Sandwich-like NiO/rGO nanoarchitectures for 4 V solid-state asymmetric-supercapacitors with high energy density

Hierarchical NiO/reduced graphene oxide (rGO) nanohybrids with tunable microstructures were fabricated via the thermal decomposition of Ni(OH)(2)/rGO formed by the electrostatic attraction between exfoliated Ni(OH)(2) and GO nanosheets. Characterization study revealed that the size of intercalated NiO nanocrystals could be tuned from 2 nm to 10 nm, and the specific surface area of optimized nanohybrids reached to 255 m(2)/g. Ionogel polymer electrolyte was prepared by entrapping ionic liquid (EMImBF(4)) and lithium salt (LiTFSI) into copolymer (PVdF-HFP). Effect of NiO particle size on the electrochemical performances was evaluated systemically. Asymmetric supercapacitors with as-prepared nanohybrids as anode and commercial activated carbon as cathode were assembled. Aqueous 6 M KOH solution, organic LiPF(6)solution and ionogel polymer were utilized as electrolytes to check their compatibility with nanohybrids. Our study shows that supercapacitors exhibit energy densities of 31.6 Wh/kg, 49 Wh/kg and 146 Wh/kg, respectively, with the above mentioned electrolytes. These results clearly demonstrate that high performance can be actualized by the subtle combination of hybridized electrodes with high voltage formulated ionogel polymer electrolytes. (C) 2018 Elsevier Ltd. All rights reserved.