A self-healing sulfide solid-state electrolyte membrane and a preparation method thereof

Abstract

This invention discloses a self-healing sulfide solid electrolyte membrane and its preparation method, belonging to the field of solid electrolyte membrane technology. By constructing a rigid-flexible dual-network interlocking three-dimensional structure, combined with a dynamic bonding mechanism and interface anchoring design, this invention fundamentally solves the technical problems of traditional sulfide solid electrolyte membranes, such as high brittleness, lack of self-healing ability, inconsistency between ion conduction and mechanical properties, and poor interface stability.

Description

Technical Field

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

[0002] Solid-state lithium batteries have become the core development direction of the next generation of energy storage batteries due to their advantages such as high safety, high energy density, and wide operating temperature range. Sulfide solid electrolytes have become a research hotspot in the field of solid electrolytes because they have high ionic conductivity comparable to liquid electrolytes at room temperature and good lithium metal compatibility. Among them, silver-germanium sulfide electrolytes such as Li6PS5Cl have become mainstream candidate materials due to their excellent comprehensive performance.

[0003] However, in practical applications, especially when preparing self-supporting electrolyte membranes for full-cell assembly, sulfide solid electrolytes still face many key technological bottlenecks, which seriously restrict their industrialization process. The specific problems are as follows: 1. Intrinsic brittleness leads to interface failure and structural damage: Sulfide electrolytes are typical inorganic ceramic phases with high intrinsic brittleness and low fracture toughness. Under the mechanical stress during battery assembly and the dynamic stress generated by the expansion / contraction of electrode volume during cycling, electrolyte membrane cracking and contact failure between sulfide particles are very likely to occur, resulting in a sharp increase in interface impedance, rapid decline in battery cycle performance, and even internal short circuit.

[0004] 2. Incompatibility between traditional binders and sulfide systems: To improve the film-forming properties of sulfide electrolytes, existing technologies often introduce traditional polymer binders such as styrene-butadiene rubber (SBR) and polyvinylidene fluoride (PVDF). However, these binders only have physical adsorption with sulfide particles, resulting in weak bonding and easy debonding under stress. At the same time, the binders are prone to agglomeration, leading to a decrease in electrolyte membrane density, hindering lithium-ion transport, significantly reducing ionic conductivity, and chemical / electrochemical side reactions easily occur at the interface between the binder and the sulfide, damaging the interface stability.

[0005] 3. Lack of intrinsic self-healing ability and irreversible damage: Existing sulfide electrolyte membranes and composite membranes do not have effective self-healing properties. Microcracks generated during use will continue to expand, which will not only further aggravate the ion transport resistance, but also cause lithium dendrites to grow rapidly along the cracks, eventually leading to battery short circuit failure. Although a few studies have introduced self-healing binders, they can only repair the damage to the binder phase itself and cannot restore the ion transport pathways between the broken sulfide particles. The repair effect has no practical application value.

[0006] 4. Ion conduction and mechanical properties exhibit a "contradictory" effect: In the current preparation of composite membranes, although increasing the polymer binder content can enhance the flexibility and film-forming properties of the membrane, it will significantly encroach on the contact space of sulfide particles, disrupt the continuous pathway of ion transport, and lead to a significant decrease in ionic conductivity. On the other hand, although reducing the polymer content can retain high ionic conductivity, it is impossible to prepare a flexible membrane with self-supporting properties, which is difficult to meet the mechanical requirements of battery assembly and cycling, and cannot simultaneously achieve high ionic conductivity and good mechanical flexibility.

[0007] 5. Poor interface stability and insufficient lithium dendrite suppression: When sulfide electrolytes come into direct contact with lithium metal anodes, interfacial side reactions are prone to occur, forming a high-resistivity interface layer. At the same time, traditional sulfide electrolyte membranes are unable to effectively block the growth and penetration of lithium dendrites due to insufficient mechanical properties. The continuous growth of lithium dendrites will further damage the electrolyte membrane structure, leading to battery safety hazards and performance degradation.

[0008] In summary, developing a sulfide solid electrolyte membrane that combines high ionic conductivity, excellent mechanical flexibility, intrinsic self-healing ability, and the ability to effectively suppress lithium dendrites and improve interface stability is the core direction for solving the current key problems in the industrialization of sulfide solid lithium batteries, and it is also a technical challenge that urgently needs to be overcome in this field. Summary of the Invention

[0009] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a self-healing sulfide solid electrolyte membrane and its preparation method. By constructing a rigid-flexible dual-network interlocking three-dimensional structure and combining dynamic bonding mechanism and interface anchoring design, the technical problems of traditional sulfide solid electrolyte membranes, such as high brittleness, lack of self-healing ability, contradiction between ion conduction and mechanical properties, and poor interface stability, are fundamentally solved.

