A lithium fluoride solid-state electrolyte, a preparation method and application thereof

Abstract

This invention provides a lithium fluoride solid electrolyte, its preparation method, and its applications. The lithium fluoride solid electrolyte comprises a conductive polymer, a lithium salt, and a lithium fluoride composite nanomaterial. The lithium fluoride composite nanomaterial and the lithium salt are uniformly dispersed in the conductive polymer. The lithium fluoride composite nanomaterial comprises a modified nanomaterial and a first lithium fluoride. The surface of the modified nanomaterial has a modification layer formed by a silane coupling agent or by grafting and crosslinking a silane coupling agent with a functional organic compound. The first lithium fluoride is grafted to the modification layer at least through chemical bonding. This invention solves the problem of the difficulty in uniformly dispersing lithium fluoride in solid electrolytes with high content by constructing a lithium fluoride composite nanomaterial and distributing it uniformly in the conductive polymer. It also forms a solid electrolyte system with dual ion transport channels, improving ionic conductivity.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, specifically relating to a lithium fluoride solid electrolyte, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles and 5G communication technology, higher requirements have been placed on the safety, energy density, and cycle performance of lithium-ion batteries. However, the liquid carbonate compounds currently used in commercial lithium-ion battery electrolytes pose safety hazards such as leakage, expansion, corrosion, and flammability. Solid electrolytes can be used to mitigate these risks and manufacture safer lithium batteries. Based on their composition, they can be classified into nano-solid electrolytes, polymer solid electrolytes, and composite solid electrolytes.

[0003] To facilitate lithium-ion transport between the solid electrolyte and the electrode active material, a stable and robust interfacial contact is required between the electrode and the solid electrolyte membrane. Traditional polymer all-solid-state electrolytes, due to their excellent high-temperature ductility and high chemical stability to air and lithium metal anodes, simplified the fabrication process of all-solid-state lithium metal batteries, making them the earliest commercially available all-solid-state electrolytes. However, polymer all-solid-state electrolytes generally have a narrow electrochemical window, are prone to decomposition in high-voltage regions, and typically exhibit low ionic conductivity, making them difficult to apply at room temperature. Practical applications usually require temperatures up to 60°C.

[0004] To overcome the above problems, nanofillers are incorporated into polymer all-solid electrolytes to form all-solid electrolyte membranes. These membranes not only meet the requirements of high ionic conductivity, high-voltage charge-discharge stability, and suppression of lithium dendrite growth during long cycles, but also simplify complex steps in battery manufacturing, improving production efficiency and reducing production costs. Nanofillers play three main roles: 1) reducing crystallinity and increasing the amorphous phase region, which is beneficial for Li... + Migration; 2) Rapid Li can form near the filler particles. + 3) Enhance the mechanical properties of the polymer matrix to facilitate film formation. Based on their ion-conducting capabilities, nanofillers can be categorized into inert fillers and active fillers. Inert fillers do not transport lithium ions and are primarily composed of silica, alumina, and zirconium oxide. Active materials can participate in ion conduction processes and are mainly composed of oxide solid electrolyte fillers and sulfide solid electrolyte fillers.

[0005] LiF is generally considered an important component in the construction of the SEI layer in liquid electrolytes, and it remains a promising candidate for solid electrolytes. However, due to its inherent low solubility and chemical inertness, how to introduce LiF into solid electrolyte systems and achieve good and uniform dispersion is one of the most pressing problems to be solved. Summary of the Invention

[0006] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions:

[0007] A first aspect of the present invention provides a lithium fluoride solid electrolyte comprising a conductive polymer, a lithium salt, and a lithium fluoride composite nanomaterial, wherein the lithium fluoride composite nanomaterial and the lithium salt are uniformly dispersed in the conductive polymer;

[0008] The lithium fluoride composite nanomaterial includes a modified nanomaterial and a first lithium fluoride. The surface of the modified nanomaterial has a modification layer, which is formed by a silane coupling agent or by grafting and crosslinking a silane coupling agent with a functional organic compound. The first lithium fluoride is grafted onto the modification layer at least by chemical bonding.

[0009] This invention employs silane coupling agents and selectable functional organic compounds to modify nanomaterials. Utilizing the interaction between lithium fluoride and the modification layer, lithium fluoride is grafted onto the modified nanofiller to form a core-shell structure, achieving a stable composite of lithium fluoride and the modified nanomaterials. The resulting lithium fluoride composite nanomaterial with a lithium fluoride-rich modified interface can be uniformly distributed within conductive polymers and is less prone to agglomeration. This solves the problem of lithium fluoride's inherent low solubility and chemical inertness, which makes it difficult to introduce high concentrations and achieve good, uniform dispersion in solid-state electrolyte systems.

