Preparation method and application of flame-retardant N and S-containing in-situ polymerization gel electrolyte

Abstract

The invention belongs to the technical field of polymer solid-state batteries, and particularly relates to a preparation method and application of a flame-retardant N and S-containing in-situ polymerization gel electrolyte. The gel electrolyte is composed of a diolefin chain extender, a disulfydryl chain extender, a trifunctional isocyanurate-containing cross-linking agent, a catalyst, an organic electrolyte and a lithium salt, and in-situ polymerization is carried out in the battery through a sulfydryl-alkene click chemical reaction to form a three-dimensional network structure. Wherein the isocyanurate unit can improve the interfacial compatibility of the electrolyte and the electrode and the cycling stability of the battery. The electrolyte has the advantages of high ionic conductivity, low interface impedance, excellent thermal stability, incombustibility and the like, is suitable for lithium primary batteries and lithium secondary batteries, and is particularly suitable for in-situ polymerization lithium metal batteries with high requirements on safety. The method is simple and convenient in process, mild in reaction condition, highly compatible with an existing liquid battery manufacturing process, and beneficial to realizing large-scale industrial application.

Description

Technical Field

[0001] This invention belongs to the field of polymer solid-state battery technology, specifically relating to a method for preparing and applying a flame-retardant N,S-containing in-situ polymerized gel electrolyte. Background Technology

[0002] Lithium metal batteries, with their high energy density and low reduction potential, are widely recognized as a key technology for building next-generation high-energy-density energy storage systems. However, traditional liquid electrolytes (LEs) are inherently flammable, and their side reactions with the lithium metal anode can induce lithium dendrite growth. These two major problems severely restrict the large-scale commercial application of lithium metal batteries. Although researchers have developed polymer solid-state electrolytes in recent years to suppress lithium dendrite formation, these electrolytes generally suffer from high interfacial impedance with lithium metal and low ionic conductivity, making it difficult to industrialize all-solid-state lithium metal batteries to date.

[0003] Gel polymer electrolytes (GPEs) significantly improve ionic conductivity while maintaining a certain level of mechanical strength by introducing liquid electrolyte as a plasticizer into the polymer matrix. Further employing in-situ polymerization technology to directly initiate monomer cross-linking reactions within the battery to construct GPE in situ can effectively reduce the interfacial impedance between the electrolyte and the electrodes. Moreover, this technology is highly compatible with existing liquid battery manufacturing processes, which will help promote the large-scale mass production of lithium metal batteries.

