Solid-state battery positive electrode-electrolyte integrated assembly and preparation method thereof

Abstract

The application discloses a solid-state battery positive electrode-electrolyte integrated assembly and a preparation method thereof, and belongs to the technical field of solid-state battery manufacturing. The method comprises the following steps: gradually thinning a solid-state electrolyte material containing a binder through multi-stage rolling, in the process, by controlling the linear velocity difference between adjacent rollers, the electrolyte film layer is continuously transferred between different rollers, and the non-self-supporting state is maintained during the whole thinning process; when the film layer reaches the target thickness, it is directly transferred to the surface of a pre-prepared positive electrode sheet, and finally, the integrated assembly is obtained through composite rolling. The application innovatively combines the final forming of the electrolyte film and the interface compounding into one step, avoids the film layer defects and winding difficulties caused by repeated peeling and independent winding in the traditional dry process from the root, and realizes the in-situ dense combination with the positive electrode sheet in the state of the highest surface energy of the electrolyte film, reduces the interface impedance, and is suitable for the continuous production of ultra-thin and high-performance solid-state batteries.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, and more specifically, to an integrated cathode-electrolyte assembly for a solid-state battery and its preparation method. Background Technology

[0002] All-solid-state lithium batteries are considered a key development direction for next-generation energy storage technology due to their high energy density and high safety. Among them, the large-scale, defect-free fabrication of the solid electrolyte layer, as well as the construction of a low-impedance interface between it and the positive electrode layer, are the core challenges driving the industrialization of this technology.

[0003] Currently, the dry process is one of the mainstream technologies for preparing solid electrolyte films. It involves mixing electrolyte powder with a small amount of binder (such as polytetrafluoroethylene, PTFE) and then stretching it into a film through multi-stage rolling. However, this process has the following significant drawbacks: First, during the repeated rolling and thinning process, the electrolyte film needs to be peeled off from the roller surface multiple times. This process easily introduces microscopic defects such as cracks and pores into the film surface. At the same time, when the film thickness is reduced to a certain extent, its mechanical strength is insufficient to support independent winding operations, leading to film breakage and severely restricting the feasibility of continuous production.

[0004] Secondly, in traditional cathode-electrolyte composite processes, pre-prepared independent electrolyte membranes are typically laminated with cathode sheets and then bonded together via hot pressing. Since both are rigid solids, their contact interface is essentially a limited point contact, resulting in excessively high interfacial impedance, severely impacting the battery's rate performance and cycle life. Existing technologies often employ methods such as coating the cathode or electrolyte surface with a flexible interface layer or applying extremely high hot-pressing pressure to improve interfacial contact. However, these methods increase process complexity and cost, and their improvement effects are limited.

[0005] Therefore, developing a novel process that can simultaneously solve the challenges of continuous production of dry electrolyte membranes and achieve their combination with low impedance of the positive electrode has significant technological value and industrial implications. Summary of the Invention

[0006] To address the aforementioned problems, this invention aims to overcome the shortcomings of existing technologies and provide a method for preparing an integrated cathode-electrolyte assembly for solid-state batteries. This method achieves non-destructive and continuous preparation of the electrolyte membrane, enabling it to bond with the cathode layer in its optimal physical state, thereby fundamentally reducing interfacial impedance. The core idea of ​​this method is to change the traditional paradigm of "independent membrane formation followed by composite bonding," creatively proposing an in-situ integrated strategy of "simultaneous forming and bonding." Through precise coordination of process parameters, a perfect bond with the cathode is achieved in the instantaneous state of optimal electrolyte membrane performance. Another objective of this invention is to provide an integrated assembly with an excellent interfacial structure prepared by this method.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: On one hand, the present invention provides a method for preparing an integrated positive electrode-electrolyte assembly for a solid-state battery, comprising the following steps: S1: Provides the positive electrode plate; S2: The solid electrolyte material containing the binder is gradually thinned through multi-stage rolling to form an electrolyte film layer; S3: After the electrolyte membrane layer is thinned to the target thickness, it is directly transferred from the surface of the currently attached roller to the surface of the positive electrode sheet; S4: The positive electrode sheet carrying the electrolyte membrane layer is subjected to composite rolling to form an integrated positive electrode-electrolyte assembly; In the multi-stage rolling process, the electrolyte membrane layer is continuously transferred between different rollers by controlling the difference in linear velocity between adjacent rollers, and the electrolyte membrane layer always remains in a non-self-supporting state throughout the thinning process.

