Composite multilayer solid electrolyte membrane, preparation method thereof and all-solid-state lithium battery

Abstract

The application discloses a composite multilayer solid electrolyte film, a preparation method thereof and a full solid-state lithium battery. The composite multilayer solid electrolyte film comprises a porous base film, a polymer solid electrolyte layer formed on one side of the porous base film, a sulfide solid electrolyte layer formed on the other side of the porous base film, and a halide and / or oxide solid electrolyte layer; wherein the sulfide solid electrolyte layer is arranged immediately adjacent to the porous base film. The high-strength porous base film is used as a mechanical support framework, and the sulfide electrolyte with high ionic conductivity is combined with the porous base film in the form of filling pores, so that the composite multilayer solid electrolyte film has high room temperature ionic conductivity and improved overall tensile strength, and the structural reliability during battery assembly and circulation is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, specifically to a composite multilayer solid electrolyte membrane, its preparation method, and an all-solid-state lithium battery. Background Technology

[0002] With the increasing demand for new energy electric vehicles, high-energy-density energy storage systems, and high-safety special power supplies, lithium-ion batteries are developing towards higher energy density, higher safety, and longer service life. Traditional liquid lithium-ion batteries, due to the flammability and leakage of their organic liquid electrolytes, pose significant safety hazards under high voltage, high temperature, or mechanical impact conditions, and have gradually become a major factor restricting further improvements in battery energy density.

[0003] With the increasing demand for high-energy-density and high-safety batteries in electric vehicles and energy storage systems, all-solid-state lithium batteries have attracted much attention because they promise to completely solve the safety hazards of traditional liquid lithium-ion batteries, such as flammability and leakage. Solid-state electrolytes are the core of all-solid-state batteries, among which sulfide solid electrolytes (such as Li-ion batteries) are the most important. 10 GeP2S 12 (Type) has an ultra-high ionic conductivity (10) at room temperature comparable to that of liquid electrolytes. -3 ~ 10 -2 Sulfide solid electrolytes (S / cm) are considered one of the most promising systems for application. However, they generally suffer from low mechanical strength, high brittleness, and difficulty in fabricating self-supporting films. They are prone to cracking during battery assembly and cycling, leading to battery failure. Furthermore, sulfide electrolytes are susceptible to oxidative decomposition when in contact with high-voltage cathodes (such as lithium cobalt oxide and high-nickel ternary materials), and are prone to reduction reactions when in contact with lithium metal anodes, potentially inducing lithium dendrite growth, resulting in poor interfacial stability. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing all-solid-state lithium batteries, such as low mechanical strength, easy cracking of sulfide solid electrolyte membranes, and the difficulty in simultaneously achieving high ionic conductivity and electrode interface stability in a single electrolyte system. This invention provides a high-strength, high-ionic-conductivity composite multilayer solid electrolyte membrane and its preparation method.

[0005] To achieve the above objectives, the present invention provides a composite multilayer solid electrolyte membrane, the composite multilayer solid electrolyte membrane comprising: a porous base membrane, a polymer solid electrolyte layer formed on one side of the porous base membrane, a sulfide solid electrolyte layer formed on the other side of the porous base membrane, and a halide and / or oxide solid electrolyte layer; wherein the sulfide solid electrolyte layer is disposed adjacent to the porous base membrane.

[0006] Optionally, the porous base membrane has a tensile strength greater than 100 MPa and a porosity of 60% to 70%.

[0007] Optionally, the thickness of the halide solid electrolyte layer and / or oxide solid electrolyte layer is 1 μm to 5 μm, the thickness of the polymer solid electrolyte layer is 0.5 μm to 3 μm, the thickness of the sulfide solid electrolyte layer is 8 μm to 12 μm, and the thickness of the composite multilayer solid electrolyte membrane is 15 μm to 25 μm.

