Preparation method of flexible composite solid electrolyte and application thereof

Abstract

The application relates to the technical field of solid-state batteries, and particularly relates to a flexible composite solid-state electrolyte preparation method and application thereof, which comprises, by weight, polyvinylidene fluoride-co-hexafluoropropylene 6-10 parts, modified LAYTPZn nanoparticles 5-8 parts, LATP particles 5-8 parts, lithium bistrifluoromethanesulfonimide 5-10 parts, N,N-dimethylformamide 10-15 parts, modified PVDF-HFP nanofiber felt 4-6 parts and fluorine-containing propylene acrylate copolymer 2-4 parts. The scheme provided in the application forms modified LAYTPZn nanoparticle material through double-element and doped LATP, breaks through the technical bottleneck from the double dimensions of crystal lattice structure and interface compatibility, effectively avoids material decomposition and conductive performance degradation, and further breaks through the limitation of single-element doping for optimizing single performance, so that the performance of the flexible composite solid-state electrolyte of the solid-state battery is improved.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and in particular to a method for preparing a flexible composite solid-state electrolyte and its application. Background Technology

[0002] Solid-state batteries, also known as solid-state batteries, are batteries that use solid electrodes and solid electrolytes. Unlike traditional lithium-ion batteries, solid-state batteries do not contain any liquid, giving them significant advantages in safety, energy density, and charging speed. Solid-state batteries operate based on ion flow; lithium ions move within the solid electrolyte to store and release electrical energy. This design allows solid-state batteries to maintain high performance even under high temperature and high pressure conditions.

[0003] Solid-state electrolytes are solid ionic conductors and electronic insulators. They are solid at room temperature or within the operating temperature range, capable of conducting lithium ions or other metal ions while blocking electrons. They replace the liquid electrolyte in traditional lithium batteries and have become the core component of solid-state batteries.

[0004] Among various solid electrolytes, sodium-type LATP electrolytes exhibit excellent air stability and a wide electrochemical window; however, the interfacial reaction between sodium-type LATP electrolytes and lithium metal can lead to… Reduction, material decomposition, and increased interfacial impedance lead to a degradation in conductivity, and the ionic conductivity is lower than that of traditional liquid electrolytes. Therefore, ion doping is chosen to improve its performance. However, existing single-element doping research focuses on optimizing a single performance and ignores the impact of lattice stability on long-term cycling. It is also difficult to break through the key threshold for improving ionic conductivity. Therefore, the design and preparation of LATP electrolytes with high ionic conductivity and high stability through multi-element doping still has the problem of low stability. Summary of the Invention

[0005] To overcome the problems existing in related technologies, this application provides a method for preparing a flexible composite solid electrolyte and its application.

[0006] To achieve the above objectives, the first aspect of the present invention provides a flexible composite solid electrolyte, comprising, by weight:

[0007] 6-10 parts of polyvinylidene fluoride-co-hexafluoropropylene, 5-8 parts of modified LAYTPZn nanoparticles, 5-8 parts of LATP particles, 5-10 parts of lithium bis(trifluoromethanesulfonylimide), 10-15 parts of N,N-dimethylformamide, 4-6 parts of modified PVDF-HFP nanofiber mat, and 2-4 parts of fluorinated acrylate copolymer.

[0008] The specific steps for preparing the modified LAYTPZn nanoparticles are as follows:

[0009] A1, prepare citric acid, tetrabutyl titanate, lithium nitrate, ammonium dihydrogen phosphate, aluminum nitrate nonahydrate, nano zinc oxide, anhydrous ethanol, deionized water and yttrium nitrate Y hexahydrate as raw materials;

[0010] A2, dissolve citric acid in deionized water, stir for 30 min to transparent, form citric acid aqueous solution, at the same time, dissolve tetrabutyl titanate in anhydrous ethanol, stir for 30 min to uniform, get tetrabutyl titanate solution, then drop citric acid aqueous solution into tetrabutyl titanate solution, and stir at the same time, stir in 80℃ water bath for 8h, form transparent citric acid titanium complex solution for standby;

[0011] A3, dissolve lithium nitrate and ammonium dihydrogen phosphate in citric acid aqueous solution, and continue to stir for 30 min to mix, get mixed mother liquor, at the same time, mix aluminum nitrate nonahydrate and yttrium nitrate Y hexahydrate, dissolve the mixture in citric acid aqueous solution, then transfer the mixed solution to ultrasonic dispersion machine to carry out ultrasonic dispersion for 30 min, get uniform suspension, at this time, drop the mixed mother liquor and the suspension into citric acid titanium complex solution in turn, stir for 30 min at constant temperature of 30℃, form milky white colloid;

[0012] A4, drop 2mol / L ammonia water into the milky white colloid to adjust pH to 7, then transfer the milky white colloid to oil bath pot with temperature of 120℃, heat and stir for 6h to form translucent elastic gel, then crush the translucent elastic gel and place it in crucible, heat to 900℃ at the rate of 10℃ / min, calcine in air atmosphere for 6h to remove organic matter and form porous LAYTP nano powder;

[0013] A5, put nano zinc oxide and porous LAYTP nano powder into agate mortar, manually grind for 15 min to preliminary mix, then transfer the mixture to zirconium dioxide ball mill jar and add anhydrous ethanol, use the zirconium dioxide ball mill jar to set 600rpm planetary ball milling for 6h, then transfer the ball milled mixture to ultrasonic dispersion machine to carry out ultrasonic dispersion for 1h, get uniform suspension;

[0014] A6, put the suspension into drying oven to remove ethanol, the drying temperature of the drying oven is 80℃, the drying time is 3h, after drying, further grind the solid into powder mixture, transfer the powder mixture to container, then put the container into sintering equipment to carry out multi-stage sintering treatment on the powder mixture, after sintering, take out the sintered sample and put it into oven to cool, then get modified LAYTPZn nanoparticles.

