nanoparticles are introduced as functional fillers into the composite electrolyte system. Due to its high dielectric constant, when placed in an electric field, it will be polarized to generate an internal reverse electric field, thereby effectively promoting the dissociation of lithium salts, increasing the concentration of freely moving lithium ions, increasing the ionic conductivity, and thus improving the ion transport ability of the solid-state lithium metal battery.

[0022] Next, through the drawings and examples, the technical solutions of the present invention will be further described in detail. Description of the Drawings

[0023] Figure 1 It 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 It is a scanning electron microscope image of the high-dielectric flexible inside and rigid outside composite solid electrolyte prepared in Example 1 of the present invention;

[0025] Figure 3 It 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 4AC impedance spectra of the high-dielectric soft-exterior and rigid-interior composite solid electrolyte prepared in Example 4 of the present invention, the high-dielectric integral composite solid electrolyte obtained in Comparative Example 1, and the lanthanum titanate lithium-based high-dielectric soft-exterior and rigid-interior composite solid electrolyte obtained in Comparative Example 3;

[0027] Figure 5 Charge and discharge test curves at 0.5C of the high-dielectric soft-exterior and rigid-interior composite solid electrolyte prepared in Example 4 of the present invention and the soft-exterior and rigid-interior composite solid electrolyte obtained in Comparative Example 2. Detailed implementation mode

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

[0029] The present invention can be more specifically explained by the following examples. The purpose of disclosing the present invention is to protect all changes and improvements within the scope of the present invention. The present invention is not limited to the following examples.

[0030] Example 1

[0031] S1. Add lithium germanium aluminum phosphate ceramic nanoparticles with a volume fraction of 60 vol% to ethoxylated trimethylolpropane triacrylate, and obtain a mixed solution A after stirring evenly.

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

[0033] S3. Place the printing paste in S2 on a printing platform, and perform photocuring 3D printing at an ultraviolet laser power of 1000 mW / cm 2 , a scanning speed of 500 mm / s, and a scanning width of 0.03 mm, and obtain a ceramic framework with a porous array structure after cleaning.

[0034] S4. Add a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonyl)imide to N-methylpyrrolidone according to a mass ratio of 3.5:1, and obtain a mixed solution B after stirring evenly.

[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 the solution B in S4. The barium titanate nanoparticles are 5 wt% of the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene, and obtain a polymer paste after mixing evenly.

[0037] S6. Pour the polymer slurry in S5 into the ceramic framework in S3. The mass ratio of the polymer slurry to the ceramic framework is 5:5. Then, perform vacuum drying at 50 °C for 48 h to obtain a high-dielectric soft-on-the-outside-and-rigid-on-the-inside composite solid electrolyte.

[0038] As Figure 1 shown, the porous array composite solid electrolyte has a pore structure with uniform distribution, which can serve as the skeleton of the composite electrolyte and provide sufficient space for filling the polymer electrolyte slurry. As Figure 2 shown, the composite solid electrolyte obtained in this example has a relatively flat and uniform surface morphology.

[0039] Example 2

[0040] S1. Add lithium germanium aluminum phosphate ceramic nanoparticles with a volume fraction of 70 vol% to polyethylene glycol diacrylate, and stir evenly to obtain a mixed solution A.

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

[0042] S3. Place the printing slurry in S2 on a printing platform, and perform photocuring 3D printing at an ultraviolet laser power of 1500 mW / cm 2 , a scanning speed of 1000 mm / s, and a scanning width of 0.04 mm. After cleaning, a ceramic framework with a porous array structure is obtained.

[0043] S4. Add a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonyl)imide to N,N-dimethylformamide according to a mass ratio of 4:1, and stir evenly to obtain a mixed solution B.

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

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

[0046] S6. Pour the polymer slurry in S5 into the ceramic framework in S3. The mass ratio of the polymer slurry to the ceramic framework is 6:4. Then, perform vacuum drying at 55 °C for 40 h to obtain a high-dielectric soft-on-the-outside-and-rigid-on-the-inside composite solid electrolyte.

