Aramid fiber / LLZTO composite solid electrolyte membrane and preparation method and application thereof

Abstract

The invention relates to the technical field of solid electrolyte, in particular to an aramid fiber / LLZTO composite solid electrolyte membrane as well as a preparation method and application thereof. The invention relates to an aramid fiber / LLZTO composite solid electrolyte membrane, which comprises a three-dimensional porous nanofiber skeleton formed by aramid fiber nanofibers and LLZTO ceramic particles, pores of the three-dimensional porous nanofiber skeleton are filled with the polymer electrolyte, and the polymer electrolyte comprises polyethylene oxide (PEO) and lithium salt. According to the invention, an aramid fiber / LLZTO three-dimensional porous skeleton is constructed through an electrostatic spinning technology, and then is filled with a PEO-based polymer electrolyte. The unique rigid framework and flexible filling structure enables the high mechanical strength of the aramid fiber, the high ionic conductivity of the LLZTO ceramic and the flexible interface of the PEO matrix to be perfectly combined, and the comprehensive performance is superior to that of a simple blending system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state electrolyte, in particular to a aramid fiber / LLZTO composite solid-state electrolyte film and a preparation method and application thereof. BACKGROUND

[0002] With the increasing demand for energy storage technology worldwide, lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and renewable energy storage due to their high energy density and long cycle life. However, the existing commercial lithium-ion batteries generally use organic liquid electrolytes, which are prone to decomposition or combustion under extreme conditions such as high temperature and high voltage, posing certain safety risks. In addition, the fluidity of liquid electrolytes makes lithium-ion batteries prone to electrolyte leakage, lithium dendrite growth, and other problems during use, which seriously affects the long-term safety and performance of the battery. Therefore, the development of solid-state electrolytes with high safety and high energy density has become a research hotspot for the next generation of lithium battery technology.

[0003] Compared with traditional liquid electrolytes, solid-state electrolytes have higher thermal stability and electrochemical stability window, which can fundamentally avoid the risk of leakage and combustion of liquid electrolytes. At the same time, solid-state electrolytes have good mechanical strength, which can effectively inhibit the growth of lithium dendrites. However, single-component solid-state electrolytes often have difficulty in balancing various properties. For example, polymer electrolytes (such as PEO) have good flexibility and interface contact, but have low room temperature ionic conductivity and insufficient mechanical strength. Inorganic ceramic electrolytes (such as LLZTO) have high ionic conductivity and mechanical modulus, but their intrinsic brittleness is large, and the solid-solid interface contact with the electrode is poor, resulting in a large interface impedance.

[0004] Therefore, the combination of organic polymers and inorganic ceramic electrolytes to prepare organic-inorganic composite solid-state electrolytes is considered an effective way to take advantage of both and make up for their respective shortcomings. However, how to achieve uniform dispersion of inorganic fillers in the polymer matrix, build efficient ion transport channels, and ensure that the electrolyte film has excellent overall performance is still a challenge in this field. SUMMARY

[0005] The present application aims to solve the problems of existing solid-state electrolytes, such as low ionic conductivity, poor compatibility with electrode interfaces, and difficulty in balancing mechanical flexibility and strength, and provides a aramid fiber / LLZTO composite solid-state electrolyte film with high ionic conductivity, excellent mechanical properties, high thermal stability, and high safety.

[0006] The technical scheme adopted by the present application to solve its technical problems is:

[0007] An aramid / LLZTO composite solid-state electrolyte membrane, comprising: a three-dimensional porous nanofiber framework composed of aramid nanofibers and LLZTO ceramic particles; and a polymer electrolyte filled in the pores of the three-dimensional porous nanofiber framework, the polymer electrolyte comprising polyethylene oxide (PEO) and a lithium salt;

[0008] The LLZTO is Ta-doped Li 7-x La3Zr 2-x Ta x O 12 , wherein 0 < x ≤ 0.6.

[0009] Preferably, the three-dimensional porous nanofiber framework is prepared from an electrospinning solution precursor containing meta-aramid fibers (PMIA), LLZTO, polyethylene oxide and a lithium salt, the electrospinning solution precursor containing, in 5 mL of solvent, 0.1-0.5 g of PMIA, 0.05-0.2 g of LLZTO, 0.01-0.05 g of polyethylene oxide and 0.05-0.3 g of lithium salt.

