Preparation method and application of organic polymer solid electrolyte composite additive

Abstract

The application discloses a preparation method and application of an organic polymer solid electrolyte composite additive. The application adopts a "click chemistry" reaction to prepare polyethylene glycol diacrylate-mercaptopropyl trimethoxysilane-Li6PS5Cl composite additive material. The two end functional groups of the mercaptopropyl trimethoxysilane molecule are respectively coupled with polyethylene glycol diacrylate and Li6PS5Cl inorganic electrolyte to construct a stable "organic matrix-silane coupling agent-inorganic matrix" combination interface under the action of chemical bond valence force. The application overcomes the problems of traditional inorganic additive, such as serious particle agglomeration and poor compatibility with the polymer solid electrolyte interface. Starting from the internal interface stability and ion channel construction of the additive, and relying on the defect regulation between the organic polymer functional group and the inorganic additive, the material interface compatibility and the ion high-efficiency and fast transmission capacity are significantly improved. The application can realize the internal interface high-efficiency ion transmission and long-term cycle stability of the organic polymer solid electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical technology, specifically relating to a method for preparing and applying an organic polymer solid electrolyte composite additive. More specifically, it discloses a composite material of polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl and its application as a solid electrolyte additive in all-solid-state lithium batteries. Background Technology

[0002] With the deepening of global energy structure transformation and green and low-carbon development strategies, high-energy-density and high-safety solid-state lithium batteries have become an important research direction in the energy storage field. Among them, polymer solid-state electrolytes are considered an ideal material system to overcome the safety bottlenecks of traditional liquid lithium-ion batteries due to their excellent flexibility, lightweight characteristics, and good interfacial compatibility with electrodes. However, existing polymer solid-state electrolytes still have key problems such as insufficient ionic conductivity, difficulty in synergistically optimizing mechanical strength and ion transport performance, and high electrode / electrolyte interfacial impedance, which seriously restrict their industrial application. Against this backdrop, developing efficient and multifunctional additives to directionally regulate the microstructure and macroscopic properties of polymer electrolytes has become an important breakthrough for promoting the technological innovation of solid-state batteries.

[0003] Current research on polymer solid electrolytes largely focuses on optimizing the polymer matrix and lithium salts. However, due to inherent limitations such as high polymer chain crystallinity and large lithium-ion migration barriers, simply modifying the matrix is ​​insufficient to simultaneously improve ionic conductivity and mechanical strength. Furthermore, lithium dendrite growth and side reactions at the electrode / electrolyte interface can easily lead to capacity decay and safety hazards. Studies have shown that introducing functional additives can, through molecular design or composite effects, construct rapid ion transport channels in the polymer matrix, inhibit crystalline phase formation, and enhance interfacial stability, thereby achieving synergistic optimization of material properties. For example, inorganic nanofillers can reduce polymer crystallinity and broaden the electrochemical window; plasticizers can improve chain segment mobility, but excessive addition may sacrifice mechanical strength; while fluoropolymers or lithium salt derivatives can optimize interfacial lithium-ion flux distribution and inhibit dendrite growth. However, existing additive systems generally suffer from single functionality and insufficient compatibility, necessitating the development of novel multi-dimensional synergistic composite additives.

[0004] Based on this, this invention innovatively proposes a composite additive system to address the aforementioned bottlenecks in polymer solid-state electrolytes. This additive, through organic-inorganic chemical bonding design, achieves the following synergistic effects at the molecular scale: (1) introducing inorganic fillers to disrupt the polymer crystalline region and construct low-barrier ion transport pathways; (2) enhancing mechanical properties through cross-linking networks, suppressing dendrite formation, and maintaining dynamic flexibility of chain segments; and (3) reducing the interfacial impedance between the additive and the polymer matrix through hydrogen bonding. The implementation of this invention will significantly improve the energy density, cycle life, and safety of solid-state batteries, providing key technical support for the commercialization of next-generation high-energy-density energy storage devices. Summary of the Invention

