Sulfur-containing solid polymer electrolyte membrane for energy storage battery as well as preparation method and application of sulfur-containing solid polymer electrolyte membrane

Abstract

The invention discloses a sulfur-containing solid polymer electrolyte membrane for an energy storage battery as well as a preparation method and application of the sulfur-containing solid polymer electrolyte membrane, and belongs to the technical field of polymer electrolyte. The preparation method of the sulfur-containing solid polymer electrolyte membrane comprises the following steps: uniformly mixing dimethyl tetrasulfide and dithiodibenzoic acid, and carrying out condensation polymerization to obtain a solid polymer; the preparation method comprises the following steps: dissolving a solid polymer in N, N-dimethylformamide to obtain a mixed solution, adding lithium bis (trifluoromethanesulfonyl) imide into the mixed solution, and uniformly mixing to obtain a precursor solution; and performing electrostatic spinning on the precursor solution to form a fiber membrane, and performing vacuum drying to obtain the sulfur-containing solid polymer electrolyte membrane. According to the sulfur-containing solid polymer electrolyte membrane provided by the invention, through a four-dimensional synergistic conduction mechanism, unified synergy of improvement of ionic conductivity, enhancement of interface stability and optimization of mechanical properties is realized. The lithium metal battery assembled by the electrolyte membrane has the comprehensive advantages of high safety, long cycle life, excellent electrochemical performance and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer electrolytes, and in particular relates to a sulfur-containing solid polymer electrolyte membrane for energy storage batteries, a preparation method thereof, and applications thereof. Background Art

[0002] Lithium metal batteries (LiM batteries) show great potential as next-generation high-energy-density energy storage systems. However, the currently used organic liquid electrolytes present significant safety issues, such as high flammability and explosiveness. More critically, organic liquid electrolytes are prone to inducing severe corrosion reactions at the LiM anode interface and are difficult to effectively inhibit the random growth of Li dendrites. These issues constitute major obstacles to the commercial application of LiM batteries.

[0003] As the core component of high-energy-density lithium batteries, solid-state electrolytes have formed two major systems in recent years: inorganic and polymer systems. Compared with inorganic systems, polymer solid electrolytes are considered to be a more practical option due to their outstanding mechanical flexibility, safety and processability. However, traditional polymer electrolytes represented by polyethylene oxide (PEO) face severe challenges: low lithium ion mobility at room temperature, large solid-solid interface contact impedance, narrow electrochemical stability window, and easy oxidative decomposition under high-voltage charging conditions. These problems seriously restrict their performance in solid-state batteries. Although the new polymer systems developed subsequently, such as nitrile-based, siloxane-based and polyvinylidene fluoride-based, have made breakthroughs in a single performance dimension, it is difficult to simultaneously meet the multiple requirements of high ionic conductivity, excellent mechanical strength and a wide electrochemical window.

[0004] In this context, the discovery of sulfur-containing polymer electrolytes (Poly (organopolysulfide)) provides a new idea for technological breakthroughs. The densely distributed lone pairs of sulfur atoms in its molecular chain can form high-density lithium ion coordination sites, building a unique "solvation" transport network; sulfur ions (S 2- )'s lower electronegativity further weakens the binding effect on lithium ions, reducing the activation energy of ion migration, thereby achieving a significant improvement in ionic conductivity and cycle stability. In addition, -(SS) n -The introduction of flexible segments not only improves the electrode-electrolyte interface contact and compatibility, but also effectively inhibits the growth of lithium dendrites and prolongs battery life.

[0005] Although sulfur-containing polymers have shown significant advantages in ion conduction and interface adaptability, existing solid polymer electrolyte systems still face fundamental challenges: first, the ionic conductivity at room temperature is generally low, which makes it difficult to meet the needs of fast charging; second, insufficient solid-solid interface contact leads to persistently high interface impedance; third, the problem of interface stability attenuation caused by volume deformation during long-term cycling has not yet been solved. These technical bottlenecks have seriously restricted the practical application of solid-state batteries. Summary of the Invention

[0006] In order to overcome the problems of low ionic conductivity, large interfacial impedance and poor interfacial stability in the above-mentioned existing solid polymer electrolytes, the present invention provides a sulfur-containing solid polymer electrolyte membrane for energy storage batteries and its preparation method and application, to achieve high safety, long life and high energy density solid-state battery integration.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a sulfur-containing solid polymer electrolyte membrane, which is prepared by hot melting, spinning and evaporation of a sulfur-containing solid polymer, wherein the general structural formula of the sulfur-containing solid polymer is:

[0008] Wherein, n is the degree of polymerization, 5000<n<50000.

[0009] A further improvement of the present invention is that the thickness of the sulfur-containing solid polymer electrolyte membrane is 70µm±5µm.

[0010] In a second aspect, the present invention further provides a method for preparing a sulfur-containing solid polymer electrolyte membrane, comprising the following steps: Dimethyl tetrasulfide and dibenzoyl disulfide are mixed to obtain a solid polymer through a polycondensation reaction; dissolving a solid polymer in N,N-dimethylamide to obtain a mixed solution, and adding lithium bis(trifluoromethanesulfonylimide) to the mixed solution and mixing them uniformly to obtain a precursor solution; The precursor solution is electrospun to form a fiber membrane, which is then vacuum dried to obtain a sulfur-containing solid polymer electrolyte membrane.

