An intercalation type composite solid electrolyte and a preparation method and application thereof

Abstract

The application relates to the technical field of solid-state lithium batteries, in particular to an intercalation type composite solid-state electrolyte and a preparation method and application thereof. Sodium-based montmorillonite is obtained through ion exchange, centrifugal washing, freeze drying and other processes to obtain lithiumated montmorillonite nanosheets; the lithiumated montmorillonite nanosheets and polyethylene oxide are added into N,N-dimethylformamide to obtain slurry A; a high-molecular polymer material and a lithium salt are added into N,N-dimethylformamide to obtain slurry B; the slurry A is added dropwise into the slurry B to obtain a precursor solution; the precursor solution is scraped and coated on a glass substrate, and is placed, vacuum dried and demolded to obtain the intercalation type composite solid-state electrolyte. The application has the advantages of simple process, easily obtained raw materials, high ionic conductivity of the obtained electrolyte, a wide voltage window, excellent mechanical properties and flame retardant properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state lithium batteries, in particular to an intercalation type composite solid-state electrolyte and a preparation method and application thereof. BACKGROUND

[0002] After more than thirty years of development, the energy density of liquid lithium ion batteries has approached the theoretical limit, and at the same time, due to the flammable electrolyte, fire and explosion accidents have occurred frequently; solid-state lithium metal batteries are considered as the ultimate replacement of current liquid lithium ion batteries due to their high energy density and intrinsic safety. Among them, polymer solid-state electrolytes have become one of the most promising material systems for solid-state batteries due to their excellent flexibility, interface compatibility and easy processing characteristics. However, the room temperature ionic conductivity of polymer solid-state electrolytes is generally low, the voltage window is narrow, and the mechanical strength is low, which makes it difficult to be used on a large scale. The composite of inorganic fast ion conductor and polymer matrix can effectively solve the above problems, but such materials are expensive and require high energy consumption processes, resulting in high overall cost of composite solid-state electrolytes.

[0003] Chinese patent document with publication number CN120149511A discloses a montmorillonite-doped composite solid-state polymer electrolyte and its preparation method and application. It uses low-cost montmorillonite as a basic inorganic material, and after modification treatment with silane coupling, it is compounded with polyethylene oxide and lithium salt to prepare a composite solid-state electrolyte. This improves the performance indicators such as ionic conductivity and electrochemical stability window to some extent, but the overall ionic conductivity is still low, making it difficult to be used at room temperature. In addition, the inorganic material content is low, and the low-cost advantage of montmorillonite cannot be fully realized.

[0004] Chinese patent document with publication number CN109244534A discloses a montmorillonite-based composite solid electrolyte and a solid-state lithium battery. It greatly takes advantage of the low cost of montmorillonite, and its room temperature ionic conductivity, voltage window and lithium ion transference number are all relatively excellent; but since the composite electrolyte is mainly formed by hot pressing with adhesive, its mechanical strength is generally low, and it is difficult to resist lithium dendrite puncture, which has a high safety risk.

[0005] The document Electrochimica Acta 187, 535-542 (2016) prepared a composite solid-state polymer electrolyte using montmorillonite, lithium bis(trifluoromethanesulfonyl)imide, polyvinylidene fluoride and polyvinyl alcohol copolymer as raw materials. Although its room temperature ionic conductivity reached 4.31×10 -4 Scm -1However, the lithium ion transference number and mechanical strength thereof are not ideal, resulting in poor affinity of the composite electrolyte with lithium metal, and the corresponding solid-state lithium metal battery can only operate under small rate conditions. In addition, the proportion of montmorillonite in the electrolyte is only 4wt%, which cannot effectively reduce the cost of the composite electrolyte and cannot effectively improve the thermal safety. SUMMARY

[0006] The purpose of the present application is to provide an intercalation type composite solid electrolyte and a preparation method and application thereof, which solves the problems of low room temperature ionic conductivity, narrow voltage window, low mechanical strength and high cost of composite materials of the existing polymer solid electrolyte.

