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Asymmetric supercapacitors based on a NiCo₂O₄/three dimensional graphene composite and three dimensional graphene with high energy density
- Sun, Shumin, Wang, Shen, Li, Shaodan, Li, Yannan, Zhang, Yonghui, Chen, Junli, Zhang, Zhihong, Fang, Shaoming, Wang, Peiyuan
- Journal of materials chemistry A 2016 v.4 no.47 pp. 18646-18653
- X-ray diffraction, X-ray photoelectron spectroscopy, annealing, capacitance, crosslinking, electrodes, electrolytes, energy density, graphene, hot water treatment, nanoparticles, potassium hydroxide, synergism, transmission electron microscopy
- A NiCo₂O₄ nanoparticle/three dimensional porous graphene (NiCo₂O₄/3D-G) composite was synthesized through a facile hydrothermal method combined with subsequent annealing treatment. X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy analyses indicate that the NiCo₂O₄ nanoparticles were tightly anchored on the graphene sheets in the NiCo₂O₄/3D-G composite. When used as a supercapacitor electrode material, the obtained NiCo₂O₄/3D-G displayed a high specific capacitance of 2300 F g⁻¹ at 1.0 A g⁻¹ in 2.0 M KOH electrolyte. The asymmetric supercapacitor utilizing NiCo₂O₄/3D-G and 3D-G as positive and negative electrodes, respectively, delivered a high energy density of 73.8 W h kg⁻¹ with a power density of 800 W kg⁻¹ and long cycle stability (94.3% capacitance retention after 5000 cycles). The excellent supercapacitive performance of the NiCo₂O₄/3D-G can be ascribed to the synergistic effect of the porous and conductive three-dimensional cross-linking 3D-G and the high pseudocapacitive performance of the NiCo₂O₄ nanoparticles.