A fluorinated modified eggshell membrane-based solid-state polymer electrolyte, and a preparation method and application thereof

Abstract

The present application relates to the technical field of all-solid-state lithium metal battery, and particularly relates to a solid-state polymer electrolyte and a preparation method and application thereof. In the present application, trifluoroethanol is used to fluorinate eggshell membrane powder in natural eggshell, which is used as a polyethylene oxide-based solid-state polymer electrolyte additive. This can adjust the network structure of the polymer, enhance the electrochemical and mechanical performance of the solid-state electrolyte, inhibit lithium dendrite growth, and enhance the cycle performance of the lithium metal battery. The lithium ion transfer number of the improved solid-state electrolyte battery is determined by chronamperometry, and the lithium ion transfer number is higher, and it is easier to generate fluorinated lithium and lithium oxide, and better inhibit the growth of lithium dendrites. The addition of trifluoroethanol to fluorinate the eggshell membrane solid-state electrolyte in the natural eggshell makes the lithium symmetrical battery and the lithium iron phosphate full battery exhibit excellent performance in various cases.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of all-solid-state lithium metal batteries, in particular to a biomass-based solid-state polymer electrolyte and a preparation method and application thereof. BACKGROUND

[0002] Lithium metal batteries, with a high theoretical specific capacity (3860 mAh / g) and an extremely low redox potential (-3.04 V vs. SHE), are considered as the core of the next generation of high-energy-density energy storage systems. However, the uncontrollable lithium dendrite growth caused by the mismatch of lithium ion deposition dynamics, the parasitic side reactions caused by the high activity of the electrode / electrolyte interface, and the inherent flammable and explosive characteristics of organic solvents significantly exacerbate the risk of thermal runaway of the battery, which seriously hinders the practical application of lithium metal anodes. Under this background, solid-state electrolytes, with high flame retardancy, high mechanical modulus for inhibiting lithium dendrites, and interface stability under a wide electrochemical window, have become a key technology direction to solve the above problems. Among them, solid-state polymer electrolytes are concerned in the field of solid-state batteries due to their unique molecular designability, excellent interface conformal contact characteristics, lightweight flexibility, and potential for large-scale processing.

[0003] Early polyethylene oxide solid-state polymer electrolytes are limited by low room temperature conductivity and low lithium ion transference number. In recent years, through molecular design, plasticization strategy and inorganic filler composite, the conductivity of solid-state polymer electrolytes has been improved, but the solid-solid interface impedance, polymer aging and lithium / electrolyte interface passivation mechanism are still challenges. In addition, the "trade-off effect" between mechanical strength and ion transport requires precise regulation of the microstructure. However, the high impedance of the solid-solid interface, the aging and decomposition of the polymer chain segment in long-term cycling, and the formation mechanism of the dynamic passivation layer at the lithium metal / electrolyte interface are still the core challenges that restrict its practical application. SUMMARY

[0004] In view of the above prior art, the present application provides a biomass-based solid-state polymer electrolyte and a preparation method and application thereof. In the present application, fluorinated eggshell membrane powder is used as an additive of the solid-state polymer electrolyte to obtain an improved solid-state polymer electrolyte. The use of eggshell membrane powder as a filler can effectively regulate the network structure of the polymer matrix, which not only inhibits the growth of lithium dendrites, but also effectively improves the electrochemical performance of the solid-state lithium metal battery. In addition, the addition of fluorinated eggshell membrane powder can effectively improve the lithium ion transference number and promote the formation of fluorinated lithium and oxidized lithium on the surface of lithium metal, guiding the uniform deposition of lithium.

[0005] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0006] A preparation method of a fluorinated modified eggshell membrane-based solid-state polymer electrolyte, comprising the following steps:

[0007] (1) Preparation of the fluorinated eggshell membrane powder: the eggshell membrane and trifluoroethanol (TFE) are mixed uniformly, and then placed in a blast drying oven for reaction. After the reaction is completed, the product is washed, centrifuged, dried, and ground into powder to obtain the fluorinated eggshell membrane powder.

[0008] (2) Preparation of the fluorinated modified eggshell membrane-based solid-state polymer electrolyte: the fluorinated eggshell membrane powder, polyethylene oxide (PEO), dimethyl sulfoxide (DMSO), lithium salt, and anhydrous acetonitrile are stirred and mixed. After sufficient mixing, a polymer electrolyte containing fluorinated eggshell membrane is obtained. The polyethylene oxide solid-state electrolyte containing fluorinated eggshell membrane powder is uniformly coated on a carrier to form a film. After film formation, the product is transferred to a vacuum drying oven for drying until the dimethyl sulfoxide is completely volatilized, to obtain the fluorinated modified eggshell membrane-based solid-state polymer electrolyte.

