A 3D-printed gradient-distributed composite solid electrolyte, its preparation method and application

Abstract

This invention discloses a 3D-printed gradient-distributed composite solid electrolyte, its preparation method, and its application, belonging to the field of solid-state lithium metal battery technology. First, cellulose acetate is added to a solvent and stirred thoroughly at a certain temperature. Second, lithium bis(trifluoromethanesulfonyl)imide is added to the above mixed solution and stirred evenly. Subsequently, photosensitive resin and initiator are added to the above solution and stirred evenly. Finally, fast-ion conductor ceramic nanoparticles are added to the above mixed solution and stirred evenly to obtain the final 3D printing slurry. Photopolymerization printing is then performed to obtain the 3D-printed gradient-distributed composite solid electrolyte. This invention effectively enhances interfacial compatibility, reduces interfacial resistance, and promotes uniform lithium deposition. The side rich in fast-ion conductor ceramic nanoparticles contacts the positive electrode, which can improve the mechanical strength and high-voltage resistance of the electrolyte, inhibit lithium dendrite penetration, and thus effectively improve the cycle life of solid-state lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of solid-state lithium metal battery technology, and in particular to a 3D-printed gradient distribution composite solid electrolyte, its preparation method, and its application. Background Technology

[0002] With the widespread application of energy storage technology in new energy vehicles and portable electronic devices, building high-efficiency energy storage systems has become an important direction for industrial upgrading. Lithium metal anode materials, due to their excellent theoretical performance parameters (3860 mAh / g specific capacity and low redox potential relative to the standard hydrogen electrode of -3.04 V), have become a key material system for breaking through the energy density bottleneck of existing lithium batteries.

[0003] It is worth noting that traditional liquid electrolyte systems suffer from technical challenges such as poor thermal stability and numerous interfacial side reactions. Solid-state lithium metal battery systems, which combine high safety and high energy density, are becoming a cutting-edge research direction in the field of energy storage materials. Currently, in solid-state lithium metal batteries, traditional layered oxide cathodes are prone to interfacial side reactions with the solid electrolyte under high voltage, and face challenges such as poor ion / electron transport kinetics and structural stress caused by volume expansion. Lithium metal anodes, on the other hand, suffer from uncontrolled lithium dendrite growth during cycling, interfacial instability of the solid electrolyte interface due to interfacial side reactions, and volume deformation and interfacial contact failure caused by repeated lithium metal deposition / stripping. These challenges collectively limit the cycle life and safety of solid-state batteries.

[0004] As a core component of solid-state battery technology, solid electrolyte systems mainly encompass three categories: organic polymers, inorganic ceramics, and their composite materials. Among these, polymer electrolytes have attracted attention due to their excellent interfacial compatibility and molding / processing characteristics; however, their inherent low ion mobility and insufficient mechanical modulus remain unresolved. Inorganic ceramic electrolytes exhibit high room-temperature ionic conductivity and excellent thermal stability; however, their inherent brittleness makes it difficult to control the stress at the electrode / electrolyte interface, easily leading to interfacial contact failure during cycling. Therefore, the combination of rigid ceramics and flexible polymers can mutually compensate for each other, mitigating interfacial problems and improving ionic conductivity. Currently, multilayer composite electrolytes have been reported to enhance the oxidation resistance of high-voltage cathodes, suppress dendrite formation in lithium anodes, and ensure tight interfacial contact, thus simultaneously addressing the challenges of both the positive and negative electrodes in solid-state lithium metal batteries. However, the fabrication process of multilayer electrolytes is complex, thickness controllability is poor, and the integration of multiple structures may introduce new interfacial problems.

