Composite solid electrolyte based on waste lyocell fibers as well as preparation method and application of composite solid electrolyte

Abstract

The invention belongs to the field of solid-state lithium ion battery materials, and particularly relates to a composite solid electrolyte based on waste lyocell fibers as well as a preparation method and application of the composite solid electrolyte. The preparation method comprises the following steps: firstly, preparing a fiber membrane prepared by blending and electrostatic spinning of waste lyocell fibers and LLZTO, and then preparing the composite solid electrolyte membrane by pouring an interface regulation and control layer. The used waste lyocell fiber base material is green and environment-friendly and is applied to the composite solid electrolyte membrane, so that high-added-value recycling of waste textiles is realized, and the green and environment-friendly requirements are met. After a battery is assembled, the battery has good performance, the ionic conductivity at room temperature is greater than 10 <-4 > S.cm <-1 >, the cycle stability exceeds 500 hours, and the battery has stable long cycle performance and high coulombic efficiency.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solid-state lithium ion battery materials, and particularly relates to a composite solid-state electrolyte based on waste lyocell fibers and a preparation method and application thereof. BACKGROUND

[0002] With the increasing demand for high energy density and high safety lithium ion batteries in new energy vehicles, intelligent electronic devices and the like, solid-state lithium metal batteries have become a research hotspot due to their excellent safety performance and potential high energy density. As a core material, the solid-state electrolyte directly affects the ion conduction efficiency and cycle stability of the battery. In recent years, doped oxide electrolytes such as Li7La3Zr2O 12 (LLZO) have attracted much attention due to their excellent ion conductivity and chemical stability, especially through the optimization of their crystal structure and interface performance by doping elements. However, traditional ceramic solid-state electrolytes have the problems of high brittleness and high processing difficulty, which limit their application in flexible batteries and complex structure batteries. To solve the above problems, the research on composite solid-state electrolyte materials has gradually emerged, which combines inorganic particles with a polymer matrix, and has high ion conductivity and excellent mechanical flexibility, becoming the current development trend. In addition, environmental protection and resource recycling are increasingly important, and the recycling of waste fiber materials has become an important direction of materials science.

[0003] Lyocell fiber, as a renewable cellulose material with abundant sources, low cost and biodegradability, has good solubility and film-forming property. Using it as an organic component of the composite solid-state electrolyte not only improves the sustainability of the material, but also realizes efficient preparation and microstructure control of the fiber membrane through electrospinning technology. Combined with doped modified LLZTO nanoparticles with high ion conductivity, a green and environmentally friendly composite solid-state electrolyte with excellent ion conductivity, mechanical flexibility and interface stability can be prepared. At present, there is still a lack of effective process to prepare high-performance composite fiber membranes by electrospinning of waste lyocell fibers and doped LLZTO nanoparticles. With the rapid development of all-solid-state lithium metal batteries, the demand for high-performance solid-state electrolytes is increasing. Although traditional polymer matrices such as PVDF, PAN and PEO are widely used, they lack environmental performance and are difficult to meet the requirements of green development. The composite solid-state electrolyte prepared by taking advantage of waste lyocell fibers and LLZTO in the present application shows good physical and chemical properties, high ion conductivity and excellent cycle life in battery test, effectively promoting the development of solid-state electrolyte materials. SUMMARY

[0004] The present application aims to solve the problem of high value-added utilization of waste fiber materials in the prior art, and in view of the poor mechanical flexibility, poor interface compatibility with the electrode, and the need to improve the ionic conductivity of the solid electrolyte, a composite solid electrolyte based on waste lyocell fibers is provided, which has excellent ion conduction performance, mechanical strength and interface adaptability.

[0005] The technical solution adopted by the present application to solve its technical problems is:

[0006] A composite solid electrolyte, comprising: a three-dimensional porous fiber framework composed of lyocell nanofibers and LLZTO ceramic particles; and an interface regulating layer filled in the pores of the three-dimensional porous fiber framework and / or covering the surface thereof, the interface regulating layer comprising a polymer and a lithium salt;

[0007] The three-dimensional porous fiber framework is prepared by electrospinning method, and the raw materials thereof comprise waste lyocell fibers, paraformaldehyde (PF), LLZTO, a first polymer and a first lithium salt.

[0008] As a preferred, the first polymer is selected from one or more of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), hydroxymethyl cellulose, carboxymethyl cellulose (CMC), guar gum, gelatin, starch acetate, carboxymethyl starch or sodium alginate.