[0011] A further improvement of the present invention is that the mass ratio of dimethyl tetrasulfide to dibenzoylmethanesulfide is 1:(1-10).

[0012] A further improvement of the present invention is that the polycondensation reaction is carried out in an oil bath environment at a temperature of 100-180° C. for a reaction time of 30-120 min, and after the reaction is completed, the mixture is cooled to room temperature to obtain a solid polymer.

[0013] The further improvement of the application is that the amount of the added lithium bistrifluoromethanesulfonimide is 20% to 80% of the total mass of dimethyl tetrasulfide and dithiobenzoic acid.

[0014] The further improvement of the application is that lithium bistrifluoromethanesulfonimide is added to the mixed solution, and the mixed solution is stirred magnetically at a temperature of 25-60 DEG C for 12-48 h until the precursor solution is obtained.

[0015] The further improvement of the application is that in the electrospinning process: The inner diameter of the needle is 0.3-0.8 mm, the voltage is 5-20 kV, the solution flow rate is 0.5-2 ml / h, the distance between the needle and the receiving plate is 12-18 cm, and the spinning time is 1-3 h.

[0016] The further improvement of the application is that the temperature of the vacuum drying is 25-130 DEG C, and the time is 12-24 h.

[0017] In a third aspect, the application further provides an application of the sulfur-containing solid-state polymer electrolyte film, and the sulfur-containing solid-state polymer electrolyte film is used in a lithium ion battery.

[0018] Compared with the prior art, the application has the following beneficial effects: The application provides a sulfur-containing solid-state polymer electrolyte film, and through a four-dimensional synergistic conduction mechanism of "sulfur chain conduction-carboxyl chelation-hydrogen bond anchoring-dynamic repair", the unity and synergy of the improvement of ionic conductivity, the enhancement of interface stability and the optimization of mechanical performance are realized. + The weak coordination bond is formed, the flexible sulfur chain with a low rotation potential barrier of S-S bond is combined, the "relay type" transmission of Li + is realized through local conformation change, and the ion migration activation energy is significantly reduced; meanwhile, the C=O group on the benzene ring produces strong electrostatic interaction with Li + , a stable Li + ·O=C coordination site is formed, and the two synergistically build an efficient ion conduction network, which greatly improves the ionic conductivity and electrochemical performance of the electrolyte film. The O-H in the carboxylic acid (-COOH) forms a hydrogen bond network with the lithium salt anion (such as TFSI - ), effectively anchors the anion and inhibits its migration, and significantly improves the Li +The migration number also hinders the oxidative decomposition of anions, thereby optimizing the ion transfer efficiency and giving the material excellent cycle stability. The dynamic reversible characteristics of the flexible SS bond give the material self-healing ability, which can repair the cracks in the solid electrolyte interface film (SEI) generated during the cycle in real time, avoiding the risk of lithium dendrites piercing the diaphragm and causing short circuits; at the same time, the hydrogen bonds of the -COOH groups form a dynamic physical cross-linking network at the interface, synergistically inhibiting crack propagation, significantly improving the negative electrode interface compatibility and long-term structural integrity. In addition, the rigid polymer skeleton formed by the stacking of benzene rings gives the electrolyte membrane high mechanical strength and tensile properties, which not only ensures the process feasibility of battery assembly, but also provides mechanical support for the electrode interface, ultimately achieving the unity of high safety, long cycle life and high energy density, and providing key technical support for practical breakthroughs in solid-state lithium batteries.

[0019] The present invention also provides a method for preparing a sulfur-containing solid polymer electrolyte membrane. First, dimethyl tetrasulfide and dibenzoyl disulfide are directly mixed. The two are subjected to a condensation reaction to form a polymer skeleton having both a sulfur chain conduction network and hydrogen bond anchoring capabilities. From the molecular design level, a "sulfur chain-carboxyl" synergistic conduction structure is directly constructed, laying the foundation for subsequent ion transport and interface stability. Secondly, N,N-dimethylamide is selected as a solvent. Its high polarity can fully dissolve the polymer and evenly disperse the lithium salt, ensuring molecular-level mixing of the lithium salt and the polymer matrix in the precursor solution to form a homogenized ion transmission channel. At the same time, the low boiling point of N,N-dimethylamide is conducive to the rapid removal of the solvent during the vacuum drying process, avoiding the influence of residual on the electrochemical performance. Finally, the precursor solution is subjected to an electrospinning and vacuum drying process to obtain a sulfur-containing solid polymer electrolyte membrane. The thickness of the electrolyte membrane can be precisely controlled and a dense, non-porous structure can be formed, which not only ensures the high mechanical strength of the electrolyte membrane, but also achieves real-time repair of interface cracks through the dynamic repair ability of the sulfur chain and the physical cross-linking effect of the carboxylic acid hydrogen bond, significantly improving the cycle stability of the lithium metal battery. This preparation method uses three core operations to simultaneously achieve precise control of chemical structure, optimization of interface ion channels, preservation of dynamic functional groups, and enhancement of mechanical properties, significantly reducing manufacturing costs and making it suitable for large-scale production, providing core process support for the industrialization of solid-state batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the various components in the drawings are merely schematic and are used to help understand the present invention, and are not intended to specifically limit the shapes and proportional dimensions of the various components of the present invention.

