A 3D printed multi-layer composite all-solid-state electrolyte membrane and its preparation method

Abstract

The present invention discloses a 3D printed multilayer composite all-solid-state electrolyte membrane and a preparation method thereof, belonging to the field of all-solid-state electrolyte technology. The preparation method of the present invention comprises the following steps: (1) solution premixing: mixing a photosensitive resin, an aprotic polar solution, an inorganic filler, a photoinitiator and a lithium salt to obtain a mixed solution; (2) preparation of slurry A and slurry B: taking the mixed solution, adding polyvinylidene fluoride and polyethylene oxide respectively, after ultrasonic treatment, performing oil bath heating to obtain slurry A and slurry B respectively; (3) preparation of electrolyte membrane: pouring slurry A and slurry B into the printing tank of a 3D printer in sequence for printing, the membrane printed by slurry A serves as the middle interlayer membrane, and the membrane printed by slurry B serves as the top and bottom membranes. After printing is completed, washing and drying are performed to obtain a 3D printed multilayer composite all-solid-state electrolyte membrane. This preparation method effectively suppresses the penetration of lithium dendrites and enhances the overall stability and durability of the membrane.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state electrolytes, and specifically relates to a 3D-printed multi-layer composite all-solid-state electrolyte membrane and a preparation method thereof. Background Art

[0002] UV curing technology has garnered widespread attention in recent years for its rapid prototyping and low energy consumption. SLA and DLP 3D printers can fully leverage this technology. While there are a wide variety of photosensitive resins available for 3D printing, only a handful are currently suitable for battery applications. Applying 3D printing to the development of all-solid-state electrolytes holds great promise. 3D printing can fully meet the individual requirements of all-solid-state electrolytes and may play a key role in certain areas.

[0003] All-solid-state electrolytes are considered an ideal choice for next-generation lithium-ion batteries due to their high energy density, long cycle life, and improved safety compared to traditional liquid electrolytes. Solid polymer electrolytes are generally flexible, allowing for better interfacial contact with electrode materials. However, at room temperature, solid polymer electrolytes typically have low ionic conductivity and insufficient mechanical properties. Ceramic solid electrolytes offer high ionic conductivity at room temperature, along with good interfacial stability and mechanical properties. However, they exhibit high interfacial impedance with electrode materials, leading to volume changes during charge and discharge, which can cause interfacial detachment and void formation, impacting the battery's cycle life. Organic-inorganic composite electrolytes combine the advantages and disadvantages of both types of electrolytes, but their production processes are complex and challenging. Therefore, the development of high-performance organic-inorganic composite solid electrolytes for commercial applications is urgent. Traditional organic-inorganic composite electrolyte membranes are typically single-layer structures. To maintain mechanical properties, they often sacrifice flexibility, resulting in reduced contact area with the positive and negative electrodes, which in turn affects ion conduction efficiency. Furthermore, if the electrolyte membrane is too flexible but insufficiently rigid, it can also pose safety risks such as lithium dendrite penetration. Therefore, in order to maintain good mechanical properties while ensuring a large interface contact area and good ionic conductivity, the use of a multilayer composite electrolyte membrane, that is, covering a layer of flexible electrolyte membrane on the surface of a rigid membrane, is an effective way to solve the above problems.

[0004] As a high-molecular-weight organic compound, photosensitive resin has a high degree of polymerization, which makes it unfavorable for the dissociation of lithium salts. Polar solutions are often added to promote lithium salt dissociation, but this also reduces the resin's degree of polymerization, thus affecting its performance. Purely organic all-solid-state electrolytes have a small electrochemical window, limiting their stable operation at high voltages. Traditionally, ceramic electrolytes have been introduced to improve mechanical properties and expand the electrochemical window. Polyvinylidene fluoride, as a polymer electrolyte, has good chemical and thermal stability, but its poor contact with the positive and negative electrodes limits its application in all-solid-state electrolytes. On the other hand, polyethylene oxide electrolytes have strong conductivity in the molten state and can effectively contact the positive and negative electrode surfaces. However, due to their weak mechanical properties, they are easily pierced by lithium dendrites during cycling, affecting battery safety and life. Therefore, how to prepare composite all-solid-state electrolyte membranes that ensure good mechanical properties while maintaining a large contact area and high ionic conductivity has become a major challenge in the field of solid-state batteries.

