Polymer composite solid electrolyte membrane and method for preparing the same

Abstract

The application provides a polymer composite solid electrolyte membrane preparation method, comprising the following steps: step one, dispersing a polymer base in an organic solvent according to a mass ratio of 0.05-0.8; step two, dispersing HNTs particles in the organic solvent according to a mass ratio of 0.01-0.1; step three, dispersing additive particles in the organic solvent according to a mass ratio of 0.01-0.1; step four, pouring the HNTs and additive slurries into the solution obtained in step one; step five, pouring the electrolyte slurry into a polytetrafluoroethylene mold to obtain a polymer composite solid electrolyte layer, and then placing the polymer composite solid electrolyte layer into a hot press to obtain a final solid electrolyte membrane. The application also provides a polymer composite solid electrolyte membrane formed by using the above preparation method. The application improves the conductivity of the polymer solid electrolyte, and improves the mechanical strength and interface stability after film formation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid-state batteries, in particular to a preparation process of a polymer composite solid-state electrolyte film. BACKGROUND

[0002] With the development of the electric vehicle industry, lithium ion batteries have become the core of new energy technology. With the evolution of technology, the limitations of traditional liquid lithium ion batteries have gradually emerged. Solid-state batteries, with their innovative electrolyte design and material advantages, have shown the ability to surpass lithium batteries in terms of safety and energy density.

[0003] Solid-state electrolyte is the core material of all-solid-state batteries. As a kind of solid-state electrolyte, polymer electrolyte has the characteristics of high ionic conductivity, good processing performance, and low cost, and has become the most widely used electrolyte in solid-state batteries. In the polymer composite solid-state electrolyte film, the movement of the polymer chain segment and the ion conduction of the inorganic solid-state electrolyte work together to achieve the transmission of lithium ions. The movement of the polymer chain segment can provide a channel for the migration of lithium ions, while the inorganic solid-state electrolyte provides a region of high ionic conductivity, allowing lithium ions to be quickly transported within the film. Ionic conductivity needs to be improved: although the ionic conductivity of the polymer composite solid-state electrolyte film has been improved compared to pure polymer electrolyte, it still lags behind liquid electrolyte. At low temperatures, the ionic conductivity will further decrease, affecting the performance of the battery. Interface stability problem: the interface stability between the electrolyte film and the electrode is still a challenge. During the long-term charging and discharging process, chemical reactions, element diffusion, and other phenomena may occur at the interface, leading to an increase in interface resistance and affecting the performance and life of the battery. Higher cost: Currently, the preparation cost of the polymer composite solid-state electrolyte film is relatively high, mainly due to the high price of inorganic solid-state electrolyte materials and the complexity of the preparation process. This limits its application in large-scale energy storage and electric vehicles. When the battery is charged, lithium ions migrate from the positive electrode to the negative electrode through the electrolyte film; when discharged, lithium ions return from the negative electrode to the positive electrode, thus completing the charging and discharging process of the battery. However, the common polymer solid-state electrolyte has low ionic conductivity at room temperature and a small electrochemical window, and the pure polymer solid-state electrolyte film has poor mechanical strength and poor interface stability, which limits its application to some extent.

[0004] Therefore, how to improve the conductivity of the polymer solid-state electrolyte, increase the mechanical strength and interface stability of the film after formation, is a problem that needs to be solved in the industry. SUMMARY

[0005] One main object of the present application is to overcome at least one of the above-mentioned defects of the prior art, and to provide a polymer composite solid electrolyte membrane capable of improving the electrical conductivity of the polymer solid electrolyte, and a method for preparing the same.

[0006] To achieve the above-mentioned objects, the present application adopts the following technical solutions.

[0007] According to one aspect of the present application, there is provided a method for preparing a polymer composite solid electrolyte membrane, comprising the following steps:

[0008] Step 1: dispersing a polymer substrate in an organic solvent at a mass ratio of 0.05-0.8, stirring until completely dissolved to obtain a polymer solution; adding a lithium salt to the polymer solution and stirring;

[0009] Step 2: dispersing HNTs particles in the organic solvent at a mass ratio of 0.01-0.1, and performing room temperature ultrasonic treatment to obtain an HNTs slurry;

[0010] Step 3: dispersing additive particles in the organic solvent at a mass ratio of 0.01-0.1, and performing room temperature ultrasonic treatment to obtain an additive slurry;

[0011] Step 4: pouring the HNTs and additive slurries into the solution obtained in Step 1, and stirring to obtain an electrolyte slurry;

[0012] Step 5: pouring the electrolyte slurry into a polytetrafluoroethylene mold, performing vacuum drying to obtain a polymer composite solid electrolyte layer, placing aluminum foil on both sides of the polymer solid electrolyte layer, and placing it in a hot press to obtain a final solid electrolyte membrane.

