Lithium metal battery composite polymer electrolyte and preparation method and application thereof

Abstract

The application belongs to the field of lithium metal battery materials, and discloses a lithium metal battery composite polymer electrolyte and a preparation method and application thereof; the preparation method is as follows: a mixed dispersion liquid containing an organic polymer matrix and hybrid fillers (including active fillers and inert fillers) is cast into a film to obtain a composite polymer film, and then the composite polymer film is cut into small round pieces with a target diameter to obtain the composite polymer electrolyte. The application also discloses the composite polymer electrolyte prepared by the preparation method and application of the composite polymer electrolyte in lithium metal batteries. The composite polymer electrolyte has good ionic conductivity, high lithium ion transference number and electrochemical stability, and can be used in various high-energy secondary batteries with metal lithium as a negative electrode.

Description

Technical Field

[0001] This invention belongs to the field of lithium metal battery materials, specifically relating to a lithium metal battery composite polymer electrolyte, its preparation method, and its application. Background Technology

[0002] With the urgent need for high-energy-density and high-safety energy storage devices in the global energy transition, all-solid-state lithium metal batteries have become a research focus in the field of electrochemistry due to their ability to effectively solve the safety hazards of traditional liquid electrolytes, such as flammability and leakage. Among many solid-state electrolyte systems, polyepoxy vinyl polymer electrolytes show broad application prospects due to their excellent flexibility, easy processing, and good interfacial compatibility with lithium metal anodes. However, because polyepoxy vinyl segments are extremely prone to crystallization at room temperature, their ionic conductivity is relatively low (<10). -5 S cm -1 Furthermore, under high-temperature operating conditions, the mechanical strength is significantly reduced, making it difficult to suppress lithium dendrite puncture, which severely restricts the high-rate performance and long cycle life of polyvinyl oxide batteries.

[0003] Hydroxypropyl methylcellulose, a biomass derivative, can anchor anions through Lewis acid-base interactions and utilize its steric hindrance effect to reduce the crystallinity of polyethylene oxide, thus constructing efficient amorphous transport channels. The introduction of hydroxypropyl methylcellulose endows the electrolyte with good flexibility and interfacial stability. However, purely organic composite systems still have limitations in improving bulk ion conduction rates and providing absolute physical strength to resist dendrite penetration. Especially when facing high current density charging and discharging, a more rigid mechanical barrier and a faster ion migration path need to be constructed within the electrolyte.

[0004] Rocco et al. prepared a mixed polymer electrolyte by blending poly(ethylene oxide) and poly(methyl vinyl ether maleic acid). After blending, the hydrogen bonds formed between poly(ethylene oxide) and poly(methyl vinyl ether maleic acid) improved the mechanical strength of the electrolyte, while its ionic conductivity at room temperature was increased, and the electrochemical window was also effectively improved. At the same time, by developing a single-ion conductor polymer to fix the anion center, the concentration polarization during the charge and discharge process was fundamentally suppressed and the lithium dendrite growth was effectively delayed, significantly improving the ion transport efficiency. (AM Rocco, Pereira RP, Felisberti MI. Miscibility, crystallinity and morphological behavior of binary blends of poly(ethylene oxide) and poly(methyl vinyl ether–maleic acid) [J]. Polymer, 2001, 42(12): 5199-5205.) By combining in-situ polymerization film formation technology to achieve molecular-level integrated contact between electrolyte and electrode materials, the interfacial contact impedance is greatly reduced and the electrochemical stability window of the electrolyte on the high-voltage cathode side is broadened. This multi-dimensional strategy, which includes bulk modification, composite enhancement, carrier regulation and interfacial integration, is synergistically promoting the industrialization of all-solid-state polymer batteries towards the goal of high safety and high specific energy. However, the above-mentioned battery has a small improvement in ionic conductivity, and the scheme does not explore the electrochemical performance of the electrolyte under high temperature conditions. Summary of the Invention

[0005] To address the problems existing in the prior art, the primary objective of this invention is to provide a method for preparing a composite polymer electrolyte for lithium metal batteries, aiming to prepare a composite polymer electrolyte with excellent performance in the field of lithium metal batteries.

[0006] The second objective of this invention is to provide a lithium metal battery composite polymer electrolyte prepared by the method for preparing the aforementioned lithium metal battery composite polymer electrolyte.

