Lithium clay mineral PVDF-based composite solid-state electrolyte membrane, preparation method and application thereof, and quasi-solid-state battery

Abstract

The invention provides a lithiated clay mineral PVDF-based composite solid-state electrolyte membrane, a preparation method and application thereof, and a quasi-solid-state battery, and belongs to the technical field of solid-state lithium batteries. The preparation method comprises the following steps: mixing lithium halide, clay minerals and water for the first time, and carrying out ion exchange reaction to obtain lithiated clay minerals; mixing lithiated clay minerals, PVDF, organic lithium salt and an organic solvent for the second time to obtain composite slurry; and applying the composite slurry to the surface of a substrate, and carrying out thermocuring to obtain the lithiated clay mineral PVDF-based composite solid electrolyte membrane. The lithiated clay mineral is introduced into a mixed system of PVDF and organic lithium salt, so that the crystallinity of PVDF can be effectively reduced, an amorphous region is increased, conversion of PVDF crystals to beta-type PVDF is promoted, and the dissociation process of the lithium salt in the electrolyte is promoted; meanwhile, the lithiated clay mineral is introduced, so that the ionic conductivity can be obviously improved, an electrochemical window is widened, the mechanical property is improved, and the growth of lithium dendrites is inhibited.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state lithium batteries, in particular to a lithiumized clay mineral PVDF-based composite solid electrolyte film, a preparation method and application thereof, and a quasi-solid-state battery. BACKGROUND

[0002] Lithium metal anode has become an ideal choice for high-energy-density energy storage devices due to its low redox potential and excellent specific capacity characteristics. Among various electrochemical energy storage systems, rechargeable lithium-ion batteries have become the most promising energy storage solution in the field of electric vehicles and mobile electronic devices due to their excellent mass energy density, stable cycle characteristics, and good portability. However, commercial lithium-ion batteries have safety risks due to the use of organic liquid electrolyte systems. Studies have shown that the use of solid-state electrolytes can effectively solve the above-mentioned problems and can be used with lithium metal anodes, greatly optimizing battery performance.

[0003] The use of solid-state electrolytes instead of liquid electrolytes not only significantly improves the safety of the battery, but also exhibits excellent chemical stability and lithium dendrite suppression ability, thereby improving the electrochemical performance and cycle performance of the battery. Among them, polyvinylidene fluoride (PVDF) is widely used in solid-state electrolytes due to its good film-forming performance, high ductility, and high dielectric constant. However, PVDF has low intrinsic ionic conductivity, high crystallinity, and other problems that hinder ion migration, affecting battery performance. Therefore, a strategy of introducing inorganic fillers into the polymer system is often used to improve the above-mentioned situation. Currently, commonly used inorganic fillers include lithium aluminum titanate (LATP) and lithium lanthanum titanate oxide (LLTO) containing Li + conductive particles, but the above inorganic fillers have the problem of high price, and their effect on improving ionic conductivity is also general. SUMMARY

[0004] Therefore, the purpose of the present application is to provide a lithiumized clay mineral PVDF-based composite solid electrolyte film, a preparation method and application thereof, and a quasi-solid-state battery. The lithiumized clay mineral PVDF-based composite solid electrolyte film provided by the present application uses a lithiumized clay mineral as an inorganic filler, which is low in cost and can significantly improve the ion transmission rate and the ionic conductivity of PVDF.

[0005] In order to achieve the above-mentioned application purpose, the present application provides the following technical solutions: The present application provides a preparation method of a lithiumized clay mineral PVDF-based composite solid electrolyte film, comprising the following steps: mixing lithium halide, clay mineral and water first, carrying out ion exchange reaction to obtain lithiumized clay mineral; mixing the lithiumized clay mineral, polyvinylidene fluoride, organic lithium salt and organic solvent second to obtain a composite slurry; The composite slurry is applied on the surface of the substrate, and heat curing is performed to obtain a lithiated clay mineral PVDF-based composite solid electrolyte film.

[0006] Preferably, the clay mineral comprises one or more of sodium montmorillonite, calcium montmorillonite, halloysite, attapulgite, hectorite, diatomite and vermiculite. The mass ratio of the lithium halide to the clay mineral is (1-10):1.