[0047] Example 3

[0048] S1. Add lithium aluminum germanium phosphate ceramic nanoparticles with a volume fraction of 75 vol% to butyl acrylate, and obtain a mixed solution A after stirring evenly.

[0049] S2. Add 2-methyl-1-(4-methylthiophenyl)-2-morpholin-1-one to the mixed solution A in S1 according to a mass ratio of 1:100 with butyl acrylate, and obtain a printing paste after stirring evenly.

[0050] S3. Place the printing paste in S2 on a printing platform, and perform photocuring 3D printing under an ultraviolet laser power of 2000 mW / cm 2 , a scanning speed of 1500 mm / s, and a scanning width of 0.05 mm. After cleaning, a ceramic framework with a porous array structure is obtained.

[0051] S4. Add a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonyl)imide to N,N-dimethylacetamide according to a mass ratio of 4.5:1, and obtain a mixed solution B after stirring evenly.

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

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

[0054] S6. Pour the polymer paste in S5 into the ceramic framework in S3. The mass ratio of the polymer paste to the ceramic framework is 7:3. Then, perform vacuum drying at 60 °C for 32 h to obtain a high-dielectric flexible inside and rigid outside composite solid electrolyte.

[0055] Example 4

[0056] S1. Add lithium aluminum germanium phosphate ceramic nanoparticles with a volume fraction of 80 vol% to ethoxylated trimethylolpropane triacrylate, and obtain a mixed solution A after stirring evenly.

[0057] S2. Add 2-hydroxy-2-methyl-1-phenylpropan-1-one to the mixed solution A in S1 according to a mass ratio of 1:100 with ethoxylated trimethylolpropane triacrylate, and obtain a printing paste after stirring evenly.

[0058] S3. Place the printing paste in S2 on a printing platform, and perform photocuring 3D printing under an ultraviolet laser power of 3000 mW / cm 2 , a scanning speed of 2000 mm / s, and a scanning width of 0.07 mm. After cleaning, a ceramic framework with a porous array structure is obtained.

[0059] S4. Add the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonyl)imide into N-methylpyrrolidone at a mass ratio of 5.5:1, and stir evenly to obtain a 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 into the solution B in S4. The barium titanate nanoparticles are 20 wt% of the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene, and stir evenly to obtain a polymer slurry.

[0062] S6. Pour the polymer slurry in S5 into the ceramic frame in S3. The mass ratio of the polymer slurry to the ceramic frame is 7.5:2.5, and then carry out vacuum drying at 70 °C for 24 h to obtain a high-dielectric flexible inside and rigid outside composite solid electrolyte.

[0063] Comparative Example 1

[0064] S1. Add the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonyl)imide into N-methylpyrrolidone at a mass ratio of 5.5:1, and stir evenly to obtain a 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 into the solution A in S1. The barium titanate nanoparticles are 20 wt% of the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene, and stir evenly to obtain a polymer slurry.

[0067] S3. Add lithium germanium phosphate aluminum ceramic nanoparticles into the polymer slurry in S2. The lithium germanium phosphate aluminum ceramic nanoparticles are 20 wt% of the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene, and stir evenly to obtain an electrolyte mixed slurry.

[0068] S4. Pour the electrolyte mixed slurry in S3 onto a polytetrafluoroethylene mold, and then carry out vacuum drying at 70 °C for 24 h to obtain a high-dielectric integral composite solid electrolyte.

[0069] As Figure 3 shown, some protrusions of ceramic nanoparticles can be seen on the surface of the composite solid electrolyte prepared in this comparative example, and the overall balance is poor.

[0070] Comparative Example 2

[0071] S1. Add lithium germanium aluminum phosphate ceramic nanoparticles with a volume fraction of 80 vol% into ethoxylated trimethylolpropane triacrylate, and obtain a mixed solution A after stirring evenly.