[0009] Preferably, the eggshell membrane is the eggshell membrane in a natural eggshell, which can be one or more of a chicken egg membrane, a duck egg membrane, and a goose egg membrane.

[0010] Preferably, in step (1), the mass ratio (such as g / g) of the eggshell membrane to trifluoroethanol is 0.2-0.4: 16.7-33.4, preferably 0.3:25. For example, the mass of the eggshell membrane is 0.2-0.4 g, and the mass of the trifluoroethanol is 16.7-33.4 g.

[0011] Preferably, in step (1), the reaction temperature of the blast drying oven is 75-85°C, preferably 80°C, and the time is 10-15 h, preferably 12 h.

[0012] Preferably, in step (1), the washing is deionized water washing, and the number of centrifugation is 3-5 times.

[0013] Preferably, the lithium salt is lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0014] Preferably, the carrier is a polytetrafluoroethylene disc.

[0015] Preferably, the ratio of the fluorinated eggshell membrane powder, polyethylene oxide, dimethyl sulfoxide, lithium salt, and anhydrous acetonitrile is 0.019-0.023 g: 1.8-2.2 g: 0.8-1.2 mL: 0.79-0.83 g: 18-21 mL.

[0016] Preferably, in step (2), the temperature for stirring and mixing is 20-25°C.

[0017] Preferably, in step (2), the fluorinated eggshell membrane powder, PEO, dimethyl sulfoxide, lithium salt and anhydrous acetonitrile are mixed at 20-25℃, continuously stirred for 45-50h at a speed of 500-600rpm until each component is completely dissolved and a homogeneous solution is formed, obtaining a polymer electrolyte containing fluorinated eggshell membrane powder.

[0018] Preferably, in step (2), the solid-state polymer electrolyte containing fluorinated eggshell membrane powder is coated in the carrier at a rate of 0.1-0.3mL / cm 2 (0.2mL / cm 2 ) to form a film.

[0019] Preferably, in step (2), the drying condition is: temperature 50-55℃, time 3-5h. After film formation, it is moved to a vacuum drying oven and dried at 50-55℃ for 3-5h to obtain the solid-state polymer electrolyte.

[0020] The application protects the fluorinated modified eggshell membrane-based solid-state polymer electrolyte prepared by the above preparation method. The natural eggshell membrane (chicken egg membrane, duck egg membrane, goose egg membrane, etc.) is introduced into the solid-state polymer electrolyte.

[0021] The application also protects the use of the above fluorinated modified eggshell membrane-based solid-state polymer electrolyte in the preparation of all-solid-state lithium metal batteries.

[0022] Preferably, the application method is: cutting the fluorinated eggshell membrane powder solid-state polymer electrolyte into a disc, transferring it to an argon-filled glove box, placing the negative electrode shell, spring, gasket, negative lithium sheet, solid-state polymer electrolyte in turn, then placing the positive electrode sheet, covering the positive electrode shell and pressing the battery.

[0023] Preferably, the positive electrode sheet is selected from a positive lithium sheet or a lithium iron phosphate (LFP) sheet.

[0024] In the application, trifluoroethanol is used to fluorinate the chicken egg membrane (or duck egg membrane, goose egg membrane, etc.) powder in the natural eggshell, which is used as an additive for solid-state polymer electrolyte. This can adjust the network structure of the polymer, enhance the electrochemical and mechanical performance of the solid-state electrolyte, inhibit the growth of lithium dendrites, and enhance the cycle performance of the lithium metal battery. The lithium ion transfer number of the improved solid-state electrolyte battery is determined by chronamperometry, which has a higher lithium ion transfer number and is more prone to the formation of lithium fluoride and lithium oxide, etc., and better inhibits the growth of lithium dendrites. The addition of trifluoroethanol to fluorinate the chicken egg membrane in the natural eggshell solid-state electrolyte makes the lithium symmetrical battery and lithium iron phosphate full battery exhibit excellent performance in various conditions.

[0025] Compared with the prior art, the application has the following advantages:

[0026] 1. The fluorinated modified egg membrane-based solid polymer electrolyte of the present invention effectively inhibits the formation of lithium dendrites by utilizing the advantage of the mineralization process of natural macromolecules in egg membrane powder to regulate inorganic crystals.

