Preparation of LiCoO2 composite coated with graphene and PEDOT∶PSS with enhanced electrochemical properties at high voltage for lithium-ion batteries

Abstract

LiCoO2 coated with graphene and PSS:PEDOT（GP-LCO）is synthesized by a facile and scalable method. The structure and morphology of LiCoO2（LCO）and GP-LCO have been investigated by X-ray diffraction（XRD）and scanning electron microscopy（SEM）. Transmission electron microscopy（TEM）further demonstrate the existence of graphene and PSS:PEDOT. The electrochemical properties of the composites are investigated by cyclic voltammetry and AC impedance measurements, which show that the conductive film of graphene（1%）and PSS:PEDOT（2%）on the surface significantly decreases the charge transfer resistance and improves the cycle stability of LiCoO2. Galvanostatic charge-discharge test reveals that with only 2% Super P as conductive additive, the GP-LCO delivers a capacity of 173.9 mAh/g at 0.1 C and 118.0 mAh/g at 10 C, which are higher than the pristine LCO in the potential range of 3.0-4.5 V（vs. Li/Li+）. Moreover, it is clearly noticed that the GP-LCO exhibits a capacity retention of 76.6% after 100 cycles at 0.1C, while the LCO only presents a capacity retention of 41.1%.

Keywords

• licoo2
• graphene
• pss∶pedot
• surface coating
• electrochemical properties