[0004] However, most current GPE systems still rely on flammable organic electrolytes as plasticizers, resulting in insufficient intrinsic safety and potential combustion hazards. Therefore, developing flame-retardant gel polymer electrolytes is crucial for improving the safety performance of lithium metal batteries. Currently, there are two main technical approaches to achieving flame-retardant functionality in GPEs: one is to add flame-retardant additives, which, while inexpensive, often exhibit poor electrochemical stability within the operating potential window of lithium metal batteries, easily inducing side reactions and thus impairing cycle life; the other is to introduce flame-retardant functional monomer units into the polymer backbone of GPE through chemical bonding. This approach not only endows the material with intrinsic flame-retardant properties but also promises to synergistically improve battery safety and cycle stability. Therefore, developing flame-retardant gel polymer electrolytes using flame-retardant monomers has significant research value and application prospects. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a flame-retardant in-situ polymerized gel electrolyte containing nitrogen and sulfur elements. This gel electrolyte is composed of a diene chain extender, a dithiol chain extender, a trifunctional isocyanurate-containing crosslinking agent, a catalyst, an organic electrolyte, and a lithium salt. It is polymerized in-situ within the battery via a thiol-olefin click chemistry reaction, forming a three-dimensional network structure. This invention utilizes the advantages of the thiol-olefin click reaction—mild reaction conditions, simple operation, high efficiency, and no side reactions—to successfully achieve the in-situ preparation of polymer gel electrolytes, which is expected to have wide applications in the field of smart lithium batteries.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a flame-retardant N,S-containing in-situ polymerized gel electrolyte, wherein the gel electrolyte comprises a diene chain extender, a dithiol chain extender, a trifunctional isocyanurate-containing crosslinking agent, a catalyst, an organic electrolyte, and a lithium salt; The diene chain extender is a polymer containing two vinyl and propylene double-bonded functional groups, selected from one or more of divinyl ketone, diallyl ether, divinyl sulfone, 1,3-diallyl-2,2-dimethylmalonate, N,N-diallylacrylamide, dipropyleneamine, divinylbenzene, ethylene glycol dimethacrylate, and polyethylene glycol diacrylate (molecular weight between 200 and 10,000); the dithiol chain extender... The agent is selected from 1,2-ethanedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, 1,8-octanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,16-hexadecadithiol, 1,2-propanedithiol, 1,2-benzenedithiol, 1,2-octanedithiol, butane-2,2-dithiol, pyridine-2,6-dithiol, p-terphenyl-4,4'-dithiol, stilbene-2,2'-dithiol, thiophene-3, One or more of the following: 4-dithiol, duren-α1,α2-dithiol, 2,3-piperazindithiol, naphthalene-2,3-dithiol, 1,3-dithiol-2-one, 2,7-naphthalenedithiol, 1,2-cyclohexanedithiol, 3,7-dithia-1,9-nonanedithiol, 3,6-dioxo-1,8-octanedithiol, 2,2′-thiobis(ethanethiol), and 4',4-dimercaptodiphenyl sulfide; wherein the trifunctional group contains isocyanurate. The crosslinking agent is selected from one or more of triglycidyl isocyanurate, tris(2-acryloyloxyethyl) isocyanurate, tris(2-hydroxyethyl) isocyanurate triacrylate, triallyl isocyanurate, and tris[2-(3-mercaptopropionic acid)ethyl] isocyanurate; the catalyst is selected from one or more of triethylamine, n-hexylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and dimethylphenylphosphine.

[0007] The gel electrolyte provided by this invention is polymerized in situ inside the battery via a mercapto-olefin click chemistry reaction, forming a three-dimensional network structure. The isocyanurate unit not only provides a high nitrogen content to impart intrinsic flame-retardant properties to the electrolyte, but its carbonyl group also promotes lithium salt dissociation. Nitrogen and sulfur elements contribute to the formation of a stable SEI film rich in inorganic components such as Li3N on the surface of the lithium metal anode, thereby improving the interfacial compatibility between the electrolyte and the electrode and the cycle stability of the battery. Thus, this electrolyte possesses advantages such as high ionic conductivity, low interfacial impedance, excellent thermal stability, and non-flammability, making it suitable for both primary and secondary lithium batteries, especially for in-situ polymerized lithium metal batteries where high safety is required.

[0008] Preferably, the diene chain extender is selected from ethylene glycol dimethacrylate, the dithiol chain extender is selected from 3,6-dioxo-1,8-octanedithiol, the trifunctional isocyanurate crosslinking agent is selected from tris[2-(3-mercaptopropionic acid)ethyl]isocyanurate, and the catalyst is selected from triethylamine.

[0009] Preferably, the organic electrolyte comprises one or more mixed solvents selected from ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and propylene carbonate (PC).

[0010] Preferably, the lithium salt is selected from one or more of LiClO4, LiPF6, LiCF3SO3, LiBF4, LiAsF6, LiSbF6, LiN(CF3SO2)2, LiCF3CF2SO3, lithium difluoro(oxalic acid)borate, and lithium (malonidoxalic acid)borate.

[0011] The second aspect of this invention also provides a method for preparing the flame-retardant N,S-containing in-situ polymerized gel electrolyte described in the first aspect, the method comprising the following steps: S1. A polymer solution is prepared by mixing a diene chain extender, a dithiol chain extender, and a trifunctional crosslinking agent containing isocyanurate. S2. Add organic electrolyte and lithium salt to the polymer solution of S1, stir evenly, then add catalyst, stir and obtain precursor solution; S3. The precursor solution of S2 is heated after being left to stand, and then crosslinked in situ through a mercapto-alkene click reaction to form a nitrogen- and sulfur-containing polymer network, which is eventually polymerized to form a gel electrolyte.

[0012] Preferably, in the diene chain extender, the dithiol chain extender, and the trifunctional isocyanurate crosslinking agent, the molar ratio of double bonds to thiol groups is 1:1.