[0007] Preferably, the ion exchange reaction is performed under stirring, and the stirring rate is 400-1000 r / min. The heating temperature of the ion exchange reaction is 30-60℃, and the stirring time is 6-12h.

[0008] Preferably, the mass ratio of the polyvinylidene fluoride to the lithiated clay mineral is 10:(0.1-2). The mass ratio of the organic lithium salt to the polyvinylidene fluoride is 1:(0.8-2). The mass ratio of the organic solvent to the polyvinylidene fluoride is (1-12):1.

[0009] Preferably, the organic lithium salt comprises lithium bis(trifluoromethylsulfonyl)imide and / or lithium bisfluorosulfonylimide. The mixing temperature is 25-45℃, and the mixing time is 6-12h.

[0010] Preferably, the heat curing temperature is 60-80℃, and the heat curing time is 8-24h.

[0011] The present application provides a lithiated clay mineral PVDF-based composite solid electrolyte film prepared by the above preparation method.

[0012] Preferably, the thickness of the lithiated clay mineral PVDF-based composite solid electrolyte film is 30-80μm.

[0013] The present application provides an application of the above lithiated clay mineral PVDF-based composite solid electrolyte film in a lithium ion battery.

[0014] The present application provides a quasi-solid-state battery, comprising a lithium iron phosphate positive electrode sheet, the above lithiated clay mineral PVDF-based composite solid electrolyte film and a lithium metal negative electrode sheet arranged in sequence. The two side surfaces of the lithiated clay mineral PVDF-based composite solid electrolyte film are applied with an electrolyte.

[0015] The application provides a preparation method of a lithiumized clay mineral PVDF-based composite solid electrolyte film, and comprises the following steps: first mixing lithium halide, a clay mineral and water to perform an ion exchange reaction to obtain a lithiumized clay mineral; second mixing the lithiumized clay mineral, polyvinylidene fluoride, an organic lithium salt and an organic solvent to obtain a composite slurry; and applying the composite slurry on the surface of a substrate to perform heat curing to obtain the lithiumized clay mineral PVDF-based composite solid electrolyte film. The application takes the clay mineral as the main component of inorganic fillers, and greatly reduces the cost compared with LATP and LLTO. The application replaces the hydrated cations (such as Na + , Mg 2+ , K + , Ca 2+ ) in the natural clay mineral into Li + , provides a two-dimensional diffusion path with a low energy barrier for Li + , and improves the ionic conductivity; the obtained lithiumized clay mineral participates in the lithium ion intercalation / deintercalation process in the charging and discharging process, maintains the lithium ion concentration balance at the electrode interface, can compensate the active lithium consumed due to the formation of a solid electrolyte interface (SEI) or lithium dendrites in the cycle process, and significantly alleviates the capacity attenuation. The application introduces the lithiumized clay mineral into the mixed system of polyvinylidene fluoride and an organic lithium salt, can effectively reduce the crystallinity of PVDF, increases the amorphous region, promotes the transformation of PVDF crystals into β-type PVDF, and thus promotes the dissociation process of lithium salts in the electrolyte; meanwhile, the introduction of the lithiumized clay mineral can significantly improve the ionic conductivity, widen the electrochemical window, improve the mechanical properties and inhibit the growth of lithium dendrites.

