To test its applicability in lithium-ion batteries, the researchers prepared a working electrode by mixing 85% Li-RGO with 10% carbon black and 5% binder (polytetrafluoroethylene), then carried out electrochemical measurements by taking a 1 M solution of LiPF₆ in a 1:1 (v/v) mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) as the electrolyte and Li foil as counter and reference electrode.

Cyclic voltammograms (CV) of the Li-RGO electrode demonstrated that lithium could reversibly intercalate and deintercalate into graphene sheets.

Li-RGO showed reversible discharge capacities of 410 mAh/g, compared to 300 mAh/g for graphite and 340 mAh/g for RGO.

The enhancement in the capacity of Li-RGO as compared to graphite and RGO can be attributed to the presence of electrochemically active defects (i.e., edge and basal-plane defects) formed during the reduction of graphite oxide and also due to the absorption of Li on the internal surfaces of the disordered graphene sheets.

The interface between liquid electrolyte and the outer surface of each graphene sheet involves SEI formation and results in huge irreversible capacity loss in the first discharge, whereas defects present in the Li-RGO usually undergo a reversible Li intercalation/deintercalation process without involving SEI formation and result in enhanced capacity compared to graphite and RGO.

—Kumar et al.

The team concludes that the partial intercalation of lithium ions in between graphene layers makes this material a good candidate for electrochemical energy storage applications.

Resources

• Ashavani Kumar, Arava Leela Mohana Reddy, Arnab Mukherjee, Madan Dubey, Xiaobo Zhan, Neelam Singh, Lijie Ci, W. Edward Billups, John Nagurny, Gandhi Mital, Pulickel M. Ajayan (2011) Direct Synthesis of Lithium-Intercalated Graphene for Electrochemical Energy Storage Application. ACS Nano doi: 10.1021/nn201527p