Graphene sheets as anode materials for Li-ion batteries: preparation, structure, electrochemical properties and mechanism for lithium storage

Abstract

Varied graphene sheets were prepared from the graphite oxide (GO) with different degrees of oxidation and furthermore their structural characteristics and electrochemical properties as anode materials for Li-ion batteries were investigated. From the expandable graphite with a low oxidation level, the obtained graphene sheets had a thick and intact sheet structure with good crystallinity. Its specific surface area was quite low and no porous structure was detected. The graphene sheets prepared from the GO precursor with a high degree of oxidation were quite thin and disordered, along with high specific surface area and plenty of pores. These ultrathin graphene sheets demonstrated high reversible capacity mainly in the way of lithium absorption, where the specific surface area was the key structural parameter. The thick graphene sheets prepared from the expandable graphite had good crystallinity with few defects and pores, and had a similar lithium storage mechanism to graphite, whereby lithium storage is carried out by intercalation reactions.