[0072] S2. Add 2-hydroxy-2-methyl-1-phenylpropanone into the mixed solution A in S1 according to the mass ratio of 1:100 to ethoxylated trimethylolpropane triacrylate, and obtain a printing paste after stirring evenly.

[0073] S3. Place the printing paste in S2 on a printing platform, and perform photocuring 3D printing under the conditions of an ultraviolet laser power of 3000 mW / cm 2 , a scanning speed of 2000 mm / s, and a scanning width of 0.07 mm. After cleaning, a ceramic framework with a porous array structure is obtained.

[0074] S4. Add a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonyl)imide into N-methylpyrrolidone according to the mass ratio of 5.5:1, and obtain a polymer paste after stirring evenly.

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

[0076] S5. Pour the polymer paste in S4 into the ceramic framework in S3. The mass ratio of the polymer paste to the ceramic framework is 7.5:2.5. Then, perform vacuum drying at 70 °C for 24 h to obtain a flexible-on-the-outside and rigid-on-the-inside composite solid electrolyte.

[0077] Comparative Example 3

[0078] S1. Add lithium lanthanum titanate ceramic nanoparticles with a volume fraction of 80 vol% into ethoxylated trimethylolpropane triacrylate, and obtain a mixed solution A after stirring evenly.

[0079] S2. Add 2-hydroxy-2-methyl-1-phenylpropanone into the mixed solution A in S1 according to the mass ratio of 1:100 to ethoxylated trimethylolpropane triacrylate, and obtain a printing paste after stirring evenly.

[0080] S3. Place the printing paste in S2 on a printing platform, and perform photocuring 3D printing under the conditions of an ultraviolet laser power of 3000 mW / cm 2 , a scanning speed of 2000 mm / s, and a scanning width of 0.07 mm. After cleaning, a ceramic framework with a porous array structure is obtained.

[0081] S4. Add a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonyl)imide into N-methylpyrrolidone according to the mass ratio of 5.5:1, and obtain a mixed solution B after stirring evenly.

[0082] The mass ratio of N-methylpyrrolidone and 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 the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene. After mixing evenly, a polymer slurry is obtained.

[0084] S6. Pour the polymer slurry in S5 into the ceramic frame in S3. The mass ratio of the polymer slurry to the ceramic frame is 7.5:2.5. Subsequently, vacuum drying is carried out at 70 °C for 24 h to obtain a lithium lanthanum titanate-based high-dielectric flexible-on-the-outside-and-rigid-on-the-inside composite solid electrolyte.

[0085] Performance testing of the composite solid electrolytes prepared in each example:

[0086] Assemble the high-dielectric flexible-on-the-outside-and-rigid-on-the-inside composite solid electrolyte (with a thickness of 200 μm) obtained in Example 4 with a lithium iron phosphate positive electrode slurry and a lithium metal negative electrode into CR2032 battery one.

[0087] Assemble the high-dielectric integrated composite solid electrolyte obtained in Comparative Example 1 and Comparative Example 3, and the lithium lanthanum titanate-based high-dielectric flexible-on-the-outside-and-rigid-on-the-inside composite solid electrolyte with a lithium iron phosphate positive electrode slurry and a lithium metal negative electrode into CR2032 battery two and CR2032 battery five respectively.

[0088] Assemble the high-dielectric flexible-on-the-outside-and-rigid-on-the-inside composite solid electrolyte obtained in Example 4 with a lithium metal negative electrode into CR2032 symmetric battery three.

[0089] Assemble the flexible-on-the-outside-and-rigid-on-the-inside composite solid electrolyte obtained in Comparative Example 2 with a lithium metal negative electrode into CR2032 symmetric battery four.