[0005] Photopolymerization 3D printing technology, with its high-precision layer-by-layer construction characteristics, can achieve precise control and integrated molding of the spatial gradient arrangement and microstructure of multi-component materials during the preparation of solid electrolytes. It not only ensures the continuity of ion transport channels, but also controls the interaction and contact mode between electrolyte and electrode through concentration gradient. It has potential advantages in improving the oxidation resistance of the positive electrode and the interface problem of the negative electrode of solid lithium metal battery, and provides an efficient preparation route for the preparation of high-performance composite solid electrolytes. Summary of the Invention

[0006] The purpose of this invention is to provide a 3D-printed gradient distribution composite solid electrolyte, its preparation method, and its application. The obtained 3D-printed gradient distribution composite solid electrolyte, when used in battery fabrication, has its cellulose acetate-rich side in contact with the lithium metal anode, which can effectively enhance interfacial compatibility, reduce interfacial resistance, and promote uniform lithium deposition. The side rich in fast ion conductor ceramic nanoparticles is in contact with the cathode, which improves the mechanical strength and high voltage resistance of the electrolyte, inhibits lithium dendrite penetration, and effectively improves the cycle life of the battery.

[0007] To achieve the above objectives, this invention provides a method for preparing a 3D-printed gradient distribution composite solid electrolyte, which includes the following steps:

[0008] S1. Add cellulose acetate to the solvent and stir thoroughly. Add lithium bis(trifluoromethanesulfonylimide), photosensitive resin and initiator and stir evenly to obtain a mixed solution. Add lithium aluminum germanium phosphate ceramic nanoparticles and cellulose acetate at a mass ratio of 1:3 to the mixed solution and stir evenly to obtain 3D printing slurry A.

[0009] S2. Add lithium aluminum germanium phosphate ceramic nanoparticles and cellulose acetate at a mass ratio of 1:1 to the mixed solution and stir evenly to obtain 3D printing slurry B;

[0010] S3. Add lithium aluminum germanium phosphate ceramic nanoparticles and cellulose acetate at a mass ratio of 3:1 to the mixed solution and stir evenly to obtain 3D printing slurry C;

[0011] S4. Spread the 3D printing paste A from step S1 onto the printing platform and perform photocuring 3D printing.

[0012] S5. Spread the 3D printing paste B from step S2 onto the surface of the printed component obtained in step S4 and perform photocuring 3D printing.

[0013] S6. Spread the 3D printing paste C from step S3 onto the surface of the printed component obtained in step S5 and perform photocuring 3D printing.

[0014] S7. Clean and dry the 3D printed component obtained in step S6 to obtain a 3D printed gradient distribution composite solid electrolyte.

[0015] As a preferred embodiment of the preparation method of the 3D printed gradient distribution composite solid electrolyte of the present invention: In step S1, 20-30% by mass of cellulose acetate is added to the solvent and stirred thoroughly at 50-80 °C; lithium bis(trifluoromethanesulfonyl)imide is added at a mass ratio of 1:10-12 to cellulose acetate and stirred evenly; photosensitive resin and initiator are added and stirred evenly to obtain a mixed solution, wherein the mass ratio of photosensitive resin to initiator is 120-150:1, and the photosensitive resin accounts for 5-10% of the mass of the mixed solution.

[0016] As a preferred embodiment of the preparation method of the 3D printed gradient distribution composite solid electrolyte of the present invention: in step S1, the cellulose acetate is monoacetate cellulose with an acetyl substitution degree of 0.6.

[0017] As a preferred embodiment of the preparation method of the 3D printed gradient distribution composite solid electrolyte of the present invention: in step S1, the photosensitive resin is trimethylolpropane triacrylate.

[0018] As a preferred embodiment of the preparation method of the 3D printed gradient distribution composite solid electrolyte of the present invention: in step S1, the initiator is azobisisobutyronitrile.

[0019] As a preferred embodiment of the preparation method of the 3D printed gradient distribution composite solid electrolyte of the present invention: in step S1, the solvent is N-methylpyrrolidone and / or N,N-dimethylformamide.

[0020] As a preferred embodiment of the preparation method of the 3D printed gradient distribution composite solid electrolyte of the present invention: in step S4, the ultraviolet laser power of the photopolymerization 3D printing is 3000~4000 mW / cm 2 The scanning speed is 300~500mm / s, and the scanning width is 0.02~0.03 mm.

