Composite solid electrolyte and method for preparing the same

Abstract

This application provides a composite solid electrolyte comprising a polymer matrix, a metal salt, and fast-ion conductor ceramic particles. Both the metal salt and the fast-ion conductor ceramic particles are dispersed within the polymer matrix. The fast-ion conductor ceramic particles are sequentially coated from the inside out with an inorganic oxide layer and a fluorinated silane coupling agent. The fluorinated silane coupling agent is chemically bonded to the inorganic oxide layer. This application also provides a method for preparing the composite solid electrolyte. Through both material and process innovation, this application prepares a composite solid electrolyte with high dispersibility, high ionic conductivity, and high interfacial compatibility.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery technology, and more specifically, to a composite solid-state electrolyte and its preparation method. Background Technology

[0002] Solid-state batteries use solid electrolytes instead of liquid electrolytes, avoiding the safety hazards of liquid electrolytes such as flammability and explosion. They also have advantages such as high energy density, wide electrochemical window, and long cycle life, and have become a key development direction for next-generation energy storage technology.

[0003] In existing solid electrolytes, to balance high ionic conductivity and good film-forming properties, electrolyte systems combining inorganic fast ion conductor ceramics and organic polymers have emerged. However, due to the significant interfacial energy difference between the fast ion conductor ceramic particles and the polymer matrix, phase separation easily occurs during solution blending, leading to the aggregation of fast ion conductor ceramic particles into micron-sized particles. This not only causes discontinuities in ion transport paths and forms ion migration barriers, but also significantly reduces the overall ionic conductivity of the composite solid electrolyte. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a composite solid electrolyte and its preparation method.

[0005] The composite solid electrolyte disclosed in this application includes: a polymer matrix, a metal salt, and fast ion conductor ceramic particles. The metal salt and fast ion conductor ceramic particles are both dispersed in the polymer matrix. The fast ion conductor ceramic particles are coated with an inorganic oxide layer and a fluorinated silane coupling agent from the inside to the outside. The fluorinated silane coupling agent is chemically bonded to the inorganic oxide layer.

[0006] Preferably, the fast ion conductor ceramic particles are selected from at least one of LATP, LATP derivatives, LLZO, LLZO derivatives, LAGP, LAGP derivatives, LLTO, and LLTO derivatives.

[0007] Preferably, the inorganic oxide layer includes at least one of SiO2, SiO2 hydrate, Al2O3, Al2O3 hydrate, ZrO2, ZrO2 hydrate, TiO2, and TiO2 hydrate.

[0008] Preferably, the fluorinated silane coupling agent includes at least one of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and heptadecafluorodecyltrimethoxysilane.

[0009] Preferably, the polymer matrix is ​​obtained by copolymerization of vinylidene fluoride monomers and fluorine-containing ionic liquid monomers, wherein the vinylidene fluoride monomers include vinylidene fluoride.

[0010] Preferably, the vinylidene fluoride monomer further includes at least one of hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, and trifluorochloroethylene.

[0011] Preferably, the fluorinated ionic liquid monomer is selected from at least one of 1-vinyl-3-(trifluoroethyl)imidazolium and 1-vinyl-3-(pentafluoropropyl)pyrrolidineonium.

[0012] Preferably, the metal salt is selected from at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonate)imide, lithium hexafluorophosphate, lithium di(oxalate)borate, lithium di(fluorooxalate)borate, lithium nitrate, lithium perchlorate, lithium tetrafluoroborate, and lithium trifluoromethanesulfonate.

[0013] This application also discloses a method for preparing a composite solid electrolyte, comprising the following steps: S1: forming an inorganic oxide layer on the surface of fast ion conductor ceramic particles by surface deposition to obtain fast ion conductor ceramic particles coated with an inorganic oxide layer; S2: modifying the fast ion conductor ceramic particles coated with an inorganic oxide layer using a fluorinated silane coupling agent to obtain fast ion conductor ceramic particles coated with an inorganic oxide layer and a fluorinated silane coupling agent sequentially from the inside out; S3: dissolving the fast ion conductor ceramic particles coated with an inorganic oxide layer and a fluorinated silane coupling agent sequentially from the inside out, a vinylidene fluoride monomer, a fluorinated ionic liquid monomer, a metal salt, and an initiator in a first solvent, performing an in-situ thermal polymerization reaction, and drying to obtain a composite solid electrolyte.

