Method for preparing and use of a multilayer composite solid electrolyte membrane

Abstract

The application discloses a preparation method and application of a multilayer composite solid electrolyte membrane. A high-valence metal atom doped rare earth metal oxide rich in oxygen vacancies is prepared by using electrostatic spinning and high-temperature heat treatment technology as inorganic filler of the composite solid electrolyte; and then the inorganic filler is dispersed into a solvent together with a lithium salt and a polymer matrix to obtain different electrostatic spinning precursor solutions, and the multilayer composite solid electrolyte nanofiber membrane is spun on a receiver in sequence. The multilayer composite solid electrolyte nanofiber membrane prepared by the application has good compatibility with lithium metal, can be matched with high-voltage positive electrode materials, improves the energy density of lithium batteries and widens the electrochemical window, and meanwhile, the ultrathin interface modification layer can effectively avoid problems such as increase of the volume, weight and total resistance of the battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of new energy battery materials, and relates to a lithium battery solid electrolyte, in particular to a multilayer composite solid electrolyte film, a preparation method thereof and application thereof in preparation of a solid-state lithium battery. BACKGROUND

[0002] Due to the high theoretical specific capacity (3860mAh·g -1 ) and low potential (-3.04V) of lithium metal, lithium metal batteries are considered to be a potential technology in the future of smart grids, electric vehicles and other fields. However, the commercial lithium metal battery uses flammable and electrochemically unstable organic electrolyte, and has a series of safety problems. For example, the electrolyte is prone to cause thermal runaway during the use of the battery, especially in the case of overcharge or short circuit, which may cause the battery to catch fire or explode.

[0003] At present, the development of solid-state electrolyte without liquid flow, non-flammable and explosive, good flexibility and good processability is considered to be a better solution to eliminate the safety hazards of organic liquid electrolyte. At the same time, the solid-state electrolyte can effectively inhibit the growth of lithium dendrites, thereby avoiding the side reactions caused by the lithium dendrites piercing the separator. However, the solid-state electrolyte is limited in the application in lithium metal batteries due to its low room temperature ionic conductivity, poor mechanical strength, poor thermal stability, poor interface contact with the positive and negative electrodes and poor compatibility. In view of this series of problems, researchers have proposed solutions from different angles, such as adding plasticizers, nano fillers, block copolymers and the like in the polymer electrolyte. However, the above methods cannot meet the characteristics of the ideal high-performance solid-state electrolyte. A single polymer structure usually does not have a wide enough energy band gap to withstand the reduction of the lithium metal negative electrode and the oxidation of the high-voltage positive electrode. Designing a multilayer structure composite electrolyte is an effective strategy to solve this problem. SUMMARY

[0004] The application provides a preparation method and application of a multilayer composite solid electrolyte film. The technical scheme adopted is as follows: first, a high-valence metal atom doped rare earth metal oxide rich in oxygen vacancies is prepared by using electrospinning and high-temperature heat treatment technology as an inorganic filler of the composite solid electrolyte; then the lithium salt and the polymer matrix are dispersed in the solvent to obtain different electrospinning precursor solutions, and the multilayer composite solid electrolyte nanofiber film is spun on the receiver in sequence. The multilayer composite solid electrolyte nanofiber film has good compatibility with lithium metal and can match high-voltage positive electrode materials, thereby improving the energy density of the lithium battery and widening the electrochemical window. Meanwhile, the ultra-thin interface modification layer can effectively avoid the problems of increased volume, weight and total resistance of the battery.

[0005] In order to achieve the above object, the technical scheme adopted by the present application is as follows:

[0006] In the first aspect of the present application, a preparation method of a multilayer composite solid electrolyte membrane is provided, comprising the following steps:

[0007] (1) Preparation of inorganic filler

[0008] The high-valence metal salt, the rare earth metal salt and the low-decomposition-temperature polymer are mixed and dissolved in the solvent A according to a certain mass ratio to obtain a spinning precursor solution B, and the precursor fiber membrane layer is obtained by electrospinning.

[0009] The high-valence metal salt is selected from any one of gadolinium nitrate, ytterbium nitrate and yttrium acetate;

[0010] The rare earth metal salt is selected from one of lanthanum chloride and cerium nitrate hexahydrate;

[0011] The low-decomposition-temperature polymer is selected from one of polyvinylpyrrolidone, polymethyl methacrylate and polystyrene;

[0012] The mass ratio of the high-valence metal salt to the rare earth metal salt is 1:1-20, the mass ratio of the total mass of the metal salt to the low-decomposition-temperature polymer is 1:1-4, and the concentration of the low-decomposition-temperature polymer is 8wt-15wt%.

[0013] The solvent A is selected from one of dimethyl sulfoxide, N,N-dimethylacetamide and N,N-dimethylformamide;

[0014] The electrospinning conditions are as follows: voltage 12-20kV, humidity 10-30%, distance from the spinning needle to the receiver 8-24cm;

[0015] During calcination, the precursor fiber membrane layer is placed in a tube furnace, heated at a rate of 5℃ per minute in an air atmosphere, and annealed after calcination at a temperature of 200-500℃ for 2-3 hours.

