Solid-state electrolyte membrane and method for producing the same

Abstract

The application provides a solid-state electrolyte film and a preparation method thereof. The solid-state electrolyte film comprises a first solid-state electrolyte layer, a base film containing a porous structure and a second solid-state electrolyte layer which are sequentially stacked along the thickness direction of the solid-state electrolyte film, wherein the first solid-state electrolyte in at least part of the first solid-state electrolyte layer is filled in the porous structure of the base film, and the porous structure comprises through holes. The filling of the first solid-state electrolyte in the porous structure of the base film improves the mechanical strength of the solid-state electrolyte film and prevents the battery from short-circuiting due to being punctured. The through holes make the contact between the first solid-state electrolyte and the second solid-state electrolyte more close, and improve the lithium ion transmission efficiency. Meanwhile, the thickness of the solid-state electrolyte film ensures that it has a high energy density, so that the solid-state electrolyte film has excellent mechanical properties while having low impedance and high energy density.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte membrane technology, and more specifically, to a solid electrolyte membrane and its preparation method. Background Technology

[0002] Solid-state electrolytes are a core component of solid-state battery technology. They replace the liquid electrolytes used in traditional batteries, significantly reducing internal flammability and improving safety, while also optimizing energy density and cycle stability. Solid-state electrolytes are typically composed of inorganic ceramics or polymer materials, which possess high ionic conductivity and good chemical stability, making them crucial for realizing next-generation high-performance batteries. Summary of the Invention

[0003] Solid electrolyte membranes (SEMs), which contain solid electrolytes, are key components of solid-state batteries. They not only isolate the positive and negative electrodes and prevent internal short circuits, but their microstructure also directly affects lithium-ion transport within the battery, thus influencing its electrochemical performance. However, solid electrolyte membranes face multiple challenges in industrial production, the most significant being the trade-off between thickness and performance. Excessively thick SEMs, while improving mechanical properties, also increase battery impedance and reduce energy density; conversely, excessively thin SEMs have low puncture resistance, making them prone to puncture during fabrication and potentially leading to short circuits.

[0004] Therefore, solid electrolyte membranes need to have appropriate thickness and high puncture strength to reduce battery impedance while ensuring mechanical strength.

[0005] Existing solid electrolyte membranes cannot simultaneously address the issues of battery impedance and energy density while ensuring mechanical properties.

[0006] Furthermore, the fabrication process of solid electrolyte membranes also poses challenges to industrial-scale production. Continuous production requires solid electrolyte membranes to have highly consistent thickness and uniform structure to ensure the stability of battery performance. However, existing coating, calendering, and other processes cannot simultaneously meet the requirements of thickness control, mechanical strength, and electrochemical performance. Especially under large-scale production conditions, maintaining the uniformity and consistency of the membrane layer has become an urgent problem to be solved.

[0007] Therefore, developing a solid-state electrolyte membrane that can reduce battery impedance while ensuring mechanical performance and is compatible with continuous production operations is of great significance for promoting the commercialization of solid-state battery technology. This requires in-depth research and innovation in the selection of materials, microstructure design, and fabrication processes of solid-state electrolyte membranes to overcome the above challenges and achieve large-scale production of high-performance solid-state batteries.

[0008] The main objective of this invention is to provide a solid electrolyte membrane and its preparation method.

[0009] To achieve the above objectives, according to one aspect of the present invention, a solid electrolyte membrane is provided, comprising a first solid electrolyte layer, a base membrane having a porous structure, and a second solid electrolyte layer stacked sequentially along the thickness direction of the solid electrolyte membrane, wherein at least a portion of the first solid electrolyte in the first solid electrolyte layer is filled in the porous structure of the base membrane, and the porous structure includes through-holes.

[0010] As one implementation, the porous structure described above also includes staggered holes.

[0011] In one embodiment, 30wt% to 70wt% of the first solid electrolyte layer is filled in the porous structure of the base film, or 40wt% to 60wt% of the first solid electrolyte layer is filled in the porous structure of the base film.

[0012] As one embodiment, the mechanical strength of the solid electrolyte membrane is 20 MPa to 100 MPa; and / or the ionic conductivity of the solid electrolyte membrane is 1 × 10⁻⁶. -5 S / cm ~ 9×10 -3 S / cm; and / or the impedance of the above solid electrolyte membrane is 10Ω~1100Ω.

[0013] In one embodiment, the melting point of the second solid electrolyte in the base film and the second solid electrolyte layer is higher than the melting point of the first solid electrolyte in the first solid electrolyte layer.

[0014] In one embodiment, the aperture of the through hole is 25μm~150μm, or 30μm~50μm; and / or the gap between adjacent through holes is 10μm~200μm, or 10μm~50μm.

[0015] In one implementation, the air permeability of the base membrane is 70% to 80%; and / or the porosity of the base membrane is 50% to 60%; the porosity of the base membrane is 70% to 90%.

[0016] In one embodiment, the melting point of the base film is 200°C to 600°C, or 300°C to 400°C.

[0017] In one embodiment, the thickness of the base film is 3μm to 20μm, or 3μm to 12μm.

[0018] In one embodiment, the base film is selected from any one or more of polyethylene, polypropylene, nonwoven fabric, aramid, polyvinylidene fluoride, silicon dioxide, and aluminum oxide.

[0019] In one embodiment, the melting point of the first solid electrolyte is 50°C to 150°C, or 50°C to 100°C.

[0020] In one embodiment, the first solid electrolyte is selected from polyethylene glycol, polyethylene oxide, lithium borohydride, lithium phosphorus sulfide, lithium bis(trifluoromethanesulfonyl)imide, and Li7La3Zr2O. 12 And any of the anti-perovskites.

[0021] In one embodiment, the melting point of the second solid electrolyte in the second solid electrolyte layer is 200°C to 500°C, or 250°C to 350°C.

[0022] In one embodiment, the thickness of the second solid electrolyte layer is 20μm to 50μm, or 30μm to 40μm.

[0023] In one embodiment, the second solid electrolyte layer comprises a sulfide solid electrolyte, which is selected from Li6PS5Cl, Li 10 GeP2S 12 Li3PS4 and Li7P3S 11 At least one of them.

[0024] In one embodiment, the average particle size of both the first solid electrolyte and the second solid electrolyte is 5 μm to 20 μm.

[0025] In one embodiment, the thickness of the solid electrolyte membrane is 20 μm to 80 μm.

[0026] In one embodiment, the thickness of the solid electrolyte membrane is 30 μm to 50 μm.

[0027] According to another aspect of the present invention, a method for preparing the above-mentioned solid electrolyte membrane is provided, the method comprising: step S1: mixing a first solid electrolyte, a first binder and a first solvent to obtain a first slurry; mixing a second solid electrolyte, a second binder and a second solvent to obtain a second slurry; step S2: coating the first slurry and the second slurry onto two opposite surfaces in the thickness direction of a base film to obtain a wet film; step S3: subjecting the wet film to heat treatment to obtain a solid electrolyte membrane; wherein the heat treatment includes hot pressing, the temperature of which is higher than the melting point temperature of the first solid electrolyte and lower than the melting point temperatures of the second solid electrolyte and the base film.

[0028] In one embodiment, the mass ratio of the first solid electrolyte to the first binder is (49:1) to (4:1), and / or the mass ratio of the first solid electrolyte to the first solvent is (6:4) to (7:5).