[0007] In order to achieve the above purpose, the present application realizes the following technical scheme:

[0008] In the first aspect, the present application provides a preparation method of an intercalation type composite solid electrolyte, comprising the following steps:

[0009] S1. Sodium-based montmorillonite (MNa) is added to a hydrochloric acid solution and stirred under water bath heating, the supernatant is discarded after standing, and the excess H + and Cl - are removed by washing and centrifugation to obtain acidified montmorillonite (MH) mud; lithium hydroxide solution is added to the MH mud, and the slurry is stirred under water bath heating, the supernatant is discarded after standing overnight, and the slurry is washed and centrifuged; freeze-drying for 24-48h to remove as much water as possible; then vacuum drying at 120-150℃ for 12-24h to remove adsorbed water and bound water, and grinding and sieving to obtain lithium montmorillonite nanosheets (MLi);

[0010] S2. MLi and polyethylene oxide (PEO) are added to N,N-dimethylformamide (DMF) and heated and stirred to obtain slurry A;

[0011] S3. High molecular polymer material and lithium salt are added to N,N-dimethylformamide and heated and stirred to obtain slurry B;

[0012] S4. Slurry A is added dropwise to slurry B, and heated and stirred to obtain a precursor solution;

[0013] S5. The precursor solution is blade-coated on a glass substrate, and then left to stand, vacuum dried and demolded to obtain an intercalation type composite solid electrolyte (MPPLi); the thickness of the intercalation type composite solid electrolyte is 20-100pm.

[0014] Preferably, in step S1, the concentration of the hydrochloric acid solution is 0.1-0.5molL -1 , and the mass fraction of MNa in the hydrochloric acid solution is 5wt%-10wt%; the concentration of the lithium hydroxide solution is 0.1-0.5molL -1, the mass fraction of MH in the lithium hydroxide solution is 5-10 wt%; the water bath temperature is 60-90 DEG C, the stirring time is 6-10 h, the stirring speed is 800-1000 rmp; the washing and centrifugation times are both 6-8 times.

[0015] Preferably, in the step S2, the mass ratio of the lithiated montmorillonite nanosheet and the polyethylene oxide is 7:1-2; the heating and stirring temperature is 50-80 DEG C, the stirring speed is 1200-1500 rmp, and the stirring time is 12-18 h.

[0016] Preferably, in the step S3, the high molecular polymer material comprises one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), and polyacrylonitrile (PAN); the lithium salt is selected from one or more of lithium bis-trifluorosulfonylimide (LiTFSI), lithium bisfluorosulfonylimide (LiFSI), and lithium hexafluorophosphate (LiPF6); the mass ratio of the high molecular polymer material and the lithium salt is 6:3-8; the heating and stirring reaction temperature is 50-65 DEG C, the stirring speed is 400-800 rmp, and the time is 4-6 h.

[0017] Preferably, in the step S4, the slurry A and the slurry B are mixed in equal volumes; the heating and stirring temperature is 40-60 DEG C, the stirring speed is 1200-1500 rmp, and the stirring time is 12-24 h.

[0018] Preferably, in the step S5, the vacuum drying temperature is 50-60 DEG C, the drying time is 12-48 h, and the vacuum degree is -90 to -99 kPa.

[0019] In a second aspect, the application provides an intercalation type composite solid-state electrolyte prepared by the preparation method.

[0020] In a third aspect, the application provides the use of the intercalation type composite solid-state electrolyte in the preparation of a solid-state lithium ion battery.

[0021] Compared with the prior art, the application has the following beneficial effects:

[0022] 1. The MPPLi prepared by the application has a "sandwich" intercalation structure; the molecular chains of the high molecular polymer are inserted between the MLi layers, the "O-H" bonds at the bottom of the MLi are coupled and coordinated with the molecular chains of the high molecular polymer to form a firm chemical structure, which greatly enhances the mechanical strength of the electrolyte, and the introduced PEO further enhances the flexibility of the electrolyte. This "rigidity and flexibility" characteristic can ensure that the electrolyte film has good interface compatibility with the battery pole piece, thereby reducing the interface impedance, and also inhibiting the growth of lithium dendrites and improving the cycle performance of the battery.

[0023] 2. In this invention, the sandwich structure formed by MLi and the polymer material can lock in some DMF solvent molecules like a reservoir, preventing them from evaporating. The solvent molecules greatly promote the dissociation of lithium salts. MLi also contributes to the dissociation of TFSI. - FSI - PF6 - The locking effect of the anionic groups will further promote the Li + Due to the dissociation of MPPLi, the MPPLi prepared in this invention exhibits a high room temperature ionic conductivity (5.96–6.18 × 10⁻⁶). -4 Scm -1 ) and lithium-ion transference number (0.56–0.67).

[0024] 3. The MPPLi prepared by this invention contains a large amount of MLi, and MLi itself has strong electrochemical stability, which gives MPPLi a wide electrochemical window (0-4.8V), thus it can be matched with a high-voltage cathode.