[0021] The present invention also provides a composite solid electrolyte prepared by the method for preparing the 3D printed gradient distribution composite solid electrolyte, wherein the composite solid electrolyte has a gradient distribution structure, which is rich in cellulose acetate on the side near the negative electrode and rich in fast ion conductor ceramic nanoparticles on the side near the positive electrode.

[0022] Applications of the aforementioned composite solid electrolyte: This composite solid electrolyte is used in the preparation of solid lithium metal batteries.

[0023] Therefore, the beneficial effects of the present invention are as follows:

[0024] 1. Photopolymerization 3D printing technology can realize the integrated forming of composite solid electrolytes and achieve precise control of electrolyte layer thickness and 3D structure. It effectively avoids new interface problems caused by the integration of multiple structures. At the same time, the whole process is simple to operate and solves the problems of complex preparation process and poor thickness control of traditional integrated multilayer electrolytes.

[0025] 2. The gradient distribution structure can simultaneously alleviate the problems faced by the positive and negative electrodes of solid-state lithium metal batteries. When assembling batteries using composite solid electrolytes, contacting the side rich in cellulose acetate with the lithium metal negative electrode can effectively enhance interfacial compatibility, reduce interfacial resistance, and promote uniform lithium deposition. Contacting the side rich in fast ion conductor ceramic nanoparticles with the positive electrode can improve the mechanical strength and high voltage resistance of the electrolyte, suppress lithium dendrite penetration, and thus jointly improve the cycle life of solid-state lithium batteries.

[0026] 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

[0027] Figure 1 This is a flowchart illustrating the preparation process of the 3D-printed gradient distribution solid electrolyte in this invention.

[0028] Figure 2 This is a schematic diagram of the assembly of the solid-state lithium metal battery in this invention;

[0029] Figure 3 This is a scanning electron microscope image of the gradient distribution composite solid electrolyte prepared in Example 1 of this invention;

[0030] Figure 4 The graphs show the cycling performance of battery 1 (based on the 3D-printed gradient distribution composite solid electrolyte in Example 1), battery 5 (based on the 3D-printed non-gradient composite solid electrolyte in Comparative Example 1), and battery 6 (based on the non-3D-printed gradient distribution composite solid electrolyte in Comparative Example 2) under a 1 C current density condition. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] 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.

[0033] Example 1

[0034] S1. Add 20% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 50 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 5% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:3 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry A.

[0035] S2. Add 20% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 50 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 5% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry B.

[0036] S3. Add 20% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 50 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 5% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 3:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry C.

[0037] S4. Spread the printing paste A from S1 onto the printing platform and perform photopolymerization 3D printing. The ultraviolet laser power is 3000 mW / cm². 2 At a scanning speed of 300 mm / s, the scanning width is 0.02 mm;

[0038] S5. Spread the slurry B from S2 onto the surface of the printed component from S4 and perform photopolymerization 3D printing. The UV laser power is 3000 mW / cm². 2 At a scanning speed of 300 mm / s, the scanning width is 0.02 mm;

[0039] S6. Spread the slurry C from S3 onto the surface of the printed component from S5 and perform photopolymerization 3D printing. The UV laser power is 3000 mW / cm². 2 At a scanning speed of 300 mm / s, the scanning width is 0.02 mm;

[0040] S7. Clean and dry the final 3D printed component to obtain a 3D printed gradient distribution composite solid electrolyte.

[0041] like Figure 3 As shown, the gradient distribution composite solid electrolyte prepared in this embodiment has a relatively smooth, uniform, and dense surface morphology without obvious cracks, indicating that the cellulose acetate and fast ion conductor lithium germanium aluminum phosphate ceramic nanoparticles are mixed uniformly, thereby giving the electrolyte sufficient ability to suppress lithium dendrite growth, reduce the risk of battery short circuit, and improve safety performance.

[0042] Example 2

[0043] S1. Add 23% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 60 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 6% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:3 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry A.

