Stabilizing microstructure of Co-Ni layered double hydroxides by magnesium doping and confinement in carbonaceous mesopores for ultrahighly-stable asymmetric supercapacitor

Abstract

Increasing the inherent conductivity and improving the structural stability of the metal hydroxides based electrode materials would break through the bottleneck of poor cycling lifespan of the metal hydroxides based supercapacitor resulted from the poor structural stability upon continual charge/discharge process. However, to create a metal hydroxide having both characteristics at the same time remains a challenge. Herein, we presented a Mg-coordinated self-assembly and ion-exchange method to grow Co-Ni LDH into carbonaceous mesopores forming a confined structure with magnesium doping. The parent substrate of mesoporous carbon not only favors the increase of conductivity of Co-Ni LDH but also provides a confined space stabilizing its microstructure, while, the non-electrochemically-active component of Mg(OH)2 could make the active skeleton stable enough to resist repeated charge/discharge. Benefiting to these unique features of confined structure and magnesium doping, the resultant Co-Ni LDH/MC based asymmetric supercapacitor exhibit a superior energy storage level including high energy density of 37 Wh/kg@750 W/kg and superlong cycling stability with about 91.1 % capacitance retention of the first cycle after 30,000 cycle continual charge/discharge, offering great potential as qualified candidate for energy storage device.