[0010] Furthermore, the solid electrolyte provided by the present invention is a solid electrolyte with a dual-channel conductive network, which includes a first ion transport channel and a second ion transport channel. The lithium fluoride composite nanomaterial provides the first ion transport channel (i.e., bulk transport on the surface of the lithium fluoride composite nanomaterial), and the lithium salt and the conductive polymer are cross-linked to form the second ion transport channel, thereby significantly improving the ion conductivity.

[0011] This solid-state electrolyte, with its unique core-shell coating structure and dual-channel conductive network design, also possesses excellent mechanical properties and interfacial stability. During battery charge-discharge cycles, it can effectively suppress the growth of lithium dendrites and reduce the occurrence of interfacial side reactions, thereby significantly improving the cycle life and safety performance of solid-state batteries.

[0012] In some embodiments, the silane coupling agent may include one or a combination of multiple selected from polyethylene glycol acrylate, 3-(trimethoxysilyl)propyl methacrylate, triethoxysilane polyethylene glycol acrylate, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, and epoxysilane. These silane coupling agents can be modified onto the surface of nanomaterials using silane coupling technology to form a modified layer. The first lithium fluoride is chemically bonded to the modified layer formed by the silane coupling agent.

[0013] In some embodiments, the functional organic compound is a small molecule organic compound with a molecular weight in the range of 2000 Da to 20000 Da.

[0014] In some embodiments, the functional organic compound may include one or more of the following: ester organic compounds, carboxymethyl cellulose, chitosan, silk fibroin, dopamine hydrochloride, and polyacrylonitrile. The ester organic compounds may include, for example, one or more of the following: ethylene carbonate, diethyl carbonate, fluoroethylene carbonate, methyl ethyl carbonate, triethyl borate, propylene carbonate, triphenyl phosphate, tetraethyl silicate, diethyl sulfate, difluoroethylene carbonate, ethylene ethylene carbonate, and polymethyl methacrylate.

[0015] It should be noted that if the silane coupling agent is selected from the aforementioned acrylate silane esters (such as polyethylene glycol acrylate, 3-(trimethoxysilyl)propyl methacrylate, or triethoxysilane polyethylene glycol acrylate), and / or in embodiments where the functional organic material is further selected and grafted with the silane coupling agent to form a modified layer, if the functional organic material is selected from the aforementioned ester organic materials, then a portion of the first lithium fluoride can also be dissolved in these ester materials and remain free in the organic chain segments of the modified layer. In this case, a portion of the first lithium fluoride is grafted onto the modified layer through chemical bonding, and a portion of the first lithium fluoride dissolves in the organic chain segments of the modified layer.

[0016] In some embodiments, the nanomaterials used to form the modified nanomaterials can be suitable nanomaterials known in the art, such as any one or more of inert nanofillers, active nanomaterials, and functional nanofillers.

[0017] For example, inert nanofillers include, but are not limited to, any one or more of SiO2, TiO2, Al2O3, and Ga2O3; active nanomaterials include, but are not limited to, active oxide-based perovskites, NASICON-type or garnet structures and sulfides, and may further specifically be lithium saponite, LATP, LLZTO, LLTO, Li 10 GeP2S 12 Li7P3S 11 Li6PS5X (where X is Cl, Br, or I); functional nanofillers include, but are not limited to, silver nanoparticles, copper nanoparticles, MOFs, two-dimensional materials (graphene oxide, hexagonal boron nitride, clay sheets, etc.), succinic acid, etc. Any type of nanofiller can be selected, or multiple combinations can be used.

[0018] The lithium salt refers to a lithium salt other than lithium fluoride. The lithium salt can be any suitable lithium salt known in the art, such as one or more combinations of LiCl, LiPF6, LiTFSI, LiFSI, LiClO4, LiBF4, LiAsF6, LiDFOB, and LiBOB, but is not limited thereto.

[0019] The conductive polymer can be any suitable known polymer used in the preparation of solid electrolytes in the art, including but not limited to one or more of the following: silk protein, chitosan, carboxymethyl cellulose, dopamine hydrochloride, sodium alginate, polyamide, polymethyl methacrylate, polyacrylonitrile, polyvinyl alcohol, polyethylene oxide, polyethylene glycol, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, polyvinylpyrrolidone, and mirin.

[0020] In some embodiments, the mass ratio of the conductive polymer to the lithium salt is (1-10):1.

[0021] In some embodiments, the mass ratio of the lithium fluoride composite nanomaterial to the conductive polymer is (0.05-0.5):1.