[0009] As a preferred, the polymer in the interface regulating layer is a second polymer, and the second polymer is selected from one or more of polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) and polyethylene oxide (PEO).

[0010] As a preferred, the LLZTO is Ta-doped Li 6.4 La3Zr 1.4 Ta 0.6 O 12 .

[0011] As a preferred, the first lithium salt and / or the lithium salt in the interface regulating layer is selected from one or more of lithium perfluoroethanesulfonylimide (LiFTFSI), lithium triflate (LiOTf), lithium fluorophosphate (LiFO2P), lithium bis-trifluoroethanesulfonimide (LiBETI), lithium nitrate (LiNO3), lithium perfluorobutanesulfonylimide (LiPBSI) or lithium bis-trifluoropropanesulfonimide (LiTFPSI).

[0012] A preparation method of the composite solid-state electrolyte according to the present application, the method comprising the following steps: (a) preparing an electrospinning precursor solution: dispersing or dissolving waste lyocell fibers, paraformaldehyde (PF), LLZTO, a first polymer and a first lithium salt in a first solvent; (b) electrospinning: electrospinning the electrospinning precursor solution obtained in step (a) to obtain the three-dimensional porous fiber framework; (c) applying an interface regulating layer: casting or spin-coating the interface regulating layer on the three-dimensional porous fiber framework, the interface regulating layer comprising a second polymer, a second lithium salt and a second solvent; (d) drying: drying the product treated in step (c) to obtain the composite solid-state electrolyte.

[0013] Preferably, the first solvent in step (a) is selected from one or more of N-methyl pyrrolidone (NMP), N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO) and N-methylmorpholine-N-oxide (NMMO).

[0014] Preferably, the preparation of the electrospinning precursor solution comprises: S1 dissolving: after crushing the lyocell fibers, dissolving them in the first solvent, adding paraformaldehyde (PF) and LLZTO, heating to 115℃±10℃ until the lyocell fibers are dissolved, and then obtaining a fiber solution by ultrasonic dispersion or high-shear stirring; S2 blending: adding the first polymer and the first lithium salt to the obtained fiber solution to obtain the electrospinning precursor solution.

[0015] Preferably, the mass ratio of the lyocell fibers to the first solvent is 1:(60-100), the mass ratio of the lyocell fibers to LLZTO is 1:(1-5), the mass ratio of PF to the lyocell fibers is (1-3):1, the mass ratio of the first polymer to the lyocell fibers is (10-20):1, and the mass ratio of the first lithium salt to the lyocell fibers is (1-3):1.

[0016] Preferably, the mass ratio of the lyocell fibers to LLZTO is 1:(1-3). Such a selection allows the lyocell fibers to be well dispersed in the solution, and the addition of LLZTO in an appropriate amount can provide better physical and chemical properties for the subsequent preparation of the composite solid-state electrolyte.

[0017] Preferably, the mass ratio of the first polymer to the lyocell fibers is (15-20):1. The use of the first polymer can achieve better electrospinning effect, making the spinning more stable and uniform and forming a good fiber structure. More preferably, the mass ratio of the lyocell fibers to the first solvent is 1:100, and the mass ratio of the first polymer to the lyocell fibers is 15:1.

[0018] Preferably, in step (a), the average molecular weight of the first polymer is in the range of 10 4 to 10 6 g / mol. The first polymer and the first lithium salt are used to improve the ion transference number, electrochemical stability, and interfacial film-forming ability of the polymer system. The addition of the lithium salt can, to a certain extent, improve the conductivity of the membrane, which is ultimately reflected in the improvement of the ionic conductivity of the assembled battery.

[0019] Preferably, the process parameters of electrospinning in step (b) are: the spinning solution is ejected through a needle with a diameter of 0.3 to 0.8 mm at a propulsion speed of 0.5 to 1 ml per hour, the distance between the needle and the collecting drum is controlled in the range of 8 to 15 cm, the applied electrostatic voltage is 5 to 30 kilovolts, the collecting drum speed is set at 200 to 1000 revolutions per minute, the relative humidity of the spinning environment is less than 30%, and the temperature is maintained between 15 and 35 degrees Celsius. The process can be carried out in a normal pressure atmosphere or an inert gas environment to ensure uniform fiber formation and stable performance.

