A ternary synergistic composite solid-state electrolyte, a preparation method and application thereof

Abstract

The application belongs to the technical field of solid-state batteries, and relates to a ternary synergistic composite solid electrolyte and a preparation method and application thereof. + -TFSI ‑ pairing, improves the dissociation degree of lithium salt, and two-dimensional channels promote Li + vertical conduction; the ZIF-8 porous framework provides a three-dimensional transmission channel, and the Lewis acidic site enhances the dissolution of lithium salt and Li + uniform dispersion; FG anchors TFSI ‑ , suppresses anion disorder movement, and improves Li + migration number, simultaneously regulates the segment movement in the polymer matrix, enhances the amorphous structure, and promotes Li + diffusion; FG and g-C3N4 induce the formation of uniform LiF and Li3N protective layers at the interface, inhibit lithium dendrite growth, and significantly improve the interface stability and cycle life of the battery.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, specifically relating to a ternary synergistic composite solid electrolyte, its preparation method, and its application. Background Technology

[0002] Lithium metal batteries have become a research hotspot for next-generation energy storage technology due to their ultra-high theoretical energy density. Solid-state electrolytes are considered key materials for effectively improving battery safety and suppressing lithium dendrite growth. However, existing solid-state electrolytes still have the following problems in practical applications: At high current densities, insufficient dissociation of lithium salts in solid-state electrolytes leads to a decrease in the concentration of migratable lithium ions and insufficient ion transference number, causing severe polarization, resulting in decreased battery voltage efficiency and difficulty in fully utilizing capacity; the solid-solid interface contact between the electrolyte and the electrode (especially the lithium metal anode) is unstable, with continuous interfacial side reactions and uneven growth of lithium dendrites, leading to a continuous increase in interfacial impedance over time and a rapid deterioration in cycle stability. Especially in high-rate cycling, the uneven distribution of ion current on the surface of the lithium metal anode exacerbates the risk of local lithium deposition and dendrite penetration, easily causing electrolyte structural damage or even internal short circuits, posing safety hazards.

[0003] Currently, research commonly employs the method of adding functional fillers to solid electrolytes. However, conventional single-component or simple composite filler designs often only offer limited optimization for a specific performance aspect (such as improving bulk ionic conductivity or enhancing mechanical modulus), making it difficult to achieve efficient ion transport and stable interface compatibility synergistically under high-rate conditions. This singularity and incoordination in performance improvement leads to sluggish ion transport kinetics and accelerated interface degradation in batteries under high load and fast charge / discharge scenarios. Summary of the Invention

[0004] The purpose of this invention is to provide a ternary synergistic composite solid electrolyte, its preparation method and application, thereby overcoming the shortcomings of the prior art. By optimizing the lithium-ion transport path through the synergistic effect of multiple components, it simultaneously improves interface stability and high-rate performance, providing technical support for high-energy-density lithium metal batteries.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: On the one hand, the present invention provides a ternary synergistic composite solid electrolyte, comprising a polymer matrix and a lithium salt dispersed in the polymer matrix and a filler; The fillers include fluorinated graphene and porous composite powders; The porous composite material has the chemical formula ZIF-8@g-C3N4 and has a core-shell structure, including a ZIF-8 core and a g-C3N4 shell covering the surface of the core.

[0006] The fluorinated graphene in this ternary synergistic composite solid electrolyte can form a fast lithium-ion conduction channel in the polymer matrix and improve the mechanical properties and interfacial stability of the electrolyte. The porous composite powder with a core-shell structure (ZIF-8@ g-C3N4) has both high ionic conductivity and excellent interfacial compatibility. Its porous structure is conducive to lithium salt dissociation and lithium-ion transport, while the outer shell g-C3N4 can inhibit the adsorption of lithium salt by ZIF-8 and enhance interfacial stability.

[0007] Secondly, the present invention provides a method for preparing a ternary synergistic composite solid electrolyte, comprising the following steps: g-C3N4 powder was added to a solution containing a zinc source and stirred to prepare a mixture; a 2-methylimidazole solution was added to the mixture and stirred to prepare a solvothermal reaction; after the reaction was completed, the mixture was centrifuged, washed and dried to obtain a porous composite powder. Porous composite powder, polymer matrix and lithium salt are added to fluorinated graphite dispersion, stirred and mixed to form a slurry, the slurry is coated onto the surface of a carrier, dried and the carrier is removed to obtain a ternary synergistic composite solid electrolyte. For example, the solvent in the solution containing zinc source and the solution containing 2-methylimidazole is methanol.

[0008] This preparation method achieves uniform and controllable synthesis of core-shell porous composite powder by in-situ growth of g-C3N4 on the surface of ZIF-8 via a one-step solvothermal method. The operation is simple and the coating effect is good. The composite powder, polymer matrix and lithium salt are mixed in a pre-dispersed fluorinated graphene dispersion to ensure uniform dispersion of each component in the electrolyte. Finally, the electrolyte membrane is continuously and controllably prepared by a blade coating process. The overall process is simple, efficient and easy to scale up.