[0008] Optionally, the composite multilayer solid electrolyte membrane has an ionic conductivity of not less than 1 mS / cm, a tensile strength of not less than 25 MPa, and an elongation at break of not less than 50% at room temperature.

[0009] The present invention also provides a method for preparing a composite multilayer solid electrolyte membrane as described in any one of the above claims, characterized by comprising the following steps: Step S1: Provide a porous base membrane, and use a micro-mesh coating process to coat a sulfide solid electrolyte slurry onto the surface of the porous base membrane, so that the sulfide solid electrolyte slurry fills the pores of the porous base membrane to form a sulfide solid electrolyte layer. The sulfide solid electrolyte slurry contains sulfide solid electrolyte particles and a fluorine-based single-ion conductor polymer binder. Step S2: On one side of the sulfide solid electrolyte layer, a slurry containing halide or oxide solid electrolyte particles and fluorine-based single-ion conductor polymer binder is coated to form a halide / oxide solid electrolyte layer. Step S3: On the other side of the sulfide solid electrolyte layer, a slurry containing a fluorine-based ion conductor polymer and a crystalline porous polymer is coated to form a polymer solid electrolyte layer. Step S4: Perform in-situ curing treatment on the coated multilayer structure to obtain the composite multilayer solid electrolyte membrane.

[0010] Optionally, different solid electrolyte layers are coated using coating rollers with different cavity structures: coating rollers used to coat sulfide solid electrolyte layers have grooved cavity structures; coating rollers used to coat halide / oxide solid electrolyte layers have regular hexagonal closed cavity structures; and coating rollers used to coat polymer solid electrolyte layers have rhomboid microgroove structures.

[0011] Optionally, the particle size of the sulfide solid electrolyte particles is no greater than 100 nm.

[0012] Optionally, the fluorine-based single-ion conductor polymer is a fluorine-containing polymeric ion conductor in which sulfonamide structural units are contained in the main chain or side chain.

[0013] Optionally, the in-situ curing process may also include chemical grafting modification of the interface between different solid electrolyte layers using a fluorine-based coupling agent to enhance interlayer bonding and maintain ion transport continuity.

[0014] The present invention also provides an all-solid-state lithium battery comprising a positive electrode, a negative electrode, and a composite multilayer solid electrolyte membrane as described above; wherein the halide / oxide solid electrolyte layer is disposed facing the positive electrode, and the polymer solid electrolyte layer is disposed facing the negative electrode.

[0015] Compared to the prior art, the beneficial effects of the present invention include at least the following: (1) The composite multilayer solid electrolyte membrane of the present invention comprises a porous base membrane, a polymer solid electrolyte layer formed on one side of the porous base membrane, a sulfide solid electrolyte layer formed on the other side of the porous base membrane, and a halide and / or oxide solid electrolyte layer; wherein the sulfide solid electrolyte layer is disposed adjacent to the porous base membrane. Using a high-strength porous base membrane as a supporting framework, a sulfide electrolyte with high ionic conductivity is composited with it in a pore-filling manner, allowing the sulfide solid electrolyte layer to primarily perform ion conduction, while its mechanical fragility is borne by the base membrane with a tensile strength exceeding 100 MPa. This results in a composite multilayer solid electrolyte membrane maintaining a high level of ionic conductivity at room temperature while significantly improving overall tensile strength.

[0016] (2) The halide / oxide solid electrolyte layer on the positive electrode side utilizes its high oxidation stability to effectively isolate the direct contact between the sulfide and the high voltage positive electrode and suppress interfacial side reactions; the polymer solid electrolyte layer on the negative electrode side improves the interfacial contact with lithium metal, buffers volume changes, and suppresses dendrites; furthermore, the fluorine-based single-ion conductor polymer is used for interfacial chemical grafting to form stable covalent bond connections at the interfaces of each layer, which not only enhances the interlayer bonding force and prevents delamination, but also the fixed anions in the fluorine-based single-ion conductor polymer can coordinate with the cations on the surface of the inorganic electrolyte, maintaining a continuous lithium-ion transport channel across the interface and avoiding the ion transport interruption problem common in physical stacking interfaces.

