Energy storage lithium battery and sulfur-containing polymer solid electrolyte membrane and preparation method

Abstract

The application discloses a kind of energy storage lithium battery and sulfur-containing polymer solid electrolyte membrane and preparation method, belong to polymer electrolyte technical field, in solid electrolyte membrane, add functional polymer, the functional polymer is polyethylene glycol dimethyl methacrylate PEGDMA and diphenyl disulfide DPDS is quickly interwoven by thermal initiation polymerization, the sulfur-containing polymer solid electrolyte membrane of the application can simultaneously improve the voltage resistance characteristic and high ionic conduction performance of polymer electrolyte, to solve the problems, such as low room temperature ionic conductivity of existing sulfur-containing polymer solid electrolyte membrane, high interface impedance, poor mechanical properties and high crystallinity, battery cycle and stability have great gain.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of polymer electrolyte, and particularly relates to a kind of energy storage lithium battery and sulphur-containing polymer solid electrolyte membrane and preparation method. BACKGROUND

[0002] Lithium ion batteries are widely used in wireless communication, notebook computers, new energy vehicles and other fields due to their high voltage, sufficient energy density and long cycle life. However, lithium ion batteries have always faced two major challenges: limited energy density and poor safety, thus failing to meet the growing demand for higher energy density and higher safety batteries. Commercial lithium ion batteries mainly use liquid electrolytes composed of flammable organic carbonates, which are extremely volatile and flammable. In addition, when using liquid electrolytes in lithium ion batteries, the growth of lithium dendrites is particularly prone to occur. As an important component of lithium ion batteries, electrolytes have a great influence on the electrochemical performance of lithium ion batteries.

[0003] Solid-state lithium batteries have attracted attention due to their high safety and excellent high-temperature performance. Solid-state electrolytes in lithium batteries are divided into inorganic solid-state electrolytes and polymer solid-state electrolytes. Compared with inorganic solid-state electrolytes, polymer electrolytes are promising as electrolytes for solid-state lithium batteries due to their good flexibility, high safety and good processability. Therefore, they have better development prospects. Before that, solid-state polymer electrolytes represented by polyethylene oxide electrolytes are severely hindered from being widely used in solid-state lithium batteries due to their excessively low ionic conductivity at room temperature, poor interface contact between electrolytes and electrodes, narrow electrochemical window and easy oxidation at high charging potential. In addition, researchers have also developed nitrile-based polymer electrolytes, siloxane-based polymer electrolytes, carbonate-based polymer electrolytes and polymer electrolytes based on vinylidene fluoride. However, due to the single nature of the polymer backbone, there are still problems of low room temperature ionic conductivity, high interface impedance, poor mechanical properties and high crystallinity of sulphur-containing polymer solid electrolyte membranes. SUMMARY

[0004] The present application provides a kind of energy storage lithium battery and sulphur-containing polymer solid electrolyte membrane and preparation method, in the solid electrolyte membrane added functional polymer, the functional polymer is poly (ethylene glycol) dimethacrylate PEGDMA (Poly (ethylene glycol) dimethacrylate) and diphenyl disulfide DPDS (Diphenyl Disulfide) is quickly interwoven by thermal initiation polymerization, can solve the problems of low room temperature ionic conductivity, high interface impedance, poor mechanical properties and high crystallinity of sulphur-containing polymer solid electrolyte membrane in the prior art.

[0005] To achieve the above object, the application provides the following technical scheme: a sulfur-containing polymer solid electrolyte membrane, comprising a functional polymer, a general structure of the functional polymer is as follows:

[0006]

[0007] wherein n and m represent the polymerization degree or the number of repeating units.

[0008] Further, the functional polymer is obtained by thermal initiation polymerization of polyethylene glycol dimethacrylate and diphenyl disulfide.

[0009] Further, the mass ratio of the polyethylene glycol dimethacrylate and the diphenyl disulfide is 1: (1-10).

[0010] Further, the application further comprises a lithium salt, the functional polymer solution is mixed with the lithium salt, spread, dried, and a sulfur-containing polymer solid electrolyte membrane is obtained.

[0011] Further, the addition amount of the lithium salt is 20%-80% of the mass of the functional polymer.

[0012] The application provides a preparation method of a sulfur-containing polymer solid electrolyte membrane, comprising:

[0013] Polyethylene glycol dimethacrylate PEGDMA and diphenyl disulfide DPDS are uniformly mixed according to a preset ratio, cooled to room temperature after reaction, and a polymer solid is obtained.