[0022] In some embodiments, the mass ratio of the modified nanomaterial to the first lithium fluoride in the lithium fluoride composite nanomaterial is (1~10):(0.05~1), or (1~10):(0.05~0.5).

[0023] In some embodiments, the lithium fluoride solid electrolyte further includes a second lithium fluoride, which is uniformly dispersed in the conductive polymer, and the mass ratio of the second lithium fluoride to the conductive polymer is (0.01~0.05):1. Adding the second lithium fluoride allows the electrolyte system to contain saturated or excess lithium fluoride, forming a lithium fluoride-rich solid electrolyte. The LiF-rich design can suppress the growth of lithium dendrites.

[0024] The lithium fluoride solid electrolyte provided by this invention exhibits good interfacial compatibility with the electrode, as well as high ionic conductivity and excellent mechanical strength and properties. Solid-state lithium metal batteries prepared based on this dual-channel lithium fluoride-rich solid electrolyte demonstrate excellent cycle performance and rate performance.

[0025] A second aspect of the present invention provides a method for preparing a lithium fluoride solid electrolyte, comprising: A modification layer is formed on the surface of a nanomaterial using a silane coupling agent and a selectable functional organic compound, and the first lithium fluoride is grafted onto the modification layer at least by chemical bonding. The lithium fluoride composite nanomaterial and lithium salt are uniformly dispersed in a conductive polymer to obtain a lithium fluoride solid electrolyte.

[0026] In some embodiments, the preparation method specifically includes: silanizing the nanomaterial with a silane coupling agent to obtain modified nanomaterials; then mixing the modified nanomaterials with a first lithium fluoride to carry out a first reaction to obtain the lithium fluoride composite nanomaterials.

[0027] In some embodiments, the silane coupling agent includes one or a combination of multiple of the following: polyethylene glycol acrylate, 3-(trimethoxysilyl)propyl methacrylate, triethoxysilane polyethylene glycol acrylate, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, and epoxysilane.

[0028] The silanization of nanomaterials can be achieved using currently known silane coupling techniques, and this invention does not impose any particular limitations. After hydrolysis, the aforementioned silane coupling agent forms XOH groups (X represents the nanomaterial) on the surface of the nanomaterial through its SiOH groups, and rapidly adsorbs onto the nanomaterial surface via a condensation reaction, forming Si-OX covalent bonds at the particle interface.

[0029] In some embodiments, the reaction temperature of the first reaction is 20°C to 120°C.

[0030] In some embodiments, the first reaction time is 1 hour to 10 hours.

[0031] In some embodiments, the mass ratio of the silane coupling agent to the nanomaterial used in the silanization can be (1~10):(0.05~1).

[0032] In some embodiments, the mass ratio of the modified nanomaterial to the first lithium fluoride used in the first reaction is (1~10):(0.05~1), or (1~10):(0.05~0.5).

[0033] In some embodiments, the preparation method specifically includes: subjecting a mixed reaction system containing a silane coupling agent, a functional organic compound, and nanomaterials to a second reaction, and then adding a first lithium fluoride and a selectable crosslinking agent to a third reaction to obtain the lithium fluoride composite nanomaterial.

[0034] In some embodiments, the reaction temperature of the second reaction is 20°C to 120°C.

[0035] In some embodiments, the reaction time of the second reaction is 1 hour to 10 hours.

[0036] In some embodiments, the reaction temperature of the third reaction is 20°C to 120°C.

[0037] In some embodiments, the reaction time of the third reaction is 1 hour to 10 hours.

[0038] In some embodiments, the mass ratio of silane coupling agent, functional organic compound, and nanomaterial in the mixed reaction system is (0.01~5):(0.1~10):(0.05~5), and the mass ratio of the added nanomaterial to lithium fluoride is (1~10):(0.05~1).

[0039] In some embodiments, the silane coupling agent includes one or a combination of multiple of the following: polyethylene glycol acrylate, 3-(trimethoxysilyl)propyl methacrylate, triethoxysilane polyethylene glycol acrylate, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, and epoxysilane.

[0040] In some embodiments, the functional organic compound includes one or more of the following: carboxymethyl cellulose, chitosan, silk fibroin, dopamine hydrochloride, polyacrylonitrile, ethylene carbonate, diethyl carbonate, fluoroethylene carbonate, methyl ethyl carbonate, triethyl borate, propylene carbonate, triphenyl phosphate, tetraethyl silicate, diethyl sulfate, difluoroethylene carbonate, ethylene ethylene carbonate, and polymethyl methacrylate.