[0017] (3) Differentiated micro-mesh coating rollers are used to precisely control the amount of slurry transfer in response to the different rheological properties of sulfide, halide and polymer slurries. This effectively avoids problems such as particle agglomeration of high solids slurry and uneven spreading of low viscosity slurry, thereby ensuring that the thickness of each functional layer is uniform and without defects. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the composite multilayer solid electrolyte membrane of the present invention.

[0019] Figure 2The images shown are electron microscope images of the porous base membrane used in Example 1 of the present invention and after coating; wherein, (a) is an electron microscope image of the porous base membrane before coating; and (b) is an electron microscope image of the porous base membrane after coating with sulfide solid electrolyte slurry.

[0020] Figure 3 This is an X-ray computed tomography image of the porous polyethylene membrane coated with sulfide solid electrolyte material in Example 1 of the present invention.

[0021] Figure 4 This is a scanning electron microscope (SEM) image of the cross-section of the composite multilayer solid electrolyte membrane prepared in Example 1 of the present invention.

[0022] Figure 5 The impedance data for measuring the ionic conductivity of the composite multilayer solid electrolyte membrane prepared in Example 1 of this invention are shown.

[0023] Figure 6 The mechanical properties of the composite multilayer solid electrolyte membrane prepared in Example 1 of the present invention are shown in the figure.

[0024] Figure 7 This is a charge-discharge curve obtained by applying the composite multilayer solid electrolyte membrane prepared in Example 2 of the present invention to an all-solid-state battery.

[0025] Figure 8 The diagram shows the mechanical properties of the solid electrolyte membrane prepared in Comparative Example 1 of this invention.

[0026] Attached Figure Labels Polymer solid electrolyte layer, 2-porous base membrane, 3-sulfide solid electrolyte layer, 4-halide and / or oxide solid electrolyte layer. Detailed Implementation

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] To improve interfacial stability, a halide or oxide solid electrolyte is introduced as a buffer layer between the sulfide electrolyte and the positive electrode. The high oxidation stability potential of the halide or the chemical inertness of the oxide are used to suppress interfacial side reactions. On the negative electrode side, a polymer electrolyte layer is introduced to improve the interfacial contact with lithium metal.

[0029] However, the multilayer composite electrolyte structures prepared using the above methods often suffer from insufficient interlayer bonding and interfacial discontinuities. The physical contact interfaces between different electrolyte materials are prone to micropores, delamination, or interruption of ion transport, which can become new sources of impedance. In addition, various solid electrolyte slurries differ significantly in particle content, viscosity, and rheological behavior. If the same coating method is used for film formation, uneven coating, particle agglomeration, or local delamination can easily occur, resulting in poor film thickness and performance consistency, making it difficult to meet the requirements for large-scale preparation.

[0030] Furthermore, currently used polymer binders are mostly traditional dual-ion conductors or electrically insulating polymers. While improving mechanical properties, these inevitably dilute the effective ion transport phase of the solid electrolyte, reducing the lithium-ion transference number and exacerbating concentration polarization, making it difficult to achieve effective matching with high-ionic-conductivity sulfide electrolytes. In addition, the contact between different electrolyte layers is mainly physical, lacking a stable chemical bonding mechanism, making them prone to interfacial degradation under long-term charge-discharge or temperature fluctuation conditions.