[0015] Preferably, the sintering of the powder mixture comprises the following steps:

[0016] A6.1, preheating section: the sintering temperature is 300-500℃, pre-sintering is performed at a temperature rising rate of 5℃ / min from room temperature to 500℃, the sintering time is 3h, and then the temperature is kept at 300℃ for 1h to remove the residual organic matter in the powder mixture;

[0017] A6.2, sintering section: the sintering temperature is 500-850℃, the pre-sintered powder after the low-temperature sintering is further sintered, and the temperature rising rate is adjusted to 10℃ / min, and when the temperature rises to 600℃, high-temperature crystallization is performed;

[0018] A6.3, holding section: when the sintering temperature is 850℃ in the medium-temperature section, the sintering is continuously performed at this temperature for 6h, so that a double-continuous phase network is formed at the grain boundaries of the porous LAYTP, and after sintering, the modified LAYTPZn nanoparticles are obtained.

[0019] Preferably, the preparation method of the modified PVDF-HFP nanofiber felt specifically comprises the following steps:

[0020] B1, polyvinylidene fluoride-co-hexafluoropropylene is selected and slowly added into a N,N-dimethylformamide solution, the stirring speed is set to 300-500r / min, and the stirring time is about 12-24h until the polyvinylidene fluoride-co-hexafluoropropylene is completely dissolved to form a uniform transparent solution, then 1wt.% lithium bis(trifluoromethanesulfonyl)imide is added, and the stirring is continued for 6-8h to obtain a mixed solution, and then the mixed solution is degassed by ultrasonic for 40min to remove the bubbles in the mixed solution;

[0021] B2, an electrospinning device is prepared, the liquid flow rate of the electrospinning device is controlled at 0.5-1.5mL / h, the voltage is set to 15-20kV, the distance between the needle of the electrospinning device and the receiving screen is kept at 15-20cm, the temperature is set to 20-30℃, and the humidity is kept at 30%-50%, the prepared mixed solution is loaded into a syringe and installed on the electrospinning device, the device is started to spin, the receiving screen is a drum type, the rotating speed of the receiving screen is set to 300-600r / min, the spinning time is 2-6h, and the mixed solution is spun into a fiber felt by the electrospinning device;

[0022] B3, the nanofiber felt obtained by spinning is taken off from the receiving screen and placed in a vacuum drying oven for drying treatment, the drying temperature is set to 60-80℃, the drying time is 12-24h, so as to remove the residual solvent in the fiber felt, after drying, the fiber felt is soaked in a silane coupling agent ethanol solution with a mass fraction of 2%-5%, the soaking time is 1-2h, after soaking, the fiber felt is taken out and cleaned by ethanol, then is placed in a vacuum drying oven for drying at 60℃ for 6-12h, to obtain a modified PVDF-HFP nanofiber felt, then the modified PVDF-HFP nanofiber felt is cut into a required size and shape.

[0023] To achieve the above object, the second aspect of the present application provides a preparation method of a flexible composite solid electrolyte, which is applied to the flexible composite solid electrolyte, and the preparation method of the flexible composite solid electrolyte is prepared by the following steps:

[0024] S1, polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, fluorine-containing acrylic ester copolymer, lithium bis-trifluoromethanesulfonimide, N,N-dimethylformamide are prepared, then the polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, fluorine-containing acrylic ester copolymer are added to N,N-dimethylformamide for dissolution, to obtain a mixed solution, then the mixed solution is transferred to a high-speed shearing dispersion machine, and the high-speed shearing dispersion machine is started to break the mixed solution into agglomerates;

[0025] S2, after the agglomerates are processed by the high-speed shearing dispersion machine, the agglomerates are transferred to a constant-temperature magnetic stirrer, the constant-temperature magnetic stirrer is started to further stir and mix the agglomerates, to form a uniform mixed suspension, then lithium bis-trifluoromethanesulfonimide is added to the constant-temperature magnetic stirrer, and stirring is continued until complete dissolution and mixing, to obtain a transparent light brown mixed solution, which is an inner liquid;

[0026] S3, polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, lithium bis-trifluoromethanesulfonimide, N,N-dimethylformamide are prepared, and are processed according to the same preparation process of S1 and S2, to generate a middle layer solution;

[0027] S4, polyvinylidene fluoride-co-hexafluoropropylene, LATP particles, lithium bis-trifluoromethanesulfonimide, N,N-dimethylformamide are prepared, the polyvinylidene fluoride-co-hexafluoropropylene and the LATP particles are first added to an ultrasonic dispersion machine, and the ultrasonic dispersion machine is started to disperse and mix the materials, to obtain a mixture, and the subsequent preparation process is the same as that of S1 and S2, to obtain an outer solution;

[0028] S5, the modified PVDF-HFP nanofiber mat is laid on a clean glass plate, and then a small amount of N, N-dimethylformamide is sprayed on the surface of the modified PVDF-HFP nanofiber mat to uniformly spray the surface and enhance the adhesion with the functional layer. Then, an inner layer solution is uniformly coated on the surface of the modified PVDF-HFP nanofiber mat using a doctor blade coater, a 50-micron coating blade is used to form a lithium-philic interface layer, and then the glass plate coated with the lithium-philic interface layer is transferred to a fume hood, and is left still at room temperature of 25℃ for 1h and humidity of <30% to form a semi-solid gel film. Then, a 100-micron coating blade is used to replace the 50-micron coating blade, the glass plate coated with the lithium-philic interface layer is taken out of the fume hood, and then the middle layer solution is uniformly coated on the surface of the lithium-philic interface layer to form a conductive layer. Then, the glass plate coated with the two layers is placed in the fume hood in the same way as above for drying, the coating blade of the doctor blade coater is replaced with a 50-micron blade, and the outer layer solution is coated on the surface of the conductive layer to form an anti-puncture surface layer;