[0016] (2) Preparation of multilayer composite solid electrolyte fiber membrane

[0017] 2-1 Preparation of spinning precursor solution

[0018] The lithium salt and the inorganic filler prepared in step (1) are dissolved in the organic solvent C, and then the fluorine-containing polymer is dissolved therein to obtain a spinning precursor solution D; the lithium salt and the inorganic filler prepared in step (1) are dissolved in the organic solvent E, and then the polar polymer is dissolved therein to obtain a spinning precursor solution F.

[0019] The fluorine-containing polymer content in the spinning precursor solution D is 6wt%-12wt%, the mass ratio of lithium salt to fluorine-containing polymer is 1:1-5, and the mass ratio of inorganic filler to lithium salt is 1:1-5;

[0020] The polar polymer content in the spinning precursor solution F is 3wt%-7wt%, the mass ratio of lithium salt to polar polymer is 1:1-5, and the mass ratio of inorganic filler to lithium salt is 1:1-5.

[0021] The lithium salt is selected from any one or a combination of lithium trifluoromethanesulfonate, lithium nitrate, lithium hexafluorophosphate, and lithium borohydride;

[0022] The organic solvent C is selected from any one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone;

[0023] The fluorine-containing polymer is selected from any one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and fluorine rubber;

[0024] The organic solvent E is selected from any one of acetonitrile, N,N-dimethylformamide, and dimethyl sulfoxide;

[0025] The polar polymer is selected from one of polyethylene oxide, polyacrylonitrile, and polyimide.

[0026] 2-2 Three-layer composite solid electrolyte fiber membrane spinning

[0027] A fluorine-containing composite solid electrolyte interface modified fiber membrane layer (membrane layer thickness controlled at 5 microns-20 microns) is obtained by electrospinning with the spinning precursor solution D as raw material and the peelable paper as receiver; then, a double-layer composite solid electrolyte fiber membrane layer (thickness of 80-150 microns) in a "Janus" structure is obtained by electrospinning of the spinning precursor solution F on the fluorine-containing composite solid electrolyte interface modified fiber membrane layer as receiver; finally, a three-layer "sandwich" structure composite solid electrolyte fiber membrane is obtained by electrospinning of the spinning precursor solution D on the double-layer composite solid electrolyte fiber membrane layer as receiver (thickness also 5 microns-20 microns). After removing the peelable paper, the multi-layer composite solid electrolyte fiber membrane is obtained after vacuum drying at 60°C for 2-5h.

[0028] The electrospinning conditions are: voltage 12-20kV, humidity 10%-30%, distance from spinning needle to receiver 8-24cm.

[0029] In a second aspect, the application provides a multilayer composite solid-state electrolyte membrane prepared by the method described above. In the detailed description section, the ion conductivity and specific capacity retention of different layer numbers of composite solid-state electrolyte membranes constructed by different types of high-valence metal atom-doped rare earth metal oxide inorganic fillers were tested, and the results showed that the short rod-shaped one-dimensional nanofiber inorganic filler prepared by the method of the application could effectively accelerate the transmission rate of lithium ions, and the electrospinning technology enhanced the mechanical strength and chemical stability of the multilayer composite solid-state electrolyte membrane, and had a higher specific capacity retention in the charge and discharge cycle, greatly prolonging the cycle life of the lithium metal battery.

[0030] In a third aspect, the application provides the use of the multilayer composite solid-state electrolyte membrane in the preparation of a solid-state lithium ion battery.

[0031] In a fourth aspect, the application provides a solid-state lithium ion battery, wherein the electrolyte is the multilayer composite solid-state electrolyte membrane described above.

[0032] The beneficial technical effects of the application are as follows:

[0033] (1) The high-valence metal atom-doped rare earth metal oxide inorganic filler prepared by electrospinning and high-temperature heat treatment technology can reduce the crystallinity of the polymer, provide more transmission channels for lithium ions, and promote the dissociation of lithium salt through Lewis acid-base interaction between the rich oxygen vacancies and the lithium salt, thereby increasing the number of free Li ions and significantly improving the ion conductivity. At the same time, the one-dimensional short rod-shaped nanofiber can form a Li ion transmission seepage network to provide a high-speed channel for Li ion transmission.

[0034] (2) The multilayer structure composite solid-state polymer electrolyte prepared by the application has a stable electrochemical performance of the fluorine-containing composite electrolyte interface modification layer, which can form a positive electrode electrolyte interface CEI in contact with the positive electrode, effectively enhance the oxidation resistance of the composite solid-state electrolyte, and broaden the electrochemical window, perfectly match the high-voltage positive electrode material on the market, significantly improve the energy density of the solid-state battery, and meet the actual application requirements. It can also form a negative electrode electrolyte interface SEI in contact with the negative electrode, and the excellent mechanical strength of the fluorine-containing polymer can effectively inhibit the lithium dendrite from piercing the electrolyte to cause battery short circuit and other safety problems, reduce the concentration difference polarization and reaction byproducts in the battery system, prevent uneven deposition of metal lithium, and thus ensure the cycle stability of the solid-state battery.

[0035] (3) The strategy of preparing a multilayer composite solid electrolyte by electrospinning proposed in the application not only can construct a three-dimensional skeleton structure with precise control of porosity, form a continuous ion transmission channel, and improve the ionic conductivity of the electrolyte, but also is easy to regulate the thickness of the multilayer structure of the composite nanofiber membrane electrolyte, so that the multilayer structure has excellent interface compatibility, reduces the interface resistance, and enhances the interface stability. The preparation process is greatly simplified, the production efficiency is improved, and more effective solutions and innovative technologies are provided for reasonably designing and preparing a multilayer composite solid electrolyte which can simultaneously stabilize and be compatible with a high-voltage positive electrode and a lithium metal negative electrode.