[0025] 4. The MPPLi provided by this invention contains MLi with excellent flame-retardant properties, and the MLi encapsulates polymer molecular chains. Therefore, this electrolyte exhibits excellent flame-retardant properties; when heated by the outer flame of an alcohol lamp, it only smokes and does not ignite, and extinguishes itself upon removal of the alcohol lamp's outer flame. Therefore, the MPPLi prepared by this invention can greatly enhance the safety of solid-state batteries.

[0026] 5. The preparation of MPPLi in this invention involves raw material MNa, which is rich in exchangeable cations in its interlayer domains, thus exhibiting lithium-ion conductivity through lithium-ion exchange. Sodium-based montmorillonite exhibits a nanosheet structure at the microscopic level, with abundant charges at its broken bond edges, which can form a micro-electric field locally, creating a basic condition for the preparation of intercalated composite solid electrolytes. In addition, the cost of sodium-based montmorillonite (<10,000 RMB / ton) is much lower than the cost of fast ion conductors (800,000 to 3,000,000 RMB / ton). Since the MPPLi provided by this invention has a high MLi content (>30 wt%), the cost of MPPLi materials can be significantly reduced.

[0027] 6. The preparation of MPPLi in this invention involves the inorganic material MLi, which is prepared using a freeze-drying process. The freezing process causes the inorganic particles to oriented along the temperature gradient, and the freeze-drying process preserves the large lamellar structure of montmorillonite. Figure 1 Furthermore, the lithiated montmorillonite prepared by freeze-drying is very fluffy and easy to peel and disperse in the precursor solution, which lays the foundation for the intercalation structure.

[0028] 7. The MPPLi provided by this invention has a relatively simple preparation method, and the wet coating process is highly compatible with liquid lithium-ion battery production lines, making it suitable for mass production.

[0029] 8. The application develops an intercalation type composite solid electrolyte with lower cost, excellent thermal stability and good electrochemical performance by compounding MLi with high molecular polymer material and lithium salt, which shows satisfactory cycle performance in full battery test, proving the potential value of clay minerals applied to solid-state batteries. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Optical picture of MLi in Example 1;

[0031] Figure 2 X-ray diffraction pattern (XRD) of MPPLi-1, MLi and MNa in Example 1;

[0032] Figure 3 Scanning electron microscope image (SEM) of MLi in Example 1;

[0033] Figure 4 Optical picture of MPPLi-1 in Example 1;

[0034] Figure 5 Scanning electron microscope image (SEM) of MPPLi-1 cross section in Example 1;

[0035] Figure 6 Flame retardant performance diagram of MPPLi-1 in Example 1;

[0036] Figure 7 Tensile strength test curve of MPPLi-1 in Example 1 and MPLi in Comparative Example 1;

[0037] Figure 8 Infrared spectrum image of MPPLi-1, DMF and PVDF in Example 1;

[0038] Figure 9 Thermogravimetric test curve of MPPLi-1, MNa, PEO and PVDF in Example 1;

[0039] Figure 10 Schematic diagram of lithium ion conduction mechanism of MPPLi in Example;

[0040] Figure 11 Ion conductivity and temperature function curve of MPPLi-1 in Example 1;

[0041] Figure 12 Linear voltammetry (LSV) scan curve of SS / MPPLi-1 / Li battery assembled using MPPLi-1 in Example 1;

[0042] Figure 13The DC polarization test curve and AC impedance spectrum before and after polarization of MPPLi-1 in Example 1 are shown.

[0043] Figure 14 The image shows a long-cycle charge-discharge test of the Li / MPPLi-1 / Li symmetric battery assembled using MPPLi-1 in Example 1.

[0044] Figure 15 The charge-discharge curves of the LiFePO4 / MPPLi-1 / Li full cell assembled using MPPLi-1 in Example 1 are shown at 0.1C, 0.3C, and 0.5C.

[0045] Figure 16 This is a comparison chart showing the cycle performance of the LiFePO4 / MPPLi-1 / Li solid-state battery assembled using MPPLi-1 in Example 1 at 0.5C rate with that of a liquid lithium-ion battery at the same rate.

