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

Abstract

The embodiment of the invention provides a composite solid electrolyte membrane, a preparation method thereof and a solid-state battery. The composite solid electrolyte membrane comprises a first electrolyte membrane, a second electrolyte membrane and a third electrolyte membrane which are sequentially stacked, the first electrolyte membrane contains a first solid electrolyte with D50 being A1, the second electrolyte membrane contains a second solid electrolyte with D50 being A2, the third electrolyte membrane contains a third solid electrolyte with D50 being A3, and both A1 and A3 are larger than A2; the content of the first solid electrolyte in the first electrolyte membrane is recorded as W1, the content of the second solid electrolyte in the second electrolyte membrane is recorded as W2, the content of the third solid electrolyte in the third electrolyte membrane is recorded as W3, and W1 > W2 > W3. Through gradient optimization of the content of the solid electrolyte and control of the particle size relation of the solid electrolyte, the problem that the sulfide solid-state battery is poor in electrical performance and cycle performance is solved.

Description

Technical Field

[0001] This application relates to the field of solid-state batteries, specifically to a composite solid-state electrolyte membrane, its preparation method, and a solid-state battery. Background Technology

[0002] As a next-generation energy storage technology, the performance of all-solid-state batteries hinges on the choice of solid-state electrolyte materials. Among the three major categories of solid-state electrolytes—oxide, polymer, and sulfide—sulfide solid-state electrolytes, especially Li6PS5X (X=Cl,Br,I) materials, possess the highest room-temperature ionic conductivity (10⁻⁶) among all solid-state electrolytes. -3 ~10 -2 S·cm -1 This is considered one of the most promising pathways to achieve high energy density and high power density all-solid-state batteries.

[0003] Given the significant advantages of sulfide solid electrolytes in electrochemical performance, their film-forming technology has become crucial for industrialization. Wet processes have been extensively studied due to their ease of large-area, continuous production. However, existing technologies typically employ a single sulfide solid electrolyte membrane, such as Li6PS5Cl (LPSC), mixed with a small amount of binder and coated onto a substrate. However, electrolyte membranes prepared by this method often suffer from poor mechanical strength and inadequate compatibility with the electrode interface, making direct demolding and application in the stacking process of pouch cells difficult.

[0004] In summary, although sulfide solid electrolyte materials exhibit outstanding ionic conductivity, existing technologies for the preparation and performance control of solid electrolyte membranes still have significant shortcomings: First, there is a contradiction between mechanical and electrochemical properties. Increasing the binder content can enhance the membrane's flexibility and strength, but it severely sacrifices ionic conductivity; conversely, reducing the binder content increases membrane brittleness, making it impossible to detach or stack. Second, interface issues are prominent. For example, homogeneous monolayer electrolyte membranes struggle to simultaneously maintain interfacial stability and compatibility with both positive and negative electrode materials. Third, process compatibility is poor. Electrolyte membranes prepared by existing methods often require a carrier and cannot form self-supporting membranes, making them difficult to cut and stack like traditional separators, thus limiting their application in pouch cells.

[0005] In other words, existing solid electrolyte membranes have the problem of not being able to balance mechanical and electrochemical performance, and also have serious interface problems, thus making it difficult to provide stable support for the electrical and cycle performance of the solid-state battery.

[0006] There is currently no good solution to the above problems. Summary of the Invention

[0007] This application provides a composite solid electrolyte membrane, its preparation method, and a solid battery, to at least solve the technical problem in the prior art where the solid electrolyte membrane has poor interfacial performance and is difficult to balance mechanical and electrochemical performance, resulting in poor electrical and cycle performance of the solid battery.

[0008] According to a first aspect of the embodiments of this application, a composite solid electrolyte membrane is provided, comprising a first electrolyte membrane, a second electrolyte membrane, and a third electrolyte membrane stacked sequentially. The first electrolyte membrane contains a first solid electrolyte with a D50 of A1, the second electrolyte membrane contains a second solid electrolyte with a D50 of A2, and the third electrolyte membrane contains a third solid electrolyte with a D50 of A3, wherein A1 and A3 are both greater than A2. The content of the first solid electrolyte in the first electrolyte membrane is denoted as W1, the content of the second solid electrolyte in the second electrolyte membrane is denoted as W2, and the content of the third solid electrolyte in the third electrolyte membrane is denoted as W3, where W1 > W2 > W3.

[0009] Furthermore, the first electrolyte membrane also contains a first binder, the second electrolyte membrane also contains a second binder, and the third electrolyte membrane also contains a third binder, and: in the first electrolyte membrane, the weight ratio of the first solid electrolyte to the first binder is (90~99):(1~10); in the second electrolyte membrane, the weight ratio of the second solid electrolyte to the second binder is (70~80):(20~30); in the third electrolyte membrane, the weight ratio of the third solid electrolyte to the third binder is (40~50):(50~60).