[0029] S6, then the coated glass plate is placed in a vacuum oven, the vacuum degree of the vacuum oven is set to 50pa, the semi-solid gel film coated on the glass plate is heated to 60℃, and then dried at room temperature for 12h. After drying is completed, the vacuum degree of the vacuum oven is set to 10pa, and the semi-solid gel film coated on the glass plate is heated to 80℃. After heating is completed, drying is continued for 12h, and the finished product is taken off from the glass plate to obtain a film sheet;

[0030] S7, while step S6 is being performed, a 5wt.% F-AC / DMF solution is prepared by stirring and mixing a fluorine-containing acrylate copolymer and N, N-dimethylformamide. The 5wt.% F-AC / DMF solution is uniformly coated on both sides of the film sheet using a micropipette, and then the film sheet is placed in an oven for drying, with an oven temperature of 60℃ and a drying time of 30min-1h;

[0031] S8, finally, a stainless steel punch with a diameter of 16mm is used to punch a disc in the center area of the film sheet to obtain a finished product film sheet, which is then immediately transferred to a dry glove box with a water / oxygen content of <1ppm, sealed in a sealed bag to avoid moisture absorption or oxidation, to obtain a finished electrolyte film sheet.

[0032] Preferably, the rotation speed of the high-speed shearing disperser in S1 is 8000rpm, and the shearing dispersion time is 10-20min;

[0033] The stirring speed of the magnetic stirrer in S2 is 200rpm, the stirring temperature is 65-80℃, the stirring time is 12-24h, and the stirring time after adding lithium bis-trifluoromethanesulfonimide in the constant-temperature magnetic stirrer is 15-30h.

[0034] The ultrasonic dispersion time of the ultrasonic dispersion machine in S4 is 30-60 min, and the power of the ultrasonic dispersion machine is 200 W.

[0035] Preferably, the lithiumophilic interface layer in S5 is a wet film with a thickness of 10-15 microns, the conductive layer is a wet film with a thickness of 60-70 microns, the anti-puncture surface layer is a wet film with a thickness of 10-15 microns, and the application thickness of the modified PVDF-HFP nanofiber felt is 5-10 microns.

[0036] The total film thickness of the modified PVDF-HFP nanofiber felt, the lithiumophilic interface layer, the conductive layer and the anti-puncture surface layer is 90-110 microns.

[0037] To achieve the above-mentioned purpose, the third aspect of the present application provides a full solid-state battery, a solid-state electrolyte obtained according to the preparation method of the flexible composite solid-state electrolyte or the application of the flexible composite solid-state electrolyte in the full solid-state battery.

[0038] Preferably, the parts by weight include:

[0039] The battery positive electrode aluminum foil, the battery negative electrode lithium foil, the flexible composite solid-state electrolyte, the solvent and the binder;

[0040] The manufacturing method of the full solid-state battery is specifically as follows:

[0041] Q1, the flexible composite solid-state electrolyte powder, the active material, the solvent and the binder are mixed and stirred into a uniform slurry, the slurry is coated on the battery positive electrode aluminum foil of the positive electrode current collector and the battery negative electrode lithium foil of the negative electrode current collector, and then dried to remove the solvent;

[0042] Q2, the shell of the full solid-state battery is prepared, then the flexible composite solid-state electrolyte film is added into the shell and stacked, and then the battery positive electrode aluminum foil and the battery negative electrode lithium foil are hot-pressed to the two ends of the shell of the full solid-state battery to obtain the full solid-state battery.

[0043] To achieve the above-mentioned purpose, the fourth aspect of the present application provides a power utilization equipment, characterized in that it comprises the full solid-state battery.

[0044] The technical scheme provided in the present application can include the following beneficial effects:

[0045] 1、The present application forms a modified LAYTPZn nanoparticle material by doping LATP with two elements And Break through the technical bottleneck of the prior art from the dual dimensions of crystal lattice structure and interface compatibility, and form a modified LAYTPZn nanoparticle material from the crystal lattice level, And Substituting the LATP lattice respectively at and Site, form lattice distortion and expand lithium ion migration channel, make ion conductivity from pure LATP to , while High redox potential inhibits Spontaneous reduction at the lithium metal interface, combined with surface modification, forms a fluorine-containing polymer affinity layer on the surface of the modified LAYTPZn nanoparticles, reduces the interfacial impedance of the electrolyte and lithium foil from 200Ω・cm 2 to 50Ω・cm 2 Below, effectively avoid material decomposition and degradation of conductive performance, and then break through the limitation of single element doping only optimizing single performance, through multi-element collaborative doping and surface functionalization, synchronous realization interface stability and ion conduction ability promotion, solve the core problem of poor compatibility of LATP-based electrolyte and lithium metal;

[0046] 2、On the basis of double element doping, through the gradient composite structure of "nanofiber support layer-function conduction layer-puncture protection layer", further optimize the interface contact and mechanical properties of the electrolyte, the middle conduction layer uses modified PVDF-HFP nanofiber felt, its three-dimensional porous structure not only provides fast migration channel for lithium ions, but also improves the tensile strength of the electrolyte film to meet the service requirements of flexible battery bending radius, the inner layer introduces fluorine-containing acrylic ester copolymer as an interface modifier, forms a lithiumophilic interface layer through the hydrogen bond between fluorine-containing groups and the hydroxyl groups on the surface of the positive electrode made of lithium nickel cobalt manganese oxide, reduces the positive electrode / electrolyte interface impedance and improves the conductive performance, the outer layer adds LATP particles, uses its high hardness to build a physical barrier to inhibit lithium dendrite puncture, and controls the interface impedance increase in the cycle process within 10%, the structure design realizes the gradient matching of material components and film layer function, improves the interface stability while giving the electrolyte excellent mechanical adaptability, solves the problems of poor interface and toughness of solid electrolyte, improves the toughness and fracture resistance of solid electrolyte, and interface strength;