[0021] Figure 1 The XRD pattern of the sulfur-containing solid polymer electrolyte membrane prepared in Example 2 of the present invention; Figure 2Impedance test graphs of polymer electrolyte membranes prepared in Examples 1-3 of the present invention and Comparative Example 1; FIG3 (a) is a SEM electron micrograph of the sulfur-containing solid polymer electrolyte membrane prepared in Example 2 of the present invention; Figure 3 (b) is a SEM electron microscope image of the polymer electrolyte membrane prepared in Comparative Example 1 of the present invention; Figure 4 The polymer electrolyte membranes prepared in Example 1 of the present invention and Comparative Example 1 are the rate performance of batteries at 25°C. DETAILED DESCRIPTION

[0022] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0023] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0024] All features, such as values, amounts, contents, and concentrations, described herein as numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values ​​within the range (including integers and fractions).

[0025] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0026] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0027] The present invention provides a sulfur-containing solid polymer electrolyte membrane, which is prepared by hot melting, spinning and evaporation of a sulfur-containing solid polymer, wherein the general structural formula of the sulfur-containing solid polymer is:

[0028] Wherein, n is the degree of polymerization, 5000<n<50000.

[0029] The thickness of the sulfur-containing solid polymer electrolyte membrane is 70µm±5µm.

[0030] The sulfur-containing solid polymer electrolyte membrane of the present invention achieves dual functional integration of traditional liquid electrolyte and diaphragm components through its unique solid-state ion conduction properties and physical structural design. Specifically, its solid polymer matrix not only assumes the core function of ion transport, but its dense and robust physical structure also simultaneously replaces the physical isolation function of the diaphragm. This innovative design of structural and functional integration breaks through the inherent limitations of traditional batteries, bringing about a leap in inherent safety, huge potential for energy density improvement, long-life cycle guarantee, and adaptability to extreme operating conditions, laying the technical foundation for a new generation of high-safety, high-energy-density, long-life solid-state batteries.

[0031] The present invention also provides a method for preparing a sulfur-containing solid polymer electrolyte membrane, comprising the following steps: Dimethyl tetrasulfide (DMTS) and 4,4'-Dithiobisbenzoic acid (DTBA) are mixed evenly and a solid polymer is obtained through polycondensation reaction; The solid polymer is dissolved in N,N-dimethylformamide (DMF) to obtain a mixed solution, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is added to the mixed solution and mixed uniformly to obtain a precursor solution; The precursor solution was electrospun to form a fiber membrane, which was then vacuum dried to obtain a sulfur-containing solid polymer electrolyte membrane, denoted as P(DMTS). x -DTBA y ), where x and y represent the mass ratio of dimethyl tetrasulfide and dibenzoylmethanesulfide, that is, x=1, 1≤y≤10.

[0032] In some embodiments, the mass ratio of dimethyl tetrasulfide to dibenzoylmethanesulfonate is 1:(1-10).

[0033] In some embodiments, the polycondensation reaction is carried out in an oil bath environment at a temperature of 100-180° C. for 30-120 min. After the reaction is completed, the mixture is cooled to room temperature to obtain a solid polymer.

[0034] In some embodiments, the amount of lithium bis(trifluoromethanesulfonyl)imide added is 20% to 80% of the total mass of dimethyl tetrasulfide and dibenzoylmethanesulfide.

[0035] In some embodiments, lithium bis(trifluoromethanesulfonyl imide) is added to the mixed solution, and the mixture is stirred magnetically at a temperature of 25-60° C. for 12-48 hours until the mixture is uniformly mixed to obtain a precursor solution.

[0036] In some embodiments, the specific method of electrospinning the precursor solution to form a fiber membrane is: The precursor solution is loaded into the syringe, and after standing to expel bubbles, the needle is installed, the high-voltage power supply is turned on, and the voltage is gradually increased until the fiber at the needle forms a stable fiber jet. The syringe pump is started to push the precursor solution, and a continuous polymer jet is formed under the action of the electric field. The polymer jet is directionally sprayed onto the receiving plate, and the spinning time is controlled to obtain a fiber membrane; The inner diameter of the needle is 0.3-0.8 mm, the high-voltage power supply is 5-20 kV, the flow rate of the syringe pump is 0.5-2 ml / h, the distance between the polymer jet and the plate is 12-18 cm, and the spinning time is 1-3 h.

[0037] Electrospinning uses electric forces to induce the formation of interwoven submicron fibers with controllable diameters. Combined with precise control of flow rate, distance, and time, it can construct a highly porous, self-supporting three-dimensional interconnected network. This structure simultaneously achieves high ionic conductivity and enhanced mechanical strength, and boasts a wide process parameter window, making it particularly well-suited to the high viscosity of solid electrolyte precursors while avoiding the risk of interfacial side reactions.