[0010] Furthermore, in the first electrolyte membrane, the D50 of the first solid electrolyte is 3μm to 5μm; in the second electrolyte membrane, the D50 of the second solid electrolyte is 500nm to 1μm; and in the third electrolyte membrane, the D50 of the third solid electrolyte is 3μm to 5μm.

[0011] Furthermore, the first solid electrolyte and the third solid electrolyte are first sulfide electrolytes; the second solid electrolyte is selected from at least one of second sulfide electrolytes, oxide electrolytes and halide electrolytes.

[0012] Furthermore, W1:W2:W3 is (18~20):(15~16):(4~10); A1:A2:A3 is (8~4):1:(8~4).

[0013] Furthermore, the thickness of the composite solid electrolyte membrane is 30±2μm, and the thickness ratio of the first electrolyte membrane, the second electrolyte membrane, and the third electrolyte membrane is (0.7~0.8):1:(0.7~0.8).

[0014] According to a second aspect of the embodiments of this application, a method for preparing the above-mentioned composite solid electrolyte membrane is also provided, comprising: step S1, preparing a first solid electrolyte, a second solid electrolyte, and a third solid electrolyte into a first slurry, a second slurry, and a third slurry, respectively; step S2, preparing a composite membrane layer by coating treatment, wherein the composite membrane layer includes a first membrane layer, a second membrane layer, and a third membrane layer stacked sequentially; and the composite membrane layer is sequentially dried and rolled to obtain a composite solid electrolyte membrane.

[0015] Further, in step S1, the solid content of the first slurry, the second slurry, and the third slurry is independently 40%~60%; the first slurry, the second slurry, and the third slurry each independently use at least one of butyl butyrate, butyl isobutyrate, anisole, toluene, p-xylene, n-heptane, dichloromethane, dichloroethane, dichloropropane, dibromomethane, dibromoethane, dibromopropane, and cyclohexane as a solvent.

[0016] Furthermore, in step S2, the drying process includes a first stage at a temperature of 50±5℃ and a second stage at a temperature of 80±5℃, performed sequentially; the rolling is carried out under a rolling pressure of 5±0.5MPa.

[0017] According to a third aspect of the embodiments of this application, a solid-state battery is also provided, including a positive electrode film, a negative electrode film, and an electrolyte film, wherein the electrolyte film is the aforementioned composite solid-state electrolyte film, and the first electrolyte film in the composite solid-state electrolyte film is disposed opposite to the positive electrode film, and the third electrolyte film is disposed opposite to the negative electrode film.

[0018] In this embodiment, a multi-layer composite structure design is adopted, and the ion transport channels inside the composite electrolyte membrane are regulated and its mechanical properties are optimized by gradient optimization of the solid electrolyte content and control of the solid electrolyte particle size relationship. This achieves the goal of effectively balancing mechanical and electrochemical performance, thereby significantly improving the cycle stability and capacity retention of the all-solid-state soft-pack battery, and solving the problem of poor electrical and cycle performance of sulfide solid-state batteries. Attached Figure Description

[0019] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0020] Figure 1 This is a schematic diagram of the structure of the composite solid electrolyte membrane provided according to Embodiment 1 of this application.

[0021] The above figures include the following reference numerals:

[0022] 10. First electrolyte membrane; 20. Second electrolyte membrane; 30. Third electrolyte membrane. Detailed Implementation

[0023] 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 embodiments.

[0024] As described in the background section, existing solid electrolyte membranes suffer from poor interfacial performance and difficulty in balancing mechanical and electrochemical properties, leading to poor electrical and cycle performance in solid-state batteries. To address these issues, according to a first aspect of this application, a composite solid electrolyte membrane is provided, comprising a first electrolyte membrane 10, a second electrolyte membrane 20, and a third electrolyte membrane 30 stacked sequentially. The first electrolyte membrane 10 contains a first solid electrolyte with a D50 of A1, the second electrolyte membrane 20 contains a second solid electrolyte with a D50 of A2, and the third electrolyte membrane 30 contains a third solid electrolyte with a D50 of A3, where A1 and A3 are both greater than A2. The content of the first solid electrolyte in the first electrolyte membrane 10 is denoted as W1, the content of the second solid electrolyte in the second electrolyte membrane 20 as W2, and the content of the third solid electrolyte in the third electrolyte membrane 30 as W3, where W1 > W2 > W3.

[0025] This application employs a multi-layer composite structure design and, by optimizing the solid electrolyte content through gradient optimization and controlling the particle size relationship of the solid electrolyte, regulates the ion transport channels within the composite electrolyte membrane and optimizes its mechanical properties, achieving an effective balance between mechanical and electrochemical performance. Specifically, in the aforementioned composite solid electrolyte membrane: the first electrolyte membrane 10 (high electrolyte content layer) ensures close contact with the cathode material, improves ionic conductivity, and enhances the rate performance of the battery; the third electrolyte membrane 30 (low electrolyte, i.e., high binder content layer) serves as a mechanical support, endowing the electrolyte membrane with good flexibility and mechanical strength, facilitating demolding and stacking; while the second electrolyte membrane 20 (intermediate layer) not only fills the particle voids between the first and third layers but also promotes the formation of ion transport channels, while inhibiting the growth of lithium dendrites, thus improving battery safety.

