Preparation method of polymer-sulfide solid-state electrolyte based on multi-scale interface design and application thereof in all-solid-state lithium battery

Abstract

The application discloses a preparation method of a polymer-sulfide solid-state electrolyte based on a multi-scale interface design and application of the polymer-sulfide solid-state electrolyte in a full-solid-state lithium battery. 10 SiP2S 12 Three functionally complementary sulfide electrolyte particles, Li7P2S8I and Li3PS4, are used, and a gradient distribution technology is used to make the three particles form a dense and ion transmission path optimized structure in a polymer matrix, micrometer-level particles construct a high-speed ion conduction backbone, and nanometer and submicron particles are closely packed to greatly reduce interface impedance, the introduction of Li7P2S8I widens the electrochemical window from the material source, and the self-repairing functional component in the outermost layer endows the interface with dynamic intelligent response capability, when a microcrack is generated in the interface, the dynamic bond contained in the interface can be reversibly broken and reconstructed, self-repairing of the damage is realized, and the interface is enhanced to resist mechanical and chemical strain caused by temperature change and long-term cycle, and finally, high ion conductivity, excellent interface stability and wide temperature range adaptability are successfully and synergistically realized.

Description

Technical Field

[0001] This invention relates to the field of electrolyte technology, and more particularly to a method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design and its application in all-solid-state lithium batteries. Background Technology

[0002] With ever-increasing demands for high energy density, safety, and cycle life, all-solid-state lithium batteries, due to their use of solid-state electrolytes instead of traditional liquid electrolytes, exhibit superior safety performance and electrochemical stability, becoming an important development direction for next-generation energy storage systems. Among various solid-state electrolytes, sulfide solid-state electrolytes stand out due to their high ionic conductivity (10⁻⁶ Ω·cm). –4 ~10 –2 With its good machinability and high efficiency (S / cm), sulfide solid electrolytes have attracted widespread attention. Typical sulfide solid electrolytes include the Li₂S-P₂S₅ series (such as Li₃PS₄, Li₇P₃S₁₁) and the Li₂S-GeS₂ series (such as Li₂S₂, Li₂S₃S₁₁). 10 GeP2S 12 LGPS (Li₂S-SiS₂) and other systems, such as Li₂S-SiS₂. Among them, LGPS has a room-temperature ionic conductivity of up to 10⁻⁶. –2 S / cm, close to the level of liquid electrolytes.

[0003] However, sulfide solid electrolytes still face the following key problems in practical applications: 1) Poor interfacial stability: When sulfide solid electrolytes come into contact with electrode materials (especially cathode materials), interfacial side reactions easily occur, forming a high-resistivity interfacial layer, which affects ion transport; 2) Narrow electrochemical window: Most sulfide solid electrolytes have a narrow electrochemical stability window (approximately 1.7-2.5 V vs. Li). + / Li), which is prone to oxidation and decomposition under high voltage cathode materials; 3) Poor interface contact: The solid-solid interface has a limited contact area, resulting in high interface impedance and affecting battery performance; 4) Sensitivity to moisture: Sulfide solid electrolytes are extremely sensitive to moisture, and will generate H2S gas when in contact with water, which increases the difficulty of preparation and use; 5) Temperature change leads to interface problems: During temperature change, the thermal expansion coefficients of electrode materials and electrolytes are mismatched, resulting in interface separation or cracking, which further increases the interface impedance.

[0004] To address these issues, researchers have proposed various interface modification strategies. For example, coating the electrode surface with a protective layer (such as Li3PO4, LiNbO3, etc.) to suppress interfacial side reactions; adding polymer electrolytes to form composite electrolytes to improve interfacial contact; and employing in-situ interface layer formation methods, such as generating Li2S-P2S5 glass in situ on the electrode surface. However, existing interface modification technologies still have the following limitations: 1) Single-scale interface design: Most interface modification methods focus only on single-scale (such as nanoscale or microscale) interface structures, ignoring multi-scale synergistic effects; 2) Static interface structure: Existing interface layers are usually static structures, unable to adapt to the dynamic changes of the battery under different temperatures and charge / discharge states; 3) Poor compatibility between the interface layer and the electrode / electrolyte: Many interface layers, while suppressing interfacial side reactions, have poor compatibility with the electrode or electrolyte, creating new interface problems; 4) Complex preparation processes: Some interface modification methods require complex equipment and processes, making large-scale production difficult.

[0005] In recent years, polymer-in-ceeramic structures have shown promise as a novel composite electrolyte structure for improving interfacial properties. This structure forms a continuous ion transport network by introducing a small amount of polymer between sulfide particles, while maintaining the high ionic conductivity of the sulfide electrolyte. However, existing polymer-in-ceeramic structure designs mainly focus on a single scale, lacking consideration for multi-scale synergistic design.

[0006] Therefore, developing a sulfide solid electrolyte based on multi-scale interface design and constructing an interface structure that combines high ionic conductivity, good interface stability, and adaptability to temperature changes is of great significance for promoting the practical application of all-solid-state lithium batteries. Summary of the Invention

[0007] This invention overcomes the shortcomings of the prior art and provides a method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design and its application in all-solid-state lithium batteries.

[0008] To achieve the above objectives, the technical solution adopted by this invention is as follows: a method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design, comprising the following steps: S1: The sulfide precursors were mixed and heat-treated to obtain Li. 10 SiP2S 12 Li7P2S8I and Li3PS4 sulfide solid electrolyte particles; S2: Li 10 SiP2S 12Sulfide solid electrolyte particles of 1-10 μm, 100-1000 nm and 10-100 nm were prepared from Li7P2S8I and Li3PS4, respectively, and were mixed with polymer precursors. A multi-scale interface structure was constructed by using gradient distribution technology. S3: A highly elastic and tough polymer is coated on the surface of a multi-scale interface structure to form a buffer interface layer; S4: Coat a self-healing functional component onto the buffer interface layer. The self-healing functional component is one or more of a polymer containing dynamic covalent bonds, a supramolecular polymer, or an ionic cross-linked polymer, to obtain a polymer-sulfide solid electrolyte based on multi-scale interface design.