[0090] Use a Bio-Logic VSP electrochemical workstation to perform AC impedance testing on CR2032 symmetric battery one and CR2032 symmetric battery two. The test frequency range is 0.1 - 200 KHz. The results are as Figure 4 shown. It can be seen that the interfacial impedance of the high-dielectric integrated composite solid electrolyte in Comparative Example 1 is 413 Ω, and the interfacial impedance of the lithium lanthanum titanate-based high-dielectric flexible-on-the-outside-and-rigid-on-the-inside composite solid electrolyte in Comparative Example 3 is 376 Ω. In contrast, the high-dielectric flexible-on-the-outside-and-rigid-on-the-inside composite solid electrolyte in Example 4 exhibits a lower interfacial impedance of 128 Ω. This may be because Ti in lithium lanthanum titanate 4+ will be reduced to Ti when contacting the lithium metal negative electrode 3+ , resulting in the formation of a high-impedance compound at the interface and causing a significant increase in the interfacial resistance.

[0091] Using the CT-4000 Neware battery tester, constant current charge and discharge tests were performed on CR2032 battery three and CR2032 battery four in the voltage range of 2.5 - 3.8V, and the results are as Figure 5 shown. It can be seen that the initial discharge specific capacity of the soft outer and rigid inner composite solid electrolyte of CR2032 battery four in Comparative Example 2 is 146.8 mA h / g, and the capacity retention rate after 100 cycles is 52.1%, and the Coulomb efficiency is 96.5%; in contrast, the initial discharge specific capacity of the high-dielectric soft outer and rigid inner composite solid electrolyte of CR2032 symmetric battery three in Example 4 is 164.6 mA h / g, and it has a higher capacity retention rate (93.6%) after 100 cycles, and the Coulomb efficiency is stable at 99.0%, showing 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 are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a high-dielectric flexible outer and rigid inner composite solid electrolyte, characterized in that: including the following steps, S1. Add inorganic oxide ceramic nanoparticles with a volume fraction of 60 - 80 vol% into a photosensitive resin, and after stirring evenly, obtain a mixed solution A; S2. Add a photoinitiator into the mixed solution A in S1 according to a mass ratio of 0.5 - 2:100 to the photosensitive resin, and after stirring evenly, obtain a printing paste; S3. Place the printing slurry in S2 on the printing platform, and under the conditions that the ultraviolet laser power is 1000 - 3000 mW / cm 2 , the scanning speed is 500 - 2000 mm / s, and the scanning width is 0.03 - 0.07 mm, perform photocuring 3D printing. After cleaning, a ceramic frame with a porous array structure is obtained; S4. Add a block copolymer of polyvinylidene fluoride and polytetrafluoroethylene and lithium bis(trifluoromethanesulfonyl)imide into a solvent according to a mass ratio of 3.5 - 5.5:1, and after stirring evenly, obtain a mixed solution B; S5. Add barium titanate nanoparticles into the solution B in S4, where the barium titanate nanoparticles are 5 - 20 wt% of the block copolymer of polyvinylidene fluoride and polytetrafluoroethylene, and after mixing evenly, obtain a polymer paste; S6. Pour the polymer paste in S5 into the ceramic framework in S3, where the mass ratio of the polymer paste to the ceramic framework is 5 - 7.5:5 - 2.5, and then carry out vacuum drying at 50 - 70 °C for 24 - 48 h to obtain a high-dielectric soft-on-the-outside-and-rigid-on-the-inside composite solid electrolyte.

2. The preparation method of the high-dielectric soft-on-the-outside-and-rigid-on-the-inside composite solid electrolyte according to claim 1, wherein: In S1, the inorganic oxide ceramic nanoparticles are lithium germanium aluminophosphate ceramic nanoparticles.

3. The preparation method of the high-dielectric soft-external and rigid-internal 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 preparation method of the high-dielectric soft-on-the-outside-and-rigid-on-the-inside 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-phenylpropan-1-one, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one.

5. The preparation method of the high-dielectric soft-on-the-outside-and-rigid-on-the-inside 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 preparation method of the high-dielectric flexible outer and rigid inner 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 soft-external and rigid-internal 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-structured inorganic oxide ceramic electrolyte framework, and the outer layer is a flexible block polymer electrolyte.

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

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