Carbon nanotubes refined mesoporous NiCoO2 nanoparticles for high−performance supercapacitors

Abstract

For rapid charge/discharge application, capacitive energy storage technology is an attractive approach. The low energy density, one of disadvantages, can be ameliorated by promising pseudocapacitive materials that harvest energy through redox reactions. In this work, a composite of bimetal oxide and carbon nanotubes (CNTs), NiCoO2@CNT, with a novel mesoporous grape−like structure is prepared by a mild method, in which metal oxide nanoparticles are bonded to CNTs like vines tightly. Due to the synergistic effect and the unique structure as well as the facilitation of CNTs, impressive properties are performed for the NiCoO2@CNT composite. With an excellent stability and rate capability, it achieves 1587 F g−1 at 1 A g−1. As revealed in the charge storage mechanism, the surface−controlled process plays a dominant role, which can be ascribed to the large proportion of redox reactions on the surface of small NiCoO2 nanoparticles and the presence of CNTs. NiCoO2@CNT and activated carbon are then applied to fabricate an asymmetric supercapacitor. It exhibits a high energy density of 41.8 Wh kg−1 at 412 W kg−1 and an outstanding cycling property with 92% maintained after 5000 cycles, indicating a great potential for the actual application.