Hybrid electrochemical capacitors, electronic devices using such capacitors, and associated methods are disclosed. In an example, a hybrid electrochemical capacitor can include a first electrode made from Mg, Na, Zn, Al, Sn, or Li, a second electrode made from a porous material such as porous carbon or passivated porous silicon, and an electrolyte. The hybrid electrochemical capacitors can have enhanced voltage and energy density compared to other electrochemical capacitors, and enhanced power density compared to batteries.