3D printing multilayer composite all-solid-state electrolyte membrane and preparation method thereof

Abstract

The invention discloses a 3D printing multilayer composite all-solid-state electrolyte membrane and a preparation method thereof, and belongs to the technical field of all-solid-state electrolyte. The preparation method comprises the following steps: (1) solution premixing: mixing photosensitive resin, an aprotic polar solution, an inorganic filler, a photoinitiator and a lithium salt to obtain a mixed solution; (2) preparing a slurry A and a slurry B: taking the mixed solution, respectively adding polyvinylidene fluoride and polyoxyethylene, carrying out ultrasonic treatment, and then carrying out oil bath heating to respectively obtain the slurry A and the slurry B; and (3) preparing an electrolyte membrane: sequentially pouring the slurry A and the slurry B into a printing groove of a 3D printer for printing, taking a membrane printed by the slurry A as a middle interlayer membrane, taking a membrane printed by the slurry B as a top layer membrane and a bottom layer membrane, and after printing is completed, washing and drying to obtain the 3D printed multi-layer composite all-solid-state electrolyte membrane. According to the preparation method, penetration of lithium dendrites is effectively inhibited, and the overall stability and durability of the membrane are enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state electrolytes, and in particular 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 received widespread attention in recent years due to its rapid prototyping and low energy consumption, and SLA or DLP 3D printers can give full play to UV curing technology. There are many types of photosensitive resins that can be used for 3D printing, but only a handful of types are currently used for batteries. The application of 3D printing technology to the development of all-solid-state electrolytes has broad prospects. 3D printing technology can fully meet the personalized requirements of all-solid-state electrolytes and play a key role in certain fields.

[0003] All-solid-state electrolytes are considered to be the ideal choice for the next generation of lithium-ion batteries due to their high energy density, long cycle life, and higher safety compared to traditional liquid electrolytes. Solid polymer electrolytes are usually flexible and can form better interface contact with electrode materials. However, at room temperature, the ionic conductivity of solid polymer electrolytes is usually low and the mechanical properties are insufficient. Ceramic solid electrolytes have high ionic conductivity at room temperature and good interface stability and mechanical properties, but the interface impedance with electrode materials is large. The volume of electrode materials changes during charging and discharging, which may cause interface detachment and form gaps, affecting the cycle life of the battery. Organic-inorganic composite electrolytes can combine the advantages and disadvantages of these two electrolytes, but their process is complex and difficult to make. Therefore, it is urgent to develop high-performance organic-inorganic composite solid electrolytes with commercial applications. Traditional organic-inorganic composite electrolyte membranes are usually only single-layer structures. In order to ensure the mechanical properties of the membrane, it is often necessary to sacrifice a certain degree of flexibility, which will lead to a reduction in the contact area with the positive and negative electrodes, thereby affecting the ion conduction efficiency. If the electrolyte membrane is too flexible and not rigid enough, it is also prone to safety hazards 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 matter, photosensitive resin has a high degree of polymerization, which makes it unfavorable for the dissociation of lithium salts. It is usually necessary to add polar solutions to promote the dissociation of lithium salts, but at the same time this will also reduce the degree of polymerization of the resin, thereby affecting its performance. The electrochemical window of pure organic system all-solid electrolytes is small, which limits their stable operation under high voltage. In the traditional method, ceramic electrolytes are 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 electrolytes. On the other hand, polyethylene oxide electrolytes have strong conductivity in the molten state and can have good contact with the positive and negative electrode surfaces, but due to their weak mechanical properties, they are easily pierced by lithium dendrites during the cycle, thereby affecting the safety and life of the battery. Therefore, how to prepare a composite all-solid electrolyte membrane that can ensure good mechanical properties while maintaining a large contact area and high ionic conductivity has become an important 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 view of the above problems, the present invention provides a 3D printed multilayer 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 membranes have 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 electrolyte membrane comprises the following steps:

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

[0010] (2) Preparation of slurry A and slurry B: taking a mixed solution, adding polyvinylidene fluoride and polyethylene oxide respectively, after ultrasonic treatment, heating in an oil bath, and obtaining slurry A and slurry B respectively; the mass fraction of polyvinylidene fluoride in the slurry A to the mixed solution is 1 to 4 wt%, and the mass fraction of polyethylene oxide in the slurry B to the mixed solution is 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 is used as the middle interlayer membrane, and the membrane printed with slurry B is used as the top and bottom membranes. After printing, it 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; the inert filler is one or more of aluminum oxide, silicon dioxide 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 min.

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

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

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

[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 preparing the 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, it helps the lithium salt to dissolve and generate a solution with higher ionic conductivity.