[0007] A third objective of this invention is to provide the application of the composite polymer electrolyte in a lithium metal battery, and to provide a lithium metal battery equipped with the composite polymer electrolyte.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: This invention provides a method for preparing a composite polymer electrolyte for lithium metal batteries. The method involves mixing an organic polymer matrix, a hybrid filler (including an inert filler and an active filler), and a lithium salt, then casting the mixture into a film to obtain a composite polymer film, which is then cut to obtain a polymer electrolyte.

[0009] This invention, by mixing and dispersing active fillers and inert fillers into an organic polymer matrix, can produce a composite polymer electrolyte that has both high ionic conductivity and high mechanical strength.

[0010] Further, the organic polymer matrix is ​​polyethylene oxide, polyvinylidene fluoride, polyacrylonitrile, etc., and the hybrid filler is an inert filler, hydroxypropyl methylcellulose (viscosity 2%, methoxy content 28%-30%, hydroxypropyl content 7%-12%). The active filler is lithium titanium aluminum phosphate; the lithium salt is lithium bis(trifluoromethanesulfonyl)imide (purity 99.9%); in the polymer membrane, the mass fraction of both the inert filler and the active filler is 5%-25%. The lithium salt is added at a ratio of [EO:Li] = 18:1.

[0011] Furthermore, the preparation method of lithium titanium aluminum phosphate employs a sol-gel method to prepare lithium titanium aluminum phosphate solid electrolyte powder. LiNO3, Al(NO3)3·9H2O, Ti(OC4H9)4, and NH4H2O4 are used as raw materials. 1g LiNO3, 1.141g Al(NO3)3·9H2O, 5.866g Ti(OC4H9)4, and 3.5g NH4H2O4 are weighed according to stoichiometric ratios. During the preparation process, an excess of 0.1-0.2g LiNO3 is added to compensate for the loss of Li during calcination. + Lithium loss due to volatilization. The specific preparation method is as follows: LiNO3 and Al(NO3)3·9H2O were placed in a beaker containing an appropriate amount of anhydrous ethanol and completely dissolved under magnetic stirring. Ti(OC4H9)4 was then added and stirred thoroughly (denoted as solution A). Next, an appropriate amount of NH4H2PO4 was dissolved in deionized water in another beaker and completely dissolved under magnetic stirring (denoted as solution B). Solution B was slowly added dropwise to solution A while continuously stirring until homogeneous. The pH was adjusted to alkaline with ammonia water, and stirring was continued for 1-2 hours to allow aging and obtain a white lithium aluminum titanium phosphate precursor solution. The lithium aluminum titanium phosphate precursor solution was dried at 80℃ for 24-48 hours to obtain the lithium aluminum titanium phosphate precursor. The lithium aluminum titanium phosphate precursor was finely ground in an agate mortar, then placed in an alumina crucible and compacted. It was then calcined in a muffle furnace at 800℃ for 6-9 hours. After cooling, it was ground using a ball mill to obtain lithium aluminum titanium phosphate solid electrolyte powder.

[0012] In this invention, the organic polymer matrix and the hybrid filler are dissolved or dispersed in the same solvent. The organic polymer matrix and the hybrid filler are thoroughly mixed by magnetic stirring and ultrasonic dispersion, and then cast into a film. The resulting composite polymer film is then cut into small discs of the target diameter to obtain the composite polymer electrolyte.

[0013] Furthermore, the composite polymer film obtained by casting is naturally dried at room temperature, and then the polymer electrolyte film is placed in a vacuum oven and dried at 60℃-80℃ for 48-72 h to completely remove the residual organic solvent inside.

[0014] The present invention provides a method for preparing a composite polymer electrolyte for lithium metal batteries.

[0015] Furthermore, the composite polymer electrolyte component comprises an organic polymer matrix, a hybrid filler, and a lithium salt.

[0016] Furthermore, the thickness of the composite polymer film is 100-150µm, and the thickness of the resulting composite polymer electrolyte is 100-150µm.

[0017] The present invention also provides the application of the composite polymer electrolyte, using the composite polymer electrolyte as a polymer electrolyte for lithium metal batteries.

[0018] Furthermore, the lithium metal battery is a lithium ternary battery, a lithium-sulfur battery, a lithium-air battery, a lithium-oxygen battery, a lithium-selenium battery, a lithium-tellurium battery, a lithium-iodine battery, a lithium-carbon dioxide battery, or a lithium-nitrogen battery.

[0019] Furthermore, the lithium metal battery is a solid-state lithium metal battery, comprising the composite polymer electrolyte; the cell of the solid-state lithium metal battery includes a positive electrode, a negative electrode, and a composite polymer electrolyte sandwiched between the positive and negative electrodes.