[0005] To address the shortcomings of the aforementioned technologies, this invention utilizes the mercaptopropyltrimethoxysilane (MPTMS) molecule, with its thiol (-SH) and methoxysilane (-Si-O-) functional groups at both ends, to chemically couple with the acrylate groups of polyethylene glycol diacrylate (PEGDA) and the surface of Li6PS5Cl, respectively, constructing a stable heterogeneous interface. This effectively solves the problems of easy aggregation and poor compatibility with the polymer matrix interface of traditional inorganic additives. Molecular design achieves synergistic optimization of the organic-inorganic interface chemical bonding and ion transport channels. On one hand, the silane coupling effect of MPTS enhances the binding strength between the organic polymer and Li6PS5Cl particles, inhibiting inorganic phase aggregation and promoting rapid ion migration at the interface. On the other hand, the flexible segments of PEGDA complement the rigid structure of the inorganic particles, reducing the lithium-ion migration barrier and improving the overall ionic conductivity by regulating the defect distribution in the composite system. Furthermore, the organic functional groups in the composite additive can form a hydrogen bond network with the solid electrolyte matrix, further optimizing the electrode / electrolyte interface stability, inhibiting lithium dendrite growth, and extending battery cycle life. The additive has a simple preparation process and is suitable for large-scale production. The resulting solid electrolyte has high ionic conductivity, excellent mechanical strength and wide electrochemical window, exhibiting high energy density and long cycle stability in solid lithium metal batteries, providing an innovative solution for next-generation high-performance energy storage devices.

[0006] First, the organic solvent is preheated at 40-90℃ for 10 min. Then, polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 3:1 to 1:3 are added to the organic solvent, along with a photoinitiator. The mixture is then irradiated with natural light or artificial light (UV lamp) to induce bonding between the HS- functional groups in MPTMS and the C=C functional groups in PEGDA for 10-60 seconds. The mixture is then magnetically stirred at 40-90℃ for 2-10 h. Next, under an inert atmosphere, Li6PS5Cl in a mass ratio of 1:2 to 1:50 with PEGDA is added to the reacted solution, along with a thermal initiator. The mixture is then magnetically stirred at 30-120℃ for 6-12 h. After cooling to room temperature, a composite additive of polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl is obtained.

[0007] The present invention discloses a method for preparing an organic polymer solid electrolyte composite additive, the specific steps of which are as follows:

[0008] (1) Preheat the organic solvent at 40-90℃ for 10 min; wherein the organic solvent is one or a mixture of several of the following: acetone, N-methylpyrrolidone, N,N-dimethylformamide, anhydrous acetonitrile, and tetrahydrofuran.

[0009] (2) Polyethylene glycol diacrylate and mercaptopropyltrimethoxysilane are added to the preheated organic solvent in step (1) for reaction. The mixture is magnetically stirred until completely homogeneous. Then, a photoinitiator is added, with the photoinitiator accounting for 0.5%–5% of the total mass of polyethylene glycol diacrylate and mercaptopropyltrimethoxysilane. Under natural or artificial light irradiation, the HS- functional groups in mercaptopropyltrimethoxysilane are induced to form bonds with the C=C functional groups in polyethylene glycol diacrylate. Magnetic stirring is continued for 2–5 hours to obtain an organic mixture with mercapto-bonded groups, the molecular formula of which is…

[0010]

[0011] The photoinitiator is selected from one or a mixture of several of acylphosphine oxides, benzoin ethers, and α-hydroxyketones in any proportion. The mass ratio of polyethylene glycol diacrylate to mercaptopropyltrimethoxysilane is 3:1 to 1:3. The selected artificial light source is preferably an ultraviolet lamp with a wavelength of 200-400 nm and a light intensity of 10-100 mW / cm². 2The irradiation time is 10-60 seconds, the reaction temperature is controlled at 40-90℃, and the magnetic stirring is carried out for 2-5 hours; the average molecular weight of PEGDA is 200-400000, preferably 600-2000, and the reaction temperature is 40-90℃; the mass ratio of PEGDA to MPTMS is 3:1 to 1:3; the reaction time is 2-5 hours; under inert atmosphere, Li6PS5Cl and thermal initiator are added to the organic mixture obtained in step (2), the reaction temperature is controlled at 30-120℃, the magnetic stirring is carried out for 6-12 hours, and the chemically coupled organic / inorganic composite additive is obtained after cooling at room temperature; the mass ratio of Li6PS5Cl to PEGDA is 1:2 to 1:50; the thermal initiator is selected from one or a mixture of several of azobisisobutyronitrile, benzoyl peroxide, ammonium persulfate, potassium persulfate and sodium persulfate, and the mass of the thermal initiator accounts for 0.1% to 3% of the total mass of Li6PS5Cl and PEGDA.