[0041] In some embodiments, the crosslinking agent may include, for example, one or more of the following: epichlorohydrin, tetrabutylammonium chloride, copper fluoride, triphenyl phosphite, triallyl phosphate, triphenyl phosphate, ammonium hexafluorophosphate, boron nitride, 1,2,3,6-tetrahydrophthalic anhydride, metal-organic framework (MOF), covalent organic framework (COF), silver nanoparticles, and copper nanoparticles, but is not limited thereto.

[0042] In some embodiments, the mass ratio of the conductive polymer to the lithium salt is (1-10):1.

[0043] In some embodiments, the mass ratio of the lithium fluoride composite nanomaterial to the conductive polymer is (0.05-0.5):1.

[0044] In some embodiments, the preparation method specifically includes: uniformly dispersing the lithium fluoride composite nanomaterial, lithium salt, and second lithium fluoride in the conductive polymer, wherein the mass ratio of the second lithium fluoride to the conductive polymer is (0.01~0.05):1.

[0045] In some embodiments, the preparation method specifically includes: uniformly mixing a mixture containing the lithium fluoride composite nanomaterial, lithium salt, conductive polymer, optional second lithium fluoride, and solvent, and sequentially performing drying, film formation, and hot pressing treatment. This produces a lithium fluoride solid electrolyte membrane with a thickness of 3μm-100μm, such as any value of 3μm, 10μm, 30μm, and 100μm, or any combination of two values. In the mixture, the solid content of the lithium fluoride composite nanomaterial can be 0.01wt%-20wt%, and the solid content of the second lithium fluoride can be 0.01wt%-20wt%.

[0046] In some embodiments, the conductive polymer and lithium salt are first dispersed in a solvent at a mass ratio of (1~10):1, and then 5%-50% of the mass of the conductive polymer is added as lithium fluoride composite nanomaterial to form the mixture. The mixture is then dried to form a film.

[0047] In some embodiments, the solvent used to prepare the mixture may include one or more of the following: water, ethanol, formic acid, acetic acid, acetonitrile, dichloromethane, tetrahydrofuran, n-hexane, n-heptane, toluene, xylene, n-decane, methylformamide, hexafluoroisopropanol, N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, fluoroethylene carbonate, vinylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, 1,3-dioxolane, 2-methyltetrahydrofuran, dimethoxymethane, 1,2-dimethoxyethylene, diethylene glycol dimethyl ether, and ionic liquids.

[0048] In some embodiments, the hot-pressing treatment involves a pressure of 1 MPa to 100 MPa, a temperature of 30°C to 80°C, and a time of 3 min to 180 min. The resulting solid electrolyte is characterized by its ultrathin and dense structure.

[0049] The preparation method provided in the second aspect of this invention can be used to prepare the lithium fluoride solid electrolyte described in the first aspect of this invention. The preparation method provided by this invention is simple, operates under mild conditions, and is easily scalable, laying a solid foundation for the widespread application of lithium fluoride solid electrolytes in the field of high-performance solid-state batteries.

[0050] A third aspect of the present invention provides a lithium fluoride solid electrolyte, which is prepared by the preparation method described in any of the technical solutions.

[0051] A fourth aspect of the present invention provides a solid-state lithium metal battery, comprising a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte is a lithium fluoride solid electrolyte as described in any of the technical solutions.

[0052] Solid-state lithium metal batteries based on the dual-channel conductive network solid electrolyte of this invention exhibit excellent electrochemical performance, demonstrating superior cycle performance and rate performance.

[0053] Compared with the prior art, the present invention has at least the following beneficial effects: The present invention uses silane coupling agents and selective functional organic compounds to modify nanomaterials, and utilizes the interaction between lithium fluoride and the modification layer to form lithium fluoride composite nanomaterials on modified nanofillers, and uniformly distributes them on conductive polymers to form solid electrolytes. This not only solves the problem that it is difficult to introduce high content and uniformly disperse lithium fluoride in solid electrolyte systems due to its low solubility and chemical inertness, but also enables the construction of a lithium fluoride-rich solid electrolyte system with dual ion transport channels. This design gives it high conductivity and inhibits the growth of lithium dendrites, thus improving the performance of solid-state batteries. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram showing the uniform dispersion of lithium fluoride composite nanomaterials in a conductive polymer framework in the dual-channel lithium fluoride solid electrolyte membrane prepared in Example 1.

[0056] Figure 2 These are photographs of the SiO2 nanomaterials in Example 1 before and after silanization using γ-GPS;

[0057] Figure 3 These are photographs and SEM images of the dual-channel lithium fluoride solid electrolyte membrane prepared in Example 1.

[0058] Figure 4 These are photographs of the LLZTO nanomaterials in Example 2 before and after silanization.

[0059] Figure 5 These are photographs and SEM images of the dual-channel lithium fluoride solid electrolyte membrane prepared in Example 2.

