Preparation method and application of organic polymer solid electrolyte composite additive

Abstract

The invention discloses a preparation method and application of an organic polymer solid electrolyte composite additive. According to the preparation method, a poly (ethylene glycol) diacrylate-mercaptopropyl trimethoxy silane-Li6PS5Cl composite additive material is prepared by adopting a click chemistry reaction; functional groups at two ends of a mercaptopropyl trimethoxy silane molecule are respectively coupled with chemical bonds of polyethylene glycol diacrylate and Li6PS5Cl inorganic electrolyte to construct a stable bonding interface of organic matrix-silane coupling agent-inorganic matrix under the action of chemical bond valence force. The problems that traditional inorganic additives are serious in particle aggregation, poor in compatibility with a polymer solid electrolyte body interface and the like are solved, and by starting with the stability of the internal interface of the additives and construction of ion channels, the organic polymer solid electrolyte is prepared by means of defect regulation and control between organic polymer functional groups and the inorganic additives. The interfacial compatibility and the efficient and rapid ion transmission capability of the material are obviously improved. According to the invention, efficient ion transmission and long-acting cycle stability of an internal interface of the organic polymer solid electrolyte can be realized.

Description

Technical Field

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

[0002] With the in-depth promotion of the global energy structure transformation and green and low-carbon development strategy, high-energy-density and high-safety solid-state lithium batteries have become an important research direction in the field of energy storage. Among them, polymer solid electrolytes are regarded as an ideal material system to break through the safety bottleneck of traditional liquid lithium-ion batteries due to their excellent flexibility, lightweight characteristics and good interface compatibility with electrodes. However, existing polymer solid electrolytes still have key problems such as insufficient ionic conductivity, difficulty in co-optimizing mechanical strength and ion transport performance, and high electrode / electrolyte interface impedance, which seriously restrict their industrial application process. In this context, the development of efficient and multifunctional additives to direct the microstructure and macroscopic properties of polymer electrolytes has become an important breakthrough in promoting the innovation of solid-state battery technology.

[0003] Currently, research on polymer solid electrolytes focuses on the optimization of polymer matrices and lithium salts. However, due to inherent defects such as high crystallinity of polymer segments and large energy barriers for lithium ion migration, it is difficult to achieve simultaneous improvement of ionic conductivity and mechanical strength simply through matrix modification. In addition, lithium dendrite growth and side reactions at the electrode / electrolyte interface can easily lead to capacity decay and safety hazards. Studies have shown that the introduction of functional additives can construct fast ion transport channels, inhibit crystalline phase formation, and enhance interface stability in the polymer matrix through molecular design or composite effects, thereby achieving synergistic optimization of material properties. For example, inorganic nanofillers can reduce polymer crystallinity and broaden the electrochemical window; plasticizers can enhance segment mobility, but their excessive addition may sacrifice mechanical strength; and fluorinated polymers or lithium salt derivatives can optimize interfacial lithium ion flux distribution and inhibit dendrite growth. However, existing additive systems generally have problems such as single function and insufficient compatibility, and there is an urgent need to develop new multi-dimensional synergistic composite additives.

[0004] Based on this, the present invention innovatively proposes a composite additive system to address the above-mentioned bottlenecks of polymer solid electrolytes. This additive achieves the following synergistic effects at the molecular scale through organic-inorganic chemical bonding design: (1) Inorganic fillers are introduced to destroy the polymer crystalline region and construct a low-energy barrier ion transport path; (2) Mechanical properties are enhanced through the cross-linked network, dendrite formation is inhibited, and the dynamic flexibility of the chain segments is maintained; (3) The interface impedance between the additive and the polymer matrix is reduced by 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] In response to the above-mentioned technical deficiencies, the present invention uses the mercapto (-SH) and methoxysilane (-Si-O-) functional groups at both ends of the mercaptopropyltrimethoxysilane MPTMS molecule to chemically couple with the acrylate group of polyethylene glycol diacrylate PEGDA and the Li6PS5Cl surface, respectively, to construct a stable heterogeneous interface, effectively solving the problem of easy agglomeration of traditional inorganic additives and poor interfacial compatibility with the polymer matrix. Through molecular design, the synergistic optimization of organic-inorganic interface chemical bonding and ion transport channels is achieved. On the one hand, the silane coupling effect of MPTMS enhances the bonding strength between the organic polymer and Li6PS5Cl particles, inhibits inorganic phase agglomeration and promotes rapid migration of ions at the interface; on the other hand, the flexible chain segments of PEGDA complement the rigid structure of the inorganic particles, and by regulating the defect distribution in the composite system, the energy barrier for lithium ion migration is reduced, thereby improving the overall ionic conductivity. In addition, the organic functional groups in the composite additive can form a hydrogen bond network with the solid electrolyte matrix, further optimizing the stability of the electrode / electrolyte interface, inhibiting the growth of lithium dendrites, and extending the battery cycle life. The preparation process of this additive is simple and suitable for large-scale production. The solid electrolyte produced has high ionic conductivity, excellent mechanical strength and a wide electrochemical window. It exhibits high energy density and long cycle stability in solid-state lithium metal batteries, providing an innovative solution for the next generation of high-performance energy storage devices.