[0026] In summary, this application effectively overcomes the interlayer compatibility problem by adjusting the particle size and content of solid electrolytes in different layers. The high content of solid electrolyte in the first electrolyte membrane 10 ensures good contact with the positive electrode, while the third electrolyte membrane 30 ensures compatibility with the negative electrode material. Simultaneously, the second electrolyte membrane 20 effectively fills the voids in the microstructure through its mediating effect, promoting a tight bond between the formed composite solid electrolyte membrane and the electrode material, reducing interfacial impedance, and ultimately improving the battery's rate performance and capacity retention.

[0027] In several embodiments, the first electrolyte membrane 10 further includes a first binder, the second electrolyte membrane 20 further includes a second binder, and the third electrolyte membrane 30 further includes a third binder. Specifically: in the first electrolyte membrane 10, the weight ratio of the first solid electrolyte to the first binder is (90-99):(1-10); in the second electrolyte membrane 20, the weight ratio of the second solid electrolyte to the second binder is (70-80):(20-30); and in the third electrolyte membrane 30, the weight ratio of the third solid electrolyte to the third binder is (40-50):(50-60). The above preferred embodiments further define the weight ratio of solid electrolyte to binder in each layer to more significantly optimize the physical and electrochemical properties of each layer. Specifically, the first electrolyte membrane 10 employs a high electrolyte (90-99) to low binder (1-10) ratio, thereby maximizing the retention of free migration space for ions and thus significantly improving the conductivity of lithium ions. The ratio of solid electrolyte to binder in the second electrolyte membrane 20 (70-80:20-30) better alleviates stress differences between different layers, reduces crack formation, and further promotes the uniform distribution of lithium ions in the electrolyte membrane, enhancing the overall stability and consistency of the membrane. The low electrolyte (40-50) and high binder (50-60) ratio in the third electrolyte membrane 30 forms a stronger three-dimensional network structure, further enhancing the mechanical properties of the resulting composite electrolyte membrane. This allows it to better withstand compression and bending during battery assembly without cracking. Ultimately, the resulting composite electrolyte membrane maintains higher long-term stability and safety in the battery.

[0028] In practical applications, in the first electrolyte membrane 10, the weight ratio of the first solid electrolyte to the first binder can be 90:10, 91:9, 92:8, 93:7, 94:6, 95:5, 96:4, 97:3, 98:2, 99:1, or any range of the above values. In the second electrolyte membrane 20, the weight ratio of the second solid electrolyte to the second binder can be 70:30, 71:29, 72:28, 73:27, 74:26, 75:25, 76:24, 77:23, 78:22, 79:21; 80:20, or any range of the above values. In the third electrolyte membrane 30, the weight ratio of the third solid electrolyte to the third binder can be 40:60, 41:59, 42:58, 43:57, 44:56, 45:55, 46:54, 47:53, 48:52, 49:51; 50:50, or any of the above values ​​within a range.

[0029] Specifically, the first adhesive, the second adhesive, and the third adhesive may each be independently selected from one or more of the following: styrene-butadiene-styrene triblock copolymer (SEBS, manufacturer may be Macklin), hydrogenated styrene-isoprene-styrene block copolymer (SEPS, manufacturer may be Aladdin), polyvinyl acetate (PVAC, manufacturer may be Macklin), nitrile rubber (NBR, manufacturer may be Aladdin), hydrogenated nitrile rubber (HNBR, manufacturer may be Aladdin), polyvinylidene fluoride (PVDF, manufacturer may be Alfa), polyacrylic acid (PAA, manufacturer may be Aladdin), and polyvinyl alcohol (PVA, manufacturer may be Aladdin).

[0030] In some embodiments, the D50 particle size of the solid electrolytes in the three layers is specifically optimized as follows: in the first electrolyte membrane 10, the D50 of the first solid electrolyte is 3 μm to 5 μm; in the second electrolyte membrane 20, the D50 of the second solid electrolyte is 500 nm to 1 μm; and in the third electrolyte membrane 30, the D50 of the third solid electrolyte is 3 μm to 5 μm. The larger particle size of the solid electrolytes in the first and third electrolyte membranes 10 and 30 can better disperse stress and reduce the formation of microcracks. Even when subjected to external forces during battery use, they can better maintain the structural integrity of the electrolyte membrane, thereby further reducing the risk of short circuits. Meanwhile, the smaller particle size of the electrolyte particles in the second electrolyte membrane 20 can be more tightly packed during the membrane fabrication process, thereby further reducing the gaps and contact resistance between particles, promoting more efficient lithium-ion transport, and improving its electrochemical response capability at high current densities, thus significantly improving the energy efficiency and cycle performance of the final solid-state battery.