[0038] In some embodiments, the vacuum drying is performed in a vacuum oven at a temperature of 25-130° C. for a drying time of 12-24 h.

[0039] The present invention also provides an application of the above-mentioned sulfur-containing solid polymer electrolyte membrane. The sulfur-containing solid polymer electrolyte membrane is used in lithium-ion batteries. The lithium metal battery assembled with this electrolyte membrane has comprehensive advantages such as high safety, long cycle life, high energy density potential and excellent electrochemical performance.

[0040] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0041] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0042] Example 1 This embodiment provides a method for preparing a sulfur-containing solid polymer electrolyte membrane, comprising the following steps: Step 1, DMTS and DTBA were mixed uniformly in a mass ratio of 1:1, and magnetically stirred in an oil bath at a temperature of 150° C. for 120 minutes. After reacting at high temperature, the mixture was cooled to room temperature to obtain a solid polymer; Step 2: dissolving the solid polymer obtained in step 1 in DMF, adding 40% by weight of LiTFSI and mixing evenly, and magnetically stirring at room temperature for 24 hours to obtain a precursor solution; Step 3: The precursor solution is loaded into a syringe, and after standing to expel bubbles, a needle with an inner diameter of 0.5 mm is installed. The high-voltage power supply is turned on and controlled to 5 kV. The voltage is gradually increased to 20 kV until a stable fiber jet is formed at the needle. The syringe pump is started to push the precursor solution at a flow rate of 1 ml / h to form a continuous polymer jet under the action of the electric field. The polymer jet is directionally sprayed onto the receiving plate so that the distance between the receiving plate and the polymer jet is 15 cm, and the spinning time is controlled to 2 h to obtain a fiber membrane. The fiber membrane on the plate is then placed in an oven for 16 h to ensure a vacuum atmosphere in the oven at a temperature of 120 ° C. The dried polymer electrolyte membrane is cut into 16 mm diameter discs using a sheet punch to obtain a sulfur-containing solid polymer electrolyte membrane, recorded as P (DMTS1-DTBA1) @ LiTFSI.

[0043] P(DMTS1-DTBA1)@LiTFSI was stored in a glove box under an argon atmosphere (water < 0.1 ppm, oxygen < 0.1 ppm).

[0044] The P(DMTS1-DTBA1)@LiTFSI prepared in Example 1 was assembled with a positive electrode sheet (lithium iron phosphate, LEP) and a negative electrode sheet (metal lithium sheet) into a CR2025 button battery for performance testing.

[0045] The positive electrode active material LEP, conductive agent (acetylene black) and binder (polyvinylidene fluoride, PVDF) were dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 96.8:2.0:1.2 to prepare a positive electrode slurry, and 1% ethylene carbonate (EC) was added to wet the electrode; the positive electrode slurry was then coated on an aluminum foil current collector and vacuum dried to obtain a positive electrode sheet.

[0046] Before assembling CR2025 coin cells for cycle testing, ≤5 μL of a commercially available electrolyte (LiPF6in EC / DMC) was added to the P(DMTS1-DTBA2)@LiTFSI electrolyte membrane surface as an interfacial wetting agent, allowing it to penetrate the membrane-electrode interface via capillary action. This treatment was only used during the testing phase to enhance initial interfacial compatibility. After addition, the solution was allowed to stand for 5 minutes to allow the solvent to evaporate and form a thin layer of wetting at the interface.

[0047] Example 2 This embodiment provides a method for preparing a sulfur-containing solid polymer electrolyte membrane, comprising the following steps: Step 1, DMTS and DTBA were uniformly mixed in a mass ratio of 1:3, and magnetically stirred in an oil bath at a temperature of 150° C. for 120 minutes. After reacting at high temperature, the mixture was cooled to room temperature to obtain a solid polymer; Step 2: dissolving the solid polymer obtained in step 1 in DMF, adding 40% by weight of LiTFSI and mixing evenly, and magnetically stirring at room temperature for 24 hours to obtain a precursor solution; Step 3: The precursor solution is loaded into a syringe, and after standing to expel bubbles, a needle with an inner diameter of 0.5 mm is installed. The high-voltage power supply is turned on and controlled to 5 kV. The voltage is gradually increased to 20 kV until a stable fiber jet is formed at the needle. The syringe pump is started to push the precursor solution at a flow rate of 1 ml / h to form a continuous polymer jet under the action of the electric field. The polymer jet is directionally sprayed onto the receiving plate so that the distance between the receiving plate and the polymer jet is 15 cm, and the spinning time is controlled to 2 h to obtain a fiber membrane. The plate is then placed in an oven for 16 h to ensure a vacuum atmosphere and an oven temperature of 120 ° C. The dried polymer electrolyte membrane is cut into 16 mm diameter discs using a sheet punch to obtain a sulfur-containing solid polymer electrolyte membrane, recorded as P (DMTS1-DTBA3) @ LiTFSI.