[0012] Another object of the present invention is the application of the prepared composite additive in organic solid electrolytes. The composite additive is added to the organic solid electrolyte for the preparation of all-solid-state lithium-ion and lithium metal batteries. The organic solid electrolyte includes a polymer matrix, a composite electrolyte additive, and a lithium salt, wherein the amount of the composite additive added is 15-30 wt% of the organic solid electrolyte, and the amount of the lithium salt added is 20-30 wt% of the amount of the polymer matrix added.

[0013] The lithium salt is one or any combination of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

[0014] The polymer matrix is ​​one or a mixture of any proportions of polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, and polymethyl methacrylate. The average molecular weight of the polymer matrix is ​​200-1,000,000, preferably 20,000-400,000. The polymer matrix and the composite additive are connected by hydrogen bonds / van der Waals bonds.

[0015] The principle of this invention is as follows: This invention synthesizes a composite additive through a "click chemistry" reaction. The composite additive consists of polyethylene glycol diacrylate (PEGDA), mercaptopropyltrimethoxysilane (MPTMS), and a sulforaphane-germanium ore-type inorganic electrolyte Li6PS5Cl, forming a multi-level composite system with an "organic matrix-silane coupling agent-inorganic matrix" structure. Specifically, the mercapto (-SH) and methoxysilane (-Si-O-) functional groups at both ends of the MPTMS molecule are chemically coupled to the acrylate groups of PEGDA and the surface of Li6PS5Cl, respectively, constructing a stable heterogeneous interface. This effectively solves the problems of easy aggregation and poor compatibility with polymer matrix interfaces in traditional inorganic additives. The composite additive achieves synergistic optimization of organic-inorganic interface chemical bonding and ion transport channels through molecular design. On the one hand, the silane coupling effect of MPTMS enhances the bonding strength between the organic polymer and Li6PS5Cl particles, inhibits inorganic phase aggregation, and promotes rapid ion migration at the interface. On the other hand, the flexible segments of PEGDA complement the rigid structure of the inorganic particles, reducing the lithium-ion migration barrier and improving the overall ionic conductivity by regulating the defect distribution in the composite system. Furthermore, the organic functional groups in the composite additive can form a hydrogen bond network with the solid electrolyte matrix, further optimizing the electrode / electrolyte interface stability, inhibiting lithium dendrite growth, and extending battery cycle life. This additive has a simple preparation process, is suitable for large-scale production, and the resulting solid electrolyte exhibits high ionic conductivity, excellent mechanical strength, and a wide electrochemical window, demonstrating high energy density and long cycle stability in solid-state lithium metal batteries, providing an innovative solution for next-generation high-performance energy storage devices.

[0016] The beneficial effects of this invention are:

[0017] (1) This invention significantly improves the bonding form of active groups at the interface through chemical coupling bonding technology, eliminates the transport barrier of ions at the interface of organic and inorganic solid electrolyte phases, constructs multi-directional ion diffusion channels, and realizes efficient ion migration and electronic conduction.

[0018] (2) The uniform morphology and good mechanical properties also provide a solution to the dendrite problem generated during the ion extraction / intercalation process, avoiding battery failure caused by puncture. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the preparation of the composite additive of the present invention and its application in film formation in polymer solid electrolytes;

[0020] Figure 2 This is the Fourier transform infrared (FTIR) spectrum of the solid electrolyte prepared in Example 3 of this invention;

[0021] Figure 3This is a scanning electron microscope (SEM) image of the solid electrolyte prepared in Example 2 of the present invention;

[0022] Figure 4 This is a graph showing the long-cycle performance of the composite additive prepared in Example 1 of this invention in a lithium-ion battery system;

[0023] Figure 5 This is a graph showing the long-cycle performance of the composite additive prepared in Example 2 of this invention in a lithium-ion battery system;

[0024] Figure 6 This is a graph showing the long-cycle performance of the composite additive prepared in Example 3 of this invention in a lithium-ion battery system. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the content described.

[0026] Example 1: A method for preparing an organic polymer solid electrolyte composite additive, such as... Figure 1 As shown, the details are as follows:

[0027] (1) Preheat N,N-dimethylformamide at 40°C for 10 min;

[0028] (2) Polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 1:0.8 were added to N,N-dimethylformamide in (1) and reacted at 65°C. After complete mixing, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide was added. The reaction was induced by irradiation with an ultraviolet lamp to form bonds between the HS- functional groups in MPTMS and the C=C functional groups in PEGDA. The wavelength of the light was 200 nm and the intensity was 40 mW / cm. 2 The irradiation time was 37 seconds, and the magnetic stirring was performed at 400 rpm for 2 hours.