[0060] Figure 6 This is a schematic diagram of the structure of an assembled lithium metal solid-state battery;

[0061] Figure 7 This is an electrochemical stability window diagram of the dual-channel lithium fluoride solid electrolyte membranes in Examples 1-3. Detailed Implementation

[0062] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0063] In addition, unless otherwise specified, all raw materials used in the following embodiments can be purchased from the market or other sources, and all production and testing equipment used are known in the art, as are the testing methods used.

[0064] Example 1

[0065] This embodiment provides a dual-channel lithium fluoride solid electrolyte membrane and its preparation method, specifically including the following steps:

[0066] (1) Preparation of lithium fluoride composite nanomaterials:

[0067] 300 mg of SiO2 was dispersed in a mixture of 90 ml ethanol and 10 ml deionized water by ultrasonic treatment, and then 30 mg of 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane (γ-GPS) was added to form a dispersion. Under vigorous stirring, the pH of the dispersion was adjusted to 4 with oxalic acid and stirred vigorously at 75 °C for 4 hours. Afterward, the γ-GPS-grafted SiO2 was collected by centrifugation, and then washed several times with a mixture of DI water and ethanol. Finally, the product was dried at 60 °C overnight to obtain the modified nanomaterial.

[0068] Lithium fluoride was dissolved in hydrochloric acid to prepare a lithium fluoride hydrochloric acid solution. The modified nanomaterials prepared above were added to the solution, with a mass ratio of modified nanomaterials to lithium fluoride of 1:0.05. The resulting precipitate was dispersed in anhydrous ethanol and ultrasonically treated to obtain lithium fluoride composite nanomaterials.

[0069] (2) Preparation of dual-channel lithium fluoride solid electrolyte membrane: Polyethylene oxide (PEO) and LiTFSI with a mass ratio of 5:1 and a total mass of 3g were mixed and dissolved in 30mL of anhydrous acetonitrile. The lithium fluoride composite nanomaterial and LiF prepared above were added to the above solution. The amount of lithium fluoride composite nanomaterial added was 5wt% of the mass of polyethylene oxide and the amount of LiF added was 5wt% of the mass of polyethylene oxide, and a mixture was obtained. The mixture was stirred at 60℃ and 500r / min for 8h, and then vacuum dried at 60℃ for 8h to obtain an electrolyte membrane. The obtained membrane was hot-pressed at 80℃ for 90min under a pressure of 60MPa to obtain a dual-channel lithium fluoride solid electrolyte membrane with a membrane thickness in the range of 40μm-80μm.

[0070] Figure 1 This is a schematic diagram showing the uniform dispersion of lithium fluoride composite nanomaterials in a conductive polymer framework in the dual-channel lithium fluoride solid electrolyte membrane prepared in this embodiment. Figure 2 These are photographs of the SiO2 nanomaterials in Example 1 before and after silanization using γ-GPS. Figure 3 These are photographs and SEM images of the dual-channel lithium fluoride solid electrolyte membrane prepared in Example 1.

[0071] Example 2

[0072] This embodiment provides a dual-channel lithium fluoride solid electrolyte membrane and its preparation method, specifically including the following steps:

[0073] (1) Preparation of lithium fluoride composite nanomaterials:

[0074] 0.39 g of LLZTO nanomaterials were dissolved in 1.6 g of ethylene carbonate (EC), and 0.01 g of 3-(trimethoxysilyl)propyl methacrylate was added. The mixture was stirred at 100 °C for 2 h. Then, 0.05 g of epichlorohydrin and 0.2 g of LiF were added to the reaction system, and the mixture was stirred at room temperature for another 1 h to obtain lithium fluoride composite nanomaterials.

[0075] (2) Preparation of dual-channel lithium fluoride solid electrolyte membrane: Polyethylene oxide (PEO) and LiTFSI with a mass ratio of 5:1 and a total mass of 3g were dissolved in 30mL of anhydrous acetonitrile. The LiF-EC-LLZTO and LiF prepared above were added to the above solution. The amount of lithium fluoride composite nanomaterial added was 5wt% of the mass of polyethylene oxide and the amount of LiF added was 5wt% of the mass of polyethylene oxide, and a mixture was obtained. After stirring at 500r / min for 8h, the mixture was vacuum dried at 60℃ for 8h to obtain an electrolyte membrane. The obtained membrane was hot-pressed at 80℃ for 90min under a pressure of 60MPa to obtain a dual-channel lithium fluoride solid electrolyte membrane with a thickness in the range of 60μm-100μm.