[0010] Preferably, the weight ratio of PMIA to LLZTO in the electrospinning solution precursor is 16:15-18. The battery prepared from the composite solid-state electrolyte membrane with this ratio has the highest electrochemical window (about 4.7 V), the best stability at high voltage, and can be stably cycled for more than 450 hours.

[0011] Preferably, the polymer electrolyte is formed by impregnating and drying a solution containing 0.1-0.5 wt% of a lithium salt and 4-10 wt% of polyethylene oxide (PEO). Preferably, the solution for preparing the polymer electrolyte contains, in 5 mL of solvent, 0.01-0.02 g of lithium salt and 0.2-0.5 g of polyethylene oxide.

[0012] Preferably, the Ta doping amount of the LLZTO particles is 0.2-0.6, and the particle size of the LLZTO particles ranges from 50 nm to 500 nm.

[0013] Preferably, the lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiTFSI), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4) and lithium bis(oxalato)borate (LiBOB).

[0014] Preferably, the porosity of the electrospun membrane is 30% to 70%, and / or the thickness of the composite solid-state electrolyte membrane is 50 μm to 200 μm. The porosity of the electrospun membrane is 30% to 70% to ensure a fast transport path of lithium ions in the electrolyte. The thickness of the composite solid-state electrolyte membrane is 50 μm to 200 μm to ensure sufficient mechanical strength, inhibit lithium dendrite penetration, and enhance battery safety.

[0015] A method for preparing the aramid / LLZTO composite solid-state electrolyte membrane according to the present application, the method comprising the following steps: (a) preparing a first precursor solution: dissolving meta-aramid fibers, LLZTO, polyethylene oxide, and a lithium salt in a solvent to obtain a first precursor solution; (b) electrospinning: electrospinning the first precursor solution to obtain a three-dimensional porous nanofiber skeleton composed of aramid nanofibers and LLZTO ceramic particles; (c) soaking and drying: soaking the three-dimensional porous nanofiber skeleton in a second precursor solution containing polyethylene oxide and a lithium salt, and then drying to obtain the composite solid-state electrolyte membrane.

[0016] Preferably, the process parameters of the electrospinning in step (b) are: a voltage of 5 kV to 20 kV, a distance between the spinning needle and the receiver of 5-10 cm, a spinning rate of 0.5-1 mL / h, and an ambient air humidity of 30% and below.

[0017] Preferably, the solvent of the first precursor solution in step (a) is one or a mixture of several of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), or acetonitrile (ACN); and / or the viscosity of the first precursor solution is 1000-5000 mPa·s. The viscosity of the first precursor is 1000-5000 mPa·s to ensure the stability and continuity of the jet during spinning, which helps to form uniform, fine, and structurally complete nanofibers.

[0018] The present application utilizes electrospinning technology to prepare a composite solid-state electrolyte membrane. Through this technology, the composite solid-state electrolyte membrane can be produced efficiently and at low cost, which is suitable for large-scale production applications. Through the electrospinning process, a uniform and nanoscale fiber structure can be obtained, which provides a continuous ion conduction path for the solid-state electrolyte membrane, effectively improving the ion conductivity and stability of the energy storage device, and meeting the needs of flexible energy storage devices, and has broad application prospects.

[0019] The present application adopts meta-aramid (PMIA) as the main matrix material of the solid-state electrolyte membrane. Aramid has excellent mechanical strength, chemical stability and thermal stability, which makes it an ideal material for high-performance solid-state electrolyte membranes. The aramid matrix can provide good flexibility and tensile strength for the composite membrane, and maintain stability under high temperature or extreme working conditions. In addition, the high toughness of aramid fiber can effectively prevent the solid-state electrolyte membrane from breaking or deforming during use, improving the overall structural stability of the membrane. Through electrospinning technology, aramid fibers can be uniformly distributed in the composite membrane, forming a continuous nanoscale fiber structure, thereby enhancing the mechanical strength of the membrane and providing a more stable transmission path for lithium ions.