[0008] Furthermore, the adhesive is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, styrene-butadiene rubber, polyacrylates and their derivatives.

[0009] Further, based on the total mass of the solid electrolyte material, the polytetrafluoroethylene content is 0.1% to 10%. The solid electrolyte material is at least one of sulfide solid electrolyte, oxide solid electrolyte, halide solid electrolyte, or polymer solid electrolyte.

[0010] Furthermore, the positive electrode is a dry-process positive electrode, comprising a positive electrode active material, a solid electrolyte, a conductive agent, and a polytetrafluoroethylene binder.

[0011] Furthermore, during the multi-stage rolling process, the operating temperature of the rollers is between 20°C and 150°C.

[0012] Furthermore, during the multi-stage rolling process, the linear velocity difference between adjacent rollers is controlled within the range of 5% to 30%. By controlling the linear velocity difference, the electrolyte membrane layer is transferred from the surface of the roller with higher linear velocity to the surface of the roller with lower linear velocity.

[0013] Furthermore, the target thickness is 20 micrometers to 100 micrometers.

[0014] Furthermore, in step S3, the direct transfer step is completed at the penultimate roller of the multi-stage roller pressing device.

[0015] Furthermore, the transfer is achieved by bringing the positive electrode sheet into contact with the penultimate roller bearing the electrolyte membrane layer.

[0016] On the other hand, the present invention also proposes an integrated solid-state battery cathode-electrolyte assembly, which is prepared by the method described above.

[0017] Compared with the prior art, the present invention has the following significant advantages: (1) Solved the problem of continuous production of dry electrolyte membranes: By controlling the differential speed between rollers, the membrane layer is continuously transferred and kept in a non-self-supporting state, which completely avoids the membrane layer damage and winding breakage caused by repeated peeling in the traditional process, and provides a feasible path for the continuous production of ultrathin electrolyte membranes.

[0018] (2) In-situ construction of low-impedance interfaces is achieved: This invention creatively combines the final forming step of the electrolyte membrane with the positive electrode-electrolyte interface composite step into one step. The electrolyte membrane is directly transferred to the surface of the positive electrode sheet in its "optimal state"—when it has been compacted to the target thickness but has not yet peeled off the roller surface, has the highest surface energy, and is free of contamination—and then undergoes final composite. This "in-situ composite" method allows for sufficient microscopic contact between the two materials, resulting in a strong bond. Especially when PTFE is used as a binder, the resulting fiber network forms an interpenetrating structure at the interface during the transfer and composite process, greatly enhancing the interfacial bonding force and providing continuous ion transport channels.

[0019] (3) Improved product performance and process compatibility: The resulting integrated module has a dense structure and low interface impedance, which can be directly used for subsequent battery stacking, simplifying the production process. Experiments show that the integrated module prepared by the method of this invention can reduce the positive electrode / electrolyte interface impedance by more than 45% compared with the traditional lamination method, and the electrolyte layer thickness can be stably controlled below 50 micrometers while maintaining excellent mechanical integrity. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the fabrication process of the integrated solid-state battery cathode-electrolyte assembly of the present invention. Figure 2 This is a schematic diagram of the process of the solid-state battery cathode-electrolyte integrated assembly of the present invention; Figure 3 This is the appearance morphology of the solid-state battery positive electrode-electrolyte integrated assembly of the present invention; Figure 4 The appearance morphology of a traditional electrolyte membrane that has undergone multiple thinning processes; Figure 5 This is a comparison of the impedance spectra of the solid-state battery cathode-electrolyte integrated component of this invention and the battery assembled with a traditional electrolyte membrane. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] Example 1

[0023] Reference Figure 1 The process flow shown in this embodiment details the fabrication of an integrated cathode-electrolyte module for a sulfide-based solid-state battery. The specific steps are as follows: 1. Material preparation: (1) Preparation of positive electrode sheet: High-nickel ternary positive electrode active material (NCM811), Li6PS5Cl sulfide solid electrolyte powder, conductive carbon black (Super P) and 2% by mass of polytetrafluoroethylene (PTFE) emulsion are mixed and the PTFE is fibrousized by high-speed stirring to form a positive electrode mixture. Then, the mixture is pressed into a dry positive electrode sheet with a thickness of about 80μm and self-supporting by a dry rolling process.