[0010] The technical solution of this invention is as follows: On the one hand, the present invention provides a method for preparing a self-healing sulfide solid electrolyte membrane, comprising the following steps: Synthesis of S1 supramolecular polymers: S1-1: Dissolve 2,2′-dithiodiethanol (DTDE, containing disulfide bonds) and isophorone diisocyanate (IPDI) in anhydrous tetrahydrofuran (THF); add the catalyst dibutyltin dilaurate (DBTDL), and stir the reaction under nitrogen protection at 60-70℃ for 4-5 h to obtain a prepolymer solution. S1-2 dissolves UPy-NH2 (an adduct of 2-amino-4-hydroxy-6-methylpyrimidine and hexamethylene diisocyanate) in anhydrous tetrahydrofuran and adds it dropwise to the above prepolymer solution; the reaction is continued at 60-70℃ for 6-8 hours to obtain a polyurethane-urea copolymer containing UPy and disulfide bonds. In step S1-3, acrylonitrile is added to the reaction system and the reaction is continued at 60-70℃ for 2-3 hours to graft acrylonitrile onto the polymer chain. After the reaction is completed, the resulting solution is added dropwise to n-hexane to precipitate, filtered, and dried under vacuum to obtain the target supramolecular polymer. Synthesis of S2 sulfide electrolyte Li6PS5Cl: Li2S, P2S5 and LiCl were ball-milled in an argon glove box to obtain an amorphous precursor; the precursor was transferred to a quartz tube, vacuum sealed, and heat-treated at 550-650℃ for 5-6 hours, then cooled in the furnace, ground and sieved to obtain crystalline sulfide electrolyte Li6PS5Cl powder. S3 Composite Slurry Preparation: In a glove box, the supramolecular polymer obtained in step S1 is dissolved in anhydrous toluene and stirred until completely dissolved to obtain a polymer solution; the crystalline sulfide electrolyte powder obtained in step S2 is added to the above polymer solution while stirring; a dispersant is added and stirring is continued to allow the polymer to be fully adsorbed on the surface of the sulfide particles; shear dispersion is performed to obtain a uniform and stable slurry; S4 Coating Film Forming: The above slurry is coated onto a PET release film, vacuum dried to allow the solvent to completely evaporate, and then peeled off from the PET film to obtain a self-healing sulfide solid electrolyte film.

[0011] Preferably, in step S1-1, the mass-to-volume ratio of 2,2′-dithiodiethanol, isophorone diisocyanate, catalyst dibutyltin dilaurate, and anhydrous tetrahydrofuran is (50-60) g:(85-95) g:1 g:(500-600) mL.

[0012] Preferably, the mass-volume ratio of UPy-NH2, anhydrous tetrahydrofuran in step S1-2 to the catalyst dibutyltin dilaurate in step S1-1 is (30-40) g: (200-250) mL: 1 g.

[0013] Preferably, the mass ratio of acrylonitrile in step S1-3 to the catalyst dibutyltin dilaurate in step S1-1 is (10-15):1.

[0014] Preferably, in step S2, the mass ratio of Li2S, P2S5 to LiCl is (3-4):(2-3):1.

[0015] Preferably, in step S3, the concentration of the polymer solution is 5-10 wt.%.

[0016] Preferably, in step S3, the supramolecular polymer of step S1 accounts for 5-25% of the total mass of the polymer and the crystalline sulfide electrolyte powder of step S2.

[0017] Preferably, in step S3, the dispersant is triethyl phosphate, and the amount added is 0.5-1.5% of the total mass of the crystalline sulfide electrolyte powder in step S2 and the supramolecular polymer in step S1.

[0018] Preferably, in step S4, the slurry coating thickness is 100-200 μm.

[0019] On the other hand, the present invention provides a self-healing sulfide solid electrolyte membrane, which is prepared by the above-described method for preparing a self-healing sulfide solid electrolyte membrane.

