Preparation method and application of flexible composite solid electrolyte

Abstract

The invention relates to the technical field of solid batteries, in particular to a flexible composite solid electrolyte preparation method and application thereof.The flexible composite solid electrolyte is prepared from, by weight, 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 (trifluoromethanesulfonimide) and 5-10 parts of N, N-dimethylformamide. The coating is prepared from, by weight, 10-15 parts of N, N-dimethylformamide, 4-6 parts of modified PVDF-HFP nanofiber felt and 2-4 parts of fluorinated acrylate copolymer. According to the scheme provided by the invention, the modified LAYTPZn nano-particle material is formed through double elements and doped LATP, the bottleneck in the prior art is broken through from the double dimensions of lattice structure and interfacial compatibility, material decomposition and conductivity degradation are effectively avoided, the limitation that only single performance is optimized through single element doping is broken through, and the performance of the material is improved. And the performance of the flexible composite solid electrolyte of the solid-state battery is improved.

Description

Technical Field

[0001] The present application relates to the field of solid battery technology, and in particular to a method for preparing a flexible composite solid electrolyte and its application. Background Art

[0002] Solid-state batteries, also known as solid batteries, are batteries that use solid electrodes and solid electrolytes. Unlike traditional lithium-ion batteries, solid-state batteries do not contain any liquid inside, which gives them significant advantages in terms of safety, energy density, and charging speed. The working principle of solid-state batteries is based on ion flow, with lithium ions moving in the solid electrolyte to store and release electrical energy. This design allows solid-state batteries to maintain high performance even in high-temperature and high-pressure environments.

[0003] A solid-state electrolyte is a solid ion conductor and electronic insulating material that remains solid at room temperature or within the operating temperature range. It conducts lithium ions or other metal ions while blocking electrons. It replaces the liquid electrolyte in traditional lithium batteries and becomes a core component of solid-state batteries.

[0004] Among various solid electrolytes, sodium-based LATP electrolytes exhibit excellent air stability and a wide electrochemical window. However, the interfacial reaction between sodium-based LATP electrolytes and lithium metals can lead to the degradation of Ti 4+ Reduction, material decomposition and increased interface impedance lead to degraded conductive properties, 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 single performance optimization and ignores the impact of lattice stability on long-term cycling. It is difficult to break through the critical threshold for ionic conductivity improvement. Therefore, the design and preparation of high ionic conductivity and high stability LATP electrolytes through multi-element doping still has the problem of low stability. Summary of the Invention

[0005] In order to overcome the problems existing in the related art, the present application provides a method for preparing a flexible composite solid electrolyte and its application.

[0006] To achieve the above objectives, the present invention provides a first aspect of 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(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.

[0008] Preferably, the preparation method of the modified LAYTPZn nanoparticles comprises the following specific steps:

[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 hexahydrate Y as raw materials;

[0010] A2. Dissolve citric acid in deionized water and stir for 30 minutes until transparent to form a citric acid aqueous solution. Simultaneously, dissolve tetrabutyl titanate in anhydrous ethanol and stir for 30 minutes until uniform to obtain a tetrabutyl titanate solution. Then, dropwise add the citric acid aqueous solution to the tetrabutyl titanate solution while stirring. Stir in an 80°C water bath for 8 hours to form a transparent citric acid titanium complex solution for later use.

[0011] A3, lithium nitrate and ammonium dihydrogen phosphate were dissolved in a citric acid aqueous solution and stirred for 30 minutes to obtain a mixed mother liquor, and aluminum nitrate nonahydrate and yttrium nitrate hexahydrate were mixed and dissolved in a citric acid aqueous solution. The mixture was then transferred to an ultrasonic disperser for ultrasonic dispersion for 30 minutes to obtain a uniform suspension. The mixed mother liquor and the suspension were then added dropwise to the titanium citrate complex solution in sequence, and stirred at a constant temperature of 30° C. for 30 minutes to form a milky white colloid;

[0012] A4. 2 mol / L ammonia water was added dropwise to the milky white colloid to adjust the pH to 7. The milky white colloid was then transferred to an oil bath at 120° C. and heated with stirring for 6 h to form a translucent elastic gel. The translucent elastic gel was then crushed and placed in a crucible. The temperature was raised to 900° C. at 10° C. / min and calcined in air for 6 h to remove organic matter and form porous LAYTP nanopowder.

[0013] A5. Nano-zinc oxide and porous LAYTP nanopowders were placed in an agate mortar and manually ground for 15 min until initially mixed. The mixture was then transferred to a zirconium dioxide ball mill, anhydrous ethanol was added, and the zirconium dioxide ball mill was set at 600 rpm for 6 h. The ball-milled mixture was then transferred to an ultrasonic disperser and ultrasonically dispersed for 1 h to obtain a uniform suspension.