[0013] According to one embodiment of the present application, the polymer substrate is at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, polyacrylonitrile, polymethyl methacrylate, and polyimide.

[0014] According to one embodiment of the present application, the organic solvent is at least one of ethanol, acetonitrile, N,N-dimethylformamide, tetrahydrofuran, butanedinitrile, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methyl pyrrolidone.

[0015] According to one embodiment of the present application, the lithium salt in Step 1 is at least one of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl)imide, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium difluoro(oxalato)borate, and lithium trifluoromethanesulfonate.

[0016] According to an embodiment of the present application, the additive is at least one of a solid-state electrolyte material and a nano-oxide material.

[0017] According to an embodiment of the present application, the solid-state electrolyte material is lithium lanthanum zirconium oxide and / or lithium titanium aluminum phosphate, and the particle size of the solid-state electrolyte material is 300 nm or less.

[0018] According to an embodiment of the present application, the nano-oxide material includes one or more of nano-SiO2, nano-Al2O3, nano-TiO2, nano-ZrO2, and nano-ZnO.

[0019] According to an embodiment of the present application, the mass percentage of the polymer substrate, functional agent HNTs, additive, and lithium salt is (10-85):(5-20):(5-50):(5-50).

[0020] According to an embodiment of the present application, the hot-pressing temperature in step five is 30-60℃, the pressure is 0.1T-1T, the hot-pressing time is 10-30S, and the thickness of the polymer solid-state electrolyte film after film formation is 10-100 microns.

[0021] To achieve the above-mentioned application purposes, the present application also adopts the following technical solutions:

[0022] According to another aspect of the present application, a polymer composite solid-state electrolyte film is provided, which is formed using the preparation method as described above.

[0023] From the above technical solutions, the polymer composite solid-state electrolyte film and method of the present application have the following advantages and positive effects:

[0024] In the present application, the prepared solid-state electrolyte slurry is uniform and has no particle agglomeration. In terms of the composition of the composite solid-state electrolyte, the addition of the functional agent HNTs itself can bind Li+ by using the abundant negative charges on the surface, thereby playing a role in transporting lithium ions, and secondly, enhancing the mechanical strength of the solid-state electrolyte film. The addition of the additive can improve the amorphousness of the polymer solid-state electrolyte and improve the ionic conductivity. The combination of points, lines, and surfaces formed among the three can form a solid-state electrolyte with high room temperature ionic conductivity, which helps to improve the electrochemical performance. The present application improves the conductivity of the polymer solid-state electrolyte, improves the mechanical strength and interface stability after film formation. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 is a cycle life curve diagram of the solid-state electrolyte film obtained in Example 1 of the present application for a solid-state battery. DETAILED DESCRIPTION

[0026] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations, however, can be implemented in many different forms and should not be construed as limited to the implementations set forth herein; rather, these implementations are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example implementations to those skilled in the art. Like reference numerals refer to like elements throughout the various figures, so that detailed descriptions of the figures are omitted for clarity.

[0027] In the following description of the various examples of the application, reference is made to the accompanying drawings, which form a part of this application, and in which are shown by way of illustration various example structures, systems, and steps in which aspects of the application can be practiced. It is to be understood that other specific arrangements of parts, structures, example devices, systems, and steps can be utilized and that structural and functional modifications can be made without departing from the scope of the present application. Also, while the terms "top," "bottom," "front," "back," "side," and the like can be used in this specification to describe various example features and elements of the application, these terms are used herein as a shorthand notations for ease of description only, and are not intended to limit the scope of the application in any way. Nothing in this specification should be construed as requiring a specific three-dimensional orientation of structures in order to fall within the scope of the application.

[0028] The application obtains a solid electrolyte membrane with high ionic conductivity through the compounding of HNTs, additives and polymers. The application obtains a composite solid electrolyte slurry with uniform mixing and no particle agglomeration through step-by-step preparation, and further forms a solid electrolyte membrane, which has the characteristics of high ionic conductivity and high mechanical processing strength.

[0029] The application provides a preparation method of a polymer composite solid electrolyte membrane.

