| Because of nanofiber membrane its thin thickness, high porosity, well tunable nanoscale porous structure, high specific surface area, high electrolyte uptake and so on. It makes Li+ ion easily transport through the separator, Improving the cycle performance and Extending the service life of the lithium ion battery. At present, widespread method prepare nanofiber membrane is electrospinning, but there exist some big bottle-neck of technology, such as low production efficiency and high production costs make it hard actual applicant in lithium ion battery.This experiment based on the theoretical basis of Melt Extrusion Phase Separation Method, Thermoplastic poly(vinyl alcohol-co-ethylene)(EVOH) and Cellulose Acetate Butyrate(CAB) resin by melt blending extrusion. Then get EVOH/CAB blend fiber after by solvent extraction to get EVOH nanofibers. After mixing with co-solvent mixture using high-speed shear machine make EVOH nanofibers prepare into suspension. Under high speed air flow then spray the suspension on the surface of PET nonwoven fabric. Get a hierarchically structured NFs/PET/NFs membrane. Furthermore, the surface modification with inorganic Al2O3 nanoparticle and get a kind of hybrid Al2O3@NFs/PET/NFs membrane. Through the characteristic of SEM, porosity, contact angle of liquid, show NFs/PET/NFs and Al2O3@NFs/PET/NFs membrane possess hierarchically structured, high porosity and superior electrolyte affinity. Assemble them into different simulated cell, according to the characteristic of the electrochemical stability window, ionic conductivity, interfacial resistant and other electrochemical performance. It shows high value of the electrochemical stability window, high ionic conductivity, Al2O3@NFs/PET/NFs membrane show low interfacial resistance but the NFs/PET/NFs membrane show high interfacial resistance than other membranes. Assemble them in LiFePO4/Li half-cell, tested the performance of Charge/Discharge, C-Rate capability and cycle performance at constant current density 0.2C Al2O3@NFs/PET/NFs and NFs/PET/NFs membrane all show high discharge capacity and high discharge platform. With increase of discharge current density all kinds of separator show decline in discharge capacity and discharge platform. However, the Al2O3@NFs/PET/NFs and NFs/PET/NFs membrane always show high discharge capacity and discharge platform. After 100 cycles, the Al2O3@NFs/PET/NFs and NFs/PET/NFs membrane show high retention of discharge capacity than commercial separator. Al2O3@NFs/PET/NFs and NFs/PET/NFs membrane show excellent cell performance. It will be a promossing material to alternative traditional polyolefinbased separator apply in lithium ion battery as a result of its facile fabrication, low cost production, high production efficiency and excellent performance. |
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