[0031] In some embodiments, the first solid electrolyte and the third solid electrolyte are first sulfide electrolytes; the second solid electrolyte is selected from at least one of second sulfide electrolytes, oxide electrolytes, and halide electrolytes. Based on this preferred embodiment, sulfide electrolytes are preferred as materials for the first and third layers because they have high ionic conductivity at room temperature, which can more effectively promote the rapid transport of lithium ions between the positive and negative electrodes, crucial for improving the charge / discharge speed and energy density of the battery. Simultaneously, sulfide solid electrolytes have high chemical stability, enabling stable operation over a wide voltage range, which helps extend the battery's lifespan. Furthermore, the variety of materials available for the second layer allows for a better balance of the performance differences between the first electrolyte membrane 10 and the third electrolyte membrane 30, creating a more stable and efficient ion transport environment, thereby comprehensively improving the overall performance of the resulting composite solid electrolyte membrane.

[0032] In practical applications, the first sulfide electrolyte and the second sulfide electrolyte are each independently selected from at least one of the following types: Li6PS5X, where X is Cl, Br, or I; Li 10 MP2S 12 Where M is Si, Ge, or Sn; (100-x)Li₂S·xP₂S₅, where x is 20-30; the oxide electrolyte is selected from at least one of the following types: Li₅La₃M₂O 12 Where M is Nb or Ta; Li7La3Zr2O 12 LiM2(PO4)3, where M is Al, La, Ti, or Ge; the chemical formula of the halide electrolyte is Li a MX b Where X is F, Cl, Br, or I, and M is Sc, Y, La, Al, Ga, In, Ti, Mn, Fe, Cu, Zn, or Mg. Preferably, both the first and third solid electrolytes are Li6PS5Cl (LPSC), and the second solid electrolyte is preferably Li7La3Zr2O. 12 (LLZO) can better utilize the synergistic effect of large-particle-size LPSC and small-particle-size LLZO to achieve better performance of solid electrolyte membranes in terms of mechanical strength, ionic conductivity and electrochemical stability.

[0033] In some embodiments, to better optimize the charge carrier concentration in each layer, thereby strengthening the lithium-ion transport path and accelerating charge migration while forming a more robust interface structure and more effectively preventing the formation and penetration of lithium dendrites, the preferred ratio of W1:W2:W3 is (18~20):(15~16):(4~10). Furthermore, to promote the formation of a more robust framework structure by the large-particle-size first and third solid electrolytes, and to better fill the space formed by the large-particle-size second solid electrolyte, creating a denser ion transport path, the preferred ratio of A1:A2:A3 is (8~4):1:(8~4).

[0034] In some more specific embodiments, the first electrolyte membrane 10 contains a first solid electrolyte with a D50 of 4±0.5μm and a content of 95wt%~97wt%, the second electrolyte membrane 20 contains a second solid electrolyte with a D50 of 500nm~1μm and a content of 75wt%~80wt%, and the third electrolyte membrane 30 contains a third solid electrolyte with a D50 of 4±0.5μm and a content of 45wt%~50wt%. This more detailed and precise selection of electrolyte content and particle size in each layer enables the construction of a more stable microstructure, increasing the membrane's elasticity and toughness while significantly reducing impedance, thereby obtaining a composite solid electrolyte membrane with higher electrical performance and stability.

[0035] In some embodiments, the thickness of the composite solid electrolyte membrane is 30±2 μm, and the thickness ratio of the first electrolyte membrane 10, the second electrolyte membrane 20, and the third electrolyte membrane 30 is (0.7~0.8):1:(0.7~0.8). For the above-mentioned composite solid electrolyte membrane, by optimizing its total thickness and the thickness relationship of each layer, it is possible to better maintain the rational allocation of the functions of each layer while achieving a thinner composite membrane, thereby better meeting the requirements of the resulting composite solid electrolyte membrane in terms of energy density and structural stability.

[0036] The embodiments of this application also provide a method for preparing the above-mentioned composite solid electrolyte membrane, including: step S1, preparing a first solid electrolyte, a second solid electrolyte, and a third solid electrolyte into a first slurry, a second slurry, and a third slurry, respectively; step S2, preparing a composite membrane layer by coating treatment, wherein the composite membrane layer includes a first membrane layer, a second membrane layer, and a third membrane layer stacked sequentially; the composite membrane layer is then subjected to drying and rolling to obtain a composite solid electrolyte membrane.

[0037] Regarding the aforementioned method for preparing composite solid electrolyte membranes, by separately preparing the first, second, and third solid electrolytes into slurries, and then preparing the composite membrane layer through steps such as coating, drying, and rolling, uniform coating and densification of the electrolyte membrane can be achieved, ultimately yielding a high-performance composite solid electrolyte membrane. Furthermore, the "sequential coating-rolling-demolding" preparation method provided in this application is simple and easily scalable for large-area continuous production. The resulting self-supporting multilayer composite solid electrolyte membrane can be directly cut and stacked, perfectly compatible with existing liquid battery electrode assembly processes, requiring no modification to existing production lines, thus significantly reducing the industrialization threshold and cost of all-solid-state batteries.