[0009] Thirdly, this invention provides the application of a ternary synergistic composite solid electrolyte in lithium metal solid-state batteries. By constructing a "ternary synergistic" solid electrolyte comprising a polymer matrix, lithium salt, and a porous composite material of fluorinated graphene and ZIF-8@g-C3N4, the ionic conductivity, mechanical strength, and interfacial stability of the electrolyte are significantly improved, thereby effectively suppressing lithium dendrite growth and enhancing battery safety. Simultaneously, this method is simple, scalable, and the resulting solid-state battery exhibits excellent electrochemical performance, good cycle life, and high safety.

[0010] Fourthly, the present invention provides a lithium metal solid-state battery, comprising a positive electrode, a negative electrode, and a ternary polymer solid electrolyte.

[0011] The beneficial effects of this invention are: (1) This invention utilizes nitrogen-rich sites on the surface of g-C3N4 to effectively weaken Li + -TFSI - Pairing increases free Li+ Concentration; simultaneously, the highly electronegative fluorine atoms on the surface of fluorinated graphene (FG) can anchor TFSI. - Anions are used to suppress their disordered migration, thereby increasing the lithium-ion transference number and reducing polarization. Combined with the physical transport channels provided by the ZIF-8 porous framework, the ternary components construct a highly efficient ion conduction network under Lewis acid-base interaction and steric synergy, resulting in a lithium-ion transference number of 0.67, which is 25%–179% higher than the two comparative systems FG@Z and CN@Z, and a room temperature ionic conductivity of 2.6 × 10⁻⁶. - ³ S / cm, which is 26 times higher than traditional solid polymer electrolytes, and can achieve 10C ultra-high rate charge and discharge, meeting the requirements of fast-charging batteries.

[0012] (2) The present invention obtains a tightly structured CN@Z core-shell composite porous material through an in-situ growth strategy. It has both the two-dimensional vertical ion channel of g-C3N4 and the three-dimensional porous framework of ZIF-8, realizing uniform ion transport and orderly deposition across scales, effectively controlling the ion flow distribution and promoting the transfer of interfacial charge.

[0013] (3) The LiF induced by fluorinated graphene and the Li3N induced by g-C3N4 together form a high mechanical strength SEI film at the interface, which can significantly inhibit the growth of lithium dendrites, broaden the electrochemical stability window of the electrolyte to 5.0V, and greatly improve the interface stability and safety performance of the battery. Attached Figure Description

[0014] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0015] Figure 1 The XRD patterns of FG@Z@CN, CN@Z, ZIF-8 and g-C3N4 prepared in Example 1 of this invention; Figure 2 The images shown are SEM images of the composite solid electrolytes prepared in Example 1 and Comparative Examples 1-2 of this invention. In the images, a is the SEM image of Example 1 at a 50 μm scale, b is the SEM image of Example 1 at a 20 μm scale, c is the SEM image of Comparative Example 1 at a 50 μm scale, d is the SEM image of Comparative Example 1 at a 20 μm scale, e is the SEM image of Comparative Example 2 at a 50 μm scale, and f is the SEM image of Comparative Example 2 at a 20 μm scale. Figure 3 The following are linear sweep voltammetry (LSV) curves at room temperature for Embodiment 1 and Comparative Examples 1-2 of the present invention; Figure 4 These are the rate performance diagrams for Embodiment 1 and Comparative Examples 1-2 of the present invention; in, Figures 3-4 In this context, FG@Z@CN represents the composite solid electrolyte prepared in Example 1, FG@Z represents the composite solid electrolyte prepared in Comparative Example 1, and CN@Z represents the composite solid electrolyte prepared in Comparative Example 2. Detailed Implementation

[0016] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Fluorinated graphene (FG) was purchased from Xianfeng Nanomaterials, model XF079.

[0017] The preparation method of ZIF-8 is as follows: 1 mmol of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 8 mmol of 2-methylimidazole were dissolved in 15 mL of methanol respectively. The zinc nitrate methanol solution was sonicated for 10 min and denoted as solution A. Under magnetic stirring, the 2-methylimidazole methanol solution was slowly added dropwise to solution A, followed by vigorous stirring for 1 h. The above mixed solution was transferred to a stainless steel high-pressure reactor and reacted solvothermically at 150 °C for 4 h. After the reaction was completed, the precipitate was collected by centrifugation, washed repeatedly with methanol, and dried under vacuum at 60 °C to obtain ZIF-8 powder.

[0018] The preparation method of fluorinated graphdiyne (F-GDY) is as follows: 80g of trifluorotriiodobenzene, 4g of cuprous iodide, and 2g of bis(triphenylphosphine)palladium dichloride were added to a reaction vessel. After three argon purgings, 300mL of a 2% (w / w) triethylamine solution was added. The mixture was stirred for 40min at 20℃ and 500 r / min. Then, 50mL of 1,3,5-dichlorobenzene solution, which had undergone deprotection, extraction, and rotary evaporation treatment, was added. After the trifluorobenzene was dissolved by stirring, it was heated to 60°C and stirred for 72 hours. The mixture was then filtered, and the precipitate was washed twice with 1% hydrochloric acid solution and deionized water, respectively. The precipitate was then dried under vacuum at 60°C for 1 hour to obtain fluorinated graphdiyne powder.