[0020] In the present application, inorganic particles LLZTO (Li 7-x La3Zr 2-x Ta x O 12 ) are used as additives. The addition of LLZTO ceramic particles further improves the performance of the composite solid-state electrolyte membrane. LLZTO has extremely high ionic conductivity and excellent chemical stability, which can effectively enhance the ionic conductivity of the electrolyte membrane. LLZTO particles are tightly combined with the aramid matrix through the electrospinning process, forming an organic-inorganic composite structure, which not only improves the ionic conductivity of the membrane, but also enhances the thermal stability and high-temperature resistance of the membrane. In addition, the addition of LLZTO ceramic particles can effectively inhibit the growth of lithium dendrites, reducing the safety risks that may occur during battery operation, especially in high-voltage or high-temperature environments, further improving the safety and long-term stability of the composite membrane.

[0021] The present application also adopts an optimized lithium salt selection strategy to improve the ionic conductivity of the composite solid-state electrolyte membrane. The selected lithium salts include lithium hexafluorophosphate (LiPF6), lithium bisfluoromethanesulfonimide (LiTFSI), etc. These lithium salts have high ionic conductivity and chemical stability. In the electrolyte membrane, the addition of lithium salt can significantly improve the mobility of lithium ions in the solid-state electrolyte, thereby enhancing the charge and discharge efficiency of the battery. In addition, the selected lithium salt forms a stable coordination complex with the polymer matrix, which helps to improve the interface stability of the electrolyte membrane and reduce side reactions during battery operation. This optimized ratio of lithium salt not only improves the performance of the battery, but also improves the safety of the solid-state electrolyte membrane under extreme working conditions.

[0022] As a preferred, the temperature during spinning in step (b) is 20-30℃, and the air humidity is 10-30%, to ensure that the volatilization rate of the solvent during electrospinning is moderate, promote the uniform formation and rapid solidification of nanofibers, prevent fiber adhesion, breakage or structural defects, and obtain a dense structure and stable performance of the electrolyte membrane.

[0023] As a preference, the power supply voltage used in the spinning process is set to 5-20 kV. The voltage in this range can affect the jetting characteristics and charge distribution of the nanofiber, and have an impact on the morphology and arrangement structure of the fiber.

[0024] As a preference, the rate of spinning in step (b) is controlled to be 0.5-1 mL / h. In this range, the stability of the solution jet and the uniform stretching of the nanofiber can be maintained, forming a continuous, uniform and dense fiber membrane structure.

[0025] As a preference, the distance between the receiver of the electrospinning device and the spinning needle in step (b) should be kept at 5-10 cm. This distance range can ensure that the jet has enough time to stretch and the solvent to evaporate, which is conducive to the formation of continuous and uniform nanofiber.

[0026] As a preference, the nanofiber membrane obtained after spinning in step (b) is placed in a 50℃ oven for drying for more than 12h to remove the residual solvent in the fiber membrane, prevent the membrane structure from collapsing due to solvent evaporation during subsequent use, and prevent the performance from being unstable, or from having a side reaction with lithium salt and electrode material, thereby affecting the ion conductivity, thermal stability of the electrolyte and the safety performance of the overall battery.

[0027] As a preference, the method comprises the following steps: (a) preparing a first precursor solution: dissolving meta-aramid fibers, LLZTO, polyethylene oxide and lithium salt in a solvent, stirring at 80℃ for more than 48h to obtain a first precursor solution; (b) electrospinning: electrospinning the first precursor solution to obtain a three-dimensional porous nanofiber skeleton composed of aramid nanofiber and LLZTO ceramic particles; the electrospinning process is carried out at room temperature; the obtained nanofiber membrane needs to be stored in a 50℃±5℃ oven; (c) infiltration and drying:

[0028] Preparation of the second precursor solution: mix 0.1-0.5 wt% of lithium salt, 4-10 wt% of polyethylene oxide (PEO) and the rest of the solvent (such as acetonitrile), and stir at room temperature for more than 12h;

[0029] Infiltrate the three-dimensional porous nanofiber skeleton obtained in step (b) in the second precursor solution containing polyethylene oxide and lithium salt,

[0030] Cut the three-dimensional porous nanofiber skeleton (nanofiber membrane) obtained in step (b) into small pieces and place them on a polytetrafluoroethylene plate, pour the prepared second precursor solution on the nanofiber membrane, and dry the poured sample in a 50℃±5℃ oven for 24h-32h to obtain a composite solid electrolyte membrane.