[0014] The obtained polymer solid is dissolved in a solvent, and a lithium salt is added for mixing, and a precursor solution is obtained.

[0015] The precursor solution is spread, dried, and a sulfur-containing polymer solid electrolyte membrane PEGDMA-DPDS is obtained. x -DPDS y wherein x and y are the mass ratio of the two substances.

[0016] Further, the polyethylene glycol dimethacrylate and the diphenyl disulfide are stirred and reacted at 60-130 DEG C for 10-120 min, and the polymer solid is obtained after cooling to room temperature.

[0017] Further, the obtained polymer solid is dissolved in N,N-dimethylformamide, and lithium bis (trifluoromethanesulfonyl) imide is added for stirring at room temperature for 12-24 h to obtain a precursor solution.

[0018] Further, the precursor solution is cast on the surface of a PTFE mold, the precursor solution is uniformly spread, and the sulfur-containing polymer solid electrolyte membrane is obtained by drying at 60-130 DEG C under vacuum.

[0019] The present invention also provides an energy storage lithium battery, wherein the electrolyte membrane of the energy storage lithium battery adopts the above-mentioned sulfur-containing polymer solid electrolyte membrane.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] The present invention discloses a sulfur-containing polymer solid electrolyte membrane, which introduces a functional polymer synthesized by rapid cross-linking of PEGDMA and DPDS through thermal polymerization. This functional polymer cleverly combines the characteristics of the two raw materials. The ether oxygen bond (-O-) of PEGDMA has excellent lithium salt dissociation ability, which can be used for lithium ions (Li + ) constructs fast migration channels, greatly improving the transmission efficiency of lithium ions. The disulfide bonds (-SS-) of DPDS effectively reduce the crystallinity of the polymer, making the conduction of ions in the membrane smoother and significantly improving the ionic conductivity. At the same time, the sulfur-containing structure plays an important role at the electrode / electrolyte interface, effectively suppressing potential polarization and side reactions, and enhancing electrochemical stability. In addition, the benzene rings in DPDS give the electrolyte membrane high mechanical rigidity, which can effectively prevent lithium dendrites from penetrating and ensure the safe operation of the battery. The three-dimensional cross-linked network structure of the electrolyte membrane ensures the uniformity of film formation and provides strong support for the long-term cycling performance of the battery. In practical applications, the prepared sulfur-containing polymer solid electrolyte membrane has a moderate thickness (25μm~35μm), low impedance at room temperature (only 1200Ω), and an electrochemical window of 4.2V. The lithium deposition / stripping curve also demonstrates its good interfacial compatibility with the electrode, which can effectively suppress the growth of lithium dendrites and exhibit excellent cycling stability.

[0022] The preparation method of the present invention has the characteristics of easy preparation and simple molding process. Through thermally initiated polymerization, PEGDMA and DPDS are rapidly cross-linked to synthesize functional polymers, thereby preparing sulfur-containing polymer solid electrolyte membranes. This preparation method avoids complex and tedious process flows, reduces production costs, and improves production efficiency. During the preparation process, the reaction conditions can be precisely controlled to ensure that the structure and performance of the functional polymer meet the expected requirements. Through a simple molding process, an electrolyte membrane with uniform thickness and stable performance can be prepared to meet the needs of different lithium batteries. This preparation method not only provides new ideas for the research and development of solid electrolyte membranes, but also brings new opportunities for the development of the lithium battery industry.

[0023] The sulfur-containing polymer solid electrolyte membrane of the present invention is applied to lithium batteries. In terms of interface stability, the assembled lithium battery has an initial discharge capacity of 146 mAh·g at a 0.5C rate. -1, indicating that the electrolyte membrane has good interface compatibility with the electrode, can effectively reduce the interface impedance and improve the performance of the battery. At the same time, the electrolyte membrane can effectively inhibit the growth of lithium dendrites, greatly improve the safety of the battery, and reduce the safety hazards such as short circuit, fire and the like caused by lithium dendrites piercing the separator. In addition, its excellent electrochemical stability and cycle stability make the battery have a longer service life, and reduce the use cost of the battery. Moreover, the application of the solid-state electrolyte membrane provides a new path for high-safety, long-life semi-solid-state batteries, and is expected to promote the wider application of lithium battery technology in electric vehicles, energy storage and other fields, and bring new changes to energy storage and utilization. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0025] Figure 1 Impedance spectrum of the battery equipped with the sulfur-containing polymer solid-state electrolyte membrane prepared in Embodiment 1 of the present application;