[0009] In a preferred embodiment of the present invention, the sulfide precursor is selected from one or more of the following: Li2S, P2S5, GeS2, SiS2, B2S3.

[0010] In a preferred embodiment of the present invention, the polymer precursor is selected from one or more of the following: polyethylene glycol dimethyl ether (PEGDME), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene glycol (PEG), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN).

[0011] In a preferred embodiment of the present invention, the gradient distribution technology includes: layer-by-layer assembly, gradient deposition, and centrifugal separation.

[0012] In a preferred embodiment of the present invention, the highly elastic and tough polymer network is formed by the following methods: in-situ polymerization, crosslinking reaction, and grafting reaction.

[0013] In a preferred embodiment of the present invention, the heat treatment temperature in S1 is 200-600℃ and the time is 1-24h.

[0014] In a preferred embodiment of the present invention, the mass ratio of the sulfide solid electrolyte particles to the polymer precursor in step S2 is 70-95:5-30.

[0015] In a preferred embodiment of the present invention, the thickness of the buffer interface layer is 1-20 μm, and the content of the self-healing functional component in the interface layer is 1-20 wt%.

[0016] To achieve the above objectives, the second technical solution adopted by this invention is: a sulfide solid electrolyte multi-scale interface structure: the room temperature ionic conductivity of the sulfide solid electrolyte multi-scale interface structure is 1×10⁻⁶. –3 Up to 1×10 –2 S / cm, electrochemical stability window is 0-5 V (vs. Li) + / Li).

[0017] To achieve the above objectives, the third technical solution adopted by this invention is: the application of a polymer-sulfide solid electrolyte based on multi-scale interface design in an all-solid-state lithium battery, resulting in an all-solid-state lithium battery comprising a positive electrode, a sulfide solid electrolyte multi-scale interface structure, and a negative electrode. The positive electrode includes LiCoO2, LiNiO2, LiMn2O4, LiFePO4, and LiNi x Co y Mn z One or more of O2 (x+y+z=1); The negative electrode is one or more of metallic lithium, lithium alloy, carbon material, silicon-based material or tin-based material; The positive electrode also includes a conductive agent and a binder in a mass ratio of 70-90 : 5-15 : 5-15; The all-solid-state lithium battery retains no less than 90% of its capacity after 400 cycles at a 1 C current density.

[0018] This invention addresses the shortcomings of the prior art and has the following beneficial effects: This invention utilizes three functionally complementary sulfide electrolyte particles (Li10SiP2S12, Li7P2S8I, and Li3PS4) and employs gradient distribution technology to form a dense structure with optimized ion transport pathways within a polymer matrix. Micron-sized particles construct a high-speed ion conduction backbone, while nano- and submicron-sized particles tightly fill the matrix, significantly reducing interfacial impedance. Simultaneously, the introduction of Li7P2S8I broadens the electrochemical window from the material's origin, fundamentally and synergistically enhancing the bulk ionic conductivity and interfacial chemical stability of the composite electrolyte. Compared to existing technologies, the flexible polymer buffer layer on the surface effectively adapts to electrode volume changes during charging and discharging, maintaining the integrity of physical contact. The outermost self-healing functional component endows the interface with dynamic intelligent response capabilities. When microcracks develop at the interface due to cycling or temperature fluctuations, the dynamic bonds within the layer can undergo reversible breakage and reconstruction, achieving autonomous damage repair. This enhances the interface's tolerance to mechanical and chemical strains caused by temperature changes and long-term cycling, ultimately achieving a unified balance of high ionic conductivity, excellent interfacial stability, and wide temperature range adaptability.

[0019] By designing a multi-scale interface structure, a gradient distribution interface from the nanoscale to the microscale was constructed, realizing the multi-scale synergistic effect of ion transport channels and significantly improving ion transport efficiency and interface stability. This invention provides an elastic buffer layer that can adapt to volume changes by constructing a tough buffer interface layer, which effectively alleviates temperature changes and mechanical stress during charging and discharging, and improves the mechanical stability of the interface. This invention employs a Polymer-in-Ceramic structure design, which improves interfacial contact, reduces interfacial impedance, and expands the electrochemical stability window while maintaining the high ionic conductivity of the sulfide electrolyte. This invention introduces a dynamic repair interface, which enables the interface to automatically repair microcracks or defects under temperature changes or mechanical stress, thus achieving long-term stability of the interface. The sulfide solid electrolyte multi-scale interface structure prepared by this invention has excellent comprehensive performance, including high ionic conductivity, wide electrochemical window, good interface stability and ability to adapt to temperature changes, providing a new material option for the practical application of all-solid-state lithium batteries.