[0005] Based on the above, the present invention proposes a 3D printed multi-layer composite all-solid-state electrolyte membrane, which solves the problem of lithium dendrite penetration in single-layer composite electrolyte membranes in traditional methods by rationally optimizing the ratio and structural design of materials at different levels. Summary of the Invention

[0006] In response to the above problems, the present invention provides a 3D-printed multi-layer composite all-solid-state electrolyte membrane and a preparation method thereof. By optimizing the interaction force between the polyethylene oxide molecular chains in the top and bottom membranes, the membrane has a higher ionic conductivity and can contact more active substances, thereby effectively improving the specific capacity of the battery. The middle interlayer of the membrane adopts polyvinylidene fluoride material, and its unique fluorination characteristics give the membrane good mechanical properties and thermal stability, effectively solving the problem of insufficient mechanical strength of the top and bottom membranes, effectively inhibiting the penetration of lithium dendrites, and enhancing the overall stability and durability of the membrane.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for preparing a 3D printed multilayer composite all-solid-state electrolyte membrane comprises the following steps:

[0009] (1) Pre-mixing of the solution: adding a photoinitiator and a lithium salt to an aprotic polar solution, stirring and ultrasonicating them to fully dissolve them, adding a photosensitive resin and mixing them thoroughly, then adding an inorganic filler and stirring and ultrasonicating them again to uniformly disperse them in the solution to obtain a mixed solution; the mass ratio of the photoinitiator, lithium salt, aprotic polar solution, photosensitive resin and inorganic filler is 0.05-0.2:0.5-2:1-4:1:1-4;

[0010] (2) Preparation of slurry A and slurry B: a mixed solution was prepared, polyvinylidene fluoride and polyethylene oxide were added respectively, and after ultrasonic treatment, the mixture was heated in an oil bath to obtain slurry A and slurry B respectively; the mass fraction of polyvinylidene fluoride in the slurry A to the mixed solution was 1 to 4 wt%, and the mass fraction of polyethylene oxide in the slurry B to the mixed solution was 1 to 4 wt%;

[0011] (3) Preparation of electrolyte membrane: Slurry A and slurry B are poured into the printing tank of a 3D printer in sequence for printing. The membrane printed with slurry A serves as the middle interlayer membrane, and the membrane printed with slurry B serves as the top and bottom membranes. After printing, the membrane is washed with a non-proton polar solution and vacuum dried to obtain a 3D printed multilayer composite all-solid-state electrolyte membrane.

[0012] Furthermore, in step (1) and step (3), the aprotic polar solution is one or more of N-methylpyrrolidone, N,N-dimethylformamide, acetonitrile and acetone.

[0013] Furthermore, in step (1), the inorganic filler is composed of an active filler and an inert filler in a mass ratio of 2 to 4:1; the active filler is one or more of lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, lithium aluminum germanium phosphate, lithium lanthanum titanate and tantalum-doped lithium lanthanum zirconium oxide; and the inert filler is one or more of alumina, silica and barium carbonate.

[0014] Furthermore, in step (1), the photosensitive resin is one or more of trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate and ethoxylated pentaerythritol tetraacrylate.

[0015] Furthermore, in step (1), the photoinitiator is trimethylamine dihydrate, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide or 2-hydroxy-2-methylpropiophenone.

[0016] Furthermore, in step (1), the lithium salt is one or more of lithium bis(trifluorosulfonyl)imide, lithium difluorooxalatoborate and lithium perchlorate.

[0017] Furthermore, in step (2), the oil bath heating is heating and stirring at 50-80° C. for 4-6 hours; and the ultrasonic treatment time is 10-20 minutes.

[0018] Furthermore, in step (3), the thickness of the film printed by slurry A is 90-100 μm, and the thickness of the film printed by slurry B is 45-50 μm; and the printing time is 5-10 minutes.

[0019] Furthermore, in step (3), the vacuum drying is performed at 60-80° C. for 10-12 hours.

[0020] A 3D printed multi-layer composite all-solid-state electrolyte membrane prepared by the preparation method described above.