[0014] A6. The suspension is placed in a drying oven for drying to remove ethanol. The drying oven has a drying temperature of 80° C. and a drying time of 3 hours. After drying, the solid matter is further ground into a powder mixture. The powder mixture is transferred to a container, and the container is then placed in a sintering device. The powder mixture is subjected to multi-stage sintering treatment. After the sintering is completed, the sintered sample is taken out and placed in an oven for cooling to obtain modified LAYTPZn nanoparticles.

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

[0016] A6.1. Preheating: The sintering temperature is 300-500°C. When the powder mixture is sintered, the temperature is raised from room temperature to 500°C at a rate of 5°C / min for 3 hours. The mixture is then kept at 300°C for 1 hour to remove any residual organic matter.

[0017] A6.2, Sintering stage: The sintering temperature is 500-850℃. The pre-sintered powder sintered in the low temperature stage is further sintered. The heating rate is adjusted to 10℃ / min. When the temperature rises to 600℃, high temperature crystallization is carried out.

[0018] A6.3. Holding stage: When the sintering temperature in the medium temperature stage is 850°C, the sintering is continued at this temperature for 6 hours to form a bicontinuous phase network at the porous LAYTP grain boundary and solidify. After the sintering is completed, the modified LAYTPZn nanoparticles can be obtained.

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

[0020] B1. Select polyvinylidene fluoride-co-hexafluoropropylene and slowly add it to the N,N-dimethylformamide solution with a stirring speed of 300-500 r / min for about 12-24 hours until the 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 hours to obtain a mixed solution. Then, use ultrasonic degassing for 40 minutes to remove bubbles in the mixed solution.

[0021] B2. Prepare an electrospinning device, set the liquid flow rate of the electrospinning device to 0.5-1.5 mL / h, the voltage to 15-20 kV, the distance between the needle of the electrospinning device and the receiving screen to 15-20 cm, the temperature to 20-30 ° C, and the humidity to 30% to 50%. Put the prepared mixed solution into a syringe, install it on the electrospinning device, start the device for spinning, use a drum-type receiving screen, set the speed of the receiving screen to 300-600 r / min, and the spinning time to 2-6 hours. Spin the mixed solution into a fiber mat through the electrospinning device;

[0022] B3. Remove the nanofiber felt obtained by spinning from the receiving screen and place it in a vacuum drying oven for drying. The drying temperature is set to 60-80°C and the drying time is 12-24 hours to remove the residual solvent in the fiber felt. After drying, soak the fiber felt in an ethanol solution of a silane coupling agent with a mass fraction of 2% to 5% for 1-2 hours. After soaking, take out the fiber felt and rinse it with ethanol. Then, place it in a vacuum drying oven and dry it at 60°C for 6-12 hours to obtain a modified PVDF-HFP nanofiber felt. Then, cut the modified PVDF-HFP nanofiber felt into the required size and shape.

[0023] To achieve the above object, the third aspect of the present invention provides a method for preparing a flexible composite solid electrolyte, which is applied to the flexible composite solid electrolyte. The flexible composite solid electrolyte is prepared by the following steps:

[0024] S1. Prepare polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, a fluorinated acrylate copolymer, lithium bis(trifluoromethanesulfonyl imide), and N,N-dimethylformamide, then add the polyvinylidene fluoride-co-hexafluoropropylene, the modified LAYTPZn nanoparticles, and the fluorinated acrylate copolymer into N,N-dimethylformamide for dissolution to obtain a mixed solution, then transfer the mixed solution to a high-speed shear disperser, and start the high-speed shear disperser to break the mixed solution into agglomerates;

[0025] S2. After the agglomerates are obtained by the high-speed shear disperser, the agglomerates are transferred to a constant temperature magnetic stirrer, and the constant temperature magnetic stirrer is started to further stir and mix the agglomerates to form a uniform mixed suspension, and then lithium bis(trifluoromethanesulfonyl imide) is added to the constant temperature magnetic stirrer, and stirring is continued until the agglomerates are completely dissolved and mixed to obtain a transparent light brown mixed solution, which is the inner layer liquid;

[0026] S3, preparing polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, lithium bis(trifluoromethanesulfonyl)imide, and N,N-dimethylformamide, and processing them according to the same preparation process as steps S1 and S2 to generate a middle layer solution;

[0027] S4. Prepare polyvinylidene fluoride-co-hexafluoropropylene, LATP particles, lithium bis(trifluoromethanesulfonyl imide), and N,N-dimethylformamide. First, add polyvinylidene fluoride-co-hexafluoropropylene and LATP particles to an ultrasonic disperser, and 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 an outer layer solution.

[0028] S5. Spread 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, evenly spray the surface to enhance the bonding force with the functional layer, and then use a doctor blade coater to evenly coat the inner layer solution on the surface of the modified PVDF-HFP nanofiber felt to form a lithium-philic interface layer. Use a 50-micron coating blade, then transfer the glass plate coated with the lithium-philic interface layer to a fume hood, let it stand at room temperature of 25°C for 1 hour, 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, and then evenly coat the middle layer solution on the surface of the lithium-philic interface layer to form a conductive layer. Then, in the same way as above, place the two-layer coated glass plate into a fume hood for drying, and then change the coating blade of the doctor blade coater to a 50-micron specification, and coat the outer layer solution on the surface of the conductive layer to form a puncture-resistant surface layer.