[0020] This invention fundamentally solves the technical problems of traditional sulfide solid electrolyte membranes, such as high brittleness, lack of self-healing ability, inconsistency between ion conduction and mechanical properties, and poor interface stability, by constructing a rigid-flexible dual-network interlocking three-dimensional structure and combining dynamic bonding mechanism and interface anchoring design. Compared with the prior art, it has the following significant advantages: 1. This invention constructs a rigid conductive network using crystalline Li6PS5Cl sulfide particles. By optimizing particle size distribution and polymer content, a continuous lithium-ion permeation and transport pathway is formed, enabling the electrolyte membrane to achieve a room temperature ionic conductivity of 1.6-2.1 mS / cm, approaching the level of pure inorganic sulfide electrolytes and far exceeding that of traditional polymer binder composite membranes and commercial polymer electrolyte membranes. Simultaneously, a flexible self-healing network is constructed using supramolecular polymers containing dynamic bonds. This network is chemically anchored and coated onto the surface of the sulfide particles and fills the gaps, resulting in an electrolyte membrane tensile strength of 12-15 MPa, an elongation at break of 85-120%, and a bending radius of <2 cm. This achieves a synergistic unity of high ionic conductivity and excellent flexibility and tensile strength, overcoming the inherent contradiction of traditional composite membranes being either too strong or too weak. The prepared self-supporting membrane is only 25-30 μm thick, much thinner than traditional dry-pressed inorganic electrolyte sheets, making it more suitable for the lightweight design of solid-state batteries.

[0021] 2. The supramolecular polymer of this invention simultaneously introduces UPy quadruple hydrogen bonds and dynamic disulfide bonds, forming a dual dynamic bonding mechanism that endows the electrolyte membrane with excellent self-healing properties: the self-healing efficiency can reach 92-95% within 24 hours at room temperature, and up to 98% within 1 hour at 60°C. It can not only repair microcracks in the polymer phase, but also restore ion transport pathways between sulfide particles through the recombination of dynamic bonds, fundamentally solving the problem of irreversible damage in traditional electrolyte membranes. Mechanical cracks generated during battery cycling can self-repair, effectively avoiding the surge in interfacial impedance and lithium dendrite penetration caused by crack propagation, significantly improving the service life and stability of the electrolyte membrane.

[0022] 3. This invention grafts anchoring groups such as cyano groups onto the supramolecular polymer molecular chain, which can form coordination chemical bonds with metal ions on the surface of sulfide particles. This results in a strong bond between the polymer layer and the sulfide particles, rather than traditional physical adsorption, effectively avoiding the interfacial debonding problem caused by electrode volume changes during battery cycling. Simultaneously, the polymer layer isolates the sulfide electrolyte from direct contact with the lithium metal anode, significantly suppressing interfacial chemical / electrochemical side reactions and reducing the formation of high-resistivity interfacial layers. Testing showed that after 500 cycles, the interfacial impedance of the electrolyte membrane assembled with this invention increased by only 35%, far lower than that of traditional PVDF binder composite membranes (210%) and ordinary polyurethane composite membranes (150%), achieving long-term interfacial stability.

[0023] 4. The dual-network interlocking structure of this invention achieves efficient lithium dendrite suppression through a triple effect of physical blocking, stress homogenization, and interface passivation: the rigid sulfide particle network physically blocks the growth of lithium dendrite tips, while the flexible polymer network uniformly disperses the localized tip stress generated by lithium deposition throughout the entire membrane, preventing membrane cracking caused by stress concentration; the self-healing properties promptly repair micro-defects caused by lithium dendrite punctures, and the interface passivation further inhibits the continuous growth of lithium dendrites. The critical current density of the electrolyte membrane of this invention reaches 2.2-2.5 mA / cm². 2 The assembled Li|electrolyte|Li symmetric battery has a cycle life of over 3500h, which is far superior to traditional inorganic electrolyte sheets, PVDF composite membranes and commercial PEO-based electrolyte membranes. It effectively solves the short circuit problem caused by lithium dendrites in sulfide solid batteries and improves the safety performance of the battery.

[0024] 5. The electrolyte membrane of this invention exhibits excellent compatibility with the NCM811 positive electrode and lithium metal negative electrode. The assembled pouch cell achieves an initial 1C discharge capacity of 165 mAh / g, a capacity retention rate of 92% after 500 1C cycles, and a 3C discharge capacity retention rate of 88%, demonstrating superior high-rate performance and long-cycle stability. Compared to traditional composite membranes, the electrolyte membrane of this invention shows significant performance advantages under high-rate and long-cycle conditions, meeting the practical application requirements of solid-state lithium batteries.

[0025] In summary, the self-healing sulfide solid electrolyte membrane of this invention integrates high ionic conductivity, excellent mechanical properties, high self-healing capability, strong lithium dendrite suppression, and high interface stability. The preparation method is simple and controllable, and the assembled solid-state battery has long cycle life, excellent rate performance, and high safety factor. It provides a core solution for the industrial application of sulfide solid lithium batteries and has broad application prospects in the fields of power batteries, energy storage batteries, and consumer electronics batteries. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.