[0020] This invention not only fundamentally suppresses the side reactions between the sulfide electrolyte and the high-voltage positive electrode, thus broadening the electrochemical stability window, but also effectively adapts to the volume changes and mechanical stress of the electrode under dynamic operating conditions, and possesses the ability to autonomously repair interface damage. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Figure 1 This is a schematic diagram of the multi-scale interface structure of the sulfide solid electrolyte of the present invention; Figure 2 The lithium-ion transference number is the composite solid electrolyte prepared in Example 1 of this invention; Figure 3 The ionic conductivity of the composite solid electrolyte prepared in Example 1 of this invention; Figure 4 The electrochemical stability window of the composite solid electrolyte prepared in Example 1 of this invention; Figure 5 The cycle performance of the solid lithium metal symmetric battery assembled with the composite solid electrolyte prepared in Example 1 of this invention; Figure 6 The cycling performance of the full battery assembled with the composite solid electrolyte prepared in Example 1 of this invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0024] A method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design includes the following steps: S1: The sulfide precursors were mixed and heat-treated to obtain Li. 10 SiP2S 12 Li7P2S8I and Li3PS4 sulfide solid electrolyte particles; S2: Li 10 SiP2S 12 Sulfide solid electrolyte particles of 1-10 μm, 100-1000 nm and 10-100 nm were prepared from Li7P2S8I and Li3PS4, respectively, and were mixed with polymer precursors. A multi-scale interface structure was constructed by using gradient distribution technology. S3: A highly elastic and tough polymer is coated on the surface of a multi-scale interface structure to form a buffer interface layer; S4: Coat the buffer interface layer with a self-healing functional component, which is one or more of a polymer containing dynamic covalent bonds, a supramolecular polymer, or an ionic cross-linked polymer, to obtain a polymer-sulfide solid electrolyte based on multi-scale interface design.

[0025] This invention provides an innovative polymer-sulfide solid electrolyte based on multi-scale interface design and its application in all-solid-state lithium batteries. It aims to fundamentally address the severe technical challenges faced by existing all-solid-state lithium batteries in terms of interface stability, electrochemical window, solid-solid contact efficiency, and long-term cycle adaptability through precise structural engineering and materials science collaboration. The technical solution achieves comprehensive optimization of high ionic conductivity, excellent interface stability, a wide electrochemical stability window, and superior cycle life by constructing a composite solid electrolyte interface that combines multi-scale structure, tough buffering function, and self-healing capability.

[0026] The core of the present invention, which relates to a polymer-sulfide solid electrolyte based on multi-scale interface design and its preparation method, lies in the fine preparation, classification and structural assembly of sulfide solid electrolyte particles, and on this basis, the introduction of a polymer layer with unique functions to form a highly integrated and functionally graded composite interface.

[0027] The sulfide precursor is selected from one or more of the following: Li2S, P2S5, GeS2, SiS2, B2S3.

[0028] The first step, the precise preparation of sulfide solid electrolyte particles, is the foundation of this invention. This process aims to obtain Li with a specific crystal phase structure and high purity. 10 SiP2S 12 Li7P2S8I and Li3PS4 sulfide solid electrolytes. Specifically, for Li 10 SiP2S 12 The preparation process begins with high-purity (typically not less than 99.9%) Li₂S, P₂S₅, and SiS₂ as precursors. These precursors are purchased from specialized chemical reagent suppliers and pretreated in a strictly inert atmosphere glove box (H₂O and O₂ content both below 0.1 ppm) before use to remove any adsorbed moisture and oxygen. Li₂S, P₂S₅, and SiS₂ are weighed at a precise molar ratio of 5:1:1 and placed in a hard zirconia grinding jar. The jar is filled with high-purity zirconia balls (5 mm in diameter), with a ball-to-material ratio typically controlled at 10:1. The jar is then sealed and transferred to a high-energy ball mill (e.g., a planetary ball mill, model PM 100) under an argon protective atmosphere. The ball milling parameters are set as follows: rotation speed 400 rpm, grinding time 24 hours. High-energy ball milling not only achieves uniform mixing of the precursors but also promotes crystal structure formation by mechanically assisting the chemical reaction. After ball milling, the resulting mixture was transferred to a quartz crucible and heat-treated in a tube furnace. The heat treatment temperature was precisely controlled at 550°C and maintained at that temperature for 5 hours. The temperature rise rate was controlled at 5°C / min to avoid structural defects caused by thermal shock. After heat treatment, the sample was allowed to cool naturally to room temperature. X-ray diffraction (XRD) analysis confirmed the presence of Li. 10 SiP2S 12 The characteristic peaks of the tetragonal crystal structure were observed, and the elemental composition was verified to conform to the theoretical design by combining inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0029] For the preparation of Li7P2S8I, high-purity Li2S, P2S5, and LiI were used as precursors. These precursors were weighed and mixed in an inert atmosphere, with the molar ratio precisely controlled at 7:2:1. The mixture was then placed in a zirconia grinding jar and subjected to high-energy ball milling under a high-purity argon protective atmosphere for 30 hours at a speed of 400 rpm. Subsequently, the ball-milled sample was heat-treated at a constant temperature of 220°C for 4 hours. Precise control of the heat treatment temperature was crucial for suppressing the volatilization of LiI and ensuring the stable crystalline phase of Li7P2S8I. After heat treatment, XRD and ICP-OES analyses were performed to ensure the acquisition of Li7P2S8I with high ionic conductivity and a specific crystalline phase structure.

[0030] For the preparation of Li3PS4, Li2S and P2S5 were selected as precursors, with a precise molar ratio of 3:1. High-energy ball milling was performed for 20 hours under an argon protective atmosphere at a rotation speed of 400 rpm. Subsequently, the samples were heat-treated at a constant temperature of 250°C for 3 hours. The relatively low heat treatment temperature helps maintain the glassy or partially crystalline state of Li3PS4, which has a positive effect on subsequent polymer compounding. All heat treatment processes were carried out under a strictly inert atmosphere (high-purity argon) to avoid side reactions between the sulfides and moisture and oxygen in the air, which could lead to material performance degradation. Through strict control of the precursor ratio, milling process parameters, and heat treatment conditions, it was ensured that each prepared sulfide solid electrolyte possessed high purity, the target crystal structure, and excellent lithium-ion conductivity.