[0029] S6, then placing the coated glass plate in a vacuum oven for heating, wherein the vacuum degree of the vacuum oven is set to 50 Pa, heating the semi-solid gel film coated on the glass plate to 60° C., and then drying 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, continue drying for 12 hours, and remove the finished product from the glass plate to obtain a membrane sheet;

[0030] S7. While step S6 is being performed, prepare a 5 wt.% F-AC / DMF solution, wherein the 5 wt.% F-AC / DMF solution is prepared by stirring and mixing a fluorinated acrylate copolymer and N,N-dimethylformamide. Use a micropipette to evenly apply the 5 wt.% F-AC / DMF solution to both sides of the membrane. Then, place the membrane in an oven for drying at 60° C. for 30 minutes to 1 hour.

[0031] S8. Finally, use a stainless steel die with a diameter of 16 mm to punch out a disc in the center area of ​​the membrane to obtain a finished membrane. Then, immediately transfer the finished membrane to a dry glove box with a water / oxygen content of less than 1 ppm and seal it with a sealed bag to avoid moisture absorption or oxidation to obtain a finished electrolyte membrane.

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

[0033] The stirring speed of the magnetic stirrer in S2 is 200 rpm, the stirring temperature is 65-80°C, the stirring time is 12-24 hours, and the stirring time after adding lithium bis(trifluoromethanesulfonyl)imide to the constant temperature magnetic stirrer is 15-30 hours;

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

[0035] Preferably, the lithium 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;

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

[0037] To achieve the above-mentioned purpose, the third aspect of the present invention provides an all-solid-state battery, wherein the solid electrolyte obtained according to the flexible composite solid electrolyte or the preparation method of the flexible composite solid electrolyte is mainly used for the application of the flexible composite solid electrolyte in an all-solid-state battery.

[0038] Preferably, the ingredients are calculated by weight:

[0039] Battery positive electrode aluminum foil, battery negative electrode lithium foil, flexible composite solid electrolyte, solvent and binder;

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

[0041] Q1. Mix the flexible composite solid electrolyte powder, active material, solvent and binder, stir them into a uniform slurry, apply the slurry on the battery positive electrode aluminum foil of the positive electrode collector and the battery negative electrode lithium foil of the negative electrode collector, and then dry them to remove the solvent;

[0042] Q2. Prepare the shell of the all-solid-state battery, then add flexible composite solid-state electrolyte membranes into the shell and stack them, and then hot-press the battery positive electrode aluminum foil and the battery negative electrode lithium foil to the two ends of the shell of the all-solid-state battery to obtain an all-solid-state battery.

[0043] To achieve the above-mentioned purpose, the fourth aspect of the present invention provides an electrical device, characterized in that it includes the above-mentioned all-solid-state battery.

[0044] The technical solution provided by this application may have the following beneficial effects:

[0045] 1. The present invention uses dual element Zn 2+ and Y 3+ Doping LATP to form modified LAYTPZn nanoparticle materials breaks through the existing technical bottleneck from the dual dimensions of lattice structure and interface compatibility. At the lattice level, Zn 2+ and Y3+ Substitute Ti in the LATP lattice 4+ He Li + sites, forming lattice distortion and expanding lithium ion migration channels, increasing the ionic conductivity from 8×10 -5 S / cm increased to 1.2×10 -4 S / cm, while Y 3+ The high redox potential inhibits Ti 4+ The spontaneous reduction at the lithium metal interface, combined with surface modification, forms a fluorinated polymer affinity layer on the surface of the modified LAYTPZn nanoparticles, which reduces the interfacial impedance between the electrolyte and lithium foil from 200Ω·cm 2 Down to 50Ω·cm 2 This effectively avoids material decomposition and degradation of conductive properties, thus breaking through the limitation of single-element doping that only optimizes a single property. Through multi-element synergistic doping and surface functionalization, it simultaneously achieves improvements in interface stability and ion conductivity, solving the core problem of poor compatibility between LATP-based electrolytes and lithium metal.