[0029] In one embodiment, the mass ratio of the second solid electrolyte to the second binder is (49:1) to (4:1), and / or the mass ratio of the second solid electrolyte to the second solvent is (6:4) to (7:5).

[0030] In one embodiment, the first adhesive and the second adhesive are each independently selected from at least one of polyacrylic acid, nitrile rubber, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinylidene fluoride, and polyethylene oxide; the first solvent and the second solvent are each independently selected from at least one of toluene, dichloromethane, ethylene glycol dimethyl ether, acetonitrile, chloroform, cyclohexanone, methyl acetate, ethyl acetate, and tetrahydrofuran.

[0031] In one embodiment, the mixing operation in step S1 further includes a first stirring of the materials of the first solid electrolyte, the first binder and the first solvent, and the mixing operation in step S2 further includes a second stirring of the materials of the second solid electrolyte, the second binder and the second solvent, wherein the rotation speed of the first stirring and the second stirring are each independently 1000 r / min to 1800 r / min, and the stirring time of the first stirring and the second stirring are each independently 1 h to 2 h.

[0032] In one implementation method, the above heat treatment process involves first drying the wet film and then hot pressing it.

[0033] In one implementation method, the drying temperature is 60℃~100℃, and / or the drying time is 6h~12h.

[0034] In one implementation method, the hot pressing temperature is 65℃~250℃, the hot pressing pressure is 1MPa~30MPa, and the hot pressing time is 5min~60min.

[0035] By applying the technical solution of this invention, the solid electrolyte membrane with the above-described structure and composition, on the one hand, partially fills the porous structure of the base membrane with the first solid electrolyte, effectively improving the mechanical strength of the solid electrolyte membrane while maintaining the same thickness, thus preventing battery short circuits caused by punctures. On the other hand, at least a portion of the first and second solid electrolyte layers can directly contact each other through the pores (such as through-holes) of the base membrane, resulting in a tighter contact between the first and second solid electrolytes. This helps reduce interfacial impedance and improve lithium-ion transport efficiency. Therefore, through these multiple factors, the solid electrolyte membrane can achieve both excellent mechanical properties and low impedance and high energy density, while also being suitable for continuous production, thus achieving the dual goals of high performance and industrial application. Attached Figure Description

[0036] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0037] Figure 1 (a) shows the EIS diagram of the solid-state battery corresponding to the solid electrolyte membrane before hot pressing in Comparative Example 1 of this application;

[0038] Figure 1(b) shows the corresponding solid-state battery EIS diagram of the hot-pressed solid electrolyte membrane in Embodiment 1 of this application;

[0039] Figure 2 The cycle performance test graph of a full battery using the solid electrolyte membrane shown in Embodiment 1 of this application is shown. Detailed Implementation

[0040] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] As analyzed in the background section of this application, existing technologies have the problem that solid electrolyte membranes cannot simultaneously ensure mechanical properties while also taking into account battery impedance and energy density. In order to solve the above problems, this application provides a solid electrolyte membrane and its preparation method.

[0042] In a typical embodiment of this application, a solid electrolyte membrane is provided, which includes a first solid electrolyte layer, a base membrane with a porous structure, and a second solid electrolyte layer stacked sequentially along the thickness direction of the solid electrolyte membrane, wherein at least a portion of the first solid electrolyte in the first solid electrolyte layer is filled in the porous structure of the base membrane, and the porous structure includes through holes.

[0043] The solid electrolyte membrane with the above-described structure and composition, on the one hand, partially fills the porous structure of the base membrane with the first solid electrolyte, effectively improving the mechanical strength of the solid electrolyte membrane while maintaining a constant membrane thickness, thus preventing battery short circuits caused by punctures. On the other hand, at least a portion of the first and second solid electrolyte layers can directly contact each other through the pores (such as through-holes) of the base membrane, resulting in a tighter contact between the first and second solid electrolytes. This helps reduce interfacial impedance and improve lithium-ion transport efficiency. Therefore, through these multiple factors, the solid electrolyte membrane can achieve both excellent mechanical properties and low impedance with high energy density.

[0044] Furthermore, the thickness of the solid electrolyte membrane can be 20 μm to 80 μm, or 30 μm to 50 μm. More specifically, the thickness of the solid electrolyte membrane can be 20 μm, 22 μm, 24 μm, 26 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, 52 μm, 54 μm, 55 μm, 58 μm, 60 μm, 65 μm, 70 μm, 72 μm, 75 μm, or 80 μm. Of course, the thickness of the solid electrolyte membrane can be any value within the range of 20 μm to 80 μm, which will not be elaborated further here.

[0045] In some embodiments of this application, the porous structure described above also includes staggered holes.

[0046] In addition to through-holes, the porous structure in the base film can also include interlaced pores. Firstly, the interlaced pore layout enhances the structural stability of the solid electrolyte membrane. By dispersing stress in different directions, it improves the membrane's resistance to external pressure, increases the complexity and toughness of the membrane layer, and helps alleviate stress caused by volume changes during battery charge-discharge cycles, reducing the risk of breakage during processing and use, thereby improving battery cycle stability and extending service life. Secondly, the presence of interlaced pores not only increases the contact area between the first and second solid electrolyte layers but also forms a more complex ion transport network. Even if some pathways are blocked, lithium ions can still move freely through other pathways, thus maintaining low impedance and high ionic conductivity. Thirdly, during heat treatment, the interlaced pore structure helps the first solid electrolyte fill the pores of the base film more uniformly, increasing the filling density. This allows the solid electrolyte membrane to form a denser and more uniform structure after undergoing the melting and solidification processes, further reducing interfacial impedance. Fourthly, the staggered pore design in the porous structure can enhance the membrane's support capacity while ensuring a certain level of air permeability. This is crucial for the battery's performance under high-rate charge and discharge conditions, ensuring a good balance between ion transport efficiency and the stability of the solid electrolyte membrane.

[0047] In some embodiments of this application, 30wt% to 70wt% of the first solid electrolyte layer is filled in the porous structure of the base film.

[0048] Controlling the mass percentage of the first solid electrolyte within the porous structure of the base membrane helps achieve a balance between mechanical strength and electrochemical performance, significantly improving the performance of the solid electrolyte membrane, including reducing interfacial impedance, increasing ionic conductivity, enhancing energy density, and improving charge-discharge performance. Specifically, by filling the porous structure of the base membrane with the first solid electrolyte, the mechanical strength of the solid electrolyte can be increased without significantly increasing its total thickness. The solid electrolyte particles filling the pores of the base membrane form mechanical interlocks, enhancing the solid electrolyte's ability to withstand external pressure and reducing the risk of solid electrolyte breakage due to mechanical stress during battery manufacturing and use. Furthermore, the solid electrolyte particles filling the porous structure create more continuous ion transport pathways, reducing obstacles encountered by lithium ions as they pass through the membrane, thereby improving ion transport efficiency.

[0049] Furthermore, by controlling the filling ratio of the first solid electrolyte, the repeatability and consistency of the membrane preparation process can be improved. This is particularly important for mass production of solid electrolyte membranes and ensuring the stability of battery performance. Alternatively, 40wt% to 60wt% of the first solid electrolyte layer can be filled into the porous structure of the base membrane. Specifically, the first solid electrolyte can be 30wt%, 40wt%, 42wt%, 45wt%, 48wt%, 50wt%, 52wt%, 55wt%, 60wt%, 65wt%, or 70wt% of the total mass of the first solid electrolyte layer, or any value within the range of 40wt% to 60wt%, which will not be elaborated further here.

