Building energy storage device on a single nanowire.

Hybrid electrochemical energy storage devices combine the advantages of battery and supercapacitors, resulting in systems of high energy and power density. Using LiPF(6) electrolyte, the Ni-Sn/PANI electrochemical system, free of Li-based electrodes, works on a hybrid mechanism based on Li intercalation at the anode and PF(6)(-) doping at the cathode. Here, we also demonstrate a composite nanostructure electrochemical device with the anode (Ni-Sn) and cathode (polyaniline, PANI) nanowires packaged within conformal polymer core-shell separator. Parallel array of these nanowire devices shows reversible areal capacity of ∼3 μAh/cm(2) at a current rate of 0.03 mA/cm(2). The work shows the ultimate miniaturization possible for energy storage devices where all essential components can be engineered on a single nanowire.