[0046] Figure 17 The diagram shows the combustion experiment of the corresponding electrolyte in Comparative Example 1;

[0047] Figure 18 The image shows a scanning electron microscope (SEM) image of lithiated montmorillonite in Comparative Example 3. Detailed Implementation

[0048] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the reagents used are all commercially available and readily accessible to those skilled in the art. Example 1

[0049] (I) The following describes the preparation of intercalated composite solid electrolytes. The materials used in this example are MNa, PVDF, PEO, and LiTFSI. The specific implementation steps are as follows:

[0050] S1: Weigh 10.00g MNa and add it to 200mL of 0.1mol / L solution. -1 The mixture was placed in a hydrochloric acid solution and stirred continuously at 800 rpm for 6 hours in an 80°C water bath. After standing for 1 hour, the supernatant was discarded. The mixture was washed repeatedly with deionized water and centrifuged 6 times to obtain MH slurry. 200 mL of 0.1 mol / L lithium hydroxide solution was added and stirred into a slurry. The mixture was then placed in an 80°C water bath and stirred continuously at 800 rpm for 6 hours. After standing overnight, the supernatant was discarded. The mixture was washed with deionized water and centrifuged 6 times. It was then freeze-dried in a freeze dryer for 24 hours to obtain the slurry. Figure 1The lithium montmorillonite with a large layered structure shown was then heated in a vacuum oven at 120°C for 24 hours; it was then ground through a 1000-mesh sieve to obtain MLi.

[0051] Depend on Figure 2 It can be seen that impurities such as calcite and quartz are significantly reduced in MLi, and the interplanar spacing (d) of its (001) crystal plane is also reduced. 001 The ion radius also decreased from 12.27 Å to 11.59 Å, meaning that lithium ions with smaller ionic radii replaced sodium ions. The relevant ion exchange reaction equations are as follows:

[0052] MNa+H + →MH

[0053] MH+Li + →MLi

[0054] MLi was observed under a scanning electron microscope. Figure 3 As can be seen, MLi exhibits typical characteristics of two-dimensional layered nanomaterials, displaying a large sheet-like morphology. This is due to the fact that during the freeze-drying process, water molecules form layered crystals along the temperature gradient direction, constructing an ice template for lithium-ionized montmorillonite; when the ice template is freeze-dried, the lithium-ionized montmorillonite retains the oriented crystallization along the temperature gradient direction, thus forming a large layered structure, which, after grinding and crushing, becomes a two-dimensional nanosheet structure.

[0055] S2: Prepare the mixture according to a mass ratio of MLi to PEO of 7:1. Weigh out 0.9440g of MLi and 0.1348g of PEO (Mw=10). 6 Add 10 mL of LDM solution and stir at 1300 rpm for 16 h at 50 °C to obtain slurry A.

[0056] S3: Prepare the mixture according to a PVDF to LiTFSI mass ratio of 6:7. Weigh 0.8092g of PVDF and 0.9440g of LiTFSI and disperse them in 10ml of LMF solution. Stir continuously at 50℃ and 500rpm for 4h to obtain a light yellow and clear slurry B.

[0057] S4: Add slurry A dropwise to slurry B, and stir at 50°C and 1300 rpm for 12 hours to obtain the precursor solution.

[0058] S5: Accurately measure 10 mL of the precursor solution using a pipette and pour it onto a glass substrate. Then, use a scraper to evenly and slowly coat the substrate into a film. After standing for 1 hour to allow the coating to stabilize, carefully transfer it into a vacuum oven and vacuum dry it at 50°C for 24 hours (maintaining a vacuum level of -90 to -99 kPa). Remove the film and transfer it into a glove box to obtain the intercalated composite solid electrolyte MPPLi-1. Figure 4As shown, the composite electrolyte has a thickness of 50 μm, a yellowish-gray appearance, a plastic film-like luster, and good flexibility.

[0059] (ii) The following physical characterization was performed on MPPLi-1:

[0060] like Figure 2 As shown in the figure, XRD revealed that the characteristic diffraction peaks of the montmorillonite (001) crystal plane in the MPPLi-1 sample shifted significantly towards the smaller angle, indicating a significant increase in interplanar spacing, which is clearly due to the intercalation of PVDF molecular chains. Further SEM characterization of the cross-section of MPPLi-1 was performed. Figure 5 It was found that the electrolyte membrane exhibited a distinct layered stacking structure. Therefore, this electrolyte is a sandwich-structured intercalated composite electrolyte. Combustion experiments were conducted on MPPLi-1 ( Figure 6 It was found that the electrolyte has excellent flame retardant properties and does not burn under the outer flame of an alcohol lamp. Figure 7 The mechanical property test curves of the electrolyte show that the strength (14.14 MPa) and tensile modulus (76%) of MPPLi-1 are significantly better than those of Comparative Example 1 without MLi (MPLi). Figure 8 Infrared spectroscopy revealed the presence of DMF functional groups in the MPPLi-1 sample, indicating the presence of DMF residue within the electrolyte membrane. This was confirmed by thermogravimetric analysis. Figure 9 The residual DMF content was found to be approximately 8 wt%. Figure 10 The transport mechanism of lithium ions in MPPLi.