[0014] Preferably, step S1 includes the following sub-steps: S11: mixing and dispersing fast ion conductor ceramic particles with a second solvent; S12: adjusting the pH of the solution to alkaline, adding an inorganic oxide precursor, and heating to react; S13: washing and drying to obtain fast ion conductor ceramic particles coated with an inorganic oxide layer.

[0015] Preferably, step S2 includes the following sub-steps: dissolving fast ion conductor ceramic particles coated with an inorganic oxide layer and a fluorinated silane coupling agent in a third solvent; placing them in a protective atmosphere and heating them to react; washing and drying them to obtain fast ion conductor ceramic particles coated with an inorganic oxide layer and a fluorinated silane coupling agent sequentially from the inside out.

[0016] Preferably, the mass ratio of fast ion conductor ceramic particles, vinylidene fluoride monomers, fluorine-containing ionic liquid monomers, metal salts and initiators, which are sequentially coated with an inorganic oxide layer and a fluorine-containing silane coupling agent from the inside out, is 1~6:5~18:1~10:1~15:0.01~1.

[0017] Preferably, the in-situ thermal polymerization reaction is carried out under the assistance of a protective atmosphere, a magnetic field, and pulsed ultrasound.

[0018] Preferably, the temperature of the in-situ thermal polymerization reaction is 70℃~100℃, the reaction time is 5h~48h, the magnetic field strength is 0.1T~0.5T, the frequency of the pulsed ultrasound is 10kHz~50kHz, and the duty cycle is 30%~90%.

[0019] The beneficial effects of this application are as follows: the composite solid electrolyte of this application effectively improves its comprehensive performance through synergistic innovation in material system and preparation process. Firstly, by performing gradient interface modification on fast ion conductor ceramic particles, an inorganic oxide layer and a fluorinated silane coupling agent are sequentially coated on their surface. Since the surface of the inorganic oxide layer is rich in hydroxyl groups, the fluorinated silane coupling agent chemically bonds with the hydroxyl groups on the surface of the inorganic oxide layer. Simultaneously, the low surface energy fluorinated alkyl groups are arranged on the outermost layer, reducing the surface energy of the gradient interface-modified fast ion conductor ceramic particles. This results in higher interfacial compatibility with the low surface energy polymer matrix, making phase separation less likely during solution blending. Furthermore, the reduced surface energy weakens the van der Waals forces between the fast ion conductor ceramic particles, suppressing particle aggregation and facilitating more uniform dispersion of the gradient interface-modified fast ion conductor ceramic particles in the polymer matrix. The uniform dispersion of the gradient interface-modified fast ion conductor ceramic particles in the polymer matrix forms continuous ion transport channels, thereby improving the ionic conductivity of the composite solid electrolyte.

[0020] Simultaneously, fluorinated ionic liquid monomers are introduced into the polymer matrix to participate in copolymerization, forming fluorinated ionic liquid graft chains. This effectively disrupts the regular arrangement of polymer chain segments, reduces the crystallinity of the polymer matrix, and thus improves ionic conductivity. Based on this, a low-temperature in-situ thermal polymerization process is employed to promote close interfacial contact while avoiding thermal decomposition of the gradient-interface-modified fast ion conductor ceramic particles and the polymer matrix. Furthermore, the synergistic effect of pulsed ultrasound and magnetic field is combined: ultrasonic cavitation breaks up particle agglomeration, and the magnetic field induces the directional alignment of the gradient-interface-modified fast ion conductor ceramic particles, jointly constructing a continuous and efficient ion conduction network. Ultimately, a composite solid electrolyte with high dispersibility, high ionic conductivity, and high interfacial compatibility is obtained. Attached Figure Description

[0021] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0022] Figure 1 Here is a SEM image of the composite solid electrolyte membrane in Example 1;

[0023] Figure 2 The image shows a SEM image of the composite solid electrolyte membrane in Comparative Example 1. Detailed Implementation

[0024] Several embodiments of this application will be disclosed below. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details should not be used to limit this application. That is, in some embodiments of this application, these practical details are not essential.