[0020] Furthermore, the positive electrode can be made of a positive electrode material well-known in the field of lithium metal batteries. The negative electrode is a lithium metal foil or a composite material containing lithium metal.

[0021] The beneficial effects of this invention are: This invention ingeniously utilizes a mixture of inert filler hydroxypropyl methylcellulose and active filler lithium titanium aluminum phosphate, combined with an organic polymer matrix and lithium salt, to form a composite polymer film through casting. This results in a composite polymer electrolyte with high mechanical strength. Hydroxypropyl methylcellulose, as a cellulose ether, has abundant hydroxypropyl (-OCH2CHOHCH3) and methoxy (-OCH3) branches on its molecular chain. On one hand, it significantly reduces the crystallinity of the polyethylene oxide chain by breaking the ordered arrangement of the segments through steric hindrance and intermolecular hydrogen bonds. On the other hand, its polar functional groups can generate Lewis acid-base interactions with lithium salt anions, promoting lithium salt dissociation and anchoring anions, thereby increasing the lithium ion transport number. Lithium titanium aluminum phosphate, as a NASICON-type ceramic filler, constructs a three-dimensional open framework with [TiO6] octahedra and [PO4] tetrahedra sharing vertices, providing continuous bulk migration channels for lithium ions. Its surface Ti... 4+Al 3+ As a strong Lewis acid site, it can effectively anchor anions and induce polymer segment decrystallization. In synergy, hydroxypropyl methylcellulose acts as a "molecular bridge," forming a multiple hydrogen bond network with the surface of lithium titanium aluminum phosphate and polyoxyethylene segments through its hydroxyl groups. This inhibits lithium titanium aluminum phosphate aggregation and constructs continuous interfacial percolation transport channels, ultimately achieving a simultaneous improvement in ionic conductivity, mechanical strength, and electrochemical window. Experimental results show that the composite polymer electrolyte prepared by the method described in this invention exhibits good ionic conductivity, high lithium-ion transference number, and high electrochemical stability in lithium metal batteries. Attached Figure Description

[0022] Figure 1 The graph shows the ionic conductivity test results of the polymer electrolyte in Example 1.

[0023] Figure 2 The graph shows the ionic conductivity test results of the polymer electrolyte in Example 2.

[0024] Figure 3 The graph shows the ionic conductivity test results of the polymer electrolyte in Example 3.

[0025] Figure 4 The graph shows the ionic conductivity test results of the polymer electrolyte in Comparative Example 1. Detailed Implementation

[0026] The present invention will be described below with reference to specific embodiments. Those skilled in the art will understand that these embodiments are for illustrative purposes only and do not limit the scope of the invention in any way.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all reagents and materials used in the following examples are commercially available products.

[0028] Hydroxypropyl methylcellulose was purchased from Maclean's, CAS number H811105 Polyethylene oxide was purchased from Aladdin, Mw=600000 The lithium bis(trifluoromethanesulfonyl)imide was purchased from Aladdin, CAS number B822763.

[0029] Preparation of lithium titanium aluminum phosphate: Solid electrolyte powder of lithium titanium aluminum phosphate was prepared by sol-gel method using LiNO3, Al(NO3)3·9H2O, Ti(OC4H9)4, and NH4H2O4 as raw materials. 1g of LiNO3 and 1.141g of Al(NO3)3·9H2O were placed in a beaker containing an appropriate amount of anhydrous ethanol and completely dissolved under magnetic stirring. Then, 5.866g of Ti(OC4H9)4 was added and stirred thoroughly (denoted as solution A). Next, 3.5g of NH4H2PO4 was dissolved in deionized water in another beaker and completely dissolved under magnetic stirring (denoted as solution B). Solution B was slowly added dropwise to solution A while continuously stirring until homogeneous. The pH was adjusted to alkaline with ammonia water, and stirring was continued for 1-2 hours to allow aging, yielding a white lithium titanium aluminum phosphate precursor solution. The lithium titanium aluminum phosphate precursor can be obtained by drying the lithium titanium aluminum phosphate precursor solution at 80℃ for 24-48 h. The lithium titanium aluminum phosphate precursor is then finely ground in an agate mortar, placed in an alumina crucible and compacted, and then calcined in a muffle furnace at 800℃ for 6-9 h. After cooling, it is ground with a ball mill to obtain lithium titanium aluminum phosphate solid electrolyte powder.