[0020] Preferably, in step (c), the interface regulation layer is a mixture of a second polymer, a second lithium salt and a second solvent (such as acetonitrile), which account for 20-30 wt%, 5-10 wt% and 50-60 wt% respectively.

[0021] Preferably, the interface control layer comprises 25-30% of the second polymer, 5-8% of the second lithium salt, and the balance of acetonitrile. The addition of the second polymer complements the properties of the lyocell fiber, filling the gaps. The appropriate ratio of the three ensures a moderate solution viscosity, preventing the cast fiber membrane from being too thick or sticky, and imparting excellent physical properties.

[0022] The drying temperature in step (d) is generally set to 50-100° C. Preferably, the temperature of the oven in S5 is set to 50-60° C. A lower oven temperature can ensure the evaporation of the solvent while preventing the evaporation rate from being too fast, which may cause shrinkage or unevenness of the composite solid electrolyte fiber membrane.

[0023] A lithium battery comprising the composite solid electrolyte of the present invention. The present invention cuts the prepared electrospun composite solid electrolyte fiber membrane into discs of a specified size, and assembles the discs with a positive electrode and a lithium negative electrode to form a battery for use.

[0024] The beneficial effects of the present invention are:

[0025] 1. The present invention uses waste lyocell fibers from a wide range of sources as a structural base material, providing an effective way for the green and high-value utilization of waste textiles, and meeting the requirements of sustainable development.

[0026] 2、The application constructs a composite structure of rigidity and flexibility through a two-step method of "electrospun skeleton + interface regulation layer". The lyocell / LLZTO skeleton provides mechanical support and a rapid ion transmission channel, and the filled interface regulation layer makes up the gap between the fibers, forms a dense solid-solid interface, and effectively enhances the contact stability with the lithium metal negative electrode.

[0027] 3、The composite solid electrolyte prepared by the application has a uniform and complete structure, a continuous ion transmission path, and the assembled battery (full solid-state lithium metal battery) exhibits high room temperature ionic conductivity (>10 -4 S·cm -1 ), a wide electrochemical window (about 4.8V), excellent cycle stability (>500 hours) and a high critical current density, which provides a possibility for the development of flexible wearable energy storage devices. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a scanning electron microscope (SEM) image of the lyocell / LLZTO three-dimensional porous fiber skeleton prepared in Example 1 of the application;

[0029] Figure 2 is a cross-sectional SEM image of the final composite solid electrolyte prepared in Example 2 of the application;

[0030] Figure 3 is an ion electrochemical impedance diagram of a stainless steel symmetric battery assembled by the composite solid electrolyte fiber membrane;

[0031] Figure 4 is an electrochemical window diagram of a half-cell assembled by the composite solid electrolyte fiber membrane;

[0032] Figure 5 is a long cycle performance diagram of a lithium symmetric battery assembled by the composite solid electrolyte fiber membrane;

[0033] Figure 6 is a critical current density diagram of a lithium symmetric battery assembled by the composite solid electrolyte fiber membrane;

[0034] Figure 7 is a long cycle performance diagram of a full battery with LiFePO4 as the positive electrode and metal lithium as the negative electrode;

[0035] Figure 8 is an ion electrochemical impedance diagram of a stainless steel symmetric battery assembled by the composite solid electrolyte of Comparative Example 1;

[0036] Figure 9 is an ion electrochemical impedance diagram of a stainless steel symmetric battery assembled by the composite solid electrolyte of Comparative Example 2;

[0037] Figure 10is a long cycle performance chart of a lithium symmetric battery assembled by the composite solid electrolyte of Comparative Example 1;

[0038] Figure 11 is a long cycle performance chart of a lithium symmetric battery assembled by the composite solid electrolyte of Comparative Example 2. DETAILED DESCRIPTION

[0039] The technical solutions of the present application are further specifically described below through specific examples. It should be understood that the implementation of the present application is not limited to the following examples, and any form of variation and / or change made to the present application will fall within the scope of protection of the present application.

[0040] In the present application, unless specified, all parts, percentages are weight units, and the equipment and raw materials used are commercially available or commonly used in the art. The methods in the following examples are conventional methods in the art, unless otherwise specified.

[0041] The reagents used in the following examples can be purchased from conventional biochemical reagent stores, unless otherwise specified. 6.4 La3Zr 1.4 Ta 0.6 O 12 , LLZTO, purchased from the Youyan platform.