[0026] Figure 2 Impedance spectrum of the battery equipped with the sulfur-containing polymer solid-state electrolyte membrane prepared in Embodiment 2 of the present application;

[0027] Figure 3 Impedance spectrum of the battery equipped with the sulfur-containing polymer solid-state electrolyte membrane prepared in Embodiment 3 of the present application;

[0028] Figure 4 Electrochemical window diagram of the sulfur-containing polymer solid-state electrolyte membrane prepared in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects of the present application more clearly understood, the following will further describe the present application in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0030] The present application provides a sulfur-containing polymer solid-state electrolyte membrane, wherein a functional polymer is added, the functional polymer is a copolymer rapidly synthesized by thermal initiation polymerization of polyethylene glycol dimethacrylate PEGDMA and diphenyl disulfide DPDS, and the structure of the polymer is as follows:

[0031]

[0032] Wherein, n, m represent the degree of polymerization or the number of repeating units. Denotes the average number of times of repeating connection of monomer units (or structural units) constituting the polymer chain.

[0033] The PEGDMA-DPDS polymer is prepared by the fast cross-linking of polyethylene glycol dimethacrylate PEGDMA and diphenyl disulfide DPDS through thermal initiation polymerization, and the preparation of the solid-state electrolyte from the PEGDMA-DPDS polymer can realize high ionic conductivity at room temperature, overcomes the low ionic conductivity at room temperature in the prior art, and expands the application range of the electrolyte film in a low-temperature environment; the PEGDMA-DPDS polymer has the structure of -S-S- and the structure of -PEG-. - Lithium salt dissociation and Li + migration energy barrier; the -S-S- bond reduces the crystallinity, and the sulfur atom lone pair directly promotes Li + jumping, significantly improves the ion transmission efficiency, solves the problem of low ion transmission efficiency of the polymer solid-state electrolyte in the prior art, and adopts the sulfur-containing component design to directly promote Li + jumping through the sulfur atom lone pair, improves the ion transmission efficiency, stabilizes the electrolyte and electrode interface, effectively suppresses polarization and side reactions, reduces the interface impedance, improves the rate performance of the battery, and meets the high-power density application demand; the DPDS benzene ring has the characteristics of enhancing the mechanical strength, the mechanical strength of the polymer solid-state electrolyte is improved through the cross-linking and entanglement of the molecular chain, the lithium dendrite penetration is effectively prevented, the mechanical properties of the polymer solid-state electrolyte are improved through the optimized molecular structure design, the microcracks generated in the sheet preparation process are reduced, the problem that the lithium dendrite grows along the microcracks and penetrates the electrolyte sheet to cause short circuit is effectively prevented, and the sulfur-containing polymer solid-state electrolyte film has excellent interface stability and mechanical strength through the fast cross-linking and the optimized molecular structure design, and the cycle life and electrochemical performance of the electrolyte are significantly improved.

[0034] The application further provides a preparation method of the above-mentioned sulfur-containing polymer solid-state electrolyte film, comprising the following steps:

[0035] Step one, uniformly mixing polyethylene glycol dimethacrylate PEGDMA and diphenyl disulfide DPDS according to a mass ratio of 1:1 to 1:10, magnetically stirring in an oil bath at a temperature of 60-130 DEG C for 10-120 min, cooling to room temperature after reaction, and obtaining a polymer solid;

[0036] Step two, dissolving the obtained polymer solid in N,N-dimethylformamide (DMF) and adding lithium bis(trifluoromethanesulfonyl)imide (LITFSI), magnetically stirring at room temperature for 12-24 h, and obtaining a precursor solution;

[0037] The adding amount of lithium bis(trifluoromethanesulfonyl)imide (LITFSI) is 20% to 80% of the total mass of polyethylene glycol dimethacrylate (PEGDMA) and diphenyl disulfide (DPDS).

[0038] Step three, pouring the precursor solution on the surface of the PTFE mold, spreading the precursor solution evenly, and drying the precursor solution in a vacuum oven at 60 DEG C to 130 DEG C to obtain a sulfur-containing polymer solid electrolyte film PEGDMA x -DPDS y Wherein x, y is the mass ratio of the two substances.

