High-Performance Nico2o4@C-Based Supercapacitors with Suppressed Self-Discharge and Robust Cycling Stability

Abstract

Pseudocapacitors based on the Faradaic processes usually possess high capacitance capacity yet exhibit active self-discharge behavior and poor cycle life. Herein, the free-standing NiCo2O4@C electrodes based on NiCo2O4 nanowire bundles wrapped by carbon shell are prepared. In addition to the optimized specific capacitance (1098 F g-1 at 1 A g-1), the designed NiCo2O4@C electrode reveals excellent suppression of self-discharge behavior. The duration can last for ~20639 s before the open-circuit potential of NiCo2O4@C electrode dropping from 0.5 V to 0.3 V, which is extended more than 4 times in comparison to that of pure NiCo2O4 electrode (3900 s). The simulation result confirms that the inhibited self-discharge behavior originates from the improved adsorption between NiCo2O4@C surface and electrolyte ions. Furthermore, the assembled asymmetric supercapacitor via using NiCo2O4@C-20 as positive electrode and active carbon as negative electrode presents robust cycling stability with 94% capacity retention after 25000 cycles. Current work is expected to give some inspirations on the rational design of pseudocapacitive electrode materials, which favors the exploration of pseudocapacitors with long-acting energy storage and reliable energy output.

Keywords: NiCo2O4 nanowire bundles, Carbon-coating, Supercapacitor, Self-discharge, cycling stability