[0029]

[0030] (3) Under an inert atmosphere, Li6PS5Cl (mass ratio of 1:5 to PEGDA) was added to the reacted solution, along with azobisisobutyronitrile (AIBN). The mixture was magnetically stirred at 50°C for 9 hours. After cooling to room temperature, a composite material of polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl was obtained. The structural formula of this composite additive is as follows:

[0031]

[0032] Weigh 0.3g of the polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl composite material prepared in this example, 0.2g of lithium perchlorate, and 1.0g of polyethylene oxide. Stir magnetically at 350rpm for 5 hours at 40℃, and then coat the mixture into a film using a flow coating method with a doctor blade height of 150μm. After removing the solvent through a two-stage drying process of room temperature and atmospheric pressure followed by negative pressure and high temperature, the film is hot-pressed into shape.

[0033] In an argon-filled glove box (O2 content < 1 ppm, water content < 1 ppm), lithium-lithium symmetric coin cells are assembled using conventional methods.

[0034] The long-cycle performance of the lithium-lithium symmetric battery prepared in this embodiment is shown in the figure below. Figure 4 As shown. From Figure 4 As can be seen from this embodiment, the material prepared as an additive for lithium-ion solid-state batteries exhibits excellent cycle performance at 0.1 mA / cm². -2 It exhibits stable long-cycle capability at current density.

[0035] Example 2: An organic polymer solid electrolyte composite additive, its preparation method, and its application are as follows:

[0036] (1) Preheat anhydrous acetonitrile at 60℃ for 10 min;

[0037] (2) Polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 1:1 were added to anhydrous acetonitrile in (1), along with benzoin methyl ether. Ultraviolet light was used to induce the HS- functional groups in MPTMS to bond with the C=C functional groups in PEGDA. The wavelength was 250 nm and the light intensity was 50 mW / cm². 2 The irradiation time was 40 seconds, and the mixture was magnetically stirred at 400 rpm for 5 hours at 65°C to obtain an organic mixture with thiol bonding.

[0038] (3) Under an inert atmosphere, Li6PS5Cl with a mass ratio of 1:25 to PEGDA was added to the reacted solution, along with benzoyl peroxide. The mixture was magnetically stirred at 30°C for 6 hours and then cooled to room temperature to obtain a composite material of polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl.

[0039] Weigh 0.35g of the polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl composite material prepared in this example, 0.3g of lithium hexafluorophosphate, and 1.0g of polyacrylonitrile. Stir magnetically at 350rpm for 5 hours at 40℃, and then coat the mixture into a film using a flow coating method with a doctor blade height of 250μm. After removing the solvent through a two-stage drying process of ambient temperature and pressure followed by high temperature under negative pressure, the film is hot-pressed into shape.

[0040] In an argon-filled glove box (O2 content < 1 ppm, water content < 1 ppm), lithium-lithium symmetric coin cells are assembled using conventional methods.

[0041] The scanning electron microscope image of the solid electrolyte material prepared in this embodiment is shown below. Figure 3 The long-cycle performance of lithium-ion symmetric batteries is shown in the figure below. Figure 5 As shown. From Figure 3 It can be seen that the solid electrolyte prepared in this embodiment has good uniformity. From Figure 5 As can be seen from this embodiment, the material prepared as an additive for lithium-ion solid-state batteries exhibits excellent cycle performance at 0.1 mA / cm². -2 It exhibits stable long-cycle capability at current density.

[0042] Example 3: An organic polymer solid electrolyte composite additive, its preparation method, and its application are as follows:

[0043] (1) Preheat N-methylpyrrolidone at 90℃ for 10 min;

[0044] (2) Polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 1:1.2 were added to N-methylpyrrolidone in (1), along with 2-hydroxy-2-methylphenylacetone (α-hydroxy ketone). Ultraviolet light was used to induce bonding between the HS- functional groups in MPTMS and the C=C functional groups in PEGDA. The wavelength was 300 nm and the light intensity was 60 mW / cm². 2 The irradiation time was 23 seconds, and the mixture was magnetically stirred at 400 rpm for 3 hours at 65°C to obtain an organic mixture with thiol bonding.

[0045] (3) Under an inert atmosphere, Li6PS5Cl with a mass ratio of 1:20 to PEGDA was added to the reacted solution, along with sodium persulfate. The mixture was magnetically stirred at 80°C for 8 hours. After cooling to room temperature, a composite material of polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl was obtained.