[0047] 3、The present application realizes the leap-forward improvement of the long-term cycle stability of solid electrolyte through the three-dimensional technical path of "doping modification-interface modification-structure enhancement", through the cooperation of multiple technologies, breaks through the bottleneck that the ion conductivity and stability of existing LATP-based electrolyte are difficult to be considered, and provides stability support for the manufacture of high-energy-density solid-state battery.

[0048] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0049] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the figures, and in which:

[0050] Figure 1 is a schematic diagram of LAYTP-Zn ceramic sheet shown in the embodiments of the present application;

[0051] Figure 2 is a schematic diagram of the preparation process of LAYTP-Zn solid electrolyte shown in the embodiments of the present application;

[0052] Figure 3 is a schematic diagram of Rietveld refinement curve of LAYTP-Zn and LATP shown in the embodiments of the present application;

[0053] Figure 4 is a schematic diagram of XRD and EIS spectrum of solid electrolyte and LAYTP shown in the embodiments of the present application;

[0054] Figure 5 is a schematic diagram of total elemental spectrum of LAYTP-Zn shown in the embodiments of the present application;

[0055] Figure 6 is a schematic diagram of Li+ migration potential barrier transported by vacancy migration in LATP, LATP-Zn and LAYTP-Zn shown in the embodiments of the present application;

[0056] Figure 7 is a schematic diagram of charge density difference of LATP, LATP-Zn and LAYTP-Zn shown in the embodiments of the present application;

[0057] Figure 8 is a schematic diagram of total and partial density of states of calculated LATP, LATP-Zn and LAYTP-Zn structure shown in the embodiments of the present application. DETAILED DESCRIPTION

[0058] The preferred embodiments of the present application will be described in detail with reference to the drawings. Although the preferred embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0059] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in this application, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "and / or", as used herein, refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0060] It should be noted that when an element is referred to as being "fixed" or "set" to another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or indirectly connected to the other element.

[0061] In the description of the application, it should be understood that the terms "thickness", "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0062] In the description of the application, it should be noted that unless otherwise specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0063] The technical solutions of the embodiments of the application are described in detail below with reference to the drawings.

[0064] Embodiment 1

[0065] In this embodiment, a flexible composite solid electrolyte comprises, by weight parts:

[0066] Polyvinylidene fluoride-co-hexafluoropropylene 6-10 parts, modified LAYTPZn nanoparticles 5-8 parts, LATP particles 5-8 parts, lithium bis-trifluoromethanesulfonimide 5-10 parts, N,N-dimethylformamide 10-15 parts, modified PVDF-HFP nanofiber felt 4-6 parts, fluorine-containing acrylate copolymer 2-4 parts;

[0067] The preparation method of the flexible composite solid electrolyte is prepared according to the following steps:

[0068] S1, prepare polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, fluorine-containing acrylic ester copolymer, lithium bis-trifluoromethanesulfonimide, N, N-dimethylformamide, then add polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, fluorine-containing acrylic ester copolymer to N, N-dimethylformamide for dissolution, to obtain a mixed solution, then transfer the mixed solution to a high-speed shearing dispersion machine, start the high-speed shearing dispersion machine to break the mixed solution into agglomerates;

[0069] S2, after the high-speed shearing dispersion machine is processed to obtain the agglomerates, the agglomerates are transferred to a constant temperature magnetic stirrer, the constant temperature magnetic stirrer is started to further stir and mix the agglomerates, a uniform mixed suspension is formed, then lithium bis-trifluoromethanesulfonimide is added to the constant temperature magnetic stirrer, and stirring is continued until complete dissolution and mixing, to obtain a transparent light brown mixed solution, which is an inner layer liquid;

[0070] S3, prepare polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, lithium bis-trifluoromethanesulfonimide, N, N-dimethylformamide, process according to the same preparation process of S1 and S2 to generate a middle layer solution;

[0071] S4, prepare polyvinylidene fluoride-co-hexafluoropropylene, LATP particles, lithium bis-trifluoromethanesulfonimide, N, N-dimethylformamide, first add polyvinylidene fluoride-co-hexafluoropropylene and LATP particles to an ultrasonic dispersion machine, start the ultrasonic dispersion machine to disperse and mix the materials to obtain a mixture, the subsequent preparation process is the same as that of S1 and S2, to obtain an outer layer solution;

[0072] S5, lay the modified PVDF-HFP nanofiber felt on a clean glass plate, then spray a small amount of N, N-dimethylformamide on the surface of the modified PVDF-HFP nanofiber felt, uniformly spray the surface to enhance the adhesion with the functional layer, then use a doctor blade coater to uniformly coat the inner layer solution on the surface of the modified PVDF-HFP nanofiber felt, use a 50-micron coating blade to form a lithium-philic interface layer, then transfer the glass plate coated with the lithium-philic interface layer to a fume hood, stand still for 1 h at room temperature 25℃ and humidity <30%, to form a semi-solid gel film, then replace the 100-micron coating blade, take out the glass plate coated with the lithium-philic interface layer from the fume hood, then uniformly coat the middle layer solution on the surface of the lithium-philic interface layer to form a conductive layer, then put the glass plate coated with two layers into the fume hood in the same way as above for drying, then replace the coating blade of the doctor blade coater with a 50-micron blade, and coat the outer layer solution on the surface of the conductive layer to form a puncture-resistant surface layer;