[0016] The results of the embodiments show that the LFP||Li quasi-solid-state battery assembled by using the lithiumized clay mineral PVDF-based composite solid electrolyte film has excellent electrochemical performance, the lithium ion transference number is as high as 0.6, and has a wide electrochemical stability window (4.86V); the first circle discharge specific capacity of the assembled LFP||Li quasi-solid-state battery reaches 143.3mAh / g, and in the long-term cycle test, the battery exhibits good cycle stability, and the capacity retention rate reaches 93.5% after 580 hours of continuous work. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the XRD spectrum of the NaMMT and LiMMT obtained in Example 1 of the application; Figure 2 is the XPS spectrum of the NaMMT and LiMMT obtained in Example 1 of the application; Figure 3 is the actual picture of the PVDF-based solid electrolyte slurry obtained in Example 1 of the application; Figure 4 is the actual picture of the PVDF-based solid electrolyte film obtained in Example 1 of the application; Figure 5 SEM images of the PVDF-based solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application; Figure 6 SEM images of the cross sections of the solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application; Figure 7 XRD spectra of the solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application; Figure 8 Tensile property curves of the solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application; Figure 9 Linear sweep voltammetry curves of the solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application; Figure 10 Impedance spectra of the solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application at different temperatures; Figure 11 Ionic conductivities of the solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application at different temperatures; Figure 12 Activation energies of the solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application; Figure 13 DC and AC spectra of the solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application; Figure 14 Cycle performance of the LFP||Li quasi-solid-state battery corresponding to the solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application at 0.5C and 25℃; Figure 15 Rate performance of the LFP||Li quasi-solid-state battery corresponding to the solid-state electrolyte films obtained in Examples 1-3 and Comparative Example 1 of the present application; Figure 16 Cycle performance of the NCM811||Li quasi-solid-state battery corresponding to the solid-state electrolyte film obtained in Example 1 of the present application at 0.5C and 25℃. DETAILED DESCRIPTION

[0018] The present application provides a preparation method of a lithiumated clay mineral PVDF-based composite solid-state electrolyte film, comprising the following steps: Mixing lithium halide, clay mineral and first water to perform ion exchange reaction to obtain lithiumated clay mineral; Mixing the lithiumated clay mineral, polyvinylidene fluoride, organic lithium salt and organic solvent to obtain composite slurry; Applying the composite slurry on the surface of the substrate to perform thermal curing to obtain lithiumated clay mineral PVDF-based composite solid-state electrolyte film.

[0019] The present application first mixes lithium halide, clay mineral and water, and then carries out ion exchange reaction to obtain lithiumized clay mineral. In the present application, the clay mineral includes one or more of sodium montmorillonite, calcium montmorillonite, halloysite, attapulgite, hectorite, diatomite and vermiculite, and is more preferably sodium montmorillonite. In the present application, the particle size of the clay mineral is preferably 1-2 μm.

[0020] In the present application, the lithium halide preferably includes one or more of lithium fluoride, lithium chloride, lithium bromide and lithium iodide, and is more preferably lithium chloride. In the present application, the mass ratio of lithium halide to clay mineral is preferably (1-10):1, more preferably (2-8):1, and further preferably 5:1, and can be specifically 1:1, 2:1, 3:1, 5:1, 6:1, 8:1 or 10:1.

[0021] In the present application, the mass ratio of lithium halide to water is preferably 1:(5-12), and more preferably 1:(8-10).

[0022] In the present application, the ion exchange reaction is preferably carried out under stirring, and the stirring speed is preferably 400-1000 r / min, and more preferably 800 r / min. The temperature of the ion exchange reaction is preferably 30-60℃, and more preferably 50-60℃, and the time is preferably 6-12 h, and more preferably 10-12 h.

[0023] After the ion exchange reaction, the present application preferably carries out centrifugation on the obtained ion exchange reaction liquid, discards the supernatant to obtain the lower sediment. In the present application, the centrifugation speed is preferably 4000-6000 r / min, and more preferably 6000 r / min. After collecting the lower sediment, the present application preferably mixes the lower sediment again with lithium halide and water, and repeats the operation of ion exchange reaction-centrifugation. In the present application, the number of repetitions is preferably 2-3 times. The present application carries out ion exchange reaction for multiple times, aiming to replace the hydrated cation Na + with Li + , and construct two-dimensional transport channels with low diffusion energy barrier, thereby significantly improving the ion transport rate of the material.

[0024] After obtaining the lithiumized clay mineral, the present application preferably carries out water washing, centrifugation and drying on the lithiumized clay mineral. In the present application, the drying is preferably vacuum drying, the drying temperature is preferably 60-110℃, and more preferably 80℃, and the drying time is preferably 8-24 h, and more preferably 12 h.

[0025] The lithiumated clay mineral, polyvinylidene fluoride, organic lithium salt and organic solvent are second mixed to obtain a composite slurry.