[0030] In order to achieve the above-mentioned purpose of the application, the following technical solutions are adopted:

[0031] A preparation method of a polymer composite solid electrolyte membrane, comprising the following steps:

[0032] Step one: according to the mass ratio of the polymer substrate and the organic solvent being 0.05-0.8, the polymer substrate is dispersed in the organic solvent, and stirring is performed until complete dissolution to obtain a polymer solution; lithium salt is added to the polymer solution and stirring is performed;

[0033] Step two: the mass ratio of the functional agent HNTs and the organic solvent is 0.01-0.1, the HNTs particles are dispersed in the organic solvent, and room temperature ultrasonic treatment is performed to obtain an HNTs turbid liquid;

[0034] Step three: the additive and organic solvent mass ratio is 0.01-0.1, the additive particles are dispersed in the organic solvent, and ultrasonic treatment is carried out at room temperature to obtain an additive slurry;

[0035] Step four: the HNTs and the additive slurry are poured into the solution obtained in step one respectively, and stirring is carried out to obtain an electrolyte slurry;

[0036] Step five: the electrolyte slurry is poured into a polytetrafluoroethylene mold, vacuum drying is carried out, and a polymer composite solid electrolyte layer is obtained. After the polymer solid electrolyte layer is placed in a hot press with aluminum foils on both sides and hot pressed, a final solid electrolyte film is obtained.

[0037] The polymer substrate includes at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, polyacrylonitrile, polymethyl methacrylate, and polyimide.

[0038] The lithium salt in step one includes at least one of lithium hexafluorophosphate, lithium bis-trifluoromethylsulfonylimide, lithium tetrafluoroborate, lithium bis-oxalate borate, lithium bis-fluorosulfonylimide, lithium difluoro-oxalate borate, and lithium trifluoromethanesulfonate.

[0039] The organic solvent includes at least one of ethanol, acetonitrile, N,N-dimethylformamide, tetrahydrofuran, butanedinitrile, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methyl pyrrolidone.

[0040] The additive includes at least one of a solid electrolyte material and a nano-oxide material, wherein the solid electrolyte material is lithium lanthanum zirconium oxide (LLZO) or lithium aluminum titanium phosphate (LATP); preferably, the particle size of the solid electrolyte material is less than 300 nm, and the nano-oxide material includes nano-SiO2, nano-Al2O3, nano-TiO2, nano-ZrO2, and nano-ZnO; preferably, the particle size of the solid electrolyte material is less than 50 nm.

[0041] The mass percentage of the polymer substrate, functional agent HNTs, additive, and lithium salt is (10-85):(5-20):(3-50):(20-50).

[0042] The hot pressing temperature in step five is 30-50°C, the pressure is 0.1T-1T, the hot pressing time is 10-30S, and the thickness of the polymer solid electrolyte film is 10-100 microns.

[0043] The beneficial effects of the present application are: the HNTs have a relatively regular tubular structure, and the surface electronegativity is conducive to promoting the dissociation of lithium salt, conducive to providing a stable lithium ion transmission channel, reducing the diffusion energy barrier of lithium ions, and improving the migration number of lithium ions, thereby being conducive to improving the ionic conductivity of the polymer solid electrolyte; in addition, the additive also reduces the crystallinity of the polymer, thereby improving the ionic conductivity of the polymer solid electrolyte, and further being conducive to improving the lithium ion cycle performance. The polymer substrate, the functional agent HNTs, and the additive respectively provide the transmission of lithium ions on the surface, line, and point, and the three are compounded, thereby improving the ionic conductivity of the solid electrolyte.

[0044] The present application will be described below with reference to specific examples, and it should be noted that these examples are merely descriptive and do not limit the present application in any way.

[0045] Example 1

[0046] (1) 10 g of polyethylene oxide was dissolved in 50 g of acetonitrile, and stirred by a magnetic stirrer until completely dissolved to obtain a polymer solution;

[0047] (2) 2 g of lithium triflate was added to the polymer solution of step (1) and stirred until completely dissolved;

[0048] (3) 2 g of functional agent HNTs was added to 20 g of acetonitrile, and ultrasonic treatment was performed at room temperature for 2 hours to uniformly disperse the HNTs in the solvent to obtain an HNTs slurry;

[0049] (4) 1 g of LATP was added to 10 g of acetonitrile, and ultrasonic treatment was performed at room temperature for 2 hours to uniformly disperse the LATP in the solvent to obtain an additive slurry;

[0050] (5) The HNTs of step (3) and the LATP slurry of step (4) were poured into the solution of step (2) respectively, and stirred to obtain an electrolyte slurry;

[0051] (6) The electrolyte slurry of step (5) was poured into a polytetrafluoroethylene mold, and vacuum drying was performed at a vacuum degree of -0.3 MPa and a temperature of 60°C for 12 hours to obtain a polymer composite solid electrolyte layer.

