Cross-Linking Polyimide Fibrous Membrane Prepared By Electrospinning And Its Application As Lithium-Ion Battery Separator

With the rapid development of the electronics industry, lithium-ion battery has been widely used, while more and more attentions have been focused on the safety of the lithium ion battery. Abnormal temperature rising leads to many security problems duing to the overcharge and short circuit of LIBs. The current commercial separators of polyolefin lithium ion battery have many advantages, such as high strength, good chemical resistance, low cost, low electrolyte uptake. However, they’re weak under high temperature. At those conditions, the separators experiences two stages:(1) the separators of LIBs become weak while overheated.(2) the separator was broken and can’t isolate the positive and negative electrodes and causes explosion, therefore, lithium battery separators with strong high temperature stability are of great demands.Electrospun membranes have many excellent characteristics, such as large specific surface area, high porosity. Polyimide, as one kind of engineering plastics, posses many perfect performances, including high modulus and high strength, perfect resistance to high and low temperature, outstanding radiation resistance, good solvent resistance and good dimensional stability, excellent properties such as high strength. Traditional thermosetting polyimides are poor in solubility, which limit the diversity of processing. Thermoplastic polyimide inheriting comprehensive and excellent performances from polyimide, has the solution processing and melt processing characteristics, and realizes industrialization production as adequate sources of raw materials.In this paper, nonwoven polyimide membrane are firstly prepared by electrospinning and then processed by the thermal micro-crosslinked process, which makes adjacent fibers of the prepared non-woven melt, introducing cross-linking points to the nonwoven. By changing the processing parameters, different types of cross-linked morphology of thermoplastic polyimide fiber membrane have been produced, which improves the mechanical strength and the open pore structure, giving cross-linked membranes with desirable pore structure, high porosity, high electrolyte uptake, and good resistance to high temperature. In this paper, the crosslinked thermoplastic polyimides are used in lithium battery as separator. The rescults indicate the lithium-ion battery with crosslinked separators can keep working in both high or low current under charge and discharge modes with long life, high electrochemical stability window, and more stable pore structure even after many charge-discharge processes, which makes them more promising in application.