[0036] The project relied on by the application is as follows: project type: Shanghai Municipal Science and Technology Commission, basic research special zone plan; project number: 22T01400100-18; project name: design, preparation and application of key materials for solid-state batteries. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A flowchart of the preparation method of the multilayer composite solid electrolyte in the application is shown;

[0038] Figure 2 A field emission scanning electron microscope photo of the high-valence metal atom doped rare earth metal oxide inorganic filler constructed in Example 1 is shown;

[0039] Figure 3 The ionic conductivity of the multilayer composite solid electrolyte constructed in Example 1 at different temperatures is shown;

[0040] Figure 4 The capacity and coulombic efficiency of the multilayer composite solid electrolyte constructed in Example 1 in the charge and discharge cycle process of the lithium metal battery are shown. DETAILED DESCRIPTION

[0041] In order to more clearly illustrate the application, the application will be further described below in conjunction with preferred embodiments. Those skilled in the art should understand that the specific description below is illustrative rather than limiting, and should not limit the protection scope of the application.

[0042] Figure 1 The preparation process of the multilayer composite solid electrolyte film of the application is shown, which mainly includes two processes: (1) synthesis of high-valence metal atom doped rare earth metal oxide inorganic filler rich in oxygen vacancies; and (2) preparation of a “sandwich” type multilayer structure formed by fluorine-containing polymer interface modified composite solid electrolyte, polar polymer composite solid electrolyte and fluorine-containing polymer interface modified composite solid electrolyte.

[0043] The application explores inorganic fillers of different raw material types and the multilayer composite solid electrolyte films constructed therefrom, and specific reference is made to the following Examples 1 to 6.

[0044] Example 1

[0045] The preparation method of the multilayer composite solid electrolyte of the present embodiment is specifically as follows:

[0046] (1) Using electrospinning and high-temperature heat treatment technology to prepare high-valence metal atom-doped rare earth metal oxide rich in oxygen vacancies as inorganic filler of the composite solid electrolyte

[0047] a. Dissolve ytterbium nitrate, cerium nitrate hexahydrate and polyvinylpyrrolidone in N,N-dimethylformamide according to a certain mass ratio to obtain a spinning precursor solution B. The mass ratio of ytterbium nitrate to cerium nitrate hexahydrate is controlled to be 1:4, and the mass ratio of the total mass of ytterbium nitrate and cerium nitrate hexahydrate to the mass of polyvinylpyrrolidone is 1:1.25, and the content of polyvinylpyrrolidone is 12wt%;

[0048] b. Using the spinning precursor solution B, an aluminum foil as the receiver, and spinning through the electrospinning machine to obtain a precursor fiber membrane layer, and the thickness of the membrane layer is controlled to be 200 microns. The electrospinning conditions are as follows: the voltage is 18kV, the humidity is 10%, and the distance from the spinning needle to the receiver is 20cm;

[0049] c. Place the precursor fiber membrane layer in a tube furnace, heat it to 250℃ at a rate of 5℃ per minute, and then heat it to 400℃ at a rate of 5℃ per minute for 3 hours to obtain ytterbium-doped cerium oxide inorganic filler.

[0050] Characterized by field emission scanning electron microscopy, as shown in Figure 2 , it can be seen that the inorganic filler is a short rod-shaped one-dimensional hollow nanotube. This hollow structure has a large specific surface area, and its surface is rich in oxygen vacancies and positively charged active sites, which promotes the dissociation of lithium salt through Lewis acid-base interaction, thereby generating more lithium ions. At the same time, the one-dimensional nanotube can form a lithium ion transmission seepage network, providing a high-speed channel for the transmission of lithium ions, significantly improving the conductivity of the composite electrolyte.

[0051] (2) Using electrospinning to spin the composite solid electrolyte nanofiber membrane with a multilayer structure layer by layer

[0052] a. Dissolve lithium trifluoromethanesulfonate and ytterbium-doped cerium oxide inorganic filler into N,N-dimethylformamide, and then dissolve fluoro rubber into the above solution to obtain a spinning precursor solution D. The content of fluoro rubber is controlled to be 8wt%, the mass ratio of lithium trifluoromethanesulfonate to fluoro rubber is 1:2, and the mass ratio of ytterbium-doped cerium oxide inorganic filler to lithium trifluoromethanesulfonate is 1:2;

[0053] b. Lithium trifluoromethanesulfonate and ytterbium-doped cerium oxide inorganic filler are dissolved in acetonitrile, and then polyethylene oxide is dissolved in the above solution to obtain spinning precursor solution F. The polyethylene oxide content is controlled at 5 wt%, the mass ratio of lithium trifluoromethanesulfonate to polyethylene oxide is 1:2, and the mass ratio of ytterbium-doped cerium oxide to lithium trifluoromethanesulfonate is 1:2.