[0052] (7) Aluminum foil was placed on both sides of the polymer solid electrolyte layer of step (6), and the hot press was placed in a hot press at 40°C, 0.2T, and 20S to obtain a final solid electrolyte film.

[0053] Example 2

[0054] (1) 10 g of polyvinylidene fluoride-hexafluoropropylene was dissolved in 150 g of N-methylpyrrolidone, and stirred by a magnetic stirrer until completely dissolved to obtain a polymer solution;

[0055] (2) Add 3 g of lithium triflate to the polymer solution of step (1) and stir until completely dissolved using a magnetic stirrer;

[0056] (3) Add 5 g of functional agent HNTs to 20 g of N-methylpyrrolidone and ultrasonically treat at room temperature for 2 hours to uniformly disperse the HNTs in the solvent to obtain an HNTs slurry;

[0057] (4) Add 2 g of nano-TiO2 to 50 g of N-methylpyrrolidone and ultrasonically treat at room temperature for 2 hours to uniformly disperse the nano-TiO2 in the solvent to obtain an additive slurry;

[0058] (5) Pour the HNTs slurry of step (3) and the additive slurry of step (4) into the solution of step (2) respectively, and stir to obtain an electrolyte slurry;

[0059] (6) Pour the electrolyte slurry of step (5) into a polytetrafluoroethylene mold, and vacuum dry at a vacuum degree of -0.3 MPa and a temperature of 80°C for 12 hours to obtain a polymer composite solid-state electrolyte layer.

[0060] (7) Place the polymer solid-state electrolyte layer of step (6) between two aluminum foils, and place in a hot press to heat press at 30°C, 0.5T, and 20S to obtain a final solid-state electrolyte film.

[0061] Example 3

[0062] (1) Dissolve 10 g of polyvinylidene fluoride in 200 g of N-methylpyrrolidone, and stir until completely dissolved using a magnetic stirrer to obtain a polymer solution;

[0063] (2) Add 2.5 g of lithium triflate to the polymer solution of step (1) and stir until completely dissolved using a magnetic stirrer;

[0064] (3) Add 4 g of functional agent HNTs to 20 g of acetonitrile and ultrasonically treat at room temperature for 2 hours to uniformly disperse the HNTs in the solvent to obtain an HNTs slurry;

[0065] (4) Disperse 3 g of nano-SiO2 in 50 g of N-methylpyrrolidone and ultrasonically treat at room temperature for 2 hours to uniformly disperse the nano-SiO2 in the solvent to obtain an additive slurry;

[0066] (5) Pour the HNTs slurry of step (3) and the nano-SiO2 slurry of step (4) into the solution of step (2) respectively, and stir to obtain an electrolyte slurry;

[0067] (6) Pour the electrolyte slurry of step (5) into a polytetrafluoroethylene mold, vacuum dry, vacuum degree -0.3 MPa, temperature 80°C for 12 hours, to obtain a polymer composite solid electrolyte layer.

[0068] (7) Put the polymer solid electrolyte layer of step (6) between two aluminum foils, and put it into a hot press to heat press at 50°C, 0.8T, 10S, to obtain a final solid electrolyte film.

[0069] Example 4

[0070] (1) Dissolve 10g of polyethylene oxide in 100g of acetonitrile, and stir until completely dissolved by a magnetic stirrer, to obtain a polymer solution;

[0071] (2) Add 5g of lithium triflate to the polymer solution of step (1) and stir until completely dissolved by a magnetic stirrer;

[0072] (3) Add 4g of functional agent HNTs to 50g of acetonitrile, and ultrasonically treat at room temperature for 2 hours to uniformly disperse the HNTs in the solvent, to obtain an HNTs slurry;

[0073] (4) Disperse 3g of nano ZrO2 in 50g of acetonitrile, and ultrasonically treat at room temperature for 2 hours to uniformly disperse the nano ZrO2 in the solvent, to obtain an additive slurry;

[0074] (5) Pour the HNTs slurry of step (3) and the additive slurry of step (4) into the solution of step (2) respectively, and stir for 6 hours by a magnetic stirrer, to obtain an electrolyte slurry;

[0075] (6) Pour the electrolyte slurry of step (5) into a polytetrafluoroethylene mold, vacuum dry, vacuum degree -0.3 MPa, temperature 60°C for 12 hours, to obtain a polymer composite solid electrolyte layer.