[0046] 2. Based on dual-element doping, the interface contact and mechanical properties of the electrolyte are further optimized through the gradient composite structure of "nanofiber support layer-functional conductive layer-anti-puncture protective layer". The middle conductive layer adopts modified PVDF-HFP nanofiber felt. Its three-dimensional porous structure not only provides a rapid migration channel for lithium ions, but also improves the tensile strength of the electrolyte membrane to meet the service requirements of the bending radius of flexible batteries. The inner layer introduces a fluorinated acrylate copolymer as an interface modifier. Through the hydrogen bonding between the fluorinated group and the hydroxyl group on the surface of the positive electrode made of lithium nickel cobalt manganese oxide, a lithium-philic interface layer is formed, which reduces the positive electrode / electrolyte interface impedance and improves the conductivity. LATP particles are added to the outer layer, and their high hardness is used to build a physical barrier to inhibit lithium dendrite puncture, and the increase in interface impedance during the cycle is controlled within 10%. This structural design improves the interface stability while giving the electrolyte excellent mechanical adaptability through the gradient matching of material components and membrane functions, solving the problems of poor interface and toughness of solid electrolytes, and improving the toughness, anti-fracture and interface strength of solid electrolytes.

[0047] 3. The present invention achieves a leap-forward improvement in the long-term cycling stability of solid-state electrolytes through the three-dimensional technical path of "doping modification-interface modification-structural enhancement". Through the collaboration of multiple technologies, it breaks through the bottleneck of the existing LATP-based electrolytes that is difficult to balance ionic conductivity and stability, and provides stability support for the manufacture of high-energy-density solid-state batteries.

[0048] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The above and other objects, features and advantages of the present application will become more apparent through a more detailed description of exemplary embodiments of the present application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the present application.

[0050] Figure 1 Schematic diagram of a LAYTPZn ceramic sheet shown in an embodiment of the present application;

[0051] Figure 2 Schematic diagram of the preparation process of LAYTP-Zn solid electrolyte shown in the embodiment of the present application;

[0052] Figure 3 Schematic diagram of the Rietveld refinement curves of LAYTP-Zn and LATP shown in the examples of this application;

[0053] Figure 4 1 is the XRD and LAYTP EIS spectrum of the solid electrolyte shown in the examples of the present application;

[0054] Figure 5 This is the total element spectrum of LAYTP-Zn shown in the examples of this application;

[0055] Figure 6 Schematic diagram of the Li+ migration barrier in LATP, LATP-Zn and LAYTP-Zn due to vacancy migration shown in the embodiments of the present application;

[0056] Figure 7 Schematic diagram of the charge density difference of LATP, LATP-Zn and LAYTP-Zn shown in the examples of the present application;

[0057] Figure 8 Schematic diagram of the total density of states and partial density of states of the LATP, LATP-Zn and LAYTP-Zn structures calculated in the examples of this application. DETAILED DESCRIPTION

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

[0059] The terms used in this application are for the purpose of describing specific embodiments only and are not intended to limit this application. As used in this application and the appended claims, the singular forms "a," "an," "the," and "the" are intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the term "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 on” or “disposed on” another element, it may 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 may be directly connected to the other element or indirectly connected to the other element.

[0061] In the description of this application, it should be understood that the terms "thickness", "up", "down", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application.

[0062] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

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

[0064] Example 1

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

[0066] 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(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.

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

[0068] S1. Prepare polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, a fluorinated acrylate copolymer, lithium bis(trifluoromethanesulfonyl imide), and N,N-dimethylformamide, then add the polyvinylidene fluoride-co-hexafluoropropylene, the modified LAYTPZn nanoparticles, and the fluorinated acrylate copolymer into N,N-dimethylformamide for dissolution to obtain a mixed solution, then transfer the mixed solution to a high-speed shear disperser, and start the high-speed shear disperser to break the mixed solution into agglomerates;

[0069] S2. After the agglomerates are obtained by the high-speed shear disperser, the agglomerates are transferred to a constant temperature magnetic stirrer, and the constant temperature magnetic stirrer is started to further stir and mix the agglomerates to form a uniform mixed suspension. Then, lithium bis(trifluoromethanesulfonyl imide) 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 solution, which is the inner layer liquid;

[0070] S3, preparing polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, lithium bis(trifluoromethanesulfonyl)imide, and N,N-dimethylformamide, and processing them according to the same preparation process as steps S1 and S2 to generate a middle layer solution;

[0071] S4. Prepare polyvinylidene fluoride-co-hexafluoropropylene, LATP particles, lithium bis(trifluoromethanesulfonyl imide), 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 an outer layer solution.

[0072] S5. Spread 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, evenly spray the surface to enhance the bonding force with the functional layer, and then use a doctor blade coater to evenly coat the inner layer solution on the surface of the modified PVDF-HFP nanofiber felt to form a lithium-philic interface layer. Use a 50-micron coating blade, then transfer the glass plate coated with the lithium-philic interface layer to a fume hood, let it stand at room temperature of 25°C for 1 hour, 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, and then evenly coat the middle layer solution on the surface of the lithium-philic interface layer to form a conductive layer. Then, in the same way as above, place the two-layer coated glass plate into a fume hood for drying, and then change the coating blade of the doctor blade coater to a 50-micron specification, and coat the outer layer solution on the surface of the conductive layer to form a puncture-resistant surface layer.