[0042] Example 1: Preparation of Lyocell / LLZTO three-dimensional porous fiber framework (1) Preparation of electrospinning precursor solution: 0.1 g of crushed waste Lyocell fiber, 0.1 g of polyformaldehyde (PF), 0.3 g of LLZTO (Li 6.4 La3Zr 1.4 Ta 0.6 O 12 ) were weighed and added to a mixed solvent of 5 ml of DMAC and 5 ml of DMF. The mixture was first heated to 115°C and stirred until the Lyocell fiber was dissolved, and then ultrasonic dispersion treatment was performed to obtain a uniform suspension.

[0043] To the above obtained suspension, 1.5 g of PVDF (polyvinylidene fluoride) and 0.1 g of LiTFSI (lithium bisfluorosulfonimide) were added, and after mixing, a uniform and stable electrospinning precursor solution was obtained. (2) Electrospinning: The electrospinning precursor solution prepared above was electrospun. The process parameters were: spinning voltage 15KV, distance between needle and receiving drum 10cm, solution advancing speed 1ml / h, and ambient temperature room temperature. The spinning product was collected on the drum to obtain a Lyocell / LLZTO three-dimensional porous fiber framework. Its micro-morphology is shown in Figure 1 .

[0044] Example 2: Preparation of composite solid electrolyte (1) Take the lyocell / LLZTO three-dimensional porous fiber skeleton prepared in Example 1 and spread it flat on a clean substrate. (2) Preparation of interface control layer solution: Dissolve 0.49g PEO (polyethylene oxide) and 0.32g LiTFSI in 10ml acetonitrile and stir evenly to obtain interface control layer solution. (3) Casting interface control layer: Use a syringe to draw 5ml of the interface control layer solution prepared in step (2) and evenly drop or cast it on a 50cm 2 The surface of the fiber skeleton in step (1) is fully infiltrated and the pores are filled.

[0045] Subsequently, the whole sample was moved into a vacuum oven at 50°C and dried for 12 hours to remove the solvent, and finally a composite solid electrolyte was obtained. Figure 2 As shown, the pores of the fiber skeleton are filled with a dense interface regulation layer.

[0046] Application Example 1

[0047] The composite solid electrolyte fiber membrane prepared in Example 2 was assembled into a battery to measure its performance. The prepared membrane was cut into discs with a diameter of 12 mm and assembled into a stainless steel symmetrical battery. The ionic conductivity at different temperatures was measured. Figure 3 It can be seen that with the increase of temperature, the ionic conductivity also shows an increasing trend. The overall ionic conductivity is high, with a value greater than 10 at room temperature. -4 S cm -1 The ionic conductivity meets the application requirements.

[0048] The membrane was cut into 16 mm diameter discs and assembled into half-cells to test the electrochemical window of the composite solid electrolyte fiber membrane. The test results are as follows: Figure 4 , and found that its electrochemical window was 4.8V. The wider the electrochemical window, the more suitable it is for high-voltage batteries. This shows that the prepared composite solid electrolyte fiber membrane has good interface stability with the electrode, can form a stable SEI, and has broad application prospects.

[0049] Figure 5 、 Figure 6 The long-term cycling performance and critical current density of the assembled lithium symmetric battery were measured. The membrane size used was also a 16mm diameter disc. The composite solid electrolyte fiber membrane can support the battery's stable cycling for more than 500 hours, showing good cycling performance. The results of the measurement at different current densities showed that the 0.6mA cm -2 The critical current density can meet the basic charging and discharging requirements.

[0050] Application Example 2

[0051] The composite solid electrolyte fiber membrane prepared in Example 2 was assembled into a full cell to determine its long cycle performance as shown in Figure 7 The positive electrode material was LiFePO4. The steps for preparing the positive electrode were as follows:

[0052] (1) The positive electrode active material was subjected to vacuum drying treatment at 100°C to remove moisture;

[0053] (2) Super P / positive electrode active material / PEO / lithium salt were dispersed in acetonitrile at a weight ratio of 1:6:2:1 to form a uniform slurry;

[0054] (3) The slurry was coated on a carbon-coated aluminum foil and subjected to vacuum drying treatment at 80°C for 24 hours, so that the active material loading of the positive electrode material was about 1-5 mg·cm −2 .

[0055] (4) The prepared positive electrode material was cut into small round pieces with a diameter of 12 mm, and a full cell was assembled, and the long cycle performance of the full cell was tested.