[0048] P(DMTS1-DTBA3)@LiTFSI was stored in a glove box under an argon atmosphere (water < 0.1 ppm, oxygen < 0.1 ppm).

[0049] The P(DMTS1-DTBA3)@LiTFSI prepared in Example 2 was assembled with the positive electrode sheet and the negative electrode sheet into a CR2025 button battery for performance testing.

[0050] like Figure 1 As shown, Figure 1 The XRD pattern of the sulfur-containing solid polymer electrolyte membrane prepared in Example 2 is as follows: Figure 1 It can be found that the XRD pattern shows a broad peak of the polymer, indicating that the polymer was successfully synthesized.

[0051] Example 3 This embodiment provides a method for preparing a sulfur-containing solid polymer electrolyte membrane, comprising the following steps: Step 1, DMTS and DTBA were uniformly mixed in a mass ratio of 1:5, and magnetically stirred in an oil bath at a temperature of 150° C. for 120 minutes. After the reaction at high temperature, the mixture was cooled to room temperature to obtain a solid polymer; Step 2: dissolving the solid polymer obtained in step 1 in DMF, adding 40% by weight of LiTFSI and mixing evenly, and magnetically stirring at room temperature for 24 hours to obtain a precursor solution; Step 3: The precursor solution is loaded into a syringe, and after standing to expel bubbles, a needle with an inner diameter of 0.5 mm is installed. The high-voltage power supply is turned on and controlled to 5 kV. The voltage is gradually increased to 20 kV until a stable fiber jet is formed at the needle. The syringe pump is started to push the precursor solution at a flow rate of 1 ml / h to form a continuous polymer jet under the action of the electric field. The polymer jet is directionally sprayed onto the receiving plate so that the distance between the receiving plate and the polymer jet is 15 cm, and the spinning time is controlled to 2 h to obtain a fiber membrane. The plate is then placed in an oven for 16 h to ensure a vacuum atmosphere and an oven temperature of 120 ° C. The dried polymer electrolyte membrane is cut into 16 mm diameter discs using a sheet punch to obtain a sulfur-containing solid polymer electrolyte membrane, recorded as P (DMTS1-DTBA5) @ LiTFSI.

[0052] P(DMTS1-DTBA5)@LiTFSI was stored in a glove box under an argon atmosphere (water < 0.1 ppm, oxygen < 0.1 ppm).

[0053] The P(DMTS1-DTBA5)@LiTFSI prepared in Example 3 was assembled with the positive electrode sheet and the negative electrode sheet into a CR2025 button battery for performance testing.

[0054] Example 4 This embodiment provides a method for preparing a sulfur-containing solid polymer electrolyte membrane, comprising the following steps: Step 1, DMTS and DTBA were uniformly mixed in a mass ratio of 1:6, and magnetically stirred in an oil bath at a temperature of 180° C. for 30 minutes. After reacting at high temperature, the mixture was cooled to room temperature to obtain a solid polymer; Step 2: dissolving the solid polymer obtained in step 1 in DMF, adding 20% ​​by weight of LiTFSI and mixing evenly, and magnetically stirring at room temperature for 12 hours to obtain a precursor solution; Step 3: The precursor solution is loaded into a syringe, and after standing to expel bubbles, a needle with an inner diameter of 0.3 mm is installed. The high-voltage power supply is turned on and controlled to 5 kV. The voltage is gradually increased to 20 kV until a stable fiber jet is formed at the needle. The syringe pump is started to push the precursor solution at a flow rate of 0.5 ml / h to form a continuous polymer jet under the action of the electric field. The polymer jet is directionally sprayed onto the receiving plate so that the distance between the receiving plate and the polymer jet is 12 cm, and the spinning time is controlled to 1 hour to obtain a fiber membrane. The plate is then placed in an oven for 12 hours to ensure a vacuum atmosphere and an oven temperature of 130°C. The dried polymer electrolyte membrane is cut into 16 mm diameter discs using a sheet punch to obtain a sulfur-containing solid polymer electrolyte membrane, recorded as P (DMTS1-DTBA6) @ LiTFSI.

[0055] P(DMTS1-DTBA6)@LiTFSI was stored in a glove box under an argon atmosphere (water < 0.1 ppm, oxygen < 0.1 ppm).

[0056] The P(DMTS1-DTBA6)@LiTFSI prepared in Example 4 was assembled with the positive electrode sheet and the negative electrode sheet into a CR2025 button battery for performance testing.