[0026] In the present application, the organic lithium salt preferably includes lithium bis(trifluoromethylsulfonyl)imide and / or lithium bisfluorosulfonylimide; and the organic solvent preferably includes one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone and acetonitrile, more preferably N,N-dimethylformamide.

[0027] In the present application, the mass ratio of polyvinylidene fluoride to lithiumated clay mineral is preferably 10:(0.1-2), more preferably 10:(0.1-1), and specifically can be 10:0.1, 10:0.5, 10:1, 10:1.5 or 10:2. In the present application, the mass ratio of organic lithium salt to polyvinylidene fluoride is preferably 1:(0.8-2), more preferably 1:(1-1.25), and specifically can be 1:0.8, 1:1, 1:1.25, 1:1.5 or 1:2.

[0028] In the present application, the mass ratio of organic solvent to polyvinylidene fluoride is preferably (1-12):1, more preferably (4-10):1, and more preferably 8:1.

[0029] In the present application, the second mixing is preferably carried out under stirring, and the stirring rate is preferably 600-1200 r / min, more preferably 1000 r / min. The temperature of the second mixing is preferably 25-45℃, more preferably 30-40℃, and the time is preferably 6-12 h, more preferably 8-10 h.

[0030] After obtaining the composite slurry, the present application applies the composite slurry on the surface of a substrate, and carries out heat curing to obtain a lithiumated clay mineral PVDF-based composite solid-state electrolyte film. In the present application, the substrate is preferably a glass substrate. In the present application, the application mode of the slurry is preferably blade coating, and the specification of the blade used for the blade coating is preferably 100-600 μm, more preferably 300-500 μm.

[0031] The present application preferably carries out the heat curing under vacuum drying. In the present application, the temperature of the heat curing is preferably 60-80℃, more preferably 60-70℃, and the time is preferably 8-24 h, more preferably 12-18 h.

[0032] After the heat curing, the present application preferably separates the lithiumated clay mineral PVDF-based composite solid-state electrolyte film from the substrate.

[0033] The present application provides a lithiumized clay mineral PVDF-based composite solid electrolyte membrane prepared by the above preparation method. In the present application, the thickness of the lithiumized clay mineral PVDF-based composite solid electrolyte membrane is preferably 30-80 μm, and more preferably 30-50 μm. The present application does not have special requirements for the diameter of the lithiumized clay mineral PVDF-based composite solid electrolyte membrane, and the corresponding design can be made according to the actual use. As a specific embodiment of the present application, the diameter of the lithiumized clay mineral PVDF-based composite solid electrolyte membrane is 16 mm.

[0034] The present application provides an application of the above lithiumized clay mineral PVDF-based composite solid electrolyte membrane in a lithium ion battery.

[0035] The present application provides a quasi-solid-state battery, which comprises a lithium iron phosphate (LFP) positive electrode sheet, the above lithiumized clay mineral PVDF-based composite solid electrolyte membrane and a lithium metal negative electrode sheet arranged in sequence. In the present application, the loading amount of lithium iron phosphate on the surface of the lithium iron phosphate positive electrode sheet is preferably 1-2 mg / cm 2 , and more preferably 1-1.5 mg / cm 2 .

[0036] In the present application, electrolyte is applied to the two side surfaces of the lithiumized clay mineral PVDF-based composite solid electrolyte membrane. In the present application, the components of the electrolyte include an electrolyte and a solvent, the electrolyte is preferably LiPF6, and the solvent is preferably a mixed solvent of DMC, EC and EMC, and the volume ratio of DMC, EC and EMC in the mixed solvent is preferably 1:1:1. In the present application, the concentration of the electrolyte in the electrolyte is preferably 1 mol / L.

[0037] In the present application, the application amount of the electrolyte on the single side surface of the lithiumized clay mineral PVDF-based composite solid electrolyte membrane is preferably 3-15 μL, and more preferably 5-10 μL.

[0038] In the present application, the quasi-solid-state battery further preferably comprises a negative electrode shell, a spring sheet, a gasket and a positive electrode shell. The present application is preferably assembled and packaged in the order of negative electrode shell, lithium metal negative electrode sheet, lithiumized clay mineral PVDF-based composite solid electrolyte membrane, lithium iron phosphate positive electrode sheet, spring sheet, gasket and positive electrode shell.