[0013] Preferably, in S3, the standing is at room temperature for 10-15 hours, and the heating is at 40-60°C for 10-48 hours.

[0014] The third aspect of the present invention also provides the application of the flame-retardant N,S-containing in-situ polymerized gel electrolyte described in the first aspect in lithium metal batteries.

[0015] Preferably, the lithium metal battery is a gel polymer lithium battery or an all-solid-state polymer lithium battery, including a primary lithium battery and a secondary lithium battery.

[0016] Preferably, the specific application method is as follows: after preparing a precursor solution by diolefin chain extender, dithiol chain extender, trifunctional crosslinking agent containing isocyanurate, catalyst, organic electrolyte and lithium salt, the precursor solution is injected into a battery casing containing a positive electrode, a porous membrane and a lithium metal negative electrode. After in-situ polymerization, a gel electrolyte is formed inside the battery to obtain a lithium metal battery.

[0017] More preferably, the positive electrode sheet is composed of a positive electrode active material, a conductive agent, a binder, and a current collector. Its preparation method is as follows: the positive electrode active material, the conductive agent, and the binder are ground and mixed in a certain proportion, a solvent is added and mixed evenly, and the resulting slurry is uniformly coated onto the surface of the current collector to obtain the electrode sheet.

[0018] Furthermore, the positive electrode active material includes lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4), or vanadium oxide, etc.

[0019] Furthermore, the conductive agent includes Ketjen black, conductive carbon black, conductive graphite, or carbon nanotubes, etc.

[0020] Furthermore, the adhesive includes PVDF, PVDF-HFP, CMC, PVA, or SBR, etc.

[0021] Furthermore, the porous membrane is a PP membrane, PE membrane, cellulose membrane, glass fiber membrane, or PI membrane, etc.

[0022] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a flame-retardant in-situ polymerized gel electrolyte containing nitrogen and sulfur. The gel electrolyte is composed of a diene chain extender, a dithiol chain extender, a trifunctional isocyanurate-containing crosslinking agent, a catalyst, an organic electrolyte, and a lithium salt. It is polymerized in-situ within the battery via a mercapto-olefin click chemistry reaction, forming a three-dimensional network structure, thus in-situ constructing the polymerized gel electrolyte. This method utilizes the advantages of the mercapto-olefin click reaction, including mild reaction conditions, simple operation, high efficiency, and no side reactions, successfully achieving the in-situ preparation of the polymer gel electrolyte. First, the isocyanurate unit is introduced into the gel electrolyte system as a crosslinking agent, effectively improving the thermal stability of the polymer backbone. Due to the high nitrogen content of the isocyanurate, the flame-retardant properties of the electrolyte are significantly enhanced, thereby improving battery safety. Second, the carbonyl group in the isocyanurate promotes the dissociation of the lithium salt, and the nitrogen element also helps to form inorganic components such as Li3N in the SEI film, thereby improving the interfacial stability of the lithium metal battery and extending its cycle life. The prepared gel electrolyte possesses advantages such as high ionic conductivity, low interfacial impedance, excellent thermal stability, and non-flammability, making it suitable for both primary and secondary lithium batteries, especially for in-situ polymerized lithium metal batteries where high safety is required. Furthermore, the process of this invention is simple, the reaction conditions are mild, and it is highly compatible with existing liquid battery manufacturing processes, which is conducive to large-scale industrial application. Attached Figure Description

[0023] Figure 1 This diagram illustrates the in-situ construction of a nitrogen- and sulfur (N,S) polymer network via a mercapto-olefin click chemistry reaction. It shows the structure of a three-dimensional cross-linked network formed by a click reaction between a diene chain extender, a bis-mercapto chain extender, and a trifunctional isocyanurate cross-linker.

[0024] Figure 2 Fourier transform infrared (FT-IR) spectra of the polymer precursor before and after the mercapto-alkene click reaction (i.e., the precursor solution after standing at room temperature for 12 hours + heating at 50°C for 24 hours).

[0025] Figure 3 An optical photograph of the gel electrolyte prepared by in-situ mercapto-olefin click reaction.

