Can the performance of graphene nanosheets for lithium storage in Li-ion batteries be predicted?

Graphene nanosheets (GNS) were prepared from graphitic oxide (GO) in two different ways: (a) thermal exfoliation at different temperatures; and (b) wet chemistry, using aqueous N2H4 and KBH4 as reducing agents. Irrespective of the synthetic method used, the materials exhibited a high irreversible capacity and strong polarization in their charge curves, when used in a Li-ion battery. The GNS synthesized with N2H4 exhibited the best performance. Thus, at 149 mA g(-1) the average specific capacity delivered was ca. 600 mA h g(-1) after 100 cycles. On the other hand, the worst performance, irrespective of rate, was that of GNS synthesized with KBH4 and the thermal GNS obtained at 800 degrees C. The physical and chemical analyses allowed various parameters to be derived for correlation with the electrochemical properties. Unfortunately, no clear-cut correlation was apparent. A comparison with reported data revealed that no correlation appears to exist with physical and chemical properties that allows a simple strategy for tailoring an effective graphene anode to be designed.