[0057] Example 5 This embodiment provides a method for preparing a sulfur-containing solid polymer electrolyte membrane, comprising the following steps: Step 1, DMTS and DTBA were mixed uniformly in a mass ratio of 1:8, and magnetically stirred in an oil bath at a temperature of 100° C. for 60 minutes. After reacting at high temperature, the mixture was cooled to room temperature to obtain a solid polymer; Step 2: dissolving the solid polymer obtained in step 1 in DMF, adding 60% by weight of LiTFSI and mixing evenly, and magnetically stirring at room temperature for 24 hours to obtain a precursor solution; Step 3: The precursor solution is loaded into a syringe, and after standing to expel bubbles, a needle with an inner diameter of 0.8 mm is installed. The high-voltage power supply is turned on and controlled to 5 kV. The voltage is gradually increased to 20 kV until a stable fiber jet is formed at the needle. The syringe pump is started to push the precursor solution at a flow rate of 2 ml / h to form a continuous polymer jet under the action of the electric field. The polymer jet is directionally sprayed onto the receiving plate so that the distance between the receiving plate and the polymer jet is 18 cm, and the spinning time is controlled to 3 h to obtain a fiber membrane. The plate is then placed in an oven for 24 h to ensure a vacuum atmosphere and an oven temperature of 25 ° C. The dried polymer electrolyte membrane is cut into 16 mm diameter discs using a sheet punch to obtain a sulfur-containing solid polymer electrolyte membrane, recorded as P (DMTS1-DTBA8) @ LiTFSI.

[0058] P(DMTS1-DTBA8)@LiTFSI was stored in a glove box under an argon atmosphere (water < 0.1 ppm, oxygen < 0.1 ppm).

[0059] The P(DMTS1-DTBA8)@LiTFSI prepared in Example 5 was assembled with the positive electrode sheet and the negative electrode sheet into a CR2025 button battery for performance testing.

[0060] Example 6 This embodiment provides a method for preparing a sulfur-containing solid polymer electrolyte membrane, comprising the following steps: Step 1, DMTS and DTBA were mixed uniformly in a mass ratio of 1:10, and magnetically stirred in an oil bath at a temperature of 160° C. for 90 minutes. After reacting at high temperature, the mixture was cooled to room temperature to obtain a solid polymer; Step 2: dissolving the solid polymer obtained in step 1 in DMF, adding 80% by weight of LiTFSI, mixing evenly, and magnetically stirring at 60° C. for 48 hours to obtain a precursor solution; Step 3: The precursor solution is loaded into a syringe, and after standing to expel bubbles, a needle with an inner diameter of 0.5 mm is installed. The high-voltage power supply is turned on, and the high-voltage power supply is controlled to 5 kV. The voltage is gradually increased to 20 kV until the fiber at the needle forms a stable fiber jet. The injection pump is started to push the precursor solution at a flow rate of 1 ml / h. A continuous polymer jet is formed under the action of the electric field. The polymer jet is directed to the receiving plate so that the distance between the receiving plate and the polymer jet is 15 cm, and the spinning time is controlled to 2 h to obtain a fiber membrane. The plate is then placed in an oven for 20 h. The oven ensures a vacuum atmosphere and the oven temperature is 60 ° C. The dried polymer electrolyte membrane is cut into 16 mm diameter discs using a sheet punching machine to obtain a sulfur-containing solid polymer electrolyte membrane, recorded as P (DMTS1-DTBA 10 )@LiTFSI.

[0061] P(DMTS1-DTBA 10 )@LiTFSI was stored in a glove box under an argon atmosphere (water < 0.1 ppm, oxygen < 0.1 ppm).

[0062] The P(DMTS1-DTBA prepared in Example 6 10 ) @LiTFSI is assembled with the positive and negative electrodes into a CR2025 button battery for performance testing.

[0063] Comparative Example 1 This comparative example 1 provides a method for preparing a PEO@LiTFSI electrolyte membrane, comprising the following steps: Step 1: PEO and LiTFSI are mixed in the typical ratio EO:Li + =16:1 (mass ratio is 10:4) was dissolved in acetonitrile (ACN) solvent to obtain a mixed solution; Step 2: Load the mixed solution into a syringe, let it stand to expel bubbles, then install a needle with an inner diameter of 0.5 mm, turn on the high-voltage power supply, control the high-voltage power supply to 5 kV, and gradually increase the voltage to 20 kV until the fiber at the needle forms a stable fiber jet. Start the injection pump and push the precursor solution at a flow rate of 1 ml / h to form a continuous polymer jet under the action of the electric field. Direct the polymer jet to the receiving plate so that the distance between the receiving plate and the polymer jet is 15 cm, and control the spinning time to 2 h to obtain a fiber membrane. Then, vacuum dry the solvent at 60 ° C for 24 h, remove the film from the mold, and use a punching machine to cut it into 16 mm diameter discs to obtain a PEO@LiTFSI electrolyte membrane.

[0064] The PEO@LiTFSI electrolyte membrane prepared in Comparative Example 1 was assembled into a battery with the positive electrode sheet and the negative electrode sheet for performance testing.

[0065] Table 1 Basic performance parameters of polymer electrolyte membranes prepared in Examples 1-6 and Comparative Example 1

[0066] Basic performance tests were performed on the polymer electrolyte membranes prepared in Examples 1-6 and Comparative Example 1. The test results are shown in Table 1.