[0050] In some embodiments of this application, the mechanical strength of the solid electrolyte membrane is 20 MPa to 100 MPa; and / or the ionic conductivity of the solid electrolyte membrane is 1 × 10⁻⁶. -5 S / cm ~ 9×10 -3 S / cm; and / or the impedance of the above solid electrolyte membrane is 10Ω~1100Ω.

[0051] Solid electrolyte membranes with the above-mentioned mechanical strength exhibit excellent durability, helping to resist various stresses during battery manufacturing, such as hot pressing and rolling, as well as mechanical stresses during battery use. This reduces the risk of solid electrolyte membrane cracking or deformation during manufacturing and use, and also lowers the risk of internal short circuits and reduced battery life. Simultaneously, sufficiently strong mechanical properties allow the battery to adapt to more complex operating environments, improving its overall safety and reliability. The mechanical strength of solid electrolyte membranes can range from 20 MPa to 100 MPa. The mechanical strength of the solid electrolyte membrane can be 20MPa, 25MPa, 30MPa, 35MPa, 40MPa, 45MPa, 50MPa, 51MPa, 55MPa, 60MPa, 65MPa, 70MPa, 72MPa, 73MPa, 75MPa, 80MPa, 81MPa, 82MPa, 83MPa, 85MPa, 90MPa, 92MPa, 95MPa, or 100MPa. Of course, it can also be any value from 20MPa to 100MPa, which will not be elaborated here.

[0052] Solid electrolyte membranes with the above-mentioned ionic conductivity effectively promote lithium-ion migration, which is crucial for battery charge-discharge performance. High ionic conductivity means that lithium ions can pass through the solid electrolyte membrane more quickly, thus helping to improve the battery's power density and energy efficiency. Simultaneously, high ionic conductivity also helps reduce charge transfer resistance within the battery, thereby mitigating heat generation and capacity decay issues during high-rate charge-discharge cycles. Specifically, the ionic conductivity of the aforementioned solid electrolyte membrane is 1.0 × 10⁻⁶. -5 S / cm ~ 9.0 × 10 -3 S / cm, or 5.0 × 10 -5 S / cm ~ 6.0 × 10 -3 S / cm, or 5.0 × 10 -4 S / cm ~8.0×10 -4 The ionic conductivity of the aforementioned solid electrolyte membrane can be 1.0 × 10⁻⁶ S / cm. - 5 S / cm, 2.5×10 -5 S / cm, 5.0×10 -5 S / cm, 1.0×10 -4 S / cm, 2.5×10 -4 S / cm, 5.0×10 -4 S / cm, 5.02×10 -4 S / cm, 5.12×10 -4 S / cm, 5.16×10 -4 S / cm, 5.5×10 -4 S / cm, 5.53×10-4 S / cm, 6.0×10 -4 S / cm, 6.01×10 -4 S / cm, 6.04×10 -4 S / cm, 6.2×10 -4 S / cm, 6.26×10 -4 S / cm, 6.5×10 -4 S / cm, 6.57×10 -4 S / cm, 7.07×10 -4 S / cm, 7.13×10 -4 S / cm, 8.0×10 -4 S / cm, 8.05×10 -4 S / cm, 9.0×10 -4 S / cm, 1.0×10 -3 S / cm, 2.5×10 -3 S / cm, 5.0×10 -3 S / cm or 9.0×10 -3 S / cm, or of course, 1.0 × 10⁻⁶. -5 S / cm ~ 9.0 × 10 -3 Any value in S / cm will not be elaborated here.

[0053] Impedance is the resistance of a solid electrolyte membrane to the flow of current during battery charging and discharging. A solid electrolyte membrane with the aforementioned low impedance means that the battery experiences less energy loss and higher efficiency during charging and discharging. By optimizing the materials and structure of the solid electrolyte membrane and reducing its impedance, the electrochemical performance of the battery can be significantly improved, including increasing the charging and discharging speed and cycle life. It can also reduce internal heat generation during charging and discharging, thus improving overall safety. Specifically, the impedance of the aforementioned solid electrolyte membrane is 10Ω~1100Ω, or 50Ω~600Ω, or 80Ω~432Ω. Specific impedance values ​​for the aforementioned solid electrolyte membranes can be 10Ω, 20Ω, 50Ω, 80Ω, 84Ω, 100Ω, 101Ω, 105Ω, 106Ω, 107Ω, 150Ω, 153Ω, 200Ω, 202Ω, 212Ω, and 2... 15Ω, 250Ω, 300Ω, 309Ω, 350Ω, 400Ω, 432Ω, 450Ω, 500Ω, 550Ω, 600Ω, 650Ω, 700Ω, 750Ω, 800Ω, 850Ω, 900Ω, 950Ω, 1000Ω, 1050Ω, or 1100Ω. Of course, it can also be any value from 10Ω to 1100Ω, which will not be elaborated here.

[0054] In summary, solid electrolyte membranes with high mechanical strength, high ionic conductivity, and low impedance help improve the power density, energy efficiency, and cycle stability of solid-state batteries, making them more competitive in demanding applications such as electric vehicles and energy storage systems.

[0055] In some embodiments of this application, the melting point of the base film and the melting point of the second solid electrolyte in the second solid electrolyte layer are both higher than the melting point of the first solid electrolyte in the first solid electrolyte layer.

[0056] The low melting point of the first solid electrolyte allows it to melt, flow, and fill the pores of the base film during heat treatment (such as hot pressing), forming a continuous ion-conducting network. This enhances both the integrity and mechanical properties of the solid electrolyte membrane. The base film and the second solid electrolyte layer remain solid during heat treatment, unaffected by temperature changes, maintaining their structural integrity. This results in a tighter interfacial contact after hot pressing, reducing interfacial impedance and improving lithium-ion transport efficiency. Furthermore, the second solid electrolyte layer provides additional ion conduction pathways and, together with the base film, synergistically maintains the overall structural stability and ion conductivity of the solid electrolyte membrane.

[0057] The high melting points of the base film and the second solid electrolyte also mean that they can remain stable within the battery's operating temperature range and will not undergo phase transitions or performance degradation due to temperature changes. This is of great significance for maintaining the long-term electrochemical stability and cycle performance of the battery.

[0058] In summary, by setting the melting point of the base film and the second solid electrolyte to be higher than that of the first solid electrolyte, this application is able to prepare a solid electrolyte film with high thermal stability, low interfacial impedance, high mechanical strength, and adaptability to continuous production. These characteristics work together to improve the overall performance of solid-state batteries.

[0059] In some embodiments of this application, the pore size of the aforementioned through holes is 25μm~150μm, or 30μm~50μm; and / or the gap between adjacent through holes is 10μm~200μm, or 10μm~50μm; and / or the air permeability of the base film is 70%~80%; and / or the porosity of the base film is 50%~60%; the porosity of the base film is 70%~90%.

[0060] Controlling the pore size within this range helps to create a microstructure in the base film that provides both efficient lithium-ion transport and sufficient structural strength. A pore size of 30μm to 50μm further ensures the high efficiency of the ion transport path while limiting the risk of decreased mechanical strength due to excessively large pore sizes. The pore size can be 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 105μm, 110μm, 115μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, or 150μm. Of course, the pore size can also be any value within the range of 25μm to 150μm, which will not be elaborated further here.