[0021] Preparation principle of the 3D printed multi-layer composite all-solid-state electrolyte membrane of the present invention:

[0022] (1) The mixed solution of the present invention is composed of a photoinitiator, a lithium salt, an aprotic polar solution, a photosensitive resin and an inorganic filler, wherein the photosensitive resin and the photoinitiator are the main raw materials for the preparation of 3D printing slurry. The photoinitiator can absorb the energy of the 3D printer laser and convert it into an excited state, thereby promoting the polymerization of the photosensitive resin monomer. Due to the high degree of polymerization of the photosensitive resin, it does not have ionic conductivity. Therefore, the present invention adds an aprotic polar solution to inhibit excessive polymerization, and at the same time, through its polarity, solvation effect and higher dielectric constant and other characteristics, helps the lithium salt to dissolve, thereby generating a solution with higher ionic conductivity.

[0023] Purely organic all-solid-state electrolytes typically have a small electrochemical window. The introduction of inorganic fillers, consisting of active and inert fillers, can effectively increase the electrolyte's electrochemical window and enhance the toughness of the electrolyte membrane. Because inorganic fillers are dense and prone to sedimentation, an appropriate amount of binder, such as polyvinylidene fluoride or polyethylene oxide, is required to ensure uniformity and stability during the preparation process, avoid precipitation, and maintain the performance of the electrolyte.

[0024] (2) The slurry A of the present invention uses polyvinylidene fluoride as a binder. Polyvinylidene fluoride has good mechanical properties and thermal stability due to its fluorination characteristics. The membrane made from slurry A can serve as a rigid and stable intermediate layer. The high mechanical strength can inhibit the further growth or rupture of lithium dendrites, thereby preventing them from directly penetrating the membrane and causing internal short circuits in the battery. Slurry B uses polyethylene oxide as a binder, and the membranes made from it serve as the top and bottom membranes. The flexible molecular chains of polyethylene oxide can form good contact with the positive and negative electrode surfaces by contacting the surface and adapting to deformation, and can contact more active substances, ensuring that the ion conduction path of the battery is unobstructed, effectively improving the specific capacity of the battery.

[0025] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0026] 1. The multilayer composite all-solid-state electrolyte membrane of the present invention optimizes the interaction between the polyethylene oxide molecular chains in the top and bottom membranes, allowing them to maintain a loose arrangement of molecular chains at lower temperatures. This results in higher ionic conductivity and allows for contact with more active substances, thereby effectively improving the specific capacity of the battery. Furthermore, the membrane's interlayer is made of polyvinylidene fluoride, a material whose unique fluorination properties impart excellent mechanical properties and thermal stability to the membrane. This effectively addresses the issue of insufficient mechanical strength in the top and bottom membranes, effectively inhibits the penetration of lithium dendrites, and enhances the overall stability and durability of the membrane.

[0027] 2. The electrochemical window of the multi-layer composite all-solid electrolyte membrane of the present invention reaches above 5V, and its initial specific capacity is 145.9mAh·g -1 After 100 cycles, the specific capacity is 133.4 mAh g -1 , the specific capacity is reduced by 12.5mAh·g -1 , while the initial specific capacity of the traditional single-layer composite all-solid-state electrolyte membrane is 140.5 mAh g -1 After 100 cycles, the specific capacity is 116.4 mAh g -1 , the specific capacity decreased by 24.1 mAh g -1 Compared with the traditional single-layer composite all-solid-state electrolyte membrane, the multi-layer composite all-solid-state electrolyte membrane of the present invention has better stability.

[0028] 3. The multilayer composite all-solid electrolyte membrane of the present invention is 0.2 mA·cm -2 Compatibility testing was carried out under current density, and no short circuit occurred during the test for 1000 hours, while the traditional single-layer composite all-solid-state electrolyte membrane short-circuited after 350 hours of testing, indicating that the multi-layer composite all-solid-state electrolyte membrane has a smaller overvoltage and a longer cycle life than the single-layer composite all-solid-state electrolyte membrane.

[0029] 4. The present invention uses aprotic polar solutions and inorganic fillers to interfere with the orderly arrangement of polymer chains, inhibit the formation of crystallization nuclei and increase the freedom of chain segment movement, making it more difficult for the polymer to form crystalline regions, thereby reducing crystallinity.