[0031] A flexible energy storage device comprising a composite solid electrolyte membrane as described in the present application.

[0032] Compared with the prior art, the application has the following beneficial effects:

[0033] The application constructs aramid / LLZTO three-dimensional porous framework by electrospinning technology, and then fills PEO-based polymer electrolyte. The unique 'rigid framework + flexible filling' structure enables the perfect combination of the high mechanical strength of aramid fibers, the high ionic conductivity of LLZTO ceramic and the flexible interface of the PEO matrix, and the comprehensive performance is better than that of a simple blending system.

[0034] The continuous nanofiber network formed by electrospinning and the presence of LLZTO particles provide efficient and continuous transmission channels for lithium ions, significantly improving the ionic conductivity. At the same time, the aramid framework with high mechanical strength can effectively inhibit the growth and penetration of lithium dendrites, greatly improving the safety and cycle life of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a scanning electron microscope (SEM) image of the aramid / LLZTO nanofiber membrane prepared in Example 1 of the application; Figure 2 is an electrochemical impedance spectrum (EIS) graph of the composite solid-state electrolyte membrane obtained in Example 1 of the application; Figure 3 is a linear sweep voltammetry (LSV) curve of the composite solid-state electrolyte membranes obtained in Example 1 (a), Example 2 (b) and Example 3 (c) of the application; Figure 4 is a long cycle performance curve of the lithium symmetric battery assembled by the composite solid-state electrolyte membranes obtained in Example 1 (a), Example 2 (b) and Example 3 (c) of the application under a specific current density; Figure 5 is a long cycle performance curve of the full battery assembled by the composite solid-state electrolyte membrane in Application Example 1 of the application. DETAILED DESCRIPTION

[0036] The technical solutions of the application will be further described below through specific embodiments. It should be understood that the implementation of the application is not limited to the following examples, and any form of modification and / or change made to the application will fall within the scope of the application.

[0037] In the application, unless specified, all parts and percentages are by weight, and the equipment and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following examples are conventional methods in the art, unless otherwise specified.

[0038] The reagents used in the following examples can be purchased from conventional biochemical reagent stores, unless otherwise specified.

[0039] Para-aramid, purchased from Teijin Aramid,

[0040] LLZTO, purchased from Shenzhen Huaqing New Material Technology Co., Ltd.,

[0041] LiTFSI, Ta-doped Li7La3Zr 1.5 Ta 0.5 O 12 , purchased from Shanghai Aladdin Biochem Technology Co., Ltd.

[0042] Example 1: A preparation method of aramid / LLZTO composite solid-state electrolyte membrane, the specific steps are as follows:

[0043] (1) Preparation of the first precursor solution: 0.16 g of para-aramid (PMIA), 0.1 g of LLZTO (Ta-doped, particle size about 300 nm), 0.03 g of polyethylene oxide (PEO, viscosity average molecular weight 600,000) and 0.1 g of LiTFSI were added into 5 mL of N,N-dimethylacetamide (DMAc), and the mixture was magnetically stirred at 80°C for 48 h to obtain a uniform and stable first precursor solution (electrospinning solution).