[0006] First, an organic solvent is preheated at 40-90°C for 10 minutes. Then, polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) are added to the organic solvent in a mass ratio of 3:1 to 1:3. A photoinitiator is also added. The mixture is irradiated with natural or artificial ultraviolet light for 10-60 seconds to induce bonding between the H₆S- functional groups in MPTMS and the C═C functional groups in PEGDA. The mixture is magnetically stirred at 40-90°C for 2-10 hours. Next, under an inert atmosphere, Li₆PS₅Cl₃ is added to the resulting solution in a mass ratio of 1:2 to 1:50 to PEGDA. A thermal initiator is also added, and the mixture is magnetically stirred at 30-120°C for 6-12 hours. After cooling to room temperature, the resulting composite additive of polyethylene glycol diacrylate, mercaptopropyltrimethoxysilane, and Li₆PS₅Cl₃ is obtained.

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

[0008] (1) Preheating an organic solvent at 40-90° C. for 10 min; wherein the organic solvent is one of acetone, N-methylpyrrolidone, N,N-dimethylformamide, anhydrous acetonitrile, tetrahydrofuran, or a mixture of any of the above.

[0009] (2) adding polyethylene glycol diacrylate and mercaptopropyl trimethoxysilane to the organic solvent preheated in step (1) to react, and magnetically stirring, and adding a photoinitiator after being completely mixed, wherein the mass of the photoinitiator accounts for 0.5% to 5% of the total mass of polyethylene glycol diacrylate and mercaptopropyl trimethoxysilane, inducing the HS-functional group in mercaptopropyl trimethoxysilane to form a bond with the C=C functional group in polyethylene glycol diacrylate under natural light or artificial light irradiation environment, and continuing magnetic stirring for 2-5 hours to obtain an organic mixed material after mercapto bonding, the molecular formula is

[0010]

[0011] The photoinitiator is selected from one of acylphosphine oxides, benzoin ethers and α-hydroxyketone compounds or a mixture of any of them. The mass ratio of the added polyethylene glycol diacrylate to mercaptopropyltrimethoxysilane is 3:1 to 1:3. The artificial light selected is preferably an ultraviolet lamp with a wavelength of 200-400nm and a light intensity of 10-100mW / cm 2, the irradiation time is 10-60 seconds, the reaction temperature is controlled at 40-90°C, and the magnetic stirring is carried out for 2-5 hours; wherein the average molecular weight of PEGDA is 200-400000, preferably 600-2000, and the reaction temperature is 40-90°C; the mass ratio of PEGDA to MPTMS is 3:1 to 1:3; the reaction time is 2-5 hours; under inert atmosphere conditions, Li6PS5Cl and a thermal initiator are added to the organic mixture obtained in step (2), the reaction temperature is controlled at 30-120°C, magnetic stirring is carried out for 6-12 hours, and after cooling to room temperature, a chemically coupled organic / inorganic composite additive is obtained; wherein the mass ratio of Li6PS5Cl to PEGDA is 1:2 to 1:50; the thermal initiator is selected from one or a mixture of any 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 to use the prepared composite additive in an organic solid electrolyte. The composite additive is added to the 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 to 30 wt% of the organic solid electrolyte, and the amount of the lithium salt added is 20 to 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 of polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, and polymethyl methacrylate, or a mixture of any multiple thereof. 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 through hydrogen bonds / van der Waals bonds.