[0026] Figure 4 The electrochemical impedance spectroscopy (Nyquist plot) of the flame-retardant N,S-containing in-situ polymerized gel electrolytes prepared in different embodiments.

[0027] Figure 5 The linear sweep voltammetry (LSV) curve of the gel electrolyte prepared in Example 3 is shown.

[0028] Figure 6The long-cycle charge-discharge performance of the LiFePO4 / GPE / Li battery assembled using the gel electrolyte of Example 3 and the control battery (LiFePO4 / LE / Li) using a commercial liquid electrolyte (LE) is compared at 1C rate.

[0029] Figure 7 The results of the comparative test of the flame retardant properties of the flame-retardant N,S-containing in-situ polymerized gel electrolyte prepared in the example and the commercial liquid electrolyte are presented. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0032] Example 1: (1) Preparation of flame-retardant N,S-containing in-situ polymerized gel electrolyte precursor ( Figure 1 ): Ethylene glycol dimethacrylate (EGDMA) (5 mmol, 0.991 g; CAS No. 97-90-5), 3,6-dioxo-1,8-octanedithiol (DODT) (4.25 mmol, 0.775 g; CAS No. 14970-87-7), and tris[2-(3-mercaptopropionic acid)ethyl]isocyanurate (TEMPIC) (0.5 mmol, 0.263 g; CAS No. 36196-44-8) were weighed and sonicated at 40 kHz for 30 minutes to obtain a homogeneous solution. The resulting polymer solution was then transferred to a glove box. Next, 5.90 g of lithium salt-containing electrolyte (1 M LiPF6 in EC:DMC = 1:1 vol%) was added to the obtained polymer solution. After stirring until homogeneous, 60 µL of triethylamine was added as a catalyst, and the mixture was stirred for 30 minutes to obtain the precursor solution.

[0033] (2) Formation and application of flame-retardant N,S-containing in-situ polymerized gel electrolytes: The battery is assembled in the following order: lithium metal anode, precursor solution, PP separator, precursor solution, and lithium iron phosphate cathode. After encapsulation, it is left to stand at room temperature for 12 hours and then heated at 50°C for 24 hours to crosslink and form a polymeric gel electrolyte, thereby obtaining a flame-retardant GPE lithium metal battery.

[0034] like Figure 2As shown in the figure, 2564 cm -1 The S–H stretching vibration peak at 1633 cm⁻¹ and the peak at 1633 cm⁻¹ -1 The C=C stretching vibration peak at the point of origin significantly weakened or disappeared, indicating that the thiol group and the double bond had undergone a click reaction, successfully constructing a polymer network inside the battery. Simultaneously, the precursor solution obtained in this embodiment can form a stable gel with self-supporting capabilities inside the battery. Figure 3 ).in, Figure 2 The results were obtained by testing the same precursor solution after it was left to stand at room temperature for 12 hours and then heated at 50°C for 24 hours to form a gel. It was not an in-situ test inside the battery.

[0035] Example 2: (1) Preparation of flame-retardant N,S-containing in-situ polymerized gel electrolyte precursor ( Figure 1 ): Ethylene glycol dimethacrylate (EGDMA) (5 mmol, 0.991 g), 3,6-dioxo-1,8-octanedithiol (DODT) (4.25 mmol, 0.775 g), and tris[2-(3-mercaptopropionic acid)ethyl]isocyanurate (TEMPIC) (0.5 mmol, 0.263 g) were weighed and ultrasonically mixed to obtain a homogeneous solution. The resulting polymer solution was then transferred to a glove box. At a polymer solution to electrolyte mass ratio of 1:1, 3.93 g of lithium salt-containing electrolyte (1 M LiPF6 in EC:DMC = 1:1 vol%) was added to the obtained polymer solution. After stirring until homogeneous, 60 µL of triethylamine was added as a catalyst, and the mixture was stirred for 30 minutes to obtain the precursor solution.

[0036] (2) Formation and application of flame-retardant N,S-containing in-situ polymerized gel electrolyte Similar to Example 1, a polymer network was successfully constructed, and the resulting precursor solution can form a stable gel with self-supporting capabilities inside the battery. Figure 3 ).