[0039] Step four, the prepared sulfur-containing polymer solid electrolyte film PEGDMA x -DPDS y Stored in an argon environment, and the water in the argon environment is less than 0.1 ppm, and the oxygen is less than 0.1 ppm.

[0040] In the above preparation method, the mass ratio of PEGDMA and DPDS is 1:1 to 1:10, and the adding amount of LITFSI is 20% to 80% of the total mass of PEGDMA and DPDS. The selection of these parameter ranges can achieve the best ratio of each component, and further optimize the performance of the electrolyte; in the above preparation method, the oil bath temperature is 60 DEG C to 130 DEG C, the magnetic stirring time is 10 min to 120 min, the precursor solution is stirred in DMF at room temperature for 12 h to 24 h, and the vacuum oven drying temperature is 60 DEG C to 130 DEG C. Precise control of these parameters helps to ensure the uniformity and stability of the sulfur-containing polymer solid electrolyte film.

[0041] The solid electrolyte film is extremely easy to prepare, the forming process is simple, the prepared sulfur-containing polymer solid electrolyte film has a thickness of 25 mu m to 35 mu m, the impedance at room temperature is only 1200 ohms, and the electrochemical window is 4.2V. The lithium deposition / stripping curve proves that the interface compatibility between the electrolyte film and the electrode is good, and the growth of lithium dendrites can be effectively inhibited, showing excellent cycle stability. When it is applied to LFP-Li solid-state battery, the interface stability of the assembled lithium battery is measured at 0.5C rate, and the initial discharge specific capacity of the battery is 146 mAh·g -1 , which provides a new way for high-safety and long-life semi-solid batteries.

[0042] In the following examples, unless otherwise specified, each material used can be obtained through ordinary channels; the test method used is a conventional method in the art.

[0043] Example 1

[0044] The embodiment provides a preparation method of a sulfur-containing polymer solid electrolyte membrane, and comprises the following steps.

[0045] Step one, uniformly mix PEGDMA and DPDS according to a mass ratio of 1:5, magnetically stir in an oil bath with a temperature of 130 DEG C for 120 min, cool to room temperature after reaction, and obtain a polymer solid.

[0046] Step two, dissolve the obtained polymer solid in DMF, add LITFSI, magnetically stir at room temperature for 24 h, and obtain a precursor solution. The addition amount of LITFSI is 40% of the mass sum of PEGDMA and DPDS.

[0047] Step three, cast the precursor solution on the surface of a PTFE mold, uniformly spread the precursor solution, ensure a vacuum atmosphere in an oven, dry the precursor solution in a vacuum oven at 130 DEG C for 12 h, and obtain a sulfur-containing polymer solid electrolyte membrane PEGDMA1-DPDS5.

[0048] Step four, store the prepared sulfur-containing polymer solid electrolyte membrane PEGDMA1-DPDS5 in an argon environment, and the water in the argon environment is less than 0.1 ppm, and the oxygen is less than 0.1 ppm.

[0049] Example 2

[0050] The embodiment prepares a sulfur-containing polymer solid electrolyte membrane (PEGDMA1-DPDS 2.5 ) and the specific steps are as follows: basically the same as those in Example 1, except that the mass ratio of PEGDMA and DPDS in step one is 1:2.5.

[0051] Example 3

[0052] The embodiment prepares a sulfur-containing polymer solid electrolyte membrane (PEGDMA1-DPDS1) and the specific steps are as follows: basically the same as those in Example 1, except that the mass ratio of PEGDMA and DPDS in step one is 1:1.

[0053] Example 4:

[0054] The embodiment provides a preparation method of a sulfur-containing polymer solid electrolyte membrane, and comprises the following steps.

[0055] Step one, uniformly mix PEGDMA and DPDS according to a mass ratio of 1:5, magnetically stir in an oil bath with a temperature of 130 DEG C for 120 min, cool to room temperature after reaction, and obtain a polymer solid.

[0056] Step two, the obtained polymer solid is dissolved in DMF, and LITFSI is added, and magnetic stirring is carried out at room temperature for 18h to obtain a precursor solution. Among them, the addition amount of LITFSI is 50% of the mass sum of PEGDMA and DPDS.

[0057] Step three, the precursor solution is cast on the surface of the PTFE mold, the precursor solution is uniformly spread, the oven ensures a vacuum atmosphere, and the sulfur-containing polymer solid electrolyte film PEGDMA1-DPDS5 is obtained by drying in a vacuum oven at 80℃ for 12h.