[0039] The lithiumized clay mineral PVDF-based composite solid electrolyte membrane, the preparation method and the application thereof and the quasi-solid-state battery provided by the present application will be described in detail below with reference to the examples, but they should not be understood as limiting the scope of protection of the present application.

[0040] Example 1 (1) Lithiumized clay mineral preparation method, the following steps are adopted: Anhydrous lithium chloride and sodium montmorillonite (NaMMT, particle size 1-2 μm) were used as raw materials. 5.0 g of NaMMT and 25 g of anhydrous lithium chloride (LiCl) were accurately weighed and placed in a 500 mL beaker. Under continuous stirring, 200 mL of deionized water was slowly added to form a uniform mixed system. Then the mixed solution was placed in a 60°C constant temperature water bath and stirred at a speed of 800 r / min for 12 h to promote the exchange of Li + with the interlayer hydrated cations of NaMMT. After the reaction was completed, the mixed solution was centrifuged at a speed of 6000 r / min, and the lower precipitate was collected. The above exchange process was repeated three times, and 25 g of LiCl and 200 mL of deionized water were added each time to ensure sufficient ion exchange. The final precipitate obtained by centrifugation was dried in a vacuum at 80°C for 12 h to obtain the target product, lithium montmorillonite (LiMMT).

[0041] The obtained lithium montmorillonite was subjected to XRD analysis, and the results are shown in Figure 1 . Figure 1 The XRD analysis results show that the crystal structure of montmorillonite is completely preserved during the modification process. Notably, compared with NaMMT, the d(001) crystal plane diffraction peak position of LiMMT shifts from 5.82° to 7.14°. According to the Bragg equation, the interlayer distance of the original NaMMT is 15.17 Å, while the interlayer distance of LiMMT is reduced to 12.37 Å. This change in interlayer distance is mainly due to the replacement of Na + (0.102 nm) with smaller radius Li + (0.076 nm) during the ion exchange process, resulting in a shorter distance between adjacent silicate layers.

[0042] The obtained lithium montmorillonite was subjected to XPS analysis, and the results are shown in Figure 2 . The XPS characterization results show that after ion exchange treatment, the Si, Al and O elements in the framework structure of montmorillonite do not change significantly. However, from the high-resolution XPS spectrum of LiMMT, a significant Li 1s characteristic peak can be observed, and no Na 1s signal is detected. This phenomenon confirms that most of the Na + in the interlayer of the original NaMMT has been replaced by Li + during the modification process.

[0043] (2) A method for preparing a lithium clay mineral PVDF-based composite solid electrolyte membrane, which comprises the following steps: Accurately take 0.45 g of polyvinylidene fluoride (PVDF), 0.3 g of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and 0.0045 g of LiMMT, place the sample in a 20 mL screw glass sample bottle, add 3.6 g of N,N-dimethylformamide dropwise, and seal the sample bottle with sealing glue. Place the sealed sample bottle in a constant temperature stirrer and keep stirring at a constant speed at 30°C for 12 hours for full reaction to obtain a composite slurry. The physical map of the obtained composite slurry is shown in Figure 3 .

[0044] Use a doctor blade with a height of 600 μm to control the doctor blade thickness, and coat the uniformly mixed slurry on the surface of the glass substrate. Then place the sample in a vacuum environment at 60°C for 12 hours of drying and curing treatment, and finally obtain a lithiumated clay mineral PVDF-based composite solid electrolyte film with a thickness of 30-40 μm, which is recorded as PVDF-LiTFSI@LiMMT(1%). The physical map of the composite solid electrolyte film is shown in Figure 4 .

[0045] Example 2 The difference from Example 1 is that the mass ratio of PVDF to lithiumated clay mineral is 10:0.5, and the prepared lithiumated clay mineral PVDF-based composite solid electrolyte film is recorded as PVDF-LiTFSI@LiMMT(5%).

[0046] Example 3 The difference from Example 1 is that the mass ratio of PVDF to lithiumated clay mineral is 10:1, and the prepared lithiumated clay mineral PVDF-based composite solid electrolyte film is recorded as PVDF-LiTFSI@LiMMT(10%).

