N-Doped carbon as the anode and ZnCo2O4/N-doped carbon nanocomposite as the cathode for high-performance asymmetric supercapacitor application

Herein, we report a one-pot hydrothermal assisted synthesis of ZnCo2O4/N-doped carbon nanocomposite (ZC/NC) for high-performance asymmetric supercapacitor applications. The morphological analysis of the as-prepared nanocomposite reveals the nanosphere and nanocube-like structures on the surface of porous N-doped carbon. The as-fabricated nanocomposite electrode exhibits a maximum half-cell specific capacitance of 1500 F g−1 at 1 A g−1, with 15% of the EDLC and 85% of the diffusion-controlled capacitive contribution. The as-fabricated asymmetric supercapacitor device (ASC) delivered a maximum full-cell specific capacitance, specific energy, and specific power of 146 F g−1 at 1 A g−1, 81.32 W h kg−1 at 1 A g−1, and 2668.3 W kg−1 at 10 A g−1, respectively. To the best of our knowledge, an ASC device with a battery-type electrode in a carbon matrix has been tested for the first time at an extended voltage of 1.8 V for about 10 000 cycles holding 81.9% capacitance retention. The ZC/NC nanocomposite exhibits high electrical conductivity with a lower internal solution and charge-transfer resistance. This superior electrochemical performance of the ASC device can be attributed to the interspace between the ZC nanoparticles and the N-doped carbon network. Moreover, including N-functionality into the carbon skeleton reduces the oxygen content and increases the sp2 hybridized carbon content, which contributes to the rapid electron transfer and improvement in the performance, stability, and conductivity. Thus, ZC/NC is a promising electrode material for high-performance supercapacitor applications.