[0073] S6, then the coated glass plate is placed into a vacuum oven for heating, the vacuum degree of the vacuum oven is set to 50 pa, the semi-solid gel film coated on the glass plate is heated to 60°C, then normal temperature drying is performed for 12 h, after drying is completed, the vacuum degree of the vacuum oven is set to 10 pa, and the semi-solid gel film coated on the glass plate is heated to 80°C, after heating is completed, drying is continuously performed for 12 h, the finished product is taken off from the glass plate, and a film piece is obtained;

[0074] S7, while step S6 is performed, a 5wt.% F-AC / DMF solution is prepared, the 5wt.% F-AC / DMF solution is prepared by stirring and mixing fluorine-containing acrylate copolymer and N,N-dimethylformamide, the 5wt.% F-AC / DMF solution is uniformly coated on both sides of the film piece by using a micro pipette, then the film piece is placed into an oven for drying, the oven temperature is 60°C, and the drying time is 30 min to 1 h;

[0075] S8, finally, a stainless steel punch die with a diameter of 16 mm is used to punch a circular piece in the central region of the film piece, a finished product film piece is obtained, then the finished product film piece is immediately transferred to a dry glove box, the water / oxygen content of the dry glove box is less than 1 ppm, the film piece is packaged in a sealed bag to avoid moisture absorption or oxidation, and a finished product electrolyte film piece is obtained.

[0076] Example 2

[0077] In this embodiment, a flexible composite solid-state electrolyte includes, by weight:

[0078] 6-10 parts of polyvinylidene fluoride-co-hexafluoropropylene, 5-8 parts of LATP particles, 5-10 parts of lithium bis(trifluoromethanesulfonyl)imide, 10-15 parts of N,N-dimethylformamide, 4-6 parts of modified PVDF-HFP nanofiber felt, and 2-4 parts of fluorine-containing acrylate copolymer;

[0079] The preparation method of the flexible composite solid-state electrolyte is as follows:

[0080] The preparation process is the same as that in example 1, except that the modified LAYTPZn nanoparticles are not added compared with example 1.

[0081] Example 3

[0082] In this embodiment, a flexible composite solid-state electrolyte includes, by weight:

[0083] 6-10 parts of polyvinylidene fluoride-co-hexafluoropropylene, 5-8 parts of LATP particles, 5-8 parts of modified LAYTPZn nanoparticles, 5-10 parts of lithium bis(trifluoromethanesulfonyl)imide, 10-15 parts of N,N-dimethylformamide, and 2-4 parts of fluorine-containing acrylate copolymer;

[0084] The preparation method of the flexible composite solid electrolyte is as follows:

[0085] The preparation process is the same as that of Example 1, except that no modified PVDF-HFP nanofiber felt is added as the base layer of the electrolyte film compared with Example 1.

[0086] Comparative Example 1

[0087] Polyvinylidene fluoride-co-hexafluoropropylene 6 parts, LATP particles 5 parts, lithium bis-trifluoromethanesulfonimide 9 parts, N,N-dimethylformamide 12 parts.

[0088] The preparation method is the preparation process of the existing solid electrolyte, specifically, polyvinylidene fluoride-co-hexafluoropropylene, LATP particles, lithium bis-trifluoromethanesulfonimide and N,N-dimethylformamide are mixed, then coated by a doctor blade, dried at 80°C for 24 hours in vacuum, to form a single-layer unsupported electrolyte film.

[0089] Test experiment

[0090] Ion conductivity test at different temperatures

[0091] Sample preparation:

[0092] The electrolyte films of each example and comparative example are punched into φ16mm round pieces, and the thickness uniformity error is ≤±5μm.

[0093] Test equipment:

[0094] Electrochemical workstation (using Shanghai Chenhua CHI660E model), stainless steel blocking electrode (φ16mm, purity ≥99.9%).

[0095] Test steps:

[0096] The electrode / film / electrode is assembled into a sandwich structure, and a pressure of 10kPa is applied for fixation;

[0097] The frequency scanning range is 1Hz-1MHz, and the amplitude of the alternating signal is 5mV;

[0098] The impedance spectrum is fitted, the bulk resistance Rb is extracted, and the conductivity is calculated by the formula σ=d / (Rb×A), where σ is the ion conductivity, d is the film thickness, and A is the electrode area.

[0099] Activation energy, Li+transference number, electrochemical window and loading capacity test

[0100] Battery assembly:

[0101] Lithium foil (φ18mm, thickness 50μm, Sigma-Aldrich) / electrolyte film / lithium foil, assembled into a CR2032 button cell.

[0102] Test equipment:

[0103] The same electrochemical workstation, test frequency 10 4 -10 6 Hz.

[0104] Data processing:

[0105] Fitting the high-frequency region semicircle arc diameter to obtain the activation energy, Li+ migration number, electrochemical window and loading data.

[0106] Tensile strength and bending radius test

[0107] Tensile strength:

[0108] Sample: cut into 50mm x 10mm long strip, uniform in thickness direction;

[0109] Equipment: Instron5967 universal material testing machine, selected from Shanghai Stema Industrial Co., Ltd., clamping distance 20mm, tensile speed 5mm / min;

[0110] Index: record the maximum stress (MPa) at break.

[0111] Bending radius:

[0112] Manually repeat the bending of the film until cracks appear, and record the minimum bending radius (mm) when there are no cracks.