[0019] To address the limitations of existing technologies that rely on single fillers to synergistically solve the problems of ion transport efficiency and interface stability under high-rate conditions, this invention proposes a method for preparing a ternary synergistic composite solid-state electrolyte (FG@Z@CN) and its application in high-rate lithium metal batteries. This invention relates to the field of lithium metal solid-state battery technology, specifically to a method for preparing a ternary synergistic composite solid-state electrolyte and its application in high-rate lithium metal batteries. The aim is to overcome the technical bottlenecks of existing solid polymer electrolytes (SPEs), such as low ionic conductivity, high interface impedance at high rates, and uncontrollable lithium dendrite growth, providing a novel electrolyte system that combines high ion conduction efficiency, a wide electrochemical window, and high-rate performance.

[0020] A typical embodiment of the present invention provides a ternary synergistic composite solid electrolyte, comprising a polymer matrix, a lithium salt dispersed in the polymer matrix, and a filler; The fillers include fluorinated graphene and porous composite powders; The porous composite material has a core-shell structure, consisting of a ZIF-8 core and a g-C3N4 shell covering the surface of the core.

[0021] Carbon nitride (g-C3N4) can significantly improve lithium-ion migration efficiency due to its two-dimensional layered structure and high specific surface area. The abundant nitrogen sites on the g-C3N4 surface promote lithium salt dissociation through Lewis acid-base interactions, increasing the number of free Li-ions. + The concentration induces the in-situ formation of a stable solid electrolyte interphase (SEI) film rich in Li3N on the surface of the lithium metal anode, and its defect structure can also provide a vertical transport channel for lithium ions.

[0022] Fluorinated graphene (FG) can effectively anchor lithium salt anions (such as TFSI) due to the strong electronegativity of its surface fluorine atoms. - ), inhibiting the disordered movement of anions, thereby improving Li + Migration number. FG can form a LiF interface layer in lithium metal batteries, effectively suppressing dendrite growth.

[0023] ZIF-8, as a metal-organic framework (MOF) material, possesses a microporous structure and Lewis acidic sites that enhance lithium salt solubility and provide physical channels for ion transport. The pore structure of ZIF-8 can promote the solubility of Li-24 lithium salts. + Targeted migration improves interface contact.

[0024] This invention provides a ternary synergistic composite solid electrolyte composed of fluorinated graphene (FG), carbon nitride (g-C3N4), and a ZIF-8 metal-organic framework (ZIF-8). Through the synergistic effect of the ternary components, the lithium-ion transport pathway is optimized, and the interfacial stability is significantly improved.

[0025] In some other embodiments, the mass ratio of polymer matrix, lithium salt and filler is 1:1:(2-4).

[0026] For example, the mass ratio of polymer matrix, lithium salt, and filler is any value or range of 1:1:2, 1:1:3, and 1:1:4. Within this range, the equal mass ratio of polymer matrix to lithium salt provides a basis for ion transport, while sufficient filler can form a continuous ion transport network in the system, thereby significantly enhancing the ionic conductivity, mechanical strength, and interfacial stability of the electrolyte.

[0027] In some other embodiments, the mass ratio of fluorinated graphene to porous composite powder is 1:(7-14). The molar ratio of ZIF-8 to g-C3N4 in the porous composite material is 1:(1-3).

[0028] For example, the mass ratio of fluorinated graphene to porous composite powder is 1:7, 1:8, 1:10, 1:12, and 1:14; the molar ratio of ZIF-8 to g-C3N4 is any one or a range of 1:1, 1:1.5, 1:1.8, 1:2, 1:2.5, and 1:3. Within this range, uniform coating of g-C3N4 on the ZIF-8 surface is achieved, constructing a structurally stable heterogeneous composite material with tight interfacial bonding. This method not only effectively combines the advantages of ZIF-8's high specific surface area and porosity with g-C3N4's excellent photocatalytic activity, but also improves charge separation and mass transfer efficiency by regulating interfacial interactions. The process is simple, and the composite material properties are tunable.

[0029] In other embodiments, the polymer matrix includes polyvinylidene fluoride (PVDF) and polyvinylidene fluoride (PVDE). One or more of hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polypropylene carbonate, polyurethane, polyvinyl chloride, polypropylene oxide, polyvinylidene chloride, polyphosphazene, and polysiloxane.

[0030] In other embodiments, the lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium trifluoromethanesulfonate, and lithium bis(trifluoromethanesulfonyl)imide.

[0031] A typical embodiment of the present invention provides a method for preparing a ternary synergistic composite solid electrolyte, comprising the following steps: g-C3N4 powder was added to a zinc source solution and stirred to prepare a mixture; a 2-methylimidazole solution was added to the mixture and stirred to prepare a solvothermal reaction; after the reaction was completed, the mixture was centrifuged, washed and dried to obtain a porous composite powder. Porous composite powder, polymer matrix, and lithium salt are added to a fluorinated graphite dispersion and stirred to form a slurry. The slurry is then coated onto a carrier surface, dried, and the carrier is removed to obtain the ternary synergistic composite solid electrolyte. For example, methanol is used as the solvent in both the zinc source solution and the 2-methylimidazole solution.

[0032] The preparation method of CN@Z@CN in the ternary synergistic composite solid electrolyte uses g-C3N4 as the growth substrate for ZIF-8. In-situ growth is employed to coat the ZIF-8 surface with g-C3N4. This effectively prevents the aggregation of ZIF-8 and ensures a more uniform distribution of ZIF-8 within the polymer matrix. Furthermore, the in-situ growth process fosters a closer interfacial contact between ZIF-8 and g-C3N4, avoiding interfacial compatibility and structural instability issues that may arise when directly adding the two fillers.