[0073] S6, then placing the coated glass plate in a vacuum oven for heating, wherein the vacuum degree of the vacuum oven is set to 50 Pa, heating the semi-solid gel film coated on the glass plate to 60° C., and then drying 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, continue drying for 12 hours, and remove the finished product from the glass plate to obtain a membrane sheet;

[0074] S7. While step S6 is being performed, prepare a 5 wt.% F-AC / DMF solution, wherein the 5 wt.% F-AC / DMF solution is prepared by stirring and mixing a fluorinated acrylate copolymer and N,N-dimethylformamide. Use a micropipette to evenly apply the 5 wt.% F-AC / DMF solution to both sides of the membrane. Then, place the membrane in an oven for drying at 60° C. for 30 minutes to 1 hour.

[0075] S8. Finally, use a stainless steel die with a diameter of 16 mm to punch out a disc in the center area of ​​the membrane to obtain a finished membrane. Then, immediately transfer the finished membrane to a dry glove box. The water / oxygen content in the dry glove box is less than 1 ppm and package it in a sealed bag to avoid moisture absorption or oxidation to obtain a finished electrolyte membrane.

[0076] Example 2

[0077] In this embodiment, a flexible composite solid 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 fluorinated acrylate copolymer;

[0079] The preparation method of the flexible composite solid electrolyte is prepared by the following steps:

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

[0081] Example 3

[0082] In this embodiment, a flexible composite solid 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 fluorinated acrylate copolymer;

[0084] The preparation method of the flexible composite solid electrolyte is prepared by the following steps:

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

[0086] Comparative Example 1

[0087] 6 parts of polyvinylidene fluoride-co-hexafluoropropylene, 5 parts of LATP particles, 9 parts of lithium bis(trifluoromethanesulfonyl)imide, and 12 parts of N,N-dimethylformamide.

[0088] The preparation method is the existing solid electrolyte preparation process, specifically mixing polyvinylidene fluoride-co-hexafluoropropylene, LATP particles, lithium bis(trifluoromethanesulfonylimide) and N,N-dimethylformamide, followed by doctor blade coating and vacuum drying at 80°C for 24 hours to form a single-layer unsupported electrolyte membrane.

[0089] Test Experiment

[0090] Ionic conductivity test at different temperatures

[0091] Sample preparation:

[0092] The electrolyte membranes of each embodiment and comparative example were punched into Wafer, thickness uniformity error ≤ ±5μm.

[0093] Test equipment:

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

[0095] Test steps:

[0096] The electrode / membrane / electrode was assembled into a sandwich structure and fixed with a pressure of 10 kPa;

[0097] Frequency scanning range 1Hz-1MHz, AC signal amplitude 5mV;

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

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

[0100] Battery Assembly:

[0101] Lithium foil ( Thickness 50μm, Sigma-Aldrich) / electrolyte membrane / lithium foil, assembled into CR2032 button battery.

[0102] Test equipment:

[0103] Same as above electrochemical workstation, test frequency 10 4 -10 6 Hz.

[0104] Data processing:

[0105] The semicircular diameter in the high-frequency region was fitted to obtain the activation energy, Li+ transfer number, electrochemical window and loading capacity data.

[0106] Tensile strength and bending radius test

[0107] Tensile Strength:

[0108] Sample: Cut into 50mm×10mm strips with uniform thickness;

[0109] Equipment: Instron 5967 universal material testing machine, manufactured by Sterma (Shanghai) Industrial Co., Ltd., with a clamping distance of 20 mm and a tensile speed of 5 mm / min;

[0110] Indicator: Record the maximum stress at fracture (MPa).

[0111] Bending radius:

[0112] Manually bend the diaphragm repeatedly until cracks appear, and record the minimum bending radius (mm) when there is no crack.

[0113] 50℃ cycle capacity retention test

[0114] Full battery assembly:

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

[0116] Negative electrode: lithium foil

[0117] Electrolyte membrane: The disc was injected with 10 μL of carbonate electrolyte (only wets the interface, not liquid electrolyte).

[0118] Test equipment:

[0119] Xinwei battery testing system, model CT-4008, is manufactured by Shenzhen Xinwei and has a 50°C constant temperature chamber (accuracy ±1°C).

[0120] Test method:

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

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

[0123] Test items Example 1 Example 2 Example 3 Comparative Example 1 <![CDATA[σ(S / cm -1 )30℃]]> <![CDATA[7.92×10 -4 ]]> <![CDATA[5.68×10 -4 ]]> <![CDATA[7.86×10 -4 ]]> <![CDATA[4.86×10 -4 ]]> <![CDATA[σ(S / cm -1 )40℃]]> <![CDATA[8.85×10 -4 ]]> <![CDATA[5.86×10 -4 ]]> <![CDATA[7.96×10 -4 ]]> <![CDATA[4.93×10 -4 ]]> <![CDATA[σ(S / cm -1 )50℃]]> <![CDATA[1.006×10 -3 ]]> <![CDATA[5.95×10 -4 ]]> <![CDATA[0.94×10 -3 ]]> <![CDATA[4.96×10 -4 ]]> <![CDATA[σ(S / cm -1 )60℃]]> <![CDATA[1.41×10 -3 ]]> <![CDATA[6.04×10 -4 ]]> <![CDATA[1.12×10 -3 ]]> <![CDATA[5.06×10 -4 ]]>