[0061] (III) Electrochemical performance testing of MPPLi-1:

[0062] (1) Assemble SS / MPPLi-1 / SS symmetric blocking cells and test ionic conductivity

[0063] The prepared MPPLi-1 was cut into circular pieces with a diameter of 19 mm; a stainless steel sheet (SS sheet) with a diameter of 16 mm and a thickness of 1 mm was selected as the blocking electrode, and the surface of the blocking electrode was cleaned and polished; a CR2032 button battery shell was selected, and in a glove box filled with argon gas, the negative electrode shell, spring sheet, SS (steel sheet) sheet, MPPLi-1, SS sheet and positive electrode shell were assembled in sequence, and sealed with a sealing machine under a pressure of 60 MPa.

[0064] The electrochemical impedance spectroscopy (EIS) spectra of the above-mentioned batteries were tested using an electrochemical workstation. The test environment temperature was 80–25 °C, and the test frequency was 10. 6 ~10 -2 The excitation voltage is 5mV and the frequency is Hz. The bulk resistance of the electrolyte membrane is read from the AC impedance spectrum, and the ionic conductivity is calculated using the following formula:

[0065] δ=L / SR

[0066] Where δ is the ionic conductivity, L is the electrolyte membrane thickness, S is the electrolyte membrane area, and R is the bulk resistance. Plotting logδ against 1 / T yields... Figure 11 The curve shown illustrates that the ionic conductivity of MPPLi-1 increases significantly with increasing temperature. Its room temperature ionic conductivity reaches 6.18 × 10⁻⁶. -4 Scm -1 .

[0067] (2) Assemble SS / MPPLi-1 / Li battery and test electrochemical window

[0068] The assembly method is similar to that described in (1), except that a lithium sheet with a diameter of 16 mm and a thickness of 500 μm is used as the negative electrode. The battery assembly sequence is negative electrode shell, spring sheet, gasket, lithium sheet, electrolyte membrane, stainless steel sheet, and positive electrode shell. The sealing pressure is 60 MPa, and the operation is carried out in a glove box filled with argon gas.

[0069] The electrochemical window of the electrolyte membrane was tested using the linear voltammetry (LSV) module on the electrochemical workstation. The negative electrode casing of the coin cell was connected to the negative electrode lead of the clamp, and the positive electrode casing was connected to the positive electrode lead of the clamp. The voltage range was set to 0–6 V, and the scan rate was 0.1 mV / s. The test results are as follows: Figure 12 As shown, at 25 °C, MPPLi-1 and the electrochemical window can reach 4.8 V.

[0070] (3) Assemble Li / MPPLi-1 / Li symmetric cells and test lithium-ion transference number

[0071] A CR2032 button cell casing was selected as the test mold. The battery was assembled in an argon-filled glove box in the following order: negative electrode casing, spring contact, gasket (0.5mm thick), lithium sheet, electrolyte membrane, lithium sheet again, gasket, and positive electrode casing. The sealing pressure was 60MPa. Before sealing, the surface oxide layer of the lithium sheet was carefully removed to minimize interfacial resistance. Simultaneously, the battery was held at pressure for 1 minute during sealing to maximize interfacial contact.

[0072] The ion mobility number of MPPLi-1 was measured using a combination of potentiostatic DC polarization and AC impedance methods. The polarization voltage for the potentiostatic DC polarization test was 10 mV.

[0073] The polarization time is 4000 min; the frequency range for AC impedance testing is 10. 6 ~10 -2 Hz, bias voltage 5mV. The formula for calculating the lithium-ion transport number is as follows:

[0074]

[0075] in This represents the lithium-ion transference number. The applied polarization voltage, and These are the initial current and steady-state current during the polarization process, respectively. and These represent the bulk resistance of the electrolyte membrane before polarization and the bulk resistance after polarization, respectively. The test results are as follows: Figure 13 As shown, the lithium-ion transference number of MPPLi-1 is 0.67 at 25°C.

[0076] (4) Assemble Li / MPPLi-1 / Li batteries and measure the cycle performance of symmetrical batteries.