[0044] S2. Add 23% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 60 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 6% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry B.

[0045] S3. Add 23% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 60 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 6% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 3:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry C.

[0046] S4. Spread the printing paste A from S1 onto the printing platform and perform photopolymerization 3D printing. The ultraviolet laser power is 3300 mW / cm². 2 At a scanning speed of 380 mm / s, the scanning width is 0.024 mm;

[0047] S5. Spread the slurry B from S2 onto the surface of the printed component from S4 and perform photopolymerization 3D printing. The UV laser power is 3300 mW / cm². 2 At a scanning speed of 380 mm / s, the scanning width is 0.024 mm;

[0048] S6. Spread the slurry C from S3 onto the surface of the printed component from S5 and perform photopolymerization 3D printing. The UV laser power is 3300 mW / cm². 2 At a scanning speed of 380 mm / s, the scanning width is 0.024 mm;

[0049] S7. Clean and dry the final 3D printed component to obtain a 3D printed gradient distribution composite solid electrolyte.

[0050] Example 3

[0051] S1. Add 27% (w / w) cellulose acetate to the solvent N,N-dimethylformamide and stir thoroughly at 70 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 8% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:3 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry A.

[0052] S2. Add 27% (w / w) cellulose acetate to the solvent N,N-dimethylformamide and stir thoroughly at 70 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 8% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry B.

[0053] S3. Add 27% (w / w) cellulose acetate to the solvent N,N-dimethylformamide and stir thoroughly at 70 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 8% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 3:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry C.

[0054] S4. Spread the printing paste A from S1 onto the printing platform and perform photopolymerization 3D printing. The ultraviolet laser power is 3600 mW / cm². 2 At a scanning speed of 450 mm / s, the scanning width is 0.028 mm;

[0055] S5. Spread the slurry B from S2 onto the surface of the printed component from S4 and perform photopolymerization 3D printing. The UV laser power is 3600 mW / cm². 2 At a scanning speed of 450 mm / s, the scanning width is 0.028 mm;

[0056] S6. Spread the slurry C from S3 onto the surface of the printed component from S5 and perform photopolymerization 3D printing. The UV laser power is 3600 mW / cm². 2 At a scanning speed of 450 mm / s, the scanning width is 0.028 mm;

[0057] S7. Clean and dry the final 3D printed component to obtain a 3D printed gradient distribution composite solid electrolyte.

[0058] Example 4

[0059] S1. Add 30% (w / w) cellulose acetate to the solvent N,N-dimethylformamide and stir thoroughly at 80 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 10% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:3 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry A.

[0060] S2. Add 30% (w / w) cellulose acetate to the solvent N,N-dimethylformamide and stir thoroughly at 80 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 10% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry B.

[0061] S3. Add 30% (w / w) cellulose acetate to the solvent N,N-dimethylformamide and stir thoroughly at 80 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 10% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 3:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry C.

[0062] S4. Spread the printing paste A from S1 onto the printing platform and perform photopolymerization 3D printing. The ultraviolet laser power is 4000 mW / cm². 2 At a scanning speed of 500 mm / s, the scanning width is 0.03 mm;

[0063] S5. Spread the slurry B from S2 onto the surface of the printed component from S4 and perform photopolymerization 3D printing. The UV laser power is 4000 mW / cm². 2 At a scanning speed of 500 mm / s, the scanning width is 0.03 mm;

[0064] S6. Spread the slurry C from S3 onto the surface of the printed component from S5 and perform photopolymerization 3D printing. The UV laser power is 4000 mW / cm². 2 At a scanning speed of 500 mm / s, the scanning width is 0.03 mm;

[0065] S7. Clean and dry the final 3D printed component to obtain a 3D printed gradient distribution composite solid electrolyte.

[0066] Comparative Example 1

[0067] S1. Add 20% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 50 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 5% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry.