[0033] In some other embodiments, the preparation method of g-C3N4 powder is as follows: Melamine is calcined in air to fully polymerize the precursor and form a g-C3N4 framework. The calcination temperature is 500-600℃, the time is 3-5h, and the heating rate is 2-5℃ / min. Then, it is heat-treated in air to remove residual intermediate products, optimize the interlayer structure, and reduce the defect density. The heat treatment temperature is 450-500℃, the time is 1-3h, and the heating rate is 5-8℃ / min, thus obtaining g-C3N4 powder. In some other embodiments, the zinc source includes zinc nitrate hexahydrate and zinc chloride; The molar ratio of zinc source to 2-methylimidazole is (1-2):(8-10); The temperature of the solvothermal reaction is 120-180℃, and the time is 3-5h.

[0034] For example, the zinc source is zinc nitrate hexahydrate, and the molar ratio of zinc source to 2-methylimidazole is any value or range of 1:8, 1:10, and 2:10; the solvothermal reaction temperature is any value or range of 120, 150, and 180 °C, and the time is any value or range of 3, 4, and 5 h. This numerical range can obtain ZIF-8 products with high crystallinity, regular morphology, and less agglomeration. At the same time, the excess ligand effectively promotes the directional growth and stability of crystals, ensuring that the material has excellent specific surface area and porous structure.

[0035] Furthermore, the inventors discovered during their research that if the tightly structured CN@Z core-shell composite porous material prepared through the in-situ growth strategy is subjected to high-temperature calcination, it will destroy the nitrogen-rich sites and other functional groups in the material, leading to the loss of Lewis base sites and the collapse of the porous framework, thereby reducing the performance of the composite filler.

[0036] In some other embodiments, the fluorinated graphene dispersion is prepared as follows: fluorinated graphene is added to N-methylpyrrolidone, heated and stirred to disperse, and then ultrasonically broken and dispersed to obtain the fluorinated graphene dispersion. Add 80-120 mL of N-methylpyrrolidone per gram of fluorinated graphite; The heating, stirring, and dispersion process is carried out at a temperature of 70-90℃ for 10-15 hours; the ultrasonic disruption and dispersion process is carried out for 1-3 hours. Ultrasonic disruption and dispersion involves using an ultrasonic cell disruptor for advanced ultrasonic treatment.

[0037] For example, 80, 100, and 120 mL of N-methylpyrrolidone were added per gram of fluorinated graphite; The heating and stirring dispersion temperature is any value or range from 70, 80, and 90℃, and the time is any value or range from 10, 12, and 15 h; the ultrasonic dispersion time is any value or range from 1, 2, and 3 h. This range of values ​​enables the efficient and stable preparation of uniformly dispersed fluorinated graphene dispersions that are not prone to agglomeration. The process is simple to operate and has good repeatability, which is beneficial for obtaining high-quality fluorinated graphene materials.

[0038] A typical embodiment of the present invention provides the application of a ternary synergistic composite solid electrolyte in lithium metal solid batteries.

[0039] A typical embodiment of the present invention provides a lithium metal solid-state battery, comprising a positive electrode, a negative electrode, and a ternary polymer solid electrolyte.

[0040] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0041] Example 1 This embodiment provides a ternary synergistic composite solid electrolyte FG@Z@CN and its preparation method, specifically including the following steps: (1) 5g of melamine was placed in a covered crucible and heated to 550℃ at a heating rate of 3℃ / min. It was then calcined in air for 4h to obtain a yellow powder. Subsequently, the lid was removed and the powder was heated to 500℃ at a heating rate of 5℃ / min in air and held for 2h for heat treatment. The color of the product changed from yellow to light yellow, and g-C3N4 powder was obtained.

[0042] (2) 1g of fluorinated graphite was dispersed in 100mL of N-methylpyrrolidone (NMP) and continuously stirred magnetically at 80℃ for 12h. Then, it was subjected to high-precision ultrasonic treatment for 2h using an ultrasonic cell disruptor to obtain a uniform fluorinated graphite FG dispersion.

[0043] (3) Dissolve 1 mmol of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 8 mmol of 2-methylimidazole in 15 mL of methanol. Disperse 150 mg g-C3N4 powder in the zinc nitrate methanol solution and sonicate for 10 min, which is denoted as solution A. Under magnetic stirring, slowly add the 2-methylimidazole methanol solution to solution A, followed by vigorous stirring for 1 h. Transfer the above mixed solution to a stainless steel high-pressure reactor and solvothermal react at 150 °C for 4 h. After the reaction is complete, collect the precipitate by centrifugation, wash repeatedly with methanol, and dry under vacuum at 60 °C to obtain CN@Z composite powder.

[0044] (4) Mix 0.3g CN@Z powder, 0.1g polyvinylidene fluoride (PVDF) powder, and 0.1g lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) powder, add 2g FG dispersion, and stir with a magnetic stirrer for 12h to form a uniform slurry. Coat the slurry onto a glass plate with a doctor blade and vacuum dry at 60℃ for 12h to obtain an FG@Z@CN composite solid electrolyte membrane.