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

[0125]

[0126]

[0127] Table 3 shows the long-term cycle performance test results of the solid electrolyte membrane:

[0128] Number of cycles Example 1 (%) Example 2 (%) Example 3 (%) Comparative Example 1 (%) 100 laps 95 88.6 90.4 75.8 500 laps 89.7 84.2 85.4 65.4 1000 laps 86.8 81.1 83.3 59.5

[0129] It can be seen that the ionic conductivity of Examples 1 and 3 is ≥1.2×10 -4 S / cm, compared with Example 2 and Comparative Example 1 (1.2×10 -5 S / cm and 7.5×10 -5 S / cm) increased by 60% to 73%, proving that the Zn2 + / Y3 + Doping expands lithium ion channels through lattice distortion, breaking through the conductivity bottleneck of traditional LATP.

[0130] The conductivity of Example 1 increased slightly to 1.3×10 -4 S / cm, which is attributed to the increased porosity of the support layer providing a smoother path for ion migration.

[0131] Interface stability: synergistic effect of surface modification and gradient modification

[0132] In Example 1, double-sided modification (0.8 μm) resulted in an impedance increase of only +30% after 1000 cycles (comparative example 1 +150%), effectively suppressing interfacial side reactions (such as lithium dendrite growth and Mn dissolution).

[0133] Mechanical properties: Nanofiber support layer is key

[0134] The tensile strength of Examples 1-3 (12-15 MPa) was increased by 50% to 87.5% compared to Comparative Example 1 (8 MPa). The modified PVDF-HFP nanofiber mat (8-10 μm thick) provided a three-dimensional mesh support, and the elongation at break was greater than 100%.

[0135] Example 3 has no cracks when the bending radius is ≤5mm, which meets the folding requirements of flexible batteries, while Comparative Example 1 breaks when the bending radius is greater than 15mm, verifying that the gradient structure significantly improves flexibility.

[0136] Long-term cycling stability: full gradient design achieves breakthrough

[0137] The capacity retention rate of Example 1 after 1000 cycles at 50°C is 86.8%, far exceeding the 59.5% of Comparative Example 1 and the 83.3% of Example 3. This is due to:

[0138] The outer layer of LATP particles forms a physical barrier, and the lithium dendrite penetration time is greater than 500h (only 150h in comparative example 1);

[0139] High porosity support layer (70%) reduces membrane shrinkage (thickness change <5%) and avoids mechanical fatigue during cycling;

[0140] The double-sided interface modification layer evenly covers the positive and negative electrodes, suppressing the increase of interface impedance (increase of 30% vs. 150% in comparative example 1).

[0141] It can be seen that Example 1 uses dual-element doping as the core mechanism to break through the LATP conductivity and interface stability, and the gradient composite structure realizes functional layered optimization and full gradient enhancement design. Compared with Example 2 and Example 3, all indicators have been significantly improved, and compared with the above-mentioned comparative example 1, there is a more obvious performance improvement.

[0142] Table 4 is a summary table of LAYTP-Zn ion conductivity (based on Example 1):

[0143] Y content Thickness (mm) Diameter (mm) Impedance (Ω) σ(mS·cm-1) Y content X＝0 0.93 13.65 185 0.34 X＝0 X＝0.01 0.91 13.61 87 0.72 X＝0.01 X＝0.025 0.88 13.81 21 2.8 X＝0.025 X＝0.040 0.85 13.82 34.3 1.67 X＝0.040 X＝0.055 1.0 13.84 38.9 1.52 X＝0.055 X＝0.070 0.81 13.7 49.4 1.11 X＝0.070 X＝0.10 1.05 14.83 194 0.31 X＝0.10 X＝0.15 0.98 14.49 235 0.25 X＝0.15 X＝0.20 1.05 14.60 268 0.23 X＝0.20

[0144] Regarding the apparatus in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated again here.

[0145] The scheme of the present application has been described in detail above with reference to the accompanying drawings. In the above embodiments, the descriptions of each embodiment have their own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments. Those skilled in the art should also be aware that the actions and modules involved in the description are not necessarily required for this application. In addition, it is understood that the steps in the method of the embodiment of the present application can be adjusted in sequence, merged and deleted according to actual needs, and the modules in the device of the embodiment of the present application can be merged, divided and deleted according to actual needs.

[0146] The embodiments of the present application have been described above. The above description is illustrative and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements to the technology in the market, or to enable other persons skilled in the art to understand the embodiments disclosed herein.

Claims

1. A flexible composite solid electrolyte, characterized in that: Servings 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(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.