[0076] Figure 4 These are photographs of the LLZTO nanomaterials in Example 2 before and after silanization. Figure 5 These are photographs and SEM images of the dual-channel lithium fluoride solid electrolyte membrane prepared in Example 2.

[0077] Example 3

[0078] This embodiment provides a dual-channel lithium fluoride solid electrolyte membrane and its preparation method, specifically including the following steps:

[0079] (1) Preparation of lithium fluoride composite nanomaterials:

[0080] 0.39 g of LLZTO nanomaterials were dissolved in 20 g of anhydrous acetonitrile solvent, and 0.01 g of acrylate polyethylene glycol silane and 0.16 g of carboxymethyl cellulose (CMC) were added. The mixture was stirred for 2 h. Then, 0.2 g of LiF was added to the reaction system and the mixture was stirred for another 1 h to allow LiF to be grafted and copolymerized with carboxyl groups to obtain lithium fluoride composite nanomaterials.

[0081] (2) Preparation of dual-channel lithium fluoride solid electrolyte membrane: Polyethylene oxide (PEO) and LiTFSI with a mass ratio of 5:1 and a total mass of 3g were mixed and dissolved in 30mL of anhydrous acetonitrile. 1.25g of the lithium fluoride composite nanomaterial and 0.1g of LiF were added to the solution. After stirring at 500r / min for 8h, the solution was dried under vacuum at 60℃ for 8h to obtain an electrolyte membrane. The membrane was then hot-pressed at 80℃ for 90min under a pressure of 60MPa to obtain a dual-channel lithium fluoride solid electrolyte membrane with a thickness in the range of 10μm-30μm.

[0082] Example 4

[0083] The only difference between Example 4 and Example 1 is that in Example 4, when preparing the dual-channel lithium fluoride solid electrolyte membrane, the conductive polymer used is polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and the solvent for dispersing PVDF-HFP is dimethylformamide (DMF). The rest of the process is the same as in Example 1, and will not be repeated here.

[0084] Example 5

[0085] This embodiment provides a dual-channel lithium fluoride solid electrolyte membrane and its preparation method, specifically including the following steps:

[0086] (1) Preparation of lithium fluoride composite nanomaterials:

[0087] 0.39 g of LLZTO nanomaterials, 1.6 g of dopamine hydrochloride and 0.01 g of 3-(trimethoxysilyl)propyl methacrylate were mixed and stirred in an oxygen atmosphere for 2 h; then 0.05 g of organic branched salt tetrabutylammonium chloride and 0.2 g of LiF were added, and stirring was continued for 1 h to obtain lithium fluoride composite nanomaterials.

[0088] (2) Preparation of dual-channel lithium fluoride solid electrolyte membrane: Polyethylene oxide (PEO) and LiTFSI with a mass ratio of 5:1 and a total mass of 3g were dissolved in 30mL of anhydrous acetonitrile. The LiF-PDa-LLZTO and LiF prepared above were added to the above solution. The amount of lithium fluoride composite nanomaterial added was 5wt% of the mass of polyethylene oxide and the amount of LiF added was 5wt% of the mass of polyethylene oxide, and a mixture was obtained. After stirring at 500r / min for 8h, the mixture was vacuum dried at 60℃ for 8h to obtain an electrolyte membrane. The obtained membrane was hot-pressed at 80℃ for 90min under a pressure of 60MPa to obtain a dual-channel lithium fluoride solid electrolyte membrane with a thickness of 60μm-100μm.

[0089] Example 6

[0090] The only difference between Example 6 and Example 2 is that, in the preparation of the dual-channel lithium fluoride solid electrolyte membrane, the mass ratio of polyethylene oxide and LiTFSI is 1:1, the amount of lithium fluoride composite nanomaterial is 5 wt% of the mass of polyethylene oxide, and the amount of LiF is 1 wt% of the mass of polyethylene oxide. The rest is the same as in Example 2, and will not be repeated here.

[0091] Example 7

[0092] The only difference between Example 7 and Example 2 is that, in the preparation of the dual-channel lithium fluoride solid electrolyte membrane, the mass ratio of polyethylene oxide to LiTFSI is 10:1, the amount of lithium fluoride composite nanomaterial is 50 wt% of the mass of polyethylene oxide, and the amount of LiF is 5 wt% of the mass of polyethylene oxide. The rest is the same as in Example 2, and will not be repeated here.

[0093] Example 8

[0094] The only difference between Example 8 and Example 2 is that the hot pressing process conditions in the preparation of the dual-channel lithium fluoride solid electrolyte membrane are: pressure of 1 MPa, temperature of 30°C, and time of 180 min.

[0095] The rest is the same as in Example 2, and will not be described again here.