[0077] The Li / MPPLi-1 / Li symmetric cell was assembled using the same method as in (3), and the result was measured at 0.1 mA / cm. -2 Constant current cyclic charge-discharge tests were conducted with current density and charge-discharge cycles of 1 hour each. Figure 14 It can be seen that at 25℃ and 0.1 mAcm -2 The coin cell battery can cycle for over 1000 hours, demonstrating good cycle stability, which means that lithium dendrite growth can be effectively suppressed.

[0078] (5) Assembly and testing of LiFePO4 / MPPLi-1 / Li full cells

[0079] The CR2032 button cell battery casing was assembled inside a glove box ([H2O] < 0.1ppm, [O2] < 0.1ppm). The assembly sequence was as follows: negative electrode shell spring, gasket, lithium sheet, electrolyte membrane, LiFePO4 positive electrode sheet (12mm in diameter), and positive electrode shell. The sealing pressure was 60MPa.

[0080] The charge-discharge performance of the assembled full battery was tested under different rate conditions ranging from 2.8 to 3.4V. Figure 15 As shown, the full battery has a discharge specific capacity exceeding 160 mAh g at a 0.1C rate. -1 Even at a 0.5C rate, it still has a capacity of over 120mAh. -1 It has a high discharge specific capacity and exhibits good reversibility during charge and discharge.

[0081] The cycle performance of the assembled full cell was tested under conditions of 2.8–3.4V and 0.5C (25°C). Figure 16 As shown, after 100 cycles of the full battery, the capacity hardly decreases, which is significantly better than the cycle performance of liquid lithium metal batteries under the same conditions, and shows better stability. Example 2

[0082] The preparation method and testing and characterization of MPPLi in this embodiment are the same as those in Example 1, except that: the stirring speed in step S1 is 1000 rpm; in step S3, LiPF6 is used instead of LiTFSI, and the ingredients are prepared according to the mass ratio of PVDF to LiPF6 of 6:3, and the heating and stirring time is 5 h; in step S4, the stirring speed is 1500 rpm. Example 3

[0083] The preparation method and characterization of MPPLi in this embodiment are the same as in Example 1, except that: in step S1, the mass fraction of sodium-based montmorillonite in the acid solution is 8 wt%, the mass fraction of acidified montmorillonite slurry in the lithium hydroxide solution is 8 wt%, the water bath heating temperature is 60℃ for 8 h, the freeze-drying time is 36 h, and the subsequent vacuum drying conditions are 130℃ for 12 h; in step S2, the mass ratio of lithium-ionized montmorillonite nanosheets to polyethylene oxide is 7:1.5, and the heating and stirring time is 18 h; in step S3, LiPF6 is used instead of LiTFSI, and the PVDF to LiPF6 mass ratio is 6:5, the heating and stirring speed is 400 rpm for 6 h; in step S4, the heating and stirring temperature is 40℃; in step S5, the vacuum drying temperature is 55℃, and the drying time is 48 h. Example 4

[0084] The preparation method and characterization of MPPLi in this embodiment are the same as in Example 3, except that: in step S1, the concentrations of hydrochloric acid solution and lithium hydroxide solution are both 0.3 mol L⁻¹, and the heating and stirring time is 10 h; in step S2, the heating and stirring temperature is 60 °C, the stirring speed is 1200 rpm, and the stirring time is 12 h; in step S3, PAN is used instead of PVDF, the mass ratio of PAN to LiTFSI is 6:7, the heating and stirring temperature is 60 °C, and the time is 4 h; in step S4, the heating and stirring time is 24 h. Example 5

[0085] The preparation method and characterization of MPPLi in this embodiment are the same as those in Example 4, except that: in step S1, the heating and stirring speed is 1000 rpm, and the subsequent vacuum drying time is 24 h; in step S2, the heating and stirring speed is 1300 rpm and the stirring time is 18 h; in step S3, the heating and stirring time is 5 h; in step S4, the heating and stirring speed is 1500 rpm and the time is 12 h; and in step S5, the vacuum drying time is 12 h. Example 6

[0086] The preparation method and characterization of MPPLi in this embodiment are the same as in Example 4, except that: in step S1, the mass fraction of sodium-based montmorillonite in the acid solution is 10 wt%, the mass fraction of acidified montmorillonite slurry in the lithium hydroxide solution is 10 wt%, the heating and stirring conditions are 90℃, stirring speed 1000 rpm, time 6 h, freeze-drying time is 48 h, and subsequent vacuum drying temperature is 150℃; in step S2, the mass ratio of lithium-ionized montmorillonite nanosheets to polyethylene oxide is 7:2, and the heating and stirring temperature is 80℃; in step S3, PVDF-HFP is used instead of PAN, and the materials are prepared according to a mass ratio of PVDF-HFP to LiTFSI of 6:8, the heating and stirring speed is 600 rpm, and time is 6 h; in step S4, the heating and stirring temperature is 60℃, the stirring speed is 1200 rpm, and time is 12 h; in step S5, the vacuum drying temperature is 60℃, and time is 12 h.