[0076] (7) Put the polymer solid electrolyte layer of step (6) between two aluminum foils, and put it into a hot press to heat press at 35°C, 1T, 10S, to obtain a final solid electrolyte film.

[0077] Example 5

[0078] (1) Dissolve 10g of polyethylene oxide in 80g of acetonitrile, and stir until completely dissolved by a magnetic stirrer, to obtain a polymer solution;

[0079] (2) Add 3g of lithium triflate to the polymer solution of step (1) and stir until completely dissolved by a magnetic stirrer;

[0080] (3) 3 g functional agent HNTs were added to 10 g ethanol, and ultrasonic treatment was performed at room temperature for 2 hours to uniformly disperse the HNTs in the solvent to obtain an HNTs slurry;

[0081] (4) 1 g LLZO was added to 10 g acetonitrile, and ultrasonic treatment was performed at room temperature for 2 hours to uniformly disperse the LLZO in the solvent to obtain an additive slurry;

[0082] (5) The HNTs slurry of step (3) and the additive slurry of step (4) were respectively poured into the solution of step (2), and stirring was performed by a magnetic stirrer for 6 hours to obtain an electrolyte slurry;

[0083] (6) The electrolyte slurry of step (5) was poured into a polytetrafluoroethylene mold, vacuum drying was performed at a vacuum degree of -0.3 MPa and a temperature of 60°C for 12 hours to obtain a polymer composite solid electrolyte layer.

[0084] (7) Aluminum foils were placed on both sides of the polymer solid electrolyte layer of step (6), and the obtained structure was placed into a hot press to perform hot pressing at 60°C, 0.8T, and 20S to obtain a final solid electrolyte film.

[0085] Example 6

[0086] (1) 8 g polyethylene oxide and 2 g polyvinylidene fluoride were dissolved in 100 g N,N-dimethylformamide by stirring with a magnetic stirrer until complete dissolution to obtain a polymer solution;

[0087] (2) 5 g lithium bisfluorosulfonylimide was added to the polymer solution of step (1) and stirring was performed with a magnetic stirrer until complete dissolution;

[0088] (3) 5 g functional agent HNTs were added to 20 g N,N-dimethylformamide, and ultrasonic treatment was performed at room temperature for 2 hours to uniformly disperse the HNTs in the solvent to obtain an HNTs slurry;

[0089] (4) 1 g LATP was added to 10 g N,N-dimethylformamide, and ultrasonic treatment was performed at room temperature for 2 hours to uniformly disperse the LLZO in the solvent to obtain an additive slurry;

[0090] (5) The HNTs slurry of step (3) and the additive slurry of step (4) were respectively poured into the solution of step (2), and stirring was performed by a magnetic stirrer for 6 hours to obtain an electrolyte slurry;

[0091] (6) The electrolyte slurry of step (5) was poured into a polytetrafluoroethylene mold, vacuum drying was performed at a vacuum degree of -0.3 MPa and a temperature of 80°C for 12 hours to obtain a polymer composite solid electrolyte layer.

[0092] (7) The polymer solid electrolyte layer described in step (6) is placed between two aluminum foils, and after hot pressing at 50°C, 0.3T, and 30S in a hot press, a final solid electrolyte film is obtained.

[0093] Example 7

[0094] (1) 8g of polyethylene oxide and 2g of polyvinylidene fluoride are dissolved in 100g of N,N-dimethylformamide by magnetic stirrer until completely dissolved to obtain a polymer solution;

[0095] (2) 3g of lithium tetrafluoroborate is added to the polymer solution described in step (1) and stirred using a magnetic stirrer until completely dissolved;

[0096] (3) 4g of functional agent HNTs is added to 20g of N,N-dimethylformamide, and ultrasonic treatment is carried out at room temperature for 2 hours to uniformly disperse the HNTs in the solvent to obtain an HNTs slurry;

[0097] (4) 2g of nano ZrO2 is added to 10g of acetonitrile, and ultrasonic treatment is carried out at room temperature for 2 hours to uniformly disperse the nano ZrO2 in the solvent to obtain an additive slurry;

[0098] (5) The HNTs slurry described in step (3) and the additive slurry described in step (4) are poured into the solution described in step (2) respectively, and stirred by magnetic stirrer for 6 hours to obtain an electrolyte slurry;

[0099] (6) The electrolyte slurry described in step (5) is poured into a polytetrafluoroethylene mold, vacuum dried at a vacuum degree of -0.3MPa and a temperature of 80°C for 12 hours to obtain a polymer composite solid electrolyte layer.

