High Performance Flexible Pseudocapacitor based on Nano-architectured Spinel Nickel Cobaltite Anchored Multiwall Carbon Nanotubes

Abstract

We demonstrate a facile two-step fabrication method for nano-architectured spinel nickel cobaltite (NiCo2O4) anchored multiwall carbon nanotubes (MWCNTs) based electrodes for high performance flexible energy-storage devices. As electrode materials for flexible supercapacitors, the NiCo2O4 anchored MWCNTs exhibits a high specific capacitance of 2032 Fg−1, which is nearly 1.62 times greater than pristine NiCo2O4 nanoflakes at 1 Ag−1. The synthesized NiCo2O4 anchored MWCNTs composite shows excellent rate performance (83.96% capacity retention at 30 Ag−1) and stability with coulombic efficiency over 96% after 5,000 cycles when being fully charged/discharged at 1 Ag−1. Furthermore, NiCo2O4 anchored MWCNTs achieve a maximum energy density of 48.32 Whkg−1 at a power density of 480 Wkg−1 which is 60% higher than pristine NiCo2O4 electrode and significantly outperformed electrode materials based on NiCo2O4 which are currently used in the state-of-the-art supercapacitors throughout the literature. This superior rate performance and high-capacity value offered by NiCo2O4 anchored MWCNTs is mainly due to enhanced electronic and ionic conductivity, which provides a short diffusion path for ions and an easy access of electrolyte flow to nickel cobaltite redox centers besides the high conductivity of MWCNTs.