Hybrid electrochemical energy storage devices combine the advantages of battery and supercapacitors, resulting in systems of high energy and power density. Using LiPF₆ 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 PF₆^– 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/cm² at a current rate of 0.03 mA/cm². The work shows the ultimate miniaturization possible for energy storage devices where all essential components can be engineered on a single nanowire.