[0030] 5. The polarity of the aprotic polar solution N-methylpyrrolidone, N,N-dimethylformamide and the like used in the present invention is very high, which can provide sufficient electrostatic shielding to reduce the lithium ion (Li + ) and the interaction force between the bis(trifluoromethanesulfonyl)imide ion (TFSI-). This makes it easier for the lithium salt bis(trifluorosulfonyl)imide lithium to dissociate into separate Li + and TFSI-, this dissociation increases the concentration of lithium ions, thereby improving the ionic conductivity of the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of the 3D printed multi-layer composite all-solid-state electrolyte membrane of the present invention.

[0032] Figure 2 This is the LSV diagram of the 3D printed multi-layer composite all-solid-state electrolyte membrane prepared in Example 1.

[0033] Figure 3 These are charge and discharge cycle test diagrams of lithium-ion half-cells assembled with the 3D-printed multi-layer composite all-solid-state electrolyte membrane and the 3D-printed single-layer composite all-solid-state electrolyte membrane prepared in Example 1 and Comparative Example 1, respectively.

[0034] Figure 4 The lithium symmetric battery assembled with the 3D printed multi-layer composite all-solid electrolyte membrane and the 3D printed single-layer composite all-solid electrolyte membrane prepared in Example 1 and Comparative Example 1 was tested at 0.2 mA·cm -2 Compatibility test diagram under current density. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below through examples. These examples are only used to illustrate the present invention and do not limit the scope of protection of the present invention.

[0036] Example 1

[0037] Preparation of 3D printed multilayer composite all-solid-state electrolyte membrane:

[0038] (1) Pre-mixing of the solution: 0.18 g of trimethylamine dihydrate and 1.5 g of lithium bis(trifluorosulfonyl)imide were added to 4 g of N-methylpyrrolidone, stirred at high speed and ultrasonicated until they were fully dissolved and transparent, then 2 g of ethoxylated trimethylolpropane triacrylate was added and mixed thoroughly, and then 3 g of lithium aluminum titanium phosphate and 1 g of aluminum oxide were added and stirred and ultrasonicated again until they were evenly dispersed in the solution to obtain a mixed solution;

[0039] (2) Preparation of slurry A and slurry B: A mixed solution was prepared, polyvinylidene fluoride and polyethylene oxide were added, respectively, and the mixture was ultrasonically treated for 20 min, and then heated in an oil bath at 60°C for 6 h to obtain slurry A and slurry B, respectively; the mass fraction of polyvinylidene fluoride in slurry A to the mixed solution was 2 wt%, and the mass fraction of polyethylene oxide in slurry B to the mixed solution was 2 wt%;

[0040] (3) Preparation of electrolyte membrane: Using the UV curing method, slurry A and slurry B were poured into the printing tank of the 3D printer in turn for printing. The thickness of the membrane printed by slurry A was 100 μm, serving as the middle rigid interlayer, and the thickness of the membrane printed by slurry B was 50 μm, serving as the top and bottom layers. The printing time was 5 min. After printing was completed, the surface slurry was washed off with N-methylpyrrolidone. After vacuum drying at 60°C for 12 h, a 3D printed multilayer composite all-solid-state electrolyte membrane was obtained. Its structural schematic diagram is shown in FIG. Figure 1 As shown. Figure 1 It can be seen that the top and bottom layers of the electrolyte membrane contain flexible polyethylene oxide (PEO) in contact with the positive and negative electrodes, and the middle layer is a rigid structure containing polyvinylidene fluoride (PVDF).

[0041] Example 2

[0042] Preparation of 3D printed multilayer composite all-solid-state electrolyte membrane:

[0043] (1) Pre-mixing of the solution: 0.20 g of trimethylamine dihydrate, 1 g of lithium difluorooxalatoborate, and 0.8 g of lithium perchlorate were added to 4.5 g of N,N-dimethylformamide, stirred at high speed and ultrasonicated to fully dissolve them, and then 1 g of trimethylolpropane triacrylate and 1 g of ethoxypentaerythritol tetraacrylate were added and mixed thoroughly, and then 2.5 g of lithium lanthanum zirconium oxide, 1.5 g of lithium aluminum germanium phosphate, and 1 g of barium carbonate were added and stirred and ultrasonicated again to uniformly disperse them in the solution to obtain a mixed solution;