[0027] 2. The fluorinated modified egg membrane-based solid polymer electrolyte obtained by the preparation method of this invention has high ionic conductivity and a wide electrochemical window. The addition of trifluoroethanol-fluorinated egg membrane powder enhances the performance of the solid polymer electrolyte. The strong electron-withdrawing effect of trifluoromethyl (-CF3) reduces the viscosity of the solid polymer electrolyte, thereby increasing the lithium-ion migration rate. The trifluoroethanol-fluorinated egg membrane powder contains F... - The introduction of this compound, with its strong electron-withdrawing effect, makes solvent molecules more difficult to oxidize, thereby expanding the high-voltage tolerance range of solid polymer electrolytes and making them suitable for high-voltage cathode materials.

[0028] 3. The fluorinated modified egg membrane-based solid polymer electrolyte prepared by the method of this invention achieves long-term cycle stability in lithium metal batteries. The low viscosity of this electrolyte enhances ion transport rate, alleviates concentration polarization, and suppresses lithium dendrite formation. After cycling, lithium metal batteries assembled using the fluorinated modified egg membrane-based solid polymer electrolyte exhibit a stable lithium fluoride-rich interface layer at the electrode / electrolyte interface with significantly low interfacial impedance. Furthermore, in symmetric battery testing, the battery containing the fluorinated modified egg membrane-based solid polymer electrolyte maintains a stable overpotential after approximately 1000 hours of cycling, indicating that this electrolyte possesses excellent electrochemical stability and long cycle life, effectively suppressing lithium dendrite growth and interfacial side reactions. In LFP full-cell testing, the LFP full cell containing the fluorinated modified egg membrane-based solid polymer electrolyte maintains 130 mAh / g after 100 cycles at 1C. -1 It maximizes capacity utilization, achieving a coulomb efficiency of up to 99%. Attached Figure Description

[0029] Figure 1 Here is a SEM image of the solid polymer electrolyte surface of the fluorinated modified egg membrane powder prepared in Example 1;

[0030] Figure 2 Here is a cross-sectional SEM image of the solid polymer electrolyte in the fluorinated modified egg membrane powder prepared in Example 1.

[0031] Figure 3 Visual image of the fluorinated modified egg membrane powder solid polymer electrolyte prepared in Example 1;

[0032] Figure 4 Electrochemical impedance spectroscopy of a lithium-ion symmetric battery assembled using the fluorinated modified egg membrane powder solid polymer electrolyte prepared in Example 1.

[0033] Figure 5 The graph shows the lithium-ion transference number of a lithium symmetric battery assembled using the fluorinated egg membrane powder solid polymer electrolyte prepared in Example 1. The inset is an enlarged view of the Nyquist curves at different temperatures.

[0034] Figure 6 This is an electrochemical stability window diagram of a lithium-symmetric battery assembled using the fluorinated egg membrane powder solid polymer electrolyte prepared in Example 1.

[0035] Figure 7 The image shows a combustion test result of the fluorinated egg membrane powder solid polymer electrolyte prepared in Example 1.

[0036] Figure 8 The XPS spectrum of the lithium-symmetric battery assembled from fluorinated egg membrane powder solid polymer electrolyte in Example 1 after cycling is shown.

[0037] Figure 9 0.1mA cm -2 0.1mAh cm -2 The following is a charging and discharging distribution diagram of a fluorinated modified eggshell membrane solid polymer electrolyte lithium symmetric battery assembled using fluorinated eggshell membrane powder solid polymer electrolyte of Example 1 of the present invention.

[0038] Figure 10 0.1mA cm -2 0.1mAh cm -2 The following are charge-discharge curves of the fluorinated modified eggshell membrane solid polymer electrolyte lithium symmetric battery assembled using the fluorinated eggshell membrane powder solid polymer electrolyte of Example 1 of the present invention at the 100th, 200th, 300th, 400th and 500th cycles.

[0039] Figure 11 The coulombic efficiency diagram of the fluorinated modified eggshell membrane solid polymer electrolyte lithium symmetric LFP full cell assembled using the fluorinated eggshell membrane powder solid polymer electrolyte of Example 1 of the present invention at a rate of 1C. Detailed Implementation

[0040] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental materials and methods described in the embodiments of the present invention are conventional methods.

[0041] It should be noted that the professional terms used in the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the protection scope of the present application. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present application can be purchased from the market or prepared by the existing method.