[0054] c. Using a spinning precursor solution D and an oil-film paper as the receiver, an electrospinning process is employed to obtain a fluororubber composite solid electrolyte interface-modified fiber membrane with a thickness controlled at 10 micrometers. Then, using the fluororubber composite solid electrolyte interface-modified fiber membrane as the receiver, a spinning precursor solution F is electrospinned to cover the interface-modified precursor fiber membrane. Finally, a spinning precursor solution D is electrospinned to cover the surface of the solid electrolyte precursor fiber membrane, resulting in a "sandwich" structure composite solid electrolyte fiber membrane with a thickness controlled at 110 micrometers. After removing the oil-film paper, the membrane is dried in a vacuum drying oven at 60°C for 4 hours to remove residual solvent, yielding a three-layer composite solid electrolyte. The electrospinning conditions were: voltage 17kV, humidity 10%, and distance from the spinning needle to the receiver 18cm.

[0055] The composite solid electrolyte nanofiber membrane constructed in this embodiment was used to build a lithium metal battery, and the battery was subjected to conductivity tests and charge-discharge cycle tests at different temperatures. The results are as follows: Figure 3 As shown, the conductivity of the multilayer composite solid electrolyte can reach 1.12 × 10⁻⁶ at 30 °C. -4 S / cm. Additionally, according to Figure 4 The results show that the multilayer composite solid-state lithium metal battery achieves a charge-discharge specific capacity of 135 mAh / g at a high current density of 2C, and retains approximately 99.6% of its capacity after 50 cycles. This indicates that the construction scheme in this embodiment effectively enhances the interfacial stability and cycle stability between the electrode and the electrolyte, enabling the device to operate efficiently and stably even at high current densities, exhibiting excellent electrochemical performance.

[0056] Example 2

[0057] The preparation method of the multilayer composite solid electrolyte in this embodiment includes the following steps:

[0058] (1) Using electrospinning and high-temperature heat treatment techniques, high-valence metal atom-doped rare earth metal oxides rich in oxygen vacancies were prepared as inorganic fillers for composite solid electrolytes.

[0059] a. Gadolinium nitrate, cerium nitrate hexahydrate and polymethyl methacrylate are dissolved and mixed in N,N-dimethylacetamide according to a certain mass ratio to obtain a spinning precursor solution B, the mass ratio of gadolinium nitrate to cerium nitrate hexahydrate is controlled to be 1:10, the mass ratio of the total mass of gadolinium nitrate and cerium nitrate hexahydrate to the mass of polymethyl methacrylate is 1:2, and the content of polymethyl methacrylate is 10wt%;

[0060] b. The spinning precursor solution B is used to spin by an electrostatic spinning machine with aluminum foil as a receiver to obtain a precursor fiber membrane layer, and the thickness of the membrane layer is controlled to be 200 microns. The electrostatic spinning conditions are as follows: the voltage is 16kV, the humidity is 10%, and the distance from the spinning needle to the receiver is 18cm;

[0061] c. The precursor fiber membrane layer is placed in a tube furnace, and the temperature is raised to 300℃ at a rate of 5℃ per minute, and then annealed by constant temperature calcination for 2 hours, and then the temperature is raised to 400℃ at a rate of 5℃ per minute, and then annealed by constant temperature calcination for 3 hours to obtain gadolinium-doped cerium oxide inorganic filler.

[0062] (2) Using electrostatic spinning to spin a multi-layer structure of composite solid electrolyte nanofiber membrane layer by layer

[0063] a. Lithium trifluoromethanesulfonate and gadolinium-doped cerium oxide inorganic filler are dissolved into N,N-dimethylformamide, and then polyvinylidene fluoride is dissolved into the above solution to obtain a spinning precursor solution D, the content of polyvinylidene fluoride is controlled to be 10wt%, the mass ratio of lithium trifluoromethanesulfonate to polyvinylidene fluoride is 1:3, and the mass ratio of gadolinium-doped cerium oxide inorganic filler to lithium trifluoromethanesulfonate is 1:3;

[0064] b. Lithium trifluoromethanesulfonate and gadolinium-doped cerium oxide inorganic filler are dissolved into acetonitrile, and then polyethylene oxide is dissolved into the above solution to obtain a spinning precursor solution F, the content of polyethylene oxide is controlled to be 5wt%, the mass ratio of lithium trifluoromethanesulfonate to polyethylene oxide is 1:3, and the mass ratio of gadolinium-doped cerium oxide to lithium trifluoromethanesulfonate is 1:3;

[0065] c. The spinning precursor solution D is used to spin by an electrostatic spinning machine with an oil film paper as a receiver to obtain a polyvinylidene fluoride composite solid electrolyte interface modification fiber membrane layer, and the thickness of the membrane layer is controlled to be 15 microns; then, the polyvinylidene fluoride composite solid electrolyte interface modification fiber membrane layer is used as a receiver, and the spinning precursor solution F is used to cover the interface modification precursor fiber membrane layer by electrostatic spinning to obtain a composite solid electrolyte fiber membrane layer with an asymmetric "Janus" structure, and the thickness is controlled to be 100 microns. After removing the oil film paper, it is placed in a vacuum drying box for drying at 60℃ for 3h to remove the residual solvent to obtain a double-layer composite solid electrolyte, and the electrostatic spinning conditions are as follows: the voltage is 18kV, the humidity is 10%, and the distance from the spinning needle to the receiver is 20cm.