[0044] The LLZTO is Ta-doped Li7La3Zr 1.5 Ta 0.5 O 12 (2) Preparation of the second precursor solution: 0.25 g of polyethylene oxide (PEO) and 0.015 g of LiTFSI were dissolved in 5 mL of acetonitrile (ACN), and the mixture was magnetically stirred at room temperature for 12 h to obtain the second precursor solution. (3) Electrospinning: the first precursor solution prepared in step (1) was loaded into a syringe with a metal needle, and electrospinning was performed. The electrospinning parameters were as follows: the spinning rate was 1 mL / h, the distance between the receiver (aluminum foil) and the needle was 10 cm, the power voltage was 10 kV, and the spinning was performed at room temperature and air humidity of about 25%. After the spinning was completed, the obtained aramid / LLZTO nanofiber membrane was peeled off from the aluminum foil. (4) Composite and drying: the nanofiber membrane obtained in step (3) was placed in a 50°C oven for 12 h to remove the residual solvent. Then it was cut into a size of 8×8 cm and placed on a polytetrafluoroethylene plate, and the second precursor solution (5 mL) prepared in step (2) was uniformly poured onto the nanofiber membrane to allow it to fully soak. Finally, the poured sample was placed in a 50°C oven for vacuum drying for 24 h to obtain the composite solid-state electrolyte membrane.

[0045] Performance test and analysis:

[0046] The sample prepared in Example 1 was tested.

[0047] Morphology characterization: The nanofiber membrane obtained in step (3) was tested by scanning electron microscopy (SEM). The results are as follows: Figure 1 As shown. As can be seen from the figure, the fibers prepared by electrospinning are continuous nanoscale in size, with uniform diameter distribution, and the fibers are interwoven with each other to form a three-dimensional network structure with high porosity. It can be observed that the LLZTO particles are uniformly embedded or attached to the surface of the aramid nanofibers, forming a composite fiber skeleton. Electrochemical performance: The composite solid electrolyte membrane obtained in step (4) was cut into thin sheets with a diameter of 12 mm using a punching die, and assembled into a stainless steel (SS) | electrolyte membrane | SS symmetrical battery. The electrochemical impedance spectroscopy (EIS) test was carried out at room temperature, and the results are shown as follows. Figure 2 As shown. Spectral calculation shows that the ionic conductivity of the composite solid electrolyte membrane at room temperature reaches 2.16 × 10 -4 S / cm, showing excellent ion conductivity.

[0048] The membrane was assembled into a lithium metal | electrolyte membrane | stainless steel (SS) battery. The voltage range was 2-6 V at a scan rate of 1 mV / s at 50°C. Figure 3 As shown in a, the electrochemical stability window of the electrolyte membrane reaches 4.6 V.

[0049] The electrolyte membrane was assembled into a lithium symmetric battery at 50 °C and 0.1 mA / cm -2 The constant current charge and discharge cycle test was carried out under the current density, and the results were as follows Figure 4 As shown in a, the battery short-circuited after cycling for 120 h.

[0050] Example 2: Preparation and characterization of composite solid electrolyte membranes with different LLZTO contents

[0051] Except that the amount of LLZTO in step (1) was changed to 0.15 g, the remaining steps and conditions were the same as those in Example 1 to prepare a composite solid electrolyte membrane.

[0052] The cells were assembled into lithium (Li) | electrolyte membrane | SS batteries and subjected to linear sweep voltammetry (LSV) tests at a scan rate of 1 mV / s. Figure 3 As shown in b. As can be seen from the figure, the electrolyte membrane has no obvious oxidative decomposition current before 4.7 V, indicating that it has a wide electrochemical stability window and can match high-voltage positive electrode materials.

[0053] They were assembled into a Li / / Li symmetrical battery and subjected to constant current charge and discharge cycle tests at 50°C and a current density of 0.1 mA / cm². The results are as follows: Figure 4As shown in FIG. b, the battery can be stably cycled for more than 450 hours, and the polarization voltage always remains at a low level, without the phenomenon of short circuit caused by lithium dendrite growth. It is illustrated that the battery with the LLZTO addition amount has better electrochemical stability.

[0054] Example 3: Preparation and characterization of composite solid electrolyte films with different LLZTO contents

[0055] Except that the amount of LLZTO in step (1) is changed to 0.05 g, the remaining steps and conditions are the same as those in Example 1, and a composite solid electrolyte film is prepared.

[0056] Assemble it into lithium (Li) | electrolyte film | SS battery, and perform linear sweep voltammetry (LSV) test at a scan rate of 1 mV / s, and the results are as shown in FIG. Figure 3 As shown in FIG. c, the electrochemical window of the battery assembled by the electrolyte film is 4.5 V, and remains stable in a lower voltage range.