[0042] In the prior art, although solid-state electrolytes are highly expected due to their significant advantages, a series of major challenges still need to be overcome in the practical application level. The solid-state electrolyte is limited by low room temperature conductivity, low lithium ion transference number and poor solid-solid interface contact between the solid-state electrolyte and the electrode, which significantly increases the interface impedance and affects the overall performance of the battery. In view of these technical defects, the present application provides a preparation method of fluorinated eggshell membrane powder solid-state polymer electrolyte. The fluorinated eggshell membrane powder solid-state polymer electrolyte prepared by the present application effectively inhibits the formation of lithium dendrites by introducing eggshell membrane powder in the eggshell and utilizing the advantage of natural macromolecular mineralization process to regulate inorganic crystals. In addition, the excellent flexibility of the solid-state polymer electrolyte can better fit the electrode, solving the problem of poor interface contact between the electrode and the electrolyte. The low viscosity characteristic improves the ion transmission rate and relieves the concentration polarization, providing good conditions for the long-term stable cycle of the battery.

[0043] The purity of dimethyl sulfoxide (DMSO) in the following examples is 99%, and the molecular weight (Mw) of polyethylene oxide is 600000.

[0044] The technical solutions of the present application are further explained and described below by using examples, as follows:

[0045] Example 1

[0046] A preparation method of fluorinated eggshell membrane powder solid-state polymer electrolyte, comprising the following steps:

[0047] (1) The preparation method of the fluorinated eggshell membrane powder is as follows: 0.3g of eggshell membrane powder and 25g of trifluoroethanol (TFE) are uniformly mixed, then placed in a forced air drying oven for reaction at 80℃ for 12h, washed and centrifuged for 3 times, the obtained solid-state is dried and ground into powder to obtain the fluorinated eggshell membrane powder.

[0048] (2) Preparation of fluorinated modified eggshell membrane powder solid-state polymer electrolyte: 0.021g of fluorinated eggshell membrane powder, 2.0g of PEO, 1.0mL of DMSO, 0.82g of LiTFSI and 20mL of anhydrous acetonitrile are stirred and mixed (25℃, rotation speed 550rpm), and after continuous stirring for 48h, a polymer electrolyte containing fluorinated eggshell membrane is obtained; the polyethylene oxide solid-state electrolyte containing fluorinated eggshell membrane powder is coated on the surface of the lithium metal electrode at a rate of 0.2mL / cm 2Coating in a polytetrafluoroethylene disc with a diameter of 10 cm, coating uniform static film forming, after film forming into a vacuum drying oven (52℃, 4h) drying to DMSO completely volatilize, get fluorinated modified egg membrane powder solid state polymer electrolyte (PEO@Fegg).

[0049] Example 2

[0050] A method for preparing a fluorinated egg membrane powder solid state polymer electrolyte, comprising the following steps:

[0051] (1) The preparation method of the fluorinated eggshell membrane powder is: 0.3g eggshell membrane powder and 25g trifluoroethanol (TFE) are uniformly mixed, then placed in a blast drying oven and reacted at 80℃ for 12h, washed and centrifuged 3 times, and the obtained solid is dried and ground into powder to obtain the fluorinated eggshell membrane powder.

[0052] (2) Preparation of fluorinated modified egg membrane powder solid state polymer electrolyte: 0.019g fluorinated eggshell membrane powder, 1.8g PEO, 0.8mL DMSO, 0.79g LiTFSI and 18mL anhydrous acetonitrile are stirred and mixed (25℃, rotation speed 550rpm), and after continuous stirring for 48h, a polymer electrolyte containing fluorinated eggshell membrane is obtained; the polyethylene oxide solid electrolyte containing fluorinated eggshell membrane powder is coated in a polytetrafluoroethylene disc with a diameter of 10 cm, and the coating is uniform and static film forming, after film forming into a vacuum drying oven (52℃, 4h) drying to DMSO completely volatilize, get fluorinated modified egg membrane powder solid state polymer electrolyte (PEO@Fegg). 2 Coating in a polytetrafluoroethylene disc with a diameter of 10 cm, coating uniform static film forming, after film forming into a vacuum drying oven (52℃, 4h) drying to DMSO completely volatilize, get fluorinated modified egg membrane powder solid state polymer electrolyte (PEO@Fegg).

[0053] Example 3

[0054] A method for preparing a fluorinated egg membrane powder solid state polymer electrolyte, comprising the following steps:

[0055] (1) The preparation method of the fluorinated eggshell membrane powder is: 0.3g eggshell membrane powder and 25g trifluoroethanol (TFE) are uniformly mixed, then placed in a blast drying oven and reacted at 80℃ for 12h, washed and centrifuged 3 times, and the obtained solid is dried and ground into powder to obtain the fluorinated eggshell membrane powder.

