CN-121992575-A - Preparation method and application of composite membrane with multi-stage nano-branched structure

Abstract

The application provides a preparation method and application of a composite diaphragm with a multi-stage nano-branched structure, and belongs to the technical field of lithium metal batteries. The method comprises the steps of forming a precursor solution by a polymer matrix, a first structure inducer and a second structure inducer, wherein the precursor solution is subjected to electrostatic spinning technology to form a multi-stage structure composite membrane with a main-branch characteristic through in-situ induction, the first structure inducer is a quaternary ammonium salt compound, and the second structure inducer is an imidazole ionic liquid. The dual inducer system of the application gives the lithium metal negative electrode interface stability and cycle reliability.

Inventors

• YU YUAN
• LI MENGHUA
• GUO YUHAI
• YU BIN
• ZHU HAILIN
• ZHANG LILI
• ZHAO SHUANGSHUANG
• WANG MENGHUI

Assignees

• 浙江理工大学

Dates

Publication Date

20260508

Application Date

20260409

Claims (10)

1. 1. A preparation method of a composite membrane with a multi-stage nano-branch structure is characterized in that a precursor solution is formed by a polymer matrix, a first structure inducer and a second structure inducer, the precursor solution is subjected to an electrostatic spinning process to form the composite membrane with the multi-stage structure with a main-branch characteristic through in-situ induction, and the first structure inducer is a quaternary ammonium salt compound, and the second structure inducer is an imidazole ionic liquid.
2. 2. The method for preparing a composite membrane according to claim 1, wherein the total addition amount of the first structure inducer and the second structure inducer is 3-30% of the mass of the polymer matrix.
3. 3. The method for preparing the composite membrane with the multi-stage nano-branched structure according to claim 2, wherein the first structure inducer is added in an amount of 12-18% of the mass of the polymer matrix, and the second structure inducer is added in an amount of 8-12% of the mass of the polymer matrix.
4. 4. The method for preparing a composite membrane with a multi-stage nano-branched structure according to claim 1, wherein the first structure inducer is tetrabutylammonium chloride and the second structure inducer is 1-ethyl-3-methylimidazole bis (fluorosulfonyl) imide salt.
5. 5. The method for preparing a composite membrane with a multi-stage nano-branched structure according to claim 1, wherein the polymer matrix is polyvinylidene fluoride-hexafluoropropylene.
6. 6. The preparation method of the composite membrane with the multi-stage nano-branched structure of claim 1, wherein the precursor solution further comprises a mixed solvent, and the mixed solvent is obtained by mixing DMF and acetone according to a volume ratio of 5-7:3-5.
7. 7. The method for preparing the composite membrane with the multi-stage nano-branched structure according to claim 6, wherein the polymer matrix is dissolved in a mixed solvent to obtain a solution with the mass concentration of 10-16%, and the first structure inducer and the second structure inducer are added to uniformly disperse to obtain a precursor solution.
8. 8. Use of the composite separator made by the method of claim 1 in a liquid lithium metal battery.
9. 9. The use of claim 8, wherein the liquid lithium metal battery comprises a lithium metal negative electrode, a high voltage positive electrode, an electrolyte and a composite separator.
10. 10. The method of claim 8, wherein the liquid lithium metal battery is a Li|diaphragm|Li symmetrical battery or a Li|diaphragm|NCM 811 full battery.

Description

Preparation method and application of composite membrane with multi-stage nano-branched structure Technical Field The application relates to a preparation method and application of a composite diaphragm with a multi-stage nano-branched structure, and belongs to the technical field of lithium metal batteries. Background Lithium metal anodes are considered as ideal choices for next generation high energy density batteries due to their extremely high theoretical specific capacity, but commercialization is limited by the problems of safety risks and short cycle life caused by lithium dendrite growth. Conventional polyolefin (PE/PP) separators have poor wettability, insufficient thermal stability, and uniform structure, and it is difficult to effectively homogenize lithium ion flow and suppress dendrites. Although the polymer nanofiber membrane prepared by the electrostatic spinning method has higher porosity and good electrolyte affinity, the fiber structure is generally uniform, and effective regulation and control of ion migration paths and local electric field distribution on a microscopic scale are difficult. The improvement on the electrostatic spinning diaphragm is mainly focused on the introduction of a single structural scale or a single functional component, and the methods are complex in process, so that the cooperative optimization of the microstructure regulation and the interfacial chemical behavior of the diaphragm is difficult to realize in the same system. How to construct a membrane in situ, which can promote rapid ion transmission, guide uniform deposition of lithium and stabilize the structure of an interface, through a simple process is still a technical problem to be solved. Disclosure of Invention In view of the above, the present application aims to provide a method for preparing a composite membrane with a multi-stage nano-branched structure, which is different from the conventional uniform nanofiber membrane, by using inducers with two types of structures, the inducers with two types of structures act together in the electrostatic spinning jet evolution process instead of acting independently, so that the multi-stage nano-branched structure which is difficult to form by a single inducer system is constructed in situ, and the ion migration path and the local electric field distribution are reconstructed on a microscopic scale, so that the lithium ion flow is uniformly distributed in the thickness direction of the membrane. In order to achieve the above purpose, the present invention adopts the following technical scheme: A preparation method of a composite membrane with a multi-stage nano-branch structure comprises the steps of forming a precursor solution by a polymer matrix, a first structure inducer and a second structure inducer, wherein the precursor solution is subjected to an electrostatic spinning process to form the composite membrane with the multi-stage structure with a main-branch characteristic by in-situ induction, the first structure inducer is a quaternary ammonium salt compound, and the second structure inducer is an imidazole ionic liquid. The application adopts two structures of quaternary ammonium salt and ionic liquid to form a double inducer system, and generates physical-chemical synergistic effect in the jet evolution stage of single-step electrostatic spinning, thereby realizing in-situ construction of the homogeneous composite membrane with the multi-stage nano structure with the main-branch characteristic. According to the composite membrane, the ion migration path and the local electric field distribution in the membrane are reconstructed on a microscopic scale, so that the lithium ion deposition behavior is changed obviously, meanwhile, the inducer ionic liquid participates in interfacial film forming to form a stable inorganic component enrichment type SEI film which is chemically stable in interface, the growth of lithium dendrite is inhibited fundamentally, and the interfacial stability and the cycling reliability of a lithium metal cathode are improved cooperatively. Further, as preferable: The total addition amount of the first structure inducer and the second structure inducer is 3-30% of the mass of the polymer matrix. More preferably: The addition amount of the first structure inducer is 12-18% of the mass of the polymer matrix, and is optimal to 15%. The addition amount of the second structure inducer is 8-12% of the mass of the polymer matrix, and is optimally 10%. The first structure inducer is tetrabutylammonium chloride (TBAC), and the second structure inducer is 1-ethyl-3-methylimidazole bis (fluorosulfonyl) imide ([ EMIM ] [ FSI ]). The polymer matrix is polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP). The precursor solution also comprises a mixed solvent, and the mixed solvent is obtained by mixing N, N-Dimethylformamide (DMF) and acetone according to a volume ratio of 5-7:3-5 (optimally 6:4). The preparation method of the precursor sol