[0096] Example 9

[0097] The only difference between Example 9 and Example 2 is that the hot pressing process conditions in the preparation of the dual-channel lithium fluoride solid electrolyte membrane are: pressure of 100 MPa, temperature of 60°C, and time of 3 min.

[0098] The rest is the same as in Example 2, and will not be described again here.

[0099] Example 10

[0100] The only difference between Example 10 and Example 2 is that in Example 10, during the preparation of the dual-channel lithium fluoride solid electrolyte membrane, LiF is not added separately. Instead, a composite nanomaterial of polyethylene oxide (PEO), LiTFSI, and lithium fluoride is used to prepare the dual-channel lithium fluoride solid electrolyte membrane, with the same amount of each as in Example 2. The rest of the process is the same as in Example 2 and will not be repeated here.

[0101] Comparative Example 1

[0102] The difference between Comparative Example 1 and Example 2 is that Comparative Example 1 does not use lithium fluoride composite nanomaterials, but instead directly uses polyethylene oxide (PEO), LiTFSI, and LiF to prepare a solid electrolyte membrane, with the same amount of the three as in Example 2. The rest of the procedures are the same as in Example 2, and will not be repeated here.

[0103] Comparative Example 2

[0104] The difference between Comparative Example 2 and Example 2 is that Comparative Example 2 does not use 3-(trimethoxysilyl)propyl methacrylate and ethylene carbonate to modify the LLZTO nanomaterials. Instead, it directly mixes the LLZTO nanomaterials with polyethylene oxide, LiTFSI, and LiF to prepare a solid electrolyte membrane. Furthermore, the amount of LiF used in Comparative Example 2 is equal to the total amount of LiF on the lithium fluoride composite nanomaterials in Example 2 plus any additional LiF added during the preparation of the electrolyte membrane. The rest of the procedures are the same as in Example 1 and will not be repeated here.

[0105] The ionic conductivity of the dual-channel lithium fluoride solid electrolyte membrane prepared in the above embodiments was tested, and the test results of the dual-channel lithium fluoride solid electrolyte membrane are summarized in Table 1.

[0106] Table 1. Relevant test results of dual-channel lithium fluoride solid electrolyte membrane

[0107] Figure 7 This is an electrochemical stability window diagram of the dual-channel lithium fluoride solid electrolyte membranes used in Examples 1-3. (The last sentence appears to be incomplete and possibly refers to a different method.) Figure 7 It can be seen that the system has a high electrochemical window and can be adapted to high-voltage systems.

[0108] The present invention also uses the dual-channel lithium fluoride solid electrolyte membrane prepared in the above specific embodiments to assemble lithium metal solid batteries, and uses CR2032 button batteries (MTI Corporation) to assemble them in an argon-filled glove box, where the H2O and O2 content in the assembly environment is less than 0.3ppm. Figure 6 This is a schematic diagram of the assembled lithium metal solid-state battery. The dual-channel lithium fluoride solid electrolyte membrane of this invention is disposed between the positive electrode material (NMC and LFP) and the lithium metal. An aluminum foil is disposed on the side of the positive electrode material away from the dual-channel lithium fluoride solid electrolyte membrane. Cycle performance tests were performed on the battery, and the test results are shown in Table 2.

[0109] Table 2

[0110] As shown in Table 2, the battery based on the dual-channel lithium fluoride solid electrolyte membrane of the present invention has better cycle stability.

[0111] In addition, the applicant also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the foregoing embodiments, and obtained relatively ideal results in all cases.

[0112] All aspects, embodiments, features, and examples of this invention should be considered illustrative and used to explain and illustrate the invention, but not to limit the invention. The scope of the invention is defined only by the claims.

[0113] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims.

Claims

1. A lithium fluoride solid electrolyte, characterized in that, The invention comprises a conductive polymer, a lithium salt, and a lithium fluoride composite nanomaterial, wherein the lithium fluoride composite nanomaterial and the lithium salt are uniformly dispersed in the conductive polymer. The lithium fluoride composite nanomaterial includes a modified nanomaterial and a first lithium fluoride. The surface of the modified nanomaterial has a modification layer, which is formed by a silane coupling agent or by grafting and crosslinking a silane coupling agent with a functional organic compound. The first lithium fluoride is grafted onto the modification layer at least by chemical bonding.

2. The lithium fluoride solid electrolyte according to claim 1, characterized in that: The silane coupling agent includes one or a combination of multiple of the following: acrylate polyethylene glycol silane, 3-(trimethoxysilyl)propyl methacrylate, triethoxysilane polyethylene glycol acrylate, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, and epoxysilane.