[0027] Example 1 The method for preparing the self-healing sulfide solid electrolyte membrane in this embodiment includes the following steps: Synthesis of S1 supramolecular polymers Preparation of S1-1 prepolymer Weigh 5g of DTDE and 8.5g of IPDI, and dissolve them in 50mL of THF. Add 0.1g of catalyst DBTDL, and stir the mixture at 60℃ under nitrogen protection for 5h to obtain a prepolymer solution.

[0028] S1-2 introduces the UPy unit. Weigh 3.2 g of UPy-NH2, dissolve it in 20 mL of THF, and add it dropwise to the above prepolymer solution. Continue the reaction at 60 °C for 8 h to obtain a polyurethane-urea copolymer containing UPy and disulfide bonds.

[0029] S1-3 introduces anchoring groups Weigh 1g of acrylonitrile and add it to the reaction system. Continue the reaction at 60℃ for 2 hours to graft acrylonitrile onto the polymer chain. After the reaction is complete, add the resulting solution dropwise into n-hexane to precipitate, filter, and dry under vacuum at 40℃ for 24 hours to obtain the target supramolecular polymer, denoted as P(SS-UPy-CN).

[0030] Synthesis of S2 sulfide electrolyte Li6PS5Cl In an argon-filled glove box, 6.9 g of Li₂S, 5.6 g of P₂S₅, and 2.1 g of LiCl were weighed and placed in a zirconia ball mill jar. The mixture was ball-milled at 500 rpm for 20 h to obtain an amorphous precursor. The precursor was transferred to a quartz tube, sealed under vacuum, and heat-treated at 550 °C for 6 h, followed by furnace cooling. After grinding and sieving, crystalline Li₆PS₅Cl powder was obtained.

[0031] S3 Composite Slurry Preparation In a glove box, 0.5 g of P(SS-UPy-CN) polymer was weighed and dissolved in 9.5 g of anhydrous toluene, stirred until completely dissolved, to obtain a 5 wt.% polymer solution. 4.75 g of Li6PS5Cl powder was weighed and added to the polymer solution while magnetically stirring. 0.05 g of triethyl phosphate dispersant was added, and stirring continued for 12 h to allow the polymer to fully adsorb onto the surface of the sulfide particles. The mixture was then dispersed for 15 min using a high-speed shear disperser (10000 rpm) to obtain a uniform and stable slurry.

[0032] S4 coating film formation The above slurry was transferred to a coating machine and coated onto a PET release film using a doctor blade coating method, controlling the wet film thickness to 150 μm. It was then vacuum dried at 50°C for 6 hours to allow complete solvent evaporation. The self-healing sulfide solid electrolyte membrane was then peeled off the PET film. The membrane was then punched to the required size and set aside.

[0033] Example 2 The method for preparing the self-healing sulfide solid electrolyte membrane in this embodiment includes the following steps: Synthesis of S1 supramolecular polymers Preparation of S1-1 prepolymer Weigh 5.5g of DTDE and 9g of IPDI, and dissolve them in 55mL of THF. Add 0.1g of catalyst DBTDL, and stir the mixture at 65℃ under nitrogen protection for 4 hours to obtain a prepolymer solution.

[0034] S1-2 introduces the UPy unit. Weigh 3g of UPy-NH2, dissolve it in 20mL of THF, and add it dropwise to the above prepolymer solution. Continue the reaction at 65℃ for 7h to obtain a polyurethane-urea copolymer containing UPy and disulfide bonds.

[0035] S1-3 introduces anchoring groups Weigh 1.2 g of acrylonitrile and add it to the reaction system. Continue the reaction at 65 °C for 3 h to graft acrylonitrile onto the polymer chain. After the reaction is complete, add the resulting solution dropwise into n-hexane to precipitate, filter, and dry under vacuum at 40 °C for 24 h to obtain the target supramolecular polymer, denoted as P(SS-UPy-CN).

[0036] Synthesis of S2 sulfide electrolyte Li6PS5Cl In an argon-filled glove box, 6.9 g of Li₂S, 5.6 g of P₂S₅, and 2.1 g of LiCl were weighed and placed in a zirconia ball mill jar. The mixture was ball-milled at 500 rpm for 20 h to obtain an amorphous precursor. The precursor was transferred to a quartz tube, sealed under vacuum, and heat-treated at 600 °C for 5.5 h, followed by furnace cooling. After grinding and sieving, crystalline Li₆PS₅Cl powder was obtained.