[0045] Example 2 This embodiment provides a ternary synergistic composite solid electrolyte FG@Z@CN and its preparation method, specifically including the following steps: (1) 5 g of melamine was placed in a covered crucible and heated to 550 °C at a heating rate of 3 °C / min. The mixture was then calcined in air for 4 h to obtain a yellow powder. The lid was then removed and the powder was heated to 500 °C at a heating rate of 5 °C / min in air and held for 2 h for heat treatment. The color of the product changed from yellow to light yellow, and g-C3N4 powder was obtained.

[0046] (2) 1g of fluorinated graphite was dispersed in 100mL of N-methylpyrrolidone (NMP) and continuously stirred magnetically at 80℃ for 12h. Then, it was subjected to high-precision ultrasonic treatment for 2h using an ultrasonic cell disruptor to obtain a uniform FG dispersion.

[0047] (3) Dissolve 2 mmol of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 8 mmol of 2-methylimidazole in 15 mL of methanol. Disperse 200 mg g-C3N4 powder in the zinc nitrate methanol solution and sonicate for 10 min, which is denoted as solution A. Under magnetic stirring, slowly add the 2-methylimidazole methanol solution to solution A, followed by vigorous stirring for 1 h. Transfer the above mixed solution to a stainless steel high-pressure reactor and solvothermal react at 120 °C for 4 h. After the reaction is complete, collect the precipitate by centrifugation, wash repeatedly with methanol, and dry under vacuum at 60 °C to obtain CN@Z composite powder.

[0048] (4) Mix 0.2g CN@Z powder, 0.1g polyvinylidene fluoride (PVDF) powder, and 0.1g lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) powder, add 1.6g FG dispersion, and stir with a magnetic stirrer for 12h to form a uniform slurry. Coat the slurry onto a glass plate with a doctor blade and vacuum dry at 60℃ for 12h to obtain an FG@Z@CN composite solid electrolyte membrane.

[0049] Example 3 This embodiment provides a ternary synergistic composite solid electrolyte FG@Z@CN and its preparation method, specifically including the following steps: (1) 5g of melamine was placed in a covered crucible and heated to 550℃ at a heating rate of 3℃ / min. The mixture was then calcined in air for 4h to obtain a yellow powder. The lid was then removed and the powder was heated to 500℃ at a heating rate of 5℃ / min in air for 2h for heat treatment. The color of the product changed from yellow to light yellow, and g-C3N4 powder was obtained.

[0050] (2) 2g of fluorinated graphite was dispersed in 100mL of N-methylpyrrolidone (NMP) and continuously stirred magnetically at 80℃ for 12h. Then, it was subjected to high-precision ultrasonic treatment for 2h using an ultrasonic cell disruptor to obtain a uniform FG dispersion.

[0051] (3) Dissolve 1 mmol of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 10 mmol of 2-methylimidazole in 20 mL of methanol. Disperse 180 mg g-C3N4 powder in the zinc nitrate methanol solution and sonicate for 10 min, which is denoted as solution A. Under magnetic stirring, slowly add the 2-methylimidazole methanol solution to solution A, followed by vigorous stirring for 1 h. Transfer the above mixed solution to a stainless steel high-pressure reactor and solvothermal react at 180 °C for 4 h. After the reaction is complete, collect the precipitate by centrifugation, wash repeatedly with methanol, and dry under vacuum at 60 °C to obtain CN@Z composite powder.

[0052] (4) Mix 0.1g CN@Z powder, 0.1g polyvinylidene fluoride (PVDF) powder, and 0.1g lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) powder, add 1.2g FG dispersion, and stir with a magnetic stirrer for 12h to form a uniform slurry. Coat the slurry onto a glass plate with a doctor blade and vacuum dry at 60℃ for 12h to obtain an FG@Z@CN composite solid electrolyte membrane.

[0053] Comparative Example 1 This comparative example provides a binary composite solid electrolyte CN@Z and its preparation method, specifically including the following steps: (1) 5 g of melamine was placed in a covered crucible and heated to 550 °C at a heating rate of 3 °C / min. The mixture was then calcined in air for 4 h to obtain a yellow powder. The lid was then removed and the powder was heated to 500 °C at a heating rate of 5 °C / min in air and held for 2 h for heat treatment. The color of the product changed from yellow to light yellow, and g-C3N4 powder was obtained.

[0054] (2) Dissolve 1 mmol of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 8 mmol of 2-methylimidazole in 15 mL of methanol. Disperse 150 mg g-C3N4 powder in the zinc nitrate methanol solution and sonicate for 10 min, which is denoted as solution A. Under magnetic stirring, slowly add the 2-methylimidazole methanol solution to solution A, followed by vigorous stirring for 1 h. Transfer the above mixed solution to a stainless steel high-pressure reactor and solvothermal react at 150 °C for 4 h. After the reaction is complete, collect the precipitate by centrifugation, wash repeatedly with methanol, and dry under vacuum at 60 °C to obtain CN@Z composite powder.

[0055] (3) Mix 0.3g CN@Z powder, 0.1g polyvinylidene fluoride (PVDF) powder, and 0.1g lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) powder, add an appropriate amount of NMP solution, and stir with a magnetic stirrer for 12h to form a uniform slurry. Coat the slurry onto a glass plate with a doctor blade and vacuum dry at 60℃ for 12h to obtain a CN@Z composite solid electrolyte membrane.