[0057] By comparing the results of the three groups of examples, it can be concluded that Example 2 has the highest electrochemical window (about 4.7 V), which means that it has the best stability at high voltage and is suitable for high voltage application environment. The LLZTO inorganic particles have excellent thermal stability and electrochemical stability, and can withstand a wider voltage range. With the increase of its content, the stable voltage range of the overall composite electrolyte becomes wider, so that it can remain stable at a higher voltage.

[0058] Assemble it into Li | electrolyte film | Li symmetric battery, and perform constant current charge and discharge cycle test at 50°C and a current density of 0.1 mA / cm², and the results are as shown in FIG. Figure 4 c. As can be seen from the figure, the symmetric battery can be stably cycled for more than 300 hours.

[0059] Application Example 1: Assembly and performance test of all-solid-state lithium metal battery

[0060] (1) Preparation of positive electrode: lithium iron phosphate (LFP) powder, polyethylene oxide (PEO), conductive carbon black (Super P) and LiTFSI are mixed in a mass ratio of 6:2:1:1, and an appropriate amount of acetonitrile solvent is added, and the slurry is ball milled to uniform. The slurry is uniformly coated on the carbon-coated aluminum foil, and dried at 60°C under vacuum conditions for 12h, and punched into a round piece to obtain a positive electrode piece. (2) Full battery assembly: lithium metal piece (negative electrode), aramid / LLZTO composite solid electrolyte film prepared in Example 1 (as the electrolyte of the battery), and the positive electrode piece prepared in step (1) are stacked to assemble a CR2032 type button cell. (3) Performance test: the assembled full battery is tested for long cycle performance at 50°C and 0.2C rate, and the results are as shown in FIG. Figure 5The capacity retention rate of the full battery is still as high as 95.3% after 50 cycles, which shows excellent cycle stability and application potential.

[0061] The present application utilizes high-strength aramid nanofiber as an organic skeleton, and realizes efficient coupling of inorganic LLZTO particles and organic matrix through electrospinning technology, and constructs a solid-state electrolyte membrane with a three-dimensional network structure. The whole preparation process includes the preparation of aramid-based electrospinning solution, spinning to form nanofiber membrane, and the assembly of the battery. During the operation, the aramid dissolution system, the content of inorganic fillers, and the electrospinning parameters are all optimized and controlled to obtain a composite electrolyte membrane with stable structure and high ionic conductivity. The core innovation of the present application is that aramid and LLZTO cooperatively form a rigid-flexible combined electrolyte network, which not only improves the ionic conductivity and mechanical strength of the membrane, but also significantly improves the interface compatibility, thereby promoting the practicalization process of flexible lithium metal batteries in wearable, micro energy storage devices and other fields.

[0062] The present application adopts electrospinning technology and combines LLZTO inorganic particles with high-performance aramid matrix material, effectively improving the overall stability and flexibility of the solid-state electrolyte. Aramid material has excellent thermal stability, mechanical strength and chemical inertness, and can realize long-term operation of the composite electrolyte in complex environment as the main chain support skeleton. At the same time, by coating LLZTO particles on the surface of aramid nanofiber and forming a three-dimensional porous network structure by electrospinning, a fast and continuous migration channel for lithium ions is realized. The composite solid-state electrolyte membrane constructed on the basis of this structure not only improves the overall ionic conductivity, but also effectively inhibits the generation of lithium dendrites and enhances the interface contact stability between the lithium metal anode and the electrolyte. Compared with traditional polymer electrolyte, the material system has higher structural integrity and electrochemical performance, providing a feasible path for the new generation of high-safety flexible batteries.

[0063] In summary, the present application prepares aramid / LLZTO composite solid-state electrolyte by electrospinning method, which combines the high strength of aramid fiber and the excellent ionic conductivity of LLZTO ceramic, and has significant performance advantages. The present application uses meta-aramid (PMIA) as the main matrix material of the solid-state electrolyte membrane, which has excellent mechanical strength, chemical stability and thermal stability. The addition of LLZTO ceramic particles further improves the performance of the composite solid-state electrolyte membrane. The three-dimensional network structure formed by electrospinning provides an ideal channel for efficient transmission of lithium ions, significantly enhances the ionic conductivity of the electrolyte membrane, effectively inhibits the formation of lithium dendrites, and improves the safety and service life of the battery. The present application has the following characteristics:

[0064] (1) The aramid / LLZTO composite solid-state electrolyte prepared by electrospinning method can form a uniform nanofiber structure, improve ion conductivity, and simplify the manufacturing process and reduce costs.