[0031] To solve the above technical problems, such as Figure 1 As shown, this invention provides a composite multilayer solid electrolyte membrane, comprising: a porous base membrane 2, a polymer solid electrolyte layer 1 formed on one side of the porous base membrane 2, a sulfide solid electrolyte layer 3 formed on the other side of the porous base membrane 2, and a halide and / or oxide solid electrolyte layer 4; wherein the sulfide solid electrolyte layer 3 is disposed adjacent to the porous base membrane 2. Using the high-strength porous base membrane 2 as a flexible support framework, the sulfide solid electrolyte material fills and anchors in the pores of the porous base membrane 2, significantly improving the overall mechanical strength and structural stability of the composite multilayer solid electrolyte membrane while maintaining the high ionic conductivity advantage of the sulfide solid electrolyte. The composite multilayer solid electrolyte membrane is suitable for the high-voltage environment of the positive electrode and the interface stability requirements of the negative electrode. By utilizing differentiated microgrid coating technology and interface chemical grafting modification, the film formation uniformity and interlayer bonding strength of each layer are improved, maintaining continuous lithium-ion transport channels across the interface.

[0032] The present invention provides a method for preparing a composite multilayer solid electrolyte membrane, comprising the following steps: Step S1: A porous base membrane is provided. A micro-mesh coating process is used to coat a sulfide solid electrolyte slurry onto the surface of the porous base membrane. The coating parameters are controlled so that the sulfide solid electrolyte slurry enters and fills the pores of the porous base membrane during the coating process. After repeated coating and intermediate drying, a sulfide solid electrolyte layer is formed, creating a continuous and dense sulfide solid electrolyte conductive network on the surface and within the pores of the porous base membrane. The sulfide solid electrolyte slurry contains sulfide solid electrolyte particles and a fluorine-based single-ion conductor polymer binder.

[0033] In some embodiments, the porous base membrane is a polyethylene membrane with a continuous through-pore structure and a tensile strength greater than 100 MPa. Its main function is to bear the mechanical load of the composite electrolyte membrane, thereby eliminating the need for the sulfide solid electrolyte material to solely perform structural support functions and avoiding the problems of cracking and pulverization common in traditional sulfide self-supporting membranes. Through this structural division of labor, the functions of "mechanical support" and "ion conduction" in the electrolyte membrane are effectively decoupled.

[0034] In step S2, on one side of the sulfide solid electrolyte layer, a slurry containing halide or oxide solid electrolyte particles and a fluorine-based single-ion conductor polymer binder is coated using a dual-die micro-mesh coating process to form a halide / oxide solid electrolyte layer. The halide / oxide solid electrolyte layer is positioned facing the positive electrode of the all-solid-state lithium battery. It has good compatibility with the positive electrode material in terms of chemical composition or crystal structure, thereby effectively suppressing interfacial side reactions under high voltage conditions and reducing the rate of interfacial impedance growth during battery operation.

[0035] In step S3, on the other side of the sulfide solid electrolyte layer, a slurry containing a fluorine-based ion-conducting polymer and a crystalline porous polymer is coated using a micro-mesh coating process to form a polymer solid electrolyte layer. This polymer solid electrolyte layer faces the negative electrode of the all-solid-state lithium battery. During the subsequent in-situ curing process, by controlling the curing temperature, time, and pressure, the polymer chains rearrange to form a dense and continuous polymer network structure. This network structure possesses both rigid support and flexible buffering capabilities, mitigating volume changes caused by lithium deposition / dissolution during battery charging and discharging. Simultaneously, it enhances the lithium-ion transference number and reduces concentration polarization through its single-ion conductor properties.

[0036] Step S4: Perform in-situ curing treatment on the coated multilayer structure to obtain the composite multilayer solid electrolyte membrane.

[0037] In some embodiments, the thickness of the halide solid electrolyte layer and / or oxide solid electrolyte layer is 1 μm to 5 μm, which is used to improve the interfacial stability of the electrolyte membrane under high pressure; the thickness of the polymer solid electrolyte layer is 0.5 μm to 3 μm; the thickness of the sulfide solid electrolyte layer is 8 μm to 12 μm; and the thickness of the composite multilayer solid electrolyte membrane is 15 μm to 25 μm.