[0025] Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0026] To further understand the content, features, and effects of this application, the following embodiments are provided, and detailed descriptions are given in conjunction with the accompanying drawings.

[0027] The composite solid electrolyte in this embodiment includes a polymer matrix, a metal salt, and fast ion conductor ceramic particles. Both the metal salt and the fast ion conductor ceramic particles are dispersed in the polymer matrix. The fast ion conductor ceramic particles are coated with an inorganic oxide layer and a fluorinated silane coupling agent from the inside out. The fluorinated silane coupling agent is chemically bonded to the inorganic oxide layer.

[0028] In this embodiment, the core function of the fast ion conductor ceramic particles is to provide efficient metal ion migration pathways. That is, the fast ion conductor ceramic particles have the characteristic of allowing metal ions to conduct rapidly within their crystal lattice structure or along grain boundaries. Their intrinsic ionic conductivity is significantly higher than that of the polymer matrix. Thus, when the fast ion conductor ceramic particles form an interconnected conductive network in the polymer matrix, they can create continuous low-impedance channels for metal ions, thereby effectively improving the ionic conductivity of the composite solid electrolyte. Preferably, the fast ion conductor ceramic particles are selected from at least one of lithium aluminum titanium phosphate (LATP), derivatives of lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconate (LLZO), derivatives of lithium lanthanum zirconate (LLZO), lithium aluminum germanium phosphate (LAGP), derivatives of lithium aluminum germanium phosphate (LAGP), lithium lanthanum titanate (LLTO), and derivatives of lithium lanthanum titanate (LLTO).

[0029] Preferably, the inorganic oxide layer includes at least one of SiO2, SiO2 hydrate, Al2O3, Al2O3 hydrate, ZrO2, ZrO2 hydrate, TiO2, and TiO2 hydrate.

[0030] Preferably, the fluorinated silane coupling agent includes at least one of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and heptadecafluorodecyltrimethoxysilane.

[0031] Preferably, the polymer matrix is ​​obtained by copolymerization of vinylidene fluoride monomers and fluorinated ionic liquid monomers, wherein the vinylidene fluoride monomers include vinylidene fluoride. In specific applications, the fluorinated ionic liquid monomers are selected from at least one of 1-vinyl-3-(trifluoroethyl)imidazolium and 1-vinyl-3-(pentafluoropropyl)pyrrolidineonium. The polymer backbone formed by the polymerization of vinylidene fluoride monomers provides the necessary mechanical strength and film-forming properties for the composite solid electrolyte, while the fluorinated ionic liquid monomers, through their vinyl groups participating in copolymerization, introduce fluorinated ionic liquid graft chains into the polymer backbone, which can effectively suppress the regular arrangement of polymer chain segments, reduce the crystallinity of the polymer matrix, and significantly improve ionic conductivity.

[0032] Preferably, the vinylidene fluoride monomer further includes at least one of hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, and trifluorochloroethylene. In specific applications, the vinylidene fluoride monomer may include only vinylidene fluoride, or it may be a combination of fluoropolymer monomers with vinylidene fluoride (VDF) as the main component, and the combination components may also include one or more of hexafluoropropylene (HFP), tetrafluoroethylene (TFE), trifluoroethylene (TrFE), and trifluorochloroethylene (CTFE).

[0033] Preferably, the metal salt is selected from at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonate)imide, lithium hexafluorophosphate, lithium di(oxalato)borate, lithium di(fluorooxalato)borate, lithium nitrate, lithium perchlorate, lithium tetrafluoroborate, and lithium trifluoromethanesulfonate. In specific applications, the metal salt in this embodiment is a lithium salt. In the composite solid electrolyte system, the lithium salt dissolves in the polymer matrix and ionizes, providing mobile lithium ions as charge carriers.

