Mesoporous Cr2O3 nanotubes as an efficient catalyst for Li–O2 batteries with low charge potential and enhanced cyclic performance

Abstract

Hexagonal close packed Cr₂O₃, fabricated by an electrospinning technique combined with a heating method, is adopted for the first time as a catalyst for non-aqueous lithium–oxygen (Li–O₂) batteries. The synthesized highly mesoporous Cr₂O₃ nanotubes (Cr₂O₃-MNT) with a large surface area of 53.4 m² g⁻¹ are confirmed by field emission scanning electron microscopy (FESEM), field emission high-resolution transmission electron microscopy (TEM) and nitrogen adsorption/desorption isotherms (BET). By using the prepared Super P (SP) (60 wt%)/Cr₂O₃ (30 wt%)/polyvinylidenefluoride (PVDF) (10 wt%) composite as an oxygen electrode, the Li–O₂ battery shows an astonishingly enhanced capacity of 8280 mA h g⁻¹ at a current density of 50 mA g⁻¹. More encouragingly, when the current densities are fixed at 25, 50, 100 and 200 mA g⁻¹ with a limited capacity of 500 mA h g⁻¹, the charging potentials are 3.47, 3.51, 3.78 and 4.01 V, respectively, which are among the lowest charge potentials reported to date. By using a capacity-controlled method (1000 mA h g⁻¹) at a current density of 100 mA g⁻¹, the cell shows excellent cyclic stability up to 50 cycles. The reversible formation and dissociation of Li₂O₂ are verified by X-ray diffusion (XRD) and SEM, indicating that the as-prepared Cr₂O₃ nanotubes are a promising catalyst for Li–O₂ batteries.