[0068] S2. Spread the printing paste from S1 evenly on the printing platform and perform photopolymerization 3D printing, controlling the total printing thickness to be consistent with the example, with an ultraviolet laser power of 3000 mW / cm. 2 At a scanning speed of 300 mm / s, the scanning width is 0.02 mm;

[0069] S3. Clean and dry the final 3D printed component to obtain a 3D printed gradient-distributed composite solid electrolyte.

[0070] Comparative Example 2

[0071] S1. Add 20% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 50 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 5% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:3 to cellulose acetate and stir thoroughly to obtain the final polymerization precursor solution A.

[0072] S2. Add 20% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 50 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 5% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 1:1 to cellulose acetate and stir thoroughly to obtain the final polymerization precursor solution B.

[0073] S3. Add 20% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 50 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above mixed solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 5% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above mixed solution at a mass ratio of 3:1 to cellulose acetate and stir thoroughly to obtain the final polymerization precursor solution C.

[0074] S4. Polymerize the polymerization precursor solution A in S1 under ultraviolet light irradiation to form a film. The reaction time is 30s.

[0075] S5. Spread the polymerization precursor solution B from S2 onto the membrane surface of S4, and carry out the polymerization reaction to form a film under ultraviolet light irradiation for 30 s.

[0076] S6. Spread the polymerization precursor solution C from S3 onto the membrane surface of S5, and carry out the polymerization reaction to form a film under ultraviolet light irradiation for 30 s.

[0077] S7. The final composite membrane is dried to obtain a non-3D printed gradient distribution composite solid electrolyte.

[0078] Methods for verifying the electrochemical performance of composite solid electrolytes:

[0079] Using lithium iron phosphate as the positive electrode slurry and lithium metal as the negative electrode, the 3D-printed gradient distribution composite solid electrolyte prepared in Example 1 was assembled into CR2032 battery one; the 3D-printed gradient distribution composite solid electrolyte prepared in Example 2 was assembled into CR2032 battery two; the 3D-printed gradient distribution composite solid electrolyte prepared in Example 3 was assembled into CR2032 battery three; the 3D-printed gradient distribution composite solid electrolyte prepared in Example 4 was assembled into CR2032 battery four; the 3D-printed non-gradient composite solid electrolyte prepared in Comparative Example 1 was assembled into CR2032 battery five; and the non-3D-printed gradient distribution composite solid electrolyte prepared in Comparative Example 2 was assembled into CR2032 battery six. The constant current charge-discharge curves of batteries one, two, three, four, five, and six were tested using a CT-4000 Newway battery analyzer, with a voltage range of 2.5-3.8 V.

[0080] Table 1 shows a comparison of the cycle performance of battery 1 based on Example 1, battery 2 based on Example 2, battery 3 based on Example 3, battery 4 based on Example 4, battery 5 based on Comparative Example 1, and battery 6 based on Comparative Example 1 under a 1 C current density condition.

[0081] Table 1

[0082]

[0083] To further and more clearly demonstrate the impact of gradient structure design and 3D printing technology on battery cycle performance, Figure 4 The sequential performance charts for batteries one, five, and six are listed, starting from... Figure 4 As can be seen, firstly, Battery 1 in Example 1 exhibits better cycle stability and coulombic efficiency compared to Battery 5 in Comparative Example 1. Specifically, the Battery 1 system, based on a 3D-printed gradient-distributed composite solid electrolyte, achieved an initial discharge specific capacity of 163.6 mA h / g, and maintained a capacity of 157.7 mA h / g after 100 complete cycles (capacity retention rate of 96.4%). Its average coulombic efficiency remained stable at a high level of 99.1%, fully verifying the stability of the material structure. In contrast, the Battery 5 system, based on a 3D-printed non-gradient composite solid electrolyte, had an initial discharge specific capacity of 154.5 mA h / g, but after the same cycle test, its capacity plummeted to 103.7 mA h / g (capacity retention rate of 67.1%), with an average coulombic efficiency of 98.2%, indicating a rapid decline in electrochemical performance. The above comparative experiments demonstrate the crucial role of gradient structure design in improving the electrochemical stability of batteries.