[0087] Example 7

[0088] The preparation method and characterization of MPPLi in this embodiment are the same as in Example 6, except that in step S1, the concentrations of both the hydrochloric acid solution and the lithium hydroxide solution are 0.5 mol / L. -1 The heating and stirring time is 8 hours and the stirring speed is 800 rpm. In step S3, the mass ratio of PVDF-HFP to LiFSI is 6:7, the heating and stirring temperature is 65℃ and the time is 4 hours. In step S4, the heating and stirring time is 24 hours. Example 8

[0089] The preparation method and characterization of MPPLi in this embodiment are the same as in Example 7, except that: the heating and stirring time is 10 h, and the subsequent vacuum drying time is 24 h; in step S2, the heating and stirring speed is 1500 rpm; in step S3, PMMA is used instead of PVDF-HFP, and the materials are prepared according to the mass ratio of PMMA to LiTFSI of 6:8, the heating and stirring speed is 800 rpm, and the time is 5 h; in step S4, the heating and stirring speed is 1500 rpm, and the time is 12 h. Comparative Example 1

[0090] In this comparative example, the preparation method and testing and characterization of the solid electrolyte are the same as in Example 1. The difference is that the material involved in step S2 does not contain MLi, and the remaining preparation steps are the same as in Example 1. Comparative Example 2

[0091] In this comparative example, the preparation method and testing and characterization of the solid electrolyte are the same as in Example 1. The difference is that the material involved in step S2 does not contain PEO, and the remaining preparation steps are the same as in Example 1. Comparative Example 3

[0092] In this comparative example, the preparation method and characterization of the solid electrolyte are the same as in Example 1, except that the preparation process of MLi in step S1 lacks the freeze-drying process. The remaining preparation steps are the same as in Example 1. Comparative Example 4

[0093] In this comparative example, the preparation method and testing and characterization of the solid electrolyte are the same as in Example 1, except that the mass ratio of PVDF to LiTFSI in step S3 is 6:12.

[0094]

[0095] As shown in Table 1, the room temperature ionic conductivity of Examples 1-8 is approximately 6 × 10⁻⁶. -4 Scm -1 The lithium-ion transference numbers were all greater than 0.5, which is relatively high compared to Comparative Example 1. This is because the added MLi played a key role. MLi can form a "sandwich" intercalation structure with the polymer material. This structure has a strong adsorption capacity for highly polar solvent molecules, which can lock in some DMF solvent molecules and prevent them from evaporating. The solvent molecules will greatly promote the dissociation of lithium salt. The positive charge carried by the edge of MLi is also beneficial to TFSI. - Locking effect of anionic groups ( Figure 10 This will further promote Li + The dissociation of lithium salts is relatively low. In contrast, the electrolyte in Comparative Example 1 does not contain MLi and therefore lacks a "sandwich" intercalation structure. As a result, it has a lower solvent residue and a poorer degree of lithium salt dissociation, leading to lower room temperature ionic conductivity and ion transport number.

[0096] Examples 1-8 all exhibit tensile strengths above 14 MPa and corresponding deformations greater than 50%, demonstrating better flexibility compared to Comparative Examples 1 and 2. This is because the polymer chains couple with the broken "OH" bonds at the bottom of MLi, forming a robust chemical structure that significantly enhances the mechanical strength of the electrolyte. The doped PEO further increases the electrolyte's flexibility. Therefore, while maintaining high tensile strength, it also exhibits good tensile deformation. Comparative Example 1, lacking MLi, lacks the strong chemical forces associated with intercalation and therefore has lower tensile strength. Comparative Example 2, lacking PEO, has higher rigidity, exhibiting high tensile strength (reaching 16.09 MPa) but smaller tensile deformation.