[0046] Weigh 0.5g of the polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl composite material prepared in this example, 0.4g of lithium bis(fluorosulfonyl)imide, and 1.7g of polyvinylidene fluoride-hexafluoropropylene copolymer. Stir magnetically at 350 rpm for 5 hours at 40°C, and then coat the mixture into a film using a casting method with a doctor blade height of 200 μm. After removing the solvent through a two-stage drying process of room temperature and atmospheric pressure followed by negative pressure and high temperature, the film is hot-pressed into shape.

[0047] In an argon-filled glove box (O2 content < 1 ppm, water content < 1 ppm), lithium-lithium symmetric coin cells are assembled using conventional methods.

[0048] The Fourier transform infrared spectrum of the solid electrolyte material prepared in this embodiment is as follows: Figure 2 The long-cycle performance of lithium-ion symmetric batteries is shown in the figure below. Figure 6 As shown. From Figure 2 It can be seen that the solid electrolyte additive material prepared in this embodiment has complete and controllable bonding. From Figure 6 As can be seen from this embodiment, the material prepared as an additive for lithium-ion solid-state batteries exhibits excellent cycle performance at 0.1 mA / cm². -2 It exhibits stable long-cycle capability at current density.

[0049] Example 4: An organic polymer solid electrolyte composite additive, its preparation method, and its application are as follows:

[0050] (1) Preheat acetone and N-methylpyrrolidone in a volume ratio of 1:1 at 90°C for 10 min;

[0051] (2) Polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 1:1.2 were added to the solvent described in (1), along with 2-hydroxy-2-methylphenylacetone (α-hydroxy ketone). Ultraviolet light was used to induce bonding between the HS- functional groups in MPTMS and the C=C functional groups in PEGDA. The wavelength was 400 nm and the light intensity was 20 mW / cm². 2 The irradiation time was 60 seconds, and the mixture was magnetically stirred at 400 rpm for 5 hours at 90°C.

[0052] (3) Under an inert atmosphere, Li6PS5Cl with a mass ratio of 1:2 to PEGDA was added to the reacted solution, along with ammonium persulfate. The mixture was magnetically stirred at 80°C for 6 hours. After cooling to room temperature, a composite material of polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl was obtained.

[0053] Weigh 0.5g of the polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl composite material prepared in this example, 0.4g of lithium bis(trifluoromethanesulfonyl)imide, and 1.7g of polymethyl methacrylate. Stir magnetically at 350 rpm for 5 hours at 40°C. Cure the mixture into a film by casting. Inject the mixture of composite additives, lithium salt, and polymer matrix into a mold, controlling the film thickness to be 50-300 μm. Then, allow it to cure statically in an inert atmosphere at 40°C for 30 hours.

[0054] In an argon-filled glove box (O2 content <1ppm, water content <1ppm), lithium-lithium symmetric coin cells are assembled using conventional methods.

[0055] Example 5: An organic polymer solid electrolyte composite additive, its preparation method, and its application are as follows:

[0056] (1) Preheat tetrahydrofuran at 90°C for 10 min.

[0057] (2) Polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 1:1.2 were added to tetrahydrofuran in (1), along with 2-hydroxy-2-methylphenylacetone. Ultraviolet light was used to induce bonding between the HS- functional groups in MPTMS and the C=C functional groups in PEGDA. The wavelength was 200 nm and the light intensity was 15 mW / cm². 2 The irradiation time was 10 seconds, and the mixture was magnetically stirred at 400 rpm for 4 hours at 40°C.

[0058] (3) Under an inert atmosphere, Li6PS5Cl with a mass ratio of 1:50 to PEGDA was added to the reacted solution, along with azobisisobutyronitrile and potassium persulfate in a mass ratio of 1:1. The mixture was magnetically stirred at 80°C for 12 h. After cooling to room temperature, a composite material of polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl was obtained.

[0059] Weigh 0.5g of the polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl composite material prepared in this example, 0.4g of lithium tetrafluoroborate, and 1.7g of polyvinylidene fluoride. Stir magnetically at 350 rpm for 5 hours at 40°C. Form a film using a photocuring method. Add 2-hydroxy-2-methylphenylacetone to the mixed slurry. After coating, cure under ultraviolet light with a wavelength of 250 nm and an intensity of 50 mW / cm². 2 The irradiation time is 45 seconds.

