Smart adjustment of active mass loading on positive and negative electrodes, significant enhancement of energy density with long-term durability is achieved due to expand of operating potential window of the electrochemical capacitor. In the present contribution, two different carbon materials like indigenous activated carbon fibres and commercial Kuraray YP-50 carbon are utilised as electrodes and the equal/unequal mass configurations of electrochemical capacitor are systematically investigated by using 1 M tetraethylammonium tetrafluoroborate/AN as an organic electrolyte. The electrochemical performances of equal/unequal mass configurations are examined in terms of potential stability window and the durability of the electrochemical capacitor. The unequal mass configuration of carbon fibres electrodes shows 25% higher gravimetric energy density than unequal commercial YP-50 electrodes. Besides, unequal mass configuration of carbon fibres exhibit 41% higher gravimetric energy density as compared with commercial YP-50 carbon at 2.7 V as extensively reported in the literature. This result clearly explores the benefits of unequal mass configurations of electrochemical capacitor for extending the operation voltage window of organic electrolyte with long durability and this strategy enlightens the design of well-defined carbon-carbon based electrodes for commercial implementation. (C) 2018 Elsevier Ltd. All rights reserved.