[0031] Furthermore, the second step focuses on constructing a multi-scale interface structure of the polymer-sulfide solid electrolyte, which is key to achieving functional gradient in this invention. This step first involves precise particle size control and classification of the three sulfide solid electrolytes prepared in the first step. Using physical methods such as high-energy ball milling, sieving, and aerodynamic classification, the Li... 10 SiP2S 12The average particle size of the sulfide solid electrolyte particles was precisely controlled between 1 micrometer and 10 micrometers, which could be achieved by adjusting the ball milling time, ball-to-material ratio, or by using a precision sieve. The average particle size of the Li7P2S8I sulfide solid electrolyte particles was precisely controlled between 100 nanometers and 1000 nanometers, typically achieved by controlling the ball milling intensity and time, combined with centrifugation or wet grinding. The average particle size of the Li3PS4 sulfide solid electrolyte particles was precisely controlled between 10 nanometers and 100 nanometers, achieved through long-term grinding using wet ultrasonic dispersion, high-speed shear grinding, or nanoscale grinding balls, combined with precision centrifugation or membrane filtration for classification. The particle size distribution was characterized and confirmed using a laser particle size analyzer (e.g., Malvern Mastersizer 3000) and scanning electron microscopy (SEM).

[0032] Subsequently, these precisely graded sulfide solid electrolyte particles are uniformly mixed with a selected polymer precursor. The polymer precursor is selected from one or more of the following: polyethylene glycol dimethyl ether (PEGDME), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene glycol (PEG), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN).

[0033] In a preferred embodiment of the present invention, the polymer precursor is selected from polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). PVDF-HFP is dissolved in N-methyl-2-pyrrolidone (NMP) to form a polymer solution with a concentration of 5 wt%. In an anhydrous and oxygen-free inert atmosphere glove box, sulfide particles of different sizes are weighed with the polymer solution at a solid mass ratio of 70:30 to 95:5. Specifically, for the first layer, Li₂ with an average particle size of 5 micrometers is used. 10 SiP2S 12 Sulfide particles were mixed with PVDF-HFP polymer at a mass ratio of 90:10 (based on solids content). For the second layer, Li7P2S8I sulfide particles with an average particle size of 500 nm were mixed with PVDF-HFP polymer at a mass ratio of 85:15. For the third layer, Li3PS4 sulfide particles with an average particle size of 50 nm were mixed with PVDF-HFP polymer at a mass ratio of 80:20. The mixing process employed a planetary mixer, performing high-speed shear mixing under vacuum for 30 minutes to ensure uniform dispersion of the polymer precursor and thorough wetting of the sulfide particle surface, forming a homogeneous and stable slurry. The viscosity of the slurry was precisely controlled by adjusting the amount of NMP used to suit subsequent coating processes.

[0034] Gradient distribution techniques are key processes for constructing multi-scale interface structures. These techniques include layer-by-layer assembly, gradient deposition, and centrifugation.

[0035] This invention employs a layer-by-layer assembly method to achieve a multi-scale interface structure with continuous gradient changes. First, a Li₂ structure with an average particle size of 5 micrometers is prepared. 10 SiP2S 12 A slurry of sulfide particles and PVDF-HFP polymer (90:10 solids by mass ratio) was prepared. This slurry was uniformly coated onto a pretreated copper foil substrate using a high-precision doctor blade at a speed of 20 mm / s, maintaining a film thickness of 20 micrometers, to form the first layer. This first layer, through its micrometer-scale sulfide framework, primarily functions as a pathway for high-speed, long-range lithium-ion transport, providing a low-impedance bulk transport path for the overall interface. After coating, the substrate was dried in a vacuum oven at 80°C for 2 hours to remove solvents and cure. Subsequently, after the first layer was completely dried and cured, a slurry containing Li7P2S8I sulfide particles with an average particle size of 500 nm and PVDF-HFP polymer (85:15 solids by mass ratio) was prepared. This slurry was uniformly deposited on top of the first layer using a similar doctor blade coating process, maintaining a film thickness of 10 micrometers, to form the second layer. The second layer, through the inherent chemical stability and high ionic conductivity of submicron-sized Li7P2S8I, broadens the interfacial electrochemical window and effectively suppresses oxidative decomposition side reactions with the electrode material. After coating, it is also dried in a vacuum oven at 80°C for 2 hours. Finally, after the second layer has dried and cured, a slurry containing Li3PS4 sulfide particles with an average particle size of 50 nm and PVDF-HFP polymer (solid mass ratio 80:20) is prepared. This slurry is uniformly deposited on top of the second layer using a fine coating process, with a film thickness controlled at 5 μm, forming the third layer. The third layer significantly reduces interfacial impedance by providing a dense and ionically conductive interfacial contact layer and can better adapt to microscopic deformation, thereby greatly improving the solid-solid contact problem between the sulfide electrolyte and the electrode. After coating, it is dried in a vacuum oven at 80°C for 2 hours. Through this precise layer-by-layer deposition process, the ion transport path from the macroscopic bulk phase to the microscopic interface is successfully optimized, and a solid electrolyte layer with a layered structure and functional gradient is formed at the interface. Cross-sectional analysis using scanning electron microscopy (SEM) clearly revealed the three-layer structure and its gradient particle size distribution. This multi-scale interface structure exhibits a room-temperature (25°C) lithium-ion conductivity of 2.5 × 10⁻⁶, as measured by electrochemical impedance spectroscopy (EIS). --3 S / cm, and from 0V to 5V (relative to Li + It exhibits excellent stability within a wide electrochemical stability window (Li electrode potential).

[0036] The third step involves coating the surface of the multi-scale interface structure with a highly elastic and tough polymer to form a buffer interface layer. The core function of this buffer interface layer is to provide the battery with a flexible barrier that can effectively absorb and buffer the mechanical stress generated by the volume expansion and contraction of the electrodes during charging and discharging, while maintaining the efficient transport capacity and excellent chemical stability of lithium ions. The highly elastic and tough polymer network is formed through the following methods: in-situ polymerization, cross-linking reaction, and grafting reaction.