[0015] The principle of the present invention is as follows: the present invention synthesizes a composite additive through a "click chemistry" reaction. The composite additive is composed of polyethylene glycol diacrylate (PEGDA), mercaptopropyltrimethoxysilane (MPTMS) and argyrodite-type inorganic electrolyte Li6PS5Cl, forming a composite system with a multi-level structure of "organic matrix-silane coupling agent-inorganic matrix". Among them, the mercapto (-SH) and methoxysilane (-Si-O-) functional groups at both ends of the MPTMS molecule are chemically coupled with the acrylate group of PEGDA and the surface of Li6PS5Cl respectively to construct a stable heterogeneous interface, effectively solving the problem that traditional inorganic additives are easy to agglomerate and have poor compatibility with the polymer matrix interface. The composite additive achieves the synergistic optimization of organic-inorganic interface chemical bonding and ion transmission channels through molecular design. On the one hand, the silane coupling effect of MPTMS enhances the bonding strength between the organic polymer and the Li6PS5Cl particles, inhibiting the agglomeration of the inorganic phase and promoting the rapid migration of ions at the interface; on the other hand, the flexible chain segments of PEGDA complement the rigid structure of the inorganic particles, reducing the energy barrier for lithium ion migration and improving the overall ionic conductivity by regulating the defect distribution in the composite system. In addition, the organic functional groups in the composite additive can form a hydrogen bond network with the solid electrolyte matrix, further optimizing the stability of the electrode / electrolyte interface, inhibiting the growth of lithium dendrites, and extending the battery cycle life. The preparation process of this additive is simple and suitable for large-scale production. The resulting solid electrolyte combines high ionic conductivity, excellent mechanical strength, and a wide electrochemical window. It exhibits high energy density and long cycle stability in solid-state lithium metal batteries, providing an innovative solution for the next generation of high-performance energy storage devices.

[0016] The beneficial effects of the present invention are:

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

[0018] (2) The uniform morphology and good mechanical properties also provide a solution to the dendrite problem generated during the ion extraction / embedding process of the material, avoiding battery failure caused by puncture. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the preparation of the composite additive of the present invention and its film-forming application in polymer solid electrolyte;

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

[0021] Figure 3is 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 the present 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 the present 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 the present invention in a lithium-ion battery system. DETAILED DESCRIPTION

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

[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) Add polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 1:0.8 to N,N-dimethylformamide in (1) and react at 65°C. After being completely mixed, add bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and irradiate with ultraviolet light to induce the HS-functional group in MPTMS to form a bond with the C=C functional group in PEGDA. The light wavelength is 200 nm and the light intensity is 40 mW / cm 2 , irradiation time was 37 seconds, magnetic stirring was 400 rpm for 2 hours,

[0029]

[0030] (3) Under inert atmosphere, the reaction solution was added with Li6PS5Cl in a mass ratio of 1:5 to PEGDA, and azobisisobutyronitrile was added, and the mixture was 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 the composite additive is

[0031]

[0032] 0.3 g of the polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl composite prepared in this example, 0.2 g of lithium perchlorate, and 1.0 g of polyethylene oxide were weighed and coated at 40°C with magnetic stirring at 350 rpm for 5 hours. The film was formed using a cast-coat method with a blade height of 150 μm. After drying in two stages, both at room temperature and pressure and at a reduced pressure and high temperature, the film was then hot-pressed to form a film.

[0033] In a glove box filled with argon (O2 content <1 ppm, water content <1 ppm), lithium-lithium symmetric button cells were assembled using conventional methods.

[0034] The long cycle performance of the lithium-lithium symmetrical battery prepared in this embodiment is shown in the figure below: Figure 4 As shown. Figure 4 It can be seen that the material prepared in this embodiment shows excellent cycle performance as a lithium-ion solid-state battery additive. -2 It exhibits stable long-term cycling capability at low current densities.