[0038] In step S1, in order to further improve the uniformity and stability of the formed composite membrane and enable the three membrane layers to perform their functions more significantly, it is preferred that the solid content of the first slurry, the second slurry and the third slurry are each independently 40% to 60%; the first slurry, the second slurry and the third slurry each independently use at least one of butyl butyrate, butyl isobutyrate, anisole, toluene, p-xylene, n-heptane, dichloromethane, dichloroethane, dichloropropane, dibromomethane, dibromoethane, dibromopropane and cyclohexane as solvent.

[0039] In step S2, to reduce porosity and cracks caused by rapid solvent evaporation, more effectively maintain the density and uniformity of the film layer, and better preserve particle integrity and film structure stability, the drying process preferably includes a first stage at a temperature of 50±5℃ and a second stage at a temperature of 80±5℃; the rolling is performed under a rolling pressure of 5±0.5MPa. In practical applications, the coating process is performed on a substrate, and the substrate is selected from polyethylene terephthalate (PET) carrier, copper foil, aluminum foil, and polyethylene (PE) separator.

[0040] Embodiments of this application also provide a solid-state battery, including a positive electrode film, a negative electrode film, and an electrolyte film. The electrolyte film is the aforementioned composite solid-state electrolyte film, wherein a first electrolyte film 10 is disposed opposite to the positive electrode film, and a third electrolyte film 30 is disposed opposite to the negative electrode film. Based on the aforementioned high-performance composite solid-state electrolyte film, when it is assembled into a solid-state battery, the resulting solid-state battery exhibits higher electrical performance and cycle stability. Specifically, the high ionic conductivity of the first electrolyte film 10 helps to accelerate the transport of lithium ions between the positive electrode material and the electrolyte film, improving the rate performance of the battery; while the high mechanical strength of the third electrolyte film 30 can reduce the interfacial impedance between the negative electrode material and the electrolyte film, enhancing the cycle stability of the battery, while preventing the formation of lithium dendrites and improving the safety of the battery.

[0041] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0042] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0043] 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.

[0044] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0045] Example 1

[0046] A structural schematic diagram is shown below. Figure 1 Preparation method of composite solid electrolyte membrane:

[0047] (1-1) Li6PS5Cl (LPSC, D50=4.0 μm) and styrene-butadiene-styrene triblock copolymer (SEBS) were mixed in butyl butyrate solvent at a mass ratio of 95:5, with a solid content of 50%. The stirring speed was set to 60 r / min revolution and 3000 r / min dispersion speed. The mixture was homogenized for 30 min to obtain a uniform first slurry.

[0048] (1-2) Li7La3Zr2O 12(LLZO, D50=500 nm) and SEBS were mixed in butyl butyrate solvent at a mass ratio of 75:25, with a solid content of 55%. The stirring speed was set to 60 r / min revolution and 3000 r / min dispersion speed. The mixture was homogenized for 30 min to obtain a uniformly mixed second slurry.

[0049] (1-3) Li6PS5Cl (LPSC, D50=4.0 μm) and SEBS were mixed in butyl butyrate solvent at a mass ratio of 45:55, with a solid content of 45%. The stirring speed was set to 60 r / min revolution and 3000 r / min dispersion speed. The mixture was homogenized for 30 min to obtain a uniformly mixed third slurry.

[0050] (2) On a wide (≥200 mm) polyethylene terephthalate (PET) carrier, a third slurry, a second slurry and a first slurry are sequentially coated to form a third film layer with a thickness of 35 μm, a second film layer with a thickness of 50 μm and a first film layer with a thickness of 40 μm, respectively. After being dried at a stepped temperature of 50°C to 80°C and rolled at 5 MPa, it is then vacuum dried at 120°C for 12 h. After cooling, it is completely peeled off from the PET carrier to obtain a self-supporting multilayer composite solid electrolyte membrane containing a first electrolyte membrane 10, a second electrolyte membrane 20 and a third electrolyte membrane 30, with a total thickness of about 30 μm.

[0051] In the resulting composite solid electrolyte membrane, the first electrolyte membrane 10 contains a first solid electrolyte Li6PS5Cl with a D50 of 4 μm and a content of 95 wt%, and the second electrolyte membrane 20 contains a second solid electrolyte Li7La3Zr2O with a D50 of 500 nm and a content of 75 wt%. 12 The third electrolyte membrane 30 contains a third solid electrolyte Li6PS5Cl with a D50 of 4μm and a content of 45wt%. The thickness ratio of the first electrolyte membrane 10, the second electrolyte membrane 20, and the third electrolyte membrane 30 is 8:10:7.

[0052] Example 2

[0053] A method for preparing a composite solid electrolyte membrane:

[0054] The only difference between this embodiment and Embodiment 1 is that:

[0055] In step (1-1), the mass ratio of the first solid electrolyte LPSC to SEBS is changed to 97:3;

[0056] In step (1-2), the mass ratio of the second solid electrolyte LLZO and SEBS is changed to 80:20;

[0057] In steps (1-3), the mass ratio of the third solid electrolyte LPSC and SEBS is changed to 50:50.