[0100] (7) The polymer solid electrolyte layer described in step (6) is placed between two aluminum foils, and after hot pressing at 40°C, 0.5T, and 30S in a hot press, a final solid electrolyte film is obtained.

[0101] Example 8

[0102] (1) 10g of polyvinylidene fluoride-hexafluoropropylene is dissolved in 50g of N,N-dimethylformamide by magnetic stirrer until completely dissolved to obtain a polymer solution;

[0103] (2) 4g of lithium difluoro(oxalato)borate is added to the polymer solution described in step (1) and stirred using a magnetic stirrer until completely dissolved;

[0104] (3) 3g of functional agent HNTs is added to 20g of N,N-dimethylformamide, and ultrasonic treatment is carried out at room temperature for 2 hours to uniformly disperse the HNTs in the solvent to obtain an HNTs slurry;

[0105] (4) 1 g of LATP was added into 10 g of acetonitrile, and ultrasonic treatment was performed at room temperature for 2 hours to uniformly disperse the LLZO in the solvent to obtain an additive slurry;

[0106] (5) The HNTs slurry of step (3) and the additive slurry of step (4) were respectively poured into the solution of step (2), and stirring was performed by a magnetic stirrer for 6 hours to obtain an electrolyte slurry;

[0107] (6) The electrolyte slurry of step (5) was poured into a polytetrafluoroethylene mold, vacuum drying was performed at a vacuum degree of -0.3 MPa and a temperature of 80°C for 12 hours to obtain a polymer composite solid electrolyte layer.

[0108] (7) Aluminum foils were placed on both sides of the polymer solid electrolyte layer of step (6), and the obtained structure was placed into a hot press to perform hot pressing at 50°C, 0.2T, and 30S to obtain a final solid electrolyte film.

[0109] Example 9

[0110] (1) 2 g of polyethylene oxide and 8 g of polyvinylidene fluoride were dissolved in 100 g of N,N-dimethylformamide by stirring with a magnetic stirrer until complete dissolution to obtain a polymer solution;

[0111] (2) 3 g of lithium bisfluorosulfonylimide was added to the polymer solution of step (1), and stirring was performed with a magnetic stirrer until complete dissolution;

[0112] (3) 4 g of functional agent HNTs was added into 20 g of N,N-dimethylformamide, and ultrasonic treatment was performed at room temperature for 2 hours to uniformly disperse the HNTs in the solvent to obtain an HNTs slurry;

[0113] (4) 1 g of nano-ZrO2 was added into 10 g of N,N-dimethylformamide, and ultrasonic treatment was performed at room temperature for 2 hours to disperse the nano-ZrO2 in the solvent to obtain an additive slurry;

[0114] (5) The HNTs slurry of step (3) and the additive slurry of step (4) were respectively poured into the solution of step (2), and stirring was performed by a magnetic stirrer for 6 hours to obtain an electrolyte slurry;

[0115] (6) The electrolyte slurry of step (5) was poured into a polytetrafluoroethylene mold, vacuum drying was performed at a vacuum degree of -0.3 MPa and a temperature of 80°C for 12 hours to obtain a polymer composite solid electrolyte layer.

[0116] (7) Aluminum foils were placed on both sides of the polymer solid electrolyte layer of step (6), and the obtained structure was placed into a hot press to perform hot pressing at 40°C, 0.2T, and 30S to obtain a final solid electrolyte film.

[0117] Example 10

[0118] (1) 10 g of polymethyl methacrylate was dissolved in 60 g of acetonitrile by stirring with a magnetic stirrer until completely dissolved to obtain a polymer solution;

[0119] (2) 3 g of lithium difluoro(oxalato)borate was added to the polymer solution of step (1) and stirred with a magnetic stirrer until completely dissolved;

[0120] (3) 2 g of functional agent HNTs was added to 20 g of acetonitrile and ultrasonically treated at room temperature for 2 hours to uniformly disperse the HNTs in the solvent to obtain an HNTs slurry;

[0121] (4) 1 g of LATP and 1 g of nano-Al2O3 were added to 50 g of acetonitrile and ultrasonically treated at room temperature for 2 hours to uniformly disperse the LATP and nano-Al2O3 in the solvent to obtain an additive slurry;

[0122] (5) The HNTs slurry of step (3) and the additive slurry of step (4) were poured into the solution of step (2) and stirred with a magnetic stirrer for 6 hours to obtain an electrolyte slurry;

[0123] (6) The electrolyte slurry of step (5) was poured into a polytetrafluoroethylene mold and vacuum dried at a vacuum degree of -0.3 MPa and a temperature of 60°C for 12 hours to obtain a polymer composite solid electrolyte layer.