[0056] Comparative Example 2 This comparative example provides a binary composite solid electrolyte FG@Z and its preparation method, specifically including the following steps: (1) 1g of fluorinated graphite was dispersed in 100mL of N-methylpyrrolidone (NMP) and continuously stirred magnetically at 80℃ for 12h. Then, it was subjected to high-precision ultrasonic treatment for 2h using an ultrasonic cell disruptor to obtain a uniform FG dispersion.

[0057] (2) Dissolve 1 mmol of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 8 mmol of 2-methylimidazole in 15 mL of methanol. Under magnetic stirring, the 2-methylimidazole methanol solution was slowly added dropwise to solution A, followed by vigorous stirring for 1 h. The mixture was then transferred to a stainless steel high-pressure reactor and reacted solvothermically at 150 °C for 4 h. After the reaction was complete, the precipitate was collected by centrifugation, washed repeatedly with methanol, and dried under vacuum at 60 °C to obtain ZIF-8 powder.

[0058] (3) Mix 0.3g ZIF-8 powder, 0.1g polyvinylidene fluoride (PVDF) powder, and 0.1g lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) powder, add 2g FG dispersion, and stir with a magnetic stirrer for 12h to form a uniform slurry. Coat the slurry onto a glass plate with a doctor blade and vacuum dry at 60℃ for 12h to obtain an FG@Z composite solid electrolyte membrane.

[0059] Comparative Example 3 Unlike Example 1, ZIF-8 powder, g-C3N4, and FG were used as fillers to prepare a solid electrolyte membrane. Specifically, 0.3 g of ZIF-8 powder, 0.1 g of g-C3N4, 0.1 g of polyvinylidene fluoride (PVDF) powder, and 0.1 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) powder were mixed, and 2.4 g of FG dispersion was added. The mixture was stirred with a magnetic stirrer for 12 h to form a uniform slurry. The slurry was then coated onto a glass plate using a doctor blade and vacuum dried at 60 °C for 12 h to obtain the composite solid electrolyte membrane.

[0060] Comparative Example 4 Unlike Example 1, fluorinated graphene (FG) was replaced with an equal amount of fluorinated graphyne (F-GDY), while the other steps remained unchanged.

[0061] Comparative Example 5 Unlike Example 1, a solid electrolyte membrane was prepared using only g-C3N4 filler. Specifically, 0.3 g g-C3N4, 0.1 g polyvinylidene fluoride (PVDF) powder, and 0.1 g lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) powder were mixed and stirred with a magnetic stirrer for 12 hours to form a homogeneous slurry. The slurry was then coated onto a glass plate using a doctor blade and vacuum dried at 60°C for 12 hours to obtain the solid electrolyte membrane.

[0062] Comparative Example 6 Unlike Example 1, a solid electrolyte membrane was prepared using only a single type of precipitate (FG). Specifically, 0.1 g of polyvinylidene fluoride (PVDF) powder, 0.1 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) powder, and FG were mixed and stirred with a magnetic stirrer for 12 h to form a homogeneous slurry. The slurry was then coated onto a glass plate using a doctor blade and vacuum dried at 60 °C for 12 h to obtain the solid electrolyte membrane.

[0063] Comparative Example 7 Unlike Example 1, a solid electrolyte membrane was prepared using only ZIF-8 powder. Specifically, 0.3 g of ZIF-8 powder, 0.1 g of polyvinylidene fluoride (PVDF) powder, and 0.1 g of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) powder were mixed and stirred with a magnetic stirrer for 12 h to form a homogeneous slurry. The slurry was then coated onto a glass plate using a doctor blade and vacuum dried at 60 °C for 12 h to obtain the solid electrolyte membrane.

[0064] Performance testing (1) XRD test: by Figure 1 It can be seen that the crystal structures of FG@Z@CN, CN@Z, ZIF-8, and g-C3N4 prepared in the examples show significant differences. ZIF-8 exhibits sharp characteristic diffraction peaks, indicating good crystallinity. In contrast, the sharp peaks of FG@Z@CN disappear within the corresponding angular range, and broadened diffuse diffraction peaks are observed in the 20°-30° range, indicating a significantly reduced crystallinity and a highly composite and amorphous structural characteristic. This structure is beneficial for providing more transport channels and active sites for ion migration, thereby effectively improving the ionic conductivity of the material.

[0065] (2) SEM testing: by Figure 2 As shown in a and b, FG@Z@CN exhibits a uniform and dense surface morphology, with significantly refined grain size and tight interparticle connections; in contrast, the FG@Z sample surface is covered with irregular dense cracks. Figure 2 The CN@Z samples (c and d) exhibit larger particle sizes and more pores. Figure 2 (e and f in the text). This morphological difference directly confirms that the introduction of fluorinated graphene (FG) can effectively regulate grain growth and inhibit excessive particle aggregation, thereby forming a denser structure. This structure is beneficial for expanding the contact interface between the electrode and the electrolyte, shortening the ion transport path, and thus improving the ionic conductivity and electrochemical performance of the material.

[0066] (3) Linear sweep voltammetry (LSV) test: Specific testing methods: This study employed linear sweep voltammetry (LSV) to determine the electrochemical window of the composite electrolyte using a CHI600E electrochemical workstation from Shanghai Chenhua Instrument Co., Ltd. In the experiment, a 16mm diameter, 0.5mm thick stainless steel sheet was used as the working electrode, and a 16mm diameter lithium metal sheet was used as the reference electrode. The electrolyte material was cut into a 19mm diameter circle and sandwiched between the lithium metal sheet and the stainless steel sheet, forming a semi-blocked battery structure (Li / CSE / SS). The electrochemical window was tested at room temperature with a voltage scan range of 2-6V and a scan rate of 5 mV / s.

