Co-precipitation synthesis of CuCo2O4 nanoparticles for supercapacitor electrodes with large specific capacity and high rate capability

Ultra-fine CuCo2O4 nanoparticles were synthesized using a facile co-precipitation method assisted by NaBH4 and CTAB, and they were explored as supercapacitor electrode material to achieve a large specific capacity and a high rate capability. The synthesized CuCo2O4–250 nanoparticles had a large surface area of 159.6 m2g−1, which provided numerous active sites to enhance their specific capacity. The abundant mesopores with a pore volume of 0.3599 cm3 g−1 effectively provided numerous channels for the electrolyte ions to diffuse onto the active surface of nanoparticles. The CuCo2O4–250 nanoparticles based electrodes exhibited both battery-type and capacitive-type behavior in the charging/discharging processes. It achieved a large specific capacity of 401.2 C g−1 at a current density of 0.5 A g−1 in 2 M KOH electrolyte. Results showed that when the current density was increased from 1 A g−1 to 10 A g−1, a retained specific capacity of 77.5% was achieved, indicating a good rate capability. An asymmetric supercapacitor with CuCo2O4–250 nanoparticles and activated carbon as positive and negative electrodes exhibited a high energy density of 29.5 Wh kg−1 at a power density of 832.6 W kg−1 and a capacity retention of 72.7% at 10 A g−1 after 10,000 cycles.