High energy ultracapacitor based on carbon xerogel electrodes and sodium sulfate electrolyte

► An ultracapacitor based on carbon electrodes and sodium sulfate electrolyte was tested in the voltage range 0-1.8 V. ► The UCap exhibited good capacitance, high specific energy and excellent cycling stability. ► The UCap had specific energy (17.5 Wh kg−1) remarkably higher than similar UCaps reported in literature.