[0058] Step four, the prepared sulfur-containing polymer solid electrolyte film PEGDMA1-DPDS5 is stored in an argon environment, and the water in the argon environment is <0.1ppm, and the oxygen is <0.1ppm.

[0059] Example 5:

[0060] The embodiment provides a preparation method of a sulfur-containing polymer solid electrolyte film, comprising the following steps:

[0061] Step one, PEGDMA and DPDS are uniformly mixed according to a mass ratio of 1:7, magnetic stirring is carried out in an oil bath with a temperature of 100℃ for 45min, and the polymer solid is obtained after reaction and cooling to room temperature.

[0062] Step two, the obtained polymer solid is dissolved in DMF, and LITFSI is added, and magnetic stirring is carried out at room temperature for 20h to obtain a precursor solution. Among them, the addition amount of LITFSI is 30% of the mass sum of PEGDMA and DPDS.

[0063] Step three, the precursor solution is cast on the surface of the PTFE mold, the precursor solution is uniformly spread, the oven ensures a vacuum atmosphere, and the sulfur-containing polymer solid electrolyte film PEGDMA1-DPDS7 is obtained by drying in a vacuum oven at 100℃ for 12h.

[0064] Step four, the prepared sulfur-containing polymer solid electrolyte film PEGDMA1-DPDS7 is stored in an argon environment, and the water in the argon environment is <0.1ppm, and the oxygen is <0.1ppm.

[0065] Example 6:

[0066] The embodiment provides a preparation method of a sulfur-containing polymer solid electrolyte film, comprising the following steps:

[0067] Step one, PEGDMA and DPDS are uniformly mixed according to a mass ratio of 1:9, magnetic stirring is carried out in an oil bath with a temperature of 120℃ for 15min, and the polymer solid is obtained after reaction and cooling to room temperature.

[0068] Step two, the obtained polymer solid is dissolved in DMF, and LITFSI is added, and magnetic stirring is carried out at room temperature for 12 h to obtain a precursor solution. Among them, the addition amount of LITFSI is 60% of the mass sum of PEGDMA and DPDS.

[0069] Step three, the precursor solution is cast on the surface of the PTFE mold, the precursor solution is uniformly spread, the oven ensures a vacuum atmosphere, and the sulfur-containing polymer solid electrolyte film PEGDMA1-DPDS9 is obtained by drying in a vacuum oven at 90°C for 12h.

[0070] Step four, the prepared sulfur-containing polymer solid electrolyte film PEGDMA1-DPDS9 is stored in an argon environment, and the water in the argon environment is <0.1 ppm, and the oxygen is <0.1 ppm.

[0071] Example 7:

[0072] The embodiment provides a preparation method of a sulfur-containing polymer solid electrolyte film, comprising the following steps:

[0073] Step one, PEGDMA and DPDS are uniformly mixed according to a mass ratio of 1:10, magnetic stirring is carried out in an oil bath with a temperature of 110°C for 20 min, and the polymer solid is obtained after reaction and cooling to room temperature.

[0074] Step two, the obtained polymer solid is dissolved in DMF, and LITFSI is added, and magnetic stirring is carried out at room temperature for 16 h to obtain a precursor solution. Among them, the addition amount of LITFSI is 50% of the mass sum of PEGDMA and DPDS.

[0075] Step three, the precursor solution is cast on the surface of the PTFE mold, the precursor solution is uniformly spread, the oven ensures a vacuum atmosphere, and the sulfur-containing polymer solid electrolyte film PEGDMA1-DPDS 10 .

[0076] Step four, the prepared sulfur-containing polymer solid electrolyte film PEGDMA1-DPDS 10 is stored in an argon environment, and the water in the argon environment is <0.1 ppm, and the oxygen is <0.1 ppm.

[0077] Comparative Example 1

[0078] The specific steps of preparing the polymer solid electrolyte film in the comparative example are as follows: 10.00g of polyvinylidene fluoride-hexafluoropropylene copolymer PVDF-HFP and 4.00g of lithium bis(trifluoromethanesulfonyl)imide LiTFSI are dissolved in 50ml of N,N-dimethylformamide DMF solution, the obtained solution is cast on the surface of a glass plate, and a polymer solid electrolyte film is obtained by vacuum drying at 60°C for 24 hours.