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

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

[0037] (2) Add polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 1:1 to anhydrous acetonitrile in (1), and add benzoin methyl ether. Irradiate with ultraviolet light at a wavelength of 250 nm and an intensity of 50 mW / cm to induce the HS-functional group in MPTMS to form a bond with the C=C functional group in PEGDA. 2 The irradiation time was 40 seconds, and the mixture was stirred at 65°C and 400 rpm for 5 hours to obtain an organic mixed material after thiol bonding;

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

[0039] Weigh 0.35g of the polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl composite prepared in this example, 0.3g of lithium hexafluorophosphate, and 1.0g of polyacrylonitrile. The composite was then coated using a cast-coat method at 40°C with magnetic stirring at 350 rpm for 5 hours, using a doctor blade height of 250μm. After drying in two stages (at ambient temperature and pressure, then at negative pressure and high temperature) to remove the solvent, the composite was hot-pressed.

[0040] In a glove box filled with argon (O2 content <1 ppm, water content <1 ppm), lithium-lithium symmetric button cells were assembled using conventional methods.

[0041] The scanning electron microscope image of the solid electrolyte material prepared in this embodiment is as follows Figure 3 , the long cycle performance of lithium-lithium symmetrical battery is shown in the figure Figure 5 As shown. Figure 3 It can be seen that the solid electrolyte prepared in this embodiment has good uniformity. Figure 5 It can be seen that the material prepared in this embodiment shows excellent cycle performance as a lithium-ion solid-state battery additive. -2 It exhibits stable long-term cycling capability at low current densities.

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

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

[0044] (2) Add polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 1:1.2 to N-methylpyrrolidone in (1), and add 2-hydroxy-2-methylpropiophenone (α-hydroxyketone compound). Irradiate with ultraviolet light at a wavelength of 300 nm and an intensity of 60 mW / cm to induce the HS- functional group in MPTMS to form a bond with the C=C functional group in PEGDA. 2 The irradiation time was 23 seconds, and the mixture was stirred at 65°C and 400 rpm for 3 hours to obtain an organic mixed material after thiol bonding;

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

[0046] 0.5 g of the polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl composite prepared in this example, 0.4 g of lithium bis(fluorosulfonyl)imide, and 1.7 g of poly(vinylidene fluoride)-hexafluoropropylene copolymer were weighed and coated using a cast-on method at 40°C with magnetic stirring at 350 rpm for 5 hours. The film was formed using a scraper height of 200 μm. After drying in two stages, both at room temperature and pressure and at a reduced pressure and high temperature, the film was then hot-pressed to form a film.

[0047] In a glove box filled with argon (O2 content <1 ppm, water content <1 ppm), lithium-lithium symmetric button cells were assembled using conventional methods.

[0048] The Fourier transform infrared spectrum of the solid electrolyte material prepared in this embodiment is shown in FIG. Figure 2 , the long cycle performance of lithium-lithium symmetrical battery is shown in the figure Figure 6 As shown. Figure 2 It can be seen that the solid electrolyte additive material prepared in this embodiment has complete and controllable bonding. Figure 6 It can be seen that the material prepared in this embodiment shows excellent cycle performance as a lithium-ion solid-state battery additive. -2 It exhibits stable long-term cycling capability at low current densities.

[0049] Example 4: An organic polymer solid electrolyte composite additive and its preparation method and 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) Add polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 1:1.2 to the solvent in (1), and add 2-hydroxy-2-methylpropiophenone (α-hydroxy ketone compound). Irradiate with ultraviolet light at a wavelength of 400 nm and an intensity of 20 mW / cm to induce the HS- functional group in MPTMS to form a bond with the C=C functional group in PEGDA. 2 The irradiation time was 60 seconds, and the mixture was stirred at 90°C and 400 rpm for 5 hours.

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

[0053] Weigh 0.5 g of the composite material of polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl prepared in this example, 0.4 g of lithium bis(trifluoromethanesulfonyl)imide, and 1.7 g of polymethyl methacrylate, stir magnetically at 350 rpm at 40 ° C for 5 h, and cure into a film by a casting method. The mixed slurry of the composite additive, lithium salt and polymer matrix is injected into a mold to control the film thickness to 50-300 μm, and then stand and cure in an inert atmosphere at a curing temperature of 40 ° C for 30 h.

[0054] In a glove box filled with argon (O2 content <1 ppm, water content <1 ppm), lithium-lithium symmetric button cells were assembled using conventional methods.