2. A flexible composite solid electrolyte according to claim 1, characterized in that: The specific steps of the preparation method of 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 Y as raw materials; A2. Dissolve citric acid in deionized water and stir for 30 minutes until transparent to form a citric acid aqueous solution. Simultaneously, dissolve tetrabutyl titanate in anhydrous ethanol and stir for 30 minutes until uniform to obtain a tetrabutyl titanate solution. Then, dropwise add the citric acid aqueous solution to the tetrabutyl titanate solution while stirring. Stir in an 80°C water bath for 8 hours to form a transparent citric acid titanium complex solution for later use. A3, lithium nitrate and ammonium dihydrogen phosphate were dissolved in a citric acid aqueous solution and stirred for 30 minutes to obtain a mixed mother liquor, and aluminum nitrate nonahydrate and yttrium nitrate hexahydrate were mixed and dissolved in a citric acid aqueous solution. The mixture was then transferred to an ultrasonic disperser for ultrasonic dispersion for 30 minutes to obtain a uniform suspension. The mixed mother liquor and the suspension were then added dropwise to the titanium citrate complex solution in sequence, and stirred at a constant temperature of 30° C. for 30 minutes to form a milky white colloid; A4. 2 mol / L ammonia water was added dropwise to the milky white colloid to adjust the pH to 7. The milky white colloid was then transferred to an oil bath at 120° C. and heated with stirring for 6 h to form a translucent elastic gel. The translucent elastic gel was then crushed and placed in a crucible. The temperature was raised to 900° C. at 10° C. / min and calcined in air for 6 h to remove organic matter and form porous LAYTP nanopowder. A5. Nano-zinc oxide and porous LAYTP nanopowders were placed in an agate mortar and manually ground for 15 min until initially mixed. The mixture was then transferred to a zirconium dioxide ball mill, anhydrous ethanol was added, and the zirconium dioxide ball mill was set at 600 rpm for 6 h. The ball-milled mixture was then transferred to an ultrasonic disperser and ultrasonically dispersed for 1 h to obtain a uniform suspension. A6. The suspension is placed in a drying oven for drying to remove ethanol. The drying oven has a drying temperature of 80° C. and a drying time of 3 hours. After drying, the solid matter is further ground into a powder mixture. The powder mixture is transferred to a container, and the container is then placed in a sintering device. The powder mixture is subjected to multi-stage sintering treatment. After the sintering is completed, the sintered sample is taken out and placed in an oven for cooling to obtain modified LAYTPZn nanoparticles.

3. A flexible composite solid electrolyte according to claim 2, characterized in that: The sintering of the powder mixture comprises the following steps: A6.

1. Preheating: The sintering temperature is 300-500°C. When the powder mixture is sintered, the temperature is raised from room temperature to 500°C at a rate of 5°C / min for 3 hours. The mixture is then kept at 300°C for 1 hour to remove any residual organic matter. A6.2, Sintering stage: The sintering temperature is 500-850℃. The pre-sintered powder sintered in the low temperature stage is further sintered. The heating rate is adjusted to 10℃ / min. When the temperature rises to 600℃, high-temperature crystallization occurs. A6.

3. Holding stage: When the sintering temperature in the medium temperature stage is 850°C, the sintering is continued at this temperature for 6 hours to allow the porous LAYTP to form a bicontinuous phase network and solidify. After the sintering is completed, the modified LAYTPZn nanoparticles can be obtained.

4. The flexible composite solid electrolyte according to claim 1, characterized in that: The specific steps of the preparation method of the modified PVDF-HFP nanofiber mat are as follows: B1. Select polyvinylidene fluoride-co-hexafluoropropylene and slowly add it to the N,N-dimethylformamide solution with a stirring speed of 300-500 r / min for about 12-24 hours until the 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 hours to obtain a mixed solution. Then, use ultrasonic degassing for 40 minutes to remove bubbles in the mixed solution. 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 of the electrospinning equipment and the receiving screen to 15-20 cm, the temperature to 20-30 ° C, and the humidity to 30%-50%. Put the prepared mixed solution into a syringe, install it on the electrospinning equipment, start the equipment for spinning, use a drum-type receiving screen, set the speed of the receiving screen to 300-600 r / min, and the spinning time to 2-6 hours. Spin the mixed solution into a fiber mat through the electrospinning equipment; B3. Remove the nanofiber felt obtained by spinning from the receiving screen and place it in a vacuum drying oven for drying. The drying temperature is set to 60-80°C and the drying time is 12-24 hours to remove the residual solvent in the fiber felt. After drying, soak the fiber felt in an ethanol solution of a silane coupling agent with a mass fraction of 2% to 5% for 1-2 hours. After soaking, take out the fiber felt and rinse it with ethanol. Then, place it in a vacuum drying oven and dry it at 60°C for 6-12 hours to obtain a modified PVDF-HFP nanofiber felt. Then, cut the modified PVDF-HFP nanofiber felt into the required size and shape.

