Preparation of graphene based on liquid phase exfoliation and its application on LiFePO₄ electrode for lithium ion battery

Abstract

High-crystallinity and low-defect graphene nanosheets with nano pores were prepared from natural flake graphite via high-pressure homogenization liquid phase exfoliation method.The morphology and structure of as-prepared samples were investigated with scanning electron microscopy,transmission electron microscopy, atomic force microscope, X-ray diffraction and Raman spectroscopy.The electrochemical performance was performed using coin cells assembled in an argon-filled glovebox.It was found that the wrinkled graphene sheets with nanoholes consisted of 5 layers,which had high crystallinity.As conductive additives for LiFePO4 cathode,graphene constructed fast pathway for electron and ion transport in the bulk electrode,resulting in superior rate performance.Electrochemical tests showed that the electrode achieved a high reversible capacity of 90 mAh/g at 10 C rate;in addition,the discharge capacity achieved 90 mAh/g when charging and discharging at 5 C rate for 200 cycles,maintaining 100% capacity retention.The approach preparing graphene is facile,which can be suitable for industrial scale production of graphene materials.

Keywords

• liquid phase exfoliation
• graphene
• conductive additive
• rate performance