[0061] Smaller gaps between adjacent vias help increase the contact area between the first and second solid electrolyte layers, promoting ion conduction and reducing interfacial impedance. A gap of 10 μm to 50 μm between adjacent vias further facilitates the formation of a denser lithium-ion transport network, while reducing the risk of material crowding and decreased porosity caused by excessively small gaps. The gap between adjacent vias can be 10μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, 105μm, 110μm, 115μm, 120μm, 125μm, 130μm, 135μm, 140μm, 145μm, 150μm, 155μm, 160μm, 165μm, 170μm, 175μm, 180μm, 185μm, 190μm, 195μm, or 200μm. Of course, the gap between adjacent vias can also be any value from 10μm to 200μm, which will not be elaborated here.

[0062] High air permeability means that the base film has high pore connectivity, which is conducive to the rapid migration of lithium ions and improves the power density and efficiency of the battery. At the same time, maintaining the air permeability within this range helps the base film to provide a lithium ion transport path while also having sufficient supporting strength. The air permeability of the base film can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80%. Of course, the air permeability of the base film can also be any value within 70% to 80%, which will not be elaborated further here.

[0063] Setting the porosity helps maintain the structural stability and uniform pore distribution of the base film, thereby improving the uniform transport of lithium ions between the positive and negative electrodes, reducing the risk of forming local high-resistivity regions, and improving the overall performance of the battery. The porosity of the base film can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, or 60%. Of course, the porosity of the base film can be any value between 50% and 60%, which will not be elaborated further here.

[0064] High porosity helps to form sufficient lithium-ion transport pathways in the base film, but it is also necessary to ensure that mechanical strength is not compromised. Within this range, the base film can provide sufficient porosity to promote rapid lithium-ion migration, while its mechanical strength is enhanced by the filling of the first solid electrolyte layer. The porosity of the base film can be 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, or 90%. Of course, the porosity of the base film can be any value between 70% and 90%, which will not be elaborated further here.

[0065] By carefully adjusting the parameters of the base membrane, it is possible to optimize the electrochemical performance of the solid electrolyte membrane while ensuring sufficient mechanical strength.

[0066] In some embodiments of this application, the melting point of the base film is 200°C to 600°C, or 300°C to 400°C.

[0067] The control of the base film's melting point reduces the risk of thermal deformation, enhances its mechanical strength, promotes the flow and filling of low-melting-point solid electrolytes, reduces interfacial impedance, optimizes lithium-ion transport, improves structural stability under high-temperature battery manufacturing processes, and enhances the overall electrochemical performance and safety of the battery. The melting point of the base film can be 200℃, 220℃, 250℃, 270℃, 300℃, 320℃, 350℃, 400℃, 420℃, 450℃, 500℃, 520℃, 550℃, or 600℃. Of course, the melting point can be any value within the range of 200℃ to 600℃, which will not be elaborated further here.

[0068] In some embodiments of this application, the thickness of the base film is 3μm~20μm or 3μm~12μm.

[0069] The base film with the above thickness satisfies the requirement for a thin and lightweight solid-state electrolyte membrane, thereby reducing the overall weight of the battery and increasing energy density. Furthermore, the base film of this thickness provides support within the solid-state electrolyte membrane, maintaining its mechanical stability and reducing the risk of internal short circuits. The thickness of the base film can be 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, or 20μm. Of course, the thickness can also be any value within the range of 3μm to 20μm, which will not be elaborated further here.

[0070] In some embodiments of this application, the base film is selected from any one or more of polyethylene, polypropylene, nonwoven fabric, aramid, polyvinylidene fluoride, silicon dioxide, and aluminum oxide.

[0071] The aforementioned base membrane materials were selected based on their compatibility with solid electrolytes, melting point, cost, and suitability for manufacturing processes. Different base membrane materials offer different mechanical strengths and chemical properties; for example, polyethylene and polypropylene have good chemical stability and mechanical strength, while silica and alumina offer high-temperature stability and good porosity.

[0072] In some embodiments of this application, the melting point of the first solid electrolyte is 50°C to 150°C, or 50°C to 100°C.

[0073] The first solid electrolyte, possessing the above melting points, can melt under mild heat treatment conditions, filling the pores of the base film, enhancing the interlayer bonding of the solid electrolyte film, reducing impedance, improving lithium-ion conduction efficiency, while ensuring structural integrity and optimizing battery performance and production compatibility. The melting point of the first solid electrolyte can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, or 150℃. Of course, the melting point of the first solid electrolyte can be any value within the range of 50℃ to 150℃, which will not be elaborated further here.

[0074] In some embodiments of this application, the first solid electrolyte is selected from polyethylene glycol, polyethylene oxide, lithium borohydride, lithium phosphorus sulfide, lithium bis(trifluoromethanesulfonyl)imide, and Li7La3Zr2O. 12 And any of the anti-perovskites.

[0075] Selecting specific first solid electrolyte materials, such as polyethylene glycol and polyethylene oxide, is beneficial because their low melting point helps them flow and fill the pores of the base film during heat treatment, enhancing the mechanical strength of the solid electrolyte film while maintaining low impedance, promoting efficient lithium-ion conduction, optimizing battery performance, and being particularly suitable for continuous production, thus achieving the dual goals of high performance and industrial application.

[0076] In some embodiments of this application, the melting point of the second solid electrolyte in the second solid electrolyte layer is 200°C to 500°C, or 250°C to 350°C.

[0077] The second solid electrolyte, with its above melting point, makes the structure more stable at battery processing temperatures, reducing the risk of melting and deformation. At the same time, it complements the first solid electrolyte layer with its low melting point, enhancing the overall mechanical properties of the solid electrolyte membrane, maintaining high ionic conductivity, and improving battery safety and energy density. The melting point of the second solid electrolyte can be 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, or 500℃. Of course, the melting point of the second solid electrolyte can also be any value between 200℃ and 500℃, which will not be elaborated here.

[0078] In some embodiments of this application, the thickness of the second solid electrolyte layer is 20 μm to 50 μm, or 30 μm to 40 μm.

[0079] The thickness of the second solid electrolyte layer helps to coordinate with the thickness of the first solid electrolyte layer, keeping the overall thickness of the solid electrolyte membrane within a certain range. Simultaneously, it helps provide necessary ion conduction channels, maintaining good electrochemical performance, without excessively increasing battery impedance and thickness, thus balancing energy density and safety, making it suitable for high-efficiency battery production and applications. The thickness of the second solid electrolyte layer can be 20μm, 22μm, 25μm, 28μm, 30μm, 20μm, 38μm, 40μm, 45μm, or 50μm. Of course, the thickness of the second solid electrolyte layer can be any value within the range of 20μm to 50μm, which will not be elaborated further here.

[0080] In some embodiments of this application, the second solid electrolyte layer comprises a sulfide solid electrolyte, which is selected from Li6PS5Cl, Li 10 GeP2S 12Li3PS4 and Li7P3S 11 At least one of them.