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

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

[0057] (2) Add polyethylene glycol diacrylate (PEGDA) and mercaptopropyltrimethoxysilane (MPTMS) in a mass ratio of 1:1.2 to tetrahydrofuran in (1), and add 2-hydroxy-2-methylpropiophenone. Irradiate with ultraviolet light at a wavelength of 200 nm and an intensity of 15 mW / cm to induce bonding between the HS-functional group in MPTMS and the C=C functional group in PEGDA. 2 The irradiation time was 10 seconds, and the mixture was stirred at 400 rpm for 4 hours at 40 °C.

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

[0059] 0.5 g of the composite material of polyethylene glycol diacrylate-mercaptopropyltrimethoxysilane-Li6PS5Cl prepared in this example, 0.4 g of lithium tetrafluoroborate, and 1.7 g of polyvinylidene fluoride were weighed and stirred at 40 ° C. and 350 rpm for 5 h. A film was formed by photocuring. 2-hydroxy-2-methylpropiophenone was added to the mixed slurry. After coating, the film was cured by ultraviolet light. The ultraviolet light wavelength was 250 nm and the light intensity was 50 mW / cm 2 , the irradiation time is 45 seconds.

[0060] In a glove box filled with argon (O2 content <1 ppm, water content <1 ppm), lithium-lithium symmetric button cells were assembled using conventional methods.

[0061] The above describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the scope 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) preheating the organic solvent; (2) adding polyethylene glycol diacrylate and mercaptopropyl trimethoxysilane to the organic solvent preheated in step (1) to react, and magnetically stirring, and adding a photoinitiator after being completely mixed, wherein the mass of the photoinitiator accounts for 0.5% to 5% of the total mass of polyethylene glycol diacrylate and mercaptopropyl trimethoxysilane, inducing the HS-functional group in mercaptopropyl trimethoxysilane to form a bond with the C=C functional group in polyethylene glycol diacrylate under natural light or artificial light irradiation environment, and continuing magnetic stirring for 2-5 hours to obtain an organic mixed material after mercapto bonding, the molecular formula is (3) Under inert atmosphere, Li6PS5Cl and a thermal initiator are added to the thiol-bonded organic mixed material obtained in step (2) to react, and magnetically stirred. After cooling to room temperature, a chemically coupled composite additive is obtained. The composite additive has the structural formula:

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

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, preferably 600-2,000; the reaction temperature is controlled at 40-90°C, the mass ratio of the added polyethylene glycol diacrylate to mercaptopropyltrimethoxysilane is 3:1 to 1:3; the selected artificial light is preferably an ultraviolet lamp, the wavelength of the light is 200-400nm, and the light intensity is 10-100mW / cm 2 , the irradiation time is 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 of acylphosphine oxides, benzoin ethers and α-hydroxyketone compounds or a mixture of several of them in any ratio, and 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: The mass ratio of Li6PS5Cl to polyethylene glycol diacrylate in step (3) is 1:2 to 1:50; the reaction temperature is 30-120°C, 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 in step (3) is one selected from azobisisobutyronitrile, benzoyl peroxide, ammonium persulfate, potassium persulfate and sodium persulfate, or a mixture of any of them, and the mass of the thermal initiator accounts for 0.1% to 3% of the total mass of Li6PS5Cl and polyethylene glycol diacrylate.

7. Use of the composite additive prepared by the preparation method according to claims 1 to 6 in an organic solid electrolyte, characterized in that: The composite additive is added to an organic solid electrolyte for preparing all-solid-state lithium ion and lithium metal batteries. The organic solid electrolyte comprises a polymer matrix, a composite electrolyte additive, and a lithium salt. The amount of the composite additive added is 15 to 30 wt% of the organic solid electrolyte, and the amount of the lithium salt added is 20 to 30 wt% of the polymer matrix added.

8. Use of the composite additive according to claim 7 in all-solid-state lithium ion and lithium metal batteries, characterized in that: The lithium salt is one or any combination of lithium bis(trifluoromethanesulfonyl imide), lithium bis(fluorosulfonyl imide), lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium borohydride and lithium hexafluoroarsenate.

9. The organic solid electrolyte according to claim 7, characterized in that: The polymer matrix is one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, and polymethyl methacrylate, or a mixture of any multiple thereof. 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 through hydrogen bonds / van der Waals bonds.

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