[0113] 50℃ cycle capacity retention rate test

[0114] Full cell assembly:

[0115] Positive electrode: lithium nickel cobalt manganese oxide 80 parts + conductive carbon black 10 parts + PVDF-HFP 10 parts (coated on aluminum foil, surface capacity 1.5mAh / cm 2 );

[0116] Negative electrode: lithium foil (φ18mm);

[0117] Electrolyte membrane: φ16mm round piece, inject 10μL carbonate electrolyte (only wet the interface, not liquid electrolyte).

[0118] Test equipment:

[0119] New Wei battery test system, model CT-4008, selected from Shenzhen Xinnwei production and manufacturing, 50℃ constant temperature box (accuracy ±1℃).

[0120] Test method:

[0121] 0.5C rate charge-discharge (1C=200 mA / g), voltage window 3.0-4.2V, cycle 1000 times, record the first cycle and every 100 cycles discharge capacity.

[0122] Table 1 is the performance test results of the solid electrolyte membrane ion conductivity at different temperatures:

[0123] ;

[0124] Table 2 is the performance test results of the solid electrolyte membrane:

[0125] ;

[0126] Table 3 is the long-term cycle performance test results of the solid electrolyte membrane:

[0127] ;

[0128] It can be seen that the ion conductivities of Examples 1 and 3 are both ≥1.2×10 -4 S / cm, which is increased by 60% to 73% compared with Example 2 and Comparative Example 1 (1.2×10 -5 S / cm and 7.5×10 -5 S / cm), proving that the Zn 2+ / Y 3+ doping of the modified LAYTPZn nanoparticles expands the lithium ion channel through lattice distortion, breaking through the traditional LATP conductivity bottleneck.

[0129] The slight increase in the conductivity of Example 1 to 1.3×10 -4 S / cm is due to the increase in the porosity of the support layer, which provides a more unobstructed path for ion migration.

[0130] Interface stability: synergistic effect of surface modification and gradient modification

[0131] The double-sided modification (0.8 μm) of Example 1 makes the impedance increase by only +30% after 1000 cycles (Comparative Example 1 +150%), effectively inhibiting the interface side reactions (such as lithium dendrite growth, Mn dissolution).

[0132] Mechanical properties: nanofiber support layer is the key

[0133] The tensile strength (12-15 MPa) of Examples 1-3 is increased by 50% to 87.5% compared with Comparative Example 1 (8 MPa), and the modified PVDF-HFP nanofiber mat (8-10 μm thick) provides three-dimensional network support, and the elongation at break is all >100%;

[0134] Example 3 has no cracks with a bending radius ≤5 mm, meeting the folding requirements of flexible batteries, while Comparative Example 1 is broken with a bending radius >15 mm, verifying the significant improvement in flexibility of the gradient structure.

[0135] Long-term cycling stability: breakthrough by full-gradient design

[0136] The capacity retention of Example 1 is 86.8% after 1000 cycles at 50°C, far exceeding 59.5% of Comparative Example 1 and 83.3% of Example 3, thanks to:

[0137] The outer LATP particles construct a physical barrier, and the lithium dendrite penetration time is >500h (only 150h for Comparative Example 1);

[0138] The high-porosity support layer (70%) reduces the shrinkage of the membrane layer (thickness change <5%), avoiding mechanical fatigue during cycling;

[0139] The double-sided interface modification layer uniformly covers the positive and negative electrodes, suppressing the increase of interface impedance (30% increase vs. 150% increase of Comparative Example 1).

[0140] Therefore, Example 1 realizes functional layering optimization and full-gradient enhancement design by double-element doping, which is the core mechanism for breaking through the LATP conductivity and interface stability. Compared with Comparative Example 2 and Example 3, each index has obvious improvement, and compared with the above Comparative Example 1, the performance has more obvious improvement.

[0141] Table Four is a summary table of LAYTP-Zn ion conductivity (Example 1 as standard):

[0142] ;

[0143] As to the apparatus in the above examples, the specific manner in which each module performs operations has been described in detail in the embodiments related to the method, and will not be described in detail here.

[0144] The solutions of the present application have been described in detail above with reference to the accompanying drawings. In the above examples, the description of each example has its own focus, and the parts not described in detail in a certain example can be referred to the relevant description of other examples. It should also be known by those skilled in the art that the actions and modules involved in the specification are not necessarily required by the present application. In addition, it can be understood that the steps in the method of the embodiments of the present application can be adjusted, combined and reduced in sequence according to actual needs, and the modules in the device of the embodiments of the present application can be combined, divided and reduced according to actual needs.

[0145] Having described various embodiments of the application, it is to be understood that the above description is meant not to limit and not to encompass all of the possible embodiments. Many modifications and variations of this application can be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. It is intended that the scope of the application be defined by the scope of the patent and by the claims as allowed by the patent office, which can include adaptations based on the description, equivalents, and / or substitutions of elements individually or collectively to the entire disclosure.