[0056] The full cell can be stably cycled for 50 times, and the battery has good cycle stability, and the coulombic efficiency is maintained at about 99% after 50 cycles.

[0057] Preparation and performance comparison of composite solid electrolyte without LLZTO

[0058] Purpose: This comparative example aims to prove the key role of the inorganic solid electrolyte filler LLZTO added in the present application in improving the comprehensive performance of the electrolyte.

[0059] (1) Skeleton preparation: Steps (1), (2), and (3) of Example 1 were repeated, with the only difference being that 0.3 g of LLZTO was not added in step (1). All other raw materials, amounts, and process parameters remained completely unchanged. Finally, a lyocell / PVDF three-dimensional porous fiber skeleton without LLZTO was obtained.

[0060] (2) Composite solid electrolyte preparation: All the steps of Example 2 were repeated, and the above fiber skeleton without LLZTO was infiltrated and dried with the same interfacial regulation layer solution to obtain a comparative composite solid electrolyte without LLZTO.

[0061] Preparation of composite solid electrolyte by traditional solution blending method

[0062] Purpose: This comparative example aims to prove the superiority of the two-step method of "first constructing a three-dimensional porous skeleton, and then filling a polymer electrolyte" adopted in the present application, compared to the traditional one-step solution blending technology, in terms of constructing efficient ion transport channels and improving electrochemical stability.

[0063] (1) Electrolyte slurry preparation: To ensure the consistency of components, we used the exact same material ratio as the final product of Example 2. 0.3 g of LLZTO, 1.5 g of PVDF, 0.49 g of PEO, and 0.42 g of LiTFSI (0.1 g + 0.32 g) were weighed and added together into 15 ml of DMF solvent. After 24 hours of strong magnetic stirring at 60°C, followed by 1 hour of ultrasonic dispersion, a uniform blended slurry was formed.

[0064] (2) Blade coating film formation: The above slurry was uniformly coated on a polytetrafluoroethylene plate with a blade gap of 200 μm.

[0065] (3) Drying: The substrate loaded with the slurry was first dried in a 80°C air oven for 4 hours to remove most of the solvent, then transferred to a 60°C vacuum oven for continued drying for 24 hours, obtaining a composite solid-state electrolyte film prepared by traditional blending method.

[0066] Performance test and data comparison

[0067] 1. Ionic conductivity

[0068] The ionic conductivity of the present invention (Example 2) is 1.2×10 −4 S·cm −1 , which is 2.4 times that of Comparative Example 1 (0.5×10 −4 S·cm −1 ), which shows that the introduction of LLZTO nanoparticles significantly improves the ionic conduction ability of the electrolyte, as it forms efficient ion fast channels in the polymer matrix. The ionic conductivity of the said Comparative Example 1 is shown in Figure 8 .

[0069] Compared with the ionic conductivity of 0.2×10 −4 S·cm −1 of the traditional blending method (Comparative Example 2), the electrolyte prepared by the two-step method of the present invention performs better. This is because in the structure of the present invention, the LLZTO particles are anchored on the fiber skeleton, forming a continuous and through ion conduction network, while in the traditional blending method, the LLZTO particles are completely wrapped by the polymer, distributed randomly, and difficult to form an effective long-range conduction path. The ionic conductivity of the said Comparative Example 2 is shown in Figure 9 .

[0070] 2. Solid-state electrolyte lithium symmetric long cycle

[0071] The cycle life of the lithium symmetric battery of the present invention far exceeds that of Comparative Examples 1 and 2. Example 2 has a cycle life of 0.2 mA·cm −2, 50℃ under the condition of realizing >500 hours of stable cycle, while the comparative example 1 in <300 hours occurred short circuit, comparative example 2 in <50 hours appeared voltage polarization increased. This shows that the introduction of LLZTO and the unique three-dimensional porous framework structure of the application effectively inhibits the growth of lithium dendrites, improves the mechanical strength and interface stability of the electrolyte, thereby significantly prolonging the cycle life of the battery. The cycle life of the lithium symmetric battery of the comparative example 1 and the comparative example 2 is as shown in Figure 10 and Figure 11 .

[0072] The composite solid-state electrolyte fiber membrane prepared by the application can improve the cycle stability, ion migration rate and interface stability of the battery after being assembled into a full solid-state lithium metal battery, and inhibit the growth of lithium dendrites, which brings an important breakthrough for the development of flexible wearable energy storage devices.