[0034] In this embodiment, the composite solid electrolyte is prepared by gradient interface modification of fast ion conductor ceramic particles. An inorganic oxide layer and a fluorinated silane coupling agent are sequentially coated onto the surface of the particles. Since the inorganic oxide layer is rich in hydroxyl groups, the fluorinated silane coupling agent chemically bonds with these hydroxyl groups, while the low-surface-energy fluorinated alkyl groups are arranged on the outermost layer. This reduces the surface energy of the gradient interface-modified fast ion conductor ceramic particles, resulting in higher interfacial compatibility with the low-surface-energy polymer matrix and reducing the likelihood of phase separation during solution blending. Furthermore, the reduced surface energy weakens the van der Waals forces between the fast ion conductor ceramic particles, suppressing particle aggregation and promoting more uniform dispersion of the particles within the polymer matrix. This uniform dispersion of the gradient interface-modified fast ion conductor ceramic particles within the polymer matrix forms continuous ion transport channels, thereby improving the ionic conductivity of the composite solid electrolyte. Meanwhile, fluorinated ionic liquid monomers are introduced into the polymer matrix to participate in copolymerization, forming fluorinated ionic liquid graft chains, which effectively disrupts the regular arrangement of polymer chain segments, reduces the crystallinity of the polymer matrix, and thus improves ionic conductivity.

[0035] The preparation method of the composite solid electrolyte in this embodiment includes the following steps:

[0036] S1: An inorganic oxide layer is formed on the surface of fast ion conductor ceramic particles by surface deposition, resulting in fast ion conductor ceramic particles coated with an inorganic oxide layer. In specific applications, the surface deposition method can be any one of the following: sol-gel method, chemical vapor deposition (CVD), atomic layer deposition (ALD), or magnetron sputtering.

[0037] Preferably, step S1 includes the following steps:

[0038] S11: Mix and disperse the fast ion conductor ceramic particles with the second solvent. In specific applications, the fast ion conductor ceramic particles and the second solvent are mixed at a mass ratio of 1:(0.5-100) and ultrasonically dispersed for 30 min to 120 min. Preferably, the second solvent is a mixed solution of ethanol and water.

[0039] S12: Adjust the pH of the solution to alkaline, add the inorganic oxide precursor, and heat the reaction. In specific applications, adjust the pH of the solution to 8-12 with ammonia water, and add an inorganic oxide precursor with a mass of 0.01-1 times that of the fast ion conductor ceramic particles dropwise under continuous stirring. React at 40℃-100℃ for 0.5h-10h. Preferably, the inorganic oxide precursor is a precursor that can undergo hydrolysis to form at least one of SiO2, SiO2 hydrate, Al2O3, Al2O3 hydrate, ZrO2, ZrO2 hydrate, TiO2, and TiO2 hydrate, preferably at least one of tetraethyl orthosilicate, aluminum isopropoxide, tetrabutyl titanate, and zirconium isopropoxide.

[0040] S13: After washing and drying, fast ion conductor ceramic particles coated with an inorganic oxide layer are obtained. In specific applications, after the reaction in step S12 is completed, the particles are filtered, washed with deionized water 1-10 times, washed with ethanol 1-10 times, and finally dried in a forced-air dryer at 50℃-100℃ for 1h-24h to obtain fast ion conductor ceramic particles with an inorganic oxide layer on the surface.

[0041] S2: Fast ion conductor ceramic particles coated with an inorganic oxide layer are modified using a fluorinated silane coupling agent to obtain fast ion conductor ceramic particles coated with an inorganic oxide layer and a fluorinated silane coupling agent from the inside out.

[0042] Preferably, step S2 includes the following sub-steps:

[0043] S21: Dissolve the fast ion conductor ceramic particles coated with an inorganic oxide layer and the fluorinated silane coupling agent in a third solvent. In specific applications, the fast ion conductor ceramic particles with an inorganic oxide layer formed on their surface obtained in step S13 and the fluorinated silane coupling agent are dissolved in a third solvent at a mass ratio of 1:(0.01-1). In this embodiment, the third solvent is toluene.

[0044] S22: Place the mixture in a protective atmosphere and heat it to react. In specific applications, place the mixed solution obtained in step S21 in a N2 protective atmosphere and reflux at 50℃-100℃ for 3h-24h.