[0058] Example 3

[0059] A method for preparing a composite solid electrolyte membrane:

[0060] The only difference between this embodiment and Embodiment 1 is that, in step (1-2), the D50 of the second solid electrolyte LLZO used is changed to 700nm.

[0061] Example 4

[0062] A method for preparing a composite solid electrolyte membrane:

[0063] The only difference between this embodiment and Embodiment 1 is that, in step (1-2), the D50 of the second solid electrolyte LLZO used is changed to 1 μm.

[0064] Example 5

[0065] A method for preparing a composite solid electrolyte membrane:

[0066] The only difference between this embodiment and Embodiment 1 is that:

[0067] In step (1-1), the mass ratio of the first solid electrolyte LPSC and SEBS is changed to 80:20;

[0068] In step (1-2), the mass ratio of the second solid electrolyte LLZO and SEBS is changed to 60:40;

[0069] In steps (1-3), the mass ratio of the third solid electrolyte LPSC and SEBS is changed to 55:45.

[0070] Example 6

[0071] A method for preparing a composite solid electrolyte membrane:

[0072] The only difference between this embodiment and Embodiment 1 is that:

[0073] In step (1-1), the mass ratio of the first solid electrolyte LPSC to SEBS is changed to 99.9:0.1;

[0074] In step (1-2), the mass ratio of the second solid electrolyte LLZO and SEBS is changed to 90:10;

[0075] In steps (1-3), the mass ratio of the third solid electrolyte LPSC and SEBS is changed to 30:70.

[0076] Example 7

[0077] A method for preparing a composite solid electrolyte membrane:

[0078] The only difference between this embodiment and Embodiment 1 is that:

[0079] In step (1-1), the D50 of the first solid electrolyte LPSC is changed to 6 μm;

[0080] In step (1-2), the D50 of the second solid electrolyte LLZO is changed to 300 nm;

[0081] In steps (1-3), the D50 of the third solid electrolyte LPSC is changed to 2 μm.

[0082] Example 8

[0083] A method for preparing a composite solid electrolyte membrane:

[0084] The only difference between this embodiment and Embodiment 1 is that:

[0085] In step (1-1), the D50 of the first solid electrolyte LPSC is changed to 2 μm;

[0086] In step (1-2), the D50 of the second solid electrolyte LLZO is changed to 1.5 μm;

[0087] In steps (1-3), the D50 of the third solid electrolyte LPSC is changed to 6 μm.

[0088] Example 9

[0089] A method for preparing a composite solid electrolyte membrane:

[0090] The only difference between this embodiment and Embodiment 1 is that the coating conditions are changed in step (2) to obtain a third film layer with a thickness of 25 μm, a second film layer with a thickness of 50 μm, and a first film layer with a thickness of 50 μm. At this time, in the final composite solid electrolyte membrane, the thickness ratio of the first electrolyte membrane 10, the second electrolyte membrane 20, and the third electrolyte membrane 30 is 1:1:0.5.

[0091] Example 10

[0092] A method for preparing a composite solid electrolyte membrane:

[0093] The only difference between this embodiment and Embodiment 1 is that the coating conditions are changed in step (2) to obtain a third film layer with a thickness of 50 μm, a second film layer with a thickness of 50 μm, and a first film layer with a thickness of 25 μm. At this time, in the final composite solid electrolyte membrane, the thickness ratio of the first electrolyte membrane 10, the second electrolyte membrane 20, and the third electrolyte membrane 30 is 0.5:1:1.

[0094] Comparative Example 1

[0095] A method for preparing a solid electrolyte membrane:

[0096] The only difference between this comparative example and Example 1 is that the second electrolyte membrane 20 and the third electrolyte membrane 30 are not provided; instead, the first electrolyte membrane 10 alone is used directly as the obtained solid electrolyte membrane sample.

[0097] However, during the preparation process, the individual first electrolyte membrane 10 formed in this comparative example could not be detached due to insufficient strength, and thus could not be stacked.

[0098] Comparative Example 2

[0099] A method for preparing a solid electrolyte membrane:

[0100] The only difference between this comparative example and Example 1 is that the first electrolyte membrane 10 and the third electrolyte membrane 30 are not provided; instead, the second electrolyte membrane 20 alone is used directly as the obtained solid electrolyte membrane sample.

[0101] Comparative Example 3

[0102] A method for preparing a solid electrolyte membrane:

[0103] The only difference between this comparative example and Example 1 is that the first electrolyte membrane 10 and the second electrolyte membrane 20 are not provided; instead, the third electrolyte membrane 30 alone is used directly as the obtained solid electrolyte membrane sample.