[0030] Example 1 (1) Weigh 1 g of dried polyethylene oxide and add it to a sample bottle. Then add 25 mL of anhydrous acetonitrile and stir slowly for 8 h to dissolve it completely. Then add 20% hydroxypropyl methylcellulose to the solution and continue stirring for 3 h until it is completely dissolved.

[0031] (2) Add 0.35 g of lithium bis(trifluoromethanesulfonyl)imide and stir for 4 h to completely dissolve it. Place the reagent bottle in an ultrasonic cleaner for ultrasonic treatment for 2 h to ensure uniform distribution and remove air bubbles. Pour the solution into a polytetrafluoroethylene mold and allow it to dry naturally at room temperature. Then place the polymer electrolyte film in a vacuum oven and dry it at 60°C for 48 h to completely remove any residual organic solvent. Finally, peel the completely dried polymer electrolyte film from the mold to obtain an electrolyte film with a thickness of approximately 100 μm. Cut the film into discs with a diameter of 18 mm and store them in a glove box for later use.

[0032] Example 2 (1) Weigh 1 g of dried polyethylene oxide and add it to a sample bottle. Then add 25 mL of anhydrous acetonitrile and stir slowly for 8 h to dissolve it completely. Then add 20% hydroxypropyl methylcellulose to the solution and continue stirring for 3 h until it is completely dissolved.

[0033] (2) Add 10% lithium titanium aluminum phosphate and stir for 2 h until it is completely dissolved.

[0034] (3) Add 0.35g of lithium bis(trifluoromethanesulfonyl)imide and stir for 4 h to completely dissolve it. Then, place the reagent bottle in an ultrasonic cleaner for ultrasonic treatment for 2 h to ensure uniform distribution and remove air bubbles. Pour the solution into a polytetrafluoroethylene mold and allow it to dry naturally at room temperature. Then, place the polymer electrolyte film in a vacuum oven and dry it at 60°C for 48 h to completely remove any residual organic solvent. Finally, peel the completely dried polymer electrolyte film from the mold to obtain an electrolyte film with a thickness of approximately 100 μm. Cut the film into discs with a diameter of 18 mm and store them in a glove box for later use.

[0035] Example 3 (1) Weigh 1 g of dried polyethylene oxide and add it to a sample bottle. Then add 25 mL of anhydrous acetonitrile and stir slowly for 8 h to dissolve it completely. Then add 20% hydroxypropyl methylcellulose to the solution and continue stirring for 3 h until it is completely dissolved.

[0036] (2) Add 0.35 g of lithium bis(trifluoromethanesulfonylimide) and stir for 4 h to dissolve completely. Place the reagent bottle in an ultrasonic cleaner and sonicate for 2 h to distribute the solution evenly and remove air bubbles.

[0037] (3) Draw sufficient solution into a 10 mL plastic syringe to ensure solution fluidity. Connect the syringe and needle using a PTFE tube with an inner diameter of 0.5 mm. Use a 23 G stainless steel flat-tipped needle with an inner diameter of 0.3 mm. Fix the needle on a Z-shaped support and apply high voltage. Dry the electrospun membrane in a vacuum drying oven to obtain an electrolyte membrane, which is then stored in a glove box for later use.

[0038] Comparative Example 1 (1) Weigh 1 g of dried polyethylene oxide and add it to the sample bottle. Then add 25 mL of anhydrous acetonitrile and stir slowly for 8 h to dissolve it completely. Then add lithium bis(trifluoromethanesulfonyl)imide in a [EO:Li] ratio of 18:1 and stir for 4 h to dissolve it completely.

[0039] (2) Place the reagent bottle in an ultrasonic cleaner for ultrasonic treatment for 2 h to ensure uniform distribution and remove air bubbles. Pour the solution into a polytetrafluoroethylene mold and allow it to dry naturally at room temperature. Then place the polymer electrolyte film in a vacuum oven and dry it at 60°C for 48 h to completely remove any residual organic solvent. Finally, peel the completely dried polymer electrolyte film from the mold to obtain an electrolyte film with a thickness of approximately 100 μm. Cut the film into discs with a diameter of 18 mm and store them in a glove box for later use.