Claims

1. A flexible composite solid electrolyte, characterized in that, Portions by weight include: 6-10 parts of polyvinylidene fluoride-co-hexafluoropropylene, 5-8 parts of modified LAYTPZn nanoparticles, 5-8 parts of LATP particles, 5-10 parts of lithium bis(trifluoromethanesulfonylimide), 10-15 parts of N,N-dimethylformamide, 4-6 parts of modified PVDF-HFP nanofiber mat, and 2-4 parts of fluorinated acrylate copolymer. The specific steps for preparing the modified LAYTPZn nanoparticles are as follows: A1. Prepare citric acid, tetrabutyl titanate, lithium nitrate, ammonium dihydrogen phosphate, aluminum nitrate nonahydrate, nano zinc oxide, anhydrous ethanol, deionized water and yttrium nitrate hexahydrate as raw materials; A2. Dissolve citric acid in deionized water and stir for 30 minutes until transparent to form an aqueous citric acid solution. At the same time, dissolve tetrabutyl titanate in anhydrous ethanol and stir for 30 minutes until homogeneous to obtain a tetrabutyl titanate solution. Then, add the aqueous citric acid solution dropwise to the tetrabutyl titanate solution while stirring. Stir in an 80°C water bath for 8 hours to form a transparent titanium citrate complex solution for later use. A3. Lithium nitrate and ammonium dihydrogen phosphate are dissolved in an aqueous citric acid solution and stirred continuously for 30 minutes to obtain a mixed mother liquor. At the same time, aluminum nitrate nonahydrate and yttrium nitrate hexahydrate are mixed and dissolved in an aqueous citric acid solution. The mixture is then transferred to an ultrasonic disperser for ultrasonic dispersion for 30 minutes to obtain a uniform suspension. At this time, the mixed mother liquor and the suspension are added dropwise to a titanium citrate complex solution and stirred at a constant temperature of 30°C for 30 minutes to form a milky white colloid. A4. Add 2 mol / L ammonia to the milky white colloid to adjust the pH to 7. Then transfer the milky white colloid to an oil bath at 120°C and heat and stir for 6 hours to form a translucent elastic gel. Then break the translucent elastic gel and place it in a crucible. Increase the temperature to 900°C at 10°C / min and calcine in air atmosphere for 6 hours to remove organic matter and form porous LAYTP nanopowder. A5. Add nano zinc oxide and porous LAYTP nano powder into an agate mortar and grind by hand for 15 minutes until initially mixed. Then transfer the mixture to a zirconia ball mill jar and add anhydrous ethanol. Use the zirconia ball mill jar to set 600 rpm for planetary ball milling for 6 hours. Then transfer the ball-milled mixture to an ultrasonic disperser and ultrasonically disperse for 1 hour to obtain a uniform suspension. A6. The suspension is placed in a drying oven to remove ethanol. The drying temperature of the drying oven is 80°C and the drying time is 3 hours. After drying, the solid is further ground into a powder mixture. The powder mixture is transferred to a container and then placed in a sintering device to perform multi-stage sintering treatment on the powder mixture. After sintering is completed, the sintered sample is taken out and placed in an oven for cooling to obtain modified LAYTPZn nanoparticles.

2. The flexible composite solid electrolyte according to claim 1, characterized in that, The sintering of the powder mixture includes the following steps: A6.1 Preheating section: The sintering temperature is 300-500℃. During the sintering of the powder mixture, the temperature is increased from room temperature to 500℃ at a heating rate of 5℃ / min for pre-sintering. The sintering time is 3h. Then, the temperature is kept at 300℃ for 1h to remove the residual organic matter in the powder mixture. A6.2 Sintering section: The sintering temperature is 500-850℃. The pre-sintered powder that has been sintered in the low-temperature section is sintered again. The heating rate is adjusted to 10℃ / min. High-temperature crystallization occurs when the temperature rises to 600℃. A6.3, Heat preservation section: When the sintering temperature in the medium temperature section is 850℃, the sintering is continued at this temperature for 6 hours to solidify the porous LAYTP into a bicontinuous phase network. After sintering is completed, modified LAYTPZn nanoparticles can be obtained.

3. The flexible composite solid electrolyte according to claim 1, characterized in that, The specific steps for preparing the modified PVDF-HFP nanofiber mat are as follows: B1. Select polyvinylidene fluoride-co-hexafluoropropylene and slowly add it to N,N-dimethylformamide solution. Set the stirring speed to 300-500 r / min and the stirring time to about 12-24 h until polyvinylidene fluoride-co-hexafluoropropylene is completely dissolved to form a uniform and transparent solution. Then add 1 wt.% lithium bis(trifluoromethanesulfonyl)imide and continue stirring for 6-8 h to obtain a mixture. Then use ultrasonic degassing for 40 min to remove air bubbles from the mixture. B2. Prepare the electrospinning equipment. Set the liquid flow rate of the electrospinning equipment to 0.5-1.5 mL / h, the voltage to 15-20 kV, the distance between the needle and the receiving screen to 15-20 cm, the temperature to 20-30℃, and the humidity to 30%-50%. Load the prepared mixture into the syringe, install it on the electrospinning equipment, and turn on the equipment to start spinning. The receiving screen is a roller type, and the rotation speed of the receiving screen is set to 300-600 r / min. The spinning time is 2-6 hours. The mixture is spun into fiber mat through the electrospinning equipment. B3. Remove the nanofiber felt obtained from the spinning screen and place it in a vacuum drying oven for drying. Set the drying temperature to 60-80℃ and the drying time to 12-24h to remove residual solvent from the fiber felt. After drying, immerse the fiber felt in a 2%-5% silane coupling agent ethanol solution for 1-2h. After immersion, remove the fiber felt, rinse it with ethanol, and then place it in a vacuum drying oven at 60℃ for 6-12h to obtain modified PVDF-HFP nanofiber felt. Then cut the modified PVDF-HFP nanofiber felt into the required size and shape.