[0104] Comparative Example 4

[0105] A method for preparing a composite solid electrolyte membrane:

[0106] The only difference between this comparative example and Example 1 is that:

[0107] In step (1-1), the mass ratio of the first solid electrolyte LPSC and SEBS is changed to 95:5;

[0108] In step (1-2), the mass ratio of the second solid electrolyte LLZO and SEBS is changed to 45:55;

[0109] In steps (1-3), the mass ratio of the third solid electrolyte LPSC and SEBS is changed to 75:25.

[0110] Comparative Example 5

[0111] A method for preparing a composite solid electrolyte membrane:

[0112] The only difference between this comparative example and Example 1 is that:

[0113] In step (1-1), the mass ratio of the first solid electrolyte LPSC and SEBS is changed to 75:25;

[0114] In step (1-2), the mass ratio of the second solid electrolyte LLZO and SEBS is changed to 95:5;

[0115] In steps (1-3), the mass ratio of the third solid electrolyte LPSC and SEBS is changed to 45:55.

[0116] Comparative Example 6

[0117] A method for preparing a composite solid electrolyte membrane:

[0118] The only difference between this comparative example and Example 1 is that, in steps (1-2), the D50 of the second solid electrolyte LLZO is changed to 4 μm.

[0119] Test methods

[0120] Tensile strength of electrolyte membrane samples: Each electrolyte membrane sample was cut into rectangular strips 10 mm wide and 60 mm long. The samples were tested using a universal testing machine at a tensile rate of 10 mm / min. The tensile strength (MPa) was calculated based on the ratio of the maximum tensile force (N) before fracture to the initial cross-sectional area of ​​the strip.

[0121] Ionic conductivity of electrolyte membrane samples: Each prepared electrolyte membrane was punched into circular samples with a diameter of 9.8 mm. A pressurized mold battery was assembled in a glove box: a. The thickness of the empty mold was measured; b. The 9.8 mm diameter circular samples were sandwiched between two blocking electrodes and pre-pressed to 3.5 MPa using a hydraulic press, holding the pressure for 1 min; c. The mold was assembled into a stainless steel casing, and pressurized to 9.5 MPa using a hydraulic press. The bolts were tightened, and the pressure was further increased to 9.5 MPa. The pressure drop was observed to be <0.5 MPa within 1 min. The AC impedance of the mold battery (1 MHz ~ 0.1 Hz) was tested using an electrochemical workstation. The stainless steel casing of the pressurized mold battery was disassembled, the thickness difference of the mold was measured, and the ionic conductivity was calculated.

[0122] Battery sample preparation:

[0123] Weigh 80 wt.% LiNi into the glove box. 0.8 Co 0.1 Mn 0.1 O2 cathode material, 15 wt.% solid electrolyte, 2 wt.% VGCF conductive agent, and 3 wt.% SEBS binder were placed in a sealed ball mill jar and ball-milled in an inert atmosphere at a speed of 600 r / min for 4 h. After ball milling, the cathode mixture was uniformly dispersed in a solvent to prepare a cathode slurry, which was then uniformly coated onto an aluminum foil current collector. The cathode film was obtained through baking, rolling, slitting, and die-cutting processes. The cathode film was then stacked with a solid electrolyte film and a 50 μm lithium foil. After hot pressing at 80℃ and 2 MPa, aluminum-plastic film encapsulation, and isostatic pressing at 500 MPa for 30 min, a fully solid-state soft-pack battery sample was prepared.

[0124] Cycle performance testing of battery samples:

[0125] The cycle performance of each assembled all-solid-state pouch battery at 0.5C and 1000 cycles was tested using a Blue Electricity Tester at 35℃. The energy density E (Wh / kg) was calculated using E=C×V / m, where C is the measured discharge capacity (Ah), V is the average voltage during discharge (V), and m is the mass of the finished battery (kg).

[0126] The solid electrolyte membrane samples obtained in each embodiment and comparative example were subjected to the above tests, and the results are shown in Table 1.

[0127] Table 1

[0128]

[0129] As can be seen from the above description, compared to the comparative examples, the embodiments of the present invention, through a gradient design of the solid electrolyte content in the solid electrolyte membrane and optimization of the electrolyte particle size in different layers, achieve the preparation of a high-performance composite solid electrolyte membrane. The resulting composite solid electrolyte membrane effectively balances mechanical and electrochemical properties, while also better mitigating interface issues with the positive and negative electrodes. When assembled into a solid-state battery, the resulting solid-state battery exhibits superior electrical and cycle performance.

[0130] More specifically, in the various embodiments:

[0131] Comparing Examples 5 and 6 with Example 1, it can be seen that by optimizing the weight ratio of solid electrolyte to binder in the three membrane layers, the physical and electrochemical properties of each layer can be optimized more significantly, ultimately enabling the resulting composite electrolyte membrane to maintain higher long-term stability and safety in the battery.