[0045] S23: After washing and drying, fast ion conductor ceramic particles are obtained, which are sequentially coated with an inorganic oxide layer and a fluorinated silane coupling agent from the inside out. In specific applications, after step S22, the particles are filtered and washed 1-10 times with deionized water and 1-10 times with ethanol. Then, they are dried in a forced-air dryer at 50℃-100℃ for 1-24 hours to obtain gradient interface modified fast ion conductor ceramic particles.

[0046] S3: Fast ion conductor ceramic particles, vinylidene fluoride monomers, fluorine-containing ionic liquid monomers, metal salts and initiators, which are sequentially coated with inorganic oxide layers and fluorine-containing silane coupling agents from the inside out, are dissolved in a first solvent and subjected to in-situ thermal polymerization reaction. After drying, a composite solid electrolyte is obtained.

[0047] Preferably, the mass ratio of fast ion conductor ceramic particles coated with an inorganic oxide layer and a fluorinated silane coupling agent, vinylidene fluoride monomer, fluorinated ionic liquid monomer, metal salt, and initiator, from the inside out, is 1~6:5~18:1~10:1~15:0.01~1. In specific applications, the mass fractions of each component are as follows: 1-6 parts of gradient interface-modified fast ion conductor ceramic particles, 5-18 parts of vinylidene fluoride monomer, 1-10 parts of fluorinated ionic liquid monomer, 1-15 parts of metal salt, 0.01-1 part of initiator, and 20-100 parts of first solvent. The initiator is selected from at least one of azobisisobutyronitrile (AIB) and benzoyl peroxide. The first solvent is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, acetonitrile, acetone, and ethanol.

[0048] Preferably, the in-situ thermal polymerization reaction is carried out under the assistance of a protective atmosphere, a magnetic field, and pulsed ultrasound. In specific applications, the protective atmosphere prevents oxidation of the reaction components. The role of pulsed ultrasound is to break up the agglomeration of the gradient interface-modified fast ion conductor ceramic particles, allowing them to be uniformly dispersed in the solution. Since some of the gradient interface-modified fast ion conductor ceramic particles possess weak magnetism, the magnetic field can induce the dispersed gradient interface-modified fast ion conductor ceramic particles to oriented. Finally, low-temperature in-situ thermal polymerization uniformly disperses the gradient interface-modified fast ion conductor ceramic particles in the polymer matrix, forming continuous ion transport channels.

[0049] Preferably, the in-situ thermal polymerization reaction is carried out at 70℃-100℃ for 5h-48h. The protective atmosphere is at least one of nitrogen and argon. The magnetic field strength is 0.1T-0.5T. The pulsed ultrasonic frequency is 10kHz-50kHz, and the duty cycle is 30%-90%. Drying is carried out by vacuum drying at a temperature of 50℃-100℃ for 1h-30h.

[0050] It should be noted that, in specific implementations, the composite solid electrolyte described in this invention is preferably prepared into a composite solid electrolyte membrane through a film-forming process for use. The following embodiments illustrate the morphology of the membrane, but should not be construed as limiting the scope of protection of this invention.

[0051] The composite solid electrolyte in this embodiment is prepared by a low-temperature in-situ thermal polymerization process, which avoids thermal decomposition of the gradient interface modified fast ion conductor ceramic particles and the polymer matrix while promoting close interfacial contact. Combined with the synergistic effect of pulsed ultrasound and magnetic field, namely, the ultrasonic cavitation effect breaks particle agglomeration, and the magnetic field induces the gradient interface modified fast ion conductor ceramic particles to achieve directional alignment, together constructing a continuous and efficient ion conduction network, and finally obtaining a composite solid electrolyte with high dispersibility, high ionic conductivity and high interfacial compatibility.

[0052] Example 1:

[0053] The preparation method of the composite solid electrolyte in this embodiment includes the following steps:

[0054] S1: LATP particles were mixed with an ethanol / water mixed solvent at a mass ratio of 1:40 and ultrasonically dispersed for 30 minutes. The mass ratio of ethanol to water in the ethanol / water mixed solvent was 4:1. Then, the pH of the solution was adjusted to 9.5 with ammonia. Tetraethyl orthosilicate (TEOS) with a mass of 0.16 times that of the LATP particles was added dropwise while stirring. The reaction was carried out at 60°C for 3 hours. After the reaction was completed, the mixture was filtered, washed three times with deionized water, and washed three times with ethanol. Finally, it was dried in a forced-air environment at 60°C for 3 hours to obtain LATP particles with a surface modified with an inorganic oxide layer of SiO2.