[0047] Comparative Example 1 The difference from Example 1 is only that no LiMMT is added, and the prepared PVDF-based solid electrolyte is recorded as PVDF-LiTFSI.

[0048] Structural characterization and performance test (1) Figure 5 SEM images of the solid electrolytes obtained in Examples 1-3 and Comparative Example 1. Figure 5PVDF-LiTFSI, b is PVDF-LiTFSI@LiMMT (1%), c is PVDF-LiTFSI@LiMMT, d is PVDF-LiTFSI@LiMMT (10%). It can be seen that the solid-state electrolytes obtained in Examples 1-3 and Comparative Example 1 all exhibit a flat surface morphology; in particular, it is worth noting that the sample of PVDF-LiTFSI@LiMMT (1%) exhibits the optimal surface characteristics, and the structure is uniform, dense and smooth, which helps to improve the compatibility of the electrode / electrolyte interface, thereby improving the migration efficiency of lithium ions at the interface.

[0049] Figure 6 SEM images of the cross-section of the solid-state electrolytes obtained in Examples 1-3 and Comparative Example 1. Figure 6 PVDF-LiTFSI, b is PVDF-LiTFSI@LiMMT (1%), c is PVDF-LiTFSI@LiMMT, d is PVDF-LiTFSI@LiMMT (10%). The cross-section of the solid-state electrolyte was observed by SEM, and the SEM images showed that the thickness of the solid-state electrolytes obtained in Examples 1-3 and Comparative Example 1 was in the range of 30 to 40 microns.

[0050] (2) The composite solid-state electrolytes obtained in Examples 1-3 and Comparative Example 1 were subjected to XRD testing, and the results are shown in Figure 7 The XRD analysis results are shown in Figure 7 The PVDF powder exhibits characteristic diffraction peaks at 18.3°, 19.9° and 26.3°, corresponding to the alpha, beta and gamma three crystal phases, respectively; after film forming treatment, the diffraction peaks of the alpha and gamma phases are significantly weakened, and the beta phase becomes the dominant crystal form in the solid-state electrolyte system. It is worth noting that the beta phase PVDF with a higher dielectric constant can promote the dissociation of lithium salt and effectively improve the ionic conductivity.

[0051] (3) The composite solid-state electrolytes obtained in Examples 1-3 and Comparative Example 1 were subjected to tensile testing, and the results are shown in Figure 8 Figure 8 ​The tensile property test results show that the introduction of LiMMT significantly improves the mechanical properties of the PVDF-LiTFSI-based solid electrolyte membrane. Compared with the PVDF-LiTFSI group, when the content of LiMMT is 1%, the composite solid electrolyte membrane exhibits excellent ductility and toughness; and when the content of LiMMT increases to 5%, the tensile strength of the material slightly increases, the ductility slightly decreases, but the stress-strain curve is slightly different from that of the sample with an addition amount of 1%. It is worth noting that the addition of excessive LiMMT (10%) will cause the mechanical properties of the electrolyte membrane to decrease significantly, losing the modification advantage. This phenomenon shows that there is an optimal range of the addition amount of LiMMT, and excessive addition will weaken the enhancement effect of LiMMT on the mechanical properties of the polymer electrolyte.

[0052] (4) The electrochemical window was measured by linear sweep voltammetry (LSV) method. Li||SS battery was used as the test battery, and the open circuit voltage was slowly scanned to the positive voltage at a scan rate of 0.1 mV S -1 . The linear sweep voltammetry curve of the solid electrolyte obtained in Example 1-3 and Comparative Example 1 is shown in Figure 9 . Figure 9 The LSV test data show that, compared with Comparative Example 1 (4.05 V), Example 2 (4.55 V) and Example 3 (3.98 V), Example 1 exhibits a significantly widened electrochemical window, and the decomposition voltage is increased to 4.86 V; this excellent electrochemical performance enables it to adapt to high-voltage electrochemical systems, and has the potential to be practically applied to commercial lithium batteries.