[0066] Example 3

[0067] The preparation method of the multi-layer composite solid electrolyte provided by the embodiment comprises the following steps:

[0068] (1) Using electrospinning and high-temperature heat treatment technology to prepare high-valence metal atom doped rare earth metal oxide rich in oxygen vacancies as inorganic filler of the composite solid electrolyte

[0069] a. Dissolve yttrium acetate, lanthanum chloride and polyvinylpyrrolidone in N,N-dimethylformamide according to a certain mass ratio to obtain a spinning precursor solution B, control the mass ratio of yttrium acetate to lanthanum chloride to be 1:6, and the mass ratio of the total mass of yttrium acetate and lanthanum chloride to the mass of polyvinylpyrrolidone to be 1:2.5, and the content of polyvinylpyrrolidone is 8wt%;

[0070] b. Using the spinning precursor solution B, taking aluminum foil as the receiver, spinning through the electrospinning machine to obtain a precursor fiber membrane layer; the thickness of the membrane layer is controlled to be 250 microns, and the above electrospinning conditions are: voltage is 18kV, humidity is 10%, the distance from the spinning needle to the receiver is 23cm;

[0071] c. Place the precursor fiber membrane layer in a tube furnace, heat to 250℃ at a rate of 5℃ per minute, and then heat to 400℃ at a rate of 5℃ per minute for 3 hours to obtain yttrium-doped lanthanum oxide inorganic filler.

[0072] (2) Using electrospinning to spin the multi-layer structure of the composite solid electrolyte nanofiber membrane layer by layer

[0073] a. Dissolve lithium nitrate and yttrium-doped lanthanum oxide inorganic filler into N-methylpyrrolidone, and then dissolve polyvinylidene fluoride into the above solution to obtain a spinning precursor solution D, control the content of polyvinylidene fluoride to be 12wt%, the mass ratio of lithium nitrate to polyvinylidene fluoride to be 1:2.5, and the mass ratio of yttrium-doped lanthanum oxide inorganic filler to lithium nitrate to be 1:2.5;

[0074] b. Dissolve lithium nitrate and yttrium-doped lanthanum oxide inorganic filler into N,N-dimethylformamide, and then dissolve polyacrylonitrile into the above solution to obtain a spinning precursor solution F, control the content of polyacrylonitrile to be 6wt%, the mass ratio of lithium nitrate to polyacrylonitrile to be 1:2.5, and the mass ratio of yttrium-doped lanthanum oxide to lithium nitrate to be 1:2.5;

[0075] c. Using the spinning precursor solution D, an oil film paper is used as the receiver, and a polyvinylidene fluoride composite solid electrolyte interface modified fiber membrane layer is spun by an electrostatic spinning machine, the thickness of the membrane layer is controlled at 8 microns; then, using the polyvinylidene fluoride composite solid electrolyte interface modified fiber membrane layer as the receiver, the interface modified precursor fiber membrane layer is covered by electrostatic spinning using the spinning precursor solution F, and finally, the solid electrolyte precursor fiber membrane layer is covered by electrostatic spinning using the spinning precursor solution D on the surface of the solid electrolyte precursor fiber membrane layer, a "sandwich" structure of the composite solid electrolyte fiber membrane is obtained, and the thickness is controlled at 100 microns. After removing the oil film paper, it is placed in a vacuum drying oven at 60°C for 4h to remove the residual solvent, and a three-layer composite solid electrolyte is obtained. The above electrospinning conditions: voltage is 16kV, humidity is 20%, the distance between the spinning needle and the receiver is 19cm.

[0076] Example 4

[0077] The preparation method of the multi-layer composite solid electrolyte provided by the embodiment includes the following steps:

[0078] (1) Using electrospinning and high-temperature heat treatment technology to prepare high-valence metal atom doped rare earth metal oxide rich in oxygen vacancies as inorganic filler of composite solid electrolyte

[0079] a. Ytterbium nitrate, lanthanum chloride and polystyrene are dissolved and mixed in dimethyl sulfoxide according to a certain mass ratio to obtain a spinning precursor solution B, the mass ratio of ytterbium nitrate to lanthanum chloride is controlled at 1:15, the mass ratio of the total mass of ytterbium nitrate and lanthanum chloride to the mass of polystyrene is 1:4, and the content of polystyrene is 8wt%;

[0080] b. Using the spinning precursor solution B, an aluminum foil is used as the receiver, and a precursor fiber membrane layer is spun by an electrostatic spinning machine; the thickness of the membrane layer is controlled at 300 microns, and the above electrospinning conditions: voltage is 16kV, humidity is 10%, the distance between the spinning needle and the receiver is 22cm;

[0081] c. The precursor fiber membrane layer is placed in a tube furnace, heated to 300℃ at a rate of 5℃ per minute in an air atmosphere, and then annealed after calcination for 3 hours to obtain ytterbium doped lanthanum oxide inorganic filler.