[0037] S3 Composite Slurry Preparation In a glove box, 0.8 g of P(SS-UPy-CN) polymer was weighed and dissolved in 9.5 g of anhydrous toluene, stirred until completely dissolved, to obtain a 5 wt.% polymer solution. 4.75 g of Li6PS5Cl powder was weighed and added to the polymer solution while magnetically stirring. 0.05 g of triethyl phosphate dispersant was added, and stirring continued for 12 h to allow the polymer to fully adsorb onto the surface of the sulfide particles. The mixture was then dispersed for 15 min using a high-speed shear disperser (10000 rpm) to obtain a uniform and stable slurry.

[0038] S4 coating film formation The above slurry was transferred to a coating machine and coated onto a PET release film using a doctor blade coating method, controlling the wet film thickness to 150 μm. It was then vacuum dried at 50°C for 6 hours to allow complete solvent evaporation. The self-healing sulfide solid electrolyte membrane was then peeled off the PET film. The membrane was then punched to the required size and set aside.

[0039] Example 3 The method for preparing the self-healing sulfide solid electrolyte membrane in this embodiment includes the following steps: Synthesis of S1 supramolecular polymers Preparation of S1-1 prepolymer Weigh 6g of DTDE and 9.5g of IPDI, and dissolve them in 60mL of THF. Add 0.1g of catalyst DBTDL, and stir the mixture at 70℃ under nitrogen protection for 4h to obtain a prepolymer solution.

[0040] S1-2 introduces the UPy unit. Weigh 4g of UPy-NH2, dissolve it in 25mL of THF, and add it dropwise to the above prepolymer solution. Continue the reaction at 70℃ for 6h to obtain a polyurethane-urea copolymer containing UPy and disulfide bonds.

[0041] S1-3 introduces anchoring groups Weigh 1.5 g of acrylonitrile and add it to the reaction system. Continue the reaction at 70 °C for 2 h to graft acrylonitrile onto the polymer chain. After the reaction is complete, add the resulting solution dropwise into n-hexane to precipitate, filter, and dry under vacuum at 40 °C for 24 h to obtain the target supramolecular polymer, denoted as P(SS-UPy-CN).

[0042] Synthesis of S2 sulfide electrolyte Li6PS5Cl In an argon-filled glove box, 6.9 g of Li₂S, 5.6 g of P₂S₅, and 2.1 g of LiCl were weighed and placed in a zirconia ball mill jar. The mixture was ball-milled at 500 rpm for 20 h to obtain an amorphous precursor. The precursor was transferred to a quartz tube, sealed under vacuum, and heat-treated at 650 °C for 5 h, followed by furnace cooling. After grinding and sieving, crystalline Li₆PS₅Cl powder was obtained.

[0043] S3 Composite Slurry Preparation In a glove box, 1.2 g of P(SS-UPy-CN) polymer was weighed and dissolved in 9.5 g of anhydrous toluene, stirred until completely dissolved, to obtain a 5 wt.% polymer solution. 4.75 g of Li6PS5Cl powder was weighed and added to the polymer solution while magnetically stirring. 0.05 g of triethyl phosphate dispersant was added, and stirring continued for 12 h to allow the polymer to fully adsorb onto the surface of the sulfide particles. The mixture was then dispersed for 15 min using a high-speed shear disperser (10000 rpm) to obtain a uniform and stable slurry.

[0044] S4 coating film formation The above slurry was transferred to a coating machine and coated onto a PET release film using a doctor blade coating method, controlling the wet film thickness to 150 μm. It was then vacuum dried at 50°C for 6 hours to allow complete solvent evaporation. The self-healing sulfide solid electrolyte membrane was then peeled off the PET film. The membrane was then punched to the required size and set aside.

[0045] Comparative Example 1 The difference from Example 1 is that step S1 is omitted, and only the Li6PS5Cl powder synthesized in step S2 is used.

[0046] Dry pressing was used to form the following: 0.5g of Li6PS5Cl powder was weighed, placed in a mold, and cold-pressed into a disc with a diameter of 16mm and a thickness of about 500μm under a pressure of 300MPa.