[0037] Example 3: (1) Preparation of flame-retardant N,S-containing in-situ polymerized gel electrolyte precursor ( Figure 1 ): Ethylene glycol dimethacrylate (EGDMA) (5 mmol, 0.991 g), 3,6-dioxo-1,8-octanedithiol (DODT) (4.25 mmol, 0.775 g), and tris[2-(3-mercaptopropionic acid)ethyl]isocyanurate (TEMPIC) (0.5 mmol, 0.263 g) were weighed and ultrasonically mixed to obtain a homogeneous solution. The resulting polymer solution was then transferred to a glove box. At a polymer solution to electrolyte mass ratio of 1:1, 5.90 g of lithium salt-containing electrolyte (1 M LiPF6 in EC:DMC = 1:1 vol%) was added to the obtained polymer solution. After stirring until homogeneous, 60 µL of triethylamine was added as a catalyst, and the mixture was stirred for 30 minutes to obtain the precursor solution.

[0038] 2. Formation and application of flame-retardant N,S-containing in-situ polymerized gel electrolytes Similar to Example 1, a polymer network was successfully constructed, and the resulting precursor solution can form a stable gel with self-supporting capabilities inside the battery. Figure 3 ).

[0039] Example 4: (1) Preparation of flame-retardant N,S-containing in-situ polymerized gel electrolyte precursor ( Figure 1 ) Ethylene glycol dimethacrylate (EGDMA) (5 mmol, 0.991 g), 3,6-dioxo-1,8-octanedithiol (DODT) (4.25 mmol, 0.775 g), and tris[2-(3-mercaptopropionic acid)ethyl]isocyanurate (TEMPIC) (0.5 mmol, 0.263 g) were weighed and ultrasonically mixed to obtain a homogeneous solution. The resulting polymer solution was then transferred to a glove box. At a polymer solution to electrolyte mass ratio of 1:1, 7.86 g of lithium salt-containing electrolyte (1 M LiPF6 in EC:DMC = 1:1 vol%) was added to the obtained polymer solution. After stirring until homogeneous, 60 µL of triethylamine was added as a catalyst, and the mixture was stirred for 30 minutes to obtain the precursor solution.

[0040] (2) Formation and application of flame-retardant N,S-containing in-situ polymerized gel electrolyte Similar to Example 1, a polymer network was successfully constructed, but the resulting precursor solution failed to form a gel inside the battery. Figure 3 This demonstrates that even with an electrolyte content as high as 75 wt% (as in Example 3), a stable gel with self-supporting capabilities can still be formed.

[0041] Example 5: (1) Preparation of flame-retardant N,S-containing in-situ polymerized gel electrolyte precursor ( Figure 1 ) Ethylene glycol dimethacrylate (EGDMA) (5 mmol, 0.991 g), 3,6-dioxo-1,8-octanedithiol (DODT) (4.25 mmol, 0.775 g), and tris[2-(3-mercaptopropionic acid)ethyl]isocyanurate (TEMPIC) (0.5 mmol, 0.263 g) were weighed and ultrasonically mixed to obtain a homogeneous solution. The resulting polymer solution was then transferred to a glove box. At a polymer solution to electrolyte mass ratio of 1:1, 9.83 g of lithium salt-containing electrolyte (1 M LiPF6 in EC:DMC = 1:1 vol%) was added to the obtained polymer solution. After stirring until homogeneous, 60 µL of triethylamine was added as a catalyst, and the mixture was stirred for 30 minutes to obtain the precursor solution.

[0042] (2) Formation and application of flame-retardant N,S-containing in-situ polymerized gel electrolyte Similar to Example 1, a polymer network was successfully constructed, but the resulting precursor solution failed to form a gel inside the battery. Figure 3 ).

[0043] Comparative Example 1: The flame-retardant GPE lithium metal battery was assembled according to Example 3, but unlike Example 3, it directly used electrolyte (1M LiPF6 in EC :DMC=1:1 vol%) as a precursor solution to assemble the battery.

[0044] Comparative Example 2: The flame-retardant GPE lithium metal battery was assembled according to Example 3, except that it used 60 µg of AIBN (azobisisobutyronitrile) free radical thermal initiator as a catalyst.