3. The lithium fluoride solid electrolyte according to claim 1, characterized in that: The functional organic compounds include one or more of the following: carboxymethyl cellulose, chitosan, silk fibroin, dopamine hydrochloride, polyacrylonitrile, ethylene carbonate, diethyl carbonate, fluoroethylene carbonate, methyl ethyl carbonate, triethyl borate, propylene carbonate, triphenyl phosphate, tetraethyl silicate, diethyl sulfate, difluoroethylene carbonate, ethylene ethylene carbonate, and polymethyl methacrylate.

4. The lithium fluoride solid electrolyte according to claim 1, characterized in that: The mass ratio of the conductive polymer to the lithium salt is (1~10):1, and the mass ratio of the lithium fluoride composite nanomaterial to the conductive polymer is (0.05~0.5):

1. And / or, in the lithium fluoride composite nanomaterial, the mass ratio of the modified nanomaterial to the first lithium fluoride is (1~10):(0.05~1); And / or, the lithium fluoride solid electrolyte further includes a second lithium fluoride, which is uniformly dispersed in the conductive polymer, and the mass ratio of the second lithium fluoride to the conductive polymer is (0.01~0.05):

1.

5. The method for preparing lithium fluoride solid electrolyte according to claim 1, characterized in that, include: A modification layer is formed on the surface of a nanomaterial using a silane coupling agent and a selectable functional organic compound, and the first lithium fluoride is grafted onto the modification layer at least by chemical bonding. The lithium fluoride composite nanomaterial and lithium salt are uniformly dispersed in a conductive polymer to obtain a lithium fluoride solid electrolyte.

6. The preparation method according to claim 5, characterized in that, Specifically, it includes: Modified nanomaterials were prepared by silanizing nanomaterials with silane coupling agents. Then, the modified nanomaterial is mixed with lithium fluoride to carry out a first reaction, thereby obtaining the lithium fluoride composite nanomaterial; Alternatively, a second reaction is carried out in a mixed reaction system containing a silane coupling agent, a functional organic compound, and nanomaterials, followed by the addition of a first lithium fluoride and a selective crosslinking agent to carry out a third reaction, thereby obtaining the lithium fluoride composite nanomaterials.

7. The preparation method according to claim 6, characterized in that: The reaction temperature of the first reaction is 20℃~120℃; and / or, the reaction time of the first reaction is 1h~10h; and / or, the mass ratio of the modified nanomaterial to the first lithium fluoride used in the first reaction is (1~10):(0.05~1). And / or, the reaction temperature of the second and third reactions is 20℃~120℃; and / or, the reaction time of the second and third reactions is 1h~10h; And / or, in the mixed reaction system, the mass ratio of silane coupling agent, functional organic compound, and nanomaterial is (0.01~5):(0.1~10):(0.05~5), and the mass ratio of the added nanomaterial to lithium fluoride is (1~10):(0.05~0.5). And / or, the silane coupling agent comprises one or more of the following: polyethylene glycol acrylate, 3-(trimethoxysilyl)propyl methacrylate, triethoxysilane polyethylene glycol acrylate, 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane, and epoxysilane; And / or, the functional organic compound includes one or more combinations of carboxymethyl cellulose, chitosan, silk fibroin, dopamine hydrochloride, polyacrylonitrile, ethylene carbonate, diethyl carbonate, fluoroethylene carbonate, methyl ethyl carbonate, triethyl borate, propylene carbonate, triphenyl phosphate, tetraethyl silicate, diethyl sulfate, difluoroethylene carbonate, ethylene ethylene carbonate, and polymethyl methacrylate.

8. The preparation method according to claim 5, characterized in that: The mass ratio of the conductive polymer to the lithium salt is (1-10):1, and the mass ratio of the lithium fluoride composite nanomaterial to the conductive polymer is (0.05-0.5):

1. And / or, the preparation method specifically includes: uniformly dispersing the lithium fluoride composite nanomaterial, lithium salt, and second lithium fluoride in the conductive polymer, wherein the mass ratio of the second lithium fluoride to the conductive polymer is (0.01~0.05):1; And / or, the preparation method specifically includes: uniformly mixing a mixture containing the lithium fluoride composite nanomaterial, lithium salt, conductive polymer and solvent, and sequentially performing drying, film formation and hot pressing treatment; the pressure of the hot pressing treatment is 1 MPa-100 MPa, the temperature is 30℃-80℃ and the time is 3 min-180 min.

9. A lithium fluoride solid electrolyte, characterized in that, It is prepared by the preparation method according to any one of claims 5-8.

10. A solid-state lithium metal battery, comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that, The electrolyte is the lithium fluoride solid electrolyte according to any one of claims 1-4 and 9.

Images