Engineering oxygen vacancy on iron oxides/hollow carbon cloth electrode toward stable lithium-ion batteries

Abstract

Recently, establishing lithium-ion battery electrodes (LIBs) with high activity and high mass loading is propitious to high-performance lithium storage. Herein, a facile metal salt-immersion approach followed by sintering treatment is exhibited to prepare porous iron oxides/ hollow tubular carbon cloth (HCC) electrode. An optimal sintering temperature of 700 °C not only creates electrolyte-accessible HCC current collector, but also tunes the surface structure and internal compositions of adherent iron oxides, thereby boosting the lithium-ion diffusion kinetics. This as-prepared integrated electrode delivers a high areal capacity of 5.46 mAh cm−2 (at 0.2 mA cm−2). For fully cognizing the advantages of our integrated electrode, we are further devoted to exploring the electrochemical mechanism and physical superposition of multi-layer electrodes. The experimental data demonstrate that, repeated conversion-type reaction could transform Fe3O4-FeO hybrid structure into finer Fe3O4 nanoparticles with rich oxygen vacancy (Vo). The density functional theory (DFT) discloses that, forming Vo sites in Fe3O4 structure could significantly upraise electrical conductivity and Li+ diffusion, which benefits to stabilizing the electrochemical performance. For both several-fold promoting mass loading and maintaining loading thickness at a finite electrode area, the single-layer, double-layer and triple-layer integrated electrodes are assembled into LIBs, which exhibits high average capacities of 5.33, 9.23 and 11.12 mAh cm−2. Toward several electronic equipments, the double-layer electrodes exhibit a long endurance time, further validating the superior energy-storage capacity.