[0045] Comparative Example 3: The flame-retardant GPE lithium metal battery was assembled according to Example 3, except that it used 60 µg DMPA (2,2-dimethoxy-phenylacetophenone) free radical photoinitiator as a catalyst.

[0046] Comparative Example 4: The flame-retardant GPE lithium metal battery was assembled according to Example 3, except that it used a nitrogen-free trimethylolpropane tris(3-mercaptopropionate) agent (0.5 mmol, 0.082 g) as a crosslinking agent.

[0047] Experimental example: The electrochemical performance of the flame-retardant N,S-containing in-situ polymerized gel electrolytes prepared in Examples 1-3 was tested. Figure 4 The AC impedance spectra (Nyquist plots) are shown. Based on the fitting results, the ionic conductivities for Examples 1, 2, and 3 are calculated to be 4.8 × 10⁻⁶. -4S / cm, 7.2×10 -4 S / cm and 1.9×10 -3 S / cm. Given that Example 3 exhibits the best ion transport performance, all subsequent electrochemical performance tests were based on this example. For example... Figure 5 As shown in the linear sweep voltammetry (LSV) curve, the flame-retardant N,S-containing in-situ polymerized gel electrolyte prepared in Example 3 has an electrochemical stability window of up to 4.8 V (vs. Li). + / Li), meeting the operating voltage requirements of conventional lithium metal batteries. For example... Figure 6 As shown, the LiFePO4 / GPE / Li battery assembled using the gel electrolyte of Example 3 maintained a capacity retention of 93.2% after 300 cycles at 1C rate. In contrast, the control battery (LiFePO4 / LE / Li) using commercial liquid electrolyte (LE) only maintained a capacity retention of 34.6% under the same conditions, fully demonstrating that the gel electrolyte prepared in this invention can significantly improve the cycle stability of lithium metal batteries. Figure 7 The flame retardant performance comparison test results show that the commercial liquid electrolyte can continue to burn for more than 20 seconds after ignition for 3 seconds; while the flame retardant N,S-containing in-situ polymerized gel electrolyte prepared in Example 3 immediately self-extinguishes after the fire source is removed, showing excellent intrinsic flame retardant properties.

[0048] Meanwhile, linear sweep voltammetry (LSV) and charge-discharge tests at 1C rate were conducted on the electrolytes of Example 3 and Comparative Examples 1, 2, 3, and 4, respectively. The test results are shown in Table 1.

[0049] The test results in Table 1 show that the gel electrolyte prepared by the triethylamine-catalyzed mercapto-ene Michael addition reaction (Example 3) is significantly superior to commercial liquid electrolytes (Comparative Example 1) and thermal / photo-initiated free radical polymerization systems (Comparative Examples 2 and 3) in terms of safety and electrochemical performance. It is evident that, compared to commercial liquid electrolytes which are flammable and have poor cycle stability, the gel electrolyte of this invention is not only non-flammable but also maintains a capacity retention of 93.2% after 300 cycles. While thermal initiation (AIBN) can also form a gel, incomplete polymerization leads to interfacial failure, resulting in almost complete capacity decay. When using photoinitiation (DMPA), a large number of acrylate groups undergo self-polymerization, causing most mercapto groups to fail to react fully, thus hindering molecular weight growth and preventing gel formation. These results fully demonstrate that the triethylamine-catalyzed click chemistry pathway can achieve uniform, complete, and side-reaction-free in-situ crosslinking under mild conditions, which is key to obtaining high-performance solid-state battery electrolytes.