[0079] The solid-state electrolyte films prepared in Examples 1-7 and Comparative Example 1 were subjected to mechanical property tests, and the data are shown in Table 1:

[0080] Table 1 is the mechanical property test data

[0081]

[0082] As shown in Table 1, the electrolyte film of the present application exhibits ultra-high flexibility (elongation at break 300%-500%) due to the dynamic reversible characteristics of the -S-S- bond in DPDS: during the stretching process, the -S-S- bond breaks / recombines as a “sacrificial bond” to absorb energy, so that the elongation at break of Example 2 (PEGDMA1-DPDS 2.5 ) reaches 500%; at the same time, the benzene ring structure of DPDS provides moderate rigid support to avoid the collapse of strength caused by high flexibility (tensile strength of Example 1 is 1.5 MPa). Compared with the rigidity defect of the traditional material (Comparative Example 1) (elongation at break is only 15% and Young's modulus is 110.5 MPa), the present application realizes “rigidity and flexibility” by adjusting the proportion of DPDS: Example 3 (PEGDMA1-DPDS1) has a high proportion of benzene rings, resulting in an increase in Young's modulus (8.5 MPa), but it is still significantly lower than that of Comparative Example 1; Example 2 has the optimal crosslinking density, maintaining a tensile strength of 0.8 MPa while achieving the highest elongation at break (500%); Example 7 shows that as the DPDS content increases, the increase in the proportion of DPDS significantly increases the crosslinking density of the disulfide bond, which dominates the increase in material rigidity, the increase in Young's modulus, and the decrease in ductility, corresponding to the decrease in elongation at break and the increase in tensile strength. At the same time, the π-π stacking effect of the benzene ring under high DPDS content cooperates with the crosslinking, further strengthening the rigidity and brittleness trend of the network, making the material harder and more brittle in the high crosslinking region, which provides a key mechanical guarantee for inhibiting lithium dendrites. The data prove that the -S-S- bond of DPDS is the core design for balancing ultra-flexibility and structural integrity.

[0083] Example 8

[0084] As Figure 4 shown, Example 1 (PEGDMA1-DPDS5) exhibits a relatively optimal 4.2 V electrochemical window, which benefits from its moderate crosslinking network: it provides sufficient disulfide bond stability and chain segment regularity to inhibit electrolyte decomposition, and avoids the side reactions that may be caused by excessive aggregation or dense crosslinking of benzene rings under high DPDS, thereby maintaining good electrochemical stability.

[0085] The sulfur-containing polymer solid-state electrolyte film prepared in Example 1 was assembled with a positive electrode (lithium iron phosphate) and a negative electrode (metal lithium sheet) to form a 2025 type button cell, and the performance was tested: the conductivity at room temperature was measured to be 3.3×10 -4S / cm -1 To test the application of the sulfur-containing polymer solid-state electrolyte film in a full solid-state lithium battery, the film was assembled into a LiFePO4 / PEGDMA1-DPDS5 / Li battery, which was tested for charge-discharge cycling at 60°C. The first discharge specific capacity of the battery was measured to be 150 mAh·g -1 .

[0086] The polymer solid-state electrolyte film prepared in Comparative Example 1 was assembled into a LiFePO4 / PVDF-HFP / Li battery, which was tested for charge-discharge cycling at 60°C. The room temperature conductivity of the polymer solid-state electrolyte film was measured to be 3.96 x 10 -5 S / cm -1 The first discharge specific capacity of the battery was measured to be 102 mAh·g -1 The impedance of the LiFePO4 / PVDF-HFP / Li battery after 100 cycles was 12400Ω.

[0087] Example 9

[0088] The sulfur-containing polymer solid-state electrolyte films prepared in Examples 2 and 3 were used to prepare full solid-state lithium batteries by the method of Example 8. The impedance plots of the batteries after 100 cycles are shown in Figures 1-3 It can be seen that the excellent performance of Example 1 (PEGDMA1-DPDS5, impedance 1200Ω) is due to the synergistic effect of a high DPDS ratio (1:5). The dynamic-S-S-bond greatly increases the proportion of amorphous regions (>80%), and a continuous Li⁺ channel is constructed. At the same time, the ether oxygen bond (-O-) and the sulfur atom lone pair of electrons form a two-site coordination, which synergistically reduces the Li⁺ migration activation energy and increases the migration number (>0.45). The sulfur-containing component further generates a uniform SEI layer at the interface, significantly reducing the interfacial impedance. By contrast, Example 2 (PEGDMA1-DPDS 2.5 , impedance 2300Ω) has a reduced DPDS (1:2.5), which weakens the dynamic crosslinking and causes the density of the -S-S-bond to decrease, resulting in the blocking of the ion channel in the local crystalline region. In addition, the sulfur atom competes with the ether oxygen bond for coordination of Li⁺, reducing the migration efficiency. The extremely high impedance of Example 3 (PEGDMA1-DPDS1, impedance 4200Ω) exposes structural defects: the low DPDS content (1:1) causes the -S-S-bond transmission contribution to disappear, and the stacking of benzene rings forms a barrier layer, which, combined with the high crystallinity (40%), forces Li⁺ to migrate around. In summary, the impedance gradient clearly reveals that the -S-S-bond through dynamic crosslinking and two-site coordination is the core of breaking through the transmission bottleneck.