[0037] In a preferred embodiment of the present invention, the highly elastic and tough polymer is prepared by blending polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) with a specific plasticizer, triethyl phosphate (TEP), and adding an appropriate amount of lithium bis(trifluoromethanesulfonyl)imide lithium (LiTFSI). Specifically, 10 parts by weight of PVDF-HFP (molecular weight approximately 400,000) are dissolved in 100 mL of N-methyl-2-pyrrolidone (NMP) to form a homogeneous solution. Subsequently, 5 parts by weight of TEP as a plasticizer and 2 parts by weight of LiTFSI as a lithium salt are added, with a molar ratio of LiTFSI to PVDF-HFP of approximately 1:20. All components are thoroughly mixed in an inert atmosphere glove box, typically using a magnetic stirrer at 50°C for 2 hours, to ensure that all components are uniformly dissolved and form a stable coating solution. This coating solution has suitable viscosity and rheological properties.

[0038] Subsequently, a high-precision blade coating process was used to uniformly coat the surface of the multi-scale interface structure constructed in the second step with a layer of solution. The blade gap was precisely set to 50 micrometers, and the coating speed was 15 mm / s to ensure the consistency of the coating thickness. After coating, the sample was transferred to a vacuum oven and dried and cured at a constant temperature of 80°C for 3 hours. This drying process effectively removed the NMP solvent and promoted the formation of a dense polymer network with high elasticity and toughness in the PVDF-HFP / TEP / LiTFSI mixture. The final thickness of the buffer interface layer was precisely measured using cross-sectional SEM and contact profilometry, controlled between 5 and 10 micrometers. This thickness range was optimized to ensure that it effectively buffers the macroscopic mechanical stress generated by the 20% to 30% volume change of the electrode material during cycling, thereby effectively preventing interface separation and microcrack formation, while avoiding a significant increase in lithium-ion transport path resistance due to excessive thickness. This buffer layer, through its excellent flexibility and extensibility, can undergo reversible deformation when the electrode volume changes, thereby ensuring the long-term integrity of the interfacial physical contact and maintaining a stable ion transport channel. The mechanical properties of the buffer interface layer were characterized by tensile testing. Its elongation at break can reach more than 200%, and its Young's modulus is 10 MPa, showing excellent elasticity and toughness.

[0039] The fourth step involves coating a self-healing functional component onto the buffer interface layer to obtain a polymer-sulfide solid electrolyte based on multi-scale interface design, thereby endowing the interface with dynamic intelligent response capabilities. This step aims to enable the interface to autonomously repair microcracks or defects caused by long-term cycling or temperature fluctuations, thus significantly improving the long-term stability of the interface and the cycle life of the battery. In a preferred embodiment of the invention, the self-healing functional component is composed of a polymer containing reversible Diels-Alder addition reaction groups. Specifically, this polymer is formed by polymerizing polyethylene glycol (PEG, molecular weight 6000) with isophorone diisocyanate (IPDI) to form a polyurethane prepolymer, followed by introducing furan and maleimide groups onto the polyurethane backbone or side chains through end-group modification or side-linking. For example, active groups are successfully introduced by reacting with furan derivatives and maleimide derivatives containing hydroxyl groups. The specific preparation process is as follows: First, PEG (1 molar equivalent) and IPDI (2 molar equivalent) are reacted in anhydrous toluene at 80°C for 4 hours under the catalysis of dibutyltin dilaurate (DBTDL) to form an isocyanate-terminated polyurethane prepolymer. Subsequently, hydroxymethyl furan and maleimide propionic acid (based on the isocyanate groups at the polyurethane end groups) in a molar ratio of 1.8:1 are added, and the reaction continues at 60°C for 6 hours to form a self-healing polymer containing Diels-Alder addition reaction groups. The molecular weight of this polymer is typically between 20,000 and 50,000.

[0040] The coating process for the self-healing functional component specifically includes: dissolving the polymer containing dynamic covalent bonds in a specific solvent, tetrahydrofuran (THF), to form a homogeneous solution with a concentration of 2 wt%. Subsequently, the solution is uniformly coated onto the surface of the buffer interface layer formed in the third step using a spraying process. The spraying parameters are precisely set as follows: nozzle diameter 0.5 mm, spraying pressure 0.2 MPa, and spraying distance 15 cm to ensure a uniform and thin coating. After coating, the sample is reacted at a constant temperature of 60°C for 6 hours. This heating process helps promote the formation of Diels-Alder bonds and the construction of the polymer network structure. The final content of the self-healing functional component in the interface layer is precisely measured by thermogravimetric analysis (TGA) and controlled between 5 wt% and 10 wt%.

[0041] When microcracks or structural defects develop at the interface due to mechanical stress (e.g., volume changes in electrodes during charge-discharge cycles) or temperature changes (e.g., increased battery operating temperature), dynamic covalent bonds (Diels-Alder bonds) can undergo reversible dissociation and reconstruction under specific external stimuli. Specifically, when the interface is damaged and cracks form, some Diels-Alder bonds break at the crack surface due to stress concentration, exposing new active furan and maleimide groups. When external stimuli are present (e.g., appropriate heating to 60-80°C), these active sites can recombine, undergoing reverse and forward Diels-Alder reactions, achieving spontaneous crack healing. This "instant repair" mechanism, through the reversible nature of dynamic covalent bonds, ensures that the interface actively maintains its physical integrity during long-term cycling, effectively suppressing irreversible growth of interface impedance, thereby significantly extending interface stability and the cycle life of all-solid-state lithium batteries. Self-healing efficiency was assessed by measuring the resistance of the scratched surface and observing it under an optical microscope. After the crack heals, the resistance can be restored to more than 95% of the initial value.