[0053] (5) The ion conductivity of the electrolyte was measured by electrochemical impedance spectroscopy (EIS). SS||SS battery was used as the test battery for electrochemical impedance test, the test temperature range was 30-80℃, the frequency range was 0.1-10 5 Hz, and the amplitude was 10 mV. After the impedance test, the impedance spectra of Comparative Example 1 (a), Example 1 (b), Example 2 (c), and Example 3 (d) at different temperatures are shown in Figure 10 . The thickness of the electrolyte membrane was measured by disassembling the battery, and the ion conductivity was calculated according to the formula σ=d / (R·S), wherein the R value was taken from the impedance spectrum results. The calculation results are shown in Figure 11 . It can be found by observation that, among all the electrolyte systems, Example 1 always exhibits the highest ion conductivity in the temperature range of 30-80℃ (30-80℃), which is 1.06×10 -3 S / cm at 30℃ and 2.03×10 -3 S / cm at 80℃; the σ value is brought into the Arrhenius equation σT=Aexp(-Ea / RT) to calculate the activation energy of the electrolyte, as shown in Figure 12As shown, the Ea of Example 1 is 0.122 eV, which is much lower than that of Comparative Example 1 (0.249 eV), Example 2 (0.243 eV), and Example 3 (0.175 eV). This indicates that the Li in the electrolyte of Example 1 is significantly lower than that of Comparative Example 1 (0.249 eV), Example 2 (0.243 eV), and Example 3 (0.175 eV). + With a lower migration barrier, migration behavior is more likely to occur, which can effectively avoid concentration polarization and ensure Li + Uniform deposition.

[0054] The lithium-ion transference number was obtained through testing of Li||Li symmetric cells using a combination of chronoamperometry and impedance spectroscopy, employing a modified Bruce-Vincent-Evans formula. Li + =(I s (ΔV-I0R0)) / (I0(ΔV-I s R s Calculations were performed, and all tests were conducted at room temperature. The DC and AC spectra of the solid electrolytes obtained in Comparative Example 1(a), Example 1(b), Example 2(c), and Example 3(d) are shown below. Figure 13 As shown. Test results indicate that there are significant differences in migration performance among the various embodiments. Specifically, Embodiment 1 ( Figure 13 Sample b) exhibited the best migration characteristics, with a migration number as high as 0.6, significantly better than other samples: Comparative Example 1 (0.25, Figure 13 a) Example 2 (0.33, Figure 13 c) Example 3 (0.35, Figure 13 (d) This result fully demonstrates the significant advantage of Example 1 in terms of migration performance.

[0055] Application Example 1 The solid electrolyte membranes obtained in Examples 1-3 and Comparative Example 1 were used to prepare quasi-solid-state batteries, as follows: A quasi-solid-state battery mainly consists of: a negative electrode shell, a lithium metal negative electrode, an electrolyte dropped onto the first contact surface of a solid electrolyte membrane, a solid electrolyte membrane, an electrolyte dropped onto the second contact surface of the solid electrolyte membrane, a lithium iron phosphate positive electrode sheet, a gasket, a spring, and a positive electrode shell. The lithium iron phosphate positive electrode sheet has a loading capacity of 1.2 mg / cm³. 2 .

[0056] The first contact surface of the solid electrolyte membrane is the contact surface between the solid electrolyte and the lithium iron phosphate positive electrode, and the second contact surface is the contact surface between the solid electrolyte membrane and the lithium metal negative electrode. The electrolyte used is 1M LiPF6 in DMC:EC:EMC=1:1:1 Vol%, with a drop volume of 5μL added to each contact surface. The solid electrolyte is cut into 16mm diameter discs to fit the dimensions of the positive and negative electrode shells. Assembled in the above order, a quasi-solid-state battery based on the LFP||Li system is obtained.

[0057] The cycle performance test was carried out at 25℃, 0.5C (the cycle voltage window was 2.5-4.0V), and the results are shown in Figure 14 It can be seen that the first circle discharge specific capacity of the battery of Example 1 is as high as 143.3mAh / g, which is much higher than the discharge specific capacity of the other three groups of batteries, and still maintains a discharge specific capacity of 134mAh / g after 150 cycles, the capacity retention rate is 93.5%, which shows excellent cycle stability.

