Carbonate doped nickel-cobalt layered double hydroxide for high performance asymmetric supercapacitors

Abstract

In this work, a facile chemical co-precipitation method to prepare nickel-cobalt layered double hydroxide (Ni, Co-LDH) is reported. Through the addition of NaHCO 3 , carbonate ions (CO 3 2- ) are introduced into the LDH in a controlled way. The doping of CO 3 2- causes the original nanosheet structure to bend and interconnect, which increases the contact area between the electrode and the electrolyte, enhancing the energy storage characteristics of materials. Appropriate CO 3 2- doping effectively increases the specific capacity of Ni, Co-LDH. When the doping ratio of carbonate is 5% (Ni, Co-LDH/CO 3 -5%), the specific capacity is improved from 1432 F g -1 (undoped) to 1970 F g -1 at 1 A g -1 . Furthermore, the electrode exhibits satisfactory rate capability, retaining 82.8% of the specific capacity at 20 A g -1 . Moreover, an asymmetric supercapacitor (ASC), assembled with Ni, Co-LDH/CO 3 -5% as the positive electrode and activated carbon as the negative electrode, possesses a high energy density of 54.8 Wh kg -1 at a power density of 374.9 W kg -1 and remains 80.8% after 10000 cycles at 10 A g -1 , demonstrating excellent cyclic stability. The doping of CO 3 2- causes the original nanosheet structure to bend and interconnect, which increase the contact area between the electrode and the electrolyte, enhancing the energy storage characteristics of materials. An asymmetric supercapacitor, assembled with Ni, Co-LDH/CO 3 -5% as the positive electrode and activated carbon as the negative electrode, possesses a high energy density of 54.8 Wh kg-1 at a power density of 374.9 W kg -1 , 80.8% of the initial capacitance after 10000 cycles at 10 A/g. • Ni, Co-LDH/CO 3 - x were prepared by co-precipitation method. • The Ni, Co-LDH/CO 3 -5% exhibits specific capacity of 1970 F g -1 . • The ASC shows a high energy density of 54.8 Wh kg -1 .