From graphite to porous graphene-like nanosheets for high rate lithium-ion batteries

Graphene nanosheets possess a promising potential as electrodes in Li-ion batteries (LIBs); consequently, the development of low-cost and high-productivity synthetic approaches is crucial. Herein, porous graphene-like nanosheets (PGSs) have been synthesized from expandable graphite (EG) by initially intercalating phosphoric acid, and then performing annealing to enlarge the interlayer distance of EG, thus facilitating the successive intercalation of zinc chloride. Subsequently, the following pyrolysis of zinc chloride in the EG interlayer promoted the formation of the porous PGS structure; meanwhile, the gas produced during the formation of the porous structure could exfoliate the EG to graphene-like nanosheets. The synthetic PGS material used as LIB anode exhibited superior Li⁺ storage performance, showing a remarkable discharge capacity of 830.4 mAh·g^-1 at 100 mA·g^-1, excellent rate capacity of 211.6 mAh·g^-1 at 20, 000 mA·g^-1, and excellent cycle performance (near 100% capacity retention after 10, 000 cycles). The excellent rate performance is attributed to the Li⁺ ion rapid transport in porous structures and the high electrical conductivity of graphene-like nanosheets. It is expected that PGS may be widely used as anode material for high-rate LIBs via this facile and low-cost route by employing EG as the raw material.