[0040] Application and performance testing The composite polymer electrolytes obtained in Examples 1-3 and Comparative Example 1 were assembled sequentially in the following order: CR2032 positive electrode shell, stainless steel sheet or lithium sheet, composite polymer electrolyte, stainless steel sheet or lithium sheet, and CR2032 negative electrode shell. After being covered with tweezers, they were placed in a sealing machine for sealing at 50 kg / cm³. 2 The pressure seal was applied for 60 seconds. Two types of batteries, assembled from lithium / composite polymer electrolyte / lithium batteries and stainless steel sheet / composite polymer electrolyte / stainless steel sheet batteries, were used for testing ionic conductivity, lithium-ion transport number, and electrochemical window.

[0041] The ionic conductivity was measured using the AC impedance method, employing a battery with a stainless steel sheet / composite polymer electrolyte / stainless steel sheet structure. Ionic conductivity is expressed by the formula σ = The calculations are performed, where L represents the thickness of the composite polymer electrolyte, S represents the contact area between the stainless steel sheet and the composite polymer electrolyte, and R represents the bulk impedance measured by AC impedance spectroscopy. The test data are shown in Table 2. It can be seen that in Examples 1, 2, 3 and Comparative Example 1, the increase in hydroxypropyl methylcellulose filler increased the ionic conductivity because the cellulose in the filler acts as a rigid framework, limiting the excessive swelling of the polyepoxy vinyl body. Further increases in lithium titanium aluminum phosphate filler improved the electrochemical performance because it provides a continuous bulk migration channel for lithium ions while supplementing the lithium source.

[0042] The lithium-ion transport number was measured using an alternating current impedance method combined with a potentiostatic polarization method, employing a lithium / composite polymer electrolyte / lithium structure battery. The lithium-ion transport number is given by the formula... Calculate, where Is and Iss represent the initial current after applying a constant voltage and the current after equilibrium, respectively, and R S and R SS The values ​​represent the bulk impedance of the composite polymer electrolyte before and after constant potential polarization, respectively, with ΔV representing the applied constant voltage. The test data are shown in Table 2. As can be seen from Table 2, the addition of hydroxypropyl methylcellulose and lithium aluminum titanium phosphate in Examples 1, 2, and 3 improves the lithium-ion transference number of the composite polymer electrolyte, exhibiting a superior lithium-ion transference number compared to Comparative Example 1. This improved performance helps reduce the polarization effect caused by anion migration, which is significant for improving the cycle performance and rate performance of the battery.

[0043] The electrochemical window was determined using linear sweep voltammetry (LSV). At room temperature, the stable voltage limit of the polymer electrolyte was tested using LSV. The prepared solid electrolyte was sliced ​​into 18 mm diameter discs and assembled into an asymmetrical battery in the following order: negative electrode shell - gasket - lithium sheet - solid electrolyte - gasket - positive electrode shell. The relationship between current and voltage was then measured. The test voltage range was 2-6 V, and the scan rate was 0.01 V / s. The intercept of the slope on the x-axis corresponding to the sudden increase in the curve is the decomposition voltage of the electrolyte. The test data are shown in Table 2. The data in the table show that, compared to Comparative Example 1, the electrochemical stability window of Examples 1, 2, and 3 is larger. This indicates that the addition of hydroxypropyl methylcellulose and lithium aluminum titanium phosphate fillers is beneficial to the composite polymer electrolyte, resulting in high electrochemical stability.

[0044] Tensile strength was tested using a universal tensile testing machine at a speed of 20 mm / min to stretch a dumbbell-shaped specimen. The specific dimensions of the dumbbell-shaped specimen conformed to standard ISO 527-3-1995. In Comparative Example 1, the tensile strength of the composite polymer film was 1.34 MPa with a strain of 41%; in Example 1, the tensile strength of the composite polymer film was 2.78 MPa with a strain of 101%; and in Example 2, the tensile strength of the composite polymer film was 3.22 MPa with a strain of 110%.

[0045] Table 1 shows the amount of raw materials added in Examples 1-3 and Comparative Example 1.

[0046] Table 1

[0047] Table 2 shows the electrochemical test results for Examples 1-3 and Comparative Example 1. The ionic conductivity test results for Examples 1, 2, 3 and Comparative Example 1 are shown in Table 2. Figures 1-4 .