[0038] In some embodiments, to adapt to the rheological properties of different slurries, different solid electrolyte layers are coated using coating rollers with different cell structures: For sulfide solid electrolyte slurries with high particle content, the coating rollers used to form sulfide solid electrolyte layers have a grooved cell structure to improve slurry capacity and transfer; for halide solid electrolyte slurries with medium viscosity, the coating rollers used to form halide / oxide solid electrolyte layers have a regular hexagonal closed cell structure to enhance the uniformity control of the thin coating; for low-viscosity fluoropolymer slurries, the coating rollers used to form polymer solid electrolyte layers have a rhombic microgroove structure, and the cell contour accuracy is optimized through fine processing to ensure the stability of quantitative slurry transfer. This differentiated coating method of the present invention can effectively reduce common defects in multilayer structure preparation processes, such as uneven coating, particle agglomeration, and local delamination, and improve the structural consistency of composite multilayer solid electrolyte membranes.

[0039] In some embodiments, the in-situ curing treatment is achieved through thermal curing or chemical curing, forming a continuous and dense structure between the layers and controlling the film thickness deviation within ±0.5 μm. During the in-situ curing process, a fluorinated coupling agent is added, and upon heating, it undergoes a chemical grafting reaction at the interfaces of different solid electrolyte layers, forming stable covalent bonds between the layers, thereby enhancing interfacial adhesion and maintaining continuous ion transport channels across the interfaces.

[0040] The composite multilayer solid electrolyte membrane prepared by this invention has an ionic conductivity of not less than 1 mS / cm, a tensile strength of not less than 25 MPa, and an elongation at break of not less than 50% at room temperature.

[0041] The composite multilayer solid electrolyte membrane prepared by this invention can be directly applied to all-solid-state lithium batteries. In use, the halide / oxide solid electrolyte layer is positioned towards the positive electrode, and the polymer solid electrolyte layer is positioned towards the negative electrode, allowing for stable operation without the need for additional liquid electrolyte. This composite multilayer solid electrolyte membrane ensures high ion conductivity while also possessing good mechanical strength and interfacial stability, making it suitable for high-energy-density, high-safety all-solid-state lithium battery systems.

[0042] Example 1 This embodiment prepares a composite multilayer solid electrolyte membrane based on a sulfide / halide / polymer three-layer structure. A lightweight porous polyethylene membrane with a thickness of 6 μm, a porosity of 65%, a pore size of 150 nm, and a tensile strength greater than 100 MPa is selected as the porous base membrane. Figure 2 As shown in (a), a large number of pores can be seen in the porous base membrane. The preparation method of this embodiment includes: Step S1: Disperse sulfide solid electrolyte powder (particle size D50≈80 nm) in an organic solvent, add fluorine-based single-ion conductor polymer as a binder, and prepare sulfide solid electrolyte slurry. The room temperature ionic conductivity of the sulfide electrolyte is 1.5 × 10⁻⁶. -2 S / cm.

[0043] Step S2 involves using a micro-mesh coating roller with a grooved mesh structure to coat the sulfide solid electrolyte slurry onto one side of a lightweight porous polyethylene membrane. Through four repeated coating processes and intermediate drying, the sulfide solid electrolyte material fully fills and embeds itself into the pores of the lightweight porous polyethylene membrane, forming a sulfide solid electrolyte layer with a thickness of approximately 10 μm. Figure 2 As shown in (b), the pores of the lightweight porous polyethylene membrane can be seen to be filled with ion conductors. Figure 3 As shown in the figure, the grooved mesh structure of the micro-mesh coating roller can be seen.

[0044] Step S3: On the side of the sulfide solid electrolyte layer facing the positive electrode, a dual-die micro-mesh coating process is used to coat the surface of the sulfide solid electrolyte layer with a hexagonal closed-cell coating roller. The halide solid electrolyte slurry contains a fluorine-based single-ion conductor polymer as a binder to form a halide solid electrolyte layer with a thickness of about 3 μm.