Claims

1. A composite solid electrolyte, characterized in that include: A three-dimensional porous fiber skeleton composed of lyocell nanofibers and LLZTO ceramic particles; and an interface regulation layer filling the pores of the three-dimensional porous fiber skeleton and / or covering the surface thereof, the interface regulation layer comprising a polymer and a lithium salt; The three-dimensional porous fiber skeleton is prepared by an electrospinning method, and its raw materials include waste lyocell fiber, paraformaldehyde (PF), LLZTO, a first polymer and a first lithium salt.

2. The composite solid electrolyte according to claim 1, characterized in that The first polymer is selected from one or more of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), hydroxymethyl cellulose, carboxymethyl cellulose (CMC), guar gum, gelatin, starch acetate, carboxymethyl starch or sodium alginate; The polymer in the interface regulation layer is a second polymer, and the second polymer is selected from one or more of polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), and polyethylene oxide (PEO).

3. The composite solid electrolyte according to claim 1, characterized in that The LLZTO is Ta-doped Li 6.4 La3Zr 1.4 Ta 0.6 O 12 .

4. The composite solid electrolyte according to claim 1, characterized in that The first lithium salt and / or the lithium salt in the interface control layer is selected from one or more of lithium perfluoroethanesulfonyl imide (LiFTFSI), lithium trifluoromethanesulfonate (LiOTf), lithium fluorophosphate (LiFO2P), lithium bis(trifluoroethanesulfonyl imide) (LiBETI), lithium nitrate (LiNO3), lithium perfluorobutanesulfonyl imide (LiPBSI) or lithium bis(trifluoropropanesulfonyl imide) (LiTFPSI).

5. A method for preparing the composite solid electrolyte according to claim 1, characterized in that: The method comprises the following steps: (a) preparing an electrospinning precursor solution: dispersing or dissolving waste lyocell fiber, paraformaldehyde (PF), LLZTO, a first polymer and a first lithium salt in a first solvent; (b) electrospinning: electrospinning the electrospinning precursor solution obtained in step (a) to obtain the three-dimensional porous fiber skeleton; (c) applying an interface regulation layer: casting or spin-coating the interface regulation layer on the three-dimensional porous fiber skeleton, the interface regulation layer comprising a second polymer, a second lithium salt and a second solvent; (d) drying: drying the product treated in step (c) to obtain the composite solid electrolyte.

6. The preparation method according to claim 5, characterized in that In step (a), the first solvent is selected from one or more of N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N-methylmorpholine-N-oxide (NMMO).

7. The preparation method according to claim 5, characterized in that Preparation of electrospinning precursor solution includes: S1 dissolution: lyocell fiber is crushed and dissolved in a first solvent, and paraformaldehyde (PF) and LLZTO are added, mixed, and heated to 115°C ± 10°C until the lyocell fiber is dissolved, and then ultrasonic dispersion or high shear stirring is performed to obtain a fiber solution; S2 blending: adding the first polymer and the first lithium salt to the obtained fiber solution and blending them to obtain an electrospinning precursor solution; The mass ratio of the lyocell fiber to the first solvent is 1: (60-100), the mass ratio of the lyocell fiber to LLZTO is 1: (1-5), and the mass ratio of PF to lyocell fiber is (1-3):

1. The mass ratio of the first polymer to the lyocell fiber is (10-20):1, and the mass ratio of the first lithium salt to the lyocell fiber is (1-3):

1.

8. The preparation method according to claim 5, characterized in that The process parameters for electrospinning in step (b) are as follows: the spinning solution is ejected through a needle with a diameter of 0.3 to 0.8 mm at a propulsion rate of 0.5 to 1 ml per hour, the distance between the needle and the collecting drum is controlled within the range of 8 to 15 cm, the applied electrostatic voltage is 5 to 30 kilovolts, the collecting drum speed is set at 200 to 1000 revolutions per minute, the relative humidity of the spinning environment is less than 30%, and the temperature is maintained between 15 and 35 degrees Celsius.

9. The preparation method according to claim 5, characterized in that In step (c), the interface regulation layer is a mixture of a second polymer, a second lithium salt, and a second solvent, which account for 20-30 wt%, 5-10 wt%, and 50-60 wt%, respectively.

10. A lithium battery, characterized in that: The method comprises the composite solid electrolyte according to any one of claims 1 to 4.

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