[0067] First, a single-factor comparative analysis of Examples 1-3 revealed the following electrochemical window order: Example 3 > Example 2 > Example 1. This is due to the rigid benzene ring skeleton and disulfide bonds (-S-S-) in DTBA imparting excellent high-voltage antioxidant properties, effectively inhibiting DTBA's decomposition at potentials >4.0V. Meanwhile, the flexible -S4- chains in DMT are susceptible to oxidative cleavage at high voltages >4.1V, resulting in decreased stability. Example 3 (DMTS:DTBA mass ratio of 1:5) contains DTBA as the primary component and therefore exhibits the widest electrochemical stability window.

[0068] In terms of ionic conductivity, the order is: Example 1 > Example 2 > Example 3 > Comparative Example 1. The flexible -S4- chain of DMT can form a Li + The fast-migrating "sulfur chain tunnel" significantly improves ion conductivity; while the rigid benzene ring structure of DTBA hinders chain segment movement and inhibits ion migration. Example 1 (DTBA:DMT=1:1) has the highest DMT ratio and the conductivity is close to that of liquid electrolytes. This conclusion is consistent with the impedance data ( Figure 2 ) confirm each other: Example 1 has the lowest impedance (185Ω), and Comparative Example 1 has the highest impedance (613Ω), and the conductivity and impedance value are clearly inversely proportional.

[0069] In terms of mechanical strength, the order of tensile strength is Example 3 > Example 2 > Example 1. The benzene ring structure of DTBA forms a physical crosslinking network through intermolecular π-π stacking, significantly enhancing the material's rigidity; whereas the long, flexible chains of DMT weaken mechanical properties. Example 3 (with a high DTBA content) achieves a tensile strength of 4.2 MPa, approaching the requirements for commercial separators and fully demonstrating the reinforcing effect of the rigid component.

[0070] A comprehensive analysis of the data in Table 1 shows that the sulfur-containing solid polymer electrolyte membranes prepared in Examples 1-6 significantly surpassed Comparative Example 1 in key indicators. The electrochemical window range of Examples 1-6 was 4.1V-4.65V, while that of Comparative Example 1 was only 3.9V, indicating that the sulfur-containing solid polymer electrolyte membranes prepared in the examples had stronger antioxidant capacity and could match higher voltage electrode materials. In terms of ionic conductivity, Examples 1-6 were generally more than one order of magnitude higher than that of Comparative Example 1, and the tensile strength was significantly improved, proving that the technical solution of the present invention has a breakthrough advantage in balancing high ion transmission efficiency and structural stability.

[0071] Table 2 Stability and cycle performance parameters of polymer electrolyte membranes prepared in Examples 1-6 and Comparative Example 1

[0072] As shown in Table 2, +In terms of ion migration number, Example 1>Example 2>Example 3, mainly due to the sulfur atom of the -S4- chain in DMT and Li + Affinity of soft acid sulfur atoms (Li + ), forming a selective transport channel; and the carboxyl group (-COOH) of DTBA may capture Li + The superimposed benzene ring structure lacks ion conductivity, resulting in a decrease in the migration number of samples with a high DTBA ratio (such as Example 3). When the ratio of Example 1 is 1:1, t + =0.45 is optimal.

[0073] Li-Li symmetric battery tests showed that the polarization degree was Example 3 > Example 2 > Example 1. The flexible chains of DMT improved the contact uniformity of the electrode / electrolyte interface and significantly reduced the interfacial impedance. In contrast, the rigid benzene rings of DTBA caused point contact defects at the electrode / electrolyte interface, increasing the resistance to ion migration and causing the polarization voltage of Example 3 to continue to rise.

[0074] In order to further verify the effect of P(DMTS1-DTBA3)@LiTFSI on the stability of lithium metal anode, SEM analysis was performed at 0.2 mA cm -1 The surface morphology of the lithium sheet in a Li-Li symmetric battery after 100 cycles at a current density of 100. As shown in Figure 3(a), after 100 cycles using the P(DMTS1-DTBA3)@LiTFSI electrolyte membrane, the lithium anode surface is smooth and dendrites are suppressed; while in Figure 3(b), PEO@LiTFSI exhibits lithium corrosion and uneven deposition, verifying the strong correlation between interface stability and polarization data.

[0075] The order of cycle retention is Example 3 > Example 2 > Example 1. This is because DTBA's mechanical strength (physical cross-linking enhancement) and antioxidant properties (disulfide bonds and benzene rings) jointly inhibit dendrite growth and decomposition side reactions, but at the expense of ion transport rate. While DMT improves conduction rate, it weakens interfacial stability during long-term cycling.

[0076] like Figure 4 As shown, the rate performance of the electrolyte membranes prepared in Example 1 of the present invention and Comparative Example 1 at 25°C for LFP|P(DMTS1-DTBA2)@LiTFSI@LiTFSI|Li and LFP|PEO@LiTFSI|Li batteries is shown. Figure 4 It can be found that the discharge capacity of the lithium battery assembled using P(DMTS1-DTBA2)@LiTFSI is 153 mAh g at 0.1C, 0.2C and 0.5C respectively. -1 , 148mAh g -1 and 138mAh g -1The discharge capacity of lithium metal batteries made with PEO@LiTFSI at 0.1C, 0.2C and 0.5C were 111 mAh g -1 , 104mAh g -1 and 97mAh g -1 When the discharge rate is reduced to 0.1C, the discharge capacity of the lithium battery using P(DMTS1-DTBA2)@LiTFSI increases to 152 mAh g -1 , while the discharge capacity of the lithium battery using LFP|PEO@LiTFSI|Li only increased to 108 mAh g -1 , indicating that P(DMTS1-DTBA2)@LiTFSI has good rate performance and capacity recovery performance. This is mainly due to the dynamic flexibility of the sulfur chain promoting ion migration, while the dual coordination effect of the amino group stabilizes ion binding. The two work together to significantly improve the ion transmission rate and reduce capacity loss during fast charging and discharging.