[0050] Table 1. Test results for different electrolytes The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A flame-retardant N,S-containing in-situ polymerized gel electrolyte, characterized in that, The gel electrolyte comprises a diene chain extender, a dithiol chain extender, a trifunctional isocyanurate crosslinking agent, a catalyst, an organic electrolyte, and a lithium salt; The diolefin chain extender is selected from one or more of diallyl ether, divinyl sulfone, 1,3-diallyl-2,2-dimethylmalonate, N,N-diallylacrylamide, dipropyleneamine, divinylbenzene, ethylene glycol dimethacrylate, and polyethylene glycol diacrylate; the dithiol chain extender is selected from 1,2-ethylenedithiol, 1,5-pentanedithiol, 1,6-hexanedithiol, and 1,8-dithiol. -Octadithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 1,16-hexadecadithiol, 1,2-propanedithiol, 1,2-benzenedithiol, 1,2-octadithiol, butane-2,2-dithiol, pyridine-2,6-dithiol, p-terphenyl-4,4'-dithiol, stilbene-2,2'-dithiol, thiophene-3,4-dithiol, duren-α1,α2-dithiol, 2,3 - Piperazine dithiol, naphthalene-2,3-dithiol, 1,3-dithiol-2-one, 2,7-naphthalene dithiol, 1,2-cyclohexane dithiol, 3,7-dithia-1,9-nonanedithiol, 3,6-dioxo-1,8-octanedithiol, 2,2′-thiobis(ethanethiol), 4',4-dimercaptodiphenyl sulfide; the trifunctional isocyanurate crosslinking agent is selected from one or more of triglycidyl isocyanurate, tris(2-acryloyloxyethyl) isocyanurate, tris(2-hydroxyethyl) isocyanurate triacrylate, triallyl isocyanurate, tris[2-(3-mercaptopropionic acid)ethyl] isocyanurate; the catalyst is selected from one or more of triethylamine, n-hexylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), dimethylphenylphosphine.

2. The flame-retardant N,S-containing in-situ polymerized gel electrolyte according to claim 1, characterized in that, The diene chain extender is selected from ethylene glycol dimethacrylate, the bis-mercapto chain extender is selected from 3,6-dioxo-1,8-octanedithiol, the trifunctional isocyanurate crosslinking agent is selected from tris[2-(3-mercaptopropionic acid)ethyl]isocyanurate, and the catalyst is selected from triethylamine.

3. The flame-retardant N,S-containing in-situ polymerized gel electrolyte according to claim 1, characterized in that, The organic electrolyte contains one or more of the following mixed solvents: ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

4. The flame-retardant N,S-containing in-situ polymerized gel electrolyte according to claim 1, characterized in that, The lithium salt is selected from one or more of LiClO4, LiPF6, LiCF3SO3, LiBF4, LiAsF6, LiSbF6, LiN(CF3SO2)2, LiCF3CF2SO3, lithium difluoro(oxalic acid)borate, and lithium (malonidoxalic acid)borate.

5. The method for preparing the flame-retardant N,S-containing in-situ polymerized gel electrolyte according to any one of claims 1-4, characterized in that, Includes the following steps: S1. A polymer solution is prepared by mixing a diene chain extender, a dithiol chain extender, and a trifunctional crosslinking agent containing isocyanurate. S2. Add organic electrolyte and lithium salt to the polymer solution of S1, stir evenly, then add catalyst, stir and obtain precursor solution; S3. The precursor solution of S2 is heated after being left to stand, and then crosslinked in situ through a mercapto-alkene click reaction to form a nitrogen- and sulfur-containing polymer network, which is eventually polymerized to form a gel electrolyte.

6. The preparation method of the flame-retardant N,S-containing in-situ polymerized gel electrolyte according to claim 5, characterized in that, In the diene chain extender, the dithiol chain extender, and the trifunctional isocyanurate crosslinking agent, the molar ratio of double bonds to thiol groups is 1:

1.

7. The preparation method of the flame-retardant N,S-containing in-situ polymerized gel electrolyte according to claim 5, characterized in that, In S3, the standing period is 10-15 h at room temperature, and the heating period is 40-60℃ for 10-48 h.

8. The application of the flame-retardant N,S-containing in-situ polymerized gel electrolyte according to any one of claims 1-4 in lithium metal batteries.

9. The application according to claim 8, characterized in that, The lithium metal battery is a gel polymer lithium battery or an all-solid-state polymer lithium battery, including a primary lithium battery and a secondary lithium battery.

10. The application according to claim 8, characterized in that, The specific application method is as follows: After preparing a precursor solution by diolefin chain extender, dithiol chain extender, trifunctional crosslinking agent containing isocyanurate, catalyst, organic electrolyte and lithium salt, the precursor solution is injected into a battery casing containing a positive electrode, a porous membrane and a lithium metal negative electrode. After in-situ polymerization, a gel electrolyte is formed inside the battery, thus obtaining a lithium metal battery.

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