[0058] The rate performance of the four groups of solid electrolytes was evaluated at 25℃, and the charge and discharge rates were set to 0.1C, 0.2C, 0.5C, 1C and 2C in turn, and the rate performance diagram of the quasi-solid battery is shown in Figure 15 The experimental data show that, compared with other samples, Example 1 shows the most excellent rate cycle performance, and its discharge specific capacity maintains a leading level in the whole test interval. Especially under high rate conditions, when the current density is increased to 1.0C, the discharge specific capacity of Example 1 can reach 118.2mAh / g; even if it is further increased to 2.0C, it can still maintain a discharge specific capacity of 92mAh / g.

[0059] Application Example 2 The high voltage resistance performance of the lithiated clay mineral PVDF-based composite solid electrolyte film of Example 1 was evaluated by using NCM811||Li battery system (the cycle window was 3.0-4.3V), the electrolyte was 1M LiPF6in DMC:EC:EMC=1:1:1 Vol%, the drop amount was 5μL per contact surface, and a total of 10μL was added in the whole battery. The test was carried out at 0.5C rate and room temperature, and the cycle performance diagram is shown in Figure 16 The cycle results show that the initial discharge specific capacity is 172.2mAh / g, and after 100 cycles, it still maintains a reversible capacity of 127.5mAh / g, and the corresponding cycle capacity retention rate is 74%. The results show that the lithiated clay mineral PVDF-based composite solid electrolyte film obtained by the application has good cycle stability under high voltage conditions.

[0060] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the technical field, some improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A method for preparing a lithiumated clay mineral PVDF-based composite solid-state electrolyte membrane, characterized in that, The method comprises the following steps: mixing lithium halide, clay mineral and water first to perform ion exchange reaction to obtain lithiumated clay mineral; mixing the lithiumated clay mineral, polyvinylidene fluoride, organic lithium salt and organic solvent second to obtain composite slurry; applying the composite slurry on the surface of a substrate and performing thermal curing to obtain lithiumated clay mineral PVDF-based composite solid electrolyte film.

2. The production method according to claim 1, characterized by, The clay mineral comprises one or more of sodium montmorillonite, calcium montmorillonite, halloysite, attapulgite, hectorite, diatomite and vermiculite. The mass ratio of the lithium halide to the clay mineral is (1-10):

1.

3. The production method according to claim 1 or 2, characterized by, The ion exchange reaction is performed under stirring, and the stirring rate is 400-1000 r / min. The ion exchange reaction is performed at a heating temperature of 30-60℃ and a stirring time of 6-12 h.

4. The method of claim 1, wherein, The mass ratio of the polyvinylidene fluoride to the lithiumated clay mineral is 10:(0.1-2). The mass ratio of the organic lithium salt to the polyvinylidene fluoride is 1:(0.8-2). The mass ratio of the organic solvent to the polyvinylidene fluoride is (1-12):

1.

5. The production method according to claim 1 or 4, characterized by, The organic lithium salt comprises lithium bis(trifluoromethylsulfonyl)imide and / or lithium bisfluorosulfonylimide. The second mixing is performed at a temperature of 25-45℃ for 6-12 h.

6. The method of claim 1, wherein, The thermal curing is performed at a temperature of 60-80℃ for 8-24 h.

7. The lithiumated clay mineral PVDF-based composite solid electrolyte film prepared by the preparation method of any one of claims 1-6.

8. The lithiated clay mineral PVDF-based composite solid-state electrolyte membrane according to claim 7, characterized in that, The thickness of the lithiumated clay mineral PVDF-based composite solid electrolyte film is 30-80 μm.

9. The lithiumated clay mineral PVDF-based composite solid electrolyte film of claim 7 or 8 for use in a lithium ion battery.

10. A quasi-solid-state battery, characterized by, The lithium ion battery comprises, in sequence, a lithium iron phosphate positive electrode sheet, the lithiumated clay mineral PVDF-based composite solid electrolyte film of claim 7 or 8, and a lithium metal negative electrode sheet. The two side surfaces of the lithiumated clay mineral PVDF-based composite solid electrolyte film are applied with electrolyte.

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