[0089] In summary, the reason for the low conductivity of the polymer solid-state electrolyte film prepared in Comparative Example 1 is that PVDF-HFP has a high crystallinity, which inhibits the migration of Li +The migration of the sulfide group will further cause the low ionic conductivity of the electrolyte, and the present application solves the three bottlenecks of the solid-state electrolyte by simultaneously regulating the proportion of DPDS: high DPDS content (1:5) uses the-S-S- bond to cooperate with the ether oxygen bond to reduce the impedance to 1200 Ω, which is comparable to the conduction efficiency of liquid electrolyte; the in-situ formation of a stable SEI layer at the electrode interface by the sulfur-containing polymer significantly inhibits potential polarization and side reactions (such as LiTFSI decomposition), and improves the cycle life; the dynamic cross-linked network gives the film a 300%~500% elongation at break, making the risk of lithium dendrite penetration close to zero. This ternary synergistic effect of "high ionic conductivity-interface stability-mechanical flexibility" provides a solution for the development of high-energy-density, high-safety solid-state lithium batteries.

[0090] The above examples are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the above examples, the ordinary skilled in the art can still modify or equivalently replace the specific embodiments of the present application, and any modification or equivalent replacement without departing from the spirit and scope of the present application is within the protection scope of the claims of the application to be approved.

Claims

1. A sulfur-containing polymer solid electrolyte membrane, characterized in that: It includes a functional polymer, the general structural formula of which is shown below: Where n and m represent the degree of polymerization or the number of repeating units; The functional polymer is obtained by thermally initiating polymerization of polyethylene glycol dimethacrylate and diphenyl disulfide; The mass ratio of the polyethylene glycol dimethacrylate to diphenyl disulfide is 1:(1-10); It also includes lithium salt, and the functional polymer solution and the lithium salt are mixed, spread out, and dried to obtain a sulfur-containing polymer solid electrolyte membrane; The added amount of the lithium salt is 20% to 80% of the mass of the functional polymer.

2. The method for preparing a sulfur-containing polymer solid electrolyte membrane according to claim 1, characterized in that: include: Polyethylene glycol dimethacrylate PEGDMA and diphenyl disulfide DPDS are mixed uniformly according to a preset ratio, and cooled to room temperature after the reaction to obtain a polymer solid; dissolving the obtained polymer solid in a solvent, and adding a lithium salt to mix, to obtain a precursor solution; The precursor solution was spread and dried to obtain the sulfur-containing polymer solid electrolyte membrane PEGDMA. x -DPDS y , where x and y are the mass ratios of the two substances.

3. The method for preparing a sulfur-containing polymer solid electrolyte membrane according to claim 2, characterized in that: Polyethylene glycol dimethacrylate and diphenyl disulfide are stirred and reacted at 60° C. to 130° C. for 10 min to 120 min, and then cooled to room temperature to obtain a polymer solid.

4. The method for preparing a sulfur-containing polymer solid electrolyte membrane according to claim 2, characterized in that: The obtained polymer solid is dissolved in N,N-dimethylamide, and lithium bis(trifluoromethanesulfonyl)imide is added and stirred at room temperature for 12 h to 24 h to obtain a precursor solution.

5. The method for preparing a sulfur-containing polymer solid electrolyte membrane according to claim 2, characterized in that: The precursor solution is cast on the surface of a PTFE mold to spread the precursor solution evenly, and is dried at 60° C. to 130° C. in a vacuum environment to obtain a sulfur-containing polymer solid electrolyte membrane.

6. A lithium energy storage battery, characterized in that: The electrolyte membrane of the energy storage lithium battery adopts the sulfur-containing polymer solid electrolyte membrane described in claim 1.

Images