[0023] Pure organic system all-solid electrolytes usually have a small electrochemical window. By introducing inorganic fillers composed of active fillers and inert fillers, the electrochemical window of the electrolyte can be effectively increased and the toughness of the electrolyte membrane can be improved. Since inorganic fillers have a large density and are easy to settle, it is necessary to add an appropriate amount of binder, such as polyvinylidene fluoride or polyethylene oxide, to ensure that the slurry is uniform and stable 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 of slurry A can be used 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 are used as 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 electrolyte membrane of the present invention optimizes the interaction force of the polyethylene oxide molecular chains in the top and bottom membranes, so that the molecular chains can still be loosely arranged at a relatively low temperature, have a relatively high ionic conductivity, and can contact more active substances, thereby effectively improving the specific capacity of the battery. At the same time, 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.

[0027] 2. The electrochemical window of the multilayer composite all-solid electrolyte membrane of the present invention reaches above 5V, and its initial specific capacity is 145.9 mAh·g -1 After 100 cycles, the specific capacity is 133.4 mAh g -1 , the specific capacity is reduced by 12.5 mAh g -1 , while the initial specific capacity of the traditional single-layer composite all-solid 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 non-proton polar solution and inorganic filler 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 non-proton polar solution N-methylpyrrolidone, N,N-dimethylformamide and other solutions used in the present invention have very high polarity and can provide sufficient electrostatic shielding to reduce the lithium ion (Li + ) and 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 and thus improves the ionic conductivity of the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a 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 the 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 0.2 mA·cm -2 Compatibility test diagram under current density. DETAILED DESCRIPTION

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

[0036] Example 1

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

[0038] (1) Premixing 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 and stirred at high speed and ultrasonicated to fully dissolve them in a transparent state, then 2 g of ethoxylated trimethylolpropane triacrylate was added and mixed thoroughly, and then 3 g of lithium titanium aluminum phosphate and 1 g of aluminum oxide were added and stirred and ultrasonicated again to uniformly disperse them in the solution to obtain a mixed solution;

[0039] (2) Preparation of slurry A and slurry B: Take a mixed solution, add polyvinylidene fluoride and polyethylene oxide respectively, after ultrasonic treatment for 20 minutes, heat in an oil bath at 60° C. for 6 hours, and obtain slurry A and slurry B respectively; the mass fraction of polyvinylidene fluoride in slurry A to the mixed solution is 2wt%, and the mass fraction of polyethylene oxide in slurry B to the mixed solution is 2wt%;

[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, which served as the middle rigid interlayer. The thickness of the membrane printed by slurry B was 50 μm, which served as the top and bottom layers. The printing time was 5 min. After printing, 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 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) premixing 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 and stirred at high speed and ultrasonicated to fully dissolve them, then 1 g of trimethylolpropane triacrylate and 1 g of ethoxypentaerythritol tetraacrylate were added and mixed thoroughly, then 2.5 g of lithium lanthanum zirconium oxide and 1.5 g of lithium aluminum germanium phosphate and 1 g of barium carbonate were added and stirred and ultrasonicated again to make them uniformly dispersed in the solution to obtain a mixed solution;

[0044] (2) Preparation of slurry A and slurry B: a mixed solution was taken, polyvinylidene fluoride and polyethylene oxide were added respectively, and after ultrasonic treatment for 15 min, the mixture was 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 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 UV curing method, slurry A and slurry B were poured into the printing tank of a 3D printer in turn for printing. The thickness of the membrane printed with slurry A was 90 μm, serving as the middle rigid interlayer, and the thickness of the membrane printed with slurry B was 45 μm, serving as the top and bottom layers. The printing time was 5 min. After printing, 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) Premixing of the solution: 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 the mixture. 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 taken, 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 UV curing method, slurry A and slurry B were poured into the printing tank of a 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, the surface slurry was washed off with N,N-dimethylformamide. After vacuum drying at 70°C for 10 h, a 3D printed multilayer composite all-solid-state electrolyte membrane was obtained.

[0051] Example 4

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

[0053] (1) Premixing 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 to make it transparent. Then, 2 g of 1,6-hexanediol diacrylate was added and the mixture was fully mixed. Then, 3 g of lithium lanthanum titanate and 1 g of barium carbonate were added and the mixture was stirred and ultrasonicated again to make the mixture uniformly dispersed in the solution to obtain a mixed solution.