[0067] Depend on Figure 3 It can be seen that the three solid electrolyte materials FG@Z@CN, CN@Z and FG@Z are effective at voltages between 2.5V and 6.0V (Li / Li + Significant differences in electrochemical stability were observed across the voltage range. Specifically, the current of the FG@Z@CN composite material began to increase significantly at 5.0V, indicating that its electrochemical stability window can be extended to approximately 5.0V, which is significantly better than CN@Z (approximately 4.8V) and FG@Z (approximately 4.7V). This result demonstrates that the synergistic effect of FG and g-C3N4 effectively promotes the formation of a stable solid electrolyte interfacial film (SEI), suppresses interfacial side reactions under high voltage, and thus significantly improves the high-voltage resistance and interfacial stability of the composite solid electrolyte.

[0068] (4) Ratio performance test: Specific testing methods: Constant current charge-discharge cycle tests were performed on the NEWARE battery testing system and the Blue Battery testing system. The electrode material was lithium iron phosphate, the test temperature was room temperature (25℃), and the voltage range was 2.5-3.8V.

[0069] Depend on Figure 4 It can be seen that, under gradually increasing current density (0.1C to 10C), the FG@Z@CN composite material exhibits the best specific capacity and capacity retention rate in all rate ranges. At 0.1C, the initial discharge specific capacity of FG@Z@CN is as high as 168.7 mAh / g, which is higher than that of FG@Z (151.3 mAh / g) and CN@Z (158.8 mAh / g), indicating that it has better ion storage capacity. As the rate increases, the discharge specific capacity decay trend of FG@Z@CN is significantly slower than that of the other two groups, and at 2C, it can still maintain a discharge specific capacity of 122.7 mAh / g, which is significantly higher than that of FG@Z (119.5 mAh / g) and CN@Z (109.5 mAh / g), indicating that it has lower ion migration resistance and less polarization at high rates. Especially under extremely high rate conditions (10C), FG@Z@CN still provides a reversible capacity of 59.5 mAh / g, while the capacities of FG@Z and CN@Z samples have dropped sharply to 6.1 mAh / g and 2.4 mAh / g, respectively, almost losing their lithium storage capacity. This result fully demonstrates that the synergistic effect of fluorinated graphene and g-C3N4 in FG@Z@CN significantly optimizes the ion transport channel and electrode-electrolyte interface stability, giving it excellent high-rate performance and kinetic characteristics.

[0070] The electrolytes and battery performance obtained in the examples and comparative examples are shown in Table 1.

[0071] Table 1 Electrolyte and Battery Performance

[0072] As shown in Table 1, compared with Comparative Examples 1-2, Example 1, through Lewis acid-base interaction and spatial synergy, constructs a highly efficient ion transport network, which improves the lithium-ion transference number (0.67) by 25% to 179% compared with the CN@Z and FG@Z comparative systems (CN@Z: 0.52; FG@Z: 0.24), and the ionic conductivity at room temperature (2.6×10-3 S / cm) is 26 times higher than that of traditional SPEs, supporting 10 C ultra-high rate charge and discharge (capacity maintained at 59.5 mAh / g at 10 C), meeting the requirements of fast-charging batteries.

[0073] Comparing Example 1 with Examples 2 and 3 reveals that the in-situ growth process and component ratio are crucial for constructing a highly efficient ion transport network, resulting in an 8% and 15% increase in the lithium-ion transference number (0.67) compared to Examples 2 (0.62) and 3 (0.58), respectively, and a decrease in the ionic conductivity at room temperature (2.6 × 10⁻⁶). -3 S / cm) compared to Example 2 (2.2×10 -3 S / cm) and Example 3 (2.14×10 -3 The S / cm ratio is increased by 18% and 21%, respectively, and it supports 10C ultra-high rate charge and discharge (the capacity remains at 59.5 mAh / g at 10C), which is far superior to Example 2 (15.3 mAh / g) and Example 3 (13.5 mAh / g), meeting the requirements of fast charging batteries.

[0074] Comparing Example 1 with Comparative Example 4, it was found that fluorinated graphyne (F-GDY) has an amorphous, disordered layered structure, lacking long-range ordered layered stacking. This limits ion transport to a limited number of rigid channels within its framework, restricting ion conduction in three dimensions. Despite its sp and sp... 2 The hybrid carbon skeleton can form a local potential well through uneven electron distribution, thereby inducing the directional migration of lithium ions. However, the overall conductivity mechanism relies excessively on the "molecular sieve" effect, that is, it relies on the pore size to screen lithium ions and hinder the migration of anions. As a result, although the ion migration selectivity is improved, the actual conductivity is still limited by the disordered structure and limited pore connectivity. Its 10 C discharge specific capacity (3.2 mAh / g) is much lower than that of Example 1 (59.5 mAh / g).