[0055] S2: The LATP particles with SiO2 inorganic oxide layer obtained in step S1 were dissolved in toluene with 1H,1H,2H,2H-perfluorooctyltriethoxysilane at a mass ratio of 1:0.1. The mixture was placed under a nitrogen protective atmosphere and refluxed at 80°C for 12 hours. After filtration, the mixture was washed three times with deionized water and three times with ethanol, and then dried at 60°C for 3 hours to obtain LATP particles with gradient interface modification.

[0056] S3: Gradient-interface modified LATP particles, vinylidene fluoride (VDF) monomer, 1-vinyl-3-(trifluoroethyl)imidazolium (TFSI), lithium bis(trifluoromethanesulfonate)imide (LiTFSI), azobisisobutyronitrile (AIBN), and N,N-dimethylformamide (DMF) were mixed in a mass ratio of 4:12:2:7:0.1:60. Under nitrogen protection, the mixture was placed in a 0.3T magnetic field environment with 35kHz pulsed ultrasound (60% duty cycle) and subjected to in-situ thermal polymerization at 80℃ for 24 hours. After polymerization to form a film, it was vacuum dried at 90℃ for 24 hours to obtain a composite solid electrolyte membrane.

[0057] Comparative Example 1:

[0058] The preparation method of the composite solid electrolyte in this comparative example includes the following steps:

[0059] S1: Unmodified LATP particles, vinylidene fluoride (VDF) monomer, azobisisobutyronitrile (AIBN), lithium bis(trifluoromethanesulfonate)imide (LiTFSI), and N,N-dimethylformamide (DMF) are mixed in a mass ratio of 4:12:2:7:0.1:60 to obtain a mixed solution.

[0060] S2: Place the mixed solution obtained in step S1 in a nitrogen protective atmosphere and initiate a thermal polymerization reaction at 80°C for 24 hours.

[0061] S3: After polymerization, the film is dried under vacuum at 90°C for 24 hours to obtain a composite solid electrolyte membrane.

[0062] The composite solid electrolyte membranes from Example 1 and Comparative Example 1 were subjected to ionic conductivity and tensile strength tests. The ionic conductivity test method was as follows: the composite solid electrolyte membrane was cut into 18mm diameter discs and dried in a vacuum drying oven at 60°C for 5 hours. Then, it was assembled into a button cell using a structure of positive electrode shell-spring sheet-steel sheet-composite solid electrolyte membrane-steel sheet-spring sheet-negative electrode shell, with 40µL of conventional electrolyte added for thorough wetting during assembly. After the button cell was allowed to stand for 3 hours, electrochemical impedance spectroscopy (EIS) was performed at a frequency range of 1MHz-1Hz and a voltage amplitude of 10mV. The ionic conductivity was then calculated using the formula σ=d / (R×S), where d is the thickness of the composite solid electrolyte membrane, S is the area of ​​the contact surface between the composite solid electrolyte membrane and the steel sheet, and R is the resistance.

[0063] The tensile strength test method was as follows: The composite solid electrolyte membrane was cut into samples 15cm long and 1.5cm wide using a mold; the electronic tensile testing instrument was powered on and set to electrolyte membrane tensile mode, with a tensile speed of 250mm / min; the sample was vertically and flatly clamped between the upper and lower clamps, and the tensile strength test was started. The test results are shown in Table 1.

