Porous NiCo2O4 spheres tuned through carbon quantum dots utilised as advanced materials for an asymmetric supercapacitor

• Main Authors: Zhu, Yirong, Wu, Zhibin, Jing, Mingjun, Hou, Hongshuai, Yang, Yingchang, Zhang, Yan, Yang, Xuming, Song, Weixin, Jia, Xinnan, Ji, Xiaobo
• Format: Article
• Language: English
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c4ta05507a

Carbon quantum dots (CQDs) tuned porous NiCo 2 O 4 sphere composites are prepared for the first time via a reflux synthesis route followed by a post annealing treatment. Benefiting from the advantages of the unique porous structure with a large specific surface area, high mesoporosity and superior electronic conductivity, the as-obtained CQDs/NiCo 2 O 4 composite electrode exhibits high specific capacitance (856 F g −1 at 1 A g −1 ), excellent rate capability (83.9%, 72.5% and 60.8% capacity retention rate at 20, 50 and 100 A g −1 , respectively) and exceptional cycling stability (98.75% of the initial capacity retention over 10 000 cycles at 5 A g −1 ). Furthermore, the assembled AC//CQDs/NiCo 2 O 4 asymmetric supercapacitor manifests a high energy density (27.8 W h kg −1 ) at a power density of 128 W kg −1 or a high power density (10.24 kW kg −1 ) at the reasonable energy density of 13.1 W h kg −1 and remarkable cycling stability (101.9% of the initial capacity retention over 5000 cycles at 3 A g −1 ). The results above suggest a great potential of the porous CQDs/NiCo 2 O 4 composites in the development of high-performance electrochemical energy storage devices for practical applications. Carbon quantum dots tuned porous NiCo 2 O 4 sphere composites are prepared and assembled into AC//CQDs/NiCo 2 O 4 asymmetric supercapacitor, exhibiting high energy or power density and remarkable cycling stability.