Nitrogen-doped activated carbons (NACs) were prepared through a one-step process. The obtained NACs show high surface areas of up to 2900 m2 g−1 with a moderate N content of up to 4 wt%. Electrochemical evaluation of the NACs shows a high specific capacity of 129 mA h g−1 (185 F g−1) in an organic electrolyte at a current density of 0.4 A g−1, as well as excellent rate capability and cycling stability. The hybrid-type supercapacitor assembled using the NACs and a Si/C electrode exhibits a high material level energy density of 230 W h kg−1 at 1747 W kg−1. The hybrid device achieved 76.3% capacity retention after 8000 cycles tested at 1.6 A g−1.