[0081] The inherent properties of sulfides help form a dense layer, enhancing the isolation between electrodes and ensuring the safety and performance consistency of the battery. Therefore, Li6PS5Cl and Li... 10 GeP2S 12 Sulfides, as a second solid electrolyte, have high ionic conductivity and chemical stability, which help to significantly improve the charge and discharge efficiency and cycle life of batteries.

[0082] In some embodiments of this application, the average particle size of the first solid electrolyte and the second solid electrolyte is independently 5 μm to 20 μm.

[0083] A suitable average particle size for the first and second solid electrolytes helps form a continuous and stable lithium-ion conduction pathway, improving the ionic conductivity of the solid electrolyte membrane and thus enhancing the battery's charge-discharge performance. The aforementioned average particle size of the first and second solid electrolytes facilitates close contact between the first and second solid electrolyte layers, reducing interfacial impedance, ensuring efficient ion transport, and increasing battery energy density. Furthermore, during the coating process, particles of 5μm to 20μm easily form a uniform coating, reducing the risk of uneven distribution due to excessively large particles affecting battery performance consistency. In addition, during the heat treatment stage, an appropriate average particle size for the first and second solid electrolytes helps ensure uniform heating, improving the controllability of the melting and filling process, and reducing the risk of incomplete melting due to excessively large particles or excessive flow due to excessively small particles. The average particle size of the first solid electrolyte and the second solid electrolyte can be independently 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm or 20 μm. Of course, the average particle size of the first solid electrolyte and the second solid electrolyte can also be any value from 5 μm to 20 μm, which will not be elaborated here.

[0084] In some embodiments of this application, the thickness of the solid electrolyte membrane is 20 μm to 80 μm, or 30 μm to 50 μm.

[0085] The thickness of a solid electrolyte membrane (SEM) is the sum of the thickness of the base membrane, the first solid electrolyte layer, and the second solid electrolyte layer. The thickness of the SEM directly affects its mechanical strength and ion transport efficiency. An excessively thick SEM may increase its impedance and reduce its energy density; conversely, an excessively thin SEM may reduce its mechanical strength, potentially leading to a short circuit. Appropriate membrane thickness optimizes the battery's mechanical properties, ionic conductivity, and energy density. Specifically, selecting a solid electrolyte membrane thickness of 30μm to 50μm helps to better achieve the high energy density of 354Wh / kg in the battery, while also facilitating more comprehensive matching with continuous production operations in the manufacturing process and ensuring the mechanical properties of the solid electrolyte membrane. Furthermore, the energy density of the battery can reach 200Wh / kg to 354Wh / kg, such as 204Wh / kg, 224Wh / kg, 226Wh / kg, 227Wh / kg, 242Wh / kg, 279Wh / kg, 281Wh / kg, 283Wh / kg, 288Wh / kg, 310Wh / kg, or 354Wh / kg. The thickness of the solid electrolyte membrane can be 20μm, 22μm, 25μm, 30μm, 32μm, 35μm, 38μm, 40μm, 42μm, 45μm, 48μm, 50μm, 52μm, 55μm, 58μm, 60μm, 62μm, 65μm, 68μm, 70μm, 72μm, 75μm, or 80μm. Of course, the thickness of the solid electrolyte membrane can be any value within the range of 20μm to 80μm, which will not be elaborated here.

[0086] In another typical embodiment of this application, a method for preparing the above-mentioned solid electrolyte membrane is provided. The method includes: step S1: mixing a first solid electrolyte, a first binder, and a first solvent to obtain a first slurry; mixing a second solid electrolyte, a second binder, and a second solvent to obtain a second slurry; step S2: coating the first slurry and the second slurry onto two opposite surfaces in the thickness direction of the base film to obtain a wet film; step S3: subjecting the wet film to heat treatment to obtain a solid electrolyte membrane; wherein the heat treatment includes hot pressing, and the hot pressing temperature is higher than the melting point temperature of the first solid electrolyte and lower than the melting point temperatures of the second solid electrolyte and the base film.

[0087] The key to the preparation method of the aforementioned solid electrolyte membrane lies in the control of heat treatment conditions. The heat treatment involves first drying the wet membrane and then hot-pressing it. The hot-pressing temperature is controlled to be higher than the melting point of the first solid electrolyte, and simultaneously lower than the melting points of the second solid electrolyte and the base membrane, ensuring the integrity of the membrane structure and optimizing its performance. Specifically, the controlled hot-pressing temperature promotes the thermal melting of the first solid electrolyte during the hot-pressing process, allowing some of it to fill into the porous structure of the base membrane, forming a more continuous structure. This increases the mechanical strength of the solid electrolyte membrane, while simultaneously removing the solvent introduced during slurry mixing, ensuring the density and purity of the solid electrolyte membrane. The contact between the first and second solid electrolyte layers reduces the interfacial resistance between the base membrane and the solid electrolyte layer.

[0088] In addition, the hot pressing process can also adjust the microstructure of the solid electrolyte membrane, reduce interfacial impedance, and improve electrical performance.

[0089] The solid electrolyte membrane prepared by the above method effectively improves the mechanical strength of the solid electrolyte membrane while maintaining the same thickness, preventing short circuits caused by punctures. Furthermore, the first and second solid electrolyte layers can directly contact each other through the pores (through holes) in the base film, resulting in a tighter contact between the two layers. This helps reduce interfacial impedance and improve lithium-ion transport efficiency. Therefore, through these multiple factors, the solid electrolyte membrane achieves excellent mechanical properties while also exhibiting low impedance and high energy density.

[0090] In some embodiments of this application, the mass ratio of the first solid electrolyte to the first binder is (49:1) to (4:1), and the mass ratio of the first solid electrolyte to the first solvent is (6:4) to (7:5); the first binder is selected from at least one of polyacrylic acid, nitrile rubber, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinylidene fluoride, and polyethylene oxide; the first solvent is selected from at least one of toluene, dichloromethane, ethylene glycol dimethyl ether, acetonitrile, chloroform, cyclohexanone, methyl acetate, ethyl acetate, and tetrahydrofuran.

[0091] The first binder, such as polyacrylic acid, sodium carboxymethyl cellulose, or polyvinylidene fluoride, helps enhance the bonding force between the solid electrolyte particles and the base film. The first solvent, such as toluene or dichloromethane, disperses the solid electrolyte and binder during the slurry mixing process, thus facilitating the coating of the first slurry onto the base film. Appropriate combinations of the types of first binder and first solvent, the mass ratio of the first solid electrolyte to the first binder, and the mass ratio of the first solid electrolyte to the first solvent help to leverage the synergistic effect among the first solid electrolyte, first binder, and first solvent, thereby contributing to a uniformly mixed first slurry. This results in a more uniform distribution of the first solid electrolyte layer formed on the base film, further enhancing the structural stability of the solid electrolyte membrane. Simultaneously, the selected first solvents are effectively removed during heat treatment without affecting the structure of the solid electrolyte membrane.

[0092] In some embodiments of this application, the mass ratio of the second solid electrolyte to the second binder is (49:1) to (4:1), and the mass ratio of the second solid electrolyte to the second solvent is (6:4) to (7:5); the second binder is selected from at least one of polyacrylic acid, nitrile rubber, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinylidene fluoride, and polyethylene oxide; the second solvent is selected from at least one of toluene, dichloromethane, ethylene glycol dimethyl ether, acetonitrile, chloroform, cyclohexanone, methyl acetate, ethyl acetate, and tetrahydrofuran.

