Cellulose based Hybrid Separators for High Performance Li-ion Batteries

Abstract

Separators not only affect the safety but also electrochemical performance and they are important components in lithium ion batteries. Many researches have been conducted to fabricate separators with high electrochemical properties and high thermal stability. High porosity is important for high performance and thermal stability is vital for safety of the cells. Electrospinning can be used to produce nanofibers with high thermal stability and high porosity. Ceramic particles could also be used to improve electrochemical performance. Electro-spraying can be applied to incorporate ceramic nanoparticles in separators. Cellulose based hybrid nanofiber membrane separators were prepared via electrospinning and electro-spraying. Morphology and structural properties of hybrid separators were studied by using SEM, XRD and FTIR. N-butanol was used for porosity measurements. EIS were used for ionic conductivity and interfacial resistance studies. Electrochemical performance of the hybrid separators was also evaluated for use as separator membrane in lithium-ion batteries. It was found that cellulose hybrid nanofiber membranes had superior electrochemical performance with good electrochemical stability due to large porosity of nanofibers and electro-sprayed SiO2 nanoparticles. Large liquid electrolyte uptake of 240%, high electrochemical oxidation limit of over 4.5 V, and low interfacial resistance of 190 ohm·cm2 with lithium were observed when hybrid membranes were used in Li/LiFePO4 cells. In addition, high cell capacities of above 160 mAh/g and good cycling performance were demonstrated.