[0124] (7) The polymer solid electrolyte layer of step (6) was sandwiched between aluminum foils and placed in a hot press to be hot pressed at 50°C, 0.5T, and 20S to obtain a final solid electrolyte membrane.

[0125] The following are two examples of existing methods for forming a solid electrolyte membrane.

[0126] Comparative Example 1

[0127] (1) 8 g of polyethylene oxide was dissolved in 60 g of acetonitrile by stirring with a magnetic stirrer until completely dissolved to obtain a polymer solution;

[0128] (2) 1 g of lithium trifluoromethanesulfonate was added to the polymer solution of step (1) and stirred with a magnetic stirrer until completely dissolved;

[0129] (3) The slurry of step (2) was poured into a polytetrafluoroethylene mold and vacuum dried at a vacuum degree of -0.3 MPa and a temperature of 60°C for 12 hours to obtain a polymer composite solid electrolyte layer.

[0130] (4) The polymer solid electrolyte layer of step (3) is placed between two aluminum foils, and then is put into a hot press to be hot-pressed at 30°C, 0.1T, and 30S to obtain a final solid electrolyte film.

[0131] Comparative Example 2

[0132] (1) 10 g of polyvinyl carbonate is dissolved in 80 g of ethanol by using a magnetic stirrer until completely dissolved to obtain a polymer solution;

[0133] (2) 2 g of lithium triflate is added to the polymer solution of step (1) and stirred by using a magnetic stirrer until completely dissolved;

[0134] (3) 3 g of nano-ZrO2 is added to 15 g of acetonitrile, and is ultrasonically treated at room temperature for 2 hours to disperse the nano-ZrO2 in the solvent to obtain an additive turbid liquid;

[0135] (4) The additive turbid liquid of step (3) is poured into the solution of step (2) respectively, and is stirred by using a magnetic stirrer for 6 hours to obtain an electrolyte slurry;

[0136] (5) The electrolyte slurry of step (4) is poured into a polytetrafluoroethylene mold, and is vacuum-dried at a vacuum degree of -0.3 MPa and a temperature of 80°C for 12 hours to obtain a polymer composite solid electrolyte layer.

[0137] (6) The polymer solid electrolyte layer of step (5) is placed between two aluminum foils, and then is put into a hot press to be hot-pressed at 50°C, 0.8T, and 30S to obtain a final solid electrolyte film.

[0138] The above-obtained electrolyte sheet is subjected to battery assembly and testing.

[0139] The above-prepared composite polymer solid electrolyte sheet is subjected to SS / CSEs / SS simulation battery test with two stainless steel electrodes (SS). The battery assembly process is carried out in a glove box with a water and oxygen content of less than 0.1 ppm. The electrochemical impedance of the composite polymer solid electrolyte is determined by alternating current impedance spectroscopy (EIS) test in a frequency range of 1 Hz-1 MHz at room temperature. The impedance data obtained by EIS test are used to calculate the ionic conductivity of the prepared composite polymer solid electrolyte.

[0140] The above-prepared composite polymer solid electrolyte film is subjected to coin cell battery test with lithium iron phosphate (LiFePO4) positive electrode and lithium metal negative electrode. The coin cell battery is prepared in a glove box. The coin cell battery is subjected to charge-discharge cycle test at a rate of 0.1C, and the attenuation of the discharge capacity is detected.

[0141]

[0142]

[0143] Table 1

[0144] From the data in Table 1, it can be seen that the electrolyte sheet obtained in Examples 1-10 has a higher ionic conductivity at room temperature compared with Comparative Examples 1 and 2. From the data in Table 1, it can be seen that the button cell assembled in Examples 1-10 has a better cycle performance, and the button cell assembled in Comparative Examples 1 and 2 has a very poor cycle performance.

[0145] Figure 1 is a cycle life curve diagram of the solid-state electrolyte film obtained in Example 1 for a solid-state battery. Figure 1 The cycle life curve diagram of the solid-state electrolyte film obtained in Example 1 for a solid-state battery is shown, and the LiFePO4 specific capacity in Example 1 still remains above 140 mAh / g after more than 100 cycles. It can be seen that the composite polymer solid-state electrolyte film of the present application not only has a higher ionic conductivity at room temperature, but also can improve the cycle performance of the battery when the composite polymer solid-state electrolyte film is applied to the battery.