4. A method for preparing a flexible composite solid electrolyte, applied to the flexible composite solid electrolyte according to any one of claims 1-3, characterized in that, The flexible composite solid electrolyte is prepared by the following steps: S1. Prepare polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, fluorinated acrylate copolymer, lithium bis(trifluoromethanesulfonyl)imide, and N,N-dimethylformamide. Then, dissolve the polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, and fluorinated acrylate copolymer in N,N-dimethylformamide to obtain a mixture. Then, transfer the mixture to a high-speed shear disperser and start the high-speed shear disperser to break the mixture into agglomerates. S2. After the high-speed shear disperser processes the agglomerates, the agglomerates are transferred to a constant temperature magnetic stirrer. The constant temperature magnetic stirrer is started to further stir and mix the agglomerates to form a uniform mixed suspension. Then, lithium bis(trifluoromethanesulfonylimide) is added to the constant temperature magnetic stirrer and stirring is continued until it is completely dissolved and mixed to obtain a transparent light brown mixed liquid, which is the inner liquid. S3. Prepare polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, lithium bis(trifluoromethanesulfonylimide), and N,N-dimethylformamide, and process them according to the same preparation process as steps S1 and S2 to generate a middle layer solution. S4. Prepare polyvinylidene fluoride-co-hexafluoropropylene, LATP particles, lithium bis(trifluoromethanesulfonylimide), and N,N-dimethylformamide. First, add polyvinylidene fluoride-co-hexafluoropropylene and LATP particles to an ultrasonic disperser. Start the ultrasonic disperser to disperse and mix the materials to obtain a mixture. The subsequent preparation process is the same as steps S1 and S2 to obtain the outer layer solution. S5. The modified PVDF-HFP nanofiber felt is laid flat on a clean glass plate. Then, a small amount of N,N-dimethylformamide is sprayed onto the surface of the modified PVDF-HFP nanofiber felt to evenly coat the surface and enhance the adhesion to the functional layer. Then, the inner layer solution is evenly coated onto the surface of the modified PVDF-HFP nanofiber felt using a doctor blade coater with a 50-micron coating blade to form a lithiophilic interface layer. The glass plate coated with the lithiophilic interface layer is then transferred to a fume hood and left to stand at room temperature (25°C) for 1 hour with a humidity of <30% to form a semi-solid gel film. Then, the doctor blade is replaced with a 100-micron coating blade, and the glass plate coated with the lithiophilic interface layer is taken out of the fume hood. The middle layer solution is then evenly coated onto the surface of the lithiophilic interface layer to form a conductive layer. The glass plate coated with both layers is then placed into a fume hood for drying in the same manner as above. Then, the doctor blade of the doctor blade coater is replaced with a 50-micron blade, and the outer layer solution is coated onto the surface of the conductive layer to form a puncture-resistant surface layer. S6. Then, the coated glass plate is placed in a vacuum oven and heated. The vacuum degree of the vacuum oven is set to 50 Pa. The semi-solid gel film coated on the glass plate is heated to 60°C and then dried at room temperature for 12 hours. After drying, the vacuum degree of the vacuum oven is set to 10 Pa and the semi-solid gel film coated on the glass plate is heated to 80°C. After heating, the semi-solid gel film is dried for another 12 hours. The finished product is then removed from the glass plate to obtain the film. S7. While performing step S6, prepare a 5wt.% F-AC / DMF solution. The 5wt.% F-AC / DMF solution is prepared by stirring and mixing a fluorinated acrylate copolymer and N,N-dimethylformamide. Use a micropipette to uniformly coat the 5wt.% F-AC / DMF solution onto both sides of the membrane. Then, place the membrane in an oven to dry it. The oven temperature is 60°C and the drying time is 30 min to 1 h. S8. Finally, using a 16mm diameter stainless steel die, a circular piece is punched in the center area of ​​the membrane to obtain the finished membrane. The finished membrane is then immediately transferred to a drying glove box. The drying glove box has a water / oxygen content of <1ppm and is sealed in a sealed bag to prevent moisture absorption or oxidation, thus obtaining the finished electrolyte membrane.

5. The method for preparing a flexible composite solid electrolyte according to claim 4, characterized in that: The high-speed shear disperser described in S1 has a rotation speed of 8000 rpm and a shear dispersion time of 10-20 min; The magnetic stirrer described in S2 has a stirring speed of 200 rpm, a stirring temperature of 65-80℃, and a stirring time of 12-24 h. After adding lithium bis(trifluoromethanesulfonyl)imide to the constant-temperature magnetic stirrer, the stirring time is 15-30 h. The ultrasonic dispersion time of the ultrasonic disperser in S4 is 30-60 minutes, and the power of the ultrasonic disperser is 200W.

6. The method for preparing a flexible composite solid electrolyte according to claim 4, characterized in that: The lithiophilic interface layer in S5 is a wet film with a thickness of 10-15 μm, the conductive layer is a wet film with a thickness of 60-70 μm, the puncture-resistant surface layer is a wet film with a thickness of 10-15 μm, and the coating thickness of the modified PVDF-HFP nanofiber felt is 5-10 μm. The total film thickness of the modified PVDF-HFP nanofiber mat, the lithiophilic interface layer, the conductive layer, and the puncture-resistant surface layer is 90-110 micrometers.

7. An all-solid-state battery, comprising a solid electrolyte obtained by the preparation method of a flexible composite solid electrolyte according to any one of claims 1-3 or any one of claims 4-6, mainly for the application of the flexible composite solid electrolyte in all-solid-state batteries.

8. A solid-state battery according to claim 7, characterized in that, include: Battery positive electrode aluminum foil, battery negative electrode lithium foil, flexible composite solid electrolyte, solvent and binder; The specific method for manufacturing the all-solid-state battery is as follows: Q1. Flexible composite solid electrolyte powder, active material, solvent and binder are mixed and stirred into a uniform slurry. The slurry is coated on the positive electrode aluminum foil of the battery with positive electrode current collector and the negative electrode lithium foil of the battery with negative electrode current collector. Then it is dried to remove the solvent. Q2. Prepare the casing of the all-solid-state battery, then add flexible composite solid electrolyte membranes inside the casing and stack them, and then hot-press the positive electrode aluminum foil and the negative electrode lithium foil to both ends of the all-solid-state battery casing to obtain the all-solid-state battery.

9. An electrical appliance, characterized in that, Including the all-solid-state battery as described in claim 7.

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