Controlled synthesis and enhanced electrochemical performance of Prussian blue analogue-derived hollow FeCo2O4 nanospheres as lithium-ion battery anodes

Abstract

Porous metal oxides have attracted great interest as anode materials for lithium ion batteries owing to their improved electrochemical properties. In this study, we propose a Prussian blue analogue (PBA)-derived strategy to successfully prepare hollow porous Fe_xCo_3−xO₄ (FCO) with controlled morphologies (nanospheres and nanocubes) using surfactants as “soft templates”. In comparison with FCO nanocubes (FCO-NCs) and FCO nanoparticles (FCO-NPs), FCO spheres (FCO-NSs) show a much better cycling stability and rate capability as an anode material for lithium ion batteries. The cycling capacity of FCO-NSs at the 50^th cycle has been largely enhanced to 1060 mA h g⁻¹ from only 721 (FCO-NCs) and 389 mA h g⁻¹ (FCO-NPs). The capacity of FCO-NSs at a current density of 1000 mA g⁻¹ has been considerably improved to 823 mA h g⁻¹ from 504 and 152 mA h g⁻¹ for FCO-NCs and FCO-NPs, respectively, indicating a much better rate capability. The greatly enhanced cycling stability and rate capability can be largely attributed to the hollow porous structure of FCO-NSs with a wider pore distribution, a slightly higher Co content (compared to FCO-NCs) and higher mechanical strength, which facilitates Li⁺ and electron diffusion and migration.