[0146] Finally, the present application provides a polymer composite solid-state electrolyte film. According to an embodiment of the present application, the polymer solid-state electrolyte film comprises a polymer substrate, a functional agent, an additive and a lithium salt, wherein the functional agent is halloysite multi-walled nanotubes.

[0147] Halloysite multi-walled nanotubes (HNTs, Al2Si2O5(OH)4·nH2O) are a kind of natural, environmentally friendly, low-cost, biocompatible, thermally stable and mechanically good natural clay material, which has a nano-hollow multi-walled tube structure, forms a multi-layer structure by aluminum oxide octahedron and adjacent silicon tetrahedral layer, and has a negative surface in a very wide pH value range. These active points make it possible for halloysite to be widely used. HNTs have unique and excellent properties such as large aspect ratio, high strength, good corrosion resistance, good thermal conductivity and high electrical conductivity. In the present application, HNTs are used as the functional agent of the polymer substrate, which can construct a light skeleton (three-dimensional porous coating) and provide a fast ion transmission channel to improve the ionic conductivity. At the same time, the construction of the inorganic framework also improves the mechanical strength of the polymer solid-state electrolyte layer.

[0148] Although the embodiments of the present application have been shown and described above, it should be understood by those ordinary skilled in the art that the above embodiments are exemplary and cannot be understood as limiting the present application, and those ordinary skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application. Those ordinary skilled in the art should understand that the specific structures and processes shown in the above detailed implementation part are only exemplary and are not limiting. Moreover, those ordinary skilled in the art can combine the various technical features shown above in various possible ways to form new technical solutions, or make other modifications, which all belong to the scope of the present application.

Claims

1. A method for preparing a polymer composite solid electrolyte membrane, characterized by, The method comprises the following steps: Step 1: dispersing a polymer substrate in an organic solvent at a mass ratio of 0.05-0.8, stirring until completely dissolved to obtain a polymer solution; adding a lithium salt to the polymer solution and stirring; Step 2: dispersing HNTs in the organic solvent at a mass ratio of 0.01-0.1, and performing room temperature ultrasonic treatment to obtain an HNTs slurry; Step 3: dispersing an additive in the organic solvent at a mass ratio of 0.01-0.1, and performing room temperature ultrasonic treatment to obtain an additive slurry, the additive being at least one of a solid electrolyte material and a nano-oxide material; Step 4: pouring the HNTs and additive slurries into the solution obtained in Step 1, and stirring to obtain an electrolyte slurry; Step 5: pouring the electrolyte slurry into a polytetrafluoroethylene mold, performing vacuum drying to obtain a polymer composite solid electrolyte layer, placing aluminum foils on both sides of the polymer solid electrolyte layer, and placing in a hot press to obtain a final solid electrolyte film; the polymer substrate in Steps 1-5 is at least one of polyethylene oxide, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polycarbonate, polyacrylonitrile, polymethyl methacrylate, and polyimide; the organic solvent is at least one of ethanol, acetonitrile, N,N-dimethylformamide, tetrahydrofuran, butanedinitrile, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methyl pyrrolidone; and the lithium salt is at least one of lithium hexafluorophosphate, lithium bis-trifluoromethylsulfonylimide, lithium tetrafluoroborate, lithium bis-oxalato-borate, lithium bis-fluorosulfonylimide, lithium difluoro-oxalato-borate, and lithium trifluoromethanesulfonate. The solid-state electrolyte material is lithium lanthanum zirconium oxygen and lithium titanium aluminum phosphate, the particle size of the solid-state electrolyte material is 300 nm or less, the nano-oxide material includes one or more than two combinations of nano-SiO2, nano-Al2O3, nano-TiO2, nano-ZrO2, and nano-ZnO, and the mass percentage of the polymer substrate, functional agent HNTs, additives, and lithium salt is (10-85):(5-20):(5-50):(5-50), and the hot pressing temperature of the fifth step is 30-60 o C, the pressure is 0.1T-1T, the hot pressing time is 10-30S, and the thickness of the polymer solid-state electrolyte film is 10-100 microns.

2. A polymer composite solid-state electrolyte membrane, characterized by: The polymer composite solid electrolyte film is formed using the preparation method of claim 1.

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