Nano-Sized Structurally Disordered Metal Oxide Composite Aerogels as High-Power Anodes in Hybrid Supercapacitors
Abstract
A general method for preparing nano-sized metal oxide nanoparticles with highly disordered crystal structure and their processing into stable aqueous dispersions is presented. With these nanoparticles as building blocks, a series of nanoparticles@reduced graphene oxide (rGO) composite aerogels are fabricated and directly used as high-power anodes for lithium-ion hybrid supercapacitors (Li-HSCs). To clarify the effect of the degree of disorder, control samples of crystalline nanoparticles with similar particle size are prepared. The results indicate that the structurally disordered samples show a significantly enhanced electrochemical performance compared to the crystalline counterparts. In particular, structurally disordered Ni xFe yO z@rGO delivers a capacity of 388 mAh g-1 at 5 A g-1, which is 6 times that of the crystalline sample. Disordered Ni xFe yO z@rGO is taken as an example to study the reasons for the enhanced performance. Compared with the crystalline sample, density functional theory calculations reveal a smaller volume expansion during Li+ insertion for the structurally disordered Ni xFe yO z nanoparticles, and they are found to exhibit larger pseudocapacitive effects. Combined with an activated carbon (AC) cathod...Continue Reading
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