[0082] (2) Using electrospinning to spin a multi-layer structure of composite solid electrolyte nanofiber membrane layer by layer

[0083] a. Lithium hexafluorophosphate and ytterbium doped lanthanum oxide inorganic filler are dissolved into N,N-dimethylacetamide, and then fluoro rubber is dissolved into the above solution to obtain a spinning precursor solution D, the content of fluoro rubber is controlled at 11wt%, the mass ratio of lithium hexafluorophosphate to fluoro rubber is 1:1.5, and the mass ratio of ytterbium doped lanthanum oxide inorganic filler to lithium hexafluorophosphate is 1:1.5;

[0084] b. Dissolve lithium hexafluorophosphate and ytterbium-doped lanthanum oxide inorganic filler into dimethyl sulfoxide, and then dissolve polyacrylonitrile into the above solution to obtain a spinning precursor solution F, the content of polyacrylonitrile is controlled to be 6wt%, the mass ratio of lithium hexafluorophosphate to polyacrylonitrile is 1:1.5, and the mass ratio of ytterbium-doped lanthanum oxide to lithium hexafluorophosphate is 1:1.5;

[0085] c. The spinning precursor solution D is used to spin by an electrospinning machine with an oil film paper as a receiver to obtain a fluororubber composite solid electrolyte interface modified fiber membrane layer, the thickness of the membrane layer is controlled to be 5 microns; then, the fluororubber composite solid electrolyte interface modified fiber membrane layer is used as a receiver, and the spinning precursor solution F is used to cover the interface modified precursor fiber membrane layer by electrospinning to obtain a composite solid electrolyte fiber membrane layer with an asymmetric "Janus" structure, the thickness is controlled to be 80 microns. After removing the oil film paper, the double-layer composite solid electrolyte is placed in a vacuum drying box for drying at 60°C for 2 hours to remove residual solvents, and the above electrospinning conditions are as follows: the voltage is 19kV, the humidity is 10%, and the distance between the spinning needle and the receiver is 18cm.

[0086] Example 5

[0087] The preparation method of the multi-layer composite solid electrolyte provided in the embodiment includes the following steps:

[0088] (1) A yttrium-doped cerium oxide inorganic filler rich in oxygen vacancies is prepared by electrospinning and high-temperature heat treatment technology as a composite solid electrolyte

[0089] a. Yttrium acetate, cerium nitrate hexahydrate and polystyrene are dissolved and mixed in N,N-dimethylacetamide according to a certain mass ratio to obtain a spinning precursor solution B, the mass ratio of yttrium acetate to cerium nitrate hexahydrate is controlled to be 1:8, the mass ratio of the total mass of yttrium acetate and cerium nitrate hexahydrate to the mass of polystyrene is 1:3, and the content of polystyrene is 14wt%;

[0090] b. The spinning precursor solution B is used to spin by an electrospinning machine with an aluminum foil as a receiver to obtain a precursor fiber membrane layer, the thickness of the membrane layer is controlled to be 300 microns. The electrospinning conditions are as follows: the voltage is 17kV, the humidity is 20%, and the distance between the spinning needle and the receiver is 20cm;

[0091] c. The precursor fiber membrane layer is placed in a tube furnace, and the temperature is raised to 300°C at a rate of 5°C per minute under an air atmosphere, and then annealed after constant temperature calcination for 2 hours to obtain a yttrium-doped cerium oxide inorganic filler.

[0092] (2) A multi-layer composite solid electrolyte nanofiber membrane is spun by electrospinning layer by layer

[0093] a. Dissolve lithium borohydride and yttrium-doped ceria inorganic filler into N-methylpyrrolidone, and then dissolve polyvinylidene hexafluoropropylene into the above solution to obtain a spinning precursor solution D, with the content of polyvinylidene hexafluoropropylene controlled at 10 wt%, the mass ratio of lithium borohydride to polyvinylidene hexafluoropropylene controlled at 1:3, and the mass ratio of yttrium-doped ceria inorganic filler to lithium borohydride controlled at 1:3;

[0094] b. Dissolve lithium borohydride and yttrium-doped ceria inorganic filler into dimethyl sulfoxide, and then dissolve polyimide into the above solution to obtain a spinning precursor solution F, with the content of polyimide controlled at 4 wt%, the mass ratio of lithium borohydride to polyimide controlled at 1:3, and the mass ratio of yttrium-doped ceria to lithium borohydride controlled at 1:3;

[0095] c. Using the spinning precursor solution D, an oil film paper as a receiver, and an electrostatic spinning machine, polyvinylidene hexafluoropropylene composite solid electrolyte interface modified fiber membrane layers are spun, with the thickness of the membrane layers controlled at 20 microns; then, using the polyvinylidene hexafluoropropylene composite solid electrolyte interface modified fiber membrane layers as a receiver, a spinning precursor solution F is used to spin an interface modified precursor fiber membrane layer to cover the interface modified precursor fiber membrane layer, to obtain a double-layer Janus composite solid electrolyte fiber membrane layer with a double-layer structure, with the thickness controlled at 130 microns. After the oil film paper is removed, the double-layer composite solid electrolyte is placed in a vacuum drying box and dried at 60°C for 4 hours to remove residual solvents, to obtain a double-layer composite solid electrolyte. The electrostatic spinning conditions are as follows: a voltage of 17.5 kV, a humidity of 10%, and a distance between the spinning needle and the receiver of 21 cm.

