Superior electrochemical properties of alpha-Fe2O3 nanofibers with a porous core/dense shell structure formed from iron acetylacetonate-polyvinylpyrrolidone composite fibers

Abstract

Porous core/dense shell alpha-Fe2O3 nanofibers were prepared by heat-treating electrospun gel nanofibers containing iron acetylacetonate-polyvinylpyrrolidone at 500 degrees C. Diffusion of Fe to the outer part of the nanofibers during the heating process results in a polyvinylpyrrolidone (PVP)-rich interior. Combustion of phase separated nanofibers produces alpha-Fe2O3 nanofibers with a porous core/dense shell structure. The nanofiber shell thickness and core diameter are 26 and 130 nm, respectively. The initial discharge and charge capacities of the alpha-Fe2O3 nanofibers at a current density of 1000 m Ag-1 are 1392 and 1112 mA h g(-1), respectively; the discharge capacities for the 2nd and 100th cycles are 1149 and 1225 mA h g(-1), respectively. The stable reversible discharge capacities of the nanofibers decreased from 1198 to 1061 mA h g(-1) as the current density increased from 500 to 3000 m Ag-1. (C) 2014 Elsevier Ltd. All rights reserved.