[0056] (2) Preparation of fluorinated modified egg membrane powder solid state polymer electrolyte: 0.019g fluorinated eggshell membrane powder, 1.8g PEO, 0.8mL DMSO, 0.79g LiTFSI and 18mL anhydrous acetonitrile are stirred and mixed (25℃, rotation speed 550rpm), and after continuous stirring for 48h, a polymer electrolyte containing fluorinated eggshell membrane is obtained; the polyethylene oxide solid electrolyte containing fluorinated eggshell membrane powder is coated in a polytetrafluoroethylene disc with a diameter of 10 cm, and the coating is uniform and static film forming, after film forming into a vacuum drying oven (52℃, 4h) drying to DMSO completely volatilize, get fluorinated modified egg membrane powder solid state polymer electrolyte (PEO@Fegg). 2Coating in a polytetrafluoroethylene disc with a diameter of 10 cm, coating uniform static film forming, after film forming into a vacuum drying oven (52℃, 4h) drying to DMSO completely volatilize, get fluorinated modified egg membrane powder solid state polymer electrolyte (PEO@Fegg).

[0057] Example 4

[0058] A method for preparing a fluorinated egg membrane powder solid state polymer electrolyte, comprising the following steps:

[0059] (1) The preparation method of the fluorinated eggshell membrane powder is: 0.25g eggshell membrane powder and 20.9g trifluoroethanol (TFE) are uniformly mixed, then placed in a blast drying oven and reacted at 80℃ for 12h, washed, centrifuged 3 times, and the obtained solid is dried and ground into powder to obtain the fluorinated eggshell membrane powder.

[0060] (2) Preparation of fluorinated modified egg membrane powder solid state polymer electrolyte: 0.022g fluorinated eggshell membrane powder, 2.1g PEO, 1.1mL DMSO, 0.82g LiTFSI and 21mL anhydrous acetonitrile are stirred and mixed (25℃, rotation speed 550rpm), and after continuous stirring for 48h, a polymer electrolyte containing fluorinated eggshell membrane is obtained; the polyethylene oxide solid electrolyte containing fluorinated eggshell membrane powder is coated in a polytetrafluoroethylene disc with a diameter of 10 cm, and the coating is uniform and static film forming, after film forming into a vacuum drying oven (52℃, 4h) drying to DMSO completely volatilize, get fluorinated modified egg membrane powder solid state polymer electrolyte (PEO@Fegg). 2 Coating in a polytetrafluoroethylene disc with a diameter of 10 cm, coating uniform static film forming, after film forming into a vacuum drying oven (52℃, 4h) drying to DMSO completely volatilize, get fluorinated modified egg membrane powder solid state polymer electrolyte (PEO@Fegg).

[0061] Example 5

[0062] A method for preparing a fluorinated egg membrane powder solid state polymer electrolyte, comprising the following steps:

[0063] (1) The preparation method of the fluorinated eggshell membrane powder is: 0.25g eggshell membrane powder and 20.9g trifluoroethanol (TFE) are uniformly mixed, then placed in a blast drying oven and reacted at 80℃ for 12h, washed, centrifuged 3 times, and the obtained solid is dried and ground into powder to obtain the fluorinated eggshell membrane powder.

[0064] (2) Preparation of fluorinated modified egg membrane powder solid state polymer electrolyte: 0.022g fluorinated eggshell membrane powder, 2.1g PEO, 1.1mL DMSO, 0.82g LiTFSI and 21mL anhydrous acetonitrile are stirred and mixed (25℃, rotation speed 550rpm), and after continuous stirring for 48h, a polymer electrolyte containing fluorinated eggshell membrane is obtained; the polyethylene oxide solid electrolyte containing fluorinated eggshell membrane powder is coated in a polytetrafluoroethylene disc with a diameter of 10 cm, and the coating is uniform and static film forming, after film forming into a vacuum drying oven (52℃, 4h) drying to DMSO completely volatilize, get fluorinated modified egg membrane powder solid state polymer electrolyte (PEO@Fegg). 2The PEO@Fegg was obtained by coating the fluorinated modified eggshell membrane powder in a polytetrafluoroethylene disc with a diameter of 10 cm to form a uniform static film, and then drying in a vacuum drying oven (52°C, 4h) to completely volatilize DMSO.

[0065] The fluorinated eggshell membrane powder solid-state polymer electrolyte was prepared in Examples 1-5. The solid-state polymer electrolyte prepared in Example 1 was taken as an example for research, and the specific research methods and results are shown below.

