ABSTRACT
Design of complex hollow nanostructures of two or more transition metal oxides seems to be necessary to answer the demand for novel energy storage electrodes owning outstanding performance for advanced developments of modern electronics. Herein, we develop a metal-organic frameworks (MOFs) assistance self-templated method for the synthesis of double-shell CuCo2O4 hollow spheres as battery-type electrode material with a large surface area of 93â¯m2 g-1. This electrode material reveals excellent electrochemical performance with an ultrahigh specific capacity of 701â¯Câ¯g-1 at 2â¯Aâ¯g-1. Additionally, remarkably high cycling performance is exhibited with maintaining more than 93.6% of the initial capacity after 6000 cycles. The assembly of the double-shell hollow spheres electrode with reduced graphene oxide (rGO) electrode in an asymmetric cell results in a high-performance supercapacitor with an energy density of 38.4â¯Whâ¯kg-1 and a power density of 16â¯kWâ¯kg-1, that is remarkably higher than that of conventional supercapacitors and comparable with Ni-MH batteries. Additionally, we display that assembling two asymmetric devices in series could effectively power blue, green, and red LED indicators. The excellent electrochemical performance of the ZCCO electrode shows its high potential for the production of advanced energy storage devices.
ABSTRACT
Activated carbon (AC), as a material for asymmetric supercapacitor (ASC), is the most widely used as negative electrode. However, AC has some electrode kinetic problems which are corresponded to inner-pore ion transport that restrict the maximum specific energy and power that can be attained in an energy storage system. Therefore, it is an important topic for researchers to extend the carbonaceous material with qualified structure for negative electrode supercapacitor. In this work, novel promoted ASC have been fabricated using nanoarrays of polyaniline grown on graphene oxide sheets (PANI-GO) as positive electrode and also, carbonized nitrogen-doped carbon nanoarrays grown on the surface of graphene (CPANI-G) as negative electrode. The porous structure of the as-synthesized CPANI-G can enlarge the specific surface area and progress ion transport into the interior of the electrode materials. From the other point of view, nitrogen doping can impressively improve the wettability of the carbon surface in the electrolyte and upgrade the specific capacitance by a pseudocapacitive effect. Because of the high specific capacitance and distinguished rate performance of PANI-GO and CPANI-G and moreover, the synergistic effects of the two electrodes with the optimum potential window, the ASC display excellent electrochemical performances. In comparison with the symmetric cell based on PANI-GO (40â¯Whâ¯kg-1), the fabricated PANI-GO//CPANI-G ASC exhibits a remarkably enhanced maximum energy density of 52â¯Whâ¯kg-1. Furthermore, ASC electrode exhibits excellent cycling durability, with 90.3% specific capacitance preserving even after 5000 cycles. These admirable results show great possibilities in developing energy storage devices with high energy and power densities for practical applications.
