LAUSR

Abstract FePO4 and porous Fe2P2O7 laundry-ball-like nanostructures (FePO4 LBs and p-Fe2P2O7 LBs, respectively) were prepared to investigate their functionalities as oxygen-electrode (O2-electrode) electrocatalysts in Li–O2 batteries. These structures were synthesized in two steps, via hydrothermal and thermal reactions. FePO4 LBs were synthesized through thermal dehydrogenation of as-prepared FePO4·2H2O precursors (FePO4·2H2O → FePO4 + 2H2O), and p-Fe2P2O7 LBs were synthesized through thermochemical reduction of same precursors under an H2 atmosphere (2FePO4·2H2O + H2 → Fe2P2O7 + 5H2O). As an O2-electrode electrocatalyst in Li–O2 cells, p-Fe2P2O7 LBs exhibited a higher discharge capacity (30,000 mA h gcatalyst–1 at a current density of 500 mA gcatalyst–1), higher reversibility (300 cycles at a current rate of 500 mA gcatalyst–1), and lower voltage gap, compared to FePO4 LBs. These superior performances of p-Fe2P2O7 LBs result from the Fe2+/Fe3+ redox effect and porous structure, which enhance the oxygen reduction or evolution reaction activities.