Facile synthesis of N-doped activated carbon derived from cotton and CuCo2O4 nanoneedle arrays electrodes for all-solid-state asymmetric supercapacitor

Nitrogen-doped activated carbon (NAC) with a high specific surface area was successfully fabricated through graphitization derived from cotton and ammonia doping. The obtained NAC exhibits an enhanced specific capacitance of 156.4 F g−1 at 0.5 A g−1 and good cycling stability with capacitance retention of 95% after 5000 cycles. Hydrothermal route was used to synthesize CuCo2O4 nanoneedles with diameter of 20 to 50 nm. CuCo2O4 electrode showed good electrochemical performance with specific capacitance of 390 F g−1 at 0.5 A g−1 and high stability. Based on the two electrodes, an all-solid-state asymmetric supercapacitor (ASC) was assembled, which can achieve specific capacitance of 26.2 F g−1 at 1 A g−1, energy density of 8.2 Wh kg−1 at a power density of 750 W kg−1 and still retains 5.6 Wh kg−1 at power density of 7500 W kg−1. Two ASCs in series successfully illuminated 52 LEDs connected in parallel, indicating the practical application of the device.