[0065] (2) Using meta-aramid as the main material, thanks to its excellent mechanical strength and thermal stability, it can effectively enhance the structural stability of the electrolyte membrane, improve the safety and cycle life of the battery.

[0066] (3) Adding LLZTO inorganic particles can significantly improve the ion conductivity, thermal stability and mechanical strength of the electrolyte, effectively inhibit the formation of lithium dendrites, and enhance the interface stability and safety of the electrolyte membrane.

Claims

1. An aramid / LLZTO composite solid electrolyte membrane, characterized in that: include: A three-dimensional porous nanofiber skeleton composed of aramid nanofibers and LLZTO ceramic particles; and a polymer electrolyte filled in the pores of the three-dimensional porous nanofiber skeleton, the polymer electrolyte comprising polyethylene oxide (PEO) and a lithium salt; The LLZTO is Ta-doped Li 7-x La3Zr 2-x Ta x O 12 , where 0 < x ≤ 0.

6.

2. The aramid / LLZTO composite solid electrolyte membrane according to claim 1, characterized in that: The three-dimensional porous nanofiber skeleton is prepared from an electrospinning solution precursor containing meta-aramid fiber (PMIA), LLZTO, polyethylene oxide and lithium salt. The components in the electrospinning solution precursor contain 0.1-0.5 g of PMIA, 0.05-0.2 g of LLZTO, 0.01-0.05 g of polyethylene oxide and 0.05-0.3 g of lithium salt based on 5 mL of solvent.

3. The aramid / LLZTO composite solid electrolyte membrane according to claim 1, characterized in that: The polymer electrolyte is formed by infiltrating a solution containing 0.1-0.5 wt% of lithium salt and 4-10 wt% of polyethylene oxide (PEO) and then drying the solution.

4. The aramid / LLZTO composite solid electrolyte membrane according to claim 1, characterized in that: The Ta doping amount of the LLZTO particles is 0.2-0.6, and the particle size of the LLZTO particles ranges from 50 nm to 500 nm.

5. The aramid / LLZTO composite solid electrolyte membrane according to claim 1, characterized in that: The lithium salt is selected from one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluoromethanesulfonyl)imide (LiTFSI), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4) and lithium bis(oxalatoborate) (LiBOB).

6. The aramid / LLZTO composite solid electrolyte membrane according to claim 1, characterized in that: The thickness of the composite solid electrolyte membrane is 50 μm to 200 μm.

7. A method for preparing an aramid / LLZTO composite solid electrolyte membrane according to any one of claims 1 to 6, characterized in that: The method includes the following steps: (a) preparing a first precursor solution: dissolving meta-aramid fiber, LLZTO, polyethylene oxide and lithium salt in a solvent to obtain a first precursor solution; (b) electrospinning: electrospinning the first precursor solution to obtain a three-dimensional porous nanofiber skeleton composed of aramid nanofibers and LLZTO ceramic particles; (c) infiltration and drying: infiltrating the three-dimensional porous nanofiber skeleton in a second precursor solution containing polyethylene oxide and lithium salt, and then drying to obtain the composite solid electrolyte membrane.

8. The preparation method according to claim 7, characterized in that: The process parameters of the electrospinning in step (b) are: voltage of 5 kV to 20 kV, a distance between the spinning needle and the receiver of 5-10 cm, a spinning rate of 0.5-1 mL / h, and an ambient air humidity of 30% or less.

9. The preparation method according to claim 7, characterized in that: In step (a), the solvent of the first precursor solution is one or a mixture of N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF) or acetonitrile (ACN); and / or the viscosity of the first precursor solution is 1000-5000 mPa·s.

10. A flexible energy storage device, characterized in that: The method comprises the composite solid electrolyte membrane according to any one of claims 1 to 6.

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