[0064] Table 1: Performance Comparison of Comparative Example 1 and Example 1

[0065]

[0066] The performance test results of Example 1 and Comparative Example 1 in Table 1 show that the composite solid electrolyte prepared by this invention achieves significant improvements in both ionic conductivity and mechanical properties. The ionic conductivity of Example 1 reaches 1.02 mS / cm, an improvement of over 60% compared to 0.63 mS / cm in Comparative Example 1. This improvement is mainly due to the gradient interface modification improving the interfacial compatibility between the fast ion conductor ceramic particles and the polymer matrix, promoting the uniform dispersion of the fast ion conductor ceramic particles in the polymer matrix, forming continuous lithium-ion transport channels. Simultaneously, the introduction of the fluorinated ionic liquid monomer effectively reduces the crystallinity of the polymer matrix, and the magnetic field-induced directional alignment of the gradient interface-modified fast ion conductor ceramic particles further enhances the ionic conductivity. Regarding mechanical properties, the tensile strength of Example 1 reaches 10.7 MPa, an improvement of approximately 30% compared to 8.13 MPa in Comparative Example 1. This is attributed to the enhanced inorganic-organic interfacial bonding strength resulting from the gradient interface modification, and the reduced stress concentration effect caused by the uniform distribution of the fast ion conductor ceramic particles, enabling effective stress transfer when the material is subjected to external forces, thereby significantly improving the mechanical integrity of the composite solid electrolyte.

[0067] Depend on Figure 1 and Figure 2It can be seen that the composite solid electrolyte membrane of Comparative Example 1 has larger agglomerated particles, while the composite solid electrolyte membrane of Example 1 has smaller particles, indicating that the particle dispersibility of the composite solid electrolyte membrane in Example 1 is significantly improved.

[0068] In summary, the composite solid electrolyte of this embodiment effectively improves its overall performance through synergistic innovation in material system and preparation process. Firstly, by performing gradient interface modification on the fast ion conductor ceramic particles, an inorganic oxide layer and a fluorinated silane coupling agent are sequentially coated on their surface. Since the inorganic oxide layer is rich in hydroxyl groups, the fluorinated silane coupling agent chemically bonds with these hydroxyl groups, while the low-surface-energy fluorinated alkyl groups are arranged on the outermost layer. This reduces the surface energy of the gradient interface-modified fast ion conductor ceramic particles, resulting in higher interfacial compatibility with the low-surface-energy polymer matrix and reducing the likelihood of phase separation during solution blending. Furthermore, the reduced surface energy weakens the van der Waals forces between the fast ion conductor ceramic particles, suppressing particle aggregation and facilitating more uniform dispersion of the gradient interface-modified fast ion conductor ceramic particles within the polymer matrix. The uniform dispersion of the gradient interface-modified fast ion conductor ceramic particles within the polymer matrix forms continuous ion transport channels, thereby improving the ionic conductivity of the composite solid electrolyte. Simultaneously, fluorinated ionic liquid monomers are introduced into the polymer matrix to participate in copolymerization, forming fluorinated ionic liquid graft chains. This effectively disrupts the regular arrangement of polymer chain segments, reduces the crystallinity of the polymer matrix, and thus improves ionic conductivity. Based on this, a low-temperature in-situ thermal polymerization process is employed to promote close interfacial contact while avoiding thermal decomposition of the gradient-interface-modified fast ion conductor ceramic particles and the polymer matrix. Furthermore, the synergistic effect of pulsed ultrasound and magnetic field is combined: ultrasonic cavitation breaks up particle agglomeration, and the magnetic field induces the directional alignment of the gradient-interface-modified fast ion conductor ceramic particles, jointly constructing a continuous and efficient ion conduction network. Ultimately, a composite solid electrolyte with high dispersibility, high ionic conductivity, and high interfacial compatibility is obtained.

[0069] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A composite solid electrolyte, characterized in that, include: The composition comprises a polymer matrix, a metal salt, and fast ion conductor ceramic particles. Both the metal salt and the fast ion conductor ceramic particles are dispersed in the polymer matrix. The fast ion conductor ceramic particles are coated from the inside out with an inorganic oxide layer and a fluorinated silane coupling agent. The fluorinated silane coupling agent is chemically bonded to the inorganic oxide layer.

2. The composite solid electrolyte according to claim 1, characterized in that, The fast ion conductor ceramic particles are selected from at least one of LATP, LATP derivatives, LLZO, LLZO derivatives, LAGP, LAGP derivatives, LLTO, and LLTO derivatives.