[0044] (2) Preparation of slurry A and slurry B: A mixed solution was prepared, polyvinylidene fluoride and polyethylene oxide were added, respectively, and ultrasonically treated for 15 min, followed by heating in an oil bath at 80°C for 4 h to obtain slurry A and slurry B, respectively; the mass fraction of polyvinylidene fluoride in slurry A to the mixed solution was 3 wt%, and the mass fraction of polyethylene oxide in slurry B to the mixed solution was 3 wt%;

[0045] (3) Preparation of electrolyte membrane: Using the ultraviolet light curing method, slurry A and slurry B were poured into the printing tank of the 3D printer in turn for printing. The thickness of the membrane printed by slurry A was 90 μm, serving as the middle rigid interlayer, and the thickness of the membrane printed by slurry B was 45 μm, serving as the top and bottom layers. The printing time was 5 min. After printing was completed, the surface slurry was washed off with N-methylpyrrolidone and acetone. After vacuum drying at 80°C for 10 h, a 3D printed multilayer composite all-solid-state electrolyte membrane was obtained.

[0046] Example 3

[0047] Preparation of 3D printed multilayer composite all-solid-state electrolyte membrane:

[0048] (1) Solution premixing: 0.15 g of 2-hydroxy-2-methylpropiophenone and 2.0 g of lithium difluorooxalatoborate were added to a solution of 3 g of N-methylpyrrolidone and 2 g of acetone, and the mixture was stirred at high speed and ultrasonicated to fully dissolve. Then, 2 g of ethoxypentaerythritol tetraacrylate was added and the mixture was fully mixed. Then, 4 g of tantalum-doped lithium lanthanum zirconium oxide, 1 g of silicon dioxide, and 0.5 g of barium carbonate were added and the mixture was stirred and ultrasonicated again to uniformly disperse the mixture in the solution to obtain a mixed solution.

[0049] (2) Preparation of slurry A and slurry B: A mixed solution was prepared, polyvinylidene fluoride and polyethylene oxide were added, respectively, and after ultrasonic treatment for 20 min, the mixture was heated in an oil bath at 60°C for 6 h to obtain slurry A and slurry B, respectively; the mass fraction of polyvinylidene fluoride in slurry A to the mixed solution was 1.5 wt%, and the mass fraction of polyethylene oxide in slurry B to the mixed solution was 1.5 wt%;

[0050] (3) Preparation of electrolyte membrane: Using the ultraviolet curing method, slurry A and slurry B were poured into the printing tank of the 3D printer in turn for printing. The thickness of the membrane printed by slurry A was 100 μm, serving as the middle rigid interlayer, and the thickness of the membrane printed by slurry B was 50 μm, serving as the top and bottom layers. The printing time was 10 min. After printing was completed, the surface slurry was washed off with N,N-dimethylformamide, and the membrane was vacuum dried at 70°C for 10 h to obtain a 3D printed multilayer composite all-solid-state electrolyte membrane.

[0051] Example 4

[0052] Preparation of 3D printed multilayer composite all-solid-state electrolyte membrane:

[0053] (1) Pre-mixing of the solution: 0.22 g of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide and 2.3 g of lithium perchlorate were added to a solution of 3.2 g of N,N-dimethylformamide and 1 g of acetonitrile, and the mixture was stirred at high speed and ultrasonicated to fully dissolve the mixture and become transparent. 2 g of 1,6-hexanediol diacrylate was then added and the mixture was fully mixed. 3 g of lithium lanthanum titanate and 1 g of barium carbonate were then added and the mixture was stirred and ultrasonicated again to uniformly disperse the mixture in the solution to obtain a mixed solution.