[0084] Furthermore, Battery 1 in Example 1 exhibits superior cycle stability and coulombic efficiency compared to Battery 6 in Comparative Example 2: the initial discharge specific capacity of Battery 6, based on a non-3D-printed gradient composite solid electrolyte, was only 149.2 mAh / g, and after the same cycle test, the capacity plummeted to 90.3 mA h / g (capacity retention of 60.5%), with an average coulombic efficiency of 93.6%, indicating a significant decline in electrochemical performance. This result verifies the crucial role of 3D printing technology in improving the cycle stability of composite solid electrolytes compared to traditional composite processes.

[0085] In this invention, the degree of acetyl substitution in cellulose acetate affects the mechanical properties and ion transport performance of the solid electrolyte. The preferred degree of acetyl substitution in cellulose acetate is 0.6. If the substitution is too high, the interactions between the cellulose chains will be too loose, affecting mechanical properties and indirectly impacting the stability of ion transport. If the substitution is too low, the dense molecular chains and strong hydrogen bond network in the cellulose acetate molecule will reduce Li⁺ transport kinetics and processability due to the presence of numerous hydroxyl groups. Therefore, selecting a suitable degree of acetyl substitution is essential for maintaining both mechanical properties and stability.

[0086] Meanwhile, the selection of azobisisobutyronitrile (AIBN) is also crucial in this invention. AIBN ensures that the polymerization reaction completes within a suitable timeframe. If the initiator's reaction rate is too fast, the polymerization reaction becomes overly vigorous, leading to localized overheating, which in turn affects the uniformity and performance of the solid electrolyte. The type of initiator also affects the molecular weight distribution of the polymer. Different initiators generate free radicals with varying activities during polymerization, thus influencing the growth and termination of polymer chains. AIBN generates relatively uniform polymer chains during polymerization, thereby improving the mechanical properties and ionic conductivity of the solid electrolyte.

[0087] 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 gradient-distributed composite solid electrolyte using 3D printing, characterized in that: Includes the following steps, S1. Add 23% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 60 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the solution obtained above at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the solution above and stir until homogeneous, wherein the photosensitive resin accounts for 6% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the solution above at a mass ratio of 1:3 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry A. S2. Add 23% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 60 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 6% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above solution at a mass ratio of 1:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry B. S3. Add 23% (w / w) cellulose acetate to the solvent N-methylpyrrolidone and stir thoroughly at 60 °C. Add lithium bis(trifluoromethanesulfonyl)imide to the above solution at a mass ratio of 1:10 to cellulose acetate and stir until homogeneous. Add the photosensitive resin trimethylolpropane triacrylate and the initiator azobisisobutyronitrile at a mass ratio of 150:1 to the above solution and stir until homogeneous, wherein the photosensitive resin accounts for 6% of the solution system. Add the fast ion conductor lithium aluminum germanium phosphate ceramic nanoparticles to the above solution at a mass ratio of 3:1 to cellulose acetate and stir thoroughly to obtain the final 3D printing slurry C. S4. Spread the printing paste A from S1 onto the printing platform and perform photopolymerization 3D printing. The ultraviolet laser power is 3300mW / cm². 2 At a scanning speed of 380 mm / s, the scanning width is 0.024 mm; S5. Spread the slurry B from S2 onto the surface of the printed component from S4 and perform photopolymerization 3D printing. The UV laser power is 3300 mW / cm². 2 At a scanning speed of 380 mm / s, the scanning width is 0.024 mm; S6. Spread the slurry C from S3 onto the surface of the printed component from S5 and perform photopolymerization 3D printing. The UV laser power is 3300 mW / cm². 2 At a scanning speed of 380 mm / s, the scanning width is 0.024 mm; S7. Clean and dry the 3D printed component obtained in the above steps to obtain a 3D printed gradient-distributed composite solid electrolyte. In S1, the cellulose acetate is monoacetate cellulose with an acetyl substitution degree of 0.6.

Images