[0093] Secondary binders, such as polyacrylic acid, sodium carboxymethyl cellulose, and polyvinylidene fluoride, help enhance the bonding force between solid electrolyte particles and the base film. Secondary solvents, such as toluene and dichloromethane, disperse the solid electrolyte and binder during the slurry mixing process, thus facilitating the coating of the second slurry onto the base film. Appropriate combinations of second binders and second solvents, the mass ratio of the second solid electrolyte to the second binder, and the mass ratio of the second solid electrolyte to the second solvent help to leverage the synergistic effect between the second solid electrolyte, the second binder, and the second solvent, thereby contributing to a uniformly mixed second slurry. This results in a more uniform distribution of the second solid electrolyte layer formed on the base film, further enhancing the structural stability of the solid electrolyte membrane. Simultaneously, the selected types of secondary solvents facilitate effective removal during heat treatment without affecting the structure of the solid electrolyte membrane.

[0094] In some embodiments of this application, the mixing operation in step S1 further includes a first stirring of the materials of the first solid electrolyte, the first binder and the first solvent, and the mixing operation in step S2 further includes a second stirring of the materials of the second solid electrolyte, the second binder and the second solvent, wherein the rotation speed of the first stirring and the second stirring are each independently 1000 r / min to 1800 r / min, and the stirring time of the first stirring and the second stirring are each independently 1 h to 2 h.

[0095] On the one hand, the set stirring speed and time help to fully disperse the first binder (second binder), the first solvent (second solvent), and the first solid electrolyte (second solid electrolyte), forming a uniform first slurry (second slurry). This step is crucial for the uniformity of subsequent coating and the microstructure of the solid electrolyte membrane. Insufficient stirring speed may lead to agglomeration of the solid electrolyte powder in the slurry, affecting the consistency of the coating and the performance of the membrane. On the other hand, the above stirring speed and time help to refine the solid electrolyte particles, making them more uniform and smaller in size. This helps the particles to better fill the porous structure of the base membrane during heat treatment, thereby enhancing the mechanical strength and conductivity of the solid electrolyte membrane. Sufficient stirring time allows for adequate contact and mixing between the slurry components, forming a stable composite structure. When the solid electrolyte layer contacts the base membrane or another solid electrolyte layer, this stable composite structure can reduce the impedance at the interface and improve the lithium-ion transport efficiency.

[0096] The rotational speeds of the first and second stirring operations can each be independently 1000 r / min, 1100 r / min, 1200 r / min, 1300 r / min, 1400 r / min, 1500 r / min, 1600 r / min, 1700 r / min, or 1800 r / min. Of course, the rotational speeds of the first and second stirring operations can each be any value within the range of 1000 r / min to 1800 r / min, which will not be elaborated further here. The stirring times of the first and second stirring operations can each be independently 0.2 h, 0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, or 1 h. Of course, the stirring times of the first and second stirring operations can also each be any value within the range of 0.2 h to 1 h, which will not be elaborated further here.

[0097] In addition, appropriate stirring speed and time can effectively remove air bubbles in the slurry, reduce defects in the solid electrolyte membrane, and ensure the membrane's density and consistency, which has a direct impact on improving battery performance and lifespan.

[0098] In one embodiment, in step S1, the first binder (second binder) and the first solvent (second solvent) are added together to the mixing tank to allow them to disperse evenly. Then, the first solid electrolyte (second solid electrolyte) is added to the mixing tank and stirred to ensure maximum uniform dispersion, resulting in uniform first and second slurries. In another embodiment, during the mixing process in step S1, the feeding time does not exceed 3 minutes at a time, and the number of feedings is 3 to 10 times.

[0099] In one implementation method, the base film in step S2 contains a through-hole structure, which can be formed by piercing with a heated needle roller. That is, a through-hole structure (through hole) can be formed by piercing a common base film with a heated needle roller. The size of the through hole is adjusted by adjusting the height of the roller, and the piercing position is adjusted by adjusting the base plate. The heating temperature is adjusted according to the specific common material. This results in a single through-hole diameter of 25μm~150μm and a gap between adjacent through holes of 10μm~200μm, thereby maximizing ion transport efficiency.

[0100] The above-mentioned perforation increases the porosity of the base film through physical means, promotes ion migration, and also adjusts the mechanical properties of the base film.

[0101] In some embodiments of this application, the above-mentioned heat treatment process involves first drying the wet film and then hot pressing it. The drying temperature is 60°C to 100°C and the drying time is 6h to 12h; and / or the hot pressing temperature is 65°C to 250°C, the hot pressing pressure is 1MPa to 30MPa, and the hot pressing time is 5min to 60min.

[0102] The presence of solvents may reduce the mechanical strength and electrical properties of the membrane. The main purpose of drying is to remove the solvent introduced in step S1. The specific drying temperature depends on the type of solvent used, thereby efficiently removing the solvent from the wet membrane.

[0103] On the one hand, controlling the drying temperature and time is to effectively remove the solvent introduced in step S1, thereby improving the structural stability of the obtained solid electrolyte membrane and reducing the risk of deformation or damage to the solid electrolyte membrane structure caused by solvent residue. On the other hand, controlling the drying temperature and time helps to reduce the risk that excessive heat treatment at high temperatures may cause denaturation of the solid electrolyte and affect its ionic conductivity. The drying temperature can be 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, or 100℃. Of course, the drying temperature can also be any value within the range of 60℃ to 100℃, which will not be elaborated further here. The drying time can be 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h, or 12h. Of course, the drying time can also be any value within the range of 6h to 12h, which will not be elaborated further here. The hot-pressing temperature can be 65℃, 70℃, 75℃, 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, or 250℃. Of course, the hot-pressing temperature can also be any value within the range of 65℃ to 250℃, which will not be elaborated further here. The hot-pressing pressure can be 1 MPa, 5 MPa, 10 MPa, 15 MPa, 20 MPa, 25 MPa, or 30 MPa. Again, the hot-pressing pressure can be any value within the range of 1 MPa to 30 MPa, which will not be elaborated further here. The hot pressing time can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min. Of course, the hot pressing time can also be any value between 5 min and 60 min, which will not be elaborated here.

[0104] The selection of the hot-pressing temperature ensures that the first solid electrolyte melts, but the base film and the second solid electrolyte do not. This allows the low-melting-point first solid electrolyte layer to melt and flow into the pores of the base film, thereby enhancing the mechanical strength of the solid electrolyte film, improving its puncture resistance, and reducing the risk of short circuits. Simultaneously, it helps form a continuous ion-conducting network, enhancing the ionic conductivity of the solid electrolyte film. The selected hot-pressing temperature also facilitates closer contact between the first and second solid electrolyte layers during the hot-pressing process, reducing interfacial impedance and improving lithium-ion transport efficiency within the film. The chosen combination of pressure and time during hot-pressing helps optimize the microstructure of the solid electrolyte film, including more uniform particle distribution and increased film density, all of which contribute to improved overall performance. Furthermore, the hot-pressing operation method can be selected from any one or more of the following: flat plate hot-pressing, pneumatic hot-pressing, and plate hot-pressing.

[0105] The above heat treatment process ensures that the solid electrolyte membrane has sufficient mechanical strength to withstand various pressure conditions in battery manufacturing, and also ensures that the solid electrolyte membrane has low impedance and high ionic conductivity, which significantly improves the charge and discharge efficiency and cycle performance of the battery.