5. A method for preparing a flexible composite solid electrolyte, applied to a flexible composite solid electrolyte according to any one of claims 1 to 4, characterized in that: The preparation method of the flexible composite solid electrolyte is prepared by the following steps: S1. Prepare polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, a fluorinated acrylate copolymer, lithium bis(trifluoromethanesulfonyl imide), and N,N-dimethylformamide, then add the polyvinylidene fluoride-co-hexafluoropropylene, the modified LAYTPZn nanoparticles, and the fluorinated acrylate copolymer into N,N-dimethylformamide for dissolution to obtain a mixed solution, then transfer the mixed solution to a high-speed shear disperser, and start the high-speed shear disperser to break the mixed solution into agglomerates; S2. After the agglomerates are obtained by the high-speed shear disperser, the agglomerates are transferred to a constant temperature magnetic stirrer, and the constant temperature magnetic stirrer is started to further stir and mix the agglomerates to form a uniform mixed suspension, and then lithium bis(trifluoromethanesulfonyl imide) is added to the constant temperature magnetic stirrer, and stirring is continued until the agglomerates are completely dissolved and mixed to obtain a transparent light brown mixed solution, which is the inner layer liquid; S3, preparing polyvinylidene fluoride-co-hexafluoropropylene, modified LAYTPZn nanoparticles, lithium bis(trifluoromethanesulfonyl)imide, and N,N-dimethylformamide, and processing 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(trifluoromethanesulfonyl imide), and N,N-dimethylformamide. First, add polyvinylidene fluoride-co-hexafluoropropylene and LATP particles to an ultrasonic disperser, and 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 an outer layer solution. S5. Spread 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, evenly spray the surface to enhance the bonding force with the functional layer, and then use a doctor blade coater to evenly coat the inner layer solution on the surface of the modified PVDF-HFP nanofiber felt to form a lithium-philic interface layer. Use a 50-micron coating blade, then transfer the glass plate coated with the lithium-philic interface layer to a fume hood, let it stand at room temperature of 25°C for 1 hour, 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, and then evenly coat the middle layer solution on the surface of the lithium-philic interface layer to form a conductive layer. Then, in the same way as above, place the two-layer coated glass plate into a fume hood for drying, and then change the coating blade of the doctor blade coater to a 50-micron specification, and coat the outer layer solution on the surface of the conductive layer to form a puncture-resistant surface layer. S6, then placing the coated glass plate in a vacuum oven for heating, wherein the vacuum degree of the vacuum oven is set to 50 Pa, heating the semi-solid gel film coated on the glass plate to 60° C., and then drying 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, continue drying for 12 hours, and remove the finished product from the glass plate to obtain a membrane sheet; S7. While step S6 is being performed, prepare a 5 wt.% F-AC / DMF solution, wherein the 5 wt.% F-AC / DMF solution is prepared by stirring and mixing a fluorinated acrylate copolymer and N,N-dimethylformamide. Use a micropipette to evenly apply the 5 wt.% F-AC / DMF solution to both sides of the membrane. Then, place the membrane in an oven for drying at 60° C. for 30 min to 1 h. S8. Finally, use a stainless steel die with a diameter of 16 mm to punch out a disc in the center area of ​​the membrane to obtain a finished membrane. Then, immediately transfer the finished membrane to a dry glove box with a water / oxygen content of less than 1 ppm and seal it with a sealed bag to avoid moisture absorption or oxidation to obtain a finished electrolyte membrane.

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

7. The method for preparing a flexible composite solid electrolyte according to claim 5, characterized in that: The lithium 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 felt, the lithium interface layer, the conductive layer and the puncture-resistant surface layer is 90-110 microns.

8. An all-solid-state battery, comprising a solid electrolyte obtained by the method for preparing a flexible composite solid electrolyte according to any one of claims 1 to 4 or a flexible composite solid electrolyte according to any one of claims 5 to 7, mainly comprising an application of the flexible composite solid electrolyte in an all-solid-state battery.

9. The all-solid-state battery according to claim 8, characterized in that: include: Battery positive electrode aluminum foil, battery negative electrode lithium foil, flexible composite solid electrolyte, solvent and binder; The manufacturing method of the all-solid-state battery is specifically as follows: Q1. Mix the flexible composite solid electrolyte powder, active material, solvent and binder, stir them into a uniform slurry, apply the slurry on the battery positive electrode aluminum foil of the positive electrode collector and the battery negative electrode lithium foil of the negative electrode collector, and then dry them to remove the solvent; Q2. Prepare the shell of the all-solid-state battery, then add flexible composite solid-state electrolyte membranes into the shell and stack them, and then hot-press the battery positive electrode aluminum foil and the battery negative electrode lithium foil to the two ends of the shell of the all-solid-state battery to obtain an all-solid-state battery.

10. An electrical device, characterized in that: Including the all-solid-state battery as described in claim 8.

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