[0066] I. Battery assembly

[0067] The lithium symmetric battery (PEO@Fegg-Li) or LFP full battery (PEO@Fegg-LFP) was assembled using the fluorinated eggshell membrane powder solid-state polymer electrolyte prepared in Example 1.

[0068] Taking a CR2032 button cell as an example, the fluorinated eggshell membrane powder solid-state polymer electrolyte prepared in Example 1 was cut into a disc with a diameter of 16 mm, and then placed in an argon-filled glove box. The negative electrode shell, spring, gasket, negative lithium sheet, and solid-state polymer electrolyte were sequentially placed. According to the type of battery to be assembled, a positive lithium sheet or a lithium iron phosphate sheet was placed, and the positive electrode shell was covered and the battery was compressed to obtain a PEO@Fegg-Li battery or a PEO@Fegg-LFP battery.

[0069] II. Results and discussion

[0070] In the present application, the fluorinated modified eggshell membrane powder solid-state electrolyte was prepared by mixing TFE fluorinated natural eggshell membrane powder with anhydrous acetonitrile, DMSO, PEO, and lithium salt in a certain proportion, stirring uniformly, and then static drying. Due to the presence of PEO and lithium salt, PEO exhibits excellent solubility and coordination ability, which enables it to establish strong coordination interaction with the fluorinated eggshell membrane powder to form a stable complex. The eggshell membrane powder, as a natural biological macromolecule, can adjust the network structure of the polymer, enhance the electrochemical and thermal mechanical performance of the solid-state electrolyte, and inhibit the growth of lithium dendrites.

[0071] Figure 1 In the present application, the fluorinated modified eggshell membrane powder solid-state polymer electrolyte has a dense and uniform surface morphology and no phase separation phenomenon, which can effectively reduce the contact impedance of the electrode / electrolyte interface.

[0072] The PEO@Fegg-Li battery or the PEO@Fegg-LFP battery prepared in the present application has a high capacity, a long cycle life, and a high energy density. Figure 2It is concluded that the cross-section morphology of the fluorinated modified eggshell membrane powder solid-state polymer electrolyte shows excellent microstructure characteristics: under scanning electron microscope (SEM) observation, the cross-section shows a highly dense continuous phase distribution with no obvious pore defects. This indicates that the cross-section has ideal isotropic characteristics. The thickness of the fluorinated modified eggshell membrane-based solid-state polymer electrolyte is about 100 μm.

[0073] In order to reflect the good physical properties of the fluorinated modified eggshell membrane powder solid-state polymer electrolyte, the fluorinated modified eggshell membrane-based solid-state polymer electrolyte film was displayed for visual effect.

[0074] As shown in Figure 3 , the fluorinated modified eggshell membrane powder solid-state polymer electrolyte was bent, which indicates that the fluorinated modified eggshell membrane-based solid-state polymer electrolyte has good flexibility. The good flexibility of the solid-state electrolyte has significant advantages in the battery system, mainly reflected in the improvement of the interface stability, the optimization of the mechanical properties, and the enhancement of the long-term cycle performance of the battery, etc. The solid-state electrolyte with good flexibility can effectively disperse local stress through elastic deformation and block lithium dendrite penetration. At the same time, it can also maintain conformal contact with the electrode, avoiding micro-cracks caused by volume changes of the rigid interface.

[0075] Based on the research purpose of exploring the correlation between the lithium ion transport kinetics and the microstructure of the fluorinated modified eggshell membrane powder solid-state polymer electrolyte, the ion conductivity of the electrolyte material at 298 K temperature was measured by the electrochemical impedance spectroscopy (EIS) system.

[0076] As shown in Figure 4 , through the electrochemical impedance spectroscopy (EIS) analysis, it was found that the lithium metal symmetric battery using the fluorinated modified eggshell membrane-based solid-state polymer electrolyte showed a typical charge transfer dominated capacitive arc characteristic in the high frequency region of 0.1 Hz-100000 Hz, and the charge transfer resistance (R ct ) of the modified electrolyte system was low. This indicates that the fluorinated modified eggshell membrane-based solid-state polymer electrolyte has smaller resistance to Li + migration and faster electrochemical reaction rate. In addition, the ion conductivity of the fluorinated modified eggshell membrane-based solid-state polymer electrolyte at different temperatures was studied by the EIS system.