[0106] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0107] Example 1

[0108] Step S1, Slurry preparation: Mix 0.70 g polyethylene oxide solid electrolyte (PEO), 0.07 g polyacrylic acid binder, and 0.50 g acetonitrile solvent, and stir at 1000 r / min for 1 h to obtain the first slurry; add 0.70 g Li 10 GeP2S 12 The sulfide solid electrolyte, 0.07 g of polyacrylic acid binder and 0.50 g of acetonitrile solvent were mixed and stirred at a speed of 1000 r / min for 0.5 h to obtain the second slurry.

[0109] Step S2, Coating: The aramid base film is placed in a mechanical perforation device. The aramid base film is perforated to obtain through holes with a diameter of 65μm and a gap of 100μm. The air permeability of the aramid base film is 60%, the through-hole rate is 70%, and the porosity is 80%. The perforated film is first placed in a glove box oven or vacuum drying oven at 60°C for 4 hours. Then, an 80μm doctor blade is used to coat the first slurry and the second slurry onto the surface of the base film in the thickness direction, respectively. The solvent is allowed to evaporate at room temperature to obtain a wet film with a first solid electrolyte layer and a second solid electrolyte layer. The thickness of the aramid base film is 12μm and the melting point is 500°C. The thickness of the first solid electrolyte layer is 20μm and the melting point is 60°C. The thickness of the second solid electrolyte layer is 20μm and the melting point is 200°C.

[0110] Step S3, heat treatment: The wet film is transferred to a vacuum drying oven for drying at 60°C for 12 hours to ensure that the solvent is removed. The dried membrane is then cut to a fixed size and subjected to hydraulic treatment. After hydraulic treatment, to prevent the sulfide solid electrolyte from contacting water in the air, it is vacuum sealed and then transferred to a flatbed hot press for hot pressing. After sealing, it is then subjected to hot pressing at 80°C and 20 MPa for 20 minutes to obtain a solid electrolyte membrane. The thickness of the solid electrolyte membrane after hot pressing is 32 μm. The first solid electrolyte, accounting for 50 wt% of the total mass of the first solid electrolyte layer, fills the porous structure of the aramid-based membrane.

[0111] Example 2

[0112] The difference between Example 2 and Example 1 is that in step S2, the thickness of the second solid electrolyte layer is 100 μm, the pore diameter of the aramid base film is 130 μm and the gap between the pores is 10 μm, the air permeability of the aramid base film is 70%, the porosity of the aramid base film is 70%, and the porosity of the aramid base film is 80%, thus obtaining a solid electrolyte membrane. In this membrane, the first solid electrolyte, accounting for 40 wt% of the total mass of the first solid electrolyte layer, is filled in the porous structure of the aramid base film.

[0113] Example 3

[0114] The difference between Example 3 and Example 1 is that in step S2, the thickness of the second solid electrolyte layer is 100 μm, the pore diameter of the aramid film obtained by perforation is 130 μm, the gap between the pores is 10 μm, the air permeability of the aramid film is 80%, the porosity of the aramid film is 70%, and the porosity of the aramid film is 80%, thus obtaining a solid electrolyte membrane. In this membrane, the first solid electrolyte, which accounts for 60 wt% of the total mass of the first solid electrolyte layer, is filled in the porous structure of the aramid film.

[0115] Example 4

[0116] The difference between Example 4 and Example 1 is that in step S2, the thickness of the second solid electrolyte layer is 100 μm, the pore diameter of the aramid film obtained by perforation is 130 μm, the gap between the pores is 10 μm, the air permeability of the aramid film is 70%, the porosity of the aramid film is 60%, and the porosity of the aramid film is 70%, thus obtaining a solid electrolyte membrane. In this membrane, the first solid electrolyte, accounting for 30 wt% of the total mass of the first solid electrolyte layer, is filled in the porous structure of the aramid film.

[0117] Example 5

[0118] The difference between Example 5 and Example 1 is that in step S2, the thickness of the second solid electrolyte layer is 100 μm, the pore diameter of the aramid film obtained by perforation is 130 μm, the gap between the pores is 10 μm, the air permeability of the aramid film is 80%, the porosity of the aramid film is 80%, and the porosity of the aramid film is 90%, and finally a solid electrolyte membrane is obtained, wherein the first solid electrolyte, accounting for 70 wt% of the total mass of the first solid electrolyte layer, is filled in the porous structure of the aramid film.

[0119] Example 6

[0120] The difference between Example 6 and Example 1 is that in step S1, the first binder is styrene-butadiene rubber binder, the first solvent is toluene, the mass ratio of the first solid electrolyte to the first binder is 49:1, and the mass ratio of the first solid electrolyte to the first solvent is 6:4. The second binder is nitrile rubber binder, the second solvent is toluene, the mass ratio of the second solid electrolyte to the second binder is 49:1, and the mass ratio of the second solid electrolyte to the second solvent is 6:4. The aramid-based film has a melting point of 500℃ and a thickness of 12μm. The first solid electrolyte is a polyethylene oxide solid electrolyte-LiFSI composite electrolyte, corresponding to a melting point of 50℃ and a thickness of 80μm for the first solid electrolyte layer. The second solid electrolyte is Li7P3S. 11 The melting point of the second solid electrolyte layer is 350℃.

[0121] In step S3, the hot pressing temperature is 65℃, and a solid electrolyte membrane with a thickness of 30μm is finally obtained.

[0122] Example 7

[0123] The difference between Example 7 and Example 1 is that in step S1, the first binder is styrene-butadiene rubber binder, the first solvent is toluene, the mass ratio of the first solid electrolyte to the first binder is 4:1, and the mass ratio of the first solid electrolyte to the first solvent is 7:3. The second binder is nitrile rubber binder, the second solvent is toluene, the mass ratio of the second solid electrolyte to the second binder is 4:1, and the mass ratio of the second solid electrolyte to the second solvent is 7:3. The aramid-based film has a melting point of 500℃ and a thickness of 12μm. The first solid electrolyte is a PVDF copolymer, corresponding to a melting point of 150℃ and a thickness of 80μm for the first solid electrolyte layer. The second solid electrolyte is Li. 10 GeP2S 12 The melting point of the second solid electrolyte layer is 500℃.

[0124] In step S3, the hot pressing temperature is 160℃, and a solid electrolyte membrane with a thickness of 40μm is finally obtained.

[0125] Example 8

[0126] The difference between Example 8 and Example 1 is that in step S3, the hot pressing temperature is 180°C, and a solid electrolyte membrane is finally obtained.

[0127] Example 9

[0128] The difference between Example 9 and Example 1 is that in step S3, the hot pressing temperature is 190°C, and a solid electrolyte membrane is finally obtained.

[0129] Example 10

[0130] The difference between Example 10 and Example 1 is that in step S2, the coating thickness of the first solid electrolyte layer and the second solid electrolyte layer is 20 μm; in step S3, hot pressing is performed at 80 °C and 20 MPa for 30 min to finally obtain a solid electrolyte membrane with a thickness of 20 μm.

[0131] Example 11

[0132] The difference between Example 11 and Example 1 is that in step S2, the coating thickness of the first solid electrolyte layer and the second solid electrolyte layer is 80 μm; in step S3, hot pressing is performed at 80 °C and 13 MPa for 30 min to finally obtain a solid electrolyte membrane with a thickness of 80 μm.

