Designing freestanding electrodes with Fe2O3-based conversion type anode material for sodium-ion batteries

Abstract

Fe2O3-based nanomaterials are promising conversion type anodes due to their high theoretical capacity (∼1000 mAhg−1). However, the issues related to poor electronic conductivity and severe volume change during electrochemical sodiation/desodiation impose serious challenges for practical implementations. Herein, we have proposed a carbon fiber-based freestanding electrode architecture, which can effectively reduce the pulverization and conductivity issue by embedding Fe2O3 nanoparticles on the carbon fiber network. Fe2O3 nanomaterial is synthesized by the surfactant-assisted precipitation method. The conventional Fe2O3 electrode exhibits poor cycling stability, even though it delivered 653 mAh g−1 capacity during 1st discharge cycle. In comparison, the freestanding electrode exhibits an enhanced initial capacity of 1154 mAh g−1 with 70 % capacity retention and 28 times faster Na-ion diffusivity at the 100th cycle. The carbon fiber network provides the conductive backbone facilitating ionic and electronic transport. Furthermore, the repeated sodiation/desodiation process in this electrode indicates good electrochemical stability. This work enlightens the electrode structuring approach, in which 3D carbon fiber-based mat can be used to fabricate binder-less, metal current collector-free, freestanding electrodes for improving electrochemical performance in Na-ion cells.