[0077] Comprehensive analysis of the data in Table 2 shows that the Li-Li symmetric polarization voltages (32-177 mV) of all examples are much lower than those of Comparative Example 1 (330 mV), with the highest reduction reaching 90.3%, proving that the electrode / electrolyte interface impedance obtained in the examples of the present invention is significantly reduced; the cycle retention rates of Examples 1-6 are all better than those of Comparative Example 1, and the Li + The migration number is increased by 16%-18%, indicating that the battery assembled with the sulfur-containing solid polymer electrolyte membrane prepared by the method of the present invention can effectively improve the cycle life and ion transfer efficiency.

[0078] The above data show that different embodiments have their own performance advantages due to differences in component proportions. In actual application, the formula needs to be selected according to the needs of the scenario. Example 1 is selected for the high-power battery scenario. It is based on the "sulfur chain tunnel" effect formed by the high-flexibility chain dominated by DMT, achieving optimal ionic conductivity and low polarization characteristics, meeting the needs of fast charging and high-rate discharge; Example 2 is selected for the long cycle life scenario. While maintaining a high ion mobility, it also has the mechanical strength enhanced by DTBA, ensuring structural stability during the cycle process, controllable polarization and excellent capacity retention; Example 3 is used for the high-voltage system scenario. Relying on the rigid benzene ring and disulfide bond antioxidant properties of DTBA, it broadens the electrochemical window and is suitable for high-voltage battery environments such as lithium cobalt oxide and high-nickel positive electrodes.

[0079] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A sulfur-containing solid polymer electrolyte membrane, characterized in that: It is prepared by hot melting, spinning and evaporation of a sulfur-containing solid polymer, wherein the general structural formula of the sulfur-containing solid polymer is: Wherein, n is the degree of polymerization, 5000<n<50000.

2. A sulfur-containing solid polymer electrolyte membrane according to claim 1, characterized in that: The thickness of the sulfur-containing solid polymer electrolyte membrane is 70µm±5µm.

3. A method for preparing the sulfur-containing solid polymer electrolyte membrane according to claim 1, characterized in that: The following steps are involved: Dimethyl tetrasulfide and dibenzoyl disulfide are uniformly mixed to obtain a solid polymer through polycondensation reaction; dissolving a solid polymer in N,N-dimethylamide to obtain a mixed solution, adding lithium bis(trifluoromethanesulfonyl)imide to the mixed solution and mixing uniformly to obtain a precursor solution; The precursor solution is electrospun to form a fiber membrane, which is then vacuum dried to obtain a sulfur-containing solid polymer electrolyte membrane.

4. The method for preparing a sulfur-containing solid polymer electrolyte membrane according to claim 3, characterized in that: The mass ratio of the dimethyl tetrasulfide to dibenzoyl disulfide is 1:(1-10).

5. The method for preparing a sulfur-containing solid polymer electrolyte membrane according to claim 3, characterized in that: The polycondensation reaction is carried out in an oil bath environment at a temperature of 100-180° C. for 30-120 min. After the reaction is completed, the mixture is cooled to room temperature to obtain a solid polymer.

6. The method for preparing a sulfur-containing solid polymer electrolyte membrane according to claim 3, characterized in that: The added amount of the lithium bis(trifluoromethanesulfonyl)imide is 20% to 80% of the total mass of dimethyl tetrasulfide and dibenzoylmethanesulfide.

7. The method for preparing a sulfur-containing solid polymer electrolyte membrane according to claim 3, characterized in that: Lithium bis(trifluoromethanesulfonyl)imide is added to the mixed solution, and the mixture is magnetically stirred at a temperature of 25-60° C. for 12-48 hours until the mixture is uniformly mixed to obtain a precursor solution.

8. The method for preparing a sulfur-containing solid polymer electrolyte membrane according to claim 3, characterized in that: During the electrospinning process: The inner diameter of the needle is 0.3~0.8mm, the voltage is 5~20kV, the solution flow rate is 0.5~2ml / h, the distance between the needle and the receiving plate is 12~18cm, and the spinning time is 1~3h.

9. The method for preparing a sulfur-containing solid polymer electrolyte membrane according to claim 3, characterized in that: The vacuum drying temperature is 25-130° C., and the time is 12-24 hours.

10. Use of the sulfur-containing solid polymer electrolyte membrane according to claim 1 or 2, characterized in that: The sulfur-containing solid polymer electrolyte membrane is used in lithium-ion batteries.

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