[0077] As shown in Figure 5 , the resistance of the fluorinated modified eggshell membrane powder solid-state polymer electrolyte at 25℃-65℃ can be used to calculate the ion conductivity at each temperature according to the formula: σ (ion conductivity, S / m) = L / (Rb*S). Where L is the thickness of the separator (cm), Rb represents the bulk resistance (Ω), and S represents the effective area of the solid-state electrolyte (cm 2)。It can be seen that with the increase of experimental temperature, the ionic conductivity gradually increases. Through the calculation of ionic conductivity at different temperatures, it can be seen that the fluorinated modified eggshell membrane-based solid-state polymer electrolyte has good ion migration dynamics. In addition to ionic conductivity, ion transference number is also(t Li + ) is another key factor of high-performance lithium metal batteries. In addition, the exchange current density (j0) is determined by means of Tafel diagram to evaluate the charge transfer dynamics of electrode-electrolyte interface.

[0078] From Figure 6 It can be seen that through the electrochemical stability window (LSV) test, the fluorinated modified eggshell membrane powder solid-state polymer electrolyte exhibits an ultra-wide electrochemical stability window of 5.1V. This characteristic is derived from the synergistic effect of strong polarization of C-F bond formed in the fluorination process and three-dimensional cross-linked structure, which effectively inhibits the oxidative degradation of polymer chain segments at high voltage. This solid-state polymer electrolyte exhibits important engineering application value in the field of constructing high-energy-density solid-state lithium metal batteries.

[0079] As shown in Figure 7 , the thermal imaging test shows that the fluorinated modified eggshell membrane powder solid polymer electrolyte does not heat up rapidly after heating for 40s compared with PEO solid polymer electrolyte, indicating its excellent thermal stability and no thermal runaway phenomenon in battery application.

[0080] As shown in Figure 8 , the lithium metal battery assembled by the fluorinated modified eggshell membrane powder solid-state polymer electrolyte has a stable interface layer rich in LiF at the electrode / electrolyte interface after 20h of cycling at a current density of 0.1mA cm -2 + , which has high mechanical strength and can block the penetration of lithium dendrites, and LiF has a low diffusion barrier to Li + , which can promote the uniform deposition / dissolution of lithium ions, and it is shown that the fluorinated modified eggshell membrane-based solid-state polymer electrolyte is chemically stable, which prolongs the cycle life of the battery.

[0081] The present application is to further explore the interface stability mechanism of the fluorinated modified eggshell membrane-based solid-state polymer electrolyte to the lithium metal anode, and the lithium symmetric battery system is systematically evaluated by constant current cycling test method. Under the conditions of current density of 0.1mA cm -2 and capacity of 0.1mAh cm -2 , the effect of modified electrolyte on the inhibition of lithium dendrite growth and the stability of electrode / electrolyte interface is explored by continuously carrying out lithium deposition / dissolution cycle experiment.

[0082] As shown in Figure 9As shown, the overpotential of the battery assembled using the fluorinated modified eggshell membrane powder solid-state polymer electrolyte is stable, and the polarization phenomenon of the battery using the fluorinated modified eggshell membrane-based solid-state polymer electrolyte is still small after 1000h of continuous use. Therefore, the fluorinated modified eggshell membrane-based solid-state polymer electrolyte realizes stable lithium plating and stripping, and has a long cycle life.

[0083] Figure 10 As shown, the capacity-voltage curve of the lithium symmetric battery assembled using the fluorinated modified eggshell membrane powder solid-state polymer electrolyte at a current density of 0.1mAcm -2 and a surface capacity of 0.1mAh cm -2 , the curve shows that after 100 cycles, the voltage rises to about +13mV during the lithium deposition stage (charging) and remains flat, indicating uniform lithium deposition and stable interface impedance; during the stripping stage (discharge), the voltage drops to about -13mV and forms a symmetrical negative platform, with a hysteresis voltage difference AV of 26mV. After 500 cycles, AV only increases to 40mV, and the platform also only appears slight fluctuations, and the lithium symmetric battery assembled based on the fluorinated modified eggshell membrane solid-state polymer electrolyte exhibits excellent cycle stability.

[0084] In order to further study the role of the fluorinated modified eggshell membrane powder solid-state polymer electrolyte in stabilizing the LFP battery, the present application carried out a continuous lithium ion plating and stripping process at a rate of 1C.

[0085] As shown in Figure 11 , the present application carried out a study on the entire battery between the voltage limits of 2.5V and 4.2V at a static charge and discharge current density of 1C. The PEO@Fegg-LFP full battery exhibits stable cycling, maintaining a capacity of 130mAh·g -1 after 100 cycles, with a coulombic efficiency of nearly 99%. The fluorinated modified eggshell membrane powder solid-state polymer electrolyte has the dual advantages of inhibiting lithium dendrite growth and improving the cycle stability of the battery, and inhibiting lithium dendrite and long cycle stability of the battery.