[0047] Comparative Example 2 Comparative Example 2: Preparation of a conventional PVDF adhesive composite film: 4.75 g of Li6PS5Cl powder from step S2 of Example 1 was mixed with 0.25 g of PVDF (polyvinylidene fluoride, molecular weight 1 million). 10 g of NMP solvent was added, and the mixture was stirred for 12 h to disperse. Subsequently, it was coated onto a PET film, vacuum dried at 80 °C for 6 h, and the film was peeled off to obtain the PVDF adhesive composite film.

[0048] Comparative Example 3 Comparative Example 3: Preparation of PU Composite Film: 4.75 g of Li6PS5Cl powder from step S2 of Example 1 was mixed with 0.25 g of polyurethane (PU). 10 g of THF solvent was added, and the mixture was stirred and dispersed. The mixture was then coated and dried to obtain the PU composite film.

[0049] Comparative Example 4 The difference from Example 1 is that steps S3 and S4 of the example are replaced by the following operation: 4.75 g of Li6PS5Cl powder from step S2 of Example 1 is dry-mixed with 0.25 g of P(SS-UPy-CN) polymer from step S1 of Example 1 (ball milling for 1 h). The mixed powder is then directly compressed into tablets (operation is the same as Comparative Example 1).

[0050] Comparative Example 5 Purchase commercial PEO-based polymer electrolyte membranes (50 μm thickness, approximately 10 ionic conductivity). -5 S / cm).

[0051] The electrolyte membranes of Examples 1-3 and Comparative Examples 1-5 were subjected to performance tests, and the test methods are as follows: Ionic conductivity: AC impedance method, test temperature 25℃; Tensile strength / elongation at break: Universal testing machine; Self-healing performance: A scratch with a depth of about 50% thickness was made on the membrane surface with a blade. After placement, the repair status was observed by SEM, and the ionic conductivity before and after repair was tested. Cyclic performance: Assemble a Li|electrolyte|Li symmetric cell and test its constant current cycle life; Critical current density (CCD): The current density is gradually increased until a short circuit occurs.

[0052] The test results are shown in Table 1: Table 1 Performance test results of electrolyte membranes in Examples 1-3 and Comparative Examples 1-5 The electrolyte membranes of Examples 1-3 and Comparative Examples 1-5 were matched with NCM811 positive electrodes and lithium metal negative electrodes to assemble soft-pack full cells, and their performance was tested. The test results are shown in Table 2. Table 2 Performance test results of pouch cells assembled in Examples 1-3 and Comparative Examples 1-5 As shown in Tables 1-2, Comparative Example 1 is a pure inorganic sulfide electrolyte membrane, manufactured using a dry pressing process. It lacks a polymer flexible network support and consists solely of a pure inorganic ceramic phase structure. It is brittle, with an elongation at break of <1%, and is inflexible. Its thickness reaches 500 μm, making it impossible to achieve self-supporting flexible film formation or adapt to the mechanical stress and dynamic stress of battery assembly and cycling. This directly results in the inability to assemble a soft-pack full cell for electrochemical testing; its critical current density is only 0.4 mA / cm². 2The Li|Li symmetric battery short-circuited after only 200 hours of cycling. Because the inorganic phase has no stress dispersion ability, the local stress of lithium deposition directly caused the film to crack, and lithium dendrites grew rapidly along the cracks and pierced the electrolyte. It has no self-healing ability: the inorganic ceramic phase has no dynamic bonding structure, and the microcracks continue to expand after they are generated, and the interface contact failure is irreversible.

[0053] Comparative Example 2 is a traditional PVDF binder composite film. PVDF is only a physical adsorption type binder, without dynamic bonds or interfacial anchoring groups, and cannot form an effective dual network. It also has poor compatibility with sulfide systems. The room temperature ionic conductivity is only 0.8 mS / cm, far lower than the example. This is because PVDF agglomeration occupies the contact space of sulfide particles, disrupting the continuous lithium-ion transport pathway. Furthermore, PVDF is a non-ionic conductive phase, hindering ion migration. The tensile strength is 8 MPa, elongation at break is 15%, and the bending radius is 5 cm, indicating significantly lower flexibility than the example. The physical adsorption binding force is weak, and the polymer and sulfide particles easily debond, failing to disperse the dynamic stress during battery cycling. There is no self-healing capability: PVDF is an inert polymer with no dynamic bonding mechanism, making crack repair impossible and causing a continuous increase in interfacial impedance. After 500 cycles, the interfacial impedance increases by 210%. Because PVDF and sulfide are only physically bonded, electrode volume changes during cycling cause interfacial debonding. Moreover, PVDF cannot isolate the direct contact between the sulfide and the lithium anode, leading to severe interfacial side reactions and the continuous formation of a high-impedance interfacial layer. The critical current density is 1 mA / cm². 2 The Li|Li symmetric battery cycled for only 600 hours, lacked stress homogenization and self-healing capabilities, and lithium dendrites easily pierced the membrane; the initial discharge capacity at 1C was 158 mAh / g, the capacity retention rate after 500 cycles was 78%, and the rate retention rate at 3C was 65%. Due to low ionic conductivity, a surge in interface impedance, and interference from lithium dendrites, its high-rate and long-cycle performance was significantly inferior to the example.

