Storing energy in carbon nanotubes

Figure 5 Lithium ion insertion in a graphite working electrode shows almost ideal electrochemical behavior. The electrolyte is LiPF₆ (1 M) in 1:1 ethylene carbonate–dimethyl carbonate.
The blue curve is the first insertion half-cycle (small steps shown in the inset correspond to structural-phase transitions). Most of the lithium is removed by reversing the current (red curve), with an irreversible loss of 10% of the lithium at ~2 V. The next insertion half-cycle (dotted curve) shows a reversible Li/C sorption capacity of ~1:6.