[0096] Example 6

[0097] The preparation method of the multi-layer composite solid electrolyte in this example includes the following steps:

[0098] (1) Using electrostatic spinning and high-temperature heat treatment technology, a high-valence metal atom-doped rare earth metal oxide rich in oxygen vacancies is prepared as an inorganic filler of a composite solid electrolyte

[0099] a. Dissolve gadolinium nitrate, lanthanum chloride, and polyvinylpyrrolidone in N,N-dimethylformamide according to a certain mass ratio to obtain a spinning precursor solution B, with the mass ratio of gadolinium nitrate to lanthanum chloride controlled at 1:15, the mass ratio of the total mass of yttrium acetate and lanthanum chloride to the mass of polyvinylpyrrolidone controlled at 1:3, and the content of polyvinylpyrrolidone controlled at 12 wt%;

[0100] b. Using the spinning precursor solution B, an aluminum foil as a receiver, and an electrostatic spinning machine, a precursor fiber membrane layer is spun, with the thickness of the membrane layer controlled at 300 microns. The electrostatic spinning conditions are as follows: a voltage of 17 kV, a humidity of 10%, and a distance between the spinning needle and the receiver of 22 cm.

[0101] c. The precursor fiber membrane layer is placed in a tube furnace, and annealed at 250°C for 2 hours and then at 400°C for 3 hours at a rate of 5°C per minute in an air atmosphere, to obtain gadolinium-doped lanthanum oxide inorganic filler.

[0102] (2) Using electrospinning to spin a multi-layer structure of composite solid electrolyte nanofiber membrane layer by layer

[0103] a. Dissolve lithium nitrate and gadolinium-doped lanthanum oxide inorganic filler into N-methyl pyrrolidone, and then dissolve polyvinylidene hexafluoropropylene into the above solution to obtain spinning precursor solution D, with the content of polyvinylidene hexafluoropropylene controlled at 9wt%, the mass ratio of lithium nitrate to polyvinylidene hexafluoropropylene at 1:2, and the mass ratio of gadolinium-doped lanthanum oxide inorganic filler to lithium nitrate at 1:1.5;

[0104] b. Dissolve lithium nitrate and gadolinium-doped lanthanum oxide inorganic filler into acetonitrile, and then dissolve polyethylene oxide into the above solution to obtain spinning precursor solution F, with the content of polyethylene oxide controlled at 5wt%, the mass ratio of lithium nitrate to polyethylene oxide at 1:2, and the mass ratio of yttrium-doped lanthanum oxide to lithium nitrate at 1:1.5;

[0105] c. Using spinning precursor solution D, an oil film paper is used as the receiver, and electrospinning is performed to obtain a polyvinylidene hexafluoropropylene composite solid electrolyte interface modification fiber membrane layer, with the membrane layer thickness controlled at 10 microns; then, using the polyvinylidene hexafluoropropylene composite solid electrolyte interface modification fiber membrane layer as the receiver, electrospinning is performed using spinning precursor solution F to cover the interface modification precursor fiber membrane layer, and finally, electrospinning is performed using spinning precursor solution D on the surface of the solid electrolyte precursor fiber membrane layer to cover the solid electrolyte precursor fiber membrane layer, to obtain a “sandwich” structure of composite solid electrolyte fiber membrane, with the thickness controlled at 120 microns. After removing the oil film paper, it is placed in a vacuum drying oven at 60°C for 4h to remove residual solvents, to obtain a three-layer composite solid electrolyte. The above electrospinning conditions are: voltage of 18.5kV, humidity of 20%, and distance between the spinning needle and the receiver of 18cm.

[0106] Comparative Example 1

[0107] Using the raw materials of Example 1, a single-layer composite solid electrolyte is prepared using a casting method, including the following steps:

[0108] (1) Using a glass plate casting method and high-temperature heat treatment technology to prepare high-valence metal atom-doped rare earth metal oxides rich in oxygen vacancies as inorganic fillers for composite solid electrolytes

[0109] a. The same as Example 1, to obtain casting solution B;

[0110] b. Casting the casting solution B on a flat glass plate to form a film, vacuum drying for 24h, and obtaining a precursor film layer after the solvent is completely evaporated, with the thickness controlled to be 200 microns.

[0111] c. The same as in Example 1, to obtain the inorganic filler;

[0112] (2) Preparation of the composite solid-state electrolyte by using the glass plate casting method

[0113] a. Dissolving lithium trifluoromethanesulfonate and the inorganic filler prepared in (1) into acetonitrile, and then dissolving polyethylene oxide into the above solution to obtain a casting solution F, with the polyethylene oxide content controlled to be 5wt%, the mass ratio of lithium trifluoromethanesulfonate to polyethylene oxide being 1:2, and the mass ratio of the inorganic filler to lithium trifluoromethanesulfonate being 1:2;

[0114] b. Casting the casting solution F on a flat glass plate to form a film, vacuum drying at 60℃ for 12h, and obtaining a composite solid-state electrolyte film layer after the solvent is completely evaporated, with the thickness controlled to be 100 microns.

[0115] In addition, the composite solid-state lithium metal batteries constructed in Examples 1-6 and Comparative Example 1 were subjected to electrochemical performance tests under dynamic and static conditions, and the specific test results are shown in Table 1:

[0116] Table 1 Test results of the integrated composite solid-state lithium metal batteries constructed in Examples 1-6 and Comparative Example 1

[0117]

[0118] Comparing the data shown in Table 1, the fiber membrane spun by the ytterbium-doped cerium oxide inorganic filler and the fluororubber interface modification layer system exhibits higher ionic conductivity and cycle stability. Compared with Comparative Example 1, the short rod-shaped one-dimensional nanofiber inorganic filler spun by electrospinning can effectively accelerate the transmission rate of lithium ions, and the electrospinning technology enhances the mechanical strength and chemical stability of the multilayer composite solid-state electrolyte film, has a higher specific capacity retention rate in the charge and discharge cycle, and greatly prolongs the cycle life of the lithium metal battery.

