Engineering oxygen vacancy-rich CoAl layered double hydroxides coupled with N-doped carbon nanotubes as electrodes for supercapacitors

Abstract

Layered double hydoxides (LDHs) as electrode materials for supercapacitors still suffer from unsatisfactory rate capability owing to their limited electrical conductivity and sluggish ion diffusion kinetics. In this work, a vacancy engineering strategy coupled with a nanocomposite method is proposed to construct oxygen vacancy (Ov)-rich CoAl-LDH nanosheets coupled with N-doped carbon nanotubes (N-CNTs) using a one-step precipitation-reduction reaction. Experimental analyses and theoretical calculation results indicate that the rich Ov defects in CoAl-LDHs not only effectively enhance the electrical conductivity but also reduce the surface adsorption barrier of electrolyte ions, thereby triggering fast charge storage kinetics. In addition, Ov-rich CoAl-LDH nanosheets coupled with N-CNTs are well dispersed, which not only enrich electroactive sites but also further increase the charge transport. Consequently, the obtained N-CNT@Ov-CoAl-LDH nanocomposites demonstrate a specific capacity of 1068 C g−1 at 3 A g−1 and maintain a capacity retention of 78% even at 20 A g−1, together with a capacity retention of 91% after 10,000 cycles at 10 A g−1. This work provides insights for designing and engineering LDHs-based electrodes with improved charge storage performance through coupling the vacancy engineering with the nanocomposite method.