[0054] (2) Preparation of slurry A and slurry B: A mixed solution was prepared, polyvinylidene fluoride and polyethylene oxide were added, respectively, and the mixture was ultrasonically treated for 10 min, and then heated in an oil bath at 50°C for 6 h to obtain slurry A and slurry B, respectively; the mass fraction of polyvinylidene fluoride in slurry A to the mixed solution was 2 wt%, and the mass fraction of polyethylene oxide in slurry B to the mixed solution was 2 wt%;

[0055] (3) Preparation of electrolyte membrane: Using the ultraviolet light curing method, slurry A and slurry B were poured into the printing tank of the 3D printer in turn for printing. The thickness of the membrane printed by slurry A was 90 μm, serving as the middle rigid interlayer, and the thickness of the membrane printed by slurry B was 45 μm, serving as the top and bottom layers. The printing time was 5 min. After printing was completed, acetonitrile was used to wash off the surface slurry. After vacuum drying at 60°C for 12 h, a 3D printed multilayer composite all-solid-state electrolyte membrane was obtained.

[0056] Example 5

[0057] Preparation of 3D printed multilayer composite all-solid-state electrolyte membrane:

[0058] (1) Pre-mixing of the solution: 0.25 g of trimethylamine dihydrate, 1 g of lithium bis(trifluorosulfonyl)imide, and 1 g of lithium perchlorate were added to 4.5 g of acetone, stirred at high speed, and ultrasonicated to fully dissolve them in a transparent state. Then, 1.2 g of ethoxylated trimethylolpropane triacrylate and 0.8 g of 1,6-hexanediol diacrylate were added and mixed thoroughly. Then, 2.5 g of lithium lanthanum zirconium oxide, 1.5 g of lithium aluminum germanium phosphate, and 1 g of silicon dioxide were added and stirred again and ultrasonicated to uniformly disperse them in the solution to obtain a mixed solution.

[0059] (2) Preparation of slurry A and slurry B: A mixed solution was prepared, polyvinylidene fluoride and polyethylene oxide were added, respectively, and after ultrasonic treatment for 20 minutes, the mixture was heated in an oil bath at 70°C for 5 hours to obtain slurry A and slurry B, respectively; the mass fraction of polyvinylidene fluoride in slurry A to the mixed solution was 3.5 wt%, and the mass fraction of polyethylene oxide in slurry B to the mixed solution was 3.5 wt%;

[0060] (3) Preparation of electrolyte membrane: Using the ultraviolet light curing method, slurry A and slurry B were poured into the printing tank of the 3D printer in turn for printing. The thickness of the membrane printed by slurry A was 100 μm, serving as the middle rigid interlayer, and the thickness of the membrane printed by slurry B was 50 μm, serving as the top and bottom layers. The printing time was 10 min. After printing was completed, acetone was used to wash off the surface slurry. After vacuum drying at 80°C for 10 h, a 3D printed multilayer composite all-solid-state electrolyte membrane was obtained.

[0061] Example 6

[0062] Preparation of 3D printed multilayer composite all-solid-state electrolyte membrane:

[0063] (1) Solution premixing: 0.3 g of 2-hydroxy-2-methylpropiophenone, 1.5 g of lithium difluorooxalatoborate and 2 g of lithium perchlorate were added to a solution of 2 g of acetonitrile and 3 g of acetone, and the mixture was stirred at high speed and ultrasonicated until the mixture was fully dissolved and transparent. Then, 2 g of ethoxypentaerythritol tetraacrylate was added and the mixture was fully mixed. Then, 4 g of lithium aluminum germanium phosphate, 1 g of aluminum oxide and 0.5 g of bismuth were added and the mixture was stirred and ultrasonicated again until the mixture was uniformly dispersed in the solution to obtain a mixed solution.

[0064] (2) Preparation of slurry A and slurry B: A mixed solution was prepared, polyvinylidene fluoride and polyethylene oxide were added, respectively, and the mixture was ultrasonically treated for 15 min, and then heated in an oil bath at 80°C for 4 h to obtain slurry A and slurry B, respectively; the mass fraction of polyvinylidene fluoride in slurry A to the mixed solution was 2 wt%, and the mass fraction of polyethylene oxide in slurry B to the mixed solution was 2 wt%;

[0065] (3) Preparation of electrolyte membrane: Using the ultraviolet light curing method, slurry A and slurry B were poured into the printing tank of the 3D printer in turn for printing. The thickness of the membrane printed by slurry A was 90 μm, serving as the middle rigid interlayer, and the thickness of the membrane printed by slurry B was 45 μm, serving as the top and bottom layers. The printing time was 5 min. After printing was completed, the surface slurry was washed off with N-methylpyrrolidone, and after vacuum drying at 60°C for 12 h, a 3D printed multilayer composite all-solid-state electrolyte membrane was obtained.