[0119] The above only describes the preferred embodiments of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above-mentioned technical content without departing from the technical solution range of the present application, and any simple modification, equivalent change and modification of the above embodiments based on the technical essence of the present application are still within the scope of the present application.

Claims

1. A method for producing a multilayer composite solid electrolyte membrane, characterized by, Comprising the following steps: (1) Inorganic filler preparation Dissolve high valence metal salt, rare earth metal salt and low decomposition temperature polymer in solvent A according to a certain mass ratio to obtain spinning precursor solution B, and spin to obtain precursor fiber membrane layer by electrospinning; After calcination at 200-500℃ and annealing, high valence metal atom doped rare earth metal oxide inorganic filler is obtained, The high valence metal salt is selected from any one of gadolinium nitrate, ytterbium nitrate and yttrium acetate; the rare earth metal salt is selected from one of lanthanum chloride and cerium nitrate hexahydrate; the low decomposition temperature polymer is selected from one of polyvinylpyrrolidone, polymethyl methacrylate and polystyrene; the mass ratio of high valence metal salt to rare earth metal salt is 1:1-20, the mass ratio of total metal salt to low decomposition temperature polymer is 1:1-4, and the low decomposition temperature polymer concentration is 8wt-15wt%; (2) Preparation of multi-layer composite solid electrolyte fiber membrane Dissolve lithium salt and the inorganic filler prepared in step (1) into organic solvent C, and then dissolve fluorine-containing polymer therein to obtain spinning precursor solution D; Dissolve lithium salt and the inorganic filler prepared in step (1) into organic solvent E, and then dissolve polar polymer therein to obtain spinning precursor solution F; Use spinning precursor solution D as raw material to spin to obtain fluorine-containing composite solid electrolyte interface modification fiber membrane layer by electrospinning process; Then, use the fluorine-containing composite solid electrolyte interface modification fiber membrane layer as a receiver, cover it with spinning precursor solution F by electrospinning to obtain a double-layer composite solid electrolyte fiber membrane layer; finally, use the double-layer composite solid electrolyte fiber membrane layer as a receiver, cover it with spinning precursor solution D by electrospinning to obtain a three-layer composite solid electrolyte fiber membrane, and then obtain the multi-layer composite solid electrolyte fiber membrane after vacuum drying at 60℃, The fluorine-containing polymer content in the spinning precursor solution D is 6wt-12wt%, the mass ratio of lithium salt to fluorine-containing polymer is 1:1-5, and the mass ratio of inorganic filler to lithium salt is 1:1-5; The polar polymer content in the spinning precursor solution F is 3wt-7wt%, the mass ratio of lithium salt to polar polymer is 1:1-5, and the mass ratio of inorganic filler to lithium salt is 1:1-5; The fluorine-containing polymer is selected from any one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene and fluorine rubber; The organic solvent E is selected from any one of acetonitrile, N,N-dimethylformamide and dimethyl sulfoxide; The polar polymer is selected from one of polyethylene oxide, polyacrylonitrile and polyimide.

2. The preparation method of the multi-layer composite solid electrolyte membrane according to claim 1, characterized in that: In step (1), the solvent A is selected from one of dimethyl sulfoxide, N,N-dimethylacetamide and N,N-dimethylformamide; wherein The electrospinning conditions are as follows: voltage 12-20 kV, humidity 10-30%, and distance between spinning needle and receiver 8-24 cm. ​ ​ ​ During calcination, the precursor fiber membrane layer is placed in a tube furnace, heated at a rate of 5 ℃ per minute in an air atmosphere, and annealed after calcination at a temperature of 200-500 ℃ for 2-3 hours.

3. The method according to claim 1, wherein: wherein In step (2), the lithium salt is selected from any one or a combination of lithium trifluoromethane sulfonate, lithium nitrate, lithium hexafluorophosphate, and lithium borohydride; The organic solvent C is selected from any one of N, N-dimethylformamide, N, N-dimethylacetamide, and N-methylpyrrolidone.

4. The method according to claim 1, wherein: wherein, In step (2), the electrospinning conditions are: voltage 12-20 kV, humidity 10-30%, and distance between the spinning needle and the receiver 8-24 cm; When the fluorine-containing composite solid-state electrolyte interface modification fiber membrane layer is prepared, the peelable paper is used as the receiver, and the thickness of the membrane layer is controlled to be 5-20 microns; the thickness of the double-layer composite solid-state electrolyte fiber membrane layer is 80-150 microns; and the thickness of the third fluorine-containing composite solid-state electrolyte interface modification fiber membrane layer is also 5-20 microns; The three-layer composite solid-state electrolyte fiber membrane is vacuum dried at 60 ℃ for 2-5 hours to obtain the multi-layer composite solid-state electrolyte fiber membrane.

5. A multilayer composite solid-state electrolyte membrane, characterized by, The multi-layer composite solid-state electrolyte fiber membrane is prepared by the method according to any one of claims 1-4.

6. The multi-layer composite solid-state electrolyte membrane according to claim 5 is used in the preparation of a solid-state lithium ion battery.

7. A solid-state lithium-ion battery, characterized by, The electrolyte is the multi-layer composite solid-state electrolyte membrane according to claim 5.

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