[0132] Comparing Examples 7 and 8 with Example 1, by optimizing the D50 of the solid electrolyte in the three film layers, stress is better dispersed, microcrack formation is reduced, and the structural integrity of the electrolyte film is better maintained even when subjected to external forces during battery use, thereby further reducing the risk of short circuits. Simultaneously, the voids and contact resistance between particles are further reduced, promoting more efficient lithium-ion transport and improving its electrochemical response at high current densities, thus significantly enhancing the energy efficiency and cycle performance of the final solid-state battery.

[0133] Comparing Examples 9 and 10 with Example 1, by optimizing the thickness ratio of the three membrane layers, it is possible to better maintain the rational allocation of the functions of each layer while achieving a thinner composite membrane, thereby better meeting the requirements of the obtained composite solid electrolyte membrane in terms of energy density and structural stability.

[0134] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0135] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. A composite solid electrolyte membrane, characterized in that, It includes a first electrolyte membrane (10), a second electrolyte membrane (20) and a third electrolyte membrane (30) stacked in sequence. The first electrolyte membrane (10) contains a first solid electrolyte with D50 of A1, the second electrolyte membrane (20) contains a second solid electrolyte with D50 of A2, and the third electrolyte membrane (30) contains a third solid electrolyte with D50 of A3, wherein A1 and A3 are both greater than A2; Let W1 be the content of the first solid electrolyte in the first electrolyte membrane (10), W2 be the content of the second solid electrolyte in the second electrolyte membrane (20), and W3 be the content of the third solid electrolyte in the third electrolyte membrane (30), where W1 > W2 > W3.

2. The composite solid electrolyte membrane according to claim 1, characterized in that, The first electrolyte membrane (10) further comprises a first adhesive, the second electrolyte membrane (20) further comprises a second adhesive, and the third electrolyte membrane (30) further comprises a third adhesive, and: In the first electrolyte membrane (10), the weight ratio of the first solid electrolyte to the first binder is (90~99):(1~10). In the second electrolyte membrane (20), the weight ratio of the second solid electrolyte to the second binder is (70~80):(20~30); In the third electrolyte membrane (30), the weight ratio of the third solid electrolyte to the third binder is (40~50):(50~60).

3. The composite solid electrolyte membrane according to claim 1 or 2, characterized in that, In the first electrolyte membrane (10), the D50 of the first solid electrolyte is 3μm~5μm; In the second electrolyte membrane (20), the D50 of the second solid electrolyte is 500 nm to 1 μm; In the third electrolyte membrane (30), the D50 of the third solid electrolyte is 3μm~5μm.

4. The composite solid electrolyte membrane according to any one of claims 1 to 3, characterized in that, The first solid electrolyte and the third solid electrolyte are both first sulfide electrolytes; The second solid electrolyte is selected from at least one of a second sulfide electrolyte, an oxide electrolyte, and a halide electrolyte.

5. The composite solid electrolyte membrane according to any one of claims 1 to 4, characterized in that, W1:W2:W3 is (18~20):(15~16):(4~10); A1:A2:A3 is (8~4):1:(8~4).

6. The composite solid electrolyte membrane according to any one of claims 1 to 5, characterized in that, The thickness of the composite solid electrolyte membrane is 30±2μm, and the thickness ratio of the first electrolyte membrane (10), the second electrolyte membrane (20) and the third electrolyte membrane (30) is (0.7~0.8):1:(0.7~0.8).

7. A method for preparing a composite solid electrolyte membrane according to any one of claims 1 to 6, characterized in that, include: Step S1: The first solid electrolyte, the second solid electrolyte, and the third solid electrolyte are respectively prepared into a first slurry, a second slurry, and a third slurry; Step S2: After coating treatment, the first slurry, the second slurry, and the third slurry are prepared into a composite membrane layer, which includes a first membrane layer, a second membrane layer, and a third membrane layer stacked in sequence; the composite membrane layer is then dried and rolled in sequence to obtain the composite solid electrolyte membrane.

8. The method for preparing the composite solid electrolyte membrane according to claim 7, characterized in that, In step S1 The solid content of the first slurry, the second slurry, and the third slurry is each independently 40%~60%; The first slurry, the second slurry, and the third slurry each independently use at least one of butyl butyrate, butyl isobutyrate, anisole, toluene, p-xylene, n-heptane, dichloromethane, dichloroethane, dichloropropane, dibromomethane, dibromoethane, dibromopropane, and cyclohexane as a solvent.

9. The method for preparing the composite solid electrolyte membrane according to claim 7, characterized in that, In step S2 The drying process includes a first stage at a temperature of 50±5℃ and a second stage at a temperature of 80±5℃, performed sequentially. The rolling process is carried out under a rolling pressure of 5 ± 0.5 MPa.

10. A solid-state battery, comprising a positive electrode film, a negative electrode film, and an electrolyte film, characterized in that, The electrolyte membrane is a composite solid electrolyte membrane according to any one of claims 1 to 6, wherein the first electrolyte membrane (10) in the composite solid electrolyte membrane is disposed opposite to the positive electrode membrane, and the third electrolyte membrane (30) is disposed opposite to the negative electrode membrane.

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