[0045] Step S4: On the side of the sulfide solid electrolyte layer facing the negative electrode, a micro-mesh coating roller with a diamond-shaped microgroove structure is used to coat the surface of the sulfide solid electrolyte layer with a polymer precursor slurry formed by the composite of fluorine-based single-ion conductor polymer and crystalline porous polymer, forming a polymer solid electrolyte layer with a thickness of about 1.5 μm.

[0046] Step S5: After coating, the prepared composite film is placed in a curing oven and cured in situ at 80°C. Heptadecafluorodecyltriethoxysilane is introduced as a fluorinated coupling agent to chemically graft and modify the interfaces of each layer, such as... Figure 4 As shown, a composite multilayer solid electrolyte membrane with a total thickness of approximately 20 μm was finally prepared.

[0047] Test results: such as Figure 5 As shown, the composite multilayer solid electrolyte membrane prepared in this embodiment has an ionic conductivity of 1.2 mS / cm at room temperature. Figure 6 As shown, the tensile strength is 29.0 MPa and the elongation at break is approximately 108.2%, making it suitable for direct application in all-solid-state lithium batteries that do not require liquid electrolytes.

[0048] Example 2 This embodiment prepares a composite multilayer solid electrolyte membrane based on a sulfide / oxide / polymer three-layer structure. A lightweight porous polyethylene membrane with a thickness of 8 μm, a porosity of 60%, and a pore size of 120 nm is selected as the porous base membrane. The preparation method of this embodiment includes: Step S1: Disperse sulfide solid electrolyte powder (particle size D50≈80 nm) in an organic solvent, add fluorine-based single-ion conductor polymer as a binder, and prepare sulfide solid electrolyte slurry. The room temperature ionic conductivity of the sulfide electrolyte is 1.5 × 10⁻⁶. -2 S / cm.

[0049] Step S2: Using a micro-mesh coating roller with a grooved mesh structure, the sulfide solid electrolyte slurry is coated on one side of a lightweight porous polyethylene membrane. Through five repeated coatings and intermediate drying treatments, the sulfide solid electrolyte material is fully filled and embedded in the pores of the lightweight porous polyethylene membrane, forming a sulfide solid electrolyte layer with a thickness of about 12 μm.

[0050] Step S3: On the side of the sulfide solid electrolyte layer facing the positive electrode, an oxide solid electrolyte slurry is coated onto the surface of the sulfide solid electrolyte layer using a regular hexagonal closed-cell coating roller. The oxide solid electrolyte slurry contains a fluorine-based single-ion conductor polymer as a binder, forming an oxide solid electrolyte layer with a thickness of approximately 4 μm.

[0051] Step S4: On the side of the sulfide solid electrolyte layer facing the negative electrode, a micro-mesh coating roller with a diamond-shaped microgroove structure is used to coat the surface of the sulfide solid electrolyte layer with a polymer precursor slurry formed by the composite of fluorine-based single-ion conductor polymer and crystalline porous polymer, forming a polymer solid electrolyte layer with a thickness of about 2 μm.

[0052] Step S5: After coating is completed, the prepared composite membrane is placed in a curing oven and cured in situ at 90°C. Heptadecafluorodecyltriethoxysilane is introduced as a fluorine coupling agent to chemically graft and modify the interfaces of each layer, and finally a composite multilayer solid electrolyte membrane with a total thickness of about 24 μm is prepared.

[0053] Test results: such as Figure 7 As shown, when the composite multilayer solid electrolyte membrane prepared in this embodiment is applied to an all-solid-state lithium battery, the battery can operate normally at room temperature and achieve a specific capacity of 196.1 mAh / g.

[0054] Example 3 This embodiment prepares a composite multilayer solid electrolyte membrane focusing on the stability of the negative electrode interface. A lightweight porous polyethylene membrane with a thickness of 5 μm, a porosity of 70%, and a pore size of 180 nm is selected as the porous base membrane. The preparation method of this embodiment includes: Step S1: Disperse the sulfide solid electrolyte powder in an organic solvent, add a fluorine-based single-ion conductor polymer as a binder, and prepare a sulfide solid electrolyte slurry. The room temperature ionic conductivity of the sulfide electrolyte is 1.5 × 10⁻⁶. -2 S / cm.