[0054] Comparative Example 3 is a conventional polyurethane (PU) composite film without dynamic bonds. PU is merely a common flexible polymer, lacking UPy quadruple hydrogen bonds and dynamic disulfide bonds. Its self-healing efficiency is extremely low: only 8% after 24 hours at room temperature and only 12% after 1 hour at 60°C. It can only achieve very shallow surface repair through slight physical deformation of the polymer, failing to restore the ion transport pathways between sulfide particles, making the damage essentially irreversible. After 500 cycles, the interfacial impedance increases by 150%. Although PU's flexibility is slightly better than PVDF, and the stability of the physical bond is slightly improved, the lack of chemical bond anchoring still results in interfacial debonding and cannot effectively suppress interfacial side reactions. The critical current density is 1.2 mA / cm². 2The Li|Li symmetric battery, after 800 hours of cycling, lacks self-healing ability to promptly repair microcracks, and lithium dendrites continue to grow along the cracks. Relying solely on flexible stress dispersion is far less effective than the triple suppression effect of the example. The initial 1C discharge capacity of 162 mAh / g is close to that of the example, but the retention rate after 500 cycles is 82%, and the 3C rate retention rate is 72%. Due to the surge in interface impedance and microcrack propagation in the later stages, the cycling performance rapidly declines.

[0055] Comparative Example 4 did not employ a solution dispersion coating process; it only used a dry physical mixing method to combine the supramolecular polymer and sulfide particles. The polymer could not uniformly coat the particle surface, nor could it form chemical bonds for anchoring, resulting in the complete failure of the dual-network structure. The resulting film was brittle, inflexible, and 500 μm thick. Physical mixing led to uneven polymer dispersion, preventing the formation of a continuous, flexible network. The sulfide particles remained in an unsupported aggregated state, retaining the intrinsic brittleness of the pure inorganic phase. The thermal conductivity at room temperature was only 0.5 mS / cm, the lowest among all samples. This was because physical mixing caused "phase separation" between the polymer and sulfide particles, disrupting the ion conduction pathways of the sulfides and preventing the polymer coating from providing auxiliary ion transport. The critical current density was only 0.3 mA / cm². 2 The Li|Li symmetric battery only experienced a short circuit after 150 hours of cycling. It lacks a flexible network to disperse stress, has no anchoring interface, and lacks self-healing ability. The growth rate of cracks and lithium dendrites is much faster than that of the pure inorganic phase. Although the polymer itself contains dynamic bonds, the recombination of dynamic bonds cannot act on the contact interface between sulfide particles due to the uneven coating of particles. Therefore, the repair is meaningless and it is impossible to assemble a soft-pack full cell for testing.

[0056] Comparative Example 5 is a commercial PEO-based polymer electrolyte membrane, which lacks a rigid conductive network of sulfides and inherently cannot simultaneously achieve high ionic conductivity and lithium dendrite suppression. Its lithium-ion conductivity at room temperature is only 0.01 mS / cm, far lower than that of sulfide-based electrolytes. This is because lithium-ion conduction in PEO relies on chain segment movement; at room temperature, the chain segment activity is low, and the ion migration rate is extremely slow, failing to meet the requirements for high-rate discharge; the critical current density is only 0.2 mA / cm. 2The Li|Li symmetric battery cycled for only 50 hours. Its rigid structure, lacking physical barriers to lithium dendrites in its pure organic phase, allowed lithium dendrites to directly penetrate the membrane, making it the most prominent type of lithium dendrite problem in solid-state electrolytes. After 500 cycles, the interfacial impedance increased by 350%. PEO and the lithium metal anode easily underwent side reactions, generating large amounts of high-resistivity lithium salts and polymer degradation products, and there was no interfacial passivation layer to isolate these side reactions. The initial 1C discharge capacity was only 145 mAh / g, with a 45% retention rate after 500 cycles and a 50% retention rate at 3C. Due to its extremely low ionic conductivity, lithium ions could not be transported quickly at high rates, and the combined effects of lithium dendrites and interfacial side reactions led to rapid performance degradation. Although it exhibited excellent flexibility with a 180% elongation at break and a bending radius of <1 cm, this advantage could not compensate for the fatal flaws in ionic conductivity and lithium dendrite suppression, making it unsuitable for the demands of high-energy-density, high-rate solid-state lithium batteries.