[0086] In summary, the fluorinated modified eggshell membrane powder solid-state polymer electrolyte prepared by the present application is beneficial to inhibit lithium dendrites, improve ion mobility, and provide the possibility of realizing stable and long cycle life and high capacity solid-state batteries.

[0087] It should be particularly noted that the technical meaning of the numerical range mentioned in the claims of the present application should be interpreted as covering both end point values of the range and any continuous or discrete numerical points between the end points. In order to avoid redundant description, the preferred technical solutions are exemplarily illustrated herein only through typical embodiments, but this does not constitute a limitation on the protection scope. Based on the understanding of the core innovative idea of the present application, those skilled in the art can make equivalent replacements, parameter adjustments or process improvements to the embodiments. Therefore, the protection scope of the present application should be subject to the claims, and its legal effect covers all reasonable variations and adaptive modifications based on the basic technical concept of the present application.

Claims

1. A method for preparing a fluorinated modified eggshell membrane-based solid polymer electrolyte, characterized in that, Includes the following steps: (1) Preparation of fluorinated eggshell membrane powder: After the eggshell membrane and trifluoroethanol are mixed evenly, they are placed in a drying oven for reaction. After the reaction is completed, the mixture is washed and centrifuged. The resulting solid is dried and ground into powder to obtain fluorinated eggshell membrane powder. (2) Preparation of fluorinated eggshell membrane-based solid polymer electrolyte: Fluorinated eggshell membrane powder is stirred and mixed with polyethylene oxide, dimethyl sulfoxide, lithium salt and anhydrous acetonitrile. After thorough mixing, a polymer electrolyte containing fluorinated eggshell membrane powder is obtained. The solid electrolyte containing fluorinated eggshell membrane powder is uniformly coated on a carrier and allowed to stand to form a film. After film formation, it is dried to obtain fluorinated eggshell membrane solid polymer electrolyte.

2. The method for preparing a fluorinated modified eggshell membrane-based solid polymer electrolyte according to claim 1, characterized in that, The eggshell membrane is one or more of the following: chicken egg membrane, duck egg membrane, and goose egg membrane.

3. The method for preparing a fluorinated modified eggshell membrane-based solid polymer electrolyte according to claim 1, characterized in that, In step (1), the mass ratio of the eggshell membrane to trifluoroethanol is 4~8:48~52; the reaction temperature of the forced-air drying oven is 75~85℃, and the time is 10~15h; the washing is done by rinsing with deionized water, and the number of centrifugations is 3~5 times.

4. The method for preparing a fluorinated modified eggshell membrane-based solid polymer electrolyte according to claim 1, characterized in that, The lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

5. The method for preparing a fluorinated modified eggshell membrane-based solid polymer electrolyte according to claim 1, characterized in that, The carrier is a polytetrafluoroethylene disc.

6. The method for preparing a fluorinated modified eggshell membrane-based solid polymer electrolyte according to claim 1, characterized in that, In step (2), the ratio of fluorinated eggshell membrane powder, polyethylene oxide, dimethyl sulfoxide, lithium salt and anhydrous acetonitrile is 0.019~0.023 g: 1.8~2.2 g: 0.8~1.2 mL: 0.79~0.83 g: 18~21 mL.

7. The method for preparing a fluorinated modified eggshell membrane-based solid polymer electrolyte according to claim 1, characterized in that, In step (2), the stirring temperature is 20~25℃, the stirring speed is 500~600rpm, and the time is 45~50h; the solid polymer electrolyte containing fluorinated egg membrane powder is added at a concentration of 0.1~0.3 mL / cm. 2 The coating is placed on a carrier and allowed to stand to form a film; the drying conditions are: temperature 50~55℃, time 3~5 h.

8. Fluorinated modified eggshell membrane-based solid polymer electrolyte prepared by any one of claims 1-7.

9. The application of the fluorinated modified eggshell membrane-based solid polymer electrolyte according to claim 8 in the preparation of all-solid-state lithium metal batteries.

10. The application according to claim 9, characterized in that, The application method is as follows: The dried fluorinated eggshell membrane powder polymer electrolyte is cut into discs and transferred to a glove box filled with argon. The negative electrode shell, spring sheet, gasket, negative electrode lithium sheet, and solid polymer electrolyte are placed in sequence, and then the positive electrode sheet is placed in. The positive electrode shell is then covered and the battery is pressed tightly. The positive electrode is selected from lithium positive electrode sheets or lithium iron phosphate positive electrode sheets.

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