[0055] Step S2: Using a micro-mesh coating roller with a grooved mesh structure, the sulfide solid electrolyte slurry is coated on one side of a lightweight porous polyethylene membrane. Through three repeated coatings and intermediate drying treatments, the sulfide solid electrolyte material is fully filled and embedded in the pores of the lightweight porous polyethylene membrane, forming a sulfide solid electrolyte layer with a thickness of about 8 μm.

[0056] Step S3: On the side of the sulfide solid electrolyte layer facing the positive electrode, a dual-die micro-mesh coating process is used. A regular hexagonal closed-cell coating roller is used to coat the surface of the sulfide solid electrolyte layer with a halide solid electrolyte slurry. The halide solid electrolyte slurry contains a fluorine-based single-ion conductor polymer as a binder to form a halide solid electrolyte layer with a thickness of about 2 μm, which is used to isolate the sulfide from direct contact with the high-voltage positive electrode.

[0057] In step S4, on the side of the sulfide solid electrolyte layer facing the negative electrode, a micro-mesh coating roller with a diamond-shaped microgroove structure is used to coat the surface of the sulfide solid electrolyte layer with a polymer precursor slurry formed by a high proportion of fluorine-based single-ion conductor polymer and crystalline porous polymer. The polymer chain arrangement is controlled by hot pressing combined with in-situ curing process to form a composite structure of "rigid skeleton-flexible chain segment" and a polymer solid electrolyte layer with a thickness of about 3μm.

[0058] Step S5: After coating, the prepared composite membrane is placed in a curing oven and cured in situ at 80°C. Heptadecafluorodecyltriethoxysilane is introduced as a fluorine coupling agent to chemically graft and modify the interfaces of each layer, and finally a composite multilayer solid electrolyte membrane with a total thickness of about 18 μm is prepared.

[0059] Comparative Example 1 This comparative example is a composite multilayer solid electrolyte membrane that does not contain a high-strength porous base membrane. The difference between this comparative example and Example 1 is that the sulfide solid electrolyte slurry is directly coated onto an inert, flat substrate. All other steps are the same as in Example 1, and a composite multilayer solid electrolyte membrane with a thickness of approximately 20 μm is finally prepared.

[0060] Test results: The composite multilayer solid electrolyte membrane prepared in Comparative Example 1 has an ionic conductivity of approximately 1.1 mS / cm at room temperature, which is not significantly different from that in Example 1, but its tensile strength is only about 1.2 MPa. Figure 8This membrane is prone to cracking under bending or slight stretching conditions. During battery assembly and cycling, the membrane is susceptible to structural damage, and its cycling stability is significantly worse than that of the composite multilayer solid electrolyte membrane prepared in Example 1.

[0061] The above results demonstrate that, without the introduction of a high-strength porous base membrane and without embedding the sulfide solid electrolyte into the porous structure of the base membrane, even using the same electrolyte material system and interface modification method, it is still difficult to simultaneously achieve high ionic conductivity and high mechanical strength in the resulting composite multilayer solid electrolyte membrane. This invention significantly improves the overall mechanical properties and engineering applicability of the composite multilayer solid electrolyte membrane by using a high-strength porous base membrane to support the pores and combining it with a sulfide solid electrolyte to fill the pores.

[0062] In summary, the composite multilayer solid electrolyte membrane of the present invention comprises a porous base membrane, a polymer solid electrolyte layer disposed on one side of the porous base membrane, a sulfide solid electrolyte layer disposed on the other side of the porous base membrane, and a halide and / or oxide solid electrolyte layer; wherein the sulfide solid electrolyte layer is disposed adjacent to the porous base membrane. By using a high-strength porous base membrane as a mechanical support framework and composited with a sulfide electrolyte layer that fills the pores, the composite multilayer solid electrolyte membrane maintains a high level of ionic conductivity at room temperature while also improving overall tensile strength, significantly enhancing the structural reliability during battery assembly and cycling.