[0042] The polymer-sulfide solid electrolyte multi-scale interface structure constructed in this invention has the following defined structural and performance characteristics. The interface structure exhibits a multi-scale gradient distribution that gradually transitions from the electrode side to the electrolyte bulk side. Specifically, it includes a tightly contacted nanoscale Li3PS4 sulfide-polymer composite layer with a thickness of 5 micrometers, primarily providing interfacial contact and micro-deformation adaptability; a submicrometer-scale Li7P2S8I sulfide-polymer stabilizing buffer layer with a thickness of 10 micrometers, used to broaden the electrochemical window and suppress side reactions; and a micrometer-scale Li... 10 SiP2S 12 A 20-micrometer-thick sulfide-polymer high-speed transport backbone layer provides a long-range lithium-ion transport path. Beyond this layered structure, a 5-10-micrometer-thick tough buffer interface layer, composed of PVDF-HFP / TEP / LiTFSI composite material, provides mechanical buffering against electrode volume changes; and a 5-10-micrometer-thick self-healing functional layer containing Diels-Alder dynamic covalent bonds, endowing it with self-repairing capabilities for interface damage. The room-temperature (25°C) ionic conductivity of the sulfide solid electrolyte multi-scale interface structure ranges from 1×10⁻⁶. -3 S / cm to 1×10 -2 The ratio is between S / cm, and in practice it can reach 2.5×10. -3 S / cm. The electrochemical stability window of the interface structure was determined by linear sweep voltammetry (LSV), reaching 0V to 5V (relative to Li). +The / Li electrode potential significantly broadens the stable voltage range of existing sulfide electrolytes. Furthermore, long-term cycling and high / low temperature tests demonstrate that the interfacial structure maintains its physical and chemical stability under long-term cycling and temperature variations (e.g., -20°C to 60°C), effectively suppressing interfacial side reactions.

[0043] Furthermore, this invention provides an application of a polymer-sulfide solid electrolyte based on multi-scale interface design in all-solid-state lithium batteries. The application involves integrating the aforementioned ingeniously designed polymer-sulfide solid electrolyte multi-scale interface structure into an all-solid-state lithium battery, forming a novel high-performance all-solid-state lithium battery. All-solid-state lithium batteries typically include a positive electrode, the sulfide solid electrolyte multi-scale interface structure of this invention, and a negative electrode, which are tightly stacked to form a dense battery system.

[0044] LiNi is selected as the cathode material. 0.8 Co 0.15 Al 0.05 O2 (NCA) is used to ensure high energy density of the battery. The preparation of the positive electrode slurry specifically involves: thoroughly mixing 90 parts by weight of NCA active material, 5 parts by weight of conductive agent (acetylene black), and 5 parts by weight of binder (polyvinylidene fluoride, PVDF) in N-methyl-2-pyrrolidone (NMP) solvent. The mixing process uses a planetary mixer under vacuum for 60 minutes to form a uniform positive electrode slurry with suitable viscosity. This slurry is then uniformly coated onto an aluminum foil current collector using a blade coating process, with the coating thickness controlled at 100 micrometers. The coated positive electrode sheet is dried in a vacuum oven at 80°C for 4 hours, followed by compaction on a roller press to achieve a compaction density of 3.0 g / cm³, thereby improving its volumetric energy density and electronic conductivity.

[0045] In a preferred embodiment of this invention, the negative electrode material is high-purity (99.9%) lithium metal foil. The lithium metal negative electrode possesses the highest theoretical specific capacity (3860 mAh / g) and the lowest electrochemical potential, maximizing the energy potential of the positive electrode material. The lithium foil is typically 50 micrometers thick.

[0046] The assembly of the all-solid-state lithium battery is carried out in an extremely rigorous inert atmosphere glove box (dew point below -70°C). First, a compacted positive electrode sheet (12 mm in diameter) is placed at the bottom of the battery case, followed by the precise stacking of the multi-scale interface structure of this invention (14 mm in diameter), ensuring close contact between the interface structure and the positive electrode sheet. Finally, a lithium metal negative electrode sheet (14 mm in diameter) is placed on top of the multi-scale interface structure. After the entire battery (e.g., a CR2032 coin cell) is assembled, an external pressure of approximately 10 MPa is applied to ensure good solid-solid contact between the layers and minimize interfacial impedance.

[0047] The polymer-sulfide solid electrolyte multi-scale interface structure designed in this invention exhibits superior performance advantages in all-solid-state lithium batteries due to its unique multi-scale layering, tough buffering, and self-healing functions. To quantify the superiority of this invention, this section will provide a detailed description through examples and comparative models.

[0048] Example 1: Fabrication of nanoscale-microscale multi-scale interface structures based on LGPS, specifically as follows: (1) Preparation of sulfide solid electrolytes: Li₂S, SiS₂, and P₂S₅ were mixed in a molar ratio of 5:1:1, ball-milled for 24 hours under an argon atmosphere, and then heat-treated at 550 °C for 5 hours to obtain a sulfide solid electrolyte. X-ray diffraction (XRD) and Raman spectroscopy confirmed that the product was Li₂S. 10 SiP2S 12 Li₂S, P₂S₅, and LiI were mixed in a molar ratio of 7:2:1, ball-milled for 30 hours under an argon atmosphere, and then heat-treated at 220 °C for 4 hours to obtain a Li₇P₂S₈I sulfide solid electrolyte. X-ray diffraction (XRD) and Raman spectroscopy confirmed the product to be the Li₇P₂S₈I phase. Li₂S and P₂S₅ were mixed in a molar ratio of 3:1, ball-milled for 20 hours under an argon atmosphere, and then heat-treated at 250 °C for 3 hours to obtain a Li₃PS₄ sulfide solid electrolyte. X-ray diffraction (XRD) and Raman spectroscopy confirmed the product to be the β-Li₃PS₄ phase.

