Enhanced electrochemical performance of cobalt-doped FeOF@activated carbon sponge for high-performance sodium-ion cathode

Abstract

In this work, Co2+-doped FeOF is successfully synthesized and integrated with activated carbon sponge (ACS) to serve as a cathode for sodium-ion batteries. Doping aliovalent Co2+ enhances the ionic conductivity of FeOF by creating oxygen defects in the crystal structure of FeOF. Furthermore, the combined effects of ACS and Co2+ synergistically improve the electrical conductivity of FeOF. This feature results in an impressive discharge capacity of 465 mAh g−1 with a fading rate of 0.18 % per cycle after 100 cycles at 100 mAh g−1 in the voltage range of 1.2–4.0 V. A full-cell battery is also assembled with an ACS anode and exhibits a high energy density of 633 Wh kg−1cathode with a fading rate of 0.97 % per cycle. The mechanistic aspects of the enhanced electrochemical performance are thoroughly investigated by several ex-situ analyses and density functional theory calculations.