[0063] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A composite multilayer solid electrolyte membrane, characterized in that, The composite multilayer solid electrolyte membrane comprises: a porous base membrane, a polymer solid electrolyte layer formed on one side of the porous base membrane, a sulfide solid electrolyte layer formed on the other side of the porous base membrane, and a halide and / or oxide solid electrolyte layer; wherein the sulfide solid electrolyte layer is disposed adjacent to the porous base membrane.

2. The composite multilayer solid electrolyte membrane as described in claim 1, characterized in that, The porous base membrane has a tensile strength greater than 100 MPa and a porosity of 60% to 70%.

3. The composite multilayer solid electrolyte membrane as described in claim 1, characterized in that, The thickness of the halide solid electrolyte layer and / or oxide solid electrolyte layer is 1 μm to 5 μm, the thickness of the polymer solid electrolyte layer is 0.5 μm to 3 μm, the thickness of the sulfide solid electrolyte layer is 8 μm to 12 μm, and the thickness of the composite multilayer solid electrolyte membrane is 15 μm to 25 μm.

4. The composite multilayer solid electrolyte membrane as described in claim 1, characterized in that, The composite multilayer solid electrolyte membrane has an ionic conductivity of not less than 1 mS / cm at room temperature, a tensile strength of not less than 25 MPa, and an elongation at break of not less than 50%.

5. A method for preparing a composite multilayer solid electrolyte membrane as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Step S1: Provide a porous base membrane, and use a micro-mesh coating process to coat a sulfide solid electrolyte slurry onto the surface of the porous base membrane, so that the sulfide solid electrolyte slurry fills the pores of the porous base membrane to form a sulfide solid electrolyte layer. The sulfide solid electrolyte slurry contains sulfide solid electrolyte particles and a fluorine-based single-ion conductor polymer binder. Step S2: On one side of the sulfide solid electrolyte layer, a slurry containing halide or oxide solid electrolyte particles and fluorine-based single-ion conductor polymer binder is coated to form a halide / oxide solid electrolyte layer. Step S3: On the other side of the sulfide solid electrolyte layer, a slurry containing a fluorine-based ion conductor polymer and a crystalline porous polymer is coated to form a polymer solid electrolyte layer. Step S4: Perform in-situ curing treatment on the coated multilayer structure to obtain the composite multilayer solid electrolyte membrane.

6. The preparation method according to claim 5, characterized in that, Different solid electrolyte layers are coated using coating rollers with different cavity structures: the coating roller used to coat sulfide solid electrolyte layers has a grooved cavity structure; the coating roller used to coat halide / oxide solid electrolyte layers has a regular hexagonal closed cavity structure; and the coating roller used to coat polymer solid electrolyte layers has a rhombic microgroove structure.

7. The preparation method according to claim 5, characterized in that, The particle size of the sulfide solid electrolyte particles is no greater than 100 nm.

8. The preparation method according to claim 5, characterized in that, The fluorine-based single-ion conductor polymer is a fluorine-containing polymeric ion conductor in which sulfonamide structural units are contained in the main chain or side chain.

9. The preparation method according to claim 5, characterized in that, In-situ curing also includes the use of fluorine-based coupling agents to chemically graft and modify the interfaces of different solid electrolyte layers in order to enhance interlayer bonding and maintain ion transport continuity.

10. A fully solid-state lithium battery, characterized in that, The device comprises a positive electrode, a negative electrode, and a composite multilayer solid electrolyte membrane as described in any one of claims 1 to 4; wherein the halide / oxide solid electrolyte layer is disposed facing the positive electrode, and the polymer solid electrolyte layer is disposed facing the negative electrode.

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