[0133] Example 12

[0134] The difference between Example 12 and Example 1 is that in step S2, the coating thickness of the first solid electrolyte layer and the second solid electrolyte layer is 15 μm; in step S3, the solid electrolyte membrane is hot-pressed for 30 min at 80 °C and 27 MPa, and the thickness of the solid electrolyte membrane is 15 μm.

[0135] Comparative Example 1

[0136] The difference between Comparative Example 1 and Example 1 is that in step S3, no hot pressing treatment was performed, and a solid electrolyte membrane was finally obtained.

[0137] Comparative Example 2

[0138] The difference between Comparative Example 2 and Example 1 is that in step S3, the hot pressing temperature is 40°C, and a solid electrolyte membrane is finally obtained.

[0139] Comparative Example 3

[0140] The difference between Comparative Example 3 and Example 1 is that in step S1, the aramid-based membrane has no pores, that is, the porosity is 0, and a solid electrolyte membrane is finally obtained.

[0141] Performance testing:

[0142] Mechanical strength of solid electrolyte membrane: its tensile strength was tested according to ASTM D882 standard;

[0143] The ionic conductivity of a solid electrolyte membrane is calculated using the formula L / RS, where L represents the membrane thickness (cm), R represents the ohmic resistance (Ω), and S represents the membrane area (cm²). 2 );

[0144] Impedance of solid electrolyte membrane: The steel plate is clamped on both sides of the membrane, and its impedance is tested on an electrochemical workstation;

[0145] The solid electrolyte membranes of the above embodiments and comparative examples were respectively coupled with high-nickel ternary cathode NCM811 (Ni 0.8 Co 0.1 Mn 0.1 The graphite anode was assembled into a lithium-ion solid-state battery. EIS testing was performed under the condition of AC voltage amplitude of 5 mV in the frequency range of 1 MHz to 0.1 Hz. Figure 1(a) is the EIS diagram of the solid-state battery corresponding to the solid electrolyte membrane before hot pressing in Comparative Example 1, and Figure 1(b) is the EIS test diagram of the solid-state battery corresponding to the solid electrolyte membrane after hot pressing in Example 1.

[0146] The test results in the figure show that the impedance value decreases significantly after hot pressing. The smaller the impedance value, the higher the battery charging and discharging efficiency.

[0147] Figure 2This is a cycle performance test graph of the full cell using the solid electrolyte membrane shown in Example 1 of this application. Figure 2 It can be seen that the battery using this solid electrolyte membrane has high charge and discharge capabilities at high rates. At a 1C rate, the battery is charged at a constant current to 4.25V and discharged at a constant current to 2.5V. At a 1C rate, the capacity retention rate remains at 88% after 240 cycles.

[0148] The capacity retention and energy density of the lithium-ion solid-state batteries obtained in the above embodiments and comparative examples were tested after 240 cycles at a 1C rate, and all the test results are listed in Table 1.

[0149] Table 1

[0150]

[0151] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0152] The solid electrolyte membrane with the above-described structure and composition, on the one hand, partially fills the porous structure of the base membrane with the first solid electrolyte, effectively improving the mechanical strength of the solid electrolyte membrane while maintaining a constant membrane thickness, thus preventing battery short circuits caused by punctures. On the other hand, at least a portion of the first and second solid electrolyte layers can directly contact each other through the pores (such as through-holes) of the base membrane, resulting in a tighter contact between the first and second solid electrolytes. This helps reduce interfacial impedance and improve lithium-ion transport efficiency. Therefore, through these multiple factors, the solid electrolyte membrane can achieve both excellent mechanical properties and low impedance with high energy density.

[0153] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A solid electrolyte membrane, characterized in that, The solid electrolyte membrane includes a first solid electrolyte layer, a base membrane with a porous structure, and a second solid electrolyte layer stacked sequentially along the thickness direction of the solid electrolyte membrane, wherein at least a portion of the first solid electrolyte in the first solid electrolyte layer fills the porous structure of the base membrane, and the porous structure includes through holes.

2. The solid electrolyte membrane according to claim 1, characterized in that, The first solid electrolyte, accounting for 30wt% to 70wt% of the total mass of the first solid electrolyte layer, is filled in the porous structure of the base film.

3. The solid electrolyte membrane according to claim 1, characterized in that, The mechanical strength of the solid electrolyte membrane is 20 MPa to 100 MPa; and / or the ionic conductivity of the solid electrolyte membrane is 1 × 10⁻⁶. -5 S / cm ~ 9×10 -3 S / cm; and / or the impedance of the solid electrolyte membrane is 10Ω~1100Ω.

4. The solid electrolyte membrane according to any one of claims 1 to 3, characterized in that, The melting point of the base film and the melting point of the second solid electrolyte in the second solid electrolyte layer are both higher than the melting point of the first solid electrolyte in the first solid electrolyte layer.

5. The solid electrolyte membrane according to any one of claims 1 to 3, characterized in that, The diameter of the through hole is 25μm to 150μm; and / or the gap between adjacent through holes is 10μm to 200μm.

6. The solid electrolyte membrane according to any one of claims 1 to 3, characterized in that, The base film has a melting point of 200℃~600℃.

7. The solid electrolyte membrane according to claim 1, characterized in that, The thickness of the base film is 3μm to 20μm; and / or the base film is selected from any one or more of polyethylene, polypropylene, nonwoven fabric, aramid, polyvinylidene fluoride, silicon dioxide and aluminum oxide.

8. The solid electrolyte membrane according to any one of claims 1 to 3, characterized in that, The melting point of the first solid electrolyte is 50℃~150℃; and / or the first solid electrolyte is selected from polyethylene glycol, polyethylene oxide, lithium borohydride, lithium phosphorus sulfide, lithium bis(trifluoromethanesulfonyl)imide, Li7La3Zr2O 12 And any of the anti-perovskites.

9. The solid electrolyte membrane according to any one of claims 1 to 3, characterized in that, The melting point of the second solid electrolyte in the second solid electrolyte layer is 200℃~500℃; and / or the second solid electrolyte layer includes a sulfide solid electrolyte, wherein the sulfide solid electrolyte is selected from Li6PS5Cl, Li 10 GeP2S 12 Li3PS4 and Li7P3S 11 At least one of them.

10. The solid electrolyte membrane according to any one of claims 1 to 3, characterized in that, The thickness of the solid electrolyte membrane is 20μm~80μm.

11. A method for preparing a solid electrolyte membrane according to any one of claims 1 to 10, characterized in that, The preparation method includes: Step S1: Mix the first solid electrolyte, the first binder, and the first solvent to obtain a first slurry; mix the second solid electrolyte, the second binder, and the second solvent to obtain a second slurry; Step S2: The first slurry and the second slurry are respectively coated on two opposite surfaces in the thickness direction of the base film to obtain a wet film; Step S3: Perform heat treatment on the wet membrane to obtain a solid electrolyte membrane; The heat treatment includes hot pressing, wherein the temperature of the hot pressing is higher than the melting point temperature of the first solid electrolyte and lower than the melting point temperatures of the second solid electrolyte and the base film.

12. The preparation method according to claim 11, characterized in that, The hot pressing temperature is 65℃~250℃, the hot pressing pressure is 1MPa~30MPa, and the hot pressing time is 5min~60min.

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