[0048] Table 2

[0049] Compared to Examples 1 and 3 and Comparative Example 1, Example 2 simultaneously added active filler lithium titanium aluminum phosphate and inert filler hydroxypropyl methylcellulose. The resulting composite polymer electrolyte exhibits both high ionic conductivity and high mechanical strength. This is because the polar hydroxyl functional groups of hydroxypropyl methylcellulose act as "molecular bridges," forming a multi-hydrogen bond network with the surface of lithium titanium aluminum phosphate particles and polyethylene oxide segments. On the one hand, this inhibits the aggregation of lithium titanium aluminum phosphate nanoparticles, and on the other hand, it constructs a continuous organic-inorganic interface percolation channel—this interface has a lower lithium-ion migration activation energy than the pure polymer bulk phase. At the same time, the rigid lithium titanium aluminum phosphate particles act as load-bearing centers, forming a bicontinuous mechanical support structure with the flexible hydroxypropyl methylcellulose / polyethylene oxide network, resulting in a tensile strength of 3.22 MPa (240% higher than pure PEO). Thus, high ionic conductivity and high mechanical strength are achieved simultaneously.

[0050] Compared to Examples 1 and 2 and Comparative Example 1, Example 3 reconstructs the same material system into a three-dimensional interconnected nanofiber network using electrospinning technology. Its advantage lies in the fact that the long-range continuous ion channels constructed from high aspect ratio fibers significantly reduce transport tortuosity, increasing the ionic conductivity at 60°C to 1.56 × 10⁻⁶. -3 S / cm; secondly, the huge specific surface area of ​​nanofibers induces strong interfacial effects, with the polar groups of hydroxypropyl methylcellulose densely exposed on the fiber surface, which is beneficial to TFSI. - The anchoring effect of anions is significantly enhanced, pushing the lithium-ion transference number to 0.68. Furthermore, the three-dimensional framework forms an overall reinforcing network through physical cross-linking points between fibers, providing a more uniform stress dispersion mechanism while maintaining flexibility. However, because no active filler was added in Example 3, even with electrospinning, the final ionic conductivity remained low, and the electrochemical window was narrow. The overall effect was not as good as in Example 2, which simultaneously added the active filler lithium aluminum titanium phosphate and the inert filler hydroxypropyl methylcellulose.

[0051] The above embodiments are merely preferred embodiments of the present invention and are only used to explain the present invention, not to limit the present invention. Any changes, substitutions, modifications, etc., made by those skilled in the art without departing from the spirit and essence of the present invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a lithium metal battery composite polymer electrolyte, characterized in that, It is composed of an organic polymer matrix, a hybrid filler, and a lithium salt mixture, wherein the hybrid filler includes inert fillers and active fillers.

2. The preparation method according to claim 1, characterized in that, The organic polymer matrix is ​​polyethylene oxide; the inert filler is hydroxypropyl methylcellulose; the active filler is lithium titanium aluminum phosphate; and the lithium salt is lithium bis(trifluoromethanesulfonyl)imide.

3. The preparation method according to claim 2, characterized in that, The hydroxypropyl methylcellulose has a viscosity of 2%, a methoxy content of 28%-30%, and a hydroxypropyl content of 7%-12%.

4. The preparation method according to claim 1, characterized in that, The method for preparing lithium titanium aluminum phosphate employs a sol-gel method to prepare lithium titanium aluminum phosphate solid electrolyte powder.

5. The preparation method according to claim 4, characterized in that, LiNO3 and Al(NO3)3·9H2O were dissolved in anhydrous ethanol to obtain solution A, and Ti(OC4H9)4 was added and stirred thoroughly. NH4H2PO4 was dissolved in deionized water to obtain solution B. Solution B was added dropwise to solution A and stirred continuously to ensure uniform mixing. The pH was adjusted to alkaline with ammonia water, and stirring was continued to allow aging to obtain a lithium titanium aluminum phosphate precursor solution. After drying, lithium titanium aluminum phosphate precursor was obtained. The lithium titanium aluminum phosphate precursor was ground and calcined to obtain lithium titanium aluminum phosphate solid electrolyte powder.

6. The preparation method according to claim 1, characterized in that, The mass fraction of hydroxypropyl methylcellulose in the composite polymer membrane is 5%-25%.

7. The preparation method according to claim 1, characterized in that, The method for mixing the organic polymer matrix and the hybrid filler is magnetic stirring and ultrasonic dispersion.

8. The composite polymer electrolyte prepared by the method of claim 1 for preparing lithium metal battery composite polymer electrolyte.

9. The application of the composite polymer electrolyte of claim 8 in lithium metal batteries.

10. The application according to claim 9, characterized in that, The lithium metal battery is a solid-state lithium metal battery. The cell of the solid-state lithium metal battery includes a positive electrode, a negative electrode, and a composite polymer electrolyte sandwiched between the positive and negative electrodes.

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