It is challenging to handle heavy-metal-rich plants that grow in contaminated soil. The role of heavy metals in biomass on the physicochemical structure and electrochemical properties of their derived carbon has not been considered in previous research. In this study, Cu-ion hybrid nanoporous carbon (CHNC) is prepared from Cu content-contaminated biomass through subcritical hydrocharization (HTC) coupling pyrolytic activation processes. The CHNCs are used as advanced electrode material for energy storage applications, exhibiting an impressively ultrahigh capacitance of 562 F g−1 at a current density of 1 A g−1 (CHNC-700-4-25), excellent energy density of 26.15 W h kg−1, and only 7.59% capacitance loss after enduring 10,000 cycles at a current density of 10 A g−1, making CHNCs rank in the forefront of previously known carbon-based supercapacitor materials. These comprehensive characterizations demonstrate that copper ions introduce new electrochemically active sites and enhance the conductivity and charge transport performance of the electrode material, elevating the specific capacitance of CHNC from 463 to 562 F g−1. These findings offer valuable insights into the effective energy storage application of heavy-metal-contaminated biomass wastes.