[0054] (2) Preparation of slurry A and slurry B: a mixed solution was taken, polyvinylidene fluoride and polyethylene oxide were added respectively, and after ultrasonic treatment for 10 min, the mixture was 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 UV curing method, slurry A and slurry B were poured into the printing tank of a 3D printer in turn for printing. The thickness of the membrane printed with slurry A was 90 μm, serving as the middle rigid interlayer, and the thickness of the membrane printed with slurry B was 45 μm, serving as the top and bottom layers. The printing time was 5 min. After printing, 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) Premixing 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 and stirred at high speed and ultrasonicated to make them fully dissolved and transparent, 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 and ultrasonicated again to make them uniformly dispersed in the solution to obtain a mixed solution;

[0059] (2) Preparation of slurry A and slurry B: A mixed solution was taken, polyvinylidene fluoride and polyethylene oxide were added respectively, and after ultrasonic treatment for 20 min, the mixture was heated in an oil bath at 70° C. for 5 h 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 UV curing method, slurry A and slurry B were poured into the printing tank of a 3D printer in turn for printing. The thickness of the membrane printed with slurry A was 100 μm, serving as the middle rigid interlayer, and the thickness of the membrane printed with slurry B was 50 μm, serving as the top and bottom layers. The printing time was 10 min. After printing, the surface slurry was washed off with acetone. 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) Premixing of the solution: 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 to make them fully dissolved and transparent, and then 2 g of ethoxypentaerythritol tetraacrylate was added and mixed thoroughly, and then 4 g of lithium aluminum germanium phosphate, 1 g of aluminum oxide and 0.5 g were added and stirred and ultrasonicated again to make them uniformly dispersed in the solution to obtain a mixed solution;

[0064] (2) Preparation of slurry A and slurry B: a mixed solution was taken, polyvinylidene fluoride and polyethylene oxide were added respectively, and after ultrasonic treatment for 15 min, the mixture was 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 UV curing method, slurry A and slurry B were poured into the printing tank of a 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, 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.

[0066] Comparative Example 1

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

[0068] (1) Premixing 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 and stirred at high speed and ultrasonicated to fully dissolve them in a transparent state, then 2 g of ethoxylated trimethylolpropane triacrylate was added and mixed thoroughly, and then 3 g of lithium titanium aluminum phosphate and 1 g of aluminum oxide were added and stirred and ultrasonicated again to uniformly disperse them in the solution to obtain a mixed solution;

[0069] (2) Preparation of single-layer composite electrolyte membrane slurry: Take a mixed solution, add polyvinylidene fluoride, ultrasonically treat for 15 minutes, and 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 single-layer composite all-solid-state electrolyte membrane slurry in the mixed solution is 2wt%.

[0070] (3) Preparation of electrolyte membrane: Using the ultraviolet light 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 h, 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 having a diameter of 15.8 mm 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 multilayer composite all-solid electrolyte membrane of Example 1 and the 3D printed single-layer composite all-solid electrolyte membrane (denoted as PVDF) of Comparative Example 1 were further assembled into batteries by assembling the lithium iron phosphate (LFP) positive electrode sheet, the all-solid electrolyte membrane and the lithium sheet into a CR2032 button battery in an argon-filled glove box. The performance of the CR2032 button battery was then tested at 60°C. The charge and discharge cycle test diagram of the CR2032 button battery 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 145.9 mAh g -1 After 100 cycles, the specific capacity is 133.4 mAh g -1 , the specific capacity is reduced by 12.5 mAh g -1 The initial specific capacity of the single-layer composite all-solid 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 is effectively improved.

[0074] The 3D printed multilayer 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 symmetric 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 4It can be seen that the multilayer composite all-solid electrolyte membrane has no short circuit after 1000h of testing, while the single-layer composite all-solid electrolyte membrane has a sudden overvoltage drop after 350h of testing, indicating that a short circuit has occurred at this time. The multilayer composite all-solid electrolyte membrane of the present invention has a smaller overvoltage and a longer cycle life than the single-layer composite all-solid electrolyte membrane, and has 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 principle of the present invention should be included in the protection scope 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) Premixing 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 fully, and then adding an inorganic filler and stirring and ultrasonicating them again to make them evenly dispersed in the solution to obtain a mixed solution; the mass ratio of the photoinitiator, the lithium salt, the aprotic polar solution, the photosensitive resin and the inorganic filler is 0.05-0.2:0.5-2:1-4:1:1-4; (2) Preparation of slurry A and slurry B: taking a mixed solution, adding polyvinylidene fluoride and polyethylene oxide respectively, after ultrasonic treatment, heating in an oil bath, and obtaining slurry A and slurry B respectively; the mass fraction of polyvinylidene fluoride in the slurry A to the mixed solution is 1 to 4 wt%, and the mass fraction of polyethylene oxide in the slurry B to the mixed solution is 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 is used as the middle interlayer membrane, and the membrane printed with slurry B is used as the top and bottom membranes. After printing, it 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, characterized in that: 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, characterized in that: 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, characterized in that: 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 multilayer 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 multilayer 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 multilayer composite all-solid electrolyte membrane according to claim 1, characterized in that: 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.

8. The method for preparing a 3D printed multilayer 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 90-100 μm, and the thickness of the film printed by slurry B is 45-50 μm; the printing time is 5-10 minutes.

9. The method for preparing a 3D printed multilayer 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 multilayer composite all-solid electrolyte membrane prepared by the preparation method according to any one of claims 1 to 9.

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