Claims

1. A method for preparing a self-healing sulfide solid electrolyte membrane, characterized in that, Includes the following steps: Synthesis of S1 supramolecular polymers: S1-1: Dissolve 2,2′-dithiodiethanol and isophorone diisocyanate in anhydrous tetrahydrofuran; Add the catalyst dibutyltin dilaurate and stir the reaction at 60-70℃ under nitrogen protection for 4-5 hours to obtain the prepolymer solution; S1-2 Dissolves UPy-NH2 in anhydrous tetrahydrofuran and adds it dropwise to the above prepolymer solution; the reaction is continued at 60-70℃ for 6-8 hours to obtain a polyurethane-urea copolymer containing UPy and disulfide bonds; S1-3 Acrylonitrile was added to the reaction system and the reaction was continued at 60-70℃ for 2-3 hours. After the reaction was completed, the resulting solution was added dropwise to n-hexane to precipitate, filtered, and dried under vacuum to obtain the target supramolecular polymer. Synthesis of S2 sulfide electrolyte: Li2S, P2S5 and LiCl were ball-milled in an argon glove box to obtain an amorphous precursor; the precursor was transferred to a quartz tube, vacuum sealed, and heat-treated at 550-650℃ for 5-6 hours, then cooled in the furnace, ground and sieved to obtain crystalline sulfide electrolyte powder. S3 Composite Slurry Preparation: In a glove box, the supramolecular polymer obtained in step S1 is dissolved in anhydrous toluene and stirred until completely dissolved to obtain a polymer solution; the crystalline sulfide electrolyte powder obtained in step S2 is added to the above polymer solution while stirring; a dispersant is added and stirring is continued to allow the polymer to be fully adsorbed on the surface of the sulfide particles; shear dispersion is performed to obtain a uniform and stable slurry; S4 Coating Film Forming: The above slurry is coated onto a PET release film, vacuum dried to allow the solvent to completely evaporate, and then peeled off from the PET film to obtain a self-healing sulfide solid electrolyte film.

2. The method for preparing a self-healing sulfide solid electrolyte membrane as described in claim 1, characterized in that, In step S1-1, the mass-to-volume ratio of 2,2′-dithiodiethanol, isophorone diisocyanate, catalyst dibutyltin dilaurate, and anhydrous tetrahydrofuran is (50-60) g: (85-95) g: 1 g: (500-600) mL.

3. The method for preparing a self-healing sulfide solid electrolyte membrane as described in claim 1, characterized in that, The mass-volume ratio of UPy-NH2, anhydrous tetrahydrofuran in step S1-2 to the catalyst dibutyltin dilaurate in step S1-1 is (30-40) g: (200-250) mL: 1 g.

4. The method for preparing a self-healing sulfide solid electrolyte membrane as described in claim 1, characterized in that, The mass ratio of acrylonitrile in step S1-3 to the catalyst dibutyltin dilaurate in step S1-1 is (10-15):

1.

5. The method for preparing a self-healing sulfide solid electrolyte membrane as described in claim 1, characterized in that, In step S2, the mass ratio of Li2S, P2S5 to LiCl is (3-4):(2-3):

1.

6. The method for preparing a self-healing sulfide solid electrolyte membrane as described in claim 1, characterized in that, In step S3, the concentration of the polymer solution is 5-10 wt.%.

7. The method for preparing a self-healing sulfide solid electrolyte membrane as described in claim 1, characterized in that, In step S3, the supramolecular polymer of step S1 accounts for 5-25% of the total mass of the polymer and the crystalline sulfide electrolyte powder of step S2.

8. The method for preparing a self-healing sulfide solid electrolyte membrane as described in claim 1, characterized in that, In step S3, the dispersant is triethyl phosphate, and the amount added is 0.5-1.5% of the total mass of the crystalline sulfide electrolyte powder in step S2 and the supramolecular polymer in step S1.

9. The method for preparing a self-healing sulfide solid electrolyte membrane as described in claim 1, characterized in that, In step S4, the slurry coating thickness is 100-200 μm.

10. A self-healing sulfide solid electrolyte membrane, characterized in that, It is prepared by the method for preparing a self-healing sulfide solid electrolyte membrane as described in any one of claims 1-9.

Images