[0075] As shown in Comparative Example 3, physical mixing results in uneven filler dispersion, poor interfacial compatibility, and an inability to form a continuous and dense ion transport network. This loose physical contact leads to extremely high interfacial impedance, severely hindering lithium-ion transport. Its lithium-ion transference number (0.35) and room-temperature ionic conductivity (1.0 × 10⁻⁶) are significantly reduced. -3The S / cm ratio was significantly lower than that of Example 1, and the 10 C discharge specific capacity (3.0 mAh / g) was only 5.0% of that of Example 1.

[0076] As shown in Comparative Example 5, although the single g-C3N4 filler can promote lithium salt dissociation, it is still difficult to maintain interface stability at high rates, and the interface impedance increases exponentially with the number of cycles. This results in a 10 C discharge specific capacity (12.5 mAh / g) that is much lower than that of Example 1.

[0077] As shown in Comparative Example 6, the single FG filler has poor interfacial compatibility with the polymer matrix and lacks efficient ion transport channels, resulting in uneven filler dispersion and intensified local polarization at the interface, which limits its application performance in high-rate scenarios. Its 10C discharge specific capacity (4.0 mAh / g) is only 6.7% of that in Example 1.

[0078] As shown in Comparative Example 7, the agglomeration tendency of single ZIF-8 filler easily forms a local high-resistivity region at the interface, and the adsorption of lithium ions by its pores leads to the formation of mobile Li... + As the concentration decreases, interfacial polarization increases significantly at high rates, affecting cycle life. Its lithium-ion transference number (0.26) and room-temperature ionic conductivity (0.85 × 10⁻⁶) are also affected. -3 The S / cm ratio was significantly lower than that of Example 1, and the 10 C discharge specific capacity (1.0 mAh / g) was only 1.7% of that of Example 1.

[0079] In summary, this invention optimizes the lithium-ion transport path through the synergistic effect of multiple components, simultaneously improving interface stability and high-rate performance, thus providing technical support for high-energy-density lithium metal batteries.

[0080] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A ternary synergistic composite solid electrolyte, characterized in that, Includes a polymer matrix, a lithium salt dispersed in the polymer matrix, and fillers; The filler includes fluorinated graphene and porous composite powder; The porous composite powder has the chemical formula ZIF-8@g-C3N4 and has a core-shell structure, including a ZIF-8 core and a g-C3N4 shell covering its surface.

2. The ternary synergistic composite solid electrolyte according to claim 1, characterized in that, The mass ratio of the polymer matrix, lithium salt and filler is 1:1:(2-4).

3. The ternary synergistic composite solid electrolyte according to claim 1, characterized in that, The mass ratio of the fluorinated graphene to the porous composite powder is 1:(7-14). The molar ratio of ZIF-8 to g-C3N4 in the porous composite powder is 1:(1-3).

4. The ternary synergistic composite solid electrolyte according to claim 1, characterized in that, The polymer matrix includes polyvinylidene fluoride and polyvinylidene fluoride. One or more of hexafluoropropylene, polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polypropylene carbonate, polyurethane, polyvinyl chloride, polypropylene oxide, polyvinylidene chloride, polyphosphazene, and polysiloxane.

5. The ternary synergistic composite solid electrolyte according to claim 1, characterized in that, The lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium bis(oxalate-borate), lithium difluorooxalate-borate, lithium trifluoromethanesulfonate, and lithium bis(trifluoromethanesulfonyl)imide.

6. A method for preparing a ternary synergistic composite solid electrolyte according to any one of claims 1-5, characterized in that, Includes the following steps: g-C3N4 powder was added to a zinc source solution and stirred to prepare a mixture; a 2-methylimidazole solution was added to the mixture and stirred to prepare a solvothermal reaction; after the reaction was completed, the mixture was centrifuged, washed and dried to obtain a porous composite powder. Porous composite powder, polymer matrix and lithium salt are added to fluorinated graphene dispersion, stirred and mixed to form a slurry, the slurry is coated on the surface of a carrier, and the carrier is removed after drying to obtain a ternary synergistic composite solid electrolyte.

7. The method for preparing the ternary synergistic composite solid electrolyte according to claim 6, characterized in that, The preparation method of the g-C3N4 powder is as follows: Melamine was calcined in air and then heat-treated in air to obtain g-C3N4 powder. The calcination treatment is performed at a temperature of 500-600℃ for 3-5 hours, with a heating rate of 2-5℃ / min. The heat treatment is performed at a temperature of 450-500℃ for 1-3 hours, with a heating rate of 5-8℃ / min.

8. The method for preparing the ternary synergistic composite solid electrolyte according to claim 6, characterized in that, The zinc source includes zinc nitrate hexahydrate and zinc chloride; The molar ratio of the zinc source to 2-methylimidazole is (1-2):(8-10). The solvothermal reaction is carried out at a temperature of 120-180℃ for 3-5 hours.

9. The method for preparing the ternary synergistic composite solid electrolyte according to claim 6, characterized in that, The preparation method of the fluorinated graphene dispersion is as follows: fluorinated graphene is added to N-methylpyrrolidone, heated and stirred to disperse, and then ultrasonically crushed and dispersed to obtain the fluorinated graphene dispersion. Add 80-120 mL of N-methylpyrrolidone per gram of fluorinated graphene; The heating, stirring, and dispersion temperature is 70-90℃, and the time is 10-15h; the ultrasonic crushing and dispersion time is 1-3h.

10. The application of the ternary synergistic composite solid electrolyte according to any one of claims 1-5 in lithium metal solid batteries.

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