[0066] Comparative Example 1

[0067] Preparation of 3D printed single-layer composite all-solid-state electrolyte membrane:

[0068] (1) Pre-mixing of the solution: 0.18 g of trimethylamine dihydrate and 1.5 g of lithium bis(trifluorosulfonyl)imide were added to 4 g of N-methylpyrrolidone, stirred at high speed and ultrasonicated until they were fully dissolved and transparent, then 2 g of ethoxylated trimethylolpropane triacrylate was added and mixed thoroughly, and then 3 g of lithium aluminum titanium phosphate and 1 g of aluminum oxide were added and stirred and ultrasonicated again until they were evenly dispersed in the solution to obtain a mixed solution;

[0069] (2) Preparation of single-layer composite electrolyte membrane slurry: Take the mixed solution, add polyvinylidene fluoride, ultrasonically treat for 15 minutes, and then heat in an oil bath at 80°C for 4 hours to obtain a single-layer composite all-solid-state electrolyte membrane slurry; the mass fraction of polyvinylidene fluoride in the mixed solution in the single-layer composite all-solid-state electrolyte membrane slurry is 2 wt%.

[0070] (3) Preparation of electrolyte membrane: Using the ultraviolet curing method, a single-layer composite all-solid-state electrolyte membrane slurry was poured into the printing tank of a 3D printer for printing. The thickness of the printed membrane was 200 μm. After printing, the surface slurry was washed off with N-methylpyrrolidone. After vacuum drying at 60°C for 12 hours, a 3D printed single-layer composite all-solid-state electrolyte membrane was obtained.

[0071] Material performance analysis

[0072] The performance of the 3D printed multilayer composite all-solid electrolyte membrane (denoted as PEO / PVDF / PEO) of Example 1 was analyzed. The multilayer composite all-solid electrolyte membrane was used as a positive electrode with a gasket of 15.8 mm in diameter and a negative electrode with a lithium sheet. The electrochemical window was tested by linear sweep voltammetry (LSV). The results are as follows: Figure 2 As shown. Figure 2 It can be seen that the electrochemical window of the multilayer composite all-solid-state electrolyte membrane reaches above 5V.

[0073] The 3D printed multi-layer composite all-solid electrolyte membrane of Example 1 and the 3D printed single-layer composite all-solid electrolyte membrane of Comparative Example 1 (denoted as PVDF) were further assembled into batteries. The method was as follows: in an argon-filled glove box, a lithium iron phosphate (LFP) positive electrode sheet, an all-solid electrolyte membrane, and a lithium sheet were assembled into a CR2032 button cell. The performance of the CR2032 button cell was then tested at 60°C. The charge and discharge cycle test diagram of the CR2032 button cell is shown in the figure below. Figure 3 As shown. Figure 3 It can be seen that under the same active material and 0.5C charge and discharge rate, the initial specific capacity of the multilayer composite all-solid electrolyte membrane is 145.9mAh·g -1 After 100 cycles, the specific capacity is 133.4 mAh g -1 , the specific capacity is reduced by 12.5mAh·g -1 The initial specific capacity of the single-layer composite all-solid-state electrolyte membrane is 140.5 mAh g -1 After 100 cycles, the specific capacity is 116.4 mAh g -1 , the specific capacity decreased by 24.1 mAh g -1 , and its specific capacity change is greater than that of the multilayer composite all-solid-state electrolyte membrane. This shows that compared with the single-layer composite all-solid-state electrolyte membrane, the multilayer composite all-solid-state electrolyte membrane has better stability and its stability has been effectively improved.

[0074] The 3D printed multi-layer composite all-solid electrolyte membrane of Example 1 and the 3D printed single-layer composite all-solid electrolyte membrane of Comparative Example 1 were assembled into lithium symmetrical batteries, and the batteries were tested at 0.2 mA·cm -2 Compatibility test under current density, the results are as follows Figure 4 As shown. Figure 4The multilayer composite all-solid-state electrolyte membrane showed no short circuit after 1000 hours of testing, while the single-layer composite all-solid-state electrolyte membrane experienced a sudden overvoltage drop after 350 hours of testing, indicating a short circuit. Compared to single-layer composite all-solid-state electrolyte membranes, the multilayer composite all-solid-state electrolyte membrane of the present invention has lower overvoltage, longer cycle life, and better stability.