[0049] (2) Construction of multi-scale interface structures: Li 10 SiP2S 12 Li7P2S8I and Li3PS4 were ball-milled to obtain LGPS particles with average particle sizes of 50 nm, 500 nm, and 5 μm, respectively. A layer-by-layer assembly method was used to sequentially deposit micron-sized, submicron-sized, and nano-sized LGPS composite layers. For the first layer, Li7P2S8I with an average particle size of 5 μm was used. 10 SiP2S 12 Sulfide particles were mixed with PVDF-HFP polymer at a mass ratio of 90:10 (based on solids content). For the second layer, Li7P2S8I sulfide particles with an average particle size of 500 nm were mixed with PVDF-HFP polymer at a mass ratio of 85:15. For the third layer, Li3PS4 sulfide particles with an average particle size of 50 nm were mixed with PVDF-HFP polymer at a mass ratio of 80:20. The thicknesses of the micron-scale, submicron-scale, and nano-scale LGPS composite layers were 15 μm, 7 μm, and 2 μm, respectively, constructing a multi-scale interface structure.

[0050] (3) Formation of a toughness buffer interface layer: A solution composed of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) and LiTFSI in a mass ratio of 9:1, with NMP as the solvent, was coated on the surface of a multi-scale interface structure to form a tough buffer interface layer with a solid content of 8 wt%. The solution was dried at 80 °C for 4 hours to form a tough buffer interface layer with a thickness of about 5 μm.

[0051] (4) Construction of the dynamic repair function interface: A polymer containing dynamic covalent bonds (a polyurethane (number-average molecular weight Mn = 50,000 g / mol) formed by the reaction of polyethylene glycol and diisocyanate in a molar ratio of 1:1.1, containing reversible Diels-Alder addition reaction groups) was dissolved in tetrahydrofuran to obtain a 2 wt% dynamic covalent bond treatment solution. This solution was then used to impregnate a toughness buffer interface layer and reacted at 60 °C for 6 hours to form an interface structure with self-healing function.

[0052] Example 2: The difference between this example and Example 1 is that the thickness of the submicron LGPS composite layer is 3μm, while the rest are the same.

[0053] Example 3: The difference between this example and Example 1 is that the thickness of the submicron LGPS composite layer is 5μm, while the rest are the same.

[0054] Example 4: The difference between this example and Example 1 is that the thickness of the submicron LGPS composite layer is 9μm, while the rest are the same.

[0055] Example 5: The difference between this example and Example 1 is that the thickness of the submicron LGPS composite layer is 11 μm, while the rest are the same.

[0056] Performance testing and characterization 1. Ion mobility testing The composite solid electrolyte prepared in Example 1 was pressed into a disc with a diameter of 16 mm and a thickness of 0.1 mm, and assembled into a CR2032 coin cell using a lithium metal anode as the electrode. Lithium-ion transport number (LTON) The steady-state current method was used for determination. The battery was characterized using DC polarization and AC impedance before and after polarization. Calculations were performed according to the formula.

[0057] in I 0 For the initial current, I ss For steady-state current, R0 The initial resistance of the passivation layer. R ss This represents the resistance of the passivation layer after polarization. In the experiment, a voltage bias was applied. ΔV = 10 mV.

[0058] Test results are as follows Figure 2 As shown, the lithium-ion transference number is 0.62, indicating that lithium-ions have good conductivity in this system. Compared to electrons, lithium-ions have a stronger migration ability. High mobility means that lithium-ions can be conducted in the battery more quickly, especially during charge and discharge, which can improve the battery's electrochemical performance.

[0059] 1. Ionic conductivity test The sulfide solid electrolyte prepared in Example 1 was pressed into discs with a diameter of 16 mm and a thickness of 0.1 mm. Carbon paste was coated on both sides as electrodes, and these discs were assembled into CR2032 coin cells. AC impedance testing was performed at different temperatures using an electrochemical workstation, with a frequency range of 1 Hz–1 MHz and an amplitude of 10 mV. The ionic conductivity was calculated using the formula σ = L / (R × S), where L is the electrolyte thickness, R is the impedance, and S is the electrode area.

[0060] Test results are as follows Figure 3 As shown, the LGPS-based multi-scale interface structure sulfide solid electrolyte prepared in Example 1 has an ionic conductivity of 5.9 × 10⁻⁶ at room temperature (25 °C). –3 The S / cm ratio is significantly higher than that of traditional single-scale sulfide solid electrolytes. This is because the multi-scale interface design creates continuous ion transport channels, improving ion transport efficiency.

[0061] 2. Electrochemical stability window testing The electrochemical stability window of the sulfide solid electrolyte prepared in Example 1 was determined using linear sweep voltammetry (LSV). A three-electrode system was employed, with a stainless steel working electrode and lithium metal as both the counter and reference electrodes. The scan rate was 0.1 mV / s, and the voltage range was 0–5 V (vs. Li). + / Li).

[0062] Test results are as follows Figure 4 As shown, the electrochemical stability window of the sulfide solid electrolyte prepared in Example 1 reaches 0-4.3 V (vs. Li). + The stability window of the sulfide electrolyte ( / Li) is significantly higher than that of traditional sulfide solid electrolytes (approximately 1.7-2.5 V). This is mainly due to the multi-scale interface design and the protective effect of the tough buffer interface layer, which effectively suppresses the oxidative decomposition of the sulfide electrolyte.

[0063] 3. Battery performance testing The all-solid-state lithium metal symmetric battery prepared in Example 1 was subjected to cycle performance testing. The test was conducted at 1 mA cm⁻¹. –2 Current density and 1 mAh cm –2 It loops within a certain capacity.