[0060] In an argon-filled glove box (O2 content <1ppm, water content <1ppm), lithium-lithium symmetric coin cells are assembled using conventional methods.

[0061] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing an organic polymer solid electrolyte composite additive, characterized in that, The preparation method is as follows: (1) Preheat the organic solvent; (2) Add polyethylene glycol diacrylate and mercaptopropyltrimethoxysilane to the preheated organic solvent from step (1) and react them under magnetic stirring. After complete mixing, add a photoinitiator, wherein the mass of the photoinitiator accounts for 0.5% to 5% of the total mass of polyethylene glycol diacrylate and mercaptopropyltrimethoxysilane. Induce the HS- functional group in mercaptopropyltrimethoxysilane to form bonds with the C=C functional group in polyethylene glycol diacrylate under natural or artificial light irradiation. Continue magnetic stirring for 2-5 hours to obtain an organic mixture with mercapto-bonded groups, the molecular formula of which is [insert molecular formula here]. ； (3) Under an inert atmosphere, Li6PS5Cl and a thermal initiator were added to the thiol-bonded organic mixture obtained in step (2) for reaction. The mixture was then magnetically stirred and cooled to room temperature to obtain a chemically coupled composite additive. The structural formula of the composite additive is as follows: .

2. The method for preparing an organic polymer solid electrolyte composite additive according to claim 1, characterized in that: The organic solvent mentioned in step (1) is one or a mixture of several of the following: acetone, N-methylpyrrolidone, N,N-dimethylformamide, anhydrous acetonitrile, and tetrahydrofuran, and the preheating temperature is 40-90℃.

3. The method for preparing an organic polymer solid electrolyte composite additive according to claim 1, characterized in that: The structural formula of mercaptopropyltrimethoxysilane in step (2) is: The structural formula of polyethylene glycol diacrylate is: The average molecular weight is 200-400,000; the reaction temperature is controlled at 40-90℃; the mass ratio of polyethylene glycol diacrylate to mercaptopropyltrimethoxysilane is 3:1 to 1:3; the selected artificial light is an ultraviolet lamp with a wavelength of 200-400 nm, a light intensity of 10-100 mW / cm², and an irradiation time of 10-60 seconds.

4. The method for preparing an organic polymer solid electrolyte composite additive according to claim 1, characterized in that: In step (2), the photoinitiator is selected from one or a mixture of several of the following: acylphosphine oxide, benzoin ether, and α-hydroxy ketone compounds. The mass of the photoinitiator accounts for 0.5% to 5% of the total mass of polyethylene glycol diacrylate and mercaptopropyltrimethoxysilane.

5. The method for preparing an organic polymer solid electrolyte composite additive according to claim 1, characterized in that: In step (3), the mass ratio of Li6PS5Cl to polyethylene glycol diacrylate is 1:2 to 1:50; the reaction temperature is 30-120℃ and the reaction time is 6-12h.

6. The method for preparing an organic polymer solid electrolyte composite additive according to claim 1, characterized in that: The thermal initiator mentioned in step (3) is selected from one or a mixture of several of azobisisobutyronitrile, benzoyl peroxide, ammonium persulfate, potassium persulfate and sodium persulfate, and the mass of the thermal initiator accounts for 0.1% to 3% of the total mass of Li6PS5Cl and polyethylene glycol diacrylate.

7. The application of the composite additive prepared by the method according to any one of claims 1 to 6 in organic solid electrolytes, characterized in that, This composite additive is added to an organic solid electrolyte to prepare all-solid-state lithium-ion and lithium metal batteries. The organic solid electrolyte includes a polymer matrix, a composite electrolyte additive, and a lithium salt. The amount of the composite additive added is 15-30 wt% of the organic solid electrolyte, and the amount of the lithium salt added is 20-30 wt% of the amount of the polymer matrix added.

8. The application of the composite additive according to claim 7 in organic solid electrolytes, characterized in that: The lithium salt is one or any combination of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium perchlorate, lithium hexafluorophosphate, and lithium tetrafluoroborate.

9. The application of the composite additive according to claim 7 in organic solid electrolytes, characterized in that: The polymer matrix is ​​one or a mixture of any proportions of polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, and polymethyl methacrylate. The average molecular weight of the polymer matrix is ​​200-1,000,000. The polymer matrix and the composite additive are connected by hydrogen bonds / van der Waals bonds.

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