3. The composite solid electrolyte according to claim 1, characterized in that, The inorganic oxide layer includes at least one of SiO2, SiO2 hydrate, Al2O3, Al2O3 hydrate, ZrO2, ZrO2 hydrate, TiO2, and TiO2 hydrate.

4. The composite solid electrolyte according to claim 1, characterized in that, The fluorinated silane coupling agent includes at least one of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and heptadecafluorodecyltrimethoxysilane.

5. The composite solid electrolyte according to claim 1, characterized in that, The polymer matrix is ​​obtained by copolymerization of vinylidene fluoride monomers and fluorine-containing ionic liquid monomers, wherein the vinylidene fluoride monomers include vinylidene fluoride.

6. The composite solid electrolyte according to claim 5, characterized in that, The vinylidene fluoride monomers also include at least one of hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, and trifluorochloroethylene.

7. The composite solid electrolyte according to claim 5, characterized in that, The fluorinated ionic liquid monomer is selected from at least one of 1-vinyl-3-(trifluoroethyl)imidazolium and 1-vinyl-3-(pentafluoropropyl)pyrrolidineonium.

8. The composite solid electrolyte according to claim 1, characterized in that, The metal salt is selected from at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonate)imide, lithium hexafluorophosphate, lithium di(oxalate)borate, lithium di(fluorooxalate)borate, lithium nitrate, lithium perchlorate, lithium tetrafluoroborate, and lithium trifluoromethanesulfonate.

9. A method for preparing a composite solid electrolyte as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: An inorganic oxide layer is formed on the surface of fast ion conductor ceramic particles by surface deposition, resulting in fast ion conductor ceramic particles coated with an inorganic oxide layer. S2: Modify the fast ion conductor ceramic particles coated with inorganic oxide layers using a fluorinated silane coupling agent to obtain fast ion conductor ceramic particles coated with inorganic oxide layers and fluorinated silane coupling agents from the inside out. S3: The fast ion conductor ceramic particles, vinylidene fluoride monomers, fluorine-containing ionic liquid monomers, metal salts and initiators, which are sequentially coated with inorganic oxide layers and fluorine-containing silane coupling agents from the inside to the outside, are dissolved in a first solvent and subjected to in-situ thermal polymerization reaction, and then dried to obtain a composite solid electrolyte.

10. The method for preparing the composite solid electrolyte according to claim 9, characterized in that, Step S1 includes the following sub-steps: S11: Mix and disperse fast ion conductor ceramic particles with a second solvent; S12: Adjust the pH of the solution to alkaline, add the inorganic oxide precursor, and heat the reaction. S13: After washing and drying, fast ion conductor ceramic particles coated with an inorganic oxide layer are obtained.

11. The method for preparing the composite solid electrolyte according to claim 9, characterized in that, Step S2 includes the following sub-steps: The fast ion conductor ceramic particles coated with an inorganic oxide layer are dissolved in a third solvent along with a fluorinated silane coupling agent. Place the mixture in a protective atmosphere and heat it to react. After washing and drying, fast ion conductor ceramic particles are obtained, which are coated with an inorganic oxide layer and a fluorinated silane coupling agent from the inside out.

12. The method for preparing the composite solid electrolyte according to claim 9, characterized in that, The mass ratio of the fast ion conductor ceramic particles, which are sequentially coated with an inorganic oxide layer and a fluorinated silane coupling agent from the inside out, the vinylidene fluoride monomer, the fluorinated ionic liquid monomer, the metal salt, and the initiator is 1~6:5~18:1~10:1~15:0.01~1.

13. The method for preparing the composite solid electrolyte according to claim 9, characterized in that, The in-situ thermal polymerization reaction is carried out under the assistance of a protective atmosphere, a magnetic field, and pulsed ultrasound.

14. The method for preparing the composite solid electrolyte according to claim 13, characterized in that, The in-situ thermal polymerization reaction is carried out at a temperature of 70℃~100℃ and a reaction time of 5h~48h; the magnetic field strength is 0.1T~0.5T; the pulse ultrasound frequency is 10kHz~50kHz and the duty cycle is 30%~90%.

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