[0064] like Figure 5 As shown, the all-solid-state lithium battery prepared in Example 1 remained stable during 800 cycles, with the polarization voltage maintained at 66 mV, exhibiting good kinetic performance and excellent cycle stability. This is mainly attributed to the high ionic conductivity, good interface stability, and dynamic repair function of the sulfide solid electrolyte's multi-scale interface structure, which effectively suppressed the growth of interface impedance and the occurrence of side reactions.

[0065] Cyclic performance tests were conducted on the all-solid-state batteries prepared in Example 1 and Comparative Example 1, which were assembled with lithium metal as the negative electrode and lithium iron phosphate as the positive electrode. The batteries were cycled at a current density of 1 C and the voltage range was 2.4-4 V.

[0066] like Figure 6 As shown, the all-solid-state lithium battery prepared in Example 1 was cycled at a 1 C current density. The first cycle capacity was 140.44 mAh g⁻¹. –1 After 400 cycles, the capacity retention rate was 94.19%, demonstrating excellent cycling stability.

[0067] 4. Best Practice Implementation Test The ionic conductivity of Examples 1-5 was tested at room temperature (25°C), and the test data are shown in Table 1.

[0068] Table 1 shows the ionic conductivity test data of Examples 1-5 at room temperature (25°C).

[0069] As shown in Table 1, with the gradual increase in the thickness of the submicron-scale LGPS composite layer, the ionic conductivity at room temperature (25°C) first increases and then decreases. This is because increasing the thickness of the submicron layer effectively connects the lower micron-scale and the upper nano-scale, forming a good gradient from macroscopic continuity to microscopic density, optimizing the ion transport path in the vertical direction, and reducing the contact resistance between interfaces, thereby increasing the total ionic conductivity. However, when the submicron layer is excessively thickened, its relatively low density and the possible presence of more grain boundaries become the dominant region for ion transport. This means that ions must traverse a longer submicron particle layer with less than optimal impedance, which increases the overall transport resistance. At the same time, an excessively thick intermediate layer may also disrupt the high-quality interface constructed by nanoparticles that is in close contact with the electrode active material, causing the ionic conductivity to decrease. The preferred embodiment is Example 1.

[0070] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design, characterized in that, Includes the following steps: S1: The sulfide precursors were mixed and heat-treated to obtain Li. 10 SiP2S 12 Li7P2S8I and Li3PS4 sulfide solid electrolyte particles; S2: Li 10 SiP2S 12 Sulfide solid electrolyte particles of 1-10 μm, Li7P2S8I of 100-1000 nm, and Li3PS4 of 10-100 nm were prepared and mixed with polymer precursors respectively. A multi-scale interface structure was constructed using a gradient distribution technique. The gradient distribution technique is a layer-by-layer assembly method, and the thickness of the coating corresponding to the Li7P2S8I sulfide solid electrolyte particles is one of 3 μm, 5 μm, 7 μm, 9 μm, and 11 μm. S3: A highly elastic and tough polymer is coated on the surface of a multi-scale interface structure to form a buffer interface layer; the highly elastic and tough polymer network is prepared by blending polyvinylidene fluoride-hexafluoropropylene with triethyl phosphate and adding lithium salt bis(trifluoromethanesulfonyl)imide lithium; S4: Coat a self-healing functional component onto the buffer interface layer. The self-healing functional component is one or more of a polymer containing dynamic covalent bonds, a supramolecular polymer, or an ionic cross-linked polymer, to obtain a polymer-sulfide solid electrolyte based on multi-scale interface design.

2. The method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design according to claim 1, characterized in that: The sulfide precursor is selected from one or more of the following: Li2S, P2S5, GeS2, SiS2, B2S3; Li7P2S8I is a mixture of Li2S, P2S5 and LiI.

3. The method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design according to claim 1, characterized in that: The polymer precursor is selected from one or more of the following: polyethylene glycol dimethyl ether (PEGDME), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyethylene glycol (PEG), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN).

4. The method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design according to claim 1, characterized in that: The heat treatment in S1 is carried out at a temperature of 200-600℃ for a time of 1-24 hours.

5. The method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design according to claim 1, characterized in that: The mass ratio of the sulfide solid electrolyte particles to the polymer precursor in S2 is 70-95:5-30.

6. The method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design according to claim 1, characterized in that: The thickness of the buffer interface layer is 1-20 μm, and the content of the self-healing functional component in the interface layer is 1-20 wt%.

7. A multi-scale interface structure for a sulfide solid electrolyte, based on a method for preparing a polymer-sulfide solid electrolyte based on multi-scale interface design according to any one of claims 1-6, characterized in that: The room temperature ionic conductivity is 1×10⁻⁶. –3 Up to 1×10 –2 S / cm, electrochemical stability window is 0-5 V (vs. Li) + / Li).

8. An application of a polymer-sulfide solid electrolyte based on multi-scale interface design in all-solid-state lithium batteries, based on the multi-scale interface structure of a sulfide solid electrolyte as described in claim 7, characterized in that... A fully solid-state lithium battery is obtained, comprising a positive electrode, a sulfide solid electrolyte multi-scale interface structure, and a negative electrode: The positive electrode includes LiCoO2, LiNiO2, LiMn2O4, LiFePO4, and LiNi 0.8 Co 0.15 Al 0.05 One or more of O2; The negative electrode is one or more of metallic lithium, lithium alloy, carbon material, silicon-based material or tin-based material; The positive electrode also includes a conductive agent and a binder in a mass ratio of 70-90 : 5-15 : 5-15; The all-solid-state lithium battery retains no less than 90% of its capacity after 400 cycles at a 1 C current density.

Images