[0024] (2) Preparation of electrolyte materials: Li6PS5Cl sulfide solid electrolyte powder and PTFE powder with a mass ratio of 2% are physically mixed evenly in a glove box, and then combed and sheared to make it preliminarily fibrous to obtain electrolyte precursor materials.

[0025] 2. Multi-stage roller pressing and differential speed continuous transfer: The electrolyte precursor material is fed into a three-stage roller pressing system. All roller temperatures are set to 80°C. The linear velocity difference between the first-stage roller (V1) and the second-stage roller (V2) is controlled at 10% (V2's linear velocity is higher than V1). Utilizing the shearing and traction forces generated by this velocity difference, the initially compacted sheet material is completely transferred from the surface of roller V1 to the surface of roller V2, and thinned in the process. Subsequently, the linear velocity difference between roller V2 and the third-stage roller (V3, acting as a transfer roller) is controlled at 5% (V3>V2), further compacting and thinning the film layer on roller V3. The final electrolyte film layer adhering to the surface of roller V3 is approximately 50 μm thick (target thickness), with a smooth and dense surface, firmly attached to the roller surface due to the adhesion of the PTFE fiber network, in an ideal state of "non-self-supporting" but structurally intact. Crucially, from the time of feeding until this point, the film layer has never peeled off from either roller.

[0026] 3. In-situ transfer: The dry-process positive electrode sheet (active material side facing out) prepared in step 1 is guided to form a roller-to-roll contact with the V3 roller (transfer roller). The linear speeds of the guide roller and the V3 roller are precisely controlled to ensure speed synchronization. At the instant the positive electrode sheet contacts the V3 roller with the attached electrolyte membrane, due to the stronger adhesion between the positive electrode sheet surface (containing PTFE) and the electrolyte membrane (containing PTFE), as well as the pressure generated by the roller pressing, the 50μm thick electrolyte membrane is completely and undamagedly "transferred" from the V3 roller surface to the positive electrode sheet surface.

[0027] 4. Composite Roller Pressing: The positive electrode sheet, carrying the fresh electrolyte membrane, then enters the final composite compaction roller pair. Final rolling is performed at 100℃ and 50MPa pressure. During this process, the PTFE fibers at the interface between the positive electrode layer and the electrolyte layer further fuse and interpenetrate under the influence of temperature and pressure, forming a strong interfacial bond. Simultaneously, the electrolyte layer is further densified. The final result is a structurally integrated, interface-fused positive electrode-electrolyte assembly with a total thickness of approximately 130μm, of which the electrolyte layer has a uniform thickness of approximately 50μm.

[0028] Comparative Example 1

[0029] Comparative samples were prepared using a traditional stepwise method: A sulfide solid electrolyte self-supporting membrane with the same composition and thickness (50 μm) as in Example 1 was prepared independently. During the preparation process, the membrane needed to be peeled off from the roller and wound up after each roll forming thinning before the next roll forming was performed, finally obtaining the self-supporting membrane.

[0030] The aforementioned independent electrolyte membrane and the dry-process positive electrode sheet of the same embodiment 1 were precisely stacked in a glove box.

[0031] The laminates were placed in a hot press and hot-pressed at 200 MPa pressure and 100°C for 5 minutes to simulate the traditional composite process, resulting in a comparative sample.