[0075] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a 3D printed multilayer composite all-solid electrolyte membrane, characterized in that: The following steps are involved: (1) Pre-mixing of the solution: adding a photoinitiator and a lithium salt to an aprotic polar solution, stirring and ultrasonicating them to fully dissolve them, adding a photosensitive resin and mixing them thoroughly, then adding an inorganic filler and stirring and ultrasonicating them again to uniformly disperse them in the solution to obtain a mixed solution; the mass ratio of the photoinitiator, lithium salt, aprotic polar solution, photosensitive resin and inorganic filler is 0.05-0.2:0.5-2:1-4:1:1-4; (2) Preparation of slurry A and slurry B: a mixed solution was prepared, polyvinylidene fluoride and polyethylene oxide were added respectively, and after ultrasonic treatment, the mixture was heated in an oil bath to obtain slurry A and slurry B respectively; the mass fraction of polyvinylidene fluoride in the slurry A to the mixed solution was 1 to 4 wt%, and the mass fraction of polyethylene oxide in the slurry B to the mixed solution was 1 to 4 wt%; (3) Preparation of electrolyte membrane: Slurry A and slurry B are poured into the printing tank of a 3D printer in sequence for printing. The membrane printed with slurry A serves as the middle interlayer membrane, and the membrane printed with slurry B serves as the top and bottom membranes. After printing, the membrane is washed with a non-proton polar solution and vacuum dried to obtain a 3D printed multilayer composite all-solid-state electrolyte membrane.

2. The method for preparing a 3D printed multilayer composite all-solid electrolyte membrane according to claim 1, wherein: In step (1) and step (3), the aprotic polar solution is one or more of N-methylpyrrolidone, N,N-dimethylformamide, acetonitrile and acetone.

3. The method for preparing a 3D printed multilayer composite all-solid electrolyte membrane according to claim 1, wherein: In step (1), the inorganic filler is composed of an active filler and an inert filler in a mass ratio of 2 to 4:1; the active filler is one or more of lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, lithium aluminum germanium phosphate, lithium lanthanum titanate and tantalum-doped lithium lanthanum zirconium oxide; the inert filler is one or more of aluminum oxide, silicon dioxide and barium carbonate.

4. The method for preparing a 3D printed multilayer composite all-solid electrolyte membrane according to claim 1, wherein: In step (1), the photosensitive resin is one or more of trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanediol diacrylate and ethoxylated pentaerythritol tetraacrylate.

5. The method for preparing a 3D printed multi-layer composite all-solid electrolyte membrane according to claim 1, characterized in that: In step (1), the photoinitiator is trimethylamine dihydrate, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide or 2-hydroxy-2-methylpropiophenone.

6. The method for preparing a 3D printed multi-layer composite all-solid electrolyte membrane according to claim 1, characterized in that: In step (1), the lithium salt is one or more of lithium bis(trifluorosulfonyl)imide, lithium difluorooxalatoborate and lithium perchlorate.

7. The method for preparing a 3D printed multi-layer composite all-solid electrolyte membrane according to claim 1, characterized in that: In step (2), the oil bath heating is performed at 50-80° C. with stirring for 4-6 hours; and the ultrasonic treatment time is 10-20 minutes.

8. The method for preparing a 3D printed multi-layer composite all-solid electrolyte membrane according to claim 1, characterized in that: In step (3), the thickness of the film printed by slurry A is 90 to 100 μm, and the thickness of the film printed by slurry B is 45 to 50 μm; the printing time is 5 to 10 minutes.

9. The method for preparing a 3D printed multi-layer composite all-solid electrolyte membrane according to claim 1, characterized in that: In step (3), the vacuum drying is performed at 60 to 80° C. for 10 to 12 hours.

10. A 3D printed multi-layer composite all-solid-state electrolyte membrane prepared by the preparation method according to any one of claims 1 to 9.

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