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

Abstract

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.