[0032] Performance Testing and Comparative Analysis

[0033] Appearance and microstructure: such as Figure 3 As shown, the integrated component prepared in Embodiment 1 of the present invention has a uniform, smooth, and defect-free electrolyte layer on its surface, exhibiting excellent mechanical integrity, with an electrolyte layer thickness of 50 μm. And as... Figure 4 As shown in the comparative example, obvious longitudinal cracks and local color inhomogeneity (caused by stress concentration) can be observed on the surface of the independent electrolyte membrane prepared by the traditional process, indicating poor mechanical integrity.

[0034] Interfacial electrochemical impedance spectroscopy (EIS) was used to measure the cathode / electrolyte interfacial area ratio impedance of Example 1 and the comparative sample. The results are as follows: Figure 5 As shown. The tests were conducted in a symmetrical battery (positive electrode / electrolyte / positive electrode) structure. The sample in Example 1 showed an interfacial impedance of approximately 8 Ω·cm. 2 The comparative sample, however, has an interfacial impedance as high as approximately 15 Ω·cm. 2 Calculations show that the method of this invention reduces the cathode / electrolyte interface impedance by approximately 47%. This directly demonstrates the superior effect of the "in-situ integrated" process of this invention in constructing low-impedance interfaces.

[0035] The above description is merely a specific embodiment of the present invention. However, those skilled in the art will understand that various modifications and variations can be made to the above embodiments without departing from the principles and spirit of the present invention. For example, the number of rolling stages can be adjusted to two or more than three stages according to the target thickness; the type and content of the binder can be adjusted within a certain range; and the preparation method and specific composition of the positive electrode sheet can also be changed. All such modifications and variations should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing an integrated positive electrode-electrolyte assembly for a solid-state battery, characterized in that, Includes the following steps: S1: Provides the positive electrode plate; S2: The solid electrolyte material containing the binder is gradually thinned through multi-stage rolling to form an electrolyte film layer; S3: After the electrolyte membrane layer is thinned to the target thickness, it is directly transferred from the surface of the currently attached roller to the surface of the positive electrode sheet; S4: The positive electrode sheet carrying the electrolyte membrane layer is subjected to composite rolling to form an integrated positive electrode-electrolyte assembly; In the multi-stage rolling process, the electrolyte membrane layer is continuously transferred between different rollers by controlling the difference in linear velocity between adjacent rollers, and the electrolyte membrane layer always remains in a non-self-supporting state throughout the thinning process. During the multi-stage rolling process, the linear velocity difference between adjacent rollers is controlled within the range of 5% to 30%. By controlling the linear velocity difference, the electrolyte membrane layer is transferred from the surface of the roller with higher linear velocity to the surface of the roller with lower linear velocity. In step S3, the direct transfer step is completed at the penultimate roller of the multi-stage roller pressing device; the transfer is achieved by bringing the positive electrode sheet into contact with the penultimate roller to which the electrolyte membrane layer is attached.

2. The method for preparing an integrated solid-state battery cathode-electrolyte assembly according to claim 1, characterized in that, The adhesive is selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyethylene oxide, styrene-butadiene rubber, polyacrylates and their derivatives.

3. The method for preparing a solid-state battery positive electrode-electrolyte integrated component according to claim 2, characterized in that, The polytetrafluoroethylene content is 0.1% to 10% based on the total mass of the solid electrolyte material; the solid electrolyte material is at least one of sulfide solid electrolyte, oxide solid electrolyte, halide solid electrolyte or polymer solid electrolyte.

4. The method for preparing an integrated solid-state battery cathode-electrolyte assembly according to claim 1, characterized in that, The positive electrode is a dry-process positive electrode, comprising a positive electrode active material, a solid electrolyte, a conductive agent, and a polytetrafluoroethylene binder.

5. The method for preparing an integrated solid-state battery cathode-electrolyte assembly according to claim 1, characterized in that, During the multi-stage rolling process, the operating temperature of the rollers is between 20°C and 150°C.

6. The method for preparing an integrated solid-state battery cathode-electrolyte assembly according to claim 1, characterized in that, The target thickness is 20 micrometers to 100 micrometers.

7. A solid-state battery positive electrode-electrolyte integrated component, characterized in that, Prepared by the method according to any one of claims 1-6.

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