Dimensionality Synergy in Fe3o4 Nanostructures on Potassium-Ion Storage

Abstract

In this study, 0D-1D Fe3O4 nanotubes and 0D-2D Fe3O4 nanobelts were used as model structures to disclose dimensionality synergy on K+ storage. It was found that dimensionality synergy triggered three-step reactions on storing K+: (i) conversion reactions of surface 0D Fe3O4 NPs, (ii) catalytic degradation of surface electrolyte, and (iii) conversion reactions of Fe3O4 nanotubes/nanobelts. Besides, dimensionality synergy also triggered an electrochemical sintering process, in which surface reduction species exerted pinning effect on structural expansion during potassiation. Further, a correlation coefficient was proposed to quantitatively evaluate dimensionality synergy. By collecting experimental data and performing calculations, this coefficient of 0D-1D nanotube was much closer to 1 than that of 0D-2D nanobelt. The larger the correlation coefficient was, the stronger the dimensionality synergy became, and the better the K+-storage performance exhibited. As a result, the 0D-1D Fe3O4 nanotubes showed a negative fading behavior and delivered a final capacity of 419.1 mAh g-1 at 0.2 A g-1 after 900 cycles. By contrast, the 0D-2D Fe3O4 nanobelts showed a continuous capacity decrement upon cycling and delivered K+-storage capacity of 315.1 mAh g-1 under the same test condition.

Keywords: Potassium-ion storage, Conversion anode, Nanostructure, Dimensionality