[0097] Examples 1-8 did not ignite or burn, demonstrating good safety performance. This is related to the presence of a large amount (>30%) of highly flame-retardant MLi in MPPLi. Since Comparative Example 1 did not contain MLi, it ignited and burned. Figure 17 Solid-state batteries have poor thermal safety. Therefore, the MPPLi prepared in Examples 1-8 can greatly enhance the thermal safety of solid-state batteries.

[0098] In Comparative Example 3, although lithium-ionized montmorillonite was also used, this lithium-ionized montmorillonite was not prepared using a freeze-drying process and was not in the form of nanosheets but rather as particulate material. Figure 18 Therefore, it is difficult to intercalate with polymers to form intercalated composite solid electrolytes, and thus it does not possess the high room temperature ionic conductivity and lithium-ion transference number corresponding to Examples 1-8. Similarly, due to the lack of a "sandwich" intercalation structure, its mechanical strength is also poor, and its thermal safety is reduced.

[0099] In Comparative Example 4, due to the use of a large amount of LiTFSI, the precursor solution had very poor film-forming properties, making it difficult to form a self-supporting electrolyte using the same preparation method.

[0100] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Therefore, equivalent changes made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing an intercalated composite solid electrolyte, characterized in that, Includes the following steps: S1. Sodium-based montmorillonite was added to hydrochloric acid solution, stirred under water bath heating, allowed to stand and the supernatant was discarded, washed and centrifuged to obtain acidified montmorillonite slurry; lithium hydroxide solution was added to acidified montmorillonite slurry, stirred under water bath heating to form a slurry, allowed to stand and the supernatant was discarded, washed and centrifuged, freeze-dried for 24-48 h, then vacuum-dried at 120-150 °C for 12-24 h, ground and sieved to obtain lithium-ionized montmorillonite nanosheets; S2. Lithium-ionized montmorillonite nanosheets and polyethylene oxide are added to N,N-dimethylformamide, heated and stirred to obtain slurry A; the mass ratio of lithium-ionized montmorillonite nanosheets to polyethylene oxide is 7:1-2. S3. Add the polymer material and lithium salt to N,N-dimethylformamide, heat and stir to obtain slurry B; S4. Add slurry A dropwise into slurry B, heat and stir to obtain a precursor solution; S5. The precursor solution is coated onto a glass substrate, allowed to stand, vacuum dried, and then demolded to obtain an intercalated composite solid electrolyte; the thickness of the intercalated composite solid electrolyte is 20–100 μm. In step S3, the polymer material includes one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, and polyacrylonitrile; the mass ratio of the polymer material to the lithium salt is 6:3 to 8.

2. The method for preparing the intercalated composite solid electrolyte according to claim 1, characterized in that, In step S1, the mass fraction of sodium-based montmorillonite in the hydrochloric acid solution is 5–10 wt%; the concentration of the hydrochloric acid solution is 0.1–0.5 mol / L. -1 The concentration of the lithium hydroxide solution is 0.1–0.5 mol / L. -1 The mass fraction of the acidified montmorillonite slurry in the lithium hydroxide solution is 5-10 wt%; the water bath heating temperature is 60-90℃, the stirring time is 6-10 h, and the stirring speed is 800-1000 rpm.

3. The method for preparing the intercalated composite solid electrolyte according to claim 1, characterized in that, In step S2, the heating and stirring temperature is 50-80℃, the stirring speed is 1200-1500 rpm, and the stirring time is 12-18 hours.

4. The method for preparing the intercalated composite solid electrolyte according to claim 1, characterized in that, In step S3, the lithium salt is selected from one or more of lithium bis(trifluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium hexafluorophosphate; the heating and stirring reaction temperature is 50-65°C, the stirring speed is 400-800 rpm, and the time is 4-6 h.

5. The method for preparing the intercalated composite solid electrolyte according to claim 1, characterized in that, In step S4, slurry A and slurry B are mixed in equal volumes; the stirring and heating temperature is 40-60℃, the stirring speed is 1200-1500 rpm, and the stirring time is 12-24 hours.

6. The method for preparing the intercalated composite solid electrolyte according to claim 1, characterized in that, In step S5, the vacuum drying temperature is 50-60℃, the drying time is 12-48h, and the vacuum degree is -90--99kPa.

7. An intercalated composite solid electrolyte, characterized in that, The intercalated composite solid electrolyte is prepared by the preparation method described in any one of claims 1-6.

8. An application of an intercalated composite solid electrolyte, characterized in that, The intercalated composite solid electrolyte as described in claim 7 is used in solid / semi-solid lithium-ion batteries.

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